JP4149683B2 - Variable magnification finder attachment - Google Patents

Description

【００１７】
しかるに、アタッチメント非装着時に、このカメラの視度補正機構を使用して−1.82dpに調整したときのファインダ光学系の焦点距離は、71.45mmとなる。このように、同じ視度で比較した場合、112.1%のファインダ−倍率の向上となる。
【００１８】
図2に、このときの収差の値を表としたものを示す。なお、以下の実施の形態２から4までの収差の値もここに示す。
なお、この後の実施の形態を通じて、収差図に使用する波長は、d線587.56nm（図中1）、F線486.13nm（図中2）、Ｃ線656.27nm（図中3）である。なお、以下特に断らない限り、各収差は、像高21.7mmの場合、瞳径4mmとして求めてある。
【００１９】
図3から11では、歪曲収差以外はmm表示を採用している。球面収差(SA,OSC)と 非点収差(AS)は、縦軸がそれぞれ最大入射高と像高21.7mmまで表示され、横軸は共通の縮尺で右側が＋1.0mmまで、左側が−1.0mmまで表示される。歪曲（ＤＩＳＴ）の縦軸は、上記非点収差(AS)同様、像高21.7mmまで表示される。また歪曲（DIST）の横軸は、物体位置を使用者の目側、像位置を焦点板として解析した都合上、右側がー3.0%、左側が＋3.0%まで表示してある。図2では、これを視度（dp）又は分（min）に換算してある。
【００２０】
球面収差(SA,OSC)と非点収差(AS)の距離表示を、視度（dp）に変換するには、ファインダ光学系の焦点距離をｆとして、1000/fの2乗という換算にて行った。図2の球面収差(SA,OSC)の値はこのような換算に基づき、d線の場合について、設定視度からのずれをdioptre(dp)表示したもので、像高21.7mmについて求めてある。非点収差(AS)の値は、d線の場合について、設定視度からのずれをdp表示したもので、それぞれサジッタル(S)とタンジェンシャル(T)につき、像高21.7mmまで求めてある。
【００２１】
横収差は、図3から11では、下から上に向かい最大像高の各0(軸上),0.55,0.83,1.0倍の位置（像高0mm時、像高12.0mm時、像高18.0mm時、像高21.7mm）を主光線の位置として、右に示すサジッタル（DX）方向と左に示すタンジェンシャル(DY)につき描画してある。各縦軸の範囲は、下が−0.2mm、上が＋0.2mmである。横軸は、サジッタル（DX）においては瞳径φ4mmの半分である2mmについて、片側のみ示してある。タンジェンシャル(DY)については瞳径φ4mm分示してある。図2に記載の横収差の値は、分(min)表示とし、瞳径4mmの場合について、d線のタンジェンシャル(DY)の左端の値を換算して記載する。ここで、mmからminへの換算は、arctan(1/f)の60倍により求めてある。
【００２２】
図3と４に、上記アタッチメントを装着して−1.82dpとなったときの収差曲線と、このカメラ本体のファインダの−1.82dp時の収差曲線を比較する。図2からわかるように、歪曲収差が+1.5%から+3.3%に増大するが、ファインダに通常要求される±5％の許容範囲内である。アイレリ−フは14.4mmとなり、これは通常、眼鏡使用者でも視野がケラレないレベルである。なお、アイレリーフは、この実施例およびこの後の実施例を通じて、瞳径14ｍｍの場合について、最大像高へ入射する光線が近軸と交差する点として示してある。
【００２３】
一方、アタッチメントを装着した図3では、587.56nmの波長の光に対する球面収差は−0.04dp、サジッタルとタンジェンシャルの視度の差はそれぞれ最大−0.55dpと−0.50dp。これに対して、未装着時の図4では、587.56nmの波長の光に対する球面収差は−0.09dp、サジッタルとタンジェンシャルの視度の差は、それぞれ最大−0.68dpと−1.22dp。従って、アッタチメントを装着すれば、球面収差と非点収差の両方とも減少させることができる。
【００２４】
アタッチメント装着時は、画面中心の視度と画面の隅の視度の差が少なく、目の視度調節機能に負担をかけず、視度が合いやすい。中心で視度を合わせてから周辺を見る際に、目による視度の調整機能が停滞して、周辺がしばらく見えにくくなる現象が生じるが、上記アタッチメント装着時にはこの現象が軽減されるようになる。特に、近点の視度調整機能が減退する老眼や長時間ファインダを覗いて、生理的に視度が固定されるような場合には有効である。
【００２５】
また、このアタッチメントを装着すると、図3にあるように、横収差ではサジッタルとタンジェンシャルの周辺光線が、主光線から画面上移動する量を減少させる。従って、像点内のより小さい面積に照度が集中し、コントラストの高い像を結ぶ。
また像高18mmにおける波長486.13nm、587.56nm、656.27nmの3色間の倍率色収差も、図4の装着しない場合の3.56minに対して、許容値内の5.35minなので、色にじみは気にならない。通常10min以内であれば色にじみは問題ないとされている。
【００２６】
この実施の形態のものを作成し、実際に装着すると倍率が大きく、極めてピントあわせのしやすいファインダ画像が得られる。焦点距離51.8mmの撮影レンズをアタッチメント非装着のカメラに装着した場合、同じ視度−1.82dpで、0.696倍のファインダ−倍率が得られ、本願にかかわるアタッチメントを装着した場合、この倍率は0.780倍まで向上する。
従って、画面中心では112.1％の倍率向上でピントあわせが容易になるだけでなく、画面周辺でも、倍率向上と視度変化の減少と光束の収束が図れ、結果として画面周辺でのピントあわせが容易となる。また片平レンズの使用によりアッタチメントの光軸上全体長を縮減でき、ファインダ視野のケラレが生じない。
【００２７】
実施の形態2
実施の形態１と同様に、ファインダ本体の視度補正機構は、10面と11面の間隔及び12面と13面の間隔を変えて視度が調節出来る構成となっている。アタッチメント非装着の状態で、−3.04dpとなるよう調節してある。このときカメラ本体のファインダ光学系全体の焦点距離は72.29mmである。実施の形態１では、ファインダアタッチメント10を構成する負レンズ11と正レンズ12は、2枚の片面平レンズで、レンズ間に空気間隙は設けていなかった。この実施の形態では、ケース13内において、2枚のレンズの間に0.5mmの空気間隙を設けている。負レンズ11の曲率半径は−25.95mm、中心厚は2mmであり、正レンズ12の曲率半径は−25.84ｍｍ、中心厚は3.23mmとしてある。上記ファインダアタッチメントを装着すると、視度は−1.74dpとなり、上記ファインダアタッチメントを含めたファインダ光学系の焦点距離は63.61mmとなる。
【００２８】
このときの上記アタッチメントを含めたカメラのファインダ光学系の構成は以下のとおりである。

しかるに、アタッチメント未装着のカメラの視度補正機能を使用して、上記アタッチメント装着時と同じ−1.74dpにしたときのファインダ光学系の焦点距離は71.39mmとなり、71.39/63.61＝112.2%のファインダ−倍率の向上となる。
【００２９】
図の見方については、上記実施の形態1に説明したとおりである。図5と6に、其々、アタッチメントを装着して−1.74dpとなったときの収差曲線と、このカメラ本体の−1.74dp時の収差曲線とを比較する。図2のデ−タおよび図5の収差曲線をみれば、歪曲は+3.3％と許容値内、587.56nmの波長の光に対する球面収差は−0.05dpと小さくファインダ画像中心部は鮮鋭となる。非点収差はサジッタルで最大−0.57dp、タンジェンシャルで最大−0.55dpで、いずれも目にとって視度の調整負担が低い値である。波長486.13nm、587.56nm、656.27nmの3色間の倍率色収差は、像高さ18mm、中心部で、5.52minと、許容値10min以内。サジッタルの横収差と乖離する図中左側のタンジェンシャルの横収差は、瞳径4mmの場合で−1.04minと、コマ収差は発生しない。さらに上記アタッチメントを装着すると、図5に示すように、横収差では、サジッタルとタンジェンシャルの周辺光線が、主光線から画面上移動する量を減少させる。従って、像点内のより小さい面積に照度が集中し、コントラストの高い像を結ぶ。
【００３０】
これに対して、図2および図6の収差曲線をみれば、歪曲は+1.1％、587.56nmの波長の光に対する球面収差は−0.13dp。非点収差はサジッタルで最大−0.69dp、タンジェンシャルで最大−1.25dp.。波長486.13nm、587.56nm、656.27nmの3色間の倍率色収差は、像高さ18mm、中心部で4.49min。サジッタルの横収差と乖離する図中左側のタンジェンシャルの横収差は、瞳径4mmの場合で−4.14minである。比較してわかるように、非装着時に大きかった球面収差、非点収差および横収差を改善することができる。
【００３１】
このように、上記実施の形態１と同様に、画面内の観察点間の視度変化が少なくなることで目の視度調整の負荷を軽減させると同時に、ファインダ倍率を112.2%向上することができる。なお、アイレリーフは14.1mmと、眼鏡使用者でも視野のケラレがないレベルである。従って、画面中心では112.2%の倍率向上でピントあわせが容易になるだけでなく、画面周辺でも倍率向上と視度変化の減少と光束の収束が図れ、結果として画面周辺でのピントあわせも容易となる。
【００３２】
さらに、倍率の更なる向上を望む場合、すなわち、例えば、上記構成において、空気間隔を1.5mmにした場合について述べる。空気間隔の増減はヘリコイドやワッシャ−の増減などの方法で可能である。たとえばこの第1レンズと第2レンズとワッシャ−を同一の外径としておけば、ワッシャ−を増減して、簡単に空気間隔を変更できる。ワッシャーとしては、内面反射を考え、リング状としたステンレス等の金属に酸化クロムを施したものや、ラバーやフィルムを打ち抜いたものなどが考えられる。
このアタッチメント装着時、視度は−1.40dp、ファインダ光学系の焦点距離は61.77mmとなる。このときの収差図を図7に示す。同じ視度に調整したカメラ本体のファインダ光学系の焦点距離は71.15mmであるので、ファインダ−倍率は115.2%向上する。アイレリーフは12.4mmと、眼鏡使用者でも視野のケラレがないレベルである。
【００３３】
