Design Of Micro-displacement Measurement System Based On Four-quadrant Detector

With the development of modern technology and the improvement of people's safety consciousness,people pay more and more attention to industrial production and harmful gas in the environment,especially trace gases such as CH₄ and H₂S.Therefore,how to quickly and effectively detect the composition and concentration of trace gases has become a key issues in gas detection.Nowadays trace gas detection method based on cantilever microphone is a research hotspot.At present,Fourier transform spectroscopy is in general use to measure the displacement of the free end of cantilever,and further obtain the gas concentration to be measured,but its cost is high.In this paper,a micro-displacement measurement system based on four-quadrant detector is designed and completed.The displacement of the free end of the cantilever beam is realized by bi-directionally counting of the interference fringes and compensating the refractive index of the air by indirect measurement.The main contents of the thesis are as follows:?1?The dynamic characteristics of the free end of the cantilever beam and the interference fringes caused by the cantilever motion are studied.Based on this,the overall scheme of the micro-displacement measurement system is formulated,and the optical path and hardware and software implementation of the system are designed.?2?A micro-displacement measurement system based on four-quadrant detector is built.The optical path of the system includes laser beam expanding collimation,Michelson interferometer and the processing of the measured beam;The hardware necessities of the system includes four quadrant detector,preamplifier circuit,signal processing circuit based on C8051F310 microcontroller,environment parameter measurement circuit based on DHT22 and Bmp280 sensor,and it has completed the acquisition of interference fringe data and environment parameters;The software of our system is developed based on Labview,completed the real-time measurement of interference fringe parameters such as serial data transmission,phase difference et al,and realized bi-directionally counting of the interference fringes,cyclic measurement of air refractive index and displacement calculation before and after the refractive index compensation.?3?The functional and the feasibility of the micro-displacement measurement system is tested and verify in the experiment.The displacement measurement of non-uniform movement is completed in the laboratory environment,and the error caused by the optical path and human factors of the system is analyzed.The minimum measurable displacement of the system is 0.0791?m.In the measurement range of 10?m,the maximum measurement error is 0.1120?m.