US Patent 7734167 Focus controller, optical apparatus using the same, and control method

A focus controller configured to control focus of an optical system that has a focus lens includes a switching circuit configured to select a first driver for the electrization to a coil of a motor in performing focus control using a first focus detector, and to select a second driver in an electrization to the coil of the motor in performing focus control using a second focus detector. The first driver is configured to switch an electrization to the coil in the motor according to an output of the position sensor. The second driver is configured to switch an electrization to the coil of the motor according to a determined time interval.