JP5186073B2 - Imaging optical system - Google Patents

Description

ここで、（ａ）式の第１項は球面項、第２項は自由曲面項である。
【００２５】
球面項中、
ｃ：頂点の曲率
ｋ：コーニック定数（円錐定数）
ｒ＝√（Ｘ² ＋Ｙ² ）
である。
【００２６】
自由曲面項は、

ただし、Ｃ_j （ｊは２以上の整数）は係数である。
【００２７】
上記自由曲面は、一般的には、Ｘ−Ｚ面、Ｙ−Ｚ面共に対称面を持つことはないが、Ｘの奇数次項を全て０にすることによって、Ｙ−Ｚ面と平行な対称面が１つだけ存在する自由曲面となる。また、Ｙの奇数次項を全て０にすることによって、Ｘ−Ｚ面と平行な対称面が１つだけ存在する自由曲面となる。
【００２８】
また、上記の回転非対称な曲面形状の面である自由曲面の他の定義式として、Ｚｅｒｎｉｋｅ多項式により定義できる。この面の形状は以下の式（ｂ）により定義する。その定義式（ｂ）のＺ軸がＺｅｒｎｉｋｅ多項式の軸となる。回転非対称面の定義は、Ｘ−Ｙ面に対するＺの軸の高さの極座標で定義され、ＲはＸ−Ｙ面内のＺ軸からの距離、ＡはＺ軸回りの方位角で、Ｘ軸から測った回転角で表せられる。
【００２９】

ただし、Ｄ_m （ｍは２以上の整数）は係数である。なお、Ｘ軸方向に対称な光学系として設計するには、Ｄ₄ ，Ｄ₅ ，Ｄ₆ 、Ｄ₁₀，Ｄ₁₁，Ｄ₁₂，Ｄ₁₃，Ｄ₁₄，Ｄ₂₀，Ｄ₂₁，Ｄ₂₂…を利用する。
【００３０】
上記定義式は、回転非対称な曲面形状の面の例示のために示したものであり、他のいかなる定義式に対しても同じ効果が得られることは言うまでもない。
【００３１】
ところで、本発明による撮像光学系をその奥行き方向の厚さを小さくするには、絞りの中心を通り、撮像面の中心に到る光線を軸上主光線とするとき、物体空間での軸上主光線方向に対する絞りを通過するときの軸上主光線方向の偏角θが、
４５°＜θ＜１３５° ・・・（２）
を満たすことが望ましい。
【００３２】
ここで、上記定義の偏角θは、物体空間での軸上主光線の方向と絞りを通過するときの軸上主光線の方向が同じで平行な場合に０°で、反対向きで平行な場合に１８０°になるもので、この偏角θが上記条件（２）を満たすことにより、絞りより後の後群を前群と並べて配置できるので、撮像光学系の奥行き方向の厚さを薄く構成することが可能になる。その条件の上限の１３５°を越えると、後群が前群より前側に出て、また、下限の４５°を越えると、逆に後群が前群より後ろ側に位置することになり、何れも奥行き方向の厚さを薄くすることができなくなる。
【００３３】
特に、絞りより前側に反射面を１面のみ持つ１つの偏心プリズムが配置されて前群が構成される場合、
９２°＜θ＜１３５° ・・・（３）
を満たすことが望ましい。
【００３４】
この条件（３）の下限の９２°より小さくなると、前群の偏心プリズムで発生した偏心収差の影響が大きく、非対称収差が補正できなくなる。上限の１３５°よりも大きくなると、前群の偏心プリズムと後群の偏心プリズムとの干渉が発生する。この干渉を避けようとすると、光学系が大きくなってしまう。
【００３５】
より好ましくは、
９５°＜θ＜１２５° ・・・（３−１）
を満たすようにすることが望ましい。
【００３６】
さらに好ましくは、
９８°＜θ＜１１５° ・・・（３−２）
を満たすようにすることが最も良い。
【００３７】
次に、物体空間における光軸に沿った撮像光学系の厚さｔを測ることを考える。物体空間における光軸に沿う軸をＺ軸とするときに、本発明の撮像光学系のＺ軸に沿って最も物体側に突出した点から物体から最も遠い点までのＺ軸に沿って測った厚さを光学系の厚さｔとし、この厚さｔが以下の式を満たすことが望ましい。
【００３８】
ｔ＜２０ｍｍ ・・・（４）
この条件の上限の２０ｍｍを越えると、厚さが厚すぎ携帯性に欠けるものとなってしまう。
【００３９】
より好ましくは、
ｔ＜１０ｍｍ ・・・（４−１）
を満たすようにすることが望ましい。
【００４０】
さらに好ましくは、
ｔ＜６．５ｍｍ ・・・（４−２）
を満たすようにすることが最も良い。
【００４１】
なお、厚さが余り小さくなりすぎると、光の波長に比べて光学系が小さくなりすぎ、回折の影響で画像の品質が保てなくなる。
【００４２】
また、以上のような本発明の撮像光学系と、その撮像光学系によって形成された物体像を受光する位置に配置された電子撮像素子と、その電子撮像素子によって光電変換された電子信号を処理する処理手段と、操作者がその処理手段に入力したい情報信号を入力するための入力部と、その処理手段からの出力を表示する表示素子と、その処理手段からの出力を記録する記録媒体とを含み、その処理手段は、撮像光学系によって電子撮像素子に受光された物体像を表示素子に表示するように構成されている情報処理装置を本発明に基づいて構成することができる。
【００４３】
この場合に、その入力部がキーボードにて構成され、撮像光学系と電子撮像素子とが表示素子の周辺部又はキーボードの周辺部に内蔵されているパソコン装置を本発明に基づいて構成することができる。
【００４４】
また、以上のような本発明の撮像光学系と、その撮像光学系によって形成された物体像を受光する位置に配置された電子撮像素子と、電話信号を送信及び受信するためのアンテナと、電話番号等の信号を入力するための入力部と、その電子撮像素子によって受光された物体像を送信可能な信号に変換する信号処理部とを含んでいる電話装置を本発明に基づいて構成することができる。
【００４５】
また、以上のような本発明の撮像光学系と、その撮像光学系によって形成された物体像を受光する位置に配置された電子撮像素子と、その電子撮像素子によって光電変換された電子信号を処理する処理手段と、その電子撮像素子で受光された物体像を観察可能に表示する表示素子とを有し、電子撮像素子で受光された物体像の像情報を記録するための記録部材を内蔵又は挿脱するように構成され、その処理手段が、電子撮像素子に受光された物体像を表示素子に表示する表示処理機能と、電子撮像素子に受光された物体像を記録媒体に記録する記録処理機能とを有する電子カメラ装置を本発明に基づいて構成することができる。
【００４６】
【発明の実施の形態】
以下、本発明の撮像光学系の実施例１〜６について説明する。なお、実施例１については本願発明の参考例として掲載したものである。
【００４７】
実施例１〜６の構成パラメータは下記に示すが、面番号は、物体から光学系の前群を経て、絞り２を通り、後群を通って撮像素子の配置される像面３へ向う順光線追跡の面番号として示してある。座標の取り方に関しては、図１に示すように、軸上主光線１を、絞り２の中心を通り、像面（撮像素子の撮像面）３中心に到る光線で定義する。そして、軸上主光線１と前群の第１面３１の交点を偏心光学面の原点として、軸上主光線１に沿う方向をＺ軸正方向とし、このＺ軸と像面３中心を含む平面をＹ−Ｚ平面とし、原点を通りＹ−Ｚ平面に直交し、紙面の手前から裏面側に向かう方向をＸ軸正方向とし、Ｘ軸、Ｚ軸と右手直交座標系を構成する軸をＹ軸とする。また、光軸は紙面のＹ−Ｚ面内で折り曲げられるものとする。
【００４８】
そして、後記する構成パラメータ中において、偏心面については、光学系の原点の中心からその面の面頂位置の偏心量（Ｘ軸方向、Ｙ軸方向、Ｚ軸方向をそれぞれＸ，Ｙ，Ｚ）と、その面の中心軸（自由曲面については、前記（ａ）式のＺ軸）のＸ軸、Ｙ軸、Ｚ軸それぞれを中心とする傾き角（それぞれα，β，γ（°））とが与えられている。その場合、αとβの正はそれぞれの軸の正方向に対して反時計回りを、γの正はＺ軸の正方向に対して時計回りを意味する。なお、面の中心軸のα，β，γの回転のさせ方は、面の中心軸とそのＸＹＺ直交座標系を、まずＸ軸の回りで反時計回りにα回転させ、次に、その回転した面の中心軸を新たな座標系のＹ軸の回りで反時計回りにβ回転させると共に１度回転した座標系もＹ軸の回りで反時計回りにβ回転させ、次いで、その２度回転した面の中心軸を新たな座標系の新たな座標系のＺ軸の回りで時計回りにγ回転させるものである。
【００４９】
また、各実施例の光学系を構成する光学作用面の中、特定の面とそれに続く面が共軸光学系を構成する場合には、面間隔が与えられており、その他、媒質の屈折率、アッベ数が慣用法に従って与えられている。
【００５０】
また、本発明で用いられる自由曲面の面の形状は前記（ａ）式により定義し、その定義式のＺ軸が自由曲面の軸となる。
【００５１】
なお、データの記載されていない自由曲面に関する項は０である。屈折率については、ｄ線（波長５８７．５６ｎｍ）に対するものを表記してある。長さの単位はｍｍである。
【００５２】
また、自由曲面の他の定義式として、前記の（ｂ）式で与えられるＺｅｒｎｉｋｅ多項式がある。
【００５３】
その他の面の例として、次の定義式（ｃ）があげられる。
【００５４】
Ｚ＝ΣΣＣ_nmＸＹ
例として、ｋ＝７（７次項）を考えると、展開したとき、以下の式で表せる。
【００５５】

