Xerox PHASER 7500, Service Manual

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2-78 Phaser 7500 Printer Service Manual
Theory of Operation
Color Shift Correction
The detected Color Registration shift amount is computed and converted into the
following corrective elements. The correction itself is performed by the LPH control.
• Intra engine difference image start occurrence
• Slow scan write position correction (Y fine)
• Slow scan write position correction (Y super fine)
• Slow scan skew/ bow/ LPH linearity correction
• Fast scan write position correction (X rough/X fine)
Mark On Belt Sensor
The Mark On Belt (MOB) Sensor detects marks on the belt.
• The MOB Sensor is a reflective sensor that projects the Regi Con (chevron)
patch image that was formed on the opaque belt onto the Detection Unit,
and then outputs a pulse when the center line of the patch is aligned with the
center line of the Detection Unit.
• The above-mentioned Detection Unit consists of only one Photo Diode that is
perpendicular to the belt surface and one LED for diffused light illumination.
• The Sensors (x2) are placed downstream of the last color engine, on the axis
perpendicular to the slow scan direction (in other words, on the axis parallel to
the fast scan direction) in order to detect the relative Color Shift between the
Regi Con patches that were formed by the respective color engines.
s7500-428
Belt
Toner Image
Lens (100%)
Detection PD
Diffusion LED