CHAPTER 4 LASER EXPOSURE SYSTEMCOPYRIGHT © 2002 CANON INC. 2000 CANON iR1600/iR2000 REV.1 JAN. 20024-63 Laser Driver Circuit3.1 Laser ControlThe laser driver circuit is used to drive the semiconductor laser according to the video sig-nals from the image processor PCB.The following items of control relate to the laser driver circuit:1. Laser emission control2. 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 emittedwhen it goes ‘0’.[2] image formation enable signal. It is used to control the output of the video signals; emis-sion 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 themage 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 sen-sor (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 in-tensity 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 levelfrom the DC controller are identical.[8] laser intensity switch signal. It is used to switch the laser intensity between laser start-upand printing. During printing, it is fixed to ‘0’.
