Patent ID: 8233787
Filing Date: 2012-07-31
Classification: G03B

Abstract:
1. A focus method for a photographic device having a zoom lens comprising: (a) detecting a beginning position of the zoom lens, wherein the beginning position is a position of the zoom lens before performing the focus method; (b) acquiring image information of the beginning position, image information of a first position, and image information of a second position with the zoom lens, wherein the first position is relative to the beginning position and away from the photographic device, and the second position is relative to the beginning position and close to the photographic device; (c) determining which one has the highest contrast value among the image information of the beginning position, the image information of the first position, and the image information of the second position; (d) if the image information of the beginning position has the highest contrast value, detecting an accurate focus position with the zoom lens according to the beginning position; and (e) if the image information of the first position has the highest contrast value, performing: acquiring a coarse focus position with a non-equivalent distance interval; (f) acquiring image information of a third position with the zoom lens, wherein the third position is away from the photographic device and relative to the first position away from a moving distance; (g) determining whether a contrast value of the image information of the third position is decreasing; (h) if the contrast value of the image information of the third position is decreasing, setting the third position as the coarse focus position for detecting the accurate focus position according to the coarse focus position; and (i) if the contrast value of the image information of the third position is increasing, setting the first position as the beginning position, setting the third position as the first position, and repeating (f) to (h) to acquire the coarse focus position, wherein the moving distance is to add a non-equivalent distance, wherein the non-equivalent distance is an equal difference distance or a geometric distance; and acquiring the accurate focus position with a constant distance interval; (o) acquiring a plurality of image information of adjacent positions in front of the coarse focus position, wherein each of the adjacent positions is substantially separated by a specific distance from each other; and (p) calculating each image information of each of these adjacent positions by using an algorithm for detecting the accurate focus position.