Gas microchannel plate-pixel detector for X-ray polarimetry

POLAR-2 is a gamma-ray burst(GRB)polarimeter that is designed to study the polarization in GRB radiation emissions,aiming to improve our knowledge of related mechanisms.POLAR-2 is expected to utilize an on-board polarimeter that is sensitive to soft X-rays(2-10 keV),called low-energy polarization detector.We have developed a new soft X-ray polari-zation detector prototype based on gas microchannel plates(GMCPs)and pixel chips(Topmetal).The GMCPs have bulk resistance,which prevents charging-up effects and ensures gain stability during operation.The detector is composed of low outgassing materials and is gas-sealed using a laser welding technique,ensuring long-term stability.A modulation factor of 41.28%±0.64% is obtained for a 4.5 keV polarized X-ray beam.A residual modulation of 1.96%±0.58% at 5.9 keV is observed for the entire sensitive area.

天空可见-近红外光谱偏振态自动测量仪设计

太阳光在地球大气传输过程中产生的散射会呈现出固有的偏振特性,因此利用大气散射偏振态分布特性及其与太阳照射几何以及地表观测几何之间存在的对应关系,为地球大气层内导航提供了可能。然而因气象变化造成的大气组分改变会直接影响光散射分布,从而影响基于偏振态分布的方向定位精度,因此在偏振导航实际应用过程中,其方向指引精度受大气状况影响较大。为研究不同气象条件下天空偏振态变化内在机理,研制了一台天空可见-近红外光谱偏振态自动测量仪。该仪器可按需进行定时段、定天区、多天候天空光谱偏振态测量,采用分时偏振同时分谱非成像测量体制。仪器主要由偏振分析模块、偏振检测方位定位驱动电机、微型光谱仪、GPS定位模块、嵌入式采集控制模块、二维载重转台等部分组成,光谱范围为390~960nm,光谱分辨率为1.5nm,观测视场为3°,光谱线偏振度测量精度优于98.85%,偏振角测量精度优于0.1°,单点观测时间小于9s。经实验室定标和外场测试,表明该仪器可在多种气象条件下稳定观测天空光谱偏振态,其测量数据可用于天空偏振态影响机理相关研究。

Current Status and Future Challenges of Weather Radar Polarimetry: Bridging the Gap between Radar Meteorology/Hydrology/Engineering and Numerical Weather Prediction

After decades of research and development, the WSR-88 D(NEXRAD) network in the United States was upgraded with dual-polarization capability, providing polarimetric radar data(PRD) that have the potential to improve weather observations,quantification, forecasting, and warnings. The weather radar networks in China and other countries are also being upgraded with dual-polarization capability. Now, with radar polarimetry technology having matured, and PRD available both nationally and globally, it is important to understand the current status and future challenges and opportunities. The potential impact of PRD has been limited by their oftentimes subjective and empirical use. More importantly, the community has not begun to regularly derive from PRD the state parameters, such as water mixing ratios and number concentrations, used in numerical weather prediction(NWP) models.In this review, we summarize the current status of weather radar polarimetry, discuss the issues and limitations of PRD usage, and explore potential approaches to more efficiently use PRD for quantitative precipitation estimation and forecasting based on statistical retrieval with physical constraints where prior information is used and observation error is included. This approach aligns the observation-based retrievals favored by the radar meteorology community with the model-based analysis of the NWP community. We also examine the challenges and opportunities of polarimetric phased array radar research and development for future weather observation.

Crosstalk-free achromatic full Stokes imaging polarimetry metasurface enabled by polarization-dependent phase optimization

Imaging polarimetry is one of the most widely used analytical technologies for object detection and analysis.To date,most metasurface-based polarimetry techniques are severely limited by narrow operating bandwidths and inevitable crosstalk,leading to detrimental effects on imaging quality and measurement accuracy.Here,we propose a crosstalkfree broadband achromatic full Stokes imaging polarimeter consisting of polarization-sensitive dielectric metalenses,implemented by the principle of polarization-dependent phase optimization.Compared with the single-polarization optimization method,the average crosstalk has been reduced over three times under incident light with arbitrary polarization ranging from 9μm to 12μm,which guarantees the measurement of the polarization state more precisely.The experimental results indicate that the designed polarization-sensitive metalenses can effectively eliminate the chromatic aberration with polarization selectivity and negligible crosstalk.The measured average relative errors are 7.08%,8.62%,7.15%,and 7.59%at 9.3,9.6,10.3,and 10.6μm,respectively.Simultaneously,the broadband full polarization imaging capability of the device is also verified.This work is expected to have potential applications in wavefront detection,remote sensing,light-field imaging,and so forth.

