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

R. Henselmans; D. Nijkerk; M. Lemmen; N. Rijnveld; F. Kamphues

doi:10.1117/12.926484

13 September 2012 Design, analysis, and testing of the optical tube assemblies for the ESO VLT four laser guide star facility

R. Henselmans, D. Nijkerk, M. Lemmen, N. Rijnveld, F. Kamphues

Author Affiliations +

Proceedings Volume 8447, Adaptive Optics Systems III; 84474N (2012) https://doi.org/10.1117/12.926484
Event: SPIE Astronomical Telescopes + Instrumentation, 2012, Amsterdam, Netherlands

Abstract

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.

Citation Download Citation

R. Henselmans, D. Nijkerk, M. Lemmen, N. Rijnveld, and F. Kamphues "Design, analysis, and testing of the optical tube assemblies for the ESO VLT four laser guide star facility", Proc. SPIE 8447, Adaptive Optics Systems III, 84474N (13 September 2012); https://doi.org/10.1117/12.926484

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available