JP2006047814A - Focus detector, and camera system having the same - Google Patents
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Abstract
Description
本発明は焦点検出装置に関し、例えば、銀塩フィルムを使う一眼レフレックスカメラや、固体撮像素子を使うデジタル一眼レフレックスカメラなどの撮像装置に好適なものである。 The present invention relates to a focus detection apparatus, and is suitable for an imaging apparatus such as a single-lens reflex camera using a silver salt film or a digital single-lens reflex camera using a solid-state imaging device.
最近、多くの銀塩カメラあるいはデジタルカメラは、対物レンズ(撮影レンズ)の焦点を自動的に調節する自動焦点調節機能を内蔵している。 Recently, many silver halide cameras or digital cameras have built-in automatic focus adjustment functions that automatically adjust the focus of an objective lens (photographing lens).
特に、厳しいピント精度が要求される一眼レフカメラには、焦点検出装置として対物レンズによる結像光束を一対の明るさ絞りへ導き、これら明るさ絞りの近傍に配置された再結像レンズによって被写体像に関する一対の光量分布を光電変換素子(受光手段)の受光素子列(画素列、センサー)上に形成し、該光電変換素子で、一対の光量分布の相対的位置関係より対物レンズの焦点調節状態を検出する所謂、像ずれ方式と称される焦点検出装置が用いられている(特許文献1,2)。 In particular, in a single-lens reflex camera that requires strict focus accuracy, the imaging light flux from the objective lens is guided to a pair of aperture stops as a focus detection device, and the subject is formed by a re-imaging lens placed near these aperture stops. A pair of light quantity distributions relating to an image is formed on a light receiving element array (pixel array, sensor) of a photoelectric conversion element (light receiving means), and the focus of the objective lens is adjusted by the photoelectric conversion element based on the relative positional relationship between the pair of light quantity distributions. A so-called image shift method focus detection apparatus that detects a state is used (Patent Documents 1 and 2).
この方法において、焦点を検出するためには、原理的に光電変換素子の受光素子列方向にパターン(濃度パターン)を有する被写体の光量分布の検出が必要であり、被写体のパターンが受光素子列方向に光量分布が生じないときには、焦点検出が出来ないという欠点を有している。 In this method, in order to detect the focus, in principle, it is necessary to detect the light amount distribution of a subject having a pattern (density pattern) in the direction of the light receiving element array of the photoelectric conversion element. However, when there is no light quantity distribution, the focus detection cannot be performed.
これを解決するために、受光素子列を直交させた2対の受光素子列を用いて、被写体の光量分布の方向によらずに焦点検出を可能とする焦点検出装置が提案され、実用化されている。 In order to solve this problem, a focus detection apparatus has been proposed and put into practical use that enables focus detection regardless of the direction of the light amount distribution of a subject using two pairs of light receiving element arrays in which the light receiving element arrays are orthogonal. ing.
像ずれ方式の焦点検出装置では、一対の明るさ絞りの開口間隔によって焦点検出装置の検出性能が決定される。一般には、F値(Fナンバー)の大きい(暗い)対物レンズでも焦点検出を可能とするため、明るさ絞りの開口間隔が制限されている。このため、F値の小さい(明るい)対物レンズを装着したときには明るさ絞りの開口間隔を大きくできるにも関わらず、焦点検出の精度を高くすることができない。 In the image shift type focus detection device, the detection performance of the focus detection device is determined by the opening interval of the pair of aperture stops. In general, in order to enable focus detection even with a (dark) objective lens having a large F value (F number), the aperture distance between the aperture stops is limited. For this reason, when a small (bright) objective lens having a small F-number is attached, the focus detection accuracy cannot be increased despite the fact that the aperture distance between the aperture stops can be increased.
F値の小さい対物レンズの焦点検出精度を上げることができれば、例えF値の大きい対物レンズを装着したときの検出精度は低くとも、レンズ(カメラシステム)全体として見たときに焦点検出精度の上昇に繋がる。また、明るい対物レンズを頻繁に使用するであろうハイアマチュアの要求にも応えることができる。 If the focus detection accuracy of an objective lens with a small F value can be increased, the focus detection accuracy increases when viewed as a whole lens (camera system), even if the detection accuracy when an objective lens with a large F value is attached is low. It leads to. It can also meet the demands of high amateurs who often use bright objective lenses.
これを解決するために、撮影範囲中の略同一焦点検出領域に対して、F値の大きい対物レンズの焦点検出に用いられる明るさ絞りの開口間隔を狭くした焦点検出系と、F値の小さい対物レンズの焦点検出に用いられる明るさ絞りの開口間隔を広くした焦点検出系との2つを備えた焦点検出装置が提案、実用化されている。
焦点検出を被写体像の光量分布の方向に依らない多様な被写体に対して可能としたり、小さなF値を持つ明るい対物レンズを装着した場合であっても、焦点検出精度を向上させるには、焦点検出系を多数設置すれば良い。 In order to improve focus detection accuracy even when focus detection is possible for various subjects that do not depend on the direction of the light amount distribution of the subject image, or when a bright objective lens having a small F value is attached, A large number of detection systems may be installed.
