THERMAL-EXPANSION TENSOR MEASUREMENT BY SPECKLE INTERFEROMETRY

Using a block of anisotropic material from the point of view of therma l expansion, six bars are cut in different spatial directions. A doubl e-exposure photograph of speckle is taken of the six bars, one before and one after the temperature is increased. Only one double exposure i s required for the six bars altogether. Illuminating two points of the double specklegram of each bar with a narrow laser beam and measuring the angle between the diffraction maxima, the longitudinal expansion is obtained for each bar and the thermal expansion tensor of the mater ial is calculated.