JPH08334687A - Optical scanning optical system - Google Patents
Optical scanning optical systemInfo
- Publication number
- JPH08334687A JPH08334687A JP16289395A JP16289395A JPH08334687A JP H08334687 A JPH08334687 A JP H08334687A JP 16289395 A JP16289395 A JP 16289395A JP 16289395 A JP16289395 A JP 16289395A JP H08334687 A JPH08334687 A JP H08334687A
- Authority
- JP
- Japan
- Prior art keywords
- lens
- scanning direction
- optical
- image forming
- main scanning
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Links
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- Mechanical Optical Scanning Systems (AREA)
- Lenses (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は光走査光学系に関し、特
に光源手段から射出された光ビームを回転多面鏡等の光
偏向器を介して記録媒体面である被走査面上に導光し光
走査することにより、文字や情報等を記録するようにし
た、例えばレーザービームプリンタ（ＬＢＰ）やディジ
タル複写機等の装置に好適な光走査光学系に関するもの
である。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning optical system, and in particular, it guides a light beam emitted from a light source means onto a surface to be scanned, which is a recording medium surface, through an optical deflector such as a rotating polygon mirror. The present invention relates to an optical scanning optical system suitable for an apparatus such as a laser beam printer (LBP) or a digital copying machine, which records characters and information by optical scanning.
【０００２】[0002]
【従来の技術】従来より回転多面鏡より成る光偏向器の
各反射面（偏向面）で偏向反射された光ビームを利用し
て被走査面上を光走査するようにした光走査光学系が、
例えば特公昭６２−３６２１０号公報や特開平４−１５
３６１６号公報や米国特許第５０６２６７９号で種々と
提案されている。2. Description of the Related Art Conventionally, an optical scanning optical system has been known which optically scans a surface to be scanned by using a light beam deflected and reflected by each reflection surface (deflection surface) of an optical deflector composed of a rotating polygon mirror. ,
For example, Japanese Examined Patent Publication No. 62-36210 and Japanese Patent Laid-Open No. 4-15
Various proposals have been made in Japanese Patent No. 3616 and US Pat. No. 5,062,679.
【０００３】特公昭６２−３６２１０号公報で提案され
ている光走査光学系は光偏向器と被走査面との間に主走
査方向にｆθ特性を有する光走査用の結像手段を設け、
該結像手段の１つであるトーリックレンズの副走査方向
の屈折力を適切に設定することにより、光偏向器の反射
面が回転軸に対して平行となっていなく倒れているとき
の角度誤差、所謂面倒れを補正している。The optical scanning optical system proposed in Japanese Patent Publication No. 62-36210 is provided with an image forming means for optical scanning having an fθ characteristic in the main scanning direction between an optical deflector and a surface to be scanned.
By properly setting the refracting power of the toric lens, which is one of the image forming means, in the sub-scanning direction, an angular error when the reflecting surface of the optical deflector is tilted instead of being parallel to the rotation axis The so-called troublesomeness is corrected.
【０００４】即ち、トーリックレンズを用いて光偏向器
の反射面と被走査面（被照射体面）とを光学的に共役関
係にして面倒れによる悪影響を除去している。これによ
り反射面により反射偏向された光ビームの走査面上の進
行方向が補正されて走査線のピッチにムラが生じないよ
うにしている。That is, a toric lens is used to make the reflecting surface of the optical deflector and the surface to be scanned (the surface of the object to be irradiated) optically conjugate with each other to eliminate the adverse effect of the surface tilt. As a result, the traveling direction of the light beam reflected and deflected by the reflecting surface on the scanning surface is corrected to prevent unevenness in the pitch of the scanning lines.
【０００５】又、特開平４−１５３６１６号公報で提案
されている光走査光学系では、結像手段の１つであるト
ーリックレンズの材質をプラスチック材より形成すると
共にその両レンズ面を非球面形状より形成している。In the optical scanning optical system proposed in Japanese Patent Laid-Open No. 4-153616, the material of the toric lens, which is one of the image forming means, is made of a plastic material and both lens surfaces are aspherical. More formed.
【０００６】一般にトーリックレンズは主走査方向と副
走査方向とで互いに曲率が異なる為、例えばガラス材で
加工する場合、加工方法が複雑になり、加工時間も非常
に長くかかる為、コスト高につながる要因となってい
た。Generally, a toric lens has different curvatures in the main scanning direction and the sub-scanning direction. For example, when processing a glass material, the processing method is complicated and the processing time is very long, resulting in high cost. It was a factor.
【０００７】そこでこのトーリックレンズをプラスチッ
ク化することにより、一体成形が可能となり、これによ
り加工方法の簡素化及び加工時間の短縮化が可能とな
り、大幅なコストダウンが図れる。Therefore, by making this toric lens into a plastic, it becomes possible to integrally mold it, which simplifies the processing method and shortens the processing time, resulting in a significant cost reduction.
【０００８】又、米国特許５０６２６７９号で提案され
ている光走査光学系では、結像手段の１つであるトーリ
ックレンズの副走査方向の曲率半径を光軸から離れるに
従い変化させて形成している。これはトーリックレンズ
をプラスチック化することにより加工が可能となり、こ
れにより副走査方向の像面湾曲を良好に補正することが
できる。Further, in the optical scanning optical system proposed in US Pat. No. 5,062,679, the toric lens, which is one of the image forming means, is formed by changing the radius of curvature in the sub-scanning direction with distance from the optical axis. . This can be processed by making the toric lens plastic, and thereby the field curvature in the sub-scanning direction can be satisfactorily corrected.
【０００９】[0009]
【発明が解決しようとする課題】特公昭６２−３６２１
０号公報の光走査光学系におけるｆθ特性を有した光走
査用の結像手段は光偏向器側より順に球面より成る単レ
ンズとトーリックレンズとより成っている。[Problems to be Solved by the Invention] Japanese Patent Publication No. 62-3621
The image forming means for optical scanning having the f.theta. Characteristic in the optical scanning optical system of Japanese Patent No. 0 is composed of a single lens and a toric lens each having a spherical surface in order from the optical deflector side.
【００１０】このようなレンズ構成での光走査光学系は
走査画角がさほど大きくない場合、収差補正が良好に行
なわれ、所望の光学性能が容易に得られる。しかしなが
らトーリックレンズは主走査方向と副走査方向とで互い
に異なる曲率を有する特殊レンズである為、前述した如
くその加工方法は複雑であり、非常に長い加工時間を要
する為に大きなコストアップの要因となり、又走査画角
が大きくなると収差が著しく悪化する傾向にあった。In the optical scanning optical system having such a lens structure, when the scanning angle of view is not so large, the aberration is favorably corrected and the desired optical performance is easily obtained. However, since the toric lens is a special lens having different curvatures in the main scanning direction and the sub-scanning direction, the processing method is complicated as described above, and it takes a very long processing time, which causes a large cost increase. Also, when the scanning angle of view becomes large, the aberration tends to be significantly deteriorated.
【００１１】そこで従来では前記の特開平４−１５３６
１６号公報や米国特許５０６２６７９号等で提案されて
いるようにトーリックレンズをプラスチック化にすると
共にレンズ面を非球面形状より形成し、更にトーリック
レンズの副走査方向の曲率半径を光軸から離れるに従っ
て変化させることによって、低コスト化を図ると共に全
画角にわたり良好に収差を補正している。Therefore, in the prior art, the above-mentioned Japanese Patent Laid-Open No. 1536 / 4-1536 is used.
As disclosed in Japanese Patent No. 16 and US Pat. No. 5,062,679, the toric lens is made plastic and the lens surface is formed of an aspherical surface, and the radius of curvature of the toric lens in the sub-scanning direction is further away from the optical axis. By changing it, the cost is reduced and the aberration is corrected well over the entire angle of view.
【００１２】しかしながら更なる高画質化、広画角化を
図る場合には主走査方向における光偏向器の反射面の移
動、即ち該光偏向器の回転に伴なう光ビームの反射位置
の移動（入射瞳の移動）が無視できなくなってくる。そ
してこの結果生じるｆθ特性及び主走査方向の像面湾曲
の光軸に対する非対称性を良好に補正することが困難と
なってくるという問題点があった。However, in order to further improve image quality and widen the angle of view, the reflection surface of the optical deflector is moved in the main scanning direction, that is, the reflection position of the light beam is moved as the optical deflector rotates. (Movement of entrance pupil) cannot be ignored. Then, there is a problem that it is difficult to satisfactorily correct the resulting fθ characteristic and the asymmetry of the field curvature in the main scanning direction with respect to the optical axis.
【００１３】本発明は結像手段のレンズ構成、レンズ形
状そしてレンズの材質等を適切に設定すると共に少なく
とも１つのレンズ面を該結像手段の光軸中心に対して主
走査方向又は主走査方向と副走査方向に関して非対称な
非球面形状より形成することにより、主走査方向のｆθ
特性及び像面湾曲を良好に補正することができる光走査
光学系の提供を目的とする。According to the present invention, the lens structure of the image forming means, the lens shape, the material of the lens and the like are properly set, and at least one lens surface is in the main scanning direction or the main scanning direction with respect to the optical axis center of the image forming means. And fθ in the main scanning direction by forming an aspherical shape asymmetric with respect to the sub scanning direction.
It is an object of the present invention to provide an optical scanning optical system that can satisfactorily correct characteristics and field curvature.
【００１４】[0014]
【課題を解決するための手段】本発明の光走査光学系
は、 （１−１）光源手段から射出した光ビームを偏向手段に
導光し、該偏向手段で偏向反射させた該光ビームを結像
手段により被走査面上に導光し光走査する光走査光学系
において、該結像手段は該偏向手段側から順に主走査方
向と副走査方向とで互いに異なる曲率半径のレンズ面を
両面に持つトーリックレンズより成る第１レンズ、主走
査方向と副走査方向との双方に異なる正の屈折力を有す
るアナモフィックレンズより成る第２レンズ、そして主
走査方向と副走査方向とで互いに異なる曲率半径のレン
ズ面を両面に持つトーリックレンズより成る第３レンズ
との３枚のレンズを有し、少なくとも１つのレンズ面は
該結像手段の光軸中心に対して主走査方向又は主走査方
向と副走査方向に関して非対称な非球面形状よりなって
いることを特徴としている。In the optical scanning optical system of the present invention, (1-1) a light beam emitted from a light source means is guided to a deflecting means, and the light beam deflected and reflected by the deflecting means is reflected. In an optical scanning optical system for guiding light onto a surface to be scanned by an image forming means and performing optical scanning, the image forming means has lens surfaces having different radii of curvature in order from the deflecting means side in the main scanning direction and the sub scanning direction. A toric lens having a first lens, a second lens having an anamorphic lens having positive refractive powers different in both the main scanning direction and the sub-scanning direction, and a radius of curvature different from each other in the main scanning direction and the sub-scanning direction. 3 lens including a toric lens having both lens surfaces on both sides and at least one lens surface with respect to the optical axis center of the image forming means in the main scanning direction or in the main scanning direction and the sub-direction. Scanning direction Is characterized by having an asymmetrical aspherical shape.
