JP3681874B2 - Light source device, multi-beam scanning device and image forming apparatus for multi-beam scanning device - Google Patents

Description

【００３１】
この結果から、一見するとイ．ロの場合は上記実施の形態が有利であり、ハ．ニの場合には、従来方式が有利である。
しかし、発明の解決課題に立ち戻ると、この発明において問題としている画素密度切り替え時間の短縮は、画像形成装置が動作できない時間を短縮することにあり、画素密度の切り換えに伴う画像形成装置における各種の条件の再設定のための時間である「画素密度切り換え時間」には、前記光源ユニットの回転に要する時間：Ｔ（回転）、作像条件の変更や回転多面鏡の回転数等の再設定に要する時間：Ｔ（設定）があり、一般に、Ｔ（回転）＞Ｔ（設定）であるので、上記画素密度切り換え時間は通常、時間：Ｔ（回転）により規制させる。
【００３２】
従って、画素密度の選択が新たになされるときは、画像形成装置の動作が可能になるまでに、必然に時間：Ｔ（設定）を必要とし、時間：Ｔ（回転）を時間：Ｔ（設定）よりも短くしてみても、全体としての画素密度切り替え時間が短縮されるわけでなく、画素密度切り替え時間を実質的に短縮するには、Ｔ（回転）＞Ｔ（設定）の条件において、Ｔ（回転）を短縮する必要があるのである。
【００３３】
このような観点からすると、従来方式は画素密度切り替え時間の有効な短縮につながらず、上記実施の形態の場合は、従来方式の場合に比して、画素密度を切り換えるときのＴ（回転）が有効に短縮されることにより、画素密度切り替え時間を有効に短縮することができる。
【００３４】
ところで、上に説明した実施の形態の場合、光源ユニットを基準態位：Ｈ．Ｐに位置させるのは例えば、画像形成装置のメインスイッチがオンにされたときだけであり、以後、光源ユニットは待機態位：ａを基準として回転制御が行われるので、回転に伴う微小な態位誤差が積み重なって、所望の画素密度に対応する動作態位に狂いが生じる虞れがある。
これを避ける方法の一つは、選択された画素密度で動作が終了したら、光源ユニットを必ず基準態位へ戻し（基準態位検出手段で検出する）、基準態位を確保した上で、基準態位を基準として定まる待機態位：ａに光源ユニットを位置させるようにすればよい。ただし、この方法だと、例えば、６００ｄｐｉでの動作が終わった直後に４００ｄｐｉでの動作が要求されるような場合に、一旦基準位置へ戻り、次いで待機態位へ移動し、さらに動作態位：Ｂへ移動するので、上記実施の形態に比して、時間：Ｔ（回転）が上記実施の形態の場合よりも長くなってしまう。
【００３５】
このような問題を回避するには、図４に示すように基準態位：Ｈ．Ｐと待機態位：ａとを合致させればよい。即ち、基準態位検出手段により検出される光源ユニットの基準態位：Ｈ．Ｐを待機態位：ａとして定める（請求項２）のである。
【００３６】
このようにすれば、待機態位：ａが常に一定するので、動作態位：Ａ，Ｂを常に正確に設定でき、しかも、画素密度切り替え時間を有効に短縮できる。
【００３７】
図５は、この発明の画像形成装置の実施の１形態を示している。この画像形成装置は、デジタルのカラー複写装置を兼ねたカラープリンタである。
先ずプリンタ部１２を説明する。
「潜像担持体」である光導電性の感光体２５は、帯電手段２６により均一帯電されたのち、先に、図１〜３に即して説明したマルチビーム走査装置（符号４０Ａで示す）による２ライン同時の光走査によりＹ潜像（イエロートナーにより化視化されるべき潜像）を書き込まれる。書込みのためにマルチビーム走査装置４０Ａに印加される画像信号は、後述する「読取部」において原稿を読み取って得られる画像信号でも、コンピュータ等で生成されたイメージ情報でもよく、フロッピディスク等に格納されたプリント用の画像情報をイメージ情報化したものでもよい。
【００３８】
書き込まれた静電潜像は現像装置２８（繁雑をさけるため、単一の装置として描いているが、実際には、Ｙ(イエロー)、Ｍ(マゼンタ)、Ｃ(シアン)、Ｋ(黒)色の各トナーによる現像を行う４つの現像装置の集合体である。）においてＹトナーで現像される。現像で得られたＹ画像は、カセット３３〜３５の何れかから配紙されたシート状の記録媒体（転写紙やＯＨＰシート(オーバヘッドプロジェクタ用の記録シート)）に転写される。
即ち、配紙された記録媒体はレジストローラ３６により、Ｙ画像の移動に同期をとって転写部へ送りこまれ、転写手段３０によりＹ画像を転写され、分離手段３１により感光体２５から分離する。分離した記録媒体は搬送ベルト３７により定着装置３８でＹ画像を定着され、装置下部の循環路５０により再度レジストローラ３６の位置に戻される。この間に、感光体２５はクリーニング装置３２により残留Ｙトナーを除去され、帯電手段２６により均一帯電され、マルチビーム走査装置４０ＡによりＭ潜像を書き込まれ、書き込まれたＭ潜像を現像装置２８にによりＭトナーで現像される。得られたＭ画像は、上記Ｙ画像と同様にして記録媒体に転写・定着され、上記と同様に循環路５０を介してレジストローラ３６の位置に戻される。同様にして、Ｃ潜像の形成・現像・Ｃ画像の転写・定着、Ｋ潜像の形成・現像・Ｋ画像の転写・定着が行われると、記録媒体上にはＹ，Ｎ，Ｃ，Ｋ画像の「４色画像の重なりあい」によりカラー画像が形成される。カラー画像を形成された記録媒体はトレイ３９上に排出される。
以上は、カラー画像形成の場合を説明したが、単色画像を形成する場合には、感光体２５の帯電・静電潜像の書込み、所望の色のトナーによる現像、得られた画像の記録媒体への転写・定着を行ってトレイ３９上に排出すればよい。
【００３９】
即ち、プリンタ部１２は、潜像担持体２５に静電潜像を形成し、形成された静電潜像をトナー像として顕像化し、得られるトナー画像を直接、シート状の記録媒体に転写し、転写されたトナー画像を記録媒体に定着するプロセスを行う画像形成装置であって、均一帯電された潜像担持体に静電潜像を書き込むための光走査装置として、図１等に即して説明した請求項６記載のマルチビーム走査装置を用いる画像形成装置（請求項７）である。
【００４０】
図５に示す画像形成装置はまた、複写すべき画像を読取り、画像信号化する手段を有する。この「複写すべき画像を読取り、画像信号化する手段」は、図５に示す、画像読取部１１である。読取るべき画像を有する原稿をＡＤＦ（自動原稿配紙装置）１３にセットすると、ＡＤＦ１３は該原稿を自動的にコンタクトガラス１４上にセットする。セットされた原稿はリフレクタ１６を有するランプ１５により照明される。ランプ１５はミラー１７とともに、図の右方へ所定の速度：Ｖで移動して原稿を照明走査する。ミラー１７による反射光束を折り返すミラー１８，１９は一体となって図の右方へ速度：Ｖ／２で移動し、原稿面からレンズ２１へ至る光路長を一定に保つ。光束はレンズ２１への入射に先立ってフィルタ２０により色分解され、固体イメージセンサ２２上に結像し、光電変換される。
