JP3674975B2

JP3674975B2 - Focus detection device

Info

Publication number: JP3674975B2
Application number: JP2716195A
Authority: JP
Inventors: 宏一小林
Original assignee: Nikon Corp
Current assignee: Nikon Corp
Priority date: 1995-02-15
Filing date: 1995-02-15
Publication date: 2005-07-27
Anticipated expiration: 2020-07-27
Also published as: JPH08220422A

Description

【０００１】
【産業上の利用分野】
本発明は、投射光学系により被写体に投射して焦点検出を行なうアクティブ型の焦点検出装置に関する。
【０００２】
【従来の技術】
一般にレンズ交換式のカメラでは、多種類の交換レンズに対応するため撮影レンズを通過した外界からの光を利用して焦点検出を行う、いわゆるパッシブ型の焦点検出装置が主流となっている。
しかし、このようなパッシブ型の焦点検出装置では、外界が暗い時や被写体のコントラストが低い時には焦点検出が困難あるいは不能になる。このようなパッシブ型の欠点を解決するため、所定の照明装置から補助光を投射して焦点検出を行うアクティブ型の焦点検出装置が知られている（例えば、特開昭６１−１３８２２２号公報参照）。
【０００３】
図５はアクティブ型の焦点検出装置を備えたカメラの横断面図である。このカメラでは、撮影レンズ７０１を通過した被写体からの光束は、メインミラー７０２の透光部を通過してサブミラー７０３で下方に反射され、焦点検出ユニット７０４へ入射する。一方、カメラ７０５の上面に設けられたアクセサリーシュー７０６には閃光装置７０７が装着され、この閃光装置７０７内には投影光源７０８、投影パターンフィルム７０９、投射レンズ７１０を有する投射光学系７１１が設置されている。
外界が暗い時や被写体のコントラストが低い時には、投影光源７０８から例えば赤外光が発光され、投影パターンフィルム７０９と投射レンズ７１０を通り、被写体に投影パターンフィルム７０９の投影パターン像が投射される。その反射光は撮影レンズ７０１とミラー７０２，７０３を介して例えば公知の位相差方式の焦点検出部７０４へ入射し、撮影レンズ７０１の焦点調節状態が検出される。
【０００４】
図６は位相差方式による焦点検出の原理を示す。図において、８０１はフィルム面と等価な撮影レンズ７０１の予定結像面であり、８０２はコンデンサーレンズ８０３と一対の再結像レンズ８０４，８０５を有する焦点検出光学系に対して予定結像面８０１と共役な面である。
撮影レンズ７０１により予定結像面８０１上に形成された前ピン像Ａ、合焦像Ｂおよび後ピン像Ｃは、コンデンサーレンズ８０３と一対の再結像レンズ８０４，８０５によって予定結像面８０２上にそれぞれ第１の像Ａ１，Ｂ１，Ｃ１および第２の像Ａ２，Ｂ２，Ｃ２として再結像される。ここで、第１と第２の像の間隔は撮影レンズ７０１の焦点調節状態によって変化する。
したがって、予定結像面８０２あるいはその近傍にＣＣＤなどの光電変換器８０６を配置し、その出力に基づいて第１と第２の像が最もよく一致するときの２像の間隔を求め、その像間隔に基づいて撮影レンズ７０１の焦点調節状態を検出することができる。
なお、図６において、８０７は撮影レンズの光軸、８０８は一対の絞り開口を再結像レンズ８０４，８０５の直前に形成するための絞りマスクである。
【０００５】
図７は、従来の焦点検出装置の投影パターンフィルム７０９のパターンの一例を示す。従来の投影パターンでは、不透明部６０１の幅ｐ、透明部６０２の幅ｑおよびそれらの繰り返し周期（ｐ＋ｑ）が全く不規則に形成されている。
これは、位相差方式の焦点検出装置に同一幅の不透明部６０１を複数個設けると、再結像レンズ８０４，８０５により形成される２つの投影パターン像の一致する組が複数組検出されることになり、焦点検出を誤ることになるからである。
【０００６】
【発明が解決しようとする課題】
しかしながら、従来の焦点検出装置では、投影パターンフィルムの不透明部の幅と透明部の幅がそれぞれの部分で異なり、その繰り返し周期も全く不規則に形成されているので、次のような問題がある。
例えばＣＣＤなどの光電変換器上に、不規則で単数または複数の不透明部と透明部の投影パターン像が形成されている場合、不透明部が大きかったり小さかったりするので、ＣＣＤ内に照明される部分が大きい場合と小さい場合が発生し、複数の焦点検出領域のＣＣＤの出力が異なり、焦点検出に誤りが生じる可能性がある。
また、不透明部の幅と透明部の幅を不規則に配列すると投影パターンフィルムの製造が困難になるという問題がある。
【０００７】
本発明の目的は、焦点検出の誤りが発生しないパターンの投影パターンフィルムを有する焦点検出装置を提供することにある。
【０００８】
【課題を解決するための手段】
上記目的を達成するために、本発明は、投影光源と投影パターンフィルムと投射レンズとを有する投射光学系により被写体に補助光を投射し、焦点検出光学系により撮影レンズを通過した被写体からの複数対の光束を光電変換器上に導いて複数対の被写体像を結像し、複数対の被写体像の像ずれ量に基づいて複数の焦点検出領域における撮影レンズの焦点調節状態を検出する焦点検出装置に適用され、投影パターンフィルムのパターンを以下のように定めたものである。
