JP3990081B2 - Electronic imaging apparatus and imaging optical system - Google Patents

Description

【００９９】

【０１００】

【０１０１】

【０１０２】

【０１０３】
各収差量
Lｈ＝０．０８６５ｍｍ
Lｇ＝０．０３２４ｍｍ
Lｄ＝０．００６１ｍｍ
（Lｈ−Lｄ）／Ｆmin＝０．０３９４ｍｍ＝１３．１Ｐ
（Lλ―Lｄ）／Fmin＝０．０５ｍｍとなるとき
Lλ＝０．０９５９ｍｍ 、 λ1＝４０１ｎｍ
（Lλ―Lｄ）／Fmin＝０．０４ｍｍとなるとき
Lλ＝０．０７５５ｍｍ 、 λ1＝４０９ｎｍ
（Lλ―Lｄ）／Fmin＝０．０３ｍｍとなるとき
Lλ＝０．０５５１ｍｍ 、 λ1＝４２０ｎｍ
【０１０４】
｜Ｓｈ｜＝０．０２１８ｍｍ＝７．３Ｐ
｜Ｓｇ｜＝０．００８３ｍｍ
｜Ｓλ｜＝０．０２５ｍｍとなるとき
λ2＝４００ｎｍ
｜Ｓλ｜＝０．０２ｍｍとなるとき
λ2＝４０８ｎｍ
｜Ｓλ｜＝０．０１５ｍｍとなるとき
λ2＝４１８ｎｍ
【０１０５】
実施例２
図２０は本実施形態による撮像光学系の第２実施例を示すレンズ断面図、図２１は本実施例の撮像光学系における無限遠合焦時の球面収差図とｄ線に対する倍率の色収差を表す図である。
第２実施例では軸上の色収差を補正しているが、倍率の色収差が補正しきれていない例として示してある。
以下に、本実施例の数値データを数値例２として示す。
【０１０６】

