JPS63204225A - Optical mechanism for light beam scanner - Google Patents
Optical mechanism for light beam scannerInfo
- Publication number
- JPS63204225A JPS63204225A JP3704087A JP3704087A JPS63204225A JP S63204225 A JPS63204225 A JP S63204225A JP 3704087 A JP3704087 A JP 3704087A JP 3704087 A JP3704087 A JP 3704087A JP S63204225 A JPS63204225 A JP S63204225A
- Authority
- JP
- Japan
- Prior art keywords
- lens
- curvature
- concave cylindrical
- scanning
- light beam
- 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.)
- Pending
Links
- 230000003287 optical effect Effects 0.000 title claims abstract description 24
- 230000005499 meniscus Effects 0.000 claims description 4
- 238000010586 diagram Methods 0.000 description 6
- 238000003384 imaging method Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000002131 composite material Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 108091008695 photoreceptors Proteins 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
Landscapes
- Mechanical Optical Scanning Systems (AREA)
- Lenses (AREA)
Abstract
Description
【発明の詳細な説明】
本発明は、レーザプリンタ等に用いる光ビーム走査装置
用光学機構に関するものである。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical mechanism for a light beam scanning device used in a laser printer or the like.
[従来の技術]
従来、レーザプリンタ等では、光源から発生するレーザ
ご−ムを記録すべく情報信号によって変調し、さらに変
調されたレーザビームを整形光学系を介して回転多面反
射鏡などの偏向手段で等角速度で偏向し、結像レンズ系
で感光体上に集光させるようにしている。この場合、結
像レンズ系としてfθレンズが広く用いられる。このf
θレンズは等角速度でのレーザビームの偏向を補正して
その光スポットが走査面上で等速に移動するようにする
ためのもので、光軸からθの角度で偏向点より入射した
レーザビームは焦点距離fの結像レンズの光軸からf×
θの像高位置に集光することを意味してこの名称で呼ば
れている。[Prior Art] Conventionally, in laser printers and the like, a laser beam generated from a light source is modulated by an information signal in order to record the beam, and the modulated laser beam is then deflected by a rotating polygonal reflector or the like through a shaping optical system. The beam is deflected at a constant angular velocity by a means, and is focused onto a photoreceptor by an imaging lens system. In this case, an fθ lens is widely used as the imaging lens system. This f
A θ lens is used to correct the deflection of a laser beam at a constant angular velocity so that the light spot moves at a constant speed on the scanning surface. is f× from the optical axis of the imaging lens with focal length f
This name means that the light is focused at the image height position of θ.
面倒れ補正とは、偏向手段に用いられる回転多面鏡の鏡
面の傾き誤差等により発生する走査スポットの走査方向
と直交する方向への位置ずれを補正することであるが、
走査面と直交する面内において偏向点位置と被走査位置
とがほぼ共役関係になるように光学系を構成することに
よって面倒れ補正が可能となる。Surface tilt correction is to correct the positional deviation of the scanning spot in the direction perpendicular to the scanning direction, which is caused by the tilt error of the mirror surface of the rotating polygon mirror used in the deflection means.
By configuring the optical system so that the deflection point position and the scanned position have a substantially conjugate relationship in a plane perpendicular to the scanning plane, surface tilt correction becomes possible.
従来、この面倒れ補正光学系としてシリンドリカルレン
ズを用いるもの、あるいは特開昭61−175616号
、61−170715号、56−36622号に開示さ
れているようにfθレンズとトロイダルレンズすたは非
球面レンズを組合せて構成したもの、または特開昭59
−84218号に開示されているように負と正のパワー
を持つ2枚のfθレンズと円筒鏡を組合せて構成したも
のがある。Conventionally, a cylindrical lens has been used as the surface tilt correction optical system, or an f-theta lens and a toroidal lens have an aspherical surface, as disclosed in Japanese Patent Laid-Open No. 61-175616, No. 61-170715, and No. 56-36622. A combination of lenses, or JP-A-59
As disclosed in Japanese Patent Application No. 84218, there is one constructed by combining two fθ lenses with negative and positive powers and a cylindrical mirror.
