JPH1184229A - Single focus lens - Google Patents

Single focus lens

Info

Publication number
JPH1184229A
JPH1184229A JP9252814A JP25281497A JPH1184229A JP H1184229 A JPH1184229 A JP H1184229A JP 9252814 A JP9252814 A JP 9252814A JP 25281497 A JP25281497 A JP 25281497A JP H1184229 A JPH1184229 A JP H1184229A
Authority
JP
Japan
Prior art keywords
lens
image
single focus
order
refractive power
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.)
Granted
Application number
JP9252814A
Other languages
Japanese (ja)
Other versions
JP3880147B2 (en
Inventor
Hiroki Yoshida
博樹 吉田
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.)
Canon Inc
Original Assignee
Canon Inc
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 Canon Inc filed Critical Canon Inc
Priority to JP25281497A priority Critical patent/JP3880147B2/en
Publication of JPH1184229A publication Critical patent/JPH1184229A/en
Application granted granted Critical
Publication of JP3880147B2 publication Critical patent/JP3880147B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related 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
    • G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B9/00—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or -
    • G02B9/34—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or - having four components only

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Lenses (AREA)

Abstract

PROBLEM TO BE SOLVED: To obtain a single focus lens small in size, reduced in the number of lenses, low in cost and excellent in performance while securing sufficient back focus by using a diffraction optical element. SOLUTION: This single focus lens is constituted of a front group I provided with a lens whose concave surface faces to an image surface side and having negative refractive power, a diaphragm S, and a rear group II having positive refractive power in order from an object side. The front group I is constituted of a meniscus lens L1 whose concave surface faces to the image surface side and which has negative refractive power and a positive lens L2 whose convex surface faces to the image surface side in order from the object side, and further the rear group II is constituted of a negative meniscus lens L3 whose concave surface faces to the image surface, and a biconvex lens L4 in order from the object side. An aspherical surface and a diffraction optical surface are applied to the image surface side lens surface of the lend L4 which is the surface of the rear group II on the nearest side to the image surface.

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【０００１】[0001]

【発明の属する技術分野】本発明は、ビデオカメラやデ
ジタルカメラ等に好適な全長の短い小型でローコストな
単焦点レンズに関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small, low-cost single focus lens having a short overall length and suitable for a video camera, a digital camera and the like.

【０００２】[0002]

【従来の技術】近年、ビデオカメラの発達と共にデジタ
ルカメラが種々開発されている。デジタルカメラでは撮
像素子の前方にローパスフィルタ、色フィルタ等の各種
のガラス材を配置する場合が多い。このため、デジタル
カメラは有効画面が比較的小さいにも拘わらず、バック
フォーカスを写真用の一眼レフカメラ等に比べて長くし
ておく必要がある。例えば、３５ｍｍフィルムの写真用
一眼レフカメラでは有効画面の対角長をＬとすると、バ
ックフォーカスは０．８Ｌ程度であるが、デジタルカメ
ラでは有効画面の対角長を１とすると、バックフォーカ
スは１．０１程度必要となる。また、一般にデジタルカ
メラはカメラ全体の小型化、ローコスト化のために、比
較的レンズ枚数の少ない小型で簡単な構成の撮影レンズ
が要求されている。2. Description of the Related Art In recent years, with the development of video cameras, various digital cameras have been developed. In a digital camera, various glass materials such as a low-pass filter and a color filter are often arranged in front of an image sensor. For this reason, although the effective screen of the digital camera is relatively small, the back focus needs to be longer than that of a single-lens reflex camera for photography or the like. For example, when the diagonal length of the effective screen is L in a 35 mm film photographic single-lens reflex camera, the back focus is about 0.8 L. In the digital camera, when the diagonal length of the effective screen is 1, the back focus is About 1.01 is required. In general, in order to reduce the size and cost of the entire camera, a digital camera is required to have a photographic lens having a relatively small number of lenses and a simple configuration.

【０００３】このため、デジタルカメラでは比較的バッ
クフォーカスを長くすることができ、しかも簡易な構成
のものとして、従来から物体側から負レンズ、正レン
ズ、負レンズ、正レンズ、正レンズの５枚で構成された
レトロフォーカス型レンズが種々提案されている。例え
ば、特公昭４６−２４１９４号公報では、バックフォー
カスが焦点距離の１．３倍程度で、Ｆナンバ３．５のも
のが開示されている。しかしながら、これでもバックフ
ォーカスは十分ではなく、Ｆナンバも３．５と暗くなっ
ている。[0003] For this reason, a digital camera can have a relatively long back focus and has a simple structure. Conventionally, there are five lenses of a negative lens, a positive lens, a negative lens, a positive lens, and a positive lens from the object side. Various types of retrofocus type lenses constituted by the above have been proposed. For example, Japanese Patent Publication No. 46-24194 discloses an apparatus having a back focus of about 1.3 times the focal length and an F number of 3.5. However, even in this case, the back focus is not sufficient, and the F number is also as dark as 3.5.

【０００４】また、バックフォーカスも長く、Ｆナンバ
も明るいものとしては、特開昭６１−２００５１９号公
報を挙げることができる。この公報では、バックフォー
カスが有効画面の２倍程度で、Ｆナンバが２．０のもの
を開示しているが、近年では撮像素子も発展しており、
バックフォーカスをここまで長くし、Ｆナンバを明るく
する必要がなくなっているため、レンズの小型化には適
していない。Japanese Patent Application Laid-Open No. Sho 61-200519 discloses a device having a long back focus and a bright F number. In this publication, the back focus is about twice as large as the effective screen, and the F number is 2.0.
Since it is no longer necessary to lengthen the back focus and brighten the F number, it is not suitable for downsizing the lens.

【０００５】また、特開平２−８５８１６号公報、特開
平３−６３６１３号公報では、バックフォーカスが焦点
距離より長く、Ｆナンバが１．４〜１．６程度のものが
開示されているが、バックフォーカスを長くし、Ｆナン
バを明るくするためにレンズが大型化し、更には歪曲が
大きくなって、デジタルカメラ用としては不満足な性能
である。Japanese Patent Application Laid-Open Nos. 2-85816 and 3-63613 disclose a device having a back focus longer than a focal length and an F number of about 1.4 to 1.6. In order to extend the back focus and brighten the F number, the size of the lens is increased, and further the distortion is increased, which is an unsatisfactory performance for a digital camera.

【０００６】一方、色収差の発生を抑制する方法とし
て、近年では回折光学素子を撮像光学系に応用する提案
がなされている。例えば、特開平４−２１３４２１号公
報、特開平６−３２４２６２号公報では、単レンズに回
折光学素子を応用することで色収差の低減を図っている
が、レンズ枚数の削減や小型化は十分には達成されてい
ない。On the other hand, as a method for suppressing the occurrence of chromatic aberration, in recent years, proposals have been made to apply a diffractive optical element to an imaging optical system. For example, in JP-A-4-213421 and JP-A-6-324262, chromatic aberration is reduced by applying a diffractive optical element to a single lens, but the reduction in the number of lenses and the miniaturization are not sufficient. Not achieved.

【０００７】[0007]

【発明が解決しようとする課題】本発明の目的は、回折
光学素子を用いることで、上記の従来例の欠点を改善
し、十分なバックフォーカスを確保しながら、小型でレ
ンズ枚数が少ないローコストで性能が良好な単焦点レン
ズを提供することにある。SUMMARY OF THE INVENTION It is an object of the present invention to improve the above-mentioned drawbacks of the prior art by using a diffractive optical element, to secure a sufficient back focus, to be small in size and to reduce the number of lenses at low cost. It is to provide a single focus lens having good performance.

【０００８】[0008]

【課題を解決するための手段】上述の目的を達成するた
めの本発明に係る単焦点レンズは、物体側から順に、像
面側に凹面を向けたレンズを有する負の屈折力を持つ前
群、正の屈折力を有する後群から構成した単焦点レンズ
において、光軸に対して回転対称な１枚の回折光学面を
有することを特徴とする。A single focus lens according to the present invention for achieving the above-mentioned object comprises, in order from the object side, a front group having a negative refractive power and a lens having a concave surface facing the image plane side. A single focus lens composed of a rear group having a positive refractive power is characterized by having one diffraction optical surface rotationally symmetric with respect to the optical axis.

