JPH06235855A - Focus detector - Google Patents

Abstract

PURPOSE:To satisfy both of the enlargement of a focusing range and the improvement of focusing accuracy and also to make the structure compact by making a direction of reflection light with respect to incident light different from at least one of the other reflection faces. CONSTITUTION:Plural luminous fluxes transmitted through different areas in a photographic lens 11 are received by a photoelectric conversion means through reflecting members 14a and 14b, brightness diaphragms 15a and 15b and image reforming lenses 16a and 16b, and such the focus detection that the phase difference between plural luminous fluxes is detected based on the light intensity distribution on the light receiving face of the photoelectric conversion means is carried out. At least one of the reflecting faces of the reflecting members 14a and 14b is arranged on a plane different from the other one reflecting face, that is, arranged so that the reflecting faces may not be on the same plane, then, the direction of the reflecting light with respect to the incident light is made different from at least one of the other reflecting faces. Thus, the focusing accuracy is improved, the focusing range is enlarged, and also, the structure of the device can be made compact.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus detecting device for a camera.

[0002]

2. Description of the Related Art An image formed by a taking lens is divided into two by a re-imaging optical system and re-formed on a photoelectric conversion element array (light receiving element array), and a positional deviation between the two images is detected. A number of focus detection optical systems for performing focus detection have been proposed so far, for example, Japanese Patent Laid-Open No. 55-1180.
19, JP-A-58-106511 and JP-A-60-32012. The relationship between the width of the distance measuring range and the focusing accuracy in the focus detection optical system is as follows.

That is, although the respective light receiving elements of the light receiving element array are normally arranged at equal intervals, if the interval is 1 pitch, the focusing accuracy is expressed as a relative scale with respect to 1 pitch. When the focusing accuracy is 1 / M of one pitch (M is a constant), and the defocus amount per pitch on the image plane is α,
The focusing accuracy Δ on the image plane is Δ = ± (1 / M) · α (1). Here, the larger Δ is, the worse the focusing accuracy is, and the smaller Δ is, the better the focusing accuracy is. Further, when the number of light receiving elements is N, the defocus range Σ on the image plane where distance measurement is possible
Is Σ = | ± N · α | (2). Here, if α is increased, the range Σ is increased, but the focusing accuracy Δ is deteriorated. On the contrary, if α is reduced, the focusing accuracy Δ is improved, but the distance measuring range Σ is reduced. In other words, it can be understood that the number N of light receiving elements should be increased in order to increase the distance measuring range Σ without degrading the focusing accuracy Δ.

However, if the number N of light receiving elements is large, the total length of the light receiving element array becomes long, which causes structural inconvenience.
FIG. 5 shows an example of the focus detection optical system having the above-mentioned relationship. In the figure, 1 is a taking lens, 2 is a planned imaging plane, and 3 is
Is a condenser lens, 5 is an aperture stop having apertures 5a and 5b, 6a and 6b are re-imaging lenses, 7a and 7b are light receiving element arrays, and O is an optical axis of the condenser lens 3. As is clear from FIG. 5, the light receiving element array 7a having the length shown by the solid line,
When the number of light receiving elements 7b is increased, the entire length of each light receiving element array extends to the length shown by the dotted line, and the light receiving element arrays interfere with each other at the shaded portion, and the focus detection optical system cannot be configured. If the distance L between the centers C _7a and C _7b of the light-receiving element rows 7a and 7b is increased so that the light-receiving element rows do not interfere with each other, the focus detection optical system itself must be upsized.

As a focus detecting optical system which satisfies the demands of expanding the range-finding range and improving focusing accuracy while keeping the overall structure compact, for example, Japanese Patent Laid-Open No. 52-95221. , JP-A-59-42507
JP-A-2-253222 and JP-A-2-253222. FIG. 6 and FIG. 7 respectively show JP-A-2-253222.
FIG. 3 is a diagram showing a schematic configuration of a focus detection optical system described in Japanese Patent Publication and a perspective view thereof. In the figure, 8a and 8b are the entrance pupils of the focus detection optical system determined by the condenser lens 3 and the apertures 5a and 5b of the aperture stop 5, and the light receiving element arrays 7a and 7a in FIG.
7b is arranged such that its longitudinal direction is perpendicular to the paper surface.

