JPH0646258B2 - Wide-angle fθ lens system - Google Patents

Wide-angle fθ lens system

Info

Publication number
JPH0646258B2
JPH0646258B2 JP4198686A JP4198686A JPH0646258B2 JP H0646258 B2 JPH0646258 B2 JP H0646258B2 JP 4198686 A JP4198686 A JP 4198686A JP 4198686 A JP4198686 A JP 4198686A JP H0646258 B2 JPH0646258 B2 JP H0646258B2
Authority
JP
Japan
Prior art keywords
lens
group
angle
lens system
concave
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.)
Expired - Lifetime
Application number
JP4198686A
Other languages
Japanese (ja)
Other versions
JPS62200314A (en
Inventor
洋治 久保田
隆明 田中
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nidec Sankyo Corp
Original Assignee
Nidec Sankyo Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Nidec Sankyo Corp filed Critical Nidec Sankyo Corp
Priority to JP4198686A priority Critical patent/JPH0646258B2/en
Publication of JPS62200314A publication Critical patent/JPS62200314A/en
Publication of JPH0646258B2 publication Critical patent/JPH0646258B2/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/0005—Optical objectives specially designed for the purposes specified below having F-Theta characteristic

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Mechanical Optical Scanning Systems (AREA)
  • Lenses (AREA)

Description

【発明の詳細な説明】 〔産業上の利用分野〕 本発明は、レーザビームプリンタ等の光走査装置に利用
される広角ｆθレンズ系に関する。The present invention relates to a wide-angle fθ lens system used in an optical scanning device such as a laser beam printer.

〔従来技術〕[Prior art]

ポリゴンミラー等の回転多面鏡を用いた光走査装置に
は、レンズ系としては一般にｆθレンズ系が採用されて
いることはよく知られている。It is well known that an fθ lens system is generally adopted as a lens system in an optical scanning device using a rotary polygon mirror such as a polygon mirror.

ｆθレンズ系とは周知のように、像高をｙ、レンズ系の
焦点距離をｆ、回転多面鏡の回転角をθとした時に、ｙ
＝ｆθとなるように歪曲収差を補正したレンズ系のこと
である。As is well known as the fθ lens system, when the image height is y, the focal length of the lens system is f, and the rotation angle of the rotary polygon mirror is θ, y
A lens system in which distortion aberration is corrected so that = fθ.

光走査装置は光源、回転多面鏡及びモーター、ｆθレン
ズ系の三つの主要な部分によって構成されており、これ
らの中で光源からのビーム径と、回転多面鏡の面数によ
り決まる走査角とがｆθレンズ系のＦNO、即ち口径比と
画角とを決定する要素になっている。レーザビームプリ
ンタ用の光走査装置には、そのプリントスピードによっ
て高速型と低速型の２種類に分類することができるが、
高速型では光源に高出力の気体レーザを用い、回転多面
鏡の面数も10面乃至12面と、走査効率の高いことを目指
しているのでｆθレンズ系の画角は40゜乃至50゜程度で
充分対応することができるのに対し、低速型においては
主として小型化と低コスト化を追求しているので、光源
には安価な半導体レーザを用い、回転多面鏡の面数は５
面乃至６面と少なく、従ってｆθレンズ系には画角が90
゜乃至100゜程度の広角なレンズ系が必要となってく
る。The optical scanning device is composed of three main parts: a light source, a rotary polygon mirror and a motor, and an fθ lens system. Among these, the beam diameter from the light source and the scanning angle determined by the number of surfaces of the rotary polygon mirror are set. It is a factor that determines F NO of the fθ lens system, that is, the aperture ratio and the angle of view. Optical scanning devices for laser beam printers can be classified into two types, high speed type and low speed type, depending on their printing speed.
The high-speed type uses a high-output gas laser as the light source, and the number of faces of the rotating polygon mirror is 10 to 12, aiming for high scanning efficiency, so the angle of view of the fθ lens system is about 40 ° to 50 °. While the low-speed type mainly pursues miniaturization and cost reduction, an inexpensive semiconductor laser is used as the light source and the number of faces of the rotating polygon mirror is 5
There are as few as 6 to 6 surfaces, so the fθ lens system has an angle of view of 90
A wide-angle lens system of about 100 ° to 100 ° is required.

