Apparatus for changing the size of the photographing aperture in a camera
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus for changing the size of a photographing aperture in a camera, for example, from a standard size to a panoramic size (or a half size, etc.) and back to the standard size. 
     2. Description of Related Art 
     There are known cameras in which the size of a photographing aperture can be varied from a standard size (24 mm×36 mm) to a small size, e.g., a panoramic size (13 mm×36 mm), while a film roll is inserted in the camera. To change the photographing aperture size, it is known to provide a pair of light intercepting plates in the vicinity of a photographing aperture which defines a standard size photographing aperture. The pair of light intercepting plates are advanced into the photographing aperture by a predetermined amount to reduce the size of the photographing aperture. When the photographing aperture size is changed back to the standard size, the pair of light intercepting plates are retracted from the photographing aperture. In the known photographing aperture changing apparatus, the pair of light intercepting plates are positioned in the vicinity of the photographing aperture on the side of a photographing lens (i.e., object side) of the camera and are moved into and retracted from the photographing aperture in a linear manner (i.e., the plates are moved in a plane perpendicular to an optical axis of the photographing lens). 
     In a conventional camera having the above structure, since the pair of light intercepting plates are positioned in the vicinity of the photographing aperture, but on the side of the photographing aperture nearest to the photographing lens, the pair of light intercepting plates and the film plane are further apart from one another than the photographing aperture and the film. As a result, when a picture is taken with the reduced size aperture, a pair of edges of a photographing image on a film are likely to be blurred. The blurred edges correspond to the edges of the light intercepting plates. Furthermore, when a picture is taken with the reduced size aperture, the aperture which is defined by the pair of light intercepting plates sometimes does not correspond to the actual size of the photographing image on a film. Specifically, in the case of an SLR camera to which various types of photographing lenses can be detachably attached, the actual photographing image on a film tends not to correspond to a desired photographing size, since an angle of light rays incident on an image surface varies depending upon the focal length of the photographing lens. 
     SUMMARY OF THE INVENTION 
     The primary object of the present invention is to provide a photographing aperture size changing apparatus which makes it possible to obtain a stable reduced size photographing image that corresponds to the reduced size photographing aperture regardless of the type of photographing lens or focal length, and also to obtain a reduced size photographing image having clearly defined edges. 
     To achieve the object mentioned above, according to the present invention, there is provided an apparatus for changing a size of a photographing aperture of a camera, wherein the photographing aperture defines an image area on a film. The apparatus comprises a mechanism for intercepting light within the photographing aperture. The light intercepting mechanism is movable between a retracted position, in which the aperture is fully opened, and a projected position in which the aperture is partly covered. The apparatus further comprises an association mechanism which moves the light intercepting mechanism between the retracted position and the projected position, wherein at least a forward most projecting edge of the light intercepting mechanism is moved towards the film when moved into the projected position. 
     With this structure, since the forward most projecting edge of the light intercepting mechanism is moved towards the film when in the projected position, a stable photographing image on a film can be obtained regardless of the focal length. Furthermore, a reduced size photographing image having sharp edges can be obtained. 
     The present disclosure relates to subject matter contained in Japanese utility model application No. 05-223 (filed on Jan. 8, 1993) which is expressly incorporated herein by reference in its entirety. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be described below in detail with reference to the accompanying drawings, in which; 
     FIG. 1 is an isometric view of a main portion of a photographing aperture size changing apparatus, illustrating light intercepting plates in a retracted position, seen from a side of a photographing lens barrel, according to an embodiment of the present invention; 
     FIG. 2 is a front elevational view of the main portion of FIG. 1, illustrating light intercepting plates in a retracted position, seen from a side of a photographing lens barrel; 
     FIG. 3 is a longitudinal sectional view along line III--III shown in FIG. 2; 
     FIG. 4 is a front elevational view of the main portion of FIG. 1, illustrating light intercepting plates in a panoramic position, seen from a side of a photographing lens barrel; and, 
     FIG. 5 is a longitudinal sectional view along line V--V shown in FIG. 4. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A photographing aperture size changing apparatus 10 is provided adjacent to a photographing aperture 11 and orthogonal to an optical axis direction of a photographing lens (not shown). The aperture 11 is formed in a camera body 9 (see FIG. 3) and is defined by aperture edges 11a, 11b, 11c, and 11d formed on the camera body 9. The aperture 11 defines a standard size photographing aperture. The photographing aperture size changing apparatus 10 includes a pair of light intercepting plates, i.e., light intercepting plates 21 and 31. When a standard size aperture is selected, the light intercepting plates 21 and 31 are positioned outside the aperture 11, above the aperture edge 11b, and below the aperture edge 11d, so that they do not intercept a photographing light path defined by the aperture 11. When a reduced size, i.e., panoramic size aperture is selected, the light intercepting plates 21 and 31 are advanced into the aperture 11 by a predetermined amount, and plate edges 21a and 31a define upper and lower edges of a panoramic size photographing aperture. Right and left edges of the panoramic size photographing aperture are defined by the aperture edges 11a and 11c. In FIGS. 3 and 5, numerals 15, 16, and 17 designate a film, a pressure plate, and a back cover, respectively. 
