GB1270597A - Apparatus including an automatic range finder mechanism - Google Patents

Abstract

1,270,597. Automatic focusing. EASTMAN KODAK CO. 3 July, 1969 [9 July, 1968], No. 33568/69. Heading H4D. [Also in Division G2] Specification describes an automatic rangefinding and focusing arrangement particularly for use on a camera and comprising a pivoting mirror 70, Figs. 2 and 7 scanning a beam of light from a modulated light source 94 across a subject plane and a receiving lens 26 directing light reflecting from the subject S, visually positioned directly in front of lens 26, on to two photo-detectors 116, 118, an electronic 106 circuit detecting and producing an output when the detectors are equally illuminated indicating that the light beam is directed at the subject, said output stopping the movement of the mirror 70. Pivotal movement of the mirrors is coupled with rotary movement of a cam 32, the surface 36 of which controls the position of the focusing lens 12. In detail the cam 32 is initially rotated anticlockwise against spring 34 and locked in position by tooth 76 engaging in rack 80. To start the automatic focusing button 20 is depressed, releasing tooth 76 and allowing the cam to rotate clockwise. This causes three actions:-(a) contacts 52 are closed by cam surface 50 whereby electrical energy is supplied to circuit 106 and to light source 94; (b) chopper read actuator 58 is pivoted about 60 by means of follower 56 and cam groove 54, whereby a read 102 is vibrated to amplitude modulate the light beam from source 94, and (c) mirror 70 commences to turn about 68 by means of follower 64 riding slot 62 and scan the modulated light beam. Part of the light beam is detected by means 104 and a signal fed to circuit 106 for synchronous demodulated of the reflected light beam signal. When photodetectors 116 and 118 are equally illuminated circuit 106 (Specification 1,270,596) feeds a signal to solenoid 82 whereby plunger 84 moves to cause tooth 86 to lock into rack 80 and stop the cam rotation. Button 22 is now depressed, moving lever 44 and releasing lens 12 whereby it moves under the action of spring 42, until follower 38 abuts cam surface 36 marked in range units. Button 22 also actuates the shutter release lever 124.