A swing arm profilometer for large telescope mirror element metrology

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

Research output: Chapter in Book/Report/Conference proceedingConference contribution

6 Citations (Scopus)

Abstract

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 l 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 (NFL). 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 l 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 u-phase interferometer. The method of attachment of the Arden AWS-SO 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.

Original languageEnglish
Title of host publicationOptomechanical Technologies for Astronomy
Subtitle of host publicationSPIE Astronomical Telescopes and Instrumentation 2006
EditorsEli Atad-Ettedgui, Joseph Antebi, Dietrich Lemke
PublisherSPIE
Number of pages12
Volume6273
ISBN (Print)9780819463388
DOIs
Publication statusPublished - 6 Jul 2006
Externally publishedYes
EventOptomechanical Technologies for Astronomy - Orlando, United States
Duration: 24 May 200631 May 2006

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume6273
ISSN (Print)0277-786X

Conference

ConferenceOptomechanical Technologies for Astronomy
CountryUnited States
CityOrlando
Period24/05/0631/05/06

Fingerprint

profilometers
Metrology
Telescopes
metrology
Telescope
Convex Surface
Mirror
Mirrors
telescopes
mirrors
Probe
apertures
Aspheric Surface
Extremely Large Telescopes
Radius of curvature
Optical Sensor
Polishing
Grinding
Measurement Techniques
Ring or annulus

Cite this

Callender, M. J., Efstathiou, A., King, C. W., Walker, D. D., Gee, A. E., Lewis, A. J., ... Steel, R. M. (2006). A swing arm profilometer for large telescope mirror element metrology. In E. Atad-Ettedgui, J. Antebi, & D. Lemke (Eds.), Optomechanical Technologies for Astronomy: SPIE Astronomical Telescopes and Instrumentation 2006 (Vol. 6273). [62732R] (Proceedings of SPIE - The International Society for Optical Engineering; Vol. 6273 ). SPIE. https://doi.org/10.1117/12.671304
Callender, M. J. ; Efstathiou, A. ; King, C. W. ; Walker, D. D. ; Gee, A. E. ; Lewis, A. J. ; Oldfield, S. ; Steel, R. M. / A swing arm profilometer for large telescope mirror element metrology. Optomechanical Technologies for Astronomy: SPIE Astronomical Telescopes and Instrumentation 2006. editor / Eli Atad-Ettedgui ; Joseph Antebi ; Dietrich Lemke. Vol. 6273 SPIE, 2006. (Proceedings of SPIE - The International Society for Optical Engineering).
@inproceedings{46d25bb1fcf34e65a178aae5539d55e9,
title = "A swing arm profilometer for large telescope mirror element metrology",
abstract = "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 l 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 (NFL). 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 l 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 u-phase interferometer. The method of attachment of the Arden AWS-SO 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.",
keywords = "Asphere, Extremely large telescope, Metrology, Swing arm profilometer",
author = "Callender, {M. J.} and A. Efstathiou and King, {C. W.} and Walker, {D. D.} and Gee, {A. E.} and Lewis, {A. J.} and S. Oldfield and Steel, {R. M.}",
year = "2006",
month = "7",
day = "6",
doi = "10.1117/12.671304",
language = "English",
isbn = "9780819463388",
volume = "6273",
series = "Proceedings of SPIE - The International Society for Optical Engineering",
publisher = "SPIE",
editor = "Eli Atad-Ettedgui and Joseph Antebi and Dietrich Lemke",
booktitle = "Optomechanical Technologies for Astronomy",
address = "United States",

}

Callender, MJ, Efstathiou, A, King, CW, Walker, DD, Gee, AE, Lewis, AJ, Oldfield, S & Steel, RM 2006, A swing arm profilometer for large telescope mirror element metrology. in E Atad-Ettedgui, J Antebi & D Lemke (eds), Optomechanical Technologies for Astronomy: SPIE Astronomical Telescopes and Instrumentation 2006. vol. 6273, 62732R, Proceedings of SPIE - The International Society for Optical Engineering, vol. 6273 , SPIE, Optomechanical Technologies for Astronomy, Orlando, United States, 24/05/06. https://doi.org/10.1117/12.671304

A swing arm profilometer for large telescope mirror element metrology. / Callender, M. J.; Efstathiou, A.; King, C. W.; Walker, D. D.; Gee, A. E.; Lewis, A. J.; Oldfield, S.; Steel, R. M.

Optomechanical Technologies for Astronomy: SPIE Astronomical Telescopes and Instrumentation 2006. ed. / Eli Atad-Ettedgui; Joseph Antebi; Dietrich Lemke. Vol. 6273 SPIE, 2006. 62732R (Proceedings of SPIE - The International Society for Optical Engineering; Vol. 6273 ).

Research output: Chapter in Book/Report/Conference proceedingConference contribution

TY - GEN

T1 - A swing arm profilometer for large telescope mirror element metrology

AU - Callender, M. J.

AU - Efstathiou, A.

AU - King, C. W.

AU - Walker, D. D.

AU - Gee, A. E.

AU - Lewis, A. J.

AU - Oldfield, S.

AU - Steel, R. M.

PY - 2006/7/6

Y1 - 2006/7/6

N2 - 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 l 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 (NFL). 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 l 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 u-phase interferometer. The method of attachment of the Arden AWS-SO 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.

AB - 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 l 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 (NFL). 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 l 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 u-phase interferometer. The method of attachment of the Arden AWS-SO 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.

KW - Asphere

KW - Extremely large telescope

KW - Metrology

KW - Swing arm profilometer

UR - http://www.scopus.com/inward/record.url?scp=33749596569&partnerID=8YFLogxK

U2 - 10.1117/12.671304

DO - 10.1117/12.671304

M3 - Conference contribution

SN - 9780819463388

VL - 6273

T3 - Proceedings of SPIE - The International Society for Optical Engineering

BT - Optomechanical Technologies for Astronomy

A2 - Atad-Ettedgui, Eli

A2 - Antebi, Joseph

A2 - Lemke, Dietrich

PB - SPIE

ER -

Callender MJ, Efstathiou A, King CW, Walker DD, Gee AE, Lewis AJ et al. A swing arm profilometer for large telescope mirror element metrology. In Atad-Ettedgui E, Antebi J, Lemke D, editors, Optomechanical Technologies for Astronomy: SPIE Astronomical Telescopes and Instrumentation 2006. Vol. 6273. SPIE. 2006. 62732R. (Proceedings of SPIE - The International Society for Optical Engineering). https://doi.org/10.1117/12.671304