（１）請求項１による焦点検出装置における投影パターンフィルムのパターンは、複数の格子状の不透明部と透明部を交互に並べて一つのグループを形成するとともに、グループ内の不透明部の幅と透明部の幅を所定の規則にしたがって設定して小パターンを形成し、グループを複数並べて小パターンが周期的に現れるように配列したものであって、グループは不透明部と透明部の組を複数組有し、各組の不透明部の幅と透明部の幅の比率を各組間で異ならせて小パターンを形成することを特徴とする。
【０００９】
（２）請求項２による焦点検出装置における投影パターンフィルムのパターンは、複数の格子状の不透明部と透明部を交互に並べて一つのグループを形成するとともに、グループ内の不透明部の幅と透明部の幅を所定の規則にしたがって設定して小パターンを形成し、グループを複数並べて小パターンが周期的に現れるように配列したものであって、グループは不透明部と透明部の組を複数組有し、各組の不透明部の幅と透明部の幅の和を各組間で等しくするとともに、各組の不透明部の幅と透明部の幅の比率を各組間で異ならせて小パターンを形成することを特徴とする。
【００１０】
（３）請求項３による焦点検出装置における投影パターンフィルムのパターンは、複数の格子状の不透明部と透明部を交互に並べて一つのグループを形成するとともに、グループ内の不透明部の幅と透明部の幅を所定の規則にしたがって設定して小パターンを形成し、グループを複数並べて小パターンが周期的に現れるように配列したものであって、グループは不透明部と透明部の組を複数組有し、各組の不透明部の幅と透明部の幅の和を各組間で異ならせるとともに、各組の不透明部の幅と透明部の幅を等しくして小パターンを形成することを特徴とする。
【００１１】
（４）請求項４の発明は、請求項１〜３のいずれかの項に記載の焦点検出装置において、撮影レンズは短焦点レンズであり、各焦点検出領域においては、光電変換器上に結像されるパターンの像の周期が一対の被写体像の像ずれ量を検出する際の最大像ずらし量よりも大きくなるようにパターンの周期を設定することを特徴とする。
（５）請求項５の発明は、請求項１〜３のいずれかの項に記載の焦点検出装置において、撮影レンズは長焦点レンズであり、各焦点検出領域においては、パターンの周期を光電変換器上に結像されたパターンの像の範囲よりも大きくすることを特徴とする。
（６）請求項６の発明は、請求項１〜５のいずれかの項に記載の焦点検出装置において、投射光学系をカメラの外部に取り付けることを特徴とする。
（７）請求項７の発明は、請求項１〜５のいずれかの項に記載の焦点検出装置において、投射光学系をカメラに内蔵することを特徴とする。
【００１２】
【作用】
（１）請求項１の焦点検出装置では、投影パターンフィルムのパターンを次のように定めた。複数の格子状の不透明部と透明部を交互に並べて一つのグループを形成するとともに、グループ内の不透明部の幅と透明部の幅を所定の規則にしたがって設定して小パターンを形成し、グループを複数並べて小パターンが周期的に現れるように配列する。そして、グループは不透明部と透明部の組を複数組有し、各組の不透明部の幅と透明部の幅の比率を各組間で異ならせて小パターンを形成する複数の不透明部と透明部を周期的に配列する。このような投影パターンフィルムを用いた投射光学系により被写体に補助光を投射し、焦点検出光学系により撮影レンズを通過した被写体からの一対の光束を光電変換器上に導いて一対の被写体像を結像し、一対の被写体像の像ずれ量に基づいて撮影レンズの焦点調節状態を検出する。
（２）請求項２の焦点検出装置では、投影パターンフィルムのパターンを次のように定めた。グループは不透明部と透明部の組を複数組有し、各組の不透明部の幅と透明部の幅の和を各組間で等しくするとともに、各組の不透明部の幅と透明部の幅の比率を各組間で異ならせて小パターンを形成する。そして、このような投影パターンフィルムを用いた投射光学系により被写体に補助光を投射し請求項１の手順と同様に撮影レンズの焦点調節状態を検出する。
（３）請求項３の焦点検出装置では、投影パターンフィルムのパターンを次のように定めた。グループは不透明部と透明部の組を複数組有し、各組の不透明部の幅と透明部の幅の和を各組間で異ならせるとともに、各組の不透明部の幅と透明部の幅を等しくして小パターンを形成する。そして、このような投影パターンフィルムを用いた投射光学系により被写体に補助光を投射し、請求項１の手順と同様に撮影レンズの焦点調節状態を検出する。
【００１３】
【実施例】
図１〜図４により本発明の焦点検出装置の実施例を説明する。なお、実施例の焦点検出装置とその焦点検出装置を備えたカメラの構成は図５および図６に示すものと同様であり、それらの図を参照しながら本発明の実施例を説明する。
【００１４】
図１は一実施例の投影パターンフィルム７０９Ａを示す。
このフィルム７０９Ａのパターンは、複数の不透明部と透明部を一定の規則にしたがって周期的に配列したものである。つまり、不透明部１０１、透明部１０２、不透明部１０３、透明部１０４、不透明部１０５、透明部１０６をそれぞれ幅１：２：３：１：２：３の比率で形成し、周期Ｌ１で周期的に配列する。
なお、図１では１周期分の配列パターンの不透明部と透明部に対してそれぞれ符号を付して説明したが、他の組の配列パターンも同様であり、符号とその説明を省略する。
【００１５】
図２は一実施例の投影パターンフィルム７０９Ｂを示す。
