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Showing papers on "Image resolution published in 2005"


Journal ArticleDOI
TL;DR: Using a high-efficiency grating interferometer for hard X rays (10-30 keV) and a phase-stepping technique, separate radiographs of the phase and absorption profiles of bulk samples can be obtained from a single set of measurements.
Abstract: Using a high-efficiency grating interferometer for hard X rays (10-30 keV) and a phase-stepping technique, separate radiographs of the phase and absorption profiles of bulk samples can be obtained from a single set of measurements. Tomographic reconstruction yields quantitative three-dimensional maps of the X-ray refractive index, with a spatial resolution down to a few microns. The method is mechanically robust, requires little spatial coherence and monochromaticity, and can be scaled up to large fields of view, with a detector of correspondingly moderate spatial resolution. These are important prerequisites for use with laboratory X-ray sources.

1,264 citations


Journal ArticleDOI
30 Jun 2005-Nature
TL;DR: The achievement of sub-15-nm spatial resolution with a soft X-ray microscope—and a clear path to below 10 nm—using an overlay technique for zone plate fabrication is reported.
Abstract: The study of nanostructures is creating a need for microscopes that can see beyond the limits of conventional visible light and ultraviolet microscopes. X-ray imaging is a promising option. A new microscope described this week achieves unprecedented resolution, and has the ability to see through containing material. It features a specially made two-component zone plate — a lens with concentric zones rather like the rings in the Fresnel lenses familiar in overhead projectors and elsewhere — that makes use of diffraction to project an image into a CCD camera sensitive to soft X-rays. Spatial resolution of better than 15 nm is possible. Analytical tools that have spatial resolution at the nanometre scale are indispensable for the life and physical sciences. It is desirable that these tools also permit elemental and chemical identification on a scale of 10 nm or less, with large penetration depths. A variety of techniques1,2,3,4,5,6,7 in X-ray imaging are currently being developed that may provide these combined capabilities. Here we report the achievement of sub-15-nm spatial resolution with a soft X-ray microscope—and a clear path to below 10 nm—using an overlay technique for zone plate fabrication. The microscope covers a spectral range from a photon energy of 250 eV (∼5 nm wavelength) to 1.8 keV (∼0.7 nm), so that primary K and L atomic resonances of elements such as C, N, O, Al, Ti, Fe, Co and Ni can be probed. This X-ray microscopy technique is therefore suitable for a wide range of studies: biological imaging in the water window8,9; studies of wet environmental samples10,11; studies of magnetic nanostructures with both elemental and spin-orbit sensitivity12,13,14; studies that require viewing through thin windows, coatings or substrates (such as buried electronic devices in a silicon chip15); and three-dimensional imaging of cryogenically fixed biological cells9,16.

842 citations


Journal ArticleDOI
TL;DR: This paper presents a comprehensive framework, the general image fusion (GIF) method, which makes it possible to categorize, compare, and evaluate the existing image fusion methods.
Abstract: There are many image fusion methods that can be used to produce high-resolution multispectral images from a high-resolution panchromatic image and low-resolution multispectral images Starting from the physical principle of image formation, this paper presents a comprehensive framework, the general image fusion (GIF) method, which makes it possible to categorize, compare, and evaluate the existing image fusion methods Using the GIF method, it is shown that the pixel values of the high-resolution multispectral images are determined by the corresponding pixel values of the low-resolution panchromatic image, the approximation of the high-resolution panchromatic image at the low-resolution level Many of the existing image fusion methods, including, but not limited to, intensity-hue-saturation, Brovey transform, principal component analysis, high-pass filtering, high-pass modulation, the a/spl grave/ trous algorithm-based wavelet transform, and multiresolution analysis-based intensity modulation (MRAIM), are evaluated and found to be particular cases of the GIF method The performance of each image fusion method is theoretically analyzed based on how the corresponding low-resolution panchromatic image is computed and how the modulation coefficients are set An experiment based on IKONOS images shows that there is consistency between the theoretical analysis and the experimental results and that the MRAIM method synthesizes the images closest to those the corresponding multisensors would observe at the high-resolution level

793 citations


Journal ArticleDOI
TL;DR: The authors present a technique which takes into account the physical electromagnetic spectrum responses of sensors during the fusion process, which produces images closer to the image obtained by the ideal sensor than those obtained by usual wavelet-based image fusion methods.
Abstract: Usual image fusion methods inject features from a high spatial resolution panchromatic sensor into every low spatial resolution multispectral band trying to preserve spectral signatures and improve spatial resolution to that of the panchromatic sensor. The objective is to obtain the image that would be observed by a sensor with the same spectral response (i.e., spectral sensitivity and quantum efficiency) as the multispectral sensors and the spatial resolution of the panchromatic sensor. But in these methods, features from electromagnetic spectrum regions not covered by multispectral sensors are injected into them, and physical spectral responses of the sensors are not considered during this process. This produces some undesirable effects, such as resolution overinjection images and slightly modified spectral signatures in some features. The authors present a technique which takes into account the physical electromagnetic spectrum responses of sensors during the fusion process, which produces images closer to the image obtained by the ideal sensor than those obtained by usual wavelet-based image fusion methods. This technique is used to define a new wavelet-based image fusion method.

