| 摘要 |
PURPOSE:To obtain a stable responsiveness without causing a response delay, overshooting, hunting, etc., by calculating the change quantity of a signal near focusing with time from a time series signal and adjusting the moving speed of a photographing lens in accordance with the calculated change quantity. CONSTITUTION:The outputs A, B of respective elements 4a, 4b of a photodetec tor 4 are integrated and a difference (A-B) between the signals A and B is made. The difference is converted to a digital quantity by an A/D converter built in a signal processing circuit S, which determines a signal (y) by making the operation y=(A-B)/(A+B); i.e., (A-B)/(2L). The influence of the relative movement of an object O and a camera can be detected when the photodetector 4 moves and enters a straight part (y=K.t) near the focusing point. The speed of a motor 6 is changed by this constant (k). More specifically, judgement is made that the object O is approaching the camera if the coefft. (k) is larger than the prescribed value. The speed of the motor 6 is then decreased. Judge ment is made that the object O is parting distance from the camera if the coefft. (k) is smaller than the prescribed value. The speed of the motor 6 is then increased. |
