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Pattern Analysis and Machine Intelligence, IEEE Transactions on

Issue 3 • Date March 1997

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Displaying Results 1 - 12 of 12
  • Comments on "Symmetry as a Continuous Feature"

    Publication Year: 1997 , Page(s): 246 - 247
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (31 KB)  

    We point out the existence of a theoretical difficulty that underlies the symmetry detection studied by Zabrodsky et al. (1995) and present a possible solution to it. View full abstract»

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  • Autonomous exploration: driven by uncertainty

    Publication Year: 1997 , Page(s): 193 - 205
    Cited by:  Papers (55)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3228 KB)  

    Passively accepting measurements of the world is not enough, as the data we obtain is always incomplete, and the inferences made from it uncertain to a degree which is often unacceptable. If we are to build machines that operate autonomously, they will always be faced with this dilemma, and can only be successful if they play a much more active role. This paper presents such a machine. It deliberately seeks out those parts of the world which maximize the fidelity of its internal representations, and keeps searching until those representations are acceptable. We call this paradigm autonomous exploration, and the machine an autonomous explorer. This paper has two major contributions. The first is a theory that tells us how to explore, and which confirms the intuitive ideas we have put forward previously. The second is an implementation of that theory. In our laboratory, we have constructed a working autonomous explorer and here, for the first time, show it in action. The system is entirely bottom-up and does not depend on any a priori knowledge of the environment. To our knowledge, it is the first to have successfully closed the loop between gaze planning and the inference of complex 3D models View full abstract»

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  • A paraperspective factorization method for shape and motion recovery

    Publication Year: 1997 , Page(s): 206 - 218
    Cited by:  Papers (169)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1472 KB)  

    The factorization method, first developed by Tomasi and Kanade (1992), recovers both the shape of an object and its motion from a sequence of images, using many images and tracking many feature points to obtain highly redundant feature position information. The method robustly processes the feature trajectory information using singular value decomposition (SVD), taking advantage of the linear algebraic properties of orthographic projection. However, an orthographic formulation limits the range of motions the method can accommodate. Paraperspective projection, first introduced by Ohta et al. (1981), is a projection model that closely approximates perspective projection by modeling several effects not modeled under orthographic projection, while retaining linear algebraic properties. Our paraperspective factorization method can be applied to a much wider range of motion scenarios, including image sequences containing motion toward the camera and aerial image sequences of terrain taken from a low-altitude airplane View full abstract»

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  • The role of model-based segmentation in the recovery of volumetric parts from range data

    Publication Year: 1997 , Page(s): 259 - 267
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    We present a method for segmenting and estimating the shape of 3D objects from range data. The technique uses model views, or aspects, to constrain the fitting of deformable models to range data. Based on an initial region segmentation of a range image, regions are grouped into aspects corresponding to the volumetric parts that make up an object. The qualitative segmentation of the range image into a set of volumetric parts not only captures the coarse shape of the parts, but qualitatively encodes the orientation of each part through its aspect. Knowledge of a part's coarse shape, its orientation, as well as the mapping between the faces in its aspect and the surfaces on the part provides strong constraints on the fitting of a deformable model (supporting both global and local deformations) to the data. Unlike previous work in physics-based deformable model recovery from range data, the technique does not require presegmented data. Furthermore, occlusion is handled at segmentation time and does not complicate the fitting process, as only 3D points known to belong to a part participate in the fitting of a model to the part. We present the approach in detail and apply it to the recovery of objects from range data View full abstract»

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  • Recovery of ego-motion using region alignment

    Publication Year: 1997 , Page(s): 268 - 272
    Cited by:  Papers (55)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (692 KB)  

    A method for computing the 3D camera motion (the ego-motion) in a static scene is described, where initially a detected 2D motion between two frames is used to align corresponding image regions. We prove that such a 2D registration removes all effects of camera rotation, even for those image regions that remain misaligned. The resulting residual parallax displacement field between the two region-aligned images is an epipolar field centered at the FOE (Focus-of-Expansion). The 3D camera translation is recovered from the epipolar field. The 3D camera rotation is recovered from the computed 3D translation and the detected 2D motion. The decomposition of image motion into a 2D parametric motion and residual epipolar parallax displacements avoids many of the inherent ambiguities and instabilities associated with decomposing the image motion into its rotational and translational components, and hence makes the computation of ego-motion or 3D structure estimation more robust View full abstract»

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  • A fast algorithm for the nearest-neighbor classifier

    Publication Year: 1997 , Page(s): 277 - 282
    Cited by:  Papers (15)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (80 KB)  

    A fast algorithm that finds the nearest neighbor (NN) of an unknown sample from a design set of labeled samples is proposed. This algorithm requires a quite moderate preprocessing effort and a rather excessive storage, but it accomplishes substantial computational savings during classification. The performance of the algorithm is described and compared to the performance of the conventional one. Results on simulated data are provided to illustrate the computational savings that may be achieved using this fast algorithm View full abstract»

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  • Determination of the script and language content of document images

