| 摘要 |
PURPOSE:To improve the responsibility of a photodetecting element which photodetects reflected light from a subject by making a specific quantity of luminous flux incident on the photodetecting element before flash dimming operation. CONSTITUTION:When a main capacitor 5 is charged with the output of a DC-DC converter 2 up to a voltage high enough to emit flash light, the output of a comparator 9 is inverted to a level H and an LED36 turns on through a resistance 37. Part of the light emitted by the LED36 is passed through a light guide L to illuminate a phototransistor 32 and then when a synchro switch 13 is turned on, a transistor (TR) 12 turns on and a thyristor 14 also turns on to invert the output of the comparator 9 to a level L, turning off the LED36. Thus, the thyristor 14 turns on and a thyristor 20 also turns on to start the light emission of a discharge tube 19, so that the reflected light from the subject is incident on the phototransistor 32. The phototransistor 32 is irradiated preliminarily after the main capacitor 5 is charged completely, so the device is used in a high responsibility state during flash photography. |
