HIGH-ACCURACY, WIDE-RANGE, ROTATION ANGLE MEASUREMENT BY THE USE OF 2PARALLEL INTERFERENCE PATTERNS

Eased on the idea of measuring small rotation angles with a parallel i nterference pattern (PIP), a method is developed to measure large rota tion angles accurately. Two parallel PIP's that have different periods are used to measure a rotation angle of an object. The measurement ma de with a small-period PIP provides a high accuracy, and the measureme nt made with a large-period PIP provides a wide range. An accurate mea surement for wide-range angles is made by combining the two measured v alues. The accuracy of the phase detection is determined by the period s of two PIP's. Rotation angles from approximately -30 to 30 are min c an be measured with an accuracy of 0,2 are sec. Analytical results are supported by experimental results. (C) 1997 Optical Society of Americ a.