In the figure, a light beam emitted from an object to be focused passes through the photographing lens 1 and reaches a planned image forming surface 2, and when the photographing lens 1 is in focus, it is formed on the planned image forming surface 2. Image. The light flux that has passed through the planned image plane 2 is a condenser lens 3
Then, the pupil is relayed, passes through the openings 5a and 5b of the aperture stop 5, and enters the re-imaging lenses 6a and 6b. The re-imaging lenses 6a and 6b have their respective tops on the optical axis O and the planned imaging plane 2 respectively.
Are arranged at positions symmetrical with respect to a plane (not shown) including the respective principal rays of the entrance pupils 8a and 8b that form an image on the plane (a plane perpendicular to the paper surface including the optical axis O in FIG. 6). The light flux incident on the imaging lenses 6a and 6b is
Similarly, the light is guided to the light receiving element rows 7a and 7b which are arranged in parallel at positions symmetrical with respect to a plane not shown. With this configuration, the total length of the light receiving element array can be increased without increasing the size of the focus detection optical system.

[0007]

However, in the configuration shown in FIGS. 6 and 7, the two light beams have different refraction effects due to the component perpendicular to the pupil division direction, and the light beams are reflected by the re-imaging lens. Since the light enters from the off-axis, aberrations are likely to occur, and the aberration correction range expands as the light receiving element array expands, which makes it difficult to correct the aberrations. In this case, if the aberration at the center of a particularly important range-finding range is different, this becomes a factor of degrading the focusing accuracy, which rather deteriorates the focusing accuracy. In addition to these factors, there are other manufacturing factors such as component manufacturing error, assembly error, and phase difference calculation error. However, these factors cannot be reduced or suppressed in the configuration of the prior art described above. There wasn't.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to satisfy both the expansion of the distance measuring range and the improvement of focusing accuracy at the same time. And to provide a focus detection device having a compact structure.

[0009]

In the focus detecting device of the present invention, a focus detecting optical system having a plurality of entrance pupils arranged at intervals capable of ensuring focusing accuracy is provided in the vicinity of a planned image forming surface of a photographing lens. A condenser lens, an aperture stop having a plurality of apertures, a reflecting member disposed between the condenser lens and the aperture stop and having a reflection surface corresponding to the aperture, and re-imaging. The photoelectric conversion means comprises a lens and a plurality of light receiving element rows arranged in parallel corresponding to each of the openings, and a plurality of light fluxes passing through different areas of the photographing lens are reflected by a reflecting member and brightness. In the focus detecting device, which is received by the photoelectric conversion unit through the diaphragm and the re-imaging lens, and which performs focus detection by detecting the phase difference of the plurality of light beams from the light intensity distribution of the light receiving surface of the photoelectric conversion unit, Anti At least one of the reflecting surface of the member, on a different plane from the other of the at least one reflecting surface,
That is, it is characterized in that they are provided so as not to be on the same surface, and the direction of reflected light with respect to incident light is made different from that of at least one other reflecting surface.

According to the above arrangement, first, the light flux emitted from the object to be focused is subjected to the image forming action by the photographing lens and passes through the planned image forming surface. At this time, the light flux passes through the entrance pupils of the plurality of focus detection optical systems arranged at intervals that can apparently secure the focusing accuracy. Further, if the taking lens is in focus, it forms an image on the planned image forming surface. Further, this light flux is transmitted by the pupil from the condenser lens, is reflected by the reflecting member, changes the optical path, and reaches the aperture stop. Since at least one of the reflecting surfaces of the reflecting member is provided on a plane different from other reflecting surfaces, the light fluxes that emit the same object point and are guided to the centers of the respective aperture diaphragms are different from each other. Each has a different optical path inclination. Then, the light fluxes that have passed through the respective aperture diaphragms are subjected to the image forming action by the re-imaging lens,
It is guided to the light receiving element array.

