Development of a Double-Ended Gauge Block Interferometer for Measurement of the Absolute Length

Abstract

The work presented in this thesis describes a prototype version of a double-ended interferometer built at Physikalisch-Technische Bundesanstalt (PTB) for measuring the length of short as well as long gauge blocks. In this setup, more than one wavelength is used which makes this interferometer much more effective for accurate extraction of the integer orders of interference. A special design for the light source is found to allow the same adjustment states at the different wavelengths. The PTB double-ended interferometer prototype shows consistent results for the two wavelengths used and a good agreement with well-established PTB gauge block interferometers (INKO5 and Koster). The current uncertainty of the double-ended interferometer prototype is limited by the gauge block temperature deviation from the reference temperature of 20.000 °C. The phase change on reflection of steel gauge blocks is measured using the stack method. It shows a good agreement with the calculated ones. The phase correction of ceramic gauge block is estimated from the difference between the double-ended interferometer and the INKO5 measurement results and is measured using the stack method. Its value is compatible with the values reported in the literature using the same method. The good experimental results introduce this interferometer as a traceable tool for other gauge block length interferometers.