【０１０７】

【０１０８】

【０１０９】
各収差量
Lｈ＝０．０２９７２ｍｍ
Lｇ＝０．０４７３４ｍｍ
Lｄ＝０．０４０４１ｍｍ
（Lｈ−Lｄ）／Fmin＝−０．００３ｍｍ＝−１Ｐ
（Lλ―Lｄ）／Fmin＝０．０５ｍｍとなるとき
Lλ＝０．１０３６ｍｍ 、 λ1＝３４４ｎｍ
（Lλ―Lｄ）／Fmin＝０．０４ｍｍとなるとき
Lλ＝０．０７４８ｍｍ 、 λ1＝３５１ｎｍ
（Lλ―Lｄ）／Fmin＝０．０３ｍｍとなるとき
Lλ＝０．０４６０ｍｍ 、 λ1＝３６０ｎｍ
【０１１０】
｜Ｓｈ｜＝０．０２２６ｍｍ＝７．５Ｐ
｜Ｓｇ｜＝０．０１００ｍｍ
｜Ｓλ｜＝０．０２５ｍｍとなるとき
λ2＝４００ｎｍ
｜Ｓλ｜＝０．０２ｍｍとなるとき
λ2＝４０９ｎｍ
｜Ｓλ｜＝０．０１５ｍｍとなるとき
λ2＝４２０ｎｍ
【０１１１】
その他、本実施形態の電子撮像装置は、図２２に示すように、撮影光学系１と電子撮像素子２とを含む電子撮像装置本体１３において撮影光学系１を着脱可能にするマウント部２５を有しても良い。それにより撮影条件に応じて種々の撮影光学系１に交換して撮像でき、また、各々の状態で色フレア補正ができる。なお、マウント部２５としては、スクリュータイプやバヨネットタイプ等を用いるとよい。なお、その他の構成は、基本的には、図６に示す撮像光学系とほぼ同様である。
【０１１２】
本実施形態による電子撮像装置は、以上のように構成したので、撮像光学系を小型軽量化したことにより色収差が発生するような場合であっても、撮像される映像の輝度信号や色信号を調節することで、色のにじみを低減させた電子撮像装置を実現することができる。
【０１１３】
次に、本発明による電子撮像装置の第２実施形態を図２３に示す。なお、第１実施形態と同じ構成は、同じ番号を付しその説明は省略する。
本実施形態の電子撮像装置は、波長補正を行なうための波長補正フィルターを用いて光学的に色フレアを除去する構成となっている。
具体的には、信号処理系には色フレアを除去する構成の代わりに、平行平面板の片面に波長補正を行なうコーティング膜を施して短波長域の光線の透過率を低減させた波長補正フィルター３を、撮像光学系１の光路中に配設した点で、第１実施形態と構成が異なる。
【０１１４】
撮像光学系１には、上記第１実施例または第２実施例の数値データに示す撮像光学系を用いてよい。
なお、この撮像光学系は、焦点距離の決定に関わる光学素子は、屈折現象のみを用いた光学素子で構成されている。
そして、撮像光学系におけるこれらの光学素子のみの部分（撮影光学系１'）の分光透過率曲線と、波長補正フィルター３を介した場合の分光透過率曲線とを図２４に示す。
図２４に示すように、波長補正フィルター３を介した場合には、撮影光学系１'のみの特性に比べて、色フレアの発生しやすい短波長側の光量を低下させることで良好な像が得られることがわかる。
以下に、本実施形態における撮像光学系の具体的な数値データを数値例３として示す。
【０１１５】
数値例３
λｃ＝４３０ｎｍ
τｈ＝０％
τｇ＝６０％
電子撮像素子のｇ線での感度特性／ｅ線での感度特性＝０．３５とする。
【０１１６】
数値例１との組み合わせにおいて
（Lλ―Lｄ）／Fmin＝０．０５ｍｍとなるとき
τ（λ1）＝０％
τ（λ1＋３０）＝５２％
（Lλ―Lｄ）／Fmin＝０．０４ｍｍとなるとき
τ（λ1）＝０％
τ（λ1＋３０）＝６２％
（Lλ―Lｄ）／Fmin＝０．０３ｍｍとなるとき
τ（λ1）＝５％
τ（λ1＋３０）＝８２％
【０１１７】
｜Ｓλ｜＝０．０２５ｍｍとなるとき
τ（λ2）＝０％
τ（λ2＋３０）＝５０％
｜Ｓλ｜＝０．０２ｍｍとなるとき
τ（λ2）＝０％
τ（λ2＋３０）＝６３％
｜Ｓλ｜＝０．０１５ｍｍとなるとき
τ（λ2）＝４％
τ（λ2＋３０）＝８０％
【０１１８】
（Lｈ−Lｄ）／Fmin×τｈ ＝０
（Lｇ−Lｄ）／Fmin×τｇ ＝０．０１１３３ｍｍ
｜Ｓｈ｜×τｈ ＝０
｜Ｓｇ｜×τｇ ＝０．００４９８ｍｍ
【０１１９】
数値例２との組み合わせにおいて
（Lλ―Lｄ）／Fmin＝０．０５ｍｍとなるとき
τ（λ1）＝０％
τ（λ1＋３０）＝０％
（Lλ―Lｄ）／Fmin＝０．０４ｍｍとなるとき
τ（λ1）＝０％
τ（λ1＋３０）＝０％
（Lλ―Lｄ）／Fmin＝０．０３ｍｍとなるとき
τ（λ1）＝０％
τ（λ1＋３０）＝０％
【０１２０】
｜Ｓλ｜＝０．０２５ｍｍとなるとき
τ（λ2）＝０％
τ（λ2＋３０）＝５０％
｜Ｓλ｜＝０．０２ｍｍとなるとき
τ（λ2）＝０％
τ（λ2＋３０）＝６５％
｜Ｓλ｜＝０．０１５ｍｍとなるとき
τ（λ2）＝５％
τ（λ2＋３０）＝８２％
【０１２１】
（Lｈ−Lｄ）／Fmin×τｈ ＝０
（Lｇ−Lｄ）／Fmin×τｇ ＝０．００４１５８ｍｍ
｜Ｓｈ｜×τｈ ＝０
｜Ｓｇ｜×τｇ ＝０．００６ｍｍ
【０１２２】
また、本実施形態の撮像装置は、図２３の電子撮像装置とは別タイプの撮像装置にも適用可能であり、図２５に示すように、電子撮像素子より物体側で、光束を分割し観察者眼球に光路を導く観察用光路とし、ファインダー光学系２６に導く所謂ＴＴＬファインダー形式の撮像装置に適用できる。なお、図２５の撮像光学装置においても撮像光学系１は上記各数値例に示したものを使用している。このＴＴＬファインダー形式のタイプのものは、電力の消費を少なくし、被写体を観察することができるという特徴がある。また、図２５のタイプの撮像装置では、ファインダー光学系２６と撮影光学系１'との光路分割手段として、ハーフミラープリズム２７を用いている。そして、電子撮像素子としてのＣＣＤ２のｇ線での感度特性がｅ線での感度特性の３０％以上の感度を有する撮像領域を有し、電子撮像素子側の光路のみに、上述の波長補正を行なうコーテイング膜２８を射出面に施し入射面側を凸凹に形成したローパスフィルター６を配設している。
【０１２３】
なお、ローパスフィルター６を赤外カットフィルターの代わりに、片面に先のコーテイング膜を施しても良い。
また、透過率がｇ線とｈ線との間、及び６００ｎｍと７００ｎｍとの間において透過率がｄ線の透過率に対し半値となる波長が存在する特性を示すようにコーティングをすることによって、赤外カットフィルターの作用と色フレア低減作用をさせてもよい。
また、図１７に示すような３板式の撮像素子において、ｇ線での感度特性がｅ線での感度特性の３０％以上の感度を有する撮像領域を有する青色撮像用の撮像素子（Ｂ）側の光路のみに点線で示す波長補正素子３を配してもよい。
【０１２４】
さらに、本発明による電子撮像装置の他の実施形態の要部の構成を図２６に示す。本実施形態では、撮像光学系１と電子撮像素子２の間の光軸５の光路上に、０段、−１段、−２段、−３段の明るさ調節を可能とするターレット２９を配置している。なお、撮像光学系等のその他の構成は上記各実施形態と同様である。
【０１２５】
ターレット２９には、平行平板３０、−１段ＮＤフィルター３１、−２段ＮＤフィルター３２、−３段ＮＤフィルタ３３―が配設され、ターレット２９の回動に併せて光軸５の光路上に順次位置するように構成されている。それにより、撮像素子２の入射する光量を調節している。平行平板３０及び各ＮＤフィルターの表面には、ｇ線とｈ線との間において透過率がｅ線の透過率の半値となる波長補正作用を備えるコーテイング膜２８を施して、短波長の色収差による色フレアを低減させるようになっている。なお、コーテイング膜と光学系との分光感度特性は、先に示した図２４に同じである。そして、各ＮＤフィルターに対応して、全体の透過率が１／２、１／４、１／８と低下するように作用する。
【０１２６】
以上、種々の実施形態を説明したが、本発明はこれらの実施形態に限定されることなく、設計の必要に応じて上記各実施形態において記載された構成を種々組み合わせたり、変更しても構わないことは言うまでもない。
以上説明したように、本発明による電子撮像装置及び撮像光学系は、特許請求の範囲に記載された特徴のほかに下記に示すような特徴も備えている。
【０１３６】
（１）カラー画像を得るための３つ以上の異なる分光特性を有する複数の画素を含む電子撮像素子と、前記電子撮像素子の撮像面上に被写体像を形成する撮像光学系を接続可能とするマウント部と、前記電子撮像素子の隣接する一定の画素間での輝度差が一定レベル以上になる領域の有無を検出する高輝度差検出手段と、前記高輝度差検出手段が一定レベル以上の輝度差を検出した際に警告を発する警告手段とを備えたことを特徴とする電子撮像装置。
【０１３７】
（２）カラー画像を得るための３つ以上の異なる分光特性を有する複数の画素を含み、前記画素が受光した像を輝度及び色の情報を含む電気信号に変換し出力する電子撮像素子と、前記電子撮像素子の撮像面上に被写体像を形成する撮像光学系を接続可能とするマウント部と、前記電子撮像素子の隣接する一定の画素間での輝度差が一定レベル以上になる境界部を検出する高輝度差境界部検出手段と、前記高輝度差境界部検出手段が一定レベル以上の輝度差を検出した際に前記一定レベル以上の輝度差を含む境界部近傍の色フレアを低減するように前記輝度及び色の情報を含む電気信号を電気的に調節する信号処理手段とを備えたことを特徴とする電子撮像装置。
【０１３８】
（３）カラー画像を得るための３つ以上の異なる分光特性を有する複数の画素を含み、前記画素が受光した像を輝度及び色の情報を含む電気信号に変換し出力する電子撮像素子と、前記電子撮像素子の撮像面上に被写体像を形成する撮像光学系を接続可能とするマウント部と、前記電子撮像素子上の撮影領域の適正露出値を算出する適正露出算出手段と、前記適正露出に対して２ＥＶ以下のアンダー露出にて露出レベルが飽和した画素及び／または前記飽和した画素に隣接する飽和していない画素を検出することで輝度差の大きい境界部を検出する高輝度差境界部検出手段と、前記高輝度差境界部検出手段により検出された前記境界部近傍の色フレアを低減するように前記輝度及び色の情報を含む電気信号を電気的に調節する信号処理手段とを備えたことを特徴とする電子撮像装置。
【０１３９】
（４）電子撮像素子上に被写体像を形成する撮像光学系であって、該光学系の最小Ｆ値をＦｍｉｎとし、Ｆ値がＦｍｉｎのときの任意の波長λのマージナル光線の球面収差量の絶対値をＬλ、ｄ線（５８７．５６ｎｍ）におけるマージナル光線の球面収差量の絶対値をＬｄとしたときに次の条件式（３）
（Ｌλ−Ｌｄ）／Ｆｍｉｎ ＝０．０５ｍｍ ……（３）
を満足する波長をλ１としたときに、λ１がｄ線以下の波長域に存在し、透過率がｄ線の透過率に対し半値となる波長λｃが、次の条件式（４）を満足する特性を示すことを特徴とする撮像光学系。
λ１≦λｃ≦ｄ線（５８７．５６ｎｍ） ……（４）
【０１４０】
（５）電子撮像素子上に被写体像を形成する撮像光学系であって、任意の波長λの最大像高の像高比０．９におけるｄ線（５８７．５６ｎｍ）に対する倍率色の横収差量をＳλとしたときに次の条件式（５）
｜Ｓλ｜＝０．０２５ｍｍ ……（５）
を満足する波長をλ２としたときに、λ２がｄ線以下の波長域に存在し、透過率がｄ線の透過率に対し半値となる波長λｃが、次の条件式（６）を満足する特性を示すことを特徴とする撮像光学系。
λ２≦λｃ≦ｄ線（５８７．５６ｎｍ） ……（６）
【０１４１】
（６）電子撮像素子上に被写体像を形成する撮像光学系であって、該光学系の最小Ｆ値をＦｍｉｎとし、Ｆ値がＦｍｉｎのときの任意の波長λのマージナル光線の球面収差量の絶対値をＬλ、ｄ線（５８７．５６ｎｍ）におけるマージナル光線の球面収差量の絶対値をＬｄとしたときに次の条件式（３）
（Ｌλ−Ｌｄ）／Ｆｍｉｎ ＝０．０５ｍｍ ……（３）
を満足する波長をλ１としたときに、λ１が次の条件式（８）を満足すると共に、透過率がｄ線の透過率に対し半値となる波長λｃが、次の条件式（７）を満足する特性を示すことを特徴とする撮像光学系。
３９０ｎｍ≦λｃ≦４４０ｎｍ ……（７）
３９０ｎｍ≦λ１≦４３０ｎｍ ……（８）
【０１４２】
（７）電子撮像素子上に被写体像を形成する撮像光学系であって、任意の波長λの最大像高の像高比０．９におけるｄ線（５８７．５６ｎｍ）に対する倍率色の横収差量をＳλとしたときに次の式（５）
｜Ｓλ｜＝０．０２５ｍｍ ……（５）
を満足する波長をλ２としたときに、λ２が次の条件式（７）を満足すると共に、透過率がｄ線の透過率に対し半値となる波長λｃが、次の条件式（９）を満足する特性を示すことを特徴とする撮像光学系。
３９０ｎｍ≦λｃ≦４４０ｎｍ ……（７）
３９０ｎｍ≦λ２≦４３０ｎｍ ……（９）
【０１４３】
（８）電子撮像素子上に被写体像を形成する撮像光学系であって、該光学系の最小Ｆ値をＦｍｉｎとし、Ｆ値がＦｍｉｎのときの任意の波長λのマージナル光線の球面収差量の絶対値をＬλ、ｄ線（５８７．５６ｎｍ）におけるマージナル光線の球面収差量の絶対値をＬｄとしたときに次の条件式（３）
（Ｌλ−Ｌｄ）／Ｆｍｉｎ＝０．０５ｍｍ ……（３）
を満足する波長をλ１とし、λ１が次の条件式（１０）を満足し、ｄ線の透過率に対する波長λ１での光学系の透過率比をτ（λ１）、ｄ線の透過率に対する波長λ１＋３０ｎｍでの光学系の透過率比をτ（λ１＋３０）としたときに、次の条件式（１１）、（１２）を満足する特性を示すことを特徴とする撮像光学系。
３５０ｎｍ≦λ１≦５５０ｎｍ ……（１０）
τ（λ１）≦１０％ ……（１１）
τ（λ１＋３０）≧５０％ ……（１２）
【０１４４】
（９）電子撮像素子上に被写体像を形成する撮像光学系であって、任意の波長λの最大像高の像高比０．９におけるｄ線（５８７．５６ｎｍ）に対する倍率色の横収差量をＳλとしたときに次の条件式（５）
｜Ｓλ｜＝０．０２５ｍｍ ……（５）
を満足する波長をλ２とし、λ２が次の条件式（１３）を満足し、ｄ線の透過率に対する波長λ２での光学系の透過率比をτ（λ２）、ｄ線の透過率に対する波長λ２＋３０ｎｍでの光学系の透過率比をτ（λ２＋３０）としたときに、次の条件式（１４）、（１５）を満足する特性を示すことを特徴とする撮像光学系。
３５０ｎｍ≦λ２≦５５０ｎｍ ……（１３）
τ（λ２）≦１０％ ……（１４）
τ（λ２＋３０）≧５０％ ……（１５）
【０１４５】
（１０）上記条件式（３）を次の式（３’）に置き換えたことを特徴とする上記（１３）、（１５）、（１７）のいずれかに記載の撮像光学系。
（Ｌλ−Ｌｄ）／Ｆｍｉｎ ＝０．０４ｍｍ ……（３’）
【０１４６】
（１１）上記条件式（３）を次の条件式（３”）に置き換えたことを特徴とする上記（１３）、（１５）、（１７）のいずれかに記載の撮像光学系。
（Ｌλ−Ｌｄ）／Ｆｍｉｎ ＝０．０３ｍｍ ……（３”）
【０１４７】
（１２）上記条件式（５）を次の条件式（５’）に置き換えたことを特徴とする上記（１４）、（１６）、（１８）のいずれかに記載の撮像光学系。
｜Ｓλ｜＝０．０２ｍｍ ……（５’）
【０１４８】
（１３）上記条件式（５）を次の条件式（５”）に置き換えたことを特徴とする上記（１４）、（１６）、（１８）のいずれかに記載の撮像光学系。
｜Ｓλ｜＝０．０１５ｍｍ ……（５”）
【０１４９】
（１４）電子撮像素子上に被写体像を形成する撮像光学系であって、該撮像光学系の最小Ｆ値をＦｍｉｎとし、Ｆ値がＦｍｉｎのときのｈ線（４０４．７ｎｍ）のマージナル光線の球面収差量の絶対値をＬｈ、ｇ線（４３５．８ｎｍ）のマージナル光線の球面収差量の絶対値をＬｇ、ｄ線（５８７．５６ｎｍ）のマージナル光線の球面収差量の絶対値をＬｄ、ｄ線の透過率に対する前記撮像光学系のｈ線の透過率比をτｈ、ｄ線の透過率に対するｇ線の透過率比をτｇとしたときに、次の条件式（１６）を満足し、且つ、透過率がｄ線の透過率に対し半値となる波長λｃが、次の条件式（１７）を満足する特性を示すことを特徴とする撮像光学系。
（Ｌｈ−Ｌｄ）／Ｆｍｉｎ×τｈ ≦ （Ｌｇ−Ｌｄ）／Ｆｍｉｎ×τｇ
……（１６）
ｈ線（４０４．７ｎｍ）＜λｃ＜ｇ線（４３５．８ｎｍ） ……（１７）
【０１５０】
（１５）電子撮像素子上に被写体像を形成する撮像光学系であって、最大像高の像高比０．９におけるｄ線（５８７．５６ｎｍ）に対するｈ線（４０４．７ｎｍ）の倍率色の横収差量をＳｈ、最大像高の像高比０．９におけるｄ線（５８７．５６ｎｍ）に対するｇ線（４３５．８ｎｍ）の倍率色の横収差量をＳｇ、ｄ線に対する前記撮像光学系のｈ線の透過率比をτｈ、ｄ線に対するｇ線の透過率比をτｇとしたときに、次の条件式（１８）を満足し、且つ、透過率がｄ線の透過率に対し半値となる波長λｃが、次の条件式（１７）を満足する特性を示すことを特徴とする撮像光学系。
｜Ｓｈ｜×τｈ ≦ ｜Ｓｇ｜×τｇ ……（１８）
ｈ線（４０４．７ｎｍ）＜λｃ＜ｇ線（４３５．８ｎｍ） ……（１７）
【０１５１】
（１６）波長補正を行なうためのコーティング膜を平面上に施したことを特徴とする上記（４）〜（１５）のいずれかに記載の撮像光学系。
【０１５２】
（１７）前記撮像光学系中にローパスフィルターを配設すると共に、前記ローパスフィルターの少なくとも一面に波長補正を行なうコーティング膜を施したことを特徴とする上記（４）〜（１５）のいずれかに記載の撮像光学系。
【０１５３】
（１８）前記撮像光学系中に赤外光成分を低減する赤外カットフィルターを配設すると共に、前記赤外カットフィルターの少なくとも一面に波長補正を行なうコーティング膜を施したことを特徴とする上記（４）〜（１５）のいずれかに記載の撮像光学系。
【０１５４】
（１９）ｇ線とｈ線の間、及び６００ｎｍと７００ｎｍとの間において透過率がｄ線の透過率に対し半値となる波長が存在する特性を示すコーティング膜を、前記撮像光学系中に施したことを特徴とする上記（４）〜（１５）のいずれかに記載の撮像光学系。
【０１５５】
（２０）前記撮像光学系の光路中に光路分割手段を設け、前記電子撮像素子のｇ線での感度特性がｅ線での感度特性の３０％以上の感度を有する撮像領域を有する撮像素子側の光路のみに、波長補正素子を配設したことを特徴とする上記（４）〜（１５）のいずれかに記載の撮像光学系。
【０１５６】
（２１）前記光路分割手段によって分割される光路のうちの一つを、観察者の眼球に光路を導く観察用光路としたことを特徴とする上記（２０）に記載の撮像光学系。
【０１５７】
（２２）前記光路分割手段にて複数の光路に分割し、分割された光路のうちの複数の光路の各々に分光感度特性が異なる撮像素子を配設すると共に、ｇ線での感度特性がｅ線での感度特性の３０％以上の感度を有する撮像領域を有する撮像素子側の光路のみに前記波長補正素子を配設したことを特徴とする上記（２０）に記載の撮像光学系。
【０１５８】
（２３）電子撮像素子上に被写体像を形成する撮像光学系であって、前記光学系の光路中に光量調節を行なう調節素子を有し、前記調節素子が、ｇ線とｈ線の間における透過率がｅ線の透過率の半値となる波長補正作用を備えていることを特徴とする撮像光学系。
【０１５９】
（２４）前記撮像光学系中の焦点距離の決定に関わる光学素子を、屈折現象のみを用いた光学素子で構成したことを特徴とする上記（４）〜（２３）のいずれかに記載の撮像光学系。
【０１６０】
（２５）前記撮像光学系の後側焦点位置に、カラー画像を得るための３つ以上の異なる分光感度特性を有する電子撮像素子を配設したことを特徴とする上記（４）〜（２４）のいずれかに記載の撮像光学系を有する電子撮像装置。
【０１６１】
（２６）前記カラー画像を得るための３つ以上の異なる分光感度特性を有する電子撮像素子のうち、少なくとも一つの電子撮像素子の分光特性は、２つの高いピーク波長を持ち、その２つのピーク波長の間に、２つのピーク波長の双方に対して５０％以下の感度の波長を有することを特徴とする請求項１乃至４、上記（１）〜（３）、（２５）のいずれかに記載の電子撮像装置。
【０１６２】
【発明の効果】
以上のように、本発明によれば、簡易な構成で、幅広い自然の被写体に対して、色を含め良好な像の再現を可能とする撮像光学系及び撮像装置を提供することができる。
【図面の簡単な説明】
【図１】色フレアを光学的に低減させる本発明にかかる撮像光学系の概念図である。
【図２】図１の撮像光学系の球面収差図である。
【図３】図１の撮像光学系を後側焦点部分の断面で見たときの最大入射高における焦点位置のずれ量を示す状態説明図である。
【図４】図１の撮像光学系におけるｄ線に対する波長λの倍率の色収差を示す収差図である。
【図５】図１の撮像光学系において像面上の像高比０．９における色収差の様子を近軸像面上で表した図である。
【図６】本発明による電子撮像装置の第１実施形態を示す所謂デジタルカメラ１３の構成図である。
【図７】本実施形態の電子撮像装置に用いる二次元エリア測光センサーの概略構成図である。
【図８】晴天を背景とした室内撮影のような明暗差の激しい被写体を撮影するときの状態説明図である。
【図９】撮像面の一部を拡大した各画素ごとの適正露出に対する輝度差の例を示す状態説明図である。
【図１０】本実施形態の電子撮像装置に用いる二次元エリア測光センサーの状態説明図である。
【図１１】電子撮像素子の撮像面上に感度低下手段としてのＮＤフィルターを施した複数の測光エリアとしての画素を設け、その画素での受光した輝度信号を用いて上記記載の如く境界部を検出する様に構成した図である。
【図１２】本実施形態の電子撮像装置におけるコントローラー７内の信号処理のフローチャートである。
【図１３】本実施形態に用いる原色フィルターの概略構成図である。
【図１４】本実施形態に用いる補色フィルターの概略構成図である。
【図１５】図１３の原色フィルターの波長特性図である。
【図１６】図１４の補色フィルターの波長特性図である。
【図１７】色分解プリズムを用いた本実施形態の撮像光学系の変形例を示す概略構成図である。
【図１８】本実施形態の撮像光学系における第１実施例（数値例１）のレンズ断面図である。
【図１９】図１８の撮像光学系における広角端の無限遠合焦時の球面収差図とｄ線に対する倍率の色収差を表す図である。
【図２０】本実施形態の撮像光学系における第２実施例（数値例２）のレンズ断面図である。
【図２１】図２０の撮像光学系における無限遠合焦時の球面収差図とｄ線に対する倍率の色収差を表す図である。
【図２２】本実施形態の変形例を示す概略構成図である。
【図２３】波長補正を行なうための波長補正フィルターを用いて光学的に色フレアを除去した本発明による電子撮像装置の第２実施形態を示す概略構成図である。
【図２４】本実施形態の撮像光学系における撮像光学系のみの分光透過率曲線と、波長補正フィルター３を介した場合の分光透過率曲線を示す図である。
【図２５】本実施形態の変形例として、撮像素子より物体側で、光束を分割し観察者眼球に光路を導く観察用光路とし、ファインダー光学系２６に導く所謂ＴＴＬファインダー形式の観察光学系を示す概略構成図である
【図２６】本発明のさらに別の実施形態を示す要部構成図である。
【図２７】５５０nmの波長で屈折力（焦点距離の逆数）が１となる単レンズを代表的な硝子材料と超低分散ガラスと呼ばれる材質で構成した時の、波長による屈折力の変化を示す図である。
【図２８】５００nmを基準にした時、一般的な屈折型光学素子のみからなる光学系の波長に対する後側焦点位置のずれ量を示す図で、横軸が波長で縦軸がずれ量である。
【符号の説明】
１ 撮像光学系
１' 撮影光学系
２ 電子撮像素子
３ 撮像素子
４ 像面
５ 近軸像面４上の光軸
６ ローパスフィルター
７ コントローラー
８ 内蔵メモリ
９ インターフェース
１０ Ｐ．Ｃ．
１１ 液晶モニタ
１２ 補助メモリ
１３ 電子撮像装置
１４ 張り合わせプリズム
１５ 二次元エリア測光センサー
１６ 測光エリア
１７ ストロボ機構
１８ ブザー
１９ 色フレア
２０ 第１プリズム
２１ 第２プリズム２１
２３ 第３プリズム
２４ 色分解プリズム
２５ マウント
２６ ファインダー光学系
２７ ハーフミラープリズム
２８ コーテイング膜
２９ ターレット
３０ 平行平板
３１ −１段ＮＤフィルタ
３２ −２段ＮＤフィルタ
３３ −３段ＮＤフィルタ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an imaging optical system and an electronic imaging apparatus that form a subject image on an imaging surface of an electronic imaging device including a plurality of pixels having three or more different spectral characteristics for obtaining a color image such as a CCD. .
[0002]
[Prior art]
In an electronic image pickup apparatus using a conventional electronic image pickup element, sensitivity from a short wavelength of visible light to an ultraviolet wavelength is ensured in order to secure the amount of light received by the electronic image pickup element. In addition, when the amount of light received by the electronic image sensor is weak, by controlling the gamma characteristic, an output higher than the input ratio to the photoelectric conversion element may be obtained during image reproduction. In this case, there is no particular problem if the spectral state of the subject is substantially constant. However, when the energy of the wavelength near the h-line is larger than, for example, near the g-line, the color of the reproduced image is the actual human eye. There is a problem that it becomes blue with respect to the color seen in. This is because even though the sensitivity of the human eye is considerably low for the short wavelength side of the visible range, the electronic image sensor is highly sensitive even in the short wavelength range, so the short wavelength is easily visible to the human eye. It is because it will be played back.
[0003]
On the other hand, with the recent increase in the number of pixels, the reduction in price, and the downsizing of digital cameras, there has been an increasing demand for higher performance, downsizing, higher functions such as zooming, and lower costs in the imaging optical system. In order to achieve high performance, it is necessary to improve the imaging performance in the entire wavelength region with the light receiving sensitivity of the optical system. Here, the change in imaging performance due to wavelength is called chromatic aberration.
[0004]
Chromatic aberration is generally corrected by utilizing the fact that the rate of change (dispersion) in the refractive index with respect to the wavelength differs for each material. For example, in the case of an optical system having a positive focal length, chromatic aberration is corrected by using a material with low dispersion for an optical element having positive refractive power and a material with high dispersion for an optical element having negative refractive power.
[0005]
In addition, when correcting chromatic aberration by combining optical elements as described above, not only chromatic aberration but also the imaging performance of the entire image surface must be taken into consideration, so measures such as increasing the number of optical elements can be taken. Be taken. In a zoom lens system that changes the focal length of the entire system by changing the interval between a plurality of lens groups including a lens group having a positive focal length and a lens group having a negative focal length, a more complicated combination of optical elements is used. Necessary. At this time, when the refractive optical element (lens) is formed of glass or plastic material, there is a difference depending on the material, but the refractive index increases as the wavelength changes from long wavelength to short wavelength, and the extent of the change Becomes intense.
[0006]
FIG. 27 is a diagram showing a change in refractive power depending on a wavelength when a single lens having a refractive power (reciprocal of focal length) of 1 at a wavelength of 550 nm is made of a typical glass material and a material called ultra-low dispersion glass. It is. FIG. 28 is a diagram showing the amount of deviation of the back focal position with respect to the wavelength of an optical system composed only of a general refractive optical element, with a wavelength of 500 nm as a reference. The horizontal axis is the wavelength and the vertical axis is the vertical axis. The amount of deviation.
[0007]
As can be seen from FIG. 27, the refractive optical element is composed of a refractive optical element made of a material in a practical range since the change in power with respect to the wavelength tends to be the same for both ordinary materials and ultra-low dispersion materials. The on-axis chromatic aberration of the imaging optical system is substantially V-shaped as shown by the solid line in FIG. 28, forms an image at the same point only at two wavelengths, and the chromatic aberration increases on the short wavelength side and the long wavelength side. . The chromatic aberration is particularly severe on the short wavelength side. In order to alleviate this chromatic aberration, it has been proposed to use special glass such as meteorite and ultra-low dispersion glass. These special glasses also have characteristics as shown in FIG. It is difficult to sufficiently reduce the side chromatic aberration.
[0008]
Therefore, when an electronic image pickup device is used, a color blur on the short wavelength side appears due to chromatic aberration and is recognized as an unnatural color blur.
