The present invention relates to a method of recording marks representing data in an information layer of a record carrier by irradiating the information layer by means of a pulsed radiation beam, each mark being written by a sequence of pulses, the recorded marks being erasable by irradiating the information layer with an erase radiation beam. The invention further relates to a corresponding optical recording device for recording marks representing data in an information layer of a record carrier by irradiating the information layer by means of a pulsed radiation beam, the device comprising a radiation source providing said radiation beam and a control unit for controlling the power of said radiation beam such that each mark is written by a sequence of pulses, the recorded marks being erasable by irradiating the information layer with an erase radiation beam.
Such a method and device are known from the WO01/04885 A1. Therein a mark is written in a phase change layer of a record carrier by a sequence of radiation pulses. A trailing power level having a value higher than the erase power level is introduced after a last write pulse in a sequence of radiation pulses. Additionally, the power level of the last write pulse in a sequence may be raised. This results in a reduced jitter of the marks being written, especially when writing takes place at high recording speeds. In this way marks are written in a phase change layer of a record carrier. The area between two successive marks is referred to as a space. The pattern of marks and spaces on a record carrier represents the information stored on that record carrier.
A factor-of-two storage capacity increase of a rewritable optical recording media can be achieved by introduction of a second recording layer such as described in “Title Phase-Change Recording: Options for 10 to 20 GB (dual layer, high NA, and blue)”, Wierenga H. A., Proceedings of the SPIE The International Society for Optical Engineering (USA), vol. 3401, p. 64-70, 1998. To access both recording layers, the layer closer to the objective lens of the recording device needs to be transparent. Making such a transparent recording layer requires a major change of the recording layer stack-design. In single layer discs, this stack consists typically of a metal mirror layer, dielectric interference layers, and a phase-change layer. However, these types of stacks are not transparent due to the metal mirror layer. Leaving out of the metal mirror layer in dual-layer discs has not only consequences for the behavior of the stack (that is becoming at least partially transparent), but also for its thermal characteristics.
In transparent dual-layer recording stacks, transparent heat sinks are introduced to achieve at least a moderate cooling of the phase-change layer without compromising the transparency of the stack. The slower cooling characteristic of such a stack results in a heat accumulation which causes two kinds of problems. First, longer cooling gaps in between the write pulses are needed during writing of marks. This can be achieved by using shorter write pulses. Second, the temperature of the heat sink needs to be low at the beginning of a mark. The most straightforward solutions are a reduction of the erase power during the space write-strategy or the introduction of a cooling gap before the first write pulse. However, experiments in optical recording systems (such as, for example, DVD) have shown that both strategies result in a poor overwrite performance.
It is therefore an object of the present invention to provide a method and a device for recording marks in an information layer of a record carrier by which a reduction of the temperature of a transparent heat sink is accomplished without compromising the overwrite performance.
This object is achieved according to the present invention by providing a method according to the preamble wherein said erase radiation beam has a first erase power level for a first erase period, a second erase power level higher than or equal to said first erase power level for a second erase period, and a third erase power level lower than said second power level for a third erase period. The object is further achieved by providing a corresponding recording device.
The present invention is based on the idea to divide the space write strategy into at least two, preferably three, different power levels. At the beginning of a space, a one- or two-stage erase power level boost is used to heat the stack quickly. The initial stage of a one-stage boost or the first stage in case of a two-stage boost is needed to prevent re-crystallization at the end of the previous mark. Thereafter, that is after said initial stage or after the second boost of a two-stage boost, the erase power is lowered to a value which is substantially lower than that required in conventional space write strategies without a boost. The net result is the desired reduction of the stack temperature before the following mark to be recorded.
The combination of the above described new write strategy and a stack with one transparent heat sink layer, preferably made of Indium Tin Oxyde (ITO), especially results in a very good overwrite performance.
In another embodiment, the third erase power level is lower than the erase power level applied in conventional space write strategies, while at least the second erase power level is higher than the conventional erase power level.
In an embodiment of the invention, the first and third erase power levels are substantially equal and lower than the second erase power level.
Furthermore, the sum of the first and second erase periods is preferably shorter than half the shortest effect (i.e. mark) length, for example a 1 T duration for a code with 2 T as the shortest effect (i.e. mark) length.
The space write strategy according to the present invention using a two-stage erase boost is preferably applied to direct overwrite (DOW) in a (semi-) transparent layer of an optical record carrier comprising at least two information layers. Write strategies using such an erase boost could, for example, be applied in DVD and DVR dual-layer recording.
The information layer is preferably of the type which has a phase which is reversibly changeable between a crystal phase and an amorphous phase. Because of the similarity of the cooling problems in dual-layer record carriers and in high speed recording of single layer record carriers, the method and recording device according to the present invention, in which the above described erase power level boost is applied, could also be advantageously applied to high-speed CD-RW, DVD, and DVR recording.