【０００９】[0009]

【発明の実施の形態】本発明を図示の実施例に基づいて
詳細に説明する。図１は実施例１のレンズ断面図であ
る。物体側から順に、像面側に凹面を向けたレンズを有
する負の屈折力を持つ前群Ｉ、絞りＳ、正の屈折力を有
する後群IIにから構成した単焦点レンズであり、光軸に
対して回転対称な１枚の回折光学面を有している。DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the illustrated embodiment. FIG. 1 is a sectional view of a lens according to a first embodiment. A single focus lens composed of, in order from the object side, a front group I having a negative refractive power having a lens with a concave surface facing the image plane side, a stop S, and a rear group II having a positive refractive power. Has one diffraction optical surface that is rotationally symmetric with respect to.

【００１０】この実施例１においては、前群Ｉを物体側
から順に像面側に凹面を向けた負の屈折力を持つメニス
カスレンズＬ１、像面側に凸面を持つ正レンズＬ２から
構成し、更に後群IIを物体側から順に像面に凹面を向け
た負のメニスカスレンズＬ３、両凸レンズＬ４にから構
成している。In the first embodiment, the front unit I is composed of, in order from the object side, a meniscus lens L1 having a negative refractive power with a concave surface facing the image surface side, and a positive lens L2 having a convex surface on the image surface side. Further, the rear unit II includes, in order from the object side, a negative meniscus lens L3 having a concave surface facing the image surface, and a biconvex lens L4.

【００１１】上記のように構成することにより、前群Ｉ
と後群IIの間隔を短くし、全長が短く比較的広い範囲の
画角を持ち易い単焦点レンズとしている。特に、前群Ｉ
に対し上記の形状をレンズに与えることにより、歪曲収
差等の収差を軽減し易くしている。逆に、上記のような
形状を採らない場合は、特に軸外光線の影響を受け易い
収差を打ち消し合うことができなくなり、性能が劣化す
る。更に、後群IIを上記のように構成することにより、
焦点距離に対して比較的長いバックフォーカスを取り易
くし、ローパスフィルタ等の光学素子を挿入し易くして
いる。With the above configuration, the front group I
The distance between the lens and the rear group II is shortened, so that the total length is short and a single focus lens which is easy to have a relatively wide angle of view. In particular, the front group I
By giving the above shape to the lens, it is easy to reduce aberrations such as distortion. On the other hand, if the above shape is not adopted, it is not possible to cancel aberrations that are particularly susceptible to off-axis rays, and the performance is degraded. Further, by configuring the rear group II as described above,
It is easy to take a relatively long back focus with respect to the focal length, and to insert an optical element such as a low-pass filter.

【００１２】上記の形状をレンズに与えることにより、
後群II全体をコンパクトまとめながら球面収差やコマ収
差を減少することができる。仮に、このような形状を採
らない場合には、形状的により多くの場所を必要とする
ので小型化を阻害することになり兼ねない。By giving the above shape to the lens,
Spherical aberration and coma can be reduced while the entire rear group II is compactly arranged. If such a shape is not adopted, more space is required for the shape, which may hinder miniaturization.

【００１３】また、後群IIの最も像面側の凸レンズＬ４
の像面側レンズ面に非球面及び回折光学面を施してい
る。これらをこの位置に施すことにより、歪曲収差及び
色収差を軽減している。他の面で用いた場合には、軸上
光線の影響の大きい収差、軸外光線の影響を受け易い収
差を共に改善することが困難になる。Also, the convex lens L4 closest to the image plane in the rear group II
Has an aspherical surface and a diffractive optical surface on the image side lens surface. By applying them to this position, distortion and chromatic aberration are reduced. When used on other surfaces, it is difficult to improve both aberrations that are greatly affected by on-axis rays and aberrations that are easily affected by off-axis rays.

【００１４】本実施例では、像面側に凹面を向けたレン
ズを有する負の屈折力を持つ前群Ｉ、正の屈折力を有す
る後群IIで構成することにより、レンズ系全体の焦点距
離に対し、比較的長いバックフォーカスを取り易くし、
ローパスフイルタ等の光学素子を入れ易くしている。ま
た、像面側に凹面を向けたレンズを有することにより、
歪曲収差等の収差の補正を容易にしている。更に、本実
施例では後群IIの最も像面側のレンズ面に回折光学面を
設けている。もし、この回折光学面を設けなければ、本
実施例のような少ないレンズ構成においては、倍率色収
差を始めとする収差を軽減することが困難になってしま
う。In this embodiment, the front lens group I having a negative refractive power and the rear lens group II having a positive refractive power having a lens whose concave surface faces the image surface side are provided, so that the focal length of the entire lens system is increased. To make it easier to take a relatively long back focus,
An optical element such as a low-pass filter is easily inserted. Also, by having a lens with a concave surface facing the image side,
Correction of aberrations such as distortion is facilitated. Further, in this embodiment, a diffractive optical surface is provided on the lens surface closest to the image plane of the rear group II. If the diffractive optical surface is not provided, it is difficult to reduce aberrations such as chromatic aberration of magnification in a small lens configuration as in the present embodiment.

【００１５】なお、本実施例では回折光学面に非球面を
施している。非球面を施さないとき、本実施例のような
レンズ枚数の少ない光学系では歪曲収差等の収差補正が
容易ではなく、性能の劣化を招き易い。In this embodiment, the diffractive optical surface has an aspherical surface. When an aspherical surface is not provided, in an optical system having a small number of lenses as in the present embodiment, it is not easy to correct aberrations such as distortion and performance is likely to deteriorate.

【００１６】更に、前群Ｉと後群IIの間隔をｄ、レンズ
系全体の焦点距離をｆ、最も像面側のレンズの像面側レ
ンズ面から像面までの空気換算での長さをｂｆ、像面の
対角長をＩＳとしたとき、次の条件式を満足することが
好ましい。 ０．１＜ｄ／ｆ＜０．４ ・・・(1) ０．９＜ｂｆ／ＩＳ＜１．２ ・・・(2) Further, the distance between the front unit I and the rear unit II is d, the focal length of the entire lens system is f, and the length of the lens closest to the image plane from the image plane lens surface to the image plane is the air conversion length. When bf and the diagonal length of the image plane are IS, it is preferable to satisfy the following conditional expression. 0.1 <d / f <0.4 (1) 0.9 <bf / IS <1.2 (2)

【００１７】条件式(1) は前群Ｉ及び後群IIの適切な間
隔を与えるものであり、下限を超えて間隔を狭くする
と、第１レンズのパワーが強くなり収差補正が困難にな
る。更に、前群Ｉと後群IIの間に絞りをおくことが困難
になり、十分な射出瞳を得ることが困難になる。逆に、
上限を超えて間隔を広げると、第１レンズの外径が大型
化しレンズ全体が大型化し、更にバックフォーカスも短
くなり過ぎるという問題が発生する。Conditional expression (1) gives an appropriate distance between the front group I and the rear group II. If the distance is narrowed below the lower limit, the power of the first lens is increased and aberration correction becomes difficult. Further, it becomes difficult to place a stop between the front group I and the rear group II, and it becomes difficult to obtain a sufficient exit pupil. vice versa,
If the interval is increased beyond the upper limit, the outer diameter of the first lens becomes large, the entire lens becomes large, and the back focus becomes too short.

【００１８】条件式(2) はバックフォーカスに関する条
件式で、実施例のようなタイプのレンズは比較的広角の
レンズが多いため、レンズの焦点距離に対してバックフ
ォーカスが長いだけでは、十分なバックフォーカスが得
られていないため、像面の対角長に対するバックフォー
カスの比を採っている。この条件式(2) の上限を超えて
バックフォーカスが長くなると、全長が長くなり大型化
し第１レンズのパワーが強くなり、歪曲収差の補正が困
難になる。逆に、下限を超えてバックフォーカスが短く
なると、ローパスフイルタや、色フィルタを入れること
が困難になる。Conditional expression (2) is a conditional expression relating to the back focus. Since many lenses of the type described in the embodiment are relatively wide-angle lenses, it is not sufficient if the back focus is long only with respect to the focal length of the lens. Since the back focus is not obtained, the ratio of the back focus to the diagonal length of the image plane is used. If the back focus becomes longer than the upper limit of the conditional expression (2), the overall length becomes longer and larger, the power of the first lens becomes stronger, and it becomes difficult to correct distortion. Conversely, when the back focus is shorter than the lower limit, it becomes difficult to incorporate a low-pass filter or a color filter.

