Abstract: An optical system is provided. The optical system comprises a first polarizing beamsplitter (PBS), a first reflecting image-forming device, and a first quarter-wave retarding element. An optical system is also provided that comprises an image-forming device, a reflective polarizing layer, at least a first birefringent element disposed on an optical path between the image-forming device and the polarizing layer, and a quarter-wave retarding element. Further provided is an optical system comprising a color combiner unit, at least two polarizing beamsplitters (PBSs), and a first quarter-wave retarding element. The present application also provides methods of compensating for birefringence in an image projection system.

Abstract: An optical system is provided. The optical system comprises a first polarizing beamsplitter (PBS), a first reflecting image-forming device, and a first quarter-wave retarding element. An optical system is also provided that comprises an image-forming device, a reflective polarizing layer, at least a first birefringent element disposed on an optical path between the image-forming device and the polarizing layer, and a quarter-wave retarding element. Further provided is an optical system comprising a color combiner unit, at least two polarizing beamsplitters (PBSs), and a first quarter-wave retarding element. The present application also provides methods of compensating for birefringence in an image projection system.

Abstract: An optical imaging system including an illumination system, a Cartesian PBS, and a prism assembly. The illumination system provides a beam of light, the illumination system having an ƒ/# less than or equal to 2.5. The Cartesian polarizing beam splitter has a first tilt axis, oriented to receive the beam of light. A first polarized beam of light having one polarization direction is folded by the Cartesian polarizing beam splitter and a second polarized beam of light having a second polarization direction is transmitted by the Cartesian polarizing beam splitter. The Cartesian polarizing beam splitter nominally polarizes the beam of light with respect to the Cartesian beam splitter to yield the first polarized beam in the first polarization direction. The color separation and recombination prism is optically aligned to receive the first polarized beam. The prism has a second tilt axis, a plurality of color separating surfaces, and a plurality of exit surfaces.

Abstract: Single imager projection systems suffer from low light throughput, compared to three imager systems, because only one color band is illuminated at any one time. As a result, there is a need to increase the operating efficiency of the single imager projection system. The invention is directed to the incorporation of a high extinction ratio pre-polarizer, such as a compensated, multi-layer polarizer, in a single or dual imager projection system. This permits illumination with low f-number illumination light, and thus increases the efficiency of the projection system. The pre-polarizer may be incorporated within a polarization recovery unit to further enhance system efficiency.

Abstract: A projection system includes an image-forming device and a polarizing beamsplitter. Illumination light illuminates the image-forming device via the first polarizing beamsplitter. A retardation element is disposed between the image-forming device and the polarizing beamsplitter. A bias controller applies a bias to pixels of the image-forming device in the dark state so as to substantially maximize contrast in image light reflected from image-forming device. In some arrangements, the volume between the polarizing beamsplitter and the image-forming device is sealed, with the retarding element being disposed within the sealed volume and being attached to either the polarizing beamsplitter or the image-forming device.

Abstract: An optical system is provided. The optical system comprises a first polarizing beamsplitter (PBS), a first reflecting image-forming device, and a first quarter-wave retarding element. An optical system is also provided that comprises an image-forming device, a reflective polarizing layer, at least a first birefringent element disposed on an optical path between the image-forming device and the polarizing layer, and a quarter-wave retarding element. Further provided is an optical system comprising a color combiner unit, at least two polarizing beamsplitters (PBSs), and a first quarter-wave retarding element. The present application also provides methods of compensating for birefringence in an image projection system.

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.

Abstract: Generally, the present invention relates to an apparatus for reducing astigmatism in a projection system that is particularly well suited to reducing astigmatism in LCD projection systems. A projection system includes a light source to generate light, conditioning optics to condition the light from the light source and an imaging core to impose on image on conditioned light from the conditioning optics to form image light. The imaging core includes a polarizing beamsplitter and at least one imager, and at least one element in the imaging core is adapted to reduce astigmatism in the image light. The astigmatism may arise in the polarizing beamsplitter. A projection lens system projects the astigmatism-reduced image light from the imaging core.

Abstract: Single imager projection systems suffer from low light throughput, compared to three imager systems, because only one color band is illuminated at any one time. As a result, there is a need to increase the operating efficiency of the single imager projection system. The invention is directed to the incorporation of a high extinction ratio pre-polarizer, such as a compensated, multi-layer polarizer, in a single or dual imager projection system. This permits illumination with low f-number illumination light, and thus increases the efficiency of the projection system. The pre-polarizer may be incorporated within a polarization recovery unit to further enhance system efficiency.

