Scanner Unit
A844
SCANNER FUNCTIONS
SM 18-5 A265/A267
2.2 SCANNER FUNCTIONS
2.2.1 SELF DIAGNOSTICS
Every time the main power switch has just been turned on, the scanner board
performs the self diagnostics and the following items will be done automatically.
•
SRAM read/write test
•
Flash ROM read test
•
Battery test
•
Initializes the network interface circuit
•
Application software for scanner controller test
•
Connection test between the scanner board and the main body
If an error is detected, an appropriate error message or condition will be generated
(refer to the Troubleshooting section).
2.2.2 IMAGE PROCESSING IN THE SCANNER CONTROLLER
The image processing for scanner mode is done in the IPU chip on the BICU
board. However, the following processes are done in the scanner controller.
•
Image compression
•
Sub-scan magnification
Also, the scanner controller has a gamma table and dither matrix for scanner
mode. When the user selects the image mode using the scanner driver, the
appropriate gamma table and dither matrix are downloaded to the BICU board.
Then the IPU chip does the image processing using these tables or matrixes.
Image compression
The image compression method for binary picture processing uses MH, MR, or
MMR, depending on scanner SP mode 002. Grayscale processing uses JPEG.
This is done by the software.
Sub-scan magnification
Usually, the sub-scan magnification is done by changing the scanner motor speed.
However, when the amount of data being transferred is high (e.g, low resolution in
grayscale processing mode), the scanner controller deletes every other line.
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