WO2002091371A2

WO2002091371A2 - Method for producing a data carrier comprising a holographic memory for fast data storage

Info

Publication number: WO2002091371A2
Application number: PCT/DE2002/001467
Authority: WO
Inventors: Frank Bormann; Dirk Fischer; Matthias Schumacher; Frank Kappe
Original assignee: Orga Kartensysteme Gmbh
Priority date: 2001-05-09
Filing date: 2002-04-22
Publication date: 2002-11-14
Also published as: WO2002091371A3; DE10122341A1

Abstract

The invention relates to a method for producing a data carrier with holographic storage material for fast data storage, characterised in that the storage material is introduced into the card, with unintentionally describing it or illuminating it and that the storage material is subsequently provided with a covering so that is it protected in a sustainable manner from unintentional description. According to the invention, fast, holographic storage of a large amount of data occurs in a data carrier, particularly a chip card, whereby a data transfer rate of 1 GBit/s is obtained on a surface of 1 cm<2> in the storage material of said data support.

Description

Method for producing a data carrier With holographic memory for fast data storage

The present invention relates to a method for producing a data carrier with holographic memory for fast data storage, according to the preamble of claim 1. Furthermore, the invention describes a method for fast holographic data storage of large amounts of data in a data carrier, in particular a chip card, with holographic storage material ,

In principle, the usual processing principles for writing and reading data also apply to optical data processing, as is known from magnetic storage methods. These also show essential parameters regarding processing speed and data density, which have to be optimized. Another criticism for fast data processing high Amounts of data are the question of environmental conditions when writing or the storage options and storage conditions of blank data carriers and also the data resistance of data carriers described.

So far, optical surface memories are known which have a data density of 1 to a maximum of 10 bits / μm ² . These are known as CDs and DVDs.

If you are looking for another way to optically store data, the holographic method is a good choice. This is characterized by a high data density> 100 bit / μm ² and high data transfer rates due to the parallel data transfer. Because holographic data carriers are photosensitive polymers, there is the problem, however, that the data carriers must not simply be exposed to daylight, since these would otherwise be fixed in their structure and would therefore no longer be writable. It is currently only possible to write to data carriers immediately after manufacture and then to fix them. An essential parameter is therefore the data transfer rate. For example, photoaddressable polymers PAP are known as materials, but they have a low sensitivity. However, this low sensitivity has the effect that the write speed is extremely slow, which has a negative effect especially for larger amounts of data. For example, it takes around 14 hours to store one Gbit / cm ² , which results in a correspondingly restricted area of application.

With the data transfer rate, one must also differentiate between the write rate and the read rate. The reading rate is determined by the dynamic range of the storage material, which indicates the diffraction efficiency with which a single data page (bit pattern) can be reconstructed. The write rate of holographic data storage (HDS) is essentially limited by the sensitivity of the storage material. In the book Holographic Data Storage, HJ Coufal, D. Psaltis, GT Sincerbox, Springer 2000, an overview can be found on page 106, Table 1. The materials with the highest sensitivity (> 20 cm ² / J) are the photopolymers (e.g. Dupont HRF-150, Aprilis ULSH 500). You have an elevated Daylight sensitivity, ie they polymerize in a fraction of a second in the daylight spectrum and cannot be described further afterwards.

As a rule, the material must be processed and written in the dark or under orthochromatic light (<680 nm). It is then fixed and is then stable in daylight.

A disadvantage of the holographic data storage method known hitherto is that when the data carrier is manufactured, the data are immediately stored, which is undesirable for certain data carriers.

For example, if you want to design a data carrier as a chip card, you first have to produce it and then personalize it. The prior art does not provide any suggestions as to how this could be done.

The invention is therefore based on the object of specifying a method for producing a data carrier, in particular a chip card, with holographic memory for fast data storage.

The problem is solved by the technical teaching of claim 1.

The method makes it possible to initially manufacture the data carrier in large numbers in order to personalize it at a much later time after production. Personalization here means the assignment of personalized data to the holographic data memory.

It is therefore essential that a large number of blank discs of the data carrier can first be produced and that these discs are written with data at any time, i. H. can be personalized.

