Transparent rear projection screen
US4561720A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 2, 1984 |
| Grant date | Dec 31, 1985 |
| Priority date | — |
| Expiry date | Oct 2, 2004 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03B21/625
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A transparent rear projection screen has a Fresnel lens for paralleling light arriving from behind. In the front surface the screen is provided with grooves which extend in the vertical direction in the position of use of the screen. Each of the side flanks of the grooves adjoins a side part of an adjacent, also vertically extending convex lens. The side flanks of the grooves are totally reflecting to parallelled light arriving from behind in order to increase the deflection in the lateral direction of a part of the light arriving from behind by means of reflection into the adjacent lens. The angle which a side flank forms together with the side part of the adjacent lens is so small that total reflection from the inner surface of the side part of the lense of light which is totally reflected of the side flank in question is avoided. Moreover, between the vertical lenses to which the side flanks adjoin, at least one further lens is arranged. The further lens has the cross section of an iscoceles triangle with a rounded top which faces forward with respect to the screen. The side surfaces of the triangular lenses form an angle together with a normal to the screen which is so small th…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.