Dr. Andrew J. Lewis Profile

Dr. Andrew J. Lewis

Principal Research Scientist at National Physical Lab

SPIE Involvement:

Author

Proceedings Article | 26 June 2017 Paper

Development of a high-accuracy multi-sensor, multi-target coordinate metrology system using frequency scanning interferometry and multilateration

B. Hughes, M. Campbell, A. Lewis, G. Lazzarini, N. Kay

Proceedings Volume 10332, 1033202 (2017) https://doi.org/10.1117/12.2273644

KEYWORDS: Metrology, Interferometry, Calibration, Sensors, Distance measurement, Computing systems, Spherical lenses, Glasses, Retroreflectors

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Proceedings Article | 6 July 2006 Paper

A swing arm profilometer for large telescope mirror element metrology

M. Callender, A. Efstathiou, C. King, D. Walker, A. Gee, A. Lewis, S. Oldfield, R. Steel

Proceedings Volume 6273, 62732R (2006) https://doi.org/10.1117/12.671304

KEYWORDS: Profilometers, Metrology, Mirrors, Optics manufacturing, Aspheric lenses, Optical spheres, Surface finishing, Optical sensors, Telescopes, Interferometry

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The next generation of ground-based extremely large telescopes of 30 m to 100 m aperture calls for the manufacture of several hundred sub-aperture segments of 1 m to 2 m diameter. Each annulus of the overall aperture is formed from separate elements of the appropriate off-axis conic section (usually a paraboloid). Manufacture of these segments requires a systematic approach to in- and post-process metrology for all stages of manufacture, including the grinding stage, despite the fact that the resulting ground surface is generally not amenable to optically reflective measurement techniques. To address the need for measurements on such 1 m to 2 m telescope segments, a swing arm profilometer has been constructed as part of a collaborative project between University College London (UCL) and the UK National Physical Laboratory (NPL). The current swing-arm profilometer is intended as a proof-of-concept device and has the capability to measure concave and convex surfaces of up to 1 m in diameter with a minimum radius of curvature of 1.75 m for concave and 1.25 m for convex surfaces. Results will be traceable to national length standards. Principles of the swing-arm instrument will be described together with the mechanics of the arm design, its bearing and adjustment arrangements and surface probe options. We assess the performance requirements of 20 nm RMS form measurement accuracy in the context of the tolerances of the selected profilometer components, the error budget, and preliminary system measurements. Initial results are presented with a Solartron linear encoder. We also plan to mount optical sensors on the end of the arm as an alternative to traditional contact probes. Initially these will include an Arden AWS-50 wavefront curvature sensor and a Fisba μ-phase interferometer. The method of attachment of the Arden AWS-50 is outlined. The swing arm profilometer is to be located at a specialised facility, the OPtiC Technium, Denbigh, North Wales, where it will form part of a tool-kit of metrology and polishing devices for researching the production of large aspheric surfaces.

Proceedings Article | 20 November 2003 Paper

Fully traceable miniature CMM with submicrometer uncertainty

Andrew Lewis

Proceedings Volume 5190, (2003) https://doi.org/10.1117/12.503349

KEYWORDS: Interferometers, Calibration, Metrology, Autocollimators, Mirrors, Sensors, Optical spheres, Capacitance, 3D metrology, Motion measurement

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Conference Committee Involvement (2)

Recent Developments in Traceable Dimensional Measurements III

31 July 2005 | San Diego, California, United States

Recent Developments in Traceable Dimensional Measurements II

4 August 2003 | San Diego, California, United States

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