Polarimetry feature parameter deriving from Mueller matrix imaging and auto-diagnostic signicance to distinguish HSIL and CSCC

High-grade squamous intraepithelial lesion(HSIL)is regarded as a serious precancerous state of cervix,and it is easy to progress into cervical invasive carcinoma which highlights the importance of earlier diagnosis and treatment of cervical lesions.Pathologists examine the biopsied cervical epithelial tissue through a microscope.The pathological examination will take a long time and sometimes results in high inter-and intra-observer variability in outcomes.Polarization imaging techniques have broad application prospects for biomedical diagnosis such as breast,liver,colon,thyroid and so on.In our team,we have derived polarimetry feature parameters(PFPs)to characterize microstructural features in histological sections of breast tissues,and the accuracy for PFPs ranges from 0.82 to 0.91.Therefore,the aim of this paper is to distinguish automatically microstructural features between HSIL and cervical squamous cell carcinoma(CSCC)by means of polarization imaging techniques,and try to provide quantitative reference index for patho-logical diagnosis which can alleviate the workload of pathologists.Polarization images of the H&E stained histological slices were obtained by Mueller matrix microscope.The typical path-ological structure area was labeled by two experienced pathologists.Calculate the polarimetry basis parameter(PBP)statistics for this region.The PBP statistics(stat PBPs)are screened by mutual information(MI)method.The training method is based on a linear discriminant analysis(LDA)classier whichnds the most simplied linear combination from these stat PBPs and the accuracy remains constant to characterize the specic microstructural feature quantitatively in cervical squamous epithelium.We present results from 37 clinical patients with analysis regions of cervical squamous epithelium.The accuracy of PFP for recognizing HSIL and CSCC was 83.8%and 87.5%,respectively.This work demonstrates the ability of PFP to quantitatively charac-terize the cervical squamous epithelial lesions in the H&E pathological sections.Signicance:Polarization detection technology provides an effcient method for digital pathological diagnosis and points out a new way for automatic screening of pathological sections.

Assessment of C-band compact polarimetry SAR for sea ice classification

The C-band synthetic aperture radar（SAR） data from the Bohai Sea of China, the Labrador Sea in the Arctic and the Weddell Sea in the Antarctic are used to analyze and discuss the sea ice full polarimetric information reconstruction ability under compact polarimetric modes. The type of compact polarimetric mode which has the highest reconstructed accuracy is analyzed, along with the performance impact of the reconstructed pseudo quad-pol SAR data on the sea ice detection and sea ice classification. According to the assessment and analysis, it is recommended to adopt the CTLR mode for reconstructing the polarimetric parameters σ_（HH）~0,σ_（VV）~0, H and α,while for reconstructing the polarimetric parameters σ_（HV）~0, ρ_（H-V）, λ_1 and λ_2, it is recommended to use the π/4 mode.Moreover, it is recommended to use the π/4 mode in studying the action effects between the electromagnetic waves and sea ice, but it is recommended to use the CTLR mode for studying the sea ice classification.

The Study of Retinal Nerve Fiber Layer Thickness of Normal Eyes Using Scanning Laser Polarimetry

