JP2006003472A - Focus detector and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a focus detector which can be efficiently stored in a limited space in a camera and is capable of high precise pupil adjustment, and to provide an imaging apparatus comprising the focus detector. <P>SOLUTION: The focus detector for detecting a focus from object light which is image-formed on an imaging device comprises a focus detecting optical system which guides the object light onto the imaging device, a holding member for holding the focus detecting optical system which has a pair of axis parts extended in the longitudinal direction of the imaging device and is rotatable around the axis parts and an eccentric cam which is fitted to one side of the axis parts and moves the axis parts in the width direction of the imaging device. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention generally relates to an imaging apparatus, and more particularly to a focus detection apparatus that detects the focus of subject light. The present invention is suitable, for example, for a focus detection device that detects the focus state of a photographic lens from the phase difference between two subject images that are transmitted through different pupil regions of a projection lens.

  In a secondary imaging phase difference type focus detection device used in a single-lens reflex camera or the like, a sub mirror is provided between a photographing lens and a photographing element, and a part of subject light is bent by the sub mirror to be used as a focus detection device. Incident. Therefore, an adjustment mechanism that aligns the optical axis of the focus detection device and the optical axis of the image sensor, that is, a so-called pupil adjustment mechanism is required.

  For example, an optical path folding mirror is placed between the aperture of the secondary optical system and a field lens that projects the aperture onto the pupil of the photographic lens, and the mirror angle is adjusted by the screwing amount of the adjusting screw attached to the optical path folding mirror. A focus detection apparatus having an angle adjustment mechanism for adjustment has been proposed (see, for example, Patent Document 1). Such a focus detection apparatus adjusts the image position of the aperture projected on the photographing lens pupil via the field lens by changing the angle of the optical path bending mirror, thereby performing pupil adjustment.

  In addition, there are three contact surfaces for attaching to the camera body, and two of them can be changed in height by the screwing amount of the screw, and the inclination of the focus detection device with respect to the camera is controlled by the screwing amount of the two screws. The focus detection device (for example, refer to Patent Document 2) that adjusts and adjusts the pupil exit, or the focus detection device is attached to the camera using three screws and a spring, and the screw detection amount of the focus detection device with respect to the camera is adjusted. A focus detection apparatus that adjusts the tilt has also been proposed (see, for example, Patent Document 3).

Furthermore, a focus detection apparatus that performs pupil adjustment without using screws has also been proposed (see, for example, Patent Document 4). Such a focus detection apparatus has a holding member that holds a focus detection optical system, and the holding member can be rotated by a pair of shafts extending in the front-rear direction of the camera, and one of the shafts is fitted into the inclined long hole. The axis position can be adjusted with. Therefore, the tilting of the focus detection device with respect to the camera can be adjusted and the pupil adjustment can be performed by rotating the shaft and adjusting the position of the shaft.
Japanese Patent Publication No. 7-27110 Japanese Examined Patent Publication No. 7-31303 JP 2000-19382 A Japanese Patent Publication No. 6-7220

  However, since the conventional pupil adjustment mechanism proposed in Patent Documents 1 to 3 performs pupil adjustment based on the screwing amount of the screw, it is limited by the pitch of the screw, and high-precision adjustment is difficult. There was a problem.

  On the other hand, the pupil adjustment mechanism proposed in Patent Document 4 is not limited by the pitch of the screw, and thus can be adjusted with high accuracy. However, there is a lens communication unit for communicating between the camera and the photographing lens in front of the focus detection device, and a shutter unit behind the focus detection device, so there is no room in the front-rear direction. For this reason, it is very difficult to provide a pair of shafts, a bearing mechanism, and a shaft position adjusting mechanism in the front-rear direction of the holding member of the focus detection optical system in a limited space in the camera. Furthermore, in the case of a digital single-lens reflex camera, a low-pass filter that reduces color moire is disposed between the shutter unit and the image sensor. Therefore, the shutter unit is further disposed in front of the camera, and the space between the lens communication unit and the shutter unit is further narrowed.

  Therefore, the present invention solves such a conventional problem, and can be efficiently stored in a limited space in the camera, and can perform high-precision pupil adjustment, and a focus detection device and an imaging device For illustrative purposes.

  In order to achieve the above object, a focus detection apparatus according to an aspect of the present invention is a focus detection apparatus that detects a focus from subject light imaged on an image sensor, and the subject light is projected onto the image sensor. A focus detection optical system that guides light, a pair of shaft portions extending in a longitudinal direction of the imaging element, and a holding member that holds the focus detection optical system and is rotatable about the shaft portions; And an eccentric cam that is fitted to one of the shaft portions and moves the shaft portion in a short direction of the imaging element.

  An imaging device according to another aspect of the present invention is an imaging device that captures an image of a subject, and surrounds the above-described focus detection device and the focus detection device and attaches the focus detection device to the imaging device. And a member.

  According to still another aspect of the present invention, a focus detection apparatus detects a focus from subject light imaged on an image sensor, and uses the focus detection apparatus for an imaging device that captures an image of a subject reflected by the subject light. And it has a focus detection optical system for guiding the subject light on the image sensor and a pair of shaft portions extending in the longitudinal direction of the image sensor, and is rotatable around the shaft portion. A holding member that holds the focus detection optical system, an eccentric cam that fits in one of the shaft portions and moves the shaft portion in the short direction of the image sensor, and extends in the short direction of the image sensor And a metal member that attaches the focus detection optical system, the holding member, and the eccentric cam to the imaging device. It is characterized by having.

