Patent GB-1267137-A (GB)
IPC: G03B13/20
Filed: 1970-07-16
Abstract: 1,267,137. View-finding and focusing means. SANKYO KOGAKU KOGYO K.K. July 16, 1970 [July 31, 1969; March 26, 1970J, No.34418/70. Heading G2A. In a camera view-finding and range-finding arrangement, two light beams passing along respective paths O 3  and O 4  are combined into a single beam by reflectors 17, 21, one of these reflectors being pivotable by means operable in response to movement of a focusing lens; after passing through a magnifying optical system the beam is reflected by a movable reflector 20, which can move between a first position in which the beam is reflected into the view-finder 16 and a second position in which the reflector 20 is out of the optical path of the view-finder system. As shown, the subject to the photographed lies on the optical axis O 1 , the light passing through a zoom lens system 4a, 4b and an image-forming lens 10 which produces an inverted image on the film 11. Part of the light is deflected by a small mirror 12 to pass through a finder lens 13, and is deflected by a mirror 14 through a field lens 15, and is received by a view-finder system 16. The two focusing beams enter by windows 6, 7 disposed above the lens system 4a, 4b and pass along paths O 3  and O 4  . The beam entering window 6 passes through a semitransparent mirror 17, and the beam entering window 7 is reflected by a fixed mirror 21 and then by mirror 17. Thus after leaving mirror 17 the two beams are coincident. Mirror 17 is mounted on a lever 23 which is linked by a cam and lever arrangement 24, 25, 28, 29 to the front lens 4a. Pin 29 bears against the rear surface of the mounting of lens 4a, so that as this is rotated and hence caused to move axially, mirror 17 is angularly rotated through a small angle until the two images are brought into coincidence. From mirror 17 the coincident beams pass through a magnifying lens system 18, and are reflected downwards by a mirror 19 to a movable mirror 20. When mirror 20 occupies the position shown in full lines, it is out of the optical path of the view-finder 16. Thus an observer looking through the view-finder eye-piece 5 will see only the view-finder field, and the picture angle may be determined by operating the zoom lens. To perform a focusing operation, a button 3, which is exterior of the camera, is pressed. This pushes a slide 31 against the action of a spring 34. A bevelled edge 31c of this slide engages a pin 36 on another similar slide 35 on which the mirror 20 is mounted, and causes it to move downwards. This brings the mirror 20 into the position shown in broken lines, in which it blocks the optical axis O 2  of the view-finder 16. Thus an observer looking through the eye-piece 5 no longer sees the view-finder field through the lens 4a but the focusing field through the windows 6, 7. When the button 3 is released, mirror 20 moves out of the finder path, and the finder field comes into view, so that an exposure can now be made immediately. Figs 4, 5, 8 and 9 (not shown) illustrate alternative methods of effecting the movement of the mirror 20 between the two positions of intercepting or not intercepting the optical path O 2 .