WO2006003574A2

WO2006003574A2 - Method and apparatus for recording data in an optical record

Info

Publication number: WO2006003574A2
Application number: PCT/IB2005/052088
Authority: WO
Inventors: Erwin R. Meinders
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2004-06-28
Filing date: 2005-06-24
Publication date: 2006-01-12
Also published as: WO2006003574A3; TW200617905A

Abstract

The present invention relates to a method for recording data in an optical record carrier (10) which is intended to be readout without being rotated. In accordance with the invention the method comprises the following steps: providing an optical record carrier (10); rotating said written optical record carrier (10); and recording said data in said written optical record carrier (10) by writing pits in said written optical record carrier (10) with a modulated laser beam. The invention is also directed to an apparatus for recording data in an optical record carrier (10) and to an optical record (10).

Description

Method and apparatus for recording data in an optical record

FIELD OF THE INVENTION

The present invention relates to a method and an apparatus for recording data in an optical record carrier which is intended to be readout without being rotated. Furthermore, the present invention relates to an optical record carrier.

BACKGROUND OF THE INVENTION

A major disadvantage of conventional optical storage concepts is the presence of rotating parts in the optical drive. Rotating parts have a lot of disadvantages, for example a sensitivity to wear and noise, the consumption of a rather high electrical power, in particular at high rotation speeds, etc. For example the T-ROM concept, based on the Talbot effect, was proposed as an optical readout principle without rotating parts for use in an optical card system. This concept is based on a two-dimensional periodic light interference pattern that is generated through a matrix of equidistantly spaced holes. The optical card (for example a ROM medium) is located in between this matrix of multiple light sources and a detector, for example a CCD like detector. The optical card, i.e. the optical record carrier, is readout in a transmission mode. The unwritten areas transmit more light than the written areas (pits) or the other around. In this way, binary data encoded in the transmission level of the different pixels can be readout. However, the absence of moving parts makes recording of data in such a device very complicated. Therefore, for example the T-ROM card reader is almost per definition a player of pre-recorded optical record carriers. ROM media are perfect for content distribution, but personalized content is becoming more and more important. Therefore, a write-once concept would be a valuable addition to optical card readers that possess only play functionality.

It is therefore the object of the present invention to further develop the methods, apparatuses and optical record carriers of the type mentioned at the beginning such that the optical carriers may be recorded reasonable by the end user.

SUMMARY OF THE INVENTION This object is solved by the features of the independent claims. Further developments and preferred embodiments of the invention are outlined in the dependant claims.

In accordance with a first aspect of the present invention, a method for recording data in an optical record carrier which is intended to be readout without being rotated is characterised by the following steps: providing an optical record carrier; rotating said optical record carrier; and recording said data in said optical record carrier by writing pits in said written optical record carrier with a modulated laser beam.

The basic idea of this solution is that optical drives which rotate the optical record carrier, for example a T-ROM medium, may be obtained at a reasonable price. For example the optical record carrier can be placed in conventional optical drives, such as CD- R/RW, DVD+R/RW or BD-RE drives, that are further developed in accordance with the present invention as it will be described in more detail below. In general, the present invention makes it possible to write personalized data into an optical card that subsequently can be readout in an optical card reader, for example on the basis of the Talbot effect.

With preferred embodiments of the method in accordance with the invention said pits are written in a rectangular matrix arrangement. Such a rectangular matrix arrangement is very advantageous in connection with optical cards.

In this connection it is highly preferred that for writing said pits in said rectangular matrix arrangement a mapping for converting between Cartesian coordinates and polar coordinates is performed. Such conversions are necessary in many cases since the position of the laser beam relative to the optical record carrier needs to be given in polar coordinates for devices rotating the optical record carrier, while the position of the pits to be written in a rectangular matrix arrangement is given in Cartesian coordinates.

