JP2016142876A

JP2016142876A - Optical scanning device and image forming apparatus

Info

Publication number: JP2016142876A
Application number: JP2015017856A
Authority: JP
Inventors: 友之川野; Tomoyuki Kawano; 朗大日比野; Akihiro Hibino; 工藤　源一郎; Genichiro Kudo; 源一郎工藤
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2015-01-30
Filing date: 2015-01-30
Publication date: 2016-08-08

Abstract

PROBLEM TO BE SOLVED: To provide a configuration in which a support member 40 can be downsized.SOLUTION: An optical scanning device 3 comprises: an optical member guiding a laser beam reflected by a rotary polygon mirror 33 to a photosensitive drum 1; and a support member 40 supporting a semiconductor laser 30, the rotary polygon mirror 33 and the optical member. The optical scanning device 3 scans a predetermined area EA of the photosensitive drum 1 with a laser beam. Da>Db, and La>Lb are satisfied, where Da denotes a length of a portion of the predetermined area EA of the photosensitive drum 1 at a side where the semiconductor laser 30 is arranged from a reference line Z with respect to a scanning direction, Db denotes a length of a portion of the area at a side where no semiconductor laser 30 is arranged from the reference line Z, La denotes a length of a portion of the optical member at a side where the semiconductor laser 30 is arranged from the reference line Z with respect to the scanning direction, and Lb denotes a length of a portion at a side where no semiconductor laser 30 is arranged from the reference line Z.SELECTED DRAWING: Figure 6

Description

本開示は、レーザビームプリンタやデジタル複写機等の画像形成装置に設けられる光学走査装置、及び、画像形成装置に関する。 The present disclosure relates to an optical scanning device provided in an image forming apparatus such as a laser beam printer or a digital copying machine, and an image forming apparatus.

電子写真方式の画像形成装置に用いられる光学走査装置では、特許文献１に示すように、光源、偏向手段、各種レンズやミラーなどの光学部材を支持部材に固定する構成が知られている。支持部材の画像形成装置への取付け方法としては、支持部材を画像形成装置の枠体内に挿入して固定する構成が特許文献２に開示されている。 In an optical scanning device used in an electrophotographic image forming apparatus, as shown in Patent Document 1, a configuration is known in which optical members such as a light source, a deflecting unit, various lenses and mirrors are fixed to a support member. As a method of attaching the support member to the image forming apparatus, Patent Document 2 discloses a configuration in which the support member is inserted into the frame of the image forming apparatus and fixed.

特開２０１４−１３４７８１号公報JP 2014-134781 A 特開２０１０−０３６４４６号公報JP 2010-036446 A

近年、光学走査装置に使用される材料削減による低コスト化や、光学走査装置を画像形成装置への搭載する際の組み立て性の改善、又は画像形成装置自体の小型化などの要求から、光学走査装置の支持部材を小型化することが求められている。しかしながら、支持部材の大きさは、支持部材が支持する各種光学部材の大きさや配置によってある程度決まってしまうため、一定のサイズ以下にすることが困難であった。 In recent years, optical scanning has been performed in response to demands for cost reduction due to reduction of materials used for optical scanning devices, improvement of assembly when mounting optical scanning devices on image forming apparatuses, or miniaturization of image forming apparatuses themselves. There is a demand for downsizing the support member of the apparatus. However, since the size of the support member is determined to some extent by the size and arrangement of various optical members supported by the support member, it has been difficult to make the size smaller than a certain size.

そこで本開示は、支持部材を小型化可能な構成を開示することを目的とする。 Then, this indication aims at disclosing the structure which can reduce a support member in size.

本開示は、レーザ光を出射する光源と、前記光源から出射されたレーザ光を反射しつつ反射方向を変化させる偏向手段と、前記偏向手段により反射されたレーザ光を被走査面へ導く光学部材と、前記光源、前記偏向手段、及び前記光学部材を支持する支持部材と、を有し、前記反射方向の変化により前記被走査面上のレーザ光の照射位置を前記被走査面上で走査方向に移動させ、前記被走査面の所定の領域をレーザ光で走査する光学走査装置において、前記偏向手段によって反射され前記走査方向に直交する方向に前記被走査面に入射するレーザ光の主光線を基準線とすると、前記被走査面の前記所定の領域のうち、前記走査方向に関して、前記基準線よりも前記光源が配置されている側の領域の長さをＤａ、前記基準線よりも前記光源が配置されていない側の領域の長さをＤｂ、前記光学部材のうち、前記走査方向に関して、前記基準線よりも前記光源が配置されている側の部分の長さをＬａ、前記基準線よりも前記光源が配置されていない側の部分の長さをＬｂとすると、Ｄａ＞Ｄｂ、且つ、Ｌａ＞Ｌｂなる条件を満たすことを特徴とする。 The present disclosure relates to a light source that emits laser light, a deflection unit that changes a reflection direction while reflecting the laser beam emitted from the light source, and an optical member that guides the laser beam reflected by the deflection unit to a surface to be scanned. And a support member that supports the light source, the deflecting unit, and the optical member, and the irradiation position of the laser beam on the scanned surface is changed in the scanning direction on the scanned surface by the change in the reflection direction. In the optical scanning device that scans a predetermined region of the scanned surface with laser light, the principal ray of the laser light that is reflected by the deflecting means and is incident on the scanned surface in a direction orthogonal to the scanning direction is When the reference line is used, the length of the region on the side where the light source is disposed with respect to the scanning direction in the predetermined region of the surface to be scanned is Da, and the light source with respect to the reference line. Is arranged The length of the region on the non-applied side is Db, and the length of the portion of the optical member on the side where the light source is arranged with respect to the scanning direction with respect to the scanning direction is La, with respect to the reference line. Assuming that the length of the portion on which the light source is not disposed is Lb, the condition that Da> Db and La> Lb are satisfied.

また、本開示は、レーザ光を出射する光源と、前記光源から出射されたレーザ光を反射しつつ反射方向を変化させる偏向手段と、前記偏向手段により反射されたレーザ光を被走査面へ導く光学部材と、前記光源、前記偏向手段、及び前記光学部材を支持する支持部材と、を有し、前記反射方向の変化により前記被走査面上のレーザ光の照射位置を前記被走査面上で走査方向に移動させ、前記被走査面の所定の領域をレーザ光で走査する光学走査装置において、前記偏向手段によって反射され前記走査方向に直交する方向に前記被走査面に入射するレーザ光の主光線を基準線とすると、前記支持部材の前記光学部材が配置されている部分について、前記走査方向に関して、前記基準線よりも前記光源が配置されている側の部分の長さをＢａ、前記基準線よりも前記光源が配置されていない側の部分の長さをＢｂ、前記光学部材のうち、前記走査方向に関して、前記基準線よりも前記光源が配置されている側の部分の長さをＬａ、前記基準線よりも前記光源が配置されていない側の部分の長さをＬｂとすると、Ｂａ＞Ｂｂ、且つ、Ｌａ＞Ｌｂなる条件を満たすことを特徴とする。 Further, the present disclosure provides a light source that emits laser light, a deflecting unit that changes a reflection direction while reflecting the laser light emitted from the light source, and guides the laser light reflected by the deflecting unit to a surface to be scanned. An optical member; and a light source, the deflecting unit, and a support member that supports the optical member, and the irradiation position of the laser beam on the scanned surface is changed on the scanned surface by the change in the reflection direction. In an optical scanning device that moves in a scanning direction and scans a predetermined region of the surface to be scanned with laser light, the main part of the laser light that is reflected by the deflecting means and incident on the surface to be scanned in a direction perpendicular to the scanning direction Assuming that the light beam is a reference line, the length of the portion of the support member where the optical member is disposed is Ba, the length of the portion on the side where the light source is disposed relative to the reference line with respect to the scanning direction. Bb is the length of the portion on the side where the light source is not disposed with respect to the reference line, and the length of the portion of the optical member on the side where the light source is disposed with respect to the scanning direction in the scanning direction. If the length of the portion on the side where the light source is not arranged with respect to La and the reference line is Lb, the conditions of Ba> Bb and La> Lb are satisfied.

本開示によれば、支持部材を小型化可能とすることができる。 According to the present disclosure, the support member can be reduced in size.

画像形成装置の概略断面図Schematic sectional view of the image forming apparatus 光学走査装置の概略斜視図Schematic perspective view of optical scanning device 走査光学系の副走査断面図Sub-scan sectional view of scanning optical system 入射光学系の副走査断面図Sub-scan sectional view of the incident optical system 光学走査装置の主走査断面図Main scanning cross section of optical scanning device 光学走査装置の主走査断面図Main scanning cross section of optical scanning device 光学走査装置の主走査断面図Main scanning cross section of optical scanning device （ａ）画像形成装置の枠体の概略構成を示す斜視図、（ｂ）画像形成装置の枠体の概略構成を示す斜視図(A) Perspective view showing schematic configuration of frame of image forming apparatus, (b) Perspective view showing schematic configuration of frame of image forming apparatus

＜第１実施形態＞
［画像形成装置］
第１実施形態について説明する。まず画像形成装置の構成について説明する。図１は画像形成装置の概略断面図である。 <First Embodiment>
[Image forming apparatus]
A first embodiment will be described. First, the configuration of the image forming apparatus will be described. FIG. 1 is a schematic sectional view of the image forming apparatus.

図１に示す画像形成装置１００は、イエローＹ、マゼンタＭ、シアンＣ、ブラックＫの４色の現像剤（トナー）を備え、記録材１０上にトナー画像を形成する電子写真方式のカラー画像形成装置である。 An image forming apparatus 100 shown in FIG. 1 includes four color developers (toners) of yellow Y, magenta M, cyan C, and black K, and forms an electrophotographic color image on a recording material 10. Device.

