Search

RESUMELe spectrometre-imageur a raie de fluorescence FLI (Fluorescence Line Imager) a ete concu et fabrique pour le ministere des Peches et Oceans (en 1981) dans le cadre de la phase 1 d'un projet visant la mise au point d'un capteur satellitaire perfectionne equipe de detecteurs a transfert de charge (D.T.C.) pour l'etude de la surface terrestre. Une version plus compacte constituee d'une seule camera existe sur le marche depuis 1990: il s'agit du spectrometre-imageur CASI (Compact Airborne Spectral Imager). Les deux instruments offrent la souplesse de fonctionnement permise par la conception d'un spectrometre-imageur pourvu de detecteurs en peigne qui assurent un pouvoir eleve de resolution spatiale dans le visible et le proche-infrarouge selon des modes spectraux controles par ordinateur. Ils permettent egalement l'obtention de spectres complets le long du meme intervalle spectral avec un pouvoir de resolution spatiale plus faible. Depuis 1983, ils survolent une grande variete de cibles situees tant su...

There are currently no fielded technologies for noncontact detection of tripwires. Itres Research Ltd. and DRDC Suffield have been conducting research on optical detection of tripwires since 1996, both for hand-held and vehicle-mounted roles. A proof-of-concept brassboard imager, initially for a vehicle-mounted role, has been constructed. The imager uses a high spatial resolution, panchromatic focal plane array whose high degree of integration includes on-board digitization and flexible addressing capabilities for windowing and subimaging. Command, control and signal processing are accomplished by a computer, based on dual 1GHz Pentium III processors. Using a high level, rapid prototyping language, 1 image frame can be processed in 3 seconds. Straightforward improvements should allow true real-time operation to be achieved. Preliminary testing of the imager was conducted in the outdoor DRDC Suffield Mine Pen in January 2003. Taut, sagging and undulating tripwires of various materials were partially hidden, often nearly invisible to the naked eye, in a number of types of local vegetation. Preliminary, quasi-real-time results showed that many of the wires were detected, although a significant number of false alarms occurred. As expected with the present algorithm, sagging, undulating and highly obscured wires were often difficult to detect. The instrument, results of the trial, planned improvements and future research will be discussed.

A ground vehicle-based, real-time, surface mine detection system, utilizing a Compact Airborne Spectrographic Image (casi), efficient mine detection algorithms, and real-time processing systems, was designed and tested. The combined real-time system was capable of 'learning' the in-situ spectra of various mines, thus providing a spectral library for the detection algorithms. The real-time processing of the casi data involved three steps. The first step was the radiometric correction of the raw data. The second step involved the application of the mine detection algorithms to the corrected data, referencing the spectral library. In the final step, the results of the real-time processes were stored and displayed, usually within a few frame times of the data acquisition. To the authors knowledge, this system represents the first hyperspectral imager to detect mines in real-time. This paper describes the generation of the in-situ mine spectral library, the collection of the scene data, the real-time processing of the scene data and the subsequent display and recording of the detection data. The limitation and expansion capabilities of the real-time system are discussed as well as various techniques that were implemented to achieve the goals. Planned future improvements that have been identified to create a more robust and higher performance, yet simpler processing systems are also discussed.

The feasibility of detecting surface-laid and, in some circumstances, buried mines by analysis of visible to near- IR (VNIR) hyperspectral imagery has been demonstrated by the authors in previous studies. An important factor in the practical success of such technology is being able to achieve the necessary spatial and spectral resolution to allow discrimination of mines from background. With some restrictions, both can be improved by increasing the instrument data output rate or decreasing the platform speed and both can be traded off against one another. The optimum trade-off must be determined for a given problem, including the choice of algorithm. Airborne VNIR hyperspectral data were collected over several controlled surface-laid mine fields using a casi hyperspectral imager and a helicopter. The combination of the imager's high speed data recording coupled with the low airspeed of the helicopter enabled the collection of hyperspectral data ranging from four 136 nm wide spectral bands at 10 cm resolution to nine 60 nm wide spectral bands at 20 cm resolution. Each mine field contained a variety of mines ranging form small anti- personnel mines to large anti-vehicle mines. An assessment of the feasibility and practicality of using airborne hyperspectral data to detect various surface-laid mines and mine fields was conducted. In addition, the trade-offs between spectral and spatial resolution for the detectability of surface-laid miens and mine fields are discussed.

