JP2010096792A

JP2010096792A - Optical scanner and image forming apparatus

Info

Publication number: JP2010096792A
Application number: JP2008264811A
Authority: JP
Inventors: Naoki Miyatake; 直樹宮武; Kazunori Watanabe; 一範渡辺
Original assignee: Ricoh Co Ltd
Current assignee: Ricoh Co Ltd
Priority date: 2008-10-14
Filing date: 2008-10-14
Publication date: 2010-04-30

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanner, wherein large size and cost increase are suppressed, and uneven light quantity on a face to be scanned is reduced, and to provide an image forming apparatus using the optical scanner. <P>SOLUTION: The optical scanner includes: light sources which are so arranged to be turned around an axis in the emitting directions of emitting light beams so that adjacent light-emitting points have a distance in a main-scanning direction and in a subscanning direction; an optical deflector 4 which scanningly deflects the light beam which is made incident from the light source to the deflecting and reflecting surface in a state where the light beam includes more P-polarization components than S-polarization components; a scanning optical system which images the light beam deflected with the optical deflector 4 onto a photoreceptor 7; and folding mirrors M1, M2 which guide the light beam to the photoreceptor 7, wherein the folding mirrors M1, M2 are disposed closer to the photoreceptor 7 than a scanning lens L composing a scanning system and having positive refractive power in the main-scanning direction, and the light sources are so arranged to be turned in the direction that the reflectance of the folding mirror M2, which has the largest deflection angle among the folding mirrors, increases at the side opposite to the light sources across the optical axis of the scanning lens. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

本発明は、デジタル複写機、レーザプリンタ、レーザファクシミリ等の光走査装置、及び、これを用いた画像形成装置に関する。 The present invention relates to an optical scanning device such as a digital copying machine, a laser printer, and a laser facsimile, and an image forming apparatus using the same.

レーザプリンタ等に関連して広く知られた光走査装置は一般に、光源側からの光ビームを光偏向器により偏向させ、ｆθレンズ等の走査結像光学系により被走査面に向けて集光して被走査面上に光スポットを形成し、この光スポットで被走査面を光走査(主走査)するように構成されている。被走査面の実体をなすものは光導電性の感光体等である感光媒体の感光面である。 In general, an optical scanning device widely known in relation to a laser printer or the like generally deflects a light beam from a light source side by an optical deflector and collects the light beam toward a surface to be scanned by a scanning imaging optical system such as an fθ lens. Thus, a light spot is formed on the surface to be scanned, and the surface to be scanned is optically scanned (main scan) with this light spot. What constitutes the surface to be scanned is a photosensitive surface of a photosensitive medium such as a photoconductive photosensitive member.

光偏向器は、回転多面鏡を高速回転する物が一般的であり、光偏向器を略密閉した空間に配置する構成により、高速回転に伴う騒音を抑制する、光偏向器の高速回転に伴う熱の発生を、走査光学系を構成する走査レンズなどの光学素子に伝えることを抑制する、空気中のちりなどの偏向反射面への付着を防ぐなどの効果を得ることができる。 The optical deflector is generally an object that rotates a rotating polygon mirror at a high speed, and the optical deflector is arranged in a substantially sealed space to suppress noise accompanying the high speed rotation. It is possible to obtain effects such as suppressing the generation of heat to an optical element such as a scanning lens constituting the scanning optical system, and preventing adhesion to a deflecting reflecting surface such as dust in the air.

近年、走査レンズ等の光学素子は光学特性向上のため、自由な面形状を形成可能な樹脂製のものが多く採用されており、前記光偏向器の熱が空気中を伝播して光学素子に伝わることにより、走査レンズの特に主走査方向に温度分布が生じ、レンズ面形状が乱れ、光学性能を著しく低下させてしまう。また、光偏向器の偏向反射面にちりなどが付着し曇りが生じると、偏向走査される方向に光量むらが発生し、画像における濃度むらの発生、カラー機においては色味の変化などが生じ光学特性が著しく低下してしまう。このちり等による偏向反射面の曇りは、回転下流側のエッジ部に付着するため、光偏向器の偏向方向により光束が曇り部にかかり光量むらが生じる。この光量むらは、経時的な変動として現れるため曇り自体を発生させない構造にする必要がある。 In recent years, optical elements such as scanning lenses are often made of resin capable of forming a free surface shape in order to improve optical characteristics, and the heat of the optical deflector propagates in the air to the optical element. As a result, a temperature distribution is generated in the scanning lens, particularly in the main scanning direction, the lens surface shape is disturbed, and the optical performance is significantly deteriorated. In addition, if dust or the like adheres to the deflecting reflection surface of the optical deflector and fogging occurs, unevenness in the amount of light occurs in the direction of deflection scanning, causing unevenness in density in the image, and changing color in a color machine. The optical characteristics are significantly deteriorated. The fogging of the deflection reflecting surface due to this dust or the like adheres to the edge portion on the downstream side of the rotation, so that the light flux is applied to the clouding portion depending on the deflection direction of the optical deflector, resulting in unevenness in the amount of light. Since this unevenness in the amount of light appears as a change with time, it is necessary to have a structure that does not generate fogging itself.

光源としては、高速化、高密度化の要求に答えるためにマルチビーム光源が多く用いられる。その方式は様々であるが、複数の発光点を直線上に配列し１つのパッケージに収めているＬＤ（ＬａｓｅｒＤｉｏｄｅ）アレイを用いることが多い。複数のＬＤを用いて合成する方式もあるが、１つのパッケージで複数の発光点を持つＬＤアレイは温度変動などの外乱に対し安定であり、特に被走査面上で所望の副走査方向でのビームピッチを安定して得ることができる方式である。 As a light source, a multi-beam light source is often used in order to meet the demand for higher speed and higher density. Although there are various methods, an LD (Laser Diode) array in which a plurality of light emitting points are arranged in a straight line and contained in one package is often used. Although there is a method of synthesizing using a plurality of LDs, an LD array having a plurality of light emitting points in one package is stable against disturbances such as temperature fluctuations, and particularly in a desired sub-scanning direction on the surface to be scanned. In this method, the beam pitch can be obtained stably.

通常、発光点間隔は狭いもので１４〜３０μｍ程度離れており、光学系と組み合わせて被走査面上で所望の副走査ビームピッチを得るためには、ＬＤアレイを光軸周りに回転させ、副走査方向の発光点間隔を調整する必要がある。この調整量（回転量）は、組み合わせる光学系の倍率により決定されるが、例えば３０μｍの発光点間隔を持つＬＤアレイを用いる場合、光偏向器で光ビームが偏向される断面に対し１０〜４５ｄｅｇ程度で使用されることが多い。 Usually, the light emitting point interval is narrow and is about 14-30 μm apart. In order to obtain a desired sub-scanning beam pitch on the surface to be scanned in combination with the optical system, the LD array is rotated around the optical axis, It is necessary to adjust the interval between the light emitting points in the scanning direction. This adjustment amount (rotation amount) is determined by the magnification of the optical system to be combined. For example, when an LD array having a light emitting point interval of 30 μm is used, it is 10 to 45 degrees with respect to the cross section where the light beam is deflected by the optical deflector. Often used at a degree.

従来から、前記被走査面としての感光体上で主走査方向の光量分布は、画像における濃度むら、色味の変化などの発生を生じさせるため課題として捕らえられている。 Conventionally, the light quantity distribution in the main scanning direction on the photoconductor as the surface to be scanned has been regarded as a problem because it causes the occurrence of density unevenness, color change, etc. in the image.

特許文献１においては、光源の偏光の方向をポリゴンミラーの回転軸に対し傾かせた光走査装置において、光路中で最も上流に位置する折り返しミラーの、光源に近い側のＳ偏光の割合を、反光源側のＳ偏光の割合に対し小さくし、ポリゴンミラーによる偏向で発生する反射率の変化を補正し前記課題の解決を試みている。 In Patent Document 1, in the optical scanning device in which the polarization direction of the light source is tilted with respect to the rotation axis of the polygon mirror, the ratio of the S-polarized light on the side closer to the light source of the folding mirror located most upstream in the optical path is: An attempt is made to solve the above problem by reducing the ratio of the S-polarized light on the side opposite to the light source and correcting the change in reflectance caused by the deflection by the polygon mirror.

しかし、特許文献１においては、最も上流に配置される折り返しミラーでの反射率を反光源側で高くなるようにすることで課題解決を目論んでいるが、最も偏角が大きい折り返しミラーが最も上流に配置されず、且つ、図７に示すが如く副走査方向に折り返す方向が最も上流側の折り返しミラーと異なる場合（図中Ａ）などは、上流の折り返しミラーでの反射率を特許文献１の通りとしても、下流側の折り返しミラーによる光量むらの発生が大きくなり課題解決は困難である。 However, in Patent Document 1, the problem is solved by increasing the reflectance of the folding mirror disposed on the most upstream side on the side opposite to the light source, but the folding mirror having the largest declination is the most upstream. 7 and the direction of folding back in the sub-scanning direction is different from the most upstream folding mirror as shown in FIG. 7 (A in the figure), the reflectance at the upstream folding mirror is Even if it is true, the occurrence of unevenness in the amount of light by the folding mirror on the downstream side becomes large, and it is difficult to solve the problem.

また、特許文献１においては、主走査方向に屈折力を持つ走査レンズを複数の折り返しミラーの間に配置し、下流側の折り返しミラーへの主走査方向両端での入射角度を小さくし、光量むらの発生感度を最も上流の折り返しミラーのほうが高くなるようにすることを前提としているが、主走査方向に屈折力を持つ走査レンズより上流側に折り返しミラーを配置した場合、走査レンズを光偏向器より離す必要があり、走査レンズが大型化し光走査装置の大型化、コストアップなど別の課題も生じる。 In Patent Document 1, a scanning lens having a refractive power in the main scanning direction is disposed between a plurality of folding mirrors, the incident angles at both ends in the main scanning direction to the downstream folding mirror are reduced, and unevenness in the amount of light is achieved. However, when the folding mirror is arranged upstream of the scanning lens having refractive power in the main scanning direction, the scanning lens is used as an optical deflector. It is necessary to separate them, and another problem such as an increase in the size of the optical scanning device and an increase in cost arises because the scanning lens becomes larger.