  Further objects and other features of the present invention will become apparent from the preferred embodiments described below with reference to the accompanying drawings.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to accommodate efficiently in the limited space in a camera, the focus detection apparatus and imaging device which can adjust pupil extraction with high precision can be provided.

  Hereinafter, a focus detection apparatus and an imaging apparatus including the focus detection apparatus according to an aspect of the present invention will be described with reference to the accompanying drawings. In addition, in each figure, the same reference number is attached | subjected about the same member and the overlapping description is abbreviate | omitted.

  FIG. 1 is a schematic perspective view showing an optical system of an imaging apparatus (camera) 1 having a focus detection apparatus 100 of the present invention. FIG. 2 is a schematic cross-sectional view from the side of the imaging apparatus 1. In this embodiment, the imaging device 1 is a single-plate digital color camera using an imaging device 40 such as a CCD or CMOS sensor (hereinafter referred to as “camera 1”), and the imaging device is continuous or single-shot. To obtain an image signal representing a moving image or a still image. The camera 1 includes an imaging optical system 10, a main mirror 20, a sub mirror 30, an image sensor 40, an optical low-pass filter 50, a shutter unit 60, and a lens communication unit 70.

  The main mirror 20 divides the subject light flux from the photographing optical system 10. A part of the main mirror 20 is a half mirror, which transmits a part of the subject luminous flux and reflects the remaining subject luminous flux upward.

  The sub mirror 30 reflects the subject light beam transmitted through the main mirror 20 downward. A focus detection device 100 that detects the focus state of the photographing optical system 10 is disposed below the sub mirror 30, and the subject light flux reflected by the sub mirror 30 is guided to the focus detection device 100.

  As shown in FIG. 2, the main mirror 20 is pivotally supported on the camera body by a shaft portion 22, and is configured to be rotatable with respect to the camera body. The sub mirror 30 is pivotally supported by the holding member of the main mirror 20 by the shaft portion 32 and is configured to be rotatable with respect to the main mirror 20. As a result, the main mirror 20 is rotated at the shaft portion 22 and the sub mirror 30 is rotated at the shaft portion 32, the main mirror 20 is inclined 45 degrees with respect to the optical axis of the photographing optical system 10, and the sub mirror 30 is moved downward. A state inclined by 33 degrees (hereinafter referred to as “mirror-down state”) and a state where both the main mirror 20 and the sub mirror 30 are folded upward and completely retracted from the subject light beam (hereinafter referred to as “mirror-up state”). It is possible to take two states.

  In the mirror-down state, the subject light flux from the photographing optical system 10 is divided into two directions: an upper finder optical system direction and a lower focus detection device 100 direction. On the other hand, in the mirror-up state, the subject luminous flux from the photographic optical system 10 is all guided to the image sensor 40.

  The image sensor 40 has a function of receiving a subject light beam imaged by the photographing optical system 10 and converting it into an image signal. In this embodiment, the image sensor 40 is an area sensor of a type that converts the exposed light into an electrical signal for each pixel, accumulates charges according to the amount of light, and reads the charges.

  The image sensor 40 is packaged, for example, and is embodied as a CMOS process compatible sensor (hereinafter abbreviated as “CMOS sensor”) which is one of amplification type solid-state image sensors. In the CMOS sensor, the MOS transistor of the area sensor part and peripheral circuits such as an image sensor, a drive circuit, an AD conversion circuit, and an image processing circuit can be formed in the same process. It can be greatly reduced. The CMOS sensor can randomly access any pixel. As a result, it is easy to read out data for display, and real-time display can be performed at a high display rate. The image sensor 40 performs the display image output operation and the high-definition image output operation using such features.

  An optical low-pass filter that limits the cut-off frequency of the imaging optical system 10 so that a spatial frequency component higher than necessary of the object image is not transmitted to the imaging element 40 in the optical path from the imaging optical system 10 to the imaging element 40. 50 is provided. The optical low-pass filter 50 is also formed with an infrared cut filter.

  On the light incident surface side of the optical low-pass filter 50, a shutter unit 60 for limiting the exposure time of the subject light beam incident on the image sensor 40 is disposed. The shutter unit 60 travels in the short direction of the image sensor 40 and has a front curtain 62 and a rear curtain 64 composed of a plurality of sheets. The shutter time is determined by the travel interval between the front curtain 62 and the rear curtain 64. Control.

  The shutter unit 60 requires a space for storing the rear curtain 64 in the upper part and a space for storing the front curtain 64 in the lower part. Accordingly, the shutter unit 60 requires a large space in the vertical direction other than the opening 60a. Therefore, as shown in FIG. 2, the shutter unit 60 is also present behind the focus detection device 100, and there is almost no room for space behind the focus detection device 100. That is, it is very difficult to provide a rotation shaft behind the focus detection device 100.

  The lens communication unit 70 has a function of performing communication between the detachable photographing lens included in the photographing optical system 10 and the camera body. The lens communication unit 70 is preferably provided below the vicinity of the joint between the photographic lens and the camera because of the mirror storage space when the main mirror 20 and the sub mirror 30 are mirrored up. Thereby, the lens communication unit 70 exists in front of the focus detection apparatus 100, and there is almost no space in front of the focus detection apparatus 100. That is, it is very difficult to provide a rotation shaft in front of the focus detection apparatus 100.

  The focus detection apparatus 100 has a function of performing focus detection by a phase difference detection method. The focus detection apparatus 100 includes two subjects obtained from a pair of different pupil regions (first pupil regions 12a and 12b, second pupil regions 14a and 14b, and third pupil regions 16a and 16b) of the photographing optical system 10. The focus state of the photographic optical system 10 is detected from the relative positional relationship of the images. Note that detecting the focus state of the photographic optical system 10 based on the relative positional relationship between two subject images obtained from a pair of different pupil regions of the photographic optical system 10 is a technique well known to those skilled in the art. Detailed explanation on is omitted.