図2のデ−タ及び図7の収差曲線をみれば、歪曲は+3.8％と許容値内、587.56nmの波長の光に対する球面収差は−0.09dpと小さく、ファインダ画像中心部は鮮鋭となる、非点収差はサジッタルで最大−0.57dp、タンジェンシャルで最大−0.50dpで、いずれも目にとって視度の調整負担が低い値である。波長486.13nm、587.56nm、656.27nmの3色間の倍率色収差は、像高さ18mm、中心部で、5.77minと、許容値10min以内。サジッタルの横収差と乖離する図中左側のタンジェンシャルの横収差は、瞳径4mmの場合で、−0.66minと、コマ収差は発生しない。むしろ、横収差ではサジッタルとタンジェンシャルの周辺光線が、主光線から画面上移動する量を減少させる。従って、像点内のより小さい面積に照度が集中し、コントラストの高い像を結ぶ。
【００３４】
上記アタッチメント非装着のカメラに、51.8mmの撮影レンズを装着し、視度を−1.40dpに調整した時のファインダ倍率は、0.699倍となる。これに対して、上記図7に示すアタッチメントを装着したカメラに、51.8mmの撮影レンズを装着した時のファインダ倍率は、0.805倍となる。従って、画面中心では115.2%のファインダ倍率向上でピントあわせが容易になるだけでなく、画面周辺でも同じ倍率向上と視度変化の減少と光束の収束が図れ、結果として画面周辺でのピントあわせも容易となる。また、片平レンズを使用することでアッタチメントの光軸上全体長を縮減でき、ファインダ視野のケラレが生じない。
【００３５】
実施の形態3
この実施の形態では、上記実施の形態2に記載のアタッチメント10装着時に、さらに視度をマイナス寄りあるいはプラス寄りに調整する例を示す。実施の形態2と同じように、2枚のレンズの間に0.5mmの空気間隙を設けている。目側から、負レンズの曲率半径は−25.95mmで、中心厚は2mmであり、正レンズの曲率半径は−25.84ｍｍで、中心厚は3.23mmとしてある。カメラ本体の視度補正機構は−3.04 dpとなるよう調節してある。
【００３６】
上記ファインダアタッチメントを装着すると、視度は−1.74dpとなり、ファインダアタッチメントを含めたファインダ光学系の焦点距離は63.61mmとなる。ここでさらに、アタッチメントレンズとカメラ本体の間に−967mm程度の焦点距離（−500mmの曲率半径）を有する−1dp程度の凹レンズを装着すると、視度をマイナス方向最大−2.91dpまでとすることができる。そのときのファインダ−光学系の焦点距離は65.91mmである。アイレリ−フは14.0mmで眼鏡使用者にもケラレのないレベルである。アタッチメント非装着のカメラ本体の視度調整機能を使用して、同じ−2.91dpとしたときのファインダ光学系の焦点距離は72.20mmとなる。したがってファインダ倍率は109.5%の向上となる。
【００３７】
本実施の形態にかかわる−967mm程度の焦点距離の視度補正レンズを追加したアタッチメント装着時のファインダ光学系の構成を下に示す。

【００３８】
図の見方については、上記実施の形態1に説明したとおりである。上記ファインダアタッチメントを装着したときの各収差を図8に示す。図2のデ−タ及び図8の収差曲線をみれば、歪曲は+3.4％と許容値内、587.56nmの波長の光に対する球面収差は−0.05dpと小さく、ファインダ画像は鮮鋭となる、非点収差はサジッタルで最大−0.41dp、タンジェンシャルで最大−0.20dpであり、いずれも目にとって視度の調整負担が低い値である。波長486.13nm、587.56nm、656.27nmの3色間の倍率色収差は、像高さ18mm、中心部で、5.33minと、許容値10min以内。サジッタルの横収差と乖離する図中左側のタンジェンシャルの横収差は、瞳径4mmの場合で0.39minと極わずかなコマ収差を発生するが、通常の目の分解能1minより小さい値で、目視で識別できるレベルではない。むしろ、横収差では、サジッタルとタンジェンシャルの周辺光線の主光線からの画面上移動量を減少させる。従って、像点内のより小さい面積に照度が集中し、コントラストの高い像を結ぶ。従って、マイナス方向への視度調節可能範囲を拡大しつつ、画面中心では109.5%の倍率向上でピントあわせが容易になるだけでなく、画面周辺でも倍率向上と視度変化の減少と光束の収束が図れ、結果として画面周辺でのピントあわせも容易となる。
【００３９】
また上記では−1dpの視度補正レンズを例示したが、更に焦点距離の短い負レンズ、例えば−2dpから−4dpの視度補正レンズを使用することで、アタッチメント装着時と非装着時の視度を近づけて、アタッチメントを跳ね上げ式とすることで、拡大倍率のかかった状態とかからない状態の2つの視野を容易に切り替えることが可能となる。これによりファインダ上の歪曲を減少させて像を観察したいときは跳ね上げ、拡大倍率を上げて観察したいときはアタッチメントを使用することが簡単にできるようになる。なお、視度補正レンズを光軸上移動可能に設置すれば、視度が更に微調整可能となる。この場合、視度補正レンズの位置は観察者目側が好ましいが、カメラファインダ側でも良いことは言うまでもない。移動させるための手段としては、ネジやヘリコイドなどが使用できる。
【００４０】
逆に、プラスの視度補正レンズを挿入すれば、視度をプラス方向に振ることができるとともに、倍率をさらに向上させることができる。
【００４１】
さらに、倍率の向上を望む場合、すなわち例えば、上記−1dpの視度補正レンズを追加した構成において、空気間隔を1.5mmにした場合について述べる。空気間隔の増減はヘリコイドやワッシャ−の増減などの方法で可能である。たとえば、この第1レンズと第2レンズとワッシャ−を同一の外径としておけば、ワッシャ−を増減して簡単に空気間隔を変更できる。この場合視度は−2.61dpとなり、焦点距離は64.00mmである。アイレリーフは15.0mmと眼鏡使用者にもケラレのないレベルである。
【００４２】
図9に空気間隔を1.5mmとした場合の収差図を示す。図の見方については、上記実施の形態1に説明したとおりである。図2のデ−タ及び図9の収差曲線をみれば、歪曲は+4.0％と許容値内、587.56nmの波長の光に対する球面収差は−0.10dpと小さく、画像中心は鮮鋭となる。非点収差は、サジッタルで最大−0.39dp、タンジェンシャルで最大−0.07dpと、いずれも目にとって非常に視度の調整負担が低い値である。波長486.13nm、587.56nm、656.27nmの3色間の倍率色収差は、像高さ18mm、中心部で、5.73minと、許容値10min以内。サジッタルの横収差と乖離する図中左側のタンジェンシャルの横収差は、瞳径4mmの場合で+1.19minと若干のコマ収差を発生する。もっとも、この値は一般的な人の目の最小分解能に近い値で、ほとんど認識できない量である。むしろ、横収差ではサジッタルとタンジェンシャルの周辺光線が、主光線から画面上移動する量を減少させることができる。従って、像点内のより小さい面積に照度が集中し、コントラストの高い像を結ぶ。従って、視度のマイナス方向への調整範囲を拡大するとともに、画面中心では112.5%の倍率向上でピントあわせが容易になるだけでなく、画面周辺でも倍率向上と視度変化の減少と光束の収束が図れ、結果として画面周辺でのピントあわせも容易となる。
【００４３】
また上記では−1dpの視度補正レンズを例示したが、更に焦点距離の短い負レンズ、例えば−2dpから−4dpの視度補正レンズを使用することで、アタッチメント装着時と非装着時の視度を近づけて、アタッチメントを跳ね上げ式とすることで、拡大倍率のかかった状態とかからない状態の2つの視野を容易に切り替えることが可能となる。これによりファインダ上の歪曲を減少させて像を観察したいときは跳ね上げ、拡大倍率を上げて観察したいときはアタッチメントを使用することが簡単にできるようになる。
逆に、プラスの視度補正レンズを挿入すれば、視度をプラス方向に振ることができるとともに、倍率をさらに向上させることができる。
また、さらに、視度補正機構を内蔵せず、視度補正レンズにより視度を調整するようになっているファインダに使用しても、ファインダ本体の視度と同程度の視度を確保したまま倍率を向上できる。この場合、一眼レフカメラに限らずレンジファインダにも使用可能で、倍率を向上できることは言うまでもない。またその他の形式のファインダやルーペにも使用可能で、倍率の向上を図れる。
【００４４】
実施の形態4
この実施の形態では、上記実施の形態 3と同じように、上記実施の形態2のアタッチメント10装着時に、さらに視度を調整する例を示す。ただし、プラスまたはマイナスの視度補正レンズの挿入位置はファインダとアタッチメントの間ではなく、負レンズ11と正レンズ12の間である。2枚のレンズの間の間隙は、視度補正レンズとその前後の空気間隔で埋められる。上記負レンズ11の曲率半径は−25.95mm、中心厚は2mmであり、上記正レンズの曲率半径は−25.84mm、中心厚は3.23mmとしてある。カメラ本体の視度補正機構は−3.04 dpとなるよう調節してある。−967mm程度の焦点距離を有する視度補正レンズを介在させたファインダアタッチメントを装着すると、視度は−2.54dpとなり、ファインダアタッチメントを含めたファインダ光学系の焦点距離は63.73mmとなる。アタッチメント非装着のカメラ本体の視度調整機能を使用して、同じ−2.54dpとしたときのファインダ光学系の焦点距離は71.95mmとなる。したがって、ファインダ倍率は112.9%倍の向上となる。
【００４５】
アタッチメント非装着のカメラに、51.8mmの撮影レンズを装着して、視度を−2.54dpに調整した時のファインダ倍率は0.691倍となる。これに対して、上記アタッチメントを装着したカメラに51.8mmの撮影レンズを装着した時のファインダ倍率は0.780倍となる。また、上記アタッチメント装着時、アイレリーフは13.2mmで眼鏡使用時でも通常ケラレがないレベルである。
【００４６】
上記−967mm程度の焦点距離（−500mmの曲率半径）の視度補正レンズを追加したアタッチメント装着時のファインダ光学系の構成を下に示す。

【００４７】
上記アタッチメント装着時の各収差を図10に、アタッチメント非装着時に視度を−2.54dpに調整した場合の各収差を、図11にそれぞれ示す。図の見方については上記実施の形態1に説明したとおりである。図2及び図10のアタッチメント装着時の収差曲線をみれば、歪曲は+3.8％と許容値内、587.56nmの波長の光に対する球面収差は−0.01dpと極めて小さい。非点収差はサジッタルで最大−0.42dp、タンジェンシャルで最大−0.16dpと、いずれも目にとって視度の調整負担が低い値である。波長486.13nm、587.56nm、656.27nmの3色間の倍率色収差は、像高18mm、中心部で、5.75minと、許容値10min以内。タンジェンシャルの横収差は、瞳径4mmの場合で、0.80minと若干のコマ収差を発生するが、ほとんど認識できないレベルの量である。図11のアタッチメント非装着時の収差曲線をみれば、歪曲は+1.5％、587.56nmの波長の光に対する球面収差は＋0.02dp、非点収差はサジッタルで最大−0.59dp、タンジェンシャルで最大−0.92dp。波長486.13nm、587.56nm、656.27nmの3色間の倍率色収差は、像高18mm、中心部で、4.03min。サジッタルの横収差と乖離する側のタンジェンシャルの横収差は瞳径4mmの場合で−3.19minである。
