Patent Grant
7643400
The field of the present disclosure relates to optical encoding of data. In particular, distributed diffractive structures (i.e. sets of diffractive elements) are formed in or on an optical medium for encoding the data.
Optical recording media in the form of compact disks (CDs), digital versatile discs or digital video discs (DVDs), and more advanced format optical discs play an important role in the distribution of software, data, music, video, or other content. Such discs typically include a data layer wherein localized micron- or sub-micron-scale marks (typically recessed pits, raised bumps, index or density variations, or other suitable marks) are optically or mechanically written, which is overlaid with a substantially transparent protective layer. Upon readout, a reading laser beam is typically focused through the transparent layer to a spot of a size similar to the size of the data marks when it reaches the data layer, and a portion of the reading beam is redirected by the data mark (usually back-reflected). Upon entering the transparent protective layer, the reading laser spot size is typically substantially larger, i.e. many times the size of data marks of the data layer (tens or hundreds of microns or more). The larger size of the reading laser spot as it enters the transparent protective layer reduces the effect of dust, scratches, nicks, or other imperfections or irregularities on the exterior surface of the disc. The light back-reflected from the data layer is detected and monitored for variations as the disk spins and the focused reading laser spot sweeps across the data marks and areas of the disc between the data marks. Variations in the detected, back-reflected optical signal arise from differences between the back-reflected reading laser beam reflected from the data marks and from areas between the data marks. Such differences may be differences of back-reflected power or intensity, back-reflected beam size or geometry, or other selected property of the back-reflected beam.
An exemplary geometry of a single data layer 100 and its protective transparent overcoat layer 102 are shown in
The data marks 101 are shown as bumps (from the read side) in
Various embodiments, implementations, and adaptations of optical waveguides, diffractive element sets, or distributed diffractive structures are disclosed in:
Application Ser. No. 11/376,714 is hereby incorporated by reference as if fully set forth herein. Application Ser. No. 11/376,714 and many of the other references listed above are indicative of the state of the art for forming diffractive elements. Some of these cited references describe diffractive elements formed in a one- or two-dimensional optical waveguide, wherein the input or output optical signal propagates in the waveguide. Some of these cited references describe diffractive elements forming surface gratings, wherein both input and output optical signals propagate as diffraction-guided optical beams. For one or more of the references cited hereinabove, it may be the case that the devices, structures, embodiments, implementations, adaptations, procedures, or techniques disclosed therein may be employed, within the scope of the present disclosure or appended claims, for optical encoding of data.
An optical data storage medium comprises an optical medium with multiple data marks. Each data mark is arranged for modifying a portion of an optical reading beam incident thereon. At least one of the data marks is a delocalized data mark comprising a set of multiple diffractive elements collectively arranged for modifying a portion of the optical reading beam incident thereon. A method for recording data on an optical data storage medium comprises forming on or in the optical medium multiple data marks encoding the recorded data, including the at least one delocalized data mark. A method for reading an optical data storage medium comprises: successively illuminating with the optical reading beam the multiple data marks; sensing variations among the respective portions of the optical reading beam modified by the multiple data marks; and decoding from the sensed variations data encoded by the multiple data marks.
Objects and advantages pertaining to optical encoding of data using distributed diffractive structures may become apparent upon referring to the exemplary embodiments illustrated in the drawings and disclosed in the following written description and/or claims.
The embodiments shown in the Figures are exemplary, and should not be construed as limiting the scope of the present disclosure and/or appended claims.
Oval-like structures that may appear in various of the Figure showing diffractive element sets are artifacts of the printing/display method, and are not part of the depicted diffractive element set.
An example of a suitable distributed diffractive structure 204 is schematically shown in
In one example, the diffractive element set 204 of
The back diffracted light from the distributed diffractive structure 204 (i.e. the delocalized data mark) of data layer 206 may be employed to produce detected back-reflected reading laser power level fluctuations that may be interpreted by the disc reader decoding hardware or software as data bits encoded in the usual way with localized data marks 201. Distributed diffractive structures 204 may thus provide an additional functional data layer 206; the disc reader may react as if a data bit were encoded as the localized virtual data mark 205 in data layer 200 even though the physical back-reflecting mechanism is a delocalized data mark 204 in data layer 206 at a different surficial or interfacial layer. A given disc may include both data layers 200 and 206, or may include only data layer 206. In a modification of this arrangement shown in
Localized data marks 201 and delocalized data marks 204 have been described as modifying the intensity of a back-reflected portion of reading-laser beam 203, with the read data encoded in the detected intensity fluctuations. Other implementations of localized data marks 201 and delocalized data marks 204 may be employed which reflect, refract, redirect, attenuate, or otherwise modify at least a portion of reading-laser beam 203, with the read data encoded in the detected fluctuations of the portion of the reading-laser beam thus modified.