    Publication Year: 1997 , Page(s): 235 - 245
    Cited by:  Papers (76)  |  Patents (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    Most document recognition work to date has been performed on English text. Because of the large overlap of the character sets found in English and major Western European languages such as French and German, some extensions of the basic English capability to those languages have taken place. However, automatic language identification prior to optical character recognition is not commonly available and adds utility to such systems. Languages and their scripts have attributes that make it possible to determine the language of a document automatically. Detection of the values of these attributes requires the recognition of particular features of the document image and, in the case of languages using Latin-based symbols, the character syntax of the underlying language. We have developed techniques for distinguishing which language is represented in an image of text. This work is restricted to a small but important subset of the world's languages. The method first classifies the script into two broad classes: Han-based and Latin-based. This classification is based on the spatial relationships of features related to the upward concavities in character structures. Language identification within the Han script class (Chinese, Japanese, Korean) is performed by analysis of the distribution of optical density in the text images. We handle 23 Latin-based languages using a technique based on character shape codes, a representation of Latin text that is inexpensive to compute View full abstract»

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  • The active recovery of 3D motion trajectories and their use in prediction

    Publication Year: 1997 , Page(s): 219 - 234
    Cited by:  Papers (39)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2052 KB)  

    This paper describes the theory and real-time implementation using an active camera platform of a method of planar trajectory recovery, and of the use of those trajectories to facilitate prediction over delays in the visual feedback loop. Image-based position and velocity demands for tracking are generated by detecting and segmenting optical flow within a central region of the image, and a projective construct is used to map the camera platform's joint angles into a Euclidean coordinate system within a plane, typically the ground plane, in the scene. A set of extended Kalman filters with different dynamics is implemented to analyze the trajectories, and these compete to provide the best description of the motion within an interacting multiple model. Prediction from the optimum motion model is used within the visual feedback loop to overcome visual latency. It is demonstrated that prediction from the 3D planar description gives better tracking performance than prediction based on a filtered description of observer-based 2D motion trajectories View full abstract»

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  • Acquiring 3D models of non-rigid moving objects from time and viewpoint varying image sequences: a step toward left ventricle recovery

    Publication Year: 1997 , Page(s): 253 - 259
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1344 KB)  

    This paper describes a method for the accurate recovery of time-varying 3D shapes with known cycle from images with different viewpoints as well as times; aiming at the recovery of the left ventricular shapes. Our recovery method is based on the integration of apparent contours from different viewpoints. We perform direct fitting to a 4D closed surface model based on B-splines so as to deal with fragmented contours such as extracted from X-ray cineangiocardiograms. The method is quantitatively evaluated using synthesized and real image sequences View full abstract»

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  • An adaptive stochastic approximation algorithm for simultaneous diagonalization of matrix sequences with applications

    Publication Year: 1997 , Page(s): 282 - 287
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (88 KB)  

    We describe an adaptive algorithm based on stochastic approximation theory for the simultaneous diagonalization of the expectations of two random matrix sequences. Although there are several conventional approaches to solving this problem, there are many applications in pattern analysis and signal detection that require an online (i.e., real-time) procedure for this computation. In these applications, we are given two sequences of random matrices {Ak } and {Bk} as online observations, with limk→∞E[Ak]=A and limk→∞E[Bk]=B, where A and B are real, symmetric and positive definite. For every sample (Ak, Bk), we need the current estimates Φk and Λk, respectively of the eigenvectors Φ and eigenvalues Λ of A-1 B. We have described such an algorithm where Φk and Λk converge provably with probability one to Φ and Λ respectively. A novel computational procedure used in the algorithm is the adaptive computation of A. Besides its use in the generalized eigen-decomposition problem, this procedure can be used on its own in several feature extraction problems. The performance of the algorithm is demonstrated with an example of detecting a high-dimensional signal in the presence of interference and noise, in a digital mobile communications problem. Experiments comparing computational complexity and performance demonstrate the effectiveness of the algorithm in this real-time application View full abstract»

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  • Patch-based stereo in a general binocular viewing geometry

    Publication Year: 1997 , Page(s): 247 - 253
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (324 KB)  

    This paper presents a one-stage stereo algorithm that yields 3D planar surface patches directly from matching image patch intensity information. The method allows an arbitrary rotation and translation between the cameras; it is not limited to parallel-axis, narrow-baseline, or vergent geometries. The key to the approach is to match image patches that have positions, shapes, sizes, orientations, and samplings consistent with a hypothesized surface patch and with each other. The match error then reflects only the mismatch of patch contents and not the mismatch of patch geometries or samplings. The algorithm is quantitatively evaluated against ground truth on real images with difficult viewing geometries, and demonstrates an average accuracy of about 1% in estimating surface depths and 10° in estimating surface normals View full abstract»

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  • A fast algorithm for bottom-up document layout analysis

    Publication Year: 1997 , Page(s): 273 - 277
    Cited by:  Papers (27)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (84 KB)  

    This paper describes a new bottom-up method for document layout analysis. The algorithm was implemented in the CLIDE (Chemical Literature Data Extraction) system, but the method described here is suitable for a broader range of documents. It is based on Kruskal's algorithm and uses a special distance-metric between the components to construct the physical page structure. The method has all the major advantages of bottom-up systems: independence from different text spacing and independence from different block alignments. The algorithms computational complexity is reduced to linear by using heuristics and path-compression View full abstract»

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Aims & Scope

The IEEE Transactions on Pattern Analysis and Machine Intelligence (TPAMI) is published monthly. Its editorial board strives to present most important research results in areas within TPAMI's scope.

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Editor-in-Chief
David A. Forsyth
University of Illinois