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Nanometer level freeform surface measurements with the NANOMEFOS non-contact measurement machine

Author: Henselmans, R. · Cacace, L. · Ramer, G. · Rosielle, P.C.J.N. · Steinbuch, M.
Institution: TNO Industrie en Techniek
Source:Burge, J.H.Fähnle, O.W.Williamson, R., Optical Manufacturing and Testing VIII, 4 August 2009 through 5 August 2009, San Diego, CA, 7426
Proceedings of SPIE - The International Society for Optical Engineering
Identifier: 242588
doi: doi:10.1117/12.826067
ISBN: 9780819477163
Article number: 742606
Keywords: Instruments · Asphere · Freeform · Measurement · Metrology · NANOMEFOS · Non-contact · Optics · Asphere · Freeform · Metrology · NANOMEFOS · Non-contact · Computer software · Optical systems · Probes · Surface measurement · Uncertainty analysis · Measurements


Applying aspherical and freeform optics in high-end optical systems can improve system performance while decreasing the system mass, size and number of required components. The NANOMEFOS measurement machine is capable of universal non-contact and fast measurement of aspherical and freeform optics up to Ø500 mm, with an uncertainty of 30 nm (2σ). In this machine, the surface is placed on a continuously rotating air bearing spindle, while a specially developed optical probe is positioned over it by a motion system. A separate metrology system measures the probe and product position relative to a metrology frame. The prototype realization, including custom electronics and software, has been completed. The noise level at standstill is 0.88 nm rms. A reference flat was measured with 13 μm and 0.73 mm tilt. Both measurements show an rms flatness of about 8 nm rms, which correspond to the NMi measurement. A hemisphere has also been measured up to 50° slope, and placed 0.2 mm eccentric on the spindle. These measurements reproduce to about 5 nm rms. Calibration and software are currently being improved and the machine is applied in TNO aspherical and freeform optics production. © 2009 SPIE.