【００１５】特に前記結像手段の光軸中心に対して非対
称な非球面形状より成るレンズの材質はプラスチック材
で形成されていることや、前記第３レンズの主走査方向
における焦点距離をｆ３ａ、前記結像手段全系の主走査
方向における合成焦点距離をｆａとしたとき ０．０２＜｜ｆａ／ｆ３ａ｜＜０．０６ ‥‥‥‥（１） なる条件を満足することや、前記第３レンズの副走査方
向における焦点距離をｆ３ｂ、前記結像手段全系の主走
査方向における合成焦点距離をｆａとしたとき ０．０８＜｜ｆａ／ｆ３ｂ｜＜０．２５ ‥‥‥‥（２） なる条件を満足することや、前記結像手段全系の主走査
方向における合成焦点距離をｆａ、前記第３レンズと前
記被走査面との間の距離をＬ３としたとき ０．７＜｜Ｌ３／ｆａ｜＜１．８ ‥‥‥‥（３） なる条件を満足することや、前記第３レンズの副走査方
向における焦点距離をｆ３ｂ、前記第３レンズの光軸方
向の最大肉厚をｄ３ｍａｘとしたとき ｜ｄ３ｍａｘ／ｆ３ｂ｜＜０．０２５ ‥‥‥‥（４） なる条件を満足することや、前記第１レンズの副走査方
向における焦点距離をｆ１ｂ、前記第３レンズの副走査
方向における焦点距離をｆ３ｂとしたとき ｜ｆ３ｂ／ｆ１ｂ｜＜５ ‥‥‥‥（５） なる条件を満足すること等を特徴としている。Particularly, the material of the lens having an aspherical shape asymmetric with respect to the optical axis center of the image forming means is a plastic material, and the focal length of the third lens in the main scanning direction is f3a, When the combined focal length of the entire image forming unit system in the main scanning direction is fa, 0.02 <| fa / f3a | <0.06 (1) is satisfied, and the third condition is satisfied. When the focal length of the lens in the sub-scanning direction is f3b and the combined focal length of the entire image forming unit system in the main scanning direction is fa 0.08 <| fa / f3b | <0.25 (2) 0.7 <| L3 when the following conditions are satisfied, and the combined focal length of the entire image forming unit system in the main scanning direction is fa and the distance between the third lens and the surface to be scanned is L3. /Fa|<1.8 ‥‥‥‥ ( ) When the following conditions are satisfied, the focal length of the third lens in the sub-scanning direction is f3b, and the maximum thickness of the third lens in the optical axis direction is d3max: | d3max / f3b | <0.025. (4) When the following condition is satisfied, the focal length of the first lens in the sub-scanning direction is f1b, and the focal length of the third lens in the sub-scanning direction is f3b: | f3b / f1b | < It is characterized by satisfying the following condition (5).
【００１６】（１−２）光源手段から射出した光ビーム
を偏向手段に導光し、該偏向手段で偏向反射させた該光
ビームを結像手段により被走査面上に導光し光走査する
光走査光学系において、該結像手段は該偏向手段側から
順に被走査面側に凸の曲率半径を有する球面レンズより
成る第１レンズ、被走査面側に主走査方向と副走査方向
の曲率半径が互いに異なるレンズ面を有するトーリック
レンズより成る第２レンズとの２枚のレンズを有し、少
なくとも１つのレンズ面は該結像手段の光軸中心に対し
て主走査方向又は主走査方向と副走査方向に関して非対
称な非球面形状よりなっていることを特徴としている。(1-2) The light beam emitted from the light source means is guided to the deflecting means, and the light beam deflected and reflected by the deflecting means is guided to the surface to be scanned by the image forming means for optical scanning. In the optical scanning optical system, the image forming means has a first lens composed of a spherical lens having a convex radius of curvature in order from the deflecting means side to the surface to be scanned, and the curvature in the main scanning direction and the sub-scanning direction on the surface to be scanned. It has two lenses, a second lens composed of a toric lens having lens surfaces having different radii, and at least one lens surface is in the main scanning direction or the main scanning direction with respect to the optical axis center of the image forming means. It is characterized by having an aspherical shape which is asymmetric with respect to the sub-scanning direction.
【００１７】特に前記結像手段の光軸中心に対して非対
称な非球面形状より成るレンズの材質はガラス材で形成
されていることや、前記第２レンズの主走査方向におけ
る焦点距離をｆ２ａ、前記結像手段全系の主走査方向に
おける合成焦点距離をｆａとしたとき ０．４＜｜ｆａ／ｆ２ａ｜＜１．２ ‥‥‥‥（６） なる条件を満足することや、前記第２レンズの副走査方
向における焦点距離をｆ２ｂ、前記結像手段全系の主走
査方向における合成焦点距離をｆａとしたとき １．７＜｜ｆａ／ｆ２ｂ｜＜４．６ ‥‥‥‥（７） なる条件を満足することや、前記結像手段全系の主走査
方向における合成焦点距離をｆａ、前記第２レンズと前
記被走査面との間の距離をＬ２としたとき ０．８＜｜Ｌ２／ｆａ｜＜２．２ ‥‥‥‥（８） なる条件を満足すること等を特徴としている。In particular, the material of the lens having an aspherical shape which is asymmetric with respect to the optical axis center of the image forming means is a glass material, and the focal length of the second lens in the main scanning direction is f2a, When the combined focal length of the whole system of the image forming means in the main scanning direction is fa, 0.4 <| fa / f2a | <1.2 (6) is satisfied, and the second condition is satisfied. When the focal length of the lens in the sub-scanning direction is f2b and the combined focal length of the entire image forming unit in the main scanning direction is fa, 1.7 <| fa / f2b | <4.6 (7) When the following condition is satisfied, the combined focal length of the entire image forming unit system in the main scanning direction is fa, and the distance between the second lens and the surface to be scanned is L2, 0.8 <| L2 /Fa|<2.2 ... (8) It is characterized in that, etc. to foot.
【００１８】[0018]
【実施例】図１は本発明の実施例１の光学系の要部平面
図（主走査断面図）、図２は図１の主走査断面において
垂直な要部断面図（副走査断面図）である。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a plan view (main-scan sectional view) of an essential part of an optical system according to a first embodiment of the present invention, and FIG. 2 is a sectional view (sub-scan sectional view) of a main part perpendicular to the main-scan section of FIG. Is.
【００１９】図中、１は光源手段としての例えば半導体
レーザである。２はコリメーターレンズであり、光源手
段１から射出された光ビームを平行光束としている。３
は開口絞りであり、通過光束径を整えている。４はシリ
ンドリカルレンズであり、主走査断面に関しては屈折力
は有しておらず副走査断面に関して所定の屈折力を有し
ている。５は偏向手段としての例えば回転多面鏡より成
る光偏向器であり、矢印Ａ方向に一定速度で回転してい
る。In the figure, 1 is a semiconductor laser as a light source means. A collimator lens 2 collimates the light beam emitted from the light source means 1 into a parallel light flux. Three
Is an aperture stop, which adjusts the diameter of the passing light beam. Reference numeral 4 denotes a cylindrical lens, which has no refracting power in the main scanning cross section and has a predetermined refracting power in the sub scanning cross section. Reference numeral 5 denotes an optical deflector as a deflecting means, which is composed of, for example, a rotating polygon mirror, and rotates at a constant speed in the direction of arrow A.
【００２０】１０は本発明に係る結像手段（ｆθレンズ
系）であり、光偏向器５側から順に主走査断面に負の屈
折力、副走査断面に正の屈折力を有するプラスチック材
料で形成された第１レンズとしてのトーリックレンズ６
と、該トーリックレンズ６の被走査面側近傍に配置され
主走査断面と副走査断面とで互いに異なる正の屈折力を
有するガラス材料で形成された第２レンズとしてのアナ
モフィックレンズ７と、該アナモフィックレンズ７の被
走査面側近傍に配置され主走査断面に正の屈折力、副走
査断面に負の屈折力を有するプラスチック材料で形成さ
れた第３レンズとしてのトーリックレンズ８との３枚の
レンズより構成している。Reference numeral 10 denotes an image forming means (fθ lens system) according to the present invention, which is formed of a plastic material having a negative refracting power in the main scanning section and a positive refracting power in the sub-scanning section in order from the optical deflector 5 side. Toric lens 6 as the first lens
An anamorphic lens 7 as a second lens which is arranged near the surface to be scanned of the toric lens 6 and is formed of a glass material having positive refractive powers different from each other in the main scanning section and the sub scanning section; Three lenses, a toric lens 8 as a third lens, which is arranged near the surface to be scanned of the lens 7 and is made of a plastic material having a positive refractive power in the main scanning cross section and a negative refractive power in the sub scanning cross section It is made up of.
【００２１】シリンドリカルレンズ４とアナモフィック
レンズ７はｆθ特性と像面湾曲を良好に補正する為のレ
ンズ形状より形成している。トーリックレンズ８は広画
角にわたってｆθ特性と像面湾曲を良好に微補正する為
にコンセントリックな形状（トーリックレンズ８の両レ
ンズ面の曲率半径の中心が光偏向器５の反射面近傍にあ
る）で形成し、かつ主走査方向に関して光偏向器５側の
レンズ面を光軸中心に対して対称な非球面形状とし、被
走査面側のレンズ面を光軸中心に対して非対称な非球面
形状より形成している。The cylindrical lens 4 and the anamorphic lens 7 are formed in a lens shape for satisfactorily correcting the fθ characteristic and the field curvature. The toric lens 8 has a concentric shape in order to finely correct the fθ characteristic and the field curvature over a wide angle of view (the center of the radius of curvature of both lens surfaces of the toric lens 8 is near the reflecting surface of the optical deflector 5). ), And the lens surface on the optical deflector 5 side with respect to the main scanning direction has an aspherical shape symmetrical with respect to the optical axis center, and the lens surface on the scanned surface side is asymmetrical with respect to the optical axis center. It is formed from the shape.
