JP3911715B2 - Camera focus detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a focus detection device incorporated in a general camera or an electronic still camera, and more particularly to a structure of a holder that holds a secondary imaging lens and a line sensor.
[0002]
[Prior art]
Conventionally, as this type of focus detection device, as disclosed in, for example, Japanese Utility Model Laid-Open No. 5-16568 (hereinafter referred to as the prior invention), two re-imaging optical systems are provided behind the focus position of the photographing lens. There has been proposed a secondary image phase difference type focus detection device for detecting the relative position of an image re-imaged by a line sensor such as a CCD to detect the focus state of the taking lens.
[0003]
This focus detection apparatus includes a field mask and a field lens arranged in the vicinity of a focal plane of a photographic lens, a mask plate having a pair of openings arranged behind them and a pair of re-imaging lenses, and a general connection of each of them. And a line sensor having a pair of light receiving portions arranged on the image plane. Furthermore, a mirror or the like that bends the optical path is often disposed between the field lens and the mask plate in order to reduce the size of the apparatus. In the focus detection of the secondary image phase difference method, the relative distance between these elements greatly affects the focus detection accuracy. Therefore, they are configured to be held by one support made by molding of plastic or the like, that is, a holder. It is customary.
[0004]
FIG. 7 is an exploded perspective view of the focus detection apparatus shown in the prior art, and FIG. 8 is a cross-sectional view showing the apparatus. In these drawings, reference numeral 10 denotes a holder disposed on the bottom side of the mirror box of the camera. This holder 10 is integrally formed of synthetic resin or the like, and a field mask 11 is provided in the upper surface opening, and a field lens 12 is provided inside. The secondary imaging lens 14, the line sensor 15 and the mirror 16 are incorporated.
[0005]
The line sensor 15 has a light receiving portion 15b formed on a substrate 15a made of ceramic or the like, and the light receiving portion 15b is sealed by a transparent protective glass 15d attached to the substrate 15a via a spacer 15c. The line sensor 15 needs to be attached to the holder 10 so that the light receiving portion 15b coincides with the position of the image plane accurately re-imaged. Therefore, the flat portion 15e of the substrate 15a is pressed against the front surface of the holder 10, the line sensor 15 is moved within the plane, and alignment is performed while viewing the output of the line sensor 15 and the like, and then the line sensor 15 is bonded to the holder 10. A method of fixing with an agent or the like is employed.
[0006]
In that case, in order to obtain the orthogonality with respect to the optical axis 18 of the line sensor 15, the notch portions 17a and 17b are formed in the center portions of the front end edges of the upper wall 10a and the lower wall 10b of the holder 10, respectively. Both end portions 15e1 and 15e2 of the substrate 15a are in intimate contact only with the front end surfaces 19a and 19b of the side walls 10c and 10d, and the front end surfaces 19c and 19d at both ends of the upper wall 10a and the lower wall 10b. Thereby, the position of the line sensor 15 is determined only by the front end surfaces 19a, 19b, 19c, and 19d of the holder 15. Note that after the line sensor 15 is bonded to the holder 10, the cutout portions 17a and 17b are closed by a light shielding member 20 such as a tape in order to prevent light from entering.
[0007]
As described above, the relative distance between the components disposed in the holder 10, particularly the accuracy of the distance between the re-imaging lens 14 in front of the line sensor 15 and the light receiving portion 15 b of the line sensor 15 is determined by the focus detection. Since this greatly affects the accuracy, the thickness of the front half where the line sensor 15 and the re-imaging lens 14 are attached and the thickness of the partition wall 21 forming the attachment portion of the re-imaging lens 14 are increased. The deformation to the force applied at the time of adjustment and attachment is suppressed, and the deformation at the time of attaching the focus detection device to the camera is suppressed. For this reason, when the holder 10 is made of a plastic material such as polycarbonate containing glass, the thickness of the front half and the partition wall 21 is set to about 2 mm so as to obtain sufficient strength.
[0008]
On the other hand, such a focus detection device for a camera is disposed on the bottom side of the mirror box, and reflects light transmitted through a semi-transmissive movable mirror (not shown) by the sub mirror 22 (see FIG. 10) and travels toward the bottom of the mirror box. By making the light incident on the field lens 12 in this manner, it is used as a light beam for focus detection. However, in recent cameras, a TTL (lens transmitted light metering) light adjustment sensor and a photometric lens are often disposed at this location. The TTL light control sensor is disposed with the optical axis of the photometric lens facing the center of the screen in order to receive the reflected light from the film surface. Examples thereof are shown in FIG. 9 and FIG. 24 is a photometric lens, 25 is a photometric sensor, and 26 is a mirror box. The photometric lens 21 forms an image of the reflected light from the film surface X on the photometric sensor 25, and measures the light by detecting it with the photometric lens 25.
