| 摘要 |
<p>1527306 Camera indicators FRANKE & HEIDECKE GmbH [Trading as ROLLEIWERKE FRANKE & HEIDECKE] 16 Nov 1976 [20 Dec 1975] 47693/76 Heading G2A The exposure time and/or the diaphragm aperture in a camera can be set automatically in dependence on subject brightness, or manually, and an indicator device comprising a number of light sources shows the difference, in the case of manual setting, between the value set manually and the value which would have been set automatically. Section 1 of the circuit shown determines the optimum setting, either of exposure time or aperture setting, in accordance with the subject brightness as measured by a photocell 6. Potentiometer 3 is set according to the film sensitivity. If the exposure time is set automatically, the diaphragm aperture is set manually by potentiometer 4, and the automatic exposure can be switched out in favour of manual setting by potentiometer 5. Similarly if the aperture is set automatically the exposure time is set manually by potentiometer 4 and the automatic aperture setting can be switched out in favour of manual setting by potentiometer 5. The changeover from automatic (A) to manual (M) setting is governed by a changeover switch 15 forming part of an asymmetric astable multi-vibrator 14. This is switched off in the A position, and in the M position presents a series of pulses to the bases of transistors 12, 13 forming the electronic part of the changeover switch. Potentiometers 3, 4 and 5 are connected to an analogue computer 2, the output signal from computer 2 passes to an analoguedigital converter 16 which converts to a corresponding digital combination. A decoder 17 decodes the digital combination and actuates one of eight outputs, each of which can light up one of the luminous diodes in an array 18. Each diode indicates either a specific exposure time or a specific diaphragm setting when the camera is being used with automatic timing or diaphragm (switch position A). With manual operation (switch position M), a long pulse is presented to transistor 12, but only a short pulse to transistor 13. Thus two diodes are lit up alternately by light flashes of different duration, corresponding to the value set manually and the value which would have been set automatically. These may be brought into coincidence by adjusting potentiometer 5. Instead of being of different duration the two light signals can be of different brightness or colour. They may be arranged to be visible in the view-finder.</p> |
