Tim J. Williams
University of Hawaii at Manoa
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Featured researches published by Tim J. Williams.
SPIE's International Symposium on Optical Science, Engineering, and Instrumentation | 1998
Paul G. Lucey; Tim J. Williams; Marc Mignard; Jeffrey Julian; Daniel Kobubun; Gregory Allen; David Hampton; William Schaff; Michael J. Schlangen; Edwin M. Winter; William Kendall; Alan D. Stocker; Keith A. Horton; Anu P. Bowman
The AHI (Airborne Hyperspectral Imager) system was designed to detect the presence of buried land mines from the air through detection of along wave IR observable associated with mine installation. The system is a helicopter-borne LWIR hyperspectral imager with real time on-board radiometric calibration and mine detection. It collects hyperspectral imagery from 7.5 to 11.5 μm in either 256 or 32 spectral bands. At all wavelengths the AHI noise equivalent delta (NEΔT) temperature is less than 0.1K at 300K and the NESR is less than .02 watts/m2-sr-μm.
Applied Optics | 2008
Paul G. Lucey; Keith A. Horton; Tim J. Williams
Field and laboratory measurements using an interferometer spectrometer based on the Sagnac interferometer using a microbolometer array detector are presented. Remotely obtained signatures collected with this instrument and with a cryogenic IR spectrometer are compared and shown to closely correspond. Ground-to-ground and air-to-ground image products are presented that demonstrate the image quality of the sensor. Signal-to-noise measurements are presented and compared with a simple parametric performance model that predicts the sensor performance. The performance model is used to predict the performance of this technology when equipped with cooled detectors.
Proceedings of SPIE | 1993
Paul G. Lucey; Keith A. Horton; Tim J. Williams; K. Hinck; C. Budney; Bruce Rafert; T. B. Rusk
We describe a novel cryogenically cooled, spatially modulated, imaging, Fourier transform interferometer spectrometer for spectral measurements in the 1 - 5 micrometers range. Using spatial modulation and a detector array to sample the interferogram, the instrument employs no moving parts to obtain spectra. It is extremely robust and potentially more reliable than other interferometers in addition to taking advantage of the multiplexing afforded by array detectors. The instrument technology possesses a unique combination of characteristics which forms a niche for spectral measurement not widely known but of great potential value. These characteristics include broad wavelength range, wide field of view if desired, simultaneous measurement of all spectral channels, compactness, no moving parts, and moderate resolution. We present a small amount of test data derived from the instrument.
Proceedings of SPIE | 2001
Paul G. Lucey; Tim J. Williams; John Lewis Hinrichs; Michael E. Winter; Donovan Steutel; Edwin M. Winter
The AHI sensor consists of a long-wave infrared pushbroom hyperspectral imager and a boresighted 3-color visible high resolution CCD linescan camera. The system used a background suppression system to achieve good noise characteristics (less than 1(mu) fl NESR). Work with AHI has shown the utility of the long-wave infrared a variety of applications. The AHI system has been used successfully in the detection of buried land mines using infrared absorption features of disturbed soil. Recently, the AHI has been used to examine the feasibility active and passive hyperspectral imaging under outdoor and laboratory conditions at three ranges. In addition, the AHI was flown over a coral reef ecosystem on the Hawaiian island of Molokai to study fresh water intrusion into coral reef ecosystems. Theoretical calculations have been done propose extensions to the AHI design in order to produce an instrument with a higher signal to noise ratio.
Proceedings of SPIE | 1993
Joan Kruthers; Tim J. Williams; Gary F. O'Brien; Kristina Le; James D. Howe
Focal plane array (FPA) families for a new generation of Forward Looking Infrared (FLIR) systems are currently being developed under the direction of the U.S. Army. The new FPA will have an impact on the performance of Automatic Target Recognizers (ATRs) which perform target detection and identification. Described in this paper are the results of an experiment designed to study the effects of various infrared FPA parameters on the image quality of a FLIR. The research was conducted using a computer simulation of a FLIR imaging sensor without the use of specific ATR algorithms. The study determined the amount of image degradation and information loss caused by specific FPA parameters. Among the parameters studied were detector size, detector geometry, noise, detector response nonuniformity, and array sampling effects, most of which were investigated at three different ranges.
