Density Correction - Canon 1000 Service Manual

3. OPERATION AND TIMING

3. Density Correction

The relationship between video signals and
image densities is as shown in Figure 3-413. As
can be learned, using the video signals as they are
for laser exposure will not result in the faithful
reproduction of image densities.
To ensure that the image density will be reproduced throughout the entire range of the video signals, the
video signals are converted along the correction curve (Figure 3-414), thereby bringing the output
characteristics closer to the ideal characteristics.
255
0
Video signal input
The correction curve for conversion is stored in the density correction RAM on the video controller in
relation to the data for SALT and PASCAL*.
*See chapter 3. V. IMAGE FORMATION SYSTEM, C. Stabilizing Image.
DC controller PCB
The video data (YMCBk) is corrected against the correction curve for correction and sent to the laser
driver.
3-70
COPYRIGHT © 2001 CANON INC.
Correction curve
255
Video controller PCB
SALT/PASCAL data
Video signal
Y,M,C,Bk
Image density
0
Image density
0
Figure 3-414
Density correction
Figure 3-415
CANON CLC1000/1000S/3100 REV.2 MAY 2001 PRINTED IN JAPAN (IMPRIME AU JAPON)
Output image darker
than original
Output image lighter
than original
Video signal
Figure 3-413
Ideal characteristics
255
Video signal
255