The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 15, 2008
Filed:
Mar. 23, 2005
David J. W. Aastuen, Shoreview, MN (US);
Charles L. Bruzzone, Woodbury, MN (US);
Jiaying MA, Maplewood, MN (US);
David J. W. Aastuen, Shoreview, MN (US);
Charles L. Bruzzone, Woodbury, MN (US);
Jiaying Ma, Maplewood, MN (US);
3M Innovative Properties Company, St. Paul, MN (US);
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.