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:
Aug. 13, 1991
Filed:
Oct. 03, 1989
Kenji Yamada, Yachiyo, JP;
Yoichi Iki, Kawasaki, JP;
Nikon Corporation, Tokyo, JP;
Abstract
In an optical system a semitransparent mirror which is disposed at a predetermined angle with respect to an optical axis and which has a semitransparent surface (for instance, a front surface) and a transparent surface (for instance, a rear surface) is so designed as to split a diverging or converging light incident thereon into a first optical path of light flux reflected from the semitransparent surface and a second light path of light flux transmitted through both the semitransparent and transparent surfaces. Furthermore, in order that the position of an image focused by the light flux reflected from the transparent surface coincides with the position of an image focused by the light flux reflected from the semitransparent surface, the transparent surface is made non-parallel with the semitransparent surface of the semitransparent mirror. The thickness of the mirror decreases or increases toward image planes depending upon whether converging light flux or diverging light flux is incident on the mirror.