特に、カラー機などに対応した複数の感光媒体が単一の光偏向器を共用する方式の光走査装置においては、最も偏角が大きい折り返しミラーを最も上流に配置することは、装置の大型化につながり現実的ではない。 In particular, in an optical scanning apparatus in which a plurality of photosensitive media corresponding to a color machine share a single optical deflector, disposing the folding mirror with the largest deflection angle at the most upstream side increases the size of the apparatus. Is not realistic.

更に、特許文献１では、折返しミラーを１枚の構成とする場合は、主走査方向に屈折力を持つ複数の走査レンズの間に配置しているが、レイアウト上の制約は大きく、特にカラー機の場合は装置の大型化につながることが考えられ、光学レイアウト上の新たな課題が生じる。 Further, in Patent Document 1, when the folding mirror has a single configuration, it is arranged between a plurality of scanning lenses having refractive power in the main scanning direction, but there are great restrictions on the layout. In this case, it is considered that the size of the apparatus is increased, which causes a new problem in the optical layout.

また、主走査方向に正の屈折力を持つ走査レンズより被走査面側に折り返しミラーを配置したほうが、折り返しミラーへの入射角を小さくすることができ、偏光が光軸に対し回転する方向にばらついた時に、光量むらへの影響を低減可能となる。 In addition, if the folding mirror is arranged closer to the surface to be scanned than the scanning lens having a positive refractive power in the main scanning direction, the incident angle to the folding mirror can be reduced, and the polarized light rotates in the direction of rotation with respect to the optical axis. When it varies, it is possible to reduce the influence on the unevenness of the light amount.

更に、前記説明の通り、光学特性の劣化の抑制、感光体上での経時的な主走査方向の光量分布の発生を抑制するために、光偏向器を略密閉した空間に配置する構成にし、光ビームの入射出部を平行平板ガラスとする必要がある。この時、平行平板ガラスにおいても透過率が主走査方向に変化するため、感光体上での光量むらを低減するためには無視できない値となり、特許文献１の技術では課題解決が難しい。 Furthermore, as described above, the optical deflector is arranged in a substantially sealed space in order to suppress the deterioration of optical characteristics and to suppress the occurrence of the light amount distribution in the main scanning direction over time on the photosensitive member, The incident / exit part of the light beam needs to be parallel flat glass. At this time, since the transmittance also changes in the main scanning direction even in the parallel flat glass, it becomes a value that cannot be ignored in order to reduce the unevenness of the amount of light on the photoconductor.

特開２００５-３２６７４４号公報JP 2005-326744 A

本発明は、以上の従来技術における問題に鑑みてなされたものであり、光学特性の劣化を低減した光走査装置において、大型化、コストアップを抑え、被走査面上での光量むらを低減する光走査装置及び該光走査装置を用いた画像形成装置を提供することを目的とする。
また、本発明は、カラー機において、各色の光量むらを低減させ、且つ、各色の光量むらの発生量及び発生状態を一致させる光走査装置及び該光走査装置を用いた画像形成装置を提供することを目的とする。
また、本発明は、出力画像において濃度むら、色味の変化を抑える光走査装置及び該光走査装置を用いた画像形成装置を提供することを目的とする。 The present invention has been made in view of the above-described problems in the prior art, and in an optical scanning device with reduced deterioration of optical properties, suppresses increase in size and cost, and reduces unevenness in the amount of light on the surface to be scanned. An object is to provide an optical scanning device and an image forming apparatus using the optical scanning device.
In addition, the present invention provides an optical scanning device that reduces unevenness in the amount of light of each color and matches the amount and state of occurrence of unevenness in the amount of light in each color, and an image forming apparatus using the optical scanning device. For the purpose.
It is another object of the present invention to provide an optical scanning device that suppresses uneven density and color change in an output image, and an image forming apparatus using the optical scanning device.

前記課題を解決するために提供する本発明は、以下の通りである。
〔１〕複数の発光点を直線上に配列してなり、隣接する該発光点間で主走査方向及び副走査方向に距離を持つように、出射する光ビームの射出方向を回転軸として回転して配置される光源と、該光源から偏向反射面に対しＳ偏光成分よりＰ偏光成分を多く含む状態で入射する光ビームを主走査方向に偏向走査する光偏向器と、該光偏向器で偏向された光ビームを被走査面に結像する走査光学系と、前記光ビームを被走査面に導く折り返しミラーと、を備える光走査装置において、前記折り返しミラーは、前記走査光学系を構成する主走査方向に正の屈折力を持つ走査レンズより被走査面側に配置され、前記光源は、前記折り返しミラーのうち最も偏角が大きい折り返しミラーの反射面で、前記走査レンズ光軸を挟み光源側よりも該光源の反対側で入射する光ビームの反射率が高くなる方向に回転され配置されていることを特徴とする光走査装置。
〔２〕前記〔１〕に記載の光走査装置において、前記折り返しミラーを複数持ち、該複数の折り返しミラーの全てが、前記走査光学系を構成する主走査方向に正の屈折力を持つ走査レンズより被走査面側に配置されることを特徴とする光走査装置。
〔３〕前記〔１〕または〔２〕に記載の光走査装置において、光偏向器を配置する空間をその他の空間に対し略密閉する構造とし、該密閉空間への光ビームの入射出用の開口部に配置される平行平板を持ち、前記平行平板の透過率は、前記走査レンズ光軸を挟み反光源側で高くなっていることを特徴とする光走査装置。
〔４〕複数の被走査面に対応して、それぞれ複数の発光点を直線上に配列してなり、隣接する該発光点間で主走査方向及び副走査方向に距離を持つように、出射する光ビームの射出方向を回転軸として回転して配置される複数の光源と、前記複数の光源それぞれから偏向反射面に対しＳ偏光成分よりＰ偏光成分を多く含む状態で入射する光ビームを主走査方向に偏向走査する単一の光偏向器と、光偏向器で偏向された光ビームを対応する被走査面に結像する走査光学系と、前記複数の光源毎に、光ビームを対応する被走査面に導く複数の折り返しミラーと、を備える光走査装置において、前記折り返しミラーは、前記走査光学系を構成する主走査方向に正の屈折力を持つ走査レンズより対応する被走査面側に配置され、前記複数の光源はそれぞれ、対応する前記折り返しミラーのうち最も偏角が大きい折り返しミラーの反射面で、前記走査レンズ光軸を挟み光源側よりも該光源の反対側で入射する光ビームの反射率が高くなる方向に回転され配置されていることを特徴とする光走査装置。
〔５〕前記〔４〕に記載の光走査装置において、光偏向器を配置する空間をその他の空間に対し略密閉する構造とし、該密閉空間への光ビームの入射出用の開口部に配置される平行平板を持ち、前記平行平板の透過率は、前記走査レンズ光軸を挟み反光源側で高くなっていることを特徴とする光走査装置。
〔６〕電子写真プロセスを実行することによって画像を形成する画像形成装置であって、電子写真プロセスの露光プロセスを実行する手段として前記〔１〕〜〔５〕のいずれかに記載の光走査装置を具備した画像形成装置。 The present invention provided to solve the above problems is as follows.
[1] A plurality of light emitting points are arranged on a straight line, and the light beam emitted from the light emitting point is rotated about the light emitting direction as a rotation axis so that the adjacent light emitting points have a distance in the main scanning direction and the sub-scanning direction. And a light deflector that deflects and scans a light beam incident from the light source in a state including more P-polarized light component than S-polarized light component on the deflecting reflection surface in the main scanning direction, and deflected by the light deflector A scanning optical system that forms an image of the light beam on the surface to be scanned and a folding mirror that guides the light beam to the surface to be scanned, wherein the folding mirror is a main component of the scanning optical system. A scanning lens having a positive refracting power in the scanning direction is arranged on the scanning surface side, and the light source is a reflecting surface of a folding mirror having the largest deflection angle among the folding mirrors, and sandwiches the scanning lens optical axis and is on the light source side Than the opposite of the light source An optical scanning device, wherein the optical scanning device is rotated and arranged in a direction in which the reflectance of the incident light beam increases.
[2] The optical scanning device according to [1], wherein the plurality of folding mirrors are provided, and all of the plurality of folding mirrors have a positive refractive power in the main scanning direction constituting the scanning optical system. An optical scanning device, wherein the optical scanning device is arranged closer to the surface to be scanned.
[3] In the optical scanning device according to [1] or [2], the space in which the optical deflector is disposed is substantially sealed with respect to the other spaces, and the light beam is incident on and released from the sealed space. An optical scanning device having a parallel plate disposed in an opening, wherein the transmittance of the parallel plate is high on the side opposite to the light source across the optical axis of the scanning lens.
[4] A plurality of light emitting points are arranged on a straight line corresponding to a plurality of scanned surfaces, and the light is emitted so that the adjacent light emitting points have a distance in the main scanning direction and the sub-scanning direction. Main scanning with a plurality of light sources arranged rotating about the light beam emission direction as a rotation axis, and a light beam incident from each of the plurality of light sources in a state including more P-polarized light components than S-polarized light components on the deflecting reflection surface A single optical deflector that deflects and scans in the direction, a scanning optical system that forms an image of the light beam deflected by the optical deflector on a corresponding surface to be scanned, and a corresponding light beam for each of the plurality of light sources. An optical scanning device comprising a plurality of folding mirrors that lead to a scanning surface, wherein the folding mirror is disposed on the corresponding scanned surface side from a scanning lens having a positive refractive power in the main scanning direction that constitutes the scanning optical system. And the plurality of light sources are A direction in which the reflectance of the light beam incident on the opposite side of the light source is higher than the light source side across the optical axis of the scanning lens on the reflecting surface of the corresponding folding mirror having the largest deflection angle. An optical scanning device, wherein the optical scanning device is rotated and arranged.
[5] The optical scanning device according to [4], wherein the space in which the optical deflector is disposed is substantially sealed with respect to other spaces, and is disposed in an opening for entering and exiting the light beam into the sealed space. An optical scanning device characterized in that the transmittance of the parallel plate is high on the side opposite to the light source across the optical axis of the scanning lens.
[6] An image forming apparatus for forming an image by executing an electrophotographic process, the optical scanning apparatus according to any one of [1] to [5] as means for executing an exposure process of an electrophotographic process An image forming apparatus comprising:

