JP4565262B2 - Fisheye lens - Google Patents
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- JP4565262B2 JP4565262B2 JP2003197315A JP2003197315A JP4565262B2 JP 4565262 B2 JP4565262 B2 JP 4565262B2 JP 2003197315 A JP2003197315 A JP 2003197315A JP 2003197315 A JP2003197315 A JP 2003197315A JP 4565262 B2 JP4565262 B2 JP 4565262B2
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Description
【０００１】
【発明の属する技術分野】
本発明は、小型でありながらレンズ最終面から像面までの空気換算距離を充分に確保した一眼レフカメラ用、特にデジタル一眼レフカメラに最適な魚眼レンズに関するものである。
【０００２】
【従来の技術】
従来、一眼レフカメラ用の魚眼レンズの殆どは、受光面の大きさ（イメージサイズ）が３５mmフィルムサイズに対応したレンズである。それらの魚眼レンズをそのままデジタル一眼レフカメラに用いたとしても、受光面の大きさ（イメージサイズ）の違いによりレンズの焦点距離と画角の関係が従来の銀塩一眼レフカメラとは異なるため、１８０度の画角を保つことが出来ない。
【０００３】
一般的にデジタル一眼レフカメラに用いられる撮像素子の受光面の大きさは、３５mmフィルムのフルサイズよりも少し小さめのサイズである。その結果、一般的に「３５mmフィルムイメージサイズの対角線」を「撮像素子のイメージサイズの対角線」で割った値をレンズの焦点距離に掛けた値がデジタル一眼レフカメラにおける焦点距離になってしまう。
【０００４】
従って、銀塩一眼レフカメラで１８０度の画角を持っていた魚眼レンズをそのままデジタル一眼レフカメラに使用した場合は、単なる超広角レンズの効果しか得られない。
【０００５】
【発明が解決しようとする課題】
撮影画面が３５mmフィルムのフルサイズよりも少し小さいデジタル一眼レフカメラ用レンズの画角は上述した理由から必然的に狭くなる。従って、魚眼レンズのように広い範囲を写し込もうとすると焦点距離をより短く設定しなければならない。その結果、デジタル一眼レフカメラ用魚眼レンズのバックフォーカスは焦点距離の３倍以上必要になるため、光学系として物体側に極端に強い発散系を配置する必要が生じる。
【０００６】
魚眼レンズにおいては、主点を後方へ出すレトロフォーカスタイプが用いられるが、上記理由から光学系として物体側に強い発散系を配置することにより、像面湾曲および非点収差による性能劣化を招きやすい。
【０００７】
さらに、レトロフォーカスタイプは、前群の負レンズの外径が大きくなる傾向があり、魚眼レンズの大型化、重量化を伴うという問題点もある。
【０００８】
本発明は、上述の事情に鑑みて行われたものであり、バックフォーカスを充分に確保し、像面湾曲が良好に補正され優れた光学性能を有する明るくコンパクトな、デジタルカメラに適した、魚眼レンズを提供することを目的とする。
【０００９】
【課題を解決するための手段】
上記目的を達成するため、本発明に係る魚眼レンズは、物体側より複数の負レンズを有し全体として負の屈折力の前群と、前記前群に対して軸上間隔をあけて配置され全体として正の屈折力の後群とから構成され、前記後群は物体側から順に、正レンズと、負レンズと正レンズとから成る接合レンズと、正レンズとからなり、かつ以下の条件を満足することを特徴とする。
（１）５．９０５≦Σｄ／ｆ≦６．３９４
但し、
ｆ ：前記魚眼レンズ全系の焦点距離、
Σｄ：前記魚眼レンズが無限遠に合焦した時の最も物体側レンズ面から最も像側レンズ面までの距離である。
【００１０】
また、本発明に係る魚眼レンズでは、前記前群は、前記複数の負レンズより像側に、少なくとも１組の接合レンズを有することが好ましい。
【００１１】
また、本発明に係る魚眼レンズは、以下の条件を満足することが好ましい。
（２）１．５≦ｆ２／ｆ≦４.０
但し、
ｆ２：前記後群の焦点距離である。
【００１３】
また、本発明に係る魚眼レンズでは、次の条件を満足ことが好ましい。
（３）０．５＜ｄ１／ｆ＜２．０
但し、
ｄ１：前記前群と前記後群との軸上間隔である。
【００１４】
また、本発明に係る魚眼レンズは、以下の条件を満足することが好ましい。
（４）３０≦νＲ凸−νＲ凹≦６０
但し、
νＲ凸：前記後群中の前記正レンズのアッベ数の平均値、
νＲ凹：前記後群中の前記負レンズのアッベ数の平均値である。
【００１５】
また、本発明に係る魚眼レンズは、以下の条件を満足することが好ましい。
（５）０．２≦ｎＲ凹−ｎＲ凸≦０．４５
但し、
ｎＲ凹：前記後群中の前記負レンズのｄ線（λ＝５８７．６ｎｍ）の屈折率の平均値、
ｎＲ凸：前記後群中の前記正レンズのｄ線（λ＝５８７．６ｎｍ）の屈折率の平均値である。
【００１６】
また、本発明に係る魚眼レンズは、前記前群および前記後群の全てのレンズ面は、各々球面または平面のいずれか一方で構成されていることが好ましい。
【００１７】
また、本発明に係る魚眼レンズでは、前記魚眼レンズは、無限遠物体から近距離物体へ合焦する際に、前記前群と前記後群との空気間隔を拡大しながら物体方向に移動することが好ましい。
【００１８】
【発明の実施の形態】
以下、本発明に係る魚眼レンズの実施の形態に付いて説明する。
本発明に係る魚眼レンズは、物体側より複数の負レンズを有し全体として負の屈折力の前群と、前群に対し軸上間隔をあけて配置され全体として正の屈折力の後群とから構成され、後群は少なくとも１組の接合レンズを有する構成にしている。
【００１９】
前群は、１８０度という大きな角度から入射する光束を光軸と平行な方向へ大きく曲げる働きを行う強い発散作用を有する負レンズを有するため、複数の負レンズで構成することにより、負レンズによって発生する収差を分散（分担）させることが可能になる。
【００２０】
条件式（１）は、本発明に係る魚眼レンズにおいて、バックフォーカスを十分に保ちながら軸外収差を補正しつつ全系の大型化、重量化を抑えるための条件である。上限値を超えるとバックフォーカスが短くなりすぎるため、一眼レフカメラ用に使用できない。さらに１８０度の光束を通すためには最も物体側に配置されたレンズの径（前玉径）が極端に大型化してしまい全系の大型化、重量化を招いてしまう。より効果をあげるには上限値を８．０にするのが好ましい。下限値を超えるとバックフォーカスは十分に取ることは可能になるが、１８０度の画角を保つことが不可能になるため好ましくない。より効果をあげるには下限値を５．０にするのが好ましい。