[0009]
As a prior art regarding this point, a proposal for sufficiently reducing the chromatic aberration on the short wavelength side by using a diffractive optical element is described in JP-A-10-170822.
In the technique described in this publication, the chromatic aberration in the used order light is corrected by utilizing the inverse dispersion characteristic of the diffractive optical element. However, in the diffractive optical element, diffracted light of orders other than the used order light appears as unnecessary order light, which causes ghost and flare. In this regard, the technique described in this publication reduces the influence of unnecessary order light of the diffractive optical element by limiting the wavelength band.
[0010]
[Problems to be solved by the invention]
However, this unnecessary order light reaches the image plane discontinuously (independently) from the used order light. The spectral wavelength characteristics are also discontinuous between the unnecessary order light and the use order light.
The technique described in this publication reduces unnecessary-order light that is completely unrelated to normal (using use-order light) imaging by paying attention to the difference in wavelength characteristics.
Therefore, in order to obtain a good image, it is necessary to greatly reduce the intensity of the image due to unnecessary order light.
[0011]
In the technique described in this publication, an optical system having almost no sensitivity at a wavelength of 420 nm is proposed as a specific example.
However, the wavelength of 420 nm has an influence especially on color perception in human vision, and this wavelength range is extremely reduced from the viewpoint of color reproducibility. The component will be reduced, and there is a high possibility that natural color reproduction will be impaired.
Therefore, in the technology described in this publication, in order to make the influence of unnecessary order light inconspicuous, it is necessary to greatly cut the short wavelength region that affects human vision, so that the color reproducibility at a high level and There was a problem that it was difficult to achieve both flare removal.
[0012]
In view of the above-described problems, the present invention provides an electronic imaging apparatus and an imaging optical system that can reproduce a good image with a reduced color flare with a simple configuration and a wide range of natural subjects. Objective.
[0013]
[Means for Solving the Problems]
  In an imaging device such as a camera that captures a visible light region, the imaging optical system is generally optimized based on the vicinity of the intermediate wavelength in the visible light region. At this time, if an attempt is made to obtain good optical performance in the entire visible light range, it is necessary to use a special glass material to correct chromatic aberration or to increase the number of lenses, and the optical system becomes expensive. End up.
  Therefore, the gist of the configuration of the present invention is to allow a certain degree of chromatic aberration and to issue a warning to that effect to the observer in a situation where color flare due to the chromatic aberration is likely to occur.RukoAs a result, an imaging optical system and an imaging apparatus that are inconspicuous in color flare even with an inexpensive optical system are realized.
[0014]
  A first configuration of an electronic imaging device according to the present invention for solving the above-described problem is an electronic imaging device including a plurality of pixels having three or more different spectral characteristics for obtaining a color image, and chromatic aberration.ButOccurrenceBeforeHigh-intensity difference detection that detects the presence or absence of an area where the luminance difference between an imaging optical system that forms a subject image on the imaging surface of the electronic imaging element and a certain pixel adjacent to the electronic imaging element exceeds a certain level And a warning means for issuing a warning when the high brightness difference detecting means detects a brightness difference of a certain level or more.In the imaging optical system, the minimum pixel pitch of the electronic imaging element is P, the minimum F value is Fmin, and the absolute value of the spherical aberration amount of the marginal ray at the h-line (wavelength 404.7 nm) when the F value is Fmin. When the absolute value of the spherical aberration of the marginal ray at Lh, d line (wavelength 587.56 nm) is Ld, the following conditional expression (1) is satisfied:It is characterized by that.
      (Lh−Ld) / Fmin ≧ 2P                      (1)
  Further, the second configuration of the electronic imaging device according to the present invention for solving the above-described problem is that an electronic imaging device including a plurality of pixels having three or more different spectral characteristics for obtaining a color image and chromatic aberration are generated. A high-luminance difference for detecting the presence or absence of a region where the luminance difference between an imaging optical system that forms a subject image on the imaging surface of the electronic imaging element and a certain pixel adjacent to the electronic imaging element exceeds a certain level A boundary detection unit; and a warning unit that issues a warning when the high luminance difference boundary detection unit detects a luminance difference of a certain level or more, and the imaging optical system sets a minimum pixel pitch of the electronic imaging device. When the lateral aberration amount of magnification color of h line (wavelength 404.7 nm) with respect to wavelength 587.56 nm at any of image height ratios 0.9, 0.7, 0.5 of P and maximum image height is Sh Satisfies the following conditional expression (2) It is characterized in.
      | Sh | ≧ 2P                                      (2)
[0015]
  With this configuration, it is possible to notify the photographer that the subject is in a situation where color flare with a large change in contrast is likely to occur, and the photographer approaches the subject so as not to cause a contrast difference. In addition, it is possible to take measures such as setting the camera angle to follow light, or using a strobe to reduce the luminance difference, and an image with little or no color flare can be obtained.In the above conditional expressions (1) and (2), when the value of 2P is sufficiently small, the generated chromatic aberration itself is small, so that signal processing becomes unnecessary.
[0016]
  The warning means may be a warning sound such as a buzzer, a warning display on the display in the finder or the liquid crystal display part of the camera body, or a strobe operation for reducing the luminance difference. Of course, in a camera capable of exchanging lenses, a mount unit that can connect an imaging optical system equipped with a screw mount or the like may be used.
  In addition, at least one of the electronic imaging elements having three or more different spectral sensitivity characteristics for obtaining the color image has spectral characteristics having two high peak wavelengths, and the two peaks. If a so-called complementary color mosaic filter having a wavelength of sensitivity of 50% or less with respect to both of the two peak wavelengths is used between wavelengths, the sensitivity on the short wavelength side becomes higher than necessary. It is effective when applied to each configuration of the present invention.
[0028]
In the present invention, the conditional expression (1) may be replaced with the following conditional expression (1 ′).
(Lh-Ld) / Fmin ≧ 4P (1 ')
[0029]
In the present invention, the conditional expression (1) may be replaced with the following conditional expression (1 ″).
(Lh-Ld) / Fmin ≧ 6P (1 '')
[0030]
In the present invention, the conditional expression (2) may be replaced with the following conditional expression (2 ′).
| Sh | ≧ 3P (2 ')
[0031]
In the present invention, the conditional expression (2) may be replaced with the following conditional expression (2 ″).
｜ Sh | ≧ 5P ...... (2 '')
[0032]
In the present invention, chromatic aberration increases as the conditional expressions satisfying the above conditional expressions (1 ′), (1 ″), (2 ′), and (2 ″) are effective. Miniaturization can be achieved.
[0033]
Next, a configuration for optically reducing color flare due to chromatic aberration in the present invention will be described.
FIG. 1 is a conceptual diagram of an imaging optical system according to the present invention that optically reduces color flare. The imaging optical system 1 includes a filter 3 as wavelength correction means. The light beam that has passed through the imaging optical system 1 forms a subject image on the imaging device 2. An image including the entire visible light region is formed on the image plane 4. Note that the image formation state at the center of the image plane can be determined based on the spherical aberration diagram.
[0034]
FIG. 2 is a spherical aberration diagram of the imaging optical system of FIG. In FIG. 2, the absolute value of the difference between the paraxial image point and the position at which the marginal ray of each wavelength at the maximum incident height at the minimum F value Fmin and the optical axis intersect at the minimum F value Fmin, that is, the amount of spherical aberration. Is expressed as Lλ. If λ is the d line (587.56 nm), the absolute value of the spherical aberration amount of the d line is represented as Ld.
[0035]
In the aberration diagram of FIG. 2, Ld and Lλ indicate the amount of shift of the focal position at the maximum incident height, and this is shown in FIG. 3 when viewed in a cross-sectional view of the rear focal portion of the imaging optical system 1. .
In FIG. 3, the solid line indicates the marginal ray having the maximum incident height of the d-line, and the broken line indicates the marginal ray having the maximum incident height of an arbitrary wavelength λ. The deviation of the image plane of each wavelength with respect to the paraxial image plane 4 is recognized as a color flare on the paraxial image plane.
[0036]
In FIG. 3, the flare diameters centered on the optical axis 5 on the paraxial image plane 4 are represented as Ld / Fmin and Lλ / Fmin, respectively.
If the difference between Ld / Fmin and Lλ / Fmin is large, color flare is likely to occur. However, it is difficult to correct chromatic aberration particularly on the shorter wavelength side than the d line, and it is difficult to correct chromatic aberration well in the entire imaging optical system. Since it is difficult, in order to achieve an inexpensive imaging optical system, chromatic aberration on the short wavelength side must remain to some extent.
[0037]
Therefore, in the imaging optical system according to the present invention, the difference between Ld / Fmin and Lλ / Fmin is 0.05 mm, that is, the following conditional expression (3)
(Lλ−Ld) /Fmin=0.05mm (3)
Where λ1 is within a range that can be sensed by an electronic imaging device having a d-line or less, and a good d-line of an image secures a light quantity necessary for image formation and color In order to reduce the amount of light having a wavelength λ1 that becomes a flare, the wavelength λc at which the transmittance is half the value of the transmittance of the d-line is configured to exhibit characteristics satisfying the following conditional expression (4).
λ1 ≦ λc ≦ d line (587.56nm) ...... (4)
[0038]
With this configuration, the amount of light in the vicinity of the d-line with good imaging performance can be secured, and the amount of light having the wavelength λ1 that causes color flare can be reduced and reproduced. Even so, color flare can be suppressed. When λc becomes smaller than the lower limit of the conditional expression (4), color flare becomes conspicuous. If the upper limit is exceeded, color reproducibility deteriorates.
[0039]
It has been described that it is preferable to satisfy the above conditional expression (4) for the wavelength λ1 at which the difference between Ld / Fmin and Lλ / Fmin is 0.05 mm. However, the obtained electronic image is stretched and observed. In consideration, it is more preferable that the wavelength at which the difference between Ld / Fmin and Lλ / Fmin is 0.04 mm is λ1, and the conditional expression (4) is satisfied. Further, it is more preferable that the wavelength at which the difference between Ld / Fmin and Lλ / Fmin is 0.03 mm is λ1, and the conditional expression (4) is satisfied.
In order to satisfy the above conditional expression (4), the spectral transmittance characteristic of the wavelength correction filter 3 or the spectral transmittance characteristic of the entire imaging optical system 1 by applying a wavelength correction coating or the like is adjusted. do it.
[0040]
So far, chromatic aberration on the optical axis has been described, but the same applies to chromatic aberration of magnification. FIG. 4 is an aberration diagram showing the amount of chromatic aberration at a magnification of wavelength λ with respect to the d-line. In FIG. 4, the lateral aberration amount Sλ of the magnification color of the wavelength λ with respect to the d-line at the maximum image height IH with respect to the maximum image height IH is 0.9. When this is expressed on the paraxial image plane 2 in FIG. 1, the state of chromatic aberration at an image height ratio of 0.9 on the image plane is as shown in FIG. 5, and color flare occurs.
[0041]
Therefore, the imaging optical system according to the present invention has a paraxial image plane 4 when the lateral aberration amount of the magnification color with respect to the d-line (587.56 nm) at the image height ratio of 0.9 at the maximum image height at an arbitrary wavelength λ is Sλ. The above deviation amount | Sλ | is 0.025 mm, that is, the following conditional expression (5)
| Sλ | = 0.025mm (5)
Where λ2 is a wavelength shorter than the d-line, and the wavelength λc at which the transmittance is half the d-line transmittance satisfies the following conditional expression (6). It is preferable to configure so as to exhibit the characteristics.
λ2 ≦ λc ≦ d line (587.56nm) ...... (6)
When the wavelength λc becomes smaller than the lower limit of the conditional expression (6), the color flare becomes conspicuous. If the upper limit is exceeded, color reproducibility deteriorates.
[0042]
It has been described that it is preferable to satisfy the above conditional expression (6) for the wavelength λ2 at which | Sλ | is 0.025 mm. However, considering that the obtained electronic image is enlarged and observed, | Sλ | It is more preferable that the wavelength of 0.02 mm is λ2, and the conditional expression (6) is satisfied. Further, it is more preferable that the wavelength at which | Sλ | is 0.015 mm is λ2, and the conditional expression (6) is satisfied.
[0043]
In addition, when configured as an imaging optical system that exhibits a spectral transmittance that satisfies the above conditional expression (4) and conditional expression (6) simultaneously, color flare can be suppressed both on the optical axis and off the optical axis. An imaging optical system can be achieved.
[0044]
