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Reflective LCD projection system using wide-angle Cartesian polarizing beam splitter
| Details |
Inventors: Bruzzone, Charles L.; Aastuen, David J. W.; Strharsky, Roger J.; Eckhardt, Stephen K.; Weber, Michael F.; Boyd, Gary T.;
Assignee: 3M Innovative Properties Company (St. Paul, MN)
Primary Examiner: Shafer; Ricky D.
Assistant Examiner:
Attorney, Agent or Firm: Florczak; Yen Tong
An optical imaging system including a wide-angle Cartesian polarizing beam splitter, light valve illumination optics having an f/#.ltoreq.2.5, and at least one reflective light valve. The Cartesian polarizing beam splitter (PBS) has a structural orientation defining fixed polarization axes. The use of a Cartesian PBS allows the development of systems using curved PBS that provide higher light output and/or replace or augment other optical components. By recognizing and advantageously applying properties of wide-angle Cartesian polarizers, the present invention discloses a high-efficiency optical imaging system capable of functioning at f/#'s equal to or below f/2.5 while maintaining a contrast ratio of at least 100 to 1, or, more preferably, 150 to 1 in a projection system configuration. |
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DETAILED DESCRIPTION The present invention describes an optical imaging system including and advantageously employing a wide-angle "Cartesian" polarizer beam splitter ("PBS").
A Cartesian PBS is defined as a PBS in which the polarization of separate beams is referenced to invariant, generally orthogonal principal axes of the PBS film.
In contrast with a MacNeille.
PBS, in a Cartesian PBS the polarization of the separate beams is substantially independent of the angle of incidence of the beams.
The use of a Cartesian PBS film also allows the development of systems using curved PBS that provide higher light output and/or replace or augment other optical components.
A wide-angle PBS is defined as a PBS capable of receiving a cone of light rays with an angle of incidence up to 11.
degree.
or more, while maintaining acceptable system contrast.
By recognizing and advantageously applying properties of wide-angle Cartesian polarizers, the present invention discloses a high-efficiency optical imaging system capable of functioning at f/#'s equal to or below f/2.
5 while maintaining a contrast ratio of at least 100 to 1, or, more preferably, 150 to 1 in a projection system configuration.
An optical imaging system in accordance with the present invention includes a wide-angle Cartesian polarizing beam splitter, light valve illumination optics having an f/#.
ltoreq.
2.
5, and at least one reflective light valve.
The Cartesian polarizing beam splitter (PBS) has a structural orientation defining fixed polarization axes.
A reflective Cartesian PBS substantially reflects those components of a beam of light which are polarized along one such fixed axis, called the Material Axis.
Those components of a beam of light with polarization not along the Material Axis are substantially transmitted.
The polarizing beam splitter therefore splits incident light into a first and a second substantially polarized beam having polarization states referenced to the fixed polarization axes and the polarizing beam splitter directs the first polarized beam onto the reflective light valve
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Lighting 
