WO2006013519A1

WO2006013519A1 - Method of storing data in an information carrier, system for reading such an information carrier.

Info

Publication number: WO2006013519A1
Application number: PCT/IB2005/052450
Authority: WO
Inventors: Peter Van Der Walle; Thomas Jan De Hoog; Boon Keat Chong; Robert Frans Maria Hendriks
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2004-07-26
Filing date: 2005-07-21
Publication date: 2006-02-09
Also published as: TW200627417A

Abstract

The invention relates to a method of storing data in an information carrier comprising a plurality of adjacent macro-cells (MC1, MC2, MC3...), each macro-cell comprising a set of elementary data areas (MC1a, MC1b, MC1c, MC1d ... ), said method comprising the steps of setting a light transmission coefficient to each elementary data area for coding a data at the elementary data area level, controlling that the number (NB) of elementary data areas having the same light transmission coefficient is such that the average light transmission coefficient of each macro-cell characterizes the value of a data at the macro-cell level. The invention also relates to a system for reading such an information carrier. Use: Information carrier, reading apparatus.

Description

"Method of storing data in an information carrier, system for reading such an information carrier"

FIELD OF THE INVENTION

The invention relates to an information carrier having a new structure. The invention also relates to a system for reading such an information carrier. The invention also relates to various apparatus including such a reading system.

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.

Recently, 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 an optical storage solution.

This system comprises an information carrier 101. The information carrier 101 comprises a set of square adjacent elementary data areas having size referred to as s and 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 ²log(N)-states data).

This system also comprises an optical element 104 for generating an array of light spots 102 which are intended to be applied to said elementary data areas. The optical element 104 may correspond to a two-dimensional array of apertures at the input of which the coherent input light beam 105 is applied. Such an array of apertures is illustrated in Fig.2. The apertures correspond for example to circular holes having a diameter of 1 μm or much smaller.

The array of light spots 102 is generated by the array of apertures in exploiting the Talbot effect which is a diffraction phenomenon working as follows. When a coherent light beam, such as the input light beam 105, is applied to an object having a periodic diffractive structure (thus forming light emitters), such as the array of apertures, the diffracted lights recombines into identical images of the emitters at a plane located at a predictable distance zθ from the diffracting structure. This distance zθ is known as the Talbot distance. The Talbot distance zθ is given by the relation zθ = 2.n.d² / λ, where d is the periodic spacing of the light emitters, λ is the wavelength of the input light beam, and n is the refractive index of the propagation space. More generally, re-imaging takes place at other distances z(m) spaced further from the emitters and which are a multiple of the Talbot distance z such that z(m) = 2.n.m.d² / λ, where m is an integer. Such a re- imaging also takes place for m = Vi + an integer, but here the image is shifted over half a period. The re-imaging also takes place for m = ¹A + an integer, and for m = ³A + an integer, but the image has a doubled frequency which means that the period of the light spots is halved with respect to that of the array of apertures.

Exploiting the Talbot effect allows generating an array of light spots of high quality at a relatively large distance from the array of apertures (a few hundreds of μm, expressed by z(m)), without the need of optical lenses. This allows inserting for example a cover layer between the array of aperture and the information carrier 201 for preventing the latter from contamination (e.g. dust, finger prints ...). Moreover, this facilitates the implementation and allows increasing in a cost-effective manner, compared to the use of an array of micro-lenses, the density of light spots which are applied to the information carrier.

Each light spot is intended to be successively 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. Advantageously, one pixel of the detector is intended to detect a set of elementary data, said set of elementary data being arranged in a so-called macro-cell data, each elementary data area 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.3 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 PXl is intended to detect data stored on the macro-cell data MCl 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 MCl comprises elementary data referred to as MC Ia-MC Ib- MClc-MCld.

Fig.4 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 an 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 areas, 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 period 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 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.

To read the information carrier, a scanning of the information carrier by the array of light spots is done in a plane parallel to the information carrier. A scanning device provides translational movement of the light spots in the two directions x and y for scanning all the surface of the information carrier.

