Techniques of multi-degree-of-freedom measurement on the linear motion errors of precision machines

Any axis of precision machines possesses six-degree- of-freedom (6-DOF) motion errors, also called the geometric errors, due to manufacturing tolerances and assembly errors, namely three linear and three angular errors. Conventional optical instruments allow measurement of only one or two errors at a time. In order to achieve fast measurement, many multi-degree-of-freedom measurement (MDFM) systems have been developed over the past 20 years, from three-degree-of-freedom (3-DOF) to 6-DOF. This article summarizes reports of optical measurement techniques of MDFM systems for precision linear, planar and XYZ stages. Comments are also given for the applicability to practical uses.