Fourth International Asia-Pacific Environmental Remote Sensing Symposium 2004: Remote Sensing of the Atmosphere, Ocean, Environment, and Space | 2005
David J. Williams; Barry L. Feldman; Tim J. Williams; Drew Pilant; Paul G. Lucey; L. Dorsey Worthy
Airborne longwave infrared (LWIR) hyperspectral imagery was utilized to detect and identify gaseous chemical release plumes at sites in southern Texas. The Airborne Hyperspectral Imager (AHI), developed by the University of Hawai’i, was flown over a petrochemical facility and a confined animal feeding operation on a modified DC-3 during April, 2004. Data collected by the AHI system was successfully used to detect and identify numerous plumes at both sites. Preliminary results indicate the presence of benzene and ammonia and several other organic compounds. Emissions were identified using regression analysis on atmospherically compensated data. Data validation was conducted using facility emission inventories. This technology has great promise for monitoring and inventorying facility emissions, and may be used as means to assist ground inspection teams to focus on actual fugitive emission points.
International Symposium on Optical Science and Technology | 2000
Paul G. Lucey; Tim J. Williams; Michael E. Winter; Edwin M. Winter
The AHI sensor consists of a long-wave infrared pushbroom hyperspectral imager and a boresighted 3- color visible high resolution CCD linescan camera. The system used a background suppression system to achieve good noise characteristics (less than 1µfl NESR). Work with AHI has shown the utility of the longwave infrared a variety of applications. The AHI system has been used successfully in the detection of buried land mines using infrared absorption features of disturbed soil. Gas detection was also shown feasible, with gas absorption being clearly visible in the thermal IR. This allowed the mapping of a gas release using a matched filter. Geological mapping using AHI can be performed using the thermal band absorption features of different minerals. A large-scale geological map was obtained over a dry lake area in California using a mosaic of AHI flightlines, including mineral spectra and relative abundance maps.
Proceedings of SPIE | 2012
Balvinder Kaur; Jill K. Nelson; Tim J. Williams; Barbara L. O'Kane
Respiration rate is a key guide for evaluating the physiological state of an individual during triage. Recent work has shown that high resolution thermal cameras can passively and remotely obtain respiration signals under controlled environmental conditions. This paper introduces an automatic end-to-end respiration signal measurement (through signal detection) approach based on statistical computation of the image intensities around the human nostril area in a thermal video. A method is presented to detect and track the nostril area and to calculate statistical values of the pixel intensity around the nostril area and correlate the statistical values with respiration signals from a contact sensor such as transducer belt. Results are based upon data collected from 200 subjects across two different experiments. This work provides not only a new image processing tool for tracking facial ROIs in thermal imagery, but also enhances our capability to provide non-contact, remote, passive, and real-time methods for measuring respiration for security and medical applications.
Proceedings of SPIE | 2001
Michael E. Winter; Paul G. Lucey; Tim J. Williams; Donovan Steutel
The MUlti Sensor Trial 2000 experiment was a multi-platform remote sensing deployment in Cairns Australia. Included in the deployment were both visible and infrared airborne hyperspectral images. The University of Hawaiis Airborne Hyperspectral Imager represented the thermal infrared portion of the data collect. The ability to discriminate various targets using the thermal infrared was explored. Consequent data processing involved separating targets from clutter using matched filters. In addition, a preliminary atmospheric correction algorithm was developed based on the ISIS algorithm used in SEBASS.
Archive | 2002
Paul G. Lucey; Tim J. Williams; Keith A. Horton