Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
1999-01-05
2003-07-08
Huber, Paul W. (Department: 2753)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S120000
Reexamination Certificate
active
06590852
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally concerns devices, methods, imaging systems and media for radiatively recording (writing) and radiatively reading digital data within the three-dimensional volume of optical media, principally optical disks.
The present invention particularly concerns a (i) two-photon (two-beam) writing method, and single-photon (single-beam) readout method, using a (ii) doubly-telecentric afocal imaging system for the (iii) massively parallel recording (writing) and (iv) reading of digital data within the three-dimensional volume of an optical medium, preferably a rotating optical disk containing a photoactive chemical.
The present invention still more particularly concerns a digital video/versatile disk (“DVD”), compact disk (“CD”) any kind of optical disk (generically “CDs”) in which digital data storage is three-dimensional (3-D), thus a “3-D CD”.
Key words to the present invention include: optical memory; three-dimensional memory; volume memory; two-photon memory; multilayer imaging; depth transfer objective (“DTO”); DTO with a non-immersed detector; DTO with an immersed detector; DTO with aberration correction; Non-1:1 DTO imaging systems; doubly telecentric imaging; afocal imaging; 4-f imaging configurations; three-dimensional optical or compact disks (“3-D CDs”); and three-dimensional Digital Video Disks or Digital Versatile Disks (“3-D DVDs”).
2. Description of the Prior Art
2.1 General Background
Information processing applications once in the realm of supercomputing (e.g., 3-D visualization, virtual reality, data mining) are now moving to the desktop and even to mobile computing platforms. This rapid evolution of the information age has led to an explosive growth in the demand for high-capacity/high-performance secondary storage. Optical storage has been a candidate to meet this demand for some time. The optical disk, most particularly the compact disk (CD) and the newer Digital Video Disk (DVD) (sometimes called Digital Versatile Disk), are successful forms of inexpensive mass digital data storage. Although optical storage has greatly evolved, so also has the magnetic, Winchester, disk evolved greatly. Moreover, magnetic recording is still rapidly evolving, including by new exploitation of the giant magnetorestrictive effect.
The strengths of optical recording and recording media—large storage capacities and low cost—will likely ensure the perpetuation of this method and media into the foreseeable future. However, an even larger role for optical recording, and media, could be foreseen if, while preserving and even enhancing its present strengths, optical recording was to draw closer to or, preferably, even exceed the performance of magnetic recording in any of (i) gross capacity, (ii) cost per bit stored, (iii) seek, or latency, time, (iv) sustained data transfer rate for both reading and writing, and (v) reusability, and longevity. At the present time (circa 1998) many things differ between optical and magnetic storage. The weights, sizes and power consumption of optical and magnetic disk drives are slightly different. One or another media can, in one form or another, store more (or less) than forms of the other media. Optical disks have generally had, until recently, similar or greater capacity per disk platter than magnetic disks. However, the tiny size of the heads of magnetic disks permits many disk platters—typically 14 to 16 in present-day 49 Gbyte capacity drives—to be stacked on one spindle with a head on each side of each disk platter, thus greatly increasing the overall capacity of a magnetic disk drive over an optical disk drive. On the other hand, optical disks have typically offered lower cost for high capacity, easy removability, and long archival lifetimes.
Data transfer rates are commensurate for magnetic and for optical disks. However, latency times to access data on a spinning magnetic disk are presently superior to those of an optical disk. Additionally, those generally more expensive forms of optical disk that can be written at all can generally be written only but much slower than can magnetic disks, and often for only but a limited number of times.
The present invention will soon be seen, by effectively “stacking” optical disk platters, to greatly change many of these previous relationships of cost, speed and latency. However, antecedent activities to the present invention are first discussed.
To meet the demand for high-performance optical digital data storage, there are two main trends apparent in present-day (circa 1998) research and development. Volumetric storage and data channel parallelism together are the key routes to achieving the capacities and transfer rates needed in future military and commercial applications. Both of these techniques require the development of novel parallel optical pick-up heads. See K. Kayanuma, T. Iwanaga, H. Inada, K. Okanoue, R. Katayama, K. Yoshihara, Y. Yamanaka, M. Tsunekane, O. Okada, “
High track density magneto
-
optical recording using crosstalk canceler
,” Proc. SPIE 1316, 35 (1990). See also T. Maeda, H. Sugiyama, A. Saitou, K. Wakabayashi, H. Miyamoto, and H. Awan, “
High
-
density recording by two
-
dimensional signal processing
,” Proc. SPIE 2514,70(1995). See also S. Gopalaswamy and B. V. K. V. Kumar, “
Multichannel decision feedback equalizer for high track density in optical recording
,” Opt Eng. 35,2386 (1996).
Recent developments in optical storage also include the evolution of CD-ROM technology to volumetric systems such as the 2-layer digital versatile disk (DVD) standard. The present invention will be seen to extend this concept to a technology enabling the recording and reading of disks having hundreds or thousands of layers, potentially leading to more than a 100 times increase in capacity. See F. B. McCormick, I. Cokgor, S. C. Esener, A. S. Dvornikov, and P. M. Rentrepis, “
Two
-
photon absorption
-
based
3-
D optical memories
,” in High Density Data Recording and Retrieval Technologies, Ted. A. Schwartz; Martin Francis, Editors, Proc. SPIE 2604,23-32(1996). See also I. Cokgor, P. B. McCormick, A. S. Dvornikov, M. M. Wang, N. Kim, K. Coblentz; S. C. Esener, P. M. Rentrepis, “
Multilayer disk recording using
2-
photon absorption and the numerical simulation of the recording process
,” in Optical Data Storage '97, 1997 OSA Technical Digest Series (Optical Society of America, Washington, DC, 1996).
2.2 Two-Photon Optical Processes
One embodiment of the optical storage in accordance with the present invention will be seen to rely on recording bits in a volume by process of two-photon absorption (i.e., “3-D 2-P”). A spot is written in the volume of a molded organic polymer only at points of temporal and spatial intersection of two beams collectively having sufficient photon energies—beam one carrying information (i.e., at 1064 nm) and the other intersecting so as to specify location (i.e., at 532 nm)—so as to change the optical property of a photochemical at the region of intersection, and nowhere else. The simultaneous absorption of photons from both beams results in a photochemical change in the active molecules doped into the polymer, which changes the absorption and fluorescence spectra of the material (though changes in refractive index, electrical characteristics, etc., may also be obtained with appropriately engineered dopant molecules).
The recorded bits are read by fluorescence when excited by single green photons absorbed within the written spot volume(s). By intersecting a sheet of light with a 2-D page of data bits, lines (vectors) or planes of data marks may be both written and, at other times, read, in parallel. Using this method, the assignee of the present invention—Call/Recall Corporation—has demonstrated multiple image storage in read only memory (“ROM”) configuration in a portable player unit. The results indicate no crosstalk between layers and excellent stability of the written bits at room temperature. As many as 100 layers have been stored in an 8 mm thick cube. See M. M. Wang, S. E. Esener,
Call/Recall Inc.
Fuess & Davidenas
Huber Paul W.
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