Optical disc drive apparatus, method for measuring tilt of an optical disc, and method for correcting tilt of an optical disc

Optical disc drive apparatus, comprising:

• rotating means defining a rotating axis for an optical disc;
• optical scanning means for scanning an optical disc with a light beam, said optical scanning means comprising:
• a light beam generating means for generating a light beam;
• a displaceable objective lens for focussing the light beam onto said optical disc;
• the apparatus further comprising:
• radial actuator means for radially displacing said objective lens;
• axial actuator means for axially displacing said objective lens;
• pivot actuator means for pivoting said objective lens;
• control means for controlling said radial actuator means, said axial actuator means, and said pivot actuator means;
• said control means being designed for measuring tilt in a measuring location of an optical disc by:
• by pivoting and axially displacing the objective lens, bringing said objective lens to a first focus measuring location such as to focus the light beam in a first anchor point having substantially the same angular coordinate φ as said measuring location and having a small radial distance Δr1 from said measuring location;
• by pivoting and axially displacing the objective lens, bringing said objective lens to a second focus measuring location such as to focus the light beam in a second anchor point having substantially the same angular coordinate φ as said measuring location and having a small radial distance Δr2 from said measuring location, said first and second anchor points being located on opposite sides of said measuring location;
• calculating tilt in said measuring location from the coordinates of said two focus measuring locations of said objective lens.

In an optical disc drive apparatus, of a type comprising:

• rotating means defining a rotating axis for an optical disc;
• optical scanning means for scanning an optical disc with a light beam, said optical scanning means comprising a displaceable objective lens for focussing the light beam onto said optical disc, said objective lens being displaceable in axial direction and capable of being pivoted about an axis directed in tangential direction;
• a method for setting an operational pivot angle of the objective lens;
• the method comprising the steps of:
• [a] selecting an initial pivot offset;
• [b] bringing the objective lens to an initial focus position (x0, 0, z0, Ψ0);
• [c] with respect to said initial focus position (x0, 0, z0, Ψ0), pivoting the objective lens over a first angle towards smaller radius to a position (x0, 0, z0, Ψ0−Δψ1);
• [d] displacing the objective lens axially over a first axial distance such that the optical beam is again focused on the disc;
• [e] with respect to said initial focus position (x0, 0, z0, Ψ0), pivoting the objective lens over a second angle towards larger radius to a position (x0, 0, z0, Ψ0+Δψ2), wherein the second angle is equal to said first angle;
• [f] displacing the objective lens axially over a second axial distance such that the optical beam is again focused on the disc;
• [g] comparing said first axial distance with said second axial distance;
• [h1] if said first axial distance is not, within a certain limit, substantially equal to said second axial distance, readjust the pivot offset and repeat steps [b]–[g];
• [h2] if said first axial distance is substantially equal to said second axial distance, set the operational pivot angle of the objective lens on the basis of the current value of the pivot offset.

In an optical disc drive apparatus, of a type comprising:

• rotating means defining a rotating axis for an optical disc;
• optical scanning means for scanning an optical disc with a light beam, said optical scanning means comprising a displaceable objective lens for focussing the light beam onto said optical disc, said objective lens being displaceable in axial direction and capable of being pivoted about an axis directed in tangential direction;
• a method for setting an operational pivot angle of the objective lens;
• the method comprising the steps of:
• [a] selecting an initial pivot offset;
• [b] bringing the objective lens to an initial focus position (x0, 0, z0, Ψ0);
• [c] with respect to said initial focus position (x0, 0, z0, Ψ0), axially displacing the objective lens over an axial distance towards the disc;
• [d] pivoting the objective lens over a first pivot angle towards smaller radius to a position (x0, 0, z0, Ψ0−Δψ1), such that the optical beam is again focused on the disc;
• [e] pivoting the objective lens over a second pivot angle towards larger radius to a position (x0, 0, z0, Ψ0+Δψ2) such that the optical beam is again focused on the disc;
• [f] comparing said first pivot angle with said second pivot angle;
• [g1] if said first pivot angle is not, within a certain limit, substantially equal to said second pivot angle, readjust the pivot offset and repeat steps [b]–[f];
• [g2] if said first pivot angle is substantially equal to said second pivot angle, set the operational pivot angle of the objective lens on the basis of the current value of the pivot offset.

