JPH11352396A - Focus detector and optical equipment using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable focus detection to be accurately executed by appropriately setting the respective elements of an optical means for focus detection provided on the image surface side of an objective lens (photographing lens). SOLUTION: A 1st reflection mirror 4 is arranged obliquely to the optical axis 1 on the image surface side of the objective lens 101. The light incident side of an image reformation lens block 9 equipped with an aspherical surface and a diffraction lens surface is a single concave aspherical surface having the center on the optical axis of the lens 101 deflected by the mirror 4, and the exit side thereof is composed of two pairs of convex lens surfaces 9e,...9g,... that are made eccentric in the opposite direction to each other. A detection system using luminous flux passing through some element separates the exit pupil of the objective lens in a longitudinal direction, while a detection system using the luminous flux passing through another element separates the exit side of the objective lens in the lateral direction. The 1st focus detection system separates a pupil in the longitudinal direction and the 2nd detection system separates the pupil in the lateral direction. Namely, a secondary object paired by separating the pupil of the objective lens on a 2nd plane PL2 orthogonally crossing a 1st plane is formed on a photoelectric conversion element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus detection device suitable for a photographic camera, a video camera, an observation device, and the like, and an optical apparatus using the same. And forming a light amount distribution for a plurality of subject images (object images) using the light flux passing through each area, and obtaining a relative positional relationship between the plurality of light amount distributions, thereby obtaining a focusing state of the objective lens. Is suitable for detecting over a wide area in the photographing range.

[0002]

2. Description of the Related Art Conventionally, there has been a so-called image shift method (position difference detection method) in a light receiving type focus detection apparatus utilizing a light beam passing through an objective lens.

[0003] This image shift type focus detection device is characterized in that the amount of defocus that can be detected is large and that the focus state can be detected satisfactorily regardless of the subject distance.

In an image shift type focus detection apparatus, one stop system having a pair of apertures on the image plane side of an objective lens and one detection system having a pair of secondary imaging systems (re-imaging lenses) corresponding thereto. Alternatively, a plurality of optical units are provided, and the optical unit forms a plurality of light amount distributions on the subject image using light beams passing through different regions of the pupil of the objective lens, and a relative positional relationship between the plurality of light amount distributions. Is obtained by a photoelectric conversion element composed of a plurality of elements, and the in-focus state of the objective lens is detected using a signal from the photoelectric conversion element.

[0005]

In an image shift type focus detection device, the configuration of a detection system for forming a secondary object image greatly affects the focus detection accuracy.

The present invention relates to a focus detection device capable of performing focus detection with high accuracy by appropriately setting each element of a focus detection optical means provided on an image plane side of an objective lens (photographing lens), and a focus detection device therefor. The purpose of the present invention is to provide an optical device using the same.

[0007]

According to the present invention, there is provided a focus detecting apparatus comprising: (1-1) an object using an optical means provided on an image plane side of an objective lens by using a light beam having passed through different regions of a pupil of the objective lens; A plurality of light quantity distributions for an image are formed, a relative positional relationship between the plurality of light quantity distributions is obtained by a photoelectric conversion element including a plurality of elements, and a focusing state of the objective lens is determined using a signal from the photoelectric conversion element. In one or a plurality of regions in the field of view, the optical means comprises a light-collecting reflection forming an object image on a predetermined surface which bends an optical path in a direction different from the optical axis of the objective lens. A first detection system including a mirror, an aspheric surface, and a diffractive lens surface, and separating a pupil of the objective lens in a first plane to form a paired secondary object image on the photoelectric conversion element; A diffractive lens surface, orthogonal to the first plane Secondary object image forming a pair are separated pupil of the objective lens in the second plane is characterized by a second detection system to be formed on the photoelectric conversion element that.

In particular, (1-1-1) the parallax due to the pupil separation of the first detection system is smaller than that of the second detection system, and the photoelectric conversion of the secondary object image by the first detection system is performed. The light receiving area of the conversion element has a higher angle of view than that of the second detection system.

