Light emitting device with improved radiation distribution and method of making thereof
A light emitting device includes a substrate, a plurality of light emitting diodes located over the substrate, and a plurality of micro-lenses. Each of the plurality of micro-lenses is located over a respective one of the plurality of light emitting diodes. Each of the plurality of micro-lenses has a first symmetry axis, each of the plurality of light emitting diodes has a second symmetry axis, and at least some of the plurality of micro-lenses have the first symmetry axis which is laterally displaced relative to the second symmetry axis of the respective one of the plurality of light emitting diodes.
1 . A light emitting device, comprising:
a substrate;
a plurality of light emitting diodes located over the substrate; and
a plurality of micro-lenses, wherein each of the plurality of micro-lenses is located over a respective one of the plurality of light emitting diodes,
wherein each of the plurality of micro-lenses has a first symmetry axis, each of the plurality of light emitting diodes has a second symmetry axis, and at least some of the plurality of micro-lenses have the first symmetry axis which is laterally displaced relative to the second symmetry axis of the respective one of the plurality of light emitting diodes,
wherein:
the plurality of light emitting diodes is configured as an ordered array of pixels with each pixel comprising a red subpixel, a blue subpixel, and a green subpixel;
the substrate includes electrical circuitry configured to control the plurality of light emitting diodes such that the light emitting device is configured as a display that generates an image; and
a spatial extent of the image is determined by displacements of the plurality of micro-lenses relative to the respective light emitting diodes, and
a displacement of each of the plurality of micro-lenses varies from lens to lens such that the light emitting device generates the image having a first size that is enlarged relative to a second size of the light emitting device.
2 . The light emitting device of claim 1 , wherein the plurality of light emitting diodes are arranged in a first array, the plurality of micro-lenses are arranged in a second array, and the first array has a smaller period than the second array in two orthogonal directions which are parallel to a top surface of the substrate.
3 . The light emitting device of claim 1 , wherein the plurality of light emitting diodes are arranged in a first array, the plurality of micro-lenses are arranged in a second array, and the first array has a larger period than the second array in two orthogonal directions which are parallel to a top surface of the substrate.
4 . The light emitting device of claim 1 , wherein the displacement of each of the plurality of micro-lenses has a common value such that the light emitting device generates the image that is directed at an angle relative to a direction perpendicular to a surface of the substrate on which the plurality of light emitting diodes is formed.
5 . The light emitting device of claim 4 , wherein the plurality of light emitting diodes are arranged in a first array, the plurality of micro-lenses are arranged in a second array, and the first array has a same period as the second array in two orthogonal directions which are parallel to a top surface of the substrate.
6 . The light emitting device of claim 5 , wherein all the plurality of micro-lenses have the first symmetry axis which is laterally displaced relative to the second symmetry axis of the respective one of the plurality of light emitting diodes.
7 . The light emitting device of claim 1 , further comprising:
a plurality of optical cavities each bounded by a cavity wall, wherein each of the plurality of light emitting diodes is located in a respective optical cavity and is configured to emit blue or ultraviolet radiation incident photons; and
a color conversion material located over each of the plurality of light emitting diodes that is configured to absorb the incident photons emitted by the light emitting diode and to generate converted photons having a longer peak wavelength than a peak wavelength of the incident photons.
8 . The light emitting device of claim 1 , wherein each of the plurality of micro-lenses is configured to receive photons generated by the respective one of the plurality of light emitting diodes, and to form a radiation pattern of the photons that is peaked in a predetermined direction that is determined based on a lateral displacement of the first symmetry axis of the micro-lens relative to the second symmetry axis of the respective one of the plurality of light emitting diodes.
9 . The light emitting device of claim 8 , wherein the predetermined direction varies in a first range from greater than 0 degrees to 30 degrees, relative to a direction of the first symmetry axis, as the first symmetry axis is laterally displaced relative to the second symmetry axis in a second range from greater than 0 microns to 1 micron.
10 . The light emitting device of claim 8 , wherein the predetermined direction varies as an approximately linear function of the displacement of the first symmetry axis relative to the second symmetry axis.
11 . The light emitting device of claim 1 , wherein a first diameter of each of the plurality of micro-lenses is approximately larger than a second diameter of a respective one of the plurality of light emitting diodes.
12 . The light emitting device of claim 11 , wherein the first diameter is 9 microns or less and the second diameter is 3 microns or less.
13 . The light emitting device of claim 11 , wherein all of the plurality of micro-lenses have a same diameter and a same height.
14 . The light emitting device of claim 1 , wherein the light emitting device comprises a display device.
15 . The light emitting device of claim 14 , wherein the display device comprises a virtual reality display device.
16 . The light emitting device of claim 14 , wherein the display device comprises an augmented reality display device.
17 . The light emitting device of claim 14 , wherein the display device comprises a heads up display device.