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Showing papers in "Optical Engineering in 2000"


Journal ArticleDOI
TL;DR: An overview of 3-D shape measurement using various optical methods, and a focus on structured light tech- niques where various optical configurations, image acquisition technology, data postprocessing and analysis methods and advantages and limitations are presented.
Abstract: We first provide an overview of 3-D shape measurement us- ing various optical methods. Then we focus on structured light tech- niques where various optical configurations, image acquisition tech- niques, data postprocessing and analysis methods and advantages and limitations are presented. Several industrial application examples are presented. Important areas requiring further R&D are discussed. Finally, a comprehensive bibliography on 3-D shape measurement is included, although it is not intended to be exhaustive. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)00101-X)

1,481 citations


Journal ArticleDOI
TL;DR: It is shown that the position-dependent bias in a numerical study can lead to apparent strains of the order of 40% of the actual strain level, and methods are presented to reduce this bias to acceptable levels.
Abstract: Recently, digital image correlation as a tool for surface defor- mation measurements has found widespread use and acceptance in the field of experimental mechanics. The method is known to reconstruct displacements with subpixel accuracy that depends on various factors such as image quality, noise, and the correlation algorithm chosen. How- ever, the systematic errors of the method have not been studied in detail. We address the systematic errors of the iterative spatial domain cross- correlation algorithm caused by gray-value interpolation. We investigate the position-dependent bias in a numerical study and show that it can lead to apparent strains of the order of 40% of the actual strain level. Furthermore, we present methods to reduce this bias to acceptable lev- els. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)00911-9)

602 citations


Journal ArticleDOI
TL;DR: An optical double random-phase encryption method using a joint transform correlator architecture is proposed, in which the joint power spectrum of the image to be encrypted and the key codes is recorded as the encrypted data.
Abstract: An optical double random-phase encryption method using a joint transform correlator architecture is proposed. In this method, the joint power spectrum of the image to be encrypted and the key codes is recorded as the encrypted data. Unlike the case with classical double random-phase encryption, the same key code is used to both encrypt and decrypt the data, and the conjugate key is not required. Computer simulations and optical experimental results using a photorefractive- crystal-based processor are presented. © 2000 Society of Photo-Optical Instru- mentation Engineers. (S0091-3286(00)03508-X)

335 citations



Journal ArticleDOI
TL;DR: A new concept for 3-D shape measurement of complex ob- jects is proposed, which is based on photogrammetry and fringe evaluation, and the shape of a partial view is determined by a combination of the phase-shift method for fringe evaluation and a photogrammetric triangu- lation to calculate3-D coordinates related to the sensor coordinate system.
Abstract: A new concept for 3-D shape measurement of complex ob- jects is proposed, which is based on photogrammetry and fringe projec- tion. The shape of a partial view is determined by a combination of the phase-shift method for fringe evaluation and a photogrammetric triangu- lation to calculate the 3-D coordinates related to the sensor coordinate system. For the measurement of complex objects, partial views are taken from different sensor positions. The problem of matching the par- tial views into each other is solved by transforming each sensor position and the relating point cloud of the shape in a global coordinate system by photogrammetric matching of reference targets. © 2000 Society of Photo- Optical Instrumentation Engineers. (S0091-3286(00)02701-X)

228 citations


Journal ArticleDOI
TL;DR: In this article, a realization of laser-induced breakdown spectroscopy for real-time, in situ and remote analysis of trace amounts in liquid samples is described, which is potentially applicable to the analysis of pollutants in water in harsh or difficult-to-reach environments.
Abstract: A realization of laser-induced breakdown spectroscopy for real-time, in situ and remote analysis of trace amounts in liquid samples is described, which is potentially applicable to the analysis of pollutants in water in harsh or difficult-to-reach environments. Most of the measurements were conducted using a fiber assembly that is capable of both delivering the laser light and collecting the light emitted from the micro plasma, up to about 30 m from the target area. Alternatively, a telescopic arrangement for line-of-sight measurements was employed, with a range of 3 to 5 m. For internal standardization and the generation of concentration calibration curves, reference lines of selected elements were used. In the majority of cases calibration against the matrix element hydrogen was employed using the H?, H?, and H? lines, but also spiking with selected reference species was utilized. In order to provide high reliability and repeatability in the analyses, we also measured plasma parameters such as electron density, plasma temperature, and line- shape functions, and determined their influence on the measurement results. Numerous elements, including a range of toxic heavy metals, have been measured over a wide range of concentrations (Al, Cr, Cu, Pb, Tc, U, and others). Limits of detection usually were in the range of a few parts per million; for several elements even lower concentrations could be measured.