Purpoe: To evaluate retinal nerve fiber layer (RNFL) thickness measurements in local normal Chinese subjects of different age groups and analyse the correlation of RNFL thickness with age using scanning laser polarimetry (SLP,GDxVCC). To assess the reproducibility of RNFL thickness measurement with GDxVCC. Methods: The RNFL thickness of 67 normal subjects (123 eyes) were measured by GDxVCC. The average TSNIT parameters were calculated. The differences of RNFL thickness between sex,right and left eyes,superior and inferior were compared. The relationship between RNFL thickness and age was analyzed with correlation analysis and linear regression analysis. The intraclass correlation coefficients (ICC) of three images in every eye were calculated. Results: The average peripapillary RNFL thickness at the superior,inferior and whole ellipse regions in 123 eyes of 67 normal subjects were (70.30±6.76)(?)m,(67.35±6.77)(?)m and (56.87±4.53)(?) m,respectively. The average TNSIT standard deviation was 23.68±4.61 and the average inter-eye symmetric value was 0.86±0.11. There were significant difference of RNFL thickness between superior and inferior (t=4.952,P < 0.001). There were significant difference of inferior RNFL thickness and TNSIT standard deviation between right and left eyes (P=0.005 and 0.002),while not significant difference of superior RNFL thickness and whole mean RNFL thickness between right and left eye (P=0.086 and 0.529). There was no significant difference in TSNIT parameters between different genders. There was a slight negative correlation average RNFL thickness in superior sector with age (decreased approximately 0.15 microns per year,P=0.047) in the subjects aged below 60 years old. The ICC values of RNFL thickness were >0.8 in superior,inferior and global. Conclusions: The RNFL thickness can be measured accurately by GDxVCC and the reproducibility of RNFL thickness measurement by GDxVCC is good. There was a slight negative correlation between average RNFL thickness in superior with age. More researches on the effects of age on RNFL thickness by GDxVCC are needed.

Multi-polarization reconstruction from compact polarimetry based on modified four-component scattering decomposition

An improved algorithm for multi-polarization reconstruction from compact polarimetry （CP） is proposed. According to two fundamental assumptions in compact polarimetric reconstruction, two improvements are proposed. Firstly, the four-component model-based decomposition algorithm is modified with a new volume scattering model. The decomposed helix scattering component is then used to deal with the non-reflection symmetry condition in compact polarimetric measurements. Using the decomposed power and considering the scattering mechanism of each component, an average relationship between copolarized and crosspolarized channels is developed over the original polarization state extrapolation model. E-SAR polarimetric data acquired over the Oberpfaffenhofen area and JPL/AIRSAR polarimetric data acquired over San Francisco are used for verification, and good reconstruction results are obtained, demonstrating the effectiveness of the proposed algorithm.

基于全偏振成像和机器学习的肝细胞癌与肝内胆管癌鉴别诊断研究

目的探讨全偏振成像和机器学习在肝细胞癌与肝内胆管癌鉴别诊断中的作用。方法利用全偏振显微镜对术后经病理确诊为低分化肝细胞癌和低分化肝内胆管癌病例各8例进行偏振成像;病理医生根据HE切片选取3块感兴趣区域,测量每块区域的穆勒矩阵,并根据穆勒矩阵参数提取分析方法计算出一系列的偏振基准参数;将偏振特征参数输入到人工神经网络模型中,采用了8折交叉验证方法对模型进行三分类的训练和验证。结果模型结果显示,基于图像偏振特征区分肝细胞癌、肝内胆管癌与除了癌变细胞以外的其他组织的准确率为0.8463,灵敏度为0.8107。结论基于全偏振成像和机器学习构建的肝细胞癌和肝内胆管癌诊断模型具有重要的病理辅助诊断价值。

2.16 m望远镜偏振光度计

为了使2.16 m望远镜具备线偏振测光观测能力,开展了偏振光度计研制。该系统采用双通道分时偏振成像方案,具有偏振定标单元、偏振测量单元,可实现偏振定标、偏振测量和多色测光。完成系统研制后,将其安装在2.16 m望远镜上开展实测,依照该偏振光度计偏振观测流程拍摄了一系列非偏振标准星、偏振标准星、流量标准星;按照偏振定标和偏振态解算数据处理方法,对获取图像进行数据处理。结果显示:该偏振光度计视场为4.63′×4.63′,像元比例尺为0.54(″)/pixel,偏振度测量精度优于0.01,60 s曝光时间可以拍摄到V波段信噪比约为141的15.3等星。该偏振光度计使2.16 m望远镜具备V波段线偏振测光和快速多色测光观测能力。

一种基于频域解模糊的星载P波段全极化SAR法拉第旋转效应校正方法

星载P波段合成孔径雷达(Synthetic Aperture Radar,SAR)极化测量性能易受电离层法拉第旋转(Faraday Rotation,FR)效应的影响,随着系统带宽增加,以及中心频率对应的法拉第旋转角(FR Angle,FRA)增大,FR效应色散特征突显,将导致距离向成像恶化以及额外的极化测量误差.针对色散FR效应,提出了一种基于频域解模糊的星载P波段全极化SAR法拉第旋转效应校正方法,通过模糊度一致化以及频域拟合等关键步骤,解决了P波段SAR系统FRA估计值模糊问题,最后在频域实现色散FR效应的校正.利用机载P波段全极化SAR数据开展了仿真验证实验,与传统的图像域校正方法相比,有效抑制了色散的FR效应,显著改善了交叉极化通道图像之间的相关性.

