Measurement of microdisplacements by machine vision photogrammetry (DISMAP)

Abstract

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.