Therefore, if re-imaging lenses are arranged on the reflection optical paths of the respective reflecting surfaces so as to correspond to the respective aperture diaphragms, the refraction effect received by the respective light fluxes in the component perpendicular to the pupil division direction. Can be made substantially the same, and the occurrence of aberration can be suppressed. Further, if one re-imaging lens that corresponds to the light fluxes that have passed through the respective aperture diaphragms on the same incident surface is installed, the re-imaging lens arrangement becomes a problem when it is composed of a plurality of re-imaging lenses. Assembly error due to the accuracy of the spacing,
It is possible to reduce factors of deterioration in focusing accuracy due to manufacturing errors, such as variations in performance of individual reimaging lenses.

A plurality of light receiving element rows arranged in parallel corresponding to the aperture stop can be formed on one chip when they are arranged on the same plane, which is preferable in terms of manufacturing cost and detection accuracy. Further, by integrally forming the reflecting member and the aperture stop, the assembly accuracy can be improved, which is preferable. It should be noted that a method of using a prism instead of the reflecting member having a different inclination of the reflecting surface is also conceivable, but in this case, the refraction action of the prism received by each light beam in a component perpendicular to the pupil division direction is different, and Since the manufacturing and assembling errors of the prism No. 1 influence focusing accuracy, it is not preferable.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. First Embodiment FIG. 1 is a schematic cross-sectional view of a single-lens reflex camera in which the focus detection device of the present embodiment is arranged at the bottom, and FIG. 2 is an enlarged view of a main part of FIG.
In the figure, the focus detection apparatus of the present embodiment includes a photographing lens 1
The condenser lens 13 installed in the vicinity of the first planned image forming surface 12 and the reflecting members 14a and 14b each having a flat reflecting surface and are arranged behind the condenser lens 13 with different reflection angles from each other. And the aperture diaphragms 15 having openings and arranged behind the reflecting members 14a and 14b, respectively.
a, 15b, and the reflecting member 1 passing through the center of the planned image plane 12
Re-imaging lenses 16a and 16b, which are respectively arranged with their optical axes substantially coincident with the light fluxes that reflect the light beams 4a and 14b and pass through the aperture centers of the aperture stops 15a and 15b, respectively.
The light receiving element arrays 17a and 17b are arranged in the vicinity of the image forming positions of the light beams emitted from a and 16b, respectively.
The aperture stops 15a and 15b are arranged so that their aperture planes are perpendicular to the light flux passing through the center of the apertures, and the aperture stops 15a and 15b, the reflection members 14a and 14b, and the re-illuminators 15a and 15b. The respective members of the imaging lenses 16a and 16b are arranged side by side in the direction perpendicular to the paper surface in the figure. Further, the light receiving element rows 17a and 17b are arranged so that the longitudinal direction thereof is perpendicular to the paper surface. 18
Is a quick return mirror, and 19 is a sub-mirror.

In the above structure, the light flux emitted from the object to be focused passes through the taking lens 11 and the quick return mirror 18, which is a half mirror, and then changes the optical path by the sub-mirror 19 to form a projected image. Reach surface 12.
When the taking lens 11 is in focus, an image is formed on the planned image forming surface 12. The light flux that has passed through the planned image forming surface 12 is relayed to the pupil by the condenser lens 13, and is reflected by the reflecting members 14a, 14
The light path is changed by reflecting at b. At this time, the reflection member 1
Since the respective reflecting surfaces of 4a and 14b are respectively provided on different planes which are not the same so that the directions of the reflected light with respect to the incident light are different, the respective light fluxes incident on the reflecting surfaces are directed in different directions. The light is reflected and reaches the aperture diaphragms 15a and 15b provided on the respective reflection optical paths. Therefore, when the respective light fluxes pass through the aperture diaphragms 15a and 15b, the condenser lens 13 and the aperture diaphragm 15
The entrance pupils of the focus detection optical system, which are determined by a and 15b, are arranged at intervals that can secure the focusing accuracy.

