Fresnel lens, backprojection screen, and corresponding backprojection system and unit
US7342728B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | May 17, 2004 |
| Grant date | Mar 11, 2008 |
| Priority date | — |
| Expiry date | Feb 3, 2025 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03B21/62
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
The invention relates to a Fresnel lens. Each refractive structure of the lens is bounded by two surfaces, the second surface making a second angle with the normal to the plane of incidence. At least two zones of refractive structures are provided in which the second angle is equal to the entrance angle of a beam. Each first surface refracts the light along a direction parallel or not parallel to the axis of the lens depending on the zone. The invention also relates to a system comprising a folding mirror and a Fresnel lens, in which system the second angle is equal to the entrance angle of a parasitic ray obtained by reflection on the Fresnel lens and then on the mirror. The invention also relates to a corresponding back projection screen and a corresponding back projection unit.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.