基于光纤的能见度测量方法

提出了一种利用前向散射光束和透射光束测量近地大气横向能见度的方法。以阶跃折射率光纤作为空间滤波器限制散射光束和透射光束接收的视场角以及前向散射测量光束和大气散射辐射的背景干扰;采用相关检测法,排除测量通道视场角内的大气背景干扰,提高洁净大气条件下散射光强度信号测量的信噪比;对测量装置结构进行优化设计,减小热形变的影响;另一方面引入阶跃折射率光纤,使投射到光电探测器接收表面的光束光斑位置保持不变,进一步减弱形变对测量精度的影响。能见度的值用散射光强度和透射光强度之比表示,光源强度的变化和光学元件的污染对测量的影响可不考虑。用此方法测得的能见度与按严格定义的透射法所测能见度的相关系数约为98.2％。

Measuring method of visibility with optical fiber

A measuring method to terrain atmospheric visibility with forward scattered light and transmitted light was introduced. Visibility is expressed by ratio of the intensity of the scattered light to the intensity of transmitted light. Spatial filters are utilized to limit visual angle of scattered light and transmitted light, and background interferences of measured forward scattered light and atmospheric scattered light. Using the correlation detection, atmospheric background noise is eliminated and signal-to-noise ratio for scattered light to background is enhanced. In order to keep spot of being measured light beam on the photo-detector unchanged, step index optical fiber is used in the set for improving the influence of thermal deformation on measuring error. Another characteristic is that changing in the light source and pollution to the optical elements may be ignored. The correlation coefficient between visibility from proposed method and accurate transmission method is about 98.2 %.