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:
Jun. 17, 1980
Filed:
Feb. 21, 1979
Joachim Proske, Mascherode, DE;
Rollei-Werke Franke & Heidecke, Braunschweig, DE;
Abstract
A focusing screen of a viewfinder system for a photographic camera is designed as a liquid crystal cell having two transparent bodies which lie opposite one another with plane surfaces at a short distance from each other, these plane surfaces carrying electrodes. By applying a current to the electrodes, or by cutting off such current, the character of the focusing screen is changed, providing a single multi-purpose screen and obviating the need to change the screen when focusing for a different type of photography. The liquid crystal screen may be used in conjunction with or may be formed as part of a field lens or a Fresnel lens forming part of the viewfinder system. Various arrangements of the electrodes for changing the character of the screen over only part of the area thereof, rather than the entire area thereof, are disclosed.