OpenRaiser/Intern-Atlas huggingface dataset:
Active camera controlling for manipulation
Authors: Jiang Yu Zhen, Fumio Kishino, Qian Chen 0001, Saburo Tsuji
Venue: CVPR
Year: 1991

A method for object manipulation using an active camera is introduced. By actively moving the camera to proper positions with desired viewing angle from objects of interest, it is possible to acquire data to realize the robust visual feedback control of a robot. This approach avoids complicated 3-D modeling, and the image processing carried out is driven by tasks. Active camera control for robot guidance and image understanding is addressed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Estimation of illuminant direction, albedo, and shape from shading
Authors: Qinfen Zheng, Rama Chellappa
Venue: CVPR
Year: 1991

A robust approach to the recovery of shape from shading information is presented. Assuming uniform albedo and Lambertian surface for the imaging model, two methods for estimating the azimuth of the illuminant are presented. One is based on local estimates on smooth patches, and the other method uses shading information along image contours. The elevation of the illuminant and surface albedo are estimated from image statistics, taking into consideration the effect of self-shadowing. With the estimated reflectance map parameters, the authors then compute the surface shape using a procedure that implements the smoothness constraint by requiring the gradients of reconstructed density to be close to the gradients of the input image. The algorithm is data driven, stable, updates the surface slope and height maps simultaneously, and significantly reduces the residual errors in irradiance and integrability terms. A hierarchical implementation of the algorithm is presented. Typical results on synthetic and images are given to illustrate the usefulness of the approach.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Weak Lambertian assumption for determining cylindrical shape and pose from shading and contour
Authors: Minoru Asada, Takayuki Nakamura, Yoshiaki Shirai
Venue: CVPR
Year: 1992

Weak Lambertian assumption is proposed and used to determine shape and pose of cylindrical objects from a monocular intensity image. The method does not require the knowledge of lighting conditions (light intensity and lighting direction), surface properties, or albedos. Experimental results for both synthesized and real images showing the validity of the method are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Spatial-quefrency approach to optical echo analysis
Authors: Esfandiar Bandari, James Little 0001
Venue: CVPR
Year: 1992

A methodology for optical flow analysis based on cepstral filtering is introduced. The power cepstrum is extended to multiframe analysis. A correlative cepstral technique, cepsCorr, is developed. It significantly increases the signal-to-noise ratio, reduces ambiguities, and it provides a predictive or multievidence approach to visual motion analysis.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Some invariant linear methods in photogrammetry and model-matching
Authors: Eamon B. Barrett, Michael H. Brill, Nils N. Haag, Paul M. Payton
Venue: CVPR
Year: 1992

For several useful tasks in photogrammetry and in model-based vision, noniterative methods that require only the inversion of systems of linear equations are developed. The methods are based on the theory of projective invariants. The tasks addressed are resection, intersection, and transfer, or model matching (with or without ground control points). The following kinds of transfer are examined: (a) coplanar object points (transfer to image 2 done using four reference points in image 1); (b) stereo camera system (transfer to stereo camera pair 2 done using four reference points in stereo pair 1); (c) general multicamera configuration (transfer of a ninth point to image 3 done using eight tie points in images 1 and 2).< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Performance of optical flow techniques
Authors: John L. Barron, David J. Fleet, Steven S. Beauchemin, T. A. Burkitt
Venue: CVPR
Year: 1992

The performance of six optical flow techniques is compared, emphasizing measurement accuracy. The most accurate methods are found to be the local differential approaches, where nu is computed explicitly in terms of a locally constant or linear model. Techniques using global smoothness constraints appear to produce visually attractive flow fields, but in general seem to be accurate enough for qualitative use only and insufficient as precursors to the computations of egomotion and 3D structures. It is found that some form of confidence measure/threshold is crucial for all techniques in order to separate the inaccurate from the accurate. Drawbacks of the six techniques are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
The alignment of objects with smooth surfaces: error analysis of the curvature method
Authors: Ronen Basri
Venue: CVPR
Year: 1992

The recognition of objects with smooth bounding surfaces from their contour images is addressed. In particular, the curvature method is applied to ellipsoidal objects and the error for different rotations of the objects is computed analytically. It is seen that the error depends on the exact shape of the ellipsoid (namely, the relative lengths of its axes), and it increases as the ellipsoid becomes elongated in the Z-direction. It is shown that the errors are usually small, and that, in general, a small number of models is required to predict the appearance of an ellipsoid from all possible views.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Hybrid weak-perspective and full-perspective matching
Authors: J. Ross Beveridge, Edward M. Riseman
Venue: CVPR
Year: 1992

