| 摘要 |
PURPOSE:To obtain an automatic focus device where a video image pattern is not unsightly by judging the focusing state of a focus adjusting lens through the detection of a peak point of a sharpness signal obtained from a high frequency component included in a video signal. CONSTITUTION:When the focus adjusting lens 8 is driven by a lens drive circuit 7 for focusing, the video image signal supplied from an input terminal 1 changes its state depending on the movement. A color signal is eliminated from the video image signal by a color signal eliminating circuit 2 and supplied to a differentiation circuit 3 and a high frequency component of a luminance signal is detected. The high frequency component is fed to a detection circuit 5 via a gate circuit 4 to form the suitable sharpness corresponding to the sharpness of the video signal. The sharpness signal is fluctuated attended with the movement of the lens 8 and when its peak value is detected by a maximum value detecting means 6 and a lens movement stop signal is outputted from the detecting means 6 to stop the movement of the lens 8. |
