Discrimination and quantification of scar tissue by Mueller matrix imaging with machine learning

Scarring is one of the biggest areas of unmet need in the long-term success of glaucoma filtration surgery.Quantitative evaluation of the scar tissue and the post-operative structure with micron scale resolution facilitates development of anti-fibrosis techniques.However,the distinguishment of conjunctiva,sclera and the scar tissue in the surgical area still relies on pathologists'experience.Since polarized light imaging is sensitive to anisotropic properties of the media,it is ideal for discrimination of scar in the subconjunctival and episcleral area by characterizing small differences between proportion,organization and the orientation of the fibers.In this paper,we defined the conjunctiva,sclera,and the scar tissue as three target tissues after glaucoma filtration surgery and obtained their polarization characteristics from the tissue sections by a Mueller matrix microscope.Discrimination score based on parameters derived from Mueller matrix and machine learning was calculated and tested as a diagnostic index.As a result,the discrimination score of three target tissues showed significant difference between each other(p<0.001).The visualization of the discrimination results showed significant contrast between target tissues.This study proved that Mueller matrix imaging is effective in ocular scar discrimination and paves the way for its application on other forms of ocular fibrosis as a substitute or supplementary for clinical practice.

Mueller matrix analysis for all optical fiber co-existence of birefringence-polarization dependent gain-mode coupling at a single wavelength

Birefringence （polarization-related phase-shift）, polarization dependent gain （PDG） and mode coupling are three factors that may synchronously influence the transmission of single-wavelength polarized light in optical fibers. This paper obtains a new Mueller matrix analysis, which can be used under conditions that all these three factors are existing and changing. According to our transmission model, the state of polarization （SOP） changes along an optical mierostructure fiber with co-existence of birefringence-PDG-mode coupling were simulated. The simulated results, which show the phenomena of SOP constringency, are in good agreement with previous theoretical analyses.

CHARACTERISTIC FEATURES OF MUELLER MATRIX PATTERNS FOR POLARIZATION SCATTERING MODEL OF BIOLOGICAL TISSUES

We developed a model to describe polarized photon scattering in biological tissues.In this model,tissues are simplified to a mixture of scatterers and surrounding mpdium.There are t wo types ofscatterers in the model:solid spheres and infinitely long solid cylinders.Variables related to thescatterers include:the densities and sizes of the spheres and cylinders,the orientation and angulardistribution of cylinders.Variables related to the surrounding medium include:the refractiveindex,absorption coeficient and birefringence.In this paper,as a development we introduce anoptical activity effct to the model.By comparing experiments and Monte Carlo simulations,we analyze the backscater ing Mueller matrix patterms of several tissue-like media,and summarizethe different effects coming from anisotropic scattering and optical properties.In addition,wepropose a possible method to extract the optical activity values for tissues.Both the experimentaland simulated results show that,by analyzing the Mueller matrix patterns,the microstructureand optical properties of the medium can be obtained.The characteristic features of Muellermatrix patterns are potentilly powerful tools for studying the contrast mechanisms of polari-zation imaging for medical diagnosis.

QUANTITATIVE MUELLER MATRIX POLARIMETRY TECHNIQUES FOR BIOLOGICAL TISSUES

We propose and conduct both the rotating linear polarization imaging(RLPI)and Mueller matrix transformation(MMT)measurements of different biological tissue samples,and testify the capability of the Mueller matrix polarimetry for the anisotropic scattering media.The independent parameters extracted from the RLPI and MMT techniques are compared and analyzed.The tissue experimental results show that the parameters are closely related to the structural characteristics of the turbid scattering media,including the sizes of the scatterers,the angular distribution and order of alignment of thefibers.The results and conclusions in this paper may provide a potential method for the detection of precancerous and early stage cancerous tissues.Also,such studies represent the Mueller matrix transformation procedure which results in a set of parameters linking up the Mueller matrix elements to the structural and optical properties of the media.

