JP3559608B2 - Image transmission optical system - Google Patents

Description

【００２７】

【００２８】
例３

【００２９】

【００３０】

【００３１】

【００３２】

【００３３】

【００３４】

【００３５】

【００３６】

【００３７】

【００３８】

この表に示す収差係数は、３次の球面収差ＳＡ３、３次のコマ収差ＣＭ３、３次の非点収差ＡＳ３、３次の歪曲収差ＤＩＳＴ３、３次のペッツバール和ＰＴＺ３、軸上色収差ＰＡＣであり、ラジアル型不均質レンズの物体側の面、媒質、像側の面のそれぞれの収差係数の値とこれらの合計値である。また、ここではラジアル型不均質レンズの面の曲率半径を変化させた時にＮ_１０，Ｎ_２０，Ｖ_１０の値を変数とし、焦点距離ｆ_Ｇ ＝１０ｍｍ、３次の球面収差ＳＡ３≒０、軸上色収差ＰＡＣ≒０になるように設計されている。
【００３９】
上記の表において、例１〜９は、第２面（像側の面）を平面（ｒ_２Ｇ＝∞）とし、第１面（物体側の面）をｒ_１Ｇ＝∞，２０，１０，８，６，−２０，−１０，−８，−６（ｍｍ）にした時の夫々の収差係数を示してある。又例１０〜１２は、第１面ｒ_１Ｇ，第２面ｒ_２Ｇを曲面とし、表に示す値の時の収差係数を示してある。
【００４０】
例１は両面平面形状（ｒ_１Ｇ＝ｒ_２Ｇ＝∞）にした例で、いずれの収差も非常に小さい値である。
【００４１】
例２〜例５は、第２面を平面（ｒ_２Ｇ＝∞）とした状態で、第１面の曲率半径ｒ_１Ｇを順次小さくして面の屈折力が正の方向に強くなるようにしている。これらの例から明らかなように、例１の平面に比較して第１面の曲率半径ｒ_１Ｇが小さくなるにつれて、特にペッツバール和と非点収差の値が大になることがわかる。これは、ペッツバール和を表わす式（ｈ）からわかるように、媒質よりも面に大きな正の屈折力を持たせるとトータルで発生するペッツバール和の値が大きくなるためである。非点収差に関しても同様に、面の屈折力を大にすると発生量が大になる。このことから、ラジアル型不均質レンズの面が正の屈折力を持つ場合は、ペッツバール和、非点収差を悪化させないためには、媒質の屈折力に対して面の屈折力はある程度弱くした方が好ましい。
【００４２】
また例６〜例９は、第１面の曲率半径ｒ_１Ｇが凹面で、順に小さくなっており、面の負の屈折力が強くなるようにした例である。これらの例から、ペッツバール和や非点収差を含めていずれの収差も、第１面の負の屈折力を強くしても両平面形状と比較して悪化しない。しかし、特に球面収差において明らかなように、面と媒質とにおける収差発生量は、いずれも例１の両平面形状の場合に比較して大になっているが面と媒質とで符号の異なる収差を発生するために互いにキャンセルされてレンズトータルでは発生量が小になっている。例えばｒ_１Ｇ＝−６ｍｍである例９の場合、例１と比較して面と媒質とで発生する収差は、約２０倍である。つまり例１では、第１面（ｒ_１Ｇ）での球面収差係数ＳＡ３＝０、媒質（Ｇ）での球面収差係数ＳＡ３＝０．００４９０、第２面（ｒ_２Ｇ）での球面収差係数ＡＳ３＝−０．００４９９で、トータルではＳＡ３≒０である。これに対して、例９は、第１面（ｒ_１Ｇ）での球面収差係数ＳＡ３＝−０．１１３１、媒質（Ｇ）での球面収差係数ＳＡ３＝０．１１５５９、第２面（ｒ_２Ｇ）での球面収差係数ＳＡ３＝−０．００５９５であって、トータルではＳＡ３≒０．００３５である。そのために、例９は、例１と比べてラジアル型不均質レンズの公差が非常に厳しく、コストアップや偏芯による性能の劣化を生ずるためレンズ系を作製する点では好ましくない。そのため、ラジアル型不均質レンズの面が負の屈折力を有する場合、製造公差を緩くするために媒質の屈折力に対して面の屈折力はある程度弱い方が望ましい。
【００４３】
また例１０〜例１３は、両面曲面であるメニスカス形状の例である。いずれの例も、例１と比べてトータルの収差発生量はそれ程大きくはない。しかし、特に軸上色収差と球面収差は面と媒質における発生量が大きく互いにキャンセルすることによりトータルの発生量が小さくなっている。例えば例１２では、第１面の曲率半径がｒ_１Ｇ＝−１０ｍｍ、第２面の曲率半径がｒ_２Ｇ＝−１０ｍｍと両面の曲率半径が等しくレンズの近軸的な面の屈折力は０である。この点では例１と同じであるが面と媒質の夫々で発生する収差量は大である。つまり、軸上色収差に関しては、例１では第１面（ｒ_１Ｇ）ではＰＡＣ＝０、媒質（Ｇ）ではＰＡＣ＝０．００９８４、第２面（ｒ_２Ｇ）ではＰＡＣ＝−０．００９８４で、トータルではＰＡＣ≒０である。これに対し、例１２では、第１面（ｒ_１Ｇ）はＰＡＣ＝０．０１１７２、媒質（Ｇ）はＰＡＣ＝０．０１３０４、第２面（ｒ_２Ｇ）はＰＡＣ＝−０．０２４７０で、トータルではＰＡＣ≒０であり各面、媒質での発生量は 約１．３〜２．５倍となっている。又球面収差も、例１では第１面（ｒ_１Ｇ）はＳＡ３＝０、媒質（Ｇ）はＳＡ３＝０．００４９０、第２面（ｒ_２Ｇ）は、０．００４９９、トータルでＳＡ３＝０であるのに対して、例１２では、第１面（ｒ_１Ｇ）はＳＡ３＝−０．０３４３６、媒質（Ｇ）はＳＡ３＝０．０２７４３、第２面（ｒ_２Ｇ）はＳＡ３＝０．００６４３、トータルはＳＡ３≒０であり、約５．５〜６．５倍となっている。このため、例１２の場合、例１に比べてラジアル型不均質レンズの製造公差が非常に厳しく、レンズ系を作製する点では好ましくない。
【００４４】
これらの例からわかるように、ラジアル型不均質レンズの面がメニスカス形状の場合には、製造公差を緩くするために媒質の屈折力に対して面の屈折力はある程度弱い方が望ましい。
【００４５】
以上述べた点を考慮して、本発明の光学系においては、諸収差を悪化させることなしに軸上色収差を補正し、また製造公差を緩くするためにラジアル型不均質レンズが条件（３），（４），（５）を満足するようにした。
【００４６】
条件（３），条件（４）は、ラジアル型不均質レンズのトータルの屈折力に対する面の屈折力に関する条件であって、この条件を満足していれば面の屈折力が媒質の屈折力に比較して極端に大きくならずラジアル型不均質レンズの補正効果を十分に得ることが出来る。
【００４７】
また条件（５）は、本発明のレンズ系が条件（３），（４）を満足する時、ラジアル型不均質レンズにより軸上色収差を良好に補正するためにＶ_１０の値の範囲を規定したものである。もしも、条件（３），（４）を満足しないと、面の屈折力が媒質の屈折力に対して大きくなりすぎて諸収差の悪化や製造公差が厳しくなる。また、もし条件（５）を満足しないと、ラジアル型不均質レンズで軸上色収差を良好に補正することが困難になる。
【００４８】
また、本発明の光学系の第３の構成は、ほぼ等倍結像であって、物体から像までの１リレー中に式（ａ）にて表わされるラジアル型不均質レンズを１枚用い、ラジアル型不均質レンズよりも物体側に１枚乃至複数枚のレンズを配置し、又ラジアル型不均質レンズよりも像側に物体側のレンズと枚数が等しく、曲率半径、レンズ厚の略等しいレンズをラジアル型不均質レンズを中心として光軸上にほぼ対称に配置したことを特徴としている。
【００４９】