本発明の光走査装置によれば、複数の発光点を直線上に配列してなり、隣接する該発光点間で主走査方向及び副走査方向に距離を持つように、出射する光ビームの射出方向を回転軸として回転して配置される光源と、該光源から偏向反射面に対しＳ偏光成分よりＰ偏光成分を多く含む状態で入射する光ビームを主走査方向に偏向走査する光偏向器と、該光偏向器で偏向された光ビームを被走査面に結像する走査光学系と、前記光ビームを被走査面に導く折り返しミラーと、を備える光走査装置において、前記折り返しミラーは、前記走査光学系を構成する主走査方向に正の屈折力を持つ走査レンズより被走査面側に配置されるので、光学素子のレイアウト性を向上し、且つ大型化、コストアップなどを抑制することができる。また、前記光源は、前記折り返しミラーのうち最も偏角が大きい折り返しミラーの反射面で、前記走査レンズ光軸を挟み光源側よりも該光源の反対側で入射する光ビームの反射率が高くなる方向に回転され配置されているので、被走査面上の光量むらを低減させることができる。さらに、タンデム型カラー機に対応した光走査装置として、各色での光量むらの低減、各色の主走査方向での光量むらの一致させることが可能となる。
また本発明の画像形成装置によれば、本発明の光走査装置の採用により、濃度むら、色味の変化の少ない画像形成装置を実現することができる。 According to the optical scanning device of the present invention, a plurality of light emitting points are arranged in a straight line, and the light beam is emitted so that the adjacent light emitting points have a distance in the main scanning direction and the sub-scanning direction. A light source that is rotated with the direction as a rotation axis, and an optical deflector that deflects and scans a light beam incident from the light source in a state including more P-polarized light components than S-polarized light components on the deflecting reflection surface in the main scanning direction. An optical scanning device comprising: a scanning optical system that forms an image of the light beam deflected by the optical deflector on a surface to be scanned; and a folding mirror that guides the light beam to the surface to be scanned. Since it is arranged closer to the surface to be scanned than a scanning lens having a positive refractive power in the main scanning direction constituting the scanning optical system, it is possible to improve the layout of the optical element and to suppress an increase in size and cost. it can. The light source is a reflecting surface of the folding mirror having the largest deflection angle among the folding mirrors, and the reflectance of the light beam incident on the opposite side of the light source is higher than the light source side across the optical axis of the scanning lens. Since it is rotated and arranged in the direction, unevenness in the amount of light on the surface to be scanned can be reduced. Further, as an optical scanning device compatible with a tandem type color machine, it is possible to reduce unevenness in the amount of light for each color and to match unevenness in the amount of light in the main scanning direction for each color.
In addition, according to the image forming apparatus of the present invention, by employing the optical scanning apparatus of the present invention, it is possible to realize an image forming apparatus with little density unevenness and color change.

以下に、本発明に係る光走査装置及び画像形成装置の構成について図面を参照して説明する。
図１は、本発明に係る光走査装置の第１の実施の形態を説明するための概略配置図である。
先ず、図１を参照すると、少なくとも光源１、カップリングレンズ２、シリンドリカルレンズ３、ポリゴンミラー４の偏向走査面、走査レンズＬは、同一平面上に配置されており、光源１は、走査光学系であって主走査方向を長手とする走査レンズＬに対して主走査方向の一方の端部側に配置されている。なお、折り返しミラーは省略している。 The configurations of the optical scanning device and the image forming apparatus according to the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic layout diagram for explaining a first embodiment of an optical scanning device according to the present invention.
First, referring to FIG. 1, at least a light source 1, a coupling lens 2, a cylindrical lens 3, a deflection scanning surface of a polygon mirror 4, and a scanning lens L are arranged on the same plane, and the light source 1 is a scanning optical system. In this case, it is arranged on one end side in the main scanning direction with respect to the scanning lens L having the main scanning direction as a longitudinal direction. Note that the folding mirror is omitted.

ここで、光源１の一態様である半導体レーザから放射された発散性の光束はカップリングレンズ２により以後の光学系に適した光束形態に変換される。カップリングレンズ２により変換された光束形態は、平行光束であることも、弱い発散性あるいは弱い集束性の光束であることもできる。 Here, the divergent light beam emitted from the semiconductor laser which is an embodiment of the light source 1 is converted into a light beam shape suitable for the subsequent optical system by the coupling lens 2. The form of the light beam converted by the coupling lens 2 may be a parallel light beam, or may be a light beam with weak divergence or weak convergence.

ついでカップリングレンズ２からの光束はシリンドリカルレンズ３により副走査方向に集光され、光偏向器としてのポリゴンミラー４の偏向反射面に入射する。 Next, the light beam from the coupling lens 2 is condensed in the sub-scanning direction by the cylindrical lens 3 and enters the deflection reflection surface of the polygon mirror 4 as an optical deflector.

偏向反射面により反射された光束は、ポリゴンミラー４の等速回転とともに等角速度的に偏向し、走査光学系としての走査レンズＬを透過して被走査面である感光体７上に集光する。これにより、偏向光束は被走査面上に光スポットを形成し、被走査面の光走査を行う。 The light beam reflected by the deflecting reflecting surface is deflected at a constant angular velocity as the polygon mirror 4 rotates at a constant speed, passes through a scanning lens L as a scanning optical system, and is condensed on a photoconductor 7 as a scanning surface. . Thereby, the deflected light beam forms a light spot on the surface to be scanned, and performs optical scanning of the surface to be scanned.

図２に、本発明に係る光走査装置の基本構成としての副走査断面図を示す。光源１から走査レンズＬまでは前記説明の通りであるが、走査レンズＬ以降では被走査面としての感光体７に光ビームを導くために折り返しミラーＭ１，Ｍ２が配置される。 FIG. 2 shows a sub-scanning sectional view as a basic configuration of the optical scanning device according to the present invention. The description from the light source 1 to the scanning lens L is as described above. However, after the scanning lens L, folding mirrors M1 and M2 are arranged to guide the light beam to the photosensitive member 7 as the surface to be scanned.

本発明では、光源１には発光点が直線上に並んだＬＤアレイを用いている。そして、光学系の倍率にあわせて被走査面上で所望の副走査ピッチが得られるように、図３に示すように、出射する光ビームの射出方向を回転軸として回転され配置される。この時の回転方向は、図中の発光点Ｐ１，Ｐ２間あるいは発光点Ｐ１’，Ｐ２’間のように副走査方向の間隔（図中△）が得られていればどちら側に回転していても問題は無い。しかし、後で説明する光量むらの発生に関係し、具体的には副走査方向に光ビームを折り返す折り返しミラーの主走査方向両端での反射率が光量むらを低減するようになる方向に光源１を回転させる必要がある。なお、光源１の回転量は、光偏向器（ポリゴンミラー４）で偏向される偏向面に対し１０〜４５ｄｅｇ程度で使われることが多い。 In the present invention, the light source 1 uses an LD array in which light emitting points are arranged on a straight line. Then, as shown in FIG. 3, the light beam is rotated and arranged with the emission direction of the emitted light beam as a rotation axis so as to obtain a desired sub-scanning pitch on the surface to be scanned in accordance with the magnification of the optical system. The direction of rotation at this time is rotating to any side as long as an interval in the sub-scanning direction (Δ in the figure) is obtained, such as between the light emitting points P1 and P2 or between the light emitting points P1 ′ and P2 ′ in the figure. There is no problem. However, the light source 1 is related to the occurrence of unevenness in the amount of light, which will be described later, specifically in the direction in which the reflectance at both ends in the main scanning direction of the folding mirror that folds the light beam in the sub-scanning direction reduces the unevenness in the amount of light. Need to rotate. The rotation amount of the light source 1 is often used at about 10 to 45 degrees with respect to the deflection surface deflected by the optical deflector (polygon mirror 4).

まず、ポリゴンミラー４における反射を考える。
この場合、ＬＤアレイの光源１は、発光点が並ぶ方向に偏光方向が向いているため、光偏向器としてのポリゴンミラー４に対してはＳ偏光成分よりもＰ偏光成分が多く含まれる状態で入射する。この結果、ポリゴンミラー４での反射率は、ポリゴンミラーの回転に伴うポリゴンミラーへの入射角の変化に応じて、光源１側に偏向される時に高く、反光源側（光源１とは反対側）に偏向される時に低くなる。この傾向は、ポリゴンミラー４に入射する光ビームの偏光がＰ偏光成分を多く含むほど強くなる。つまり、先に述べたように実際にはＬＤアレイはその発光点間隔が３０μｍ程度あることから、１０〜４５ｄｅｇ程度回転し使用されることが多く、Ｐ偏光成分が多く含まれた状態でポリゴンミラー４に入射されていることとなる。なお、光源１側への偏向とは、ポリゴンミラー４での反射光が走査レンズＬの光軸を中心として、光源１側に反射されることといい、反光源側への偏向とは、前記光軸に対して光源１とは反対側に反射されることをいう。 First, the reflection at the polygon mirror 4 is considered.
In this case, since the light source 1 of the LD array has the polarization direction in the direction in which the light emitting points are arranged, the polygon mirror 4 as an optical deflector contains more P-polarized components than S-polarized components. Incident. As a result, the reflectance at the polygon mirror 4 is high when deflected to the light source 1 side according to the change in the incident angle to the polygon mirror accompanying the rotation of the polygon mirror, and is opposite to the light source side (the side opposite to the light source 1). ) Becomes lower when deflected. This tendency becomes stronger as the polarization of the light beam incident on the polygon mirror 4 includes more P-polarized components. In other words, as described above, since the LD array actually has a light emitting point interval of about 30 μm, it is often used by rotating about 10 to 45 deg. 4 is incident. The deflection to the light source 1 side means that the reflected light from the polygon mirror 4 is reflected to the light source 1 side with the optical axis of the scanning lens L as the center. This means that the light is reflected to the opposite side of the light source 1 with respect to the optical axis.

この状態において、ポリゴンミラー４の反射率に対して、光源１の回転方向による影響は小さい。これは、ポリゴンミラー４の偏光反射面４ｍへの入射光と反射光を含む平面（図４中点線）が、偏向する方向に寄らず一定であるためである。反射においては、前記平面に直交する方向（Ｓ偏光）での反射率が高くなる。そして、図４に示すように、回転方向が異なっていてもＳ偏光成分、Ｐ偏光成分の比率は変わらないため反射率の変化は小さくなることとなる。なお、図４において実線の矢印が入射する光ビームの偏光方向を示している。図中の点線、矢印は模式的に表しておりその角度は実際とは異なる。 In this state, the influence of the rotation direction of the light source 1 on the reflectance of the polygon mirror 4 is small. This is because the plane (indicated by the dotted line in FIG. 4) including the incident light and the reflected light on the polarization reflecting surface 4m of the polygon mirror 4 is constant regardless of the direction of deflection. In reflection, the reflectance in the direction orthogonal to the plane (S-polarized light) increases. As shown in FIG. 4, even if the rotation directions are different, the ratio of the S-polarized component and the P-polarized component does not change, so the change in reflectance becomes small. In FIG. 4, a solid line arrow indicates the polarization direction of the incident light beam. The dotted lines and arrows in the figure are schematically shown, and the angles are different from actual ones.

