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  • 1
    Electronic Resource
    Electronic Resource
    OBJECT PERCEPTION AS BAYESIAN INFERENCE (2004)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Psychology 55 (2004), S. 271-304 
    Details
    ISSN: 0066-4308
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Psychology
    Notes: We perceive the shapes and material properties of objects quickly and reliably despite the complexity and objective ambiguities of natural images. Typical images are highly complex because they consist of many objects embedded in background clutter. Moreover, the image features of an object are extremely variable and ambiguous owing to the effects of projection, occlusion, background clutter, and illumination. The very success of everyday vision implies neural mechanisms, yet to be understood, that discount irrelevant information and organize ambiguous or noisy local image features into objects and surfaces. Recent work in Bayesian theories of visual perception has shown how complexity may be managed and ambiguity resolved through the task-dependent, probabilistic integration of prior object knowledge with image features.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.psych.55.090902.142005
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  • 2
    Electronic Resource
    Electronic Resource
    A computational theory for the perception of coherent visual motion (1988)
    [s.l.] : Nature Publishing Group
    Nature 333 (1988), S. 71-74 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The theory divides the computation of motion into two stages which we refer to as the measuring and the smoothing stages. The measuring stage estimates or restricts the velocity field from the image information. In humans, two processes have been Fig. 1 Motion cooperativity. a, One hundred ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/333071a0
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  • 3
    Electronic Resource
    Electronic Resource
    Stereo and controlled movement (1990)
    Springer
    International journal of computer vision 4 (1990), S. 141-152 
    Details
    ISSN: 1573-1405
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We describe a method to solve the stereo correspondence using controlled head (or camera) movements. These movements, which can be due to eye rotation, head rotation, or head translation, essentially supply additional imageframes which can be used to constrain the stereo matching by supplying monocular cues. Because the movements are small, traditional methods of stereo with multiple frame will not work. We develop an alternative approach using a systematic analysis to define a probability distribution for the errors. Our matching strategy then matches the most probable points first (based on the monocular cues), thereby reducing the ambiguity for the remaining matches. We demonstrate this algorithm in detail for the cases of head and eye rotation and illustrate it with some examples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00127814
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  • 4
    Electronic Resource
    Electronic Resource
    The Bas-Relief Ambiguity (1999)
    Springer
    International journal of computer vision 35 (1999), S. 33-44 
    Details
    ISSN: 1573-1405
    Keywords: variable illumination ; shadows ; shape ambiguity ; object representation ; object recognition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract When an unknown object with Lambertian reflectance is viewed orthographically, there is an implicit ambiguity in determining its 3-d structure: we show that the object's visible surface f(x, y) is indistinguishable from a “generalized bas-relief” transformation of the object's geometry, $$ {\bar f} $$ (x, y) = λf(x, y) + μx + νy, and a corresponding transformation on the object's albedo. For each image of the object illuminated by an arbitrary number of distant light sources, there exists an identical image of the transformed object illuminated by similarly transformed light sources. This result holds both for the illuminated regions of the object as well as those in cast and attached shadows. Furthermore, neither small motion of the object, nor of the viewer will resolve the ambiguity in determining the flattening (or scaling) λ of the object's surface. Implications of this ambiguity on structure recovery and shape representation are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008154927611
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  • 5
    Electronic Resource
    Electronic Resource
    Guest Editorial: Statistical and Computational Theories of Vision: Modeling, Learning, Sampling and Computing, Part I (2000)
    Springer
    International journal of computer vision 40 (2000), S. 5-6 
    Details
    ISSN: 1573-1405
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026531017760
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  • 6
    Electronic Resource
    Electronic Resource
    Occlusions and binocular stereo (1995)
    Springer
    International journal of computer vision 14 (1995), S. 211-226 
    Details
    ISSN: 1573-1405
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Binocular stereo is the process of obtaining depth information from a pair of cameras. In the past, stereo algorithms have had problems at occlusions and have tended to fail there (though sometimes post-processing has been added to mitigate the worst effects). We show that, on the contrary, occlusions can help stereo computation by providing cues for depth discontinuities. We describe a theory for stereo based on the Bayesian approach, using adaptive windows and a prior weak smoothness constraint, which incorporates occlusion. Our model assumes that a disparity discontinuity, along the epipolar line, in one eyealways corresponds to an occluded region in the other eye thus, leading to anocclusion constraint. This constraint restricts the space of possible disparity values, thereby simplifying the computations. An estimation of the disparity at occluded features is also discussed in light of psychophysical experiments. Using dynamic programming we can find the optimal solution to our system and the experimental results are good and support the assumptions made by the model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01679683
