JPH05127080A - Endoscope objective - Google Patents

Endoscope objective

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Publication number
JPH05127080A
JPH05127080A JP29392891A JP29392891A JPH05127080A JP H05127080 A JPH05127080 A JP H05127080A JP 29392891 A JP29392891 A JP 29392891A JP 29392891 A JP29392891 A JP 29392891A JP H05127080 A JPH05127080 A JP H05127080A
Authority
JP
Japan
Prior art keywords
lens
refractive index
gradient index
line
group
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP29392891A
Other languages
Japanese (ja)
Inventor
Akira Kikuchi
彰 菊地
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.)
Olympus Corp
Original Assignee
Olympus Optical Co Ltd
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 Olympus Optical Co Ltd filed Critical Olympus Optical Co Ltd
Priority to JP29392891A priority Critical patent/JPH05127080A/en
Priority to US07/961,543 priority patent/US5359456A/en
Publication of JPH05127080A publication Critical patent/JPH05127080A/en
Pending legal-status Critical Current

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  • Instruments For Viewing The Inside Of Hollow Bodies (AREA)

Abstract

PURPOSE:To decrease the number of lenses and excellently compensate aberrations by employing a gradient index lens as at least one lens in a rear- group convergence system and specifying its refractive index distribution. CONSTITUTION:This objective consists of a front-group divergence system which has negative power, a brightness stop, and the rear-group convergence system which has positive power in order from the object side; and at least one lens in the rear-group convergence system is the gradient index lens, whose refractive index distribution satisfies an equation II when approximated by equations I. Here, Nd(r), NF(r), and NC(r) refractive index distributions regarding a (d) line, an F line, and a C line when the radial distances from the optical axis are denoted as (r), N0d-N3d refractive index distribution coefficients regarding the (d) line, N0F-N3F refractive index distribution coefficients regarding the F line, N0C-N3C refractive index distribution coefficients regarding the C line, and nu0d and nu1d Abbe numbers represented by (4) and (5) among the equations I using N1d, N1F, and N1C.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【産業上の利用分野】本発明は、屈折率分布型レンズを
用いた内視鏡対物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 an endoscope objective lens using a gradient index lens.

【０００２】[0002]

【従来の技術】内視鏡対物レンズとして、特公昭６０−
４６４１０号公報に記載されたような図３１に示す通り
の構成のレンズ系が多く知られている。それは、明るさ
絞りを挟んで前群に発散光学系を、又後群に収斂光学系
を夫々配置したレトロフォーカスタイプのレンズ系であ
る。そして前群発散光学系は、視野角を広角化するとと
もに、ペッツバール和を小さくして像面湾曲の発生を少
なくする効果がある。又後群収斂レンズ系は、３枚の凸
レンズと一組の接合レンズにて構成してパワーを分散す
るようにしている。このようにパワーを分散することに
より各面での収差の発生量を小さくし、全体の諸収差が
良好に補正されるようにしている。2. Description of the Related Art Japanese Patent Publication No.
Many lens systems having a configuration as shown in FIG. 31 as described in Japanese Patent No. 46410 are known. It is a retrofocus type lens system in which a divergence optical system is arranged in the front group and a converging optical system is arranged in the rear group with an aperture stop interposed therebetween. The front lens group diverging optical system has the effects of widening the viewing angle and reducing the Petzval sum to reduce the occurrence of field curvature. Further, the rear group convergent lens system is composed of three convex lenses and a set of cemented lenses to disperse the power. By dispersing the power in this way, the amount of aberration generated on each surface is reduced, and the various aberrations as a whole are favorably corrected.

【０００３】しかしながら、この従来例は、構成枚数が
多くなるために全長が長くなる。又構成枚数を減らし全
長を短くするために、非球面レンズを用いることによっ
て後群収斂光学系の構成枚数を減らしつつザイデル収差
（球面収差，非点収差，コマ収差）を良好に補正するこ
とが出来るが色収差は補正できない。However, in this conventional example, the total length is long because the number of constituent elements is large. Further, in order to reduce the number of constituent elements and shorten the total length, it is possible to satisfactorily correct Seidel aberrations (spherical aberration, astigmatism, coma aberration) while reducing the number of constituent elements of the rear group converging optical system by using an aspherical lens. Yes, but chromatic aberration cannot be corrected.

【０００４】レトロフォーカス型の内視鏡対物レンズ
は、前記のように絞りを挟んで前群と後群とにて構成さ
れているが、前群発散系は、物体側の面が平面で像側の
面が凹面の１枚構成のものが多い。この前群発散系は、
負のパワーであるが明るさ絞りより前に位置しているた
めに、負の倍率色収差が発生する。又後群収斂系は、基
本的には構成要素のすべてが正のパワーであるために倍
率色収差は大きく負に発生する。As described above, the retrofocus type endoscope objective lens is composed of a front group and a rear group with a diaphragm interposed therebetween. In the front group diverging system, the object side surface is a plane image. Many of them have a single concave surface. This front group divergence system is
Although it has a negative power but is located in front of the aperture stop, negative lateral chromatic aberration occurs. Further, in the rear-group convergent system, basically, all the constituent elements have positive power, so that the chromatic aberration of magnification is largely negative.

【０００５】この前群と後群とで発生する大きな負の倍
率の色収差を補正するためには、従来、後群収斂系中に
低分散ガラスの凸レンズと高分散ガラスの凹レンズとを
接合した接合レンズを用いている。又後群収斂系中のレ
ンズに比較的高屈折率低分散のガラスを用いて各面での
倍率色収差の発生量を極力小さくしている。In order to correct the chromatic aberration of large negative magnification generated in the front group and the rear group, conventionally, a cemented lens in which a low-dispersion glass convex lens and a high-dispersion glass concave lens are cemented in a rear lens system is used. It uses a lens. Further, glass with a relatively high refractive index and low dispersion is used for the lens in the rear lens system to minimize the amount of lateral chromatic aberration generated on each surface.

【０００６】前記の従来例の特公昭６０−４６４１０号
公報のレンズ系は、広角でかつ諸収差が良好に補正され
た内視鏡対物レンズである。The lens system of Japanese Patent Publication No. 60-46410 of the prior art is an endoscope objective lens having a wide angle and various aberrations well corrected.

【０００７】しかしながら、この従来例は、レンズ枚数
が６枚と多いため、構造が複雑になり高価である。又レ
ンズ系の全長が長く、医療用内視鏡に用いた場合、内視
鏡を体内に挿入する先端部の硬質部が長くなり内視鏡の
先端部湾曲構造を用いた検査を行ないにくい欠点があ
る。However, in this conventional example, since the number of lenses is as large as six, the structure is complicated and it is expensive. In addition, the total length of the lens system is long, and when it is used for a medical endoscope, the hard portion of the distal end portion into which the endoscope is inserted into the body becomes long, which makes it difficult to perform an inspection using the distal end curved structure of the endoscope. There is.

【０００８】又内視鏡対物レンズに屈折率分布型レンズ
を用いた従来例に特公昭４７−２８０６１号公報のレン
ズ系が知られている。このレンズ系は、両端面が平面で
径方向に屈折率が分布している屈折率分布型レンズを用
いている。A lens system disclosed in Japanese Patent Publication No. 47-28061 is known as a conventional example using a gradient index lens as an objective lens for an endoscope. This lens system uses a gradient index lens in which both end surfaces are flat and the refractive index is distributed in the radial direction.

【０００９】この特公昭４７−２８０６１号公報のレン
ズ系は、構成が簡単であり、内視鏡用としては望ましい
が、視野角が屈折率分布で決まってしまい、広角化でき
ず、又外径がある程度太くなり、像高が大きくなると軸
外の諸収差の発生量が増え、外径の太い内視鏡対物レン
ズには使用出来ない。The lens system disclosed in JP-B-47-28061 has a simple structure and is desirable for endoscopes, but the viewing angle is determined by the refractive index distribution, and the wide angle cannot be achieved. Becomes thicker to some extent and the image height becomes larger, the amount of off-axis aberrations increases, which cannot be used for an endoscope objective lens having a large outer diameter.

【００１０】[0010]

【発明が解決しようとする課題】本発明は、レンズ枚数
の少ない安価なかつ諸収差が良好に補正されている内視
鏡対物レンズを提供することを目的とする。SUMMARY OF THE INVENTION It is an object of the present invention to provide an endoscope objective lens which has a small number of lenses and is inexpensive and in which various aberrations are well corrected.

【００１１】[0011]

【課題を解決するための手段】本発明の内視鏡対物レン
ズは、例えば図１に示す構成のものである。即ち物体側
から順に負のパワーを有する前群発散系と、明るさ絞り
と、正のパワーを有する後群収斂系とからなり、前記後
群収斂系中の少なくとも１枚のレンズが屈折率分布型レ
ンズよりなっている。そしてこの屈折率分布型レンズ
は、屈折率分布を下記の式（１）〜（５）で近似した
時、式（６），（７）を満足するものである。 （１） Ｎd(r)＝Ｎ0d＋Ｎ1dｒ2 ＋Ｎ2dｒ4 ＋Ｎ3dｒ6 （２） ＮF(r)＝Ｎ0F＋Ｎ1Fｒ2 ＋Ｎ2Fｒ4 ＋Ｎ3Fｒ6 （３） ＮC(r)＝Ｎ0C＋Ｎ1Cｒ2 ＋Ｎ2Cｒ4 ＋Ｎ3Cｒ6 （４） ν0d＝（１−Ｎ0d）／（Ｎ0F−Ｎ0C） （５） ν1d＝Ｎ1d／（Ｎ1F−Ｎ1C） （６） Ｎ1d＜０ （７） ０≦ν0d≦ν1d ただしＮd(r)，ＮF(r)，ＮC(r)は夫々光軸からの径方向
の距離をｒとした時のｄ線、Ｆ線，Ｃ線に関する屈折率
分布、Ｎ0d，Ｎ1d，Ｎ2d，Ｎ3dはｄ線に関する屈折率分
布係数、Ｎ0F，Ｎ1F，Ｎ2F，Ｎ3FはＦ線に関する屈折率
分布係数、Ｎ0C，Ｎ1C，Ｎ2C，Ｎ3CはＣ線に関する屈折
率分布係数、ν0d，ν1dはＮ1d，Ｎ1F，Ｎ1Cを用いて式
（４），（５）に表わされるアッベ数である。An endoscope objective lens of the present invention has a structure shown in FIG. 1, for example. That is, it comprises a front lens group diverging system having a negative power in order from the object side, an aperture stop, and a rear lens group focusing system having a positive power, and at least one lens in the rear lens group focusing system has a refractive index distribution. It consists of a mold lens. The gradient index lens satisfies the equations (6) and (7) when the refractive index distribution is approximated by the following equations (1) to (5). (1) N d (r) = N 0d + N 1d r 2 + N 2d r 4 + N 3d r 6 (2) N F (r) = N 0F + N 1F r 2 + N 2F r 4 + N 3F r 6 (3) N C (r) = N 0C + N 1C r 2 + N 2C r 4 + N 3C r 6 (4) ν 0d = (1-N 0d ) / (N 0F -N 0C ) (5) ν 1d = N 1d / (N 1F -N 1C) (6) N 1d <0 (7) 0 ≦ ν 0d ≦ ν 1d however N d (r), N F (r), N C (r) is the radial distance from the respective optical axis Where r is the d-line, F-line and C-line refractive index distributions, N 0d , N 1d , N 2d and N 3d are d-line refractive index distribution coefficients, N 0F , N 1F , N 2F and N 3F Is the refractive index distribution coefficient for the F line, N 0C , N 1C , N 2C , and N 3C are the refractive index distribution coefficients for the C line, and ν 0d and ν 1d are N 1d , N 1F , and N 1C using the equation (4). , (5) is the Abbe number.

【００１２】本発明の内視鏡対物レンズは、負の前群発
散系と正の後群収斂系とのパワーバランスによって良好
な性能を得るようにしたものである。つまり前群発散系
によって広い視野を得ると共にペッツバール和を小さく
し像面湾曲の発生を抑えている。また後群収斂系の少な
くとも一枚を屈折率分布型レンズにし、その屈折率分布
を制御することによって後群収斂系の構成枚数を減らし
ながらしかもコマ収差、非点収差を良好に補正するよう
にした。更に後群の枚数を減らしたことによってレンズ
系の全長を短くした。The endoscope objective lens of the present invention is designed to obtain good performance by the power balance between the negative front lens group diverging system and the positive rear lens group converging system. In other words, a wide field of view is obtained by the front group divergence system and the Petzval sum is reduced to suppress the occurrence of field curvature. In addition, at least one lens in the rear lens system is made to be a gradient index lens, and by controlling the refractive index distribution, the number of constituent lenses in the rear lens system is reduced so that coma and astigmatism can be corrected well. did. Furthermore, the total number of lens systems is shortened by reducing the number of lenses in the rear group.

【００１３】更に本発明内視鏡対物レンズにおいては後
群を次のように構成することによって、屈折率分布型レ
ンズを有効に利用できるようにした。つまり後群収斂系
を物体側から順に屈折率分布型レンズ、凸のレンズ成分
とにて構成し次の条件（８）を満足するようにした。 （８） ０．２≦｜φe/φR ｜≦３．６ ただしφR は後群収斂系のパワー、φe は屈折率分布型
レンズのパワーである。Further, in the endoscope objective lens of the present invention, the rear group is constructed as follows, so that the gradient index lens can be effectively used. That is, the rear lens group converging system is composed of a gradient index lens component and a convex lens component in order from the object side so that the following condition (8) is satisfied. (8) 0.2 ≦ | φ e / φ R | ≦ 3.6 where φ R is the power of the rear lens system and φ e is the power of the gradient index lens.