図１において、帯電手段となる帯電ローラ２Ｙ、２Ｂ、２Ｃ、２Ｋにより一様に帯電された像担持体となる感光ドラム１Ｙ、１Ｂ、１Ｃ、１Ｋの表面には光学走査装置３から出射されたレーザ光ＬＹ、ＬＭ、ＬＣ、ＬＫが照射される。レーザ光ＬＹ、ＬＭ、ＬＣ、ＬＫは、不図示の画像データ入力部から入力された画像データに基づいて点灯し、各レーザ光Ｌによる走査で各感光ドラム１の感光面である表面（被走査面）に静電潜像を形成する。 In FIG. 1, the optical scanning device 3 emits light onto the surfaces of the photosensitive drums 1Y, 1B, 1C, and 1K as image carriers uniformly charged by the charging rollers 2Y, 2B, 2C, and 2K as charging means. Laser light LY, LM, LC, LK is irradiated. The laser beams LY, LM, LC, and LK are turned on based on image data input from an image data input unit (not shown), and the surface (scanned surface) of each photosensitive drum 1 is scanned by each laser beam L. Electrostatic latent image is formed on the surface.

各感光ドラム１Ｙ、１Ｂ、１Ｃ、１Ｋの表面に形成された静電潜像に対して現像手段となる現像装置４Ｙ、４Ｍ、４Ｃ、４Ｋ内の現像ローラ６Ｙ、６Ｂ、６Ｃ、６Ｋから各色のトナーが供給されて付着する。このように、静電潜像にトナーを付着させて現像することで、各感光ドラム１Ｙ、１Ｂ、１Ｃ、１Ｋの表面に各色のトナー像が形成される。 The developing rollers 4Y, 4M, 4C, and 4K, which serve as developing means for the electrostatic latent images formed on the surfaces of the photosensitive drums 1Y, 1B, 1C, and 1K, develop the respective colors from the developing rollers 6Y, 6B, 6C, and 6K. Toner is supplied and adheres. As described above, by developing the toner by attaching the toner to the electrostatic latent image, a toner image of each color is formed on the surface of each of the photosensitive drums 1Y, 1B, 1C, and 1K.

各感光ドラム１Ｙ、１Ｂ、１Ｃ、１Ｋに対向して像担持体となる中間転写ベルト８が張架して配置されている。各感光ドラム１Ｙ、１Ｂ、１Ｃ、１Ｋの表面に形成された各色毎のトナー像は中間転写ベルト８の外周面に順次に一次転写される。この一次転写は、中間転写ベルト８の内周面側に配置された一次転写手段となる一次転写ローラ７Ｙ、７Ｍ、７Ｃ、７Ｋに一次転写バイアス電圧が印加されることにより行なわれる。 An intermediate transfer belt 8 serving as an image carrier is stretched over the photosensitive drums 1Y, 1B, 1C, and 1K. The toner images for each color formed on the surfaces of the photosensitive drums 1Y, 1B, 1C, and 1K are sequentially primary-transferred sequentially to the outer peripheral surface of the intermediate transfer belt 8. The primary transfer is performed by applying a primary transfer bias voltage to primary transfer rollers 7Y, 7M, 7C, and 7K serving as primary transfer units disposed on the inner peripheral surface side of the intermediate transfer belt 8.

一方、給送カセット９には記録材１０が積載されており、給送ローラ１１により給送された後、搬送ローラ１２により搬送される。 On the other hand, a recording material 10 is loaded on the feeding cassette 9 and is fed by a feeding roller 11 and then conveyed by a conveying roller 12.

その後、所定のタイミングで中間転写ベルト８と、二次転写手段となる二次転写ローラ１３とのニップ部からなる二次転写部１４へ搬送される。そして、二次転写ローラ１３に二次転写バイアス電圧が印加されることで中間転写ベルト８の外周面上のトナー像が記録材１０に転写される。 Thereafter, the intermediate transfer belt 8 and a secondary transfer roller 13 serving as a secondary transfer unit are conveyed to a secondary transfer unit 14 including a nip portion at a predetermined timing. A toner image on the outer peripheral surface of the intermediate transfer belt 8 is transferred to the recording material 10 by applying a secondary transfer bias voltage to the secondary transfer roller 13.

その後、記録材１０は二次転写部１４の二次転写ローラ１３と、中間転写ベルト８とに挟持搬送されて定着手段となる定着装置１５に送られ、該定着装置１５により加熱及び加圧されてトナー像が記録材１０に定着され、排出ローラ１６によって搬送される。 Thereafter, the recording material 10 is nipped and conveyed between the secondary transfer roller 13 of the secondary transfer unit 14 and the intermediate transfer belt 8 and sent to a fixing device 15 serving as a fixing unit, and is heated and pressed by the fixing device 15. The toner image is fixed on the recording material 10 and conveyed by the discharge roller 16.

［光学走査装置］
次に光学走査装置３の構成について図２〜図４を用いて説明する。図２は、光学走査装置３の内部を示す斜視図である。図３は、走査光学系について説明するための図で、図２で示す＋Ｙ方向から見た副走査平面での断面図（走査光学系の副走査断面図）である。また、図４は入射光学系について説明するための図で、＋Ｘ方向から見た副走査平面での断面図（入射光学系の副走査断面図）である。光学走査装置３は、側壁４０ａを外側に備える箱形状の支持部材４０と入射光学系と走査光学系の各種光学部材と、レーザ駆動基板３５とを有する。 [Optical scanning device]
Next, the configuration of the optical scanning device 3 will be described with reference to FIGS. FIG. 2 is a perspective view showing the inside of the optical scanning device 3. FIG. 3 is a diagram for explaining the scanning optical system, and is a cross-sectional view (sub-scanning cross-sectional view of the scanning optical system) in the sub-scanning plane viewed from the + Y direction shown in FIG. FIG. 4 is a diagram for explaining the incident optical system, and is a sectional view (sub-scanning sectional view of the incident optical system) in the sub-scanning plane as viewed from the + X direction. The optical scanning device 3 includes a box-shaped support member 40 having a side wall 40a on the outside, an incident optical system, various optical members of the scanning optical system, and a laser driving substrate 35.

光源としての半導体レーザ３０Ｙ、３０Ｍ、３０Ｃ、３０Ｋはレーザ駆動基板３５の電気回路によって駆動制御されレーザ光を発する。半導体レーザ３０Ｙ、３０Ｍ、３０Ｃ、３０Ｋから出射された発散光のレーザ光ＬＹ、ＬＭ、ＬＣ、ＬＫは、コリメータレンズ３１Ｙ、３１Ｍ、３１Ｃ、３１Ｋによって平行化されたレーザ光束に変換される。このレーザ光ＬＹ、ＬＭ、ＬＣ、ＬＫは、シリンドリカルレンズ３２を透過することによって、副走査方向にのみ収束され回転多面鏡（偏向手段）３３の反射面上に線像として結像する。ここまでの装置構成が入射光学系を構成する。副走査断面におけるレーザ光ＬＣ、ＬＭの回転多面鏡３３の反射面への入射角はθ１、レーザ光ＬＫ、ＬＹの回転多面鏡３３の反射面への入射角はθ２である。 Semiconductor lasers 30Y, 30M, 30C, and 30K as light sources are driven and controlled by an electric circuit of a laser driving substrate 35 to emit laser light. The diverging laser beams LY, LM, LC, and LK emitted from the semiconductor lasers 30Y, 30M, 30C, and 30K are converted into collimated laser beams by the collimator lenses 31Y, 31M, 31C, and 31K. The laser beams LY, LM, LC, and LK pass through the cylindrical lens 32 and are converged only in the sub-scanning direction to form a line image on the reflection surface of the rotary polygon mirror (deflection unit) 33. The apparatus configuration so far constitutes the incident optical system. The incident angles of the laser beams LC and LM on the reflecting surface of the rotating polygon mirror 33 in the sub-scanning section are θ1, and the incident angles of the laser beams LK and LY on the reflecting surface of the rotating polygon mirror 33 are θ2.

次に、回転多面鏡３３はスキャナモータ３４によって回転駆動され、レーザ光ＬＹ、ＬＭ、ＬＣ、ＬＫをそれぞれ反射する。レーザ光ＬＹ、ＬＭが回転多面鏡３３で反射される側を回転多面鏡３３の回転中心を基準に＋Ｘ側とすると、レーザ光ＬＣ、ＬＫは−Ｘ側に反射される。回転多面鏡３３によって反射されたレーザ光ＬＹ、ＬＭは、共に第１の走査レンズ３６ａを透過後、ＬＹは第２の走査レンズ３７ｂを透過し、走査ミラー３８ｃで反射された後、感光ドラム１Ｙにスポット像として結像する。一方、レーザ光ＬＭは、走査ミラー３８ｂで反射された後、第２の走査レンズ３７ａを透過し、走査ミラー３８ａで反射され、感光ドラム１Ｍに結像する。 Next, the rotary polygon mirror 33 is driven to rotate by the scanner motor 34 and reflects the laser beams LY, LM, LC, and LK, respectively. If the side on which the laser beams LY and LM are reflected by the rotary polygon mirror 33 is the + X side with respect to the rotation center of the rotary polygon mirror 33, the laser beams LC and LK are reflected on the -X side. The laser beams LY and LM reflected by the rotary polygon mirror 33 are both transmitted through the first scanning lens 36a, and LY is transmitted through the second scanning lens 37b and reflected by the scanning mirror 38c, and then the photosensitive drum 1Y. To form a spot image. On the other hand, the laser beam LM is reflected by the scanning mirror 38b, then passes through the second scanning lens 37a, is reflected by the scanning mirror 38a, and forms an image on the photosensitive drum 1M.

