Showing papers on "Orientation (computer vision) published in 2005"

Geometric context from a single image

Abstract: Many computer vision algorithms limit their performance by ignoring the underlying 3D geometric structure in the image. We show that we can estimate the coarse geometric properties of a scene by learning appearance-based models of geometric classes, even in cluttered natural scenes. Geometric classes describe the 3D orientation of an image region with respect to the camera. We provide a multiple-hypothesis framework for robustly estimating scene structure from a single image and obtaining confidences for each geometric label. These confidences can then be used to improve the performance of many other applications. We provide a thorough quantitative evaluation of our algorithm on a set of outdoor images and demonstrate its usefulness in two applications: object detection and automatic single-view reconstruction.

Efficiently combining positions and normals for precise 3D geometry

Abstract: Range scanning, manual 3D editing, and other modeling approaches can provide information about the geometry of surfaces in the form of either 3D positions (e.g., triangle meshes or range images) or orientations (normal maps or bump maps). We present an algorithm that combines these two kinds of estimates to produce a new surface that approximates both. Our formulation is linear, allowing it to operate efficiently on complex meshes commonly used in graphics. It also treats high-and low-frequency components separately, allowing it to optimally combine outputs from data sources such as stereo triangulation and photometric stereo, which have different error-vs.-frequency characteristics. We demonstrate the ability of our technique to both recover high-frequency details and avoid low-frequency bias, producing surfaces that are more widely applicable than position or orientation data alone.

Methods and apparatuses for image guided medical procedures

Abstract: Methods and apparatuses for the image guidance and documentation of medical procedures. One embodiment includes combining small field of view images into a recorded image of with a large field of view and aligning the small field of view real time image with the recorded image through correlation of imaging data. A location and orientation determination system may be used to track the imaging system and provide a starting set of image alignment parameters and/or provide change updates to a set of image alignment parameters, which is then further improved through correlating imaging data. The recorded image may be selected according to real time measurement of a cardiac parameter during an image guided cardiac procedure. Image manipulations planned based on the recorded image can be stored and applied to the real time information. The position of the medical device may be determined and recorded through manipulating a cursor in a 3-D image space shown in two non-parallel views.

Optimal imaging parameters for fibre-orientation estimation in diffusion MRI

Abstract: This study uses Monte Carlo simulations to investigate the optimal value of the diffusion weighting factor b for estimating white-matter fiber orientations using diffusion MRI with a standard spherical sampling scheme. We devise an algorithm for determining the optimal echo time, pulse width, and pulse separation in the pulsed-gradient spin-echo sequence for a specific value of b. The Monte Carlo simulations provide an estimate of the optimal value of b for recovering one and two fiber orientations. We show that the optimum is largely independent of the noise level in the measurements and the number of gradient directions and that the optimum depends only weakly on the diffusion anisotropy, the maximum gradient strength, and the spin-spin relaxation time. The optimum depends strongly on the mean diffusivity. In brain tissue, the optima we estimate are in the ranges [0.7, 1.0] x 10(9) s m(-2) and [2.2, 2.8] x 10(9) s m(-2) for the one- and two-fiber cases, respectively. The best b for estimating the fractional anisotropy is slightly higher than for estimating fiber directions in the one-fiber case and slightly lower in the two-fiber case. To estimate Tr(D) in the one-fiber case, the optimal setting is higher still. Simulations suggest that a ratio of high to low b measurements of 5 to 1 is a good compromise for measuring fiber directions and size and shape indices.

Detection and classification of edges in color images

Abstract: Up to now, most of the color edge detection methods are monochromatic-based techniques, which produce, in general, better than when traditional gray-value techniques are applied. In this overview, we focus mainly on vector-valued techniques because it is easy to understand how to apply common edge detection schemes to every color component. Opposed to this, vector-valued techniques are new and different. The second part of the article addresses the topic of edge classification. While edges are often classified into step edges and ramp edges, we address the topic of physical edge classification based on their origin into shadow edges, reflectance edges, orientation edges, occlusion edges, and specular edges. In the rest of this article we discuss various vector-valued techniques for detecting discontinuities in color images. Then operators are presented based on vector order statistics, followed by presentation by examples of a couple of results of color edge detection. We then discuss different approaches to a physical classification of edges by their origin.

