CeFO-Related Publications

@article{Hu2021,

title = {Morphology and waveguiding properties of ultrafast-laser-inscribed type-II waveguides in IG2},

author = {W. Hu and M. Kilinc and W. Gebremichael and C. Dorrer, and J. Qiao},

url = {https://opg.optica.org/ome/fulltext.cfm?uri=ome-12-1-360&id=466364},

year  = {2021},

date = {2021-12-24},

urldate = {2021-12-24},

journal = {Optical Materials Express},

volume = {12},

number = {1},

pages = {360-373},

abstract = {Ultrafast-laser-inscribed type-II waveguides inside the chalcogenide glass IG2 and the morphology of the inscribed tracks are presented for the first time to our knowledge. Self-organized periodic structures induced by the ultrafast laser in the tracks are characterized. The near-infrared waveguiding properties are studied for various pulse energies, durations, repetition rates, and polarization states, as well as different separations between the two written tracks. A propagation loss of ∼ 2.3 dB/cm is demonstrated in a type-II waveguide formed in IG2.},

keywords = {manufacturing, related},

pubstate = {published},

tppubtype = {article}

}

@article{Feng2021,

title = {Femtosecond-Laser-Ablation Dynamics in Silicon Revealed by Transient Reflectivity Change},

author = {T. Feng and G. Chen and H. Han and J. Qiao},

url = {https://www.mdpi.com/2072-666X/13/1/14#

https://centerfreeformoptics.org/wp-content/uploads/2023/02/micromachines-13-00014-v2.pdf},

doi = {https://doi.org/10.3390/mi13010014},

year  = {2021},

date = {2021-12-23},

urldate = {2021-12-23},

journal = {Micromachines},

volume = {13},

number = {1},

abstract = {The dynamics of ablation in monocrystalline silicon, from electron-hole plasma generation to material expansion, upon irradiation by a single femtosecond laser pulse (1030 nm, 300 fs pulse duration) at a wide range of fluences is investigated using a time-resolved microscopy technique. The reflectivity evolution obtained from dynamic images in combination with a theoretical Drude model and a Two-Temperature model provides new insights on material excitation and ablation process. For all fluences, the reflectivity increased to a temporary stable state after hundreds of femtoseconds. This behavior was predicted using a temperature-dependent refractive index in the Drude model. The increase in velocity of plasma generation with increasing fluence was theoretically predicted by the Two-Temperature model. Two ablation regimes at high fluences (>0.86 J/cm2) were identified through the measured transient reflectivity and ablation crater profile. The simulation shows that the fluence triggering the second ablation regime produces a boiling temperature (silicon, 2628 K).},

keywords = {manufacturing, related},

pubstate = {published},

tppubtype = {article}

}

@article{Swain2021,

title = {Telephoto-lens-based Optical Differentiation Wavefront Sensor for freeform metrology},

author = {BR Swain and C. Dorrer and J. Qiao},

url = {https://opg.optica.org/oe/fulltext.cfm?uri=oe-29-23-38395&id=464483},

doi = {https://doi.org/10.1364/OE.443558},

year  = {2021},

date = {2021-11-03},

urldate = {2021-11-03},

journal = {Opt. Express},

volume = {29},

number = {23},

pages = {38395-38403},

abstract = {We report an Optical Differentiation Wavefront Sensor based on a telephoto lens system and binary pixelated filters. It provides a five-fold reduction in the system length compared to a 4f system with identical effective focal length. Measurements of phase plates with this system are compared to measurements performed with a commercial low-coherence interferometer. The telephoto-lens-based system can measure wavefronts with accuracy better than λ/10 Root Mean Squared (RMS) at λ=633 nm. Experimental investigation shows that the system has a high tolerance to components alignment errors.},

keywords = {metrology, related},

pubstate = {published},

tppubtype = {article}

}

@article{Sahoo2020,

title = {Dynamic pulse propagation modelling for predictive femtosecond-laser-microbonding of transparent materials},

