WO2005024798A2

WO2005024798A2 - Tracking method, recording means and a recorder for an optical disc

Info

Publication number: WO2005024798A2
Application number: PCT/IB2004/051593
Authority: WO
Inventors: Erwin R. Meinders; Joachim W. Hellmig; Gerardus R. Langereis
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2003-09-11
Filing date: 2004-08-27
Publication date: 2005-03-17
Also published as: TW200519890A; WO2005024798A3

Abstract

When writing or reading with multiple spots the spots are positioned on a line. By using the outer two spots for tracking the remaining spots can be precisely positioned. When the line forms an angle with the writing direction a situation can be created where the modulator only needs to consider data already present in one adjacent track, not both adjacent tracks, leading to a reduction in complexity of the modulator.

Description

Tracking method, recording means and a recorder for an optical disc

The invention relates to a method of tracking an N dimensional data array on a record carrier by irradiating multiple regions forming an N-1 dimensional array of regions, and to reading or writing means for reading or writing an N-dimensional data array, comprising at least one emitter for projecting multiple doses of energy on multiple regions forming an N-1 dimensional pattern, and to a reading device and a writing device comprising such a reading or writing means.

Such a method is known from high speed CD reading devices where multiple tracks on the record carrier are read at the same time using multiple laser beams. In order to ensure that the individual laser beams track the corresponding tracks on the record carrier complex tracking mechanisms are employed. When multidimensional data arrays are present on the record carrier it becomes increasingly difficult to take each laser beam's tracking into consideration.