ラジアル型不均質レンズは、均質レンズに比較してレンズ単体にて軸上色収差を補正する能力を持っている。したがって、これを本発明の光学系に用いることにより軸上色収差を良好なレベルに補正することが出来る。また、光学系の諸収差を補正する上で、前述のように、ラジアル型不均質レンズを中心としてその前後のレンズ成分を、レンズの枚数を等しく、曲率半径、レンズの厚さのほぼ等しいレンズを、ラジアル型不均質レンズを中心に光軸上にほぼ対称に配置することが望ましい。光学系をこのように構成すれば、ラジアル型不均質レンズの前側のレンズ成分で発生する歪曲収差、倍率色収差、コマ収差と、後ろ側のレンズ成分で発生する歪曲収差、倍率の色収差、コマ収差とが互いに打消し合って１リレー内でこれら収差の発生量を非常に小さくすることが出来る。これは、これら歪曲収差、倍率の色収差、コマ収差の発生量は、軸外光線の光線高の奇数乗に比例するためであり、前述のような対称な配置にすれば、ラジアル型不均質レンズの後ろ側のレンズ成分にて発生するこれら収差の発生量は、ラジアル型不均質レンズの前側のレンズ成分にて発生する収差とほぼ等しく符号が反対であるためである。もしも前後のレンズ枚数やレンズ形状が異なると、例えほぼ対称に配置したとしても、それら全体の収差発生量をほぼ０にすることは困難である。また前後のレンズ枚数やレンズ形状がほぼ等しくても、光軸上にほぼ対称に配置しなければ、これら収差をほぼ０にすることが困難である。
【００５０】
更に、本発明光学系の第４の構成は、物体から像までの１リレーが少なくとも３枚以上であって、ほぼ等倍結像の光学系であって、１枚のレンズが式（ａ）にて表わされるラジアル型不均質レンズであり、以下の条件（６），（７）を満足することを特徴としている。
【００５１】
（６） −０．１＜Ｎ_１０×ＩＨ^２ ＜０
（７） ０．８＜ｄ_Ｇ ／ＩＨ＜１５
ただし、ｄ_Ｇ はラジアル型不均質レンズのレンズ厚、ＩＨは像高である。
【００５２】
ラジアル型不均質レンズは、均質レンズと比較してレンズ単体で軸上色収差を補正する能力を持つため、これを本発明のレンズ系に用いれば軸上色収差を良好なレベルに補正することが可能であるが、さらにラジアル型不均質レンズを効果的に用いることを考えると、前記条件（６），（７）を満足することが望ましい。
【００５３】
式（ｂ）から明らかなように、軸上色収差を良好に補正するためには、媒質の屈折力φ_ｍ が十分大きな値を持つ必要がある。もしもφ_ｍ の値が非常に小さい場合、均質単レンズと同じ程度の補正能力になり好ましくない。また式（ｃ）より、媒質の屈折力φ_ｍ は２次の屈折率分布係数Ｎ_１０とラジアル型不均質レンズのレンズ厚ｄの積に比例するので、φ_ｍ の値を十分に大きくするために、本発明では、条件（６），（７）を満足するようにした。
【００５４】
もし、条件（６）の上限を越えると媒質の屈折力が負の値を持つことになり、特にペッツバール和が悪化する。又下限を越えると光軸と周辺とで屈折率差が大きくなりすぎて、ラジアル型不均質レンズ素材の作製コストが高くなり、公差も厳しくなる。また条件（７）の上限を越えるとラジアル型不均質レンズのレンズ厚が厚くなりすぎてラジアル型不均質レンズの作製コストが高くなり公差が厳しくなる。また下限を越えると媒質の屈折力が弱くなり軸上色収差を良好なレベルに補正することが困難である。
【００５５】
又、本発明の光学系の前記の第１〜第４の構成において製作性を考慮すると、ラジアル型不均質レンズの両面がほぼ平面形状であることがコスト等の点で望ましい。
【００５６】
ラジアル型不均質レンズは、媒質に屈折力を持つので面形状がほぼ平面であってもレンズ作用を有する。また、式（ｂ）から面形状がほぼ平面でφ_Ｓ ≒０であっても、Ｖ_１０を適当な値に設定することによって軸上色収差を所望の値にコントロールすることが可能である。これによりラジアル型不均質レンズの面形状をほぼ両平面にすると軸上色収差を良好に補正する作用に加えてレンズ研磨に要するコスト、時間を削減することが出来る。
【００５７】
また、本発明の光学系は、硬性鏡等に用いることが可能であるが、硬性鏡は、例えば人体あるいは航空機のエンジン内部などに挿入して内部の状況を観察する。したがって硬性鏡の外形形状は細長い形状で、物体から像までの１リレーを複数組配置する。また、全体の収差が配置した数だけ積算されるため、１リレーで発生する諸収差を良好に補正しなければならない。
【００５８】
本発明の光学系の前述の第１〜第４構成のものは、いずれも１リレーで諸収差を補正することが可能であり、これらを連続して用いた場合、全系での諸収差が良好に補正されたシステムを構成することが出来る。
【００５９】
また、本発明光学系の前述の第１〜第４の構成のものにおいて軸上色収差を良好に補正するには条件（８），（９）を満足することが望ましい。
【００６０】
（８） ｜（Ｎ_００−１）／ｒ_１Ｇ｜＜０．６５×（１／ｆ_Ｇ ）
（９） ｜（Ｎ_００−１）／ｒ_２Ｇ｜＜０．６５×（１／ｆ_Ｇ ）
ラジアル型不均質レンズの補正作用を効果的に利用するためには、面の屈折力と媒質の屈折力を適当な値にすることが必要である。特に、ラジアル型不均質レンズを効果的に用いるためには面の形状を曲率半径の大きい面にすることが望ましく、前記条件（８），（９）を満足することが望ましい。もしもこれら条件（８），（９）を満足しないとラジアル型不均質レンズにより軸上色収差を良好に補正することが困難になる。
【００６１】
また、本発明の光学系の第１〜第４の構成のものは、軸上色収差をさらに良好に補正するためには条件（１０）を満足することが望ましい。
【００６２】
（１０） −０．０５＜Ｎ_１０×ＩＨ^２ ＜−０．０００５
軸上色収差を良好なレベルに補正するためにラジアル型不均質レンズを効果的に用いるためには条件（１０）を満足することが望ましい。式（ｂ）から明らかなように、軸上色収差を補正するためには媒質の屈折力φ_ｍ が十分大きな値を持つことが必要であり、条件（１０）を満足すればφ_ｍ を十分大きな値にすることが可能である。もし条件（１０）の上限を越えると媒質の屈折力が弱くなり軸上色収差が補正不足になる。下限を越えると光軸と周辺とでの屈折率差が大になりすぎラジアル型不均質レンズ素材の作製コストが高くなり、公差も厳しくなる。
【００６３】
更に本発明の第１〜第４の構成の光学系において、軸上色収差を良好に補正するためには条件（１１）を満足することが望ましい。
【００６４】
（１１） １＜ｄ_Ｇ ／ＩＨ＜９
前述のように式（ｂ）から軸上色収差を補正するためには媒質の屈折力が大きな値を持つ必要がある。また式（ｃ）よりφ_ｍ は、２次の屈折率分布係数Ｎ_１０とラジアル型不均質レンズの厚さｄとの積に比例する。そのためφ_ｍ を大にするためには、上記条件（１１）を満足する必要がある。
【００６５】
もし条件（１１）の上限を越えるとラジアル型不均質レンズの厚さが大になりすぎてラジアル型不均質レンズの作製コストが高くなり公差も厳しくなる。また条件（１１）の下限を越えると媒質の屈折力が弱くなり軸上色収差を良好に補正し得なくなる。
【００６６】
【実施例】
次に本発明の像伝送光学系の各実施例を示す。
【００６７】