【００２１】
条件式（２）は、本発明に係る魚眼レンズにおいて、バックフォーカスを十分に保ちながら軸外収差を補正するために後群の焦点距離を規定した条件である。上限値を超えると非点収差及びコマ収差の補正が困難なるばかりか１８０度の画角を保つことも困難になり好ましくない。下限値を超えるとバックフォーカスが短くなりすぎるため、一眼レフカメラ用に使用できない。
【００２２】
条件式（３）は、本発明に係る魚眼レンズにおいて、前群と後群との軸上間隔を規定したものである。上限値を超えると倍率色収差が過大になりすぎて補正するのが難しくなる。またバックフォーカスが短くなりすぎるため一眼レフカメラ用に使用できない。下限値を超えると非点収差及びコマ収差の補正が困難なるばかりか１８０度の画角を保つことも困難になり好ましくない。なお、条件式（３）の下限値を０．７にすると更によい結果が得られる。
【００２３】
条件式（４）は、本発明に係る魚眼レンズにおいて、前群で発生した倍率色収差及び軸上色収差を補正するため後群中の正レンズと負レンズのアッベ数の差を規定したものである。上限値を超えると軸上色収差の補正が困難になるばかりか実在する硝材でレンズ系を構成することが困難になる。下限値を超えると前群の負レンズによる倍率色収差を後群で補正しきれなくなりｇ線（λ＝４３５．８ｎｍ）の倍率色収差がマイナス傾向になり好ましくない。
【００２４】
条件式（５）は、本発明に係る魚眼レンズにおいて、像面湾曲及び非点収差を補正するための条件である。負レンズをできる限り高い屈折率、正レンズを低い屈折率とすることにより、全系のペッツバール和を小さくすることができ、像面湾曲及び非点収差を小さく抑えることが可能になる。上限値を超えると、負レンズと正レンズのアッベ数の差を大きく付けなければならなくなり、前群で発生する軸上の色収差の補正が困難になる。下限値を超えると全系のペッツバール和が大きくなり像面湾曲が大きく発生するため好ましくない。
【００２５】
また前群に１組の接合レンズを有することにより、倍率色収差の発生を緩和することが可能になる。また、前群および後群の全てのレンズ面は、各々球面または平面のいずれか一方で構成されていることが好ましい。また、無限遠物体から近距離物体へ合焦する際に、近距離合焦時における光学特性の劣化を防ぐために、前群と後群との空気間隔を拡大しながら物体方向に移動させる構成が好ましい。
【００２６】
（実施例）
以下に、本発明に係る魚眼レンズの各実施例を示す。なお、各実施例において、「レンズ成分」は、「レンズ」を示す。
図１、図３、図５、図７、図９、図１１、図１３、図１５、図１７、図１９は、それぞれ本発明に係る魚眼レンズの第１実施例から第１０実施例のレンズ断面図を示している。断面図中のＳは開口絞り、平行平面板Ｐはフィルターを表していおり、前群Ｇ１と後群Ｇ２との間に配置されている。フィルターは光学系中どこに挿入しても性能に影響はなく、また光学系中にフィルターの挿入がなくても基本的な性能に影響は及ばさない。
【００２７】
図２、図４、図６、図８、図１０、図１２、図１４、図１６、図１８、図２０は、それぞれ本発明に係る魚眼レンズの第１実施例から第１０実施例の諸収差図を示している。各収差図中のｄはｄ線（λ＝５８７．６ｎｍ）における収差、ｇはｇ線（λ＝４３５．８ｎｍ）における収差、ｍはメリジオナル像面、ｓはサジタル像面を表している。ＦＮＯはＦナンバー、２ωは画角（単位：度）を示している。歪曲収差は等立体角射影y=2fsin(ω/2)からのズレ量を示している。そして各収差図とも、収差が良好に補正されている。
なお、以下の各実施例の表中、諸元値において、ｆは全系の焦点距離(mm)、FNOはＦナンバー、２ωは画角(単位：度)、Bfはバックフォーカス(mm)、TLは全長(mm)をあらわしている。また、レンズデータにおいて、左端の数値は面番号、rは曲率半径(mm)、dは面間隔(mm)、ｎｄはｄ線（λ＝５８７．６ｎｍ）に対する屈折率、νｄはアッベ数を示す。
【００２８】
なお、以下の全ての実施例の表において、掲載されている焦点距離ｆ、曲率半径ｒ、面間隔ｄその他の長さは、特記の無い場合一般に「ｍｍ」が使われるが、光学系は比例拡大または比例縮小しても同等の光学性能が得られるので、これに限られるものではない。また、単位は「ｍｍ」に限定されること無く他の適当な単位を用いることもできる。
【００２９】
（第１実施例）
図１に示す第１実施例に係る魚眼レンズは、物体側より順に、物体側に凸面を向けた負メニスカス形状の第１レンズ成分Ｌ１と、物体側に凸面を向けた負メニスカス形状の第２レンズ成分Ｌ２と、負レンズと正レンズとの接合からなり全体として正屈折力を有する第３レンズ成分Ｌ３とからなる全体として負屈折力を有する前群Ｇ１と、前記前群Ｇ１に対して軸上間隔をあけて配置され像側により強い凸面を向けた両凸形状の第４レンズ成分Ｌ４と、負レンズと正レンズとの接合からなり全体として正屈折力を有する第５レンズ成分Ｌ５と、両凸形状の正屈折力の第６レンズ成分Ｌ６とからなる全体として正屈折力を有する後群Ｇ２とから構成している。
【００３０】
【表１】
（第２実施例）
図３に示す第２実施例に係る魚眼レンズは、物体側より順に、物体側に凸面を向けた負メニスカス形状の第１レンズ成分Ｌ１と、物体側に凸面を向けた負メニスカス形状の第２レンズ成分Ｌ２と、物体側により強い凸面を向けた両凹形状の第３レンズ成分Ｌ３と、正レンズと負レンズとの接合からなり全体として正屈折力を有する第４レンズ成分Ｌ４とからなる全体として負屈折力を有する前群Ｇ１と、前記前群Ｇ１に対して軸上間隔をあけて配置され像側により強い凸面を向けた正メニスカス形状の第５レンズ成分Ｌ５と、負レンズと正レンズとの接合からなり全体として負屈折力を有する第６レンズ成分Ｌ６と、両凸形状の正屈折力の第７レンズ成分Ｌ７とからなる全体として正屈折力を有する後群Ｇ２とから構成している。
【００３２】
【表２】
（第３実施例）
図５に示す第３実施例に係る魚眼レンズは、物体側より順に、物体側に凸面を向けた負メニスカス形状の第１レンズ成分Ｌ１と、物体側に凸面を向けた負メニスカス形状の第２レンズ成分Ｌ２と、両凸形状の正屈折力の第３レンズ成分Ｌ３と、正レンズと負レンズとの接合からなり全体として負屈折力を有する第４レンズ成分Ｌ４とからなる全体として負屈折力を有する前群Ｇ１と、前記前群Ｇ１に対して軸上間隔をあけて配置され両凸形状の正屈折力の第５レンズ成分Ｌ５と、負レンズと正レンズとの接合からなり全体として負屈折力を有する第６レンズ成分Ｌ６と、両凸形状の正屈折力の第７レンズ成分Ｌ７とからなる全体として正屈折力を有する後群Ｇ２とから構成している。
【００３４】
【表３】
（第４実施例）
