Light-emitting devices providing asymmetrical propagation of light
First Claim
1. A light emitting device, comprising:
- a plurality of light emitting elements configured to emit light in a first spectral power distribution in a forward direction including along a first axis;
a light scattering element having a rear-facing surface facing the light emitting elements and a forward-facing surface opposite the rear-facing surface, the light scattering element positioned along the first axis spaced apart from and to receive light in the first spectral power distribution emitted from the light emitting elements, the light scattering element comprising a phosphor material that Stokes shifts light in the first spectral power distribution to a second spectral power distribution, at least some of the light in the first and second spectral power distributions being emitted by the light scattering element through the forward-facing surface to be emitted by the light emitting device;
an optical coupler positioned between the light emitting elements and the light scattering element, the optical coupler comprising an input aperture for receiving light emitted by the light emitting elements and an exit aperture facing the light scattering element, the optical coupler having surfaces which reflect incident light within the optical coupler in the first spectral power distribution towards the exit aperture; and
an extractor element positioned to receive the light emitted from the forward-facing surface of the light scattering element and emit the light as emitted light from the light emitting device,wherein, for a cross-section through at least one of the light emitting elements and coinciding with the first axis, the optical coupler has a width, as measured orthogonal to the first axis, that is narrower at the input aperture than at the exit aperture.
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Abstract
A variety of light-emitting devices for general illumination utilizing solid state light sources (e.g., light emitting diodes) are disclosed. In general, the devices include a scattering element in combination with an extractor element. The scattering element, which may include elastic and/or inelastic scattering centers, is spaced apart from the light source element. Opposite sides of the scattering element have asymmetric optical interfaces, there being a larger refractive index mismatch at the interface facing the light emitting element than the interface between the scattering element and the extractor element. Such a structure favors forward scattering of light from the scattering element. In other words, the system favors scattering out of the scattering element into the extractor element over backscattering light towards the light source element. The extractor element, in turn, is sized and shaped to reduce reflection of light exiting the light-emitting device at the devices interface with the ambient environment.
141 Citations
21 Claims
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1. A light emitting device, comprising:
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a plurality of light emitting elements configured to emit light in a first spectral power distribution in a forward direction including along a first axis; a light scattering element having a rear-facing surface facing the light emitting elements and a forward-facing surface opposite the rear-facing surface, the light scattering element positioned along the first axis spaced apart from and to receive light in the first spectral power distribution emitted from the light emitting elements, the light scattering element comprising a phosphor material that Stokes shifts light in the first spectral power distribution to a second spectral power distribution, at least some of the light in the first and second spectral power distributions being emitted by the light scattering element through the forward-facing surface to be emitted by the light emitting device; an optical coupler positioned between the light emitting elements and the light scattering element, the optical coupler comprising an input aperture for receiving light emitted by the light emitting elements and an exit aperture facing the light scattering element, the optical coupler having surfaces which reflect incident light within the optical coupler in the first spectral power distribution towards the exit aperture; and an extractor element positioned to receive the light emitted from the forward-facing surface of the light scattering element and emit the light as emitted light from the light emitting device, wherein, for a cross-section through at least one of the light emitting elements and coinciding with the first axis, the optical coupler has a width, as measured orthogonal to the first axis, that is narrower at the input aperture than at the exit aperture. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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Specification