Further, in the imaging in the visible light region, since the sensitivity of the human eye is low on the short wavelength side of the visible light region, visible light close to the ultraviolet region is difficult to be recognized by the human eye. On the other hand, unlike the sensitivity of the human eye, the imaging device reproduces the visible light region close to the ultraviolet region to a level that can be recognized by the human eye. For this reason, it is necessary to reduce the reproducibility of the region close to the ultraviolet ray while ensuring the amount of light in the region that is strongly recognized by human eyes.
[0045]
Therefore, in order to reduce the amount of light on the shorter wavelength side than 390 nm, which is difficult to be recognized by the human eye, and to ensure the amount of light on the longer wavelength side than 430 nm, which is easily recognized by the human eye, the transmittance is d-line. It is preferable to use an imaging optical system in which the wavelength λc, which is a half value for the transmittance, satisfies the following conditional expression (7).
390 nm ≦ λc ≦ 440 nm (7)
[0046]
Correspondingly, even if the chromatic aberration on the optical axis of the imaging optical system itself is deteriorated at the shorter wavelength side than the above wavelength range, the effect on the reproduced image is small.
Therefore, the minimum F value of this imaging optical system is Fmin, and when the F value is Fmin, the absolute value of the spherical aberration amount of the marginal ray of any wavelength λ is Lλ, and the spherical aberration of the marginal ray at the d-line (587.56 nm) Conditional expression (3) when the absolute value of quantity is Ld
(Lλ-Ld) /Fmin=0.05mm (3)
It is preferable to configure the optical system so that λ1 satisfies the following conditional expression (8), where λ1 is a wavelength that satisfies the above.
390nm ≦ λ1 ≦ 430nm (8)
[0047]
If the wavelength λ1 becomes smaller than the lower limit of the conditional expression (8), the accuracy of the optical system is required, and the optical system cannot be configured at low cost. If the upper limit is exceeded, color flare cannot be completely removed.
If the lower limit of the conditional expression (7) is exceeded, color flare on the short wavelength side becomes conspicuous. If the upper limit is exceeded, color reproducibility deteriorates.
[0048]
It has been described that it is preferable to satisfy the above conditional expression (8) for the wavelength λ1 at which the difference between Ld / Fmin and Lλ / Fmin is 0.05 mm. However, the obtained electronic image should be stretched and observed. In consideration, it is more preferable that the wavelength at which the difference between Ld / Fmin and Lλ / Fmin is 0.04 mm is λ1, and the conditional expression (8) is satisfied. It is more preferable that the wavelength at which the difference between Ld / Fmin and Lλ / Fmin is 0.03 mm is λ1, and the conditional expression (8) is satisfied.
[0049]
Further, the imaging optical system according to the present invention similarly applies the wavelength λ with respect to the d-line (587.56 nm) at the image height ratio of 0.9 in the state where the conditional expression (7) is satisfied for the chromatic aberration of magnification. Conditional expression (5) where Sλ is the lateral aberration of the magnification color of
| Sλ | = 0.025mm (5)
It is preferable that λ2 exhibit a characteristic satisfying the following conditional expression (9), where λ2 is a wavelength satisfying the above.
390nm ≦ λ2 ≦ 430nm (9)
[0050]
If λ2 becomes smaller than the lower limit of the conditional expression (9), the accuracy of the optical system is required, so that the optical system cannot be configured at low cost. If the upper limit is exceeded, color flare cannot be completely removed.
[0051]
Although it has been described that it is preferable that the conditional expression (9) is satisfied for the wavelength λ2 at which | Sλ | is 0.025 mm, considering that the obtained electronic image is enlarged and observed, | Sλ | It is more preferable that the wavelength of 0.02 mm is λ2 and the conditional expression (9) is satisfied. Further, it is more preferable that the wavelength at which | Sλ | is 0.015 mm is λ2, and the conditional expression (9) is satisfied.
[0052]
If the conditional expressions (7), (8), and (9) are satisfied at the same time, an imaging optical system that suppresses color flare both on the optical axis and off the optical axis can be achieved.
[0053]
The imaging optical system of the present invention is an imaging optical system that forms a subject image on an electronic imaging device. The minimum F value of the imaging optical system is Fmin, and an arbitrary wavelength λ when the F value is Fmin. When the absolute value of the spherical aberration of the marginal ray is Lλ and the absolute value of the spherical aberration of the marginal ray at the d-line (587.56 nm) is Ld, the following conditional expression (3)
(Lλ-Ld) /Fmin=0.05mm (3)
Where λ1 satisfies the following conditional expression (10), the transmittance ratio of the imaging optical system at the wavelength λ1 with respect to the d-line transmittance is τ (λ1), and the d-line transmittance is It may be configured to exhibit characteristics satisfying the following conditional expressions (11) and (12) when the transmittance ratio of the imaging optical system at the wavelength λ1 + 30 nm is τ (λ1 + 30).
350nm ≦ λ1 ≦ 550nm (10)
τ (λ1) ≦ 10% …… (11)
τ (λ1 + 30) ≧ 50% …… (12)
[0054]
With this configuration, it is possible to reduce the wavelength that causes color flare on the short wavelength side where chromatic aberration occurs on the optical axis, and suppress the influence of chromatic aberration in the wavelength range recognized by the human eye, and It is possible to achieve a small imaging optical system that can secure a light amount and achieve both color reproducibility and rendering performance.
[0055]
If the wavelength λ1 becomes smaller than the lower limit of the conditional expression (10), the accuracy of the imaging optical system is required, so that the imaging optical system cannot be configured at low cost. If the upper limit is exceeded, color flare cannot be completely removed.
Further, when the transmittance at the wavelength λ1 exceeds 10%, the color flare becomes conspicuous. If the transmittance at λ1 + 30 nm is less than 50%, the color reproducibility is deteriorated.
[0056]
It has been described that it is preferable to satisfy the above conditional expression (10) for the wavelength λ1 at which the difference between Ld / Fmin and Lλ / Fmin is 0.05 mm. However, the obtained electronic image is stretched and observed. In consideration, it is more preferable that the wavelength at which the difference between Ld / Fmin and Lλ / Fmin is 0.04 mm is λ1, and the conditional expressions (10), (11), and (12) are satisfied. It is more preferable that the wavelength at which the difference between Ld / Fmin and Lλ / Fmin is 0.03 mm is λ1, and the conditional expressions (10), (11), and (12) are satisfied.
[0057]
The imaging optical system according to the present invention also has a magnification chromatic aberration of wavelength λ with respect to the d-line (587.56 nm) at an image height ratio of 0.9 at the maximum image height in the same manner as the chromatic aberration on the optical axis. When the lateral aberration amount of S is Sλ, the following conditional expression (5)
| Sλ | = 0.025mm (5)
Where λ2 satisfies the following conditional expression (13), the transmittance ratio of the imaging optical system at the wavelength λ2 with respect to the transmittance of the d-line is τ (λ2), When the transmittance ratio of the imaging optical system at the wavelength λ2 + 30 nm with respect to the transmittance is τ (λ2 + 30), the following conditional expressions (14) and (15) may be satisfied.
350nm ≦ λ2 ≦ 550nm (13)
τ (λ2) ≦ 10% …… (14)
τ (λ2 + 30) ≧ 50% …… (15)
[0058]
This configuration reduces the wavelength that causes color flare on the short wavelength side where chromatic aberration of magnification occurs, suppresses the effect of chromatic aberration in the wavelength range recognized by the human eye, and secures the amount of light to achieve color reproduction. Therefore, it is possible to achieve a small imaging optical system that achieves both high performance and imaging performance.
[0059]
Note that when the wavelength λ2 becomes smaller than the lower limit of the conditional expression (13), the accuracy of the imaging optical system is required, and the imaging optical system cannot be configured at low cost. If the upper limit is exceeded, color flare cannot be completely removed.
Further, when the transmittance at the wavelength λ2 exceeds 10%, the color flare becomes conspicuous. If the transmittance at λ2 + 30 nm is less than 50%, the color reproducibility is deteriorated.
[0060]
Although it has been described that it is preferable that the conditional expressions (13), (14), and (15) are satisfied for the wavelength λ2 at which | Sλ | is 0.025 mm, the obtained electronic image is enlarged and observed. In consideration of the above, it is more preferable that the wavelength at which | Sλ | is 0.02 mm is λ2, and the conditional expressions (13), (14), and (15) are satisfied. Further, it is more preferable that the wavelength at which | Sλ | is 0.015 mm is λ2, and the conditional expressions (13), (14), and (15) are satisfied.
[0061]
Also, when the above conditional expressions (10), (11), (12), (13), (14), and (15) are satisfied at the same time, color flare is suppressed both on the optical axis and off the optical axis. An imaging optical system can be achieved.
[0062]
The imaging optical system according to the present invention is an imaging optical system that forms a subject image on an electronic imaging device. The minimum F value of the imaging optical system is Fmin, and h line (404.7 when the F value is Fmin). nm) the absolute value of the spherical aberration of the marginal ray of Lh, the absolute value of the spherical aberration of the g ray (435.8 nm) of Lg, the absolute value of the spherical ray of the marginal ray of d line (587.56 nm). When the transmission ratio of h-line of this imaging optical system to Ld and d-line is τh and the transmission ratio of g-line to d-line is τg, the following conditional expression (16) is satisfied and transmission A wavelength λc having a half-value with respect to the transmittance of the d-line may exist between the g-line and the h-line, that is, a characteristic satisfying the following conditional expression (17) may be exhibited.
(Lg−Ld) / Fmin × τh ≦ (Lg−Ld) / Fmin × τg (16) h line (404.7 nm) <λc <g line (435.8 nm) (17)
[0063]
The left side of the conditional expression (16) is obtained by multiplying the h-ray color blur and the h-line transmittance with respect to the d-line color blur near the optical axis. On the other hand, the right side is obtained by multiplying the size of the g-line color blur and the g-line transmittance with respect to the d-line color blur near the optical axis.
[0064]
In general, an imaging optical system using a visible light region as a light source is designed so that no aberration occurs near the d-line. For this reason, the h-line and the g-line are more likely to have color blur, so if the h-line transmittance is reduced and the g-line transmittance is increased to satisfy the above conditional expression (16). , Color flare depending on h line can be suppressed.
If the above conditional expression (17) is satisfied so that the wavelength λc at which the transmittance is half the value of the transmittance of the d-line exists between the g-line and the h-line, the amount of light of the g-line is secured. Color reproducibility can be secured.
[0065]
Further, the imaging optical system according to the present invention also provides the chromatic aberration of magnification with respect to the d-line (587.56 nm) with respect to the d-line (587.56 nm) at an image height ratio of 0.9, similarly to the condition for chromatic aberration on the optical axis. ) Is the lateral aberration amount of the chromaticity of Sh and the imaging of the lateral aberration amount of the chromaticity of the g-line (435.8 nm) with respect to the d-line (587.56 nm) at the maximum image height ratio of 0.9 is Sg and the d-line. When the transmittance ratio of h-line of the optical system is τh and the transmittance ratio of g-line to d-line is τg, the following conditional expression (18) is satisfied, and the transmittance is the transmittance of d-line. On the other hand, it is preferable that the conditional expression (17) is satisfied so that a wavelength λc which is a half value exists between the g-line and the h-line.
| Sh | × τh ≦ | Sg | × τg (18)
[0066]
The left side of the conditional expression (18) is obtained by multiplying the color deviation of the h line with respect to the d line due to the chromatic aberration of magnification and the transmittance of the h line. On the other hand, the right side is obtained by multiplying the color deviation of the g-line with respect to the d-line by the chromatic aberration of magnification and the transmittance of the g-line.
In the same manner as described above, the h-line and the g-line are more likely to have color blur. Therefore, the transmittance of the h-line is decreased and the transmittance of the g-line is increased to increase the conditional expression (18 ), The color flare depending on the h line can be suppressed.
If the above conditional expression (17) is satisfied so that the wavelength λc at which the transmittance is half the value of the transmittance of the d-line exists between the g-line and the h-line, the amount of light of the g-line is secured. Color reproducibility can be secured.
[0067]
The restriction contents of each wavelength used in the above conditional expressions may be achieved in total for the glass material of the optical system. However, a filter as a wavelength correction element for mainly performing wavelength correction is provided in the imaging optical system. May be achieved. It may also be achieved by applying a coating for wavelength correction on the lens surface.
[0068]
Further, when a coating film for performing wavelength correction is applied on a flat surface, the manufacture becomes easy.
Further, if a low-pass filter is provided in the imaging optical system and at least one surface of the low-pass filter is coated with wavelength correction, the number of parts can be reduced.
[0069]
Further, if an infrared cut filter for reducing the infrared light component is disposed in the imaging optical system, and at least one surface of the infrared cut filter is coated with a wavelength correction, the number of parts can be reduced.
[0070]
In addition, if a coating is applied such that there is a wavelength at which the transmittance is between the g-line and h-line, and between 600 nm and 700 nm, the transmittance is half that of the d-line transmittance, an infrared cut filter There is no need to separately arrange the components, and the number of parts can be reduced.
[0071]
In addition, when wavelength correction is performed by providing an optical path dividing means in the optical path of the imaging optical system, the imaging element having an imaging region in which the sensitivity characteristic at the g line has a sensitivity of 30% or more of the sensitivity characteristic at the e line. The wavelength correcting element may be disposed only in the optical path on the side.
