THEORETICAL ANALYSIS OF FREQUENCY AND TIME DOMAIN METHODS FOR OPTICAL CHARACTERIZATION OF ABSORBING AND SCATTERING MEDIA

摘要

Measurements of the temporal distribution of radiation transmitted and/or reflected by an absorbing and scattering medium, subject to a very short pulse of light, are likely to provide information on radiative properties of the sample. However, this procedure requires precise solutions of the transient radiative transfer problem as well as appropriate nano/pico response time from detection devices. In this work, a different approach is investigated: the transient radiative transfer problem is solved in the space-frequency domain using a Discrete Ordinates - Finite Volume method and is shown to provide accurate results. Recent research work has proposed promising optical diagnostic techniques based on a radiation beam for which intensity is modulated. As a result, a preliminary sensitivity analysis is performed to determine some optimal parameters for the design of frequency-modulation based optical diagnostic techniques. The novelty here also arises from the application of the space-frequency method to media that are not necessarily optically thick.