2015
Yao, J.; Meemon, P.; Ponting, M.; Rolland, J. P.
Metrology of 3D freeform spherical gradient index preforms Conference
Imaging and Applied Optics 2015OSA Technical Digest, no. FT3B.3 , 2015, (Imaging and Applied Optics 2015, OSA Technical Digest, paper FT3B.3 (2015). ).
Abstract | Links | BibTeX | Tags: related, testing
@conference{Yao15pa,
title = {Metrology of 3D freeform spherical gradient index preforms},
author = {Yao, J. and P. Meemon and M. Ponting and J. P. Rolland},
doi = {https://doi.org/10.1364/FREEFORM.2015.FT3B.3},
year = {2015},
date = {2015-06-08},
urldate = {2015-06-08},
booktitle = {Imaging and Applied Optics 2015OSA Technical Digest},
number = {FT3B.3 },
abstract = {We present an angular-scan swept-source optical coherence tomography system for 3D imaging and concentricity characterization of two generations of spherical gradient index preforms with a method to decouple the physical thickness and the index measurements.},
note = {Imaging and Applied Optics 2015, OSA Technical Digest, paper FT3B.3 (2015). },
keywords = {related, testing},
pubstate = {published},
tppubtype = {conference}
}
We present an angular-scan swept-source optical coherence tomography system for 3D imaging and concentricity characterization of two generations of spherical gradient index preforms with a method to decouple the physical thickness and the index measurements.
Evans, C. J.; Browy, E. C.; Childs, T. H. C.; Paul, E.
Interferometric measurements of single crystal diamond tool wear Journal Article
In: CIRP Annals - Manufacturing Technology, vol. 64, pp. 125-128, 2015.
Abstract | Links | BibTeX | Tags: related, testing
@article{Evans15,
title = {Interferometric measurements of single crystal diamond tool wear},
author = {Evans, C. J. and E.C. Browy and T.H.C. Childs and E. Paul },
doi = {https://doi.org/10.1016/j.cirp.2015.04.066},
year = {2015},
date = {2015-05-04},
urldate = {2015-05-04},
journal = {CIRP Annals - Manufacturing Technology},
volume = {64},
pages = {125-128},
abstract = {Interferometric measurements of plunge cuts made in a reference component intermittently during cutting tool wear tests allow measurement of the detail of tool edge recession without removing the tool from the machine. Hence the evolution of the tool wear can be evaluated with a resolution of less than 5 nm. A plunge cut using the new tool is subtracted from subsequent measurements, providing a direct measure of wear and removing bias from the scanning white light interferometer that would arise from non-zero slopes in the field of view. The method is illustrated with results from single crystal diamond tool wear tests when machining a family of nickel-copper alloys of varying composition. The dominant wear mechanism depends on the alloy and the cutting parameters. Nose flattening, leading edge recession, chipping, and formation of Pekelharing grooves can all be identified.},
keywords = {related, testing},
pubstate = {published},
tppubtype = {article}
}
Interferometric measurements of plunge cuts made in a reference component intermittently during cutting tool wear tests allow measurement of the detail of tool edge recession without removing the tool from the machine. Hence the evolution of the tool wear can be evaluated with a resolution of less than 5 nm. A plunge cut using the new tool is subtracted from subsequent measurements, providing a direct measure of wear and removing bias from the scanning white light interferometer that would arise from non-zero slopes in the field of view. The method is illustrated with results from single crystal diamond tool wear tests when machining a family of nickel-copper alloys of varying composition. The dominant wear mechanism depends on the alloy and the cutting parameters. Nose flattening, leading edge recession, chipping, and formation of Pekelharing grooves can all be identified.
Huang, J.; Tankam, P.; Hindman, H. B.; Aquavella, J. V.; Clarkson, E.; Kupinski, M. A.; Rolland, J. P.
Tear film thickness estimation using optical coherence tomography and maximum-likelihood estimation Presentation
02.05.2015.
