| 摘要 |
PURPOSE:To remove disturbance due to superposed background light by inputting a photodetection signal, such as object detecting pulses of an automatic focusing camera, to a resonant circuit for amplification, and by extracting its output which exceeding a prescribed level. CONSTITUTION:When the shutter button of an automatic focusing camera is pushed, a swithc 27 is closed prior to the release of a shutter 34 and while a photodetection part 12 is put in operation, a trigger switch 11 is closed to emit light from the detecting light emitting tube 9 of a strobe emission part 1. Intense pulse reflected light from an object at a short-distance position is inputted to a photodetection diode 13 to energize a resonant circuit 15. The output of the circuit 15 has a relatively large high-frequency gain and is inputted to a crest-value discriminating circuit 12 through an amplifier 14, and a pulse output exceeding a prescribed lelvel is extracted and separated from a background light output. The position of a lens 33 is controlled with the output of the circuit 12 through an electromagnet 31 to perform photographing. |
