| When a beam of light emitted from a laser source is reflected or scattered back into the laser cavity by an external target, the reflected light will mix with the light inside the cavity, causing a modulation of the laser output power. So it is called optical feedback self-mixing interference(OFSMI). The laser self-mixing interference system has a very simple and compact set-up and autocollimation capability. Because of carrying external reflector information, the system can be used for multi physical quantity sensor testing, especially suitable for sensing measurement of mechanical quantities such as displacement, vibration, distance, contour. Light interference measurement with high resolution, high precision characteristics, which makes the optical feedback self mixing interference technology has broad prospects in the sensing measurement field.This paper focuses on the research of two kinds of method to eliminate noise in the OFSMI signal.One is based on EEMD threshold processing and the other one is based on fractional fourier transform of LMS adaptive filter. Through the simulation experiment, the signal-to-noise ratio is improved greatly.Then,this paper introduces the analysis model of the OFSMI theory and analysis of the optical feedback level factor effect on the OFSMI signal,which lays a theoretical foundation for the displacement measurement.The disappearance of self-mixing interference fringes in the high feedback regime decreases the displacement measurement accuracy. The proposed method detects and compensates the fringe-loss with a large optical feedback factor C. A self-mixing interference displacement measurement algorithm is presented that is able to remedy the influence of fringe-loss. It has been compared with traditional method by counting the fringe numbers and the accuracy is improved.Finally, conclusions are drawn from the whole paper and the further research issues are pointed out. |
PDF Full Text Request