光電変化された信号は画像処理部２３において２値化、多値化、階調処理、変倍処理等の画像処理を施され、色分解された画像の画像信号となり、マルチビーム走査装置４０Ａに送られる。上記の読取プロセスをフィルタ２０における色分解色を赤・緑・青の３色に順次換えて行うことで原稿画像が３原色に色分解して読み取られる。
【００４１】
なお、上には、動作態位がＡ，Ｂの２態位である場合の実施の形態を説明したが、この発明は、上記の場合に限らず３以上の動作態位がある場合に容易に適用できることはいうまでもない。
【００４２】
【発明の効果】
以上に説明したように、この発明によれば新規なマルチビーム走査装置用の光源装置・マルチビーム走査装置および画像形成装置を実現できる。
この発明のマルチビーム走査装置用の光源装置（請求項１〜５）によれば、画素密度切り替えに伴う光源ユニットの回転量を有効に小さくして画素密度切り替え時間の有効な短縮化を計ることができる。また請求項２記載の発明の光源装置は、待機態位：ａが基準態位として検出されるので、常に正確な動作態位を実現できる。請求項１記載の発明の光源装置は、最も離れた２つの動作態位の何れへも略等しい時間で光源ユニットを回転させることができる。請求項３記載の光源装置は、ステッピングモータの逆回転時のバックラッシュに起因する誤差を除くことができる。
【００４３】
また、この発明のマルチビーム走査装置（請求項６）は、上記光源装置を用いることにより画素密度の切り替えを速やかに実現でき、この発明の画像形成装置（請求項７）は、上記マルチビーム走査装置を用いることにより副数種の画素密度で画像形成を実行でき、画素密度の切り替えを速やかに行うことができる。
【図面の簡単な説明】
【図１】この発明のマルチビーム走査装置の実施の１形態を説明するための図である。
【図２】上記実施の形態における光源装置の光源ユニットの回転機構を説明するための図である。
【図３】上記実施の形態における光源ユニットの回転による、動作態位の切り替えを説明するための図である。
【図４】光源ユニットの回転による、動作態位の切り替えの別例を説明するための図である。
【図５】この発明の画像形成装置の実施の１形態を説明するための図である。
【符号の説明】
１ 光源ユニット
４ ステッピングモータ
４０ 光源装置
２５ 潜像担持体
４１ シリンドリカルレンズ
４４ ｆθレンズ
４２ 回転多面鏡[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light source device, a multi-beam scanning device, and an image forming apparatus for a multi-beam scanning device.
[0002]
[Prior art]
An image forming apparatus that forms an electrostatic latent image on a latent image carrier, visualizes the electrostatic latent image as a toner image, and transfers and fixes the obtained toner image to a sheet-like recording medium to obtain a desired image Is widely known as various printers and copiers. In such an image forming apparatus, in order to form an electrostatic latent image, an electrostatic latent image is written on a uniformly charged latent image carrier using an optical scanning device. Yes.
In an image forming apparatus that forms a latent image by optical scanning, as an optical scanning apparatus, a plurality of beams from a plurality of light emitting sources that are controlled to blink independently are deflected by a common optical deflector, and a common imaging optical system is used. It is intended to use a multi-beam scanning device that focuses light on a surface to be scanned as a plurality of light spots separated from each other in the sub-scanning direction, and simultaneously scans a plurality of lines.
As a light source device of such a multi-beam scanning device, a light source unit that emits a plurality of beams can be rotated around a predetermined reference axis, and a plurality of light spots on a surface to be scanned can be rotated by rotating the light source unit by a rotating means. It is intended to change the pixel density in the electrostatic latent image to be written by changing the separation width in the sub-scanning direction and changing the scanning line pitch of multi-beam scanning.