702 citations


Journal ArticleDOI
TL;DR: The product of spatial resolutions of the ghost image and ghost diffraction experiments is shown to overcome a limit which seemed to be achievable only with entangled photons.
Abstract: High-resolution ghost image and ghost diffraction experiments are performed by using a single classical source of pseudothermal speckle light divided by a beam splitter. Passing from the image to the diffraction result solely relies on changing the optical setup in the reference arm, while leaving the object arm untouched. The product of spatial resolutions of the ghost image and ghost diffraction experiments is shown to overcome a limit which seemed to be achievable only with entangled photons.

648 citations


Journal ArticleDOI
TL;DR: By reducing the signal strength using higher image resolution, the ratio of physiologic to image noise could be reduced to a regime where increased sensitivity afforded by higher field strength still translated to improved SNR in the fMRI time-series.

622 citations


Journal ArticleDOI
TL;DR: This model shows that visual artifacts after demosaicing are due to aliasing between luminance and chrominance and could be solved using a preprocessing filter, and gives new insights for the representation of single-color per spatial location images.
Abstract: There is an analogy between single-chip color cameras and the human visual system in that these two systems acquire only one limited wavelength sensitivity band per spatial location. We have exploited this analogy, defining a model that characterizes a one-color per spatial position image as a coding into luminance and chrominance of the corresponding three colors per spatial position image. Luminance is defined with full spatial resolution while chrominance contains subsampled opponent colors. Moreover, luminance and chrominance follow a particular arrangement in the Fourier domain, allowing for demosaicing by spatial frequency filtering. This model shows that visual artifacts after demosaicing are due to aliasing between luminance and chrominance and could be solved using a preprocessing filter. This approach also gives new insights for the representation of single-color per spatial location images and enables formal and controllable procedures to design demosaicing algorithms that perform well compared to concurrent approaches, as demonstrated by experiments.

346 citations


Proceedings ArticleDOI
20 Jun 2005
TL;DR: A novel algorithm aiming to estimate the 3D shape, the texture of a human face, along with the3D pose and the light direction from a single photograph by recovering the parameters of a 3D morphable model is presented.
Abstract: We present a novel algorithm aiming to estimate the 3D shape, the texture of a human face, along with the 3D pose and the light direction from a single photograph by recovering the parameters of a 3D morphable model. Generally, the algorithms tackling the problem of 3D shape estimation from image data use only the pixels intensity as input to drive the estimation process. This was previously achieved using either a simple model, such as the Lambertian reflectance model, leading to a linear fitting algorithm. Alternatively, this problem was addressed using a more precise model and minimizing a non-convex cost function with many local minima. One way to reduce the local minima problem is to use a stochastic optimization algorithm. However, the convergence properties (such as the radius of convergence) of such algorithms, are limited. Here, as well as the pixel intensity, we use various image features such as the edges or the location of the specular highlights. The 3D shape, texture and imaging parameters are then estimated by maximizing the posterior of the parameters given these image features. The overall cost function obtained is smoother and, hence, a stochastic optimization algorithm is not needed to avoid the local minima problem. This leads to the multi-features fitting algorithm that has a wider radius of convergence and a higher level of precision. This is shown on some example photographs, and on a recognition experiment performed on the CMU-PIE image database.

341 citations


Journal ArticleDOI
TL;DR: An improved method of image fusion is introduced which is based on the amelioration de la resolution spatiale par injection de structures (ARSIS) concept using the Curvelet transform, because the curvelet transform represents edges better than wavelets.
Abstract: A useful technique in various applications of remote sensing involves the fusion of different types of satellite images, namely multispectral (MS) satellite images with a high spectral and low spatial resolution and panchromatic (Pan) satellite image with a low spectral and high spatial resolution. Recent studies show that wavelet-based image fusion provides high-quality spectral content in fused images. However, the results of most wavelet-based methods of image fusion have a spatial resolution that is less than that obtained via the Brovey, intensity-hue-saturation, and principal components analysis methods of image fusion. We introduce an improved method of image fusion which is based on the amelioration de la resolution spatiale par injection de structures (ARSIS) concept using the curvelet transform, because the curvelet transform represents edges better than wavelets. Because edges are fundamental in image representation, enhancing the edges is an effective means of enhancing spatial resolution. Curvelet-based image fusion has been used to merge a Landsat Enhanced Thematic Mapper Plus Pan and MS image. The proposed method simultaneously provides richer information in the spatial and spectral domains.

