Interactive Displays: Natural Human-Interface Technologies

Chapter 6Real-Time Stereo 3D Imaging Techniques

Lazaros Nalpantidis

Robotics, Vision and Machine Intelligence lab., Department of Mechanical and Manufacturing Engineering, Aalborg University Copenhagen, Denmark

6.1 Introduction

Stereo vision involves the simultaneous use of two vision sensors and leads to the recovery of depth. It is based on the principal, first utilized by nature, that two spatially differentiated views of the same scene provide enough information to enable perception of the depth of the portrayed objects. This fact was first realized by Sir Charles Wheatstone, about two centuries ago, who stated: “…the mind perceives an object of three dimensions by means of the two dissimilar pictures projected by it on the two retinae…” [1].

Calculating the depth of various points, or any other primitive, in a scene relative to the position of a camera, is one of the important tasks of computer and robot vision systems. The most common method for extracting depth information from intensity images is by means of a pair of synchronized camera images acquired by a stereo rig, as the ones shown in Figure 6.1. Matching pixels of one image to pixels of the second image (also known as the stereo correspondence problem) results in the so called disparity map [2]. Disparity is defined as the difference of the coordinates of a matched pixel in the two images, which is proportional to its depth value. For rectified stereo pairs, the vertical disparity is always zero and, as a result, ...