JP3884533B2 - Fiber optic device, light receiving component, and pattern acquisition device - Google Patents

Description

【００３１】
この表に示されるように、コア３２は、ＳｉＯ₂、Ａｌ₂Ｏ₃、Ｋ₂Ｏ、及びＰｂＯからなる透明ガラスから構成されており、屈折率１．９２を有している。また、光吸収体３４は、ＳｉＯ₂、Ｋ₂Ｏ、ＰｂＯ、ＭｎＯ₂、及びＣｒ₂Ｏ₃からなる黒色ガラスである。この黒色ガラスの厚さ２２２μｍの場合における分光透過率のスペクトラムを図５に示す。
【００３２】
図２に最も良く示されるように、コア３２の両端面３５ａ、３５ｂがコアの軸線３８に対して角度α₁で傾斜していることから、これらの端面３５ａ、３５ｂをそれぞれ含む入力端面２２及び出力端面２４も、軸線３８に対して角度α₁で傾斜している。本実施形態では、傾斜角α₁は、空気中からコア３２内に入射した光がコア３２の軸線３８からずれた方向に進行するように、所定の最大傾斜角α_1m以下に設定される。この最大傾斜角α_1mは、入射角９０°でコア３２に入射した光がコアの軸線３８と同一方向に進行するような傾斜角である。以下、図６を参照しながら、この最大傾斜角α_1mについて説明する。
【００３３】
図６は、傾斜角αが最大傾斜角α_1mに等しい場合におけるファイバ光学部品２０の部分拡大縦断面図である。図６中、ｎ_1コアはコア３２の屈折率、ｎ_aは空気の屈折率である。符号７０ａは空気中から入射角９０°でコア３２の端面３５ａに入射する光線、符号７０ｂは入射光線７０ａのコア３２中における屈折光線であり、β₁は、屈折光線７０ｂと端面３５ａの法線２８とがなす角度、すなわち屈折角である。図６では、最大傾斜角α_1mに対応する屈折角β₁をβ_1mと表している。
【００３４】
図６に示されるように、コア３２の端面３５ａの最大傾斜角α_1mは、入射角９０°でコア３２に入射した光がコア３２中を軸線３８と同一方向に進行するような傾斜角度である。この最大傾斜角α_1mは、次の２式から求めることができる。
【００３５】
ｎ_a・ｓｉｎ９０°＝ｎ_1コア・ｓｉｎβ_1m …（２）
α_1m＋β_1m＝９０° …（３）
この２式を解くと、
α_1m＝９０°−β_1m
＝９０°−ｓｉｎ^-1（ｎ_a／ｎ_1コア） …（４）
ｎ_a＝１と考えると、
α_1m＝９０°−ｓｉｎ^-1（１／ｎ_1コア） …（５）
のように表すことができる。
【００３６】
図７は、上記（５）式に基づいてコア３２の屈折率ｎ_1コアと最大傾斜角α_1mとの関係を示したグラフである。この図に示されるように、コア３２の屈折率が大きくなるに従って最大傾斜角も大きくなる。
【００３７】
端面３５ａの傾斜角α₁が上記の最大傾斜角α_1mに等しいとき、入射角９０°未満で空気中からコア３２に入射した光の屈折角はβ_1m未満となる。このような屈折角を有する屈折光線はコア３２の軸線方向からずれた方向に進行してコア３２と光吸収体３４との境界面に向かい、光吸収体３４に吸収されて減衰又は除去される。また、傾斜角α₁が最大傾斜角α_1mよりも小さい場合には、入射角９０°以内で入射する全ての光の屈折角がβ_1m未満となり、コア３２の軸線方向からずれた方向に進行するので、空気中から任意の入射角でコア３２に入射した光が光吸収体３４によって吸収され、減衰又は除去されることになる。結局、端面３５ａの傾斜角α₁が最大傾斜角α_1m以下であれば、空気中から端面３５ａを介してコア３２に入射した光のコア内での伝搬を実質的に阻止することができる。
【００３８】
本実施形態では、コア３２の屈折率は１．９２であり、この値に対応する最大傾斜角α_1mの値は５８．６°である。入力及び出力端面２２、２４の傾斜角α₁は、この最大傾斜角α_1mの値（＝５８．６°）に設定されている。
【００３９】
図８は、ファイバ光学部品２０の入力端面２２に検出対象物の一例である指８０を密着させ、光源８６を用いて指８０の背後から光８７を照射した状況において、部品２０の入力端面２２付近の内部構造を拡大して示した部分縦断面図である。指紋の凹凸構造に対応して、コアの端面３５ａと指８０の凸部８１とが密着する領域、及び端面３５ａと指の凹部８２とが空隙８３を挟んで密着していない領域が形成される。光源８６からの光８７のうち指８０を透過し凹部８２から出射して空隙８３中を進行する光線７２ａ、７３ａは、端面３５ａを透過してコア３２内に入射する。これらの光線７２ａ、７３ａの屈折光線７２ｂ、７３ｂは、上述のように、コア３２中においてコア３２の軸線方向からずれた方向に進行し、光吸収体３４によって減衰又は除去される。一方、指紋の凸部８１とコアの端面３５ａとが密着した領域に関しては、指８０の屈折率は空気の屈折率よりも大であることから、光源８６からの光８７のうち指８０の凸部８１を透過して端面３５ａに到達する光線の入射角と屈折角との関係が非密着領域における関係から変化する。このため、指紋の凸部８１から密着領域を通過してコア３２内に入射した光の中にはコア３２の軸線方向に進行する光線（例えば、図８の光線７１）も存在するようになる。このような光線は、光吸収体３４によって吸収されずにコア３２中を伝搬し、コア３２の端面３５ａの反対に位置する端面３５ｂに到達する。
【００４０】
このように、ファイバ光学部品２０においては、入力端面２２に密着した物体表面の凸部からコア３２内に入射する光のみが出力端面２４に到達する。物体表面の凹部から空隙を通過してコア３２内に入射する光は、光吸収体３４の吸収によりその伝搬過程で減衰し、実質的に消滅する。これにより、物体表面の凹凸に対応する明暗像、すなわち凹凸パターン像が、ファイバ光学部品２０によって入力端面２２から出力端面２４まで高いコントラストで伝送されることになる。
【００４１】
従来のファイバ光学デバイスの入力及び出力端面の最大傾斜角α_0mを、本実施形態に係るファイバ光学部品２０の入力及び出力端面の最大傾斜角α_1mと比較する。既に述べたように、従来のファイバ光学デバイスの最大傾斜角α_0mは、コアの屈折率をｎ_0コア、クラッドの屈折率をｎ_{0クラッド}と表すと、
α_0m＝ｓｉｎ^-1（ｎ_{0クラッド}／ｎ_0コア）−ｓｉｎ^-1（ｎ_a／ｎ_0コア） …（１）
である。これに対し、本実施形態に係るファイバ光学部品２０の最大傾斜角α_1mは、上記（４）式に示されるように、α_1m＝９０°−ｓｉｎ^-1（ｎ_a／ｎ_1コア）である。従って、α_0m＜α_1mが常に成立する。これは、空気中からコアに入射する光が除去されるような傾斜角は、クラッドを有しないファイバ光学部品２０の方がクラッドを有する従来のファイバ光学デバイスよりも大きくできることを示している。このため、ファイバ光学部品２０の出力端面２４に対する側面２５、２６の傾斜を比較的緩やかにして、部品２０の横幅を小さくすることが可能である。
【００４２】
次に、上述のように、第１ファイバ光学部品２０では、空気中からコア３２に入射した光がコア３２の軸線方向からずれた方向に進行するような角度で入力及び出力端面２２、２４が傾斜している。従って、逆に、出力端面２４と隣接する媒質が空気の場合は、コア３２内を軸線からずれた方向に進行する光しか出力端面２４から出射することができない。つまり、コア３２内を軸線にそって伝搬する光は、出力端面２４と隣接する媒質が空気であれば、端面３５ｂで全反射され出射できなくなる。従って、第１ファイバ光学部品２０と第２ファイバ光学部品４０とを連結する場合、部品２０の出力端面２４と部品４０の入力端面４２との間に空気が入り込まないようにする必要がある。このことに鑑みて、本実施形態では、出力端面２４と入力端面４２との間に光学接着剤６０を介在させている。この接着剤６０は、これらの端面間への空気の進入を防ぐシール材としての役割を果たしている。
【００４３】
次に、図２及び図４を参照しながら、第２のファイバ光学部品４０の構造を説明する。ファイバ光学部品４０も部品２０と同様に、光導波部である棒状のコア５２を複数備えており、これらの各コアは、各々の軸線５８が実質的に平行となるように延びている。これらのコア５２は、各々の軸線５８の間隔が実質的に均一となるように配置されている。各コア５２は、その軸線５８に垂直な円形の断面を有している。各コア５２の両端面５５ａ及び５５ｂは実質的に平行であり、軸線５８に対して共に角度α₂で傾斜している。この傾斜角度α₂は、図２においてコアの軸線５８のコア端面上への正射影から軸線５８に向かって時計回りに取った角度である。これらのコア５２の側面は、コア５２と同一方向に延びる筒状のクラッド５３によって密着包囲されている。コア５２の両端面と同様に、クラッド５３の両端面５６ａ及び５６ｂも実質的に平行であり、コアの軸線５８に対して共に角度α₂で傾斜している。このクラッド５３は、コア５２の屈折率よりも低い屈折率を有している。クラッド５３の側面は、光吸収体５４によって密着包囲されている。この光吸収体５４は、可視光域全域にわたってクラッド５３の材料よりも大きな吸収係数を示す材料から構成されている。この光吸収体５４は、コア５２及びクラッド５３と同一方向に延びながらクラッド５３の間に介在している。コア５２及びクラッド５３の両端面と同様に、光吸収体５４の両端面５７ａ及び５７ｂも実質的に平行であり、コアの軸線５８に対して共に角度α₂で傾斜している。コアの端面５５ａ、クラッドの端面５６ａ及び光吸収体の端面５７ａ、並びにコアの端面５５ｂ、クラッドの端面５６ｂ及び光吸収体の端面５７ｂは、それぞれ実質的に面一に集合して部品４０の側面４２、４４を形成している。このように、ファイバ光学部品４０は、コア５２、クラッド５３及び光吸収体５４が特定の方向に延びた構造体であり、側面４２、４４はこの構造体の両端面である。これらの端面４２、４４は、それぞれ第１ファイバ光学部品２０から出力された凹凸パターンが入力される面、出力される面となるので、以下では、面４２をファイバ光学部品４０の入力端面、面４４をファイバ光学部品４０の出力端面と呼ぶ。部品４０の出力端面４４は、本実施形態に係るデバイス１０の出力端面でもある。
【００４４】
第２ファイバ光学部品４０中のコア５２の配列ピッチは、第１部品２０中のコア３２の配列ピッチよりも小さくなっている。言い換えると、各ファイバ光学部品におけるコアの密度は、第２部品４０の方が第１部品２０よりも大きくなっている。これにより、製造時において第１部品２０と第２部品４０とが接着されるときに、第１部品２０中のコアの出力端面３５ｂと第２部品４０中のコアの入力端面５５ａとが効率よく対向するようになるので、第１部品２０から第２部品４０に効率よく光を伝送することができ、デバイス１０から明るい光学像を出力できるようになる。
【００４５】
コア５２、クラッド５３及び光吸収体５４は、第１ファイバ光学部品２０のコア３２や光吸収体３４と同様に、ファイバ光学デバイスを形成するのに従来から用いられている任意の材料を用いて構成することができる。本実施形態に係るコア５２、クラッド５３及び光吸収体５４の組成を、以下の表に示す。
【００４６】
【表２】

【００４７】
