A high-sensitivity optical touch trigger probe for down scaled 3D CMMs

Abstract

With the reduction in dimensions of products in the last decade, the need for highly accurate dimensional inspection and measurement increases, which requires down scaled measuring tools. The key element for a powerful down scaled dimensional measuring tool coordinate measuring machine is the downscaled probe. In order to satisfy the ongoing increasing demand for highly accurate geometrical measurements on small parts and small structures, a new measuring probe having high sensitivity and small geometrical dimension with low contact forces needs to be developed. In this paper, a novel probing system, which combines a FBG (Fibre Bragg Grating) embedded optical fibre tactile probe with an optical sensing technique, is proposed for down scaled 3D micro-CMMs. The Bragg wavelength shifts with the strain developed along the fibre once the fibre touches the surface of the part. With high-resolution interferometric wavelength demodulation technology, a resolution of 5nm could be achieved by the FBG integrated system. With the sensor elements integrated into the probe tip directly, the system sensitivity can be increased significantly for 3 dimensional measurements.