【００１４】上記の条件（８）は、後群のパワーをどの
程度屈折率分布型レンズに分担させたらよいかを示すも
のである。The above condition (8) shows how much the power of the rear group should be shared by the gradient index lens.

【００１５】条件（８）の下限を越えると前記の後群中
の凸のレンズ成分が受け持つパワーが大になり、均質レ
ンズである凸のレンズ成分の面の曲率が強くなるため、
このレンズ成分で発生するコマ収差、非点収差が大にな
り望ましくない。又条件（８）の上限を越えると、屈折
率分布型レンズの受け持つパワーが大になり、屈折率分
布型レンズの媒質や両屈折面で発生する球面収差、コマ
収差、非点収差の発生量が大になり好ましくない。When the value goes below the lower limit of the condition (8), the power of the convex lens component in the rear group becomes large, and the curvature of the surface of the convex lens component, which is a homogeneous lens, becomes strong.
The coma and astigmatism generated by this lens component become large, which is not desirable. If the upper limit of the condition (8) is exceeded, the power of the gradient index lens will be large, and the amount of spherical aberration, coma, and astigmatism generated in the medium of the gradient index lens and both refracting surfaces will be increased. Is large, which is not preferable.

【００１６】又本発明のレンズ系において、前記条件
（８）の代りに下記条件（８’）を満足するようにすれ
ば一層好ましい。 （８’） ０．５≦｜φe/φR ｜≦１．５ 更に前記の屈折率分布型レンズで発生する諸収差を一層
小さくするためには、屈折率分布型レンズ単体のパワー
配分つまり媒質のパワーと面のパワーとの配分が次の条
件（９）を満足することが望ましい。 （９） ０．０１≦｜φM/φe ｜≦３．０ この条件（９）の下限を越えて媒質のパワーが小さくな
ると、屈折率分布型レンズの空気接触面の曲率を強くし
てレンズ全体のパワーを得るようにしなければならず、
空気接触面での球面収差、コマ収差、非点収差の発生量
が大なり、屈折率分布型レンズの屈折率分布による媒質
での収差補正効果や、屈折率分布型レンズの空気接触面
での屈折力が媒質の屈折率分布に伴って漸次変化するこ
とによって得られる収差補正効果や、後群中の他の均質
レンズの収差補正効果では、全系の収差を良好に補正す
ることが出来ない。又条件（１６）の上限を越えて媒質
のパワーが大になると、媒質での諸収差発生量が大にな
り、同様の理由から好ましくない。In the lens system of the present invention, it is more preferable to satisfy the following condition (8 ') instead of the condition (8). (8 ′) 0.5 ≦ | φ e / φ R | ≦ 1.5 Further, in order to further reduce various aberrations generated in the gradient index lens, the power distribution of the gradient index lens unit, that is, It is desirable that the distribution of the power of the medium and the power of the surface satisfy the following condition (9). (9) 0.01 ≦ | φ M / φ e | ≦ 3.0 If the power of the medium becomes smaller than the lower limit of this condition (9), the curvature of the air contact surface of the gradient index lens is increased. You have to get the power of the whole lens,
The amount of spherical aberration, coma, and astigmatism generated on the air contact surface is large, and the aberration correction effect in the medium due to the refractive index distribution of the gradient index lens and the air contact surface of the gradient index lens Aberrations of the entire system cannot be satisfactorily corrected by the aberration correction effect obtained by gradually changing the refractive power according to the refractive index distribution of the medium or the aberration correction effect of other homogeneous lenses in the rear group. .. Further, when the power of the medium becomes large beyond the upper limit of the condition (16), the amount of various aberrations generated in the medium becomes large, which is not preferable for the same reason.

【００１７】次の本発明レンズ系における各収差の補正
に関して説明する。The correction of each aberration in the lens system of the present invention will be described below.

【００１８】球面収差は、前群発散系の凹面でプラス側
に発生し、これを後群収斂系の屈折率分布型レンズの像
側の凸面でマイナス側に発生させてトータルで極めて小
さい値になるように補正している。この場合、後群中の
屈折率分布型レンズの像側の凸面でのマイナス側の球面
収差の発生量が前群発散系での発生量とほぼ等しくなる
ようにする。つまり後群の屈折率分布型レンズの像側の
凸面の屈折力が周辺に行くにしたがって徐々に弱くなる
ように上記屈折率分布型レンズの屈折率分布を定めてい
る。Spherical aberration is generated on the positive side on the concave surface of the front lens group diverging system, and is generated on the negative side on the image side convex surface of the rear lens group-converging gradient index lens to a very small total value. I am correcting so that. In this case, the amount of negative spherical aberration generated on the image-side convex surface of the gradient index lens in the rear group is made substantially equal to the amount generated in the front group diverging system. That is, the refractive index distribution of the gradient index lens is determined so that the refractive power of the image-side convex surface of the gradient index lens of the rear group becomes gradually weaker toward the periphery.

【００１９】又コマ収差は、前群発散系の凹面で内コマ
側に発生し、後群収斂系中の屈折率分布型レンズの物体
側の面と凸レンズの物体側の面で外コマ側に発生させて
補正している。後群の屈折率分布型レンズの媒質とその
像側の面でのコマ収差の発生量はほぼ等しく、符号が反
対であるので互いにキャンセルするようにしている。Further, coma is generated on the inner coma side by the concave surface of the front lens group diverging system, and on the outer coma side by the object side surface of the gradient index lens and the object side surface of the convex lens in the rear lens system. It is generated and corrected. The amounts of coma aberration generated in the medium of the gradient index lens of the rear group and the surface on the image side are substantially equal to each other, and the signs are opposite to each other, so that they cancel each other.

【００２０】更に非点収差は、前群発散系の発生量は比
較的小さくほとんど問題にはならない。又後群収斂系の
屈折率分布型レンズの物体側の面と媒質で発生する非点
収差を、その像側の面と凸レンズとで発生する非点収差
で補正している。その場合、屈折率分布型レンズの屈折
率分布を周辺に行くにしたがって屈折力が徐々に弱くな
るようにして補正を可能にしている。Further, astigmatism causes almost no problem because the amount of light generated in the front group divergent system is relatively small. Further, the astigmatism generated on the object-side surface and medium of the rear-group convergence type gradient index lens is corrected by the astigmatism generated on the image-side surface and the convex lens. In this case, the refractive index distribution of the gradient index lens is corrected so that the refractive power is gradually weakened toward the periphery.

【００２１】以上述べたように、後群収斂系を正のパワ
ーの屈折率分布型レンズと凸のレンズ成分とで構成して
諸収差を良好に補正することが可能であるが、更に後群
収斂系の構成枚数を減らして屈折率分布型レンズ１枚に
て構成しても十分良好な性能を得ることが出来る。As described above, it is possible to satisfactorily correct various aberrations by constructing the rear lens group converging system with a positive power gradient index lens element and a convex lens component. Even if the number of the converging system components is reduced and one lens is constructed of a gradient index lens, sufficiently good performance can be obtained.

【００２２】即ち、後群の屈折率分布型レンズの屈折率
分布定数Ｎ1dを十分に小さくして光軸と周辺との屈折率
差を大きくすることによって、媒質の凸のパワーを増大
させ後群収斂系に必要なパワーを得ることが出来る。That is, the refractive index distribution constant N 1d of the gradient index lens of the rear group is made sufficiently small to increase the refractive index difference between the optical axis and the periphery, thereby increasing the convex power of the medium. You can obtain the power required for the group convergence system.

【００２３】上記のように後群を一つの屈折率分布型レ
ンズにした時も、収差補正の様子は、後群収斂系が、屈
折率分布型レンズと凸のレンズ成分とで構成されている
場合と同様である。Even when the rear lens group is formed of one gradient index lens as described above, the aberration correction state is such that the rear lens group convergence system is composed of the gradient index lens element and the convex lens component. It is similar to the case.

【００２４】ここで、前群と後群の屈折率分布型レンズ
の収差補正を能力を見極めるために、屈折率分布型レン
ズの屈折率を通常の光学ガラスに置き換えて考える。Here, in order to determine the aberration correction capability of the front and rear lens groups, the refractive index of the gradient index lens will be replaced with a normal optical glass.

【００２５】像面湾曲を補正するための条件としてペッ
ツバール和の次の式（１０）が知られている。 （１０） Σφ/N＝０ ただしＮは屈折率である。The following equation (10) of Petzval sum is known as a condition for correcting the field curvature. (10) Σφ / N = 0 where N is the refractive index.

【００２６】上記式（１０）のφ／Ｎに着目してこれら
屈折率分布型レンズと通常のガラスの屈折率とが等価で
あるとし、レンズ系が薄肉系であると仮定すると、次の
式（１１）が成立つ。 （１１） φe/Ｎe ＝φS/Ｎ0d＋φM/Ｎ0d 2 ここでＮe は両屈折率分布型レンズの屈折率分布をいず
れも通常の光学ガラスの屈折率に置き換えたもの（以下
等価屈折率という）、φSは屈折率分布型レンズの各面
のパワーの和、φM は屈折率分布型レンズの媒質のパワ
ーである。尚φM ，φS は次の式で表わされる。 φM ＝−２Ｎ1d sin（α・ｄM ）／α （Ｎ1d＜０のとき）， −２Ｎ1d sinｈ（α・ｄM ）／α （Ｎ1d＞０のとき） ≒−２ｄM ・Ｎ1d φS ＝（Ｎ0d−１）（1/r1−1/r2） ただしｄM は前記屈折率分布型レンズの面間隔、αは下
記の式で定義される。 α＝｜２Ｎ1d／Ｎ0d｜1/2 ここでφe ＝φS ＋φM と近似し、式（１１）を変形す
れば次の式（１２）が得られる。 （１２） Ｎe ＝Ｎ0d 2/{(1-Ｎ0d)/(1＋φS/（−２×Ｎ1d×dM))＋Ｎ0d｝ この式（１２）から、Ｎ1d，ｄM を大きくすると等価屈
折率Ｎe が大になることがわかる。したがってＮ1d，ｄ
M を大きくするとペッツバール和を小さくすることがで
きる。またＮe を通の光学ガラスより大きくできるの
で、後群収斂系に必要なパワーを、小さな曲率のレンズ
で得ることが出来、それら曲面での収差の発生量が比較
的小さく、屈折率分布型レンズでの屈折率分布による非
球面的な収差補正効果とあいまって、レンズ枚数の削減
とレンズ系の全長を短くする上で効果がある。Focusing on φ / N in the above equation (10), assuming that the gradient index lens and the ordinary glass have the same refractive index, and assuming that the lens system is a thin system, the following equation is obtained. (11) is established. (11) φ e / N e = φ S / N 0d + φ M / N 0d 2 Here, N e is obtained by replacing the refractive index distributions of both gradient index lenses with the refractive index of ordinary optical glass ( Hereinafter, referred to as an equivalent refractive index), φ S is the sum of the powers of the respective surfaces of the gradient index lens, and φ M is the power of the medium of the gradient index lens. Note that φ M and φ S are expressed by the following equations. φ M = −2N 1d sin (α · d M ) / α (when N 1d <0), −2N 1d sinh (α · d M ) / α (when N 1d > 0) ≈−2d M · N 1d φ S = (N 0d −1) (1 / r 1 −1 / r 2 ), where d M is defined by the surface spacing of the gradient index lens, and α is defined by the following equation. α = | 2N 1d / N 0d | 1/2 Here, if φ e = φ S + φ M is approximated and equation (11) is modified, the following equation (12) is obtained. (12) N e = N 0d 2 / {(1-N 0d ) / (1 + φ S / (− 2 × N 1d × d M )) + N 0d } From this equation (12), N 1d and d M are increased. Then, it can be seen that the equivalent refractive index N e becomes large. Therefore N 1d , d
Increasing M can reduce Petzval sum. Further, since it can be made larger than the optical glass through N e , the power required for the rear lens group converging system can be obtained with a lens having a small curvature, and the amount of aberration generated on those curved surfaces is relatively small, so that the refractive index distribution type Combined with the aspherical aberration correction effect due to the refractive index distribution in the lens, it is effective in reducing the number of lenses and shortening the total length of the lens system.

【００２７】この場合、次の式（１３）を満足すること
が望ましい。 （１３） Ｎe ／Ｎ0d≧１．１ この条件（１３）を外れると屈折率分布型レンズを用い
た効果が少なく諸収差を良好に補正することが出来な
い。In this case, it is desirable to satisfy the following expression (13). (13) N e / N 0d ≧ 1.1 If the condition (13) is not satisfied, the effect of using the gradient index lens is small and various aberrations cannot be corrected well.

【００２８】[0028]

【実施例】次に本発明の内視鏡対物レンズの各実施例を
示す。EXAMPLES Next, examples of the endoscope objective lens of the present invention will be shown.

