THERMAL-EXPANSION TENSOR MEASUREMENT BY SPECKLE INTERFEROMETRY

Using a block of anisotropic material from the point of view of thermal expansion, six bars are cut in different spatial directions. A double-exposure photograph of speckle is taken of the six bars, one before and one after the temperature is increased. Only one double exposure is 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 material is calculated.