219 citations


Journal ArticleDOI
TL;DR: A new optical encryption technique using the fractional Fourier transform to decrypt the data correctly, in which the input plane, encryp- tion plane, and output planes exist, in addition to the key used for encryption.
Abstract: We propose a new optical encryption technique using the fractional Fourier transform. In this method, the data are encrypted to a stationary white noise by two statistically independent random phase masks in fractional Fourier domains. To decrypt the data correctly, one needs to specify the fractional domains in which the input plane, encryp- tion plane, and output planes exist, in addition to the key used for en- cryption. The use of an anamorphic fractional Fourier transform for the encryption of two-dimensional data is also discussed. We suggest an optical implementation of the proposed idea. Results of a numerical simulation to analyze the performance of the proposed method are pre- sented. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)01811-0)

215 citations


Journal ArticleDOI
TL;DR: In this article, a polarization-encoding system for optical security verification is proposed, where the polarization information is bonded to an identification card for security verification, and the expressions for polarization encoded input images are developed using Jones polarization calculus.
Abstract: A polarization-encoding system for optical security verification is proposed. The polarization information is bonded to an identification card for security verification. As the polarization state cannot be imaged by an ordinary intensity-sensitive device such as a CCD camera, it can provide an additional degree of freedom in using optics to secure information. The expressions for polarization encoded input images are developed using Jones polarization calculus. A nonlinear joint transform correlator is used to provide an optical validation system. Computer simulations and optical experimental results are shown in support of the proposed method.

184 citations


Journal ArticleDOI
TL;DR: The basic concepts and experimental arrange- ments of self-calibrating 3-D measurement systems using structured- light illumination (fringe projection), which ensure a high number of ob- ject points, rapid data acquisition, and a simultaneous determination of coordinates and system parameters (self-calibration), making the system completely insensitive to environmental changes are reported.
Abstract: We report the basic concepts and experimental arrange- ments of self-calibrating 3-D measurement systems using structured- light illumination (fringe projection), which ensure a high number of ob- ject points, rapid data acquisition, and a simultaneous determination of coordinates and system parameters (self-calibration), making the system completely insensitive to environmental changes. Furthermore, it is un- necessary to have any marker on the object surface and a subsequent matching of the single views is not required to obtain a full-body mea- surement. For this purpose, the test object is successively illuminated with two grating sequences perpendicular to each other from at least two different directions, resulting in surplus phase values for each measure- ment point. Based on these phase values one can calculate the orienta- tion parameters as well as the 3-D coordinates simultaneously. Different measurement setups that have the ability to measure the entire surface (full-body measurement) are reported. Results are presented showing the power of this concept, for example, by measuring of the complete 3-D shape of specular technical surfaces, whereas the object volumes can differ strongly. Theoretical estimations proven by first measurements show a coordinate measurement accuracy of up to 10 25 of the measure- ment field size. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)01801-8)

168 citations


Journal ArticleDOI
TL;DR: A contrast-based image fusion method using the wavelet multiresolution analysis and a new concept called directive contrast is presented, which shows that the fused image can integrate the details of each original image.
Abstract: We introduce a contrast-based image fusion method using the wavelet multiresolution analysis. This method includes three steps. First, the multiresolution architectures of the two original input images are obtained using the discrete wavelet transform. A new concept called directive contrast is presented. Second, the multiresolution architecture (MRA) of the fused image can be achieved by selecting the corresponding subband signals of each input image based on the directive contrast. Finally, the fused image is reconstructed using the inverse wavelet transform. This algorithm is relevant to visual sensitivity and is tested by merging visual and IR images. The result shows that the fused image can integrate the details of each original image. The visual aesthetics and the computed SNRs of the fused images show that the new approaches can provide better fusion results than some previous multiresolution fusion methods.