It is an object of the present invention to provide a method for ensuring adequate tracking for multi-dimensional data arrays on a record carrier. In order to achieve this objective the method is characterized in that the method comprises the steps of : aligning a first irradiation of a first region of the multiple regions with a first tracking guide aligning a second irradiation of a second region of the multiple regions with a second tracking guide. Instead of controlling the tracking of each individual laser beam out of multiple beams a limited number of beams are dedicated to tracking while the remaining beams can be used for reading or writing the data in the multi-dimensional data array. This reduces the complexity of the tracking because a limited number of beams have to be considered while still appropriate tracking can be achieved. For instance in a three- dimensional data array tracking can be performed with three beams instead of all beams An embodiment of the invention is characterized in that N=2. When the data array is a two-dimensional data array the tracking can be achieved with only two beams instead of processing all beams. A further embodiment of the method is characterized in that in that the regions are positioned on a line. When two of the regions forming a line are placed in a plane the focusing of the remaining regions is automatically correct. Thus only two beams have to be focused correctly, reducing the complexity of the tracking. A further embodiment of the method is characterized in that the line is positioned to form an angle with the writing or reading direction. When the line is positioned at an angle the regions forming the line can be spaced apart further easing the manufacture requirements for the reading or writing means. Further more cross talk between the regions is reduced. A further embodiment of the method is characterized in that the angle is such that when recording adjacent to a previously recorded track a region of the pattern which region is closest to the previously recorded track is more advanced in the reading or writing direction than all other regions of the pattern. By letting the aligning of the second irradiation of the second region trail the aligning of the first irradiation of the first region with respect to the reading direction an angle between the line and the reading direction is created. Thus an accurate measurement of the angle between the line and the reading direction is not required. The trailing of the second irradiation compared to the first irradiation can be more accurately controlled by deriving timing information from the tracking guides on the record carrier. This simplifies the tracking. A further embodiment of the method is characterized in that the first tracking guide is delimiting the data array and the second tracking guide is delimiting the data array. By spacing the tracking guides as far apart as possible, i.e. delimiting the data array instead of embedding the tracking guides in the data, the first irradiation of the first region and the second irradiation of the second region will be as far apart as possible, thus allowing a more accurate control of the angle between the line and the reading direction. A further embodiment of the method is characterized in that the first tracking guide is a groove with a physical characteristic differing from grooves located in the data array. By providing the tracking guides with a physically different groove the tracking means can easily distinguish between the data array and tracking means. A further embodiment of the method is characterized in that the physical characteristic is a groove depth or a groove width or a groove wall angle. The physical characteristic differing between the tracking guides and the data array can be groove depth, groove width or groove wall angle. These physical characteristics can be easily detected by the tracking means. A further embodiment of the method is characterized in that first irradiation and the second irradiation are reading dose irradiations when other irradiations of other regions of the multiple regions are writing dose irradiations. When writing data in the data array on the record carrier the tracking beams do not need to use writing doses of irradiation. A reading dose is sufficient to allow the tracking of the tracking guides. A reading or writing means for reading or writing an N-dimensional data array, comprising at least one emitter for projecting multiple doses of energy on multiple regions forming an N-1 dimensional pattern, characterized in that the reading or writing means is arranged for projecting a first dose of optical energy on a first tracking guide and for projecting the a second dose of optical energy on a second tracking guide. Instead of controlling the tracking of each individual laser beam out of multiple beams a limited number of beams are dedicated to tracking while the remaining beams can be used for reading or writing the data in the multi-dimensional data array. This reduces the complexity of the tracking because a limited number of beams have to be considered while still appropriate tracking can be achieved. For instance in a three- dimensional data array tracking can be performed with three beams instead of all beams An embodiment of the reading or writing means is characterized in that N=2 When the data array is a two-dimensional data array the tracking can be achieved with only two beams instead of processing all beams. A further embodiment of the reading or writing means is characterized in that the N-1 dimensional pattern is a line When two of the regions forming a line are placed in a plane the focusing of the remaining regions is automatically correct. Thus only two beams have to be focused correctly, reducing the complexity of the tracking. A further embodiment of the reading or writing means is characterized in that reading or writing means is arranged for positioning the line to form an angle with the writing or reading direction. When the line is positioned at an angle the regions forming the line can be spaced apart further easing the manufacture requirements for the reading or writing means. Further more cross talk between the regions is reduced. A further embodiment of the reading or writing means is characterized in that the writing or reading means is arranged for aligning of the first irradiation of the first region with the first tracking guide and the aligning of the second irradiation of the second region with the second tracking guide and positioning the line to form an angle with the writing or reading direction. By letting the aligning of the second irradiation of the second region trail the aligning of the first irradiation of the first region with respect to the reading direction an angle between the line and the reading direction is created. Thus an accurate measurement of the angle between the line and the reading direction is not required. The trailing of the second irradiation compared to the first irradiation can be more accurately controlled by deriving timing information from the tracking guides on the record carrier. This simplifies the tracking. A further embodiment of the reading or writing means is characterized in that the first optical dose delimits the line and the second optical dose delimits the line. By spacing the tracking guides as far apart as possible, i.e. delimiting the data array instead of embedding the tracking guides in the data, the first irradiation of the first region and the second irradiation of the second region will be as far apart as possible, thus allowing a more accurate control of the angle between the line and the reading direction. A further embodiment of the reading or writing means is characterized in that the reading or writing means is arranged for projecting the optical dose with a groove with a physical characteristic differing from grooves located in the data array. By using tracking guides with a physically different groove the tracking means can easily distinguish between the data array and tracking means. A further embodiment of the reading or writing means is characterized in that the physical characteristic is a groove depth or a groove width or a groove wall angle. The physical characteristic differing between the tracking guides and the data array can be groove depth, groove width or groove wall angle. These physical characteristics can be easily detected by the tracking means. The reading or writing means can determine groove depth using the focusing circuits already present. Also groove width can be determined by adjusting tracking and observing variations in the reflections from the record carrier. Furthermore variation of the angle of the groove wall also results in different reflections from the record carrier. A further embodiment of the reading or writing means is characterized in that first irradiation and the second irradiation are reading dose irradiations when other irradiations of other regions of the multiple regions are writing dose irradiations. When writing on the record carrier there is no need for the writing means to use a writing dose to perform tracking. This reduces the energy consumption by the optical pickup unit and associated heat dissipation problems, in addition to preventing the dye on the record carrier above the tracking grooves from being altered, and potentially interfering A reading device according to the invention advantageously comprises a reading means as detailed in the reading means embodiments above. The reading device benefits from the reading means in that data retrieval from the record carrier can be performed with reduced tracking efforts. A writing device according to the invention advantageously comprises a writing means as detailed in the writing means embodiments above. The writing device benefits from the writing means in that the recording of data on the record carrier can be performed with reduced tracking efforts.

The invention will now be discussed based on figures. Figure 1 shows a record carrier comprising a spiral track. Figure 2 shows tracking perpendicular to the writing direction. Figure 3 shows tracking at an angle to the writing direction. Figure 4 shows tracking at an angle to the writing direction. Figure 5 shows tracking at an angle to the writing direction. Figure 6 shows a recorder using the invention. Figure 7 shows a section of a broad spiral comprising multiple grooves.

