(2) Scanner Gamma Correction (RGB Gamma)
The RGB video signals detected by the CCD are converted to 8-bit digital
signals in the scanner section and sent to the IPU section. These signals are
proportional to the light intensity reflected from the original image (Fig. 1).
However, the IPU section converts the signal levels as shown in figure 2 by
using a gamma correction table in order to improve the accuracy of RGB to
CMY (also referred to as "YMC" later in this section) color conversion, which
is done later in the image process. The same table is used for R, G, and B
signals. The scanner
γ
correction converts the video signal levels as follows:
Dark (Black) Light (White)
Scanner Input (RGB) 0 255
After γ Correction (RGB)
255 0
↓ Color Conversion
Printer Output (CMY) 255 0
Fig. 1
Fig. 2
IMAGE PROCESSING
A166/A187/A189 2-46 SM
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