JP2012185251A - Focusing screen holding mechanism for camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focusing screen holding mechanism capable of holding a focusing screen in a set position with a stable energizing force compactly and inexpensively.SOLUTION: A focusing screen holding mechanism for a camera which can be moved between a focus observation position and a replacement (attachment and detachment) position includes a screen holding member 18 including a hinge part 18a for rotating a focusing screen 4 and pressing means 30 for pressing the focusing screen 4 in an optical axis direction.

Description

  The present invention relates to a single-lens reflex camera, a digital single-lens reflex camera, and the like, and particularly to a focusing screen holding mechanism of a camera having a focusing screen exchanging mechanism.

  For single-lens reflex cameras and single-lens reflex digital still cameras, cameras that are configured so that the focusing screen can be replaced according to the lens used and the state of the subject have already been released.

As a focusing screen holding mechanism of such a camera, for example, there is one disclosed in Patent Document 1, and this camera uses a screen holding frame formed by a spring to bring the focusing screen into an abutting portion in the optical axis direction. A structure is adopted in which the focusing screen is fixed to the focus observation position by biasing. In Patent Document 2, a plate spring is incorporated in the focusing screen holding frame, and the focusing screen is moved in the optical axis direction by the plate spring. The focusing screen is fixed to the focus observation position by energizing the abutting portion of the lens.

JP 2001-174880 A JP 2007-25554 A

  However, the conventional techniques disclosed in the above-mentioned patent documents have the following problems.

  Generally, the focusing screen is formed of a mold such as acrylic and has a plate-like shape. When an excessive biasing force is applied when biasing in the optical axis direction, the focusing screen is deformed, and the viewfinder There will be a difference between the focus and the focus of the shooting system.

  In Patent Document 1, the screen holding frame formed by a spring is configured to urge the focusing screen against the abutting portion in the optical axis direction, so that the screen holding frame is prevented from being deformed at the time of replacement. Rigidity is required, and the spring constant becomes high. For this reason, there is a problem that the biasing force varies greatly when the spring stroke is changed due to the dimensional variation of parts, and an excessive biasing force is applied.

  In Patent Document 2, since a plate spring is incorporated in the screen holding frame, it is possible to set a low spring constant while maintaining the rigidity of the holding frame, and the spring stroke changes due to component variations and the like. However, it is possible to set an urging force that does not apply an excessive urging force, but there is a problem that a space is required to fix the leaf spring to the holding frame, and the holding frame itself must be enlarged. . In addition, welding or the like is required to fix the leaf spring to the holding frame, which increases the cost.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a focusing screen holding mechanism for a camera that can hold the focusing screen at a set position in the optical axis direction with a stable urging force with a small size and low cost.

  The focusing screen holding mechanism of the camera according to the present invention includes a screen holding member (18) that holds the focusing screen (4), and a reference plane (2b) that determines the position of the focusing screen in the optical axis direction during focus observation. The focusing screen of the camera in which the screen holding member (18) is movable between “a set position where the focusing screen (4) is fixed at a focus observation position” and “a detachable position where the focusing screen is exchanged / removed”. In the holding mechanism, the screen holding member (18) includes a hinge portion (18a) for rotating between the setting position and the attachment / detachment position of the focusing screen (4), and an inner side of the screen holding member (18). , Means for pressing the focusing screen (4) in the optical axis direction (3 The pressing means (30) has a fulcrum in the vicinity of the central part of the long side facing the hinge part (18a) of the screen holding member (18) and in the vicinity of the hinge part (18a) of the left and right short sides. And by pressing the convex portion (4d) on the outer peripheral portion of the focusing screen (4) by the pressing means (30), the focusing screen (4) is biased to the reference surface (2b) when in the set position state. It is characterized by doing.

  According to the present invention, it is possible to provide a focusing screen holding mechanism for a camera that can hold the focusing screen at a set position in the optical axis direction with a stable urging force with a small size and low cost.

