Influence Of Divergence Angle On Spatial-resolved Diffuse Reflectance At Short Source-detector Separation Studied By Monte Carlo Method

Study of spatial resolved diffusion reflectance of biological tissue close to the source becomes focus of biomedical photonics in recent years. A new technology which can measure the parameters of tissue is provided by the study. P3 approximation and Monte Carlo simulation are the main theories used to describe the optical properties of biological tissue close to the source. However, the reflectance formula given by P3 approximation is very complex, so Monte Carlo method is used to study the reflectance close to the source in this paper. Influence of different sourse to spatial resolved diffusion reflectance is discussed deeply.First the theory of Monte Carlo method is described in detail, then, the limitation of the original programme in simulating the situation close to the source (the source-detector separation is from 0 to 1.5 mm) and how to modify the program are discussed on basis of theory. How to set the incident condition by considering divergence angle of incident beam is introduced as keystone. Spatial resolved diffusion reflectance in different source is simulated by use of the modified program, and analysis the influence of different source sizes,properties,divergence angles and power to the diffusion reflectance. Several groups of reflectance with different parameters(absorption coefficient,diffusion coefficient) are simulated to found a database. How to get the parameters(absorption coefficient,diffusion coefficient) from the simulated results is studied. At last, the simulated results,the measurement results and the theory results are compared, the measurement results accord well with the simulated results, and the diffusion approximation theory is checked up out of use.