In contrast to a localized data mark 301 in data layer 300 (
A focused-spot-laser-based disc writer or burner is typically designed to generate localized marks of particular character on a disc's data layer, and the form of these marks typically resembles dots or dashes extending along the scanning or reading direction on the disc. A virtual data mark 405 can be generated by a distributed diffractive structure 404 (i.e. a delocalized data mark) having non-standard properties or spatial shape or extent. In the schematic illustrations of
Diffractive element sets (i.e. delocalized data marks) corresponding to point-like or extended virtual data marks may be stamped, molded, embossed, etched, or otherwise formed on a top or interfacial surface of a transparent protective layer of an optical disc. Such delocalized data marks maybe used to encode data that may be reproduced (typically point-like virtual data marks), or that may not be readily reproduced (typically extended, e.g. radial, virtual data marks), by a focused-spot-laser-based disc writer. A point-like virtual data mark may be characterized as a localized mark of a size, in a dimension perpendicular to a scanning or reading direction on the disc, similar to that of a focused spot of a reading laser beam in a typical disc reader (i.e. marks of micron-scale width). An extended virtual data mark may be characterized as a localized mark many times the size of the focused spot of the reading laser in the dimension perpendicular to the scanning or reading direction on the disc (i.e. marks many microns wide).
If virtual data marks are to be placed in close proximity so that the corresponding distributed diffractive structures overlap, the diffractive elements may be arranged according to the teachings of various of the references cited hereinabove. For example, the diffractive elements depicted in
As disclosed in various of the references cited hereinabove, the curvilinear shape of the diffractive element contours may be determined by a variety of standard optical imaging system design tools or via calculated interference of simulated design optical beams. Simple curves (e.g. conic sections) may be employed as approximations of the fully optimized contours. A variety of suitable arrangements and adaptations for distributed diffractive structures are described in the cited references, and may be employed for implementing delocalized data marks according to the present disclosure.
In one example, design of distributed diffractive structures resulting in specific virtual data marks may be formulated as follows: At the wavelength of interest (presumably the reading laser wavelength), a mathematically-simulated design input optical field exhibiting spatial and spectral properties of the desired input optical signal beam (the reading beam) is computationally interfered with a mathematically-simulated design output optical field exhibiting spatial and spectral properties of the desired output optical beam (the detected beam). Diffractive elements spanning the region over which the simulated interference pattern exists diffractively route part of the input beam into the output beam. The input and output beams are stipulated to pass through schematic ports on entry or exit. The ports may be defined by spatial location, positional wavefront, beam direction, etc. “Mathematically-simulated” may denote an optical signal simulated analytically or numerically, while “computation” may denote analytical computation or numerical computation. The input and output fields (denoted by subscripts 1 and 2, respectively) may be given by the real part of:
where Si is a spatial mode field amplitude distribution, Ti is a temporal envelope, ωi is the optical frequency, ki is the modal wavevector spatial distribution, and ∂ki/∂ωi is the inverse of the group velocity. Note that Si and ki are related in a manner that satisfies Maxwell's equations, while ωi, ki, and ∂ki/∂ωi are related by the dispersion properties of the medium in which the signals propagate. In general the product of Si and Ti may be normalized in any suitable way. If the optical signals are continuous-wave (cw), then Ti is constant for both signals (assume Ti=1). In a first computational step for such continuous-wave optical signals with ω1≅ω2, an optical interference pattern between the two optical signal fields is calculated as:
where Δk≡k2−k1 and φ≡Arg(S1S2*) (all functions of position). Designs for various types of diffractive element sets (i.e., various types of delocalized data marks or corresponding virtual data marks) may be derived from the interference pattern in several ways. In many examples (but not all), the first two terms of Eq. 2 are discarded, and a diffractive element design is derived from the third term of Eq. 2 (referred to as the interferogram, which physically spans the diffractive transformation region).
For the specific case of two interfering fields, the interferogram may be decomposed into three factors: a first magnitude factor |S1(x)|, which spatially varies in proportion to the magnitude of the simulated design input optical field; a second magnitude factor |S2(x)|, which spatially varies in proportion to the magnitude of the simulated design output optical field; and a phase factor cos(Δk·x+φ), which depends on the phase difference between the simulated design input and output optical fields and which typically varies spatially on a relatively rapid scale. The product |S1(x)∥S2(x)| may be referred to as the interferogram intensity function, while cos(Δk·x+φ) may be referred to as the interferogram phase function. In many instances only the interferogram phase function is employed for designing a diffractive element set, while in other instances the interferogram intensity function or one of the individual magnitude factors may be employed as well. It is understood that the mathematical expression given for simulated design input and output fields is only one possible expression for such fields and others may be used as well. In all cases, an interference pattern may be calculated, which may be decomposed into terms analogous to those given above. Any suitable mathematical expressions for simulated design optical beams or the resulting interference pattern or interferogram shall fall within the scope of the present disclosure. In the calculation of surficial diffractive structures, it is the intersection of the full three-dimensional interference pattern 110 (in the case that the input and output beams are diffraction-guided beams) with the surface of substrate 120 that forms the basis of design.
