Prof. David Douglas Walker Profile

Prof. David Douglas Walker

Professor / Research Director at Univ of Huddersfield and Zeeko Ltd

SPIE Involvement:

Author

Publications (66)

Proceedings Article | 12 July 2018 Paper

Paper

Composite material evaluation at cryogenic temperatures for applications in space-based far-infrared astronomical instrumentation

Locke Spencer, Ian Veenendaal, David Naylor, Brad Gom, Geoffrey R. Sitwell, Anthony Huber, Adam Christiansen, Chris Benson, Sudhakar Gunuganti, Martyn Jones, Richard Day, David Walker, Navid Zobeiry, Anoush Poursartip

Proceedings Volume 10706, 107063R (2018) https://doi.org/10.1117/12.2314211

KEYWORDS: Cryogenics, Aluminum, Laser metrology, Metrology, Laser systems engineering, Temperature metrology, Photonics, Fiber lasers, Composites, Astronomical instrumentation

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Proceedings Article | 10 July 2018 Presentation + Paper

Presentation + Paper

A novel hyper-crossing tool path generation algorithm for sub-aperture polishing

Christina Reynolds, David Walker, Guoyu Yu, Hongyu Li

Proceedings Volume 10706, 107060F (2018) https://doi.org/10.1117/12.2312827

KEYWORDS: Polishing, Surface finishing, Algorithm development, Robotics, Optimization (mathematics), Precision optics, Mirrors, Aspheric lenses, Process control

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Proceedings Article | 15 June 2018 Paper

Paper

Advanced techniques for robotic polishing of aluminum mirrors

Hongyu Li, David Walker, Xiao Zheng, Guoyu Yu, Christina Reynolds, Wang Zhang, Tony Li

Proceedings Volume 10692, 106920N (2018) https://doi.org/10.1117/12.2311625

KEYWORDS: Polishing, Surface finishing, Aluminum, Mirrors, Robots, Aspheric lenses, Robotics, Single point diamond turning, Glasses

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Proceedings Article | 15 June 2017 Paper

Paper

More steps towards process automation for optical fabrication

David Walker, Guoyu Yu, Anthony Beaucamp, Matt Bibby, Hongyu Li, Lee McCluskey, Sanja Petrovic, Christina Reynolds

Proceedings Volume 10326, 103260S (2017) https://doi.org/10.1117/12.2275231

KEYWORDS: Optical fabrication, Artificial intelligence, Metrology, Robots, Manufacturing, Optics manufacturing, Data processing, Data modeling, Polishing, Head

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Proceedings Article | 11 November 2016 Paper

Paper

Development of swinging part profilometer for optics

Peng Zhang, Jie Li, Guoyu Yu, David Walker

Proceedings Volume 10151, 101510B (2016) https://doi.org/10.1117/12.2256295

KEYWORDS: Optical testing, Profilometers, Metrology, Polishing, Surface finishing, Interferometers, Photovoltaics, Mirrors, MATLAB, Astronomical imaging

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Proceedings Article | 29 July 2016 Paper

Paper

Performance of a cryogenic test facility for 4 K interferometer delay line investigations

Ian Veenendaal, David Naylor, Brad Gom, Sudhakar Gunuganti, Calvin Winter, Martyn Jones, David Walker

Proceedings Volume 9904, 99045E (2016) https://doi.org/10.1117/12.2233609

KEYWORDS: Cryogenics, Interferometers, Space telescopes, Copper, Temperature metrology, Mirrors, Head, Far infrared, Autocollimators, Telescopes

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Proceedings Article | 29 July 2016 Paper

Paper

CFRP mirror technology for cryogenic space interferometry: review and progress to date

Martyn Jones, David Walker, David Naylor, Ian Veenendaal, Brad Gom

Proceedings Volume 9904, 99046F (2016) https://doi.org/10.1117/12.2233645

KEYWORDS: Composites, Space telescopes, Mirrors, Finite element methods, Telescopes, Space telescopes, Mirrors, Telescopes, Cryogenics, Finite element methods, Space mirrors, Polymers, Interferometers, Data modeling

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Proceedings Article | 22 July 2016 Paper

Paper

Optimisation of grolishing freeform surfaces with rigid and semi-rigid tools

Guoyu Yu, Hsing-Yu Wu, David Walker, Xiao Zheng, Hongyu Li, Christina Dunn, Caroline Gray

Proceedings Volume 9912, 99123Q (2016) https://doi.org/10.1117/12.2232657

KEYWORDS: Mirrors, Aspheric lenses, Abrasives, Polishing, Aspheric lenses, Metrology, Surface finishing, Glasses, Spindles, Photovoltaics, Robots

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Proceedings Article | 30 June 2016 Paper

Paper

Analysis of tool-mass-acceleration effects onto sub-aperture computer controlled polishing (CCP)

Oliver Faehnle, Guoyu Yu, David Walker

Proceedings Volume 10009, 1000903 (2016) https://doi.org/10.1117/12.2236024

KEYWORDS: Polishing, Aspheric lenses, Surface finishing, Ion beams, Testing and analysis, Aspheric optics, Freeform optics, Shape analysis, Magnetorheological finishing, Kinematics

