Ricoh PRIPORT VT 2000 Series Service Manual page 55

28 February '91
VT2300/VT2500 Circuit:
Amp
VPH of Shading
Distortion
Memory
VPH of Platten/
Original
Background
Black Level
Correction
Output of
Selector 1
Standard
Voltage: 1.4V
CN601-24
Density: 0
CN601-25 Density: 1
Shading Distortion Correction (Photo Mode)
Shading Distortion Correction (Line Mode)
Photo Mode
Line Mode
This circuit converts the analog input signal (V
using both the white level reference (V
In each mode, the settings of the "X" and "Y" switches in Selector 2 are
automatically determined by the PHOTO and SHMRT signals as shown in
the above table.
Photo Mode
Selector
3
95%
2
80%
X
1
80%
0
70%
3
10%
2
10%
Y
1
40%
0
40%
A B
Line Mode
Selector
3
2
X
1
0
70%
3
40%
2
Y
20%
1
0
A B
Line/Photo
Selector 2
3
2
X
1
0
3
2
Y
1
53%
0
B A
PHOTO SHMRT
L
H
L
H
) to a 4-bit digital signal
S
) and the black level reference (V
H
2-28
VH
M1
M2
VL
A/D CONVERSION
PHOTO
SHMRT
Line/Photo
Selector 2 (X,
Y)
L SW0 ON
L SW1 ON
H SW2 ON
H SW3 ON
VS
4 bit
Image
Signal
).
L