| 摘要 |
1294074 Photographic exposure controls EASTMAN KODAK CO. 8 Jan 1970 [9 Jan 1969] 1001/70 Heading G2A An exposure control device of a camera had an avalanche photo-diode 7 exposed to scene illumination through a diaphragm slot 4 of a rotary diaphragm plate 5 having a second slot 6 in the optical path to a film 3. The photo-diode 7 is in circuit with a transistor 8 that conduct's to energize a trainsducer 9 which produces a counter clockwise rotation of the diaphragm plate 7 against the action of a spring 12. The plate 5 oscillates at a high frequency when the device is balanced, such that the photo-diode 7 is alternately illuminated above and below the level where it conducts. In a modification Fig. 2 (not shown) the spring 12 is dispensed with by using a dual coil having oppositely poled windings (9<SP>1</SP> and 9<SP>2</SP>) each transducer connected to separate transistors |