In connection with the method in accordance with the invention it is preferred that said step of providing said optical record carrier comprises providing an optical record carrier having at least one tracking groove for guiding said modulated laser beam during recording said data. The relative position on a master disc, expressed in track-pitch variation, is very well controlled in a Laser Beam Recorder (LBR), used to make stampers for replication of pre-recorded ROM and recordable write-once and rewritable discs. However, the rotation stability of optical drives is much worse. Therefore, tracking grooves are required to enable recording of data in an ordered manner (spiral). For recording a grid of data points in an optical card, it is also advantageous to provide tracking grooves in or on the optical record carrier to ensure an accurate relative position of the grid points, i.e. the pits. The optical record carrier therefore for example contains a spirally-oriented groove used for tracking of the focussed laser beam. Optimum push-pull tracking will lead to an optical spot that perfectly follows the pre-groove. If a two-dimensional high-density relief structure is required, such as a two-dimensional optical card, a stamp for micro-contact printing or a raster, an accurate positioning of the laser spot is required. Using a record carrier with a small track pitch is a possibility, but a minimum track-pitch is required to enable tracking (a sufficiently large push-pull signal is required). In case of a blue laser spot (numerical aperture of 0.85 and laser wvelength of 405 nm) a minium track pithc of about 250 nm is required. A more accurate positioning of the recorded marks can be achieved by placing the focussed laser spot somewhat off-axis. With an off-set in the push-pull signal, the spot can be deliberately placed off-track. In this way, the track-pitch of the pre-groove determines the nominal position of the spot, the off-set gives a radial deviation to this nominal position. The laser pulse train is synchronised during recording with the optical record carrier rotation.

However, there might arise the problem that the tracking grooves may harm the readout of data from the optical card. This problem can be solved if the tracking grooves are visible during recording of data, but are more or less invisible during readout of data in the optical card reader. Possibilities to achieve this are disclosed in the following. A first possibility is that a layer comprising said tracking groove is removed after recording said data. In general, to enhance the reflection of the grooved areas, a thin reflective layer may be deposited on the groove surface. In such a case the removal of the layer with the tracking grooves also removes the reflective layer after recording the data. The grooves may for example be replicated in a foil that can be easily removed from the disc. Although the grooves need to be in the plane of focus, the grooves may be separated from the recording layer. In this connection it is to be noted that this is different from conventional dye recording in which the dye is present in the grooves as well. For example by removing a foil there may arise a loss of protection of the written data pattern. To overcome this disadvantage it is for example possible to provide a home made protection coating which is attached to the recorded layer.

A second possibility is that the wavelength of said modulated laser beam used for tracking and writing said pits is different from a wavelength of a laser beam intended to readout said data. For example, it is possible to design an optical record carrier with a tracking groove structure that is reflective in red (670 nm) or infrared (780 nm), but is transparent for blue laser light (405 nm). For writing of data, the recording layer should absorb enough laser light for thermal or photochemical decomposition or alteration at the writing wavelength (600 - 800 nm). For readout, the pits in the optical record carrier should absorb/reflect sufficient laser light at the readout wavelength (405 nm in this particular example) to provide contrast. Furthermore, the tracking grooves should be optimised for 600 - 800 nm in combination with the numerical aperture of the focus lens. In this example the pits are preferably written with a larger spot (d~λ/NA) than the readout spot. Thereby, a lower data density is achieved. The opposite situation is also possible, i.e. tracking and writing is performed with blue light (404 nm) and readout is performed with red light (670 or 780 nm), for example.

A third possibility is that the wavelength of said modulated laser beam and light used for tracking is different. For example, writing and readout is done at red (670 or 780 nm) and tracking is performed with blue light (405 nm). The preferably closely spaced tracking grooves (TP=320 nm) allow for a more accurate positioning of the marks in a rectangular data pattern (during conversion from polar to rectangular coordinates).

A fourth possibility is that said written optical record carrier comprises a switchable mirror layer covering said tracking groove. The mirror layer, for example deposited on the tracking groove structure, can be electrically switched between a reflective and a transparent state. In the reflective state, the grooves are visible to allow for tracking. In the transparent state, the data pits are readout without being hampered since the tracking groove structure is invisible. The mirror layer can be transformed from a transparent state into a reflective state by so-called thermochromic materials. Such switchable recording stacks contain a thermochromic layer, an electrolyte and transparent electrodes. An electric current is required to induce the thermochromic effect. Methods to electrically address different layers in a rotating disc are subject of different applications of the applicant. However, other ways of selecting the layer are also possible, for example the use of the photochromic effect. The fourth solution is of special interest in cases where the optical record carrier is placed in a cartridge kind of holder to enable recording for example in a conventional drive. Contacting the different transparent electrodes to enable the thermochromic switch is quite easy to realize if a cartridge is used.

For all embodiments of the method in accordance with the invention it can be advantageous that at least some of the pits are written overlapping for creating pits larger than an optical spot of said modulated laser beam. This may in particular be of interest for the first generation optical card readers in which the data resolution may be limited by the readout channel of the reader.

