Table of Contents
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1. Operation
a.
Image processing
The following processing is performed by the ICB
(image control board):
(1) AOC (Auto Offset Control)
During shading correction, a read operation
takes place while L1 (exposure lamp) is OFF, and
the analog offset voltage of the output from the
CCD sensor is automatically adjusted so that the
resulting level is the lower limit of the A/D con-
verter.
(2) AGC (Auto Gain Control)
During shading correction, the white reference
plate is read, and the amplification of the analog
output from the CCD sensor is automatically
adjusted so that the resulting level is the upper of
the A/D converter.
(3) Shading correction
<Timing>
• When SW1 (main switch) is turned ON
(4) Brightness/density conversion
(5) EE processing
(6) Text/dot pattern judgment
(7) Filtering/magnification change processing
(8) Magnification change processing
(9) Copy gamma correction
(10) Skew correction
(11) Error diffusion processing
(12) Data compression
(13) Write density control
b.
Write
The ICB (image control board) sends image data
on a pixel basis to LDB1 and LDB2 according to
the control signals from the PRCB (printer con-
trol board).
LDB1 and LDB2 cause the lasers to emit for a
period corresponding to the image data. This
laser light is radiated onto the drum surface.
(1) MPC (Maximum Power Control)
ICB informs LDB1 and LDB2 of the maximum
output value and sets that value for the laser
beam emission. LDB1 and LDB2 store this set-
ting value and maintain the quantity of the laser
beam emission using the APC (Auto Power Con-
trol).
<MPC timing>
• When SW1 (main switch) is turned ON
(2) APC (Auto Power Control)
The ICB outputs an APC start instruction to the
LDB at the following timing, after MPC is set.
<APC timing>
• The LDB1 and LDB2 automatically monitor the
laser drive current one line at a time, and con-
trols it so that the light intensity remains the
MPC value.
(3) Write timing
a) Main scanning direction
Using INDEX signal from INDXSB, deter-
mines the laser write reference position for
each scan in the drum rotation direction, and
writes the image to copy paper using the
paper position information derived from the
paper position detection by PS1 (paper mis-
centering).
INDEX
Laser
output 1
Laser
output 2
a
Symbol
a
Laser goes ON for first scan.
b
Index sensor goes ON.
b-c
The timing at the left is controlled
c-d
by counting the LD1 IRCLK and
d-e
LD2 IRCLK signals. It differs
depending on the document size.
b) Sub scanning direction
Specified interval after PS44 (registration)
detects the tip of the copy paper.
(4) Laser beam position correction
a) Main scanning direction
The index sensor detects the deviation of the
positions of the two beams. This error is cor-
rected by changing the timing of the light
emission from the laser.
b) Sub scanning direction
The index sensor detects the deviation of the
positions of two beams in order to change the
angle of the fine adjustment prism of the LD1
laser using M24 (laser correction), thus
adjusting the vertical angle of the beam.
2-D-5
WRITE UNIT
Image area
b
c
d
e
1st scanning
2nd scanning
Description
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