Full-perspective mappings between 3-D objects and 2-D images are more complicated than weak-perspective mappings, which consider only rotation, translation, and scaling. Therefore, in 3-D model-based robot navigation, it is important to understand how and when full-perspective must be taken into account. A probabilistic combinatorial optimization algorithm is used to search for an optimal match between 3-D landmarks and 2-D image features. Three variations are considered. A weak-perspective algorithm rotates, translates, and scales an initial 2-D projection of the 3-D landmark. A full perspective selects a most promising alternative, but then updates the pose and reprojects the landmark. Like the full-perspective algorithm, the hybrid algorithm reliably recovers the true pose of the robot, and like the weak-perspective algorithm, it runs 5 to 10 faster than the full-perspective algorithm.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Accurate calibration of CCD-cameras
Authors: Horst A. Beyer
Venue: CVPR
Year: 1992

A basic review of the bundle adjustment with self-calibration is given. The mathematical model, parameter estimation, and quality analysis of calibration and positioning are covered. The calibration procedure, hardware, and testfield of an accuracy investigation with off-the-shelf CCD (charge-coupled device) camera, lens, and frame grabber are described. A relative accuracy in object space of 1 part in 30000 and an accuracy of 1/45 in image space were verified by independent measurements with theodolites.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
A simple algorithm for shape from shading
Authors: Martin Bichsel, Alex Pentland
Venue: CVPR
Year: 1992

A shape-from-shading algorithm that recovers depth from a brightness image typically in fewer than ten iterations, is described. This algorithm, which is a simplification of the algorithm of J. Oliensis and P. Dupuis (1991), is based on a minimum downhill principle that guarantees continuous surfaces and stable results. The algorithm is applicable to a broad variety of objects and reflectance maps.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Geometric image primitives by complex moments in Gabor space and the application to texture segmentation
Authors: Josef Bigün, J. M. Hans du Buf
Venue: CVPR
Year: 1992

An approach to image feature extraction is proposed. Complex moments of the Gabor power spectrum are used to detect linear, rectangular, hexagonal/triangular, and other structures with very fine to very coarse resolutions. When the method is applied to texture segmentation, good results are obtained.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Correcting chromatic aberrations using image warping
Authors: Terrance E. Boult, George Wolberg
Venue: CVPR
Year: 1992

Chromatic aberration is due to refraction affecting each color channel differently. This paper addresses the use of image warping to reduce the impact of these aberrations in vision applications. The warp is determined using edge displacements which are fit with cubic splines. A new image reconstruction algorithm is used for nonlinear resampling. The main contribution of this work is to analyze the quality of the warping approach by comparing it with active lens control. Two different imaging systems are tested. 1 Introduction In an imaging system, refraction causes each color channel to focus differently. This phenomenon is called chromatic aberration. Chromatic aberration (hereafter CA) is generally broken up into two categories: axial chromatic aberrations (ACA) and lateral chromatic aberrations (LCA), e.g. see [7]. ACA manifests itself as blurring; LCA as geometric distortions. Often these sources of degradation cause measurable differences in color images, e.g., a simple CCTV le...
Matching complex images to multiple 3D objects using view description networks
Authors: J. Brian Burns, Edward M. Riseman
Venue: CVPR
Year: 1992

The effective matching of a single 2D image of a cluttered scene to a library of multiple polyhedral models is achieved by organizing the 3D models into a network of descriptions of their 2D projections from expected views. The process of efficiently searching for image-model matches via a view description network is presented and demonstrated on images containing multiple objects and outdoor scenes. The experiments show that a recognition system based on view description networks is capable finding the correct matches to 3D objects in complex images with a potentially high level of efficiency.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Off-line handwritten word recognition (HWR) using a single contextual hidden Markov model
Authors: Mou-Yen Chen, Amlan Kundu 0001, Jian Zhou
Venue: CVPR
Year: 1992

A complete scheme for totally unconstrained handwritten word recognition based on a single contextual hidden Markov model (HMM) is proposed. The scheme includes a morphology- and heuristics-based segmentation algorithm and a modified Viterbi algorithm that searches the (l+1)st globally best path based on the previous l best paths. The results of detailed experiments for which the overall recognition rate is up to 89.4% are reported.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Surface reconstruction using neural networks
Authors: David S. Chen, Ramesh C. Jain, Brian G. Schunck
Venue: CVPR
Year: 1992

