Patent Application
20080212459
The present invention relates to a method of writing information on an optical recording medium, and in particular for writing labeling information on an optical recording medium. The present invention further relates to an optical recording medium on which labeling information can be written and to a method of manufacturing such an optical recording medium.
Methods of generating labels on an optical recording medium, like CD or DVD, are known. According to one of those methods, data readable by an optical readout device is recorded on one side of the disc, and then the disc is flipped manually in order for the label side to be printed. For label printing, infrared laser light is focused on the label side where, due to a significant amount of spherical aberration, a spot of about 20 μm is formed. With over 45 mW of power, dark concentric circles are written at densities varying from 175 TPI (tracks per inch) to 1200 TPI. Several problems are related to the known method:
As the linear writing speed is limited to 0.25 m/s, a complete label takes about 40 minutes to be written in the highest density mode. Even at a medium resolution of 600 TPI, a complete label takes 20 minutes to be written. Considering the time it takes to write the disc's data side (3 min for a CD at 52×, 9 min for a DVD at 8×) the label writing time appears as a major drawback. It is desired that label writing is at least as fast as data writing.
Further, due to the huge amount of spherical aberration in the spot that is focused on the label side, the focus S-curve in any of the known focus systems (Foucault, stigmatic) is completely distorted. Consequently, an open loop feed forward focus system is applied which needs frequent, time-consuming adjustments. It is not possible to use conventional focus servo loops.
Additional problems with the known concept relate to the manufacturing of the discs, particularly since the application of the label writing sensitive layer is done in a separate step.
It is therefore an object of the invention to provide a method of writing information on an optical recording medium, an optical recording medium and a method of manufacturing an optical recording medium, thereby avoiding the mentioned prior art problems, thus being able to write a label with high speed, making it possible to use a conventional servo system, and to facilitate the manufacturing of the disc.
The above objects are solved by the features of the independent claims. Further developments and preferred embodiments of the invention are outlined in the dependent claims.
In accordance with the invention, there is provided a method of writing information on an optical recording medium, the optical recording medium having at least one data layer for storing data readable by use of an optical readout device and at least one label layer for storing visible information, the method comprising the steps of:
focusing a first wavelength laser beam onto the at least one data layer for writing data on the data layer, and
focusing a second wavelength laser beam onto the at least one label layer for writing visible information on the label layer, thereby a laser spot size being usable that is also employable when using the second wavelength laser beam for writing data on a data layer for storing data readable by use of an optical readout device.
Thus, in contrast to the mentioned prior art, a label writing with small aberration is provided. The label writing can be performed at least as fast as the data writing, conventional focus servo loops can be used, and the manufacturing of the optical recording medium is simplified.
According to a preferred embodiment, the first wavelength is different from the second wavelength. Thus, wavelengths used for different standards of optical recording can be used for writing data and labels, respectively.
It is also possible that the first wavelength and the second wavelength are identical. Thus, the same laser and, preferably, the same optics can be used for writing data and labels.
According to one basic concept of the present invention, the optical recording medium is flipped between writing data on the data layer and writing visible information on the label layer. On the basis of this flipping, many embodiments of the invention are provided, as will be discussed hereinafter.
For example, the first wavelength is a wavelength (405 nm) used for Blu-ray Disc (BD) recording projected through a BD optics, and the second wavelength is a wavelength (780 nm) used for CD recording projected through a CD laser optics. A BD is in essence an inverted CD. While the BD has a cover with a thickness of 0.1 mm and a substrate with a thickness of 1.1 mm, the CD can be considered to have a 1.1 mm cover and a 0.1 mm substrate. After writing data through the 0.1 mm layer by using the BD optics, the disc is flipped, and the CD laser can be easily focused on the mirror side of the BD layer by using the CD optics.
According to a further embodiment the first wavelength is a wavelength used for CD recording projected through a CD optics, and the second wavelength is a wavelength used for BD recording projected through a BD optics. Thus, the mentioned CD/BD combination method can be turned around in the sense that the CD is used for data recording and the label is written by the BD wavelength using a BD laser optics. In this case, the label layer is covered by a cover of approximately 0.1 mm thickness, while the data layer is covered by a material having a thickness of 1.1 mm.
