Showing papers by "Takeo Kanade published in 1990"

Determining shape and reflectance of hybrid surfaces by photometric sampling

Abstract: A method is presented for determining the shapes of hybrid surfaces without prior knowledge of the relative strengths of the Lambertian and specular components of reflection. The object surface is illuminated using extended light sources and is viewed from a single direction. Surface illumination using extended sources makes it possible to ensure the detection of both Lambertian and specular reflections. Uniformly distributed source directions are used to obtain an image sequence of the object. This method of obtaining photometric measurements is called photometric sampling. An extraction algorithm uses the set of image intensity values measured at each surface point to compute orientation as well as relative strengths of the Lambertian and specular reflection components. The simultaneous recovery of shape and reflectance parameters enables the method to adapt to variations in reflectance properties from one scene point to another. Experiments were conducted on Lambertian surfaces, specular surfaces, and hybrid surfaces. >

Shape from interreflections

Abstract: An iterative algorithm is presented that simultaneously recovers the actual shape and the actual reflectance from the pseudo estimates. The recovery algorithm works on Lambertian surfaces of arbitrary shape with possibly varying and unknown reflectance. The general behavior of the algorithm and its convergence properties are discussed. Both simulation and experimental results are included to demonstrate the accuracy and stability of the algorithm. >

A locally adaptive window for signal matching

Abstract: The authors presents a signal matching algorithm that can select an appropriate window size adaptively so as to obtain both precise and stable estimation of correspondences. A statistical model is presented for disparity variation within a window, and it is used to establish a link between the window size and the uncertainty of the computed disparity. This makes it possible to choose the window size that minimizes uncertainty in the disparity computed at each point. A theory is presented for the model and the resultant algorithm, together with analytical and experimental results that demonstrate their effectiveness. >

High resolution terrain map from multiple sensor data

Abstract: Describes a terrain mapping 3D vision system to build a high resolution terrain map from multiple range images and a digital elevation model (DEM). To build a composite map of the environment from multiple sensor data, the terrain mapping system needs a representation of the terrain that must be appropriate for multiple sensor data. Building a composite terrain map also requires estimating motion between sensor views and merging these views into a composite map. The terrain representation described consists of a grid-based representation, called elevation map. The authors develop the locus method to build elevation maps from range images. The locus method uses a model of the sensor to interpolate at arbitrary resolution without making any assumptions on the terrain shape other than the continuity of the surface. They also present a pixel-based or iconic terrain matching algorithm to estimate the vehicle motion from a sequence of range images. This terrain matching method uses the locus method to solve correspondence and occlusion problems. Comprehensive test results using a long sequence of range images and a DEM for rugged outdoor terrain are given. >

Shape and motion without depth

Abstract: Inferring the depth and shape of remote objects and the camera motion from a sequence of images is possible in principle, but is an ill-conditioned problem when the objects are distant with respect to their size. This problem is overcome by inferring shape and motion without computing depth as an intermediate step. On a single epipolar plane, an image sequence can be represented by the F*P matrix of the image coordinates of P points tracked through F frames. It is shown that under orthographic projection this matrix is of rank three. Using this result, the authors develop a shape-and-motion algorithm based on singular value decomposition. The algorithm gives accurate results, without relying on any smoothness assumption for either shape or motion. >

Finding natural clusters having minimum description length

Abstract: A two-step procedure that finds natural clusters in geometric point data is described. The first step computes a hierarchical cluster tree minimizing an entropy objective function. The second step recursively explores the tree for a level clustering having minimum description length. Together, these two steps find natural clusters without requiring a user to specify threshold parameters or so-called magic numbers. In particular, the method automatically determines the number of clusters in the input data. The first step exploits a new hierarchical clustering procedure called numerical iterative hierarchical clustering (NIHC). The output of NIHC is a cluster tree. The second step in the procedure searches the tree for a minimum-description-length (MDL) level clustering. The MDL formulation, equivalent to maximizing the posterior probability, is suited to the clustering problem because it defines a natural prior distribution. >

Integrated sensor and rangefinding analog signal processor

Abstract: A light-stripe rangefinding system consisting of a 6*10 array of pixels is described. Each pixel contains a photodiode to detect the light stripe and a primarily analog signal processor to determine and store the time at which the light stripe crosses that photodiode. Incorporating signal processing into each pixel makes it possible to modify the light-stripe rangefinding algorithm to achieve a frame rate over two orders of magnitude faster than conventional light-stripe rangefinding methods; i.e. over 100 frames/s. The novelty of this approach is its use of smart sensors, ones which provide signal processing at the point of sensing. In this case, the increase in cell complexity from sensing-only to sensing-and-processing makes the modification of the operational principle of rangefinding practical, which in turn results in a dramatic improvement in performance. >

