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根据辐射传输和Mie散射理论,给出了分析雾的前向散射对距离选通成像系统影响的计算方法。首先,采用雾的含水量和能见度的经验公式估计雾滴谱。其次,已知雾滴谱计算Mie散射相函数;进而获得视消光系数。最后,给出了考虑前向散射光的影响时,前向散射光、后向散射光和信号光在距离选通成像系统光电阴极面上的照度随时间的变化规律,以及光电阴极面上目标与背景图像的对比度。结果是目标上的照度、后向散射光和信号光在光电阴极面上的照度增加,目标与背景图像的对比度降低;前向散射光在光电阴极面上的照度远小于后向散射光。
Based on the theory of radiative transfer and Mie scattering, a method to calculate the influence of fog forward scattering on the distance gated imaging system is given. First, the fog droplet spectrum is estimated using empirical formulas of moisture content and visibility of the fog. Second, the Mie scattering phase function is known for the fog droplet spectroscopy; further, the apparent extinction coefficient is obtained. Finally, the variation of the illumination intensity of forward scattered light, backscattered light and signal light on the photocathode surface of the distance-gated imaging system with time is considered in consideration of the influence of the forward-scattered light, and the change of the target Contrast with the background image. As a result, the illuminance of the target, the illuminance of the backscattered light and the signal light on the photocathode surface increase, and the contrast between the target image and the background image decreases. The illuminance of the forward scattered light on the photocathode surface is much smaller than that of the backscattered light.