Patent ID: 7630622

Claim:
An automatic focusing method, implemented in an image capture device comprising a lens and a sensor module, wherein the relative positions of lens and the sensor module are adjustable for automatic focusing based on a factor regarding the relative positions of components of the image capture device, comprising: adjusting the relative positions of the lens and the sensor module based on a first unit of the factor to determine a plurality of states of the lens and the sensor module, where the lens renders clearer images on the sensor module, and wherein the adjusting step comprises: increasing the factor by one first unit for each adjustment of the relative positions of the lens and the sensor module from a minimum to a maximum of the factor; each time when the factor is increased to a value, capturing an image through the lens, thus, to capture a plurality of images corresponding to different values of the factor; and evaluating clarity of the captured images; utilizing the determined states to estimate a best state achievable by focus adjustment based on a second unit of the factor, comprising: retrieving three values of the factor corresponding to the determined states; and estimating a value of the factor corresponding to the best state utilizing the retrieved values; where the lens renders a clearest image on the sensor module, wherein the second unit is finer than the first unit, wherein the determined states comprise three states where the lens renders clearer images on the sensor module, the lens comprises groups of lenses, and the factor is the position of a focusing group, the three states comprise a first position P 2 of the focusing group where the lens renders, on the sensor module, an image the clarity of which is optimized by position adjustment of the focusing group based on the first unit, and said three states further comprise a former position P 1 and a latter position P 3 adjacent to the first position P 2 , when the former position P 1 , the first position P 2 , and the latter position P 3 respectively correspond to clarity values M 1 , M 2 , and M 3 , a position P 21 of the focusing group corresponding to the best state is estimated by the following formula: P 21 = P 2 - 1 2 ⁢ ( P 2 - P 1 ) + M 2 - M 3 ( M 2 - M 1 ) + ( M 2 - M 3 ) × ( P 2 - P 1 ) , and the clarity value M 2 exceeds the clarity values M 1 and M 3 ; and driving the lens and the sensor module to the best state.