Stereo vision technology for object measurement

This paper is concerned with research into machine vision techniques for measuring the size and shape of objects. Considerable potential is considered to exist for the application of portable hand-held vision metrology systems. However, unlike a bench-mounted system, a hand held device will be subjected to movement during the measurement process. Employment of active techniques, such as a scanning laser line, usually result in measurement errors due to movements that can occur during capture of the sequence of images involved. In contrast, passive techniques such as stereo vision can operate rapidly, with two images being captured simultaneously in order to construct a three dimensional map of the object. Unfortunately, stereo vision is subject to a number of technological difficulties. These include the 'Correspondence Problem' (i.e. the challenge of relating points in the image to points in 3D space), and the presence of relatively high levels of noise in the distance measurements for the points in the image. In this paper, a hybrid approach is described for alleviation of these problems, in a methodology that combines structured light and stereo vision techniques.