Static information storage and retrieval – Systems using particular element – Molecular or atomic
Reexamination Certificate
2002-03-26
2004-03-30
Hoang, Huan (Department: 2818)
Static information storage and retrieval
Systems using particular element
Molecular or atomic
C365S106000, C365S215000
Reexamination Certificate
active
06714437
ABSTRACT:
The invention relates to a method of writing information in a data storage medium comprising an optical information medium, and also a data storage medium.
DE 298 16 802 describes a data storage medium comprising an optical information medium which contains a polymer carrier in the form of a polymer film. Cited as a material for the polymer film is polymethyl methacrylate, and also a polymer film which is marketed by Beiersdorf AG under the designation “crystal-clear Tesafilm”, which has biaxially oriented polypropylene. In the case of this data storage medium, the polymer film is wound spirally in a plurality of plies on to a winding core, there being an adhesion layer in each case between adjacent plies. Information can be written in the data storage medium by the polymer film being heated locally with the aid of a write beam from a data drive. This is because the energy stored in the polypropylene as a result of biaxial stretching during film production is liberated again during the local heating by the write beam (short laser pulses), the polymer film material contracting locally and therefore changing its refractive index at those locations exposed to the write beam. This leads to a local change in the reflective power (the reflectivity) at the interface of the polymer film, which can be registered with the aid of a read beam in the data drive. By means of focusing the write beam or read beam, information can be written specifically into a preselected ply of the information medium or can be read out from it. The winding core can be optically transparent and, at its center, have a recess, which is used to accommodate the writing and reading device of a data drive. In this case, the writing and reading device is moved relative to the data storage medium, while the data storage medium is stationary, so that the data storage medium need not be balanced to take account of rapid rotational motion.
In order to convert the output of the write beam effectively into heat and, in this way, to achieve a local change in the refractive index of the order of magnitude of 0.2, which is sufficient to store information, an absorber, which is contained in the adhesion layer, is used in the data storage medium previously disclosed. However, the absorber is disadvantageous, since it also attenuates the read beam. This has a disruptive effect, in particular in the case of multi-ply systems like the data storage medium previously disclosed. In addition, it is desirable for the achievable change in the refractive index to be still greater, in order to obtain a stronger signal from the read beam.
It is an object of the invention to provide improved options for a data storage medium comprising an optical information medium which has a polymer carrier.
This object is achieved by a method of writing information in a data storage medium comprising an optical information medium having the features of claim 1, and also by data storage media having the features of claims 11 and 12. Advantageous refinements of the invention emerge from the dependent claims.
The method according to the invention is used to write information in a data storage medium comprising an optical information medium which has a polymer carrier. In this case, atoms and/or molecules that change the refractive index are introduced into the polymer carrier, at individual locations associated with information units, as a function of the information to be entered.
The atoms and/or molecules that change the refractive index and are located in the area of the polymer carrier envisaged for the storage of an information unit effect a change in the refractive index. The result of this is a local change in the reflective power (the reflectivity) at the interface or at the interfaces of the polymer carrier with an adjacent medium. This can be registered with the aid of a read beam which, at the location considered, is reflected as a function of the information entered, that is to say the local content of atoms and/or molecules that change the refractive index. As a result of introducing the atoms and/or molecules that change the refractive index into the polymer carrier, the optical properties of the polymer carrier can be changed effectively and in a defined way. For example, local changes in refractive index of the order of magnitude of 0.2 and more may be achieved, which is sufficient for the data entered to be read out, for example with the aid of a read beam. A suitable polymer carrier is, for example, a polymer film.
In the polymer carrier, the information units are formed by changing the optical properties in an area having a preferred size of less than 1 &mgr;m. Here, the information can be stored in a binary form, that is to say at the location of an information unit, the local reflectivity assumes only two values. In other words, if the reflectivity is above a defined threshold value, a “1”, for example, is stored at the considered location on the information medium and if it lies below this threshold value or below a different, lower threshold value, it is accordingly a “0”. However, it is also conceivable to store the information in a plurality of gray stages. This is possible if the optical properties of the polymer carrier, at the location of an information unit, can be changed in a specific way by means of defined setting of the refractive index without saturation being reached in the process.
In an advantageous refinement of the method according to the invention, the atoms and/or molecules that change the refractive index are diffused into the polymer carrier, to be specific, preferably by means of local heating. In this case, the atoms and/or molecules that change the refractive index can originate from a layer which is applied to the polymer carrier. In order to introduce the atoms and/or molecules that change the refractive index into the polymer carrier at the location of an information unit, the layer or the polymer carrier adjacent thereto is heated in the relevant area, so that the atoms and/or molecules that change the refractive index can migrate out of the layer and diffuse into the polymer carrier. Since no atoms and/or molecules that change the refractive index diffuse into the polymer carrier from adjacent areas which are not heated, in this way a two-dimensional distribution of atoms and/or molecules that change the refractive index can be arranged in the polymer carrier, said distribution corresponding to the pattern of the information to be entered.
If the rest of the layer from which the atoms and/or molecules that change the refractive index originate, is removed from the polymer carrier after the information has been entered, the signals registered by a read beam are particularly clear, since the atoms and/or molecules that change the refractive index are virtually all located in the polymer carrier. It is not therefore possible for any disruptive influence to originate from atoms and/or molecules which change the refractive index in the rest of the layer.
After the rest of the layer has been removed, however, no new or further information can be written in the data storage medium. However, it is not absolutely necessary to remove the rest of the layer from the polymer carrier after information has been entered. This is because the atoms and/or molecules that change the refractive index have, in the molecular surroundings of the polymer carrier, different optical properties than in the layer in which they are generally stored in a higher concentration and, depending on the embodiment, in a matrix. However, a part is also played by the interface between the polymer carrier and the interface of the polymer carrier opposite the layer, whose reflectivity is predominantly influenced by the atoms and/or molecules that change the refractive index and have diffused into the polymer carrier, and not by the rest of the layer located on the other side of the polymer carrier.
One other possible way of introducing the atoms and/or molecules that change the refractive index into the polymer carrier is to implant them into t
Leiber Jörn
Mussig Bernhard
Stadler Stefan
Hoang Huan
Nixon & Vanderhye PC
Tesa AG
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