Patent ID: 6991338

Claim:
A projection optical system which projects luminous flux from an image forming element which forms an original image onto a projection plane, the projection optical system comprising: a first reflecting portion which is disposed the closest to the projection plane in an optical path from the image forming element to the projection plane out of a plurality of reflecting portions with curvatures; a second reflecting portion which is disposed second closest to the projection plane in the optical path out of the reflecting portions, a third reflecting portion which is disposed third closest to the projection plane in the optical path out of the reflecting portions, wherein the first reflecting portion, the second reflecting portion and the third reflecting portion are different from one another; a reference axis is defined as a path of a central principal ray which is a principal ray of luminous flux from the center of the original image to the center of a finally formed image projected onto the projection plane, and the reference axis on an incident side and the reference axis on an emerging side of the projection optical system are oblique to each other; and the reference axis between the second reflecting portion and the third reflecting portion intersects with the reference axis between the first reflecting portion and the projection plane.