WO2005122158A1

WO2005122158A1 - Improved information carrier

Info

Publication number: WO2005122158A1
Application number: PCT/IB2005/051876
Authority: WO
Inventors: Thomas J. De Hoog; Robert F. M. Hendriks
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2004-06-11
Filing date: 2005-06-08
Publication date: 2005-12-22
Also published as: TW200614245A

Abstract

The invention relates to an information carrier comprising a set of elementary data areas forming parallel data stripes (DS1, DS2...), said parallel data stripes being alternated with non-transparent stripes (NTS1, NTS2...). The invention also relate to an information carrier comprising a set of elementary data areas arranged according to adjacent square macro-cells data, said macro-cells data comprising parallel data stripes being alternated with non-transparent stripes, said parallel data stripes and said non-transparent stripes being alternated from one macro-cell data to another. The invention also relates to an information carrier comprising a set of elementary data areas being alternated with non-transparent areas so as to form a checkerboard pattern. Use: Information carrier

Description

Improved information carrier

FIELD OF THE INVENTION The invention relates to an information carrier intended to store data.

The invention has applications in the field of optical data storage.

BACKGROUND OF THE INVENTION The use of optical storage solutions is nowadays widespread for content distribution, for example in storage systems based on the DVD (Digital Versatile Disc) standards. Optical storage has a big advantage over hard-disc and solid-state storage in that the information carrier are easy and cheap to replicate. However, due to the large amount of moving elements in the drives, known applications using optical storage solutions are not robust to shocks when performing read/write operations, considering the required stability of said moving elements during such operations. As a consequence, optical storage solutions cannot easily and efficiently be used in applications which are subject to shocks, such as in portable devices. New optical storage solutions have thus been developed. These solutions combine the advantages of optical storage in that a cheap and removable information carrier is used, and the advantages of solid-state storage in that the information carrier is still and that its reading requires a limited number of moving elements.

Fig.l depicts a three-dimensional view of system illustrating such a new optical storage solution. This system comprises an information carrier 101. The information carrier 101 comprises a set of adjacent elementary data areas arranged as in a matrix. Data are coded on each elementary data area via the use of a material intended to take different transparency levels, for example two levels in using a material being transparent or non-transparent for coding a 2-states data, or more generally N transparency levels (for example N being an integer power of 2 for coding a log₂(N)-states data). This system also comprises means (such as a periodic array of apertures or an array of optical fibres, not shown) for generating an array of light spots 102 which are intended to be applied to said elementary data areas. Each light spot is intended to be applied to an elementary data area. According to the transparency state of said elementary data areas, the light spot is transmitted (not at all, partially or fully) to a CMOS or CCD detector 103 comprising pixels intended to convert the received light signal, so as to recover the data stores on said elementary data area. To read the information carrier, a scanning of the information carrier 101 by the array of light spots 102 is done in a plane (x, y) parallel to the information carrier. A scanning device (not shown) provides translational movement in the two directions x and y for scanning all the surface of the information carrier. Advantageously, one pixel of the detector is intended to detect a set of elementary data, said set of elementary data forming a so-called macro-cell data, each data among this macro-cell data being successively read by a single light spot of said array of light spots 102. This way of reading data on the information carrier 101 is called macro-cell scanning in the following and will be described after.

Fig.2 depicts a partial cross-section and detailed view of the information carrier 101, and of the detector 103. The detector 103 comprises pixels referred to as PX1-PX2-PX3, the number of pixels shown being limited for facilitating the understanding. In particular, pixel PX1 is intended to detect data stored on the macro-cell data MCI of the information carrier, pixel PX2 is intended to detect data stored on the macro-cell data MC2, and pixel PX3 is intended to detect data stored on the macro-cell data MC3. Each macro-cell data comprises a set of elementary data. For example, macro-cell data MCI comprises elementary data referred to as MCla-MClb-

MClc-MCld.

