| 摘要 |
PROBLEM TO BE SOLVED: To stabilize A/D conversion of an analog image signal with high precision. SOLUTION: This image-reading equipment is provided with a line sensor 11a, a variable gain amplifier 11d for amplifying an analog image signal of the sensor, and an A/D converter 11f for converting an output data of the amplifier. Adjusting means 12e, 11g read a reference original document with the sensor 11a, detect a peak Ddp and holds image data Dd of a specified pixel. When the peak Ddp lies outside of a target range DdL to DdH, an upper reference voltage Vrefd when A/D converter the original document is changed. When the peak Ddp lies in the target range DdL-DdH, a reference white plate 15 is read by the sensor 11a. When image data Dw of the prescribed image data lie outside of a prescribed range (Dd-A) to (Dd+A), where the image data Dd of the prescribed pixel held when reading the reference original document is reference, the adjusting means 12e, 11g change an upper reference voltage Vrefw, when the A/D converter 11f reads the reference white plate. COPYRIGHT: (C)2004,JPO
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