author = {Pankaj K. Sahoo and Tao Feng and Jie Qiao},

doi = {https://doi.org/10.1364/OE.402493},

year  = {2020},

date = {2020-10-02},

urldate = {2020-10-02},

journal = {Opt. Express},

volume = {28},

number = {21},

pages = {31103-31118},

abstract = {A dynamic pulse propagation modeling for femtosecond laser bonding of Borofloat glass is presented. The temperature evolution and internal modifications are predicted by incorporating the nonlinear electron dynamics along with temperature dependent thermal properties. The modelling predicts the spatial and temporal distribution of absorption coefficient and plasma density that gives quantitative estimations of the heat affected zone and weld geometry. The impact of focusing condition on heat affected zone and weld geometry is investigated, which for the first time to our knowledge allows to numerically determine the desired relative position between the geometrical focus of a femtosecond-laser-pulse and the interface of the two substrates to be welded. The prediction of the modelling on the offset distance is applied to weld Borofloat glass plates having optical contact and can be applied to other dielectric solids.},

keywords = {manufacturing, related},

pubstate = {published},

tppubtype = {article}

}

@article{Horvath19-ab,

title = {Grinding of additively manufactured silicon carbide surfaces for optical applications},

author = {Nicholas Horvath and Andrew Honeycutt and Matthew A. Davies},

url = {https://doi.org/10.1016/j.cirp.2020.04.079},

year  = {2020},

date = {2020-05-19},

journal = {CIRP Annals},

volume = {69},

pages = {509-512},

abstract = {Many of the properties of Silicon carbide (SiC) are advantageous for optical applications, such as telescope mirrors and industrial laser systems. However, the base shapes of complex components are costly and difficult to manufacture. Leveraging additive manufacturing, near net complex components are readily processed. Here, we investigate the post processing of additively manufactured SiC (AM SiC) compared to chemical vapor deposited (CVD) SiC. The specific grinding energy for the AM SiC was lower than CVD, however the trends were the same. A specular finish was observed on both materials but the AM SiC finish was limited due to residual porosity.},

keywords = {manufacturing, related},

pubstate = {published},

tppubtype = {article}

}

@article{ALONSOALEMAN2019,

title = {Study of reflectors for illumination via conformal maps},

author = {LUIS A. ALEMÁN-CASTAÑEDA AND MIGUEL A. ALONSO},

editor = {Optical Society of America },

doi = {https://doi.org/10.1364/OL.44.003809},

year  = {2019},

date = {2019-07-02},

urldate = {2019-07-02},

journal = {Optics Letters},

volume = {44},

number = {15},

pages = {3809-3812},

abstract = {We present an approach for the study and design of reflectors with rotational or translational symmetry that redirect light from a point source into any desired radiant intensity distribution. This method is based on a simple conformal map that transforms the reflector’s shape into a curve that describes light’s direction after reflection. Both segmented reflectors and continuous reflectors are discussed, illustrating how certain reflector characteristics become apparent under this transformation. This method can also be used to study extended sources via translations.},

keywords = {design, related},

pubstate = {published},

tppubtype = {article}

}

@article{ALEMÁN-CASTANEDA2019,

title = {Shearing interferometry via geometric phase},

author = {LUIS A. ALEMÁN-CASTANEDA, BRUNO PICCIRILLO, ENRICO SANTAMATO, LORENZO MARRUCCI, AND MIGUEL A. ALONSO},

url = {https://doi.org/10.1364/OPTICA.6.000396},

doi = {10.1364/OPTICA.6.000396},

year  = {2019},

date = {2019-03-21},

journal = {Optica},

volume = {6},

number = {4},

pages = {396-399},

abstract = {We propose an approach based on geometric phase for per- forming several types of shearing interferometry through a ro- bust, compact, common-path setup. The key elements are two identical parallel plates with spatially varying birefringence distributions, which perform the shearing by writing opposite geometric phases on the two circular polarization components of the linearly polarized incident wavefront. This setup allows the independent control of the shearing magnitude and rela- tive phase of the two wavefront replicas. The approach is first illustrated for the simplest case of lateral shearing, and then extended to other geometries where the magnitude and direc- tion of the shear vary smoothly over the wavefront.},

keywords = {metrology, related},

pubstate = {published},

tppubtype = {article}

}

@article{LaurenApp18,

title = {Direct binary search for improved beam shaping and optical differentiation wavefront sensing},

author = {C. Dorrer and J. Qiao},

doi = {https://doi.org/10.1364/AO.57.008557},

year  = {2018},

date = {2018-06-01},

urldate = {2018-06-01},

journal = {Applied Optics},

volume = {57},

number = {29},

pages = {8557-8565 },

abstract = {Spatially dithered distributions of binary amplitude pixels are optimized using a full direct binary search, taking into account the experimental configuration for amplitude modulation of coherent waves. This design process is shown to yield a significant reduction of the noise induced by binarization and pixelation over the region of interest. We demonstrate this approach for beam shaping and optical differentiation wavefront sensing, where the region of interest is in an image plane of the pixel distribution, and in the far field of the pixel distribution, respectively. The observed reduction in error compared to a standard error diffusion algorithm is significant for both applications because it improves performance without the tighter fabrication tolerance and cost associated with smaller pixels.},

