Folding converging light into a lightpipe
US7252399B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Aug 12, 2004 |
| Grant date | Aug 7, 2007 |
| Priority date | — |
| Expiry date | Feb 14, 2025 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N9/3152
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
The present invention relates to a folded front end unit used in a light engine of a projection display device. The front end unit comprises a light source for generating a beam of light, and a lightpipe for providing spatial uniformity to the beam of light. Polarization-dependent front end units include polarization beam splitters for separating the light into orthogonally polarized sub-beams, and a polarization rotating element, e.g. a waveplate, for rotating the polarization of one of the sub-beams. In accordance with the present invention, a prism is positioned between the light source and the lightpipe for reflecting the light into the lightpipe. The difference in refractive index between the air and the prism decreases the cone angle of the beam of light enough to effectively increase the distance between the light source and the lightpipe to compensate for the added distance required to fold the light.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.