Additionally or alternatively at least some of said pits are written with different width and/or depth to create a multi-level layout. Larger or deeper pits will transmit less light than smaller or less deeper pits, enabling multi-level readout. Larger or deeper pits may be created by the use of a higher laser power.

With preferred embodiments of the method in accordance with the invention rotating said written optical record carrier comprises placing said written optical record carrier onto a rotation table of a recording apparatus. The rotating table preferably is adapted to eject the written optical record carrier, as it is generally known in the art.

In this connection a further development of the method in accordance with the invention is that said record carrier is arranged in a cartridge before being placed onto said rotation table. As already mentioned, using a cartridge is advantageous, particularly in connection with a switchable mirror layer. In accordance with a second aspect of the present invention the object mentioned above is solved by an optical record carrier which is intended to be readout without being rotated and which comprises at least one tracking groove for guiding a modulated laser beam which is used for recording data in said optical record carrier while said optical record carrier is rotated. By equipping the optical record carrier, which is intended to be readout without being rotated, with suitable tracking grooves, for example a spiral tracking groove, it is possible to record the optical record carrier using a reasonable optical drive which rotates the optical record carrier for writing and/or reading, wherein the laser pulse train is synchronised with the disc rotation. If any spiral tracking groove is used, the track pitch is preferably selected such that the pits can be written with a distance suitable for optical cards.

With preferred embodiments of the invention the optical record carrier comprises data in form of written pits which are arranged in a rectangular matrix. For writing such a rectangular matrix it is in many cases necessary that the device used for recording the optical record carrier is adapted to perform mapping routines for converting between polar and Cartesian coordinates, to create a rectangular grid of data points.

As already mentioned above in connection with the method in accordance with the invention, the tracking grooves may harm the readout of data. In connection with the following four solutions for overcoming this problem, reference is made to the corresponding explanations in connection with the method in accordance with the invention, to avoid repetitions.

In accordance with a first possibility the optical record carrier comprises a removable layer comprising said tracking groove. In accordance with a second possibility the optical record carrier is adapted to be recorded with said modulated laser beam having a first wavelength which is also used for tracking, and to be readout by a modulated laser beam having a second wavelength which is different from said first wavelength.

In accordance with a third possibility the optical record carrier is adapted to be recorded with said modulated laser beam having a first wavelength, and it is adapted to support tracking on the basis of light having a different wavelength than said first wavelength.

A fourth possibility is that the optical record carrier comprises a switchable mirror layer covering said tracking groove. With all embodiments of the optical record carrier in accordance with the invention it is possible that the written optical record carrier comprises at least some overlapping pits creating pits larger than an optical spot of said modulated laser beam used for recording said data. As already mentioned in connection with the method of the invention, this solution may in particular be of interest for the first generation of optical card readers in which the data resolution may be limited by the readout channel of the reader.

Furthermore, it is possible that the written optical record carrier comprises at least some pits differing in width and or in depth to create a multi-level layout. By providing such a multi-level layout the data density may be increased.

For all embodiments of the optical record carrier in accordance with the invention it is preferred that the optical record carrier is adapted to be placed onto a rotation table of a recording apparatus.

In this connection it is possible that the optical record carrier is adapted to be arranged in a cartridge suitable for being placed onto said rotation table.

In accordance with a third aspect of the present invention the object mentioned above is solved by an apparatus, particularly an apparatus adapted to carry out the method in accordance with the invention, for recording data in an optical record carrier, particularly in an optical record carrier in accordance with the invention, which is intended to be readout without being rotated, wherein the apparatus comprises: a rotating table for rotating said written optical record carrier; means for creating a modulated laser beam for recording data in said written optical record carrier; and means for guiding said modulated laser beam such that for recording data, pits are written in said written optical record carrier in a rectangular matrix arrangement. Such an apparatus may be either a standalone device or a conventional optical drive, for example a CD-R/RW, a DVD+R/RW, or a BD-RD drive, which is further developed such that it is able to write a rectangular matrix of pits which can be readout by an optical card reader.

In this connection it is necessary in many cases that said means for guiding said modulated laser beam comprise mapping means for converting between Cartesian coordinates and polar coordinates, as already mentioned above.

