A weight average method to improve the uncertainty of length measurement in a two-color interferometer

Some phase errors in a two-color interferometer result in a large uncertainty in length measurement due to the large A coefficient. We analyzed three kinds of phase errors, correlation, semi-correlation and non-correlation errors, and presented a weight average method to deal with different errors by using different weight factors. The uncertainties in length measurement can be reduced without effects on the resolution of length measurement. The experimental results show that the length can be obtained with a standard deviation of approximately 0.1 μ m by measuring the phase of the interference fringe using a heterodyne interferometry and processing the measured data using a weight average method.