太阳高度角的变化对地物表面三维2π空间反射率的影响研究

Study on the Influence of Incident Angle on the Object Surface Reflected Spectrum

在实验室内进行模拟太阳高度角的变化对地物表面2π空间反射率的影响研究。以岩石表面为例,主要研究入射光的角度变化对岩石表面在半球空间的多角度反射光谱特征的影响。结果表明,太阳高度角(光线入射角)的不同,对地物表面在2π空间内的反射率影响非常明显。当入射角以小角度入射时(一般小于20°),岩石表面可以很好地看成朗伯体,这与过去人们通常的假定一致。但是当入射角以大角度入射时(大于30°),岩石表面失去朗伯体特征,镜面反射特征开始增强,加上朗伯反射,此时可合成为椭圆光谱。其次,在大角度入射时,此时镜面反射在实际的观测中表现出裙带现象,并不符合理论上那种简单的反射定律。

This paper studies the influence of the incident angle upon the surface reflectance spectrum of rocks in a hemisphere space. The object surface reflectance spectrum in 2π space changes dramatically when the incident angle varies. But unfortunately researches in this aspect are just a few. We managed to have done a large quantity of experiments with many kinds of rocks. And according to the experiment results, the incident angle strongly affected the characteristics of reflectance spectrum in 2π space. When the incidence angle is smaller than 20°, the surface of rocks can be regarded as a fine Lambertian, just as what people usually assume. But when the incident angle turns bigger （ above 30°）, the rock surface would not possess the Lambertian characteristics, whereas mirror surface reflection character reveals itself more and more. And the bigger the angle, the more intense the mirror reflection character. Besides, the reflection could not be regarded as the simple one, because it shows a petticoat phenomenon, which could not be explained by a simple reflection theory.