JP2014026210A

JP2014026210A - Optical system, and optical device having the same

Info

Publication number: JP2014026210A
Application number: JP2012168252A
Authority: JP
Inventors: Mikio Kobayashi; 幹生小林
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2012-07-30
Filing date: 2012-07-30
Publication date: 2014-02-06

Abstract

PROBLEM TO BE SOLVED: To provide an optical system in which an entire system is small, and various aberrations including color aberration can be corrected easily so as to easily attain high optical performance.SOLUTION: In an optical system having a total length of a lens shorter than a focal distance and an aperture diaphragm, one or more first deflection optical elements Gcr and one or more second deflection optical elements Gr are provided on an image side with respect to the aperture diaphragm; a refractive index on a d line of the first deflection optical element Gcr is set to Ncr, an Abbe number is set to νcr; and an optical coefficient ΔNcr, a partial distribution ratio θgFr on a g-F line of the first deflection optical element Gcr, an Abbe number νr, and abnormal partial distribution ratio ΔθgFr, are appropriately set respectively.

Description

本発明は、光学系及びそれを有する光学機器に関し、例えば、銀塩フィルム用カメラ、デジタルスチルカメラ、ビデオカメラ、望遠鏡、双眼鏡、プロジェクター、デジタル複写機等の光学機器に用いられる光学系として好適なものである。 The present invention relates to an optical system and an optical apparatus having the same, and is suitable as an optical system used in optical apparatuses such as a silver salt film camera, a digital still camera, a video camera, a telescope, a binocular, a projector, and a digital copying machine. Is.

一般にデジタルカメラやビデオカメラ等の光学機器に用いられる撮影光学系（撮像光学系）は、レンズ全長（第１レンズ面から像面までの距離）が短く、全系が小型であることが要望されている。レンズ全長を短縮し、光学系全体の小型化を図ろうとすると、該収差、特に軸上色収差及び倍率色収差などの色収差が多く発生してくる。このため、光学性能が大きく低下してくる。特にレンズ全長の短縮化を図ったテレフォトタイプ（望遠型）の撮影光学系では、焦点距離を伸ばすほど（長くするほど）諸収差のうち色収差が多く発生してくる。 In general, an imaging optical system (imaging optical system) used for an optical apparatus such as a digital camera or a video camera has a short overall lens length (distance from the first lens surface to the image plane), and the entire system is required to be small. ing. When an attempt is made to shorten the overall length of the lens and reduce the size of the entire optical system, a large amount of such aberrations, particularly chromatic aberrations such as axial chromatic aberration and lateral chromatic aberration, occur. For this reason, the optical performance is greatly reduced. In particular, in a telephoto type (telephoto) photographic optical system in which the total lens length is shortened, the chromatic aberration among the various aberrations increases as the focal length increases (increases).

このときの色収差の発生を低減する方法として、光学材料に異常部分分散材料を用いる方法や光路中に回折光学素子を用いる方法がある。テレフォトタイプの撮影光学系では多くの場合、近軸軸上光線と瞳近軸光線の光軸からの通過位置が比較的に高くなる前方レンズ群に、蛍石等の異常部分分散を持った低分散の光学材料を用いて色収差を低減している。テレフォトタイプの撮影光学系において蛍石等の異常部分分散を持った低分散の光学材料を用いて色収差を補正した撮影光学系が知られている（特許文献１）。 As a method for reducing the occurrence of chromatic aberration at this time, there are a method using an abnormal partial dispersion material as an optical material and a method using a diffractive optical element in an optical path. Telephoto imaging optical systems often have anomalous partial dispersion such as fluorite in the front lens group, where the paraxial-axis rays and pupil paraxial rays pass from the optical axis relatively high. Chromatic aberration is reduced by using a low dispersion optical material. In a telephoto type photographing optical system, a photographing optical system in which chromatic aberration is corrected using a low dispersion optical material having an abnormal partial dispersion such as fluorite is known (Patent Document 1).

また、テレフォトタイプの撮影光学系において、異常部分分散性が非常に高い材料を、前方レンズ群に用いて、諸収差を補正した撮影光学系が知られている（特許文献２）。また、テレフォトタイプの撮影光学系において、異常部分分散の光学材料を用いず、回折光学素子を用いて、色収差の補正を行った撮像光学系が知られている（特許文献３）。特許文献３には、回折型光学素子と屈折型光学素子とを組み合わせて、色収差を良好に補正したＦナンバーＦ２．８程度のテレフォトタイプの撮影光学系が開示されている。 In addition, in a telephoto type photographing optical system, a photographing optical system in which various aberrations are corrected by using a material having extremely high anomalous partial dispersibility for a front lens group is known (Patent Document 2). In addition, an imaging optical system in which chromatic aberration is corrected using a diffractive optical element without using an abnormal partial dispersion optical material in a telephoto type photographing optical system is known (Patent Document 3). Patent Document 3 discloses a telephoto type photographing optical system having an F number of about F2.8, in which chromatic aberration is favorably corrected by combining a diffractive optical element and a refractive optical element.

一般に回折光学素子は、アッベ数に相当する数値の絶対値が３．４５と小さく、回折によるパワー（焦点距離の逆数）を僅かに変化させるだけで、球面収差、コマ収差、非点収差等にほとんど影響を与えることなく、色収差を大きく変化することができる。また、扱う光が回折光であるため、入射光の波長の変化に対してパワーが線形変化し、色収差係数の波長特性は完全な直線となる。
一方近年、透光性セラミックスが開発され、それを光学材料として用いた撮影光学系が種々と提案されている。透光性セラミックスは、光学ガラスに比べて屈折率が高く、又硬度と強度に優れている。従来、この性質を利用して、レンズ系全体の薄型化を図りつつ、光学性能の向上を図った撮影光学系が知られている（特許文献４）。 In general, the diffractive optical element has a small absolute value corresponding to the Abbe number of 3.45, and it can reduce spherical aberration, coma aberration, astigmatism, etc. by changing the power (reciprocal of focal length) slightly by diffraction. The chromatic aberration can be greatly changed with little influence. Further, since the handled light is diffracted light, the power changes linearly with respect to the change in the wavelength of the incident light, and the wavelength characteristic of the chromatic aberration coefficient becomes a complete straight line.
On the other hand, in recent years, translucent ceramics have been developed, and various photographing optical systems using them as optical materials have been proposed. Translucent ceramics have a higher refractive index than optical glass, and are excellent in hardness and strength. 2. Description of the Related Art Conventionally, there has been known a photographing optical system that utilizes this property to improve the optical performance while reducing the thickness of the entire lens system (Patent Document 4).

特開平１１−１１９０９２号公報JP-A-11-119092 特開２００６−１４５８２３号公報JP 2006-145823 A 特開平６−３３１８８７号公報JP-A-6-331887 特開２００８−２０３４１５号公報JP 2008-203415 A

光学材料に蛍石を使ったテレフォトタイプの撮影光学系は、レンズ全長を長めに設定すれば色収差の補正が容易となる。しかしながら、レンズ全長を短くすると色収差が多く発生し、これを良好に補正することが困難となる。この理由は、蛍石の材料が持つ低分散と異常部分分散を利用して、正の屈折力の前玉レンズ系で発生する色収差を単に低減しているからである。 In a telephoto type photographing optical system using fluorite as an optical material, correction of chromatic aberration can be facilitated if the overall lens length is set longer. However, if the total lens length is shortened, a lot of chromatic aberration is generated, and it is difficult to correct this well. This is because chromatic aberration generated in the front lens system having a positive refractive power is simply reduced by utilizing the low dispersion and abnormal partial dispersion of the fluorite material.

レンズ全長の短縮に伴って増大した色収差を補正する場合、例えば、蛍石のようなアッベ数の大きい低分散ガラスを使ったレンズでは、レンズ面の屈折力を大きく変化させないと色収差の補正が難しい。このため、高い光学性能を得るには、色収差と、屈折力を大きくしたことによって発生する球面収差、コマ収差、非点収差などの諸収差をバランス良く補正することが重要になってくる。 When correcting chromatic aberration that has increased with the shortening of the overall lens length, for example, in lenses using low dispersion glass with a large Abbe number such as fluorite, it is difficult to correct chromatic aberration unless the refractive power of the lens surface is significantly changed. . For this reason, in order to obtain high optical performance, it is important to correct chromatic aberration and various aberrations such as spherical aberration, coma aberration, and astigmatism generated by increasing the refractive power in a balanced manner.

一方、回折光学素子は色収差の補正作用が十分ある。しかしながら回折光学素子は実際に用いる設計回折次数以外の不要な回折次数の回折光が発生してくる。この不要な回折光が色の付いたフレア光となって結像性能を悪化させる原因となってくる。この不要な回折光を減ずる方法として、複数のブレーズ型の回折格子を光軸方向に積層した、所謂、積層型の回折光学素子を用い、これによって設計回折次数へエネルギーを集中させ、不要な回折光を大幅に減らす方法がある。 On the other hand, the diffractive optical element has a sufficient correction function for chromatic aberration. However, the diffractive optical element generates diffracted light of an unnecessary diffraction order other than the designed diffraction order actually used. This unnecessary diffracted light becomes colored flare light and causes image formation performance to deteriorate. As a method of reducing this unnecessary diffracted light, a so-called stacked diffractive optical element in which a plurality of blazed diffraction gratings are stacked in the optical axis direction is used, thereby concentrating energy on the designed diffraction order, and unnecessary diffraction. There are ways to significantly reduce light.

しかしながら、この方法を用いたとしても高輝度な被写体を撮影する場合では依然として不要な回折光によるフレアが生じて光学性能が低下する原因となってくる。また、回折光学素子の製造方法として、紫外線硬化樹脂等を金型で成形する方法が知られている。この方法は、回折光学素子の回折効率の敏感度が製造上極めて高い為、金型に非常に高い精度が要求され、また高い成形精度が要求され、製造が難しい。 However, even when this method is used, when a high-luminance subject is photographed, flare due to unnecessary diffracted light still occurs, causing a decrease in optical performance. As a method for manufacturing a diffractive optical element, a method of molding an ultraviolet curable resin or the like with a mold is known. In this method, since the sensitivity of the diffraction efficiency of the diffractive optical element is extremely high in manufacturing, a very high accuracy is required for the mold, and a high molding accuracy is required, which makes it difficult to manufacture.

また、一般に光学ガラスは、屈折率を縦軸に上方向が大きな値となるように、アッベ数を横軸に左方向が大きな値となるように取ったグラフ（以下「ｎｄ−νｄ図」と呼ぶ）上にマッピングさせると、ほぼいくつかの曲線に沿って分布することが知られている。また一般に光学ガラスの屈折率が大きくなると、アッベ数は小さくなり、分散が大きくなる特性がある。 In general, optical glass is a graph (hereinafter referred to as “nd-νd diagram”) in which the refractive index is set to a large value on the vertical axis and the Abbe number is set to a large value on the left side on the horizontal axis. It is known that it is distributed along some curves. In general, when the refractive index of the optical glass increases, the Abbe number decreases and the dispersion increases.

一方、可視光領域で光透過率の高いセラミックスや酸化物の単結晶および多結晶の中には、屈折率とアッベ数の関係が、前述のｎｄ−νｄ図において通常の光学ガラスとは異なる領域に存在するものが知られている。すなわち同じアッベ数を有する光学ガラスに比べ、高い屈折率を有する材料が知られている。このような性質を有するセラミックスを光学材料として用いると、収差補正及び光学系全体の小型化が容易になる。 On the other hand, among single crystals and polycrystals of ceramics and oxides having high light transmittance in the visible light region, the relationship between the refractive index and the Abbe number is different from that of ordinary optical glass in the nd-νd diagram described above. What exists in is known. That is, a material having a higher refractive index than that of optical glass having the same Abbe number is known. Using ceramics having such properties as an optical material facilitates aberration correction and downsizing of the entire optical system.

しかしながら、セラミックス材料の異常部分分散性は通常のガラスとあまり変わらないものが多く、単にセラミックスより成るレンズをテレフォトタイプの撮影光学系に用いても、色収差を良好に補正することが難しい。 However, anomalous partial dispersibility of ceramic materials is not much different from that of ordinary glass, and it is difficult to correct chromatic aberration satisfactorily even if a lens made of ceramics is simply used in a telephoto type photographing optical system.

本発明は、全系が小型で、しかも色収差を含め諸収差の補正が容易で高い光学性能が容易に得られる光学系及びそれを有する光学機器の提供を目的とする。 An object of the present invention is to provide an optical system in which the entire system is small, and correction of various aberrations including chromatic aberration is easy and high optical performance can be easily obtained, and an optical apparatus having the optical system.

本発明の光学系は、レンズ全長が焦点距離よりも短く、開口絞りを有する光学系において、前記開口絞りよりも像側に、一つ以上の第１の屈折光学素子Ｇｃｒと、一つ以上の第２の屈折光学素子Ｇｒを有し、前記第１の屈折光学素子Ｇｃｒの材料のｄ線における屈折率をＮｃｒ、アッベ数をνｃｒとし、光学係数ΔＮｃｒを、
ΔＮｃｒ＝Ｎｃｒ−（５．９４×１０^−５×νｃｒ^２−１．５７×１０^−２×νｃｒ）
とし、前記第２の屈折光学素子Ｇｒの材料のｇ−Ｆ線における部分分散比をθｇＦｒ、アッベ数をνｒとし、異常部分分散比ΔθｇＦｒを、
ΔθｇＦｒ＝θｇＦｒ−(−１．６６５×１０^−７×νｒ^３＋５．２１３×１０^−５×νｒ^２−５．６５６×１０^−３×νｒ＋０．７２７８)
とするとき、
２．４４＜ΔＮｃｒ＜２．９５
１５＜νｃｒ＜７０
０．０２７２＜ΔθｇＦｒ＜０．２８３２
なる条件式を満たすことを特徴としている。 The optical system of the present invention has an overall lens length shorter than the focal length, and has an aperture stop. The optical system has one or more first refractive optical elements Gcr and one or more first refractive optical elements Gcr closer to the image side than the aperture stop. A second refractive optical element Gr, the refractive index of the material of the first refractive optical element Gcr at the d-line is Ncr, the Abbe number is νcr, and the optical coefficient ΔNcr is
ΔNcr = Ncr− (5.94 × 10 ⁻⁵ × νcr ² −1.57 × 10 ⁻² × νcr)
And the partial dispersion ratio at the g-F line of the material of the second refractive optical element Gr is θgFr, the Abbe number is νr, and the abnormal partial dispersion ratio ΔθgFr is
ΔθgFr = θgFr − (− 1.665 × 10 ⁻⁷ × νr ³ + 5.213 × 10 ⁻⁵ × νr ² −5.656 × 10 ⁻³ × νr + 0.7278)
And when
2.44 <ΔNcr <2.95
15 <νcr <70
0.0272 <ΔθgFr <0.2832
It is characterized by satisfying the following conditional expression.