Optical fields used for interference pattern generation may be realizable by physical sources, however, the present disclosure also encompasses use of simulated design fields that are merely theoretical and may or may not be conveniently obtainable with actual light sources or in the waveguide geometries of interest. Moreover, when using actual optical signals to generate an interference pattern, it is not possible to drop the first two terms of Eq. 2 to isolate the interferogram, as is possible when using simulated optical signals. Exemplary embodiments shown and described herein may include the use of only two simulated design fields to generate the interference pattern. More generally, three or more simulated optical fields maybe employed for forming an interference pattern and for designing diffractive element sets, and such use of three or more simulated design optical fields shall fall within the scope of the present disclosure or appended claims. Such multi-beam-interference-designed distributed optical structures may be useful for coupling multiple input signals to a single output beam, a single input signal to multiple output beams (i.e. an optical splitter), or multiple inputs each to one or more outputs.
A design for a diffractive element set may be derived from the interferogram as it intersects the design surface of interest. A diffractive element set on a substrate (flat, as is most lithographically convenient, or curved) may be regarded as a two-dimensional spatial distribution of optical-field reflection strength, which may also be referred to as a diffractive strength distribution. The diffractive strength distribution is derived computationally from the interferogram by a well-defined mapping of the value of the interferogram (either as originally generated from the simulated fields or suitably modified thereafter) at a given position to an optical field reflection coefficient value at that position. The diffractive strength distribution may be realized physically in various ways, many of which are described in the various references cited hereinabove. Typically, a diffractive element set comprising the diffractive strength distribution is fabricated in the form of a two-dimensional surface relief structure. Such a distribution may be fabricated in various ways, e.g. by etching, molding, embossing, stamping, or otherwise forming suitably shaped trenches, which may or may not be coated with a reflective material such as a single layer of metal or dielectric. The surface relief structure may be formed on the top surface of the transparent protective layer of the disc, or may be formed at an interfacial surface within the protective layer (i.e. the surface relief structure may be overcoated with a dielectric layer sufficiently thick to fill or partially fill surface features resulting in a robust nearly flat final surface). Phase extremes on transmission or reflection may be on the order of π to 2π or may span any other suitable range. In the reflective case, the device may also be overcoated with a protective layer after reflection enhancing layer(s) are applied or even if no enhancing layer is applied and back diffracted signal strength is tied to the index differential between the substrate material and the overcoating material. It may be desirable in some cases to fill diffractive relief structures with a material such as a polymer similar to that used elsewhere in the transparent protective layer of the disc so that disassembly to analyze the diffractive pattern encoded is difficult or intractable.
When designing a distributed diffractive structure corresponding to an extended virtual data mark (as in
For purposes of the present disclosure and appended claims, the conjunction “or” is to be construed inclusively (e.g., “a dog or a cat” would be interpreted as “a dog, or a cat, or both”; e.g., “a dog, a cat, or a mouse” would be interpreted as “a dog, or a cat, or a mouse, or any two, or all three”), unless: i) it is explicitly stated otherwise, e.g., by use of “either . . . or”, “only one of . . . ”, or similar language; or ii) two or more of the listed alternatives are mutually exclusive within the particular context, in which case “or” would encompass only those combinations involving non-mutually-exclusive alternatives. It is intended that equivalents of the disclosed exemplary embodiments and methods shall fall within the scope of the present disclosure and/or appended claims. It is intended that the disclosed exemplary embodiments and methods, and equivalents thereof, may be modified while remaining within the scope of the present disclosure or appended claims.
