近红外光谱范围生物组织表面漫反射率的研究

首先分析了近红外光在均匀生物组织中的传播过程,在此基础上提出一种计算分层生物组织表面漫反射率的理论模型。利用这种理论模型,讨论了两种不同组成的生物组织的表面漫反射率,得到双层介质表面漫反射率随探测距离的变化趋势与其他文献报道的研究结果一致。     

利用深度探测函数研究双层介质的空间分辨漫反射率

提出了一种研究双层介质空间分辨漫反射率的理论模型。考虑到不同深度分布的光子对探测信号的贡献不同,引入深度探测函数a(z,p),用其描述探测光子与散射介质空间面的相互作用,进而提出了一种研究双层散射介质空间分辨漫反射率的理论方法。给出了双层散射介质的空间分辨漫反射率的理论分析结果,并与Monte Carlo模拟结果进行比较,结果表明两者符合得较好。     

205光学介质表面的光散射模型探索

２０５光学介质表面的光散射模型探索田来科（西北大学物理系，７１００６９）藤霖（西北工业大学十系，７１００６８）刘芳，高昕（西北大学物理系，７１００６９）瑞利散射定律给出了光在介质内的散射规律，反射和朗伯漫反射定律则分别反映了光在理想光滑表面和理想漫反...     

双层组织模型中漫反射光与内层光学参数关系

研究了双层组织光学参数变化对组织表面漫反射情况的影响规律.采用一个简化的生物组织双层模型,利用Monte Carlo方法和实验进行了研究.结果表明表面漫反射光随内层吸收系数增加而减小,随内层散射系数增加而增强,特别是内层吸收系数或散射系数为小值时,表面漫反射光对内层吸收系数或散射系数的变化非常敏感.     

四层匹配介质漫射方程的稳态研究

文中根据光在生物体内传播的漫射方程理论,以人体组织为多层介质,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四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四层体系的漫射方程,发现,我们给出的理论解不仅可以包括两层体系模型的空间分辨漫反射的解,与A. Kienle的两层体系的结论一致,而且在四层体系中,四层体系漫射方程的空间分辨漫反射的解和蒙特卡罗方法的基本一致。通过估计吸收系数和等效各项同性散射系数,这个模型在医疗和诊断上具有潜在的应用价值。     

高散射介质参数对超短脉冲激光传输的定量影响

近年来，研究无辐射损伤的生物组织光学成像方法和技术引起了国内外的重视．生物组织是由不同大小、不同成分的细胞组成的高散射介质，光在这种介质中传输时将产生散射和吸收．超短脉冲激光在离散射介质中传输时，将因漫散射使脉冲展宽，这是脉冲光与散射吸收体相互作用的统计反映，因此漫反射、漫透射光中也必然含有介质光学特性的信息．通过研究散射光的时间行为，将可能间接获得介质内部非均匀性的空间位置信息，从而对介质中的散射吸收体（如生物组织中的肿瘤等）成像．红光与辽红外光人射到高散射介质后，在其内部主要以漫散射光的形式…     

生物组织光学特性参量的图像测量研究

为了测量生物组织的光学特性参量,采用CCD漫反射法和透射法,通过分析CCD摄取的待测样品表面的漫反射光分布图像,利用漫射近似理论,实现了漫反射法对生物组织模拟液(intralipid-20%稀释液)、牛肌肉、猪肌肉和鸡胸肉光学特性参量的测量,获得了样品的吸收系数和有效散射系数;测量了不同浓度生物组织模拟液的透射光强度,根据Beer-Lambert定律,实现了透射法对光学特性参量的测量,获得了样品的散射系数,进而得到了有效散射系数;并将漫反射法和透射法对同种样品光学特性参量的测量结果以及他人的测量结果进行了比较。结果表明,漫反射法和透射法的测量结果有很好的吻合性,测量生物组织光学特性参量采用的CCD测量装置和处理方法具有较高的精度。     

组织的特征长度微距空间分辨漫反射

从辐射传输理论的相似天系出发,根据P1近似和P3近似满足的一阶和三阶相似关系,引入了特征长度的参量。利用半无限介质的空间分辨漫反射的P3的近似解,对光源附近组织的空间分辨漫反射与特征长度之间的关系进行了研究。研究表明．当需要在光源附近对组织进行测量时,最近的距离与描述该组织的特征长度有天,根据组织的特征长度可以确定探测器的大致宽度,并结合实际光纤直径估计测量光纤的数目。     

由漫射图像测量生物组织的光学特性

为了获取生物组织的光学特性参量,采用CCD无损测量系统来获得生物组织的漫反射图像,通过数据分析获取组织表面的漫射光分布,首先对具有不同光学特性参最的组织模拟液进行测量,用实验所得数据训练神经网络,并用另一组实验数据对神经网络的有效性和精确度进行了验证,然后对牛肉、猪肉以及人体表皮组织在633nm光照下进行了测量,由经实...     