[0003]
In order to switch the pixel density, the light source unit is rotated to deflect the scanning line pitch, and the image forming system (latent image carrier, developing device, transfer device) is adapted to the newly set pixel density. The image forming conditions in the fixing device etc. and the rotational speed of the rotary polygon mirror serving as the optical deflector must be set. As described above, the time for setting various conditions in the image forming apparatus accompanying the switching of the pixel density (hereinafter referred to as the pixel density switching time) is T (rotation), which is the time required for the rotation of the light source unit. Assuming that the time required to set the conditions and the rotational speed of the rotating polygon mirror is T (setting), generally T (rotation)> T (setting), and therefore the pixel density switching time is usually determined by time: T (rotation). It will be regulated.
Since “image formation cannot be performed” during the pixel density switching time, it is desirable that the pixel switching time be as short as possible. The time: T (setting) is normally not a problem because it ends between the time when the start button of the image forming apparatus is pressed and the time when the optical scanning is started. If the (rotation) is long, the user of the image forming apparatus is “waited” for the time until the apparatus becomes usable.
For this reason, attempts have been made to shorten the pixel density switching time required for rotation of the light source unit, but it is still not sufficient.
[0004]
[Problems to be solved by the invention]
It is an object of the present invention to effectively shorten the time for rotating a light source unit in association with pixel density switching in a light source device of a multi-beam scanning device.
[0005]
[Means for Solving the Problems]
The light source device of the multi-beam scanning device according to the present invention “couples beams from a plurality of light emitting sources whose flashing is controlled independently to obtain a plurality of beams, and deflects the plurality of beams by a common optical deflector. In a multi-beam scanning device that condenses light beams separated in the sub-scanning direction on a surface to be scanned by a common imaging optical system, and simultaneously scans a plurality of lines, a beam from a plurality of light sources is emitted. A light source device that switches a pixel density in optical writing by rotating a light source unit that couples and emits a plurality of beams around a reference axis, thereby changing the interval between a plurality of lines that are simultaneously optically scanned. However, it is characterized by the following points.
That is, first, “reference position detection means” is provided.
The reference position detection means is means for detecting the reference position of the light source unit with respect to rotation around the reference axis.
Secondly, as the operation state of the light source unit, the operation states: A, B,. . N and standby state: a are set.
The “operating state” is a state in which the light source unit performs image writing by multi-beam scanning, and the “pixel density” varies depending on the operating state. That is, the pixel density is switched by switching the operation state.
The “standby state” is a state occupied when the light source unit does not perform multi-beam scanning.
[0006]
The operation state and the standby state are determined based on the reference state.
The standby state: a is set between the most distant operation states: A and N (so as not to overlap the operation states A and N). The most distant operating state: the angle between A and N is “an angle of 180 degrees or less”, and the standby state: a is included in the region of the angle of 180 degrees or less. When there is another operation state: B between the operation states: A and N, the standby state: a and the operation state: B may overlap.
[0007]
Third, control means (such as a microcomputer) for controlling the rotating means for rotating the light source unit controls the rotating means so that the light source unit is returned to the standby position after the completion of the desired optical scanning. Therefore, when a new multi-beam scan is performed, the light source device rotates from the standby state to the operation state corresponding to the desired pixel density.
Note that the plurality of lines simultaneously scanned by the plurality of light spots on the surface to be scanned may be adjacent to each other, and the lines scanned by the adjacent light spots have an interval of a plurality of lines. Also good.
[0008]
The reference position of the light source unit can be set as a position different from both the operating position and the standby position, but the reference position of the light source unit detected by the reference position detection means is the standby position: It can also be defined as a (Claim 2).
The standby position: a can be set as the most distant operation position: an intermediate position between A and N. (Claim 1) . In this way, the light source unit can be reached in substantially the same time when it rotates toward the operating state: A and when it rotates toward the operating state: N.
The standby state: a may also be set in the vicinity of the most frequently used state among the operation states: A to N. Alternatively, when there are three operation states, for example, these operation states are the operation states: A, B, N, and the operation states: A and N are farthest from each other, and the operation state: B Is between the operating states A and N, and the operating state: B is the most frequently used state, the standby state: a and the operating state: B may be matched. .
[0009]
As the “rotation drive means” of the rotation means for rotating the light source unit, various servo motors, in particular stepping motors, can be suitably used. Alternatively, it is preferable to cause the stepping motor to perform a backlash removal operation when it is positioned in the “standby position or reference position”. (Claim 3) . This is because the position error caused by backlash can be eliminated.
Operating means: A to N are equal to the number of types of switchable pixel densities, and this number is determined as a design condition of the image forming apparatus, but as a practical case, a light source unit corresponding to a different pixel density The operation state can be only two states of operation state: A and operation state: B. (Claim 4) .
In the above light source device, the light emitting sources that are controlled to blink independently are two semiconductor lasers, the beams from each semiconductor laser are coupled by separate coupling lenses, and then beam synthesis is performed using the polarization state of each beam. Can be emitted from the light source unit. (Claim 5) .
[0010]
The multi-beam scanning device according to the present invention is configured to “couple a beam from a plurality of light emitting sources whose blinking is controlled independently, and deflect the coupled plurality of beams by a common optical deflector. Is a multi-beam scanning device that condenses light beams that are separated from each other in the sub-scanning direction and simultaneously scans a plurality of lines on the surface to be scanned. Claims 1-5 A light source device for a multi-beam scanning device according to any one of the above is used. (Claim 6) .
Further, the image forming apparatus according to the present invention “forms an electrostatic latent image on a latent image carrier, visualizes the formed electrostatic latent image as a toner image, and the obtained toner image is directly or via an intermediate transfer medium. An image forming apparatus for performing a process of transferring a toner image to a sheet-like recording medium and fixing the transferred toner image on the recording medium, and for writing an electrostatic latent image on a uniformly charged latent image carrier As a scanning device, Claim 6 Use of the described multi-beam scanning device (Claim 7) .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 (a) Claim 6 It is a figure which shows one Embodiment of described "multi-beam scanning apparatus." In FIG. 1A, reference numeral 40 denotes a “light source device”.