[0009]
In the conventional case of TTL dimming that receives only reflected light from the central portion of the screen and its peripheral portion, it was possible to use only a silicon photodiode (SPD) without a lens. As in the case of the above-mentioned photometry, divided photometry has been performed in TTL dimming. In this case, a pupil or a plurality of photometric lenses for forming an image of the reflected light from the film is indispensable. In addition, from the SPD that simply outputs a photocurrent corresponding to the brightness, a type in which an interface circuit such as an amplifier is incorporated is often used for the photometric sensor in order to prevent signal noise. This increases the size of the sensor package along with the increase in the area of the light receiving portion due to the split photometry.
[0010]
[Problems to be solved by the invention]
Increasing the size of the TTL light control optical system including such a photometric sensor is a significant limitation on the arrangement of the focus detection device. That is, when the focus detection device is arranged below the TTL light control sensor 25, the light control sensor 25 and the focus detection device have a positional relationship as shown in FIG. Since the light control sensor 25 is not raised so much because there is a limitation on the conjugate relationship with the film surface X and the height of the floor of the mirror box 26, the lower end portion 25a of the light control sensor 25 and the holder 10 Needless to say, the position of the upper wall 10a does not interfere, and the focus detection device has to be lowered to a position where there is room for movement by adjusting the tilt of the optical axis (so-called Yaw Pitch adjustment) after the focus detection device is incorporated. The recent increase in size of the TTL light control sensor increases the amount of reduction. However, this is not only because the bottom surface of the camera is lowered to accommodate the focus detection device, but the camera body is not only enlarged, but also the field mask 11 and the field lens 12 that must originally be disposed near the focal plane of the photographing lens. Is further away from the focal plane T (see FIG. 10), and the focus detection accuracy itself is affected, for example, by reducing the degree of freedom in designing the focus detection optical system and increasing the stray light harmful to focus detection. Come out.
[0011]
The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to reduce the amount of descent of the focus detection device and reduce the size of the camera. To provide a focus detection device.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, an object image formed by a photographic lens is further re-imaged on a pair of line sensors by a secondary imaging lens, and the focal point of the photographic lens is determined from the relative deviation of the secondary object image. In a focus detection device for a secondary image phase difference camera that detects a state, a through hole is formed in a wall portion of a holder that integrally holds the line sensor and the secondary imaging lens, and the through hole has the A part of the optical system having a sensor for measuring light transmitted through the photographing lens can be entered in a state independent of the holder.
Further, according to the present invention, an object image formed by the photographic lens is further re-imaged on the pair of line sensors by the secondary imaging lens, and the focus state of the photographic lens is detected from the relative deviation of the secondary object image. In a focus detection device for a secondary image phase difference camera, a concave portion is formed in a wall portion of a holder that integrally holds the line sensor and the secondary imaging lens, and a tripod seat of the camera is formed in the concave portion. It is characterized in that a part can be entered.
[0013]
Further, the present invention is characterized in that the through hole has a sheet-like member that shields the through hole , and the sheet member is formed of the same material as the light shielding member that shields the gap between the holder and the line sensor. To do.
Furthermore, the present invention provides a lens body close to a through hole among a plurality of sets of lens bodies provided in the secondary imaging lens, and a side edge facing the through hole among the side edges of the secondary imaging lens. The interval is set to be smaller than the interval between the lens body and the side edge in the other part.
[0014]
In the present invention, the through-hole and recess provided in the holder by a part of the TTL flash optics and tripod enters each narrowing TTL light optical system, the distance between the tripod and the holder, respectively.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
FIG. 1 is a sectional view showing an embodiment of a focus detection apparatus according to the present invention, and FIG. 2 is a perspective view of a holder. Note that the same components as those shown in the prior art column are denoted by the same reference numerals, and description thereof will be omitted as appropriate. In these drawings, the holder 10 is integrally formed of a synthetic resin, and a field mask 11 is disposed in an opening provided at the rear end portion of the upper surface, and a field lens 12, a secondary imaging lens 14, a line sensor are provided therein. 15 and mirror 16 are incorporated. Above the front end of the holder 10, a photometric lens 24 and a photometric sensor 25 constituting the TTL light control optical system 30 are disposed in the vicinity of the upper wall 10 a of the holder 10. Further, a recessed portion 31 is formed in a portion facing the lower end portion of the TTL light control optical system 30 near the upper surface front end portion of the upper wall 10a. The recessed portion 31 is formed by a through hole 32 having an inverted trapezoidal cross section formed in the upper wall 10a and a thin sheet-like member 33 that shields the through hole 32. The lower end portion of the TTL light control optical system 30 Has entered from above. As described above, when the lower end portion of the TTL light control optical system 30 is inserted into the recessed portion 31, the lowering amount of the holder 10 can be reduced accordingly. In other words, the height of the entire camera can be reduced.