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Proceedings Article | 30 June 2016 Paper

Paper

Closing the metrology/process loop in CNC polishing

David Walker, Guoyu Yu, Matt Bibby, Hongyu Li, Christina Dunn

Proceedings Volume 10009, 100090O (2016) https://doi.org/10.1117/12.2235530

KEYWORDS: Metrology, Manufacturing, Polishing, Polishing equipment, Optical alignment, Robots, Interferometers, Surface finishing, Interferometry, Precision optics

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Proceedings Article | 27 August 2015 Paper

Paper

The role of robotics in computer controlled polishing of large and small optics

David Walker, Christina Dunn, Guoyu Yu, Matt Bibby, Xiao Zheng, Hsing Yu Wu, Hongyu Li, Chunlian Lu

Proceedings Volume 9575, 95750B (2015) https://doi.org/10.1117/12.2189203

KEYWORDS: Robots, Spindles, Optics manufacturing, Polishing, Abrasives, Surface finishing, Metrology, Robotics, Prototyping, Diamond

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Proceedings Article | 14 March 2015 Paper

Paper

Optical and quasi-optical analysis of system components for a far-infrared space interferometer

C. Bracken, C. O'Sullivan, A. Donohoe, A. Murphy, G. Savini, R. Juanola-Parramon, Nicola Baccichet, A. Guisseau, P. Ade, E. Pascale, L. Spencer, I. Walker, K. Dohlen, John Lightfoot, W. Holland, Martyn Jones, D. Walker, Alison McMillan

Proceedings Volume 9362, 93620N (2015) https://doi.org/10.1117/12.2076385

KEYWORDS: Mirrors, Telescopes, Space telescopes, Interferometers, Visibility, Beam propagation method, Wavefronts, Interferometry, Monochromatic aberrations, Spatial resolution

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Proceedings Article | 2 September 2014 Paper

Paper

Active edge control in the precessions polishing process for manufacturing large mirror segments

Hongyu Li, Wei Zhang, David Walker, Gouyo Yu

Proceedings Volume 9280, 928007 (2014) https://doi.org/10.1117/12.2069790

KEYWORDS: Polishing, Surface finishing, Finite element methods, Mirrors, Telescopes, Control systems, Manufacturing, Photovoltaics, Zerodur, Segmented mirrors

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SPIE Journal Paper | 5 May 2014 Open Access

Open Access

Coordinate transformation of an industrial robot and its application in deterministic optical polishing

Wei Wang, Guoyu Yu, Min Xu, David Walker

OE, Vol. 53, Issue 05, 055102, (May 2014) https://doi.org/10.1117/12.10.1117/1.OE.53.5.055102

KEYWORDS: Polishing, Surface finishing, Robotic systems, Optics manufacturing, Polishing equipment, Optical engineering, Optical signal processing, Head, Astronomical imaging, Aspheric lenses

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Proceedings Article | 7 September 2013 Paper

Paper

Fast manufacturing of E-ELT mirror segments using CNC polishing

C. Gray, I. Baker, G. Davies, R. Evans, N. Field, T. Fox-Leonard, W. Messelink, J. Mitchell, P. Rees, S. Waine, D. Walker, G. Yu

Proceedings Volume 8838, 88380K (2013) https://doi.org/10.1117/12.2023475

KEYWORDS: Polishing, Metrology, Manufacturing, Aspheric lenses, Surface finishing, Prototyping, Mirrors, Optical testing, Optics manufacturing, Telescopes

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Proceedings Article | 16 October 2012 Paper

Paper

Research on fabrication of mirror segments for E-ELT

Guoyu Yu, David Walker, Hongyu Li

Proceedings Volume 8416, 841602 (2012) https://doi.org/10.1117/12.2009290

KEYWORDS: Polishing, Surface finishing, Mirrors, Spatial frequencies, Photovoltaics, Metrology, Aspheric lenses, Abrasives, Interferometry, Optics manufacturing

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The next generation ground-based giant telescope, the European Extremely Large Telescope (E-ELT), under development by the European Southern Observation (ESO) ¹, will have nearly 1000 hexagonal segments of 1.45m across the flats. Fast processing of these segments with high form and edge specifications has proven to be a challenge. The Zeeko Precessions sub-aperture bonnet polishing plays an important role providing capability for polishing the surface and correcting the form to meet this target ^2,3. BoX^TM grinding has been adopted. This technology has the advantage of fast generating of aspheric surface with very low subsurface damage (SSD) ⁴. This will avoid the need of removing thick layer of stock at polishing stage to remove SSD. However the result grinding signatures has proven to be problematic for direct polishing with Zeeko’s standard bonnet technology. A novel ‘grolishing’ process which stands between ‘grinding’ and ‘polishing’ has been developed to deal with mid-spatial features left by BoX^TM grinding. This tool is designed base on Zeeko’s R80 bonnet which will fits directly into the company’s IRP series machines. The process parameters have been optimised to have signatures less than 10 nm PV. The edge profile is 1μm upstand within 40 mm edge zone. The ‘grolished’ surface can be directly pre-polished together with all the form corrections. To meet the fabrication time target, R160 bonnet is used with 50 mm polishing spot, this will provide removal rate of 9.8 mm³/minute, which can be employed at pre-polishing stage and some form correction. Process parameters have been developed to leave slow upstand at edge zone without any form of sharp edge downturn. The following form correction stage, which employs smaller polishing spot of about 20 mm diameter, will continue to remove form errors of spatial frequency between 0.02 – 0.05 1/mm. Furthermore, the upstand edge will be, to a large part, removed at this stage. It is demonstrated that the form specs can be achieved after this process. The following smoothing process will improve surface textures and remove edge errors. Local edge rectification is normally necessary to bring the edge at same level. A final smoothing process will bring the bulk area and edge zone to meet all the specifications.

