Patent ID: 7463431

Claim:
An optical system adapted to form a full-360° angle-of-view image on an image plane or project an image located in the image plane onto a full-360° angle of view, characterized by comprising: a front unit including at least two reflective surfaces rotationally symmetric about a center axis and a rear unit that is rotationally symmetric about the center axis and has a positive power, wherein: said front unit comprises, in order of travel of a light ray when said optical system is an imaging system or in an opposite order when said optical system is a projection system, a first reflective surface that is located facing away from an entrance pupil in a section including the center axis, on which entrance pupil a light beam from afar is incident, with the center axis located between them, and a second reflective surface that is located facing away from said first reflective surface with the center axis located between them, wherein a center of said first reflective surface is positioned on a rear unit side with respect to a center of said second reflective surface in a center axis direction, and the entrance pupil in the section including the center axis is located between an outer periphery of said first reflective surface and an outer periphery of said second reflective surface, and the light beam incident from afar travels through said front unit and said rear unit in order and is imaged at a position of said image plane off the center axis; in the section including the center axis, the entrance pupil is positioned off the center axis and positioned on the center axis in a plane that is orthogonal to a plane including the center axis and includes a center light ray of said light beam; and said rear unit is constructed of an optical system that comprises at least two groups and has a positive power.