Self-zero-adjustment of probes in the methods constructing software datum for large profile measurement

This paper presents a new technique to estimate zero-adjustment errors of multiple probes which are used to construct software datum for large profile measurements. Three kinds of software datum are considered, which are the 3-point method, the differential laser autocollimation (DLA) method and the mixed method, respectively. The proposed new technique can estimate the zero-adjustment error by using only the data of profile measurement of the workpiece. Therefore it does not require any reference surface or any reversal measurement process. This paper discusses the accuracy and the reliability of the proposed technique in the profile measurement of a large mirror with a length of about 1 m through theoretical analyses and computer simulations. An experimental system of profile measurement using the DLA method was also constructed.