In other words, the fact that the sensitivity characteristic at the g-line has 30% or more of the sensitivity characteristic at the e-line means that color flare at a short wavelength is likely to occur. Therefore, if the wavelength that causes chromatic aberration is reduced by the wavelength correction element, the influence of short wavelengths is small in the other optical paths, so that the amount of light can be secured without providing the wavelength correction element.
[0072]
For example, if one of the optical paths divided by the optical path dividing means is an observation optical path that guides the optical path to the observer's eyeball, the human eye originally has low sensitivity on the short wavelength side, and therefore it is necessary to provide a wavelength correction element. There is no.
In addition, when used in a so-called multi-plate type imaging apparatus in which an optical element is divided into a plurality of optical paths by an optical path dividing means and an imaging element having a different spectral sensitivity characteristic is provided in each of the divided optical paths, a short wavelength is used. In the optical path on the imaging element side where the light receiving sensitivity of the region is small, the wavelength correction element is not necessary.
[0073]
An imaging optical system according to the present invention is an imaging optical system that forms a subject image on an electronic imaging element, and has an adjustment element that adjusts the amount of light in the optical path of the imaging optical system. It is preferable to provide a wavelength correction function in which the transmittance between the line and the h line is half the transmittance of the e line.
[0074]
If comprised in this way, it is not necessary to provide a wavelength correction means separately, and can reduce a number of parts.
Specifically, the wavelength correction action can be achieved by mixing a coating or absorbing dye with the adjusting element.
In the present invention, of course, it is more preferable that the characteristics satisfy at least one of the above-described conditional expressions.
The above conditional expressions may be arbitrarily combined.
[0075]
In the imaging optical system according to the present invention, it is preferable that the optical element related to the determination of the focal length in the imaging optical system is constituted by an optical element using only a refraction phenomenon because the configuration becomes simple.
[0076]
Further, the imaging apparatus according to the present invention may be configured by disposing three or more electronic imaging elements having different spectral sensitivity characteristics for obtaining a color image at the rear focal position of the imaging optical system.
[0078]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 6 is a block diagram of a so-called digital camera 13 showing a first embodiment of an electronic imaging apparatus according to the present invention.
In the digital camera of this embodiment, a light beam emitted from an object point is composed of an optical element that uses only a refraction phenomenon, and is subjected to an imaging action by a photographing optical system 1 ′ that generates chromatic aberration, and a CCD or the like. An image is formed on the electronic image sensor 2. At this time, a low-pass filter 6 having a low-pass effect is arranged on the object side of the imaging surface 4 of the electronic imaging device 2 in order to prevent a so-called moire phenomenon that occurs because the imaging device is a regular collection of photoelectric conversion elements (pixels). Yes. In addition, you may arrange | position the IR cut filter which has the effect of IR cut which cuts infrared light as needed for design.
[0079]
Mosaic filters having three or more different spectral characteristics for obtaining a color image are arranged on the incident surface of the electronic image pickup device 2, and light beams in respective wavelength ranges are incident on each pixel.
The light beam incident on the electronic image sensor 2 is converted into an electrical signal including luminance and color information in each pixel which is a photoelectric conversion element, and the electrical signal including luminance and color information in each pixel of the image sensor is converted to the controller 7. Then, the controller 7 performs signal processing such as gamma correction and image compression processing, and outputs the result to the personal computer 10 or the like via the built-in memory 8 or the interface 9. In addition, the photographer can confirm the image to be photographed and the photographed image transmitted from the controller 7 to the liquid crystal monitor 11. In addition, image data can be transmitted from the built-in memory 8 to an auxiliary memory 12 such as a so-called smart media (trade name).
[0080]
Here, as a feature of the electronic imaging apparatus of the present embodiment, an optical path dividing optical element composed of a bonding prism 14 is disposed on an optical path transmitted through the photographing optical system 1, and high luminance is provided on one of the divided optical paths. A two-dimensional area photometric sensor 15 is provided as a difference boundary detection means. An ND filter is disposed on the surface of the two-dimensional area sensor 15 so that the sensitivity is -3 stages, that is, 1/8, that of the image sensor 2.
[0081]
On the two-dimensional area photometric sensor 15, an image that is substantially the same as the image on the imaging surface 4 is formed. As shown in FIG. 7, the two-dimensional area photometric sensor 15 has a light receiving surface on which a plurality of photometric areas 16 are regularly arranged, and information on the luminance of the subject received in each photometric area 16. An electrical signal including is transmitted to the controller 7.
[0082]
In the controller 7, based on the luminance information of the electrical signal including the luminance and color information from the image sensor 3, the image reading time (shutter speed in a silver halide camera) and the aperture value (F number) are set so as to achieve proper exposure. ) To decide. In addition, instead of the luminance information from the image sensor 3, the image reading time and the aperture value may be adjusted so that an appropriate exposure is obtained from an electric signal including luminance information of the two-dimensional area photometric sensor 15. .
[0083]
Using the electronic image pickup apparatus of the present embodiment configured as described above, a subject with a strong contrast between light and dark, such as indoor shooting in a backlit state against a clear sky as shown in FIG. There is a situation in which a certain number of pixels (for example, pixels having a light reception level of +2 EV or more and pixels of −1 EV or less with respect to proper exposure) exist between a certain number of adjacent pixels (for example, between 6 pixels). When the image sensor 2 or the two-dimensional area photometric sensor 15 calculates the electric signal including the luminance information via the controller 7, the color flare 19 due to the chromatic aberration of the photographing optical system 1 becomes conspicuous.
[0084]
Therefore, on the liquid crystal monitor 11, a display indicating that a region with a high brightness difference is on the screen is displayed, the observer is prompted to change the camera angle, and the strobe mechanism 17 is automatically popped up to prepare auxiliary illumination. The operation for reducing the color flare by reducing the difference in brightness at the time of shooting is performed. Further, a warning sound may be emitted through the buzzer 18.
[0085]
In addition, when an image is taken including a region with a sharp contrast, an image including large chromatic aberration is formed on the imaging surface 4. For this reason, a boundary portion where the luminance difference is greater than or equal to a certain level between a certain number of pixels is detected via the controller 7, and a color flare in the vicinity of the detected boundary portion (here, one pixel to the boundary portion and the periphery). In order to reduce this, an electrical signal including luminance and color information from the image sensor 3 is electrically adjusted.
[0086]
FIG. 9 is a state explanatory diagram illustrating an example of a luminance difference with respect to appropriate exposure for each pixel in which a part of the imaging surface 4 is enlarged. In the figure, each square represents a pixel 20. In the present embodiment, the luminance signal of each pixel 20 is analyzed by the controller 7, and after calculating an area of +2 EV or more and an area of −1 EV or less with respect to proper exposure, a boundary portion of 6 pixels or less is determined between them. It has become. In FIG. 9, pixels corresponding to the boundary portion are represented by x marks. Then, signal processing is performed via the controller 7 so as to remove the color flare in that range including one pixel adjacent to the boundary (shown by hatching in the figure). As long as this signal processing is correction in the vicinity of the boundary portion, any method may be used, such as correction of only the boundary portion or removal of the most peripheral pixels of the boundary portion from the correction target.
[0087]
The determination of the boundary portion may be calculated from the signal of the photometric sensor 15 by making each photometric area 16 of the two-dimensional area photometric sensor 15 correspond to each pixel 20 instead of calculating from the signal of the image sensor.
[0088]
Next, a signal processing method will be described.
As an example of the signal processing method, color blur can be reduced by reducing the saturation of the video near the boundary. Color blur tends to cause long-wavelength or short-wavelength color flare from the bright part to the dark part, so that blue and red appear stronger than the actual image, resulting in an unnatural brightness color. Therefore, among the spectral characteristics corresponding to each pixel, the color reproducibility corresponding to the pixel with strong luminance is reduced to the luminance level of other colors, so that the saturation and luminance are reduced, and the color blur is conspicuous. Can be eliminated.
[0089]
Alternatively, the controller 7 as a signal processing means causes the chromaticity in the vicinity of the boundary portion on the dark portion side adjacent to the boundary portion and the low luminance portion to be separated from the boundary portion to the dark portion by a certain pixel (for example, two pixels) or more. Color blur may be reduced by adjusting the frequency to be close to the chromaticity of the side.
[0090]
Further, as a method of detecting the boundary portion of the high luminance difference, appropriate exposure is produced via the controller 7, and proper exposure is obtained via the two-dimensional area photometric sensor 15 shown in FIG. , A pixel corresponding to an area where the exposure level is saturated (shaded portion in the figure) and an unsaturated pixel adjacent to the saturated pixel are detected, and a boundary having a large luminance difference is detected between the pixels. It may be detected as a part.
[0091]
Further, instead of the two-dimensional area photometric sensor 15 shown in FIG. 6, a plurality of photometric areas 16, as shown in FIG. 11, on which an ND filter as a sensitivity reduction unit is applied on the imaging surface 4 of the electronic image sensor 2. Pixels may be provided, and a boundary portion may be detected in the same manner as described above using luminance information of an electrical signal including information on luminance received by each pixel.
A schematic flowchart of signal processing in the controller 7 is shown in FIG. As shown in FIG. 12, an electric signal including luminance and color information from each pixel of the electronic image sensor is converted into a luminance signal and a color signal by a circuit unit. This luminance signal and / or color signal is also included in the concept of an electric signal including luminance and color information of the present application.
[0092]
Next, the color filter used for the electronic image sensor 2 will be described.
In order to obtain a color image, a color filter as shown in FIG. 13 or FIG. 14 is arranged on the electromagnetic imaging device so as to have three or more photoelectric conversion elements having different wavelength characteristics. FIG. 13 shows a type called a primary color filter, which is composed of red (R), green (G), and blue (B) filters. Each wavelength characteristic is shown in FIG. FIG. 15 is a type called a complementary color filter, and is composed of cyan (C) magenta (M), yellow (Ye), and green (G) filters. Each wavelength characteristic is shown in FIG.
[0093]
Here, in the case of a complementary color filter, C, M, Ye, and G are converted into R, G, and B by performing the following processing in the controller 7.
Luminance signal
Y = | G + M + Ye + C | × 1/4
Color signal
R−Y = | (M + Ye) − (G + C) |
B−Y = | (M + C) − (G + Ye) |
The primary color filter can be easily processed for color reproduction, and the complementary color filter can reduce the amount of light to the photoelectric conversion surface.
[0094]
In order to obtain a color image, for example, as shown in FIG. 17, a color separation prism 24 including a first prism 20, a second prism 21, and a third prism 23 is arranged on the image side of the photographing optical system 1. The light from the imaging optical system may be decomposed into R, G, and B to form an image on three or more imaging elements 2R, 2G, and 2B.
[0095]
Here, an example of an imaging optical system in which chromatic aberration is used, which is used in the above-described configuration, is shown as numerical data.
Example 1
FIG. 18 is a lens cross-sectional view showing a first example of the image pickup optical system according to the present embodiment. FIG. 19 is a spherical aberration diagram at the wide-angle end in focus at infinity in the image pickup optical system of this example and the magnification with respect to the d line. It is a figure showing chromatic aberration.
[0096]
In the numerical data shown below, r1, r2, r3... Are the radius of curvature of each lens surface, d1, d2, d3... Are the thickness or air spacing of each lens, n1, n2, n3. The refractive index of each lens at the d-line (587.56 nm), v1, v2, v3... Is the Abbe number of each lens.
[0097]
The aspherical shape is z in the optical axis direction, y in the direction perpendicular to the optical axis, r is the radius of curvature, k is the conical coefficient, and AC is the aspherical coefficient.₂, AC_Four, AC₆, AC₈, AC_Ten, AC₁₂Is expressed by the following equation.
z = (y²/ R) / [1 + √ {1- (1 + k) · (y / r)²}] + AC₂y²+ AC_Foury^Four+ AC₆y⁶+ AC₈y⁸+ AC_Teny^Ten+ AC₁₂y¹²
In the following numerical data, the minimum pixel pitch P of the electronic image sensor is set to 0.003 mm.
In the following, the numerical data of this example is shown as Numerical Example 1.
[0098]