[発明が解決しようとする問題点]
ところが、シリンドリカルレンズを用いるものでは、偏
光角を大きくすると走査方向に直交する方向の像面わん
曲が大きくなるので、これを小さくするために配置位置
を被走査面に近付けなければならなくなり、コンパクト
化が困難になるという問題がある。[Problems to be Solved by the Invention] However, in a lens that uses a cylindrical lens, as the polarization angle increases, the field curvature in the direction perpendicular to the scanning direction increases, so in order to reduce this, the arrangement position must be changed. There is a problem in that it has to be placed close to the scanning surface, making it difficult to make it compact.
また、fθレンズとトロイダルレンズとを用いるもので
は、製造が難しいという問題がある。さらに2枚のfθ
レンズと円筒鏡を用いるものでは、負のパワーが強くバ
ックフォーカスが長くなり、コンパクト化が困難である
という問題がある。Further, there is a problem in that it is difficult to manufacture a device using an fθ lens and a toroidal lens. Two more fθ
A device using a lens and a cylindrical mirror has a problem in that it has a strong negative power and a long back focus, making it difficult to make it compact.
本発明は、上述した事情に鑑みてなされたもので、偏向
角が大きく、かつコンパクト化と製造が容易で像面わん
曲を良好に補正することができる光ビーム走査装置用光
学機構を提供することを目的としている。The present invention has been made in view of the above-mentioned circumstances, and provides an optical mechanism for a light beam scanning device that has a large deflection angle, is compact and easy to manufacture, and can satisfactorily correct field curvature. The purpose is to
E問題点を解決するための手段]
本発明は、fθレンズとこのfθレンズと共に面倒れ補
正光学系を構成する補正光学部材とを有し、上記fθレ
ンズは走査平面内において偏向点側にパワーの弱いメニ
スカス形状をした第1レンズと、像側にパワーの強い凸
面を向けた平凸形状をした第2レンズとから成り、かつ
上記第2レンズの偏向点側の面は走査平面と直交する方
向にのみ曲率をもつ凹円筒面により構成され、さらに、
上記補正光学部材は上記fθレンズと被走査面との間に
配置され、走査平面と直交する方向にのみ曲率をもつ凹
円面鏡で構成したものである。Means for Solving Problem E] The present invention includes an fθ lens and a correction optical member that constitutes a surface tilt correction optical system together with the fθ lens, and the fθ lens has a power on the deflection point side within the scanning plane. It consists of a first lens with a meniscus shape with a weak power, and a second lens with a plano-convex shape with a convex surface with a strong power facing the image side, and the surface of the second lens on the deflection point side is perpendicular to the scanning plane. It is composed of a concave cylindrical surface with curvature only in the direction, and furthermore,
The correction optical member is arranged between the fθ lens and the scanned surface, and is composed of a concave circular mirror having curvature only in a direction perpendicular to the scanning plane.
[作用]
fθレンズを構成する第1レンズと第2レンズの各焦点
距離を適宜に設定することにより、歪曲収差が少なく、
かつ良好なfθ特性が得られたうえ、走査走行の像面わ
ん曲も少なくなる。更に第2レンズに持たせた凹円筒面
により、凹円面鏡だけでは除去し得ない走査方向と直交
する方向の像面わん曲も少なくすることができる。そし
て、この凹円筒面の存在によって凹円面鏡を被走査面か
ら遠ざけて配置しても良好な縁面わん曲が得られ、光学
系全体をコンパクトにすることができる。[Function] By appropriately setting the focal lengths of the first and second lenses that make up the fθ lens, distortion can be reduced.
In addition, good fθ characteristics are obtained, and field curvature during scanning is also reduced. Furthermore, the concave cylindrical surface provided on the second lens can also reduce field curvature in the direction perpendicular to the scanning direction, which cannot be removed by using a concave circular mirror alone. Due to the presence of this concave cylindrical surface, a good edge surface curvature can be obtained even if the concave circular mirror is placed away from the surface to be scanned, and the entire optical system can be made compact.