Proceedings Article | 27 September 2012 Paper

Paper

Thin glass shell oriented to wide field x-ray telescope

M. Civitani, O. Citterio, S. Campana, P. Conconi, E. Mattaini, G. Pareschi, G. Tagliaferri, G. Parodi, V. Burwitz, G. Hartner, J. Arnold, S. Schuler, H. Combrinck, R. Freeman, R. Morton, P. Simpson, D. Walker

Proceedings Volume 8443, 84430Q (2012) https://doi.org/10.1117/12.925906

KEYWORDS: X-rays, Calibration, X-ray telescopes, Polishing, Glasses, Atomic force microscopy, Sensors, Silica, Mirrors, Metrology

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Proceedings Article | 13 September 2012 Paper

Paper

Edge-control and surface-smoothness in sub-aperture polishing of mirror segments

D. Walker, A. Beaucamp, R. Evans, T. Fox-Leonard, N. Fairhurst, C. Gray, S. Hamidi, H. Li, W. Messelink, J. Mitchell, P. Rees, G. Yu

Proceedings Volume 8450, 84502A (2012) https://doi.org/10.1117/12.926183

KEYWORDS: Polishing, Aspheric lenses, Surface finishing, Mirrors, Telescopes, Spherical lenses, Space telescopes, Spatial frequencies, Prototyping, Optics manufacturing

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Proceedings Article | 12 October 2011 Paper

Paper

Progress on precise grinding and polishing of thin glass monolithic shell (towards WFXT)

O. Citterio, M. Civitani, J. Arnold, S. Campana, H. Combrinck, P. Conconi, V. Cotroneo, R. Freeman, E. Mattaini, R. Morton, G. Motta, G. Pareschi, G. Parodi, L. Proserpio, S. Schuler, P. Simpson, G. Tagliaferri, D. Walker

Proceedings Volume 8147, 814714 (2011) https://doi.org/10.1117/12.895309

KEYWORDS: Polishing, Mirrors, Surface finishing, Glasses, Silica, X-ray telescopes, X-rays, Spatial resolution, Off axis mirrors, Manufacturing

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Proceedings Article | 27 September 2011 Paper

Paper

Technologies for producing segments for extremely large telescopes

D. Walker, C. Atkins, I. Baker, R. Evans, S. Hamidi, P. Harris, H. Li, W. Messelink, J. Mitchell, M. Parry-Jones, P. Rees, G. Yu

Proceedings Volume 8126, 812604 (2011) https://doi.org/10.1117/12.893360

KEYWORDS: Polishing, Aspheric lenses, Manufacturing, Metrology, Profilometers, Large telescopes, Prototyping, Polishing equipment, Mirrors, Optical testing

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SPIE Journal Paper | 1 July 2011

Misfit of rigid tools and interferometer subapertures on off-axis aspheric mirror segments

Ci Song, David Walker, Guoyu Yu

OE, Vol. 50, Issue 07, 073401, (July 2011) https://doi.org/10.1117/12.10.1117/1.3597328

KEYWORDS: Raster graphics, Aspheric lenses, Mirrors, Interferometers, Interferometry, Prototyping, Polishing, Surface finishing, Abrasives, Off axis mirrors

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Proceedings Article | 23 July 2008 Paper

Paper

Active control of edges and global microstructure on segmented mirrors

D. Walker, A. Beaucamp, C. Dunn, R. Evans, R. Freeman, R. Morton, S. Wei, G. Yu

Proceedings Volume 7018, 701812 (2008) https://doi.org/10.1117/12.787930

KEYWORDS: Polishing, Surface finishing, Raster graphics, Zerodur, Large telescopes, Segmented mirrors, Mirrors, Radium, Infrared radiation, Microfluidics

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Proceedings Article | 23 July 2008 Paper

Paper

Sub-surface damage issues for effective fabrication of large optics

X. Tonnellier, P. Shore, P. Morantz, A. Baldwin, D. Walker, G. Yu, R. Evans

Proceedings Volume 7018, 70180F (2008) https://doi.org/10.1117/12.790639

KEYWORDS: Surface finishing, Surface roughness, Polishing, Lens grinding equipment, Glasses, Radium, Zerodur, Platinum, Diamond, Etching

