Multiple layer protective glass, particularly a protective glass for a welding shield
US4240709A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 24, 1979 |
| Grant date | Dec 23, 1980 |
| Priority date | — |
| Expiry date | Apr 24, 1999 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02F1/1396
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A multiple layer protective glass, particularly a protective glass for a welding shield, for damping the light transmission, the layers of which are in turn comprised at least of a first polarizer, a first electrooptical cell, a second polarizer, a second electrooptical cell and a third polarizer, the electrooptical cells consisting of liquid crystals enclosed between transparent parallel plates coated with electrically conducting layers, said crystals being arranged in their non-excited condition to form a helically twisted structure for rotating the plane of polarization of the passing polarized light. The planes of polarization of the first and the second polarizer (2,4) are at right angles to each other. The planes of polarization of the second and the third polarizer (4,6) enclose an angle which is between 0.degree. and 60.degree.. The angle of rotation of the helical structure formed by the liquid crystals in the second electrooptical cell (5) is between 90.degree. and 30.degree. and the said angle and the angle of rotation are complementary angles. Means (13) are provided for exciting the two electrooptical cells (3,5) in opposite modes by the application of a voltage betwee…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.