Thermal imagers sensitive in MWIR and LWIR spectral bands are one of crucial surveillance technologies for defense/security sector. These imagers have also found mass applications outside defense sector. Testing thermal imagers is needed for both manufacturers, maintenance workshops and final users for a set of different and important reasons. Hi-tech test equipment can help significantly in manufacturing, maintenance, training, purchase optimization, and optimal use of these expensive imagers.
DT system offered in a series of versions is the most popular Inframet system for testing thermal imagers. It can be used for testing at laboratory/depot conditions virtially all surveillance thermal imagers offered on international markets, including long range thermal imagers for space application. All important parameters can be measured. Vertical configuration design method (blackbody and rotary wheel is on the collimator) enables design of compact test systems of high thermal uniformity of projected reference images.
|Fig.1. Photos of several DT systems: a)DT150, b)DT110, c)DT400|
SIM is a simple, low cost system designed to enable focusing and resolution measurement of thermal imagers. SIM can be treated a significantly simplified DT system. Both DT and SIM are stationary systems to be used at laboratory/depot conditions.
LAFT is mobile test station designed to enable basic testing surveillance thermal imagers at field/depot conditions.
DTR is small version of classical DT test system built using a refractive collimator and optimized for testing WFOV thermal imagers.
WAP is a portable wide angle projector optimized for testing imagers of wide FOV. Small size and mass combined with wide projection angle are big advantages of this system.
SAFT is a small test system testing measurement thermal imagers designed for short distance observation.
Fig.2. Photos of several additional test systems: a)SIM, b)DTR, c)LAFT, d) WAP, e) SAFT system
NON UNIFORMITY CALIBRATION
All thermal imagers must be factory-calibrated to generate non-uniformity compensation (NUC) coefficients which are applied automatically by the camera in real time to maintain good image quality. NUC coefficients are typically calculated on basis of images of an large area blackbody that fill FOV of tested imager at two temperatures: 1) high temperature in range from about 60ºC to about 120ºC depending on model of thermal imager, 2)laboratory ambient temperature (sometimes slightly increased to be approximately equal to the image sensor temperature).
Inframet offers DAP double blackbodies as near perfect cost effective solution for non uniformity calibration of thermal imagers. DAP double blackbody is practically a set of two blackbodies: TCB blackbody that operates typically at high temperature and PBB blackbody that operates at near ambient temperature. In this way DAP is an equivalent to two blackbodies typically used two point NUC but is offered at cost only slightly higher than typical TCB blackbody. At the same time ultra high accuracy of differential temperature between two emitters of DAP blackbody is achieved.