この表に示されるように、コア５２は、第１ファイバ光学部品２０のコア３２と同様に、ＳｉＯ₂、Ａｌ₂Ｏ₃、Ｋ₂Ｏ、及びＰｂＯからなる透明ガラスから構成されており、コア３２と同じ屈折率１．９２を有している。クラッド５３は、ＳｉＯ₂、Ａｌ₂Ｏ₃、Ｎａ₂Ｏ、Ｋ₂Ｏ、及びＰｂＯからなる透明ガラスから構成されており、屈折率１．５６を有する。光吸収体５４は、第１ファイバ光学部品２０の光吸収体３４と同様に、ＳｉＯ₂、Ｋ₂Ｏ、ＰｂＯ、ＭｎＯ₂、及びＣｒ₂Ｏ₃からなる黒色ガラスである。
【００４８】
光吸収体５４は、クラッド５３に進入した光を減衰させ又は除去するために設けられている。すなわち、光吸収体５４が設けられていない場合は、第１ファイバ光学部品２０中のコアの出力端面３５ｂから第２ファイバ光学部品４０中のあるクラッド５３内に入射した光が、そのクラッド５３を透過してそのクラッドに隣接するコア５２内に入射することがある。これにより、クラッド５３に入射した光とコア５２に入射した光とが一つのコア５２内で混在することになるので、デバイスの位置分解能が劣化してしまう。このことに鑑み、本実施形態では、クラッド５３に隣接するように光吸収体５４が設けられている。光吸収体５４はクラッド５３に入射した光を吸収してこの光を減衰させ又は除去するので、ファイバ光学部品４０では、クラッド５３に入射した光とコア５２に入射した光との混合が防止され、比較的高い解像度の光学像を出力できるようになっている。
【００４９】
上述のように、コア５２の両端面５５ａ、ｂは、コアの軸線５８に対して角度α₂で傾斜しているので、入力端面４２及び出力端面４４も、軸線５８に対して角度α₂で傾斜している。本実施形態に係るファイバ光学デバイスでは、傾斜角α₂は、第１部品２０中のコア３２から第２部品４０中のコア５２に入射した光がコア５２及びクラッド５３間の全反射条件を満足するような範囲に設定される。
【００５０】
以下、図９を参照しながら、傾斜角α₂の範囲について説明する。ここで、図９は、第１ファイバ光学部品２０と第２ファイバ光学部品４０との連結部分を拡大して示す部分縦断面図である。図９中、符号７４ａは入力側のコア３２中をコア３２の軸線方向に伝搬して端面３５ｂに向かう光線、符号７４ｂは光線７４ａの接着剤６０中における屈折光線であり、符号７４ｃは光線７４ｂの出力側コア５２中における屈折光線である。φ_iは、コア３２及び接着剤６０間の境界面への光線７４ａの入射角であり、φ_r′は、屈折光線７４ｂの屈折角であり、φ_rは、屈折光線７４ｃの屈折角であり、θはコア５２及びクラッド５３間の境界面に対する光線７４ｃの入射角の補角である。
【００５１】
入力側コア３２の屈折率をｎ_1コア、接着剤６０の屈折率をｎ_AD、出力側コア５２の屈折率をｎ_2コア、クラッド５３の屈折率をｎ_{2クラッド}と表すと、入力側コア３２と接着剤６０との境界面、及び接着剤６０と出力側コア５２との境界面におけるスネルの法則は、それぞれ
ｎ_1コア・ｓｉｎφ_i＝ｎ_AD・ｓｉｎφ_r′ …（６）
ｎ_AD・ｓｉｎφ_r′＝ｎ_2コア・ｓｉｎφ_r …（７）
のように表される。また、図９から明らかに、
α₁＋φ_i＝９０° …（８）
が成り立つ。更に、図９においてコア５２及びクラッド５３間の境界面、光線７４ｃ、並びに端面５５ａによって囲まれて形成される三角形の内角に関して、
（９０°−φ_r）＋（１８０°−α₂）＋θ＝１８０° …（９）
が成り立つ。
【００５２】
上記式から、出力側コアの端面５５ａ及び５５ｂの傾斜角α₂は、
α₂＝ｃｏｓ^-1（ｎ_1コア・ｃｏｓα₁／ｎ_2コア）＋θ …（１０）
と表される。
【００５３】
一方、入力側コア３２から出力側コア５２に入射した光がコア５２及びクラッド５３間の境界面における全反射条件を満足するためには、この光のコア５２及びクラッド５３間の境界面への入射角が臨界角以上であることが必要である。言い換えると、出力側コア５２に入射した光のコア５２及びクラッド５３間の境界面への入射角の補角が臨界角の補角以下であること、すなわち、
０≦θ≦θ_C（＝ｃｏｓ^-1（ｎ_{2クラッド}／ｎ_2コア）） …（１１）
θ_C：コア５２及びクラッド５３間の境界面における臨界角の補角
であることが必要である。
【００５４】
上記（１０）及び（１１）式より、入力側コア３２から出力側コア５２に入射した光がコア５２及びクラッド５３間の境界面における全反射条件を満足するような傾斜角α₂の範囲は、
ｃｏｓ^-1（ｎ_1コア・ｃｏｓα₁／ｎ_2コア）≦α₂
≦ｃｏｓ^-1（ｎ_1コア・ｃｏｓα₁／ｎ_2コア）＋ｃｏｓ^-1（ｎ_{2クラッド}／ｎ_2コア）
…（１２）
と求まる。
【００５５】
図９を参照した上記の説明では、α₂≧９０°−φ_rの場合を考えたが、α₂≦９０°−φ_rの場合も、光線７４ｃはコア５２及びクラッド５３間の境界面における全反射条件を満たしうる。図１０は、α₂≦９０°−φ_rの場合において、第１ファイバ光学部品２０と第２ファイバ光学部品４０との連結部分を拡大して示す部分縦断面図である。図１０においてコア５２及びクラッド５３間の境界面、光線７４ｃ、並びに端面５５ａによって囲まれて形成される三角形の内角に関して、
（９０°＋φ_r）＋α₂＋θ＝１８０° …（９Ａ）
が成り立つ。また、α₂≦９０°−φ_rの場合も、上記（６）〜（８）式が成り立つ。（６）〜（８）及び（９Ａ）式から、角度α₂は、
α₂＝ｃｏｓ^-1（ｎ_1コア・ｃｏｓα₁／ｎ_2コア）−θ …（１０Ａ）
と表される。この（１０Ａ）式及び上記（１１）式より、α₂≦９０°−φ_rの場合において入力側コア３２から出力側コア５２に入射した光がコア５２及びクラッド５３間の境界面における全反射条件を満足するような角度α₂の範囲は、
ｃｏｓ^-1（ｎ_1コア・ｃｏｓα₁／ｎ_2コア）−ｃｏｓ^-1（ｎ_{2クラッド}／ｎ_2コア）
≦α₂≦ｃｏｓ^-1（ｎ_1コア・ｃｏｓα₁／ｎ_2コア） …（１２Ａ）
と求まる。
【００５６】
上記（１２）及び（１２Ａ）をまとめると、コア３２からの光がコア５２及びクラッド５３間の境界面における全反射条件を満足するような傾斜角α₂の範囲は、
ｃｏｓ^-1（ｎ_1コア・ｃｏｓα₁／ｎ_2コア）−ｃｏｓ^-1（ｎ_{2クラッド}／ｎ_2コア）
≦α₂≦ｃｏｓ^-1（ｎ_1コア・ｃｏｓα₁／ｎ_2コア）＋ｃｏｓ^-1（ｎ_{2クラッド}／ｎ_2コア）
…（１２Ｂ）
と求まる。本実施形態のファイバ光学デバイスでは、ｎ_1コア＝１．９２、ｎ_2コア＝１．９２、ｎ_{2クラッド}＝１．５６、α₁＝５８．６°であるから、式（１２Ｂ）より、
２２．９°≦α₂≦９４．３° …（１３）
である。
【００５７】
本実施形態における傾斜角α₂は、更に、上記不等式（１３）で表される範囲内において、出力側コア５２内を進行する光がコア５２の出力端面５５ｂから端面５５ｂに対して垂直に出射するように定められている。角度α₂の値をこのように定めることで、出力端面４４に隣接する媒質にかかわらず出力端面４４から常に光が出射できるようになる。
【００５８】
図９を参照すると、α₁及びα₂が共に鋭角の場合、コア５２及びクラッド５３間の境界面、光線７４ｃ及び端面５５ｂによって囲まれて形成される三角形の内角に関して、
α₂＋θ＝９０° …（１４）
が成り立つ。この式と上記（１０）式から、傾斜角α₂は、
α₂＝（ｃｏｓ^-1（ｎ_1コア・ｃｏｓα₁／ｎ_2コア）＋９０°）／２ …（１５）
のように表される。本実施形態のファイバ光学デバイスでは、ｎ_1コア＝１．９２、ｎ_2コア＝１．９２、α₁＝５８．６°であるから、α₂＝７４．３°である。この値は、上記不等式（１３）を満足している。
【００５９】
なお、上記の不等式（１３）に示されるように、角度α₂は９０°の場合もありうる。つまり、第２ファイバ光学部品４０の入力及び出力端面４２、４４は、コア５２の軸線に対して傾斜している必要は必ずしもない。従って、α₂は、「第２ファイバ光学部品の端面と第２ファイバ光学部品中のコアの軸線とがなす角度」と一般的に呼ばれるべきである。この角度α₂は鈍角であっても良いが、α₁が鋭角でα₂が鈍角の場合、コア５２の伝搬光は端面５５ｂに対して垂直に出射することはできない。
【００６０】
α₁が鈍角の場合は、本実施形態のファイバ光学デバイス１０をこれまでと反対側から見た場合（図１のII−II線が伴う矢印の方向と反対方向から見た場合）であるから、α₁が鋭角の場合と同様に考えることができる。すなわち、α₁が鈍角でα₂が鋭角の場合は、α₁が鋭角でα₂が鈍角の場合と同様であり、α₁及びα₂が共に鈍角の場合は、α₁及びα₂が共に鋭角の場合と同様である。
【００６１】
本実施形態の出力側ファイバ光学部品４０と同じ値の屈折率を有するコア、クラッドを備えた従来技術のファイバ光学デバイスの端面の傾斜角α₀は、上記（１）式に基づいて、α₀≦２３．０°と求まる。本実施形態のファイバ光学デバイスにおいて、出力端面４４と第２ファイバ光学部品中のコアの軸線とがなす角度α₂の範囲は上記のように２２．９°≦α₂≦９４．３°であるから、角度α₂は従来技術における出力端面の傾斜角α₀よりも大きな値に設定することができる。このように、本実施形態のファイバ光学デバイス１０では、出力端面４４と第２ファイバ光学部品中のコアの軸線とがなす角度を比較的９０°に近く設定し、これにより出力端面４４に対する側面４５、４６の傾斜を緩やかにすることが可能である。
【００６２】
上記（４）式から明らかなように、入力側のファイバ光学部品２０のコア３２の屈折率が大きいほど、ファイバ光学デバイス１０の入力端面２２の最大傾斜角α_1mは大きくなる。また、上記（１５）式から明らかなように、入力側部品２０のコア３２の屈折率と傾斜角α₁を所定値に定めた場合、出力側のファイバ光学部品４０のコア５２の屈折率が大きいほど、ファイバ光学デバイス１０の出力端面４４から光が垂直に出射するような角度α₂の値は大きくなる。更に、上記（１５）式から明らかなように、２つのコア３２、５２の屈折率を所定値に定めた場合、ファイバ光学デバイス１０の入力端面２２の傾斜角α₁が大きいほど、ファイバ光学デバイス１０の出力端面４４から光が垂直に出射するような角度α₂の値も大きくなる。以上の事項から、出力端面４４から光が垂直に出射するようにファイバ光学デバイス１０を設計する場合において、角度α₁及びα₂を大きくするためには、第１及び第２ファイバ光学部品のコア３２、５２の屈折率を共にできる限り大きく定めることが望ましいことが分かる。
【００６３】
既に述べたように、本実施形態に係るファイバ光学デバイス１０の入力端面２２の傾斜角α₁は、従来のファイバ光学デバイスの入力端面の傾斜角より大きくすることが可能である。また、ファイバ光学デバイス１０の出力端面４４と第２ファイバ光学部品中のコアの軸線とがなす角度α₂も、従来のファイバ光学デバイスにおける出力端面の傾斜角よりも、より９０°に近い値にすることが可能である。このように、本実施形態に係るファイバ光学デバイス１０は、出力端面４４に対する側面４５、４６の傾斜を比較的緩やかにすることが可能なので、ＣＣＤ撮像素子等の光検出器に容易に取り付けることができる。また、ファイバ光学デバイス１０は、入力端面２２に対する側面２５、２６の傾斜、並びに出力端面４４に対する側面４５、４６の傾斜を比較的緩やかできるので、その横幅を比較的小さくすることが可能である。従って、本実施形態のデバイス１０を光検出器に取り付けることで、コンパクトな受光部品を作製することができる。
【００６４】