In a first solution depicted in Fig.5, the scanning device corresponds to an H-bridge.

The optical element generating the array of light spots (i.e. the array of micro-lenses or the array of apertures) is implemented in a first sledge 501 which is movable along the y axis compared to a second sledge 502. To this end, the first sledge 501 comprises joints 503-504-

505-506 in contact with guides 507-508. The second sledge 502 is movable along the x axis by means of joints 511-512-513-514 in contact with guides 509-510. The sledges 501 and 502 are translated by means of actuators (not represented), such as by step-by-step motors, magnetic or piezoelectric actuators acting as jacks.

In a second solution depicted in Fig.6, the scanning device is maintained in a frame 601. The elements used for suspending the frame 601 are depicted in a detailed three- dimensional view in Fig.7. These elements comprise: - a first leaf spring 602, a second leaf spring 603, a first piezoelectric element 604 providing the actuation of the scanning device 601 along the x axis,

- a second piezoelectric element 605 providing the actuation of the scanning device 601 along the y axis.

The second solution depicted in Fig.6 has less mechanical transmissions than the H- bridge solution depicted in Fig.5. The piezoelectric elements, in contact with the frame 601, are electrically controlled (not represented) so that a voltage variation results in a dimension change of the piezoelectric elements, leading to a displacement of the frame 601 along the x and/or the y axis.

The position Posl depicts the scanning device 601 in a first position, while the position Pos2 depicts the scanning device 601 in a second position after translation along the x axis. The flexibility of the leaf springs 602 and 603 is put in evidence. A similar configuration can be built with four piezoelectric elements, the two extra piezoelectric elements replacing the leaf springs 602 and 603. In that case, opposite pair of piezoelectric elements act together in one dimension in the same way as an antagonist pair of muscles.

Macro-cell scanning is a nice feature for increasing data storage, but it unfortunately has so limitations.

First, macro-cell scanning requires that the light spots are accurately aligned with the elementary data areas. This constraint is not necessarily respected when the information carrier is introduced in the reading apparatus.

Moreover, performing macro-cell scanning involves a displacement of the light spots from an elementary data area to another adjacent elementary data area. The positioning control of the light spots may- thus require some time since light spots must be accurately positioned in front of each elementary data areas, and also because the light spots must be applied during a minimum duration because of the exposure duration needed by the pixels of the detector. OBJECT AND SUMMARY OF THE INVENTION

It is an object of the invention to propose a method of storing data in an information carrier which can be recovered either with or without using macro-cell scanning.

To this end said method comprising the steps of : setting a light transmission coefficient to each elementary data area for coding a data at the elementary data area level, controlling that the number of elementary data areas having the same light transmission coefficient is such that the average light transmission coefficient of each macro-cell characterizes the value of a data at the macro-cell level.

This method allows to store data which can be recovered not only via a macro-cell scanning, but also without using macro-cell scanning. Data defined at the elementary data area level are intended to represent the most important storage capacity amount of the information carrier, while data defined at the macro-cell level are intended to represent only a limited storage capacity amount of the information carrier. Defining two data channels in the information carrier is advantageous since data at the macro-cell level can be easily and quickly recovered, i.e. without too much constraints on the position of the information carrier in a reading apparatus compared to the array of light spots, and without using advanced scanning techniques.

Preferably : said step of setting is intended to select either a first coefficient value or a second coefficient value for defining said light transmission coefficient, - said step of controlling is intended to verify that the number of elementary data areas, in each macro-cell, having a light transmission coefficient which equals said first coefficient value, is equal to a value taken among a set of N different integer values.

Storing data at the elementary data area level while imposing such a constraint allows to code and store a N-levels data at the macro-cell level.

Preferably : said step of setting is intended to select either a first coefficient value or a second coefficient value for defining said light transmission coefficient, - said step of controlling is intended to verify that the number of elementary data areas, in each macro-cell, having a light transmission coefficient which equals said first coefficient value, is in a range taken among a set of N different ranges of integer values.