Efficient magnetic localization and orientation technique for capsule endoscopy

Abstract: To build a new wireless robotic capsule endoscope with external guidance for controllable and interactive GI tract examination, a sensing system is needed for tracking 3D location and 2D orientation of the capsule movement. An appropriate sensing approach is to enclose a small permanent magnet in the capsule. The magnet establishes a magnetic field around the patient's body. With the sensing data of magnetic sensor array outside the patient's body, the 3D location and 2D orientation of the capsule can be calculated. Higher localization and orientation accuracy can be obtained if more sensors and proper optimization algorithm are applied. In this paper, different nonlinear optimization algorithms are evaluated, and we have found that Levenberg-Marquardt method provides higher accuracy and faster speed. Simulations were done for investigating the de-noise ability of this algorithm based on different sensor arrays. Furthermore, the real experiment shows that the results are satisfactory with high accuracy.

Fingerprint image enhancement using STFT analysis

Abstract: Contrary to popular belief, despite decades of research in fingerprints, reliable fingerprint recognition is still an open problem. Extracting features out of poor quality prints is the most challenging problem faced in this area. This paper introduces a new approach for fingerprint enhancement based on Short Time Fourier Transform(STFT) Analysis. STFT is a well known technique in signal processing to analyze non-stationary signals. Here we extend its application to 2D fingerprint images.The algorithm simultaneously estimates all the intrinsic properties of the fingerprints such as the foreground region mask, local ridge orientation and local frequency orientation. We have evaluated the algorithm over a set of 800 images from FVC2002 DB3 database and obtained a 17% relative improvement in the recognition rate.

System and method for position determination

Abstract: A method for determining the position and orientation of a camera, which may not rely on the use of special markers. A set of reference images may be stored, together with camera pose and feature information for each image. A first estimate of camera position is determined by comparing the current camera image with the set of reference images. A refined estimate can be obtained using features from the current image matched in a subset of similar reference images, and in particular, the 3D positions of those features. A consistent 3D model of all stored feature information need not be provided.

Fingerprint reference-point detection

Abstract: A robust fingerprint recognition algorithm should tolerate the rotation and translation of the fingerprint image. One popular solution is to consistently detect a unique reference point and compute a unique reference orientation for translational and rotational alignment. This paper develops an effective algorithm to locate a reference point and compute the corresponding reference orientation consistently and accurately for all types of fingerprints. To compute the reliable orientation field, an improved orientation smoothing method is proposed based on adaptive neighborhood. It shows better performance in filtering noise while maintaining the orientation localization than the conventional averaging method. The reference-point localization is based on multiscale analysis of the orientation consistency to search the local minimum. The unique reference orientation is computed based on the analysis of the orientation differences between the radial directions fromthe reference point, which are the directions of the radii emitted from the reference point with equivalent angle interval, and the local ridge orientations along these radii. Experimental results demonstrate that our proposed algorithm can consistently locate a unique reference point and compute the reference orientation with high accuracy for all types of fingerprints.

FTRAC--a robust fluoroscope tracking fiducial.

Abstract: C-arm fluoroscopy is ubiquitous in contemporary surgery, but it lacks the ability to accurately reconstruct three-dimensional (3D) information. A major obstacle in fluoroscopic reconstruction is discerning the pose of the x-ray image, in 3D space. Optical/magnetic trackers tend to be prohibitively expensive, intrusive and cumbersome in many applications. We present single-image-based fluoroscope tracking (FTRAC) with the use of an external radiographic fiducial consisting of a mathematically optimized set of ellipses, lines, and points. This is an improvement over contemporary fiducials, which use only points. The fiducial encodes six degrees of freedom in a single image by creating a unique view from any direction. A nonlinear optimizer can rapidly compute the pose of the fiducial using this image. The current embodiment has salient attributes: small dimensions (3x3x5 cm); need not be close to the anatomy of interest; and accurately segmentable. We tested the fiducial and the pose recovery method on synthetic data and also experimentally on a precisely machined mechanical phantom. Pose recovery in phantom experiments had an accuracy of 0.56 mm in translation and 0.33 deg. in orientation. Object reconstruction had a mean error of 0.53 mm with 0.16 mm STD. The method offers accuracies similar to commercial tracking systems,more » and appears to be sufficiently robust for intraoperative quantitative C-arm fluoroscopy. Simulation experiments indicate that the size can be further reduced to 1x1x2 cm, with only a marginal drop in accuracy.« less