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Proceedings Article | 18 July 2008 Paper

Paper

Removal of diamond-turning signatures on x-ray mandrels and metal optics by fluid-jet polishing

A. Beaucamp, R. Freeman, R. Morton, Karthik Ponudurai, D. Walker

Proceedings Volume 7018, 701835 (2008) https://doi.org/10.1117/12.787960

KEYWORDS: Surface finishing, Polishing, Mirrors, Aspheric lenses, X-rays, Microfluidics, Metal optics, Metals, Diffraction, Servomechanisms

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Proceedings Article | 21 September 2007 Paper

Paper

A quantitative comparison of three grolishing techniques for the Precessions process

D. Walker, A. Baldwin, R. Evans, R. Freeman, S. Hamidi, P. Shore, X. Tonnellier, S. Wei, C. Williams, G. Yu

Proceedings Volume 6671, 66711H (2007) https://doi.org/10.1117/12.735488

KEYWORDS: Polishing, Silicon carbide, Diamond, Surface finishing, Zerodur, Abrasives, Polyurethane, Raster graphics, Nickel, Aluminum

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Proceedings Article | 31 August 2006 Paper

Paper

Commissioning of the first Precessions 1.2m CNC polishing machines for large optics

D. Walker, A. T. H. Beaucamp, V. Doubrovski, C. Dunn, R. Evans, R. Freeman, G. McCavana, R. Morton, D. Riley, J. Simms, G. Yu, X. Wei

Proceedings Volume 6288, 62880P (2006) https://doi.org/10.1117/12.684091

KEYWORDS: Polishing, Surface finishing, Polishing equipment, Aspheric lenses, Raster graphics, Spherical lenses, Optics manufacturing, Polyurethane, Oxides, Crystals

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Proceedings Article | 27 July 2006 Paper

Paper

Automated optical fabrication: first results from the new Precessions 1.2m CNC polishing machine

D. Walker, A. T. H. Beaucamp, V. Doubrovski, C. Dunn, R. Evans, R. Freeman, J. Kelchner, G. McCavana, R. Morton, D. Riley, J. Simms, G. Yu, X. Wei

Proceedings Volume 6273, 627309 (2006) https://doi.org/10.1117/12.671098

KEYWORDS: Polishing, Surface finishing, Astronomical imaging, Metrology, Polishing equipment, Mirrors, Spherical lenses, Computer programming, Control systems, Optical fabrication

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Proceedings Article | 6 July 2006 Paper

Paper

Wheel wear and surface/subsurface qualities when precision grinding optical materials

X. Tonnellier, P. Shore, X. Luo, P. Morantz, A. Baldwin, R. Evans, D. Walker

Proceedings Volume 6273, 627308 (2006) https://doi.org/10.1117/12.670770

KEYWORDS: Zerodur, Silicon carbide, Surface finishing, Polishing, Lens grinding equipment, Diamond, Etching, Mirrors, Manufacturing, Glasses

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Proceedings Article | 6 July 2006 Paper

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 October 2005 Paper

Paper

Recent advances in the control of form and texture on free-form surfaces

D. Walker, A. Beaucamp, V. Doubrovski, C. Dunn, R. Freeman, G. Hobbs, G. McCavana, R. Morton, D. Riley, J. Simms, X. Wei

Proceedings Volume 5965, 59650S (2005) https://doi.org/10.1117/12.625796

KEYWORDS: Polishing, Surface finishing, Metrology, Profilometers, Interferometers, Aspheric lenses, Telescopes, Mirrors, Large telescopes, Spherical lenses

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Proceedings Article | 24 August 2005 Paper

Paper

New results extending the Precessions process to smoothing ground aspheres and producing freeform parts

D. Walker, A. T. H. Beaucamp, V. Doubrovski, C. Dunn, R. Freeman, G. McCavana, R. Morton, D. Riley, J. Simms, X. Wei

Proceedings Volume 5869, 58690E (2005) https://doi.org/10.1117/12.617067

KEYWORDS: Polishing, Surface finishing, Diamond, Aspheric lenses, Abrasives, Metals, Spherical lenses, Lens grinding equipment, Interferometers, Large telescopes

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Proceedings Article | 14 October 2004 Paper

Paper

Recent developments of Precessions polishing for larger components and free-form surfaces

David Walker, Anthony Beaucamp, David Brooks, V. Doubrovski, Matthew Cassie, C. Dunn, Richard Freeman, Andrew King, M. Libert, Gerry McCavana, Roger Morton, David Riley, John Simms

Proceedings Volume 5523, (2004) https://doi.org/10.1117/12.559531

KEYWORDS: Polishing, Surface finishing, Interferometers, Aspheric lenses, Metrology, Mirrors, Interferometry, Control systems, Raster graphics, Optical spheres

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Proceedings Article | 24 September 2004 Paper

Paper

New results from the Precessions polishing process scaled to larger sizes

David Walker, Anthony Beaucamp, David Brooks, V. Doubrovski, Matthew Cassie, C. Dunn, Richard Freeman, Andrew King, M. Libert, Gerry McCavana, Roger Morton, David Riley, John Simms

