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23. Image processing
23. Image processing
23.1 Scanner section image processing block diagram
1. Photoelectric conversion
2. Analog-to-digital conversion
3. Shading correction
4. Line-to-line variation correction/color aberration correction
To the MFP board
• The following detail the image processing operations performed by the scanner section.
1. A reduction type CCD sensor is used to read the light reflected off the original and
convert the optical data to a corresponding electric signal. To make data process-
ing faster, data transfer and output are done through two channels, one for even-
numbered pixels and the other for odd-numbered pixels.
2. The odd and even analog signals output from the CCD sensor chips are synthe-
sized to form a single string of signal data which is in turn converted to 8-bit digital
signals (256 gradation levels).
3. A correction is made of errors that occur due to variations in sensitivity of each
CCD chip and the light distribution varying along the length of the exposure lamp.
The shading correction is made by holding the peak value, i.e., the maximum value
of readings taken of multiple lines, to prevent adverse effects on the image due to
dust on the shading sheet.
4. Memory called FIFO is employed to compensate for a deviation in the scanning
position of the original, which represents a gap between two adjacent CCD chips,
thereby matching the output timing of R, G, and B data. Also, the color aberration of
the lens is compensated at this time.
• The image data is transmitted to MFP board on the write section through the interface
cable.
164
Theory of Operation Ver. 8.0 Jun. 2008
CCD sensor board
Theory of Operation
Image processing board
Y107522-3
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