An image processing system is described for use in micromechanics research on materials, such as for determining the displacements and strains surrounding crack tips. This vision system is a machine implementation of the stereoimaging technique that was developed for making submicron measurements of displacements under high resolution conditions. It uses a Cognex 2000 image processing system, cameras to obtain digital images from analog photographs, a graphics display terminal and track ball for operator interaction with the system, and a video display monitor for display of the measured displacements. Displacements are sent directly to an associated VAX that computes strains and permits their graphical display. The system is described in detail and examples of its use in micromechanics research are given.

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A method for isolating three-dimensional features of known height in the presence of noisy data is presented. The approach is founded upon observing the locations of a single light stripe in the image planes of two spatially separated cameras. Knowledge relating to the heights of sought features is used to define regions of interest in each image which are searched in order to isolate the light stripe. This approach is advantageous since spurious features that may result from random reflections or refractions in the region of interest of one image usually do not appear in the corresponding region of interest of the other image. It is shown that such a system is capable of robustly locating features such as very thin vertical dividers even in the presence of spurious or noisy image data that would normally cause conventional single camera light striping systems to fail. The discussion that follows summarizes the advantages of the methodology in relation to conventional passive steroscopic systems as well as light striped triangulation systems. Results that characterize the approach in noisy images are also provided.