Visibility measurement using multi-angle forward scattering by liquid droplets

A multi-angle forward scattering method is presented, which can be used to detect the extinction coefficient of liquid droplets in atmosphere visibility measurement. The wavelength of LED in the transmitter is 850 nm, and the forward scattering signals are collected by three receivers which are arranged at angles of 20°, 35° and 50°, respectively. Atmosphere visibility is measured by the receiver which is arranged at 35° angle. It can determine the type of weather by the ratio between scattering phase function P(20°) and P(50°), and also find the different ranges of these ratios in different weather. Compared to other visibility meters, the meter proposed not only measures the visibility accurately, but also distinguishes weather types such as fog, haze and mist.