In general, there are two types of data processing. The first is the non-rewritable processing of the disk and the second in the at least partially rewritable data processing. In both cases, however, it is necessary to protect the storage medium from light.

When installing a photosensitive material in a data carrier (e.g. 5 chip card), the following problems arise, which are solved by this invention.

1. The photosensitive material must be inserted into the card in such a way that it is not exposed in the daylight spectrum during production and before writing with data (personalization) in order to maintain the writeability of the U memory. The storage material is covered by scratch or pill off

Labels or the use of appropriate filters provided.

2. In contrast to other holographic memories with photosensitive material, the card with the memory is supposed to meet the ISO standard conditions for optical

Memory cards are operated, d. that is, the relevant ISO / IEC standards 11694-3 and 10373-5 for chip cards are observed.

It is therefore usually necessary to fix the data after writing.

The holographic data storage (HDS) offers two decisive advantages over the optical surface storage mentioned at the beginning:

1. Since it is a volume storage, high storage densities can be

(greater than 100 bit / μm ² ). In comparison, a conventional optical surface memory (CD, DVD) offers a storage density of 1 to a maximum of 10 bits / μm ² .

Volume storage is understood to mean that the data are stored in the structure of the storage medium at different levels. , The holographic data storage takes place in parallel (bit pattern for bit pattern) and not serial (bit for bit), as in conventional optical memories. As a result, very high data transfer rates of over 1 GBit / s can be achieved by combining an appropriately powerful laser to read the memory with a sensitive electronic camera. Conventional optical memories are in the range of 10 Mbyte / s due to the serial data transfer.

There are also cases in which it is not desirable to fix the data in order to ensure that it can be rewritten. Special filter layers, e.g. B. dielectric, narrow-band filters are used, which allow writing with the laser wavelength (z. B. 532 nm), but block the majority of the daylight spectrum, so-called daylight filter.

Therefore, the idea of the invention is to switch to very sensitive but non-rewritable materials such as photopolymers in order to achieve short writing times.

Another idea is to switch to very sensitive (1 cm ² / J) photorefractive crystals. These have the advantage of being rewritable, combined with the fast write times, but they place increased demands on the structure and use of filter layers.

The invention therefore provides that a photosensitive, holographic storage material is introduced into the card in such a way that it can be written (personalized) after the card has been produced and the card can then be used in the daylight spectrum. Such a method can be used not only for holographic data storage, but also for personalized holograms on cards.

The photosensitive material, e.g. B. a photopolymer or a crystal 1 x 1 x 0.05 cm is this under orthochromatic light in a side opaque recess made in the card body. The card body is covered from both sides with an approx. 100 μm overlay film with high optical quality, e.g. B. PMMA covered.

The two end faces of the storage material are covered with an opaque label (scratch or pill off) on the surface. It is also conceivable to vaporize special narrow-band interference onto the crystal surface or the overlay film, which block a large part of the daylight spectrum. The scratch or pill off label is then removed before the cards are personalized.

The subject matter of the present invention results not only from the subject matter of the individual patent claims, but also from the combination of the individual patent claims with one another.

All of the information and features disclosed in the documents, including the summary, in particular the spatial design shown in the drawings are claimed to be essential to the invention, insofar as they are new to the prior art, individually or in combination.

In the following, the invention will be explained in more detail with reference to drawings showing only one embodiment. Here, from the drawings and their description, further features and advantages of the invention that are essential to the invention emerge.

Show it:

Figure 1: shows a schematic plan view of a data carrier in the form of a plastic card;

Figure 2: Section through the data carrier of Figure 1; FIG. 3: the transmission curve of a cover for covering the photosensitive storage material;

Figure 4: an embodiment of a filter curve modified compared to Figure 3.

FIG. 1 schematically shows the top view of a data carrier with a holographic memory.

At least one recess 4, in which a holographic data memory is arranged, is arranged in a data carrier 11, which is generally designed as a plastic card. This data memory is drawn out as a separate block on the right in FIG. 1 and has, for example, the dimensions of 1 x 1 x 0.05 cm. According to the general description, it consists of a photopolymer.

Instead of using a photopolymer, however, other materials can be used, such as. B. double doped LiNbO ₃ : Fe: Mg.

FIG. 2 shows the structure of the data carrier 11 according to FIG. 1 in more detail.

