Patent attributes
A projection optical system includes a first lens group having negative power and a second and third lens group having positive power, and a first optical path deflector disposed between two lens groups. The first lens group includes three negative lenses. The second lens group includes at least one positive lens. The third lens group includes a plurality of positive lenses. The three negative lenses of the first lens group are each a single lens. The third lens group includes a jointed lens including at least one of the plurality of positive lenses. f is a focal length of the entire project in optical system, d is a length between two lens groups where the first optical path defector is disposed, Dst is a distortion aberration at a reduction-side maximum image height, and the projection optical system satisfies Conditional Expressions (1) and (2) below:0.4<d/f<12.0 (1)−45%<Dst<−10% (2).
