Flexible and fast non-contact measurement of a large off-axis non-circular AR-coated freeform optic
On demand | Presented live 18 October 2021
The NMF600 S non-contact measurement machine for freeform optics by Dutch United Instruments (DUI) was used to measure a large concave surface with a polygon outside contour with typical diagonal of 250 mm. The surface is a higher order freeform off-axis surface, which was measured centered on the table. The total non-rotationally symmetric freeform departure during this measurement was 3.5 mm PV. Moreover, the surface has an anti-reflective coating. Depending on the pointspacing and measurement aperture, the measurements take between 7 and 23 minutes. They show a repeatability of well below 5 nm rms on a total form error after 6DOF fitting of 1.53 um rms. The pointspacing of 0.1 mm clearly shows the mid-spatial errors and raster polishing residuals.
Dutch United Instruments (Netherlands)
Rens Henselmans studied Mechanical Engineering at Technische Universiteit Eindhoven, and graduated on the concept design of a measurement machine for freeform optics in 2003. This development was continued in a PhD project, resulting in a working prototype machine in 2009. He then moved to TNO, together with the machine, and worked there as a system architect on various space and astronomy instruments, while also continuing work on the machine. From 2013 to 2017 he worked as system architect at NTS-Group on semicon and medical projects, from prototype to series production ready products. In 2018 he joined DUI as CTO for the development and commercialization of the NMF measurement machine, which is based on his graduation concept.