According to a further “flipping” embodiment, the first wavelength is a wavelength used for BD recording projected through a BD optics, and the second wavelength (670 nm) is a wavelength used for DVD recording projected through a DVD optics. The data writing is performed on the BD data layer through a cover layer of approximately 0.1 mm thickness. The label layer is about 0.5 mm below the data layer, so that after flipping the disc, the label can be written with the DVD wavelength and optics through a layer of approximately 0.6 mm.
According to a still further embodiment the first wavelength is a wavelength used for DVD recording projected through a DVD optics, and the second wavelength is a wavelength used for BD recording projected through a BD optics. As mentioned before, the BD wavelength can be used for data writing, while the DVD wavelength is used for label writing. On the basis of a different recording medium having a label layer covered by a layer of approximately 0.1 mm, a data layer having a distance of approximately 0.5 mm from the label layer and a cover covering the data layer of approximately 0.6 mm, the label writing can be performed by the BD wavelength and optics, while the data writing is the usual DVD data writing.
Further, it is possible that the first wavelength is a wavelength used for BD recording projected through a BD optics, and the second wavelength is a wavelength used for HD-DVD recording projected through a HD-DVD optics. Such an embodiment is interesting for the situation of optical devices that are able to read and write in the BD and in the HD-DVD formats, while preferably also being able to read and write in the CD and DVD formats. As in the case of label writing with the DVD wavelength and optics, the writing of the label by the HD-DVD wavelength optics is performed through the cover layer thickness of 0.6 mm that is typical for HD-DVD writing/reading.
According to a further embodiment it is possible that the first wavelength is a wavelength used for HD-DVD recording projected through a HD-DVD optics, and the second wavelength is a wavelength used for BD recording projected through a BD optics. Writers that are able to write in the BD and in the HD-DVD formats have the ability to write data through a 0.6 mm cover using the HD-DVD equipment, while the label is written from the other side through a 0.1 mm cover using the BD equipment.
A further method according to the present invention in which the disc is flipped between data writing and label writing is provided when the first wavelength is a wavelength used for DVD recording projected through a DVD optics, and the second wavelength is a wavelength used for DVD recording projected through a DVD laser optics. This is a special case in which for both writing actions the same laser and the same optics can be used. The embodiment is realized by providing an optical recording medium having a substrate thickness that is comparable to the cover thickness. Thus, after writing data to the disc and flipping the disc, the beam can be focused on the label layer through the substrate having an adequate thickness.
According to the present invention it is possible that the first wavelength is a wavelength used for DVD recording projected through a DVD optics, and the second wavelength is a wavelength used for HD-DVD recording projected through a HD-DVD optics. For both DVD and HD-DVD, the cover layer is approximately 0.6 mm. With a label layer directly below the data layer, this label layer will be accessible by the wavelength used for HD-DVD using the HD-DVD laser optics.
The present invention is also employable when the first wavelength is a wavelength used for HD-DVD recording projected through a HD-DVD optics, and the second wavelength is a wavelength used for DVD recording projected through a DVD optics. The DVD-HD/DVD combination has already been discussed as being particularly useful since the cover layers for both HD-DVD and DVD is approximately 0.6 mm. Thus, the HD-DVD wavelength can also be used for data writing, while the DVD wavelength is used for label writing.
Further, it is possible that the first wavelength is a wavelength used for HD-DVD recording projected through a HD-DVD optics, and the second wavelength is a wavelength used for HD-DVD recording projected through a HD-DVD optics. Similar as in the DVD/DVD case, also both writing processes can be performed by the HD-DVD wavelength and optics.
After having discussed various possibilities in which the optical recording medium is flipped between the data and label writing, a further group of embodiments will be mentioned in which the optical recording medium is illuminated from the same side when writing data on the data layer and when writing visible information on the label layer. Such a method can be performed on the basis of an optical recording medium having a hybrid mirror which is substantially transparent for a first wavelength but substantially reflective for a second wavelength.
For example, the first wavelength is a wavelength used for BD recording projected through a BD optics, and the second wavelength is a wavelength used for CD recording projected through a CD optics. On the basis of an optical medium having a data layer underneath a 0.1 mm cover followed by a hybrid mirror that is reflective for the BD wavelength, data can be written by the BD laser and optics. In a distance of approximately 1.0 mm underneath the hybrid mirror, a label layer is provided on which the CD wavelength beam can be focused using the CD laser and the CD optics, since the hybrid mirror is transmissive for the CD wavelength.
