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Measuring Long Gage Blocks with the NIST Line Scale Interferometer



John S. Beers


An improved method for temporarily converting long gage blocks into line scales is described. The new process employs fused silica rather than previously used steel conversion gage blocks. Conversion blocks are pairs of small (13 mm) gage blocks with graduation lines on their side faces. When the pair is wrung to a long gage block, one at each end with the graduated faces upward, the long block becomes a line scale. Converted blocks can be measured by fringe counting (dynamic) interferometry in the NIST line scale interferometer. This measurement can serve as an independent long block measurement, or it can be used to establish the order of interference for measuring a long block by single wavelength static interferometry. The new conversion blocks have several advantages as shown by experimental evidence. Measurement uncertainties of the static and dynamic interferometric processes are compared.
Technical Note (NIST TN) - 1410
Report Number


gage blocks, interferometry, length, line scales, uncertainty


Beers, J. (1995), Measuring Long Gage Blocks with the NIST Line Scale Interferometer, Technical Note (NIST TN), National Institute of Standards and Technology, Gaithersburg, MD (Accessed April 17, 2024)
Created January 1, 1995, Updated February 19, 2017