回転多面鏡３３によって反射されたレーザ光ＬＣ、ＬＫは、共に第１の走査レンズ３６ｂを透過後、ＬＫは第２の走査レンズ３７ｄを透過し、走査ミラー３８ｆで反射された後、感光ドラム１Ｋにスポット像として結像する。一方、レーザ光ＬＣは、走査ミラー３８ｅで反射された後、第２の走査レンズ３７ｃを透過し、走査ミラー３８ｄで反射され、感光ドラム１Ｃに結像する。このように、走査光学系の各種光学部材（各第１の走査レンズ３６、各第２の走査レンズ３７、各走査ミラー３８）は、回転多面鏡３３によって反射されたレーザ光ＬＹ、ＬＭ、ＬＣ、ＬＫを、対応する４つの感光ドラム１Ｙ、１Ｂ、１Ｃ、１Ｋへ導く。ここまでの装置構成が走査光学系を構成する。 The laser beams LC and LK reflected by the rotary polygon mirror 33 are both transmitted through the first scanning lens 36b, and LK is transmitted through the second scanning lens 37d and reflected by the scanning mirror 38f, and then the photosensitive drum 1K. To form a spot image. On the other hand, the laser beam LC is reflected by the scanning mirror 38e, then passes through the second scanning lens 37c, is reflected by the scanning mirror 38d, and forms an image on the photosensitive drum 1C. In this way, the various optical members (each first scanning lens 36, each second scanning lens 37, each scanning mirror 38) of the scanning optical system are reflected by the laser beams LY, LM, LC reflected by the rotary polygon mirror 33. , LK are guided to the corresponding four photosensitive drums 1Y, 1B, 1C, 1K. The apparatus configuration so far constitutes a scanning optical system.

更に走査光学系について説明する。回転多面鏡３３の回転により反射面の角度が変化し、回転多面鏡３３による各レーザ光Ｌの反射方向が連続的に変化する。これにより、各レーザ光Ｌが回転多面鏡３３によって偏向される。これにより各感光ドラム１の表面上（被走査面上）に各レーザ光Ｌが結像した各スポット像（レーザ光の照射位置）が各感光ドラム１の表面上を移動する（主走査）。その移動方向は、各感光ドラムの回転軸方向と平行であり、走査方向と称す。レーザ光ＬＹ、ＬＭの走査方向は−Ｙ方向、レーザ光ＬＣ、ＬＫの走査方向は＋Ｙ方向である。この走査方向は、各レーザ光Ｌの対応する感光ドラム１の表面の位置における主走査方向と一致する。また、各感光ドラム１が回転軸を中心に回転することにより、各レーザ光Ｌのスポット像は各感光ドラム１の表面上を走査方向に直交する方向に移動（副走査）する。このような、回転多面鏡３３及び各感光ドラム１の回転により、各感光ドラム１の表面に対して、各レーザ光のスポット像が走査方向、及び走査方向に直交する方向に移動でき、各感光ドラム１の表面に二次元的な光走査を行う。 Further, the scanning optical system will be described. The angle of the reflecting surface is changed by the rotation of the rotating polygon mirror 33, and the reflection direction of each laser beam L by the rotating polygon mirror 33 is continuously changed. Thereby, each laser beam L is deflected by the rotary polygon mirror 33. As a result, each spot image (laser beam irradiation position) in which each laser beam L forms an image on the surface of each photosensitive drum 1 (on the surface to be scanned) moves on the surface of each photosensitive drum 1 (main scanning). The moving direction is parallel to the rotation axis direction of each photosensitive drum and is referred to as a scanning direction. The scanning direction of the laser beams LY and LM is the -Y direction, and the scanning direction of the laser beams LC and LK is the + Y direction. This scanning direction coincides with the main scanning direction at the position of the surface of the photosensitive drum 1 corresponding to each laser beam L. Further, as each photosensitive drum 1 rotates about the rotation axis, the spot image of each laser beam L moves (sub-scan) on the surface of each photosensitive drum 1 in a direction perpendicular to the scanning direction. By such rotation of the rotary polygon mirror 33 and each photosensitive drum 1, the spot image of each laser beam can move in the scanning direction and in the direction perpendicular to the scanning direction with respect to the surface of each photosensitive drum 1. Two-dimensional light scanning is performed on the surface of the drum 1.

入射光学系及び走査光学系の各種光学部材（半導体レーザ３０、コリメータレンズ３１、シリンドリカルレンズ３２、回転多面鏡３３、第１の走査レンズ３６、第２の走査レンズ３７、走査ミラー３８等）は、支持部材４０に支持され、位置決め固定されている。支持部材は箱形状であり、上述した各種光学部材を内包して支持した状態で、不図示の蓋により内部が覆われた状態で画像形成装置１００に取り付けられる。 Various optical members of the incident optical system and the scanning optical system (semiconductor laser 30, collimator lens 31, cylindrical lens 32, rotary polygon mirror 33, first scanning lens 36, second scanning lens 37, scanning mirror 38, etc.) It is supported by the support member 40 and is positioned and fixed. The support member has a box shape, and is attached to the image forming apparatus 100 in a state in which the above-described various optical members are included and supported and the interior is covered by a lid (not shown).

［光学系の構成］
次に本実施形態に関わる特徴的な構成について図５で説明する。図５は、光学走査装置３におけるレーザ光ＬＹ、ＬＭ、ＬＣ、ＬＫのうち、レーザ光ＬＹとＬＫの光学系の主走査断面を示す図である。なお、図５では走査ミラーによる反射後の光学系についても展開して同一平面上に記載している。またレーザ光ＬＭ、ＬＣの光学系についても同様なため、これらの説明は省略する。 [Configuration of optical system]
Next, a characteristic configuration relating to the present embodiment will be described with reference to FIG. FIG. 5 is a diagram showing a main scanning section of the optical system of the laser beams LY and LK among the laser beams LY, LM, LC, and LK in the optical scanning device 3. In FIG. 5, the optical system after reflection by the scanning mirror is also developed and described on the same plane. Since the same applies to the optical systems of the laser beams LM and LC, the description thereof is omitted.

主走査断面で見た場合、半導体レーザ３０Ｙ、３０Ｋから放射されたレーザ光ＬＹ、ＬＫは、回転多面鏡３３の同一面に同じ方向から入射する。回転多面鏡３３で反射されたレーザ光ＬＹ、ＬＫが、走査方向に直交する角度で対応する感光ドラム１Ｙ、１Ｋの表面に入射するときのレーザ光ＬＹ、ＬＫの主光線を、走査光学系におけるレーザ光ＬＹとＬＫの基準線Ｚとする。なお、図５において感光ドラム１Ｙ、１Ｋの表面を線分１Ｋ、１Ｌとして記載しているが、この線分１Ｋ、１Ｌは感光ドラム１Ｙ、１Ｋの回転軸及び走査方向に平行な線分である。 When viewed in the main scanning section, the laser beams LY and LK emitted from the semiconductor lasers 30Y and 30K enter the same surface of the rotary polygon mirror 33 from the same direction. The chief rays of the laser beams LY and LK when the laser beams LY and LK reflected by the rotary polygon mirror 33 enter the corresponding surfaces of the photosensitive drums 1Y and 1K at an angle orthogonal to the scanning direction are used in the scanning optical system. A reference line Z of the laser beams LY and LK is used. In FIG. 5, the surfaces of the photosensitive drums 1Y and 1K are described as line segments 1K and 1L. These line segments 1K and 1L are line segments parallel to the rotation axes of the photosensitive drums 1Y and 1K and the scanning direction. .

