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Electrical and Computer Engineering
Electrical and Computer Engineering Faculty Publications and Presentations
- Keyword
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- Speckle (3)
- Optics -- Statistical methods (2)
- Underwater acoustics (2)
- Acoustical engineering (1)
- Aerosols -- Optical properties (1)
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- Backscattering -- Measurement (1)
- Electron beams (1)
- Image processing -- Digital techniques (1)
- Imaging systems (1)
- Laser Doppler velocimeter (1)
- Medical instruments and apparatus (1)
- Noise -- Measurement (1)
- Optical coherence tomography (1)
- Optical data processing (1)
- Optical radar (1)
- Optical spectroscopy (1)
- Optical tomography -- Technological innovations (1)
- Radiative transfer -- Mathematical models (1)
- Remote sensing -- Aerosols (1)
- Speckle -- Statistics (1)
- Theory of wave-motion (1)
Articles 1 - 8 of 8
Full-Text Articles in Engineering
Lidar System Model For Use With Path Obscurants And Experimental Validation, J. W. Giles, I. N. Bankman, R. M. Sova, T. R. Morgan, Donald D. Duncan, J. A. Millard, W. J. Green, F. J. Marcotte
Lidar System Model For Use With Path Obscurants And Experimental Validation, J. W. Giles, I. N. Bankman, R. M. Sova, T. R. Morgan, Donald D. Duncan, J. A. Millard, W. J. Green, F. J. Marcotte
Electrical and Computer Engineering Faculty Publications and Presentations
When lidar pulses travel through a short path that includes a relatively high concentration of aerosols, scattering phenomena can alter the power and temporal properties of the pulses significantly, causing undesirable effects in the received pulse. In many applications the design of the lidar transmitter and receiver must consider adverse environmental aerosol conditions to ensure the desired performance. We present an analytical model of lidar system operation when the optical path includes aerosols for use in support of instrument design, simulations, and system evaluation. The model considers an optical path terminated with a solid object, although it can also be …
Modeling Broadband Ocean Acoustic Transmissions With Time-Varying Sea Surfaces, Martin Siderius, Michael B. Porter
Modeling Broadband Ocean Acoustic Transmissions With Time-Varying Sea Surfaces, Martin Siderius, Michael B. Porter
Electrical and Computer Engineering Faculty Publications and Presentations
Solutions to ocean acoustic scattering problems are often formulated in the frequency domain, which implies that the surface is "frozen" in time. This may be reasonable for short duration signals but breaks down if the surface changes appreciably over the transmission time. Frequency domain solutions are also impractical for source-receiver ranges and frequency bands typical for applications such as acoustic communications (e.g. hundreds to thousands of meters, 1-50 kHz band). In addition, a driving factor in the performance of certain acoustic systems is the Doppler spread, which is often introduced from sea-surface movement. The time-varying nature of the sea surface …
Measurement Of Oxygen Saturation In The Retina With A Spectroscopic Sensitive Multi Aperture Camera, Jessica C. Ramella-Roman, Scott A. Mathews, Haripriya Kandimalla, Afshin Nabili, Donald D. Duncan, Salvatore A. D'Anna, Syed M. Shah, Quan D. Nguyen
Measurement Of Oxygen Saturation In The Retina With A Spectroscopic Sensitive Multi Aperture Camera, Jessica C. Ramella-Roman, Scott A. Mathews, Haripriya Kandimalla, Afshin Nabili, Donald D. Duncan, Salvatore A. D'Anna, Syed M. Shah, Quan D. Nguyen
Electrical and Computer Engineering Faculty Publications and Presentations
We introduce a new multi aperture system capable of capturing six identical images of the human fundus at six different spectral bands. The system is based on a lenslet array architecture and is well suited for spectroscopy application. The multi-aperture system was interfaced with a fundus camera to acquire spectroscopic sensitive images of the retina vessel and ultimately to calculate oxygen saturation in the retina in vivo. In vitro testing showed that the system is able to accurately reconstruct curves of partially oxygenated hemoglobin. In vivo testing on healthy volunteers was conducted and yielded results of oxygen saturation similar to …
Bottom Profiling By Correlating Beam-Steered Noise Sequences, Chris H. Harrison, Martin Siderius
Bottom Profiling By Correlating Beam-Steered Noise Sequences, Chris H. Harrison, Martin Siderius