【００６８】

【００６９】

【００７０】

【００７１】

【００７２】

【００７３】

【００７４】

【００７５】

【００７６】

【００７７】

【００７８】

【００７９】

ただしｒ_１ ，ｒ_２ ，・・・ はレンズ各面の曲率半径、ｄ_１ ，ｄ_２ ，・・・ は各レンズの肉厚およびレンズ間隔、ｎ_１ ，ｎ_２ ，・・・ は各レンズのｄ線の屈折率、ν_１ ，ν_２ ，・・・ は各レンズのアッベ数である。
【００８０】
実施例１は、図１に示す構成で、物体から像までの１リレーの光学系が、物体側から順に、正の屈折力を持ち両凸形状の第１レンズ成分と、正の屈折力を持ちメニスカス形状の第２レンズ成分と、正の屈折力を持ち両凸形状の第３レンズ成分の３枚のレンズにて構成されていて、第２レンズ成分がラジアル型不均質レンズである。そしてＮＡ＝０．０７２、像高が１．０ｍｍ、レンズ端面から像までの距離が４．９ｍｍの像伝送光学系である。
【００８１】
通常このようなレンズ構成で第２レンズ成分を１枚の均質レンズのみにて構成すると、軸上色収差を良好に補正することが出来ない。
【００８２】
この実施例１は、この第２レンズ成分としてラジアル型不均質レンズを用いることにより軸上色収差を良好に補正している。
【００８３】
この実施例１の収差状況は、図１０に示す通りであって、３枚のレンズのみで高い光学性能を有することがわかる。
【００８４】
実施例２は、図２に示す構成で、物体から像までの１リレーの光学系が、物体側より順に、正の屈折力を持ち両凸形状の第１レンズ成分と、正の屈折力を持ち両凸形状の第２レンズ成分と、正の屈折力を持ち両凸形状の第３レンズ成分との３枚のレンズにて構成され、第２レンズ成分がラジアル型不均質レンズである。又ＮＡ＝０．０７２、像高が１．０ｍｍ、レンズ端面から像までの距離が４．９ｍｍの像伝送光学系である。
【００８５】
又本発明の構成の光学系では、全系で負の球面収差が発生する傾向にあるが、この実施例では、ラジアル型不均質レンズを下記条件（１２）を満足させることによりこれを補正している。
【００８６】
（１２） Ｎ_２０＞０
ラジアル型不均質レンズの４次の屈折率分布係数Ｎ_２０が正の値を持てば媒質では正の球面収差を発生することになり、全系の球面収差を良好に補正することが可能である。もしも条件（１２）を満足しないと、媒質では負の球面収差を発生することになり、全系で球面収差を良好に補正することが困難になる。
【００８７】
この実施例２は、条件（１２）を満足することにより球面収差を補正することも特徴とするが、他の実施例１２においてもこの補正手段を適用することが出来る。
【００８８】
この実施例２の収差状況は、図１１に示す通りで、この実施例はレンズ枚数が３枚であるにもかかわらず高い光学性能を有することがわかる。
【００８９】
実施例３は、図３に示すもので、物体から像までの１リレーの光学系が、物体側より順に、正の屈折力を持つ凸平形状の第１レンズ成分と、正の屈折力を持ち凹平形状の第２レンズ成分と、正の屈折力を持ち平凸形状の第３レンズ成分との３枚のレンズで構成され、第２レンズ成分がラジアル型不均質レンズである。そしてＮＡが０．０７３で像高１．０ｍｍ、レンズ端面から像までの距離が５ｍｍの像伝送光学系であり、平面を多用してレンズ研磨に要するコスト削減を図った例で、１リレーの６面中３面までが平面である。
【００９０】
この実施例の収差状況は、図１２に示す通りであり、３枚構成でしかも平面を多用しているにもかかわらず、高い光学性能を有している。
【００９１】
実施例４は、図４に示すもので、１リレーの光学系が物体側より順に、凸平形状の第１レンズ成分と、両凸形状の第２レンズ成分と、平凸形状の第３レンズ成分との３枚のレンズで構成され、第２レンズ成分がラジアル型不均質レンズである。又この実施例は、ＮＡが０．０７３、像高１．０ｍｍ、レンズ端面から像までの距離が４．９ｍｍの像伝送光学系である。この実施例４は、第２レンズ成分であるラジアル型不均質レンズを中心として物体側と像側のレンズ形状が対称であり、歪曲収差、コマ収差、倍率の色収差の補正が有利な形状になっている。
【００９２】
この実施例４の収差形状は、図１３に示す通りで３枚のレンズのみからなっているにもかかわらず良好な光学性能を有している。
【００９３】
実施例５は、図５に示す構成のもので、１リレーの光学系が物体側より順に、凸平形状の第１レンズ成分と両凹形状の第２レンズ成分と平凸形状の第３レンズ成分とにて構成された３枚のレンズからなっており、第２レンズ成分がラジアル型不均質レンズである。この実施例は、ＮＡ０．０７３、像高１．０ｍｍ、レンズ端面から像までの距離が４．９ｍｍの像伝送光学系である。この実施例５も実施例４と同じようにラジアル型不均質レンズを中心として物体側に像側のレンズ形状が対称であり、歪曲収差、コマ収差、倍率の色収差の補正に有利な形状になっている。
【００９４】
この実施例５の収差状況は、図１４に示す通りで、３枚のレンズのみからなっているにもかかわらず高い光学性能を有している。
【００９５】
実施例６は、図６に示す構成で、１リレーの光学系が物体側より順に、正の屈折力を持つ凸平形状の第１レンズ成分と正の屈折力を持つ両平面形状の第２レンズ成分と正の屈折力を持つ平凸形状の第３レンズ成分とにて構成された３枚のレンズよりなり、第２レンズ成分がラジアル型不均質レンズである。この実施例は、ＮＡ０．０７３、像高１．０ｍｍ、レンズ端面から像までの距離が４．９ｍｍの像伝送光学系である。この実施例は、平面を多用してレンズ研磨に要するコストの削減をはかったもので、１リレーのレンズの６面中４面を平面にした。又第１レンズ成分と第３レンズ成分を等しい形状のレンズとし第２レンズ成分（ラジアル型不均質レンズ）を中心として対称に配置して、歪曲収差、コマ収差、倍率の色収差の補正に有利な構成にしてある。又第２レンズ成分をラジアル型不均質レンズとし軸上色収差、球面収差を良好に補正している。
【００９６】
この実施例６の収差状況は図１５に示す通りで、３枚のレンズで平面を多用したにもかかわらず高い光学性能を有している。
【００９７】
実施例７も図６に示す構成で、１リレーの光学系が物体側より順に、正の屈折力を持つ両凸形状の第１レンズ成分と正の屈折力を持つ両平面形状の第２レンズ成分と正の屈折力を持つ両凸形状の第３レンズ成分とにて構成された３枚のレンズよりなり、第２レンズ成分がラジアル型不均質レンズである。この実施例は、ＮＡ０．１３、像高２．８、レンズ端面から像までの距離が５ｍｍの３枚のレンズからなる像伝送光学系である。この実施例は、ＮＡ０．１３と明るくした例で、ＮＡを大にした時に特に問題になる球面収差をラジアル型不均質レンズを用いて補正している。
【００９８】
この実施例７の収差状況は、図１６に示す通りで、明るく３枚のレンズのみからなるにもかかわらず高い光学性能を有している。
【００９９】
実施例８は図６に示す構成で、１リレーの光学系が物体側より順に、凸面を物体側に向けた正の屈折力を持つメニスカス形状の第１レンズ成分と正の屈折力を持つ両平面形状の第２レンズ成分と凸面を像側に向けた正の屈折力を持つ両凸形状の第３レンズ成分とで構成された３枚のレンズからなり、第２レンズ成分がラジアル型不均質レンズである。そしてＮＡ０．１５、像高２ｍｍ、レンズ端面から像までの距離が６ｍｍの像伝送光学系である。この実施例は、ＮＡが０．１５で、実施例７よりも更に明るくなっている。つまり、実施例７と同様にラジアル型不均質レンズを用いて球面収差を一層良好に補正してより明るい光学系にした。
【０１００】
この実施例８の収差状況は、図１７に示す通りで、レンズ枚数が３枚で、又ＮＡ０．１５と明るいにもかかわらず高い光学性能を有する。
【０１０１】
実施例９は図６に示す構成で、１リレーの光学系が物体側より順に、正の屈折力を持つ凸平形状の第１レンズ成分と正の屈折力を持つ両平面形状の第２レンズ群と正の屈折力を持つ平凸形状の第３レンズ成分とで構成された３枚のレンズからなり、第２レンズ成分がラジアル型不均質レンズである。そしてＮＡ０．１２９、像高２．８１ｍｍ、レンズ端面から像までの距離が５ｍｍの像伝送光学系である。この実施例は、ＮＡ０．１２９と明るく、更に６面中４面を平面としているが、ラジアル型不均質レンズを用いて球面収差を良好に補正している。
【０１０２】
この実施例９の収差状況は、ＮＡ０．１３と明るくレンズ枚数３枚であるにもかかわらず、高い光学性能を有している。
【０１０３】
実施例１０は、図７に示す構成で、１リレーの光学系が物体側より順に、正の屈折力を持ち負レンズと正レンズとの接合レンズからなる第１レンズ成分と、正の屈折力を持つ両平面形状の第２レンズ成分と正の屈折力を持ち正レンズと負レンズとの接合レンズからなる第３レンズ成分とにて構成された３枚のレンズよりなり、第２レンズ成分がラジアル型不均質レンズである。又この実施例１０は、ＮＡ０．１４、像高２．８ｍｍ、レンズ端面から像までの距離が５ｍｍの像伝送光学系である。
【０１０４】
この実施例１０は、第１レンズ成分と第３レンズ成分を接合レンズにして特に非点収差を良好に補正した。本発明の光学系を硬性鏡に用いる場合、対物レンズと組合わせ用いることが多い。そのため、一般に対物レンズで発生する非点収差を像伝送光学系で発生する非点収差により打ち消して全体の非点収差が良好に補正されるようにしている。しかし像伝送光学系単独に非点収差を良好に補正することが望ましい場合がある。そのような場合この実施例は有効である。
【０１０５】
この実施例１０の収差状況は、図１９に示す通りで、非点収差を含め諸収差が良好に補正されている。
【０１０６】
実施例１１は、図６に示す構成で、１リレーの光学系が物体側より順に、凸面を物体側に向けた正の屈折力を持つ凸平形状の第１レンズ成分と正の屈折力を持つ両平面形状の第２レンズ成分と凸面を像側に向けた正の屈折力を持つ平凸形状の第３レンズ成分とにて構成された３枚のレンズからなり第２レンズ成分がラジアル型不均質レンズである。そしてＮＡ０．１、像高１．４ｍｍ、レンズ端面から像までの距離が７ｍｍの像伝送光学系である。この実施例では、第１レンズ成分の物体側の面と第３レンズ成分の像側の面とに非球面を用いて主として非点収差を良好に補正している。
【０１０７】
この実施例のように、ラジアル型不均質レンズと非球面とを組合わせることによって、軸上色収差と球面収差とを主として第２レンズ成分のラジアル型不均質レンズにて補正し、非点収差を主として第１レンズ成分と第３レンズ成分に設けた非球面にて補正し、更に第２レンズ成分を中心として物体側と像側を対称なレンズ形状になるようにして、コマ収差、歪曲収差、倍率の色収差とを補正して、すべての収差が良好に補正されるようにした。
【０１０８】
この実施例にて用いる非球面の形状は下記の式にて表わされる。