なお、本発明の実施例では、前記（ａ）式を用いた自由曲面で面形状が表現されているが、上記（ｂ）式、（ｃ）式を用いても同様の作用効果を得られるのは言うまでもない。
【００５６】
図１〜図６は、それぞれ本発明による実施例１〜６の撮像光学系のＹ−Ｚ断面とその光路を示す図である。
【００５７】
図１〜図５の実施例１〜５の撮像光学系は同じタイプのものであり、物体側から光の通る順に、絞り２より前の前群は、前面３１と後面３２が平行な平面からなるカバーガラス３０と第１プリズム１０からなり、絞り２より後の後群は、第２プリズム２０からなり、その第２プリズム２０の射出面２４の直後に像面（結像面）３が位置する。これらの実施例においては、像面３に入射する軸上主光線１と物体空間での軸上主光線１の方向は平行で同じ方向である。
【００５８】
そして、第１プリズム１０は第１面１１から第３面１３で構成され、その第１面１１は入射面、第２面１２は反射面、第３面１３は射出面であり、物体からの光線は、入射面１１を透過し、反射面１２で内面反射され、射出面１３を透過し、また、第２プリズム２０は第１面２１から第４面２４で構成され、その第１面２１は入射面、第２面２２は第１反射面、第３面２３は第２反射面、第４面２４は射出面であり、第１プリズム１０から絞り２を経た光線は、入射面２１を透過し、第１反射面２２で内面反射され、第２反射面２３で内面反射され、射出面２４を透過して像面３上に結像する。この撮像光学系においては、絞り２は開口絞りを構成し、中間像を形成しない。また、第２プリズム２０の第１面２１と第２面２２とがプリズム媒質を挟んで対向配置され、第３面２３と第４面２４とがプリズム媒質を挟んで対向配置され、第１面２１と第２面２２とを結ぶ光路が、第３面２３と第４面２４とを結ぶ光路とプリズム内で交差している。なお、実施例１〜５何れにおいても、第１プリズム１０の第１面１１〜第３面１３、第２プリズム２０の第１面２１から第４面２４は全て自由曲面からなる。
【００５９】
ここで、図１の実施例１の水平半画角は２５．２°、垂直半画角は１９．４４°、撮像面のサイズは３．２ｍｍ×２．４ｍｍ、焦点距離は３．４ｍｍ、Ｆナンバーは２．８であり、第１プリズム１０、第２プリズム２０は異なる種類のガラスからなり、２つのガラスプリズムを組み合わせて比較的小型な構成となっている。
【００６０】
図２の実施例２の水平半画角は２５．４８°、垂直半画角は１９．６７°、撮像面のサイズは４．４８ｍｍ×３．３６ｍｍ、焦点距離は４．７ｍｍ、Ｆナンバーは２．８であり、第１プリズム１０、第２プリズム２０は異なる種類のガラスからなり、２つのガラスプリズムを組み合わせて比較的大型な構成となっている。
【００６１】
図３の実施例３の水平半画角は２５．２°、垂直半画角は１９．４４°、撮像面のサイズは３．２ｍｍ×２．４ｍｍ、焦点距離は３．４ｍｍ、Ｆナンバーは２．８であり、第１プリズム１０はプラスチック、第２プリズム２０はガラスからなり、プラスチックプリズムとガラスプリズムを組み合わせて比較的小型な構成となっている。
【００６２】
図４の実施例４の水平半画角は２５．４８°、垂直半画角は１９．６７°、撮像面のサイズは４．４８ｍｍ×３．３６ｍｍ、焦点距離は４．７ｍｍ、Ｆナンバーは２．８であり、第１プリズム１０、第２プリズム２０は異なる種類のプラスチックからなり、２つのプラスチックを組み合わせて比較的大型な構成となっている。
【００６３】
図５の実施例５の水平半画角は２５．２°、垂直半画角は１９．４４°、撮像面のサイズは３．２ｍｍ×２．４ｍｍ、焦点距離は３．４ｍｍ、Ｆナンバーは２．８であり、第１プリズム１０、第２プリズム２０は異なる種類のプラスチックからなり、２つのプラスチックを組み合わせて比較的小型な構成となっている。
【００６４】
図６の実施例６の撮像光学系は以上の実施例と異なるタイプのものであり、物体側から光の通る順に、絞り２より前の前群は、前面３１と後面３２が平行な平面からなるカバーガラス３０と第１プリズム１０からなり、絞り２より後の後群は、第２プリズム２０からなり、その第２プリズム２０の射出面２４の直後に像面（結像面）３が位置する。この実施例においては、像面３に入射する軸上主光線１と物体空間での軸上主光線１の方向は平行で反対方向となる。
【００６５】
そして、第１プリズム１０は第１面１１から第３面１３で構成され、その第１面１１は入射面、第２面１２は反射面、第３面１３は射出面であり、物体からの光線は、入射面１１を透過し、反射面１２で内面反射され、射出面１３を透過し、また、第２プリズム２０は第１面２１から第４面２４で構成され、その第１面２１は入射面、第２面２２は全反射面の第１反射面と射出面とを兼用する兼用面、第３面２３は第２反射面、第４面２４は第３反射面であり、第１プリズム１０から絞り２を経た光線は、入射面２１を透過し、第１反射面２２で全反射され、第２反射面２３で内面反射され、第３反射面２４で内面反射され、今度は第２面２２を透過して像面３上に結像する。この撮像光学系においては、絞り２は開口絞りを構成し、中間像を形成しない。また、第２プリズム２０中では、光線が１回転して、第１面２１と第２面２２とを結ぶ光路が、第４面２４と第２面２２とを結ぶ光路とプリズム内で交差している。そして、第１プリズム１０の第１面１１〜第３面１３、第２プリズム２０の第１面２１から第４面２４は全て自由曲面からなる。
【００６６】
ここで、図６の実施例６の水平半画角は２５．２°、垂直半画角は１９．４４°、撮像面のサイズは３．２ｍｍ×２．５ｍｍ、焦点距離は３．４ｍｍ、Ｆナンバーは２．８であり、第１プリズム１０、第２プリズム２０は異なる種類のガラスからなる。
【００６７】
以下に、実施例１〜８の数値データを示す。これら表中の“ＦＦＳ”は自由曲面、“ＲＥ”は反射面を示す。
【００６８】

【００６９】

【００７０】

【００７１】

【００７２】

【００７３】

【００７４】
次に、上記実施例１、６の横収差図をそれぞれ図７、図８に示す。これらの横収差図において、括弧内に示された数字は（水平（Ｘ方向）画角，垂直（Ｙ方向）画角）を表し、その画角における横収差を示す。
【００７５】
次に、上記各実施例の条件（１）、（３）、（４）に関する値を以下に示す。
【００７６】