本発明によれば、全系が小型で、しかも色収差を含め諸収差の補正が容易で高い光学性能が容易に得られる光学系が得られる。 According to the present invention, it is possible to obtain an optical system in which the entire system is small, and various aberrations including chromatic aberration can be easily corrected and high optical performance can be easily obtained.

（Ａ），（Ｂ）実施例１の光学系の光学断面図と収差図(A), (B) Optical sectional view and aberration diagram of the optical system of Example 1 （Ａ），（Ｂ）実施例２の光学系の光学断面図と収差図(A), (B) Optical sectional view and aberration diagram of the optical system of Example 2 （Ａ），（Ｂ）実施例３の光学系の光学断面図と収差図(A), (B) Optical sectional view and aberration diagram of the optical system of Example 3 （Ａ），（Ｂ）実施例４の光学系の光学断面図と収差図(A), (B) Optical sectional view and aberration diagram of optical system of Example 4 （Ａ），（Ｂ）実施例５の光学系の光学断面図と収差図(A), (B) Optical sectional view and aberration diagram of optical system of Example 5 本発明の撮像装置の要部概略図Schematic diagram of main parts of an imaging apparatus of the present invention 本発明の条件式（１ａ）,（１ｂ）の範囲を説明する図The figure explaining the range of conditional expressions (1a) and (1b) of the present invention 本発明の条件式（２ｂ）,（２ｃ）の範囲を説明する図The figure explaining the range of conditional expressions (2b) and (2c) of the present invention

以下、本発明の光学系及びそれを有する光学機器について説明する。本発明の光学系は、レンズ全長（第１レンズ面から像面までの距離）が焦点距離よりも短く、開口絞りを有する。そして開口絞りよりも像側に、後述する条件式（２ａ），（２ｂ）を満足する材料よりなる一つ以上の第１の屈折光学素子Ｇｃｒと、後述する条件式（１ｂ）を満足する材料よりなる一つ以上の第２の屈折光学素子Ｇｒを有している。 Hereinafter, the optical system of the present invention and the optical apparatus having the same will be described. The optical system of the present invention has an overall aperture length (distance from the first lens surface to the image plane) shorter than the focal length and has an aperture stop. One or more first refractive optical elements Gcr made of a material satisfying conditional expressions (2a) and (2b) to be described later, and a material satisfying conditional expression (1b) to be described later, on the image side from the aperture stop. And one or more second refractive optical elements Gr.

図１（Ａ），（Ｂ）は本発明の実施例１の光学系のレンズ断面図と収差図であり、それぞれ無限遠物体に合焦しているときを示している。図２（Ａ），（Ｂ）は本発明の実施例２の光学系のレンズ断面図と収差図であり、それぞれ無限遠物体に合焦しているときを示している。図３（Ａ），（Ｂ）は本発明の実施例３の光学系のレンズ断面図と収差図であり、それぞれ無限遠物体に合焦しているときを示している。図４（Ａ），（Ｂ）は本発明の実施例４の光学系のレンズ断面図と収差図であり、それぞれ無限遠物体に合焦しているときを示している。 FIGS. 1A and 1B are a lens cross-sectional view and an aberration diagram of the optical system according to Example 1 of the present invention, each showing a state in which an object at infinity is in focus. FIGS. 2A and 2B are a lens cross-sectional view and aberration diagrams of the optical system according to Example 2 of the present invention, each showing a state in which an object at infinity is in focus. FIGS. 3A and 3B are a lens cross-sectional view and aberration diagrams of the optical system according to Example 3 of the present invention, each showing a state in which an object at infinity is in focus. FIGS. 4A and 4B are a lens cross-sectional view and aberration diagrams of the optical system according to Example 4 of the present invention, and each shows a state in which an object at infinity is in focus.

図５（Ａ），（Ｂ）は本発明の実施例５の光学系のレンズ断面図と収差図であり、それぞれ無限遠物体に合焦しているときを示している。図６は本発明の光学系を有する光学機器の要部概略図である。図７はアッベ数と部分分散比との関係を示す説明図である。図８は「ｎｄ−νｄ図」の説明図である。 FIGS. 5A and 5B are a lens cross-sectional view and aberration diagrams of the optical system according to Example 5 of the present invention, each showing a state in which an object at infinity is in focus. FIG. 6 is a schematic diagram of a main part of an optical apparatus having the optical system of the present invention. FIG. 7 is an explanatory diagram showing the relationship between the Abbe number and the partial dispersion ratio. FIG. 8 is an explanatory diagram of the “nd-νd diagram”.

レンズ断面図において、左方が物体側（前方）で、右方が像側（後方）である。レンズ断面図において、ＯＬは光学系である。ＳＰは開口絞りである。Ｌ１は正の屈折力の第１レンズ群、Ｌ２は負の屈折力の第２レンズ群、Ｌ３は第３レンズ群である。無限遠物体から近距離物体へのフォーカシングは第２レンズ群Ｌ２を像側へ移動させて行っている。ＩＰは像面であり、ビデオカメラやデジタルスチルカメラの撮影光学系として使用する際にはＣＣＤセンサやＣＭＯＳセンサ等の固体撮像素子（光電変換素子）の撮像面が、銀塩フィルム用カメラの撮影光学系として使用する際にはフィルム面に相当する。 In the lens cross-sectional view, the left side is the object side (front), and the right side is the image side (rear). In the lens cross-sectional view, OL is an optical system. SP is an aperture stop. L1 is a first lens group having a positive refractive power, L2 is a second lens group having a negative refractive power, and L3 is a third lens group. Focusing from an infinitely distant object to a close object is performed by moving the second lens unit L2 to the image side. IP is an image plane, and when used as an imaging optical system for a video camera or a digital still camera, the imaging surface of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor is taken by a silver salt film camera. When used as an optical system, it corresponds to the film surface.

収差図においては、ｄ，ｇはそれぞれｄ線及びｇ線、ΔＭ，ΔＳはそれぞれｄ線のメリディオナル像面、ｄ線のサジタル像面である。歪曲はｄ線、倍率色収差はｇ線によって表わしている。ＦｎｏはＦナンバー、ωは撮影半画角（度）である。 In the aberration diagrams, d and g are the d-line and g-line, respectively, and ΔM and ΔS are the meridional image plane of the d-line and the sagittal image plane of the d-line, respectively. Distortion is represented by d-line, and lateral chromatic aberration is represented by g-line. Fno is the F number, and ω is the shooting half angle of view (degrees).

本発明の光学系は、デジタルカメラ、ビデオカメラ、銀塩フィルム用カメラ等の撮像装置の撮影光学系として用いられるものである。また、本発明の光学系は、レンズ全長が焦点距離よりも小さい、テレフォトタイプの光学系である。 The optical system of the present invention is used as a photographing optical system of an imaging apparatus such as a digital camera, a video camera, or a silver salt film camera. The optical system of the present invention is a telephoto type optical system in which the total lens length is smaller than the focal length.

ここでいうレンズ全長とは、物体側の第１レンズ面から像面までの長さのことを示す。
各実施例のテレフォトタイプの光学系は、開口絞りＳＰよりも像側に、異常部分分散比の大きい（高い）固体材料（常温常圧）から構成される第２の屈折光学素子Ｇｒを１つ以上有している。更に同じアッベ数を有する光学ガラスに比べ、高い屈折率を有する材料から構成される第１の屈折光学素子Ｇｃｒを１つ以上有している。 The total lens length here refers to the length from the first lens surface on the object side to the image plane.
The telephoto type optical system of each embodiment has a second refractive optical element Gr made of a solid material (normal temperature and normal pressure) having a large (high) abnormal partial dispersion ratio on the image side of the aperture stop SP. Have more than one. Furthermore, it has one or more first refractive optical elements Gcr made of a material having a high refractive index as compared with optical glass having the same Abbe number.

実施例５では第１レンズ群Ｌ１は１以上の回折光学面を有している。そして第１の屈折光学素子Ｇｃｒの材料のｄ線における屈折率をＮｃｒ、アッベ数をνｃｒとし、光学係数ΔＮｃｒを次式の如く定義する。 In Example 5, the first lens unit L1 has one or more diffractive optical surfaces. The refractive index at the d-line of the material of the first refractive optical element Gcr is Ncr, the Abbe number is νcr, and the optical coefficient ΔNcr is defined as follows.

ΔＮｃｒ＝Ｎｃｒ−（５．９４×１０^−５×νｃｒ^２−１．５７×１０^−２×νｃｒ）
・・・（１ａ）
また第２の屈折光学素子Ｇｒの材料のｇ−Ｆ線における部分分散比をθｇＦｒ、アッベ数をνｒとする。そして異常部分分散比ΔθｇＦｒを、
ΔθｇＦｒ＝θｇＦｒ−(−１．６６５×１０^−７×νｒ^３＋５．２１３×１０^−５×νｒ^２−５．６５６×１０^−３×νｒ＋０．７２７８) ・・・（２ａ）
とする。このとき、
０．０２７２＜ΔθｇＦｒ＜０．２８３２・・・（２ｂ）
２．４４＜ΔＮｃｒ＜２．９５・・・（１ｂ）
１５＜νｃｒ＜７０・・・（１ｃ）
なる条件式を満たしている。 ΔNcr = Ncr− (5.94 × 10 ⁻⁵ × νcr ² −1.57 × 10 ⁻² × νcr)
... (1a)
Further, the partial dispersion ratio of the material of the second refractive optical element Gr in the g-F line is θgFr, and the Abbe number is νr. Then, the abnormal partial dispersion ratio ΔθgFr is
ΔθgFr = θgFr − (− 1.665 × 10 ⁻⁷ × νr ³ + 5.213 × 10 ⁻⁵ × νr ² −5.656 × 10 ⁻³ × νr + 0.7278) (2a)
And At this time,
0.0272 <ΔθgFr <0.2832 (2b)
2.44 <ΔNcr <2.95 (1b)
15 <νcr <70 (1c)
The following conditional expression is satisfied.

なお、本発明において、材料のアッベ数νｄ、部分分散比θｇＦの定義は一般に用いられるものと同じであり、ｇ線、Ｆ線、ｄ線、Ｃ線に対する屈折率をそれぞれＮｇ，ＮＦ，Ｎｄ，ＮＣとするとき、それぞれ次式で表される。 In the present invention, the definition of the Abbe number νd and the partial dispersion ratio θgF of the material is the same as that generally used, and the refractive indexes for the g-line, F-line, d-line, and C-line are Ng, NF, Nd, When NC, it is expressed by the following formula.

νｄ＝（Ｎｄ−１）／（ＮＦ−ＮＣ）
θｇＦ＝（Ｎｇ−ＮＦ）／（ＮＦ−ＮＣ）
図７は、アッベ数と部分分散比θｇFについて、本発明にかかる条件式（２ｂ）の範囲と、後述する表１の物質及び一般の光学ガラスとの関係を示したものである。 νd = (Nd−1) / (NF−NC)
θgF = (Ng−NF) / (NF−NC)
FIG. 7 shows the relationship between the range of the conditional expression (2b) according to the present invention, the substances in Table 1 described later, and general optical glass with respect to the Abbe number and the partial dispersion ratio θgF.

図８は、アッベ数と屈折率の関係を示す図であり、本発明にかかる第１の屈折光学素子Ｇｃｒを成す高屈折率低分散な材料のアッベ数と屈折率を示している。さらに条件式（１ｂ）の範囲と、各実施例で用いている第１の屈折光学素子Ｇｃｒ、そして一般の光学ガラスとの関係を示したものである。尚、ここで屈折光学素子とは屈折作用でパワーが生じる、例えば屈折レンズ等を意味し、回折作用でパワーが生じる回折光学素子を含んでいない。 FIG. 8 is a diagram showing the relationship between the Abbe number and the refractive index, and shows the Abbe number and refractive index of the high refractive index and low dispersion material forming the first refractive optical element Gcr according to the present invention. Further, the relationship between the range of the conditional expression (1b), the first refractive optical element Gcr used in each example, and general optical glass is shown. Here, the refractive optical element means a refractive lens that generates power by a refraction action, for example, and does not include a diffractive optical element that generates power by a diffraction action.

また、固体材料とは、光学系を使用する状態で固体の材料を指し、製造時などの状態においてはどのような状態であっても良い。例えば、製造時には液体材料であっても、それを硬化させて固体材料としたものも、ここでいう固体材料に該当する。 Further, the solid material refers to a solid material in a state where the optical system is used, and may be in any state in a state such as manufacturing. For example, even if it is a liquid material at the time of manufacture, the solid material obtained by curing it corresponds to the solid material here.

各実施例の光学系中に用いられる第２の屈折光学素子Ｇｒ（光学素子）は、光入射側（前方、拡大側）と光射出側（後方、縮小側）が共に屈折面であり、このうち少なくとも一方の屈折面に屈折力がある。そして材料のアッベ数をνｒ、部分分散比をθｇＦｒとするとき、異常部分分散比ΔθｇＦｒが条件式（２ｂ）を満足する常温常圧で固体材料より成っている。ただし、異常部分分散比ΔθｇＦｒは条件式（２ａ）で定義されるものである。 The second refractive optical element Gr (optical element) used in the optical system of each embodiment has both a light incident side (front and enlargement side) and a light exit side (rear and reduction side) as refractive surfaces. At least one of the refractive surfaces has a refractive power. When the Abbe number of the material is νr and the partial dispersion ratio is θgFr, the abnormal partial dispersion ratio ΔθgFr is made of a solid material at normal temperature and normal pressure satisfying the conditional expression (2b). However, the abnormal partial dispersion ratio ΔθgFr is defined by the conditional expression (2a).

さらに、各実施例の光学系中に用いられる屈折光学素子（光学素子）Ｇｃｒは、第１の屈折光学素子Ｇｃｒの材料のｄ線における屈折率をＮｃｒ、アッベ数をνｃｒとする。このとき光学係数ΔＮｃｒが条件式（１ｂ）、アッベ数νｃｒが条件式（１ｃ）を満足する材料より成っている。ただし、光学係数ΔＮｃｒは条件式（１ａ）で定義されるものである。 Further, in the refractive optical element (optical element) Gcr used in the optical system of each embodiment, the refractive index of the material of the first refractive optical element Gcr at the d-line is Ncr, and the Abbe number is νcr. At this time, the optical coefficient ΔNcr is made of a material that satisfies the conditional expression (1b) and the Abbe number νcr satisfies the conditional expression (1c). However, the optical coefficient ΔNcr is defined by the conditional expression (1a).