しかしながら、この方法は焦点検出装置の増大を招く。特に光電変換素子列を形成するセンサーチップの面積の拡大は、製作が難しくコストの増大となる。 However, this method causes an increase in the focus detection device. In particular, the expansion of the area of the sensor chip forming the photoelectric conversion element array is difficult to manufacture and increases the cost.
また、焦点検出系を複数設置することは、センサーチップ上に被写体像を複数投影することであり、焦点検出に必要ではない光がセンサーの感度域に入射し、ゴーストが発生し、焦点検出精度が低下してくる。又感度域への入射を防ぐ手段を設けなければならず、装置が複雑になってくる。 In addition, installing multiple focus detection systems means projecting multiple subject images on the sensor chip. Light that is not necessary for focus detection is incident on the sensitivity range of the sensor, resulting in ghosting and focus detection accuracy. Will fall. Also, a means for preventing incidence on the sensitivity range must be provided, and the apparatus becomes complicated.
本発明は、多様な被写体の焦点検出を可能とし、明るい対物レンズの焦点検出の精度を上昇させつつも、受光手段の受光面積の増大を小さく、かつ、より配置効率のよい焦点検出装置の提供を目的とする。 The present invention provides a focus detection apparatus that can detect the focus of various subjects, increase the focus detection accuracy of a bright objective lens, and reduce the increase in the light receiving area of the light receiving means and improve the arrangement efficiency. With the goal.
本発明の焦点検出装置は、
◎対物レンズの瞳上で光軸からの高さが異なる2対の光束が通過する2対の開口を設けられた絞りと、該2対の開口に対応した2対の2次結像レンズを含む2次結像系と、該2対の2次結像レンズにより被写体像に対応する2対の光量分布が形成される2対の受光素子を含む受光手段とを有し、該受光手段からの信号を用いて該対物レンズの焦点位置を検出する焦点検出装置であって、該受光手段の2対の受光素子のうち、該対物レンズの瞳上で光軸からの高さが高いほうの1対の光束を受光する1対の受光素子の重心間隔をD1、該対物レンズの瞳上で光軸からの高さが低いほうの1対の光束を受光する1対の受光素子の重心間隔をD2とするとき、
2≦D1/D2
なる条件を満足することを特徴としている。
The focus detection apparatus of the present invention is
A diaphragm provided with two pairs of apertures through which two pairs of light beams with different heights from the optical axis pass on the pupil of the objective lens, and two pairs of secondary imaging lenses corresponding to the two pairs of apertures Including a secondary image forming system and a light receiving means including two pairs of light receiving elements in which two pairs of light quantity distributions corresponding to a subject image are formed by the two pairs of secondary image forming lenses. A focus detection device that detects the focal position of the objective lens using the signal of the two of the pair of light receiving elements of the light receiving means, the one whose height from the optical axis is higher on the pupil of the objective lens The center-of-gravity interval between a pair of light-receiving elements that receive a pair of light beams is D1, and the center-of-gravity distance between a pair of light-receiving elements that receive a pair of light beams having a lower height from the optical axis on the pupil of the objective lens. Is D2,
2 ≦ D1 / D2
It is characterized by satisfying the following conditions.
特に、
前記焦点検出装置は長方形視野内の所定の位置に対応する対物レンズの焦点位置を検出するものであり、前記2対の受光素子は前記長方形視野の長辺方向に並んで位置していることや、
前記絞りは前記長方形視野の短辺方向に並んだ1対の開口を更に有し、前記2次結像系は前記長方形視野の短辺方向に並んだ1対の開口に対応した1対の2次結像レンズを更に有し、前記受光手段は前記長方形視野の短辺方向に並んだ1対の開口に対応した1対の2次結像レンズにより被写体像に対応する1対の光量分布が形成される1対の受光素子を更に有すること等を特徴としている。
In particular,
The focus detection device detects a focus position of an objective lens corresponding to a predetermined position in a rectangular field, and the two pairs of light receiving elements are positioned side by side in the long side direction of the rectangular field. ,
The stop further includes a pair of apertures arranged in the short side direction of the rectangular field, and the secondary imaging system has a pair of two corresponding to the pair of apertures arranged in the short side direction of the rectangular field. The light-receiving means has a pair of secondary image-forming lenses corresponding to a pair of apertures arranged in the short side direction of the rectangular field of view and has a pair of light quantity distributions corresponding to the subject image. It further has a pair of light receiving elements to be formed.