A surface reconstruction method using multilayer feedforward neural networks is proposed. The parametric form represented by multilayer neural networks can model piecewise smooth surfaces in a way that is more general and flexible than many of the classical methods. The approximation method is based on a robust backpropagation (BP) algorithm, which extends the basic BP algorithm to handle errors, especially others, in the training data.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Surface segmentation from stereo
Authors: Liang-Hua Chen, Wei-Chung Lin
Venue: CVPR
Year: 1992

An algorithm for extracting and segmenting surface descriptions from stereo images is presented. Compared with the advance of range image segmentation, the progress of surface segmentation from stereo images is slow. The algorithm integrates the boundary-based and region-based approaches to achieve more satisfactory segmentation results. The algorithm yields such a rich description of a scene in terms of global surface patches and closed surface boundaries. These shape primitives are useful for subsequent high-level processing.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Spatial reasoning based on multivariate belief functions
Authors: Shiuh-Yung Chen, Wei-Chung Lin, Chin-Tu Chen
Venue: CVPR
Year: 1992

The authors propose knowledge representation and evidence propagation schemes based on multivariate belief functions and present a medical image recognition system to demonstrate the effectiveness of their application to spatial reasoning. The proposed system, which is based on the blackboard architecture, can mimic the reasoning process of a human expert in identifying the anatomical structures in a set of correlated images acquired from X-ray CT and PD- and T/sub 2/-weighted MRI. In the blackboard-oriented system, different kinds of evidence provided by various knowledge sources form a hierarchy of evidential space to which the Dempster-Shafer theory is applied. The multivariate belief functions are used to represent domain specific knowledge such as rules or facts.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
On Poisson solvers and semi-direct methods for computing area based optical flow
Authors: Atul K. Chhabra, Timothy A. Grogan
Venue: CVPR
Year: 1992

Simchony, Chellappa, and Shao (1990) proposed a semi-direct method for computing area based optical flow. Their method is based on the iterative application of a direct Poisson solver. This method is restricted to Dirichlet boundary conditions, i.e., it is applicable only when velocity vectors at the boundary of the domain are known a priori. The authors show, both experimentally and through analysis, that the semi-direct method converges only for very large smoothness. At such levels of smoothness, the solution is obtained merely by filling in the known boundary values; the data from the image is almost totally ignored. Next, the authors consider the Concus and Golub method (1973), another semi-direct method, for computing optical flow. This method always converges, but the convergence is too slow to be of any practical value. The authors conclude that semi-direct methods are not suited for the computation of area based optical flow.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Recovering LSHGCs and SHGCs from stereo
Authors: Ronald C.-K. Chung, Ramakant Nevatia
Venue: CVPR
Year: 1992

The problem of computing volumetric shape from stereo is examined. It is argued that intermediate two-and-one-half-dimensional dense or wire-frame descriptions may not be always possible from stereo, especially when there are curved surfaces in the scene, and that 3D volumetric descriptions of objects may have to be derived directly from stereo correspondences. Methods are then presented for recovering volumetric shape with linear straight homogeneous generalized cones (LSHGCs) and straight homogeneous generalized cones (SHGCs) as the shape models, using some invariant properties in their monocular and stereo projections. Experimental results on images of objects with curved surfaces are given.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Deformable models for 3-D medical images using finite elements and balloons
Authors: Laurent D. Cohen, Isaac Cohen
Venue: CVPR
Year: 1992

A 3-D generalization of the balloon model as a 3-D deformable surface, which evolves in 3-D images, is presented. It is deformed under the action of internal and external forces attracting the surface toward detected edge elements by means of an attraction potential. To solve the minimization problem for a surface, two simplified approaches are shown, defining a 3-D surface as a series of 2-D planar curves. Then the 3-D model is solved using the finite-element method, yielding greater stability and faster convergence. This model has been used to segment magnetic resonance images.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
3-D recognition and shape estimation from image contours using invariant 3-D object curve models
Authors: Fernand S. Cohen, Jin-Yinn Wang
Venue: CVPR
Year: 1992

The problem of recognizing and estimating the shape of objects with special markings (text, symbols, drawings, etc.) on their surfaces using B-spline curve modeling and a pair of binocular images is considered. As a direct consequence of the invariance of the B-splines to affine transformations the computation of the 3-D coordinates of the object curve points from a pair of stereo images becomes a straightforward task, and is obtained using minimum-mean-square-error estimation. The 3-D curve is recovered from the estimated object curve control points, and is subsequently used for the object shape estimation and classification.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Single plane model extension using projective transformations and data fusion
Authors: Robert T. Collins
Venue: CVPR
Year: 1992