【０１０９】
ただし、上式はｘ軸を光軸方向にとり、ｙ軸を光軸と直角方向にとったもので、ｒは光軸上の曲率半径、Ａ_２ｉは非球面係数である。
【０１１０】
この実施例１１の収差状況は、図２０に示す通りで、レンズ枚数が３枚であるにもかかわらず高い光学性能を有している。
【０１１１】
実施例１２は、図８に示す構成で、実施例６の像伝送光学系を光軸上に５組連続して配置した構成で、像を５回伝送する光学系である。
【０１１２】
この実施例は、実施例６の光学系を５組連続して配置したものであるが、他の実施例を用いての複数回伝送することが可能である。このように本発明の像伝送光学系を複数組配置することによって本発明の目的を達成し得る像を複数回伝送する光学系を構成し得る。
【０１１３】
この実施例１２の収差状況は、図２１に示す通りで、複数回像を伝送した場合でも高い光学性能を有している。
【０１１４】
実施例１３は、実施例１２に示す５回像伝送を行なう光学系の物体側に対物レンズを配置した構成で、図９に示す通りである。図９には対物レンズのみの構成を示し像伝送光学系は、対物レンズ側の先端部のみでその他は省略した。この実施例の対物レンズは、主として歪曲収差を補正するために非球面を用いている。尚ｒ_１３は対物レンズにより形成される物体像である。
【０１１５】
この実施例の収差状況は、図２２に示す通りで像伝送光学系にさらに対物レンズを配置した光学系で高い光学性能を有している。
【０１１６】
本発明の像伝送光学系は、特許請求の範囲に記載した光学系のほか、次に示す各項の光学系も含まれる。
【０１１７】
（１）特許請求の範囲の請求項１，３又は４に記載されている光学系で、更に下記の条件（３），（４），（５）を満足する像伝送光学系。
（３） ｜（Ｎ_００−１）／ｒ_１Ｇ｜＜０．９×（１／ｆ_Ｇ ）
（４） ｜（Ｎ_００−１）／ｒ_２Ｇ｜＜０．９×（１／ｆ_Ｇ ）
（５） １／Ｖ_１０＜１／Ｖ_００
【０１１８】
（２）特許請求の範囲の請求項１又は４に記載されている光学系で、ラジアル型不均質レンズの物体側および像側に夫々１枚乃至複数枚の等しい数のレンズが配置され、前記物体側および像側のレンズが曲率半径、レンズ厚がほぼ等しく前記ラジアル型不均質レンズを中心として光軸上にほぼ対称に配置されている像伝送光学系。
【０１１９】
（３）特許請求の範囲の請求項１に記載されている光学系で、下記条件（６），（７）を満足する像伝像光学系。
（６） −０．１＜Ｎ_１０×ＩＨ^２ ＜０
（７） ０．８＜ｄ_Ｇ ／ＩＨ＜１５
【０１２０】
（４）特許請求の範囲の請求項２又は前記（１）の項に記載されている光学系で、条件（３），（４）の代りに下記条件（８），（９）を満足する像伝送光学系。
（８） ｜（Ｎ_００−１）／ｒ_１Ｇ｜＜０．６５×（１／ｆ_Ｇ ）
（９） ｜（Ｎ_００−１）／ｒ_２Ｇ｜＜０．６５×（１／ｆ_Ｇ ）
【０１２１】
（５）特許請求の範囲の請求項１又は３に記載されている光学系で、下記条件（８），（９）を満足する像伝送光学系。
（８） ｜（Ｎ_００−１）／ｒ_１Ｇ｜＜０．６５×（１／ｆ_Ｇ ）
（９） ｜（Ｎ_００−１）／ｒ_２Ｇ｜＜０．６５×（１／ｆ_Ｇ ）
【０１２２】
（６）特許請求の範囲の請求項１，２，３又は４あるいは前記（１），（２），（４）又は（５）の項に記載されている光学系で、下記条件（１０）を満足する像伝送光学系。
（１０） −０．０５＜Ｎ_１０×ＩＨ^２ ＜−０．０００５
【０１２３】
（７）特許請求の範囲の請求項１，１，３又は４あるいは前記（１），（２），（４）又は（５）の項に記載されている光学系で、条件（１１）を満足する像伝送光学系。
（１１） １＜ｄ_Ｇ ／ＩＨ＜９
【０１２４】
（８）前記（３）の項に記載されている光学系で、条件（６）の代りに下記条件（１０）を満足する像伝送光学系。
（１０） −０．０５＜Ｎ_１０×ＩＨ^２ ＜−０．０００５
【０１２５】
（９）前記（３）の項に記載されている光学系で、条件（７）の代りに下記条件（１１）を満足する像伝送光学系。
（１１） １＜ｄ_Ｇ ／ＩＨ＜９
【０１２６】
（１０）特許請求の範囲の請求項１，２，３又は４あるいは前記（１），（２），（３），（４），（５），（６），（７），（８）又は（９）に記載されている光学系で、ラジアル型不均質レンズの両面がほぼ平面形状である像伝送光学系。
【０１２７】
（１１）特許請求の範囲の請求項１，２，３又は４あるいは前記（１），（２），（３），（４），（５），（６），（７），（９）又は１０に記載されている光学系で、物体から像までの１リレーの光学系を複数組光軸上に配置して物体像を複数回リレーする像伝送光学系。
【０１２８】
【発明の効果】
本発明の像伝送光学系は、１枚のラジアル型不均質レンズを含む少ない枚数のレンズであるにもかかわらず、特に軸上色収差が良好に補正された高い光学性能を有している。
【図面の簡単な説明】
【図１】本発明の実施例１の構成を示す図
【図２】本発明の実施例２の構成を示す図
【図３】本発明の実施例３の構成を示す図
【図４】本発明の実施例４の構成を示す図
【図５】本発明の実施例５の構成を示す図
【図６】本発明の実施例６，７，８，９，１１の構成を示す図
【図７】本発明の実施例１０の構成を示す図
【図８】本発明の実施例１２の構成を示す図
【図９】本発明の実施例１３の構成を示す図
【図１０】本発明の実施例１の収差曲線図
【図１１】本発明の実施例２の収差曲線図
【図１２】本発明の実施例３の収差曲線図
【図１３】本発明の実施例４の収差曲線図
【図１４】本発明の実施例５の収差曲線図
【図１５】本発明の実施例６の収差曲線図
【図１６】本発明の実施例７の収差曲線図
【図１７】本発明の実施例８の収差曲線図
【図１８】本発明の実施例９の収差曲線図
【図１９】本発明の実施例１０の収差曲線図
【図２０】本発明の実施例１１の収差曲線図
【図２１】本発明の実施例１２の収差曲線図
【図２２】本発明の実施例１３の収差曲線図
【図２３】従来の像伝送光学系の構成を示す図
【図２４】他の従来の像伝送光学系の構成を示す図
【図２５】他の従来の像伝送光学系の構成を示す図
【図２６】他の従来の像伝送光学系の構成を示す図[0001]
[Industrial applications]
The present invention relates to an image transmission optical system using a heterogeneous lens, particularly a so-called radial type heterogeneous lens whose refractive index changes in a radial direction.
[0002]
[Prior art]
An image transmission optical system used for a rigid endoscope or the like includes, for example, one relay from an object to an image described in JP-A-49-76536 shown in FIG. The one described in JP-A-200515 is known. Each of these conventional examples includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. Are composed of two or three cemented lenses. These conventional image transmission optical systems mainly correct longitudinal chromatic aberration by using the second lens group as a cemented lens. In order to reduce the number of lenses in these conventional lens systems, it is conceivable to use a single lens for the second lens group. However, in the case of a homogeneous single lens, it is necessary to satisfactorily correct axial chromatic aberration of the entire lens system. This makes it difficult to achieve an image transmission optical system having high imaging performance.
[0003]
Therefore, it is conceivable to use a radial type heterogeneous lens which has the ability to correct axial chromatic aberration by itself. As an example of an image transmission optical system using one radial type heterogeneous lens, an optical system according to an eleventh embodiment of Japanese Patent Application Laid-Open No. 62-24208 shown in FIG. 26 is known. However, in this conventional example, despite the use of a radial type heterogeneous lens effective for correcting chromatic aberration, correction of chromatic aberration that is so important as to determine the imaging performance of the image transmission optical system is not described. Further, in this conventional example, since a radial type heterogeneous lens is used as a cemented lens, the joining cost is higher than a lens system that does not use a cemented lens. Generally, a cemented lens is used to correct chromatic aberration.However, unlike a homogeneous lens, a radial type heterogeneous lens has the ability to correct axial chromatic aberration by itself, so a radial type heterogeneous lens is used. Making a cemented lens is not an effective method of use. When a radial heterogeneous lens is used in an image transmission optical system, it is necessary to effectively use the aberration correction effect of the radial heterogeneous lens.
[0004]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION The present invention provides an image transmission optical system used for a rigid mirror or the like, which corrects axial chromatic aberration generated by one relay to a favorable level with a small number of lenses.
[0005]
[Means for Solving the Problems]
The image transmission optical system according to the present invention is a substantially equal-magnification image, and one relay from the object to the image has a first lens component having a positive refractive power and a second lens component having a positive refractive power in order from the object side. The third lens component has a positive refractive power, and the second lens component is composed of one radial heterogeneous lens represented by the formula (a). It satisfies (2).
[0006]
(A) N (r) = N₀₀+ N₁₀r²  + N₂₀r⁴  ＋ ・ ・ ・
(1) N₁₀<0
(2) 1 / V₁₀<2 / V₀₀
In the above equation (a), r is the distance in the radial direction from the optical axis, N (r) is the refractive index of the reference wavelength at the point of radius r, N₀₀Is the refractive index on the optical axis of the reference wavelength, N₁₀, N₂₀,... Are the refractive index distribution coefficients of the second, fourth,.₀₀, V₁₀Represents the dispersion of the radial type heterogeneous lens, and is represented by the following equations.
[0007]
V₀₀= (N_00d  -1) / (N_00F  -N_00C  )
V₁₀= N_10d  / (N_10F  -N_10C  )
Where N_00d, N_00F, N_00CIs the refractive index for the d, F and C lines on the optical axis, respectively, N_10d, N_10F, N_10CIs a secondary refractive index distribution coefficient for the d, F, and C lines, respectively.
