Multicolor holographic replication by masking
A multicolor hologram (e.g., a two-color hologram) is replicated (copied) into a photosensitive layer by masking to produce a copy (replicate) of the hologram in a manner such that the copy is an accurate and true replication of the hologram (e.g., master hologram), and the copy is characterized to possess a high brightness level and color fidelity comparable to that of the multicolor hologram that was replicated. Both flood and scan modes can be employed in the replication.
1. A method for replicating a volume reflection two-color master hologram comprising, in sequence as listed below:
a) providing a photosensitive layer having a side and an opposing side;
b) placing the side of the photosensitive layer in contact with or proximate to the master hologram;
c) placing a first mask in contact with or proximate to the opposing side of the photosensitive layer masking at least one area of the photosensitive layer;
d) exposing the photosensitive layer through the first mask with coherent actinic radiation of a first wavelength λ 1 resulting in a first wavelength exposed layer;
e) removing the first mask; and
f) exposing the first wavelength exposed layer with coherent actinic radiation of a second wavelength λ 2 resulting in a first and second wavelength exposed layer, wherein the first and second wavelength exposed layer is a replicate of the volume reflection two-color master hologram.
2. The method of claim 1 wherein after exposing the first mask to the coherent actinic radiation, the first mask is replaced with a second mask, prior to f) being executed.
3. The method of claim 2 wherein the second mask is chosen such that it will effectively block actinic radiation during the second exposure from reaching areas of the first wavelength exposed layer that were previously exposed during the first exposure.
4. The method of claim 1 wherein coherent actinic radiation of the first wavelength λ 1 and coherent actinic radiation of the second wavelength λ 2 are within a visible region of the electromagnetic spectrum.
5. The method of claim 4 wherein coherent actinic radiation of the first wavelength λ 1 and coherent actinic radiation of the second wavelength λ 2 are independently selected to correspond to light from the group consisting of red light, blue light, and green light with the proviso that light of the first wavelength and light of the second wavelength correspond to different colors.
6. The method of claim 1 wherein coherent actinic radiation of the first wavelength λ 1 or coherent actinic radiation of the second wavelength λ 2 corresponds to blue light and wherein at least one of the first wavelength exposed layer and the first and second wavelength exposed layer is color-tuned such that the replicate of the two-color master hologram plays back in a green region of visible light.
7. The method of claim 1 wherein coherent actinic radiation of the first wavelength λ 1 or coherent actinic radiation of the second wavelength λ 2 corresponds to green light and wherein at least one of the first wavelength exposed layer and the first and second wavelength exposed layer is color-tuned such that the replicate of the two-color master hologram plays back in a red region of visible light.
8. The method of claim 1 wherein the photosensitive layer is a photopolymer.
9. The method of claim 8 wherein the photopolymer is a holographic recording film.
10. The method of claim 1 wherein the exposing steps d) and f) are done in a flood exposure mode.
11. The method of claim 1 wherein the exposing steps d) and f) are done in a scan exposure mode with a moving beam of coherent actinic radiation.
12. The method of claim 1 wherein the absolute value of the first wavelength λ 1 minus the second wavelength λ 2 is at least 7 nm.
13. The method of claim 1 wherein the placing of the side of the photosensitive layer is such that the side of the photosensitive layer is in contact with the master hologram.
14. The method of claim 1 wherein the placing of the first mask in c) is such that the first mask is in contact with the opposing side of the photosensitive layer.