海洋目标光学偏振辐射特性研究

发布时间：2018-09-11 15:19

【摘要】：光与物质相互作用表现的偏振特性为光学偏振遥感技术的应用提供了科学依据。海洋环境目标及背景的反射和散射而产生的偏振辐射特性及其差异有利于海洋偏振观测。采用多角度偏振探测技术获取海洋目标的光谱偏振辐射特性参数,分析海水背景以及典型海洋目标的偏振特性变化趋势,为海洋目标偏振遥感提供理论依据和实验验证。首先,从偏振探测原理出发,根据分时偏振探测方式设计并制作了用于获取目标偏振光谱特性的野外便携式双向偏振反射分布函数(Bidirectional Polarized-reflectance Distribution Function,BPDF)测量系统。该系统包括 BPDF测量支架与偏振光谱仪。BPDF测量支架的天顶弧和方位弧轨道半径均为0.9m,配合使用偏振光谱仪,可在半球空间内获取多种野外目标的多角度偏振辐射信息。其次,针对本研究使用的偏振光谱仪和偏振相机,进行了辐射和偏振定标检测,其偏振测量精度优于2%。随后,针对背景水体,采用大型BPDF测量支架搭载偏振相机,开展室外目标光学偏振辐射特性的测量实验。结合Fresnel反射定律分析了平静水面的反射的偏振特性,并在室外测量了平静水面的多角度偏振特性,实验结果表明,观测天顶角对水体偏振度的影响较大,偏振度随观测天顶角的增大明显增大,最大值可达到0.8左右;结合Cox-Munk粗糙海表面BPDF模型分析了动态背景水体的偏振辐射特性,并测量了动态水体的偏振辐射特性。动态水体在后向散射方向最大偏振度为0.23,前向散射方向最大偏振度达到1。最后,针对典型海洋目标,选取了船只和岛礁目标作为研究对象,重点测量了4种船只材料板、船只缩比模型、植被、土壤以及沙石混合地等目标,获取了目标大量偏振光谱信息和成像信息。就辐射特性而言,反射率最大值都出现在主平面内,船只材料板由于表面光滑,镜面反射明显,植被存在热点效应,土壤有着强后向散射特性,沙石混合地呈现一定的朗伯特性;就偏振特性而言,各种目标的偏振度的变化趋势基本一致,但有着各自的波段特性和方向特性。船只材料板偏振度波段特性不明显,随观测角度变化明显,植被、土壤和沙石混合地的偏振度则具有明显的波段特性,在490nm处的偏振度略高于550nm和670nm处的偏振度,最大值分别为0.25、0.07和0.15。因此在进行海洋目标观测时,需要根据不同的目标选择合适的观测波段与观测方向。
[Abstract]:The polarization characteristics of light-matter interaction provide a scientific basis for the application of optical polarization remote sensing technology. The polarization radiation characteristics and their differences caused by the reflection and scattering of targets and backgrounds in the marine environment are beneficial to the observation of marine polarization. Firstly, based on the principle of polarization detection, a portable bi-directional polarization reflectance distribution function is designed and fabricated in the field to obtain the polarization spectrum characteristics of the target. Bidirectional Polarized-reflectance Distribution Function (BPDF) measurement system, including BPDF measurement scaffolds and polarization spectrometer, BPDF measurement scaffolds zenith arc and azimuth arc orbital radius are 0.9m, together with the use of polarization spectrometer, can obtain a variety of field targets in hemisphere multi-angle polarization radiation information. Secondly, for polarization spectrometer and polarization camera used in this study, radiation and polarization calibration were carried out, and the polarization measurement accuracy was better than 2%. Then, for the background water, a large BPDF measuring scaffold was used to carry out polarization camera to measure the optical polarization radiation characteristics of outdoor targets. The polarization characteristics of the reflection of the still water surface are measured outdoors. The experimental results show that the zenith angle has a great influence on the degree of polarization of the water. The degree of polarization increases with the zenith angle, and the maximum value can reach about 0.8. The polarization radiation characteristics of the water body are measured. The maximum polarization degree of the dynamic water body is 0.23 in the backscattering direction and 1 in the forward scattering direction. In terms of radiation characteristics, the maximum reflectance appears in the main plane. Because of the smooth surface, the mirror reflection is obvious, the vegetation has the hot spot effect, the soil has the strong backscattering characteristic, and the sand-rock mixture land. As far as polarization characteristics are concerned, the polarization degrees of various targets have the same trend, but have their own band characteristics and directional characteristics. The degree of polarization at 490 nm is slightly higher than that at 550 nm and 670 nm, with the maximum values of 0.25, 0.07 and 0.15 respectively.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O436.3

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