JP4242593B2 - Electronic imaging device - Google Patents

Description

【０１０２】

【０１０３】

【０１０４】

【０１０５】

【０１０６】
上記実施例１の無限遠にフォーカシングした場合の収差図を図３に、第３レンズ群Ｇ３を物体側に移動することで撮影距離１０ｃｍにフォーカシングした場合の収差図を図４にそれぞれ示す。実施例２の同様の収差図を図５と図６に、実施例３の同様の収差図を図７と図８に、実施例４の同様の収差図を図９と図１０に、実施例５の同様の収差図を図１１と図１２にそれぞれ示す。これら収差図の（ａ）は広角端、（ｂ）は中間状態、（ｃ）は望遠端での収差を表し、“ＳＡ”は球面収差、“ＡＳ”は非点収差、“ＤＴ”は歪曲収差、“ＣＣ”は倍率色収差を示す。また、各収差図中、“ＦＩＹ”は像高を示す。
【０１０７】
次に、上記各実施例における条件（１）〜（６）、（８）〜（１６）の値、条件（７）に関するAsp21F、Asp21R、及び、Ｌ、Ｚの値を示す。

【０１０８】
なお、実施例１〜５のローパスフィルターの総厚ｔ_LPF は何れも１．５００（ｍｍ）で３枚重ねで構成している。もちろん、上述の実施例は、例えばローパスフィルターＦを１枚で構成する等、前記した構成の範囲内で種々変更可能である。
【０１０９】
ここで、有効撮像面の対角長Ｌと画素間隔ａについて説明しておく。図１３は、撮像素子の画素配列の１例を示す図であり、画素間隔ａでＲ（赤）、Ｇ（緑）、Ｂ（青）の画素あるいはシアン、マゼンダ、イエロー、グリーン（緑）の４色の画素（図１７）がモザイク状に配されている。有効撮像面は撮影した映像の再生（パソコン上での表示、プリンターによる印刷等）に用いる撮像素子上の光電変換面内における領域を意味する。図中に示す有効撮像面は、光学系の性能（光学系の性能が確保し得るイメージサークル）に合わせて、撮像素子の全光電変換面よりも狭い領域に設定されている。有効撮像面の対角長Ｌは、この有効撮像面の対角長である。なお、映像の再生に用いる撮像範囲を種々変更可能としてよいが、そのような機能を有する撮像装置に本発明のズームレンズを用いる際は、その有効撮像面の対角長Ｌが変化する。そのような場合は、本発明における有効撮像面の対角長Ｌは、Ｌのとり得る範囲における最大値とする。
【０１１０】
また、赤外カット手段については、赤外カット吸収フィルターと赤外シャープカットコートとがあり、赤外カット吸収フィルターはガラス中に赤外吸収体が含有される場合で、赤外シャープカットコートは吸収でなく反射によるカットである。したがって、前記したように、この赤外カット吸収フィルターを除去して、ローパスフィルターに直接赤外シャープカットコートを施してもよいし、ダミー透明平板上に施してもよい。
【０１１１】
この場合の近赤外シャープカットコートは、波長６００ｎｍでの透過率が８０％以上、波長７００ｎｍでの透過率が１０％以下となるように構成することが望ましい。具体的には、例えば次のような２７層の層構成からなる多層膜である。ただし、設計波長は７８０ｎｍである。
【０１１２】
基 板 材質 物理的膜厚（ｎｍ） λ／４
───────────────────────────────
第１層 Ａｌ₂ Ｏ₃ ５８．９６ ０．５０
第２層 ＴｉＯ₂ ８４．１９ １．００
第３層 ＳｉＯ₂ １３４．１４ １．００
第４層 ＴｉＯ₂ ８４．１９ １．００
第５層 ＳｉＯ₂ １３４．１４ １．００
第６層 ＴｉＯ₂ ８４．１９ １．００
第７層 ＳｉＯ₂ １３４．１４ １．００
第８層 ＴｉＯ₂ ８４．１９ １．００
第９層 ＳｉＯ₂ １３４．１４ １．００
第10層 ＴｉＯ₂ ８４．１９ １．００
第11層 ＳｉＯ₂ １３４．１４ １．００
第12層 ＴｉＯ₂ ８４．１９ １．００
第13層 ＳｉＯ₂ １３４．１４ １．００
第14層 ＴｉＯ₂ ８４．１９ １．００
第15層 ＳｉＯ₂ １７８．４１ １．３３
第16層 ＴｉＯ₂ １０１．０３ １．２１
第17層 ＳｉＯ₂ １６７．６７ １．２５
第18層 ＴｉＯ₂ ９６．８２ １．１５
第19層 ＳｉＯ₂ １４７．５５ １．０５
第20層 ＴｉＯ₂ ８４．１９ １．００
第21層 ＳｉＯ₂ １６０．９７ １．２０
第22層 ＴｉＯ₂ ８４．１９ １．００
第23層 ＳｉＯ₂ １５４．２６ １．１５
第24層 ＴｉＯ₂ ９５．１３ １．１３
第25層 ＳｉＯ₂ １６０．９７ １．２０
第26層 ＴｉＯ₂ ９９．３４ １．１８
第27層 ＳｉＯ₂ ８７．１９ ０．６５
───────────────────────────────
空 気 。
【０１１３】
上記の近赤外シャープカットコートの透過率特性は図１５に示す通りである。
【０１１４】
また、ローパスフィルターの射出面側には、図１６に示すような短波長域の色の透過を低滅する色フィルターを設けるか若しくはコーティングを行うことで、より一層電子画像の色再現性を高めている。
【０１１５】
具体的には、このフィルター若しくはコーティングにより、波長４００ｎｍ〜７００ｎｍで透過率が最も高い波長の透過率に対する４２０ｎｍの波長の透過率の比が１５％以上であり、その最も高い波長の透過率に対する４００ｎｍの波長の透過率の比が６％以下であることが好ましい。
【０１１６】
それにより、人間の目の色に対する認識と、撮像及び再生される画像の色とのずれを低減させることができる。言い換えると、人間の視覚では認識され難い短波長側の色が、人間の目で容易に認識されることによる画像の劣化を防止することができる。
【０１１７】
上記の４００ｎｍの波長の透過率の比が６％を越えると、人間の目では認識され難い単波長城が認識し得る波長に再生されてしまい、逆に、上記の４２０ｎｍの波長の透過率の比が１５％よりも小さいと、人間の認識し得る波長城の再生が低くなり、色のバランスが悪くなる。
【０１１８】
このような波長を制限する手段は、補色モザイクフィルターを用いた撮像系においてより効果を奏するものである。
【０１１９】
上記各実施例では、図１６に示すように、波長４００ｎｍにおける透過率を０％、４２０ｎｍにおける透過率を９０％、４４０ｎｍにて透過率のピーク１００％となるコーティングとしている。
【０１２０】
前記した近赤外シャープカットコートとの作用の掛け合わせにより、波長４５０ｎｍの透過率９９％をピークとして、４００ｎｍにおける透過率を０％、４２０ｎｍにおける透過率を８０％、６００ｎｍにおける透過率を８２％、７００ｎｍにおける透過率を２％としている。それにより、より忠実な色再現を行っている。
【０１２１】
また、ローパスフィルターは、像面上投影時の方位角度が水平（＝０°）と±４５°方向にそれぞれ結晶軸を有する３種類のフィルターを光軸方向に重ねて使用しており、それぞれについて、水平にａμｍ、±４５°方向にそれぞれSQRT(1/2) ×ａだけずらすことで、モアレ抑制を行っている。ここで、ＳＱＲＴは前記のようにスクエアルートであり平方根を意味する。
【０１２２】
また、上記実施例１〜５の像面Ｉに配置するＣＣＤの撮像面上には、図１７に示す通り、シアン、マゼンダ、イエロー、グリーン（緑）の４色の色フィルターを撮像画素に対応してモザイク状に設けた補色モザイクフィルターを設けている。これら４種類の色フィルターは、それぞれが略同じ数になるように、かつ、隣り合う画素が同じ種類の色フィルターに対応しないようにモザイク状に配置されている。それにより、より忠実な色再現が可能となる。
【０１２３】
補色モザイクフィルターは、具体的には、図１７に示すように少なくとも４種類の色フィルターから構成され、その４種類の色フィルターの特性は以下の通りであることが好ましい。
【０１２４】
グリーンの色フイルターＧは波長Ｇ_P に分光強度のピークを有し、
イエローの色フィルターＹ_e は波長Ｙ_P に分光強度のピークを有し、
シアンの色フィルターＣは波長Ｃ_P に分光強度のピークを有し、
マゼンダの色フィルターＭは波長Ｍ_P1とＭ_P2にピークを有し、以下の条件を満足する。
【０１２５】
５１０ｎｍ＜Ｇ_P ＜５４０ｎｍ
５ｎｍ＜Ｙ_P −Ｇ_P ＜３５ｎｍ
−１００ｎｍ＜Ｃ_P −Ｇ_P ＜−５ｎｍ
４３０ｎｍ＜Ｍ_P1＜４８０ｎｍ
５８０ｎｍ＜Ｍ_P2＜６４０ｎｍ
さらに、グリーン、イエロー、シアンの色フィルターはそれぞれの分光強度のピークに対して波長５３０ｎｍでは８０％以上の強度を有し、マゼンダの色フィルターはその分光強度のピークに対して波長５３０ｎｍでは１０％から５０％の強度を有することが、色再現性を高める上でより好ましい。
【０１２６】
上記各実施例におけるそれぞれの波長特性の一例を図１８に示す。グリーンの色フィルターＧは５２５ｎｍに分光強度のビークを有している。イエローの色フィルターＹ_e は５５５ｎｍに分光強度のピークを有している。シアンの色フイルターＣは５１０ｎｍに分光強度のピークを有している。マゼンダの色フィルターＭは４４５ｎｍと６２０ｎｍにピークを有している。また、５３０ｎｍにおける各色フィルターは、それぞれの分光強度のピークに対して、Ｇは９９％、Ｙ_e は９５％、Ｃは９７％、Ｍは３８％としている。
【０１２７】
このような補色フイルターの場合、図示しないコントローラー（若しくは、デジタルカメラに用いられるコントローラー）で、電気的に次のような信号処理を行い、
輝度信号
Ｙ＝｜Ｇ＋Ｍ＋Ｙ_e ＋Ｃ｜×１／４
色信号
Ｒ−Ｙ＝｜（Ｍ＋Ｙ_e ）−（Ｇ＋Ｃ）｜
Ｂ−Ｙ＝｜（Ｍ＋Ｃ）−（Ｇ＋Ｙ_e ）｜
の信号処理を経てＲ（赤）、Ｇ（緑）、Ｂ（青）の信号に変換される。
【０１２８】
ところで、上記した近赤外シャープカットコートの配置位置は、光路上のどの位置であってもよい。また、ローパスフィルターの枚数も前記した通り２枚でも１枚でも構わない。
【０１２９】
さて、以上のような本発明の撮像装置は、ズームレンズで物体像を形成しその像をＣＣＤ等の電子撮像素子に受光させて撮影を行う撮影装置、とりわけデジタルカメラやビデオカメラ、情報処理装置の例であるパソコン、電話、特に持ち運びに便利な携帯電話等に用いることができる。以下に、その実施形態を例示する。
【０１３０】
図１９〜図２１は、本発明によるズームレンズをデジタルカメラの撮影光学系４１に組み込んだ構成の概念図を示す。図１９はデジタルカメラ４０の外観を示す前方斜視図、図２０は同後方斜視図、図２１はデジタルカメラ４０の構成を示す断面図である。デジタルカメラ４０は、この例の場合、撮影用光路４２を有する撮影光学系４１、ファインダー用光路４４を有するファインダー光学系４３、シャッター４５、フラッシュ４６、液晶表示モニター４７等を含み、カメラ４０の上部に配置されたシャッター４５を押圧すると、それに連動して撮影光学系４１、例えば実施例１のズームレンズを通して撮影が行われる。撮影光学系４１によって形成された物体像が、近赤外カットコートをダミー透明平板上に施してなる赤外カット吸収フィルターＩＦ、光学的ローパスフィルターＬＦを介してＣＣＤ４９の撮像面上に形成される。このＣＣＤ４９で受光された物体像は、処理手段５１を介し、電子画像としてカメラ背面に設けられた液晶表示モニター４７に表示される。また、この処理手段５１には記録手段５２が接続され、撮影された電子画像を記録することもできる。なお、この記録手段５２は処理手段５１と別体に設けてもよいし、フロッピーディスクやメモリーカード、ＭＯ等により電子的に記録書込を行うように構成してもよい。また、ＣＣＤ４９に代わって銀塩フィルムを配置した銀塩カメラとして構成してもよい。
【０１３１】
さらに、ファインダー用光路４４上にはファインダー用対物光学系５３が配置してある。このファインダー用対物光学系５３によって形成された物体像は、像正立部材であるポロプリズム５５の視野枠５７上に形成される。このポリプリズム５５の後方には、正立正像にされた像を観察者眼球Ｅに導く接眼光学系５９が配置されている。なお、撮影光学系４１及びファインダー用対物光学系５３の入射側、接眼光学系５９の射出側にそれぞれカバー部材５０が配置されている。
【０１３２】
このように構成されたデジタルカメラ４０は、撮影光学系４１が広画角で高変倍比であり、収差が良好で、明るく、フィルター等が配置できるバックフォーカスの大きなズームレンズであるので、高性能・低コスト化が実現できる。
【０１３３】
なお、図２１の例では、カバー部材５０として平行平面板を配置しているが、パワーを持ったレンズを用いてもよい。
【０１３４】
以上の本発明の電子撮像装置は例えば次のように構成することができる。
【０１３５】
〔１〕 ズームレンズとその像側に配された電子撮像素子を有する電子撮像装置において、
前記ズームレンズは、物体側より順に、全体として負の屈折力を有する第１レンズ群と、全体として正の屈折力を有する第２レンズ群と、全体として正の屈折力を有する第３レンズ群とからなり、
前記第２レンズ群は２つのレンズ成分からなり、その中像側のレンズ成分は像面側に凹面を向けたメニスカス形状であり、
前記第３レンズ群は１つの正レンズ成分からなり、
少なくとも前記第２レンズ群は無限遠物点合焦時における広角端から望遠端への変倍時に物体側のみへ移動し、前記第３レンズ群は変倍に際して前記第２レンズ群とは異なる量で移動し、合焦動作時に前記第３レンズ群は移動し、
前記第３レンズ群の全ての屈折面は以下の条件を満足することを特徴とする電子撮像装置。
【０１３６】
（１） ０≦｜Asp3｜＜３．０×１０^-3・Ｌ
ただし、Ｌは電子撮像素子における有効撮像領域の対角長であり、Asp3は第３レンズ群の各々の屈折面の非球面偏倚量であり、光軸上における曲率半径を有する基準球面に対する光軸からの高さが０．４Ｌでの非球面偏倚量とし、屈折面が球面の場合は非球面偏奇量Asp3を０とする。
【０１３７】
〔２〕 以下の条件を満足することを特徴とする上記１記載の電子撮像装置。
【０１３８】
（２） −１．０＜（Ｒ_3F＋Ｒ_3R）／（Ｒ_3F−Ｒ_3R）＜０．７
ただし、Ｒ_3F、Ｒ_3Rはそれぞれ第３レンズ群の最も物体側の面、 最も像側の面の光軸上の曲率半径である。
【０１３９】
〔３〕 前記第２レンズ群の像側のレンズ成分は、物体側から、正レンズ、負レンズの順で接合された接合レンズ成分により構成され、以下の条件を満足することを特徴とする上記１又は２記載の電子撮像装置。
【０１４０】
（３） ０．４５＜Ｒ_22R ／Ｒ_22F ＜０．９
（４） ０＜Ｌ／Ｒ_22C ＜１．０
（５） ０＜ｎ_22R −ｎ_22F ＜０．３
ただし、Ｒ_22F 、Ｒ_22R 、Ｒ_22C はそれぞれ第２レンズ群像側レンズ成分の最も物体側の面、最も像側の面、接合面の光軸上の曲率半径、ｎ_22F 、ｎ_22R は第２レンズ群像側レンズ成分のそれぞれ物体側レンズ、像側レンズの媒質のｄ線の屈折率である。
【０１４１】
〔４〕 前記第２レンズ群の物体側のレンズ成分は１枚の単レンズにより構成され、以下の条件を満足することを特徴とする上記１から３の何れか１項記載の電子撮像装置。
【０１４２】
（６） ０．１＜ （Ｒ_21F ＋Ｒ_21R ）／（Ｒ_21F −Ｒ_21R ）＜５
ただし、Ｒ_21F 、Ｒ_21R はそれぞれ第２レンズ群の物体側のレンズ成分の物体側の面、像側の面の光軸上の曲率半径である。
【０１４３】
〔５〕 前記第２レンズ群の物体側のレンズ成分は、物体側の空気接触面と像側の空気接触面の両方が非球面であり、光軸上における曲率半径を有する基準球面に対して両空気接触面は何れも物体側に偏倚した非球面であることを特徴とする上記１から４の何れか１項記載の電子撮像装置。
【０１４４】
〔６〕 以下の条件を満足することを特徴とする上記５記載の電子撮像装置。
【０１４５】
（７） ５．０×１０^-4・Ｌ＜｜Asp21R｜＜｜Asp21F｜＜３．０×１０^-2・Ｌ
ただし、Asp21F、Asp21Rは第２レンズ群の物体側のレンズ成分のそれぞれ物体側の空気接触面と像側の空気接触面における非球面偏倚量であり、光軸上における曲率半径を有する基準球面に対する光軸からの高さが０．３Ｌでの非球面偏倚量である。
【０１４６】
〔７〕 以下の条件を満足することを特徴とする上記１から６の何れか１項記載の電子撮像装置。
【０１４７】
（８） １．４５＜−β_2T＜２．１
ただし、β_2Tは無限遠物点合焦時の望遠端での第２レンズ群全体の倍率である。
【０１４８】
〔８〕 前記第２レンズ群の２つのレンズ成分は、物体側より順に、正レンズ成分、負レンズ成分であることを特徴とする上記１から７の何れか１項記載の電子撮像装置。
【０１４９】
〔９〕 前記第１レンズ群は、非球面を含む負レンズ及び正レンズの２枚のレンズで構成されており、以下の条件を満足することを特徴とする上記１から８の何れか１項記載の電子撮像装置。
【０１５０】
（９） １０＜ν₁₁−ν₁₂＜２４
（10） −４＜（Ｒ₁₃＋Ｒ₁₄）／（Ｒ₁₃−Ｒ₁₄）＜−１．１
ただし、ν₁₁は第１レンズ群の負レンズのｄ線基準での媒質のアッベ数、ν₁₂は第１レンズ群の正レンズのｄ線基準での媒質のアッベ数、Ｒ₁₃は第１レンズ群の正レンズの物体側面の光軸上での曲率半径、Ｒ₁₄は第１レンズ群の正レンズの像側面の光軸上での曲率半径である。
【０１５１】
〔１０〕 以下の条件を満足することを特徴とする上記９記載の電子撮像装置。
【０１５２】
（11） ０．２＜ｄ₁₁／Ｌ＜０．６５
ただし、ｄ₁₁は第１レンズ群の負レンズと正レンズの光軸上での空気間隔である。
【０１５３】
〔１１〕 前記第３レンズ群は１枚の正レンズで構成されていることを特徴とする上記１から１０の何れか１項記載の電子撮像装置。
【０１５４】
〔１２〕 前記電子撮像素子の有効撮像領域の対角長Ｌが以下の条件を満足することを特徴とする上記１から１１の何れか１項記載の電子撮像装置。
【０１５５】
３．０ｍｍ＜Ｌ＜１２．０ｍｍ
〔１３〕 広角端における対角方向の半画角ω_W が以下の条件を満足することを特徴とする上記１乃至１２の何れか１項記載の電子撮像装置。
【０１５６】
２７．５°＜ω_W
【０１５７】
【発明の効果】
以上の本発明により、沈胴厚が薄く、収納性に優れ、かつ、高倍率で、リアフォーカスにおいても結像性能の優れたズームレンズを得ることができ、ビデオカメラやデジタルカメラの徹底的薄型化を図ることが可能である。
【図面の簡単な説明】
【図１】本発明の電子撮像装置に用いられるズームレンズの実施例１の無限遠物点合焦時の広角端（ａ）、中間状態（ｂ）、望遠端（ｃ）でのレンズ断面図である。
【図２】実施例２のズームレンズの図１と同様のレンズ断面図である。
【図３】実施例１の無限遠物点合焦時の収差図である。
【図４】実施例１の被写体距離１０ｃｍ合焦時の収差図である。
【図５】実施例２の無限遠物点合焦時の収差図である。
【図６】実施例２の被写体距離１０ｃｍ合焦時の収差図である。
【図７】実施例３の無限遠物点合焦時の収差図である。
【図８】実施例３の被写体距離１０ｃｍ合焦時の収差図である。
【図９】実施例４の無限遠物点合焦時の収差図である。
【図１０】実施例４の被写体距離１０ｃｍ合焦時の収差図である。
【図１１】実施例５の無限遠物点合焦時の収差図である。
【図１２】実施例５の被写体距離１０ｃｍ合焦時の収差図である。
【図１３】電子撮像素子にて撮影を行う場合の有効撮像面の対角長について説明するための図である。
【図１４】本発明のおける非球面偏倚量の定義を説明するための図である。
【図１５】近赤外シャープカットコートの一例の透過率特性を示す図である。
【図１６】ローパスフィルターの射出面側に設ける色フィルターの一例の透過率特性を示す図である。
【図１７】補色モザイクフィルターの色フィルター配置を示す図である。
【図１８】補色モザイクフィルターの波長特性の一例を示す図である。
【図１９】本発明によるズームレンズを組み込んだデジタルカメラの外観を示す前方斜視図である。
【図２０】図１９のデジタルカメラの後方斜視図である。
【図２１】図１９のデジタルカメラの断面図である。
【符号の説明】
Ｇ１…第１レンズ群
Ｇ２…第２レンズ群
Ｇ３…第３レンズ群
Ｓ…開口絞り
Ｆ…赤外カット吸収フィルターとローパスフィルターの組み合わせ
ＣＧ…カバーガラス
Ｉ…像面
ＩＦ…赤外カット吸収フィルター
ＬＦ…光学的ローパスフィルター
Ｅ…観察者眼球
４０…デジタルカメラ
４１…撮影光学系
４２…撮影用光路
４３…ファインダー光学系
４４…ファインダー用光路
４５…シャッター
４６…フラッシュ
４７…液晶表示モニター
４９…ＣＣＤ
５０…カバー部材
５１…処理手段
５２…記録手段
５３…ファインダー用対物光学系
５５…ポロプリズム
５７…視野枠
５９…接眼光学系[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electronic image pickup apparatus, and more particularly to an electronic image pickup apparatus such as a video camera or a digital camera that is thinned in the depth direction by devising an optical system portion such as a zoom lens. In addition, the zoom lens relates to a lens that enables rear focus.
[0002]
[Prior art]
In recent years, digital cameras (electronic cameras) have attracted attention as next-generation cameras that replace silver salt 35 mm film (commonly known as Leica version) cameras. Furthermore, it has come to have a number of categories in a wide range from a high-function type for business use to a portable popular type.
[0003]
In the present invention, focusing on the category of portable popular type, it is aimed to provide a technology for realizing a video camera and a digital camera with a small depth while ensuring a high image quality. The biggest bottleneck in reducing the depth direction of the camera is the thickness from the most object-side surface to the imaging surface of the optical system, particularly the zoom lens system. Recently, it has become the mainstream to adopt a so-called collapsible lens barrel that protrudes the optical system from the camera body during shooting and stores the optical system in the camera body when carried.
[0004]
