Canon CANOSCAN FB1210U Service Manual page 31

CHAPTER 2
2. D/A Converter
D/A converter removes ununiform analog data generated by the CCD. It adjusts CCD output
to keep max. 5V of input signal to the A/D converter, to make the black level of the image
constant.
3. A/D Converter
The A/D converter converts the black-level-corrected image signal (analog signal) to a 14-bit
image data (digital signal) in the order of red, green and blue image signal.
5V is applied to the VRT terminal and reference voltage is applied to the VRB terminal. A/D
converter outputs "0" when input signal is 5V, and outputs "16383" when input signal is
reference voltage. This converts 1 pixel signal into the image data of 16384 gradations for red,
green and blue each.
Blue Image Signal
Green Image Signal
Red Image Signal
2 - 12
A/D Converter
B
G
R
Reference Voltage
V
+5V
OFFSET
Figure 2-11
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COPYRIGHT 2000 CANON INC. CANOSCAN FB1210U REV.0 APR. 2000 PRINTED IN JAPAN (IMPRIME AU JAPON)
Image Data
0 1
0 1
0 1
0 1
0 1
0 1
Output
0 1
0 1
0 1
0 1
0 1
0 1
0 1
0 1