本発明によれば、多様な被写体の焦点検出を可能とし、明るい対物レンズの焦点検出の精度を上昇させつつも、受光手段の受光面積の増大を小さく、かつ、より配置効率のよい焦点検出装置が得られる。 According to the present invention, it is possible to detect the focus of various subjects, and while increasing the focus detection accuracy of a bright objective lens, the focus detection device with a small increase in the light receiving area of the light receiving means and a better arrangement efficiency Is obtained.
図1は本発明の焦点検出装置を一眼レフレックスカメラに適用した実施例の構成図である。図1において紙面内が縦方向(垂直方向)、紙面と垂直方向が横方向(水平方向)である。 FIG. 1 is a configuration diagram of an embodiment in which the focus detection apparatus of the present invention is applied to a single-lens reflex camera. In FIG. 1, the inside of the paper is the vertical direction (vertical direction), and the direction perpendicular to the paper is the horizontal direction (horizontal direction).
図1において、21はカメラ本体CBに脱着可能または固定の対物レンズ(撮影レンズ)、8は対物レンズ21の瞳、1は対物レンズ21の光軸である。光軸1にそって入射する光束は半透過部を備えるクイックリターンミラー22に達し、反射光と透過光の二つの光束に分割される。 In FIG. 1, reference numeral 21 denotes an objective lens (photographing lens) that can be attached to and detached from the camera body CB, 8 denotes a pupil of the objective lens 21, and 1 denotes an optical axis of the objective lens 21. A light beam incident along the optical axis 1 reaches a quick return mirror 22 having a semi-transmissive portion, and is divided into two light beams of reflected light and transmitted light.
反射側には光軸1に沿ってフォーカシングスクリーン23、ペンタプリズム24、接眼レンズ25が配置され、これらの部材はフォーカシングスクリーン23上に形成されたファインダー像の視認のためファインダー系を構成する。 On the reflection side, a focusing screen 23, a pentaprism 24, and an eyepiece lens 25 are disposed along the optical axis 1, and these members constitute a finder system for visualizing a finder image formed on the focusing screen 23.
一方、クイックリターンミラー22の透過する側には、光軸1に沿って、可動のサブミラー26、ついで図中、2乃至7の各要素で示される位相差方式の焦点検出系(焦点検出装置)FDが配置される。自動焦点検出の際には、焦点検出系FDからの出力に基づき、図示されていない駆動機構によって対物レンズ21のフォーカス部が駆動され焦点状態が調節される。 On the other hand, on the transmission side of the quick return mirror 22, a movable sub-mirror 26 along the optical axis 1, and then a phase difference type focus detection system (focus detection device) indicated by elements 2 to 7 in the figure. FD is arranged. At the time of automatic focus detection, based on the output from the focus detection system FD, the focus section of the objective lens 21 is driven by a drive mechanism (not shown) to adjust the focus state.
焦点検出系FDの詳細について説明する。2は対物レンズ21の焦点面又はその近傍に置かれる視野マスクである。3はフィールドレンズ、4は反射ミラー、5は開口絞り(明るさ絞り)、6は被写体像に関する2次像を形成する為の再結像レンズ、7は被写体像に関する2次像の光量分布(像ずれ)を検出するための受光センサー(受光手段)である。受光センサー7は光電変換素子によって構成される。視野マスク2から再結像レンズ6に至る各要素で2次結像光学系を構成している。 Details of the focus detection system FD will be described. Reference numeral 2 denotes a field mask placed at or near the focal plane of the objective lens 21. 3 is a field lens, 4 is a reflecting mirror, 5 is an aperture stop (brightness stop), 6 is a re-imaging lens for forming a secondary image relating to the subject image, and 7 is a light quantity distribution of the secondary image relating to the subject image ( This is a light receiving sensor (light receiving means) for detecting (image shift). The light receiving sensor 7 is constituted by a photoelectric conversion element. Each element from the field mask 2 to the re-imaging lens 6 constitutes a secondary imaging optical system.
本実施例は、対物レンズ21の瞳8の異なる領域を通過した光束を用いて、被写体像に関して、水平方向に2対以上を含む複数対の分量分布を形成する2次光学系2〜6と、複数対の光量分布の相対的な位置関係を各々検出する複数対の受光素子列を含む受光手段7とを有し、受光手段7からの信号を用いて、対物レンズ21の焦点位置を検出している。 In this embodiment, secondary optical systems 2 to 6 that form a plurality of pairs of quantity distributions including two or more pairs in the horizontal direction with respect to a subject image using light beams that have passed through different regions of the pupil 8 of the objective lens 21; And a light receiving means 7 including a plurality of pairs of light receiving element arrays for detecting the relative positional relationship between the plurality of pairs of light quantity distributions, and the focal position of the objective lens 21 is detected using a signal from the light receiving means 7. is doing.
