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:
Sep. 05, 1989
Filed:
May. 03, 1988
Nikon Corporation, Tokyo, JP;
Abstract
An apparatus for detecting the level of an object surface comprises a light source for supplying a light beam obliquely incident on the object surface, an imaging optical system provided to image the light beam reflected by the object surface, a light-receiving element having a detecting surface coincident with the imaging plane of the imaging optical system and determining the level of the object surface on the basis of the position of the image of the light beam on the detecting surface, and polarization correcting optics provided on an optical path leading from the light source via the object surface to the detecting surface for adjusting the intensity ration between the two mutally orthogonal polarized light components of the light beam.