A non-Michelson type three-axis grating interferometer using linear scale gratings

A non-Michelson type grating interferometer with multiple measurement beams is proposed to make three-axis displacement measurements using a combination of four linear scale gratings instead of a planar grating scale. The configuration of the optical system and the measurement principle are described. A theoretical uncertainty evaluation is conducted to evaluate the influence of the grating installation errors. The result indicates that when the angular installation error of the gratings is <0.1°, the corresponding measurement uncertainty is on the order of 10 nm within a 10 mm measurement range. Finally, the feasibility of three-axis displacement measurement is demonstrated experimentally.