francis daniel

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$Research paper thumbnail of The use of parabolic mirrors in combined low-coherence and confocal refractive index measurement$

The use of parabolic mirrors in combined low-coherence and confocal refractive index measurement

Low-coherence interferometry is combined with confocal scanning to provide remote refractive inde... more Low-coherence interferometry is combined with confocal scanning to provide remote refractive index and thickness measurements of transparent materials. The influence of lens aberrations in the confocal measurement is assessed through investigation of the axial point-spread functions (APSFs) generated using optical configurations comprised of paired aspherics and paired achromats. Off-axis parabolic mirrors are suggested as an alternative to lenses and are shown to exhibit much more symmetric APSFs provided the system numerical aperture is not too high. Refractive index and thickness measurements are made with each configuration with most mirror pairings offering better than twice the repeatability and accuracy of either lens pairing.

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Bridges 99: Mathematical Connections in Art, Music and Science

Nexus Network Journal, 1999

The second annual conference, Bridges: Mathematical Connections in Art, Music, and Science, was a... more The second annual conference, Bridges: Mathematical Connections in Art, Music, and Science, was a gathering of visual artists, computer graphicists, mathematicians, musicians, and scientists from several schools and countries -as close as Canada and as far away as Kuwait. The purpose of the conference was to explore the links among disciplines through mathematical properties of objects and matter. The conference was held at Southwestern College, Winfield, Kansas in the United States, during a three day period, July 30-August 1, 1999. It included three General Sessions in the mornings, six Special Sessions, and three Workshop Sessions in the afternoons. In addition to the three-day conference, there was also an activity day structured for high school students titled "Bridges for the Next Generation". On this day, some of the invited extramural speakers joined presenters from Southwestern College to work with these public school students. The Proceedings of the Conference, a 310-page book with approximately 200 illustrations, included peer-reviewed papers by presenters and was distributed during the conference. The conference exhibited artwork by some of its participants. Among these was Brent Collins, a sculptor from Kansas City, Missouri, USA, who brought wooden and bronze casts of his work. Janusz Kapusta, a New York Times cartoonist, exhibited his geometrical elevensided shape called the K-Dron. He distributed a sample of this form among participants of the conference as well as a complimentary book on the history of the evolution of the K-Dron. Robert Fathauer, the founder of Tesselations Company in Tempe, Arizona, exhibited his fractal and post-Escher tilings. Irene Rousseau, an artist and art historian from New Jersey, exhibited "Mosaics". Additional exhibits included John Sullivan's "Optiverse and other Sphere Inversions" and Nat Friedman's "Geos". The conference started with an official welcome from President Dick Merriman of Southwestern College. He talked about the excitement in academics and in life being generated at the borders of fields and ideas. Nat Friedman from SUNY-Albany next spoke on hyper-seeing and showed a series of slides of his sculpture to illustrate his concept.

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$Research paper thumbnail of Refractive index and dispersion measurement using low-coherence interferometry with broadband confocal scanning$

Refractive index and dispersion measurement using low-coherence interferometry with broadband confocal scanning

Measurement of the refractive index and thickness of transparent plates is demonstrated using com... more Measurement of the refractive index and thickness of transparent plates is demonstrated using combined low-coherence interferometry and confocal scanning. The low-coherence measurement provides a quantity related to the group index and the confocal scan provides a parameter related to the phase index. Calculation of both the phase and group indices also requires a measurement of the confocal parameter at multiple wavelengths. This is achieved using a broadband source and a line-scan spectrometer to interrogate different regions of the spectrum. Measurements are made on a range of transparent optical materials with the mean percentage errors of each measurand being 0.08%, 0.06%, and 0.12% for np, ng, and thickness t respectively.

Conference Report—Bridges 2004: Mathematical Connections in Art, Music, and Science

Nexus Network Journal, 2004

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Frequency-division multiplexing for multicomponent shearography

Applied optics, 2013

A new method of multiplexing the speckle patterns needed in multicomponent digital shearography s... more A new method of multiplexing the speckle patterns needed in multicomponent digital shearography systems is presented. Frequency-division multiplexing (FDM) of the measurement channels is achieved by recording speckle patterns from objects illuminated by intensity-modulated sources. Each source is modulated at a discrete frequency, which is less than half of the camera frame rate, and a bank of images of the modulated speckle patterns is captured. This allows for pixel-by-pixel Fourier-based extraction of the individual speckle patterns from peaks in the power spectra. The approach is demonstrated with a two-component in-plane shearography instrument.

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