Target Signature: The spectral, spatial, and thermal features that distinguish a target from the background.
TE Cooler: Acronym for Thermo Electric cooler, this cooler utilizes the Peltier effect to perform moderate cooling, or more often, thermal stabilization of thermal imagers.
Temporal: Time-dependent.
Thermal Clutter: A condition in which multiple objects with thermal intensities similar to that of the desired target are in the same image as that target. Thermal clutter can make interpretation of images more difficult.
Thermal Contrast: The difference in thermal intensity between a target and the background.
Thermal Imager: An imager or camera sensitive to thermal (‘heat’) emissions, typically either MWIR or LWIR. Often, the terms “infrared imager” and “thermal imager” are used interchangeably.
Thermal Intertia: The tendency of a target to maintain its instantaneous temperature, even in the presence of an external temperature difference. Objects with large thermal inertia tend to heat up or cool down slowly.
Thermal Resolution: Casual term for the smallest thermal difference in an image that can be resolved. Often, the term “thermal resolution” is used (incorrectly) in place of either the Noise Equivalent Temperature Difference (NETD) or the Minimum Resolvable Temperature Difference (MRTD), which are two distinctly different quantities.
Thermoelectric (TE) Cooler: A cooling system with no moving parts (often used in LWIR systems) based on the Peltier effect, in which the junction between two dissimilar metals can be cooled (or heated) by applying a Voltage potential.
Transmittance: The fraction of incoming energy (at a given wavelength or at a given waveband) that passes through a target. See Conservation of Energy.
