Re-writable optical disk having reference clock information permanently formed on the disk

Abstract

An optical disk structure and optical disk recorder which enables data to be rewritten onto the recording layer of the optical disk. A clock reference structure is permanently formed along servo tracks of the optical disk. An optical transducer is coupled to the clock reference structure and generates a clock reference signal simultaneously with writing new data onto the recording layer of the optical disk. The data is written as data marks along the servo tracks. Each of the data marks includes edges. The edges of the data marks are recorded in synchronization with a write clock. The write clock is phase-locked with the clock reference signal. Therefore, the edges of the data marks are aligned with the clock reference structure with sub-bit accuracy. Standard DVD-ROM disk readers are not able to detect the high spatial frequency of the clock reference structure. Therefore, the optical disk structure and optical disk recorder of this invention allow production of re-writable optical disks which can be read by standard DVD-ROM disk readers.

Description

Where the track pitch P is the radial distance between track centers. The MTF curves of FIG. 18 have been derived for the same optical transducers that are represented by MTF curves 116 and 118 of FIG. 11. Curves 116 and 118 are shown again as dotted curves in FIG. 18. In FIG. 18, the MTF of the optical transducer in an optical disk recorder is represented by curve 118. When a clock reference signal is detected using radial push pull detection, the MTF of the optical transducer is reduced. Curve 125 shows the reduced MTF. The cutoff frequency has also been reduced, from 2.46 cycles/um for curve 118 to 2.06 cycles/um for curve 125. This MTF decline associated with radial push pull detection significantly reduces the modulation of a clock reference signal having a spatial frequency above the cutoff frequency of a standard optical disk reader. For this reason, the preferred configuration of this embodiment uses a clock reference structure having a spatial frequency below the cutoff frequency of a standard optical disk reader. Note that the MTF reduction illustrated with reference to FIG. 18 applies only to the detection of the clock reference structure and does not affect the resolution of the optical transducer for the purpose of recording data.

Note that the radial push pull signal contains tracking error information at frequencies substantially below the clock reference signal frequency and may also be used generate a tracking error signal for use by a tracking positioner.

The invention can include other clock reference structures such as a clock reference structure which consists of a groove having a single edge which oscillates. The three clock reference structures described here are by way of example.

FIG. 21 shows another embodiment of the optical disk recorder of the invention which includes a second optical transducer 182 for reading data stored on an optical disk 80. The optical disk recorder 81 has a first optical transducer 82 and a second optical transducer 182 which are optically coupled to the recording layer of the optical disk 80. The first optical transducer 82 is used for recording data and operates as previously described with reference to FIG. 10. The second optical transducer 182 follows a servo track as the optical disk 80 rotates. The data marks cause the second optical transducer 182 to produce a data signal as the optical disk 80 rotates. The second optical transducer 182 includes several optical devices and has many similarities with optical transducer 82. A laser 190 emits a linearly polarized beam of light 192 which is collimated by a collimator lens 194. The light beam 192 passes through a polarization beam splitter 196. The light beam 192 is converted from linear polarization to circular polarization by a quarter wave retardation plate 198. The light beam 192 is focused by an objective lens 200 onto the recording layer of the optical disk 80 containing recorded data marks. A portion of the light beam 192 is reflected by the optical disk 80 and returns through the objective lens 200 and the quarter wave plate 198. Upon passing back through the quarter wave retardation plate 198, the light beam 192 is again linearly polarized. However the polarization direction of the light beam 192 is rotated 90 degrees relative to its initial orientation. Therefore, the polarization beam splitter 196 reflects substantially all of light beam 192 towards beam splitter 202. The beam splitter 2020 splits the beam 192 into a first light beam 204 and a second light beam 206. The first light beam 204 is collected by a first light beam 204 and a second light beam 206. The first light beam 204 is collected by a first lens 208 onto a first detector 210 which is arranged to produce a focus-error signal. The second light beam 206 is collected by a second lens 212 onto a second detector 214 which is arranged to produce a data signal. The second detector 214 also produces a tracking-error signal used by a tracking positioner. Detectors 210 and 214 generally include multiple detection areas and produce multiple detection signals as is well known in the art. Many alternative arrangements of the optical components and detectors are possible, including arrangements which combine or eliminate optical components shown in FIG. 21.

