| 摘要 |
PURPOSE:To prevent the titled device from being affected by natural light by projecting light emitted from a xenon discharge tube as a range finding signal consisting of infrared rays or visual light including infrared rays, integrating the reflected light and driving a photographing lens in accordance with the integrated state. CONSTITUTION:A main discharging capacitor 4 is charged by a DC/DC converter 1 through a diode 5. A timer 11 generates constant voltages V1, V2 when a switch SW12 is closed, actuates a trigger circuit consisting of a capacitor 8 and a transformer 9, etc. through an SCR10, so that the xenon discharging tube emits light through an infrared-ray filter 7. A phototransistor 15 converts the reflected infrared rays photoelectrically and a capacitor 16 integrates the electrical signal by the time set up by a timer circuit consisting of a resistor 18, a capacitor 19 and a transistor 20. The integrated voltage from the capacitor 16 is compared by a comparator 23, and when the integrated voltage is more than reference voltage, the comparator generates an output signal, so that an electromagnetic device 26 is turned on and the photograhic lens is prevented from displacement. |
