JP2004354623A - Method of converting regular reflected light output, method of converting diffuse reflected light output, method of converting powder stuck amount, image forming apparatus, powder stuck amount detector, and gradation pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make always stably and accurately detectable a stuck amount over the entire stuck amount of a gradation pattern. <P>SOLUTION: The regular reflected light output and the diffuse reflected light output of the gradation pattern are sampled and the regular reflected light output is decomposed into (the regular reflected light component) and (a diffuse reflected light component), and then only (a regular reflected light component) is extracted. A (diffused light component from toner) is extracted by removing (the diffuse reflected light component) from a (belt surface part) from the diffuse reflected light output. By using a primary linear relation with respect to the stuck amount of two mutually independent output conversion values, a diffuse reflected light output conversion value is corrected in terms of sensitivity so that the diffuse reflected light output conversion value of a certain regular reflected light output conversion value (or the stuck amount) is set to a certain value in a stuck amount range (a low stuck amount area) where the stuck amount with regular reflected light is detected, and then the diffuse reflected light output (a correction value) for the stuck amount is unequivocally defined and stuck amount conversion processing is performed by the relation of "the stuck amount" and "the diffuse reflected light output correction value" previously obtained. Thus, the stuck amount is always stably and also highly accurately detected regardless of factors such as the lot variation of the output of a light emitting element and that of a light receiving element, a change and deterioration with time due to temperature characteristic and the deterioration of a detection object surface with time. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００３８】
表１から、発光素子側では２倍弱、受光素子側では４倍弱の出力ばらつきがあることが判った。
素子ばらつきの大きさは、素子の種別（トップビュータイプ、サイドビュータイプ）、及び製造メーカにより異なると思われるが、少なくとも調整が必要となるレベルでのばらつきはどの素子を用いた場合でもあるはずである。
この点について、上記各従来技術においては何ら言及されていない。これは当然のことだという認識からであると思われるが、従来技術に記載されているような手法で正確な付着量検知を行うためには、センサ（素子）の出荷検査段階で厳密な出力調整が必要である。
【００３９】
そこでもし仮に調整がなかった場合にどうなるかについて、実験データを基にして予測した結果を以下に説明する。
図６は、図４に示すセンサを用いて、転写ベルト上のカラートナー付着量を測定した結果であり、横軸：付着量に対し、縦軸に正反射光出力電圧、及び拡散反射光出力電圧をプロットしたものである。
ここで、発光素子、正反射光受光素子、拡散反射光素子それぞれに素子ばらつきがあった場合でも、少なくとも正反射光出力については、ベルト地肌部にて出力が最大となる特性を持つことから、ベルト地肌部での出力がある値（この場合は３．０Ｖ）となるようにＬＥＤ電流を調整すれば、発光素子、正反射光受光素子ばらつきによる出力ばらつきを吸収することができるために、付着量に対するセンサ出力としてほぼ一義的な出力特性が得られる。
【００４０】
図６の大きな□印はＬＥＤ調整後の拡散光出力をプロットした点であるが、もし仮に受光素子ばらつきが２倍あったとして、拡散反射光出力の受光素子を受光感度が１／２のものに変えたとすると、そのときの拡散光出力は小さな□印で表す出力（Ｖｄ／２）となるため、それぞれの場合について正反射光（Ｖｒ）との差分をとると、図７に示す通り、付着量に対する出力関係が一義的には決まらない。これは、比をとった場合でも同様である。
また、図７に示すように、付着量ゼロの点では２条件の値が一致していて、高付着量域ではこれがずれている場合には、従来より知られている正反射光出力の正規化処理のような演算を行ったとしても決して一義的に決めることはできない。
以上より、「正反射光出力」と「拡散反射光出力」との差分、あるいは比データを元に付着量変換を行う場合には、「正反射光出力」と「拡散反射光出力」の関係が常にある関係を満足する必要があり、そのためには例えばセンサの出荷検査段階で、ある基準板に対する正反射光出力と拡散反射光出力との関係を厳密に調整する等のばらつき補正が必要となる。
【００４１】
仮に上記従来技術に記載された手法が上に述べた通りの調整がなされた上での話であったとしても、やはり単に差分を取る、あるいは比を取るというだけでは、（２）、（３）に挙げた変動要因（センサの変動、ベルトの変動）により、正確な付着量検知ができない。
（３）についての説明
画像出力時、転写ベルトは常にシート状記録媒体としての転写紙と接触しているために、摩耗により経時的にベルト表面が荒れてきてしまう。また、白色剤が多く含まれる転写紙を連続的に通紙した場合には、経時的にベルト表面が白色化してきてしまう。
これについての実験結果を示す前に、正反射光出力、及び拡散反射光出力の状態変化要因について説明する。
正反射光出力とは、検知対象面で鏡面反射する光（入射角と反射角とが等しい）のことであり、検知対象面がつるつる（＝鏡面光沢度が高い）の場合、図８に示すように、照射された光６１は検知対象面５３で僅かに拡散されるのみで、殆どが正反射光６２として鏡面反射される。図８において、符号６３は正反射光感度を、６４は拡散反射光感度をそれぞれ分布領域的に示している。
【００４２】
図９に示すように、検知対象面５３に粉体としてのトナー６５が付着した場合、入射光６１はトナー６５で拡散されるために、正反射光６２が減少し、逆に拡散反射光６６が増加する。但し、拡散反射光６６が増加するというのは、トナー６５がカラートナーの場合であり、黒トナーである場合には、照射された光６１はほとんど吸収されてしまうために、拡散反射光６６はほとんど増加しない。
つまり、正反射光は検知対象物体の「表面性状特性（光沢度、表面粗さ等）の状態変化」により出力が変化し、拡散反射光出力は検知対象物体の「色特性（明度等）の状態変化」により出力が変化するという具合に、互いに全く独立した要因によって出力が変化するものなのである。
【００４３】
実験結果について説明する。図１に示す４連タンデム直接転写方式のカラー画像形成装置において、経時で転写ベルト表面が荒れた場合、及び白色化した場合を想定して、「鏡面光沢度（Ｇｓ）」と「明度（Ｌ^＊）」が異なる３種類の転写ベルト上に１６階調パターンを作像し、これらパターンのセンサ検知出力の比較により経時変動した場合の結果の予測を行った。以下に実験の諸条件を示す。
＜転写ベルト（検知対象面）＞
黒色ベルト・・・鏡面光沢度：Ｇｓ（６０）＝５７、 明度：Ｌ^＊＝１０
茶色ベルト・・・鏡面光沢度：Ｇｓ（６０）＝２７、 明度：Ｌ^＊＝２５
灰色ベルト・・・鏡面光沢度：Ｇｓ（６０）＝５、 明度：Ｌ^＊＝１８
＜検知センサ（光学的検知手段）＞ 図４に示したセンサの詳細仕様
発光側
素子：ＧａＡｓ赤外発光ダイオード（ピーク発光波長：λｐ＝９５０ｎｍ）、トップビュータイプ
スポット径：φ１．０ｍｍ
受光側
素子：Ｓｉフォトトランジスタ（ピーク分光感度：λｐ＝８００ｎｍ）、トップビュータイプ
スポット径：
正反射光受光側：φ１．０ｍｍ
拡散反射光受光側：φ３．０ｍｍ
検出距離：５ｍｍ（センサ上部〜検知対象面までの距離）
ＬＥＤ電流：２５ｍＡ固定
＜線速＞
１２５ｍｍ／ｓｅｃ
＜サンプリング周波数＞
５００Ｓａｍｐｌｉｎｇ／ｓｅｃ（＝２ｍｓｅｃ毎）
注１：鏡面光沢度測定値は、日本電色製の光沢度計ＰＧ−１を使い、測定角度６０°で測定した値である。
注２：明度は、Ｘ−Ｒｉｔｅ社製の分光測色計：Ｘ−Ｒｉｔｅ９３８を使い、光源：Ｄ５０、視野角：２°で測定した値である。
【００４４】
図１０に黒トナー付着量に対する正反射光出力特性を、図１１にカラートナー付着量に対する正反射光出力特性を示す。
この実験ではセンサ側入力条件を固定（ＬＥＤ電流：Ｉｆ＝２５ｍＡ固定）として行っているので、ベルト地肌部の影響が及ばない高付着量域（Ｍ／Ａ＝０．４ｍｇ／ｃｍ^２以上）では３種類のベルトで正反射光出力（電圧）が略一致するが、ベルト地肌部の影響を受ける低付着量域（Ｍ／Ａ＝０．４ｍｇ／ｃｍ^２以下）では一致しない。
この結果から判る通り、経時的に転写ベルトの鏡面光沢度が低下、すなわち表面粗さが悪化した場合、付着量がゼロのベルト地肌部が露出している低付着量域では矢印で示すように正反射光出力（電圧）が低下してしまうことが判る。
【００４５】
〔従来技術（タイプ▲１▼のセンサを用いた場合）の不具合についての考察〕
上記実験事実により、もし正反射出力のみしかもたないタイプ▲１▼のセンサにて付着量検知を行った場合の最大の難点は、カラー付着量検知において、付着量検知可能範囲が転写ベルトの光沢度低下に伴い経時的に狭くなってしまうということである。
その理由は、従来技術ではカラー付着量の付着量検知を以下のような付着量検知アルゴリズムで行うため、付着量に対するセンサ出力特性が図１１に示される変曲点（極小値）以上の付着量は検知できないからである。
＜従来の正反射光出力タイプの付着量変換式＞
図１１で、各ベルトの出力最小値を近似曲線の変曲点計算により求めると、経時的にベルトが劣化するに従い、検知可能な最大付着量が０．３６（５７）、０．３０（２７）、０．１７（５）という具合に狭くなっていることが判る。（ ）内は光沢度値を示す。付着量検知可能範囲は出力値と最小値となる付着量までである。
なお、黒トナー付着量検知については、単に出力ＳＮ比が低下するだけで、多少の検知精度の低下が生じるものの検知可能な最大付着量はほとんど変わることなく検知することができる。
【００４６】
次に、横軸：黒トナー付着量に対する拡散光出力特性を図１２に、横軸：カラートナー付着量に対する拡散反射光出力特性を図１３に示す。
拡散反射光出力もベルト地肌部の影響を受けない高付着量域では３種類のベルトでは出力がほぼ一致するが、ベルト地肌部の明度変化の影響を受ける低付着量域では、明度変化の影響により出力が一致しない。
つまり、経時的に転写ベルトが白色化してきた場合、転写ベルト地肌部の拡散反射光出力が上昇することが判る。
【００４７】
〔従来技術（タイプ▲２▼のセンサを用いた場合）の不具合についての考察〕
上記実験事実により、拡散反射光出力のみしかもたないタイプ▲２▼のセンサにて付着量検知を行った場合の最大の難点は、まず第１に、検知対象面の経時的な特性変化を補正する手段を持たないこと、第２に、特には検知対象面が明度：Ｌ^＊＜２０のような黒色であった場合において、センサ感度の校正を検知対象面で行えないこと、が挙げられる。
明度：Ｌ^＊＜２０で感度校正ができなくなる理由は、地肌部からの拡散反射光出力がほぼゼロとなってしまうからである。
参考までに、本出願人が従来機に対して行っていたセンサの感度校正方法について述べると、工場にて画像形成装置に対しセンサを取り付けた後、ある白色基準板に対するセンサ出力がある値となるようにセンサ発光側ＬＥＤ電流調整を行っていた。ただ、このようにすれば初期的には調整できたとしても、センサの温度特性、経時のＬＥＤ劣化等による感度変化に対する補正手段を持たないために、経時品質に対する確かなる保証が得られない。
【００４８】
図１４に鏡面光沢度と正反射光出力との相関について調べた結果を、図１５に明度と拡散反射光出力との相関について調べた結果を示す。
図１４は、「光沢度」と「明度」とがそれぞれ異なる４２種類の転写ベルトを、図４に示した反射型フォトセンサを用いて、ＬＥＤ電流：２０ｍＡ固定としたときの正反射光出力を横軸：６０°光沢度に対してプロットしたものである。
横軸の光沢度測定値は、日本電色製の光沢度計ＰＧ−１を使い、測定角度６０°で測定した値である。
図９に示すように、正反射光出力には拡散反射光成分が含まれるため、結果を明度の範囲毎にソートすれば、正反射光出力電圧は光沢度にほぼ直線的に比例する関係が得られることが判る。
このように直線的な比例関係が得られるのは、鏡面光沢度に対しては正に正反射光そのものを測定している関係にあるからである。（ＪＩＳＺ８７４１ 鏡面光沢度−測定方法を参照）
【００４９】
図１５は、これと同時に測定した拡散反射光出力を、横軸：ベルトの明度に対してプロットしたグラフである。図１５において［−］は単位が無いことを意味する。
横軸の明度は、Ｘ−Ｒｉｔｅ社製の分光測色計：Ｘ−Ｒｉｔｅ９３８を使い、光源：Ｄ５０、視野角：２°で測定した値である。
両者の関係は光源、測定角度等の違いがあるために直線的な関係とはならないが、光沢度の影響を受けることなく、ほぼ同一カーブ上にプロットされることから、拡散反射光出力は正反射光出力に対し独立であることが判る。
【００５０】
経時で転写ベルト表面が荒れてきてベルト地肌部の正反射光出力が低下した場合、または白色化して地肌部の拡散反射光出力が増加した場合、もしくはこれら２つが同時に進行した場合、これらのいずれにおいても「正反射光出力」と「拡散反射光出力」との関係は崩れてしまうために、単に２出力の差分を取る、もしくは比を取るだけでは出力を初期状態と同じにはできない。
故に、これに基づいて付着量変換を行っても、決して初期と同じ結果を得ることはできない。また、付着量変換までせず、この結果を直接濃度制御にフィードバックしても、初期とずれた結果となるだけである。
【００５１】
そこで、ベルト光沢度低下により正反射光出力が低下した場合、その分ＬＥＤ電流を上げて補正することが考えられるが、例えば、ベルト地肌部の正反射光出力が初期値となるような調整を行えば、少なくともベルト地肌部だけは初期値と同じとなるが、図１６に示す通り、カラートナーの場合、付着量全域に亘って出力が上がってしまう。
それのみならず、拡散反射光出力電圧も受光光量の増加に伴い出力が上昇するため、その結果として得られる差分出力は、図１７に示されるように、低着量域ではなんとか初期と合わせられても、高付着量域ではずれが生じるため、やはり初期と同じ結果を得ることはできない。これは、差分出力ではなく、比を取った場合でも同じことである。
【００５２】
（２）についての説明
上記のような経時変動が全くなかったとしても、周囲温度の上昇により半導体である発光素子、受光素子の出力特性に変化が生じた場合には、やはり同様にして初期に定めた状態とは出力結果が異なってしまう。
【００５３】
以上説明したように、これまで挙げてきた高付着量域における付着量検知、特にはカラー画像形成装置で多く用いられている黒ベルト上での高付着量域までのトナー付着量検知に対する解決手段として提案された従来技術に示される手法では、（ａ）階調パターン検知技術を使いこなすためには、これに用いる濃度検知センサの２出力が予め厳密に調整されていること、すなわち出荷検査段階で非常に厳密な調整を必要としていることを大前提としていると思われ、（ｂ）濃度検知センサの経時、環境変動に対する対処がなく、（ｃ）検知対象面（転写ベルト）の経時変動に対する対処がないことを考慮すれば、階調パターンの検知において未だ技術的には課題が山積しているといえる。
つまり、如何にして拡散反射光出力の感度調整ができない黒ベルト上で、（ａ）センサロットばらつきによる出力ばらつき、（ｂ）濃度検知センサの経時、環境変動、（ｃ）検知対象面（転写ベルト）の経時変動の何れの要因にも左右されず、常に安定した高付着量域のトナー付着量検知を如何に行うかが解決すべき技術課題として浮かび上がってくる。
【００５４】
本発明は、従来技術において潜んでいた上記課題を解決すべくなされたものであって、
（１）センサ側（ハードウエア側）での「正反射光出力」と「拡散反射光力」との出力関係の厳密な調整を不要とし、すなわち、出荷段階での自由度を大きくして製造コストの低減に寄与し、
（２）上記３つの要因の存在に拘わらずソフトウエア側の特徴によって自動補正可能とし、階調パターンの検知の高精度化を実現しようとするものである。
本発明の上記狙いは、以下に説明する本発明に係る付着量変換アルゴリズム、及びそれを用いた画像形成装置等にて達成される。
具体的には、階調パターンを▲３▼、▲４▼のタイプである「正反射光出力」、「拡散反射光出力」の２出力を持つ反射型光センサにて読み取り、正反射光による付着量検知が可能な付着量域で、この２つの出力を付着量に対して線形関係を持つ値に変換し、付着量に対し一義的な関係が得られる正反射光出力の変換値を基に、拡散反射光出力変換値の感度補正を行うことにより、拡散反射光出力についても付着量に対して一義的に決まる値に変換するアルゴリズムにより達成される。
【００５５】
以下、本発明の第１の実施形態を具体的構成に基づいて説明する。
図１に示すように、本実施形態における画像形成装置としての且つ粉体付着量検出装置としての４連タンデム直接転写方式のカラーレーザプリンタの概略構成を説明する。
カラーレーザープリンタは、１つの手差しトレイ３６、２つの給紙カセット３４（第１給紙トレイ）、３４（第２給紙トレイ）の３つの給紙トレイを有しており、手差しトレイ３６より給紙されたシート状記録媒体としての図示しない転写紙は給紙コロ３７により最上のものから順に１枚ずつ分離され、レジストローラ対２３へ向けて搬送される。第１給紙トレイ３４又は第２給紙トレイ３４から給紙された転写紙は、給紙コロ３５により最上のものから順に１枚ずつ分離され、搬送ローラ対３９を介してレジストローラ対２３へ向けて搬送される。
給紙された転写紙は、レジストローラ対２３で一旦停止され、スキューを修正された後、後述する最上流に位置する感光体ドラム１４Ｙ上に形成された画像の先端と転写紙の搬送方向の所定位置とが一致するタイミングで、図示しないレジストクラッチのオン制御によるレジストローラ対２３の回転動作により転写ベルト１８へ向けて搬送される。
転写紙は、転写ベルト１８とこれに当接した紙吸着ローラ４１とで構成される紙吸着ニップを通過する際、紙吸着ローラ４１に印加されるバイアスにより転写ベルト１８に静電力で吸着され、プロセス線速１２５ｍｍ／ｓｅｃにて搬送される。
【００５６】
転写ベルト１８に吸着された転写紙には、転写ベルト１８を挟んで各色の感光体ドラム１４Ｂ、１４Ｃ、１４Ｍ、１４Ｙと対向した位置に配置された転写ブラシ２１Ｂ、２１Ｃ、２１Ｍ、２１Ｙにトナーの帯電極性（マイナス）と逆極性の転写バイアス（プラス）が印加されることにより、各感光体ドラム１４Ｂ、１４Ｃ、１４Ｍ、１４Ｙに作像された各色のトナー像がイエロー（Ｙ）、マゼンタ（Ｍ）、シアン（Ｃ）、黒（Ｂｋ）の順で転写される。
各色の転写工程を経た転写紙は、下流側の駆動ローラ１９部位で転写ベルト１８から曲率分離され、定着装置２４へ搬送される。定着装置２４における定着ベルト２５と加圧ローラ２６により構成される定着ニップを通過することにより、トナー像が熱と圧力により転写紙に定着される。定着がなされた転写紙は、片面印刷モードの場合には、装置本体上面に形成されたＦＤ（フェイスダウン）トレイ３０へと排出される。
予め両面印刷モードが選択されている場合には、定着装置２４を出た転写紙は、図示しない反転ユニットへ送られ、該ユニットにて表裏を反転されてから転写ユニット下部に位置する両面搬送ユニット３３に搬送される。転写紙は該両面搬送ユニット３３から再給紙され、搬送ローラ対３９を経てレジストローラ対２３へ搬送される。以降は、片面印刷モード時と同様の動作を経て定着装置２４を通過し、ＦＤトレイ３０へと排出される。
【００５７】
次に、上記カラーレーザプリンタの画像形成部における構成及び作像動作を詳細に説明する。
画像形成部は、各色共に同様の構成及び動作を有しているのでイエロー画像を形成する構成及び動作を代表して説明し、その他については各色に対応する符号を付して説明を省略する。
転写紙搬送方向の最上流側に位置する感光体ドラム１４Ｙの周囲には、帯電ローラ４２Ｙ、クリーニング手段４３Ｙを有する作像ユニット１２Ｙと、現像ユニット１３Ｙ、光書き込みユニット１６等が設けられている。
画像形成時、感光体ドラム１４Ｙは図示しないメインモータにより時計回り方向に回転駆動され、帯電ローラ４２Ｙに印加されたＡＣバイアス（ＤＣ成分はゼロ）により除電され、その表面電位が略−５０ｖの基準電位となる。
【００５８】
次に、感光体ドラム１４Ｙは、帯電ローラ４２ＹにＡＣバイアスを重畳したＤＣバイアスを印加することによりほぼＤＣ成分に等しい電位に均一に帯電され、その表面電位がほぼ−５００ｖ〜−７００ｖ（目標帯電電位はプロセス制御部により決定される）に帯電される。
プリント画像として図示しないコントローラ部より送られてきたデジタル画像情報は、各色毎の２値化されたＬＤ発光信号に変換され、シリンダレンズ、ポリゴンモータ、ｆθレンズ、第１〜第３ミラー、及びＷＴＬレンズ等を有する光書き込みユニット１６により感光体ドラム１４Ｙ上に露光光１６Ｙが照射される。照射された部分のドラム表面電位が略−５０ｖとなり、画像情報に対応した静電潜像が形成される。
【００５９】
感光体ドラム１４Ｙ上のイエロー画像情報に対応した静電潜像は、現像ユニット１３Ｙにより可視像化される。現像ユニット１３Ｙの現像スリーブ４４ＹにＡＣバイアスを重畳したＤＣ（−３００〜−５００ｖ）が印加されることにより、書き込みにより電位が低下した画像部分にのみトナー（Ｑ／Ｍ：−２０〜−３０μＣ／ｇ）が現像され、トナー像が形成される。
作像された各色の感光体ドラム１４Ｂ、１４Ｃ、１４Ｍ、１４Ｙ上のトナー画像は、転写ベルト１８上に吸着された転写紙上に上記転写バイアスにより転写される。
【００６０】
なお、本実施形態におけるカラーレーザプリンタでは、上記のような画像形成モードとは別に、電源投入時、またはある所定枚数通紙後に各色の画像濃度を適正化するためにプロセスコントロール動作動作（以下プロコン動作と略す）が実行される。
このプロコン動作では、各色複数の濃度検知用パッチ（以下Ｐパターンと略す）を、帯電バイアス、現像バイアスとを適当なタイミングで順次切り替えることにより転写ベルト上に作像し、これらＰパターンの出力電圧を、駆動ローラ１９の近傍における転写ベルト１８の外部に配置された濃度検知センサ（以下Ｐセンサと略す）４０により検知し、その出力電圧を本発明の付着量変換アルゴリズム（粉体付着量変換方法）により付着量変換して、現在の現像能力を表す（現像γ、Ｖｋ）の算出を行い、この算出値に基づき、現像バイアス値及びトナー濃度制御目標値の変更をする制御を行っている。
【００６１】
Ｐセンサの構成は、図４に示す通りのものであり、またその諸元については既述した通りである。
ここでは受光素子としてＰＴｒ（フォトトランジスタ）を用いたが、ＰＤ（フォトダイオード）などの受光素子を用いても良い。
【００６２】
以下に、先に示した図１０〜図１３の実験結果を基に、本発明（本実施形態）における付着量変換アルゴリズムの説明をする。このアルゴリズムでは、以下の手順に従い、拡散光出力を付着量値に変換している。
（１）階調パターンの正反射光出力、拡散反射光出力をサンプリング（図１１、図１３参照）し、
（２）正反射光出力を［正反射光成分］と［拡散反射光成分］とに成分分解することにより、［正反射光成分］のみを抽出し、
（３）拡散反射光出力から［ベルト地肌部からの拡散反射光成分］を除去することにより、［トナーからの拡散光成分］を抽出し、
（４）（２）、（３）により求めた互いに独立する（交差する）２つの出力変換値の付着量に対する１次線形関係を利用し、正反射光による付着量検知が可能な付着量範囲（低付着量域）において、ある正反射光出力変換値（または付着量）の拡散反射光出力変換値がある値となるように、拡散反射光出力変換値を感度補正することにより、付着量に対する拡散反射光出力（補正値）を一義的に定め、（５）予め求めた「付着量」と「拡散反射光出力補正値」の関係から、付着量変換処理を行っている。
【００６３】
（１）〜（５）について、以下に順を追って説明する。
（１）についての説明
図１１、図１３は、転写ベルト１８に作像した図１８に示す濃度検知用のＰパターン７０を、図４に示すＰセンサ４０により検出した「正反射光出力電圧」及び「拡散反射光出力電圧」を電子天秤により精密に測定したカラートナー付着量［ｍｇ／ｃｍ^２］に対しプロットしたものである。階調パターン７０はベルト移動方向上流側がトナーの付着量が多くなる。
転写ベルト１８としては、上述のように、鏡面光沢度、明度がそれぞれ異なる３種類のものを用いている。
【００６４】
（２）についての説明
ここで、図１０に示した黒トナー付着量に対する正反射光出力特性と、図１１に示したカラートナー付着量に対する正反射光出力特性とを比較すると、図１１では正反射光出力がある付着量（この場合には０．２〜０．４ｍｇ／ｃｍ^２）以上で単調減少から単調増加に転じているのが判るが、これは図１９、図２０に示す通り、正反射光として正反射光受光素子５２で受光される光には、純粋な［正反射光成分］に加え、［ベルト面からの拡散反射光成分］、［トナー層からの拡散反射光成分］が含まれているからである。図１９（ｂ）において、符号５４はシアンのベタ部を示す。
ＬＥＤ５１からの照射光が、図１９に示す通り、検知対象面で均等拡散していることを考えると、正反射光受光素子５２に受光される拡散反射光成分と拡散光受光素子５５に入る拡散反射光との間にはｎ倍の関係が成り立つはずである。
ここで用いたｎ倍の値は、各受光素子５２、５５の受光径及び配置等の光学的レイアウトによって決まる値である。
【００６５】
実際の出力は各受光素子５２、５５に入った反射光が回路内でＯＰアンプでＩ−Ｖ変換された後、電圧として出力されるので、両者の出力関係には各出力のＯＰアンプのゲインの違いも積算され、α倍の関係が成り立つはずである。
この様な係数αを求めることができれば、正反射光出力を「正反射成分」と「拡散反射成分」とに成分分解できるものと考える。
ここで、係数αをどう求めるかについて考えてみると、Ｂｋトナーについては拡散反射成分がほぼゼロに等しいほど小さいので、図１０に示されるＢｋの正反射光出力特性がカラートナーの拡散反射光成分を除去した正反射成分出力特性とほぼ等しいと考えられる。
図１０に示されるように、Ｂｋトナーの正反射光出力特性は付着量の増加に従い、出力値ほぼゼロ、あるいは僅かにプラスの値となり、決してマイナスとはならないことから、カラートナーの各Ｐパターン毎に正反射光出力と拡散反射光出力の比の最小値を求め、この比の最小値を拡散反射光出力に乗じて、正反射光出力から引いてやれば、狙い通りの正反射成分のみ出力特性を取り出すことができるはずである。
【００６６】
以下に、図１１に示した茶色ベルト（Ｇｓ＝２７、Ｌ^＊＝２５）の出力結果を基に処理フローについて説明する。なお、以下説明中の記号（略号）の意味は以下の通りである。
Ｖｓｇ・・・転写ベルト１８の地肌部の出力電圧
Ｖｓｐ・・・各パターン部の出力電圧
Ｖｏｆｆｓｅｔ・・・オフセット電圧（ＬＥＤ５１のオフ時の出力電圧）
＿ｒｅｇ．・・・正反射光出力（Ｒｅｇｕｌａｒ Ｒｅｆｌｅｃｔｉｏｎの略）
＿ｄｉｆ．・・・拡散反射光出力（Ｄｉｆｆｕｓｅ Ｒｅｆｌｅｃｔｉｏｎの略、ＪＩＳＺ８１０５ 色に関する用語参照）
［ｎ］ ・・・要素数：ｎの配列変数
（ＳＴＥＰ１）：データサンプリング：ΔＶｓｐ、ΔＶｓｇの算出（図２１、図２２参照）
まず、はじめに、正反射光出力、拡散反射光出力ともに、全ポイント［ｎ］についてオフセット電圧との差分を計算する。
これは、最終的には「センサ出力の増分をカラートナーの付着量の変化による増分」のみで表したいためである。
【００６７】
【数１】

