Amplitude and phase signals of the photothermal deflection images

Noncontact photothermal deflection (PTD) techniques are: applied to the non destructive photothermal detection of buried structures. The data are analy zed to take account of the finite radius of the excitation laser; The calcu lated PTD signals and the experimental data are compared. The modulation fr equency dependence of both the PTD amplitude and phase signals has been use d to estimate the thermal diffusivity. The phase spectra are moire sensitiv e to the buried structure in the deep interior than the amplitude signals a nd are able to show the sharp edge at the corner of a buried structure. The case where: the laser radius is larger than the buried structure is also i nvestigated using fine cross pattern samples.