The optical apparatus according to the present invention performs the focusing by driving the focusing lens constituting the objective lens using the signal from the focus detecting device having the constitution (2-1). It is characterized in that a subject image is formed on a surface.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 are schematic views of a main part of a first embodiment when a focus detection device according to the present invention is applied to an optical apparatus such as a camera. FIG. 1 shows a first detection system for separating a pupil of an objective lens (photographing lens) in a vertical direction in a focus detection device, and FIG. 2 shows a second detection system for separating a pupil of an objective lens in a horizontal direction. I have.

In the figure, reference numeral 101 denotes an objective lens, 1 denotes an optical axis of the objective lens 101, 2 denotes a film (imaging surface), 3 denotes a semi-transmissive main mirror arranged on the optical axis 1 of the objective lens 101,
Reference numeral 103 denotes a reticle, on which a subject image formed by the objective lens 101 is formed via the main mirror 3.

Reference numeral 4 denotes a first reflecting mirror disposed obliquely on the image plane side of the objective lens 101 with respect to the optical axis 1, and comprises a condensing concave mirror, an elliptical mirror, or the like. Reference numeral 5 denotes a paraxial image plane conjugate to the film 2 formed by the first reflecting mirror 4, on which a subject image is formed. 6 is a second reflecting mirror, 7 is an infrared cut filter, 8 is a stop having four openings 8e, 8f, 8g, 8h, 9 is arranged corresponding to the four openings of the stop 8, each of which is aspherical And four lenses having a diffractive lens surface known from JP-A-10-133149,
Secondary imaging system (re-imaging lens block) having 9e, 9f, 9g, 9h as convex lens surfaces, 10 is a third reflecting mirror, 11 is an area sensor, and two pairs of two-dimensional light receiving area sensors 11e , 11f, 11g, and 11h, respectively. First
The reflecting mirror 4, the second reflecting mirror 6, the stop 8 and the secondary imaging system 9 constitute one element of the optical means.

Each of the light receiving area sensors 11e to 11f is composed of a plurality of sensor rows, and the sensor rows also form a pair.

Here, the first reflecting mirror 4 is an elliptical mirror, and the two focal points defining the ellipse reverse the optical path after the light beam on the optical axis 1 of the objective lens 101 is refracted by the main mirror 3. First, on the line extended to the objective lens 101 side and the ray
Are positioned on lines extending the optical path after being reflected by the reflecting mirror 4. The first reflecting mirror 4 also functions as a field mask that limits the focus detection area, so that only the necessary area reflects light. The second reflecting mirror 6 ′ and the third reflecting mirror 10 may be either a plane mirror or an elliptical mirror (or a converging mirror). It is. The optically functioning portions of these components are all symmetrical with respect to the paper.

FIG. 3 is a plan view of the stop 8. In FIG. 3, the stop 8 is a stop made of a light-shielding thin plate made of metal or resin, 8e to 8f are stop openings (openings), 8i and 8j.
Is a positioning hole. The stop 8 is fixed to the re-imaging lens block 9 via the positioning holes 8i and 8j.

The light incident side of the re-imaging lens block 9 is the first
A single concave aspheric surface having a center on the optical axis of the objective lens 101 deflected by the reflecting mirror 4, and the exit side is a pair of convex lens surfaces 9e to 9h eccentric in opposite directions. Here, all of the lens surfaces 9e to 9h become diffraction lens surfaces, that is, lens action surfaces using a diffraction phenomenon known in Japanese Patent Application Laid-Open No. 10-133149. Further, the center of the concave spherical surface is located on the paraxial imaging plane 5 of the objective lens 101 formed by the first reflecting mirror 4, and the center of the two pairs of lens portions 9e to 9h is located at the aperture openings 8e to 8h. Are set substantially equal to each other. By arranging the power of the lens in this manner, it is possible to perform highly accurate focus detection over a wide wavelength range and in a plurality of regions of the photographing range.

The positional relationship between the stop 8 and the re-imaging lens block 9 is such that two pairs of lenses 9e to 9h are located behind the stop 8 as shown by broken lines in FIG. The aperture centroids of the aperture openings 8e and 8g are parallel to the optical path near the optical axis of the objective lens 101 and are on a first plane (paper surface in FIG. 1) PL1 including the centers of curvature P6 and P7 of the lens portions 9e and 9g. The center of curvature of the apertures 8f and 8h and the center of curvature of the lens sections 9f and 9h include a second plane (including the optical path near the optical axis of the objective lens 101) and orthogonal to the first plane PL1 (the plane of FIG. 2). ) On PL2.