     The first light intercepting plate 21 is connected to a first frame member 23 through a deformable hinge 22. The first frame member 23 is formed in a manner such that it surrounds a photographing light path defined by the aperture 11. The first frame member 23 is guided by a guiding member (not shown) in a direction perpendicular to the optical axis. The second light intercepting plate 31 is connected to a second frame member 33 through a deformable hinge 32. The second frame member 33 is positioned outside the photographing light path on the opposite side of the first light intercepting plate 21. The first and second frame members 23 and 33 are interlocked in a manner such that they can move towards and away from each other in parallel directions by means of first and second levers 41 and 42. The first and second levers 41 and 42 are rotatable about a pivot 43. The pivot 43 is fixed to the camera body 9. More details regarding the first and second frame members 23 and 33 will be discussed later. 
     A leaf spring 24, which biases the first light intercepting plate 21 towards the film 15 is fixed on a surface of the first frame member 23 near the center thereof on a photographing lens side (i.e., object side). The tip of the leaf spring 24 biases the first light intercepting plate 21 in a direction in which the first light intercepting plate 21 rotates at the deformable hinge 22 towards the film 15. Pins 25a and 25b are provided on the first light intercepting plate 21. The pins 25a and 25b are positioned at right and left sides of the first light intercepting plate 21 on the photographing lens side, respectively, in the vicinity of a plate edge 21a of the first light intercepting plate 21. 
     The pins 25a and 25b are biased against guiding rails 12 and 13 by a restoring force of the leaf spring 24. The guiding rails 12 and 13 are formed on the camera body 9 at right and left sides of the aperture 11. The pins 25a and 25b are always in slidable contact with the guiding rails 12 and 13 due to the restoring force of the leaf spring 24. The pins 25a and 25b slide along the guiding rails 12 and 13, respectively, when a photographing aperture size is changed. Accordingly, the positions of the pins 25a and 25b in a direction perpendicular to a plane of the film 15 are defined by the guiding rails 12 and 13. Numeral 23c designates a projection which is interlocked with an operating switch (not shown) provided on the camera body 9. The operating switch is for changing the size of the photographing aperture and is operated when a photographer desires to change the photographing aperture size. In accordance with the operation of the operating switch, the projection 23c is moved up or down as shown in FIGS. 2 and 4. 
     A couple of leaf springs 34a and 34b, which bias the second light intercepting plate 31 towards the film 15, are fixed on a surface of the second frame member 33 at predetermined positions on the photographing lens side. The tips of the leaf springs 34a and 34b bias the second light intercepting plate 31 towards the film 15. The second light intercepting plate 31 rotates about the deformable hinge 32 due to the force of the leaf springs 34a and 34b. Pins 35a and 35b are provided on the second light intercepting plate 31. The pins 35a and 35b are positioned at right and left sides of the second light intercepting plate 31 on the photographing lens side, respectively, in the vicinity of a plate edge 31a of the second light intercepting plate 31. 
     The pins 35a and 35b are biased against the guiding rails 12 and 13 by a restoring force of the leaf springs 34a and 34b. The pins 35a and 35b are always in slidable contact with the guiding rails 12 and 13 due to the restoring force of the leaf springs 34a and 34b. The pins 35a and 35b slide along the guiding rails 12 and 13, respectively, when a photographing aperture size is changed. Accordingly, the positions of the pins 35a and 35b in a direction perpendicular to a plane of the film 15 are defined by the guiding rails 12 and 13. 
     The first and second levers 41 and 42 are positioned outside of the photographing light path defined by the aperture 11. The first frame member 23 is positioned between the first and second levers 41 and 42. An elongated hole 41a is formed in one end of the first lever 41. A pin 23a is provided on the first frame member 23 and is engaged with the elongated hole 41a. An elongated hole 41b is formed in the other end of the first lever 41. A pin 33b is provided on the second frame member 33 and is engaged with the elongated hole 41b. 
     Likewise, an elongated hole 42a is formed in one end of the second lever 42. A pin 33a is provided on the second frame member 33 and is engaged with the elongated hole 42a. An elongated hole 42b is formed in the other end of the second lever 42. A pin 23b is provided on the second frame member 23 and is engaged with the elongated hole 42b. With this structure, when the first frame member 23 is moved towards the second frame member 33 (i.e., in the direction in which the photographing aperture size is changed to the panoramic size), the second frame member 33 moves towards the first frame member 23, as shown in FIG. 2. To the contrary, when the first frame member 23 is moved away from the second frame member 33 (i.e., in the direction in which the photographing aperture size is changed to the standard size), the second frame member 33 moves away from the first frame member 23, as shown in FIG. 2. 