155 citations


Journal ArticleDOI
TL;DR: In this paper, a confocal setup based on microlenses for shape investigation, defect analysis and surface topography measurement is presented, where the axial resolution is the same as in a comparable confocal microscope based on a Nipkow disk.
Abstract: A confocal setup based on microlenses for shape investigation, defect analysis and surface topography measurement is presented. The major advantage of this technique is its high light efficiency and the possibility to realize larger object fields without reducing the numerical aperture. Different variations of the setup for different applications are presented. An increased working distance yields a greater variety of its applications. Furthermore, the arrangement of the microlenses on a rotating disk leads to an increased spatial sampling and a high scanning rate. The axial resolution is the same as in a comparable confocal microscope based on a Nipkow disk. The microlens confocal system enables measurements on large field sizes down to microscopic ones. In addition, by using chromatic aberrations it is possible to achieve realtime images with color-coded height information. The topography of the sample can be determined from one color image, which leads to a reduction in measuring time. To reduce measuring times on curved surfaces, for instance, it is useful to adapt the focal lengths of the microlenses to the individual shape of the object. Hence, only the difference between the focal distribution and the real shape must be determined.


Journal ArticleDOI
TL;DR: A mixed ray-tracing-deterministic algorithm is developed that assures that each ray contributes to the final channel response function as many times as it rebounds with an obstacle and increases dramatically the number of contributions and reduces the time required for an accurate simulation.
Abstract: A modified Monte Carlo algorithm for the calculation of the impulse response on infrared wireless indoor channels is presented. As is well known, the characteristics of the room where the IR diffuse channel is implemented can lead to problems in communication, such as a multipath penalty on the maximum baud rate or hidden-station situations. Classical algorithms require large computational effort to calculate the impulse response in an ordinary-size room. Monte Carlo offers the possibility of validating the assumptions made for these classic algorithms (basically, the Lambertian nature of all reflections) with a computational complexity that is determined by the accuracy desired by the user. We have developed a mixed ray-tracing-deterministic algorithm that assures that each ray contributes to the final channel response function as many times as it rebounds with an obstacle. It increases dramatically the number of contributions and reduces, to the same extent, the time required for an accurate simulation. Extensive simulation results are presented and are compared with those of other simulation methods. We demonstrate that the method presented here is much faster than Monte Carlo classical simulation schemes. It can be used as a method of simulation in itself or as a validation algorithm for other comparative studies of pulse broadening.

Journal ArticleDOI
TL;DR: In this article, a finite-element method is presented to calculate 3D surface profiles of refractive microlenses fabricated by melting-resist technology (reflow technique), where gravity can have an advantageous influence on the profile form, so that smaller focal spots can be achieved.
Abstract: We present a finite-element method to calculate 3-D surface profiles of refractive microlenses fabricated by melting-resist technology (reflow technique). The geometry of the microlenses can be arbitrary. Surface tension and gravity are taken into account. Gravity can have an advantageous influence on the profile form, so that smaller focal spots can be achieved. A simple scaling law is given to estimate the influence of gravity on the profile form for given microlens parameters. We compared various theoretical and measured surface profiles of microlenses fabricated by melting-resist technology and found good agreement. Finally, the usefulness of this method for the design of refractive microstructures for smart masks is shown.

Journal ArticleDOI
TL;DR: This paper presents an approach, called the target-constrained interference-minimized filter (TCIMF), which does not require one to identify interferers, but can minimize the effects caused by interference.
Abstract: Hsuan Ren Chein-I Chang, MEMBER SPIE Remote Sensing Signal and Image Processing Laboratory Department of Computer Science and Electrical Engineering University of Maryland Baltimore County Baltimore, Maryland 21250 Abstract. Due to significantly improved spatial and spectral resolution, hyperspectral sensors can now detect many substances that cannot be resolved by multispectral sensors. However, this comes at the price that many unknown and unidentified signal sources, referred to as interferers, may also be extracted unexpectedly. Such interferers generally produce additional noise effects on target detection and must therefore be taken into account. The problem associated with this interference is challenging because its nature is generally unknown and it cannot be identified from an image scene. This paper presents an approach, called the target-constrained interference-minimized filter (TCIMF), which does not require one to identify interferers, but can minimize the effects caused by interference. It designs a finite-impulse-response filter that specifies targets of interest in such a way that the desired targets and undesired targets will be passed through and rejected by the filter, respectively; the filter output energy resulting from unknown signal sources is also minimized. More precisely, the TCIMF accomplishes three tasks simultaneously: detection of the desired targets, elimination of the undesired targets, and minimization of interfering effects. A recently developed technique, constrained energy minimization (CEM), can be considered as a suboptimal version of the TCIMF. Computer simulations and hyperspectral image experiments are conducted to demonstrate advantages of the TCIMF over the CEM. © 2000 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(00)02912-3]