各実施例の光学系は、条件式（２ｂ）を満足する固体材料より成る第２の屈折光学素子Ｇｒと、条件式（１ｂ）、（１ｃ）を満足する第１の屈折光学素子Ｇｃｒを、共に光学系中において開口絞りよりも像側に用いている。これによって、コマ収差、非点隔差、像面湾曲等の諸収差と、ｇ線からＣ線の広い波長帯域にわたっての色収差を、共に良好に補正している。 The optical system of each embodiment includes a second refractive optical element Gr made of a solid material that satisfies the conditional expression (2b), and a first refractive optical element Gcr that satisfies the conditional expressions (1b) and (1c). Both are used on the image side of the aperture stop in the optical system. As a result, various aberrations such as coma, astigmatism, curvature of field, and chromatic aberration over a wide wavelength band from the g-line to the C-line are corrected well.

条件式（２ｂ）を満足する固体材料（以下「光学材料」ともいう。）の具体例としては、例えば樹脂がある。様々な樹脂の中でも特にＵＶ硬化樹脂（Ｎｄ＝１．６３５，νｄ＝２２．７，θｇＦ＝０．６９）やＮ−ポリビニルカルバゾール（以下ＰＶＣｚともいう。）（Ｎｄ＝１．６９６，νｄ＝１７．７，θｇＦ＝０．６９）は条件式（１ａ）を満足する光学材料である。尚、条件式（２ｂ）を満足する材料であれば、これらに限定するものではない。また、一般の硝材とは異なる特性を持つ光学材料として、下記の無機酸化物ナノ微粒子を合成樹脂中に分散させた混合体がある。 A specific example of the solid material (hereinafter also referred to as “optical material”) that satisfies the conditional expression (2b) is, for example, a resin. Among various resins, UV curable resin (Nd = 1.635, νd = 22.7, θgF = 0.69) and N-polyvinylcarbazole (hereinafter also referred to as PVCz) (Nd = 1.696, νd = 17). .7, θgF = 0.69) is an optical material that satisfies the conditional expression (1a). Note that the material is not limited to these as long as it satisfies the conditional expression (2b). Further, as an optical material having characteristics different from those of general glass materials, there is a mixture in which the following inorganic oxide nanoparticles are dispersed in a synthetic resin.

すなわち、ＴｉＯ_２（Ｎｄ＝２．３０４，νｄ＝１３．８），Ｎｂ_２Ｏ_５（Ｎｄ＝２．３６７，νｄ＝１４．０），ＩＴＯ（Ｎｄ＝１．８５８１，νｄ＝５．５３），Ｃｒ_２Ｏ_３（Ｎｄ＝２．２１７８，νｄ＝１３．４）等がある。更にＢａＴｉＯ_３（Ｎｄ＝２．４３６２，νｄ＝１１．３）等がある。 That is, TiO ₂ (Nd = 2.304, νd = 13.8), Nb ₂ O ₅ (Nd = 2.367, νd = 14.0), ITO (Nd = 1.8581, νd = 5.53) , Cr ₂ O ₃ (Nd = 2.2178, νd = 13.4). Furthermore, there is BaTiO ₃ (Nd = 2.4362, νd = 11.3) and the like.

これらの無機酸化物の中では、ＴｉＯ_２（Ｎｄ＝２．３０４，νｄ＝１３．８，θｇＦ＝０．８７）微粒子を合成樹脂中に適切なる体積比で分散させた場合、上記条件式（２ｂ）を満足する光学材料が得られる。ＴｉＯ_２は様々な用途で使われる材料であり、光学分野では反射防止膜などの光学薄膜を構成する蒸着用材料として用いられている。他にも光触媒、白色顔料などとして、またＴｉＯ_２微粒子は化粧品材料として用いられている。 Among these inorganic oxides, when TiO ₂ (Nd = 2.304, νd = 13.8, θgF = 0.87) fine particles are dispersed in a synthetic resin at an appropriate volume ratio, the above conditional expression ( An optical material satisfying 2b) is obtained. TiO ₂ is a material used in various applications, and is used as an evaporation material for forming an optical thin film such as an antireflection film in the optical field. In addition, photocatalysts, white pigments and the like, and TiO ₂ fine particles are used as cosmetic materials.

また、ポリマーの光学定数の特性としても、異常部分分散比が比較的大きいポリマー、あるいはアッベ数が比較的小さいポリマーか、両者を満たすポリマーが良く、Ｎ−ポリビニルカルバゾール、スチレン、ポリメタクリル酸メチル（アクリル）、などが適用できる。 In addition, as a characteristic of the optical constant of the polymer, a polymer satisfying both of a polymer having a relatively large anomalous partial dispersion ratio or a polymer having a relatively small Abbe number is preferable. N-polyvinylcarbazole, styrene, polymethyl methacrylate ( Acrylic), etc. can be applied.

各実施例では、条件式（２ｂ）を満足する光学材料を光学系中のレンズやレンズ表面に設けられた屈折力のある層（面）に適用している。さらに、この光学材料で構成された屈折面を非球面形状としても良く、これによれば色の球面収差などの色収差フレアを良好に補正することが容易となる。また、条件式（１ｂ），（１ｃ）を満足する材料の具体例としては、例えば透光性のセラミックスや、酸化物の単結晶、多結晶等がある。 In each example, an optical material that satisfies the conditional expression (2b) is applied to a lens (surface) having a refractive power provided on a lens or a lens surface in the optical system. Furthermore, the refracting surface made of this optical material may be aspherical, which makes it easy to satisfactorily correct chromatic aberration flare such as chromatic spherical aberration. Specific examples of the material satisfying the conditional expressions (1b) and (1c) include translucent ceramics, oxide single crystals, polycrystals, and the like.

条件式（１ｂ）、（１ｃ）を満足する材料は、屈折率とアッベ数の関係が、前述のｎｄ−νｄ図において通常の光学ガラスとは異なる領域に存在するものである。すなわち同じアッベ数を有する光学ガラスに比べ、高い屈折率を有する材料である。 The material satisfying the conditional expressions (1b) and (1c) has a relationship between the refractive index and the Abbe number in a region different from that of normal optical glass in the nd-νd diagram. That is, it is a material having a higher refractive index than optical glass having the same Abbe number.

次に各実施例のテレフォトタイプ（望遠型）の光学系（望遠レンズ）の収差補正の特徴を説明する。テレフォトタイプの光学系において、軸上色収差を補正する際には、通常、近軸軸上光線の入射高さの高い物体側に、異常部分分散比が高い蛍石等の材料を用いた正レンズとして用いて補正することが考えられる。しかし、レンズ全長を短縮していった場合、各レンズのパワーを大きくする必要がある。このため、軸上色収差、特にｇ線の軸上色収差を開口絞りＳＰよりも前群（前方のレンズ群）で補正すると、倍率色収差が過剰補正となり、逆に色収差が悪化してしまう。 Next, the aberration correction characteristics of the telephoto type (telephoto type) optical system (telephoto lens) of each embodiment will be described. When correcting axial chromatic aberration in a telephoto type optical system, it is normal to use a material such as fluorite with a high abnormal partial dispersion ratio on the object side where the incident height of the paraxial axial ray is high. It is conceivable to use the lens for correction. However, when the total lens length is shortened, it is necessary to increase the power of each lens. For this reason, if axial chromatic aberration, particularly g-line axial chromatic aberration, is corrected in the front group (front lens group) before the aperture stop SP, lateral chromatic aberration is excessively corrected, and chromatic aberration is worsened.

そのため、開口絞りＳＰよりも後群（後方のレンズ群）において、前群とは逆の材料の使い方を用いて、倍率色収差を補正する必要がある。すなわち、開口絞りＳＰよりも後群において、負レンズに異常部分分散比が大きく、アッベ数が大きい材料を用いるか、もしくは正レンズには異常部分分散比が小さく、アッベ数がある程度小さい材料を用いる。これによれば、倍率色収差を補正することができる。その際、瞳近軸光線の入射高さが高く、近軸軸上光線の入射高さが低い、像側に近い箇所に該材料を用いると、軸上色収差をさほど変化させることなく、倍率色収差を補正するが容易となる。 Therefore, it is necessary to correct the lateral chromatic aberration in the rear group (the rear lens group) from the aperture stop SP by using a material opposite to the front group. That is, in the rear group of the aperture stop SP, a material having a large abnormal partial dispersion ratio and a large Abbe number is used for the negative lens, or a material having a small abnormal partial dispersion ratio and a small Abbe number is used for the positive lens. . According to this, lateral chromatic aberration can be corrected. In this case, if the material is used in a position close to the image side where the incident height of the pupil paraxial ray is high and the incident height of the paraxial axial ray is low, the lateral chromatic aberration does not change much, and the lateral chromatic aberration does not change much. It becomes easy to correct.

しかしながら、上記の例えば負レンズに用いる、異常部分分散比が大きく、アッベ数が大きい材料は、通常硝材としては屈折率が低いものが多い。また、同様に、正レンズに用いる、異常部分分散比が小さく、アッベ数がある程度小さい材料は、通常硝材としては屈折率が高いものが多い。そのため、光学系全体のペッツバール和が負の方向に増大しやすくなり、非点格差や像面湾曲、しいてはコマ収差等も悪化しやすくなる。 However, many of the materials having a large anomalous partial dispersion ratio and a large Abbe number used for the above-described negative lens, for example, are usually low in refractive index. Similarly, a material having a small anomalous partial dispersion ratio and a small Abbe number used for a positive lens usually has a high refractive index as a normal glass material. For this reason, the Petzval sum of the entire optical system tends to increase in the negative direction, and astigmatism, field curvature, and coma aberration tend to deteriorate.

そこで、各実施例では、同じアッベ数において、通常の材料よりも高い屈折率を持つ材料を負レンズとして用いることで、ペッツバール和を良好に改善しつつ、コマ収差、非点収差、像面湾曲等も良好に補正している。しかし、それだけでは、色収差、特にｇ線の曲がりを直すことが難しい。 Therefore, in each example, a material having a higher refractive index than a normal material at the same Abbe number is used as a negative lens, so that the Petzval sum is improved satisfactorily, and coma aberration, astigmatism, field curvature is improved. Etc. are corrected well. However, it is difficult to correct the chromatic aberration, particularly the g-line curvature.

次に異常部分分散比が大きい光学材料でパワーのある光学部材を光学系中に用いたときの光学系の収差補正に及ぼす作用について説明する。光学材料の屈折率の波長依存特性（分散特性）において、アッベ数は分散特性曲線の全体の傾きを表し、部分分散比は分散特性曲線の曲がり具合を表している。 Next, the effect on the aberration correction of the optical system when an optical member having a large abnormal partial dispersion ratio and having power is used in the optical system will be described. In the wavelength dependence characteristic (dispersion characteristic) of the refractive index of the optical material, the Abbe number represents the overall slope of the dispersion characteristic curve, and the partial dispersion ratio represents the degree of bending of the dispersion characteristic curve.

一般的に光学材料は、短波長側の屈折率が長波長側の屈折率よりも高く（アッベ数が正の値）、分散特性曲線は下に凸状（部分分散比が正の値）の軌跡を描き、短波長側になるほど波長の変化に対する屈折率の変化は大きくなる。そして、アッベ数の小さい分散の大きな光学材料ほど部分分散比が大きくなり、分散特性曲線は下に凸状が強まる傾向にある。部分分散比が大きな光学材料では、その光学材料を用いたレンズ面の色収差係数の波長依存特性曲線は、部分分散比が小さな光学材料を用いた場合に比べて短波長側でより大きな曲がりを示す。 In general, an optical material has a refractive index on the short wavelength side higher than a refractive index on the long wavelength side (Abbe number is a positive value), and the dispersion characteristic curve is convex downward (a partial dispersion ratio is a positive value). A trace is drawn, and the shorter the wavelength, the greater the change in refractive index with respect to the change in wavelength. Then, the optical dispersion material having a small Abbe number and a large dispersion has a higher partial dispersion ratio, and the dispersion characteristic curve tends to be convex downward. In an optical material with a large partial dispersion ratio, the wavelength-dependent characteristic curve of the chromatic aberration coefficient of the lens surface using the optical material shows a larger curve on the short wavelength side than when an optical material with a small partial dispersion ratio is used. .

一方、部分分散比が小さな光学材料では、その光学材料を用いたレンズ面の色収差係数の波長依存特性曲線は波長域全体でより直線に近い形状を示す。硝材など一般的な光学材料の部分分散比は、アッベ数に対してほとんど直線的な変化をする。この直線的な変化から外れた特性を持つ光学材料が、異常部分分散性を示す光学材料である。異常部分分散を持つ光学材料として、一般的には分散の小さな蛍石などがある。 On the other hand, in an optical material having a small partial dispersion ratio, the wavelength-dependent characteristic curve of the chromatic aberration coefficient of the lens surface using the optical material shows a shape closer to a straight line over the entire wavelength region. The partial dispersion ratio of a general optical material such as a glass material changes almost linearly with respect to the Abbe number. An optical material having characteristics deviating from this linear change is an optical material exhibiting anomalous partial dispersion. As an optical material having anomalous partial dispersion, there is generally fluorite having a small dispersion.

異常部分分散を持つ光学材料を屈折力のあるレンズとして用いた場合、レンズ面の色収差係数の波長依存特性曲線は一般の硝材を用いた場合と比べると、より線形性が高くなるか（部分分散比が小さい）又は、より曲がりが大きくなる（部分分散比が大きい）。色収差係数の波長依存特性曲線の線形性が高いという点で、回折光学素子は部分分散比が極めて小さい。回折光学素子を用いた光学系では、全波長域に渡って色収差を良好に補正するのが容易となる。 When an optical material with extraordinary partial dispersion is used as a lens with refractive power, is the wavelength dependence characteristic curve of the chromatic aberration coefficient of the lens surface more linear than when using ordinary glass materials (partial dispersion)? The ratio is small) or the bending becomes larger (the partial dispersion ratio is large). The diffractive optical element has a very small partial dispersion ratio in that the linearity of the wavelength-dependent characteristic curve of the chromatic aberration coefficient is high. In an optical system using a diffractive optical element, it becomes easy to satisfactorily correct chromatic aberration over the entire wavelength range.

しかし回折と屈折では光への影響が全く異なる。一般の光学材料は、上述の様にアッベ数は常に正の値をとり、また分散特性曲線は多かれ少なかれ下に凸状となる。これに対して回折光学素子では逆に長波長側の屈折率の方が短波長側の屈折率よりも高くなり、また屈折率の波長に対する変化も一様となる。したがって回折光学素子のアッベ数は−３．４５と負の値をとり、またその分散特性は直線となる。 However, diffraction and refraction have completely different effects on light. In general optical materials, the Abbe number always takes a positive value as described above, and the dispersion characteristic curve is more or less convex downward. On the other hand, in the diffractive optical element, the refractive index on the long wavelength side is higher than the refractive index on the short wavelength side, and the change of the refractive index with respect to the wavelength is uniform. Therefore, the Abbe number of the diffractive optical element takes a negative value of −3.45, and its dispersion characteristic is a straight line.

