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:
Apr. 05, 1989
Abstract
A beam splitter, a first polarizing plate and a quarterwave plate are provided in that order on the optical axis of an image formation lens between an image formation plane and an objective lens. The first polarizing plate comprises a non-polarizing region for transmitting illuminating light and reflected light and a polarizing region provided to enclose the non-polarizing region for transmitting the illuminating light but limiting the reflected light which is rendered out of phase with the illuminating light by the quarterwave plate. Thus, the angular aperture of the illuminating light can be increased and an irradiated plane can be observed with no hindrance even if the same is inferior in flatness, while illuminance of the irradiated plane can be sufficiently ensured. At the same time, the angular aperture of the objective lens can be reduced, and the depth of focus Q is increased.