共查询到15条相似文献,搜索用时 78 毫秒
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基于Delta-P1近似漫反射光学模型, 推导了双点源近似下空间分辨漫反射解对于Henyey-Greenstein散射相函数的二阶参量γ的灵敏度表达式, 研究了参量γ对漫反射分布的影响. 研究表明, 与漫射近似模型相比, Delta-P1近似漫反射光学模型不仅含有散射相函数的二阶参量γ, 而且在弱吸收或强吸收的情况下, 参量γ对于光源附近(ρ<1.0 mm)的空间分辨漫反射都存在较大的影响(极值大于30%). 因此利用γ研究漫反射光分布对于获取组织光学信息具有重要的意义. 相似文献
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以delta-P1近似光学模型为基础, 推导了双点源近似下空间分辨漫反射一阶散射参量μs'灵敏度的解析式, 并进行了数值分析和比较. 研究表明, 与混合漫射近似模型和漫射近似模型相比, delta-P1 近似模型能更好地描述强散射较强吸收情况下近光源区域生物组织漫反射光子的分布, 且在有效反照率a'>0.83时, 获得最佳优化距离ρopt, ρopt 随μs' 的增大而减小, 且在距光源约2.7—4个输运平均自由程处μs'的变化对测量吸收的影响最小. 这项研究对于优化传感器几何结构以及生物组织光学参量的测量具有重要意义. 相似文献
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光源附近的空间分辨漫反射与散射介质的高阶光学参量有关.为了研究高阶参量对漫反射的影响,定义了二阶参量灵敏度和三阶参量灵敏度,它们表示了由于高阶参量变化导致漫反射变化的相对量.从P3近似理论出发,推导了二阶参量灵敏度和三阶参量灵敏度的解析表示,并进行了数值分析和比较.研究表明,在大于一个输运平均自由程的非漫射近似区域,反射率随二阶光学参量增加而增加,其灵敏度随着空间变化,并在小于两个输运平均自由程内出现极大值;相比之下,三阶光学参量对漫反射率的影响可以忽略.
关键词:
漫反射
3近似')" href="#">P3近似
灵敏度 相似文献
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光源附近组织的空间分辨漫反射是近年来生物医学光子学领域的一个研究热点,其目的是发展一种能够测定活体生物组织光学参量的新技术。漫射近似理论研究光源附近组织的空间分辨漫反射具有很大局限性。P3近似理论考虑了相函数的三阶矩,能较准确地描述光源附近组织的光辐射分布。研究了基于P3近似的空间分辨漫反射,从输运理论的PN方程组出发,导出了P3近似方程组和P3近似的格林函数解;阐述了漫射近似与P1近似的关系,给出了外推边界条件下,准直光束近似后的P3近似漫反射率的完整表示,讨论了相函数二阶参量对P3近似漫反射的影响,并与漫射近似和蒙特卡罗模拟结果进行了比较,指出了P3近似的应用范围。 相似文献
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平稳状态下匹配介质三层漫射方程的空间分辨漫反射 总被引:5,自引:1,他引:5
如果应用漫射方程分析和确定生物表面组织的光学特性,就能够确定生物活体是否发生病变,实现生物活体的无损探测。目前,光在生物体内传播常用的基本模型是半无限厚模型和两层介质模型。而实际上,人体组织为多层介质。根据漫射方程理论,在平稳状态条件下,使用外推边界条件,精确给出了匹配介质中平稳状态下三层体系光的漫射方程格林函数的解。通过此解,可以算出空间分辨漫反射。使用蒙特卡罗方法来验证三层体系的漫射方程,发现我们给出的理论解,不仅可以包括与Kienle的结论一致的两层体系模型的空间分辨漫反射的解,而且三层体系漫射方程的空间分辨漫反射解和蒙特卡罗方法基本一致。 相似文献
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M. M. Korol’ A. S. Slesar’ M. V. Parkhots A. Ya. Khairullina T. V. Ol’shanskaya 《Journal of Applied Spectroscopy》2009,76(2):260-267
We present a fiber-optic device for noninvasive determination of the optical properties of biological tissues and photosensitizer
concentration. The device developed can be used in two modes: the mode for detection of the spatial distribution of diffuse
reflectance, and the fluorescence mode. We tested the device in vitro on specimens simulating tissue and on whole blood, and
also in vivo on rats. We have shown that with additional modification and adaptation, the device can be used for in vivo monitoring
of parameters important for photodynamic therapy. 相似文献
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Mahesh Ravishankar Maathangi Sankar 《Journal of Quantitative Spectroscopy & Radiative Transfer》2010,111(14):2052-7001
The first-order spherical harmonics method (or P1 approximation) has found prolific usage for approximate solution of the radiative transfer equation (RTE) in participating media. However, the accuracy of the P1 approximation deteriorates as the optical thickness of the medium is decreased. The modified differential approximation (MDA) was originally proposed to remove the shortcomings of the P1 approximation in optically thin situations. This article presents algorithms to apply the MDA to arbitrary geometry—in particular, geometry with obstructions, and inhomogeneous media. The wall-emitted component of the intensity was computed using a combined