Patent attributes
An optical system is adapted to form an image having a full 360° angle of view on an image plane. The optical system includes a front unit having at least two reflecting surfaces, each rotationally symmetric about a center axis, and a rear unit that is rotationally symmetric about the center axis and has positive power. The first reflecting surface is located opposite to an entrance pupil, and the second reflecting surface is located on the same side as the first reflecting surface. The entrance pupil in a section including the center axis is located between the outer periphery of the first reflecting surface and the outer periphery of the second reflecting surface. A light beam coming from afar passes through the front unit and the rear unit in order, forming an image at a position of an image plane off the center axis.
