Patent ID: 7542218
Filing Date: 2009-06-02
Classification: G02B

Abstract:
1. An optical system comprising: a front unit formed of a transparent medium which is rotationally symmetric about a center axis; an aperture located coaxially with the center axis; and a rear unit which is rotationally symmetric about the center axis and has positive power; wherein said front unit includes two entrance pupils symmetrically disposed about the center axis in a meridional section, a first transmitting surface through which a light beam from an object point is incident on said front unit, a first reflecting surface for reflecting a light beam after transmission through said first transmitting surface, a second reflecting surface for reflecting a light beam after reflection at said first reflecting surface, and a second transmitting surface through which a light beam leaves said transparent medium after reflection at said second reflecting surface; and wherein a light beam coming from a hemispherical object surface, which is rotationally symmetric about the center axis, travels through said front unit and said rear unit in this order, forming a rotationally symmetric, annular image of the hemispherical object surface on an image plane of the system, at points away from the center axis.