System and method for controlling focus in an optical disc drive

• US 20020145955A1
• Filed: 09/10/2001
• Published: 10/10/2002
• Est. Priority Date: 01/25/2001
• Status: Active Grant

• Current Assignee: RPX Corporation
• Original Assignee: DataPlay, Inc. (DPHI Incorporated)
• Inventors: Kadlec, Ron J., Watt, Charles R., Turner, Christopher J.
• Granted Patent: US 7,054,242 B2
• Time in Patent Office: Days
• US Class Current: 369/44.29
• CPC Class Codes: G11B 19/28 Speed controlling, regulating, or indicating G11B19/24 takes precedence
• CPC Class Codes: G11B 7/08505 Methods for track change, selection or preliminary positioning by moving the head
• CPC Class Codes: G11B 7/08523 with both tracking and focusing pull-in
• CPC Class Codes: G11B 7/08529 Methods and circuits to control the velocity of the head as it traverses the tracks
• CPC Class Codes: G11B 7/08541 involving track counting to determine position
• CPC Class Codes: G11B 7/08576 Swinging-arm positioners
• CPC Class Codes: G11B 7/09 with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
• CPC Class Codes: G11B 7/0901 for track following only G11B7/0925, G11B7/094, G11B7/0941, G11B7/0943, G11B7/0945, G11B7/0946, G11B7/0948 take precedence
• CPC Class Codes: G11B 7/0912 by push-pull method
• CPC Class Codes: G11B 7/0938 servo format, e.g. guide tracks, pilot signals
• CPC Class Codes: G11B 7/094 Methods and circuits for servo offset compensation
• CPC Class Codes: G11B 7/0941 Methods and circuits for servo gain or phase compensation during operation for initialising servos G11B7/0945
• CPC Class Codes: G11B 7/0943 Methods and circuits for performing mathematical operations on individual detector segment outputs
• CPC Class Codes: G11B 7/0946 specially adapted for operation during external perturbations not related to the carrier or servo beam, e.g. vibration
• CPC Class Codes: G11B 7/0948 specially adapted for detection and avoidance or compensation of imperfections on the carrier, e.g. dust, scratches, dropouts G11B7/095 takes precedence
• CPC Class Codes: G11B 7/0953 to compensate for eccentricity of the disc or disc tracks
• CPC Class Codes: G11B 7/0956 to compensate for tilt, skew, warp or inclination of the disc, i.e. maintain the optical axis at right angles to the disc
• CPC Class Codes: G11B 7/123 Integrated head arrangements, e.g. with source and detectors mounted on the same substrate
• CPC Class Codes: G11B 7/131 Arrangement of detectors in a multiple array
• CPC Class Codes: G11B 7/1356 Double or multiple prisms, i.e. having two or more prisms in cooperation

Abstract

A system for controlling focus in an optical disc drive for optical media with a premastered area that cannot be overwritten and a user-writeable area that can be overwritten includes instructions for turning focus on and off; and for acquiring focus on the optical media in response to a command to acquire focus. The actuator arm is moved according to a sinusoidal ramp function to prevent exciting resonances in the actuator arm. The amount of push-away force used while moving the actuator arm can be adjusted to avoid overshoot. The integrity of a focus error signal is determined and an attempt to re-acquire focus is made if the focus error signal indicates a bad focus status. The system turns focus off when at least one of the following conditions are met: (1) current state is a ramp focus acquire state and the maximum ramp position was reached; (2) current state is a focus push retry state and best push away value is greater than or equal to a predetermined fraction of a nominal push away value; or (3) a focus problem develops while in a focus active state.

Claims

1. An apparatus for controlling focus in an optical disc drive for optical media with a premastered area that cannot be overwritten and a user-writeable area that can be overwritten, comprising:

means for turning focus on and off; and

means for acquiring focus on the optical media.

2. The apparatus, as set forth in claim 1, further comprising means for receiving a command to acquire focus.

3. The apparatus, as set forth in claim 1, further comprising means for ramping an actuator arm away from the optical media to a predetermined position.

4. The apparatus, as set forth in claim 1, further comprising means for ramping an actuator arm towards the optical media until a status indicator indicates whether focus is closed.

