Patent ID: 7685559

Claim:
A method for identifying candidate globally optimum inputs for generation of outputs that optimally approximate according to a performance metric a binary target pattern of areas constrained to be bright and areas constrained to be dark, where the output is inherently non-negative and depends in a quadratic way on the inputs, comprising: forming a solution space for the inputs from dominant joint eigenvectors for quadratic forms of bright and dark areas of a target pattern, mapping the solution space to identify regions that include at most one local minimum, selecting at least some of the regions for test point analysis; generating stepped intensity contours for the dark areas and stepped constraint surfaces at individual test points, within each selected region, progressively moving an individual test point to the lowest intensity contour step along all constraint steps present in the large region, for each individual test point at the lowest intensity contour step of the large region, reducing intensity to a lowest intensity contour step in an adjacent selected region if available; for each individual test point at an edge of an intensity contour step, testing whether an intensity contour step of an adjacent selected region is lower, and if so, reducing intensity of that individual test point to a lowest intensity contour step of the adjacent region to yield a final test point; compiling the final test points at their respective lowest intensity contour step as a set of candidate global optima, evaluating the candidate global optima using the performance metric to determine one globally optimum input solution; and making a mask from the one globally optimum input solution.