keywords = {CeFO related, manufacturing, related},

pubstate = {published},

tppubtype = {article}

}

@article{yao18,

title = {Point-cloud noncontact metrology of freeform optical surfaces},

author = {Jianing Yao and Alexander Anderson and Jannick P. Rolland},

url = {https://doi.org/10.1364/OE.26.010242},

doi = {10.1364/OE.26.010242},

year  = {2018},

date = {2018-04-09},

journal = {Optics Express},

volume = {26},

number = {8},

pages = {10242-10265},

abstract = {In this paper, we demonstrate the development of a point-cloud metrology method for the noncontact, high resolution, high precision testing of freeform surfaces. The method leverages swept source optical coherence tomography together with a common-path setup in the sample arm configured to mitigate the axial jitter caused by scanning and environmental perturbations. The lateral x-y scanning field was also rigorously evaluated for the sampling step, linearity, straightness, and orthogonality. Based on the finely engineered system hardware, a comprehensive system model was developed capable of characterizing the vertical displacement sensitivity and lateral scanning noise. The model enables predicting the point-cloud surface-metrology uncertainty map of any freeform surface and guiding the selection of optimum experimental conditions. A system was then assembled and experimentally evaluated first with flat and spherical standards to demonstrate the measurement uncertainty. Results of measuring an Alvarez freeform surface with 400-µm peak-to-valley sag show 93 nm (< λ/14) precision and 128 nm (< λ/10) root-mean-square residual from the nominal shape. The high resolution measurements also reveal mid spatial frequency structures on the test part.},

keywords = {metrology, related},

pubstate = {published},

tppubtype = {article}

}

@article{nanzhao18,

title = {Experimental investigation in nodal aberration theory (NAT) with a customized Ritchey-Chrétien system: third-order coma},

author = {Nan Zhao and Jonathan C. Papa and Kyle Fuerschbach and Yanfeng Qiao and Kevin P. Thompson and Jannick P. Rolland},

url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-26-7-8729},

doi = {10.1364/OE.26.008729},

year  = {2018},

date = {2018-04-02},

journal = {Optics Express},

volume = {26},

number = {7},

pages = {8729-8743},

abstract = {Nodal aberration theory (NAT) describes the aberration properties of optical systems without symmetry. NAT was fully described mathematically and investigated through real-ray tracing software, but an experimental investigation is yet to be realized. In this study, a two-mirror Ritchey-Chrétien telescope was designed and built, including testing of the mirrors in null configurations, for experimental investigation of NAT. A feature of this custom telescope is a high-precision hexapod that controls the secondary mirror of the telescope to purposely introduce system misalignments and quantify the introduced aberrations interferometrically. A method was developed to capture interferograms for multiple points across the field of view without moving the interferometer. A simulation result of Fringe Zernike coma was generated and analyzed to provide a direct comparison with the experimental results. A statistical analysis of the measurements was conducted to assess residual differences between simulations and experimental results. The interferograms were consistent with the simulations, thus experimentally validating NAT for third-order coma.},

keywords = {metrology, related},

pubstate = {published},

tppubtype = {article}

}

@article{AlonsoVella2017,

title = {Birefringent masks that are optimal for generating bottle fields},

author = {ANTHONY VELLA, HIPPOLYTE DOURDENT, LUKAS NOVOTNY, AND MIGUEL A. ALONSO},

editor = {OSA},

doi = {https://doi.org/10.1364/OE.25.009318},

year  = {2017},

date = {2017-04-17},

journal = {Optics Express},

volume = {25},

number = {8},

pages = {9318-9332},

abstract = {An optical bottle field containing a three-dimensional intensity null at the focal point can be generated by placing a spatially inhomogeneous birefringent mask at the pupil of an aplanatic high-NA focusing system. We derive the optimal birefringence distribution for which a uniformly polarized input beam is converted into a bottle field with the sharpest possible null in intensity. We show that a stress engineered optical (SEO) window, which has a radially varying retardance, followed by a half-wave plate, performs nearly as well as the optimal solution. Experimental results corroborate that an SEO element can be used to generate a bottle field.},