【００１９】更に、回折光学面を持つ群全体の焦点距離
をｆｂ、回折光学面を持つレンズの焦点距離をｆｄ、及
び回折光学面を持つレンズから回折光学面のみを取り除
いたときのこのレンズの焦点距離をｆｄ’とするとき、
次の条件式を満足することが好ましい。 ０＜ｆｂ（１／ｆｄ−１／ｆｄ’）＜１．２６×１０-1 ・・・(3) Further, the focal length of the entire lens group having the diffractive optical surface is fb, the focal length of the lens having the diffractive optical surface is fd, and the lens having the diffractive optical surface has only the diffractive optical surface removed. When the focal length is fd ′,
It is preferable that the following conditional expression is satisfied. 0 <fb (1 / fd−1 / fd ′) <1.26 × 10 −1 (3)

【００２０】条件式(3) は回折光学面のパワーに関する
のものであり、条件式(3) の上限を超えて回折光学面の
屈折力が強くなり過ぎると、回折光学素子での色消し効
果を大きくし過ぎて、２次スペクトルによる光学性能劣
化が大きくなる。Conditional expression (3) relates to the power of the diffractive optical surface. If the refractive power of the diffractive optical surface exceeds the upper limit of conditional expression (3) and the refractive power of the diffractive optical surface becomes too strong, the achromatizing effect of the diffractive optical element is obtained. Is too large, the optical performance degradation due to the secondary spectrum increases.

【００２１】逆に、条件式(3) の下限を超えて回折光学
面の屈折力が負になってしまうと、通常の屈折光学系と
発生する色収差が同じになってしまい、回折光学面によ
る色消し効果が得られず、光学系全域で十分な色収差の
補正が行えない。Conversely, if the lower limit of conditional expression (3) is exceeded and the refractive power of the diffractive optical surface becomes negative, the chromatic aberration generated by the ordinary refractive optical system becomes the same, and An achromatic effect cannot be obtained, and sufficient chromatic aberration cannot be corrected in the entire optical system.

【００２２】図２は実施例２のレンズ断面図である。前
群Ｉを物体側から順に像面側に凹面を向けた負の屈折力
を持つメニスカスレンズＬ５、像面側に凸面を持つ正レ
ンズＬ６にから構成し、更に後群IIを物体側から順に像
面側に凸面を持つ正レンズＬ７、像面に凹面を向けた負
のメニスカスレンズＬ８で構成している。FIG. 2 is a sectional view of a lens according to the second embodiment. The front unit I includes a meniscus lens L5 having a negative refractive power with a concave surface facing the image surface side in order from the object side, and a positive lens L6 having a convex surface on the image surface side, and the rear unit II is sequentially arranged from the object side. It comprises a positive lens L7 having a convex surface on the image surface side, and a negative meniscus lens L8 having a concave surface facing the image surface.

【００２３】前群Ｉを上記のように構成することによ
り、実施例１で述べたように前群Ｉと後群IIの間隔を短
くし、全長が短く比較的広い範囲の画角を持ち易い単焦
点レンズとしている。また、上記の形状をレンズに与え
ることにより歪曲収差等の収差を軽減し易くしている。By configuring the front group I as described above, the distance between the front group I and the rear group II is shortened as described in the first embodiment, the overall length is short, and it is easy to have a relatively wide range of angle of view. It is a single focus lens. Further, by giving the above-described shape to the lens, it is easy to reduce aberrations such as distortion.

【００２４】更に、後群IIを上記のように構成すること
により、前群Ｉと後群IIの間に間隔を取り易くし、絞り
Ｓをこの位置に入れ易くしている。絞りＳをこの位置に
入れられない場合には後群IIの後方に置くしかないが、
この場合にはローパスフィルタ等の光学素子を置く関係
上、より長いバックフォーカスを必要とし更に射出瞳位
置を像面に近付け過ぎるので好ましくない。また、上記
の形状をレンズに与えることにより、球面収差及びコマ
収差を軽減し易くしている。逆に、上記のような形状が
採れないとき、上記の収差を軽減するどころか悪化させ
てしまい、性能の劣化を招いてしまう。Further, by arranging the rear group II as described above, it is easy to provide an interval between the front group I and the rear group II, and to easily put the stop S in this position. If the aperture S cannot be set at this position, it must be placed behind the rear group II,
In this case, a longer back focus is required because an optical element such as a low-pass filter is placed, and the exit pupil position is too close to the image plane, which is not preferable. Further, by giving the above-described shape to the lens, it is easy to reduce spherical aberration and coma. Conversely, when the above-mentioned shape cannot be adopted, the above-mentioned aberrations are worsened rather than reduced, resulting in deterioration of performance.

【００２５】実施例２においては、実施例１と同様に最
も像面側のレンズＬ９の像面側レンズ面に非球面及び回
折光学面を施している。この位置にそれぞれの面を施す
ことにより、歪曲収差及び色収差を軽減している。In the second embodiment, similarly to the first embodiment, the aspherical surface and the diffractive optical surface are formed on the image-side lens surface of the lens L9 closest to the image surface. By providing each surface at this position, distortion and chromatic aberration are reduced.

【００２６】図３は実施例３のレンズ断面図である。前
群Ｉを物体側から順に像面側に凸面を持つ正レンズＬ
９、像面側に凹面を向けた負の屈折力を持つメニスカス
レンズＬ１０から構成し、更に後群IIを物体側から順に
像面側に凸面を持つ正レンズＬ１１、物体側に凹面を向
けた負のメニスカスレンズＬ１２で構成している。FIG. 3 is a sectional view of a lens according to the third embodiment. The front lens group I is a positive lens L having a convex surface on the image surface side in order from the object side.
9. Consisting of a meniscus lens L10 having a negative refractive power with the concave surface facing the image surface side, and the rear unit II is further provided with a positive lens L11 having a convex surface on the image surface side in order from the object side, and a concave surface facing the object side. It comprises a negative meniscus lens L12.

【００２７】前群Ｉを上記のように構成することによ
り、前群Ｉと後群IIの間隔を取り易くし、絞りをこの位
置に入れ易くしている。また、上記の形状をレンズに与
えることにより歪曲収差等の収差を軽減し易くしてい
る。逆に、上記のような形状を採らないとき、特に軸外
光線の影響を受け易い収差を打ち消し合うことができな
くなり、性能が劣化する。By configuring the front unit I as described above, the distance between the front unit I and the rear unit II can be easily set, and the stop can be easily set at this position. Further, by giving the above-described shape to the lens, it is easy to reduce aberrations such as distortion. Conversely, when the above shape is not adopted, aberrations that are particularly susceptible to off-axis rays cannot be canceled out, and the performance deteriorates.

【００２８】更に、後群IIを上記のように構成すること
により、更に前群Ｉと後群IIの間隔を取り易くし、絞り
をこの位置に入れ易くしている。また、上記の形状をレ
ンズに与えることにより、球面収差及びコマ収差ばかり
でなく前群Ｉで補正しきれなかった歪曲収差をも軽減し
易くしている。Further, by arranging the rear unit II as described above, the interval between the front unit I and the rear unit II can be further easily set, and the stop can be easily set at this position. Further, by giving the above-mentioned shape to the lens, it is easy to reduce not only spherical aberration and coma, but also distortion which cannot be corrected by the front unit I.

【００２９】逆に、上記のような形状が採れないとき、
上記の収差を軽減するどころか悪化させてしまい、性能
の劣化を招いてしまう。特に、負のメニスカスレンズを
像面に凹面を向けるように配置すると、前群Ｉで取りき
れなかった歪曲収差を更に悪化させてしまう。Conversely, when the above shape cannot be taken,
The above-mentioned aberrations are worsened rather than reduced, resulting in performance degradation. In particular, if the negative meniscus lens is arranged so that the concave surface faces the image plane, the distortion that cannot be completely eliminated by the front unit I will be further deteriorated.

