| 摘要 |
PROBLEM TO BE SOLVED: To carry out a clamp processing with simple operation at a blank period where horizontal synchronizing signals are located, in the case of an unstable clamp processing and so on. SOLUTION: This device for processing image signal is constructed by: a latch circuit 7 to latch a level value for a blank period of an image signal at output side of A/D conversion circuit 1, a difference value computing circuit 8 which compares a latched level value with a predetermined target value to compute the difference value and puts out the entire difference value when a switching signal 105 is zero (black level) and puts out the difference value subtracted by a difference value between the black level and the level of the blank period when the switching signal 105 is 1 (blank period), a D/A conversion circuit 9 for converting the above output to an analog voltage and keeping the voltage, an addition-subtraction circuit 3 which performs addition-subtraction between a standard clamp level 107 and a corrected voltage 110 to put out a clamp level 109, an analog switch 2 which turns on at the black level when the switching signal 105 is zero and turns on at the blank period when it is 1 to clamp.
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