【００７７】
以上の実施例では、絞りの前後にそれぞれ１個の偏心プリズムを配置していたが、何れか一方あるいは両方に複数の偏心プリズムを配置してもよいし、偏心プリズム以外のミラーやレンズを配置してもよい。このような場合においても、絞りの前側にある何れかの偏心プリズムの媒質と、絞りの後側にある何れかの偏心プリズムの媒質とが異なっていればよい。
ところで、本発明の絞りの両側に配置する偏心プリズムとしては、図１〜図６に示したような内部反射回数が１回〜３回の偏心プリズムに限定されずに、内部反射回数が２回以上の公知の種々の偏心プリズムを用いることができる。その例を以下に示す。なお、何れも順光線追跡で遠方に位置する物体を瞳１３１を経て像面１３６に結像する偏心プリズムＰとして説明するが、光路を逆にして像面１３６側から光線が入射し、瞳１３１側に結像する偏心プリズムＰとしても使用することができる。
【００７８】
図９の場合は、偏心プリズムＰは第１面１３２、第２面１３３、第３面１３４、第４面１３５からなり、入射瞳１３１を通って入射した光は、第１面１３２で屈折して偏心プリズムＰに入射し、第２面１３３で内部反射し、第３面１３４でＺ字型の光路を形成するように内部反射し、第４面１３５に入射して屈折されて、像面１３６に結像する。
【００７９】
図１０の場合は、偏心プリズムＰは第１面１３２、第２面１３３、第３面１３４、第４面１３５からなり、入射瞳１３１を通って入射した光は、第１面１３２で屈折して偏心プリズムＰに入射し、第２面１３３で内部反射し、第３面１３４に入射して全反射し、第４面１３５に入射して内部反射し、再び第３面１３４に入射して今度は屈折されて、像面１３６に結像する。
【００８０】
図１１の場合は、偏心プリズムＰは第１面１３２、第２面１３３、第３面１３４、第４面１３５からなり、入射瞳１３１を通って入射した光は、第１面１３２で屈折して偏心プリズムＰに入射し、第２面１３３で内部反射し、第３面１３４に入射して内部反射し、第２面１３３に再度入射して内部反射し、第４面１３５に入射して屈折されて、像面１３６に結像する。
【００８１】
図１２の場合は、偏心プリズムＰは第１面１３２、第２面１３３、第３面１３４、第４面１３５からなり、入射瞳１３１を通って入射した光は、第１面１３２で屈折して偏心プリズムＰに入射し、第２面１３３で内部反射し、第３面１３４に入射して内部反射し、第２面１３３に再度入射して内部反射し、第４面１３５に入射して内部反射し、第２面１３３に再度入射して今度は屈折されて、像面１３６に結像する。
【００８２】
図１３の場合は、偏心プリズムＰは第１面１３２、第２面１３３、第３面１３４からなり、入射瞳１３１を通って入射した光は、第１面１３２で屈折して偏心プリズムＰに入射し、第２面１３３で内部反射し、再び第１面１３２に入射して今度は全反射し、第３面１３４で内部反射し、三たび第１面１３２に入射して全反射し、第３面１３４に再度入射して今度は屈折されて、像面１３６に結像する。
【００８３】
図１４の場合は、偏心プリズムＰは第１面１３２、第２面１３３、第３面１３４からなり、入射瞳１３１を通って入射した光は、第１面１３２で屈折して偏心プリズムＰに入射し、第２面１３３で内部反射し、再び第１面１３２に入射して今度は全反射し、第３面１３４で内部反射し、三たび第１面１３２に入射して全反射し、再び第３面１３４に入射して内部反射し、四たび第１面１３２に入射して今度は屈折されて、像面１３６に結像する。
【００８４】
さらには、後記の図１６の第２プリズム２０のように、第１面２１から第４面２４からなり、プリズム内で３回の反射をするものであってもよく、あるいは、後記の図１７の第２プリズム２０のように、第１面２１から第３面２３からなり、その第２面２２が全反射面と射出面を兼用するプリズム内で２回の反射をするものであってもよく、あるいは、後記の図１８の第２プリズム２０のように、第１面２１から第３面２３からなり、その第１面２１が入射面と全反射面を兼用するプリズム内で２回の反射をするものであってもよく、これらを絞り２の前側あるいは、後側の偏心プリズムとして用いるようにすることもできる。
【００８５】
以下の図１５〜図１９に、前記実施例１〜６の場合とは異なるプリズムの組み合わせの本発明の撮像光学系を示す。ただし、数値データは省く。
【００８６】
図１５の場合は、第１プリズム１０にも、実施例１〜５の第２プリズム２０と同様の偏心プリズムを用いた例であり、第１プリズム１０は第１面１１から第４面１４で構成され、その第１面１１は入射面、第２面１２は第１反射面、第３面１３は第２反射面、第４面１４は射出面であり、物体からの光線は、入射面１１を透過し、第１反射面１２で内面反射され、第２反射面１３で内面反射され、射出面１４を透過し、また、第２プリズム２０は第１面２１から第４面２４で構成され、その第１面２１は入射面、第２面２２は第１反射面、第３面２３は第２反射面、第４面２４は射出面であり、第１プリズム１０から絞り２を経た光線は、入射面２１を透過し、第１反射面２２で内面反射され、第２反射面２３で内面反射され、射出面２４を透過して像面３上に結像する。第１プリズム１０、第２プリズム２０共、その第１面１１、２１と第２面１２、２２とがプリズム媒質を挟んで対向配置され、第３面１３、２３と第４面１４、２４とがプリズム媒質を挟んで対向配置され、第１面１１、２１と第２面１２、２２とを結ぶ光路が、第３面１３、２３と第４面１４、２４とを結ぶ光路とプリズム内で交差している。
【００８７】
図１６の場合は、第１プリズム１０は図１５の場合と同じであり、第２プリズム２０として、第１面２１から第４面２４でなり、その第１面２１は入射面と第２反射面を兼用する兼用面、第２面２２は第１反射面、第３面２３は第３反射面、第４面２４は射出面であり、第１プリズム１０から絞り２を経た光線は、入射面２１を透過し、第１反射面２２で反射され、今度は第１面２１で全反射され、第３反射面２３で内面反射され、射出面２４を透過して像面３上に結像する。この第２プリズム２０においては、プリズム中で光線はＭ字型の光路を形成するように内部反射する。
【００８８】
図１７の場合は、第１プリズム１０は前記実施例１〜６の場合と同じであり、第２プリズム２０として、第１面２１から第３面２３でなり、その第１面２１は入射面、第２面２２は第１反射面と射出面を兼用する兼用面、第３面２３は第２反射面であり、第１プリズム１０から絞り２を経た光線は、入射面２１を透過し、第１反射面２２で全反射され、第２反射面２３で内面反射され、今度は第２面２２を透過して像面３上に結像する。
【００８９】
図１８の場合は、第１プリズム１０は前記実施例１〜６の場合と同じであり、第２プリズム２０として、第１面２１から第３面２３でなり、その第１面２１は入射面と第２反射面を兼用する兼用面、第２面２２は第１反射面、第３面２３は射出面であり、第１プリズム１０から絞り２を経た光線は、入射面２１を透過し、第１反射面２２で反射され、今度は第１面２１で全反射され、射出面２３を透過して像面３上に結像する。
【００９０】
図１９は、絞り２より前側に１つの偏心プリズム１０を、絞り２より後側に２つの偏心プリズム２０、２０’を配置して本発明の撮像光学系を構成する場合を示す図であり、何れの偏心プリズム１０、２０、２０’もプリズム内で１回の反射をする偏心プリズムを用いている。
【００９１】
さて、以上のような本発明の撮像光学系は、物体像を形成しその像をＣＣＤや銀塩フィルムといった撮像素子に受光させて撮影を行う撮影装置、とりわけカメラに用いることができる。また、物体像を接眼レンズを通して観察する観察装置、とりわけカメラのファインダー部の対物光学系としても用いることが可能である。
【００９２】
図２０〜図２２は、本発明の撮像光学系を電子カメラのファインダー部の対物光学系に組み込んだ構成の概念図を示す。図２０は電子カメラ４０の外観を示す前方斜視図、図２１は同後方斜視図、図２２は電子カメラ４０の構成を示す断面図である。電子カメラ４０は、この例の場合、撮影用光路４２を有する撮影光学系４１、ファインダー用光路４４を有するファインダー光学系４３、シャッター４５、フラッシュ４６、液晶表示モニター４７等を含み、カメラ４０の上部に配置されたシャッター４５を押圧すると、それに連動して撮影用対物光学系４８を通して撮影が行われる。撮影用対物光学系４８によって形成された物体像が、ローパスフィルター、赤外カットフィルター等のフィルター５１を介してＣＣＤ４９の撮像面５０上に形成される。このＣＣＤ４９で受光された物体像は、処理手段５２を介し、電子画像としてカメラ背面に設けられた液晶表示モニター４７に表示される。また、この処理手段５２にはメモリ等が配置され、撮影された電子画像を記録することもできる。なお、このメモリは処理手段５２と別体に設けらてもよいし、フロッピーディスク等により電子的に記録書込を行うように構成してもよい。また、ＣＣＤ４９に代わって銀塩フィルムを配置した銀塩カメラとして構成してもよい。
【００９３】
さらに、ファインダー用光路４４上には、ファインダー用対物光学系５３が配置されており、このファインダー用対物光学系５３は、カバーレンズ５４、第１プリズム１０、開口絞り２、第２プリズム２０、フォーカス用レンズ６６からなり、カバーレンズ５４あるいは第１プリズム１０から第２プリズム２０までの結像光学系として、本発明による撮像光学系を用いている。また、カバー部材として用いられているカバーレンズ５４は、負のパワーを有するレンズであり、画角を拡大している。また、第２プリズム２０の後方に配置されているフォーカス用レンズ６６は光軸の前後方向へ位置調節可能になっており、ファインダー用対物光学系５３のピント調節に用いられる。このファインダー用対物光学系５３によって結像面６７上に形成された物体像は、像正立部材であるポロプリズム５５の視野枠５７上に形成される。なお、視野枠５７は、ポロプリズム５５の第１反射面５６と第２反射面５８との間を分離し、その間に配置されている。このポロプリズム５５の後方には、正立正像にされた像を観察者眼球Ｅに導く接眼光学系５９が配置されている。
【００９４】
このように構成されたカメラ４０は、ファインダー用対物光学系５３を少ない光学部材で構成でき、高性能・低コスト化が実現できると共に、対物光学系５３の光路自体を折り曲げて構成できるため、カメラ内部での配置の自由度が増し、設計上有利となる。
【００９５】
なお、図２２の構成において、撮影用対物光学系４８の構成については言及しなかったが、撮影用対物光学系４８としては屈折型同軸光学系の他に、本発明による２つ以上のプリズム１０、２０からなる何れかのタイプの撮像光学系を用いることも当然可能である。
【００９６】
次に、図２３は、本発明の撮像光学系を電子カメラ４０の撮影部の撮影用対物光学系４
８に組み込んだ構成の概念図を示す。この場合は、撮影用光路４２上に配置された撮影用対物光学系４８に、第１プリズム１０、開口絞り２、第２プリズム２０からなる本発明による撮像光学系を用いている。この撮影用対物光学系４８により形成された物体像は、ローパスフィルター、赤外カットフィルター等のフィルター５１を介してＣＣＤ４９の撮像面５０上に形成される。このＣＣＤ４９で受光された物体像は、処理手段５２を介し、液晶表示素子（ＬＣＤ）６０上に電子像として表示される。また、この処理手段５２は、ＣＣＤ４９で撮影された物体像を電子情報として記録する記録手段６１の制御も行う。ＬＣＤ６０に表示された画像は、接眼光学系５９を介して観察者眼球Ｅに導かれる。この接眼光学系５９は偏心プリズムからなり、この例では、入射面６２と、反射面６３と、反射と屈折の兼用面６４の３面から構成されている。また、２つの反射作用を持った面６３、６４の中、少なくとも一方の面、望ましくは両方の面が、光束にパワーを与え、かつ、偏心収差を補正する唯一の対称面を持つ面対称自由曲面にて構成されている。そして、この唯一の対称面は、撮影用対物光学系４８のプリズム１０、２０が有する面対称自由曲面の唯一の対称面と略同一平面上に形成されている。また、この撮影用対物光学系４８は他のレンズ（正レンズ、負レンズ）をプリズム１０、２０の物体側、プリズム間あるいは像側にその構成要素として含んでいてもよい。
【００９７】
このように構成されたカメラ４０は、撮影用対物光学系４８を少ない光学部材で構成でき、高性能・低コスト化が実現できると共に、光学系全体を同一平面上に並べて配置できるため、この配置平面と垂直方向の厚みの簿型化が実現できる。
【００９８】
なお、本例では、撮影用対物光学系４８のカバー部材６５はとして、平行平面板を配置しているが、前例と同様に、パワーを持ったレンズを用いてもよい。
【００９９】
ここで、カバー部材を設けずに、本発明の撮像光学系中の最も物体側に配置された面をカバー部材と兼用することもできる。
【０１００】
次に、図２４〜図２６は本発明の撮像光学系を情報処理装置の一例であるパソコンに内蔵した構成を示す概念図である。
【０１０１】
図２４はパソコン３００のカバーを開いた前方斜視図、図２５はパソコン３００の撮影光学系３０３の断面図、図２６は図２４の状態の側面図である。図２４〜図２６に示されるように、パソコン３００は、外部から繰作者が情報を入力するためのキーボード３０１と、図示を省略した情報処理手段や記録手段と、情報を操作者に表示するモニター３０２と、操作者自身や周辺の像を撮影するための撮影光学系３０３とを有している。ここで、モニター３０２は、図示しないバックライトにより背面から照明する透過型液晶表示素子や、前面からの光を反射して表示する反射型液晶表示素子や、ＣＲＴディスプレイ等であってよい。また、図中、撮影光学系３０３は、モニター３０２の右上に内蔵されているが、その場所に限らず、モニター３０２の周囲や、キーボード３０１の周囲のどこであってもよい。
【０１０２】
この撮影光学系３０３は、撮影光路３０４上に、本発明の撮像光学系からなる対物光学系１００と、像を受光する撮像素子チップ１６２とを有している。これらはパソコン３００に内蔵されている。
【０１０３】
ここで、撮像素子チップ１６２上には付加的にｌＲカットフィルター１８０が貼り付けられて撮像ユニット１６０として一体に形成され、対物光学系１００の鏡枠１０１の後端にワンタッチで嵌め込まれて取り付け可能になっているため、対物光学系１００と撮像素子チップ１６２の中心合わせや面間隔の調整が不要であり、組立が簡単となっている。また、鏡枠１０１の先端には、対物光学系１００を保護するためのカバーガラス１０２が配置されている。
【０１０４】
撮像素子チップ１６２で受光された物体像は、端子１６６を介して、パソコン３００の処理手段に入力され、電子画像としてモニター３０２に表示される、図２５には、その一例として、操作者の撮影された画像３０５が示されている。また、この画像３０５は、処理手段を介し、インターネットや電話を介して、遠隔地から通信相手のパソコンに表示されることも可能である。
【０１０５】
次に、情報処理装置の他の例として電話、特に、その中でも持ち運びに便利な携帯電話に本発明の撮像光学系を内蔵した例を図２７に示す。
【０１０６】
図２７（ａ）は携帯電話４００の正面図、図２７（ｂ）は側面図、図２７（ｃ）は撮影光学系４０５の断面図である。図２７（ａ）〜（ｃ）に示されるように、携帯電話４００は、操作者の声を情報として入力するマイク部４０１と、通話相手の声を出力するスピーカ部４０２と、操作者が情報を入力する入力ダイアル４０３と、操作者自身や通話相手等の撮影像と電話番号等の情報を表示するモニター４０４と、撮影光学系４０５と、通信電波の送信と受信を行うアンテナ４０６と、画像情報や通信情報、入力信号等の処理を行う処理手段（図示せず）とを有している。ここで、モニター４０４は液晶表示素子である。また、図中、各構成の配置位置は、特にこれらに限られない。この撮影光学系４０５は、撮影光路４０７上に配置された本発明の撮像光学系からなる対物光学系１００と、像を受光する撮像素子チップ１６２とを有している。これらは、携帯電話４００に内蔵されている。
【０１０７】
ここで、撮像素子チップ１６２上には付加的にｌＲカットフィルター１８０が貼り付けられて撮像ユニット１６０として一体に形成され、対物レンズ１２の鏡枠１３の後端にワンタッチで嵌め込まれて取り付け可能になっているため、対物レンズ１２と撮像素子チップ１６２の中心合わせや面間隔の調整が不要であり、組立が簡単となっている。また、鏡枠１０１の先端には、対物光学系１００を保護するためのカバーガラス１０２が配置されている。
【０１０８】
撮影素子チップ１６２で受光された物体像は、端子１６６を介して、図示していない処理手段に入力され、電子画像としてモニター４０４に、又は、通信相手のモニターに、又は、両方に表示される。また、通信相手に画像を送信する場合、撮像素子チップ１６２で受光された物体像の情報を、送信可能な信号へと変換する信号処理機能が処理手段には含まれている。
【０１０９】
以上の本発明の撮像光学系は、例えば次のように構成することができる。
【０１１０】
〔１〕 絞りの両側にそれぞれ回転非対称な反射面を持つ少なくとも１つの偏心プリズムが配置され、中間像を結像しない撮像光学系において、絞りより前の少なくとも１つの偏心プリズムの媒質の光学的性質と絞りより後の少なくとも１つの偏心プリズムの媒質の光学的性質とが異なることを特徴とする撮像光学系。
【０１１１】
〔２〕 前記絞りより前の少なくとも１つの偏心プリズムの媒質と前記絞りより後の少なくとも１つの偏心プリズムの媒質のアッベ数の差の絶対値Δνが、
５＜Δν＜８０ ・・・（１）
を満たすことを特徴とする上記１記載の撮像光学系。
【０１１２】
〔３〕 絞りより前側のパワーが負で、絞りより後側のパワーが正で、前記絞りより前の少なくとも１つの偏心プリズムの媒質のアッベ数が小さく、前記絞りより後の少なくとも１つの偏心プリズムの媒質のアッベ数がより大きいことを特徴とする上記２記載の撮像光学系。
【０１１３】
〔４〕 絞りより前側の屈折力を有する要素の最も物体側の面が正のパワー有することを特徴とする上記３記載の撮像光学系。
【０１１４】
〔５〕 前記各偏心プリズムの入射面又は射出面の少なくとも何れか一方が曲面からなることを特徴とする上記１から４の何れか１項記載の撮像光学系。
【０１１５】
〔６〕 前記曲面が球面以外の面からなることを特徴とする上記５記載の撮像光学系。
【０１１６】
〔７〕 前記曲面が回転非対称な面からなることを特徴とする上記６記載の撮像光学系。
【０１１７】
〔８〕 前記絞りの中心を通り、撮像面の中心に到る光線を軸上主光線とするとき、物体空間での軸上主光線方向に対する前記絞りを通過するときの軸上主光線方向の偏角θが、
４５°＜θ＜１３５° ・・・（２）
を満たすことを特徴とする上記１から７の何れか１項記載の撮像光学系。
【０１１８】
〔９〕 絞りより前側に反射面を１面のみ持つ１つの偏心プリズムが配置され、次の条件を満たすことを特徴とする上記８記載の撮像光学系。
【０１１９】
９２°＜θ＜１３５° ・・・（３）
〔１０〕 物体空間における光軸に沿う軸をＺ軸とするときに、光学系のＺ軸に沿って最も物体側に突出した点から物体から最も遠い点までのＺ軸に沿って測った厚さをｔとするとき、が以下の式を満たすこと特徴とする上記１から９の何れか１項記載の撮像光学系。
【０１２０】
ｔ＜２０ｍｍ ・・・（４）
〔１１〕 上記１から１０の何れか１項記載の撮像光学系と、前記撮像光学系によって形成された物体像を受光する位置に配置された電子撮像素子と、前記電子撮像素子によって光電変換された電子信号を処理する処理手段と、操作者が前記処理手段に入力したい情報信号を入力するための入力部と、前記処理手段からの出力を表示する表示素子と、前記処理手段からの出力を記録する記録媒体とを含み、
前記処理手段は、前記撮像光学系によって前記電子撮像素子に受光された物体像を前記表示素子に表示するように構成されていることを特徴とする情報処理装置。
【０１２１】
〔１２〕 上記１１において、
前記入力部がキーボードにて構成され、前記撮像光学系と前記電子撮像素子とが前記表示素子の周辺部又は前記キーボードの周辺部に内蔵されていることを特徴とするパソコン装置。
【０１２２】
〔１３〕 上記１から１０の何れか１項記載の撮像光学系と、前記撮像光学系によって形成された物体像を受光する位置に配置された電子撮像素子と、電話信号を送信及び受信するためのアンテナと、電話番号等の信号を入力するための入力部と、前記電子撮像素子によって受光された物体像を送信可能な信号に変換する信号処理部とを含んでいることを特徴とする電話装置。
【０１２３】
〔１４〕 上記１から１０の何れか１項記載の撮像光学系と、前記撮像光学系によって形成された物体像を受光する位置に配置された電子撮像素子と、前記電子撮像素子によって光電変換された電子信号を処理する処理手段と、前記電子撮像素子で受光された物体像を観察可能に表示する表示素子とを有し、前記電子撮像素子で受光された物体像の像情報を記録するための記録部材を内蔵又は挿脱するように構成され、前記処理手段が、前記電子撮像素子に受光された物体像を前記表示素子に表示する表示処理機能と、前記電子撮像素子に受光された物体像を前記記録媒体に記録する記録処理機能とを有することを特徴とする電子カメラ装置。
【０１２４】
【発明の効果】
以上の説明から明らかなように、本発明によると、特に倍率の色収差を始めとして諸収差を良好に補正した小型で高性能な複数の偏心プリズムからなる撮像光学系を提供することができる。
【図面の簡単な説明】
【図１】本発明の実施例１の撮像光学系の断面と光路を示す図である。
【図２】本発明の実施例２の撮像光学系の断面と光路を示す図である。
【図３】本発明の実施例３の撮像光学系の断面と光路を示す図である。
【図４】本発明の実施例４の撮像光学系の断面と光路を示す図である。
【図５】本発明の実施例５の撮像光学系の断面と光路を示す図である。
【図６】本発明の実施例６の撮像光学系の断面と光路を示す図である。
【図７】実施例１の撮像光学系の横収差図である。