Physics-based models for early vision by machine

Abstract: Research in early (low-level) vision, tooth for machines and humans, has traditionally been based on the study of idealized images or image patches such as step edges, gratings, flat fields, and Mondrians. Real images, however, exhibit much richer and more complex structure, whose nature is determined by the physical and geometric properties of illumination, reflection, and imaging. By understanding these physical relationships, a new kind of early vision analysis is made possible. In this paper, we describe a progression of models of imaging physics that present a much more complex and realistic set of image relationships than are commonly assumed in early vision research. We begin with the Dichromatic Reflection Model, which describes how highlights and color are related in images of dielectrics such as plastic and painted surfaces. This gives rise to a mathematical relationship in color space to separate highlights from object color. Perceptions of shape, surface roughness/texture, and illumination color are readily derived from this analysis. We next show how this can be extended to images of several objects, by deriving local color variation relationships from the basic model. The resulting method for color image analysis has been successfully applied in machine vision experiments in our laboratory. Yet another extension is to account for inter-reflection among multiple objects. We have derived a simple model of color inter-reflection that accounts for the basic phenomena, and report on this model and how we are applying it. In general, the concept of illumination for vision should account for the entire "illumination environment", rather than being restricted to a single light source. This work shows that the basic physical relationships give rise to very structured image properties, which can be a more valid basis for early vision than the traditional idealized image patterns.

Integrated circuit having at least a sensor and a processor thereon

Abstract: The present invention pertains to an integrated circuit. The integrated circuit comprises a sensor which produces a sensor signal corresponding to energy received. The integrated circuit is also comprised of a processing element connected to the sensor which receives the sensor signal only from the sensor and produces a processing signal corresponding to the sensor signal. Additionally, there is a memory connected to the processing element for receiving the processing signal and storing the processing signal. In a preferred embodiment, the integrated circuit is also comprised of a buffer connected to the sensor and the processing element for receiving the sensor signal and buffering the sensor signal for reception by the processing element. The sensor can include a photodiode which receives the sensor signal corresponding to light energy it receives. In a more preferred embodiment, the integrated circuit includes a photosensitive array comprised of cells for use in a light stripe rangefinder wherein a plane of light is moved across a scene. Each cell is able to detect and remember the time in which it observes the light intensity thereon.

Development of a 5-DOF walking robot for Space Station application: overview

Abstract: An overview of the development of a robot walker for use on the NASA Space Station is presented. The robot is designed to perform such tasks as inspection, transport of parts, and simple manipulation. The robot hardware and grippers, the real-time control hardware and software for precise, stable control of the highly flexible, three-dimensional robot, and a gravity compensation system are discussed

Car Recognition for the CMU Navlab

Abstract: LASSIE (Land mark Acquisition SubSystem Improving Exploration) is a program which recognizes a car from several points of view. Trapezoids are formed from groups of lines extracted from a color image; instances of the car model are found by searching for sets of trapezoids which fit the constraints between parts of the car such as the windows, roof, and trunk. No information is used about the dimensions of the various parts, setting LASSIE apart from many other programs which use features extracted from images to recognize objects. 1 The remainder of the introduction sketches out the varied functions of object recognition in the navigation system of an autonomous vehicle and discusses the choice of domain for this work. The next section of the report discusses related work, followed by a section giving a detailed description of the LASSIE program. Results are shown for a number of images. The report closes with a discussion of directions for further work on LASSIE.

1989 Year End Report Autonomous Planetary Rover at Carnegie Mellon

Abstract: This report describes progress in research on an autonomous robot for planetary exploration performed during 1989 at the Robotics Institute, Carnegie Mellon University. The report begins with an introduction, summary of achievements, and lists of personnel and pubIications. It also includes several papers resulting from the research. The research program includes a broad agenda in the development of an autonomous mobile robot. In the year covered by this report, we addressed two key topics: Six-Legged Walking Robot To overcome shortcomings exhibited by existing wheeled and walking robot mechanisms, we configured the Ambler as a walking robot. The fundamental advantage of the Ambler configuration-which has implications for efficiency, mechanism modeling, and control simplicity-is that actuators for b d y support are independent of those for propulsion; a subset of the planar joints propel the body, and the vertical actuators support and level the body over terrain. During 1989 we configured, designed, and constructed the Ambler. In addition, we developed models of its dynamics, and studied leveling control. Integrated Single Leg Walking We implemented and tested an integrated system capable of walking with a single leg over rugged terrain. A prototype of an Ambler leg is suspended below a carriage that slides along rails. To walk, the system uses a laser scanner to find a clear, flat foothold, positions the leg above the foothold, contacts the terrain with the foot, and applies force enough to advance the carriage along the rails. Walking both forward and backward, the system has traversed hundreds of meters of rugged terrain including obstacles too tall to step over, mnches too deep to step in, closely spaced rocks, and sand hills. In addition, we conducted preliminary experiments with concurrent planning and execution, and developed a leg recovery planner that generates time and power efficient 3D trajectories using 2D search. Mobile Manipulation with Hero Robot Indoor mobile manipulator tasks include collecting cups from the lab floor, retrieving printer output, and recharging when its battery gets low. The robot monitors its environment, and handles exceptional conditions in a robust fashion. For example, it uses vision to track the appearance and disappearance of cups, uses onboard sonars to detect imminent collisions, and monitors battery level periodically. This research is primarily sponsored by the National Aeronautics and Space Administration. Portions of this research are also supported by the National Science Foundation and the Defense Advanced Research Pmjects Agency.

