Achromatic apparatus for producing a wavelength-independent high contrast light signal
AssigneeKoninklijke Philips Electronics N.V.
InventorsDuncan J. Anderson, Khalid Shahzad
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Abstract
An apparatus for improved contrast in projection optical systems consists of a polarizing beam splitter (PBS) in combination with two or more waveplates whose fast exes are aligned perpendicular to each other. The apparatus has an effective broadband frequency response that is better than that of the individual retarders acting alone, and through the selection of a birefringence factor and thickness of the individual retarders, wavelength dependencies are minimized.
Claims20
An apparatus for improving contrast in a projection liquid crystal display (LCD), said apparatus comprising:
- a polarizing beam splitter (PBS);
- a first waveplate having a fast axis;
- at least a second waveplate having a fast axis;
- a mounting structure incorporating said PBS and said waveplates in a predetermined orientation;
- wherein the fast axes of the first waveplate and the at least a second waveplate are aligned either parallel or perpendicular to one another;
- and
- wherein an incident light is sequentially reflected and directed by said PBS beam through said waveplates to the LCD, reflected and redirected by the LCD through said waveplates to said PBS, and reflected and redirected by said PBS to a light source of the incident light.
An apparatus for providing a wavelength-independent optical signal in response to an incident optical signal, said apparatus comprising:
- a projection liquid crystal display (LCD);
- a polarizing beam splitter (PBS);
- a first achromatic waveplate having a fast axis;
- at least a second achromatic waveplate having a fast axis;
- a mounting structure incorporating the PBS and the waveplates in a predetermined orientation;
- wherein the fast axes of the first waveplate and the at least a second waveplate are aligned either parallel or perpendicular to one another;
- and
- wherein the incident optical signal is sequentially reflected and directed by said PBS beam through said waveplates to said LCD, reflected and redirected by the LCD through said waveplates to said PBS, and reflected by said PBS as the wavelength independent optical signal.
Dependencies are inferred from the claim text.