5. The apparatus, as set forth in claim 1, further comprising means for determining the integrity of a focus error signal.

6. The apparatus, as set forth in claim 5, further comprising means for re-attempting to acquire focus if the focus error signal indicates a bad focus status.

7. The apparatus, as set forth in claim 1, further comprising means for turning off focus when at least one of the following conditions are met:

(1) current state is a ramp focus acquire state and the maximum ramp position was reached;

(2) current state is a focus push retry state and best push away value is greater than or equal to a predetermined fraction of a nominal push away value;

or (3) a focus problem develops while in a focus active state.

8. The apparatus, as set forth in claim 1, further comprising means for issuing a focus event when focus is to be turned off.

9. The apparatus, as set forth in claim 1, further comprising means for ramping an actuator arm to prevent exciting resonances in the actuator arm.

10. The apparatus, as set forth in claim 9, further comprising means for adjusting the amount of push-away force used while ramping the actuator arm.

11. A method for controlling focus in an optical disc drive for optical media with a premastered area that cannot be overwritten and a user-writeable area that can be overwritten, comprising:

turning focus on and off; and

acquiring focus on the optical media.

12. The method, as set forth in claim 11, further comprising receiving a command to acquire focus.

13. The method, as set forth in claim 11, further comprising ramping an actuator arm away from the optical media to a predetermined position.

14. The method, as set forth in claim 11, further comprising ramping an actuator arm towards the optical media until a status indicator indicates whether focus is closed.

15. The method, as set forth in claim 11, further comprising determining the integrity of a focus error signal.

16. The method, as set forth in claim 15, further comprising re-attempting to acquire focus if the focus error signal indicates a bad focus status.

17. The method, as set forth in claim 11, further comprising turning off focus when at least one of the following conditions are met:

(1) current state is a ramp focus acquire state and the maximum ramp position was reached;

(2) current state is a focus push retry state and best push away value is greater than or equal to a predetermined fraction of a nominal push away value;

or (3) a focus problem develops while in a focus active state.

18. The method, as set forth in claim 11, further comprising issuing a focus event when focus is to be turned off.

19. The method, as set forth in claim 11, further comprising positioning an actuator arm according to a sinusoidal ramp function to prevent exciting resonances in the actuator arm.

20. The method, as set forth in claim 19, further comprising adjusting the amount of push-away force used while positioning the actuator arm.

21. A computer program product comprising:

instructions to implement the method of claim 11.

22. A data signal comprising:

instructions to implement the method of claim 11.

24. The system, as set forth in claim 23, further comprising instructions operable to receive a command to acquire focus.

25. The system, as set forth in claim 23, further comprising instructions operable to ramp an actuator arm away from the optical media to a predetermined position.

26. The system, as set forth in claim 23, further comprising instructions operable to ramp an actuator arm towards the optical media until a status indicator indicates whether focus is closed.

27. The system, as set forth in claim 23, further comprising instructions operable to determine the integrity of a focus error signal.

28. The system, as set forth in claim 27, further comprising instructions operable to re-attempt to acquire focus if the focus error signal indicates a bad focus status.

29. The system, as set forth in claim 23, further comprising instructions operable to turn off focus when at least one of the following conditions are met:

(1) current state is a ramp focus acquire state and the maximum ramp position was reached;

(2) current state is a focus push retry state and best push away value is greater than or equal to a predetermined fraction of a nominal push away value;

or (3) a focus problem develops while in a focus active state.

30. The system, as set forth in claim 23, further comprising instructions operable to issue a focus event when focus is to be turned off.

31. The system, as set forth in claim 23, further comprising instructions operable to position an actuator arm according to a sinusoidal ramp function to prevent exciting resonances in the actuator arm.

32. The system, as set forth in claim 31, further comprising instructions operable to adjust the amount of push-away force used while positioning the actuator arm.

23. A system for controlling focus in an optical disc drive for optical media with a premastered area that cannot be overwritten and a user-writeable area that can be overwritten, comprising:

instructions operable to turn focus on and off; and

instructions operable to acquire focus on the optical media.