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8
Radiometric measurement
Note
• The auto-exposure process looks for the best integration time for the actual thermal
scene. It may be the case that this preferred integration time is not achievable be-
cause it is limited by the camera's frame rate. In this case, the auto-exposure process
is stopped, and the preferred integration is not applied.
The auto-exposure process is not designed to handle multiple integration times.
8.3 Bad pixel replacement
8.3.1 General
Once an NUC has been carried out, bad pixels can be detected and replaced. This is
done by replacing the bad pixels by the median value of the eight neighboring pixels.
There are three kinds of bad pixels:
• Bad pixels relative to the gain of the non-uniformity correction. In this case the system
will consider a pixel as bad if the gain coefficient from the NUC is lower or higher than
the predefined percentage. For instance, if the threshold is 25%, the system will deter-
mine a pixel as bad if the gain is <0.75 but >1.25.
• Bad pixels relative to the offset of the NUC. In this case the system will consider a pix-
el as a bad if the offset coefficient from the NUC table is lower or higher than the pre-
defined threshold. For instance, if the threshold is 30% and if the range of digitization
is 16 384 digital levels (DL), the system will determine a pixel as bad if the offset is <–
4915 DL but >4915 DL.
• Bad pixels relative to its level of root-mean-square (RMS) noise. In this case the sys-
tem will consider a pixel as bad if the RMS noise is lower or higher than the predefined
threshold. For instance, if the threshold is 3.5 and the mean and standard deviation of
the noise image are, respectively, 5.0 and 1.0, the system will determine a pixel as
bad if the RMS noise is >8.5. With the absolute threshold, the system considers a pix-
el as bad if its value is higher than this threshold.
8.4 Camera file management
8.4.1 Procedure
1. Connect your camera to a computer using the USB port.
2. You can add or delete camera calibration files directly in the directory FlashFS/nuc/.
3. Reboot the camera to apply the modification
Note
If you are using Microsoft Windows 7:
• The camera must be connected to the computer using USB.
• The USB drivers must be correctly installed.
8.5 Frame rate and integration modes
8.5.1 General
The frame rate is the number of images taken by the camera per second. The integration
time is the "exposure time"—the period of time for which the camera views the scene.
Achievable frame rates are based on the camera settings, the camera overhead, and the
integration settings. A brief review of the processes that occur during a frame is needed
to understand how to determine maximum achievable frame rates.
There are two basic integration modes: integrate then read (ITR) and integrate while
read (IWR). ITR is the most basic behavior of the camera and shows the process most
clearly.
#T810204; r. AA/43079/43091; en-US
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