そのとき、各感光ドラム１の、走査方向に関して潜像を形成可能な領域を有効走査領域（所定の領域）ＥＡとし、その両端部を端部Ａと端部Ｂとする。有効走査領域ＥＡの走査方向に関して基準線Ｚよりも光源３０が配置されている側の領域（端部Ａから基準Ｃまでの領域）の走査方向の長さがＤａ（１２５ｍｍ）であり、その部分を走査するのに必要な画角はθａである。つまり、端部Ａに向かうレーザ光の主光線と基準線Ｚとが成す画角がθａである。また、有効走査領域ＥＡの走査方向に関して基準線Ｚよりも光源３０が配置されていない側の領域（基準Ｃから端部Ｂまでの領域）の走査方向の長さがＤｂ（８５ｍｍ）であり、その部分を走査するのに必要な画角はθｂである。つまり、端部Ｂに向かうレーザ光の主光線と基準線Ｚとが成す画角がθｂである。そして上述したＤａ、Ｄｂ、θａ、θｂは、以下の条件（１）を満たすように設定されている。
Ｄａ＞Ｄｂ、θａ＞θｂ・・・・（１）
また、半導体レーザ３０Ｙ、３０Ｋから回転多面鏡３３で反射されて感光ドラム１Ｙ、１Ｋに向かうレーザ光ＬＹ、ＬＫの光路で最も下流に配置された光学部材である走査ミラー３８ｃ、３８ｆの走査方向の長さについて説明する。上述のように、基準線Ｚから端部Ｂ側では画角θｂよりも大きい画角にてレーザ光ＬＹ、ＬＫを感光ドラム１Ｋ、１Ｌに入射させる必要が無い。このため、走査ミラー３８ｃ、３８ｆは基準線Ｚから端部Ｂ側で画角θｂ分だけミラーの有効領域（走査に必要なミラー性能が保障された領域）となっていればよい。このため、走査ミラー３８ｃ、３８ｆは基準線Ｚから端部Ｂ側では、画角θｂよりも大きい画角に対応する部分は無くてもよい。そこで、走査ミラー３８ｃ、３８ｆでは、基準線Ｚから端部Ａ側では画角θａ分、基準線Ｚから端部Ｂ側では画角θｂ分のミラーの有効領域を確保しつつ、下記のような形状としている。即ち、走査ミラー３８ｃ、３８ｆは、走査方向に関して、基準線Ｚから端部Ａ側の部分の長さをＬ１ａ、基準線Ｚから端部Ｂ側の部分の長さをＬ１ｂとし、Ｌ１ａ、Ｌ１ｂが以下の条件（２）を満たすような形状である。
Ｌ１ａ＞Ｌ１ｂ・・・・（２）
また、走査ミラー３８ａ、３８ｂ、３８ｄ、３８ｅについても、走査ミラー３８ｃ、３８ｆと同様の配置、形状となっている。 At this time, an area where a latent image can be formed in the scanning direction of each photosensitive drum 1 is defined as an effective scanning area (predetermined area) EA, and both end portions thereof are defined as an end portion A and an end portion B. The length in the scanning direction of a region (region from the end A to the reference C) on the side where the light source 30 is arranged with respect to the scanning direction of the effective scanning region EA is Da (125 mm). The angle of view necessary for scanning is θa. That is, the angle of view formed by the chief ray of the laser beam toward the end A and the reference line Z is θa. In addition, the length in the scanning direction of the area on the side where the light source 30 is not disposed with respect to the scanning direction of the effective scanning area EA (the area from the reference C to the end B) is Db (85 mm). The angle of view required to scan that portion is θb. That is, the angle of view formed by the chief ray of the laser beam toward the end B and the reference line Z is θb. The above-described Da, Db, θa, and θb are set so as to satisfy the following condition (1).
Da> Db, θa> θb (1)
In addition, the scanning mirrors 38c and 38f, which are optical members disposed on the most downstream side in the optical path of the laser beams LY and LK reflected from the semiconductor lasers 30Y and 30K by the rotary polygon mirror 33 and directed toward the photosensitive drums 1Y and 1K, in the scanning direction. The length will be described. As described above, the laser beams LY and LK need not be incident on the photosensitive drums 1K and 1L at an angle of view larger than the angle of view θb on the end B side from the reference line Z. For this reason, the scanning mirrors 38c and 38f need only be in the effective area of the mirror (an area in which the mirror performance necessary for scanning is ensured) by the angle of view θb on the end B side from the reference line Z. For this reason, the scanning mirrors 38c and 38f may have no portion corresponding to an angle of view larger than the angle of view θb on the end B side from the reference line Z. Therefore, in the scanning mirrors 38c and 38f, the effective area of the mirror corresponding to the angle of view θa from the reference line Z to the end A side and the angle of view θb from the reference line Z to the end B is secured as follows. It has a shape. That is, in the scanning direction, the scanning mirrors 38c and 38f have L1a as the length of the portion on the end A side from the reference line Z, and L1b as the length of the portion on the end B side from the reference line Z. The shape satisfies the following condition (2).
L1a> L1b (2)
In addition, the scanning mirrors 38a, 38b, 38d, and 38e have the same arrangement and shape as the scanning mirrors 38c and 38f.

さらに、前述したレーザ光ＬＹ、ＬＫの光路で走査ミラー３８ｃ、３８ｆよりも一つ上流に配置された光学部材である第２の走査レンズ３７ｂ、３７ｄの走査方向の長さについて説明する。上述のように、基準線Ｚから端部Ｂ側では画角θｂよりも大きい画角にてレーザ光ＬＹ、ＬＫを感光ドラム１Ｋ、１Ｌに入射させる必要が無い。このため、第２の走査レンズ３７ｂ、３７ｄは基準線Ｚから端部Ｂ側で画角θｂ分だけレンズの有効領域（走査に必要なレンズ性能が保障された領域）となっていればよい。このため、第２の走査レンズ３７ｂ、３７ｄは基準線Ｚから端部Ｂ側では、画角θｂよりも大きい画角に対応する部分は無くてもよい。そこで、第２の走査レンズ３７ｂ、３７ｄでは、基準線Ｚから端部Ａ側では画角θａ分、基準線Ｚから端部Ｂ側では画角θｂ分のレンズの有効領域を確保しつつ、下記のような形状としている。即ち、第２の走査レンズ３７ｂ、３７ｄは、走査方向に関して、基準線Ｚから端部Ａ側の部分の長さをＬ２ａ、基準線Ｚから端部Ｂ側の部分の長さをＬ２ｂとし、Ｌ２ａ、Ｌ２ｂが以下の条件（３）を満たすような形状である。
Ｌ２ａ＞Ｌ２ｂ・・・・（３）
また、第２の走査レンズ３７ａ、３７ｃについても、第２の走査レンズ３７ｂ、３７ｄと同様の配置、形状となっている。 Further, the length in the scanning direction of the second scanning lenses 37b and 37d, which are optical members arranged one upstream of the scanning mirrors 38c and 38f in the optical paths of the laser beams LY and LK described above, will be described. As described above, the laser beams LY and LK need not be incident on the photosensitive drums 1K and 1L at an angle of view larger than the angle of view θb on the end B side from the reference line Z. For this reason, the second scanning lenses 37b and 37d need only be in an effective area of the lens by an angle of view θb on the end B side from the reference line Z (an area in which lens performance necessary for scanning is ensured). For this reason, the second scanning lenses 37b and 37d may not have a portion corresponding to an angle of view larger than the angle of view θb on the end B side from the reference line Z. Therefore, in the second scanning lenses 37b and 37d, the effective area of the lens corresponding to the angle of view θa on the end A side from the reference line Z and the angle of view θb on the end B side from the reference line Z are secured as follows. The shape is as follows. That is, in the scanning direction, the second scanning lenses 37b and 37d have L2a as the length of the portion on the end A side from the reference line Z, and L2b as the length of the portion on the end B side from the reference line Z. , L2b satisfies the following condition (3).
L2a> L2b (3)
Also, the second scanning lenses 37a and 37c have the same arrangement and shape as the second scanning lenses 37b and 37d.

また、支持部材４０のうちの前述したレーザ光ＬＹ、ＬＫの光路で最下流に配置された走査ミラー３８ｃ、３８ｆを少なくとも内包する部分（「走査光学系内包部分」と称す）の走査方向に関する長さについて説明する。走査方向に関して、支持部材４０の基準線Ｚから端部Ａ側の部分の長さをＢａ、基準線Ｚから端部Ｂ側の長さをＢｂとする。このとき、Ｂａ、Ｂｂは以下の条件（４）を満たすように設定されている。
Ｂａ＞Ｂｂ・・・・（４）
［比較例との比較］
次に図６を用いて、本実施形態と比較例との比較について説明する。光学走査装置３におけるレーザ光ＬＫの光学系の主走査断面を示す図である。本実施形態の光学系αを実線で描写し、比較例の光学系βを破線で描写する。なお、図６ではレーザ光ＬＫ側の光学系のついてのみ説明し、レーザ光ＬＹ、ＬＭ、ＬＣの光学系については同様であるため説明は省略する。図６では基準線Ｚ同士が重なるように光学系α、βを重ねて記載している。 In addition, the length of the support member 40 in the scanning direction of a portion (referred to as a “scanning optical system inclusion portion”) including at least the scanning mirrors 38c and 38f disposed on the most downstream side in the optical paths of the laser beams LY and LK described above. This will be described. Regarding the scanning direction, the length of the portion of the support member 40 on the end A side from the reference line Z is Ba, and the length on the end B side from the reference line Z is Bb. At this time, Ba and Bb are set to satisfy the following condition (4).
Ba> Bb (4)
[Comparison with comparative example]
Next, a comparison between this embodiment and a comparative example will be described with reference to FIG. 3 is a diagram illustrating a main scanning section of an optical system of laser light LK in the optical scanning device 3. FIG. The optical system α of the present embodiment is depicted by a solid line, and the optical system β of the comparative example is depicted by a broken line. In FIG. 6, only the optical system on the laser beam LK side will be described, and the optical systems of the laser beams LY, LM, and LC are the same, and the description thereof will be omitted. In FIG. 6, the optical systems α and β are overlapped so that the reference lines Z overlap each other.

走査方向に関して、光学系αの有効走査領域ＥＡの長さ（端部Ａから端部Ｂまでの長さ）、光学系βの有効走査領域ＥＡ´の長さ（端部Ａ´から端部Ｂ´までの長さ）は同じで２１０ｍｍである。 Regarding the scanning direction, the length of the effective scanning area EA of the optical system α (the length from the end A to the end B) and the length of the effective scanning area EA ′ of the optical system β (the end A ′ to the end B) The length up to 'is the same and is 210 mm.

光学系αでは、上述のように、Ｄａ＞Ｄｂ、及び、θａ＞θｂの関係となっている。また、第２の走査レンズ３７ｄは、画角θａ、θｂに合わせて基準線Ｚを中心とした走査方向の長さをＬ２ａ＞Ｌ２ｂとしていて、基準線Ｚを対称線としたとき非対称の光学性能を有している。走査ミラー３８ｆについても同様で、基準線Ｚを中心とした走査方向の長さをＬ１ａ＞Ｌ１ｂの関係としている。 In the optical system α, as described above, the relations Da> Db and θa> θb are satisfied. Further, the second scanning lens 37d has an asymmetric optical performance when the length in the scanning direction centered on the reference line Z is L2a> L2b and the reference line Z is a symmetric line in accordance with the angles of view θa and θb. have. The same applies to the scanning mirror 38f, and the length in the scanning direction centered on the reference line Z has a relationship of L1a> L1b.