しかし、前記説明の通り、Ｐ偏光成分が多く含まれた状態でポリゴンミラー４の偏向反射面４ｍに光ビームが入射するため、光源１側に対し反光源側で光量が低くなって光量むらが発生することになる。 However, as described above, the light beam is incident on the deflecting / reflecting surface 4m of the polygon mirror 4 in a state where a large amount of P-polarized light component is contained. Will occur.

つぎに、折り返しミラーにおける反射を考える。
折り返しミラーは、光偏向器（ポリゴンミラー４）で偏向される光ビームを副走査方向に反射する機能を持つ。このため、入射光と反射光を含む平面は、主走査方向の光源１側、中央、反光源側という位置によって異なる。ここで、折り返しミラーに入射する光ビームの偏光方向は、主走査方向の位置に寄らず略一定（偏向方向が逆転するほどの大きな変化は無い）であるため、入射光の偏光方向（ＬＤアレイ（光源１）の回転方向）により、反射率が主走査方向で異なることとなる。 Next, the reflection at the folding mirror is considered.
The folding mirror has a function of reflecting the light beam deflected by the optical deflector (polygon mirror 4) in the sub-scanning direction. For this reason, the plane including the incident light and the reflected light differs depending on the positions of the light source 1 side, the center, and the counter light source side in the main scanning direction. Here, the polarization direction of the light beam incident on the folding mirror is substantially constant regardless of the position in the main scanning direction (there is no significant change that reverses the deflection direction). Depending on (the rotation direction of the light source 1), the reflectance varies in the main scanning direction.

そこで、本発明では、前記説明の光偏向器（ポリゴンミラー４）における光量むらを低減する為に、折り返しミラーの反射率が走査レンズの光軸（走査レンズ光軸）を挟み反光源側で高くなるように入射光の偏光方向、つまり、ＬＤアレイ（光源１）の回転方向を決める。この時、副走査方向に反射する偏角が最も大きい折り返しミラーでＬＤアレイ（光源１）の回転方向を決める必要がある。 Therefore, in the present invention, in order to reduce unevenness in the light deflector (polygon mirror 4) described above, the reflectivity of the folding mirror is high on the side opposite to the light source across the optical axis of the scanning lens (scanning lens optical axis). Thus, the polarization direction of incident light, that is, the rotation direction of the LD array (light source 1) is determined. At this time, it is necessary to determine the rotation direction of the LD array (light source 1) with a folding mirror having the largest deflection angle reflected in the sub-scanning direction.

例えば、図２に示すような光走査装置においては、２枚の折り返しミラーＭ１，Ｍ２のうち上流側の折り返しミラーＭ１を基準としてＬＤアレイ（光源１）の回転方向を決めると、光偏向器（ポリゴンミラー４）での光量むらを低減できず、より光量むらを大きく発生させてしまう。これは、上流側のミラーＭ１の副走査方向の偏角が鋭角で、下流側の折り返しミラーＭ２の副走査方向の偏角が鈍角である点、光ビームを副走査方向に折り返す方向が異なる点によるものである。なお、ここでいう偏角とは、入射光と反射光のなす角をいう。 For example, in the optical scanning device as shown in FIG. 2, when the rotation direction of the LD array (light source 1) is determined with reference to the upstream folding mirror M1 of the two folding mirrors M1, M2, the optical deflector ( The unevenness in the amount of light at the polygon mirror 4) cannot be reduced, and the unevenness in the amount of light is generated more greatly. This is because the deflection angle in the sub-scanning direction of the upstream mirror M1 is an acute angle, the deflection angle in the sub-scanning direction of the downstream folding mirror M2 is an obtuse angle, and the direction in which the light beam is folded back in the sub-scanning direction is different. Is due to. The declination here refers to an angle formed between incident light and reflected light.

図５に、２枚の折り返しミラーＭ１，Ｍ２での光ビームの偏光方向と、入射光と反射光を含む平面を示す。図５（ａ）が折り返しミラーＭ１の反射面、図５（ｂ）が折り返しミラーＭ２の反射面である。
図５において、入射光と反射光を含む平面を点線、偏光方向を実線とすると、上流側の折り返しミラーＭ１と下流側の折り返しミラーＭ２で、副走査方向に反射する方向が異なるため、入射光と反射光を含む平面を示す点線の向きが変化する。一方、偏光方向は変化しない（図中はミラー面を入射方向から見ているため反転）ため、各々の折り返しミラーＭ１，Ｍ２で反射率が高くなる方向は異なることとなる。本実施例では、上流の折り返しミラーＭ１では光源１側で反射率が高くなり、下流側の折り返しミラーＭ２では反光源側で反射率が高くなる。説明を加えると、例えば下流側の折り返しミラーＭ２の反光源側は点線に対し垂直な方向のＳ偏光成分が多く（点線に直交する成分）、光源１側はＳ偏光成分が少ない（偏光方向が点線に近い）。この結果、反光源側で反射率が高いこととなる。 FIG. 5 shows the polarization direction of the light beam at the two folding mirrors M1 and M2, and a plane including the incident light and the reflected light. FIG. 5A shows the reflecting surface of the folding mirror M1, and FIG. 5B shows the reflecting surface of the folding mirror M2.
In FIG. 5, if the plane including the incident light and the reflected light is a dotted line and the polarization direction is a solid line, the reflected light in the sub-scanning direction is different between the upstream folding mirror M1 and the downstream folding mirror M2. And the direction of the dotted line indicating the plane including the reflected light changes. On the other hand, since the polarization direction does not change (in the figure, the mirror surface is reversed because it is viewed from the incident direction), the direction in which the reflectivity increases in each of the folding mirrors M1 and M2 is different. In the present embodiment, the reflectance of the upstream folding mirror M1 is high on the light source 1 side, and the reflectance of the downstream folding mirror M2 is high on the side opposite to the light source. For example, the anti-light source side of the folding mirror M2 on the downstream side has many S-polarized components in the direction perpendicular to the dotted line (component perpendicular to the dotted lines), and the light source 1 side has few S-polarized components (the polarization direction is small). Close to the dotted line). As a result, the reflectance is high on the side opposite to the light source.

次に、各々の折り返しミラーＭ１，Ｍ２の副走査方向の偏角について説明する。
偏角が小さいほど、図５に示す入射光と反射光を含む平面（点線）は、両端で中央の状態に近づく（図中垂直になる方向に動く）。つまり、折り返しミラーでの左右両端での反射率の差は小さくなる。下流側のミラーＭ２では、偏角が大きいため、入射光と反射光を含む平面（点線）は、両端でより倒れていくため、折り返しミラーでの左右両端での反射率の差は大きくなる。 Next, the deflection angles in the sub-scanning direction of the respective folding mirrors M1 and M2 will be described.
As the declination is smaller, the plane (dotted line) including the incident light and the reflected light shown in FIG. 5 approaches the center state at both ends (moves in a direction perpendicular to the figure). That is, the difference in reflectance between the left and right ends of the folding mirror is small. Since the downstream mirror M2 has a large declination, the plane (dotted line) including the incident light and the reflected light is more inclined at both ends, so that the difference in reflectance between the left and right ends of the folding mirror becomes large.

つまり、上流側の折り返しミラーＭ１で反射率を最適化する方向に、偏光方向、つまりＬＤアレイ（光源１）の回転方向を決めると、下流側のミラーＭ２での反射率の差が大きいため、被走査面（感光体７）上で光量むらを低減できないこととなる。このため、副走査方向への偏角が最も大きい（鈍角となる）折り返しミラー（図２では下流側の折り返しミラーＭ２）にて、ＬＤアレイ（光源１）の回転方向を決める必要がある。 That is, when the polarization direction, that is, the rotation direction of the LD array (light source 1) is determined in the direction in which the reflectance is optimized by the upstream folding mirror M1, the difference in reflectance at the downstream mirror M2 is large. The unevenness in the amount of light cannot be reduced on the surface to be scanned (photoconductor 7). For this reason, it is necessary to determine the rotation direction of the LD array (light source 1) at the folding mirror (the folding mirror M2 on the downstream side in FIG. 2) having the largest declination in the sub-scanning direction (oblique angle).

以上のように本発明では、副走査方向への偏角が最も大きい（鈍角となる）折り返しミラー（図２では下流側の折り返しミラーＭ２）を基準として、図５（ｂ）の関係になるように、ＬＤアレイ（光源１）を回転させる。図６にその具体例を示す。この図は、図１においてカップリングレンズ２から光源１をみたときの発光点の回転状態を示している。このとき、２つの発光点が水平状態のときから左方向に所定角度αで回転している。所定角度αは、１０〜４５ｄｅｇが好ましい。 As described above, in the present invention, the relationship shown in FIG. 5B is established with reference to the folding mirror (the folding mirror M2 on the downstream side in FIG. 2) having the largest declination in the sub-scanning direction (oblique angle). Then, the LD array (light source 1) is rotated. A specific example is shown in FIG. This figure shows the rotation state of the light emitting point when the light source 1 is viewed from the coupling lens 2 in FIG. At this time, the two light emitting points are rotated leftward at a predetermined angle α from the horizontal state. The predetermined angle α is preferably 10 to 45 deg.

更に、折り返しミラーの配置として、折り返しミラーが１枚、あるいは複数枚のいずれの場合でも、全ての折り返しミラーを主走査方向に屈折力を持つ走査レンズより被走査面側に置く構成がよい。これは、例えば１枚構成の走査レンズの場合など、折り返しミラーを走査レンズより上流に配置すると、光偏向器から走査レンズを離す必要が生じ、走査レンズが大型化したり光学レイアウトが困難となり光走査装置が大型化してしまうためである。
また、２枚構成においても走査レンズ間の距離が近い拡大系の走査光学系においては、前記説明と同様である。 Further, as the arrangement of the folding mirrors, it is preferable that all the folding mirrors are placed closer to the surface to be scanned than the scanning lens having refractive power in the main scanning direction regardless of the number of the folding mirrors. This is because, for example, in the case of a single-lens scanning lens, when the folding mirror is arranged upstream of the scanning lens, it becomes necessary to separate the scanning lens from the optical deflector, and the scanning lens becomes large and the optical layout becomes difficult. This is because the apparatus becomes larger.
In the two-lens configuration, the magnification scanning optical system in which the distance between the scanning lenses is short is the same as described above.