However, the thickness when the optical system is retracted varies greatly depending on the lens type and filter used. In particular, in order to set the specifications such as the zoom ratio and F value high, the so-called positive leading zoom lens in which the lens unit closest to the object side has positive refractive power has a large thickness and dead space of each lens element, Even if the lens barrel is retracted, the thickness is not reduced (Japanese Patent Laid-Open No. 11-258507). The negative leading type, especially the zoom lens having 2 to 3 groups, is advantageous in this respect, but it is retracted even when the number of elements in the group is large, the thickness of the element is large, or the most object side lens is a positive lens. However, it does not become thin (JP-A-11-52246). As an example of what is currently known and suitable for an electronic image pickup device, has good imaging performance including a zoom ratio, an angle of view, an F value, and the like, and has the possibility of making the collapsible thickness the thinnest, Japanese Patent Laid-Open No. Hei 11- No. 287953, Japanese Patent Laid-Open No. 2000-267209, Japanese Patent Laid-Open No. 2000-275520, and the like.
[0005]
In order to make the first group thinner, it is preferable to make the entrance pupil position shallower. For this purpose, the magnification of the second group is increased. On the other hand, this not only increases the burden on the second group and makes it difficult to reduce the thickness of the second group, but also increases the difficulty of aberration correction and the effect of manufacturing errors. In order to reduce the thickness and size of the image sensor, the image sensor can be made smaller. However, in order to obtain the same number of pixels, it is necessary to reduce the pixel pitch, and the lack of sensitivity must be covered by the optical system. The same is true for diffraction.
[0006]
In order to obtain a camera body with a small depth, it is effective in terms of the layout of the drive system to move the lens at the time of focusing with the so-called rear focus instead of the front group. Then, it becomes necessary to select an optical system with less aberration fluctuation when rear focus is performed.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of such a situation in the prior art, and its object is to have a small number of components, a small and simple mechanism layout such as a rear focus method, and a stable and high connection from infinity to a short distance. Select a zoom system or zoom configuration with image performance, and further reduce the total lens thickness by reducing the lens elements of the zoom lens, and considering the selection of filters, video cameras and digital cameras It is to achieve a thorough thinning.
[0008]
[Means for Solving the Problems]
  In order to achieve the above object, an electronic image pickup apparatus according to the present invention includes a zoom lens and an electronic image pickup element arranged on the image side thereof.
  The zoom lens includes, in order from the object side, a first lens group having a negative refractive power as a whole, a second lens group having a positive refractive power as a whole, and a third lens group having a positive refractive power as a whole. And consist of
  The second lens group includes two lens components, and the lens component on the middle image side has a meniscus shape with a concave surface facing the image surface side,
  The third lens group consists of one positive lens component,
  At least the second lens unit moves only to the object side upon zooming from the wide-angle end to the telephoto end when focusing on an object point at infinity, and the third lens unit is different from the second lens unit in zooming. The third lens group moves during focusing operation,
  All refractive surfaces of the third lens group satisfy the following conditions:
    (1) 0 ≦ | Asp3 | <3.0 × 10^-3・ L
  The lens component on the image side of the second lens group is composed of a cemented lens component that is cemented in the order of a positive lens and a negative lens from the object side, and satisfies the following conditions.
    (3) 0.45 <R_22R/ R_22F<0.9
    (4) 0 <L / R_22C<1.0
    (5) 0 <n_22R-N_22F<0.3
    (2) -1.0 <(R_3F+ R_3R) / (R_3F-R_3R<0.3
Here, L is the diagonal length of the effective imaging area in the electronic imaging device, Asp3 is the aspherical deviation amount of each refractive surface of the third lens group, and the optical axis relative to the reference spherical surface having the radius of curvature on the optical axis And the aspherical deviation amount Asp3 is set to 0 when the refractive surface is a spherical surface. R_22F, R_22R, R_22CIs the radius of curvature of the second lens group image side lens component on the optical axis of the most object side surface, most image side surface, and cemented surface, n_22F, N_22RIs the refractive index of the d-line of the object side lens and the image side lens medium of the second lens group image side lens component, R_3F, R_3RAre the curvature radii on the optical axis of the most object-side surface and the most image-side surface of the third lens unit, respectively.
[0009]
  Another electronic imaging device of the present invention is an electronic imaging device having a zoom lens and an electronic imaging device arranged on the image side thereof.
  The zoom lens includes, in order from the object side, a first lens group having a negative refractive power as a whole, a second lens group having a positive refractive power as a whole, and a third lens group having a positive refractive power as a whole. And consist of
  The second lens group includes two lens components, and the lens component on the middle image side has a meniscus shape with a concave surface facing the image surface side,
  The third lens group consists of one positive lens component,
  At least the second lens unit moves only to the object side upon zooming from the wide-angle end to the telephoto end when focusing on an object point at infinity, and the third lens unit is different from the second lens unit in zooming. The third lens group moves during focusing operation,
  All refractive surfaces of the third lens group satisfy the following conditions:
    (1) 0 ≦ | Asp3 | <3.0 × 10^-3・ L
  The lens component on the image side of the second lens group is constituted by a cemented lens component that is cemented in order of a positive lens and a negative lens from the object side.
  The lens component on the object side of the second lens group is such that both the air contact surface on the object side and the air contact surface on the image side are aspheric surfaces, and both air contacts with a reference spherical surface having a radius of curvature on the optical axis. Each of the surfaces is an aspherical surface deviated toward the object side, and satisfies the following conditions.
    (3) 0.45 <R_22R/ R_22F<0.9
    (4) 0 <L / R_22C<1.0
    (5) 0 <n_22R-N_22F<0.3
    (7) 8.0 × 10^-Four・ L <| Asp21R | <| Asp21F |
                                                  <3.0 × 10^-2・ L
Here, L is the diagonal length of the effective imaging area in the electronic imaging device, Asp3 is the aspherical deviation amount of each refractive surface of the third lens group, and the optical axis relative to the reference spherical surface having the radius of curvature on the optical axis And the aspherical deviation amount Asp3 is set to 0 when the refractive surface is a spherical surface. R_22F, R_22R, R_22CIs the radius of curvature of the second lens group image side lens component on the optical axis of the most object side surface, most image side surface, and cemented surface, n_22F, N_22RIs the object side lens of the second lens group image side lens component, the d-line refractive index of the medium of the image side lens, Asp21F and Asp21R are the air contact surface and image on the object side of the lens component of the object side of the second lens group, respectively. The aspherical deviation amount on the air contact surface on the side, and the aspherical deviation amount when the height from the optical axis with respect to the reference spherical surface having the radius of curvature on the optical axis is 0.3L.
[0010]
Hereinafter, the reason and effect | action which take the said structure in this invention are demonstrated.
[0011]
In order to achieve the above object, an electronic imaging device of the present invention is an electronic imaging device having a zoom lens and an electronic imaging device arranged on the image side. The zoom lens is negative in order from the object side. The first lens group having refractive power, the second lens group having positive refractive power as a whole, and the third lens group having positive refractive power as a whole, and the second lens group is composed of two lens components. The lens component on the middle image side has a meniscus shape with the concave surface facing the image surface side, the third lens unit is composed of one positive lens component, and at least the second lens unit is in focus at an object point at infinity. The zoom lens moves only to the object side during zooming from the wide-angle end to the telephoto end, the third lens unit moves by a different amount from the second lens unit during zooming, and the third lens unit moves during focusing operation. Adopted.
[0012]
In particular, when the lens is retracted, the amount of movement of the lens is as small as possible, since the lens barrel can be simplified and the volume can be reduced. For this purpose, the second lens group is composed of two lens components, and the lens component on the image side has a meniscus shape with a concave surface facing the image side.
[0013]
In the present invention, the term “lens” refers to a unit made of a single medium lens, and a cemented lens consists of a plurality of lenses. Moreover, a lens component means the lens group which does not arrange | position an air space | interval between them, and means a single lens or a cemented lens.
[0014]
