Holographic data-storage medium Number:7,151,623 from the United States Patent and Trademark Office (PTO) owispatent In an example holographic data storage medium, which has a polymer film which serves as a storage layer and can be changed locally by heating, the polymer film is set up as a top layer of the data storage medium. Arranged underneath the polymer film is an absorber layer which has an absorber dye. The absorber dye is set up to at least partly absorb a write beam serving to put information in and to discharge the heat produced in the process at least partly locally to the polymer film. In an advantageous refinement of the example data storage medium, there is an adhesive layer underneath the absorber layer and a partly transparent reflective layer between the polymer film and the absorber layer.<H Holographic, storage, Holographic, dat, 7151623.html, Patent, pto, 7151623

Title: Holographic data-storage medium

Abstract: In an example holographic data storage medium, which has a polymer film which serves as a storage layer and can be changed locally by heating, the polymer film is set up as a top layer of the data storage medium. Arranged underneath the polymer film is an absorber layer which has an absorber dye. The absorber dye is set up to at least partly absorb a write beam serving to put information in and to discharge the heat produced in the process at least partly locally to the polymer film. In an advantageous refinement of the example data storage medium, there is an adhesive layer underneath the absorber layer and a partly transparent reflective layer between the polymer film and the absorber layer.

Patent Number: 7,151,623 Issued on 12/19/2006 to Leiber, et al.

Inventors: Leiber; Jorn (Hamburg, DE), Blazejewski; Anna (Hamburg, DE), Noehte; Steffen (Weinheim, DE), Stadler; Stefan (Hamburg, DE), Dietrich; Christoph (Heidelberg, DE), Gerspach; Matthias (Dossenheim, DE)
Assignee: Tesa Scribos GmbH (Heidelberg, DE)

Appl. No.: 10/480,817

Filed: February 25, 2002

PCT Filed: February 25, 2002

PCT No.: PCT/EP02/01951

371(c)(1),(2),(4) Date: December 15, 2003

PCT Pub. No.: WO02/103689

PCT Pub. Date: December 27, 2002

Foreign Application Priority Data


Jun 15, 2001 [DE]			101 28 902

Current U.S. Class: 359/3 ; 359/1; 359/22; 359/6; 430/1

Current International Class: G03H 1/02 (20060101)

Field of Search: 359/3,1,6,9,22 430/1,2

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Primary Examiner: Assaf; Fayez G.
Attorney, Agent or Firm: Nixon & Vanderhye, PC

Claims

What is claimed is:

1. A holographic data storage medium, comprising a self-supporting polymer film which is set up as a storage layer, which can be changed locally by heating and which is set up as a top layer of the data storage medium, and comprising an absorber layer which is arranged underneath the polymer film and has an absorber dye which is set up to at least partly absorb a write beam serving to write information and to discharge the heat produced by absorbing the write beam at least partly locally to the polymer film, wherein the holographic data storage medium further comprises a partly transparent reflective layer arranged between the storage layer and the absorber layer.

2. The holographic data storage medium as claimed in claim 1, further comprising an adhesive layer arranged underneath the absorber layer.

3. The holographic data storage medium as claimed in claim 1, wherein the reflective layer has a thickness in the range from 1 nm to 50 nm.

4. The holographic data storage medium as claimed in claim 1, wherein the reflective layer comprises aluminum.

5. The holographic data storage medium as claimed in claim 1, wherein the self-supporting polymer film is oriented.

6. The holographic data storage medium as claimed in claim 5 wherein the self-supporting polymer film is biaxially oriented.

7. The holographic data storage medium as claimed in claim 1, wherein the self-supporting polymer film comprises a material which is selected from the following group: polypropylene, polyvinylchloride, polyester, polyethylene terephthalate, polyethylene naphthalate, polymethylpentene, polyimide.

8. The holographic data storage medium as claimed in claim 1, wherein the absorber layer comprises a binder.

9. The holographic data storage medium as claimed in claim 1, wherein the refractive index of the self-supporting polymer film can be changed locally by heating, it being possible for optical phase information to be stored via the local optical path length in the self-supporting polymer film.

10. The holographic data storage medium as claimed in claim 1, wherein the interface structure of the self-supporting polymer film can be changed locally by heating, it being possible for holographic information to be stored via the local interface structure of the self-supporting polymer film.

11. The holographic data storage medium as claimed in claim 1, wherein the absorber dye is set up such that its optical properties can be changed locally when it absorbs a write beam serving to write information.

12. The holographic data storage medium as claimed in claim 1, further comprising stored holographic information.

13. Use of a data storage medium comprising a self-supporting polymer film which is set up as a storage layer, can be changed locally by heating and which is set up as a top layer of the data storage medium, and comprising an absorber layer which is arranged underneath the self-supporting polymer film and has an absorber dye which is set up to at least partly absorb a write beam serving to write information and to discharge the heat produced by absorbing the write beam at least partly locally to the self-supporting polymer film, as a holographic data storage medium, wherein the data storage medium further comprises a partly transparent reflective layer arranged between the storage layer and the absorber layer.

14. The use as claimed in claim 13, wherein the data storage medium has the features of the holographic data storage medium as claimed in claim 2.

15. The use as claimed in claim 13, wherein the refractive index of the self-supporting polymer film can be changed locally by heating, it being possible for optical phase information to be stored via the local optical path length in the self-supporting polymer film and the self-supporting polymer film is transilluminated in transmission when reading out information.

16. The use as claimed in claim 13, wherein the interface structure of the self-supporting polymer film can be changed locally by heating, it being possible for holographic information to be stored via the local interface structure of the self-supporting polymer film.

