Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Patent
1997-11-20
2000-09-05
Neyzari, Ali
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
369284, 430 19, G11B 700
Patent
active
061153443
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention concerns a data carrying method or medium, including a fluorescent layer arranged on a substrate, wherein data carrying structures are provided in the fluorescent layer in its surface or from its surface and towards the substrate.
BACKGROUND OF INVENTION
Digital optical data storage media of the WORM type (Write Once, Read Many times) stores information written on a thin layer by means of a light pulse of high intensity, typically a strongly focused laser beam. Once data is written on to the layer, the layer cannot be returned to its original state, but it can be read many times by a weaker light beam which does not further influence the layer's physical state. Well known means in this context are thin metal film, flat glass or plastic surfaces or thin polymer film which contains a light-absorbing dye. In most cases such layers are provided between other layers, e.g. reflecting or protective layers. The layer stores information by undergoing a change under the influence of the powerful write light pulse and constitutes the actual data storage layer in the medium.
For the most part today's optical storage technology is almost exclusively based on the reflective contrast between written marks in the data storage layer or its immediate surroundings. A focused laser beam is passed along the data storage layer and changes in the intensity of the reflected laser light are recorded when the beam passes a write mark. A typical mark may be in the form of small round or elongated pits, with dimensions of between 0.5 and 7 .mu.m. Optical data storage media which are based on reflection normally employ a strongly reflecting layer, e.g. a vaporized aluminium layer in a multilayer structure where the data storage layer regulates the amount of light incident on the medium which is reflected.
Data storage media are also known which are based on transmission contrast for light which is detected after having passed through the data storage medium. In this case, the data storage layer can have a low light transmission capacity in an unknown condition and be more transparent at the write marks which are formed by the powerful write beam. Alternatively the data storage layer can be converted from transparent to opaque at the write marks.
It is also known that data storage media are under development in which the contrast is based on stimulated light emission. During the reading of data one or more light beams scan the data storage medium which reacts by emitting light of an intensity which is dependent on how the medium was treated early in the write phase. The light energy emitted results from either the release of captured electrons in a high energy state in the data storage layer or down conversion of the scanning light beam. Holographic data storage media have also been proposed, with storage of data both on volume and layers. An important contrast mechanism in this connection is light-induced alteration of the refraction index.
Data storage media may also be based on the fluorescent properties, of a data storage layer. For instance, EP-A1-503428 discloses an erasable optical recording medium comprising at least one recording layer which includes a fluorescent material and a photo-reactive bistable quencher capable of quenching the fluorescence emitted from the fluorescent material. The photo-reactive bistable quencher produces two isomers, one having an absorption wavelength spectrum which is different from the other and the one being convertible into the other by an irradiation with light. One of these bistable isomers acts as a quencher for quenching the fluorescence emitted by the fluorescent material. Particularly the photo-reactive bistable quencher is a photo-chromic compound having a quenching action. Information is digitally recorded by utilising the two bistable isomers of the photo-reactive bistable quencher. In the erased state the absorption spectrum of the photo-bistable quencher is that of the long wavelength isomer, while in the recorded state the absorption spectrum
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Gudesen Hans Gude
Nordal Per-Erik
Neyzari Ali
Opticom ASA
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