Study on calibrating and inversing method of light emitting diodes-differential optical absorption spectroscopy

In order to avoid the serious energy wastage and unnecessary interference using xenon arc lamps as the broadband hot light source in active differential optical absorption spectroscope(DOAS) systems,the light emitting diode(LED) is developed as a new type of cold light source for optical remote sensing DOAS systems in this paper.A study on calibrating and inversing method of light emitting diodes differential optical absorption spectroscopy(LEDs-DOAS) system is introduced.Firstly,the structure of LEDs-DOAS system is described,and the inversing principle of atmospheric trace gases concentrations is analyzed based on the differential absorption of trace gases.The line-shaped absorption spectrum of Hg lamp is introduced into LEDs-DOAS instrument to get the instrument function.The standard absorption section of trace gas is convoluted with the instrument function.Then the absorption strength of the trace gas is gained by the LEDs-DOAS system.Concentrations of trace gases are retrieved based on the least-squares fitting method.At last,the NO2 cells are also used to test the accuracy of the LEDs-DOAS system.Experimental results show that the measuring relative error is less than 5%,which demonstrates that the light-emitting diode as a light source of LEDs-DOAS system is feasible and reliable to measure the atmospheric trace gases.