【００３０】また実施例３においては、実施例１、２と
同様に最も像面側のレンズＬ１２の像面側レンズ面に非
球面及び回折光学面を施している。この位置にそれぞれ
の面を施すことにより、歪曲収差及び色収差を軽減して
いる。In the third embodiment, similarly to the first and second embodiments, the aspherical surface and the diffractive optical surface are provided on the image-side lens surface of the lens L12 closest to the image surface. By providing each surface at this position, distortion and chromatic aberration are reduced.

【００３１】図４は実施例４のレンズ断面図である。前
群Ｉを物体側から順に像面側に凹面を向けた負の屈折力
を持つ１枚のメニスカスレンズＬ１３のみで構成し、更
に後群IIを物体側から順に像面側に凸面を持つ正レンズ
Ｌ１４、物体側に凹面を向けた負のメニスカスレンズＬ
１５で構成している。FIG. 4 is a sectional view of a lens according to a fourth embodiment. The front unit I includes only one meniscus lens L13 having a negative refractive power with the concave surface facing the image surface side in order from the object side, and the rear unit II further includes a positive surface having a convex surface on the image surface side in order from the object side. Lens L14, negative meniscus lens L with concave surface facing object side
15.

【００３２】前群Ｉを上記のように構成することに、よ
り簡素でローコストな単焦点レンズが得られる。また、
上記の形状をレンズに与えることにより、歪曲収差等の
収差を発生し難くしている。逆に、上記のような形状を
採らないとき、特に軸外光線の影響を受け易い収差を発
生させ易くし性能が劣化する。By configuring the front unit I as described above, a simpler and lower cost single focus lens can be obtained. Also,
By giving the above-mentioned shape to the lens, it becomes difficult to generate aberrations such as distortion. Conversely, when the above shape is not adopted, aberrations that are particularly susceptible to off-axis light rays are likely to be generated, and performance is deteriorated.

【００３３】更に、後群IIを上記のように構成すること
により、前群Ｉと後群IIの間隔を取り易くし、絞りをこ
の位置に入れ易くしている。また、上記の形状をレンズ
に与えることにより、球面収差及びコマ収差ばかりでな
く、前群Ｉで補正しきれなかった歪曲収差をも軽減し易
くしている。Further, by configuring the rear unit II as described above, the interval between the front unit I and the rear unit II can be easily set, and the stop can be easily set at this position. Further, by giving the above-described shape to the lens, not only spherical aberration and coma aberration, but also distortion which cannot be completely corrected by the front unit I can be easily reduced.

【００３４】逆に、上記のような形状が取れないとき、
上記の収差を軽減するどころか悪化させてしまい、性能
の劣化を招いてしまう。特に、負のメニスカスレンズを
像面に凹面を向けるように配置すると、前群Ｉで取りき
れなかった歪曲収差を更に悪化させてしまう。Conversely, when the above shape cannot be obtained,
The above-mentioned aberrations are worsened rather than reduced, resulting in performance degradation. In particular, if the negative meniscus lens is arranged so that the concave surface faces the image plane, the distortion that cannot be completely eliminated by the front unit I will be further deteriorated.

【００３５】また、本実施例においては前群Ｉを構成す
る唯一のレンズＬ１３の像面側レンズ面に非球面を施す
と共に、実施例１、２、３と同様に、最も像面側のレン
ズ１５の像面側レンズ面に非球面及び回折光学面を施し
ている。この位置にこれらの面を施すことにより、歪曲
収差及び色収差を軽減している。In the present embodiment, the aspherical surface is applied to the image-side lens surface of the only lens L13 constituting the front unit I, and the lens closest to the image-side as in the first, second and third embodiments. An aspherical surface and a diffractive optical surface are provided on the 15 image-side lens surfaces. By providing these surfaces at this position, distortion and chromatic aberration are reduced.

【００３６】仮に、非球面を１面のみとするならば、球
面収差及びコマ収差又は像面湾曲及び歪曲収差の何れか
の収差を補正しきれなくなり、満足な性能を持つレンズ
を構成できない。また、この収差補正に回折光学素子を
積極的に用いれば、そのときは色収差が悪化してしま
う。If there is only one aspherical surface, any one of spherical aberration and coma or curvature of field and distortion cannot be corrected, and a lens having satisfactory performance cannot be constructed. Also, if a diffractive optical element is positively used for this aberration correction, then the chromatic aberration will deteriorate.

【００３７】図５は実施例５のレンズ断面図である。前
群Ｉを像面側に凹面を向けた負の屈折力を持つ１枚のメ
ニスカスレンズＬ１６のみで構成し、更に後群IIを像面
側に凸面を持つ１枚の正レンズＬ１７のみで構成してい
る。FIG. 5 is a lens sectional view of the fifth embodiment. The front unit I includes only one meniscus lens L16 having a negative refractive power with the concave surface facing the image surface side, and the rear unit II includes only one positive lens L17 having a convex surface on the image surface side. doing.

【００３８】前群Ｉを上記のように構成することによ
り、簡素でローコストな単焦点レンズが得られる。ま
た、上記の形状をレンズに与えることにより、歪曲収差
等の収差を発生し難くしている。逆に、上記のような形
状をとらないとき、特に軸外光線の影響を受け易い収差
を発生させ易くし、性能が劣化する。By configuring the front unit I as described above, a simple and low-cost single focus lens can be obtained. In addition, by giving the above-mentioned shape to the lens, it is made difficult to generate aberrations such as distortion. Conversely, when the above-mentioned shape is not taken, aberrations that are particularly susceptible to off-axis rays are apt to occur, and performance is deteriorated.

【００３９】更に、後群IIを上記のように構成すること
により、更に簡素でローコストな単焦点レンズを構成し
ている。また、上記の形状をレンズに与えることによ
り、球面収差及びコマ収差ばかりでなく、前群Ｉで補正
しきれなかった歪曲収差をも軽減し易くしている。Further, by configuring the rear group II as described above, a simpler and lower cost single focus lens is configured. Further, by giving the above-described shape to the lens, not only spherical aberration and coma aberration, but also distortion which cannot be completely corrected by the front unit I can be easily reduced.

【００４０】逆に、上記のような形状が採れないとき、
上記の収差を軽減するどころか悪化させてしまい、性能
の劣化を招いてしまう。特に、負のメニスカスレンズを
像面に凹面を向けるように配置すると、前群Ｉで取りき
れなかった歪曲収差を更に悪化させてしまう。Conversely, when the above shape cannot be taken,
The above-mentioned aberrations are worsened rather than reduced, resulting in performance degradation. In particular, if the negative meniscus lens is arranged so that the concave surface faces the image plane, the distortion that cannot be completely eliminated by the front unit I will be further deteriorated.

【００４１】また、実施例５においては、実施例４と同
様に前群Ｉを構成する唯一のレンズＬ１６の像面側レン
ズ面に非球面を施し、後群IIを構成する唯一のレンズＬ
１７の像面側レンズ面に非球面及び回折光学面を施して
いる。これらの位置に、それぞれの面を施すことによ
り、歪曲収差及び色収差を軽減している。In the fifth embodiment, as in the fourth embodiment, the aspheric surface is formed on the image-side lens surface of the sole lens L16 constituting the front unit I, and the only lens L constituting the rear unit II is formed.
An aspherical surface and a diffractive optical surface are provided on the image-side lens surface 17. By applying respective surfaces to these positions, distortion and chromatic aberration are reduced.

【００４２】仮に、非球面を１面のみとすれば、球面収
差及びコマ収差又は像面湾曲及び後面歪曲の何れかの収
差を補正しきれなくなり、満足な性能を持つレンズを構
成できない。また、この収差補正に回折光学素子を積極
的に用いれば、そのときは色収差が悪化してしまう。If there is only one aspherical surface, it is impossible to correct any of spherical aberration and coma or curvature of field and back surface distortion, and a lens having satisfactory performance cannot be constructed. Also, if a diffractive optical element is positively used for this aberration correction, then the chromatic aberration will deteriorate.

