Dynamic information storage or retrieval – Storage medium structure – Optical track structure
Reexamination Certificate
2000-08-15
2001-06-19
Hindi, Nabil (Department: 2651)
Dynamic information storage or retrieval
Storage medium structure
Optical track structure
C369S285000, C369S278000
Reexamination Certificate
active
06249507
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field Of the Invention
This invention in general relates to the field of optical recording systems and media and, in particular, to storage media comprising optically differentiated or discriminated data sites by which means a greater resolution and storage density is attained.
2. Description of the Prior Art
Technical data relevant to the present application can be found in sources such as:
Optical Physics
, Lipson and Lipson, Cambridge University Press, 1969.
Optical Materials
, S. Musikant, Marcel Dekker, Inc., New York, 1985. P. 64-76.
Guerra, J. M., Phase Controlled Evanescent Field Systems and Methods for Optical Recording and Retrieval, U.S. Pat. No. 5,754,514, issued May 19, 1998.
Conventional optical storage media commonly use a “land and groove” configuration in which alternating data tracks are separated in height by &lgr;/6, where &lgr; is the illumination wavelength. The purpose of this height differentiation between tracks is to cause destructive interference, or cancellation, of the ringing caused by the coherent illumination, thereby allowing spacing, or track pitch, that is closer to the resolution limit of an incoherently illuminated system. However, the alternating height is usually binary, and does not allow super-resolution (i.e. track separation smaller than the resolution limit of the optical system).
Other examples of differentiated tracks or sites include the red, green, and blue color filter stripes or dot matrix such as found in color television monitors, and similar red, green, and blue color stripes in Polaroid's™ instant color slide film and Polavision™ instant movie film. In both cases, the purpose of the color stiripes was to cause selective local color change from white to black and any shade of color in between by combining one or all of the RGB color elements in various intensity combinations. However, in neither example was the intent or effect to cause super-resolution, nor means for optical data storage in the case of the former.
U.S. Pat. No. 5,910,940 issued Jun. 8, 1999, “Optical Recording Systems and Media with Integral Near-Field Optics” issued to Guerra discloses optical storage media having an integral micro-optical structure to effect higher resolution. In part, the higher resolution results from the larger system numerical aperture tht is obtained by combining the micro-optics in the medium with the drive objective optics. This larger numerical aperture allows the higher spatial frequencies contained in the evanescent, or “near-field,” to contribute to the image, thereby increasing resolution and storage density.
SUMMARY OF THE INVENTION
An optical storage media comprising optically differentiated data sites is disclosed, where the data sites are optically isolated or discriminated by additional optical elements in the optical system. The differentiated tracks may be read sequentially by a single head or in parallel wither with multiple objectives or a single objective with a multi-channel filtered detector. In near-field optical recording, tracks may be differentiated by physical height, or phase, or refractive index, such that the returning light is different for neighboring tracks. Accordingly, there is achieved optical storage density much greater than the resolution limit of an optical system by optically isolating and differentiating the active optical sites, said sites made as small as the detection limit of the optical system.
In the present application, the active optical layer comprises micro-optical properties for the increase of resolution and information storage density, primarily for use in, but not limited to, a propagating light non-flying optical data storage system. The micro-optical structures or domains in the optical media optically isolate, discriminate, and differentiate adjacent optical active sites or optical artifacts such that the detection limit, rather than the much larger resolution limit, of the optical data storage system may be fully utilized for higher storage density.
Optical visibility and detection, rather than optical resolution, serve to increase the storage density of optical data systems. Optically-differentiated sites smaller than the resolution limit of an optical system are detected, or made visible, by that system if the sites are separated by more than the resolution limit. Particles as small as 4 nanometers can be seen in normal dark-field microscopes, for example, if those particles are far enough apart. That is to say they must be separated at least by a distance which is equal to or greater than the resolution limit “d,” defined as the illumination wavelength &lgr; divided by the numerical aperture (N.A.) of the optical system:
d=&lgr;/N.A. (or &lgr;/2N.A. for oblique illumination),
Where the numerical aperture is a product of the index n of refraction in which the object to be resolved is immersed, and the sine of the half angle &thgr; subtended by the optical system at the object:
N.A.=n(sin &thgr;),
Equation (1) is the well-known resolution limit for a mictoscope as worked out first by Abbe in 1888.
The measured size of the particles will be much larger, on the order of the Airy disc for that system. Whether a particle is {fraction (1/10)} or ½ the optical system resolution, the resulting Airy discs will be equivalent in diameter to each other and to the resolution limit. However, the Airy disk for the smaller particle will be less bright. Given enough light for the required signal-to-noise, a particle much smaller than the resolution limit is visible, as long as it is isolated from the nearest particles by at least the resolution limit. Bright-field microscopes, for example, also show particles smaller than their resolution limit, as do near-field microscopes as well.
As disclosed, data tracks comprise a width much smaller than the resolution limit of the optical read/write head objective, and the tracks are spaced closer than the resolution limit of the optics as well. However, each track is differentiated by color, polarization, height, intensity, reflection, absorption, phase, refractive index, geometry (height or slope), or other parameter such that like tracks or sites are many tracks apart and separated by at least or more than the resolution limit.
For ease of illustration, color differentiation is described here, though other ways of differentiation, some mentioned above, may be preferable. Consider red, green and blue alternating optical data tracks, where the track width is ⅙ and track pitch is ⅓ the resolution limit of the objective. If a single unfiltered objective is used to read the data in white light, the tracks will not be resolved. However, adding a red filter (or providing red illumination) eliminates the green and blue tracks, and the remaining red tracks, which are separated by the resolution limit, are resolved. Similarly, inserting green and blue filters will reveal the green and blue data tracks, respectively.
“Like” data sets light up as a single channel in whole-field illumination that is keyed to the isolating optical property of that data set, somewhat like a radio tuner being tuned to a specific channel. The more discriminating the tuner, the higher the number of channels that may be fit into the receiver bandwidth, to further the analogy. If a detector array is used, and each pixel in the array is optically keyed to a discrete channel comprising an optically isolated data set, then a plurality of channels can be read in parallel.
At present the burden of resolution in an optical data storage system is borne largely by the optical read/write head, such that higher data storage density requires shorter and shorter illumination wavelengths or larger and larger numerical apertures. In the embodiments disclosed herein, the resolution burden is shifted in large degree to the medium itself, while decreasing the optical tracking and focus servo requirements on the optical drive. However, this shifting of burden to the medium can be done at little additional economic cost because of mas
Hindi Nabil
Thyfault Paul
Van Pelt & Yi LLP
LandOfFree
Information storage systems utilizing media with... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Information storage systems utilizing media with..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Information storage systems utilizing media with... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2523895