Notch filters with cholesteric polarizers with birefringent film and linear polarizer
US5548422A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 28, 1993 |
| Grant date | Aug 20, 1996 |
| Priority date | — |
| Expiry date | Jun 28, 2013 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02F1/133638
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
An optical notch filter component in a color LCD display comprises an electronically controllable variable retarder interposed between circularly polarizing elements. Entering light in a particular spectral region is circularly polarized by a first of the circularly polarizing elements, and selectively retarded by zero or a half wavelength by the retarder so as to controllably yield right or left handed circular polarization. The second circular polarizer transmits only one of the circular polarizations of the light. By controlling the circular polarization of the light with the retarder, the light is either transmitted or attenuated. More uniform stopband attenuation is provided when the optical notch filter component comprises oppositely handed circular polarizing elements and a variable retarder which applies zero retardation in one of its states. A direct view display system substantially without parallax effects is formed from a stacked assembly of the notch filter components with thin substrate construction. Higher contrast is provided by doubly analyzing each color band.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.