Abstract:
A camera has an AE sensor  10  and a display member  32  disposed in the vicinity of the focusing screen  4,  and a field frame switcher having a light interrupting wing capable of changing a field frame. The light-interrupting wing crosses and interrupts a predetermined luminous flux path used for obtaining information necessary for photographing while the field frame is changed. The light-interrupting wing is disposed close to the predetermined luminous flux path to reduce the space needed to house the structure.

Description:
This application is based on application No. H9-330288 filed in Japan, the contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a finder field frame switcher for cameras, and more particularly, to a finder field frame switcher in the advanced photo system having a plurality of image plane formats. 
     2. Description of the Prior Art 
     In the advanced photo system (hereinafter, referred to as APS) that have been commercialized in recent years, the image size format can be selected from among the following three types: a wide type (hereinafter, referred to as “H type”) with a length-to-width ratio of 9:16; a standard type (hereinafter, referred to as “C type”) with a length-to-width ratio of 2:3 in which, compared to the H type, the length is the same and the width is shorter; and a panorama type (hereinafter, referred to as “P type”) with a length-to-width ratio of 1:3 in which, compared to the H type, the width is the same and the length is shorter. 
     When an image size is selected by the user, it is necessary to switch the finder field frame. A conventional camera having a finder field frame switcher is arranged, for example, as shown in FIG.  1 . According to FIG. 1, a luminous flux A emanating from a subject and entering a camera  1  through a taking lens  2  is reflected at a reflecting mirror  3  and imaged at a focusing screen  4 . 
     In photographing, since the reflecting mirror  3  rotates so as to retreat to the vicinity of the focusing screen  4  and a shutter  12  is released for a predetermined time, the luminous flux A reaches a film  9  to expose the film  9 . In the APS, since image size information is recorded onto the film  9  by magnetic writing by use of a magnetic head (not shown) or by identification mark recording by use of a light emitting device (not shown), even if the film  9  is not shielded from light according to the image size format, the image size is decided based on the recorded image size information and printing onto photographic paper is performed. 
     On the other hand, in another system, for example, in a 135-type system, to switch between the standard image plane and the panoramic image plane, a field frame switching mechanism is necessarily provided in the front or in the rear of the shutter  12 . 
     In the rear of the focusing screen  4  on the optical path of the luminous flux A, a fixed field frame  5  having an H-type field frame and light interrupting wings  6  being rotatable are provided so that the light interrupting wings  6  rotate to switch between the H-type field frame and a P-type field frame. In the figure, the P-type field frame is selected when the light interrupting wings  6  are lying. The light interrupting wings  6  are also provided in positions parallel to the plane of the figure so as to switch between the H-type field frame and a C-type field frame. The image formed at the focusing screen  4  is reflected at a pentagonal Dach mirror  11  and enlarged by an eyepiece  8  so that the user can confirm the image of the desired field frame. 
     In order to automatically adjust exposure, a part (luminous flux A 2 ) of the luminous flux A having been imaged at the focusing screen  4  is captured by the automatic exposure (AE) sensor  10  to detect brightness. Further describing with reference to a detailed view shown in FIG. 2, the focusing screen  4  and the AE sensor  10  are disposed so that the luminous flux A 2  to be captured by the AE sensor  10  is not interrupted by the light interrupting wing  6  when the light interrupting wing  6  is standing upright to form the H-type or the C-type field frame. 
     Subsequently, another conventional example will be described. As shown in FIG. 3, a finder field  21  which can be viewed by the user includes an image display portion  22  having an image plane corresponding to the H type, and information display portions  25   a  and  25   b . When the C-type or the P-type field frame is selected, the focusing screen  4  (see subsequently-described FIG. 4) is shielded from light, so that a field  23  or  24  is displayed on the image display portion  22 . 
     On the information display portions  25   a  and  25   b , information such as the aperture value, the shutter speed, the flash indicator and the in-focus indicator is displayed so that the user is informed of the information. 
     A method of displaying information on the information display portions  25   a  and  25   b  will be described with reference to FIG.  4 . In FIG. 4, the fixed field frame  5  and light interrupting wings  6   a  and  6   b  are disposed above the focusing screen  4  in the structure of the camera  1  similar to that of FIG.  1 . The light interrupting wings  6   a  and  6   b  are rotatable between a position that covers a field limiting portion  5   a  of the fixed field frame  5  and a position that is retreated from the field limiting portion  5   a  so that the field frame can be switched between the P type and the H type. 
