Optical recording and/or reproduction apparatus, tracking method, and optical recording medium

A tracking method for use with an optical recording medium, the optical recording medium including a recording layer and a substrate which has a guiding portion where concave portions and convex portions are periodically formed along a predetermined direction, the method comprising steps of:

• (a) emitting a first light beam;
• (b) diffracting a portion of the first light beam so as to output a first diffracted light beam and a second diffracted light beam, and for converging the other portion of the first light beam, thereby outputting a second light beam so as to be converged at a predetermined convergence point;
• and
• (c) controlling the optical system,
• wherein the first and second diffracted light beams interfere with each other to generate interference fringes which extend in a direction substantially perpendicular to the recording layer,
• the interference fringes include bright portions and dark portions which occur alternately along the predetermined direction,
• the step (b) includes a step of (d) outputting the first and second diffracted light beams and the second light beam such that the bright portions of the interference fringes form light spots on the guiding portion when the predetermined convergence point of the second light beam is present within the recording layer,
• the tracking method further includes a step of (e) detecting the interference fringes reflected by the guiding portion so as to output a detection signal, and
• the step (c) includes a step of (f) controlling the optical system based on the detection signal such that the optical spots follow at least either of the concave portions and the convex portions.

An optical recording and/or reproduction apparatus for use with an optical recording medium, the optical recording medium including a recording layer and a substrate which has a guiding portion where concave portions and convex portions are periodically formed along a predetermined direction, the optical recording and/or reproduction apparatus comprising:

• a light source for emitting a first light beam;
• an optical system for diffracting a portion of the first light beam so as to output a first diffracted light beam, a second diffracted light beam, a third diffracted light beam, and a fourth diffracted light beam, and for converging the other portion of the first light beam, thereby outputting a second light beam so as to be converged at a predetermined convergence point;
• and
• a controlling section for controlling the optical system,
• wherein the first and second diffracted light beams interfere with each other to generate first interference fringes which extend in a direction substantially perpendicular to the recording layer,
• the third and fourth diffracted light beams interfere with each other to generate second interference fringes which extend in a direction substantially perpendicular to the recording layer,
• the first and second interference fringes include bright portions and dark portions which occur alternately along the predetermined direction,
• the frequency of the first interference fringes and the frequency of the second interference fringes are shifted with respect to each other along the predetermined direction,
• the optical system outputs the first, second, third, and fourth diffracted light beams and the second light beam such that the bright portions of the first and second interference fringes form light spots on the guiding portion when the predetermined convergence point of the second light beam is present within the recording layer,
• the optical recording and/or reproduction apparatus further includes a detection section for detecting the first and second interference fringes reflected by the guiding portion so as to output a detection signal, and
• the control section controls the optical system based on the detection signal such that the optical spots follow at least either of the concave portions and the convex portions.

An optical recording and/or reproduction apparatus for use with an optical recording medium, the optical recording medium including a plurality of recording layers and a substrate which has a guiding portion where concave portions and convex portions are periodically formed along a predetermined direction, the optical recording and/or reproduction apparatus comprising:

• a light source for emitting a first light beam;
• an optical system for diffracting a portion of the first light beam so as to output a first diffracted light beam and a second diffracted light beam, and for converging the other portion of the first light beam, thereby outputting a second light beam so as to be converged at a predetermined convergence point;
• and
• a controlling section for controlling the optical system,
• wherein the first and second diffracted light beams interfere with each other to generate interference fringes which extend in a direction substantially perpendicular to the plurality of recording layers,
• the interference fringes include bright portions and dark portions which occur alternately along the predetermined direction,
• the optical system outputs the first and second diffracted light beams and the second light beam such that the bright portions of the interference fringes form light spots on the guiding portion when the predetermined convergence point of the second light beam is present within one of the plurality of recording layers,
• the optical recording and/or reproduction apparatus further includes a detection section for detecting the interference fringes reflected by the guiding portion so as to output a detection signal, and
• the control section controls the optical system based on the detection signal such that the optical spots follow at least either of the concave portions and the convex portions.

A tracking method for use with an optical recording medium, the optical recording medium including a plurality of recording layers and a substrate which has a guiding portion where concave portions and convex portions are periodically formed along a predetermined direction, the method comprising steps of:

• (a) emitting a first light beam;
• (b) diffracting a portion of the first light beam so as to output a first diffracted light beam and a second diffracted light beam, and for converging the other portion of the first light beam, thereby outputting a second light beam so as to be converged at a predetermined convergence point;
• and
• (c) controlling the optical system,
• wherein the first and second diffracted light beams interfere with each other to generate interference fringes which extend in a direction substantially perpendicular to the plurality of recording layers,
• the interference fringes include bright portions and dark portions which occur alternately along the predetermined direction,
• the step (b) includes a step of (d) outputting the first and second diffracted light beams and the second light beam such that the bright portions of the interference fringes form light spots on the guiding portion when the predetermined convergence point of the second light beam is present within one of the plurality of recording layers,
• the tracking method further includes a step of (e) detecting the interference fringes reflected by the guiding portion so as to output a detection signal, and
• the step (c) includes a step of (f) controlling the optical system based on the detection signal such that the optical spots follow at least either of the concave portions and the convex portions.