Auto-focus image system

Abstract

An auto-focus image system includes a focus signal generator and a pixel array coupled thereto that captures an image that includes a plurality of edges. The generator computes a focus signal from a plurality of edge-sharpness measures, each measured from and contributed by a different edge as a quantity with a unit that is a power of a unit of length. The generator reduces a relative weight of the contribution of an edge depending on a shape of a normalized gradient profile of the edge as identified by an n-tuple of values of n different shape measures (n≧2). Each shape measure varies across normalized gradient profiles of different shapes. One shape measure may be the edge-sharpness measure itself. The weight may be zero if the n-tuple falls outside a predetermined region. At least one symmetrical shape that has perfect reflection symmetry receives reduced weight.

1 . A method for generating a focus signal from a plurality of edges of an image of a scene to indicate a degree of image sharpness, comprising:
 determining a relative extent to which an edge will weigh in contributing to the focus signal as compared with other edges that contribute to the focus signal,   wherein the relative extent is assigned a value at least according to a shape of a normalized gradient profile of the edge, the shape being identified by an n-tuple of values of n different shape measures (n≧2), each one of the n different shape measures being variable across normalized gradient profiles of different shapes, the n different shape measures being mutually independent, determination of each one of the n different shape measures requiring no more information than a normalized gradient profile of the edge,   wherein at least one shape of the normalized gradient profile that has perfect reflection symmetry is either rejected or causes a reduction of the relative extent.   
     
     
         2 - 22 . (canceled)