Holographic diffuser display
A display uses a projector to project an image onto a holographic diffuser. The holographic diffuser scatters light of the projected image to at least one holographic element having optical power, which forms an image in angular domain for a direct observation by a user. The holographic diffuser and the holographic optical element, such as a freeform lens or a reflector, may be disposed on a transparent substrate in which the image light propagates. The architecture that immerses a display (HOE diffuser) and the eyepiece lens into the substrate may reduce the form factor of the system compared to the VR headset architecture, while being suitable for operation in AR configuration.
1. A display comprising:
a substrate transparent for visible light, the substrate having first and second opposed surfaces;
a holographic diffuser at the second surface of the substrate;
a projector for projecting an image onto the holographic diffuser through the first surface of the substrate, wherein the holographic diffuser is configured to scatter light of the image projected thereon back to the first surface within a pre-defined range of angles; and
a holographic lens disposed at the first surface of the substrate and configured to receive the light scattered by the holographic diffuser for forming a corresponding image in angular domain at a distance from the holographic lens.
2. The display of claim 1 , wherein the holographic diffuser is immersed into the substrate.
3. The display of claim 1 , wherein the pre-defined range of angles of scattering light is at least two times wider than a cone angle of the light emitted by the projector and converging to a single pixel of the image projected onto the holographic diffuser.
4. The display of claim 1 , wherein the holographic diffuser is coupled to the substrate without an air gap therebetween.
5. A display comprising:
a substrate transparent for visible light, the substrate having first and second opposed surfaces;
a holographic diffuser at the second surface of the substrate;
a projector for projecting an image onto the holographic diffuser through the first surface of the substrate, wherein the holographic diffuser is configured to scatter light of the image projected thereon back to the first surface within a pre-defined range of angles; and
a holographic reflector having optical power, disposed at the second surface of the substrate, and configured to reflect the light scattered by the holographic diffuser and reflected from the first surface back towards the first surface of the substrate, for forming a corresponding image in angular domain at a distance from the holographic reflector.
6. The display of claim 5 , wherein an angle of incidence of light emitted by the projector onto the holographic diffuser exceeds 45 degrees.
7. A display comprising:
a substrate transparent for visible light, the substrate having first and second opposed surfaces;
a holographic diffuser at the second surface of the substrate;
a projector for projecting an image onto the holographic diffuser through the first surface of the substrate, wherein the holographic diffuser is configured to scatter light of the image projected thereon back to the first surface within a pre-defined range of angles;
a first holographic reflector having optical power, disposed at the first surface of the substrate, and configured to reflect the light scattered by the holographic diffuser back towards the second surface of the substrate; and
a second holographic reflector having optical power, disposed at the second surface of the substrate, and configured to form the image in angular domain at a distance from the first holographic reflector.
8. The display of claim 7 , wherein the second holographic reflector is coupled to the holographic diffuser without an air gap therebetween.
9. The display of claim 7 , wherein the first holographic reflector, the substrate, the holographic diffuser, and the second holographic reflector form an optical stack.
10. The display of claim 9 , wherein the optical stack transmits at least a portion of outside light, enabling a user of the display to see outside environment through the optical stack.
11. The display of claim 9 , wherein an angle of incidence of light emitted by the projector onto the optical stack exceeds 45 degrees.
12. A method of displaying an image, the method comprising:
projecting an image through a first surface of a transparent substrate onto a holographic diffuser disposed at a second surface of the substrate opposed to the first surface;
scattering, using the holographic diffuser, light of the image projected thereon back to the first surface within a pre-defined range of angles; and
forming, using a first holographic element having optical power, an image in angular domain at a distance from the first holographic element, the image in angular domain corresponding to the image projected onto the holographic diffuser, wherein:
the first holographic element is a holographic reflector disposed at the first surface of the substrate for reflecting the light back towards the second surface of the substrate; and
the image in angular domain is formed using the first holographic element and a second holographic element having optical power, the second holographic element being disposed at the second surface of the substrate.
13. The method of claim 12 , wherein the light of the image projected onto the holographic diffuser is scattered at angles exceeding a total internal reflection (TIR) critical angle in the substrate.
14. The method of claim 12 , wherein the second holographic element is a holographic reflector forming the image in angular domain at a distance from the second holographic element.
15. A display comprising:
a projector for projecting an image;
a transparent substrate having first and second opposed surfaces;
a holographic diffuser disposed at the second surface downstream of the projector for receiving the image through the first surface and scattering light of the image back to the first surface within a pre-defined range of angles;
a holographic reflector having optical power, disposed at the first surface, and configured for receiving the light scattered by the holographic diffuser and reflecting the light back towards the second surface; and
a holographic element having optical power, disposed at the second surface for forming an image in angular domain corresponding to the image projected by the projector, at a distance from the holographic element.
16. The display of claim 15 , wherein:
the holographic diffuser, the substrate, and the holographic reflector, and the holographic element form an optical stack; and
the pre-defined range of angles is above a total internal reflection (TIR) critical angle for the light scattered by the holographic diffuser into the substrate.