JP2009092957A - Focus detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a focus while simplifying device constitution and promoting the miniaturization of the device. <P>SOLUTION: A focus detecting device is configured as follows: a condenser lens 31 for partly condensing an object luminous flux from a photographing optical system is disposed in the lower rear part of a camera body 10 while facing obliquely upward, and the luminous flux from the condenser lens 31 is reflected behind the optical axis of the photographing optical system by a first mirror 32, then, the luminous flux reflected by the first mirror 32 is transmitted through an IR cut filter 34, thereafter, the luminous flux is reflected downward by a second mirror 33, separated by a separator lens 35, and made incident on an AF sensor 36 so as to detect the focus. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a focus detection device used in, for example, an autofocus type single-lens reflex camera.

  In general, in this type of focus detection apparatus, a part of an optical image captured by a photographing optical system is captured by a condenser lens via a movable reflective main mirror and sub mirror. The light flux taken into the condenser lens is guided to the AF sensor via the reflection optical system and the separator lens, and the focal length is detected.

In such a focus detection apparatus, when a light beam condensed by a condenser lens is guided as a reflection optical system, for example, the light beam is bent into a Z shape and guided to a separator, whereby a required optical path length with the AF sensor is obtained. Has been proposed (see, for example, Patent Document 1).
JP-A-2003-195134

  However, the above-described focus detection device has a problem that even if the captured light is bent into a Z shape by the reflection optical system, the height dimension increases and the camera body becomes large.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a focus detection apparatus that can realize focus detection that can be simplified in configuration and promote miniaturization.

  The present invention provides a focus detection device for a single-lens reflex camera, a condenser lens that is arranged at the lower part of the camera body and condenses a part of a subject luminous flux from a photographing optical system toward an obliquely upward direction behind the camera, A first mirror that reflects the luminous flux from the condenser lens to the rear of the optical axis of the photographing optical system; a second mirror that reflects the luminous flux reflected by the first mirror downward of the camera; and the second mirror A separator lens that divides the light beam reflected by the mirror, an AF sensor that is disposed below the separator lens and receives the light beam divided by the separator lens, and the first mirror and the second mirror. And an infrared cut filter disposed between them.

  According to the above configuration, a part of the subject luminous flux from the photographing optical system is condensed by the condenser lens, reflected by the first mirror to the rear of the optical axis of the photographing optical system, and is sent to the AF sensor by the infrared cut filter. After unnecessary infrared light components are removed, the light is reflected downward by the second mirror and incident on the AF sensor through the separator lens to be used for focus detection.

  As a result, the height dimension in the assembled state can be reduced while maintaining the required optical path length with the AF sensor, which can contribute to the promotion of downsizing of the camera body. The infrared cut filter is separated from other optical elements such as a condenser lens, a separator lens, the first mirror, and the second mirror, and more specifically, is disposed between the first and second mirrors. Therefore, generation of unnecessary flares and ghosts is suppressed as compared with the case where they are arranged close to or in close contact with these, and the AF sensor is accurate while removing unnecessary infrared light. Focus detection can be performed.

The present invention also provides a condenser lens for focusing a part of a subject light beam from a photographing optical system, which is disposed at a lower part of a camera body and is directed obliquely upward at the rear of the camera. A first mirror that reflects the light beam from the condenser lens to the rear of the optical axis of the photographing optical system, a second mirror that reflects the light beam reflected by the first mirror downward in the camera, and the first mirror A separator lens that divides the light beam reflected by the two mirrors, and an AF sensor that is disposed below the separator lens and receives the light beam divided by the separator lens, and the optical axis of the condenser lens is The first line segment, the line segment connecting the reflection center of the first mirror and the reflection center of the second mirror is defined as a second line segment, and the second mirror is being reflected. A line segment connecting the center of the AF sensor and the center of the AF sensor is a third line segment, an intersection angle between the optical axis of the imaging optical system and the first line segment is α, and the first and second line segments are Β is the intersection angle with γ, and γ is the intersection angle between the second and third line segments.
α <90 °, β <90 °, γ <90 °
It was configured to set to.

  According to the above configuration, part of the subject luminous flux from the photographing optical system is collected by the condenser lens, reflected by the first mirror to the rear of the optical axis of the photographing optical system, and below the camera by the second mirror. After being reflected, the light enters the AF sensor through the separator lens and is used for focus detection.

  As a result, the height dimension in the assembled state can be reduced while maintaining the required optical path length with the AF sensor, which can contribute to the promotion of downsizing of the camera body.