The method without flipping is also applicable when the first wavelength is a wavelength used for DVD recording projected through a DVD optics, and the second wavelength is a wavelength used for BD recording projected through a BD optics. In this case, a medium is provided in which on top of the label layer a cover of approximately 0.1 mm is provided. Underneath the label layer a hybrid mirror is positioned that is reflective for the BD wavelength and transmissive for the DVD wavelength. In a distance of approximately 0.5 mm underneath the hybrid mirror a data layer is provided in which data can be written by using the DVD wavelength and optics.
As another example, the first wavelength is a wavelength used for HD-DVD recording projected through a HD-DVD optics, and the second wavelength is a wavelength used for CD recording projected through a CD optics. On the basis of an optical medium having a data layer underneath a 0.6 mm cover followed by a hybrid mirror that is reflective for the HD-DVD wavelength, data can be written by the HD-DVD laser and optics. In a distance of approximately 0.5 mm underneath the hybrid mirror, a label layer is provided on which the CD wavelength beam can be focused using the CD laser and the CD optics, since the hybrid mirror is transmissive for the CD wavelength.
The method without flipping is also applicable when the first wavelength is a wavelength used for DVD recording projected through a DVD optics, and the second wavelength is a wavelength used for HD-DVD recording projected through a HD-DVD optics. In this case, a medium is provided in which on top of the label layer a cover of approximately 0.6 mm is provided. Underneath the label layer a hybrid mirror is positioned that is reflective for the HD-DVD wavelength and transmissive for the DVD wavelength. In a small distance underneath the hybrid mirror a data layer is provided in which data can be written by using the DVD wavelength and optics.
According to a preferred embodiment, the method of the present invention comprises the further steps of:
(a) providing an optical pickup unit (OPU),
(b) using a wavelength used for BD recording as the first wavelength and a BD optics,
(c) using a wavelength used for CD recording as the second wavelength and a CD laser optics,
(d) positioning the OPU relative to the optical recording medium by using the first wavelength and a BD laser optics for determining the position of the OPU relative to the optical recording medium,
(e) turning on a laser beam having the second wavelength using the CD laser optics,
(f) writing a visible information item on the label layer by the laser beam having the second wavelength using the CD laser optics, and
(g) repeating steps (d) to (f) until a desired label has been written.
This method is employable with the present invention in case that the optical recording medium is illuminated from the same side when writing data and when writing visible information. Thus, the disc is brought in focus using the BD branch. The positioning during CD recording is performed on the basis of the BD laser optics and information on the BD data layer, particularly addresses in pre-groove (ADIP). It is also possible to count the number of tracks on the BD data layer while the OPU is moving on the basis of the TCS (track cross signal) or by using the DPD (differential phase detection) signal and counting the phase jumps.
Particularly, positioning of the OPU in step (d) comprises shifting the OPU.
Additionally it is possible that positioning of the OPU in step (d) comprises tilting the OPU.
Furthermore, after step (e), if the CD laser beam is not sufficiently focused, the OPU is re-positioned.
According to a preferred embodiment, the positioning of the OPU in step (d) is performed such that in step (f) the CD laser spot is positioned adjacent an item of information written during a previous execution of step (f). This is possible when the accuracy of OPU positioning is better than the spot size of the CD laser.
According to a preferred embodiment of the present invention, the writing of visible information on the label layer is performed by writing spiral tracks, the track pitch defining the optical contrast of the visible information. The label is an image formed by several pixels. Each pixel consists of several tracks written by the laser spot. If the track pitch is small, the contrast of the label is high. A greater track pitch will lead to less contrast.
The present invention is further related to an optical recording medium for being used in a method according to the present invention.
Particularly, the at least one data layer and the at least one label layer are covered by layers that are transparent for the applied wavelengths, the layers having a thickness that allows focusing of the laser beams onto the data layer and onto the label layer to a spot size that is employable for writing data on a data layer for storing data readable by use of an optical readout device.
For example, the optical recording medium comprises the following sequence of layers:
a polycarbonate layer,
a label layer or label layer stack, a data layer or data layer stack, and a polycarbonate layer.
In a further embodiment the optical recording medium comprises the following sequence of layers:
a polycarbonate layer,
a label layer or label layer stack,
a thermal isolation layer,
a data layer or data layer stack, and
a polycarbonate layer.
