Measurement of Surface and Volume Effects of Inhomogenity in a Multiple Scattering Medium by Diffuse Photon-Pairs Density Wave (DPPDW)

From conventional diffusion theory, the diffuse photon density wave (DPDW) which is generated in a multiple scattering medium satisfies the diffusion equation where the gradient D (D ) related to a small spatial variation of diffusion coefficient D is ignored because the magnitude of detected signal is much less than the excess noise induced by laser intensity fluctuation by using a high frequency intensity modulator in conventional photometric approach. This results in the limitation on spatial resolution of the recovered image of an inhomogeneity in turbid media. In order to improve the spatial resolution of the recovered image, we proposed to setup a theoretical model based on our previous proposed diffusive photon-pairs density wave (DPPDW) in multiple scattering media and association with the perturbation theory of DPPDW that is able to solve the diffusion equation including ( D) for surface effect derivation and computer simulation of a small object in turbid media. Then, in the second year, the experiment is setup in which a tunable frequency stabilized laser beam is integrated with an acousto-optics modulator (AOM) to produce a dual-frequency paired linear polarized laser beam for the surface effect measurement in order to verify the correctness of the developed perturbation theory of DPPDW. In the third year, the image reconstruction method based on DPPDW is developed that the measured DPPDW is able to demonstrate the ability of the improvement on spatial resolution of the recovered image compared with one obtained by using DPDW method.

Project ID:PB9807-2491
External Project ID:NSC98-2221-E182-063-MY3