図2は、図1の焦点検出系FDの各要素2〜7のうち、反射ミラー4を省略して光路を展開した形で図示した説明図である。 FIG. 2 is an explanatory diagram illustrating the optical path expanded from the elements 2 to 7 of the focus detection system FD of FIG.
図3〜7は各々図2の一部分の説明図である。次に図1及至図7をつかって本発明の焦点検出装置の各部材の構成を説明する。 3 to 7 are explanatory views of a part of FIG. Next, the structure of each member of the focus detection apparatus of the present invention will be described with reference to FIGS.
図3は正面(光軸1方向)から視野マスク2を見たときの説明図である。十字状の開口2aを持ち、これは横方向(水平方向)に長い第一焦点検出領域に対応した開口2Hと、縦方向(垂直方向)に長い第2焦点検出領域に対応した開口2Vとで構成されている。 FIG. 3 is an explanatory diagram when the field mask 2 is viewed from the front (in the direction of the optical axis 1). It has a cross-shaped opening 2a, which has an opening 2H corresponding to the first focus detection area that is long in the horizontal direction (horizontal direction) and an opening 2V corresponding to the second focus detection area that is long in the vertical direction (vertical direction). It is configured.
図4は、2次結像系の開口絞り5を正面から見たときを示している。横に長い第1焦点検出領域に対応した横方向に配列された2対の開口部5a1,5a2と、縦に長い第2焦点検出領域に対応した縦方向に配列された1対の開口部5a3とを持つ。 FIG. 4 shows the aperture stop 5 of the secondary imaging system as viewed from the front. Two pairs of openings 5a1 and 5a2 arranged in the horizontal direction corresponding to the horizontally long first focus detection area, and one pair of openings 5a3 arranged in the vertical direction corresponding to the vertically long second focus detection area. And have.
横方向に配列された2対の開口部5a1,5a2において、開口の重心間隔の広い組み合わせの長さをL1、狭い重心間隔の長さをL2としている。開口部5a1は開口部5a2に比べてFナンバーの小さい(明るい)対物レンズに対応した検出系に相当している。 In the two pairs of openings 5a1 and 5a2 arranged in the horizontal direction, the length of the wide combination of the center-of-gravity intervals of the openings is L1, and the length of the narrow center-of-gravity interval is L2. The opening 5a1 corresponds to a detection system corresponding to an objective lens having a smaller F number than the opening 5a2.
図5は再結像レンズ6の正面図であり、絞り5の開口部5a1〜5a3に対応した3対のレンズ部分6a1〜6a3を有し、図3の視野マスク2の開口部2aをとおして対物レンズ21によって形成される被写体像を受光センサー7の各受光素子列上に再び結像する作用を有する。 FIG. 5 is a front view of the re-imaging lens 6, which has three pairs of lens portions 6 a 1 to 6 a 3 corresponding to the openings 5 a 1 to 5 a 3 of the diaphragm 5 and through the opening 2 a of the field mask 2 of FIG. The object image formed by the objective lens 21 is formed again on each light receiving element array of the light receiving sensor 7.
図6は受光センサー7を正面から見た説明図である。再結像レンズ6により結像される被写体像の光量分布を電気信号に変換する。 FIG. 6 is an explanatory view of the light receiving sensor 7 as seen from the front. The light quantity distribution of the subject image formed by the re-imaging lens 6 is converted into an electric signal.
図1,図2において視野マスク2の開口2aを通った光束はフィールドレンズ3の絞り6,再結像レンズ6を通過し、被写体像の2次像を、受光手段7上に再結像する。 1 and 2, the light beam that has passed through the aperture 2a of the field mask 2 passes through the aperture 6 and the re-imaging lens 6 of the field lens 3, and re-forms the secondary image of the subject image on the light receiving means 7. .
図6の受光手段7面上には、光電変換を行うための多数の画素よりなる画素列(受光素子列)7a1,7a2の組に、画素列を囲む点線で示す領域2a’に視野マスク2の開口形状2aに切り取られた被写体像の2次像が形成されている。 On the surface of the light receiving means 7 in FIG. 6, a field mask 2 is provided in a region 2a ′ indicated by a dotted line surrounding a pixel row in a set of pixel rows (light receiving element rows) 7a1 and 7a2 made up of a large number of pixels for photoelectric conversion. A secondary image of the subject image cut out in the opening shape 2a is formed.
一つの絞り6の開口部に対応する再結像レンズ6によって図6の点線のように物体の2次像2a’は形成され、2次像2a’は対物レンズ21の焦点調整状態によって受光素子列7a1〜7a3の長手方向に移動する。 The secondary image 2a ′ of the object is formed by the re-imaging lens 6 corresponding to the opening of one aperture 6 as shown by the dotted line in FIG. 6, and the secondary image 2a ′ is a light receiving element depending on the focus adjustment state of the objective lens 21. It moves in the longitudinal direction of the rows 7a1 to 7a3.
