A new, easily adjusted and very stable interferometer, defining a semistatic fringe field by reflection on two mirrors, has permitted a simple solution to the problem of rapid and accurate alignment of moving carriages, of fixed reference beams, and of carriage-ways in the interferometric domain. Precisions in the 0.1-sec-of-arc range are easily obtained in visual work in rotations up to minutes of arc, <i>without</i> the usual limitations of slow fringe counting and of loss of fringe-contrast at large path differences in particular. In fact, the fringe-contrast is independent of the distance from the reference-support to the moving mirrors in this interferometer, and permits measurements and alignments over traverses and distances of many feet if required. Precisions in the 0.01-sec-of-arc range and better can be obtained with the help of electronic location of interference fringes. Experiments with carriages moving at rates up to 1-foot/sec and over distances of the order of 1½ ft have demonstrated the versatility of the alignment interferometer in various applications, in particular in the alignment of ways on a velocity-of-light apparatus and on ruling engines.
GEORGE W. STROKE, "An Alignment Interferometer for Precision Straightness-Measurements and Control Even of Rapidly Moving Carriages," J. Opt. Soc. Am. 51, 1340-1341 (1961)