From the above it may be seen that the present invention results in an apparatus, a method and an optical record carrier for recording data in an optical card for readout in a separate card reader. The recording device comprises a rotation table to mount the optical record carrier and a modulated laser beam for writing pits in the record carrier. The device can also comprise a cartridge in which the record medium is clamped. The cartridge can be used in conventional optical data drives. Tracking grooves are preferably provided for moving the laser in a spirally shaped trajectory over the optical record carrier. Preferably mapping routines are used to write a rectangular matrix of pits on the rotating disc. The tracking grooves may have no other functionality than guiding the laser during writing. The laser modulation preferably is synchronised with the rotation of the disc, such that a matrix of pits is written.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a flow chart illustrating an embodiment of the method in accordance with the invention;

Figure 2a illustrates an optical record carrier comprising a rectangular matrix ofpits;

Figure 2b illustrates the writing of the marks by position the laser at a nominal position, imposed by the track-pitch of the spiral, and at a deviated position with respect to the nominal position, due to a deliberate offset in the push-pull signal; Figure 3 is a sectional view of a first embodiment of the optical record carrier in accordance with the invention;

Figure 4 is a sectional view of a second embodiment of the optical record carrier in accordance with the invention; Figure 5 is a sectional view of a third embodiment of the optical record carrier in accordance with the invention;

Figure 6 is a sectional view of a fourth embodiment of the optical record carrier in accordance with the invention;

Figure 7a is a top view of a uniform pit pattern; Figure 7b is a top view of a multilevel pit pattern; and

Figure 8 is a schematic block diagram of an apparatus in accordance with the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS Figure 1 is a flow chart illustrating an embodiment of the method in accordance with the invention. The illustrated method starts in step Sl. In step S2 an optical record carrier having a tracking groove is provided. Without being limited thereto the optical record carrier may particularly be one of the optical record carriers described below with reference to Figures 3 to 6. In step S3 the optical record carrier is arranged in a cartridge which for example may have the dimensions of a conventional CD or DVD. This cartridge is placed on the rotating table of an optical drive. In step S5 the cartridge is rotated. For a given set of data to be written on the optical record carrier, in step S6 a mapping between polar and Cartesian coordinates of pits to be written at predetermined positions on the optical record carrier is performed. In the following step S7 the laser beam is modulated in a suitable manner and is guided on the basis of said tracking groove to write the pits at the predetermined positions on the optical record carrier. The pits are written such that a rectangular matrix arrangement of pits is created which is suitable to be readout by the separate optical card reader. The steps S6 and S7 may be performed successively or simultaneously. After writing is completed the optical record carrier is taken out in step S8 and the method ends in step S9.

Figure 2a shows an example of a rectangular data pattern 54 of pits 34 written on a rotating disc. The Cartesian coordinates of P (i, j) are x = Rcos (θ) and y = Rsin(θ).

Figure 2b shows an example of a rectangular data pattern 54 of pits 34 that is written on a rotating disc, wherein only one quadrant is shown. The nominal position of the focussed laser spot, indicated by the solid line 70, is determined by the track-pitch of the pre- grooved spiral. The outer bounds of the focused laser spot are shown at 72 and 74. The deviation of the nominal position is obtained by a deliberate offset in the push-signal that causes a slight off-centre placement of the optical spot. If the deviation equals half the track pitch (=TP/2) the entire the surface of the optical record carrier ca be covered within one passage of the laser spot. In that case, a very accurate rectangular grid of data pits can be written.

Figures 3 to 6 show different embodiments of the optical record carrier in accordance with the invention. As a first step the common features of the optical record carriers 10, 12, 14, 16 shown in Figures 3 to 6 are now described. The illustrated discs 10, 12, 14, 16 comprise a substrate layer 18. By using a stamper a replicated disc is provided comprising a spiral tracking groove 20. In this connection an injection moulding process or a glass/2P process may for example be used. A separation layer 24 is deposited, for example by spincoating, to level the groove structure 20. The separation layer may be a PMMA or another organic compound. The preferred thickness of the separation layer is between 10 and 500 nm. Subsequently, a recording layer 28 is deposited, for example by spincoating, over the separation layer 24. Suitable recording materials are AZO, Phthalo-cyanines, etc, optimised for the wavelength in question (dyes for 780 nm, 670 nm and 450 nm are well known to the person skilled in the art). The applied type of dye depends on the wavelength of the readout system. The illustrated optical record carriers 10, 12, 14, 16 comprise optional dielectric layers 26 and 30 underneath and on top of the recoding layer 28. The dielectric layers 26, 30 are provided to enhance the contrast. Finally, a cover layer 32 is provided.

The embodiments in accordance with Figures 3 to 5 additionally comprise a reflective layer 22 arranged directly over the groove structure 20. Silver is an interesting candidate for this reflective layer 22 since silver has a relatively high transmittance in blue (405 nm) while it is reflective in red (600 to 800 nm). The silver layer 22 may for example have a thickness between 10 and 50 nm.

