Nanometre-accurate form measurement machine for E-ELT M1 segments

To enable important scientific discoveries, ESO has defined a new ground-based telescope: the European Extremely Large Telescope (E-ELT). The baseline design features a telescope with a 39-m-class primary mirror (M1), making it the largest and most powerful telescope in the world. The M1 consists of 798 hexagonal segments, each about 1.4 m wide,...

Design of a nanometer-accurate form measurement machine for segmented large telescope mirrors

EXTREMELY LARGE TELESCOPES. The planned extremely large telescope observatories with segmented giant primary mirrors will require metrology with nanometer accuracy. The two extremely large ground telescopes, the European Extremely Large Telescope (E-ELT [2]) and Thirty Meter Telescope (TMT [3]), feature telescopes with 39 meter and 30 meter...

Design of an E-ELT M1 segment measurement machine with nanometer accuracy

The baseline design of the European Extremely Large Telescope features a telescope with a 39-meter-class primary mirror (M1), consisting of 798 hexagonal segments. A measurement machine design is presented based on a non-contact single-point scanning technique, capable of measuring the form error of each segment with nanometer uncertainty, fast,...

The TROPOMI telescope: Design, fabrication and test of a freeform optical system

In this paper, we discuss the two-mirror pushbroom telescope for TROPOMI. Using freeform optics, it has unprecedented resolution. The complete cycle of freeform optical design, analysis, manufacturing, metrology and functional test on a breadboard setup is described, focusing on the specific complexities concerning freeforms. The TROPOMI flight...

Manufacturing of high precision aspherical and freeform optics

Aspherical and freeform optical elements have a large potential in reducing optical aberrations and to reduce the number of elements in complex high performance optical systems. However, manufacturing a single piece or a small series of aspherical and freeform optics has for long been limited by the lack of flexible metrology tools. With the...

Design, analysis and testing of the Optical Tube Assemblies for the ESO VLT Four Laser Guide Star Facility

TNO has developed the Optical Tube Assemblies (OTAs) for the ESO VLT Four Laser Guide Star Facility. The OTAs are Galilean 20x beam expanders, expanding a ∅15 mm input beam (25W, 589 nm CW) to a steerable ∅300 mm output beam. TNO has recently successfully completed acceptance testing of the four units, showing compliance to the challenging...

Manufacturing of high precision aspherical and freeform optics

Aspherical and freeform optical elements have a large potential in reducing optical aberrations and to reduce the number of elements in complex high performance optical systems. However, manufacturing a single piece or a small series of aspherical and freeform optics has for long been limited by the lack of flexible metrology tools. With the...

The NANOMEFOS non-contact measurement machine for freeform optics

Aspherical and freeform optics are applied to reduce geometrical aberrations as well as to reduce the required number of components, the size and the weight of the system. To measure these optical components with nanometre level uncertainty is a challenge. The NANOMEFOS machine was developed to provide suitable metrology (high accuracy,...

Creating artificial stars: Optical tube assemblies for ESO VLT four laser guide star facility

Athermal design of the optical tube assemblies for the ESO VLT four laser guidestar facility

TNO is developing the Optical Tube Asssemblies (OTAs) for the ESO VLT Four Laser Guide Star Facility. The OTAs are Galilean 20x beam expanders, expanding a Ø15 mm input beam to a steerable Ø300 mm output beam with a wavefront quality requirement of 50 nm rms. The allowed defocus under the influence of the changing environmental air temperature ...

Athermal laser launch telescopes

ESO has developed a concept for a compact laser guide star unit for use in future Adaptive Optics (AO) systems. A small powerful laser is combined with a telescope that launches the beam, creating a single modular unit that can be mounted directly on a large telescope. This approach solves several of the stability problems experienced with a...

A tip / tilt mirror with large dynamic range for the ESO VLT Four Laser Guide Star Facility

One of the critical elements in the Four Laser Guide Star Facility (4LGSF) for the ESO Very Large Telescope (VLT) is the Optical Tube Assembly (OTA), consisting of a stable 20x laser beam expander and an active tip/tilt mirror, the Field Selector Mechanism (FSM). This paper describes the design and performance testing of the FSM. The driving...

Application of the NANOMEFOS non-contact measurement machine in asphere and freeform optics production

The NANOMEFOS machine is capable of fast, non-contact and universal measurement of aspheres and freeforms, up to ø500 mm with a measurement uncertainty below 30 nm (2σ). It is now being applied in asphere and freeform production at TNO.

Development and performance demonstration of the NANOMEFOS non-contact measurement machine for freeform optics

This paper shows the machine concept, the realization and the test results of the completed NANOMEFOS non-contact measurement machine for freeform optics. The separate short metrology loop results in a stability at standstill of 0.9 nm rms over 0.1 s. Measurements of a tilted flat show a repeatability of 2-4 nm rms, depending on the applied tilt...

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

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)....

Accuracy of freeform manufacturing processes

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...

Design, realization and testing of the nanomefos non-contact measurement machine for freeform optics

By applying freeform optics (figure 1) in high-end optical systems such as used in space, science and lithography applications, system performance can be improved while decreasing the system mass, size and number of required components (for instance [1]). The applicability of classical metrology methods is limited for freeform surfaces, which is...

Design of a machine for the universal non-contact measurement of large free-form optics with 30 nm uncertainty

A new universal non-contact measurement machine design for measuring free-form optics with 30 nm expanded uncertainty is presented. In the cylindrical machine concept, an optical probe with 5 mm range is positioned over the surface by a motion system. Due to a 2nd order error effect when measuring smoothly curved surfaces, only 6 position...