【図８】実施例６の撮像光学系の横収差図である。
【図９】本発明の撮像光学系に使用可能な偏心プリズムの１つの変形例を示す図である。
【図１０】偏心プリズムの別の変形例を示す図である。
【図１１】偏心プリズムの別の変形例を示す図である。
【図１２】偏心プリズムの別の変形例を示す図である。
【図１３】偏心プリズムの別の変形例を示す図である。
【図１４】偏心プリズムの別の変形例を示す図である。
【図１５】実施例１〜６とは異なるプリズムの組み合わせからなる本発明の撮像光学系の例を示す図である。
【図１６】実施例１〜６とは異なるプリズムの組み合わせからなる本発明の撮像光学系の別の例を示す図である。
【図１７】実施例１〜６とは異なるプリズムの組み合わせからなる本発明の撮像光学系の別の例を示す図である。
【図１８】実施例１〜６とは異なるプリズムの組み合わせからなる本発明の撮像光学系の別の例を示す図である。
【図１９】実施例１〜６とは異なるプリズムの組み合わせからなる本発明の撮像光学系の別の例を示す図である。
【図２０】本発明の撮像光学系を適用した電子カメラの外観を示す前方斜視図である。
【図２１】図２０の電子カメラの後方斜視図である。
【図２２】図２０の電子カメラの構成を示す断面図である。
【図２３】本発明の撮像光学系を適用した別の電子カメラの概念図である。
【図２４】本発明の撮像光学系が対物光学系として組み込れたパソコンのカバーを開いた前方斜視図である。
【図２５】パソコンの撮影光学系の断面図である。
【図２６】図２４の状態の側面図である。
【図２７】本発明の撮像光学系が対物光学系として組み込れた携帯電話の正面図、側面図、その撮影光学系の断面図である。
【符号の説明】
１…開口絞り
２…軸上主光線（光軸）
３…像面（結像面）
１０…第１プリズム
１１…第１面
１２…第２面
１３…第３面
１４…第４面
２０…第２プリズム
２０’…第３プリズム
２１…第１面
２２…第２面
２３…第３面
２４…第４面
３０…カバーガラス
３１…前面（第１面）
３２…後面（第２面）
４０…電子カメラ
４１…撮影光学系
４２…撮影用光路
４３…ファインダー光学系
４４…ファインダー用光路
４５…シャッター
４６…フラッシュ
４７…液晶表示モニター
４８…撮影用対物光学系
４９…ＣＣＤ
５０…撮像面
５１…フィルター
５２…処理手段
５３…ファインダー用対物光学系
５４…カバーレンズ
５５…ポロプリズム
５６…第１反射面
５７…視野枠
５８…第２反射面
５９…接眼光学系
６０…液晶表示素子（ＬＣＤ）
６１…記録手段
６２…入射面
６３…反射面
６４…反射と屈折の兼用面
６５…カバー部材
６６…フォーカス用レンズ
６７…結像面
１００…対物光学系
１０１…鏡枠
１０２…カバーガラス
１３１…瞳
１３２…第１面
１３３…第２面
１３４…第３面
１３５…第４面
１３６…像面
１６０…撮像ユニット
１６２…撮像素子チップ
１６６…端子
１８０…ｌＲカットフィルター
３００…パソコン
３０１…キーボード
３０２…モニター
３０３…撮影光学系
３０４…撮影光路
３０５…画像
４００…携帯電話
４０１…マイク部
４０２…スピーカ部
４０３…入力ダイアル
４０４…モニター
４０５…撮影光学系
４０６…アンテナ
４０７…撮影光路
Ｅ…観察者眼球
Ｐ…偏心プリズム[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an imaging optical system, and more particularly to a compact and high-performance imaging optical system using a catadioptric optical system.
[0002]
[Prior art]
There have been many proposals for prism optical systems using free-form surfaces. Among them, with respect to an imaging optical system in which a plurality of decentered prisms are arranged with a diaphragm interposed therebetween, JP-A-10-20196, JP-A-2000-19401 to 19407, JP-A-2000-11799-111800, JP-A-2000-121943. Etc. have been proposed. In these, the same medium is used for the eccentric prism.
[0003]
[Problems to be solved by the invention]
By the way, as the image pickup optical system is made smaller, the pixels of the image pickup element become smaller and higher definition, and the image pickup optical system needs to have high performance with various aberrations corrected correspondingly. In an imaging optical system using such a decentered prism, coma and the like can be improved by arranging a stop near the center of the optical system so as to improve symmetry, but it results from chromatic dispersion of the refractive index. The chromatic aberration of magnification becomes a problem.
[0004]
The present invention has been made in view of such problems of the prior art, and an object thereof is an imaging optical system in which a plurality of decentered prisms are arranged with a diaphragm interposed therebetween, particularly various chromatic aberrations including magnification. The objective is to provide a compact and high-performance lens with good aberration correction.
[0005]
[Means for Solving the Problems]
In the imaging optical system of the present invention that achieves the above object, at least one decentered prism having rotationally asymmetric reflecting surfaces is arranged on both sides of the stop, and in the imaging optical system that does not form an intermediate image, at least before the stop. The optical property of the medium of one decentered prism is different from the optical property of the medium of at least one decentered prism after the stop.
[0006]
In this case, the absolute value Δν of the difference between the Abbe numbers of the medium of at least one eccentric prism before the diaphragm and the medium of at least one eccentric prism after the diaphragm is
5 <Δν <80 (1)
It is desirable to satisfy.
[0007]
Further, the power on the front side of the stop is negative, the power on the back side of the stop is positive, the Abbe number of the medium of at least one decentered prism before the stop is small, and the medium of the medium of at least one decentered prism after the stop is small. It is desirable that the Abbe number is larger.
[0008]
Hereinafter, the reason and effect | action which take the said structure in this invention are demonstrated.
[0009]
As described above, at least one decentered prism having a rotationally asymmetric reflecting surface on each side of the stop is disposed, and in an imaging optical system that does not form an intermediate image, the stop is disposed near the center of the optical system. However, since the symmetry can be improved, monochromatic aberration such as coma is improved. However, since the entrance surface and exit surface of each prism are both refracting surfaces, chromatic aberration caused by chromatic dispersion of the refractive index, especially magnification. This chromatic aberration cannot be corrected even if it is a rotationally asymmetric free-form surface as the surface shape of the prism. In particular, when the optical system is downsized, the wavelength becomes relatively large, and it becomes difficult to correct the chromatic aberration of magnification.
[0010]
Therefore, in the present invention, by making the optical property of the medium of at least one decentered prism before the stop different from the optical property of the medium of at least one decentered prism after the stop, chromatic aberration, in particular, The chromatic aberration of magnification is corrected. Thus, if the optical properties of the medium of the decentered prism in the front group after the stop and the optical properties of the medium of the decentered prism in the rear group after the stop are made different, chromatic aberration based on dispersion on the refractive surface of the prism, In particular, the lateral chromatic aberration can be satisfactorily corrected.
[0011]
Here, the optical properties of the medium are specifically the refractive index and the Abbe number, but at least one of them needs to be different.
[0012]
Also, typically, as shown in the embodiments described later, the imaging optical system of the present invention is configured to have one decentered prism before the stop and one decentered prism after the stop. It is also possible to configure with an eccentric prism. In that case, if the optical properties of the medium of one prism in the lowest front group and one prism in the rear group are different, chromatic aberration can be corrected.
[0013]
More specifically, the absolute value Δν of the difference between the Abbe numbers of the medium of at least one decentered prism in the front group and the medium of at least one decentered prism in the rear group is:
5 <Δν <80 (1)
It is desirable to satisfy.
[0014]
If the lower limit of 5 of this condition is exceeded, it will be difficult to correct lateral chromatic aberration. If the upper limit of 80 is exceeded, it is preferable for correcting chromatic aberration of magnification, but the number of types of media is reduced, making it difficult to correct other aberrations.
[0015]
More preferably,
10 <Δν <60 (1-1)
It is desirable to satisfy.
[0016]
More preferably,
20 <Δν <40 (1-2)
It is best to satisfy.
[0017]
By the way, when imaging using an electronic imaging device, it is necessary to have a telecentric configuration in which an imaged ray enters the imaging surface substantially perpendicularly. In that case, the power of the group after the stop needs to be positive. When the rear group is set to positive power, the power of the front group may be positive or negative. However, if the power of the front group is set to positive, the imaging surface may be embedded in the rear group. There are many. Therefore, it is desirable to set the power of the front group to be negative with the retro focus type.
[0018]
With such a power arrangement, since the stop is in the middle of the system, the image height of the incident off-axis principal ray is highest on the refracting surface of the first front surface. By arranging a medium with high dispersion (Abbe number is relatively small) on this surface, it is possible to easily correct lateral chromatic aberration.
[0019]
In this case, if the surface closest to the object side of the element having the refractive power on the front side of the stop, for example, the incident surface of the decentered prism excluding the cover glass has positive power, the effect of correcting the chromatic aberration of magnification can be further enhanced. it can.
[0020]
Here, it is desirable that at least one of the entrance surface and the exit surface of each eccentric prism is a curved surface.
[0021]
By configuring at least one of the entrance surface and exit surface, which are the refracting surfaces of each prism, as a curved surface, it is possible to share a part of the power of the front group and the rear group or a part of aberration correction. it can.
[0022]
In this case, the curved surface may be a rotationally symmetric aspherical surface other than a spherical surface, but by using a rotationally asymmetric surface, it is possible to correct aberrations caused by decentration.
[0023]
Here, as a rotationally asymmetric curved surface used for the reflecting surface and the refracting surface of the eccentric prism, for example, a free curved surface can be used. The free-form surface is defined by the following formula. The Z axis of this defining formula is the axis of the free-form surface.
[0024]