The present invention also provides a focus detection device for a single-lens reflex camera that reflects a subject luminous flux from a photographing optical system and guides it to an eyepiece optical system, and transmits a part of the subject luminous flux. A sub-mirror disposed behind the mirror and reflecting a part of the subject luminous flux downward; and a part of the subject luminous flux disposed below the sub-mirror and reflected by the sub-mirror toward the diagonally upward direction behind the camera , A first mirror that reflects the light beam from the condenser lens to the rear of the optical axis of the photographing optical system, and a second mirror that reflects the light beam reflected by the first mirror to the lower side of the camera. Mirror, a separator lens that splits the light beam reflected by the second mirror, and a separator lens disposed below the separator lens. An AF sensor on which the incident light flux is incident, the optical axis of the condenser lens is a first line segment, and a line segment connecting the reflection center of the first mirror and the reflection center of the second mirror is A second line segment, a line segment connecting the reflection center of the second mirror and the AF sensor center is defined as a third line segment, and the optical axis of the photographing optical system intersects with the first line segment. If the angle is α, the crossing angle between the first line segment and the second line segment is β, and the crossing angle between the second line segment and the third line segment is γ,
α <90 °, β <90 °, γ <90 °
Configured to set.

  According to the above configuration, the subject luminous flux from the photographing optical system is guided by the main mirror to the eyepiece optical system and the sub mirror, and a part of the subject luminous flux guided to the sub mirror is guided to the condenser lens and condensed. After being reflected by the first mirror behind the optical axis of the photographic optical system and reflected by the second mirror below the camera, it enters the AF sensor through the separator lens and is used for focus detection.

  Accordingly, it is possible to reduce the height dimension in the assembled state while maintaining the dimensional accuracy of the distance from the AF sensor in the optical axis direction, which can contribute to the promotion of downsizing of the camera body.

  As described above, according to the present invention, it is possible to provide a focus detection apparatus that can achieve focus detection that can be simplified in configuration and promote miniaturization.

  Hereinafter, a focus detection apparatus for a single-lens reflex camera according to an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a single-lens reflex camera equipped with a focus detection apparatus according to an embodiment of the present invention. A camera body 10 includes a front cover 101, a strobe cover 102, a rear cover 103, and the like. Among these, the front cover 101 is provided with a body mount portion 11 at a substantially central portion of the front surface thereof, and a photographing optical system (not shown) is selectively attached to the body mount portion 11 for photographing.

  A main mirror 12 and a sub mirror 13 are movably disposed in a substantially central part at the rear of the body mount portion 11. In the camera body 10, a focusing plate 14, a pentaprism 15, and an eyepiece optical system 16 are sequentially arranged above the camera on the reflected light path of the main mirror 12, and a focus detection unit constituting a focus detection device below the camera. 30 is arranged corresponding to the reflected light path of the sub-mirror 13.

  An imaging unit 19 including an imaging element is disposed on the optical path behind the sub mirror 13 via a shutter device 17 and a low-pass filter 18. The imaging unit 19 is electrically connected to a printed wiring board 20 on which a CPU (not shown) constituting the processing control unit is mounted.

  As shown in FIGS. 2 and 3, the focus detection unit 30 includes a condenser lens 31, a first mirror 32, a second mirror 33, an infrared cut filter 34, a separator lens 35, and an AF (autofocus) sensor 36. As will be described later, the frame members 37 are assembled and arranged. As this AF sensor 36, for example, a phase difference type sensor using a known sensor array is used.

  The condenser lens 31 is attached to the frame member 37 in a diagonally upward direction behind the camera. An attachment frame 371 is disposed above the optical axis of the condenser lens 31 and is transmitted through the condenser lens 31 below. The first mirror 32 is disposed so as to reflect the incident light beam to the rear of the photographing optical system. The second mirror 33 is arranged on the reflected light path of the first mirror 32 so that the light beam reflected by the first mirror 32 is reflected downward of the camera.

  The separator lens 35 is disposed opposite to the reflected light path of the second mirror 33 via a separator diaphragm 38 (see FIG. 2). On the reflection surfaces of the first and second mirrors 32 and 33, mirror stops 39 and 40 are arranged, respectively.

  The infrared cut filter 34 is arranged in the reflected light path of the first mirror 32 and in the middle of the first and second mirrors 32 and 33. The infrared cut filter 34 is supported by the frame member 37 and is disposed on the reflection light path of the first mirror 32. The infrared light filter 34 is not necessary for the AF sensor 36 from the light flux after being reflected by the first mirror 32. The external light component is removed and reflected by the second mirror 33.

