| 摘要 |
PURPOSE:To enable to get a proper photoelectrically converted signal even in case of light intensity of a light source for illumination is falling without being affected by dust or a stain by providing the means to control an amplifying ratio and a calculating means of adding balance. CONSTITUTION:A holder 2 whose interior has a white reference surface, getting near the read surface of a manuscript 1, is established. When it is photoelectrically converted through the solid-state image pickup element, its white reference surface is scanned in plural lines for a certain period, and its level of the maximum value is stored. Next, plural line read scanning is performed while moving the white reference surface, and the amplification ratio of an input analog signal is controlled by its maximum output value through an amplifier 11. Thus, the white reference signal controlled up to the certain level of amplitude is processed in adding balance by an addition balance 12, and the output of each pixel in the maximum value is rectified as a rectifying signal through rectifier 13. Therefore, the photoelectrically converted signal having a proper, white reference surface can be obtained without being affected by dust or a stain, even in case that light power of light source for illumination falls.
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