[0008]
In the image transmission optical system which is composed of a positive first lens component, a positive second lens component, and a positive third lens component in this order from the object side, the second lens component is a single lens. In order to satisfactorily correct the axial chromatic aberration which is a problem in the case of the configuration, it is preferable that the second lens component is configured by one radial type heterogeneous lens.
[0009]
Here, it is known that the axial chromatic aberration PAC generated by the radial type heterogeneous lens is represented by the following equation (b).
[0010]
PAC = K (φ_S  / V₀₀+ Φ_m  / V₁₀(B)
Where K is a constant depending on the ray height and the final paraxial ray angle, φ_S  , Φ_m  Is the refractive power of the surface of the radial heterogeneous lens and the refractive power of the medium, respectively.
[0011]
Also, the refractive power of the medium φ_m  Is also known to be approximated by the following equation:
[0012]
φ_m  ≒ -2N₁₀d (c)
Here, d is the lens thickness of the radial heterogeneous lens.
[0013]
Here, Abbe number V on the optical axis of the radial type heterogeneous lens₀₀Is approximately the same as the Abbe number of existing homogeneous glass in terms of material production, so that 30 <V₀₀<A value within a range of about 90. This V₀₀When the value of satisfies this range, in order to correct axial chromatic aberration by a radial type heterogeneous lens having a total positive refractive power of the surface and the medium, the following ranges (d) to (g) are required. Can be considered.
[0014]
o <φ_m  <Φ_S  , V₁₀<0 (d)
φ_m  <0 <φ_S  , 0 <V₁₀<V₀₀                  (E)
0 <φ_S  <Φ_m  , V₁₀<0 (f)
φ_s  <0 <φ_m  , V₀₀<V₁₀                      (G)
Among the above, for example, the range of (d) is when the refractive power of both the surface and the medium has a positive value and the refractive power of the surface is larger than the refractive power of the medium.₁₀Is a negative value, it indicates that the effect of correcting axial chromatic aberration is larger than that of a homogeneous lens having the same refractive power. If a radial heterogeneous lens that satisfies any of the above conditions (d) to (g) is used, axial chromatic aberration can be corrected.
[0015]
Furthermore, considering the correction of Petzval sum in addition to the correction of axial chromatic aberration, in the case of (e) in which the medium of the radial type heterogeneous lens has a negative refractive power, there is a problem that the Petzval sum deteriorates.
[0016]
Here, the Petzval sum PTZ of the radial type heterogeneous lens is represented by the following equation.
[0017]
PTZ = φ_s  / N₀₀+ Φ_m  / N₁₀ ²                  (H)
According to equation (d), when the refractive power of the medium is a negative value, the Petzval sum becomes larger than that of a homogeneous lens having the same refractive power.
Also, the refractive power of the medium φ_m  Has a positive value,₁₀Is V₀₀If the value is positive and extremely small, the axial chromatic aberration cannot be corrected.
[0018]
For the above reasons, in the present invention, the conditions (1) and (2) are satisfied. In the optical system of the present invention, if the radial type heterogeneous lens satisfies the condition (1), the medium has a positive refractive power from the expression (c). If the condition (2) is satisfied, axial chromatic aberration can be reduced without deteriorating the Petzval sum as compared with a homogeneous lens having the same refractive power.
[0019]
If the condition (1) is not satisfied, the medium of the radial type inhomogeneous lens has a negative refractive power, which is not preferable because the Petzval sum is deteriorated. If the condition (2) is not satisfied, it is difficult to satisfactorily correct axial chromatic aberration generated in the radial heterogeneous lens.
[0020]
Further, in the optical system of the present invention, the ray height of the axial ray is highest in the positive second lens component, and the axial chromatic aberration tends to be large in the second lens component. It is effective to use a single radial type heterogeneous lens.
[0021]
Further, a second configuration of the present invention is an optical system that is an approximately equal-magnification image in which one relay from an object to an image is configured by at least three or more lenses, and one of the lenses is represented by the formula ( An image transmission optical system, which is a radial type heterogeneous lens represented by a) and satisfies the following conditions (3), (4), and (5).
[0022]
(3) | (N₀₀-1) / r_1G| <0.9 × (1 / f_G  )
(4) | (N₀₀-1) / r_2G| <0.9 × (1 / f_G  )
(5) 1 / V₁₀<1 / V₀₀
Where r_1G, R_2GIs the radius of curvature of the object-side and image-side surfaces of the radial type heterogeneous lens, respectively, f_G  Is the focal length of the radial heterogeneous lens.
[0023]
As is clear from equation (b), the radial heterogeneous lens has₁₀By controlling the value of, the axial chromatic aberration can be controlled by the lens alone. However, for example, if the value of the refractive power of the medium given by the expression (c) is extremely small with respect to the refractive power of the surface of the radial type heterogeneous lens, the effect of correcting the chromatic aberration in the medium cannot be sufficiently obtained. Absent.
[0024]
Further, the radial type heterogeneous lens can control the amount of aberration other than chromatic aberration, such as Petzval sum and spherical aberration, as compared with the homogeneous lens, and these are affected by the refractive power of the surface and the refractive power of the medium. For example, the Petzval sum PTZ of a radial heterogeneous lens is given by equation (h). From this equation (h), if the surface has a strong positive refracting power with respect to the refracting power of the medium, a strong positive Petzval sum is generated in the radial type heterogeneous lens, and the image plane falls to the object side. Therefore, in order to satisfactorily correct axial chromatic aberration using a radial type heterogeneous lens, V₁₀It is necessary to set the refractive power of the medium and the refractive power of the surface to appropriate values in addition to the above values.
[0025]
Here, the focal length f of the radial type heterogeneous lens single lens_G  = 10 mm, image height 1 mm, object point infinity, F-number 4.0, lens thickness d = 5 mm, N₀₀= 1.6, V₀₀The following table shows changes in the aberration coefficient when the refractive power of the surface and the refractive power of the medium are changed when = 40.
[0026]