The light source device 40 has a “light source unit” that can rotate around a reference axis. In this embodiment, two light beams are converted from the light source unit into parallel luminous fluxes, beam-shaped, and circularly polarized. In the state).
Two beams emitted from the light source device 40 (the two beams are close to each other and are shown as one beam in FIG. 1A in order to avoid complication of the drawing) are processed by the cylindrical lens 41 in the sub-scanning corresponding direction. Are formed in the vicinity of the deflection reflection surface of the rotary polygon mirror 42 as an optical deflector as a long line image in the direction corresponding to the main scanning, and when reflected by the deflection reflection surface, the fθ lens 44 and the optical path bending mirror 45 are formed. Through the exit window 46 of the housing 27 and irradiates the photoconductive photoconductor 25 which is the substance of the surface to be scanned, and forms an image as two light spots on the photoconductor 25 by the action of the fθ lens 44. To do. These two light spots are separated from each other in the sub-scanning direction. When the rotary polygon mirror 42 rotates at a constant speed, the photosensitive member 25 is simultaneously scanned by two lines.
Prior to the optical scanning, the two beams to be deflected are received by the light receiving element 48 via the mirror 47 and generate a synchronization signal for starting the optical scanning.
[0012]
In other words, the multi-beam scanning device according to the embodiment shown in FIG. 1 (a) couples beams from a plurality of light emitting sources whose flashing is controlled independently, and couples the coupled beams to a common optical deflector. A multi-beam scanning device which condenses light beams as a plurality of light spots which are deflected by a light source 41 and separated from each other in the sub-scanning direction on a scanning surface 25 by a common imaging optical system 41 and 44 and simultaneously scans a plurality of lines. Yes, as will be described later, the “light source device for a multi-beam scanning device” of the present invention is used as the light source device 40. (Claim 6) .
[0013]
FIG. 1B shows an optical arrangement inside the light source unit in the light source device 40.
In the light source unit, as shown in (b), semiconductor lasers 111 and 112 as two light emitting sources, coupling lenses 121 and 122 for coupling light beams from the semiconductor lasers 111 and 112, and a half wavelength A plate 130 and a polarizing prism 140, an aperture 150 and a quarter wave plate 160 are included.
The polarization prism 140 has a polarization separation film 142, which transmits approximately 100% of P-polarized light and reflects approximately 100% of S-polarized light.
Although the semiconductor lasers 111 and 112 are controlled to blink independently, the polarization reflection film 142 emits light as P-polarized light. Therefore, when the beam from the semiconductor laser 111 is coupled by the coupling lens 121, it passes through the polarization separation film 142 of the polarizing prism 140, passes through the aperture 150, and passes through the quarter wavelength plate 160 to be a light source unit. Ejected from. When the beam from the semiconductor laser 112 is coupled by the coupling lens 122, the beam is transmitted through the half-wave plate 130, and the polarization plane is rotated 90 degrees to become “S-polarized light with respect to the polarization separation film 142”. The light is totally reflected by the prism surface 141 of the polarizing prism 140, further reflected by the polarization separation film 142, exits from the polarizing prism 140, passes through the aperture 150, passes through the quarter wavelength plate 160, and exits from the light source unit.
[0014]
The action of the coupling lenses 121 and 122 is that the beam after the coupling becomes a “parallel beam” or “a divergent or convergent beam” according to the design of the optical system in the multi-beam scanning device. In this embodiment, it is assumed that the beam after the coupling becomes a “parallel beam”, that is, a “collimating effect”. Therefore, two light beams converted into parallel light beams are emitted from the light source unit.
[0015]
The coupling lenses 121 and 122 are “optical axis aligned with each other”.
That is, when light rays that coincide with the optical axes of the coupling lenses 121 and 122 are virtually traced, these light rays “match each other” in the optical path after the polarization separation film 142. As described above, the optical axes of the coupling lenses 121 and 122 that coincide with each other in the optical path after the polarization separation film 142 are referred to as “reference optical axes” of the light source unit.
At least one of the light emitting portions of the semiconductor lasers 111 and 112 is disposed at a minute distance from the optical axis of the corresponding coupling lens. For this reason, the two beams emitted from the light source unit form a minute angle with each other.
The aperture 150 blocks the peripheral portion of each beam and performs so-called “beam shaping” on each beam. Beam shaping is performed in order to make the spot shape of the light spot to be formed on the surface to be scanned an appropriate shape. The quarter-wave plate 160 is used to set each beam emitted from the light source unit to a “circularly polarized light” state so that “arrival light energy” on the scanned surface is not greatly affected by the polarization state of each beam. It is done. The aperture 150 and the quarter wavelength plate 160 may be provided separately from the light source unit.
[0016]
In the light source device 40 having the light source unit having the optical arrangement shown in FIG. 1B, the number of light emitting sources whose blinking is controlled independently is 2, and these light emitting sources are the semiconductor lasers 111 and 112, and each semiconductor The beams from the laser are coupled by separate coupling lenses 121 and 122, and then synthesized by utilizing the polarization state of each beam. (Claim 5) .
[0017]
In FIG. 1C, reference numerals 1110 and 1120 indicate “virtual two light emitting units in two beams” synthesized by the beam synthesizing unit. That is, in reality, the light emitting sections of the semiconductor lasers 111 and 112 are spaced apart from each other by a predetermined distance as shown in FIG. 1B, but the two light beams synthesized by the beam synthesizing means are virtually directed toward the light source side. If it follows, it will become the light emission parts 1110 and 1120 which adjoined each other, as shown in FIG.1 (c). These virtual light emitting units 1110 and 1120 are separated by a distance: dm in the main scanning correspondence direction, and are separated by a distance: ds in the sub scanning correspondence direction. When the linear distance between the virtual light emitting units 1110 and 1120 is “1” and the angle θ is defined as shown in the figure, dm = 1 · cos θ and ds = 1 · sin θ.
