1. An automatic focus searching method for an image capture device, the image capture device having a lens and an image sensor, the method comprising: setting an exposure time of the image sensor; computing a focal sweep trajectory of the lens based on at least the exposure time; during the exposure time, moving the lens along the focal sweep trajectory while exposing the image sensor; reading out pixel data of the image sensor that is generated during the exposure time; and applying a filtering operation upon the pixel data to generate an output image.