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Papers by Ernest Armstrong

Research paper thumbnail of <title>Model-based real-time nonuniformity correction in focal plane array detectors</title>

Proceedings of SPIE, Aug 26, 1998

ABSTRACT

Research paper thumbnail of <title>High-resolution image reconstruction from a sequence of rotated and translated infrared images</title>

Proceedings of SPIE, Jun 16, 1997

ABSTRACT

Research paper thumbnail of <title>Nonuniformity correction for improved registration and high-resolution image reconstruction in IR imagery</title>

Proceedings of SPIE, Oct 18, 1999

ABSTRACT

Research paper thumbnail of High Resolution Image Reconstruction from Digital Video with In-Scene Motion

International Conference on Image Processing, Oct 26, 1997

This paper describes a technique for reconstructing a high resolution image from a sequence of lo... more This paper describes a technique for reconstructing a high resolution image from a sequence of low resolution frames. The input frames must contain some scene motion relative to the focal plane array so that some unique samples are provided with each frame. We consider global scene motion and a special case of non-global scene motion. The global motion algorithm is

Research paper thumbnail of <title>Improved airdrop capabilities using a 2-μm laser radar system</title>

Laser Radar Technology and Applications, 1996

One of the primary difficulties with high altitude airdrop missions is the effect of the wind fie... more One of the primary difficulties with high altitude airdrop missions is the effect of the wind field on the objects dropped. Aircraft crews currently obtain wind fields using a combination of measuring winds at altitude during flight, data from local weather stations and data from balloon launches (radiosondes). This data is used to adjust the cargo release point to compensate for the intervening winds. Since these methods have limited utility, a desired alternative would be a sensor placed on board the aircraft able to accurately measure real time wind fields at any location. The purpose of the project presented is to demonstrate a flightworthy eye-safe solid state laser radar system meeting these criteria. The system, which was assembled from available subsystems not designed nor engineered for this particular application, was named `Interim Operational Capability'. These subsystems were hardened and integrated together in such a way as to be installed on an operational Air Force aircraft in a short time-frame, thereby providing a near term wind field measuring capability for airdrop missions, should the need arise.

Research paper thumbnail of The advantage of nonuniformity correction pre-processing on infrared image registration

Research paper thumbnail of High resolution image reconstruction from digital video with global and non-global scene motion

This paper describes a technique for reconstructing a high resolution image from a sequence of lo... more This paper describes a technique for reconstructing a high resolution image from a sequence of low resolution frames. The input frames must contain some scene motion relative to the focal plane array so that some unique samples are provided with each frame. We consider global scene motion and a special case of non-global scene motion. The global motion algorithm is

Research paper thumbnail of The Use of Fourier Self-Deconvolution to Resolve Overlapping X-Ray Powder Diffraction Peaks

Powder Diffraction, 1989

Fourier self-deconvolution has been successfully applied as a means of obtaining semi-quantitativ... more Fourier self-deconvolution has been successfully applied as a means of obtaining semi-quantitative information by resolving the overlapping peaks in X-ray powder diffractograms collected from mixtures of kaolinite and ripidolite. A series of diffractograms were collected from known mixtures of the two minerals. The diffractograms were then processed using Fourier self-deconvolution over a selected range between 23 and 27° 2θ (encompassing the overlapping peaks of kaolinite (002) and ripidolite (004) at 24.85 and 25.13° 2θ, respectively). Once deconvoluted, areas under individual peaks of kaolinite and ripidolite were calculated using curve fitting. The calculated percentage of kaolinite in the mixtures was then plotted versus the true weight percent of kaolinite. The same procedure was conducted on the original diffractograms using only curve fitting without first deconvoluting. A comparison of results shows that, provided the number of peaks are known, both methods give nearly equa...