更に、主走査方向に正の屈折力を持つ走査レンズより被走査面側に折り返しミラーを持つ場合、折り返しミラー両端での主走査方向の入射角は若干小さくなる。これは、前記折り返しミラー両端での反射率差が無くなるほどの効果は無く、前記効果は失われない範囲であるが、折り返しミラーへ入射する光ビームの偏光方向が若干ばらついた場合において、図５での点線が若干垂直方向になるため光量むら変動への影響は小さくなる。 Further, when the folding mirror is provided on the scanning surface side with respect to the scanning lens having a positive refractive power in the main scanning direction, the incident angles in the main scanning direction at both ends of the folding mirror are slightly reduced. This is not so effective that there is no difference in reflectance at both ends of the folding mirror, and the above effect is not lost. However, in the case where the polarization direction of the light beam incident on the folding mirror varies slightly, FIG. Since the dotted line in FIG. 4 becomes slightly vertical, the influence on the fluctuation in the amount of light is reduced.

走査レンズ間隔の広い走査光学系においては、被走査面側に配置される走査レンズの主走査方向の屈折力は弱く、負の屈折力、もしくはゼロに近い屈折力とすることが可能であり、この場合は、レイアウト性向上、装置の小型化のために走査レンズ間に折り返しミラーを配置しても前記効果は得られることとなる。 In a scanning optical system having a wide scanning lens interval, the refractive power in the main scanning direction of the scanning lens arranged on the scanned surface side is weak, and can be negative refractive power or refractive power close to zero. In this case, the above-mentioned effect can be obtained even if a folding mirror is arranged between the scanning lenses in order to improve the layout and reduce the size of the apparatus.

以上のことをまとめると、本発明に係る光走査装置（図２）は、複数の発光点を直線上に配列してなり、隣接する該発光点間で主走査方向及び副走査方向に距離を持つように、出射する光ビームの射出方向を回転軸として回転して配置される光源（図３）と、該光源から偏向反射面に対しＳ偏光成分よりＰ偏光成分を多く含む状態で入射する光ビームを主走査方向に偏向走査する光偏向器（ポリゴンミラー４）と、該光偏向器で偏向された光ビームを被走査面（感光体７）に結像する走査光学系（走査レンズＬ）と、前記光ビームを被走査面に導く折り返しミラー（折り返しミラーＭ１，Ｍ２）と、を備える光走査装置において、前記折り返しミラーは、前記走査光学系を構成する主走査方向に正の屈折力を持つ走査レンズ（走査レンズＬ）より被走査面側に配置され、前記光源は、前記折り返しミラーのうち最も偏角が大きい折り返しミラー（折り返しミラーＭ２）の反射面で、前記走査レンズ光軸を挟み光源側よりも該光源の反対側で入射する光ビームの反射率が高くなる方向に回転され配置されていることを特徴とするものである。 In summary, the optical scanning device according to the present invention (FIG. 2) is formed by arranging a plurality of light emitting points on a straight line, and the distance between adjacent light emitting points in the main scanning direction and the sub-scanning direction. And a light source (FIG. 3) that is arranged to rotate with the exit direction of the emitted light beam as the rotation axis, and the light source is incident on the deflecting reflection surface in a state that includes more P-polarized components than S-polarized components. An optical deflector (polygon mirror 4) that deflects and scans the light beam in the main scanning direction, and a scanning optical system (scanning lens L) that focuses the light beam deflected by the optical deflector on the surface to be scanned (photosensitive member 7). ) And folding mirrors (folding mirrors M1 and M2) for guiding the light beam to the surface to be scanned, the folding mirror has a positive refractive power in the main scanning direction constituting the scanning optical system. Scanning lens (scanning lens L) The light source is a reflection surface of a folding mirror (folding mirror M2) having the largest deflection angle among the folding mirrors, and is opposite to the light source than the light source side with the scanning lens optical axis in between. The light beam incident on the side is rotated and arranged in a direction in which the reflectance of the light beam increases.

つぎに、本発明に係る光走査装置の第２の実施の形態として、カラー機に対応する光走査装置について説明する。
図７は、本発明に係る光走査装置の第２の実施の形態の構成を示す概略図である。
すなわち、本発明に係る光走査装置（光走査装置３０）は、複数の被走査面（感光体７Ｙ，７Ｍ，７Ｃ，７Ｋ）に対応して、それぞれ複数の発光点を直線上に配列してなり、隣接する該発光点間で主走査方向及び副走査方向に距離を持つように、出射する光ビームの射出方向を回転軸として回転して配置される複数の光源（例えば、図３に示すもの）と、前記複数の光源それぞれから偏向反射面に対しＳ偏光成分よりＰ偏光成分を多く含む状態で入射する光ビームを主走査方向に偏向走査する単一の光偏向器（ポリゴンミラー４）と、光偏向器で偏向された光ビームを対応する被走査面に結像する走査光学系（走査レンズＬ１，Ｌ２，Ｌ３，Ｌ４）と、前記複数の光源毎に、光ビームを対応する被走査面に導く複数の折り返しミラー（折り返しミラーＭ１１，Ｍ１２，Ｍ１３，Ｍ１４，Ｍ１５，Ｍ１６，Ｍ１７，Ｍ１８）と、を備える光走査装置において、前記折り返しミラーは、前記走査光学系を構成する主走査方向に正の屈折力を持つ走査レンズより対応する被走査面側に配置され、前記複数の光源はそれぞれ、対応する前記折り返しミラーのうち最も偏角が大きい折り返しミラー（折り返しミラーＭ１２，Ｍ１４，Ｍ１６，Ｍ１８）の反射面で、前記走査レンズ光軸を挟み光源側よりも該光源の反対側で入射する光ビームの反射率が高くなる方向に回転され配置されていることを特徴とするものである。 Next, an optical scanning device corresponding to a color machine will be described as a second embodiment of the optical scanning device according to the present invention.
FIG. 7 is a schematic diagram showing the configuration of the second embodiment of the optical scanning device according to the present invention.
That is, the optical scanning device (optical scanning device 30) according to the present invention has a plurality of light emitting points arranged in a straight line corresponding to a plurality of scanned surfaces (photosensitive members 7Y, 7M, 7C, 7K). A plurality of light sources (for example, as shown in FIG. 3) are arranged so as to have a distance in the main scanning direction and the sub-scanning direction between the adjacent light emitting points. And a single optical deflector (polygon mirror 4) that deflects and scans in the main scanning direction a light beam incident from a plurality of light sources in a state including more P-polarized light components than S-polarized light components on the deflecting reflecting surface. A scanning optical system (scanning lenses L 1, L 2, L 3, L 4) that forms an image of the light beam deflected by the optical deflector on a corresponding scanned surface, and a corresponding light beam for each of the plurality of light sources. Multiple folding mirrors leading to the scanning surface (folding An optical scanning device comprising mirrors M11, M12, M13, M14, M15, M16, M17, M18), and the folding mirror is a scanning lens having a positive refractive power in the main scanning direction constituting the scanning optical system. The plurality of light sources are arranged on the corresponding scanning surface side, and each of the plurality of light sources is a reflection surface of a folding mirror (folding mirror M12, M14, M16, M18) having the largest deflection angle among the corresponding folding mirrors. The optical axis is rotated and arranged in a direction in which the reflectance of the light beam incident on the opposite side of the light source is higher than that on the light source side across the lens optical axis.

図８に、本実施形態における折り返しミラーの２種類の配置例を示す。なお、光源１の回転方向と折り返しミラーの関係による光量むら低減については第１の実施の形態と同じ効果が得られるため説明を割愛する。
図８において、楕円で囲っている折り返しミラー（図８（ａ）では折り返しミラーＭ１２，Ｍ１４，Ｍ１６，Ｍ１８、図８（ｂ）では折り返しミラーＭ２２，Ｍ２４，Ｍ２６，Ｍ２８）が、副走査方向の偏角が最も大きくなる折り返しミラーであり、このミラーで反光源側の反射率が高くなるように、ＬＤアレイ（光源１）の回転方向を決めることとなる。 FIG. 8 shows two types of arrangement examples of the folding mirror in the present embodiment. In addition, since the same effect as 1st Embodiment is acquired about the light quantity nonuniformity reduction by the relationship between the rotation direction of the light source 1 and a folding mirror, description is omitted.
8, folding mirrors (folding mirrors M12, M14, M16, and M18 in FIG. 8A and folding mirrors M22, M24, M26, and M28 in FIG. 8B) surrounded by an ellipse are arranged in the sub-scanning direction. The folding mirror has the largest declination, and the rotational direction of the LD array (light source 1) is determined so that the reflectance on the side opposite to the light source is increased by this mirror.

なお、カラー画像を形成する画像形成装置（カラー機）に対応する光走査装置においては、図８に示す通り、各色（感光体７Ｙ，７Ｍ，７Ｃ，７Ｋそれぞれ）に対応する折り返しミラーは複数配置される。例えば、図８（ａ）の感光体７Ｙには２つの折り返しミラーＭ１１，Ｍ１２が配置される。この時、最も上流側の折り返しミラーを副走査方向の偏角が最も大きくすることは現実的ではない。また、主走査方向に正の屈折力を持つ走査レンズの前、すなわち図中、光偏向器（ポリゴンミラー４）と走査レンズ（走査レンズＬ１，Ｌ２，Ｌ３，Ｌ４）の間に配置することは、複数の感光体を単一の光偏向器で走査する光学系においては現実的ではない。 In an optical scanning device corresponding to an image forming apparatus (color machine) that forms a color image, as shown in FIG. 8, a plurality of folding mirrors corresponding to each color (photosensitive members 7Y, 7M, 7C, and 7K) are arranged. Is done. For example, two folding mirrors M11 and M12 are arranged on the photoconductor 7Y in FIG. At this time, it is not realistic to make the deflection angle in the sub-scanning direction the largest upstream folding mirror. Further, it is arranged before the scanning lens having a positive refractive power in the main scanning direction, that is, between the optical deflector (polygon mirror 4) and the scanning lens (scanning lenses L1, L2, L3, L4) in the drawing. In an optical system that scans a plurality of photoconductors with a single optical deflector, it is not realistic.

