典型地面目标热辐射偏振特性研究

The non-Lambertian emission of radiation not only has the three-dimensional spatial distribution features but also is of polarization. Traditional thermal infrared remote sensing mainly gains the two-dimensional spatial distribution features from the surface objects and the polarization of the emitted radiation of the target surface objects is not involved. This study, through investigating the thermal infrared polarization mechanism of the surface objects, is aimed to measure the thermal infrared polarization features of five main typical categories of surface objects: vegetation, water, rock and mineral, soil and snow, and to quantitatively analyze and probe the influence of zenith angle, azimuth, band, type of surface objects and their interaction on the thermal radiation polarization features of these five categories by orthogonal experimental design, fractal, wavelet theory and spectroscopy so as to draw some common regular patterns. This research is the extension and expansion of the previous four National Natural Science Foundations. The research ideas, methods, results and experience of the previous researches are of significant reference; the previous researches concern the reflection polarization characteristics of the typical surface objects, while this new one focuses on the emission polarization characteristics of typical surface objects; wavelength is extended from 0.4-2.5μm to 8-14μm. This study provides a basis for the development and application of thermal infrared polarization remote sensing information, the identification and classification of surface objects, and the research and development of sensors; it is of great theoretical significance and broad application prospect.

来自非朗伯体的发射辐射，不但具有三维空间分布特征，还具有偏振性。传统的热红外遥感主要获取地物自身发射的二维空间分布特征，未涉及目标地物发射辐射的偏振性。本项研究旨在通过对地物的热红外偏振机理探讨，测量植被、水体、岩矿、土壤以及冰雪五大类典型地面目标的热红外偏振特性，并通过正交试验设计，以分形、小波理论、光谱分析技术定量分析探测天顶角、方位角、波段、地物类型以及交互作用对其热辐射偏振特性的影响，以便从中得出某些带有共性的规律。本课题的研究是前四个国家自然科学基金研究的延伸与拓展。其研究思路、方法、成果与经验对新课题研究有非常重要的借鉴作用；以前研究的均是典型地面目标的反射偏振特性，而新课题研究的是典型地面目标的自身发射偏振特性；波长从0.4-2.5μm，拓展至8-14μm。本研究为热红外偏振遥感信息的开发和应用，地物的识别、分类、传感器的研制提供了依据，具有重要的理论意义和广阔的应用前景。

本课题在探讨热红外偏振机理的基础上，从多角度（包括探测方位角、探测天顶角、偏振角）、多光谱、不同温度条件下，对不同地物类型的偏振信息特征进行提取，并且对影响地面目标热红外偏振的因子及其交互作用进行定量分析。在研究过程中完全按照研究计划进行。在执行研究计划过程中，首先，研究了水体的热辐射偏振特性，发现水的偏振辐射亮度对波段非常敏感，偏振亮度温度对温度非常敏感。其次，通过对冰的热辐射特性进行研究，发现探测角对冰热辐射特性影响极其显著且受偏振角影响。第三，通过对雪的热辐射特性进行研究，发现雪的辐射亮度和亮度温度均随探测天顶角的增大而增大，当探测天顶角>30°时，增长速度加快，且探测天顶角对雪的亮度温度的影响较辐射亮度更为显著。第四，研究表明，当仅探测天顶角变化时，随着探测天顶角的增大，坡地植物在可见光波段光谱特征变化并不明显，在近红外波段反射比逐渐减小。最后，发现不同土壤类型的偏振辐射亮度温度不同，呈现草甸黑上>淋溶黑钙上>典型黑钙上>草甸风沙上的规律。以上研究为热红外偏振遥感基础理论研究提供重要依据。