Illuminative treatment of holographic media
The present invention relates to embodiments of a process for subjecting a holographic storage medium to illuminative treatment to: (1) enhance or optimize recording of holographic data; (2) enhance or optimize reading of recorded holographic data; and/or (3) erase recorded holographic data. The present invention also relates to embodiments of a system comprising: (a) an illuminative treatment beam; (b) means for reducing the coherence of the beam and (c) means for transmitting the reduced coherence beam to cause illuminative treatment of: (1) an unrecorded portion of a holographic storage medium to provide pre-cured portions having increased ability to stably record holographic data; (2) a recorded portion of a holographic storage medium to provide a post-cured portion having reduced residual sensitivity; and/or (3) a recorded portion of a holographic storage medium having holographic data to provide an erased portion wherein at least some of the recorded holographic data is erased.
1 . A process comprising the following steps:
(a) providing a holographic storage medium having an uncured portion; and
(b) subjecting the uncured portion to illuminative pre-curing with a curing beam having reduced coherence and a substantially uniform intensity distribution to provide a pre-cured portion having increased ability to stably record holographic data.
2 . The process of claim 1 , wherein step (b) is carried out with a curing beam having the same wavelength of light as that of recording light used to subsequently record holographic data to the pre-cured portion.
3 . The process of claim 1 , wherein step (b) is carried out with a curing beam having a different wavelength of light from that of recording light used to subsequently record holographic data to the pre-cured portion.
4 . The process of claim 3 , wherein step (b) is carried out with a curing beam having a wavelength providing maximum absorption by photoactive materials present in the holographic medium.
5 . The process of claim 1 , wherein step (b) is carried out for a predetermined period.
6 . The process of claim 1 , wherein step (b) is carried out for a period of time believed to be sufficient to provide a pre-cured portion, and wherein an additional step (c) is carried out by recording one or more test holograms in the pre-cured portion to determine whether step (b) has been sufficiently carried out.
7 . The process of claim 1 , wherein step (b) is carried out so as to pre-cure substantially all of the holographic medium.
8 . The process of claim 1 , wherein step (a) is carried out by providing a holographic medium comprising a free radical photoinitiator and a polymerizable component comprising a photoactive polymerizable material that is caused to be polymerized by a free radical photoinitiator.
9 . The process of claim 1 , wherein step (b) is carried out by multi-pass curing of the uncured portion.
10 . The process of claim 1 , wherein step (b) is carried out so as to pre-cure only a selected uncured portion of the holographic medium.
11 . The process of claim 10 , wherein step (b) is carried out by moving the holographic medium relative to the curing beam while simultaneously and continuously illuminating the selected portion with the curing beam.
12 . The process of claim 11 , wherein movement of the holographic medium carried out in step (b) comprises a substantially linear translation of the holographic medium.
13 . The process of claim 11 , wherein movement of the holographic medium carried out in step (b) alternates between: (1) a substantially linear translation of the holographic medium in a first direction; and (2) a substantially linear translation of the holographic medium in a second direction which is transverse to the first direction.
14 . The process of claim 13 , wherein the first and second directions of the holographic medium are substantially orthogonal.
15 . The process of claim 11 , wherein movement of the holographic medium carried out in step (b) comprises a continuous, unidirectional rotation of the holographic medium.
16 . The process of claim 11 , wherein movement of the holographic medium carried out in step (b) alternates between: (1) continuous, unidirectional rotation of the holographic medium; and (2) a substantially linear translation of the holographic medium.
17 . The process of claim 11 , wherein movement of the holographic medium carried out in step (b) comprises simultaneously performing (1) continuous, unidirectional rotation of the holographic medium; and (2) a substantially linear translation of the holographic medium.
18 . The process of claim 10 , wherein step (b) is carried out by incrementally illuminating the selected portion with a curing beam at discrete locations to provide a selected pre-cured portion having a contiguous or nearly contiguous tiled geometry.
19 . The process of claim 10 , wherein step (b) is carried out so as to pre-cure only a selected portion of the holographic medium in which holographic data is to be recorded during a recording session.
20 . The process of claim 1 , wherein step (a) comprises providing a holographic storage medium comprising photoactive luminescent materials and wherein the degree of pre-curing during step (b) is determined by monitoring the luminescence of the luminescent materials.
21 . The process of claim 20 , wherein step (a) comprises providing a holographic storage medium comprising photoactive fluorescent materials.
22 . The process of claim 20 , wherein step (a) comprises providing a holographic storage medium comprising photoactive phosphorescent materials.
23 . The process of claim 1 , wherein step (b) is carried out with a curing beam having a coherence length which is less than the thickness of the holographic medium.
24 . The process of claim 1 , wherein step (b) is carried out while concurrently carrying out the following additional step (c) of recording holographic data in a different portion of the holographic medium.
25 . The process of claim 1 , wherein the degree of pre-curing during step (b) is determined by monitoring the transmittance of the curing beam.
26 . A system comprising:
a curing beam;
means for reducing coherence of the curing beam to provide a curing beam having reduced coherence; and
means for transmitting the reduced coherence curing beam with a substantially uniform intensity distribution to cause illuminative curing of an uncured portion of a holographic storage medium to provide pre-cured portions having increased ability to stably record holographic data.
27 . The system of claim 26 , which is part of a holographic data storage system.
28 . The system of claim 27 , wherein the curing beam is generated by a laser from the holographic data storage system.
29 . The system of claim 28 , wherein the laser is adjustable to provide a first wavelength of light for recording holographic data, and a second different wavelength of light for generating the curing beam.
30 . The system of claim 26 , which further comprises a separate non-recording light source to generate the curing beam.
31 . The system of claim 30 , wherein the separate non-recording light source is a laser.
32 . The system of claim 30 , wherein the separate non-recording light source is a light emitting diode.
33 . The system of claim 30 , which is separate from a holographic data storage system.
34 . The system of claim 30 , which is part of a holographic data storage system.
35 . The system of claim 26 , wherein the coherence reducing means comprises a diffuser.
36 . The system of claim 35 , wherein the coherence reducing means comprises means for imparting motion to the diffuser.
37 . The system of claim 26 , wherein the coherence reducing means comprises integrating rods.
38 . The system of claim 26 , wherein the curing beam is generated by a laser and wherein the coherence reducing means comprises means for modulating the electrical current to the laser generating the curing beam.
39 . The system of claim 26 , wherein the transmitting means comprises means for shaping the curing beam so as to cause illuminative pre-curing of a selected portion of the holographic medium.
40 . The system of claim 39 , wherein the shaping means shapes the curing beam to a predetermined shape.
41 . The system of claim 40 , wherein the shaping means comprises a combination of a lenslet array and a transform lens.
42 . The system of claim 26 , wherein the transmitting means comprises at the least a portion of an optical path of a holographic data storage system.
43 . The system of claim 42 , wherein the optical path comprises a reference beam optical path.
44 . The system of claim 42 , wherein the optical path comprises the data beam optical path.
45 . The system of claim 26 , wherein the transmitting means includes means for reflecting at least a portion of unabsorbed curing beam through the holographic medium to cause multi-pass pre-curing of the uncured portion.
46 . The system of claim 45 , wherein the curing beam is transmitted to one side of the holographic medium and wherein the reflecting means is positioned on the opposite of the holographic medium.
47 . The system of claim 46 , wherein the reflecting means comprises a mirror.
48 . The system of claim 47 , wherein the reflecting means comprises a parabolic mirror or the combination of one or more lenses and a mirror.