3-Line Ccd Position Matching Circuit; Sensor Color Correction Circuit - Canon CLC 1120 Service Manual

C. 3-Line CCD Position Matching Circuit
The copier's CCD consists of three lines and, as such, signals resulting from a line image
scanned by the scanner at a single point will reach the CCD with a discrepancy (about 0.38 mm in
relation to the copyboard glass; equivalent of 6 lines).
To correct such a discrepancy, the 3-line CCD position matching circuit temporarily stores the
R and B image signals in a line memory for output together with the G image signal. (See Figure 4-
403.)
Reference:
The delay of the G image signal is maximum at a 400% ratio. As a result, the R image signal
and the B image signal are sent out with a delay of 48 lines and 24 lines, respectively.
D. Sensor Color Correction Circuit
The sensor color correction circuit serves to correct the transmission characteristics of the B, G,
and R filters found inside the CCD.
Ideally, each filter should pass light of specific wavelengths and block light of other
wavelengths. In reality, however, light of wavelengths within a and c in Figure 3-312 is let to pass,
while light of wavelengths within b is blocked, requiring the use of the circuit. (See Figure 4-404.)
Volume 4>Chapter 4>IV-D "Color Correction for the Sensor"
0.38 mm (equivalent of 6 lines)
Original
G BR
Figure 4-403
COPYRIGHT © 1999 CANON INC.
(scanning direction)
R
B
G
CCD
CANON CLC1120/1130/1150 REV.0 MAR. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 4 IMAGE PROCESSING SYSTEM
Degree of
filter transmission
a
Figure 4-404
Ideal
characteristics
b
Actual
characteristics
c
Wavelength (nm)
4-7