Optical apparatus for recording a holographic device and method of recording
An apparatus for recording a holographic device comprises: a master hologram comprising a multiplicity of holographic elements each characterized by one of a predefined set of grating prescriptions; a transparent substrate supporting a layer of holographic material; and a light source. Each holographic element diffracts source light onto a predefined region of the layer. Each prescription modulates at least one of phase, amplitude, and angle of the light. There is further provided a method of recording a holographic device, comprising the steps of: providing said apparatus; exposing the master to illumination from the source; and diffracting light from each holographic element onto a predefined region of the layer.
1. An optical apparatus for recording a hologram comprising:
a first hologram comprising a multiplicity of holographic elements having a predefined pattern, each of said holographic elements characterized by one of a predefined set of grating prescriptions;
a cell having a first transparent substrate supporting a layer of recordable holographic material; and
a light source to provide incident light,
wherein said hologram is operative to propagate a set of one or more beams from said incident light,
wherein said set of beams are projected onto a predefined region of said layer such that said holographic material can be recorded within said cell to form a second hologram in accordance with said pattern of said holographic elements,
wherein each said prescription is designed for modulating at least one of phase, amplitude, and angle of said light.
2. The apparatus of claim 1 , wherein said first hologram is a computer-generated hologram.
3. The apparatus of claim 1 , wherein said holographic material is a mixture of photopolymer and liquid crystal such that holographically formed, polymer dispersed liquid crystal (HPDLC) is formed within said cell when recorded.
4. The apparatus of claim 1 , wherein said layer is sandwiched by a said first substrate and a second transparent substrate.
5. The apparatus of claim 1 , wherein said layer is sandwiched by said first substrate and a second substrate to form a waveguide.
6. The apparatus of claim 1 , wherein said layer is sandwiched by said first substrate and a second substrate, wherein transparent electrodes are applied to said substrates, wherein at least one of said electrodes is patterned into independently addressable elements overlapping said predefined regions, wherein said holographic material records a holographic element with a diffraction efficiency controlled by a voltage applied across the element.
7. The apparatus of claim 1 , wherein said master first hologram is disposed between said source and said substrate.
8. The apparatus of claim 1 , wherein a holographic element of said multiplicity of holographic elements has a prescription characterized as a grating vector such that said predefined region of said layer corresponding to the holographic element can be recorded having the same grating vector.
9. The apparatus of claim 1 , wherein a holographic element of said multiplicity of holographic elements is configured to provide at least one of optical power or diffusion such that said predefined region of said layer corresponding to the holographic element can be recorded having the same optical power or diffusion.
10. The apparatus of claim 1 , wherein a holographic element direction of said multiplicity of holographic elements is configured to generate a set of one or more beams from said incident light, each of said beams having a set of fanning beam lets propagated from said first hologram.
11. The apparatus of claim 1 , wherein a holographic element of said multiplicity of holographic elements is configured to provide phase retardation such that said predefined region of said layer corresponding to the holographic element can be recorded having the same phase retardation.
12. The apparatus of claim 1 , wherein said multiplicity of said holographic elements is patterned into a two-dimensional array such that said layer can be recorded having the same two-dimensional array pattern.
13. The apparatus of claim 1 , further comprising a beam steering mirror and a beamsplitter, wherein the beamsplitter splits light from the light source into said incident light that is used to generate said set of beams and into a reference beam, wherein said reference beam is directed towards said beam steering mirror by the beamsplitter, and wherein said beam steering mirror reflects said reference beam towards said cell.
14. The apparatus of claim 1 , wherein said source is a laser.
15. A method of recording a holographic device, comprising the steps of:
providing a first hologram comprising a multiplicity of holographic elements having a predefined pattern, each of said holographic elements with prescriptions for modulating at least one of phase, amplitude, and angle of said light;
providing a light source;
providing a cell having a first transparent substrate supporting a layer of recordable holographic material;
exposing said first hologram to illumination from said source;
wherein said first hologram is operative to generate a set of one or more beams from said incident light,
wherein said set of beams are formed by diffraction using said multiplicity of holographic elements, of said incident light,
wherein said set of beams are projected onto a predefined region of said layer such that said holographic material can be recorded within said cell to form a second hologram in accordance with said pattern of said holographic elements.
16. The method of claim 15 , wherein providing a cell further comprises:
providing a second substrate;
forming a cell having said first and said second substrate disposed on opposite sides such that a thin cavity is formed;
filling said cavity with holographic material.
17. The method of claim 16 , wherein providing a cell further comprises:
coating said substrates with transparent electrode material.
18. The method of claim 15 , wherein said first hologram is a computer-generated hologram.
19. The method of claim 15 , wherein each said holographic material is a mixture of photopolymer and liquid crystal such that holographically formed, polymer dispersed liquid crystal (HPDLC) is formed within said cell when recorded.
20. The apparatus of claim 1 , wherein said second hologram is an electrically switchable Bragg grating (ESBG).
21. The method of claim 15 , wherein each of said beams comprises a set of fanning beamlets.