In the area of a core layer 3, a recess 4, which penetrates the core layer 3, is preferably arranged. However, the invention is not limited to this because the recess 4 can also have a closed bottom surface on at least one side, but this bottom surface must be transparent for the corresponding exposure.

If transmission holograms are to be used, the recess should be continuous. In another embodiment, however, provision can also be made for it to be stored in the reflection mode, it then being sufficient for the recess 4 to be designed as a blind hole or pocket recess.

In any case, FIG. 2 shows the storage in transmission mode, which presupposes that the recess is continuous and, according to the invention, must be covered from both sides by a corresponding opaque cover 5, 6.

Likewise, in the proposed transmission mode, FIG. 2 assumes that the side walls (end faces 8) of the recess are also opaque in order to prevent light from entering the recess 4 from the side.

The core layer 3 is covered on the upper side by an overlay layer 1 and likewise on the opposite side by an overlay layer 2 of the same design.

The overlay layers 1, 2 should therefore be transparent, at least in the region of the recess 4, for the corresponding exposure spectrum which is required in order to holographically expose the storage material 7 introduced into the recess 4.

When writing, the material is exposed by two light beams 9a, 9b, a signal beam and a reference beam. When reading, the material is only irradiated with the reference beam 9b, the data being output in the form of an output beam 10.

FIG. 2 shows that the covers 5, 6 are opaque and are preferably designed as a peel-off label.

In addition to training as a peel-off label, other covers can also be used, such as. B. film-like covers that can be peeled off or other mechanically or chemically removable covers. This also includes thermally removable covers.

In FIGS. 3 and 4, so-called dielectric filters are indicated as a further embodiment for such covers 5, 6. These embodiments assume that the covers 5, 6 remain at the location of their attachment, but are designed as a filter film or filter layer and have dielectric properties.

It is a multiple layer structure of such a dielectric filter, which is characterized in that this layer structure only for a laser exposure in the range of z. B. 532.2 nm is permeable, while it is not permeable in the other region. This ensures that z. B. there is no undesired exposure in the visible range and only this cover is permeable to the reading holographic detector.

This means that the narrow-band, dielectric filter layer filters out the daylight spectrum and instead only ensures that the enrolling and the reading laser can penetrate the filter layer.

FIG. 4 shows, as a further exemplary embodiment, a filter curve of another interference filter that is not used for the exposure of the holographic one

Material is determined from a photopolymer, but for the exposure of a photorefractive crystal, the composition of which has already been mentioned in the general part of the description.

With UV excitation, for example in the range of 350-420 nm, this crystal is first "activated" for recording as a holographic data memory and is then open for a corresponding holographic storage for a certain period of time. During this period, the storage can take place, the read and write operation taking place, for example, at 532 nm, while the activation of the crystal takes place in the range of 350-420 nm.

The covers 5, 6 must then ensure that the violet spectrum (350-420 nm) is reliably faded out in order, for example, B. to prevent permanent activation of the holographic crystal in the range of 350-420 nm.

The cover layers 5, 6 must accordingly be designed as filter layers to a narrow-band interference filter with high transmission at z. B. 365 or 380 nm, so that a targeted activation by an Hg vapor lamp (365 nm) or a GaNb ₃ diode (380 nm) is possible.

The advantage of the invention is that, for example, map dimensions of z. B. 84 x 54 x 0.76 mm it is now possible for the first time in the recess 4 with a volume of z. B. 1 x 1 x 0.05 cm a data storage with a storage density of z. B. 1 GBit per cm ² . So far this has not been possible.

It is important that the card can be used in the daylight spectrum and that the filter layers mentioned are so narrow-banded that they are only permeable to the corresponding enrolling and reading laser. H. enable UV activation at certain wavelengths.

This makes it possible for the first time to use a plastic card with a holographic memory that is exposed to normal daylight without restriction, without having to fear corresponding deletion actions or fear that the functions will be impaired.

Due to the sensitive materials used, there is an extraordinarily high write rate of 1 GBit per second, which was not possible with the previous materials. Just that mentioned in the description instructions and for the

Data storage suitable photopolymer is only in the absence of daylight in appropriate data carriers - especially in computer drives - where strict attention must be paid to the exclusion of daylight.

