Canon iR1600 Series, Service Manual

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CHAPTER 4 LASER EXPOSURE SYSTEM
COPYRIGHT© 2002 CANON INC. 2000 CANON iR1600/iR2000/iR1610/iR2010 SERIES REV.0 MAR. 2002
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3 Laser Driver Circuit
3.1 Laser Control
The laser driver circuit is used to drive the semiconductor laser according to the video
signals from the image processor PCB.
The following items of control relate to the laser driver circuit:
1. Laser emission control
2. Laser power auto control (APC control)
The signals have the following functions:
[1] laser emission signal. It is generated based on the BD input signal; laser light is emit-
ted when it goes ‘0’.
[2] image formation enable signal. It is used to control the output of the video signals;
emission of laser light is enabled when it goes ‘0’.
[3] video signal: It is a low-amplitude (for noise suppression) drive signal.
[4] video out signal. It is a low voltage drive signal converted from a video signal. When
the mage formation enable signal is ‘0’, it turns on/off the laser light.
[5] registration signal. It generates the TOP signal when paper reaches the registration
sensor (PS102) mounted to the front of the registration roller.
[6] The laser intensify is monitored when laser light is emitted, and a level suited to the
intensity of the light is fed back to the laser drive circuit.
[7] The output is controlled so that the level arriving as feedback and the reference level
from the DC controller are identical.
[8] laser intensity switch signal. It is used to switch the laser intensity between laser start-
up and printing. During printing, it is fixed to ‘0’.