Two algorithms for depth estimation are presented. The first algorithm simply looks for the focus level that maximizes the focus measure at each image point. The second algorithm uses a Gaussian model to interpolate t...
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Two algorithms for depth estimation are presented. The first algorithm simply looks for the focus level that maximizes the focus measure at each image point. The second algorithm uses a Gaussian model to interpolate the focus measures to obtain more accurate depth estimates. The algorithms were implemented and tested on surfaces of different roughness and reflectance properties. The results indicate that the shape-from-focus method may be applied to a variety of industrial vision problems.< >
Relaxation labeling uses contextual information for finding consistent labelings of graphs. Although relaxation labeling is parallel and iterative, the complexity of updating with standard rules is too costly for prac...
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Relaxation labeling uses contextual information for finding consistent labelings of graphs. Although relaxation labeling is parallel and iterative, the complexity of updating with standard rules is too costly for practical implementation. A description is given of a computationally more efficient updating rule that utilizes radial projection instead of normal projection to avoid the complexities incurred by previous update rules when boundaries to the labeling space are encountered. This reduction in complexity is achieved by first restricting support vectors to the positive quadrant, and then using radial projection onto the constraint instead of normal projection. Crucial order information is conserved through smooth convergence towards the optimum and a rate of convergence proportional to the magnitudes of the support functions.
An approach is described for curve inference that is based on curvature information. The inference procedure is divided into two stages: a trace inference stage, which is the subject of the present work, and a curve s...
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An approach is described for curve inference that is based on curvature information. The inference procedure is divided into two stages: a trace inference stage, which is the subject of the present work, and a curve synthesis stage. It is shown that recovery of the trace of a curve requires estimating local models for the curve at the same time, and that tangent and curvature information are sufficient. These make it possible to specify powerful constraints between estimated tangents to a curve, in terms of a neighborhood relationship called cocircularity, and between curvature estimates, in terms of a curvature consistency relation. Because all curve information is quantized, special care must be taken to obtain accurate estimates of trace points, tangents, and curvatures. This issue is addressed specifically to the introduction of a smoothness constraint and a maximum curvature constraint. The procedure is applied to two types of images: artificial images designed to evaluate curvature and noise sensitivity, and natural images.
The problem of obtaining reliable estimates of the optic flow field and its variation is discussed. It is argued that circuitry in the middle temporal (MT) visual area is arranged to provide mean field approximations ...
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The problem of obtaining reliable estimates of the optic flow field and its variation is discussed. It is argued that circuitry in the middle temporal (MT) visual area is arranged to provide mean field approximations of the optical flow field, that is, the maximal neighborhood over which the local field can be well-approximated as uniform, parallel translation. In addition, the way the mean field approximation varies with neighborhood size and position is informative about the variation of the flow field. It is shown how receptive fields can be synthesized to represent the first-order differential information about the flow field. The same ideas are applicable to the binocular disparity vector field, and lead one to predict the existence of extrastriate neurons that are specialized for the local shear and stretch of the disparity and motion vector fields.< >
A joint-trajectory-generation scheme for redundant robots is proposed which uses the redundancy to improve motion performance according to certain objective functions. The objective function can be either analytical o...
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A joint-trajectory-generation scheme for redundant robots is proposed which uses the redundancy to improve motion performance according to certain objective functions. The objective function can be either analytical or nonanalytical. For nonanalytical objective functions, a least-squares scheme is proposed to estimate the gradient vector. In addition, an approximation scheme is developed to compute the pseudoinverse of the Jacobian. Application of the scheme to a 4-link revolute planar robot manipulator is demonstrated through simulation. Several motion performance criteria are considered and their results analyzed.< >
Orientation selection is the inference of orientation information out of images. It is one of the foundations on which other visual structures are built, since it must precede the formation of contours out of pointill...
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Orientation selection is the inference of orientation information out of images. It is one of the foundations on which other visual structures are built, since it must precede the formation of contours out of pointillist data and surfaces out of surface markings. We take a differential geometric view in defining orientation selection and develop algorithms for actually doing it. The goal of these algorithms is formulated in mathematical terms as the inference of a vector field of tangents (to the contours), and the algorithms are studied in both abstract and computational forms. They are formulated as matching problems, and algorithms for solving them are reduced to biologically plausible terms. We show that two different matching problems are necessary, the first for 1-dimensional contours (which we refer to as Type I processes) and the second for 2-dimensional flows (or Type II processes).
Much of the emphasis in computervisionresearch has been on recognizing objects. However, in order to perform tasks such as manipulating and avoiding collisions with objects, one needs to consider how to derive appro...
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Much of the emphasis in computervisionresearch has been on recognizing objects. However, in order to perform tasks such as manipulating and avoiding collisions with objects, one needs to consider how to derive appropriate three-dimensional descriptions of objects from available sensor data. A description is given of a computational approach that has been successful in deriving renditions of shaded images in terms of volumetric primitives such as ellipsoids and cylinders.< >
A robotically assisted field material handling system designed for loading and unloading of a planar pallet with a forklift in unstructured field environment is'presented The system uses combined acoustic/visual s...
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A novel method is presented for grouping range image regions such that each group of regions represents a meaningful part of an object. The set of regions, defined as a convex region set (CRS), is obtained by analyzin...
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A novel method is presented for grouping range image regions such that each group of regions represents a meaningful part of an object. The set of regions, defined as a convex region set (CRS), is obtained by analyzing the boundary types between a pair of regions. The boundary types are classified as convex, concave and jump boundaries. If two regions share a convex boundary it is assumed that they are inseparable regions, thus describing the same part (object). The CRSs are determined by a region boundary graph (RBG) which is defined as a graph whose nodes represent regions, and the edges represent boundaries: convex and concave. Since jump boundaries represent no physical contact in 3-D, they are represented as null edges. A CRS is defined as a set of regions (or nodes in an RBG) such that for each pair of regions in the set, there is a path, which is represented only by convex edges. The physical interpretation is that a CRS represents part of an object such that the regions in the set cannot be separated.< >
The paper summarizes the current research in the computervisionresearchlaboratory at the University of Michigan. The laboratory concentrates on developing generic vision algorithms for industrial applications. Gene...
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