| 摘要 |
PURPOSE:To remove an irregular illumination, to emphasize an outline and a structure and to suppress noise in a part in which the S/N is small by independently variably setting the quantity of suppression of a gain in a low frequency side and the quantity of the gain in a high frequency side. CONSTITUTION:A picture signal of an optical image photoelectrically converted by a solid-state image pickup element 4 is amplified by a preamplifier 14 of low noise exponent and inputted to a logarithmic filter circuit 21. A signal is passed through a filter characteristic change circuit 25 of a next step capable of independently variably setting the gain in the low frequency side and the gain in the high frequency side respectively. In this case, when the filter characteristic change circuit 25 suppresses the gain of the low frequency side, the influence due to the irregular illumination produced in the low frequency side can be removed or lowered. If the high frequency side is emphasized, the outline and the structure in the high frequency band can be emphasized.
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