| 摘要 |
PURPOSE:To improve binary-coding precision, to set a threshold value without any adjustment, and to shorten the process of manufacture by utilizing the mean value of the amplitude of a video signal to be compared as the threshold value when converting the video signal into a binary signal. CONSTITUTION:A section limiting circuit 13 consists of an analog switch 13A and a section limit signal generator 13B and is controlled by a driving circuit 7. An averaging circuit 14 is composed of the low-pass filter consisting of a resistor 14A and a capacitor 14B. To one input terminal of a comparator 9, a video signal supplied from a sensor 6 through a contour emphasizing circuit 8 (differentiating circuit) is inputted and to the other input temrinal, the video signal is inputted through the section limiting circuit 13 and the averaging circuit 14. Consequently, the video signal passed through the contour emphasizing circuit 8 is converted into the binary signal on the basis of the mean value of its amplitude. |
