| 摘要 |
An automatic offset and gain control method for use in an electronic high quality scanner apparatus, operating on the source signal representing the optical density of a source document, produces a corrected output signal which represents the full range of black and white or colour levels of the original. In this method first a minimal density value relative to the specific source document has to be chosen. Secondly, a calibrated high density value and a calibrated low density value are scanned sequentially and a control unit fully automatically calculates and stores the pixel-related offset and gain. During subsequent scanning of the original, the automatic offset and gain control method continually corrects the input signals. <IMAGE>
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