受光素子列の組7a1〜7a3はそれぞれに対応する視野マスク2の開口部2aの像について、受光手段7上の2次像の相対間隔をそれぞれにおいて検出する事により、それぞれの焦点検出領域における、対物レンズ21の焦点調節状態を検出している。 The sets 7a1 to 7a3 of the light receiving element arrays respectively detect the relative intervals of the secondary images on the light receiving means 7 with respect to the images of the openings 2a of the field mask 2 corresponding to the sets 7a1 to 7a3, respectively. The focus adjustment state of the objective lens 21 is detected.
本実施例では、図6に示すように、受光手段7の複数対の受光素子列7a1〜7a3のうちの水平方向の2対の受光素子列7a1,7a2の各対の重心間隔を各々D1,D2とするとき、
2≦D1/D2
を満足している。
In this embodiment, as shown in FIG. 6, the distance between the centers of gravity of each pair of the two pairs of light receiving element rows 7a1 and 7a2 in the horizontal direction among the plurality of pairs of light receiving element rows 7a1 to 7a3 of the light receiving means 7 is D1, respectively. When D2
2 ≦ D1 / D2
Is satisfied.
更に重心間隔D1,D2は、
D1/D2≦2.5
を満足している。
Furthermore, the center-of-gravity intervals D1, D2 are
D1 / D2 ≦ 2.5
Is satisfied.
これによって多様な被写体の焦点検出を可能とし、明るい対物レンズの焦点検出の精度を上昇させつつも、受光手段の受光面積の増大を抑制し、かつ、より配置効率のよい焦点検出装置を達成している。 This makes it possible to detect the focus of a variety of subjects, and while increasing the focus detection accuracy of a bright objective lens, achieves a focus detection device that suppresses an increase in the light receiving area of the light receiving means and has better arrangement efficiency. ing.
次に本発明の構成の特徴について説明を行う。焦点検出を被写体像の光量分布の方向に依らない多様な被写体に対して焦点検出するためには、F値(Fナンバー)の小さい(明るい)対物レンズから大きい(暗い)対物レンズにまで対応した焦点検出系を十字状の形に組み合わせることが不可欠である。これによりF値の大きさに関わらず、多様な被写体に対し焦点検出が可能となる。 Next, features of the configuration of the present invention will be described. In order to perform focus detection on various subjects that do not depend on the direction of the light amount distribution of the subject image, it corresponds from a small (bright) objective lens with a small F value (F number) to a large (dark) objective lens. It is essential to combine the focus detection system in a cross shape. As a result, focus detection can be performed on various subjects regardless of the F value.
ただし、このままの焦点検出装置では、精度の高い焦点検出が可能であるF値の小さい対物レンズにおいても、F値の大きい対物レンズと同等の検出精度しか出すことができない。従って、F値の小さい対物レンズに対応した焦点検出系をここに加える必要がある。 However, with the focus detection apparatus as it is, even with an objective lens having a small F value, which can perform focus detection with high accuracy, only a detection accuracy equivalent to that of an objective lens having a large F value can be obtained. Therefore, it is necessary to add a focus detection system corresponding to an objective lens having a small F value.
ここで図7のようにF値の小さい対物レンズに対応した検出光学系も、暗い対物レンズと同じく十字状に配置することは可能である。 Here, the detection optical system corresponding to the objective lens having a small F value as shown in FIG. 7 can also be arranged in a cross shape like the dark objective lens.
しかしながら、受光手段7の受光面積の増大を考えると、光学系を一つ加えたときは面積がF値の暗い焦点検出系の十字状の配置の面積に対し2倍になるのに対し、十字状の配置によって縦方向、横方向共に受光手段7の長さが2倍となるため、面積は4倍に増えることとなる。受光手段の製作困難さ(コスト)は、面積に比例するため製作上の困難さ(コスト)も4倍となるため避けるべきである。 However, considering the increase in the light receiving area of the light receiving means 7, when one optical system is added, the area becomes twice as large as the area of the cross-shaped arrangement of the dark focus detection system having the F value. Since the length of the light receiving means 7 is doubled in both the vertical direction and the horizontal direction due to the arrangement of the shapes, the area is increased four times. The manufacturing difficulty (cost) of the light receiving means is proportional to the area, so that the manufacturing difficulty (cost) is also quadrupled and should be avoided.
