| 摘要 |
PURPOSE:To attain the quick and smooth auto-focus control with application of a mount climbing system by deciding the driving value of a pulse motor to successively improve the in-focus degree comparing the precedent accuracy and the present accuracy. CONSTITUTION:An area setting circuit 7 decides an area to extract an auto- focus control signal (AF signal) out of the vertical and horizontal synchronizing signals received from a camera circuit 6. A CPU 11 obtains the AF signal at the fall of the area signal received from the circuit 7, i.e., the end position of the decided area, performs the operations to obtain a difference signal between the AF signal and the precedent AF signal, a gradient signal from the difference signal, and a zoom position signal, etc., and performs the decision based on these signals. Thus, the CPU 11 decides the next driving value of a master lens driving pulse motor 15. Then, the motor 15 is driven asynchronously with the generating cycle of the video signal. |