【００４８】
アタッチメント装着時には、歪曲は増大するが、球面収差と非点収差は減少して目の視度調整負担は軽減される。倍率色収差は増大するが、依然許容値以内である。コマ収差は若干発生するが、目の最小分解能とされる1min以下であり、目視で問題になるレベルではないので、画面上の光束の広がりは狭まり、像の鮮鋭さはむしろ増大する。つまり、本実施の形態の場合、横収差ではサジッタルとタンジェンシャルの周辺光線が、主光線から画面上移動する量を減少させる。従って、像点内のより小さい面積に照度が集中し、コントラストの高い像を結ぶ。従って、画面中心では112.9%の倍率向上でピントあわせが容易になるだけでなく、画面周辺でも倍率向上と視度変化の減少と光束の収束が図れ、結果として画面周辺でのピントあわせも容易となる。また、片平レンズの使用によりアッタチメントの光軸長全体長を縮減でき、ファインダ視野のケラレが生じない。
【００４９】
なお、正負2つのレンズ間の空気間隙を増やすと倍率が向上する傾向にあり、視度補正レンズをこの実施の形態のように間に挿入することで、アタッチメントの全長を増加させずに、実施の形態３の例に比べてより一層の倍率向上と視度補正を両立できる。
【００５０】
また、上記では−1dpの視度補正レンズを例示したが、更に焦点距離の短い負レンズ、例えば−2dpから−4dpの視度補正レンズを使用することで、アタッチメント装着時と非装着時の視度を近づけて、さらにアタッチメントを跳ね上げ式とすることで、拡大倍率のかかった状態とかからない状態の2つの視野を容易に切り替えることが可能となる。これによりアタッチメントなしで像を観察したいときは跳ね上げ、拡大倍率を上げて観察したいときはアタッチメントを使用することが簡単にできるようになる。このように、アタッチメントに移動機構を備え、光軸上と光軸外間を瞬時に切り替え可能な構成とできる。
【００５１】
逆に、＋967mm程度の焦点距離を有する正レンズである＋1dpの視度補正レンズを挿入すれば、視度をプラス方向に振ることができるとともに、倍率をさらに向上させることができる。この場合―0.22ｄｐで117.5%の倍率向上となる。すなわち、51.8mmの焦点距離のレンズ装着時には、ファインダ倍率は0．833倍となる。歪曲は3.8%、球面収差は0.00dp、非点格差はサジッタルが−0.72dp、タンジェンシャルがー0.78dp。像高18mmの、主光線位置の、倍率色収差が波長486.13nm、587.56nm、656.27nmの3色間で、5.97minと許容値10min以内。タンジェンシャルの横収差は瞳径4mmの場合で−1.71minと、コマ収差は発生しない。
【００５２】
また、絞りを上記アタッチメントの2つのレンズ間、アタッチメント前、アタッチメント後のいずれかまたは複数の位置に挿入すれば、収差の調整ができる。例えば、コマ収差が気になる状況下では、円形絞り等をレンズ間やアタッチメントの後端などに挿入して、コマ収差を減少させるようなことが可能である。
【００５３】
また、さらに、視度補正機構を内蔵せず、視度補正レンズにより視度を調整するようになっているファインダに使用しても、ファインダ本体の視度と同程度の視度を確保したまま倍率を向上できる。この場合、一眼レフに限らずレンジファインダにも使用可能で、倍率を向上できることは言うまでもない。またその他の種類のファインダ形式やルーペにも使用可能で倍率の向上を図れる。この際、一つのアッタチメントに、複数のファインダへの取付を可能とするようなネジや溝のような複数のファインダ取り付け部を設けておけば、複数のカメラ等に取付可能でアッタチメントの共用がはかれる。またその際、機種に応じてレンズを入替ることも容易にできる。
【００５４】
【発明の効果】
片面平レンズを使用した簡単な構成で倍率を向上できるので、製造コストを低くできる。また、片面平レンズの使用によりアッタチメントの光軸上全体長を縮減可能で、ファインダ視野のケラレがない。また、簡単に倍率や視度の変更が行え、使用者の状況に幅広く対応できる。また、着脱が容易でコンパクトである。
【００５５】
また、より視度の数字の小さい視度補正レンズを併用することで、アタッチメント装着時と非装着時の視度を近づけて、さらに上記アタッチメントを跳ね上げ式とすることで、拡大倍率のかかった状態とかからない状態の2つの視野を容易に切り替えることが可能となる。これによりアタッチメント非装着で像を観察したいときは跳ね上げ、拡大倍率を上げて観察したいときはアタッチメントを使用するように、光軸上と光軸外の間でアタッチメントの位置を瞬時に切り替え可能ことが簡単にできるようになる。
また、視度補正レンズを移動可能として、視度の微調整を可能とする。
また、本発明のアタッチメントを使用すれば、レンジファインダ−カメラのファインダや2眼レフカメラのファインダやビュ−カメラのル−ペ等の観察倍率も向上できる。
また、視度補正機構を内蔵しないファインダに使用し倍率を向上できる。
また、一つのアッタチメントを、複数のカメラに流用できる。
また、最近流行している銀塩カメラをデジタルカメラに流用したり、銀塩カメラをデジタルカメラに変換するための裏蓋などが開発されているが、これらのファインダに使用することで、銀塩カメラのフォーマットよりも小さい面積の撮像素子に対応する撮影範囲を拡大観察することを可能とする。
【図面の簡単な説明】
【図１】 本発明にかかわるファインダアタッチメントを、たとえば一眼レフカメラのファインダに装着した状態を側面から示す部分断面図である。
【図２】 実施の形態1から4までの各収差の値を示す表である。
【図３】 本願第1の実施の形態にかかわるアタッチメントを装着したファインダの−1.82dp時の各収差曲線である。
【図４】 アタッチメント非装着のファインダの視度を調整して−1.82dpとした時の各収差曲線である。
【図５】 本願第2の実施の形態にかかわる空気間隔0.5mmのアタッチメントを装着したファインダの−1.74dp時の各収差曲線である。
【図６】 本願第2の実施の形態に関連して、アタッチメント非装着のファインダの視度を調整して−1.74dpとした時の各収差曲線である。
【図７】 本願第2の実施の形態にかかわる空気間隔1.5mmのアタッチメントを装着したファインダの−1.40dp時の各収差曲線である。
【図８】 本願第3の実施の形態にかかわる空気間隙0.5mmのアタッチメントを装着し、さらに−1dpの視度補正レンズをアタッチメントのファインダ側に装着した場合の各収差曲線である。
【図９】 本願第3の実施の形態にかかわる空気間隙1.5mmのアタッチメントを装着し、さらに−1dpの視度補正レンズをアタッチメントのファインダ側に装着した場合の各収差曲線である。
【図１０】 本願第4の実施の形態にかかわる−1dpの視度補正レンズをアタッチメント内レンズ間に介在させた場合の各収差曲線である。
【図１１】 本願第4の実施の形態に関連して、アタッチメント非装着のファインダ本体の−2.54dp時の各収差曲線である。
【図１２】 本願第4の実施の形態に関連して、複数の取り付け部を備えた変倍ファインダアタッチメントの半断面図である。
【符号の説明】
１ d線587.56nm、 2 F線486.13nm、 3 Ｃ線656.27nm、
10 変倍ファインダアタッチメント、 11 負レンズ、 12 正レンズ、
13 ケース、 14 ファインダ取り付け部、 15 ファインダ取り付け部、
21 ガラス平面板、 22 可動接眼レンズ、 23 固定接眼レンズ、
24 ペンタプリズム、 25 コンデンサーレンズ、 26 焦点板[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a finder such as a photographic camera.
[0002]
[Prior art]
When shooting with the camera, the user checks the field of view and focus through the viewfinder, but the subject image observed from the viewfinder optical system becomes easier to see when the observation magnification is higher, and from the exit surface of the viewfinder optical system. The larger the maximum distance to the position at which the subject image can be observed without vignetting (hereinafter referred to as eye relief), the easier it is to see, especially for eyeglass users. Therefore, there is an eye height type (eye level) magnifier that is mounted outside the viewfinder to enlarge a part of the field of view and enlarge the magnification. This enlarges the central image in order to facilitate confirmation of focus. There is also a so-called angle magnifier that makes it easier to check the focus by looking down from the top of the camera. This angle magnifier is also known as an erect image that expands the field of view by a factor of 1.2.
[0003]