[0099]

[0100]

[0101]

[0102]

[0103]
Aberration amount
Lh = 0.0865mm
Lg = 0.0324mm
Ld = 0.0061mm
(Lh−Ld) /Fmin=0.0394 mm = 13.1P
When (Lλ-Ld) /Fmin=0.05mm
Lλ = 0.0959mm, λ1 = 401nm
When (Lλ-Ld) /Fmin=0.04mm
Lλ = 0.0755mm, λ1 = 409nm
When (Lλ-Ld) /Fmin=0.03mm
Lλ = 0.0551mm, λ1 = 420nm
[0104]
| Sh | = 0.0218mm = 7.3P
| Sg | = 0.0083mm
When | Sλ | = 0.025mm
λ2 = 400nm
When | Sλ | = 0.02mm
λ2 = 408nm
When | Sλ | = 0.015mm
λ2 = 418nm
[0105]
Example 2
FIG. 20 is a lens cross-sectional view showing a second example of the image pickup optical system according to the present embodiment. FIG. 21 shows a spherical aberration diagram at the time of focusing on infinity in the image pickup optical system of this example and chromatic aberration of magnification with respect to the d line. FIG.
In the second embodiment, axial chromatic aberration is corrected, but the chromatic aberration of magnification is not corrected completely.
In the following, the numerical data of this example is shown as Numerical Example 2.
[0106]

[0107]

[0108]