図１１は、本実施形態に係るファイバ光学デバイス１０が光検出器の一例であるＣＣＤ撮像素子９０に取り付けられて成る受光部品１００を示す概略図である。ＣＣＤ撮像素子９０は、ハウジング９４の凹部９５内にＣＣＤチップ９２を備えており、ＣＣＤチップ９２の受光面９３に入射した光学像を光電変換作用により電気信号に変換する。この電気信号は、ハウジング９４を通って外部に延びているリード端子９６を介して出力される。ファイバ光学デバイス１０の出力端面４４は、ＣＣＤ撮像素子９０の受光面９３に光学接着剤９８を介して接合されている。第１部品２０と第２部品４０との接着に用いた光学接着剤６０と同様に、光学接着剤９８としては、バルサム、エポキシ樹脂接着剤、紫外線硬化型樹脂などを任意に使用することができる。本実施形態では、セメダイン−１５６５が光学接着剤９８として使用されている。
【００６５】
この受光部品１００は、物体表面の凹凸パターン、例えば指紋、を取得する装置に使用することができる。図１２は、受光部品１００を用いた指紋取得装置の構成を示す概略図である。この指紋取得装置は、受光部品１００に加えて、受光部品１００の入力端面２２を照明するための光源８６、受光部品１００のリード端子９６に電気的に接続された信号処理装置１１０、信号処理装置１１０に電気的に接続された表示装置１１２を備えている。入力端面２２に指８０を押しつけて密着させ、その後、光源８６から光８７が指８０に照射されると、指８０の指紋パターン光学像が入力端面２２を介してファイバ光学デバイス１０に入力される。この指紋パターン像は、出力端面４４まで伝送され、ここから出射して、ＣＣＤチップ９２の受光面９３に入射する。これにより、指８０の指紋パターン像は、電気信号に変換されて信号処理装置１１０に送られる。信号処理装置１１０は、ＣＣＤ撮像素子９０からの出力に基づいて適切な処理を行い、その結果得られる画像信号を表示装置１１２に送って、表示装置１１２の画面上に指紋パターン像を表示させる。
【００６６】
本実施形態のファイバ光学デバイス１０では、出力端面４４から光が垂直に出射するように上記の角度α₂が定められているので、出力端面４４から出射した光はＣＣＤ撮像素子９０の受光範囲に確実に入射するようになる。この結果、ＣＣＤ撮像素子９０の出力のＳ／Ｎを高めて解像度の高いパターンを検出し、あるいは比較的明るいパターンを検出することが可能になる。
【００６７】
本発明は、上記実施形態に限定されるわけではなく、様々な変形が可能である。例えば、上記実施形態における出力側ファイバ光学部品４０の光吸収体５４はクラッド５３の側面を包囲するように設けられていたが、このような配置に限定されるわけではない。図１３は、上記実施形態と異なる光吸収体５４′を含んだ変形例に係る出力側ファイバ光学部品の横断面図である。この図に示される出力側ファイバ光学部品では、コア５２の側面を取り囲むクラッド５３′中に、コア５２と平行に延びる棒状の光吸収体５４′が埋設されている。
【００６８】
また、上記実施形態における出力側ファイバ光学部品４０は光吸収体５４を備えていたが、コアとコアを取り囲むクラッドのみから成り光吸収体を備えないファイバ光学部品を出力側ファイバ光学部品として用いることも可能である。但し、上述したように、出力側ファイバ光学部品が光吸収体を備えていると、クラッド内を進行する光が光吸収体により吸収されて減衰又は除去されるので、入力側のファイバ光学部品から出力側部品のクラッドに入射した光がコアに進入してコアの伝搬光と混在することによりパターン像の解像度が劣化する現象を抑制又は防止することができる。
【００６９】
また、上記実施形態では、入力側部品２０と出力側部品４０とが光学接着剤６０を用いて接着されているが、これ以外の方法により両部品を連結しても良い。例えば、入力側部品２０の出力端面２４と出力側部品４０の入力端面４２との間にシール材を介在させてから粘着テープ等を用いて両部品を連結することも可能である。シール材としては、透光性を有し、出力端面２４と入力端面４２との間に空気が介在することを防止できる任意の材料、例えばマッチングオイル等の屈折率整合材、を使用することができる。
【００７０】
上記実施形態に係るファイバ光学デバイス１０は、出力端面４４に対して垂直に光が出射するように構成されており、これにより、出力端面４４に隣接する媒質にかかわらず出力端面４４から光が出射できるようになっているので、応用範囲が広い。上記では、本実施形態に係るファイバ光学デバイス１０を光学接着剤でＣＣＤチップ９２に固定する例を説明したが、これ以外にも、例えば、本実施形態に係るファイバ光学デバイス１０と光検出器とを空気を介在させて離間し、両者の間にレンズを配置して両者を光学的に結合させるようなことが可能である。
【００７１】
以上、本発明の実施形態を詳細に説明したが、以下では、参考のために、本発明を考案するにあたって本発明者が行った幾つかの考察について述べておく。
【００７２】
本発明者は、上記実施形態と同様の構成の第１及び第２ファイバ光学部品からなるファイバ光学デバイスを考え、第２ファイバ光学部品の端面の傾斜角と第２部品の出力端面から空気中へ出射する光の出射角との関係について考察した。ここでは、第１部品のコアの屈折率を１．６２０、傾斜角は３５°とし、第２部品のコア、クラッドの屈折率をそれぞれ１．８２０、１．４９５とした。
【００７３】
図１４は、この場合における第２ファイバ光学部品の傾斜角と光の出射角との関係を示す図である。図１４の（I）はクラッドを有さない第１ファイバ光学部品、（II）はクラッドを有する第２ファイバ光学部品、（III）は空気層をそれぞれ示している。なお、図を分かり易くするために、（I）、（II）にはコアのみが図示されており、また、（I）は（１）〜（６）について共通に図示されている。（I）及び（II）中には、各ファイバ光学部品内を伝搬する光の進路が示されている。（III）中に示される角度は、空気中への光の出射角である。また、図１４の（１）〜（６）は、第２部品の端面の種々の傾斜角に対応している。
【００７４】
図１４（６）に示されるように、第２ファイバ光学部品の端面が傾斜していない場合は、光は伝達されずにコア外へ抜けていく。第２部品の傾斜角が７８．１９°の場合から光の伝達が可能になり（図１４（５））、その時の空気中への出射角は４５．７８°である。傾斜角が６６．６０°の場合、出射角は０°で垂直方向出射となり（図１４（３））、傾斜角が４９．９３°の場合（図示せず）に出射角は−９０°となって出力端面に沿った方向へ光が出射するようになる。
【００７５】
図１５（ａ）は、第１部品と第２部品とを連結したファイバ光学デバイス内の光の伝搬の様子を示し、図１５（ｂ）は、第２部品の傾斜角と光の出射角との関係を示している。出射角の範囲は上述のように４５．７８°〜−９０°であり、スラント角が４９．９３°以下であれば光は出力端面で反射され、空気中へは出射できなくなる。
【００７６】
次に、クラッドを有さない第１ファイバ光学部品とクラッドを有する第２ファイバ光学部品を直列に連結したときに空気中への出射方向が第２部品の出力端面に対して垂直になる場合を考察すると、図１６及び図１７のようになる。ここで、図１６は、第２部品の出力端面から光が垂直に出射する場合の第１及び第２部品の傾斜角を示す図である。図１６の（I）は第１部品（コアのみを図示）、（II）は第２部品（コアのみを図示）、（III）は空気層を示している。（I）及び（II）中には、各部品内を伝搬する光の進路が示されている。また、図１６の（１）〜（５）は、第１部品の傾斜角が５１．８８°、５０°、４５°、３５°、２５°の場合にそれぞれ対応している。
【００７７】
上述の（５）式から明らかなように、クラッドを有しない第１部品は、コアの屈折率が１．６２のとき傾斜角が５１．８８°以下であると、空気中からの外乱光がコア内を伝達できなくなる。５１．８８°以下の傾斜角と第２部品（コア屈折率１．８２０、クラッド屈折率１．４９５）の傾斜角との関係は、図１７に示されるようになる。第１部品の傾斜角が大きい程、第２部品の傾斜角も大きくしなければ、光が第２部品の出力端面から垂直方向に出射しないことが分かる。
【００７８】
【発明の効果】
以上、詳細に説明したように、本発明のファイバ光学デバイスでは、第１ファイバ光学部品の入力端面の傾斜角や、第２ファイバ光学部品の出力端面と第２コアの軸線とがなす角度を、比較的９０°に近くすることができるので、光検出器に容易に取り付けることができ、また、この取り付けにより形成される受光部品をコンパクトにすることができる。
【図面の簡単な説明】
【図１】本発明の一実施形態に係るファイバ光学デバイスを示す全体斜視図である。
【図２】図１のファイバ光学デバイスのII−II線に沿った部分縦断面図である。
【図３】図２のファイバ光学デバイスのIII−III線に沿った部分横断面図である。
【図４】図２のファイバ光学デバイスのIV−IV線に沿った部分横断面図である。
【図５】第１ファイバ光学部品中の光吸収体を構成する黒色ガラスの分光透過率のスペクトラムである。
【図６】入力端面の傾斜角が最大傾斜角に等しい場合における第１ファイバ光学部品の部分拡大縦断面図である。
【図７】第１ファイバ光学部品のコアの屈折率と入力端面の最大傾斜角α_1mとの関係を示すグラフである。
【図８】第１ファイバ光学部品の入力端面に指を密着させた状況における第１ファイバ光学部品の部分拡大縦断面図である。
【図９】第１ファイバ光部品と第２ファイバ光学部品との連結部分、及び第２ファイバ光学部品の端面を拡大して示す部分縦断面図である。
【図１０】第１ファイバ光部品と第２ファイバ光学部品との連結部分を示す部分縦断面図である。
【図１１】実施形態に係るファイバ光学デバイスをＣＣＤ撮像素子に取り付けてなる受光部品を概略的に示す図である。
【図１２】図１１の受光部品を備えた指紋取得装置の構成を示す概略図である。
【図１３】変形例に係る第２ファイバ光学部品の部分横断面図である。
【図１４】第２ファイバ光学部品の傾斜角と空気中への光の出射角との関係を示す図である。
【図１５】（ａ）は、第１ファイバ光学部品と第２ファイバ光学部品とを連結したファイバ光学デバイス内の光の伝搬の様子を示す図であり、（ｂ）は、第２ファイバ光学部品の傾斜角と光の出射角との関係を示す図である。
【図１６】第２ファイバ光学部品の出力端面から光が垂直に出射する場合の第１及び第２ファイバ光学部品の傾斜角を示す図である。
【図１７】第１ファイバ光学部品の傾斜角と第２ファイバ光学の傾斜角との関係を示す図である。
【図１８】従来技術のファイバ光学デバイスを示す全体斜視図である。
【図１９】図１８のファイバ光学デバイスのXIX−XIX線に沿った部分縦断面図である。
【図２０】図１８のファイバ光学デバイスをＣＣＤ撮像素子に取り付けてなる受光部品を概略的に示す図である。
【符号の説明】
１０…ファイバ光学デバイス、２０…第１ファイバ光学部品、２２…第１部品の入力端面、２４…第１部品の出力端面、３２…コア、３４…光吸収体、４０…第２ファイバ光学部品、４２…第２部品の入力端面、４４…第２部品の出力端面、５２…コア、５３…クラッド、５４…光吸収体、６０…光学接着剤。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fiber optic device used in a pattern acquisition apparatus such as a fingerprint detection apparatus.
