US Patent No. 9,329,373

CATADIOPTRIC OPTICAL SYSTEM WITH MULTI-REFLECTION ELEMENT FOR HIGH NUMERICAL APERTURE IMAGING


Patent No. 9,329,373
Issue Date May 03, 2016
Title Catadioptric Optical System With Multi-reflection Element For High Numerical Aperture Imaging
Inventorship Masatsugu Nakano, Tucson, AZ (US)
Jose Manuel Sasian-Alvarado, Tucson, AZ (US)
Tamer T. Elazhary, Tucson, AZ (US)
Assignee Canon Kabushiki Kaisha, Tokyo (JP) The Arizona Board of Regents on Behalf ...

Claim of US Patent No. 9,329,373

1. A catadioptric optical system comprising:
a first catadioptric group configured to form an intermediate image of an object; and
a second catadioptric group and a lens group configured to form an object image based on the intermediate image,
wherein the first catadioptric group consists of a solid lens having an object-side surface and an image-side surface,
wherein the object-side surface includes an input surface provided around an optical axis and an object-side reflective surface
provided around the input surface;

wherein the image-side surface includes an exit surface provided around the optical axis and an image-side reflective surface
provided around the exit surface;

wherein a light flux from the object enters the solid lens through the input surface, and undergoes four or more reflections
between the image-side reflective surface and the object-side reflective surface, prior to exiting through the exit surface;
and

wherein:
the lens group includes a field lens group and a dioptric group,
the first catadioptric group has a positive refractive power and generates outward Petzval curvature,
the second catadioptric group has positive refractive power and generates outward Petzval curvature and overcorrected axial
chromatic aberration,

the field lens group has positive refractive power and generates inward Petzval curvature and overcorrected axial chromatic
aberration, and

the dioptric group has positive refractive power and generates outward Petzval curvature and undercorrected axial chromatic
aberration.