  The second mirror 33 reflects the incident light beam toward the separator lens 35. The AF sensor 36 is disposed on the optical axis of the separator lens 35, and the light beam from the second mirror 33 incident through the separator diaphragm 38 is divided into, for example, four parts and guided to the AF sensor 36.

  The AF sensor 36 is attached to the frame member 37 via, for example, a holder member 372 and is electrically connected to the printed wiring board 20 via a flexible printed wiring board 41. The AF sensor 36 detects the focal position based on the light beam incident from the separator lens 35 and outputs the detection signal to the printed wiring board 20 via the flexible printed wiring board 41.

Here, for example, as shown in FIG. 3, the focus detection unit 30 sets the optical axis of the condenser lens 31 to the first line segment O <b> 1, and reflects the reflection center of the first mirror 32 and the reflection of the second mirror 33. A line segment connecting the center is defined as a second line segment O2, and a line segment connecting the reflection center of the second mirror 33 and the center of the AF sensor 36 is defined as a third line segment O3. The intersection angle that is an acute angle between the optical axis O and the first line segment O1 is α, the intersection angle that is the acute angle between the first line segment and the second line segment O2 is β, and the second line segment O2 is If the intersection angle that is an acute angle with the third line segment O3 is γ,
α <90 °, β <90 °, γ <90 °
Is set to

  Further, the extension line of the second line segment O2 is not parallel to the optical axis of the photographing optical system, and is an acute crossing angle δ on the optical axis extension line of the photographing optical system and behind the sub mirror 13. Cross at.

  Here, the infrared cut filter 34 is disposed at an intermediate portion between the first mirror 32 and the second mirror 33 on the second line segment O2, and is reflected by the first mirror 32 as described above. The light beam from which the infrared light component unnecessary for the AF sensor 36 is removed is guided to the second mirror 33.

  In this way, the condenser lens 31, the first and second mirrors 32 and 33, and the separator lens 35 are set to the intersection angles α, β, γ, and δ of the first to third line segments O1, O2, and O3. Accordingly, it is possible to minimize the height dimension H (see FIG. 3) during assembly while maintaining the required optical path length with the AF sensor 36.

  On the rear surface of the camera body 10, a finder eyepiece frame 21 is disposed on the upper side behind the eyepiece optical system 16, and a back monitor 22 is disposed below the finder eyepiece frame 21 in parallel.

  In the above configuration, the subject light beam captured by the photographing optical system is reflected by the main mirror 12 and guided to the focusing screen 14 and the sub mirror 13. Of these, the subject luminous flux guided to the focusing screen 14 is observed via a finder eyepiece frame 21 guided to the eyepiece optical system 16 via the pentaprism 15.

  Then, a part of the subject light beam that has passed through the main mirror 12 is guided to the sub mirror 13 to be condensed and reflected by the first mirror 32 to the rear of the optical axis of the photographing optical system. The light beam reflected by the first mirror 32 is reflected by the second mirror 33 below the camera after the infrared light component is removed by the infrared cut filter 34.

  The light beam reflected by the second mirror 33 is split through the separator diaphragm 38 and the separator lens 35 and is incident on the AF sensor 36. The AF sensor 36 detects the focal length based on the light beam incident through the separator lens 35, and outputs the detected detection signal to the CPU of the printed wiring board 20 via the flexible printed wiring board 41. The CPU executes a predetermined luminance process based on the input detection signal to generate a drive signal, and drives the adjustment mechanism of the photographing optical system based on the drive signal to perform focus adjustment.

  As described above, the focus detection device arranges the condenser lens 31 that collects a part of the subject light flux from the photographing optical system at the lower part of the camera body 10 in the obliquely upward direction behind the camera. The light flux from the condenser lens 31 is reflected by the first mirror 32 to the rear of the optical axis of the photographic optical system, and the light flux reflected by the first mirror 32 is passed through the infrared cut filter 34, The second mirror 33 is reflected downward from the camera, is divided by the separator lens 35 and is incident on the AF sensor 36 to detect the focal point.

  According to this, the height dimension in the assembled state can be reduced while maintaining the required optical path length between the condenser lens 31 and the AF sensor 36 in the focus detection unit, and the miniaturization of the camera body 10 is promoted. Can contribute.

  The infrared cut filter 34 is separated from other optical elements such as the condenser lens 31, the separator lens 35, the first mirror 32, and the second mirror 33, and more specifically, the first and second reflections. Since it is disposed between the mirrors 32 and 33, generation of unnecessary flare and ghost is suppressed as compared with the case where they are disposed close to or in close contact with these, and the AF sensor 36 is irradiated with unnecessary light. Accurate focus detection can be performed while removing certain infrared light.

