UF-590, UF-790, DX-600, DX-800 - Panasonic Fax Other Service Manuals (repair manual). Page 13

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The Shading Correction Circuit, included in IC30, is provided to correct for reduction in LED lamp inten-
sity around the optical lens and LED lamp intensity distortion due to shading of each bit. This circuit
scans the white reference on the transmitting document plate immediately before the document reaches
the scanning position and writes a compensation value according to the distortion of the waveform, at
the time, into the S-RAM (IC31).When the actual picture signal is input, the circuit corrects the picture
signal shading, according to this compensation value. This shading is carried out for each page during 
transmission or copy.

The Offset Control Circuit consists of Q15, Q13, IC30 and IC28, and controls the black level of the CCD
output to be at 0V by using the input.

The Picture Signal Binary Coding Correction Circuit is included in IC30. It is used to obtain a binary cod-
ing signal which is a corrected picture and error diffused signal of a false halftone signal, which is
detected from a shaded picture signal.

CCD Output

ABC Circuit Output

R288

C175

R285

IC28, 1

IC28, 2

32

37

19

41

39

40

IC30

Control

Circuit

OS

DOS

0V

3V

0V

-5V

+5V

Q15

Q13