【００４３】また、実施例４、５のように前群Ｉを１枚
のレンズのみとし、更に後群IIを１枚又は２枚のレンズ
で構成しているものは、前群Ｉ及び後群IIにそれぞれ１
面以上の非球面を持つようにしている。Further, as in the fourth and fifth embodiments, the front group I includes only one lens, and the rear group II includes one or two lenses. 1 for each II
It has more aspherical surface than surface.

【００４４】上述の実施例における非球面形状は、光軸
方向にＸ軸、光軸と垂直方向にＨ軸、光の進行方向を正
とし、Ｒを近軸曲率半径、Ｂ、Ｃ、Ｄ、Ｅ、Ｆをそれぞ
れ非球面係数としたとき、 Ｘ＝（Ｈ2 ／Ｒ）／［１＋｛１＋（１＋Ｋ)(Ｈ／Ｒ)2}
1/2］＋ＢＨ4 ＋ＣＨ6＋ＤＨ8 ＋ＥＨ10＋ＦＨ12 なる式で表している。The aspherical shape in the above embodiment has an X-axis in the optical axis direction, an H-axis in a direction perpendicular to the optical axis, a positive traveling direction of light, and R is a paraxial radius of curvature, B, C, D, When E and F are each an aspheric coefficient, X = (H 2 / R) / [1+ {1+ (1 + K) (H / R) 2 }
1/2 ] + BH 4 + CH 6 + DH 8 + EH 10 + FH 12

【００４５】回折光学面は、位相をφ（ｈ）とし、λを
基準波長（ｄ線）、ｈを光軸からの距離とすると、次式
で表している。 φ（ｈ）＝（２π／λ）（C2・ｈ2 ＋C4・ｈ4 ＋・・・
・＋C2・i・ｈ2・i ）The phase of the diffractive optical surface is represented by the following equation, where the phase is φ (h), λ is the reference wavelength (d-line), and h is the distance from the optical axis. φ (h) = (2π / λ) (C 2 · h 2 + C 4 · h 4 + ...
・ ＋ C 2 ・ i・ h 2 ・ i )

【００４６】次に、実施例１〜５の数値実施例１〜５を
示す。なお、これらの数値実施例において、riは物体側
から順に第ｉ番目の曲率半径、diは第ｉ番目のレンズ厚
又は空気間隔、niとνi はそれぞれ第ｉ番目のレンズの
ガラス屈折率とアッべ数である。また、数値実施例にお
ける最も像面側の屈折力を持たない２面は、光学フィル
タ、フェースプレート等を表している。Next, Numerical Embodiments 1 to 5 of Embodiments 1 to 5 will be described. In these numerical examples, ri is the i-th radius of curvature in order from the object side, di is the i-th lens thickness or air space, and ni and νi are the glass refractive index of the i-th lens and It is a power. The two surfaces having no refractive power closest to the image plane in the numerical examples represent an optical filter, a face plate, and the like.

【００４７】 数値実施例１ ｆ=4.00000 fno=1:2.45 2ω= 61.9° r1 = 46.511 d1 = 0.70 n1=1.58313 ν1=59.4 r2 = 3.130 d2 = 1.00 r3 =-26.961 d3 = 1.55 n2=1.88300 ν2=40.8 r4 = -5.947 d4 = 1.90 r5 = 0.000(絞り) d5 = 2.82 r6 = 8.758 d6 = 0.60 n3=1.84666 ν3=23.8 r7 = 5.075 d7 = 0.20 r8 = 8.611 d8 = 1.65 n4=1.77250 ν4=49.6 r9 = -5.044 d9 = 0.50 r10= 0.000 d10= 2.55 n5=1.51633 ν5=64.1 r11= 0.000 非球面係数 r9 K=4.90853・10-1 B=9.34489・10-4 C=-3.97099・10-4 D=8.92849・10-5 位相係数 r9 C2=-7.91012・10-3 C3=0.00000・100 C4=5.67665・10-4 C5=0.00000・100 C6=2.68744・10-4 C7=0.00000・100 C8=-6.63884・10-5 Numerical Example 1 f = 4.00000 fno = 1: 2.45 2ω = 61.9 ° r1 = 46.511 d1 = 0.70 n1 = 1.58313 ν1 = 59.4 r2 = 3.130 d2 = 1.00 r3 = -26.961 d3 = 1.55 n2 = 1.88300 ν2 = 40.8 r4 = -5.947 d4 = 1.90 r5 = 0.000 (aperture) d5 = 2.82 r6 = 8.758 d6 = 0.60 n3 = 1.84666 ν3 = 23.8 r7 = 5.075 d7 = 0.20 r8 = 8.611 d8 = 1.65 n4 = 1.77250 ν4 = 49.6 r9 = -5.044 d9 = 0.50 r10 = 0.000 d10 = 2.55 n5 = 1.51633 ν5 = 64.1 r11 = 0.000 aspheric coefficients r9 K = 4.90853 · 10 -1 B = 9.34489 · 10 -4 C = -3.97099 · 10 -4 D = 8.92849 · 10 - 5 Phase coefficient r9 C 2 = -7.91012 ・ 10 -3 C 3 = 0.00000 ・ 10 0 C 4 = 5.67665 ・ 10 -4 C 5 = 0.00000 ・ 10 0 C 6 = 2.68744 ・ 10 -4 C 7 = 0.00000 ・ 10 0 C 8 = -6.63884 ・ 10 -5

【００４８】 数値実施例２ ｆ=4.56737 fno=1:2.73 2ω= 55.4° r1 = 6.419 d1 = 0.70 n1=1.77250 ν1=49.6 r2 = 2.655 d2 = 1.10 r3 = -9.077 d3 = 1.00 n2=1.84666 ν2=23.8 r4 = -5.463 d4 = 1.06 r5 = 0.000(絞り) d5 = 2.99 r6 = 52.707 d6 = 2.10 n3=1.83400 ν3=37.2 r7 = -5.074 d7 = 0.11 r8 = 35.173 d8 = 0.70 n4=1.84666 ν4=23.8 r9 = 17.619 d9 = 2.53 r10= 0.000 d10= 4.60 n5=1.51633 ν5=64.2 r11= 0.000 非球面係数 r9 K=-1.01248・100 B=3.93281・10-3 C=-1.19865・10-3 D=2.43266・10-4 位相係数 r9 C1=0.00000・100 C2=-1.14544・10-2 C3=0.00000・100 C4=-2.02726・10-3 C5=0.00000・100 C6=1.11759・10-3 C7=0.00000・100 C8=-2.14339・10-4 Numerical Example 2 f = 4.56737 fno = 1: 2.73 2ω = 55.4 ° r1 = 6.419 d1 = 0.70 n1 = 1.77250 ν1 = 49.6 r2 = 2.655 d2 = 1.10 r3 = -9.077 d3 = 1.00 n2 = 1.84666 ν2 = 23.8 r4 = -5.463 d4 = 1.06 r5 = 0.000 (aperture) d5 = 2.99 r6 = 52.707 d6 = 2.10 n3 = 1.83400 ν3 = 37.2 r7 = -5.074 d7 = 0.11 r8 = 35.173 d8 = 0.70 n4 = 1.84666 ν4 = 23.8 r9 = 17.619 d9 = 2.53 r10 = 0.000 d10 = 4.60 n5 = 1.51633 ν5 = 64.2 r11 = 0.000 aspheric coefficients r9 K = -1.01248 · 10 0 B = 3.93281 · 10 -3 C = -1.19865 · 10 -3 D = 2.43266 · 10 - 4 phase coefficient r9 C 1 = 0.00000 · 10 0 C 2 = -1.14544 · 10 -2 C 3 = 0.00000 · 10 0 C 4 = -2.02726 · 10 -3 C 5 = 0.00000 · 10 0 C 6 = 1.11759 · 10 - 3 C 7 = 0.00000 ・ 10 0 C 8 = -2.143339 ・ 10 -4