また、カラー機において、各色に対応する光源１全てを第１の実施形態で説明した構成にすることで、各色で残存している光量むらの状況は揃うこととなる。この結果、単色での濃度むらのみでなく、各色の画像を重ね合わせてカラー画像を得る際の主走査方向での色味の変化も低減することが可能となる。つまり、カラー機で特有の課題となる画像品質である色むらの低減を達成可能となる。 Further, in the color machine, all the light sources 1 corresponding to the respective colors are configured as described in the first embodiment, so that the unevenness of the amount of light remaining in the respective colors is uniformed. As a result, it is possible to reduce not only the density unevenness in a single color, but also the change in color in the main scanning direction when a color image is obtained by superimposing the images of the respective colors. That is, it is possible to achieve a reduction in color unevenness, which is an image quality that is a particular problem in color machines.

ところで、図２，図７に示す光走査装置において、光偏向器（ポリゴンミラー４）を配置する空間をその他の空間（周辺空間）に対し略密閉する構造とし、前記密閉空間への光ビームの入射出用の開口部に配置される平行平板を持ち、前記平行平板の透過率は、走査レンズ光軸を挟み反光源側で高くなっていることが望ましい。 By the way, in the optical scanning device shown in FIGS. 2 and 7, the space in which the optical deflector (polygon mirror 4) is arranged is substantially sealed with respect to other spaces (peripheral spaces), and the light beam to the sealed space is formed. It is desirable to have a parallel plate disposed in the entrance / exit opening, and the transmittance of the parallel plate is high on the side opposite to the light source across the optical axis of the scanning lens.

平行平板の必要性、つまり光偏向器を配置する空間をその他の空間に対し略密閉する構造とする効果については、前にも述べたが、（１）高速回転に伴う騒音を抑制する、（２）光偏向器の高速回転に伴う熱の発生を、走査光学系を構成する走査レンズなどの光学素子に伝えることを抑制する、（３）空気中のちりなどの偏向反射面への付着を防ぐなどの効果を得ることができる。 The necessity of the parallel plate, that is, the effect of making the space in which the optical deflector is disposed substantially sealed with respect to other spaces has been described above, but (1) suppresses noise accompanying high-speed rotation. 2) Suppressing the generation of heat associated with the high-speed rotation of the optical deflector to an optical element such as a scanning lens constituting the scanning optical system, (3) Adhering to a deflecting reflecting surface such as dust in the air Effects such as prevention can be obtained.

近年、走査レンズ等の光学素子は光学特性向上のため、自由な面形状を形成可能な樹脂製のものが多く採用されており、前記光偏向器（ポリゴンミラー４）の熱が空気中を伝播して光学素子に伝わることにより、走査レンズの特に主走査方向に温度分布が生じ、レンズ面形状が乱れ、光学性能を著しく低下させてしまう。また、光偏向器の偏向反射面にちりなどが付着し曇りが生じると、偏向走査される方向に光量むらが発生し、画像における濃度むらの発生、カラー機においては色味の変化などが生じ光学特性が著しく低下してしまう。このちり等による偏向反射面の曇りは、回転下流側のエッジ部に付着するため、光偏向器の偏向方向により光束が曇り部にかかり光量むらが生じる。この光量むらは、経時的な変動として現れるため曇り自体を発生させない構造にする必要がある。 In recent years, in order to improve optical characteristics, many optical elements such as scanning lenses are made of resin capable of forming a free surface shape, and the heat of the optical deflector (polygon mirror 4) propagates in the air. By being transmitted to the optical element, a temperature distribution is generated in the scanning lens, particularly in the main scanning direction, the lens surface shape is disturbed, and the optical performance is remarkably deteriorated. In addition, if dust or the like adheres to the deflecting reflection surface of the optical deflector and fogging occurs, unevenness in the amount of light occurs in the direction of deflection scanning, causing unevenness in density in the image, and changing color in a color machine. The optical characteristics are significantly deteriorated. The fogging of the deflection reflecting surface due to this dust or the like adheres to the edge portion on the downstream side of the rotation, so that the light flux is applied to the clouding portion depending on the deflection direction of the optical deflector, resulting in unevenness in the amount of light. Since this unevenness in the amount of light appears as a change with time, it is necessary to have a structure that does not generate fogging itself.

以上のことから、本発明に係る光走査装置では光偏向器（ポリゴンミラー４）を配置する空間を略密閉とし、平行平板を介して光ビームが光偏向器（ポリゴンミラー４）に入射出する構成とする。 From the above, in the optical scanning device according to the present invention, the space in which the optical deflector (polygon mirror 4) is arranged is substantially sealed, and the light beam enters and exits the optical deflector (polygon mirror 4) via the parallel plate. The configuration.

なお、平行平板を光ビームが透過する際に、光源側と反光源側で光量差が生じる。これは、平行平板を偏芯配置する偏芯量により比率が変化するためである（偏芯配置の方向は例えば図７に示す通りである）。この時、前記平行平板の透過率は、走査レンズ光軸を挟み反光源側で高くなるように配置することが望ましい。先に述べた光偏向器（ポリゴンミラー４）での光源１側と反光源側での反射率の差は大きく、前記折り返しミラーとＬＤアレイ（光源１）の回転方向のみでなく、平行平板の偏芯を用いて光量むらを低減することが可能となる。 When the light beam is transmitted through the parallel plate, a light amount difference occurs between the light source side and the counter light source side. This is because the ratio changes depending on the amount of eccentricity in which the parallel flat plates are arranged eccentrically (the direction of the eccentric arrangement is as shown in FIG. 7, for example). At this time, it is desirable that the transmittance of the parallel plate is arranged to be higher on the side opposite to the light source across the scanning lens optical axis. The difference in reflectance between the light source 1 side and the non-light source side in the optical deflector (polygon mirror 4) described above is large, and not only the rotation direction of the folding mirror and the LD array (light source 1), but also the parallel plate It is possible to reduce unevenness in the amount of light using eccentricity.

次に、本発明に係る光走査装置を用いた画像形成装置の一実施の形態を、図９を参照しながら説明する。本実施の形態は、本発明に係る光走査装置３０をタンデム型フルカラーレーザプリンタに適用した例である。
図９において、画像形成装置１００内の下部側には水平方向に配設された給紙カセット１３から給紙される転写紙Ｓを搬送する搬送ベルト１７が設けられている。この搬送ベルト１７上にはイエローＹ用の感光体７Ｙ，マゼンタＭ用の感光体７Ｍ，シアンＣ用の感光体７Ｃ及びブラックＫ用の感光体７Ｋが、転写紙の搬送方向上流側から順に等間隔で配設されている。なお、以下、符号に対する添字Ｙ，Ｍ，Ｃ，Ｋを適宜付けて区別するものとする。 Next, an embodiment of an image forming apparatus using the optical scanning device according to the present invention will be described with reference to FIG. This embodiment is an example in which the optical scanning device 30 according to the present invention is applied to a tandem type full color laser printer.
In FIG. 9, a conveying belt 17 that conveys the transfer sheet S fed from the sheet feeding cassette 13 disposed in the horizontal direction is provided on the lower side in the image forming apparatus 100. On the conveying belt 17, a photosensitive member 7Y for yellow Y, a photosensitive member 7M for magenta M, a photosensitive member 7C for cyan C, and a photosensitive member 7K for black K are sequentially arranged from the upstream side in the conveying direction of the transfer paper. They are arranged at intervals. Hereinafter, subscripts Y, M, C, and K are appropriately added to the reference numerals for distinction.

これらの感光体７Ｙ，７Ｍ，７Ｃ，７Ｋは全て同一径に形成されたもので、その周囲には、電子写真プロセスにしたがって各プロセスを実行するプロセス部材が順に配設されている。感光体７Ｙを例に採れば、帯電チャージャ８Ｙ、光走査装置３０の一部である光走査光学系６Ｙ、現像装置１０Ｙ、転写チャージャ１１Ｙ、クリーニング装置１２Ｙ等が順に配設されている。他の感光体７Ｍ，７Ｃ，７Ｋに対しても同様である。即ち、本実施の形態では、感光体７Ｙ，７Ｍ，７Ｃ，７Ｋの表面を各色毎に設定された被走査面ないしは被照射面とするものであり、各々の感光体に対して光走査装置３０の一部である光走査光学系６Ｙ，６Ｍ，６Ｃ，６Ｋが１対１の対応関係で設けられている。 These photoreceptors 7Y, 7M, 7C, and 7K are all formed to have the same diameter, and process members that perform each process according to the electrophotographic process are sequentially arranged around the photoreceptors. Taking the photoconductor 7Y as an example, a charging charger 8Y, an optical scanning optical system 6Y that is a part of the optical scanning device 30, a developing device 10Y, a transfer charger 11Y, a cleaning device 12Y, and the like are sequentially arranged. The same applies to the other photoconductors 7M, 7C, and 7K. In other words, in the present embodiment, the surfaces of the photoconductors 7Y, 7M, 7C, and 7K are used as scan surfaces or irradiation surfaces set for the respective colors, and the optical scanning device 30 is applied to each photoconductor. The optical scanning optical systems 6Y, 6M, 6C, and 6K, which are a part of each, are provided in a one-to-one correspondence.

また、搬送ベルト１７の周囲には、感光体７Ｙよりも上流側に位置させてレジストローラ１６と、ベルト帯電チャージャ２０が設けられ、感光体７Ｋよりもベルト１７の回転方向下流側に位置させてベルト分離チャージャ２１、除電チャージャ１８、クリーニング装置１２等が順に設けられている。また、ベルト分離チャージャ２１よりも転写紙搬送方向下流側には定着装置２４が設けられ、排紙トレイ２６に向けて排紙ローラ２５で結ばれている。 In addition, a registration roller 16 and a belt charging charger 20 are provided around the transport belt 17 on the upstream side of the photoconductor 7Y, and are positioned on the downstream side in the rotation direction of the belt 17 with respect to the photoconductor 7K. A belt separation charger 21, a charge removal charger 18, a cleaning device 12, and the like are provided in this order. Further, a fixing device 24 is provided downstream of the belt separation charger 21 in the transfer paper conveyance direction, and is connected to a paper discharge tray 26 by a paper discharge roller 25.