Abstract | Links | BibTeX | Tags: related, testing
@misc{Huangarvo,
title = {Tear film thickness estimation using optical coherence tomography and maximum-likelihood estimation},
author = {Huang, J. and P. Tankam and H. B. Hindman and J. V. Aquavella and E. Clarkson and M. A. Kupinski and J. P. Rolland},
doi = {10.1117/12.2083160},
year = {2015},
date = {2015-05-02},
urldate = {2015-05-02},
abstract = {In biophotonics imaging, one important and quantitative task is layer-thickness estimation. In this study, we investigate the approach of combining optical coherence tomography and a maximum-likelihood (ML) estimator for layer thickness estimation in the context of tear film imaging. The motivation of this study is to extend our understanding of tear film dynamics, which is the prerequisite to advance the management of Dry Eye Disease, through the simultaneous estimation of the thickness of the tear film lipid and aqueous layers. The estimator takes into account the different statistical processes associated with the imaging chain. We theoretically investigated the impact of key system parameters, such as the axial point spread functions (PSF) and various sources of noise on measurement uncertainty. Simulations show that an OCT system with a 1 μm axial PSF (FWHM) allows unbiased estimates down to nanometers with nanometer precision. In implementation, we built a customized Fourier domain OCT system that operates in the 600 to 1000 nm spectral window and achieves 0.93 micron axial PSF in corneal epithelium. We then validated the theoretical framework with physical phantoms made of custom optical coatings, with layer thicknesses from tens of nanometers to microns. Results demonstrate unbiased nanometer-class thickness estimates in three different physical phantoms.},
keywords = {related, testing},
pubstate = {published},
tppubtype = {presentation}
}
In biophotonics imaging, one important and quantitative task is layer-thickness estimation. In this study, we investigate the approach of combining optical coherence tomography and a maximum-likelihood (ML) estimator for layer thickness estimation in the context of tear film imaging. The motivation of this study is to extend our understanding of tear film dynamics, which is the prerequisite to advance the management of Dry Eye Disease, through the simultaneous estimation of the thickness of the tear film lipid and aqueous layers. The estimator takes into account the different statistical processes associated with the imaging chain. We theoretically investigated the impact of key system parameters, such as the axial point spread functions (PSF) and various sources of noise on measurement uncertainty. Simulations show that an OCT system with a 1 μm axial PSF (FWHM) allows unbiased estimates down to nanometers with nanometer precision. In implementation, we built a customized Fourier domain OCT system that operates in the 600 to 1000 nm spectral window and achieves 0.93 micron axial PSF in corneal epithelium. We then validated the theoretical framework with physical phantoms made of custom optical coatings, with layer thicknesses from tens of nanometers to microns. Results demonstrate unbiased nanometer-class thickness estimates in three different physical phantoms.
Leach, R.; Evans, C.; He, L.; Davies, A.; Duparre, A.; Henning, A.; Jones, C.; O'Connor, D.
Open Questions in Surface Topography Measurement: a roadmap Journal Article
In: Surface Topography: Metrology and Properties, vol. 3, no. 1, pp. 013001, 2015.
Abstract | Links | BibTeX | Tags: related, testing
@article{Leach15,
title = {Open Questions in Surface Topography Measurement: a roadmap},
author = {Leach, R. and C. Evans and L. He and A. Davies and A. Duparre and A. Henning and C. Jones and D. O'Connor},
doi = {10.1088/2051-672X/3/1/013001},
year = {2015},
date = {2015-03-31},
urldate = {2015-03-31},
journal = {Surface Topography: Metrology and Properties},
volume = {3},
number = {1},
pages = {013001},
abstract = {Control of surface topography has always been of vital importance for manufacturing and many other engineering and scientific disciplines. However, despite over one hundred years of quantitative surface topography measurement, there are still many open questions. At the top of the list of questions is 'Are we getting the right answer?' This begs the obvious question 'How would we know?' There are many other questions relating to applications, the appropriateness of a technique for a given scenario, or the relationship between a particular analysis and the function of the surface. In this first 'open questions' article we have gathered together some experts in surface topography measurement and asked them to address timely, unresolved questions about the subject. We hope that their responses will go some way to answer these questions, address areas where further research is required, and look at the future of the subject. The first section 'Spatial content characterization for precision surfaces' addresses the need to characterise the spatial content of precision surfaces. Whilst we have been manufacturing optics for centuries, there still isn't a consensus on how to specify the surface for manufacture. The most common three methods for spatial characterisation are reviewed and compared, and the need for further work on quantifying measurement uncertainties is highlighted. The article is focussed on optical surfaces, but the ideas are more pervasive. Different communities refer to 'figure, mid-spatial frequencies, and finish' and 'form, waviness, and roughness', but the mathematics are identical. The second section 'Light scattering methods' is focussed on light scattering techniques; an important topic with in-line metrology becoming essential in many manufacturing scenarios. The potential of scattering methods has long been recognized; in the 'smooth surface limit' functionally significant relationships can be derived from first principles for statistically stationary, random surfaces. For rougher surfaces, correlations can be found experimentally for specific manufacturing processes. Improvements in computational methods encourage us to revisit light scattering as a powerful and versatile tool to investigate