Abstract: A thermal wave three-dimensional imaging and tomography apparatus and a thermal wave detector therefor are provided. The apparatus includes a light source for generating a laser beam which is modulated and then focussed onto one side of a solid test material. A thin pyroelectric polymer electret (.beta.-PVDF) film having an electroded upper surface and an electrodeless lower surface supports the other side of the test material on its electroded surface. A single thin metal elongate pin or an array of thin metal elongate pins are disposed beneath the electrodeless lower surface. The pin or pins generate(s) signals upon detection of thermal waves passing through the solid test material resulting from the laser excitation due to the photopyroelectric (P.sup.2 E) effect. Since the pins are small, the signals generated by the pins represent local thermal wave progagation through the test material.