このフィルム７０９Ｂのパターンは、不透明部の幅ｐと透明部の幅ｑを一定の規則にしたがって設定するとともに、複数の不透明部と透明部を周期的に配列したものである。つまり、各不透明部とそれらの不透明部の配列方向の特定側（図では右側）に隣接する透明部とを１組とし、各組の不透明部の幅ｐと透明部の幅ｑとの和（ｐ＋ｑ）がすべて等しくなるように設定するとともに、不透明部２０１、透明部２０２、不透明部２０３、透明部２０４、不透明部２０５、透明部２０６、不透明部２０７、透明部２０８をそれぞれ幅２：３：１：４：３：２：４：１の比率で形成し、周期Ｌ２で周期的に配列する。
なお、図２では１周期分の配列パターンの不透明部と透明部に対してそれぞれ符号を付して説明したが、他の組の配列パターンも同様であり、符号と説明を省略する。
【００１６】
図３は一実施例の投影パターンフィルム７０９Ｃを示す。
このフィルム７０９Ｃのパターンは、不透明部の幅ｐと透明部の幅ｑを一定の規則にしたがって設定するとともに、複数の不透明部と透明部を周期的に配列したものである。つまり、各不透明部とそれらの不透明部の配列方向の特定側（図では右側）に隣接する透明部とを１組とし、各組の不透明部の幅ｐと透明部の幅ｑとが等しくなるように設定するとともに、不透明部３０１、透明部３０２、不透明部３０３、透明部３０４、不透明部３０５、透明部３０６をそれぞれ３：３：２：２：１：１の比率で形成し、周期Ｌ３で周期的に配列する。
なお、図３では１周期分の配列パターンの不透明部と透明部に対してそれぞれ符号を付して説明したが、他の組の配列パターンも同様であり、符号と説明を省略する。
【００１７】
上述した図１〜図３に示すフィルム７０９Ａ〜７０９Ｃのパターンはそれぞれ周期Ｌ１，Ｌ２，Ｌ３で周期的に配列されているので、これら周期性のパターンを有する投影パターンフィルムを用いれば焦点検出用の光電変換器の出力が安定し、焦点検出の誤りがなくなるとともに、容易に投影パターンフィルムの製造が可能となる。
これらの投影パターンフィルムは、例えば図５に示すように、投射光学系７１１の投射レンズ７１０の一方の焦点位置近くに配置され、投射レンズ７１０はそれらの投影パターン像を被写体上に投射し、投影光源７０８、例えば発光ダイオードからの光での照明により被写体上のコントラストが小さくなっても、その被写体上に投影パターン像によるコントラストを作り出す。これにより、焦点検出が困難または不能となる問題が解決され、焦点検出が可能となる。
【００１８】
投影パターンフィルムのパターン１周期の幅は、次のようにして決定する。
図４は、無地の被写体に投影された１周期の投影パターン像を焦点検出面から見た図である。
図において、ｘは一次像面上の焦点検出用の光電変換器８０６の一画素分の幅であり、ｈは投影パターンの１周期Ｌ０の中の不特定のパターンの幅である。画素幅ｘが最大のパターン幅ｈよりも大きい場合は、投影パターン像が一画素内で移動しても光電変換器８０６全体としては出力レベルが変化せず、したがって、投影パターン像の光電変換器８０６上での位置を正しく検出できない。
一方、画素幅ｘが最大のパターン幅ｈ以下の場合はこのような問題は発生しないが、パターン幅ｈが画素幅ｘに対してかなり大きくなると、パターンの１周期が大きくなり、投影パターン像の内の焦点検出に用いられる部分は一部分であるからその焦点検出部分の周期性がなくなる上に、コントラストが低下する。
【００１９】
また、パターンの１周期の幅は周期性による焦点検出の誤りを防ぐことを考慮しなければならず、交換可能な撮影レンズ７０１の種類により焦点検出の誤りを起こさない方法が異なる。すなわち、被写体に投射された投影パターン像全体の内、焦点検出に用いられる部分（ＣＣＤに入力される部分）は投影パターン像の一部分のみであり、また、被写体が一定の距離にある場合、撮影レンズの焦点検出距離により焦点検出に用いられる部分は大きく異なる。
撮影レンズが短焦点である場合は、至近から無限までのピントズレ量、いわゆる最大デフォーカス量が小さいため、図６に示す位相差方式による焦点検出装置の一対の再結像レンズ８０４，８０５により形成される一対の投影パターン像のずれ量を検出する際の最大像ずらし量も小さく、この最大像ずらし量が光電変換器８０６上の投影パターン像の周期よりも十分に小さければ焦点検出の誤りは起こらない。すなわち換言すると、光電変換器８０６上に結像される投影パターン像の周期が一対の投影パターン像の像ずれ量を検出する際の最大像ずらし量よりも大きくなるようにパターンの周期を設定すればよい。
また、長焦点レンズの場合は、光電変換器８０６上の投影パターン像が大きくなり、この光電変換器８０６上に結像する投影パターン像の範囲が、投影パターンフィルム７０９のパターンの１周期よりも小さければ焦点検出の誤りは起こらない。すなわち換言すると、パターンの周期を光電変換器８０６上に結像された投影パターン像の範囲よりも大きくすればよい。
このように、投影パターンフィルム７０９のパターンの１周期の幅は、コントラスト低下を抑制することも考慮して焦点検出の誤りが起こらない最小値にするのが好ましい。
【００２０】
なお、上述した実施例では投射光学系７１１を閃光装置７０７内に設けた例を示したが、投射光学系７１１を閃光装置７０７外に単独で設けてもよいし、カメラ７０５に適当な取り付け部を設けてそこに取り付けるようにしてもよい。さらに、カメラ７０５に内蔵してもよい。
また、投影パターンフィルムのパターンは上述した実施例に限定されない。