【００２２】又、トーリックレンズ６は温度変化が生じ
た場合のトーリックレンズ８のピント移動を補正する為
のレンズ形状より形成しており、該トーリックレンズ６
とトーリックレンズ８とのピント移動が全系として相殺
されるように最適な屈折力に設定している。９は被走査
面としての感光ドラムである。The toric lens 6 is formed in a lens shape for correcting the focus movement of the toric lens 8 when the temperature changes.
The optimum refractive power is set so that the focus movement between the toric lens 8 and the toric lens 8 is canceled as a whole system. Reference numeral 9 is a photosensitive drum as a surface to be scanned.
【００２３】本実施例において光源手段１より射出され
た光ビームはコリメータレンズ２により略平行光束とさ
れ、該平行光束は開口絞り３によってその光束断面の大
きさが制限されてシリンドリカルレンズ４に入射する。In the present embodiment, the light beam emitted from the light source means 1 is made into a substantially parallel light beam by the collimator lens 2, and the parallel light beam is incident on the cylindrical lens 4 with the size of the light beam cross section being limited by the aperture stop 3. To do.
【００２４】シリンドリカルレンズ４は入射した平行光
束のうち主走査断面においてはそのまま平行光束の状態
で射出させ、副走査断面においては集束して光偏向器５
の反射面５ａにほぼ線像光束として結像させている。そ
して光偏向器５の反射面５ａで高速に反射偏向してい
る。光偏向器５で反射偏向された光ビームはトーリック
レンズ６とアナモフィックレンズ７そしてトーリックレ
ンズ８を通過することによってその走査直線性が補正さ
れ感光ドラム９面上に結像されて略等速度直線運動で該
感光ドラム９面上を光走査する。The cylindrical lens 4 causes the parallel light flux of the incident parallel light flux to be emitted as it is in the main scanning cross section, and is focused in the sub scanning cross section to be converged in the sub scanning cross section.
It is formed on the reflecting surface 5a of the above as an almost linear image light flux. The reflection surface 5a of the optical deflector 5 reflects and deflects at high speed. The light beam reflected and deflected by the light deflector 5 passes through the toric lens 6, the anamorphic lens 7 and the toric lens 8 so that its scanning linearity is corrected and an image is formed on the surface of the photosensitive drum 9 to form a substantially uniform linear motion. Then, the surface of the photosensitive drum 9 is optically scanned.
【００２５】図２においてＰは光偏向器５の反射面位置
を示しており、副走査断面では前述した様にほぼこの反
射面位置Ｐに光ビームが集光するようにしている。In FIG. 2, P indicates the position of the reflecting surface of the optical deflector 5, and in the sub-scanning cross section, the light beam is focused substantially on this reflecting surface position P as described above.
【００２６】ここで反射面位置Ｐと感光ドラム９とは結
像手段１０に関してそれぞれ光学的に略共役な位置関係
になっている。これにより反射面が副走査断面において
傾いても、所謂面倒れがあっても光ビームが感光ドラム
９面上の同一走査線上に結像するようにしている。この
様にして本実施例では光偏向器５の面倒れの補正を行っ
ている。Here, the reflecting surface position P and the photosensitive drum 9 are in a substantially optically conjugate positional relationship with respect to the image forming means 10. As a result, the light beam is focused on the same scanning line on the surface of the photosensitive drum 9 even if the reflecting surface is tilted in the sub-scanning cross section or there is so-called surface tilt. In this way, in this embodiment, the surface tilt of the optical deflector 5 is corrected.
【００２７】次に結像手段１０を構成するトーリックレ
ンズ６とアナモフィックレンズ７とトーリックレンズ８
のレンズ構成の特徴について説明する。Next, a toric lens 6, an anamorphic lens 7 and a toric lens 8 which form the image forming means 10.
The features of the lens configuration will be described.
【００２８】本実施例におけるトーリックレンズ６とト
ーリックレンズ８は前述の如く副走査断面においてそれ
ぞれ順に正、負の屈折力を有しており、両トーリックレ
ンズ６，８ともその材質をプラスチック材で形成してい
る。As described above, the toric lens 6 and the toric lens 8 in the present embodiment have positive and negative refracting powers in the sub-scanning section, respectively, and both toric lenses 6 and 8 are made of a plastic material. are doing.
【００２９】このようなレンズ構成をとることによっ
て、本実施例では温度変動等によるプラスチック材の屈
折率変化によって発生する負の屈折力を有するトーリッ
クレンズ８のピント移動を正の屈折力を有するトーリッ
クレンズ６のピント移動で相殺させ、全系としてピント
移動を微小化させている。By adopting such a lens structure, in the present embodiment, the focus movement of the toric lens 8 having a negative refracting power caused by the change in the refractive index of the plastic material due to temperature fluctuation or the like causes the toric lens having a positive refracting power to move. The focus movement of the lens 6 is offset, and the focus movement of the entire system is reduced.
【００３０】本実施例では上記のピント移動を補正する
ピント移動補正光学系が結像手段１０の内部で構成され
ているので、倒れ補正光学系を構成する共役結像関係に
は何も影響を与えることなく、ピント移動を補正するこ
とができる。In this embodiment, since the focus movement correction optical system for correcting the focus movement is constructed inside the image forming means 10, there is no influence on the conjugate image forming relationship forming the tilt correction optical system. The focus movement can be corrected without giving.
【００３１】このように本実施例においてはプラスチッ
クレンズを用いた場合の所定のピント移動補正光学系を
可能とし、面倒れ補正についても副走査方向に結像関係
を持たせることによって良好なる補正性能を得た上で、
従来の技術的な問題点である主走査方向のｆθ特性及び
像面湾曲の非対称性による残存収差を良好に補正してい
る。As described above, in the present embodiment, a predetermined focus movement correction optical system using a plastic lens is made possible, and good correction performance is also provided for surface tilt correction by providing an image forming relationship in the sub-scanning direction. On getting
The residual aberration due to the asymmetry of the fθ characteristic in the main scanning direction and the curvature of field, which are technical problems of the related art, is corrected well.
【００３２】図１においてトーリックレンズ８は前述の
如く被走査面側のレンズ面が主走査方向において光軸中
心に対して非対称な非球面形状より形成している。In FIG. 1, the toric lens 8 has a lens surface on the surface to be scanned formed of an aspherical surface asymmetric with respect to the optical axis center in the main scanning direction as described above.
【００３３】ここで図１においてｆθレンズ系（結像手
段）１０の光軸方向をＸ軸、それと垂直な被走査面上の
走査方向をＹ軸とすると、光ビームと光偏向器５の反射
面との交点（反射点）は光偏向器５の回転に伴ない一般
的に図３、図４に示すように変動する。尚図３、図４に
おいて横軸の像高は百分率（％）で表わしている。交点
の移動は入射瞳の移動に対応し、図３、図４に示す説明
図からも分かるようにＸ座標、Ｙ座標ともに像高０％の
走査に対し非対称に変動している。Here, in FIG. 1, when the optical axis direction of the fθ lens system (imaging means) 10 is the X axis and the scanning direction on the surface to be scanned perpendicular to the X axis is the Y axis, the light beam and the reflection of the optical deflector 5 are reflected. The intersection (reflection point) with the surface generally fluctuates as shown in FIGS. 3 and 4 as the optical deflector 5 rotates. In FIGS. 3 and 4, the image height on the horizontal axis is expressed as a percentage (%). The movement of the intersection corresponds to the movement of the entrance pupil, and as can be seen from the explanatory views shown in FIGS. 3 and 4, both the X coordinate and the Y coordinate fluctuate asymmetrically with respect to the scan at the image height of 0%.
【００３４】一般に入射瞳の移動に対するｆθ特性（歪
曲収差）、像面湾曲は収差論より以下の式より表わされ
る。但し、瞳移動を表わすパラメータをγとする。Generally, the fθ characteristic (distortion aberration) and the field curvature with respect to the movement of the entrance pupil are expressed by the following equations from the theory of aberration. However, the parameter indicating the pupil movement is γ.
【００３５】III´＝ III−２γII＋γ2 I V´ ＝ V−γ（２III ＋IV）＋３γ2II −γ3I ここで III´， V´はそれぞれ順に瞳移動後の非点収
差、歪曲収差等の３次収差係数、I ，II，III ，IV，V
はそれぞれ順に移動前の球面収差、コマ収差、非点収
差、球欠像面湾曲、歪曲収差等の３次収差係数である。[0035] III' = III-2γII + γ 2 IV' = V-γ (2III + IV) + 3γ 2 II -γ 3 I wherein III', astigmatism after pupil navigate to each V', 3 such distortion Next-order aberration coefficient, I, II, III, IV, V
Are the third-order aberration coefficients such as spherical aberration, coma aberration, astigmatism, stigmatic field curvature, and distortion aberration before moving.
【００３６】即ち、入射瞳が非対称に変動すれば、それ
に伴なう各収差も非対称性を持って表われることにな
る。That is, if the entrance pupil fluctuates asymmetrically, each aberration associated therewith also appears asymmetrically.
【００３７】そこで本実施例ではこのような非対称性を
持った残存収差を補正する為に前述の如くトーリックレ
ンズ８の被走査面側のレンズ面形状も光軸中心に対して
非対称な非球面形状より形成することにより、全画角に
わたり主走査方向のｆθ特性及び像面湾曲を良好に補正
することができる。Therefore, in this embodiment, in order to correct the residual aberration having such asymmetry, the lens surface shape of the toric lens 8 on the surface to be scanned side is asymmetrical with respect to the optical axis center as described above. By forming the above, the fθ characteristic and the field curvature in the main scanning direction can be satisfactorily corrected over the entire angle of view.
【００３８】図５、図６は各々本発明の実施例１による
光走査範囲における被走査面上での主走査方向のｆθ特
性（歪曲収差）及び像面湾曲を示す説明図である。図
５、図６は各々トーリックレンズの被走査面側の主走査
方向のレンズ面形状を、光軸に対して対称なレンズ面形
状を補正前、非対称なレンズ面形状を補正後として比較
して示してある。図５、図６に示すように全画角にわた
り良好に収差が補正されていることが分かる。5 and 6 are explanatory views showing the fθ characteristic (distortion aberration) and the field curvature in the main scanning direction on the surface to be scanned in the optical scanning range according to the first embodiment of the present invention. 5 and 6 respectively compare the lens surface shape in the main scanning direction on the surface to be scanned of the toric lens before correction of the lens surface shape symmetrical with respect to the optical axis and after correction of the asymmetric lens surface shape. It is shown. As shown in FIGS. 5 and 6, it can be seen that the aberration is well corrected over the entire angle of view.