【００２９】ただしｒ1，ｒ2，・・・は各レンズ面の曲
率半径、ｄ1，ｄ2，・・・は各レンズの肉厚及びレンズ
間隔、ｎ1，ｎ2，・・・は各レンズの屈折率、ν1，
ν2，・・・は各レンズのアッベ数である。又、ｒa，ｒ
b，・・・は夫々各屈折率分布型レンズの物体側および
像側の面の曲率半径を表わしている。 実施例1 f=1.000 ,F/2.508 ,IH=0.9240 ,物体距離=-15.4004 r1 =∞ d1 =0.4107 n1 =1.51633 ν1 =64.15 r2 =0.7938 d2 =0.5166 r3 =∞(絞り) d3 =0.0000 r4 =-16.5987 d4 =2.0619 n2 (屈折率分布型レンズ) r5 =-1.4540 d5 =0.6360 r6 =3.1075 d6 =2.1941 n3 =1.58913 ν3 =61.18 r7 =∞ 屈折率分布型レンズ (波長) N0 N1 N2 N3 587.56 1.58913 -0.10622 -0.75321×10-3 0.00000 656.28 1.58618 -0.10569 -0.74944×10-3 0.00000 486.13 1.59600 -0.10746 -0.76199×10-3 0.00000 ν 60.00000 0.60000×102 0.60000×102 0.00000 dM =2.0619,ra =-16.5987,rb =-1.454,φR =0.748 ,φM =0.438, φS =0.370 ,φe =0.808 ,νe =60.000,Ne =1.989 ,νe/ν0d=1.000, Ne/Nod=1.252 ,φe/φR =1.080 ,φM/φe =0.542 実施例2 f=1.000 ,F/2.419 ,IH=0.9336 ,物体距離=-15.5602 r1 =∞ d1 =0.4149 n1 =1.51633 ν1 =64.15 r2 =0.8486 d2 =0.8113 r3 =∞(絞り) d3 =0.0000 r4 =-55.8404 d4 =2.1747 n2 (屈折率分布型レンズ１) r5 =-1.6947 d5 =0.3192 r6 =7.3237 d6 =2.7851 n3 (屈折率分布型レンズ２) r7 =∞ 屈折率分布型レンズ１ (波長) N0 N1 N2 N3 587.56 1.58913 -0.95019×10-1 0.00000 0.00000 656.28 1.58618 -0.94544×10-1 0.00000 0.00000 486.13 1.59600 -0.96128×10-1 0.00000 0.00000 ν 60.00000 0.60000×102 0.00000 0.00000 dM =2.1747,ra =-55.8404,rb =-1.6947 ,φR =0.662 ,φM =0.413, φS =0.337 ,φe =0.750 ,νe =60.000,Ne =1.997 ,νe/ν0d=1.000, Ne/Nod=1.257 ,φe/φR =1.133 ,φM/φe =0.551 屈折率分布型レンズ２ (波長) N0 N1 N2 N3 587.56 1.58913 -0.25906×10-1 0.00000 0.00000 656.28 1.58618 -0.25777×10-1 0.00000 0.00000 486.13 1.59600 -0.26209×10-1 0.00000 0.00000 ν 60.00000 0.60000×102 0.00000 0.00000 dM =2.7851,ra =7.3237,rb =∞ ,φR =0.662 ,φM =0.144, φS =0.080 ,φe =0.225 ,νe =60.000,Ne =2.086 ,νe/ν0d=1.000, Ne/Nod=1.312 ,φe/φR =0.339 ,φM/φe =0.642 実施例3 f=1.000 ,F/2.500 ,IH=0.9524 ,物体距離=-15.8730 r1 =∞ d1 =0.4233 n1 =1.51633 ν1 =64.15 r2 =0.8596 d2 =0.4585 r3 =∞(絞り) d3 =0.0000 r4 =-5.3730 d4 =2.8996 n2 (屈折率分布型レンズ) r5 =-1.7177 屈折率分布型レンズ (波長) N0 N1 N2 N3 587.56 1.58913 -0.12950 0.87158×10-2 -0.16842 ×10-2 656.28 1.58618 -0.12885 0.86722×10-2 -0.16757 ×10-2 486.13 1.59600 -0.13101 0.88175×10-2 -0.17038 ×10-2 ν 60.00000 0.60000×102 0.60000×102 0.60000 ×102 dM =2.8996,ra =-5.373,rb =-1.7177 ,φR =0.736 ,φM =0.751, φS =0.233 ,φe =0.984 ,νe =60.000,Ne =2.216 ,νe/ν0d=1.000, Ne/Nod=1.394 ,φe/φR =1.337 ,φM/φe =0.763 実施例4 f=1.000 ,F/2.511 ,IH=0.9464 ,物体距離=-15.7729 r1 =∞ d1 =0.4206 n1 =1.51633 ν2 =64.15 r2 =0.7425 d2 =0.5256 r3 =∞(絞り) d3 =0.0000 r4 =-22.5089 d4 =2.1125 n2 (屈折率分布型レンズ) r5 =-1.5555 d5 =0.9786 r6 =2.3620 d6 =0.7653 n3 =1.58913 ν3 =61.18 r7 =-2.6288 d7 =1.0652 n4 =1.84666 ν4 =23.78 r8 =∞ 屈折率分布型レンズ (波長) N0 N1 N2 N3 587.56 1.58913 -0.11920 -0.69327×10-2 0.00000 656.28 1.58618 -0.11860 -0.68981×10-2 0.00000 486.13 1.59600 -0.12059 -0.70136×10-2 0.00000 ν 60.00000 0.60000×102 0.60000×102 0.00000 dM =2.1125,ra =-22.5089,rb =-1.5555 ,φR =0.74,φM =0.504, φS =0.353 ,φe =0.856 ,νe =60.000,Ne =2.032 ,νe/ν0d=1.000, Ne/Nod=1.279 ,φe/φR =1.157 ,φM/φe =0.588 実施例5 f=1.000 ,F/2.508 ,IH=0.9009 ,物体距離=-15.0150 r1 =∞ d1 =0.4004 n1 =1.51633 ν1 =64.15 r2 =0.7119 d2 =0.9118 r3 =∞(絞り) d3 =0.0000 r4 =4.7744 d4 =2.1961 n2 (屈折率分布型レンズ) r5 =-1.0211 d5 =0.1502 n3 =1.84666 ν3 =23.78 r6 =-2.1650 d6 =0.3532 r7 =2.0145 d7 =2.5116 n4 =1.51633 ν4 =64.15 r8 =∞ 屈折率分布型レンズ (波長) N0 N1 N2 N3 587.56 1.58913 -0.10709 -0.33719×10-1 -0.57394 ×10-1 656.28 1.58618 -0.10629 -0.33382×10-1 -0.56533 ×10-1 486.13 1.59600 -0.10897 -0.34506×10-1 -0.59403 ×10-1 ν 60.00000 0.40000×102 0.30000×102 0.20000 ×102 dM =2.1961,ra =4.7744,rb =-1.0211 ,φR =0.649 ,φM =0.470, φS =0.700 ,φe =1.171 ,νe =49.963,Ne =1.867 ,νe/ν0d=0.833, Ne/Nod=1.175 ,φe/φR =1.804 ,φM/φe =0.402 実施例6 f=1.000 ,F/2.458 ,IH=0.9202 ,物体距離=-15.3374 r1 =∞ d1 =0.4090 n1 =1.51633 ν1 =64.15 r2 =0.8584 d2 =0.6281 r3 =∞(絞り) d3 =0.1633 r4 =-3.9373 d4 =2.9962 n2 (屈折率分布型レンズ１) r5 =-2.6541 d5 =1.4374 n3 (屈折率分布型レンズ２) r6 =-3.9683 屈折率分布型レンズ１ (波長) N0 N1 N2 N3 587.56 1.58913 -0.19338 -0.10122×10-4 0.00000 656.28 1.58618 -0.19217 -0.10122×10-4 0.00000 486.13 1.59600 -0.19621 -0.10122×10-4 0.00000 ν 60.00000 0.47883×102 0.00000 0.00000 dM =2.9962,ra =-3.9373 ,rb =-2.6541 ,φR =0.714 ,φM =1.159, φS =0.072 ,φe =1.231 ,νe =48.458,Ne =2.441 ,νe/ν0d=0.808, Ne/Nod=1.536 ,φe/φR =1.724 ,φM/φe =0.941 屈折率分布型レンズ２ (波長) N0 N1 N2 N3 587.56 1.60000 0.54940×10-1 -0.99324×10-6 0.00000 656.28 1.59550 0.51849×10-1 -0.99324×10-6 0.00000 486.13 1.61050 0.62152×10-1 -0.99324×10-6 0.00000 ν 40.00000 0.53323×10 0.00000 0.00000 dM =1.4374,ra =-2.6541 ,rb =-3.9683 ,φR =0.714 ,φM =-0.158 φS =-0.075,φe =-0.233,νe =7.393 ,Ne =2.146 ,νe/ν0d=0.185, Ne/Nod=1.341 ,φe/φR =-0.326,φM/φe =0.678 実施例7 f=1.000 ,F/2.516 ,IH=0.9091 ,物体距離=-15.1515 r1 =∞ d1 =0.4040 n1 =1.51633 ν1 =64.15 r2 =1.0932 d2 =0.5706 r3 =∞(絞り) d3 =0.3179 r4 =-6.1292 d4 =2.9043 n2 (屈折率分布型レンズ１) r5 =-2.5847 d5 =1.4989 n3 (屈折率分布型レンズ２) r6 =∞ 屈折率分布型レンズ１ (波長) N0 N1 N2 N3 587.56 1.58913 -0.20056 0.15606×10-2 0.34841 ×10-4 656.28 1.58618 -0.19955 0.15507×10-2 0.34579 ×10-4 486.13 1.59600 -0.20292 0.15839×10-2 0.35450 ×10-4 ν 60.00000 0.59491×102 0.47000×102 0.40000 ×102 dM =2.9043,ra =-6.1292 ,rb =-2.5847, φR =0.799 ,φM =1.165, φS =0.132 ,φe =1.297 ,νe =59.542,Ne =2.383 ,νe/ν0d=0.992, Ne/Nod=1.499 ,φe/φR =1.623 ,φM/φe =0.898 屈折率分布型レンズ２ (波長) N0 N1 N2 N3 587.56 1.60000 0.41751×10-1 -0.82240×10-2 -0.14197 ×10-3 656.28 1.59550 0.38456×10-1 -0.81623×10-2 -0.13132 ×10-3 486.13 1.61050 0.49440×10-1 -0.83679×10-2 -0.16682 ×10-3 ν 40.00000 0.38011×10 0.40000×102 0.40000 ×10 dM =1.4989,ra =-2.5847 ,rb =∞ ,φR =0.799 ,φM =-0.125, φS =-0.232,φe =-0.357,νe =9.225 ,Ne =1.842 ,νe/ν0d=0.231, Ne/Nod=1.151 ,φe/φR =-0.447,φM/φe =0.350 実施例8 f=1.000 ,F/2.453 ,IH=1.0345 ,物体距離=-17.2414 r1 =∞ d1 =0.4023 n1 =1.84666 ν1 =23.78 r2 =-5.6322 d2 =0.4023 n2 =1.51633 ν2 =64.15 r3 =0.8717 d3 =0.6060 r4 =∞（絞り） d4 =0.0000 r5 =-6.2112 d5 =3.0465 n3 (屈折率分布型レンズ) r6 =-1.6142 屈折率分布型レンズ (波長) N0 N1 N2 N3 587.56 1.58913 -0.11266 0.11896×10-1 0.29127 ×10-2 656.28 1.58618 -0.11210 0.11837×10-1 0.28981 ×10-2 486.13 1.59600 -0.11398 0.12035×10-1 0.29467 ×10-2 ν 60.00000 0.60000×102 0.60000×102 0.60000 ×102 dM =3.0465,ra =-6.2112 ,rb =-1.6142 ,φR =0.709 ,φM =0.686, φS =0.270 ,φe =0.957 ,νe =60.000,Ne =2.165 ,νe/ν0d=1.000, Ne/Nod=1.362 ,φe/φR =1.349 ,φM/φe =0.718 実施例9 f=1.000 ,F/2.464 ,IH=1.0502 ,物体距離=-17.5029 r1 =∞ d1 =0.4084 n1 =1.84666 ν1 =23.78 r2 =-5.6009 d2 =0.3501 n2 =1.51633 ν2 =64.15 r3 =0.8614 d3 =0.8279 r4 =∞(絞り) d4 =0.0000 r5 =19.1703 d5 =2.4563 n3 (屈折率分布型レンズ) r6 =-1.8041 d6 =0.6483 r7 =1.8563 d7 =0.8922 n4 =1.51633 ν4 =64.15 r8 =-2.1004 d8 =1.0519 n5 =1.84666 ν5 =23.78 r9 =∞ 屈折率分布型レンズ (波長) N0 N1 N2 N3 587.56 1.58913 -0.88999×10-1 -0.23419×10-2 0.00000 656.28 1.58618 -0.88554×10-1 -0.23302×10-2 0.00000 486.13 1.59600 -0.90037×10-1 -0.23692×10-2 0.00000 ν 60.00000 0.60000×102 0.60000×102 0.00000 dM =2.4563,ra =19.1703 ,rb =-1.8041 ,φR =0.711 ,φM =0.437, φS =0.357 ,φe =0.794 ,νe =60.000,Ne =1.996 ,νe/ν0d=1.000, Ne/Nod=1.256 ,φe/φR =1.117 ,φM/φe =0.550 実施例10 f=1.000 ,F/2.439 ,IH=0.9772 ,物体距離=-16.2866 r1 =∞ d1 =0.5429 n1 (屈折率分布型レンズ１) ｒ２ ＝０．９２６２ ｄ２ ＝０．