[0018]
FIG. 1 (d) shows light spots H1 and H2 formed on the surface to be scanned corresponding to the virtual light emitting portions 1110 and 1120, respectively. The light spots H1 and H2 are separated by a distance Dm in the main scanning direction and a distance Ds in the sub scanning direction.
If the imaging magnification of the common imaging optical systems 41 and 44 is “Mm” in the direction corresponding to the main scan and “Ms” in the direction corresponding to the sub-scan, “Dm = dm · Mm = Mm · l · cos θ” “Ds = ds · Ms = Ms · l · sin θ”.
Accordingly, by rotating the light source unit and changing the angle θ in FIG. 1C, the separation amount Ds in the sub-scanning direction of the light spots H1 and H2 on the surface to be scanned can be changed. . Therefore, by utilizing the rotation of the light source unit, the separation amount in the sub-scanning direction of the light spots H1 and H2 can be changed, and the pixel density can be switched by changing the scanning line pitch.
[0019]
Next, the rotation of the light source unit in the light source device will be described with reference to FIG.
2A and 2B, reference numeral 1 denotes a “light source unit”, reference numeral 2 denotes a “bracket”, reference numeral 3 denotes a “light source control board”, reference numeral 4 denotes a “stepping motor”, and reference numeral 6 denotes a “photo interrupter”. ”, 7 indicates“ spring ”, and 8 indicates“ control means ”.
As shown in FIG. 2A, the light source unit 1 having the optical arrangement described with reference to FIG. 1B has a cylindrical portion 100 (the quarter wavelength plate 160 is disposed in this portion. Are fitted in the fitting holes of the bracket 2. The tip of the cylindrical portion 100 is a flange 101, and a compressible spring 104 is provided between the flange 101 and the bracket 2, and the light source unit 1 can rotate to the bracket 2 by the elastic force of the spring 104. And it is equipped stably. The central axis Ax of the cylindrical portion 100 is the rotation axis of the light source unit 1 and is the “reference axis” described above, and substantially coincides with the “reference optical axis”. Therefore, the light source unit 1 can rotate around the reference axis Ax with respect to the bracket 2. The light source device 40 shown in FIG. 1 is attached to the housing 27 by the bracket 2 shown in FIG.
The light emission source control board 3 is for “performing light emission control of each light source in the light source unit”, and a harness from an external main board is inserted into a socket (not shown). The light source control board 3 is integrated with the light source unit 1 by being screwed to the screw fastening portions 201, 202, 203 formed on the light source unit 1 by screws 301, 302, 303.
A part of the light source unit 1 extends as a filler portion 102, and a tip portion thereof becomes a bent portion 103, which is located between the light emitting portion and the light receiving portion in the photo interrupter 6 (fixed to the bracket 2). It is like that. The “position of the light source unit 1” when the photo interrupter 6 detects the bent portion 103 is the reference position of the light source unit 1. Therefore, the bent portion 103 and the photo interrupter 6 constitute “reference position detecting means”.
[0020]
As shown in FIG. 2B, a tension spring 7 is applied between the filler portion 102 and the bracket 2, and the elastic force of the spring 7 applies a counterclockwise torque to the light source unit 1. . The counterclockwise rotation behavior of the light source unit 1 due to this torque is stopped when the rotation driving member by the stepping motor 4 contacts the filler portion 102.
The stepping motor 4 is held by a holding portion 201 formed on the bracket 2 as shown in FIG. 2A, and the rotation drive member is fixed around the bracket 2 as shown in FIG. Piercing through the boss 205 and contacting the filler portion 102.
2C, a male screw is formed on the rotating shaft 4a of the stepping motor 4, and the rotation driving member 401 is formed with a female screw that is cap-shaped and screwed into the male screw. It is screwed to the rotating shaft 4a. As shown in FIG. 2D, the outer peripheral portion of the rotation drive member 401 has a “shape obtained by cutting a part of a cylinder in parallel with the cylinder axis”, and has a cross-sectional shape of the rotation drive member 401. The rotation is prevented by passing through the “hole”.
Therefore, when the rotation shaft 4a of the stepping motor 4 rotates, the rotation driving member 401 is displaced in the direction of the rotation axis of the stepping motor 4 due to the meshing of the screws. Due to this displacement, the filler portion 102 rotates the light source unit 1 clockwise in FIG. 2B against the elastic force of the spring 7 or the elastic force of the spring 7 rotates the light source unit 1 counterclockwise. Let As a result, the light source unit 1 can be rotated in the forward and reverse directions. That is, the filler unit 102 of the light source unit 1, the stepping motor 4 and the rotation driving member 401, the detent 205, and the spring 7 constitute “rotating means”, and the stepping motor 4 constitutes “rotation driving means”. The driving of the stepping motor 4 is controlled by the control means 8.
[0021]
In the embodiment being described, the “pixel density” of writing by multi-beam scanning is switched between “two pixel densities” of 600 dpi and 400 dpi.
In FIG. 3, the operation state: A is “the operation state of the light source unit that performs writing at a pixel density of 600 dpi”, and the operation state: B is “the operation state of the light source unit that performs writing at a pixel density of 400 dpi”. The operation states of the light source unit 1 corresponding to different pixel densities are only two states of operation state: A and operation state: B. (Claim 4) . Reference symbol Ax indicates the “reference axis (substantially coincident with the reference optical axis)”.
Reference H. P indicates “reference position”. P is detected by the “reference position detection means” by the bent portion 103 and the photo interrupter 6 described above.
