| 摘要 |
PURPOSE:To obtain a detecting signal which scarcely includes noise, and to execute operation with high accuracy be eliminating the impulsive noise in the output of photodetectors by a limiter provided on a circuit detecting a focusing degree corresponding to a state of a pair of photodetectors. CONSTITUTION:Outputs of two-split photodetectors 12A, 12B interlocked with focus driving of a photograhic lens are inputted to amplifiers 13A, 13B and 14A, 14B to be amplified, thereafter, made to pass through through limiters 15A, 15B, a part of which is inputted to an automatic gain controlling circuit 17 through an OR circuit 16, and the gain of each amplifier 14A, 14B is controlled. Outputs of the limiters 15a, 15B are integrated by integrators 19A, 19B through changeover switches 18A, 18B. By making said outputs pass through the limiters 15A, 15B in such a way, impulsive noise is eliminated, a detecting circuit obtains a detecting signal which scarcely has noise and the gain is controlled properly, and also the operation of the detecting circuit can be executed with high accuracy. |