surface and thin film topographies, potentially providing information on both topography and defects over large areas at high speed. Future scattering techniques will be applied for complex film systems and for sub-surface damage measurement, but more research is required to quantify and standardise such measurements. A fundamental limitation of all topography measurement systems is their finite spatial bandwidth, which limits the slopes that they can detect. The third section 'Optical measurements of surfaces containing high slope angles' discusses this limitation and potential methods to overcome it. In some cases, a rough surface can allow measurement of slopes outside the classical optics limit, but more research is needed to fully understand this process. The last section 'What are the challenges for high dynamic range surface measurement?' presents the challenge facing metrologists by the use of surfaces that need measurement systems with very high spatial and temporal bandwidths, for example, those found in roll-to-roll manufacturing. High resolution, large areas and fast measurement times are needed, and these needs are unlikely to be fulfilled by developing a single all-purpose instrument. A toolbox of techniques needs to be developed which can be applied for any specific manufacturing scenario. The functional significance of surface topography has been known for centuries. Mirrors are smooth. Sliding behaviour depends on roughness. We have been measuring surfaces for centuries, but we still face many challenges. New manufacturing paradigms suggest that we need to make rapid measurements online that relate to the functional performance of the surface. This first 'open questions' collection addresses a subset of the challenges facing the surface metrology community. There are many more challenges which we would like to address in future 'open questions' articles. We welcome your feedback and your suggestions.},
keywords = {related, testing},
pubstate = {published},
tppubtype = {article}
}
Control of surface topography has always been of vital importance for manufacturing and many other engineering and scientific disciplines. However, despite over one hundred years of quantitative surface topography measurement, there are still many open questions. At the top of the list of questions is 'Are we getting the right answer?' This begs the obvious question 'How would we know?' There are many other questions relating to applications, the appropriateness of a technique for a given scenario, or the relationship between a particular analysis and the function of the surface. In this first 'open questions' article we have gathered together some experts in surface topography measurement and asked them to address timely, unresolved questions about the subject. We hope that their responses will go some way to answer these questions, address areas where further research is required, and look at the future of the subject. The first section 'Spatial content characterization for precision surfaces' addresses the need to characterise the spatial content of precision surfaces. Whilst we have been manufacturing optics for centuries, there still isn't a consensus on how to specify the surface for manufacture. The most common three methods for spatial characterisation are reviewed and compared, and the need for further work on quantifying measurement uncertainties is highlighted. The article is focussed on optical surfaces, but the ideas are more pervasive. Different communities refer to 'figure, mid-spatial frequencies, and finish' and 'form, waviness, and roughness', but the mathematics are identical. The second section 'Light scattering methods' is focussed on light scattering techniques; an important topic with in-line metrology becoming essential in many manufacturing scenarios. The potential of scattering methods has long been recognized; in the 'smooth surface limit' functionally significant relationships can be derived from first principles for statistically stationary, random surfaces. For rougher surfaces, correlations can be found experimentally for specific manufacturing processes. Improvements in computational methods encourage us to revisit light scattering as a powerful and versatile tool to investigate surface and thin film topographies, potentially providing information on both topography and defects over large areas at high speed. Future scattering techniques will be applied for complex film systems and for sub-surface damage measurement, but more research is required to quantify and standardise such measurements. A fundamental limitation of all topography measurement systems is their finite spatial bandwidth, which limits the slopes that they can detect. The third section 'Optical measurements of surfaces containing high slope angles' discusses this limitation and potential methods to overcome it. In some cases, a rough surface can allow measurement of slopes outside the classical optics limit, but more research is needed to fully understand this process. The last section 'What are the challenges for high dynamic range surface measurement?' presents the challenge facing metrologists by the use of surfaces that need measurement systems with very high spatial and temporal bandwidths, for example, those found in roll-to-roll manufacturing. High resolution, large areas and fast measurement times are needed, and these needs are unlikely to be fulfilled by developing a single all-purpose instrument. A toolbox of techniques needs to be developed which can be applied for any specific manufacturing scenario. The functional significance of surface topography has been known for centuries. Mirrors are smooth. Sliding behaviour depends on roughness. We have been measuring surfaces for centuries, but we still face many challenges. New manufacturing paradigms suggest that we need to make rapid measurements online that relate to the functional performance of the surface. This first 'open questions' collection addresses a subset of the challenges facing the surface metrology community. There are many more challenges which we would like to address in future 'open questions' articles. We welcome your feedback and your suggestions.
