Patent ID: 7382902

Claim:
A method for selecting an eye image from a set of digital images based on its definition, the method comprising: calculating a first approximate characteristic definition score based on a cumulating of the gradients in a single direction of light intensities of pixels of an image; selecting a subset of images for which said first score is greater than a predetermined threshold; and for each image of the subset of images, calculating a second characteristic definition score by an evaluation method including: approximately locating a pupil in the image; defining, from the approximate location of the pupil, an examination window centered on the approximate location; and applying a gradient accumulation operation to luminance values of pixels of the examination window, an accumulating total being proportional to the second characteristic definition score of the image; wherein approximately locating a pupil in the image includes: dividing the image into blocks of identical size, the size is chosen according to an expected approximate size of the pupil to be located; calculating, for each block, the average luminance; and searching for a block having the smallest luminance, an approximate position of the pupil in the image corresponding to a position of the block having the smallest luminance; and wherein dividing the image includes dividing the image into blocks which overlap one another, and a pitch in two directions between two overlapping blocks ranges between one tenth and three quarters of the size of the blocks.