Simple applications of non-destructive evaluation with low cost, uncooled IR cameras

New low cost uncooled infrared devices (such as PalmIR 250 (Raytheon), Thermacam 540 (FLIR), Indigo...) are giving new possibilities for small or medium sized companies. Even if each pixel of the temperature image is noisy, even if the global signal is randomly shifted due to the technology of ferromagnetic or bolometric detectors and even the caracteristics of the detectors of the matrix are not uniform, it is possible to use these cameras for Non Destructive Evaluation (NDE). The main idea is to use the video output data and associate to such devices recording and real time systems with adapted processing methods, in order to set out a very cheap NDE system. We present, in this framework, some processing methods based on the estimation of thermophysical parameters variations around a nominal value by an asymptotic gradient development. Theoretical arguments will illustrate this purpose and several examples in various industrial domains will be shown: Estimation of thickness variations of a PVC plate. Estimation of density variation of ceramic plates. Estimation of thermal conductivity variation of textile layers.