７３８６ ｒ３ ＝∞(絞り) d3 =0.1323 r4 =8.4788 d4 =2.3626 n2 (屈折率分布型レンズ２) r5 =-1.7368 d5 =0.4522 r6 =2.1579 d6 =1.1059 n3 =1.58913 ν3 =61.18 r7 =-1.9001 d7 =1.8039 n4 =1.84666 ν4 =23.78 r8 =∞ 屈折率分布型レンズ１ (波長) N0 N1 N2 N3 587.56 1.67000 -0.54518×10-1 0.00000 0.00000 656.28 1.66330 -0.51247×10-1 0.00000 0.00000 486.13 1.68563 -0.62151×10-1 0.00000 0.00000 ν 30.00000 0.50000×10 0.00000 0.00000 dM =0.5429,ra =∞,rb =0.9262,φR =0.684 ,φM =0.059, φS =-0.723,φe =-0.664,νe =54.115,Ne =1.612 ,νe/ν0d=1.804, Ne/Nod=0.965 ,φe/φR =-0.971,φM/φe =-0.089 屈折率分布型レンズ２ (波長) N0 N1 N2 N3 587.56 1.58913 -0.60781×10-1 -0.56118×10-4 -0.61034 ×10-4 656.28 1.58618 -0.60477 ×10-1 -0.55838×10-4 -0.60729 ×10-4 486.13 1.59600 -0.61490×10-1 -0.56773×10-4 -0.61746 ×10-4 ν 60.00000 0.60000×102 0.60000×102 0.60000 ×102 dM =2.3626,ra =8.4788,rb =-1.7368 ,φR =0.684 ,φM =0.287, φS =0.409 ,φe =0.696 ,νe =60.000,Ne =1.876 ,νe/ν0d=1.000, Ne/Nod=1.181 ,φe/φR =1.017 ,φM/φe =0.413 実施例11 f=1.000 ,F/2.481 ,IH=0.9815 ,物体距離=-16.3577 r1 =∞ d1 =0.8724 n1 (屈折率分布型レンズ１) r2 =0.8853 d2 =0.7109 r3 =∞(絞り) d3 =0.0695 r4 =9.6787 d4 =2.3314 n2 (屈折率分布型レンズ２) r5 =-1.6455 d5 =0.4338 r6 =2.0726 d6 =1.1054 n3 =1.58913 ν3 =61.18 r7 =-1.9084 d7 =1.8177 n4 =1.84666 ν4 =23.78 r8 =∞ 屈折率分布型レンズ１ (波長) N0 N1 N2 N3 587.56 1.67000 -0.44819×10-1 0.00000 0.00000 656.28 1.66330 -0.42899×10-1 0.00000 0.00000 486.13 1.68563 -0.49301×10-1 0.00000 0.00000 ν 30.00000 0.70000×10 0.00000 0.00000 dM =0.8724,ra =∞ ,rb =0.8858,φR =0.702 ,φM =0.078, φS =-0.756,φe =-0.678,νe =48.299,Ne =1.596 ,νe/ν0d=1.610, Ne/Nod=0.956 ,φe/φR =-0.966,φM/φe =-0.115 屈折率分布型レンズ２ (波長) N0 N1 N2 N3 587.56 1.58913 -0.59491×10-1 -0.54602×10-4 -0.59461 ×10-4 656.28 1.58618 -0.59194×10-1 -0.54347×10-4 -0.59163 ×10-4 486.13 1.59600 -0.60186×10-1 -0.55257×10-4 -0.60154 ×10-4 ν 60.00000 0.60000×102 0.60000×102 0.60000 ×102 dM =2.3314,ra =9.6787,rb =-1.6455 ,φR =0.702 ,φM =0.277, φS =0.419 ,φe =0.696 ,νe =60.000,Ne =1.865 ,νe/ν0d=1.000, Ne/Nod=1.173 ,φe/φR =0.992 ,φM/φe =0.398 実施例12 f=1.000 ,F/2.447 ,IH=1.0066 ,物体距離=-16.7771 r1 =∞ d1 =0.8948 n1 (屈折率分布型レンズ１) ｒ２ ＝０．９０５２ ｄ２ ＝０．７２９０ ｒ３ ＝∞(絞り) d3 =0.0725 r4 =11.6414 d4 =2.3916 n2 (屈折率分布型レンズ２) r5 =-1.6886 d5 =0.5508 r6 =2.1855 d6 =1.1329 n3 =1.58913 ν3 =61.18 r7 =-1.9573 d7 =1.5304 n4 =1.84666 ν4 =23.78 r8 =∞ 屈折率分布型レンズ１ (波長) N0 N1 N2 N3 587.56 1.67000 -0.45769×10-1 0.00000 0.00000 656.28 1.66330 -0.43808×10-1 0.00000 0.00000 486.13 1.68563 -0.50346×10-1 0.00000 0.00000 ν 30.00000 0.70000×10 0.00000 0.00000 dM =0.8948,ra =∞ ,rb =0.9052,φR =0.695 ,φM =0.082, φS =-0.740,φe =-0.658,νe =50.748,Ne =1.591 ,νe/ν0d=1.692, Ne/Nod=0.952 ,φe/φR =-0.947,φM/φe =-0.124 屈折率分布型レンズ２ (波長) N0 N1 N2 N3 587.56 1.58913 -0.67241×10-1 0.65406×10-3 0.28639 ×10-3 656.28 1.58618 -0.66736×10-1 0.64425×10-3 0.28639 ×10-3 486.13 1.59600 -0.68417×10-1 0.67696×10-3 0.28639 ×10-3 ν 60.00000 0.40000×102 0.20000×102 0.00000 dM =2.3916,ra =11.6414 ,rb =-1.6886 ,φR =0.695 ,φM =0.322, φS =0.399 ,φe =0.721 ,νe =49.059,Ne =1.904 ,νe/ν0d=0.818, Ne/Nod=1.198 ,φe/φR =1.038 ,φM/φe =0.446 実施例13 f=1.000 ,F/2.512 ,IH=0.9444 ,物体距離=-15.7398 r1 =∞ d1 =0.4197 n1 (屈折率分布型レンズ１) ｒ２ ＝１．３３６０ ｄ２ ＝０．３６６２ ｒ３ ＝∞(絞り) d3 =0.0000 r4 =-4.0246 d4 =2.7540 n2 (屈折率分布型レンズ２) ｒ５ ＝−２．０１９９ 屈折率分布型レンズ１ (波長) N0 N1 N2 N3 587.56 1.75000 -0.81739×10-1 0.00000 0.00000 656.28 1.74250 -0.75608×10-1 0.00000 0.00000 486.13 1.76750 -0.96043×10-1 0.00000 0.00000 ν 30.00000 0.40000×10 0.00000 0.00000 dM =0.4197,ra =∞ ,rb =1.336 ,φR =0.812 ,φM =0.069, φS =-0.561,φe =-0.493,νe =315.947 ,Ne =1.651 , νe/ν0d=10.532,Ne/Nod=0.944 ,φe/φR =-0.607,φM/φe =-0.139 屈折率分布型レンズ２ (波長) N0 N1 N2 N3 587.56 1.58913 -0.17504 0.16003×10-1 -0.85767 ×10-2 656.28 1.58618 -0.17416 0.15923×10-1 -0.85338 ×10-2 486.13 1.59600 -0.17708 0.16190×10-1 -0.86768 ×10-2 ν 60.00000 0.60000×102 0.60000×102 0.60000 ×102 dM =2.754 ,ra =-4.0246 ,rb =-2.0199 ,φR =0.812 ,φM =0.964, φS =0.145 ,φe =1.109 ,νe =60.000,Ne =2.344 ,νe/ν0d=1.000, Ne/Nod=1.475 ,φe/φR =1.366 ,φM/φe =0.869 実施例14 f=1.000 ,F/2.420 ,IH=1.0056 ,物体距離=-16.7598 r1 =∞ d1 =0.3352 n1 =1.78472 ν2 =25.68 r2 =-11.1732 d2 =0.4469 n2 (屈折率分布型レンズ１) ｒ３ ＝０．９９２７ ｄ３ ＝０．５３５７ ｒ４ ＝∞(絞り) d4 =0.0000 r5 =-12.4470 d5 =3.0522 n3 (屈折率分布型レンズ２) ｒ６ ＝−１．６１５６ 屈折率分布型レンズ１ (波長) N0 N1 N2 N3 587.56 1.67000 -0.48870×10-1 0.00000 0.00000 656.28 1.66330 -0.41539×10-1 0.00000 0.00000 486.13 1.68563 -0.65974×10-1 0.00000 0.00000 ν 30.00000 0.20000×10 0.00000 0.00000 dM =0.4469,ra =-11.1732,rb =0.9927,φR =0.694 ,φM =0.044, φS =-0.735,φe =-0.691,νe =260.207 ,Ne =1.629 , νe/ν0d=8.674, Ne/Nod=0.975 ,φe/φR =-0.996,φM/φe =-0.063 屈折率分布型レンズ２ (波長) N0 N1 N2 N3 587.56 1.58913 -0.10909 0.12255×10-1 0.31761 ×10-2 656.28 1.58618 -0.10854 0.12194×10-1 0.31602 ×10-2 486.13 1.59600 -0.11036 0.12398×10-1 0.32131 ×10-2 ν 60.00000 0.60000×102 0.60000×102 0.60000 ×102 dM =3.0522,ra =-12.447 ,rb =-1.6156 ,φR =0.694 ,φM =0.666, φS =0.317 ,φe =0.983 ,νe =60.000,Ne =2.122 ,νe/ν0d=1.000, Ne/Nod=1.335 ,φe/φR =1.417 ,φM/φe =0.677 実施例15 f=1.000 ,F/2.503 ,IH=0.8825 ,物体距離=-14.7085 ｒ１ ＝∞ d1 =0.3922 n1 (屈折率分布型レンズ１) r2 =1.3187 d2 =0.4372 r3 =∞(絞り) d3 =0.3327 r4 =-6.2473 d4 =2.8124 n2 (屈折率分布型レンズ２) ｒ５ ＝−２．９１２２ ｄ５ ＝１．６３３２ ｎ３ （屈折率
分布型レンズ３) ｒ６ ＝∞ 屈折率分布型レンズ１ (波長) N0 N1 N2 N3 587.56 1.60000 -0.24865×10-1 0.70810×10-2 -0.75187 ×10-2 656.28 1.59640 -0.23835×10-1 0.70102×10-2 -0.72932 ×10-2 486.13 1.60840 -0.27269×10-1 0.72462×10-2 -0.80450 ×10-2 ν 50.00000 0.72406×10 0.30000×102 0.10000 ×102 dM =0.3922,ra =∞ ,rb =1.3187,φR =0.854 ,φM =0.020, φS =-0.455,φe =-0.435,νe =67.980,Ne =1.574 ,νe/ν0d=1.360, Ne/Nod=0.983 ,φe/φR =-0.510,φM/φe =-0.045 屈折率分布型レンズ２ (波長) N0 N1 N2 N3 587.56 1.80000 -0.20871 0.28165×10-2 -0.79986 ×10-3 656.28 1.79520 -0.20743 0.27922×10-2 -0.79187 ×10-3 486.13 1.81120 -0.21171 0.28732×10-2 -0.81852 ×10-3 ν 50.00000 0.48760×102 0.34764×102 0.30012 ×102 dM =2.8124,ra =-6.2473 ,rb =-2.9122 ,φR =0.854 ,φM =1.174, φS =0.147 ,φe =1.321 ,νe =48.895,Ne =2.976 ,νe/ν0d=0.978, Ne/Nod=1.653 ,φe/φR =1.546 ,φM/φe =0.889 屈折率分布型レンズ３ (波長) N0 N1 N2 N3 587.56 1.60000 0.44519×10-1 -0.92446×10-2 0.29229 ×10-3 656.28 1.59550 0.40164×10-1 -0.84232×10-2 0.23193 ×10-3 486.13 1.61050 0.54681×10-1 -0.11161×10-1 0.43311 ×10-3 ν 40.00000 0.30668×10 0.33767×10 0.14529 ×10 dM =1.6332,ra =-2.9122 ,rb =? ,φR =0.799 ,φM =-1.454, φS =-0.206,φe =-1.660,νe =3.464 ,Ne =2.383 ,νe/ν0d=0.087, Ne/Nod=1.489 ,φe/φR =-1.944,φM/φe =0.876 ただしｒ1 ，ｒ2 ，・・・ は各レンズ面の曲率半径、ｄ
1 ，ｄ2 ，・・・ は各レンズの肉厚およびレンズ間隔、ｎ
1 ，ｎ2 ，・・・ は各レンズの屈折率、ν1 ，ν2 ，・・・
は各レンズのアッベ数である。Where r 1 , r 2 , ... Are the radii of curvature of each lens surface, d 1 , d 2 , ... Are the wall thicknesses and lens intervals of each lens, and n 1 , n 2 ,. Refractive index of each lens, ν 1 ,
ν 2 , ... Is the Abbe number of each lens. Also, r a , r
b , ... Represent the curvature radii of the object-side and image-side surfaces of each gradient index lens. Example 1 f = 1.000, F / 2.508, IH = 0.9240, object distance = -15.4004 r 1 = ∞ d 1 = 0.4107 n 1 = 1.51633 ν 1 = 64.15 r 2 = 0.7938 d 2 = 0.5166 r 3 = ∞ (aperture ) d 3 = 0.0000 r 4 = -16.5987 d 4 = 2.0619 n 2 (gradient lens) r 5 = -1.4540 d 5 = 0.6360 r 6 = 3.1075 d 6 = 2.1941 n 3 = 1.58913 ν 3 = 61.18 r 7 = ∞ Gradient index lens (wavelength) N 0 N 1 N 2 N 3 587.56 1.58913 -0.10622 -0.75321 × 10 -3 0.00000 656.28 1.58618 -0.10569 -0.74944 × 10 -3 0.00000 486.13 1.59600 -0.10746 -0.76199 × 10 -3 0.00000 ν 60.00000 0.60000 × 10 2 0.60000 × 10 2 0.00000 d M = 2.0619, r a = -16.5987, r b = -1.454, φ R = 0.748, φ M = 0.438, φ S = 0.370, φ e = 0.808, ν e = 60.000, N e = 1.989 , ν e / ν 0d = 1.000, N e / N od = 1.252, φ e / φ R = 1.080, φ M / φ e = 0.542 example 2 f = 1.000, F / 2.419 , IH = 0.9336, object distance = -15.5602 r 1 = ∞ d 1 = 0.4149 n 1 = 1.51633 ν 1 = 64.15 r 2 = 0.8486 d 2 = 0.8113 r 3 = ∞ (aperture) d 3 = 0.0000 r 4 = -55.8404 d 4 = 2.1747 n 2 (gradient index lens 1) r 5 = -1.6947 d 5 = 0.3192 r 6 = 7.3237 d 6 = 2.7851 n 3 (Gradient index lens 2) r 7 = ∞ Gradient index lens 1 (Wavelength) N 0 N 1 N 2 N 3 587.56 1.58913 -0.95019 × 10 -1 0.00000 0.00000 656.28 1.58618 -0.94544 × 10 -1 0.00000 0.00000 486.13 1.59600 -0.96128 × 10 -1 0.00000 0.00000 ν 60.00000 0.60000 × 10 2 0.00000 0.00000 d M = 2.1747, r a = -55.8404, r b = -1.6947, φ R = 0.662, φ M = 0.413, φ S = 0.337, φ e = 0.750, ν e = 60.000, N e = 1.997, ν e / ν 0d = 1.000, N e / N od = 1.257, φ e / φ R = 1.133, φ M / φ e = 0.551 gradient index lens 2 (wavelength) N 0 N 1 N 2 N 3 587.56 1.58913 -0.25906 × 10 -1 0.00000 0.00000 656.28 1.58618 -0.25777 × 10 -1 0.00000 0.00000 486.13 1.59600 -0.26209 × 10 -1 0.00000 0.00000 ν 60.00000 0.60000 × 10 2 0.00000 0.00000 d M = 2.7851, r a = 7.3237, r b = ∞, φ R = 0.662, φ M = 0.144, φ S = 0.080, φ e = 0.225, ν e = 60.000, N e = 2.086 , ν e / ν 0d = 1.000, N e / N od = 1.312, φ e / φ R = 0.339, φ M / φ e = 0.642 Example 3 f = 1.000, F / 2.500, IH = 0.9524, Object distance = -15.8730 r 1 = ∞ d 1 = 0.4233 n 1 = 1.51633 ν 1 = 64.15 r 2 = 0.8596 d 2 = 0.4585 r 3 = ∞ (aperture) d 3 = 0.0000 r 4 = -5.3730 d 4 = 2.8996 n 2 (gradient index lens) r 5 = -1.7177 Refractive index Distributed lens (wavelength) N 0 N 1 N 2 N 3 587.56 1.58913 -0.12950 0.87158 × 10 -2 -0.16842 × 10 -2 656.28 1.58618 -0.12885 0.86722 × 10 -2 -0.16757 × 10 -2 486.13 1.59600 -0.13101 0.88175 × 10 -2 -0.17038 × 10 -2 ν 60.00000 0.60000 × 10 2 0.60000 × 10 2 0.60000 × 10 2 d M = 2.8996, r a = -5.373, r b = -1.7177, φ R = 0.736, φ M = 0.751, φ S = 0.233, φ e = 0.984, ν e = 60.000, N e = 2.216, ν e / ν 0d = 1.000, N e / N od = 1.394, φ e / φ R = 1.337, φ M / φ e = 0.763 Example 4 f = 1.000, F / 2.511, IH = 0.9464, object distance = -15.7729 r 1 = ∞ d 1 = 0.4206 n 1 = 1.51633 ν 2 = 64.15 r 2 = 0.7425 d 2 = 0.5256 r 3 = ∞ ( Aperture) d 3 = 0.0000 r 4 = -22.5089 d 4 = 2.1125 n 2 (gradient lens) r 5 = -1.5555 d 5 = 0.9786 r 6 = 2.3620 d 6 = 0.7653 n 3 = 1.58913 ν 3 = 61.18 r 7 = -2.6288 d 7 = 1.0652 n 4 = 1.84666 ν 4 = 23.78 r 8 = ∞ distributed index lenses (wave ) N 0 N 1 N 2 N 3 587.56 1.58913 -0.11920 -0.69327 × 10 -2 0.00000 656.28 1.58618 -0.11860 -0.68981 × 10 -2 0.00000 486.13 1.59600 -0.12059 -0.70136 × 10 -2 0.00000 ν 60.00000 0.60000 × 10 2 0.60000 × 10 2 0.00000 d M = 2.1125, r a = -22.5089, r b = -1.5555, φ R = 0.74, φ M = 0.504, φ S = 0.353, φ e = 0.856, ν e = 60.000, N e = 2.032, ν e / ν 0d = 1.000, N e / N od = 1.279, φ e / φ R = 1.157, φ M / φ e = 0.588 Example 5 f = 1.000, F / 2.508, IH = 0.9009, Object distance =- 15.0150 r 1 = ∞ d 1 = 0.4004 n 1 = 1.51633 ν 1 = 64.15 r 2 = 0.7119 d 2 = 0.9118 r 3 = ∞ (aperture) d 3 = 0.0000 r 4 = 4.7744 d 4 = 2.1961 n 2 (Refractive index distribution Type lens) r 5 = -1.0211 d 5 = 0.1502 n 3 = 1.84666 ν 3 = 23.78 r 6 = -2.1650 d 6 = 0.3532 r 7 = 2.0145 d 7 = 2.5116 n 4 = 1.51633 ν 4 = 64.15 r 8 = ∞ refraction Rate distribution lens (wavelength) N 0 N 1 N 2 N 3 587.56 1.58913 -0.10709 -0.33719 × 10 -1 -0.57394 × 10 -1 656.28 1.58618 -0.10629 -0.33382 × 10 -1 -0.56533 × 10 -1 486.13 1.59600- 0.10897 -0.34506 × 10 -1 -0.59403 × 10 -1 ν 60.00000 0.40000 × 1 0 2 0.30000 × 10 2 0.20000 × 10 2 d M = 2.1961, r a = 4.7744, r b = -1.0211, φ R = 0.649, φ M = 0.470, φ S = 0.700, φ e = 1.171, ν e = 49.963 , N e = 1.867, ν e / ν 0d = 0.833, N e / N od = 1.175, φ e / φ R = 1.804, φ M / φ e = 0.402 example 6 f = 1.000, F / 2.458 , IH = 0.9202, object distance = -15.3374 r 1 = ∞ d 1 = 0.4090 n 1 = 1.51633 ν 1 = 64.15 r 2 = 0.8584 d 2 = 0.6281 r 3 = ∞ (aperture) d 3 = 0.1633 r 4 = -3.9373 d 4 = 2.9962 n 2 (gradient index lens 1) r 5 = -2.6541 d 5 = 1.4374 n 3 (gradient index lens 2) r 6 = -3.9683 Graded index lens 1 (wavelength) N 0 N 1 N 2 N 3 587.56 1.58913 -0.19338 -0.10122 × 10 -4 0.00000 656.28 1.58618 -0.19217 -0.10122 × 10 -4 0.00000 486.13 1.59600 -0.19621 -0.10122 × 10 -4 0.00000 ν 60.00000 0.47883 × 10 2 0.00000 0.00000 d M = 2.9962, r a = -3.9373, r b = -2.6541, φ R = 0.714, φ M = 1.159, φ S = 0.072, φ e = 1.231, ν e = 48.458, N e = 2.441, ν e / ν 0d = 0.808, N e / N od = 1.536, φ e / φ R = 1.724, φ M / φ e = 0.941 Graded index lens 2 (wavelength) N 0 N 1 N 2 N 3 587.56 1.60000 0.54940 × 10 -1 -0.99324 × 10 -6 0.00000 656.28 1.59550 0.51849 × 10 -1 -0.99324 × 10 -6 0.00000 486.13 1.61050 0.62152 × 10 -1 -0.99324 × 10 -6 0.00000 ν 40.00000 0.53323 × 10 0.00000 0.00000 d M = 1.4374, r a = -2.6541, r b = -3.9683, φ R = 0.714, φ M = -0.158 φ S = -0.075, φ e = -0.233, ν e = 7.393, N e = 2.146, ν e / ν 0d = 0.185, N e / N od = 1.341, φ e / φ R = -0.326, φ M / φ e = 0.678 example 7 f = 1.000, F / 2.516 , IH = 0.9091, Object distance = -15.1515 r 1 = ∞ d 1 = 0.4040 n 1 = 1.51633 ν 1 = 64.15 r 2 = 1.0932 d 2 = 0.5706 r 3 = ∞ (aperture) d 3 = 0.3179 r 4 = -6.1292 d 4 = 2.9043 n 2 (refractive index distribution type lens 1) r 5 = -2.5847 d 5 = 1.4989 n 3 (gradient distribution type lens 2) r 6 = ∞ refractive index distribution type lens 1 (wavelength) N 0 N 1 N 2 N 3 587.56 1.58913 -0.20056 0.15606 × 10 -2 0.34841 × 10 -4 656.28 1.58618 -0.19955 0.15507 × 10 -2 0.34579 × 10 -4 486.13 1.59600 -0.20292 0.15839 × 10 -2 0.35450 × 10 -4 ν 60.00000 0.59491 × 10 2 0.47000 × 10 2 0.40000 × 10 2 d M = 2.9043, r a = -6.1292 , r b = -2.5847, φ R = 0.799, φ M = 1.165, φ S = 0.132, φ e = 1.297, ν e = 59.542, N e = 2.383, ν e / ν 0d = 0.992, N e / N od = 1.499, φ e / φ R = 1.623, φ M / φ e = 0.898 Gradient index lens 2 (wavelength) N 0 N 1 N 2 N 3 587.56 1.60000 0.41751 × 10 -1 -0.82 240 × 10 -2 -0.14197 × 10 -3 656.28 1.59550 0.38456 × 10 -1 -0.81623 × 10 -2 -0.13132 × 10 -3 486.13 1.61050 0.49440 × 10 -1 -0.83679 × 10 -2 -0.16682 × 10 -3 ν 40.00000 0.38011 × 10 0.40000 × 10 2 0.40000 × 10 d M = 1.4989, r a = -2.5847, r b = ∞, φ R = 0.799, φ M = -0.125, φ S = -0.232, φ e = -0.357, ν e = 9.225, N e = 1.842, ν e / ν 0d = 0.231, N e / N od = 1.151, φ e / φ R = -0.447, φ M / φ e = 0.350 example 8 f = 1.000, F / 2.453 , IH = 1.0345, Object distance = -17.2414 r 1 = ∞ d 1 = 0.4023 n 1 = 1.84666 ν 1 = 23.78 r 2 = -5.6322 d 2 = 0.4023 n 2 = 1.51633 ν 2 = 64.15 r 3 = 0.8717 d 3 = 0.6060 r 4 = ∞ (Aperture) d 4 = 0.0000 r 5 = -6.2112 d 5 = 3.0465 n 3 (Gradient distribution type lens) r 6 = -1.6142 Gradient distribution type lens (wavelength) N 0 N 1 N 2 N 3 587.56 1 .58913 -0.11266 0.11896 × 10 -1 0.29127 × 10 -2 656.28 1.58618 -0.11210 0.11837 × 10 -1 0.28981 × 10 -2 486.13 1.59600 -0.11398 0.12035 × 10 -1 0.29467 × 10 -2 ν 60.00000 0.60000 × 10 2 0.60000 × 10 2 0.60000 × 10 2 d M = 3.0465, r a = -6.2112, r b = -1.6142, φ R = 0.709, φ M = 0.686, φ S = 0.270, φ e = 0.957, ν e = 60.000, N e = 2.165, ν e / ν 0d = 1.000, N e / N od = 1.362, φ e / φ R = 1.349, φ M / φ e = 0.718 example 9 f = 1.000, F / 2.464 , IH = 1.0502, object Distance = -17.5029 r 1 = ∞ d 1 = 0.4084 n 1 = 1.84666 ν 1 = 23.78 r 2 = -5.6009 d 2 = 0.3501 n 2 = 1.51633 ν 2 = 64.15 r 3 = 0.8614 d 3 = 0.8279 r 4 = ∞ ( Aperture) d 4 = 0.0000 r 5 = 19.1703 d 5 = 2.4563 n 3 (gradient lens) r 6 = -1.8041 d 6 = 0.6483 r 7 = 1.8563 d 7 = 0.8922 n 4 = 1.51633 ν 4 = 64.15 r 8 = -2.1004 d 8 = 1.0519 n 5 = 1.84666 ν 5 = 23.78 r 9 = ∞ Gradient index lens (wavelength) N 0 N 1 N 2 N 3 587.56 1.58913 -0.88999 × 10 -1 -0.23419 × 10 -2 0.00000 656.28 1.58618 -0.88554 x 10 -1 -0.23302 x 10 -2 0.00000 486.13 1.59600 -0.90037 x 10 -1 -0.23692 × 10 -2 0.00000 ν 60.00000 0.60000 × 10 2 0.60000 × 10 2 0.00000 d M = 2.4563, r a = 19.1703, r b = -1.8041, φ R = 0.711, φ M = 0.437, φ S = 0.357, φ e = 0.794, ν e = 60.000, N e = 1.996, ν e / ν 0d = 1.000, N e / N od = 1.256, φ e / φ R = 1.117, φ M / φ e = 0.550 Example 10 f = 1.000, F / 2.439, IH = 0.9772, Object distance = -16.2866 r 1 = ∞ d 1 = 0.5429 n 1 (gradient index lens 1) r 2 = 0.9262 d 2 = 0.7386 r 3 = ∞ ( Aperture) d 3 = 0.1323 r 4 = 8.4788 d 4 = 2.3626 n 2 (Gradation index lens 2) r 5 = -1.7368 d 5 = 0.4522 r 6 = 2.1579 d 6 = 1.1059 n 3 = 1.58913 ν 3 = 61.18 r 7 = -1.9001 d 7 = 1.8039 n 4 = 1.84666 ν 4 = 23.78 r 8 = ∞ Gradient index lens 1 (wavelength) N 0 N 1 N 2 N 3 587.56 1.67000 -0.54518 × 10 -1 0.00000 0.00000 656.28 1.66330- 0.51247 × 10 -1 0.00000 0.00000 486.13 1.68563 -0.62151 × 10 -1 0.00000 0.00000 ν 30.00000 0.50000 × 10 0.00000 0.00000 d M = 0.5429, r a = ∞, r b = 0.9262, φ R = 0.684, φ M = 0.059, φ S = -0.723, φ e = -0.664, ν e = 54.115, N e = 1.612 , ν e / ν 0d = 