A six-degree-of-freedom surface encoder for precision positioning of a planar motion stage.

Highlights: [•] A multi-axis surface encoder, which can measure 6-DOF motions of a planar motion stage, has been developed. [•] It has been verified that the surface encoder could distinguish 2nm step motions in the Δx-, Δy- and Δz-directions. [•] It has been verified that the surface encoder could distinguish 0.1arcsecond step motions in the θx- and θy-directions, 0.3arcsecond step motion in the θz-direction. [•] The peak-to-valley amplitudes of the interpolation errors were less than ±7nm in X-, Y- and Z-directions, respectively. [•] Nonlinear error components were within 2.5arcseconds for θ x , θ y and θ z , respectively. [ABSTRACT FROM AUTHOR]