Patent ID: 7734167

Claim:
A focus controller configured to control focus of an optical system that includes a focus lens, said focus controller comprising: an AF sensor configured to obtain information corresponding to a distance to a subject based on a luminous flux from the subject; a first focus detector configured to detect a focus state based on a measurement result of the AF sensor; a second focus detector configured to detect the focus state based on a contrast value of an image formed by the optical system; a motor that is configured to drive the focus lens and includes a rotor having a magnet, and a stator having a coil configured to provide a torque to the magnet; a position sensor configured to detect a position of the rotor of the motor; a first driver configured to switch an electrization to the coil in the motor in accordance with an output of the position sensor; a second driver configured to switch the electrization to the coil of the motor in accordance with a preset time interval; and a switching circuit configured to select the first driver for the electrization to the coil of the motor in performing focus control using the first focus detector, and to select the second driver in the electrization to the coil of the motor in performing focus control using the second focus detector.