【００２１】
【発明の効果】
以上説明したように本発明による投影パターンでは、複数の格子状の不透明部と透明部を交互に並べて一つのグループを形成するとともに、グループ内の不透明部の幅と透明部の幅を所定の規則にしたがって設定して小パターンを形成し、グループを複数並べて小パターンが周期的に現れるように配列する。したがって、複数の焦点検出領域を有する場合でも、周期性のあるパターンの投影パターンフィルムを用いると、複数の焦点検出領域のそれぞれに対応する複数のＣＣＤには同じような投影パターン像が入力され、複数のＣＣＤの出力も同じようなものになり、焦点検出の誤りをなくすことができる。
撮影レンズが短焦点の場合には、光電変換器上に結像されるパターンの像の周期が一対の被写体像の像ずれ量を検出する際の最大像ずらし量よりも大きくなるようにパターンの周期を設定し、撮影レンズが長焦点の場合には、パターンの周期を光電変換器上に結像されたパターンの像の範囲よりも大きくするようにしたので、どのような撮影レンズに対しても焦点検出の誤りをなくすことができる。
【図面の簡単な説明】
【図１】一実施例の投影パターンフィルムのパターンを示す図。
【図２】投影パターンフィルムの他のパターンを示す図。
【図３】投影パターンフィルムの他のパターンを示す図。
【図４】投影パターンフィルムのパターンの１周期の幅の決定方法を説明する図。
【図５】焦点検出装置を搭載したカメラの横断面図。
【図６】位相差方式による焦点検出の原理を示す図。
【図７】投影パターンフィルムの従来のパターンを示す図。
【符号の説明】
１０１，１０３，１０５、２０１，２０３，２０５，２０７、３０１，３０３，３０５不透明部
１０２，１０４，１０６，２０２，２０４，２０６，２０８，３０２，３０４，３０６透明部
７０９Ａ，７０９Ｂ，７０９Ｃ投影パターンフィルム[0001]
[Industrial application fields]
The present invention relates to an active focus detection apparatus that performs focus detection by projecting onto a subject using a projection optical system.
[0002]
[Prior art]
In general, in a lens interchangeable camera, a so-called passive focus detection apparatus that performs focus detection using light from the external environment that has passed through a photographing lens has become the mainstream in order to support various types of interchangeable lenses.
However, with such a passive focus detection device, focus detection is difficult or impossible when the outside is dark or when the contrast of the subject is low. In order to solve such a disadvantage of the passive type, an active type focus detection device that performs focus detection by projecting auxiliary light from a predetermined illumination device is known (see, for example, JP-A-61-138222). ).
[0003]
FIG. 5 is a cross-sectional view of a camera equipped with an active focus detection device. In this camera, the light beam from the subject that has passed through the photographing lens 701 passes through the light transmitting portion of the main mirror 702, is reflected downward by the sub mirror 703, and enters the focus detection unit 704. On the other hand, a flash device 707 is attached to an accessory shoe 706 provided on the upper surface of the camera 705, and a projection optical system 711 having a projection light source 708, a projection pattern film 709, and a projection lens 710 is installed in the flash device 707. ing.