Here, the first term of the equation (a) is a spherical term, and the second term is a free-form surface term.
[0025]
In the spherical term,
c: vertex curvature
k: Conic constant (conical constant)
r = √ (X²+ Y²)
It is.
[0026]
The free-form surface term is

However, C_j(J is an integer of 2 or more) is a coefficient.
[0027]
In general, the free-form surface does not have a symmetric surface in both the XZ plane and the YZ plane, but by setting all odd-order terms of X to 0, the plane of symmetry is parallel to the YZ plane. Is a free-form surface with only one. Further, by setting all odd-numbered terms of Y to 0, a free-form surface having only one symmetry plane parallel to the XZ plane is obtained.
[0028]
Further, another defining formula of the free-form surface which is a surface of the rotationally asymmetric curved surface can be defined by a Zernike polynomial. The shape of this surface is defined by the following formula (b). The Z axis of the defining formula (b) is the axis of the Zernike polynomial. The definition of the rotationally asymmetric surface is defined by polar coordinates of the height of the Z axis with respect to the XY plane, R is the distance from the Z axis in the XY plane, A is the azimuth around the Z axis, and the X axis It is expressed by the rotation angle measured from.
[0029]

However, D_m(M is an integer of 2 or more) is a coefficient. To design an optical system that is symmetric in the X-axis direction, D_Four, D_Five, D₆, D_Ten, D₁₁, D₁₂, D₁₃, D₁₄, D₂₀, D_{twenty one}, D_{twenty two}Use….
[0030]
The above definition formula is shown for illustration of a rotationally asymmetric curved surface, and it goes without saying that the same effect can be obtained for any other definition formula.
[0031]
By the way, in order to reduce the thickness in the depth direction of the imaging optical system according to the present invention, when the light beam that passes through the center of the stop and reaches the center of the imaging surface is the axial principal ray, it is on-axis in the object space. The deflection angle θ of the axial principal ray direction when passing through the stop with respect to the principal ray direction is
45 ° <θ <135 ° (2)
It is desirable to satisfy.
[0032]
  Here, the declination θ defined above is 0 ° when the direction of the axial principal ray in the object space and the direction of the axial principal ray when passing through the stop are the same and parallel, and is parallel in the opposite direction. In this case, the angle θ becomes 180 °. By satisfying the above condition (2), the rear group after the stop can be arranged side by side with the front group, so that the thickness of the imaging optical system in the depth direction is reduced. It becomes possible to configure. When the upper limit of 135 ° is exceeded, the rear group comes out of the front group, and when the lower limit of 45 ° is exceeded, the rear group is positioned behind the front group. However, it becomes impossible to reduce the thickness in the depth direction.
[0033]
In particular, when the front group is configured by arranging one eccentric prism having only one reflecting surface in front of the stop,
92 ° <θ <135 ° (3)
It is desirable to satisfy.
[0034]
If the lower limit of 92 ° of the condition (3) is not reached, the influence of the decentration aberration generated by the decentering prism in the front group is large, and the asymmetric aberration cannot be corrected. When the upper limit of 135 ° is exceeded, interference between the front group eccentric prism and the rear group eccentric prism occurs. An attempt to avoid this interference results in a large optical system.
[0035]
More preferably,
95 ° <θ <125 ° (3-1)
It is desirable to satisfy.
[0036]
More preferably,
98 ° <θ <115 ° (3-2)
It is best to satisfy.
[0037]
Next, consider measuring the thickness t of the imaging optical system along the optical axis in the object space. When the axis along the optical axis in the object space is defined as the Z axis, the measurement was performed along the Z axis from the point that protruded closest to the object side along the Z axis of the imaging optical system of the present invention to the point farthest from the object. It is desirable that the thickness be the thickness t of the optical system, and this thickness t satisfy the following formula.
[0038]
t <20mm (4)
When the upper limit of 20 mm is exceeded, the thickness is too thick and lacks portability.
[0039]
More preferably,
t <10mm (4-1)
It is desirable to satisfy.
[0040]
More preferably,
t <6.5 mm (4-2)
It is best to satisfy.
[0041]
If the thickness is too small, the optical system becomes too small compared to the wavelength of light, and the image quality cannot be maintained due to the influence of diffraction.
[0042]
Also, the imaging optical system of the present invention as described above, an electronic imaging device arranged at a position for receiving an object image formed by the imaging optical system, and an electronic signal photoelectrically converted by the electronic imaging device are processed. Processing means, an input unit for inputting an information signal that the operator wants to input to the processing means, a display element for displaying the output from the processing means, and a recording medium for recording the output from the processing means And an information processing apparatus configured to display an object image received by the electronic imaging device by the imaging optical system on the display device, based on the present invention.
[0043]
In this case, a personal computer device in which the input unit is configured by a keyboard and the imaging optical system and the electronic imaging element are built in the peripheral part of the display element or the peripheral part of the keyboard can be configured based on the present invention. it can.
[0044]
Further, the imaging optical system of the present invention as described above, an electronic imaging device arranged at a position for receiving an object image formed by the imaging optical system, an antenna for transmitting and receiving telephone signals, and a telephone A telephone apparatus including an input unit for inputting a signal such as a number and a signal processing unit for converting an object image received by the electronic image sensor into a signal that can be transmitted is configured according to the present invention. Can do.
[0045]
Also, the imaging optical system of the present invention as described above, an electronic imaging device arranged at a position for receiving an object image formed by the imaging optical system, and an electronic signal photoelectrically converted by the electronic imaging device are processed. Or a display element that displays the object image received by the electronic image sensor so as to be observable, and has a recording member for recording image information of the object image received by the electronic image sensor. A display processing function configured to display the object image received by the electronic image sensor on the display element, and a recording process for recording the object image received by the electronic image sensor on a recording medium. An electronic camera device having a function can be configured based on the present invention.
[0046]
DETAILED DESCRIPTION OF THE INVENTION
Examples 1 to 6 of the imaging optical system according to the present invention will be described below.In addition, about Example 1, it published as a reference example of this invention.
[0047]
The configuration parameters of Examples 1 to 6 are shown below. The surface numbers pass from the object through the front group of the optical system, through the diaphragm 2, and through the rear group toward the image plane 3 where the image sensor is arranged. It is shown as a ray tracing surface number. As to how to obtain the coordinates, as shown in FIG. 1, the axial principal ray 1 is defined by a ray that passes through the center of the stop 2 and reaches the center of the image plane (imaging plane of the imaging device) 3. Then, the intersection of the axial principal ray 1 and the first surface 31 of the front group is the origin of the decentered optical surface, the direction along the axial principal ray 1 is the Z axis positive direction, and this Z axis and the center of the image plane 3 are included. The plane is the YZ plane, passes through the origin and is orthogonal to the YZ plane, the direction from the front of the page to the back side is the X axis positive direction, and the axes constituting the X axis, the Z axis, and the right hand orthogonal coordinate system The Y axis is assumed. The optical axis is bent in the YZ plane of the paper.
[0048]
In the constituent parameters to be described later, with respect to the decentered surface, the decentering amount from the center of the origin of the optical system to the surface top position of the surface (X-axis direction, Y-axis direction, and Z-axis direction are X, Y, and Z, respectively) And tilt angles (α, β, γ (°), respectively) about the X axis, the Y axis, and the Z axis of the central axis of the surface (for the free-form surface, the Z axis in the equation (a)) Is given. In this case, positive α and β mean counterclockwise rotation with respect to the positive direction of each axis, and positive γ means clockwise rotation with respect to the positive direction of the Z axis. Note that the α, β, and γ rotations of the central axis of the surface are performed by first rotating the central axis of the surface and its XYZ orthogonal coordinate system by α counterclockwise around the X axis, and then rotating the rotation. The center axis of the surface is rotated β counterclockwise around the Y axis of the new coordinate system, and the coordinate system rotated once is also rotated β counterclockwise around the Y axis and then rotated twice. The center axis of the surface is rotated γ clockwise around the Z axis of the new coordinate system.
[0049]
Further, among the optical action surfaces constituting the optical system of each embodiment, when a specific surface and a subsequent surface constitute a coaxial optical system, a surface interval is given, and in addition, the refractive index of the medium , Abbe numbers are given according to idioms.
[0050]
Further, the shape of the surface of the free curved surface used in the present invention is defined by the equation (a), and the Z axis of the defining equation becomes the axis of the free curved surface.
[0051]
In addition, the term regarding the free-form surface for which no data is described is zero. The refractive index is shown for d-line (wavelength 587.56 nm). The unit of length is mm.
[0052]
Another defining equation for free-form surfaces is the Zernike polynomial given by equation (b) above.
[0053]
The following definition formula (c) can be given as an example of other aspects.
[0054]
Z = ΣΣC_nmXY
As an example, when k = 7 (seventh order term) is considered, when expanded, it can be expressed by the following expression.
[0055]

