| 摘要 |
PURPOSE:To perform auto-focusing in a short time with a high precision in a simple constitution by providing a variable control means which detects a maximum value and a minimum value of a picture signal and moves an optical system in the direction where the difference is maximum. CONSTITUTION:The maximum value and the minimum value of the picture read signal form a photoelectric transducer 15 are detected by a maximum value peak holding circuit 18 and a minimum value peak holding circuit 19 respectively. These information are inputted to a CPU 21 through an A/D converter 20, and the difference between the maximum value and the minimum value obtained by one scan, namely, density difference information is obtained. A signal is sent to a driving mechanism 17 through a driver 22 to move a lens 5 by one step, and the photoelectric transducer 15 is scanned once to obtain density difference information similarly, and the lens 5 is moved in the same direction by one step if this obtained density difference information is not different from or larger than preceding density difference information. If density difference information is smaller than preceding density difference information, the lens 5 is moved to the position of the maximum density difference in the opposite direction and is stopped. |