F値の小さい対物レンズに対応した光学系を導入するために、次に問題となるのは絞り5の開口部をどの方向に開けるかである。可能性としては縦や横に限らず、任意の斜めの角度を持たせて絞り5を配置することができる。しかし、焦点検出の精度とコスト増大の回避を考えたときには、横方向に開口部を設けることが一番よい。 In order to introduce an optical system corresponding to an objective lens having a small F value, the next problem is in which direction the opening of the diaphragm 5 is opened. Possibility is not limited to vertical and horizontal, and the diaphragm 5 can be arranged with an arbitrary oblique angle. However, when considering the accuracy of focus detection and avoiding an increase in cost, it is best to provide an opening in the lateral direction.
まず精度の問題を挙げる。一眼レフレックスカメラにおいて焦点検出装置FDは、カメラCB内で図1に示されるように、クイックリターンミラー22を透過した後に配置される。このとき、光束が通過する位置や角度の変化の違いからクイックリターンミラー22を通過する光路が異なる。 First, accuracy issues are listed. In the single-lens reflex camera, the focus detection device FD is disposed after passing through the quick return mirror 22 in the camera CB as shown in FIG. At this time, the optical path passing through the quick return mirror 22 differs depending on the position where the light beam passes and the difference in angle.
これが原因となり、受光センサー7上において数μmの誤差が生じる。受光センサー7上での精度としてサブミクロンの精度が必要である焦点検出装置においては、数μmの差は大きなものである。しかし絞り5の開口を上下に開けて分割された光束では、光路長が異なり光学的作用が異なるのに対し、左右に開口を開けた絞り5では光学的に全く同じ光路を通るために同じ収差を持ち、受光センサー7上で比較される被写体像のズレを生じることがない。 This causes an error of several μm on the light receiving sensor 7. In a focus detection apparatus that requires submicron accuracy as the accuracy on the light receiving sensor 7, the difference of several μm is large. However, in the light beam divided by opening the aperture of the diaphragm 5 up and down, the optical path length is different and the optical action is different. And the object image to be compared on the light receiving sensor 7 is not displaced.
つまり、絞り5の開口を左右方向(横方向)に分割することが焦点検出性能において最良である。 That is, it is best in focus detection performance to divide the aperture of the diaphragm 5 in the left-right direction (lateral direction).
次に、縦或いは横方向に絞り5の開口を設ける上での、受光手段7の面積の増大について説明する。 Next, an increase in the area of the light receiving means 7 when the aperture of the diaphragm 5 is provided in the vertical or horizontal direction will be described.
近年、対物レンズ1の結像面内に複数の焦点検出領域を配置し、中央だけではなく画面の周辺部分においても焦点を合わせる焦点検出装置が広く利用されている。 2. Description of the Related Art In recent years, focus detection apparatuses in which a plurality of focus detection areas are arranged in the imaging plane of the objective lens 1 and focus on not only the center but also the peripheral part of the screen have been widely used.
図8には、画面上に焦点検出領域を7つ備え、中央に十字開口2a1の焦点検出系をもつ視野マスク2の一例と、図9にはそれに対応した受光センサー7を示す。 FIG. 8 shows an example of a field mask 2 having seven focus detection areas on the screen and a focus detection system having a cross opening 2a1 in the center, and FIG. 9 shows a light receiving sensor 7 corresponding thereto.
撮像素子の形状は銀塩フィルムに代表されるように、横長である。このため、焦点検出領域は縦方向よりも横方向に高い像高を持って配置される。 The shape of the image sensor is horizontally long as represented by a silver salt film. For this reason, the focus detection area is arranged with a higher image height in the horizontal direction than in the vertical direction.
同様に、受光センサー7の受光素子列7aの配列も縦方向に高い像高を持って配置される。このとき、F値の小さい対物レンズに対応した焦点検出系を中央部に導入することを考える。 Similarly, the arrangement of the light receiving element rows 7a of the light receiving sensor 7 is also arranged with a high image height in the vertical direction. At this time, it is considered that a focus detection system corresponding to an objective lens having a small F value is introduced in the central portion.
図10に受光センサー7の受光素子列7aの配列を横方向に挿入した時の受光素子列の配列、図11には縦方向に挿入した時の受光センサー7の受光素子列7aの配列を示してある。センサーチップは、シリコンウェハーから切り取る時に四角の形状で切り取る。 FIG. 10 shows the arrangement of the light receiving element array 7a when the light receiving element array 7a of the light receiving sensor 7 is inserted in the horizontal direction, and FIG. 11 shows the arrangement of the light receiving element array 7a of the light receiving sensor 7 when inserted in the vertical direction. It is. When the sensor chip is cut from the silicon wafer, it is cut into a square shape.
このためセンサー形状は四角にならざるを得ない制約を考慮すると、受光センサー7の受光素子列7aの配列を縦方向に挿入したときよりも、横方向に挿入した時の方が増大する受光手段の面積を抑えることができることが、図9から図10へ、図9から図11への面積変化を比較からわかる。 For this reason, in consideration of the restriction that the sensor shape must be square, the light receiving means increases when the array of the light receiving element rows 7a of the light receiving sensor 7 is inserted in the horizontal direction rather than when it is inserted in the vertical direction. It can be seen from comparison that the area change from FIG. 9 to FIG. 10 and from FIG. 9 to FIG.