In Japanese Patent Publication No. 2000-180920 and Japanese Patent Laid-Open No. 11-337847, for the purpose of enlarging the photographing area of an image sensor such as a CCD or CMOS system which is smaller than the film size for a silver halide camera, especially for digital cameras which have been popular recently. There has been proposed a lens that converts the magnification by combining lenses.
[0004]
[Problems to be solved by the invention]
In recent cameras, it has become the mainstream to substitute the function of focusing on the finder by visual observation with an autofocus. Along with this, the finder is designed mainly to confirm the composition. Also, in order to cope with various eye conditions such as myopia, hyperopia, and presbyopia, the mainstream is a camera with a built-in continuous diopter correction mechanism or a diopter correction lens. ing. For focusing by autofocus, a high finder magnification is not adopted because of the necessity of incorporating a continuous diopter correction mechanism of the camera, a built-in strobe in the camera body, or cost.
[0005]
However, a lens with a large aperture ratio (small open F value) that is difficult to focus on may cause a situation in which the user cannot be satisfied with the autofocus function. First, in the autofocus, the distance measuring range has a certain area, and it is not possible to focus on one arbitrary fine point on the finder image. Therefore, when a plurality of objects that are separated from each other are present in the distance measurement range, the user may not be able to determine where the focus is.
[0006]
In addition, the distance measurement range cannot be a part of the finder image selected arbitrarily. Since the arrangement of the elements for distance measurement is determined and designed in advance, the focus is adjusted only at the arranged part. Therefore, after focusing, the camera is moved for composition and shooting. At this time, a so-called cosine error occurs. This cosine error greatly affects the photographing result with a lens having a small open F value, and a situation in which the focus at a desired position cannot be obtained occurs.
[0007]
Accordingly, there has been a demand for a finder that can focus on any one point arbitrarily selected in the finder image. One way to achieve this is to improve the finder observation magnification. If the finder observation magnification can be greatly improved, a point restricted by the eye resolution can be magnified and focused more precisely.
[0008]
In the first conventional technique, when the eye level magnifier is used, the entire field of view cannot be confirmed. Therefore, after adjusting the focus, it is necessary to confirm the entire field of view and adjust the composition. For this reason, it is necessary to attach / remove the magnifier or jump it up. It is cumbersome and inconvenient for the operation of the camera to perform such attachment and removal during shooting. Further, since only the center part of the screen is enlarged, the advantage of magnification enlargement cannot be obtained when focusing is performed at a part other than the center part.
Next, angle magnifiers are difficult to use depending on the object to be photographed because of restrictions on the photographing posture.
[0009]
In Japanese Patent Laid-Open No. 2000-180920, which is a second conventional technique, the enlargement magnification due to the variable magnification attachment is not so high as about 107%, and there is a concern about vignetting when used for a silver salt camera. In Japanese Patent Laid-Open No. 11-337847, although the enlargement magnification is improved, the original field of view of the camera cannot be maintained and vignetting occurs. Further, the magnification and aberration cannot be finely adjusted according to the demands of many users.
[0010]
This application is attached to the camera finder, etc., and does not cause vignetting of the field of view, while allowing a wide range of diopter, magnification, and aberration adjustments according to the user, the finder observation magnification of the attached camera is the same diopter It is an object of the present invention to provide an inexpensive finder attachment that can be larger than 109% under the comparative conditions. It is also effective when diverting a silver halide camera that has been in fashion recently to a digital camera or using a back cover for converting a silver salt camera to a digital camera. That is, by using it for the viewfinder, it is possible to enlarge and observe a photographing range corresponding to an image sensor smaller than the format of the silver salt camera.