keywords = {design, related},

pubstate = {published},

tppubtype = {article}

}

@article{Fienup16,

title = {Ptychography for optical metrology with limited translation knowledge},

author = {Moore, D. B. and J. R. Fienup},

url = {https://www.osapublishing.org/ao/abstract.cfm?uri=ao-55-17-4596},

doi = {https://doi.org/10.1364/AO.55.004596},

year  = {2016},

date = {2016-06-07},

urldate = {2016-06-07},

journal = {Applied Optics},

volume = {55},

number = {17},

pages = {4596-4610},

abstract = {We introduce unknown-transverse translation diversity phase retrieval: a ptychographic algorithm for optical metrology when a subaperture is translating through a plane conjugate to the exit pupil in a very poorly known fashion. The algorithm estimates the direction of translation and the distance traveled by the subaperture from one point spread function (PSF) to the next. It also estimates unknown point target motion and rotations of the subaperture between PSF acquisitions from the PSF data.},

keywords = {related, testing},

pubstate = {published},

tppubtype = {article}

}

@article{Huang16,

title = {In vivo thickness dynamics measurement of tear film lipid and aqueous layers with optical coherence tomography and maximum-likelihood estimation},

author = {Huang, J. and H. B. Hindman and J. P. Rolland},

doi = {https://doi.org/10.1364/OL.41.001981},

year  = {2016},

date = {2016-04-15},

urldate = {2016-04-15},

journal = {Optics Letters},

volume = {41},

number = {9},

pages = {1981-1984 },

abstract = {Dry eye disease (DED) is a common ophthalmic condition that is characterized by tear film instability and leads to ocular surface discomfort and visual disturbance. Advancements in the understanding and management of this condition have been limited by our ability to study the tear film secondary to its thin structure and dynamic nature. Here, we report a technique to simultaneously estimate the thickness of both the lipid and aqueous layers of the tear film in vivo using optical coherence tomography and maximum-likelihood estimation. After a blink, the lipid layer was rapidly thickened at an average rate of 10 nm/s

 over the first 2.5 s before stabilizing, whereas the aqueous layer continued thinning at an average rate of 0.29 μm/s

 of the 10 s blink cycle. Further development of this tear film imaging technique may allow for the elucidation of events that trigger tear film instability in DED.},

keywords = {related, testing},

pubstate = {published},

tppubtype = {article}

}

@article{ao-55-10-2526.bib,

title = {Subaperture translation estimation accuracy in transverse-translation diversity phase retrieval},

author = {Moore, D.B. and J.R. Fienup},

url = {https://www.osapublishing.org/ao/abstract.cfm?uri=ao-55-10-2526&origin=search},

doi = {10.1364/AO.55.002526},

year  = {2016},

date = {2016-03-22},

journal = {Applied Optics},

volume = {55},

number = {10},

pages = {2526-2536},

abstract = {For optical metrology by transverse translation diversity phase retrieval (or ptychography), information theoretic limits on the ability to estimate subaperture translation, essential for accurate metrology, are assessed as a function of the optical aberrations of the system being measured. Special attention is given to the case that an unknown linear phase aberration, or equivalent detector or target motion, is present that varies with each point spread function in the measured data.},

keywords = {related, testing},

pubstate = {published},

tppubtype = {article}

}

@article{YAO2016,

title = {Volumetric rendering and metrology of spherical gradient refractive index lens imaged by angular scan optical coherence tomography system},

author = {Yao, J. and K. Thompson and B. Ma and J. P. Rolland},

url = {https://centerfreeformoptics.org/wp-content/uploads/2017/01/oe-24-17-19388-1.pdf, Full paper},

doi = {10.1364/OE.24.019388 },

year  = {2016},

date = {2016-00-00},

journal = {Optics Express},

volume = {24},

number = {17},

pages = {19388-19404},

abstract = {In this paper, we develop the methodology, including the refraction correction,

geometrical thickness correction, coordinate transformation, and layer segmentation

algorithms, for 3D rendering and metrology of a layered spherical gradient refractive index

(S-GRIN) lens based on the imaging data collected by an angular scan optical coherence

tomography (OCT) system. The 3D mapping and rendering enables direct 3D visualization

and internal defect inspection of the lens. The metrology provides assessment of the surface

geometry, the lens thickness, the radii of curvature of the internal layer interfaces, and the

misalignment of the internal S-GRIN distribution with respect to the lens surface. The OCT

metrology results identify the manufacturing defects, and enable targeted process

development for optimizing the manufacturing parameters. The newly fabricated S-GRIN

lenses show up to a 7x spherical aberration reduction that allows a significantly increased

utilizable effective aperture.