Triangulating point set surfaces with bounded error

Abstract: We introduce an algorithm for constructing a high-quality triangulation directly from Point Set Surfaces. Our algorithm requires no intermediate representation and no post-processing of the output, and naturally handles noisy input data, typically in the form of a set of registered range scans. It creates a triangulation where triangle size respects the geometry of the surface rather than the sampling density of the range scans. Our technique does not require normal information, but still produces a consistent orientation of the triangles, assuming the sampled surface is an orientable two-manifold. Our work is based on using Moving Least-Squares (MLS) surfaces as the underlying representation. Our technique is a novel advancing front algorithm, that bounds the Hausdorff distance to within a user-specified limit. Specifically, we introduce a way of augmenting advancing front algorithms with global information, so that triangle size adapts gracefully even when there are large changes in surface curvature. Our results show that our technique generates high-quality triangulations where other techniques fail to reconstruct the correct surface due to irregular sampling on the point cloud, noise, registration artifacts, and underlying geometric features, such as regions with high curvature gradients.

Monitoring Crack Changes in Concrete Structures

Abstract: This study proposes a crack-monitoring sys- tem to quantify the change of cracks from multitempo- ral images during the monitoring period. A series of images were taken from an off-the-shelf digital camera. Concrete cracks were extracted from the digital images by employing a series of image-processing techniques. The image coordinates and orientation of same cracks can be changed since the position and direction of the portable camera vary at every exposure time. To moni- tor the crack changes (width and length), it is critical to transform the image coordinates of cracks extracted from each image into the same object coordinates of the con- crete surface. In this study, such a geometric relationship was automatically recovered using the two-dimensional (2D) projective transformation based on the modified it- erated Hough transform (MIHT) algorithm, the result of which solved the transformation parameters. To improve the computational operation of MIHT, regions of param- eter estimation were also investigated. The developed al- gorithms were applied to monitor the crack of the concrete specimen. As a result, the change of cracks on the concrete specimen was successfully detected and accurately quan- tified.

Hybrid bronchoscope tracking using a magnetic tracking sensor and image registration

Abstract: In this paper, we propose a hybrid method for tracking a bronchoscope that uses a combination of magnetic sensor tracking and image registration The position of a magnetic sensor placed in the working channel of the bronchoscope is provided by a magnetic tracking system Because of respiratory motion, the magnetic sensor provides only the approximate position and orientation of the bronchoscope in the coordinate system of a CT image acquired before the examination The sensor position and orientation is used as the starting point for an intensity-based registration between real bronchoscopic video images and virtual bronchoscopic images generated from the CT image The output transformation of the image registration process is the position and orientation of the bronchoscope in the CT image We tested the proposed method using a bronchial phantom model Virtual breathing motion was generated to simulate respiratory motion The proposed hybrid method successfully tracked the bronchoscope at a rate of approximately 1 Hz

A steerable complex wavelet construction and its application to image denoising

Abstract: This work addresses the design of a novel complex steerable wavelet construction, the generation of transform-space feature measurements associated with corner and edge presence and orientation properties, and the application of these measurements directly to image denoising. The decomposition uses pairs of bandpass filters that display symmetry and antisymmetry about a steerable axis of orientation. While the angular characterization of the bandpass filters is similar to those previously described, the radial characteristic is new, as is the manner of constructing the interpolation functions for steering. The complex filters have been engineered into a multirate system, providing a synthesis and analysis subband filtering system with good reconstruction properties. Although the performance of our proposed denoising strategy is currently below that of recently reported state-of-the-art techniques in denoising, it does compare favorably with wavelet coring approaches employing global thresholds and with an "Oracle" shrinkage technique, and presents a very promising avenue for exploring structure-based denoising in the wavelet domain.

