Atmospheric microorganism laser detection alarm system

[0030] Such as figure 1 As shown, the system mainly includes a laser 1, a reflector 2, a receiving telescope 3, a 1×2 optical signal transmission fiber 4, a collimating mirror 5, a 450nm filter 6, a 540nm filter 7, a PMT photodetector 8, A data acquisition card 9, a computer 10, and a flash buzzer 11, wherein the computer 10 is responsible for the control and data processing and analysis of the entire system.

[0031] When the system is working, the laser 1 generates a 355nm pulsed laser beam first, and the laser beam is reflected by two mirrors 2 and then shoots to the target area. The induced fluorescence signal generated by the interaction between the atmosphere in the target area and the laser beam is received by the receiving telescope 3.

[0032] The laser 1 and the receiving telescope 3 are coaxial, that is, the optical axis of the outgoing beam coincides with the optical axis of the receiving telescope. The fluorescent signal is received and converged by the receiving te

[0035] Such as figure 2 As shown, the computer 10 sends a trigger signal to the laser 1, and the laser 1 emits pulsed laser light. After the receiving telescope 3 receives the fluorescent signal and the 1×2 optical fiber 4 splits the fluorescent signal, the computer 10 sends a trigger signal to the PMT photodetector 8, and turns on the PMT photodetector 8 to perform photoelectric conversion of the fluorescent signal in the target band and generate an electrical signal. Then the computer 10 triggers the data acquisition card 9 to perform data acquisition. After the data collection is finished, the computer 10 sends a trigger signal to the laser 1 to emit the next laser pulse.

[0037] The system parameters are selected as follows: the laser emission wavelength is 355nm, the laser pulse energy is 20mJ, the pulse repetition frequency is 20Hz, the receiving telescope aperture is 114mm, the optical reflectivity is 90%, the optical fiber signal coupling efficiency is 80%, and the PMT photodetector quantum efficiency is 20%.

[0038] The air microbial parameters are selected as follows: the air microbial is set to Escherichia coli, the concentration (alarm threshold) is 40ACPLA, and the diameter of the microbial air mass is 0.5m.

[0039] Atmospheric visibility and background light condition parameters are as follows: Atmospheric visibility is 5km, the atmospheric model is the 1976 American Standard Atmospheric Model, and the atmospheric background illuminance is 5.0mw / (m 2 nm sr).

[0040] According to the lidar equation, the number N of fluorescent signal photons received by the PMT photodetector can be expressed as follows:

[0041]

[0042] The elec