Figure 1 shows a record carrier comprising a spiral track. Figure 1 serves to show that when looking at a spiral track 1 on a record carrier, locally the spiral track is, for the purpose of the invention, equivalent to a record carrier with concentric tracks. When dealing with a section 2 of the spiral track 1 it can be observed that the section 2 comprises sections 3, 4, 5, 6 of tracks. When observing these sections 3, 4, 5, 6 of tracks locally the sections 3, 4, 5, 6 of tracks do in essence not differ from sections of tracks when the tracks would be concentric. Hence the present invention will work equally well with a spiral track as with concentric tracks. Figure 2 shows tracking perpendicular to the writing direction. For clarity reasons only four spots 21, 22, 23, 24 and six sections of track 3, 4, 5, 6, 25, 27 are shown, the multi spot readout or multi spot writing can however be implemented with more optical spots allowing more data to be read from or written to more tracks at the same time. The previously written track 25 is situated directly next to one of the tracks currently being read or written. On the other side of the stripe consisting of the tracks 3, 4, 5, 6 a track 27 is shown that is to be recorded later. Figure 2 shows the situation where four tracks 3, 4, 5, 6 are being written in a stripe wise fashion. Writing direction is from the bottom to the top of the drawing. The more densely hatched area indicates recorded areas of the tracks, while the lightly hatched areas indicate areas of the tracks that are still to be recorded. Tracking can be performed using two of the four spots. Advantageously the spots are spaced apart as far as possible so the first spot 21 and the fourth spot 24 would be. chosen as tracking spots. As can be seen the spots 21, 22, 23, 24 are close together. When writing a mark on the first track 3 a modulation that considers the influence of the recording of data on the adjacent tracks only needs to consider the data on the adjacent track comprising data. The empty track 27 comprises no data and does not need to be considered , by the modulation. When considering the fourth track 6 it is obvious that the data in both the adjacent tracks 5, 25 must be incorporated in the modulation. Further more one track 5 is being written while the previously recorded track 25 already comprises data, thus allowing planning by the modulator to plan the modulation such that desirable patterns result when recording the data in the track 6. Consequently three different situations must be handled by the modulator: both adjacent tracks comprise data, one being already recorded, one being currently recorded - both adjacent tracks comprise data, both adjacent tracks being currently recorded one adjacent track is empty, the other adjacent track is currently being recorded. This leads to an undesirable differentiation is cases to be distinguished by the modulator. Figure 3 shows tracking at an angle to the writing direction When the writing is performed by a row 36 of spots which forms an angle A to the read/write direction 38 which is larger than 90 degrees only a single situation has to be considered by the modulator. For each track 3, 4, 5, 6, 35, 37 the modulator only needs to consider one adjacent track that already comprises data. For each track 3, 4, 5, 6, 35, 37 the modulator only needs to consider the data of a single adjacent track which reduces the complexity of the system because each track 3, 4, 5, 6, 35, 37 can be treated in exactly the same manner. For reasons of explanation the four spots 31, 32, 33, 34 are named from left to right in figure 3 the first spot 31, the second spot 32, the third spot 33, and the fourth spot 34. The tracks 3, 4, 5, 6, 35, 37 are named from left to right in figure 3 the first track 37, the second track 3, the third track 4, the fourth track 5, the fifth track 6 and the sixth track 35. For example when considering the fifth track 6 adjacent to the previously recorded sixth track 35 the sixth track 35 comprises data in the section directly adjacent to the position of the fourth spot 34 on the fifth track 6. There is no data on the fourth track 5 directly adjacent to the fourth spot because the third spot 33 on the fourth track 5 adjacent to the fifth track 6 is trailing the fourth spot 34. For the second and third spots 32, 33 a similar situation exists. For example when considering the fourth track 5 the fifth track 6 comprises data in the section directly adjacent to the position of the third spot 33 on the fourth track 5 because the fourth spot 34 on the fifth track 6 is leading, i.e. further advanced in the writing direction relative to the third spot 33 because of the angle between the row 36 of spots used for recording and the writing direction. There is no data on the third track 4 directly adjacent to the third spot 33 because the second spot 32 on the third track 4 adjacent to the fourth track 5 is trailing the third spot 33. For the first spot 31 a similar situation exists. The third track 4 comprises data in the section directly adjacent to the position of the first spot 31 on the second track 3 because the second spot 32 on the third track 4 is leading, i.e. further advanced in the writing direction relative to the first spot 31 because of the angle between the row 36 of spots used for recording and the writing direction.. There is no data on the first track 37 directly adjacent to the first spot 31 because the first track 37 is not yet recorded and is not part of the stripe currently being recorded by the row 36 of spots, i.e. there is no data in the first track 37 at all when recording an empty record carrier, for instance a write once or rewriteable recording medium. Figure 4 shows tracking at an angle to the writing direction. When the writing is performed by a row 46 of spots which forms an angle B to the read/write direction 48 which is smaller than 90 degrees three different situations must be considered by the modulator. For reasons of explanation the four spots 41, 42, 43, 44 are named from left to right in figure 4 the first spot 41, the second spot 42, the third spot 43, and the fourth spot 44. The tracks 3, 4, 5, 6, 45, 47 are named from left to right in figure 4 the first track 47, the second track 3, the third track 4, the fourth track 5, the fifth track 6 and the sixth track 