Optical: systems and elements – Holographic system or element – Copying by holographic means
Reexamination Certificate
2000-04-11
2002-12-31
Spyrou, Cassandra (Department: 2872)
Optical: systems and elements
Holographic system or element
Copying by holographic means
C359S010000, C359S022000, C359S024000
Reexamination Certificate
active
06501571
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally concerns optical data storage, coherence and statistical optics, volume holographic gratings, and holographic optical elements.
The present invention particularly concerns a volume holographic element, and the use of same for the simultaneous optical stamping of data into multiple layers of a three- dimensional bit-oriented optical medium that exhibits a suitable sensitivity threshold.
2. Description of the Prior Art
2.1 Stamping of Optical Disks
Owing to the relative economy of the medium, and the ease of reproduction, optical discs are currently (circa 2000) the preferred method for distribution of large quantities of information. Computer software, music, and video are among the most popular forms of data encoded on digital optical discs.
Unfortunately, theoretical limits in terms of the capacity of the planar, single-recorded-layer, optical disc are quickly being reached. Despite the small gains that may be made from alternative laser sources and improved coding techniques, it is becoming more and more apparent that a new storage technology will be necessary as the successor to the reflective optical disc.
There are several new optical technologies currently being investigated including multi-layer reflective media, volume holography, two-photon storage, near-field recording, and others. Although many of these technologies have shown promise as being re-writable and having very high data densities, none of these technologies have retained the one main advantage of the standard optical disc which is its ease of production.
For example, some 4.7 GB of information on a Digital Versatile Disc, or DVD, is presently (circa 2000) mechanically stamped onto each disc, permitting a fabrication line to produce discs at a rate of 1 every 12 seconds. No other advanced optical storage system currently under investigation today has exhibited a mass replication process as simple and practical as that for optical discs.
2.2 Recent Developments in Volume Optical Materials
Meanwhile, recent advances in non-linear optical materials have stimulated interest in the development of three-dimensional memory technologies. In particular, demonstrations have been made using polymeric materials that exhibit a non-linear optical response for multi-layer (volumetric) data storage. See J. H. Strickler and W. W. Webb,“Three-dimensional optical data storage in refractive media by two-photon point excitation,” Opt. Lett. 16, 1780-1782 (1991); S. Kawata and A. Toriumi,“Three-dimensional Optical Memory Using Photopolymer, Photorefractive Crystals, and Photochromic Materials,” Proc. SPIE 3109, 174-180 (1997); and M. M. Wang and S. C. Esener,“Three-dimensional optical memory in fluorescent dye-doped photopolymer,” submitted to Applied Optics (Dec. 12, 1998).
Demonstrations have been also been made of the use of polymeric materials for three-dimensional micro-component fabrication. See S. Maruo, O. Nakamura, and S. Kawata,“Three-5 dimensional microfabrication with two-photon-absorbed photopolymerization,” Opt. Lett. 22, 132-134 (1997).
A key factor which will determine whether these new technologies will become practical for the mass production of memory devices that are already recorded at the time of sale will be the speed and economy at which these devices may be fabricated.
Two possible approaches to increasing the fabrication rate are, first, to increase the sensitivity of the materials to allow high speed serial raster recording of the desired data, and, second, to attempt to record data in some degree of parallelism. The present invention is concerned with second possibility, specifically with three-dimensional data stamping, meaning the recording of data in parallel into each of multiple regions, normally planes, of a three-dimensional bit-oriented volume optical medium.
Any ability to emplace voluminous digital data in parallel, and all at the same time, within the three-dimensional volume of a optical memory, normally an optical disk, as a type of“data stamping” would be very useful in many areas. Data stamping is projected to be useful for data recording in fields including (i) entertainment, such as audio, video, and multimedia information distribution, video games; (ii) computer data storage, such as software distribution, large database, data archiving, 3D video; (iii) information processing, such as image recognition, voice recognition, relational databases; and (iv) optoelectronics, such as fiber optics, free-space optics, optical processing and communication.
Additionally, if the data stamping transpires at sufficiently fine spatial resolution, and if the process is not adversely affected when extensive spatial volumes are written entirely to one binary state or the other, then data stamping can be envisioned as a means of creating three-dimensional objects, complete with cavities and voids if any be present. The object created by three-dimensional data stamping might appear, proper materials being chosen, as if encased in glass or might actually, proper materials being chosen, become separable from a surrounding“unwritten” matrix, and usable as a“formed” object.
SUMMARY OF THE INVENTION
The present invention contemplates a new 3D optical storage technology which has the potential to replace standard optical discs as the next generation of distributable optical media. The invention is manifest in a new technique by which digital data may be optically stamped, in a process called“data stamping”, simultaneously into (i) bit-oriented (ii) multiple layers within (iii) the 3D volume of a volume optical memory, typically a (thick) disc. The virgin optical memory medium, prior to being data stamped, is typically as a continuum, and without any content or indexing (optical or otherwise) whatsoever. The data stamping “writes” the entire volume of the media simultaneously in one operation, leaving (most typically) multiple layers of data each of which layers is fully organized into addressable voxels.
Multi-layer volume optical memories, particularly in the form of optical discs, have the advantage of being able to significantly increase the data capacity of a single disc without incurring a large increase in access time. The technique of the present invention is directed to recording digital data just as quickly, cheaply and reliably as single-layer planar optical discs are recorded today (circa 2000). Components similar to those used in the technique of the present invention have been in use for many years, and have already been demonstrated to possess all the necessary performance requirements for use in the present invention.
1. A (i) Particular Holographic Element for (ii) Data Stamping (iii) A Volume Optical Memory Made From a Non-linear Optical Medium
The present invention has several parts. In aggregate, the present invention teaches a multi-step process. First, an appropriate special holographic“data stamping” element is generated. Then, second, this generated holographic data stamping element is used and re-used for the simultaneous optical data stamping of multi-layer data into the volume of a three-dimensional optical medium. Importantly, this optical medium must, and does, exhibit a suitable non-linear response—manifested as a sharp radiation sensitivity threshold—so as to permit the recording of large numbers of data bits in parallel.
Each of the processes of (i) generating the special holographic data stamping element (and the holographic element so generated), (ii) performing the optical data stamping by use of the generated holographic element, and (iii) using an appropriately non-linear three-dimensional optical medium, constitute separate parts of the present invention.
1.1 Generating a Holographic Data Stamping Element
The (i) generating of the holographic data stamping element, and the holographic data stamping element so generated, are special both for (a) how the element is generated, and (b) what the element contains. If the holographic element is to “stamp data” in each of multiple planes, then
Esener Sadik
Wang Mark
Boutsikaris Leo
Fuess & Davidenas
Spyrou Cassandra
The Regents of the University of California
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