このような一般の屈折材料とは全く異なる特性を活かした、回折光学素子を用いた光学系では、回折光学素子以外の部分で発生した比較的大きな色収差を回折光学素子でキャンセルすることができる。これにより全波長域に渡って色収差を良好に補正することができる。このように、部分分散比が極めて小さな光学材料を用いると光学系全体で全波長域に渡って色収差を良好に補正することができる。 In an optical system using a diffractive optical element utilizing characteristics completely different from those of a general refractive material, a relatively large chromatic aberration generated in a portion other than the diffractive optical element can be canceled by the diffractive optical element. Thereby, chromatic aberration can be favorably corrected over the entire wavelength range. As described above, when an optical material having a very small partial dispersion ratio is used, chromatic aberration can be corrected well over the entire wavelength range in the entire optical system.

後述する各実施例では異常部分分散材料のうち一般の硝材と比べて部分分散比が高い光学材料を用いて光学系全体で全波長域に渡って色収差を良好に補正している。また、この短波長側の曲がりは光学材料の分散特性の曲がりによるものである。ここで今、単純化のためにｄ線の屈折率とアッベ数が等しい光学材料を例にとって、異常部分分散性が高い材料を用いた場合について説明する。 In each of the embodiments described later, an chromatic aberration is corrected well over the entire wavelength range in the entire optical system by using an optical material having a higher partial dispersion ratio than an ordinary glass material among abnormal partial dispersion materials. Further, this short wavelength side bend is due to the bend of the dispersion characteristic of the optical material. Here, for the sake of simplification, a case where a material having high anomalous partial dispersibility is used will be described by taking an optical material having the same Abbe number as the d-line refractive index as an example.

部分分散比が大きい材料、部分分散比が普通の材料（一般の光学材料）を同じ屈折力でレンズとして使ったとする。この短波長側と長波長側の色収差係数の差をそれぞれΔＮ高、ΔＮ中とすると、これらの関係は以下の式で表される。 It is assumed that a material having a large partial dispersion ratio and a material having a normal partial dispersion ratio (general optical material) are used as a lens with the same refractive power. Assuming that the difference between the chromatic aberration coefficients on the short wavelength side and the long wavelength side is ΔN high and ΔN, respectively, these relationships are expressed by the following equations.

ΔＮ高＞ΔＮ中＞０・・・（ａ）
片方のレンズを異常部分分散の材料で構成した２枚のレンズの組み合わせから成る光学系について説明する。 ΔN high> ΔN medium> 0 (a)
An optical system composed of a combination of two lenses in which one lens is made of an abnormal partial dispersion material will be described.

まず異常部分分散比が普通の材料と異常部分分散比が大きな材料で構成される同じ屈折力のレンズが２枚並んでいるとすると、この光学系の短波長側と長波長側の色収差係数の差は、ΔＮ中＋ΔＮ高となる。これは部分分散比が普通の材料を２枚用いた時と比べると、ΔＮ高−ΔＮ中だけ増えている。したがって、波長依存特性曲線の曲がりの大きい部分分散比が大きな材料を用いた場合は、逆に短波長側の色収差を増やしてしまう。 First, assuming that two lenses having the same refractive power and made of a material having an abnormal partial dispersion ratio and a material having a large abnormal partial dispersion ratio are arranged side by side, the chromatic aberration coefficients of the short wavelength side and the long wavelength side of this optical system are The difference is medium ΔN + ΔN high. This is an increase in ΔN high−ΔN as compared with the case where two normal dispersion ratios are used. Therefore, when a material having a large partial dispersion ratio with a large curve of the wavelength dependence characteristic curve is used, the chromatic aberration on the short wavelength side is increased.

しかし、これは部分分散比が大きな材料と部分分散比が小さな材料を同じ屈折力で用いた場合である。
この状態で部分分散比が大きな材料を用いたレンズの屈折力を正，負逆にする、つまり２枚並んでいるレンズのうち片方のレンズの屈折力を正，負逆にして、そこに部分分散比が大きな材料を用いる。すると部分分散比の大きな材料を用いた場合は、部分分散比が普通の材料を２枚用いたときと比べると逆にΔＮ高−ΔＮ中だけ短波長側の収差を減らすことができる。部分分散比が普通の材料を組み合わせても、色収差係数の波長依存特性曲線の曲がり成分と傾き成分を同時に波長域全体で色収差を良好に補正することは困難である。 However, this is a case where a material having a large partial dispersion ratio and a material having a small partial dispersion ratio are used with the same refractive power.
In this state, the refractive power of the lens using a material having a large partial dispersion ratio is made positive / negative, that is, the refractive power of one of the two lenses arranged side by side is made positive / negative, and there is a partial A material having a large dispersion ratio is used. Then, when a material having a large partial dispersion ratio is used, the aberration on the short wavelength side can be reduced only during ΔN high-ΔN, as compared with the case where two materials having normal partial dispersion ratios are used. Even when materials having an ordinary partial dispersion ratio are combined, it is difficult to correct chromatic aberration satisfactorily in the entire wavelength region at the same time by bending and tilting components of the wavelength dependence characteristic curve of the chromatic aberration coefficient.

そこで部分分散比が大きな材料を、部分分散比が普通の材料とは逆の屈折力で、適切に用いることで色収差を補正することができる。なお、屈折力の正、負が異なるということは、部分分散比が大きな材料と部分分散比が小さな材料では短波長側以外でも逆の作用をする。したがって、それとバランスを取るための光学系の他の硝材の動かし方も逆になる。このことを、望遠レンズでの色消し作用を例にとり説明する。まず、望遠レンズを、部分分散比が大きな材料を用いた屈折光学素子（光学素子）Ｇｒと、それ以外の、部分分散比が大きくない普通の材料を用いた屈折光学素子Ｇに分けて考える。 Therefore, chromatic aberration can be corrected by appropriately using a material having a large partial dispersion ratio with a refractive power opposite to that of a material having a normal partial dispersion ratio. Note that the difference between positive and negative refractive powers has the opposite effect on a material having a large partial dispersion ratio and a material having a small partial dispersion ratio, except for the short wavelength side. Therefore, the method of moving other glass materials of the optical system for balancing with it is also reversed. This will be described by taking the achromatic action with a telephoto lens as an example. First, the telephoto lens is divided into a refractive optical element (optical element) Gr using a material having a large partial dispersion ratio and another refractive optical element G using a normal material having a small partial dispersion ratio.

最初に、屈折光学素子Ｇが部分系としてある程度、色収差が補正された状態から、屈折光学素子Ｇを構成する負レンズに比較的、部分分散比の大きな材料を選択する。ここで一般的に部分分散比の大きな材料は同時に分散が大きいので、屈折光学素子Ｇの色収差係数の波長依存特性曲線は、もとの状態よりも大きく曲がりながら全体の傾きが変化する。 First, a material having a relatively large partial dispersion ratio is selected for the negative lens constituting the refractive optical element G from a state in which the chromatic aberration is corrected to some extent as the refractive optical element G as a partial system. Here, since a material having a large partial dispersion ratio generally has a large dispersion at the same time, the wavelength-dependent characteristic curve of the chromatic aberration coefficient of the refractive optical element G changes as a whole while being bent larger than the original state.

この状態で、第２の屈折光学素子Ｇｒに適当な屈折力を与える。ところが、第２の屈折光学素子Ｇｒをアッベ数に対して一様な異常部分分散比を持つ一般の光学材料で構成している場合、第２の屈折光学素子Ｇｒは、屈折光学素子Ｇの色収差係数の波長依存特性曲線の、曲がり成分と傾き成分に同時に一定の割合で寄与する。
このため、そのどちらの成分も同時にキャンセルすることができない。 In this state, an appropriate refractive power is given to the second refractive optical element Gr. However, when the second refractive optical element Gr is made of a general optical material having a uniform anomalous partial dispersion ratio with respect to the Abbe number, the second refractive optical element Gr is a chromatic aberration of the refractive optical element G. Contributes to the curve component and the slope component of the wavelength dependence characteristic curve of the coefficient simultaneously at a constant rate.
For this reason, neither of these components can be canceled simultaneously.

これに対し、第２の屈折光学素子Ｇｒを一般の光学材料に比べて高い異常部分分散比な材料で構成している場合は、第２の屈折光学素子Ｇｒは主に屈折光学素子Ｇの色収差係数の波長依存特性曲線の全体の曲がり成分に寄与する。このため、主に曲がり成分だけをキャンセルさせることができる。 On the other hand, when the second refractive optical element Gr is made of a material having an extraordinary partial dispersion ratio higher than that of a general optical material, the second refractive optical element Gr is mainly chromatic aberration of the refractive optical element G. This contributes to the entire bending component of the wavelength-dependent characteristic curve of the coefficient. For this reason, it is possible to cancel only the bending component.

その結果、色収差係数の波長依存特性曲線の全体の曲がり成分を第２の屈折光学素子Ｇｒに、傾き成分を屈折光学素子Ｇの他のレンズへと分配することができ、それぞれ独立に同時にキャンセルさせることができる。このため、設計の自由度が増し収差補正が容易になる。また第２の屈折光学素子Ｇｒに材料のアッベ数の絶対値が小さい、すなわち高分散の材料を用いれば、色収差を独立に補正することが容易となるので好ましい。 As a result, the entire bending component of the wavelength-dependent characteristic curve of the chromatic aberration coefficient can be distributed to the second refractive optical element Gr, and the tilt component can be distributed to the other lenses of the refractive optical element G, which are canceled independently at the same time. be able to. For this reason, the degree of freedom in design increases and aberration correction becomes easy. Further, it is preferable to use a material having a small absolute value of the Abbe number of the material for the second refractive optical element Gr, that is, a highly dispersed material, because it becomes easy to independently correct chromatic aberration.

次にこのことをレンズ面の軸上色収差係数及び倍率色収差係数を用いて説明する。屈折レンズ（屈折光学素子）のレンズ面の屈折力変化をΔψとするとレンズ面での軸上色収差係数の変化ΔＬと倍率色収差係数の変化△Ｔは、次のように表せる。 Next, this will be described using the axial chromatic aberration coefficient and the lateral chromatic aberration coefficient of the lens surface. If the refractive power change of the lens surface of the refractive lens (refractive optical element) is Δψ, the change in axial chromatic aberration coefficient ΔL and the change in magnification chromatic aberration coefficient ΔT on the lens surface can be expressed as follows.

ΔＬ ∝ Δψ／ν ・・・（ｂ）
ΔＴ ∝ Δψ／ν ・・・（ｃ）
式（ｂ）及び式（ｃ）から明らかなとおり、レンズ面の屈折力変化に対する各収差係数の変化は、アッベ数の絶対値が小さい（すなわち、分散が大きい）ほど大きくなる。 ΔL ∝ Δψ / ν (b)
ΔT ∝ Δψ / ν (c)
As apparent from the equations (b) and (c), the change in each aberration coefficient with respect to the change in the refractive power of the lens surface increases as the absolute value of the Abbe number decreases (that is, the dispersion increases).

したがって、アッベ数の絶対値が小さい高分散材料を用いれば、必要な色収差を得るための屈折力変化量は小さくて済むことになる。このことは収差論上、球面収差、コマ収差や非点収差などに大きな影響を及ぼすことなく色収差をコントロールでき、色収差補正の独立性が高まることを意味する。逆に、低分散材料を用いると、必要な色収差を得るための屈折力変化量は大きくなり、それに伴って球面収差などの諸収差が大きく変化し、色収差補正の独立性が弱まることになる。 Therefore, if a high dispersion material having a small absolute value of the Abbe number is used, the amount of change in refractive power for obtaining necessary chromatic aberration can be reduced. This means that chromatic aberration can be controlled without greatly affecting spherical aberration, coma aberration, astigmatism, etc. in terms of aberration theory, and the independence of chromatic aberration correction is enhanced. On the other hand, when a low dispersion material is used, the amount of change in refractive power for obtaining the necessary chromatic aberration increases, and accordingly, various aberrations such as spherical aberration change greatly, and the independence of chromatic aberration correction is weakened.

また第２の屈折光学素子Ｇｒは一般の光学材料と組み合わせて使用するため、第２の屈折光学素子Ｇｒに用いられる材料の部分分散比は一般の光学材料とは異なることが必要ではあるが、あまりかけ離れすぎては良くない。あまりに一般の光学材料とかけ離れた材料より成るレンズとして用いた場合、そのレンズ面の色収差係数の波長依存特性曲線の短波長側の曲がりが特に大きくなる。その大きな曲がりを打ち消すためには、他のレンズの屈折力も強くしなければならず、結局、球面収差、コマ収差や非点収差などに大きな影響を及ぼし、収差補正が困難となる。 Since the second refractive optical element Gr is used in combination with a general optical material, the partial dispersion ratio of the material used for the second refractive optical element Gr needs to be different from that of a general optical material. Too far away is not good. When used as a lens made of a material far from a general optical material, the short wavelength side curve of the wavelength dependent characteristic curve of the chromatic aberration coefficient of the lens surface becomes particularly large. In order to cancel out such a large bend, the refractive power of other lenses must be strengthened, which ultimately has a great influence on spherical aberration, coma aberration, astigmatism, and the like, making aberration correction difficult.

つまり、第２の屈折光学素子Ｇｒの材料としては、一般の光学材料に比べて部分分散比が大きな光学材料であり、かつ一般の光学材料と比べて部分分散比がかけ離れすぎないことも重要である。 That is, it is also important that the material of the second refractive optical element Gr is an optical material having a large partial dispersion ratio compared to a general optical material, and that the partial dispersion ratio is not too far compared with a general optical material. is there.

各実施例で特定する光学素子Ｇｒに関する条件式（２ｂ）は、上で説明した原理に基づいて色収差を良好に補正するためのアッベ数と部分分散比の関係を表したものである。条件式（２ｂ）の範囲を外れると色収差の補正が困難になる。なお、条件式（２ｂ）の数値範囲は、以下の範囲とすると更に色収差の補正が容易になる。 Conditional expression (2b) relating to the optical element Gr specified in each example expresses the relationship between the Abbe number and the partial dispersion ratio for satisfactorily correcting chromatic aberration based on the principle described above. If the range of the conditional expression (2b) is not satisfied, it becomes difficult to correct chromatic aberration. If the numerical range of conditional expression (2b) is set to the following range, correction of chromatic aberration is further facilitated.