このように、走査ミラー３８ｆ、走査レンズ３７ｄについて、基準線Ｚを中心として走査方向に関して画角が小さい側（光源の反対側）の部分の方が、画角が小さい側（光源側）の部分に比べて走査方向の長さが短くなるようにしている。このため支持部材４０の走査光学系内包部分について、走査方向に関して画角が小さい側（光源の反対側）の走査方向の長さＢｂを短くすることができる。一方で、支持部材４０走査光学系内包部分の走査方向に関して画角が大きい側（光源側）の走査方向の長さＢａは長くなるものの、入射光学系の感光ドラム１Ｋの軸方向の長さＩの方が長い（Ｂａ＜Ｉ）である。なお、入射光学系の感光ドラム１Ｋの軸方向の長さＩとは、半導体レーザ３０Ｋの発光点から基準線Ｚまでの走査方向の長さである。このため、支持部材４０の全体の、感光ドラム１Ｋの軸方向（＋Ｙ方向）の長さＷは、Ｗ＝Ｂｂ＋Ｉと表せる。 As described above, with respect to the scanning mirror 38f and the scanning lens 37d, the portion on the side with the smaller angle of view (opposite to the light source) with respect to the scanning direction around the reference line Z is the portion with the smaller angle of view (light source side). The length in the scanning direction is made shorter than that in FIG. For this reason, about the scanning optical system inclusion part of the support member 40, the length Bb in the scanning direction on the side where the angle of view is small in the scanning direction (the side opposite to the light source) can be shortened. On the other hand, the length Ba in the scanning direction on the side with the larger angle of view (light source side) with respect to the scanning direction of the supporting member 40 scanning optical system inclusion portion becomes longer, but the axial length I of the photosensitive drum 1K of the incident optical system. Is longer (Ba <I). The length I in the axial direction of the photosensitive drum 1K of the incident optical system is the length in the scanning direction from the emission point of the semiconductor laser 30K to the reference line Z. Therefore, the entire length W of the support member 40 in the axial direction (+ Y direction) of the photosensitive drum 1K can be expressed as W = Bb + I.

なお、第１の走査レンズ３６ｂについては、走査に必要な画角がθａ＞θｂの関係であっても、基準線Ｚを対称線として、両側へθａの画角を走査できるような対称の光学性能を有している。これは、光路上で第１の走査レンズ３６ｂが回転多面鏡３３に比較的近い位置に配置されており、第１の走査レンズ３６ｂの走査方向の長さが比較的短いからである。つまり、第１の走査レンズ３６ｂについて、基準線Ｚを中心として画角が大きい側（光源側）の部分よりも画角が小さい側（光源の反対側）の部分の長さを短くしても、走査光学系内包部分の走査方向の長さＢｂを短くすることができず、支持部材４０の全体の走査方向の長さＷにも影響が無いからである。もちろん、第１の走査レンズ３６ｂについて、画角が小さい側（光源の反対側）の部分については画角θｂ分でレンズの有効領域を確保しつつ、画角がθｂよりも大きい部分を無くしてもよい。つまり、画角が小さい側（光源の反対側）の部分の走査方向の長さを画角が大きい側（光源側）の部分より短くしてもよい。 For the first scanning lens 36b, even if the angle of view required for scanning is θa> θb, the optical axis is symmetrical so that the angle of view of θa can be scanned on both sides with the reference line Z as the symmetric line. Has performance. This is because the first scanning lens 36b is disposed at a position relatively close to the rotary polygon mirror 33 on the optical path, and the length of the first scanning lens 36b in the scanning direction is relatively short. In other words, even if the length of the first scanning lens 36b on the side with the smaller angle of view (the side opposite to the light source) is made shorter than the portion with the larger angle of view (on the light source side) with the reference line Z as the center. This is because the length Bb of the scanning optical system inclusion portion in the scanning direction cannot be shortened, and the entire length W of the support member 40 in the scanning direction is not affected. Of course, with respect to the first scanning lens 36b, the portion with the smaller angle of view (the opposite side of the light source) secures the effective area of the lens by the angle of view θb, and eliminates the portion with the larger angle of view than θb. Also good. That is, the length in the scanning direction of the portion with the smaller angle of view (opposite the light source) may be shorter than the portion with the larger angle of view (light source side).

光学系βについては以下のような配置となっている。有効走査領域ＥＡ´の走査方向に関して基準線Ｚよりも光源３０ｋ´が配置されている側の領域（端部Ａ´から基準Ｃまでの領域）の走査方向の長さがＤａ´（１０５ｍｍ）であり、その部分を走査するのに必要な画角はθａ´である。また、有効走査領域ＥＡ´の走査方向に関して基準線Ｚよりも光源３０ｋ´が配置されていない側の領域（基準Ｃから端部Ｂ´までの領域）の走査方向の長さがＤｂ´（１０５ｍｍ）であり、その部分を走査するのに必要な画角はθｂ´である。このように、基準線Ｚを対称線とした時、有効走査領域ＥＡの走査方向の長さは同じである。つまり、光学系βでは、Ｄａ´＝Ｄｂ´の関係、及びθａ´＝θｂ´の関係を満たしている。 The optical system β is arranged as follows. The length in the scanning direction of the region (region from the end A ′ to the reference C) on the side where the light source 30k ′ is arranged with respect to the scanning direction of the effective scanning region EA ′ is Da ′ (105 mm). There is an angle of view necessary to scan the portion. In addition, the length in the scanning direction of the region (region from the reference C to the end B ′) on the side where the light source 30k ′ is not disposed with respect to the reference line Z with respect to the scanning direction of the effective scanning region EA ′ is Db ′ (105 mm). ), And the angle of view necessary to scan the portion is θb ′. Thus, when the reference line Z is a symmetric line, the length of the effective scanning area EA in the scanning direction is the same. That is, the optical system β satisfies the relationship Da ′ = Db ′ and the relationship θa ′ = θb ′.

従って、走査ミラー３８ｆ´は走査方向の長さが基準線Ｚを中心に光源側がＬ１ａ´、光源の反対側がＬ１ｂ´で、Ｌ１ａ´、Ｌ１ｂ´が同じ値（Ｌ１ａ´＝Ｌ１ｂ´）という形状である。同様に、第２の走査レンズ３７ｄ´は走査方向の長さが基準線Ｚ´を中心に光源側がＬ２ａ´、光源の反対側がＬ２ｂ´で、Ｌ２ａ´、Ｌ２ｂ´が同じ値（Ｌ２ａ´＝Ｌ２ｂ´）という形状である。このため、支持部材４０の走査光学系内包部は走査方向の長さが基準線Ｚを中心に光源側がＢａ´、光源の反対側がＢｂ´で、Ｂａ´、Ｂｂ´が同じ値（Ｂａ´＝Ｂｂ´）という形状である。また、走査光学系内包部の光源側の長さＢａ´よりも関して入射光学系の方が長さＩの方が長い（Ｂａ´＜Ｉ）。このため、支持部材４０´全体の、感光ドラム１Ｋの軸方向（＋Ｙ方向）の長さＷ´は、Ｗ´＝Ｂｂ´＋Ｉ´と表せる。 Accordingly, the scanning mirror 38f ′ has a length in the scanning direction centered on the reference line Z, L1a ′ on the light source side, L1b ′ on the opposite side of the light source, and L1a ′ and L1b ′ have the same value (L1a ′ = L1b ′). is there. Similarly, the length of the second scanning lens 37d ′ in the scanning direction is L2a ′ on the light source side around the reference line Z ′, L2b ′ on the opposite side of the light source, and L2a ′ and L2b ′ have the same value (L2a ′ = L2b). '). For this reason, the scanning optical system inner part of the support member 40 has a length in the scanning direction centered on the reference line Z, Ba ′ on the light source side, Bb ′ on the opposite side of the light source, and Ba ′ and Bb ′ have the same value (Ba ′ = Bb ′). Further, the length I of the incident optical system is longer (Ba ′ <I) than the length Ba ′ of the scanning optical system inclusion portion on the light source side. Therefore, the length W ′ of the entire support member 40 ′ in the axial direction (+ Y direction) of the photosensitive drum 1 K can be expressed as W ′ = Bb ′ + I ′.

ここで、走査方向に関して基準線Ｚよりも光源３０ｋ、３０ｋ´が無い側について比較する。有効走査領域ＥＡの方が有効走査領域ＥＡ´よりも−Ｙ方向にずれた位置にあるので、基準線Ｚを基準として見ると、走査ミラー３８ｆの端部が走査ミラー３８ｆ´の端部に対して−Ｙ方向に距離ΔＬ１（＝Ｌ１ｂ´−Ｌ１ｂ）の分だけ基準線Ｚ側に配置される。同様に第２の走査レンズ３７ｄが第２の走査レンズ３７ｄ´に対して−Ｙ方向に距離ΔＬ２（＝Ｌ２ｂ´−Ｌ２ｂ）の分だけ基準線Ｚ側に配置される。従って、この距離ΔＬ１、Ｌ２に対応する分だけ支持部材４０の側壁４０ａを支持部材４０´の側壁４０ａ´よりも−Ｙ方向に基準線Ｚ側に配置することが可能となる。その距離をΔＷとする。そうすると支持部材４０の感光ドラム１ｋの軸方向の幅Ｗは、支持部材４０´の幅Ｗ´を用いて、以下のように表せる。
Ｗ＝Ｗ´−ΔＷ
即ち、光学系αの方が長さΔＷの分だけ、走査方向に関して支持部材４０を小型化することができる。 Here, the side where the light sources 30k and 30k ′ are not present from the reference line Z in the scanning direction will be compared. Since the effective scanning area EA is at a position shifted in the −Y direction from the effective scanning area EA ′, the end of the scanning mirror 38f is located with respect to the end of the scanning mirror 38f ′ when viewed from the reference line Z. In the −Y direction, the distance ΔL1 (= L1b′−L1b) is arranged on the reference line Z side. Similarly, the second scanning lens 37d is arranged on the reference line Z side by a distance ΔL2 (= L2b′−L2b) in the −Y direction with respect to the second scanning lens 37d ′. Therefore, the side wall 40a of the support member 40 can be disposed closer to the reference line Z side in the −Y direction than the side wall 40a ′ of the support member 40 ′ by an amount corresponding to the distances ΔL1 and L2. Let that distance be ΔW. Then, the width W of the support member 40 in the axial direction of the photosensitive drum 1k can be expressed as follows using the width W ′ of the support member 40 ′.
W = W′−ΔW
That is, the support member 40 can be downsized in the scanning direction by the length ΔW of the optical system α.

