Demcon has successfully developed an industrial and modern variant of the Nanomefos for Dutch United Instruments. The optomechatronic concept of the Nanomefos was developed by TNO and Eindhoven University of Technology more than ten years ago and is now being further developed by Demcon. Nanomefos stands for Nanometer Accuracy Non‑contact Measurement of Freeform Optical Surfaces. However, a substantial demand for freeform metrology has only arisen in recent years, since the production of optics with aspheric and freeform surfaces really started to take off. Freeform optics are used in lithography, space travel and astronomy, as well as in smartphones and microscopes. This concerns mirrors and lenses that need to be produced with nanometre precision.
Due to its ingenious mechatronic design, Nanomefos forms a state of the art solution with a non-contact measurement principle that provides high measurement speeds. As specialist in the relevant disciplines of metrology, optics and mechatronics, Demcon has delivered the modernisation and industrialisation required for commercial application. The Focal Optomechatronic Systems business unit, in close collaboration with the CTO of DUI, Rens Henselmans, has managed a complete redesign of TNO’s laboratory design and associated software within a short space of time. The emphasis of this redesign was on cost price, robustness, manufacturability and user-convenience.
The first result of the upgrade is the NMF600 S. The 600 refers to the measuring range of 600 mm (diameter). For the target of ten nanometres, Demcon needed a design that achieves extremely high mechanical stability and a sophisticated metrology system. It is also equipped with extensive data processing to eliminate systematic measurement errors.
The design of the optical measurement head is based on a confocal measurement principle. This enables precision measurements to be carried out, even in cases of significant measurement surface tilt compared with the optical measurement head. This results in a greater level of freeform within the measuring range. The link between the optical measurement head and the rotational axis to the ‘fixed world’ has been updated to achieve precision comparable with the TNO prototype, using fewer and simpler components.
The entire system is also more compact, halving the NMF600 S footprint compared with the Nanomefos prototype. Another great advantage is that the NMF600 S can measure untreated glass surfaces. This enables measurements to be carried out at an early stage in lens production and can significantly reduce the manufacturing process time.
Demcon also made sure that the measuring machine is easy to use during the freeform optic production process, and the operation was simplified, in line with the methods and standards used. Tests on all kinds of freeform objects have now demonstrated that the NMF600 S more than satisfies the technical specifications. The first two systems have been delivered successfully, the third is being constructed and a start can soon be made on the development of the NMF350 S and NMF800 S. The ‘350’ is aimed at standard optics, the ‘800’ (and the ‘600’) are mainly intended for special optics in telescopes and applications in space. For the industrial successor of the Nanomefos, the sky’s the limit.
