Image Signal Processing - Canon CP660 Service Manual

B.

Image Signal Processing

The printer board sends video signals (VDO0 through 7*; C, M, Y, and Bk, each rep-
resenting 8-bit data) and CMD* signals (image mode switching command) to the DC con-
troller PCB. The D-CPU (IC201) on the DC controller PCB is used to generate image
mode switch signals (VDATIN8*; Note) from CMD* signals.
The video signals (DVDO0 through 7*) sent by the printer board *
troller PCB are directed to a RAM (IC205; line memory) and then to a gate array (IC204).
The video signals (DVDO0 through 7*) are subjected to image masking processing
(p. 3-3) in IC204, and are sent to the PWM IC (IC208) as video data signals (VDATO0
through 7). At the same time, the image mode switch signals (VDATIN8*) are moved
through the gate array (IC204), and are sent to the PWM IC (IC208) as PWMF1 signals.
Then, the video data signals (VDATO0 through 7) are turned into PWM demodulation
signals (VDATA*; PWM video data signals) combined with PWMF1 signals (selected
image mode) by the PWM IC (IC208); they are then sent to the laser driver PCB of the
laser scanner as two sets of laser drive signals (BDATA*, BDATA) by way of the LVDS IC
(IC209).
When making full-color copies, the foregoing operations are performed for Y, M, C,
and BK in sequence to form images. When making mono-color copies, on the other hand,
these operations are performed for one of the four colors.
At the end, the laser driver PCB is ready to send the laser drive signals (DATA*; result
of demodulation by the receiver (IC1001) to the laser drive IC (IC1002).
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* Reader controller PCB (when making copies with the reader unit installed).
Note:
Switching the Image Mode
The printer unit switches image mode (text or halftone) in response to the image mode
switch command from the reader controller PCB so as to enable the best images in
text and halftone areas.
COPYRIGHT © 1999 CANON INC.
Download free service manual at http://printer1.blogspot.com
CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 3 LASER EXPOSURE SYSTEM
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to the DC con-
3-5