1 - 3
PROCESS
0
+3
512
0V
IMAGE PROCESSING
[1] Outline
The analog signal produced by opto-electric conversion by the
CCD sensor on the A/D board is subjected to analog process-
ing, then A/D-converted, and subjected to image processing.
Image processing consists of shading correction, brightness/
density conversion,
AE
processing, text/dot pattern judge-
ment, filter/magnification change processing, copy γ correc-
tion, write density correction, and 2-beam control. In addition,
error diffusion processing and data compression are carried
out within electronic RDH.
[2] Analog Processing
In the analog processing board, the minute signals from the
CCD sensor are amplified and also level-shifted into the A/D
conversion range.
Amplification and level-shifting take place automatically at the
shading correction timing by an electronic variable resistor,
hence there is no need to perform manual adjustment.
[3] A/D Conversion
The image signals from the analog processing board are
converted one pixel at a time into 9-bit digital signals.
[4] Shading Correction
Shading correction is done to even out the light distribution of
the CCD sensor. The following correction takes place at the
specified timing.
1. White correction
The voltage output from each pixel of the CCD sensor when
the white reference plate is exposed to the light from the
exposure lamp is memorized as the maximum output value
for that pixel.
2. Black correction
The output voltage from each pixel of the CCD sensor when
the exposure lamp is out is memorized as the minimum
output voltage for that pixel.
* Based on the difference between the white and black
data for each pixel memorized in 1 and 2 above, the
calculated result that indicates the number of the step
corresponding to the image data read from the original is
output to an accuracy of 10 bits.
CCD image
sensor
A/D
conversion
A/D Board
Shading correction Copy γ correction
Selector/SGU
Write density
control
2-beam control
Fig.4
Read width
Read voltage
Read width
After shading correction
Electronic RDH
Memory
Data compression
and expansion
Image write
Error diffusion
processing
Image Processing Board
(1)
(2)
(1)····A/D input
(2)····Shading output
Fig.5
Brightness/density
conversion,
AE
processing, Text/
dot pattern
judgement, Filter/
magnification
processing
Reversal processing
White
Black
White
Black
PROCESS-1
To Next Page
Loading...