| 摘要 |
PURPOSE:To convert the amplitude distribution of an image pickup output into that of an adaptive contrast, by performing gradation conversion, based on the frquency of generation of a class equally dividing the amplitude of a video signal. CONSTITUTION:The most significant and the 2nd upper-order bits M1, M2 of a video signal are applied to a decoder 4. The decoder 4 generates the four outputs in a logical formula, a high level output is counted at counters 5-8, and data representing frequencies h0-h3 of four classes are generated from the counters. An ROM12 is stored with a converting function to convert the flat distribution into an objective amplitude distribution. The standard picture is image-picked up at first, the frequencies h0-h3 are detected, the converting function of the ROM12 is read out, a CPU11 forms a conversion table corresponding to the gradation conversion function and the table is written in an RAM14. An address selector 3 selects video data, a data selector 15 outputs the data in the RAM14 to obtain a video signal after the desired gradation conversion. |
