考虑探测器γ特性的光电偏振成像系统偏振信息重构方法

由于探测器响应的γ特性, 造成光电偏振成像中直接利用图像灰度重构的偏振信息与真实目标场景偏振信息的严重偏离, 基于重构偏振信息的后续定量化处理将完全失去意义. 为此, 提出了一种考虑探测器γ特性的光电偏振成像系统偏振信息重构方法, 分别针对分时和同时偏振成像模式分析了实现方法, 并设计进行了实际偏振成像实验. 实验数据表明: 探测器γ特性直接影响偏振成像系统重构的斯托克斯矢量和偏振度, γ值偏离1越大, 直接利用图像灰度重构的偏振度的重构误差也越大; 该偏振信息重构方法能够准确地重构出目标场景的斯托克斯矢量和偏振度信息, 为后续偏振成像的研究和定量应用奠定了理论基础.

A new algorithm for polarization information restoration with considering the γ property of optoelectronic polarimeter

The γ property of optoelectronic detector indicates that the response between incident light intensity and output digital number is non-linear. For imaging polarimeter, if light intensity is directly substituted by digital number when restoring polarization information from polarization images, the restored polarization information will apparently deviate from the true scene polarization information. This deviation makes the quantitative application of polarization information meaningless. To solve this problem, in this paper we propose a new algorithm for restoring the polarizaiton information with considering the γ property of polarimeter of the detector. Firstly, theorical γ correction equation of polarization information restoration are proposed for division-of-time polarimeter and for simultaneous polarimeter respectively. And then, specific implementation and polarization imaging test experiment are carried out. For divison-of-time polarimeter, we firstly test the γ property of the detector, and then use the tested γ parameter and the proposed restoration equation to restore polarizaiton information from the data of polarzation imaging test experiment. The degree of linear polarization (DoLP) restored with digital number directly changes from 0.932 to 0.753 when γ changes from 1.0 to 1.5. The DoLP restored with γ correction equation proposed in this paper varies from 0.932 to 0.926, which approaches to the ture scene DoLP value 1.0. For simultaneous polarimter, the instrument matrixes of the polarimeter are calibrated first under different γ setting values, and then the calibrated instrument matrixes are used to restore poliarzation information from the data of polarization imaging test experiment. The DoLP restored with digital number directly changes from 1.3763 to 1.1582 when γ changes from 1.0 to 1.5, which exceeds the possible DoLP range from 0 to 1.0. The DoLP restored with γ correction equation proposed in this paper varies from 0.8428 to 0.8683, which approaches to the ture scene DoLP value 1.0. Experimental result shows that the γ property of polarimeter has an apparent effect on the restored polarization information, and that the polarizaiton information restoration error increases with γ setting deviation from 1.0. With the restoration algorithm proposed in this paper, the restored polarization information can steadily approach to the scene polarization information with acceptable slants small. The poroposed polarization restoration algorithm with considering γ property establishes a theoretical foundation for the future study of polarimeter and its quantitative application.