（発明が解決しようとしている問題点） 上記のように、面数の少ない回転多面鏡からの走査光を
効率よく集光させるｆθレンズ系には画角が広角である
ことが必要である。(Problems to be Solved by the Invention) As described above, the fθ lens system that efficiently collects the scanning light from the rotary polygon mirror having a small number of surfaces needs to have a wide angle of view.

一般にレンズは広角であるほど設計・製作の難易は難し
くなり、またｆθレンズ系の場合には入射瞳がレンズの
外に設定される形になるので広角化はさらに難しくなっ
ている。また、市場においては小型、低コストなレーザ
ビームプリンタに対する需要が増えつつあり、光学系と
して広角なｆθレンズ系の必要性が高まっている。Generally, the wider the angle of the lens, the more difficult the design and manufacturing becomes, and in the case of the fθ lens system, the entrance pupil is set outside the lens, so that the widening of the angle becomes more difficult. Further, in the market, the demand for a small-sized and low-cost laser beam printer is increasing, and the need for a wide-angle fθ lens system as an optical system is increasing.

（問題点を解決するための手段） 本発明の目的は以上の点に鑑み、３群３枚構成という比
較的少ない構成で、90゜以上の広角化を実現した高性能
な広角ｆθレンズ系を提供することにある。(Means for Solving Problems) In view of the above points, an object of the present invention is to provide a high-performance wide-angle f.theta. Lens system that realizes a wide angle of 90.degree. To provide.

〔発明の構成〕[Structure of Invention]

本発明は、ビームの入射側から順に第１群レンズ、第２
群レンズ及び第３群レンズの３つのレンズ群によって構
成されており、第１群レンズは入射側に凹面を向けた凹
メニスカスレンズで構成され、第２群レンズは同様に入
射側に凹面を向けた凸メニスカスレンズで構成され、第
３群レンズは凸レンズによって構成されている３群３枚
構成のレンズ系である。The present invention relates to a first lens group, a second lens group in order from the beam incident side.
It is composed of three lens groups, a group lens and a third group lens, the first group lens is composed of a concave meniscus lens with a concave surface facing the incident side, and the second group lens is similarly structured with a concave surface facing the incident side. Is a convex meniscus lens, and the third lens group is a lens system having a three-group, three-lens structure.

〔実施例〕〔Example〕

以下に本発明に基く実施例を示す。広角ｆθレンズ系は
第１図に示すように、ビームの入射側から順に、第１群
レンズＬ１、第２群レンズＬ２及び第３群レンズＬ３の
３つのレンズ群によって構成されており、第１群レンズ
Ｌ１は入射側に凹面を向けた凹メニスカスレンズで構成
され、第２群レンズＬ２は同様に入射側に凹面を向けた
凸メニスカスレンズで構成され、第３群レンズＬ３は凸
レンズによって３群３枚構成のレンズ系であって、さら
に以下の条件を満たすことである。Examples based on the present invention will be shown below. As shown in FIG. 1, the wide-angle fθ lens system is composed of three lens groups of a first lens group L 1 , a second lens group L 2 and a third lens group L 3 in order from the beam incident side. , The first group lens L 1 is composed of a concave meniscus lens having a concave surface facing the incident side, and the second group lens L 2 is similarly composed of a convex meniscus lens having a concave surface facing the incident side, and the third group lens L Reference numeral 3 denotes a lens system having a three-group, three-lens structure with convex lenses, which further satisfies the following condition.

（１） 0.6ｆ ＜｜ｆ１｜＜0.9ｆ （２） 0.2ｆ ＜｜ｒ１｜＜0.24ｆ （３） 0.06ｆ ＜ｄ１＋ｄ２＜0.08ｆ 但し ｒ１、ｒ２…ｒ６：各構成レンズの曲率半径 ｄ１、ｄ２…ｄ５：各構成レンズの軸上厚みと軸上空気
間隔 ｎ１、ｎ２、ｎ３：各構成レンズの波長830nmにおける
屈折率 ｆ ：全系の焦点距離 ｆ１ ：第１群レンズの焦点距離 θ ：半画角 ＦNO ：Ｆナンバー である。 (1) 0.6f <| f 1 | <0.9f (2) 0.2f <| r 1 | <0.24f (3) 0.06f <d 1 + d 2 <0.08f However r 1, r 2 ... r 6 : each Curvature radii of constituent lenses d 1 , d 2 ... d 5 : On-axis thickness and axial air spacing of each constituent lens n 1 , n 2 , n 3 : Refractive index of each constituent lens at wavelength 830 nm f: Focus of the entire system Distance f 1 : focal length of the first lens group θ: half angle of view F NO : F number.