  Since the first pupil regions 12 a and 12 b are arranged in the longitudinal direction of the image sensor 40, the obtained two subject images are opposite to the longitudinal direction of the image sensor 40 according to the focus state of the imaging optical system 40. Move in the direction. The focus detection apparatus 100 receives two subject images with two line sensors arranged in the longitudinal direction of the image sensor 40, acquires two image signals, and calculates a relative positional deviation amount (phase difference) between the two image signals. obtain. Since the phase difference is substantially proportional to the defocus amount of the photographing optical system 10, the focus detection state of the photographing optical system 10 can be detected based on the phase difference. Therefore, in the first pupil regions 12a and 12b, good focus detection can be performed on a subject having contrast in the horizontal direction.

  On the other hand, since the second pupil regions 14a and 14b are arranged in the short direction of the image sensor 40, good focus detection can be performed on a subject having contrast in the vertical direction. Since the focus detection apparatus 100 according to the present embodiment performs focus detection using a subject light beam that has passed through a pair of pupil regions arranged in the longitudinal direction and the short direction of the image sensor 40 of the imaging optical system 10, the focus detection apparatus 100 has contrast only in the vertical direction. Focus detection can be performed for both a subject and a subject having contrast only in the horizontal direction.

  Further, the third pupil regions 16a and 16b are arranged at a distance apart from the first pupil regions 12a and 12b. The first pupil regions 12a and 12b are, for example, pupil regions corresponding to a light beam of F5.6, and are arranged in a region through which a subject light beam is transmitted when a photographing lens brighter than F5.6 is attached. On the other hand, the third pupil regions 16a and 16b are pupil regions corresponding to the light flux of F2.8, and are arranged in a region through which the subject light flux is transmitted when a photographing lens brighter than F2.8 is attached.

  The center-of-gravity interval between the pair of pupil regions is called a baseline length, and the amount of shift of the subject image obtained from the pupil region is approximately proportional to the baseline length. Since the third pupil regions 16a and 16b have a longer baseline length than the first pupil regions 12a and 12b, the amount of displacement of the subject image obtained when the photographing lens is in the same defocus state is larger. Therefore, when a lens brighter than F2.8 is attached, the third pupil regions 16a and 16b can perform focus detection with higher accuracy than the first pupil regions 12a and 12b.

  The focus detection apparatus 100 includes a cover 110, a light shielding sheet 115, a field lens 120, a holding member 125, a plate 130, an eccentric cam 140, an IR-CUT filter 150, a folding mirror 155, a diaphragm 160, A re-imaging lens 165, a sensor holder 170, a contact member 175, a focus detection sensor 180, and separators 190 and 195 are included.

  The cover 110 is a light shielding member that limits the subject light flux reflected by the sub mirror 30. The cover 110 has an opening that transmits only the light beam necessary for focus detection out of the subject light beam, and the opening is disposed in the vicinity of a substantially image forming surface of the photographing optical system 10 to focus the necessary light beam on the focus detection optical system. Guide to the system and shield unnecessary luminous flux. Since the upper surface of the cover 110 is exposed on the inner wall of the camera body, a light shielding line is provided so that the reflected light does not reach the image sensor 40.

  As shown in FIG. 3, the cover 110 has two holes 110 a and is fixed to the holding member 125 by fitting the holes 110 a to the protrusions 125 f of the holding member 125. Here, FIG. 3 is a developed perspective view in which elements constituting the focus detection apparatus 100 are developed.

  Further, as shown in FIG. 7, the cover 110 has openings 110b, 110c, 110d, and 110e that transmit only the light beam necessary for focus detection out of the subject light beam. Since the openings 110b, 110c, 110d, and 110e are disposed substantially at the position of the imaging surface of the photographing optical system 10, the shapes of the openings 110b, 110c, 110d, and 110e are substantially the same as the focus detection area on the imaging surface. It has a shape. Here, FIG. 7 is a schematic perspective view showing the focus detection apparatus 100 as viewed from the image sensor 40 side.

  The reason why the opening 110b near the center of the cover 110 has a cross shape is that the vertical visual field and the horizontal visual field cross each other. A pair of openings 110c provided above and below the cover 110 has a horizontal field of view. A pair of openings 110d provided on the left and right sides of the cover 110 has a vertical field of view. The opening 110d is an opening for two vertical visual fields arranged vertically, and the two openings are connected to form one long opening. The opening 110e provided outside the opening 110d also has a vertical field of view. The cover 110 has a cross field of view at the center, a horizontal field of view at the top and bottom, a vertical field of view that is vertically arranged at the left and right of the center cross field of view, and a vertical field of view on each of the outsides. 9-point AF is realized.

  The vertical field of view is an opening for a light beam transmitted through a pair of different pupil regions 14a and 14b of the photographing optical system 10 shown in FIG. 1 because the moving direction of the image on the focus detection sensor 180 is the vertical direction. . In the horizontal field of view, since the moving direction of the image on the focus detection sensor 180 is the horizontal direction, the light beams transmitted through a pair of different pupil regions 12a and 12b and pupil regions 16a and 16b of the photographing optical system 10 shown in FIG. Is an opening for.

  The light shielding sheet 115 further restricts the light beam transmitted through the opening of the cover 110.