Storing data at the elementary data area level while imposing such a constraint allows to code and store a N-levels data at the macro-cell level while relaxing the data storing constraint. As a consequence, more data at the elementary data area level can be stored.

The invention also relates to a system for reading data stored on an information carrier comprising a plurality of adjacent macro-cells, each macro-cell comprising a set of elementary data areas, said system comprising : generating means for alternatively generating an array of light spots or an homogenous light beam intended to be applied to said information carrier, a detector for detecting data stored at the elementary data area level in response of said array of light spots, or data stored at the macro-cell level in response of said homogenous light beam.

This system allows to easily and quickly recover data stored at the macro-cell level without too much constraints on the position of the information carrier in this reading system, and without using macro-cell scanning.

The invention also relates to various reading apparatus implementing such a reading system.

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 :

Fig.l depicts a system for reading an information carrier,

Fig.2 depicts an optical element dedicated to generate an array of light spots,

Fig.3 depicts a detailed view of said system for reading an information carrier, Fig.4 illustrates by an example the principle of macro-cell scanning of an information carrier,

Fig.5 depicts a first arrangement for scanning an information carrier, Fig.6 depicts a second arrangement for scanning an information carrier, Fig.7 depicts detailed elements of said second arrangement,

Fig.8 represents a top view of an information carrier intended to store data according to the invention,

Fig.9 illustrates data stored according to the invention on an information carrier, Fig.10 schematically depicts a system for reading data stored on an information carrier,

Fig.11 depicts a first system according to the invention for reading data stored on an information carrier,

Fig.12 depicts a second system according to the invention for reading data stored on an information carrier, Fig.13 depicts a third system according to the invention for reading data stored on an information carrier,

Fig.14 illustrates various apparatus and devices comprising a system for reading an information carrier according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Fig.8 represents a top view of an information carrier in which data are intended to be stored according to the method of the invention.

This information carrier comprises a plurality of adjacent macro-cells (MCl, MC2, MC3, ...), each macro-cell comprising a set of elementary data areas (MCIa, MCIb, MCIc,

MCId ...). In this example, each macro-cell comprises 16 elementary data areas. To facilitates the scanning of a macro-cell (similarly as in the prior art), the elementary data areas are advantageously placed adjacent and arranged according to a matrix, and have a square shape.

The method comprises a step of setting a light transmission coefficient to each elementary data area for coding a data at the elementary data area level. Each elementary data area, characterized by a light transmission coefficient, is thus intended to store one data.

The method also comprises a step of controlling that the number NB of elementary data areas having the same light transmission coefficient is such that the average light transmission coefficient of each macro-cell characterizes the value of a data at the macro-cell level.

If elementary data areas are intended to store binary data, said step of setting is intended to select either a first coefficient value Cl or a second coefficient value C2 for defining said light transmission coefficient, said first coefficient value Cl characterizing a first level of the binary data (e.g. 0), said second coefficient value C2 characterizing a second level of the binary data (e.g. 1). For example, each elementary data area is made of a transparent material (i.e. light non-absorbing) or a non-transparent material (i.e. light absorbing).

According to a first solution, said step of controlling is intended to verify that the number NB_C1 of elementary data areas, in each macro-cell, having a light transmission coefficient which equals said first coefficient value Cl, is equal to a value taken among a set of N different integer values. For example, for N=3, and if macro-cells contain 16 elementary data areas, the set S may be defined by S = (3, 9, 12).

In this case, as illustrated by Fig.9 : a first value Vl at the macro-cell level will be defined if 3 elementary data areas have the level Cl,

- a second value V2 at the macro-cell level will be defined if 9 elementary data areas have the level Cl,

- a third value V3 at the macro-cell level will be defined if 12 elementary data areas have the level Cl.