It is a camera side sectional view showing an outline of a camera which is a 1st embodiment of the present invention. It is detail drawing of the screen holding member of the said camera. It is the top view and EE sectional drawing of the screen holding mechanism of the said camera. FIG. 6 is an operation explanatory diagram of the screen holding mechanism (No. 1). It is operation | movement explanatory drawing of the said screen holding mechanism (the 2). FIG. 6 is an operation explanatory view of the screen holding mechanism (No. 3). FIG. 6 is an operation explanatory view of the screen holding mechanism (No. 4). It is a top view which shows the finder visual field in the said camera. It is a top view of the focusing screen of the camera. It is a top view of the superimpose liquid crystal of the said camera.

  FIG. 1 shows a camera according to a first embodiment of the present invention. In this figure, reference numeral 1 denotes a camera body. Hereinafter, the left side of FIG.

  Reference numeral 2 denotes a mirror box serving as a reference for a finder optical system fixed to the camera body 1. Reference numeral 3 denotes a mirror unit which is rotatable with respect to the mirror box 2, and 4 is a focusing screen. The focusing screen 4 has a Fresnel lens 4a on the light incident surface and a mat surface 4b on the light emission surface. Then, as shown in FIG. 3, a spot photometric mark 4c is engraved on the mat surface 4b. Further, as will be described later, there is a convex portion 4d that comes into contact with a biasing member that presses the focusing screen 4 against a reference surface 2b (see FIG. 4) of the mirror box 2 that serves as a focus reference.

  5 is a superimposing liquid crystal composed of a polymer network liquid crystal or the like, having a segment pattern 5a of a plurality of focus detection areas (AF detection areas), and making only selected segment areas opaque. Is displayed. The superimposing liquid crystal 5 is fixed to the mirror box 2 with high accuracy. Here, the subject image formed on the focusing screen 4 and the segment pattern 5a are displayed in an overlapping manner and observed through the eyepieces 8a, 8b, and 8c.

  6 is a condenser lens, and 7 is a pentaprism. Reference numerals 8a, 8b, and 8c denote eyepiece lenses. These constitute a finder system.

  Reference numerals 10 and 11 respectively denote a photometric sensor and a photometric lens for measuring the luminance of the subject. The photometric sensor 10 and the photometric lens 11 can perform spot photometry for measuring the area at the center of the screen (spot photometric mark 4c) and partial photometry with sensitivity to the outside.

  Reference numeral 15 is a known focus detection unit, and 16 is a shutter device. Reference numeral 17 denotes a mount which is fixed to the opening of the mirror box 2 and mounts an interchangeable lens (not shown).

  In the camera of the present embodiment configured as described above, a subject field portion as shown in FIG. 5 and a field field for displaying photographing conditions such as a shutter speed, an aperture value, and an exposure correction amount located outside the subject field portion. A viewfinder field having an external display (not shown) is obtained. As shown in FIG. 1, the subject field portion is obtained by arranging the superimposing liquid crystal 5 and the focusing screen 4 so as to overlap each other in the finder optical axis direction, and superimposing the segment pattern 5a and the photometric mark 4c on the subject image. Can be observed.

  By the way, in the camera of this embodiment, as a focusing screen, a spot metering mark 4c is engraved at the center as shown in FIG. 6A, or a grid is engraved as shown in FIG. 6B. 4 'can be selected and mounted. However, when selecting any of the focusing screens 4 and 4 ', as shown in FIGS. 7A and 7B, the segment pattern 5a displayed on the superimposing liquid crystal 5 and the focusing screen are used. It is necessary that the photometric marks 4c and grids formed on 4 and 4 'appear to overlap appropriately.

  Therefore, in the camera of the present embodiment, the focusing screens 4 and 4 'can be easily replaced, and the mounted focusing screens 4 and 4' are attached to the segment pattern 5a, that is, the camera body 1 (mirror box 2). And a focusing screen holding mechanism that can be accurately positioned.

  Reference numeral 18 denotes a screen holding member on which the focusing screen 4 is detachably loaded. A hinge portion 18a bent into a horizontal U shape is provided at the rear end portion of the screen holding member 18, and a hook portion 18b is formed at the front end portion. A shaft 21 that supports the hinge portion 18a is fixed in the vicinity of the shutter side of the mirror box 2. As a result, the screen holding member 18 is moved around the axis 21 so that the mounted focusing screen 4 is brought close to the superimposing liquid crystal 5 in the finder optical axis direction (position shown in FIG. 4D), It can be swung between an attachment / detachment position (position shown in FIG. 4A) for forming a space for attaching / detaching the focusing screen 4 to / from the impose liquid crystal 5.

