Shift tolerant lens optimized for phase conjugating holographic systems
View Patent ↗A new type of FT lens is provided that improves phase conjugation in holographic data systems. This type of FT lens has a uniquely large isoplanatic patch. This enables relaxed assembly tolerances, asymmetric reader/writer architectures, and compensation for tilted plate aberrations in the media.
1. A holographic storage device or system comprising:
a reference beam source for generating a reference beam;
a data beam source for generating a data beam; and
an extremely isoplanatic lens through which the data beam passes prior to entering a holographic storage medium, wherein the reference beam and data beam interfere in the holographic storage medium to record one or more data pages in the holographic storage medium.
2. The holographic storage recovery device or system of claim 1 , wherein the extremely isoplanatic lens is decentered.
3. The holographic storage recovery device or system of claim 1 , wherein the extremely isoplanatic lens is on axis.
4. A method comprising the following steps:
(a) passing a data beam through an extremely isoplanatic lens to form a focused data beam; and
(b) recording one or more data pages in a holographic storage medium by interfering the focused data beam with a reference beam.
5. A holographic storage recovery device or system comprising:
a reconstruction beam source for generating a reconstruction beam that passes through a holographic storage medium to thereby form a recovered beam from one or more data pages stored in the holographic storage medium;
an extremely isoplanatic lens through which the recovered beam passes; and
a camera for detecting the recovered beam after the recovered beam has passed through the extremely isoplanatic lens.
6. The holographic storage recovery device or system of claim 3 , wherein the extremely isoplanatic lens is decentered.
7. The holographic storage recovery device or system of claim 5 , wherein the extremely isoplanatic lens is on axis.
8. A method comprising:
(a) passing a reconstruction beam through a holographic storage medium to thereby form a recovered beam from one or more data pages stored in the holographic storage medium; and
(b) detecting the recovered beam after the recovered beam has passed through an extremely isoplanatic lens.
9. The method of claim 8 , further comprising the following step:
(c) storing the one or more data pages in the holographic storage medium.
10. The method of claim 9 , wherein step (c) comprises passing a data beam and a reference beam through a storage lens and wherein the extremely isoplanatic lens has fewer lens elements than the storage lens.
11. The method of claim 9 , wherein between step (c) and step (b) the holographic storage medium undergoes a total translational shift of half a book width or less and wherein the SNR loss is half a db or less.
12. The method of claim 9 , wherein between step (c) and step (b) the holographic storage medium undergoes a total rotational shift of 20% of the system NA and wherein the SNR loss is half a db or less.
13. The method of claim 8 , wherein the extremely isoplanatic lens is decentered.
14. The method of claim 8 , wherein the extremely isoplanatic lens is on axis.
15. An article comprising:
a holographic storage medium having one or more data pages stored therein, in which the one more data pages stored are obtained by interference of a reference beam and a data beam in the holographic storage medium, wherein the data beam has passed through an extremely isoplanatic lens prior to entering the holographic storage medium, and wherein the holographic storage medium has hot spots of lesser volume and irradiance than the holographic storage medium would have if the one or more data pages were stored using a conventional, diffraction limited, on-axis FT lens.
16. The article of claim 15 , wherein the holographic storage medium has a total volume of hot spots that is about 20% to 100 times less than the holographic storage medium would have if the one or more data pages were stored using a conventional, diffraction limited, on-axis FT lens.
17. The article of claim 15 , wherein the holographic storage medium has a total volume of hot spots that is about 5 times less than the holographic storage medium would have if the one or more data pages were stored using a conventional, diffraction limited, on-axis FT lens.
18. The article of claim 15 , wherein the holographic storage medium has a total irradiance of hot spots that is about 1.5 times to 500 times less than the holographic storage medium would have if the one or more data pages were stored using a conventional, diffraction limited, on-axis FT lens.
19. The article of claim 15 , wherein the holographic storage medium has a total irradiance of hot spots that is about 15 times less than the holographic storage medium would have if the one or more data pages were stored using a conventional, diffraction limited, on-axis FT lens.
20. The holographic storage recovery device or system of claim 15 , wherein the extremely isoplanatic lens is decentered.