従って、F値の小さい焦点検出系の絞り5を、縦向きではなく横向きに開口することで受光センサー7の受光面積の増加を抑えることができる。 Therefore, an increase in the light receiving area of the light receiving sensor 7 can be suppressed by opening the diaphragm 5 of the focus detection system having a small F value in the horizontal direction instead of the vertical direction.
さらに、図10に示すように、横方向に開口するF値の小さい焦点検出系の1対の受光素子列7a1の重心間隔をD1と、F値の大きい焦点検出系の1対の受光素子列7a2の重心間隔をD2としたときにD1/D2が2以上であることが良い。 対物レンズ1を通過した光束は、瞳8から視野マスク2の距離に比べ、絞り5から受光センサー7への距離が非常に短いことから、絞り5の重心位置とほぼ同じ位置を保って受光センサー7上に到達する。受光センサー7上には、視野マスク2の開口形状と相似でそれぞれの面積がほぼ等しい像が絞り5の開口数と同数投影される。この理由から絞り5の配置と受光センサー7上の像の配置には高い相関が存在する。 Further, as shown in FIG. 10, the distance between the centers of gravity of the pair of light receiving element arrays 7a1 of the focus detection system having a small F value that opens in the horizontal direction is D1, and the pair of light receiving element arrays of the focus detection system having a large F value. When the distance between the centers of gravity of 7a2 is D2, D1 / D2 is preferably 2 or more. The light beam that has passed through the objective lens 1 has a very short distance from the diaphragm 5 to the light receiving sensor 7 compared to the distance from the pupil 8 to the field mask 2. Reach 7 up. On the light receiving sensor 7, an image similar to the opening shape of the field mask 2 and having almost the same area is projected as many as the numerical aperture of the diaphragm 5. For this reason, there is a high correlation between the arrangement of the diaphragm 5 and the arrangement of the image on the light receiving sensor 7.
そして、受光センサー7上の被写体像は重なることは望ましくない。被写体像が重なる領域がでてくると、その領域には受光素子列を配置することができなくなり、無駄な領域となり受光センサーの受光面積の増大を招き、また被写体像の重なりが生じる配置では、受光センサーに入射すべきでない特定の焦点検出領域以外の迷光を検出する可能性も高くなる。 The subject images on the light receiving sensor 7 are not desirably overlapped. When an area where the subject images overlap appears, it is no longer possible to arrange the light receiving element array in the area, and it becomes a useless area, causing an increase in the light receiving area of the light receiving sensor, and where the subject images overlap, The possibility of detecting stray light other than a specific focus detection region that should not be incident on the light receiving sensor is also increased.
ここでD1/D2が2を下回ると、無駄な受光センサーの受光面積の増大を引き起こす。図10に示されるように、F値の暗い対物レンズに対応した焦点検出系により、受光手段7上にできる被写体像同士が重ならないように配置し、また受光センサー7の受光面積を小さくするという要望から、横方向に配置されたF値の大きい対物レンズ用の絞りによって作られた被写体像の重心間隔D2は、像の大きさの2倍の値となる。 Here, if D1 / D2 is less than 2, a useless increase in the light receiving area of the light receiving sensor is caused. As shown in FIG. 10, the focus detection system corresponding to the objective lens having a dark F value is arranged so that the subject images formed on the light receiving means 7 do not overlap each other, and the light receiving area of the light receiving sensor 7 is reduced. From the request, the center-of-gravity distance D2 of the subject image formed by the diaphragm for the objective lens having a large F value arranged in the horizontal direction is a value twice the size of the image.
一方、F値の小さい対物レンズ用の絞りによって作られた被写体像の重心間隔D1は、被写体像を重ねずまた、受光センサー7の受光面積を最小にする要請から、被写体像の大きさの4倍の値となる。 On the other hand, the center-of-gravity distance D1 of the subject image formed by the aperture for the objective lens having a small F value is 4 because the subject image is not overlapped and the light receiving area of the light receiving sensor 7 is minimized. Double the value.
D1/D2が2を下回るということは、F値の大きい絞りによる被写体像の間隔が被写体像の大きさの2倍以上の値となり中央部に無駄な受光領域が生じることを意味しており、受光面積の増大を引き起こす。 The fact that D1 / D2 is less than 2 means that the distance between the subject images due to the aperture having a large F value is more than twice the size of the subject image, resulting in a useless light receiving region in the center. This increases the light receiving area.
