Patent ID: 8098984

Claim:
A focus detecting apparatus for detecting an image offset of an optical system, comprising: a micro lens array arranged with a plurality of micro lenses densely arranged in a matrix in a two-dimensional plane, and allocated adjacent to a position to be a possible focusing plane; a photo-detector having a plurality of detecting elements densely arranged in a matrix in a two-dimensional plane, allocated approximately on focal points of the micro lens array, the plurality of detecting elements being provided so as to correspond to each of the plurality of micro lenses, and receiving an optical beam from the optical system via the plurality of micro lenses; and a calculator that reads out outputs from the plurality of detecting elements corresponding to the plurality of micro lenses in accordance with a focus detecting point, respectively selects a pair of detecting elements of the plurality of detecting elements, located symmetrically with respect to each other about the plurality of detecting elements and receiving respectively a pair of optical beams passing through different areas of the optical system, from the plurality of detecting elements in accordance with a plurality of aperture values of the optical system, and calculates the image offset of the optical system based on outputs from the pair of detecting elements.