[0022]
The standby state: a is set between the operation states A and B that are farthest from each other and so as not to overlap these operation states. Operating position: A, B and standby position: a is the reference position: H. P is set as a reference.
[0023]
In this embodiment, the “reference position detection” of the light source unit is periodically performed.
For example, the reference position is detected when the main switch in the image forming apparatus is turned on at “Morning first”. At this time, the light source unit is in the standby state: a, but when the main switch is turned on, the “control means” such as a microcomputer reversely rotates the stepping motor as part of the initial setting program of the image forming apparatus. The light source unit is in the reference position: Bring to P. At this time, since the stepping motor rotates in the reverse direction, a “backlash removal operation” is performed in order to eliminate an error caused by “backlash”.
This process is indicated by arrow FA in FIG.
That is, in order to eliminate an error due to backlash, the light source unit is temporarily set in the reference position: H.264. Pass P, and then reverse to the reference position: H. The control means 8 that receives the output of the reference position detection means controls the stepping motor 4 to stop at the detected position. Subsequently, the control means 8 rotates the stepping motor forward to rotate the light source unit, and brings the light source unit into the standby state: a (arrow FB). Thereafter, the reference state detection is not performed until the main switch is turned off and is newly turned on.
[0024]
When the pixel density: 600 dpi is selected, the controller 8 rotates the stepping motor in the forward direction to bring the light source unit to the operating position: A (arrow FC), and when the predetermined multi-beam scanning is completed, the stepping motor Is reversed to return the light source unit to the standby position: a (arrow FE). Also at this time, the backlash removal operation is performed. When the pixel density: 400 dpi is selected, the control device 8 reverses the stepping motor and brings the light source unit from the standby state a to the operating state: B (arrow FD “backlash removal operation” is performed. When the predetermined multi-beam scanning is completed, the stepping motor is rotated forward to return the light source unit to the standby state: a (arrow FF).
[0025]
That is, the “light source device” in the embodiment described with reference to FIGS. 1 to 3 obtains a plurality of beams by coupling beams from a plurality of light emitting sources 111 and 112 that are controlled to blink independently. The plurality of beams are deflected by a common optical deflector 42 and condensed as a plurality of light spots separated in the sub-scanning direction on the surface to be scanned 25 by a common imaging optical system 41, 44. In a multi-beam scanning device that performs optical scanning at the same time, a light source unit that couples beams from a plurality of light emission sources and emits a plurality of beams is rotated around a reference axis, thereby spacing between multiple lines that are simultaneously optically scanned. Is a light source device in which the pixel density in optical writing is switched by changing the reference position of the light source unit 1 with respect to rotation around the reference axis Ax: H Reference position detection means 103 and 6 for detecting P, and the operation states of the light source units corresponding to different pixel densities, which are determined based on the reference position, are defined as an operation state: A and an operation state: B. When the standby state of the light source unit 1 is assumed to be the standby state: a, the standby state: a is set between the operation states A and B farthest from each other, and rotating means for rotating the light source unit 1 is provided. The control means 8 for controlling controls the rotation means so that the light source unit 1 is returned to the standby state: a after the completion of the desired optical scanning (Claim 1), and the rotation drive means of the rotation means is a stepping motor. 4 and the control means 8 rotates the stepping motor 4 in the reverse direction to move the light source unit 1 in the operating state: B or the standby state: H.3. When placed in the P or reference position, the stepping motor 4 performs the backlash removal operation. (Claim 4) .
[0026]
Now, the number of steps of the stepping motor 4 required for the rotation represented by arrows FB, FC, and FF in FIG. 3 is SB, SC, and SF, respectively, and the minimum number of steps required for the backlash removal operation (reciprocating steps). Number) is SBR. Then, the number of steps SA, SD, and SE accompanying the arrows FA, FD, and FE in FIG. 3 are SA = SB + SBR, SD = SF + SBR, and SE = SC + SBR, respectively. The minimum number of steps required for the backlash removal operation: SBR requires only a few steps. From FIG. 3, SA> SB, SD> SF, SE> SC are clear.
[0027]
Conventionally, the following two methods have been intended for the rotation of the light source unit of the light source device of the multi-beam scanning device in which the pixel density of 600 dpi and 400 dpi can be switched.
In other words, in the first method, the light source unit is operated when the multi-beam scanning is not performed. P, which is rotated to realize the selected operation state: A, B, and always after the end of multi-beam scanning, the reference position: H. The method returns to P.
This method is not preferable because the time for controlling the pixel density switching time: T (rotation) is large and the pixel density switching time becomes long.
In the second method, the light source device stays in the operation state corresponding to the pixel density selected last, and when the pixel density is switched, from the previous operation state to the new operation state. It is rotated. With this method, the pixel density switching time is effectively shortened.
[0028]
Therefore, the time T (rotation) in the conventionally intended second pixel density switching method and the case of the above embodiment will be compared.
In order to simplify the explanation, in the above embodiment, the standby state: a is set to an intermediate position between the operating states: A and B (claim 1). Then, in the number of steps, there is a relationship of SC = SF and SD = SE.
[0029]
Consider the following four cases as pixel density switching.
The light source unit is in the standby state: a in the above embodiment, and in the operating state: A or B in the conventional method.
A. When operation at 400 dpi is requested after operation at 600 dpi
B. When operation at 600 dpi is required after operation at 400 dpi
C. When operation at 400 dpi is requested after operation at 400 dpi
D. When operation at 600 dpi is required after operation at 600 dpi
The time: T (rotation) associated with the switching of the operation state at this time is represented by the number of steps of the step motor (the number of steps is proportional to the time because the rotation of the step motor is constant) and listed as follows. .
[0030]

[0031]
From this result, at first glance, a. In the case of B, the above embodiment is advantageous. In the case of D, the conventional method is advantageous.
