Design and development of an interferometer with improved angular tolerance and its application to x-y theta measurement

Plane mirror interferometers are widely used in the measurement of x-y moti ons. Although large range planar motion can be measured, it suffers from ve ry tight angular tolerance. In this article an interferometer system having improved angular range and linear resolution is developed. In the system, a tilted laser beam is incident to a plane mirror attached to a moving stag e and an additional retroreflector and a plane mirror are placed off the st age to help return the measuring beam. In such a design both the resolution and angular tolerance are improved. Meanwhile, large travel ranges along b oth the x and y directions remain. The optical principle pertinent to the p roposed optical configuration is explained and an optical path analysis is performed to establish the relation between the optical path change and the motion to be measured. Based on the established relation, design of system parameters and workspace analysis are also discussed. Experimental results including resolution test and scaling procedure are then demonstrated. Usi ng the developed interferometer an x-y theta measurement scheme is introduc ed. In the proposed scheme, using three interferometers the rotation angle of an x-y theta stage can be obtained first and it can then be used to comp ensate errors of the measured linear motion. (C) 2000 American Institute of Physics. [S0034-6748(00)05412-5].