０．０３４２＜ ΔθｇＦｒ＜０．１４２２・・・（２ｂｂ）
更に望ましくは、条件式（２ｂｂ）の数値範囲を以下に示す範囲とするのが良い。 0.0342 <ΔθgFr <0.1422 (2bb)
More desirably, the numerical value range of the conditional expression (2bb) is set to the following range.

０．０３４２＜ ΔθｇＦｒ＜０．０９７２・・・（２ｂｂｂ）
条件式（１ｂ）は第１の屈折光学素子Ｇｃｒの材料の条件式（１ｂ）で定義される光学係数に関し、主に色収差をバランス良く補正するためのものである。条件式（１ｂ）を外れると色収差をバランス良く補正するのが困難になる。条件式（１ｂ）の数値範囲は、以下の範囲とすると、更にコマ収差、非点収差等の補正が容易になる。 0.0342 <ΔθgFr <0.0972 (2bbb)
Conditional expression (1b) relates to the optical coefficient defined by conditional expression (1b) for the material of the first refractive optical element Gcr, and is mainly for correcting chromatic aberration in a well-balanced manner. If the conditional expression (1b) is not satisfied, it will be difficult to correct chromatic aberration in a balanced manner. If the numerical range of the conditional expression (1b) is set to the following range, correction of coma aberration, astigmatism and the like becomes easier.

２．４４＜ ΔＮｃｒ＜２．８５・・・（１ｂｂ）
条件式（１ｂｂ）は更に望ましくは、以下に示す範囲とするのが良い。 2.44 <ΔNcr <2.85 (1bb)
The conditional expression (1bb) is more preferably in the following range.

２．４４＜ ΔＮｃｒ＜２．７５・・・（１ｂｂｂ）
また、一般にテレフォトタイプでの光学系では、倍率色収差と軸上色収差がアンダーになるため、第１の屈折光学素子Ｇｃｒを負レンズとして用いる場合、あまり高分散の材料を用いるのは良くない。このため、第１の屈折光学素子Ｇｃｒのアッベ数は条件式（１ｃ）を満足するのが良い。 2.44 <ΔNcr <2.75 (1bbb)
In general, in a telephoto type optical system, since lateral chromatic aberration and axial chromatic aberration are under, it is not good to use a material with very high dispersion when the first refractive optical element Gcr is used as a negative lens. For this reason, it is preferable that the Abbe number of the first refractive optical element Gcr satisfies the conditional expression (1c).

望ましくは、条件式（１ｃ）の数値範囲を以下の範囲とすることで、更に良好な色収差の補正が容易になる。 Desirably, by making the numerical range of the conditional expression (1c) the following range, it becomes easier to correct chromatic aberration better.

２０＜ νｃｒ＜７０・・・（１ｃｃ）
条件式（２ｂｂ）は更に望ましくは、以下に示す範囲とするのが良い。 20 <νcr <70 (1cc)
The conditional expression (2bb) is more preferably in the range shown below.

２５＜ νｃｒ＜７０・・・（１ｃｃｃ）
以上のように各実施例によれば、製造が容易で、レンズ全長が短く、かつ、高い光学性能を有する光学系が容易に得られる。 25 <νcr <70 (1 ccc)
As described above, according to each embodiment, an optical system that is easy to manufacture, has a short overall lens length, and has high optical performance can be easily obtained.

各実施例において更に好ましくは次の条件式のうち１以上を満足するのが良い。第１の屈折光学素子Ｇｃｒの空気中における焦点距離をｆｃｒ、第２の屈折光学素子Ｇｒの空気中における焦点距離をｆｒとする。開口絞りＳＰから第１の屈折光学素子Ｇｃｒの入射面までの距離をＬｃｒ、開口絞りＳＰから像面までの距離をＬｉとする。開口絞りＳＰから第２の屈折光学素子Ｇｒの入射面までの距離をＬｒとする。第２の屈折光学素子Ｇｒの材料のアッベ数をνｒとする。このとき、次の条件式のうち１以上を満足するのが良い。 In each embodiment, it is more preferable to satisfy one or more of the following conditional expressions. The focal length of the first refractive optical element Gcr in the air is fcr, and the focal length of the second refractive optical element Gr in the air is fr. Let Lcr be the distance from the aperture stop SP to the incident surface of the first refractive optical element Gcr, and Li be the distance from the aperture stop SP to the image plane. The distance from the aperture stop SP to the incident surface of the second refractive optical element Gr is Lr. The Abbe number of the material of the second refractive optical element Gr is νr. At this time, it is preferable to satisfy one or more of the following conditional expressions.

１０＜νｒ＜６０・・・（３）
０．０５＜｜ｆｃｒ／ｆｒ｜＜１．２０・・・（４）
０．０５＜Ｌｃｒ／Ｌｉ＜０．６０・・・（５）
０．０５＜Ｌｒ／Ｌｉ＜０．６０・・・（６）
条件式（３）は、色収差の補正を良好に行うための第２の屈折光学素子Ｇｒの材料を特定している。条件式（３）を外れると色収差をバランス良く補正するのが困難になる。 10 <νr <60 (3)
0.05 <| fcr / fr | <1.20 (4)
0.05 <Lcr / Li <0.60 (5)
0.05 <Lr / Li <0.60 (6)
Conditional expression (3) specifies the material of the second refractive optical element Gr for satisfactorily correcting chromatic aberration. If the conditional expression (3) is not satisfied, it will be difficult to correct chromatic aberration in a balanced manner.

条件式（３）の数値範囲は、以下の範囲とすると更に色収差の補正が容易になる。 If the numerical range of the conditional expression (3) is set to the following range, correction of chromatic aberration becomes easier.

１０＜νｒ＜４５・・・（３ａ）
更に望ましくは、条件式（３ａ）の数値範囲を以下に示す範囲とするのが良い。 10 <νr <45 (3a)
More desirably, the numerical range of the conditional expression (3a) is set to the following range.

１０＜νｒ＜３０・・・（３ａａ）
更に望ましくは、条件式（３ａａ）の数値範囲を以下に示す範囲とするのが良い。 10 <νr <30 (3aa)
More desirably, the numerical value range of the conditional expression (3aa) is set to the following range.

１０＜νｒ＜２５・・・（３ａａａ）
条件式（４）は、第１の屈折光学素子Ｇｃｒの空気中における焦点距離と、第２の屈折光学素子Ｇｒの空気中における焦点距離との比に関し、主に色収差とコマ収差、非点収差等をバランスよく補正するためのものである。 10 <νr <25 (3aaa)
Conditional expression (4) relates mainly to the ratio between the focal length of the first refractive optical element Gcr in the air and the focal length of the second refractive optical element Gr in the air, and mainly includes chromatic aberration, coma aberration, and astigmatism. Etc. in a well-balanced manner.

条件式（４）の下限値を下回ると、第２の屈折光学素子Ｇｒによる異常部分分散性が弱まり、ｇ線の色収差の補正が困難となる。逆に上限値を上回ると、ｇ線の色収差の補正が過剰となるため、他のレンズの屈折力が大きくなり、コマ収差の補正が困難になってくる。条件式（４）の数値範囲は、以下の範囲とすると、収差補正が更に容易になる。 If the lower limit value of conditional expression (4) is not reached, the anomalous partial dispersibility due to the second refractive optical element Gr is weakened, and it becomes difficult to correct the chromatic aberration of the g-line. On the contrary, if the value exceeds the upper limit value, the correction of the chromatic aberration of the g-line becomes excessive, so that the refractive power of the other lens becomes large and it becomes difficult to correct the coma aberration. When the numerical range of conditional expression (4) is set to the following range, aberration correction is further facilitated.

０．１＜｜ｆｃｒ／ｆｒ｜＜１．０・・・（４ａ）
軸上色収差と倍率色収差を共にバランス良く補正するためには、軸上光束と軸外光束が共にある程度高い位置を通過する位置に、前述した条件式を満足する第１の屈折光学素子Ｇｃｒや、第２の屈折光学素子Ｇｒを配置することが好ましい。 0.1 <| fcr / fr | <1.0 (4a)
In order to correct both axial chromatic aberration and lateral chromatic aberration in a well-balanced manner, the first refractive optical element Gcr that satisfies the above-described conditional expression at a position where both the on-axis light beam and the off-axis light beam pass through a somewhat high position, It is preferable to arrange the second refractive optical element Gr.

条件式（５）は開口絞りＳＰから第１の屈折光学素子Ｇｃｒまでの距離と、開口絞りＳＰから像面までの距離の比に関し、主に色収差や他の諸収差を良好に補正するためのものである。条件式（６）は開口絞りＳＰから第２の屈折光学素子Ｇｒまでの距離と開口絞りＳＰから像面までの距離の比に関し、主に色収差や他の諸収差をバランス良く補正するためのものである。条件式（５）や条件式（６）において、下限値を下回ると倍率色収差の補正が困難となり、また上限値を上回ると軸上色収差の補正が困難となる。更に好ましくは条件式（５），（６）の数値範囲を次の如く設定するのが良い。 Conditional expression (5) relates to the ratio of the distance from the aperture stop SP to the first refractive optical element Gcr and the distance from the aperture stop SP to the image plane, mainly for satisfactorily correcting chromatic aberration and other various aberrations. Is. Conditional expression (6) relates to the ratio of the distance from the aperture stop SP to the second refractive optical element Gr and the distance from the aperture stop SP to the image plane, mainly for correcting chromatic aberration and other aberrations in a well-balanced manner. It is. In conditional expression (5) and conditional expression (6), if the lower limit value is not reached, it will be difficult to correct lateral chromatic aberration, and if it exceeds the upper limit value, it will be difficult to correct axial chromatic aberration. More preferably, the numerical ranges of conditional expressions (5) and (6) are set as follows.

０．１＜Ｌｃｒ／Ｌｉ＜０．５・・・（５ａ）
０．１＜Ｌｒ／Ｌｉ＜０．５・・・（６ａ）
また本発明の光学系を撮像素子を有する光学機器に用いるときには次の条件式を満足するのが良い。光学系のレンズ全長をＬｔ、光学系の焦点距離をｆｔ、撮影半画角をω（度）とする。このとき、
Ｌｔ／ｆｔ＋０．９３（度）／ω＜１．２５・・・（７）
なる条件式を満たすのが良い。 0.1 <Lcr / Li <0.5 (5a)
0.1 <Lr / Li <0.5 (6a)
In addition, when the optical system of the present invention is used in an optical apparatus having an image sensor, the following conditional expression should be satisfied. Assume that the total lens length of the optical system is Lt, the focal length of the optical system is ft, and the shooting half angle of view is ω (degrees). At this time,
Lt / ft + 0.93 (degrees) / ω <1.25 (7)
It is good to satisfy the following conditional expression.

条件式（７）は、テレフォトタイプの光学系において、レンズ全長と、全系の焦点距離、そして撮影半画角を適切に設定し、主に色収差や他の諸収差をバランス良く補正するためのものである。条件式（７）において、Ｌｔ／ｆｔは、一般に望遠比と呼ばれる値であり、焦点距離が長くなる程（画角が小さくなる程）小さい値を取りやすい傾向にある。条件式（７）を外れるとレンズ全長を短くしつつ、諸収差の補正を良好に行い、高い光学性能を得るのが困難になる。更に望ましくは、条件式（７）の数値範囲を以下の範囲とすると、全系のコンパクトを図りつつ諸収差の補正が容易になる。 Conditional expression (7) is for appropriately setting the overall lens length, the focal length of the entire system, and the shooting half angle of view in a telephoto type optical system, and mainly correcting chromatic aberration and other aberrations in a well-balanced manner. belongs to. In the conditional expression (7), Lt / ft is a value generally called a telephoto ratio, and tends to take a smaller value as the focal length becomes longer (the angle of view becomes smaller). If the conditional expression (7) is deviated, it becomes difficult to correct various aberrations and obtain high optical performance while shortening the total lens length. More desirably, when the numerical range of conditional expression (7) is set to the following range, correction of various aberrations is facilitated while achieving compactness of the entire system.

Ｌｔ／ｆｔ＋０．９３（度）／ω ＜１．２３・・・（７ａ）
さらに望ましくは、条件式（７ａ）を以下に示す範囲とするのが良い。 Lt / ft + 0.93 (degrees) / ω <1.23 (7a)
More desirably, conditional expression (7a) should be in the range shown below.

Ｌｔ／ｆｔ＋０．９３（度）／ω ＜１．２０・・・（７ａａ）
次に、条件式（１）乃至（７）を満足する光学系の実施例の具体例について説明する。なお、条件式（１）乃至（７）とは、例えば（２ａ）式や（２ｂ）式、もしくは（２ｂｂｂ）などの付随した式も含むものである。以下の実施例において、条件式（２）及び（３）を満足する材料として、ＵＶ硬化樹脂１、及びＮ−ポリビニルカルバゾールを用いている。 Lt / ft + 0.93 (degrees) / ω <1.20 (7aa)
Next, specific examples of examples of the optical system that satisfy the conditional expressions (1) to (7) are described. The conditional expressions (1) to (7) include accompanying expressions such as (2a), (2b), and (2bbb). In the following examples, UV curable resin 1 and N-polyvinylcarbazole are used as materials satisfying conditional expressions (2) and (3).

［実施例１］
実施例１の光学系は、焦点距離５８８ｍｍ、撮影画角２ωが４．２２度、Ｆナンバー４．１２である。実施例１ではＵＶ硬化樹脂１より成る第２の屈折光学素子Ｇｒと、イットリウム・アルミニウム・ガーネット・セラミックスよりなる第１の屈折光学素子Ｇｃｒを用いている。イットリウム・アルミニウム・ガーネットは、「ＹＡＧ」とも呼ばれ、Ｙ_３Ａ_１５Ｏ_１２で表される可視光領域で透明な酸化物である。 [Example 1]
The optical system of Example 1 has a focal length of 588 mm, a shooting angle of view 2ω of 4.22 degrees, and an F number of 4.12. In the first embodiment, the second refractive optical element Gr made of the UV curable resin 1 and the first refractive optical element Gcr made of yttrium, aluminum, garnet, and ceramics are used. Yttrium aluminum garnet is also called “YAG”, and is an oxide that is transparent in the visible light region and is represented by Y ₃ A ₁₅ O ₁₂ .

なおＹＡＧは単結晶でもセラミックスと同等の光学特性を有しており、セラミックスの代わりに単結晶を第１の屈折光学素子Ｇｃｒの材料に用いても同様の効果が得られる。またセラミックスの製造条件等により、上記の屈折率とアッベ数の値は若干変化するが実用上全く問題ない。 Note that YAG has optical characteristics equivalent to those of ceramics even in a single crystal, and the same effect can be obtained even if a single crystal is used as the material of the first refractive optical element Gcr instead of ceramics. The refractive index and the Abbe number slightly vary depending on the ceramic manufacturing conditions, but there is no practical problem.