When the outside world is dark or the contrast of the subject is low, for example, infrared light is emitted from the projection light source 708, passes through the projection pattern film 709 and the projection lens 710, and the projection pattern image of the projection pattern film 709 is projected onto the subject. The reflected light is incident on, for example, a known phase difference type focus detection unit 704 via the photographing lens 701 and mirrors 702 and 703, and the focus adjustment state of the photographing lens 701 is detected.
[0004]
FIG. 6 shows the principle of focus detection by the phase difference method. In the figure, reference numeral 801 denotes a planned imaging plane of the photographing lens 701 equivalent to a film plane, and reference numeral 802 denotes a planned imaging plane 801 for a focus detection optical system having a condenser lens 803 and a pair of re-imaging lenses 804 and 805. This is a conjugate surface.
The front pin image A, the focused image B, and the rear pin image C formed on the planned imaging plane 801 by the photographing lens 701 are placed on the planned imaging plane 802 by the condenser lens 803 and the pair of re-imaging lenses 804 and 805. Are re-imaged as first images A1, B1, C1 and second images A2, B2, C2, respectively. Here, the interval between the first and second images varies depending on the focus adjustment state of the photographing lens 701.
Accordingly, a photoelectric converter 806 such as a CCD is disposed at or near the planned imaging plane 802, and based on the output, the interval between the two images when the first and second images best match each other is obtained. Based on the interval, the focus adjustment state of the photographing lens 701 can be detected.
In FIG. 6, reference numeral 807 denotes an optical axis of the photographing lens, and reference numeral 808 denotes an aperture mask for forming a pair of aperture openings just before the re-imaging lenses 804 and 805.
[0005]
FIG. 7 shows an example of the pattern of the projection pattern film 709 of the conventional focus detection apparatus. In the conventional projection pattern, the width p of the opaque portion 601, the width q of the transparent portion 602, and the repetition period (p + q) thereof are completely irregular.
This is because, when a plurality of opaque portions 601 having the same width are provided in the phase difference type focus detection device, a plurality of matching sets of two projection pattern images formed by the re-imaging lenses 804 and 805 are detected. This is because the focus detection is wrong.
[0006]
[Problems to be solved by the invention]
However, in the conventional focus detection device, the width of the opaque portion and the width of the transparent portion of the projection pattern film are different in each portion, and the repetition period thereof is completely irregular. Therefore, there are the following problems. .
For example, when a projection pattern image of one or a plurality of opaque portions and transparent portions is irregularly formed on a photoelectric converter such as a CCD, the opaque portion is large or small. May be large and small , CCD outputs in a plurality of focus detection areas are different, and errors may occur in focus detection.
Further, when the width of the opaque part and the width of the transparent part are irregularly arranged, there is a problem that it becomes difficult to manufacture the projection pattern film.
[0007]
An object of the present invention is to provide a focus detection apparatus having a projection pattern film having a pattern that does not cause an error in focus detection.
[0008]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention projects auxiliary light onto a subject by a projection optical system having a projection light source, a projection pattern film, and a projection lens, and a plurality of subjects from the subject that have passed through the photographing lens by a focus detection optical system. Focus detection that directs pairs of light beams onto a photoelectric converter to form multiple pairs of subject images and detects the focus adjustment state of the photographic lens in multiple focus detection areas based on the amount of image shift between the multiple pairs of subject images It is applied to the apparatus, and the pattern of the projection pattern film is defined as follows.
(1) The pattern of the projection pattern film in the focus detection apparatus according to claim 1 forms a group by alternately arranging a plurality of lattice-like opaque portions and transparent portions, and the width of the opaque portions and the transparent portions in the group. A small pattern is formed by setting the width of the pattern according to a predetermined rule, and a plurality of groups are arranged so that the small patterns appear periodically. The group has a plurality of sets of opaque portions and transparent portions. In addition, a small pattern is formed by changing the ratio of the width of the opaque portion and the width of the transparent portion in each set.
[0009]
(2) The pattern of the projection pattern film in the focus detection apparatus according to claim 2 forms a group by alternately arranging a plurality of lattice-like opaque portions and transparent portions, and the width and transparent portion of the opaque portions in the group. A small pattern is formed by setting the width of the pattern according to a predetermined rule, and a plurality of groups are arranged so that the small patterns appear periodically. The group has a plurality of sets of opaque portions and transparent portions. In addition, the sum of the width of the opaque portion and the transparent portion of each set is made equal between the sets, and the ratio of the width of the opaque portion and the transparent portion of each set is made different between each set to form a small pattern. It is characterized by forming.
[0010]
(3) The pattern of the projection pattern film in the focus detection apparatus according to claim 3 is formed by alternately arranging a plurality of lattice-like opaque portions and transparent portions to form one group, and the width of the opaque portions and the transparent portions in the group. A small pattern is formed by setting the width of the pattern according to a predetermined rule, and a plurality of groups are arranged so that the small patterns appear periodically. The group has a plurality of sets of opaque portions and transparent portions. In addition, the sum of the width of the opaque portion and the transparent portion of each set is different between the sets, and the width of the opaque portion and the transparent portion of each set is made equal to form a small pattern. To do.
