Optical pickup position control method

• US 20020054549A1
• Filed: 10/22/2001
• Published: 05/09/2002
• Est. Priority Date: 10/23/2000
• Status: Active Grant

• Current Assignee: Dropbox, Inc.
• Original Assignee: Sony Computer Entertainment Incorporated (Sony Group Corp.)
• Inventors: Ohtsu, Hiroshi
• Granted Patent: US 6,845,067 B2
• Time in Patent Office: Days
• US Class Current: 369/44.32
• 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 7/094 Methods and circuits for servo offset compensation
• CPC Class Codes: G11B 7/0945 Methods for initialising servos, start-up sequences
• 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 7/0956 to compensate for tilt, skew, warp or inclination of the disc, i.e. maintain the optical axis at right angles to the disc

Abstract

A position control method, which positions the relative position of an optical disk and an optical pickup to a position that provides the optimum value of the jitter value of the detection signal obtained by detecting the reflected light of an optical spot, has a jitter value acquisition procedure, which carries out multiple feed operations within the adjustment range of the relative position and obtains the jitter value at each feed position, an edge position setting procedure which sets as the edge positions relative positions that exceed a prescribed preset jitter threshold value, an optimum position computation procedure, which computes the optimum position that yields the optimum value for the jitter value, and an edge position setting procedure that sets the edge positions on the condition that there are at least two relative positions that yield a jitter value that exceeds the jitter threshold value.

Claims

1. An optical pickup position control method that is used in an optical disk device that records and/or plays back information by shining an optical spot from an optical pickup onto an optical disk, and that positions the relative position of said optical disk and said optical pickup in a position that gives the optimum value of a jitter value of a detection signal obtained by detecting the reflected light of said optical spot, said method comprising:

a) a jitter value acquisition procedure that performs multiple feed operations within the adjustment range of said relative position and obtains the jitter value at each feed position,

b) an edge position setting procedure that, based on the feed positions and jitter values obtained by said jitter value acquisition procedure, sets as the edge positions relative positions that will be greater than a preset prescribed jitter threshold value,

c) an optimum position computation procedure that computes the optimum position that will give the optimum value of said jitter value, based on the edge positions set by this edge position setting procedure, and

d) an optimum position adjustment procedure that adjusts the relative position of said optical disk and said optical pickup to the optimum position computed by this optimum position computation procedure,

e) wherein said edge position setting procedure sets the edge positions on the condition that there are at least two relative positions that will give a jitter value that exceeds said jitter threshold value.

2. A method as described in claim 1, wherein the acquisition of the jitter value at each feed position in said jitter value acquisition procedure is achieved by rotating said optical disk at the prescribed speed, taking in multiple jitter values along the inside circumference of said optical disk, and taking the average of the obtained multiple jitter values excluding the maximum value.

3. A method as described in claim 1 or 2, further comprising a jitter characteristics smoothing procedure that, following said jitter value acquisition procedure, smoothes the obtained jitter characteristics if the jitter characteristics by which the jitter values corresponding to the feed positions are plotted are judged not to conform to the preset jitter characteristics, and said edge position setting procedure and said optimum position computation procedure are carried out based on the jitter characteristics smoothed by this jitter characteristics smoothing procedure.

4. A method as described in claim 3, wherein said jitter characteristics smoothing procedure is carried out so that, denoting the jitter values obtained at feed position X0≦

X≦

Xmax by J(X0)≦

J(X)≦

J(Xmax), the smoothed jitter values Js(X0), Js(X), Js(Xmax) at each feed position are given by;

Js(X0)=[3xJ(X0)+J(X0+1)]/4;

Js(X)=[J(X1)+2xJ(X)+J(X+1)]/4;

Js(Xmax)=[J(Xmax−

1)+3xJ(Xmax)]/4;

said edge position setting procedure has

a first edge position setting step that takes as the first edge position the feed position of jitter value Jedge, which is the smaller of Js(X0) and Js(Xmax), and

a second edge position setting step that compares said Jedge and each Js(X) in sequence from this first edge position in the direction toward the feed position at which another Js(X0) or Js(Xmax) is taken, and takes as the second edge position the feed position at which Jedge≦

Js(X), and

said optimum position computation procedure calculates the midpoint of said first edge position and said second edge position and takes this midpoint as the optimum position.

5. A method as described in claim 1, further comprising an implementation decision procedure that decides, according to the type of said optical disk, whether to carry out said jitter value acquisition procedure, said edge position setting procedure, said optimum position computation procedure, and said optimum position adjustment procedure.

6. A method as described in claim 1, wherein said relative position is the tilt position between said optical disk and said optical pickup.

7. A method as described in claim 1, wherein said relative position is the focus position between said optical disk and said optical pickup.

8. A method as described in claim 2, further comprising an implementation decision procedure that decides, according to the type of said optical disk, whether to carry out said jitter value acquisition procedure, said edge position setting procedure, said optimum position computation procedure, and said optimum position adjustment procedure.

9. A method as described in claim 2, wherein said relative position is the tilt position between said optical disk and said optical pickup.

10. A method as described in claim 2, wherein said relative position is the focus position between said optical disk and said optical pickup.

11. A method as described in claim 3, further comprising an implementation decision procedure that decides, according to the type of said optical disk, whether to carry out said jitter value acquisition procedure, said edge position setting procedure, said optimum position computation procedure, and said optimum position adjustment procedure.

12. A method as described in claim 3, wherein said relative position is the tilt position between said optical disk and said optical pickup.

13. A method as described in claim 3, wherein said relative position is the focus position between said optical disk and said optical pickup.

14. A method as described in claim 4, further comprising an implementation decision procedure that decides, according to the type of said optical disk, whether to carry out said jitter value acquisition procedure, said edge position setting procedure, said optimum position computation procedure, and said optimum position adjustment procedure.

15. A method as described in claim 4, wherein said relative position is the tilt position between said optical disk and said optical pickup.

16. A method as described in claim 4, wherein said relative position is the focus position between said optical disk and said optical pickup.

17. A method as described in claim 5, wherein said relative position is the tilt position between said optical disk and said optical pickup.

18. A method as described in claim 5, wherein said relative position is the focus position between said optical disk and said optical pickup.