Description of the Mueller Matrix for Multiple Scatteringat 90°

Mueller matrix elements are presented represen ting scatter to 90° from an incident polarized laser beam. The cases considered include five particle sizes (such as l.24 μm, 0.494 μm, 0.36 μm, 0.123 μm, and 0.065 μm), two concentr ations (such as 0.002 5% and 0.005% by volume), and three detector depths (such as 0, l.5 cm, and 3 cm into the scat tering volume). If the magnitudes of the elements can be rounded off to the near est 0.01, a particle size dependence is described by the resulting average mat rices, which is only two matrices for d >0.22 μm and d <0.22 μm which are nonsingular and asymmetric, respectively.

Advanced Mueller matrix ellipsometry:Instrumentation and emerging applications

Mueller matrix ellipsometry(MME)provides the 4×4 Mueller matrix of a sample under test,which determines how the state of polarization is changed as light interacts with the sample.Due to the redundant information contained in the Mueller matrix,MME has gained more and more extensive applications in the characterization of surfaces,interfaces,thin films,and nanostructures.In addition,the instrumentation of MME has also achieved great developments since its advent in the 1970 s.In this paper,we will first review the basic principle as well as the common system layouts of MME for the full Mueller matrix measurement.Then,the basic procedure of ellipsometry data analysis is reviewed.After that,some new developments in MME in our lab for different applications are introduced,including the broadband MME,the high-resolution imaging MME,and the high-speed MME.Some emerging applications of the developed MMEs are also presented.Conclusions and perspectives of the advanced ellipsometry are finally drawn and discussed.

Depolarization index from Mueller matrix descatters imaging in turbid water

Polarization underwater imaging is of great potential to target detection in turbid water. Typical methods are challenged by the requirement on degrees of polarization(Do Ps) of both target light and backscattering. A polarization descattering imaging method was developed using the Mueller matrix, which in turn derived a depolarization(Dep) index from the Mueller matrix to characterize scattering media by estimating the transmittance map by combining a developed optimal function.By quantifying light attenuation with the transmittance map, a clear vision of targets can be recovered. Only using the information of scattering media, the underwater vision under diverse water turbidity was enhanced by the results of experimental data.

Characterization of irradiated nails in terms of depolarizing Mueller matrix decompositions

Mueller matrices were measured for natural （or reference） samples of human nails and samples irradiated by a 2 Gy ionizing radiation dose. The elements of the total Mueller matrix as a function of scattering angle were measured in backscattering mode at a wavelength of 632.8 nm. Several types of depolarizing Mueller matrix decompositions, namely, Ossikovsky, Williams, and Chipman, were calculated as a function of scattering angle for each nail sample. A comparative analysis of the sensitivity of the Mueller matrix decompositions in relation to the problem of emergency dose assessment in nails was performed.

Dynamic modulation performance of ferroelectric liquid crystal polarization rotators and Mueller matrix polarimeter optimization

A ferroelectric liquid crystal polarization rotator(FLCPR)has been widely used in polarization measurement due to its fast and stable modulation characteristics.The accurate characterization of the modulation performance of FLCPR directly affects the measurement accuracy of the instrument based on liquid crystal modulation.In this study,FLCPR is accurately characterized using a self-developed high-speed Stokes polarimeter.Strong linear and weak circular birefringence are observed during modulation processes,and all the optical parameters of FLCPR are dependent on driving voltage.A dual FLCPR-based Mueller matrix polarimeter is designed on the basis of the Stokes polarimeter.The designed polarimeter combines the advantages of the high modulation frequency of FLCPR and the ultrahigh temporal resolution of the fast polarization measurement system in the Stokes polarimeter.The optimal configuration of the designed polarizer is predicted in accordance with singular value decomposition.A simulated thickness measurement of a 24 nm standard SiO2 thin film is performed using the optimal configuration.Results show that the relative error in thickness measurement caused by using the unsatisfactory modulation characteristics of FLCPR reaches up to−4.34%.This finding demonstrates the importance of the accurate characterization of FLCPR in developing a Mueller matrix polarizer.