     The profiles of the guiding rails 12 and 13 in a side view of the apparatus 10 are coincident. The guiding rail 12 has raised portions 12a and 12e at upper and lower ends, respectively, for spacing the light intercepting plates 21 and 31 far from the film 15. The guiding rail 12 also has a lowered portion 12c in the middle thereof for spacing the light intercepting plates 21 and 31 close to the film 15, and connecting sloped portions 12b and 12d. The guiding rail 13 has corresponding raised portions 13a and 13e at upper and lower ends, respectively, a lowered portion 13c in the middle thereof, and connecting sloped portions 13b and 13d. When the standard size is selected, the pins 25a, 25b, 35a, and 35b are positioned on the raised portions 12a, 13a, 12e, and 13e, respectively, at a position far from the film 15 (i.e., distant position) by a predetermined distance in the optical axis direction (See FIGS. 2 and 3). When the panoramic size is selected, the pins 25a and 35a, and pins 25b and 35b are positioned on the lowered portions 12c and 13c, respectively, at a position which is close to the film 15 in the optical axis direction (See FIGS. 4 and 5). 
     The photographing aperture size changing apparatus of the present invention operates as follows: 
     When the standard photographing aperture size is selected, the first light intercepting plate 21 is positioned outside the aperture 11 above the aperture edge 11b. When the light intercepting aperture 21 is moved into the panoramic position from the standard position by an operation of the operation switch (not shown), the first lever 41, which is connected to the pin 23a, is rotated in the counterclockwise direction and the second lever 42, which is connected to the pin 23b, is rotated in the clockwise direction in FIG. 2. Accordingly, the first and second light intercepting plates 21 and 31 are slid towards each other. The pins 25a and 25b slide across the raised portions 12a and 13a, onto the connecting sloped portions 12b and 13b, and subsequently onto the lowered portions 12c and 13c, respectively. Similarly, the pins 35a and 35b slide across the raised portions 12e and 13e, onto the connecting sloped portions 12d and 13d, and subsequently onto the lowered portions 12c and 13c, respectively (see FIG. 5). Accordingly, the plate edges 21a and 31a are brought nearer the film 15. As a result, the panoramic size photographing aperture is defined by the aperture edges 11a and 11c and the plate edges 21a and 31a. 
     When the first light intercepting plate 21 is moved into the standard position by an operation of the operating switch, the first and second levers 41 and 42 are rotated in clockwise and counterclockwise directions, respectively, and the second light intercepting plate 31 is moved in the standard photographing aperture direction. The pins 25a and 25b slide across the lowered portions 12c and 13c, onto the connecting sloped portions 12b and 13b, and subsequently onto the raised portions 12a and 13a, respectively. Similarly, the pins 35a and 35b slide across the lowered portions 12c and 13c, onto the connecting sloped portions 12d and 13d, and subsequently onto the raised portions 12e and 13e, respectively. Accordingly, the first and second light intercepting plates 21 and 31 retract from the photographing light path defined by the aperture 11. 
     As can be seen from the foregoing, according to the present invention, since the plate edges 21a and 31a are brought nearer the film 15 when the panoramic size photographing aperture is selected, the selected aperture, i.e., the standard or panoramic size photographing aperture, will be substantially the same size as the corresponding photographing image on a film. Furthermore, the edges of the photographing image will be sharp, even if the angle of light rays incident upon the film 15 varies. 
     Furthermore, since the first and second light intercepting plates 21 and 31 are brought near and away from the film 15 when the photographing aperture size is changed, it is unlikely that the first and second light intercepting plates 21 and 31 will scratch and damage the film 15. Moreover, since only the first and second light intercepting plates 21 and 31 are brought towards and away from the film 15, whereas the first and second frame members 23 and 33 move in a parallel fashion, without moving nearer to the film 15, it is not necessary to increase the space for installment of apparatus 10 in the camera body 9 in the optical axis direction. Therefore, the apparatus 10 can be easily fitted in a camera, even in an SLR camera having a focal plane shutter. 
     In the above embodiment, the guiding rails 12 and 13 may be replaced with guiding grooves in which the pins 25 and 35 are slidably engaged with the corresponding grooves. It is possible to make the deformable hinges 22 and 32 of an elastic material having a restoring force which biases the first and second light intercepting plates 21 and 31 towards the film 15, respectively. In this arrangement, it is not necessary to provide the leaf springs 24 and 34. 
     In the above embodiment, the reduced photographing aperture size is directed to the panoramic size. However, it is possible to change the standard photographing aperture size to a half size or other sizes, e.g., a hi-vision size having the dimensions of 16 mm by 9 mm. 
     Although the invention has been described with reference to particular means, materials and embodiments, it is to be understood that the invention is not limited to the particulars disclosed and extends to all equivalents within the scope of the claims.