六种不同波长激光照射及光敏剂HpD对活体小鼠肿瘤表面漫反射率的影响

本文研究了激光波长及光敏剂对小鼠肿瘤表面的漫反射率的影响。实验采用一套积分球系统及三种激光器（Ａｒ＋激光器，Ｈｅ－Ｎｅ激光器，Ｎｄ：ＹＡＧ激光器）的六种波长的激光（４７６．５ｎｍ，４８８．０ｎｍ，４９６．５ｎｍ，５１４．５ｎｍ，６３２．８ｎｍ，１０６０ｎｍ），测定了注射光敏剂和没有注射光敏剂两组小鼠Ｓ１８０肉瘤表面的漫反射率，结果表明，注射光敏剂和没有注射光敏剂的小鼠肿瘤表面对六种激光的漫反射率无明显差异（Ｐ＞０．０５）；提示在激光光动力学疗法中，计算实际进入肿瘤组织的光剂量时，可以不考虑ＨｐＤ的影响。漫反射率随激光变化的曲线显示，在蓝光和红光范围内，肿瘤表面的漫反射率在５１４．５ｎｍ处有最小值，但总的来说，漫反射率的值变化不大；但在红外区的１０６０ｎｍ处，漫反射率值较大，提示在激光温热疗法中计算光剂量时，应考虑漫反射的影响。     

强散射随机介质中吸收物体的成像

以宽带连续光为光源对隐藏在强散射随机介质中的吸收物体成像进行了实验研究，用一种新的图像处理方法恢复了被散射光所淹没的吸收物体的像。由于人体组织为光的强散射介质，因此该研究在医学成像中有很大的潜在应用价值。     

On the surface photovoltaic effect in a multivalley semiconductor in an external magnetic field

A theory of the photovoltaic effect in a semi-infinite multvalley semiconductor upon the absorption of polarized light at free carriers caused by the specular reflection and diffuse scattering of electrons at a film surface is developed by us. The kinetic Boltzmann equation in the approximation of time relaxation and boundary conditions, which determine the correlation between the distribution function of electrons reflected from a semi-infinite crystal surface and the distribution function of electrons incident onto a surface for the case of both specular reflection and diffuse scattering is used. The aforementioned takes into account the fact that the distribution function of electrons diffusely scattered from a surface depends only on their energy and is determined from the condition of total electron flux vanishing at the surface. Expressions for analyzing the spectral dependence of the current which is linearly dependent on the magnetic-field strength are obtained.     

Quantifying spatial localization of optical mapping using Monte Carlo simulations

Optical mapping techniques used to study spatial distributions of cardiac activity can be divided into two categories. 1) Broad-field excitation method, in which hearts stained with voltage or calcium sensitive dyes are illuminated with broad-field excitation light and fluorescence is collected by image or photodiode arrays. 2) Laser scanning method, in which illumination uses a scanning laser and fluorescence is collected with a photomultiplier tube. The spatial localization of the fluorescence signal for these two methods is unknown and may depend upon light absorption and scattering at both excitation and emission wavelengths. We measured the absorption coefficients (micro a), scattering coefficients (micro s), and scattering anisotropy coefficients (g) at representative excitation and emission wavelengths in rabbit heart tissue stained with di-4-ANEPPS or co-stained with both Rh237 and Oregon Green 488 BAPTA 1. Monte Carlo models were then used to simulate absorption and scattering of excitation light and fluorescence emission light for both broad-field and laser methods in three-dimensional tissue. Contributions of local emissions throughout the tissue to fluorescence collected from the tissue surface were determined for both methods. Our results show that spatial localization depends on the light absorption and scattering in tissue and on the optical mapping method that is used. A tissue region larger than the laser beam or collecting area of the array element contributes to the optical recordings.     

Dynamics of temperature dependent optical properties of tissue:dependence on thermally induced alteration

Thermal damage in heated bovine myocardial tissue is assessed from measured changes in total reflection and transmission of light. Mathematical expressions, based on random walk analysis of light propagation within tissue slabs, are used to relate the diffuse reflection and transmittance to the absorption coefficient, μ_a , and effective scattering coefficient, μ'_s for samples of myocardial tissue which were subjected to rapid step changes in temperature. Time-dependent changes in μ'_s indicate two processes, one with a fast and temperature-dependent rate the other with a slow and apparently temperature-independent rate. For final temperatures above 56.8°C and for the first 500 s after the temperature change, the optical parameters are well fit by exponential forms that exhibit temperature-dependent time constants as predicted by Arrhenius reaction rate theory of thermal damage. The scattering changes are associated with an apparent activation energy, ΔE, of 162 kJ/mole and a frequency constant, A, of 3×10²³ s^-1 . This method provides a means for estimating optical coefficients which are needed to assess laser tissue dosimetry     

低角雷达跟踪时的多路径散射模型

要提高低角雷达跟踪目标的精度,就需要考虑由于地、海表面反射而产生的多径效应的影响.需要弄清产生多径效应的环境和条件,建立多径效应的数学模型,以便采取合理的方法进行抑制.本文给出了镜反射和漫散射引起的多径效应的代表性模型,以及考虑表面粗糙度、遮蔽效应等影响的修正粗糙面漫散射模型.     

介质吸收散射对半透明涂层表面双向反射特性的影响

对表面光滑、基底面漫射的吸收-散射性半透明涂层，通过建立入射光谱的辐射传递模型，采用蒙特卡罗法求解分析了涂层光学厚度、介质散射及基底面反射对涂层表面双向反射特性的影响．结果表明，即使在不考虑涂层表面Fresnel反射的条件下，吸收-散射性半透明涂层的反射也呈现明显的各向异性，其BRDF分布与吸收性半透明涂昙的BRDF特性有明显差别．     

Radar Scattering from a Diffuse Vegetation Layer over a Smooth Surface

A simple model is presented for the oblique backscatter and bistatic scatter from a smooth surface overlain by a diffuse layer. Only single scattering in the diffuse layer is taken into account. The model analysis shows that the combination of volume scattering and oblique reflection at the surface may increase appreciably the waves scattering. The scattering strongly depends on the properties of the smooth surface. These results support some of the observations made with the Seasat spaceborne imaging radar over flooded regions with heavy vegetation cover.     

LED照明光扩散膜紫外光固化的研究

光扩散膜的作用是将LED的点状光源均匀转换成面光源,达到匀光的效果。扩散膜其匀光原理系利用光在不同折射率的介质中穿过,使光线产生许多折射、反射、散射,获得光学扩散的效果。选用紫外光聚合物转印技术,建立小批量光扩散膜转移复制工艺。