  A wire spring 30 (pressing means in the claims) is locked to the bottom surface of the screen holding member 18, and the wire spring 30 is a focusing screen mounted on the screen holding member 18 as will be described later. 4 is pressed against the reference surface 2b of the mirror box 2 (see FIG. 4).

  Reference numeral 19 is made of a leaf spring, engages with a hooking portion 18b of the screen holding member 18 positioned at the set position to lock the screen holding member 18 at the set position, and biases the focusing screen in the in-plane rearward direction D. It is a latching and pressing member having a pressing portion 19a that is pressed by. (See FIG. 3A).

  Reference numeral 20 denotes a cover which is formed inside the mount 17 and covers the locking and pressing member 19 and is fixed to the mirror box 2.

  2A and 2B show the wire spring 30 and a state in which the wire spring 30 is incorporated in the screen holding member 18.

  The wire spring 30 is formed in a substantially U-shape, has a locking portion 30a near the center of the long side, and locking portions 30b and 30c at the left and right tip portions. What is the hinge portion 18a of the screen holding member 18? The holding hole 18c provided in the vicinity of the center part of the opposing long side and the locking holes 18d and 18e formed in the vicinity of the hinge part on the left and right short sides of the screen holding member 18 are held and locked. Using the vicinity of the locking portion as a fulcrum, it abuts on the convex portion 4d of the focusing screen 4 and functions as a pressing means having an urging force in the optical axis direction.

  Thus, by providing the fulcrum in the vicinity of the center of the long side and in the vicinity of the left and right hinges, the length of the spring can be utilized to the maximum, so the spring constant is kept low while maintaining the rigidity of the screen holding member 18. Even if a variation in parts occurs, it can be urged in the optical axis direction with a stable urging force. Moreover, since it hold | maintains at the screen holding member 18 by the three latching | locking parts, there is no need for welding etc., and size reduction is attained by using a wire spring.

  3A is a top view of the screen holding mechanism, and FIG. 3B is an EE cross-sectional view thereof.

  On one of the inner surfaces of the mirror box 2, a fixing pin 22R (abutting portion referred to in the claims) is integrally attached to the mirror box 2, and at the position facing the fixing pin 22R on the other side, The movable pin 22L is attached by being urged by a spring 23 in a direction protruding to the inside of the mirror box 2. The side surface contact portion of the movable pin 22L with the focusing screen 4 is tilted by a predetermined angle, and at this set position, the focusing screen 4 is pressed by the movable pin 22L with the urging force C in the in-plane direction. At the time of replacement, the focusing screen 4 can be urged to the attaching / detaching position by the urging force B by the movable pin 22L. Thus, the pressing means has a biasing force in two directions.

  Next, the procedure for loading the focusing screen 4 and the movement of the holding mechanism in the camera configured as described above will be described with reference to FIG. First, as shown in FIG. 4A, the focusing screen 4 is loaded on the screen holding member 18 with the screen holding member 18 lowered to the attachment / detachment position. In order to make it easy to load the focusing screen 4 on the screen holding member 18, the screen holding member 18 is made large so as to have back-and-forth and left-right play with respect to the focusing screen 4.

  After the focusing screen 4 is loaded on the screen holding member 18, when the screen holding member 18 is pushed up toward the set position as shown in FIG. 4B, the tips of the fixed pin 22 </ b> R and the movable pin 22 </ b> L are moved to the screen holding member 18. It protrudes to the inside of the screen holding member 18 through an opening 18f formed in the side surface of the screen.

  In the focusing screen 4, the left and right side surfaces (outer peripheral portions) abut against the distal ends of the fixed pin 22 </ b> R and the movable pin 22 </ b> L protruding inside the screen holding member 18, and the inner side of the screen holding member 18 along the curved surface of these distal ends. Move left and right (in-plane direction). As a result, the focusing screen 4 is positioned in the left-right direction while being pressed against the fixed pin 22R by the movable pin 22L. At the same time, the hooking portion 18 b of the screen holding member 18 comes into contact with the lower slope portion of the locking and pressing member 19.