このように本実施形態では、有効走査領域ＥＡのうち、走査方向に関して、基準線Ｚよりも光源３０が配置されている側の領域の長さＤａ、基準線Ｚよりも光源３０が配置されていない側の領域の長さＤｂとすると、これらの関係をＤａ＞Ｄｂとした。更に、回転多面鏡３３で反射されたレーザ光Ｌを感光ドラム１へ導く光学部材（第１、第２の走査レンズ３７、走査ミラー３８）に関しては、次に示す関係となるようにした。つまり、走査方向に関して、基準線Ｚよりも光源３０が配置されている側の部分の長さをＬａ、基準線Ｚよりも光源３０が配置されていない側の部分の長さをＬｂとすると、これらの関係をＬａ＞Ｌｂとした。これにより、走査方向における基準線Ｚからの上記光学部材の＋Ｙ方向への突出量Ｌ１ｂ、Ｌ２ｂを抑えることができる。このため、走査方向における基準線Ｚからの支持部材４０の＋Ｙ方向への突出量Ｂｂを抑え、支持部材４０の走査方向の長さＷを短くすることができる。これにより、支持部材４０自体の材料を減らしてコストダウンすることが可能である。特に、走査方向に関して、入射光学系の長さＩの方が、有効走査領域ＥＡの半分よりも長い光学系の場合（Ｉ＞（ＥＡ／２））であれば、支持部材４０の走査方向の長さＷを短くする効果を得やすい。また、走査方向に関して、光学走査装置３の基準線Ｚよりも光源側の部分の端部（図６における半導体レーザ３０Ｃ、３０Ｋ、３０Ｙ、３０Ｍのリードピンの末端）から基準線Ｚまでの長さＷＩの方が、有効走査領域ＥＡの半分よりも長くなるような光学系の場合（ＷＩ＞（ＥＡ／２））であれば、光学走査装置３全体の走査方向の長さを短くする効果を得やすい。 Thus, in the present embodiment, in the effective scanning area EA, in the scanning direction, the length Da of the area on the side where the light source 30 is disposed with respect to the reference line Z and the light source 30 are disposed with respect to the reference line Z. Assuming the length Db of the region on the non-existing side, these relationships are set to Da> Db. Further, the optical members (first and second scanning lenses 37 and scanning mirror 38) for guiding the laser beam L reflected by the rotary polygon mirror 33 to the photosensitive drum 1 have the following relationship. That is, regarding the scanning direction, if the length of the portion on the side where the light source 30 is arranged with respect to the reference line Z is La and the length of the portion on the side where the light source 30 is not arranged with respect to the reference line Z is Lb, These relationships were set to La> Lb. Thereby, protrusion amounts L1b and L2b of the optical member in the + Y direction from the reference line Z in the scanning direction can be suppressed. For this reason, the protrusion amount Bb of the supporting member 40 in the + Y direction from the reference line Z in the scanning direction can be suppressed, and the length W of the supporting member 40 in the scanning direction can be shortened. Thereby, it is possible to reduce the cost by reducing the material of the support member 40 itself. In particular, in the scanning direction, if the length I of the incident optical system is an optical system longer than half of the effective scanning area EA (I> (EA / 2)), the length of the supporting member 40 in the scanning direction is longer. It is easy to obtain the effect of shortening the length W. Further, with respect to the scanning direction, the length WI from the end of the portion closer to the light source than the reference line Z of the optical scanning device 3 (the end of the lead pins of the semiconductor lasers 30C, 30K, 30Y, and 30M in FIG. 6) to the reference line Z. If the optical system is longer than half of the effective scanning area EA (WI> (EA / 2)), the effect of shortening the length of the entire optical scanning device 3 in the scanning direction is obtained. Cheap.

また、スキャナモータ３４の位置を支持部材４０の側壁４０ａ（図２、６）に近いことから、スキャナモータ３４が振動源となった支持部材４０の振動の振幅を小さく抑えることができ、振動による画像品質悪化を防ぐことも可能となる。 Further, since the position of the scanner motor 34 is close to the side wall 40a (FIGS. 2 and 6) of the support member 40, the amplitude of vibration of the support member 40 from which the scanner motor 34 has become a vibration source can be suppressed to a small level. It is also possible to prevent image quality deterioration.

次に画像形成装置１００として見た場合について説明する。図８（ａ）、（ｂ）は、画像形成装置の枠体の概略構成を示す斜視図である。図８（ａ）に示すように、画像形成装置１００は枠体として走査方向で対向した２つの側板（側面部材）１０１ａ、１０１ｂと２つの側板を連結する連結部材１０２を備える。この枠体に各感光ドラム１等が支持されている。支持部材４０は連結部材１０２に支持されている。 Next, a case where the image forming apparatus 100 is viewed will be described. 8A and 8B are perspective views illustrating a schematic configuration of a frame body of the image forming apparatus. As shown in FIG. 8A, the image forming apparatus 100 includes a connecting member 102 that connects two side plates (side members) 101a and 101b facing each other in the scanning direction as a frame. The photosensitive drums 1 and the like are supported on the frame. The support member 40 is supported by the connecting member 102.

画像形成装置１００においては、本実施形態の光学走査装置３を用いると、走査方向に関して光源３０と光源３０に近い方の側板１０１ｂとの間の距離ΔＹをより長く確保できる。このため、例えば２つの連結部材１０２と２つの側板１０１ａ、ｂとの間に−Ｘ方向に光学走査装置３を挿入してそのまま枠体に位置決め固定する際、レーザ駆動基板３５等へのＦＦＣ等の電線１２０の接続作業を行うスペースを確保しやすい。つまり、レーザ駆動基板３５は支持部材４０と側板１０１ｂとの間に配置されているが、レーザ駆動基板３５と側板１０１ｂとの間の空間を広くとることができる。このため、電線１２０接続作業者が側板１０１ｂの反対側から側板１０１ｂを越えてレーザ駆動基板３５へアクセスするための開口を側板１０１ｂに設けなくとも接続作業が可能となる。このため、レーザ駆動基板３５へアクセスするための開口を設けない分だけ、側板１０１ｂの強度を上げたり、内部の動作音を外部へ漏れにくくさせることができる。また、作業性の向上による作業時間の短縮で生産性向上が期待できる。 In the image forming apparatus 100, when the optical scanning device 3 of the present embodiment is used, the distance ΔY between the light source 30 and the side plate 101b closer to the light source 30 in the scanning direction can be secured longer. For this reason, for example, when the optical scanning device 3 is inserted between the two connecting members 102 and the two side plates 101a and 101b in the −X direction and positioned and fixed to the frame as it is, FFC to the laser driving substrate 35 and the like It is easy to secure a space for connecting the electric wire 120. That is, the laser drive substrate 35 is disposed between the support member 40 and the side plate 101b, but a space between the laser drive substrate 35 and the side plate 101b can be widened. Therefore, it is possible to perform the connection work without providing an opening in the side plate 101b for the electric wire 120 connection operator to access the laser drive substrate 35 from the opposite side of the side plate 101b beyond the side plate 101b. For this reason, it is possible to increase the strength of the side plate 101b and to prevent the internal operation sound from leaking to the outside as much as the opening for accessing the laser drive substrate 35 is not provided. In addition, improvement in productivity can be expected by shortening the work time by improving workability.

また、図８（ｂ）に示すように走査方向に関して光源３０と光源３０に近い方の側板１０１ｂとの間の距離ΔＹをより長く確保すると次のようなことが可能となる。つまり、支持部材４０と光源３０に近い方の側板１０１ｂとの間のスペースに、画像形成装置１００に用いる他の部材を配置することができる。一例として、側板１０１ｂと支持部材４０との間に、画像形成装置１００の冷却等の為に風路を形成するためのダクト部材１３０を配置することができる。このような構成により、画像形成装置１００内の部材が配置されない無駄な空間（デッドスペース）を減らし画像形成装置１００自体を小型化することが可能となる。 Further, as shown in FIG. 8B, the following can be achieved by securing a longer distance ΔY between the light source 30 and the side plate 101b closer to the light source 30 in the scanning direction. That is, another member used for the image forming apparatus 100 can be disposed in the space between the support member 40 and the side plate 101 b closer to the light source 30. As an example, a duct member 130 for forming an air path for cooling the image forming apparatus 100 or the like can be disposed between the side plate 101 b and the support member 40. With such a configuration, it is possible to reduce a useless space (dead space) in which members in the image forming apparatus 100 are not arranged and to reduce the size of the image forming apparatus 100 itself.

