Servo processor receiving photodetector signals

• US 8,937,854 B2
• Filed: 09/26/2013
• Issued: 01/20/2015
• Est. Priority Date: 01/25/2001
• Status: Expired due to Fees

• Current Assignee: RPX Corporation
• Original Assignee: Optical Devices, LLC (OD Management Partners, LLC)
• Inventors: Kadlec, Ron J.
• Primary Examiner(s): Dinh, Tan X
• Application Number:
  US14/037,482
• Publication Number:
  US 20140029400A1
• Time in Patent Office: 481 Days
• Field of Search: 369 301- 3017, 369/44.28, 369/44.27, 369/44.29, 369/44.35
• US Class Current: 369/30.12
• CPC Class Codes: G11B 20/10046 filtering or equalising, e.g. setting the tap weights of an FIR filter
• CPC Class Codes: G11B 20/18 Error detection or correction; Testing , e.g. of drop-outs
• CPC Class Codes: G11B 27/105 of operating discs
• CPC Class Codes: G11B 27/3027 used signal is digitally coded
• CPC Class Codes: G11B 7/08505 Methods for track change, selection or preliminary positioning by moving the head
• 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 7/0901 for track following only G11B7/0925, G11B7/094, G11B7/0941, G11B7/0943, G11B7/0945, G11B7/0946, G11B7/0948 take precedence
• CPC Class Codes: G11B 7/0908 for focusing only G11B7/0925, G11B7/094, G11B7/0941, G11B7/0943, G11B7/0945, G11B7/0946, G11B7/0948 take precedence
• CPC Class Codes: G11B 7/0917 Focus-error methods other than those covered by G11B7/0909 - G11B7/0916
• 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 7/0945 Methods for initialising servos, start-up sequences

Abstract

A focus servo system for an optical disk drive includes an optical pick-up unit comprising at least one photodetector. At least one analog to digital converter is configured to digitize signals received from the at least one photodetector. At least one processor is configured to execute a digital servo algorithm to process the versions of the digitized signals to calculate a focus error signal (FES) from the versions of the digitized signals and to indicate a focus open condition based on the FES and the versions of the digitized signals.

Claims

1. A focus servo system for an optical disk drive, the focus servo system comprising:

an optical pick-up unit comprising at least one photodetector;

at least one analog to digital converter configured to digitize signals received from the at least one photodetector; and

at least one processor configured to execute a digital servo algorithm to process the versions of the digitized signals to;

calculate a focus error signal (FES) from the versions of the digitized signals;

apply an FES gain to the FES to provide a modified FES signal;

obtain a threshold value based upon the modified FES signal;

compute a sum signal from the versions of the digitized signals;

determine if the sum signal is below the threshold value; and

indicate a focus open condition if the sum signal is below the threshold value.

2. The focus servo system of claim 1, comprising at least one amplifier configured to gain adjust at least one of the signals received from the at least one photodetector prior to the at least one analog to digital converter digitizing the signals, the gain adjustment determined by the at least one processor.

3. The focus servo system of claim 2, wherein the at least one processor is configured to adjust gain of the at least one amplifier based on whether the optical disk drive is performing a read operation or a write operation.

4. The focus servo system of claim 1, wherein the at least one analog to digital converter and the at least one processor are included on the same integrated circuit.

5. The focus servo system of claim 4, wherein the integrated chip is an analog and digital processor.

6. The focus servo system of claim 1, wherein a version of at least one of the signals received from the at least one photodetector is compared to a focus OK (FOK) threshold to determine whether the focus servo system is in a near in-focus condition.

7. The focus servo system of claim 1, comprising at least one decimation filter, wherein the at least one of the versions of the digitized signals are down-sampled by the at least one decimation filter.

8. The focus servo system of claim 7, wherein at least one of the output frequency, filtering characteristics, and sample rate of the at least one decimation filter is determined by the at least one processor.

9. A focus servo system for an optical disk drive, the focus servo system comprising:

an optical pick-up unit comprising at least one photodetector;

at least one analog to digital converter configured to digitize signals received from the at least one photodetector; and

at least one processor configured to execute a digital servo algorithm to process the versions of the digitized signals to calculate a focus error signal (FES) from the versions of the digitized signals and indicate a focus open condition based on the FES and the versions of the digitized signals.

10. The focus servo system of claim 9, comprising at least one amplifier configured to gain adjust at least one of the signals received from the at least one photodetector prior to the at least one analog to digital converter digitizing the signals, the gain adjustment determined by the at least one processor.

11. The focus servo system of claim 10, wherein the at least one processor is configured to adjust gain of the at least one amplifier based on whether the optical disk drive is performing a read operation or a write operation.

12. The focus servo system of claim 9, wherein the at least one analog to digital converter and the at least one processor are included on the same integrated circuit.

13. The focus servo system of claim 12, wherein the integrated chip is an analog and digital processor.

14. The focus servo system of claim 9, wherein a version of at least one of the signals received from the at least one photodetector is compared to a focus OK (FOK) threshold to determine whether the focus servo system is in a near in-focus condition.

15. The focus servo system of claim 9, comprising at least one decimation filter, wherein the at least one of the versions of the digitized signals are down-sampled by the at least one decimation filter.

16. The focus servo system of claim 15, wherein at least one of the output frequency, filtering characteristics, and sample rate of the at least one decimation filter is determined by the at least one processor.

17. A digital servo method for an optical disk drive, comprising:

digitizing versions of photodetector signals received from an optical pick-up unit of the optical disk drive to produce digital signals;

determining, through servo algorithms in a digital signal processor, a focus error signal from the digital signals; and

determining a focus open condition based on the focus error signal and versions of the digitized signals.

18. The digital servo method of claim 17, comprising gain adjusting at least one of the photodetector signals prior to digitizing the versions of the photodetector signals, the gain adjustment determined by the digital signal processor.

19. The digital servo method of claim 18, comprising adjusting gain based on whether the optical disk drive is performing a read operation or a write operation.

20. The digital servo method of claim 17, comprising comparing a version of at least one photodetector signals to a focus OK (FOK) threshold to determine whether the focus servo system is in a near in-focus condition.

21. The digital servo method of claim 17, comprising down-sampling at least one of the versions of the digitized signals by at least one decimation filter.

22. The digital servo method of claim 21, comprising determining at least one of the output frequency, filtering characteristics, and sample rate of the at least one decimation filter by the digital signal processor.

23. A non-transitory computer readable medium storing a computer program, executable by a machine, for a digital servo method for an optical disk drive, the computer program comprising executable instructions for:

digitizing versions of the photodetector signals to produce digital signals;

determining, through servo algorithms in a digital signal processor, a focus error signal from the digital signals; and

determining a focus open condition based on the focus error signal and versions of the digitized signals.