【００４９】 数値実施例３ ｆ=5.02531 fno=1:2.85 ° 2ω= 51.1° r1 =-41.917 d1 = 0.50 n1=1.80518 ν1=25.4 r2 =-26.899 d2 = 0.07 r3 = 4.959 d3 = 0.47 n2=1.80400 ν2=46.6 r4 = 2.136 d4 = 1.40 r5 = 0.000(絞り) d5 = 1.28 r6 = 9.483 d6 = 1.59 n3=1.60311 ν3=60.6 r7 = -4.166 d7 = 3.10 r8 = -3.154 d8 = 0.70 n4=1.84666 ν4=23.8 r9 = -2.975 d9 = 1.00 r10= 0.000 d10= 3.00 n5=1.51633 ν5=64.2 r11= 0.000 非球面係数 r9 K=-8.46236・10-1 B=-1.12751・10-3 C=-1.10284・10-4 D=5.97550・10-6 位相係数 r9 C1=0.00000・100 C2=-1.25633・10-2 C3=0.00000・100 C4=1.27024・10-4 C5=0.00000・100 C6=6.44072・10-5 C7=0.00000・100 C8=-9.04684・10-6 Numerical Example 3 f = 5.02531 fno = 1: 2.85 ° 2ω = 51.1 ° r1 = -41.917 d1 = 0.50 n1 = 1.80518 ν1 = 25.4 r2 = -26.899 d2 = 0.07 r3 = 4.959 d3 = 1.80400 ν2 = 46.6 r4 = 2.136 d4 = 1.40 r5 = 0.000 (aperture) d5 = 1.28 r6 = 9.483 d6 = 1.59 n3 = 1.60311 ν3 = 60.6 r7 = -4.166 d7 = 3.10 r8 = -3.154 d8 = 0.70 n4 = 1.84666 ν4 = 23.8 r9 = -2.975 d9 = 1.00 r10 = 0.000 d10 = 3.00 n5 = 1.51633 ν5 = 64.2 r11 = 0.000 Aspherical coefficient r9 K = -8.46236 ・ 10 -1 B = -1.12751 ・ 10 -3 C = -1.10284 ・ 10 -4 D = 5.97550 ・ 10 -6 Phase coefficient r9 C 1 = 0.00000 ・ 10 0 C 2 = -1.25633 ・ 10 -2 C 3 = 0.00000 ・ 10 0 C 4 = 1.27024 ・ 10 -4 C 5 = 0.00000 ・ 10 0 C 6 = 6.44072 ・ 10 -5 C 7 = 0.00000 ・ 10 0 C 8 = -9.04684 ・ 10 -6

【００５０】 数値実施例４ ｆ=4.53000 fno=1:2.85 2ω= 55.8° r1 = 2.984 d1 = 0.50 n1=1.80400 ν1=46.6 r2 = 1.661 d2 = 1.44 r3 = 0.000(絞り) d3 = 1.34 r4 = 17.961 d4 = 1.59 n2=1.60311 ν2=60.6 r5 = -3.649 d5 = 3.10 r6 = -5.535 d6 = 0.70 n3=1.77250 ν3=49.6 r7 = -3.808 d7 = 1.00 r8 = 0.000 d8 = 3.00 n4=1.51633 ν4=64.2 r9 = 0.000 非球面係数 r2 K=-7.44163・10-1 B=2.00286・10-2 C=-5.31522・10-3 D=5.61153・10-3 r7 K=-1.07182・100 B=1.02783・10-3 C=1.11587・10-4 D=-1.48742・10-6 位相係数 r7 C1=0.00000・100 C2=-7.93341・10-3 C3=0.00000・100 C4=-3.87338・10-4 C5=0.00000・100 C6=0.00000・100 C7=0.00000・100 C8=0.00000・100 Numerical Example 4 f = 4.53000 fno = 1: 2.85 2ω = 55.8 ° r1 = 2.984 d1 = 0.50 n1 = 1.80400 ν1 = 46.6 r2 = 1.661 d2 = 1.44 r3 = 0.000 (aperture) d3 = 1.34 r4 = 17.961 d4 = 1.59 n2 = 1.60311 ν2 = 60.6 r5 = -3.649 d5 = 3.10 r6 = -5.535 d6 = 0.70 n3 = 1.77250 ν3 = 49.6 r7 = -3.808 d7 = 1.00 r8 = 0.000 d8 = 3.00 n4 = 1.51633 ν4 = 64.2 r9 = 0.000 Aspheric coefficient r2 K = -7.44163 ・ 10 -1 B = 2.00286 ・ 10 -2 C = -5.31522 ・ 10 -3 D = 5.61153 ・ 10 -3 r7 K = -1.07182 ・ 10 0 B = 1.02783 ・ 10 -3 C = 1.11587 ・ 10 -4 D = -1.48742 ・ 10 -6 Phase coefficient r7 C 1 = 0.00000 ・ 10 0 C 2 = -7.93341 ・ 10 -3 C 3 = 0.00000 ・ 10 0 C 4 = -3.87338 ・ 10 -4 C 5 = 0.00000 ・ 10 0 C 6 = 0.00000 ・ 10 0 C 7 = 0.00000 ・ 10 0 C 8 = 0.00000 ・ 10 0

【００５１】 数値実施例５ ｆ=4.53000 fno=1: 2ω= r1 = 1.807 d1 = 0.50 n1=1.80400 ν1=46.6 r2 = 1.290 d2 = 1.58 r3 = 0.000(絞り) d3= 2.30 r4 =210.310 d4 = 1.90 n2=1.69680 ν2=55.5 r5 = -3.263 d5 = 1.00 r6 = 0.000 d6 = 3.00 n3=1.51633 ν3=64.2 r7 = 0.000 非球面係数 r2 K=-1.09741・100 B=5.67534・10-2 C=7.65008・10-3 D=1.26811・10-2 r5 K=-3.63909・10-1 B=2.36064・10-3 C=-6.73486・10-5 D=1.41196・10-5 位相係数 r5 C1=0.00000・100 C2=-8.51771・10-3 C3=0.00000・100 C4=-3.21155・10-5 C5=0.00000・100 C6=0.00000・100 Ｃ７＝０．０００００・１００ Ｃ８＝−６．６３８８
４・１００Numerical Example 5 f = 4.53000 fno = 1: 2ω = r1 = 1.807 d1 = 0.50 n1 = 1.80400 ν1 = 46.6 r2 = 1.290 d2 = 1.58 r3 = 0.000 (aperture) d3 = 2.30 r4 = 210.310 d4 = 1.90 n2 = 1.69680 ν2 = 55.5 r5 = -3.263 d5 = 1.00 r6 = 0.000 d6 = 3.00 n3 = 1.51633 ν3 = 64.2 r7 = 0.000 Aspherical coefficient r2 K = -1.09741 ・ 10 0 B = 5.67534 ・ 10 -2 C = 7.65008 ・ 10 -3 D = 1.26811 ・ 10 -2 r5 K = -3.63909 ・ 10 -1 B = 2.36064 ・ 10 -3 C = -6.73486 ・ 10 -5 D = 1.41196 ・ 10 -5 Phase coefficient r5 C 1 = 0.00000 ・ 10 0 C 2 = -8.51771 · 10 -3 C 3 = 0.00000 · 10 0 C 4 = −3.21155 · 10 -5 C 5 = 0.00000 · 10 0 C 6 = 0.00000 · 10 0 C 7 = 0.000000 · 10 0 C 8 = -6.6388
4.100

【００５２】また、前述の各条件式と数値実施例におけ
る諸数値の関係を次表に示す。 実施例１ 実施例２ 実施例３ 実施例４ 実施例５ 条件式(1) 1.180 0.886 0.533 0.704 0.875 条件式(2) 1.132 1.387 1.275 1.110 1.301 条件式(3) 7.8・10-2 12.7・10-2 13.9・10-2 8.0・10-2 7.3・10-2 The following table shows the relationship between the above-mentioned conditional expressions and various numerical values in the numerical examples. Example 1 Example 2 Example 3 Example 4 Example 5 Conditional expression (1) 1.180 0.886 0.533 0.704 0.875 Conditional expression (2) 1.132 1.387 1.275 1.110 1.301 Conditional expression (3) 7.8 · 10 -2 12.7 · 10 -2 13.9 ・ 10 -2 8.0 ・ 10 -2 7.3 ・ 10 -2

【００５３】図６〜図１０はそれぞれ実施例１〜５の物
体距離が無限遠のときの収差図である。FIGS. 6 to 10 are aberration diagrams of the first to fifth embodiments when the object distance is infinity.