[実施例]
第1図は本発明の一実施例を示す構成図であり、同図(
a)はレーザビームの走査平面から見た図であり、同図
(b)は走査方向と直交する面から見た図である。これ
らの図において、1はfθレンズであり、走査平面内に
おいて偏向点P側に配置したパワーの弱いメニスカスレ
ンズ2と、被走歪面5側に凸面4を向けたパワーの強い
平凸レンズ3とから構成されている。そして、このfθ
レンズ1と被走査面5との間には、第1図(b)に示す
ように走査面と直交する方向にのみ曲率を持つ凹円面鏡
6が配置され、この凹円面鏡6とfθレンズ1とで面倒
れ補正光学系を構成している。[Example] FIG. 1 is a block diagram showing an example of the present invention, and FIG.
Figure a) is a view seen from the scanning plane of the laser beam, and figure (b) is a view seen from a plane perpendicular to the scanning direction. In these figures, 1 is an fθ lens, which includes a meniscus lens 2 with low power placed on the deflection point P side in the scanning plane, and a plano-convex lens 3 with high power with the convex surface 4 facing the distorted surface 5 side. It consists of And this fθ
As shown in FIG. 1(b), a concave circular mirror 6 having a curvature only in the direction orthogonal to the scanning plane is arranged between the lens 1 and the scanned surface 5. The fθ lens 1 constitutes a surface tilt correction optical system.
なお、平凸レンズ3の偏向点側の面は走査平面と直交す
る方向にのみ曲率を持つ凹円筒面7によって構成されて
いる。Note that the surface of the plano-convex lens 3 on the deflection point side is constituted by a concave cylindrical surface 7 having curvature only in the direction orthogonal to the scanning plane.
以上の構成において、走査面内で見たときの各レンズの
焦点距離を偏向点P側から順にfl、f2とし、合成焦
点距離をfとすると、これらは以下の条件を満たすこと
が望ましい。In the above configuration, assuming that the focal lengths of each lens when viewed within the scanning plane are fl and f2 in order from the deflection point P side, and the combined focal length is f, it is desirable that these satisfy the following conditions.
(a)−0,3≦f/f1≦0.2
(b)−0,1/f1 +0.85/f≦1/f2≦−
0,6/f1 +0.95/f
条件(a)、(b)はfθレンズ1の持つ歪曲収差を制
限し、良好なfθ特性を持たせ、かつ走査方向の像面わ
ん曲を少なくするための条件である。また、平凸レンズ
3に持たせた凹円筒面7は凹円両鏡6のみでは除去する
ことのできない走査方向と直交する方向の像面わん曲を
低減させるためのものである。この凹円筒面7の存在に
より凹円両鏡6を被走査面5から遠ざけて配置しても良
好な像面わん曲が得られ、光学系全体をコンパクトにす
ることが可能である。(a) −0,3≦f/f1≦0.2 (b) −0,1/f1 +0.85/f≦1/f2≦−
0.6/f1 +0.95/f Conditions (a) and (b) are used to limit the distortion of fθ lens 1, provide good fθ characteristics, and reduce field curvature in the scanning direction. This is the condition. Further, the concave cylindrical surface 7 provided on the plano-convex lens 3 is for reducing field curvature in the direction orthogonal to the scanning direction, which cannot be removed by the concave circular mirror 6 alone. Due to the presence of this concave cylindrical surface 7, a good field curvature can be obtained even if the concave circular mirror 6 is placed away from the scanned surface 5, and the entire optical system can be made compact.
ここで、第1図に示すようにdl、d2.d3をレンズ
面間距離、d4をレンズ3から凹円両鏡6までの距離、
d5を凹円両鏡6から被走査面5までの距離、dOを偏
向点Pからレンズ2までの距離、R1,R2、R3、R
4を走査平面内における各レンズ面の曲率半径、 R1
’、R2’、R3’、R4゛を走査平面と直交する面内
における曲率半径、R5゛を凹円両鏡6の曲率半径、N
1 、N2はレンズ2.レンズ3の硝材の屈折率、fl
、f2を走査平面内におけるレンズ2.レンズ3の焦
点距離、fを合成焦点距離とし、かつf=100として
規格化した場合、レンズ面間距離等の変化に対する像面
わん曲とfθ特性は次のようになる。Here, as shown in FIG. 1, dl, d2. d3 is the distance between the lens surfaces, d4 is the distance from the lens 3 to the concave mirror 6,
d5 is the distance from the concave circular mirror 6 to the scanned surface 5, dO is the distance from the deflection point P to the lens 2, R1, R2, R3, R
4 is the radius of curvature of each lens surface in the scanning plane, R1
', R2', R3', R4' are the radii of curvature in a plane perpendicular to the scanning plane, R5' is the radius of curvature of the concave circular mirror 6, N
1, N2 is lens 2. Refractive index of the glass material of lens 3, fl
, f2 in the scanning plane. When the focal length of the lens 3, f, is the composite focal length, and is normalized as f=100, the field curvature and fθ characteristics with respect to changes in the distance between lens surfaces, etc., are as follows.
