Laser modulating technology realizing harmonic examination of coal mine gas concentration

According to defects of former coal mine gas examination methods, it propose that using diode laser modulating technology and harmonic surveying technology to real-time remote sensing survey to coal mine methane. The second harmonic is selected by theory deduction to survey concentration of gas. This plan selects 2 v₃ absorption band R6 branch absorption line of methane to survey the smallest detectable concentration of methane, and experimental result confirms the smallest detectable concentration of methane by this plan is 4.2times10^-4 atmmiddotm. It presents low surveying power and high sensitivity characteristic, and it can realize distributed multi-points real-time monitor for methane.