【００６８】
但し、ＬＥＤ５１オフ時の各オフセット電圧値（Ｖｏｆｆｓｅｔ＿ｒｅｇ．：０．０６２１Ｖ、Ｖｏｆｆｓｅｔ＿ｄｉｆ．：０．０６３５Ｖ）が本実施形態のように無視できるレベルに十分に小さい値となるようなＯＰアンプを用いた場合、このような差分処理は不要となる。
【００６９】
（ＳＴＥＰ２）：感度補正係数αの算出（図２２参照）
ＳＴＥＰ１にて求めたΔＶｓｐ＿ｒｅｇ．［ｎ］、ΔＶｓｐ＿ｄｉｆ．［ｎ］から、各ポイント毎にΔＶｓｐ＿ｒｅｇ．［ｎ］／ΔＶｓｐ＿ｄｉｆ．［ｎ］を算出し、ＳＴＥＰ３で正反射光出力の成分分解を行う際に、拡散反射光出力（ΔＶｓｐ＿ｄｉｆ．［ｎ］）に乗ずる係数αの算出を行う。
【００７０】
【数２】

【００７１】
このようにαを比の最小値により求めたのは、正反射光出力の正反射成分の最小値はほぼゼロであり、かつ正の値となることが予め判っているからである。ここで、階調パターンは、正反射光出力と拡散反射光出力との比の最小値が得られる付着量近傍において、少なくとも１つ以上、望ましくは３つ以上の付着量パターンを持つようにする。発光手段オフ時の各出力値との差分より得られる正反射光出力増分と拡散反射光出力増分との比の最小値が得られる付着量近傍において、少なくとも１つ以上、望ましくは３つ以上の付着量パターンを持つようにしてもよい。また、正反射光出力変換値が付着量に対し一次線形関係にある付着量範囲内において、少なくとも１つ以上、望ましくは３つ以上の付着量パターンを持つようにしてもよい。
（ＳＴＥＰ３）：正反射光の成分分解（図２３参照）
以下の式により、正反射光出力の成分分解を行う。
【００７２】
【数３】

【００７３】
このように成分分解すると、感度補正係数αが求まるパターン部にて、正反射光出力の正反射成分はゼロとなる。
この処理により、図２３に示す通り、正反射光出力が［正反射光成分］と［拡散反射光成分］に成分分解される。
（ＳＴＥＰ４）：正反射光出力＿正反射成分の正規化（図２４参照）
次に、３種類のベルトの地肌部の正反射光出力の違いを補正するために、各パターン部出力のベルト地肌部出力との比を取り、０〜１までの正規化値へ変換する。
【００７４】
【数４】

【００７５】
図２４には、図１１に示した３種類のベルト全てについて同様の処理を行った正規化値への変換結果を示した。
このように、正反射光を成分分解することにより、正反射光成分のみを抽出し、これを正規化値に変換することにより、正反射光成分と付着量との関係を一義的に求めることができる。なお、この値はベルト地肌部の露出率を表しており、付着量ゼロ〜１層形成までの付着量範囲においては、この正規化値（＝ベルト地肌部の露出率）は付着量に対して１次線形の関係にある。
もし仮に、Ｍ／Ａ｝＝０〜０．４ｍｇ／ｃｍ^２までの低付着量域のトナー付着量を求めたいのであれば、図２３に示すような付着量と正規化値との関係を、予め数式あるいはテーブルデータとして実験的に求めておけば、これを逆変換、あるいはテーブル参照することにより付着量変換が可能となる。
【００７６】
ここで従来技術との比較してみる。特開２００１−２１５８５０号公報の請求項４では、正反射光＋（乱反射光−乱反射光出力ｍｉｎ）×所定係数が示されており、明細書中の実施例には、補正後出力が１次相関関係となるように所定係数を「−６」とするとの記載があるが、このような形である所定係数を乗ずるのは、前述の通り、光学的検知手段の特性ばらつきを考慮されていない点で実際上意味がないといえる。
これに対し、本実施形態においては、所定係数として正反射光及び拡散反射光のセンサ出力を基に計算される係数を乗じているため、光学的検知手段の特性ばらつきが考慮された高精度の検知を行うことができる。
【００７７】
（３）についての説明
次に、［拡散反射光出力電圧］から［ベルト地肌部からの拡散反射光出力成分］を除去する処理について説明する。
本実施形態における付着量変換アルゴリズムで最終的に求めたいのは、トナー付着量に対する拡散反射光出力との一義的な関係である。
しかしながら、図２０に示す通り、拡散反射光受光素子５５に入る光にはトナー層からの拡散反射光に加え、ベルト地肌部からの拡散反射光（ノイズ成分）が含まれているために、元出力からこの成分を除去する必要がある。
図２０において、正反射成分の「地肌部出力」と「パターン部出力」との比は、付着量に対し一義的に決まる（付着量検出可能範囲：０〜０．４ｍｇ／ｃｍ^２）。
また、トナー層からの拡散反射成分において、検知対象面への照射光が一定であれば、付着量に対する関係は一義的に決まる（付着量検出可能範囲：０〜１・０ｍｇ／ｃｍ^２）。
ＳＴＥＰ４の続きとして、図１３に示した茶色ベルト（Ｇｓ＝２７、Ｌ^＊＝２５）の出力結果を基に処理フローについて説明する。
図１３の結果が示す通り、ベルト地肌部からの拡散反射光出力は、トナーが付着していないベルト地肌部で最大となり、トナーが付着するに従い、徐々にその成分は減少する。
ベルト地肌部からダイレクトに拡散反射光受光素子５５に入る光による拡散反射光出力電圧増分の付着量との関係は、転写ベルト１８の露出比率、すなわち先に求めた正反射光出力の正反射成分の正規化値（図２４参照）に比例するために、［拡散反射光出力電圧］から［ベルト地肌部からの拡散反射光出力成分］を除去する処理は以下の通りとなる。
（ＳＴＥＰ５）：拡散光出力の地肌部変動補正（図２５参照）
【００７８】
【数５】

【００７９】
結果を図２６に示す。このような補正処理を行うことにより、転写ベルト１８の地肌部の影響を除くことができる。従って、正反射光出力が感度を持つ低付着量域の［拡散反射光出力］から、［ベルト地肌部から直接反射される拡散反射光成分］を除去することができる。
このような処理を行うことにより、付着量ゼロ〜１層形成までの付着量範囲における補正後の拡散反射光出力は、原点を通り付着量に対し１次線形関係のある値へと変換される。
【００８０】
ここで、拡散反射光についての補足説明をする。正反射光は検知対象面の表面で反射される光であるために、図２４に示す通り、検知対象面がトナーに１００％覆われてしまうとそれ以上の付着量領域では出力がほぼ変化しなくなり、正規化変換値がほぼゼロになる。
これに対し、拡散反射光は、ＬＥＤ５１より照射されてトナー層内部まで入り込んだ光が多重反射される光であるため、図１３に示す通り、トナー層が１００％以上覆われた高付着量領域でもセンサ出力は単調増加する特性を持つ。
よって、ベルト地肌部から反射されてくる光も、図２６に示す通り、ベルト地肌部から直接反射される１次成分と、トナー層を透過して反射されてくる２次、３次成分とがある。
本実施形態では、ＳＴＥＰ５において１次成分のみの補正しかしていないが、この補正のみでも少なくとも感度補正を行う低付着量域に限ってはほぼ正確にベルト地肌部の影響を除去できており、２次、３次成分は１次成分に比して十分に小さいものであるから、１次成分のみの補正でも実用上十分な精度を得ることができる。
【００８１】
（４）についての説明
以上の処理により、正反射光出力が感度を持つ低付着量域において、（２）で、正反射光よりトナー付着量との関係が一義的に表せる［正反射光成分］のみを抽出し、（３）で、拡散反射光から、［ベルト地肌部から直接反射されてくる拡散反射光成分］を除去することができたので、これらを基に拡散反射光出力の感度補正を行う。
ここで、感度補正を行う理由は、先に述べた通り、以下に対する補正を行うためである。
（１）発光素子出力及び受光素子出力のロットばらつきに対する補正
（２）発光素子出力及び受光素子出力の温度特性及び経時劣化特性に対する補正この処理における最大のポイントは、トナー層が１層までしか形成されていない低付着量域においては、
▲１▼正反射光出力（正反射成分）の正規化値、すなわち、転写ベルト地肌部の露出率はトナー付着量に対し、１次線形関係にある。
▲２▼［トナー層からの拡散反射成分］は、トナー付着量に対し原点を通る１次線形関係にある。
という正反射光、拡散反射光の２つの補正後出力がともにトナー付着量に対し１次の関係にあることを利用して、拡散反射光出力の感度補正を行う点である。この感度補正のやり方は幾つかの方法が考えられるが、ここでは実施例として２つの方法について説明する。
【００８２】
（ＳＴＥＰ６）：拡散反射光出力の感度補正（図２５参照）
＜第１の方法による処理式＞
図２７に示すように「正反射光（正反射成分）の正規化値」に対し、地肌部変動補正後の拡散反射光出力をプロットし、低付着量域における直線関係から、拡散反射光出力の感度を求め、この感度が予め定めた狙いの感度となるように、補正を行う。
ここで、拡散反射光出力の感度と述べているのは、図２７に示す直線の傾きであり、ある正規化値の地肌部変動補正後の拡散反射光出力がある値（ここでは０．３のとき１．２）となるように、現状の傾きに対して乗じる補正係数を算出し、補正する。
（１）直線の傾きを最小二乗法により求める。
【００８３】
【数６】

【００８４】
本実施例においては、計算に用いるｘの範囲の下限値を０．０６としたが、この下限値はｘ、ｙとが線形関係にある範囲内で任意に決めることができる値である。なお、上限値は、正規化値が０〜１までの値であることから１とした。
（２）こうして求められた感度から計算されるある正規化値ａがある値ｂとなるような感度補正係数γを求める。
【００８５】
【数７】

【００８６】
（３）ＳＴＥＰ５で求めた地肌部変動補正後の拡散反射光出力に対し、この感度補正係数γを乗じて補正する。感度補正を行う際の基準点（ある正反射光出力変換値の拡散反射光出力変換値が、ある値となるような補正係数を乗じる際のある正反射光出力変換値）は、正反射光による付着量検知が可能な領域である。
【００８７】
【数８】

【００８８】
＜第２の方法による処理式＞
図２４で求められた付着量（測定値）と正反射光（正反射成分）の正規化値との関係から求められた逆変換式、または変換テーブル参照により、「正反射光（正反射成分）の正規化値」を付着量（変換値）に変換し、この付着量（変換値）に対して地肌部変動補正後の拡散反射光出力をプロットし、低付着量域における直線関係から拡散反射光出力の感度を求め、この感度が予め定めた狙いの感度となるように補正を行う。
先の第１の方法との相違点は、横軸を「正反射光（正反射成分）の正規化値」から「付着量（変換値）」に変更したことである。ここで、拡散反射光出力の感度と述べているのは図２８に示す直線の傾きであり、ある付着量（変換値）の地肌部変動補正後の拡散反射光出力がある値（ここでは０．１７５のとき１．２）となるように、現状の傾きに対して乗じる補正係数を算出して補正する。
（１）直線の傾きを最小二乗法により求める。
【００８９】
【数９】

【００９０】
本実施形態においては、計算に用いるｘの範囲の上限値を０．３としたが、この上限値はｘ、ｙとが線形関係にある範囲内で任意に決めることができる値である。なお、下限値は付着量の下限値が０である事から０とした。
（２）こうして求められた感度から計算されるある正規化値ａがある値ｂとなるような感度補正係数γを求める。
【００９１】
【数１０】