また、本実施形態は、特に下記のような構成の場合にも適用可能である。図４で示すように、回転多面鏡３３の反射面に入射角θ１、θ２で入射する入射光学系の場合、回転多面鏡３３の反射面の倒れによって、走査方向の走査ムラ（ジッタ）が発生する虞がある。この場合、入射角θ１、θ２を小さくすればこの走査ムラ（ジッタ）を抑制できる。このため、入射光学系の光路長（半導体レーザ３０から偏向点Ｄに至る距離）を長くとり、コリメータレンズ３１Ｋ、３１Ｃを回転多面鏡３３から遠ざける。このことによって、コリメータレンズ３１Ｋ、３１Ｃ同士の干渉を避けることで入射角θ１、θ２を小さくすることが考えられる。しかしながら、入射光学系の光路長（図６のＩに相当）を長くすると、支持部材４０の走査方向の長さが長くなってしまうが、本実施形態の構成を採用することで、支持部材４０の走査方向の長さが長くなることを抑制できる。 The present embodiment is also applicable to the following configuration. As shown in FIG. 4, in the case of an incident optical system that is incident on the reflecting surface of the rotating polygon mirror 33 at incident angles θ 1 and θ 2, scanning unevenness (jitter) in the scanning direction occurs due to the tilting of the reflecting surface of the rotating polygon mirror 33. There is a risk of doing. In this case, the scanning unevenness (jitter) can be suppressed by reducing the incident angles θ1 and θ2. Therefore, the optical path length of the incident optical system (distance from the semiconductor laser 30 to the deflection point D) is increased, and the collimator lenses 31K and 31C are moved away from the rotary polygon mirror 33. Thus, it is conceivable to reduce the incident angles θ1 and θ2 by avoiding interference between the collimator lenses 31K and 31C. However, if the optical path length of the incident optical system (corresponding to I in FIG. 6) is increased, the length of the support member 40 in the scanning direction is increased. However, by adopting the configuration of this embodiment, the support member 40 is used. It can be suppressed that the length in the scanning direction becomes longer.

また、容積の大きい現像装置４を有する画像形成装置では、光源３０から感光ドラム１に向かう光路に関して最下流の光学部材（走査ミラー３８）と感光ドラム１との距離を長くとる場合がある。つまり、走査光学系の光路長（回転多面鏡３３から感光ドラム１までの距離）が長くなる場合がある。この場合、入射光学系の各種光学部材の位置誤差による、感光ドラム１上でのスポット像の位置の誤差（横倍率）及び結像精度の誤差（縦倍率）への影響が大きくなる（敏感度が高くなる）傾向がある。このため、入射光学系の光路長（半導体レーザ３０から偏向点Ｄに至る距離）を長くとり、コリメータレンズ３１の焦点距離を長くすることが考えられる。しかしながら、入射光学系の光路長（図６のＩに相当）を長くすると、支持部材４０の走査方向の長さが長くなってしまうが、本実施形態の構成を採用することで、支持部材４０の走査方向の長さが長くなることを抑制できる。 Further, in the image forming apparatus having the developing device 4 having a large volume, the distance between the most downstream optical member (scanning mirror 38) and the photosensitive drum 1 may be increased with respect to the optical path from the light source 30 toward the photosensitive drum 1. That is, the optical path length of the scanning optical system (distance from the rotary polygon mirror 33 to the photosensitive drum 1) may become long. In this case, the effects of the position error of various optical members of the incident optical system on the error (horizontal magnification) of the spot image on the photosensitive drum 1 and the error (vertical magnification) of the imaging accuracy are increased (sensitivity). Tends to be higher). For this reason, it is conceivable to increase the optical path length of the incident optical system (distance from the semiconductor laser 30 to the deflection point D) and to increase the focal length of the collimator lens 31. However, if the optical path length of the incident optical system (corresponding to I in FIG. 6) is increased, the length of the support member 40 in the scanning direction is increased. However, by adopting the configuration of this embodiment, the support member 40 is used. It can be suppressed that the length in the scanning direction becomes longer.

なお、本実施形態は、走査光学系の光学部材のうち、走査ミラー３８、第２の走査レンズ３７が条件（２）や条件（３）を満たしていたが、走査光学系の光学部材としてはこれらに限定されない。例えば、走査光学系の光学部材として、回折格子、波長板等の偏光子、偏光ビームスプリッタやダイクロイックミラー、その他の光学フィルタを用い、これらにも条件（２）、（３）を適用してもよい。また、支持部材４０が走査光学系の光学部材を複数個支持する場合、走査方向の長さが最も長い走査光学系の光学部材、若しくは光源から被走査面（感光ドラム）に向かうレーザ光の光路に関して、最も下流に配置されている光学部材が少なくとも条件（２）又は（３）を満たせば、上述の効果を得られる。 In this embodiment, among the optical members of the scanning optical system, the scanning mirror 38 and the second scanning lens 37 satisfy the conditions (2) and (3). However, as the optical members of the scanning optical system, It is not limited to these. For example, a diffraction grating, a polarizer such as a wave plate, a polarizing beam splitter, a dichroic mirror, or other optical filter is used as an optical member of the scanning optical system, and the conditions (2) and (3) may be applied to these. Good. When the support member 40 supports a plurality of optical members of the scanning optical system, the optical member of the scanning optical system having the longest length in the scanning direction or the optical path of the laser light from the light source toward the surface to be scanned (photosensitive drum) With respect to the above, the effect described above can be obtained if the optical member arranged on the most downstream side satisfies at least the condition (2) or (3).

また、回転多面鏡に代えて反射面を揺動させる揺動ミラーとしてもよい。また、レーザ光ＬＹ、ＬＭ、ＬＣ、ＬＫのそれぞれは１つの光束でなくても良い。つまり、半導体レーザ３０Ｙ、３０Ｍ、３０Ｃ、３０Ｋからそれぞれ複数の光束を出射し、感光ドラム１Ｙ、１Ｍ、１Ｃ、１Ｋにそれぞれ副走査方向にずれた位置に複数のスポット像を同時に結像する構成も適用してもよい。 Further, instead of the rotary polygon mirror, a swing mirror that swings the reflecting surface may be used. Further, each of the laser beams LY, LM, LC, and LK may not be one light beam. That is, a configuration is also possible in which a plurality of light beams are emitted from the semiconductor lasers 30Y, 30M, 30C, and 30K, and a plurality of spot images are simultaneously formed on the photosensitive drums 1Y, 1M, 1C, and 1K at positions shifted in the sub-scanning direction. You may apply.

＜第２実施形態＞
第２実施形態に関する構成について図７で説明する。第１実施形態の光学走査装置３は複数の感光体（感光ドラム）に対してそれぞれレーザ光を照射することが可能な光学走査装置であるのに対し、第２実施形態の光学走査装置３は１つの感光体へレーザ光を照射するための光学走査装置である。本実施形態の光学走査装置３を有する画像形成装置１００も、少なくとも１つの感光ドラム１を有し、第１実施形態の画像形成装置１００と同様の原理で画像形成を行うものである。そのため、画像形成装置１００の構成については説明を省略する。また光学走査装置３の構成についても第１実施形態と同様の部分については説明を省略し、同様の符号を付す。 Second Embodiment
A configuration related to the second embodiment will be described with reference to FIG. The optical scanning device 3 of the first embodiment is an optical scanning device capable of irradiating a plurality of photoconductors (photosensitive drums) with laser beams, whereas the optical scanning device 3 of the second embodiment is an optical scanning device 3. This is an optical scanning device for irradiating one photoconductor with laser light. The image forming apparatus 100 having the optical scanning device 3 of the present embodiment also has at least one photosensitive drum 1 and forms an image on the same principle as the image forming apparatus 100 of the first embodiment. Therefore, description of the configuration of the image forming apparatus 100 is omitted. Also, with respect to the configuration of the optical scanning device 3, the description of the same parts as those in the first embodiment is omitted, and the same reference numerals are given.

光学走査装置３によるレーザ光Ｌの照射について説明する。レーザ駆動基板５６によって駆動制御される半導体レーザ３０から出射された発散光のレーザ光Ｌは、発散光を平行光にするとともに副走査方向に収束する機能を持つ複合レンズ５１によって、回転多面鏡３３の反射面上に線像として結像する。回転多面鏡３３はロータ部５５と共にスキャナモータ３４によって回転駆動され、レーザ光Ｌを偏向し、走査レンズ５４を透過後、感光ドラム１の表面にスポット像として結像する。回転多面鏡３３の回転による走査方向は＋Ｙ方向である。これらの光学部材は、支持部材６０に支持され、位置決め固定されている。 The irradiation of the laser beam L by the optical scanning device 3 will be described. The diverging laser beam L emitted from the semiconductor laser 30 driven and controlled by the laser driving substrate 56 is converted into parallel light and converged in the sub-scanning direction by the compound lens 51 having a function of converging in the sub-scanning direction. An image is formed as a line image on the reflecting surface. The rotary polygon mirror 33 is rotationally driven by the scanner motor 34 together with the rotor unit 55, deflects the laser light L, passes through the scanning lens 54, and forms an image on the surface of the photosensitive drum 1 as a spot image. The scanning direction due to the rotation of the rotary polygon mirror 33 is the + Y direction. These optical members are supported by the support member 60 and are positioned and fixed.

