Method and device for performing tilt correction using multi-dimensional actuator

• US 20050117472A1
• Filed: 04/01/2003
• Published: 06/02/2005
• Est. Priority Date: 04/02/2002
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Raaymakers, Jeroen Arnoldus Leonardus Johannes
• Granted Patent: US 7,869,320 B2
• Time in Patent Office: Days
• US Class Current: 369/44.320
• 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

The present invention relates to method and device for performing tilt control. A focus and a tilt controlling output is generated, and a focusing and tilt state of an optical recording/reproducing beam is controlled by determining a radial tilt value based on a differentiation of focus control values obtained at different radii of said optical disk (1). The combination of e.g. a 3D actuator with the dz/dr tilt measurement provides the advantage that focus and tilt adjustment can be performed in the same element. Thereby, influences or measurement variations caused by environmental conditions and/or circuit characteristics can be minimized to reduce compensations requirements. Furthermore, a 3D actuator (11) with a split coil arrangement may be used to provide a three-dimensional focus adjustment. Thereby, the 3D actuator (11) can be used for feed forward tilt compensation without offset or gain errors and without any additional sensor.

Claims

1. A tilt control device for controlling a radial tilt of a recording surface of an optical disc (1) with respect to an optical recording/reproducing beam, said tilt control device comprising:

a) control means (10) for generating two focus controlling outputs; and

b) actuating means (11) for controlling a focusing state of the optical recording/reproducing beam based on said two focus controlling outputs and the radial tilt, characterized in that

c) said control means (10) is arranged to determine the radial tilt value based on a differentiation of focus control values obtained at different radii of said optical disk (1).

2. A device according to claim 1, characterized in that said actuating means (11) comprises a split focus coil arrangement arranged to provide focus and tilt adjustment;

and said control means (10) is arranged to supply said two focus controlling outputs to respective coils (C1, C2) of said split focus coil arrangement.

4. A device according to claim 1, characterized in that said control means (10) is arranged to position a sledge (4) at at least two different radial positions (R1 to R3), to control said actuating means (11) to adjust the focus, and to measure said focus controlling output at said at least two different radial positions.

5. A device according to claim 1, characterized in that

said control means (10) is arranged to set a mean disc tilt value in a tilt register (Rβ

).

6. A device according to claim 1, characterized in that

said control means (10) is arranged to generate said tilt control output based on measured mean focus controller outputs and corresponding radial steps between two measurements.

7. A device according to claim 5, characterized in that said tilt register value is obtained based on the following equation:

8. A device according to claim 1, further comprising a tilt table for storing an information indicating mean disc tilt values and corresponding radial positions.

9. An optical disc player comprising a tilt control device as claimed in claim 1.

3. A device according to claim, characterized in that said focus controlling output is a PID controller output.

10. A tilt control method for controlling a radial tilt of a recording surface of an optical disc (1) with respect to an optical recording/reproducing beam, said tilt control method comprising the steps of:

a) generating a focus and a tilt controlling output, and

b) controlling a focusing state of the optical recording/reproducing beam and the radial tilt based on said focus and tilt controlling output, characterized by

c) determining the radial tilt value based on a differentiation of focus control values obtained at different radii of said optical disk (1).

11. A method according to claim 10, characterized by controlling said focusing state by

using a split coil arrangement arranged to provide a focus adjustment;

and

supplying said focus and tilt controlling output to respective coils of said split coil arrangement.

12. A method according to claim 10, characterized in that said focus controlling step comprises using a mean focus controlling output for tilt control.

13. A method according to claim 10, characterized in that

said focus controlling step comprises measuring said focus controlling output at at least two different radial positions, and generating said tilt controlling output based on the mean radial tilt obtained for said two predetermined tilt angles in between said at least two different radial positions.