【００９２】
（３）ＳＴＥＰ５で求めた地肌部変動補正後の拡散反射光出力に対し、この感度補正係数γを乗じて補正する。
【００９３】
【数１１】

【００９４】
図２９には、３種類のベルト全てについて同様の処理を行った正規化値への変換結果を示した。
ここで、補正前の拡散反射光出力電圧は図１３に示される通りであるため、以上の処理により、本発明の目的である、
（１）発光素子出力、及び受光素子出力のロットばらつきに対する補正
（２）発光素子出力、及び受光素子出力の温度特性、及び経時劣化特性に対する補正
が十分にできていることが確認できた。
このような処理により、トナー付着量に対して感度補正後の拡散反射光出力を一義的に表すことができるため、予め数式あるいはテーブルデータとして実験的に求めておけば、これを逆変換、あるいは変換テーブルを参照することにより高付着量域まで正確な付着量変換が可能となる。
【００９５】
実際に、この正規化値を逆変換する事により得られた付着量（変換値）を、電子天秤による付着量測定値に対しプロットした結果を図３０に示す。
図３０に示す通り、高付着量域までほぼ正確に付着量変換できることが確認できる。高付着量域まで正確な付着量検知が可能となることにより、画像濃度制御における最大目標付着量を精度よく制御することができるようになるため、経時、環境、及びセンサのロットばらつきに拘わらず、常に安定した画質を得ることができる。
【００９６】
図３１は、濃度検知センサ２００個の試作品のうちばらつきの上限・下限品、及び中央品として抽出した３個のセンサを図１に示したレーザーカラープリンタＡの転写ベルト１８上に作成したカラートナー各色１０個ずつ計３０個のＰパターン（階調パターン）を検知した拡散反射光出力電圧を示している。図３２は、ＳＴＥＰ１〜ＳＴＥＰ６の変換アルゴリズムによる拡散反射光変換値を示している。このときのＬＥＤ電流は、転写ベルト１８の地肌部の正反射光出力電圧が４．０Ｖとなるように調整されたときの値である。
この結果により、本実施形態（本発明）のアルゴリズムを用いることにより、上述したような光学的検知手段における種々の要因による受光素子の出力ばらつきを、ハードウエア側の厳密な調整を要することなく、アルゴリズム側、すなわちソフトウエア側で自動的に且つ高精度に補正することが可能となる。
【００９７】
上記実施形態では、光学的検知手段として、図４に示した発光手段と正反射光受光素子及び拡散反射光受光素子を有するものを用いたが、図５に示したビームスプリッタを有する光学的検知手段を用いても同様の検知機能を得ることができる（第２の実施形態）。
また、上記実施形態では、検知対象面を転写体としての転写ベルト１８としたが、各感光体ドラムを検知対象面としてもよい（第３の実施形態）。この場合、Ｐセンサ４０は各感光体ドラムに対向して設けられる。
【００９８】
また、上記実施形態では、４連タンデム直接転写方式のカラー画像形成装置での例を示したが、図３３に示すように、４連タンデム構成で中間転写体へ重ね転写した後転写紙へ一括転写する方式のカラー画像形成装置においても同様に実施できる（第４の実施形態）。
本実施形態では図１８に示す濃度検知用のＰパターンが中間転写体としての中間転写ベルト２上に形成され、これを支持ローラ２Ｂの近傍に配置されたＰセンサ４０により検出する。すなわち、中間転写ベルト２を検知対象面としている。検知方式、動作（検知データの等取り扱い等）は第１の実施形態と同様である。
【００９９】
以下に、本実施形態における画像形成装置としてのタンデム型のカラー複写機の構成及び動作の概要を説明する。カラー複写機１は、装置本体中央部に位置する画像形成部１Ａと、該画像形成部１Ａの下方に位置する給紙部１Ｂと、画像形成部１Ａの上方に位置する画像読取部１Ｃを有している。
画像形成部１Ａには、水平方向に延びる転写面を有する転写体としての中間転写ベルト２が配置されており、該中間転写ベルト２の上面には、色分解色と補色関係にある色の画像を形成するための構成が設けられている。すなわち、補色関係にある色のトナー（イエロー、マゼンタ、シアン、ブラック）による像を担持可能な像担持体としての感光体ドラム３Ｙ、３Ｍ、３Ｃ、３Ｂが中間転写ベルト２の転写面に沿って並置されている。
【０１００】
各感光体ドラム３Ｙ、３Ｍ、３Ｃ、３Ｂはそれぞれ同じ反時計回り方向に回転可能なドラムで構成されており、その周りには、回転過程において画像形成処理を実行する帯電手段としての帯電装置４、各感光体ドラム３Ｙ、３Ｍ、３Ｃ、３Ｂ上に画像情報に基づいて電位Ｖ_Ｌの静電潜像を形成するための露光手段としての光書込装置５、各感光体ドラム３上の静電潜像を該静電潜像と同極性のトナーで現像する現像手段としての現像装置６、一次転写手段としての転写バイアスローラ７、印加電圧部材１５、クリーニング装置８が配置されている。各符号に付記しているアルファベットは、感光体ドラム３と同様、トナーの色別に対応している。各現像装置６にはそれぞれのカラートナーが収容されている。
中間転写ベルト２は、複数のローラ２Ａ〜２Ｃに掛け回されて感光体ドラム３Ｙ、３Ｍ、３Ｃ、３Ｂとの対峙位置において同方向に移動可能な構成を備えている。転写面を支持するローラ２Ａ、２Ｂとは別のローラ２Ｃは、中間転写ベルト２を挟んで２次転写装置９に対向している。図３３中、符号１０は中間転写ベルト２を対象としたクリーニング装置を示している。
【０１０１】
感光体ドラム３Ｙの表面が帯電装置４Ｙにより一様に帯電され、画像読取部１Ｃからの画像情報に基づいて感光体３ドラムＹ上に静電潜像が形成される。該静電潜像はイエローのトナーを収容した２成分（キャリアとトナー）現像装置６Ｙによりトナー像として可視像化され、該トナー像は第１の転写工程として、中間転写ベルト２上に、転写バイアスローラ７Ｙに印加された電圧による電界で引き付けられて転写される。
印加電圧部材１５Ｙは感光体ドラム３Ｙの回転方向における転写バイアスローラ７Ｙの上流側に設けられている。印加電圧部材１５Ｙにより、中間転写ベルト２に感光体ドラム３Ｙの帯電極性と同極性で且つ絶対値がベタ時Ｖ_Ｌより大きい電圧を印加し、転写領域にトナー像が入る以前に感光体ドラム３Ｙから中間転写ベルト２へトナーが転写することを防止して、感光体ドラム３Ｙから中間転写ベルト２へのトナーの転写時のチリによる乱れを防止する。
【０１０２】
他の感光体ドラム３Ｍ、３Ｃ、３Ｂでもトナーの色が異なるだけで同様の画像形成がなされ、それぞれの色のトナー像が中間転写ベルト２上に順に転写されて重ね合わせられる。
転写後感光体ドラム３上に残留したトナーはクリーニング装置８により除去され、また、転写後図示しない除電ランプにより感光体ドラム３の電位が初期化され、次の作像工程に備えられる。
２次転写装置９は、帯電駆動ローラ９Ａ及び従動ローラ９Ｂに掛け回されて中間転写ベルト２と同方向に移動する転写ベルト９Ｃを有している。転写ベルト９Ｃを帯電駆動ローラ９Ａにより帯電させることで、中間転写ベルト２に重畳された多色画像あるいは担持されている単一色の画像をシート状記録媒体としての用紙２８に転写することができる。
【０１０３】
２次転写位置には給紙部１Ｂから用紙２８が給送されるようになっている。給紙部１Ｂには用紙２８が積載収容される複数の給紙カセット１Ｂ１と、給紙カセット１Ｂ１に収容された用紙２８を最上のものから順に１枚ずつ分離して給紙する給紙コロ１Ｂ２と、搬送ローラ対１Ｂ３と、２次転写位置の上流に位置するレジストローラ対１Ｂ４等が設けられている。
給紙カセット１Ｂ１から給紙された用紙２８は、レジストローラ対１Ｂ４で一旦停止され、斜めずれ等を修正された後、中間転写ベルト２上のトナー像の先端と搬送方向先端部の所定位置とが一致するタイイングでレジストローラ対１Ｂ４により２次転写位置に送られる。装置本体の右側には起倒可能に手差しトレイ２９が設けられており、該手差しトレイ２９に収容された用紙２８は給紙コロ３１により給送された給紙カセット１Ｂ１からの用紙搬送路と合流する搬送路によりレジストローラ対１Ｂ４に向けて送られる。
【０１０４】
光書込装置５では、画像読取部１Ｃからの画像情報あるいは図示しないコンピュータから出力される画像情報により書き込み光が制御されて感光体ドラム３Ｙ、３Ｍ、３Ｃ、３Ｂに対して画像情報に応じた書き込み光を出射して静電潜像を形成するようになっている。
画像読取部１Ｃは、自動原稿給送装置１Ｃ１と、原稿載置台としてのコンタクトガラス８０を有するスキャナ１Ｃ２等を有している。自動原稿給送装置１Ｃ１は、コンタクトガラス８０上に繰り出される原稿を反転可能な構成を有し、原稿の表裏各面での走査が行えるようになっている。
光書込装置５により形成された感光体ドラム３上の静電潜像は現像装置６によって可視像処理され、中間転写ベルト２に１次転写される。中間転写ベルト２に対して各色毎のトナー像が重畳転写されると、２次転写装置９により用紙２８上に一括して２次転写される。２次転写された用紙２８は定着装置１１へ送られ、ここで熱と圧力により未定着画像を定着される。２次転写後の中間転写ベルト２上の残留トナーは、クリーニング装置１０により除去される。
【０１０５】
定着装置１１を通過した用紙２８は、定着装置１１の下流側に設けられた搬送路切り換え爪１２により、排紙トレイ２７に向けた搬送路と反転搬送路ＲＰとに選択的に案内される。排紙トレイ２７に向けて搬送された場合には、排紙ローラ対３２により排紙トレイ２７上に排出され、スタックされる。反転搬送路ＲＰへ案内された場合には反転装置３８により反転され、再度レジストローラ対１Ｂ４に向けて送られる。
【０１０６】
以上の構成により、カラー複写機１では、コンタクトガラス８０上に載置された原稿を露光走査することにより、あるいはコンピュータからの画像情報により、一様に帯電された感光体ドラム３に対して静電潜像が形成され、該静電潜像が現像装置６によって可視像処理された後、トナー像が中間転写ベルト２に１次転写される。
中間転写ベルト２に転写されたトナー像は、単一画像の場合にはそのまま給紙部１Ｂから繰り出された用紙２８に転写される。多色画像の場合には１次転写が繰り返されることにより重畳された後、用紙２８に一括して２次転写される。
２次転写後の用紙２８は定着装置１１により未定着画像を定着された後、排紙トレイ２７に排出され、あるいは反転されて両面画像形成のために再度レジストローラ対１Ｂ４に向けて送られる。
本実施形態では、検知対象面を転写体としての中間転写ベルト２としたが、各感光体ドラムを検知対象面としてもよい（第５の実施形態）。この場合、Ｐセンサ４０は各感光体ドラムに対向して設けられる。
【０１０７】
また、１つ感光体ドラムとリボルバー方式の現像装置を用いて各色のトナー像を形成し、各トナー像を中間転写体に重ね合わせ転写した後、シート状記録媒体としての転写紙上に一括転写する方式のカラー画像形成装置においても同様に実施することができる（第６の実施形態）。その一例を図３４に示す。
本実施形態では、図１８に示す濃度検知用のＰパターンが中間転写体としての中間転写ベルト４２６上に形成され、これを駆動ローラ４４４の近傍に配置されたＰセンサ４０により検出する。すなわち、中間転写ベルト４２６を検知対象面としている。検知方式、動作（検知データの取り扱い等）は第１の実施形態と同様である。
【０１０８】
以下に、本実施形態における画像形成装置としてのカラー複写機の構成の概要を説明する。
カラー複写機において、露光手段としての書き込み光学ユニット４００は、カラースキャナ２００からのカラー画像データを光信号に変換して原稿画像に対応した光書き込みを行い、像担持体である感光体ドラム４０２上に静電潜像を形成する。
該書き込み光学ユニット４００は、レーザーダイオード４０４、ポリゴンミラー４０６とその回転用モータ４０８、ｆθレンズ４１０や反射ミラー４１２等により構成されている。
感光体ドラム４０２は、矢印で示すように反時計回りの向きに回転され、その周囲には、感光体クリーニングユニット４１４、除電ランプ４１６、電位センサ４２０、回転式現像装置４２２のうちの選択された現像器、現像濃度パターン検知器４２４、中間転写体としての中間転写ベルト４２６等が配置されている。
【０１０９】
回転式現像装置４２２は、ブラック用現像器４２８、シアン用現像器４３０、マゼンタ用現像器４３２、イエロー用現像器４３４と、各現像器を回転させる図示しない回転駆動部を有している。各現像器は、キャリアとトナーとの混合現像剤が入った、いわゆる２成分現像方式の現像器であり、上記実施形態で示した現像装置４と同様の構成を有している。磁性キャリアの条件や仕様等も同様である。
待機状態では、回転式現像装置４２２は、ブラック現像の位置にセットされており、コピー動作が開始されると、カラースキャナ２００で所定のタイミングからブラック画像のデータの読み取りがスタートし、この画像データに基づいてレーザ光による光書き込み・静電潜像（ブラック潜像）の形成が始まる。
【０１１０】
このブラック潜像の先端部から現像するために、ブラック用現像器４２８の現像位置に潜像先端部が到達する前に、現像スリーブを回転開始してブラック潜像をブラックトナーで現像する。感光体ドラム４０２にはマイナス極性のトナーが作像される。
そして、以後、ブラック潜像領域の現像動作を続けるが、潜像後端部がブラック現像位置を通過した時点で、速やかにブラックのための現像位置から次の色の現像位置まで、回転式現像装置４２２が回転する。当該動作は、少なくとも、次の画像データによる潜像先端部が到達する前に完了させる。
像形成サイクルが開始されると、まず、感光体ドラム４０２は矢印で示すように反時計回りの向きに、中間転写ベルト４２６は時計回りの向きに、図示しない駆動モータによって回転させられる。中間転写ベルト４２６の回転に伴って、ブラックトナー像形成、シアントナー像形成、マゼンタトナー像形成、イエロートナー像形成が行われ、最終的にブラック（Ｂｋ）、シアン（Ｃ）、マゼンタ（Ｍ）、イエロー（Ｙ）の順に、中間転写ベルト４２６上に重ねられ（１次転写）、トナー像が形成される。
【０１１１】
中間転写ベルト４２６は、感光体ドラム４０２に対向する１次転写電極ローラ４５０、駆動ローラ４４４、２次転写ローラ４５４に対向する２次転写対向ローラ４４６、中間転写ベルト４２６の表面を清掃するクリーニング手段４５２に対向するクリーニング対向ローラ４４８Ａの各支持部材間に張架されており、図示しない駆動モータにより駆動制御されるようになっている。
感光体ドラム４０２に順次形成されるブラック、シアン、マゼンタ、イエローの各トナー像が中間転写ベルト４２６上で正確に順次位置合わせされ、これによって４色重ねのベルト転写画像が形成される。このベルト転写画像は２次転写対向ローラ４４６により用紙に一括転写される。
【０１１２】
給紙バンク４５６内の各記録紙カセット４５８、４６０、４６２には装置本体内のカセット４６４に収容された用紙のサイズとは異なる各種サイズの用紙が収容されており、これらのうち、指定されたサイズ紙の収容カセットから、該指定された用紙が給紙コロ４６６によってレジストローラ対４７０方向に給紙・搬送される。図３４において、符号４６８はＯＨＰ用紙や厚紙等のための手差し給紙トレイを示す。
像形成が開始される時期に、用紙は上記いずれかのカセットの給紙口から給送され、レジストローラ対４７０のニップ部で待機する。そして、２次転写対向ローラ４４６に中間転写ベルト４２６上のトナー像の先端がさしかかるときに、丁度用紙先端がこの像先端に一致するようにレジストローラ対４７０が駆動され、用紙と像のレジスト合わせが行われる。
【０１１３】
このようにして、用紙が中間転写ベルト４２６と重ねられて、トナーと同極性の電圧が印加される２次転写対向ローラ４４６の下を通過する。このとき、トナー画像が用紙に転写される。続いて、用紙は除電され、中間転写ベルト４２６から剥離して紙搬送ベルト４７２に移る。
中間転写ベルト４２６から４色重ねトナー像を一括転写された用紙は、紙搬送ベルト４７２によりベルト定着方式の定着装置４７０へ搬送され、この定着装置４７０で熱と圧力によりトナー像を定着される。定着を終えた用紙は排出ローラ対４８０で機外へ排出され、図示しないトレイにスタックされる。これにより、フルカラーコピーが得られる。
本実施形態では、検知対象面を転写体としての中間転写ベルト４２６としたが、感光体ドラム４０２を検知対象面としてもよい（第６の実施形態）。この場合、Ｐセンサ４０は感光体ドラム４０２に対向して設けられる。
【０１１４】
上記各実施形態では、正反射光出力と拡散反射光出力との比の最小値に基づいて処理する方式としたが、発光手段オフ時の各出力値との差分より得られる正反射光出力増分及び拡散反射光出力増分との比の最小値に基づいて処理する方式としても同様の検知機能を得ることができる。
また、上記各実施形態では、粉体付着量検出装置として画像形成装置を例示したが、トナー以外の粉体を扱う付着量検出分野においても同様の処理方式により同様の検知機能を得ることができる。
【０１１５】
上記各実施形態において得られる効果を以下に述べる。
従来技術では、上述した通り、検知対象面の経時的な光沢度低下によりカラー付着量検知可能範囲が徐々に狭まっていくために、経時での検知対象面の摩耗劣化が寿命の律速要因となっていたが、上記のような変換処理を行うことにより、従来の正反射光検知に比べ、付着量検知可能範囲が広がり、光沢度に依存することなく、正確な付着量検知が行うことができる。
また、上記実施形態では検知対象面の摩耗劣化に依存しないために、検知対象面の寿命を伸ばすことができる。
正反射光出力変換アルゴリズムを、カラー画像形成装置における像担持体又は転写体を検知対象面とした付着量検出に適用することにより、従来技術では濃度検知困難と言われている光沢度の低いベルトのような検知対象面でも何ら問題なく付着量変換でき、その付着量変換値に基づき濃度制御を行うことができる。
【０１１６】
また、上記変換処理を行うことにより、付着量ゼロ〜粉体１層形成までの低付着量範囲において、拡散反射光出力を付着量に対して線形関係が得られる値へ変換することができる。
また、上記変換処理（拡散光出力感度の自動補正機能）を行うことにより、濃度検知センサの発光素子、受光素子の出力ばらつきに起因する拡散光出力ばらつき（ハードウエア側）を、付着量変換アルゴリズム側（ソフトウエア側）により補正できるようになるため、従来行われてきたようなセンサ出荷検査時におけるセンサ側（ハードウエア側）での調整作業は不要、もしくは調整幅を大幅に広げることが可能となる。
因みに、本出願人が従来機に搭載していた拡散反射型センサでは、出力調整時間がセンサ１個につき約２分近く要していたのに対し、公差幅を広くできた結果、１０秒弱で調整可能となった。
これにより、センサ製造における生産性を飛躍的に改善でき、センサのコストダウン、ひいては画像形成装置のコストダウンを実現できる。
【０１１７】
また、濃度検知センサの経時的なＬＥＤ光量の低下及び発光素子、受光素子の温度特性による出力変動に対しても、拡散反射光出力感度の自動補正機能により、常に安定した付着量変換を行うことができる。
従来技術では、拡散反射光出力のみのセンサ（タイプ▲２▼）では感度校正が困難であった、検知対象面が黒色である場合においても、正確な感度校正及び付着量検知を行うことができる。
また、従来では、正反射光出力と拡散反射光出力併用タイプのセンサ（タイプ▲３▼、▲４▼）では、検知対象面の経時劣化による特性変化により、経時的に付着量検出精度が低下してしまっていたが、拡散反射光出力感度の自動補正機能により、検知対象面の経時的な特性変化をアルゴリズム側（ソフトウエア側）で吸収することができるため、検知対象面の光沢度が非常に低い場合であっても光沢度に関係無く、また黒色であっても高付着量域に亘って、拡散反射光出力を正確に付着量に変換することができる。これにより、検知対象面の長寿命化、ひいてはランニングコストの低下を実現できる。
拡散反射光出力変換アルゴリズムを、カラー画像形成装置における像担持体又は転写体を検知対象面とした付着量検出に適用することにより、従来技術では濃度検知が困難と言われている光沢度の低いベルトであっても、また検知対象面が黒のベルトであっても何ら問題なく高付着量域まで付着量検知を高精度に行うことができる。これにより、最大付着量目標値であるベタ付着量を検知でき、経時、環境の変動に拘わらず、常に安定した画像濃度制御を行うことができる。
【０１１８】
また、検知対象面である感光体又は転写ベルトのような像担持体の寿命を伸ばすことができる。転写ベルト等の検知対象面は一般に現像装置等と一体にユニット化され、一括交換する方式が採られているが、検知対象面のみの経時劣化による検知精度の低下を理由とした早期一括交換をしなくて済むので、寿命がきていない他のユニット部品との関係上、ランニングコストを大幅に低減できる。
正反射光出力と拡散反射光出力との比の最小値が得られる付着量近傍において、少なくとも１つ以上、望ましくは３つ以上の付着量パターン（付着量パッチ数）を持つこととすることにより、より精度の高い付着量変換が可能となる。
また、発光手段オフ時の各出力値との差分より得られる正反射光出力増分と拡散反射光出力増分との比の最小値が得られる付着量近傍において、少なくとも１つ以上、望ましくは３つ以上の付着量パターンを持つこととすることにより、より精度の高い付着量変換が可能となる。
また、正反射光出力変換値が付着量に対し一次線形関係にある付着量範囲内において、少なくとも１つ以上、望ましくは３つ以上の付着量パターンを持つこととすることにより、より精度の高い付着量変換が可能となる。
【０１１９】
【発明の効果】
本発明によれば、発光素子出力、受光素子出力のロットばらつき、温度特性による変化及び経時劣化、検知対象面の経時劣化等による要因に拘わらず、常に安定した付着量検知を高精度に行うことができる。
【図面の簡単な説明】
【図１】本発明の第１の実施形態における画像形成装置としてのカラーレーザプリンタの概要正面図である。
【図２】正反射光のみを検出するタイプの光学的検知手段の構成図である。
【図３】拡散反射光のみを検出するタイプの光学的検知手段の構成図である。
【図４】正反射光と拡散反射光を同時に検出するタイプの光学的検知手段の構成図である。
【図５】正反射光と拡散反射光を同時に検出するタイプで、ビームスプリッタを用いた光学的検知手段の構成図である。
【図６】カラートナー付着量に対する正反射光出力と拡散反射光出力の検知結果を示すグラフである。
【図７】カラートナー付着量と正反射光との差分との関係を示すグラフある。
【図８】検知対象面の鏡面光沢度が高いの場合の照射光の反射状態を示す模式図である。
【図９】トナーが付着して検知対象面の鏡面光沢度が低下した場合の照射光の反射状態を示す模式図である。
【図１０】黒トナー付着量に対する正反射光出力特性を示すグラフである。
【図１１】カラートナー付着量に対する正反射光出力特性を示すグラフである。
【図１２】黒トナー付着量に対する拡散反射光出力特性を示すグラフである。
【図１３】カラートナー付着量に対する拡散反射光出力特性を示すグラフである。
【図１４】検知対象面の鏡面光沢度に対する正反射光出力特性を示すグラフである。
【図１５】検知対象面の明度に対する拡散反射光出力特性を示すグラフである。
【図１６】検知対象面の経時的光沢度の低下と正反射光出力の補正との関係を示すグラフである。
【図１７】検知対象面の経時的光沢度の低下におけるカラートナー付着量と正反射光との差分との関係を示すグラフある。
【図１８】階調パターンを示す平面図である。
【図１９】正反射光として正反射光受光素子で受光される光に、純粋な正反射光成分に加え、検知対象面からの拡散反射光成分と、トナー層からの拡散反射光成分が含まれることを示す模式図である。
【図２０】光学的検知手段により実際に検知すべき反射光成分と除去すべき反射光成分の関係を示すブロック図である。
【図２１】データサンプリング時の付着量と検知出力の関係を示すグラフである。
【図２２】拡散反射光出力に乗ずる感度補正係数と付着量及び検知出力との関係を示すグラフである。
【図２３】正反射光の成分分解を示すグラフである。
【図２４】正反射光出力の正反射成分の正規化を示すグラフである。
【図２５】拡散反射光出力の地肌部変動補正量と付着量及び検知出力との関係を示すグラフである。
【図２６】ベルト地肌部から反射される成分にも複数の成分が存在することを示す模式図である。
【図２７】正反射成分の正規化値と地肌部変動補正後の拡散反射光出力との関係を示すグラフである。
【図２８】拡散反射光出力の感度を示すグラフである。
【図２９】正規化値への変換結果を示すグラフである。
【図３０】正規化値を逆変換することにより得られた付着量を、電子天秤による付着量測定値に対してプロットした結果を示すグラフである。
【図３１】多数の試作品から抽出された光学的検知手段のロットばらつきと階調パターン検知における拡散反射光出力との関係を示すグラフである。
【図３２】多数の試作品から抽出された光学的検知手段のロットばらつきと階調パターン検知における感度補正後の拡散反射光出力との関係を示すグラフである。
【図３３】４連タンデム構成で中間転写体へ重ね転写した後転写紙へ一括転写する方式のカラー画像形成装置の概要正面図である。
【図３４】１つ感光体ドラムにより各トナー像を中間転写体に重ね合わせ転写した後転写紙上に一括転写する方式のカラー画像形成装置の概要正面図である。
【符号の説明】
２、４２６ 中間転写体としての中間転写ベルト
１４Ｙ、１４Ｍ、１４Ｃ、１４Ｂ 像担持体としての感光体ドラム
１８ 検知対象面としての転写ベルト
５１ 発光手段としてのＬＥＤ
５２ 受光手段としての正反射光受光素子
５５ 受光手段としての拡散反射光受光素子
７０ 階調パターンとしてのトナーパターン
４０２ １つの像担持体としての感光体ドラム[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a regular reflection light output conversion method, a diffuse reflection light output conversion method, and a powder adhesion amount conversion method in detecting the adhesion amount of powder such as toner, and a copying machine, a printer, a facsimile, and a plotter capable of implementing these methods. The present invention relates to an image forming apparatus such as the above, a powder adhesion amount detecting apparatus capable of performing the above method, and a gradation pattern used in the above method.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a laser beam printer using an electrophotographic method, a toner patch for density detection is provided on an image carrier such as a photoconductor in order to always obtain a stable image density. (Hereinafter, also referred to as a density pattern or a density detection pattern), the patch density is detected by optical detection means, and the developing potential is changed based on the detection result (specifically, LD power, charging bias , Change of the developing bias).
In the case of the two-component developing method, the image density control is performed such that the maximum target adhesion amount (the adhesion amount for obtaining the target ID) becomes a target value by changing the toner concentration control target value in the developing device. It is carried out.
[0003]
As such a patch detecting means for density detection, a reflection type sensor combining an LED as a light emitting element (light emitting means) and a PD (photodiode) or PTr (phototransistor) as a light receiving element (light receiving means) is generally used. Are known.
The sensor configuration includes (1) a type that detects only regular reflection light as shown in FIG. 2 (see JP-A-2001-324840, etc.), and (2) a type that detects only diffuse reflection light as shown in FIG. (See JP-A-5-249787 and JP-A-3155555), and (3) as shown in FIG. 4, a type which detects both (see JP-A-2001-194843). There are two types. 2, 3, and 4, reference numerals 50A, 50B, and 50C denote element holders, 51 denotes an LED, 52 denotes a regular reflection light receiving element, 53 denotes a detection target surface, and 54 denotes a toner patch on the detection target surface. Reference numeral 55 denotes a diffuse reflection light receiving element.
In recent years, as shown in FIG. 5, a type in which a beam splitter is provided in an optical path on a light emitting side and a light receiving side (see Japanese Patent No. 2729976, Japanese Patent Application Laid-Open No. 10-221902, Japanese Patent Application Laid-Open No. 2002-72612). Has also been increasingly used (4). In FIG. 5, reference numeral 56 denotes an LED, 57 and 58 denote beam splitters, 59 denotes a photodiode as a light receiving unit for P-wave light (specular reflection light), and 60 denotes a light-receiving unit for S-wave light (diffuse reflection light). Photodiodes are shown.
[0004]
[Patent Document 1]
JP-A-2001-194843
[Patent Document 2]
Japanese Patent No. 2729976
[Patent Document 3]
JP-A-2002-72612
[Patent Document 4]
JP 2001-215850 A
[Patent Document 5]
JP 2000-39746 A
[Patent Document 6]
JP-A-2000-66463
[Patent Document 7]
JP-A-2000-227692
[Patent Document 8]
JP 2000-231254 A
[Patent Document 9]
JP-A-2000-250286
[Patent Document 10]
JP 2000-275167 A
[Patent Document 11]
JP 2001-34027 A
[Patent Document 12]
JP 2001-215762 A
[Patent Document 13]
JP 2001-212115 A
[Patent Document 14]
JP-A-2002-40746
[Patent Document 15]
JP-A-8-123110
[Patent Document 16]
JP-A-8-21990
[Patent Document 17]
JP-A-8-271230
[Patent Document 18]
JP-A-9-73215
[Patent Document 19]
JP-A-10-221902
[Patent Document 20]
JP-A-11-174753
[Patent Document 21]
JP-A-11-249373
[Patent Document 22]
Japanese Patent No. 2577354
[Patent Document 23]
JP-A-5-249787
[0005]
[Problems to be solved by the invention]
As shown in many of the above publications and patent publications, which relate to a color image forming apparatus, in a color image forming apparatus, a change in image density leads to a change in tint. It is important to accurately detect the amount of application of the application pattern and control the density.
Here, the image density to be stabilized is the "image density of the output image", whereas the conventional monochrome image forming apparatus performs density detection on the photoreceptor, while the color image forming apparatus transfers the image onto the paper. It is desirable to perform this on the transfer belt immediately before the image formation is performed, and since the aim of image density control is to control so that the maximum target adhesion amount becomes the target value, it is possible to accurately detect even the high adhesion amount region. desirable.
However, it has been difficult to perform stable and accurate detection of the attached amount over the entire attached amount region by the conventional detection method.
[0006]
The present invention relates to a specular reflection light output conversion method, a diffuse reflection light output conversion method, and a powder detection method capable of constantly and accurately detecting the amount of adhesion of powder such as toner over the entire adhesion amount. It is an object of the present invention to provide an adhesion amount conversion method, an image forming apparatus capable of implementing these methods, a powder adhesion amount detection apparatus capable of implementing the above method, and a gradation pattern used in the above method.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a tone pattern of a plurality of powders having different adhesion amounts formed continuously on the detection target surface is arranged at a position facing the detection target surface. The specular reflection light and the diffuse reflection light are detected by an optical detection means capable of simultaneously detecting the regular reflection light and the diffuse reflection light. Extracts only the specular light component by decomposing it into the reflected light component, converts this to a normalized value, and attaches the obtained normalized value to the adhering amount range where the adhering amount can be detected by specular reflection light. It was decided to obtain a first-order linear relationship in relation to the quantity.
[0008]
According to the second aspect of the present invention, a gradation pattern of powders having different adhesion amounts formed continuously on the detection target surface is disposed at a position facing the detection target surface, and includes a light emitting unit and a light receiving unit. The specular reflection light and the diffuse reflection light are simultaneously detected by an optical detection means capable of simultaneously detecting the regular reflection light output and the diffuse reflection light output (hereinafter, also referred to as “diffuse light output”) of the obtained gradation pattern. Calculate the value obtained by multiplying the minimum value of the ratio by the diffuse reflected light output, and subtract this value from the specular reflected light output to the specular reflected light output converted value, which is the ratio of the specular reflected light output of the detection target surface. (= Normalized value) was obtained, and a first-order linear relationship was obtained for the converted value of the specular reflection light output and the adhesion amount in the adhesion amount range where the adhesion amount can be detected by the regular reflection light.
[0009]
According to the third aspect of the present invention, the light emitting means and the light receiving means are provided in such a manner that a plurality of tone patterns of powder having different adhesion amounts formed continuously on the detection target surface are arranged at positions facing the detection target surface. The regular reflection light and the diffuse reflection light are detected by optical detection means capable of simultaneously detecting the light reflection means, and the regular reflection light output increment and the diffuse reflection light output increment obtained from the difference with each output value when the light emitting means is off. The value obtained by multiplying the minimum value of the ratio by the diffuse reflection light output increment is obtained, and this value is subtracted from the regular reflection light output increment, and the specular reflection light which is the ratio of the specular reflection light output increase of the detection target surface to the value obtained. An output conversion value (= normalized value) is obtained, and a first-order linear relationship is obtained for the specular reflection light output conversion value in relation to the adhesion amount in the adhesion amount range in which the adhesion amount can be detected by the regular reflection light. .