【００３９】図７、図８は各々本発明の実施例２による
光走査範囲における被走査面上での主走査方向のｆθ特
性（歪曲収差）及び像面湾曲を示す説明図である。7 and 8 are explanatory views showing the f.theta. Characteristic (distortion aberration) and the field curvature in the main scanning direction on the surface to be scanned in the optical scanning range according to the second embodiment of the present invention.
【００４０】本実施例において前述の実施例１と異なる
点は第３レンズとしてのトーリックレンズ８の主走査方
向のレンズ面形状を両レンズ面とも光軸中心に対して非
対称な非球面形状より形成したことである。その他の構
成及び光学的作用は前述の実施例１と略同様であり、こ
れにより同様な効果を得ている。本実施例においても図
７、図８に示すように全画角にわたり良好に収差が補正
されていることが分かる。The difference between this embodiment and the first embodiment described above is that the lens surface shape of the toric lens 8 as the third lens in the main scanning direction is formed of an aspherical surface asymmetric with respect to the optical axis center on both lens surfaces. That is what I did. Other configurations and optical functions are substantially the same as those in the above-described first embodiment, and the same effect is obtained. Also in this embodiment, as shown in FIGS. 7 and 8, it can be seen that the aberration is favorably corrected over the entire angle of view.
【００４１】図９、図１０は各々本発明の実施例３によ
る光走査範囲における被走査面上での主走査方向のｆθ
特性（歪曲収差）及び像面湾曲を示す説明図である。9 and 10 are fθ in the main scanning direction on the surface to be scanned in the optical scanning range according to the third embodiment of the present invention.
It is explanatory drawing which shows a characteristic (distortion aberration) and a field curvature.
【００４２】本実施例において前述の実施例１と異なる
点は第３レンズとしてのトーリックレンズ８の主走査方
向のレンズ面形状を両レンズ面とも光軸中心に対して非
対称な非球面形状より形成し、かつ副走査方向の被走査
面側のレンズ面形状を光軸中心に対して非対称な非球面
形状より形成したことである。その他の構成及び光学的
作用は前述の実施例１と略同様であり、これにより同様
な効果を得ている。本実施例においても図９、図１０に
示すように全画角にわたり良好に収差が補正されている
ことが分かる。The present embodiment differs from the above-mentioned first embodiment in that the lens surface shape of the toric lens 8 as the third lens in the main scanning direction is formed by an aspherical surface asymmetric with respect to the optical axis center on both lens surfaces. In addition, the lens surface shape on the surface to be scanned in the sub-scanning direction is formed of an aspherical surface asymmetric with respect to the optical axis center. Other configurations and optical functions are substantially the same as those in the above-described first embodiment, and the same effect is obtained. Also in this embodiment, as shown in FIGS. 9 and 10, it can be seen that the aberration is favorably corrected over the entire angle of view.
【００４３】更に各実施例１、２、３において被走査面
全体の諸収差を良好に補正し、温度変化等の影響による
被走査面上でのピント移動を防止し、かつ光走査範囲の
広画角化を容易にするには次の諸条件のうち少なくとも
１つを満足させるのが良い。Further, in each of Examples 1, 2 and 3, various aberrations on the entire surface to be scanned are satisfactorily corrected, focus movement on the surface to be scanned due to the influence of temperature change and the like is prevented, and the optical scanning range is widened. In order to make the angle of view easy, it is preferable to satisfy at least one of the following conditions.
【００４４】即ち、第１レンズ（トーリックレンズ６）
の副走査方向の焦点距離をｆ１ｂ、第３レンズ（トーリ
ックレンズ８）の主走査方向と副走査方向の焦点距離を
各々ｆ３ａ，ｆ３ｂ、第３レンズの光軸方向の最大肉厚
をｄ３ｍａｘ、結像手段全系の主走査方向における合成
焦点距離をｆａ、第３レンズと被走査面との間の距離を
Ｌ３としたとき ０．０２＜｜ｆａ／ｆ３ａ｜＜０．０６ ‥‥‥‥（１） ０．０８＜｜ｆａ／ｆ３ｂ｜＜０．２５ ‥‥‥‥（２） ０．７＜｜Ｌ３／ｆａ｜＜１．８ ‥‥‥‥（３） ｜ｄ３ｍａｘ／ｆ３ｂ｜＜０．０２５ ‥‥‥‥（４） ｜ｆ３ｂ／ｆ１ｂ｜＜５ ‥‥‥‥（５） なる条件を満足することである。That is, the first lens (toric lens 6)
, F3b is the focal length of the third lens (toric lens 8) in the main scanning direction and f3b, respectively, and the maximum thickness in the optical axis direction of the third lens is d3max. Assuming that the combined focal length of the entire image system in the main scanning direction is fa and the distance between the third lens and the surface to be scanned is L3, 0.02 <| fa / f3a | <0.06 ( 1) 0.08 <| fa / f3b | <0.25 (2) 0.7 <| L3 / fa | <1.8 (3) | d3max / f3b | <0. 025 (4) | f3b / f1b | <5 (5).
【００４５】条件式（１）は主走査方向のｆθ特性と像
面湾曲を良好に補正する為のものである。条件式（１）
の下限値を越えて焦点距離ｆ３ａが大きくなりすぎると
収差補正上有利となるが、第３レンズが被走査面側に近
づいてしまい、装置全体が大型化してしまうので良くな
い。又条件式（１）の上限値を越えて焦点距離ｆ３ａが
小さくなりすぎると逆に装置全体のコンパクト化には有
利となるが、ｆθ特性と像面湾曲の双方をバランス良く
補正するのが困難になってくるので良くない。Conditional expression (1) is for satisfactorily correcting the fθ characteristic in the main scanning direction and the field curvature. Conditional expression (1)
If the focal length f3a becomes too large beyond the lower limit of the above, it is advantageous for aberration correction, but this is not preferable because the third lens approaches the surface to be scanned and the entire apparatus becomes large. On the other hand, if the focal length f3a becomes too small beyond the upper limit of the conditional expression (1), it is advantageous for downsizing the entire device, but it is difficult to correct both the fθ characteristic and the field curvature in a well-balanced manner. It is not good because it becomes.
【００４６】条件式（２）は副走査方向の像面湾曲を良
好に補正する為のものである。条件式（２）の上限値を
越えて焦点距離ｆ３ｂが大きくなりすぎると収差補正上
は有利となるが、第３レンズが被走査面側に近づき装置
全体が大型化してくるので良くない。又条件式（２）の
下限値を越えて焦点距離ｆ３ｂが小さくなりすぎると主
走査方向と副走査方向との像面湾曲をバランス良く補正
するのが困難になってくるので良くない。Conditional expression (2) is for satisfactorily correcting the field curvature in the sub-scanning direction. If the focal length f3b exceeds the upper limit of conditional expression (2) and becomes too large, it is advantageous for aberration correction, but this is not preferable because the third lens approaches the surface to be scanned and the entire apparatus becomes large. If the focal length f3b becomes too small beyond the lower limit of conditional expression (2), it becomes difficult to correct the field curvature in the main scanning direction and the sub scanning direction in a well-balanced manner, which is not preferable.
【００４７】条件式（３）は第３レンズと被走査面との
距離Ｌ３と、結像手段全系の主走査方向における合成焦
点距離ｆａとの比に関するものである。条件式（３）の
下限値を越えると装置全体が大型化になると共に面倒れ
補正効果が少なくってくるので良くない。又条件式
（３）の上限値を越えて第３レンズの屈折力が強くなり
すぎると、特に第３レンズの材質をプラスチック材で形
成した場合、温度変化等の影響による被走査面上でのピ
ント移動が許容範囲より外れしまうので良くない。Conditional expression (3) relates to the ratio between the distance L3 between the third lens and the surface to be scanned and the combined focal length fa in the main scanning direction of the entire image forming means system. If the lower limit of conditional expression (3) is exceeded, the size of the entire apparatus will be increased and the effect of face tilt correction will be reduced, which is not preferable. If the upper limit of conditional expression (3) is exceeded and the refracting power of the third lens becomes too strong, especially when the third lens is made of a plastic material, it may occur on the surface to be scanned due to the influence of temperature change or the like. It is not good because the focus movement is out of the allowable range.
【００４８】条件式（４）は第３レンズの光軸方向の最
大肉厚ｄ３ｍａｘと第３レンズの副走査方向における焦
点距離ｆ３ｂとの比に関するものである。条件式（４）
を外れると環境変動によるピント移動を良好に防止する
ことが難しくなり、かつプラスチック材による第３レン
ズの成形が難しくなってくるので良くない。Conditional expression (4) relates to the ratio between the maximum thickness d3max of the third lens in the optical axis direction and the focal length f3b of the third lens in the sub-scanning direction. Conditional expression (4)
If it is out of the range, it becomes difficult to satisfactorily prevent focus movement due to environmental changes, and it becomes difficult to mold the third lens with a plastic material, which is not preferable.
【００４９】条件式（５）は第１レンズと第３レンズの
副走査方向の焦点距離ｆ１ｂ，ｆ３ｂとの比に関するも
のである。条件式（５）を外れると環境変動によるピン
ト移動を良好に防止することが難しくなってくるので良
くない。Conditional expression (5) relates to the ratio between the focal lengths f1b and f3b of the first lens and the third lens in the sub-scanning direction. If conditional expression (5) is not satisfied, it becomes difficult to favorably prevent focus movement due to environmental changes, which is not good.
【００５０】図１１は本発明の実施例４の光学系の要部
平面図（主走査断面図）、図１２は図１１の主走査断面
において垂直な要部断面図（副走査断面図）である。同
図において前記図１、図２に示した要素と同一要素には
同符番を付している。FIG. 11 is a plan view (main scanning cross-sectional view) of a main part of an optical system according to a fourth embodiment of the present invention, and FIG. 12 is a cross-sectional view (sub-scanning cross-sectional view) of a main part perpendicular to the main scanning cross section of FIG. is there. In the figure, the same elements as those shown in FIGS. 1 and 2 are designated by the same reference numerals.
【００５１】本実施例において前述の各実施例１，２，
３と大きく異なる点は結像手段（ｆθレンズ系）を２枚
のレンズより構成したことである。In this embodiment, each of the above-mentioned first, second,
3 is that the image forming means (fθ lens system) is composed of two lenses.
