Patent ID: 7532303

Claim:
An automatic focusing apparatus comprising: an optical lens unit including a liquid crystal lens; a photoelectric converting unit that converts an optical image formed through the optical lens unit into an electrical signal to output an image signal; and a liquid crystal lens control unit that extracts a focus signal corresponding to a focus matching degree from the image signal, and controls a driving condition of the liquid crystal lens such that the focus signal becomes maximum value, wherein the liquid crystal lens control unit includes an area setting unit that sets an area from which the focus signal is extracted of the optical image formed through the optical lens unit, a voltage applying unit that applies a predetermined voltage to the liquid crystal lens, a focus signal extracting unit that extracts a plurality of focus signals by performing, at predetermined cycles, sampling of an image signal generated based on an optical image of the area set by the area setting unit by the light that has passed through the liquid crystal lens under transient response operation caused by application of the predetermined voltage by the voltage applying unit, and a focus point judging unit that judges a maximum value of the focus signal based on the focus signals extracted by the focus signal extracting unit.