Proceedings Volume 5494, (2004) https://doi.org/10.1117/12.553044

KEYWORDS: Polishing, Surface finishing, Interferometers, Mirrors, Metrology, Optical spheres, Aspheric lenses, Interferometry, Spatial frequencies, Distortion

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Proceedings Article | 7 July 2004 Paper

Paper

Dimensional metrology of mirror segments for extremely large telescopes

Graham Peggs, Richard May-Miller, David Walker, Eli Atad-Ettedgui, Paul Shore, David Smith

Proceedings Volume 5382, (2004) https://doi.org/10.1117/12.566231

KEYWORDS: Mirrors, Metrology, Telescopes, Manufacturing, Large telescopes, Image segmentation, Polishing, Aspheric lenses, Laminated object manufacturing, Dimensional metrology

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Proceedings Article | 7 July 2004 Paper

Paper

Manufacture of segments for extremely large telescopes: a new perspective

David Walker, Paul Shore

Proceedings Volume 5382, (2004) https://doi.org/10.1117/12.566274

KEYWORDS: Polishing, Aspheric lenses, Optical spheres, Mirrors, Surface finishing, Large telescopes, Manufacturing, Telescopes, Interferometers, Standards development

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Proceedings Article | 22 December 2003 Paper

Paper

Precessions aspheric polishing: new results from the development program

David Walker, Anthony Beaucamp, Richard Bingham, David Brooks, Richard Freeman, Sug-Whan Kim, Andrew King, Gerry McCavana, Roger Morton, David Riley, John Simms

Proceedings Volume 5180, (2003) https://doi.org/10.1117/12.507462

KEYWORDS: Polishing, Surface finishing, Aspheric lenses, Spherical lenses, Mirrors, Metrology, Optical spheres, Zerodur, Large telescopes, Polyurethane

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SPIE Journal Paper | 1 July 2003

Dynamic measurement of displacement with phase-shifting technique

Yueguang Lu, Andrew Doel, David Walker, Xia Zhao

OE, Vol. 42, Issue 07, (July 2003) https://doi.org/10.1117/12.10.1117/1.1579489

KEYWORDS: Phase shifts, Sensors, Mirrors, Phase interferometry, Charge-coupled devices, Retroreflectors, Error analysis, Phase shift keying, Modulation, Data processing

Proceedings Article | 19 May 2003 Paper

Paper

New polishing technology for large mirrors and lenses

D. Walker

Proceedings Volume 10314, 103140C (2003) https://doi.org/10.1117/12.2284001

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Summary The PrecessionsTM process, and the 200mm capacity 'All' machine which embodies it, are outlined in the accompanying paper 'New method to control form and texture on industrially-sized lenses'. In this paper, we summarise the development of the process to address larger optical components. The first machines constructed for this application are of 600mm capacity. A conceptual design of a 1-2m class machine of bridge- configuration has also been produced. Unlike the All machine, the work-piece on these larger machines lies in a horizontal plane i.e. with the rotation axis of the work-piece spindle vertical. This configuration is preferred because it allows the use of a hydrostatic support-system for the work-piece; important for large optics in general, and particularly so for light-weight optics. The machine can also provide a clear vertical path above the work-piece for optical testing, or for access by lifting gear. It is interesting to consider how the PrecessionsTM process can be scaled. As an example, consider first that the type of surface-form remains the same; it might, for example, be an f/2 parabola. Consider then that the work-piece diameter, the bonnet-diameter, the polishing spot-sizes used, and the tool-path on the surface, are all stretched by a factor of two. The area of the polishing spot and that of the work-piece have both increased by a factor of 4, but the number of convolutions of the spiral tool-path remains the same. Since the spot instantaneously addresses the same fraction of the overall work-piece surface-area, the terms all cancels in relation to cycle-time. However, for the same tool-rpm, the larger bonnet delivers a proportionally higher surface-speed, because the polishing action is further from the axis of rotation. Therefore, the volumetric removal rate (proportional to contact-area times surface-speed) tends to vary as the cube rather than the square of the scale-factor. As a result, the larger bonnet working over the larger work-piece with the same polishing pressure, will remove twice the depth of material in the same time. The above scaling could, in principle, reduce cycle times on larger parts. In practice, we have found that excessive removal-rates lead to impractically short dwell-times, especially near the centre of a spiral tool-path. Such scaling also demands increased traverse-speeds and accelerations from the machine, and this rapidly becomes a limitation. Moreover, as the process converges on final form, smaller depths of material need to be removed. In practice, we have found it necessary to moderate the process by diluting the slurry and by moving from a polyurethane tool-surface to a material that delivers a lower-removal rate, such as Multitex. We are also developing bonnets that are compatible with operation at a reduced polishing pressure, in order to give additional control for fine-removal. The current status of the process development is as follows. A form error of -80nm peak-to-valley has been achieved aspherising a 100mm diameter part. This work revealed some subtle but significant limitations in the optimisation code, mostly concerned with convergence and residual ripples. Recent work has focussed on this aspect, and the revised code is now ready for polishing trials. A 150mm diameter part is currently in-process, and work is about to commence on a 300mm fused silica mirror for a space application.

