| 摘要 |
PURPOSE:To code a video signal into a binary signal stably and accurately while holding a threshold value constant by detecting and comparing the rate of a high-level or low-level state to a unit time with a preset mark rate and outputting a deviation signal corresponding to the deviation between the both. CONSTITUTION:A video signal binary coding method 2 consists of an amplifier 21 which amplifies the video signal and a comparator 22 which compares its output voltage with the preset threshold voltage. A mark rate detecting means 3 is equipped with an AND gate circuit 31 which functions as a sampling circuit for sampling high-level or low-level signals from the binary-coded signal outputted by the comparator 22 and a counter 32 which counts the sampled high-level or low-level signals. A decision means 4 is equipped with a frequency dividing circuit 41 and a counter 42 which set the reference mark rate and an arithmetic circuit 43 which compares a detected mark rate with the set mark rate to calculate their deviation.
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