Optical system, image projection apparatus, and imaging apparatus

An optical system having a reduction conjugate point on a reduction side and a magnification conjugate point on a magnification side, and having an intermediate imaging position conjugate with each of the reduction conjugate point and the magnification conjugate point inside, the optical system comprising:

• a first sub-optical system including a plurality of lenses that are rotationally symmetric with respect to an optical axis, and an aperture stop between two lenses among the plurality of lenses;
• and
• a second sub-optical system disposed on the magnification side of the first sub-optical system and including a plurality of optical surfaces,
• wherein, in a direction of the optical axis from the first sub-optical system to the second sub-optical system, a magnification conjugate plane including the magnification conjugate point is positioned in a direction of the first sub-optical system, from a viewpoint of the second sub-optical system, and
• the plurality of optical surfaces include:
• on a light path of a light flux between the first sub-optical system and the magnification conjugate point,
• a first transmitting surface located closest to the first sub-optical system;
• a second transmitting surface located closest to the magnification conjugate point;
• a first reflecting surface located closest to the first transmitting surface on the light path between the first transmitting surface and the second transmitting surface;
• and
• a second reflecting surface located closest to the second transmitting surface on the light path between the first transmitting surface and the second transmitting surface, and
• a light path from the first transmitting surface to the first reflecting surface and a light path from the second reflecting surface to the second transmitting surface intersect with each other, and
• a first effective area through which the light flux passes in the first transmitting surface and a second effective area through which the light flux passes in the second transmitting surface do not overlap each other.