Fig.3 illustrates by an example the macro-cell scanning of the information carrier 101. For facilitating the understanding, only 2-states data are considered, similar explanations holding for a N-state coding. Data stored on the information carrier have two states indicated either by a black area (i.e. non-transparent) or white area (i.e. transparent). For example, a black area corresponds to a "0" binary state while a white area corresponds to a "1" binary state. When a pixel of the detector 103 is illuminated by an output light beam generated by the information carrier 101, the pixel is represented by a white area. In that case, the pixel delivers an electric output signal (not represented) having a first state. On the contrary, when a pixel of the detector 103 does not receive any output light beam from the information carrier, the pixel is represented by a cross-hatched area. In that case, the pixel delivers an electric output signal (not represented) having a second state. In this example, each macro-cell data comprises four elementary data, and a single light spot is applied simultaneously to each set of data. The scanning of the information carrier 101 by the array of light spots 102 is performed for example from left to right, with an incremental lateral displacement which equals the pitch of the elementary data areas. In position A, all the light spots are applied to non-transparent areas so that all pixels of the detector are in the second state. In position B, after displacement of the light spots to the right, the light spot to the left side is applied to a transparent area so that the corresponding pixel is in the first state, while the two other light spots are applied to non-transparent areas so that the two corresponding pixels of the detector are in the second state. In position C, after displacement of the light spots to the right, the light spot to the left side is applied to a non-transparent area so that the corresponding pixel is in the second state, while the two other light spots are applied to transparent areas so that the two corresponding pixels of the detector are in the first state. In position D, after displacement of the light spots to the right, the central light spot is applied to a non-transparent area so that the corresponding pixel is in the second state, while the two other light spots are applied to transparent areas so that the two corresponding pixels of the detector are in the first state. Elementary data which compose a macro-cell data opposite a pixel of the detector are read successively by a single light spot. The scanning of the information carrier 101 is complete when the light spots have each been applied to all elementary data area of a macro- cell data facing a pixel of the detector. This implies a two-dimensional scanning of the information carrier.

Fig.4 represents a top- view of an information carrier 101 as depicted in Fig.l. This information carrier comprises a plurality of square adjacent macro-cells (MCI, MC2, MC3...), each macro-cell comprising a set of elementary data areas (EDA1, EDA2, ...). In this example, each macro-cell comprises 16 elementary data areas and is intended to be read by a single circular light spot (represented by dotted circles). With such a type of information carrier, the storage capacity is limited by the size of the light spots, and not by the size of the elementary data areas. Indeed, generating light spots having small diameters is a difficult issue, while defining elementary data areas of small size

(e.g. via a printing process) is easier. To increase the storage capacity of the information carrier, for a given size of the light spots, the size of the elementary data areas may be decreased. However, decreasing the size of the elementary data areas leads to the fact that the size of the light spots gets larger than the size of the elementary data areas, as represented. In that case, a part of the lights spots (situated at the periphery of the circles) will be applied to neighbouring elementary data areas. Said part of the lights spots are passed through said neighbouring elementary data areas (or partially passed through depending on the transparency state of the material), and projected to the pixels of the detector in the same way as the central part of said lights spots, creating crosstalk, i.e. inter-symbol interference. Crosstalk avoids an optimal recovery of the data stored on the information carrier and lead to data errors. If the neighbouring elementary data areas belongs to a same macro-cell, there will have some crosstalk between the data of said macro-cell. If the neighbouring elementary data areas belongs to different macro-cells, the light spot will be partially applied to different pixels of the detector, so that there will be some crosstalk between the data of different macro-cells, i.e. to a larger scale. Moreover, since a plurality of parallel light spots are simultaneously applied to the information carrier, and that the light separation between adjacent pixels of the detector is not perfect, a blurring effect occur. As a consequence, a given pixel of the detector might receive a light contribution from other light spots, which also lead to data errors.

OBJECT AND SUMMARY OF THE INVENTION It is an object of the invention to propose an information carrier intended to store data, and whose structure reduces the crosstalk between said data.

An embodiment of an information carrier according to the invention comprises a set of elementary data areas forming parallel data stripes, said parallel data stripes being alternated with non-transparent stripes. Another embodiment of an information carrier according to the invention comprises a set of elementary data areas arranged according to adjacent square macro-cells data, said macro-cells data comprising parallel data stripes being alternated with non-transparent stripes, said parallel data stripes and said non-transparent stripes being alternated from one macro-cell data to another.

Another embodiment of an information carrier according to the invention comprises a set of elementary data areas being alternated with non-transparent areas so as to form a checkerboard pattern.