1.804, N e / N od = 0.965, φ e / φ R = -0.971, φ M / φ e = -0.089 gradient index lens 2 (Wavelength ) N 0 N 1 N 2 N 3 587.56 1.58913 -0.60781 × 10 -1 -0.56118 × 10 -4 -0.61034 × 10 -4 656.28 1.58618 -0.60477 × 10 -1 -0.55838 × 10 -4 -0.60729 × 10 -4 486.13 1.59600 -0.61490 × 10 -1 -0.56773 × 10 -4 -0.61746 × 10 -4 ν 60.00000 0.60000 × 10 2 0.60000 × 10 2 0.60000 × 10 2 d M = 2.3626, r a = 8.4788, r b = -1.7368, φ R = 0.684, φ M = 0.287 , φ S = 0.409, φ e = 0.696, ν e = 60.000, N e = 1.876, ν e / ν 0d = 1.000, N e / N od = 1.181, φ e / φ R = 1.017, φ M / φ e = 0.413 Example 11 f = 1.000, F / 2.481, IH = 0.9815, Object distance = -16.3577 r 1 = ∞ d 1 = 0.8724 n 1 (Gradient index lens 1) r 2 = 0.8853 d 2 = 0.7109 r 3 = ∞ (aperture) d 3 = 0.0695 r 4 = 9.6787 d 4 = 2.3314 n 2 (gradient index lens 2) r 5 = -1.6455 d 5 = 0.4338 r 6 = 2.0726 d 6 = 1.1054 n 3 = 1.58913 ν 3 = 61.18 r 7 = -1.9084 d 7 = 1.8177 n 4 = 1.84666 ν 4 = 23.78 r 8 = ∞ Gradient index lens 1 (wavelength) N 0 N 1 N 2 N 3 587.56 1.67000 -0.44819 × 10 -1 0.00000 0.00000 656.28 1.66330 -0.42899 × 10 -1 0.00000 0.00000 486.13 1.68563 -0.49301 × 10 -1 0.00000 0.00000 ν 30.00000 0.70000 × 10 0.00000 0.00000 d M = 0.8724, r a = ∞, r b = 0.8858, φ R = 0.702, φ M = 0.078, φ S = -0.756, φ e = -0.678, ν e = 48.299, N e = 1.596, ν e / ν 0d = 1.610, N e / N od = 0.956, φ e / φ R = -0.966, φ M / φ e = -0.115 Gradient index lens 2 (wavelength) N 0 N 1 N 2 N 3 587.56 1.58913 -0.59491 × 10 -1 -0.54602 × 10 -4 -0.59461 × 10 -4 656.28 1.58618 -0.59194 × 10 -1 -0.54347 × 10 -4 -0.59163 × 10 -4 486.13 1.59600 -0.60186 × 10 -1 -0.55257 × 10 -4 -0.60154 × 10 -4 ν 60.00000 0.60000 × 10 2 0.60000 × 10 2 0.60000 × 10 2 d M = 2.3314, r a = 9.6787, r b = -1.6455, φ R = 0.702, φ M = 0.277, φ S = 0.419, φ e = 0.696, ν e = 60.000, N e = 1.865, ν e / ν 0d = 1.000, N e / N od = 1.173, φ e / φ R = 0.992, φ M / φ e = 0.398 Example 12 f = 1.000, F / 2.447, IH = 1.0066, object distance = -16.7771 r 1 = ∞ d 1 = 0.8948 n 1 ( refractive index lens 1) 2 = 0.9052 d 2 = 0.7290 r 3 = ∞ ( stop) d 3 = 0.0725 r 4 = 11.6414 d 4 = 2.3916 n 2 ( refractive index lens 2) r 5 = -1.6886 d 5 = 0.5508 r 6 = 2.1855 d 6 = 1.1329 n 3 = 1.58913 ν 3 = 61.18 r 7 = -1.9573 d 7 = 1.5304 n 4 = 1.84666 ν 4 = 23.78 r 8 = ∞ Gradient index lens 1 (wavelength) N 0 N 1 N 2 N 3 587.56 1.67000 -0.45769 × 10 -1 0.00000 0.00000 656.28 1.66330 -0.43808 × 10 -1 0.00000 0.00000 486.13 1.68563 -0.50346 × 10 -1 0.00000 0.00000 ν 30.00000 0.70000 × 10 0.00000 0.00000 d M = 0.8948, r a = ∞, r b = 0.9052, φ R = 0.695, φ M = 0.082, φ S = -0.740, φ e = -0.658, ν e = 50.748, N e = 1.591, ν e / ν 0d = 1.692, N e / N od = 0.952, φ e / φ R = -0.947, φ M / φ e = -0.124 Gradient index lens 2 (wavelength) N 0 N 1 N 2 N 3 587.56 1.58913 -0.67241 × 10 -1 0.65406 × 10 -3 0.28639 × 10 -3 656.28 1.58618 -0.66736 × 10 -1 0.64425 × 10 -3 0.28639 × 10 -3 486.13 1.59600 -0.68417 × 10 -1 0.67696 × 10 -3 0.28639 × 10 -3 ν 60.00000 0.40000 × 10 2 0.20000 × 10 2 0.0000 0 d M = 2.3916, r a = 11.6414, r b = -1.6886, φ R = 0.695, φ M = 0.322, φ S = 0.399, φ e = 0.721, ν e = 49.059, N e = 1.904, ν e / ν 0d = 0.818, N e / N od = 1.198, φ e / φ R = 1.038, φ M / φ e = 0.446 Example 13 f = 1.000, F / 2.512, IH = 0.9444, Object distance = -15.7398 r 1 = ∞ d 1 = 0.4197 n 1 (gradient index lens 1) r 2 = 1.3360 d 2 = 0.3662 r 3 = ∞ (aperture) d 3 = 0.0000 r 4 = -4.0246 d 4 = 2.7540 n 2 (Refractive index distribution type lens 2) r 5 = -2.0199 Refractive index distribution type lens 1 (wavelength) N 0 N 1 N 2 N 3 587.56 1.75000 -0.81739 × 10 -1 0.00000 0.00000 656.28 1.74250 -0.75608 × 10 -1 0.00000 0.00000 486.13 1.76750 -0.96043 × 10 -1 0.00000 0.00000 ν 30.00000 0.40000 × 10 0.00000 0.00000 d M = 0.4197, r a = ∞, r b = 1.336, φ R = 0.812, φ M = 0.069, φ S = -0.561, φ e = -0.493, ν e = 315.947, N e = 1.651, ν e / ν 0d = 10.532, N e / N od = 0.944, φ e / φ R = -0.607, φ M / φ e = -0.139 refractive Rate distribution type lens 2 (wavelength) N 0 N 1 N 2 N 3 587.56 1.589 13 -0.17504 0.16003 x 10 -1 -0.85767 x 10 -2 656.28 1.58618 -0.17416 0.15923 x 10 -1 -0.85338 x 10 -2 486.13 1.59600 -0.17708 0.16190 x 10 -1 -0.86768 x 10 -2 ν 60.00000 0.60000 x 10 2 0.60000 × 10 2 0.60000 × 10 2 d M = 2.754, r a = -4.0246, r b = -2.0199, φ R = 0.812, φ M = 0.964, φ S = 0.145, φ e = 1.109, ν e = 60.000, N e = 2.344, ν e / ν 0d = 1.000, N e / N od = 1.475, φ e / φ R = 1.366, φ M / φ e = 0.869 example 14 f = 1.000, F / 2.420 , IH = 1.0056 , Object distance = -16.7598 r 1 = ∞ d 1 = 0.3352 n 1 = 1.78472 ν 2 = 25.68 r 2 = -11.1732 d 2 = 0.4469 n 2 (gradient index lens 1) r 3 = 0.9927 d 3 = 0.5357 r 4 = ∞ (aperture) d 4 = 0.0000 r 5 = -12.4470 d 5 = 3.0522 n 3 (refractive index distribution type lens 2) r 6 = −1.6156 refractive index distribution type lens 1 (wavelength) N 0 N 1 N 2 N 3 587.56 1.67000 -0.48870 × 10 -1 0.00000 0.00000 656.28 1.66330 -0.41539 × 10 -1 0.00000 0.00000 486.13 1.68563 -0.65974 × 10 -1 0.00000 0.00000 ν 30.00000 0.20000 × 10 0.00000 0.000 00 d M = 0.4469, r a = -11.1732, r b = 0.9927, φ R = 0.694, φ M = 0.044, φ S = -0.735, φ e = -0.691, ν e = 260.207, N e = 1.629, ν e / ν 0d = 8.674, N e / N od = 0.975, φ e / φ R = -0.996, φ M / φ e = -0.063 gradient index lens 2 (wavelength) N 0 N 1 N 2 N 3 587.56 1.58913 -0.10909 0.12255 × 10 -1 0.31761 × 10 -2 656.28 1.58618 -0.10854 0.12194 × 10 -1 0.31602 × 10 -2 486.13 1.59600 -0.11036 0.12398 × 10 -1 0.32131 × 10 -2 ν 60.00000 0.60000 × 10 2 0.60000 × 10 2 0.60000 × 10 2 d M = 3.0522, r a = -12.447, r b = -1.6156, φ R = 0.694, φ M = 0.666, φ S = 0.317, φ e = 0.983, ν e = 60.000, N e = 2.122, ν e / ν 0d = 1.000, N e / N od = 1.335, φ e / φ R = 1.417, φ M / φ e = 0.677 example 15 f = 1.000, F / 2.503 , IH = 0.8825, object distance = -14.7085 r 1 = ∞ d 1 = 0.3922 n 1 (gradient index lens 1) r 2 = 1.3187 d 2 = 0.4372 r 3 = ∞ (aperture) d 3 = 0.3327 r 4 = -6.2473 d 4 = 2.8124 n 2 (gradient index lens 2) r 5 = -2.9122 d 5 = 1.6332 n 3 ( GRIN Lens 3) r 6 = ∞ gradient index lens 1 (wavelength) N 0 N 1 N 2 N 3 587.56 1.60000 -0.24865 × 10 -1 0.70810 × 10 -2 -0.75187 × 10 -2 656.28 1.59640 -0.23835 × 10 - 1 0.70102 × 10 -2 -0.72932 × 10 -2 486.13 1.60840 -0.27269 × 10 -1 0.72462 × 10 -2 -0.80450 × 10 -2 ν 50.00000 0.72406 × 10 0.30000 × 10 2 0.10000 × 10 2 d M = 0.3922, r a = ∞, r b = 1.3187 , φ R = 0.854, φ M = 0.020, φ S = -0.455, φ e = -0.435, ν e = 67.980, N e = 1.574, ν e / ν 0d = 1.360, N e / N od = 0.983, φ e / φ R = -0.510, φ M / φ e = -0.045 Gradient index lens 2 (wavelength) N 0 N 1 N 2 N 3 587.56 1.80000 -0.20871 0.28165 × 10 -2 -0.79986 × 10 -3 656.28 1.79520 -0.20743 0.27922 × 10 -2 -0.79187 × 10 -3 486.13 1.81120 -0.21171 0.28732 × 10 -2 -0.81852 × 10 -3 ν 50.00000 0.48760 × 10 2 0.34764 × 10 2 0.30012 × 10 2 d M = 2.8124, r a = -6.2473, r b = -2.9122, φ R = 0.854, φ M = 1.174, φ S = 0.147, φ e = 1.321, ν e = 48.895, N e = 2.976, ν e / ν 0d = 0.978, N e / N od = 1.653, φ e / φ R = 1.546, φ M / φ e = 0.889 refractive index distribution Lens 3 (wavelength) N 0 N 1 N 2 N 3 587.56 1.60000 0.44519 × 10 -1 -0.92446 × 10 -2 0.29229 × 10 -3 656.28 1.59550 0.40164 × 10 -1 -0.84232 × 10 -2 0.23193 × 10 -3 486.13 1.61050 0.54681 × 10 -1 -0.11161 × 10 -1 0.43311 × 10 -3 ν 40.00000 0.30668 × 10 0.33767 × 10 0.14529 × 10 d M = 1.6332, r a = -2.9122, r b =?, Φ R = 0.799, φ M = -1.454, φ S = -0.206 , φ e = -1.660, ν e = 3.464, N e = 2.383, ν e / ν 0d = 0.087, N e / N od = 1.489, φ e / φ R = - 1.944, φ M / φ e = 0.876 where r 1 , r 2 , ... Are the radius of curvature of each lens surface, d
1 , d 2 , ... Is the thickness of each lens and the lens interval, n
1 , n 2 , ... Are the refractive indices of the respective lenses, ν 1 , ν 2 ,.
Is the Abbe number of each lens.