As the optical path of the focus detection light beam, the aperture openings 8e to 8h and the lens portions 9e to 9h correspond to those indicated by the same suffix, and the light beam passing through each opening is a third reflecting mirror. A secondary object image is formed on the area sensor 11 via the reference numeral 10. It should be noted that the luminous flux passing through the elements with different subscripts does not reach a predetermined position on the area sensor and does not contribute to focus detection.

The detection system using the light beam passing through the elements indicated by the subscripts e and g separates the exit pupil of the objective lens in the vertical direction, while detecting the light beam using the light beam passing through the elements indicated by the subscripts f and h. The system laterally separates the exit pupil of the objective lens. Hereinafter, a detection system for separating the pupil in the vertical direction is referred to as a first focus detection system (first detection system), and a detection system for separating the pupil in the horizontal direction is referred to as a second focus detection system (second detection system). I will call it.

Next, the optical function of the above configuration will be described. 12e, 12g, 12f, shown in FIG. 1 and FIG.
Reference numeral 12h denotes a light beam passing through the aperture 8 and used for focus detection at the center of the screen. To add a description in the order in which these rays travel, first, the light beam from the objective lens 101 is transmitted through the main mirror 3 and then reflected by the first reflecting mirror 4 in a direction substantially along the inclination of the main mirror 3. As described above, the first reflecting mirror 4 is an elliptical mirror, and the vicinity of the two focal points can be substantially in a projection relationship.

Here, one focus detection is performed by the objective lens 10.
An optical equivalent point of one representative exit pupil position 101a is set to an optical equivalent point of the stop 8, and the other focal point is set to have a function as a field lens. Objective lens 101
The representative exit pupil position 101a is a hypothetical pupil position unique to the focus detection system which is comprehensively determined in consideration of the conditions of the exit windows of various projection lenses mounted on the camera.

The light beam reflected by the first reflecting mirror 4 is reflected again by the second reflecting mirror 6 and enters the infrared cut filter 7. Here, infrared rays which cause a reduction in the accuracy of focus detection are removed, and only the light in the wavelength range in which the aberration of the objective lens is sufficiently corrected is placed up to the aperture 8 and the re-imaging lens block 9 placed behind. To reach. The luminous flux converged by the action of the re-imaging lens block 9 passes through the third reflecting mirror 10
A next object image is formed on the area sensor 11.

FIG. 4 is a diagram showing the state of the secondary object images 22e to 22h on the area sensor 11, and is an example of a grid-like object. Four secondary object images are formed by the four lenses of the re-imaging lens block 9, and 22g,
22e and 22f, 22h are pairs of images (secondary object images) for which relative positional relationships are to be detected.

Here, the distance between the openings 8e and 8g of the stop 8 and the distance between the openings 8f and 8h are different from each other, and the second focus detection system having a wider distance is more sensitive to the movement of the secondary object image. Therefore, highly accurate focus detection is possible.

The range in which the object is projected is the secondary object image 22
g, 22e are different from the secondary object images 22f, 22h,
In the secondary object images 22g and 22e, the main mirror and the second reflection mirror are located in a region determined by the size of the first reflecting mirror 4 in the secondary object images 22f and 22h due to the difference in the distance between the aperture openings 8f and 8h. It is an area through which light rays can pass on the mirror, and is smaller than the secondary object images 22g and 22e. Further, due to the oblique arrangement of the first reflecting mirror 4, each image has a considerably large distortion without axial symmetry.

However, even if such a distortion exists, there is no problem as a focus detection device for a camera that requires particularly quick focusing if the following two conditions are satisfied.

The conditions are as follows in order to obtain an accurate focus determination. At least when the objective lens is in focus, a secondary object image corresponding to the same position on the object is projected on a pair of sensor rows to be detected, that is, in a direction orthogonal to the sensor rows. , The difference in magnification between the two images is small.

In order to obtain accurate defocus detection,. When a defocus of the objective lens occurs, a secondary object image corresponding to the same position on the object is projected with a positional phase difference on a pair of sensor rows to be detected. It is.