45. It is evident that this configuration is less desirable because the fourth spot 44 has to consider data on both adjacent tracks while when writing using the second and third spot 42, 43 the modulator only has to consider data on one adjacent track. When writing using the first spot 41 there is no adjacent data on either adjacent tracks 47, 4. Thus three different conditions have to be considered when writing with fourth spots in the configuration of figure 4. Although an increase in number of spots does not lead to an increase in conditions to be considered it still represents an unfavorable situation compared to the reading angle A of figure 3 where the spot 34 writing on the fifth track 6 directly adjacent an previously recorded track 35 is more advanced in the writing direction 38, creating an angle A larger than 90 degrees between the row 36 of spots and the writing direction 38. Figure 5 shows tracking at an angle to the writing direction For reasons of explanation the five spots 51, 52, 53, 54, 59 are named from left to right in figure 5 the first spot 51, the second spot 52, the third spot 53, the fourth spot 54, and the fifth spot 59. The tracks 57, 3, 4, 5, 6, 55 are named from left to right in figure 5 the first track 57, the second track 3, the third track 4, the fourth track 5, the fifth track 6 and the sixth track 55. This is an improved version of figure 3 where the angle A between the row 56 of spots and the writing direction 58 is larger than 90 degrees. An additional spot 59 is introduced. This additional spot 59 allows the writing of the data in the second track 3, the third track 4 the fourth track 5 and the fifth track 6 to be precisely positioned relative to the data in the sixth track 55. For this the additional spot 59 is a reading spot, while the other spots 51, 52, 53, 54 are writing spots. The recorder reads the data in the previously recorded sixth track 55 and by knowing the angle A between the row of spots and the recording direction can determine how much each spot is lagging relative to each other and relative to the additional spot 59. Thus, with simple delays the alignment perpendicular to the writing direction of the data can be achieved. A further advantage of the additional spot 59 is that it can be used for tracking, thus even further separating the tracking spots, allowing a more accurate tracking and a more accurate determination and control of the angle A. Although not shown in figure 5, yet another reading spot can be added which allows tracking to be performed by spots focused on the first track 57 and the sixth track 55, separating the spots used for tracking even more, allowing a more accurate tracking and more accurate determination and control of the angle A. Figure 6 shows a recorder using the invention The recorder 60 comprises an interface 62 that is connected to other devices via a connection 67. Via connection 67 the interface 62 receives data to be recorded on the recording medium 64. This data is passed on to the processing means 61, i.e. a microprocessor. The processing means 61 performs the necessary operations on the data received from the interface 62 to obtain an output signal that can be processed by the basic engine 63. The basic engine 63 comprises all means required to write the output signal obtained from the processing means 61 on the recording medium 64. The processing means 61 is further connected to a data storage means 65 and a interface 66. The data storage means 65 is for instance used for storing parts of the data while performing operations on other parts of the data and for holding the program that when executed by the processing means 61 allows the processing means 61 to perform the required operations. The modulator can be implemented in software, i.e. the program for the modulator is stored in the storage means 65 and executed by the processing means 61 when required. The modulator can also be implemented in hardware in the processing means 61. When writing the data on the recording medium 64 the processor also ensures that the proper delay is applied to align the data on the tracks as is described in figure 5. For this the delay lines can be implemented in hardware or in software using the storage means 65 to temporarily store the data for each track. The delay depends on the rotation speed and the angle between the row of spots and the writing direction and can be determined by the processing means 61 by writing and subsequently reading a small section of the disc 64. Further more, when a 2 dimensional writing scheme is employed where the writing by a spot not only affects its corresponding track but also adjacent locations on the same track and on adjacent tracks, the processing means can predict and adjust the writing power such that the desired amount of influence on the adjacent tracks is obtained. In this way, depending on the recording material used, pit shrinkage or annealing of the material on adjacent tracks can be obtained. Figure 7 shows a section 85 of a broad spiral 86 where the broad spiral 86 comprises multiple grooves 71, 72, 73, 74, 75 for recording data and two grooves 70, 76for tracking. Instead of tracking two grooves 71, 72, 73, 74, 75 used for data storage, the tracking can also be performed by tracking two grooves 70,76 for tracking. These grooves 70,76 for tracking can be distinguished from the other grooves 71, 72, 73, 74, 75 because they have different characteristics as discussed above. Because the tracking is performed with spots 78, 84 that are not used for writing only read-out power levels are required for the tracking spots 78, 84. Pre-recorded information in the tracking grooves 70, 76 can be read by the tracking spots 78, 84 and can be used for determining the location of the other spots 79, 80, 81, 82, 83. This way the data can be recorded in an exact predetermined location. Furthermore, the exact location of the first tracking spot 78 relative to the second tracking spot 84 can be easily determined because both the distance between the tracking grooves 70, 76 and the offset between the first tracking spot 78 and the second tracking spot 84 in the reading direction is known. The angle between the line connecting the first tracking spot 78 and the second tracking spot 84 can thus be calculated and, if required, adjusted by the recorder.