     At a side of the focusing screen  4 , a display member  32  such as a transmission-type liquid crystal panel is attached to the camera  1  by a fixing member  34 . A luminous flux B from a backlight  33  is reflected at a mirror  31  to reach the eyepiece  8  together with the luminous flux A 1  of the image on the focusing screen  4 , so that information is displayed on the information display portion  25   a  in a lower part of the finder field  21  in the previously-described FIG.  3 . 
     Moreover, by a similar structure, switching between the C-type field frame and the H-type field frame can be performed by the light interrupting wings  6   a  and  6   b . Further, by a similar structure, information can be displayed on the information display portion  25   b  in a side part of the finder field  21 . 
     In the arrangement in which the AE sensor  10  and the display member  32  are disposed in the vicinity of the focusing screen  4  as shown in FIGS. 2 and 4, the light interrupting wings  6   a  and  6   b  are disposed in positions that do not interrupt the luminous fluxes A 2  and B since the luminous fluxes A 2  and B used for obtaining information necessary for photographing cannot perform their functions if they are interrupted by the light interrupting wings  6   a  and  6   b . However, such an arrangement requires a large space (L 1  and L 2  of FIGS. 2 and 4) in the rear of the focusing screen  4  on the optical path of the luminous flux A from the subject. This has been an obstacle to size reduction of the camera. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is, in a camera having a field frame switching mechanism, to secure space for the members of the field frame switching mechanism and the switching path without increasing the size of the camera. More specifically, an object of the present invention is, in the arrangement in which the AE sensor  10  and the display member  32  are disposed in the vicinity of the focusing screen  4 , by reducing the overall size of the camera by providing a field frame switcher in which the optical path of the luminous flux A from the subject is shortened in the rear of the focusing screen by reducing the distance between the focusing screen  4  and an eyepiece  8 . 
     To achieve the above-mentioned object, according to the present invention, in a field frame switcher having a light interrupting wing capable of changing a field frame, the light interrupting wing crosses and interrupts a predetermined luminous flux path used for obtaining information necessary for photographing while the field frame is being changed. 
     According to this structure, the light interrupting wing is disposed close to the predetermined luminous flux path necessary for photographing and space in the camera can be reduced accordingly. When the field frame is switched, the light interrupting wing crosses the luminous flux path while moving to temporarily interrupt the luminous flux. However, since photographing has not been started yet when the field frame is switched, the luminous flux traveling on the luminous flux pass is not for use. Therefore, no problem arises if the luminous flux is interrupted by the light interrupting wing. Since the luminous flux traveling on the luminous flux path necessary for photographing is not interrupted by the light interrupting wing when field frame switching is finished and the light interrupting wing is stationary, photographing can be performed without any problem. 
     According to the present invention, the luminous flux path is the optical path of a luminous flux for displaying camera information in the finder field. 
     According to this structure, the light interrupting wing is disposed close to the focusing screen so as to interrupt the optical path of the luminous flux for displaying camera information in the finder field and space in the camera can be reduced accordingly. When the field frame is switched, the light interrupting wing crosses the optical path while moving to temporarily interrupt the luminous flux so that camera information is not displayed in the finder field. However, since photographing has not been started yet when the field frame is switched, no problem arises if the luminous flux is interrupted by the light interrupting wing. Since the luminous flux traveling on the optical path is not interrupted by the light interrupting wing when field frame switching is finished and the light interrupting wing is stationary, photographing can be performed with camera information displayed in the finder field without any problem. 
     According to the present invention, the luminous flux path is the optical path of a luminous flux to be captured by an AE sensor for detecting the brightness. 
     According to this structure, the light interrupting wing is disposed close to the optical path of the luminous flux to be captured by the AE sensor and space in the camera can be reduced accordingly. When the field frame is switched, the light interrupting wing crosses the optical path while moving to temporarily interrupt the luminous flux so that automatic exposure adjustment is not performed. However, since photographing has not been started yet when the field frame is switched, the luminous flux traveling on the optical pass at that time is not for use. Therefore, no problem arises if the luminous flux is interrupted by the light interrupting wing. Since the luminous flux traveling on the optical path to be captured by the AE sensor is not interrupted by the light interrupting wing when field frame switching is finished and the light interrupting wing is stationary, automatic exposure adjustment is performed, so that photographing can be performed without any problem. 