[0016]
The sheet- like member 33 is made of the same material as the light-shielding member 20 that shields light from the notch 17a formed at the front edge of the upper wall 10a of the holder 10. For this reason, in the present embodiment, the light shielding member 20 is extended to form a sheet- like member 33, and the extension is attached to the upper surface of the upper wall 10a, the upper surface of the substrate 15a, and the hole wall of the recessed portion 31, and is cut out. 17a and the through hole 32 are shielded from light. If the recessed part 31 is formed in an inverted trapezoidal shape as described above, the width of the lower end side opening of the through hole 32 is the smallest and the hole wall is inclined downward, so that the sheet- like member 33 is formed. Can be easily attached. Further, since the notch 17a and the recessed portion 31 are formed to a minimum size, the strength of the holder 10 is not affected, and the line sensor mounting surfaces 19a to 19d of the holder 10 are adhered when the line sensor 15 is bonded. Can sufficiently withstand the forces F1 and F2 received by.
[0017]
FIG. 3 is a cross-sectional view showing an embodiment in which the present invention is applied to a multi-area focus detection apparatus that performs focus detection at a plurality of points in the screen, and FIG. 4 is a diagram showing a focus detection area on the screen.
In this embodiment, focus detection areas V1 and V2 are provided not only at the center of the screen L but also at the top and bottom as shown in FIG. In such a multi-area method, since it is necessary to ensure a large space for the optical path in the vertical direction even in the focus detection device, it is necessary to increase the vertical dimension of the holder 10 even in front of the line sensor 15. Even in such a case, as described above, a part of the upper wall of the holder 10 is notched, and a part of the TTL light control optical system is inserted therein, so that it is not necessary to lower the entire focus detection device.
[0018]
Further, in the case of a multi-area focus detection device, since it is necessary to provide a pair of lens bodies for each area, the number of lens bodies 14a provided in the secondary imaging lens 14 is as shown in FIG. The size of the entire secondary imaging lens 14 in which a plurality of pairs of lens bodies 14a are integrally formed on one lens substrate 14b is inevitably increased. Normally, such a secondary imaging lens 14 is made by molding plastic or the like for an optical material, but in order to make the shape of the lens body 14a with high accuracy, it is usual to attach a certain amount of edges to the periphery. . However, if the lens body 14a for the upper and lower areas and the upper and lower edges of the lens substrate 14b are formed sufficiently symmetrically to be close to the concave portion 31 that houses the lower part of the TTL light control optical system 30, the lens body 14a is close to the concave portion 31. The upper portion of the lens substrate 14b may be higher than the portion where the recessed portion 31 of the holder 10 is provided.
[0019]
Therefore, in the present embodiment, the interval m between the upper lens body 14a close to the recessed portion 31 and the upper edge of the lens substrate 14b among the plurality of sets of lens bodies 14a provided in the secondary imaging lens 14 is set as follows. As shown in FIG. 5, the distance m1 is set smaller than the distance m1 between the lower lens body 14a and the lower edge of the lens substrate 14b. In such a secondary imaging lens 14, the secondary imaging lens 14 can be brought close to the recessed portion 31, so that the height of the holder 10 can be reduced.
[0020]
FIG. 6 is a cross-sectional view showing still another embodiment of the present invention.
In this embodiment, concave portions 31, 45 are provided near the front end portions of the upper and lower walls 10a, 10b of the holder 10, and the lower end portion of the TTL light control optical system 30 and the tripod seat 46 are provided in these concave portions 31, 45, respectively. The top of each is inserted. The upper concave portion 31 is the same as the concave portion shown in FIG. 1 and is formed by the through hole 32 and the sheet member 33, and the lower concave portion 45 is an inverted trapezoidal shape formed on the lower surface side of the lower wall 10b. It is made into the recessed part. The tripod seat 46 is provided with a screw hole 46a into which a tripod screw of a tripod is screwed.
