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:
Feb. 29, 2000
Filed:
Apr. 23, 1997
Wolfgang Dultz, Frankfurt/M., DE;
Arkadii Onokhov, St. Petersburg, RU;
Leonid Beresnev, Moscow, RU;
Wolfgang Haase, Reinheim, DE;
Deutsche Telekom AG, Bonn, DE;
Abstract
A device featuring liquid crystals for local reduction of the intensity of incident light is described. This device protects the eyes or the video camera against blinding, or the light-sensitive medium against local damage by automatically reducing the intensity of the incident light emitted by brightly illuminated objects, while the brightness of poorly illuminated objects is not suppressed. The device uses optically addressed spatial light modulators (OASLM) on the basis of a semitransparent photoconducting film in contact with ferroelectric liquid crystals (FLC). The DHF effect (deformation of the helix structure) in ferroelectric liquid crystals (FLC) with helix-shaped structure is used here. The drive voltage has a frequency of 10.sup.2 to 10.sup.3 Hz at an amplitude of .+-.20 V, which is 10-50 times higher than that of devices operating with nematic liquid crystals. The device allows moving objects to be observed against the background of a bright light source (sun, lamp, etc.). A switchable shutter on the basis of ferroelectric liquid crystals (FLC) is used at a molecular inclination of .theta..sub.o .noteq.45.degree.. To increase the average transmission of the device, a second FLC layer with chiral smectic A or C phase with a switchable molecular inclination of .theta..sub.c =45.degree.-.theta..sub.o or .theta..sub.c =.theta..sub.o is used.