Testing Displacement-Measuring Interferometer Systems
Jack A. Stone Jr., Martin Schroeck, Michael T. Stocker
We have made a study of one method for testing displacement-measuring interferometer systems, a modified back-to-back comparison, that automatically compensates for changes in the optical path length between the two interferometers. Although this method has certain disadvantages relative to other possible approaches, the ultimate achievable accuracy is entirely satisfactory, and the method provides greater flexibility than do alternate approaches. When testing interferometer systems we currently achieve a length-proportional expanded uncertainty (coverage factor k=2) of D1/1=1x10-7, where 1 is the measured displacement. Although this uncertainty is sufficiently small to satisfy present commercial demands, it may be possible to further reduce the uncertainty with modest additional effort.