Following installation of the interferometer by Hexagon Metrology, Andrew Lewis from NPL's Dimensional Measurement group travelled to QAFCC to deliver training in the calibration of gauge blocks by interferometry.
The NPL gauge block interferometer was designed and licensed to Hexagon Metrology nearly 30 years ago and several iterations and variations of the basic design were produced. The latest version of the instrument used a phase-stepping technique to measure the surface topography of the gauge block, as well as a dual laser system to determine the absolute length. Uncertainties of around 20 to 30 nanometres can be achieved on gauge blocks up to 100 millimetres in length.
The C++ instrument control software, developed at NPL, is also sold through Hexagon Metrology, and stabilised lasers used in the interferometers are manufactured by Hexagon under NPL licence. Instruments and lasers based on NPL designs have been sold to 28 different countries worldwide, with typical customers including National Measurement Institutes, accredited laboratories and high technology laboratories and organisations.