FIG. 22 illustrates another embodiment of the optical disk recorder of the invention. This embodiment includes another configuration of a second optical transducer 282 for reading data stored on an optical disk 80 and uses the same objective lens 100 as optical transducer 82 which is used for recording data. The shared objective lens is referred to as a combination objective lens 100. FIG. 22 shows the optical disk recorder 81 in which the second optical transducer 282 is optically coupled to data marks on the recording layer of optical disk 80. The second optical transducer follows a servo track as the optical disk rotates. The data marks cause the second optical transducer to produce a data signal as the optical disk rotates. As illustrated in FIG. 22, the second optical transducer 282 includes several optical devices and has many similarities with optical transducer 82. A laser 290 emits a linearly polarized beam of light 292 which is collimated by a collimator lens 294. The light beam 292 passes through a polarization beam splitter 296. The light beam 292 is converted from linear polarization to circular polarization by a quarter wave retardation plate 298. The light beam 292 then passes through an aperture stop 99 and is focused by an objective lens 100 onto the recording layer of the optical disk 80 containing recorded data marks. A portion of the light beam 292 is reflected by the optical disk 80 and returns through the objective lens 100 and the quarter wave plate 298. Upon passing back through the quarter wave retardation plate 298, the light beam 292 is again linearly polarized. However the polarization direction of the light beam 292 is rotated 90 degrees relative to its initial orientation. Therefore, the polarization beam splitter 296 reflects substantially all of light beam 292 towards beam splitter 302. The beam splitter 302 splits the beam 292 into a first light beam 304 and a second light beam 306. The first light beam 304 is collected by a first lens 308 onto a first detector 310 which is arranged to produce a focus-error signal. The second light beam 306 is collected by a second lens 312 onto a second detector 314 which is arranged to produce a tracking-error signal used by the tracking positioner, and a data signal containing information encoded in data marks on optical disk 80. Detectors 310 and 314 generally include multiple detection areas and produce multiple detection signals as is well known in the art. Many alternative arrangements of the optical components and detectors are possible, including arrangements which combine or eliminate optical components shown in FIG. 22. The laser 290 emits light at a longer wavelength than the laser 90. The beam splitter 296 is a wavelength sensitive beam splitter (sometimes called a dichroic beam splitter) which transmits light of a first wavelength and reflects light of a second wavelength. The shorter wavelength laser 90 of optical transducer 82 provides a smaller focused spot of light and a correspondingly higher MTF and cutoff frequency for recording data marks and producing a clock reference signal. The longer wavelength laser 292 of second optical transducer 282 provides a larger focused spot and a correspondingly lower MTF and cutoff frequency for reading data marks.

Another embodiment of the invention uses a variation of the components shown in FIG. 10 and previously described. As shown in FIG. 10, an optical transducer 82 performs the functions of both an optical disk recorder and an optical disk reader. When used as an optical disk recorder, the components of the optical transducer 82 perform as previously described with reference to FIG. 10. When used as an optical disk reader, the optical transducer 82 is optically coupled to data marks on the recording layer of optical disk 80. The optical transducer 82 follows a servo track as the optical disk 80 rotates. The data marks cause the optical transducer 82 to produce a data signal as the optical disk 80 rotates. The laser 90 emits a linearly polarized beam of light 92 which is collimated by a collimator lens 94. The light beam 92 passes through a polarization beam splitter 96. The light beam 92 is converted from linear polarization to circular polarization by a quarter wave retardation plate 98. The light beam 92 then passes through an aperture stop 99. The aperture stop 99 is dynamically controlled to be smaller when the optical transducer 82 is used as an optical disk reader and larger when the optical transducer 82 is used as an optical disk recorder. When the diameter of the aperture stop 99 is reduced, the effective numerical aperture of objective lens 100 is reduced. The light beam 92 passes through the objective lens 100 and onto the recording layer of the optical disk 80 containing recorded data marks. The MTF and the cutoff frequency of optical transducer 82 are reduced when the diameter of aperture stop 99 is reduced and a data signal is produced that does not contain unwanted noise produced by a clock reference structure formed on the recording layer of the optical disk 80. A portion of the light beam 92 is reflected by the optical disk 80 and returns through the objective lens 100 and the quarter wave plate 98. Upon passing back through the quarter wave retardation plate 98, the light beam 92 is again linearly polarized. However, the polarization direction of the light beam 92 is rotated 90 degrees relative to its initial orientation. Therefore, the polarization beam splitter 96 reflects substantially all of light beam 92 towards beam splitter 102. The beam 102 splits the beam 92 into a first light beam 104 and a second light beam 106. The first light beam 104 is collected by a first lens 108 onto a first detector 110 which is arranged to produce a focus-error signal. The second light beam 106 is collected by a second lens 112 onto a second detector 114 which is arranged to produce a tracking-error signal used by the tracking positioner. During data detection, detector 114 is also arranged to produce a data signal containing information encoded in data marks on optical disk 80. Detectors 110 and 114 generally include multiple detection ares and produce multiple detection signals as is well known in the art. Many alternative arrangements of the optical components and detectors are possible, including arrangements which combine or eliminate optical components shown in FIG. 10. When adjusted to a higher effective numerical aperture for recording data, the optical transducer 82 provides a smaller focused spot of light and a correspondingly higher MTF and cutoff frequency necessary for recording data marks and producing a clock reference signal. When adjusted to a lower effective numerical aperture, the optical transducer 82 provides a larger focused spot and a correspondingly lower MTF and cutoff frequency necessary for reading data marks.

