Patent ID: 8457431
Filing Date: 2013-06-04
Classification: G02B,G03B,G06K,G06T,H04N

Abstract:
1. A method to generate a focus signal from a plurality of edge widths to indicate a degree of image sharpness in an image, each edge width belonging to one among a plurality of edges in the image, comprising: rejecting or attenuating a contribution of an edge width of an edge towards the focus signal if a gradient profile associated with the edge has a lack of reflection symmetry across the edge that is excessive, wherein the lack of reflection symmetry is excessive when a parameter indicative of a degree of asymmetry of the gradient profile across the edge has a value that exceeds an asymmetry threshold or that is outside a predetermined tolerance region, wherein the gradient profile is a sequence of consecutive all-positive or all-negative gradients across a plurality of pixels arrayed side-by-side in a first direction plotted against a sequence of consecutive integers, a peak gradient within the sequence has a peak gradient value whose magnitude is maximal among magnitudes of gradient values of all gradients within the sequence, there being at least one gradient in the sequence before the peak gradient and at least one gradient in the sequence after the peak gradient.