[0002]
[Prior art]
A fiber optic device as described in JP-A-7-174947 has been conventionally known. FIG. 18 is a perspective view showing an example of such a fiber optical device, and FIG. 19 is a partial longitudinal sectional view of the device 500 taken along line XIX-XIX in FIG. This device 500 is normally used as a concavo-convex pattern image transmission means of a device (for example, a fingerprint detection device) that acquires a concavo-convex pattern on the surface of an object.
[0003]
As shown in FIGS. 18 and 19, the fiber optical device 500 has a structure in which a plurality of optical fibers are bundled and integrated so that their axes are parallel to each other. Both end surfaces 502 and 504 of the device 500 are formed by gathering both end surfaces of each optical fiber so as to be flush with each other. These end faces 502 and 504 are optical image input and output surfaces, respectively. The input end face 502 and the output end face 504 are parallel so that the optical image emitted from the output end face 504 is not distorted.
[0004]
As shown in FIG. 19, each of the optical fibers constituting the device 500 has a core 512 that is a light propagation portion as a center, and further includes a clad 513 that tightly surrounds the core 512, and a clad 513. It has a light absorber 514 that tightly surrounds it. Both end faces of each optical fiber have an angle α with respect to the axis 518 of the core.₀Therefore, the input and output end faces 502, 504 of the device are also angled α with respect to the axis 518 of the core.₀It is inclined at. In other words, the normals 506 and 508 of the input and output end faces 502 and 504 are not parallel to the core axis 518, and the angle formed by the normals 506 and 508 and the axis 518 is (90 ° −α₀). This inclination angle α₀Is set to such a value that even if light enters the core 512 from the air, the light is not totally reflected at the interface between the core 512 and the clad 513. That is, the inclination angle α of the input and output end faces 502 and 504₀Is included in an angle range in which the incident angle of light incident on the core 512 from the air with respect to the boundary surface between the core 512 and the cladding 513 is equal to or smaller than the critical angle at the boundary surface.
[0005]
As is well known, such an inclination angle α₀The range of the specific maximum tilt angle α_0mΑ ≦ α using_0mIt can be expressed as Where α_0mIs an angle that satisfies the following three expressions.
n_{0 core}・ Sinφ_C= N_{0 clad}sin 90 ° (Snell's law between core and clad)
n_{0 core}・ Sinβ_0m= N_aSin90 ° (Snell's law between air and core)
α_0m+ (90 ° + β_0m) + (90 ° -φ_C) = 180 ° (sum of interior angles of triangles)
Where n_{0 core}Is the refractive index of the core 512, n_{0 clad}Is the refractive index of the cladding 513, n_aIs the refractive index of air. Φ_CIs the critical angle at the interface between the core and cladding, and β_0mIs the angle between the refracted light beam 521 of the light beam 520 incident on the input end face 502 at an incident angle of 90 ° and the normal line 506 of the input end face 502, that is, the refraction angle of incident light at an incident angle of 90 °.
[0006]
Α obtained from the above three equations_0mUsing the tilt angle α₀The range of
α₀≦ α_0m= Sin^-1(N_{0 clad}/ N_{0 core}) -Sin^-1(N_a/ N_{0 core}(1)
It is expressed as
[0007]
When the detection target is brought into close contact with the input end face 502 and light is irradiated from behind or the side of the detection target, the light that has entered the core 512 through the air layer present in the concave portion of the detection target surface is Since it is incident on the boundary surface between the core and the clad at an incident angle that is less than the critical angle, it is not totally reflected at this boundary surface, but part of it leaks into the clad 513 and is absorbed by the light absorber 514. For this reason, the light that has entered the core 512 through the recess of the detection target is gradually attenuated, and most of the light cannot reach the output end face 504. On the other hand, since the refractive index of the detection target is larger than the refractive index of air in the region where the convex part of the detection target surface and the input end surface 502 are in close contact, the convex part of the detection target enters the core 512. Among the incident light, there is also light incident on the interface between the core and the clad at an incident angle larger than the critical angle. Such light propagates in the core while being totally reflected at the interface between the core and the clad, and reaches the output end face 504. Therefore, the light that exits from the output end face 504 is substantially only the light that has passed through the convex portion of the detection target and has entered the core 512. As a result, the device 500 can output a bright and dark image corresponding to the unevenness on the surface of the detection object, that is, an uneven pattern image with high contrast.
[0008]
FIG. 20 shows a light receiving component 600 formed by attaching the fiber optic device 500 to the CCD image sensor 90. The light receiving surface 93 of the CCD chip 92 provided in the CCD image pickup device 90 and the output end surface 504 of the device 500 are bonded using an optical adhesive 98. In this way, if the device 500 is fixed to the CCD detector 90 with the light receiving surface 93 of the CCD chip 92 and the output end surface 504 of the device 500 facing each other, it is possible to capture an uneven pattern image of the detection target. become.
[0009]
[Problems to be solved by the invention]
However, the inclination angle α of the input end face 502 set as described above.₀Since the angle is usually a considerably small angle, the shape of the longitudinal section of the fiber optic device 500 is a parallelogram having a large lateral width with a side inclined with respect to the base, as shown in FIG. When attaching the fiber optic device 500 to the CCD image pickup device 90, the device 500 is inserted into a recess 95 formed inside the housing 94 of the CCD image pickup device 90. However, since the horizontal width of the device 500 tends to increase, It is relatively difficult. Further, since the slope of the device 500 is steep, even after the device 500 is attached to the CCD image pickup device 90, problems such as the edge of the device 500 sticking out to the side of the CCD image pickup device 90 are likely to occur. There is a tendency to make the light receiving component 600 bulky.
[0010]
If the output end face 504 is perpendicular to the core axis, the light emitted from the output end face spreads over a certain range centered on the normal of the output end face, but the output end face is inclined with respect to the core axis. In the fiber optic device 500, the emitted light from the output end face spreads around the direction shifted from the normal direction of the output end face 504. For this reason, a relatively large portion of the light emitted from the output end face 504 does not fall within the light receiving range of the light receiving surface 93 of the CCD chip. As a result, the S / N of the output of the CCD image pickup device 90 is lowered, and the resolution of the uneven pattern image detected by the CCD image pickup device 90 is deteriorated, or the detected uneven pattern image is relatively dark.
[0011]
Further, as described above, the conventional fiber optic device 500 has an angle at which the incident angle of light incident on the core 512 from the air with respect to the boundary surface between the core 512 and the cladding 513 is equal to or smaller than the critical angle at the boundary surface. In contrast, since the input and output end faces 502 and 504 are inclined, when the medium adjacent to the output end face 504 is air, the incident light with respect to the interface between the core and the clad is only the core propagation light whose critical angle is less than the critical angle. The light cannot be emitted from the output end face 504. Therefore, light that is incident on the boundary surface between the core and the clad at an angle larger than the critical angle and propagates in the core by being totally reflected at this boundary surface is output if the medium adjacent to the output end surface is air. It is totally reflected at the end face and cannot be emitted. For this reason, when the fiber optic device 500 is attached to the CCD image sensor 90, a sealing material (optical adhesive or the like can be used between the output end face 504 and the light receiving face 93 of the CCD chip so that air does not enter between them. ) Is filled for the first time from the output end face 504. Therefore, the fiber optical device 500 and the CCD image pickup device 90 cannot be separated from each other through air, and a lens is disposed between them to optically couple them.
[0012]
The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a fiber optic device that can be easily attached to a photodetector and can form a compact light-receiving component for pattern acquisition. And
[0013]
[Means for Solving the Invention]
  The fiber optic device according to the present invention includes first and second fiber optic components. The first fiber optic encloses a plurality of substantially parallel first cores extending in a predetermined direction, and side surfaces of each of the first cores, and is larger than the first cores for at least one light wavelength. A first light absorber having an absorption coefficient. Both end faces of the first core and the first light absorber are substantially flush with each other to form an input end face and an output end face of the first fiber optical component. The second fiber optic comprises a plurality of substantially parallel second cores extending in a predetermined direction, a cladding surrounding each side of the second cores and having a lower refractive index than the second cores; Is included. Both end faces of the second core and the clad are substantially flush with each other to form an input end face and an output end face of the second fiber optical component. The second fiber optic component is coupled to the first fiber optic component such that its input end face faces the output end face of the first fiber optic component. The input end face of the first fiber optic is relative to the axis of the first coreSlopeInclined at an angle α1.Here, the inclination angle α of the input end face of the first fiber optical component ₁ N is the refractive index of air. _a , The refractive index of the first core is n _{1 core} Where α ₁ ≦ 90 ° -sin ^-1 (N _a / N _{1 core} ). In this case, the light incident on the first core from the air travels in a direction shifted from the axial direction of the core, and is absorbed by the light absorber and attenuated or removed. Thereby, the uneven | corrugated pattern of the object surface closely_contact | adhered to the input end surface of the 1st optical component comes to be transmitted with high contrast. The angle formed between the end face of the second fiber optic component and the axis of the second core is the refractive index of the first core n _{1 core} , The refractive index of the second core is n _{2 cores} , The refractive index of the cladding is n _{2 clad} And cos ^-1 (N _{1 core} ・ Cosα ₁ / N _{2 cores} ) -Cos ^-1 (N _{2 clad} / N _{2 cores} ) ≦ α ₂ ≦ cos ^-1 (N _{1 core} ・ Cosα ₁ / N _{2 cores} ) + Cos ^-1 (N _{2 clad} / N _{2 cores} ). If this inequality is satisfied, substantially all of the light incident on the second core from the first fiber optic will be totally reflected at the interface between the second core and the cladding, and the first fiber optic Light from the component can be efficiently transmitted by the second fiber optic component. Therefore,In this fiber optic device, the angle of inclination of the input end face of the first fiber optic component and the angle formed by the output end face of the second fiber optic component and the axis of the second core are set to values relatively close to 90 °. Can do. Therefore, this device can be easily attached to the photodetector, and the light receiving component formed by this attachment can be made compact.
