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59 results on '"Snyder, Donald R."'

1. Effects of intensity thresholding on the power spectrum of laser speckle

Author

Ducharme, Alfred D., Boreman, Glenn D., and Snyder, Donald R.

Subjects
Laser speckle -- Usage, Modulation (Electronics) -- Measurement, Charge coupled devices -- Research, Astronomy, Physics
Abstract

Spatial-frequency filtering of laser-speckle patterns has proved to be a useful tool in the measurement of the modulation transfer function for focal plane arrays. Intensity thresholding of the laser-speckle patterns offers nearly an order of magnitude savings in digital storage space. The effect of this thresholding on the spatial-frequency power spectral density of the speckle pattern is investigated. An optimum threshold level is found that minimizes distortion of the power spectrum for the classes of speckle data used for modulation transfer function testing.

Published
1994

2. Visualization of optical pulse filamentation by femtosecond time-resolved optical polarigraphy

Author

Paisley, Dennis L., Kleinfelder, Stuart, Snyder, Donald R., Thompson, Brian J., Centurion, Martin, Pu, Ye, Psaltis, Demetri, Paisley, Dennis L., Kleinfelder, Stuart, Snyder, Donald R., Thompson, Brian J., Centurion, Martin, Pu, Ye, and Psaltis, Demetri

Abstract

We have observed the filamentation of optical pulses in carbon disulfide(CS2) using femtosecond time-resolved optical polarigraphy(FTOP). A pump-probe setup is used to capture the propagation of a 150 femtosecond laser pulse in CS2. The probe pulse propagates in a direction perpendicular to the pump. The high intensity of the pump pulse causes a transient index change in the material through the Kerr effect. The induced birefringence is proportional to the intensity of the pump and can be captured by monitoring the polarization of the probe. The probe pulse is imaged on a CCD camera to recover the intensity profile of the pump pulse. We have used this technique to observe the spatial evolution of the pulse as a function of power and propagation distance. Initially, the pulse propagation causes a coarse redistribution of the intensity. The beam then breaks up into stable light filaments which propagate for several millimeters, and finally the beam profile becomes unstable to small fluctuations in the input power.

Published
2005

3. Femtosecond holography

Author

Paisley, Dennis L., Kleinfelder, Stuart, Snyder, Donald R., Thompson, Brian J., Centurion, Martin, Pu, Ye, Psaltis, Demetri, Paisley, Dennis L., Kleinfelder, Stuart, Snyder, Donald R., Thompson, Brian J., Centurion, Martin, Pu, Ye, and Psaltis, Demetri

Abstract

We present a holographic recording technique with 150 femtosecond time resolution. This technique allows us to capture either a single hologram with fine spatial resolution (4 micrometers), or a time-sequence of multiple holograms with reduced spatial resolution in a single-shot experiment, while preserving amplitude and phase information. The time resolution and the frame rate are limited only by the duration of the laser pulses. The holograms are recorded on a CCD camera and digitally reconstructed. We have used the technique to study the nonlinear propagation of high energy femtosecond pulses through liquids. We have observed dramatic differences in the pulse propagation characteristics depending on the strength of the nonlinear coefficient of the material and it's time response. The fine spatial resolution allows us to zoom in and visualize the spatial profile of the pulses breaking up into multiple filaments while the phase recovered from the holograms helps us identify the nonlinear index changes in the material. We have measured both positive and negative index changes. Very fast positive index changes are generally attributable to the Kerr nonlinearity. The negative index changes can be caused by electron plasma generated by multiphoton absorption.

Published
2005

4. Stereo at the Speed of Light: High-Speed Digital Stereo Imaging at up to 100 Million Frames Per Second

Author

AIR FORCE RESEARCH LAB EGLIN AFB FL, Snyder, Donald R., AIR FORCE RESEARCH LAB EGLIN AFB FL, and Snyder, Donald R.

Abstract

When shutter speeds approach a nanosecond you set your experiment up using a tape measure. Light-in-Flight imaging takes over when the length of the pulse and the shutter time can relate to a distance of two or three meters. This paper addresses the development of next generation ultrahigh speed digital imaging system and their application to stereo photography of ballistic, penetration, fragmentation, and spray events. Applications of high speed imaging from 1000 to 100 million frames per second are discussed along with the software used to evaluate various experimental methods. Applications range from ultra-high resolution still imaging using a laser strobe to laser illuminated digital movies., This article is from ADA404787 10th U.S. Army Gun Dynamics Symposium Proceedings

Published
2001

23. Hi-G electronic gated camera for precision trajectory analysis

Author

Snyder, Donald R., primary, Payne, Scott, additional, Keller, Ed, additional, Longo, Salvatore, additional, Caudle, Dennis E., additional, Walker, Dennis C., additional, Sartor, Mark A., additional, Keeler, Joe E., additional, Kerr, David A., additional, Fail, R. Wallace, additional, Gannon, Jim, additional, Carrol, Ernie, additional, and Jamison, Todd A., additional

Published
1997
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43. Multipath RDMA Instrumentation.

Author

McMillian, Brett, Ferguson, Dennis, McMillian, Gary, and Snyder, Donald R.

Subjects
DATA transmission systems, COMPUTER network architectures, PARALLEL programming, LOCAL area networks, ETHERNET
Abstract

Multipath remote direct memory access (RDMA) is a new networking technology that provides an order-of-magnitude increase in bandwidth through a fill-mesh backplane and through a standard Ethernet switch fabric. This article first describes full-mesh backplane technology, RDMA access over internet protocol, and Multipath RDMA, then introduces two novel Multipath RDMA instrumentation systems: an instrumentation module and an instrumen- tation blade. The instrumentation module supports Giga-sample per second (GSPS) instrumentation and operates at the end of the wire using Power-over-Ethernet Plus. The instrumentation blade goes directly into a Multipath RDMA-enabled blade chassis, supports multi- GSPS instrumentation, and gives rise to real-time or near-real-time parallel processing of data produced by multi-GSPS instrumentation. [ABSTRACT FROM AUTHOR]

Published
2008

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