By alternating non-transparent areas and elementary data areas, the number of contacts between adjacent elementary data areas is reduced. The part of the light spots which overlap neighbouring elementary data areas are no longer detected by the detector pixels (i.e. the specific pixel which faces the concerned macro-cell, or the plurality of pixels which surround said specific pixel), leading to a data cross-talk reduction at the elementary data level and at the macro-cell level, when the information carrier is read. The efficiency of the data recovery is thus improved. By alternating the position of non-transparent areas from a macro-cell to another, a given pixel of the detector receives less light contribution from neighbouring light spots. In other words, the blurring effect is reduced, so that the data error is reduced when the information carrier is read.

Detailed explanations and other aspects of the invention will be given below.

BRIEF DESCRIPTION OF THE DRAWINGS The particular aspects of the invention will now be explained with reference to the embodiments described hereinafter and considered in connection with the accompanying drawings, in which identical parts or sub-steps are designated in the same manner: Fig.l depicts a system for reading an information carrier according to the invention, Fig.2 depicts a detailed view of said system, Fig.3 illustrates by an example the principle of macro-cell scanning of an information carrier, Fig.4 depicts an information carrier intended to be read by a plurality of light spots, Fig.5 depicts a detailed view of an information carrier on which a light spot is applied, Fig.6 depicts a first information carrier according to the invention, Fig.7 depicts a detailed view of said first information carrier according to the invention, Fig.8a to 8h depict different embodiments of said first information carrier according to the invention, Fig.9a and 9b depict different embodiments of a second information carrier according to the invention, Fig.10 depicts a detailed view of said second information carrier according to the invention.

DETAILED DESCRIPTION OF THE INVENTION Fig.5 illustrates a detailed view of an information carrier as depicted in Fig.4. It represents a set of square adjacent elementary data areas on which a light spot is applied and passed through in order to be detected on a pixel of the detector facing said adjacent elementary data areas (not shown). The light spot, represented the by dotted circle, is applied on the elementary data area EDAO. Considering that the diameter of this light spot is larger than the width of the square elementary data area EDAO, this light spot overlaps on neighbouring elementary data areas

(EDA1, EDA2, ED A3, EDA4). In a first approximation, it may be assumed that the overlapping areas have all the same surface A₂. The surface Ai covered by the light spot on the central elementary data area EDAO equals the surface of said central elementary data area EDAO. The light intensity L₀ which is received by a pixel of the detector facing the central elementary data area EDAO may be modelled as follows : L₀ = Ao + Ai*Bo + A₂*(Bi + B₂ + B3 + B₄) (1) where Bi represents the data level of the elementary data area EDAi, for i = 1...4 (e.g. data level 0 or 1 if dealing with a two-levels data), Ao is a constant reflecting a background intensity level.

It is noted that with such a model, the term A₂*(Bι + B₂ + B₃ + B ) reflects a measure of the cross-talk phenomenon which has to be reduced. Fig.6 depicts a first embodiment of an information carrier according to the invention.

This information carrier comprises a set of elementary data areas forming parallel data stripes

(DSl, DS2...), said parallel data stripes (DSl, DS2...) being alternated with non-transparent stripes (NTSl, NTS2...). Each data stripe is formed by adjacent elementary data areas having preferably a square shape. The non-transparent stripes do not store any data. Their purpose is to avoid the overlapping areas having a surface A₂ of the light spot to be detected by the pixels of the detector. With such an information carrier, as illustrated by Fig.7, the light intensity Lo which is received by a pixel of the detector may now be modelled as follows : Lo = Ao + Ai *B₀ + A₂*(B₂ + B₃) (2)

Compared to relation (1), relation (2) demonstrates that the cross-talk, reflected by the term A₂*(B₂ + B₃), has been reduced.

If the information carrier is segmented into adjacent square macro-cells, the non- transparent stripes have to be placed in each macro-cell in different ways according to the size of the macro-cell : - for macro-cells having a width corresponding to an even number of elementary data areas : all the macro-cells (for example having a size of 4*4 elementary data areas, and represented in bold) in the information carrier will have non-transparent stripes placed identically (e.g. on even lines as depicted by Fig.8a, or on odd lines as depicted by Fig.8b). - for macro-cells having a width corresponding to an odd number of elementary data areas : In a first example depicted by Fig.8c (where for example the macro- cell have a size of 3*3 elementary data areas, and are represented in bold), all the macro-cells in the information carrier having an odd vertical rank will have non- transparent stripes placed on even lines and all the macro-cells in said information carrier having an even vertical rank will have non-transparent stripes placed on odd lines. In a second example depicted by Fig.8d (where for example the macro- cell have a size of 3*3 elementary data areas, and are represented in bold), all the macro-cells in the information carrier having an odd vertical rank will have non- transparent stripes placed on odd lines and all the macro-cells in said information carrier having an even vertical rank will have non-transparent stripes placed on even lines.