基于Mueller矩阵的水下偏振成像方法

水下偏振成像技术利用目标信息光与背景散射光的偏振特性差异实现清晰成像,在水下目标探测和识别等领域有重要价值。但多材质目标表面反射情况和退偏效应存在差异,无法有效提取上述偏振特性差异。针对这一问题,文中提出一种基于Mueller矩阵的水下偏振成像方法。利用Mueller矩阵探测水下场景中的光强信息以及目标物与水体的偏振信息,精确求解浑浊场景中目标物与背景散射光的偏振度信息,结合传统水下成像技术构建基于Mueller矩阵的水下偏振成像方法,有效分离目标信息光与背景散射光,提升成像质量,实现水下多材质目标物的清晰重建。

红外偏振辐射模型对铬和铜元素的优化识别

针对优化激光诱导击穿光谱技术识别铬和铜元素的问题,本文提出了一种结合红外偏振检测理论的方法。利用菲涅尔反射定律和基尔霍夫理论分析了红外偏振产生机理,根据能量守恒定律验证了目标红外自发热辐射的偏振特性;利用红外偏振辐射传输模型及菲涅尔反射穆勒矩阵,结合温度的麦克斯韦-玻尔兹曼分布特性,推导出了等离子体红外偏振辐射信号模型,用于识别各激发能量下的重金属元素;利用5种不同能量的脉冲激光验证了模型的精准性。结果表明:在相同的激光能量下,红外偏振辐射光谱可以收集到更多的特征信号峰;在低能量激励下,红外偏振辐射光谱的优势更为突出。红外偏振辐射模型的构建是科学有效的,可用于优化重金属元素的快速检测。

基于频率调制与分振幅解调的广义光谱椭偏技术

提出了一种基于频率调制与分振幅解调的广义光谱椭仪方案,与现有时间调制型与时频混合调制型广义光谱椭偏技术相比,其不含运动部件与电控元件,可实现被测样品全部16个Mueller矩阵元素光谱的实时测量。与现有频率调制型广义光谱椭偏技术相比,其测量结果的光谱分辨率更高且降低了通道串扰产生的概率。

基于Mueller矩阵成像椭偏仪的纳米结构几何参数大面积测量

为了实现有效的工艺监控,在批量化纳米制造中对纳米结构的关键尺寸等几何参数进行快速、低成本、非破坏性的精确测量具有十分重要的意义.光学散射仪目前已经发展成为批量化纳米制造中纳米结构几何参数在线测量的一种重要手段.传统光学散射测量技术只能获得光斑照射区内待测参数的平均值,而对小于光斑照射区内样品的微小变化难以准确分析.此外,由于其只能进行单点测试,必须要移动样品台进行扫描才能获得大面积区域内待测参数的分布信息,从而严重影响测试效率.为此,本文将传统光学散射测量技术与显微成像技术相结合,提出利用Mueller矩阵成像椭偏仪实现纳米结构几何参数的大面积快速准确测量.Mueller矩阵成像椭偏仪具有传统Mueller矩阵椭偏仪测量信息全、光谱灵敏度高的优势,同时又有显微成像技术高空间分辨率的优点,有望为批量化纳米制造中纳米结构几何参数提供一种大面积、快速、低成本、非破坏性的精确测量新途径.

混浊介质后向散射特性的Mueller矩阵实验测量

Mueller矩阵是一种公认的能很好地表述介质偏振特性的方法。由于散射光偏振在生物组织无创伤诊断技术等诸多领域中的重要应用价值,对组织散射特性的Mueller矩阵的研究成为国际上组织光学的热点之一。与现有测量Mueller矩阵的实验方法相比,斜入射正接收装置用来测量Mueller矩阵是一个更加行之有效的方法,再结合一种新的算法来处理后续数据,由此所获得的Mueller矩阵空间分布图的清晰度不亚于其它文献的报道。这种测量方法结构更简单,具有测量更方便、准确等优点。结果表明:入射角影响Mueller矩阵的空间分布图。随着介质浓度的增大,随机介质后向散射Mueller矩阵各元素的空间分布图样减小。