[0010]
According to the fourth aspect of the present invention, a gradation pattern of a plurality of powders having different adhesion amounts formed continuously on the detection target surface is disposed at a position facing the detection target surface, and includes a light emitting unit and a light receiving unit. The specular reflection light and the diffuse reflection light are detected by optical detection means that can simultaneously detect the regular reflection light and the diffuse reflection light. And extract only the specular reflection component, convert this to a normalization value, and multiply the obtained normalization value by the background diffuse reflection light output directly reflected from the background portion of the detection target surface. A converted value of the diffuse reflected light output is obtained by subtracting from the diffuse reflected light output, and the first-order linear relationship between the diffuse reflected light output converted value and the attached amount in the attached amount range in which the attached amount can be detected by specular reflection light. I decided to get.
[0011]
According to the fifth aspect of the present invention, a gradation pattern of a plurality of powders having different adhesion amounts formed continuously on the detection target surface is disposed at a position facing the detection target surface, and has a light emitting unit and a light receiving unit. The specular reflection light and the diffuse reflection light are simultaneously detected by the optical detection means capable of simultaneously detecting the regular reflection light and the diffuse reflection light. The value obtained by multiplying the output is calculated, and the converted value of the specular light output (= normalized value), which is the ratio of the value obtained by subtracting this value from the specular light output and the specular light output of the detection target surface, is obtained. The diffuse reflection light output conversion value is obtained by subtracting a value obtained by multiplying the regular reflection light output conversion value by the background reflection light output directly reflected from the background portion of the detection target surface from the diffuse reflection light output. Diffuse reflected light output conversion value, adhesion by specular reflection light Detected was to obtain a first-order linear relationship in relation to the adhesion amount of adhering amount as possible.
[0012]
According to the sixth aspect of the present invention, a light emitting means and a light receiving means are provided, wherein a gradation pattern of a plurality of powders having different adhesion amounts formed continuously on the detection target surface is arranged at a position facing the detection target surface. The regular reflection light and the diffuse reflection light are detected by optical detection means capable of simultaneously detecting the light reflection means, and the regular reflection light output increment and the diffuse reflection light output increment obtained from the difference with each output value when the light emitting means is off. The value obtained by multiplying the minimum value of the ratio by the diffuse reflection light output increment is obtained, and this value is subtracted from the regular reflection light output increment, and the specular reflection light which is the ratio of the specular reflection light output increase of the detection target surface to the value obtained. An output conversion value (= normalized value) is obtained, and a value obtained by multiplying the converted value of the regular reflection light output by a diffusion reflection light output increment obtained from a difference between the diffuse reflection light output value when the light emitting means is off and the diffuse reflection light output is obtained. Calculate the diffuse reflected light output conversion value by subtracting from the increment, The diffuse reflection light output conversion value, was decided in relation to the adhesion amount of adhering weight range capable adhesion amount detection by the specular reflected light obtaining a first-order linear relationship.
[0013]
According to a seventh aspect of the present invention, a specular reflection light output conversion value in the regular reflection light output conversion method according to any one of the first to third aspects, and any one of the fourth to sixth aspects. Is multiplied by a correction coefficient such that the diffuse reflection light output conversion value of a certain regular reflection light output conversion value becomes a certain value based on a linear relationship with the diffuse reflection light output conversion value in the diffuse reflection light output conversion method described in 1. Thus, the converted value of the diffuse reflection light output is converted to a value uniquely determined in relation to the amount of adhesion.
[0014]
According to an eighth aspect of the present invention, in the diffuse reflection light output conversion method according to the seventh aspect, when the brightness of the detection target surface is 20 or less, the diffuse reflection light output conversion value is replaced with the diffuse reflection light output. And
[0015]
According to a ninth aspect of the present invention, in the diffuse reflection light output conversion method according to the seventh aspect, when the brightness of the detection target surface is 20 or less, the diffuse reflection light output conversion value is used as the diffuse reflection light when the light emitting unit is off. It was decided to replace with the diffuse reflection light output increment obtained from the difference from the light output value.
[0016]
According to the tenth aspect of the present invention, a plurality of tone patterns of powder having different adhesion amounts formed continuously on the detection target surface are arranged at positions facing the detection target surface, and have light emitting means and light receiving means. The specular reflection light and the diffuse reflection light are detected by optical detection means that can simultaneously detect the regular reflection light and the diffuse reflection light. Then, only the specular reflection component is extracted and converted to a normalized value, and the obtained normalized value is attached based on a relational expression between a previously obtained attachment amount and the normalized value or a reference table. It was decided to convert to quantity.
[0017]
According to the eleventh aspect of the present invention, a plurality of tone patterns of powders having different adhesion amounts formed continuously on the detection target surface are arranged at positions facing the detection target surface, and have light emitting means and light receiving means. The specular reflection light and the diffuse reflection light are simultaneously detected by the optical detection means capable of simultaneously detecting the regular reflection light and the diffuse reflection light. The value obtained by multiplying the output is calculated, and the converted value of the specular light output (= normalized value), which is the ratio of the value obtained by subtracting this value from the specular light output and the specular light output of the detection target surface, is obtained. The converted specular reflection light output value is converted into a adhesion amount based on a relational expression between the adhesion amount previously calculated and the specular reflection light output conversion value or table data.
[0018]
According to the twelfth aspect of the present invention, a gradation pattern of powder having a different amount of adhesion formed continuously on the detection target surface is disposed at a position facing the detection target surface, and has a light emitting unit and a light receiving unit. The regular reflection light and the diffuse reflection light are detected by optical detection means capable of simultaneously detecting the light reflection means, and the regular reflection light output increment and the diffuse reflection light output increment obtained from the difference with each output value when the light emitting means is off. The value obtained by multiplying the minimum value of the ratio by the diffuse reflection light output increment is obtained, and this value is subtracted from the regular reflection light output increment, and the specular reflection light which is the ratio of the specular reflection light output increase of the detection target surface to the value obtained. An output conversion value (= normalized value) is obtained, and this specular reflection light output conversion value is converted into an adhesion amount based on a relational expression between the adhesion amount and the specular reflection output conversion value determined in advance or table data. I decided.
[0019]
According to a thirteenth aspect of the present invention, a specular reflection light output conversion value in the specular reflection light output conversion method according to any one of the first to third aspects, and one of the fourth to sixth aspects. Based on a linear relationship with the diffuse reflected light output conversion value in the diffuse reflected light output conversion method described in the above, multiplying by a correction coefficient such that the diffuse reflected light output converted value becomes a certain value with respect to a certain specular reflected light output converted value. Is converted into an adhesion amount based on a relational expression between the adhesion amount and the diffusion reflection light output conversion value which are obtained in advance or table data.
[0020]
According to a fourteenth aspect of the present invention, in the method for converting a powder adhesion amount according to the thirteenth aspect, when the brightness of the detection target surface is 20 or less, the diffuse reflection light output conversion value is replaced with the diffuse reflection light output. And
[0021]
In the invention according to claim 15, in the powder adhesion amount conversion method according to claim 13, when the lightness of the detection target surface is 20 or less, the diffuse reflection light output conversion value is changed to the diffuse reflection when the light emitting unit is off. It was decided to replace with the diffuse reflection light output increment obtained from the difference from the light output value.
[0022]
According to the sixteenth aspect of the present invention, it is possible to form a color image by sequentially superimposing and transferring toner images formed on a plurality of image carriers onto a sheet-like recording medium carried on a transfer body. The apparatus adopts a configuration in which the method according to any one of claims 1 to 15 can be performed using the transfer body as the detection target surface and the powder as toner.
[0023]
According to the seventeenth aspect of the present invention, it is possible to form a color image by successively superimposing and transferring toner images formed on a plurality of image carriers onto a sheet-like recording medium carried on a transfer body. In the apparatus, the method according to any one of the first to fifteenth aspects can be implemented such that the image carrier can be used as the detection target surface and the powder can be used as toner.
[0024]
According to the eighteenth aspect of the present invention, it is possible to obtain a color image by sequentially transferring the toner images formed on the plurality of image carriers on the intermediate transfer member in a superimposed manner, and then transferring them collectively to a sheet-shaped recording medium. In the image forming apparatus, the method according to any one of the first to fifteenth aspects can be implemented such that the intermediate transfer body can be used as the detection target surface and the powder can be used as toner.
[0025]
According to the nineteenth aspect, it is possible to obtain a color image by sequentially transferring the toner images formed on the plurality of image carriers on the intermediate transfer member in a superimposed manner, and then collectively transferring the toner images onto the sheet-shaped recording medium. In the image forming apparatus, the method according to any one of claims 1 to 15 can be performed using the image carrier as the detection target surface and the powder as toner.
[0026]
According to the twentieth aspect, it is possible to obtain a color image by sequentially transferring the toner images formed on one image carrier on the intermediate transfer body in a superimposed manner, and then collectively transferring the toner images on a sheet-shaped recording medium. In the image forming apparatus, the method according to any one of the first to fifteenth aspects can be implemented such that the intermediate transfer body can be used as the detection target surface and the powder can be used as toner.
[0027]
According to the twenty-first aspect, it is possible to obtain a color image by sequentially transferring the toner images formed on one image carrier on the intermediate transfer member in a superimposed manner, and then collectively transferring the toner images onto a sheet-shaped recording medium. In the image forming apparatus, the method according to any one of claims 1 to 15 can be performed using the image carrier as the detection target surface and the powder as toner.
[0028]
According to a twenty-second aspect of the present invention, in the image forming apparatus according to any one of the sixteenth to twenty-first aspects, the plurality of toner patterns formed on the detection target surface are converted into an adhesion amount, and the adhesion amount is determined. The image density control is performed based on the amount conversion value.
[0029]
According to a twenty-third aspect of the present invention, in the powder adhesion amount detecting device, a configuration is adopted in which any one of the first to fifteenth methods can be performed.
[0030]
According to a twenty-fourth aspect of the present invention, there is provided a gradation pattern having a different adhesion amount used in the method for converting a regular reflection light output according to any one of the first to third aspects, wherein the regular reflection light output and the diffuse reflection In the vicinity of the adhesion amount where the minimum value of the ratio to the light output is obtained, at least one, preferably three or more adhesion amount patterns are provided.
[0031]
According to a twenty-fifth aspect of the present invention, there is provided a gradation pattern having a different adhesion amount used in the regular reflection light output conversion method according to any one of the first to third aspects, wherein each of the output patterns when the light emitting means is off. In the vicinity of the adhesion amount where the minimum value of the ratio between the specular reflection light output increment and the diffuse reflection light output increment obtained from the difference between the values is at least one, preferably three or more. It has a configuration.
[0032]
According to a twenty-sixth aspect of the present invention, there is provided a gradation pattern having a different adhesion amount used in the specular light output conversion method according to any one of the first to third aspects, wherein the specular light output conversion value is different. A configuration is adopted in which at least one or more, and preferably three or more, attachment amount patterns are provided within an attachment amount range having a first-order linear relationship with the attached amount.
[0033]
According to a twenty-seventh aspect, in the gradation pattern according to any one of the twenty-fourth to twenty-sixth aspects, a configuration is adopted in which the powder is toner.
[0034]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 to 32 (excluding FIGS. 2 and 3).
First, before describing the configuration and functions in the present embodiment, the process of consideration for realizing the present invention will be described.
[Consideration on selection of optical detection means and its function]
When considering what type of sensor is used to detect the density pattern on the transfer belt as the detection target surface, there is a drawback that it is not possible to detect up to the high adhesion amount region by using only the regular reflection light of (1). In the case of the type (2) using only diffuse reflection light, if the transfer belt is black (in many cases, the transfer belt is often black because carbon is used as a resistance adjusting agent in many cases), black toner is used. There is a fatal drawback that the sensor sensitivity cannot be detected, and a drawback that the sensor sensitivity cannot be calibrated because the diffuse reflection light output at the background portion of the transfer belt is almost zero.
In order to cope with such a problem, the difference between the outputs of the two light receiving sensors may be obtained by using both types (3) and (4) (Japanese Patent No. 3155555, Japanese Patent Application Laid-Open No. 2001-194843, etc.). It is considered that many methods for detecting the amount of adhesion by taking a ratio (see Japanese Patent Application Laid-Open No. 10-221902, etc.) have been proposed.
[0035]
However, it is considered that it is difficult to always perform stable and accurate detection of the amount of adhesion with the conventional detection method using the combination type of (3) and (4) for the following reasons.
(1) No consideration is given to lot variations in the output of the light emitting element and the output of the light receiving element. ... (Sensor variation)
(2) The temperature characteristics of the output of the light emitting element and the output of the light receiving element, and deterioration with time are not taken into account. ... (Sensor fluctuation)
(3) The influence of the deterioration of the transfer belt, which is the surface to be detected, with the passage of time is not considered. ... (Variation of belt)
This will be described in detail below.
[0036]
Explanation of (1)
In order to find out how much the sensor elements vary, the LED (light-emitting element) and PTr (phototransistor) were measured for several lots (1 lot = 197 pieces) each by the following method to evaluate the variation width. went.
[Light-emitting element side]
Using the sensor head shown in FIG. 2, the light-emitting elements are sequentially replaced under the condition that Vcc = 5 V, LED current: If = 14.2 mA, and the light-receiving element is fixed, and a light-receiving element when a certain reference plate is irradiated with light. Photocurrent: IL is measured to determine the magnitude of the light emission output.
[Light receiving element side]
Using the sensor head shown in FIG. 2, the light-receiving elements were sequentially replaced under the condition that Vcc = 5 V, LED current: If = 14.2 mA, and the light-emitting element was fixed, and the light-receiving element when a certain reference plate was irradiated with light. Photocurrent: IL is measured to determine the level of light receiving sensitivity. Table 1 shows the measurement results.
[0037]
[Table 1]

