Savin SDC103A Service Manual download pdf (Page 110)

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4.3.4 Shading Circuit

(1) Shading Compensation (GA1, GA2)

Before scanning each original, the machine generates a reference white

waveform (also known as "white shading data") by scanning 5 mm of the

white reference plate [A] in the sub-scan direction (this equals 79 lines at

100% magnification).

The white shading data is calculated for each pixel across the main scan. To

do this for a particular pixel, it takes the white levels for that pixel on each of

the main scan lines taken from the white reference plate, and calculates a

value from these. The white waveform is made by repeating this process for

each pixel across the main scan.

To improve image reproduction for high density areas, the machine also

measures the black shading data. It does this by reading the black video

level at the first 4 pixels of the CCD, which should be black because these

pixels are masked off. The average of the 4 pixels is represented as the

black shading data for one CCD scan line.

[A]

Detailed

Section

Descriptions

IMAGE PROCESSING

SM 2-41 A166/A187/A189

CÓPIA NÃO CONTROLADA

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Savin SDC103A Service Manual Page 110

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