Although specific embodiments of the invention have been described and illustrated, the invention is not to be limited to the specific forms or arrangements of parts so described and illustrated. The invention is limited only by the claims.

Claims

1. An optical disk comprising;

a recording layer having servo tracks; and

a clock reference structure formed along the servo tracks, the clock reference structure permitting data marks to be written and re-written to the recording layer in data fields of indeterminate length, the reference clock structure permitting the generation of a clock reference signal which controls where first and second transition edges of data marks are written to the recording layer with sub-bit accuracy.

2. The optical disk as recited in claim 1, wherein the clock reference structure comprises a reference spatial frequency which is greater than a predetermined spatial frequency.

3. The optical disk as recited in claim 2, wherein the predetermined spatial frequency is the maximum spatial frequency detectable by a standard DVD-ROM reader.

4. The optical disk as recited in claim 2, wherein the clock reference structure comprises edges of grooves of the servo tracks which oscillate in-phase at an oscillation spatial frequency, the oscillation spatial frequency corresponding to the reference spatial frequency.

5. The optical disk as recited in claim 2, wherein the clock reference structure comprises edges of grooves of the servo tracks which oscillate substantially 180 degrees out-of-phase at an oscillation spatial frequency, the oscillation spatial frequency corresponding to the reference spatial frequency.

6. The optical disk as recited in claim 2, wherein the clock reference structure comprises pits formed along the servo tracks, the reciprocal of a distance between centers of adjacent pits corresponding to the reference spatial frequency.

7. The optical disk as recited in claim 1, wherein a first optical transducer coupled to the clock reference structure generates a clock reference signal comprising a clock reference signal frequency.

8. The optical disk as recited in claim 7, wherein the first optical transducer coupled to data marks on the recording layer generates a data signal having a frequency spectrum in which all fundamental frequency components of the frequency spectrum are less than the clock reference signal frequency.

9. The optical disk as recited in claim 8, wherein a standard DVD-ROM reader can read the data marks but cannot detect the clock reference structure.

10. An optical disk recorder comprising:

an optical disk rotatably mounted on the recorder, the optical disk having a recording layer containing servo tracks;

a first optical transducer optically coupled to the recording layer of the optical disk, the first optical transducer following a servo track as the optical disk rotates;

a clock reference structure formed along the servo tracks providing data fields of indeterminate length, the clock reference structure causing the first optical transducer to produce a clock reference signal as the optical disk rotates;

means for recording data marks on the recording layer of the optical disk, wherein the data marks are recorded to include fundamental spatial frequencies less than a predetermined spatial frequency; and

a write clock which determines the placement of first and second transition edges of data marks on the recording layer of the optical disk with sub-bit accuracy, the write clock being phase locked to the clock reference signal.

11. The optical disk recorder as recited in claim 10, wherein the predetermined spatial frequency is the greatest spatial frequency detectable by a standard DVD-ROM reader.

12. The optical disk recorder as recited in claim 10, wherein the servo tracks include grooves and the clock reference structure comprises edges of the grooves which oscillate in-phase.

