| Summary: | We describe a 2-D computational model of the optical propagation in human skin from a confocal reflectance theta microscope. As an effect of decreasing the size of the microscope so that it is more clinically useful, the usual point source and detector with a raster scan is changed to a line source with a 1-D array detector. Because there is only one dimension of scanning, the microscope is confocal in one direction, but not in the other, however, this results in additional localized decreases in signal. We hypothesize that these result from the interaction of the bi-static imaging configuration with the geometry and inhomogeneity of the index of refraction in the skin such that the source path has different aberrations than that of the receiver. To help optimize the microscope design by better understanding the propagation, the model, which includes melanin, mitochondria, and nuclei, uses infinite-difference, time domain (FDTD) computations. The model predicts signal decreases which are somewhat greater then those seen in experiments. New details of reflection from a spherical object show that imaging with the theta line-scanner leads to somewhat different results than would be seen with a common-path point scanner.
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