MEASUREMENT OF SMALL ROTATION ANGLES BY USING A PARALLEL INTERFERENCEPATTERN

We propose a method for measuring rotation angles by using a parallel interference pattern. At two points on a parallel interference pattern reflected by an object, we detect phase changes in the reflected para llel interference pattern caused by rotations of the object. A high se nsitivity, or a high ratio of the phase change to the rotation angle, 17 mrad/arcsec, can be achieved by determining the positions of two de tection points. A high spatial resolution of similar to 0.5 mm is also obtained. We analyze the measurement error caused by the alignment of the parallel interference pattern and a random measurement error caus ed by the phase detection. The theoretical analyses and the experiment al results make the characteristics of the method clear and show that the method has an accuracy of 0.2 arcsec for small rotation angles.