Identification of serous ovarian tumors based on polarization imaging and correlation analysis with clinicopathological features

Ovarian cancer is one of the most aggressive and heterogeneous female tumors in the world,and serous ovarian cancer(SOC)is of particular concern for being the leading cause of ovarian cancer death.Due to its clinical and biological complexities,ovarian cancer is still considered one of the most di±cult tumors to diagnose and manage.In this study,three datasets were assembled,including 30 cases of serous cystadenoma(SCA),30 cases of serous borderline tumor(SBT),and 45 cases of serous adenocarcinoma(SAC).Mueller matrix microscopy is used to obtain the polarimetry basis parameters(PBPs)of each case,combined with a machine learning(ML)model to derive the polarimetry feature parameters(PFPs)for distinguishing serous ovarian tumor(SOT).The correlation between the mean values of PBPs and the clinicopathological features of serous ovarian cancer was analyzed.The accuracies of PFPs obtained from three types of SOT for identifying dichotomous groups(SCA versus SAC,SCA versus SBT,and SBT versus SAC)were 0.91,0.92,and 0.8,respectively.The accuracy of PFP for identifying triadic groups(SCA versus SBT versus SAC)was 0.75.Correlation analysis between PBPs and the clinicopathological features of SOC was performed.There were correlations between some PBPs(δ,β,q_(L),E_(2),rqcross,P_(2),P_(3),P_(4),and P_(5))and clinicopathological features,including the International Federation of Gynecology and Obstetrics(FIGO)stage,pathological grading,preoperative ascites,malignant ascites,and peritoneal implantation.The research showed that PFPs extracted from polarization images have potential applications in quantitatively differentiating the SOTs.These polarimetry basis parameters related to the clinicopathological features of SOC can be used as prognostic factors.

Establishment and study of a polarized X-ray radiation facility

With the advancement in X-ray astronomical detection technology,various celestial polarization detection projects have been initiated.To meet the calibration requirements of polarimeters on the ground,a polarized X-ray radiation facility was designed for this study.The design was based on the principle that X-rays incident at 45°on a crystal produce polarized X-rays,and a second crystal was used to measure the polarization of the X-rays produced by the facility after rotation.The effects of different diaphragm sizes on the degree of polarization were compared,and the facility produced X-rays with polarization degrees of up to 99.55±0.96%using LiF200 and LiF220 crystals.This result revealed that the polarization of incident X-rays is one of the factors affecting the diffraction efficiency of crystals.The replacement of different crystals can satisfy the calibration requirements of polarized X-ray detectors with more energy points in the energy range(4-10)keV.In the future,the facility should be placed in a vacuum environment to meet the calibration requirements at lower energies.

Depolarizing metrics in the biomedical field:Vision enhancement and classification of biological tissues

Polarimetry encompasses a collection of optical techniques broadly used in a variety of fields.Nowadays,such techniques have provided their suitability in the biomedical field through the study of the polarimetric response of biological samples(retardance,dichroism and depolarization)by measuring certain polarimetric observables.One of these features,depolarization,is mainly produced by scattering on samples,which is a predominant efiect in turbid media as biological tissues.In turn,retardance and dichroic efiects are produced by tissue anisotropies and can lead to depolarization too.Since depolarization is a predominant efiect in tissue samples,we focus on studying difierent depolarization metrics for biomedical applications.We report the suitability of a set of depolarizing observables,the indices of polarimetric purity(IPPs),for biological tissue inspection.We review some results where we demonstrate that IPPs lead to better performance than the depolarization index,which is a well-established and commonly used depolarization observable in the literature.We also provide how IPPs are able to significantly enhance contrast between difierent tissue structures and even to reveal structures hidden by using standard intensity images.Finally,we also explore the classificatory potential of IPPs and other depolarizing observables for the discrimination of difierent tissues obtained from ex vivo chicken samples(muscle,tendon,myotendinous junction and bone),reaching accurate models for tissue classification.