In the embodiment of the present invention, the surface shape is expressed by a free-form surface using the equation (a). However, similar effects can be obtained by using the equations (b) and (c). Needless to say.
[0056]
FIGS. 1-6 is a figure which respectively shows the YZ cross section of the imaging optical system of Examples 1-6 by this invention, and its optical path.
[0057]
The imaging optical systems of Examples 1 to 5 in FIGS. 1 to 5 are of the same type, and the front group before the stop 2 is from a plane in which the front surface 31 and the rear surface 32 are parallel in the order in which light passes from the object side. The rear group after the stop 2 is composed of the second prism 20, and the image plane (imaging plane) 3 is positioned immediately after the exit surface 24 of the second prism 20. To do. In these embodiments, the axial principal ray 1 incident on the image plane 3 and the axial principal ray 1 in the object space are parallel and in the same direction.
[0058]
The first prism 10 is composed of a first surface 11 to a third surface 13, and the first surface 11 is an incident surface, the second surface 12 is a reflecting surface, and the third surface 13 is an exit surface. The light beam passes through the incident surface 11, is internally reflected by the reflecting surface 12, and passes through the exit surface 13, and the second prism 20 is composed of a first surface 21 to a fourth surface 24, and the first surface 21. Is the incident surface, the second surface 22 is the first reflecting surface, the third surface 23 is the second reflecting surface, the fourth surface 24 is the exit surface, and the light beam that has passed through the diaphragm 2 from the first prism 10 passes through the incident surface 21. The light is transmitted, is internally reflected by the first reflecting surface 22, is internally reflected by the second reflecting surface 23, passes through the exit surface 24, and forms an image on the image surface 3. In this imaging optical system, the stop 2 forms an aperture stop and does not form an intermediate image. Further, the first surface 21 and the second surface 22 of the second prism 20 are disposed to face each other with the prism medium interposed therebetween, and the third surface 23 and the fourth surface 24 are disposed to face each other with the prism medium sandwiched therebetween. The optical path connecting 21 and the second surface 22 intersects the optical path connecting the third surface 23 and the fourth surface 24 within the prism. In all of Examples 1 to 5, the first surface 11 to the third surface 13 of the first prism 10 and the first surface 21 to the fourth surface 24 of the second prism 20 are all free-form surfaces.
[0059]
Here, the horizontal half field angle of Example 1 of FIG. 1 is 25.2 °, the vertical half field angle is 19.44 °, the size of the imaging surface is 3.2 mm × 2.4 mm, the focal length is 3.4 mm, The F number is 2.8, and the first prism 10 and the second prism 20 are made of different types of glass, and have a relatively small configuration by combining two glass prisms.
[0060]
In FIG. 2, the horizontal half field angle is 25.48 °, the vertical half field angle is 19.67 °, the size of the imaging surface is 4.48 mm × 3.36 mm, the focal length is 4.7 mm, and the F-number is The first prism 10 and the second prism 20 are made of different types of glass, and have a relatively large structure by combining two glass prisms.
[0061]
The horizontal half field angle of Example 3 in FIG. 3 is 25.2 °, the vertical half field angle is 19.44 °, the size of the imaging surface is 3.2 mm × 2.4 mm, the focal length is 3.4 mm, and the F-number is The first prism 10 is made of plastic, and the second prism 20 is made of glass. The plastic prism and the glass prism are combined to form a relatively small size.
[0062]
In Example 4 of FIG. 4, the horizontal half field angle is 25.48 °, the vertical half field angle is 19.67 °, the size of the imaging surface is 4.48 mm × 3.36 mm, the focal length is 4.7 mm, and the F-number is The first prism 10 and the second prism 20 are made of different types of plastics, and have a relatively large structure by combining two plastics.
[0063]
In Example 5 of FIG. 5, the horizontal half field angle is 25.2 °, the vertical half field angle is 19.44 °, the imaging surface size is 3.2 mm × 2.4 mm, the focal length is 3.4 mm, and the F-number is The first prism 10 and the second prism 20 are made of different types of plastics, and have a relatively small configuration by combining two plastics.
[0064]
The imaging optical system of Embodiment 6 in FIG. 6 is of a different type from the above embodiments, and the front group before the diaphragm 2 is from a plane in which the front surface 31 and the rear surface 32 are parallel in the order in which light passes from the object side. The rear group after the stop 2 is composed of the second prism 20, and the image plane (imaging plane) 3 is positioned immediately after the exit surface 24 of the second prism 20. To do. In this embodiment, the directions of the axial principal ray 1 incident on the image plane 3 and the axial principal ray 1 in the object space are parallel and opposite to each other.
[0065]
The first prism 10 is composed of a first surface 11 to a third surface 13, and the first surface 11 is an incident surface, the second surface 12 is a reflecting surface, and the third surface 13 is an exit surface. The light beam passes through the incident surface 11, is internally reflected by the reflecting surface 12, and passes through the exit surface 13, and the second prism 20 is composed of a first surface 21 to a fourth surface 24, and the first surface 21. Is the entrance surface, the second surface 22 is the combined surface of the first reflection surface and the exit surface of the total reflection surface, the third surface 23 is the second reflection surface, the fourth surface 24 is the third reflection surface, The light beam that has passed through the diaphragm 2 from one prism 10 passes through the incident surface 21, is totally reflected by the first reflecting surface 22, is internally reflected by the second reflecting surface 23, and is internally reflected by the third reflecting surface 24. The light passes through the second surface 22 and forms an image on the image surface 3. In this imaging optical system, the stop 2 forms an aperture stop and does not form an intermediate image. In the second prism 20, the light beam makes one rotation, and the optical path connecting the first surface 21 and the second surface 22 intersects the optical path connecting the fourth surface 24 and the second surface 22 in the prism. ing. The first surface 11 to the third surface 13 of the first prism 10 and the first surface 21 to the fourth surface 24 of the second prism 20 are all free-form surfaces.
[0066]
Here, in Example 6 of FIG. 6, the horizontal half field angle is 25.2 °, the vertical half field angle is 19.44 °, the size of the imaging surface is 3.2 mm × 2.5 mm, the focal length is 3.4 mm, The F number is 2.8, and the first prism 10 and the second prism 20 are made of different types of glass.
[0067]
Below, the numerical data of Examples 1-8 are shown. In these tables, “FFS” indicates a free-form surface, and “RE” indicates a reflective surface.
[0068]

[0069]

[0070]

[0071]

[0072]

[0073]

[0074]
Next, lateral aberration diagrams of Examples 1 and 6 are shown in FIGS. 7 and 8, respectively. In these lateral aberration diagrams, the numbers shown in parentheses represent (horizontal (X direction) field angle, vertical (Y direction) field angle), and indicate lateral aberration at that field angle.
[0075]
Next, values relating to the conditions (1), (3), and (4) of the above embodiments are shown below.
[0076]