Now, this focus detection system will be described from such a viewpoint. First, regarding the first focus detection system that separates the pupil in the vertical direction, since the inclination of the first reflecting mirror 4 is in the plane of FIG. Regarding any of 22e, the distortion has a fan shape symmetric to the plane of the drawing, and the amount of the distortion itself is considerably large. However, if attention is paid to the difference in distortion between the two images, the difference is small. In particular, the image magnification difference between the secondary object images 22g and 22e in the horizontal direction in the figure corresponding to the direction orthogonal to the pupil separation is almost zero. There is no.

Therefore, if the sensor rows 11e and 11g in the light receiving area are arranged as shown in FIG. 6, the object image 22 projected on an arbitrary sensor row on one light receiving area 11e can be obtained.
The object image 22g paired with e is projected onto the corresponding sensor array on the other light receiving area 11g. That is, the above condition is satisfied.

The secondary object image is distorted by the first reflecting mirror 4, ie, the pupil projection optical system, and the distortion generated on the paraxial imaging plane 5 of the first reflecting mirror 4 is re-imaged. Lens block 9
Can be said to be projected on the area sensor 11 as it is. Therefore, the moving direction of the secondary object images 22e and 22g is the direction in which the aperture openings 8e and 8f are arranged.
On the area sensor, it is the direction of the arrow shown in FIG.

Therefore, by setting the sensor rows as shown in FIG. 6 as described above, the same condition is satisfied, and the relative positional relationship between the secondary object images 22e and 22g is compared based on this, and the defocus amount of the objective lens is determined. Is possible.

FIG. 8 shows a focus detection area on the imaging surface by the light receiving areas arranged as described above. Light receiving areas 11g and 11e in which a distorted secondary object image 22g is arranged in a rectangle.
The focus detection area 31 for photoelectric conversion by the
The shape becomes distorted as shown in the figure.

Next, a second focus detection system for separating the pupil in the horizontal direction will be described. The difference in image magnification difference between the two images in the direction orthogonal to the pupil separation is reduced only in the region near the center of the imaging surface. Therefore, if the light receiving area is limited to only this part, the object image that is paired with the object image projected on an arbitrary sensor row on one light receiving area is projected on the corresponding sensor row on the other light receiving area. Thus, the above condition is satisfied.

FIG. 7 is a plan view of the area sensor 11 showing the light receiving areas 11f and 11h for the second focus detection system in addition to the light receiving areas 11g and 11e of the first focus detection system shown in FIG. is there. Secondary object images 22f and 22 that form a pair
The moving direction of h is the direction in which the aperture openings 8f and 8h are arranged for the same reason as in the first focus detection system, and the above conditions can be satisfied by setting the sensor rows as shown in the figure. . The focus detection area on the imaging surface by such a light receiving area is as shown in FIG. 9, and the focus detection area 34 is a central portion in the imaging surface 30.

By using such an area sensor 11 to output a light amount distribution as an electric signal and detecting a relative positional relationship between images (secondary object images) on a pair of sensor rows to be detected, an object can be obtained. It is possible to detect the focal position of the lens. At this time, if the sensor row pair to be detected is appropriately selected, a two-dimensional imaging state can be detected on the imaging surface.

Further, as shown as a region 32 or 33 in FIG. 8, for example, a defocus map on the image pickup surface is obtained from the focus information of the more subdivided focus points obtained by dividing the sensor array into a plurality of regions. It is also possible to automatically control the focus of the objective lens at an arbitrary position most appropriate among the main subjects. As a result, focus detection is performed in a plurality of regions in the subject.

FIG. 10 shows a secondary object image (hereinafter referred to as an "image") 2 including a region where a sensor array of photoelectric conversion elements is not provided.
It is explanatory drawing showing the situation of 2-1 to 22-4. Image 22
-1 and the image 22-2 almost overlap when translated, but the image 22-3 and the image 22-4 are folded back in relation to the axis PL1, and the area where they overlap even when translated is only the central portion.

When photoelectrically converting the image 22-1 and the image 22-2, the corresponding sensor array 701 particularly in the X direction is used.
A corresponding image needs to be incident on 1,701-2. Similarly, when photoelectrically converting the images 22-3 and 22-4, the corresponding sensor arrays 702-3 and 70-2 in the Y direction are used.
The corresponding image needs to be incident on 2-4. However, the point P3 on the sensor rows 702-3 and 702-4
Although the point P4 is a point on the corresponding sensor row, it is not a corresponding point on the image.