高双折射保偏光纤拍长测试及Mueller矩阵分析

为了测量高双折射保偏光纤的拍长,采用偏光干涉效应的方法,构建由宽谱光源、带保偏尾纤的起偏器和光谱分析仪组成的全光纤光路测试系统。从理论上用Mueller传输矩阵方法推导了到达光谱仪的光强公式,利用该方法构建实验系统对熊猫型保偏光纤的拍长进行了测试,获得了该保偏光纤拍长的测量数据。结果表明,由待测保偏光纤的偏光干涉效应引起的光强波动以一定的周期间隔表现在光谱变化上,波动的相对幅度与待测保偏光纤主轴与起偏器的保偏尾纤主轴夹角有关,当夹角均为±45°时波动的相对幅度最大。只要在实验中测量出光谱波动的周期,就能够根据理论计算出给定波长处的保偏光纤的拍长。

铝板的偏振反射Mueller矩阵实验研究

物质材料例如涂层、金属、电介质等有其各自的偏振特性。Stokes参量或是Mueller矩阵表示了偏振量化信息与材料性质的关系。介绍了Mueller矩阵测量方法,使用He-Ne(λ=632.8 nm)激光器经起偏器产生的偏振光照射在铝样品上,并经偏振分析光学系统,获取样品Mueller矩阵元素测量图像数据.在给出延迟器校正结果的前提下,使用64个偏振测量图像,并采用最小二乘法减小误差,给出了铝板样品的偏振反射Mueller矩阵,比较分析了水平/垂直、45°/135°和左旋/右旋圆偏振分量随样品转角变化时的退偏特性曲线.结果表明,铝板的圆偏光与线偏光的退偏度显著,为使用圆偏振实现探测提供可能性.

用Fourier分解法测量材料表面的Mueller矩阵

测量系统采用双旋转延迟器结构,通过两个1/4波片的周期变化,对入射光、散射光的偏振态进行调制.由探测光强的25个Fourier分解系数可以计算得到样品的Mueller矩阵.为了检测测量系统的准确性,将测量的16个自由空间Mueller矩阵分量和理想情况下的自由空间Mueller矩阵分量进行比较,并给出了每个矩阵分量的标准误差.最后,通过测量聚四氟乙烯样品板的Mueller矩阵,定量地分析样品的退偏效应.

Lyot型光纤消偏器的Mueller矩阵分析

首次应用 Mueller矩阵推导出 L yot型光纤消偏器偏振度与消偏器各参数之间的关系 .指出消偏器输入输出端口之间的可逆性和互换性 .对上述关系作了全面的数值计算 。

用多阶Mueller矩阵解对非均匀地表植被生物量和土壤湿度的迭代反演

根据一层随机非球形粒子矢量辐射传输方程的一阶与高阶Mueller矩阵解的数值模拟及其差异 ,提出了在一些参数已知的条件下 ,用水平与垂直同极化和交叉极化的后向散射测量反演植被覆盖下地表湿度和植被散射元单位面积占空比的迭代方法。利用模拟测量数据以及机载合成孔径雷达 (AirSAR)实测数据 。

植物组织微观结构变化的Mueller矩阵成像监测

Mueller矩阵偏振成像能够全面表征被测样品物的偏振信息,从而成为获取被测样品内部微观结构信息的重要测试方法.利用双旋转波片原理搭建了后向散射Mueller矩阵偏振显微成像系统,并结合新的数据处理算法实现对各向异性植物组织的Mueller矩阵显微成像.针对植物样品的Mueller矩阵的二维分布图像及极化参数图进行分析,并在不同时间进程下通过观察各极化参数图对植物样品的变化进行监测.实验结果表明:相较于普通强度成像,Mueller偏振参数成像可以更加灵敏地反映被测样品的微观结构变化.