Stress birefringence compensation in polarizing beamsplitters and systems using same
US7357511B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Mar 23, 2005 |
| Grant date | Apr 15, 2008 |
| Priority date | — |
| Expiry date | Nov 5, 2025 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N9/315
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Some projection systems use a polarization beamsplitter (PBS) for coupling light to and from an image-forming device. The PBS is typically formed with a reflective polarizing layer disposed between glass covers. Stress birefringence in the glass cover lying between the reflective polarizing layer and the image-forming device can reduce the image contrast of the projection system. A quarter-wave retarding element positioned between the glass cover and the image-forming device is used to compensate for the birefringence, at least in part. This permits the PBS to use glass covers formed of a glass material having a higher stress optic coefficient than before, while still maintaining high image contrast.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.