| 摘要 |
PURPOSE:To execute focusing of a lens system with a high accuracy by operating a standard deviation value of a sample value of one picture portion by sampling a video signal, and moving the lens system to a position where the standard devision becomes the maximum. CONSTITUTION:A microprocessor 8 drives a motor 3 through a motor control circuit 12, and moves a lens system 2 to an initial position. Subsequently, ''0'' is stored in a prescribed position of a memory 9. Next, when it is detected that a vertical synchronizing signal (d) is applied from an infrared ray image pickup device 1 through a data input part 7, a sampling value applied from a sampling circuit 5 is stored in the memory 9 by one picture portion. The processor 8 derives a standard deviation value Hn of a sampling value stored in the memory 9, and compares it with a standard deviation Hn-1 of a cycle of the previous time stored in the previous time. In case of Hn>Hn-1, the lens system 2 is moved by a prescribed quantity, it is repeated and the lens system 2 is positioned to a position where the standard deviation Hn becomes the maximum. In this way, a focus of the lens system 2 can be positioned exactly. |
