User`s manual

48 Spyder3 S3-14 and S3-24 User's Manual
03-032-20117-00 Teledyne DALSA
Analog and Digital Signal Processing Chain
Processing Chain Overview and Description
The following diagram shows a sim plified block d iagram of the cam era’s analog and d igital processing
chain. The analog processing chain begins with an analog gain adjustment, followed by an analog offset
adjustment. These adjustments are applied to the video analog signal prior to its digitization by an A/ D
converter.
The digital processing chain contains the FPN correction, the PRNU correction, the background subtract,
and the digital gain and offset. Non-linearity look-up table (LUT) correction is available for the 4k model
of camera.
All of these elements are user programmable.
Analog Processing
Digital Processing
analog video
analog
gain
analog
offset
FPN
coefficients
digital
offset
PRNU
coefficients
background
subtract
digital system
gain
sag,ccg
sao
ccf
sdo
ccp,cpa ssb
ssg
eil
LUT
addition
4k ONLY
Figure 26: Signal Processing Chain
Analog Processing
Optimizing offset performance and gain in the analog domain allows you to achieve a better signal-to-
noise ratio and dynamic range than you would achieve by trying to optimize the offset in the digital
domain. As a result, perform all analog adjustments prior to any digital adjustments.
1. Analog gain (sag or ccg command.) is multiplied by the analog signal to increase the signal strength
before the A/ D conversion. It is used to take advantage of the full dynamic range of the A/ D
converter. For example, in a low light situation the brightest part of the image may be consistently
coming in at only 50% of the DN . An analog gain of 6 dB (2x) will ensure full use of the dynamic
range of the A/ D converter. Of course the noise is also increased. Note: To maintain valid LUT
calibration do not use the sag command with the 4k model. Instead, use the ssg command.
2. The analog offset (sao com mand ) or black level is an ―artificial‖ offset introd uced into the video path
to ensure that the A/ D is functioning properly. The analog offset should be set so that it is at least 3
times the rms noise value at the current gain.