Research paper thumbnail of Joint estimation of image, shift and nonuniformities from IR images

Research paper thumbnail of Optimization of Stepsize in X-Ray Powder Diffractogram Collection

Powder Diffraction, 1988

Fourier transform methods of smoothing and interpolation are applied to X-ray diffraction data. I... more Fourier transform methods of smoothing and interpolation are applied to X-ray diffraction data. It is shown that, frequently, too small a step size is used. Major gains are to be expected by selection of the optimum step size and use of these methods.A comparison of Fourier transforms of diffractograms of quartz measured between 67 and 69° 2θ, collected at varying step intervals (0.1 to 0.01° 2θ) was used to illustrate these applications. By examining the Fourier transform of the diffractogram and noting where it decays to die baseline, a reasonable estimate of the optimal step interval can be obtained. In addition, Fourier interpolation can be used to enhance the appearance of the diffractogram, approximating a continuous plot.

Research paper thumbnail of Scene based nonuniformity correction using video sequences and registration

Research paper thumbnail of On the fundamental limits of reconstruction-based super-resolution algorithms

Proceedings of the 2001 IEEE Computer Society Conference on Computer Vision and Pattern Recognition. CVPR 2001

Research paper thumbnail of <title>Comparison of registration techniques for speckle suppression in 2D ladar image sequences</title>

Applications of Digital Image Processing XXVII, 2004

Registration of individual images remains a significant problem in the generation of accurate ima... more Registration of individual images remains a significant problem in the generation of accurate images collected using coherent imaging systems. An investigation of the performance of eight distinct image registration algorithms was conducted using data collected from a coherent optical imaging system developed by the Air Force Research Laboratories, Sensors Division, ARFL/SNJT. A total of 400 images of three distinct scenes

Research paper thumbnail of <title>Efficient projection-based technique for registering images in the presence of fixed-pattern noise</title>

Hybrid Image and Signal Processing VII, 2000

The problem of registering two successive video frames has traditionally been addressed with the ... more The problem of registering two successive video frames has traditionally been addressed with the 2D cross-correlation shift estimator. In this paper, a computationally efficient method of image registration is investigated that can achieve improved registration performance over the 2D cross- correlator in the presence of both fixed-pattern and temporal noise. This is accomplished by transforming both the current frame and the previous frame into two vector projections formed by accumulating pixel values across the rows and the columns of the array. The 2D cross-correlator requires three 2D Fourier transforms at the size of the image. In order to avoid the use of 2D Fourier transforms for large arrays, other shift estimation procedures have been developed that rely only on gradients between the two frames to infer the inter-frame shifts. Gradient-based techniques exhibit degraded performance in comparison to the 2D cross-correlator since the gradient operation amplifies noise. The projection-based estimator alleviates the computational burden of estimating shifts while improving the performance relative to the 2D cross-correlation shift estimator. In order to demonstrate the noise rejection capability of the projection-based shift estimator, a figure of merit is developed that reflects the signal-to-noise ratio for the two different shift estimation procedures. The relative performance of the 2D cross-correlation shift estimator and the projection-based shift estimator can be compared through their associated figures of merit. These two methods are also compared through computer simulation.

Research paper thumbnail of <title>Scene-based algorithm for range/intensity estimation correction for the flash 3D ladar system</title>

Laser Radar Technology and Applications XV, 2010

In many laser radar systems the intensity value's strength is dependent on the reflectivity o... more In many laser radar systems the intensity value's strength is dependent on the reflectivity of the measured surface. High intensity values are necessary for accurate range measurements. When measuring a low-reflectivity surface the returning laser intensity will be low. This, in turn, results in high uncertainty in the range estimate. In this paper, an approach to correct the intensity values

Research paper thumbnail of Maximum <italic>a posteriori</italic> image and seeing condition estimation from partially coherent two-dimensional light detection and ranging images

