Patent ID: 7737386

Claim:
A focus detection optical system, comprising a condenser lens located near a focus detection area on a predetermined imaging plane for a taking lens, a pupil division stop having a pair of openings arranged at a spacing wide enough to make sure focusing precision corresponding to said focus detection area, a re-imaging lens group having a plurality of re-imaging lenses located corresponding to said openings, and a light receptor element array located at imaging positions by said re-imaging lenses, wherein: said light receptor element array is adapted to receive a light intensity distribution of double beams passing through different areas of said taking lens and then through said focus detection area to detect a phase difference of an output signal indicative of a light intensity distribution obtained from said light receptor element array, thereby implementing focus detection for said focus detection area, said focus detection optical system comprises at least n such focus detection areas that are adjacent to or intersect each other on said predetermined imaging plane, where n≧2, said re-imaging lens group comprises n+1 such re-imaging lenses, a (n−1)th re-imaging lens and an nth re-imaging lens are a pair of re-imaging lenses that correspond to said (n−1)th focus detection area and are adjacent to each other, an nth re-imaging lens and a (n+1)th re-imaging lens are a pair of re-imaging lenses that correspond to said nth focus detection area and are adjacent to each other, and said (n−1)th re-imaging lens and said (n+1)th re-imaging lens are located at different positions, wherein said openings corresponding to said first to (n+1)th re-imaging lenses are lined up in a row, and said first to nth focus detection areas are lined up in a row as well.