One of the most elusive measurement elements in gage block interferometry is the correction for the phase change on reflection. Techniques used to quantify this correction have improved over the years, but the measurement uncertainty has remained relatively constant because some error sources have proven historically difficult to reduce. The Precision Engineering Division at the National Institute of Standards and Technology (NIST) has recently developed a measurement technique that can quantify the phase change on reflection correction directly for individual gage blocks and eliminates some of the fundamental problems with historical measurement methods. Since only the top surface of the gage block is used in the measurement, wringing film inconsistencies are eliminated with this technique thereby drastically reducing the measurement uncertainty for the correction. However, block geometry and thermal issues still exist. This paper will describe the methods used to minimize the measurement uncertainty of the phase change on reflection evaluation using a spherical contact technique. The work focuses on gage block surface topography and drift eliminating algorithms for the data collection. The extrapolation of the data to an undeformed condition and the failure of these curves to follow theoretical estimates are also discussed. The wavelength dependence of the correction was directly measured for different gage block materials and manufacturers and the data is presented.
Proceedings Title: Proceedings of SPIE, Recent Developments in Optical Gauge Block Metrology, Jennifer E. Decker, Nicholas Brown, Editors
Conference Dates: July 20, 1998
Conference Location: San Diego, CA
Conference Title: Phase Change And Surface Roughness Effects
Pub Type: Conferences
deformation, gage block, interferometry, phase change correction, thermal drift, wringing layer