System and method for determining the position of an object in three dimensions using a machine vision system with two cameras

A method for estimating a three-dimensional position of an object using a machine vision system that acquires an image of the object containing a pattern that matches a trained pattern, the method comprising:

• providing, with a search tool adapted to register transformation of a pattern by at least two translational degrees of freedom and at least one non-translational degree of freedom, from the image based upon the trained pattern, at least a first search tool result relative to a first axis of viewing the object and a second search tool result relative to a second axis of viewing the object;
• combining the search tool results so as to determine an estimated three dimensional position of the object, including determining a first nominal coordinate position for the object alone each of the at least two translational degrees of freedom and the at least one non-translational degree of freedom and a second nominal coordinate position for the object along each of the at least two translational degrees of freedom and the at least one non-translational degree of freedom, and deriving the estimated three-dimensional position of the pattern based upon combining predicted uncertainty in the first nominal coordinate position and the second nominal coordinate position by computing (a) a respective first direction unit vector along the first axis and a second direction unit vector along the second axis, each being respectively, representative of a predetermined uncertainty in the first nominal coordinate position along the first axis and the second nominal coordinate position along the second axis, and (b) a first pair of orthonormal vectors and (c) a second pair of orthonormal vectors lying within the respective image plane, each being representative of the predetermined uncertainty;
• and
• performing an estimation based upon matching a combination of weighted values for all of the first direction unit vector, the second direction unit vector, the first pair of orthonormal vectors and the second pair of orthonormal vectors with a selected three-dimensional position estimate so as to compute an optimal three-dimensional position estimate.

A computer-readable medium including program instructions executed on a computer for estimating a three-dimensional position of an object using a machine vision system that acquires an image of the object containing a pattern that matches a trained pattern, the computer-readable medium comprising program instructions for performing the steps of:

• providing, with a search tool adapted to register transformation of a pattern by at least two translational degrees of freedom and at least one non-translational degree of freedom, from the image based upon the trained pattern at least a first search tool result relative to a first axis of viewing the object and a second search tool result relative to a second axis of viewing the object;
• combining the search tool results so as to determine an estimated three dimensional position of the object, including determining a first nominal coordinate position for the object along each of the at least two translational degrees of freedom and the at least one non-translational degree of freedom and a second nominal coordinate position for the object along each of the at least two translational degrees of freedom and the at least one non-translational degree of freedom, and deriving the estimated three-dimensional position of the pattern based upon combining predicted uncertainty in the first nominal coordinate position and the second nominal coordinate position by computing (a) a respective first direction unit vector along the first axis and a second direction unit vector along the second axis, each being respectively, representative of a predetermined uncertainty in the first nominal coordinate position along the first axis and the second nominal coordinate position along the second axis, and (b) a first pair of orthonormal vectors and (c) a second pair of orthonornal vectors lying within the respective image plane, each being representative of the predetermined uncertainty;
• and
• performing an estimation based upon matching a combination of weighted values for all of the first direction unit vector, the second direction unit vector, the first pair of orthonormal vectors and the second pair of orthonormal vectors with a selected three-dimensional position estimate so as to compute an optimal three-dimensional position estimate.