Xerox DocuColor 12/DCCS50, Service Manual

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10-76 DocuColor 12/DCCS50
Image Sensing (Digital Copier & Copier/Printer Con-
Reissue
Principles of Operation
Figure 8 Document Size Detection with Platen Cover
Figure 9 Cluster Dot Screen Patterns
Color Document Detection
Color is detected during original scanning by examining the a* parameter for a non-zero value.
is examined.
Scanning the Document
Carriage Positions
Refer to Figure 10 and Figure 11 . The True Registration Position is where the Full-Rate Car-
riage begins to scan the document original. It occurs where the REG1 Sensor detects a partic-
ular left edge on the Full-Rate Carriage. All other carriage positions are calculated relative to
True Registration Position.
The White Reference Position is where the CCD Array is directly under the middle 100 pixels of
the White Reference Strip. For machines without a DADF, this is 20 mm to the left of the True
Reference Position. For machines with a DADF, it is 62 mm to the left of the True Reference
Position.
The Home Position is where the Full-Rate Carriage rests after initialization and between jobs.
In all machines (with and without a DADF installed), this is 30 mm to the right of True Registra-
tion Position. This location places the CCD array under the document original. Therefore, the
CCD array is used to detect the Fast-Scan dimension of the original document.
The Start Position is where the Full-Rate Carriage begins moving when scanning. In the inter-
val between the Start Position and the True Registration Position, the carriage accelerates to
the appropriate speed for the selected image reproduction ratio. All possible start positions are
given in
Table 1 , and an example is shown in Figure 10 and Figure 11 . Since the Full-Rate Car-
riage moves faster at lower magnifications, a longer acceleration distance is required and the
Start Position is further from the True Registration Position.
NOTE: The Scanning speed of the Full Rate Carriage/Half Rate Carriage is determined by the
following formula:
•
Scanning Speed = 225 X 100 / magnification (mm/s) for 50 - 400% magnification
• Scanning Speed = 225 X 100 / (Magnification X 2) (mm/s) for 2 to 49% magnification
The End Position is the furthest that the Full-Rate Carriage travels when finishing a scan. The
maximum possible distance between the End Position and the True Reference Position is
approximately 432 mm or 17 inches. However, the Slow-Scan dimension of the document orig-
inal may be less than this. (The size of the original can be detected automatically or entered
manually, see
Document Size Detection .) The carriages will travel no further than necessary
for the original’s Slow-Scan dimension.
Table 1 Full-Rate Carriage Start Positions
Configuration: Reproduction Ratio
Start Position (Relative to
True Registration Position)
Without DADF 25% to 97.1% 40 mm Left
Without DADF 97.2% to 400% 20 mm Left
With DADF 25% to 97.1% 35 mm Left
With DADF 97.2% to 400% 15 mm Left
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