[0011]
[Means for Solving the Problems]
The present invention is detachably mounted on a user-side end surface of a finder optical system, and has negative refractive power and a radius of curvature in order from the user side, the other surface is a flat lens, an air interval of 0 mm or more, one surface Is a lens whose other surface has a positive refractive power and a radius of curvature. The present invention is a variable magnification finder attachment comprising two lenses that are detachably attached to the user side end face of the finder optical system. The radius of curvature of the lens surface is R1, R2, R3, R4 in order from the user side. In this case, R2 = R3 = infinity and the air spacing between the two lenses is zero or more. And above It is a finder attachment that can adjust the increase and decrease of the air interval. Further, the diopter correction lens can be attached to one or both of the front end and rear end of the finder attachment. Furthermore, it is a finder attachment having a configuration in which a diopter correction lens can be inserted into the air gap. Furthermore, the diopter correction lens is a finder attachment that can move back and forth on the optical axis. Further, the aperture is inserted between the two lenses of the attachment, before attachment, after attachment, or at a plurality of positions so that the aberration can be adjusted. Further, the attachment is provided with a moving mechanism, and can be instantaneously switched between the optical axis and the outside of the optical axis. Moreover, it is set as the structure which has a some attachment part so that attachment to a some kind of finder is possible.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1
FIG. 1 shows a state in which a finder attachment according to the present invention is mounted on a finder of a single-lens reflex camera, for example. From the user's eye side, the flat glass 21 constitutes the ninth and tenth surfaces, the movable positive lens 22 constitutes the eleventh and twelfth surfaces, and the fixed negative lens 23 constitutes the thirteenth and fourteenth surfaces. The pentaprism 24 constitutes the 15th and 16th surfaces, the condenser lens 25 constitutes the 17th and 18th surfaces, and the focusing screen 26 constitutes the 19th and 20th surfaces And The finder optical system of the camera is shown as a cross-sectional view, and the viewfinder attachment is shown as a cross-sectional view of the upper half and the lower half as a side view.
[0013]
In this example, the movable lens 22 and the fixed lens 23 are used for the finder, and one of the distance between the tenth surface and the eleventh surface and the distance between the twelfth surface and the thirteenth surface is increased while the other is decreased. The diopter can be adjusted between + 2dp and -3dp. The sum of the distance between the tenth and eleventh surfaces and the distance between the twelfth and thirteenth surfaces is 6.517 mm. With the diopter correction mechanism built in the camera body in advance, the distance between the 10th surface and the 11th surface is 6.165 mm, the distance between the 12th surface and the 13th surface is 0.352 mm, and the maximum minus direction −3.04 diopter ( The following is adjusted to dp). At this time, the focal length of the entire finder optical system of the camera body is 72.29 mm.
[0014]
The attachment 10 according to the present application can be easily and detachably attached to the user's eye side of the finder eyepiece of the camera by means such as a screw, a groove or a hinge applied to the case 13 of the magnification finder attachment. The lenses constituting the finder attachment are two single-sided flat lenses 11 and 12, which have a shape in which the eye side is dented and the lens center protrudes to the camera side, and is a meniscus lens having a positive focal length as a whole. Here, the curvature radii of the two curved surfaces are both -25.95 mm, and the total center thickness TC for two lenses is 6 mm.
[0015]
When this finder attachment is attached, the diopter of the entire finder optical system is -1.82dp, and the focal length is 63.72mm. The finder optical system equipped with the attachment at this time has the following configuration. The number of surfaces 9 to 19 is the same as the data at −3.04 dp of the camera to which this attachment is attached. Surface numbers 3, 4, 7, and 8 may or may not be used, but are described in all the embodiments in order to facilitate understanding of differences in configuration between the conventional technology and the embodiments. . The refractive index and Abbe number data are shown for the d-line (λ = 587.56 nm).
[0016]

[0017]
However, when the attachment is not attached, the focal length of the finder optical system when adjusted to −1.82 dp using the diopter correction mechanism of this camera is 71.45 mm. Thus, when compared with the same diopter, the finder magnification is improved by 112.1%.
[0018]
FIG. 2 shows a table of aberration values at this time. The aberration values in the following second to fourth embodiments are also shown here.
Throughout the following embodiments, the wavelengths used in the aberration diagrams are d-line 587.56 nm (1 in the figure), F-line 486.13 nm (2 in the figure), and C-line 656.27 nm (3 in the figure). Unless otherwise specified, each aberration is determined as a pupil diameter of 4 mm when the image height is 21.7 mm.
[0019]
In FIGS. 3 to 11, mm display is adopted except for distortion aberration. For spherical aberration (SA, OSC) and astigmatism (AS), the vertical axis shows the maximum incident height and the image height of 21.7 mm, the horizontal axis shows a common scale, the right side is +1.0 mm, and the left side is -1.0. Up to mm is displayed. The vertical axis of distortion (DIST) is displayed up to an image height of 21.7 mm, similar to the astigmatism (AS). The horizontal axis of the distortion (DIST) is displayed up to -3.0% on the right side and + 3.0% on the left side for the convenience of analysis using the object position as the user's eye side and the image position as the focusing screen. In FIG. 2, this is converted into diopter (dp) or minutes (min).
[0020]
To convert the distance display of spherical aberration (SA, OSC) and astigmatism (AS) to diopter (dp), the focal length of the finder optical system is f and converted to the square of 1000 / f. went. The values of spherical aberration (SA, OSC) in Fig. 2 are based on this conversion, and for the d-line, the deviation from the set diopter is displayed as dioptre (dp), and is obtained for an image height of 21.7 mm. . The value of astigmatism (AS) is the dp display of the deviation from the set diopter for the d-line, and the image height is obtained up to 21.7 mm for sagittal (S) and tangential (T), respectively. .
[0021]
In FIGS. 3 to 11, the lateral aberration is 0 to 0 (on the axis), 0.55, 0.83, and 1.0 times the maximum image height from bottom to top (when the image height is 0 mm, when the image height is 12.0 mm, and when the image height is 18.0 mm). The image is drawn with the sagittal (DX) direction shown on the right and the tangential (DY) shown on the left with the image height of 21.7 mm as the principal ray position. The range of each vertical axis is −0.2 mm at the bottom and +0.2 mm at the top. The horizontal axis shows only one side of 2 mm which is half of the pupil diameter φ4 mm in the sagittal (DX). The tangential (DY) is shown for the pupil diameter φ4 mm. The lateral aberration value shown in FIG. 2 is expressed in minutes (min), and the value at the left end of the d-line tangential (DY) is converted and described for a pupil diameter of 4 mm. Here, the conversion from mm to min is obtained by 60 times arctan (1 / f).
[0022]
FIGS. 3 and 4 compare the aberration curve when the attachment is set to −1.82 dp and the aberration curve of the camera body finder at −1.82 dp. As can be seen from FIG. 2, the distortion increases from + 1.5% to + 3.3%, but is within the tolerance of ± 5% normally required for the finder. The eye relief is 14.4 mm, which is usually at a level where the field of view is not vignetting even for spectacle users. Note that the eye relief is shown as a point where the light beam incident on the maximum image height intersects the paraxial axis in the case of the pupil diameter of 14 mm through this embodiment and the following embodiments.
[0023]
On the other hand, in FIG. 3 with the attachment, the spherical aberration for the light of the wavelength of 587.56 nm is −0.04 dp, and the difference between the diopter of sagittal and tangential is −0.55 dp and −0.50 dp, respectively. On the other hand, in FIG. 4 when not attached, the spherical aberration for the light of the wavelength of 587.56 nm is −0.09 dp, and the difference between the diopter of the sagittal and the tangential is −0.68 dp and −1.22 dp at maximum. Therefore, if an attachment is attached, both spherical aberration and astigmatism can be reduced.
[0024]
When the attachment is attached, the difference between the diopter at the center of the screen and the diopter at the corners of the screen is small, and the diopter adjustment function is not burdened, and the diopter is easily adjusted. When looking at the periphery after adjusting the diopter at the center, the diopter adjustment function by the eyes stagnate and the surroundings become difficult to see for a while, but this phenomenon is reduced when the attachment is attached . This is particularly effective when the diopter is fixed physiologically through a presbyopia or a long-time viewfinder in which the near-point diopter adjustment function is reduced.
