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30 March, 1999
2.4.5 IPU FUNCTIONS
Scanner γ γ γ γ Conversion and Picture Element Correction
Scanner γ γ γ γ Conversion (RGB γ γ γ γ Conversion)
1023
0
Dark
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The RGB video signals from the CCD (10-bit signal) are sent to the IPU section.
These signals are proportional to the intensity of light reflected from the original
image (Fig. 1). However, the IPU section converts the signal levels as shown in
figure 2 by using a gamma (γ) correction table in order to improve the accuracy of
RGB to CMY color conversion, which is done later in the image process. The same
table is used for R, G, and B signals.
The scanner gamma (γ) correction inverts the video signals and converts the signal
from 10-bit to 8-bit as outlined in the following table:
Scanner Input (RBG)
After γ Correction (RGB)
↓
Color Conversion
↓
Printer Output (CMYK)
Light
Dark (Black)
Light (White)
0
255
255
2-37
IMAGE PROCESSING
255
0
Dark
1023
0
0
1023
Light
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