| 摘要 |
PURPOSE:To contrive the reduction of the cost of a circuit, the reduction of power consumption and the high reliability by the use of a low speed memory by thinning out a reference signal and performing a cumulative addition at the time of reading the reference signal of a shading correction circuit. CONSTITUTION:The shading correction circuit 10 previously reads the plural lines of a black reference plate 8 and a white reference plate 9 at the end part of an original 1 before the picture of the original 1 to obtain a black reference signal and a white reference signal. Then a signal obtained by cumulatively adding one obtained by subtracting the black reference signal from a signal obtained by cumulatively adding the black reference signal plural times at every same picture element and the white reference signal plural times at every same picture element is stored in a line memory as a correction signal. At the time of reading the picture of the original, a black correction signal stored in the line memory is subtracted from the obtained picture signal and further an inverse number to a white correction signal is multiplied. In such way, in the circuit 10, the reference signal of a reading mode is thinned out and cumulatively added, thereby, the low speed memory can be used to attain the reduction of the cost of the circuit, the reduction of the power the consumption and the high reliability.
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