330 citations


Journal Article
TL;DR: The initial in vivo images of the mouse heart and spine show that U-SPECT-I can be used for novel applications in the study of dynamic biologic systems with a clear projection to clinical applications and opens up new possibilities for the suborgan-level study of radiotracers in mouse models.
Abstract: A major advance in biomedical science and diagnosis was accomplished with the development of in vivo techniques to image radiolabeled molecules, but limited spatial resolution has slowed down applications to small experimental animals. Here, we present a SPECT system (U-SPECT-I) dedicated to radionuclide imaging of murine organs at a submillimeter resolution. Methods: The high performance of U-SPECT-I is based on a static triangular detector setup, with a cylindric imaging cavity in the center and 75 gold micropinhole apertures in the cavity wall. The pinholes are focused on a small volume of interest such as the mouse heart or spine to maximize the detection yield of -photons. Three-dimensional molecular distributions are iteratively estimated using the detector data and a statistical reconstruction algorithm that takes into account system blurring and data noise to increase resolution and reduce image noise. Results: With 0.6-mm-diameter pinholes, the maximum fraction of detected photons emitted by a point source (peak sensitivity) is 0.22% for a 15%-wide energy window and remains higher than 0.12% in the central 12 mm of the central plane. In a resolution phantom, radioactively filled capillaries as small as 0.5 mm and separated by 0.5 mm can be distinguished clearly in reconstructions. Projection data needed for the reconstruction of cross sections of molecular distributions in mouse organs can readily be obtained without the need for any mechanical movements. Images of a mouse spine show 99m Tc-hydroxymethylene diphosphonate uptake down to the level of tiny parts of vertebral processes. These are separated clearly from the vertebral and intervertebral foramina. Using another tracer, one can monitor myocardial perfusion in the left and right ventricular walls, even in structures as small as the papillary muscles. Conclusion: U-SPECT-I allows discrimination between molecular concentrations in adjacent volumes of as small as about 0.1 L, which is significantly smaller than can be imaged by any existing SPECT or PET system. Our initial in vivo images of the mouse heart and spine show that U-SPECT-I can be used for novel applications in the study of dynamic biologic systems with a clear projection to clinical applications. The combination of high resolution and detection efficiency of U-SPECT-I opens up new possibilities for the suborgan-level study of radiotracers in mouse models.

328 citations


Journal ArticleDOI
TL;DR: A method for fusing multi-exposure images of a static scene taken by a stationary camera into an image with maximum information content is introduced.

Proceedings ArticleDOI
11 Sep 2005
TL;DR: This work proposes to identify the source camera of an image based on traces of the proprietary interpolation algorithm deployed by a digital camera using a set of image characteristics defined and then used in conjunction with a support vector machine based multi-class classifier to determine the originating digital camera.
Abstract: In this work, we focus our interest on blind source camera identification problem by extending our results in the direction of M. Kharrazi et al. (2004). The interpolation in the color surface of an image due to the use of a color filter array (CFA) forms the basis of the paper. We propose to identify the source camera of an image based on traces of the proprietary interpolation algorithm deployed by a digital camera. For this purpose, a set of image characteristics are defined and then used in conjunction with a support vector machine based multi-class classifier to determine the originating digital camera. We also provide initial results on identifying source among two and three digital cameras.

Journal ArticleDOI
TL;DR: In this paper, four algorithms from the two main groups of segmentation algorithms (boundary-based and region-based) were evaluated and compared and an evaluation of each algorithm was carried out with empirical discrepancy evaluation methods.
Abstract: Since 1999, very high spatial resolution satellite data represent the surface of the Earth with more detail. However, information extraction by per pixel multispectral classification techniques proves to be very complex owing to the internal variability increase in land-cover units and to the weakness of spectral resolution. Image segmentation before classification was proposed as an alternative approach, but a large variety of segmentation algorithms were developed during the last 20 years, and a comparison of their implementation on very high spatial resolution images is necessary. In this study, four algorithms from the two main groups of segmentation algorithms (boundarybased and region-based) were evaluated and compared. In order to compare the algorithms, an evaluation of each algorithm was carried out with empirical discrepancy evaluation methods. This evaluation is carried out with a visual segmentation of Ikonos panchromatic images. The results show that the choice of parameters is very important and has a great influence on the segmentation results. The selected boundary-based algorithms are sensitive to the noise or texture. Better results are obtained with regionbased algorithms, but a problem with the transition zones between the contrasted objects can be present.

