Patent ID: 7950806

Claim:
A rear projector for performing image projection, comprising: a screen including a rotationally symmetric Fresnel lens; and a projection optical system being nonaxisymmetric and making a central principle ray incident obliquely on the screen in the image projection, the projection optical system having at least one reflection surface formed of a rotationally asymmetric free curved surface; wherein the Fresnel lens has aberration that cancels out pupil aberration of the projection optical system so that principal rays of beams exiting from the Fresnel lens become substantially parallel to each other, wherein the projection optical system is a nonaxisymmetric projection optical system that does not form an intermediate image, and wherein when, within a plane including a central principal ray immediately before reaching the screen and a normal line of the screen at a point which the ray reaches, an intersection of the central principal ray and the screen is O, an intersection of an extension line La, from a screen direction, of a principal ray of a beam incident on the screen at a largest angle of incidence and an extension line Lb, from the screen direction, of a principal ray of a beam incident on the screen at a smallest angle of incidence is P, an intersection of a perpendicular line drawn from the intersection P to an extension surface of a screen surface and the extension surface of the screen surface is Q, and an amount of offset of the Fresnel lens (distance from a screen center to a rotation symmetry center of the Fresnel lens) is FO, then conditional formula (1) below is satisfied: FO<OQ (1).