In a negative-positive two-group zoom lens that has been used as a zoom lens for silver salt film cameras for a long time, the magnification of the positive rear group (second lens group) at each focal length is increased in order to reduce the size of the zoom lens. However, for this purpose, a positive lens component is added as a third lens group further to the image side of the second lens group, and the distance from the second lens group is changed when zooming from the wide-angle end to the telephoto end. Is well known. Further, the third lens group has a possibility of being used for focusing.
[0015]
In order to achieve the object of the present invention, that is, to reduce the fluctuation of off-axis aberrations such as astigmatism when the third lens unit is focused while the total thickness of the lens unit is reduced when retracted. In particular, the aberration correction capability of the second lens group is important.
[0016]
When focusing with the third lens group, fluctuations in aberrations become a problem, but if an amount of aspherical surface more than necessary enters the third lens group, the first lens group and the second lens group are used to produce the effect. Astigmatism remaining in step 3 is corrected by the third lens group. If the third lens group moves for focusing, the balance is lost, which is not preferable. Therefore, when focusing with the third lens group, the third lens group needs to be configured with a spherical system or a small aspheric amount. That is,
(1) 0 ≦ | Asp3 | <3.0 × 10^-3・ L
It is important to meet. Here, L is the diagonal length (mm) of the effective imaging area in the electronic imaging device, Asp3 is the aspherical deviation amount of each refractive surface of the third lens group, and a reference spherical surface having a radius of curvature on the optical axis The aspherical deviation amount when the height from the optical axis to 0.4L is 0.4 L, and the aspherical deviation amount Asp3 is zero when the refractive surface is spherical.
[0017]
That is, as shown in FIG. 14, the amount of aspherical deviation referred to in the present invention is the effective imaging area of the electronic imaging device with respect to a spherical surface (reference spherical surface) having a radius of curvature r on the optical axis of the target aspherical surface. Where L is the diagonal length of the aspherical surface, the amount of deviation of the aspherical surface at the position where the height from the optical axis is 0.4L. It is assumed that the electronic image sensor is used so that the wide angle end angle of view includes 55 ° or more.
[0018]
3.0 × 10, the upper limit of condition (1)^-3-When L is exceeded, the off-axis aberrations are significantly deteriorated by focusing, which is not preferable.
[0019]
It is better to do the following.
[0020]
(1) ′ 0 ≦ | Asp3 | <2.0 × 10^-3・ L
Furthermore, it is best to do the following.
[0021]
(1) ”0 ≦ | Asp3 | <1.0 × 10^-3・ L
Further, when the shape of the lens component of the third lens group is as follows, the aberration on the long distance side is good over the entire zoom range, and the variation in aberration due to focusing can be reduced.
[0022]
    (2) -1.0 <(R_3F+ R_3R) / (R_3F-R_3R<0.3
However, R_3F, R_3RAre the curvature radii on the optical axis of the most object-side surface and the most image-side surface of the third lens unit, respectively.
[0023]
  If the upper limit of 0.3 of condition (2) is exceeded, the fluctuation of astigmatism due to the rear focus becomes too large, and even if astigmatism can be corrected well at an infinite object point, Astigmatism tends to deteriorate. When the lower limit of −1.0 is exceeded, astigmatism fluctuation due to rear focus is small, but it is difficult to correct aberrations for infinite object points.
[0024]
It is better to do the following.
[0025]
(2) '-0.8 <(R_3F+ R_3R) / (R_3F-R_3R<0.3
Furthermore, it is best to do the following.
[0026]
(2) "-0.6 <(R_3F+ R_3R) / (R_3F-R_3R) <0
For the second lens group, if the lens component on the image side is configured by joining in order of a positive lens and a negative lens from the object side, and the shape is a meniscus shape with a concave surface facing the image side, Although it contributes to shortening the total length of the lens, the relative eccentricity sensitivity between the two lens components of the second lens group may be low to satisfy the following conditions. The curvature radius of the joint surface has a great influence on the chromatic aberration of spherical aberration in addition to the lateral chromatic aberration on the axis. Moreover, when trying to shorten the overall length by using the middle object side component of the two components of the second lens group as a stronger positive refractive power as in the present invention, the Petzval sum tends to be negative. Ingenuity is necessary.
[0027]
(3) 0.45 <R_22R/ R_22F<0.9
(4) 0 <L / R_22C<1.0
(5) 0 <n_22R-N_22F<0.3
However, R_22F, R_22R, R_22CAre the curvature radii on the optical axis of the most object-side surface, the most image-side surface, and the cemented surface of the second lens group image-side lens component, respectively. L is the diagonal length (mm) of the electronic image sensor to be used. It is assumed that the electronic image sensor is used so that the wide angle end angle of view includes 55 ° or more. n_22F, N_22RIs the refractive index of the d-line of the medium of the object side lens and the image side lens of the second lens group image side lens component, respectively.
[0028]
If the upper limit of 0.9 of condition (3) is exceeded, it is advantageous for correcting spherical aberration, coma aberration, and astigmatism of the entire system aberration, but the effect of reducing the sensitivity of decentration by joining is small. When the lower limit of 0.45 is exceeded, correction of spherical aberration, coma aberration, and astigmatism of the total system aberration tends to be difficult.
[0029]
Exceeding the lower limit of 0 in condition (4) is advantageous for correcting axial chromatic aberration and lateral chromatic aberration, but chromatic aberration of spherical aberration is likely to occur, and even if the spherical aberration at the reference wavelength can be corrected well, the short wavelength Spherical aberrations of the above are remarkably overcorrected and cause color bleeding in the image, which is not preferable. When the upper limit of 1.0 is exceeded, axial chromatic aberration and lateral chromatic aberration tend to be undercorrected.
[0030]
If the lower limit value 0 of the condition (5) is exceeded, the Petzval sum of the entire system tends to be a large negative value, which tends to cause off-axis aberration deterioration. On the other hand, there are only a few combinations of media exceeding the upper limit of 0.3 in nature, and they do not satisfy the Abbe number, spectral characteristics, price, and physicochemical properties.
[0031]
In addition, it is better to set one or more or all of the conditions (3) to (5) as follows.
[0032]
(3) '0.5 <R_22R/ R_22F<0.85
(4) '0.2 <L / R_22C<0.9
(5) '0 <n_22R-N_22F<0.25
Furthermore, it is better to set one or more of the conditions (3) to (5) as follows. In particular, it is best to do everything as follows.
[0033]
(3) "0.55 <R_22R/ R_22F<0.8
(4) "0.4 <L / R_22C<0.8
(5) "0 <n_22R-N_22F<0.2
Since the lens component on the image side of the second lens group is a cemented lens component, a single lens is sufficient for the object side lens component. Further, in terms of aberration correction, since the first lens unit has a negative refractive power, the divergent light beam is incident on the second lens unit. Therefore, the shape factor in the vicinity of the optical axis of the object-side positive lens component is the condition (6 ).
[0034]
(6) 0.1 <(R_21F+ R_21R) / (R_21F-R_21R<5
However, R_21F, R_21RAre the curvature radii on the optical axis of the object-side surface and the image-side surface of the object-side lens component of the second lens group, respectively.
[0035]
Regardless of whether the upper limit 5 or 0.1 of the condition (6) is exceeded, it is difficult to correct spherical aberration even if a plurality of aspheric surfaces are introduced on the object side of the second lens group.
[0036]
It is better to do the following.
[0037]
(6) '0.3 <(R_21F+ R_21R) / (R_21F-R_21R<4
Furthermore, it is best to do the following.
[0038]
(6) "0.5 <(R_21F+ R_21R) / (R_21F-R_21R<3
Further, if the object side lens component of the second lens group is composed of both aspherical surfaces, there is a great merit in terms of reducing the relative decentration sensitivity within the group and manufacturing cost in terms of correcting spherical aberration. If these aspherical surfaces are deviated toward the double-sided object side with respect to a reference spherical surface having a radius of curvature on the optical axis, they are excellent in terms of reducing relative decentration sensitivity within the group in terms of spherical aberration correction. Good.
[0039]
These aspherical surfaces should satisfy the following conditions.
[0040]
    (7) 8.0 × 10^-Four・ L <| Asp21R | <| Asp21F |
                                                  <3.0 × 10^-2・ L
However, Asp21F and Asp21R are the aspherical deviation amounts of the object-side air contact surface and the image-side air contact surface of the object-side lens component of the second lens group, respectively, with respect to a reference spherical surface having a radius of curvature on the optical axis. This is the amount of aspherical deviation when the height from the optical axis is 0.3L. This aspherical deviation amount is the same as the aspherical deviation amount described with reference to FIG. 14, and is effective for a spherical surface (reference spherical surface) having a radius of curvature r on the optical axis of the target aspherical surface. When the diagonal length of the imaging region is L, the amount of deviation of the aspheric surface at the position where the height from the optical axis is 0.3L is meant.
[0041]
  The lower limit of this condition (7) is 8.0 × 10^-Four・ If L exceeds L or if the inequality sign in the center is reversed, correction of spherical aberration is insufficient. Upper limit of 3.0 × 10^-2-When L is exceeded, the relative eccentricity sensitivity with each component in the group increases.
