Something didn't ring true here, so I did a quick check of the Ion Beam Figuring literature, and almost without exception IBF facilities used interferometric data to build a beam time erosion matrix....and then apply two or three iterations, (interferometrically checking after each pass) of the ion beam to achieve effectively molecular level precision.....not a mention knife edge test anywhere..... gosh
Quote:
Originally Posted by Satchmo
Ion beam milling still relies on feedback results from a Null test ( usually autocollimation against a large flat for Cassegrains) and the results showing where glass needed to be polished off would be just as obvious to a skilled optician using a humble knife edge at the Null focus, as placing an interferometer.
|