© 2016 Optical Society of America

OCIS codes: (120.0120) Instrumentation, measurement, and metrology; (110.4500) Optical coherence tomography;

(120.4630) Optical inspection; (110.0110) Imaging systems. },

keywords = {related, testing},

pubstate = {published},

tppubtype = {article}

}

@article{Huang15,

title = {Performance analysis of optical coherence tomography in the context of a thickness estimation task},

author = {Huang, J. and J. Yao and N. Cirucci and T. Ivanov and J. P. Rolland},

url = {https://www.spiedigitallibrary.org/journals/journal-of-biomedical-optics/volume-20/issue-12/121306/Performance-analysis-of-optical-coherence-tomography-in-the-context-of/10.1117/1.JBO.20.12.121306.full},

doi = {https://doi.org/10.1117/1.JBO.20.12.121306},

year  = {2015},

date = {2015-12-01},

urldate = {2015-12-01},

journal = {Journal of Biomedical Optics},

volume = {20},

number = {12},

pages = {121306},

abstract = {Thickness estimation is a common task in optical coherence tomography (OCT). This study discusses and quantifies the intensity noise of three commonly used broadband sources, such as a supercontinuum source, a superluminescent diode (SLD), and a swept source. The performance of the three optical sources was evaluated for a thickness estimation task using both the fast Fourier transform (FFT) and maximum-likelihood (ML) estimators. We find that the source intensity noise has less impact on a thickness estimation task compared to the width of the axial point-spread function (PSF) and the trigger jittering noise of a swept source. Findings further show that the FFT estimator yields biased estimates, which can be as large as 10% of the thickness under test in the worst case. The ML estimator is by construction asymptotically unbiased and displays a 10× improvement in precision for both the supercontinuum and SLD sources. The ML estimator also shows the ability to estimate thickness that is at least 10× thinner compared to the FFT estimator. Finally, findings show that a supercontinuum source combined with the ML estimator enables unbiased nanometer-class thickness estimation with nanometer-scale precision.},

keywords = {related, testing},

pubstate = {published},

tppubtype = {article}

}

@article{Kitt15,

title = {Visible metasurfaces and ruled diffraction gratings: a comparison},

author = {Kitt, A. and J. P. Rolland and A. N. Vamivakas},

doi = {https://doi.org/10.1364/OME.5.002895},

year  = {2015},

date = {2015-11-23},

urldate = {2015-11-23},

journal = {Opt. Express},

volume = {5},

number = {12},

pages = {2895-2901},

abstract = {Metasurface based and physical ruling based diffraction gratings function by controlling the phase of light, but the origin of the phase control is different. Here we compare the simulated optical response of a 1800 lines/mm ruled diffraction grating blazed for 650 nm light to the response of a 1800 lines/mm phase grating meta-surface designed for efficiency in the visible. The efficiencies are comparable; the transverse electric polarized efficiency of the meta-surface based grating is similar to the transverse magnetic polarized efficiency of the ruled-grating. However, due to the different mechanisms of phase accrual, the meta-surface based grating does not exhibit grating anomalies and has low efficiency for transverse magnetic polarized light.},

keywords = {design, related},

pubstate = {published},

tppubtype = {article}

}

@article{YAO15b,

title = {Simultaneous estimation of thickness and refractive index of layered gradient refractive index optics using a hybrid confocal-scan swept-source optical coherence tomography system},

author = {Yao, J. and J. Huang and P. Meemon and M. Ponting and J. P. Rolland},

doi = {https://doi.org/10.1364/OE.23.030149},

year  = {2015},

date = {2015-11-10},

urldate = {2015-11-10},

journal = {Opt. Express},

volume = {23},

number = {23},

pages = {30149-30164},

abstract = {A hybrid confocal-scan swept-source optical coherence tomography metrology system was conceived for simultaneous measurements of the refractive index and thickness profiles of polymeric layered gradient refractive index (GRIN) optics. An uncertainty analysis predicts the metrology capability of the system and guides the selection of an optimum working numerical aperture. Experimental results on both a monolithic and a GRIN layered sheet are demonstrated to be in close agreement with theoretical predictions. Index measurement precision reached 0.0001 and 0.0008 for measuring 2.8 mm and ~300 µm thick layers, respectively. The thicknesses of these layers were simultaneously measured with a precision of 0.28 and 0.17 µm, respectively.},

