Service manual

4.3.5 D/A Conversion
The CPU monitors the digital feedback signals from the shading circuits and
calculates correction factors. Then the D/A circuit converts the signals from
the CPU into analog signals and feeds them back to the operational
amplifiers and the CLPs (see section 4.3.2.(3)). Black shading data is fed
back to the CLPs to decide the reference black level. This is done every
CCD pixel to calibrate the black level, to avoid drifts in the signal with time.
4.3.6 Scan Line Correction
The three CCD lines providing the RGB signals are spaced 8 lines apart on
the original image, when full size magnification is used. To compensate for
this discrepancy, the line correction circuits synchronize the output timing of
the RGB signals to the IPU section by storing the scan data for each line in
memory. As the discrepancy between RGB video signals changes
depending on the magnification ratio, the correction data is calculated as
follows:
•
B: Standard (No correction)
•
G: (8 lines) x (Magnification ratio)
•
R: (16 lines) x (Magnification ratio)
If this calculation does not result in an integer, the correction data is set to
the closest integer, but further correction is needed (refer to 4.5.1 (1) Picture
Element Correction).
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IMAGE PROCESSING
SM 2-43 A166/A187/A189
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CÓPIA NÃO CONTROLADA