17. The use as claimed in claim 16, wherein the holographic information is stored via the local interface structure of the self-supporting polymer film to the absorber layer.

18. The use as claimed in claim 13, wherein the absorber dye is set up such that its optical properties can be changed locally when it absorbs a write beam serving to write information.

19. A method of writing information into a holographic data storage medium comprising a self-supporting polymer film which is set up as a storage layer, which can be changed locally by heating and which is set up as a top layer of the data storage medium, and comprising an absorber layer which is arranged underneath the self-supporting polymer film and has an absorber dye which is set up to at least partly absorb a write beam serving to write information and to discharge the heat produced by absorbing the write beam at least partly locally to the self-supporting polymer film, the data storage medium further comprising a partly transparent reflective layer arranged between the storage layer and the absorber layer, the method comprising calculating holographic information contained in a hologram of a stored object as a two-dimensional array, aiming a write beam from a writing device at one or both of the self-supporting polymer film and the absorber layer of the data storage medium, and driving the write beam of the writing device in accordance with the two-dimensional array such that the local properties of the self-supporting polymer film are set in accordance with the holographic information.

20. The method as claimed in claim 19, wherein the write beam is aimed at the holographic data storage medium from the side of the top layer.

21. The method as claimed in claim 19, wherein the holographic information is stored in the form of pits of predefined size.

22. The method as claimed in claim 21, wherein the holographic information is stored in a pit in a binary encoded form.

23. The method as claimed in claim 21, wherein the holographic information is stored in a pit in continuously encoded form, the local properties of the self-supporting polymer film in the pit being set in accordance with a value from a predefined value range.

24. A method of reading information out of a holographic data storage medium comprising a self-supporting polymer film which is set up as a storage layer, which can be changed locally by heating and which is set up as a top layer of the data storage medium, and comprising an absorber layer which is arranged underneath the self-supporting polymer film and has an absorber dye which is set up to at least partly absorb a write beam serving to write information and to discharge the heat produced by absorbing the write beam at least partly locally to the self-supporting polymer film, the data storage medium further comprising a partly transparent reflective layer arranged between the storage layer and the absorber layer, the method comprising aiming light at a large area of the storage layer of the data storage medium and reconstructing the information contained in the irradiated region as a holographic image which is registered at a distance from the data storage medium.

25. The method according to claim 24, wherein the light comprises coherent light.

Description

This application is the U.S. national phase of international application PCT/EP02/01951, filed in English on 25 Feb. 2002, which designated the U.S. PCT/EP02/01951 claims priority to DE Application No. 101 28 902.2 filed 15 Jun. 2001. The entire contents of these applications are incorporated herein by reference.

BACKGROUND AND SUMMARY

The invention relates to a holographic data storage medium which, for example, can be used for storing pictorial data such as photographs, logos, text and so on but also for the storage of other data.

Contained in a hologram, distributed over the area of the hologram, is optical phase information about an object, from which, when irradiated with light, and in particular coherent light from a laser, an image of the object can be reconstructed. Holograms are used in many and various ways in technology, for example in the form of largely forgery-proof identifiers. Identifiers of this type will be found, for example, on credit cards or check cards; as what are known as white light holograms, even when illuminated with natural light, they show a three-dimensional image of the object depicted. Photographically produced holograms are widespread, as are embossed holograms, in which a relief structure is embossed into the surface of a material, at which the light used to reproduce the object is scattered in accordance with the phase information stored in the hologram, so that the reconstructed image of the object is produced by interference effects.

WO 00/17864 describes a data storage medium with an optical information carrier, which contains a polymer film set up as a storage layer. The polymer film consists, for example, of biaxially oriented polypropylene. In the data storage medium previously disclosed, the polymer film is wound spirally in a plurality of layers onto a core, there being an adhesive layer in each case between adjacent layers. Information can be written into the data storage medium by the polymer film being heated locally with the aid of a write beam from a data drive, as a result of which the refractive index of the polymer film and the reflective capacity at the interface of the polymer film are changed locally. This effect can be amplified by an absorber dye which is added to the adhesive layers, which at least partly absorbs the write beam and discharges the heat produced in the process locally to the polymer film. With the aid of a read beam in the data drive, the changes in the polymer film can be registered, since the read beam is locally reflected more or less intensely at the interface of the polymer film, depending on the information written in. By focusing the write beam or read beam, information can be written specifically into a preselected position on the information carrier or read out from it.

It is an object of the invention to provide a holographic data storage medium which is inexpensive, has wide areas of application and is largely insensitive to external influences.

The holographic data storage medium according to the invention has a polymer film which is set up as a storage layer and which can be changed locally by heating. This polymer film is set up as a top layer of the data storage medium. Arranged underneath the polymer film is an absorber layer, which has an absorber dye which is set up to at least partly absorb a write beam serving to put information in and to discharge the heat produced in the process at least partly locally to the polymer film. The polymer film set up as a storage layer is preferably arranged in one layer in the data storage medium (preferably in a substantially flat arrangement), that is to say, for example, not wound up in a plurality of layers in spiral form.

Since the polymer film is set up as a top layer of the data storage medium, it can serve as the exposed outer side of the data storage medium and protects the generally relatively sensitive absorber layer located underneath. Furthermore, the changes in the polymer film which are effected by heating and using which holographic information is stored are primarily localized in the vicinity of the absorber layer, as explained in more detail further below. Therefore, this region of the polymer film provided with the stored information is likewise located in a protected zone. Undesired influences on the exposed outer side, such as scratches, therefore generally do not have any further effect and, above all, do not lead to a loss of data or to faults when putting information into the data storage medium.

The holographic data storage medium according to the invention is simply constructed, since an additional protective device can generally be dispensed with, and can therefore be produced inexpensivel