【００５２】即ち、本実施例では結像手段２０を光偏向
器５側から順に被走査面側に凸の曲率半径を有するガラ
ス材料で形成された第１レンズとしての球面レンズ１
１、被走査面側に主走査方向と副走査方向の曲率半径が
互いに異なるレンズ面を有するガラス材料で形成された
第２レンズとしてのトーリックレンズ１２の２枚のレン
ズより構成している。このうちトーリックレンズ１２の
被走査面側のレンズ面形状が主走査方向において結像手
段２０の光軸中心に対して非対称な非球面形状となるよ
うに形成している。That is, in the present embodiment, the image forming means 20 is formed from a glass material having a convex radius of curvature in order from the optical deflector 5 side to the surface to be scanned, and the spherical lens 1 as the first lens.
1. A toric lens 12 as a second lens formed of a glass material having two lens surfaces with different radii of curvature in the main scanning direction and the sub-scanning direction on the surface to be scanned. Of these, the toric lens 12 is formed such that the lens surface shape on the surface to be scanned is an aspherical shape which is asymmetric with respect to the optical axis center of the image forming means 20 in the main scanning direction.
【００５３】このように結像手段２０を構成することに
より、本実施例では前述の各実施例と同様に従来の技術
的な問題点である主走査方向のｆθ特性及び像面湾曲の
非対称性による残存収差を良好に補正している。By constructing the image forming means 20 in this way, in this embodiment, as in the above-mentioned respective embodiments, the fθ characteristic in the main scanning direction and the asymmetry of the curvature of field, which are technical problems of the prior art, are present. The residual aberration due to is well corrected.
【００５４】図１３、図１４は各々本発明の実施例４に
よる光走査範囲における被走査面上での主走査方向のｆ
θ特性（歪曲収差）及び像面湾曲を示す説明図である。
図１３、図１４は各々トーリックレンズの被走査面側の
主走査方向のレンズ面形状を、光軸に対して対称なレン
ズ面形状を補正前、非対称なレンズ面形状を補正後とし
て比較して示してある。図１３、図１４に示すように全
画角にわたり良好に収差が補正されていることが分か
る。13 and 14 show f in the main scanning direction on the surface to be scanned in the optical scanning range according to the fourth embodiment of the present invention.
It is explanatory drawing which shows (theta) characteristic (distortion aberration) and field curvature.
13 and 14 compare the lens surface shape in the main scanning direction on the surface to be scanned of the toric lens with the lens surface shape symmetric with respect to the optical axis before correction and the asymmetric lens surface shape after correction. It is shown. As shown in FIGS. 13 and 14, it can be seen that the aberration is favorably corrected over the entire angle of view.
【００５５】図１５、図１６は各々本発明の実施例５に
よる光走査範囲における被走査面上での主走査方向のｆ
θ特性（歪曲収差）及び像面湾曲を示す説明図である。15 and 16 show f in the main scanning direction on the surface to be scanned in the optical scanning range according to the fifth embodiment of the present invention.
It is explanatory drawing which shows (theta) characteristic (distortion aberration) and field curvature.
【００５６】本実施例において前述の実施例４と異なる
点は第２レンズとしてのトーリックレンズ１２の主走査
方向のレンズ面形状を両レンズ面とも光軸中心に対して
非対称な非球面形状より形成し、かつ副走査方向の被走
査面側のレンズ面形状も光軸中心に対して非対称な非球
面形状より形成したことである。その他の構成及び光学
的作用は前述の実施例４と略同様であり、これにより同
様な効果を得ている。本実施例においても図１５、図１
６に示すように全画角にわたり良好に収差が補正されて
いることが分かる。The present embodiment differs from the above-mentioned fourth embodiment in that the lens surface shape of the toric lens 12 as the second lens in the main scanning direction is formed of an aspherical surface asymmetric with respect to the optical axis center on both lens surfaces. In addition, the shape of the lens surface on the surface to be scanned in the sub-scanning direction is also formed of an aspherical surface asymmetric with respect to the optical axis center. Other configurations and optical functions are substantially the same as those of the above-described fourth embodiment, and thereby the same effect is obtained. Also in this embodiment, FIG. 15 and FIG.
As shown in FIG. 6, it can be seen that the aberration is favorably corrected over the entire angle of view.
【００５７】更に各実施例４、５において被走査面全体
の諸収差を良好に補正し、かつ光走査範囲の広画角化を
容易にするには次の諸条件のうち少なくとも１つを満足
させるのが良い。Furthermore, in each of Examples 4 and 5, at least one of the following conditions is satisfied in order to satisfactorily correct various aberrations on the entire surface to be scanned and to facilitate widening of the angle of view of the optical scanning range. It is good to let
【００５８】即ち、第１レンズ（球面レンズ１１）の副
走査方向の焦点距離をｆ１ｂ、第２レンズ（トーリック
レンズ１２）の主走査方向と副走査方向の焦点距離を各
々ｆ２ａ，ｆ２ｂ、結像手段全系の主走査方向における
合成焦点距離をｆａ、第２レンズと被走査面との間の距
離をＬ２としたとき ０．４＜｜ｆａ／ｆ２ａ｜＜１．２ ‥‥‥‥（６） １．７＜｜ｆａ／ｆ２ｂ｜＜４．６ ‥‥‥‥（７） ０．８＜｜Ｌ２／ｆａ｜＜２．２ ‥‥‥‥（８） なる条件を満足することである。That is, the focal length of the first lens (spherical lens 11) in the sub-scanning direction is f1b, the focal lengths of the second lens (toric lens 12) in the main-scanning direction and the sub-scanning direction are f2a and f2b, respectively. When the combined focal length of the entire system in the main scanning direction is fa and the distance between the second lens and the surface to be scanned is L2, 0.4 <| fa / f2a | <1.2 (6 ) 1.7 <| fa / f2b | <4.6 (...) (7) 0.8 <| L2 / fa | <2.2 (8).
【００５９】条件式（６）は主走査方向のｆθ特性と像
面湾曲を良好に補正する為のものである。条件式（６）
の下限値を越えて焦点距離ｆ２ａが大きくなりすぎると
収差補正上有利となるが、第２レンズが被走査面側に近
づいてしまい、装置全体が大型化してしまうので良くな
い。又条件式（６）の上限値を越えて焦点距離ｆ２ａが
小さくなりすぎると逆に装置全体のコンパクト化には有
利となるが、ｆθ特性と像面湾曲の双方をバランス良く
補正するのが困難になってくるので良くない。Conditional expression (6) is for satisfactorily correcting the fθ characteristic in the main scanning direction and the field curvature. Conditional expression (6)
If the focal length f2a becomes too large beyond the lower limit of the above, it is advantageous for aberration correction, but this is not preferable because the second lens approaches the surface to be scanned and the entire apparatus becomes large. On the other hand, if the focal length f2a becomes too small beyond the upper limit of the conditional expression (6), it is advantageous for downsizing the entire device, but it is difficult to correct both the fθ characteristic and the field curvature in a well-balanced manner. It is not good because it becomes.
【００６０】条件式（７）は副走査方向の像面湾曲を良
好に補正する為のものである。条件式（７）の上限値を
越えて焦点距離ｆ２ｂが大きくなりすぎると収差補正上
は有利となるが、第２レンズが被走査面側に近づき装置
全体が大型化してくるので良くない。又条件式（７）の
下限値を越えて焦点距離ｆ２ｂが小さくなりすぎると主
走査方向と副走査方向との像面湾曲をバランス良く補正
するのが困難になってくるので良くない。Conditional expression (7) is for satisfactorily correcting the field curvature in the sub-scanning direction. If the focal length f2b exceeds the upper limit of the conditional expression (7) and becomes too large, it is advantageous for aberration correction, but it is not good because the second lens approaches the surface to be scanned and the size of the entire apparatus increases. If the focal length f2b becomes too small beyond the lower limit of conditional expression (7), it becomes difficult to correct the field curvature in the main scanning direction and the sub scanning direction in a well-balanced manner, which is not preferable.
【００６１】条件式（８）は第２レンズと被走査面との
距離Ｌ２と、結像手段全系の主走査方向における合成焦
点距離ｆａとの比に関するものである。条件式（８）の
下限値を越えると装置全体が大型化になると共に面倒れ
補正効果が少なくってくるので良くない。又条件式
（８）の上限値を越えると第２レンズの屈折力が強くな
りすぎるので良くない。Conditional expression (8) relates to the ratio between the distance L2 between the second lens and the surface to be scanned and the combined focal length fa of the entire image forming means in the main scanning direction. If the lower limit of conditional expression (8) is exceeded, the size of the entire apparatus will be increased and the effect of face tilt correction will be reduced, which is not preferable. If the upper limit of conditional expression (8) is exceeded, the refracting power of the second lens becomes too strong, which is not good.
【００６２】次に本発明に係る結像手段の数値実施例を
示す。数値実施例１〜４は順に本発明の実施例１〜４の
光偏向器５以降の数値例である。Next, numerical examples of the image forming means according to the present invention will be shown. Numerical Examples 1 to 4 are numerical examples after the optical deflector 5 of Examples 1 to 4 of the present invention in order.
【００６３】各数値実施例においてトーリックレンズ６
（又は球面レンズ１１）の主走査断面における曲率半径
をＲ1 ，Ｒ2 、副走査断面における曲率半径をＲ1 ´，
Ｒ2´、アナモフィックレンズ７（又はトーリックレン
ズ１２）の主走査断面における曲率半径をＲ3 ，Ｒ4 、
副走査断面における曲率半径をＲ3 ´，Ｒ4 ´、トーリ
ックレンズ８の主走査断面にあける曲率半径をＲ5 ，Ｒ
6 、副走査断面における曲率半径をＲ5 ´，Ｒ6 ´、各
レンズ面間の距離をＤ1 〜Ｄ6 、トーリックレンズ６、
アナモフィックレンズ７そしてトーリックレンズ８の材
質の屈折率をそれぞれ順にＮ1 ，Ｎ2 ，Ｎ3 、又球面レ
ンズ１１、トーリックレンズ１２の材質の屈折率をそれ
ぞれ順にＮ1 ，Ｎ2 で表わしている。又Ａ〜Ｅ´は以下
に示す主走査断面（ｘ−ｙ平面）上でのレンズ面の高さ
ｙと距離ｘとの関係式 ｘ＝ｙ2 ／Ｒ・［１＋｛１−（１＋Ａ）（ｙ／Ｒ）2 ｝
1/2 ］＋Ｂｙ4 ＋Ｃｙ6 ＋Ｄｙ8 ＋Ｅｙ10 但し、ｙ≧０ ｘ＝ｙ2 ／Ｒ・［１＋｛１−（１＋Ａ´）（ｙ／Ｒ）
2 ｝1/2 ］＋Ｂ´ｙ4 ＋Ｃ´ｙ6 ＋Ｄ´ｙ8 ＋Ｅ´ｙ10 但し、ｙ＜０ の各次数の非球面係数、Ｆ〜Ｊ´は以下に示す副走査断
面（ｚ−ｘ平面）上でのレンズ面の高さｙと距離ｘとの
関係式 ｘ＝ｚ2 ／Ｒ´・［１＋｛１−（ｚ／Ｒ´）2 ｝1/2 ］ 但し、Ｒ″＝Ｒ´（１＋Ｆ´ｙ2 ＋Ｇ´ｙ4 ＋Ｈ´ｙ6
＋Ｉ´ｙ8 ＋Ｊ´ｙ10） ｙ≧０ ｘ＝ｚ2 ／Ｒ´・［１＋｛１−（ｚ／Ｒ´）2 ｝1/2 ］ 但し、Ｒ″＝Ｒ´（１＋Ｆ´ｙ2 ＋Ｇ´ｙ4 ＋Ｈ´ｙ6
＋Ｉ´ｙ8 ＋Ｊ´ｙ10） ｙ＜０ の各次数の非球面係数を示す。In each numerical example, the toric lens 6 is used.
