Light recycling illumination systems having restricted angular output
First Claim
1. An illumination system, comprising:
- at least one light emitting diode, wherein said at least one light emitting diode emits internally generated light having a first angular range and wherein said at least one light emitting diode has a reflectivity to incident light; and
a partially reflecting optical element, wherein said partially reflecting optical element is located in the light optical path of said internally generated light, wherein said partially reflecting optical element transmits a first portion of said internally generated light with a second angular range, smaller than said first angular range, and wherein said partially reflecting optical element reflects a second portion of said internally generated light back to said at least one light emitting diode.
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Abstract
This invention is an illumination system that incorporates a light emitting diode and a partially reflecting optical element. The light emitting diode emits internally generated light having a first angular range and reflects incident light with high reflectivity. The partially reflecting optical element transmits a first portion of the internally generated light with a second angular range, smaller than the first angular range, and reflects a second portion of the internally generated light back to the light emitting diode, where the second portion is reflected by the light emitting diode. The partially reflecting optical element can be a pyramid, an array of pyramids, a first and second orthogonal arrays of prisms or a bandpass filter. Utilizing a partially reflecting optical element and light recycling can increase the effective brightness and the output efficiency of the illumination system.
70 Citations
19 Claims
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1. An illumination system, comprising:
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at least one light emitting diode, wherein said at least one light emitting diode emits internally generated light having a first angular range and wherein said at least one light emitting diode has a reflectivity to incident light; and
a partially reflecting optical element, wherein said partially reflecting optical element is located in the light optical path of said internally generated light, wherein said partially reflecting optical element transmits a first portion of said internally generated light with a second angular range, smaller than said first angular range, and wherein said partially reflecting optical element reflects a second portion of said internally generated light back to said at least one light emitting diode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An illumination system, comprising:
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at least one light emitting diode, wherein said at least one light emitting diode has a total emitting area, wherein said at least one light emitting diode emits internally generated light and wherein said at least one light emitting diode has a reflectivity to incident light; and
a light recycling envelope that encloses said at least one light emitting diode, wherein said light recycling envelope has reflecting inside surfaces that recycle a part of said internally generated light emitted by said at least one light emitting diode back to said at least one light emitting diode;
a light output aperture in said light recycling envelope, wherein a fraction of said internally generated light emitted by said at least one light emitting diode and reflected by said light recycling envelope exits said light recycling envelope through said light output aperture, wherein the area of said light output aperture is less than said total emitting area and wherein said fraction of said internally generated light exiting said light output aperture has a first angular range; and
a partially reflecting optical element, wherein said partially reflecting optical element is located in the light optical path and proximal to said light output aperture, wherein said partially reflecting optical element transmits a first portion of said fraction of said internally generated light with a second angular range, smaller than said first angular range and wherein said partially reflecting optical element reflects a second portion of said fraction of said internally generated light back into said light recycling envelope. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification