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  Light collectors for projection systemsUSPTO Application #: 20080018861Title: Light collectors for projection systems Abstract: Disclosed herein are light collectors for use in projection applications. The light collectors gather light from surface emitting sources (e.g., LEDs) of differing color (or same color in some embodiments) using input lightpipes. A light collection system splits the light into orthogonal linear polarization states and efficiently propagates the light by use of a polarizing beamsplitter (PBS) and a reflecting element to recycle light at a port of the PBS. Further, the light collection system may efficiently homogenize the light using an output lightpipe in a lightpath from the output of the PBS. In addition, the light collection system may present a single, linear polarization at the output through the use of a half-wave switch (LC cell) in some embodiments or ColorSelect filter in other embodiments. The light collection system may be integrated into a single, monolithic glass, plastic or combination glass/plastic assembly. (end of abstract) Agent: Baker & Mckenzie LLP Patent Department - Dallas, TX, US Inventors: Miller H. Schuck, Michael G. Robinson USPTO Applicaton #: 20080018861 - Class: 353 20 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20080018861. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001]This Application claims priority to commonly-assigned provisional patent application Ser. Nos.: (1) 60/807,704, entitled "Lightpipe for projection systems," filed Jul. 18, 2006; (2) 60/829,495, entitled "Non-imaging collector for polarized, multi-primary illumination system," filed Oct. 13, 2006; and (3) 60/862,414, entitled "Light collectors for projection systems," filed Oct. 20, 2006, all of which are herein incorporated by reference. [0002]This Application relates to commonly-assigned U.S. application Ser. No. ______, entitled "Light Collectors for Projection Systems," filed Jul. 18, 2007; and also relates to commonly-assigned U.S. application Ser. No. ______, entitled "Light Collectors for Projection Systems," filed Jul. 18, 2007. TECHNICAL FIELD [0003]This disclosure generally relates to a light collection system, and more specifically relates to a non-imaging collector for a projection system. BACKGROUND [0004]tendue is a property of an optical system. It is given by the cross-sectional area of a cone of light (in the plane perpendicular to the propagation direction), times the solid angle subtended by the light. Other names for this property are acceptance, throughput, light-grasp, collecting power, and the A.OMEGA. product. Etendue is important because it never increases in any optical system. A perfect optical system produces an image with the same etendue as the source. [0005]The importance of etendue is in determining optical system throughput. Any given source emits light into an optical system with efficiency dependent on the system etendue. Most surface emitting light sources (e.g., light emitting diodes) do not match the etendue required of projection panels. The die are either too small, requiring the addition of die, or too large, requiring some sort of aperture to reduce the LED etendue to match the panel etendue. [0006]Given the aforementioned shortcomings, it would be desirable to match LED die to panel etendue in order to maximize optical system throughput. SUMMARY [0007]Disclosed herein are light collectors for use in projection applications. The light collectors gather light from surface emitting sources (e.g., LEDs) of differing color (or same color in some embodiments) using input lightpipes. In an embodiment, a light collection system splits the light into orthogonal linear polarization states and efficiently propagates the light by use of a polarizing beamsplitter (PBS) and a reflecting element to recycle light at a port of the PBS. Further, in some embodiments, the light collection system may efficiently homogenize the light using an output lightpipe in a lightpath from the output of the PBS elements. In addition, the light collection system may present a single, linear polarization at the output through the use of a ColorSelect filter in some embodiments or a switchable half-wave rotator (e.g., an LC cell) in other embodiments. The light collection system may be integrated into a single, monolithic glass, plastic or combination glass/plastic assembly. [0008]In an embodiment, an apparatus for a projection system includes first and second lightpipes, a PBS, first and second quarter wave plates, and a reflecting element. The first and second lightpipes are respectively operable to receive light from first and second light sources. The PBS has first and second input ports and first and second output ports. The first quarter wave plate is optically coupled to the first lightpipe and the first input port, and located between the first lightpipe and the first input port. The second quarter wave plate is optically coupled to the second lightpipe and the second input port, and located between the second lightpipe and the second input port. The reflecting element is located at the first output port and operable to reflect light toward the first input port. [0009]In a variation of this embodiment, the apparatus may further include a ColorSelect filter located in a light path exiting the PBS or an output lightpipe carrying light from the PBS, where the ColorSelect filter is operable to polarize an additive color spectrum along a first axis and its compliment color spectrum along a second axis. In such an embodiment the first light source may provide an additive color spectrum, while the second light source may provide a complementary color spectrum. [0010]In yet another variation on this embodiment, the apparatus may further include (instead of the ColorSelect filter) a switchable half-wave rotator located in a light path exiting the PBS or an output lightpipe carrying light from the PBS. In such an embodiment, the first and second light sources may be the same color, with the first and second light sources being temporally modulated to alternately provide a periodic high-intensity output. [0011]Others features and embodiments are shown herein with reference to the drawings, detailed description, and appended claims. BRIEF DESCRIPTION OF THE DRAWINGS [0012]FIG. 1 is a schematic diagram of a first embodiment of a light collection system in accordance with the present disclosure; [0013]FIG. 2 is a graph illustrating angular intensity distribution in the far field for exemplary red, green, and blue Light Emitting Diode (LED) devices in accordance with the present disclosure; [0014]FIG. 3A is a schematic diagram illustrating the relationship of luminous output to the aperture die area of an LED in accordance with the present disclosure; [0015]FIG. 3B is a schematic diagram illustrating the relationship of luminous output to the aperture angular output of an LED in accordance with the present disclosure; [0016]FIG. 4 is a schematic diagram showing a three-dimensional view of an exemplary tapered lightpipe in accordance with the present disclosure; [0017]FIG. 5A is a schematic diagram showing a top view of the exemplary tapered lightpipe of FIG. 4; [0018]FIG. 5B is a schematic diagram showing a side view of the exemplary tapered lightpipe of FIG. 4; [0019]FIG. 6A is a graph illustrating cross-sectional illuminance through the output lightpipe of FIG. 1 at a position of 0 mm along the optical axis, in accordance with the present disclosure; Continue reading... Full patent description for Light collectors for projection systems Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Light collectors for projection systems patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Light collectors for projection systems or other areas of interest. ### Previous Patent Application: System and method for 3d optical projection Next Patent Application: Image display apparatus, image display method, and program product therefor Industry Class: Optics: image projectors ### FreshPatents.com Support Thank you for viewing the Light collectors for projection systems patent info. 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