A consistent, reliable method of quantifying diabetic retinopathy is required, both for patient assessment and eventually for use in screening tests for diabetes. To this end, an algorithm for determining the degree o...
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ISBN:
(纸本)0819407437
A consistent, reliable method of quantifying diabetic retinopathy is required, both for patient assessment and eventually for use in screening tests for diabetes. To this end, an algorithm for determining the degree of venous beading in digitized ocular fundus images has been developed. A parallel implementation of the algorithm has also been investigated. The algorithm thresholds the fundus image to extract vein silhouettes. Morphological closing is used to fill any anomolous holes. Thinning is used to determine vein centerlines. Vein diameters are measured normal to the centerlines. A frequency analysis of vein diameter with distance along the centerline is then performed to permit estimation of veinous beading. For the parallel implementation, the binary vein silhouette and the vein centerline are rotated so that vein diameter may be estimated in one direction only. The time complexity of the parallel algorithm is O(N). Algorithm performance is demonstrated with real fundus images. A simulation of the parallel algorithm is used with actual fundus images.
A method is introducedfor implementing a 3-D vision system considering manufacturing cost constraints stringent reliability requirements and limited processing power. It entails transducer characterization and include...
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ISBN:
(纸本)0819404551
A method is introducedfor implementing a 3-D vision system considering manufacturing cost constraints stringent reliability requirements and limited processing power. It entails transducer characterization and includes a scanning algorithm and low-complexity processing algorithms providing position shape and orientation information about an unknown surface. A highly modular approach subdivides the problem into separable and sequential processing modules gradually modifying a " data matrix" obtained from a scanning algorithm. Some models considered for planar and curved surface analysis are described. Theoretical and experimental background validating the implemented algorithms is presented.
A new approach to the robust recognition of objects is presented. The fundamental picture primitives employed are local orientations, rather than the more traditionally used edge positions. A simple technique of featu...
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ISBN:
(纸本)0819407437
A new approach to the robust recognition of objects is presented. The fundamental picture primitives employed are local orientations, rather than the more traditionally used edge positions. A simple technique of feature-matching is used, based on the accumulation of evidence in binary channels (similar to the Hough transform) followed by a weighted non- linear sum of the evidence accumulators (matched filters, similar to those used in neural networks). By layering this simple feature-matcher, a hierarchical scheme is produced whose base is a binary representation of local orientations. The individual layers represent increasing levels of abstraction in the search for an object, so that the object can be arbitrarily complex. The universal algorithm presented can be implemented in less than 100 lines of a high-level programming language (e.g., Pascal). As evidenced by practical examples of various complexities, objects can be reliably and robustly identified in a wide variety of surroundings.
Detecting and imaging small wildfires with an Airborne Scanner is done against generally high background levels. The Airborne Scanner System used is a two-channel thermal IR scanner, with one channel selected for imag...
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ISBN:
(纸本)0819406686
Detecting and imaging small wildfires with an Airborne Scanner is done against generally high background levels. The Airborne Scanner System used is a two-channel thermal IR scanner, with one channel selected for imaging the terrain and the other channel sensitive to hotter targets. If a relationship can be determined between the two channels that quantifies the background signal for hotter targets, then an algorithm can be determined that removes the background signal in that channel leaving only the fire signal. The relationship can be determined anywhere between various points in the signal processing of the radiometric data from the radiometric input to the quantized output of the system. As long as only linear operations are performed on the signal, the relationship will only depend on the system gain and offsets within the range of interest. The algorithm can be implemented either by using a look-up table or performing the calculation in the system computer. The current presentation will describe the algorithm, its derivation, and its implementation in the Firefly Wildfire detection System by means of an off-the-shelf commercial scanner. Improvement over the previous algorithm used and the margin gained for improving the imaging of the terrain will be demonstrated.
Orientation-based representations (OBR) have many advantages. Three orientation-based differential geometric representations in computer vision literature are critically examined. The three representations are the ext...
