WorldCat Identities

Hildreth, Ellen Catherine

Overview
Works: 19 works in 49 publications in 1 language and 373 library holdings
Classifications: BF241, 153.754
Publication Timeline
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Publications about  Ellen Catherine Hildreth Publications about Ellen Catherine Hildreth
Publications by  Ellen Catherine Hildreth Publications by Ellen Catherine Hildreth
Most widely held works by Ellen Catherine Hildreth
The measurement of visual motion by Ellen Catherine Hildreth ( Book )
12 editions published between 1982 and 1984 in English and held by 300 WorldCat member libraries worldwide
The analysis of visual motion divides naturally into two stages: the first is the measurement of motion, for example, the assignment of direction and magnitude of velocity to elements in the image, on the basis of the changing intensity pattern; the second is the use of motion measurements, for example, to separate the scene into distinct objects, and infer their three-dimensional structure. In this paper, we present a computational study of the measurement of motion. Similar to other visual processes, the motion of elements is not determined uniquely by information in the changing image; additional constraint is required to compute a unique velocity filed. Given this global ambiguity of motion. Local measurements from the changing image, such as those provided by directionally-selective simple cells in primate visual cortex, cannot possibly specify a unique local velocity vector, and in fact, specify only one component of velocity. Computation of the full two-dimensional velocity field requires the integration of local motion measurements, either over an area, or along contours in the image. We will examine possible algorithms for computing motion, based on a range of additional constraints. Finally, we will present implications for the biological computation of motion
Implementation of a theory of edge detection by Ellen Catherine Hildreth ( Book )
3 editions published in 1980 in English and held by 11 WorldCat member libraries worldwide
Edge detection by Ellen Catherine Hildreth ( Book )
3 editions published in 1985 in English and held by 7 WorldCat member libraries worldwide
Abstract: "For both biological systems and machines, vision begins with a large and unwieldly array of measurements of the amount of light reflected from surfaces in the environment. The goal of vision is to recover physical properties of objects in the scene, such as the location of object boundaries and the structure, color and texture of object surfaces, from the two-dimensional image that is projected onto the eye or camera. This goal is not achieved in a single step; vision proceeds in stages, with each stage producing increasingly more useful descriptions of the image and then the scene. The first clues about the physical properties of the scene are provided by the changes of intensity in the image
Theory of edge detection by David Marr ( Book )
1 edition published in 1979 in English and held by 6 WorldCat member libraries worldwide
A theory of edge detection is presented. (1) Intensity changes, which occur in a natural image over a wide range of scales, are detected separately at different scales. At a given scale, this is best done by finding the zero-crossings of gradient-squared G(x, y) * (I(x, y) for image I, where G(x, y) is a two-dimensional gaussian distribution, and gradient-squared is the Laplacian. (2) The physical phenomena that give rise to the intensity changes are localized. This allows one to construct rules for combining information from the different scales into a primitive description of the image. A physiological model for zero-crossing detection is proposed. (Author)
Computations underlying the measurement of visual motion by Ellen Catherine Hildreth ( Book )
2 editions published in 1984 in English and held by 6 WorldCat member libraries worldwide
The perceptual buildup of three-dimensional structure from motion by Massachusetts Institute of Technology ( Book )
3 editions published in 1989 in English and held by 6 WorldCat member libraries worldwide
We present a set of psychophysical experiments that measure the accuracy of perceived three-dimensional structure derived from relative motion in the changing two-dimensional image. The experiments are motivated in part by a computational model proposed by Ullman (1984), called the incremental rigidity scheme, in which an accurate 3-D structure is built up incrementally, by considering images of moving objects over an extended time period. Our main conclusions are: first, the human visual system can derive an accurate model of the relative depths of moving points, even in the presence of noise in their image positions; second, the accuracy of the 3-D model improves with time, eventually reaching a plateau; and third, the 3-D structure currently perceived appears to depend on previous 3-D models. Through computer simulations, we relate the results of our psychophysical experiments with the predictions of Ullman's model. (kr)
Drivers in pursuit of perceptual and virtual targets by Erwin R Boer ( )
2 editions published in 1998 in English and held by 5 WorldCat member libraries worldwide
The computation of the velocity field by Ellen Catherine Hildreth ( Book )
2 editions published in 1983 in English and held by 5 WorldCat member libraries worldwide
The computational study of vision by Ellen Catherine Hildreth ( Book )
3 editions published in 1988 in English and Undetermined and held by 5 WorldCat member libraries worldwide
Through vision, we derive a rich understanding of what is in the world, where objects are located, and how they are changing with time. Because we obtain this understanding immediately, effortlessly, and without conscious introspection, we can be deceived into thinking that vision should therefore be a fairly simple task to perform. The computational approach to the study of vision inquires directly into the sort of information processing needed to extract important information from the changing visual image - information such as the three-dimensional (3-D) structure and movement of objects in the scene, or the color and texture of object surfaces. An important contribution that computational studies have made is to show how difficult vision is to perform, and how complex are the processes needed to perform visual tasks successfully. This article reviews some computational studies of vision, focusing on edge detection, binocular stereo, motion analysis, intermediate vision and object recognition. Keywords: Computer vision; Vision; Binocular stereo vision; Motion analysis; Object recognition; Pattern recognition. (KT)