(Or the radius of curvature of the spherical lens 11) in the main scanning section is R 1 , R 2 , the curvature radius in the sub scanning section is R 1 ′,
R 2 ′, radii of curvature in the main scanning section of the anamorphic lens 7 (or toric lens 12) are R 3 , R 4 ,
The radii of curvature in the sub-scan section are R 3 ′ and R 4 ′, and the radii of curvature in the main-scan section of the toric lens 8 are R 5 and R 5 .
6 , radiuses of curvature in the sub-scan section are R 5 ′ and R 6 ′, distances between lens surfaces are D 1 to D 6 , toric lens 6,
The refractive indexes of the materials of the anamorphic lens 7 and the toric lens 8 are sequentially represented by N 1 , N 2 , and N 3 , respectively, and the refractive indexes of the materials of the spherical lens 11 and the toric lens 12 are respectively represented by N 1 and N 2 . Further, A to E ′ are the following relational expressions between the height y of the lens surface and the distance x on the main scanning cross section (xy plane): x = y 2 / R · [1+ {1- (1 + A) ( y / R) 2 }
1/2 ] + By 4 + Cy 6 + Dy 8 + Ey 10 where y ≧ 0 x = y 2 / R · [1+ {1- (1 + A ′) (y / R)
2 } 1/2 ] + B'y 4 + C'y 6 + D'y 8 + E'y 10 However, aspherical coefficients of each order of y <0, F to J'are sub-scanning cross sections (z-x Relational expression between the height y of the lens surface on the plane and the distance x: x = z 2 / R ′ · [1+ {1- (z / R ′) 2 } 1/2 ] where R ″ = R ′ (1 + F'y 2 + G'y 4 + H'y 6
+ I'y 8 + J'y 10 ) y ≧ 0 x = z 2 / R '· [1+ {1- (z / R') 2 } 1/2 ] where R ″ = R ′ (1 + F′y 2 + G ´y 4 ＋ H´y 6
+ I'y 8 + J'y 10) shows the aspherical coefficients of each order of y <0.
【００６４】又各数値実施例１、２、３と前述の各条件
式（１）〜（５）との関係を表−１に示し、数値実施例
４と前述の各条件式（６）〜（８）との関係を表−２に
示す。 （数値実施例１） 全系焦点距離 289.27291mm 最大走査角 58.8 ° 偏向点〜R1面 38.616mm R1 =-4213.80333 D1 = 5.02325 R1′= -59.4343 N1 = 1.521794 R2 = ∞ D2 = 63.5 R2′= -45.8583 R3 = ∞ D3 = 13.0 R3′= 80.6871 N2 = 1.794120 R4 = -231.48811 D4 = 27.44653 R4′= -231.48811 R5 = -379.28217 D5 = 7.35477 N3 = 1.521794 A = -4.93824 A′= -4.93824 B = -1.9774 ×10-7 B′= -1.9774 ×10-7 C = -1.57948×10-12 C′= -1.57948×10-12 D = 2.57021×10-16 D′= 2.57021×10-16 E = -1.41493×10-20 E′= -1.41493×10-20 R5′= -23.1146 F = -1.18531×10-4 F′= -1.18531×10-4 G = -1.97792×10-9 G′= -1.97792×10-9 H = 5.82764×10-12 H′= 5.82764×10-12 I = -6.43558×10-16 I′= -6.43558×10-16 J = 9.89056×10-21 J′= 9.89056×10-21 R6 = -342.86243 D6 =263.19843 A = -3.66797×10-3 A′= -3.66832×10-3 B = -1.71964×10-7 B′= -1.71532×10-7 C = -1.06254×10-12 C′= -1.06255×10-12 D = 1.73005×10-16 D′= 1.73005×10-16 E = -9.53228×10-21 E′= -9.53228×10-21 R6′= -26.3585 F = -8.63021×10-5 F′= -8.63021×10-5 G = -5.72406×10-9 G′= -5.72406×10-9 H = 5.15404×10-12 H′= 5.15404×10-12 I = -4.73602×10-16 I′= -4.73602×10-16 J = 4.46974×10-21 J′= 4.46974×10-21 （数値実施例２） 全系焦点距離 289.27291mm 最大走査角 58.8 ° 偏向点〜R1面 38.616mm R1 =-4213.80333 D1 = 5.02325 R1′= -59.4343 N1 = 1.521794 R2 = ∞ D2 = 63.5 R2′= -45.8583 R3 = ∞ D3 = 13.0 R3′= 80.6871 N2 = 1.794120 R4 = -231.48811 D4 = 27.44653 R4′= -231.48811 R5 = -379.28217 D5 = 7.35477 N3 = 1.521794 A = -4.94247 A′= -4.78139 B = -2.00407×10-7 B′= -2.21938×10-7 C = -1.68718×10-12 C′= -1.4601 ×10-12 D = 3.06172×10-16 D′= 2.66939×10-16 E = -1.58337×10-20 E′= -1.31493×10-20 R5′= -23.1146 F = -1.18531×10-4 F′= -1.18531×10-4 G = -1.97792×10-9 G′= -1.97792×10-9 H = 5.82764×10-12 H′= 5.82764×10-12 I = -6.43558×10-16 I′= -6.43558×10-16 J = 9.89056×10-21 J′= 9.89056×10-21 R6 = -342.86243 D6 =263.19843 A = -4.06917×10-3 A′= -3.60377×10-3 B = -1.75448×10-7 B′= -1.94062×10-7 C = -9.03036×10-13 C′= -1.08256×10-12 D = 1.82896×10-16 D′= 1.95443×10-16 E = -9.13978×10-21 E′= -9.47663×10-21 R6′= -26.3585 F = -8.63021×10-5 F′= -8.63021×10-5 G = -5.72406×10-9 G′= -5.72406×10-9 H = 5.15404×10-12 H′= 5.15404×10-12 I = -4.73602×10-16 I′= -4.73602×10-16 J = 4.46974×10-21 J′= 4.46974×10-21 （数値実施例３） 全系焦点距離 289.27291mm 最大走査角 58.8 ° 偏向点〜R1面 38.616mm R1 =-4213.80333 D1 = 5.02325 R1′= -59.4343 N1 = 1.521794 R2 = ∞ D2 = 63.5 R2′= -45.8583 R3 = ∞ D3 = 13.0 R3′= 80.6871 N2 = 1.794120 R4 = -231.48811 D4 = 27.44653 R4′= -231.48811 R5 = -379.28217 D5 = 7.35477 N3 = 1.521794 A = -4.94247 A′= -4.78139 B = -2.00407×10-7 B′= -2.21938×10-7 C = -1.68718×10-12 C′= -1.4601 ×10-12 D = 3.06172×10-16 D′= 2.66939×10-16 E = -1.58337×10-20 E′= -1.3149 ×10-20 R5′= -23.1146 F = -1.18531×10-4 F′= -1.18531×10-4 G = -1.97792×10-9 G′= -1.97792×10-9 H = 5.82764×10-12 H′= 5.82764×10-12 I = -6.43558×10-16 I′= -6.43558×10-16 J = 9.89056×10-21 J′= 9.89056×10-21 R6 = -342.86243 D6 =263.19843 A = -4.06917×10-3 A′= -3.60377×10-3 B = -1.75448×10-7 B′= -1.94062×10-7 C = -9.03036×10-13 C′= -1.08256×10-12 D = 1.82896×10-16 D′= 1.95443×10-16 E = -9.13978×10-21 E′= -9.47663×10-21 R6′= -26.3585 F = -8.63021×10-5 F′= -8.37081×10-5 G = -5.72406×10-9 G′= -7.24473×10-9 H = 5.15404×10-12 H′= 5.44733×10-12 I = -4.73602×10-16 I′= -4.8682 ×10-16 J = 4.46974×10-21 J′= 3.39628×10-21 （数値実施例４） 全系焦点距離 289.982095mm 最大走査角 58.7 ° 偏向点〜R1面 27.89507mm R1 = -78.27388 D1 = 14.37 R1′= -78.27388 N1 = 1.71925 R2 = -84.23755 D2 = 55.83 R2′= -84.23755 R3 = 0 D3 = 15.41 R3′= -146.67 N2 = 1.5994 R4 = -187.39 D4 =312.64379 A = 2.58374×10-1 A′= -3.85067×10-2 B = 4.02372×10-9 B′= -2.59256×10-9 C = 8.57195×10-13 C′= 9.52373×10-13 D = -1.94867×10-16 D′= -2.60599×10-16 E = 1.99971×10-20 E′= 2.76069×10-20 R4′= -38.08 Table 1 shows the relationship between each of the numerical examples 1, 2, and 3 and each of the conditional expressions (1) to (5) described above, and the numerical example 4 and each of the conditional expressions (6) to Table 2 shows the relationship with (8). Numerical Example 1 Focal length of entire system 289.27291mm Maximum scanning angle 58.8 ° Deflection point to R1 surface 38.616mm R1 = -4213.80333 D1 = 5.02325 R1 '= -59.4343 N1 = 1.521794 R2 = ∞ D2 = 63.5 R2' = -45.8583 R3 = ∞ D3 = 13.0 R3 '= 80.6871 N2 = 1.794120 R4 = -231.48811 D4 = 27.44653 R4' = -231.48811 R5 = -379.28217 D5 = 7.35477 N3 = 1.521794 A = -4.93824 A '= -4.93824 B = -1.9774 × 10 -7 B '= -1.9774 × 10 -7 C = -1.57948 × 10 -12 C' = -1.57948 × 10 -12 D = 2.57021 × 10 -16 D '= 2.57021 × 10 -16 E = -1.41493 × 10 - 20 E '= -1.41493 x 10 -20 R5' = -23.1146 F = -1.18531 x 10 -4 F '= -1.18531 x 10 -4 G = -1.97792 x 10 -9 G' = -1.97792 x 10 -9 H = 5.82764 × 10 -12 H ′ = 5.82764 × 10 -12 I = -6.43558 × 10 -16 I ′ = -6.43558 × 10 -16 J = 9.89056 × 10 -21 J ′ = 9.89056 × 10 -21 R6 = -342.86243 D6 = 263.19843 A = -3.66797 x 10 -3 A '= -3.66832 x 10 -3 B = -1.71964 x 10 -7 B' = -1.71532 x 10 -7 C = -1.06254 x 10 -12 C '= -1.06255 × 10 -12 D = 1.73005 × 10 -16 D ′ = 1.73005 × 10 -16 E = -9.53228 × 10 -21 E ′ = -9.53 228 × 10 -21 R6 '= -26.3585 F = -8.63021 × 10 -5 F' = -8.63021 × 10 -5 G = -5.72406 × 10 -9 G '= -5.72406 × 10 -9 H = 5.15404 × 10 - 12 H '= 5.1540 4 x 10 -12 I = -4.73602 x 10 -16 I' = -4.73602 x 10 -16 J = 4.46974 x 10 -21 J '= 4.46974 x 10 -21 (Numerical example 2) All system focus Distance 289.27291mm Maximum scan angle 58.8 ° Deflection point to R1 surface 38.616mm R1 = -4213.80333 D1 = 5.02325 R1 ′ = -59.4343 N1 = 1.521794 R2 = ∞ D2 = 63.5 R2 ′ = -45.8583 R3 = ∞ D3 = 13.0 R3 ′ = 80.6871 N2 = 1.794120 R4 = -231.48811 D4 = 27.44653 R4 '= -231.48811 R5 = -379.28217 D5 = 7.35477 N3 = 1.521794 A = -4.94247 A' = -4.78139 B = -2.00407 × 10 -7 B '= -2.21938 × 10 -7 C = -1.68718 × 10 -12 C '= -1.4601 × 10 -12 D = 3.06172 × 10 -16 D' = 2.66939 × 10 -16 E = -1.58337 × 10 -20 E '= -1.31493 × 10 - 20 R5 ′ = -23.1146 F = -1.18531 × 10 -4 F ′ = -1.18531 × 10 -4 G = -1.97792 × 10 -9 G ′ = -1.97792 × 10 -9 H = 5.82764 × 10 -12 H ′ = 5.82764 × 10 -12 I = -6.43558 × 10 -16 I '= -6.43558 × 10 -16 J = 9.89056 × 10 -21 J' = 9.89056 10 -21 R6 = -342.86243 D6 = 263.19843 A = -4.06917 × 10 -3 A '= -3.60377 × 10 -3 B = -1.75448 × 10 -7 B' = -1.94062 × 10 -7 C = -9.03036 × 10 -13 C ′ = -1.08256 × 10 -12 D = 1.82896 × 10 -16 D ′ = 1.95443 × 10 -16 E = -9.13978 × 10 -21 E ′ = -9.47663 × 10 -21 R6 ′ = -26.3585 F = -8.63021 x 10 -5 F '= -8.63021 x 10 -5 G = -5.72406 x 10 -9 G' = -5.72406 x 10 -9 H = 5.15404 x 10 -12 H '= 5.15404 x 10 -12 I =- 4.73602 × 10 -16 I ′ = -4.73602 × 10 -16 J = 4.46974 × 10 -21 J ′ = 4.46974 × 10 -21 (Numerical example 3) Whole system focal length 289.27291mm Maximum scanning angle 58.8 ° Deflection point to R1 Surface 38.616mm R1 = -4213.80333 D1 = 5.02325 R1 '= -59.4343 N1 = 1.521794 R2 = ∞ D2 = 63.5 R2' = -45.8583 R3 = ∞ D3 = 13.0 R3 '= 80.6871 N2 = 1.794120 R4 = -231.48811 D4 = 27.44653 R4 ′ = -231.48811 R5 = -379.28217 D5 = 7.35477 N3 = 1.521794 A = -4.94247 A ′ = -4.78139 B = -2.00407 × 10 -7 B ′ = -2.21938 × 10 -7 C = -1.68718 × 10 -12 C ′ = -1.4601 × 10 -12 D = 3.06172 × 10 -16 D '= 2.66939 × 10 -16 E = -1.58337 × 10 -20 E = -1.3149 × 10 -20 R5 '= -23.1146 F = -1.18531 × 10 -4 F' = -1.18531 × 10 -4 G = -1.97792 × 10 -9 G '= -1.97792 × 10 -9 H = 5.82764 × 10 -12 H '= 5.82764 x 10 -12 I = -6.43558 x 10 -16 I' = -6.43558 x 10 -16 J = 9.89056 x 10 -21 J '= 9.89056 x 10 -21 R6 = -342.86243 D6 = 263.19843 A = -4.06917 × 10 -3 A ' = -3.60377 × 10 -3 B = -1.75448 × 10 -7 B' = -1.94062 × 10 -7 C = -9.03036 × 10 -13 C '= -1.08256 × 10 - 12 D = 1.82896 x 10 -16 D '= 1.95443 x 10 -16 E = -9.13978 x 10 -21 E' = -9.47663 x 10 -21 R6 '= -26.3585 F = -8.63021 x 10 -5 F' =- 8.37081 x 10 -5 G = -5.72406 x 10 -9 G '= -7.24473 x 10 -9 H = 5.15404 x 10 -12 H' = 5.44733 x 10 -12 I = -4.73602 x 10 -16 I '= -4.8682 × 10 -16 J = 4.46974 × 10 -21 J '= 3.39628 × 10 -21 (Numerical example 4) Focal length of the entire system 289.982095mm Maximum scanning angle 58.7 ° Deflection point to R1 surface 27.89507mm R1 = -78.27388 D1 = 14.37 R1 ′ = -78.27388 N1 = 1.71925 R2 = -84.23755 D2 = 55.83 R2 ′ = -84.23755 R3 = 0 D3 = 15.41 R3 ′ = -146.67 N2 = 1.5994 R4 = -187.39 D4 = 312.64379 A = 2.58374 x 10 -1 A '= -3.85067 x 10 -2 B = 4.02372 x 10 -9 B' = -2.59256 x 10 -9 C = 8.57195 x 10 -13 C '= 9.52373 x 10 -13 D =- 1.94867 x 10 -16 D '= -2.60599 x 10 -16 E = 1.99971 x 10 -20 E' = 2.76069 x 10 -20 R4 '= -38.08
【００６５】[0065]
【表１】 [Table 1]
【００６６】[0066]
【表２】 [Table 2]
【００６７】[0067]
【発明の効果】本発明によれば前述の如く結像手段のレ
ンズ構成、レンズ形状そしてレンズの材質を適切に設定
すると共に少なくとも１つのレンズ面を該結像手段の光
軸中心に対して主走査方向又は主走査方向と副走査方向
に関して非対称な非球面形状より形成することにより、
主走査方向のｆθ特性及び像面湾曲を良好に補正するこ
とができると共に高性能な光学性能を得ることができる
光走査光学系を達成することができる。According to the present invention, as described above, the lens structure, the lens shape and the material of the lens of the image forming means are appropriately set, and at least one lens surface is mainly arranged with respect to the optical axis center of the image forming means. By forming an aspherical shape that is asymmetric with respect to the scanning direction or the main scanning direction and the sub-scanning direction,
It is possible to achieve an optical scanning optical system capable of satisfactorily correcting the fθ characteristic and the field curvature in the main scanning direction and obtaining high-performance optical performance.
【００６８】又、実施例１〜３によれば結像手段を構成
する３つのレンズのうち２つのレンズをプラスチック材
料で形成することにより低価格化も同時に達成すること
ができる。Further, according to the first to third embodiments, the cost can be reduced at the same time by forming two lenses out of the three lenses forming the image forming means from the plastic material.
【図１】 本発明の実施例１の要部平面図（主走査断面
図）FIG. 1 is a plan view of a main part of a first embodiment of the present invention (main scanning sectional view).
【図２】 図１の主走査断面に垂直な要部断面図（副走
査断面図）FIG. 2 is a sectional view of a main part (sub-scan sectional view) perpendicular to the main-scan sectional view of FIG.
【図３】 本発明の実施例１の光偏向器の回転に伴なう
偏向点Ｘ座標の変化を示す説明図FIG. 3 is an explanatory diagram showing a change in the X-coordinate of the deflection point with the rotation of the optical deflector according to the first embodiment of the present invention.
【図４】 本発明の実施例１の光偏向器の回転に伴なう
偏向点Ｙ座標の変化を示す説明図FIG. 4 is an explanatory diagram showing changes in the Y coordinate of the deflection point with the rotation of the optical deflector according to the first embodiment of the present invention.
【図５】 本発明の実施例１の像面湾曲を説明する収差
図FIG. 5 is an aberration diagram illustrating field curvature of Example 1 of the present invention.
【図６】 本発明の実施例１のｆ−θ特性を説明する収
差図FIG. 6 is an aberration diagram illustrating an f-θ characteristic according to the first embodiment of the present invention.
【図７】 本発明の実施例２の像面湾曲を説明する収差
図FIG. 7 is an aberration diagram illustrating field curvature of Example 2 of the present invention.
【図８】 本発明の実施例２のｆ−θ特性を説明する収
差図FIG. 8 is an aberration diagram illustrating an f-θ characteristic according to the second embodiment of the present invention.
【図９】 本発明の実施例３の像面湾曲を説明する収差
図FIG. 9 is an aberration diagram illustrating field curvature of Example 3 of the present invention.
【図１０】 本発明の実施例３のｆ−θ特性を説明する
収差図FIG. 10 is an aberration diagram illustrating an f-θ characteristic according to the third embodiment of the present invention.
【図１１】 本発明の実施例４の要部平面図（主走査断
面図）FIG. 11 is a plan view of a main part of the fourth embodiment of the present invention (main scanning sectional view).
【図１２】 図１１の主走査断面に垂直な要部断面図
（副走査断面図）12 is a cross-sectional view of a main part (sub-scan sectional view) perpendicular to the main-scan sectional view of FIG.