【００５４】回折光学素子はホログラフィック光学素子
の製作手法で製作するのが一般的であるが、リソグラフ
ィック手法で２値的に製作した光学素子であるバイナリ
オプティクで製作してもよい。また、これらの方法で作
成した型によって成型によって製造してもよい。更に、
光学面にプラスチック等の膜を回折光学面として添付す
る方法、所謂レブリカ非球面により作成することもでき
る。The diffractive optical element is generally manufactured by a holographic optical element manufacturing method, but may be manufactured by a binary optic which is an optical element binary-manufactured by a lithographic method. Also, the mold may be manufactured by molding using a mold created by these methods. Furthermore,
A method of attaching a film of plastic or the like to the optical surface as a diffractive optical surface, that is, a so-called REBRICA aspherical surface can be used.

【００５５】前述の実施例における回折光学素子の回折
格子形状は、図１１に示すキノフォーム形状をしてい
る。この回折格子は基材１の表面に紫外線硬化樹脂を塗
布し、この樹脂部２に波長５３０ｎｍで１次回折効率が
１００％となるような格子厚ｄの回折格子３を形成して
いる。図１２はこの回折光学素子の１次回折効率の波長
依存特性を示し、設計次数での回折効率は最適化した波
長５３０ｎｍから離れるに従って低下し、一方で設計次
数近傍の次数０次、２次回折光が増大している。この設
計次数以外の回折光の増加はフレアとなり、光学系の解
像度の低下につながる。The diffraction grating of the diffractive optical element in the above-described embodiment has a kinoform shape shown in FIG. In this diffraction grating, an ultraviolet curable resin is applied to the surface of a substrate 1 and a diffraction grating 3 having a grating thickness d such that the primary diffraction efficiency becomes 100% at a wavelength of 530 nm at the resin portion 2. FIG. 12 shows the wavelength dependence of the first-order diffraction efficiency of this diffractive optical element. The diffraction efficiency in the design order decreases as the distance from the optimized wavelength of 530 nm increases, while the 0th-order and second-order diffracted light in the vicinity of the design order are reduced. Is increasing. This increase in diffracted light other than the design order causes a flare, which leads to a decrease in the resolution of the optical system.

【００５６】図１３は実施例１において回析光学面に図
１１の格子形状を採用したときの空間周波数に対するＭ
ＴＦ（Modulation transfer function）特性を示し、低
周波数領域のＭＴＦが所望の値より低下していることが
分かる。FIG. 13 shows the relationship between the spatial frequency and the M when the grating shape shown in FIG.
It shows a TF (Modulation transfer function) characteristic, and it can be seen that the MTF in the low frequency region is lower than a desired value.

【００５７】そこで、図１４に示す積層型の回折格子に
より格子形状と形成することが考えられる。基材１上に
紫外線硬化樹脂（ｎｄ＝１．４９９、νｄ＝５４）から
成る第１の回折格子４を形成し、その上に別の紫外線硬
化樹脂（ｎｄ＝ｌ．５９８、νｄ＝２８）から成る第２
の回折格子５を形成している。この材質の組み合わせで
は、第１の回折格子４の格子はｄｌはｄｌ＝１８．８μ
ｍ、第２の回折格子５の格子はｄ２はｄ＝１０．５μｍ
としている。Therefore, it is conceivable to form a lattice shape by using a laminated diffraction grating shown in FIG. A first diffraction grating 4 made of an ultraviolet curable resin (nd = 1.499, νd = 54) is formed on the substrate 1, and another ultraviolet curable resin (nd = 1.598, νd = 28) is formed thereon. The second consisting of
Are formed. With this combination of materials, the grating of the first diffraction grating 4 is dl = dl = 18.8 μm.
m, the grating of the second diffraction grating 5 is d2, d = 10.5 μm
And

【００５８】図１５はこの構成の回折光学素子の１次回
折効率の波長依存特性であり、この図１５から分かるよ
うに積層構造の回折格子にすることで、設計次数の回折
効率は、使用波長城全域で９５％以上の高い回折効率を
有している。図１６はこの場合の同じ実施例１における
空間周波数に対するＭＴＦ特性を示し、積層構造の回折
格子を用いることで、低周波数のＭＴＦは改善され、所
望のＭＴＦ特性が得られている。このように、本発明の
実施例の回折光学素子として積層構造の回折格子を用い
ることで、光学性能は更に改善される。FIG. 15 shows the wavelength dependence of the first-order diffraction efficiency of the diffractive optical element having this configuration. As can be seen from FIG. 15, the diffraction efficiency of the design order can be reduced by using a diffraction grating having a laminated structure. It has a high diffraction efficiency of 95% or more throughout the castle. FIG. 16 shows the MTF characteristic with respect to the spatial frequency in the same first embodiment in this case. By using the diffraction grating having the laminated structure, the MTF at a low frequency is improved, and a desired MTF characteristic is obtained. As described above, by using a diffraction grating having a laminated structure as the diffractive optical element of the embodiment of the present invention, the optical performance is further improved.

【００５９】なお、前述の積層構造の回折光学素子とし
て、材質を紫外線硬化樹脂に限定するものではなく、他
のプラスチック材なども使用できるし、基材によっては
第１の回折格子４を直接基材１に形成してもよい。ま
た、各格子の厚さが異なる必要はなく、材料の組み合わ
せによっては図１７に示すように２つの格子の厚みを等
しくできる。この場合には、回折光学素子の表面に格子
形状が形成されないので、防塵性に優れ、回折光学素子
の組み立て作業性が向上し、より安価な光学系が得られ
る。The material of the above-mentioned diffractive optical element having a laminated structure is not limited to an ultraviolet-curable resin, but other plastic materials or the like may be used. It may be formed on the material 1. Further, the thicknesses of the respective gratings do not need to be different, and depending on the combination of materials, the thicknesses of the two gratings can be made equal as shown in FIG. In this case, since the lattice shape is not formed on the surface of the diffractive optical element, it is excellent in dust resistance, the workability of assembling the diffractive optical element is improved, and a more inexpensive optical system can be obtained.

【００６０】[0060]

【発明の効果】以上説明したように本発明に係る単焦点
レンズは、本発明の如く構成をとることにより、デジタ
ルカメラに好適なバックフォーカスの長い、小型でロー
コストで良好な性能を達成することができる。As described above, the single focus lens according to the present invention achieves good performance at low cost with a long back focus, small size and low cost suitable for a digital camera by adopting the configuration as in the present invention. Can be.

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

【図１】実施例１のレンズ断面図である。FIG. 1 is a sectional view of a lens according to a first embodiment.

【図２】実施例２のレンズ断面図である。FIG. 2 is a sectional view of a lens according to a second embodiment.

【図３】実施例３のレンズ断面図である。FIG. 3 is a sectional view of a lens according to a third embodiment.

【図４】実施例４のレンズ断面図である。FIG. 4 is a sectional view of a lens according to a fourth embodiment.

【図５】実施例５のレンズ断面図である。FIG. 5 is a sectional view of a lens according to a fifth embodiment.

【図６】実施例１の物体距離が無限遠の時の収差図であ
る。FIG. 6 is an aberration diagram for the first embodiment when the object distance is infinity.

【図７】実施例２の物体距離が無限遠の時の収差図であ
る。FIG. 7 is an aberration diagram for Example 2 when the object distance is infinity.

【図８】実施例３の物体距離が無限遠の時の収差図であ
る。FIG. 8 is an aberration diagram for Example 3 when the object distance is infinity.

【図９】実施例４の物体距離が無限遠の時の収差図であ
る。FIG. 9 is an aberration diagram for Example 4 when the object distance is infinity.

【図１０】実施例５の物体距離が無限遠の時の収差図で
ある。FIG. 10 is an aberration diagram for Example 5 when the object distance is infinity.

【図１１】回折光学素子の断面図である。FIG. 11 is a sectional view of a diffractive optical element.

【図１２】波長依存特性のグラフ図である。FIG. 12 is a graph showing wavelength dependence characteristics.

