Xerox Phaser 6000 Service Manual page 106

Theory of Operation
Scanning Control
2-50
A CMOS image sensor is used to read image data from the document. To ensure
stabilized image reading, the CMOS image sensor output is adjusted. Adjustment
includes Automatic Gain Control (AGC) and Automatic Offset Control (AOC).
Reference data for adjustment is collected and used to perform compensation on
the read image data. Compensation includes shading compensation, white
variation compensation, and black variation compensation.
Reference data is obtained by reading image data from a white reference plate via
the CMOS image sensor.
AOC (Auto Offset Control)
AOC is performed by turning off the exposure lamp after AGC. This state is read by
the CMOS image sensor as the black reference value. The order of AGC and AOC
adjustment depends on the model.
AGC (Auto Gain Control): White Level Variation Adjustment
During AGC, the carriage assembly is moved to the position of the white reference
plate, and the exposure lamp is illuminated. The light reflected from the white
reference plate is read by the CMOS image sensor as the white reference value.
Shading Compensation
Shading compensation compensates for pixel-by-pixel sensitivity variations and
the non uniformity of lamp light in the fast scanning direction. The AGC and AOC
adjustment values are used to compensate for the image data read by the CMOS
image sensor.
Xerox Internal Use Only Phaser 6000/6010 and WC 6015 MFP