| 摘要 |
1312381 Automatic exposure control EASTMAN KODAK CO 8 May 1970 [9 May 1969] 22474/70 Heading G2A The exposure of a film 17 through a lens 16 is controlled by the position of a diaphragm aperture 15 by selective energisation of oppositely poled coils L 1 , L 2 interacting with a permanent magnet 11, as described in specification 1291954, a further coil F b begin positioned in inductive relationship with magnet 11 so that a feedback emf is induced upon movement of the magnet, the feedback emf being applied to the multi-vibrator circuit Q 1 -Q 4 to oppose the effect of photo-electric cell RC so that any movement of the magnet is subject to an opposing damping force of a magnitude proportional to the velocity of the magnet. The provision of coil F b prevents overcorrection and resultant oscillation of aperture plate 13 about the optimum position. |
