Recirculation of reflected source light in an image projection system
US6962426B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Nov 29, 2001 |
| Grant date | Nov 8, 2005 |
| Priority date | — |
| Expiry date | Oct 20, 2023 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N9/3117
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An image projection system achieves improved image brightness and optical efficiency by redirecting some of the unused polychromatic light emitted by a primary light source and reflected by a spatially nonuniform light filter back into the lamp assembly housing the light source. The unused portions of the polychromatic light are re-reflected for transmission through a different spatial region of the light filter, resulting in an approximately 30% increase in probability of transmission. Because recirculation of unused light occurs within the lamp assembly, there is no significant reduction in etendue. In a first preferred embodiment, an interference light filter reflects certain colors of light while transmitting other colors of light. In a second preferred embodiment, a polarizing light filter passes light in certain polarization states while reflecting light in other polarization states.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.