【図１３】 本発明の実施例４の像面湾曲を説明する収
差図FIG. 13 is an aberration diagram illustrating field curvature of Example 4 of the present invention.
【図１４】 本発明の実施例４のｆ−θ特性を説明する
収差図FIG. 14 is an aberration diagram illustrating an f-θ characteristic according to the fourth embodiment of the present invention.
【図１５】 本発明の実施例５の像面湾曲を説明する収
差図FIG. 15 is an aberration diagram illustrating field curvature of Example 5 of the present invention.
【図１６】 本発明の実施例５のｆ−θ特性を説明する
収差図FIG. 16 is an aberration diagram illustrating an f-θ characteristic according to the fifth embodiment of the present invention.
１ 光源手段 ２ コリメータレンズ ３ 開口絞り ４ シリンドリカルレンズ ５ 偏向手段 ６，１１ 第１レンズ ７，１２ 第２レンズ ８ 第３レンズ ９ 被走査面（感光ドラム） １０，２０ 結像手段 1 Light Source Means 2 Collimator Lens 3 Aperture Stop 4 Cylindrical Lens 5 Deflection Means 6, 11 First Lens 7, 12 Second Lens 8 Third Lens 9 Scanned Surface (Photosensitive Drum) 10, 20 Image Forming Means
Claims (12)
段に導光し、該偏向手段で偏向反射させた該光ビームを
結像手段により被走査面上に導光し光走査する光走査光
学系において、 該結像手段は該偏向手段側から順に主走査方向と副走査
方向とで互いに異なる曲率半径のレンズ面を両面に持つ
トーリックレンズより成る第１レンズ、主走査方向と副
走査方向との双方に異なる正の屈折力を有するアナモフ
ィックレンズより成る第２レンズ、そして主走査方向と
副走査方向とで互いに異なる曲率半径のレンズ面を両面
に持つトーリックレンズより成る第３レンズとの３枚の
レンズを有し、 少なくとも１つのレンズ面は該結像手段の光軸中心に対
して主走査方向又は主走査方向と副走査方向に関して非
対称な非球面形状よりなっていることを特徴とする光走
査光学系。1. An optical scanning optical system which guides a light beam emitted from a light source means to a deflecting means, and guides the light beam deflected and reflected by the deflecting means onto a surface to be scanned by an image forming means for optical scanning. In the system, the image forming means includes a first lens formed of a toric lens having lens surfaces having curvature radii different from each other in the main scanning direction and the sub scanning direction in order from the deflecting means side, the main scanning direction and the sub scanning direction. A second lens composed of anamorphic lenses having different positive refracting powers on both sides, and a third lens composed of a toric lens having lens surfaces having different radii of curvature in both the main scanning direction and the sub scanning direction on both sides. Characterized in that at least one lens surface has an aspherical shape asymmetric with respect to the optical axis center of the image forming means in the main scanning direction or in the main scanning direction and the sub scanning direction. Light scanning optical system to.
な非球面形状より成るレンズの材質はプラスチック材で
形成されていることを特徴とする請求項１の光走査光学
系。2. The optical scanning optical system according to claim 1, wherein the material of the lens having an aspherical shape asymmetric with respect to the optical axis center of the image forming means is a plastic material.
点距離をｆ３ａ、前記結像手段全系の主走査方向におけ
る合成焦点距離をｆａとしたとき ０．０２＜｜ｆａ／ｆ３ａ｜＜０．０６ なる条件を満足することを特徴とする請求項１の光走査
光学系。3. When the focal length of the third lens in the main scanning direction is f3a and the combined focal length of the entire image forming unit in the main scanning direction is fa, 0.02 <| fa / f3a | <0. The optical scanning optical system according to claim 1, characterized in that the following condition is satisfied.
点距離をｆ３ｂ、前記結像手段全系の主走査方向におけ
る合成焦点距離をｆａとしたとき ０．０８＜｜ｆａ／ｆ３ｂ｜＜０．２５ なる条件を満足することを特徴とする請求項１の光走査
光学系。4. When the focal length of the third lens in the sub-scanning direction is f3b, and the combined focal length of the entire image forming means in the main scanning direction is fa, 0.08 <| fa / f3b | <0. 25. The optical scanning optical system according to claim 1, wherein the condition 25 is satisfied.
合成焦点距離をｆａ、前記第３レンズと前記被走査面と
の間の距離をＬ３としたとき ０．７＜｜Ｌ３／ｆａ｜＜１．８ なる条件を満足することを特徴とする請求項１の光走査
光学系。5. When the combined focal length of the entire image forming means in the main scanning direction is fa and the distance between the third lens and the surface to be scanned is L3, 0.7 <| L3 / fa | The optical scanning optical system according to claim 1, wherein the condition <1.8 is satisfied.
点距離をｆ３ｂ、前記第３レンズの光軸方向の最大肉厚
をｄ３ｍａｘとしたとき ｜ｄ３ｍａｘ／ｆ３ｂ｜＜０．０２５ なる条件を満足することを特徴とする請求項１の光走査
光学系。6. When the focal length of the third lens in the sub-scanning direction is f3b and the maximum thickness of the third lens in the optical axis direction is d3max, | d3max / f3b | <0.025 is satisfied. The optical scanning optical system according to claim 1, wherein
点距離をｆ１ｂ、前記第３レンズの副走査方向における
焦点距離をｆ３ｂとしたとき ｜ｆ３ｂ／ｆ１ｂ｜＜５ なる条件を満足することを特徴とする請求項１の光走査
光学系。7. When the focal length of the first lens in the sub-scanning direction is f1b and the focal length of the third lens in the sub-scanning direction is f3b, | f3b / f1b | <5 is satisfied. The optical scanning optical system according to claim 1.
段に導光し、該偏向手段で偏向反射させた該光ビームを
結像手段により被走査面上に導光し光走査する光走査光
学系において、 該結像手段は該偏向手段側から順に被走査面側に凸の曲
率半径を有する球面レンズより成る第１レンズ、被走査
面側に主走査方向と副走査方向の曲率半径が互いに異な
るレンズ面を有するトーリックレンズより成る第２レン
ズとの２枚のレンズを有し、 少なくとも１つのレンズ面は該結像手段の光軸中心に対
して主走査方向又は主走査方向と副走査方向に関して非
対称な非球面形状よりなっていることを特徴とする光走
査光学系。8. A light scanning optical system for guiding a light beam emitted from a light source means to a deflecting means, and guiding the light beam deflected and reflected by the deflecting means onto a surface to be scanned by an image forming means for optical scanning. In the system, the image forming means has a first lens composed of a spherical lens having a convex curvature radius on the scanned surface side in order from the deflecting means side, and the curvature radii in the main scanning direction and the sub-scanning direction are mutually on the scanning surface side. Two lenses, a second lens formed of a toric lens having different lens surfaces, are provided, and at least one lens surface is a main scanning direction or a main scanning direction and a sub scanning direction with respect to the optical axis center of the image forming means. An optical scanning optical system characterized by having an aspherical shape that is asymmetrical with respect to.
な非球面形状より成るレンズの材質はガラス材で形成さ
れていることを特徴とする請求項８の光走査光学系。9. The optical scanning optical system according to claim 8, wherein the material of the lens having an aspherical shape which is asymmetric with respect to the optical axis center of the image forming means is a glass material.
焦点距離をｆ２ａ、前記結像手段全系の主走査方向にお
ける合成焦点距離をｆａとしたとき ０．４＜｜ｆａ／ｆ２ａ｜＜１．２ なる条件を満足することを特徴とする請求項８の光走査
光学系。10. When the focal length of the second lens in the main scanning direction is f2a and the combined focal length of the entire image forming means in the main scanning direction is fa, 0.4 <| fa / f2a | <1. 9. The optical scanning optical system according to claim 8, wherein the condition 2 is satisfied.
焦点距離をｆ２ｂ、前記結像手段全系の主走査方向にお
ける合成焦点距離をｆａとしたとき １．７＜｜ｆａ／ｆ２ｂ｜＜４．６ なる条件を満足することを特徴とする請求項８の光走査
光学系。11. When the focal length of the second lens in the sub-scanning direction is f2b and the combined focal length of the entire image forming means in the main scanning direction is fa, 1.7 <| fa / f2b | <4. The optical scanning optical system according to claim 8, wherein the condition 6 is satisfied.
る合成焦点距離をｆａ、前記第２レンズと前記被走査面
との間の距離をＬ２としたとき ０．８＜｜Ｌ２／ｆａ｜＜２．２ なる条件を満足することを特徴とする請求項８の光走査
光学系。12. When the combined focal length of the entire image forming means in the main scanning direction is fa and the distance between the second lens and the surface to be scanned is L2, 0.8 <| L2 / fa | 9. The optical scanning optical system according to claim 8, wherein the condition <2.2 is satisfied.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16289395A JP3437331B2 (en) | 1995-06-06 | 1995-06-06 | Optical scanning optical system and laser beam printer including the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16289395A JP3437331B2 (en) | 1995-06-06 | 1995-06-06 | Optical scanning optical system and laser beam printer including the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08334687A true JPH08334687A (en) | 1996-12-17 |
| JP3437331B2 JP3437331B2 (en) | 2003-08-18 |
Family
ID=15763255
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP16289395A Expired - Fee Related JP3437331B2 (en) | 1995-06-06 | 1995-06-06 | Optical scanning optical system and laser beam printer including the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3437331B2 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006330364A (en) * | 2005-05-26 | 2006-12-07 | Canon Inc | Optical scanner and image forming apparatus using the same |
| CN100426048C (en) * | 2000-05-25 | 2008-10-15 | 佳能株式会社 | Optical scanning apparatus and image forming apparatus using the same |
| JP2009211064A (en) * | 2008-02-07 | 2009-09-17 | Ricoh Co Ltd | Optical scanner and image forming apparatus equipped with the same |
-
1995
- 1995-06-06 JP JP16289395A patent/JP3437331B2/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100426048C (en) * | 2000-05-25 | 2008-10-15 | 佳能株式会社 | Optical scanning apparatus and image forming apparatus using the same |
| JP2006330364A (en) * | 2005-05-26 | 2006-12-07 | Canon Inc | Optical scanner and image forming apparatus using the same |
| JP4708862B2 (en) * | 2005-05-26 | 2011-06-22 | キヤノン株式会社 | Optical scanning device and image forming apparatus using the same |
| JP2009211064A (en) * | 2008-02-07 | 2009-09-17 | Ricoh Co Ltd | Optical scanner and image forming apparatus equipped with the same |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3437331B2 (en) | 2003-08-18 |
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