[0042]
It is better to do the following.
[0043]
(7) '8.0 × 10^-Four・ L <| Asp21R | <| Asp21F | <2.0 × 10^-2・ L
Furthermore, it is best to do the following.
[0044]
(7) ”1.0 × 10^-3・ L <| Asp21R | <| Asp21F | <1.0 × 10^-2・ L
In the configuration of the zoom lens according to the present invention, the magnification of the subsequent synthesizing system including the second lens group is set to −1 at approximately the center of the zooming range in order to reduce the size. That is, the magnification of the second lens group is set higher than that of a normal negative group preceding zoom lens. Therefore, the magnification at the telephoto end of the second lens group in the 3 × class is preferably set as follows.
[0045]
(8) 1.45 <−β_2T<2.1
However, β_2TIs the magnification of the entire second lens group at the telephoto end when focusing on an object point at infinity.
[0046]
If the lower limit of 1.45 of the condition (8) is exceeded, the distance between the first lens group and the second lens group at the wide-angle end is too large, and the effective diameter of the first lens group must be increased. It becomes large to the thickness. If the upper limit of 2.1 is exceeded, aberration correction for both the first lens group and the second lens group becomes more difficult.
[0047]
It is better to do the following.
[0048]
(8) ′ 1.5 <−β_2T<2.05
Furthermore, it is best to do the following.
[0049]
(8) ”1.55 <−β_2T<2.0
If the two lens components of the second lens group are made into a positive lens component and a negative lens component in order from the object side, the back focus in the photographing state does not become long even when the second lens group has a high magnification.
[0050]
Next, the chromatic aberration and each Seidel off-axis aberration can be satisfactorily corrected if the first lens group is composed of only two lenses, a negative lens including an aspherical surface and a positive lens, while satisfying the following conditions. Contributes to thinning.
[0051]
(9) 10 <ν₁₁−ν₁₂<24
(10) -4 <(R₁₃+ R₁₄) / (R₁₃-R₁₄<1.1
Where ν₁₁Is the Abbe number of the medium on the d-line basis of the negative lens of the first lens group, ν₁₂Is the Abbe number of the medium on the d-line basis of the positive lens of the first lens group, R₁₃Is the radius of curvature on the optical axis of the object side surface of the positive lens in the first lens group, R₁₄Is the radius of curvature on the optical axis of the image side surface of the positive lens in the first lens group.
[0052]
Condition (9) is defined with respect to the variation of the on-axis and lateral chromatic aberration during zooming. If the lower limit of 10 is exceeded, the axial chromatic aberration tends to be overcorrected and the lateral chromatic aberration is likely to be undercorrected. If the upper limit of 24 is exceeded, the reverse is likely.
[0053]
Condition (10) defines the shape factor of the first lens group positive lens. Exceeding the lower limit of −4 is disadvantageous in correcting astigmatism, and is disadvantageous in that it requires an extra space with the second lens group in order to avoid mechanical interference during zooming. If the upper limit of −1.1 is exceeded, correction of distortion will tend to be disadvantageous.
[0054]
In addition, it is better to set one or both of the conditions (9) and (10) as follows.
[0055]
(9) ’12 <ν₁₁−ν₁₂<22
(10) '-3.5 <(R₁₃+ R₁₄) / (R₁₃-R₁₄) <-1.3
Furthermore, it is better to set one or both of the conditions (9) and (10) as follows. In particular, it is best to do both as follows.
[0056]
(9) ”14 <ν₁₁−ν₁₂<20
(10) "-3 <(R₁₃+ R₁₄) / (R₁₃-R₁₄<1.5
In addition, the following conditions should be satisfied.
[0057]
(11) 0.2 <d₁₁/L<0.65
Where d₁₁Is the air space on the optical axis of the negative lens and the positive lens of the first lens group.
[0058]
If the upper limit of 0.65 of this condition (11) is exceeded, it is advantageous for correction of coma, astigmatism and distortion. However, if the optical system becomes thicker and the lower limit of 0.2 is exceeded, these In spite of the introduction of an aspherical surface, it becomes difficult to correct this aberration, and the relative decentering sensitivity in the first lens group tends to increase.
[0059]
It is better to do the following.
[0060]
(11) ’0.25 <d₁₁/L<0.6
Furthermore, it is best to do the following.
[0061]
(11) ”0.3 <d₁₁/L<0.55
Note that the third lens group may be composed of one positive lens. Practical aberration level correction is possible and contributes to thinning.
[0062]
Since the zoom lens of the present invention can emit off-axis chief rays in a state of being nearly perpendicular to the image plane, it is desirable to configure the zoom lens as an electronic image pickup apparatus having an image pickup element on the image plane side.
[0063]
At that time, it is more preferable that the diagonal length L of the effective imaging region of the imaging device is 3.0 mm to 12.0 mm in order to achieve both good image quality and downsizing.
[0064]
If the image sensor becomes smaller beyond the lower limit of 3.0 mm, it will be difficult to cover the lack of sensitivity. On the other hand, if the imaging element is larger than the upper limit of 12.0 mm, the zoom lens tends to be larger accompanying this, and the effect of thinning is diminished.
[0065]
The present invention is advantageous in constructing an electronic imaging device including a wide angle region. In particular, the half angle of view ω in the diagonal direction at the wide-angle end_WIs preferably used in an electronic imaging device that satisfies the following conditions (the wide angle end half angle of view described in each example below is ω_WIt corresponds to. ).
[0066]
27.5 ° <ω_W
If the wide angle end half angle of view becomes narrow beyond this lower limit of 27.5 °, it becomes advantageous in terms of aberration correction, but it is not a practical angle of view at the wide angle end.
[0067]
Furthermore, we set an upper limit,
27.5 ° <ω_W<42 °
It is good.
[0068]
When the upper limit of 42 ° is exceeded, distortion and chromatic aberration of magnification tend to occur, and the number of lenses increases.
[0069]
In addition, it is preferable that the present invention be an electronic image pickup apparatus including a zoom lens having a zoom ratio that satisfies the following conditions, because a reduction in size and a required zoom ratio can be balanced.
[0070]
2.4 <Z <4.0
Here, Z is the zoom ratio of the zoom lens, and is the telephoto end focal length / wide angle end focal length.
[0071]
Exceeding the lower limit of 2.4 of this condition is advantageous for downsizing, but does not achieve high zoom ratio. When the upper limit of 4.0 is exceeded, it is difficult to reduce the size with a small number of lenses.
[0072]
Furthermore, the lower limit value is more preferably 2.7 or 2.8. On the other hand, the upper limit value is more preferably set to 3.5 or 3.0.
[0073]
As described above, a means for improving the imaging performance while reducing the retractable thickness of the zoom lens unit has been provided.
[0074]
Next, mention is made of thinning filters. In an electronic imaging device, an infrared absorption filter having a certain thickness is usually inserted closer to the object side than the imaging device so that infrared light does not enter the imaging surface. Consider replacing this with a thin coating. Naturally, it will be thinner, but it has a side effect. The transmittance (τ) at a wavelength of 600 nm is located closer to the object side than the image sensor behind the zoom lens system.₆₀₀) Is 80% or more and transmittance at 700 nm (τ)₇₀₀) Of 8% or less near infrared sharp cut coat, the transmittance in the near infrared region of 700 nm or more is lower than that of the absorption type, and the transmittance on the red side is relatively high. The magenta tendency on the bluish-purple side, which is a defect of a solid-state image pickup device such as a CCD having the above, is alleviated by gain adjustment, and color reproduction similar to a solid-state image pickup device such as a CCD having a primary color filter can be obtained.
[0075]
That is,
(12) τ₆₀₀/ Τ₅₅₀≧ 0.8
(13) τ₇₀₀/ Τ₅₅₀≦ 0.08
It is desirable to satisfy. Where τ₅₅₀Is the transmittance at a wavelength of 550 nm.
[0076]
In addition, it is better to set one or both of the conditions (12) and (13) as follows.
[0077]
(12) ’τ₆₀₀/ Τ₅₅₀≧ 0.85
(13) ’τ₇₀₀/ Τ₅₅₀≦ 0.05
Furthermore, it is better to set one or both of the conditions (12) and (13) as follows. In particular, it is best to do both as follows.
[0078]
(12) “τ₆₀₀/ Τ₅₅₀≧ 0.9
(13) “τ₇₀₀/ Τ₅₅₀≦ 0.03
Another drawback of a solid-state imaging device such as a CCD is that the sensitivity to the near-ultraviolet wavelength of 550 nm is considerably higher than that of the human eye. This also highlights the color blur at the edge of the image due to chromatic aberration in the near ultraviolet region. In particular, it is fatal to downsize the optical system. Therefore, the transmittance at the wavelength of 400 nm (τ₄₀₀) At 550 nm (τ)₅₅₀) Ratio below 0.08, and transmittance at 440 nm (τ₄₄₀) At 550 nm (τ)₅₅₀) If an absorber or reflector with a ratio of more than 0.4 is inserted in the optical path, the wavelength range required for color reproduction is not lost (while maintaining good color reproduction), and noise such as color bleeding Is considerably reduced.
[0079]
That is,
(14) τ₄₀₀/ Τ₅₅₀≦ 0.08
(15) τ₄₄₀/ Τ₅₅₀≧ 0.4
It is desirable to satisfy.
[0080]
Note that it is better to set one or both of the conditions (14) and (15) as follows.
[0081]
(14) ’τ₄₀₀/ Τ₅₅₀≦ 0.06
(15) ’τ₄₄₀/ Τ₅₅₀≧ 0.5
Furthermore, it is better to set one or both of the conditions (14) and (15) as follows. In particular, it is best to do both as follows.
[0082]
(14) “τ₄₀₀/ Τ₅₅₀≦ 0.04
(15) “τ₄₄₀/ Τ₅₅₀≧ 0.6
These filters are preferably installed between the imaging optical system and the image sensor.
[0083]