13. The optical disk recorder as recited in claim 12, wherein data marks cause the first optical transducer to produce an unwanted data signal as the optical disk rotates, and the clock reference signal is separated from the unwanted data signal by detecting the clock reference signal using radial push-pull detection.

14. The optical disk recorder recited in claim 10, wherein the servo tracks include grooves and the clock reference structure comprises edges on the grooves which oscillate substantially 180 degrees out-of-phase.

15. The optical disk recorder recited in claim 14, wherein data marks cause the first optical transducer to produce and unwanted data signal as the optical disk rotates, and the clock reference signal is separated from the unwanted data signal by detecting the clock reference signal using split detection.

16. The optical disk recorder recited in claim 10, wherein the clock reference structure comprises pits formed along the servo tracks.

17. The optical disk recorder as recited in claim 10, wherein the data marks are positioned along the servo tracks according to a DVD-ROM standard.

18. The optical disk recorder as recited in claim 10, wherein the data marks are arbitrarily coded.

19. The optical disk recorder as recited in claim 10, further comprising a second optical transducer which is optically coupled to the data marks on the recording layer, the second optical transducer following a servo track as the optical disk rotates, the data marks causing the second optical transducer to produce a data signal as the optical disk rotates.

20. The optical disk recorder as recited in claim 19, wherein the first optical transducer comprises a first laser and a first objective lens and the second transducer comprises a second laser and a second objective lens.

21. The optical disk recorder as recited in claim 20, wherein a numerical aperture of the combination objective lens is adjustably controlled to be lower when reading data than when recording data.

22. The optical disk recorder as recited in claim 20, wherein a numerical aperture of the combination objective lens is adjustably controlled to be lower when reading data than when recording data.

23. The optical disk recorder as recited in claim 20, wherein a wavelength of the second laser is greater than a wavelength of the first laser.

24. An optical disk recorder for receiving an optical disk which is rotatably mountable on the recorder, the optical disk comprising a recording layer having servo tracks and a clock reference structure having a spatial frequency which is greater than a predetermined spatial frequency, the clock reference structure being formed along the servo tracks and providing data fields of indeterminate length, the optical disk recorder comprising:

a first optical transducer which can optically couple to a recording layer of the optical disk, the first optical transducer following the servo tracks as the optical disk rotates, the clock reference structure causing the first optical transducer to produce a clock reference signal as the optical disk rotates;

means for writing data marks on the recording layer of the optical disk; and

a write clock which determines the physical placement of first and second transition edges of data marks written on the recording layer of the optical disk with sub-bit accuracy, the write clock being phase locked to the clock reference signal.

25. The optical disk recorder as recited in claim 24, wherein the predetermined spatial frequency is the maximum spatial frequency detectable by a standard DVD-ROM reader.

26. The optical disk recorder as recited in claim 24, wherein the first optical transducer can detect higher spatial frequencies that an optical transducer of a standard DVD-ROM optical disk reader.

27. The optical disk recorder as recited in claim 24, further comprising a second optical transducer which can optically couple to the data marks on the recording layer, the second optical transducer following a servo track as the optical disk rotates, the data marks causing the second optical transducer to produce a data signal as the optical disk rotates.

28. The optical disk recorder as recited in claim 24, wherein the first optical transducer comprises a first laser and a first objective lens and the second transducer comprises a second laser and a second objective lens.

29. The optical disk recorder as recited in claim 28, wherein a combination objective lens is both the first objective lens and the second objective lens and the objective lens.

30. The optical disk recorder as recited in claim 29, wherein a numerical aperture of the combination objective lens is adjustably controlled to be lower when reading data than when recording data.

31. The optical disk recorder as recited in claim 29, wherein a wavelength of the second laser is greater than a wavelength of the first laser.

32. The optical disk as recited in claim 7, wherein the first optical transducer coupled to data marks on the recording layer generates a data signal having a frequency spectrum in which the clock reference signal frequency is within fundamental frequency components of the frequency spectrum.

33. The optical disk as recited in claim 32, further including means for optically separating the data from the clock reference signal.

34. The optical disk as recited in claim 32, further including means for optically separating the clock reference signal the form the data signal.