[0011]
(4) According to a fourth aspect of the present invention, in the focus detection device according to any one of the first to third aspects, the photographing lens is a short focus lens, and each focus detection region is connected to a photoelectric converter. The pattern period is set so that the image period of the pattern to be imaged is larger than the maximum image shift amount when detecting the image shift amount of the pair of subject images.
(5) The invention according to claim 5 is the focus detection device according to any one of claims 1 to 3, wherein the photographing lens is a long focus lens, and in each focus detection region, a pattern period is photoelectrically converted. It is characterized by being larger than the range of the image of the pattern formed on the vessel.
(6) The invention according to claim 6 is the focus detection apparatus according to any one of claims 1 to 5, wherein the projection optical system is attached to the outside of the camera.
(7) According to a seventh aspect of the present invention, in the focus detection apparatus according to any one of the first to fifth aspects, the projection optical system is built in the camera.
[0012]
[Action]
(1) In the focus detection apparatus of the first aspect, the pattern of the projection pattern film is defined as follows. A plurality of grid-like opaque portions and transparent portions are alternately arranged to form one group, and the width of the opaque portion and the transparent portion in the group are set according to a predetermined rule to form a small pattern. Are arranged so that small patterns appear periodically. The group has a plurality of sets of opaque portions and transparent portions, and a plurality of opaque portions and transparent portions that form small patterns by changing the ratio of the width of the opaque portions and the width of the transparent portions in each set. The parts are arranged periodically. A projection optical system using such a projection pattern film projects auxiliary light onto a subject, and a focus detection optical system guides a pair of luminous fluxes from the subject that have passed through the photographing lens onto a photoelectric converter to form a pair of subject images. An image is formed, and the focus adjustment state of the photographing lens is detected based on the image shift amount of the pair of subject images.
(2) In the focus detection apparatus of the second aspect, the pattern of the projection pattern film is determined as follows. The group has a plurality of pairs of opaque and transparent parts, and the sum of the width of the opaque part and the transparent part of each set is made equal between each pair, and the width of the opaque part and the transparent part of each set. A small pattern is formed by varying the ratio of each group. Then, auxiliary light is projected onto the subject by the projection optical system using such a projection pattern film, and the focus adjustment state of the photographing lens is detected in the same manner as in the procedure of claim 1.
(3) In the focus detection apparatus according to the third aspect, the pattern of the projection pattern film is determined as follows. The group has a plurality of pairs of opaque and transparent parts, and the sum of the width of the opaque part and the transparent part of each set varies between the groups, and the width of the opaque part and the transparent part of each set. Are made equal to form a small pattern. Then, auxiliary light is projected onto the subject by the projection optical system using such a projection pattern film, and the focus adjustment state of the photographing lens is detected in the same manner as in the procedure of claim 1.
[0013]
【Example】
An embodiment of the focus detection apparatus of the present invention will be described with reference to FIGS. The configuration of the focus detection apparatus of the embodiment and the camera including the focus detection apparatus are the same as those shown in FIGS. 5 and 6, and the embodiment of the present invention will be described with reference to these drawings.
[0014]
FIG. 1 shows a projection pattern film 709A of one embodiment.
The pattern of the film 709A is a pattern in which a plurality of opaque portions and transparent portions are periodically arranged according to a certain rule. That is, the opaque part 101, the transparent part 102, the opaque part 103, the transparent part 104, the opaque part 105, and the transparent part 106 are formed at a ratio of width 1: 2: 3: 1: 2: 3, respectively, and periodically with a period L1. Array.
In FIG. 1, the opaque portion and the transparent portion of the array pattern for one cycle are described with reference numerals, but the other sets of array patterns are the same, and the reference numerals and descriptions thereof are omitted.
[0015]
FIG. 2 shows a projection pattern film 709B of one embodiment.
In the pattern of the film 709B, the width p of the opaque portion and the width q of the transparent portion are set according to a certain rule, and a plurality of opaque portions and transparent portions are periodically arranged. That is, each opaque part and a transparent part adjacent to a specific side (right side in the figure) in the arrangement direction of these opaque parts are taken as one set, and the sum of the width p of the opaque part and the width q of the transparent part ( p + q) are set to be equal to each other, and the opaque part 201, the transparent part 202, the opaque part 203, the transparent part 204, the opaque part 205, the transparent part 206, the opaque part 207, and the transparent part 208 are respectively set to width 2: 3: They are formed at a ratio of 1: 4: 3: 2: 4: 1 and are arranged periodically with a period L2.
In FIG. 2, the opaque portions and the transparent portions of the array pattern for one cycle are described with reference numerals, but the other sets of array patterns are the same, and the reference numerals and descriptions are omitted.
[0016]
FIG. 3 shows a projection pattern film 709C of one embodiment.
