Ferroelectric liquid crystal device for local reduction of light intensity in the visual field
US6031588A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 23, 1997 |
| Grant date | Feb 29, 2000 |
| Priority date | — |
| Expiry date | Apr 23, 2017 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02F1/141
- WIPO fieldOptics
- WIPO sectorInstruments
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 se…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.