Proceedings Article | 19 May 2003 Paper

Paper

New method to control form and texture on industrially-sized lenses

D. Walker

Proceedings Volume 10314, 1031404 (2003) https://doi.org/10.1117/12.2283993

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Proceedings Article | 30 January 2003 Paper

Paper

Precessions process for efficient production of aspheric optics for large telescopes and their instrumentation

David Walker, A. Beaucamp, Richard Bingham, David Brooks, Richard Freeman, Sowoon Kim, Andrew King, Gerry McCavana, Roger Morton, David Riley, John Simms

Proceedings Volume 4842, (2003) https://doi.org/10.1117/12.456677

KEYWORDS: Polishing, Aspheric lenses, Surface finishing, Mirrors, Diffraction, Image segmentation, Astronomy, Large telescopes, Spherical lenses, Wavefronts

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Proceedings Article | 30 January 2003 Paper

Paper

The Euro50 extremely large telescope

Torben Andersen, Arne Ardeberg, Jacques Beckers, Alexander Goncharov, Mette Owner-Petersen, Holger Riewaldt, Ralph Snel, David Walker

Proceedings Volume 4840, (2003) https://doi.org/10.1117/12.458049

KEYWORDS: Mirrors, Telescopes, Adaptive optics, Laser guide stars, Wavefront sensors, Deformable mirrors, Polishing, K band, Sensors, Large telescopes

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Proceedings Article | 16 October 2002 Paper

Paper

Novel CNC polishing process for control of form and texture on aspheric surfaces

David Walker, A. Beaucamp, David Brooks, Richard Freeman, Andrew King, Gerry McCavana, Roger Morton, David Riley, John Simms

Proceedings Volume 4767, (2002) https://doi.org/10.1117/12.451322

KEYWORDS: Polishing, Surface finishing, Aspheric lenses, Process control, Raster graphics, Spherical lenses, Mirrors, Astronomy, Polishing equipment, Optical instrument design

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Proceedings Article | 5 February 2002 Paper

Paper

Zeeko/UCL process for polishing large lenses and prisms

David Walker, Richard Freeman, Gerry McCavana, Roger Morton, David Riley, John Simms, David Brooks, Eugene Kim, Andrew King

Proceedings Volume 4411, (2002) https://doi.org/10.1117/12.454877

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Proceedings Article | 5 February 2002 Paper

Paper

Progress on development of prototype laser reference system for stylus profilometry of large optics

Ho-Soon Yang, David Walker

Proceedings Volume 4411, (2002) https://doi.org/10.1117/12.454885

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Proceedings Article | 5 February 2002 Paper

Paper

Accidental and methodical defects of generation of precision and ultraprecision surfaces of polymer optics

Sergiy Lavrynenko, Gilbert Nixon, Keith Puttick, David Walker

Proceedings Volume 4411, (2002) https://doi.org/10.1117/12.454876

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Proceedings Article | 27 December 2001 Paper

Paper

First aspheric form and texture results from a production machine embodying the precession process

David Walker, David Brooks, Richard Freeman, Andrew King, Gerry McCavana, Roger Morton, David Riley, John Simms

Proceedings Volume 4451, (2001) https://doi.org/10.1117/12.453652

KEYWORDS: Polishing, Aspheric lenses, Surface finishing, Control systems, Metrology, Polishing equipment, Spatial frequencies, Polyurethane, Radium, Mirrors

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Proceedings Article | 24 October 2000 Paper

Paper

Novel automated process for aspheric surfaces

Richard Bingham, David Walker, Do-Hyung Kim, David Brooks, Richard Freeman, Darren Riley

Proceedings Volume 4093, (2000) https://doi.org/10.1117/12.405237

KEYWORDS: Polishing, Surface finishing, Aspheric lenses, Glasses, Abrasives, Wafer-level optics, Spatial frequencies, Radium, Physics, Astronomy

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Proceedings Article | 7 July 2000 Paper

Paper

Adaptive secondary mirror developments at UCL

Andrew Doel, Jaehun Lee, David Walker

Proceedings Volume 4007, (2000) https://doi.org/10.1117/12.390323

KEYWORDS: Mirrors, Actuators, Adaptive optics, Aluminum, Telescopes, Monochromatic aberrations, Glasses, Metals, Prototyping, Atmospheric optics

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SPIE Journal Paper | 1 April 2000

Adaptive secondary mirror demonstrator: construction and preliminary evaluation

Jun Ho Lee, David Walker, Andrew Doel

OE, Vol. 39, Issue 04, (April 2000) https://doi.org/10.1117/12.10.1117/1.602446

KEYWORDS: Mirrors, Actuators, Adaptive optics, Sensors, Glasses, Secondary tip-tilt mirrors, Telescopes, Aluminum, Polishing, Monochromatic aberrations

