| 摘要 |
PROBLEM TO BE SOLVED: To surely detect the peak of an evaluated value whether contrast is high or low by calculating both a difference between the evaluated value of present field and the evaluated value before specified field and the ratio of the evaluated value of present field to the evaluated value before specified field and deciding a just focusing state based on the difference and the ratio. SOLUTION: In order to generate 14 kinds of the evaluated values, an integrated circuit for autofocusing(AF-IC) 139 is provided with a luminance signal generation circuit 201 and an evaluated value generation circuit 202 for the respective evaluated values. In this AF system, the evaluated value is calculated by the exclusive AF-IC 139. The image signal of a video camera is inputted and the high frequency component of the specified area of the image signal is extracted to generate the evaluated value. By calculating both the difference between the evaluated value of the present field and the evaluated value before the specified field and the ratio of the evaluated value of the present field to the evaluated value before the specified field, the just focusing state is decided based on the difference and the ratio. Furthermore, a command value given to the focus driving part 111c of the lens 111 of the video camera is transmitted in accordance with the decided result. |