On the other hand, in the case of a complementary color filter, because of its high transmitted light energy, it is substantially more sensitive than a CCD with a primary color filter and is advantageous in terms of resolution. It is. The total thickness t of the other optical low-pass filter is also t._LPF(Mm) should satisfy the following conditions.
[0084]
(16) 0.15 <t_LPF/A<0.45
However, a is a horizontal pixel pitch (unit: μm) of the image sensor, and is 5 μm or less.
[0085]
In order to reduce the collapsed thickness, it is effective to make the optical low-pass filter thinner, but in general, the moire suppressing effect is reduced, which is not preferable. On the other hand, as the pixel pitch decreases, the contrast of frequency components above the Nyquist limit decreases due to the influence of diffraction of the imaging lens system, and the phenomenon of the moire suppression effect is allowed to some extent. For example, when three types of filters having crystal axes in the horizontal (= 0 °) and ± 45 ° directions are projected in the direction of the optical axis when projected on the image plane, the effect of suppressing moiré is considerably improved. It has been known. As a specification in which the filter is the thinnest in this case, it is known that the filter is shifted by SQRT (1/2) * a μm horizontally by aμm and ± 45 °. The filter thickness at this time is approximately [1 + 2 * SQRT (1/2)] * a / 5.88 (mm). Here, SQRT is a square route and means a square root. This is a specification in which the contrast is zero at a frequency corresponding to the Nyquist limit. If it is made thinner by several percent to several tens of percent than this, a little frequency contrast corresponding to the Nyquist limit appears, but it can be suppressed by the influence of the diffraction.
[0086]
It is preferable that the condition (16) is satisfied, including the case where filter specifications other than those described above, for example, two sheets are stacked or one sheet is used. If the upper limit of 0.45 is exceeded, the optical low-pass filter is too thick and hinders thinning. When the lower limit of 0.15 is exceeded, moire removal becomes insufficient. However, the condition of a in carrying out this is 5 μm or less.
[0087]
If a is 4 μm or less, it is more susceptible to diffraction.
(16) ’0.13 <t_LPF/A<0.42
It is good.
[0088]
Further, the following may be performed according to the number of low-pass filters superimposed on the horizontal pixel pitch.
[0089]
(16) ”0.3 <t_LPF/A<0.4
However, when 3 sheets are stacked and 4 ≦ a <5 (μm),
0.2 <t_LPF/A<0.28
However, when two sheets are stacked and 4 ≦ a <5 (μm),
0.1 <t_LPF/A<0.16
However, when only one sheet and 4 ≦ a <5 (μm),
0.25 <t_LPF/A<0.37
However, when 3 sheets are stacked and a <4 (μm),
0.16 <t_LPF/A<0.25
However, when two sheets are stacked and a <4 (μm),
0.08 <t_LPF/A<0.14
However, when only one sheet and a <4 (μm).
[0090]
When an electronic image sensor with a small pixel pitch is used, the image quality deteriorates due to the diffraction effect due to narrowing down. Therefore, there are a plurality of apertures having a fixed aperture size, and one of them is any one of the optical paths between the lens surface closest to the image side of the first lens group and the lens surface closest to the object side of the third lens group. An electronic imaging device that can be inserted into and can be exchanged with other apertures to adjust the illuminance of the image plane. Among the plurality of apertures, some of the apertures have transmittance for 550 nm. It is preferable to adjust the amount of light so as to have media that are different and less than 80%. Alternatively, when adjustment is performed so that the amount of light corresponds to the F value such that a (μm) / F number <0.4, the medium having different transmittances for 550 nm and less than 80% in the aperture An electronic imaging device having For example, if the medium is not within the range of the above condition from the open value, or a dummy medium with a transmittance of 550 nm or more is set to 91% or more, and if within the range, the aperture stop diameter is reduced to such an extent that diffraction is affected. It is better to adjust the amount of light with something like an ND filter.
[0091]
Alternatively, the plurality of openings may be arranged such that their diameters are reduced in inverse proportion to the F value, and optical low-pass filters having different frequency characteristics may be placed in the openings instead of the ND filters. Since the diffraction degradation increases as the aperture is narrowed down, the frequency characteristic of the optical low-pass filter is set higher as the aperture diameter decreases.
[0092]
In addition, in the above, each conditional expression is effective in any one of downsizing and high performance even if it is individually limited to the configurations described in [1] to [13] below.
[0093]
Further, for each conditional expression limitation, there is naturally the same effect even if it is limited to only the lower limit value or the upper limit value of the limited conditional expression. Further, the values corresponding to the conditional expressions in the examples described later are also the respective conditions. It can be changed near the boundary value of the expression.
[0094]
DETAILED DESCRIPTION OF THE INVENTION
Examples 1 to 5 of the zoom lens used in the electronic imaging device of the present invention will be described below. FIGS. 1 and 2 show lens cross-sectional views at the wide-angle end (a), the intermediate state (b), and the telephoto end (c) when focusing on an object point at infinity in Examples 1 and 2, respectively. Since Examples 3 to 5 are substantially the same as FIG. 2, illustration is omitted. 1 and 2, the first lens group is G1, the stop is S, the second lens group is G2, the third lens group is G3, the infrared cut absorption filter is IF, the low-pass filter is LF, and an electronic image sensor. The CCD cover glass is indicated by CG, and the CCD image plane is indicated by I. Instead of the infrared cut absorption filter IF, a transparent flat plate incident surface with a near infrared sharp cut coat may be used, or the low pass filter LF may be directly provided with a near infrared sharp cut coat. .
[0095]
As shown in FIG. 1, the zoom lens of Example 1 includes a first lens group G1 having a negative refractive power composed of a negative meniscus lens convex on the object side and a positive meniscus lens convex on the object side, an aperture stop S, Second lens group G2 having a positive refractive power composed of a biconvex positive lens, a cemented lens of a positive meniscus lens convex on the object side and a negative meniscus lens convex on the object side, and a positive refractive power composed of one biconvex positive lens The first lens group G1 moves in a concave locus on the object side when zooming from the wide-angle end to the telephoto end, and at the telephoto end is positioned on the image plane side from the wide-angle end. The second lens group G2 moves to the object side integrally with the aperture stop S, the third lens group G3 moves along a locus convex toward the object side, and is slightly closer to the object side than the wide angle end at the telephoto end. become. In order to focus on a subject at a short distance, the third lens group G3 is extended toward the object side.
[0096]
The aspheric surfaces are used for the three surfaces of the negative meniscus lens surface of the first lens group G1, the object side surface of the biconvex positive lens of the second lens group G2, and the object side surface of the cemented lens. Yes.
[0097]
As shown in FIG. 2, the zoom lenses of Examples 2 to 5 include a first lens group G1 having a negative refractive power including a negative meniscus lens convex on the object side and a positive meniscus lens convex on the object side, and an aperture stop. S, a second lens group G2 having a positive refractive power composed of a positive meniscus lens convex on the image side, a positive meniscus lens convex on the object side, and a negative meniscus lens convex on the object side, a biconvex positive lens The first lens unit G1 is composed of a single third lens unit G3 having positive refracting power. When zooming from the wide-angle end to the telephoto end, the first lens unit G1 moves along a concave locus on the object side, and at the telephoto end a wide-angle The second lens group G2 moves to the object side integrally with the aperture stop S, the third lens group G3 moves along a locus convex toward the object side, and a wide angle at the telephoto end. The position is slightly closer to the object side than the edge. In order to focus on a subject at a short distance, the third lens group G3 is extended toward the object side.
[0098]
As for the aspherical surface, Examples 2 to 4 are used for the three surfaces of the negative meniscus lens in the first lens group G1 on the image surface side and the two surfaces on the both sides of the single positive meniscus lens in the second lens group G2. In Example 5, the surface on the image side of the negative meniscus lens in the first lens group G1, the surfaces on both sides of the single positive meniscus lens in the second lens group G2, and the biconvex positive lens in the third lens group G3 are used. It is used for four surfaces on the object side.
[0099]
In the following, numerical data of each of the above embodiments is shown. Symbols are the above, f is the total focal length, ω is the half angle of view, F_NOIs the F number, WE is the wide-angle end, ST is the intermediate state, TE is the telephoto end, r₁, R₂... is the radius of curvature of each lens surface, d₁, D₂... is the distance between each lens surface, n_d1, N_d2... is the refractive index of d-line of each lens, ν_d1, Ν_d2... is the Abbe number of each lens. The aspherical shape is represented by the following formula, where x is an optical axis with the light traveling direction being positive, and y is a direction orthogonal to the optical axis.
[0100]
x = (y²/ R) / [1+ {1- (K + 1) (y / r)²}^1/2] + A_Foury^Four+ A₆y⁶+ A₈y⁸+ A_Teny^Ten
Where r is the paraxial radius of curvature, K is the cone coefficient, A_Four, A₆, A₈, A_TenAre the 4th, 6th, 8th and 10th order aspherical coefficients, respectively.
[0101]