[0109]
Aberration amount
Lh = 0.02972mm
Lg = 0.04734mm
Ld = 0.04041mm
(Lh−Ld) /Fmin=−0.003 mm = −1P
When (Lλ-Ld) /Fmin=0.05mm
Lλ = 0.1036mm, λ1 = 344nm
When (Lλ-Ld) /Fmin=0.04mm
Lλ = 0.0748mm, λ1 = 351nm
When (Lλ-Ld) /Fmin=0.03mm
Lλ = 0.0460mm, λ1 = 360nm
[0110]
| Sh | = 0.0226mm = 7.5P
| Sg | = 0.0100mm
When | Sλ | = 0.025mm
λ2 = 400nm
When | Sλ | = 0.02mm
λ2 = 409nm
When | Sλ | = 0.015mm
λ2 = 420nm
[0111]
In addition, as shown in FIG. 22, the electronic imaging apparatus of the present embodiment has a mount portion 25 that allows the imaging optical system 1 to be attached to and detached from the electronic imaging apparatus body 13 including the imaging optical system 1 and the electronic imaging element 2. You may do it. As a result, various imaging optical systems 1 can be exchanged according to imaging conditions, and color flare correction can be performed in each state. In addition, as the mount part 25, it is good to use a screw type, a bayonet type, etc. The other configuration is basically the same as that of the imaging optical system shown in FIG.
[0112]
Since the electronic imaging apparatus according to the present embodiment is configured as described above, even if chromatic aberration occurs due to the reduction in size and weight of the imaging optical system, the luminance signal and color signal of the image to be captured are displayed. By adjusting, it is possible to realize an electronic imaging device with reduced color bleeding.
[0113]
Next, a second embodiment of the electronic imaging apparatus according to the present invention is shown in FIG. In addition, the same structure as 1st Embodiment attaches | subjects the same number, and the description is abbreviate | omitted.
The electronic imaging apparatus of this embodiment is configured to optically remove color flare using a wavelength correction filter for performing wavelength correction.
Specifically, instead of a configuration that removes color flare in the signal processing system, a wavelength correction filter that reduces the transmittance of light in the short wavelength region by applying a coating film that performs wavelength correction on one side of a parallel flat plate 3 is different from the first embodiment in that 3 is disposed in the optical path of the imaging optical system 1.
[0114]
As the imaging optical system 1, the imaging optical system shown in the numerical data of the first embodiment or the second embodiment may be used.
In this imaging optical system, the optical element related to the determination of the focal length is an optical element using only a refraction phenomenon.
Then, FIG. 24 shows a spectral transmittance curve of only the optical element (imaging optical system 1 ′) in the imaging optical system and a spectral transmittance curve when the wavelength correction filter 3 is passed.
As shown in FIG. 24, when the wavelength correction filter 3 is used, a good image can be obtained by reducing the amount of light on the short wavelength side where color flare is likely to occur as compared with the characteristics of only the photographing optical system 1 ′. It turns out that it is obtained.
Specific numerical data of the imaging optical system in the present embodiment is shown as Numerical Example 3 below.
[0115]
Numerical example 3
λc = 430 nm
τh = 0%
τg = 60%
Sensitivity characteristic at the g-line / sensitivity characteristic at the e-line = 0.35 of the electronic imaging device
[0116]
In combination with Numerical Example 1
When (Lλ-Ld) /Fmin=0.05mm
τ (λ1) = 0%
τ (λ1 + 30) = 52%
When (Lλ-Ld) /Fmin=0.04mm
τ (λ1) = 0%
τ (λ1 + 30) = 62%
When (Lλ-Ld) /Fmin=0.03mm
τ (λ1) = 5%
τ (λ1 + 30) = 82%
[0117]
When | Sλ | = 0.025mm
τ (λ2) = 0%
τ (λ2 + 30) = 50%
When | Sλ | = 0.02mm
τ (λ2) = 0%
τ (λ2 + 30) = 63%
When | Sλ | = 0.015mm
τ (λ2) = 4%
τ (λ2 + 30) = 80%
[0118]
(Lh−Ld) / Fmin × τh = 0
(Lg−Ld) /Fmin×τg=0.01133 mm
| Sh | × τh = 0
| Sg | × τg = 0.498 mm
[0119]
In combination with Numerical Example 2
When (Lλ-Ld) /Fmin=0.05mm
τ (λ1) = 0%
τ (λ1 + 30) = 0%
When (Lλ-Ld) /Fmin=0.04mm
τ (λ1) = 0%
τ (λ1 + 30) = 0%
When (Lλ-Ld) /Fmin=0.03mm
τ (λ1) = 0%
τ (λ1 + 30) = 0%
[0120]
When | Sλ | = 0.025mm
τ (λ2) = 0%
τ (λ2 + 30) = 50%
When | Sλ | = 0.02mm
τ (λ2) = 0%
τ (λ2 + 30) = 65%
When | Sλ | = 0.015mm
τ (λ2) = 5%
τ (λ2 + 30) = 82%
[0121]
(Lh−Ld) / Fmin × τh = 0
(Lg-Ld) / Fmin x τg = 0.004158mm
| Sh | × τh = 0
| Sg | × τg = 0.006 mm
[0122]
Further, the imaging apparatus of the present embodiment can be applied to an imaging apparatus of a different type from the electronic imaging apparatus of FIG. 23. As shown in FIG. 25, the light beam is divided and observed on the object side from the electronic imaging element. The present invention can be applied to a so-called TTL finder type imaging apparatus that uses an observation optical path that guides the optical path to the human eyeball and guides it to the finder optical system 26. In the imaging optical apparatus of FIG. 25, the imaging optical system 1 uses the ones shown in the above numerical examples. This TTL finder type is characterized in that it consumes less power and can observe the subject. In the type of image pickup apparatus shown in FIG. 25, a half mirror prism 27 is used as an optical path dividing unit between the finder optical system 26 and the photographing optical system 1 ′. The CCD 2 as an electronic imaging device has an imaging region in which the sensitivity characteristic at the g-line has a sensitivity of 30% or more of the sensitivity characteristic at the e-line, and the above wavelength correction is performed only on the optical path on the electronic imaging element side. A low-pass filter 6 is provided in which the coating film 28 to be applied is applied to the exit surface and the entrance surface side is uneven.
[0123]
The low-pass filter 6 may be provided with a coating film on one side instead of the infrared cut filter.
Further, by coating so that the transmittance is between the g-line and the h-line, and between 600 nm and 700 nm, the transmittance is a half-value with respect to the transmittance of the d-line. An action of an infrared cut filter and a color flare reduction action may be performed.
Further, in the three-plate type image pickup device as shown in FIG. 17, the blue image pickup device (B) side having an image pickup region in which the sensitivity characteristic at the g line has a sensitivity of 30% or more of the sensitivity characteristic at the e line. The wavelength correction element 3 indicated by a dotted line may be disposed only in the optical path.
[0124]
Furthermore, the structure of the principal part of other embodiment of the electronic imaging device by this invention is shown in FIG. In the present embodiment, a turret 29 that can adjust the brightness of 0 stage, −1 stage, −2 stage, and −3 stage on the optical path of the optical axis 5 between the imaging optical system 1 and the electronic imaging device 2. It is arranged. Other configurations such as the imaging optical system are the same as those in the above embodiments.
[0125]
The turret 29 is provided with a parallel plate 30, a −1 stage ND filter 31, a −2 stage ND filter 32, and a −3 stage ND filter 33-, and on the optical path of the optical axis 5 as the turret 29 rotates. It is comprised so that it may be located sequentially. Thereby, the amount of light incident on the image sensor 2 is adjusted. The surface of the parallel plate 30 and each ND filter is provided with a coating film 28 having a wavelength correcting function in which the transmittance between the g-line and the h-line is half the transmittance of the e-line. Color flare is reduced. Note that the spectral sensitivity characteristics of the coating film and the optical system are the same as those shown in FIG. Then, corresponding to each ND filter, the entire transmittance is reduced to 1/2, 1/4, and 1/8.
[0126]
Although various embodiments have been described above, the present invention is not limited to these embodiments, and the configurations described in the above embodiments may be variously combined or changed according to design needs. It goes without saying that there is nothing.
As described above, the electronic imaging device and the imaging optical system according to the present invention have the following features in addition to the features described in the claims.
[0136]
(1)An electronic imaging device including a plurality of pixels having three or more different spectral characteristics for obtaining a color image, and a mount unit capable of connecting an imaging optical system for forming a subject image on an imaging surface of the electronic imaging device; , A high-intensity difference detection means for detecting the presence or absence of a region where the luminance difference between certain pixels adjacent to the electronic image pickup device exceeds a certain level, and the high-luminance difference detection means detects a luminance difference above a certain level An electronic imaging apparatus, comprising: a warning unit that issues a warning when an error occurs.
[0137]
(2)An electronic imaging device that includes a plurality of pixels having three or more different spectral characteristics for obtaining a color image, converts an image received by the pixel into an electrical signal including luminance and color information, and outputs the electrical image; A mount part that enables connection of an imaging optical system that forms a subject image on the imaging surface of the element, and a boundary part that detects a boundary where the luminance difference between certain adjacent pixels of the electronic imaging element exceeds a certain level. The luminance difference boundary detection unit and the high luminance difference boundary detection unit detect the luminance flare in the vicinity of the boundary including the luminance difference of the predetermined level or more when the luminance difference boundary detection unit detects the luminance difference of the specific level or more. And an electronic image pickup apparatus comprising: a signal processing unit that electrically adjusts an electric signal including color information.
[0138]
(3)An electronic imaging device that includes a plurality of pixels having three or more different spectral characteristics for obtaining a color image, converts an image received by the pixel into an electrical signal including luminance and color information, and outputs the electrical image; A mount unit capable of connecting an imaging optical system for forming a subject image on the imaging surface of the element, an appropriate exposure calculating means for calculating an appropriate exposure value of a shooting area on the electronic image sensor, and the appropriate exposure High luminance difference boundary detection means for detecting a boundary with a large luminance difference by detecting a pixel whose exposure level is saturated by underexposure of 2 EV or less and / or a non-saturated pixel adjacent to the saturated pixel; And signal processing means for electrically adjusting an electric signal including information on the luminance and color so as to reduce color flare in the vicinity of the boundary detected by the high luminance difference boundary detection means. Electronic imaging device, characterized in that.
[0139]
(4)An imaging optical system for forming a subject image on an electronic imaging device, wherein the minimum F value of the optical system is Fmin, and the absolute value of the spherical aberration amount of a marginal ray having an arbitrary wavelength λ when the F value is Fmin. When the absolute value of the spherical aberration of the marginal ray at Lλ, d line (587.56 nm) is Ld, the following conditional expression (3)
      (Lλ−Ld) /Fmin=0.05 mm (3)
Where λ1 is in the wavelength region below the d-line, and the wavelength λc at which the transmittance is half the value of the transmittance of the d-line satisfies the following conditional expression (4). An imaging optical system characterized by exhibiting characteristics.
      λ1 ≦ λc ≦ d line (587.56 nm) (4)
[0140]
(5)An imaging optical system for forming a subject image on an electronic imaging device, wherein the lateral aberration amount of the chromaticity with respect to the d-line (587.56 nm) at an image height ratio of 0.9 at the maximum image height at an arbitrary wavelength λ is Sλ When the following conditional expression (5)
      | Sλ | = 0.025mm (5)
The wavelength λc where λ2 exists in the wavelength region below the d-line and the transmittance is half the value of the transmittance of the d-line satisfies the following conditional expression (6) where λ2 is a wavelength satisfying An imaging optical system characterized by exhibiting characteristics.
      λ2 ≦ λc ≦ d line (587.56 nm) (6)
[0141]
(6)An imaging optical system for forming a subject image on an electronic imaging device, wherein the minimum F value of the optical system is Fmin, and the absolute value of the spherical aberration amount of a marginal ray having an arbitrary wavelength λ when the F value is Fmin. When the absolute value of the spherical aberration of the marginal ray at Lλ, d line (587.56 nm) is Ld, the following conditional expression (3)
      (Lλ−Ld) /Fmin=0.05 mm (3)
Where λ1 satisfies the following conditional expression (8), and the wavelength λc at which the transmittance is half the value of the d-line transmittance satisfies the following conditional expression (7): An imaging optical system characterized by exhibiting satisfactory characteristics.
      390 nm ≦ λc ≦ 440 nm (7)
      390 nm ≦ λ1 ≦ 430 nm (8)
[0142]
(7)An imaging optical system for forming a subject image on an electronic imaging device, wherein the lateral aberration amount of the chromaticity with respect to the d-line (587.56 nm) at an image height ratio of 0.9 at the maximum image height at an arbitrary wavelength λ is Sλ When the following equation (5)
      | Sλ | = 0.025mm (5)
Where λ2 satisfies the following conditional expression (7), and the wavelength λc at which the transmittance is half the d-line transmittance satisfies the following conditional expression (9): An imaging optical system characterized by exhibiting satisfactory characteristics.
      390 nm ≦ λc ≦ 440 nm (7)
      390 nm ≦ λ2 ≦ 430 nm (9)
[0143]
(8)An imaging optical system for forming a subject image on an electronic imaging device, wherein the minimum F value of the optical system is Fmin, and the absolute value of the spherical aberration amount of a marginal ray having an arbitrary wavelength λ when the F value is Fmin. When the absolute value of the spherical aberration of the marginal ray at Lλ, d line (587.56 nm) is Ld, the following conditional expression (3)
      (Lλ−Ld) /Fmin=0.05 mm (3)
Where λ1 satisfies the following conditional expression (10), the transmittance ratio of the optical system at the wavelength λ1 with respect to the d-line transmittance is τ (λ1), and the wavelength with respect to the d-line transmittance. An imaging optical system characterized by exhibiting characteristics satisfying the following conditional expressions (11) and (12) when the transmittance ratio of the optical system at λ1 + 30 nm is τ (λ1 + 30).
      350 nm ≦ λ1 ≦ 550 nm (10)
      τ (λ1) ≦ 10% (11)
      τ (λ1 + 30) ≧ 50% (12)
[0144]
(9)An imaging optical system for forming a subject image on an electronic imaging device, wherein the lateral aberration amount of the chromaticity with respect to the d-line (587.56 nm) at an image height ratio of 0.9 at the maximum image height at an arbitrary wavelength λ is Sλ When the following conditional expression (5)
      | Sλ | = 0.025mm (5)
Where λ2 satisfies the following conditional expression (13), the transmittance ratio of the optical system at the wavelength λ2 with respect to the d-line transmittance is τ (λ2), and the wavelength with respect to the d-line transmittance. An imaging optical system characterized by exhibiting characteristics satisfying the following conditional expressions (14) and (15) when the transmittance ratio of the optical system at λ2 + 30 nm is τ (λ2 + 30):
      350 nm ≦ λ2 ≦ 550 nm (13)
      τ (λ2) ≦ 10% (14)
      τ (λ2 + 30) ≧ 50% (15)
[0145]
(10)The imaging optical system according to any one of (13), (15), and (17), wherein the conditional expression (3) is replaced with the following expression (3 '):
      (Lλ−Ld) /Fmin=0.04 mm (3 ′)
[0146]
(11)The imaging optical system according to any one of (13), (15), and (17), wherein the conditional expression (3) is replaced with the following conditional expression (3 ″).
      (Lλ−Ld) /Fmin=0.03 mm (3 ″)
[0147]
(12)The imaging optical system according to any one of (14), (16), and (18), wherein the conditional expression (5) is replaced with the following conditional expression (5 ').
      | Sλ | = 0.02 mm (5 ')
[0148]
(13)The imaging optical system according to any one of (14), (16), and (18), wherein the conditional expression (5) is replaced with the following conditional expression (5 ″).
      | Sλ | = 0.015mm (5 ")
[0149]
(14)An imaging optical system for forming a subject image on an electronic imaging device, wherein the minimum F value of the imaging optical system is Fmin, and the amount of spherical aberration of the marginal ray of h line (404.7 nm) when the F value is Fmin Lh is the absolute value of the spherical aberration of the marginal ray of g line (435.8 nm), Lg is the absolute value of the spherical aberration of the marginal ray of d line (587.56 nm). When the transmittance ratio of the h-line of the imaging optical system to the transmittance is τh and the transmittance ratio of the g-line to the transmittance of the d-line is τg, the following conditional expression (16) is satisfied and the transmittance An imaging optical system characterized in that the wavelength λc at which the half-value with respect to the d-line transmittance exhibits a characteristic satisfying the following conditional expression (17):
      (Lh−Ld) / Fmin × τh ≦ (Lg−Ld) / Fmin × τg
                                                                    ...... (16)
      h line (404.7 nm) <λc <g line (435.8 nm) (17)
[0150]
(15)An imaging optical system for forming a subject image on an electronic imaging device, wherein the lateral aberration amount of magnification color of h line (404.7 nm) with respect to d line (587.56 nm) at an image height ratio of 0.9 at the maximum image height Sh, the lateral aberration amount of the magnification color of the g line (435.8 nm) with respect to the d line (587.56 nm) at the maximum image height ratio of 0.9, the amount of lateral aberration of the imaging optical system with respect to the Sg, d line When the transmittance ratio is τh and the transmittance ratio of the g-line to the d-line is τg, the wavelength λc that satisfies the following conditional expression (18) and has a half-value of the transmittance with respect to the transmittance of the d-line Shows the characteristic which satisfies the following conditional expression (17).
      | Sh | × τh ≦ | Sg | × τg (18)
      h line (404.7 nm) <λc <g line (435.8 nm) (17)
[0151]
(16)A coating film for performing wavelength correction is applied on a flat surface.(4)-(15)The imaging optical system according to any one of the above.
[0152]
(17)A low-pass filter is disposed in the imaging optical system, and at least one surface of the low-pass filter is provided with a coating film that performs wavelength correction.(4)-(15)The imaging optical system according to any one of the above.
[0153]
(18)An infrared cut filter for reducing an infrared light component is disposed in the imaging optical system, and at least one surface of the infrared cut filter is provided with a coating film for performing wavelength correction.(4)-(15)The imaging optical system according to any one of the above.
[0154]
(19)The imaging optical system is provided with a coating film exhibiting a characteristic that there exists a wavelength at which the transmittance between the g-line and the h-line and between 600 nm and 700 nm is half the value of the transmittance of the d-line. Characteristic above(4)-(15)The imaging optical system according to any one of the above.
[0155]
(20)An optical path dividing means is provided in the optical path of the imaging optical system, and only the optical path on the imaging element side having an imaging region in which the sensitivity characteristic at the g-line of the electronic imaging element has a sensitivity of 30% or more of the sensitivity characteristic at the e-line. Characterized in that a wavelength correction element is provided.(4)-(15)The imaging optical system according to any one of the above.
[0156]
(21)One of the optical paths divided by the optical path dividing means is an observation optical path that guides the optical path to the eyeball of the observer.(20)The imaging optical system described in 1.
[0157]
(22)The optical path splitting means divides the optical path into a plurality of optical paths, and an image sensor having a different spectral sensitivity characteristic is disposed in each of the plurality of optical paths, and the g-line sensitivity characteristic is e-line. The wavelength correction element is disposed only in the optical path on the image pickup element side having an image pickup region having a sensitivity of 30% or more of the sensitivity characteristic.(20)The imaging optical system described in 1.
[0158]
(23)An imaging optical system for forming a subject image on an electronic imaging device, comprising an adjustment element for adjusting a light amount in an optical path of the optical system, wherein the adjustment element has a transmittance between g-line and h-line. An imaging optical system comprising a wavelength correction function that provides a half value of e-ray transmittance.
[0159]
(24)(4) to (4) above, wherein the optical element related to the determination of the focal length in the imaging optical system is composed of an optical element using only a refraction phenomenon.(23)The imaging optical system according to any one of the above.
[0160]
(25)The electronic imaging device having three or more different spectral sensitivity characteristics for obtaining a color image is disposed at a rear focal position of the imaging optical system.(4)-(24)An electronic imaging apparatus having the imaging optical system according to any one of the above.
[0161]
(26)Among the electronic imaging elements having three or more different spectral sensitivity characteristics for obtaining the color image, the spectral characteristics of at least one electronic imaging element have two high peak wavelengths, and the two peak wavelengths are between the two peak wavelengths. It has a wavelength with a sensitivity of 50% or less for both of two peak wavelengths.Claims 1 to 4, the above (1) to (3), (25)The electronic imaging device according to any one of the above.
[0162]
【The invention's effect】
As described above, according to the present invention, it is possible to provide an image pickup optical system and an image pickup apparatus that can reproduce a good image including a color for a wide range of natural subjects with a simple configuration.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of an imaging optical system according to the present invention that optically reduces color flare.
2 is a spherical aberration diagram of the imaging optical system in FIG. 1. FIG.
3 is a state explanatory diagram showing a focal position shift amount at a maximum incident height when the imaging optical system of FIG. 1 is viewed in a cross section of a rear focal portion. FIG.
4 is an aberration diagram showing chromatic aberration of magnification of wavelength λ with respect to d-line in the imaging optical system of FIG. 1. FIG.
5 is a diagram showing a state of chromatic aberration on an image plane at an image height ratio of 0.9 on the paraxial image plane in the image pickup optical system of FIG. 1; FIG.
FIG. 6 is a configuration diagram of a so-called digital camera 13 showing a first embodiment of an electronic imaging apparatus according to the present invention.
FIG. 7 is a schematic configuration diagram of a two-dimensional area photometric sensor used in the electronic imaging apparatus of the present embodiment.
FIG. 8 is an explanatory diagram of a state when shooting a subject with a strong contrast between light and dark, such as indoor shooting against a clear sky.
FIG. 9 is a state explanatory diagram illustrating an example of a luminance difference with respect to appropriate exposure for each pixel in which a part of the imaging surface is enlarged.
FIG. 10 is an explanatory diagram of a state of a two-dimensional area photometric sensor used in the electronic imaging apparatus according to the present embodiment.
FIG. 11 is provided with a plurality of pixels as a photometric area provided with an ND filter as a sensitivity lowering unit on the imaging surface of an electronic imaging device, and using the luminance signal received by the pixels, the boundary portion is defined as described above. It is the figure comprised so that it might detect.
FIG. 12 is a flowchart of signal processing in the controller 7 in the electronic imaging apparatus of the present embodiment.
FIG. 13 is a schematic configuration diagram of a primary color filter used in the present embodiment.
FIG. 14 is a schematic configuration diagram of a complementary color filter used in the present embodiment.
15 is a wavelength characteristic diagram of the primary color filter of FIG.
16 is a wavelength characteristic diagram of the complementary color filter of FIG.
FIG. 17 is a schematic configuration diagram showing a modification of the imaging optical system of the present embodiment using a color separation prism.
FIG. 18 is a lens cross-sectional view of a first example (numerical example 1) in the imaging optical system of the present embodiment.
19 is a spherical aberration diagram at the time of focusing on infinity at the wide angle end in the imaging optical system of FIG. 18 and a diagram showing chromatic aberration of magnification with respect to the d-line.
FIG. 20 is a lens cross-sectional view of a second example (Numerical Example 2) of the imaging optical system according to the present embodiment.
FIG. 21 is a spherical aberration diagram when focusing on infinity in the imaging optical system of FIG. 20 and a diagram showing chromatic aberration of magnification with respect to d-line.
FIG. 22 is a schematic configuration diagram showing a modification of the present embodiment.
FIG. 23 is a schematic configuration diagram showing a second embodiment of an electronic imaging apparatus according to the present invention in which color flare is optically removed using a wavelength correction filter for performing wavelength correction.
24 is a diagram illustrating a spectral transmittance curve of only the imaging optical system in the imaging optical system of the present embodiment and a spectral transmittance curve when the wavelength correction filter 3 is used. FIG.
FIG. 25 shows a so-called TTL finder type observation optical system that guides to the finder optical system 26 as a modification of the present embodiment, using an observation optical path that divides a light beam on the object side from the image sensor and guides the optical path to the observer's eyeball. FIG.
FIG. 26 is a main part configuration diagram showing still another embodiment of the present invention.
FIG. 27 shows changes in refractive power depending on the wavelength when a single lens having a refractive power (reciprocal of focal length) of 1 at a wavelength of 550 nm is made of a typical glass material and a material called ultra-low dispersion glass. FIG.
FIG. 28 is a diagram showing the amount of deviation of the back focal position with respect to the wavelength of an optical system consisting only of a general refractive optical element with 500 nm as a reference, with the horizontal axis representing wavelength and the vertical axis representing deviation. .
[Explanation of symbols]
1 Imaging optics
1 'Imaging optical system
2 Electronic image sensor
3 Image sensor
4 Image plane
5 Optical axis on paraxial image plane 4
6 Low-pass filter
7 Controller
8 Internal memory
9 Interface
10 P.M. C.
11 LCD monitor
12 Auxiliary memory
13 Electronic imaging device
14 Bonding prism
15 Two-dimensional area photometric sensor
16 Metering area
17 Strobe mechanism
18 Buzzer
19 color flare
20 First prism
21 Second prism 21
23 Third prism
24 color separation prism
25 mount
26 Viewfinder optical system
27 Half mirror prism
28 Coating membrane
29 Turret
30 parallel plates
31 -1 stage ND filter
32 -2 stage ND filter
33 -3 stage ND filter

