Pulsed photothermal radiometry for noncontact spectroscopy, material testing and inspection measurements

Photothermal radiometry (PTR) is a sensitive technique for noncontact spectroscopy and inspection. Its principle is the following: a modulated beam of photons (or other particles) produces temperature transients in a sample; the corresponding transients in the IR thermal radiation emitted from the sample are analyzed. This can provide absolute absorption coefficients, as well as information on thermal diffusivity, layered structure and dimensions. Variations of PTR are possible with continuously-modulated or pulsed excitation, and with transmission or back-scattering detection. These variations are reviewed. The recent technique of pulsed PTR with back-scattering detection is described in more detail, and some important single-ended remote-sensing applications are discussed. © 1985.