Patent ID: 7486331

Claim:
An auto focus method, applied to a zoom lens of an electronic camera, wherein image signals are captured through the zoom lens driven by a motor, the method comprising: (a) identifying a start location of the zoom lens; (b) determining relative locations of a center of a focus track and the zoom lens to shift the motor in a first direction or a second direction; (c) accessing an evaluation value corresponding to the image signals and enabling a first evaluation value to equal the evaluation value; (d) shifting the motor by K unit distance in the first direction, where a value of K exceeds 1; (e) accessing a subsequent evaluation value corresponding to the image signals and enabling a second evaluation value to equal the evaluation value; (f) determining whether the second evaluation value is smaller than the first evaluation value; (g) if the second evaluation value exceeds or equals the first evaluation value, enabling the first evaluation value to equal second evaluation value and executing step (d); (h) if the second evaluation value is smaller than the first evaluation value, shifting the motor by 1 unit distance in the second direction; (i) accessing an evaluation value corresponding to the image signals and enabling a first evaluation value to equal the evaluation value; (j) shifting the motor by 1 unit distance in the second direction; (k) accessing a subsequent evaluation value corresponding to the image signals and enabling the second evaluation value to equal the evaluation value; (l) determining whether the second evaluation value is smaller than the first evaluation value; (m) if the second evaluation value exceeds or equals the first evaluation value, enabling the first evaluation value to equal the second evaluation value and executing step (j); and (n) if the second evaluation value is smaller than the first evaluation value, shifting the motor by 1 unit distance in the first direction; wherein an accessed evaluation value corresponding to a current location of the motor is the maximal evaluation value.