Canon iR4570 Series, Service Manual

Page: 191 / 876

Chapter 5
5-23
F-5-26
5.3.6.2 CCD Drive
0006-5931
iR2270 / iR2870 / iR3570 / iR4570
The machine's CCD sensor is a 1-line linear image sensor consisting of 7488 photocells. After completion of
photoelectric conversion in the light-receiving block, the signals are output to the AP circuit in the reader controller
circuit board in parallel for each channel (total eight channels) of the CCD array.
F-5-27
5.3.6.3
Gain Correction and Offset Correction of the CCD Output
0006-5932
iR2270 / iR2870 / iR3570 / iR4570
The analog video signal generated by the CCD is corrected so that it will have a specific level (gain correction);
moreover, the output voltage occurring in the absence of incident light is also corrected so that it will have a specific
CCD(1 line)
Analog
image
signal
Analog image
processing
-gain correction
-offset correction
A/D
conversion
CCD
drive control
CCD
control signal
Gain
correction
data
Digital
image signal
CCD/AP circuit
10
Digital
image signal
8
Reader controller PCB
Contact image sensor CIS)
Target value
J502
EEP-ROM
SRAM
CPU
Shading
correction
CCD7 CCD5 CCD1 CCD2 CCD8 CCD6
H L L H H L H L H H L
output
Light-receiving block