OWL 640 N/USER MANUAL/03-20/REV1.0
8.4 Non-Uniformity Correction (NUC)
The NUC state of the camera can be controlled from the
“NUC”
tab of the GUI. The camera
has a 3 point (offset, gain, dark) NUC performed live on board the FPGA of the camera,
correcting for fixed pattern noise. There is also a bad pixel correction when the 3 point NUC
is active.
By default, the 3 point NUC and bad pixel correction will be enabled (3 Point NUC On –
Gain+Dark).If wanting to output the raw data from the camera, the 3 point NUC can
be disabled (3 Point NUC Off – Raw Data).
The NUC controls are shown in Figure 12.
Bad Pixels:
Regarding bad pixels, our Short Wavelength Infra-Red (SWIR) cameras use an
InGaAs Focal-Plane Array (FPA) sensor which consists of an InGaAs layer bonded to a
CMOS read out integrated circuit (ROIC) by indium dots. This architecture makes it
extremely difficult to manufacture a sensor where all the pixels are fully functional. Issues
between the InGaAs layer, indium dots and CMOS ROIC are inevitable. Therefore, all
Raptor SWIR cameras have a pixel operability specification, describing how many pixels are
operating within normal parameters. Raptor uses the best quality sensors available on the
market achieving up to 99.5% pixel operability at delivery. The remaining 0.5% pixels can be
dead, hot or simply vary too much from the average. These must be compensated for to
achieve the best image quality. These bad pixels are corrected for in our NUC.
Bad pixels appearing over time is normal and unfortunately an inevitable aging process. To
correct for new bad pixels that have appeared over time, the bad pixel correction map on the
camera FPGA would need updated. This means that the camera would have to be returned
to Raptor to re-NUC the camera to update the bad pixel correction map. This is something
that would not be possible to do if wanting to send the camera back for every new bad pixel.
Raptor use the highest quality InGaAs sensors available on the market, however.
Figure 12: 3 Point NUC Control.
