A six-degree-of-freedom measurement system for the motion accuracy of linear stages

This paper presents a new six-degree-of-freedom measurement system (6DMS) which has the capability to measure simultaneously all six motion errors of a linear stage. This system employs three parallel laser beams to detect three relative linear distances of a moving body by Doppler effect so that the positioning, yaw and pitch errors can be separated. With an additional beam splitter and two quadrant photodetectors to detect the lateral shifts of the returned beams, the remaining two straightness errors and roll error can be obtained at the same time. In comparison with the HP5528A system, the accuracy of the positioning error is about 0.01 mu m to the range of 10 m, the straightness error is about 1 mu m within the measuring range of +/-0.1 mm, and angular errors are all about 1 arcsec within the range of +/-50 arcsecs. This system is simple in principle and can be easily equipped to any moving stages, such as linear stages, X-Y tables, CMMs, and machine tools. (C) 1998 Elsevier Science Ltd.