Flexible servicing of servo algorithms using a digital signal processor

• US 7,023,766 B2
• Filed: 09/10/2001
• Issued: 04/04/2006
• Est. Priority Date: 01/25/2001
• Status: Expired due to Fees

• Current Assignee: Northrop Grumman Corporation, RPX Corporation
• Original Assignee: DPHI Acquisitions, Inc.
• Inventors: Turner, Christopher J., Kadlec, Ron J.
• Primary Examiner(s): PSITOS, ARISTOTELIS
• Application Number:
  US09/950,373
• Publication Number:
  US 20020097644A1
• Time in Patent Office: 1,667 Days
• Field of Search: 369/44.34, 369/53.15, 369/53.23, 369/44.29, 700/56, 700/55
• 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 with a plurality of servo algorithms executing on a digital signal processor is presented. The digital signal processor receives a sensor interrupt, indicating availability of digitized data from optical sensors, and decides which of a plurality of servo algorithms to service in response to the interrupt. In some embodiments, the plurality of servo algorithms includes a tracking servo algorithm. In some embodiments, the plurality of servo algorithms includes a focus servo algorithm. In some embodiments, multi-track seek operations or one-track jump operations can also be serviced during the interrupt period.

Claims

1. A method of controlling the position of an optical pick-up unit, comprising:

receiving a sensor input interrupt in a digital signal processor, the sensor input interrupt indicating that sensor signals from the optical pick-up unit are available for processing;

deciding to service either a tacking servo algorithm or a focusing servo algorithm;

if decision is to service the tracking servo algorithm;

in the digital signal processor, calculating a tracking error signal (TES) from digitized versions of the sensor signals; and

servicing the tracking servo algorithm using the calculated tacking error signal;

if the decision is to service the focusing servo algorithm;

in the digital signal processor, calculating a focusing error signal (FES) from digitized versions of the sensor signals; and

servicing the focusing servo algorithm using the calculated focusing error signal.

2. The method of claim 1, wherein the tracking servo algorithm includes:

calculating a control signal from the tracking error signal; and

wherein the focusing servo algorithm includes calculating a control signal from the focusing error signal.

3. The method of claim 2, wherein calculating the tracking error signal includes:

receiving digitized optical signals from the optical pick-up unit;

calculating a first error signal from the optical signals;

offsetting the first error signal to form an offset error signal; and

amplifying the offset error signal to form the tracking error signal.

4. The method of claim 1, further including determining whether a seek operation is being executed;

and performing the seek algorithm if the seek operation is being executed.

5. The method of claim 1, further included servicing a one-track jump operation if a one-track jump operation is in effect.

6. The method of claim 1, further including performing a task after servicing either the focusing servo algorithm or the tracking servo algorithm.

7. The method of claim 1, wherein deciding to service either the focusing servo algorithm or the tracking servo algorithm includes choosing the servo algorithm that has not been recently serviced.

8. A servo system, comprising:

an optical pick-up unit;

an analog-to-digital converter coupled to receive signals from a plurality of detectors in the optical pick-up unit and provide digital versions of the signals from the plurality of detectors;

a digital signal processor coupled to receive the digital versions of the signals and calculate a tracking error signal, the digital signal processor calculating a control signal for driving the servo system to reduce the calculated tracking error signal; and

a driver coupled to control the position of the optical pick-up unit in response to the control signal,

wherein the digital signal processor is configured to calculate the tracking error signal in response to the receipt of a sensor input interrupt indicating that the digital signals from the analog-to-digital converter are available for processing.