Measurements of Long-Gauge Blocks Using Interferometric-Fringe-Counting Method

Abstract

Interferometric measurement method is described of long-gauge blocks using a fringe-counting interferometer with a 633-nm wavelength-stabilized He-Ne laser. Two sub-gauges, which are made of usual gauge blocks with V-type graduation lines, are optically-contacted with the both sides of a long-gauge block. Using the NRLM 2-m line standard automatic measuring-machine, several gauge blocks up to 1 m are measured with a resettability of 50 nm, and they are also measured by using a traditional excess-fractions method. The result shows that this new method can determine the length of gauge blocks up to 2 m, within an accuracy of 0.15 μm.