図７に示す第４実施例に係る魚眼レンズは、物体側より順に、物体側に凸面を向けた負メニスカス形状の第１レンズ成分Ｌ１と、物体側に凸面を向けた負メニスカス形状の第２レンズ成分Ｌ２と、両凸形状の正屈折力の第３レンズ成分Ｌ３と、正レンズと負レンズとの接合からなり全体として負屈折力を有する第４レンズ成分Ｌ４とからなる全体として負屈折力を有する前群Ｇ１と、前記前群Ｇ１に対して軸上間隔をあけて配置され両凸形状の第５レンズ成分Ｌ５と、負レンズと正レンズとの接合からなり全体として負屈折力を有する第６レンズ成分Ｌ６と、両凸形状の正屈折力の第７レンズ成分Ｌ７とからなる全体として正屈折力を有する後群Ｇ２とから構成している。
【００３６】
【表４】
（第５実施例）
図９に示す第５実施例に係る魚眼レンズは、物体側より順に、物体側に凸面を向けた負メニスカス形状の第１レンズ成分Ｌ１と、物体側に凸面を向けた負メニスカス形状の第２レンズ成分Ｌ２と、負レンズと正レンズとの接合からなり全体として負屈折力を有する第３レンズ成分Ｌ３と、正レンズと負レンズとの接合からなり全体として正屈折力を有する第４レンズ成分Ｌ４とからなる全体として負屈折力を有する前群Ｇ１と、前記前群Ｇ１に対して軸上間隔をあけて配置され両凸形状の正屈折力の第５レンズ成分Ｌ５と、負レンズと正レンズとの接合からなり全体として負屈折力を有する第６レンズ成分Ｌ６と、両凸形状の正屈折力の第７レンズ成分Ｌ７とからなる全体として正屈折力を有する後群Ｇ２とから構成している。
【００３８】
【表５】
（第６実施例）
図１１に示す第６実施例に係る魚眼レンズは、物体側より順に、物体側に凸面を向けた負メニスカス形状の第１レンズ成分Ｌ１と、物体側に凸面を向けた負メニスカス形状の第２レンズ成分Ｌ２と、負レンズと正レンズとの接合からなり全体として負屈折力を有する第３レンズ成分Ｌ３と、正レンズと負レンズとの接合からなり全体として正屈折力を有する第４レンズ成分Ｌ４とからなる全体として負屈折力を有する前群Ｇ１と、前記前群Ｇ１に対して軸上間隔をあけて配置され像側により強い凸面を向けた正メニスカス形状の正屈折力の第５レンズ成分Ｌ５と、負レンズと正レンズとの接合からなり全体として正屈折力を有する第６レンズ成分Ｌ６と、両凸形状の第７レンズ成分Ｌ７とからなる全体として正屈折力を有する後群Ｇ２とから構成している。
【００４０】
【表６】
（第７実施例）
図１３に示す第７実施例に係る魚眼レンズは、物体側より順に、物体側に凸面を向けた負メニスカス形状の第１レンズ成分Ｌ１と、物体側に凸面を向けた負メニスカス形状の第２レンズ成分Ｌ２と、負レンズと正レンズとの接合からなり全体として負屈折力を有する第３レンズ成分Ｌ３と、両凸形状の正屈折力の第４レンズ成分Ｌ４と、正レンズと負レンズとの接合からなり全体として負屈折力を有する第５レンズ成分Ｌ５とからなる全体として負屈折力を有する前群Ｇ１と、前記前群Ｇ１に対して軸上間隔をあけて配置され像側により強い凸面を向けた正メニスカス形状の正屈折力の第６レンズ成分Ｌ６と、負レンズと正レンズとの接合からなり全体として正屈折力を有する第７レンズ成分Ｌ７と、両凸形状の正屈折力の第８レンズ成分Ｌ８とからなる全体として正屈折力を有する後群Ｇ２とから構成している。
【００４２】
【表７】
（第８実施例）
図１５に示す第８実施例に係る魚眼レンズは、物体側より順に、物体側に凸面を向けた負メニスカス形状の第１レンズ成分Ｌ１と、物体側に凸面を向けた負メニスカス形状の第２レンズ成分Ｌ２と、像側により強い凸面を向けた正メニスカス形状の正屈折力の第３レンズ成分Ｌ３と、負レンズと正レンズとの接合からなり全体として正屈折力を有する第４レンズ成分Ｌ４と、正レンズと負レンズとの接合からなり全体として負屈折力を有する第５レンズ成分Ｌ５とからなる全体として負屈折力を有する前群Ｇ１と、前記前群Ｇ１に対して軸上間隔をあけて配置され像側により強い凸面を向けた正メニスカス形状の正屈折力の第６レンズ成分Ｌ６と、負レンズと正レンズとの接合からなり全体として正屈折力を有する第７レンズ成分Ｌ７と、両凸形状の正屈折力の第８レンズ成分Ｌ８とからなる全体として正屈折力を有する後群Ｇ２とから構成している。
【００４４】
【表８】
（第９実施例）
図１７に示す第９実施例に係る魚眼レンズは、物体側より順に、物体側に凸面を向けた負メニスカス形状の第１レンズ成分Ｌ１と、同じく物体側に凸面を向けた負メニスカス形状の第２レンズ成分Ｌ２と、像側に凸面を向けた正メニスカスレンズ形状の第３レンズ成分Ｌ３と、負レンズ成分と正レンズ成分との接合からなり全体として負屈折力を有する第４レンズ成分Ｌ４と、正レンズと負レンズとの接合からなり全体として負屈折力を有する第５レンズ成分Ｌ５とからなる全体として負屈折力を有する前群Ｇ１と、軸上間隔をあけて配置され負レンズ成分と正レンズ成分との接合からなり全体として正屈折力を有する第６レンズ成分Ｌ６と、両凸形状の正屈折力の第７レンズ成分Ｌ７とからなる全体として正屈折力を有する後群Ｇ２とから構成している。
【００４６】
【表９】
（第１０実施例）
図１９に示す第１０実施例に係る魚眼レンズは、物体側より順に、物体側に凸面を向けた負メニスカス形状の第１レンズ成分Ｌ１と、同じく物体側に凸面を向けた負メニスカス形状の第２レンズ成分Ｌ２と、両凹形状の第３レンズ成分Ｌ３と、両凸形状の第４レンズ成分Ｌ４と、負メニスカス形状の第５レンズ成分Ｌ５とからなり全体として負屈折力を有する前群Ｇ１と、軸上間隔をあけて配置され像側により強い凸面を向けた正メニスカス形状の第６レンズ成分Ｌ６と、負レンズ成分と正レンズ成分との接合からなり全体として正屈折力を有する第７レンズ成分Ｌ７と、両凸形状の正屈折力の第８レンズ成分Ｌ８とからなる全体として正屈折力を有する後群Ｇ２とから構成している。
【００４８】
【表１０】
本発明の第１実施例から第１０実施例に係る魚眼レンズにおける条件対応数値を以下の表に掲げる。
【００５０】
【表１１】
【発明の効果】
上述のように、本発明によれば、充分なバックフォーカスを確保しながら画角が１８０°を有しつつFナンバー2.8と明るくコンパクトな、デジタルカメラに適した、魚眼レンズを提供することが出来る。
【図面の簡単な説明】
【図１】本発明の第１実施例に係る魚眼レンズの断面図である。
【図２】本発明の第１実施例に係る魚眼レンズの諸収差図である。
【図３】本発明の第２実施例に係る魚眼レンズの断面図である。
【図４】本発明の第２実施例に係る魚眼レンズの諸収差図である。
【図５】本発明の第３実施例に係る魚眼レンズの断面図である。
【図６】本発明の第３実施例に係る魚眼レンズの諸収差図である。
【図７】本発明の第４実施例に係る魚眼レンズの断面図である。
【図８】本発明の第４実施例に係る魚眼レンズの諸収差図である。
【図９】本発明の第５実施例に係る魚眼レンズの断面図である。
【図１０】本発明の第５実施例に係る魚眼レンズの諸収差図である。
