Patent ID: 8190014

Claim:
A focus control circuit installed in an image pickup apparatus including a lens; an image pickup device configured to convert light transmitted through the lens into an electric signal; a driver element for adjusting a position of the lens; and a position detecting element for detecting the position of the lens, the focus control circuit including: an image signal processor configured to calculate a sharpness of an image signal picked up by the image pickup device in each of a plurality of positions of the lens and to determine a first target position from the plurality of positions for the lens where the sharpness is maximum; a feedback equalizer configured to generate a first drive signal used to adjust the position of the lens identified by an output signal of the position detecting element to the first target position of the lens set by the image signal processor, based on a difference between the position of the lens identified by the output signal and the target position of the lens set by the image signal processor, and further configured to control the driver element so as to adjust the lens to the first target position based on the generated first drive signal; and a feedforward equalizer, including a high-pass filter having differential characteristics, configured to generate a second drive signal for moving the lens from the first target position to a second target position when the first target position of the lens as set by the image signal processor is changed, and further configured to control the driver element so as to move the lens to the second target position based on the generated second drive signal.