Construction of a robust three-degree-of- freedom laser measurement system for measuring motion error of long-travel linear stages

This paper presents a robust and low-cost three-degree-of-freedom laser measurement system (3DOFLMS) that can measure both straightness error and roll angular error of long-travel linear stages. A low-cost laser diode is adopted as the laser source. A beam drift compensation module is employed to improve the stability of the 3DOFLMS. The relationships between the sensitivity of detector, the dual-beam parallelism and the measurement distance along the laser propagation direction are theoretical analyzed. Compensation methods are then proposed for eliminating the effects of detector sensitivity variation, beam drift and misalignment on the accuracy of the measurement system. The effectiveness of the compensation methods and the feasibility of the designed measurement system are demonstrated by a series of experiments. With the comparisons between commercial measurement instruments and the proposed measurement system in the measurement distance up to 1 m, the measurement accuracy of straightness errors and roll angular error are within +/- 1.0 mu m and +/- 1.2 arcsec, respectively. The designed measurement system is very easy to construct both in the laboratory environment and in the actual measurement environment.