Yao, J.; Meemon, P.; Ponting, M.; Rolland, J. P.
Angular scan optical coherence tomography imaging and metrology of spherical gradient refractive index preforms Journal Article
In: Opt. Express, vol. 23, no. 5, pp. 6428-6443, 2015.
Abstract | Links | BibTeX | Tags: related, testing
@article{YAO15a,
title = {Angular scan optical coherence tomography imaging and metrology of spherical gradient refractive index preforms},
author = {Yao, J. and P. Meemon and M. Ponting and J. P. Rolland},
doi = {https://doi.org/10.1364/OE.23.006428},
year = {2015},
date = {2015-03-05},
urldate = {2015-03-05},
journal = {Opt. Express},
volume = {23},
number = {5},
pages = {6428-6443},
abstract = {The fabrication of high-performance spherical gradient refractive index (S-GRIN) optics requires nondestructive metrology techniques to inspect the samples. We have developed an angular-scan, swept-source-based, Fourier-domain optical coherence tomography (OCT) system centered at 1318 nm with 5 mm imaging depth capable of 180° polar scan and 360° azimuthal scan to investigate polymeric S-GRIN preforms. We demonstrate a method that enables simultaneous mapping of the group optical thickness, physical thickness, the radially-averaged group refractive index, and the transmitted wavefront of the S-GRIN preforms. The angular scan OCT imaging and metrology enables direct visualization, molding uniformity characterization, and optical property evaluations of the preforms. The results on two generations of S-GRIN preforms are discussed that showcase the evolution of the manufacturing process in response to the OCT metrology feedback.},
keywords = {related, testing},
pubstate = {published},
tppubtype = {article}
}
The fabrication of high-performance spherical gradient refractive index (S-GRIN) optics requires nondestructive metrology techniques to inspect the samples. We have developed an angular-scan, swept-source-based, Fourier-domain optical coherence tomography (OCT) system centered at 1318 nm with 5 mm imaging depth capable of 180° polar scan and 360° azimuthal scan to investigate polymeric S-GRIN preforms. We demonstrate a method that enables simultaneous mapping of the group optical thickness, physical thickness, the radially-averaged group refractive index, and the transmitted wavefront of the S-GRIN preforms. The angular scan OCT imaging and metrology enables direct visualization, molding uniformity characterization, and optical property evaluations of the preforms. The results on two generations of S-GRIN preforms are discussed that showcase the evolution of the manufacturing process in response to the OCT metrology feedback.
2014
Thompson, K. P.; Rolland, J. P.
Cost-driven self-consistent fabrication and assembly tolerance classes Conference
Proceedings of the SPIE, vol. 9633, no. 96330U, 2014.
