AUTOMATIC ADJUSTMENT METHOD FOR WHITE LEVEL COMPRESSION CHARACTERISTIC AND DECODING CHARACTERISTIC FOR IMAGE PICKUP DEVICE

摘要

PURPOSE:To adjust a white level compression start point accurately automatically by inputting a digital reference pulse resulting from A/D conversion to a digital computing element, comparing with a prescribed reference digital value and feeding back the signal to a white level compression and reference pulse insert circuit. CONSTITUTION:A white level compression and reference pulse insert circuit 3 inserts a reference pulse 12 to an input signal based on a command given from a reference pulse insert command line 8 and decides a peak value of the reference pulse 12 and a white level compression start point to a same level according to a digital data or a DC level given through a white level compression start point control line 9. Then a digital value of a reference pulse after A/D conversion is fetched in a digital computing element 7 such as a microcomputer and compared with a prescribed reference digital value, and the result is fed back to a white level compression start point control section of the white level compression and reference pulse insert circuit 3 to make the digital value of the white level compression start point with a prescribed reference digital value. Thus, the white level compression start point of the white level compression stage is accurately adjusted automatically.