US Patent No. 9,341,831

OPTICAL SYSTEM WITH CATADIOPTRIC OPTICAL SUBSYSTEM


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.