The two aforementioned recording media can be used when the label layer and the data layer may be positioned approximately in the same depth of the medium, for example in the case of BD data recording and CD label writing with “flipping”. The thermal isolation layer is useful in order to prevent an excessive heat transfer from the data layer to the label layer or vice versa.
According to a further embodiment, the optical recording medium comprises the following sequence of layers:
a polycarbonate layer,
a label layer or label layer stack,
a polycarbonate layer,
a data layer or data layer stack, and
a polycarbonate layer.
This sequence is useful when a distance between the label layer and the data layer is required so as to enable, for example, BD label writing and DVD data recording with “flipping”.
According to a further embodiment, the optical recording medium of the present invention comprises the following sequence of layers:
a polycarbonate layer,
a label layer or label layer stack,
a polycarbonate layer,
a mirror layer being selectively transparent for different wavelengths,
a data layer or data layer stack, and
a polycarbonate layer.
Such a sequence of layers is useful for writing BD data and CD label writing from the same side of the optical recording medium.
In order to write for example DVD data and BD labels from the same side it is useful to have an optical recording medium comprising the following sequence of layers:
a polycarbonate layer,
a data layer or data layer stack,
a polycarbonate layer,
a mirror layer being selectively transparent for different wavelengths,
a label layer or label layer stack, and
a polycarbonate layer.
According to a still further embodiment of the present invention the optical recording medium comprises the following sequence of layers:
a polycarbonate layer,
a label layer or label layer stack,
a bonding layer,
a data layer or data layer stack, and
a polycarbonate layer having a groove structure.
The polycarbonate layer adjacent the data layer contains the normal groove structure for data recording. In case of DVD this layer has a thickness of approximately 0.6 mm. Further, a 0.6 mm grooved dummy disc is provided as the polycarbonate layer adjacent the label layer. The bonding layer between the label layer and the data layer provides a thermal isolation. In order to simplify this type of optical recording medium, the groove structure of the polycarbonate layer adjacent the label layer can be left out.
The present invention further relates to a method of manufacturing an optical recording medium according to the present invention, the method comprising the steps of:
providing a first stack of a polycarbonate layer having a label layer or label layer stack on top of the polycarbonate layer,
providing a second stack of a grooved polycarbonate layer having a data layer or data layer stack on top of the grooved polycarbonate layer, and
bonding the first stack and the second stack together by providing a bonding layer between the label layer and data layer, the label layer and data layer stack, the label layer stack and data layer or the label layer stack and data layer stack. In this way, a simple manufacturing process is provided that is based on a normal grooved substrate with recording layer and a dummy substrate supporting a label layer. After having prepared these two stacks, they can be glued together, the glue being thick enough (e.g. 50 μm) to prevent heat flowing from the data layer to the label layer and vice versa.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.
a to 6c illustrate surface areas of an optical recording medium according to the present invention.
In the following detailed description of preferred embodiments, identical reference numerals refer to identical or comparable features. However, it has to be noticed that also different reference numerals may refer to identical or comparable features.
In the case of a combination of CD and BD, the CD stack can be made of the same materials as the BD stack. Also a combination of different materials is possible. For reasons of costs, using the same materials for the CD stack and the BD stack is preferable. The complete stack comprising label and data layers can then be applied in one run.
The optical recording medium shown in
The optical recording medium 18 shown in
It is also possible to use dye label layers. In this connection it has to be considered that grooves in the substrate are filled by the dye. Thus, the data layers will be based on a different groove form. Therefore, the groove forms of the substrate and the filling procedure have to be adjusted so as to provide the desired groove form for the data layer.
In case of DVD data writing and DVD label writing as explained in connection with
The labeling by the DVD optics or the CD optics differs in the way tracking is used. In case of a DVD label writing, tracking can be performed in the usual way. In case of a BD data disc with CD labeling, the CD optics will not be able to follow the tracks. The movement of the spot has to be controlled by using a combination of the sledge motor and the radial movement of the actuator.
a to 6c illustrate surface areas of an optical recording medium according to the present invention. In
The movement of the spot 196 is constrained by two conditions. First, a pixel has to be written with a size dependent on the dpi (Dots Per Inch) value. The pixel size in radial direction will be determined by the TPI (Tacks Per Inch) value chosen. The distance r between the tracks has to be greater or equal to the width s of the written region on the disc. The reflection of a pixel will be less effective for a larger r. The positioning of the laser spot in adjacent tracks can be done by either a sledge motor with high resolution, by radial movement of the actuator or by tilting the head of the optical pick up unit.