     According to the present invention, the light interrupting wing is a rotary wing that rotates more than 90 degrees. 
     According to this structure, when the field frame is switched, the rotary wing rotates so as to interrupt the predetermined luminous flux path and when field frame switching is finished, the height of the rotary wing is reduced in a direction vertical to the focusing screen since the rotation angle of the rotary wing is larger than 90 degrees, so that photographing can be performed without the luminous flux path interrupted. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and features of this invention will become clear from the following description, taken in conjunction with the preferred embodiments with reference to the accompanied drawings in which: 
     FIG. 1 is a cross-sectional view showing the structure of the conventional camera; 
     FIG. 2 is a cross-sectional view showing the structure of an example of the conventional field frame switcher; 
     FIG. 3 is a schematic view showing the finder field of the camera; 
     FIG. 4 is a cross-sectional view showing the structure of another example of the conventional field frame switcher; 
     FIG. 5 is a cross-sectional view showing the structure of a field frame switcher according to a first embodiment of the present invention; 
     FIGS. 6A and 6B are views of assistance in explaining a drive mechanism for driving the field frame switcher according to the first embodiment of the present invention; 
     FIG. 7 is a cross-sectional view showing the structure of a field frame switcher according to a second embodiment of the present invention; 
     FIG. 8 is a cross-sectional view showing the structure of a field frame switcher according to a third embodiment of the present invention; 
     FIG. 9 is a cross-sectional view showing the structure of a field frame switcher according to a fourth embodiment of the present invention; 
     FIG. 10 is a cross-sectional view showing the structure of a field frame switcher according to a fifth embodiment of the present invention; 
     FIGS. 11A and 11B are views of assistance in explaining a drive mechanism for driving the field frame switcher according to the fifth embodiment of the present invention; 
     FIG. 12 is a cross-sectional view showing the structure of a field frame switcher according to a sixth embodiment of the present invention; and 
     FIG. 13 is a cross-sectional view showing the structure of a field frame switcher according to a seventh embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first embodiment of the present invention will be described with reference to FIG.  5 . In FIG. 5, the same members as those of FIG. 4 are denoted by the same reference numerals. 
     According to the figure, the display member  32  is situated lower than that of the conventional arrangement (see FIG.  4 ), and the light interrupting wing  6   b  is disposed above the display member  32 . When the field frame is switched, the light interrupting wing  6   b  interrupts the luminous flux B from the backlight  33 , so that information is not displayed in the finder. However, the time during which the luminous flux B is interrupted is extremely short and when the field frame switching is finished, information is displayed in the finder since the luminous flux B from the backlight  33  is not interrupted. Thus, photographing can be performed without any problem. 
     As described above, by disposing the light interrupting wing  6   b  in a position that temporarily interrupts the luminous flux B from the backlight  33 , the space L 4  in the rear of the focusing screen  4  on the optical path of the luminous flux A from the subject can be reduced compared to the conventional arrangement (see FIG.  4 ). 
     The light interrupting wings  6   a  and  6   b  of the above-described first embodiment can be driven, for example, by a mechanism as shown in FIGS. 6A and 6B. FIGS. 6A and 6B show a drive mechanism  60  provided at one end, along the length, of the light interrupting wings  6   a  and  6   b.    
     According to FIG. 6A, a focusing screen holder  62  for holding the focusing screen  4  so as to be positioned has two rotary members  64  and  65  integrated with rotation axes  64   a  and  65   a  and rotatable about the rotation axes  64   a  and  65   a . The rotation axes  64   a  and  65   a  pass through the focusing screen holder  62  to be also integrated with the light interrupting wings  6   a  and  6   b . The rotary members  64  and  65  have drive pins  66  and  67 . The light interrupting wings  6   a  and  6   b  are rotated by the rotation of the drive pins  66  and  67 . 
     The focusing screen holder  62  also has a drive lever  63  being rotatable about a rotation center  63   c  and engaging with an operation lever  61  that rotates about a rotation center  61   a . The drive lever  63  has guide grooves  63   a  and  63   b  for guiding the drive pins  66  and  67 . A return spring  68  engages with the drive lever  63  so that the drive lever  63  receives a force in the clockwise direction of the figure. 