[0102]

[0103]

[0104]

[0105]

[0106]
FIG. 3 is an aberration diagram when focusing on infinity in Example 1 and FIG. 4 is an aberration diagram when focusing on an imaging distance of 10 cm by moving the third lens group G3 to the object side. 5 and 6 show the same aberration diagrams of Example 2, FIGS. 7 and 8 show the same aberration diagrams of Example 3, FIG. 9 and FIG. 10 show the same aberration diagrams of Example 4, and FIG. Similar aberration diagrams of Fig. 5 are shown in Figs. 11 and 12, respectively. In these aberration diagrams, (a) represents the aberration at the wide-angle end, (b) represents the intermediate state, (c) represents the aberration at the telephoto end, “SA” represents spherical aberration, “AS” represents astigmatism, and “DT” represents distortion. Aberration, “CC” indicates lateral chromatic aberration. In each aberration diagram, “FIY” indicates the image height.
[0107]
Next, the values of the conditions (1) to (6) and (8) to (16) and the values of Asp21F, Asp21R, and L and Z relating to the condition (7) in each of the above examples are shown.

[0108]
The total thickness t of the low-pass filters of Examples 1 to 5_LPFEach of them is 1.500 (mm) and is constituted by three layers. Of course, the above-described embodiment can be variously modified within the range of the above-described configuration, for example, the low-pass filter F is composed of one sheet.
[0109]
Here, the diagonal length L of the effective imaging surface and the pixel interval a will be described. FIG. 13 is a diagram illustrating an example of a pixel array of an image sensor, and R (red), G (green), and B (blue) pixels or cyan, magenta, yellow, and green (green) pixels with a pixel interval a. Four color pixels (FIG. 17) are arranged in a mosaic pattern. The effective image pickup surface means a region in the photoelectric conversion surface on the image pickup element used for reproduction (display on a personal computer, printing by a printer, etc.) of a taken image. The effective image pickup surface shown in the figure is set to a region narrower than the entire photoelectric conversion surface of the image pickup device in accordance with the performance of the optical system (image circle that can ensure the performance of the optical system). The diagonal length L of the effective imaging surface is the diagonal length of this effective imaging surface. Note that the imaging range used for video reproduction may be variously changed. However, when the zoom lens of the present invention is used in an imaging apparatus having such a function, the diagonal length L of the effective imaging surface changes. In such a case, the diagonal length L of the effective imaging surface in the present invention is the maximum value in the range that L can take.
[0110]
As for the infrared cut means, there are an infrared cut absorption filter and an infrared sharp cut coat, and the infrared cut absorption filter is a case where an infrared absorber is contained in the glass. It is a cut by reflection rather than absorption. Therefore, as described above, the infrared cut absorption filter may be removed, and the infrared low pass filter may be directly applied to the low pass filter, or may be applied to the dummy transparent flat plate.
[0111]
In this case, the near-infrared sharp cut coat is preferably configured so that the transmittance at a wavelength of 600 nm is 80% or more and the transmittance at a wavelength of 700 nm is 10% or less. Specifically, it is a multilayer film composed of the following 27 layers, for example. However, the design wavelength is 780 nm.
[0112]
Substrate material Physical film thickness (nm) λ / 4
───────────────────────────────
1st layer Al₂O_Three    58.96 0.50
Second layer TiO₂      84.19 1.00
Third layer SiO₂    134.14 1.00
4th layer TiO₂      84.19 1.00
5th layer SiO₂    134.14 1.00
6th layer TiO₂      84.19 1.00
7th layer SiO₂    134.14 1.00
8th layer TiO₂      84.19 1.00
9th layer SiO₂    134.14 1.00
10th layer TiO₂      84.19 1.00
11th layer SiO₂    134.14 1.00
12th layer TiO₂      84.19 1.00
13th layer SiO₂    134.14 1.00
14th layer TiO₂      84.19 1.00
15th layer SiO₂    178.41 1.33
16th layer TiO₂    101.03 1.21
17th layer SiO₂    167.67 1.25
18th layer TiO₂      96.82 1.15
19th layer SiO₂    147.55 1.05
20th layer TiO₂      84.19 1.00
21st layer SiO₂    160.97 1.20
22nd layer TiO₂      84.19 1.00
23rd layer SiO₂    154.26 1.15
24th layer TiO₂      95.13 1.13
25th layer SiO₂    160.97 1.20
26th layer TiO₂      99.34 1.18
27th layer SiO₂      87.19 0.65
───────────────────────────────
Air.
[0113]
The transmittance characteristics of the near infrared sharp cut coat are as shown in FIG.
[0114]
Further, by providing a color filter that reduces transmission of colors in the short wavelength region as shown in FIG. 16 or coating on the exit surface side of the low-pass filter, the color reproducibility of the electronic image is further improved. Yes.
[0115]
Specifically, with this filter or coating, the ratio of the transmittance of the wavelength of 420 nm to the transmittance of the wavelength having the highest transmittance at a wavelength of 400 nm to 700 nm is 15% or more, and 400 nm to the transmittance of the highest wavelength. It is preferable that the ratio of the transmittances of the wavelengths is 6% or less.
[0116]
Thereby, it is possible to reduce the difference between the recognition of the color of the human eye and the color of the image to be captured and reproduced. In other words, it is possible to prevent deterioration of the image due to the human eye easily recognizing a short wavelength color that is difficult to be recognized by human vision.
[0117]
If the ratio of the transmittance at the wavelength of 400 nm exceeds 6%, the single wavelength castle which is difficult to be recognized by the human eye is regenerated to a recognizable wavelength. If the ratio is less than 15%, the reproduction of wavelength castles that can be recognized by humans becomes low, and the color balance becomes poor.
[0118]
Such means for limiting the wavelength is more effective in an imaging system using a complementary color mosaic filter.
[0119]
In each of the above embodiments, as shown in FIG. 16, the coating has a transmittance of 0% at a wavelength of 400 nm, a transmittance of 90% at 420 nm, and a transmittance peak of 100% at 440 nm.
[0120]
By multiplying the action with the above-mentioned near infrared sharp cut coat, the transmittance at 400 nm is peaked at 99%, the transmittance at 400 nm is 0%, the transmittance at 420 nm is 80%, and the transmittance at 600 nm is 82%. The transmittance at 700 nm is 2%. As a result, more faithful color reproduction is performed.
[0121]
In addition, the low-pass filter uses three types of filters with crystal axes in the horizontal (= 0 °) and ± 45 ° directions when projected on the image plane in the optical axis direction. The moiré is suppressed by shifting by a SQRT (1/2) × a in the horizontal direction of a μm and ± 45 °. Here, SQRT is a square route and means a square root as described above.
[0122]
Further, on the image pickup surface of the CCD arranged on the image plane I in the first to fifth embodiments, as shown in FIG. 17, four color filters of cyan, magenta, yellow, and green (green) correspond to the image pickup pixels. Thus, a complementary color mosaic filter provided in a mosaic shape is provided. These four types of color filters are arranged in a mosaic so that each of them has approximately the same number and adjacent pixels do not correspond to the same type of color filter. Thereby, more faithful color reproduction becomes possible.
[0123]
Specifically, the complementary color mosaic filter is composed of at least four types of color filters as shown in FIG. 17, and the characteristics of the four types of color filters are preferably as follows.
[0124]
Green color filter G has wavelength G_PHas a peak of spectral intensity,
Yellow color filter Y_eIs the wavelength Y_PHas a peak of spectral intensity,
Cyan color filter C has wavelength C_PHas a peak of spectral intensity,
Magenta color filter M has wavelength M_P1And M_P2And satisfy the following conditions.
[0125]
510nm <G_P<540 nm
5nm <Y_P-G_P<35nm
−100 nm <C_P-G_P<-5nm
430 nm <M_P1<480nm
580 nm <M_P2<640nm
Further, the green, yellow, and cyan color filters have an intensity of 80% or more at a wavelength of 530 nm with respect to each spectral intensity peak, and the magenta color filter has an intensity of 10% at a wavelength of 530 nm. From the viewpoint of improving the color reproducibility, it is more preferable that the strength is 50% to 50%.
[0126]
An example of each wavelength characteristic in each of the above embodiments is shown in FIG. The green color filter G has a spectral intensity beak at 525 nm. Yellow color filter Y_eHas a spectral intensity peak at 555 nm. The cyan color filter C has a spectral intensity peak at 510 nm. The magenta color filter M has peaks at 445 nm and 620 nm. Each color filter at 530 nm has a G of 99% and Y_e95%, C 97%, M 38%.
[0127]
In the case of such a complementary color filter, the following signal processing is performed electrically with a controller (not shown) (or a controller used in a digital camera),
Luminance signal
Y = | G + M + Y_e+ C | × 1/4
Color signal
R−Y = | (M + Y_e)-(G + C) |
B−Y = | (M + C) − (G + Y_e) ｜
The signal is converted into R (red), G (green), and B (blue) signals.
[0128]
By the way, the arrangement position of the above-mentioned near infrared sharp cut coat may be any position on the optical path. Further, the number of low-pass filters may be two or one as described above.
[0129]
The image pickup apparatus of the present invention as described above is an image pickup apparatus that forms an object image with a zoom lens and receives the image with an electronic image pickup device such as a CCD, and more particularly a digital camera, a video camera, and an information processing apparatus. It can be used for personal computers, telephones, especially mobile phones that are easy to carry. The embodiment is illustrated below.
[0130]
19 to 21 are conceptual diagrams of a configuration in which the zoom lens according to the present invention is incorporated in the photographing optical system 41 of the digital camera. 19 is a front perspective view showing the appearance of the digital camera 40, FIG. 20 is a rear perspective view thereof, and FIG. 21 is a cross-sectional view showing the configuration of the digital camera 40. In this example, the digital camera 40 includes a photographing optical system 41 having a photographing optical path 42, a finder optical system 43 having a finder optical path 44, a shutter 45, a flash 46, a liquid crystal display monitor 47, and the like. When the shutter 45 disposed in the position is pressed, photographing is performed through the photographing optical system 41, for example, the zoom lens of the first embodiment, in conjunction therewith. An object image formed by the photographing optical system 41 is formed on the imaging surface of the CCD 49 via an infrared cut absorption filter IF obtained by applying a near infrared cut coat on a dummy transparent flat plate and an optical low-pass filter LF. . The object image received by the CCD 49 is displayed as an electronic image on the liquid crystal display monitor 47 provided on the back of the camera via the processing means 51. Further, the processing means 51 is connected to a recording means 52 so that a photographed electronic image can be recorded. The recording means 52 may be provided separately from the processing means 51, or may be configured to perform recording / writing electronically using a floppy disk, memory card, MO, or the like. Further, it may be configured as a silver salt camera in which a silver salt film is arranged in place of the CCD 49.