Book
01 May 2005
Abstract: Preface Part I: Basic Imaging Principles Overview. Chapter 1Introduction. History of Medical Imaging. Physical Signals. Imaging Modalities. Projection Radiography. Computed Tomography. Nuclear Medicine. Ultrasound Imaging. Magnetic Resonance Imaging. Summary and Key Concepts. Chapter 2: Signals and Systems.Introduction. Signals. Point Impulse. Line Impulse. Comb and Sampling Functions. Rect and Sinc Functions. Exponential and Sinusoidal Signals. Separable Signals. Periodic Signals. Systems. Linear Systems. Impulse Response. Shift Invariance. Connections of LSI Systems. Separable Systems. Stable Systems. The Fourier Transform. Properties of the Fourier Transform. Linearity. Translation. Conjugation and Conjugate Symmetry. Scaling. Rotation. Convolution. Product. Separable Product. Parseval's Theorem. Separability. Transfer Function. Circular Symmetry and the Hankel Transform. Sampling. Sampling Signal Model. Nyquist Sampling Theorem. Anti-aliasing Filters. Summary and Key Concepts. Chapter 3: Image Quality.Introduction. Contrast. Modulation. Modulation Transfer Function. Local Contrast. Resolution. Line Spread Function. Full Width at Half Maximum. Resolution and Modulation Transfer Function. Subsystem Cascade. Resolution Tool. Temporal and Spectral Resolution. Noise. Random Variables. Continuous Random Variables. Discrete Random Variables.Independent Random Variables. Signal-to-Noise Ratio. Amplitude SNR. Power SNR. Differential SNR. Nonrandom Effects. Artifacts. Distortion. Accuracy. Quantitative Accuracy. Diagnostic Accuracy. Summary and Key Concepts. Part II: Radiographic Imaging.Overview. Chapter 4: Physics of Radiography.Introduction. Ionization. Atomic Structure. Electron Binding Energy. Ionization and Excitation. Forms of Ionizing Radiation. Particulate Radiation. Electromagnetic Radiation. Nature and Properties of Ionizing Radiation. Primary Energetic Electron Interactions. Primary Electromagnetic Radiation Interactions. Attenuation of Electromagnetic Radiation. Measures of X-ray Beam Strength. Narrow Beam, Monoenergetic Photons. Narrow Beam, Polyenergetic Photons. Broad Beam Case. Radiation Dosimetry. Exposure. Dose and Kerma. Linear Energy Transfer. The f --factor. Dose Equivalent. Effective Dose. Summary and Key Concepts. Chapter 5: Projection Radiography.Introduction. Instrumentation. X-ray Tubes. Filtration and Restriction. Compensation Filters and Contrast Agents. Grids, Airgaps, and Scanning Slits. Film-Screen Detectors. X-ray Image Intensifiers. Image Formation. Basic Imaging Equation. Geometric Effects. Blurring Effects. Film Characteristics. Noise and Scattering. Signal-to-Noise Ratio. Quantum Efficiency and Detective Quantum Efficiency. Compton Scattering. Summary and Key Concepts. Chapter 6: Computed Tomography.Introduction. CT Instrumentation. CT Generations. X-ray Source and Collimation. CT Detectors. Gantry, Slip Ring, and Patient Table. Image Formation. Line Integrals. CT Numbers. Parallel-Ray Reconstruction. Fan-Beam Reconstruction. Helical CT Reconstruction. Cone Beam CT. Image Quality in CT. Resolution. Noise. Artifacts. Summary and Key Concepts. Part III: Nuclear Medicine Imaging.Overview. Chapter 7: The Physics of Nuclear Medicine.Introduction. Nomenclature. Radioactive Decay. Mass Defect and Binding Energy. Line of Stability. Radioactivity. Radioactive Decay Law. Modes of Decay. Positron Decay and Electron Capture. Isomeric Transition. Statistics of Decay. Radiotracers. Summary and Key Concepts. Chapter 8: Planar Scintigraphy.Introduction. Instrumentation. Collimators. Scintillation Crystal. Photomultiplier Tubes. Positioning Logic. Pulse Height Analyzer. Gating Circuit. Image Capture. Image Formation. Event Position Estimation. Acquisition Modes. Anger Camera Imaging Equation. Image Quality. Resolution. Sensitivity. Uniformity. Energy Resolution. Noise. Factors Affecting Count Rate. Summary and Key Concepts. Chapter 9: Emission Computed Tomography.Instrumentation. SPECT Instrumentation. PET Instrumentation. Image Formation. SPECT Image Formation. PET Image Formation. Iterative Reconstruction. Image Quality in SPECT and PET. Spatial Resolution. Attenuation and Scatter. Random Coincidences. Contrast. Noise and Signal-to-Noise. Summary and Key Concepts. Part IV: Ultrasound Imaging.Overview. Chapter 10: The Physics of Ultrasound. Introduction. The Wave Equation. Three-Dimensional Acoustic Waves. Plane Waves. Spherical Waves. Wave Propagation. Acoustic Energy and Intensity. Reflection and Refraction at Plane Interfaces. Transmission and Reflection Coefficients at Plane Interfaces. Attenuation. Scattering. Doppler Effect. Beam Pattern Formation and Focusing. Simple Field Pattern Model. Diffraction Formulation. Focusing. Summary and Key Concepts. Chapter 11: Ultrasound Imaging Systems.Introduction. Instrumentation. Ultrasound Transducer. Ultrasound Probes. Pulse-Echo Imaging. The Pulse-Echo Equation. Transducer Motion. Ultrasound Imaging Modes. A-Mode Scan. M-Mode Scan. B-Mode Scan. Steering and Focusing. Transmit Steering and Focusing. Beamforming and Dynamic Focusing. Three-Dimensional Ultrasound Imaging. Summary and Key Concepts. Part V: Magnetic Resonance Imaging.Overview. Chapter 12: Physics of Magnetic Resonance.Introduction. Microscopic Magnetization. Macroscopic Magnetization. Precession and Larmor Frequency. Transverse and Longitudinal Magnetization. NMR Signals. Rotating Frame. RF Excitation. Relaxation. The Bloch Equations. Spin Echoes. Contrast Mechanisms. Summary and Key Concepts. Chapter 13: Magnetic Resonance Imaging.Instrumentation. System Components. Magnet. Gradient Coils. Radio-Frequency Coils. Scanning Console and Computer. MRI Data Acquisition. Encoding Spatial Position. Slice Selection. Frequency Encoding. Polar Scanning. Gradient Echoes. Phase Encoding. Spin Echoes. Pulse Repetition Interval. Realistic Pulse Sequences. Image Reconstruction. Rectilinear Data. Polar Data. Imaging Equations. Image Quality. Sampling. Resolution. Noise. Signal-to-Noise Ratio. Artifacts. Summary and Key Concepts. Index.