Recovering heading for visually-guided navigation by Ellen Catherine Hildreth ( Book )
3 editions published in 1991 in English and held by 5 WorldCat member libraries worldwide
We present a model for recovering the direction of heading of an observer who is moving relative to a scene that may contain self-moving objects. The model builds upon an algorithm proposed by Rieger and Lawton (1985), which is based on earlier work by Longuet-Higgins and Prazdny (1981). The algorithm uses velocity differences computed in regions of high depth variation to estimate the location of the focus of expansion, which indicates the observer's heading direction. We relate the behavior of the proposed model to psychophysical observations regarding the ability of human observers to judge their heading direction, and show how the model can cope with self-moving objects in the environment. We also discuss this model in the broader context of a navigational system that performs tasks requiring rapid sensing and response through the interaction of simple task specific routines
The computational approach to vision and motor control by Ellen Catherine Hildreth ( Book )
4 editions published in 1985 in English and held by 4 WorldCat member libraries worldwide
The visual input to steering control by Ellen Catherine Hildreth ( Book )
1 edition published in 1996 in English and held by 2 WorldCat member libraries worldwide
Examines what visual information is used to plan steering maneuvers while driving
Evidence for a fifth, smaller channel in early human vision by David Marr ( Book )
1 edition published in 1979 in English and held by 2 WorldCat member libraries worldwide
Recent studies in psychophysics and neurophysiology suggest that the human visual system utilizes a range of different size or spatial frequency tuned mechanisms in its processing of visual information. It has been proposed that there exist four such mechanisms, operating everywhere in the visual field, with the smallest mechanism having a central excitatory width of 3 in. of arc in the central fovea. This note argues that there exists indirect evidence for the existence of a fifth, smaller channel, with a central width in the fovea of 1.5 in. (Author)
Models of recognition ( Book )
2 editions published in 1998 in English and held by 2 WorldCat member libraries worldwide
Recovering three-dimensional structure from motion with surface reconstruction by Massachusetts Institute of Technology ( Book )
2 editions published in 1991 in English and held by 2 WorldCat member libraries worldwide
This paper addresses the computational role that the construction of a complete surface representation may play in the recovery of 3-D structure from motion. We first discuss the need to integrate surface reconstruction with the structure-from-motion process, both on computational and perceptual grounds. We then present a model that combines a feature-based structure-from-motion algorithm with a smooth surface interpolation mechanism. This model allows multiple surfaces to be represented in given viewing direction, incorporates constraints on surface structure from object boundaries, and groups image features on the basis of their 2-D image motion to segregate features onto multiple surfaces. We present the results of computer simulations that relate the behavior of this model to psychophysical observations. In a companion paper, we discuss further perceptual observations regarding the possible role of surface reconstruction in the human recovery of 3-D structure from motion
The incremental rigidity scheme for recovering structure from motion--position vs. velocity based formulations by Massachusetts Institute of Technology ( Book )
2 editions published in 1985 in English and held by 2 WorldCat member libraries worldwide
The Analysis of Visual Motion: From Computational Theory to Neuronal Mechanisms by Massachusetts Institute of Technology ( Book )
1 edition published in 1986 in English and held by 1 WorldCat member library worldwide
This paper reviews a number of aspects of visual motion analysis in biological systems, from a computational perspective. We illustrate the kinds of insights that have been gained through computational studies and how those observations can be integrated with experimental studies from psychology and the neurosciences, to understand the particular computations used by biological systems to analyze motion. The particular areas of motion analysis that we discuss include early motion detection and measurement, the optical flow computation, motion correspondence, the detection of motion discontinuities, and the recovery of three-dimensional structure from motion. Keywords: Image analysis, Artificial intelligence
The analysis of visual motion : from conceptual theory to neuronal mechanisms by Ellen Catherine Hildreth ( Book )
1 edition published in 1986 in English and held by 1 WorldCat member library worldwide
The Incremental Rigidity Scheme for Recovering Structure from Motion: Position versus Velocity Based Formulations ( Book )
1 edition published in 1985 in English and held by 1 WorldCat member library worldwide
Perceptual studies suggest that the visual system uses the rigidity assumption to recover three dimensional structure from motion. Ullman (1984) recently proposed a computational scheme, the incremental rigidity scheme, which uses the rigidity assumption to recover the structure of rigid and nonrigid objects in motion. The scheme assumes the input to be discrete positions of elements in motion, under orthographic projection. We present formulations of Ullman's method that use velocity information and perspective projection in the recovery of structure. Theoretical and computer analyses show that he velocity based formulations provide a rough estimate of structure quickly, but are not robust over an extended time period. The stable long term recovery of structure requires disparate views of moving objects. Our analysis raises interesting questions regarding the recovery of structure from motion in the human visual system. Keywords: Space perception. (AW)
 
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Alternative Names
Hildreth, E. (Ellen)
Hildreth, Ellen C.
Languages
English (48)