Auto-focus apparatus and method

An auto-focus apparatus, comprising:

• a lens, a lens driving component, and a focus control module;
• wherein the lens is configured to guide light transmitted from a target object, where original images are formed based on the light guided by the lens at multiple positions, respectively;
• wherein the lens driving component is configured to drive the lens to move to the multiple positions to obtain the original images;
• wherein the focus control module comprises a filter unit configured to obtain frequency respond results each of which corresponds to a portion of all pixels in one of the original images based on frequency respond values of the portion of all pixels in the corresponding original image, and the focus control module is further configured to calculate a desired frequency respond result based on the obtained frequency respond results;
• and the filter unit is a band-pass filter or a high-pass filter;
• wherein the filter unit is configured to obtain the frequency respond values of the portion of all pixels according to Equation (1):
• H
• ⁡
• (
• z
• )
• =
• b
• 1
• +
• b
• 2
• ⁢
• z
• -
• 1
• +
• …
• +
• b
• m
• +
• 1
• ⁢
• z
• -
• m
• a
• 1
• +
• a
• 2
• ⁢
• z
• -
• 1
• +
• …
• +
• a
• n
• +
• 1
• ⁢
• z
• -
• n
• ,
• Equation
• ⁢
• ⁢
• (
• 1
• )
• wherein H(z) represents the frequency respond value of one of pixels in the portion of all pixels, z represents image data of the corresponding portion of all pixels, m and n represent order numbers of the filter unit, a1 to an+1 and b1 to bm+1 represent adjustable parameters of the filter unit and are determined based on historical original images previously obtained;
• and
• wherein the lens driving component is further configured to drive the lens to a focusing position, where the focusing position is a first position of the lens corresponding to the desired frequency respond result.