Method and apparatus for evaluating sharpness of image

摘要

An auto focus image system that includes a pixel array coupled to a focus signal generator. The pixel array captures an image that has a plurality of edges. The generator generates a focus signal that is a function of a plurality of edge-sharpness measures for the plurality of edges. The generator compares a sequence of gradients across the edge with one or more reference sequences of gradients and/or reference curves defined by data retrieved from a non-volatile memory. The generator may reject or de-emphasize the edge using result of the comparison. The edge sharpness measure is a quantity whose unit is a positive or negative, integer or non-integer power of a unit of length. It may be measured from the edge and/or a reference sequence/curve matched to the edge, or may be retrieved for the matched reference sequence/curve from a non-volatile memory.

主权项

1. A method for evaluating a degree of sharpness of an image on basis of a plurality of edges within said image, comprising:
curve-fitting a gradient profile of an edge among said plurality of edges with a sequence of two or more reference gradients, among which at least two reference gradients have different gradient values; performing a comparison of said sequence with said gradient profile by a circuit; and, de-emphasizing said edge or rejecting said edge altogether on basis of a result of the comparison from entering a calculation for said degree of sharpness.