  The field lens 120 projects the pupil of the focus detection optical system onto the pupil of the photographing optical system 10. FIG. 4 is a schematic front view of the field lens 120. Referring to FIG. 4, the lens unit 121 of the field lens 120 is divided into a central lens unit 121 a that transmits the luminous flux in the central ranging area and a peripheral lens unit 121 b that transmits the luminous flux in the peripheral ranging area. Since the lens shapes of the central lens portion 121a and the peripheral lens portion 121b are different from each other, they cannot be connected completely smoothly and the edge portion 122 is generated. When the object light flux strikes the edge portion 122, scattered light is generated, which causes ghost light. Therefore, a light shielding sheet 115 is provided on the light incident surface side of the field lens 120 to completely hide the edge portion 122 of the field lens 120, thereby preventing ghosts caused by scattered light.

  The holding member 125 holds each component constituting the focus detection device 100. Specifically, the holding member 125 includes a cover 110, a light shielding sheet 115, a field lens 120, an eccentric cam 140, an IR-CUT filter 150, a folding mirror 155, an aperture 160, a re-imaging lens 165, a sensor holder 170, and a contact. The member 175, the focus detection sensor 180, and the separators 190 and 195 are held.

  FIG. 5 is a schematic perspective view showing the holding member 125. As shown in FIG. 5, the holding member 125 has a pair of shaft portions 125 a and 125 b that extend in the longitudinal direction of the image sensor 40. Since the lens communication unit 70 exists in front of the holding member 125 and the shutter unit 60 exists in the rear of the holding member 125, it is very difficult to provide the shaft portions 125a and 125b in the front-rear direction of the holding member 125. is there. Therefore, in the focus detection apparatus 100 of the present invention, by providing the pair of shaft portions 125a and 125b in the left-right direction with a relatively large space, the space in the camera 1 can be used effectively, and the size of the camera 1 can be increased. Can be prevented.

  Referring to FIG. 3, the eccentric cam 140 is fitted to the shaft portion 125 a and is rotatable with respect to the holding member 125.

  The holding member 125 is attached to the camera body via the plate 130. When the camera body and the holding member 125 are made of different materials, the linear expansion coefficient is often different. Then, the expansion / contraction rate differs between the camera body and the holding member 125 due to temperature change, and the holding member 125 may be distorted due to deformation of the camera body. Since the elements constituting the focus detection optical system are held by the holding member 125, the distortion of the holding member 125 is directly connected to the focus detection result error. Therefore, in the present invention, the holding member 125 is not directly fixed to the camera body, but is fixed via the plate 130 made of a material having a linear expansion coefficient close to that of the holding member 125. As a result, when the linear expansion coefficients are different between the camera body and the plate 130, the deformation is absorbed by the plate 130, and the holding member 125 is not distorted.

  The plate 130 has a function of attaching the holding member 125 to the camera body. The plate 130 is preferably made of a material having a large Young's modulus in order to make it difficult to transmit the deformation of the camera body to the holding member 125. For example, a plate obtained by bending a metal plate such as stainless steel or iron by pressing or the like is used as the plate 130.

  Furthermore, in order to maintain the strength of the plate 130, it is desirable that the shape be connected in an annular shape. In this embodiment, the plate 130 has an annularly connected shape surrounding the holding member 125. As a result, the strength sufficient to absorb the deformation of the camera body can be maintained, and distortion of the holding member 125 can be prevented.

  On the plate 130, U-shaped bearing portions 130a and 130b having contact portions in the short direction of the image sensor 40 are formed. The bearing portions 130a and 130b have a dimension in which the width in the front-rear direction of the camera is fitted to the shaft portions 125a and 125b, and when the shaft portions 125a and 125b are fitted to the bearing portions 130a and 130b, The position in the camera front-rear direction with respect to the plate 130 is uniquely determined. The U-shaped hole of the bearing part 130a is longer than the U-shaped hole of the bearing part 130b, and when the holding member 125 is brought to the position of the design value with respect to the plate 130, the shaft part 125a and the bearing part 130a are short of the image sensor 40. Although it does not contact in the direction, the shaft portion 125b and the bearing portion 130b are in contact with each other. That is, the shaft portion 125b and the bearing portion 130b are in contact with each other in the front-rear direction of the camera and the short side direction of the image sensor 40, and are uniquely positioned. The shaft portion 125a and the bearing portion 130a can move only in the short direction of the image sensor 40. It is configured.

  Further, as shown in FIG. 7, the plate 130 has screw holes 130 c at three locations and can be screwed to the camera body.

  The eccentric cam 140 is fitted and held in the shaft portion of the holding member 125. The eccentric cam 140 fitted to the shaft portion 125 a of the holding member 125 is in contact with the plate 130 on the outer periphery to determine the height position of the shaft portion 125 a with respect to the plate 130. Thereby, as described above, the position of the shaft portion 125 a that was movable in the short direction of the image sensor 40 is uniquely determined by the rotation angle of the eccentric cam 140. The holding member 125 is rotatable with respect to the plate 130 with the shaft portions 125a and 125b as the rotation centers. Further, the rotational operation of the optical axis of the photographing optical system 10 can be performed by changing the height position of the shaft portion 125a by the rotation of the eccentric cam 140.

  Since the lens communication unit 70 exists in front of the holding member 125 and the shutter unit 60 exists in the rear of the holding member 125, it is very difficult to arrange the eccentric cam 140 in the front-rear direction of the holding member 125. . Therefore, in the focus detection apparatus 100 of the present invention, the eccentric cam 140 is disposed in the left-right direction with a relatively large space, thereby effectively utilizing the space in the camera 1 and preventing the camera 1 from becoming large. it can.

