System and method for authentication of a workpiece using three dimensional shape recovery

Abstract

A workpiece authentication system uses shape recovery techniques to extract explicit three dimensional ('3-D') features of the surface geometry of the designated portion of a workpiece from images produced using different lighting conditions. The system then bases authentication on the 3-D surface features. The system recovers surface normals, or equivalently gradients, for selected locations within a designated portion of the workpiece from multiple enrollment images produced under different illumination conditions. The system then encodes the surface normal information into authentication indicia that is placed on the workpiece and/or stores the surface normals or related information. Thereafter, the system determines that a given workpiece is authentic if the surface normals recovered from various verification images correspond to the stored surface normal information or the surface normal information encoded into the indicia. Alternatively, the system may use the surface normals to predict what an image should contain when the workpiece is subjected to a particular lighting condition. The system then determines that the workpiece is authentic if the predicted image and the image produced using the workpiece correspond. The system may instead encode brightness patterns associated with one or more enrollment images into the indicia. The system then recovers surface normals from images produced during verification operations, predicts what the brightness image should contain and compares the enrollment image to the prediction.