Based On The Moderate Optical Feedback Self-mixing Interference Of The Vibration Measurement

The laser self-mixing interferometric technology is an exact measure technique. With the capability of very simple and compact set-up and autocollimation, The technique is has been studied and applied extensively, and it is mostly applied to geometry sensing measurement and laser parameters measurement.Optical feedback self-mixing interferometry is an emerging sensing and measurement technique. This paper aims to employ this technology to measure the vibration amplitudes of external reflecting objects. The system of simple harmonic vibration of measured objects under moderate optical feedback is researched from the following parts.Firstly, according to the basic theory and mathematic model of optical feedback self-mixing interference effect, the mathematic model of vibration measurement is created. Study on the reasons why signals lean and the vibration measurement characters. Conclusions lay a theory foundation to the design of vibration measurement methods.Secondly, based on moderate optical feedback the vibration measurement arithmetic is established. Choosing appropriate optical feedback level and line width spreading factors of lasers can get quite pure saw-tooth interference strips. The differential interference signals produce corresponding positive and negative pulses. Get the vibration amplitudes of integer stripes with pulses count method and then reset the integer parts. Reserve the decimal fraction stripes to be analyzed. Research the impacts of displacement changes to decimal fraction stripes waveform within half wavelength and find out the corresponding relations. Thereby measure the vibration amplitudes of decimal fraction stripes to implement precision measurement.Various performances of the proposed algorithm is researched by computer simulation, including the parameter selection rule, accuracy analysis, availability and anti-noise capability and so on. In addition, this paper introduces the pre-processing method for measured datum and the validity is proved by pre-processed datum. The results indicate the relative standard deviation ofΔL is 0.83% to the vibration of which amplitudes are below 3μm .At last, the algorithm in this paper is contrasted with two congeneric algorithms based on self-mixing interferometric effect. Simulation and experiment datum processing results show the algorithm of this paper is superior to existing congeneric algorithms.