A 6-DEGREE-OF-FREEDOM MEASUREMENT SYSTEM FOR THE MOTION ACCURACY OF LINEAR STAGES

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