| 摘要 |
PURPOSE:To simplify operation and to enable quick focusing by reversing the movement of a photographic lens where the lens has moved by a prescribed extent so as to restore automatically the focusing state when an object to be measured distance changes temporarily and the photographic lens starts unnecessarily scanning. CONSTITUTION:An object image to be photographed is formed with a photographic lens 3, a field lens LF, and image re-forming lenses 4, 5 on photoelectric elements 6, 7. The output thereof is inputted to a processing circuit 8, and when the circuit judges that both signals are in a correlated state, the circuit drives the lens 3 with a motor driving circuit 9 and a motor 10 according to the judgment of front focus, rear focus and focusing. The correlation signal and the driving direction of the photographic lens are inputted with terminals 22-24 to a control circuit 21, and the pulse signal interlocked to the revolution on the output side of the motor 10 is inputted with a terminal 25 to said circuit. A limiter 29 starts counting at the point of the time when the transfer to the non- correlated state is detected. When the pulse count value attains a constant (k), an inversion signal is emitted to reverse the moving direction of the photographic lens, whereby the focusing is quickly accomplished. |
