Thermal wave imaging with phase sensitive modulated thermography

Thermography and thermal wave techniques can be combined to provide in a short-time low-frequency phase angle images where nonthermal features can be suppressed. The principle is optical thermal wave generation simultaneously on the whole sample surface and sequential monitoring of all pixels using both thermographic techniques and lock-in data analysis. Due to parallel stationary excitation one can use low modulation frequencies allowing for a depth range that is of relevance for applications.