[0025]
In addition, when this attachment is attached, as shown in FIG. 3, in the lateral aberration, the amount of movement of the sagittal and tangential peripheral rays from the principal ray on the screen is reduced. Therefore, the illuminance is concentrated on a smaller area within the image point, and an image with high contrast is formed.
Also, the chromatic aberration of magnification between the three colors with wavelengths of 486.13 nm, 587.56 nm, and 656.27 nm at an image height of 18 mm is 5.35 min within the allowable value compared to 3.56 min when not installed in FIG. 4, so color bleeding is not an issue. . Usually, color bleeding is considered to be no problem within 10 minutes.
[0026]
When this embodiment is made and actually mounted, a finder image having a large magnification and extremely easy to focus is obtained. When a photographic lens with a focal length of 51.8 mm is attached to a camera with no attachment, a finder magnification of 0.696 times is obtained at the same diopter -1.82 dp, and when the attachment according to this application is attached, this magnification is 0.780 times To improve.
Therefore, not only focusing at the center of the screen is improved by 112.1% magnification, but also focusing at the periphery of the screen improves magnification, reduces diopter change, and converges the light beam. As a result, focusing around the screen is easy. It becomes. In addition, the use of a single flat lens can reduce the overall length of the attachment on the optical axis, thereby preventing vignetting in the viewfinder field.
[0027]
Embodiment 2
Similar to the first embodiment, the diopter correction mechanism of the finder body has a configuration in which the diopter can be adjusted by changing the distance between the 10th and 11th surfaces and the distance between the 12th and 13th surfaces. It is adjusted to -3.04dp with no attachment attached. At this time, the focal length of the entire finder optical system of the camera body is 72.29 mm. In Embodiment 1, the negative lens 11 and the positive lens 12 constituting the finder attachment 10 are two single-sided flat lenses, and no air gap is provided between the lenses. In this embodiment, in the case 13, an air gap of 0.5 mm is provided between the two lenses. The negative lens 11 has a radius of curvature of −25.95 mm and a center thickness of 2 mm, and the positive lens 12 has a radius of curvature of −25.84 mm and a center thickness of 3.23 mm. When the finder attachment is attached, the diopter is −1.74 dp, and the focal length of the finder optical system including the finder attachment is 63.61 mm.
[0028]
The configuration of the finder optical system of the camera including the attachment at this time is as follows.

However, using the diopter correction function of the camera with no attachment attached, the focal length of the finder optical system when 71.39dp is the same as when the attachment is attached is 71.39mm, 71.39 / 63.61 = 112.2% finder The magnification is improved.
[0029]
The way of viewing the figure is as described in the first embodiment. FIGS. 5 and 6 compare the aberration curve when the attachment is attached to −1.74 dp and the aberration curve of the camera body at −1.74 dp, respectively. From the data in FIG. 2 and the aberration curve in FIG. 5, the distortion is + 3.3% within the allowable value, the spherical aberration with respect to the light of the wavelength of 587.56 nm is as small as −0.05 dp, and the center portion of the viewfinder image is sharp. Astigmatism is a maximum of -0.57 dp for sagittal and a maximum of -0.55 dp for tangential, both of which are low values for diopter adjustment for the eyes. The chromatic aberration of magnification between the three colors with wavelengths of 486.13 nm, 587.56 nm, and 656.27 nm is 18 mm at the image height, 5.52 min at the center, and within an allowable value of 10 min. The tangential lateral aberration on the left side of the figure, which deviates from the lateral aberration of sagittal, is -1.04 min for a pupil diameter of 4 mm, and no coma aberration occurs. Further, when the attachment is mounted, as shown in FIG. 5, in the lateral aberration, the amount of movement of the sagittal and tangential peripheral rays from the principal ray on the screen is reduced. Therefore, the illuminance is concentrated on a smaller area within the image point, and an image with high contrast is formed.
[0030]
On the other hand, looking at the aberration curves in FIG. 2 and FIG. 6, the distortion is + 1.1%, and the spherical aberration for light with a wavelength of 587.56 nm is −0.13 dp. Astigmatism is up to -0.69dp for sagittal and -1.25dp for tangential. The chromatic aberration of magnification between the three colors of wavelengths 486.13nm, 587.56nm, and 656.27nm is 18mm in image height and 4.49min at the center. The tangential lateral aberration on the left side of the figure, which deviates from the lateral aberration of sagittal, is −4.14 min when the pupil diameter is 4 mm. As can be seen from comparison, spherical aberration, astigmatism and lateral aberration, which were large when the lens was not mounted, can be improved.
[0031]
As described above, in the same way as in the first embodiment, the diopter change between observation points in the screen is reduced, so that the load of eye diopter adjustment can be reduced and the finder magnification can be improved by 112.2%. it can. The eye relief is 14.1 mm, which is a level where there is no vignetting even for the eyeglass user. Therefore, not only focusing at the center of the screen is facilitated by a magnification of 112.2%, but magnification is improved, diopter change is reduced, and light flux is converged around the screen, resulting in easy focusing around the screen. Become.
[0032]
Furthermore, a case where further improvement of the magnification is desired, that is, a case where the air gap is set to 1.5 mm in the above configuration will be described. The air space can be increased or decreased by a method such as increasing or decreasing helicoids or washers. For example, if the first lens, the second lens, and the washer have the same outer diameter, the air gap can be easily changed by increasing or decreasing the washer. As the washer, in consideration of internal reflection, a ring-shaped metal such as stainless steel with chromium oxide or a rubber or film punched out can be considered.
When this attachment is mounted, the diopter is -1.40dp and the focal length of the finder optical system is 61.77mm. The aberration diagram at this time is shown in FIG. Since the focal length of the finder optical system of the camera body adjusted to the same diopter is 71.15 mm, the finder magnification is improved by 115.2%. The eye relief is 12.4mm, which is a level where there is no vignetting in eyeglasses users.
[0033]
Looking at the data in FIG. 2 and the aberration curve in FIG. 7, the distortion is within + 3.8% and the tolerance is small, the spherical aberration for light with a wavelength of 587.56 nm is as small as −0.09 dp, and the center of the viewfinder image is sharp. Astigmatism is a maximum of -0.57 dp for sagittal and a maximum of -0.50 dp for tangential, both of which are low values for diopter adjustment for the eyes. The chromatic aberration of magnification between the three colors of wavelengths 486.13nm, 587.56nm, and 656.27nm is 5.77min at the image height of 18mm and at the center, within the allowable value of 10min. The tangential lateral aberration on the left side of the figure, which deviates from the lateral aberration of sagittal, is −0.66 min when the pupil diameter is 4 mm, and no coma aberration occurs. Rather, lateral aberration reduces the amount of sagittal and tangential peripheral rays moving on the screen from the chief rays. Therefore, the illuminance is concentrated on a smaller area within the image point, and an image with high contrast is formed.
[0034]
When the 51.8mm photographic lens is attached to the camera with no attachment, and the diopter is adjusted to -1.40dp, the finder magnification is 0.699. On the other hand, the finder magnification when the 51.8 mm photographing lens is attached to the camera attached with the attachment shown in FIG. 7 is 0.805. Therefore, not only focusing at the center of the screen is facilitated by an 115.2% finder magnification improvement, but the same magnification improvement, diopter change reduction and light flux convergence can be achieved around the screen, resulting in focusing around the screen. It becomes easy. Further, by using a single flat lens, the overall length of the attachment on the optical axis can be reduced, and no vignetting in the viewfinder field occurs.
[0035]
Embodiment 3
In this embodiment, when the attachment 10 described in the second embodiment is mounted, an example is shown in which the diopter is further adjusted toward minus or plus. As in the second embodiment, an air gap of 0.5 mm is provided between the two lenses. From the eye side, the radius of curvature of the negative lens is −25.95 mm, the center thickness is 2 mm, the radius of curvature of the positive lens is −25.84 mm, and the center thickness is 3.23 mm. The dioptric correction mechanism of the camera body is adjusted to -3.04 dp.