【図１１】本発明の第６実施例に係る魚眼レンズの断面図である。
【図１２】本発明の第６実施例に係る魚眼レンズの諸収差図である。
【図１３】本発明の第７実施例に係る魚眼レンズの断面図である。
【図１４】本発明の第７実施例に係る魚眼レンズの諸収差図である。
【図１５】本発明の第８実施例に係る魚眼レンズの断面図である。
【図１６】本発明の第８実施例に係る魚眼レンズの諸収差図である。
【図１７】本発明の第９実施例に係る魚眼レンズの断面図である。
【図１８】本発明の第９実施例に係る魚眼レンズの諸収差図である。
【図１９】本発明の第１０実施例に係る魚眼レンズの断面図である。
【図２０】本発明の第１０実施例に係る魚眼レンズの諸収差図である。
【符号の説明】
Ｇ１ 前群
Ｇ２ 後群
Ｓ 開口絞り
Ｐ 平行平面板（フィルター）
Ｉ 像面[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fish-eye lens that is compact and that is optimal for a single-lens reflex camera, particularly a digital single-lens reflex camera, that sufficiently secures an air conversion distance from the final lens surface to an image plane.
[0002]
[Prior art]
Conventionally, most fisheye lenses for single-lens reflex cameras are lenses in which the size of the light-receiving surface (image size) corresponds to a 35 mm film size. Even if these fisheye lenses are used as they are in a digital single lens reflex camera, the relationship between the focal length of the lens and the angle of view differs from that of a conventional silver salt single lens reflex camera due to the difference in the size of the light receiving surface (image size). The angle of view cannot be maintained.
[0003]
Generally, the size of the light receiving surface of an image sensor used in a digital single lens reflex camera is slightly smaller than the full size of a 35 mm film. As a result, the value obtained by dividing the “diagonal line of 35 mm film image size” by the “diagonal line of image size of the image sensor” and the focal length of the lens generally becomes the focal length in a digital single lens reflex camera.
[0004]
Therefore, when a fish-eye lens having an angle of view of 180 degrees with a silver salt single-lens reflex camera is used as it is in a digital single-lens reflex camera, only a super-wide-angle lens effect can be obtained.
[0005]
[Problems to be solved by the invention]
The angle of view of a lens for a digital single lens reflex camera whose shooting screen is slightly smaller than the full size of 35 mm film is inevitably narrow for the reasons described above. Therefore, the focal length has to be set shorter when trying to capture a wide range like a fisheye lens. As a result, since the back focus of the fish-eye lens for a digital single lens reflex camera is required to be three times or more of the focal length, it is necessary to arrange an extremely strong divergence system on the object side as an optical system.
[0006]
In the fish-eye lens, a retrofocus type in which the principal point is rearward is used. However, by arranging a strong diverging system on the object side as the optical system for the above reasons, performance degradation due to field curvature and astigmatism is likely to occur.
[0007]
Furthermore, the retrofocus type has a problem that the outer diameter of the negative lens in the front group tends to be large, and the fisheye lens is increased in size and weight.
