Ricoh C211 Service Manual page 425

6. Peak Hold: SS830
+
CCD ~ Inverter Amp. "
-IUD Conversion
,
'KHST-KFVPH
Peak Hold: SS950
—CCD Board
1 ~A'DcOnversiOnBOard
CCD
OS - - Inverter
'rnp- :pKHT~A'DcOnvers'On
r
!
I I
i
r
1
—
CN601 ?5
Read o *
% CN601 -27
Tlmlng
~ :N601-2g
- Signal
~~ , =*vpH
+ Generator
Master
S CLK
7A
I
SHMRT~
A/D Conversion
Processlnga
Control Board
This circuit holds, at different stages of image processing, the peak white levels for both the
original and the platen cover (standard white). The peak white, or maximum, level is stored
as charge on a capacitor. The peak hold circuit is cleared by discharging the capacitor.
6-1. Platen Cover Peak Hold (Standard White)
The platen cover peak hold is used as standard white when processing data to create
the shading distortion data, which is later stored in memory. This data is used to correct
such distortions as bright or dull spots on the lamp or variations in the CCD output. To
create the platen cover peak hold (standard white), the machine scans the white platen
cover prior to scanning an original. The reading the machine receives is stored as a "Peak
Hold" voltage in a capacitor. The peak hold circuit stores the maximum level from three
scan lines of the white platen cover. This sets the entire machine circuitry for what it
considers "white" to be.
2-15
Rev.
8/89