A Diameter Measuring System with Laser Interferometer

INTRODUCTION The diameter measurement of ring, plug and sphere is very important in dimensional metrology. The measurement of diameter is generally carried out by a comparison method using a ring gauge comparator. Recently the commercial comparators using laser interferometer or precision linear encoder were introduced. The accuracies of these instruments are larger than 0.5 μm. A laboratory uses the coordinate measuring machine cooperating a laser interferometer and a precision probe. It provides good performance but has a limitation on operation as coordinate measuring machine. However the comparison method requires a reference gauge block, which is traceable to meter unit. So this method is time-consuming due to wringing gauge block. And it is not accurate comparing to the absolute method. So several national metrology laboratories (NMLs) designed and fabricated their own equipment using a laser interferometer.[1,2]