Apparatus and method for track access

Apparatus for moving a beam spot for writing or reading information onto or from a target track of an optical recording medium having a plurality of tracks on a surface, the apparatus comprising:

• a coarse actuator for moving an objective lens over a plurality of tracks on said surface of said optical recording medium, said objective lens directing a beam spot onto said surface;
• a fine actuator for moving a mirror to direct a beam from a light source to said objective lens;
• means for calculating a distance from a current beam spot position on said surface to a target track;
• means for generating a displacement signal, indicating a displacement of said mirror caused by said fine actuator, and a velocity signal, indicating a velocity of said mirror;
• means for generating a beam spot velocity signal indicating a velocity of the beam spot relative to said optical recording medium;
• means for generating a reference drive signal from the distance calculated by said distance calculating means, said reference drive signal being proportional to a reference acceleration of the beam spot relative to said optical recording medium;
• means for generating a reference velocity signal from said reference drive signal indicating a reference velocity of the beam spot relative to said optical recording medium;
• and
• means for generating a velocity difference signal indicating a difference between said reference velocity and said beam spot velocity;
• wherein said coarse actuator is driven in accordance with said displacement and velocity signals of said mirror, said velocity difference signal and said reference drive signal;
• and
• wherein said fine actuator is driven in accordance with said displacement and velocity signals of said mirror and said velocity difference signal.

An optical disk drive comprising:

• means for supporting and rotating an optical disk having a plurality of tracks on a recording surface;
• a light source;
• an objective lens for directing a beam emitted from said light source onto said recording surface as a beam spot for writing or reading information;
• a coarse actuator for moving said objective lens over a plurality of tracks on said surface;
• a fine actuator, carried by said coarse actuator, for moving said objective lens relative to said coarse actuator in a tracking direction;
• means for calculating a distance from a current beam spot position to a target track;
• means for generating a relative position signal, indicating the displacement of said objective lens relative to said coarse actuator, and a relative velocity signal, indicating a velocity of said objective lens relative to said coarse actuator;
• means for generating a beam spot velocity signal indicating a velocity of the beam spot relative to said disk;
• means for generating a reference drive signal from the distance calculated by said distance calculating means, said reference drive signal being proportional to a reference acceleration of the beam spot relative to said optical disk;
• means for generating a reference velocity signal from said reference drive signal indicating a reference velocity of the beam spot relative to said optical disk;
• and
• means for generating a velocity difference signal indicating a difference between said reference velocity and said beam spot velocity;
• wherein said coarse actuator is driven in accordance with said relative position and velocity signals of said objective lens, said velocity difference signal and said reference drive signal;
• and
• wherein said fine actuator is driven in accordance with said relative position and velocity signals of said objective lens and said velocity difference signal.

An optical disk drive comprising:

• means for supporting and rotating an optical disk having a plurality of tracks on a recording surface;
• a light source;
• a mirror for reflecting a beam emitted from said light source;
• an objective lens for directing the beam reflected by said mirror onto said recording surface as a beam spot for writing or reading information;
• a coarse actuator for moving said objective lens over a plurality of tracks on said surface;
• a fine actuator for moving said mirror;
• means for calculating a distance from a current beam spot position to a target track;
• means for generating a displacement signal, indicating a displacement of said mirror caused by said fine actuator, and a velocity signal, indicating a velocity of said mirror;
• means for generating a beam spot velocity signal indicating a velocity of the beam spot relative to said optical disk;
• means for generating a reference drive signal from the distance calculated by said distance calculating means, said reference drive signal being proportional to a reference acceleration of the beam spot relative to said optical disk;
• means for generating a reference velocity signal from said reference drive signal indicating a reference velocity of the beam spot relative to said optical disk;
• and
• means for generating a velocity difference signal indicating a difference between said reference velocity and said beam spot velocity;
• wherein said coarse actuator is driven in accordance with said displacement and velocity signals of said mirror, said velocity difference signal and said reference drive signal;
• and
• wherein said fine actuator is driven in accordance with said displacement and velocity signals of said mirror and said velocity difference signal.

A method of controlling an actuator that moves a beam spot for writing or reading information onto or from a target track of an optical recording medium having a plurality of tracks on a recording surface,

• said actuator comprising:
• a coarse actuator for moving an objective lens over a plurality of tracks and directing a beam spot onto said recording surface;
• and
• a fine actuator, carried by said coarse actuator, for moving said objective lens relative to said coarse actuator in a tracking direction;
• said method comprising the steps of:
• calculating a distance from a current beam spot position to a target track;
• generating a relative position signal, indicating a displacement of said objective lens relative to said coarse actuator, and a relative velocity signal, indicating a velocity of said objective lens relative to said coarse actuator;
• generating a beam spot velocity signal indicating a velocity of the beam spot relative to said optical recording medium;
• generating a reference drive signal from the distance calculated in said distance calculating step, said reference drive signal being proportional to a reference acceleration of the beam spot relative to said optical recording medium;
• generating a reference velocity signal from said reference drive signal indicating a reference velocity of the beam spot relative to said optical recording medium;
• generating a velocity difference signal indicating a difference between said reference velocity and said beam spot velocity;
• driving said coarse actuator in accordance with said relative position and relative velocity signals of said objective lens, said velocity difference signal and said reference drive signal;
• and
• driving said fine actuator in accordance with said relative position and relative velocity signals of said objective lens and said velocity difference signal.

A method of controlling an actuator that moves a beam spot for writing or reading information onto or from a target track of an optical recording medium having a plurality of tracks on a recording surface,

• said actuator comprising:
• a coarse actuator for moving an objective lens over a plurality of tracks and directing a beam spot onto said recording surface;
• and
• a fine actuator for moving a mirror used to direct a beam from a light source to said objective lens;
• said method comprising steps of:
• calculating a distance from a current beam spot position to a target track;
• generating a displacement signal, indicating a displacement of said mirror caused by said fine actuator, and a velocity signal, indicating a velocity of said mirror;
• generating a beam spot velocity signal indicating a velocity of the beam spot relative to said objective recording medium;
• generating a reference drive signal from the distance calculated in said distance calculating step, said reference drive signal being proportional to a reference acceleration of the beam spot relative to said optical recording medium;
• generating a reference velocity signal from said reference drive signal indicating a reference velocity of the beam spot relative to said optical recording medium;
• generating a velocity difference signal indicating a difference between said reference velocity and said beam spot velocity;
• driving said coarse actuator in accordance with said displacement and velocity signals of said mirror, said velocity difference signal and said reference drive signal;
• and
• driving said fine actuator in accordance with said displacement and velocity signals of said mirror and said velocity difference signal.