RMV Operations Manual Revision Copyright illunis LLC, 2014
Page 72
4.8.4: Exposure:
ADC: Black Clamp
Serial Commands
Target
Index
Command
R/W
Description
00
02
A: Clamp Level
R/W
00
22
B: Clamp Level
R/W
01
02
C: Clamp Level
R/W
01
22
D: Clamp Level
R/W
The
ADC provides an active black clamping
circuit that removes the CCD’s optical black offset. This
offset exists in the CCD’s shielded black reference pixels.
The ADC removes this offset in the input stage to mini-
mize the effects of gain change on the system black lev-
el. During the optical black (shielded) pixel interval on
each line, the ADC output is compared with a fixed black
level reference selected by the value in the clamp regis-
ter. The Clamp level is programmed in 8 bit resolution. If
external digital clamping is used during the post pro-
cessing the black clamp can be disabled.
Quick FAQ’s:
►Each tap has its own ADC and thus its own clamp-
ing circuit.
►Clamp values for each tap can be adjusted inde-
pendently.
►Clamp is often referred to as black offset.
►Use the clamp offset to raise the minimum signal
above zero to see all system noise.
►
The DGO does not subtact the ADC clamp
value before gain and offset are applied !
CLAMP
CLAMP
CDS
VGA
ADC
2dB to 36 dB
12 bits
CCD In
RMV: Sensor, CDS, Analog to digital, and Clamping