Journal ArticleDOI
TL;DR: In this article, two computer-aided optical techniques for full-field surface shape measurement are presented, one for diffuse surfaces and the other for specularly reflective surfaces, which can be easily implemented for rapid measurement of 3D surface shapes in an industrial setting.
Abstract: Two practical computer-aided optical techniques for full-field surface shape measurement are presented, one for diffuse surfaces and the other for specularly reflective surfaces. The former technique is based on projecting a computer-generated fringe pattern onto a diffuse surface, and the latter is based on reflecting the fringe pattern from a specularly reflective surface. The fringe pattern is perturbed in accordance with the object surface with the fringe phase bearing information on the depth/slope of the object surface. The computer-generated fringe pattern conveniently enables the fringe phase to be manipulated, and hence the determination of the phase distribution using a phase extraction algorithm. Instead of deriving the mathematical relationship between the fringe phase distribution and the surface depth/slope, this relationship is obtained by calibration. The techniques described can be easily implemented for rapid measurement of 3-D surface shapes in an industrial setting.

Journal ArticleDOI
TL;DR: In this paper, an in-line digital holographic sensor (DHS) for monitoring and characterizing marine particulates is presented. Butler et al. used a small 10mW diode laser to project a collimated beam through the water column and onto a lensless CCD array.
Abstract: We report an in-line digital holographic sensor (DHS) for monitoring and characterizing marine particulates. This system images individual particles over a deep depth of field (>25 cm) with a resolution of 5 {mu}m. The DHS projects a collimated beam through the water column and onto a lensless CCD array. Some light is diffracted by particulates and forms an object beam; the undeflected remainder constitutes the reference beam. The two beams combine at the CCD array and create an in-line hologram, which is then numerically reconstructed. The DHS eliminates many problems traditionally associated with holography. The CCD recording material considerably lowers the exposure time and eliminates most vibration problems. The laser power needs are low; the DHS uses a small 10-mW diode laser. Rapid numerical reconstruction eliminates photographic processing and optical reconstruction. We successfully operated the DHS underwater on a remotely operated vehicle; our test results include tracing a single particle from one hologram to the next, thus deriving a velocity vector for marine mass transport. We outline our digital holographic reconstruction procedure, and present our graphical user interface and user software tools. The DHS is particularly useful for providing in situ ground-truth measurements for environmental remote sensing. (c) 2000 Societymore » of Photo-Optical Instrumentation Engineers.« less


Journal ArticleDOI
TL;DR: In this paper, a CCD camera records the intensity distribution of the fringes that appear as intersection lines on the surface of the object, and the calibration of the 3D orientation of the second axis is realized with a special calibration body.
Abstract: The described 3-D measurement system with fringe projec- tion applies the principle of uniform scale representation by the exclusive use of phase measurement values for the coordinates of each point. The test object is successively illuminated with a grating structure from at least three different directions with a telecentric system, where gray code is combined with five 90-deg phase shifts. A CCD camera records the intensity distribution of the fringes that appear as intersection lines on the surface of the object. This provides the linearly independent absolute phase values that are necessary for the calculation of the coordinates. Note that all coordinates (x,y,z) are determined with the same accuracy. To compensate the influence of specular reflections or shadowed areas up to 15 light projection directions can be used. Moreover, the object can be rotated around a second axis, yielding other views of the object. Thus we acquire different patches of the object that are transformed into a global coordinate system without any interactive user help. During this procedure, correlation methods or special points are not necessary. The calibration of the 3-D orientation of the second axis is realized with a special calibration body. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)01701-3) Subject terms: adaptive optical three-dimensional measurement system; struc- tured light; gray code; uniform scale representation; phase measurement; calibra- tion method development.

