Patent ID: 8704933

Claim:
A focus detection apparatus comprising: a photo-electric conversion unit comprising a first pixel group which receives a light beam passing through a first pupil area of an image forming optical system that forms an image of an object, and a second pixel group which receives a light beam passing through a second pupil area of the image forming optical system; a focus detection unit configured to detect a focus state of the image forming optical system based on a first object image generated by the first pixel group and a second object image generated by the second pixel group; a correction calculator configured to perform correction calculation for the first object image and the second object image based on the output from the focus detection unit; and a determination unit configured to determine, based on the output from the focus detection unit, whether to perform the correction calculation again, wherein the correction calculator calculates a first line image corresponding to the first pupil area of the image forming optical system, and a second line image corresponding to the second pupil area of the image forming optical system, and wherein the correction calculator generates a first image signal by convolution integration of the second line image into the first object image, and generates a second image signal by convolution integration of the first line image into the second object image.