The Diamond-NOM: A non-contact profiler capable of characterizing optical figure error with sub-nanometre repeatability

We present design and implementation details of the Diamond-NOM (nanometre optical metrology)—a non-contact profiler capable of measuring the surface topography of large (up to 1500 mm long) and heavy (up to 150 kg) optical assemblies with sub-nanometre resolution and repeatability. These levels of performance are essential to fabricate and optimize next generation optics. The capabilities of the Diamond-NOM have already enabled collaborations with optic manufacturers, including production of a preferentially deposited, large (1.2 m), synchrotron mirror with a slope error of ∼0.44 μrad rms and using bimorph technology to reduce figure error of a super-polished (elastic emission machining) optic to <1 nm peak to valley. We demonstrate that the BESSY-NOM scanning pentaprism and autocollimator concept is robust, easily transferable, and repeatable.