UC Irvine

Selection of infrared (IR) detector is a key consideration in designing an experimental setup for temperature depth profiling using pulsed photothermal radiometry (PPTR). In addition to common detector characteristics, such as the spectral response, detector noise, and response speed, application-specific details must be taken into account to ensure optimal system performance. When comparing detectors with different spectral responses, blackbody emission characteristics must be considered in terms of influence on radiometric signal amplitude, as well as on background shot noise. In PPTR, optical penetration depth of the sample in the acquisition spectral band is also an important factor, affecting the stability of the temperature profile reconstruction. Moreover, due to spectral variation of IR absorption coefficient in watery tissues, the acquisition band must be appropriately narrowed to ensure the validity of the customary approximation of a constant absorption coefficient value in signal analysis. This reduces the signal-to-noise ratio, adversely affecting the stability and quality of the temperature profile reconstruction. We present a performance analysis of PPTR depth profiling in human skin using commercially available IR detectors (InSb, HgCdTe), operating in different spectral bands. A measurement simulation example, involving a simple, hyper-Gaussian temperature profile, and realistic noise levels, illustrates their expected performance.