  Therefore, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention at the stage of implementation. Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements.

  For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the effect of the invention can be obtained. In such a case, a configuration in which this configuration requirement is deleted can be extracted as an invention.

  Moreover, this invention can also obtain the following structures based on the said embodiment.

(Appendix 1)
In a focus detection device for a single-lens reflex camera,
A condenser lens disposed at the bottom of the camera and concentrating part of the subject luminous flux from the photographic optical system, facing the camera diagonally upward,
A first mirror that reflects light from the condenser lens to the rear of the optical axis of the photographing optical system;
A second mirror that reflects the light reflected by the first mirror downward in the camera;
A separator lens that separates light reflected by the second mirror;
An AF sensor disposed below the separator lens;
An infrared cut filter disposed between the first mirror and the second mirror;
A focus detection apparatus for a single-lens reflex camera.

(Appendix 2)
The optical axis of the condenser lens is defined as a first line segment, the line segment connecting the reflection center of the first mirror and the reflection center of the second mirror is defined as a second line segment, and A line segment connecting the reflection center and the center of the AF sensor is defined as a third line segment, an intersection angle between the optical axis of the photographing optical system and the first line segment is α, and the first line segment and the second line segment If the intersection angle with the line segment is β, and the intersection angle between the second line segment and the third line segment is γ,
α <90 °, β <90 °, γ <90 °
A focus detection apparatus for a single-lens reflex camera according to Supplementary Note 1, wherein the focus detection apparatus is a single-lens reflex camera.

(Appendix 3)
In a focus detection device for a single-lens reflex camera,
A condenser lens that is disposed at the bottom of the camera and condenses a part of the subject luminous flux from the photographing optical system in a diagonally upward direction behind the camera;
A first mirror that reflects light from the condenser lens to the rear of the optical axis of the photographing optical system;
A second mirror that reflects the light reflected by the first mirror downward in the camera;
A separator lens that separates light reflected by the second mirror;
An AF sensor disposed below the separator lens;
The optical axis of the condenser lens is the first line segment, the line segment connecting the reflection center of the first mirror and the reflection center of the second mirror is the second line segment, and A line segment connecting the reflection center of the mirror 2 and the center of the AF sensor is defined as a third line segment, and an intersection angle between the optical axis of the photographing optical system and the first line segment is α, and the first line segment. And the intersection angle between the second line segment and the second line segment is β, and the intersection angle between the second line segment and the third line segment is γ,
α <90 °, β <90 °, γ <90 °
A focus detection device for a single-lens reflex camera.

(Appendix 4)
4. The focus detection apparatus for a single-lens reflex camera according to appendix 3, wherein an infrared cut filter is disposed between the first mirror and the second mirror.

(Appendix 5)
In a focus detection device for a single-lens reflex camera,
A reflective main mirror that reflects the subject luminous flux from the photographic lens and guides it to the eyepiece optical system, and transmits a part of the subject luminous flux;
A sub-mirror disposed behind the reflecting mirror and reflecting a part of the subject luminous flux downward;
A condenser lens that is disposed below the sub-mirror and condenses a part of the subject luminous flux reflected by the sub-mirror in a diagonally upward direction behind the camera;
A first mirror that reflects light from the condenser lens to the rear of the optical axis of the photographing optical system;
A second mirror that reflects the light reflected by the first mirror downward in the camera;
A separator lens that separates light reflected by the second mirror;
An AF sensor disposed below the separator lens;
The optical axis of the condenser lens is the first line segment, the line segment connecting the reflection center of the first mirror and the reflection center of the second mirror is the second line segment, and A line segment connecting the reflection center of the mirror 2 and the center of the AF sensor is defined as a third line segment, and an intersection angle between the optical axis of the photographing optical system and the first line segment is α, and the first line segment. And the intersection angle between the second line segment and the second line segment is β, and the intersection angle between the second line segment and the third line segment is γ,
α <90 °, β <90 °, γ <90 °
A focus detection device for a single-lens reflex camera.

(Appendix 6)
6. The focus detection device for a single-lens reflex camera according to appendix 5, wherein an infrared cut filter is disposed between the first mirror and the second mirror.