【００３０】実施例１は、図１に示す構成で、後群収斂
系を凸の屈折率分布型レンズ１枚と凸レンズとで構成し
た。Example 1 has the configuration shown in FIG. 1 and the rear group convergence system is composed of one convex gradient index lens and a convex lens.

【００３１】実施例２は、図２に示す構成で、後群を凸
の屈折率分布型レンズ２枚で構成した。The second embodiment has the configuration shown in FIG. 2, and the rear group is composed of two convex gradient index lenses.

【００３２】実施例３は、図３に示す構成で後群を凸の
屈折率分布型レンズ１枚のみで構成した。In the third embodiment, the rear group has a structure shown in FIG. 3 and is composed of only one convex gradient index lens.

【００３３】上記各実施例の屈折率分布型レンズは、ν
1d，ν0dが式（７）で表わされると、それらレンズの屈
折率分布が光軸から周辺へ行くにしたがって屈折率が小
さくなり、それにともない分散も小さくなる。この場合
屈折率分布型レンズの色収差に関する作用は、通常の光
学ガラスを凸レンズに用いた場合と同じである。即ち、
レトロフォーカス型内視鏡対物レンズの後群収斂系に、
凸の作用でかつ式（７）で表わされ分散特性の屈折率分
布型レンズを用いれば媒質での倍率の色収差がマイナス
側に発生する。そのためこの倍率の色収差を補正する必
要が生ずる。The gradient index lens of each of the above embodiments has
When 1d and ν 0d are expressed by the equation (7), the refractive index distributions of those lenses become smaller as going from the optical axis to the periphery, and the dispersion becomes smaller accordingly. In this case, the action on the chromatic aberration of the gradient index lens is the same as that when the normal optical glass is used for the convex lens. That is,
In the rear focusing system of the retrofocus endoscope objective lens,
If a gradient index lens having a convex action and a dispersion characteristic represented by the formula (7) is used, lateral chromatic aberration occurs in the medium. Therefore, it becomes necessary to correct the chromatic aberration of this magnification.

【００３４】実施例４，５は、図４，図５に示す構成
で、後群収斂系は、屈折率分布型レンズ以外のレンズを
色消しに用いている。即ち、後群中に比較的屈折率が高
く分散が大きい凹レンズを加えている。その際、上記の
屈折率分布型レンズと凸のレンズ成分とからなり、実施
例４のようにこの凸のレンズ成分を比較的屈折率が低く
分散の小さいガラスの凸レンズと比較的屈折率が高く分
散の大きいガラスよりなる凹レンズとよりなる色消し接
合レンズとすることが望ましい。又この凸レンズと凹レ
ンズとは、接合とせず、独立したレンズにしてもよい。
また実施例５のように後群中の屈折率分布型レンズと上
記の凹レンズとを接合しても倍率の色収差を補正するこ
とが出来る。Embodiments 4 and 5 have the constructions shown in FIGS. 4 and 5, and the rear group converging system uses lenses other than the gradient index lens for achromatization. That is, a concave lens having a relatively high refractive index and a large dispersion is added to the rear group. At that time, it is composed of the above-mentioned gradient index lens and a convex lens component, and as in Example 4, the convex lens component has a relatively low refractive index and a small dispersion glass convex lens and a relatively high refractive index. It is desirable to use an achromatic cemented lens composed of a concave lens composed of glass having a large dispersion. Further, the convex lens and the concave lens may not be cemented but may be independent lenses.
Further, as in the fifth embodiment, the chromatic aberration of magnification can be corrected by cementing the gradient index lens in the rear group and the above concave lens.

【００３５】実施例６、７は夫々図６、７に示す構成で
ある。これら実施例は、後群収斂系に式（１）〜
（５），（７）、および次の式（１４）に示される屈折
率分布型レンズを加えて倍率の色収差を補正している。 （１１４） Ｎ１ｄ＞０ 即ち、これら実施例は、後群が少なくとも二つの光学素
子よりなり、そのうちの一つが式（１）〜（７）で表わ
される屈折率分布型レンズで、他の一つは式（１）〜
（５），（７），（１４）で示される屈折率分布型レン
ズである。Embodiments 6 and 7 have the configurations shown in FIGS. 6 and 7, respectively. In these examples, the rear group convergent system is represented by formulas (1) to
The chromatic aberration of magnification is corrected by adding the gradient index lens shown in (5) and (7) and the following expression (14). (114) N 1d > 0 That is, in these examples, the rear group is composed of at least two optical elements, one of which is the gradient index lens represented by the formulas (1) to (7), and the other one. One is formula (1)
It is a gradient index lens shown by (5), (7) and (14).

【００３６】この屈折率分布型レンズの色収差補正能力
は、アッベ数を通常の光学ガラスに置き換えて考えれば
よい。The chromatic aberration correction capability of this gradient index lens can be considered by replacing the Abbe number with a normal optical glass.

【００３７】軸上色収差を補正するための条件として、
次の式（１５）が一般に知られている。 （１５） Σ（φ／ν）＝０ ここで、φは通常の光学ガラスのレンズの屈折力（１／
ｆ ）、νはアッベ数である。As a condition for correcting the axial chromatic aberration,
The following equation (15) is generally known. (15) Σ (φ / ν) = 0 where φ is the refracting power (1 /
f) and ν are Abbe numbers.

【００３８】式（１５）のφ／Ｎに着目して上記の屈折
率分布型レンズと通常の光学ガラスとが等価であると仮
定すると、薄肉系では、次の式（１６）が成立つ。 （１６） φｅ／νｅ ＝φＳ／ν０ｄ＋φＭ／ν１ｄ ただしνｅ は屈折率分布型レンズのアッベ数分布を通
常の光学ガラスのアッベ数に置きかえたもの（以後等価
アッベ数と呼ぶ）である。 ここでφｅ＝φＳ ＋φＭ
と近似し、式（１６）を変形すれば次の式（１７）が
得られる。 （１７） νｅ ＝ν０ｄ×ν１ｄ／｛（ν０ｄ−ν１ｄ）×φＭ／φｅ ＋ ν１ｄ｝ 式（１７）の右辺の分子分母をν１ｄで割れば次の式
（１８）が得られる。 （１８） νｅ ＝ν０ｄ／｛（ ν０ｄ／ ν１ｄ−１） ×φＭ／φｅ ＋１｝ 上記の式（１８）から、ν１ｄを小さくするとνｅ が
ν０ｄより小さくなることがわかる。即ち、後群収斂系
に凹の屈折力を有する等価アッベ数が比較的小さい屈折
率分布型レンズを用いると、ν０ｄが同じ値をとる通常
の光学ガラスを用いた場合よりも倍率の色収差を良好に
補正することが出来る。Assuming that the gradient index lens and the ordinary optical glass are equivalent by paying attention to φ / N in the equation (15), the following equation (16) is established in the thin system. (16) φ e / ν e = φ S / ν 0d + φ M / ν 1d, where ν e is the Abbe number distribution of a graded-index lens replaced by the Abbe number of ordinary optical glass (hereinafter equivalent Abbe number and Call). Where φ e = φ S + φ M
When the equation (16) is modified, the following equation (17) is obtained. (17) ν e = ν 0d × ν 1d / {(ν 0d -ν 1d) × φ M / φ e + ν 1d} formula (17) if the numerator and denominator of the right side divided by [nu 1d the following equation (18 ) Is obtained. (18) ν e = ν 0d / {(ν 0d / ν 1d −1) × φ M / φ e +1} From the above equation (18), if ν 1d is made smaller, then ν e becomes smaller than ν 0d. Recognize. That is, when a gradient index lens having a relatively small equivalent Abbe number with a concave refractive power is used in the rear lens group convergent system, chromatic aberration of magnification is larger than that in the case of using an ordinary optical glass in which ν 0d has the same value. It can be corrected well.

【００３９】この場合次の条件（１９）を満足すること
が望ましい。 （１９） νｅ ／ν０ｄ≧０．８ 式（１９）を外れると、倍率の色収差が補正不足になり
望ましくない。In this case, it is desirable to satisfy the following condition (19). (19) ν e / ν 0d ≧ 0.8 If the equation (19) is not satisfied, the chromatic aberration of magnification is insufficiently corrected, which is not desirable.

【００４０】実施例８，９は、図８，図９に示す構成
で、前群発散系で倍率の色収差を補正するようにしてい
る。The eighth and ninth embodiments have the configuration shown in FIGS. 8 and 9 and are adapted to correct lateral chromatic aberration in the front lens group diverging system.

【００４１】つまり前群発散系を、比較的屈折率が低く
分散が小さいガラスの凹レンズと比較的屈折率が高く分
散の大きい凸レンズとにて構成している。これは、前群
だけでみるとマイナス側に倍率の色収差が発生している
が、明るさ絞りより、物体側に位置するので、プラス側
に倍率の色収差が発生することになり、全系では、倍率
の色収差が良好に補正されることになる。That is, the front lens group diverging system is composed of a glass concave lens having a relatively low refractive index and a small dispersion and a convex lens having a relatively high refractive index and a large dispersion. This is because chromatic aberration of magnification occurs on the minus side when viewed only in the front group, but since it is located on the object side of the aperture stop, chromatic aberration of magnification occurs on the plus side, and in the entire system Therefore, the chromatic aberration of magnification is satisfactorily corrected.

【００４２】実施例１０〜１４は、夫々図１０〜図１４
に記載された構成のレンズ系である。これら実施例は、
前群発散系に式（１）〜式（７）にて示される屈折率分
布型レンズを用いたものである。Embodiments 10 to 14 are shown in FIGS. 10 to 14, respectively.
The lens system has the configuration described in 1. These examples
The gradient index lens shown in Formulas (1) to (7) is used in the front group divergence system.

【００４３】前述のように、後群収斂レンズ系中に式
（１）〜式（７）にて示される屈折率分布型レンズを用
いた場合には、マイナス側に倍率の色収差が発生する。As described above, when the gradient index lens shown in the formulas (1) to (7) is used in the rear lens group lens system, lateral chromatic aberration occurs.

【００４４】前群中にこのような屈折率分布型レンズを
用いた場合、前群だけでみると、マイナス側に倍率の色
収差が発生するが、明るさ絞りを介することによって符
号が反転して像面では、プラス側に倍率色収差が発生す
ることになる。したがって全系においては、倍率の色収
差が良好に補正される。When such a gradient index lens is used in the front group, chromatic aberration of magnification occurs on the minus side when viewed only in the front group, but the sign is reversed by passing through the aperture stop. On the image plane, lateral chromatic aberration occurs on the plus side. Therefore, the chromatic aberration of magnification is satisfactorily corrected in the entire system.

【００４５】この場合、前記前群発散系に用いる屈折率
分布型レンズの等価アッベ数νe'は、次の式（２０）又
は式（２１）を満足することが好ましい。 （２０） νe '／ν0d≧１．２ （２１） νe '≦０ 式（２０）は、前群発散系で発生する負の色収差を極め
て小さい値に抑えるための条件である。又式（２１）
は、前群発散系で正の色収差を発生させるための条件で
ある。In this case, it is preferable that the equivalent Abbe number ν e ′ of the gradient index lens used in the front lens group diverging system satisfies the following equation (20) or equation (21). (20) ν e ′ / ν 0d ≧ 1.2 (21) ν e ′ ≦ 0 Expression (20) is a condition for suppressing the negative chromatic aberration generated in the front group divergence system to an extremely small value. Equation (21)
Is a condition for generating positive chromatic aberration in the front group divergence system.

【００４６】これら式（２０）又は（２１）に示す範囲
を越えると、後群収斂系で発生する負の色収差を前群発
散系で補正出来なくなるので好ましくない。When the value exceeds the range expressed by the equation (20) or (21), it is not preferable because the negative chromatic aberration generated in the rear lens group convergent system cannot be corrected by the front lens group divergent system.

【００４７】尚例えば実施例１０（図１０）において、
後群収斂系の最も像伝送系（イメージガイド）に近い凸
のレンズ成分の像側の平面の有効径部外（イメージガイ
ドを固定している口金に接する部分）を粗面とし、更に
これに黒色塗料等の光を吸収する物質を付けることによ
って、視野に悪影響を及ぼすフレアー、ゴースト等の有
害光を防止することが可能になる。For example, in Example 10 (FIG. 10),
The outer surface of the image-side plane of the convex lens component closest to the image transmission system (image guide) of the rear group convergence system outside the effective diameter portion (the portion in contact with the base fixing the image guide) is a rough surface. By adding a substance that absorbs light, such as black paint, it is possible to prevent harmful light such as flare and ghost that adversely affects the visual field.

【００４８】[0048]

【発明の効果】本発明の内視鏡対物レンズは、少ないレ
ンズ枚数の安価な、全長の短い、かつ収差の良好に補正
されたレンズ系である。The endoscope objective lens of the present invention is an inexpensive lens system having a small number of lenses, a short overall length, and good aberration correction.

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

【図１】本発明の実施例１の断面図FIG. 1 is a sectional view of a first embodiment of the present invention.

【図２】本発明の実施例２の断面図FIG. 2 is a sectional view of a second embodiment of the present invention.

【図３】本発明の実施例３の断面図FIG. 3 is a sectional view of a third embodiment of the present invention.

【図４】本発明の実施例４の断面図FIG. 4 is a sectional view of a fourth embodiment of the present invention.

【図５】本発明の実施例５の断面図FIG. 5 is a sectional view of a fifth embodiment of the present invention.

【図６】本発明の実施例６の断面図FIG. 6 is a sectional view of a sixth embodiment of the present invention.

【図７】本発明の実施例７の断面図FIG. 7 is a sectional view of a seventh embodiment of the present invention.

【図８】本発明の実施例８の断面図FIG. 8 is a sectional view of an eighth embodiment of the present invention.

【図９】本発明の実施例９の断面図FIG. 9 is a sectional view of a ninth embodiment of the present invention.

【図１０】本発明の実施例１０の断面図FIG. 10 is a sectional view of Example 10 of the present invention.

【図１１】本発明の実施例１１の断面図FIG. 11 is a sectional view of Embodiment 11 of the present invention.

【図１２】本発明の実施例１２の断面図FIG. 12 is a sectional view of embodiment 12 of the present invention.

【図１３】本発明の実施例１３の断面図FIG. 13 is a sectional view of Embodiment 13 of the present invention.

【図１４】本発明の実施例１４の断面図FIG. 14 is a sectional view of Embodiment 14 of the present invention.

【図１５】本発明の実施例１５の断面図FIG. 15 is a sectional view of Example 15 of the present invention.

【図１６】本発明の実施例１の収差曲線図FIG. 16 is an aberration curve diagram of Example 1 of the present invention.

【図１７】本発明の実施例２の収差曲線図FIG. 17 is an aberration curve diagram of Example 2 of the present invention.