Claims

CLAIMS:

1. Method of tracking an N dimensional data array on a record carrier by irradiating multiple regions forming an N-1 dimensional array of regions comprising the steps of : aligning a first irradiation of a first region of the multiple regions with a first tracking guide aligning a second irradiation of a second region of the multiple regions with a second tracking guide.

2. Method as claimed in claim 1, characterized in that N=2

3. Method as claimed in claim 2, characterized in that the regions are positioned on a line

4. Method as claimed in claim 3, characterized in that the line is positioned at an angle with the writing or reading direction.

5. Method as claimed in claim 5, characterized in that the angle is such that when recording adjacent to a previously recorded track a region of the pattern which region is closest to the previously recorded track is more advanced in the reading or writing direction than all other regions of the pattern.

6. Method as claimed in claim 5, characterized in that the first tracking guide is delimiting the data array and the second tracking guide is delimiting the data array.

7. Method as claimed in claim 6, characterized in that the first tracking guide is a groove with a physical characteristic differing from grooves located in the data array.

8. Method as claimed in claim 7, characterized in that the physical characteristic is a groove depth or a groove width or a groove wall angle.

9. Method as claimed in claim 1 to 8, characterized in that first irradiation and the second irradiation are reading dose irradiations when other irradiations of other regions of the multiple regions are writing dose irradiations.

10. Reading or writing means for reading or writing an N-dimensional data array, comprising at least one emitter for projecting multiple doses of energy on multiple regions forming an N-1 dimensional pattern, characterized in that the reading or writing means is arranged for projecting a first dose of optical energy on a first tracking guide and for projecting the a second dose of optical energy on a second tracking guide.

11. Reading or writing means as claimed in claim 10, characterized in that N=2

12. Reading or writing means as claimed in claim 11, characterized in that the N-1 dimensional pattern is a line

13. Reading or writing means as claimed in claim 12, characterized in that reading or writing means is arranged for positioning the line to form an angle with the writing or reading direction.

14. Reading or writing means as claimed in claim 13, characterized in that the writing or reading means is arranged for aligning of the first irradiation of the first region with the first tracking guide and the aligning of the second irradiation of the second region with the second tracking guide and positioning the line to form an angle with the writing or reading direction.

15. Reading or writing means as claimed in claim 14, characterized in that the first optical dose delimits the line and the second optical dose delimits the line.

16. Reading or writing means as claimed in claim 15, characterized in that the reading or writing means is arranged for projecting the optical dose with a groove with a physical characteristic differing from grooves located in the data array.

17. Reading or writing means as claimed in claim 16, characterized in that the physical characteristic is a groove depth or a groove width or a groove wall angle.

18. Reading or writing means as claimed in claim 10 to 17, characterized in that first irradiation and the second irradiation are reading dose irradiations when other irradiations of other regions of the multiple regions are writing dose irradiations.

19. Reading device comprising a reading means as claimed in claim 10 to 18.

20. Writing device comprising a writing means as claimed in claim 10 to 18.