[0077]
In the above embodiments, one eccentric prism is arranged before and after the stop, but a plurality of eccentric prisms may be arranged on either one or both, and mirrors and lenses other than the eccentric prism are arranged. May be. Even in such a case, the medium of any decentered prism on the front side of the stop need only be different from the medium of any decentered prism on the rear side of the stop.
By the way, the decentered prisms arranged on both sides of the stop of the present invention are not limited to the decentered prism having the number of internal reflections of 1 to 3 as shown in FIGS. Various known eccentric prisms as described above can be used. An example is shown below. In both cases, an object positioned far away by forward ray tracing will be described as an eccentric prism P that forms an image on the image plane 136 through the pupil 131. However, a light ray enters from the image plane 136 side with the optical path reversed, and the pupil 131 It can also be used as an eccentric prism P that forms an image on the side.
[0078]
  In the case of FIG. 9, the decentering prism P includes the first surface 132, the second surface 133, the third surface 134, and the fourth surface 135, and the light incident through the entrance pupil 131 is refracted by the first surface 132. Is incident on the decentered prism P, is internally reflected by the second surface 133, is internally reflected by the third surface 134 so as to form a Z-shaped optical path, is incident on the fourth surface 135, and is refracted. An image is formed at 136.
[0079]
  In the case of FIG. 10, the decentered prism P includes the first surface 132, the second surface 133, the third surface 134, and the fourth surface 135, and light incident through the entrance pupil 131 is refracted by the first surface 132. Is incident on the decentered prism P, is internally reflected by the second surface 133, is incident on the third surface 134, is totally reflected, is incident on the fourth surface 135, is internally reflected, and is incident on the third surface 134 again. This time it is refracted and forms an image on the image plane 136.
[0080]
  In the case of FIG. 11, the decentered prism P is composed of the first surface 132, the second surface 133, the third surface 134, and the fourth surface 135, and the light incident through the entrance pupil 131 is refracted by the first surface 132. Incident on the decentered prism P, internally reflected on the second surface 133, incident on the third surface 134, internally reflected, incident again on the second surface 133, internally reflected, and incident on the fourth surface 135. The light is refracted and forms an image on the image plane 136.
[0081]
  In the case of FIG. 12, the decentered prism P includes the first surface 132, the second surface 133, the third surface 134, and the fourth surface 135, and light incident through the entrance pupil 131 is refracted by the first surface 132. Incident on the decentered prism P, internally reflected on the second surface 133, incident on the third surface 134, internally reflected, incident again on the second surface 133, internally reflected, and incident on the fourth surface 135. The light is internally reflected, reenters the second surface 133, is refracted, and forms an image on the image surface 136.
[0082]
  In the case of FIG. 13, the decentered prism P is composed of the first surface 132, the second surface 133, and the third surface 134, and the light incident through the entrance pupil 131 is refracted by the first surface 132 and becomes the decentered prism P. Incident, internally reflected by the second surface 133, again incident on the first surface 132 and now totally reflected, internally reflected by the third surface 134, incident on the first surface 132 three times and totally reflected, The light enters the third surface 134 again and is refracted, and forms an image on the image surface 136.
[0083]
  In the case of FIG. 14, the decentered prism P is composed of a first surface 132, a second surface 133, and a third surface 134, and light incident through the entrance pupil 131 is refracted by the first surface 132 and becomes the decentered prism P. Incident, internally reflected by the second surface 133, again incident on the first surface 132 and now totally reflected, internally reflected by the third surface 134, incident on the first surface 132 three times and totally reflected, The light again enters the third surface 134 and is internally reflected, and then enters the first surface 132 four times and is refracted, and forms an image on the image surface 136.
[0084]
Furthermore, as shown in the second prism 20 in FIG. 16 described later, the first prism 21 to the fourth surface 24 may reflect three times in the prism, or FIG. 17 described later. As in the second prism 20, the first surface 21 to the third surface 23, and the second surface 22 reflects twice in a prism that serves as a total reflection surface and an exit surface. Or, like the second prism 20 in FIG. 18 to be described later, the first surface 21 is composed of the third surface 23, and the first surface 21 is used twice in the prism that serves both as the incident surface and the total reflection surface. It may be one that reflects, and these can be used as an eccentric prism on the front side or the rear side of the stop 2.
[0085]
FIGS. 15 to 19 below show the imaging optical system of the present invention having a combination of prisms different from those in the first to sixth embodiments. However, numerical data is omitted.
[0086]
In the case of FIG. 15, the first prism 10 is an example using an eccentric prism similar to the second prism 20 of the first to fifth embodiments, and the first prism 10 has a first surface 11 to a fourth surface 14. The first surface 11 is an incident surface, the second surface 12 is a first reflecting surface, the third surface 13 is a second reflecting surface, and the fourth surface 14 is an exit surface. 11, reflected internally by the first reflecting surface 12, reflected internally by the second reflecting surface 13, transmitted through the exit surface 14, and the second prism 20 is composed of the first surface 21 to the fourth surface 24. The first surface 21 is an incident surface, the second surface 22 is a first reflecting surface, the third surface 23 is a second reflecting surface, and the fourth surface 24 is an exit surface. The light beam passes through the incident surface 21, is internally reflected by the first reflecting surface 22, is internally reflected by the second reflecting surface 23, and passes through the exit surface 24. Filtered to form an image on the image plane 3. In the first prism 10 and the second prism 20, the first surfaces 11 and 21 and the second surfaces 12 and 22 are opposed to each other with the prism medium in between, and the third surfaces 13 and 23 and the fourth surfaces 14 and 24 are arranged. Are arranged opposite to each other with the prism medium interposed therebetween, and the optical path connecting the first surface 11, 21 and the second surface 12, 22 is within the prism and the optical path connecting the third surface 13, 23 and the fourth surface 14, 24. Crossed.
[0087]
In the case of FIG. 16, the first prism 10 is the same as that in FIG. 15, and the second prism 20 includes the first surface 21 to the fourth surface 24, and the first surface 21 is the incident surface and the second reflection. The second surface 22 is the first reflecting surface, the third surface 23 is the third reflecting surface, the fourth surface 24 is the exit surface, and the light beam that has passed through the aperture 2 from the first prism 10 is incident. The light passes through the surface 21, is reflected by the first reflecting surface 22, is now totally reflected by the first surface 21, is internally reflected by the third reflecting surface 23, and passes through the exit surface 24 to form an image on the image surface 3. To do. In the second prism 20, light rays are internally reflected so as to form an M-shaped optical path in the prism.
[0088]
In the case of FIG. 17, the first prism 10 is the same as in the first to sixth embodiments, and the second prism 20 is composed of the first surface 21 to the third surface 23, and the first surface 21 is the incident surface. The second surface 22 is a combined surface that serves as both the first reflecting surface and the exit surface, the third surface 23 is a second reflecting surface, and the light beam that has passed through the aperture 2 from the first prism 10 passes through the incident surface 21. The light is totally reflected by the first reflecting surface 22, is internally reflected by the second reflecting surface 23, and then passes through the second surface 22 and forms an image on the image surface 3.
[0089]
In the case of FIG. 18, the first prism 10 is the same as in the first to sixth embodiments, and the second prism 20 includes the first surface 21 to the third surface 23, and the first surface 21 is the incident surface. And the second reflection surface, the second surface 22 is the first reflection surface, the third surface 23 is the exit surface, and the light beam that has passed through the aperture 2 from the first prism 10 passes through the incident surface 21. The light is reflected by the first reflecting surface 22, is now totally reflected by the first surface 21, passes through the exit surface 23, and forms an image on the image surface 3.
[0090]
FIG. 19 is a diagram showing a case where the imaging optical system of the present invention is configured by arranging one decentering prism 10 on the front side of the stop 2 and two decentering prisms 20 and 20 ′ on the rear side of the stop 2. Any of the decentering prisms 10, 20, and 20 ′ uses an decentering prism that performs one reflection within the prism.
[0091]
The imaging optical system of the present invention as described above can be used for an imaging apparatus, particularly a camera, which forms an object image and receives the image with an imaging element such as a CCD or a silver salt film for imaging. Further, it can also be used as an observation optical device for observing an object image through an eyepiece, particularly as an objective optical system of a camera finder.
[0092]
20 to 22 are conceptual diagrams of configurations in which the imaging optical system of the present invention is incorporated in the objective optical system of the finder portion of the electronic camera. 20 is a front perspective view showing the appearance of the electronic camera 40, FIG. 21 is a rear perspective view thereof, and FIG. 22 is a sectional view showing the configuration of the electronic camera 40. In this example, the electronic camera 40 includes a photographing optical system 41 having a photographing optical path 42, a finder optical system 43 having a finder optical path 44, a shutter 45, a flash 46, a liquid crystal display monitor 47, and the like. When the shutter 45 disposed in the position is pressed, photographing is performed through the photographing objective optical system 48 in conjunction therewith. An object image formed by the photographing objective optical system 48 is formed on the imaging surface 50 of the CCD 49 via a filter 51 such as a low-pass filter or an infrared cut filter. The object image received by the CCD 49 is displayed as an electronic image on the liquid crystal display monitor 47 provided on the back of the camera via the processing means 52. In addition, the processing means 52 is provided with a memory or the like, and can record a captured electronic image. This memory may be provided separately from the processing means 52, or may be configured to perform recording and writing electronically using a floppy disk or the like. Further, it may be configured as a silver salt camera in which a silver salt film is arranged in place of the CCD 49.
[0093]
  Further, a finder objective optical system 53 is disposed on the finder optical path 44. The finder objective optical system 53 includes a cover lens 54, a first prism 10, an aperture stop 2, a second prism 20, a focus. The imaging optical system according to the present invention is used as an imaging optical system from the cover lens 54 or the first prism 10 to the second prism 20. Further, the cover lens 54 used as a cover member is a lens having negative power, and has an increased angle of view. The focus lens 66 disposed behind the second prism 20 can be adjusted in position in the front-rear direction of the optical axis, and is used for adjusting the focus of the finder objective optical system 53. The object image formed on the imaging surface 67 by the finder objective optical system 53 is formed on the field frame 57 of the Porro prism 55 that is an image erecting member. The field frame 57 separates the first reflecting surface 56 and the second reflecting surface 58 of the Porro prism 55 and is disposed therebetween. Behind the Porro prism 55, an eyepiece optical system 59 for guiding the image formed into an erect image to the observer eyeball E is disposed.
[0094]
The camera 40 configured as described above can configure the finder objective optical system 53 with a small number of optical members, achieve high performance and low cost, and bend the optical path of the objective optical system 53 itself. The degree of freedom of internal arrangement increases, which is advantageous in design.
[0095]
In the configuration of FIG. 22, the configuration of the photographic objective optical system 48 is not mentioned, but the photographic objective optical system 48 includes two or more prisms 10 according to the present invention in addition to the refractive coaxial optical system. Of course, any type of imaging optical system consisting of 20 can be used.
[0096]
  Next, FIG. 23 shows the imaging optical system of the present invention as the imaging objective optical system 4 of the imaging unit of the electronic camera 40.
8 is a conceptual diagram of the configuration incorporated in FIG. In this case, the imaging optical system according to the present invention including the first prism 10, the aperture stop 2, and the second prism 20 is used for the imaging objective optical system 48 disposed on the imaging optical path 42. An object image formed by the photographing objective optical system 48 is formed on the imaging surface 50 of the CCD 49 through a filter 51 such as a low-pass filter or an infrared cut filter. The object image received by the CCD 49 is displayed as an electronic image on a liquid crystal display element (LCD) 60 via the processing means 52. The processing means 52 also controls the recording means 61 that records the object image taken by the CCD 49 as electronic information. The image displayed on the LCD 60 is guided to the observer eyeball E through the eyepiece optical system 59. The eyepiece optical system 59 is composed of a decentered prism. In this example, the eyepiece optical system 59 is composed of three surfaces: an incident surface 62, a reflecting surface 63, and a combined reflecting / refracting surface 64. In addition, at least one of the two reflecting surfaces 63 and 64, preferably both surfaces, provides power to the light beam and has a single symmetry plane that corrects decentration aberrations. It consists of a curved surface. The only symmetry plane is formed on substantially the same plane as the only symmetry plane of the plane-symmetric free-form surface included in the prisms 10 and 20 of the photographing objective optical system 48. In addition, the photographing objective optical system 48 may include other lenses (positive lens, negative lens) as components of the prisms 10 and 20 on the object side, between the prisms, or on the image side.
[0097]
The camera 40 configured in this way can be configured with the objective optical system 48 for photographing with a small number of optical members, can achieve high performance and low cost, and can arrange the entire optical system side by side on the same plane. A book shape with a thickness in the direction perpendicular to the plane can be realized.
[0098]
In this example, a plane parallel plate is disposed as the cover member 65 of the photographing objective optical system 48, but a lens having power may be used as in the previous example.
[0099]
Here, without providing the cover member, the surface arranged closest to the object side in the imaging optical system of the present invention can also be used as the cover member.
[0100]
Next, FIGS. 24 to 26 are conceptual diagrams showing a configuration in which the imaging optical system of the present invention is built in a personal computer which is an example of an information processing apparatus.
[0101]
24 is a front perspective view with the cover of the personal computer 300 opened, FIG. 25 is a sectional view of the photographing optical system 303 of the personal computer 300, and FIG. 26 is a side view of the state of FIG. As shown in FIGS. 24 to 26, a personal computer 300 includes a keyboard 301 for a writer to input information from the outside, information processing means and recording means (not shown), and a monitor for displaying information to the operator. 302 and a photographing optical system 303 for photographing the operator himself and surrounding images. Here, the monitor 302 may be a transmissive liquid crystal display element that is illuminated from the back by a backlight (not shown), a reflective liquid crystal display element that reflects and displays light from the front, a CRT display, or the like. Further, in the drawing, the photographing optical system 303 is built in the upper right of the monitor 302. However, the imaging optical system 303 is not limited to the place, and may be anywhere around the monitor 302 or the keyboard 301.
[0102]
The photographing optical system 303 includes an objective optical system 100 including the imaging optical system of the present invention and an imaging element chip 162 that receives an image on a photographing optical path 304. These are built in the personal computer 300.
[0103]
Here, an lR cut filter 180 is additionally attached on the image sensor chip 162 to be integrally formed as an image pickup unit 160, and can be fitted and attached to the rear end of the lens frame 101 of the objective optical system 100 with one touch. Therefore, it is not necessary to align the center of the objective optical system 100 and the image sensor chip 162 and to adjust the surface interval, and the assembly is simple. A cover glass 102 for protecting the objective optical system 100 is disposed at the tip of the lens frame 101.
[0104]
The object image received by the image sensor chip 162 is input to the processing means of the personal computer 300 via the terminal 166 and is displayed on the monitor 302 as an electronic image. FIG. A rendered image 305 is shown. The image 305 can also be displayed on the personal computer of the communication partner from a remote location via the processing means, the Internet, or the telephone.
[0105]
Next, as another example of the information processing apparatus, FIG. 27 shows an example in which the imaging optical system of the present invention is built in a telephone, in particular, a mobile phone that is convenient to carry.
[0106]
FIG. 27A is a front view of the mobile phone 400, FIG. 27B is a side view, and FIG. 27C is a cross-sectional view of the photographing optical system 405. As shown in FIGS. 27A to 27C, the mobile phone 400 includes a microphone unit 401 that inputs an operator's voice as information, a speaker unit 402 that outputs a voice of a call partner, and an operator who receives information. An input dial 403 for inputting information, a monitor 404 for displaying information such as a photographed image and a telephone number of the operator and the other party, a photographing optical system 405, an antenna 406 for transmitting and receiving communication radio waves, and an image And processing means (not shown) for processing information, communication information, input signals, and the like. Here, the monitor 404 is a liquid crystal display element. In the drawing, the arrangement positions of the respective components are not particularly limited to these. The photographing optical system 405 includes an objective optical system 100 including the imaging optical system of the present invention disposed on a photographing optical path 407, and an imaging element chip 162 that receives an image. These are built in the mobile phone 400.
[0107]
Here, an lR cut filter 180 is additionally affixed on the image pickup element chip 162 to be integrally formed as an image pickup unit 160 and can be attached by being fitted to the rear end of the lens frame 13 of the objective lens 12 with one touch. Therefore, the centering of the objective lens 12 and the image sensor chip 162 and the adjustment of the surface interval are unnecessary, and the assembly is simple. A cover glass 102 for protecting the objective optical system 100 is disposed at the tip of the lens frame 101.
[0108]
The object image received by the imaging element chip 162 is input to the processing means (not shown) via the terminal 166 and displayed as an electronic image on the monitor 404, the monitor of the communication partner, or both. . Further, when transmitting an image to a communication partner, the processing means includes a signal processing function for converting information of an object image received by the image sensor chip 162 into a signal that can be transmitted.
[0109]
The above imaging optical system of the present invention can be configured as follows, for example.
[0110]
[1] In an imaging optical system in which at least one decentered prism having a rotationally asymmetric reflecting surface is arranged on each side of the stop and does not form an intermediate image, the optical properties of the medium of at least one decentered prism before the stop And an optical property of a medium of at least one decentered prism after the stop.
[0111]
[2] The absolute value Δν of the difference between the Abbe numbers of the medium of at least one eccentric prism before the diaphragm and the medium of at least one eccentric prism after the diaphragm is:
5 <Δν <80 (1)
2. The imaging optical system according to 1 above, wherein:
[0112]
[3] The power on the front side of the stop is negative, the power on the back side of the stop is positive, the Abbe number of the medium of the at least one decentered prism before the stop is small, and the at least one decentered prism after the stop 3. The imaging optical system according to 2 above, wherein the Abbe number of the medium is larger.
[0113]
[4] The imaging optical system as set forth in [3], wherein the most object side surface of the element having refractive power on the front side of the stop has a positive power.
[0114]
[5] The imaging optical system according to any one of [1] to [4], wherein at least one of an entrance surface and an exit surface of each decentered prism is a curved surface.
[0115]
[6] The imaging optical system as described in 5 above, wherein the curved surface is a surface other than a spherical surface.
[0116]
[7] The imaging optical system according to [6], wherein the curved surface is a rotationally asymmetric surface.
[0117]
[8] When a light beam that passes through the center of the stop and reaches the center of the imaging surface is an axial principal ray, the axial principal ray direction when passing through the stop with respect to the axial principal ray direction in the object space. The declination θ is
45 ° <θ <135 ° (2)
8. The imaging optical system according to any one of 1 to 7 above, wherein:
[0118]
[9] The imaging optical system as described in 8 above, wherein one eccentric prism having only one reflecting surface is disposed in front of the stop and satisfies the following condition.
[0119]
92 ° <θ <135 ° (3)
[10] Thickness measured along the Z-axis from the point that protrudes closest to the object along the Z-axis of the optical system to the point farthest from the object, where the axis along the optical axis in the object space is the Z-axis 10. The imaging optical system according to any one of 1 to 9 above, wherein t satisfies t:
[0120]
t <20mm (4)
[11] The imaging optical system according to any one of 1 to 10 above, an electronic imaging device disposed at a position for receiving an object image formed by the imaging optical system, and photoelectric conversion by the electronic imaging device. A processing unit for processing the electronic signal, an input unit for inputting an information signal that an operator wants to input to the processing unit, a display element for displaying an output from the processing unit, and an output from the processing unit. Including a recording medium for recording,
The information processing apparatus, wherein the processing means is configured to display an object image received by the electronic imaging device by the imaging optical system on the display device.
[0121]
[12] In the above item 11,
The personal computer device, wherein the input unit is configured by a keyboard, and the imaging optical system and the electronic imaging element are built in a peripheral part of the display element or a peripheral part of the keyboard.
[0122]
[13] The imaging optical system according to any one of 1 to 10 above, an electronic imaging device disposed at a position for receiving an object image formed by the imaging optical system, and a telephone signal to be transmitted and received And a signal processing unit that converts an object image received by the electronic image sensor into a signal that can be transmitted. apparatus.
[0123]
[14] The imaging optical system according to any one of 1 to 10 above, an electronic imaging device disposed at a position for receiving an object image formed by the imaging optical system, and photoelectric conversion by the electronic imaging device. For recording the image information of the object image received by the electronic image sensor, comprising: a processing means for processing the received electronic signal; and a display element for observably displaying the object image received by the electronic image sensor. A display processing function for displaying an object image received by the electronic image sensor on the display element, and an object received by the electronic image sensor. An electronic camera device having a recording processing function for recording an image on the recording medium.
[0124]
【Effect of the invention】
As is apparent from the above description, according to the present invention, it is possible to provide an imaging optical system comprising a plurality of small, high-performance decentered prisms that are well corrected for various aberrations, particularly chromatic aberration of magnification.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a cross section and an optical path of an imaging optical system according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating a cross section and an optical path of an imaging optical system according to a second embodiment of the present invention.
FIG. 3 is a diagram illustrating a cross section and an optical path of an imaging optical system according to a third embodiment of the present invention.
FIG. 4 is a diagram illustrating a cross section and an optical path of an imaging optical system according to a fourth embodiment of the present invention.
FIG. 5 is a diagram illustrating a cross section and an optical path of an imaging optical system according to a fifth embodiment of the present invention.
FIG. 6 is a diagram illustrating a cross section and an optical path of an imaging optical system according to a sixth embodiment of the present invention.
7 is a lateral aberration diagram of the image pickup optical system according to the first embodiment. FIG.
8 is a lateral aberration diagram of the image pickup optical system according to the sixth embodiment. FIG.
FIG. 9 is a view showing one modification of a decentered prism that can be used in the imaging optical system of the present invention.
FIG. 10 is a diagram showing another modification of the eccentric prism.
FIG. 11 is a diagram showing another modification of the eccentric prism.
FIG. 12 is a diagram showing another modification of the eccentric prism.
FIG. 13 is a diagram showing another modification of the eccentric prism.
FIG. 14 is a diagram showing another modification of the eccentric prism.
15 is a diagram illustrating an example of an imaging optical system according to the present invention including a combination of prisms different from those in Embodiments 1 to 6. FIG.
FIG. 16 is a diagram illustrating another example of the imaging optical system according to the present invention including a combination of prisms different from those in Embodiments 1 to 6.
FIG. 17 is a diagram illustrating another example of the imaging optical system according to the present invention including a combination of prisms different from those in Embodiments 1 to 6.
FIG. 18 is a diagram illustrating another example of the imaging optical system according to the present invention including a combination of prisms different from those in Embodiments 1 to 6.
FIG. 19 is a diagram illustrating another example of the imaging optical system according to the present invention including a combination of prisms different from those in Embodiments 1 to 6.
FIG. 20 is a front perspective view showing the appearance of an electronic camera to which the imaging optical system of the present invention is applied.
21 is a rear perspective view of the electronic camera of FIG.
22 is a cross-sectional view showing a configuration of the electronic camera of FIG.
FIG. 23 is a conceptual diagram of another electronic camera to which the imaging optical system of the present invention is applied.
FIG. 24 is a front perspective view in which a cover of a personal computer in which the imaging optical system of the present invention is incorporated as an objective optical system is opened.
FIG. 25 is a cross-sectional view of a photographing optical system of a personal computer.
26 is a side view of the state of FIG. 24. FIG.
FIG. 27 is a front view, a side view, and a sectional view of the photographing optical system of a mobile phone in which the imaging optical system of the present invention is incorporated as an objective optical system.
[Explanation of symbols]
1 ... Aperture stop
2 ... On-axis chief ray (optical axis)
3. Image plane (imaging plane)
10 ... 1st prism
11 ... first side
12 ... the second side
13 ... Third surface
14 ... Fourth side
20 ... second prism
20 '... third prism
21 ... first side
22 ... Second side
23 ... Third surface
24 ... Fourth surface
30 ... Cover glass
31 ... Front side (first side)
32 ... Rear side (second side)
40 ... Electronic camera
41. Photography optical system
42. Optical path for photographing
43. Viewfinder optical system
44. Optical path for viewfinder
45 ... Shutter
46 ... Flash
47 ... LCD monitor
48 ... Objective optical system for photographing
49 ... CCD
50: Imaging surface
51 ... Filter
52. Processing means
53. Objective optical system for viewfinder
54 ... Cover lens
55 ... Porro prism
56. First reflective surface
57 ... View frame
58 ... second reflecting surface
59 ... Eyepiece optical system
60 ... Liquid crystal display (LCD)
61 ... Recording means
62 ... Incident surface
63 ... Reflecting surface
64 ... Both reflection and refraction surfaces
65: Cover member
66 ... Focus lens
67. Imaging plane
100: Objective optical system
101 ... Mirror frame
102 ... cover glass
131 ... Eye
132 ... first side
133 ... 2nd surface
134 ... Third surface
135 ... Fourth surface
136 ... image plane
160: Imaging unit
162. Image sensor chip
166 ... Terminal
180 ... lR cut filter
300 ... PC
301 ... Keyboard
302 ... Monitor
303 ... Shooting optical system
304: Optical path for photographing
305 ... Image
400 ... mobile phone
401: Microphone part
402: Speaker unit
403 ... Input dial
404 ... Monitor
405 ... Shooting optical system
406 ... Antenna
407: Photography optical path
E ... Observer eyeball
P ... Eccentric prism