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ISBN:
(纸本)0819406988
Orientation-based representations (OBR) have many advantages. Three orientation-based differential geometric representations in computer vision literature are critically examined. The three representations are the extended Gaussian image (EGI),3 the support function based representation (SFBR),5 and the generalized Gaussian image (GGI).4 The scope of unique representation, invariant properties from matching considerations, computation and storage requirements, and relations between the three representations are analyzed. It is shown that an OBR using any combination of local descriptors is insufficient to uniquely characterize a surface. It must contain either global descriptors or connectivity information. The GGI as it was introduced4 requires the mapping of one principal vector onto the unit sphere. It is shown in this paper that this is unnecessary. This reduces the storage requirement of a GGI by half, therefore, making it a more attractive representation. It is also concluded that if the intention is to reconstruct surfaces from their representations, a SFBR should be used. If the intention is recognition, a truly orientation-based representation such as the GGI should be used.
The accurate calculation of optical flow fields or displacement estimate fields in real-world imagery can be useful for detecting military targets. A new Kalman filter based low-level displacement estimation algorithm...
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ISBN:
(纸本)0819405914
The accurate calculation of optical flow fields or displacement estimate fields in real-world imagery can be useful for detecting military targets. A new Kalman filter based low-level displacement estimation algorithm is derived. The gain matrix of the estimator turns out to be the Kalman gain matrix, which is dependent on the image statistics. A procedure is developed in which the gain matrix of the estimator is not chosen heuristically, but is calculated based on the statistics of the image. The optical flow fields obtained from this estimator is accurate, and is convergent faster compared to the previous pel recursive based algorithms.
In automatic assembly tasks guided by vision it is necessary to determine the position x,y and the orientation of a given element of the target. This work describes the image processor used to evaluate the shift of th...
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ISBN:
(纸本)0819405914
In automatic assembly tasks guided by vision it is necessary to determine the position x,y and the orientation of a given element of the target. This work describes the image processor used to evaluate the shift of the target every 20 ms and thus to obtain a better guidance dynamic response.
This paper describes an algorithm which recovers 6 degrees of freedom ( that is rotational and translational matrices R and T ) of polyhedral objects using L-corners in a monocular image. First the gradients of the ci...
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ISBN:
(纸本)0819404489
This paper describes an algorithm which recovers 6 degrees of freedom ( that is rotational and translational matrices R and T ) of polyhedral objects using L-corners in a monocular image. First the gradients of the cirtain object''s faces are determined using the constraints derived from angles of L-corners. R accompanied by the object is then determined. Second a constraint concerning T is derived from a junction point of a Lcorner. After that T is determined using a set of constraints derived from the L-corners that contributed to the determination of R. By assembling only those L-corners the cirtain object is recognized.
An algorithm is presented for speckle reduction in time varying images. The algorithm operates in the time domain and is based on a subdivision of the time evolution of each pixel in the image into homogenous zones. T...
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ISBN:
(纸本)0819405507
An algorithm is presented for speckle reduction in time varying images. The algorithm operates in the time domain and is based on a subdivision of the time evolution of each pixel in the image into homogenous zones. The algorithm operates on a finite time window. The intensity evolution in this window is processed individually for each pixel in the image. The restored time evolution is defined as a piecewise linear function with a predefined maximal number of linear segments. The maximal number of segments is a parameter of the algorithm. Dynamic programming has been applied to obtain the piecewise linear function that minimizes the mean square error. For more than one segment the algorithm finds the optimal way to subdivide the time evolution into homogenous zones. Ordinary linear curve regression is used within each homogenous time segment. Several alternatives for temporal filtering based on discontinuity detection are discussed. The proposed algorithm reduces nonstationary speckle and increases the image contrast.
Color space analysis of classification-based segmentation algorithms provides insights into the capabilities of the color vision system. In standard pattern recognition theory, classification algorithms are categorize...
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ISBN:
(纸本)081940697X
Color space analysis of classification-based segmentation algorithms provides insights into the capabilities of the color vision system. In standard pattern recognition theory, classification algorithms are categorized by their discriminant functions in feature space. This analysis is applied to color classification methods used in road detection systems. There have been many systems that use classification techniques. By examining these road detection system in color space, a relationship can be seen between their color model representation and their capabilities and limitations.
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