[0038]
From Table 1, it was found that the output variation was slightly less than twice on the light emitting element side and slightly less than four times on the light receiving element side.
The magnitude of the device variation may vary depending on the type of device (top-view type, side-view type) and the manufacturer, but the variation at least at the level that requires adjustment should be the same regardless of the device used. It is.
This point is not mentioned at all in the above-mentioned prior arts. It seems that this is a matter of course, but in order to accurately detect the adhesion amount by the method described in the prior art, it is necessary to strictly output the sensor (element) during the shipping inspection stage. Adjustments are required.
[0039]
The following describes the result of a prediction based on experimental data as to what would happen if there was no adjustment.
FIG. 6 shows the results of measuring the amount of adhered color toner on the transfer belt using the sensor shown in FIG. 4. The abscissa indicates the amount of adhered toner, and the ordinate indicates the specular reflected light output voltage and the diffuse reflected light output. It is a plot of voltage.
Here, even when the light-emitting element, the specular reflection light receiving element, and the diffuse reflection light element each have an element variation, at least for the specular reflection output, since the output has the characteristic of being maximum in the belt background portion, If the LED current is adjusted so that the output at the belt background becomes a certain value (3.0 V in this case), the output variation due to the variation in the light emitting element and the regular reflection light receiving element can be absorbed. An almost unique output characteristic is obtained as the sensor output with respect to the amount.
[0040]
The large square mark in FIG. 6 is a plot of the diffused light output after LED adjustment. If the light-receiving element variation is doubled, the diffused light output light-receiving element has a light-receiving sensitivity of 1/2. In this case, the diffused light output at that time becomes an output (Vd / 2) indicated by a small square mark, and the difference from the specularly reflected light (Vr) in each case is obtained as shown in FIG. The output relation to the amount of adhesion is not uniquely determined. This is the same even when the ratio is taken.
As shown in FIG. 7, when the values of the two conditions match at the point where the amount of adhesion is zero, and when the values are different in the high adhesion amount region, the normality of the regular reflection light output conventionally known is reduced. Even if an operation such as a conversion process is performed, it cannot be unambiguously determined.
From the above, the relationship between “specular reflection light output” and “diffuse reflection light output” when performing the adhesion amount conversion based on the difference between “specular reflection light output” and “diffuse reflection light output” or ratio data It is necessary to always satisfy a certain relationship, and for that purpose, for example, in the stage of inspection of the sensor before shipment, it is necessary to perform variation correction such as strictly adjusting the relationship between the regular reflection light output and the diffuse reflection light output with respect to a certain reference plate. Become.
[0041]
Even if the method described in the prior art described above is adjusted after the adjustment described above, simply taking the difference or taking the ratio would still require (2), (3) Due to the fluctuation factors (fluctuations in the sensors and fluctuations in the belt) described in (1), accurate detection of the amount of adhesion cannot be performed.
Explanation about (3)
At the time of image output, the transfer belt is always in contact with the transfer paper as a sheet-shaped recording medium, and the surface of the belt becomes rough with time due to wear. Further, when the transfer paper containing a large amount of the white agent is continuously passed, the surface of the belt becomes white with time.
Before showing the experimental results for this, the causes of the state change of the specular reflection light output and the diffuse reflection light output will be described.
The specular reflection light output is light that is specularly reflected on the detection target surface (the incident angle and the reflection angle are equal), and is shown in FIG. 8 when the detection target surface is slippery (= high specular gloss). As described above, the irradiated light 61 is only slightly diffused on the detection target surface 53, and almost all is specularly reflected as the regular reflection light 62. In FIG. 8, reference numeral 63 denotes specular reflection light sensitivity, and reference numeral 64 denotes diffuse reflection light sensitivity in a distribution area.
[0042]
As shown in FIG. 9, when the toner 65 as the powder adheres to the detection target surface 53, the incident light 61 is diffused by the toner 65, so that the regular reflection light 62 decreases, and conversely, the diffuse reflection light 66 Increase. However, the diffuse reflection light 66 increases when the toner 65 is a color toner, and when the toner 65 is a black toner, the irradiated light 61 is almost absorbed. Hardly increases.
That is, the output of the specular reflection light changes depending on the “state change of the surface texture characteristics (gloss, surface roughness, etc.)” of the detection target object, and the diffuse reflection light output changes the “color characteristics (lightness, etc.)” of the detection target object. The output changes due to factors completely independent of each other, for example, the output changes due to “state change”.
[0043]
The experimental results will be described. In the quadruple tandem direct transfer type color image forming apparatus shown in FIG. 1, assuming that the surface of the transfer belt is roughened over time and whitened, the “mirror gloss (Gs)” and the “brightness (L)” are assumed. ^* )) Were formed on three types of transfer belts having different types of transfer belts, and the results in the case where the patterns fluctuated with time were predicted by comparing the sensor detection outputs of these patterns. The conditions of the experiment are shown below.
<Transfer belt (target surface)>
Black belt: Specular gloss: Gs (60) = 57, Lightness: L ^* = 10
Brown belt: mirror gloss: Gs (60) = 27, lightness: L ^* = 25
Gray belt: Specular gloss: Gs (60) = 5, Lightness: L ^* = 18
<Detection sensor (optical detection means)> Detailed specifications of the sensor shown in FIG.
Light emitting side
Element: GaAs infrared light emitting diode (peak emission wavelength: λp = 950 nm), top view type
Spot diameter: φ1.0mm
Light receiving side
Element: Si phototransistor (peak spectral sensitivity: λp = 800 nm), top view type
Spot diameter:
Regular reflection light receiving side: φ1.0mm
Diffuse reflected light receiving side: φ3.0mm
Detection distance: 5mm (distance from upper part of sensor to detection target surface)
LED current: 25mA fixed
<Line speed>
125mm / sec
<Sampling frequency>
500 sampling / sec (= every 2 msec)
Note 1: The specular gloss value is a value measured at a measurement angle of 60 ° using a gloss meter PG-1 manufactured by Nippon Denshoku.
Note 2: The brightness is a value measured using a spectrophotometer: X-Rite 938 manufactured by X-Rite, with a light source of D50 and a viewing angle of 2 °.
[0044]
FIG. 10 shows the regular reflection light output characteristics with respect to the black toner adhesion amount, and FIG. 11 shows the regular reflection light output characteristics with respect to the color toner adhesion amount.
In this experiment, the input conditions on the sensor side were fixed (LED current: If = 25 mA fixed), so that the high adhesion amount area (M / A = 0.4 mg / cm), which was not affected by the belt background, was used. ² Above), the regular reflection light outputs (voltages) of the three types of belts substantially match, but the low adhesion amount area (M / A = 0.4 mg / cm) affected by the belt background ² The following does not match.
As can be seen from the results, when the mirror glossiness of the transfer belt decreases over time, that is, when the surface roughness deteriorates, as indicated by an arrow in a low adhesion amount region where the belt background portion having an adhesion amount of zero is exposed. It can be seen that the regular reflection light output (voltage) decreases.
[0045]
[Consideration on problems of conventional technology (when using type (1) sensor)]
According to the above experimental facts, the biggest difficulty in detecting the amount of adhesion with a type (1) sensor that has only specular reflection output is that in the amount of color adhesion detection, the detectable range of the amount of adhesion is the gloss of the transfer belt. That is, it becomes narrow over time as the degree decreases.
The reason for this is that, in the prior art, the adhesion amount detection of the color adhesion amount is performed by the following adhesion amount detection algorithm, so that the sensor output characteristic with respect to the adhesion amount is greater than the inflection point (minimum value) shown in FIG. Is not detectable.
<Conventional specular light output type adhesion amount conversion formula>
In FIG. 11, when the output minimum value of each belt is obtained by calculating the inflection point of the approximate curve, the maximum detectable adhesion amount becomes 0.36 (57), 0.30 (27) as the belt deteriorates with time. ) And 0.17 (5). The value in parentheses is the gloss value. The adhesion amount detectable range is up to the output value and the adhesion amount that becomes the minimum value.
In the detection of the amount of black toner attached, the maximum detectable amount of attachment can be detected with little change even if the output SN ratio is reduced and the detection accuracy is slightly reduced.
[0046]
Next, FIG. 12 shows the horizontal axis: the diffused light output characteristic with respect to the amount of adhered black toner, and FIG. 13 shows the horizontal axis: the diffuse reflected light output characteristic with respect to the amount of adhered color toner.
The diffuse reflection light output is almost the same for the three types of belts in the high adhesion area where the belt background is not affected by the belt background, but the effect of brightness change is low in the low adhesion area where the belt background is affected by the brightness change. Output does not match.
That is, when the transfer belt becomes white with time, the diffuse reflection light output of the background portion of the transfer belt increases.
[0047]
[Consideration on problems of conventional technology (when using type (2) sensor)]
According to the above experimental facts, the biggest difficulty in detecting the amount of adhesion with a sensor of type (2) that has only diffused reflected light output is that firstly, it corrects the temporal change in the characteristic of the detection target surface. Second, in particular, the detection target surface has a lightness: L ^* In the case where the color is black as in <20, the sensor sensitivity cannot be calibrated on the detection target surface.
Lightness: L ^* The reason why the sensitivity cannot be calibrated at <20 is that the diffuse reflection light output from the background becomes almost zero.
For reference, the applicant's method of calibrating the sensitivity of a sensor performed on a conventional machine will be described. After a sensor is attached to an image forming apparatus at a factory, a sensor output for a certain white reference plate has a certain value. Thus, the LED current adjustment on the sensor light emitting side has been performed. However, in this case, even if the adjustment can be performed at the initial stage, since there is no means for correcting the sensitivity change due to the temperature characteristics of the sensor and the deterioration of the LED with the lapse of time, a reliable guarantee with respect to the aging quality cannot be obtained.
[0048]
FIG. 14 shows the result of examining the correlation between the specular glossiness and the specular reflection light output, and FIG. 15 shows the result of examining the correlation between the brightness and the diffuse reflection light output.
FIG. 14 shows specular reflection light output when 42 kinds of transfer belts having different “glossiness” and “brightness” are fixed to LED current: 20 mA using the reflection type photosensor shown in FIG. 4. Horizontal axis: plotted against 60 ° gloss.
The gloss value on the horizontal axis is a value measured at a measurement angle of 60 ° using a gloss meter PG-1 manufactured by Nippon Denshoku.
As shown in FIG. 9, since the specular reflection light output includes the diffuse reflection light component, if the results are sorted for each brightness range, the specular reflection light output voltage is substantially linearly proportional to the glossiness. It turns out that it can be obtained.
The reason why such a linear proportional relationship is obtained is that the specular gloss has a relationship in which the specular reflection light itself is measured. (Refer to JISZ8741 Specular gloss-Measurement method)
[0049]
FIG. 15 is a graph in which the diffuse reflection light output measured at the same time is plotted against the horizontal axis: the brightness of the belt. In FIG. 15, [-] means that there is no unit.
The lightness on the horizontal axis is a value measured using a spectrophotometer: X-Rite 938 manufactured by X-Rite, using a light source of D50 and a viewing angle of 2 °.
The relationship between the two is not a linear relationship due to differences in the light source, measurement angle, etc., but is not affected by the glossiness and is plotted almost on the same curve. It can be seen that it is independent of the reflected light output.
[0050]
When the transfer belt surface is roughened over time and the regular reflection light output of the belt background decreases, or when the whitening increases the diffuse reflection light output of the background, or when these two simultaneously proceed, In this case, the relationship between the “specular reflection light output” and the “diffuse reflection light output” breaks down. Therefore, the output cannot be made the same as the initial state simply by taking the difference between the two outputs or taking the ratio.
Therefore, even if the adhesion amount is converted based on this, the same result as in the initial stage cannot be obtained. Further, even if this result is directly fed back to the density control without converting the adhesion amount, the result is only a deviation from the initial one.
[0051]
Therefore, when the regular reflection light output is reduced due to the reduction in the belt gloss, it is conceivable to increase the LED current to correct the output. For example, an adjustment is made so that the regular reflection light output of the belt background becomes an initial value. If it is performed, at least only the background portion of the belt becomes the same as the initial value. However, as shown in FIG. 16, in the case of the color toner, the output increases over the entire area of the adhesion amount.
In addition, since the output of the diffuse reflected light output voltage increases with an increase in the amount of received light, the resulting differential output is somehow matched with the initial one in the low deposition area, as shown in FIG. However, since the displacement occurs in the high adhesion amount region, the same result as in the initial stage cannot be obtained. This is the same even when the ratio is taken instead of the difference output.
[0052]
Explanation about (2)
Even if there is no change with time as described above, if the output characteristics of the light-emitting element and the light-receiving element, which are semiconductors, change due to an increase in the ambient temperature, the output state is also the same as the initially determined state. The result will be different.
[0053]
As described above, a solution to the above-described detection of the adhesion amount in the high adhesion amount region, particularly to the detection of the toner adhesion amount up to the high adhesion amount region on the black belt often used in the color image forming apparatus. In the technique shown in the prior art proposed as (1), in order to make full use of the gradation pattern detection technique, the two outputs of the density detection sensor used for this must be strictly adjusted in advance, that is, in the shipping inspection stage. It is presumed that very strict adjustment is required. (B) There is no countermeasure against the aging of the density detection sensor and environmental fluctuation, and (c) the countermeasure against the aging fluctuation of the detection target surface (transfer belt). Considering that there are no gradation patterns, it can be said that there are still many technical problems in detecting a gradation pattern.
That is, on a black belt where the sensitivity of the diffuse reflection light output cannot be adjusted, (a) output variation due to sensor lot variation, (b) time lapse of the density detection sensor, environmental variation, (c) detection target surface (transfer belt The problem to be solved is how to detect the toner adhesion amount in a stable and high adhesion amount region at all times without being influenced by any of the factors of the time-dependent fluctuation.
[0054]
The present invention has been made to solve the above-mentioned problems lurking in the prior art,
(1) It is not necessary to strictly adjust the output relationship between “specular reflection light output” and “diffuse reflection light power” on the sensor side (hardware side). Contribute to cost reduction,
(2) Regardless of the existence of the above three factors, automatic correction can be performed by the characteristics of the software side, and the detection of the gradation pattern can be performed with higher accuracy.
The above object of the present invention is achieved by an adhesion amount conversion algorithm according to the present invention described below, and an image forming apparatus using the algorithm.
Specifically, the gradation pattern is read by a reflection type optical sensor having two outputs of "specular reflection light output" and "diffuse reflection light output" of the types (3) and (4), and is read by specular reflection light. The two outputs are converted into a value that has a linear relationship with the amount of adhesion in the adhesion amount range where the amount of adhesion can be detected. In addition, by performing sensitivity correction of the diffuse reflection light output conversion value, the algorithm is achieved by converting the diffuse reflection light output into a value that is uniquely determined by the amount of adhesion.
[0055]
Hereinafter, a first embodiment of the present invention will be described based on a specific configuration.
As shown in FIG. 1, a schematic configuration of a quadruple tandem direct transfer type color laser printer as an image forming apparatus and a powder adhesion amount detecting apparatus according to the present embodiment will be described.
The color laser printer has three paper feed trays, one manual feed tray 36, two paper feed cassettes 34 (first paper feed tray), and 34 (second paper feed tray). Transfer paper (not shown) as a sheet-shaped recording medium is separated one by one by a paper feed roller 37 in order from the uppermost one, and is conveyed toward the registration roller pair 23. The transfer paper fed from the first paper feed tray 34 or the second paper feed tray 34 is separated one by one by the paper feed roller 35 from the top one to the registration roller pair 23 via the transport roller pair 39. It is conveyed toward.
The fed transfer paper is temporarily stopped by the pair of registration rollers 23, and after the skew is corrected, the leading end of an image formed on the photosensitive drum 14Y located at the most upstream position, which will be described later, and the transfer direction of the transfer paper. At a timing when the position coincides with the predetermined position, the sheet is conveyed toward the transfer belt 18 by rotating the registration roller pair 23 by turning on a registration clutch (not shown).
When the transfer paper passes through a paper suction nip constituted by the transfer belt 18 and a paper suction roller 41 in contact with the transfer belt 18, the transfer paper is electrostatically attracted to the transfer belt 18 by a bias applied to the paper suction roller 41, It is transported at a process linear speed of 125 mm / sec.
[0056]
Transfer brushes 21B, 21C, 21M, and 21Y, which are arranged at positions opposed to the photosensitive drums 14B, 14C, 14M, and 14Y of the respective colors with the transfer belt 18 interposed therebetween, are attached to the transfer paper that is attracted to the transfer belt 18. By applying a transfer bias (plus) having a polarity opposite to the charging polarity (minus), the toner images of the respective colors formed on the photosensitive drums 14B, 14C, 14M, and 14Y become yellow (Y) and magenta (M). ), Cyan (C), and black (Bk) in this order.
The transfer paper that has undergone the transfer process of each color is separated from the transfer belt 18 by a curvature at the position of the drive roller 19 on the downstream side, and is conveyed to the fixing device 24. By passing through a fixing nip formed by a fixing belt 25 and a pressure roller 26 in the fixing device 24, the toner image is fixed on the transfer paper by heat and pressure. The transfer paper on which the fixing has been performed is discharged to an FD (face-down) tray 30 formed on the upper surface of the apparatus main body in the single-sided printing mode.
When the double-sided printing mode is selected in advance, the transfer paper exiting the fixing device 24 is sent to a reversing unit (not shown). 33. The transfer paper is re-fed from the double-sided conveyance unit 33, and is conveyed to the registration roller pair 23 via the conveyance roller pair 39. Thereafter, the sheet passes through the fixing device 24 through the same operation as in the single-sided printing mode, and is discharged to the FD tray 30.
[0057]
Next, a configuration and an image forming operation in the image forming unit of the color laser printer will be described in detail.
Since the image forming section has the same configuration and operation for each color, the configuration and operation for forming a yellow image will be described as a representative, and the other portions will be denoted by the reference numerals corresponding to the respective colors and description thereof will be omitted.
Around the photosensitive drum 14Y located on the most upstream side in the transfer paper transport direction, there are provided an image forming unit 12Y having a charging roller 42Y and a cleaning unit 43Y, a developing unit 13Y, an optical writing unit 16, and the like.
At the time of image formation, the photosensitive drum 14Y is driven to rotate clockwise by a main motor (not shown), is discharged by an AC bias (DC component is zero) applied to the charging roller 42Y, and has a surface potential of approximately -50 V. Potential.
[0058]
Next, the photosensitive drum 14Y is uniformly charged to a potential substantially equal to a DC component by applying a DC bias in which an AC bias is superimposed on the charging roller 42Y, and has a surface potential of approximately -500v to -700v (target charging). The potential is determined by the process controller).
Digital image information sent from a controller unit (not shown) as a print image is converted into a binarized LD light emission signal for each color, and a cylinder lens, a polygon motor, an fθ lens, first to third mirrors, and WTL The exposure light 16Y is irradiated onto the photosensitive drum 14Y by the optical writing unit 16 having a lens or the like. The drum surface potential of the irradiated portion becomes approximately −50 V, and an electrostatic latent image corresponding to the image information is formed.
[0059]
The electrostatic latent image corresponding to the yellow image information on the photosensitive drum 14Y is visualized by the developing unit 13Y. By applying DC (−300 to −500 V) with an AC bias superimposed on the developing sleeve 44Y of the developing unit 13Y, the toner (Q / M: −20 to −30 μC / g) is developed to form a toner image.
The formed toner images on the photosensitive drums 14B, 14C, 14M, and 14Y of the respective colors are transferred onto the transfer paper attracted onto the transfer belt 18 by the transfer bias.
[0060]
In the color laser printer according to the present embodiment, in addition to the above-described image forming mode, a process control operation operation (hereinafter referred to as a process control operation) is performed in order to optimize the image density of each color when the power is turned on or after a predetermined number of sheets have passed. Operation).
In this process, an image is formed on a transfer belt by sequentially switching a plurality of density detection patches (hereinafter abbreviated as P patterns) of each color between a charging bias and a developing bias at an appropriate timing, and output voltages of these P patterns are formed. Is detected by a density detection sensor (hereinafter abbreviated as a P sensor) 40 disposed outside the transfer belt 18 in the vicinity of the drive roller 19, and the output voltage is detected by the adhesion amount conversion algorithm (the powder adhesion amount conversion method) of the present invention. ) Is converted to calculate (development γ, Vk) representing the current developing ability, and based on the calculated values, control is performed to change the developing bias value and the toner density control target value.
[0061]
The configuration of the P sensor is as shown in FIG. 4, and its specifications are as described above.
Here, a PTr (phototransistor) is used as the light receiving element, but a light receiving element such as a PD (photodiode) may be used.
[0062]
Hereinafter, the adhesion amount conversion algorithm in the present invention (the present embodiment) will be described based on the experimental results of FIGS. 10 to 13 described above. In this algorithm, the diffused light output is converted into an adhesion amount value according to the following procedure.
(1) The specular reflection output and the diffuse reflection light output of the gradation pattern are sampled (see FIGS. 11 and 13),
(2) Only the [specular reflection light component] is extracted by decomposing the specular reflection light output into [specular reflection light component] and [diffuse reflection light component].
(3) [Diffuse light component from toner] is extracted by removing [Diffuse light component from the belt background] from the diffuse reflection light output,
(4) An attachment amount range in which the attachment amount can be detected by specular reflection light using a first-order linear relationship with respect to the attachment amount of two output conversion values independent (intersecting) obtained from (2) and (3). In the (low adhesion amount range), the diffuse reflection light output conversion value of a certain specular reflection light output conversion value (or the adhesion amount) becomes a certain value, and the diffuse reflection light output conversion value is subjected to sensitivity correction to obtain the adhesion amount. The diffuse reflection light output (correction value) is uniquely determined, and (5) the adhesion amount conversion processing is performed based on the relationship between the “adhesion amount” and the “diffuse reflection light output correction value” obtained in advance.
[0063]
(1) to (5) will be described in order below.
Explanation of (1)
FIGS. 11 and 13 show “specular reflection light output voltage” and “diffuse reflection light output” obtained by detecting the density detection P pattern 70 shown in FIG. 18 formed on the transfer belt 18 by the P sensor 40 shown in FIG. Voltage "was precisely measured with an electronic balance and the amount of color toner attached [mg / cm ² ] Is plotted against this. In the gradation pattern 70, the amount of adhered toner increases on the upstream side in the belt movement direction.
As described above, three types of transfer belts 18 having different specular gloss and lightness are used as described above.
[0064]
Explanation about (2)
Here, comparing the specular light output characteristic with respect to the black toner adhesion amount shown in FIG. 10 and the specular reflection light output characteristic with respect to the color toner adhesion amount shown in FIG. 11, FIG. Amount (in this case 0.2-0.4 mg / cm ² From the above, it can be seen that the monotonous decrease has changed to a monotonous increase. However, as shown in FIGS. 19 and 20, the light received by the regular reflection light receiving element 52 as the regular reflection light has a pure [ This is because, in addition to the “reflected light component”, the “diffuse reflected light component from the belt surface” and the “diffuse reflected light component from the toner layer” are included. In FIG. 19B, reference numeral 54 indicates a solid portion of cyan.
Considering that the irradiation light from the LED 51 is evenly diffused on the detection target surface as shown in FIG. 19, the diffuse reflection light component received by the regular reflection light receiving element 52 and the diffusion light entering the diffuse light receiving element 55 An n-fold relationship should be established with the reflected light.
The value of n times used here is a value determined by the optical layout such as the light receiving diameter and arrangement of each of the light receiving elements 52 and 55.
[0065]
The actual output is output as a voltage after the reflected light entering each of the light receiving elements 52 and 55 is IV-converted by an OP amplifier in the circuit, and then output as a voltage. Are also integrated, and the relationship of α times should be established.
It is considered that if such a coefficient α can be obtained, the specular reflection light output can be decomposed into a “specular reflection component” and a “diffuse reflection component”.
Considering how to obtain the coefficient α, the diffuse reflection component of the Bk toner is smaller as it is almost equal to zero, so that the output characteristic of the regular reflection light of Bk shown in FIG. It is considered that the output characteristic is almost equal to the specular reflection component output characteristic after removing the component.
As shown in FIG. 10, the output value of the specular reflection light of the Bk toner becomes almost zero or slightly positive, and never becomes negative, as the amount of adhesion increases. The minimum value of the ratio between the regular reflection light output and the diffuse reflection light output is calculated for each, and the minimum value of this ratio is multiplied by the diffuse reflection light output and subtracted from the regular reflection light output, so that only the intended regular reflection component is obtained. You should be able to extract the output characteristics.
[0066]
Below, the brown belt (Gs = 27, L ^* = 25) will be described based on the output result. The meanings of symbols (abbreviations) in the following description are as follows.
Vsg: output voltage of the background portion of the transfer belt 18
Vsp: Output voltage of each pattern
Voffset: Offset voltage (output voltage when LED 51 is off)
_Reg. ... Specific reflection light output (short for Regular Reflection)
_Dif. ... Diffuse reflection output
[N] ... number of elements: n array variables
(STEP 1): Data sampling: calculation of ΔVsp and ΔVsg (see FIGS. 21 and 22)
First, the difference from the offset voltage for all points [n] is calculated for both the regular reflection light output and the diffuse reflection light output.
This is because, ultimately, it is desired to express the increment of the sensor output only by the increment due to the change in the attached amount of the color toner.
[0067]
(Equation 1)