Abstract | Links | BibTeX | Tags: assembly, design, related
@conference{Thomsponoptifab15b,
title = {Cost-driven self-consistent fabrication and assembly tolerance classes},
author = {Thompson, K.P. and J.P. Rolland},
doi = {https://doi.org/10.1117/12.2195783},
year = {2014},
date = {2014-10-11},
urldate = {2014-10-11},
booktitle = {Proceedings of the SPIE},
volume = {9633},
number = {96330U},
abstract = {At the 1994 International Optics Design Conference, a paper was presented by the author that proposed that optics costs are often driven by the fabrication and assembly tolerances. In addition, that these tolerances fall into groups (classes) that for any given shop are set typically by the capital investment in measurement equipment that the shop has access to. The premise is then that it is essential that the optical system tolerances on fabrication, e.g. radii, element thickness, wedge, surface figure, and surface finish and on assembly e.g. component tilt and decenter and spacer thickness and wedge that are assigned by the optical designer be self-consistent with the capabilities of the shops that are solicited to provide a quotation.
In the 1994 paper, five classes of optical fabricators were identified; catalog, regular, select, premium, and ultimate (lithography). For each of these classes, representative minimum tolerances were published along with estimates of the cost increment. An important concept is that if any one tolerance falls into a tighter class, then the optical system must be built in a shop capitalized to provide that one minimum tolerance and as a result all the other tolerances can typically be moved to the tighter class with little cost impact. The primary cost impact then is driven by the class of shop dictated by the minimum tolerance. In this talk, a primary purpose is to revisit the tolerances associated with a given class of shop and update the numbers to reflect advances in the intervening two decades.},
keywords = {assembly, design, related},
pubstate = {published},
tppubtype = {conference}
}
At the 1994 International Optics Design Conference, a paper was presented by the author that proposed that optics costs are often driven by the fabrication and assembly tolerances. In addition, that these tolerances fall into groups (classes) that for any given shop are set typically by the capital investment in measurement equipment that the shop has access to. The premise is then that it is essential that the optical system tolerances on fabrication, e.g. radii, element thickness, wedge, surface figure, and surface finish and on assembly e.g. component tilt and decenter and spacer thickness and wedge that are assigned by the optical designer be self-consistent with the capabilities of the shops that are solicited to provide a quotation.
In the 1994 paper, five classes of optical fabricators were identified; catalog, regular, select, premium, and ultimate (lithography). For each of these classes, representative minimum tolerances were published along with estimates of the cost increment. An important concept is that if any one tolerance falls into a tighter class, then the optical system must be built in a shop capitalized to provide that one minimum tolerance and as a result all the other tolerances can typically be moved to the tighter class with little cost impact. The primary cost impact then is driven by the class of shop dictated by the minimum tolerance. In this talk, a primary purpose is to revisit the tolerances associated with a given class of shop and update the numbers to reflect advances in the intervening two decades.
In the 1994 paper, five classes of optical fabricators were identified; catalog, regular, select, premium, and ultimate (lithography). For each of these classes, representative minimum tolerances were published along with estimates of the cost increment. An important concept is that if any one tolerance falls into a tighter class, then the optical system must be built in a shop capitalized to provide that one minimum tolerance and as a result all the other tolerances can typically be moved to the tighter class with little cost impact. The primary cost impact then is driven by the class of shop dictated by the minimum tolerance. In this talk, a primary purpose is to revisit the tolerances associated with a given class of shop and update the numbers to reflect advances in the intervening two decades.
Yao, Jianing; Rolland, Jannick P.
Freeform Optics Metrology Using Optical Coherence Tomography Conference
Optical Fabrication and Testing, OSA 2014.
Abstract | Links | BibTeX | Tags: metrology, related
@conference{Yao2014,
title = {Freeform Optics Metrology Using Optical Coherence Tomography},
author = {Jianing Yao and Jannick P. Rolland },
doi = {https://doi.org/10.1364/OFT.2014.OW3B.4},
year = {2014},
date = {2014-06-25},
urldate = {2014-06-25},
booktitle = {Optical Fabrication and Testing},
organization = {OSA},
abstract = {We investigate the capability of a custom Fourier-domain swept-source optical coherence tomography method for non-contact freeform optics metrology. First results demonstrate the feasibility of measurement of an Alvarez surface with 400 µm sag.},
keywords = {metrology, related},
pubstate = {published},
tppubtype = {conference}
}
We investigate the capability of a custom Fourier-domain swept-source optical coherence tomography method for non-contact freeform optics metrology. First results demonstrate the feasibility of measurement of an Alvarez surface with 400 µm sag.