Electrical and Computer Engineering Faculty Publications and Presentations
It has already been established that by cross-correlating ambient noisetime series received on the upward and downward steered beams of a drifting vertical array one can obtain a subbottom layer profile. Strictly, the time differential of the cross correlation is the impulse response of the seabed. Here it is shown theoretically and by simulation that completely uncorrelated surfacenoise results in a layer profile with predictable amplitudes proportional to those of an equivalent echo sounder at the same depth as the array. The phenomenon is simulated by representing the sound sources as multiple random time sequences emitted from random locations in …
Monte Carlo Modeling Of Spatial Coherence: Free-Space Diffraction, Donald D. Duncan, David G. Fischer, Scott A. Prahl
Monte Carlo Modeling Of Spatial Coherence: Free-Space Diffraction, Donald D. Duncan, David G. Fischer, Scott A. Prahl
Electrical and Computer Engineering Faculty Publications and Presentations
We present a Monte Carlo method for propagating partially coherent fields through complex deterministic optical systems. A Gaussian copula is used to synthesize a random source with an arbitrary spatial coherence function. Physical optics and Monte Carlo predictions of the first- and second-order statistics of the field are shown for coherent and partially coherent sources for free-space propagation, imaging using a binary Fresnel zone plate, and propagation through a limiting aperture. Excellent agreement between the physical optics and Monte Carlo predictions is demonstrated in all cases. Convergence criteria are presented for judging the quality of the Monte Carlo predictions.
Statistics Of Local Speckle Contrast, Donald D. Duncan, Sean J. Kirkpatrick, Ruikang K. Wang
Statistics Of Local Speckle Contrast, Donald D. Duncan, Sean J. Kirkpatrick, Ruikang K. Wang
Electrical and Computer Engineering Faculty Publications and Presentations
In describing the first-order properties of laser speckle under polarized illumination conditions, it is almost an article of faith that the contrast is unity. In many processing schemes, however, the contrast defined as the quotient of the standard deviation and the mean is calculated over a localized spatial region. In such cases, this local contrast displays a distribution of values that can depart substantially from unity. Properties of this distribution depend on details of the data acquisition and on the size of the local neighborhood over which the contrast is calculated. We demonstrate that this local contrast can be characterized …
Can Laser Speckle Flowmetry Be Made A Quantitative Tool?, Donald D. Duncan, Sean J. Kirkpatrick
Can Laser Speckle Flowmetry Be Made A Quantitative Tool?, Donald D. Duncan, Sean J. Kirkpatrick
Electrical and Computer Engineering Faculty Publications and Presentations
The ultimate objective of laser speckle flowmetry (and a host of specific implementations such as laser speckle contrast analysis, LASCA or LSCA; laser speckle spatial contrast analysis, LSSCA; laser speckle temporal contrast analysis, LSTCA; etc.) is to infer flow velocity from the observed speckle contrast. Despite numerous demonstrations over the past 25 years of such a qualitative relationship, no convincing quantitative relationship has been proven. One reason is a persistent mathematical error that has been propagated by a host of workers; another is a misconception about the proper autocorrelation function for ordered flow. Still another hindrance has been uncertainty in …
The Copula: A Tool For Simulating Speckle Dynamics, Donald D. Duncan, Sean J. Kirkpatrick
The Copula: A Tool For Simulating Speckle Dynamics, Donald D. Duncan, Sean J. Kirkpatrick
Electrical and Computer Engineering Faculty Publications and Presentations
Use of a copula for generating a sequence of correlated speckle patterns is introduced. The chief characteristic of this algorithm is that it generates a continuous speckle sequence with a specified evolution of the correlation and does so with just two arrays of random numbers. Thus, physically realistic temporally varying speckle patterns with proper first- and second-order statistics are easily realized. We illustrate use of the algorithm for generating sequences with prescribed Gaussian, exponential, and equal-interval correlations and demonstrate how correlation times can be specified independently. This approach to generating sequences of random realizations with prescribed correlations should prove useful …