Local Shape from Mirror Reflections

Abstract: We study the problem of recovering the 3D shape of an unknown smooth specular surface from a single image. The surface reflects a calibrated pattern onto the image plane of a calibrated camera. The pattern is such that points are available in the image where position, orientations, and local scale may be measured (e.g. checkerboard). We first explore the differential relationship between the local geometry of the surface around the point of reflection and the local geometry in the image.We then study the inverse problem and give necessary and sufficient conditions for recovering surface position and shape.We prove that surface position and shape up to third order can be derived as a function of local position, orientation and local scale measurements in the image when two orientations are available at the same point (e.g. a corner). Information equivalent to scale and orientation measurements can be also extracted from the reflection of a planar scene patch of arbitrary geometry, provided that the reflections of (at least) 3 distinctive points may be identified.We validate our theoretical results with both numerical simulations and experiments with real surfaces.

Vehicle localization on a digital map using particles filtering

Abstract: Localization is an important functionality for the navigation of intelligent vehicles. It is usually done using several kinds of sensors (proprioceptive, GPS, camera). All the data are uncertain and even momentarily unavailable (GPS in urban areas for example). A data fusion process is necessary for sensors data to compensate one each other. We propose here to combine GPS absolute localization with data computed by a vision system giving the position and orientation of the vehicle on the road. This last local information is transformed into a global reference using a map of the environment. The localization parameters are estimated using a particles filter making it possible to manage multimodal estimations (the vehicle can be on the left lane or on the right one for example). Many results have been obtained in real time and on real roads by implementing this solution in an experimental vehicle. The best standard deviation reached is 48 cm along the road axis and 8 cm along the axis normal to the road.

Building extraction from high resolution imagery based on multi-scale object oriented classification and probabilistic Hough transform

Abstract: In this paper, we developed a new building extraction system applied on high resolution remote sensing imagery based on multi-scale object oriented classification and probabilistic Hough transform. This can be divided into two different phases: building roof extraction, and shape reconfiguration. For the first phase, the multispectral and panchromatic high resolution satellite imageries are firstly fused for spatial resolution improvement and color information enhancement. The multiresolution image segmentation is applied on the fused image, resulting in the formation of the different level of polygon primitives at different space scale, providing different view of the scene at different resolution. In addition to the spectral information, the tone, texture, shape, context information is evaluated in an object oriented manner. The classification is based on a fuzzy rule decision tree classifier. By fuzzy evaluating of the shape, texture, context and spectral information, building roofs are extracted by reconstruction and classification from an appropriate space scale of roof polygon primitives. For the shape reconfiguration phase, we adopt the probabilistic Hough transform to delineate the roof dominant line which shows the major orientation of the specific building roof. According to the dominant line, a building squaring algorithm is applied based on rectilinear fitting of the building boundary. It is shown by our experiment that most rectangular building roofs can be correctly detected, extracted and reconfigured, demonstrating the potential application of the method.

Efficient magnetic localization and orientation technique for capsule endoscopy

Abstract: To build a new wireless robotic capsule endoscope with external guidance for controllable and interactive GI tract examination, a sensing system is needed for tracking 3D location and 2D orientation of the capsule endoscope movement. An appropriate sensing method is to enclose a small permanent magnet in the capsule. The intensities of the magnetic field produced by the magnet in different spatial points can be measured by the magnetic sensors outside the patient's body. With the sensing data of magnetic sensor array, the 3D location and 2D orientation of the capsule can be calculated. Higher calculation accuracy can be obtained if more sensors and optimal algorithm are applied. In this paper, different nonlinear optimization algorithms were evaluated to solve the magnet's 5D parameters, e.g. Powell's, Downhill Simplex, DIRECT, Multilevel Coordinate Search, and Levenberg Marquardt method. We have found that Levenberg-Marquardt method provides satisfactory calculation accuracy and faster speed. Simulations were done for investigating the de-noise ability of this algorithm based on different sensor arrays. Also the real experiment shows that the results are satisfactory with high accuracy (average localization error is 5.6 mm).