実施例１の光学系では、開口絞りよりも像側の第３レンズ群Ｌ３において軸上光束と軸外光束が共に高い位置において、第１の屈折光学素子Ｇｃｒと通常レンズの張り合わせレンズ面中にＵＶ硬化樹脂１からなる第２の屈折光学素子Ｇｒを導入している。その結果、レンズ全長が短く、軸上色収差、倍率色収差、コマ収差、非点隔差等が良好に補正されつつ、耐環境性にも優れた光学系を得ている。 In the optical system of the first embodiment, in the third lens unit L3 on the image side of the aperture stop, at the position where both the on-axis light beam and the off-axis light beam are higher, the first refractive optical element Gcr and the normal lens are in the cemented lens surface. A second refractive optical element Gr made of UV curable resin 1 is introduced. As a result, an optical system that has a short overall lens length, is well corrected for axial chromatic aberration, lateral chromatic aberration, coma aberration, astigmatism, and the like, and also has excellent environmental resistance.

［実施例２］
実施例２の光学系は、焦点距離５８８ｍｍ、撮影画角２ωが４．２２度、Ｆナンバー４．１２である。実施例２ではＵＶ硬化樹脂１より成る第２の屈折光学素子Ｇｒと、スピネル結晶からなる第１の屈折光学素子Ｇｃｒを用いている。スピネル結晶は、Ｍ_ｇＡｌ_２Ｏ_４で表される可視光領域で透明な酸化物である。 [Example 2]
The optical system of Example 2 has a focal length of 588 mm, a shooting field angle 2ω of 4.22 degrees, and an F number of 4.12. In Example 2, the second refractive optical element Gr made of the UV curable resin 1 and the first refractive optical element Gcr made of a spinel crystal are used. The spinel crystal is an oxide that is transparent in the visible light region represented by M _g Al ₂ O ₄ .

実施例２の光学系においても、実施例１と同様に、開口絞りＳＰよりも像側の第３レンズ群Ｌ３に第２の屈折光学素子Ｇｒと第１の屈折光学素子Ｇｃｒを共に用いている。これにより光学全長が短く、軸上色収差、倍率色収差、コマ収差、非点隔差等が良好に補正されつつ、耐環境性にも優れた光学系を得ている。 In the optical system of Example 2, as in Example 1, both the second refractive optical element Gr and the first refractive optical element Gcr are used for the third lens unit L3 on the image side of the aperture stop SP. . As a result, the optical total length is short, and an optical system excellent in environmental resistance is obtained while axial chromatic aberration, lateral chromatic aberration, coma aberration, astigmatism and the like are corrected well.

［実施例３］
実施例３の光学系は、焦点距離５８８ｍｍ、撮影画角２ωが４．２２度、Ｆナンバー４．１２である。実施例３ではＵＶ硬化樹脂１より成る第２の屈折光学素子Ｇｒと、株式会社村田製作所社製の透光性セラミックス「ルミセラ」（登録商標）からなる第１の屈折光学素子Ｇｃｒを用いている。実施例３の光学系では、第１の屈折光学素子Ｇｃｒの物体側に配置した正レンズの像側のレンズ面に第２の屈折光学素子Ｇｒからなる層（面）を配置している。その結果、レンズ全長が短く、軸上色収差、倍率色収差、コマ収差、非点隔差等が良好に補正された光学系を得ている。 [Example 3]
The optical system of Example 3 has a focal length of 588 mm, a shooting field angle 2ω of 4.22 degrees, and an F number of 4.12. In Example 3, the second refractive optical element Gr made of the UV curable resin 1 and the first refractive optical element Gcr made of translucent ceramics “Lumicera” (registered trademark) manufactured by Murata Manufacturing Co., Ltd. are used. . In the optical system of Example 3, the layer (surface) made of the second refractive optical element Gr is arranged on the image side lens surface of the positive lens arranged on the object side of the first refractive optical element Gcr. As a result, an optical system is obtained in which the overall lens length is short and axial chromatic aberration, lateral chromatic aberration, coma aberration, astigmatism, etc. are well corrected.

［実施例４］
実施例４の光学系は、焦点距離５８８ｍｍ、撮影画角２ωが４．２２度、Ｆナンバー４．１２である。実施例４ではＮ−ポリビニルカルバゾール（ＰｖＣｚ）より成る第２の屈折光学素子Ｇｒと、ＹＡＧからなる第１の屈折光学素子Ｇｃｒを用いている。実施例４の光学系では、開口絞りＳＰに近い位置に２つのレンズに挟まれた第２の屈折光学素子Ｇｒを用い、かつ開口絞りＳＰから少し離れた位置に第１の屈折光学素子Ｇｃｒを配置している。その結果、レンズ全長が短く、軸上色収差、倍率色収差、コマ収差、非点隔差等が良好に補正された光学系を得ている。 [Example 4]
The optical system of Example 4 has a focal length of 588 mm, a shooting field angle 2ω of 4.22 degrees, and an F number of 4.12. In Example 4, a second refractive optical element Gr made of N-polyvinylcarbazole (PvCz) and a first refractive optical element Gcr made of YAG are used. In the optical system of Example 4, the second refractive optical element Gr sandwiched between the two lenses is used at a position close to the aperture stop SP, and the first refractive optical element Gcr is provided at a position slightly away from the aperture stop SP. It is arranged. As a result, an optical system is obtained in which the overall lens length is short and axial chromatic aberration, lateral chromatic aberration, coma aberration, astigmatism, etc. are well corrected.

［実施例５］
実施例５の光学系は、焦点距離５８８ｍｍ、撮影画角２ωが４．２２度、Ｆナンバー４．１２である。実施例５ではＵＶ硬化樹脂１より成る第２の屈折光学素子Ｇｒと、ＹＡＧからなる第１の屈折光学素子Ｇｃｒを用いている。実施例５の光学系では、開口絞りＳＰよりも物体側の第１レンズ群Ｌ１の第２レンズ面に回折光学面を設けており、実施例１乃至４に対して、さらにレンズ全長が短縮されつつ、軸上色収差、倍率色収差、コマ収差、非点隔差等が良好に補正された光学系を得ている。 [Example 5]
The optical system of Example 5 has a focal length of 588 mm, a shooting field angle 2ω of 4.22 degrees, and an F number of 4.12. In Example 5, the second refractive optical element Gr made of the UV curable resin 1 and the first refractive optical element Gcr made of YAG are used. In the optical system of Example 5, a diffractive optical surface is provided on the second lens surface of the first lens unit L1 closer to the object side than the aperture stop SP, and the total lens length is further shortened compared to Examples 1 to 4. On the other hand, an optical system in which axial chromatic aberration, lateral chromatic aberration, coma aberration, astigmatism and the like are well corrected is obtained.

以下、本発明の実施例１乃至５に対応する数値実施例１乃至５の具体的な数値データを示す。各数値実施例において、ｉは物体側から数えた順序を示し、Ｒｉは第ｉ番目の光学面（第ｉ面）の曲率半径、Ｄｉは第ｉ面と第（ｉ＋１）面との間の軸上間隔を示す。Ｎｉ，νｉはそれぞれｄ線に対する第ｉ番目（第２の屈折光学素子Ｇｒと第１の屈折光学素子Ｇｃｒからなるレンズ（層）は除く）の光学部材の材料の屈折率、アッベ数を示す。 Hereinafter, specific numerical data of numerical examples 1 to 5 corresponding to the first to fifth embodiments of the present invention will be shown. In each numerical example, i indicates the order counted from the object side, Ri is the radius of curvature of the i-th optical surface (i-th surface), and Di is the axis between the i-th surface and the (i + 1) -th surface. Indicates the top spacing. Ni and νi represent the refractive index and Abbe number of the material of the optical member of the i-th (excluding the lens (layer) composed of the second refractive optical element Gr and the first refractive optical element Gcr) with respect to the d line.

第２の屈折光学素子Ｇｒのｄ線に対する屈折率、アッベ数は別途Ｎｒｊ，νｒｊ（ｊ＝１，２，・・・）で示している。同様に、第１の屈折光学素子Ｇｃｒのｄ線に対する屈折率、アッベ数は別途Ｎｃｒｊ，νｃｒｊ（ｊ＝１，２，・・・）で示している。ｆは焦点距離、ＦｎｏはＦナンバー、ωは半画角である。また、実施例５における回折光学面は、光軸に対し回転対称な回折格子により構成されており、その位相φ（ｈ）は、 The refractive index and Abbe number for the d-line of the second refractive optical element Gr are separately indicated by Nrj, νrj (j = 1, 2,...). Similarly, the refractive index and Abbe number of the first refractive optical element Gcr with respect to the d-line are separately indicated as Ncrj, νcrj (j = 1, 2,...). f is a focal length, Fno is an F number, and ω is a half angle of view. Further, the diffractive optical surface in Example 5 is configured by a diffraction grating that is rotationally symmetric with respect to the optical axis, and the phase φ (h) is

ただし、λ：波長、Ｃｉ：非球面位相係数、ｈ：光軸からの高さ
で表せる。なお、式（ｄ）中のλは、５８７．５６ｎｍ（ｄ線）と設定している。また、各位相係数における「Ｅ±ＸＸ」は「×１０±ＸＸ」を意味している。表１にＵＶ硬化樹脂１とＰｖＣｚの光学常数を示す。表２に前述した各条件式と数値実施例との関係を示す。 However, it can be expressed by λ: wavelength, Ci: aspherical phase coefficient, and h: height from the optical axis. In the equation (d), λ is set to 587.56 nm (d line). Further, “E ± XX” in each phase coefficient means “× 10 ± XX”. Table 1 shows the optical constants of the UV curable resin 1 and PvCz. Table 2 shows the relationship between the above-described conditional expressions and numerical examples.

（数値実施例１）
ｆ＝５８８Ｆｎｏ＝４．１２２ω＝４．２２°
R 1= 260.942 D 1= 20.94 N 1= 1.4339 ν 1= 95.1
R 2= -576.180 D 2= 10.00
R 3= 142.741 D 3= 17.90 N 2= 1.4339 ν 2= 95.1
R 4= 1382.286 D 4= 3.90
R 5= -884.776 D 5= 6.08 N 3= 1.8503 ν 3= 32.3
R 6= 184.642 D 6= 11.90 N 4= 1.8081 ν 4= 22.8
R 7= 497.116 D 7= 14.48
R 8= 121.477 D 8= 16.68 N 5= 1.4339 ν 5= 95.1
R 9= 5214.657 D 9= 0.52
R10= 73.243 D10= 4.60 N 6= 1.8467 ν 6= 23.9
R11= 62.400 D11= 47.92
R12= 395.072 D12= 5.11 N 7= 1.8081 ν 7= 22.8
R13=-2767.155 D13= 3.30 N 8= 1.7880 ν 8= 47.4
R14= 143.685 D14= 83.98
R15= ∞（絞り） D15= 14.55
R16= 240.398 D16= 1.70 N 9= 1.8467 ν 9= 23.9
R17= 34.491 D17= 7.74 N10= 1.6541 ν10= 39.7
R18= -179.742 D18= 5.03
R19= 68.610 D19= 1.90 N11= 1.8467 ν11= 23.9
R20= -273.494 D20= 1.50 N12= 1.7725 ν12= 49.6
R21= 35.632 D21= 1.95
R22= -126.970 D22= 1.50 N13= 1.7410 ν13= 52.6
R23= 50.784 D23= 3.00
R24= 42.077 D24= 8.03 N14= 1.6541 ν14= 39.7
R25= -25.521 D25= 0.20 Nr1= 1.6356 νr1= 22.7
R26= -33.461 D26= 1.20 Ncr1=1.8300 νcr1=53.0
R27= -847.690 D27= 7.57
R28= -57.356 D28= 1.50 N15= 1.6180 ν15= 63.3
R29= 38.483 D29= 6.20 N16= 1.5174 ν16= 52.4
R30= -56.679 D30= 1.00
R31= 70.933 D31= 3.86 N17= 1.5225 ν17= 59.8
R32= -191.616 D32= 1.00
R33= ∞ D33= 2.00 N18= 1.5163 ν18= 64.1
R34= ∞

バックフォーカスBF＝56.0
レンズ全長Lt=374.7
(Numerical example 1)
f = 588 Fno = 4.12 2ω = 4.22 °
R 1 = 260.942 D 1 = 20.94 N 1 = 1.4339 ν 1 = 95.1
R 2 = -576.180 D 2 = 10.00
R 3 = 142.741 D 3 = 17.90 N 2 = 1.4339 ν 2 = 95.1
R 4 = 1382.286 D 4 = 3.90
R 5 = -884.776 D 5 = 6.08 N 3 = 1.8503 ν 3 = 32.3
R 6 = 184.642 D 6 = 11.90 N 4 = 1.8081 ν 4 = 22.8
R 7 = 497.116 D 7 = 14.48
R 8 = 121.477 D 8 = 16.68 N 5 = 1.4339 ν 5 = 95.1
R 9 = 5214.657 D 9 = 0.52
R10 = 73.243 D10 = 4.60 N 6 = 1.8467 ν 6 = 23.9
R11 = 62.400 D11 = 47.92
R12 = 395.072 D12 = 5.11 N 7 = 1.8081 ν 7 = 22.8
R13 = -2767.155 D13 = 3.30 N 8 = 1.7880 ν 8 = 47.4
R14 = 143.685 D14 = 83.98
R15 = ∞ (aperture) D15 = 14.55
R16 = 240.398 D16 = 1.70 N 9 = 1.8467 ν 9 = 23.9
R17 = 34.491 D17 = 7.74 N10 = 1.6541 ν10 = 39.7
R18 = -179.742 D18 = 5.03
R19 = 68.610 D19 = 1.90 N11 = 1.8467 ν11 = 23.9
R20 = -273.494 D20 = 1.50 N12 = 1.7725 ν12 = 49.6
R21 = 35.632 D21 = 1.95
R22 = -126.970 D22 = 1.50 N13 = 1.7410 ν13 = 52.6
R23 = 50.784 D23 = 3.00
R24 = 42.077 D24 = 8.03 N14 = 1.6541 ν14 = 39.7
R25 = -25.521 D25 = 0.20 Nr1 = 1.6356 νr1 = 22.7
R26 = -33.461 D26 = 1.20 Ncr1 = 1.8300 νcr1 = 53.0
R27 = -847.690 D27 = 7.57
R28 = -57.356 D28 = 1.50 N15 = 1.6180 ν15 = 63.3
R29 = 38.483 D29 = 6.20 N16 = 1.5174 ν16 = 52.4
R30 = -56.679 D30 = 1.00
R31 = 70.933 D31 = 3.86 N17 = 1.5225 ν17 = 59.8
R32 = -191.616 D32 = 1.00
R33 = ∞ D33 = 2.00 N18 = 1.5163 ν18 = 64.1
R34 = ∞