Journal ArticleDOI
TL;DR: In this article, the authors presented the modeling and performance of a polarization-active active imager at l5806 nm, which operates in a monostatic configuration, using a semiconductor laser to illuminate the target and a telescope to create the image on a CCD matrix.
Abstract: We present the modeling and the performance of a polarization active imager at l5806 nm. The device operates in a monostatic configuration, using a semiconductor laser to illuminate the target and a telescope to create the image on a CCD matrix. Dual images (intensity and polarization degree) of different scenes are obtained by a new method (only two images acquired) and analyzed, showing the experimental validation of this concept. An application of this active imager to the detection of a target buried in the background (same reflectivity but different polarization degree) is proposed. Field experiment results are reported.

Journal ArticleDOI
TL;DR: An efficient algorithm is proposed for the interpolation of interlaced images by efficiently estimating the directional spatial correlations of neighboring pixels, with significant improvement over previous ELA-based algorithms.
Abstract: An efficient algorithm is proposed for the interpolation of interlaced images. On the basis of the edge-based line average (ELA) algorithm, tow useful measurements are introduced within the operation window in order to alleviate misleading decisions in determining the direction where the interpolation is to be made. By efficiently estimating the directional spatial correlations of neighboring pixels, increased interpolation accuracy has been achieved. In addition, the new method is simply structured and is therefore easy to implement. Extensive simulations conducted for different images and video sequences have shown the efficacy of the proposed interpolator, with significant improvement over previous ELA-based algorithms.

Journal ArticleDOI
TL;DR: In this article, a method of calculating the characteristics of non-collinear phase matching in both uniaxial and baoxial crystals is presented, which enables a far larger set of nonlinear crystals and configurations to be studied.
Abstract: A method of calculating the characteristics of noncollinear phase matching in both uniaxial and biaxial crystals is presented. Al- though significant work has been done to characterize collinear phase matching and to present many of its applications, noncollinear phase matching also has unique characteristics, leading to several useful ap- plications. The method presented enables calculations of both the collin- ear and noncollinear cases, and enables a far larger set of nonlinear crystals and configurations to be studied. © 2000 Society of Photo-Optical In- strumentation Engineers. (S0091-3286(00)02304-7)

Journal ArticleDOI
TL;DR: In this article, the authors report the results of their research and development in techniques for producing elliptical x-ray mirrors by controlled bending of a flat substrate and describe particular mirrors that have been built, using these techniques, to meet the requirements of the scientific program at the Advanced Light Source at Lawrence Berkeley National Laboratory.
Abstract: We report the results of our research and development in techniques for producing elliptical x-ray mirrors by controlled bending of a flat substrate. We review the theory and technique of mirror bending with emphasis on the optical engineering issues and describe our design concepts for both metal and ceramic mirrors. We provide analysis of the various classes of error that must be addressed to obtain a high quality elliptical surface and a correspondingly fine focus of the x-ray beam. We describe particular mirrors that have been built, using these techniques, to meet the requirements of the scientific program at the Advanced Light Source at Lawrence Berkeley National Laboratory. For these examples, we show optical metrology results indicating the achievement of surface accuracy values around and, in some cases, below 1 mrad as well as x-ray measurements showing submicrometer focal spots. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)01410-0)

Journal ArticleDOI
TL;DR: Experiments show that the proposed GCEM detects targets more effectively than GOSP and CEM without dimensionality expansion, and generates additional bands from original multispectral images nonlinearly so that CEM can be used for subpixel detection to extract targets embedded in multisectral im- ages.
Abstract: Subpixel detection in multispectral imagery presents a chal- lenging problem due to relatively low spatial and spectral resolution. We present a generalized constrained energy minimization (GCEM) ap- proach to detecting targets in multispectral imagery at subpixel level. GCEM is a hybrid technique that combines a constrained energy mini- mization (CEM) method developed for hyperspectral image classification with a dimensionality expansion (DE) approach resulting from a gener- alized orthogonal subspace projection (GOSP) developed for multispec- tral image classification. DE enables us to generate additional bands from original multispectral images nonlinearly so that CEM can be used for subpixel detection to extract targets embedded in multispectral im- ages. CEM has been successfully applied to hyperspectral target detec- tion and image classification. Its applicability to multispectral imagery is yet to be investigated. A potential limitation of CEM on multispectral imagery is the effectiveness of interference elimination due to the lack of sufficient dimensionality. DE is introduced to mitigate this problem by expanding the original data dimensionality. Experiments show that the proposed GCEM detects targets more effectively than GOSP and CEM without dimensionality expansion. © 2000 Society of Photo-Optical Instrumenta- tion Engineers. (S0091-3286(00)01205-8)