[0027]

[0028]
Example 3

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

[0038]

The aberration coefficients shown in this table are the third-order spherical aberration SA3, the third-order coma CM3, the third-order astigmatism AS3, the third-order distortion DIST3, the third-order Petzval sum PTZ3, and the axial chromatic aberration PAC. , The values of the aberration coefficients of the object-side surface, the medium, and the image-side surface of the radial type heterogeneous lens, and the sum of these values. Here, when the radius of curvature of the surface of the radial type heterogeneous lens is changed, N₁₀, N₂₀, V₁₀With the focal length f_G  = 10 mm, tertiary spherical aberration SA3 ≒ 0, and axial chromatic aberration PAC ≒ 0.
[0039]
In the above table, in Examples 1 to 9, the second surface (image-side surface) is a flat surface (r_2G= ∞), and the first surface (object-side surface) is r_1G= ∞, 20, 10, 8, 6, -20, -10, -8, -6 (mm) are shown for each aberration coefficient. In Examples 10 to 12, the first surface r_1G, Second surface r_2GIs a curved surface, and the aberration coefficients at the values shown in the table are shown.
[0040]
Example 1 has a two-sided planar shape (r_1G= R_2G= ∞), all aberrations are very small values.
[0041]
In Examples 2 to 5, the second surface is a plane (r_2G= ∞), the radius of curvature r of the first surface_1GAre sequentially reduced so that the refractive power of the surface increases in the positive direction. As is apparent from these examples, the radius of curvature r of the first surface is larger than that of the plane of Example 1._1GIt can be seen that the value of the Petzval sum and the value of astigmatism become particularly large as becomes smaller. This is because, as can be seen from Expression (h) representing the Petzval sum, when the surface has a larger positive refractive power than the medium, the value of the Petzval sum generated in total increases. Similarly, astigmatism increases as the refractive power of the surface increases. For this reason, when the surface of the radial type heterogeneous lens has a positive refractive power, the refractive power of the surface should be somewhat weaker than the refractive power of the medium in order not to deteriorate the Petzval sum and astigmatism. Is preferred.
[0042]
In Examples 6 to 9, the radius of curvature r of the first surface is_1GIs an example in which the surface is concave and becomes smaller in order, so that the negative refractive power of the surface becomes stronger. From these examples, any aberrations including Petzval sum and astigmatism are not deteriorated even when the negative refractive power of the first surface is increased, as compared with the two-plane shape. However, as is apparent from the spherical aberration in particular, the amount of aberration generated in the surface and the medium is larger than that in the case of the two-plane shape in Example 1, but the sign of the sign differs between the surface and the medium. Are caused to cancel each other, and the amount of generation is small in the total lens. For example, r_1GIn the case of Example 9 where = −6 mm, the aberration generated between the surface and the medium is about 20 times that of Example 1. That is, in Example 1, the first surface (r_1G), The spherical aberration coefficient SA3 in the medium (G) = 0.00490, the second surface (r_2G), The spherical aberration coefficient AS3 = −0.00499, and SA3 ≒ 0 in total. On the other hand, in Example 9, the first surface (r_1G), The spherical aberration coefficient SA3 = 0.11559 in the medium (G), the second surface (r_2G)), The spherical aberration coefficient SA3 = −0.00595, and SA3 ≒ 0.0035 in total. For this reason, Example 9 is not preferable in terms of manufacturing a lens system because the tolerance of the radial type heterogeneous lens is extremely strict compared to Example 1, and the cost is increased and the performance is degraded due to eccentricity. Therefore, when the surface of the radial heterogeneous lens has a negative refractive power, it is desirable that the refractive power of the surface is somewhat weaker than the refractive power of the medium in order to reduce the manufacturing tolerance.
[0043]
Examples 10 to 13 are examples of a meniscus shape that is a double-sided curved surface. In each example, the total amount of aberration generated is not so large as compared with Example 1. However, in particular, axial chromatic aberration and spherical aberration have large amounts of generation on the surface and medium, and cancel each other, so that the total amount of generation is small. For example, in Example 12, the radius of curvature of the first surface is r_1G= −10 mm, the radius of curvature of the second surface is r_2G= −10 mm, both surfaces have the same radius of curvature, and the refractive power of the paraxial surface of the lens is 0. This point is the same as Example 1, but the amount of aberration generated on each of the surface and the medium is large. That is, regarding the axial chromatic aberration, in Example 1, the first surface (r_1G), PAC = 0, medium (G), PAC = 0.00984, second surface (r_2G), PAC = −0.00984, and PAC ≒ 0 in total. On the other hand, in Example 12, the first surface (r_1G) Is PAC = 0.01172, medium (G) is PAC = 0.01304, and the second surface (r_2G) Is PAC = -0.02470, PACＰＡ0 in total, and the amount of generation on each surface and medium is about 1.3 to 2.5 times. Further, in Example 1, the spherical aberration was also reduced to the first surface (r_1G) Is SA3 = 0, the medium (G) is SA3 = 0.00490, and the second surface (r_2G) Is 0.00499, and SA3 = 0 in total, whereas in Example 12, the first surface (r_1G) Is SA3 = −0.03436, the medium (G) is SA3 = 0.02743, and the second surface (r_2G) Is SA3 = 0.0064 and the total is SA3 ≒ 0, which is approximately 5.5 to 6.5 times. For this reason, in the case of Example 12, the manufacturing tolerance of the radial type heterogeneous lens is very strict as compared with the case of Example 1, which is not preferable in that a lens system is manufactured.
[0044]
As can be seen from these examples, when the surface of the radial heterogeneous lens has a meniscus shape, it is desirable that the refractive power of the surface is somewhat weaker than the refractive power of the medium in order to reduce manufacturing tolerances.
[0045]
In consideration of the points described above, in the optical system of the present invention, in order to correct axial chromatic aberration without deteriorating various aberrations and to loosen manufacturing tolerance, a radial type heterogeneous lens is required to satisfy the condition (3). , (4), and (5).
[0046]
The conditions (3) and (4) are conditions relating to the refractive power of the surface with respect to the total refractive power of the radial type heterogeneous lens. If this condition is satisfied, the refractive power of the surface is reduced to the refractive power of the medium. In comparison, the correction effect of the radial type heterogeneous lens can be sufficiently obtained without becoming extremely large.
[0047]
The condition (5) is set so that when the lens system according to the present invention satisfies the conditions (3) and (4), V is set so as to favorably correct axial chromatic aberration by a radial type heterogeneous lens.₁₀Is specified. If the conditions (3) and (4) are not satisfied, the refractive power of the surface becomes too large with respect to the refractive power of the medium, so that various aberrations are deteriorated and manufacturing tolerances become severe. If the condition (5) is not satisfied, it is difficult to satisfactorily correct longitudinal chromatic aberration with a radial heterogeneous lens.
[0048]
A third configuration of the optical system according to the present invention is a substantially equal-magnification image, and uses one radial heterogeneous lens represented by the formula (a) in one relay from an object to an image. One or more lenses are disposed on the object side of the radial heterogeneous lens, and the number of lenses is equal to the object side on the image side of the radial heterogeneous lens, and the radius of curvature and the lens thickness are substantially equal. Are arranged substantially symmetrically on the optical axis about the radial type heterogeneous lens.
[0049]
Radial heterogeneous lenses have the ability to correct axial chromatic aberration with a single lens compared to homogeneous lenses. Therefore, by using this in the optical system of the present invention, longitudinal chromatic aberration can be corrected to a satisfactory level. Also, in correcting various aberrations of the optical system, as described above, the lens components before and after the radial type heterogeneous lens are equal in the number of lenses, the radius of curvature and the lens thickness are almost equal. Are desirably arranged substantially symmetrically on the optical axis about the radial type heterogeneous lens. If the optical system is configured in this manner, distortion, chromatic aberration of magnification, and coma occurring in the front lens component of the radial heterogeneous lens, and distortion, chromatic aberration of magnification, and coma occurring in the rear lens component will be described. Cancel each other, and the amount of occurrence of these aberrations can be extremely reduced within one relay. This is because the amount of generation of these distortion, chromatic aberration of magnification, and coma is proportional to the odd power of the height of off-axis light rays. This is because the amounts of these aberrations generated in the rear lens component are almost the same as those of the aberration generated in the front lens component of the radial heterogeneous lens, and have opposite signs. If the number of front and rear lenses and the shape of the lenses are different, it is difficult to reduce the total amount of aberration to almost zero even if they are arranged almost symmetrically. Even if the number of front and rear lenses and the lens shape are almost the same, it is difficult to make these aberrations almost zero unless they are arranged almost symmetrically on the optical axis.
[0050]
Further, the fourth configuration of the optical system according to the present invention is an optical system that forms at least one image with at least three relays from the object to the image, and one lens has the formula (a). And is characterized by satisfying the following conditions (6) and (7).
[0051]
(6) −0.1 <N₁₀× IH²  <0
(7) 0.8 <d_G  / IH <15
Where d_G  Is the lens thickness of the radial heterogeneous lens, and IH is the image height.
[0052]
Radial heterogeneous lenses have the ability to correct axial chromatic aberration with a single lens compared to homogeneous lenses, so using this in the lens system of the present invention can correct axial chromatic aberration to a satisfactory level. However, considering further effective use of the radial type heterogeneous lens, it is desirable to satisfy the above conditions (6) and (7).
[0053]
As is clear from equation (b), in order to favorably correct axial chromatic aberration, the refractive power of the medium φ_m  Must have a sufficiently large value. If φ_m  Is very small, the correction ability is about the same as that of a homogeneous single lens, which is not preferable. From the equation (c), the refractive power of the medium φ_m  Is the second-order refractive index distribution coefficient N₁₀And is proportional to the product of the lens thickness d of the radial type heterogeneous lens and φ_m  In the present invention, the conditions (6) and (7) are satisfied in order to sufficiently increase the value of.
[0054]
If the upper limit of the condition (6) is exceeded, the refractive power of the medium will have a negative value, and especially the Petzval sum will be worsened. If the lower limit is exceeded, the refractive index difference between the optical axis and the periphery becomes too large, the production cost of the radial type heterogeneous lens material increases, and the tolerance becomes severe. If the upper limit of the condition (7) is exceeded, the lens thickness of the radial type heterogeneous lens becomes too large, so that the manufacturing cost of the radial type heterogeneous lens increases and the tolerance becomes severe. If the lower limit is exceeded, the refractive power of the medium becomes weak, and it is difficult to correct longitudinal chromatic aberration to a satisfactory level.
[0055]
Further, in consideration of manufacturability in the first to fourth configurations of the optical system of the present invention, it is desirable that both surfaces of the radial type heterogeneous lens have a substantially planar shape in terms of cost and the like.
[0056]
The radial type heterogeneous lens has a refractive power in the medium, and thus has a lens function even if the surface shape is almost flat. From the equation (b), the surface shape is substantially flat and φ_S  Even if ≒ 0, V₁₀Is set to an appropriate value, the axial chromatic aberration can be controlled to a desired value. Accordingly, when the surface shape of the radial type heterogeneous lens is made substantially two planes, the cost and time required for lens polishing can be reduced in addition to the effect of favorably correcting axial chromatic aberration.
[0057]
Further, the optical system of the present invention can be used for a rigid endoscope or the like. The rigid endoscope is inserted into, for example, the human body or the interior of an engine of an aircraft to observe the internal state. Therefore, the external shape of the rigid endoscope is an elongated shape, and a plurality of sets of one relay from an object to an image are arranged. Also, the overall aberrationButSince the number of arrangements is integrated, various aberrations generated in one relay must be properly corrected.
[0058]
Each of the above-described first to fourth configurations of the optical system of the present invention can correct various aberrations with one relay, and when these are continuously used, various aberrations in the entire system are reduced. A well-corrected system can be configured.
[0059]
In the optical system of the present invention having the above-described first to fourth configurations, it is desirable to satisfy the conditions (8) and (9) in order to favorably correct longitudinal chromatic aberration.
[0060]
(8) | (N₀₀-1) / r_1G| <0.65 × (1 / f_G  )
(9) | (N₀₀-1) / r_2G| <0.65 × (1 / f_G  )
In order to effectively use the correction effect of the radial type heterogeneous lens, it is necessary to set the refractive power of the surface and the refractive power of the medium to appropriate values. In particular, in order to effectively use the radial type heterogeneous lens, it is desirable that the shape of the surface is a surface having a large radius of curvature, and it is desirable that the conditions (8) and (9) are satisfied. If these conditions (8) and (9) are not satisfied, it becomes difficult to satisfactorily correct axial chromatic aberration by the radial type heterogeneous lens.
[0061]
Further, it is desirable that the optical system of the first to fourth configurations of the present invention satisfies the condition (10) in order to better correct the axial chromatic aberration.
[0062]
(10) −0.05 <N₁₀× IH²  <-0.0005
In order to effectively use the radial type heterogeneous lens in order to correct the axial chromatic aberration to a favorable level, it is desirable to satisfy the condition (10). As is clear from equation (b), the refractive power φ of the medium is required to correct the axial chromatic aberration._m  Must have a sufficiently large value, and if condition (10) is satisfied, φ_m  Can be set to a sufficiently large value. If the value exceeds the upper limit of the condition (10), the refractive power of the medium becomes weak, and the axial chromatic aberration is insufficiently corrected. If the lower limit is exceeded, the refractive index difference between the optical axis and the periphery becomes too large, the production cost of the radial type heterogeneous lens material becomes high, and the tolerance becomes strict.
[0063]
Further, in the optical systems having the first to fourth configurations of the present invention, it is desirable that the condition (11) is satisfied in order to favorably correct longitudinal chromatic aberration.
[0064]
(11) 1 <d_G  / IH <9
As described above, in order to correct axial chromatic aberration from equation (b), the medium must have a large refractive power. From equation (c), φ_m  Is the second-order refractive index distribution coefficient N₁₀And the thickness d of the radial type heterogeneous lens. Therefore φ_m  In order to increase the value, it is necessary to satisfy the above condition (11).
[0065]
If the value exceeds the upper limit of the condition (11), the thickness of the radial type heterogeneous lens becomes too large, so that the manufacturing cost of the radial type heterogeneous lens increases and the tolerance becomes strict. When the value goes below the lower limit of the condition (11), the refractive power of the medium becomes weak, and it becomes impossible to satisfactorily correct axial chromatic aberration.
[0066]
【Example】
Next, embodiments of the image transmission optical system of the present invention will be described.
[0067]