Journal ArticleDOI
TL;DR: Spiral windmill-type artifacts are effectively suppressed with the z-flying focal spot technique, which has the potential to maintain a low artifact level up to pitch 1.5, in this way increasing the maximum volume coverage speed that can be clinically used.
Abstract: We present a theoretical overview and a performance evaluation of a novel z-sampling technique for multidetector row CT (MDCT), relying on a periodic motion of the focal spot in the longitudinal direction (z-flying focal spot) to double the number of simultaneously acquired slices. The z-flying focal spot technique has been implemented in a recently introduced MDCT scanner. Using 32 x 0.6 mm collimation, this scanner acquires 64 overlapping 0.6 mm slices per rotation in its spiral (helical) mode of operation, with the goal of improved longitudinal resolution and reduction of spiral artifacts. The longitudinal sampling distance at isocenter is 0.3 mm. We discuss in detail the impact of the z-flying focal spot technique on image reconstruction. We present measurements of spiral slice sensitivity profiles (SSPs) and of longitudinal resolution, both in the isocenter and off-center. We evaluate the pitch dependence of the image noise measured in a centered 20 cm water phantom. To investigate spiral image quality we present images of an anthropomorphic thorax phantom and patient scans. The full width at half maximum (FWHM) of the spiral SSPs shows only minor variations as a function of the pitch, measured values differ by less than 0.15 mm from the nominal values 0.6, 0.75, 1, 1.5, and 2 mm. The measured FWHM of the smallest slice ranges between 0.66 and 0.68 mm at isocenter, except for pitch 0.55 (0.72 mm). In a centered z-resolution phantom, bar patterns up to 15 lp/cm can be visualized independent of the pitch, corresponding to 0.33 mm longitudinal resolution. 100 mm off-center, bar patterns up to 14 lp/cm are visible, corresponding to an object size of 0.36 mm that can be resolved in the z direction. Image noise for constant effective mAs is almost independent of the pitch. Measured values show a variation of less than 7% as a function of the pitch, which demonstrates correct utilization of the applied radiation dose at any pitch. The product of image noise and square root of the slice width (FWHM of the respective SSP) is the same constant for all slices except 0.6 mm. For the thinnest slice, relative image noise is increased by 17%. Spiral windmill-type artifacts are effectively suppressed with the z-flying focal spot technique, which has the potential to maintain a low artifact level up to pitch 1.5, in this way increasing the maximum volume coverage speed that can be clinically used.