Optical Engineering, 2006

Recent developments in staring focal plane technology have spawned significant interest in the ap... more Recent developments in staring focal plane technology have spawned significant interest in the application of gated laser radar systems to battlefield remote sensing. Such environments are characterized by rapidly changing atmospheric seeing conditions and significant image distortion caused by long slant-range paths through the most dense regions of the atmosphere. Limited weight, space, and computational resources tend to prohibit the application of adaptive optic systems to mitigate atmospheric image distortion. We demonstrate and validate the use of a fast, iterative, maximum a posteriori (MAP) estimator to estimate both the original target scene and the ensemble-averaged atmospheric optical transfer function parameterized by Fried's seeing parameter. Wide-field-of-view sensor data is simulated to emulate images collected on an experimental test range. Simulated and experimental multiframe motion-compensated average images are deconvolved by the MAP estimator to produce most likely estimates of the truth image as well as the atmospheric seeing condition. For comparison, Fried's seeing parameter is estimated from experimentally collected images using a knife-edge response technique. The MAP estimator is found to yield seeing condition estimates within approximately 6% using simulated speckle images, and within approximately 8% of knife-edge derived truth for a limited set of experimentally collected image data.

Research paper thumbnail of High-resolution image reconstruction from digital video by exploitation of nonglobal motion

Optical Engineering, 1999

Many imaging systems utilize detector arrays that do not sample the scene according to the Nyquis... more Many imaging systems utilize detector arrays that do not sample the scene according to the Nyquist criterion. As a result, the higher spatial frequencies admitted by the optics are aliased. This creates undesirable artifacts in the imagery. Furthermore, the blurring effects of the optics and the finite detector size also degrade the image quality. Several approaches for increasing the sampling rate of imaging systems have been suggested in the literature. We propose an algorithm for resolution enhancement that exploits object motion in digital video sequences. Unlike previously defined techniques, we use an automated segmentation method to isolate rigid moving objects. These are accurately registered and the multiple observations of the object are used to produce an effectively high sampling rate over the object. The experimental results presented illustrate the breakdown of resolution enhancement algorithms that assume global scene motion when the actual scene motion is nonglobal. The performance of the proposed algorithm is illustrated using images from a forward looking IR imager and a visible range camera.

Research paper thumbnail of Physics Commons, and the Signal Processing Commons

This Article is brought to you for free and open access by the Department of Electrical and Compu... more This Article is brought to you for free and open access by the Department of Electrical and Computer Engineering at eCommons. It has been accepted for inclusion in Electrical and Computer Engineering Faculty Publications by an authorized administrator of eCommons. For more information, please

Research paper thumbnail of Characterization measurements of ASC FLASH 3D ladar

SPIE Proceedings, 2009

As a part of the project agreement between the Swedish Defence Research Agency (FOI) and the Unit... more As a part of the project agreement between the Swedish Defence Research Agency (FOI) and the United States of American's Air Force Research Laboratory (AFRL), a joint field trial was performed in Sweden during two weeks in January 2009. The main purpose for this trial was to characterize AFRL's latest version of the ASC (Advanced Scientific Concepts [1]) FLASH 3D LADAR sensor. The measurements were performed essentially in FOI's optical hall whose 100 m indoor range offers measurements under controlled conditions minimizing effects such as atmospheric turbulence. Data were also acquired outdoor in both forest and urban scenarios, using vehicles and humans as targets, with the purpose of acquiring data from more dynamic platforms to assist in further algorithm development. This paper shows examples of the acquired data and presents initial results.

