Allen Davis
United States Naval Research Laboratory
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by Allen Davis.
Journal of Lightwave Technology | 1995
Frank Bucholtz; Carl A. Villarruel; Allen Davis; Clay K. Kirkendall; D.M. Dagenais; J. A. McVicker; S.S. Patrick; K.P. Koo; Gunnar Wang; H. Valo; T. Lund; A.G. Andersen; R. Gjessing; E.J. Eidem; T. Knudsen
We have designed, fabricated, and operated an undersea array of eight fiber-optic vector magnetometers. Each magnetometer consists of three magnetostrictive transducers aligned on orthogonal axes and incorporated in a single Michelson interferometer. During undersea operation, each interferometer exhibited less than 1 /spl mu/rad//spl radic/ Hz phase noise, and the self-noise of each magnetic transducer was less than 0.2 nT//spl radic/ Hz at 0.1 Hz. We discuss the design and performance of the optical system including noise mechanisms. We present the results of magnetic measurements of the geomagnetic field and the magnetic tracking of ships. >
ieee international magnetics conference | 1995
Frank Bucholtz; D.M. Dagenais; Carl A. Villarruel; Clay K. Kirkendall; J.A. McVicker; Allen Davis; S.S. Patrick; K.P. Koo; G. Wang; H. Valo; E.J. Eidem; A. Andersen; T. Lund; R. Gjessing; T. Knudsen
We describe an undersea array of eight magnetic sensors. The employ magnetostrictive the transducer elements. ting principles and the ~orm~nce of the system during actual undersea
Applied Optics | 2016
Brandon Redding; Allen Davis; Clay K. Kirkendall; A. Dandridge
We present a holographic laser vibrometer designed to mitigate the effects of speckle noise when measuring the vibrational motion of a rough object. We show that multiplexing the interferometric measurement across 105 pixels provides a 50 dB reduction in the incoherent noise. Using a high-speed camera, this enables a displacement sensitivity of 50 fm/√Hz with a bandwidth of 12.5 kHz when measuring rough objects, representing a 20 dB improvement compared with a commercially available single-detector-based laser vibrometer. Finally, we show that the holographic vibrometer system is capable of stand-off acoustic sensing by measuring the acoustic-induced vibrations of a piece of paper with sensitivity as low as 10 dB (re 20 μPa). The ability to sensitively and noninvasively measure the vibrations of arbitrary rough surfaces could enable new applications in laser vibrometry.
SPIE's 1994 International Symposium on Optics, Imaging, and Instrumentation | 1994
Frank Bucholtz; Carl A. Villarruel; D.M. Dagenais; J. A. McVicker; K.P. Koo; Clay K. Kirkendall; Allen Davis; S. P. Patrick; A. Dandridge
An array of eight fiber optic vector magnetometers was designed and constructed for use in undersea applications such as harbors, ports, and waterways. We describe the design and performance characteristics of the array including the single-mode fiber optic system and magnetostrictive transducers. Data is presented from both laboratory measurements and from actual undersea operation.
Proceedings of SPIE | 2016
Brandon Redding; Allen Davis; Clay K. Kirkendall; A. Dandridge
Emerging underwater optical imaging and sensing applications rely on phase-sensitive detection to provide added functionality and improved sensitivity. However, underwater turbulence introduces spatio-temporal variations in the refractive index of water which can degrade the performance of these systems. Although the influence of turbulence on traditional, non-interferometric imaging has been investigated, its influence on the optical phase remains poorly understood. Nonetheless, a thorough understanding of the spatio-temporal dynamics of the optical phase of light passing through underwater turbulence are crucial to the design of phase-sensitive imaging and sensing systems. To address this concern, we combined underwater imaging with high speed holography to provide a calibrated characterization of the effects of turbulence on the optical phase. By measuring the modulation transfer function of an underwater imaging system, we were able to calibrate varying levels of optical turbulence intensity using the Simple Underwater Imaging Model (SUIM). We then used high speed holography to measure the temporal dynamics of the optical phase of light passing through varying levels of turbulence. Using this method, we measured the variance in the amplitude and phase of the beam, the temporal correlation of the optical phase, and recorded the turbulence induced phase noise as a function of frequency. By bench marking the effects of varying levels of turbulence on the optical phase, this work provides a basis to evaluate the real-world potential of emerging underwater interferometric sensing modalities.
Applied Optics | 2017
Brandon Redding; Allen Davis
We investigate the ability of a holographic laser vibrometer to mitigate noise introduced when operating on a moving platform or when measuring a moving target. This motion introduces a fundamental limitation on the measurement sensitivity due to the time-varying speckle pattern produced as the illumination beam scans across the target surface. In addition, since existing systems record the phase of only a single speckle grain, speckle fading imposes a limit on the coherent processing interval and thus the frequency resolution of these measurements. In this work, we show that by measuring N speckle grains in parallel using holographic detection, we are able to provide a N1/2 improvement in the system sensitivity while simultaneously overcoming the limitations on the coherent processing interval imposed by speckle fading. The ability to perform sensitive vibrational measurements of a moving target or from a moving platform could dramatically increase the applications available to laser vibrometry.
Tenth International Conference on Optical Fibre Sensors | 1994
Frank Bucholtz; Carl A. Villarruel; Clay K. Kirkendall; D.M. Dagenais; J. A. McVicker; Allen Davis; S. P. Patrick; K.P. Koo; A. Dandridge; Gunnar Wang; Terje Lund; H. Valo
The 1/r3 dependence of the magnetic field with distance r makes the vector magnetometer an ideal sensor in undersea systems for the localization and tracking of vessels. Since the undersea system typically spans several hundred meters to several kilometers, use of fiber optics for both telemetry and sensing offers inherent advantages of low cable weight, immunity to electromagnetic interference on the signal transmission paths, and high channel capability.
Electronics Letters | 1993
Frank Bucholtz; Carl A. Villarruel; Clay K. Kirkendall; D.M. Dagenais; J.A. McVicker; Allen Davis; S.S. Patrick; K.P. Koo; K.G. Wathen; A. Dandridge; Gunnar Wang; T. Lund; H. Valo
Electronics Letters | 1994
Frank Bucholtz; Gunnar Wang; Clay K. Kirkendall; C.A. Villaruel; Allen Davis; D.M. Dagenais; J.A. McVicker; S.S. Patrick; K.P. Koo; A. Andersen; H. Valo; R. Gjessing; E.J. Eidem; T. Knudsen
Electronics Letters | 1992
Allen Davis; S.S. Patrick; A. Dandridge; Frank Bucholtz