Journal Article
TL;DR: PCVIPR rapidly provides isotropic high-resolution angiographic images and permits retrospective measurement of average flow rate throughout the volume without the need to prescribe multiple 2D acquisition planes.
Abstract: BACKGROUND AND PURPOSE: Three-dimensional phase-contrast (3DPC) is limited by long imaging times, limited coverage, flow artifacts, and the need to perform multiple additional 2D examinations (2DPC) to measure flow A highly undersampled 3D radial acquisition (isotropic-voxel radial projection imaging [PCVIPR]) makes it possible to increase the product of volume coverage and spatial resolution by a factor of 30 for the same imaging time as conventional Cartesian 3DPC This provides anatomic information over a large volume with high isotropic resolution and permits retrospective measurement of average flow rates throughout the volume METHODS: PCVIPR acquires a reference and three flow-encoded acquisitions for each VIPR projection Complex difference images were formed by combining information from all flow directions Following retrospective definition of planes perpendicular to selected vessels, volume flow rates were determined by using phase-difference information The accuracy of average flow measurement was investigated in a phantom and in six volunteers Anatomic PCVIPR images acquired in three patients and three volunteers by using a 3843 matrix were compared with conventional Cartesian 3DPC RESULTS: The flow validation produced R2 = 099 in vitro and R2 = 097 in vivo PCVIPR produced minimal streak and pulsatile flow artifacts PCVIPR produced far higher resolution and volume coverage in comparable imaging times The highest acceleration factors relative to 3DPC were achieved by using gadolinium-contrast material Ultimately, acceleration factors are limited by signal-to-noise ratio CONCLUSION: PCVIPR rapidly provides isotropic high-resolution angiographic images and permits retrospective measurement of average flow rate throughout the volume without the need to prescribe multiple 2D acquisition planes

Journal ArticleDOI
TL;DR: The results show a significant increase in the accuracy of land cover maps at fine spatial resolution over that obtained from a recently proposed linear optimization approach suggested by Verhoeye and Wulf (2002).

Journal ArticleDOI
TL;DR: A novel super-resolution method for hyperspectral images that fuses information from multiple observations and spectral bands to improve spatial resolution and reconstruct the spectrum of the observed scene as a combination of a small number of spectral basis functions.
Abstract: Hyperspectral images are used for aerial and space imagery applications, including target detection, tracking, agricultural, and natural resource exploration. Unfortunately, atmospheric scattering, secondary illumination, changing viewing angles, and sensor noise degrade the quality of these images. Improving their resolution has a high payoff, but applying super-resolution techniques separately to every spectral band is problematic for two main reasons. First, the number of spectral bands can be in the hundreds, which increases the computational load excessively. Second, considering the bands separately does not make use of the information that is present across them. Furthermore, separate band super resolution does not make use of the inherent low dimensionality of the spectral data, which can effectively be used to improve the robustness against noise. In this paper, we introduce a novel super-resolution method for hyperspectral images. An integral part of our work is to model the hyperspectral image acquisition process. We propose a model that enables us to represent the hyperspectral observations from different wavelengths as weighted linear combinations of a small number of basis image planes. Then, a method for applying super resolution to hyperspectral images using this model is presented. The method fuses information from multiple observations and spectral bands to improve spatial resolution and reconstruct the spectrum of the observed scene as a combination of a small number of spectral basis functions.

Journal ArticleDOI
TL;DR: A method for constructing a video sequence of high space-time resolution by combining information from multiple low-resolution video sequences of the same dynamic scene by recovering rapid dynamic events that occur faster than regular frame-rate is proposed.
Abstract: We propose a method for constructing a video sequence of high space-time resolution by combining information from multiple low-resolution video sequences of the same dynamic scene. Super-resolution is performed simultaneously in time and in space. By "temporal super-resolution," we mean recovering rapid dynamic events that occur faster than regular frame-rate. Such dynamic events are not visible (or else are observed incorrectly) in any of the input sequences, even if these are played in "slow-motion." The spatial and temporal dimensions are very different in nature, yet are interrelated. This leads to interesting visual trade-offs in time and space and to new video applications. These include: 1) treatment of spatial artifacts (e.g., motion-blur) by increasing the temporal resolution and 2) combination of input sequences of different space-time resolutions (e.g., NTSC, PAL, and even high quality still images) to generate a high quality video sequence. We further analyze and compare characteristics of temporal super-resolution to those of spatial super-resolution. These include: the video cameras needed to obtain increased resolution; the upper bound on resolution improvement via super-resolution; and, the temporal analogue to the spatial "ringing" effect.

Journal ArticleDOI
TL;DR: Design methods of linear FM signals and mismatched filters are presented, in order to meet the higher demands on resolution in ultrasound imaging, and it is shown that for the small time-bandwidth products available in ultrasound, the rectangular spectrum approximation is not valid, which reduces the effectiveness of weighting.
Abstract: For pt.I, see ibid., vol.52, no.2, p.177-91 (2005). In the first paper, the superiority of linear FM signals was shown in terms of signal-to-noise ratio and robustness to tissue attenuation. This second paper in the series of three papers on the application of coded excitation signals in medical ultrasound presents design methods of linear FM signals and mismatched filters, in order to meet the higher demands on resolution in ultrasound imaging. It is shown that for the small time-bandwidth (TB) products available in ultrasound, the rectangular spectrum approximation is not valid, which reduces the effectiveness of weighting. Additionally, the distant range sidelobes are associated with the ripples of the spectrum amplitude and, thus, cannot be removed by weighting. Ripple reduction is achieved through amplitude or phase predistortion of the transmitted signals. Mismatched filters are designed to efficiently use the available bandwidth and at the same time to be insensitive to the transducer's impulse response. With these techniques, temporal sidelobes are kept below 60 to 100 dB, image contrast is improved by reducing the energy within the sidelobe region, and axial resolution is preserved. The method is evaluated first for resolution performance and axial sidelobes through simulations with the program Field II. A coded excitation ultrasound imaging system based on a commercial scanner and a 4 MHz probe driven by coded sequences is presented and used for the clinical evaluation of the coded excitation/compression scheme. The clinical images show a significant improvement in penetration depth and contrast, while they preserve both axial and lateral resolution. At the maximum acquisition depth of 15 cm, there is an improvement of more than 10 dB in the signal-to-noise ratio of the images. The paper also presents acquired images, using complementary Golay codes, that show the deleterious effects of attenuation on binary codes when processed with a matched filter, also confirmed by the presented simulated images.