[0008]
The present invention has been made in view of the above-described circumstances, and is a fisheye lens suitable for a bright and compact digital camera that has a sufficient back focus, is well corrected for field curvature, and has excellent optical performance. The purpose is to provide.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a fisheye lens according to the present invention has a plurality of negative lenses from the object side and has a negative refractive power front group as a whole, and is arranged at an axial interval with respect to the front group. is composed of a rear group of positive refractive power, the rear group includes, in order from the object side, satisfied a positive lens, a cemented lens consisting of a negative lens and a positive lens, and a positive lens, and the following conditions It is characterized by doing.
(1) 5.905 ≦ Σd / f ≦ 6.394
However,
f: focal length of the whole fisheye lens system,
Σd: Distance from the most object side lens surface to the most image side lens surface when the fisheye lens is focused at infinity.
[0010]
Moreover, in the fish-eye lens according to the present invention, the front group, the multiple negative lens by Ri image side, preferably has at least one cemented lens.
[0011]
In addition, the fisheye lens according to the present invention preferably satisfies the following conditions.
(2) 1.5 ≦ f2 / f ≦ 4.0
However,
f2: focal length of the rear group.
[0013]
In the fisheye lens according to the present invention, it is preferable that the following condition is satisfied.
(3) 0.5 <d1 / f <2.0
However,
d1: An on-axis distance between the front group and the rear group.
[0014]
Also, fish-eye lens according to the present invention preferably satisfies the following conditions:.
(4) 30 ≦ νR convex−νR concave ≦ 60
However,
νR convex Abbe number of the average value of the positive lens in the rear group,
νR concave: the average value of the Abbe number of the negative lens in the rear group.
[0015]
In addition, the fisheye lens according to the present invention preferably satisfies the following conditions.
(5) 0.2 ≦ nR concave−nR convex ≦ 0.45
However,
nR concave: Average of the refractive index of the negative lens at the d-line in said rear group (λ = 587.6nm),
nR convex: the average value of the refractive index of d line of the positive lens in the rear group (λ = 587.6nm).
[0016]
In the fisheye lens according to the present invention, it is preferable that all of the lens surfaces of the front group and the rear group are each configured as either a spherical surface or a flat surface.
[0017]
Further, in the fisheye lens according to the present invention, it is preferable that the fisheye lens moves in the object direction while increasing an air interval between the front group and the rear group when focusing from an object at infinity to a near object. .
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a fisheye lens according to the present invention will be described.
The fisheye lens according to the present invention has a plurality of negative lenses from the object side and has a negative power front group as a whole, and a rear group having a positive refractive power as a whole and arranged at an axial interval with respect to the front group. The rear group includes at least one pair of cemented lenses.
[0019]
The front group has a negative lens having a strong divergence function that bends a light beam incident from a large angle of 180 degrees in a direction parallel to the optical axis. It is possible to disperse (share) the generated aberration.
[0020]
Conditional expression (1) is a condition for suppressing an increase in size and weight of the entire system while correcting off-axis aberration while maintaining a sufficient back focus in the fish-eye lens according to the present invention. If the upper limit is exceeded, the back focus becomes too short, so it cannot be used for a single-lens reflex camera. Furthermore, in order to pass a light beam of 180 degrees, the diameter (front lens diameter) of the lens disposed closest to the object side becomes extremely large, leading to an increase in size and weight of the entire system. In order to obtain more effect, the upper limit is preferably set to 8.0. If the lower limit is exceeded, sufficient back focus can be obtained, but it is not preferable because it is impossible to maintain a field angle of 180 degrees. In order to obtain more effect, the lower limit is preferably set to 5.0.
[0021]
Conditional expression (2) is a condition that defines the focal length of the rear group in order to correct off-axis aberrations while maintaining sufficient back focus in the fisheye lens according to the present invention. Exceeding the upper limit is not preferable because it is difficult not only to correct astigmatism and coma but also to maintain a field angle of 180 degrees. When the lower limit is exceeded, the back focus becomes too short, so it cannot be used for a single-lens reflex camera.
[0022]
Conditional expression (3) defines the axial distance between the front group and the rear group in the fisheye lens according to the present invention. If the upper limit is exceeded, the lateral chromatic aberration will be excessive, making it difficult to correct. In addition, since the back focus becomes too short, it cannot be used for a single-lens reflex camera. Exceeding the lower limit value is not preferable because correction of astigmatism and coma becomes difficult, and it becomes difficult to maintain a field angle of 180 degrees. A better result can be obtained by setting the lower limit of conditional expression (3) to 0.7.
[0023]
Conditional expression (4) defines the difference in Abbe number between the positive lens and the negative lens in the rear group in order to correct the lateral chromatic aberration and the axial chromatic aberration generated in the front group in the fisheye lens according to the present invention. Exceeding the upper limit makes it difficult to correct axial chromatic aberration and makes it difficult to construct a lens system with existing glass materials. If the lower limit is exceeded, the lateral chromatic aberration due to the negative lens of the front group cannot be corrected by the rear group, and the lateral chromatic aberration of the g-line (λ = 435.8 nm) tends to be negative, which is not preferable.
[0024]
Conditional expression (5) is a condition for correcting curvature of field and astigmatism in the fisheye lens according to the present invention. By making the negative lens as high a refractive index as possible and the positive lens as low as possible, the Petzval sum of the entire system can be reduced, and the field curvature and astigmatism can be kept small. If the upper limit is exceeded, the difference between the Abbe numbers of the negative lens and the positive lens must be increased, and correction of axial chromatic aberration occurring in the front group becomes difficult. Exceeding the lower limit is not preferable because the Petzval sum of the entire system increases and a large curvature of field occurs.
[0025]
In addition, by having a pair of cemented lenses in the front group, it is possible to reduce the occurrence of lateral chromatic aberration. In addition, it is preferable that all lens surfaces of the front group and the rear group are each configured as either a spherical surface or a flat surface. Also, when focusing from an infinite distance object to a close distance object, in order to prevent deterioration of the optical characteristics at the close distance focus, a configuration that moves in the object direction while increasing the air gap between the front group and the rear group preferable.
[0026]
(Example)
Examples of the fisheye lens according to the present invention are shown below. In each example, “lens component” indicates “lens”.
1, 3, 5, 7, 9, 11, 13, 15, 15, 17, and 19 are cross sections of first to tenth fisheye lenses according to the present invention. The figure is shown. In the cross-sectional view, S represents an aperture stop, and the plane parallel plate P represents a filter, which is disposed between the front group G1 and the rear group G2. No matter where the filter is inserted in the optical system, the performance is not affected, and even if no filter is inserted in the optical system, the basic performance is not affected.
