The Method to Measure the Nonlinearity in Laser Heterodyne Interferometer

To reduce or restrain the nonlinearity in laser heterodyne interferometer via adjusting optical component,the mechanism and the method of measuring nonlinearity need to be researched.Based on the spectrum analysis of the measurement signal,a method to measure the nonlinearity is proposed.With the model of the amplitude relationship between the nonlinearity and measurement signal,the first harmonic nonlinearity and the second harmonic nonlinearity are counted.Then,the nonlinearity is measured accurately.The experimental result shows that the method can measure the nonlinearity accurately and can easily be adopted.