Journal ArticleDOI
07 Oct 2005-Science
TL;DR: SNFUH has been developed that provides depth information as well as spatial resolution at the 10- to 100-nanometer scale and used to image buried nanostructures, to perform subsurface metrology in microelectronic structures, and to image malaria parasites in red blood cells.
Abstract: A nondestructive imaging method, scanning near-field ultrasound holography (SNFUH), has been developed that provides depth information as well as spatial resolution at the 10- to 100-nanometer scale. In SNFUH, the phase and amplitude of the scattered specimen ultrasound wave, reflected in perturbation to the surface acoustic standing wave, are mapped with a scanning probe microscopy platform to provide nanoscale-resolution images of the internal substructure of diverse materials. We have used SNFUH to image buried nanostructures, to perform subsurface metrology in microelectronic structures, and to image malaria parasites in red blood cells.

Journal ArticleDOI
TL;DR: What is believed to be the first optical synthetic-aperture image of a fixed, diffusely scattering target with a moving aperture is reported, and a general digital signal-processing solution to the laser waveform instability problem is described and demonstrated.
Abstract: The spatial resolution of a conventional imaging laser radar system is constrained by the diffraction limit of the telescope’s aperture. We investigate a technique known as synthetic-aperture imaging laser radar (SAIL), which employs aperture synthesis with coherent laser radar to overcome the diffraction limit and achieve fine-resolution, long-range, two-dimensional imaging with modest aperture diameters. We detail our laboratory-scale SAIL testbed, digital signal-processing techniques, and image results. In particular, we report what we believe to be the first optical synthetic-aperture image of a fixed, diffusely scattering target with a moving aperture. A number of fine-resolution, well-focused SAIL images are shown, including both retroreflecting and diffuse scattering targets, with a comparison of resolution between real-aperture imaging and synthetic-aperture imaging. A general digital signal-processing solution to the laser waveform instability problem is described and demonstrated, involving both new algorithms and hardware elements. These algorithms are primarily data driven, without a priori knowledge of waveform and sensor position, representing a crucial step in developing a robust imaging system.

Journal ArticleDOI
TL;DR: A new optical concept for compact digital image acquisition devices with large field of view is developed and proofed experimentally and anamorphic lenses, where the parameters are a function of the considered optical channel, are used to achieve a homogeneous optical performance over the whole field of sight.
Abstract: A new optical concept for compact digital image acquisition devices with large field of view is developed and proofed experimentally. Archetypes for the imaging system are compound eyes of small insects and the Gabor-Superlens. A paraxial 3x3 matrix formalism is used to describe the telescope arrangement of three microlens arrays with different pitch to find first order parameters of the imaging system. A 2mm thin imaging system with 21x3 channels, 70 masculinex10 masculine field of view and 4.5mm x 0.5mm image size is optimized and analyzed using sequential and non-sequential raytracing and fabricated by microoptics technology. Anamorphic lenses, where the parameters are a function of the considered optical channel, are used to achieve a homogeneous optical performance over the whole field of view. Captured images are presented and compared to simulation results.

Journal ArticleDOI
TL;DR: In this article, a multi-band wavelet-based image fusion method is presented, which is a further development of the two-band Wavelet transformation, and a set of qualities are classified and analyzed.

Journal ArticleDOI
TL;DR: A single-sided NMR sensor to produce depth profiles with microscopic spatial resolution is presented, using a novel permanent magnet geometry that generates a highly flat sensitive volume parallel to the scanner surface.

Journal ArticleDOI
TL;DR: A statistical framework that gathers together robust methods for multiple comparisons, seasonally corrected Mann–Kendall trend tests, and a testing sequence for quadratic models of land surface phenology is presented.
Abstract: Coarse spatial resolution satellites are capable of observing large swaths of the planetary surface in each overpass resulting in image time series with high temporal resolution. Many change‐detection strategies commonly used in remote sensing studies were developed in an era of image scarcity and thus focus on comparing just a few scenes. However, change analysis methods applicable to images with sparse temporal sampling are not necessarily efficient and effective when applied to long image time series. We present a statistical framework that gathers together: (1) robust methods for multiple comparisons; (2) seasonally corrected Mann–Kendall trend tests; (3) a testing sequence for quadratic models of land surface phenology. This framework can be applied to long image time series to partition sources of variation and to assess the significance of detected changes. Using a standard image time series, the Pathfinder AVHRR Land (PAL) NDVI data, we apply the framework to address the question of whether the in...

