FLIR ADK
Getting Sta rt e d
The information contained herein does not contain technology as
defined by EAR,15 CFR772, is publicly available, and therefore
not subject to EAR.
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pulse. Please see the Boson External Sync App Note Document for more information on the
functionality of the sync feature with the Boson camera.
5 ADK Latency
5.1 Microbolometer Thermal Time Constant
The Boson Microbolometer sensor absorbs infrared radiation on the surface of the pixel,
and continuously changes its temperature in relation to it. However, the change in
temperature is not instantaneous. Instead, every microbolometer has a characteristic
thermal time constant which dictates how quickly it responds to a change in irradiance.
In the case of the ADK, the nominal Thermal time constant is 8msec. This means that if the
incoming radiation changed by a certain amount, it would take 8msec for the pixel to
change (1-e-1) or 63.2% of the difference between its value prior to the change and its
eventual steady-state value after the change. This effect is illustrated in Figure 4. Since the
camera operates at 60 Hz, each frame period is just over 2 time constants, meaning that the
thermal time constant is not noticeable in many environments.
Figure 4. Pixel Response to a 100 Count Increase in Flux
It is worthy to note that the thermal time constant does add an extra latency to the video
pipeline. Usually, the difference from one frame to another is not very abrupt. Smaller
differences in LWIR radiation between frames hide the thermal time constant as the
differences get smaller. Edges of fast-moving objects will have the most significant effect,
creating a slight blur.
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