The light fluxes passing through the aperture stops 15a and 15b are incident on the re-imaging lenses 16a and 16b. At this time, the optical axes of the re-imaging lenses 16a and 16b are located at the center of the planned image forming surface 12. Since the principal rays of the light flux from the corresponding object point substantially coincide with each other, the occurrence of aberration of the light flux emitted from the re-imaging lenses 16a and 16b can be suppressed to an extremely small level. Further, the light beams emitted from the re-imaging lenses 16a and 16b are guided to the light receiving element rows 17a and 17b arranged side by side so that their longitudinal directions are parallel to each other, and the light receiving element row 17 is provided.
From the light intensity distributions of the light receiving surfaces of a and 17b, the phase difference of the light flux is detected by an arithmetic circuit (not shown), and the focus state of the photographing lens 11 is determined.

Since this embodiment is constructed as described above, the optical paths of the light fluxes reflected by the respective reflecting surfaces of the reflecting member are changed in different directions so as to correspond to the aperture stop, and the light on each optical path is changed. By arranging the re-imaging lens and the light-receiving element array so that their axes are aligned with each other, it is possible to suppress the occurrence of aberration of the light beam emitted from the re-imaging lens, and to arrange the extended light-receiving element array without causing interference. can do. Therefore, the focusing accuracy can be improved, the distance measuring range can be expanded, and the device structure can be made compact. In this case, the reimaging lens
When focusing accuracy is improved by decentering the principal ray of the light beam from the object point corresponding to the center of the planned image forming surface and the optical axis of the re-imaging lens in terms of balance of aberrations with the condenser lens, etc. , May be arranged as such. In the present embodiment, the aperture stops are arranged so that their respective aperture surfaces are on different planes, but there is no practical problem even if they are arranged on the same plane.

Second Embodiment FIG. 3 is a diagram showing a focus detection device of this embodiment. In the figure, the focus detection apparatus of the present embodiment has a condenser lens 13 installed in the vicinity of an expected image forming surface 12 of a photographing lens (not shown) and a flat reflecting surface, and makes the reflecting angles of the reflecting surfaces different from each other. Reflecting members 14a, 14b arranged behind the condenser lens 13 and a reflecting member 1 having an opening
Brightness diaphragms 15 arranged behind 4a and 14b, respectively
a, 15b, and the reflecting member 1 passing through the center of the planned image plane 12
A re-imaging lens 26 arranged such that the optical axes are located at substantially equal distances from the two light beams that reflect the light beams 4a and 14b and pass through the centers of the respective apertures of the aperture diaphragms 15a and 15b;
The re-imaging lens 26 includes light receiving element arrays 17a and 17b arranged near the image forming position of the light beam. The brightness diaphragms 15a and 15b are arranged so that their aperture planes are perpendicular to the light flux passing through the center of the apertures, and the brightness diaphragms 15a and 15b, the reflecting members 14a and 14b, and the light receiving element array. The arrangement positions and directions of the respective members of 17a and 17b are the same as those in the first embodiment.

In the above structure, the light flux emitted from the object to be focused reaches the planned image forming surface 12 through the photographic lens, quick return mirror and sub-mirror (not shown), and when the photographic lens is in focus, the scheduled light is formed. An image is formed on the image plane 12. The light flux that has passed through the planned image forming surface 12 is relayed to the pupil by the condenser lens 13 and is reflected by the reflecting members 14a and 14b to change the optical path. At this time, the reflection member 14a,
Since the respective reflecting surfaces of 14b are provided on different planes which are not the same so that the directions of the reflected light with respect to the incident light are different, the respective light fluxes incident on the reflecting surface are reflected in different directions. And reach the brightness diaphragms 15a and 15b provided on the respective reflected light paths. Therefore,
The respective luminous fluxes pass through the aperture stops 15a and 15b, so that the condenser lens 13 and the aperture stops 15a and 15b
The entrance pupils of the focus detection optical system, which are determined by 5b, are arranged at intervals that can ensure the focusing accuracy.

The light flux that has passed through the aperture stops 15a and 15b is incident on the re-imaging lens 26. At this time, the principal ray of the light flux from the object point corresponding to the center of the planned image forming surface 12 is perpendicular to the direction in which the light receiving element arrays 17a and 17b are arranged (the plane on the paper surface). The light beams emitted from the re-imaging lens 26 are arranged in parallel with each other, and the light receiving element rows 17a, 1 are arranged in parallel.
7b respectively. Then, the light receiving element array 17
The phase difference of the light flux is detected from the light intensity distributions of the light receiving surfaces of a and 17b, and the focusing state of the photographing lens 11 is determined.

