Pascal Control (Image Gradation) - Canon imagerunner C5180 Service Manual

Chapter 9

9.5.6 PASCAL Control (image gradation)

The PASCAL control mechanism is used to stabilize gradation characteristics of images on paper.
It makes up for the changes in gradation occurring in response to changes in temperature/humidity or as the
machine is used over time.
- PASCAL Control for Half-Speed
The mechanism is used to correct the changes in the gradation characteristics that otherwise would occur when
thick paper, special paper, or transparency is used. The test print used for the mechanism is the same as the
test print used for plain paper.
Description of Control
Start-up
V
Prints out the test pattern stored in the main controller (3 types).
V
Uses the scanner to read the test print (previously printed out) set in the reader.
V
Prepares the image correction table A (data processing).
V
End
Timing of Control
- Service Person Interaction
The mechanism is executed when 'full correction'is executed while auto gradation correction is under way in
user mode.
MEMO;
Differences Among 3 Test Patterns
- Test Print 1
It shows 64 gradations expressed by means of error diffusion processing, which is not subject to moire
and, therefore, used in text/photo/map, print photo, and text mode.
- Test Print 2
It shows 64 gradations expressed by means of screening with a low number of lines, which is suitable for
the expression of gradation and, therefore, is used for print film photo mode and when priority is placed
on PDL.
- Test Print 3
It shows 64 gradations expressed by means of screening with a high number of lines, which is suitable for
the achievement of a high resolution and is, therefore, used when priority is placed on PDL resolution.
9-24
Test Print
F-9-18