However, when returning to the problem to be solved by the invention, the reduction of the pixel density switching time which is a problem in the present invention is to reduce the time during which the image forming apparatus cannot operate. In the “pixel density switching time”, which is the time for resetting the conditions, the time required for the rotation of the light source unit: T (rotation), the image forming condition change, the rotation speed of the rotary polygon mirror, etc. are reset. Since there is a time required: T (setting) and generally T (rotation)> T (setting), the pixel density switching time is normally regulated by time: T (rotation).
[0032]
Accordingly, when the pixel density is newly selected, time: T (setting) is inevitably required before the operation of the image forming apparatus becomes possible, and time: T (rotation) is set to time: T (setting). The pixel density switching time as a whole is not shortened even if it is made shorter than (), and in order to substantially shorten the pixel density switching time, under the condition of T (rotation)> T (setting), It is necessary to shorten T (rotation).
[0033]
From this point of view, the conventional method does not lead to effective shortening of the pixel density switching time, and in the case of the above embodiment, T (rotation) when switching the pixel density is smaller than that in the conventional method. By effectively shortening, the pixel density switching time can be effectively shortened.
[0034]
By the way, in the case of the embodiment described above, the light source unit is set in the reference position: H.264. For example, the light source unit is positioned at P only when the main switch of the image forming apparatus is turned on. Thereafter, the light source unit is controlled to rotate based on the standby state: a. There is a possibility that the position error accumulates and the operation state corresponding to the desired pixel density is distorted.
One way to avoid this is to always return the light source unit to the reference position (detected by the reference position detection means) when the operation is completed at the selected pixel density, and after ensuring the reference position, A standby state determined with the state as a reference: the light source unit may be positioned at a. However, with this method, for example, when an operation at 400 dpi is required immediately after the operation at 600 dpi is completed, the operation returns to the reference position, then moves to the standby state, and further moves to the operation state: Since it moves to B, time: T (rotation) will become longer than the case of the said embodiment compared with the said embodiment.
[0035]
In order to avoid such a problem, as shown in FIG. P and the standby position: a may be matched. That is, the reference position of the light source unit detected by the reference position detection means: P is defined as a standby state: a (Claim 2).
[0036]
In this way, since the standby state: a is always constant, the operation states: A and B can always be set accurately, and the pixel density switching time can be effectively shortened.
[0037]
FIG. 5 shows an embodiment of the image forming apparatus of the present invention. This image forming apparatus is a color printer that also serves as a digital color copying apparatus.
First, the printer unit 12 will be described.
The photoconductive photosensitive member 25 which is a “latent image carrier” is uniformly charged by the charging means 26, and then the multi-beam scanning device described above with reference to FIGS. A Y latent image (latent image to be visualized with yellow toner) is written by two-line simultaneous optical scanning. The image signal applied to the multi-beam scanning device 40A for writing may be an image signal obtained by reading a document in a “reading unit” described later, or image information generated by a computer or the like, and is stored on a floppy disk or the like. The image information for the printed image may be converted into image information.
[0038]
The written electrostatic latent image is drawn as a developing device 28 (in order to avoid complications, it is actually drawn as a single device, but in reality it is Y (yellow), M (magenta), C (cyan), K (black). In this case, the toner is developed with Y toner. The Y image obtained by development is transferred from one of the cassettes 33 to 35 to a sheet-like recording medium (transfer paper or OHP sheet (recording sheet for an overhead projector)) distributed.
That is, the distributed recording medium is sent to the transfer unit in synchronization with the movement of the Y image by the registration roller 36, the Y image is transferred by the transfer unit 30, and separated from the photoconductor 25 by the separation unit 31. The separated recording medium is fixed on the Y image by the fixing device 38 by the conveyance belt 37 and returned to the position of the registration roller 36 again by the circulation path 50 at the lower part of the device. During this time, the photosensitive member 25 is freed of residual Y toner by the cleaning device 32, is uniformly charged by the charging means 26, is written with an M latent image by the multi-beam scanning device 40A, and the written M latent image is supplied to the developing device 28. Is developed with M toner. The obtained M image is transferred and fixed to the recording medium in the same manner as the Y image, and returned to the position of the registration roller 36 through the circulation path 50 in the same manner as described above. Similarly, when formation / development / transfer of a C image / fixing of a C image and formation / development of a K latent image / transfer / fixation of a K image are performed, Y, N, C, K are formed on the recording medium. A color image is formed by “overlapping four color images” of the images. The recording medium on which the color image is formed is discharged onto the tray 39.
In the above, the case of forming a color image has been described. However, in the case of forming a single color image, charging of the photosensitive member 25, writing of an electrostatic latent image, development with toner of a desired color, recording medium of the obtained image It is only necessary to perform transfer / fixing to the tray 39 and discharge it onto the tray 39.
[0039]
That is, the printer unit 12 forms an electrostatic latent image on the latent image carrier 25, visualizes the formed electrostatic latent image as a toner image, and directly transfers the obtained toner image to a sheet-like recording medium. An image forming apparatus that performs a process of fixing the transferred toner image to a recording medium, and is an optical scanning apparatus for writing an electrostatic latent image on a uniformly charged latent image carrier, as shown in FIG. Explained Claim 6 Image forming apparatus using multi-beam scanning device described (Claim 7) It is.
