The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 15, 2005
Filed:
Jun. 12, 2000
Chiaki Terasawa, Utsunomiya, JP;
Hiroyuki Ishii, Utsunomiya, JP;
Takashi Kato, Utsunomiya, JP;
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
A projection optical system includes a plurality of positive lens groups having a positive refractive power, and at least one negative lens group having a negative refractive power, wherein, when L is a conjugate distance of the projection optical system and φis the sum of powers of the or each negative lens group, a relation |L×φ|>17 is satisfied, wherein, when h is a height of an axial marginal light ray and his a height of a most abaxial chief ray, at least two aspherical surfaces are formed on surfaces which satisfy a relation |h/h|>0.35, wherein, when ΔASPH is an aspherical amount of each aspherical surface, a relation |ΔASPH/L|>1.0×10is satisfied, and wherein the at least two aspherical surfaces include regions in which, from a central portion toward a peripheral portion of the surface, their local curvature powers change with mutually opposite signs.