The study of the response of a temperature field (recorded from IR cameras) to a laser spot heating is increasingly used for NDE (Non Destructive Evaluation) applications. The most classical type of application is to use the flying spot in order to detect vertical cracks and/or to measure the in plane thermal diffusivity in relation to the observation plane of opaque materials. But several other ways of applications are presented here related to tomography and also super resolution. Instead of opaque materials applications, the tomography is using the principles of the flying spot. It consists in an indirect detection on an intermediate layer (the thermoconverter) that can convert a wide range of radiation from the spot. The objective of super-resolution can also be implemented with flying spot in order to circumvent the low spatial resolution of IR imaging systems. Such methods consider spots whose diameter is small compared to the size of the pixel. Some applications of our team will be shown with multiscale considerations.
Non-destructive testing (NDT) of materials and structures is a very important industrial issue in the fields of transport, aeronautics and space as well as in the medical domain. Active infrared thermography is an NDT method that consists in providing an external excitation to cause an elevation of the temperature field in the material, consequently allowing evaluation of the resulting temperature field at the surface. However, thermal exciters that are used (flash lamps, halogen, lasers) act only on the surface of the sample. On the other hand, several energy conversion systems can lead to the generation of volumetric sources; the phenomena of thermoacoustics, thermo-induction, thermomechanics or thermochemistry can be cited. For instance, ultrasonic waves can generate volumetric heat sources if the material is viscoelastic or if there is a defect. The reconstruction of these sources is the initial process for the quantification of parameters responsible for the heating. Characterizing a heat source means reconstructing its geometry and the supplied power. Identification of volumetric heat sources from surface temperature fields is a mathematically ill-posed problem. The main cause of the issue is the diffusive nature of the temperature. In this work, 3D reconstruction of the volumetric heat sources from the resulting surface temperature field, measured by infrared thermography, is studied. An analysis of the physical problem enables specifying the limits of the reconstruction. In particular, a criterion on the achievable spatial resolution is defined, and a reconstruction limitation for in-depth sources is highlighted.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.