Since the present embodiment is constructed as described above, the optical paths of the light beams reflected by the respective reflecting surfaces of the reflecting member are changed in different directions, and this is re-imaged correspondingly on the same incident surface. By guiding the light through the lens to the light receiving element array, there is a problem when a plurality of re-imaging lenses are arranged. It is possible to reduce factors of deterioration in focusing accuracy due to manufacturing errors such as variations in performance, and it is possible to arrange the extended light receiving element arrays without interfering with each other. Therefore, the focusing accuracy can be improved, the distance measuring range can be expanded, and the device structure can be made compact. In the present embodiment as well, the aperture diaphragms are arranged so that their respective aperture surfaces are on different planes, but there is no practical problem even if they are arranged on the same plane. The reflecting members 14a and 14b in FIG. 3 may be configured to reflect light rays parallel to the optical axis of the condenser lens 13 in different directions in a component perpendicular to the paper surface as long as the focusing accuracy is improved.

Third Embodiment FIG. 4 is a diagram showing a focus detection device of this embodiment. In the figure, the focus detection apparatus of the present embodiment has a condenser lens 13 installed in the vicinity of an expected image forming surface 12 of a photographing lens (not shown) and a flat reflecting surface, and makes the reflecting angles of the reflecting surfaces different from each other. Reflecting members 14a and 14b arranged behind the condenser lens 13 and reflecting members 14a and 14b
The brightness diaphragms 25a and 25b provided integrally with the reflecting members on the respective reflecting surfaces, and the brightness diaphragms 25a and 25b reflecting the reflecting members 14a and 14b through the center of the planned image forming surface 12.
The re-imaging lens 26 arranged such that the optical axes are located at substantially equal distances from the two light beams passing through the centers of the respective apertures a and 25b, and the light beam emerging from the re-imaging lens 26. It is composed of light receiving element rows 17a and 17b respectively arranged near the image position. Of the reflecting members 14a and 14b, the aperture diaphragms 15a and 15b, and the light receiving element arrays 17a and 17b,
The arrangement position and direction of each member are the same as those in the first embodiment.

In the above structure, the light flux emitted from the object to be focused reaches the planned image forming surface 12 through the photographic lens, quick return mirror and sub-mirror (not shown), and when the photographic lens is in focus, the scheduled light is formed. An image is formed on the image plane 12. The light flux that has passed through the planned image forming surface 12 is relayed to the pupil by the condenser lens 13 and is reflected by the reflecting members 14a and 14b to change the optical path. At this time, the reflection member 14a,
Since the respective reflecting surfaces of 14b are provided on different planes which are not the same so that the directions of the reflected light with respect to the incident light are different, the respective light fluxes incident on the reflecting surface are reflected in different directions. To be Brightness diaphragms 25a and 25b are provided on the respective reflecting surfaces integrally with the reflecting members 14a and 14b.
In a and 25b, the light receiving element array 17 is reflected by the reflecting surface.
The spread (NA) of the light flux incident on a and 17b is determined. The light flux passes through the aperture diaphragms 25a and 25b respectively, so that the condenser lens 13 and the aperture diaphragms 25a and 25a
The entrance pupils of the focus detection optical system, which are determined by 25b, are arranged at intervals that can secure the focusing accuracy.

The light flux that has passed through the aperture stops 25a and 25b is incident on the re-imaging lens 26. At this time, the principal ray of the light flux from the object point corresponding to the center of the planned image forming surface 12 is perpendicular to the direction in which the light receiving element arrays 17a and 17b are arranged (the plane on the paper surface). The light beams emitted from the re-imaging lens 26 are arranged in parallel with each other, and the light receiving element rows 17a, 1 are arranged in parallel.
Can lead to 7b. Then, the light receiving element array 17a,
The phase difference of the light flux is detected from the light intensity distribution of each light receiving surface in 17b, and the focusing state of the photographing lens 11 is determined.