[0036]
When the finder attachment is attached, the diopter is −1.74 dp, and the focal length of the finder optical system including the finder attachment is 63.61 mm. Furthermore, when a concave lens of about −1 dp having a focal length of about −967 mm (−500 mm radius of curvature) is attached between the attachment lens and the camera body, the diopter may be set to −2.91 dp at the maximum in the minus direction. it can. The focal length of the finder optical system at that time is 65.91 mm. The eye relief is 14.0 mm, which is a level without vignetting even for the eyeglass user. Using the diopter adjustment function of the camera body with no attachment, the focal length of the finder optical system is 72.20mm when the same -2.91dp is used. Therefore, the viewfinder magnification is improved by 109.5%.
[0037]
The configuration of the finder optical system at the time of attaching an attachment to which a diopter correction lens having a focal length of about −967 mm according to this embodiment is added is shown below.

[0038]
The way of viewing the figure is as described in the first embodiment. Each aberration when the finder attachment is mounted is shown in FIG. Looking at the data in FIG. 2 and the aberration curve in FIG. 8, the distortion is within + 3.4%, the spherical aberration for the light of the wavelength of 587.56 nm is as small as −0.05 dp, and the viewfinder image becomes sharp, Astigmatism is a maximum of −0.41 dp for sagittal and a maximum of −0.20 dp for tangential, both of which are low values for adjusting the diopter for the eyes. The chromatic aberration of magnification between the three colors with wavelengths of 486.13 nm, 587.56 nm, and 656.27 nm is 18 mm at the image height, 5.33 min at the center, and within an allowable value of 10 min. The tangential lateral aberration on the left side of the figure, which deviates from the lateral aberration of sagittal, produces a very slight coma aberration of 0.39 min when the pupil diameter is 4 mm, but it is smaller than the normal eye resolution of 1 min. It is not an identifiable level. Rather, lateral aberration reduces the amount of movement of the sagittal and tangential peripheral rays from the chief ray on the screen. Therefore, the illuminance is concentrated on a smaller area within the image point, and an image with high contrast is formed. Therefore, while expanding the range in which diopter can be adjusted in the negative direction, focusing at the center of the screen is facilitated by increasing the magnification by 109.5%. As a result, focusing around the screen becomes easy.
[0039]
In the above, the −1 dp diopter correction lens is exemplified, but by using a negative lens with a shorter focal length, for example, a −2 dp to −4 dp diopter correction lens, the diopter when the attachment is attached and when not attached By bringing the attachment close and making the attachment flip-up type, it is possible to easily switch between the two fields of view with and without the magnification. As a result, it is possible to easily bounce up when observing an image while reducing distortion on the finder, and use an attachment when observing at an enlarged magnification. If the diopter correction lens is installed so as to be movable on the optical axis, the diopter can be further finely adjusted. In this case, the position of the diopter correction lens is preferably on the viewer's eye side, but it goes without saying that it may be on the camera finder side. A screw, a helicoid, etc. can be used as a means for moving.
[0040]
Conversely, if a positive diopter correction lens is inserted, the diopter can be swung in the positive direction and the magnification can be further improved.
[0041]
Further, a case where improvement in magnification is desired, that is, a case where the air gap is set to 1.5 mm in the configuration in which the diopter correction lens of −1 dp is added will be described. The air space can be increased or decreased by a method such as increasing or decreasing helicoids or washers. For example, if the first lens, the second lens, and the washer have the same outer diameter, the air gap can be easily changed by increasing or decreasing the washer. In this case, the diopter is -2.61 dp, and the focal length is 64.00 mm. Eye relief is 15.0mm, which is a level without vignetting even for eyeglass users.
[0042]
FIG. 9 shows aberration diagrams when the air spacing is 1.5 mm. The way of viewing the figure is as described in the first embodiment. From the data in FIG. 2 and the aberration curve in FIG. 9, the distortion is + 4.0%, within the allowable value, the spherical aberration with respect to the light of the wavelength of 587.56 nm is as small as −0.10 dp, and the image center is sharp. Astigmatism is a maximum of −0.39 dp for sagittal and a maximum of −0.07 dp for tangential, both of which are very low diopter adjustment burdens for the eyes. The chromatic aberration of magnification between the three colors of wavelengths 486.13nm, 587.56nm, and 656.27nm is 5.73min at the image height of 18mm and in the center, within the allowable value of 10min. The tangential lateral aberration on the left side of the figure, which deviates from the lateral aberration of sagittal, generates a slight coma aberration of +1.19 min when the pupil diameter is 4 mm. However, this value is close to the minimum resolution of a general human eye and is an amount that is hardly recognizable. Rather, in lateral aberration, the amount of movement of sagittal and tangential peripheral rays from the principal ray on the screen can be reduced. Therefore, the illuminance is concentrated on a smaller area within the image point, and an image with high contrast is formed. Therefore, the range of diopter adjustment in the negative direction is expanded and focusing is facilitated by a magnification of 112.5% at the center of the screen. In addition, the magnification is improved around the screen, diopter change is reduced, and light flux is converged. As a result, focusing around the screen becomes easy.
[0043]
In the above, the −1 dp diopter correction lens is exemplified, but by using a negative lens with a shorter focal length, for example, a −2 dp to −4 dp diopter correction lens, the diopter when the attachment is attached and when not attached By bringing the attachment close and making the attachment flip-up type, it is possible to easily switch between the two fields of view with and without the magnification. As a result, it is possible to easily bounce up when observing an image while reducing distortion on the finder, and use an attachment when observing at an enlarged magnification.
Conversely, if a positive diopter correction lens is inserted, the diopter can be swung in the positive direction and the magnification can be further improved.
Furthermore, even if it is used for a viewfinder that does not have a diopter correction mechanism and the diopter is adjusted by a diopter correction lens, it maintains a diopter comparable to that of the viewfinder. The magnification can be improved. In this case, it goes without saying that it can be used not only in a single-lens reflex camera but also in a range finder, and the magnification can be improved. It can also be used for other types of viewfinders and loupes, and can improve the magnification.
[0044]
Embodiment 4
In this embodiment, as in the third embodiment, an example in which the diopter is further adjusted when the attachment 10 of the second embodiment is mounted is shown. However, the insertion position of the plus or minus diopter correction lens is not between the viewfinder and the attachment, but between the negative lens 11 and the positive lens 12. The gap between the two lenses is filled with the diopter correction lens and the air space before and after it. The radius of curvature of the negative lens 11 is −25.95 mm and the center thickness is 2 mm, and the radius of curvature of the positive lens is −25.84 mm and the center thickness is 3.23 mm. The dioptric correction mechanism of the camera body is adjusted to -3.04 dp. When a finder attachment with a diopter correction lens having a focal length of about −967 mm is attached, the diopter is −2.54 dp, and the focal length of the finder optical system including the finder attachment is 63.73 mm. Using the diopter adjustment function of the camera body with no attachment, the focal length of the viewfinder optical system is 71.95mm when the same -2.54dp is used. Therefore, the viewfinder magnification is improved by 112.9%.
[0045]
When a 51.8mm photographic lens is attached to a camera with no attachment and the diopter is adjusted to -2.54dp, the viewfinder magnification is 0.691. On the other hand, the finder magnification when the 51.8 mm photographic lens is attached to the camera with the attachment is 0.780. In addition, when the attachment is mounted, the eye relief is 13.2 mm and there is no normal vignetting even when using glasses.
[0046]
The configuration of the finder optical system when the attachment is added with the diopter correction lens having a focal length of about −967 mm (−500 mm radius of curvature) is shown below.

[0047]
Each aberration when the attachment is attached is shown in FIG. 10, and each aberration when the diopter is adjusted to −2.54 dp when the attachment is not attached is shown in FIG. The way of viewing the figure is as described in the first embodiment. Looking at the aberration curves when the attachments are attached in FIGS. 2 and 10, the distortion is within an allowable value of + 3.8%, and the spherical aberration for light having a wavelength of 587.56 nm is as small as −0.01 dp. Astigmatism is a maximum of -0.42 dp for sagittal and a maximum of -0.16 dp for tangential, both of which are low values for diopter adjustment for the eyes. The chromatic aberration of magnification between the three colors of wavelengths 486.13nm, 587.56nm, and 656.27nm is 5.75min at the image height of 18mm and within the allowable value of 10min. The tangential lateral aberration is 0.80 min and a slight coma aberration occurs at a pupil diameter of 4 mm. Looking at the aberration curve when the attachment is not attached in Fig. 11, the distortion is + 1.5%, the spherical aberration for light of 587.56nm is + 0.02dp, the astigmatism is sagittal up to -0.59dp, tangential up to- 0.92dp. The chromatic aberration of magnification between the three colors of wavelengths 486.13nm, 587.56nm, and 656.27nm is 4.03min at the image height of 18mm and in the center. The tangential lateral aberration on the side deviating from the lateral aberration of sagittal is −3.19 min for a pupil diameter of 4 mm.
