COPYRIGHT © 1999 CANON INC. CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)D. Detecting the DensityFigure 4-501The density of the density detection pattern drawn on the intermediate transfer drumis checked by the density sensor. The density sensor is mounted on the density detec-tion PCB; the light of a LED is directed to the density pattern on the intermediate trans-fer drum, and the reflected light is received by the photodiode 1.The DC controller PCB generates the LED activation signal (LEDCNT) at such timesas needed. The light from the LED is checked by the photodiode 2 directly, and the resultis sent to the density detection circuit as the intensity feedback signal (DENREF), and isused to control the intensity of the LED to a specific level.The light from the LED is also directed to the density detection pattern on the inter-mediate transfer drum, and the reflected light is directed to the photodiode 1.The density detection PCB forwards the density signals to the DC controller PCB asthe toner density detection signal (DNS). The DC controller PCB, in turn, converts thedensity detection signal (analog value) into density levels (digital value) for storage inmemory.Figure 4-502CHAPTER 4 IMAGE FORMATION SYSTEM4-23Intermediate transfer drumPhotodiode 2Density detection patternDensity sensorPhotodiode 1LEDDC controllerPCB Density detection PCBDensity sensorPhotodiode1DNSIntermediatetransferdrumLEDCNTDENREFLEDPhotodiode2Download free service manual at http://printer1.blogspot.com