It is sectional drawing shown in order to demonstrate schematic structure of the single-lens reflex camera which has arrange | positioned the focus detection apparatus which concerns on one embodiment of this invention. It is the perspective view which showed the external appearance structure of the focus detection part of FIG. It is sectional drawing shown in order to demonstrate the arrangement configuration of the focus detection part of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Camera body, 101 ... Front cover, 102 ... Strobe cover, 103 ... Rear cover, 11 ... Body mount part, 12 ... Main mirror, 13 ... Sub mirror, 14 ... Focus plate, 15 ... Pentaprism, 16 ... Eyepiece optical system , 17 ... Shutter device, 18 ... Low pass filter, 19 ... Imaging unit, 20 ... Printed wiring board, 21 ... Viewfinder eyepiece frame, 22 ... Back monitor, 30 ... Focus detection unit, 31 ... Condenser lens, 32 ... First mirror , 33 ... second mirror, 34 ... infrared cut filter, 35 ... separator lens, 36 ... AF sensor, 37 ... frame member, 371 ... mounting frame, 372 ... holder member, 38 ... separator diaphragm, 39, 40 ... mirror Diaphragm, 41 ... Flexible printed circuit board.

Claims (6)

In a focus detection device for a single-lens reflex camera,
A condenser lens that is disposed at the bottom of the camera body and condenses a part of the subject luminous flux from the photographing optical system toward the obliquely upward direction behind the camera;
A first mirror that reflects the light beam from the condenser lens to the rear of the optical axis of the photographing optical system;
A second mirror that reflects the light beam reflected by the first mirror downward of the camera;
A separator lens that splits the light beam reflected by the second mirror;
An AF sensor that is disposed below the separator lens and receives a light beam divided by the separator lens;
An infrared cut filter disposed between the first mirror and the second mirror;
A focus detection apparatus comprising: The optical axis of the condenser lens is defined as a first line segment, the line segment connecting the reflection center of the first mirror and the reflection center of the second mirror is defined as a second line segment, and A line segment connecting the reflection center and the center of the AF sensor is defined as a third line segment, an intersection angle between the optical axis of the photographing optical system and the first line segment is α, and the first line segment and the second line segment If the intersection angle with the line segment is β, and the intersection angle between the second line segment and the third line segment is γ,
α <90 °, β <90 °, γ <90 °
The focus detection apparatus according to claim 1, wherein In a focus detection device for a single-lens reflex camera,
A condenser lens that is disposed at the bottom of the camera body and condenses a part of the subject luminous flux from the photographing optical system toward the obliquely upward direction behind the camera;
A first mirror that reflects the light beam from the condenser lens to the rear of the optical axis of the photographing optical system;
A second mirror that reflects the light beam reflected by the first mirror downward of the camera;
A separator lens that splits the light beam reflected by the second mirror;
An AF sensor that is disposed below the separator lens and receives a light beam divided by the separator lens;
An optical axis of the condenser lens is a first line segment, a line segment connecting the reflection center of the first mirror and the reflection center of the second mirror is a second line segment, and A line segment connecting the reflection center of the mirror 2 and the center of the AF sensor is defined as a third line segment, and an intersection angle between the optical axis of the photographing optical system and the first line segment is α, and the first line segment. And the intersection angle between the second line segment and the second line segment is β, and the intersection angle between the second line segment and the third line segment is γ,
α <90 °, β <90 °, γ <90 °
A focus detection apparatus characterized by being set to   The focus detection apparatus according to claim 3, wherein an infrared cut filter is disposed between the first mirror and the second mirror. In a focus detection device for a single-lens reflex camera,
A main mirror that reflects the subject luminous flux from the photographing optical system and guides it to the eyepiece optical system, and transmits a part of the subject luminous flux;
A sub-mirror disposed behind the main mirror and reflecting a part of the subject luminous flux downward;
A condenser lens that is disposed below the sub-mirror and condenses a part of the subject luminous flux reflected by the sub-mirror in a diagonally upward direction behind the camera;
A first mirror that reflects the light beam from the condenser lens to the rear of the optical axis of the photographing optical system;
A second mirror that reflects the light beam reflected by the first mirror downward of the camera;
A separator lens that splits the light beam reflected by the second mirror;
An AF sensor that is disposed below the separator lens and receives a light beam divided by the separator lens;
An optical axis of the condenser lens is a first line segment, a line segment connecting the reflection center of the first mirror and the reflection center of the second mirror is a second line segment, and A line segment connecting the reflection center of the mirror 2 and the center of the AF sensor is defined as a third line segment, and an intersection angle between the optical axis of the photographing optical system and the first line segment is α, and the first line segment. And the intersection angle between the second line segment and the second line segment is β, and the intersection angle between the second line segment and the third line segment is γ,
α <90 °, β <90 °, γ <90 °
A focus detection apparatus characterized by being set to   The focus detection apparatus according to claim 5, wherein an infrared cut filter is disposed between the first mirror and the second mirror.

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