GB2428130A

GB2428130A - Photographic storage of digital information

Info

Publication number: GB2428130A
Application number: GB0514401A
Authority: GB
Inventors: Rudolf Gschwind; Lukas Rosenthaler; Peter Fornaro
Original assignee: Universitaet Basel
Current assignee: Universitaet Basel
Priority date: 2005-07-06
Filing date: 2005-07-06
Publication date: 2007-01-17
Also published as: GB0514401D0

Abstract

Disclosed is a method for long term storage of digital information. According to the present invention, the digital information, which could be a digital text data, a digital picture data, a photographical image or digital audio information, is encoded (100) into a two dimensional pattern, the recorded (110) two dimensional pattern using photographic material. The recorded photographic material is stored (120) in a classical manner. Photographic film has a very long lifetime that is many times greater than any other state-of-the-art digital storage media for long-term archival purposes. The invention relates as well to a method for recovering the two dimensional pattern stored on a photographic material into digital information and the produced photographic material. Advantageously, the photographic material could be a photographic color material.

Description

Method for long term storage of digital information

Technical field of the invention

The present invention concerns a method for long term storage of digital information according to the independent claim 1, a method for recovering the digital information according to claim 13 as well as a photographic material according to claim 19 and a computer program product according to claim 23.

Description of related art

Digital storage is usually highly dependent on a given technology. The preservation of information is necessary to ensure that content in general is not rendered useless or lost. Preservation generally includes the long-term storage of information in the form of images, records, data, documents, and the like. Many organizations actively promote the use of conventional preservation systems such as microfilm, microfiche and aperture cards for content preservation. These are most commonly used to provide long-term assurance of information storage within classical archival material.

The conventional writable compact disc (CD-R) is a nonmagnetic disc used for audio, video recording or for other data storage. Information is recorded using a laser beam to burn the microscopic pits into the surface of the disc with the information being accessed by means of a low-power laser to sense the presence or absence of the pits. The actual data carrier used in such a writable optical medium is a non-stable colour dye that decays with time. A loss of information is the consequence.

Another common medium to store digital information is the DVD-R. The technique to write data is the same used by the CD-R. A DVD can be read today but will probably be unreadable in 5 to 10 years, because it requires special technical equipment such as a DVD-reader, which will become obsolete within a short time frame. In addition the problematic aspects of the decay of the information hold too. To guaranty the longevity of digital data, periodic migration to new media types and technologies is a necessity. Migration is a time and money consuming process.

Brief summary of the invention

It is one aim to achieve long term storage of digital information without any loss of information.

It is another aim of the present invention to recover the stored digital information with technology-independent equipment in an easy manner.

It is another aim of the present invention to create means for storing the digital information in a long term fashion.

According to the invention, these aims are achieved by means of a method for long term storage of digital information, the method comprising the steps of (a) encoding the digital information into a two dimensional pattern, (b) recording the two dimensional pattern using photographic material and (c) storing the recorded photographic material.

According to the invention, this aim is achieved by means of a method for recovering digital information having the features of claim 13, by photographic material with a recorded two dimensional pattern, which can be produced by a method according to any of the claims I to 12 and by a computer program product comprising computer code portions for executing the storing method of one of the claims ito 12 and/or the recovering method of one of the claims 13 to 17 when said computer code is run by a computer.

Further advantageous embodiments of the present invention are described in the dependent claims.

Photographic film has a very long lifetime that is many times greater than any other state-of-the-art digital storage media for long-term archival purposes. By encoding the original digital data to a pattern of two-dimensional values, information can he stored on any photographic medium as an image. The two-dimensional pattern and the capability of a photographic medium to reproduce continuous densities result in a code with a higher alphabet than binary. Advantageously, even a twodimensional color pattern such as a two-dimensional color bar code could be produced. In that way, the data density can be increased by the factor of three. A photographic medium has the advantage that an appropriate optical instrument like a microscope, a digital camera or a scanner can visually see the information on it. Because it can be expected that the technical specifications of imaging devices are getting better, the presented solution is highly technology independent.

In addition, a state-of-the-art error correction code (ECC) with high redundancy will be used. For further security reasons, the digital information will be distributed in space within the two dimensional pattern. As a result, a local damage in the two dimensional pattern media such as a scratch or mark, which is by its nature confined to a local neighborhood, will affect only few adjacent bits and therefore the original bits can be fully reconstructed using the mentioned error correction algorithms.

Furthermore, the visual nature of photographic film allows the original information to be stored as actual image or written text as well, e.g. the analog image (if it is an image), metadata and the description for reading back and decoding the digital information.