[0068]
However, in the case where an OP amplifier is used in which each offset voltage value (Voffset_reg .: 0.0621 V, Voffset_dif .: 0.0635 V) when the LED 51 is off is sufficiently small to a negligible level as in the present embodiment. Such a difference process becomes unnecessary.
[0069]
(STEP 2): Calculation of sensitivity correction coefficient α (see FIG. 22)
ΔVsp_reg. Obtained in STEP1. [N], ΔVsp_dif. [N], ΔVsp_reg. [N] / ΔVsp_dif. [N] is calculated, and a coefficient α for multiplying the diffuse reflection light output (ΔVsp_dif. [N]) is calculated when the component decomposition of the regular reflection light output is performed in STEP3.
[0070]
(Equation 2)

[0071]
The reason why α is obtained from the minimum value of the ratio is that it is known in advance that the minimum value of the specular reflection component of the specular reflection light output is substantially zero and a positive value. Here, the tone pattern has at least one or more, preferably three or more, adhesion amount patterns in the vicinity of the adhesion amount at which the minimum value of the ratio between the regular reflection light output and the diffuse reflection light output is obtained. . At least one, preferably three or more, in the vicinity of the adhesion amount where the minimum value of the ratio between the regular reflection light output increment and the diffuse reflection light output increment obtained from the difference between each output value when the light emitting means is off is obtained. You may make it have an adhesion amount pattern. Further, at least one or more, preferably three or more attachment amount patterns may be provided within an attachment amount range in which the specular reflected light output conversion value has a linear relationship with the attachment amount.
(STEP 3): Decomposition of specularly reflected light (see FIG. 23)
The component of the specular reflected light output is decomposed by the following equation.
[0072]
[Equation 3]

[0073]
When the components are decomposed in this manner, the specular reflection component of the specular reflection light output becomes zero in the pattern portion where the sensitivity correction coefficient α is obtained.
By this processing, as shown in FIG. 23, the specular reflected light output is decomposed into [specular reflected light component] and [diffuse reflected light component].
(STEP 4): regular reflection light output_normalization of regular reflection component (see FIG. 24)
Next, in order to correct the difference in the regular reflection light output of the background portion of the three types of belts, the ratio of the output of each pattern portion to the output of the background portion of the belt is calculated and converted to a normalized value of 0 to 1.
[0074]
(Equation 4)

[0075]
FIG. 24 shows the result of conversion to normalized values obtained by performing the same processing for all three types of belts shown in FIG.
In this way, by decomposing the specularly reflected light, only the specularly reflected light component is extracted and converted into a normalized value, thereby uniquely obtaining the relationship between the specularly reflected light component and the amount of adhesion. Can be. It should be noted that this value represents the exposure rate of the background portion of the belt, and in the range of the adhesion amount from zero to one layer, the normalized value (= the exposure ratio of the background portion of the belt) is It has a linear relationship.
If M / A｝ = 0-0.4mg / cm ² If it is desired to obtain the toner adhesion amount in the low adhesion amount region up to the above, if the relationship between the adhesion amount and the normalized value as shown in FIG. The reverse conversion or the conversion of the attached amount can be performed by referring to the table.
[0076]
Here, a comparison with the prior art will be given. In claim 4 of JP-A-2001-215850, specularly reflected light + (diffusely reflected light−diffusely reflected light output min) × predetermined coefficient is indicated. In the embodiment in the specification, the output after correction is the first order. Although there is a description that the predetermined coefficient is set to “−6” so as to have a correlation, the multiplication by the predetermined coefficient having such a form does not take into account the characteristic variation of the optical detection means as described above. It is practically meaningless in this respect.
On the other hand, in the present embodiment, since the predetermined coefficient is multiplied by a coefficient calculated based on the sensor output of the specular reflection light and the diffuse reflection light, a high-precision method considering the characteristic variation of the optical detection means is used. Detection can be performed.
[0077]
Explanation about (3)
Next, a process of removing [diffuse reflected light output component from the belt background portion] from [diffuse reflected light output voltage] will be described.
What is ultimately desired by the adhesion amount conversion algorithm in the present embodiment is a unique relationship between the amount of toner adhesion and the diffuse reflection light output.
However, as shown in FIG. 20, the light that enters the diffuse reflected light receiving element 55 contains diffuse reflected light (noise component) from the belt background in addition to the diffuse reflected light from the toner layer. This component needs to be removed from the output.
In FIG. 20, the ratio between the “background portion output” and the “pattern portion output” of the specular reflection component is uniquely determined with respect to the attached amount (the attached amount detectable range: 0 to 0.4 mg / cm). ² ).
In addition, in the diffuse reflection component from the toner layer, if the irradiation light on the detection target surface is constant, the relationship with the amount of adhesion is uniquely determined (the amount of detection of the amount of adhesion: 0 to 1.0 mg / cm). ² ).
As a continuation of STEP 4, the brown belt (Gs = 27, L ^* = 25) will be described based on the output result.
As shown in the results of FIG. 13, the diffuse reflection light output from the belt background becomes maximum at the belt background where no toner adheres, and the component gradually decreases as the toner adheres.
The relationship between the diffused reflected light output voltage increment and the amount of adhesion of the diffused reflected light output voltage due to the light directly entering the diffuse reflected light receiving element 55 from the belt background portion is determined by the exposure ratio of the transfer belt 18, that is, the specular reflection component of the specular reflected light output previously obtained. The process for removing [diffuse reflected light output component from the belt background portion] from [diffuse reflected light output voltage] in order to be proportional to the normalized value of (see FIG. 24) is as follows.
(STEP 5): Correction of background fluctuation of diffused light output (see FIG. 25)
[0078]
(Equation 5)

[0079]
The results are shown in FIG. By performing such a correction process, the influence of the background portion of the transfer belt 18 can be eliminated. Therefore, the "diffuse reflected light component directly reflected from the belt background" can be removed from the "diffuse reflected light output" in the low adhesion amount region where the specular reflected light output is sensitive.
By performing such processing, the diffuse reflection light output after correction in the adhesion amount range from the adhesion amount of zero to the formation of one layer passes through the origin and is converted into a value having a first-order linear relationship with the adhesion amount. .
[0080]
Here, a supplementary explanation of the diffuse reflection light will be given. Since the specularly reflected light is light reflected on the surface of the detection target surface, as shown in FIG. 24, if the detection target surface is 100% covered with the toner, the output substantially changes in a larger adhesion amount region. And the normalized conversion value becomes almost zero.
On the other hand, the diffusely reflected light is light that is radiated from the LED 51 and enters the inside of the toner layer and is multiply reflected. Therefore, as shown in FIG. However, the sensor output has the characteristic of increasing monotonically.
Therefore, as shown in FIG. 26, the light reflected from the belt background also has a primary component directly reflected from the belt background and a secondary and tertiary component reflected through the toner layer and reflected. is there.
In the present embodiment, only the primary component is corrected in STEP 5, but even with this correction alone, the influence of the belt background can be almost accurately removed at least in the low adhesion amount region where the sensitivity correction is performed. Next, since the tertiary component is sufficiently smaller than the primary component, practically sufficient accuracy can be obtained even by correcting only the primary component.
[0081]
Explanation about (4)
By the above processing, in the low adhesion amount region where the specular reflection light output has sensitivity, only (specular reflection light component) that can uniquely represent the relationship with the toner adhesion amount from the regular reflection light is extracted in (2), In (3), since the [diffuse reflected light component directly reflected from the belt background] can be removed from the diffuse reflected light, the sensitivity of the diffuse reflected light output is corrected based on these.
Here, the reason for performing the sensitivity correction is to perform the following correction as described above.
(1) Correction for lot variation in light emitting element output and light receiving element output
(2) Correction for Temperature Characteristics and Temporal Deterioration Characteristics of Light-Emitting Element Output and Light-Receiving Element Output The biggest point in this processing is that in the low adhesion amount region where only one toner layer is formed.
{Circle around (1)} The normalized value of the specular reflection light output (specular reflection component), that is, the exposure rate of the background portion of the transfer belt has a linear relationship with the toner adhesion amount.
{Circle around (2)} The [diffuse reflection component from the toner layer] has a first-order linear relationship passing through the origin with respect to the toner adhesion amount.
That is, the sensitivity correction of the diffuse reflection light output is performed by utilizing the fact that the two corrected outputs of the regular reflection light and the diffuse reflection light both have a linear relationship with the toner adhesion amount. Although several methods can be considered for this sensitivity correction, two methods will be described here as examples.
[0082]
(STEP 6): Sensitivity correction of diffuse reflection light output (see FIG. 25)
<Processing formula by the first method>
As shown in FIG. 27, the diffused reflected light output after the background variation correction is plotted with respect to the “normalized value of the regular reflected light (specular reflected component)”. Is obtained, and correction is performed so that the sensitivity becomes a predetermined target sensitivity.
Here, the sensitivity of the diffuse reflected light output is the slope of the straight line shown in FIG. 27, and the diffuse reflected light output after correction of the background variation of a certain normalized value is a certain value (here, 0.3). In this case, a correction coefficient by which the current inclination is multiplied is calculated and corrected so as to satisfy 1.2).
(1) The slope of the straight line is obtained by the least square method.
[0083]
(Equation 6)

[0084]
In this embodiment, the lower limit of the range of x used in the calculation is 0.06, but this lower limit is a value that can be arbitrarily determined within a range where x and y are in a linear relationship. Note that the upper limit is set to 1 because the normalized value is a value from 0 to 1.
(2) A sensitivity correction coefficient γ is calculated such that a certain normalized value a calculated from the sensitivity thus obtained becomes a certain value b.
[0085]
(Equation 7)