Research paper thumbnail of <title>The application of iterative closest point (ICP) registration to improve 3D terrain mapping estimates using the flash 3D ladar system</title>

Laser Radar Technology and Applications XV, 2010

The primary purpose of this research was to develop an effective means of creating a 3D terrain m... more The primary purpose of this research was to develop an effective means of creating a 3D terrain map image (point-cloud) in GPS denied regions from a sequence of co-bore sighted visible and 3D LIDAR images. Both the visible and 3D LADAR cameras were hard mounted to a vehicle. The vehicle was then driven around the streets of an abandoned village

Research paper thumbnail of <title>Model-based real-time nonuniformity correction in focal plane array detectors</title>

Proceedings of SPIE, Aug 26, 1998

ABSTRACT

Research paper thumbnail of <title>High-resolution image reconstruction from a sequence of rotated and translated infrared images</title>

Proceedings of SPIE, Jun 16, 1997

ABSTRACT

Research paper thumbnail of <title>Nonuniformity correction for improved registration and high-resolution image reconstruction in IR imagery</title>

Proceedings of SPIE, Oct 18, 1999

ABSTRACT

Research paper thumbnail of High Resolution Image Reconstruction from Digital Video with In-Scene Motion

International Conference on Image Processing, Oct 26, 1997

This paper describes a technique for reconstructing a high resolution image from a sequence of lo... more This paper describes a technique for reconstructing a high resolution image from a sequence of low resolution frames. The input frames must contain some scene motion relative to the focal plane array so that some unique samples are provided with each frame. We consider global scene motion and a special case of non-global scene motion. The global motion algorithm is

Research paper thumbnail of <title>Improved airdrop capabilities using a 2-μm laser radar system</title>

Laser Radar Technology and Applications, 1996

One of the primary difficulties with high altitude airdrop missions is the effect of the wind fie... more One of the primary difficulties with high altitude airdrop missions is the effect of the wind field on the objects dropped. Aircraft crews currently obtain wind fields using a combination of measuring winds at altitude during flight, data from local weather stations and data from balloon launches (radiosondes). This data is used to adjust the cargo release point to compensate for the intervening winds. Since these methods have limited utility, a desired alternative would be a sensor placed on board the aircraft able to accurately measure real time wind fields at any location. The purpose of the project presented is to demonstrate a flightworthy eye-safe solid state laser radar system meeting these criteria. The system, which was assembled from available subsystems not designed nor engineered for this particular application, was named `Interim Operational Capability'. These subsystems were hardened and integrated together in such a way as to be installed on an operational Air Force aircraft in a short time-frame, thereby providing a near term wind field measuring capability for airdrop missions, should the need arise.

Research paper thumbnail of The advantage of nonuniformity correction pre-processing on infrared image registration

Research paper thumbnail of High resolution image reconstruction from digital video with global and non-global scene motion

This paper describes a technique for reconstructing a high resolution image from a sequence of lo... more This paper describes a technique for reconstructing a high resolution image from a sequence of low resolution frames. The input frames must contain some scene motion relative to the focal plane array so that some unique samples are provided with each frame. We consider global scene motion and a special case of non-global scene motion. The global motion algorithm is

Research paper thumbnail of The Use of Fourier Self-Deconvolution to Resolve Overlapping X-Ray Powder Diffraction Peaks

Powder Diffraction, 1989

Fourier self-deconvolution has been successfully applied as a means of obtaining semi-quantitativ... more Fourier self-deconvolution has been successfully applied as a means of obtaining semi-quantitative information by resolving the overlapping peaks in X-ray powder diffractograms collected from mixtures of kaolinite and ripidolite. A series of diffractograms were collected from known mixtures of the two minerals. The diffractograms were then processed using Fourier self-deconvolution over a selected range between 23 and 27° 2θ (encompassing the overlapping peaks of kaolinite (002) and ripidolite (004) at 24.85 and 25.13° 2θ, respectively). Once deconvoluted, areas under individual peaks of kaolinite and ripidolite were calculated using curve fitting. The calculated percentage of kaolinite in the mixtures was then plotted versus the true weight percent of kaolinite. The same procedure was conducted on the original diffractograms using only curve fitting without first deconvoluting. A comparison of results shows that, provided the number of peaks are known, both methods give nearly equa...