Optical disc drive apparatus, comprising:

• rotating means defining a rotating axis for an optical disc;
• optical scanning means for scanning an optical disc with a light beam, said optical scanning means comprising:
• a light beam generating means for generating a light beam;
• a displaceable objective lens for focussing the light beam onto said optical disc;
• the apparatus further comprising:
• radial actuator means for radially displacing said objective lens;
• axial actuator means for axially displacing said objective lens;
• pivot actuator means for pivoting said objective lens;
• control means for controlling said radial actuator means, said axial actuator means, and said pivot actuator means;
• said control means being designed for setting an operational pivot angle of the objective lens by:
• [a] selecting an initial pivot offset;
• [b] activating said radial actuator means and said axial actuator means in order to bring the objective lens to an initial focus position (x0, 0, z0, ψ0);
• [c] activating said pivot actuator means in order to pivot the objective lens over a first pivot angle towards smaller radius to a position (x0, 0, z0, Ψ0−Δψ1);
• [d] activating said axial actuator means in order to axially displace the objective lens over a first axial distance such that the optical beam is again focused on the disc;
• [e] activating said pivot actuator means in order to pivot the objective lens over a second pivot angle towards larger radius to a position (x0, 0, z0, Ψ0+Δψ2), wherein the second angle is equal to said first angle;
• [f] activating said axial actuator means in order to axially displace the objective lens over a second axial distance such that the optical beam is again focused on the disc
• [g] comparing said first axial distance with said second axial distance;
• [h1] if said first axial distance is not, within a certain limit, substantially equal to said second axial distance, readjust the pivot offset and repeat steps [b]–[g];
• [h2] if said first axial distance is substantially equal to said second axial distance, set the operational pivot angle of the objective lens on the basis of the current value of the pivot offset.

Optical disc drive apparatus, comprising:

• rotating means defining a rotating axis for an optical disc;
• optical scanning means for scanning an optical disc with a light beam, said optical scanning means comprising:
• a light beam generating means for generating a light beam;
• a displaceable objective lens for focussing the light beam onto said optical disc;
• the apparatus further comprising:
• radial actuator means for radially displacing said objective lens;
• axial actuator means for axially displacing said objective lens;
• pivot actuator means for pivoting said objective lens;
• control means for controlling said radial actuator means, said axial actuator means, and said pivot actuator means;
• said control means being designed for setting an operational pivot angle of the objective lens by:
• [a] selecting an initial pivot offset;
• [b] activating said radial actuator means and said axial actuator means in order to bring the objective lens to an initial focus position (x0, 0, z0, Ψ0);
• [c] activate said axial actuator means in order to axially displace the objective lens over an axial distance towards the disc;
• [d] activate said pivot actuator means in order to pivot the objective lens over a first pivot angle towards smaller radius to a position (x0, 0, z0, Ψ0−Δψ1), such that the optical beam is again focused on the disc;
• [e] activate said pivot actuator means in order to pivot the objective lens over a second pivot angle towards larger radius to a position (x0, 0, z0, Ψ0+Δψ2) such that the optical beam is again focused on the disc;
• [f] comparing said first pivot angle with said second pivot angle;
• [g1] if said first pivot angle is not, within a certain limit, substantially equal to said second pivot angle, readjust the pivot offset and repeat steps [b]–[f];
• [g2] if said first pivot angle is substantially equal to said second pivot angle, set the operational pivot angle of the objective lens on the basis of the current value of the pivot offset.