Toshiba e-STUDIO 4500c, Service Manual

Page: 765 / 1120

August, 2006 LASER UNIT
6-49
Detailed
D
escr
iptions
How is MUSIC Done?
[A]: Rear MUSIC sensor
[B]: Center MUSIC sensor
[C]: Front MUSIC sensor
[D]: Main scan MUSIC patterns
[E]: Sub scan MUSIC patterns
The MUSIC sensors [A], [B], and [C] read the
MUSIC patterns from the ITB.
The main scan MUSIC sensor pattern [D]
consists of patches for each color (M, C, Y)
beside the black (K) color patch.
The sub scan MUSIC sensor pattern [E] consists
of patches for each color (M, C, Y) above a black
(K) patch.
This diagram shows a close-up view of the main-
scan test pattern.
K is the reference, and the positions of CMY are
adjusted with reference to the K pattern.
The CMY patterns are vertical (shown in grey in
the diagram), but the K pattern overlaps the CMY
patterns as shown.
The MUSIC sensor response is measured. The
output is the lowest when the K pattern fully
overlaps the color pattern (the dotted lines in the
diagram cross at this point). This is the “Actual”
position as shown in the diagram. But there is a
“Target” value in the machine’s software (an
example is shown on the diagram; this is not the
real target, it is just an example to explain the
process). The machine compares the “Actual” and
“Target” values, and adjusts the laser timing in
response to the results of this comparison.
Skew is also measured in the main scan direction
using the patterns at the left and right of the ITB. If
skew is detected, the machine adjusts the angle of
the 3rd mirrors.
Y
K
M
K
C
K
M
C
Y
B132D969.WMF
B132D969A.WMF
[A] [B] [C]
[D]
[E]
Target
Actual
Sensor Output
Vertical Position
in Test Pattern