This application claims benefit of U.S. provisional App. No. 60/665,635 filed Mar. 24, 2005, said provisional application being hereby incorporated by reference as if fully set forth herein.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3995937 | Baues et al. | Dec 1976 | A |
| 4006967 | Kenan et al. | Feb 1977 | A |
| 4140362 | Tien | Feb 1979 | A |
| 4387955 | Ludman et al. | Jun 1983 | A |
| 4440468 | Auracher et al. | Apr 1984 | A |
| 4660934 | Akiba et al. | Apr 1987 | A |
| 4740951 | Lizet et al. | Apr 1988 | A |
| 4743083 | Schimpe | May 1988 | A |
| 4746186 | Nicia | May 1988 | A |
| 4773063 | Hunsperger et al. | Sep 1988 | A |
| 4786133 | Gidon et al. | Nov 1988 | A |
| 4803696 | Pepper et al. | Feb 1989 | A |
| 4824193 | Maeda et al. | Apr 1989 | A |
| 4834474 | George et al. | May 1989 | A |
| 4846552 | Veldkamp et al. | Jul 1989 | A |
| 4852960 | Alferness et al. | Aug 1989 | A |
| 4923271 | Henry et al. | May 1990 | A |
| 4938553 | Maerz et al. | Jul 1990 | A |
| 5040864 | Hong | Aug 1991 | A |
| 5107359 | Ohuchida | Apr 1992 | A |
| 5165104 | Weverka | Nov 1992 | A |
| 5195161 | Adar et al. | Mar 1993 | A |
| 5357591 | Jiang et al. | Oct 1994 | A |
| 5450511 | Dragone | Sep 1995 | A |
| 5768450 | Bhagavatula | Jun 1998 | A |
| 5812318 | Babbitt et al. | Sep 1998 | A |
| 5830622 | Canning et al. | Nov 1998 | A |
| 6011884 | Dueck et al. | Jan 2000 | A |
| 6011885 | Dempewolf et al. | Jan 2000 | A |
| 6137933 | Hunter et al. | Oct 2000 | A |
| 6144480 | Li et al. | Nov 2000 | A |
| 6169613 | Amitai et al. | Jan 2001 | B1 |
| 6169614 | Whitcomb et al. | Jan 2001 | B1 |
| 6285813 | Schultz et al. | Sep 2001 | B1 |
| 6323970 | Popovich | Nov 2001 | B1 |
| 6473232 | Ogawa | Oct 2002 | B2 |
| 6553162 | Okayama | Apr 2003 | B1 |
| 6678429 | Mossberg et al. | Jan 2004 | B2 |
| 6702897 | Cullen et al. | Mar 2004 | B2 |
| 6768834 | Gruhlke | Jul 2004 | B1 |
| 6823115 | Greiner et al. | Nov 2004 | B2 |
| 6829417 | Greiner et al. | Dec 2004 | B2 |
| 6859318 | Mossberg | Feb 2005 | B1 |
| 6879441 | Mossberg | Apr 2005 | B1 |
| 6961491 | Greiner et al. | Nov 2005 | B2 |
| 6965464 | Mossberg | Nov 2005 | B2 |
| 6965716 | Greiner et al. | Nov 2005 | B2 |
| 6985656 | Iazikov et al. | Jan 2006 | B2 |
| 6987911 | Mossberg et al. | Jan 2006 | B2 |
| 6990276 | Brice et al. | Jan 2006 | B2 |
| 6993223 | Greiner et al. | Jan 2006 | B2 |
| 7009743 | Mossberg | Mar 2006 | B2 |
| 7016569 | Mule et al. | Mar 2006 | B2 |
| 7054517 | Mossberg et al. | May 2006 | B2 |
| 7062128 | Mossberg | Jun 2006 | B2 |
| 20030011833 | Yankov et al. | Jan 2003 | A1 |
| 20030039444 | Mossberg et al. | Feb 2003 | A1 |
| 20030117677 | Mossberg | Jun 2003 | A1 |
| 20040076374 | Greiner et al. | Apr 2004 | A1 |
| 20040131360 | Iazikov et al. | Jul 2004 | A1 |
| 20040170356 | Iazikov et al. | Sep 2004 | A1 |
| 20040179779 | Greiner et al. | Sep 2004 | A1 |
| 20040208466 | Mossberg et al. | Oct 2004 | A1 |
| 20040258356 | Brice et al. | Dec 2004 | A1 |
| 20050018951 | Mossberg et al. | Jan 2005 | A1 |
| 20050078912 | Iazikov et al. | Apr 2005 | A1 |
| 20050135744 | Greiner et al. | Jun 2005 | A1 |
| 20050135745 | Greiner et al. | Jun 2005 | A1 |
| 20050135747 | Greiner et al. | Jun 2005 | A1 |
| 20050152011 | Mossberg | Jul 2005 | A1 |
| 20050163425 | Greiner et al. | Jul 2005 | A1 |
| 20060023280 | Mossberg | Feb 2006 | A1 |
| 20060139712 | Mossberg | Jun 2006 | A1 |
| Number | Date | Country |
|---|---|---|
| 0 310 438 | Apr 1989 | EP |
| 2 168 215 | Jun 1986 | GB |
| WO-9935523 | Jul 1999 | WO |
| WO-9956159 | Nov 1999 | WO |
| WO 02-075411 | Sep 2002 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 60665635 | Mar 2005 | US |