このような概略構成において、例えば、フルカラーモード（複数色モード）時であれば、各感光体７Ｙ，７Ｍ，７Ｃ，７Ｋに対してＹ，Ｍ，Ｃ，Ｋ用の各色の画像信号に基づき各々の光走査装置６Ｙ，６Ｍ，６Ｃ，６Ｋによる光ビームの光走査で、各感光体表面に、各色信号に対応した静電潜像が形成される。これらの静電潜像は各々の対応する現像装置で色トナーにより現像されてトナー像となり、搬送ベルト１７上に静電的に吸着されて搬送される転写紙上に順次転写されることにより重ね合わせられ、転写紙上にフルカラー画像が形成される。このフルカラー像は定着装置２４で定着された後、排紙ローラ２５により排紙トレイ２６に排紙される。 In such a schematic configuration, for example, in the case of the full color mode (multiple color mode), each of the photoconductors 7Y, 7M, 7C, and 7K is based on image signals of colors Y, M, C, and K, respectively. In this optical scanning device 6Y, 6M, 6C, 6K, an electrostatic latent image corresponding to each color signal is formed on the surface of each photoconductor. These electrostatic latent images are developed with color toners by the corresponding developing devices to become toner images, which are superposed by being sequentially transferred onto transfer paper that is electrostatically attracted onto the transport belt 17 and transported. As a result, a full-color image is formed on the transfer paper. This full-color image is fixed by the fixing device 24 and then discharged to a discharge tray 26 by a discharge roller 25.

上記画像形成装置の光走査光学系６Ｙ，６Ｍ，６Ｃ，６Ｋを、前述の本発明に係る光走査装置３０とすることで、被走査面での光量むらを有効に補正し、濃度むら、色味の変化の小さい、高品位な画像再現性が確保できる画像形成装置を実現することができる。 By using the optical scanning optical systems 6Y, 6M, 6C, and 6K of the image forming apparatus as the optical scanning device 30 according to the present invention described above, unevenness in the amount of light on the surface to be scanned is effectively corrected, unevenness in density, and color. An image forming apparatus that can ensure high-quality image reproducibility with small change in taste can be realized.

以下、本発明の光走査装置に関する具体的な数値実施例を挙げる。
（実施例１）
図１に示す光走査装置を前提に、副走査断面の構成を図１０に示すように、走査レンズＬ以降で感光体７に光ビームを導くために折り返しミラーＭ１’，Ｍ２’を配置したものとした。このとき、光源１として用いられる半導体レーザは発光波長：６５９ｎｍのもので、放射される発散性の光束はカップリングレンズ２（焦点距離：２７ｍｍ）により「弱い発散光束」に変換され、副走査方向にのみ屈折力を持つレンズ３で、ポリゴンミラー４の偏向反射面４ｍの位置に「主走査方向に長い線像」として結像する。 Specific numerical examples relating to the optical scanning device of the present invention will be given below.
Example 1
Assuming the optical scanning device shown in FIG. 1, the configuration of the sub-scan section is shown in FIG. 10, in which folding mirrors M1 ′ and M2 ′ are arranged to guide the light beam to the photosensitive member 7 after the scanning lens L. It was. At this time, the semiconductor laser used as the light source 1 has an emission wavelength of 659 nm, and the emitted divergent light beam is converted into a “weak divergent light beam” by the coupling lens 2 (focal length: 27 mm), and is in the sub-scanning direction. With the lens 3 having a refractive power only, a “line image long in the main scanning direction” is formed at the position of the deflecting / reflecting surface 4 m of the polygon mirror 4.

ポリゴンミラー４は、偏向反射面数：６で内接円半径：１３ｍｍのものである。また、ポリゴンミラー４の回転軸と偏向反射面４ｍは平行に形成されており、偏向反射面４ｍに光ビームは、主走査方向においては像高０に向かう光束に対し約６８°で入射されている。カップリングレンズ２から射出された光束を規制するアパーチャは、主走査方向に２．３ｍｍ、副走査方向に２．２ｍｍの矩形アパーチャを用いる。 The polygon mirror 4 has a deflecting reflection surface number of 6 and an inscribed circle radius of 13 mm. Further, the rotation axis of the polygon mirror 4 and the deflecting / reflecting surface 4m are formed in parallel, and the light beam is incident on the deflecting / reflecting surface 4m at about 68 ° with respect to the light beam toward the image height 0 in the main scanning direction. Yes. The aperture that regulates the light beam emitted from the coupling lens 2 is a rectangular aperture of 2.3 mm in the main scanning direction and 2.2 mm in the sub-scanning direction.

なお、走査レンズＬは１枚構成で、面形状、配置位置は表１に示す通りである。表１における面番号として、偏向面はポリゴンミラー４の偏向反射面４ｍ、１は走査レンズＬの光入射側の面、２は光出射側の面、５は被走査面（感光体７）である。また、下記Ｘは、各面がポリゴンミラー４の回転軸に垂直な面に投影したときの光軸方向の距離を示し、表中のＮ（屈折率）は、波長６５９ｎｍでの値である。 The scanning lens L has a single lens configuration, and the surface shape and arrangement position are as shown in Table 1. As the surface numbers in Table 1, the deflection surface is the deflection reflection surface 4m of the polygon mirror 1, 1 is the light incident side surface of the scanning lens L, 2 is the light emission side surface, and 5 is the surface to be scanned (photosensitive member 7). is there. The following X indicates the distance in the optical axis direction when each surface is projected onto a surface perpendicular to the rotation axis of the polygon mirror 4, and N (refractive index) in the table is a value at a wavelength of 659 nm.

また、走査レンズＬのレンズ面形状は次式（１）で与えられる。 The lens surface shape of the scanning lens L is given by the following equation (1).

また、本実施例の走査レンズＬにおける非球面係数は表２のとおりである。 Table 2 shows the aspheric coefficients in the scanning lens L of this example.

ここで、光源１の発光点は２つで、図６に示すように、図１においてカップリングレンズ２から光源１をみたときの２つ発光点を水平状態のときから左方向にα＝１０．５ｄｅｇで回転して用いた。 Here, the light emission point of the light source 1 is two, and as shown in FIG. 6, the two light emission points when the light source 1 is viewed from the coupling lens 2 in FIG. Used by rotating at .5 deg.

また、図１０に示す形態で走査レンズＬと感光体７の間に２枚の折り返しミラーＭ１，Ｍ２を配置した。そのうち、上流側の折り返しミラーＭ１’をポリゴンミラー４の回転軸に対し１２ｄｅｇ、下流側の折り返しミラーＭ２’を４０ｄｅｇだけ副走査方向に傾けて配置した。このときの２枚の折り返しミラーＭ１’，Ｍ２’での光ビームの偏光方向と、入射光と反射光を含む平面を図１１に示す。図１１（ａ）が折り返しミラーＭ１’の反射面、図１１（ｂ）が折り返しミラーＭ２’の反射面である。また、いずれも反射面を入射側から見た図である。
また、本光学系においては、厚さ１．９ｍｍの防音ガラス（屈折率１．５１４３）を挿入し、該防音ガラスを１２ｄｅｇだけ偏向面内で傾けて配置した。 Further, two folding mirrors M1 and M2 are arranged between the scanning lens L and the photoconductor 7 in the form shown in FIG. Among them, the upstream folding mirror M1 ′ is disposed so as to be inclined by 12 degrees with respect to the rotation axis of the polygon mirror 4, and the downstream folding mirror M2 ′ is tilted by 40 degrees in the sub-scanning direction. FIG. 11 shows the polarization direction of the light beam at the two folding mirrors M1 ′ and M2 ′ and the plane including the incident light and the reflected light. FIG. 11A shows the reflecting surface of the folding mirror M1 ′, and FIG. 11B shows the reflecting surface of the folding mirror M2 ′. Moreover, all are the figures which looked at the reflective surface from the incident side.
Further, in this optical system, a soundproof glass (refractive index of 1.5143) having a thickness of 1.9 mm was inserted, and the soundproof glass was inclined by 12 deg within the deflection surface.

以上の構成で、被走査面上の光量を測定した。その結果を図１２（ａ）に示す。また、光源１の回転方向を反転させて同様の測定を行った結果を図１２（ｂ）に示す。なお、図１２における縦軸のシェーディングとは、被走査面上の主走査方向の最大光量に対する変動の比率である。 With the above configuration, the amount of light on the surface to be scanned was measured. The result is shown in FIG. Moreover, the result of having performed the same measurement by reversing the rotation direction of the light source 1 is shown in FIG. Note that the shading on the vertical axis in FIG. 12 is the ratio of fluctuation to the maximum light amount in the main scanning direction on the surface to be scanned.

なお、これまで本発明を図面に示した実施形態をもって説明してきたが、本発明は図面に示した実施形態に限定されるものではなく、他の実施形態、追加、変更、削除など、当業者が想到することができる範囲内で変更することができ、いずれの態様においても本発明の作用・効果を奏する限り、本発明の範囲に含まれるものである。 Although the present invention has been described with the embodiments shown in the drawings, the present invention is not limited to the embodiments shown in the drawings, and other embodiments, additions, modifications, deletions, etc. Can be changed within the range that can be conceived, and any embodiment is included in the scope of the present invention as long as the effects and advantages of the present invention are exhibited.

