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 uncertain ty in length measurement due to the large A coefficient. We analyzed three kinds of phase errors, correlation, semi-correlation and non-correlation er rors, and presented a weight average method to deal with different errors b y using different weight factors. The uncertainties in length measurement c an be reduced without effects on the resolution of length measurement. The experimental results show that the length can be obtained with a standard d eviation of approximately 0.1 mum by measuring the phase of the interferenc e fringe using a heterodyne interferometry and processing the measured data using a weight average method. (C) 2001 Published by Elsevier Science B.V.