  The focus detection apparatus 100 of the present invention adjusts the inclination in two directions by adjusting the shaft 125a and 125b of the holding member 125 as an axis and adjusting the height position of the shaft 125a by rotating the eccentric cam 140. Is possible. The focus detection apparatus 100 is configured to perform so-called pupil adjustment that adjusts the deviation between the optical axis of the focus detection optical system and the optical axis of the photographing optical system by adjusting the tilt in the two directions. After the pupil adjustment is completed, an instantaneous adhesive or welding agent is poured into the contact surface, and the holding member 125, the plate 130, and the eccentric cam 140 are fixed.

  If the cover 110 is attached while the bearing portions 130a and 130b of the plate 130 are in contact with the shaft portions 125a and 125b of the holding member 125, the cover 110 prevents the plate 130 from coming off. In other words, the plate 130 is configured not to be detached from the holding member 125 even if it is not bonded.

  The IR-CUT filter 150 is provided with a multilayer vapor deposition film that reflects infrared light on the glass surface, and reflects the infrared light. Since the optical low-pass filter 50 including an infrared cut filter is disposed on the light incident surface side of the image sensor 40, light having a wavelength longer than that of visible light is cut and does not reach the image sensor 40. If the spectral characteristics of light received by the focus detection sensor 180 and the image sensor 40 are different, the focus position changes. In such a case, if the photographing optical system 10 is brought to the focus position obtained by the focus detection device 100, a phenomenon that the image sensor 40 is out of focus occurs. The IR-CUT filter 150 aligns the spectral characteristics of light reaching the image sensor 40 and the focus detection sensor 180, and plays a role in preventing such problems.

  The folding mirror 155 has an aluminum deposited film on the glass surface, and reflects light having a wavelength of 400 nm to 800 nm with substantially the same reflectance. The folding mirror 155 has a function of folding the subject light flux in order to accommodate the focus detection device 100 in a limited space below the camera, and contributes to downsizing of the focus detection device 100.

  The diaphragm 160 is disposed in the optical path of the re-imaging optical system and constitutes a part of the re-imaging optical system. A pair of apertures is formed in the diaphragm 160 to limit the light beam incident on the pair of lens portions of the re-imaging lens 165. The diaphragm 160 is projected onto the pupil of the photographing optical system 10 by the field lens 120. Light beams from a pair of different pupil regions in the pupil of the photographing optical system 10 are transmitted through the projected pair of apertures of the aperture stop 130. The diaphragm 130 is made of a metal plate such as phosphor bronze or a light shielding resin sheet. In the case of using a phosphor bronze plate, the aperture 130 is manufactured by punching the phosphor bronze plate with a mold and plating the phosphor bronze plate after the punching. In the case of the light shielding resin sheet, it can be produced simply by punching with a mold.

  The re-imaging lens 165 has a pair of lenses corresponding to the pair of apertures of the diaphragm 160, and forms images of light beams from different pupil regions of the photographing optical system 10 on the image sensor 40.

  The re-imaging lens 165 has two dowels 165a, and is fitted into a reference hole 125c (see FIG. 5) provided in the holding member 125 and a reference hole 160a provided in the diaphragm 160, thereby holding the holding member 125. And the aperture 160 are positioned. The position of the re-imaging lens 165 in the optical axis direction is also determined by contacting the holding member 125 with the stop 160 sandwiched between the receiving surface 125d (see FIG. 5) of the holding member 125.

  The diaphragm 160 and the re-imaging lens 165 are fixed to the holding member 125 with an adhesive. The re-imaging lens 165 is made of a transparent resin and is manufactured by injection molding. This makes it possible to supply a large amount of high-precision re-imaging lens 165 at a low cost.

The transparent resin, which is the material of the re-imaging lens 165, and the resin, which is the material of the holding member 125, have different linear expansion coefficients, and the expansion / contraction rate changes with temperature changes. Therefore, if the holding member 125 and the re-imaging lens 165 are firmly bonded, the re-imaging lens 165 may be distorted when a temperature change occurs. Since the deformation of the re-imaging lens 165 greatly affects the detection result, the detection accuracy is lowered. Therefore, in the present embodiment, when the diaphragm 160 and the re-imaging lens 165 are bonded to the holding member 125, a soft adhesive having a Young's modulus of 10 kgf / mm ² or less is used, so that the re-imaging lens 165 due to temperature change. Is preventing the deformation.

  The sensor holder 170 is a member that holds the focus detection sensor 180. The sensor holder 170 and the focus detection sensor are fixed by an instantaneous adhesive or a welding agent. The sensor holder 170 has an opening 170a for transmitting the subject light flux. Since the opening 170a does not have a function of limiting the subject light flux, the opening 170a has a large opening with a margin more than the subject light flux effective portion.

  The sensor holder 170 and the contact member 175 are in contact with each other, can rotate around the optical axis, and can move on a plane perpendicular to the optical axis. The re-imaging lens 165 is fixed to the holding member 125. On the other hand, the focus detection sensor 180 is integrated with the sensor holder 170 and can rotate around the optical axis with respect to the contact member 175 and move on a plane perpendicular to the optical axis. . Further, the focus detection sensor 180, the sensor holder 170, and the contact member 175 are integrally rotated with respect to the holding member 125 in the directions of the arrows α and β (see FIG. 3). By providing the rotation mechanism as described above and a shift mechanism on the surface having the optical axis as a normal line, a five-axis adjustment mechanism of the re-imaging lens 165 and the focus detection sensor 180 can be realized. After the 5-axis adjustment is completed, an instantaneous adhesive, a mold welding agent, or the like is poured into the sliding surface, and the holding member 125, the contact member 175, and the sensor holder 170 are fixed.