SPIE Journal Paper | 1 September 1999

Adaptive secondary mirror demonstrator: design and simulation

Jun Ho Lee, David Walker, Andrew Doel

OE, Vol. 38, Issue 09, (September 1999) https://doi.org/10.1117/12.10.1117/1.602197

KEYWORDS: Mirrors, Actuators, Adaptive optics, Telescopes, Wavefronts, Wavefront distortions, Atmospheric optics, Gemini Observatory, Finite element methods, Astronomical telescopes

Proceedings Article | 11 September 1998 Paper

Paper

Rugged adaptive telescope secondaries: experience with a demonstrator mirror

David Walker, Jun Ho Lee, Richard Bingham, David Brooks, Mark Dryburgh, Gilbert Nixon, Heshmat Jamshidi, Sug-Whan Kim, Bruce Bigelow

Proceedings Volume 3353, (1998) https://doi.org/10.1117/12.321661

KEYWORDS: Mirrors, Actuators, Telescopes, Aluminum, Glasses, Infrared telescopes, Infrared radiation, Reliability, Safety, Control systems

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Proceedings Article | 9 July 1998 Paper

Paper

Computer-controlled polishing of moderate-sized general aspherics for instrumentation

David Walker, Sug-Whan Kim, Richard Bingham, David Brooks, Do-Hyung Kim, J. Thirtle

Proceedings Volume 3355, (1998) https://doi.org/10.1117/12.316754

KEYWORDS: Polishing, Aspheric lenses, Surface finishing, Polishing equipment, Actuators, Robotics, Mirrors, Active optics, Diamond, Optics manufacturing

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Proceedings Article | 9 July 1998 Paper

Paper

Ultrastable high-resolution spectrographs for large telescopes

Francisco Diego, Ian Crawford, David Walker

Proceedings Volume 3355, (1998) https://doi.org/10.1117/12.316768

KEYWORDS: Spectrographs, Telescopes, Spectral resolution, Stars, Diffraction gratings, Large telescopes, Gemini Observatory, Clouds, Optical fibers, Absorption

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Proceedings Article | 21 March 1997 Paper

Paper

Active compensation of flexure on the High-Resolution Optical Spectrograph for Gemini

Paolo D'Arrigo, Francisco Diego, David Walker

Proceedings Volume 2871, (1997) https://doi.org/10.1117/12.269021

KEYWORDS: Spectrographs, Telescopes, Collimators, Space telescopes, Gemini Observatory, Charge-coupled devices, Mirrors, Sensors, Active optics, Actuators

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Proceedings Article | 21 March 1997 Paper

Paper

Conceptual design of the high-resolution optical spectrograph for the Gemini South Telescope

Francisco Diego, David Brooks, Andrew Charalambous, Ian Crawford, Paolo D'Arrigo, Mark Dryburgh, Heshmat Jamshidi, Alan Radley, Trevor Savidge, David Walker

Proceedings Volume 2871, (1997) https://doi.org/10.1117/12.268999

KEYWORDS: Prisms, Gemini Observatory, Telescopes, Cameras, Spectrographs, Spectral resolution, Space telescopes, Optical instrument design, Silica, Sensors

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Proceedings Article | 21 March 1997 Paper

Paper

Testing of a magneto-strictive actuator for adaptive optics

Bruce Bigelow, David Walker, Gilbert Nixon

Proceedings Volume 2871, (1997) https://doi.org/10.1117/12.268972

KEYWORDS: Actuators, Sensors, Manufacturing, Amplifiers, Analog electronics, Adaptive optics, Deformable mirrors, Mirrors, Magnetic sensors, Packaging

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Proceedings Article | 19 August 1996 Paper

Paper

OGLP-400: an innovative computer-controlled polishing machine

Sug-Whan Kim, David Rees, David Walker, Richard Bingham, David Brooks, Brian Humm, Heshmat Jamshidi, Do-Hyung Kim, Ho-Soon Yang, Gilbert Nixon

Proceedings Volume 2775, (1996) https://doi.org/10.1117/12.246779

KEYWORDS: Polishing, Surface finishing, Mirrors, Polishing equipment, Prototyping, Control systems, Active optics, Aspheric lenses, Astronomical imaging, Aspheric optics

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Proceedings Article | 25 August 1995 Paper

Paper

Pupil-imaging wavefront gradient sensor

William Pugh, Daniel Lobb, David Walker, Thomas Williams

Proceedings Volume 2534, (1995) https://doi.org/10.1117/12.217747

KEYWORDS: Sensors, Wavefronts, Wavefront sensors, Computer simulations, Point spread functions, Telescopes, Diffraction, Image sensors, Charge-coupled devices, Stars

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Proceedings Article | 1 June 1994 Paper

Paper

Reexamination of high-resolution spectrographs for large telescopes: the Cassegrain solution

David Walker, Alan Radley, Francisco Diego, Andrew Charalambous, Mark Dryburgh, Bruce Bigelow

Proceedings Volume 2198, (1994) https://doi.org/10.1117/12.176800

KEYWORDS: Cameras, Spectrographs, Prisms, Telescopes, Gemini Observatory, Sensors, Large telescopes, Spectral resolution, Vignetting, Mirrors

