Non-contact ultra-precision metrology of superfine cylinders with a developed two-dimensional coordinate measuring device

To address the issue of measuring force of a stylus that can move and/or hook up the measured workpiece with a small dimension in the contact measurement, a spectral confocal displacement sensor and an ultra-precision linear stage are employed to develop a two-dimensional coordinate measuring machine instead of the conventional stylus contact measurement to avoid the measuring force problem, by which the non-contact ultra-precision metrology can be achieved. A coordinate modeling-dividing method is proposed for the diameter and roundness measurement of the small cylindrical workpieces with a diameter of 0.5 mm and length of 50 mm, whose cross-sectional circle is divided into several equal arcs to be scanned by the developed two-dimensional coordinate measuring machine. Thus, a set of arcs, each of which consists of large numbers of coordinate points, can be obtained. The radius of each arc can be fitted by the least square method, and the arc profile can be characterized by a series of data processing. The diameter and roundness of the measured workpiece can be obtained by averaging these fitted arcs' radii and stitching these arc profiles together, respectively. A preliminary measurement uncertainty analysis is carried out to verify the developed device and proposed method.