Constraining the number of data areas having value Cl within a macro cell limits the amount of information that can be stored in the cell. For instance, if in a cell of n bits, k bits set to be 1 are constrained, then the number of bit patterns goes down from 2ⁿ to n! / (k!*(n-k)!), where ! indicates factorial operation.

During read-out of the information carrier, the detection of the number NB_C1 of elementary data areas having the same level Cl is detected in measuring the average transmission coefficient of each macro-cell. To this end, an homogeneous light beam is applied to said macro-cell (in fact to all the surface of the information carrier), a pixel of a detector facing said macro-cell being in charge of detecting the output light signal generated in response. The pixel plays the role of averaging the different light transmission coefficients of the elementary data areas of said macro-cell. Indeed, all partial light contributions of the elementary data areas are integrated by the pixel (i.e. summed).

According to a second solution, said step of controlling is intended to verify that the number NB_C1 of elementary data areas, in each macro-cell, having a light transmission coefficient which equals said first coefficient value (Cl), is in a range of values taken among a set of N different ranges of integer values.

For example, for N=3, and if macro-cells contain 16 elementary data areas, the set S may be defined by S = ( [0,5], [6,10], [11, 16] ). a first value Vl at the macro-cell level will be defined if the number of elementary data areas having the level Cl is comprised in the range [0,5], - a second value V2 at the macro-cell level will be defined if the number of elementary data areas having the level Cl is comprised in the range [6,10], a third value V3 at the macro-cell level will be defined if the number of elementary data areas having the level Cl is comprised in the range [11, 16].

Advantageously, the ranges are not consecutive so that data at macro-cell level can be more easily recovered. For example, the set S may be defined as S = ( [0,3], [6,10], [13, 16] ).

During read-out of the information carrier, in order to determine in which range a macro-cell is classified, and then to recover the value of the macro-cell data, the average transmission coefficient of the macro-cell is derived from the pixel of the detector facing said macro-cell.

Fig.10 schematically depicts a system according to the invention for reading an information carrier 1001 as described above, where data are stored at the elementary data area level and at the macro-cell level.

Said system comprises generating means 1002 for alternatively generating an output light beam 1003 corresponding either to an array of light spots or to an homogenous light beam which are intended to be applied to said information carrier. Said system also comprises a detector 1004 for detecting data stored at the elementary data area level in response of said array of light spots, or data stored at the macro-cell level in response of said homogenous light beam. The array of light spots is used for reading data at the elementary data area as described in the prior art section, i.e. in successively applying a single light spot to a single elementary data area.

As previously described, data at macro-cell level are read in applying to each macro- cell, a light beam covering the size of said macro-cell. To this end, an homogenous light beam covering all the surface of the information carrier may be used.

According to a first solution depicted in Fig.l 1, the generating means comprise : a phase modulator 1005 intended to receive a coherent light beam 1006, for defining a quadratic phase profile or a random phase profile, an array of apertures 1007 placed in the optical path of said phase modulator for generating said output light 1003 (i.e. said array of light spots or said homogenous light beam). The array of apertures 1007 is placed at the Talbot distance zθ from the information carrier, or at a multiple or a sub- multiple of said distance.

The phase-modulator 1005 advantageously comprises a two-dimensional array of controllable liquid crystal (LC) cells for defining the phase profile φ(x). For example, pixelated linear nematic LC cells may be used. Nematic substances can be aligned by electric and magnetic fields, resulting in a phase change. Nematic cells are optically equivalent to a linear wave plate having a fixed optical axis, but whose birefringence is a function of the applied voltage. As the applied voltage varies, the birefringence changes, resulting in a change of the optical path length, thus in a phase change. When the phase-modulator 1005 defines a flat phase profile, the array of apertures

1007 fully exploits the Talbot effect so that the output light beam 1003 corresponds to an array of light spots, each light spot having the size of an elementary data area.

