| 摘要 |
PURPOSE:To obtain an autofocusing circuit where scarcely malfunction occurs by driving a photographing lens by a distance measuring signal which is identified at a part where the amplitude difference of pulsating voltage is large. CONSTITUTION:A timer 18 which starts its action with the start of the lighting of a light source 24 and finishes the action immediately after the peak value of the pulsating voltage of output from 1st and 2nd photodetectors 26 and 27 passes is provided. A lens driving circuit 34 is constituted so that it shifts to the preparation of the action in accordance with the output from the timer and drives the lens by inputting the distance measuring signal under the condition of the preparation of the action. Namely, the circuit 34 acts by inputting the distance measuring signal obtained until the point of time that is immediately after the peak of the pulsating voltage passes and does not act by the distance measuring signal at the falling part of the pulsating voltage. Therefore, it surely acts on the focus of a short distance and the focus of a long distance whether photographing is for the short distance or the long distance. |