[0068]

[0069]

[0070]

[0071]

[0072]

[0073]

[0074]

[0075]

[0076]

[0077]

[0078]

[0079]

Where r₁  , R₂  , ... are the radii of curvature of the respective surfaces of the lens, d₁  , D₂  ,... Are the thicknesses and lens intervals of each lens, n₁  , N₂  ,... Are the refractive indices of the d-line of each lens, ν₁  , Ν₂  ,... Are Abbe numbers of the respective lenses.
[0080]
In the first embodiment, the optical system of one relay from the object to the image has a positive refractive power and a biconvex first lens component in order from the object side in the configuration shown in FIG. It is composed of three lenses, a second lens component having a meniscus shape and a third lens component having a positive refractive power and a biconvex shape, and the second lens component is a radial heterogeneous lens. The image transmission optical system has an NA of 0.072, an image height of 1.0 mm, and a distance from the lens end surface to the image of 4.9 mm.
[0081]
Normally, if the second lens component is formed of only one homogeneous lens in such a lens configuration, axial chromatic aberration cannot be satisfactorily corrected.
[0082]
In the first embodiment, axial chromatic aberration is favorably corrected by using a radial type heterogeneous lens as the second lens component.
[0083]
The aberration situation in the first embodiment is as shown in FIG. 10, and it can be seen that only three lenses have high optical performance.
[0084]
In the second embodiment, in the configuration shown in FIG. 2, the optical system of one relay from the object to the image has, in order from the object side, a biconvex first lens component having a positive refractive power and a positive refractive power. The bi-convex second lens component has a positive refractive power and a bi-convex third lens component. The second lens component is a radial heterogeneous lens. The image transmission optical system has an NA of 0.072, an image height of 1.0 mm, and a distance from the lens end surface to the image of 4.9 mm.
[0085]
In the optical system having the configuration of the present invention, negative spherical aberration tends to occur in the entire system. In this embodiment, the radial type heterogeneous lens is corrected by satisfying the following condition (12). ing.
[0086]
(12) N₂₀> 0
Fourth-order refractive index distribution coefficient N of a radial type heterogeneous lens₂₀Has a positive value, a positive spherical aberration is generated in the medium, and the spherical aberration of the entire system can be satisfactorily corrected. If the condition (12) is not satisfied, a negative spherical aberration will occur in the medium, and it will be difficult to satisfactorily correct the spherical aberration in the entire system.
[0087]
The second embodiment is characterized in that the spherical aberration is corrected by satisfying the condition (12). However, this correction means can be applied to the other twelfth embodiment.
[0088]
The aberration situation of the second embodiment is as shown in FIG. 11, and it can be seen that this embodiment has high optical performance despite the fact that the number of lenses is three.
[0089]
Example 3 is shown in FIG. 3, in which the optical system of one relay from the object to the image includes, in order from the object side, a first convex lens component having a positive refractive power and a positive refractive power. The second lens component is a radial-type non-homogeneous lens which is composed of three lenses, a second lens component having a concave flat shape and a third lens component having a positive refractive power and a plano-convex shape. An image transmission optical system with an NA of 0.073, an image height of 1.0 mm, and a distance from the lens end surface to the image of 5 mm. An example in which many planes are used to reduce the cost required for lens polishing. Up to three of the six surfaces are flat.
[0090]
The state of aberration in this embodiment is as shown in FIG. 12, and has high optical performance despite the fact that it has a three-element structure and uses many planes.
[0091]
Example 4 is shown in FIG. 4, in which the optical system of one relay has, in order from the object side, a convex-planar first lens component, a biconvex second lens component, and a plano-convex third lens. The second lens component is a radial type heterogeneous lens. This embodiment is an image transmission optical system in which the NA is 0.073, the image height is 1.0 mm, and the distance from the lens end surface to the image is 4.9 mm. In the fourth embodiment, the lens shapes on the object side and the image side are symmetric with respect to the radial type heterogeneous lens which is the second lens component, so that correction of distortion, coma, and chromatic aberration of magnification is advantageous. ing.
[0092]
As shown in FIG. 13, the aberration shape of the fourth embodiment has good optical performance despite being composed of only three lenses.
[0093]
In the fifth embodiment, the optical system of one relay has a first lens component having a convex and flat shape, a second lens component having a biconcave shape, and a third lens having a plano-convex shape, in order from the object side. The second lens component is a radial type heterogeneous lens. This embodiment is an image transmission optical system having an NA of 0.073, an image height of 1.0 mm, and a distance from the lens end surface to the image of 4.9 mm. In Example 5, as in Example 4, the lens shape on the image side is symmetrical to the object side with respect to the radial type heterogeneous lens as a center, which is a shape advantageous for correcting distortion, coma, and chromatic aberration of magnification. ing.
[0094]
The aberration state of the fifth embodiment is as shown in FIG. 14, and has high optical performance despite being composed of only three lenses.
[0095]
In the sixth embodiment, in the configuration shown in FIG. 6, the optical system of one relay has, in order from the object side, a first convex lens component having a positive refractive power and a second planar component having a double refractive power having a positive refractive power. The second lens component is a radial-type heterogeneous lens composed of three lenses each including a lens component and a third lens component having a plano-convex shape having a positive refractive power. This embodiment is an image transmission optical system having an NA of 0.073, an image height of 1.0 mm, and a distance from the lens end surface to the image of 4.9 mm. In this embodiment, the cost required for lens polishing is reduced by using a lot of flat surfaces, and four out of six surfaces of one relay lens are made flat. Further, the first lens component and the third lens component are lenses having the same shape, and are arranged symmetrically with respect to the second lens component (radial heterogeneous lens), which is advantageous for correcting distortion, coma, and chromatic aberration of magnification. It has a configuration. The second lens component is a radial type heterogeneous lens, so that axial chromatic aberration and spherical aberration are satisfactorily corrected.
[0096]
The aberration state of the sixth embodiment is as shown in FIG. 15, and the optical system has high optical performance despite the fact that the three lenses frequently use a flat surface.
[0097]
Embodiment 7 also has a configuration shown in FIG. 6, in which the optical system of one relay has, in order from the object side, a biconvex first lens component having a positive refractive power and a biplanar second lens component having a positive refractive power. The second lens component is a radial non-homogeneous lens composed of three lenses including a component and a biconvex third lens component having a positive refractive power. This embodiment is an image transmission optical system including three lenses having a NA of 0.13, an image height of 2.8, and a distance from the lens end surface to the image of 5 mm. This embodiment is an example in which the NA is increased to 0.13, and spherical aberration which is particularly problematic when the NA is increased is corrected by using a radial type heterogeneous lens.
[0098]
The aberration situation of the seventh embodiment is as shown in FIG. 16, and has high optical performance despite being composed of only three bright lenses.
[0099]
Embodiment 8 has a configuration shown in FIG. 6, in which the optical system of one relay has, in order from the object side, a meniscus-shaped first lens component having a positive refractive power with the convex surface facing the object side and a lens having a positive refractive power. It is composed of three lenses composed of a planar second lens component and a biconvex third lens component having a positive refractive power with the convex surface facing the image side, wherein the second lens component is radial inhomogeneous. Lens. The image transmission optical system has an NA of 0.15, an image height of 2 mm, and a distance from the lens end surface to the image of 6 mm. In this embodiment, the NA is 0.15, which is brighter than that of the seventh embodiment. That is, similarly to the seventh embodiment, the spherical aberration was corrected more favorably by using a radial type heterogeneous lens, and a brighter optical system was obtained.
[0100]
The aberration state of the eighth embodiment is as shown in FIG. 17. The number of lenses is three, and the lens has high optical performance even though it has a bright NA of 0.15.
[0101]
In the ninth embodiment shown in FIG. 6, the optical system of one relay has, in order from the object side, a convex-planar first lens component having a positive refractive power and a biplanar second lens having a positive refractive power. The second lens component is a radial non-homogeneous lens including three lenses each including a group and a plano-convex third lens component having a positive refractive power. The image transmission optical system has an NA of 0.129, an image height of 2.81 mm, and a distance from the lens end surface to the image of 5 mm. In this embodiment, NA is as bright as 0.129, and four of the six surfaces are flat, but spherical aberration is favorably corrected using a radial type heterogeneous lens.
[0102]
The aberration state of the ninth embodiment has high optical performance despite the fact that the number of lenses is 3 and the NA is 0.13.
[0103]
In the tenth embodiment, in the configuration shown in FIG. 7, the optical system of one relay has, in order from the object side, a first lens component having a positive refractive power and a cemented lens of a negative lens and a positive lens, and a positive refractive power. And a third lens component composed of a cemented lens of a positive lens and a negative lens having a positive refractive power and a second lens component having a positive refractive power. It is a radial type heterogeneous lens. The tenth embodiment is an image transmission optical system in which the NA is 0.14, the image height is 2.8 mm, and the distance from the lens end surface to the image is 5 mm.
[0104]
In the tenth embodiment, astigmatism was particularly well corrected by using the first lens component and the third lens component as cemented lenses. When the optical system of the present invention is used for a hard mirror, it is often used in combination with an objective lens. Therefore, the astigmatism generally generated in the objective lens is canceled by the astigmatism generated in the image transmission optical system, so that the entire astigmatism is properly corrected. However, it may be desirable for the image transmission optical system alone to satisfactorily correct astigmatism. In such a case, this embodiment is effective.
[0105]
As shown in FIG. 19, the aberration state of the tenth embodiment is such that various aberrations including astigmatism are satisfactorily corrected.
[0106]
In the eleventh embodiment, the optical system of one relay has a positive refractive power with the convex surface facing the object side in order from the object side in the configuration shown in FIG.ConvexityA first lens component having a shape and a second lens component having a two-plane shape having a positive refractive power and a positive lens having a convex surface facing the image sidePlano-convexThe second lens component is a radial type non-homogeneous lens composed of three lenses each including a third lens component having a shape. The image transmission optical system has an NA of 0.1, an image height of 1.4 mm, and a distance from the lens end surface to the image of 7 mm. In this embodiment, astigmatism is mainly satisfactorily corrected by using aspheric surfaces for the object-side surface of the first lens component and the image-side surface of the third lens component.
[0107]
As in this embodiment, by combining a radial heterogeneous lens and an aspheric surface, axial chromatic aberration and spherical aberration are corrected mainly by the radial heterogeneous lens of the second lens component, and astigmatism is reduced. Correction is made mainly by the aspherical surfaces provided in the first lens component and the third lens component, and furthermore, the object side and the image side are symmetrical with respect to the second lens component so that coma aberration, distortion aberration, The chromatic aberration of magnification was corrected so that all aberrations were satisfactorily corrected.
[0108]
The shape of the aspherical surface used in this embodiment is represented by the following equation.