Herein lies the invention, which now provides to insert such a memory into a plastic card and to use this plastic card under daylight conditions and to be able to write and read the memory even under daylight conditions.

In the exemplary embodiment according to FIG. 2, there is the advantage that the covers 5, 6 can then be permanently removed when the data is written into the storage material 7 for the first time, because the storage material 7 is fixed by the writing and the data storage is therefore unchangeable.

In the exemplary embodiment according to FIG. 3, the covers 5, 6 can be left in place because they are designed as a filter layer, and in the exemplary embodiment according to FIG. 4 the covers 5, 6 also remain in place where they are attached, because they also correspond accordingly are appropriately permeable for UV excitation and also for write-in and read-out operations.

The advantage of using the material in the exemplary embodiment according to FIG. 4 is that a rewritable memory can be used, which is not the case with the previously described exemplary embodiments.

For the rest, the exemplary embodiments according to FIGS. 3 and 4 are not limited to the attachment of outer covers 5, 6 on the top and bottom of corresponding overlay layers 1, 2. It can also be provided that when these covers 5, 6 are formed as filter layers, these filter layers are either incorporated in the structure of the overlay layers 1, 2, are located below or above the overlay layers or are also introduced directly into the core layer. In the case of introduction into the core layer 3, these covers 5, 6 are then applied directly to the recess 4 as a “cover”.

You can also in the area of the recess 4 directly on the storage material stored in the recess 4! 7 be applied. This is technically easy to implement for the polished surface of the crystal.

drawing Legend

Overplate

core layer

recess

cover

storage material

face

Light beam 9a, 9b

beam of light

disk

Claims

claims

1. A method for producing a data carrier with holographic storage material for fast data storage, characterized in that the storage material (7) is introduced into the data carrier (11) without inadvertently writing to or exposing it, and that the storage material (7) with a Cover (5, 6) is provided so that it is permanently protected against unintentional writing.

2. The method as claimed in claim 1, characterized in that at least parts of the data to be stored are written at an arbitrarily definable time after the storage material (7) has been introduced into the data carrier (11), in particular personalization takes place at any time.

3. The method according to claims 1 or 2, characterized in that at least partial areas of the storage material (7) in the data carrier (11) are rewritable.

4. The method according to any one of claims 1 or 2, characterized in that the storage material (7) in the data carrier (11) is not rewritable.

5. The method according to any one of claims 1 to 4, characterized in that the storage material (7) is introduced into a recess (4) of the data carrier.

6. The method according to any one of claims 1 to 5, characterized in that the recess (4) of the data carrier (11) is continuously penetrating the data carrier.

7. The method according to any one of claims 1 to 5, characterized in that the recess (4) of the data carrier (11) is not continuously penetrating the data carrier.

8. The method according to any one of claims 1 to 7, characterized in that the storage material (7) consists of photorefractive crystals with a sensitivity of> 1 cm ² / J.

9. The method according to any one of claims 1 to 7, characterized in that the storage material (7) consists of very sensitive photopolymers with sensitivity> 20 cm ² ΛJ.

10. The method according to any one of claims 1 to 9, characterized in that the storage material (7) is provided with covers (5, 6) which contain materials that are opaque to daylight.

11. The method according to any one of claims 1 to 10, characterized in that the covers (5, 6) consist of a filter which is opaque to daylight and which is transparent for only certain wavelengths for reading and writing the holograms.

12. The method according to any one of claims 1 to 11, characterized in that the filter (5, 6) for the wavelengths 365 and 380 nm is transparent.

13. The method according to any one of claims 1 to 12, characterized in that the covers (5, 6) consist of a vapor-deposited coating.

14. The method according to any one of claims 1 to 13, characterized in that the covers (5, 6) consist of a removable coating.

15. The method according to any one of claims 1 to 13, characterized in that the covers (5, 6) consist of removable stickers.

16. The method according to any one of claims 1 to 15, characterized in that the covers (5, 6) are thermally removable.

17. The method according to any one of claims 1 to 15, characterized in that the covers (5, 6) are chemically removable.

18. The method according to any one of claims 1 to 15, characterized in that the covers (5, 6) are mechanically removable.