Claims (4)

An electronic imaging device including a plurality of pixels having three or more different spectral characteristics for obtaining a color image;
An imaging optical system for forming an object image on an imaging surface of the front Symbol electronic imaging device chromatic aberration is generated,
A high luminance difference detecting means for detecting the presence or absence of a region where the luminance difference between adjacent pixels of the electronic image sensor becomes a certain level or more;
Warning means for issuing a warning when the high luminance difference detecting means detects a luminance difference of a certain level or more ,
In the imaging optical system, the minimum pixel pitch of the electronic imaging device is P, the minimum F value is Fmin, the absolute value of the spherical aberration of the marginal ray at the wavelength 404.7 nm when the F value is Fmin, Lh, and the wavelength 587. An electronic imaging apparatus characterized by satisfying the following conditional expression (1) when an absolute value of a spherical aberration amount of a marginal ray at .56 nm is Ld .
(Lh−Ld) / Fmin ≧ 2P (1) And including an electronic image pickup element a plurality of pixels having three or more different spectral characteristics to obtain a color image,
An imaging optical system for forming an object image on an imaging surface of the front Symbol electronic imaging device chromatic aberration is generated,
High luminance difference boundary detection means for detecting the presence or absence of a region where the luminance difference between adjacent pixels of the electronic image sensor is a certain level or more;
Warning means for issuing a warning when the high-luminance difference boundary detection means detects a luminance difference of a certain level or more ,
The imaging optical system has a magnification of a wavelength of 404.7 nm with respect to a wavelength of 587.56 nm at a minimum pixel pitch of the electronic imaging device of P and a maximum image height ratio of 0.9, 0.7, or 0.5. An electronic imaging apparatus characterized by satisfying the following conditional expression (2) when the amount of lateral aberration of color is Sh .
| Sh | ≧ 2P (2) The electronic imaging device according to claim 1 or 2, further comprising a mount portion to be connected to an imaging optical system for forming an object image on the imaging surface of the front Symbol electronic image pickup device. Among the electronic imaging elements having three or more different spectral sensitivity characteristics for obtaining the color image, the spectral characteristics of at least one electronic imaging element have two high peak wavelengths, and the two peak wavelengths are between the two peak wavelengths. The electronic imaging apparatus according to claim 1, wherein the electronic imaging apparatus has a wavelength with a sensitivity of 50% or less with respect to both of the two peak wavelengths .

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