[0015]
The angle formed between the input end face of the second fiber optic component and the axis of the second core is such that the light incident on the second core from the first fiber optic component is at the critical angle at the boundary surface between the second core and the cladding. It can determine so that it may inject with the above incident angle. By defining in this way, substantially all of the light incident on the second core from the first fiber optic component is totally reflected at the interface between the second core and the cladding, and from the first fiber optic component. Of light is efficiently transmitted by the second fiber optic.
[0016]
The angle formed by the output end face of the second fiber optical component and the axis of the second core is such that light incident on the second core from the first fiber optical component is perpendicular to the output end face from the output end face of the second fiber optical component. Can be determined so as to be emitted. By determining in this way, light can be emitted from this output end face regardless of the medium adjacent to the output end face of the second fiber optical component.
[0017]
  The input end face and the output end face of the first fiber optic component may be substantially parallel, and the input end face and the output end face of the second fiber optic component may be substantially parallel. At this time, the first and second fiber optic components may be coupled so that the output end surface of the first fiber optic component and the input end surface of the second fiber optic component are substantially parallel. In this case, the angle α₂But α₂= (Cos^-1(N_{1 core}・ Cosα₁/ N_{2 cores}) + 90 °) / 2 is preferable. When this equation is satisfied, light incident on the second core from the first fiber optic component is emitted perpendicularly to the output end surface from the output end surface of the second fiber optic component. Thereby, regardless of the medium adjacent to the output end face of the second fiber optical component, light can be emitted from this output end face.
[0018]
The first and second fiber optic components may be coupled with an output end face of the first fiber optic component and an input end face of the second fiber optic component interposed with a seal layer made of a translucent material. Thereby, it is possible to prevent air from interposing between the output end face of the first fiber optical component and the input end face of the second fiber optical component.
[0019]
The second fiber optic may be configured to further include a second light absorber that extends along the cladding while in contact with the cladding and has a greater absorption coefficient than the cladding for at least one light wavelength. Both end faces of the two-light absorber may each end at the input and output end faces of the second fiber optic component. When the second fiber optical component includes such a second light absorber, light traveling in the cladding is absorbed by the second light absorber and attenuated or removed. This suppresses the phenomenon that the resolution of the pattern image transmitted by this device deteriorates when light incident on the cladding of the second component from the first fiber optical component enters the second core and mixes with the core propagation light. Or it can be prevented.
[0020]
The first cores are arranged at equal intervals so that the intervals between the axes are a predetermined value, and the second cores are arranged at equal intervals so that the intervals between the axes are smaller than the predetermined values. May be. In this case, since the end surface of the first core and the end surface of the second core are efficiently opposed to each other, light can be efficiently transmitted from the first component to the second component.
[0021]
In another aspect of the present invention, there is provided a light receiving component including the above-described fiber optical device and a photodetector that converts an optical image incident on its light receiving surface into an electrical signal and outputs the electrical signal. Here, the photodetector is arranged so that the optical image output from the output end face of the second fiber optical component in the fiber optical device is incident on the light receiving surface.
[0022]
In still another aspect of the present invention, there is provided a pattern acquisition apparatus including the light receiving component and a light source that illuminates an input end surface of a first fiber optical component in a fiber optical device included in the light receiving component.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
1 to 4 are diagrams showing the configuration of a fiber optic device according to an embodiment of the present invention. FIG. 1 is an overall perspective view of the fiber optic device of the present embodiment. FIG. FIG. 3 is a partial cross-sectional view of the fiber optic device taken along line II-II in FIG. 1, FIG. 3 is a partial cross-sectional view of the fiber optic device in FIG. 2 taken along line III-III, and FIG. FIG. 4 is a partial cross-sectional view of the embodiment of the fiber optic device taken along line IV-IV in FIG. 2. FIG. 1 shows an XYZ orthogonal coordinate system for convenience of explanation.
[0024]
As shown in FIG. 1, the fiber optic device 10 according to the present embodiment includes two fiber optic components 20 and 40, and these fiber optic components are arranged in series with their side surfaces 24 and 42 facing each other. It has the structure connected to. The first fiber optic component 20 is a parallelepiped having square side surfaces 22, 24, 25, and 26 and parallelogram side surfaces 21 and 23, with the side surfaces 21 and 23 in the ZX plane as the top and bottom surfaces, respectively. It has a quadrangular prism shape extending in the Y-axis direction of FIG. Similarly, the fiber optic component 40 is a parallelepiped having rectangular side surfaces 42, 44, 45 and 46 and parallelogram side surfaces 41 and 43. The side surfaces 41 and 43 in the ZX plane are respectively illustrated as an upper surface and a bottom surface. 1 has a quadrangular prism shape extending in the Y-axis direction. The side surfaces 22, 24 of the first fiber optic 20 and the side surfaces 42, 44 of the second fiber optic 40 are all in the XY plane and parallel to each other, and all have substantially the same area. is doing.
[0025]
As best shown in FIG. 2, the first fiber optic component 20 and the second fiber optic component 40 are transparent optical elements with the former side surface 24 and the latter side surface 42 facing each other substantially in parallel. Bonded by an adhesive 60. As the optical adhesive 60, a balsam, an epoxy resin adhesive, an ultraviolet curable resin, or the like can be arbitrarily used. In this embodiment, Cemedine-1565, which is one of epoxy resin adhesives, is used as the optical adhesive 60.
[0026]
The structure of the first fiber optic component 20 will be described with reference to FIGS. 2 and 3. As shown in FIG. 2, the fiber optical component 20 includes a plurality of rod-shaped cores 32 that are optical waveguide portions. These cores extend so that each axis 38 is substantially parallel. The cores 32 are arranged so that the intervals between the axes 38 are substantially uniform. Each core 32 has a circular cross section perpendicular to its axis 38. Both end surfaces 35a and 35b of each core 32 are substantially parallel, and are both at a predetermined angle α with respect to the axis 38.₁It is inclined at. This inclination angle α₁2 is an angle taken clockwise from the orthogonal projection of the axis 38 of the core onto the end surface of the core in FIG.
[0027]
The side surface of the core 32 is tightly surrounded by the light absorber 34. The light absorber 34 is made of a material that exhibits a larger absorption coefficient than the material of the core 32 over the entire visible light region. The light absorber 34 is interposed between the cores 32 while extending in the same direction as the cores 32. Similar to both end surfaces 35a and 35b of the core 32, both end surfaces 37a and 37b of the light absorber 34 are substantially parallel, and both are at a predetermined angle α with respect to the axis 38 of the core.₁It is inclined at. The end surface 35a of the core and the end surface 37a of the light absorber, and the end surface 35b of the core and the end surface 37b of the light absorber are substantially flush with each other to form the side surfaces 22 and 24 of the first component 20. .
[0028]
Thus, the fiber optical component 20 is a structure in which the core 32 and the light absorber 34 extend in a specific direction, and the side surfaces 22 and 24 are both end surfaces of the structure. These end surfaces 22 and 24 are surfaces to which an optical image is input and output when the fiber optical component 20 is used as an optical image transmission unit, respectively. The input end face and the face 24 are referred to as the output end face of the fiber optical component 20. The input end face 22 of the component 20 is also an input end face of the fiber optic device 10 according to the present embodiment.
[0029]
The core 32 and the light absorber 34 can be constructed using any material conventionally used to form a typical fiber optic device. An example of the composition of the light absorber is disclosed in US Pat. No. 3,797,910, for example. Commonly used glass-based light absorbers include NiO, Co₂O_Three, CuO, Fe₂O_Three, MnO₂And various colored oxides. The compositions of the core 32 and the light absorber 34 according to this embodiment are shown in the following table.
[0030]
[Table 1]

[0031]
As shown in this table, the core 32 is made of SiO.₂, Al₂O_Three, K₂It is made of transparent glass made of O and PbO and has a refractive index of 1.92. The light absorber 34 is made of SiO.₂, K₂O, PbO, MnO₂, And Cr₂O_ThreeIt is the black glass which consists of. FIG. 5 shows a spectrum of spectral transmittance when the black glass has a thickness of 222 μm.
[0032]
As best shown in FIG. 2, the end faces 35a, 35b of the core 32 are at an angle α relative to the axis 38 of the core.₁Therefore, the input end face 22 and the output end face 24 including these end faces 35a and 35b are also angle α with respect to the axis 38.₁It is inclined at. In the present embodiment, the inclination angle α₁Is a predetermined maximum inclination angle α so that light incident into the core 32 from the air travels in a direction deviated from the axis 38 of the core 32._1mSet to: This maximum inclination angle α_1mIs an inclination angle such that light incident on the core 32 at an incident angle of 90 ° travels in the same direction as the axis 38 of the core. Hereinafter, this maximum inclination angle α will be described with reference to FIG._1mWill be described.
[0033]
FIG. 6 shows that the inclination angle α is the maximum inclination angle α._1mIs a partially enlarged longitudinal sectional view of the fiber optic component 20 in the case where In FIG. 6, n_{1 core}Is the refractive index of the core 32, n_aIs the refractive index of air. Reference numeral 70a denotes a light ray incident on the end face 35a of the core 32 from the air at an incident angle of 90 °, reference numeral 70b denotes a refraction light ray in the core 32 of the incident light ray 70a, and β₁Is an angle formed by the refracted ray 70b and the normal line 28 of the end face 35a, that is, a refraction angle. In FIG. 6, the maximum inclination angle α_1mRefraction angle β corresponding to₁Β_1mIt expresses.
[0034]
As shown in FIG. 6, the maximum inclination angle α of the end surface 35 a of the core 32._1mIs an inclination angle at which the light incident on the core 32 at an incident angle of 90 ° travels in the core 32 in the same direction as the axis 38. This maximum inclination angle α_1mCan be obtained from the following two equations.
[0035]
n_a・ Sin90 ° = n_{1 core}・ Sinβ_1m                         ... (2)
α_1m+ Β_1m= 90 ° (3)
Solving these two equations,
α_1m= 90 ° -β_1m
= 90 ° -sin^-1(N_a/ N_{1 core}(4)
n_a= 1
α_1m= 90 ° -sin^-1(1 / n_{1 core}(5)
It can be expressed as
[0036]
FIG. 7 shows the refractive index n of the core 32 based on the above equation (5)._{1 core}And the maximum inclination angle α_1mIt is the graph which showed the relationship. As shown in this figure, the maximum tilt angle increases as the refractive index of the core 32 increases.
[0037]
Inclination angle α of the end face 35a₁Is the maximum inclination angle α_1m, The refraction angle of light incident on the core 32 from the air at an incident angle of less than 90 ° is β_1mLess than. A refracted light beam having such a refraction angle travels in a direction deviating from the axial direction of the core 32, travels to the boundary surface between the core 32 and the light absorber 34, and is absorbed by the light absorber 34 to be attenuated or removed. . In addition, the inclination angle α₁Is the maximum inclination angle α_1mIs smaller than the angle of refraction of all light incident within an incident angle of 90 °._1mTherefore, the light that has entered the core 32 at an arbitrary incident angle from the air is absorbed by the light absorber 34 and attenuated or removed. After all, the inclination angle α of the end face 35a₁Is the maximum inclination angle α_1mIf it is below, the propagation in the core of the light which entered into the core 32 via the end surface 35a from the air can be blocked substantially.
