Pitch deviation evaluation of a diffraction grating based on angles of diffraction of diffracted laser beams

Abstract

An optical setup for measurement of the pitch deviation of a scale grating based on a new measurement principle is designed and developed in this paper. In the setup, a pair of laser autocollimation unit is employed for detecting the changes in angles of diffraction of the positive and negative first order diffracted beam. Through the arithmetic operation with the obtained information of the changes in angles of diffraction of the positive and negative first-order diffracted beams, the influences of the angular error motion and the local slope of a scale under measurement can be cancelled. Basic performances of the developed optical setup are evaluated in experiments. In addition, the developed setup is applied for evaluating a scale grating with a nominal pitch of 1.6 μm.