US Patent 7880799 Focus detecting apparatus and image pickup apparatus

A focus detecting apparatus includes a splitter for splitting a light from an image pickup lens to form at least a pair of images, a photoelectric conversion element for photoelectrically converting at least the pair of images, the focus detecting apparatus detecting a focusing status of the image pickup lens based on a signal from the photoelectric conversion element, and a light blocking mask for blocking the light from entering the photoelectric conversion element, the light blocking mask having a curve shape in a moving direction of the image that varies according to an image height.