DE10122341A1 - Method for producing a data carrier with holographic memory for fast data storage - Google Patents

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

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

In general, the usual ones also apply to optical data processing Processing principles when writing and reading data, such as that of the magnetic storage methods are known. These also show essentials Parameters regarding processing speed and data density which it it is important to optimize. Another criticism for fast data processing high  Amount of data is the question of environmental conditions when writing or Storage possibility and the 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 / pm 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. The book Holographic Data Storage, HJ Coufal, D. Psaltis, GT Sincerbox, Springer 2000 , provides an overview 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 ). They have an increased sensitivity to daylight, ie they polymerize in a fraction of a second in the daylight spectrum and cannot be described further afterwards.

The material must therefore usually be in the dark or under orthochromatic Light (<680 nm) can be processed and described. It is then fixed and is then stable in daylight.

The disadvantage of the holographic data storage method known to date is that when the data carrier is manufactured, the data is immediately saved, what is undesirable for certain data carriers.

For example, if you want to design a data carrier as a chip card, so you have to produce it and then personalize it. The state of the Technology no suggestion how this could be done.

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

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

The process enables the data carrier to be initially produced in large numbers to manufacture it at a much later date after manufacture personalize. The personalization of the holographic data storage means personalized data.

It is therefore essential that initially a large number of blank slides of the data carrier can be manufactured and that these blanks into one any time described with data, d. H. can be personalized. In general, there are two types of data processing. The the first is the non-rewritable processing of the data carrier and  the second in the at least partially rewritable data processing. at however, both require protection of the storage medium from light.

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

• 1. The photosensitive material must be inserted into the card so that it during production and before writing data (personalization) is not exposed in the daylight spectrum, in order to ensure that the To get memory. For this, covers of the storage material are through Scratch or pill-off labels or the use of appropriate filters intended.
• 2. Unlike other holographic memories with photosensitive The card is intended to be used with the memory under the ISO standard conditions 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 HDS offers two decisive advantages over the above-mentioned optical surface storage:

• 1. Since it is a volume storage, high storage densities (greater than 100 bits / µm ² ) can be achieved. 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 means that the data are stored in the structure of the storage medium at different levels.
• 2. The holographic data storage takes place in parallel (bit pattern for bit pattern) and not serial (bit by bit) as with conventional optical memories. This has the consequence that by combining one accordingly powerful laser for reading the memory with a sensitive electronic camera very high data transfer rates of over 1 GBit / s can reach. Conventional optical storage is due to the serial data transfers in the range of 10 Mbyte / s.

There are also cases in which a fixation of the data is not desired in order to To ensure rewritability. Special filter layers, z. B. dielectric, narrow-band filters are used, the writing with the laser wavelength (e.g. 532 nm), but the majority of the Block out the daylight spectrum, i.e. so-called daylight filters.

Therefore the idea of the invention also lies in being very sensitive, however non-rewritable materials such as photopolymers 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.

Therefore, the invention provides that a photosensitive, holographic Memory material is inserted into the card so that it is after the Card production can be described (personalized) and the card itself can then be used in the daylight spectrum. Such a procedure is not only for holographic data storage, but also for Personalized holograms can be used on cards.

The photosensitive material, e.g. B. a photopolymer or a crystal 1 × 1 × 0.05 cm is introduced under orthochromatic light into a laterally opaque recess 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 a opaque label (scratch or pill off) covered on the surface. It is also conceivable, special narrowband interference on the crystal surface or the Vapor overlay film that block a large part of the daylight spectrum. In front The scratch or pill off label is then removed from the personalization of the cards.

The subject matter of the present invention results not only from the Subject of the individual claims, but also from the combination of individual claims among themselves.

All information disclosed in the documents, including the summary and features, in particular the spatial depicted in the drawings Education are claimed as essential to the invention, insofar as they are used individually or in Combination are new compared to the prior art.

In the following, the invention is explained using only one embodiment illustrative drawings explained in more detail. Here go from the drawings and their description further features and advantages of the invention Invention.

Show it:

Fig. 1 schematically shows a plan view of a data carrier in the form of a plastic card;

Fig. 2 section through the disk of Fig. 1;

FIG. 3 shows the transmission curve of a cover for covering the photosensitive storage material;

FIG. 4 shows an embodiment of a filter curve modified compared to FIG. 3.

In Fig. 1, the top view of a data carrier with insertion of a holographic memory is shown schematically.

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 × 1 × 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.

In FIG. 2, the structure of the data carrier 11 of FIG. 1 in greater 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.

To the extent that transmission holograms are to be used, the should Recess be formed continuously.  

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 must be covered from both sides by a corresponding opaque cover 5 , 6 according to the invention.

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 9 a, 9 b, a signal beam and a reference beam. When reading, the material is only irradiated with the reference beam 9 b, 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 used, such as. B. film-like covers that can be peeled off  or other mechanically or chemically removable covers. For this also include thermally removable covers.

In FIGS. 3 and 4 are shown as a further embodiment of such covers 5, 6 so-called dielectric filter. 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 Filters, which is characterized by the fact that this layer structure only for one Laser exposure in the range of e.g. B. 532.2 nm is permeable, while in other area is not permeable. This ensures that z. Legs unwanted exposure in the visible area is avoided and only this cover is transparent to the reading holographic detector.

So that is because of the narrow-band, dielectric filter layer Filtered out the daylight spectrum and instead only ensured that the enrolling and the reading laser can penetrate the filter layer.

In FIG. 4 a filter curve of another interference filter is provided as a further exemplary embodiment shown, which is not intended for the exposure of the holographic material of a photopolymer, but for the exposure of a photorefractive crystal, whose composition has already been mentioned already in the general part of the description.

With UV excitation, for example in the range of 350-420 nm, this is Crystal first for the recording as a holographic data storage "unlocked" and is then for a corresponding holographic storage open for a period of time.  

During this period, the storage can take place, the reading and Write operation takes place for example at 532 nm, while the activation of the Crystals 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 × 54 × 0.76 mm it is now possible for the first time in the recess 4 with a volume of z. B. 1 × 1 × 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 mentioned filter layers are so narrow-banded that they are only for the corresponding enrolling and reading lasers are transparent, d. H. a Allow UV activation at certain wavelengths.

This is the first time that there is the possibility of a normal daylight exposed plastic card with a holographic memory unlimited use without fear of deletion or one To fear impairment of the functions.

Due to the sensitive materials used, there is an extraordinary high write rate of 1 GBit per second, which is not the case with previous materials was possible. 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 - used, where strict attention must be paid to the exclusion of daylight.

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

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 embodiment according to FIG. 3, the covers 5 , 6 can be left at the place of their attachment because they are designed as a filter layer, and in the embodiment according to FIG. 4 the covers 5 , 6 also remain at the place of their attachment because they are are accordingly also designed to be 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.

Otherwise, 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 designed 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".

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

drawing Legend

1

Overplate

2

Overplate

3

core layer

4

recess

5

cover

6

cover

7

storage material

8th

face

9

beam of light

9

a,

9

b

10

beam of light

11

disk

Claims (18)

1. A method for producing a data carrier with holographic storage material for fast data storage, characterized in that
that the storage material ( 7 ) is introduced into the data carrier ( 11 ) without unintentionally writing to or exposing it, and
that the storage material ( 7 ) is provided with a cover ( 5 , 6 ) 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 <20 cm ² / J. 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 re-hitable 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.