Abstract: An optical imaging system including an illumination system, a Cartesian PBS, and a prism assembly. The illumination system provides a beam of light, the illumination system having an f/# less than or equal to 2.5. The Cartesian polarizing beam-splitter has a first tilt axis, oriented to receive the beam of light. A first polarized beam of light having one polarization direction is folded by the Cartesian polarizing beam splitter and a second polarized beam of light having a second polarization direction is transmitted by the Cartesian polarizing beam splitter. The Cartesian polarizing beam splitter nominally polarizes the beam of light with respect to the Cartesian beam-splitter to yield the first polarized beam in the first polarization direction. The color separation and recombination prism is optically aligned to receive the first polarized beam. The prism has a second tilt axis, a plurality of color separating surfaces, and a plurality of exit surfaces.

Abstract: In one embodiment, a projection screen includes a diffuse reflecting polarizer that diffusively reflects light polarized in a first direction and transmits light polarized in a second direction. The projection screen may also include a second polarizer adjacent a back side of the diffuse reflecting polarizer, wherein the second polarizer is oriented to transmit light polarized in the second direction. The projection screen may appear substantially diffuse when viewed from a front side and substantially transparent when viewed from a back side.

Abstract: A polarizing beam splitter (PBS) includes a first multilayer reflective polarizing film and a second multilayer reflective polarizing film disposed between two covers. The two multilayer reflective polarizing films can be the same or different. The PBS can be used in a variety of applications.

Abstract: Single imager projection systems suffer from low light throughput, compared to three imager systems, because only one color band is illuminated at any one time. As a result, there is a need to increase the operating efficiency of the single imager projection system. The invention is directed to the incorporation of a high extinction ratio pre-polarizer, such as a compensated, multi-layer polarizer, in a single or dual imager projection system. This permits illumination with low f-number illumination light, and thus increases the efficiency of the projection system. The pre-polarizer may be incorporated within a polarization recovery unit to further enhance system efficiency.

Abstract: LCD projection systems that use reflective LCD imager units commonly use one or more polarization beamsplitters to separate the light incident on the imager from the light reflected by one or more respective imagers. The polarizing beamsplitters introduce astigmatism to the image light from the imagers. According to the present invention, the polarization beamsplitters are adapted to reduce the astigmatism.

Abstract: Generally, the present invention relates to an apparatus for reducing astigmatism in a projection system that is particularly well suited to reducing astigmatism in LCD projection systems. A projection system includes a light source to generate light, conditioning optics to condition the light from the light source and an imaging core to impose on image on conditioned light from the conditioning optics to form image light. The imaging core includes a polarizing beamsplitter and at least one imager, and at least one element in the imaging core is adapted to reduce astigmatism in the image light. The astigmatism may arise in the polarizing beamsplitter. A projection lens system projects the astigmatism-reduced image light from the imaging core.

Abstract: An optical imaging system including a wide-angle Cartesian polarizing beam splitter, light valve illumination optics having an f/#≦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.

Abstract: Generally, the present invention relates to an apparatus for reducing astigmatism in a projection system that is particularly well suited to reducing astigmatism in LCD projection systems. A projection system includes a light source to generate light, conditioning optics to condition the light from the light source and an imaging core to impose on image on conditioned light from the conditioning optics to form image light. The imaging core includes a polarizing beamsplitter and at least one imager, and at least one element in the imaging core is adapted to reduce astigmatism in the image light. The astigmatism may arise in the polarizing beamsplitter. A projection lens system projects the astigmatism-reduced image light from the imaging core.

Abstract: In one embodiment, a projection screen includes a diffuse reflecting polarizer that diffusively reflects light polarized in a first direction and transmits light polarized in a second direction. The projection screen may also include a second polarizer adjacent a back side of the diffuse reflecting polarizer, wherein the second polarizer is oriented to transmit light polarized in the second direction. The projection screen may appear substantially diffuse when viewed from a front side and substantially transparent when viewed from a back side.

Abstract: An optical imaging system including a wide-angle Cartesian polarizing beam splitter, light valve illumination optics having an ƒ/#≦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 ƒ#'s equal to or below ƒ/2.5 while maintaining a contrast ratio of at least 100 to 1, or, more preferably, 150 to 1 in a projection system configuration.

Abstract: LCD projection systems that use reflective LCD imager units commonly use one or more polarization beamsplitters to separate the light incident on the imager from the light reflected by one or more respective imagers. The polarizing beamsplitters introduce astigmatism to the image light from the imagers. According to the present invention, the polarization beamsplitters are adapted to reduce the astigmatism.