Canon 1000 Service Manual page 157

d. Detecting the Image Density
Like carriers, the Bk toner absorbs infrared light, allowing the measurement of the density of the toner
layer on the developing cylinder. Bk toner is supplied based on the amount of consumption computed with
reference to the count of the video signals carrying a Bk component. As shown in Figure 3-541, the video
signals from the image processor are counted to obtain a cumulative count by the video data counter.
Video controller PCB
Y,M,C,Bk
Video signal
Bk toner supply
clutch (upper)
Bk toner supply
clutch (lower)
COPYRIGHT © 2001 CANON INC.
Bk
CL4 Toner supply signal
CL5
Figure 3-541
CANON CLC1000/1000S/3100 REV.2 MAY 2001 PRINTED IN JAPAN (IMPRIME AU JAPON)
3. OPERATION AND TIMING
Video signal
Y,M,C,Bk
Video data counter
Cumulative count
DC controller
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