Back focus BF = 56.0
Total lens length Lt = 374.7

（数値実施例２）
ｆ＝５８８Ｆｎｏ＝４．１２ ω＝４．２２°
R 1= 252.353 D 1= 18.91 N 1= 1.4339 ν 1= 95.1
R 2= -513.551 D 2= 5.00
R 3= 139.542 D 3= 18.82 N 2= 1.4339 ν 2= 95.1
R 4= 1513.469 D 4= 3.85
R 5= -873.461 D 5= 6.23 N 3= 1.8830 ν 3= 40.8
R 6= 254.068 D 6= 6.61 N 4= 1.8081 ν 4= 22.8
R 7= 410.918 D 7= 21.32
R 8= 124.138 D 8= 17.18 N 5= 1.4339 ν 5= 95.1
R 9=-7953.771 D 9= 1.72
R10= 73.258 D10= 4.60 N 6= 1.8467 ν 6= 23.9
R11= 62.447 D11= 50.92
R12= 358.633 D12= 5.31 N 7= 1.7847 ν 7= 25.7
R13=-1537.151 D13= 3.30 N 8= 1.7725 ν 8= 49.6
R14= 128.886 D14= 84.97
R15= ∞（絞り） D15= 11.21
R16= 179.944 D16= 1.70 N 9= 1.8467 ν 9= 23.9
R17= 41.985 D17= 7.76 N10= 1.6134 ν10= 44.3
R18= -272.955 D18= 5.12
R19= 69.063 D19= 3.31 N11= 1.8467 ν11= 23.9
R20= -153.975 D20= 1.50 N12= 1.7725 ν12= 49.6
R21= 38.028 D21= 2.04
R22= -102.592 D22= 1.50 N13= 1.7292 ν13= 54.7
R23= 54.461 D23= 3.00
R24= 45.045 D24= 5.57 N14= 1.6134 ν14= 44.3
R25= -29.871 D25= 0.20 Nr1= 1.6356 νr1= 22.7
R26= -45.127 D26= 1.20 Ncr1=1.7200 νcr1=63.0
R27= -347.668 D27= 7.40
R28= -55.101 D28= 1.43 N15= 1.6180 ν15= 63.3
R29= 37.791 D29= 5.75 N16= 1.5174 ν16= 52.4
R30= -59.295 D30= 1.00
R31= 72.154 D31= 3.51 N17= 1.5225 ν17= 59.8
R32= -221.013 D32= 1.00
R33= ∞ D33= 2.00 N18= 1.5163 ν18= 64.1
R34= ∞

バックフォーカスBF＝63.7
レンズ全長Lt=378.6
(Numerical example 2)
f = 588 Fno = 4.12 ω = 4.22 °
R 1 = 252.353 D 1 = 18.91 N 1 = 1.4339 ν 1 = 95.1
R 2 = -513.551 D 2 = 5.00
R 3 = 139.542 D 3 = 18.82 N 2 = 1.4339 ν 2 = 95.1
R 4 = 1513.469 D 4 = 3.85
R 5 = -873.461 D 5 = 6.23 N 3 = 1.8830 ν 3 = 40.8
R 6 = 254.068 D 6 = 6.61 N 4 = 1.8081 ν 4 = 22.8
R 7 = 410.918 D 7 = 21.32
R 8 = 124.138 D 8 = 17.18 N 5 = 1.4339 ν 5 = 95.1
R 9 = -7953.771 D 9 = 1.72
R10 = 73.258 D10 = 4.60 N 6 = 1.8467 ν 6 = 23.9
R11 = 62.447 D11 = 50.92
R12 = 358.633 D12 = 5.31 N 7 = 1.7847 ν 7 = 25.7
R13 = -1537.151 D13 = 3.30 N 8 = 1.7725 ν 8 = 49.6
R14 = 128.886 D14 = 84.97
R15 = ∞ (aperture) D15 = 11.21
R16 = 179.944 D16 = 1.70 N 9 = 1.8467 ν 9 = 23.9
R17 = 41.985 D17 = 7.76 N10 = 1.6134 ν10 = 44.3
R18 = -272.955 D18 = 5.12
R19 = 69.063 D19 = 3.31 N11 = 1.8467 ν11 = 23.9
R20 = -153.975 D20 = 1.50 N12 = 1.7725 ν12 = 49.6
R21 = 38.028 D21 = 2.04
R22 = -102.592 D22 = 1.50 N13 = 1.7292 ν13 = 54.7
R23 = 54.461 D23 = 3.00
R24 = 45.045 D24 = 5.57 N14 = 1.6134 ν14 = 44.3
R25 = -29.871 D25 = 0.20 Nr1 = 1.6356 νr1 = 22.7
R26 = -45.127 D26 = 1.20 Ncr1 = 1.7200 νcr1 = 63.0
R27 = -347.668 D27 = 7.40
R28 = -55.101 D28 = 1.43 N15 = 1.6180 ν15 = 63.3
R29 = 37.791 D29 = 5.75 N16 = 1.5174 ν16 = 52.4
R30 = -59.295 D30 = 1.00
R31 = 72.154 D31 = 3.51 N17 = 1.5225 ν17 = 59.8
R32 = -221.013 D32 = 1.00
R33 = ∞ D33 = 2.00 N18 = 1.5163 ν18 = 64.1
R34 = ∞

Back focus BF = 63.7
Total lens length Lt = 378.6

（数値実施例３）
ｆ＝５８８Ｆｎｏ＝４．１２ ω＝４．２２°

R 1= 242.093 D 1= 19.56 N 1= 1.4339 ν 1= 95.1
R 2= -500.240 D 2= 8.62
R 3= 141.261 D 3= 18.17 N 2= 1.4339 ν 2= 95.1
R 4= 1141.847 D 4= 4.48
R 5= -863.328 D 5= 7.47 N 3= 1.8830 ν 3= 40.8
R 6= 268.772 D 6= 7.39 N 4= 1.8081 ν 4= 22.8
R 7= 435.995 D 7= 17.89
R 8= 123.557 D 8= 16.55 N 5= 1.4339 ν 5= 95.1
R 9=18375.484 D 9= 0.75
R10= 72.580 D10= 4.55 N 6= 1.8467 ν 6= 23.9
R11= 62.457 D11= 45.58
R12= 333.734 D12= 3.02 N 7= 1.8467 ν 7= 23.9
R13=15364.022 D13= 3.30 N 8= 1.8348 ν 8= 42.7
R14= 146.731 D14= 81.75
R15= ∞（絞り） D15= 4.26
R16= 153.143 D16= 1.70 N 9= 1.8467 ν 9= 23.9
R17= 37.161 D17= 4.15 N10= 1.6129 ν10= 37.0
R18= -261.754 D18= 8.13
R19= 66.479 D19= 1.60 N11= 1.8467 ν11= 23.9
R20= 118.575 D20= 1.50 N12= 1.8160 ν12= 46.6
R21= 43.064 D21= 1.93
R22= -112.845 D22= 1.50 N13= 1.7292 ν13= 54.7
R23= 66.039 D23= 3.89
R24= 69.117 D24= 5.93 N14= 1.7618 ν14= 26.5
R25= -38.767 D25= 0.20 Nr1= 1.6356 νr1 =22.7
R26= -63.606 D26= 0.80
R27= -58.352 D27= 2.82 Ncr1=2.0820 νcr1=30.1
R28= -821.645 D28= 21.81
R29= -53.902 D29= 2.45 N15= 1.6031 ν15= 60.6
R30= -162.846 D30= 2.71 N16= 1.5481 ν16= 45.8
R31= -56.212 D31= 2.16
R32= 152.609 D32= 6.34 N17= 1.5481 ν17= 45.8
R33= -143.608 D33= 1.00
R34= ∞ D34= 2.00 N18= 1.5163 ν18= 64.1
R35= ∞

バックフォーカスBF＝62.6
レンズ全長Lt=378.6
(Numerical Example 3)
f = 588 Fno = 4.12 ω = 4.22 °

R 1 = 242.093 D 1 = 19.56 N 1 = 1.4339 ν 1 = 95.1
R 2 = -500.240 D 2 = 8.62
R 3 = 141.261 D 3 = 18.17 N 2 = 1.4339 ν 2 = 95.1
R 4 = 1141.847 D 4 = 4.48
R 5 = -863.328 D 5 = 7.47 N 3 = 1.8830 ν 3 = 40.8
R 6 = 268.772 D 6 = 7.39 N 4 = 1.8081 ν 4 = 22.8
R 7 = 435.995 D 7 = 17.89
R 8 = 123.557 D 8 = 16.55 N 5 = 1.4339 ν 5 = 95.1
R 9 = 18375.484 D 9 = 0.75
R10 = 72.580 D10 = 4.55 N 6 = 1.8467 ν 6 = 23.9
R11 = 62.457 D11 = 45.58
R12 = 333.734 D12 = 3.02 N 7 = 1.8467 ν 7 = 23.9
R13 = 15364.022 D13 = 3.30 N 8 = 1.8348 ν 8 = 42.7
R14 = 146.731 D14 = 81.75
R15 = ∞ (aperture) D15 = 4.26
R16 = 153.143 D16 = 1.70 N 9 = 1.8467 ν 9 = 23.9
R17 = 37.161 D17 = 4.15 N10 = 1.6129 ν10 = 37.0
R18 = -261.754 D18 = 8.13
R19 = 66.479 D19 = 1.60 N11 = 1.8467 ν11 = 23.9
R20 = 118.575 D20 = 1.50 N12 = 1.8160 ν12 = 46.6
R21 = 43.064 D21 = 1.93
R22 = -112.845 D22 = 1.50 N13 = 1.7292 ν13 = 54.7
R23 = 66.039 D23 = 3.89
R24 = 69.117 D24 = 5.93 N14 = 1.7618 ν14 = 26.5
R25 = -38.767 D25 = 0.20 Nr1 = 1.6356 νr1 = 22.7
R26 = -63.606 D26 = 0.80
R27 = -58.352 D27 = 2.82 Ncr1 = 2.0820 νcr1 = 30.1
R28 = -821.645 D28 = 21.81
R29 = -53.902 D29 = 2.45 N15 = 1.6031 ν15 = 60.6
R30 = -162.846 D30 = 2.71 N16 = 1.5481 ν16 = 45.8
R31 = -56.212 D31 = 2.16
R32 = 152.609 D32 = 6.34 N17 = 1.5481 ν17 = 45.8
R33 = -143.608 D33 = 1.00
R34 = ∞ D34 = 2.00 N18 = 1.5163 ν18 = 64.1
R35 = ∞

Back focus BF = 62.6
Total lens length Lt = 378.6

（数値実施例４）
ｆ＝５８８Ｆｎｏ＝４．１２ ω＝４．２２°
R 1= 275.769 D 1= 18.00 N 1= 1.4388 ν 1= 94.9
R 2= -505.917 D 2= 11.07
R 3= 148.642 D 3= 17.51 N 2= 1.4388 ν 2= 94.9
R 4= 1791.191 D 4= 3.66
R 5= -846.604 D 5= 6.09 N 3= 1.8503 ν 3= 32.3
R 6= 195.236 D 6= 11.08 N 4= 1.8081 ν 4= 22.8
R 7= 512.503 D 7= 21.33
R 8= 121.626 D 8= 17.60 N 5= 1.4339 ν 5= 95.1
R 9= 3897.906 D 9= 0.50
R10= 72.948 D10= 4.60 N 6= 1.8467 ν 6= 23.9
R11= 62.397 D11= 46.94
R12= 473.016 D12= 5.53 N 7= 1.8081 ν 7= 22.8
R13= -994.519 D13= 3.20 N 8= 1.7880 ν 8= 47.4
R14= 146.895 D14= 76.00
R15= ∞（絞り） D15= 15.40
R16= 218.726 D16= 1.70 N 9= 1.8348 ν 9= 42.7
R17= 40.671 D17= 0.30 Nr1 =1.6959 νr1= 17.7
R18= 34.674 D18= 8.00 N10= 1.6400 ν10= 60.1
R19= -157.893 D19= 6.83
R20= 76.572 D20= 2.45 N11= 1.8052 ν11= 25.4
R21= -351.911 D21= 1.58 N12= 1.7725 ν12= 49.6
R22= 38.188 D22= 1.85
R23= -166.301 D23= 1.20 N13= 1.7292 ν13= 54.7
R24= 50.963 D24= 4.83
R25= 45.504 D25= 5.64 N14= 1.6134 ν14= 44.3
R26= -39.853 D26= 1.20 Ncr1=1.8300 νcr1=53.0
R27= -647.356 D27= 7.72
R28= -54.671 D28= 1.53 N15= 1.6180 ν15= 63.3
R29= 44.337 D29= 5.86 N16= 1.5163 ν16= 64.1
R30= -59.066 D30= 1.00
R31= 84.225 D31= 4.06 N17= 1.5174 ν17= 52.4
R32= -120.519 D32= 1.00
R33= ∞ D33= 2.00 N18= 1.5163 ν18= 64.1
R34= ∞