[0131]
Further, a finder objective optical system 53 is disposed on the finder optical path 44. The object image formed by the finder objective optical system 53 is formed on the field frame 57 of the Porro prism 55 which is an image erecting member. Behind this polyprism 55 is an eyepiece optical system 59 that guides the erect image to the observer eyeball E. Cover members 50 are disposed on the incident side of the photographing optical system 41 and the objective optical system 53 for the viewfinder and on the exit side of the eyepiece optical system 59, respectively.
[0132]
The digital camera 40 configured in this manner is a zoom lens with a large back focus, a photographing optical system 41 having a wide angle of view and a high zoom ratio, good aberration, bright, and a filter that can be arranged with a high back focus. Performance and cost reduction can be realized.
[0133]
In the example of FIG. 21, a parallel plane plate is disposed as the cover member 50, but a lens having power may be used.
[0134]
The electronic imaging apparatus of the present invention described above can be configured as follows, for example.
[0135]
[1] In an electronic imaging device having a zoom lens and an electronic imaging device arranged on the image side thereof,
The zoom lens includes, in order from the object side, a first lens group having a negative refractive power as a whole, a second lens group having a positive refractive power as a whole, and a third lens group having a positive refractive power as a whole. And consist of
The second lens group includes two lens components, and the lens component on the middle image side has a meniscus shape with a concave surface facing the image surface side,
The third lens group consists of one positive lens component,
At least the second lens unit moves only to the object side upon zooming from the wide-angle end to the telephoto end when focusing on an object point at infinity, and the third lens unit is different from the second lens unit in zooming. The third lens group moves during focusing operation,
All the refractive surfaces of the third lens group satisfy the following conditions.
[0136]
(1) 0 ≦ | Asp3 | <3.0 × 10^-3・ L
Here, L is the diagonal length of the effective imaging area in the electronic imaging device, Asp3 is the aspherical deviation amount of each refractive surface of the third lens group, and the optical axis relative to the reference spherical surface having the radius of curvature on the optical axis And the aspherical deviation amount Asp3 is set to 0 when the refractive surface is a spherical surface.
[0137]
[2] The electronic imaging apparatus as described in 1 above, wherein the following condition is satisfied.
[0138]
(2) -1.0 <(R_3F+ R_3R) / (R_3F-R_3R) <0.7
However, R_3F, R_3RAre the curvature radii on the optical axis of the most object-side surface and the most image-side surface of the third lens unit, respectively.
[0139]
[3] The lens component on the image side of the second lens group includes a cemented lens component that is cemented from the object side in the order of a positive lens and a negative lens, and satisfies the following conditions: The electronic imaging apparatus according to 1 or 2.
[0140]
(3) 0.45 <R_22R/ R_22F<0.9
(4) 0 <L / R_22C<1.0
(5) 0 <n_22R-N_22F<0.3
However, R_22F, R_22R, R_22CIs the radius of curvature of the second lens group image side lens component on the optical axis of the most object side surface, most image side surface, and cemented surface, n_22F, N_22RIs the refractive index of the d-line of the medium of the object side lens and the image side lens of the second lens group image side lens component, respectively.
[0141]
[4] The electronic imaging apparatus according to any one of the above items 1 to 3, wherein a lens component on the object side of the second lens group includes one single lens and satisfies the following condition.
[0142]
(6) 0.1 <(R_21F+ R_21R) / (R_21F-R_21R<5
However, R_21F, R_21RAre the curvature radii on the optical axis of the object-side surface and the image-side surface of the object-side lens component of the second lens group, respectively.
[0143]
[5] The lens component on the object side of the second lens group has both an aspheric surface on the object side and an air contact surface on the image side, and a reference spherical surface having a radius of curvature on the optical axis. 5. The electronic imaging apparatus according to any one of claims 1 to 4, wherein both of the air contact surfaces are aspheric surfaces biased toward the object side.
[0144]
[6] The electronic imaging apparatus as described in 5 above, wherein the following condition is satisfied.
[0145]
(7) 5.0 × 10^-Four・ L <| Asp21R | <| Asp21F | <3.0 × 10^-2・ L
However, Asp21F and Asp21R are the aspherical deviation amounts of the object-side air contact surface and the image-side air contact surface of the object-side lens component of the second lens group, respectively, with respect to a reference spherical surface having a radius of curvature on the optical axis. This is the amount of aspherical deviation when the height from the optical axis is 0.3L.
[0146]
[7] The electronic imaging apparatus according to any one of 1 to 6, wherein the following condition is satisfied.
[0147]
(8) 1.45 <−β_2T<2.1
However, β_2TIs the magnification of the entire second lens group at the telephoto end when focusing on an object point at infinity.
[0148]
[8] The electronic imaging apparatus according to any one of 1 to 7, wherein the two lens components of the second lens group are a positive lens component and a negative lens component in order from the object side.
[0149]
[9] The first lens group includes two lenses, a negative lens including an aspherical surface and a positive lens, and satisfies the following condition. The electronic imaging device described.
[0150]
(9) 10 <ν₁₁−ν₁₂<24
(10) -4 <(R₁₃+ R₁₄) / (R₁₃-R₁₄<1.1
Where ν₁₁Is the Abbe number of the medium on the d-line basis of the negative lens of the first lens group, ν₁₂Is the Abbe number of the medium on the d-line basis of the positive lens of the first lens group, R₁₃Is the radius of curvature on the optical axis of the object side surface of the positive lens in the first lens group, R₁₄Is the radius of curvature on the optical axis of the image side surface of the positive lens in the first lens group.
[0151]
[10] The electronic imaging apparatus as described in 9 above, wherein the following condition is satisfied.
[0152]
(11) 0.2 <d₁₁/L<0.65
Where d₁₁Is the air space on the optical axis of the negative lens and the positive lens of the first lens group.
[0153]
[11] The electronic imaging apparatus according to any one of [1] to [10], wherein the third lens group includes a single positive lens.
[0154]
[12] The electronic image pickup apparatus according to any one of [1] to [11], wherein a diagonal length L of an effective image pickup area of the electronic image pickup element satisfies the following condition.
[0155]
3.0mm <L <12.0mm
[13] Half field angle ω in the diagonal direction at the wide-angle end_WThe electronic imaging device according to any one of 1 to 12 above, wherein the following condition is satisfied.
[0156]
27.5 ° <ω_W
[0157]
【The invention's effect】
With the present invention as described above, a zoom lens having a thin collapsible thickness, an excellent storage property, a high magnification, and an excellent imaging performance even in a rear focus can be obtained, and a video camera and a digital camera can be reduced in thickness. Can be achieved.
[Brief description of the drawings]
FIG. 1 is a lens cross-sectional view at a wide-angle end (a), an intermediate state (b), and a telephoto end (c) when focusing on an object point at infinity according to Embodiment 1 of a zoom lens used in an electronic imaging device of the present invention. It is.
2 is a lens cross-sectional view similar to FIG. 1 illustrating a zoom lens according to Embodiment 2. FIG.
FIG. 3 is an aberration diagram for Example 1 upon focusing on an object point at infinity.
FIG. 4 is an aberration diagram for Example 1 upon focusing on a subject distance of 10 cm.
5 is an aberration diagram for Example 2 upon focusing on an object point at infinity. FIG.
FIG. 6 is an aberration diagram for Example 2 upon focusing on a subject distance of 10 cm.
FIG. 7 is an aberration diagram for Example 3 upon focusing on an object point at infinity.
FIG. 8 is an aberration diagram for Example 3 upon focusing on a subject distance of 10 cm.
FIG. 9 is an aberration diagram for Example 4 upon focusing on an object point at infinity.
FIG. 10 is an aberration diagram for Example 4 upon focusing on a subject distance of 10 cm.
FIG. 11 is an aberration diagram for Example 5 upon focusing on an object point at infinity.
12 is an aberration diagram for Example 5 upon focusing on a subject distance of 10 cm. FIG.
FIG. 13 is a diagram for explaining a diagonal length of an effective imaging surface when imaging is performed with an electronic imaging element.
FIG. 14 is a diagram for explaining the definition of the amount of aspherical deviation in the present invention.
FIG. 15 is a diagram showing transmittance characteristics of an example of a near-infrared sharp cut coat.
FIG. 16 is a diagram illustrating a transmittance characteristic of an example of a color filter provided on the emission surface side of the low-pass filter.
FIG. 17 is a diagram illustrating a color filter arrangement of a complementary color mosaic filter.
FIG. 18 is a diagram illustrating an example of wavelength characteristics of a complementary color mosaic filter.
FIG. 19 is a front perspective view showing the appearance of a digital camera incorporating a zoom lens according to the present invention.
20 is a rear perspective view of the digital camera of FIG. 19. FIG.
21 is a cross-sectional view of the digital camera of FIG.
[Explanation of symbols]
G1: First lens group
G2: Second lens group
G3 ... Third lens group
S ... Aperture stop
F: Combination of infrared cut absorption filter and low-pass filter
CG ... Cover glass
I ... Image plane
IF ... Infrared cut absorption filter
LF: Optical low-pass filter
E ... Observer eyeball
40 ... Digital camera
41. Photography optical system
42. Optical path for photographing
43. Viewfinder optical system
44. Optical path for viewfinder
45 ... Shutter
46 ... Flash
47 ... LCD monitor
49 ... CCD
50. Cover member
51. Processing means
52. Recording means
53. Objective optical system for viewfinder
55 ... Porro prism
57 ... View frame
59 ... Eyepiece optical system