Since the present embodiment is constructed as described above, by integrating the reflecting member and the aperture stop, it is possible to reduce the factor of deterioration of the focusing accuracy due to errors such as variations in device manufacturing and assembly. it can. Further, by converting the optical paths of the light fluxes reflected by the respective reflecting surfaces of the reflecting member in different directions, it is possible to arrange the extended light receiving element rows without interfering with each other. Therefore, the focusing accuracy can be improved, and at the same time, the distance measuring range can be expanded.
Moreover, the device structure can be made compact.

In each of the above embodiments, two brightness diaphragms are used, but three or more brightness diaphragms are used to guide the light fluxes passing through each brightness diaphragm to the light receiving element array. Alternatively, focus detection may be performed based on information from two or more light receiving element arrays. In this case, information from all the light-receiving element arrays may be used, or two or more light-receiving element arrays may be selected depending on the conditions such as the focusing range and the taking lens, and the information obtained from the selected light-receiving element arrays may be used. May be. Further, the reflecting surface of the reflecting member may be a curved surface or another shape.

[0026]

As described above, according to the present invention, it is possible to provide a focus detection device which has a compact structure and which simultaneously satisfies both the expansion of the distance measuring range and the improvement of focusing accuracy.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a single-lens reflex camera in which a focus detection device according to a first exemplary embodiment of the present invention is arranged at a bottom portion.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a diagram showing a focus detection device according to a second embodiment.

FIG. 4 is a diagram showing a focus detection device according to a third embodiment.

FIG. 5 is a diagram showing an example of a conventional focus detection optical system.

FIG. 6 is a diagram showing a schematic configuration of another conventional focus detection optical system.

FIG. 7 is a perspective view of FIG.

[Explanation of symbols]

 11 ... Photographing lens 12 ... Planned image forming surface 13 ... Condenser lens 14a, 14b ... Reflecting member 15a, 15b, 25a, 25b ... Brightness diaphragm 16a. 16b, 26 ... Reimaging lens 17a. 17b: Light receiving element array

Claims (2)

[Claims] 1. A focus detection optical system having a plurality of entrance pupils arranged at intervals capable of ensuring focusing accuracy, has a condenser lens installed in the vicinity of a planned image forming surface of a photographing lens, and has a plurality of openings. An aperture stop, a reflecting member provided between the condenser lens and the aperture stop and having a reflection surface corresponding to the aperture, a re-imaging lens, and a parallel arrangement corresponding to each of the apertures. And a plurality of light beams passing through different regions of the photographing lens through the reflecting member, the aperture stop and the re-imaging lens. In a focus detection device for performing focus detection by detecting the phase difference of the plurality of light fluxes from the light intensity distribution of the light receiving surface of the photoelectric conversion means, the focus detection device having a smaller number of reflection surfaces of the reflection member. One is that it is provided on a plane different from the other at least one reflecting surface, and the direction of the reflected light with respect to the incident light is different from that of the other at least one reflecting surface. Focus detection device. 2. A focus detection optical system having a plurality of entrance pupils arranged at intervals capable of ensuring focusing accuracy, having a condenser lens installed in the vicinity of a planned image forming surface of a photographing lens and a plurality of openings. A brightness stop, a reflecting member integrally provided with the brightness stop and having a reflection surface corresponding to the opening, a re-imaging lens, and a plurality of juxtaposed corresponding to each of the openings. And a photoelectric conversion means composed of a light receiving element array of the above-mentioned, wherein a plurality of light fluxes passing through different regions of the photographing lens are passed through the reflecting member and the re-imaging lens integrated with the aperture stop, and the photoelectric conversion means. In the focus detection device, the focus detection is performed by detecting the phase difference of the plurality of light beams from the light intensity distribution of the light receiving surface of the photoelectric conversion means, and at least one of the reflection surfaces of the reflection member Is A focus detection device, which is provided on a plane different from that of the other at least one reflecting surface, and the direction of reflected light with respect to incident light is made different from that of the other at least one reflecting surface. .