It is noted that in using macro-cells having an odd size, such as embodiments depicted by Fig.8c and 8d, when a light spot is applied to a given elementary data area, the neighbouring light spots applied to the upper and lower macro-cells are applied to non-transparent elementary areas. As a consequence, these embodiments are advantageous because the pixel of the detector facing said given elementary data area receives less light contribution from neighbouring light spots, which reduces data errors when the information carrier is read.

In a preferred embodiment depicted in Fig.8e and 8f, the adjacent macro-cells have an even size of 4*4 elementary data areas. The non-transparent stripes position (i.e. odd or even) is horizontally alternated from one macro-cell to another. When a light spot is applied to a given elementary data area, the neighbouring light spots applied to the left and right macro-cells are applied to non-transparent elementary areas. As a consequence, these embodiments are advantageous because the pixel of the detector facing said given elementary data area receives less light contribution from neighbouring light spots which reduces data errors when the information carrier is read.

In a preferred embodiment depicted in Fig.8g and 8h, the adjacent macro-cells have an odd size of 3*3 elementary data areas. The non-transparent stripes position (i.e. odd or even) is either alternated horizontally and vertically from one macro-cell to another. When a light spot is applied to a given elementary data area, the neighbouring light spots applied to the left / right / upper / lower macro-cells are applied to non-transparent elementary areas. As a consequence, these embodiments are advantageous because the pixel of the detector facing said given elementary data area receives less light contribution from neighbouring light spots, which reduces data errors when the information carrier is read.

Fig.9a and Fig.9b depicts a different embodiments of a second information carrier according to the invention. This information carrier comprises a set of elementary data areas (EDA1, EDA2...) being alternated with non-transparent areas (NTA1, NTA2...) so as to form a checkerboard pattern. In other words, the elementary data areas are placed on odd diagonals of the information carrier (as depicted in Fig.9a), or alternatively on even diagonals of the information carrier (as depicted in Fig.9b). The non-transparent areas have the same size as the elementary data areas and avoid the overlapping areas having a surface A₂ of the light spot to be detected by the pixels of the detector. With such an information carrier, as illustrated by Fig.10, the light intensity L₀ which is received by a pixel of the detector facing the central elementary data area EDAO may now be modelled as follows : Lo = Ao + Aι*Bo (3)

Compared to relation (1), relation (3) demonstrates that the cross-talk has been cancelled, at least highly reduced. The elementary data areas of the information carrier depicted in Fig.9a and Fig.9b may be arranged according to adjacent square macro-cells having an odd or even size. If the square macro-cells have an odd size, the position of the elementary data areas and that of the non-transparent areas is alternated from one macro-cell data to another. With such an arrangement, for example with adjacent macro-cells having a size of 3*3 elementary data areas, when a light spot is applied to a given elementary data area, the neighbouring light spots applied to the left / right / upper / lower macro-cells are applied to non-transparent elementary areas. As a consequence, such an embodiment is advantageous because the pixel of the detector facing said given elementary data area receives less light contribution from neighbouring light spots, which reduces data errors when the information carrier is read.

The verb "comprise" does not exclude the presence of other elements than those listed in the claims.

Claims

1. Information carrier comprising a set of elementary data areas forming parallel data stripes (DSl, DS2...), said parallel data stripes being alternated with non-transparent stripes (NTS1, NTS2...).

2. Information carrier as claimed in claim 1, wherein said set of elementary data areas are arranged according to adjacent square macro-cells data having an odd size.

3. Information carrier comprising a set of elementary data areas arranged according to adjacent square macro-cells data, said macro-cells data comprising parallel data stripes being alternated with non-transparent stripes, said parallel data stripes and said non-transparent stripes being alternated from one macro-cell data to another.

4. Information carrier as claimed in claim 3, wherein said macro-cells data have an odd size.

5. Information carrier comprising a set of elementary data areas (EDA1, EDA2...) being alternated with non-transparent areas (NTA1, NTA2...) so as to form a checkerboard pattern.

6. Information carrier as claimed in claim 5, wherein said set of elementary data areas are arranged according to adjacent square macro-cells data having an odd size.