A novel phantom-less spatial and temporal ultrasound calibration method

Abstract: This paper introduces a novel method for ultrasound calibration for both spatial and temporal parameters The main advantage of this method is that it does not require a phantom, which is usually expensive to fabricate Furthermore, the method does not require extensive image processing For spatial calibration, we solve an optimization problem established by a set of equations that relate the orientations of a line (ie, calibration pointer) to the intersection points appearing in the ultrasound image The line orientation is provided through calibration of both ends of the calibration pointer Temporal calibration is achieved by processing of the captured pointer orientations and the corresponding image positions of intersection along with the timing information The effectiveness of the unified method for both spatial and temporal calibration is apparent from the quality of the 3D reconstructions of a known object

Method and medical imaging system for compensating for patient motion

Abstract: The present invention relates to a method and also an imaging system to compensate for patient motion when recording a series of images in medical imaging, in which a number of images of an area under examination of a patient (17) are recorded at intervals with an imaging system (1) and are related to one another. With the method a localization system (2) is used as the series of images are being recorded to permanently or at a time close to the recording of the individual images, record a momentary spatial location of the area under examination in a reference system permanently linked to the imaging system (1), a first spatial location of the area under examination recorded close to the time of recording of a first image is stored, and a deviation of the images recorded momentarily in each case of the first spatial location is determined and by changing the geometrical circumstances of the imaging system (1) at a time to close the recording of the spatial location and/or through geometrical adaptation of an image content of an image just recorded, is at least approximately commentated for, so that the images show the area under examination in the same position and orientation. The method does not require any time-consuming interaction with the operator and is also suitable for compensating for larger movements of the patient.

Marker detection method and apparatus, and position and orientation estimation method

Abstract: This invention relates to a mixed reality presentation apparatus for obtaining the position and orientation of an image sensing unit using markers. Whether or not a marker detected in a captured image has suspicion of partial occlusion is determined by checking if a region that neighbors a marker region includes a predetermined color, thus inhibiting information obtained from the marker with suspicion of partial occlusion from being used in position and orientation estimation of the image sensing unit. The precision of the obtained position and orientation can be improved.

System for projecting flaws and inspection locations and associated method

Abstract: A system and method for projecting an image onto a workpiece are provided The system includes a data system capable of providing information indicative of a flaw within the workpiece, wherein the information is based on data acquired by at least one sensor The system also includes an image-projecting device in communication with the data system and capable of projecting an image indicative of the flaw onto the workpiece, as well as a plurality of encoders for determining a location and/or orientation of the image-projecting device

Method for determining the orientation of an orientation indicator

Abstract: According to the invention, a separation from at least one and an image of at least three reflective regions on the orientation indicator are recorded by a separation measurement sensor and an image sensor in a measuring device (1), for the purpose of determining the orientation of an orientation indicator. The separation measurement and image recording are achieved by means of a directed emission of a collimated first beam (2) and a divergent second beam (3) with differing wavelengths and/or polarisation in the direction of the orientation indicator and a simultaneous recording of the reflected and/or scattered first and second beams (2',3'). The reflective regions on the orientation indicator are embodied and arranged such as to be positioned at a target point with a detectable geometric relationship to each other and to be simultaneously resolved by the image recorder. By means of the orientation determination, amongst other things, separations from target points, even not directly visible, can be precisely determined.

Portable electronic device with adjustable image capture orientation and method therefore

Abstract: A portable electronic device (100,200) includes an image capture means (245) for capturing an image, wherein the image capture means (245) has an orientation; and an image manager (255) coupled to the image capture means (245) for modifying the image using the orientation.