一方、D1/D2が2を超えると、F値の小さい焦点検出系の精度が上昇するだけでなく、被写体像同士の間隔が広がることで、受光センサーに入射すべきでない他の焦点検出領域を通過した迷光が受光センサーに入射する危険性が減るため、F値の小さい焦点検出系とF値の大きい焦点検出系の被写体像の間に被写体像の大きさの半分程度をマージンとして持つのがよい。 On the other hand, when D1 / D2 exceeds 2, not only the accuracy of the focus detection system having a small F value increases, but also the distance between subject images increases, so that other focus detection areas that should not be incident on the light receiving sensor can be obtained. Since the risk of incident stray light entering the light receiving sensor is reduced, there is a margin between the subject image of the focus detection system with a small F value and the focus detection system with a large F value as a margin. Good.
即ち、明るい光束(F値の小さい位置の絞りを通過した光束)と暗い光束(F値の大きい位置の絞りを通過した光束)がそれぞれ形成する像が重ならない「余裕」を受光素子間に持つのが良い。 That is, the light receiving element has a “margin” that does not overlap images formed by a bright light beam (light beam that has passed through a diaphragm having a small F value) and a dark light beam (light beam that has passed through a diaphragm having a large F value). Is good.
しかし、それより大きなマージンは受光面積の増大を引き起こすため望ましくない。このため、D1/D2≦2.5であることがより良い。 However, a larger margin is undesirable because it increases the light receiving area. For this reason, it is better that D1 / D2 ≦ 2.5.
以上のように本発明によれば、多様な被写体を多くの対物レンズにおいて焦点検出可能とするため、F値の大きい(暗い)対物レンズに対応した焦点検出系における視野マスクの開口を十字状に配列し、かつF値の大きい(明るい)対物レンズに対応した焦点検出系を適切に加えることで、高精度で受光面積のコンパクトな新たな構成の焦点検出装置を得ることができる。 As described above, according to the present invention, in order to make it possible to detect a variety of subjects with a large number of objective lenses, the opening of the field mask in the focus detection system corresponding to a large F-number (dark) objective lens has a cross shape. By appropriately adding a focus detection system that is arranged and corresponds to a (bright) objective lens having a large F value, it is possible to obtain a focus detection device having a new configuration with high accuracy and a compact light receiving area.
1 光軸
2 視野マスク
3 フィールドレンズ
4 反射ミラー
5 絞りマスク
6 再結像レンズ
7 光電変換素子
8 瞳
21 対物レンズ
22 クイックリターンミラー
23 フォーカシングスクリーン
24 ペンタプリズム
25 接眼レンズ
26 サブミラー
DESCRIPTION OF SYMBOLS 1 Optical axis 2 Field mask 3 Field lens 4 Reflection mirror 5 Aperture mask 6 Re-imaging lens 7 Photoelectric conversion element 8 Pupil 21 Objective lens 22 Quick return mirror 23 Focusing screen 24 Penta prism 25 Eyepiece 26 Sub mirror
Claims (5)
2≦D1/D2
なる条件を満足することを特徴とする焦点検出装置。 A stop provided with two pairs of apertures through which two pairs of light beams having different heights from the optical axis pass on the pupil of the objective lens; and two pairs of secondary imaging lenses corresponding to the two pairs of apertures A secondary imaging system; and a light receiving means including two pairs of light receiving elements in which two pairs of light quantity distributions corresponding to the subject image are formed by the two pairs of secondary imaging lenses. A focus detection device that detects a focal position of the objective lens using a signal, and is one of the two pairs of light receiving elements of the light receiving means, which has a higher height from the optical axis on the pupil of the objective lens. The center-of-gravity interval of a pair of light-receiving elements that receive a pair of light beams is D1, and the center-of-gravity distance of a pair of light-receiving elements that receive a pair of light beams having a lower height from the optical axis on the pupil of the objective lens. When D2
2 ≦ D1 / D2
A focus detection device satisfying the following condition:
D1/D2≦2.5
を満足することを特徴とする請求項1,2又は3の焦点検出装置。 The center-of-gravity distances D1 and D2 further satisfy D1 / D2 ≦ 2.5.
The focus detection apparatus according to claim 1, 2 or 3, wherein:
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Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS55118019A (en) * | 1979-03-05 | 1980-09-10 | Minolta Camera Co Ltd | Focusing point detector |
JPS6388511A (en) * | 1986-10-01 | 1988-04-19 | Canon Inc | Focus detector |
JPH11281885A (en) * | 1998-03-30 | 1999-10-15 | Minolta Co Ltd | Focus position detecting device |
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2004
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Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS55118019A (en) * | 1979-03-05 | 1980-09-10 | Minolta Camera Co Ltd | Focusing point detector |
JPS6388511A (en) * | 1986-10-01 | 1988-04-19 | Canon Inc | Focus detector |
JPH11281885A (en) * | 1998-03-30 | 1999-10-15 | Minolta Co Ltd | Focus position detecting device |
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