When the screen holding member 18 is further pushed up to the position shown in FIG. 4C from this state, the hook 18b rises along the inclined surface of the locking / pressing member 19, and the focusing screen of the locking / pressing member 19 is moved. The pressing portion 19a generates an urging force in the front-rear direction (in-plane direction) against the focusing screen 4, the rear end portion of the focusing screen abuts against the abutting portion 18g of the screen holding member 18, and the focusing screen 4 is locked and pressed. Positioning in the in-plane front-rear direction is performed by the member 19 while being pressed against the abutting portion 18g.
Thus, when the positioning in the left-right direction by the pressing portions 22R and 22L and the positioning in the front-rear direction by the locking and pressing member 19 are completed, the wire spring 30 is biased to the reference surface 2b in the optical axis direction. As shown in FIG. 4D, the hooking portion 18b engages with the locking portion of the locking and pressing member 19, and the screen holding member 18 is locked at the set position.

  Thus, when the focusing screen 4 is loaded on the screen holding member 18 and the screen holding member 18 is pushed up toward the set position, positioning in the in-plane left-right direction is performed by the pressing portion 22L, and then the locking and pressing member Positioning in the longitudinal direction in the plane is performed by 19, and positioning in the finder optical axis direction (vertical direction) is performed by the wire spring 30 and the locking and pressing member 19. Accordingly, the focusing screen 4 is accurately positioned with respect to the mirror box 2 in the in-plane direction and the optical axis direction.

  When the focusing screen 4 is replaced, if the locking / pressing member 19 is lifted in the release direction (front side of the camera), first, the hooking portion 18b of the screen holding member 18 and the locking portion of the locking / pressing member 19 are released. Almost simultaneously, the positioning in the front-rear direction by the locking and pressing member 19 is released, and then the positioning in the left-right direction is released by the pressing means 22L, so that the focusing screen 4 can be replaced.

  Next, referring to FIGS. 3A and 3B, the biasing force A of the wire spring 30 in the optical axis direction, the biasing force B of the spring 23 in the optical axis direction, the biasing force C in the in-plane direction, locking and pressing The magnitude relationship between the biasing force D in the in-plane direction of the member 19 will be described.

The urging force F1 applied to the focusing screen 4 in the optical axis direction is the sum of the urging force A of the wire spring 30 and the urging force B of the spring 23 in the optical axis direction, and the direction of urging the reference surface 2b of the mirror box 2 is positive. Then F1 = AB
It is represented by

Next, the frictional force F2 required to move the focusing screen 4 in the in-plane direction is obtained by using the coefficient of static friction μ between the focusing screen 4 and the reference surface 2b, F2 = μ × (F1)
It is represented by

Here, the magnitude relationship of the urging forces of the locking / pressing member 19, the pressing means 30, and the spring 23 is as follows.
・ A> B
・ B> F2
・ D> F2
Accordingly, even when the focusing screen 4 is moved away from the pressing portions 22R and 18g due to an unexpected impact, vibration, or the like during the setting of the focusing screen 4 or during photographing, the wire spring 30 and the spring 23 The repositioning can be reliably performed in the optical axis direction and the in-plane direction by the urging force of the pressing portion 19a of the locking and pressing member 19.

  Further, in order to reduce the static friction coefficient μ, the reference surface 2b is lubricated.

  As described above, according to the present embodiment, the screen holding member 18 can be lowered to the attaching / detaching position to easily attach and detach the focusing screens 4 and 4 ′ to / from the screen holding member 18. The focusing screens 4, 4 ′ can be accurately overlapped with the superimposing liquid crystal 5 on the same axis simply by a simple operation of pushing up from the attachment / detachment position to the set position. By implementing superimpose display on the focusing screen positioned with high accuracy, a camera with a high-quality finder that matches the center of the superimpose display with the center of the display on the focusing screen is realized. can do.

Also, the magnitude relationship of the urging force of each pressing means is given as A> B
・ B> F2
・ D> F2
Thus, even when the focusing screen is moved away from the pressing portions 22R and 18g due to an unexpected impact, vibration, or the like during the setting of the focusing screen or during photographing, the wire spring 30 and the spring 23 The repositioning can be reliably performed in the optical axis direction and the in-plane direction by the urging force of the pressing portion 19a of the locking and pressing member 19.

