Joan Batlle

Pattern codification strategies in structured light systems

Coded structured light is considered one of the most reliable techniques for recovering the surface of objects. This technique is based on projecting a light pattern and viewing the illuminated scene from one or more points of view. Since the pattern is coded, correspondences between image points and points of the projected pattern can be easily found. The decoded points can be triangulated and 3D information is obtained. We present an overview of the existing techniques, as well as a new and definitive classification of patterns for structured light sensors. We have implemented a set of representative techniques in this field and present some comparative results. The advantages and constraints of the different patterns are also discussed.

Recent progress in coded structured light as a technique to solve the correspondence problem: a survey

We present a survey of the most significant techniques, used in the last few years, concerning the coded structured light methods employed to get 3D information. In fact, depth perception is one of the most important subjects in computer vision. Stereovision is an attractive and widely used method, but, it is rather limited to make 3D surface maps, due to the correspondence problem. The correspondence problem can be improved using a method based on structured light concept, projecting a given pattern on the measuring surfaces. However, some relations between the projected pattern and the reflected one must be solved. This relationship can be directly found codifying the projected light, so that, each imaged region of the projected pattern carries the needed information to solve the correspondence problem.

A comparative review of camera calibrating methods with accuracy evaluation

Camera calibrating is a crucial problem for further metric scene measurement. Many techniques and some studies concerning calibration have been presented in the last few years. However, it is still difficult to go into details of a determined calibrating technique and compare its accuracy with respect to other methods. Principally, this problem emerges from the lack of a standardized notation and the existence of various methods of accuracy evaluation to choose from. This article presents a detailed review of some of the most used calibrating techniques in which the principal idea has been to present them all with the same notation. Furthermore, the techniques surveyed have been tested and their accuracy evaluated. Comparative results are shown and discussed in the article. Moreover, code and results are available in internet.

A robust-coded pattern projection for dynamic 3D scene measurement

Abstract This paper presents a new coded structured light pattern which permits to solve the correspondence problem by a single shot and without using geometrical constraints. The pattern is composed by the projection of a grid made by coloured slits in such a way that each slit with its two neighbours appears only once in the pattern. The technique proposed permits a rapid and robust 3D scene measurement, even with moving objects.

Positioning an underwater vehicle through image mosaicking

Mosaics have been commonly used as visual maps for undersea exploration and navigation. The position and orientation of an underwater vehicle can be calculated by integrating the apparent motion of the images which form the mosaic. A feature-based mosaicking method is proposed in this paper. The creation of the mosaic is accomplished in four stages: feature selection and matching, detection of points describing the dominant motion, homography computation and mosaic construction. In this work we demonstrate that the use of color and textures as discriminative properties of the image can improve, to a large extent, the accuracy of the constructed mosaic. The system is able to provide 3D metric information concerning the vehicle motion using the knowledge of the intrinsic parameters of the camera while integrating the measurements of an ultrasonic sensor. The experimental results of real images have been tested on the GARBI underwater vehicle.

A review on strategies for recognizing natural objects in colour images of outdoor scenes

Abstract This paper surveys some significant vision systems dealing with the recognition of natural objects in outdoor environments. The main goal of the paper is to discuss the way in which the segmentation and recognition processes are performed: the classical bottom–up, top–down and hybrid approaches are discussed by reviewing the strategies of some key outdoor scene understanding systems. Advantages and drawbacks of the three strategies are presented. Considering that outdoor scenes are especially complex to treat in terms of lighting conditions, emphasis is placed on the way systems use colour for segmentation and characterization proposals. After this study of state-of-the-art strategies, the lack of a consolidated colour space is noted, as well as the suitability of the hybrid approach for handling particular problems of outdoor scene understanding.

A new FPGA/DSP-based parallel architecture for real-time image processing

In this article, we present a new reconfigurable parallel architecture oriented to video-rate computer vision applications. This architecture is structured with a two-dimensional (2D) array of FPGA/DSP-based reprogrammable processors Pij. These processors are interconnected by means of a systolic 2D array of FPGA-based video-addressing units which allow video-rate links between any two processors in the net to overcome the associated restrictions in classic crossbar systems such as those which occur with butterfly connections. This architecture has been designed to deal with parallel/pipeline procedures, performing operations which handle various simultaneous input images, and cover a wide range of real-time computer vision applications from pre-processing operations to low-level interpretation. This proposed open architecture allows the host to deal with final high-level interpretation tasks. The exchange of information between the linked processors Pij of the 2D net lies in the transfer of complete images, pixel by pixel, at video-rate. Therefore, any kind of processor satisfying such a requirement can be integrated. Furthermore, the whole architecture has been designed host-independent.

Recent trends in control architectures for autonomous underwater vehicles

This article describes therecenttrends in controlarchitectures for autonomous vehicles. The study has been carried out on 22 architectures, most of which relate to the field of underwater robotics. The main aim of this article is to show the relationships between these various architectures and to show how developments in architectures for autonomous land vehicles have been extended for use in autonomous underwater vehicles. A summary of important features of the 22 architectures is presented and a new hybrid architecture is proposed for the underwater vehicle GARBI.

Designing a Fuzzy-like PD controller for an underwater robot

Abstract The design of a steering and depth control in terms of course-changing and course-keeping tracking mission and motion of an underwater vehicle is described in this paper. Fuzzy-like proportional derivative (PD) controller is used where the Fuzzy-like part of the controller is optimised based on its structure and parameter design aspects, whereas the scaling factors of the PD part is optimised based on the minimum number of experiments in a real environment. The experiments were planned using Taguchi design of experiments method. The experimental trials and their results are presented and analysed extensively.

Recent progress in structured light in order to solve the correspondence problem in stereovision

We present a summary of the most significant techniques, used in the last few years, concerning the coded structured light methods employed to get 3D information. In fact, depth perception is one of the most important subjects in computer vision. Stereovision is an attractive and widely used method, but, rather limited to make 3D surface maps, due to the correspondence problem. The correspondence problem can be improved using a method based on a structured light concept, projecting a given pattern on the measuring surfaces, although some relations between the projected pattern and the reflected one must be solved. This relationship can be directly found codifying the projected light, so that, each imaged region of the projected pattern carries the necessary information to solve the correspondence problem. We do not need to mention the numerous advantages in accurate obtention of 3D information for many research subjects, such as: robotics, autonomous navigation, shape analysis, and so on.