【図１３】ＭＴＦ特性のグラフ図である。FIG. 13 is a graph showing MTF characteristics.

【図１４】積層構造の回折光学素子の断面図である。FIG. 14 is a sectional view of a diffractive optical element having a laminated structure.

【図１５】波長依存特性のグラフ図である。FIG. 15 is a graph showing wavelength dependence characteristics.

【図１６】ＭＴＦ特性のグラフ図である。FIG. 16 is a graph showing MTF characteristics.

【図１７】他の積層構造の回折光学素子の断面図であ
る。FIG. 17 is a sectional view of a diffractive optical element having another laminated structure.

【符号の説明】[Explanation of symbols]

Ｉ 前群 II 後群 ｄ ｄ線 ｇ ｇ線 ΔＭ メリディオナル像面 ΔＳ サジタル像面 I Front group II Rear group d d-line g g-line ΔM Meridional image plane ΔS Sagittal image plane

Claims (11)

【特許請求の範囲】[Claims] 【請求項１】 物体側から順に、像面側に凹面を向けた
レンズを有する負の屈折力を持つ前群、正の屈折力を有
する後群から構成した単焦点レンズにおいて、光軸に対
して回転対称な１枚の回折光学面を有することを特徴と
する単焦点レンズ。1. A single focus lens comprising, in order from an object side, a front group having a negative refractive power and a rear group having a positive refractive power and having a lens whose concave surface faces the image plane side, A single focal length lens having a single rotationally symmetric diffractive optical surface. 【請求項２】 前記前群と後群の間隔をｄ、レンズ系全
体の焦点距離をｆ、最も像面側のレンズの像面側の面か
ら像面までの空気換算長をｂｆ、像面の対角長をＩＳと
したとき、 ０．４＜ｄ／ｆ＜１．３ １．０＜ｂｆ／ＩＳ＜１．５ なる条件を満足する請求項１に記載の単焦点レンズ。2. The distance between the front group and the rear group is d, the focal length of the entire lens system is f, the air-converted length from the image plane side of the lens closest to the image plane to the image plane is bf, and the image plane is The single focus lens according to claim 1, wherein a condition that 0.4 <d / f <1.3 1.0 <bf / IS <1.5 is satisfied when a diagonal length of IS is IS. 【請求項３】 少なくとも１面以上の非球面を有する請
求項１又は２に記載の単焦点レンズ。3. The single focus lens according to claim 1, wherein the single focus lens has at least one aspheric surface. 【請求項４】 前記前群は物体側から順に像面側に凹面
を向けた負の屈折力を持つメニスカスレンズ、像面側に
凸面を持つ正レンズから構成し、前記後群は物体側から
順に像面に凹面を向けた負のメニスカスレンズ、両凸レ
ンズから構成した請求項１〜３の何れか１つの請求項に
記載の１つの請求項に記載の単焦点レンズ。4. The front unit includes, in order from the object side, a meniscus lens having a negative refractive power with a concave surface facing the image surface side, and a positive lens having a convex surface on the image surface side, and the rear unit includes, from the object side, The single focus lens according to any one of claims 1 to 3, comprising a negative meniscus lens having a concave surface facing the image surface in order, and a biconvex lens. 【請求項５】 前記前群は物体側から順に像面側に凹面
を向けた負の屈折力を持つメニスカスレンズ、像面側に
凸面を持つ正レンズから構成し、前記後群は物体側から
順に像面側に凸面を持つ正レンズ、像面に凹面を向けた
負のメニスカスレンズから構成した請求項１〜３の何れ
か１つの請求項に記載の単焦点レンズ。5. The front unit includes, in order from the object side, a meniscus lens having a negative refractive power with a concave surface facing the image surface side, and a positive lens having a convex surface on the image surface side. The single focus lens according to any one of claims 1 to 3, comprising a positive lens having a convex surface on the image surface side in order, and a negative meniscus lens having a concave surface facing the image surface. 【請求項６】 前記前群は物体側から順に像面側に凸面
を持つ正レンズ、像面側に凹面を向けた負の屈折力を持
つメニスカスレンズから構成し、前記後群は物体側から
順に像面側に凸面を持つ正レンズ、物体側に凹面を向け
た負のメニスカスレンズから構成した請求項１〜３の何
れか１つの請求項に記載の単焦点レンズ。6. The front unit includes, in order from the object side, a positive lens having a convex surface on the image surface side, and a meniscus lens having a negative refractive power with a concave surface facing the image surface side. The single focus lens according to any one of claims 1 to 3, comprising a positive lens having a convex surface on the image surface side and a negative meniscus lens having a concave surface facing the object side in order. 【請求項７】 前記前群は物体側から順に像面側に凹面
を向けた負の屈折力を持つ１枚のメニスカスレンズから
構成し、前記後群は物体側から順に像面側に凸面を持つ
正レンズ、物体側に凹面を向けた負のメニスカスレンズ
から構成した請求項１〜３の何れか１つの請求項に記載
の単焦点レンズ。7. The front unit includes one meniscus lens having a negative refractive power with a concave surface facing the image surface side in order from the object side, and the rear unit includes a convex surface on the image surface side in order from the object side. The single focus lens according to any one of claims 1 to 3, comprising a positive lens having a negative meniscus lens having a concave surface facing the object side. 【請求項８】 前記前群は像面側に凹面を向けた負の屈
折力を持つ１枚のメニスカスレンズから構成し、前記後
群は像面側に凸面を持つ１枚の正レンズから構成した請
求項１〜３の何れか１つの請求項に記載の単焦点レン
ズ。8. The front unit comprises one meniscus lens having a negative refractive power with a concave surface facing the image surface side, and the rear unit comprises one positive lens having a convex surface on the image surface side. The single focus lens according to claim 1. 【請求項９】 前記前群及び後群はそれぞれ少なくとも
１面の非球面を持つ請求項７又は８に記載の単焦点レン
ズ。9. The single focus lens according to claim 7, wherein each of the front group and the rear group has at least one aspheric surface. 【請求項１０】 前記回折光学面を持つ群全体の焦点距
離をｆｂ、前記回折光学面を持つレンズの焦点距離をｆ
ｄ、前記回折光学面を持つレンズから回折光学面のみを
取り除いたときの該レンズの焦点距離をｆｄ’とすると
き、 ０＜ｆｂ（１／ｆｄ−１／ｆｄ’）＜１．５８・１０-1 なる条件式を満足する請求項１〜９の何れか１つの請求
項に記載の単焦点レンズ。10. The focal length of the entire group having the diffractive optical surface is fb, and the focal length of the lens having the diffractive optical surface is f.
d, where fd ′ is the focal length of the lens having only the diffractive optical surface removed from the lens having the diffractive optical surface, 0 <fb (1 / fd−1 / fd ′) <1.58 · 10 The single focus lens according to any one of claims 1 to 9, which satisfies a conditional expression of -1 . 【請求項１１】 前記回折光学面は少なくとも２層以上
から構成した請求項１又は２に記載の単焦点レンズ。11. The single focus lens according to claim 1, wherein the diffractive optical surface is composed of at least two layers.
JP25281497A 1997-09-02 1997-09-02 camera Expired - Fee Related JP3880147B2 (en)

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JPWO2008032447A1 (en) * 2006-09-15 2010-01-21 株式会社ニコン Photography lens and camera
WO2009153953A1 (en) * 2008-06-16 2009-12-23 パナソニック株式会社 Double image pickup optical system and image pickup apparatus provided therewith
JP4796660B2 (en) * 2008-06-16 2011-10-19 パナソニック株式会社 Two-disc imaging optical system and imaging apparatus including the same
US8384996B2 (en) 2008-06-16 2013-02-26 Panasonic Corporation Double image pickup optical system and image pickup apparatus provided therewith
US9182574B2 (en) 2012-01-13 2015-11-10 Tamron Co., Ltd. Infrared fixed-focus lens
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WO2014025121A1 (en) * 2012-08-08 2014-02-13 Lg Innotek Co., Ltd. Optical system
US9494767B2 (en) 2012-08-08 2016-11-15 Lg Innotek Co., Ltd. Optical system
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CN114791660A (en) * 2021-01-25 2022-07-26 东京晨美光学电子株式会社 Camera lens

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