US Patent 7831140 Apparatus for auto focusing

There is provided an apparatus for auto-focusing including: a sensing unit sensing a current position of a lens moving within a predetermined range along a moving shaft; an A/D converter converting a lens position value from the sensing unit into a digital signal; a lens position control unit generating a signal for moving the lens to a target lens position determined by an auto-focusing algorithm; a driving signal generating unit generating a square wave signal according to the signal from the lens position control unit; and an operation unit connected to the A/D converter and controlling a time at which the A/D converter performs conversion according to the square wave signal from the driving signal generating unit.