When the phase-modulator 1005 defines a phase profile varying in a quadratic way with respect to the direction x, it can be shown that the light spots generated by the array of apertures will focus above or under the surface of the information carrier if the parameters of the quadratic relation are varied. As a consequence, the light spots are no longer focussed on the information carrier. In other words, each macro-cell will receive a larger and homogeneous light beam applied to all its surface for reading data at the macro-cell level. When the phase-modulator 1005 defines a random phase profile, the array of apertures forming light emitters cannot recombine into identical images of the emitters at the Talbot distance zθ (nor at a multiple or a sub-multiple) from the array of apertures. In other words, the Talbot effect is not exploited and the output light beam generated by the array of apertures which is applied to the information carrier is considered as homogeneous. Each macro-cell will also receive a larger and homogeneous light beam applied to all its surface.

Advantageously, the system comprises processing means for averaging signals detected by the detector for different quadratic phase profiles or different random phase profiles. For example, a signal processor executing code instructions stored in a memory may be used for making such an averaging operation.

According to a second solution depicted in Fig.12, the generating means comprise : an array of apertures 1007 intended to receive a coherent light beam 1006, - an actuator 1008 (e.g. a linear servo motor) for varying the distance D of said array of apertures compared to said information carrier.

If the array of apertures is placed at the Talbot distance D = zθ (or at a multiple or sub-multiple), an array of light spots is generated for reading data at the elementary data area level.

If the array of apertures is not placed at the Talbot distance D = zθ (or at a multiple or sub-multiple), the light spots no longer focus on the information carrier, so that an homogenous light beam is applied to the information carrier for reading data at the macro-cell level.

Advantageously, the system comprises processing means for averaging signals detected by the detector when the array of apertures is placed at different distances. For example, a signal processor executing code instructions stored in a memory may be used for making such an averaging operation.

According to a third solution depicted in Fig.13, the generating means comprise :

- a first light source 1009 for generating a coherent light beam. The first light source may correspond to a laser. a second light source 1010 for generating an incoherent light beam. The second light source may correspond to a LED. an array of apertures 1007 placed in the optical path of said coherent light beam or said incoherent light beam. The array of apertures is placed at a distance D from the information carrier corresponding to the Talbot distance zθ, or at a multiple or a sub- multiple of said distance. - switching means for directing said coherent light beam to the array of apertures for generating said array of light spots, or for directing said incoherent light beam to the array of apertures for generating said homogenous light beam. Such switching means for directing may correspond to a mechanical or electronic switch (not shown) for alternatively activating said first light source or said second light source.

When the incoherent light beam is applied to the array of apertures, the Talbot effect is not exploited and the output light beam generated by the array of apertures which is applied to the information carrier is considered as homogeneous. Each macro-cell will then receive a larger and homogeneous light beam applied to all its surface for reading data at the macro-cell level.

Alternatively, the invention proposes a system for reading data stored on an information carrier (1001) comprising a plurality of adjacent macro-cells, each macro-cell comprising a set of elementary data areas. Said system comprises generating means (1002) for generating an array of light spots intended to be applied to said information carrier.

Said system also comprises a detector (1004) for detecting data in response of said array of light spots.

Said system also comprises control means (such as a timer) for applying each light spot to a given elementary data area during the exposure duration of the detector for detecting data stored at the elementary data area level.

Said system also comprises control means (such as a timer) for successively applying each light spot to all elementary data areas of a given macro-cell during the exposure duration of the detector for detecting data stored at the macro-cell level. If the light spots are quickly scanned over all elementary data areas of a given macro- cell, and if the scan duration is smaller or equal to the exposure duration of the detector (i.e. the nominal sampling period of the pixels), an average value of the light transmission coefficients of all elementary data areas is obtained, said average value reflecting the data stored at the macro-cell level. As illustrated in Fig.14, the system according to the invention may advantageously be implemented in a reading apparatus RA (e.g. home player apparatus ...), a portable device PD (e.g. portable digital assistant, portable computer, a game player unit...), or a mobile telephone MT.

