2. Digital Video Processing Steps
Overview
The analog signal from the CIS is first converted into an 8-bit digital signal.
Then it passes through some digital processes that depend on the selected
scanning modes. To process the data, the DIP uses a dedicated 8 kb video
SRAM (VRAM).
From Image Sensor
From thermistor
Dither matrix process
Auto density control
MTF
Thresholding
Erasure of irregular
dots
OR processing
A/D Conversion
Video Signal Correction
-Auto Shading
(all-black and all-white signal correction)
-Peak Hold
Halftone?
Gamma Correction
Edge detection
Error diffusion
process
Edge
enhancement
Output
Start scanning
Multiplexer
YES
NO
COPY
FAX
Analog
Digital
Reduction?
Main Scan Reduction
Mode?
NO
YES
Reduction?
Main Scan Reduction
NO
YES
Scanner Position
Fine Adjustment
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AA
AA
AA
AA
Standard resolution
15.4 l/mm
15.4 l/mm
15.4 l/mm
15.4 l/mm
3.85 l/mm
1st Line
2nd Line
3rd Line
4th Line
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Detail resolution
1st Line
2nd Line
3rd Line
4th Line
7.7 l/mm
7.7 l/mm
15.4 l/mm
15.4 l/mm
15.4 l/mm
15.4 l/mm
Conversion
to
6-bit data
Thresholding
HALFTONE PROCESS
Error diffusion
process
Dither matrix process
HALFTONE RESOLUTION
CONVERSION
*
Background
detection
H521D520.wmf
* In fax mode, if halftone is selected at standard or detail resolution,
sub scan resolution is converted as shown in the diagram, before any
digital image processing is done.
DETAILED SECTION DESCRIPTIONS
May 22nd, 1995
SCANNER
2-18