keywords = {related, testing},

pubstate = {published},

tppubtype = {article}

}

@article{Salzman15,

title = {Magnetorheological finishing of chemical-vapor-deposited zinc sulfide via chemically and mechanically modified fluids},

author = {Salzman, S. and H. J. Romanofsky and L. J. Giannechini and S. D. Jacobs and J. C. Lambropoulos},

doi = {https://doi.org/10.1364/AO.55.001481},

year  = {2015},

date = {2015-11-03},

urldate = {2015-11-03},

journal = {Applied Optics},

volume = {55},

number = {6},

pages = {1481},

abstract = {We describe the anisotropy in the material-removal rate (MRR) of the polycrystalline, chemical-vapor–deposited (CVD) zinc sulfide (ZnS). We define the polycrystalline anisotropy via microhardness and chemical erosion tests for four crystallographic orientations of ZnS: (100), (110), (111), and (311). Anisotropy in the MRR was studied under magnetorheological finishing (MRF) conditions. Three chemically and mechanically modified magnetorheological (MR) fluids at pH values of 4, 5, and 6 were used to test the MRR variations among the four single-crystal planes. When polishing the single-crystal planes and the polycrystalline with pH 5 and pH 6 MR fluids, variations were found in the MRR among the four single-crystal planes and surface artifacts were observed on the polycrystalline material. When polishing the single-crystal planes and the polycrystalline with the modified MR fluid at pH 4, however, minimal variation was observed in the MRR among the four orientations and a reduction in surface artifacts was achieved on the polycrystalline material.},

keywords = {manufacturing, related},

pubstate = {published},

tppubtype = {article}

}

@article{GRAY15,

title = {Wavefront aberration function in terms of R.V. Shack’s vector product and Zernike polynomial vectors},

author = {Gray, R. and J. P. Rolland},

doi = {https://doi.org/10.1364/JOSAA.32.001836},

year  = {2015},

date = {2015-08-18},

urldate = {2015-08-18},

journal = {JOSA A},

volume = {32},

number = {10},

pages = {1836-1847},

abstract = {Previous papers have shown how, for rotationally symmetric optical imaging systems, nodes in the field dependence of the wavefront aberration function develop when a rotationally symmetric optical surface within an imaging optical system is decentered and/or tilted. In this paper, we show how Shack’s vector product (SVP) can be used to express the wavefront aberration function and to define vectors in terms of the Zernike polynomials. The wavefront aberration function is then expressed in terms of the Zernike vectors. It is further shown that SVP fits within the framework of two-dimensional geometric algebra (GA). Within the GA framework, an equation for the third-order node locations for the binodal astigmatism term that emerge in the presence of tilts and decenters is then demonstrated. A computer model of a three-mirror telescope system is used to demonstrate the validity of the mathematical development.},

keywords = {design, related},

pubstate = {published},

tppubtype = {article}

}

@article{DUMA15,

title = {Optimization of galvanometer scanning for optical coherence tomography},

author = {Duma, V. and P. Tankam and J. Huang and J. Won and J. P. Rolland,},

doi = {https://doi.org/10.1364/AO.54.005495},

year  = {2015},

date = {2015-06-10},

urldate = {2015-06-10},

journal = {Applied Optics},

volume = {54},

number = {17},

pages = {5495-5507},

abstract = {We study experimentally the effective duty cycle of galvanometer-based scanners (GSs) with regard to three main parameters of the scanning process: theoretical/imposed duty cycle (of the input signal), scan frequency, and scan amplitude. Sawtooth and triangular input signals for the device are considered. The effects of the mechanical inertia of the oscillatory element of the GS are analyzed and their consequences are discussed in the context of optical coherence tomography (OCT) imaging. When the theoretical duty cycle and the scan amplitude are increased to the limit, the saturation of the device is demonstrated for a useful range of scan frequencies by direct measurement of the position of the galvomirror. Investigations of OCT imaging of large samples also validate this saturation, as examplified by the gaps/blurred portions obtained between neighboring images when using both triangular and sawtooth scanning at high scan frequencies. For this latter aspect, the necessary overlap between neighboring B-scans, and therefore between the corresponding volumetric reconstructions of the sample, are evaluated and implemented with regard to the same parameters of the scanning process. OCT images that are free of these artifacts are thus obtained.},

keywords = {related, testing},

pubstate = {published},

tppubtype = {article}

}

@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}

}

@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}

}

@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}

}