Canon 1000 Service Manual page 140

3. OPERATION AND TIMING
4. Controlling the Gradation Characteristics (PASCAL)
a. Outline
The relationship between the output of the laser and the image density is as shown in Figure 3-517.
In user mode, you can operate the CLC1000
so that it actually develops, transfers, fixes, and
outputs a solid patch and a 64-gradation halftone
pattern for each color and then reads them by the
CCD of the reader unit.
The density data of the solid patch is used to
obtain a contrast potential, and the 64-gradation
halftone density data is used to find out the actual
gradation characteristics; all these findings are
used for correction on the laser output so as to
enable ideal gradation characteristics.
b. Operations
For how to use user mode, see Chapter 1.
1 In user mode, generate Auto Gradation
Correction Test Print 1 (halftone and solid
patch; Figure 3-518).
2 Referring to the halftone area of the generated Test Print 1, check for differences in density and faults in
images; if an error is found, make adjustments according to the Basic Image Adjustment Procedure. If
no error is found, operate so that the reader unit reads the solid images.
The data collected by reading the solid images on the Test Print is used to determine the contrast
potential.
3 In user mode, generate Auto Gradation Correction Test Print 2 (64 gradations for each color; Figure 3-
519). Here, the contrast potential determined in 2 above is used.
4 Operate so that the generated Test Print 2 is read by the reader unit.
At this time, the CLC1000 prepares a graph of output values and reading values (Figure 3-517), thereby
determining the correction value to ensure ideal gradation characteristics.
Figure 3-518 (Test Print 1)
3-96
COPYRIGHT © 2001 CANON INC.
Halftone output
by YMCK
K solid
Y solid
C solid
M solid
CANON CLC1000/1000S/3100 REV.2 MAY 2001 PRINTED IN JAPAN (IMPRIME AU JAPON)
1.7
Actual gradation
characteristics
0 laser output
Figure 3-517
00
M C Y K
M C Y K
Figure 3-519 (Test Print 2)
Ideal gradation
characteristics
255
FF