Picture Signal Scanning Block - Panasonic UF-585 Service Manual

Panasonic UF-585 / 595
6.2.3

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 SCA/SCB 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 consists 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 consists of IC19, IC17, C187, R109 and R320 (UF-585: IC19, IC7, C113, R146 and R250). 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 IC19 and input to IC17 (UF-585: IC7), 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 C187
(UF-585: C113) is charged through R109 (UF-585: R146). This charging voltage lowers the level of the picture signal input to
IC19. 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 C187 (UF-585: C113) is discharged
through R320 (UF-585: R250). Consequently, the output of the ABC circuit is kept constant to maintain the picture quality,
regardless of changes in the CCD output level.
202
Differencial
Amplifier
CCD
Drive
Circuit
SCA/SCB Board
W
1728 bit
B
Effective Scan Width
Relay
[SCA]
IC17
MN86075
[SCB]
IC7
MN86074
IC2
DZAC000157
(PEGASUS)