Thermophotonic radar imaging: An emissivity-normalized modality with advantages over phase lock-in thermography

One major problem of frequency-domain photothermal radiometry, or alternatively in two-dimensional lock-in thermography, is the compromise one has to make between dynamic range (probing depth) and depth resolution. The thermal-wave radar incorporates chirped excitation through matched filtering to maintain good resolution and depth range inside a sample. This letter experimentally demonstrates the advantages of chirped modulation and introduces a thermophotonic modality of thermal-wave radar based on an emissivity-normalized, higher-dynamic-range contrast parameter known as cross-correlation phase. Finally, comparisons made on a biological (dental) sample show potential applications of the method.