[0086]
(3) The diffuse reflection light output after the background portion fluctuation correction obtained in STEP 5 is multiplied by the sensitivity correction coefficient γ for correction. The reference point at which the sensitivity correction is performed (the specular reflection light output conversion value when the diffuse reflection light output conversion value of a certain specular reflection light output conversion value is multiplied by a correction coefficient that becomes a certain value) is the specular reflection light. This is an area in which the amount of adhesion can be detected.
[0087]
(Equation 8)

[0088]
<Processing formula by the second method>
By referring to the inverse conversion formula or the conversion table obtained from the relationship between the adhesion amount (measured value) and the normalized value of the specular reflection light (specular reflection component) obtained in FIG. ) Is converted into an adhered amount (converted value), and the diffuse reflected light output after correction of the variation in the background is plotted against the adhered amount (converted value). The sensitivity of the reflected light output is obtained, and correction is performed so that the sensitivity becomes a predetermined target sensitivity.
The difference from the first method is that the horizontal axis is changed from “normalized value of specular reflection light (specular reflection component)” to “adhesion amount (converted value)”. Here, the sensitivity of the diffuse reflection light output is the slope of the straight line shown in FIG. 28, and the diffuse reflection light output after correction of the background variation of a certain amount of adhesion (conversion value) is a certain value (here, 0). .175, the correction is performed by calculating a correction coefficient by which the current inclination is multiplied.
(1) The slope of the straight line is obtained by the least square method.
[0089]
(Equation 9)

[0090]
In the present embodiment, the upper limit of the range of x used in the calculation is 0.3, but this upper limit is a value that can be arbitrarily determined within a range where x and y are in a linear relationship. In addition, the lower limit was set to 0 because the lower limit of the adhesion amount was 0.
(2) A sensitivity correction coefficient γ is calculated such that a certain normalized value a calculated from the sensitivity thus obtained becomes a certain value b.
[0091]
(Equation 10)

[0092]
(3) The diffuse reflection light output after the background portion fluctuation correction obtained in STEP 5 is multiplied by the sensitivity correction coefficient γ for correction.
[0093]
(Equation 11)

[0094]
FIG. 29 shows the results of conversion to normalized values obtained by performing the same processing for all three types of belts.
Here, since the diffuse reflection light output voltage before correction is as shown in FIG. 13, the object of the present invention is obtained by the above processing.
(1) Correction for lot variation in light emitting element output and light receiving element output
(2) Correction for temperature characteristics and aging deterioration characteristics of light emitting element output and light receiving element output
Has been confirmed to be sufficient.
By such processing, the diffuse reflection light output after the sensitivity correction can be uniquely expressed with respect to the toner adhesion amount, and if it is obtained experimentally in advance as a mathematical expression or table data, this is inversely transformed, or By referring to the conversion table, it is possible to perform accurate conversion of the adhesion amount up to the high adhesion amount region.
[0095]
FIG. 30 shows a result obtained by plotting the adhesion amount (converted value) obtained by actually converting the normalized value back to the adhesion amount measurement value by an electronic balance.
As shown in FIG. 30, it can be confirmed that the adhesion amount can be converted almost accurately up to the high adhesion amount region. By enabling accurate detection of the adhesion amount up to the high adhesion amount region, the maximum target adhesion amount in the image density control can be controlled with high accuracy, regardless of aging, environment, and sensor lot variation. Thus, a stable image quality can always be obtained.
[0096]
FIG. 31 is a diagram showing a color image in which three sensors extracted as upper and lower limit products of variation and three products extracted as a central product among 200 prototypes of density detection sensors are formed on the transfer belt 18 of the laser color printer A shown in FIG. The figure shows the diffused reflected light output voltage in which a total of 30 P patterns (gradation patterns) of 10 toner colors are detected. FIG. 32 shows the conversion values of the diffuse reflection light by the conversion algorithms of STEP1 to STEP6. The LED current at this time is a value when the regular reflection light output voltage of the background portion of the transfer belt 18 is adjusted to be 4.0 V.
According to the result, by using the algorithm of the present embodiment (the present invention), it is possible to reduce the output variation of the light receiving element due to various factors in the optical detection means as described above without requiring strict adjustment on the hardware side. The algorithm side, that is, the software side, can automatically and accurately correct.
[0097]
In the above embodiment, the optical detector having the light emitting means, the regular reflection light receiving element and the diffuse reflection light receiving element shown in FIG. 4 is used as the optical detection means, but the optical detection means having the beam splitter shown in FIG. The same detection function can be obtained by using the means (second embodiment).
In the above-described embodiment, the detection target surface is the transfer belt 18 as a transfer body, but each photosensitive drum may be a detection target surface (third embodiment). In this case, the P sensor 40 is provided to face each photosensitive drum.
[0098]
Further, in the above embodiment, an example of the color image forming apparatus of the four-tandem direct transfer system is shown. However, as shown in FIG. The same can be applied to a transfer type color image forming apparatus (fourth embodiment).
In the present embodiment, a P pattern for density detection shown in FIG. 18 is formed on the intermediate transfer belt 2 as an intermediate transfer body, and is detected by a P sensor 40 arranged near the support roller 2B. That is, the intermediate transfer belt 2 is set as the detection target surface. The detection method and operation (such as handling of detection data, etc.) are the same as in the first embodiment.
[0099]
An outline of the configuration and operation of a tandem-type color copying machine as an image forming apparatus according to the present embodiment will be described below. The color copying machine 1 has an image forming unit 1A located at the center of the apparatus main body, a paper feeding unit 1B located below the image forming unit 1A, and an image reading unit 1C located above the image forming unit 1A. are doing.
In the image forming section 1A, an intermediate transfer belt 2 as a transfer body having a transfer surface extending in the horizontal direction is arranged. On the upper surface of the intermediate transfer belt 2, an image of a color having a complementary color relationship with the color separation color is provided. Is provided. That is, the photosensitive drums 3Y, 3M, 3C, and 3B as image carriers capable of carrying an image with toners of complementary colors (yellow, magenta, cyan, and black) are arranged along the transfer surface of the intermediate transfer belt 2. Juxtaposed.
[0100]
Each of the photoconductor drums 3Y, 3M, 3C, and 3B is constituted by a drum rotatable in the same counterclockwise direction. Around the charging device 4, a charging device 4 serving as a charging unit that executes an image forming process in a rotating process. , The potential V on each of the photosensitive drums 3Y, 3M, 3C and 3B based on the image information. _L An optical writing device 5 as exposure means for forming an electrostatic latent image, and developing as developing means for developing the electrostatic latent image on each photosensitive drum 3 with toner having the same polarity as the electrostatic latent image. A device 6, a transfer bias roller 7 as a primary transfer unit, an applied voltage member 15, and a cleaning device 8 are arranged. The alphabet attached to each code corresponds to the color of the toner, similarly to the photosensitive drum 3. Each developing device 6 stores a respective color toner.
The intermediate transfer belt 2 is configured to be wrapped around a plurality of rollers 2A to 2C and move in the same direction at a position facing the photosensitive drums 3Y, 3M, 3C, and 3B. A roller 2C different from the rollers 2A and 2B supporting the transfer surface faces the secondary transfer device 9 with the intermediate transfer belt 2 interposed therebetween. In FIG. 33, reference numeral 10 denotes a cleaning device for the intermediate transfer belt 2.
[0101]
The surface of the photoconductor drum 3Y is uniformly charged by the charging device 4Y, and an electrostatic latent image is formed on the photoconductor drum 3Y based on image information from the image reading unit 1C. The electrostatic latent image is visualized as a toner image by a two-component (carrier and toner) developing device 6Y containing yellow toner, and the toner image is transferred onto the intermediate transfer belt 2 as a first transfer step. The transfer is performed by being attracted by an electric field due to the voltage applied to the transfer bias roller 7Y.
The applied voltage member 15Y is provided on the upstream side of the transfer bias roller 7Y in the rotation direction of the photosensitive drum 3Y. The applied voltage member 15Y causes the intermediate transfer belt 2 to have the same polarity as the charging polarity of the photosensitive drum 3Y and an absolute value V _L A higher voltage is applied to prevent transfer of toner from the photosensitive drum 3Y to the intermediate transfer belt 2 before the toner image enters the transfer area, and transfer of toner from the photosensitive drum 3Y to the intermediate transfer belt 2 Prevents turbulence due to dust.
[0102]
Similar image formation is performed on the other photosensitive drums 3M, 3C, and 3B only with different toner colors, and the toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 2 and superimposed.
After the transfer, the toner remaining on the photoconductor drum 3 is removed by the cleaning device 8, and after the transfer, the potential of the photoconductor drum 3 is initialized by a discharging lamp (not shown) to be prepared for the next image forming process.
The secondary transfer device 9 has a transfer belt 9C that is wrapped around a charging drive roller 9A and a driven roller 9B and moves in the same direction as the intermediate transfer belt 2. By charging the transfer belt 9C by the charging drive roller 9A, a multicolor image or a single-color image carried on the intermediate transfer belt 2 can be transferred onto a sheet 28 as a sheet-shaped recording medium.
[0103]
The sheet 28 is fed from the sheet feeding section 1B to the secondary transfer position. A plurality of paper feed cassettes 1B1 in which papers 28 are stacked and stored in the paper feed unit 1B, and a paper feed roller 1B2 that separates and feeds the papers 28 stored in the paper feed cassettes 1B1 one by one from the top. , A pair of conveying rollers 1B3, a pair of registration rollers 1B4 located upstream of the secondary transfer position, and the like.
The sheet 28 fed from the sheet feeding cassette 1B1 is temporarily stopped by the pair of registration rollers 1B4, and after correcting the oblique displacement or the like, the sheet 28 on the intermediate transfer belt 2 and the predetermined position of the tip in the conveyance direction are adjusted. Are sent to the secondary transfer position by the registration roller pair 1B4 with the matching tying. A manual feed tray 29 is provided on the right side of the apparatus main body so as to be able to be turned upside down. The paper 28 stored in the manual feed tray 29 joins the paper transport path from the paper feed cassette 1B1 fed by the paper feed roller 31. Then, the sheet is sent toward the registration roller pair 1B4 through the transfer path.
[0104]
In the optical writing device 5, the writing light is controlled by the image information from the image reading unit 1C or the image information output from a computer (not shown), and the photosensitive drums 3Y, 3M, 3C, and 3B respond to the image information. The writing light is emitted to form an electrostatic latent image.
The image reading unit 1C includes an automatic document feeder 1C1, a scanner 1C2 having a contact glass 80 as a document table, and the like. The automatic document feeder 1C1 has a configuration in which a document fed out onto the contact glass 80 can be inverted, and can scan each side of the document.
The electrostatic latent image on the photosensitive drum 3 formed by the optical writing device 5 is subjected to visible image processing by the developing device 6, and is primarily transferred to the intermediate transfer belt 2. When the toner images of the respective colors are superimposed and transferred onto the intermediate transfer belt 2, they are collectively and secondarily transferred onto the paper 28 by the secondary transfer device 9. The secondary-transferred sheet 28 is sent to the fixing device 11, where an unfixed image is fixed by heat and pressure. The residual toner on the intermediate transfer belt 2 after the secondary transfer is removed by the cleaning device 10.
[0105]
The sheet 28 that has passed through the fixing device 11 is selectively guided to a conveyance path toward the paper discharge tray 27 and a reversing conveyance path RP by a conveyance path switching claw 12 provided on the downstream side of the fixing apparatus 11. When the sheet is conveyed toward the sheet discharge tray 27, the sheet is discharged onto the sheet discharge tray 27 by the sheet discharge roller pair 32 and stacked. When the sheet is guided to the reversing conveyance path RP, the sheet is reversed by the reversing device 38 and sent again to the registration roller pair 1B4.
[0106]
With the above configuration, in the color copying machine 1, the original placed on the contact glass 80 is exposed and scanned, or the photosensitive drum 3 uniformly charged by the image information from the computer is statically charged. After an electrostatic latent image is formed and the electrostatic latent image is subjected to visible image processing by the developing device 6, the toner image is primarily transferred to the intermediate transfer belt 2.
In the case of a single image, the toner image transferred to the intermediate transfer belt 2 is directly transferred to the sheet 28 fed from the sheet feeding unit 1B. In the case of a multicolor image, after the primary transfer is repeated and superimposed, the secondary transfer is collectively performed on the paper 28.
After the secondary transfer, the sheet 28 after the unfixed image is fixed by the fixing device 11 is discharged to the sheet discharge tray 27 or inverted and sent again to the registration roller pair 1B4 for double-sided image formation.
In the present embodiment, the surface to be detected is the intermediate transfer belt 2 as a transfer body, but each photosensitive drum may be a surface to be detected (fifth embodiment). In this case, the P sensor 40 is provided to face each photosensitive drum.
[0107]
Further, a toner image of each color is formed by using one photosensitive drum and a revolver type developing device, and each toner image is superimposedly transferred onto an intermediate transfer member, and then transferred collectively onto transfer paper as a sheet-shaped recording medium. The present invention can be similarly implemented in a color image forming apparatus of the system (Sixth Embodiment). An example is shown in FIG.
In the present embodiment, a P pattern for density detection shown in FIG. 18 is formed on an intermediate transfer belt 426 as an intermediate transfer body, and this is detected by a P sensor 40 arranged near a driving roller 444. That is, the intermediate transfer belt 426 is set as a detection target surface. The detection method and operation (such as handling of detection data) are the same as in the first embodiment.
[0108]
Hereinafter, an outline of a configuration of a color copying machine as an image forming apparatus according to the present embodiment will be described.
In a color copier, a writing optical unit 400 as an exposure unit converts color image data from the color scanner 200 into an optical signal to perform optical writing corresponding to a document image, and performs an optical writing on a photosensitive drum 402 as an image carrier. To form an electrostatic latent image.
The writing optical unit 400 includes a laser diode 404, a polygon mirror 406, a rotation motor 408 thereof, an fθ lens 410, a reflection mirror 412, and the like.
The photoconductor drum 402 is rotated in a counterclockwise direction as indicated by an arrow, and a photoconductor cleaning unit 414, a static elimination lamp 416, a potential sensor 420, and a rotary developing device 422 are selected around the photoconductor drum 402. A developing device, a developing density pattern detector 424, an intermediate transfer belt 426 as an intermediate transfer body, and the like are arranged.
[0109]
The rotary developing device 422 includes a black developing device 428, a cyan developing device 430, a magenta developing device 432, a yellow developing device 434, and a rotation drive unit (not shown) for rotating each developing device. Each developing device is a so-called two-component developing type developing device containing a mixed developer of a carrier and a toner, and has the same configuration as the developing device 4 described in the above embodiment. The same applies to the conditions and specifications of the magnetic carrier.
In the standby state, the rotary developing device 422 is set at the position of black development, and when a copying operation is started, reading of black image data is started at a predetermined timing by the color scanner 200, and this image data is read. , The formation of the optical writing / electrostatic latent image (black latent image) by the laser beam starts.
[0110]
In order to develop from the leading end of the black latent image, before the leading end of the latent image reaches the developing position of the black developing device 428, the rotation of the developing sleeve is started to develop the black latent image with black toner. An image of negative polarity toner is formed on the photosensitive drum 402.
Thereafter, the developing operation of the black latent image area is continued, but when the rear end of the latent image passes the black developing position, the rotary developing operation is promptly performed from the developing position for black to the developing position for the next color. The device 422 rotates. This operation is completed at least before the leading end of the latent image based on the next image data arrives.
When the image forming cycle is started, first, the photosensitive drum 402 is rotated in a counterclockwise direction as indicated by an arrow, and the intermediate transfer belt 426 is rotated in a clockwise direction by a drive motor (not shown). As the intermediate transfer belt 426 rotates, black toner image formation, cyan toner image formation, magenta toner image formation, and yellow toner image formation are performed, and finally black (Bk), cyan (C), and magenta (M) , Yellow (Y) in this order on the intermediate transfer belt 426 (primary transfer) to form a toner image.
[0111]
The intermediate transfer belt 426 includes a primary transfer electrode roller 450 facing the photosensitive drum 402, a driving roller 444, a secondary transfer facing roller 446 facing the secondary transfer roller 454, and a cleaning unit that cleans the surface of the intermediate transfer belt 426. It is stretched between the respective support members of the cleaning facing roller 448A facing the 452, and is driven and controlled by a drive motor (not shown).
The black, cyan, magenta, and yellow toner images sequentially formed on the photosensitive drum 402 are accurately and sequentially aligned on the intermediate transfer belt 426, thereby forming a four-color superimposed belt transfer image. This belt transfer image is collectively transferred to the sheet by the secondary transfer opposing roller 446.
[0112]
Each of the recording paper cassettes 458, 460, and 462 in the paper supply bank 456 stores various sizes of paper different from the size of the paper stored in the cassette 464 in the apparatus main body. The designated sheet is fed and conveyed from the size paper storage cassette toward the registration roller pair 470 by the sheet feeding roller 466. In FIG. 34, reference numeral 468 denotes a manual paper feed tray for OHP paper, thick paper, and the like.
At the time when the image formation is started, the paper is fed from the paper feed port of any one of the cassettes, and waits at the nip portion of the pair of registration rollers 470. When the leading end of the toner image on the intermediate transfer belt 426 approaches the secondary transfer opposing roller 446, the registration roller pair 470 is driven so that the leading end of the sheet coincides with the leading end of the image. Is performed.
[0113]
In this way, the sheet is superimposed on the intermediate transfer belt 426 and passes under the secondary transfer opposing roller 446 to which a voltage having the same polarity as that of the toner is applied. At this time, the toner image is transferred to the paper. Subsequently, the paper is discharged, separated from the intermediate transfer belt 426 and moved to the paper transport belt 472.
The sheet on which the four-color superimposed toner image has been collectively transferred from the intermediate transfer belt 426 is conveyed by a paper conveying belt 472 to a fixing device 470 of a belt fixing system, and the fixing device 470 fixes the toner image by heat and pressure. The sheet on which fixing has been completed is discharged out of the apparatus by a discharge roller pair 480 and stacked on a tray (not shown). Thereby, a full-color copy is obtained.
In the present embodiment, the detection target surface is the intermediate transfer belt 426 as a transfer body, but the photosensitive drum 402 may be the detection target surface (sixth embodiment). In this case, the P sensor 40 is provided to face the photosensitive drum 402.
[0114]
In each of the above embodiments, the processing is performed based on the minimum value of the ratio between the regular reflection light output and the diffuse reflection light output, but the regular reflection light output increment obtained from the difference between each output value when the light emitting means is off. A similar detection function can be obtained as a method of processing based on the minimum value of the ratio with the diffuse reflection light output increment.
Further, in each of the above embodiments, the image forming apparatus is exemplified as the powder adhesion amount detection device. However, the same detection function can be obtained by the same processing method in the adhesion amount detection field which handles powder other than toner. .
[0115]
The effects obtained in the above embodiments will be described below.
In the prior art, as described above, the detectable range of the color adhesion amount gradually decreases due to the decrease in the glossiness of the detection target surface over time, so that the wear deterioration of the detection target surface over time is a rate-limiting factor of the life. However, by performing the conversion process as described above, the detectable range of the adhesion amount is broader than that of the conventional regular reflection light detection, and the accurate adhesion amount detection can be performed without depending on the glossiness. .
Further, in the above embodiment, the life of the detection target surface can be extended because it does not depend on the wear deterioration of the detection target surface.
By applying the regular reflection light output conversion algorithm to the adhesion amount detection with the image carrier or transfer body as a detection target surface in a color image forming apparatus, a belt having a low glossiness which is said to be difficult to detect in the prior art is difficult. The adhesion amount conversion can be performed without any problem on the detection target surface as described above, and the density control can be performed based on the adhesion amount conversion value.
[0116]
In addition, by performing the above conversion processing, the diffuse reflection light output can be converted into a value that gives a linear relationship with the amount of adhesion in the low amount of adhesion from zero to one layer of powder.
In addition, by performing the above conversion process (automatic correction function of diffused light output sensitivity), the diffused light output variation (hardware side) caused by the variation in the output of the light emitting element and the light receiving element of the density detection sensor is reduced by the adhesion amount conversion algorithm. Since the correction can be performed by the software (software side), adjustment work on the sensor side (hardware side) at the time of sensor shipment inspection, which has been performed conventionally, is not necessary, or the adjustment range can be greatly expanded. It becomes.
By the way, in the diffuse reflection type sensor mounted on the conventional apparatus by the present applicant, the output adjustment time required was about 2 minutes per sensor, but the tolerance range was widened, and as a result, the tolerance was reduced to less than 10 seconds. Became adjustable.
As a result, the productivity in manufacturing the sensor can be dramatically improved, and the cost of the sensor can be reduced, and the cost of the image forming apparatus can be reduced.
[0117]
In addition, even if the LED light quantity decreases over time of the density detection sensor and the output changes due to the temperature characteristics of the light-emitting element and light-receiving element, the automatic conversion function of the diffuse reflection light output sensitivity always performs the stable conversion of the adhesion amount. Can be.
In the related art, it is difficult to calibrate the sensitivity with a sensor that only outputs diffuse reflection light (type (2)). Even when the surface to be detected is black, accurate sensitivity calibration and adhesion amount detection can be performed. .
Conventionally, in the case of sensors that use both specular reflection light output and diffuse reflection light output (types (3) and (4)), the detection accuracy of the amount of adherence decreases with time due to characteristic changes due to deterioration with time of the detection target surface. However, with the automatic correction function of diffuse reflection light output sensitivity, it is possible for the algorithm side (software side) to absorb changes over time in the characteristics of the detection target surface, so that the glossiness of the detection target surface is reduced. Even if it is extremely low, regardless of the glossiness, and even if it is black, the diffuse reflection light output can be accurately converted to the adhesion amount over a high adhesion amount region. As a result, the life of the detection target surface can be prolonged, and the running cost can be reduced.
By applying the diffuse reflection light output conversion algorithm to the adhesion amount detection with the image carrier or transfer body as the detection target surface in the color image forming apparatus, the glossiness is low in the prior art, which is said to be difficult to detect. Even if it is a belt or the detection target surface is a black belt, the adhesion amount can be detected with high accuracy up to the high adhesion amount region without any problem. As a result, the solid adhesion amount, which is the maximum adhesion amount target value, can be detected, and stable image density control can always be performed irrespective of aging and environmental changes.
[0118]
In addition, the life of an image carrier such as a photoconductor or a transfer belt, which is a detection target surface, can be extended. In general, the detection target surface such as the transfer belt is integrated into a unit with the developing device, etc., and a method of batch replacement is adopted.However, early batch replacement due to deterioration of detection accuracy due to aging deterioration of only the detection target surface is adopted. Since there is no need to perform this, the running cost can be significantly reduced due to the relationship with other unit components whose life has not expired.
By having at least one or more, preferably three or more attachment amount patterns (number of attachment amount patches) in the vicinity of the attachment amount at which the minimum value of the ratio between the regular reflection light output and the diffuse reflection light output is obtained. Thus, it is possible to perform the conversion of the adhesion amount with higher accuracy.
In addition, at least one or more, and preferably three or more, in the vicinity of the adhesion amount at which the minimum value of the ratio between the regular reflection light output increment and the diffuse reflection light output increment obtained from the difference between each output value when the light emitting means is off is obtained. By having the above-mentioned adhesion amount pattern, more accurate adhesion amount conversion becomes possible.
In addition, at least one or more, preferably three or more attachment amount patterns are provided within the attachment amount range in which the specular reflection light output conversion value has a first-order linear relationship with the attachment amount, whereby higher accuracy is achieved. Conversion of the amount of adhesion becomes possible.
[0119]
【The invention's effect】
According to the present invention, it is possible to always perform stable and stable detection of the attached amount with high accuracy irrespective of factors such as lot variation of light-emitting element output and light-receiving element output, change due to temperature characteristics and aging, and aging of a detection target surface. Can be.
[Brief description of the drawings]
FIG. 1 is a schematic front view of a color laser printer as an image forming apparatus according to a first embodiment of the present invention.
FIG. 2 is a configuration diagram of an optical detection unit that detects only specularly reflected light.
FIG. 3 is a configuration diagram of an optical detection unit that detects only diffuse reflection light.
FIG. 4 is a configuration diagram of a type of optical detection means for simultaneously detecting specular reflection light and diffuse reflection light.
FIG. 5 is a configuration diagram of an optical detecting unit that detects a regular reflection light and a diffuse reflection light at the same time and uses a beam splitter.
FIG. 6 is a graph showing detection results of a regular reflection light output and a diffuse reflection light output with respect to a color toner adhesion amount.
FIG. 7 is a graph showing a relationship between a color toner adhesion amount and a difference between specularly reflected light.
FIG. 8 is a schematic diagram showing a reflection state of irradiation light when a mirror glossiness of a detection target surface is high.
FIG. 9 is a schematic diagram illustrating a reflection state of irradiation light when the specular glossiness of a detection target surface is reduced due to adhesion of toner.
FIG. 10 is a graph showing specular light output characteristics with respect to black toner adhesion amount.
FIG. 11 is a graph showing specular reflection light output characteristics with respect to the amount of attached color toner.
FIG. 12 is a graph showing a diffuse reflection light output characteristic with respect to a black toner adhesion amount.
FIG. 13 is a graph showing diffuse reflection light output characteristics with respect to the amount of attached color toner.
FIG. 14 is a graph showing specular reflection output characteristics with respect to specular glossiness of a detection target surface.
FIG. 15 is a graph showing a diffuse reflection light output characteristic with respect to brightness of a detection target surface.
FIG. 16 is a graph showing a relationship between a temporal decrease in glossiness of a detection target surface and correction of specular reflection light output.
FIG. 17 is a graph showing the relationship between the amount of color toner adhered and the difference between specular reflection light when the glossiness of the detection target surface decreases over time.
FIG. 18 is a plan view showing a gradation pattern.
FIG. 19 shows light received by a specular reflection light receiving element as specular reflection light, in addition to a pure regular reflection light component, a diffuse reflection light component from a detection target surface and a diffusion reflection light component from a toner layer. FIG.
FIG. 20 is a block diagram showing a relationship between a reflected light component to be actually detected by the optical detection means and a reflected light component to be removed.
FIG. 21 is a graph showing the relationship between the amount of adhesion and the detection output during data sampling.
FIG. 22 is a graph showing the relationship between the sensitivity correction coefficient multiplied by the diffuse reflection light output, the amount of adhesion, and the detection output.
FIG. 23 is a graph showing decomposition of specular reflected light components.
FIG. 24 is a graph showing normalization of a regular reflection component of a regular reflection light output.
FIG. 25 is a graph showing the relationship between the amount of variation correction of the background portion of diffuse reflection light output, the amount of adhesion, and the detection output.
FIG. 26 is a schematic view showing that a plurality of components are also present in components reflected from a belt background.
FIG. 27 is a graph showing the relationship between the normalized value of the specular reflection component and the diffuse reflection light output after the background portion fluctuation correction.
FIG. 28 is a graph showing the sensitivity of diffuse reflection light output.
FIG. 29 is a graph showing a result of conversion into a normalized value.
FIG. 30 is a graph showing the result of plotting the amount of adhesion obtained by inverting the normalized value against the measured value of the amount of adhesion by an electronic balance.
FIG. 31 is a graph showing the relationship between lot variation of optical detection means extracted from a large number of prototypes and diffuse reflection light output in gradation pattern detection.
FIG. 32 is a graph showing a relationship between lot variation of optical detection means extracted from a large number of prototypes and diffused reflected light output after sensitivity correction in gradation pattern detection.
FIG. 33 is a schematic front view of a color image forming apparatus of a system in which the images are superimposedly transferred to an intermediate transfer body in a four-tandem configuration and then collectively transferred to transfer paper.
FIG. 34 is a schematic front view of a color image forming apparatus of a system in which toner images are superimposedly transferred onto an intermediate transfer body by one photosensitive drum and then collectively transferred onto transfer paper.
[Explanation of symbols]
2,426 Intermediate transfer belt as intermediate transfer member
14Y, 14M, 14C, 14B Photoconductor Drum as Image Carrier
18 Transfer belt as detection target surface
51 LED as light emitting means
52 Specular reflection light receiving element as light receiving means
55 Diffuse reflected light receiving element as light receiving means
70 Toner pattern as gradation pattern
402 Photosensitive drum as one image carrier

