Theoretical and experimental possibilities are presented of a modulated photothermal method, laser‐induced photoreflectance, for inspecting thermal diffusivities and quality of interfaces in composite materials with micron‐scale spatial resolutions. The models are established for semi‐infinite materials containing interfaces parallel or perpendicular to the sample surface. The applications concern thermal diffusivity measurements of anisotropic polycrystals and detection of thermal resistance in damaged materials and at interfaces between reinforcements and matrix in composites. ©1995 American Institute of Physics.