Measurements conducted with X-Ray Calibration Interferometer. (News Briefs).

A NIST researcher completed the testing and analysis of several three-flat, five-position measurements with the X-Ray Calibration Interferometer (XCALIBIR) using 300 mm diameter flats. The XCALIBIR is a measurement system that was designed at NIST to have the flexibility to measure flats, spherical, and aspheric optics. The tests were successful and allowed two conclusions to be drawn.

First, the center of the XCALIBIR field of view is affected by substantial noise caused by diffraction in some parts of the XCALIBIR optics. Second, outside the center of the field of view, the repeatability of the flat measurements was between 0.5 nm rms and 1 nm rms. These results are very encouraging and make it clear that elimination of the noise at the center of the XCALIBIR field of view is of paramount importance for the system to meet its goal of 0.25 nm rms accuracy.

Additionally, as part of the analysis of the test data, NIST researchers built the foundation for a MATLAB-based toolbox for phase measuring interferometry (PMI). The toolbox incorporates functionality for all steps of the data analysis chain from phase measurement to visualization. This toolbox will become the only validated, documented, and open reference implementation for many numerical methods and algorithms that are used in PMI. New methods can be easily incorporated into the toolbox and it will be possible to estimate the uncertainty associated with critical data analysis procedures, such as phase unwrapping. Portions of the new toolbox, even in its current early version, exceed the functionality of commercial phase measuring software.

CONTACT: Ulf Griesmann, [phone]; [e-mail].