| 摘要 |
PURPOSE:To obtain the picture signals which are free from shading distortion by providing a memory means for the shading correction data which is delivered synchronously with the output of a photoelectric conversion element and re peating the shading corrections to set the optimum shading correction data. CONSTITUTION:The output signal S1 of a photoelectric conversion element is supplied to a variable attenuator 1 and attenuated by an attenuation factor decided by the shading correction data D4 read out of a data memory 6. Thus the signal S1 is turned into the picture signal S2. The signal S2 is digitized by an A/D converter 3 and stored in a signal memory 4. These digital signals are successively read out in the form of the picture signal D2 and synchronously with the read signal of an operator 5. The operator 5 compares the signal D2 with a desired level Y set previously. When the signal D2 has a higher level than the level Y, the shading correction data for the picture element corresponding to the signal D2 is read out of the memory 6 and added with '1' by the operator 5 to be stored in the memory 6. This processing is repeated until the signal D2 gets closest to the level Y and has the even value.
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