High-Accuracy Absolute Length Measurement Using an Optical-Comb Pulsed Interferometer: Verification of Coordinate Measuring Machines

Abstract

The optical frequency comb has become a standard for length and frequency measurements. Its pulsed laser can produce temporal coherence interference fringe patterns, and these fringes can be used as the length standard for practical measurement of absolute lengths. This research aims to develop a measuring system for coordinate measuring machine (CMM) verification, which can be used to measure the absolute length of a target in three dimensions. Thus, a spherical target has been considered. A ball lens with a refractive index of 2.0 has been selected as the target for the interferometer in this study. Using the ball lens target, the absolute length can be measured up to 10 m, covering the medium- to large-sized range of CMM applications. The experimental results demonstrate that the measurement uncertainty is smaller than that of the artifact test. In addition, the measurement time of the proposed method is 60% less than that of the artifact-test method.