This paper presents a real-time correction method of the movement errors of a translatory precision machine axis. This method is a null-balance technique in which two plane mirrors are used to generate an interferometric fringe pattern utilizing the optical principles of Twyman-Green interferometry. One mirror is fixed on a reference frame, while the other is placed on the machine axis being supported by three piezoelectric actuators. From the fringe pattern, one translatory and two rotational error components of the machine axis are simultaneously detected by using CCD camera vision and image processing techniques. These errors are then independently suppressed by activating the peizoelectric actuators by real-time feedback control while the machine axis is moving. Experimental results demonstrate that a machine axis can be controlled with movement errors less than 10nm in vertical straightness, 0.1arcsec in pitch, and 0.08arcsec in roll for 50mm travel by adopting the real-time correction method.