Claims (10)

In an electronic imaging device having a zoom lens and an electronic imaging device arranged on the image side thereof,
The zoom lens includes, in order from the object side, a first lens group having a negative refractive power as a whole, a second lens group having a positive refractive power as a whole, and a third lens group having a positive refractive power as a whole. And consist of
The second lens group includes two lens components, and the lens component on the middle image side has a meniscus shape with a concave surface facing the image surface side,
The third lens group consists of one positive lens component,
At least the second lens unit moves only to the object side upon zooming from the wide-angle end to the telephoto end when focusing on an object point at infinity, and the third lens unit is different from the second lens unit in zooming. The third lens group moves during focusing operation,
All refractive surfaces of the third lens group satisfy the following conditions:
(1) 0 ≦ | Asp3 | <3.0 × 10 ^-3 · L
The lens component on the image side of the second lens group includes a cemented lens component that is cemented in the order of a positive lens and a negative lens from the object side, and satisfies the following conditions.
(3) 0.45 <R _22R / R _22F <0.9
(4) 0 <L / R _22C <1.0
(5) 0 <n _22R −n _22F <0.3
(2) −1.0 <(R _3F + R _3R ) / (R _3F −R _3R ) <0.3
Here, L is the diagonal length of the effective imaging area in the electronic imaging device, Asp3 is the aspherical deviation amount of each refractive surface of the third lens group, and the optical axis relative to the reference spherical surface having the radius of curvature on the optical axis And the aspherical deviation amount Asp3 is set to 0 when the refractive surface is a spherical surface. Also, R _22F, R _22R, the most object-side surface of the R _22C are second lens unit image-side lens component respectively, a surface on the most image side, the curvature radius on the optical axis of the joint surface, n _22F, n _22R and the second The refractive index of the d-line of the object side lens and the image side lens medium of the lens group image side lens component, R _3F and R _3R are on the optical axis of the most object side surface and the most image side surface of the third lens group Is the radius of curvature. The lens component of the object side of the second lens group is constituted by one single lens, the electronic imaging device according to claim 1, characterized by satisfying the following condition.
(6) 0.1 <(R _21F + R _21R ) / (R _21F −R _21R ) <5
Here, R _21F and R _21R are radii of curvature on the optical axis of the object side surface and the image side surface of the object side lens component of the second lens group, respectively. In an electronic imaging device having a zoom lens and an electronic imaging device arranged on the image side thereof,
The zoom lens includes, in order from the object side, a first lens group having a negative refractive power as a whole, a second lens group having a positive refractive power as a whole, and a third lens group having a positive refractive power as a whole. And consist of
The second lens group includes two lens components, and the lens component on the middle image side has a meniscus shape with a concave surface facing the image surface side,
The third lens group consists of one positive lens component,
At least the second lens unit moves only to the object side upon zooming from the wide-angle end to the telephoto end when focusing on an object point at infinity, and the third lens unit is different from the second lens unit in zooming. The third lens group moves during focusing operation,
All refractive surfaces of the third lens group satisfy the following conditions:
(1) 0 ≦ | Asp3 | <3.0 × 10 ^-3 · L
The lens component on the image side of the second lens group is constituted by a cemented lens component that is cemented in order of a positive lens and a negative lens from the object side.
The lens component on the object side of the second lens group is such that both the air contact surface on the object side and the air contact surface on the image side are aspheric surfaces, and both air contacts with a reference spherical surface having a radius of curvature on the optical axis. An electronic imaging apparatus characterized in that each of the surfaces is an aspherical surface deviated toward the object side and satisfies the following conditions.
(3) 0.45 <R _22R / R _22F <0.9
(4) 0 <L / R _22C <1.0
(5) 0 <n _22R −n _22F <0.3
(7) 8.0 × 10 ⁻⁴ · L <| Asp21R | <| Asp21F |
<3.0 × 10 ^-2 · L
Here, L is the diagonal length of the effective imaging area in the electronic imaging device, Asp3 is the aspherical deviation amount of each refractive surface of the third lens group, and the optical axis relative to the reference spherical surface having the radius of curvature on the optical axis And the aspherical deviation amount Asp3 is set to 0 when the refractive surface is a spherical surface. Also, R _22F, R _22R, the most object-side surface of the R _22C are second lens unit image-side lens component respectively, a surface on the most image side, the curvature radius on the optical axis of the joint surface, n _22F, n _22R and the second The refractive index of the d-line of the object side lens of the lens group image side lens component and the medium of the image side lens, Asp21F and Asp21R are the air contact surface on the object side and the image side air of the lens component on the object side of the second lens group, respectively. The aspherical deviation amount on the contact surface is the aspherical deviation amount when the height from the optical axis with respect to the reference spherical surface having the radius of curvature on the optical axis is 0.3L. Electronic imaging device according to any one of claims 1 to 3, characterized by satisfying the following condition.
(8) 1.45 <−β _2T <2.1
Here, β _2T is the magnification of the entire second lens group at the telephoto end when focusing on an object point at infinity. The two lens component in the second lens group comprises, in order from the object side, a positive lens component, the electronic imaging device of any one of claims 1, wherein 4 to be a negative lens component. The said 1st lens group is comprised with two lenses, the negative lens containing an aspherical surface, and a positive lens, The following conditions are satisfied, The any one of Claim 1 to 5 characterized by the above-mentioned. Electronic imaging device.
(9) 10 <ν ₁₁ −ν ₁₂ <24
(10) -4 <(R ₁₃ + R ₁₄ ) / (R ₁₃ -R ₁₄ ) <-1.1
Where ν ₁₁ is the Abbe number of the medium on the d-line basis of the negative lens in the first lens group, ν ₁₂ is the Abbe number of the medium on the d-line basis of the positive lens in the first lens group, and R ₁₃ is the first lens. The radius of curvature on the optical axis of the object side surface of the positive lens in the group, and R ₁₄ is the radius of curvature on the optical axis of the image side surface of the positive lens in the first lens group. The electronic imaging apparatus according to claim 6, wherein the following condition is satisfied.
(11) 0.2 <d ₁₁ /L<0.65
Here, d ₁₁ is an air space on the optical axis of the negative lens and the positive lens of the first lens group. The third lens group is electronic imaging apparatus according to any one of claims 1, wherein 7 to be composed of one positive lens. Electronic imaging device according to any one of claims 1 to 8, characterized in that the diagonal length L of the effective image pickup area satisfies the following conditions of the electronic image pickup device.
3.0mm <L <12.0mm Electronic imaging device according to any one of claims 1 to 9, half angle ωW diagonal at the wide angle end and satisfies the following condition.
27.5 ° <ω _W

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