| 摘要 |
An image data reading apparatus is provided, comprising a transport part for transporting an original sheet to a reading position within the image data reading apparatus, a white reference plate provided at the reading position, a light source for generating a light projected to the reading position, a light receiving part for converting an incoming light reflected from the white reference plate into a white reference signal and for converting an incoming light reflected from the original sheet into an image signal, a correction part for eliminating a shading from the image signal based on a reference voltage, a peak level holding part for detecting and storing a peak level of a corrected signal from the correction part, a quantization part for converting an incoming signal from the correction part into digital information based on the peak level, and a switching part for turning the peak level holding part off to stop detection and storing of the peak level of the incoming signal for a prescribed time period between a time the white reference signal is received by the light receiving part from the white reference plate and at a time the original sheet is transported to the reading position, so that the peak level holding part receives no signal from the light receiving part during the prescribed time period.
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