Transmission Characteristics Of Optical Signal In The Coherence Tomography And Interference Spectroscopy System

The coherence tomography and interference spectroscopy system was tried to be established on the combining of optical coherence tomography and interference theory by using Michelson interferometer, which can be used to acquire three-dimensional image information and spectral information of the target simultaneously. The optical signal transmission characteristics of the system and optical transmission characteristics in the tissue will be investigated. The epidermis and dermis layer of the skin is investigated because of the probing depth of the system is 1-3mm. For most diseases, the internal characteristics of skin vary, especially in the epidermis and dermis. Therefore, studies on the light transmission characteristics and optical energy distribution when optical parameters change in the epidermis and dermis, will have a very important significance on diagnosis and treatment of diseases. The main research contents are summarized as follows:(1) In this paper, we investigated the basic principles of the coherence tomography and interference spectroscopy system based on the above two systems, and discussed the factors that influence optical signal transmission and the effect of optical signal in the tissue.(2) Based on Monte Carlo method and the theory of light interaction with biological tissues, The optical parameters model and simulation process in the single-layer and multi-layer biological tissues are discussed, and the influence of the optical parameters of tissue on light transmission and energy distribution are simulated and analyzed.(3) Based on optical parameters model of the actual skin acquired from the literature, the optical transmission and the energy distribution in different melanin content of three-layered skins tissue and blood levels of four-layered skins tissue are simulated by Monte Carlo method.The main research results are summarized as follows:(1) The mathematical expression of the optical signal transmission are given in the system based on the theoretical analysis of the system, and light selection, scan mode, noise of the system and the construction and optical characteristics of the tissue were proved have a great influence on the system construction and optical transmission in the system.(2) Simulation of light transmission in the single-layer and multi-layer biological tissues,the results show:Absorption coefficient/ua is larger, the light absorption intensity A(z)in the tissue is greater but the diffuse reflectance intensity R(f) is smaller; Scattering coefficient μs is larger, the scattering ability is stronger, while the diffuse reflectance intensity R(r) is greater; Anisotropy factor g is larger, intensity of absorption and scattering in tissue decreases and forward penetrate is enhanced; Refractive index n is larger, the intensity of the photons are absorbed is greater, while the scattering probability decrease; Light energy distribution shows a clear dividing line at interface of hierarchical tissue and the distribution characteristics of each layer in tissue is similar to the simulation results of the single tissue.(3) Simulation of photon transmission in the multi-layered skin tissue,the results show:the greater the content of melanin in the epidermis, the greater μa and A(z), while the smaller energy flux density F(z) and R(r) are smaller; Optical absorption energy density A(r,z) shows a clear dividing line at the junction between the layers, as μa becomes larger, the center radius of optical energy absorption is greater; the farther away from the center, the energy absorption decrease. For four-layered skins, the optical properties are different with different blood content in the dermis. A(r,z) show a significant stratification. Parameters μa、μs、g are changed in the dermis, it influences light distribution of A(r,z) in the dermis, the epidermis and muscle layer.The coherence tomography and interference spectroscopy system and optical transmission characteristics are analyzed by mathematical analysis and simulation studies, the results are consistent with the theoretical and experimental studies and seem very reasonable. This study will facilitate the development of optical imaging technology and bio-medical diagnostic technology further and service for the technological innovation and human health with a very important scientific and practical significance.