AUTOMATIC FOCUS CONTROLLER

摘要

PURPOSE:To avoid a malfunction of an automatic focus controller by dividing the video signals passed through plural BPFs of different bands into a speed control system and a direction indication system with addition of a filter peak detecting circuit and an adder circuit to both systems respectively and also driving a lens focus control system with the outputs of both circuits. CONSTITUTION:A filter detection NAM circuit 21 detects the peak of each filter, and the effects of the depth can be avoided by transmitting the outputs of amplifiers 15-17 through the circuit 21. Here a motor driving circuit 8 is controlled by a speed control circuit 22 so that the driving speed of a motor 5 is set at a low level toward a focal point D0 compared with a case where an out-of-focus degree is large to the point D0. Thus the focusing control of a lens 1 is carried out smoothly. The output of an adder circuit 18 undergoes the synchronizing wave detection through a synchronizing wave detection circuit 19 and is turned into a switch input to the focus direction. Then the circuit 8 is controlled by a switch circuit 20, and the focusing direction is decided.