Pixel Based Absolute Topography Test for Three Flats
R E. Parks, Lianzhen Shao, Christopher J. Evans
We demonstrate a new method of performing the absolute three flat test using reflection symmetries of the surfaces and an algorithm for generating the rotation of arrays of pixel data. Most of the operations involve left/right and top/bottom flips of data arrays, operations that are very fast on most frame grabbers and are available on most commercial phase measuring interferometers. We demonstrate the method with simulated data as well as with actual data from 150 mm diameter surfaces that are flat to better than 25 nm peak-to-valley.
absolute testing, interferometry, optical testing, surface metrology, three-flat test