Light Compensation; Auto Band Adjustment - Canon BJ-W3000 Service Manual

4. Light compensation

The media sensor brightness is automatically compensated for at the time of paper width
detection and automatic print position adjustment. The carriage is advanced for approx. 200mm,
the light quantity on the paper is compensated for in the order of blue and red, and then the light
quantity on the platen is compensated for in the order of blue and red.

5. Auto band adjustment

Errors in band placement due to mechanical tolerances of the head nozzles and media feeding
system can be automatically corrected.
a. Pattern
First, 2 ruled lines are printed using 10 nozzles from among 160 nozzles of the BJ print head,
from the 4th one from both ends to the 14th one (pattern 1). The interval between the centers of
these 2 rule lines corresponds to 144 nozzles. Then, the media is sent ahead for the distance
corresponding to 144 nozzles and 3 ruled lines (pattern 2) are printed. The paper feed motor
rotates twice for the above process (3200 steps).
Finally, the media is again advanced a distance corresponding to 144 nozzles, and one ruled
line (pattern 3) is printed. This printing of patterns 1 to 3 is repeated 5 times.
b. Measurement and adjustment
The interval between ruled lines A and B of pattern 1 is measured, and then the interval
between ruled line A of pattern 1 and ruled line A of pattern 2 is measured. The intervals are
compared, and the feeding distance corresponding to 1 band of the paper feed motor is adjusted.
Similarly, the interval between ruled lines B and C of pattern 2 and the interval between ruled
line B of pattern 2 and ruled line A of the pattern 3 are measured. The intervals are compared
and the feeding distance corresponding to 1 band of the paper feed motor is adjusted.
3 nozzles
5 nozzles
144 nozzles
5 nozzles
3 nozzles
CHAPTER 2. BASIC OPERATION
Pattern 1
A
B
A
Fig2-209
Pattern 2
B
C
A
Pattern 3
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