FLIR
LEPTON® Engineering Datasheet
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and therefore, not subject to EAR. NSR (6/14/2018).
Information on this page is subject to change without notice.
Lepton Engineering Datasheet, Document Number: 500-0659-00-09 Rev: 203
30
•
Radiometry enabled, TLinear enabled (default for Lepton 2.5 and 3.5)
•
Radiometry enabled, TLinear disabled
•
Radiometry disabled
3.5.1
Radiometry Enabled - TLinear
The radiometry enabled mode affects the transfer function between incident flux (scene temperature) and pixel
output. From an image-quality standpoint, both radiometry modes produce nearly identical performance (no
change in NEDT), and either mode is appropriate for strict imaging applications. However, for applications in
which temperature measurement is required, radiometry must be enabled to access the related calibration and
software features, such as TLinear and Spotmeter, which support these measurements. In radiometry enabled
mode, enabling the corresponding TLinear mode changes the pixel output from representing scene flux in 14-bit
digital counts to representing scene temperature values in Kelvin (multiplied by a scale factor to include
decimals). For example, with TLinear mode enabled with a resolution of 0.01, a pixel value of 30000 signifies that
the pixel is measuring 26.85°C (300.00K
–
273.15K). The Lepton with Radiometry configuration is intended as a
fully radiometric camera; therefore, the factory defaults are defined to have both radiometry and TLinear modes
enabled.
With radiometry mode enabled (independent of TLinear state), the Spotmeter feature can utilized. The
Spotmeter returns the mean, maximum, and minimum temperature readings in Kelvin for a given frame and ROI
via the CCI and/or telemetry. The ROI coordinates are user-selectable via CCI to allow for readings confined to any
arbitrary size or location within the array.
The radiometric accuracy over the operational temperature range is typically within ±5°C or 5%. Integration into
an end-system and environment and/or scene differences can affect the radiometric performance. To address
these factors, user-configurable parameters are available in software to account for the difference between
calibration method at the factory and the final system and application. The parameters include scene emissivity,
atmospheric temperature and transmission, background temperature, and parameters to account for the
recommended window included on a fully integrated system (transmission, reflection, temperature, and reflected
temperature). For a more detailed discussion on radiometry principles, accuracy, and calibration, reference the
Radiometry Application Note.
Note that the following discussion assumes AGC is disabled (see
). If AGC is enabled, the
differences between the two radiometry modes are completely obscured by the AGC algorithm. In other words,
with AGC enabled, any differences in signal output between radiometry-disabled and radiometry-enabled modes
are negligible.
3.5.2
Radiometry Enabled
–
Flux linear