Claims (27)

A gradation pattern of a plurality of powders having different adhesion amounts continuously formed on a detection target surface is arranged at a position facing the detection target surface, and has a light emitting unit and a light receiving unit, and has regular reflection light and diffuse reflection. Light is detected by optical detection means that can simultaneously detect light, and the specular reflected light output of the resulting gradation pattern is decomposed into specular reflected light components and diffuse reflected light components to extract only the specular reflected light components Then, this is converted into a normalized value, and the obtained normalized value obtains a first-order linear relationship in relation to the adhesion amount in the adhesion amount range in which the adhesion amount can be detected by specular reflection light. Specular reflection light output conversion method. A gradation pattern of a plurality of powders having different adhesion amounts continuously formed on a detection target surface is arranged at a position facing the detection target surface, and has a light emitting unit and a light receiving unit, and has regular reflection light and diffuse reflection. Light is detected by optical detection means capable of simultaneously detecting light, and a value obtained by multiplying the minimum value of the ratio of the regular reflection light output and the diffuse reflection light output of the obtained gradation pattern by the diffuse reflection light output is obtained, A regular reflection light output conversion value (= normalized value), which is a ratio of a value obtained by subtracting this value from the regular reflection light output and the regular reflection light output of the detection target surface, is obtained. A specular reflected light output conversion method, wherein a first-order linear relationship is obtained in relation to the attached amount in the attached amount range in which the attached amount can be detected by specular reflected light. A gradation pattern of a plurality of powders having different adhesion amounts continuously formed on a detection target surface is arranged at a position facing the detection target surface, and has a light emitting unit and a light receiving unit, and has regular reflection light and diffuse reflection. The light is detected by optical detecting means capable of simultaneously detecting light, and the diffuse reflected light is reduced to the minimum value of the ratio between the regular reflected light output increment and the diffuse reflected light output increment obtained from the difference between each output value when the light emitting means is off. Calculate a value obtained by multiplying the output increment, and subtract this value from the specular reflected light output increment to the specular reflected light output conversion value (= normalized value) which is the ratio of the specular reflected light output increment of the detection target surface. ), And obtaining a first-order linear relationship between the specular reflection light output conversion value and the adhesion amount in the adhesion amount range in which the adhesion amount can be detected by the regular reflection light. . A gradation pattern of a plurality of powders having different adhesion amounts formed continuously on the detection target surface is provided at a position opposed to the detection target surface, and has a light emitting means and a light receiving means, and has regular reflection light and diffusion. The reflected light is detected by optical detecting means capable of detecting the reflected light at the same time, and the specular reflected light output of the obtained gradation pattern is decomposed into a regular reflected light component and a diffuse reflected light component, and only the regular reflected light component is detected. Extract, convert this to a normalized value, and subtract the value obtained by multiplying the obtained normalized value by the background diffuse reflection light output directly reflected from the background surface of the detection target surface from the diffuse reflection light output. A diffuse reflection light output conversion value is obtained, and a first-order linear relationship is obtained with respect to the adhesion amount in the adhesion amount range in which the adhesion amount can be detected by specular reflection light. Reflected light output conversion method. A gradation pattern of a plurality of powders having different adhesion amounts continuously formed on a detection target surface is arranged at a position facing the detection target surface, and has a light emitting unit and a light receiving unit, and has regular reflection light and diffuse reflection. Light is detected by optical detection means capable of simultaneously detecting light, and a value obtained by multiplying the minimum value of the ratio of the regular reflection light output and the diffuse reflection light output of the obtained gradation pattern by the diffuse reflection light output is obtained, A regular reflection light output conversion value (= normalized value), which is a ratio of a value obtained by subtracting this value from the regular reflection light output and the regular reflection light output of the detection target surface, is obtained. The diffuse reflection light output conversion value is obtained by subtracting the value obtained by multiplying the background reflection light output directly reflected from the background surface of the detection target surface from the diffuse reflection light output. Adhesion amount range that can detect the adhesion amount by regular reflection light Diffuse reflection output conversion method characterized by obtaining the first-order linear relationship relative to the definitive adhesion amount. A gradation pattern of a plurality of powders having different adhesion amounts continuously formed on a detection target surface is arranged at a position facing the detection target surface, and has a light emitting unit and a light receiving unit, and has regular reflection light and diffuse reflection. The light is detected by optical detecting means capable of simultaneously detecting light, and the diffuse reflected light is reduced to the minimum value of the ratio between the regular reflected light output increment and the diffuse reflected light output increment obtained from the difference between each output value when the light emitting means is off. Calculate a value obtained by multiplying the output increment, and subtract this value from the specular reflected light output increment to the specular reflected light output conversion value (= normalized value) which is the ratio of the specular reflected light output increment of the detection target surface. ) Is obtained, and the value obtained by multiplying the converted value of the specular reflected light output by the diffuse reflected light output increment obtained from the difference between the diffuse reflected light output value when the light emitting means is turned off is subtracted from the diffuse reflected light output increment to obtain the diffuse reflected light. Output conversion value is calculated, and this diffuse reflection light output conversion value For it, the diffuse reflection light output conversion method characterized by obtaining the first-order linear relationship in relation to the adhesion amount of adhering weight range capable adhesion amount detection by the specularly reflected light. A specular reflected light output conversion value in the specular reflected light output conversion method according to any one of claims 1 to 3, and a diffuse reflected light output conversion according to any one of claims 4 to 6. Based on the first-order linear relationship with the diffuse reflection light output conversion value in the method, the diffuse reflection light output conversion value of a certain regular reflection light output conversion value is multiplied by a correction coefficient such that it becomes a certain value, whereby the diffuse reflection light output conversion is performed. A diffuse reflection light output conversion method characterized by converting a value into a value uniquely determined in relation to an amount of adhesion. The diffuse reflection light output conversion method according to claim 7,
A diffuse reflected light output conversion method, wherein when the brightness of the detection target surface is 20 or less, the diffuse reflected light output conversion value is replaced with the diffuse reflected light output. The diffuse reflection light output conversion method according to claim 7,
When the brightness of the detection target surface is 20 or less, the diffuse reflected light output conversion value is replaced with a diffuse reflected light output increment obtained from a difference from the diffuse reflected light output value when the light emitting unit is off. Diffuse reflected light output conversion method. A gradation pattern of a plurality of powders having different adhesion amounts formed continuously on the detection target surface is provided at a position opposed to the detection target surface, and has a light emitting means and a light receiving means, and has regular reflection light and diffusion. The reflected light is detected by optical detecting means capable of detecting the reflected light at the same time, and the specular reflected light output of the obtained gradation pattern is decomposed into a regular reflected light component and a diffuse reflected light component, and only the regular reflected light component is detected. Extracting, converting this into a normalized value, and converting the obtained normalized value into an attached amount based on a relational expression or a lookup table between the previously determined attached amount and the normalized value. Powder adhesion amount conversion method. A gradation pattern of a plurality of powders having different adhesion amounts continuously formed on a detection target surface is arranged at a position facing the detection target surface, and has a light emitting unit and a light receiving unit, and has regular reflection light and diffuse reflection. Light is detected by optical detection means capable of simultaneously detecting light, and a value obtained by multiplying the minimum value of the ratio of the regular reflection light output and the diffuse reflection light output of the obtained gradation pattern by the diffuse reflection light output is obtained, A regular reflection light output conversion value (= normalized value), which is a ratio of a value obtained by subtracting this value from the regular reflection light output and the regular reflection light output of the detection target surface, is obtained. Is converted into the amount of adhesion based on a relational expression between the amount of adhesion determined in advance and the converted value of the specular light output or the table data. A gradation pattern of a plurality of powders having different adhesion amounts continuously formed on a detection target surface is arranged at a position facing the detection target surface, and has a light emitting unit and a light receiving unit, and has regular reflection light and diffuse reflection. The light is detected by optical detecting means capable of simultaneously detecting light, and the diffuse reflected light is reduced to the minimum value of the ratio between the regular reflected light output increment and the diffuse reflected light output increment obtained from the difference between each output value when the light emitting means is off. Calculate a value obtained by multiplying the output increment, and subtract this value from the specular reflected light output increment to the specular reflected light output conversion value (= normalized value) which is the ratio of the specular reflected light output increment of the detection target surface. ), And converts the specular reflection light output conversion value into an adhesion amount based on a relational expression or a table data between a predetermined adhesion amount and the specular reflection light output conversion value. Amount conversion method. A specular reflected light output conversion value in the specular reflected light output conversion method according to any one of claims 1 to 3, and a diffuse reflected light output conversion according to any one of claims 4 to 6. The diffuse reflection light output obtained by multiplying a certain regular reflection light output conversion value by a correction coefficient such that the conversion value becomes a certain value based on a first-order linear relationship with the diffuse reflection light output conversion value in the method. A method for converting a powder adhesion amount, comprising converting a conversion value into an adhesion amount based on a relational expression or a table data between a previously determined adhesion amount and a diffuse reflection light output conversion value. In the powder adhesion amount conversion method according to claim 13,
When the brightness of the detection target surface is 20 or less, the diffused reflected light output conversion value is replaced with the diffused reflected light output. In the powder adhesion amount conversion method according to claim 13,
When the brightness of the detection target surface is 20 or less, the diffuse reflected light output conversion value is replaced with a diffuse reflected light output increment obtained from a difference from the diffuse reflected light output value when the light emitting unit is off. Powder adhesion amount conversion method. In an image forming apparatus capable of obtaining a color image by sequentially superimposing and transferring toner images formed on a plurality of image carriers onto a sheet-shaped recording medium carried on a transfer body,
16. An image forming apparatus, wherein the method according to claim 1 can be performed using the transfer body as the detection target surface and the powder as toner. In an image forming apparatus capable of obtaining a color image by sequentially superimposing and transferring toner images formed on a plurality of image carriers onto a sheet-shaped recording medium carried on a transfer body,
The image forming apparatus according to claim 1, wherein the method according to claim 1 can be performed using the image carrier as the detection target surface and the powder as toner. In the image forming apparatus capable of obtaining a color image by collectively transferring toner images formed on a plurality of image carriers onto the intermediate transfer body by sequentially superimposing and transferring the toner images onto a sheet-shaped recording medium,
The image forming apparatus according to claim 1, wherein the method according to claim 1 can be performed using the intermediate transfer member as the detection target surface and the powder as toner. In the image forming apparatus capable of obtaining a color image by collectively transferring toner images formed on a plurality of image carriers onto the intermediate transfer body by sequentially superimposing and transferring the toner images onto a sheet-shaped recording medium,
The image forming apparatus according to claim 1, wherein the method according to claim 1 can be performed using the image carrier as the detection target surface and the powder as toner. In an image forming apparatus capable of obtaining a color image by sequentially transferring a toner image formed on one image carrier onto an intermediate transfer body in a superimposed manner, and then collectively transferring the toner image to a sheet-shaped recording medium,
The image forming apparatus according to claim 1, wherein the method according to claim 1 can be performed using the intermediate transfer member as the detection target surface and the powder as toner. In an image forming apparatus capable of obtaining a color image by sequentially transferring a toner image formed on one image carrier onto an intermediate transfer body in a superimposed manner, and then collectively transferring the toner image to a sheet-shaped recording medium,
The image forming apparatus according to claim 1, wherein the method according to claim 1 can be performed using the image carrier as the detection target surface and the powder as toner. The image forming apparatus according to any one of claims 16 to 21,
An image forming apparatus comprising: converting a plurality of toner patterns formed on a detection target surface into an adhesion amount; and performing image density control based on the adhesion amount conversion value. 16. An apparatus for detecting an amount of applied powder, wherein the apparatus according to any one of claims 1 to 15 can be implemented. A gradation pattern having a different adhesion amount used in the specular reflection light output conversion method according to any one of claims 1 to 3,
A gradation pattern having at least one or more, preferably three or more, adhesion amount patterns in the vicinity of an adhesion amount at which the minimum value of the ratio between the regular reflection light output and the diffuse reflection light output is obtained. A gradation pattern having a different adhesion amount used in the specular reflection light output conversion method according to any one of claims 1 to 3,
At least one or more, preferably three or more, in the vicinity of the adhesion amount where the minimum value of the ratio between the regular reflection light output increment and the diffuse reflection light output increment obtained from the difference between each output value when the light emitting means is off is obtained. A gradation pattern characterized by having an adhesion amount pattern. A gradation pattern having a different adhesion amount used in the specular reflection light output conversion method according to any one of claims 1 to 3,
A gradation pattern having at least one or more, preferably three or more adhesion amount patterns within an adhesion amount range in which the specular reflection light output conversion value has a first-order linear relationship with the adhesion amount. In the gradation pattern according to any one of claims 24 to 26,
A gradation pattern, wherein the powder is a toner.

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