具体例1
f= 100,1/f1−0,000001,1/f2
−0.009dO=8.57
R1=−26,074R1°=−26,074d1=8
.57 N1=1.51
R2=−28,967R2’=−28,967d2=4
.29
R3=oo R3°=−20d3=10.
71 N2=1.71
R4=−78,889R4’=−78,889d4=3
0
R5°=−63,355
d5=81.1
第2図(a)、(b)は本具体例1の像面わん曲とfθ
特性を示す図であり、同図(a)においては破線が主走
査方向、実線がサジタル面内の像面わん曲を示しており
、また同図(b)においてはh=像高として(h−fθ
)/fθ×100%の計算結果でfθ特性を示している
。なお、本具体例以下すべての具体例においてレーザビ
ームの波長は780 nn+、画角θは44°である。Specific example 1 f = 100,1/f1-0,000001,1/f2
-0.009dO=8.57 R1=-26,074R1°=-26,074d1=8
.. 57 N1=1.51 R2=-28,967R2'=-28,967d2=4
.. 29 R3=oo R3°=-20d3=10.
71 N2=1.71 R4=-78,889R4'=-78,889d4=3
0 R5°=-63,355 d5=81.1 Figures 2 (a) and (b) show the field curvature and fθ of this specific example 1.
This is a diagram showing the characteristics. In the diagram (a), the broken line shows the main scanning direction, the solid line shows the field curvature in the sagittal plane, and in the diagram (b), h = image height (h −fθ
)/fθ×100% shows the fθ characteristic. Note that in all the specific examples following this specific example, the wavelength of the laser beam is 780 nn+, and the angle of view θ is 44°.
また凹円両鏡6の光軸はfθレンズ1の光軸と一致させ
たときの例を示しであるが、凹円両鏡6の光軸を傾けて
も、R5’の曲率半径及びR3’の曲率半径を適宜変更
することにより同等性能が得られる。Furthermore, although the example is shown in which the optical axes of the concave circular mirrors 6 are aligned with the optical axes of the fθ lens 1, even if the optical axes of the concave circular mirrors 6 are tilted, the radius of curvature of R5' and the radius of curvature of R3' Equivalent performance can be obtained by appropriately changing the radius of curvature.
1隻■ユ
f= 100.1/f1=o、oooool、1/f2
=0.009ゝdo=12.8f3
R1=−32,585R1°= −32,585d1=
10.71 N1=1.51
R2=−36,200R2°= −36,200d2=
5.00
R3=ooR3’=−20
d3=10.71 N2=1.61
84=−67,778R4°= −67,778d4=
30
R5°=−67,213
d5=81.1
第3図にこの具体例2の像面わん曲とfθ特性を示す。1 ship ■Yu f = 100.1/f1 = o, ooooool, 1/f2
=0.009ゝdo=12.8f3 R1=-32,585R1°=-32,585d1=
10.71 N1=1.51 R2=-36,200R2°=-36,200d2=
5.00 R3=ooR3'=-20 d3=10.71 N2=1.61 84=-67,778R4°=-67,778d4=
30 R5°=-67,213 d5=81.1 FIG. 3 shows the field curvature and fθ characteristics of this specific example 2.
以上の具体例から明らかなように、前述した条件(a)
、(b)を満足する範囲では偏向角を大きくとることが
でき、しかもレンス゛系全体のコンパクト化が可能にな
る。さらに、製造も容易であるという利点がある。As is clear from the above specific example, the above-mentioned condition (a)
, (b), the deflection angle can be made large, and the entire lens system can be made more compact. Furthermore, it has the advantage of being easy to manufacture.
