Flexible manufacturing of large aspheres for VLT's Optical Tube Assemblies

Gubbels, G.; Henselmans, R.; Drunen, C. van

doi:10.1117/12.893843

Cited by 4 publications

(3 citation statements)

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“…The second artefact was much larger in size compared to the small asphere described above. It was manufactured by TNO as a prototype lens used for the Optical Tube Assembly (OTA) applied for the Laser Guide Star Facility in the ESO Very Large Telescope [6], see figure 2.…”

Section: Large Conical Convex Lensmentioning

confidence: 99%

Comparison of asphere measurements by tactile and optical metrological instruments

Bergmans

Nieuwenkamp

Kok

et al. 2015

Meas. Sci. Technol.

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A comparison of topography measurements of aspherical surfaces was carried out by European metrology institutes, other research institutes and a company as part of an European metrology research project. In this paper the results of this comparison are presented. Two artefacts were circulated, a small polymer coated aspherical lens with a clear aperture of about 12 mm, and a large conical convex lens with a clear aperture of 300 mm developed for the ESO Very Large Telescope. The participating laboratories were allowed to follow their own measurement strategies. Both tactile and optical measuring instruments were used, as well as single point and imaging techniques. The measured data were compared with respect to the root-mean-square (RMS), peak-to-valley and Zernike polynomial representations of the measured deviations from the nominal shape. The comparison shows for five out of eight measuring instruments/methods a very good agreement of the measured topographies within 14 nm (RMS).

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Section: Large Conical Convex Lensmentioning

confidence: 99%

Comparison of asphere measurements by tactile and optical metrological instruments

Bergmans

Nieuwenkamp

Kok

et al. 2015

Meas. Sci. Technol.

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“…The 4 LGSF consists of a high power 25 W CW 589 nm laser, a Beam Conditioning and Diagnostics System (BCDS) and an Optical Tube Assembly (OTA). TNO has developed the OTA laser launch telescopes and successfully demonstrated its performance under operational conditions.…”

Section: The Eso Vlt 4lgsfmentioning

confidence: 99%

“…The fabrication of L2 is described in more detail in [4], a summary is given here. The aspherical L2 lenses were manufactured using TNO's unique manufacturing facilities for aspherical and freeform optics.…”

Section: L2 Fabricationmentioning

confidence: 99%

Design, analysis, and testing of the optical tube assemblies for the ESO VLT four laser guide star facility

et al. 2012

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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 requirements on output wavefront quality, thermally induced defocus under operational conditions, absolute pointing accuracy and polarization extinction ratio (PER).TNO applied its corrective polishing in combination with the NANOMEFOS measurement machine to produce the ∅380 mm aspherical output lens, resulting in 20 nm rms output wavefront quality. The thermal behaviour of the system has been analyzed by combining optical, lumped mass and FE analyses. A design that is passively athermalized over a large temperature range as well as under the influence of thermal gradients has been developed. Extensive thermal testing has shown a thermally induced defocus of less than 0.15 waves under the operational conditions of 0-15°C and upto -0.7°C/hr gradient. A custom tip-tilt mechanism was designed to steer the output beam over a 4.8 arcmin radius, with less than 0.1" (3σ) accuracy at 1 Hz update rate. The PER was also measured under operational (thermal and tilt) conditions and demonstrated to be well above 99%. This paper describes the design, modelling and analysis, and the test results of these instruments.

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System performance of the laser projection system (LPS) for the ELT

Nijenhuis,

Kamphues,

van Riel

et al. 2024

Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation VI

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Presently TNO/Demcon are manufacturing nine Laser Projection Systems (LPS). TNO is responsible for the design and manufacturing of the Optical Tube Assembly (OTA), the baseplate and the LPS cover. Demcon designed and manufactured the Beam Conditioning and Diagnostic System (BCDS). TNO is also responsible for the system performance and its verification tests. Six units will be used on the ELT. The other three are destined for the VLT. That will allow the operation of the adaptive mirrors enabling unprecedented image quality of the telescopes. The design of this system is based on the four laser guide stars units as used on the VLT. The system has been upgraded considerably compared to the units used for the VLT. Its FOV has increased to 7 arcmin (half cone). The laser power goes up to 50W and the BCDS has been completely redesigned. The BCDS is located between the laser source and the OTA that produces the Ø300 mm output beam. Maintainability and accessibility of the system have also been much improved. Prime qualities are its insensitivity to temperature changes (static and dynamic), its accuracy and its FOV. Assembly of the first unit is finished and in January the acceptance testing of the system started. The first unit is expected to be delivered to ESO in autumn 2024.

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Flexible manufacturing of large aspheres for VLT's Optical Tube Assemblies

Cited by 4 publications

References 0 publications

Comparison of asphere measurements by tactile and optical metrological instruments

Comparison of asphere measurements by tactile and optical metrological instruments

Design, analysis, and testing of the optical tube assemblies for the ESO VLT four laser guide star facility

System performance of the laser projection system (LPS) for the ELT

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