[0038]
In this embodiment, the refractive index of the core 32 is 1.92, and the maximum inclination angle α corresponding to this value._1mThe value of is 58.6 °. Inclination angle α of the input and output end faces 22 and 24₁Is the maximum inclination angle α_1m(= 58.6 °).
[0039]
FIG. 8 shows the input end face 22 of the component 20 in a state where a finger 80 as an example of a detection target is brought into close contact with the input end face 22 of the fiber optical component 20 and light 87 is irradiated from behind the finger 80 using the light source 86. It is the fragmentary longitudinal cross-sectional view which expanded and showed the internal structure of the vicinity. Corresponding to the concave-convex structure of the fingerprint, a region where the end surface 35a of the core and the convex portion 81 of the finger 80 are in close contact, and a region where the end surface 35a and the concave portion 82 of the finger are not in close contact with the gap 83 therebetween are formed. . Of the light 87 from the light source 86, light rays 72 a and 73 a that pass through the finger 80, exit from the recess 82, and travel through the gap 83 pass through the end face 35 a and enter the core 32. As described above, the refracted light beams 72b and 73b of these light beams 72a and 73a travel in the direction shifted from the axial direction of the core 32 in the core 32, and are attenuated or removed by the light absorber 34. On the other hand, in the region where the convex portion 81 of the fingerprint and the end surface 35a of the core are in close contact, the refractive index of the finger 80 is larger than the refractive index of air. The relationship between the incident angle and the refraction angle of the light beam that passes through the portion 81 and reaches the end surface 35a changes from the relationship in the non-contact region. For this reason, light that travels in the axial direction of the core 32 (for example, the light beam 71 in FIG. 8) also exists in the light that has passed through the contact area from the convex portion 81 of the fingerprint and entered the core 32. . Such a light beam is propagated through the core 32 without being absorbed by the light absorber 34, and reaches the end surface 35b positioned opposite to the end surface 35a of the core 32.
[0040]
As described above, in the fiber optical component 20, only light that enters the core 32 from the convex portion of the object surface that is in close contact with the input end face 22 reaches the output end face 24. Light entering the core 32 from the concave portion of the object surface through the air gap is attenuated in the propagation process by absorption of the light absorber 34 and substantially disappears. As a result, a bright / dark image corresponding to the unevenness of the object surface, that is, an uneven pattern image is transmitted from the input end face 22 to the output end face 24 by the fiber optical component 20 with high contrast.
[0041]
Maximum tilt angle α of the input and output end faces of conventional fiber optic devices_0mThe maximum inclination angle α of the input and output end faces of the fiber optic component 20 according to the present embodiment_1mCompare with As already mentioned, the maximum tilt angle α of conventional fiber optic devices_0mIs the refractive index of the core n_{0 core}, The refractive index of the cladding is n_{0 clad}And
α_0m= Sin^-1(N_{0 clad}/ N_{0 core}) -Sin^-1(N_a/ N_{0 core}(1)
It is. In contrast, the maximum inclination angle α of the fiber optic component 20 according to the present embodiment._1mIs expressed by α as shown in the above equation (4)._1m= 90 ° -sin^-1(N_a/ N_{1 core}). Therefore, α_0m<Α_1mIs always true. This indicates that the inclination angle at which the light incident on the core is removed from the air can be made larger in the fiber optical component 20 having no cladding than in the conventional fiber optical device having the cladding. For this reason, it is possible to make the inclination of the side surfaces 25 and 26 with respect to the output end surface 24 of the fiber optical component 20 relatively gentle, and to reduce the lateral width of the component 20.
[0042]
Next, as described above, in the first fiber optic component 20, the input and output end faces 22 and 24 are at an angle such that light incident on the core 32 from the air travels in a direction shifted from the axial direction of the core 32. Inclined. Therefore, conversely, when the medium adjacent to the output end face 24 is air, only light traveling in the direction shifted from the axis within the core 32 can be emitted from the output end face 24. That is, the light propagating along the axis in the core 32 is totally reflected by the end face 35b and cannot be emitted if the medium adjacent to the output end face 24 is air. Therefore, when connecting the first fiber optic component 20 and the second fiber optic component 40, it is necessary to prevent air from entering between the output end surface 24 of the component 20 and the input end surface 42 of the component 40. In view of this, in the present embodiment, the optical adhesive 60 is interposed between the output end face 24 and the input end face 42. The adhesive 60 serves as a sealing material that prevents air from entering between these end faces.
[0043]
Next, the structure of the second fiber optic component 40 will be described with reference to FIGS. Similar to the component 20, the fiber optical component 40 includes a plurality of rod-shaped cores 52 that are optical waveguide portions, and these cores extend so that their respective axes 58 are substantially parallel to each other. The cores 52 are arranged such that the intervals between the axes 58 are substantially uniform. Each core 52 has a circular cross section perpendicular to its axis 58. Both end faces 55a and 55b of each core 52 are substantially parallel and are both angled α relative to the axis 58.₂It is inclined at. This inclination angle α₂2 is an angle taken clockwise from the orthogonal projection of the axis 58 of the core onto the end surface of the core in FIG. The side surfaces of the cores 52 are tightly surrounded by a cylindrical clad 53 extending in the same direction as the cores 52. Similar to both end faces of the core 52, both end faces 56a and 56b of the clad 53 are substantially parallel and are both angle α relative to the axis 58 of the core.₂It is inclined at. The clad 53 has a refractive index lower than that of the core 52. The side surface of the clad 53 is tightly surrounded by the light absorber 54. The light absorber 54 is made of a material that exhibits a larger absorption coefficient than the material of the cladding 53 over the entire visible light region. The light absorber 54 is interposed between the clad 53 while extending in the same direction as the core 52 and the clad 53. Similar to the end faces of the core 52 and the cladding 53, both end faces 57a and 57b of the light absorber 54 are substantially parallel, and are both angle α relative to the axis 58 of the core.₂It is inclined at. The end face 55a of the core, the end face 56a of the clad and the end face 57a of the light absorber, and the end face 55b of the core, the end face 56b of the clad and the end face 57b of the light absorber are gathered substantially flush with each other. 42 and 44 are formed. Thus, the fiber optical component 40 is a structure in which the core 52, the clad 53, and the light absorber 54 extend in a specific direction, and the side surfaces 42 and 44 are both end faces of the structure. Since these end faces 42 and 44 are surfaces to which the concave / convex pattern output from the first fiber optical component 20 is input and output, respectively, the surface 42 is hereinafter referred to as an input end surface and a surface of the fiber optical component 40. 44 is called an output end face of the fiber optical component 40. The output end surface 44 of the component 40 is also an output end surface of the device 10 according to the present embodiment.
[0044]
The arrangement pitch of the cores 52 in the second fiber optic component 40 is smaller than the arrangement pitch of the cores 32 in the first component 20. In other words, the density of the core in each fiber optic component is larger in the second component 40 than in the first component 20. Thereby, when the 1st component 20 and the 2nd component 40 are adhere | attached at the time of manufacture, the output end surface 35b of the core in the 1st component 20 and the input end surface 55a of the core in the 2nd component 40 are efficient. Since they face each other, light can be efficiently transmitted from the first component 20 to the second component 40, and a bright optical image can be output from the device 10.
[0045]
The core 52, the clad 53, and the light absorber 54 are made of any material conventionally used to form a fiber optic device, like the core 32 and the light absorber 34 of the first fiber optic component 20. Can be configured. The compositions of the core 52, the clad 53, and the light absorber 54 according to this embodiment are shown in the following table.
[0046]
[Table 2]

[0047]
As shown in this table, the core 52 is similar to the core 32 of the first fiber optic 20 in terms of SiO 2.₂, Al₂O_Three, K₂It is made of transparent glass made of O and PbO and has the same refractive index of 1.92 as the core 32. The cladding 53 is made of SiO.₂, Al₂O_Three, Na₂O, K₂It is made of transparent glass made of O and PbO and has a refractive index of 1.56. Similar to the light absorber 34 of the first fiber optical component 20, the light absorber 54 is made of SiO 2.₂, K₂O, PbO, MnO₂, And Cr₂O_ThreeIt is the black glass which consists of.
[0048]
The light absorber 54 is provided to attenuate or remove light that has entered the cladding 53. That is, when the light absorber 54 is not provided, the light incident on the clad 53 in the second fiber optical component 40 from the output end face 35b of the core in the first fiber optical component 20 passes through the clad 53. The light may pass through and enter the core 52 adjacent to the clad. As a result, the light incident on the clad 53 and the light incident on the core 52 are mixed in one core 52, so that the position resolution of the device is deteriorated. In view of this, in the present embodiment, the light absorber 54 is provided so as to be adjacent to the clad 53. Since the light absorber 54 absorbs the light incident on the clad 53 and attenuates or removes this light, the fiber optical component 40 prevents the light incident on the clad 53 and the light incident on the core 52 from being mixed. An optical image with a relatively high resolution can be output.
[0049]
As described above, both end faces 55a and 55b of the core 52 have an angle α with respect to the axis 58 of the core.₂The input end face 42 and the output end face 44 are also at an angle α with respect to the axis 58.₂It is inclined at. In the fiber optic device according to the present embodiment, the tilt angle α₂Is set in such a range that the light incident on the core 52 in the second component 40 from the core 32 in the first component 20 satisfies the total reflection condition between the core 52 and the clad 53.
[0050]
Hereinafter, with reference to FIG.₂The range will be described. Here, FIG. 9 is a partial longitudinal sectional view showing an enlarged connection portion between the first fiber optical component 20 and the second fiber optical component 40. In FIG. 9, reference numeral 74a is a light beam propagating in the axial direction of the core 32 in the core 32 on the input side and traveling toward the end face 35b, reference numeral 74b is a refracted light beam in the adhesive 60 of the light beam 74a, and reference numeral 74c is a light beam 74b. Refracted light rays in the output side core 52. φ_iIs the incident angle of the light ray 74a to the interface between the core 32 and the adhesive 60, and φ_r′ Is the refraction angle of the refracted light beam 74b, and φ_rIs the refraction angle of the refracted light beam 74 c, and θ is the complementary angle of the incident angle of the light beam 74 c with respect to the interface between the core 52 and the cladding 53.
[0051]
The refractive index of the input side core 32 is n_{1 core}, The refractive index of the adhesive 60 is n_AD, The refractive index of the output side core 52 is n_{2 cores}, The refractive index of the cladding 53 is n_{2 clad}In other words, Snell's law on the boundary surface between the input side core 32 and the adhesive 60 and the boundary surface between the adhesive 60 and the output side core 52 is respectively
n_{1 core}・ Sinφ_i= N_AD・ Sinφ_r′… (6)
n_AD・ Sinφ_r'= N_{2 cores}・ Sinφ_r                          ... (7)
It is expressed as Also, clearly from FIG.
α₁+ Φ_i= 90 ° (8)
Holds. Further, in FIG. 9, regarding the internal angle of the triangle formed by the boundary surface between the core 52 and the clad 53, the light ray 74c, and the end surface 55a,
(90 ° -φ_r) + (180 ° −α₂) + Θ = 180 ° (9)
Holds.
[0052]
From the above formula, the inclination angle α of the end faces 55a and 55b of the output side core₂Is
α₂= Cos^-1(N_{1 core}・ Cosα₁/ N_{2 cores}) + Θ (10)
It is expressed.
