w millimeters. In addition, local angles in the surface lead to measurement errors. That is why a dual-stage probe was developed by a fellow PhD student Lennino Cacace, which makes the probe head constantly follow the surface. This makes it possible to also measure freeform shapes at a very high speed, because the fast-moving mass is low.
In addition to 2 PhDs (Henselmans and Cacace), about 20 people worked on the project to develop NANOMEFOS, including students, optical and mechanical designers and instrument manufacturers. The result was a working machine that was able to measure a freeform surface twice, with the same result down to the nanometer. However, there was no time and budget left for developing a user interface and calibration. Hence Henselmans joined TNO, and the machine was moved to the optics manufacturing department there. He worked as a system architect for astronomy and space, and further developed the user interface for NANOMEFOS. Three years later, the device was calibrated and had working software for aspherical forms and freeforms, with which the people of optics manufacturing could independently take measurements.
Between 2009 and 2018 the prototype was used in all kinds of projects at TNO. The lenses of the ESO VLT OTA Ø380 mm beam expander and the ESA TROPOMI freeform telescope on Sentinel 5P were measured with this machine
A new beginning
Gerard van den Eijkel (currently CEO of DUI) brought new life into the development. In 2016 he was the Managing Director of Demcon Focal. Demcon was asked by TNO for a possible copy of NANOMEFOS. However, to make a single machine was too expensive. A number of Asian parties showed interest in NANOMEFOS in the same year. With the orders from a Chinese distributor of optical equipment, Demcon created a business together with TNO.
Demcon and TNO decided to set up a new company, called Dutch United Instruments, in order to emphasize its Dutch origin. In addition, ‘DUI’ means ‘correct’ in Chinese. Van den Eijkel decided that it would be wise to contact Henselmans and to have an advisory role. Henselmans, who then worked at NTS, was immediately enthusiastic, but an advisory role would not be sufficient so he decided to work full-time for DUI.
In retrospect, Henselman’s expertise was indispensable. He devoted himself to redesigning the machine. Because of his extensive experience, he knew exactly what was good and what needed to be better. The new machine branded as NMF is much more user friendly, the cost price is reduced, the robustness is increased and the design is more suitable for series production, while the accuracy of the prototype from 2009 is maintained. Also the design is scalable for larger and smaller variants and there is room to add options in the future.