| 摘要 |
PURPOSE:To supply a stable image signal by a simple circuit by converting a photoelectric conversion signal corresponding to a reference white part into a digital signal by an analog-digital converting part, performing arithmetic and level decision operation by a control part, and controlling the gain of a variable gain amplifier. CONSTITUTION:One-line reference white data is sampled at intervals of (m) picture elements and evaluated with representative values. In this example, the data is digitized into a 6-bit signal and no overflow bit is provided, so 63 picture elements of picture element data are counted and substituted in N. When a video signal is small, N=0, so the gain G is increased. In this case, G is 0-15. When the video signal is to large, on the other hand, N>0, so the gain G is decreased. Thus, the gain is varied and then the reference white data is inputted again. A flag FLG is for prevention against oscillation. Consequently, 16 levels of gains are linearly selectable.
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