A novel method of a six-degree-of-freedom (DOF) posture measurement in a linear stage by employing a single unit of an optical encoder is introduced.
This method consists of a diffractive optical element, a corner cube, four separate two-dimensional position-sensitive detectors, four photodiodes and auxiliary optics components
The circularly polarizing interferometric technique was integrated to measure the displacement of the stage along the traveling axis in a robust manner.
With a single travel of the stage, it provided a six-DOF motion error with a high resolution, less than 0.03 arcsec, 20 nm and 0.4 nm for angular errors, dY and dZ, and dX, respectively, at the same time.
Measurement Science and Technology, Vol.22, 105901