[0109]
In the above equation, the x axis is taken in the direction of the optical axis, and the y axis is taken in the direction perpendicular to the optical axis, where r is the radius of curvature on the optical axis, A_2iIs an aspheric coefficient.
[0110]
The aberration state of the eleventh embodiment is as shown in FIG. 20, and high optical performance is obtained even though the number of lenses is three.
[0111]
The twelfth embodiment is an optical system for transmitting an image five times in the configuration shown in FIG. 8 in which five sets of the image transmission optical system of the sixth embodiment are continuously arranged on the optical axis.
[0112]
In this embodiment, five sets of the optical systems of the sixth embodiment are continuously arranged. However, it is possible to transmit a plurality of times by using another embodiment. Thus, by arranging a plurality of sets of the image transmission optical system of the present invention, it is possible to configure an optical system for transmitting an image a plurality of times, which can achieve the object of the present invention.
[0113]
The aberration state of the twelfth embodiment is as shown in FIG. 21, and high optical performance is obtained even when an image is transmitted a plurality of times.
[0114]
The thirteenth embodiment has a configuration in which an objective lens is arranged on the object side of the optical system for performing the five-time image transmission shown in the twelfth embodiment, as shown in FIG. FIG. 9 shows only the configuration of the objective lens, and the image transmission optical system has only the tip on the objective lens side, and the other components are omitted. The objective lens of this embodiment uses an aspheric surface mainly for correcting distortion. Note that_ThirteenIs an object image formed by the objective lens.
[0115]
The aberration state of this embodiment is as shown in FIG. 22, and the optical system in which the objective lens is further arranged in the image transmission optical system has high optical performance.
[0116]
The image transmission optical system of the present invention includes, in addition to the optical system described in the claims, the following optical systems.
[0117]
(1) An image transmission optical system according to claim 1, 3 or 4, which further satisfies the following conditions (3), (4) and (5).
(3) | (N₀₀-1) / r_1G| <0.9 × (1 / f_G  )
(4) | (N₀₀-1) / r_2G| <0.9 × (1 / f_G  )
(5) 1 / V₁₀<1 / V₀₀
[0118]
(2) In the optical system according to claim 1 or 4, an equal number of one or more lenses are arranged on the object side and the image side of the radial type heterogeneous lens, respectively. An image transmission optical system in which lenses on the object side and the image side have substantially the same radius of curvature and lens thickness, and are arranged substantially symmetrically on the optical axis about the radial type heterogeneous lens.
[0119]
(3) An image transfer optical system according to claim 1 which satisfies the following conditions (6) and (7).
(6) −0.1 <N₁₀× IH²  <0
(7) 0.8 <d_G  / IH <15
[0120]
(4) In the optical system described in claim 2 or (1), the following conditions (8) and (9) are satisfied instead of the conditions (3) and (4). Image transmission optical system.
(8) | (N₀₀-1) / r_1G| <0.65 × (1 / f_G  )
(9) | (N₀₀-1) / r_2G| <0.65 × (1 / f_G  )
[0121]
(5) An optical system according to claim 1 or 3, wherein the image transmission optical system satisfies the following conditions (8) and (9).
(8) | (N₀₀-1) / r_1G| <0.65 × (1 / f_G  )
(9) | (N₀₀-1) / r_2G| <0.65 × (1 / f_G  )
[0122]
(6) In the optical system described in claim 1, 2, 3, or 4 or the above (1), (2), (4) or (5), the following condition (10) is satisfied. Image transmission optical system that satisfies the requirements.
(10) −0.05 <N₁₀× IH²  <-0.0005
[0123]
(7) In the optical system described in claim 1, 1, 3 or 4 or (1), (2), (4) or (5), the condition (11) is satisfied. Satisfactory image transmission optical system.
(11) 1 <d_G  / IH <9
[0124]
(8) The image transmission optical system according to the above (3), wherein the following condition (10) is satisfied instead of the condition (6).
(10) −0.05 <N₁₀× IH²  <-0.0005
[0125]
(9) An image transmission optical system according to the item (3), wherein the image transmission optical system satisfies the following condition (11) instead of the condition (7).
(11) 1 <d_G  / IH <9
[0126]
(10) Claims 1, 2, 3, or 4 of the claims or (1), (2), (3), (4), (5), (6), (7), (8) Or, the optical system according to (9), wherein both surfaces of the radial heterogeneous lens are substantially planar.
[0127]
(11) Claims 1, 2, 3 or 4 of the claims or (1), (2), (3), (4), (5), (6), (7), (9) Or an image transmission optical system for relaying an object image a plurality of times by arranging a plurality of sets of one relay optical system from an object to an image on an optical axis.
[0128]
【The invention's effect】
The image transmission optical system according to the present invention has high optical performance in which axial chromatic aberration is particularly well corrected, although the number of lenses is small including one radial heterogeneous lens.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention.
FIG. 2 is a diagram showing a configuration of a second embodiment of the present invention.
FIG. 3 is a diagram showing a configuration of a third embodiment of the present invention.
FIG. 4 is a diagram showing a configuration of a fourth embodiment of the present invention.
FIG. 5 is a diagram showing a configuration of a fifth embodiment of the present invention.
FIG. 6 is a diagram showing a configuration of embodiments 6, 7, 8, 9, and 11 of the present invention.
FIG. 7 is a diagram showing a configuration of a tenth embodiment of the present invention.
FIG. 8 is a diagram showing a configuration of a twelfth embodiment of the present invention.
FIG. 9 is a diagram showing a configuration of a thirteenth embodiment of the present invention.
FIG. 10 is an aberration curve diagram according to the first embodiment of the present invention.
FIG. 11 is an aberration curve diagram according to the second embodiment of the present invention.
FIG. 12 is an aberration curve diagram according to the third embodiment of the present invention.
FIG. 13 is an aberration curve diagram according to the fourth embodiment of the present invention.
FIG. 14 is an aberration curve diagram according to the fifth embodiment of the present invention.
FIG. 15 is an aberration curve diagram according to the sixth embodiment of the present invention.
FIG. 16 is an aberration curve diagram according to the seventh embodiment of the present invention.
FIG. 17 is an aberration curve diagram according to the eighth embodiment of the present invention.
FIG. 18 is an aberration curve diagram of the ninth embodiment of the present invention.
FIG. 19 is an aberration curve diagram of the tenth embodiment of the present invention.
FIG. 20 is an aberration curve diagram of the eleventh embodiment of the present invention.
FIG. 21 is an aberration curve diagram of the twelfth embodiment of the present invention.
FIG. 22 is an aberration curve diagram according to Example 13 of the present invention.
FIG. 23 is a diagram showing a configuration of a conventional image transmission optical system.
FIG. 24 is a diagram showing a configuration of another conventional image transmission optical system.
FIG. 25 is a diagram showing a configuration of another conventional image transmission optical system.
FIG. 26 is a diagram showing a configuration of another conventional image transmission optical system.

Claims (9)

One relay from the object to the image is formed, in order from the object side, by approximately equal magnification of a first lens component having a positive refractive power, a second lens component having a positive refractive power, and a third lens component having a positive refractive power. An image transmission optical system that satisfies the following conditions (1) and (2), wherein the second lens component in the image optical system is composed of one radial type heterogeneous lens represented by the following equation (a).
(A) N (r) = N 00 + N 10 r 2 + N 20 r 4 + ···
(1) N ₁₀ <0
(2) 1 / V ₁₀ <2 / V ₀₀
Here, r is the radial distance from the optical axis, N (r) is the refractive index of the reference wavelength at a point of radius r, N ₀₀ is the refractive index of the reference wavelength on the optical axis, N _10, N _20, .. Represent the refractive index distribution coefficients of the second, fourth,... Order of the reference wavelength, and V ₀₀ and V ₁₀ represent the dispersion of the radial type heterogeneous lens, and are represented by the following equations, respectively.
V ₀₀ = (N _00d -1) / (N _00F -N _00C )
_{V 10 = N 10d / (N} 10F -N 10C)
Here, N _00d , N _00F , and N _00C are refractive indexes for d, F, and C lines on the optical axis, respectively, and N _10d , N _10F , and N _10C are secondary refractive index distributions for d, F, and C lines, respectively. It is a coefficient. One relay from the object to the image is an optical system of substantially equal magnification formed with at least three lenses, and one lens is a radial type heterogeneous lens represented by the following equation (a). An image transmission optical system satisfying the conditions (3), (4) and (5).
(A) N (r) = N 00 + N 10 r 2 + N 20 r 4 + ···
(3) | (N ₀₀ -1) / r _1G | <0.9 × (1 / f _G )
(4) | (N ₀₀ -1) / r _2G | <0.9 × (1 / f _G )
(5) 1 / V ₁₀ <1 / V ₀₀
Where r is a radial distance from the optical axis, N (r) is the refractive index of the reference wavelength at a point of radius r, N ₀₀ is the refractive index of the fundamental wavelength on the optical axis, N _10, N _20, · .. Represent the refractive index distribution coefficients of the second, fourth,... Order of the reference wavelength, and V ₀₀ and V ₁₀ represent the dispersion of the radial type heterogeneous lens, and are represented by the following equations, respectively.
V ₀₀ = (N _00d -1) / (N _00F -N _00C )
_{V 10 = N 10d / (N} 10F -N 10C)
Here, N _00d , N _00F , and N _00C are refractive indexes for d, F, and C lines on the optical axis, respectively, and N _10d , N _10F , and N _10C are secondary refractive index distributions for d, F, and C lines, respectively. It is a coefficient. R _1G and r _2G are the radii of curvature of the object-side and image-side surfaces of the radial heterogeneous lens, respectively, and f _G is the focal length of the radial heterogeneous lens. One relay from the object to the image is an optical system of approximately equal magnification formed of at least three lenses, and one lens is a radial type heterogeneous lens represented by the following equation (a). An image transmission optical system that satisfies the conditions (3), (4), (5), (6), and (7).
(A) N (r) = N 00 + N 10 r 2 + N 20 r 4 + ···
(3) | (N ₀₀ -1) / r _1G | <0.9 × (1 / f _G )
(4) | (N ₀₀ -1) / r _2G | <0.9 × (1 / f _G )
(5) 1 / V ₁₀ <1 / V ₀₀
(6) −0.1 <N ₁₀ × IH ² <0
(7) 0.8 <d _G / IH <15
Here, r is the radial distance from the optical axis, N (r) is the refractive index of the reference wavelength at a point of radius r, N ₀₀ is the refractive index of the reference wavelength on the optical axis, N _10, N _20, .. Represent the refractive index distribution coefficients of the second, fourth,... Order of the reference wavelength, and V ₀₀ and V ₁₀ represent the dispersion of the radial type heterogeneous lens, respectively, and are represented by the following equations, respectively.
V ₀₀ = (N _00d -1) / (N _00F -N _00C )
_{V 10 = N 10d / (N} 10F -N 10C)
Here, N _00d , N _00F , and N _00C are the refractive indices for the d-line, F-line, and C-line on the optical axis, respectively, and N _10d , N _10F , and N _10C are the second-orders for the d-line, F-line, and C-line, respectively. Is the refractive index distribution coefficient. R _1G and r _2G are the radii of curvature of the object-side and image-side surfaces of the radial heterogeneous lens, f _G is the focal length of the radial heterogeneous lens, IH is the image height, and d _G is the radial heterogeneous. It is the thickness of the lens. 2. The image transmission optical system according to claim 1, wherein the following conditions (3), (4), and (5) are satisfied.
(3) | (N ₀₀ -1) / r _1G | <0.9 × (1 / f _G )
(4) | (N ₀₀ -1) / r _2G | <0.9 × (1 / f _G )
(5) 1 / V ₁₀ <1 / V ₀₀ 5. The image transmission optical system according to claim 3, wherein the following conditions (8) and (9) are satisfied.
(8) | (N ₀₀ −1) / r _1G | <0.65 × (1 / f _G )
(9) | (N ₀₀ −1) / r _2G | <0.65 × (1 / f _G ) 4. The image transmission optical system according to claim 1, wherein the following condition (10) is satisfied.
(10) −0.05 <N ₁₀ × IH ² <−0.0005
Here, IH is the image height. The image transmission optical system according to claim 6, wherein the following condition (11) is satisfied.
(11) 1 <d _G / IH <9
Here, d _G is the thickness of the radial type heterogeneous lens. 4. The image transmission optical system according to claim 1, wherein both surfaces of the radial type heterogeneous lens are substantially planar. 4. The image transmission optical system according to claim 1, wherein a plurality of sets of optical systems of one relay from the object to the image are arranged on the optical axis to relay the object image a plurality of times.

Images