In the presented solution, color photographic material such as industry standard color negative or slide film, or high-resolution color microfilm can be used as digital data storage medium. The extended lifetime of the photographic material is a major advantage regarding to archival long term storage. The high stability of microfilm reduces the need for migration to an average time of more than 100 years, which is considerably better than the magnetic archival media of today.

In addition the three dye layers of photographic film can be used to separate the digital data into three independent channels. The step of encoding the digital information into a two dimensional pattern will be adapted to the properties of the photographic color material. This process is defined as channel coding. Combining the two-dimensional nature of films with the layers of dyes can be seen as pseudo three- dimensional domain that can store data. The digital information can be compressed in a conventional manner before the step of recording takes place.

Brief description of the drawings

The invention will be better understood with the aid of the description of an embodiment given by way of example and illustrated by the figures, in which: Fig. I shows as an example of a two dimensional bar code (PDF 417); Fig. 2 illustrates the steps of the method according to the present invention; and Fig. 3 illustrates the steps of the method according to the present invention.

Detailed description of possible embodiments of the invention The present invention concerns a method for long term storage digital information. As digital information, a digital text data, a digital picture data, a photographical image or digital audio information in any known format (*. tiff, *.gjf, *.jpg, *pdf *.mp3, etc.) could be encoded and stored in the inventive way. The inventive method could be used for example in fields such as Classical Archives (Industry, Museums and Art Collections), Film industry (Long-term Preservation of Movies), Broadcasting Archives (Audio-Archives), Public Authorities and Medical Environments (X-Ray-Archives), etc. Figure 2 shows the steps of the method according to the present invention.

According to the present invention, the digital information (original domain) for which long term storage is desired is in a first step 100 encoded into a two dimensional pattern such as a two dimensional digital bar code. For the step 100 of encoding the digital information, any suitable numerical algorithm that is known in the prior art could be used. In one embodiment, the programming will take place in an object-oriented language such as C++ with objects for storing bar codes together with functions to encode and decode them. This results in a digital code using a higher alphabet than the binary codes of the digital information itself In a second step 110, the two dimensional pattern is recorded by using a photographic material (media domain). This could be done in several ways, such as printing the computed two-dimensional pattern with a laser printer and then making a photograph of the printed document. In the prior art there are also computer to plate processes in order to print the photographic material directly. The recorded photographic material is stored in step 120 in a classical manner in an archive.

In addition, during this step 100 of encoding the digital information, a state- of-the-art error correction code (FCC) with high redundancy can be used. To further enhance safety against data loss, adjacent bits within the digital information will be distributed in space within the two dimensional pattern as well. As a result, a local damage in the media domain such as a scratch or mark will affect only few adjacent bits in the original domain and therefore the original bits can be reconstructed using the error correction algorithms.

Fig. I shows by way of example a PDF4 17 two dimensional barcode in black and white. As more data is encoded, the size of the barcode can be increased in both the horizontal and vertical directions, thus maintaining a manageable shape for easy scanning. Data is encoded in both the horizontal and vertical dimensions. Bar codes are easy to compute, easy to scan, they are already standardized and therefore equipment independent. Advantageously, even a two dimensional color pattern such as a two dimensional color bar code could be produced using different primary colors and densities on the photographic medium. In this way, each element of the bar code can carry more than 2 states (multilevel coding), e.g. a 24 bits/picture element can be used.

For this purpose, color photographic material such as industry standard color negative or slide film, or high-resolution color microfilm can be used as digital data storage medium. This brings advantages for archival purposes because of extended lifetime. The high stability of microfilm reduces the need for migration to an average time of more than 100 years, which is considerably better than the magnetic archival media of today.

Photographic color material is a highly non-linear media. To allow the read- back of the digital data with simple means, the non-linearity of the recording media itself will be compensated in advance during the recording step, taking into account the properties of the film and its aging. The read-back or decoding instructions will be stored on the media or on its backside as well as the error correction description in human readable form. The digital information can be compressed before the step of recording takes place.

Furthermore, the visual nature of microfilm allows at least some of the original information to be stored as actual image or written text as well, e.g. the analog image (if ii is an image), metadata and the description for reading back and decoding the digital information.