Journal ArticleDOI
TL;DR: A finite element formulation for a digital image correlation method is presented that will determine directly the complete, two-dimensional displacement field during the image correlation process on digital images.
Abstract: A finite element formulation for a digital image correlation method is presented that will determine directly the complete, two-dimensional displacement field during the image correlation process on digital images. The entire interested image area is discretized into finite elements that are involved in the common image correlation process by use of our algorithms. This image correlation method with finite element formulation has an advantage over subset-based image correlation methods because it satisfies the requirements of displacement continuity and derivative continuity among elements on images. Numerical studies and a real experiment are used to verify the proposed formulation. Results have shown that the image correlation with the finite element formulation is computationally efficient, accurate, and robust.

Journal ArticleDOI
TL;DR: Helical tomotherapy is an innovative means of delivering IGRT and IMRT using a device that combines features of a linear accelerator and a helical computed tomography (CT) scanner that enables dose guidance as well as image guidance of radiotherapy treatments.
Abstract: Helical tomotherapy is an innovative means of delivering IGRT and IMRT using a device that combines features of a linear accelerator and a helical computed tomography (CT) scanner. The HI-ART II can generate CT images from the same megavoltage x-ray beam it uses for treatment. These megavoltage CT (MVCT) images offer verification of the patient position prior to and potentially during radiation therapy. Since the unit uses the actual treatment beam as the x-ray source for image acquisition, no surrogate telemetry systems are required to register image space to treatment space. The disadvantage to using the treatment beam for imaging, however, is that the physics of radiation interactions in the megavoltage energy range may force compromises between the dose delivered and the image quality in comparison to diagnostic CT scanners. The performance of the system is therefore characterized in terms of objective measures of noise, uniformity, contrast, and spatial resolution as a function of the dose delivered by the MVCT beam. The uniformity and spatial resolutions of MVCT images generated by the HI-ART II are comparable to that of diagnostic CT images. Furthermore, the MVCT scan contrast is linear with respect to the electron density of material imaged. MVCT images do not have the same performance characteristics as state-of-the art diagnostic CT scanners when one objectively examines noise and low-contrast resolution. These inferior results may be explained, at least partially, by the low doses delivered by our unit; the dose is 1.1 cGy in a 20 cm diameter cylindrical phantom. In spite of the poorer low-contrast resolution, these relatively low-dose MVCT scans provide sufficient contrast to delineate many soft-tissue structures. Hence, these images are useful not only for verifying the patient's position at the time of therapy, but they are also sufficient for delineating many anatomic structures. In conjunction with the ability to recalculate radiotherapy doses on these images, this enables dose guidance as well as image guidance of radiotherapy treatments.

Proceedings ArticleDOI
17 Oct 2005
TL;DR: The proposed method provides an automatic and stable way to compute super-resolution and the achieved result is encouraging for both synthetic and real LR images.
Abstract: In this paper, a novel method for learning based image super resolution (SR) is presented. The basic idea is to bridge the gap between a set of low resolution (LR) images and the corresponding high resolution (HR) image using both the SR reconstruction constraint and a patch based image synthesis constraint in a general probabilistic framework. We show that in this framework, the estimation of the LR image formation parameters is straightforward. The whole framework is implemented via an annealed Gibbs sampling method. Experiments on SR on both single image and image sequence input show that the proposed method provides an automatic and stable way to compute super-resolution and the achieved result is encouraging for both synthetic and real LR images.

Journal ArticleDOI
TL;DR: Both algorithms are compared by the analysis of the spectral and spatial quality of the merged images which were obtained by applying several wavelet based, image fusion methods to merge Ikonos multispectral and panchromatic spatially degraded images.
Abstract: In the last few years, several researchers have proposed different procedures for the fusion of multispectral and panchromatic images based on the wavelet transform, which provide satisfactory high spatial resolution images keeping the spectral properties of the original multispectral data. The discrete approach of the wavelet transform can be performed with different algorithms, Mallat's and the ‘a trous’ being the most popular ones for image fusion purposes. Each algorithm has its particular mathematical properties and leads to different image decompositions. In this article, both algorithms are compared by the analysis of the spectral and spatial quality of the merged images which were obtained by applying several wavelet based, image fusion methods. All these have been used to merge Ikonos multispectral and panchromatic spatially degraded images. Comparison of the fused images is based on spectral and spatial characteristics and it is performed visually and quantitatively using statistical parameters ...