The signals are further converted into laser drive signals on the laser driver PCB(internal signals of the laser/scanner assembly) used to turn on and off the laser diode,thereby generating a laser beam.The modulated laser beam is turned into a parallel beam by means of a collimatinglens and a cylindrical lens, and is directed to a 6-facet mirror rotating at a specific speed.When reflected by the 6-facet mirror, the laser beam moves through an imaging lensand a reflecting mirror arranged in front of the 6-facet mirror to focus on the photosensi-tive drum.The 6-faced mirror rotates at a specific speed, enabling the laser beam to scan thesurface of the photosensitive drum at a specific speed.An image takes shape on the surface of the photosensitive drum as the drum rotatesat a specific speed and, while at the same time, as the laser beam scans its surface at aspecific speed.Note:Low Voltage Differential SignalThe machine’s PWM modulation circuit is on the DC controller PCB, requiring PWM-modulated laser drive signals to move through a cable for turning on and off the laser.If PWM-modulated laser drive signals were sent over a cable as they are, the noiseradiating from the cable would affect the PCBs on the way. To prevent such a problem,the signals are processed to suppress amplitude. The printer unit generates two setsof signals (differential signals) to avoid a decrease in the noise margin, otherwisecaused by low amplitude.COPYRIGHT © 1999 CANON INC. CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)CHAPTER 3 LASER EXPOSURE SYSTEM3-2Download free service manual at http://printer1.blogspot.com