[0021]
In such a structure, since the TTL light control optical system 30 and the tripod mount 46 can be brought close to the holder 10 by the recessed portions 31 and 45, the height of the entire camera can be further reduced.
[0022]
【The invention's effect】
As described above, the focus detection apparatus for a camera according to the present invention re-images an object image by a photographing lens onto a pair of line sensors by a secondary imaging lens, and detects the relative displacement of the secondary object image. In the focus detection device of the secondary image phase difference type camera that detects the focus state of the photographing lens, a through hole is formed in a wall portion of a holder that integrally holds the line sensor and the secondary imaging lens, a part of the optical system including a sensor for measuring the light transmitted through the photographing lens to the through hole, since said holder has can enter a separate state, and accuracy of size of the camera and the focus detecting optical system A degree of freedom in design can be secured. Moreover, since it is only necessary to form a through hole in the holder, the structure is simple and the holder can be easily manufactured.
[0023]
Further, according to the present invention, an object image formed by the photographic lens is further re-imaged on the pair of line sensors by the secondary imaging lens, and the focus state of the photographic lens is detected from the relative deviation of the secondary object image. In a focus detection device for a secondary image phase difference camera , a concave portion is formed in a wall portion of a holder that integrally holds the line sensor and the secondary imaging lens, and a tripod seat of the camera is formed in the concave portion. Since part of the camera can enter , the camera can be downsized in the height direction.
[0024]
The present invention, through-holes, has a sheet-like member to shield the through hole, and since the formation of the sheet member of the same material as the light blocking member for blocking the gap between the holder and the line sensor, new component There is no need to increase
[0025]
Furthermore, the present invention provides a lens body close to a through hole among a plurality of sets of lens bodies provided in the secondary imaging lens, and a side edge facing the through hole among the side edges of the secondary imaging lens. Since the interval is set to be smaller than the interval between the lens body and the side edge in the other part, the height of the holder can be reduced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a focus detection apparatus according to the present invention.
FIG. 2 is a perspective view of a holder.
FIG. 3 is a cross-sectional view showing another embodiment of the present invention.
FIG. 4 is a diagram illustrating a focus detection area on a screen.
FIG. 5 is a front view of a secondary imaging lens.
FIG. 6 is a cross-sectional view showing still another embodiment of the present invention.
FIG. 7 is an exploded perspective view of a conventional focus detection device.
FIG. 8 is a sectional view of the detection device.
FIG. 9 is a perspective view showing a configuration of a TTL light control optical system.
FIG. 10 is a cross-sectional view showing a positional relationship between a conventional focus detection device and a TTL light control optical system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Holder, 11 ... Field mask, 12 ... Field lens, 13 ... Mask plate, 14 ... Secondary imaging lens, 15 ... Line sensor, 24 ... Photometric lens, 25 ... Photometric sensor, 30 ... TTL light control optical system, 31 ... Recessed part, 32 ... Through hole, 33 ... Sheet member, 45 ... Recessed part, 46 ... Tripod seat, 46a ... Screw hole for tripod seat.

Claims (4)

A secondary image phase difference method that re-images an object image by a photographic lens onto a pair of line sensors by a secondary imaging lens and detects the focus state of the photographic lens from the relative deviation of the secondary object image. In the camera focus detection device,
A part of the optical system including a sensor for measuring the line sensor and the secondary imaging lens to form a through hole in the wall portion of the holder for holding integrally, light transmitted through the photographing lens to the through hole A focus detection device for a camera, wherein the camera can be entered independently of the holder. A secondary image phase difference method that re-images an object image by a photographic lens onto a pair of line sensors by a secondary imaging lens and detects the focus state of the photographic lens from the relative deviation of the secondary object image. In the camera focus detection device,
A camera is characterized in that a concave portion is formed in a wall portion of a holder that integrally holds the line sensor and the secondary imaging lens, and a part of a tripod seat of the camera can enter the concave portion. Focus detection device. The camera focus detection apparatus according to claim 1,
The through hole has a sheet-like member to shield the through hole, and the focus detection of the camera, characterized in that the formation of the sheet member of the same material as the light blocking member for blocking the gap between the holder and the line sensor apparatus. The focus detection apparatus for a camera according to claim 1 or 3 ,
The distance between the lens body close to the through-hole among the plurality of sets of lens bodies provided in the secondary imaging lens and the side edge facing the through-hole among the side edges of the secondary imaging lens is changed to another portion. A focus detection device for a camera, characterized in that it is set to be smaller than the distance between the lens body and the side edge.

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