Figure 3 shows a typical write-once medium 10. The illustrated optical record carrier 10 consists of the cover layer 32, a recording stack 30, 28, 26 with recording layer 28 and optional thermal protection layers or optical contrast layers 30, 26 (dielectric layers), the separation layer 24, the reflection layer 22 and the substrate 18 comprising the grooves 20. The grooves 20 and the recording area 28 are within the same focus distance of the focussed laser spot used for writing. Figure 4 shows a second embodiment of the optical record carrier 12, which may be obtained by writing to the optical record carrier 10 of Figure 3. In accordance with the embodiment of Figure 4 writing and tracking was performed with the same optical spot, i.e. the same focused laser beam. The spatial resolution of the data or mark pattern is therefore similar to the density of the tracking grooves 20, wherein the pits are shown at 34 while the lands are shown at 36.

Figure 5 shows an example of a situation in which the tracking wavelength is shorter than the writing wavelength. The track pitch of the tracking grooves 20 in this case is smaller than the data size. If the data were written in a spiral following the grooves 20, this would lead to partial overlap of the pits 34. However, because of the mapping from a rotational coordinate system to a rectangular system, in order to write an optical card with a rectangular grid of data pits, the higher tracking groove density is advantageous. If writing and tracking is performed with optical spots of different size, the tracking grooves 20 are located at a closer distance than the marks or pits 34 (the unwritten area is shown at 36). An example of an optical record carrier 16 with a switchable mirror is shown in Figure 6. The switchable mirror 38, 40, 42, 44 covers the groove structure 20 and consists of an electrochromic layer 42, an electrolyte layer 40 and two transparent electrodes 38, 44. The transparent electrodes 38, 44 are electrically connected to an electric source 46. If a voltage drop is applied across the two electrodes 38, 44, the electrochromic layer 42 changes from a transparent into a reflective state. The high reflection of the switchable mirror 38, 40, 42, 44 enables tracking and allows the writing of data according to the previously described mapping routines. After recording, a voltage with inverse polarity is applied to the electrodes 38, 44 to convert the mirror again from the reflective into the transmissive state. During readout in a separate card reader, the groove structure 20 is transparent and therefore not hampering the readout of data.

In Figure 7a an example of an equidistant uniform pattern of pits 34 forming a rectangular matrix arrangement 54 is given. In contrary thereto Figure 7b shows a multi- level ROM. The dark pits 48 are deeper than the grey pits 50 which in turn are deeper than the light grey pits 52. Deeper pits are written by using a higher laser power. Deeper pits will transmit less light than pits having a less depth, and thereby a multi-level readout is enabled. By providing such a multi-level arrangement a higher data density is achieved. Instead of deeper pits, a higher laser power may also result in broader pits. Pit size variation is also a possibility to regulate the total transmission of the laser spot, and therefore to obtain a multi¬ level readout optical record medium. Figure 8 is a schematic block diagram of an apparatus 56 in accordance with the invention. The illustrated optical drive 56 comprises an ejectable rotation table 58 on which a cartridge 60 is placed containing the optical record carrier to be recorded. Means 62 for creating a modulated laser beam are arranged such that the optical record carrier placed on the rotation table 58 may be written. An interface 68 is provided at least for receiving the data to be written on the optical record carrier. A controller 64 communicates with the interface 68 and the means 62 for generating the laser beam. Furthermore, the controller 64 controls rotation of the rotation table 58. For enabling the optical drive 56 to write a rectangular matrix of pits in the optical record carrier, the controller 64 is equipped with means 66 for converting between Cartesian coordinates and polar coordinates.

Finally, it is to be noted that equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims

CLAIMS:

1. A method for recording data in an optical record carrier (10; 12; 14; 16) which is intended to be readout without being rotated, characterized by the following steps: providing an optical record carrier (10; 12; 14; 16); rotating said optical record carrier (10; 12; 14; 16); and - recording said data in said optical record carrier (10; 12; 14; 16) by writing pits (34; 48, 50, 52) in said optical record carrier (10; 12; 14; 16) with a modulated laser beam;

2. The method according to claim 1, characterized in that said pits (34; 48, 50, 52) are written in a rectangular matrix (54) arrangement.

3. The method according to claim 2, characterized in that for writing said pits (34; 48, 50, 52) in said rectangular matrix (54) arrangement a mapping for converting between Cartesian coordinates (x, y) and polar coordinates (R, θ) is performed.

