空间调制型全偏振成像系统关键误差分析与性能优化研究

发布时间：2019-01-28 19:05

【摘要】：偏振成像系统不仅能够获取目标的二维光强度分布信息,还能够获取与目标光强度分布相对应的偏振信息——即Stokes矢量信息。Stokes矢量信息具有增强目标对比度的能力,可以将目标从复杂的背景信息中凸显出来。传统的偏振成像系统包含机械转动部件,需要分时多次采集来获取目标完整的Stokes矢量信息,因而难以对运动目标的偏振信息进行观测。空间调制型全偏振成像系统以光楔或Savart偏光镜作为空间调制模块,将Stokes矢量的4个参数S0、S1、S2、S3信息调制到不同频率的载波上,从而实现同时单次采集便能获取包含Stokes矢量信息的干涉图样。空间调制型全偏振成像系统与传统的分振幅、分孔径、分焦面同时偏振成像系统相比,有着结构简单和容易实现的优点。因此,空间调制型全偏振成像系统将会在遥感、军事和生物医学等领域有着广泛的应用前景。在实际工程应用中,系统误差必然会影响空间调制型全偏振成像系统的Stokes矢量测量精度。其中,旋转半波片和检偏器的装调角度误差是系统的关键误差,它们对偏振测量精度有着不可忽略的影响。本文给出了空间调制型全偏振成像系统的装调角度误差模型。为了分析装调角度误差所带来的影响,构造了基于空域解调算法的矩阵误差模型,通过Poincare球采样法选取入射光的不同偏振态,分别对旋转半波片装调角度误差、检偏器装调角度误差、两者的耦合角度误差对系统偏振测量精度的影响进行了仿真验证,并对仿真结果进行了分析。提出了一种基于测量矩阵条件数的性能优化方法,该方法通过寻找最小条件数的测量矩阵来获取最优系统。经研究表明,系统测量矩阵的条件数与Savart单板的厚度相关。对Savart单板厚度为6mm、10mm、12mm、23mm和25mm的系统进行仿真检验,发现Savart单板厚度为23mm时,测量矩阵条件数取得最小值2.06,装调角度误差对系统的影响最小。因此,基于测量矩阵条件数的优化方法能够提高系统的性能。然而,这种方法存在着一定的局限性。通过范数相容定理对优化方法的局限性进行研究,并给出了分析结果。在验证基于条件数的优化方法效果时,提出了一种完备的系统测量误差表征方法-——Stokes基矢量法。利用该方法只需对自然光、0°/90°线偏振光、45°/135°线偏振光、左/右旋圆偏振光这4种基态偏振光的测量误差进行检测,便可求解出存在装调角度误差时的空间调制型全偏振成像系统其偏振测量精度。
[Abstract]:The polarization imaging system can not only obtain the two-dimensional light intensity distribution information of the target, but also obtain the polarization information corresponding to the target light intensity distribution, that is, the Stokes vector information. The Stokes vector information has the ability to enhance the contrast of the target. Targets can be highlighted from complex background information. The traditional polarization imaging system contains mechanical rotation components, which need to be collected several times in time to obtain the complete Stokes vector information of the target, so it is difficult to observe the polarization information of moving targets. The spatial modulation full polarization imaging system uses the wedge or Savart polarizer as the spatial modulation module, modulates the four parameters of the Stokes vector S0 / S1 / S2 / S3 onto the carrier at different frequencies. Thus, the interference pattern containing Stokes vector information can be obtained by a single acquisition at the same time. Compared with the traditional polarization imaging system, the spatial modulation full polarization imaging system has the advantages of simple structure and easy realization. Therefore, spatial modulation full polarization imaging system will be widely used in remote sensing, military and biomedical fields. In the practical engineering application, the system error will inevitably affect the Stokes vector measurement accuracy of the spatial modulation full polarization imaging system. The angle error of rotation half-wave plate and polarizer is the key error of the system, and they have an important influence on the precision of polarization measurement. In this paper, the adjustment angle error model of spatial modulation full polarization imaging system is presented. The matrix error model based on spatial demodulation algorithm is constructed to analyze the influence of the angle error of the mounting angle. The different polarization states of the incident light are selected by the Poincare sphere sampling method, and the angle errors of the rotating half-wave plate are respectively adjusted. The influence of the angle error and coupling angle error of the polarizer on the precision of polarization measurement is verified by simulation and the simulation results are analyzed. In this paper, a performance optimization method based on the condition number of the measurement matrix is proposed. The method obtains the optimal system by finding the measurement matrix of the minimum condition number. The results show that the condition number of the system measurement matrix is related to the thickness of Savart veneer. The system with Savart veneer thickness of 6mm / 10mm / 12mm / 23mm and 25mm is tested by simulation. It is found that when the thickness of Savart veneer is 23mm, the minimum value of measuring matrix condition is 2.06, and the influence of adjustment angle error on the system is the least. Therefore, the optimization method based on the condition number of measurement matrix can improve the performance of the system. However, this method has some limitations. The limitation of optimization method is studied by norm compatibility theorem, and the analytical results are given. In order to verify the effectiveness of the conditional number based optimization method, a complete system measurement error representation method, called Stokes basis vector method, is proposed. By using this method, the measurement errors of four ground state polarized light, namely, natural light, 0 掳/ 90 掳line polarized light, 45 掳/ 135 掳line polarized light and left / right circularly polarized light, need to be detected. The precision of polarization measurement of spatial modulation full polarization imaging system with angle error can be solved.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O436.3

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