These apparatus and devices comprise an opening (OP) intended to receive an information carrier 1401 as depicted by Fig.8 and having data stored according to the method of the invention, and a system as depicted by Figs. 10 to 13 in view of recovering data stored on said information carrier.

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

Claims

1. A method of storing data in an information carrier comprising a plurality of adjacent macro-cells (MCl, MC2, MC3...), each macro-cell comprising a set of elementary data areas (MCIa, MCIb, MCIc, MCId ...), said method comprising the steps of :

- setting a light transmission coefficient to each elementary data area for coding a data at the elementary data area level, controlling that the number (NB) of elementary data areas having the same light transmission coefficient is such that the average light transmission coefficient of each macro-cell characterizes the value of a data at the macro-cell level.

2. A method as claimed in claim 1, wherein :

- said step of setting is intended to select either a first coefficient value (Cl) or a second coefficient value (C2) for defining said light transmission coefficient, said step of controlling is intended to verify that the number (NB_C1) of elementary data areas, in each macro-cell, having a light transmission coefficient which equals said first coefficient value (Cl), is equal to a value taken among a set of N different integer values.

3. A method as claimed in claim 1, wherein : said step of setting is intended to select either a first coefficient value (Cl) or a second coefficient value (C2) for defining said light transmission coefficient, said step of controlling is intended to verify that the number (NB_C1) of elementary data areas, in each macro-cell, having a light transmission coefficient which equals said first coefficient value (Cl), is in a range taken among a set of N different ranges of integer values.

4. A system for reading data stored on an information carrier (1001) comprising a plurality of adjacent macro-cells, each macro-cell comprising a set of elementary data areas, said system comprising : generating means (1002) for alternatively generating an array of light spots or an homogenous light beam intended to be applied to said information carrier, - a detector (1004) for detecting data stored at the elementary data area level in response of said array of light spots, or data stored at the macro-cell level in response of said homogenous light beam.

5. A system as claimed in claim 4, wherein said generating means (1002) comprise :

- a phase modulator (1005) intended to receive a coherent light beam (1006), for defining a quadratic phase profile or a random phase profile, an array of apertures (1007) placed in the optical path of said phase modulator for generating said array of light spots or said homogenous light beam.

6. A system as claimed in claim 4, wherein said generating means (1002) comprise : an array of apertures (1007) intended to receive a coherent light beam, an actuator (1008) for varying the distance (D) between said array of apertures and said information carrier.

7. A system as claimed in claim 4, wherein said generating means (1002) comprise : a first light source (1009) for generating a coherent light beam, a second light source (1010) for generating an incoherent light beam, an array of apertures (1007) placed in the optical path of said coherent light beam or said incoherent light beam, switching means for directing said coherent light beam to the array of apertures for generating said array of light spots, or for directing said incoherent light beam to the array of apertures for generating said homogenous light beam.

8. A system as claimed in claim 5, further comprising processing means for averaging signals detected by the detector for different quadratic phase profiles or different random phase profiles.

9. A system as claimed in claim 6, further comprising processing means for averaging signals detected by the detector when the array of apertures is placed at different distances.

10. A system for reading data stored on an information carrier (1001) comprising a plurality of adjacent macro-cells, each macro-cell comprising a set of elementary data areas, said system comprising :

- generating means (1002) for generating an array of light spots intended to be applied to said information carrier,

- a detector (1004) for detecting data in response of said array of light spots, control means for applying each light spot to a given elementary data area during the exposure duration of the detector for detecting data stored at the elementary data area level, - control means for successively applying each light spot to all elementary data areas of a given macro-cell during the exposure duration of the detector for detecting data stored at the macro-cell level.

11. A portable device comprising a system as claimed in claim 4, 5, 6, 7, 8, 9 or 10.

12. A mobile telephone comprising a system as claimed in claim 4, 5, 6, 7, 8, 9 or 10.

13. A game player unit comprising a system as claimed in claim 4, 5, 6, 7, 8, 9 or 10.