Panasonic UF-580 Technical Manual page 12

1.1.4 Picture Signal Scanning Block
The image data read by the optical unit is input to the CCD mounted on the CCD PC Board, then
transferred to the SC PC Board after the optical information is converted into an electrical signal by the
CCD. The following shows a block diagram of the picture signal scanning circuit. This picture signal
scanning circuit consist of (1) ABC circuit, (2) shading correction circuit, (3) offset control circuit, (4) picture
signal binary coding correction circuit and (5) reducing circuit.
CCD
TCD 1208P
CCD PC Board
ABC Circuit
This circuit consist of IC28, IC30, C175, R288 and R285. Its function is to prevent deterioration of picture
quality due to dirt on the document or degrading of the luminous energy of the Xenon Lamp light source.
The picture signal from the CCD is amplified in IC28 and input to IC30, where it is converted from analog
to digital and the shading is corrected. When the signal exceeds +5V as the result of this amplification
and correction, capacitor C175 is charged through R288. This charging voltage lowers the level of the
picture signal input to IC28. When the picture signal voltage rises, this charge voltage becomes higher.
When the picture signal level lowers due to the background color, etc., of a transmitting document, the
voltage of the charged capacitor C175 is discharged through R285. Consequently, the output of the ABC
circuit is kept constant to maintain the picture quality, regardless of changes in the CCD output level.
Ver 2.00
Differential
Amplifier
CCD
Drive
Circuit
SC PC Board
W
1728 bit
B
Effective Scan Width
12
Delay
[SC]
IC30
MN86075
UF-580/590/780/790
DX-600/800
IC3
DZAC000273
DEC 2003