Airborne optical remote sensing has recently seen an evolution from limited spectral discrimination into high spectral resolution imagery. Hyperspectral imagers now have the ability to sample a scene at both high spatial and high spectral resolution, permitting optimal selection from the available information to meet specific applications. Techniques have been developed which provide for high speed acquisition, radiometric calibration, conversion to spectral reflectances, geometric correction and interpretation of airborne hyperspectral data. The same technology currently in use for discrimination of subtle features in airborne scenes is available for industrial inspection applications which can benefit from combined spectral reflectance and imaging information.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A visible wavelength imaging method of identifying surface-laid mines from an airborne platform is described. A Compact Airborne Spectrographic Imager (CASI) collects multispectral radiometric images of mines and backgrounds which are converted to reflectance images using an incident light sensor. Mines are identified by classifying reflectance spectra in two ways. The first classifies individual pixels using the linear correlation coefficient as a measure of spectral similarity while the second classifies spectra using a variant of linear spectral unmixing in which the majority spectral members within an image are treated as background. In scanning manlift imagery of replica mines, targets were discriminated from a variety of background types, even when partially obscured by vegetation, for widely varying illuminations caused by diurnal and seasonal variations, sky conditions, and sun angles. In preliminary practical tests, the CASI was flown over various agricultural fields in which subpixel-size mine-like targets were laid. Visually undetectable targets were detected with good results. Comparison of classifiers revealed that the correlation method is better for high spatial resolution data. When the targets were subpixel in size, the end member analysis had a higher probability of detection than the correlation method, but had more false alarms.

A very flexible, sophisticated, low-cost and powerful commercial imaging spectrograph has been designed and developed that can provide resolutions from under one meter to several meters depending upon aircraft altitude and ground speed. The instrument uses a two-dimensional frame transfer CCD array to image a line beneath the aircraft and to sense the spectrum for each point in the scene. To keep data rates compatible with the built-in digital cassette recorder, a flexible scheme allows the operator to select the spectral bands and spatial information to be recorded. This compact airborne spectrographic imager can be employed to examine water quality, vegetation stress, fish schools, and to distinguish camouflage from vegetation.

The University of Calgary is working in conjunction with DAO (Dominion Astrophysical Observatory) and NRCC (National Research Council of Canada) to develop an experiment capable of performing UV (200-300 nm) spectroscopy on meteors. In order to perform UV spectroscopy on meteors successfully. The experiment must operate outside the earth's atmosphere because atmospheric ozone strongly attenuates UV shorter than 300 nm. NASA's GAS (Get Away Special) program has provided the University with an invaluable opportunity to place its experiment on a future shuttle flight. They will provide a cannister (5 cubic feet) in which to enclose the experiment. The GAS cannister will be attached to the inside of the shuttle's cargo bay. The spectroscope that will be used in the experiment will consist of an f/1.0 4.6 cm spectrographic camera (initially used on the 72-inch telescope at DAO), a Cs2Te MCP image intensifier and a CCD camera. The spectroscope will have a spectral resolution of 1 nm per pixel and a field of view of 13° x 10°. By studying meteors in the UV, it will be possible to detect the spectral lines of elements and compounds that have lines in the visual and near IR region coinciding with very strong fe and Ca lines. In the mid-uv, there exists an "iron-window", an under abundance of strong Fe lines. This window will permit the detection of Be, Zn and possibly B, all of which were previously undetected in meteor spectra. Thus, a comprehensive survey of meteor composition, derived from the meteors' UV spectra, will supplement previously existing data in the visual and near IR. These data will provide vital clues as to the origins of meteors.