The Analysis Of Error Of Optical Properties Estimation By Using Two Integrating Spheres

The method which is the most frequently applied to measure the optical properties of tissue in vitro is the double-integrating-sphere (DIS) technique. But light losses out of the edge of the sample with glass slides sandwiched between the two integrating spheres can not be detected by the detectors of the sphere are not taken into account correctly by the inverse adding doubling method, which introduces error for the estimation of optical properties of tissue. In this thesis, our work is carried out in the light loss out of the edge of the sample, error of tissue optical properties estimation, how to modify the error and so on.At first, a Monte Carlo algorithm (MC) is applied to simulate the measurements of sample with glass slides sandwiched between the double-integrating-sphere setup (DIS). The various parameter causing effects were analyzed and optical properties estimated by the inverse adding-doubling method (IAD) have been investigated quantificationally from the parameters of DIS, the geometry and tissue optical properties of the sample. The results show that the larger the losses, the greater the error of optical properties estimation, the error of scattering coefficient is much less than that of absorption coefficient. The error is reduced effectively by enhancing the sample port diameter or decreasing the thickness of sample. In addition, the IAD method is proved to be valid for estimating the optical properties of highly scattering or highly absorbing sample.Then, based on the data from MC simulation, we set up a data base and a software to modify the error of optical properties estimation. Optical properties of the standard models were measured by the double-integrating-sphere system and modified by our software. The modified results showed more accuracy and proved that the correctness of the theory and the software.This study is not only to evaluate the error of optical properties estimation, but also to give optimal ways for the design of DIS and scheme for acquiring accurate optical properties of tissue.