In the pattern of the film 709C, the width p of the opaque portion and the width q of the transparent portion are set according to a certain rule, and a plurality of opaque portions and transparent portions are periodically arranged. That is, each opaque portion and a transparent portion adjacent to a specific side (right side in the figure) in the arrangement direction of the opaque portions are taken as one set, and the width p of the opaque portion and the width q of the transparent portion are equal. The opaque part 301, the transparent part 302, the opaque part 303, the transparent part 304, the opaque part 305, and the transparent part 306 are formed at a ratio of 3: 3: 2: 2: 1: 1, respectively, and the period L3 is set. Arrange periodically.
In FIG. 3, the opaque portions and the transparent portions of the array pattern for one cycle are described with reference numerals, but the other sets of array patterns are the same, and the reference numerals and descriptions are omitted.
[0017]
The patterns of the films 709A to 709C shown in FIGS. 1 to 3 described above are periodically arranged in the periods L1, L2, and L3. Therefore, if a projection pattern film having these periodic patterns is used, the pattern for focus detection is used. The output of the photoelectric converter is stabilized, the focus detection error is eliminated, and the projection pattern film can be easily manufactured.
These projection pattern films are arranged near one focal position of the projection lens 710 of the projection optical system 711 as shown in FIG. 5, for example, and the projection lens 710 projects those projection pattern images onto the subject and projects them. Even when the contrast on the subject is reduced by illumination with light from a light source 708, for example, a light emitting diode, a contrast based on the projection pattern image is created on the subject. Thereby, the problem that the focus detection becomes difficult or impossible is solved, and the focus detection becomes possible.
[0018]
The width of one period of the projection pattern film is determined as follows.
FIG. 4 is a view of a projection pattern image of one cycle projected onto a plain subject as seen from the focus detection surface.
In the figure, x is the width of one pixel for the focus detection photoelectric converter 806 on the primary image plane, and h is the width of an unspecified pattern in one cycle L0 of the projection pattern. When the pixel width x is larger than the maximum pattern width h, the output level of the photoelectric converter 806 as a whole does not change even if the projection pattern image moves within one pixel. Therefore, the photoelectric converter of the projection pattern image The position on 806 cannot be detected correctly.
On the other hand, such a problem does not occur when the pixel width x is equal to or smaller than the maximum pattern width h. However, when the pattern width h is considerably larger than the pixel width x, one cycle of the pattern becomes large, and the projection pattern image Since the portion used for focus detection is a portion, the periodicity of the focus detection portion is lost and the contrast is lowered.
[0019]
Further, the width of one period of the pattern must take into consideration prevention of focus detection errors due to periodicity, and the method of not causing focus detection errors depends on the type of interchangeable photographing lens 701. That is, in the entire projection pattern image projected on the subject, the portion used for focus detection (the portion input to the CCD) is only a part of the projection pattern image, and if the subject is at a certain distance, the image is taken. The portion used for focus detection varies greatly depending on the focus detection distance of the lens.
When the photographing lens has a short focal point, the amount of defocus from the closest to infinity, the so-called maximum defocus amount, is small, and therefore it is formed by the pair of re-imaging lenses 804 and 805 of the phase difference type focus detection device shown in FIG. If the maximum image shift amount when detecting the shift amount of the pair of projection pattern images to be detected is small, and this maximum image shift amount is sufficiently smaller than the cycle of the projection pattern image on the photoelectric converter 806, the focus detection error is Does not happen. In other words, the pattern cycle is set so that the cycle of the projection pattern image formed on the photoelectric converter 806 is larger than the maximum image shift amount when detecting the image shift amount of the pair of projection pattern images. That's fine.
In the case of a long focus lens, the projection pattern image on the photoelectric converter 806 is large, and the range of the projection pattern image formed on the photoelectric converter 806 is longer than one cycle of the pattern of the projection pattern film 709. If it is small, no focus detection error occurs. That is, in other words, the pattern period may be made larger than the range of the projected pattern image formed on the photoelectric converter 806.
As described above, it is preferable that the width of one cycle of the pattern of the projection pattern film 709 is set to a minimum value that does not cause a focus detection error in consideration of suppressing a decrease in contrast.
[0020]
In the above-described embodiment, the projection optical system 711 is provided in the flash device 707. However, the projection optical system 711 may be provided outside the flash device 707, or an appropriate attachment portion for the camera 705. May be provided and attached thereto. Further, it may be built in the camera 705.
Moreover, the pattern of a projection pattern film is not limited to the Example mentioned above.
[0021]
【The invention's effect】
As described above, in the projection pattern according to the present invention, a plurality of lattice-like opaque portions and transparent portions are alternately arranged to form one group, and the width of the opaque portion and the width of the transparent portion in the group are determined according to a predetermined rule. A small pattern is formed by setting according to the above, and a plurality of groups are arranged so that the small patterns appear periodically. Therefore, even when having a plurality of focus detection areas, if a projection pattern film having a periodic pattern is used, a similar projection pattern image is input to a plurality of CCDs corresponding to each of the plurality of focus detection areas, a plurality of CCD output is also the same kind of thing, Ru can be eliminated errors in focus detection.