[発明の効果]
以上説明したように本発明によれば、偏向角を大きくと
ることができ、かつコンパクト化とIJ造が容易で偏向
手段の面倒れに伴う像面わん曲を良好に補正することか
できる。[Effects of the Invention] As explained above, according to the present invention, a large deflection angle can be obtained, compactness and IJ construction are easy, and curvature of field caused by tilting of the surface of the deflection means can be well corrected. I can do it.
第1図(a)、(b)は本発明の一実施例を示すfθレ
ンズ及び円筒鏡の構成図、第2図および第3図は第1図
の像面わん曲とfθ特性を示す図である。
1・・・fθレンス′、2・・・メニスカスレンズ、3
・・・平凸レンズ、4・・・凸面、5・・・被走査面、
6・・・凹円両鏡、7・・・凹円筒面。
イ象面わL曲 fθ言″匪第
1図FIGS. 1(a) and (b) are configuration diagrams of an fθ lens and a cylindrical mirror showing one embodiment of the present invention, and FIGS. 2 and 3 are diagrams showing the field curvature and fθ characteristics of FIG. 1. It is. 1...fθ lens', 2...meniscus lens, 3
...Plano-convex lens, 4...Convex surface, 5...Scanned surface,
6...Concave circular mirror, 7...Concave cylindrical surface. Izomenwa L song fθ word "匪 Figure 1
Claims (1)
被走査面との間に配置される光学機構であって、fθレ
ンズとこのfθレンズと共に面倒れ補正光学系を構成す
る補正光学部材とを有し、上記fθレンズは走査平面内
において偏向点側にパワーの弱いメニスカス形状をした
第1レンズと、像側にパワーの強い凸面を向けた平凸形
状をした第2レンズとから成り、かつ上記第2レンズの
偏向点側の面は走査平面と直交する方向にのみ曲率をも
つ凹円筒面により構成され、さらに、上記補正光学部材
は上記fθレンズと被走査面との間に配置され、走査平
面と直交する方向にのみ曲率をもつ凹円筒鏡で構成され
ていることを特徴とする光ビーム走査装置用光学機構。An optical mechanism disposed between a deflection point of a light beam deflected by a light beam polarizer and a scanned surface, which includes an fθ lens and a correction optical member that constitutes a surface tilt correction optical system together with the fθ lens. The fθ lens is composed of a first lens having a meniscus shape with a weak power toward the deflection point side in the scanning plane, and a second lens having a plano-convex shape with a convex surface having a strong power facing the image side, and The surface of the second lens on the deflection point side is constituted by a concave cylindrical surface having curvature only in the direction orthogonal to the scanning plane, and further, the correction optical member is disposed between the fθ lens and the scanned surface, An optical mechanism for a light beam scanning device, comprising a concave cylindrical mirror having curvature only in a direction perpendicular to a scanning plane.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP3704087A JPS63204225A (en) | 1987-02-20 | 1987-02-20 | Optical mechanism for light beam scanner |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP3704087A JPS63204225A (en) | 1987-02-20 | 1987-02-20 | Optical mechanism for light beam scanner |
Publications (1)
Publication Number | Publication Date |
---|---|
JPS63204225A true JPS63204225A (en) | 1988-08-23 |
Family
ID=12486494
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP3704087A Pending JPS63204225A (en) | 1987-02-20 | 1987-02-20 | Optical mechanism for light beam scanner |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS63204225A (en) |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5636622A (en) * | 1979-09-04 | 1981-04-09 | Canon Inc | Scanning optical system having inclination correcting function |
JPS5984218A (en) * | 1982-10-08 | 1984-05-15 | ゼロツクス・コ−ポレ−シヨン | Flying spot scanner |
-
1987
- 1987-02-20 JP JP3704087A patent/JPS63204225A/en active Pending
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5636622A (en) * | 1979-09-04 | 1981-04-09 | Canon Inc | Scanning optical system having inclination correcting function |
JPS5984218A (en) * | 1982-10-08 | 1984-05-15 | ゼロツクス・コ−ポレ−シヨン | Flying spot scanner |
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