[0027]
2, 4, 6, 8, 10, 12, 14, 16, 16, 18, and 20 are various aberrations of the first to tenth examples of the fisheye lens according to the present invention. The figure is shown. In each aberration diagram, d represents an aberration at the d-line (λ = 587.6 nm), g represents an aberration at the g-line (λ = 435.8 nm), m represents a meridional image plane, and s represents a sagittal image plane. FNO indicates the F number, and 2ω indicates the angle of view (unit: degree). The distortion aberration indicates the amount of deviation from the equisolid angle projection y = 2fsin (ω / 2). In each aberration diagram, the aberration is corrected well.
In the table of each example below, in the specification values, f is the focal length (mm) of the entire system, FNO is the F number, 2ω is the angle of view (unit: degree), Bf is the back focus (mm), TL represents the total length (mm). In the lens data, the numerical value at the left end is the surface number, r is the radius of curvature (mm), d is the surface interval (mm), nd is the refractive index with respect to the d-line (λ = 587.6 nm), and νd is the Abbe number. .
[0028]
In the tables of all the following examples, “mm” is generally used as the focal length f, radius of curvature r, surface interval d and other lengths unless otherwise specified, but the optical system is proportional. Even if it is enlarged or proportionally reduced, the same optical performance can be obtained. Further, the unit is not limited to “mm”, and other appropriate units may be used.
[0029]
(First embodiment)
The fish-eye lens according to the first embodiment shown in FIG. 1 includes, in order from the object side, a negative meniscus first lens component L1 having a convex surface facing the object side, and a negative meniscus second lens having a convex surface facing the object side. A front group G1 having a negative refracting power as a whole comprising a component L2 and a third lens component L3 having a positive refracting power as a whole, which is formed by joining a negative lens and a positive lens, and is axial on the front group G1 A biconvex fourth lens component L4 which is arranged at an interval and directs a stronger convex surface on the image side; a fifth lens component L5 which is composed of a cemented negative lens and a positive lens and has a positive refractive power as a whole; The rear lens group G2 having a positive refractive power as a whole is composed of a convex sixth lens component L6 having a positive refractive power.
[0030]
[Table 1]
(Second embodiment)
The fish-eye lens according to the second embodiment shown in FIG. 3 includes, in order from the object side, a negative meniscus first lens component L1 having a convex surface facing the object side, and a negative meniscus second lens having a convex surface facing the object side. As a whole composed of a component L2, a biconcave third lens component L3 having a stronger convex surface on the object side, and a fourth lens component L4 having a positive refractive power as a whole consisting of a cemented positive lens and a negative lens A front lens group G1 having negative refracting power, a positive meniscus fifth lens component L5 disposed on the axial side of the front lens group G1 and having a stronger convex surface on the image side, a negative lens and a positive lens And a rear group G2 having a positive refracting power as a whole and a sixth lens component L6 having a negative refracting power as a whole and a seventh lens component L7 having a biconvex positive refracting power as a whole. .
[0032]
[Table 2]
(Third embodiment)
The fisheye lens according to the third example shown in FIG. 5 includes, in order from the object side, a negative meniscus first lens component L1 having a convex surface facing the object side, and a negative meniscus second lens having a convex surface facing the object side. The negative refractive power as a whole is composed of the component L2, the third lens component L3 having a positive refractive power having a biconvex shape, and the fourth lens component L4 having a negative refractive power as a whole. A negative lens and a positive lens as a whole consisting of a front lens group G1, a fifth lens component L5 having a birefringent positive refracting power disposed on the front group G1 and spaced apart from each other on the axis. The rear lens group G2 having a positive refracting power as a whole is composed of a sixth lens component L6 having a positive power and a seventh lens component L7 having a biconvex positive refracting power.
[0034]
[Table 3]
(Fourth embodiment)
The fisheye lens according to the fourth example shown in FIG. 7 includes, in order from the object side, a negative meniscus first lens component L1 with a convex surface facing the object side, and a negative meniscus second lens with a convex surface facing the object side. The negative refractive power as a whole is composed of the component L2, the third lens component L3 having a positive refractive power having a biconvex shape, and the fourth lens component L4 having a negative refractive power as a whole. The first lens group G1 includes a front lens group G1, a fifth lens component L5 having a biconvex shape that is disposed with an axial interval with respect to the front lens group G1, and a negative lens and a positive lens. A rear group G2 having a positive refractive power as a whole is composed of a six-lens component L6 and a biconvex seventh lens component L7 having a positive refractive power.
[0036]
[Table 4]
(5th Example)
The fish-eye lens according to Example 5 shown in FIG. 9 includes, in order from the object side, a negative meniscus first lens component L1 having a convex surface facing the object side, and a negative meniscus second lens having a convex surface facing the object side. A third lens component L3 having a negative refracting power as a whole consisting of a component L2, a negative lens and a positive lens, and a fourth lens component L4 having a positive refracting power as a whole consisting of a positive lens and a negative lens. A front group G1 having a negative refractive power as a whole, a biconvex fifth lens component L5 having a positive refractive power arranged at an axial interval with respect to the front group G1, a negative lens and a positive lens And a rear lens group G2 having a positive refractive power as a whole and a sixth lens component L6 having a negative refractive power as a whole and a seventh lens component L7 having a biconvex positive refractive power as a whole. Yes.
[0038]
[Table 5]
(Sixth embodiment)
The fish-eye lens according to Example 6 shown in FIG. 11 includes, in order from the object side, a negative meniscus first lens component L1 having a convex surface facing the object side, and a negative meniscus second lens having a convex surface facing the object side. A third lens component L3 having a negative refracting power as a whole consisting of a component L2, a negative lens and a positive lens, and a fourth lens component L4 having a positive refracting power as a whole consisting of a positive lens and a negative lens. A front lens group G1 having negative refractive power as a whole, and a positive meniscus positive refractive power fifth lens component that is arranged at an axial interval with respect to the front lens group G1 and has a stronger convex surface on the image side L5, a rear lens group G2 having a positive refractive power as a whole, and a sixth lens component L6 having a positive refractive power as a whole, which is formed by cementing a negative lens and a positive lens, and a biconvex seventh lens component L7 From Forms.
