Density Correction - Canon CLC1000 Service Manual

3. OPERATIONS 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.
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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 discussions'on the image formation system and the image control.
DC contrdi r t PCB
The video data (YMCBk) is corrected against the correction curve for correction and sent to the laser
driver.
3-70
Image
density
Image density
Correction curve
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Figure 3-414
r
CANON CLCi990 REV.1 MAY 1997 PRINTEO IN JAPAN
Output image lighter
than original
255
Video signal
Figure 3-413
ideal characteristics
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Video slgnal