4. The method according to claim 1, characterized in that said step of providing said optical record carrier (10; 12; 14; 16) comprises providing an optical record carrier (10; 12; 14; 16) having at least one tracking groove (20) for guiding said modulated laser beam during recording said data.

5. The method according to claim 4, characterized in that a layer comprising said tracking groove (20) is removed after recording said data.

6. The method according to claim 4, characterized in that the wavelength of said modulated laser beam used for tracking and writing said pits (34; 48, 50, 52) is different from a wavelength of a laser beam intended to readout said data.

7. The method according to claim 4, characterized in that the wavelength of said modulated laser beam and light used for tracking is different.

8. The method according to claim 4, characterized in that said optical record carrier (10; 12; 14; 16) comprises a switchable mirror layer (38, 40, 42, 44) covering said tracking groove (20).

9. The method according to claim 1, characterized in that at least some of said pits (34; 48, 50, 52) are written overlapping for creating pits (34; 48, 50, 52) larger than an optical spot of said modulated laser beam.

10. The method according to claim 1, characterized in that at least some of said pits (48, 50, 52) are written with different width and/or depth to create a multi-level layout.

11. The method according to claim 1, characterized in that rotating said record carrier (10; 12; 14; 16) comprises placing said record carrier (10; 12; 14; 16) onto a rotation table (58) of a recording apparatus (56).

12. The method according to claim 11 , characterized in that said record carrier (10; 12; 14; 16) is arranged in a cartridge (60) before being placed onto said rotation table (58).

13. An optical record carrier (10; 12; 14; 16) which is intended to be readout without being rotated, characterized in that it comprises at least one tracking groove (20) for guiding a modulated laser beam which is used for recording data in said optical record carrier (10; 12; 14; 16) while said optical record carrier (10; 12; 14; 16) is rotated.

14. The optical record carrier (10; 12; 14; 16) according to claim 13, characterized in that it comprises data in form of written pits (34; 48, 50, 52) which are arranged in a rectangular matrix (54).

15. The optical record carrier according to claim 13 or 14, characterized in that it comprises a removable layer comprising said tracking groove (20).

16. The optical record carrier (10; 12; 14) according to claim 13 or 14, characterized in that it is adapted to be recorded with said modulated laser beam having a first wavelength which is also used for tracking, and to be readout by a modulated laser beam having a second wavelength which is different from said first wavelength.

17. The optical record carrier (10; 12; 14) according to claim 13 or 14, characterized in that it is adapted to be recorded with said modulated laser beam having a first wavelength, and in that it is adapted to support tracking on the basis of light having a different wavelength than said first wavelength.

18. The optical record carrier (16) according to claim 13 or 14, characterized in that it comprises a switchable mirror layer (38; 40; 42; 44) covering said tracking groove

(20).

19. The optical record carrier (10; 12; 14; 16) according to claim 13 or 14, characterized in that it comprises at least some overlapping pits (34; 48, 50, 52) creating pits (34; 48, 50, 52) larger than an optical spot of said modulated laser beam used for recording said data.

20. The optical record carrier (10; 12; 14; 16) according to claim 13 or 14, characterized in that it comprises at least some pits (48, 50, 52) differing in width and/or in depth to create a multi-level layout.

21. The optical record carrier (10; 12; 14; 16) according to claim 13 or 14, characterized in that it is adapted to be placed onto a rotation table (58) of a recording apparatus (56).

22. The optical record carrier (10; 12; 14; 16) according to claim 21, characterized in that it is adapted to be arranged in a cartridge (60) suitable for being placed onto said rotation table (58).

23. An apparatus (56), particularly an apparatus adapted to carry out the method in accordance with any of claims 1 to 12, for recording data in an optical record carrier (10; 12; 14; 16), particularly in an optical record carrier (10; 12; 14; 16) in accordance with any of claims 13 to 22, which is intended to be readout without being rotated, characterized in that it comprises: a rotating table ( 58) for rotating said optical record carrier (10; 12; 14; 16); means (62) for creating a modulated laser beam for recording data in said optical record carrier (10; 12; 14; 16); and means (64) for guiding said modulated laser beam such that for recording data, pits (34; 48, 50, 52) are written in said optical record carrier (10; 12; 14; 16) in a rectangular matrix (54) arrangement.

24. The apparatus (56) according to claim 23, characterized in that said means

(64) for guiding said modulated laser beam comprise mapping means (66) for converting between Cartesian coordinates (x, y) and polar coordinates (R, θ).