[0040]
[Table 6]
(Seventh embodiment)
The fish-eye lens according to Example 7 shown in FIG. 13 includes, in order from the object side, a negative meniscus first lens component L1 having a convex surface facing the object side, and a negative meniscus second lens having a convex surface facing the object side. A component L2, a third lens component L3 having a negative refractive power as a whole, which is formed by joining a negative lens and a positive lens, a biconvex fourth lens component L4 having a positive refractive power, and a positive lens and a negative lens. A front group G1 having a negative refractive power as a whole consisting of a fifth lens component L5 having a negative refractive power as a whole, and a convex surface that is arranged at an axial interval with respect to the front group G1 and is stronger on the image side A positive meniscus sixth lens component L6 having a positive refracting power, a seventh lens component L7 having a positive refracting power as a whole consisting of a cemented negative lens and a positive lens, and a biconvex positive refracting power Eighth lens component L It is composed of a group G2 after having positive refractive power as a whole composed of a.
[0042]
[Table 7]
(Eighth embodiment)
The fish-eye lens according to Example 8 shown in FIG. 15 includes, in order from the object side, a negative meniscus first lens component L1 having a convex surface facing the object side, and a negative meniscus second lens having a convex surface facing the object side. A component L2, a positive meniscus third lens component L3 having a positive refractive power with a stronger convex surface on the image side, and a fourth lens component L4 having a positive refractive power as a whole, which is formed by joining a negative lens and a positive lens. A front group G1 having a negative refractive power as a whole, which is formed by joining a positive lens and a negative lens and having a negative refractive power as a whole, and an axial interval with respect to the front group G1. A positive meniscus sixth lens component L6 having a positive refracting power and having a stronger convex surface on the image side, and a seventh lens component L7 having a positive refracting power as a whole consisting of a cemented negative lens and a positive lens, Both It is composed of a group G2 after having positive refractive power as a whole a positive refractive power eighth lens component L8 Metropolitan of shape.
[0044]
[Table 8]
(Ninth embodiment)
The fish-eye lens according to Example 9 shown in FIG. 17 includes, in order from the object side, a negative meniscus first lens component L1 having a convex surface facing the object side, and a negative meniscus second lens component having a convex surface facing the object side. A lens component L2, a third lens component L3 having a positive meniscus lens shape with a convex surface facing the image side, and a fourth lens component L4 having a negative refracting power as a whole consisting of a cemented negative lens component and positive lens component; A front group G1 having a negative refractive power as a whole, which is composed of a cemented positive lens and a negative lens and has a negative refractive power as a whole, and a negative lens component and a positive lens arranged at an axial interval. From a rear lens group G2 having a positive refracting power as a whole and a sixth lens component L6 having a positive refracting power as a whole and a seventh lens component L7 having a biconvex positive refracting power. Forms.
[0046]
[Table 9]
(Tenth embodiment)
The fish-eye lens according to Example 10 shown in FIG. 19 includes, in order from the object side, a negative meniscus first lens component L1 having a convex surface facing the object side, and a second negative meniscus second lens component having a convex surface facing the object side. A front group G1 including a lens component L2, a biconcave third lens component L3, a biconvex fourth lens component L4, and a negative meniscus fifth lens component L5. A seventh lens component consisting of a positive meniscus sixth lens component L6 arranged at an axial interval and facing a stronger convex surface on the image side, and a negative lens component and a positive lens component, and having a positive refractive power as a whole This is composed of a rear group G2 having a positive refracting power as a whole consisting of a component L7 and an eighth lens component L8 having a biconvex positive refracting power.
[0048]
[Table 10]
The numerical values corresponding to conditions in the fisheye lenses according to the first to tenth embodiments of the present invention are listed in the following table.
[0050]
[Table 11]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a fisheye lens suitable for a digital camera that has a field angle of 180 ° and has an F angle of 2.8 and is compact and bright while ensuring a sufficient back focus.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a fisheye lens according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating all aberrations of the fisheye lens according to Example 1 of the present invention.
FIG. 3 is a cross-sectional view of a fisheye lens according to a second embodiment of the present invention.
FIG. 4 is a diagram illustrating all aberrations of the fisheye lens according to Example 2 of the present invention.
FIG. 5 is a cross-sectional view of a fisheye lens according to a third embodiment of the present invention.
FIG. 6 is a diagram illustrating all aberrations of the fisheye lens according to Example 3 of the present invention.
FIG. 7 is a sectional view of a fisheye lens according to a fourth embodiment of the present invention.
FIG. 8 is a diagram illustrating all aberrations of the fisheye lens according to Example 4 of the invention.
FIG. 9 is a sectional view of a fisheye lens according to a fifth embodiment of the present invention.
FIG. 10 is a diagram illustrating all aberrations of the fisheye lens according to Example 5 of the invention.
FIG. 11 is a cross-sectional view of a fisheye lens according to a sixth embodiment of the present invention.
FIG. 12 is a diagram illustrating various aberrations of the fisheye lens according to Example 6 of the present invention.
FIG. 13 is a sectional view of a fisheye lens according to a seventh embodiment of the present invention.
FIG. 14 is a diagram illustrating all aberrations of the fisheye lens according to Example 7 of the present invention.
FIG. 15 is a cross-sectional view of a fisheye lens according to an eighth embodiment of the present invention.
FIG. 16 is a diagram illustrating all aberrations of the fisheye lens according to Example 8 of the present invention.
FIG. 17 is a cross-sectional view of a fisheye lens according to Example 9 of the present invention.
FIG. 18 is a diagram illustrating all aberrations of the fisheye lens according to Example 9 of the present invention.
FIG. 19 is a cross-sectional view of a fisheye lens according to a tenth embodiment of the present invention.
FIG. 20 is a diagram illustrating all aberrations of the fisheye lens according to Example 10 of the invention.
[Explanation of symbols]
G1 Front group G2 Rear group S Aperture stop P Parallel flat plate (filter)
I Image plane
Claims (8)
前記後群は物体側から順に、正レンズと、負レンズと正レンズとから成る接合レンズと、正レンズとからなり、かつ以下の条件を満足することを特徴とする魚眼レンズ。
（１）５．９０５≦Σｄ／ｆ≦６．３９４
但し、
ｆ ：前記魚眼レンズ全系の焦点距離、
Σｄ：前記魚眼レンズが無限遠に合焦した時の最も物体側レンズ面から最も像側レンズ面までの距離。It consists of a front group of negative refractive power as a whole having a plurality of negative lenses from the object side, and a rear group of positive refractive power as a whole arranged at an axial interval with respect to the front group,
The rear lens group includes , in order from the object side, a positive lens, a cemented lens including a negative lens and a positive lens, and a positive lens , and satisfies the following conditions.
