Patent ID: 7929044

Claim:
An autofocus searching method, comprising: calculating a focus value of an image according to each position of an object lens in the movement, wherein the focus value comprises at least an intensity value of the image; performing focus searching based on a first focus-searching step constant and a first focus-searching direction, wherein the first focus-searching step constant is a value of a function of the focus value and a focus-searching step size, and the focus value is inversely proportional to the focus-searching step size; and performing focus searching based on a second focus-searching direction and a second focus-searching step constant if a focus-searching position moves across a peak of the focus value, wherein the second focus-searching direction is opposite to the first focus-searching direction; wherein the focus value further comprises at least a contrast value or a definition value of the image, wherein the definition value of the image is calculated by means of a space differential operation of the image or a frequency domain analysis of the image, wherein the space differential operation of the definition value of the image comprises: (a) providing a mask including weight values and weight positions; (b) multiplying the weight on the mask by a pixel value corresponding to the weight position on the image by convolution; (c) after adding the multiplication results, moving the mask to the next operation position and performing the operation of the step (b); and (d) repeating the steps (b) and (c), and adding all the operation results as the definition value of the image.