     When the operation lever  61  is rotated in the direction of the arrow E 1 , the drive lever  63  engaging with the operation lever  61  rotates in the counterclockwise direction, so that the drive pins  66  and  67  being guided by the guide grooves  63   a  and  63   b  are rotated in the directions of the arrows D 1  and D 2 . This moves the light interrupting wings  6   a  and  6   b  to the positions shown in FIG.  6 B. Under this condition, the operation lever  61  can be held at the position shown in FIG. 6B by a holding mechanism (not shown) such as a click mechanism. 
     When the operation lever  61  is rotated from the position shown in FIG. 6B in the direction of the arrow E 2 , the drive lever  63  is rotated in the clockwise direction by the return spring  68 . This moves the light interrupting wings  6   a  and  6   b  to the positions shown in FIG.  6 A. 
     In the light interrupting wings  6   a  and  6   b , arms  6   a   2  and  6   b   2  formed only on both ends, along the length, of wings  6   a   1  and  6   b   2  hold the wings  6   a   1  and  6   b   1 , so that the light interrupting wings  6   a  and  6   b  does not interrupt the luminous flux B from the backlight (see FIG. 5) when they are situated at the positions shown in FIG.  6 A. 
     By the above-described drive mechanism  60 , the light interrupting wing  6   b  can be disposed above the display member  32  as shown in the previously-described FIG. 5, so that space can be saved. 
     The light interrupting wing  6  may be structured so as to move on a plane surface like in a second embodiment shown in FIG. 7, or the display member  33  may be disposed parallel to the focusing screen like in third and fourth embodiments shown in FIGS. 8 and 9. In any of these arrangements, by disposing the light interrupting wing  6  in a position that temporarily interrupts the luminous flux B from the backlight  33 , the spaces L 5 , L 6  and L 7  in the rear of the focusing screen  4  on the optical path of the luminous flux A from the subject can be reduced compared to the conventional arrangement. In FIGS. 7,  8  and  9 , the same members as those of FIG. 5 are denoted by the same reference numerals. 
     Subsequently, a fifth embodiment of the present invention will be described with reference to FIG.  10 . FIG. 10 shows an arrangement in which the distance L 3  between the AE sensor  10  and the focusing screen  4  is shorter than that in the conventional arrangement (see FIG.  2 ). 
     According to the figure, by reducing the distance L 3  between the AE sensor  10  and the focusing screen  4 , the light interrupting wing  6  is rotated more than 90 degrees. In the rotation range G, the light interrupting wing  6  interrupts a luminous flux A 2  to be captured by the AE sensor  10 , so that automatic exposure adjustment is not performed. However, since the luminous flux A 2  to be captured by the AE sensor  10  is not interrupted at positions ( 6   c  and  6   d ) where the light interrupting wing  6  is stationary, automatic exposure adjustment is performed when field frame switching is finished. Therefore, photographing can be performed without any problem. 
     In such a drive mechanism for the light interrupting wing  6 , it is difficult to rotate the light interrupting wing  6  more than 90 degrees by a drive method such that the drive pins  66  and  67  are rotated by being guided by the guide grooves  63   a  and  63   b  like in the above-described drive mechanism  60  shown in FIG.  6 . Therefore, the light interrupting wing  6  can be driven, for example, by a drive mechanism  40  as shown in FIGS. 11A and 11B. 
     According to FIG. 11A, the focusing screen holder  62  for holding the focusing screen (see FIGS. 6A and 6B) so as to be positioned has two gears  45  and  49  integrated with rotation axes  45   a  and  49   a  and rotatable about the rotation axes  45   a  and  49   a . The rotation axes  45   a  and  49   a  pass through the focusing screen holder  62  to be also integrated with the light interrupting wings  6 . 
     The focusing screen holder  62  also has an operation lever  42  that rotates about a rotation center  42   a  and drive levers  43  and  47  being rotatable about rotation centers  43   a  and  47   a . The drive levers  43  and  47  have toothed portions  43   b  and  47   b  engaging with the gears  45  and  49 . 
