Measurements of diffuse reflectance spectra using an integrating sphere are commonly used to characterize optically scattering materials and structures, such as biological tissues and organs. The analysis of the thus obtained spectra is generally based on the adjustment of analytical or numerical predictions in definition geometry, in which the sample is irradiated with a narrow light beam and the diffusely reflected light is captured from a large enough surrounding area. However, many commercial instruments work the other way around: The sample is isotropically irradiated and the light emanating from the center of the irradiated area into a relatively small solid angle is analyzed. The validity of such measurement is based on the validity of the assumption of time reversal symmetry.
In this master's thesis, we check whether this assumption is violated, analyze the error and check the possibility of its elimination when analyzing the described measurements. This is achieved by using a detailed numerical simulation, which is based on Monte Carlo method and with which we replicate the experimental procedure.
|