[0048]
When the attachment is mounted, the distortion increases, but the spherical aberration and astigmatism decrease, reducing the eye diopter adjustment burden. The chromatic aberration of magnification increases but is still within an acceptable value. Although coma aberration occurs slightly, it is 1 min or less, which is the minimum resolution of the eye, and is not at a level causing visual problems. Therefore, the spread of the light beam on the screen is narrowed, and the sharpness of the image is rather increased. That is, in the case of the present embodiment, in lateral aberration, the amount of movement of sagittal and tangential peripheral rays from the principal ray on the screen is reduced. Therefore, the illuminance is concentrated on a smaller area within the image point, and an image with high contrast is formed. Therefore, not only focusing at the center of the screen is improved by 112.9%, but focusing is also improved at the periphery of the screen, diopter change is reduced, and light flux is converged, resulting in easy focusing around the screen. Become. Further, the use of a single flat lens can reduce the overall length of the optical axis of the attachment, and vignetting in the viewfinder field does not occur.
[0049]
Increasing the air gap between the two positive and negative lenses tends to improve the magnification, and inserting the diopter correction lens between them as in this embodiment does not increase the overall length of the attachment. Compared to the example of Form 3, it is possible to achieve both further magnification improvement and diopter correction.
[0050]
In the above, the −1 dp diopter correction lens is exemplified, but a negative lens with a shorter focal length, for example, a −2 dp to −4 dp diopter correction lens is used, so that the visibility when the attachment is attached and when the attachment is not attached is shown. By making the degree closer and further flipping the attachment, it is possible to easily switch between the two fields of view with and without the magnification. As a result, it is possible to easily jump up when observing an image without an attachment, and use an attachment when observing with an increased magnification. As described above, the attachment can be provided with a moving mechanism, and can be instantaneously switched between the optical axis and the optical axis.
[0051]
Conversely, by inserting a +1 dp diopter correction lens that is a positive lens having a focal length of about +967 mm, the diopter can be swung in the positive direction and the magnification can be further improved. In this case, the magnification is improved by 117.5% at -0.22 dp. That is, when a lens with a focal length of 51.8 mm is attached, the finder magnification is 0.833 times. Distortion is 3.8%, spherical aberration is 0.00dp, astigmatic difference is -0.72dp for sagittal and -0.78dp for tangential. The chromatic aberration of magnification at the principal ray position at an image height of 18 mm is 5.97 min, within the allowable value of 10 min, for the three colors with wavelengths of 486.13 nm, 587.56 nm, and 656.27 nm. Tangential lateral aberration is -1.71 min for a pupil diameter of 4 mm, so coma does not occur.
[0052]
Aberration can be adjusted by inserting a diaphragm between the two lenses of the attachment, before attachment, after attachment, or at a plurality of positions. For example, in a situation where coma is a concern, it is possible to reduce the coma by inserting a circular diaphragm or the like between the lenses or the rear end of the attachment.
[0053]
Furthermore, even if it is used for a viewfinder that does not have a diopter correction mechanism and the diopter is adjusted by a diopter correction lens, it maintains a diopter comparable to that of the viewfinder. The magnification can be improved. In this case, it goes without saying that it can be used not only for a single-lens reflex camera but also for a range finder, and the magnification can be improved. It can also be used for other types of finder types and loupes, and can improve the magnification. At this time, if a single attachment is provided with a plurality of finder attachment portions such as screws and grooves that enable attachment to a plurality of finders, the attachment can be shared with a plurality of cameras and the like. . At that time, it is possible to easily change the lens according to the model.
[0054]
【The invention's effect】
Since the magnification can be improved with a simple configuration using a single-sided flat lens, the manufacturing cost can be reduced. Also, the use of a single-sided flat lens can reduce the overall length of the attachment on the optical axis, and there is no vignetting in the viewfinder field. In addition, the magnification and diopter can be easily changed, and it can be used in a wide range of user situations. Moreover, it is easy to attach and detach and is compact.
[0055]
Also, by using a diopter correction lens with a smaller diopter number in combination, the diopter at the time of attachment and non-attachment is made closer, and the attachment is flipped up to increase the magnification. It is possible to easily switch between the two fields of view that are not in the state. This makes it possible to instantly switch the position of the attachment between on and off the optical axis so that it can be flipped up when observing an image with no attachment attached, and can be attached when observing at an increased magnification. Can be done easily.
In addition, the diopter correction lens can be moved to enable fine adjustment of the diopter.
Further, by using the attachment of the present invention, it is possible to improve the observation magnification of a viewfinder of a range finder camera, a finder of a twin-lens reflex camera, a loupe of a view camera, or the like.
In addition, the magnification can be improved by using it in a finder that does not incorporate a diopter correction mechanism.
One attachment can be used for a plurality of cameras.
In addition, recently developed silver halide cameras have been used for digital cameras, and back covers for converting silver halide cameras to digital cameras have been developed. An imaging range corresponding to an image sensor having an area smaller than the format of the camera can be enlarged and observed.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view showing a state in which a finder attachment according to the present invention is attached to, for example, a finder of a single-lens reflex camera.
FIG. 2 is a table showing the values of aberrations in the first to fourth embodiments.
FIG. 3 shows aberration curves at −1.82 dp of a finder equipped with an attachment according to the first embodiment of the present application.
FIG. 4 is an aberration curve when the diopter of a finder with no attachment is adjusted to −1.82 dp.
FIG. 5 is an aberration curve at −1.74 dp of a finder equipped with an attachment with an air spacing of 0.5 mm according to the second embodiment of the present application.
FIG. 6 is each aberration curve when the diopter of a finder with no attachment is adjusted to −1.74 dp in relation to the second embodiment of the present application.
FIG. 7 is an aberration curve at −1.40 dp of a finder equipped with an attachment with an air spacing of 1.5 mm according to the second embodiment of the present application.
FIG. 8 shows aberration curves when an attachment with an air gap of 0.5 mm according to the third embodiment of the present application is attached and a −1 dp diopter correction lens is attached on the finder side of the attachment.
FIG. 9 shows aberration curves when an attachment with an air gap of 1.5 mm according to the third embodiment of the present application is attached and a −1 dp diopter correction lens is attached on the finder side of the attachment.
FIG. 10 shows aberration curves when a −1 dp diopter correction lens according to the fourth embodiment of the present application is interposed between lenses in an attachment.
FIG. 11 shows aberration curves at −2.54 dp of a finder body with no attachment attached in relation to the fourth embodiment of the present application.
FIG. 12 is a half cross-sectional view of a zoom finder attachment provided with a plurality of attachment portions in relation to the fourth embodiment of the present application.
[Explanation of symbols]
1 d line 587.56 nm, 2 F line 486.13 nm, 3 C line 656.27 nm,
10 variable magnification finder attachment, 11 negative lens, 12 positive lens,
13 Case, 14 Viewfinder mount, 15 Viewfinder mount,
21 glass plane plate, 22 movable eyepiece, 23 fixed eyepiece,
24 penta prism, 25 condenser lens, 26 focusing screen

Claims (6)

It consists of two lenses with negative and positive power, which are detachably mounted on the end surface of the finder optical system on the user side, and the radius of curvature of the lens surface is R1, R2, R3, R4 in order from the user side. In this case, R2 = R3 = infinity , and the zoom finder attachment in which the air space between the two lenses is zero or more and the air space can be arbitrarily increased or decreased . The zoom finder attachment according to claim 1, wherein a diopter correcting lens can be attached to at least one of a front end and a rear end of the zoom finder attachment or the air gap. The zoom finder attachment according to claim 1 or 2, wherein the diopter correction lens is movable. 4. The aberration can be adjusted by inserting an aperture in the zoom finder attachment within the air gap, before the attachment, after the attachment, or at a plurality of positions. 5. A variable magnification finder attachment according to any one of the above. The zoom finder attachment according to any one of claims 1 to 4, wherein the zoom finder attachment is provided with a moving mechanism and can be arbitrarily switched between on and off the optical axis. The variable magnification finder attachment according to any one of claims 1 to 5, further comprising a plurality of attachment portions so as to be attached to a plurality of types of finders.

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