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(2) Image process section
The image process section is composed of gate arrays A and B, the
CPU, and memories (SRAM, FIFO, EPROM). Gate array A forms
data for shading correction and calculates histogram data for auto-
matic exposure. Gate array B performs area separation, filter
process, address generation for self printing, multi-value dithering,
and electronic zooming of main scanning.
ICU image process section block diagram
EPROM
EPROM
SRAM
(program)
(data)
(work)
64K x 8
256K x 8
32K x 8
CPU
H8/3040
10MHz
Shading
correction data
Image
ICU
Density
data
CCD
conversion
LUT
control
SRAM
section
8K x 8
Visible sensitivity correction
Automatic exposure
Gate array A
Shading correction data
forming
Histogram data calculation
for automatic exposure
Image data for calculation of shading correction data
[Shading correction]
The analog image data from the CCD PWB are inputted to the CCD
control section in the ICU and converted into digital data, and passed
through gate array A in the ICU image process section, and written
into the multi-function LUT (Look Up Table). (Path shown with dotted
line in the above diagram.)
Gate array A performs thinning out of 16 lines at that time. Thinning
out of 16 lines is performed when there is dirt on the shading plate.
[Auto exposure]
The analog image data from the CCD PWB are inputted to the CCD
control section in the ICU and corrected by the shading data obtained
from the above method and converted into digital data and inputted to
gate array A. In gate array A, the total number data (simple his-
togram) of pixels in each density is calculated as shown in 1-5. The
calculated data are used to judge that the document is of background
type such as newspapers or of half tone type such as photos or of
white type with less black and without half tone such as character
documents. The data are calculated for each line. According to the
data, the CPU selects the most suitable density conversion look up
table from 32 kinds of density conversions look up tables in the
density conversion LUT.
Electronic
zoom
Image data
FIFO
FIFO
5K x 8bit
5K x 8bit
FIFO for
FIFO for
enlargement
reduction
5K x 8bit
FIFO for area separation
multi value dither
The CPU performs register setting and rewriting of LUT (look up
table) every time when the user changes the mode. It also calculates
the correction value of shading correction.
The figure below shows the flow of image signals.
Gate array B
Area separation data,
Area
self print data, multi
FIFO
separation
value dither data,
Multi value
shading correction
FIFO
Dither
data by the neural
Self print
net
FIFO
FIFO
[Electronic zooming]
The image data, after auto exposure and the visual sensitivity correc-
tion, are written into the FIFO for enlargement. Gate array B controls
the enable signal for reading the enlargement FIFO to thin out the
read data, enlarging images. For example, in enlargement of 200%,
the read enable signal is provided for every pixel to make enlarge-
ment. The image data thinned out for enlargement are inputted to
gate array B and the primary interpolation is performed as shown in
1-6. (For details, refer to 1-6.) The image data thinned out primarily
are written into the reduction FIFO. The enable signal for writing is
controlled to thin out for reduction.
[Area separation]
After electronic zooming, the image data are written into the FIFO for
area separation/filter/multi-value dithering. There are four FIFO's and
each one sends data for one line. Therefore gate array B can input
image data of five lines. Gate array B calculates the characteristic
value of peripheral pixels according to the image data of five lines
and the result is outputted to the address of the multi-function LUT.
The multi-function LUT is the same one described in the shading
correction. When the are separation mode is selected, the CPU reads
the data for area separation from the EPROM (for data) and write into
the multi-function LUT.
1 – 8
Gamma
correction
Filter
Black/white
process
reverse
(MTF
Line
correction)
alignment
SRAM
8K x 8
Multi function
Gamma correction
LUT
LUT
SRAM
32K x 8
ICU
laser control
section
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