Claims (3)

In an imaging optical system in which at least one decentered prism having a rotationally asymmetric reflecting surface is arranged on each side of the stop and does not form an intermediate image,
The optical property of the medium of at least one decentered prism before the stop is different from the optical property of the medium of at least one decentered prism after the stop,
At least one eccentric prism before the diaphragm and at least one eccentric prism after the diaphragm each have a rotationally asymmetric transmission surface;
The reflecting surface of at least one decentered prism before the stop is a surface that performs reflection only, and the transmission surface is a surface that performs transmission only.
The absolute value Δν of the difference between the Abbe numbers of the medium of at least one eccentric prism before the diaphragm and the medium of at least one eccentric prism after the diaphragm satisfies the following condition (1 ′): Imaging optical system.
5 <Δν ≦ 34.1228 (1 ′) In the diaphragm from the front side of the power is negative, the power of the rear side than the diaphragm is positive, and Abbe number of the medium of at least one decentered prism prior to the diaphragm is small, the at least one decentered prism later than the throttle The imaging optical system according to claim 1, wherein the Abbe number of the medium is larger. One eccentric prism having only one reflecting surface is arranged in front of the stop,
When a light beam that passes through the center of the stop and reaches the center of the imaging surface is an axial principal ray, the deflection angle of the axial principal ray direction when passing through the stop with respect to the axial principal ray direction in object space θ is
92 ° <θ <135 ° (3)
The imaging optical system according to claim 1, wherein:

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