実施例１ ｆ＝130 ＦNO＝65 ｆ１＝−93.4 ２θ＝94.2゜ ｒ１＝−27.5 ｄ１＝2.0 ｎ１＝1.5102 ｒ２＝−66.62 ｄ２＝8.0 ｒ３＝−77.0 ｄ３＝8.0 ｎ２＝1.78278 ｒ４＝−43.517 ｄ４＝1.0 ｒ５＝0.0 ｄ５＝9.0 ｎ３＝1.78278 ｒ６＝−119.341 実施例２ ｆ＝130 ＦNO＝65 ｆ１＝−97.5 ２θ＝94.2゜ ｒ１＝−27.5 ｄ１＝2.0 ｎ１＝1.5102 ｒ２＝−63.0 ｄ２＝8.0 ｒ３＝−77.0 ｄ３＝8.0 ｎ２＝1.78278 ｒ４＝−43.52 ｄ４＝1.0 ｒ５＝0.0 ｄ５＝9.0 ｎ３＝1.78278 ｒ６＝−124.531 実施例３ ｆ＝130 ＦNO＝65 ｆ１＝−106.6 ２θ＝94.2゜ ｒ１＝−29.5 ｄ１＝6.0 ｎ１＝1.5102 ｒ２＝−68.88 ｄ２＝3.0 ｒ３＝−80.0 ｄ３＝8.0 ｎ２＝1.78278 ｒ４＝−44.332 ｄ４＝1.0 ｒ５＝0.0 ｄ５＝9.0 ｎ３＝1.78278 ｒ６＝−135.21 上記各条件について説明する。Example 1 f = 130 F NO = 65 f 1 = -93.4 2θ = 94.2 ° r 1 = -27.5 d 1 = 2.0 n 1 = 1.5102 r 2 = -66.62 d 2 = 8.0 r 3 = -77.0 d 3 = 8.0 n 2 = 1.78278 r 4 = -43.517 d 4 = 1.0 r 5 = 0.0 d 5 = 9.0 n 3 = 1.78278 r 6 = -119.341 example 2 f = 130 F NO = 65 f 1 = -97.5 2θ = 94.2 ° r 1 = -27.5 d 1 = 2.0 n 1 = 1.5102 r 2 = -63.0 d 2 = 8.0 r 3 = -77.0 d 3 = 8.0 n 2 = 1.78278 r 4 = -43.52 d 4 = 1.0 r 5 = 0.0 d 5 = 9.0 n 3 = 1.78278 r 6 = -124.531 Example 3 f = 130 F NO = 65 f 1 = -106.6 2θ = 94.2 ° r 1 = -29.5 d 1 = 6.0 n 1 = 1.5102 r 2 = -68.88 d 2 = 3.0 r 3 = −80.0 d 3 = 8.0 n 2 = 1.78278 r 4 = −44.332 d 4 = 1.0 r 5 = 0.0 d 5 = 9.0 n 3 = 1.78278 r 6 = −135.21 Each of the above conditions will be described.

条件式（１）は主として全系のペッツバール和と歪曲収
差の補正に関するものである。凹レンズのパワーと凸レ
ンズのパワーの適当な組合せによりペッツバール和は良
好に保つことができるのであり、またｆθレンズ系では
ｆθ特性を得るために故意に負の歪曲収差を発生させね
ばならないが、本発明では第１群レンズＬ１の凹レンズ
により軸外光線を光軸よりさらに高くし、あとに続く凸
レンズによって負の歪曲収差の発生を強めている。した
がって、条件式（１）においてはその上限を越すと、ペ
ッツバール和、ｆθ特性ともに補正不足となり下限を越
すとそれぞれ補正過剰となってしまう。The conditional expression (1) mainly relates to the correction of Petzval sum and distortion of the entire system. The Petzval sum can be kept good by an appropriate combination of the power of the concave lens and the power of the convex lens, and in the fθ lens system, negative distortion must be intentionally generated in order to obtain the fθ characteristic. Then, the concave lens of the first lens unit L 1 makes the off-axis ray higher than the optical axis, and the convex lens that follows subsequently strengthens the occurrence of negative distortion. Therefore, in the conditional expression (1), if the upper limit is exceeded, both the Petzval sum and the fθ characteristic are insufficiently corrected, and if the lower limit is exceeded, each is overcorrected.

