Measurements of very small temperature variations with LWIR QWIP infrared camera

Infrared thermography, thanks to its non-contact character, can be advantageously exploited to get information in lots of temperature-dependent applications. Indeed, a vast variety of infrared imaging devices is today available, allowing measurements also in complex configurations such as in presence of fast phenomena, or moving objects. Of course, the measurement accuracy depends strongly on the magnitude of temperature differences both in space and in time; some limitations may arise when attempting to measure temperature variations which are very small and at the edge of the instrument resolution. In this regard, a difficult task is to perceive the temperature variations which are related to thermo-elastic effects, e.g., developing under relatively low loads. The purpose of this work is to deepen inside the parameters that mostly affect such critical measurements and to search for a simple and reliable solution. Measurements are performed with the LWIR QWIP SC6000 camera and the obtained data are compared with those supplied by either an InSb MWIR camera, or an un-cooled camera. Particular attention is deserved to the electronic output of the infrared imaging device and to post-processing signal procedures. It is found that, through the use of a reference area, is possible to account and avoid most of the existing noise.