Uncertainty analysis of a six-degree-of-freedom surface encoder for a planar motion stage

This paper presents an uncertainty analysis of a six-degree-of-freedom surface encoder, which is designed to measure multi-degree-of-freedom motion of a planar motion stage with a single laser beam. Since the surface encoder is composed of an optical sensor head and a two-axis scale grating, optical misalignments in the sensor head and form errors of the scale grating will affect the measurement uncertainty. In this paper, aiming to achieve further accurate measurement of translational displacement, an uncertainty budget table is built for the X-directional translational displacement measurement, while considering the above mentioned uncertainty sources.