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Abstract. Optical and tactile single scanning probes usually are used in dimensional metrology applications, especially for roughness, form, thickness and surface profile measurements. To perform assessments with nanometre level of accuracy, specific ultra-high precision machines have been developed by the National Metrology Institutes (NMIs) such as the LNE, VSL, METAS, SMD, generally in collaboration with industrials and academics partners. Such developments are not devoted only to NMIs but many industrials develop and commercialize their own ultra-high precision machines as the IBSPE and TNO companies. All these machines provide optical and tactile precise measurements and cover a large domain of application such as the form's characterization of optical lenses. In this paper the performance and capability of ultra-high precision machines of some National Metrology Institutes (LNE, VSL, SMD and METAS) and industrials companies (TNO and IBSPE), involving together in the IND10 European EMRP project titled "Optical and tactile metrology for absolute form characterization", will be detailed. Theirs probing systems and accuracies levels will be evoked. Relevant results especially for measuring optical lenses will be also presented and discussed.

The breakthrough of freeform optics is limited by manufacturing and metrology technology. However, today's manufacturing machines like polishing robots and diamond turning machines are accurate enough to produce good surface quality, so the question is how accurate can a freeform be produced. To investigate how accurate freeform optics can be diamond turned, measurable freeforms (e.g. an "off-axis" sphere) were diamond turned and they were compared to there on-axis equivalents. The results of this study are described in this paper. Furthermore, an overview of the accuracies of freeform optics that TNO diamond turned are presented. An indication of freeform accuracy for diamond turned optics is derived from this, which can be used for optical designers as a guideline in their design work.

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 ∅500 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.