The invention will now be explained in more detail hereinafter on the basis of preferred embodiments and with reference to the accompanying drawings, in which
a shows a cross-section of a dual-layer record carrier,
b shows a cross-section of a semi-transparent information layer,
a is a schematic representation of a dual-layer disc-shaped record carrier 1. The disc 1 comprises a polycarbonate substrate 10, two recording layers of the phase-change type 11, 13 separated by a spacer layer 12, and a cover layer 14. Data recorded in the information layers 11, 13 are written or read by a radiation beam 2, such as a laser light beam. If data are to be read from or written into the information layer 11, the other information layer 13 closer to the surface facing the laser beam 2 should be, at least partially transparent.
b shows an example of a cross-section of such a semi-transparent information layer 13. As shown, it comprises a phase-change layer 132 and a transparent heat sink layer 134 which are separated and covered by dielectric layers 131, 133, 135. Other stack arrangements are alternatively possible.
The data is written in an optical record carrier 1 having one or more information layers, such as an optical record carrier having two information layers as shown in
b shows a control signal 30 corresponding to the data signal 20 in an embodiment of the invention. The control signal 30 is used for modulating the power of a radiation beam with which the marks are written on the information layer, where it is assumed that the power level of the radiation beam is proportional to the level of the control signal.
At the beginning of the space 22, a two-stage boost is used to heat the stack quickly. The low-level first stage 33 having a first erase power level e1 for a first erase period t1 is used to prevent re-crystallization at the end of the previous mark 21. Thereafter, a second boost 34 is applied having a second erase power level e2 higher than the first erase power level e1 for a second erase period t2. After the second boost 34, the erase power is lowered to a third erase power level e3 lower than the first erase power level e1 for a third erase period t3, that is, for the remaining time of the space 22 (reference numeral 35).
Also shown as a dashed line in this diagram is a conventional space write-strategy without erase boost according to the invention. In such a conventional space write strategy, the erase power level is set to a constant level e0 higher than the third erase power level e3 during the whole period for writing the space 22. It should be noted that also a one-stage boost, where e1 is equal to e2, may be used.
The net result of the space write strategy according to the invention is the desired reduction of the stack temperature. The combination of this new write strategy and a stack with one transparent heat sink layer as shown in
It should be noted that the optimum values of the erase power levels e1, e2, e3 as well as the erase periods t1, t2, t3 depend on the properties of the recording medium, the laser pulse, and the laser spot on the information layer. As an example, the following values could be used:
It should be noted that, instead of the two-stage boost as shown in
It should be noted that the term “equal” does not necessarily mean “exactly the same”, but rather “approximately equal”, since slight differences from the equal level do not take the advantages of the invention away.
The control signal SC provided at the output of the control unit 60 is applied to the radiation source 51 and controls the power of the radiation beam 52 generated by the radiation source 51. The radiation beam is focused onto an information layer 11 (or 13) of the record carrier 1 by a lens 53. The disc-shaped record carrier 1 is rotated about its center by a motor 54.
Number | Date | Country | Kind |
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02077407 | Jun 2002 | EP | regional |
This is a continuation of Ser. No. 10/517,918 filed Dec. 14, 2004 and is incorporated by reference herein.
Number | Name | Date | Kind |
---|---|---|---|
5291470 | Nishiuchi et al. | Mar 1994 | A |
5412626 | Ohno et al. | May 1995 | A |
5608710 | Minemura et al. | Mar 1997 | A |
5751669 | Shiratori | May 1998 | A |
5815477 | Kimura et al. | Sep 1998 | A |
5825742 | Tanaka et al. | Oct 1998 | A |
5848043 | Takada et al. | Dec 1998 | A |
6272100 | Toda et al. | Aug 2001 | B1 |
6285647 | Van Woudenberg et al. | Sep 2001 | B1 |
6424610 | Ohno | Jul 2002 | B2 |
6456584 | Nagata et al. | Sep 2002 | B1 |
6894965 | Furumiya et al. | May 2005 | B2 |
20010012257 | Suzuki et al. | Aug 2001 | A1 |
20020003762 | Dekker | Jan 2002 | A1 |
20020018419 | Watabe | Feb 2002 | A1 |
20020031075 | Araki et al. | Mar 2002 | A1 |
20020080702 | Asada et al. | Jun 2002 | A1 |
Number | Date | Country |
---|---|---|
0286126 | Dec 1988 | EP |
0318200 | May 1989 | EP |
0851413 | Jul 1998 | EP |
0947910 | Oct 1999 | EP |
6004867 | Jan 1994 | JP |
6295440 | Oct 1994 | JP |
7105585 | Apr 1995 | JP |
07129955 | May 1995 | JP |
9091703 | Apr 1997 | JP |
11273075 | Oct 1999 | JP |
11345428 | Dec 1999 | JP |
200123367 | Apr 2000 | JP |
0060584 | Oct 2000 | WO |
0104885 | Jan 2001 | WO |
0178072 | Oct 2001 | WO |
0186642 | Nov 2001 | WO |
Number | Date | Country | |
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20100020665 A1 | Jan 2010 | US |
Number | Date | Country | |
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Parent | 10517918 | Dec 2004 | US |
Child | 12574188 | US |