第１実施形態と同様に、有効走査領域ＥＡの走査方向に関して基準線Ｚよりも光源３０が配置されている側の領域（端部Ａから基準Ｃまでの領域）の走査方向の長さをＤａ、その部分を走査するのに必要な画角をθａとする。また、有効走査領域ＥＡの走査方向に関して基準線Ｚよりも光源３０が配置されていない側の領域（基準Ｃから端部Ｂまでの領域）の走査方向の長さをＤｂ、その部分を走査するのに必要な画角をθｂとする。するとＤａ、Ｄｂ、θａ、θｂは、以下の条件（１）を満たすように設定されている。
Ｄａ＞Ｄｂ、θａ＞θｂ・・・・（１） As in the first embodiment, the length in the scanning direction of the area (the area from the end A to the reference C) on the side where the light source 30 is disposed with respect to the reference line Z with respect to the scanning direction of the effective scanning area EA is expressed by Da. The angle of view required to scan that portion is θa. Further, the length in the scanning direction of the area (the area from the reference C to the end B) on the side where the light source 30 is not disposed with respect to the reference line Z with respect to the scanning direction of the effective scanning area EA is Db, and that portion is scanned. An angle of view necessary for the measurement is θb. Then, Da, Db, θa, and θb are set to satisfy the following condition (1).
Da> Db, θa> θb (1)

また、第１実施形態と同様に、走査レンズ５４の走査方向の長さについても、基準線Ｚから端部Ａ側の部分の長さをＬ２ａ、基準線Ｚから端部Ｂ側の部分の長さをＬ２ｂとし、Ｌ２ａ、Ｌ２ｂが以下の条件（３）を満たすような形状である。
Ｌ２ａ＞Ｌ２ｂ・・・・（３） Similarly to the first embodiment, the length of the scanning lens 54 in the scanning direction is L2a from the reference line Z to the end A side, and the length from the reference line Z to the end B side. The shape is L2b, and L2a and L2b satisfy the following condition (3).
L2a> L2b (3)

更に、本実施形態では、回転多面鏡３３およびロータ部５５を、回転駆動するのに影響が無い程度、支持部材６０の側壁６０ａに近接して配置しており、スキャナモータ３４の基板に設けられた駆動回路部５７は、光源３０と回転多面鏡３３の間に設けている。これにより、走査方向に関してスキャナモータ３４の基準線Ｚから光源３０の＋Ｙ方向への突出量を抑えられるのでより支持部材４０の走査方向の長さ（Ｂａ＋Ｂｂ）を抑えることができる。 Furthermore, in the present embodiment, the rotary polygon mirror 33 and the rotor unit 55 are arranged close to the side wall 60a of the support member 60 to the extent that they do not affect the rotational drive, and are provided on the substrate of the scanner motor 34. The drive circuit unit 57 is provided between the light source 30 and the rotary polygon mirror 33. Thereby, since the amount of protrusion of the light source 30 in the + Y direction from the reference line Z of the scanner motor 34 with respect to the scanning direction can be suppressed, the length (Ba + Bb) of the support member 40 in the scanning direction can be further suppressed.

１（１Ｙ、１Ｍ、１Ｃ、１Ｋ）感光ドラム（被走査面）
３光学走査装置
３０半導体レーザ（光源）
３３回転多面鏡（偏向手段）
４０支持部材
３６（３６ａ、３６ｂ）第１の走査レンズ
３７（３７ａ、３７ｂ、３７ｃ、３７ｄ）第２の走査レンズ
３８（３８ａ、３８ｂ、３８ｃ、３８ｄ、３８ｅ、３８ｆ）走査ミラー
１００画像形成装置
Ｌ（ＬＹ、ＬＭ、ＬＣ、ＬＫ）レーザ光
ＥＡ有効走査領域 1 (1Y, 1M, 1C, 1K) Photosensitive drum (scanned surface)
3 Optical scanning device 30 Semiconductor laser (light source)
33 Rotating polygon mirror (deflection means)
40 Support member 36 (36a, 36b) First scanning lens 37 (37a, 37b, 37c, 37d) Second scanning lens 38 (38a, 38b, 38c, 38d, 38e, 38f) Scanning mirror 100 Image forming apparatus L (LY, LM, LC, LK) Laser beam EA Effective scanning area

Claims

A light source that emits laser light, a deflecting unit that changes a reflection direction while reflecting the laser light emitted from the light source, an optical member that guides the laser light reflected by the deflecting unit to a surface to be scanned, and the light source The deflection means, and a support member that supports the optical member, and the laser beam irradiation position on the scanned surface is moved in the scanning direction on the scanned surface by the change in the reflection direction, In an optical scanning device that scans a predetermined region of the scanned surface with a laser beam,
When the principal ray of the laser light reflected by the deflecting means and incident on the scanned surface in a direction perpendicular to the scanning direction is a reference line,
Of the predetermined region of the surface to be scanned, the length of the region on the side where the light source is disposed with respect to the reference line in the scanning direction is Da, and the light source is not disposed with respect to the reference line. The length of the region on the side is Db, and the length of the portion of the optical member on the side where the light source is arranged with respect to the reference line with respect to the scanning direction is La, and the light source is arranged with respect to the reference line. If the length of the part that is not made is Lb,
Da> Db and La> Lb
An optical scanning device characterized by satisfying the following condition.

Regarding the portion of the support member where the optical member is disposed, the length of the portion on the side where the light source is disposed from the reference line in the scanning direction is Ba, and the light source is disposed from the reference line. If the length of the part that is not done is Bb,
Ba> Bb
The optical scanning device according to claim 1, wherein the following condition is satisfied.

A light source that emits laser light, a deflecting unit that changes a reflection direction while reflecting the laser light emitted from the light source, an optical member that guides the laser light reflected by the deflecting unit to a surface to be scanned, and the light source The deflection means, and a support member that supports the optical member, and the laser beam irradiation position on the scanned surface is moved in the scanning direction on the scanned surface by the change in the reflection direction, In an optical scanning device that scans a predetermined region of the scanned surface with a laser beam,
When the principal ray of the laser light reflected by the deflecting means and incident on the scanned surface in a direction perpendicular to the scanning direction is a reference line,
Regarding the portion of the support member where the optical member is disposed, the length of the portion on the side where the light source is disposed from the reference line in the scanning direction is Ba, and the light source is disposed from the reference line. The length of the portion on the side that is not formed is Bb, and the length of the portion of the optical member on the side where the light source is disposed with respect to the scanning direction with respect to the scanning direction is La, and the length of the portion above the reference line If the length of the portion on which the light source is not disposed is Lb,
Ba> Bb and La> Lb
An optical scanning device characterized by satisfying the following condition.

Of the predetermined area of the surface to be scanned, with respect to the scanning direction, an angle of view for irradiating a laser beam to an area closer to the light source than the reference line is θa, and more than the reference line. Assuming that the angle of view for irradiating a laser beam to the region where the light source is not disposed is θb,
θa> θb
The optical scanning device according to claim 1, wherein the following condition is satisfied.

5. The optical scanning device according to claim 1, wherein the optical member is disposed on the most downstream side with respect to an optical path of the laser beam from the light source toward the surface to be scanned.

The optical scanning device according to claim 1, wherein the optical member is an optical member having a longest length in the scanning direction.

With respect to the optical path of the laser beam from the light source toward the surface to be scanned, the laser beam has another optical member disposed upstream of the optical member, and the reference line in the scanning direction among the other optical members. If the length of the portion on the side where the light source is arranged is L2a, and the length of the portion on the side where the light source is not arranged with respect to the reference line is L2b,
L2a> L2b
The optical scanning device according to claim 1, wherein the following condition is satisfied.

The optical scanning device according to claim 7, wherein the another optical member has a shorter length in the scanning direction than the optical member.

The optical member has another optical member whose length in the scanning direction is shorter than that of the optical member, and the portion of the other optical member on the side where the light source is arranged with respect to the reference line with respect to the scanning direction. If the length is L2a, and the length of the portion on the side where the light source is not arranged with respect to the reference line is L2b,
L2a> L2b
The optical scanning device according to claim 1, wherein the following condition is satisfied.

The optical scanning device according to claim 7, wherein the another optical member is a lens through which the laser light is transmitted.

The optical scanning device according to claim 1, wherein the optical member is a mirror that reflects the laser light.

The light source includes a light source different from the light source, and the deflection unit includes a single reflection surface, and the laser beam emitted from the light source and the laser beam emitted from the other light source are simultaneously applied to the one reflection surface. The optical scanning device according to claim 1, wherein the optical scanning device is incident.

The optical scanning device according to any one of claims 1 to 12, wherein a length from a light emitting point of the light source to the reference line in the scanning direction is longer than a half of the predetermined region. .

14. The optical scanning device according to claim 1, wherein a length from the end of the light source to the reference line in the scanning direction is longer than a half of the predetermined region.

15. An optical scanning device according to claim 1, and a photosensitive member having a photosensitive surface as the surface to be scanned, and scanning the photosensitive surface with the laser beam to form a latent image. An image forming apparatus comprising: forming and forming a toner image by attaching toner to the latent image.

A frame including two side members facing each other in the scanning direction, and a connecting member for connecting the two side members between the two side members; and driving the optical scanning device to the optical scanning device A substrate including a circuit for performing,
The support member is disposed between the two side members, and the substrate is disposed between the support member and one of the two side members. The image forming apparatus according to claim 15, wherein there is a gap between one of them.

A frame including two side members facing each other in the scanning direction and a connecting member that connects the two side members between the two side members, a light source that emits laser light, and a laser emitted from the light source A deflecting unit that changes a reflecting direction while reflecting light; a light source; a support member that supports the deflecting unit; and a duct member that forms an air passage. A laser beam irradiation position on the surface is moved in the scanning direction on the surface to be scanned, a predetermined area of the surface to be scanned is scanned with the laser beam to form a latent image, and toner is attached to the latent image. In an image forming apparatus for forming a toner image
When the principal ray of the laser light reflected by the deflection means when the laser light incident on the surface to be scanned is orthogonal to the scanning direction is a reference line,
Of the predetermined region of the surface to be scanned, the length of the region on the side where the light source is disposed with respect to the reference line in the scanning direction is Da, and the light source is not disposed with respect to the reference line. If the length of the side region is Db,
Da> Db,
Meets the conditions
The image forming apparatus, wherein the duct member is disposed between a side member disposed at a position near the light source in the scanning direction, and the support member, of the two side members.

Of the predetermined area of the surface to be scanned, with respect to the scanning direction, an angle of view for irradiating a laser beam to an area closer to the light source than the reference line is θa, and more than the reference line. Assuming that the angle of view for irradiating a laser beam to the region where the light source is not disposed is θb,
θa> θb
The optical scanning device according to claim 17, wherein the following condition is satisfied.

The position of the end of the support member on the side where the light source is disposed in the scanning direction is more than the position of the end of the predetermined region on the side where the light source is disposed in the scanning direction. The image forming apparatus according to claim 17, wherein the image forming apparatus is located at a position away from the reference line in the scanning direction.