  Further, the screen holding member 18 is held by holding the wire spring 30 in which the pressing means in the optical axis direction of the focusing screen is locked in the screen holding frame 18 so that the fulcrum is provided near the center of the long side and at the left and right end portions. Since the spring constant can be set low while maintaining the rigidity, it is possible to urge in the direction of the optical axis with a stable urging force even if variations in parts occur. Further, since the screen holding member 18 is held by the three locking portions, there is no need for welding or the like, and it can be realized at a low cost. By using a wire spring, the size can be reduced.

  In this embodiment, the abutment portion in the in-plane left-right direction is attached to the camera body 1 (mirror box 2) with a fixing pin 22R that is a separate body from the camera body 1, and the abutment reference in the in-plane front-rear direction is held on the screen. Although the case where the member 18 is provided has been described, the present invention is not limited thereto, and a portion corresponding to the fixing pin 22R may be integrally formed with the camera body 1. In addition, a portion corresponding to the contact reference 18g may be formed integrally with the camera body 1 or set separately from the screen holding member 18.

  Further, in the present embodiment, the method of directly pressing the focusing screen 4 in two directions in the in-plane direction of the focusing screen 4 has been described. However, pressing through the screen holding member 18 or urging in the optical axis direction is performed. A pressing portion in the in-plane direction may be formed integrally with the wire spring 30 that performs.

  In the present embodiment, the convex portion 4d of the focusing screen 4 and the linear spring 30 are brought into contact with each other. However, a flat portion without the convex portion 4d may be brought into contact with and urged.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

DESCRIPTION OF SYMBOLS 1 Camera body 2 Mirror box 3 Mirror unit 4 Focusing screen 4a Fresnel lens 4b Matte surface 4c Spot metering mark 2b Reference surface 4d Convex part 5 Superimposing liquid crystal 6 Condenser lens 7 Penta prism 8a, 8b, 8c Eyepiece 10 Photometry Sensor 11 Photometric lens 15 Focus detection unit 16 Shutter device 17 Mount 5a Distance field frame 4c Photometric mark 18 Screen holding member 18a Hinge portion 18b Hook portion 21 Shaft 30 Wire spring 19 Pressing portion 19a Locking and pressing member 20 Cover 30a Locking Parts 30b, 30c Locking part 18c Locking holes 18d, 18e Locking hole 18f Notch part 18g Abutting part 22R Fixed pin 22L Movable pin 23 Spring

Claims (4)

  A screen holding member (18) for holding the focusing screen (4) and a reference surface (2b) for determining the position of the focusing screen in the optical axis direction during focus observation are provided. In the focusing screen holding mechanism of the camera that can be moved between “a set position in which (4) is fixed at the focus observation position” and “an attaching / detaching position for attaching / detaching the focusing screen”, the screen holding member (18) includes: The hinge screen (4a) for rotating between the setting position and the attachment / detachment position of the focusing screen (4) and the pressing of the focusing screen (4) in the optical axis direction inside the screen holding member (18) Means (30), and the pressing means (30) includes a screen holding member ( 8) has a fulcrum in the vicinity of the central part of the long side facing the hinge part (18a) and in the vicinity of the hinge part (18a) on the left and right short sides, and the outer periphery of the focusing screen (4) by the pressing means (30). A focusing screen holding mechanism for a camera, wherein the projection screen (4d) is pressed against the reference surface (2b) when the focusing screen (4) is in the set position. When the screen holding member (18) moves from the attachment / detachment position to the set position, the focusing screen (4) is pressed against a contact portion (22R or 18g) provided on the camera body to perform this focusing. There is at least one pressing means (23 or 19a) for positioning the screen (4) in the in-plane direction, and the pressing of the pressing means for positioning in the in-plane direction is more than the frictional force by the pressing means in the optical axis direction. The focusing screen holding mechanism for a camera according to claim 1, wherein the focusing screen holding mechanism is large. The focusing screen holding mechanism for a camera according to claim 2, wherein the pressing means (30) integrally has a biasing shape capable of biasing in one direction of at least one of the optical axis direction and the in-plane direction. The focusing screen holding mechanism for a camera according to claim 2 or 3, wherein the surface of the reference surface (2b) is lubricated.