A contact probe based on multi-focus spectral confocal method for in-site measurement of form and position errors of complex surface workpieces

In order to measure the geometry of the workpiece, many contour measuring instruments have been used, such as coordinate measuring machines and cylindrometers, which are essentially in the form of offline inspection and cannot fulfill the needs of in situ measurement. For workpieces with complex structures, such as hemispherical resonators, the measurement capabilities are limited. In this paper, a contact probe based on the multi-focus spectral confocal method is proposed for in situ measurement of shape and position errors of complex surface workpieces. The position of the stylus's ruby sphere in space is detected by the mirror at the top of the stylus. The flexible hinge connects the probe and the stylus through internal and external clamping. Spectral confocal-based measurement points are used to detect the z-direction displacement and tilt of the mirror. The maximum allowable force, the minimum activation force, and the dynamic characteristics of the probe are calculated by simulation. The mathematical coordinate model of the probe is established and calibrated. The optical measurement accuracy based on the multi-focus spectral confocal method is 0.126 μm. The roundness of the needle gauge and the hemispherical resonator is measured. The roundness of the stylus is measured using a Mahr cylindricity gauge and a contact probe, respectively, and the efficacy of the contact probe has been verified. Using the contact probe to measure the roundness of the outer spherical shell of the hemispherical resonator in situ, the feasibility of the contact probe in situ measurement has been verified.