Radiometry; Converting Pixel Values To Temperatures - Teledyne FLIR A68 Series User Manual

Radiometry

The A68/A38 series cameras support radiometric temperature measurements as a
stand-alone GigE camera or as an integrated OEM part of another system. In both
cases, certain integration considerations are essential to obtain the highest camera
accuracy and performance. This section highlights the most important aspects of such
an integration.

Converting Pixel Values to Temperatures

Note: Temperature readings assume that objects have a surface
emissivity coefficient of 0.99; temperature readings of objects with
different emissivity coefficients must be adjusted accordingly.
Conversion From a 16-bit Image
One way to calculate temperature values in Celsius is to configure the camera to
output 16-bit values. To do so, set the Pixel Format (PixelFormat) feature, available in
CamExpert in the Image Format Controls Category, to Monochrome 16-Bit (Mono16).
The equations to calculate temperature or DN are:
Where:
- T = degrees Celsius (°C).
- DN = pixel value (in 16-bits image)
- radiometryOffset
degrees Celsius. By default, it is factory-initialized to 30000 but this value can be
changed.
- radiometryGain
the slope of the curve), in DN per degrees Celsius. By default, it is factory-
initialized to 100 DN per Celsius but this value can be changed.
For example, if a pixel has a value of 33851 and
have their default values, the corresponding temperature is:
33851 = (T * 100) + 30000 → (33851 – 30000)/100 = 38.51°C
44 • Features and Configuration Options
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FLIR A68/A38 Series IR Camera User's Manual
and radiometryGain