[0040]
The image forming apparatus shown in FIG. 5 also has means for reading an image to be copied and converting it to an image signal. This “means for reading an image to be copied and converting it to an image signal” is an image reading section 11 shown in FIG. When a document having an image to be read is set on an ADF (automatic document distribution device) 13, the ADF 13 automatically sets the document on the contact glass 14. The set original is illuminated by a lamp 15 having a reflector 16. The lamp 15 together with the mirror 17 moves to the right in the figure at a predetermined speed: V to illuminate and scan the document. The mirrors 18 and 19 that turn back the reflected light flux from the mirror 17 move together at a speed of V / 2 to the right in the figure, and keep the optical path length from the document surface to the lens 21 constant. Prior to entering the lens 21, the light beam is color-separated by the filter 20, imaged on the solid-state image sensor 22, and photoelectrically converted.
The photoelectrically changed signal is subjected to image processing such as binarization, multi-value conversion, gradation processing, scaling processing, and the like in the image processing unit 23 to become an image signal of a color-separated image, which is input to the multi-beam scanning device 40A. Sent. By performing the above reading process by sequentially changing the color separation color in the filter 20 to three colors of red, green, and blue, the original image is separated into three primary colors and read.
[0041]
In the above, the embodiment in the case where the operation state is the two states of A and B has been described. However, the present invention is not limited to the above case, and is easy when there are three or more operation states. Needless to say, it can be applied to the above.
[0042]
【The invention's effect】
As described above, according to the present invention, a novel light source device / multi-beam scanning device and image forming apparatus for a multi-beam scanning device can be realized.
Light source device for multi-beam scanning device of the present invention ( Claims 1-5 ), The amount of rotation of the light source unit accompanying the pixel density switching can be effectively reduced to effectively shorten the pixel density switching time. In the light source device according to the second aspect of the invention, since the standby state: a is detected as the reference state, an accurate operating state can always be realized. Claim 1 The light source device of the described invention can rotate the light source unit in substantially the same time to any of the two most distant operation states. Claim 3 The described light source device can eliminate errors caused by backlash during reverse rotation of the stepping motor.
[0043]
Also, the multi-beam scanning device of the present invention (Claim 6) Can quickly switch the pixel density by using the light source device, and the image forming apparatus according to the present invention. (Claim 7) By using the multi-beam scanning device, it is possible to execute image formation with a sub-type of pixel density, and to quickly switch the pixel density.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining one embodiment of a multi-beam scanning apparatus according to the present invention.
FIG. 2 is a diagram for explaining a rotation mechanism of a light source unit of the light source device in the embodiment.
FIG. 3 is a diagram for explaining switching of an operation state by rotation of a light source unit in the embodiment.
FIG. 4 is a diagram for explaining another example of switching of the operation state by the rotation of the light source unit.
FIG. 5 is a diagram for explaining one embodiment of an image forming apparatus according to the present invention;
[Explanation of symbols]
1 Light source unit
4 Stepping motor
40 Light source device
25 Latent image carrier
41 Cylindrical lens
44 fθ lens
42 Rotating polygon mirror

Claims (7)

A plurality of beams are obtained by coupling beams from a plurality of light sources that are controlled to blink independently, and the plurality of beams are deflected by a common optical deflector and are scanned on a surface to be scanned by a common imaging optical system. In addition, in a multi-beam scanning apparatus that condenses light beams separated in the sub-scanning direction and simultaneously scans a plurality of lines, a light source unit that emits a plurality of beams by coupling beams from a plurality of light emitting sources Is a light source device that switches the pixel density in optical writing by changing the interval between a plurality of lines that are simultaneously optically scanned by rotating around the reference axis,
Reference position detection means for detecting a reference position of the light source unit with respect to rotation around the reference axis,
The operation states of the light source units corresponding to different pixel densities, which are determined based on the above-described reference state, are the operation state: A, the operation state: B,. . When the operating state is N and the standby state of the light source unit is the standby state: a,
Standby position: a is set to the most distant operating position: an intermediate position between A and N,
The light source of the multi-beam scanning device, wherein the control means for controlling the rotating means for rotating the light source unit controls the rotating means so as to return the light source unit to the standby position after the completion of the desired optical scanning. apparatus. The light source device of the multi-beam scanning device according to claim 1,
A light source device for a multi-beam scanning device, characterized in that the reference position of the light source unit detected by the reference position detection means is defined as a standby state: a. The light source device for a multi-beam scanning device according to claim 1 or 2,
The rotation drive means of the rotation means is a stepping motor,
The control means reversely rotates the stepping motor to cause the stepping motor to perform a backlash removal operation when the light source unit is positioned in the operating state, the standby state, or the reference state. A light source device of a scanning device. The light source device of the multi-beam scanning device according to claim 1, 2 or 3,
A light source device for a multi-beam scanning device, wherein the operating states of the light source unit corresponding to different pixel densities are only two operating states: operating state: A and operating state: B. In the light source device of the multi-beam scanning apparatus according to any one of claims 1 to 4,
The number of light sources that are controlled to blink independently is 2, and these light sources are semiconductor lasers, and the beam from each semiconductor laser is coupled by a separate coupling lens, and then the polarization state of each beam A light source device for a multi-beam scanning device, characterized in that beam synthesis is performed using Beams from a plurality of light emitting sources whose flashing are controlled independently are coupled, and the coupled beams are deflected by a common optical deflector, and sub-scanned on the surface to be scanned by a common imaging optical system. A multi-beam scanning device that condenses light beams separated in a scanning direction and simultaneously scans a plurality of lines,
A light source device for a multi-beam scanning device according to any one of claims 1 to 5, wherein the light source device is a light source device. Forming an electrostatic latent image on the latent image carrier, visualizing the formed electrostatic latent image as a toner image, and transferring the obtained toner image to a sheet-like recording medium directly or via an intermediate transfer medium; An image forming apparatus that performs a process of fixing a transferred toner image to a recording medium,
As an optical scanning device for writing an electrostatic latent image on the uniformly charged image bearing member, an image forming apparatus which comprises using a multi-beam scanning apparatus according to claim 6 Symbol mounting.

Images