view-factor and ray-tracing approach. The Helmholtz equation, arising out of the medium-emitted component, was solved using an unstructured finite-volume procedure. The general procedure was validated for both two-dimensional (2D) and three-dimensional (3D) geometries against benchmark Monte Carlo results. The accuracy of MDA was found to be superior to the P1 approximation for all optical thicknesses. Its accuracy, when compared with the discrete ordinates method (both S6 and S8), was found to be clearly superior in optically thin situations, but problem dependent in optically intermediate and thick situations. For 3D geometries, calculation and storage of the view-factor matrix was found to be a major shortcoming of the MDA. In addition, for inhomogeneous media, calculation of optical distances requires a ray-tracing procedure, which was found to be a bottleneck from a computational efficiency standpoint. Several strategies to reduce both memory and computational time are discussed and demonstrated. 相似文献
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ABSTRACTIn this study, the evaluation of the salt content of canned sardines in brine using near-infrared (NIR) spectroscopy with a Fourier transform NIR spectrometer in diffuse reflectance mode over a range of 12,500–4000?cm?1 was investigated. The reference salt content of the samples was measured using an autotitrator. The optimum partial least squares regression model was developed using vector normalization spectra in the ranges of 9403.8–5446.3?cm?1 and 4605.4–4242.9?cm?1 with seven factors. The model provided a coefficient of determination for a prediction of 0.82, a root mean square error of prediction of 0.069%, a bias of ?0.019%, and a ratio of prediction deviation of 2.5. NIR spectroscopy has great potential as an alternative method for measuring the salt content of canned sardines in brine, and the calibration model is useful for the off-line quality control of canned sardines in brine processing. In addition, the oxygen–hydrogen bond stretch and deformation and the carbon–hydrogen bond stretch and deformation had obvious effects on the prediction of the salt content of canned sardines in brine. 相似文献
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To realize spectral diffuse reflectance scale in 0/d geometric condition at National Institute of Metrology in China (NIM), a facility based on a non-standard auxiliary integrating sphere method with special structure has been built up and a correction method for the influence on the thickness of PTFE (polytetrafluoroethylene) coating at the port of auxiliary integrating sphere is mainly discussed. The uncertainty of spectral diffuse reflectance in NIM is approximately 0.25% (k = 2) in 380–800 nm. This facility has been used to establish China diffuse reflectance scales in the VIS–NIR part of the spectrum. This system and correction method presented in this paper can be easily implemented on most commercial spectrophotometers with a lower cost. 相似文献
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近红外漫反射光谱法检测小麦粉过氧化苯甲酰 总被引:2,自引:0,他引:2
国家已禁止向小麦粉中添加过氧化苯甲酰(BPO),快速检测小麦粉中BPO添加量对于保障食品安全非常重要.BPO在添入小麦粉中后部分会被还原成为苯甲酸,使得对其原始添加量的检测非常繁琐.本文探讨了利用近红外漫反射光谱法进行小麦粉中BPO添加当量检测的可行性.通过向无添加剂小麦粉中添加不同量的过氧化苯甲酰粉末,制备小麦粉样本... 相似文献