太阳偏振图像高分辨重建误差仿真分析

地基太阳望远镜磁像仪在进行偏振测量时会受到大气湍流的影响,导致测量结果不准确。通过同步探测波前像差,对太阳窄带偏振图像退卷积重建的方法可以克服窄带滤光器带来的偏振测量通道光子数水平较低等问题,将高分辨图像重建算法应用到太阳偏振图像的重建中。在重建过程中,波前估计不准确会导致重建的偏振图像受到I的串扰,与真实的偏振信号之间存在一定偏差。为了研究同步重建过程中波前复原精度对偏振图像重建精度的影响,通过建立仿真模型,对不同视宁度和不同波前复原精度下I对偏振信号的串扰进行了仿真。结果表明,偏振图像的重建质量与波前复原精度正相关,在一定的条件下,增加用于图像重建的帧数和降低图像分辨率等方法也可以降低I对偏振信号的串扰。

旋光性透明液体浓度测量研究

旋光法作为一种简单并且快速的测量具有旋光性的透明液体浓度的方法,其仪器简单,操作方便,计算准确且实验成本较低,是一种理想的测量方法。以具有旋光性的葡萄糖溶液为例,设计了低成本不透光管来规避环境光对测量结果的影响,并针对葡萄糖溶液的特性及不同种类葡萄糖溶液的旋光率不同等问题进行研究,最终实现了葡萄糖溶液浓度的测量。此外,本文还提出了一种测量具有旋光性的透明液体浓度的通用方法。

Solution for polarimetric radar cross section measurement and calibration

The exact radar cross-section （RCS） measurement is difficult when the scattering of targets is low. Ful polarimetric cali-bration is one technique that offers the potential for improving the accuracy of RCS measurements. There are numerous polarimetric calibration algorithms. Some complex expressions in these algo-rithms cannot be easily used in an engineering practice. A radar polarimetric coefficients matrix （RPCM） with a simpler expression is presented for the monostatic radar polarization scattering matrix （PSM） measurement. Using a rhombic dihedral corner reflector and a metal ic sphere, the RPCM can be obtained by solving a set of equations, which can be used to find the true PSM for any target. An example for the PSM of a metal ic dish shows that the proposed method obviously improves the accuracy of cross-polarized RCS measurements.

有源转发式干扰的全极化单脉冲雷达抑制方法研究

有源转发式干扰成为防空反导、反舰攻击等典型作战场景下非常重要的一种干扰样式,对现代雷达形成了严重威胁。该文针对有源转发式干扰对雷达形成的距离欺骗性假目标干扰和角度欺骗性干扰两种典型情况,研究了全极化单脉冲雷达识别转发式干扰并加以抑制的方法,理论推导和仿真实验结果表明利用极化信息可以识别并抑制此类干扰,这对新一代极化雷达适应复杂电磁环境问题的研究具有深刻的理论指导和借鉴意义。

葡萄糖酸钠检测方法研究

介绍了4种常用的葡萄糖酸钠检测方法:HPLC法、分光光度法、非水滴定法和旋光法。其中HPLC法和非水滴定法简便且具有较好的实用性,可用于检测工业生产的葡萄糖酸钠。

大孔径静态超光谱全偏振成像技术

光谱偏振成像技术是成像光谱技术与偏振成像技术的有机融合,是当前空间光学遥感技术研究的热点和前沿。笔者于2010年在国际上首先提出了一种多信息融合的静态傅里叶变换超光谱全偏振成像方法,无运动、电控调制部件,在探测器单次积分时间内,可同时获取目标图像及图像上每一点的光谱、全偏振信息。同年,又提出时空混合调制模式的无源静态共轴干涉成像光谱全偏振探测装置,以视场光阑取代原有狭缝,进一步扩展了仪器光通量。在上述基础上,阐述了新方法的基本原理,给出了具体实现方案,推导出了新方案的调制干涉强度数据表达式及Stokes矢量解调公式,分析了新方法实现光谱、全偏振探测的物理过程。研制了原理验证样机,开展了室内、室外验证实验,首次获得了室外推扫光谱图像"数据立方体"和全色全偏振度图像,实验结果表明:新方案原理正确,技术可行。为新型空间遥感器的开发提供了基础理论及实践支持。