Xerox Phaser 6500, Руководство по обслуживанию

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2-62 Xerox Internal Use Only Phaser 6500/WorkCentre 6505 Service Manual
Theory of Operation
Image Data Flow
The image data from the document set on the document glass or ADF goes
through the following components before it is printed at the Engine section.
Document Scanning Steps
A CCD Image Sensor is used to read image data from the media. The CCD Image
Sensor output is adjusted to ensure the image reading is stabilized. 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, white variation, and black
variation compensations. These adjustment and compensation steps are
described below:
1. AGC (Auto Gain Control) : White Level Variation Adjustment
During AGC, the Scanhead 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 CCD Image Sensor as the white reference value,
which is used to adjust the CCD Image Sensor output.
2. AOC (Auto Offset Control)
AOC is performed by turning Off the Exposure Lamp after AGC. This state is
read by the CCD Image Sensor as the black reference value, which is used to
adjust the CCD Image Sensor output. (The order of AGC and AOC adjustment
depends on the model.)
3. 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 CCD Image Sensor.
s6500-078
Document
CCD Image Sensor (Scanhead)
Image Processor Board
Laser Unit
Drum (CRU)
Scanner
Engine
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