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:
Dec. 19, 1989
Filed:
Apr. 03, 1989
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
An observation system, usable with a projection optical system for optically projecting a first object upon a second object by use of a light of a first wavelength, for observing the second object by way of the projection optical system and by use of a light of a second wavelength different from the first wavelength. The observation system includes an observation optical system having a lens element and a parallel-surface plate which is inclined with respect to an optical axis of the observation optical system, wherein the observation optical system is arranged to form an image of the second object on a predetermined image surface and wherein the parallel-surface plate is arranged to substantially correct coma caused by the projection optical system.