[0053]
On the other hand, in order for the light incident from the input-side core 32 to the output-side core 52 to satisfy the total reflection condition at the interface between the core 52 and the cladding 53, the light enters the interface between the core 52 and the cladding 53. The incident angle needs to be greater than the critical angle. In other words, the complementary angle of the incident angle of the light incident on the output-side core 52 on the boundary surface between the core 52 and the cladding 53 is equal to or smaller than the complementary angle of the critical angle, that is,
0 ≦ θ ≦ θ_C(= Cos^-1(N_{2 clad}/ N_{2 cores})) ... (11)
θ_C: Complementary angle of critical angle at interface between core 52 and cladding 53
It is necessary to be.
[0054]
From the above equations (10) and (11), the inclination angle α such that the light incident on the output side core 52 from the input side core 32 satisfies the total reflection condition at the interface between the core 52 and the clad 53.₂The range of
cos^-1(N_{1 core}・ Cosα₁/ N_{2 cores}) ≦ α₂
≦ cos^-1(N_{1 core}・ Cosα₁/ N_{2 cores}) + Cos^-1(N_{2 clad}/ N_{2 cores})
(12)
It is obtained.
[0055]
In the above description with reference to FIG.₂≧ 90 ° -φ_rWas considered, but α₂≦ 90 ° -φ_rIn this case, the light ray 74 c can satisfy the total reflection condition at the interface between the core 52 and the clad 53. FIG.₂≦ 90 ° -φ_rFIG. 6 is a partial longitudinal sectional view showing an enlarged connection portion between the first fiber optical component 20 and the second fiber optical component 40 in the case of FIG. In FIG. 10, regarding the internal angle of the triangle formed by the boundary surface between the core 52 and the cladding 53, the light ray 74c, and the end surface 55a,
(90 ° + φ_r) + Α₂+ Θ = 180 ° (9A)
Holds. Α₂≦ 90 ° -φ_rIn this case, the above formulas (6) to (8) hold. From the expressions (6) to (8) and (9A), the angle α₂Is
α₂= Cos^-1(N_{1 core}・ Cosα₁/ N_{2 cores}) −θ (10A)
It is expressed. From this equation (10A) and the above equation (11), α₂≦ 90 ° -φ_rIn this case, the angle α is such that the light incident on the output side core 52 from the input side core 32 satisfies the total reflection condition at the interface between the core 52 and the clad 53.₂The range of
cos^-1(N_{1 core}・ Cosα₁/ N_{2 cores}) -Cos^-1(N_{2 clad}/ N_{2 cores})
≦ α₂≦ cos^-1(N_{1 core}・ Cosα₁/ N_{2 cores}... (12A)
It is obtained.
[0056]
Summarizing the above (12) and (12A), the inclination angle α is such that the light from the core 32 satisfies the total reflection condition at the interface between the core 52 and the cladding 53.₂The range of
cos^-1(N_{1 core}・ Cosα₁/ N_{2 cores}) -Cos^-1(N_{2 clad}/ N_{2 cores})
≦ α₂≦ cos^-1(N_{1 core}・ Cosα₁/ N_{2 cores}) + Cos^-1(N_{2 clad}/ N_{2 cores})
... (12B)
It is obtained. In the fiber optic device of this embodiment, n_{1 core}= 1.92, n_{2 cores}= 1.92, n_{2 clad}= 1.56, α₁= 58.6 ° From Equation (12B),
22.9 ° ≦ α₂≦ 94.3 ° (13)
It is.
[0057]
Inclination angle α in this embodiment₂Further, within the range represented by the inequality (13), the light traveling in the output side core 52 is determined to be emitted perpendicularly from the output end face 55b of the core 52 to the end face 55b. Angle α₂In this way, the light can always be emitted from the output end face 44 regardless of the medium adjacent to the output end face 44.
[0058]
Referring to FIG. 9, α₁And α₂Are both acute angles, the internal angle of the triangle formed by the boundary surface between the core 52 and the cladding 53, the ray 74c and the end surface 55b,
α₂+ Θ = 90 ° (14)
Holds. From this equation and the above equation (10), the inclination angle α₂Is
α₂= (Cos^-1(N_{1 core}・ Cosα₁/ N_{2 cores}) + 90 °) / 2 (15)
It is expressed as In the fiber optic device of this embodiment, n_{1 core}= 1.92, n_{2 cores}= 1.92, α₁= 58.6 °, so α₂= 74.3 °. This value satisfies the above inequality (13).
[0059]
As shown in the inequality (13) above, the angle α₂May be 90 °. That is, the input and output end faces 42 and 44 of the second fiber optical component 40 do not necessarily have to be inclined with respect to the axis of the core 52. Therefore, α₂Is generally referred to as “the angle between the end face of the second fiber optic and the axis of the core in the second fiber optic”. This angle α₂May be obtuse, but α₁Is an acute angle and α₂Is obtuse, the propagation light of the core 52 cannot be emitted perpendicularly to the end face 55b.
[0060]
α₁Is an obtuse angle when the fiber optic device 10 of this embodiment is viewed from the opposite side (when viewed from the direction opposite to the direction of the arrow along the line II-II in FIG. 1).₁Can be considered in the same manner as in the case of an acute angle. That is, α₁Is obtuse and α₂Α is acute₁Is an acute angle and α₂Is the same as the obtuse angle, α₁And α₂If both are obtuse, α₁And α₂Both are the same as in the case of an acute angle.
[0061]
Inclination angle α of the end face of a conventional fiber optic device having a core and a clad having the same refractive index as the output side fiber optic component 40 of the present embodiment₀Is based on the above equation (1), α₀≦ 23.0 ° is obtained. In the fiber optic device of the present embodiment, the angle α formed between the output end face 44 and the axis of the core in the second fiber optic component.₂The range of 22.9 ° ≦ α as described above₂Since ≦ 94.3 °, the angle α₂Is the inclination angle α of the output end face in the prior art₀Can be set to a larger value. As described above, in the fiber optical device 10 of the present embodiment, the angle formed by the output end face 44 and the axis of the core in the second fiber optical component is set to be relatively close to 90 °, thereby the side face 45 with respect to the output end face 44. , 46 can be made gentle.
[0062]
As apparent from the above equation (4), the maximum inclination angle α of the input end face 22 of the fiber optical device 10 increases as the refractive index of the core 32 of the fiber optical component 20 on the input side increases._1mBecomes bigger. Further, as is clear from the above equation (15), the refractive index and the inclination angle α of the core 32 of the input side component 20.₁Is set to a predetermined value, the angle α is such that light is emitted vertically from the output end face 44 of the fiber optic device 10 as the refractive index of the core 52 of the fiber optic component 40 on the output side increases.₂The value of increases. Further, as is clear from the above equation (15), when the refractive indexes of the two cores 32 and 52 are set to a predetermined value, the inclination angle α of the input end face 22 of the fiber optical device 10₁Is larger, the angle α at which light is emitted vertically from the output end face 44 of the fiber optic device 10.₂The value of increases. From the above, when designing the fiber optic device 10 so that light is emitted vertically from the output end face 44, the angle α₁And α₂It can be seen that it is desirable to increase the refractive index of the cores 32 and 52 of the first and second fiber optic components as much as possible in order to increase.
[0063]
As already described, the inclination angle α of the input end face 22 of the fiber optic device 10 according to this embodiment.₁Can be made larger than the inclination angle of the input end face of the conventional fiber optic device. Further, an angle α formed by the output end face 44 of the fiber optical device 10 and the axis of the core in the second fiber optical component.₂However, it is possible to make the value closer to 90 ° than the inclination angle of the output end face in the conventional fiber optical device. As described above, the fiber optical device 10 according to the present embodiment can make the inclination of the side surfaces 45 and 46 with respect to the output end surface 44 relatively gentle, so that it can be easily attached to a photodetector such as a CCD image sensor. it can. Moreover, since the inclination of the side surfaces 25 and 26 with respect to the input end surface 22 and the inclination of the side surfaces 45 and 46 with respect to the output end surface 44 can be made relatively gentle, the fiber optical device 10 can have a relatively small lateral width. Therefore, a compact light receiving component can be manufactured by attaching the device 10 of the present embodiment to the photodetector.
[0064]
FIG. 11 is a schematic view showing a light receiving component 100 in which the fiber optical device 10 according to the present embodiment is attached to a CCD image pickup device 90 which is an example of a photodetector. The CCD image pickup device 90 includes a CCD chip 92 in the recess 95 of the housing 94, and converts an optical image incident on the light receiving surface 93 of the CCD chip 92 into an electrical signal by photoelectric conversion. This electrical signal is output through a lead terminal 96 extending outside through the housing 94. The output end face 44 of the fiber optical device 10 is bonded to the light receiving surface 93 of the CCD image pickup device 90 via an optical adhesive 98. Similar to the optical adhesive 60 used for bonding the first component 20 and the second component 40, as the optical adhesive 98, a balsam, an epoxy resin adhesive, an ultraviolet curable resin, or the like can be arbitrarily used. . In this embodiment, Cemedine-1565 is used as the optical adhesive 98.
[0065]
The light receiving component 100 can be used in an apparatus that acquires an uneven pattern on an object surface, such as a fingerprint. FIG. 12 is a schematic diagram illustrating a configuration of a fingerprint acquisition apparatus using the light receiving component 100. In addition to the light receiving component 100, this fingerprint acquisition device includes a light source 86 for illuminating the input end face 22 of the light receiving component 100, a signal processing device 110 electrically connected to the lead terminal 96 of the light receiving component 100, and a signal processing device. A display device 112 electrically connected to 110 is provided. When the finger 80 is pressed and brought into close contact with the input end face 22, and then light 87 is emitted from the light source 86 to the finger 80, a fingerprint pattern optical image of the finger 80 is input to the fiber optical device 10 through the input end face 22. . This fingerprint pattern image is transmitted to the output end face 44, exits from here, and enters the light receiving surface 93 of the CCD chip 92. Thereby, the fingerprint pattern image of the finger 80 is converted into an electric signal and sent to the signal processing device 110. The signal processing device 110 performs appropriate processing based on the output from the CCD image pickup device 90, sends an image signal obtained as a result to the display device 112, and displays a fingerprint pattern image on the screen of the display device 112.
[0066]
In the fiber optic device 10 of the present embodiment, the angle α is set so that light is emitted vertically from the output end face 44.₂Therefore, the light emitted from the output end face 44 surely enters the light receiving range of the CCD image pickup device 90. As a result, it is possible to detect a pattern with high resolution by increasing the S / N of the output of the CCD image sensor 90, or to detect a relatively bright pattern.
[0067]
The present invention is not limited to the above embodiment, and various modifications can be made. For example, the light absorber 54 of the output-side fiber optic component 40 in the above embodiment is provided so as to surround the side surface of the clad 53, but is not limited to such an arrangement. FIG. 13 is a cross-sectional view of an output-side fiber optic component according to a modification including a light absorber 54 ′ different from the above embodiment. In the output side fiber optical component shown in this figure, a rod-shaped light absorber 54 ′ extending in parallel with the core 52 is embedded in a clad 53 ′ surrounding the side surface of the core 52.
[0068]
Moreover, although the output side fiber optical component 40 in the above-described embodiment includes the light absorber 54, a fiber optical component that includes only the core and the clad surrounding the core and does not include the light absorber is used as the output side fiber optical component. Is also possible. However, as described above, if the output side fiber optical component includes a light absorber, the light traveling in the clad is absorbed by the light absorber and attenuated or removed. It is possible to suppress or prevent a phenomenon in which the resolution of the pattern image deteriorates due to the light incident on the clad of the output side component entering the core and mixed with the propagation light of the core.