When the taking lens has a short focus, the pattern image is formed so that the period of the pattern image formed on the photoelectric converter is larger than the maximum image shift amount when detecting the image shift amount of the pair of subject images. When the period is set and the photographic lens has a long focal length, the pattern period is made larger than the range of the pattern image formed on the photoelectric converter. Can also eliminate errors in focus detection.
[Brief description of the drawings]
FIG. 1 is a view showing a pattern of a projection pattern film of one embodiment.
FIG. 2 is a view showing another pattern of the projection pattern film.
FIG. 3 is a view showing another pattern of the projection pattern film.
FIG. 4 is a view for explaining a method for determining the width of one cycle of a pattern of a projection pattern film.
FIG. 5 is a cross-sectional view of a camera equipped with a focus detection device.
FIG. 6 is a diagram showing the principle of focus detection by a phase difference method.
FIG. 7 is a view showing a conventional pattern of a projection pattern film.
[Explanation of symbols]
101, 103, 105, 201, 203, 205, 207, 301, 303, 305 Opaque part 102, 104, 106, 202, 204, 206, 208, 302, 304, 306 Transparent part 709A, 709B, 709C Projection pattern film

Claims

Projecting auxiliary light to the subject by a projection optical system having a a projection light source projection pattern film and the projection lens, it guides the light beam pairs from the subject having passed through the photographic lens by the focus detecting optical system on the photoelectric converter plurality and forms an object image of the pair, in the focus detecting apparatus for detecting a focusing state of the photographing lens at a plurality of focus detection areas on the basis of the image shift amount of the object image before Symbol pairs,
The pattern of the projection pattern film is formed by alternately arranging a plurality of grid-like opaque portions and transparent portions to form one group, and setting the width of the opaque portion and the width of the transparent portion in the group according to a predetermined rule. to form a small pattern, der which the small pattern by arranging a plurality of the groups are arranged so as to appear cyclically,
The group has a plurality of sets of opaque portions and transparent portions, and the small pattern is formed by changing the ratio of the width of the opaque portions and the width of the transparent portions in each set. Detection device.

A projection optical system having a projection light source, a projection pattern film, and a projection lens projects auxiliary light onto the subject, and a plurality of pairs of light beams from the subject that have passed through the photographing lens are guided onto the photoelectric converter by the focus detection optical system. In a focus detection device that forms a pair of subject images and detects a focus adjustment state of the photographing lens in a plurality of focus detection regions set on a photographing screen based on an image shift amount of the plurality of pairs of subject images.
The pattern of the projection pattern film is formed by alternately arranging a plurality of grid-like opaque portions and transparent portions to form one group, and setting the width of the opaque portion and the width of the transparent portion in the group according to a predetermined rule. Then, a small pattern is formed, and a plurality of the groups are arranged so that the small patterns appear periodically,
The group has a plurality of sets of opaque portions and transparent portions, and the sum of the widths of the opaque portions and the transparent portions of each set is made equal between the sets. A focus detection apparatus, wherein the small pattern is formed by changing a ratio of widths between groups .

A projection optical system having a projection light source, a projection pattern film, and a projection lens projects auxiliary light onto the subject, and a plurality of pairs of light beams from the subject that have passed through the photographing lens are guided onto the photoelectric converter by the focus detection optical system. In a focus detection device that forms a pair of subject images and detects a focus adjustment state of the photographing lens in a plurality of focus detection regions set on a photographing screen based on an image shift amount of the plurality of pairs of subject images.
The pattern of the projection pattern film is formed by alternately arranging a plurality of grid-like opaque portions and transparent portions to form one group, and setting the width of the opaque portion and the width of the transparent portion in the group according to a predetermined rule. Then, a small pattern is formed, and a plurality of the groups are arranged so that the small patterns appear periodically,
The group has a plurality of sets of opaque portions and transparent portions, and the sum of the widths of the opaque portions and the transparent portions of each set is different between the sets, and the widths of the opaque portions and the transparent portions of each set are changed. A focus detection apparatus that forms the small pattern with equal width .

In the focus detection apparatus according to any one of claims 1 to 3,
The photographing lens is a short focus lens, and in each focus detection region, the period of the pattern image formed on the photoelectric converter is the maximum image shift when detecting the image shift amount of a pair of subject images. A focus detection apparatus, wherein a period of the pattern is set to be larger than an amount.

In the focus detection apparatus according to any one of claims 1 to 3,
The photographing lens is a long focus lens, and in each focus detection region, the period of the pattern is made larger than the range of the pattern image formed on the photoelectric converter. .

In the focus detection apparatus according to any one of claims 1 to 5,
A focus detection apparatus, wherein the projection optical system is attached outside a camera.

In the focus detection apparatus according to any one of claims 1 to 5,
A focus detection apparatus, wherein the projection optical system is built in a camera.