For this reason, the first focus detection system in which the pupil is separated in the direction (Y direction) of the plane where the optical path is bent by the reflecting mirror can detect the focus up to a high angle of view, but on the contrary, it is orthogonal to this. The second focus detection system that separates the pupil in the direction (X direction) that can perform focus detection only at a low angle of view.

Therefore, in the present embodiment, the first detection system performs a small parallax focus detection system capable of coping with all photographing lenses, and particularly a parallax corresponding to a photographing lens having a bright FNo (from the parallax of the first detection system). Large) focus detection system
By using the detection system described above, it is possible to measure at least a wide field of view with any photographing lens.

As described above, in the present embodiment, the light path is bent in a direction different from the optical axis of the objective lens by the converging reflecting mirror 4 to form a subject image on a predetermined surface (imaging surface 5). .

In the first detection system, the pupil of the objective lens 101 is separated and a pair of secondary object images is formed on the photoelectric conversion element 11 in the first plane PL1 where the optical path is bent.

In the second detection system, a pupil of the objective lens 101 is separated and a pair of secondary object images is formed on the photoelectric conversion element in a second plane PL2 orthogonal to the first plane PL1. doing.

The parallax due to pupil separation of the first detection system is smaller than that of the second detection system, and the light receiving area of the secondary object image by the first detection system at the photoelectric conversion element is the second detection system. The angle of view is set higher than that of the system.

[0046]

As described above, according to the present invention, the focus detection can be performed with high accuracy by appropriately setting each element of the focus detection optical means provided on the image plane side of the objective lens (photographing lens). And an optical apparatus using the same.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an optical path of a first focus detection system according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an optical path of a second focus detection system according to the first embodiment of the present invention.

FIG. 3 is a plan view of the diaphragm according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a state of a secondary object image on the area sensor according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram illustrating a moving direction of a secondary object image according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram showing an arrangement direction of a sensor row according to the first embodiment of the present invention.

FIG. 7 is a plan view of the area sensor according to the first embodiment of the present invention.

FIG. 8 is a plan view of the area sensor according to the first embodiment of the present invention.

FIG. 9 is a plan view of the area sensor according to the first embodiment of the present invention.

FIG. 10 is a plan view of the area sensor according to the first embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 101 Objective lens 1 Optical axis 2 Imaging means 3 Main mirror 4 First reflecting mirror 5 Image plane 6 Second reflecting mirror 7 Infrared cut filter 8 Aperture 9 Secondary imaging lens 10 Third reflecting mirror 11 Area sensor 8e to 8h Aperture opening 9e to 9h Lens part PL1 First plane PL2 Second plane

Claims (3)

[Claims] An optical unit provided on an image plane side of an objective lens forms a plurality of light amount distributions of a subject image using light beams passing through different regions of a pupil of the objective lens, and a relative light amount distribution of the plurality of light amount distributions. In a focus detection apparatus, a relative positional relationship is determined by a photoelectric conversion element including a plurality of elements, and a focus state of the objective lens is determined in one or a plurality of regions in an imaging visual field by using a signal from the photoelectric conversion element. The optical means includes a converging reflecting mirror, an aspheric surface, and a diffractive lens surface for forming a subject image on a predetermined surface that bends an optical path in a direction different from the optical axis of the objective lens, and includes a first plane within the first plane. A first detection system for forming a secondary object image forming a pair on the photoelectric conversion element by separating a pupil of the objective lens, and an aspherical surface and a diffractive lens surface, in a second plane orthogonal to the first plane; The pupil of the objective lens is separated And a second detection system for forming a secondary object image on the photoelectric conversion element. 2. The parallax due to pupil separation of the first detection system is smaller than that of the second detection system, and the light receiving area of the secondary object image by the first detection system at the photoelectric conversion element is The second
2. The focus detection device according to claim 1, wherein the angle of view is higher than that of the detection system. 3. An object image is formed on an imaging means surface by driving a focusing lens constituting an objective lens by using a signal from the focus detecting device according to claim 1 to perform focusing. And optical equipment.