  Further, as shown in FIG. 7, the sensor holder 170 has a reference hole 170b, and has a positioning function when the sensor holder 170 to which the focus detection sensor 180 is attached is attached to the 5-axis adjustment tool.

  The contact member 175 is interposed between the sensor holder 170 and the holding member 125 to realize an adjustment mechanism that adjusts the inclination of the focus detection sensor 180. The contact member 175 has an opening 175a for transmitting the subject light beam and a pair of spherical portions 175b for contacting the holding member 125. Since the opening 175a does not have a function of limiting the subject light flux, the opening 175a is a large opening having a margin than the subject light flux effective portion. The spherical surface portions 175b are located at both ends of the contact member 175, and each has a shape obtained by cutting out a part of the spherical surface. In other words, the contact member 175 has two spheres at both ends, and comes into contact with the holding member 125.

  On the other hand, the holding member 125 has a contact surface 125e as shown in FIG. The contact surface 125e has a shape that is cut by a shape obtained by turning a sphere with a certain radius. At this time, the radius of the sphere is equal to the spherical surface portion 175 b of the contact member 175. As the contact surface 125e of the holding member 125 and the spherical surface portion 175b of the contact member 175 swing, the contact member 175 can rotate with respect to the holding member 125 in the direction of the arrow α and the direction of the arrow β. (See FIG. 3). When rotating in the direction of the arrow α, the center of rotation of the spherical portion 175b of the contact member 175 is rotated. On the other hand, when rotating in the direction of the arrow β, the contact member 175 moves along the contact surface 125e of the holding member 125, so that the center of the contact surface 125e when rotating the sphere rotates around the rotation center. To do.

  The focus detection sensor 180 is sensitive to light having a longer wavelength than visible light.

  The separators 190 and 195 have a function of preventing mixing of the subject luminous flux in the central visual field and the subject luminous flux in the peripheral visual field. When the light beam transmitted through the central lens portion 121a of the field lens 120 passes through the peripheral visual field opening of the stop 160 and reaches the focus detection sensor 180, it becomes ghost light and causes a detection error. Therefore, in the present embodiment, separators 190 and 195 are interposed in the gap between the light flux for the central visual field and the light flux for the peripheral visual field in the optical path between the field lens 120 and the IR-CUT 150 to prevent the light fluxes from being mixed. Yes.

  By interposing the separators 190 and 195, ghost light due to surface reflection of the separators 190 and 195 is also generated. When the light beam that has passed through the central lens portion 121a of the field lens 120 hits the inner side surfaces of the separators 190 and 195 and is reflected, it passes through the central visual field opening of the diaphragm 160 and reaches the light receiving portion of the focus detection sensor 180. There is a risk that. Therefore, it is desirable to use separators 190 and 195 with extremely low reflectivity, such as a black flocked sheet or black foamed urethane resin. However, in general, black flocked sheets and black foamed urethane resins are soft and difficult to maintain their shapes. For example, even if the holding member 125 is provided with a groove for inserting the separators 190 and 195 and held, the shape of the separators 190 and 195 is bent because of the softness. If the separators 190 and 195 are bent, the subject luminous flux may be lost.

  On the other hand, when the light beam that has passed through the peripheral lens portion 121b of the field lens 120 hits the outer side surface of the separators 190 and 195 and is reflected, it is assumed that it has passed through the peripheral visual field opening of the diaphragm 160 and reached the focus detection sensor 180. However, since it reaches a portion outside the scheduled image forming portion of the peripheral visual field light beam, it does not reach the light receiving portion and ghost light is not generated. Therefore, the outer side surfaces of the separators 190 and 195 are not so sensitive to ghosts, and may have a slightly higher reflectance.

  Therefore, in this embodiment, the separators 190 and 195 are made of a black flocked sheet or black urethane resin that is soft on the inside but has a low reflectance, and uses a black pet film that is hard on the outside but has a low reflectance. And having a bonded structure. In FIG. 4, 190a and 195a are black pet films, and 190b and 195b are black flocking sheets and black urethane resin. This makes it possible to realize a light beam separating means that has a very low reflectivity on the inner side where ghosts are easily influenced and can stably maintain the shape.

  On the light exit surface of the field lens 120, the clearance between the central visual field light beam and the peripheral visual field light beam is very narrow, and the space for the separators 190 and 195 is very small. This is because the peripheral luminous flux is brought toward the center toward the diaphragm 160 in order to make the focus detection apparatus 100 as small as possible. Therefore, the separators 190 and 195 must be accurately positioned with respect to the field lens 120. Therefore, grooves 120a and 120b are provided on the light exit surface of the field lens 120, and separators 190 and 195 are inserted into the grooves 120a and 120b. Thereby, the separators 190 and 195 can be positioned with respect to the field lens 120 with high accuracy.

  However, when the groove portions 120a and 120b are provided in the field lens 120, the edge portions 120c and 120d are inevitably generated. When light hits the edge portions 120c and 120d, scattered light is generated, which may be a ghost source. In the case of the edge 122 on the light incident surface side of the field lens 120, it was possible to prevent the edge 122 from being exposed to light by arranging the light shielding sheet 115 close to the light incident surface side. It is very difficult to prevent light from hitting the edge portions 120c and 120d on the surface side. Therefore, the black urethane resins 190c and 195c are partially attached further inside the black urethane resins 190b and 195, which are the inner layers of the separators 190 and 195, so that the edge portions 120c and 120d are not visible from the light emitting surface side. .

