Research On Vibration Measurement Technology Based On Homodyne Laser Interferometer

With the advantages of high measurement accuracy,large measurement range and no interference to the measured target,the homodyne laser vibrometer has been widely used in the ground testing for micro-vibration signals on spacecraft,radar target recognition,precise machinery manufacturing and material flaw detection.However in practical applications,the nonlinearity of the vibrometer due to the nonideal optical and optoelectronic devices directly impedes improving the measurement accuracy of the homodyne laser vibrometer to nanometer level or higher.Therefore,the nonlinearity compensation method has become a focus and hotspot in the research of homodyne laser vibrometer.In this paper,through the analysis of conventional nonlinearity compensation methods in homodyne laser vibrometer,a new nonlinearity compensation method is proposed,which is called Pseudo-Extremums method with the operation for Vector Phase Correction(PEVPC).In order to verify and analyze the nonlinearity suppression effect of the PEVPC method,a homodyne laser vibrometer is set up,and used to performe measurement experiments on vibration signals from 1 Hz to 100 Hz.The homodyne laser vibrometer is based on the architecture of Michelson interferometer,including a single-frequency laser source,a 90° optical hybrid,two balanced amplified photodetectors,self-designed data acquisition and transmission circuits and a computer.Experiments show that compared with the conventional extremum method,the PEVPC compensation method proposed in this paper can reduce the error caused by laser power drift,Abbe error and the bit error of digital signal transmission during measurement.Laser power drift and Abbe error make the trajectory of quadrature signals into a spiral elliptic shape.In the homodyne laser vibrometer set up in this paper,the peak-to-valley amplitude of residual error can be reduced to 0.8nm by using the PEVPC compensation method,which has a more effective suppression for nonlinear error than the conventional extremums method.Besides,the PEVPC compensation method proposed does not require to calibrate the position of pseudoextremums frequently.So the PEVPC method has a good stability.