本発明に係る光走査装置の第１の実施の形態を説明するための概略配置図である。1 is a schematic arrangement diagram for explaining a first embodiment of an optical scanning device according to the present invention; FIG. 本発明に係る光走査装置の第１の実施の形態の構成を示す断面図である。It is sectional drawing which shows the structure of 1st Embodiment of the optical scanning device based on this invention. 光源であるＬＤアレイにおける発光点の回転関係を示す図である。It is a figure which shows the rotational relationship of the light emission point in LD array which is a light source. ポリゴンミラーの偏光反射面における入射光と反射光を含む平面と光ビームの偏光方向との関係を示す図である。It is a figure which shows the relationship between the plane containing incident light and reflected light in the polarization reflective surface of a polygon mirror, and the polarization direction of a light beam. 折り返しミラーにおける入射光と反射光を含む平面と光ビームの偏光方向との関係を示す図である。It is a figure which shows the relationship between the plane containing incident light and reflected light in a folding mirror, and the polarization direction of a light beam. 図５（ｂ）に対応するＬＤアレイにおける発光点の回転状態を示す図である。It is a figure which shows the rotation state of the light emission point in the LD array corresponding to FIG.5 (b). 本発明に係る光走査装置の第２の実施の形態の構成を示す断面図である。It is sectional drawing which shows the structure of 2nd Embodiment of the optical scanning device based on this invention. 図７の光走査装置における折り返しミラーの配置例示す断面図である。It is sectional drawing which shows the example of arrangement | positioning of the folding | turning mirror in the optical scanning device of FIG. 本発明に係る画像形成装置の構成を示す断面図である。1 is a cross-sectional view illustrating a configuration of an image forming apparatus according to the present invention. 実施例１の光走査装置の副走査断面における配置関係を示す概略図である。FIG. 3 is a schematic diagram illustrating an arrangement relationship in a sub-scan section of the optical scanning device according to the first exemplary embodiment. 実施例１の折り返しミラーにおける入射光と反射光を含む平面と光ビームの偏光方向との関係を示す図である。It is a figure which shows the relationship between the plane containing incident light and reflected light in the folding mirror of Example 1, and the polarization direction of a light beam. 実施例１の被走査面上の光量の測定結果である。3 is a measurement result of a light amount on a surface to be scanned in Example 1. FIG.

符号の説明Explanation of symbols

１光源（ＬＤアレイ）
２カップリングレンズ
３シリンドリカルレンズ
４ポリゴンミラー（光偏向器）
４ｍ偏向反射面
６Ｙ，６Ｙ，６Ｍ，６Ｋ光走査光学系
７，７Ｙ，７Ｍ，７Ｃ，７Ｋ感光体（被走査面）
８Ｙ，８Ｍ，８Ｃ，８Ｋ帯電チャージャ
１０Ｙ，１０Ｍ，１０Ｃ，１０Ｋ現像装置
１１Ｙ，１１Ｍ，１１Ｃ，１１Ｋ転写チャージャ
１２Ｙ，１２Ｍ，１２Ｃ，１２Ｋクリーニング装置
１３給紙カセット
１７搬送ベルト
１８除電チャージャ
２０ベルト帯電チャージャ
２１ベルト分離チャージャ
２４定着装置
２５排紙ローラ
２６排紙トレイ
３０光走査装置
Ｌ，Ｌ１，Ｌ２，Ｌ３，Ｌ４走査レンズ（走査光学系）
Ｍ１，Ｍ２，Ｍ１’，Ｍ２’，Ｍ１１，Ｍ１２，Ｍ１３，Ｍ１４，Ｍ１５，Ｍ１６，Ｍ１７，Ｍ１８，Ｍ２１，Ｍ２２，Ｍ２３，Ｍ２４，Ｍ２５，Ｍ２６，Ｍ２７，Ｍ２８折り返しミラー
ｇ，ｇ１，ｇ２，ｇ３，ｇ４防塵ガラス
ＰＧ平行平板ガラス
Ｐ１，Ｐ１’，Ｐ２，Ｐ２’ 発光点
Ｓ転写紙 1 Light source (LD array)
2 Coupling lens 3 Cylindrical lens 4 Polygon mirror (optical deflector)
4m deflection reflection surface 6Y, 6Y, 6M, 6K optical scanning optical system 7, 7Y, 7M, 7C, 7K photoconductor (scanned surface)
8Y, 8M, 8C, 8K Charging Charger 10Y, 10M, 10C, 10K Development Device 11Y, 11M, 11C, 11K Transfer Charger 12Y, 12M, 12C, 12K Cleaning Device 13 Paper Feed Cassette 17 Conveyor Belt 18 Charger Charger 20 Belt Charger Charger 21 Belt separation charger 24 Fixing device 25 Paper discharge roller 26 Paper discharge tray 30 Optical scanning device L, L1, L2, L3, L4 Scanning lens (scanning optical system)
M1, M2, M1 ', M2', M11, M12, M13, M14, M15, M16, M17, M18, M21, M22, M23, M24, M25, M26, M27, M28 Folding mirror g, g1, g2, g3 , G4 Dust-proof glass PG Parallel flat glass P1, P1 ', P2, P2' Light emitting point S Transfer paper

Claims

複数の発光点を直線上に配列してなり、隣接する該発光点間で主走査方向及び副走査方向に距離を持つように、出射する光ビームの射出方向を回転軸として回転して配置される光源と、
該光源から偏向反射面に対しＳ偏光成分よりＰ偏光成分を多く含む状態で入射する光ビームを主走査方向に偏向走査する光偏向器と、
該光偏向器で偏向された光ビームを被走査面に結像する走査光学系と、
前記光ビームを被走査面に導く折り返しミラーと、を備える光走査装置において、
前記折り返しミラーは、前記走査光学系を構成する主走査方向に正の屈折力を持つ走査レンズより被走査面側に配置され、
前記光源は、前記折り返しミラーのうち最も偏角が大きい折り返しミラーの反射面で、前記走査レンズ光軸を挟み光源側よりも該光源の反対側で入射する光ビームの反射率が高くなる方向に回転され配置されていることを特徴とする光走査装置。 A plurality of light emitting points are arranged on a straight line, and arranged so as to be rotated about the emission direction of the emitted light beam so that the adjacent light emitting points have a distance in the main scanning direction and the sub scanning direction. A light source
An optical deflector that deflects and scans in the main scanning direction a light beam incident from the light source on the deflecting reflection surface in a state including more P-polarized light components than S-polarized light components;
A scanning optical system that forms an image of the light beam deflected by the optical deflector on a surface to be scanned;
In a light scanning device comprising a folding mirror for guiding the light beam to a surface to be scanned,
The folding mirror is disposed closer to the surface to be scanned than a scanning lens having a positive refractive power in the main scanning direction constituting the scanning optical system,
The light source is a reflecting surface of a folding mirror having the largest deflection angle among the folding mirrors, and in a direction in which the reflectance of the light beam incident on the opposite side of the light source is higher than the light source side across the scanning lens optical axis. An optical scanning device characterized by being rotated and arranged.

請求項１に記載の光走査装置において、
前記折り返しミラーを複数持ち、
該複数の折り返しミラーの全てが、前記走査光学系を構成する主走査方向に正の屈折力を持つ走査レンズより被走査面側に配置されることを特徴とする光走査装置。 The optical scanning device according to claim 1,
Having a plurality of the folding mirrors,
An optical scanning device characterized in that all of the plurality of folding mirrors are arranged closer to the surface to be scanned than a scanning lens having a positive refractive power in the main scanning direction constituting the scanning optical system.

請求項１または２に記載の光走査装置において、
光偏向器を配置する空間をその他の空間に対し略密閉する構造とし、該密閉空間への光ビームの入射出用の開口部に配置される平行平板を持ち、
前記平行平板の透過率は、前記走査レンズ光軸を挟み反光源側で高くなっていることを特徴とする光走査装置。 In the optical scanning device according to claim 1 or 2,
The space in which the optical deflector is arranged is substantially sealed with respect to the other spaces, and has a parallel plate arranged in the opening for entering and exiting the light beam into the sealed space,
The transmittance of the parallel plate is high on the side opposite to the light source across the optical axis of the scanning lens.

複数の被走査面に対応して、それぞれ複数の発光点を直線上に配列してなり、隣接する該発光点間で主走査方向及び副走査方向に距離を持つように、出射する光ビームの射出方向を回転軸として回転して配置される複数の光源と、
前記複数の光源それぞれから偏向反射面に対しＳ偏光成分よりＰ偏光成分を多く含む状態で入射する光ビームを主走査方向に偏向走査する単一の光偏向器と、
光偏向器で偏向された光ビームを対応する被走査面に結像する走査光学系と、
前記複数の光源毎に、光ビームを対応する被走査面に導く複数の折り返しミラーと、を備える光走査装置において、
前記折り返しミラーは、前記走査光学系を構成する主走査方向に正の屈折力を持つ走査レンズより対応する被走査面側に配置され、
前記複数の光源はそれぞれ、対応する前記折り返しミラーのうち最も偏角が大きい折り返しミラーの反射面で、前記走査レンズ光軸を挟み光源側よりも該光源の反対側で入射する光ビームの反射率が高くなる方向に回転され配置されていることを特徴とする光走査装置。 Corresponding to a plurality of scanned surfaces, a plurality of light emitting points are arranged on a straight line, and a light beam emitted from the adjacent light emitting points has a distance in the main scanning direction and the sub scanning direction. A plurality of light sources arranged to rotate about the emission direction as a rotation axis;
A single optical deflector that deflects and scans in the main scanning direction a light beam incident from a plurality of light sources in a state including more P-polarized light components than S-polarized light components on the deflecting reflection surface;
A scanning optical system that forms an image of the light beam deflected by the optical deflector on a corresponding scanned surface;
In each of the plurality of light sources, a plurality of folding mirrors that guide a light beam to a corresponding scanned surface, and an optical scanning device comprising:
The folding mirror is disposed on the scanning surface side corresponding to a scanning lens having a positive refractive power in the main scanning direction constituting the scanning optical system,
Each of the plurality of light sources is a reflection surface of a folding mirror having the largest deflection angle among the corresponding folding mirrors, and a reflectance of a light beam incident on the opposite side of the light source with respect to the light source side across the scanning lens optical axis. An optical scanning device characterized in that the optical scanning device is rotated and arranged in a direction in which the height of the light increases.

請求項４に記載の光走査装置において、
光偏向器を配置する空間をその他の空間に対し略密閉する構造とし、該密閉空間への光ビームの入射出用の開口部に配置される平行平板を持ち、
前記平行平板の透過率は、前記走査レンズ光軸を挟み反光源側で高くなっていることを特徴とする光走査装置。 The optical scanning device according to claim 4.
The space in which the optical deflector is arranged is substantially sealed with respect to the other spaces, and has a parallel plate arranged in the opening for entering and exiting the light beam into the sealed space,
The transmittance of the parallel plate is high on the side opposite to the light source across the optical axis of the scanning lens.

電子写真プロセスを実行することによって画像を形成する画像形成装置であって、電子写真プロセスの露光プロセスを実行する手段として請求項１〜５のいずれかに記載の光走査装置を具備した画像形成装置。 An image forming apparatus for forming an image by executing an electrophotographic process, wherein the image forming apparatus comprises the optical scanning device according to claim 1 as means for performing an exposure process of the electrophotographic process. .