US Patent No. 9,341,831


Patent No. 9,341,831
Issue Date May 17, 2016
Title Optical System With Catadioptric Optical Subsystem
Inventorship Masatsugu Nakano, Tochigi (JP)
Jose Manuel Sasian-Alvarado, Tucson, AZ (US)
Assignee Canon Kabushiki Kaisha, Tokyo (JP) The Arizona Board of Regents on Behalf ...

Claim of US Patent No. 9,341,831

1. An optical system comprising:
a catadioptric subsystem configured to collect light from an object;
a refractive subsystem configured to form an image of the object through the catadioptric subsystem; and
a baffle arranged along an optical axis of the optical system and configured to block light, which travels toward the refractive
subsystem without being reflected by the catadioptric subsystem, to form a shielded portion in a center of an exit pupil plane
of the optical system,

wherein the catadioptric subsystem includes a partially transparent surface around the optical axis so that transmissivity
of a region, other than the shielded portion, in the exit pupil plane varies in a radial direction of the exit pupil plane.