35. An optical disk comprising;

a recording layer having servo tracks;

a clock reference structure formed along the servo tracks, the clock reference structure permitting data marks to be written and re-written to the recording layer in data fields of indeterminate length, the reference clock structure permitting the generation of a clock reference signal which controls where first and second transition edges of data marks are written to the recording layer with sub-bit accuracy;

a first optical transducer coupled to the clock reference structure generating a clock reference signal comprising a clock reference signal frequency; and wherein

the first optical transducer coupled to data marks on the recording layer generates a data signal having a frequency spectrum in which the clock reference signal frequency is within fundamental frequency components of the frequency spectrum.

36. An optical disk recorder comprising:

an optical disk rotatably mounted on the recorder, the optical disk having a recording layer containing servo tracks, the servo tracks comprising grooves;

a first optical transducer optically coupled to the recording layer of the optical disk, the first optical transducer following a servo as the optical disk rotates;

a clock reference structure comprising edges of the grooves which oscillate in-phase formed along the servo tracks, the clock reference structure providing data fields of indeterminate length, the clock reference structure causing the first optical transducer to produce a clock reference signal as the optical disk rotates;

means for recording data marks on the recording layer of the optical disk, wherein the data marks are recorded to include fundamental spatial frequencies less than a predetermined spatial frequency;

a write clock which determines the placement of data marks on the recording layer of the optical disk, the write clock being phase locked to the clock reference signal; and

wherein data marks cause the first optical transducer to produce an unwanted data signal as the optical disk rotates, and the clock reference signal is separated from the unwanted data signal by detecting the clock reference signal using radial push-pull detection.

37. An optical disk recorder comprising:

an optical disk rotatably mounted on the recorder, the optical disk having a recording layer containing servo tracks, the servo tracks comprising grooves;

a first optical transducer optically coupled to the recording layer of the optical disk, the first optical transducer following a servo track as the optical disk rotates;

a clock reference structure comprising edges on the grooves which oscillate substantially 180 degrees out-of-phase formed along the servo tracks, the clock reference structure providing data fields of indeterminate length, the clock reference structure causing the first optical transducer to produce a clock reference signal as the optical disk rotates;

means for recording data marks on the recording layer of the optical disk, wherein the data marks are recorded to include fundamental spatial frequencies less than a predetermined spatial frequency;

a write clock which determines the placement of data marks on the recording layer of the optical disk, the write clock being phase locked to the clock reference signal; and

wherein data marks cause the first optical transducer to produce an unwanted data signal as the optical disk rotates, and the clock reference signal is separated from the unwanted data signal by detecting the clock reference signal using split detection.

38. An optical disk, comprising:

a recording layer having a servo track;

a high spatial frequency clock reference structure formed along the servo track; and

a data field on the recording layer,

wherein newly written data marks to the data field overlap previously written data marks in the data field when the data field is discontinuously written to the recording layer;

wherein the spatial frequency of the high spatial frequency clock reference structure is greater than the spatial frequency spectrum of data in the data field.

39. The optical disk of claim 38, wherein the optical disk does not comprise synchronization fields.

40. The optical disk as recited in claim 38, wherein the data field comprises a plurality of data marks and each data mark is positioned on the recording layer with sub-bit accuracy.

41. The optical disk as recited in claim 38, wherein the spatial period of the clock reference structure is a multiple of the channel bit length.

42. The optical disk as recited in claim 38, wherein the servo track is shaped as a groove with first and second oppositely disposed edges and further comprising track address information included in the high spatial frequency clock reference structure as a low spatial frequency modulation of the two oppositely disposed edges of the groove.

43. An optical disk, comprising:

a recording layer having a servo track for recording data fields of arbitrary length, wherein newly written data marks to the data field overlap previously written data marks in the data field when the data field is discontinuously written to the recording layer; and

a clock reference structure formed along the servo track, the clock reference structure enabling writing of data on the recording layer, and enabling generation of a clock reference signal used for writing of the data;

wherein the clock reference structure formed along the servo track comprises a first edge and a second edge of a groove of the servo track, and track address information is included in the clock reference structure as a low spatial frequency modulation of the edges of the groove.

44. The optical disk of claim 43, further comprising a plurality of data marks written to the recording layer, wherein each data mark is positioned on the recording layer with sub-bit accuracy.