Journal ArticleDOI
TL;DR: In this article, the optical properties of molecules near either edge of the liquid crystal display (LCD) that are unable to twist and tilt under the application of an external electromagnetic field were investigated.
Abstract: We present a model to more accurately describe the optical properties of a twisted nematic liquid crystal display (LCD). In particular, we study the optical properties of molecules near either edge of the LCD that are unable to twist and tilt under the application of an external elec- tric field. The properties of these layers can be deduced from the inten- sity transmittances measured using different configurations of the exter- nal linear polarizers. The agreement between the theoretical and the experimental transmittances is excellent, thus enabling the prediction of the actual modulation for any configuration of the polarizers. © 2000 So- ciety of Photo-Optical Instrumentation Engineers. (S0091-3286(00)01412-4)

Journal ArticleDOI
TL;DR: In this article, a mathematical model based on Fourier optics is developed to analyze the digital recording mechanism and properties of the system in comparison with those of the commonly used off-axis arrangement.
Abstract: Digital holography for micromeasurement is an active re- search topic. With respect to the requirement of realizing characteriza- tion of micro-scale structures in microelectromechanical systems with high resolution and accuracy, in-line configuration is studied in this paper as the fundamental structure of a digital holography system. A math- ematical model based on Fourier optics is developed to analyze the digital recording mechanism and properties of the system in comparison with those of the commonly used off-axis arrangement. Theoretical analysis and experimental results demonstrate that in-line configuration is advantageous in enhancing the system performance. Besides the re- laxed requirement of spatial resolution on the CCD sensors and the greater flexibility of the system, higher lateral resolution and lower speckle noise can be achieved. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)01812-2)

Journal ArticleDOI
TL;DR: Mouroulis et al. as mentioned in this paper described a pushbroom imaging spectrometer module demonstrating very low spectral and spatial distortion (a few percent of a pixel) and similarly small variation in spectral response function with field position.
Abstract: Pantazis Mouroulis, MEMBER SPIE Michael M. McKerns* Jet Propulsion Laboratory California Institute of Technology Pasadena, CA 91109 Abstract. Experimental results are described from a pushbroom imaging spectrometer module demonstrating very low spectral and spatial distortion (a few percent of a pixel) and similarly small variation in spectral response function with field position. These spectrometer properties significantly facilitate the extraction of accurate spectroscopic information. The spectrometer can achieve high performance despite relaxed tolerances in fabrication and alignment. A quick and effective alignment method is described that permits the spectrometer to approximate its design performance. The implications of the results for the calibration techniques of pushbroom imaging spectrometers are also discussed. © 2000 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(00)03103-2]

Journal ArticleDOI
TL;DR: The Dark HORSE 1 (Hyperspectral Overhead Reconnais- sance and Surveillance Experiment 1) flight test has demonstrated au- tonomous, real-time visible hyperspectral detection of military ground tar- gets with real- time cuing of a high-resolution framing camera.
Abstract: The Dark HORSE 1 (Hyperspectral Overhead Reconnais- sance and Surveillance Experiment 1) flight test has demonstrated au- tonomous, real-time visible hyperspectral detection of military ground tar- gets with real-time cuing of a high-resolution framing camera. An overview of the Dark HORSE 1 hyperspectral sensor system is pre- sented. The system hardware components are described in detail, with an emphasis on the visible hyperspectral sensor and the real-time pro- cessor. Descriptions of system software and processing methods are also provided. The recent field experiment in which the Dark HORSE 1 system was employed is described in detail along with an analysis of the collected data. The results evince per-pixel false-alarm rates on the or- der of 10 25 /km 2 , and demonstrate the improved performance obtained