METHOD AND PHOTOTHERMAL APPARATUS FOR CONTACTLESS DETERMINATION OF THERMAL AND OPTICAL PROPERTIES OF MATERIAL

摘要

The material under testing is irradiated with a heating beam to deform the material surface forming a protrusion on the same. At the same time a measuring beam acts on the surface so that it is reflected by the protrusion, providing a beam scattered by the protrusion curvature that is detected by a small opening as a spatial filter located closer or farther than the confocal distance. The beam transmission through the disfocal opening varies according to the protrusion curvature induced by heating. The signal transmission allows determining the magnitude of the induced dilation. Said magnitude and its dependence on the modulation frequency allow determining physical properties as the dilation coefficient or the thermal diffusion coefficient, the coating film thickness or the incident light absorption coefficient on the heating beam. Varying the wavelength of the incident radiation it is possible to determine the absorption spectrum of the sample even for very small dimension particles wherein the absorbed energy fraction is negligible.