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  • 7
    Electronic Resource
    Electronic Resource
    Feature extraction from faces using deformable templates (1992)
    Springer
    International journal of computer vision 8 (1992), S. 99-111 
    Details
    ISSN: 1573-1405
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We propose a method for detecting and describing features of faces using deformable templates. The feature of interest, an eye for example, is described by a parameterized template. An energy function is defined which links edges, peaks, and valleys in the image intensity to corresponding properties of the template. The template then interacts dynamically with the image by altering its parameter values to minimize the energy function, thereby deforming itself to find the best fit. The final parametr values can be used as descriptors for the feature. We illustrate this method by showing deformable templates detecting eyes and mouths in real images. We demonstrate their ability for tracking features.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00127169
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  • 8
    Electronic Resource
    Electronic Resource
    A mathematical analysis of the motion coherence theory (1989)
    Springer
    International journal of computer vision 3 (1989), S. 155-175 
    Details
    ISSN: 1573-1405
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In motion perception, there are a number of important phenomena involving coherence. Examples include motion capture and motion cooperativity. We propose a theoretical model, called the motion coherence theory, that gives a possible explanation for these effects [1,2]. In this framework, the aperture problem can also be thought of as a problem of coherence and given a similar explanation. We propose the concept of a velocity field defined everywhere in the image, even where there is no explicit motion information available. Theough a cost function, the model imposes smoothness on the velocity field in a more general way than in previous theories. In this paper, we provide a detailed theoretical analysis of the motion coherence theory. We discuss its relations with previous theories and show that some of them are approximations to it. A second paper [3] provides extensions for temporal coherence and comparisons to psychophysical phenomena. The theory applies to both short-range and long-range motion. It places them in the same computational framework and provides a way to define interactions between the two processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00126430
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  • 9
    Electronic Resource
    Electronic Resource
    A common framework for image segmentation (1991)
    Springer
    International journal of computer vision 6 (1991), S. 227-243 
    Details
    ISSN: 1573-1405
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We attempt to unify several approaches to image segmentation in early vision under a common framework. The Bayesian approach is very attractive since: (i) it enables the assumptions used to be explicitly stated in the probability distributions, and (ii) it can be extended to deal with most other problems in early vision. Here, we consider the Markov random field formalism, a special case of the Bayesian approach, in which the probability distributions are specified by an energy function. We show that: (i) our discrete formulations for the energy function is closely related to the continuous formulation; (ii) by using the mean field (MF) theory approach, introduced by Geiger and Girosi [1991], several previous attempts to solve these energy functions are effectively equivalent; (iii) by varying the parameters of the energy functions we can obtain connections to nonlinear diffusion and minimal description length approaches to image segmentation; and (iv) simple modifications to the energy can give a direct relation to robust statistics or can encourage hysteresis and nonmaximum suppression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00115697
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  • 10
    Electronic Resource
    Electronic Resource
    FORMS: A flexible object recognition and modelling system (1996)
    Springer
    International journal of computer vision 20 (1996), S. 187-212 
    Details
    ISSN: 1573-1405
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We describe a flexible object recognition and modelling system (FORMS) which represents and recognizes animate objects from their silhouettes. This consists of a model for generating the shapes of animate objects which gives a formalism for solving the inverse problem of object recognition. We model all objects at three levels of complexity: (i) the primitives, (ii) the mid-grained shapes, which are deformations of the primitives, and (iii) objects constructed by using a grammar to join mid-grained shapes together. The deformations of the primitives can be characterized by principal component analysis or modal analysis. When doing recognition the representations of these objects are obtained in a bottom-up manner from their silhouettes by a novel method for skeleton extraction and part segmentation based on deformable circles. These representations are then matched to a database of prototypical objects to obtain a set of candidate interpretations. These interpretations are verified in a top-down process. The system is demonstrated to be stable in the presence of noise, the absence of parts, the presence of additional parts, and considerable variations in articulation and viewpoint. Finally, we describe how such a representation scheme can be automatically learnt from examples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00208719
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