How Visibility Detector Works: From Light Emission to Visibility Calculation

In the field of meteorology, visibility is a crucial observation indicator, usually accurately represented by the meteorological optical range. In the aviation field, the precise measurement of the Visibility detector can ensure the safety of aircraft takeoffs and landings; in the transportation field, it can provide important references for road traffic safety and reduce traffic accidents caused by low visibility.

The definition of the meteorological optical range is very rigorous. It refers to a parallel light beam with a color temperature of 2700K emitted by an incandescent lamp. When its luminous flux propagates in the complex medium of the atmosphere, it will be gradually weakened by various factors. Water vapor, dust, aerosols, etc. in the atmosphere will all interfere with the propagation of light. When the luminous flux is weakened to 5% of its initial value, the path length that the light beam has passed through is the meteorological optical range. In routine ground meteorological observation work, for the convenience of recording and data comparison, the unit of measurement is generally the meter, with the symbol "m".

As a professional device for measuring visibility, the Visibility detector mainly consists of three core components: a transmitter, a receiver, and a processor. The function of the transmitter is to emit near-infrared light pulses. When these pulsed light beams propagate in the air, they will encounter various suspended particles in the air, such as dust, water vapor, aerosols, etc., and then the scattering phenomenon will occur. In foggy weather, with a high water vapor content, the scattering phenomenon is more obvious. The scattered light is keenly captured and received by the receiver. Subsequently, the built-in processor of the instrument plays a key role. Based on the relevant data of the scattered light received, it uses complex and precise algorithms to estimate the meteorological optical range, that is, the visibility we mentioned, from the scattering coefficient.