[0069]
Moreover, in the said embodiment, although the input side component 20 and the output side component 40 are adhere | attached using the optical adhesive agent 60, you may connect both components by methods other than this. For example, a sealing material may be interposed between the output end surface 24 of the input side component 20 and the input end surface 42 of the output side component 40, and then both components may be connected using an adhesive tape or the like. As the sealing material, it is possible to use any material that has translucency and can prevent air from interposing between the output end face 24 and the input end face 42, for example, a refractive index matching material such as matching oil. it can.
[0070]
The fiber optic device 10 according to the above embodiment is configured to emit light perpendicular to the output end face 44, whereby light is emitted from the output end face 44 regardless of the medium adjacent to the output end face 44. Since it can be used, it has a wide range of applications. In the above, an example in which the fiber optical device 10 according to the present embodiment is fixed to the CCD chip 92 with an optical adhesive has been described. However, for example, the fiber optical device 10 according to the present embodiment, a photodetector, Can be separated by air, and a lens can be disposed between the two to optically couple them.
[0071]
Although the embodiments of the present invention have been described in detail above, some considerations made by the present inventors in devising the present invention will be described below for reference.
[0072]
The present inventor considers a fiber optic device composed of first and second fiber optic components having the same configuration as that of the above embodiment, and the inclination angle of the end surface of the second fiber optic component and the output end surface of the second component into the air. The relationship with the emission angle of the emitted light was considered. Here, the refractive index of the core of the first component was 1.620, the inclination angle was 35 °, and the refractive indexes of the core and cladding of the second component were 1.820 and 1.495, respectively.
[0073]
FIG. 14 is a diagram showing the relationship between the inclination angle of the second fiber optical component and the light emission angle in this case. In FIG. 14, (I) shows a first fiber optical component having no cladding, (II) shows a second fiber optical component having a cladding, and (III) shows an air layer. For easy understanding of the figure, only the core is shown in (I) and (II), and (I) is shown in common for (1) to (6). In (I) and (II), the path of light propagating through each fiber optical component is shown. The angle shown in (III) is the emission angle of light into the air. Moreover, (1)-(6) of FIG. 14 respond | corresponds to the various inclination angles of the end surface of 2nd components.
[0074]
As shown in FIG. 14 (6), when the end face of the second fiber optical component is not inclined, the light is not transmitted but passes out of the core. Light can be transmitted when the inclination angle of the second part is 78.19 ° (FIG. 14 (5)), and the emission angle into the air at that time is 45.78 °. When the inclination angle is 66.60 °, the emission angle is 0 ° and the light is emitted in the vertical direction (FIG. 14 (3)). When the inclination angle is 49.93 ° (not shown), the emission angle is −90 °. Thus, light is emitted in a direction along the output end face.
[0075]
FIG. 15A shows the state of light propagation in the fiber optic device in which the first component and the second component are connected, and FIG. 15B shows the inclination angle of the second component and the light emission angle. Shows the relationship. As described above, the range of the emission angle is 45.78 ° to −90 °. If the slant angle is 49.93 ° or less, the light is reflected by the output end face and cannot be emitted into the air.
[0076]
Next, when the first fiber optical component having no cladding and the second fiber optical component having the cladding are connected in series, the emission direction into the air is perpendicular to the output end face of the second component. Considering it, it becomes like FIG. 16 and FIG. Here, FIG. 16 is a diagram illustrating the inclination angles of the first and second components when light is emitted vertically from the output end face of the second component. FIG. 16 (I) shows the first part (only the core is shown), (II) shows the second part (only the core is shown), and (III) shows the air layer. In (I) and (II), the path of light propagating in each component is shown. Also, (1) to (5) in FIG. 16 correspond to cases where the inclination angle of the first component is 51.88 °, 50 °, 45 °, 35 °, and 25 °, respectively.
[0077]
As is clear from the above equation (5), the first component having no clad has a tilt angle of 51.88 ° or less when the refractive index of the core is 1.62, and disturbance light from the air is not generated. It becomes impossible to transmit in the core. The relationship between the inclination angle of 51.88 ° or less and the inclination angle of the second component (core refractive index 1.820, cladding refractive index 1.495) is as shown in FIG. It can be seen that as the tilt angle of the first component is larger, the light does not exit in the vertical direction from the output end face of the second component unless the tilt angle of the second component is also increased.
[0078]
【The invention's effect】
As described above in detail, in the fiber optical device of the present invention, the inclination angle of the input end surface of the first fiber optical component and the angle formed between the output end surface of the second fiber optical component and the axis of the second core are as follows: Since it can be relatively close to 90 °, it can be easily attached to the photodetector, and the light receiving component formed by this attachment can be made compact.
[Brief description of the drawings]
FIG. 1 is an overall perspective view showing a fiber optic device according to an embodiment of the present invention.
2 is a partial longitudinal sectional view taken along line II-II of the fiber optic device of FIG. 1. FIG.
3 is a partial cross-sectional view of the fiber optic device of FIG. 2 taken along line III-III.
4 is a partial cross-sectional view of the fiber optic device of FIG. 2 taken along line IV-IV.
FIG. 5 is a spectrum of spectral transmittance of black glass constituting the light absorber in the first fiber optical component.
FIG. 6 is a partially enlarged longitudinal sectional view of the first fiber optic component when the tilt angle of the input end face is equal to the maximum tilt angle.
FIG. 7 shows the refractive index of the core of the first fiber optical component and the maximum tilt angle α of the input end face._1mIt is a graph which shows the relationship.
FIG. 8 is a partially enlarged longitudinal sectional view of the first fiber optical component in a state where a finger is brought into close contact with the input end face of the first fiber optical component.
FIG. 9 is a partial vertical cross-sectional view showing an enlarged connection portion between a first fiber optic component and a second fiber optic component, and an end face of the second fiber optic component.
FIG. 10 is a partial longitudinal sectional view showing a connecting portion between a first fiber optic component and a second fiber optic component.
FIG. 11 is a diagram schematically showing a light receiving component in which the fiber optic device according to the embodiment is attached to a CCD image pickup device.
12 is a schematic diagram illustrating a configuration of a fingerprint acquisition apparatus including the light receiving component of FIG.
FIG. 13 is a partial cross-sectional view of a second fiber optic component according to a modification.
FIG. 14 is a diagram showing a relationship between an inclination angle of a second fiber optical component and an emission angle of light into the air.
FIG. 15A is a diagram showing a state of light propagation in a fiber optic device in which a first fiber optic component and a second fiber optic component are connected, and FIG. 15B is a diagram showing a second fiber optic component. It is a figure which shows the relationship between the inclination-angle of this and the light emission angle.
FIG. 16 is a diagram showing the tilt angles of the first and second fiber optical components when light is emitted vertically from the output end face of the second fiber optical component.
FIG. 17 is a diagram showing the relationship between the tilt angle of the first fiber optic component and the tilt angle of the second fiber optic.
FIG. 18 is an overall perspective view showing a conventional fiber optic device.
19 is a partial longitudinal sectional view taken along line XIX-XIX of the fiber optic device of FIG. 18. FIG.
20 is a diagram schematically showing a light receiving component in which the fiber optic device of FIG. 18 is attached to a CCD image pickup device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Fiber optical device, 20 ... 1st fiber optical component, 22 ... Input end surface of 1st component, 24 ... Output end surface of 1st component, 32 ... Core, 34 ... Light absorber, 40 ... 2nd fiber optical component, 42 ... Input end face of the second part, 44 ... Output end face of the second part, 52 ... Core, 53 ... Cladding, 54 ... Light absorber, 60 ... Optical adhesive.

Claims (10)

A fiber optic device comprising first and second fiber optic components,
The first fiber optic is
A plurality of substantially parallel first cores extending in a predetermined direction;
A first light absorber surrounding each side of these first cores and having a larger absorption coefficient than these first cores for at least one light wavelength;
And both end surfaces of the first core and the first light absorber are substantially flush with each other to form an input end surface and an output end surface of the first fiber optic component,
The second fiber optic is
A plurality of substantially parallel second cores extending in a predetermined direction;
Surrounding each side of these second cores and having a lower refractive index than these second cores;
And both end faces of the second core and the clad are substantially flush with each other to form an input end face and an output end face of the second fiber optical component,
The second fiber optic component is coupled to the first fiber optic component such that its input end face faces the output end face of the first fiber optic component;
The inclination angle alpha ₁ of the input end face of the first fiber optic is inclined with respect to the axis of the first core, and the refractive index of air n _a, the refractive index of the first core and n _{1 core,}
α ₁ ≦ 90 ° -sin ^-1 (N _a / N _{1 core} )
Satisfied,
The angle α ₂ formed by the end face of the second fiber optic component and the axis of the second core is defined as follows: the refractive index of the _{first core} is n _{1 core} ; the refractive index of the _{second core} is n _{2 core} ; when the refractive index n _{2 Klatt Bu,}
cos ^-1 (N _{1 core} / cos α ₁ / n _{2 core} ) -cos ⁻¹ (n _{2 clad} / n _{2 core} )
≦ α ₂ ≦ cos ⁻¹ (n _{1 core} · cos α ₁ / n _{2 core} ) + cos ⁻¹ (n _{2 clad} / n _{2 core} )
A fiber optic device characterized by satisfying   The angle formed between the input end face of the second fiber optic component and the axis of the second core is such that light incident on the second core from the first fiber optic component is at the boundary surface between the second core and the clad. 2. The fiber optic device according to claim 1, wherein the optical fiber device is set to be incident at an incident angle greater than a critical angle at the boundary surface.   The angle formed between the output end face of the second fiber optical component and the axis of the second core is such that light incident on the second core from the first fiber optical component is output from the output end face of the second fiber optical component. 2. The fiber optic device according to claim 1, wherein the fiber optic device is set to emit perpendicular to the end face.   The input end face and the output end face of the first fiber optic are substantially parallel, the input end face and the output end face of the second fiber optic are substantially parallel, and the first and second fiber optics 2. The fiber optic device according to claim 1, wherein the component is connected so that an output end face of the first fiber optic component and an input end face of the second fiber optic component are substantially parallel to each other. The angle α ₂ is
α ₂ = (cos ⁻¹ (n _{1 core} · cos α ₁ / n _{2 core} ) + 90 °) / 2
The fiber optic device according to claim 1, wherein:   The first and second fiber optic components are connected with an output end face of the first fiber optic component and an input end face of the second fiber optic component with a seal layer made of a translucent material interposed therebetween. The fiber optic device according to claim 1.   The second fiber optic further includes a second light absorber that extends along the clad while being in contact with the clad and has a larger absorption coefficient than the clad for at least one light wavelength. 2. The fiber optic device according to claim 1, wherein both end faces of the light absorber end at input and output end faces of the second fiber optic component, respectively.   The first cores are arranged at equal intervals so that the intervals between the respective axes become a predetermined value, and the second cores are arranged so that the intervals between the respective axes become smaller than the predetermined values. 2. The fiber optic device according to claim 1, which is arranged at intervals.   A light receiving component comprising: the fiber optical device according to claim 1; and a photodetector that converts an optical image incident on the light receiving surface into an electrical signal and outputs the electrical signal, wherein the photodetector is in the fiber optical device. A light receiving component arranged such that an optical image output from the output end surface of the second fiber optical component is incident on the light receiving surface of the photodetector. A pattern acquisition apparatus comprising: the light receiving component according to claim 9 ; and a light source that illuminates an input end face of the first fiber optical component in the fiber optical device included in the light receiving component.

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