Abstract

In order to improve the measurement accuracy of the linear expansion coefficient and signal processing speed of operation, this paper proposes a novel method of second harmonic measurement of multi-beam laser heterodyne for metal linear expansion coefficient, which is converted into the measurement of the length variation of linear expansion coefficient. Based on Doppler effect and heterodyne technology, loaded the information of length variation to the frequency difference of second harmonic of the multi-beam laser heterodyne signal by the frequency modulation of the oscillating mirror, and can get value of length variation caused by temperature variety after the multi-beam laser heterodyne signal demodulation. Processing this value by fast Fourier transform, can get length variation accurately, and eventually get value of linear expansion coefficient of metal by the calculation. Using this novel method, simulates measurement for linear expansion coefficient of metal rod under different temperatures by MATLAB, the result shows that: the relative measurement error of this method is just 0.08%.

© 2017 Optical Society of America