  FIG. 6 is a schematic side view showing the separator 190 as viewed from the inside. Referring to FIG. 6, a black urethane resin 190c having an arc shape along the edge portions 120c and 120d of the field lens 120 is formed to hide the edge portions 120c and 120d. Thereby, even when light hits the edge portions 120c and 120d of the field lens 120, the scattered light does not reach the stop 130, and ghost does not occur.

  Hereinafter, pupil adjustment of the focus detection apparatus 100 will be described in detail with reference to FIGS. 8 and 9. FIG. 8 is a schematic side view for explaining the adjustment of the inclination of the image sensor 40 in the short direction. FIG. 8B shows the focus detection when FIG. 8B is at the middle position of the adjustment width. When the optical axis of the apparatus 100 is tilted θ1 backward from the intermediate position, FIG. 8C shows the case where the optical axis of the focus detection apparatus 100 is tilted θ1 forward from the intermediate position.

  Referring to FIG. 8B, the eccentric cam 140 is fitted and held on the shaft portion 125 a of the holding member 125, and is attached to the plate 130. When attaching, the holding member 125 is urged in the direction of arrow A so that the shaft portion 125 b of the holding member 125 contacts the bearing portion 130 b of the plate 130 and the outer periphery of the eccentric cam 140 contacts the plate 130.

  When adjusting the inclination of the image sensor 40 in the short direction, the holding member 125 is pushed in the direction in which it is desired to rotate, and is rotated about the shaft portions 125a and 125b. The plate 130 is fixed because it is screwed to the camera body. When the holding member 125 is rotated, all elements constituting the focus detection apparatus 100 except for the plate 130 rotate around the shaft portions 125a and 125b. In the case of rotation around the shaft portions 125a and 125b, as shown in FIGS. 8A and 8C, if the holding member 125 is rotated by θ1, the optical axis of the focus detection device 100 is also changed. Tilt by θ1.

  When the holding member 125 is pushed in the direction in which it is desired to rotate, the amount of movement is very fine. Therefore, it is preferable to press the surface of the holding member 125 with a means such as a micrometer that can control a small pressing amount. Needless to say, a means for biasing the holding member 125 in the direction opposite to the pushing direction is necessary at this time.

  The rotation around the shaft portions 125a and 125b is easy to adjust a minute amount because the contact area of the sliding surface is small and the friction is small. Therefore, in the focus detection apparatus 100 of the present invention, it is possible to adjust the inclination of the image sensor 40 in the short direction with very high accuracy.

  FIG. 9 is a schematic rear view for explaining the adjustment of the inclination of the image sensor 40 in the longitudinal direction. FIG. 9B shows a case where the image sensor 40 is at an intermediate position of the adjustment width. When tilted by θ2 to the right when viewed from the back, FIG. 9C shows a case when tilted by θ2 to the left when viewed from the back of the camera 1.

  Referring to FIG. 9B, the eccentric cam 140 is fitted and held on the shaft portion 125 a of the holding member 125, and is attached to the plate 130. When attaching, the holding member 125 is urged in the direction of arrow B so that the shaft portion 125 b of the holding member 125 contacts the bearing portion 130 b of the plate 130 and the outer periphery of the eccentric cam 140 contacts the plate 130.

  When adjusting the inclination of the image sensor 40 in the longitudinal direction, the eccentric cam 140 is rotated to change the contact surface with the plate 130 and the inclination is adjusted by moving the position of the shaft portion 125 of the holding member 125. The plate 130 is fixed because it is screwed to the camera body. When the eccentric cam 140 rotates, the position of the shaft portion 125a of the holding member 125 changes. On the other hand, the shaft portion 125b abuts on the bearing portion 130b of the plate 130 and does not change its position. Therefore, all elements constituting the focus detection device 100 except the plate 130 are in contact with the shaft portion 125b. Rotate around.

  With reference to FIG. 10, it will be described that the position of the shaft portion 125 a is changed by the rotation of the eccentric cam 140. 10B, FIG. 10B shows the case where the eccentric cam 140 is at an intermediate position of the adjustment width, FIG. 10A shows the case where the eccentric cam 140 is rotated clockwise, and FIG. The case of turning counterclockwise is shown.

  As shown in FIG. 10, the eccentric cam 140 has a rectangular recess 140 a on the side surface, and is configured such that, for example, the eccentric cam 140 can be rotated with a commercially available minus driver.

  Here, the diameter of the outer periphery circle of the eccentric cam 140 is φD, and the amount of eccentricity between the center of the shaft portion 125a and the center of the outer periphery circle of the eccentric cam 140 is t. As shown in FIG. 10A, when the eccentric cam 140 is rotated clockwise by θ4, the center of the shaft portion 125a and the outer periphery center of the eccentric cam 140 are eccentric by t. The distance from the contact surface becomes shorter by ΔY1. Then, since the eccentric cam 140 is biased upward, the position of the shaft portion 125a moves upward by ΔY1. On the other hand, as shown in FIG. 10 (c), when the eccentric cam 140 is rotated θ4 counterclockwise, the center of the shaft portion 125a and the outer periphery center of the eccentric cam 140 are eccentric by t. The distance from the contact surface with 130 is increased by ΔY1. Then, the position of the shaft portion 125 moves downward by ΔY1.

  In this embodiment, the shape of the eccentric cam 140 is set to a diameter φD = 8.6 mm and an eccentric amount t = 0.40 mm. At this time, if the eccentric cam 140 is turned by θ4, the change amount ΔY1 of the shaft portion 125a is 0.28 mm.