For example, on the basis of the present invention, a dark concentric spiral having a width of ±0.6 μm can be written with a writing speed of v=19.2 m/s which corresponds to 16× writing. The write power can be chosen as 20 mW or less. The track pitch is chosen to be 2 μm for high resolution or 4 μm for low resolution. The total time needed to write this concentric spiral on the whole disc is less than 4 minutes for high resolution and less than 2 minutes for low resolution.
The optical recording media described in connection with
The
The optical recording media described in connection with
The optical recording medium 28 is particularly advantageous.
The bonding layer 174 is thick enough (approximately 50 μm) to prevent heat flowing from the data layer 176 to the label layer 172 and vice versa. Not all elements of the label stack 172 are necessary. For example, the label stack 172 might not need a heat sink, thus the mirror layer can be left out. Since the data layer stack 176 has a mirror, the back of this mirror will act as a mirror for the data layer stack 176.
It is possible to use dye labels.
The dummy layer 170 can contain a groove structure with the necessary information in the ADIP that is needed for writing the label side.
A DVD disc can be made, fully compliant to the standard.
The optical recording medium 32 contains a label layer 42 and a data layer 40. Both of these layers can be covered by cover layers (not shown). In addition to the optical recording medium 32 the optical pick up unit (OPU) 98 is illustrated in different positions.
In order to position the OPU 98 relative to the optical recording medium 32 for label writing, the following steps are performed. The optical recording medium is brought into focus by using the BD branch. First, the disc eccentricity is measured by letting the disc spin a few times. The results can be used in a Feed Forward sense. Then, the CD branch is turned on. Now, two different observations can be made: (i) the CD laser is sufficient in focus; (ii) it is necessary to adjust the height of the OPU 98 to get the right focus for the CD laser. In case (i) the implementation is straightforward. The BD laser is used to locate the track after the OPU sledge has moved into another position. The track is read out with the objective lens located in the central position of the OPU 98. Now it can be calculated how far the head has to tilt in order to cover the whole area between the previous written label mark and the position for the next spot. In case (ii) the OPU has to be moved in order to enable the BD and CD lasers to be in focus.
In dependence on the accuracy (d) of the OPU movement two different solutions are proposed.
For an accuracy d better than the CD laser spot size s (d<s) (see
For a spot size s smaller than the accuracy d (d>s) (see
Instead of reading the ADIP addresses, the drive can also count the number of tracks while the OPU is moving. This can be done by the Track Cross Signal (TCS, looking at the open loop PushPull signal) or using the differential phase detection (DPD) signal and counting the phase jumps. Furthermore, if the OPU position is calibrated very well, this can also be used.
Preferably, the following parameters can be measured at startup of the label writing:
The spot size s.
The relation between α and writing area w.
The minimum distance d over which the OPU can be moved accurately.
The distance h between the label layer and the objective lens.
These data can be measured by using special patterns added to the inner side of the disc.
In the description of the present invention the terms layer and layer stack have been used. Generally, most of the mentioned layers can be substituted by layer stacks and, frequently, a layer stack can be substituted by a single layer.
For both, the data and the label layers, the R (write once) and the RW (rewriteable) options are applicable in any combination.
In the description of the invention the term substrate layer, cover layer, etc has been used. These terms are exchangeable in most cases. The substrate layers, the cover layers, and the intermediate distance layers are preferably made of polycarbonate. However, these layers can also be made from any other suitable material which is compliant with the optics.
The mentioned values, e.g. thicknesses, wavelengths, speeds, widths, etc. have to be taken as approximate values.
The term “visible” as used herein means that the label is visible to the naked eye, while the data written on the data layer are not visible to the naked eye.
Many combinations of data and label writing have been explained. The limited number of described combinations does not mean that the present invention is limited to these combinations. Rather, additional combinations can be employed, particularly on view of future standards.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 05105258.7 | Jun 2005 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB2006/051845 | 6/9/2006 | WO | 00 | 12/11/2007 |
