Abstract: Flash correlation instantaneously compares two or more patterns to determine whether they are the same or essentially the same, regardless of the complexity of the images, and in spite of the addition of noise, local changes, and variations in resolution and focus. Flash correlation artifacts also provide cues to quantitative assessment of relative movement, stretching, blurring, and warping of one image with respect to the other. Presence of a flash correlation artifact between two stacks of patterns is sufficient to identify the stacks as containing at least one pair of massively correlated patterns. Precise control of registration, image size and orientation is not required. An image may be combined with other images, either by overlays or concatenation, and still be identified. A Flash correlation engine may utilize optical, analog or digital processing to provide rapid sorting, classification, and identification functions with minimal computational complexity.