  In this embodiment, the distance L from the contact portion between the eccentric cam 140 and the plate 130 to the contact portion between the shaft portion 125a and the plate 130 is set to 25 mm. Therefore, when the shaft portion 125a moves by ΔY1, the tilt amount θ2 of the optical axis of the focus detection apparatus 100 is expressed as θ2 = atan (ΔY1 / L). If the change amount ΔY1 = 0.28 and the distance L = 25 are substituted for this, the inclination amount θ2 becomes θ2 = atan (0.28 / 25) = 0.64 degrees.

  That is, even if the eccentric cam 140 is rotated by 45 degrees, the tilt amount θ2 of the optical axis of the focus detection apparatus 100 changes only by 0.64 degrees, so that highly accurate tilt adjustment is possible.

  Further, in the method of rotating the eccentric cam 140, since the adjustment movement is in the rotation direction, the movement is stabilized in addition to being able to move smoothly. Therefore, it is easy to perform minute movements and tilt adjustment with good reproducibility is possible.

  As described above, the focus detection apparatus 100 adjusts the inclination of the image sensor 40 in the short direction by rotating around the shaft portions 125 a and 125 b of the holding member 125, and the length of the image sensor 40 by rotating the eccentric cam 140. The pupil adjustment can be adjusted by adjusting the inclination of the direction.

  After completion of the pupil adjustment, as shown in FIG. 9, instantaneous adhesive is poured into the contact surface between the holding member 125 and the plate 130 and the contact surface between the plate 130 and the eccentric cam 140. And the eccentric cam 140 is fixed. By fixing with the instantaneous adhesive, the tilt after completion of the pupil adjustment can be maintained even when the urging in the arrow B direction is lost.

  As described above, the focus detection apparatus 100 includes the shaft portions 125 a and 125 b of the holding member 125, the bearing portions 130 a and 130 b of the plate 130, and the eccentric cam 140 of the image sensor 40 having a relatively large space in the camera 1. By providing in the longitudinal direction, the camera 1 can be efficiently accommodated. In addition, the focus detection apparatus 100 performs pupil adjustment by the rotational movement of the eccentric cam 140, so that it can realize smooth movement with high reproducibility in addition to not high adjustment sensitivity. Pupil adjustment is possible.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist.

It is a schematic perspective view which shows the optical system of the imaging device (camera) which has the focus detection apparatus of this invention. It is a schematic sectional drawing from the side of the imaging device shown in FIG. FIG. 3 is a developed perspective view in which elements constituting the focus detection apparatus shown in FIGS. 1 and 2 are developed. FIG. 3 is a schematic front view of the field lens shown in FIG. 2. It is a schematic perspective view of the holding member shown in FIG. It is a schematic side view which shows the case where the separator shown in FIG. 4 is seen from the inner side. It is a schematic perspective view which shows the focus detection apparatus of this invention seen from the image pick-up element side. It is a schematic side view for demonstrating adjustment of the inclination of a transversal direction of an image sensor. It is a schematic back view for demonstrating adjustment of the inclination of the longitudinal direction of an image pick-up element. It is a figure for demonstrating that the position of a shaft part changes with rotation of an eccentric cam.

Explanation of symbols

1 Imaging device (camera)
DESCRIPTION OF SYMBOLS 10 Image | photographing optical system 20 Main mirror 30 Sub mirror 40 Image pick-up element 50 Optical low-pass filter 60 Shutter unit 70 Lens communication unit 100 Focus detection apparatus 110 Cover 115 Light shielding sheet 120 Field lens 125 Holding member 125a and 125b Shaft part 130 Plate 130a and 130b Bearing part 140 Eccentric cam 150 IR-CUT filter 155 Folding mirror 160 Aperture 165 Re-imaging lens 170 Sensor holder 175 Contact member 180 Focus detection sensors 190 and 195 Separator

Claims (5)

A focus detection device that detects a focus from subject light imaged on an image sensor,
A focus detection optical system for guiding the subject light onto the image sensor;
A holding member for holding the focus detection optical system, which has a pair of shaft portions extending in the longitudinal direction of the image sensor and is rotatable about the shaft portions;
A focus detection apparatus comprising: an eccentric cam that is fitted to one of the shaft portions and moves the shaft portion in a short direction of the imaging device. An imaging device that captures an image of a subject,
A focus detection device according to claim 1;
An imaging apparatus comprising: a metal member that surrounds the focus detection apparatus and attaches the focus detection apparatus to the imaging apparatus. The metal member has a U-shaped hole extending in a short direction of the image sensor,
A bearing portion that can contact the shaft portion in the short direction of the imaging element;
The shaft portion into which the eccentric cam is fitted is fitted into the U-shaped hole of the metal member,
The imaging apparatus according to claim 2, wherein the shaft portion to which the eccentric cam is not fitted is in contact with or fitted to a bearing portion of the metal member.   The imaging device according to claim 3, wherein the eccentric cam is in contact with the metal member at an outer periphery. A focus detection device used in an imaging device that detects a focus from subject light imaged on an image sensor and captures an image of the subject reflected by the subject light,
A focus detection optical system for guiding the subject light onto the image sensor;
A holding member for holding the focus detection optical system, which has a pair of shaft portions extending in the longitudinal direction of the image sensor and is rotatable about the shaft portions;
An eccentric cam that fits into one of the shaft portions and moves the shaft portion in the short direction of the imaging device;
The focus detection optical system, the holding member, and the U-shaped hole extending in the short direction of the image sensor, and the bearing portion with which the shaft portion can contact in the short direction of the image sensor. And a metal member for attaching an eccentric cam to the imaging device.