Chapter 66-9The following diagram shows the flow of the control mechanism:F-6-10Bk is used to detect the reference BD signal and, as such, laser light is directed to the surface of the polygon mirror. In other words, the write start position in mainscanning direction for Bk is determined based on actual measurement and, for this reason, the possible presence of variation in the angle of the polygon mirrorsurface will not lead to variation of Bk write start position.The laser driver for C is found directly under the Bk laser driver and, for this reason, the C laser driver directs laser light against the same polygon mirror surfaceas the Bk laser driver, eliminating the effects of variation in the angle of the polygon mirror surface. The write start position of C, for this reason, is also free ofvariation as in the case of Bk.6.2.2 Controlling the Intensity of Laser Light6.2.2.1 APC Control 0013-9608Color iR C3380G / Color iR C2880G / Color iR C3380i / Color iR C3380 / Color iR C2880i / Color iR C2880 / iR C3480 / iR C3480i / iR C3080 / iR C3080i / iRC2550The machine uses APC control to make sure that the intensity of laser light remains at a specific level.The machine uses 2 laser driver PCBs, each with a laser driver IC taking care of 2 colors and performing APC control for individual colors.The following is an outline of APC control operation, executed each time the machine is turned on and for each print job:1) The DC controller sends the laser control signal (LC_CTL_X(0)=0, LC_CTL_X(1)=1) to the laser driver IC on the laser driver PCB. (X differs depending onthe color.)2) The laser driver IC is set to APC mode, thus forcing the laser diode (LD) to go on.3) The laser driver IC monitors the laser diode (LD) by means of a photo diode (PD), adjusting the output of the laser diode until its light is a specific level ofintensity.4) The laser driver IC stores the laser output in memory for use in the next print job.Scanner motor constantspeed of rotation detectionSTARTBD intervalmeasurementWrite start correctionvalue computationWrite startposition correctionENDBD1 BD2 BD3 BD4Short interval Specific interval Specific interval Specific intervalBD1 BD2 BD3 BD4BD1T1BD2 BD3 BD4VDOT1VDOT1VDOT1VDO
