| 摘要 |
PURPOSE:To obtain an accurate and effective automatic focus circuit which can also evaluate the level change in the vertical direction by detecting the level change of a luminance signal in the neighboring horizontal direction and vertical direction adding and averaging both level changes. CONSTITUTION:An orignal signal and a 1H delaying signal which is led out from a 1H delaying circuit 12, are inputted to the first subtaction circuit 14, and in addition, they are inputted to the first square-law circuit 16 which detects the level change in the vertical direction. The delaying signal and the original signal from a delyaing circuut 13 are inputted to the second substraction circuit 15, and in addition, they are inputted to the second square-law circuit 17 which detects the level change in the horizontal directon. These two outputs of the square-law circuit are averaged 6 after adding 18, and the averaged output is made into digital by field frequency in an A/D conversion circuit 7. This digital signal is transferred to the first memory 8 and the second memory 9 by every field, and the rotational direction of focus motor is controlled by polarity of the difference of both memory outputs. |
