At the National Institute of Standards and Technology, our best capability for angle measurement is our Advanced Automated Master Angle Calibration System (AAMACS). This instrument is based on a triple-stack of indexing tables, used in conjunction with either an autocollimator or with a phase-stepping interferometer for small-angle measurement. The phase stepping interferometer has sufficient flexibility that it allows many sources of uncertainty to be quantified more convincingly than can be done when using an autocollimator. This is potentially important because autocollimator errors (which are difficult to quantify) often cause the instrument to misinterpret the angle between non-flat faces of an artifact, as evidenced by the fact that different autocollimators may give different results for the measured angle. We have not yet observed any clear differences between our autocollimator and interferometer measurements. This is particularly surprising because our two instruments implement slightly different definitions of the angle between two imperfect surfaces, so that for certain artifact geometries one can expect to get different results even if both instruments work perfectly.
Physikalisch-Technische Bundesanstalt (PTB) | 186th | Proceedings PTB-Seminar 186: Requirements and Recent Developments in High Precision Angle Metrology
The Advanced Angle Metrology System at NIST, Physikalisch-Technische Bundesanstalt (PTB) | 186th | Proceedings PTB-Seminar 186: Requirements and Recent Developments in High Precision Angle Metrology
(Accessed December 4, 2023)