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Proceedings Article | 1 June 1994 Paper

Paper

Versatile mosaic CCD controller design

Wonyong Han, Martin Clayton, David Walker

Proceedings Volume 2198, (1994) https://doi.org/10.1117/12.176721

KEYWORDS: Charge-coupled devices, Computer aided design, Control systems, Sensors, Raster graphics, Multiplexing, Imaging systems, Clocks, Prototyping, Logic

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Proceedings Article | 1 June 1994 Paper

Paper

UHRF: spectral resolution to the limit

Francisco Diego, Ian Crawford, Mike Barlow, Adrian Fish, Mark Dryburgh, David Brooks, Jason Spyromilio, Ian Howarth, David Walker

Proceedings Volume 2198, (1994) https://doi.org/10.1117/12.176704

KEYWORDS: Sensors, Collimators, Spectrographs, Spectral resolution, Diffraction gratings, Telescopes, Collimation, Clouds, Confocal microscopy, Observatories

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Proceedings Article | 31 May 1994 Paper

Paper

Optimizing a deformable secondary mirror for adaptive optics

Bruce Bigelow, Richard Bingham, David Walker

Proceedings Volume 2201, (1994) https://doi.org/10.1117/12.176115

KEYWORDS: Mirrors, Actuators, Wavefronts, Adaptive optics, Finite element methods, Deformable mirrors, Astronomy, Zernike polynomials, Aluminum, Telescopes

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Proceedings Article | 1 July 1990 Paper

Paper

Final tests and commissioning of the UCL echelle spectrograph

Francisco Diego, Andrew Charalambous, Adrian Fish, David Walker

Proceedings Volume 1235, (1990) https://doi.org/10.1117/12.19119

KEYWORDS: Prisms, Astronomy, Cameras, Lenses, Calibration, Sensors, Lamps, Charge-coupled devices, Spectrographs, Mirrors

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Proceedings Article | 1 July 1990 Paper

Paper

CORAVEL

Francisco Diego, Roger Griffin, Juan Echevarria, Richard Bingham, David Walker

Proceedings Volume 1235, (1990) https://doi.org/10.1117/12.19129

KEYWORDS: Stars, Telescopes, Photomultipliers, Lamps, Astronomy, Glasses, Scanners, Software development, Observatories, Doppler effect

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Proceedings Article | 1 July 1990 Paper

Paper

Echelle spectrographs for 8-m class telescopes

David Walker, Richard Bingham, Francisco Diego

Proceedings Volume 1235, (1990) https://doi.org/10.1117/12.19117

KEYWORDS: Prisms, Cameras, Telescopes, Spectrographs, Sensors, Charge-coupled devices, Astronomy, Space telescopes, Mirrors, Microchannel plates

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Proceedings Article | 1 July 1990 Paper

Paper

Technology for 8-m primary mirrors

Richard Bingham, David Walker, Francisco Diego

Proceedings Volume 1236, (1990) https://doi.org/10.1117/12.19228

KEYWORDS: Mirrors, Telescopes, Polishing, Polishing equipment, Segmented mirrors, Space telescopes, Optical telescopes, Control systems, Sensors, Observatories

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Showing 5 of 66 publications

Proceedings Volume Editor (3)

SPIE Conference Volume | 6 October 2010

5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Advanced Optical Manufacturing Technologies

SPIE Conference Volume | 5 February 2002

Large Lenses and Prisms

SPIE Conference Volume | 15 October 1993

Metal Mirrors

Conference Committee Involvement (17)

Astronomical Optics: Design, Manufacture, and Test of Space and Ground Systems IV

21 August 2023 | San Diego, California, United States

Optical Manufacturing and Testing XIV

22 August 2022 | San Diego, California, United States

Optical Manufacturing and Testing XIII

24 August 2020 | Online Only, California, United States

Optical Manufacturing and Testing XII

20 August 2018 | San Diego, California, United States

Fifth European Seminar on Precision Optics Manufacturing

10 April 2018 | Teisnach, Germany

Fourth European Seminar on Precision Optics Manufacturing

4 April 2017 | Teisnach, Germany

Optical Manufacturing and Testing XI

9 August 2015 | San Diego, California, United States

Optical Manufacturing and Testing X

26 August 2013 | San Diego, California, United States

Optical Manufacturing and Testing IX

22 August 2011 | San Diego, California, United States

5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Advanced Optical Manufacturing Technologies

26 April 2010 | Dalian, China

Optical Manufacturing and Testing VIII

4 August 2009 | San Diego, California, United States

Optical Manufacturing and Testing VII

28 August 2007 | San Diego, California, United States

Optical Manufacturing and Testing VI

31 July 2005 | San Diego, California, United States

Optical Fabrication, Metrology, and Material Advancements for Telescopes

24 June 2004 | Glasgow, United Kingdom

Optical Manufacturing and Testing V

3 August 2003 | San Diego, California, United States

Large Lenses and Prisms

27 March 2001 | London, United Kingdom

Metal Mirrors

12 November 1992 | London, United Kingdom

Showing 5 of 17 Conference Committees

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