Research paper thumbnail of Joint estimation of image, shift and nonuniformities from IR images

Research paper thumbnail of Optimization of Stepsize in X-Ray Powder Diffractogram Collection

Powder Diffraction, 1988

Fourier transform methods of smoothing and interpolation are applied to X-ray diffraction data. I... more Fourier transform methods of smoothing and interpolation are applied to X-ray diffraction data. It is shown that, frequently, too small a step size is used. Major gains are to be expected by selection of the optimum step size and use of these methods.A comparison of Fourier transforms of diffractograms of quartz measured between 67 and 69° 2θ, collected at varying step intervals (0.1 to 0.01° 2θ) was used to illustrate these applications. By examining the Fourier transform of the diffractogram and noting where it decays to die baseline, a reasonable estimate of the optimal step interval can be obtained. In addition, Fourier interpolation can be used to enhance the appearance of the diffractogram, approximating a continuous plot.

Research paper thumbnail of Scene based nonuniformity correction using video sequences and registration

Research paper thumbnail of On the fundamental limits of reconstruction-based super-resolution algorithms

Proceedings of the 2001 IEEE Computer Society Conference on Computer Vision and Pattern Recognition. CVPR 2001

Research paper thumbnail of <title>Comparison of registration techniques for speckle suppression in 2D ladar image sequences</title>

Applications of Digital Image Processing XXVII, 2004

Registration of individual images remains a significant problem in the generation of accurate ima... more Registration of individual images remains a significant problem in the generation of accurate images collected using coherent imaging systems. An investigation of the performance of eight distinct image registration algorithms was conducted using data collected from a coherent optical imaging system developed by the Air Force Research Laboratories, Sensors Division, ARFL/SNJT. A total of 400 images of three distinct scenes

Research paper thumbnail of <title>Efficient projection-based technique for registering images in the presence of fixed-pattern noise</title>

Hybrid Image and Signal Processing VII, 2000

The problem of registering two successive video frames has traditionally been addressed with the ... more The problem of registering two successive video frames has traditionally been addressed with the 2D cross-correlation shift estimator. In this paper, a computationally efficient method of image registration is investigated that can achieve improved registration performance over the 2D cross- correlator in the presence of both fixed-pattern and temporal noise. This is accomplished by transforming both the current frame and the previous frame into two vector projections formed by accumulating pixel values across the rows and the columns of the array. The 2D cross-correlator requires three 2D Fourier transforms at the size of the image. In order to avoid the use of 2D Fourier transforms for large arrays, other shift estimation procedures have been developed that rely only on gradients between the two frames to infer the inter-frame shifts. Gradient-based techniques exhibit degraded performance in comparison to the 2D cross-correlator since the gradient operation amplifies noise. The projection-based estimator alleviates the computational burden of estimating shifts while improving the performance relative to the 2D cross-correlation shift estimator. In order to demonstrate the noise rejection capability of the projection-based shift estimator, a figure of merit is developed that reflects the signal-to-noise ratio for the two different shift estimation procedures. The relative performance of the 2D cross-correlation shift estimator and the projection-based shift estimator can be compared through their associated figures of merit. These two methods are also compared through computer simulation.

Research paper thumbnail of <title>Scene-based algorithm for range/intensity estimation correction for the flash 3D ladar system</title>

Laser Radar Technology and Applications XV, 2010

In many laser radar systems the intensity value's strength is dependent on the reflectivity o... more In many laser radar systems the intensity value's strength is dependent on the reflectivity of the measured surface. High intensity values are necessary for accurate range measurements. When measuring a low-reflectivity surface the returning laser intensity will be low. This, in turn, results in high uncertainty in the range estimate. In this paper, an approach to correct the intensity values

Research paper thumbnail of Maximum <italic>a posteriori</italic> image and seeing condition estimation from partially coherent two-dimensional light detection and ranging images