【図１８】本発明の実施例３の収差曲線図FIG. 18 is an aberration curve diagram for Example 3 of the present invention.

【図１９】本発明の実施例４の収差曲線図FIG. 19 is an aberration curve diagram of Example 4 of the present invention.

【図２０】本発明の実施例５の収差曲線図FIG. 20 is an aberration curve diagram of Example 5 of the present invention.

【図２１】本発明の実施例６の収差曲線図FIG. 21 is an aberration curve diagram of Example 6 of the present invention.

【図２２】本発明の実施例７の収差曲線図FIG. 22 is an aberration curve diagram for Example 7 of the present invention.

【図２３】本発明の実施例８の収差曲線図FIG. 23 is an aberration curve diagram of Example 8 of the present invention.

【図２４】本発明の実施例９の収差曲線図FIG. 24 is an aberration curve diagram for Example 9 of the present invention.

【図２５】本発明の実施例１０の収差曲線図FIG. 25 is an aberration curve diagram of Example 10 of the present invention.

【図２６】本発明の実施例１１の収差曲線図FIG. 26 is an aberration curve diagram for Example 11 of the present invention.

【図２７】本発明の実施例１２の収差曲線図FIG. 27 is an aberration curve diagram of Example 12 of the present invention.

【図２８】本発明の実施例１３の収差曲線図FIG. 28 is an aberration curve diagram for Example 13 of the present invention.

【図２９】本発明の実施例１４の収差曲線図FIG. 29 is an aberration curve diagram of Example 14 of the present invention.

【図３０】本発明の実施例１５の収差曲線図FIG. 30 is an aberration curve diagram of Example 15 of the present invention.

【図３１】従来の内視鏡対物レンズの構成を示す図FIG. 31 is a diagram showing a configuration of a conventional endoscope objective lens.

【手続補正書】[Procedure amendment]

【提出日】平成４年１２月１８日[Submission date] December 18, 1992

【手続補正１】[Procedure Amendment 1]

【補正対象書類名】明細書[Document name to be amended] Statement

【補正対象項目名】請求項１[Name of item to be corrected] Claim 1

【補正方法】変更[Correction method] Change

【補正内容】[Correction content]

【手続補正２】[Procedure Amendment 2]

【補正対象書類名】明細書[Document name to be amended] Statement

【補正対象項目名】００１１[Correction target item name] 0011

【補正方法】変更[Correction method] Change

【補正内容】[Correction content]

【００１１】[0011]

【課題を解決するための手段】本発明の内視鏡対物レン
ズは、例えば図１に示す構成のものである。即ち物体側
から順に負のパワーを有する前群発散系と、明るさ絞り
と、正のパワーを有する後群収斂系とからなり、前記後
群収斂系中の少なくとも１枚のレンズが屈折率分布型レ
ンズよりなっている。そしてこの屈折率分布型レンズ
は、屈折率分布を下記の式（１）〜（５）で近似した
時、式（６），（７）を満足するものである。 （１） Ｎｄ（ｒ）＝Ｎ０ｄ＋Ｎ１ｄｒ２＋Ｎ２ｄｒ４＋Ｎ３ｄｒ６ （２） ＮＦ（ｒ）＝Ｎ０Ｆ＋Ｎ１Ｆｒ２＋Ｎ２Ｆｒ４＋Ｎ３Ｆｒ６ （３） ＮＣ（ｒ）＝Ｎ０Ｃ＋Ｎ１Ｃｒ２＋Ｎ２Ｃｒ４＋Ｎ３Ｃｒ６ （４） ν０ｄ＝（１−Ｎ０ｄ）／（Ｎ０Ｆ＝Ｎ０Ｃ） （５） ν１ｄ＝Ｎ１ｄ／（Ｎ１Ｆ−Ｎ１Ｃ） （６） Ｎ１ｄ＜０ （７） ０≦ν０ｄ≦ν１ｄ ただしＮｄ（ｒ），ＮＦ（ｒ），ＮＣ（ｒ）は夫々光軸
からの径方向の距離をｒとした時のｄ線、Ｆ線，Ｃ線に
関する屈折率分布、Ｎ０ｄ，Ｎ１ｄ，Ｎ２ｄ，Ｎ３ｄは
ｄ線に関する屈折率分布係数、Ｎ０Ｆ，Ｎ１Ｆ，
Ｎ２Ｆ，Ｎ３ＦはＦ線に関する屈折率分布係数、
Ｎ０Ｃ，Ｎ１Ｃ，Ｎ２Ｃ，Ｎ３ＣはＣ線に関する屈折率
分布係数、ν０ｄ，ν１ｄはＮ０ｄ，Ｎ０Ｆ，Ｎ０Ｃ，
Ｎ１ｄ，Ｎ１Ｆ，Ｎ１Ｃを用いて式（４），（５）に表
わされるアッベ数である。An endoscope objective lens of the present invention has a structure shown in FIG. 1, for example. That is, it comprises a front lens group diverging system having a negative power in order from the object side, an aperture stop, and a rear lens group focusing system having a positive power, and at least one lens in the rear lens group focusing system has a refractive index distribution. It consists of a mold lens. The gradient index lens satisfies the equations (6) and (7) when the refractive index distribution is approximated by the following equations (1) to (5). (1) N d (r) = N 0d + N 1d r 2 + N 2d r 4 + N 3d r 6 (2) N F (r) = N 0F + N 1F r 2 + N 2F r 4 + N 3F r 6 (3) N C (r) = N 0C + N 1C r 2 + N 2C r 4 + N 3C r 6 (4) ν 0d = (1-N 0d ) / (N 0F = N 0C ) (5) ν 1d = N 1d / (N 1F- N 1C ) (6) N 1d <0 (7) 0 ≤ ν 0d ≤ ν 1d where N d (r), N F (r), and N C (r) are radial distances from the optical axis, respectively. Where r is the d-line, F-line, and C-line refractive index distributions, N 0d , N 1d , N 2d , and N 3d are d-line refractive index distribution coefficients, N 0F , N 1F ,
N 2F and N 3F are the refractive index distribution coefficients for the F line,
N 0C , N 1C , N 2C , and N 3C are refractive index distribution coefficients for the C line, and ν 0d and ν 1d are N 0d , N 0F , and N 0C ,
It is the Abbe number represented by the equations (4) and (5) using N 1d , N 1F and N 1C .

【手続補正３】[Procedure 3]

【補正対象書類名】明細書[Document name to be amended] Statement

【補正対象項目名】００１６[Correction target item name] 0016

【補正方法】変更[Correction method] Change

【補正内容】[Correction content]

【００１６】又本発明のレンズ系において、前記条件
（８）の代りに下記条件（８’）を満足するようにすれ
ば一層好ましい。 （８’） ０．５≦｜φｅ／φＲ｜≦１．５ 更に前記の屈折率分布型レンズで発生する諸収差を一層
小さくするためには、屈折率分布型レンズ単体のパワー
配分つまり媒質のパワーと面のパワーとの配分が次の条
件（９）を満足することが望ましい。 （９） ０．０１≦｜φＭ／φｅ｜≦３．０ この条件（９）の下限を越えて媒質のパワーが小さくな
ると、屈折率分布型レンズの空気接触面の曲率を強くし
てレンズ全体のパワーを得るようにしなければならず、
空気接触面での球面収差、コマ収差、非点収差の発生量
が大なり、屈折率分布型レンズの屈折率分布による媒質
での収差補正効果や、屈折率分布型レンズの空気接触面
での屈折力が媒質の屈折率分布に伴って漸次変化するこ
とによって得られる収差補正効果や、後群中の他の均質
レンズの収差補正効果では、全系の収差を良好に補正す
ることが出来ない。又条件（９）の上限を越えて媒質の
パワーが大になると、媒質での諸収差発生量が大にな
り、同様の理由から好ましくない。In the lens system of the present invention, it is more preferable to satisfy the following condition (8 ') instead of the condition (8). (8 ′) 0.5 ≦ | φ e / φ R | ≦ 1.5 Furthermore, in order to further reduce various aberrations generated in the gradient index lens, the power distribution of the gradient index lens unit, that is, It is desirable that the distribution of the power of the medium and the power of the surface satisfy the following condition (9). (9) 0.01 ≦ | φ M / φ e | ≦ 3.0 When the power of the medium becomes smaller than the lower limit of the condition (9), the curvature of the air contact surface of the gradient index lens is increased. You have to get the power of the whole lens,
The amount of spherical aberration, coma, and astigmatism generated on the air contact surface is large, and the aberration correction effect in the medium due to the refractive index distribution of the gradient index lens and the air contact surface of the gradient index lens Aberrations of the entire system cannot be satisfactorily corrected by the aberration correction effect obtained by gradually changing the refractive power according to the refractive index distribution of the medium or the aberration correction effect of other homogeneous lenses in the rear group. .. Further, when the power of the medium becomes large beyond the upper limit of the condition (9), the amount of various aberrations generated in the medium becomes large, which is not preferable for the same reason.

Claims (1)

【特許請求の範囲】[Claims] 【請求項１】物体側から順に、負のパワーを有する前群
発散系と、明るさ絞りと、正のパワーを有する後群収斂
系とからなり、前記後群収斂系の少なくとも１枚に、屈
折率分布を次の式（１）〜（５）で近似した時、次の式
（６），（７）で表わされる屈折率分布型レンズを用い
た内視鏡対物レンズ。 （１） Ｎd(r)＝Ｎ0d＋Ｎ1dｒ2 ＋Ｎ2dｒ4 ＋Ｎ3dｒ6 （２） ＮF(r)＝Ｎ0F＋Ｎ1Fｒ2 ＋Ｎ2Fｒ4 ＋Ｎ3Fｒ6 （３） ＮC(r)＝Ｎ0C＋Ｎ1Cｒ2 ＋Ｎ2Cｒ4 ＋Ｎ3Cｒ6 （４） ν0d＝（１−Ｎ0d）／（Ｎ0F−Ｎ0C） （５） ν1d＝Ｎ1d／（Ｎ1F−Ｎ1C） （６） Ｎ1d＜０ （７） ０≦ν0d≦ν1d ただしＮd(r)，ＮF(r)，ＮC(r)は夫々光軸からの径方向
の距離をｒとした時のｄ線、Ｆ線，Ｃ線に関する屈折率
分布、Ｎ0d，Ｎ1d，Ｎ2d，Ｎ3dはｄ線に関する屈折率分
布係数、Ｎ0F，Ｎ1F，Ｎ2F，Ｎ3FはＦ線に関する屈折率
分布係数、Ｎ0C，Ｎ1C，Ｎ2C，Ｎ3CはＣ線に関する屈折
率分布係数、ν0d，ν1dはＮ1d，Ｎ1F，Ｎ1Cを用いて式
（４），（５）に表わされるアッベ数である。1. A front group diverging system having a negative power, an aperture stop, and a rear group converging system having a positive power, in order from the object side. At least one of the rear group converging system comprises: An endoscope objective lens using a gradient index lens represented by the following equations (6) and (7) when the refractive index distribution is approximated by the following equations (1) to (5). (1) N d (r) = N 0d + N 1d r 2 + N 2d r 4 + N 3d r 6 (2) N F (r) = N 0F + N 1F r 2 + N 2F r 4 + N 3F r 6 (3) N C (r) = N 0C + N 1C r 2 + N 2C r 4 + N 3C r 6 (4) ν 0d = (1-N 0d ) / (N 0F -N 0C ) (5) ν 1d = N 1d / (N 1F -N 1C) (6) N 1d <0 (7) 0 ≦ ν 0d ≦ ν 1d however N d (r), N F (r), N C (r) is the radial distance from the respective optical axis Where r is the d-line, F-line and C-line refractive index distributions, N 0d , N 1d , N 2d and N 3d are d-line refractive index distribution coefficients, N 0F , N 1F , N 2F and N 3F Is the refractive index distribution coefficient for the F line, N 0C , N 1C , N 2C , and N 3C are the refractive index distribution coefficients for the C line, and ν 0d and ν 1d are N 1d , N 1F , and N 1C using the equation (4). , (5) is the Abbe number.
JP29392891A 1991-10-15 1991-10-15 Endoscope objective Pending JPH05127080A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
JP29392891A JPH05127080A (en) 1991-10-15 1991-10-15 Endoscope objective
US07/961,543 US5359456A (en) 1991-10-15 1992-10-15 Objective lens system for endoscopes

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP29392891A JPH05127080A (en) 1991-10-15 1991-10-15 Endoscope objective

Publications (1)

Publication Number Publication Date
JPH05127080A true JPH05127080A (en) 1993-05-25

Family

ID=17800981

Family Applications (1)

Application Number Title Priority Date Filing Date
JP29392891A Pending JPH05127080A (en) 1991-10-15 1991-10-15 Endoscope objective

Country Status (1)

Country Link
JP (1) JPH05127080A (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999006866A1 (en) * 1997-08-01 1999-02-11 Olympus Optical Co., Ltd. Objective of endoscope
JP2008175991A (en) * 2007-01-17 2008-07-31 Fujinon Corp Optical element and optical unit
JP2014130072A (en) * 2012-12-28 2014-07-10 Nikon Corp Optical system and surface shape measurement device

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999006866A1 (en) * 1997-08-01 1999-02-11 Olympus Optical Co., Ltd. Objective of endoscope
US6134056A (en) * 1997-08-01 2000-10-17 Olympus Optical Co., Ltd. Objective lens system for endoscopes
JP4245800B2 (en) * 1997-08-01 2009-04-02 オリンパス株式会社 Endoscope objective lens
JP2008175991A (en) * 2007-01-17 2008-07-31 Fujinon Corp Optical element and optical unit
JP2014130072A (en) * 2012-12-28 2014-07-10 Nikon Corp Optical system and surface shape measurement device

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