The present invention has several advantages because of: * The reduced use of technology-dependent equipment, because a scanner is sufficient; * The decoding equipment will be a standard computer executing a simple algorithm; * The use of a visual medium allows the storing of fully accessible digital data, e. g.

the digital data representing a photographical image, to be combined together with an analogue visual image, which can be interpreted by the naked human eye, e.g. the algorithm for decoding the barcode image; * Photographic film has a very long lifetime that is many times greater than any other state-of-the-art digital storage media for long-term archival purposes; * A redundancy and error correction code together with a local distribution in space of the data bits protects the data on film against mechanical defects and natural ageing (color bleaching). Therefore, even a high degree of damage does not lead to a total loss of information. lip to a certain level of damage, the information can be fully regained. Above that level, a graceful degradation will occur.

As seen in Fig. 3, the present invention relates also to a method having the step 200 of decoding the two dimensional pattern stored on a photographic material into digital information. Thereafter, the recovered decoded digital information is saved in step 210 on any suitable medium. For the decoding 200, a suitable scanner and the additional information, i.e. the mentioned error correction code ECC, a description in form of an analogue visual image or written text readable for a human on how to decode the bar code and the size of the original digital information, stored in the photographic media, will be used.

Furthermore, the present invention relates to photographic material with a recorded two dimensional pattern produced by a method according to the storing method described herein and for recovering digital information according to the recovering method described herein.

In order to execute the steps of the method described herein, it is intended to protect in addition a computer program product comprising computer code portions for executing the disclosed storing method and/or the recovering method when said computer code is run by a computer.

Reference numbers Step of encoding the digital information Step of recording the two dimensional pattern on a photographic material 120 Step of storing the recorded photographic materiaj Step of decoding the two dimensional pattern 210 Step of saving the decoded digital information

Claims

Claims 1. A method for long term storage of digital information, the

method comprising the steps of (a) encoding (100) the digital information into a two dimensional pattern, (b) recording (110) the two dimensional pattern on a photographic material and (c) storing (120) the recorded photographic material.
2. The method according to claim 1, comprising the steps of encoding (100) the digital information into a two dimensional color pattern and recording the two dimensional pattern using photographic material.
3. The method according to claim 1 or 2, comprising the step of encoding (100) the digital information into a two dimensional bar code.
4. The method according to any of the claims I to 3, wherein an error correction code is used when the digital information is encoded (100) into the two dimension pattern and recorded (110) together with the two dimensional pattern.
5. The method according to any of the claims Ito 4, comprising the step of distributing in space adjacent bits within the digital information in the two dimensional pattern.
6. The method according to any of the claims I to 5, comprising the step of recording (110) in human readable form a description as analogue visual image or written text.
7. The method according to claim 6, comprising the step of recording (110) in human readable form a description as written text for reading back and decoding the digital information.
8. The method according to any of the claims I to 7, wherein the recording (110) of the two dimensional pattern is performed using industry standard color negative or slide film, or high-resolution color microfilm.
9. The method according to any of the claims 1 to 8, wherein the size of the original digital information is added to the two dimensional pattern.
10. The method according to any of the claims I to 9, wherein the step of encoding (100) the digital information into a two dimensional pattern comprises a channel coding for adapting the two dimensional pattern to the properties of the photographic material.
II. The method according to any of the claims Ito 10, wherein the original digital information is compressed before the step of recording (110) takes place.
12. The method according to any of the claims I to 11, wherein a digital information, a digital text data, a digital picture data, a photographical image or digital audio information is stored.
13. A method for recovering of digital information, the method comprising the steps of (a) decoding (200) a two dimensional pattern stored on a photographic material according to any claim 1 to 12 into digital information, (b) saving (210) the decoded digital information.
14. The method according to claim 13, comprising the step of decoding (200) stored two dimensional color pattern photographic material into digital information.
15. The method according to claims 13 or 14, comprising the step of decoding a two dimensional bar code stored on a photographic material.
16. The method according to any of the claims 13 to 15, comprising the step of using an error correction code recorded on the photographic material when the two dimensional pattern is decoded into the digital information.
17. The method according to any of the claims 13 to 16, comprising the step of using a description in human readable form stored on the photographic material in form of an analogue visual image or written text for decoding the digital information.
18. The method according to any of the claims 13 to 17, comprising the step of using the size of the original digital information stored on the two dimensional pattern for decoding the digital information.
19. Photographic material with a recorded two dimensional pattern.
20. Photographic material according to the preceding claim produced by a method according to any of the claims I to 12 and for recovering digital information according to any of the claims 13 to 18.
21. Photographic material according to the preceding claims, wherein the photographic material is a color photographic material.
22. Photographic material according to the preceding claims, wherein the photographic material is an industry standard color negative or slide film, or high- resolution color microfilm.
23. A computer program product comprising computer code portions for executing the storing method of one of the claims I to 12 and/or the recovering method of one of the claims 13 to 17 when said computer code is run by a computer.