Year End Report: Autonomous Planetary Rover at Carnegie Mellon, 1989

Abstract: : The Carnegie Mellon University program to develop an Earth-based prototype of an autonomous planetary rover is organized around three teams that are developing the locomotion, perception, and planning subsystems. A joint task is to integrate the three subsystems into an experimental robot system. We will use this system for evaluating, demonstrating, and validating the concepts and technologies developed in the program. The technical objectives of the research include the following: (1) To develop and demonstrate an autonomous Earth-based mobile robot that can survive, explore, and sample in rugged, natural terrains analogous to those of Mars; (2) To provide detailed, local representations and broad, 3-D descriptions of rugged, unknown terrain by exploiting diverse sensors and data sources; and (3) To demonstrate robot autonomy through a planning and task control architecture that incorporates robot goals, intentions, actions, exceptions, and safeguards. (KR)

Perception for Outdoor Navigation. First Year Report

Abstract: : Research supported by this contract includes perception for road following, terrain mapping for off-road navigation, and systems software for building integrated mobile robots. We overview our efforts for the year, and list our publications and personnel, then provide further detail on several of our subprojects. During the past year, this contract has supported research on color vision for road following; 3-D perception for terrain mapping and cross- country mobility; and system building for autonomous navigation. We have demonstrated autonomous navigation on a variety of roads, including single lane dirt, gravel , and paved; and multi-lane roads with and without lane markings. Our perception modules use a variety of techniques for video processing (clustering theory, symbolic feature detection, neural nets), and for range data analysis (landmark navigation, reflectance processing). We have also integrated position-based navigation (INS and GPS), and combinations of all these techniques into mobile robot systems and demonstrations. Our scientific papers this year include a book (Vision and Navigation: the CMU Navlab), three PhD dissertations, and an MS thesis.

Japan robotics aim for unmanned space exploration

Abstract: The findings of a study sponsored by the National Science Foundation and the National Aeronautics and Space Administration's Automation and Robotics Program, prepared for the US government's program evaluating Japanese technology, are summarized. They reveal that the Japanese government, industry, and university leaders have embarked on cooperative projects to develop next-generation robots for space. The goals are to minimize the enormous expense of manned space operations and to spur technology by developing a range of automated machines. Japanese robots are now employed in construction projects on land and underwater, providing experience that may be applicable in space. An overview is given of notable developments to date. >

Autonomous Planetary Rover at Carnegie Mellon

Abstract: This report describes progress in research on an autonomous robot for planetary exploration. In 1989, the year covered by this report, a six-legged walking robot, the Ambler, was configured, designed, and constructed. This configuration was used to overcome shortcomings exhibited by existing wheeled and walking robot mechanisms. The fundamental advantage of the Ambler is that the actuators for body support are independent of those for propulsion; a subset of the planar joints propel the body, and the vertical actuators support and level the body over terrain. Models of the Ambler's dynamics were developed and the leveling control was studied. An integrated system capable of walking with a single leg over rugged terrain was implemented and tested. A prototype of an Ambler leg is suspended below a carriage that slides along rails. To walk, the system uses a laser scanner to find a clear, flat foothold, positions the leg above the foothold, contacts the terrain with the foot, and applies force enough to advance the carriage along the rails. Walking both forward and backward, the system has traversed hundreds of meters of rugged terrain including obstacles too tall to step over, trenches too deep to step in, closely spaced rocks, and sand hills. In addition, preliminary experiments were conducted with concurrent planning and execution, and a leg recovery planner that generates time and power efficient 3D trajectories using 2D search was developed. A Hero robot was used to demonstrate mobile manipulation. Indoor tasks include collecting cups from the lab floor, retrieving printer output, and recharging when its battery gets low. The robot monitors its environment, and handles exceptional conditions in a robust fashion, using vision to track the appearance and disappearance of cups, onboard sonars to detect imminent collisions, and monitors to detect the battery level.