SYSTEMS, DEVICES, AND METHODS FOR HOLOGRAPHIC OPTICAL ELEMENTS
Systems, devices, and methods for holographic optical elements are described. A holographic optical element includes a first layer of holographic material and a second layer of holographic material. The first layer of holographic material includes a first hologram responsive to light in a first waveband and a second hologram responsive to light in a second waveband. The second layer of holographic material includes a third hologram responsive to light in a third waveband and may include a fourth hologram responsive to light in a fourth waveband. The first, second, third, and fourth wavebands are distinct and may comprise light of red, blue, green, and infrared wavelengths, respectively. Distribution of the three or four holograms on two layers of holographic material allows each hologram to have an index modulation of greater than 0.016, a diffraction efficiency of greater than 15%, and an angular bandwidth of greater than 12°.
1 . A holographic optical element (HOE) comprising:
a first layer of holographic material that includes a first hologram and a second hologram; and
a second layer of holographic material that includes at least a third hologram, wherein each of the first hologram, the second hologram, and the at least a third hologram has a respective index modulation of at least 0.016.
2 . The HOE of claim 1 wherein:
the first hologram is responsive to light in a first waveband and unresponsive to light outside of the first waveband;
the second hologram is responsive to light in a second waveband and unresponsive to light outside of the second waveband;
the third hologram is responsive to light in a third waveband and unresponsive to light outside of the third waveband; and
the first waveband, second waveband, and third waveband are all distinct from one another with no overlap therebetween.
3 . The HOE of claim 2 wherein the first waveband, the second waveband, and the third waveband include: a red waveband comprising light of red wavelengths, a green waveband comprising light of green wavelengths, and a blue waveband comprising light of blue wavelengths.
4 . The HOE of claim 2 wherein the second layer of holographic material further includes a fourth hologram that is responsive to light in a fourth waveband and unresponsive to light outside of the third waveband, wherein the fourth waveband is distinct from the first waveband, the second waveband, and the third waveband with no overlap therebetween.
5 . The HOE of claim 4 wherein the first waveband, the second waveband, the third waveband, and the fourth waveband include: a red waveband comprising light of red wavelengths, a green waveband comprising light of green wavelengths, a blue waveband comprising light of blue wavelengths, and an infrared waveband comprising light of infrared wavelengths.
6 . The HOE of claim 1 wherein:
the first layer of holographic material has a first surface and a second surface, the first surface of the first layer of holographic material opposite the second surface of the first layer of holographic material across a thickness of the first layer of holographic material;
the second layer of holographic material has a first surface and a second surface, the first surface of the second layer of holographic material opposite the second surface of the second layer of holographic material across a thickness of the second layer of holographic material; and wherein the HOE further comprises:
a first layer of substrate having a first surface and a second surface, the first surface of the first layer of substrate opposite the second surface of the first layer of substrate across a thickness of the first layer of substrate;
a second layer of substrate having a first surface and a second surface, the first surface of the second layer of substrate opposite the second surface of the second layer of substrate across a thickness of the second layer of substrate;
a third layer of substrate having a first surface and a second surface, the first surface of the third layer of substrate opposite the second surface of the third layer of substrate across a thickness of the third layer of substrate; wherein:
the first surface of the first layer of holographic material is physically coupled to the first surface of the first layer of substrate;
the second surface of the first layer of holographic material is physically coupled to the first surface of the second layer of substrate;
the first surface of the second layer of holographic material is physically coupled to the second surface of the second layer of substrate; and
the second surface of the second layer of holographic material is physically coupled to the first surface of the third layer of substrate.
7 . The HOE of claim 6 wherein the material of the first layer of substrate, the material of the second layer of substrate, and the material of the third layer of substrate are each selected from a group consisting of: polycarbonate, polyamide, polyimide, and triacetate.
8 . The HOE of claim 1 wherein the HOE is curved.
9 . The HOE of claim 1 wherein a respective diffraction efficiency of each of the first hologram, the second hologram, and the third hologram is at least 15%.
10 . The HOE of claim 1 wherein a respective angular bandwidth of each of the first hologram, the second hologram, and the third hologram is at least 12°.
11 . The HOE of claim 1 wherein the first layer of holographic material and the second layer of holographic material have a thickness not greater than 8 μm.
12 . The HOE of claim 1 wherein the holographic material is a photopolymer.