为了研究近红外光在皮肤组织中的传播, 建立了人体皮肤组织模型, 包括不同入射波长下表皮、真皮、皮下组织的吸收系数、散射系数、折射率和各向异性因子.结合皮肤组织的光学性质, 采用蒙特卡罗方法分析了1 000~1 900 nm范围内, 光源-探测距离不同时近红外光在皮肤组织中的传播过程和分布特点.结果表明：光子运动路径长度和穿透深度均随光源-探测距离的增加而变大, 而漫反射归一化能量随光源-探测距离的增加而变小.选取光源-探测距离为0.45 mm, 当入射波长为1 550 nm时, 光子运动路径长度为1.806 mm, 穿透深度为0.467 mm, 漫反射光归一化能量为0.001 85.根据蒙特卡罗模拟结果, 分析和设计了一种光纤探测结构, 这种分叉光纤束由18根光源光纤和4根探测光纤构成, 每根光纤间距均为0.45 mm并且刚好紧凑相邻.最后, 仿真计算了光纤收集到的漫反射光能量及照度分布.假设入射光功率为1 W, 则探测器接收的漫反射光功率为0.598 mW, 这为便携式检测光谱仪器的设计提供了参考.

In order to study the propagation of near infrared light in the skin tissue, the human skin tissue model was established, including absorption coefficient, scattering coefficient, refractive index and anisotropy factor of epidermis, dermis and subcutaneous tissue in different incident wavelengths. Combining with the optical properties of skin tissue, the near infrared light propagation and distribution characteristics in skin tissue when subjected to different light source-detection distances from 1 000 nm to 1 900 nm were analyzed using Monte Carlo method. The results showed that photon path length and penetration depth increased with the increase of the source-detection distance, while normalized energy of diffuse light decreased with the increase of the source-detection distance. The source-detection distance was selected to be 0.45 mm. When the incident wavelength was 1 550 nm, the photon path length was 1.806 mm, the penetration depth was 0.467 mm, and normalized energy of diffuse light was 0.001 85. A kind of optical fiber detection structure was analyzed and designed according to Monte Carlo simulation results. The bifurcated fiber bundle was composed of 18 source fibers and 4 detection fibers, the distance of each fiber was 0.45 mm and just compactly adjacent. Finally, the diffuse light energy and illumination distribution collected by this optical fiber were simulated. Assuming that the incident light power was 1 W, the diffuse light power received by the detector was 0.598 mW. The results could provide a reference for the design of the portable detection spectra instrument.