     An overcharge spring  46  is fixed to the operation lever  42 . The overcharge spring  46  engages with engagement portions  43   c  and  47   c  of the drive levers  43  and  47  so that the movement of the operation lever  42  is transmitted to the drive levers  43  and  47 . Return springs  44  and  48  engage with the drive levers  43  and  47 , so that a force that rotates the drive levers  43  and  47  in the directions of the arrows M 1  and M 2  acts on the drive levers  43  and  47 . 
     When the operation lever  42  is rotated in the direction of the arrow J 1 , the drive levers  43  and  47  engaging with the overcharge spring  46  rotate in the directions of the arrows H 1  and H 2 . Since the pitch circle diameters of the gears  45  and  49  are smaller than the pitch circle diameters of the toothed portions  43   b  and  47   b , the gears  45  and  49  are rotated through accordingly larger angles in the directions of the arrows K 1  and K 2 , so that the light interrupting wings  6  can be rotated more than 90 degrees as shown in FIG.  11 B. Under this condition, the operation lever  42  can be held at the position shown in FIG. 11B by a holding mechanism (not shown) such as a click mechanism. 
     When the operation lever  42  is rotated in the direction of the arrow J 2  from the position shown in FIG. 11B, the drive levers  43  and  47  are rotated in the directions of the arrows M 1  and M 2  by the return springs  44  and  48 . This moves the light interrupting wings  6  to the positions shown in FIG.  11 A. 
     By the above-described drive mechanism  40 , the light interrupting wings  6  can be rotated more than 90 degrees and the AE sensor can be disposed close to the focusing screen  4  as shown in the previously-described FIG. 10, so that space can be saved. 
     Subsequently, a sixth embodiment of the present invention will be described with reference to FIG.  12 . In FIG. 12, the light interrupting wings  6  of the fifth embodiment are replaced by L-shaped light interrupting wings  6  which are formed so that the field frame can be switched between a position ( 6   c ) that covers the field limiting portion  5   a  of the fixed field frame  5  and a position ( 6   e ) that is retreated from the field limiting portion  5   a . By providing the L-shaped light interrupting wings  6  like in FIG. 6, the rotation centers of the light interrupting wings  6  can be situated in the front of an imaging plane  4   a  of the focusing screen  4  on the optical path of the luminous flux A from the subject, so that the space in the rear on the optical path of the luminous flux A which space is necessary for the rotation of the light interrupting wings  6  can be reduced. 
     When the distance between the AE sensor  10  and the focusing screen  4  is reduced, since the position ( 6   e ) that is retreated from the field limiting portion  5   a  interrupts the luminous flux A 2  to be captured by the AE sensor  10 , it is necessary to rotate the light interrupting wing  6  to the position  6   d  and it is necessary to shift the AE sensor  10  from a position  10   a  to a position  10   b  to prevent interference between the light interrupting wing  6  and the AE sensor  10 . Although this arrangement requires more space in the horizontal direction of the figure, the space in the vertical direction can be reduced by ΔL. 
     When the field frame is switched, the light interrupting wing  6  crosses the luminous flux A 2  to be captured by the AE sensor  10  while being rotated in the rotation range F. However, the luminous flux A 2  is not interrupted when the light interrupting wing  6  is stationary (at the positions  6   c  and  6   d ), photographing can be performed without any problem arising in automatic exposure operation. 
     The light interrupting wings  6  as shown in the figure can be driven by a mechanism similar to the drive mechanism of the first embodiment (see FIGS.  6 A and  6 B). 
     Subsequently, a seventh embodiment will be described with reference to FIG.  13 . FIG. 13 is a top view of a camera  1  having instead of the pentagonal Dach mirror a relay lens optical system with an optical path bent in the shape of the letter N by a relay lens  71 . 
     A luminous flux C from the subject reflected at a mirror  72  passes above the light interrupting wings  6  disposed on the left and right sides of the focusing screen  4 , and space in the camera can also be reduced by reducing the distance between the light interrupting wings  6  and the luminous flux C until the light interrupting wings  6  are situated in positions that cross the luminous flux C only when the field frame is just being switched. Moreover, the light interrupting wings  6  can be disposed on a secondary imaging plane S in the figure. In the figure, reference numerals  73  and  74  represent a reflecting mirror and an eyepiece, respectively. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced other than as specifically described.