A priori knowledge of the relative positions of four or more coplanar points or lines is used to derive the positions of other points and lines on the same plane in a manner invariant to camera location and intrinsic camera parameters. A framework for data fusion in the projective plane is presented to merge the position estimates of coplanar points and lines derived in this way.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Real-time smooth pursuit tracking for a moving binocular robot
Authors: David Coombs, Christopher Brown 0001
Venue: CVPR
Year: 1992

The problem of a moving robot tracking a moving object with its cameras, without requiring the ability to recognize the target to distinguish it from distracting surroundings, is examined. A novel aspect of the approach taken is the use of controlled camera movements to simplify the visual processing necessary to keep the cameras locked on the target. A gaze-holding system implemented on a robot's binocular head demonstrates this approach. Even while the robot is moving, the cameras are able to track an object that rotates and moves in three dimensions. The central idea is that localizing attention on 3D space makes simple precategorical visual processing sufficient to hold gaze.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Predicting expected gray level statistics of opened signals
Authors: Wendy Swan Costa, Robert M. Haralick
Venue: CVPR
Year: 1992

The opening of a model signal with a convex, zero-height structuring element is studied empirically. Experiments are performed in which the input signal model parameters and the opening length are varied over an acceptable range and the corresponding grey level distributions in the opened signal are fit to Pearson distributions. Regressions are then used to relate the Pearson distribution parameters to the input parameters, resulting in equations that may be used to predict the effect of an opening. Characterization experiments show that the maximum absolute errors between actual and predicted cumulative distributions using these regression equations have a mean of 0.036 and a standard deviation of 0.011 (for a range of zero to one); the worst-case maximum absolute error encountered between the cumulative distributions is 0.066.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Recovering the scaling function of a SHGC from a single perspective view
Authors: Michel Dhome, R. Glachet, Jean-Thierry Lapresté
Venue: CVPR
Year: 1992

An algorithm for recovering the scaling function of a straight homogeneous generalized cylinder (SHGC) from an image contour is presented. Both location and reference cross section are supposed known. Perspective view assumption and geometric properties of SHGCs are used to derive the method. No additional constraints have been imposed on the object shape. The method has been tested on synthetic image, with promising results.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Computing stereo correspondences in the presence of narrow occluding objects
Authors: Umesh R. Dhond, Jake K. Aggarwal
Venue: CVPR
Year: 1992

Contemporary stereo correspondence algorithms disambiguate multiple candidate matches by using a spatial hierarchy mechanism. Narrow occluding objects in 3-D scenes cannot be handled by the spatial hierarchy mechanism alone. The authors propose a dynamic disparity search (DDS) framework that combines the spatial hierarchy mechanism with a new disparity hierarchy mechanism, to reduce the stereo matching errors caused by narrow occluding objects. They demonstrate the merits of the DDS approach on real stereo images.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Recovery of temporal information from static images of handwriting
Authors: David S. Doermann, Azriel Rosenfeld
Venue: CVPR
Year: 1992

A taxonomy of local, regional, and global temporal clues that, along with a detailed examination of the document, allow temporal properties to be recovered from the image is provided. It is shown that this system will benefit from obtaining a comprehensive understanding of the handwriting signal and that it requires a detailed analysis of stroke and sub-stroke properties. It is suggested that this task requires breaking away from traditional thresholding and thinning techniques, and a framework for such analysis is presented. It is shown how the temporal clues can reliably be extracted from this framework and how many of the seemingly ambiguous situations can be resolved by the derived clues and knowledge of the writing process.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Computing curvilinear structure by token-based grouping
Authors: John Dolan, Edward M. Riseman
Venue: CVPR
Year: 1992

A computational framework for computing curvilinear structure on the edge data of images is presented. The method is symbolic, operating on geometric entities/tokens. It is also constructive, hierarchical, parallel, and locally distributed. Computation proceeds independently at each token and at each stage interleaves the discovery of structure with its careful description. The process yields a hierarchy of descriptions at multiple scales. These multiscale descriptions provide efficient feature indexing both for the grouping process itself as well as for subsequent recognition processes. Experimental results are presented to demonstrate the effectiveness of the approach with respect to curvilinear structure, and its application to more general grouping problems is discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>