Abstract: A system for detecting defects on a moving web having a sequential series of identical frames uses an imaging device to form a real-time camera image of a frame and a comparitor to comparing elements of the camera image with corresponding elements of an image of an exemplar frame. The comparitor provides an acceptable indication if the pair of elements are determined to be statistically identical; and a defective indication if the pair of elements are determined to be statistically not identical. If the pair of elements is neither acceptable nor defective, the comparitor recursively compares the element of said exemplar frame with corresponding elements of other frames on said web until one of the acceptable or defective indications occur.

Abstract: A phase gradient autofocus system for use in synthetic aperture imaging accurately compensates for arbitrary phase errors in each imaged frame by locating highlighted areas and determining the phase disturbance or image spread associated with each of these highlight areas. An estimate of the image spread for each highlighted area in a line in the case of one dimensional processing or in a sector, in the case of two-dimensional processing, is determined. The phase error is determined using phase gradient processing. The phase error is then removed from the uncorrected image and the process is iteratively performed to substantially eliminate phase errors which can degrade the image.

Abstract: A method of detecting intensity edge paths in an image produced by a technique which is selected from the group consisting of X-ray, CAT scan, nuclear magnetic resonance, photographic, video recording, and photodetection techniques, includes an initial step of determining the gradient magnitude and direction of the image in an array or lattice of node points using a Gaussian weighted gradient operator. A root node having a high probability of being on an edge path is then selected by selecting a node having a high gradient magnitude. The metric for each adjacent node to the root node is then calculated. The various metrics are stored for each such adjacent node. Using the adjacent node having the highest metric, the metrics for other nodes adjacent thereto are calculated. These steps are repeated and the edge path having the highest metric is thereby determined.