Spyder 3 Camera User's Manual GigE Dual Line - Frame Grabbers

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Spyder 3 GigE User Manual
A2.2 Analog and Digital Signal Processing Chain
Processing Chain Overview and Description
The following diagram shows a simplified block diagram of the camera’s analog and
digital 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. All of these elements are user
programmable.
Figure 24: Signal Processing Chain
Analog Processing
Digital Processing
analog video
digital video
analog
gain
sag,ccg
analog
offset
sao,cao
PRNU background digital system
coefficients subtract
gain
ccp,cpa ssb ssg
FPN
coefficients
ccf
digital
offset
sdo
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 (59Hsag or 60Hccg 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.
2. The analog offset (61Hsao or 62Hcao command) or black level is an “artificial” offset
introduced 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.
Digital Processing
03-032-10158-06 DALSA