Method for holographic mastering and replication
A method for producing holograms with a multiplicity of holographic prescriptions from a single master is provided. A multiplicity of holographic substrates each having a first hologram is stacked on a second holographic recording medium substrate. The first hologram is designed to diffract light from a first direction into a second direction. When expose to illumination from the first direction zero order and diffracted light from each first hologram interfere in the second holographic recording medium substrate forming a second hologram. The second hologram is then copied into a third holographic recording medium substrate to provide the final copy hologram.
1. A method for mastering and replicating holograms, the method comprising:
a) providing N substrates each containing a first hologram for diffracting incident light from a first direction into diffracted light in a second direction; providing a second holographic recording medium; and providing a third holographic recording medium;
b) stacking in sequence the first holograms 1-N onto said second holographic recording medium;
c) illuminating an external surface of said first holograms 1-N with light of a first polarization in a first direction;
d) said first holograms 1-N diffracting said light into zero order light in said first direction and diffracted light in said second direction;
e) said first direction light and said second direction light interfering in said second holographic recording medium to form a second hologram;
f) placing said second hologram in contact with said third holographic recording medium;
g) illuminating external surface of said second hologram with light in said first direction;
h) said second hologram diffracting said light into zero order light in said first direction and diffracted light in said second direction; and
i) said diffracted and zero order light interfering in said third holographic recording medium to form a third hologram.
2. The method of claim 1 wherein said steps c) to i) are repeated for a plurality of different said first and second directions, wherein said first and second directions are limited by the diffraction efficiency angular bandwidth of said first hologram.
3. The method of claim 1 wherein the first holograms 1-N are provided by the steps of: configuring a laser holographic recording apparatus to form a first recording beam in said first direction and a second recording beams in said second direction; providing N substrates each containing a first holographic medium; and said first and second beams interfering within each said first holographic medium substrate to form said first hologram in each said substrate.
4. The method of claim 3 wherein said first holographic recording medium is a HPDLC for recording a SBG, said second holographic recording medium is a holographic photopolymer and said third holographic recording medium is a holographic photopolymer.
5. The method of claim 1 wherein said first holograms 1-N are surface relief diffractive structures.
6. The method of claim 1 further comprising in step a) providing a HWP and in step c) disposing said HWP between said second holographic recording medium substrate and said first hologram stack.
7. The method of claim 1 further comprising in step a) providing a linear polarizer and in step c) disposing said linear polarizer between said HWP and said first hologram stack.
8. The method of claim 1 wherein said third hologram is copy of said second hologram and said second hologram is a copy of said first hologram.
9. The method of claim 1 wherein said third holographic recording medium comprises HPDLC material components for forming a forward mode SBG or a reverse mode SBG.
10. The method of claim 1 wherein said zero order light and diffracted light in at least one step d) and step i) have power substantially in the ratio of 1:1.
11. The method of claim 1 wherein said second hologram and said third holographic recording medium are separated by an air gap.
12. The method of claim 1 wherein at least one index matching optical layer is provided.
13. The method of claim 1 wherein said third holographic recording medium forms part of a mechanically translatable continuous lamina.
14. The method of claim 1 further comprising a voltage generator for applied a voltage across at least one of said second hologram and said third holographic recording medium; wherein said voltage varies the refractive index modulation of at least one of said second hologram and said third during steps g) to i).
15. The method of claim 1 wherein said second holographic recording medium is one of a photo thermal refractive or holographic photopolymer, a forward mode HPDLC mixture or a reverse mode HPDLC mixture.
16. The method of claim 1 wherein said third holographic recording medium is one of a photo thermal refractive or photopolymer, a forward mode HPDLC mixture or a reverse mode HPDLC mixture.
17. The method of claim 1 wherein the diffracting thickness of said first hologram is less than or equal to 2 micron.
18. A method of mastering and replicating holograms, the method comprising:
a) providing a laser apparatus for forming a first recording beam in a first direction and a second recording beams in a second direction; N substrates each containing a first HPDLC mixture; a holography photopolymer; a copy holographic substrate containing a second HPDLC mixture; a HWP; and a linear polarizer;
b) said first and second beams interfering within each said first HPDLC mixture to form a first hologram in each said substrate;
c) stacking in sequence the linear polarizer, HWP and first holograms 1-N onto a second holographic photopolymer;
d) illuminating external surface of said holograms 1-N with light of a first polarization in said first direction;
e) said first holograms 1-N diffracting said light into zero order light in said first direction and diffracted light in said second direction;
f) said HWF rotating the incident light polarization through ninety degrees into a second polarization;
g) said polarizer removing residual first polarization light;
h) said first direction light and said second direction light interfering in said holographic photopolymer to form a second hologram;
i) placing said second hologram in contact with said copy holographic substrate;
j) illuminating external surface of said second hologram with light of said second polarization in said first direction;
k) said second hologram diffracting said light into zero order light in said first direction and diffracted light in said second direction; and
l) said diffracted and first order interfering in said copy holographic substrate to form a third hologram.
19. The method of claim 18 wherein said steps d) to l) are repeated for a plurality of different said first and second directions, wherein said first and second directions are limited by the diffraction efficiency angular bandwidth of said first hologram.
20. The method of claim 18 wherein said first polarization is P-polarization and said second polarization is S-polarization.