Claims
- 1. In an optical disk drive having a disk with concentric or spiral tracks and a laser beam, optics and detector means for tracking said tracks, servo data pits comprising:
- at least one centered servo data pit centered on a track and at least two offset servo data pits offset on opposite sides of track center by one quarter of the track pitch; each of said servo data pits being of substantially the same size and shape, and wherein two servo signals are generated using two or more of said servo data pits.
- 2. Apparatus for generating servo signals in an optical disk drive having a disk with concentric or spiral tracks and a laser beam, comprising:
- a first servo data pit centered on a track;
- a second servo data pit outwardly, radially offset from said first servo data pit;
- a third servo data pit inwardly, radially offset from said first servo data pit; and
- servo signal generator means responsive to said servo data pits and the laser beam for deriving a first servo signal using said offset pits and a second servo signal using said centered and offset pits, the second servo signal radially offset from the first by substantially 90 degrees.
- 3. Apparatus according to claim 2 wherein said servo signal generator means includes:
- means for subtracting a signal detected from said second servo data pit from a signal detected from said third servo data pit to generate said first servo signal.
- 4. Apparatus according to claim 2 wherein said servo signal generator means includes:
- means for subtracting a signal detected from said second servo data pit from a signal detected from said first servo data pit;
- means for subtracting a signal detected from said third servo data pit from said signal detected from said first servo data pit; and
- means for adding said two subtracted signals to form said second tracking signal.
- 5. Apparatus according to claim 2 wherein:
- said first, second and third servo data pits of a first track are radially aligned with the corresponding said first, second and third servo data pits of a second track.
- 6. Apparatus according to claim 2 wherein:
- said first, second and third servo data pits are recorded in an area of a track having no preformatted groove.
- 7. Apparatus according to claim 5 wherein:
- said first, second and third servo data pits are recorded in an area of a track having no preformatted groove.
- 8. Apparatus according to 2 wherein:
- said first, second and third servo data pits are recorded in a servo data area, and a plurality of said area are recorded on each track interspersed with data.
- 9. Apparatus according to claim 5 wherein:
- said first, second and third servo data pits are recorded in a servo area, and a plurality of said area are recorded on each track interspersed with data.
- 10. Apparatus according to claim 6 wherein:
- said first, second and third servo data pits are recorded in a servo data area, and a plurality of said area are recorded on each track interspersed with data.
- 11. Apparatus according to claim 7 wherein:
- said first, second and third servo data pits are recorded in a servo data area, and a plurality of said area are recorded on each track interspersed with data.
- 12. Apparatus according to claim 2 wherein:
- said first servo data pit follows said second and third servo data pits.
- 13. Apparatus according to claim 2 wherein:
- said first, second and third servo data pits are each preformatted holes one-quarter wavelength of the laser beam deep.
- 14. Apparatus according to claim 2 wherein:
- said first, second and third servo data pits are spaced longitudinally from each other at least 1.5 times the size of each pit.
- 15. Apparatus according to claim 2 wherein:
- data is recorded on said tracks in a fixed block format and said first, second and third servo data pits are recorded with at least one of said pits not having the fixed block format relationship to the other said pits.
- 16. Apparatus according to claim 2 wherein:
- data is recorded on said tracks in a fixed block format and said first, second and third servo data pits are recorded with said first servo data pit spaced from at least the adjacent one of said second or third servo data pit farther than the distance specified by the fixed block format relationship.
- 17. Apparatus according to claim 4 further comprising:
- servo system means responsive to said first servo signal, said servo system means including damping means responsive to said first servo signal and means for controlling said damping means in response to said second servo signal.
- 18. Apparatus according to claim 17 wherein:
- said means for controlling said damping means in response to said second servo signal includes means for inverting the output of said damping means when the laser beam of the optical disk is centered outside the offset servo data pits between tracks.
- 19. Apparatus according to claim 4 further comprising:
- servo system means including a quadrature direction detector means responsive to both said first and said second servo signals for determining the direction of track crossing movement.
- 20. Apparatus according to claim 19 further comprising:
- means responsive to said quadrature direction detector means and to said servo signal for counting tracks during seek operations.
- 21. Apparatus according to claim 2 wherein:
- data is recorded in a predetermined format and said first, second and third servo data pits are recorded in a pattern distinguishable from said predetermined format.
- 22. An apparatus for generating at least one servo signal in an optical disk drive having a disk with concentric or spiral tracks and a laser beam, comprising:
- a first servo data pit centered on a track;
- a second servo data pit outwardly, radially offset from said first servo data pit;
- a third servo data pit inwardly, radially offset from said first servo data pit; and
- means for generating a servo signal from said first servo data pit, said second data pit and said third servo data pit, said servo signal having a maximum when the laser beam is centered relative to said first servo data pit.
Parent Case Info
This application is a continuation-in-part of copending Ser. No. 760,450 filed July 30, 1985, and now abandoned, Kurt W. Getreuer et al. inventors, and currently assigned to Laser Magnetic Storage International Company. That part of Ser. No. 760,450 disclosed and claimed herein is the joint invention of the applicants.
US Referenced Citations (13)
Non-Patent Literature Citations (1)
Entry |
Photonics Spectra, Jun. 1985, p. 60. |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
760450 |
Jul 1985 |
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