(1) 5.905 ≦ Σd / f ≦ 6.394
However,
f: focal length of the whole fisheye lens system,
Σd: Distance from the most object side lens surface to the most image side lens surface when the fisheye lens is focused at infinity.
以下の条件を満足することを特徴とする魚眼レンズ。
（２）１.５≦ｆ２／ｆ≦４.０
但し、
ｆ２：前記後群の焦点距離。The fisheye lens according to claim 1 or 2,
A fish-eye lens satisfying the following conditions.
(2) 1.5 ≦ f2 / f ≦ 4.0
However,
f2: Focal length of the rear group.
以下の条件を満足することを特徴とする魚眼レンズ。
（３）０.５＜ｄ１／ｆ＜２.０
但し、
ｄ１：前記前群と前記後群の軸上間隔。The fisheye lens according to any one of claims 1 to 3 ,
A fish-eye lens satisfying the following conditions.
(3) 0.5 <d1 / f <2.0
However,
d1: On-axis distance between the front group and the rear group.
以下の条件を満足することを特徴とする魚眼レンズ。
（４）３０≦νＲ凸−νＲ凹≦６０
但し、
νＲ凸：前記後群中の前記正レンズのアッベ数の平均値、
νＲ凹：前記後群中の前記負レンズのアッベ数の平均値。The fisheye lens according to any one of claims 1 to 4,
A fish-eye lens satisfying the following conditions.
(4) 30 ≦ νR convex−νR concave ≦ 60
However,
νR convex: average value of Abbe number of the positive lens in the rear group,
νR concave: Average value of the Abbe number of the negative lens in the rear group.
以下の条件を満足することを特徴とする魚眼レンズ。
（５）０.２≦ｎＲ凹−ｎＲ凸≦０.４５
但し、
ｎＲ凹：前記後群中の前記負レンズのｄ線（λ＝５８７．６ｎｍ）の屈折率の平均値、
ｎＲ凸：前記後群中の前記正レンズのｄ線（λ＝５８７．６ｎｍ）の屈折率の平均値。The fisheye lens according to any one of claims 1 to 5 ,
A fish-eye lens satisfying the following conditions.
(5) 0.2 ≦ nR concave−nR convex ≦ 0.45
However,
nR concave: average value of refractive index of d-line (λ = 587.6 nm) of the negative lens in the rear group,
nR convexity: average value of refractive indices of d-line (λ = 587.6 nm) of the positive lens in the rear group.
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| JP2003197315A JP4565262B2 (en) | 2002-08-01 | 2003-07-15 | Fisheye lens |
| US10/631,760 US6844991B2 (en) | 2002-08-01 | 2003-08-01 | Fisheye lens |
| US11/008,169 US7161746B2 (en) | 2002-08-01 | 2004-12-10 | Fisheye lens |
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| JP2003197315A JP4565262B2 (en) | 2002-08-01 | 2003-07-15 | Fisheye lens |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| EP2287651B1 (en) | 2004-09-02 | 2012-05-09 | Tamron Co., Ltd. | Zoom lens with high zoom ratio |
| JP2006337691A (en) * | 2005-06-01 | 2006-12-14 | Olympus Imaging Corp | Image-formation optical system |
| KR101302271B1 (en) | 2005-12-02 | 2013-09-02 | 가부시키가이샤 니콘 | Fish-eye lens and imaging device |
| JP4683213B2 (en) * | 2005-12-02 | 2011-05-18 | 株式会社ニコン | Fisheye lens and imaging device |
| JP4919712B2 (en) * | 2006-06-20 | 2012-04-18 | 株式会社シグマ | Fisheye lens |
| KR100932850B1 (en) * | 2008-12-29 | 2009-12-21 | 주식회사 나노포토닉스 | Fisheye lens |
| JP5396888B2 (en) * | 2009-01-30 | 2014-01-22 | 株式会社ニコン | Wide angle lens, imaging device, and manufacturing method of wide angle lens |
| KR101070991B1 (en) | 2009-05-19 | 2011-10-06 | 주식회사 나노포토닉스 | Fisheye lens |
| JPWO2011077716A1 (en) | 2009-12-25 | 2013-05-02 | パナソニック株式会社 | Imaging optical system, interchangeable lens device, and camera system |
| JP5904014B2 (en) * | 2012-05-30 | 2016-04-13 | 株式会社ニコン | PHOTOGRAPHIC LENS, OPTICAL DEVICE, AND MANUFACTURING METHOD FOR PHOTOGRAPHIC LENS |
| WO2014030334A1 (en) | 2012-08-24 | 2014-02-27 | 富士フイルム株式会社 | Imaging lens, and imaging device equipped with same |
| JP6815210B2 (en) * | 2017-01-26 | 2021-01-20 | 株式会社タムロン | Imaging optical system and imaging device |
| WO2018222827A1 (en) * | 2017-06-02 | 2018-12-06 | Owl Labs, Inc. | Wide angle lens and camera system for peripheral field of view imaging |
| JP2019159188A (en) * | 2018-03-15 | 2019-09-19 | 株式会社ニコン | Optical system, optical device, and method of manufacturing optical system |
| JP7288617B2 (en) * | 2019-09-30 | 2023-06-08 | 株式会社ニコン | Optical system and optical equipment |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2002072085A (en) * | 2000-09-01 | 2002-03-12 | Matsushita Electric Ind Co Ltd | Super-wide-angle lens |
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| JPS5129136A (en) * | 1974-09-05 | 1976-03-12 | Minolta Camera Kk | |
| JPS5383623A (en) * | 1976-12-01 | 1978-07-24 | Asahi Optical Co Ltd | Equidistant projection type fisheye lens with long back focus |
| JPS6317421A (en) * | 1986-07-09 | 1988-01-25 | Canon Inc | Fisheye lens |
| JP2599312B2 (en) * | 1991-02-21 | 1997-04-09 | 株式会社コパル | Super wide angle lens |
| JPH05273459A (en) * | 1992-03-26 | 1993-10-22 | Nikon Corp | Fisheye lens equipped with short-distance correcting function |
| JP3315839B2 (en) * | 1994-10-21 | 2002-08-19 | 旭光学工業株式会社 | Super wide-angle zoom lens |
| JP3625923B2 (en) * | 1995-09-28 | 2005-03-02 | フジノン株式会社 | Retro focus lens |
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