条件式（２）は主として球面収差と非点収差の補正に関
するものである。上記のようにｆθ特性を得るために負
の歪曲収差を第２群と第３群の凸レンズＬ２、Ｌ３によ
って得ており、この部分で発生する負の球面収差を第１
群凹レンズＬ１の正の球面収差によって補正せねばなら
ない。非点収差に対しても同様である。Conditional expression (2) mainly relates to correction of spherical aberration and astigmatism. As described above, in order to obtain the fθ characteristic, the negative distortion aberration is obtained by the convex lenses L 2 and L 3 of the second group and the third group, and the negative spherical aberration generated in this portion is the first
It must be corrected by the positive spherical aberration of the group concave lens L 1 . The same applies to astigmatism.

条件式（２）は、この時の曲率半径ｒ１のベンディング
に関するもので上限を越すと、球面収差の補正過剰及び
非点収差の補正不足が発生し、下限と球面収差は補正不
足、非点収差は補正過剰となる。Conditional expression (2) relates to the bending of the radius of curvature r 1 at this time, and if the upper limit is exceeded, overcorrection of spherical aberration and undercorrection of astigmatism will occur, and undercorrection of the lower limit and spherical aberration will result in astigmatism. Aberration is overcorrected.

条件式（３）は上記の曲率半径ｒ１に関しその位置を定
めるための条件である。曲率半径ｒ１と、第２群の凸レ
ンズＬ２との間隔を適切に選ばないと球面収差と非点収
差の補正に支障が出るのは上記と同様であるが、この間
隔は特にｆθ特性とレンズ系全体の大きさに与える影響
が大きい。Conditional expression (3) is a condition for determining the position of the radius of curvature r 1 described above. It is similar to the above that the correction of spherical aberration and astigmatism is impaired unless the distance between the radius of curvature r 1 and the convex lens L 2 of the second group is properly selected. It greatly affects the size of the entire lens system.

即ち、条件式（３）の上限を越えると、軸外光束が光軸
から離れすぎるので、第２群レンズＬ２への入射高が高
くなりすぎて、ｆθ特性が補正過剰になるばかりか第２
群レンズＬ２、第３群レンズＬ３の径が大きくなり、レ
ンズが大型になってしまう。また、下限を越えると逆に
ｆθ特性が補正不足となり、不都合である。That is, if the upper limit of conditional expression (3) is exceeded, the off-axis light beam is too far away from the optical axis, so that the height of incidence on the second lens unit L 2 becomes too high and the fθ characteristic is overcorrected. Two
The diameters of the group lens L 2 and the third group lens L 3 are large, and the lenses are large. On the other hand, if the value goes below the lower limit, the fθ characteristic is insufficiently corrected, which is inconvenient.

以上のように主に第１群レンズＬ１の形状、パワー、位
置を適当に定めることにより、ｆθレンズ系の広角化を
実現することができる。As described above, mainly by appropriately setting the shape, power, and position of the first group lens L 1 , it is possible to realize a wide angle of the fθ lens system.

本発明のｆθレンズ系は上記の如き構成と、各条件を満
たすことによって画角が90゜以上のｆθレンズ系を実現
することが出来たものである。The fθ lens system of the present invention can realize an fθ lens system having an angle of view of 90 ° or more by satisfying the above-mentioned configuration and each condition.

〔発明の効果〕〔The invention's effect〕

本発明により、広角なｆθレンズ系が実現できるので、
走査幅に比べて短い焦点距離のレンズ系とすることがで
き、回転多面鏡の少面数化など走査装置全体をコンパク
ト化、低コスト化することが可能となった。Since a wide-angle fθ lens system can be realized by the present invention,
The lens system can have a focal length shorter than the scanning width, and the entire scanning device can be made compact and the cost can be reduced by reducing the number of surfaces of the rotary polygon mirror.