Optical Engineering, 2006

Recent developments in staring focal plane technology have spawned significant interest in the ap... more Recent developments in staring focal plane technology have spawned significant interest in the application of gated laser radar systems to battlefield remote sensing. Such environments are characterized by rapidly changing atmospheric seeing conditions and significant image distortion caused by long slant-range paths through the most dense regions of the atmosphere. Limited weight, space, and computational resources tend to prohibit the application of adaptive optic systems to mitigate atmospheric image distortion. We demonstrate and validate the use of a fast, iterative, maximum a posteriori (MAP) estimator to estimate both the original target scene and the ensemble-averaged atmospheric optical transfer function parameterized by Fried's seeing parameter. Wide-field-of-view sensor data is simulated to emulate images collected on an experimental test range. Simulated and experimental multiframe motion-compensated average images are deconvolved by the MAP estimator to produce most likely estimates of the truth image as well as the atmospheric seeing condition. For comparison, Fried's seeing parameter is estimated from experimentally collected images using a knife-edge response technique. The MAP estimator is found to yield seeing condition estimates within approximately 6% using simulated speckle images, and within approximately 8% of knife-edge derived truth for a limited set of experimentally collected image data.

Research paper thumbnail of High-resolution image reconstruction from digital video by exploitation of nonglobal motion

Optical Engineering, 1999

Many imaging systems utilize detector arrays that do not sample the scene according to the Nyquis... more Many imaging systems utilize detector arrays that do not sample the scene according to the Nyquist criterion. As a result, the higher spatial frequencies admitted by the optics are aliased. This creates undesirable artifacts in the imagery. Furthermore, the blurring effects of the optics and the finite detector size also degrade the image quality. Several approaches for increasing the sampling rate of imaging systems have been suggested in the literature. We propose an algorithm for resolution enhancement that exploits object motion in digital video sequences. Unlike previously defined techniques, we use an automated segmentation method to isolate rigid moving objects. These are accurately registered and the multiple observations of the object are used to produce an effectively high sampling rate over the object. The experimental results presented illustrate the breakdown of resolution enhancement algorithms that assume global scene motion when the actual scene motion is nonglobal. The performance of the proposed algorithm is illustrated using images from a forward looking IR imager and a visible range camera.

Research paper thumbnail of Physics Commons, and the Signal Processing Commons

This Article is brought to you for free and open access by the Department of Electrical and Compu... more This Article is brought to you for free and open access by the Department of Electrical and Computer Engineering at eCommons. It has been accepted for inclusion in Electrical and Computer Engineering Faculty Publications by an authorized administrator of eCommons. For more information, please

Research paper thumbnail of Characterization measurements of ASC FLASH 3D ladar

SPIE Proceedings, 2009

As a part of the project agreement between the Swedish Defence Research Agency (FOI) and the Unit... more As a part of the project agreement between the Swedish Defence Research Agency (FOI) and the United States of American's Air Force Research Laboratory (AFRL), a joint field trial was performed in Sweden during two weeks in January 2009. The main purpose for this trial was to characterize AFRL's latest version of the ASC (Advanced Scientific Concepts [1]) FLASH 3D LADAR sensor. The measurements were performed essentially in FOI's optical hall whose 100 m indoor range offers measurements under controlled conditions minimizing effects such as atmospheric turbulence. Data were also acquired outdoor in both forest and urban scenarios, using vehicles and humans as targets, with the purpose of acquiring data from more dynamic platforms to assist in further algorithm development. This paper shows examples of the acquired data and presents initial results.

Research paper thumbnail of <title>The application of iterative closest point (ICP) registration to improve 3D terrain mapping estimates using the flash 3D ladar system</title>

Laser Radar Technology and Applications XV, 2010

The primary purpose of this research was to develop an effective means of creating a 3D terrain m... more The primary purpose of this research was to develop an effective means of creating a 3D terrain map image (point-cloud) in GPS denied regions from a sequence of co-bore sighted visible and 3D LIDAR images. Both the visible and 3D LADAR cameras were hard mounted to a vehicle. The vehicle was then driven around the streets of an abandoned village