バックフォーカスBF＝59.7
レンズ全長Lt=377.0
(Numerical example 4)
f = 588 Fno = 4.12 ω = 4.22 °
R 1 = 275.769 D 1 = 18.00 N 1 = 1.4388 ν 1 = 94.9
R 2 = -505.917 D 2 = 11.07
R 3 = 148.642 D 3 = 17.51 N 2 = 1.4388 ν 2 = 94.9
R 4 = 1791.191 D 4 = 3.66
R 5 = -846.604 D 5 = 6.09 N 3 = 1.8503 ν 3 = 32.3
R 6 = 195.236 D 6 = 11.08 N 4 = 1.8081 ν 4 = 22.8
R 7 = 512.503 D 7 = 21.33
R 8 = 121.626 D 8 = 17.60 N 5 = 1.4339 ν 5 = 95.1
R 9 = 3897.906 D 9 = 0.50
R10 = 72.948 D10 = 4.60 N 6 = 1.8467 ν 6 = 23.9
R11 = 62.397 D11 = 46.94
R12 = 473.016 D12 = 5.53 N 7 = 1.8081 ν 7 = 22.8
R13 = -994.519 D13 = 3.20 N 8 = 1.7880 ν 8 = 47.4
R14 = 146.895 D14 = 76.00
R15 = ∞ (aperture) D15 = 15.40
R16 = 218.726 D16 = 1.70 N 9 = 1.8348 ν 9 = 42.7
R17 = 40.671 D17 = 0.30 Nr1 = 1.6959 νr1 = 17.7
R18 = 34.674 D18 = 8.00 N10 = 1.6400 ν10 = 60.1
R19 = -157.893 D19 = 6.83
R20 = 76.572 D20 = 2.45 N11 = 1.8052 ν11 = 25.4
R21 = -351.911 D21 = 1.58 N12 = 1.7725 ν12 = 49.6
R22 = 38.188 D22 = 1.85
R23 = -166.301 D23 = 1.20 N13 = 1.7292 ν13 = 54.7
R24 = 50.963 D24 = 4.83
R25 = 45.504 D25 = 5.64 N14 = 1.6134 ν14 = 44.3
R26 = -39.853 D26 = 1.20 Ncr1 = 1.8300 νcr1 = 53.0
R27 = -647.356 D27 = 7.72
R28 = -54.671 D28 = 1.53 N15 = 1.6180 ν15 = 63.3
R29 = 44.337 D29 = 5.86 N16 = 1.5163 ν16 = 64.1
R30 = -59.066 D30 = 1.00
R31 = 84.225 D31 = 4.06 N17 = 1.5174 ν17 = 52.4
R32 = -120.519 D32 = 1.00
R33 = ∞ D33 = 2.00 N18 = 1.5163 ν18 = 64.1
R34 = ∞

Back focus BF = 59.7
Total lens length Lt = 377.0

（数値実施例５）
ｆ＝５８８Ｆｎｏ＝４．１２２ω＝４．２２°

R 1= 177.484 D 1= 13.86 N 1= 1.4875 ν 1= 70.2
R 2= 586.790 D 2= 10.89 N 2= 1.4875 ν 2= 70.2
R 3= -855.222 D 3= 16.47
R 4= 149.352 D 4= 16.09 N 3= 1.4388 ν 3= 95.0
R 5= 653.348 D 5= 5.88
R 6=-1339.713 D 6= 5.78 N 4= 1.9027 ν 4= 35.7
R 7= 457.151 D 7= 1.40
R 8= 116.801 D 8= 13.30 N 5= 1.4339 ν 5= 95.1
R 9= 410.896 D 9= 1.01
R10= 69.880 D10= 6.72 N 6= 1.8467 ν 6= 23.9
R11= 59.408 D11= 40.46
R12= 264.601 D12= 3.30 N 7= 1.8052 ν 7= 25.4
R13=-2277.273 D13= 3.30 N 8= 1.8830 ν 8= 40.8
R14= 138.495 D14= 79.50
R15= ∞（絞り） D15= 6.24
R16= 311.600 D16= 1.70 N 9= 1.8000 ν 9= 29.8
R17= 32.766 D17= 4.55 N10= 1.5927 ν10= 35.3
R18= -129.541 D18= 1.21
R19= 136.847 D19= 2.04 N11= 1.8052 ν11= 25.4
R20= -104.310 D20= 1.50 N12= 1.6968 ν12= 55.5
R21= 55.694 D21= 3.02
R22= -168.601 D22= 1.50 N13= 1.8040 ν13= 46.6
R23= 58.314 D23= 2.70
R24= 54.090 D24= 4.11 N14= 1.5673 ν14= 42.8
R25= -34.733 D25= 0.15 Nr1= 1.6356 νr1= 22.7
R26= -54.165 D26= 1.10 Ncr1=1.8300 νcr1= 53.0
R27= -120.548 D27= 26.79
R28= 158.987 D28= 2.80 N15= 1.5174 ν15= 52.4
R29= -95.325 D29= 1.05 N16= 1.5691 ν16= 71.3
R30= 107.295 D30= 4.24
R31= 79.835 D31= 1.88 N17= 1.6259 ν17= 35.7
R32= 231.472 D32= 2.00
R33= ∞ D33= 2.00 N18= 1.5163 ν18= 64.1
R34= ∞

バックフォーカスBF＝55.0
レンズ全長Lt=343.5

R2 回折面

位相係数
第２面
c1 -1.633E-05
c2 -8.793E-11
c3 1.160E-14
(Numerical example 5)
f = 588 Fno = 4.12 2ω = 4.22 °

R 1 = 177.484 D 1 = 13.86 N 1 = 1.4875 ν 1 = 70.2
R 2 = 586.790 D 2 = 10.89 N 2 = 1.4875 ν 2 = 70.2
R 3 = -855.222 D 3 = 16.47
R 4 = 149.352 D 4 = 16.09 N 3 = 1.4388 ν 3 = 95.0
R 5 = 653.348 D 5 = 5.88
R 6 = -1339.713 D 6 = 5.78 N 4 = 1.9027 ν 4 = 35.7
R 7 = 457.151 D 7 = 1.40
R 8 = 116.801 D 8 = 13.30 N 5 = 1.4339 ν 5 = 95.1
R 9 = 410.896 D 9 = 1.01
R10 = 69.880 D10 = 6.72 N 6 = 1.8467 ν 6 = 23.9
R11 = 59.408 D11 = 40.46
R12 = 264.601 D12 = 3.30 N 7 = 1.8052 ν 7 = 25.4
R13 = -2277.273 D13 = 3.30 N 8 = 1.8830 ν 8 = 40.8
R14 = 138.495 D14 = 79.50
R15 = ∞ (aperture) D15 = 6.24
R16 = 311.600 D16 = 1.70 N 9 = 1.8000 ν 9 = 29.8
R17 = 32.766 D17 = 4.55 N10 = 1.5927 ν10 = 35.3
R18 = -129.541 D18 = 1.21
R19 = 136.847 D19 = 2.04 N11 = 1.8052 ν11 = 25.4
R20 = -104.310 D20 = 1.50 N12 = 1.6968 ν12 = 55.5
R21 = 55.694 D21 = 3.02
R22 = -168.601 D22 = 1.50 N13 = 1.8040 ν13 = 46.6
R23 = 58.314 D23 = 2.70
R24 = 54.090 D24 = 4.11 N14 = 1.5673 ν14 = 42.8
R25 = -34.733 D25 = 0.15 Nr1 = 1.6356 νr1 = 22.7
R26 = -54.165 D26 = 1.10 Ncr1 = 1.8300 νcr1 = 53.0
R27 = -120.548 D27 = 26.79
R28 = 158.987 D28 = 2.80 N15 = 1.5174 ν15 = 52.4
R29 = -95.325 D29 = 1.05 N16 = 1.5691 ν16 = 71.3
R30 = 107.295 D30 = 4.24
R31 = 79.835 D31 = 1.88 N17 = 1.6259 ν17 = 35.7
R32 = 231.472 D32 = 2.00
R33 = ∞ D33 = 2.00 N18 = 1.5163 ν18 = 64.1
R34 = ∞

Back focus BF = 55.0
Total lens length Lt = 343.5

R2 diffraction surface

Phase coefficient second surface
c1 -1.633E-05
c2 -8.793E-11
c3 1.160E-14

次に本発明の光学系を撮影光学系として用いたデジタルスチルカメラ（光学機器）の実施例を図６を用いて説明する。図６において、２０はカメラ本体、２１は本発明の光学系によって構成された撮影光学系、２２はカメラ本体に内蔵され、撮影光学系２１によって形成された被写体像を受光するＣＣＤセンサやＣＭＯＳセンサ等の撮像素子（光電変換素子）である。２３は撮像素子２２によって光電変換された被写体像に対応する情報を記録するメモリ、２４は液晶ディスプレイパネル等によって構成され、撮像素子２２上に形成された被写体像を観察するためのファインダである。 Next, an embodiment of a digital still camera (optical apparatus) using the optical system of the present invention as a photographing optical system will be described with reference to FIG. In FIG. 6, reference numeral 20 denotes a camera body, 21 denotes a photographing optical system constituted by the optical system of the present invention, 22 denotes a CCD sensor or CMOS sensor built in the camera body and receiving a subject image formed by the photographing optical system 21. It is an imaging element (photoelectric conversion element). Reference numeral 23 denotes a memory for recording information corresponding to the subject image photoelectrically converted by the image sensor 22, and reference numeral 24 denotes a finder configured by a liquid crystal display panel or the like for observing the subject image formed on the image sensor 22.

このように本発明の光学系をデジタルスチルカメラ等に適用することにより、高い光学性能を有する光学機器を実現している。この他本発明の光学系は望遠鏡、双眼鏡、プロジェクター等の光学装置にも同様に適用することができる。 Thus, by applying the optical system of the present invention to a digital still camera or the like, an optical apparatus having high optical performance is realized. In addition, the optical system of the present invention can be similarly applied to optical devices such as telescopes, binoculars, and projectors.

ＯＬ光学系Ｌ１第１レンズ群Ｌ２第２レンズ群
Ｌ３第３レンズ群ＳＰ開口絞り OL optical system L1 1st lens group L2 2nd lens group L3 3rd lens group SP Aperture stop

Claims

レンズ全長が焦点距離よりも短く、開口絞りを有する光学系において、前記開口絞りよりも像側に、一つ以上の第１の屈折光学素子Ｇｃｒと、一つ以上の第２の屈折光学素子Ｇｒを有し、前記第１の屈折光学素子Ｇｃｒの材料のｄ線における屈折率をＮｃｒ、アッベ数をνｃｒとし、光学係数ΔＮｃｒを、
ΔＮｃｒ＝Ｎｃｒ−（５．９４×１０^−５×νｃｒ^２−１．５７×１０^−２×νｃｒ）
とし、前記第２の屈折光学素子Ｇｒの材料のｇ−Ｆ線における部分分散比をθｇＦｒ、アッベ数をνｒとし、異常部分分散比ΔθｇＦｒを、
ΔθｇＦｒ＝θｇＦｒ−(−１．６６５×１０^−７×νｒ^３＋５．２１３×１０^−５×νｒ^２−５．６５６×１０^−３×νｒ＋０．７２７８)
とするとき、
０．０２７２＜ΔθｇＦｒ＜０．２８３２
２．４４＜ΔＮｃｒ＜２．９５
１５＜νｃｒ＜７０
なる条件式を満たすことを特徴とする光学系。 In an optical system having a lens overall length shorter than the focal length and having an aperture stop, one or more first refractive optical elements Gcr and one or more second refractive optical elements Gr are located closer to the image side than the aperture stop. The refractive index at the d-line of the material of the first refractive optical element Gcr is Ncr, the Abbe number is νcr, and the optical coefficient ΔNcr is
ΔNcr = Ncr− (5.94 × 10 ⁻⁵ × νcr ² −1.57 × 10 ⁻² × νcr)
And the partial dispersion ratio at the g-F line of the material of the second refractive optical element Gr is θgFr, the Abbe number is νr, and the abnormal partial dispersion ratio ΔθgFr is
ΔθgFr = θgFr − (− 1.665 × 10 ⁻⁷ × νr ³ + 5.213 × 10 ⁻⁵ × νr ² −5.656 × 10 ⁻³ × νr + 0.7278)
And when
0.0272 <ΔθgFr <0.2832
2.44 <ΔNcr <2.95
15 <νcr <70
An optical system characterized by satisfying the following conditional expression:

前記第１の屈折光学素子Ｇｃｒは負の屈折力であることを特徴とする請求項１に記載の光学系。 The optical system according to claim 1, wherein the first refractive optical element Gcr has negative refractive power.

前記第１の屈折光学素子Ｇｃｒの空気中における焦点距離をｆｃｒ、前記第２の屈折光学素子Ｇｒの空気中における焦点距離をｆｒとするとき、
０．０５＜｜ｆｃｒ／ｆｒ｜＜１．２０
なる条件式を満たすことを特徴とする請求項１又は２に記載の光学系。 When the focal length of the first refractive optical element Gcr in the air is fcr and the focal length of the second refractive optical element Gr in the air is fr,
0.05 <| fcr / fr | <1.20
The optical system according to claim 1, wherein the following conditional expression is satisfied.

前記開口絞りから前記第１の屈折光学素子Ｇｃｒの入射面までの距離をＬｃｒ、前記開口絞りから像面までの距離をＬｉとするとき、
０．０５＜Ｌｃｒ／Ｌｉ＜０．６０
なる条件式を満たすことを特徴とする請求項１乃至３のいずれか１項に記載の光学系。 When the distance from the aperture stop to the incident surface of the first refractive optical element Gcr is Lcr, and the distance from the aperture stop to the image plane is Li,
0.05 <Lcr / Li <0.60
The optical system according to claim 1, wherein the following conditional expression is satisfied.

前記開口絞りから前記第２の屈折光学素子Ｇｒの入射面までの距離をＬｒ、前記開口絞りから像面までの距離をＬｉとするとき、
０．０５＜Ｌｒ／Ｌｉ＜０．６０
なる条件式を満たすことを特徴とする請求項１乃至４のいずれか１項に記載の光学系。 When the distance from the aperture stop to the incident surface of the second refractive optical element Gr is Lr, and the distance from the aperture stop to the image plane is Li,
0.05 <Lr / Li <0.60
The optical system according to claim 1, wherein the following conditional expression is satisfied.

１０＜νｒ＜６０
なる条件式を満足することを特徴とする請求項１乃至５のいずれか１項に記載の光学系。 10 <νr <60
The optical system according to claim 1, wherein the following conditional expression is satisfied.

前記光学系は物体側より像側へ順に、正の屈折力の第１レンズ群、フォーカシングに際して移動する負の屈折力の第２レンズ群、開口絞り、第３レンズ群より構成されていることを特徴とする請求項１乃至６のいずれか１項に記載の光学系。 The optical system includes, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power that moves during focusing, an aperture stop, and a third lens group. The optical system according to any one of claims 1 to 6, wherein the optical system is characterized in that:

前記第１レンズ群は回折光学面を有することを特徴とする請求項７に記載の光学系。 The optical system according to claim 7, wherein the first lens group has a diffractive optical surface.

請求項１乃至８のいずれか１項に記載の光学系と、該光学系によって形成される像を受光する撮像素子を有することを特徴とする光学機器。 An optical apparatus comprising: the optical system according to claim 1; and an image sensor that receives an image formed by the optical system.

前記光学系のレンズ全長をＬｔ、前記光学系の焦点距離をｆｔ、撮影半画角をω（度）とするとき、
Ｌｔ／ｆｔ＋０．９３（度）／ω＜１．２５
なる条件式を満たすことを特徴とする請求項１乃至９の光学機器。 When the total lens length of the optical system is Lt, the focal length of the optical system is ft, and the shooting half angle of view is ω (degrees),
Lt / ft + 0.93 (degrees) / ω <1.25
The optical apparatus according to claim 1, wherein the following conditional expression is satisfied.