【図面の簡単な説明】[Brief description of drawings]

第１図は本発明に係る実施例のレンズ系構成図、第２図
は実施例１の球面収差（イ）、非点収差（ロ）、ｆθ特
性（ハ）、第３図は実施例２の球面収差（イ）、非点収
差（ロ）、ｆθ特性（ハ）、第４図は実施例３の球面収
差（イ）、非点収差（ロ）、ｆθ特性（ハ）を表わす。 Ｌ１……第１群レンズ、Ｌ２……第２群レンズ、 Ｌ３……第３群レンズ、ｆ……全系の焦点距離、 ｆ１……第１群の凹メニスカスレンズの焦点距離、 ｒ１〜ｒ６……各構成レンズの曲率半径、 ｄ１〜ｄ５……各構成レンズの軸上厚みと軸上空気間
隔。FIG. 1 is a lens system configuration diagram of an example according to the present invention, FIG. 2 is a spherical aberration (a), an astigmatism (b), an f.theta. Characteristic (c) of Example 1, and FIG. 4 shows the spherical aberration (a), astigmatism (b), and fθ characteristic (c). FIG. 4 shows the spherical aberration (a), astigmatism (b), and fθ characteristic (c) of the third embodiment. L 1 ... First group lens, L 2 ... Second group lens, L 3 ... Third group lens, f ... Focal length of entire system, f 1 ... Focal length of concave meniscus lens of 1st group , R 1 to r 6 ... radius of curvature of each constituent lens, d 1 to d 5 ... axial thickness and axial air distance of each constituent lens.

Claims (1)

【特許請求の範囲】[Claims] 【請求項１】ビームの入射側から順に、第１群レンズ、
第２群レンズ及び第３群レンズの３つのレンズ群によっ
て構成されており、第１群レンズは入射側に凹面を向け
た凹メニスカスレンズで構成され、第２群レンズは同様
に入射側に凹面を向けた凸メニスカスレンズで構成さ
れ、第３群レンズは凸レンズによって構成されている３
群３枚構成のレンズ系であって、さらに以下の条件を満
たすことを特徴とする広角ｆθレンズ系。 （１） 0.6ｆ ＜｜ｆ１｜＜0.9ｆ （２） 0.2ｆ ＜｜ｒ１｜＜0.24ｆ （３） 0.06f ＜ｄ１＋ｄ２＜0.08ｆ 但し、ｆは全系の焦点距離、ｆ１は第１群の凹メニスカ
スレンズの焦点距離、ｒ１は同じく第１群の凹メニスカ
スレンズのビーム入射側の曲率半径、ｄ１は同じく第１
群の凹メニスカスレンズの軸上厚さ、ｄ２は第１群レン
ズと第２群レンズの軸上空気間隔を表わす。1. A first lens group, in order from the beam incident side,
It is composed of three lens groups, a second lens group and a third lens group, the first lens group is composed of a concave meniscus lens with the concave surface facing the incident side, and the second lens group is similarly concave on the incident side. Is a convex meniscus lens, and the third lens group is a convex lens.
A wide-angle fθ lens system having a three-lens-group configuration, further satisfying the following conditions. (1) 0.6f <| f 1 | <0.9f (2) 0.2f <| r 1 | <0.24f (3) 0.06f <d 1 + d 2 <0.08f where f is the focal length of the entire system, f 1 is the focal length of the concave meniscus lens of the first group, r 1 is the radius of curvature on the beam incident side of the concave meniscus lens of the first group, and d 1 is the first
The axial thickness of the concave meniscus lens of the group, d 2 represents the axial air distance between the first group lens and the second group lens.
JP4198686A 1986-02-28 1986-02-28 Wide-angle fθ lens system Expired - Lifetime JPH0646258B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP4198686A JPH0646258B2 (en) 1986-02-28 1986-02-28 Wide-angle fθ lens system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP4198686A JPH0646258B2 (en) 1986-02-28 1986-02-28 Wide-angle fθ lens system

Publications (2)

Publication Number Publication Date
JPS62200314A JPS62200314A (en) 1987-09-04
JPH0646258B2 true JPH0646258B2 (en) 1994-06-15

Family

ID=12623520

Family Applications (1)

Application Number Title Priority Date Filing Date
JP4198686A Expired - Lifetime JPH0646258B2 (en) 1986-02-28 1986-02-28 Wide-angle fθ lens system

Country Status (1)

Country Link
JP (1) JPH0646258B2 (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2673591B2 (en) * 1989-12-20 1997-11-05 キヤノン株式会社 fθ lens and laser scanning optical system using the same
CN100593742C (en) 2008-04-28 2010-03-10 深圳市大族激光科技股份有限公司 Optical lens
CN101324696B (en) 2008-04-28 2011-05-04 深圳市大族激光科技股份有限公司 Optical lens
CN101369047B (en) 2008-04-28 2010-12-08 深圳市大族激光科技股份有限公司 Optical lens
CN101414047B (en) 2008-04-28 2010-06-09 深圳市大族激光科技股份有限公司 Optical lens

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