Optical pickup device, optical information device, and information processing device

1. An optical pickup device comprising:

a light source that emits a light beam of a predetermined wavelength;

a single objective lens that focuses the light beam from the light source to irradiate a disk-shaped recording medium;

an objective lens actuator that drives the objective lens;

a photodetector that receives, via the objective lens, a light beam reflected by a recording surface of the disk-shaped recording medium to converts the received light into an electric signal; and

an optical base that holds the light source, the objective lens actuator, and the photodetector,

wherein the objective lens actuator comprises:

a lens holder that holds the objective lens;

a support mechanism that supports the lens holder so that the lens holder is movable in a focusing direction, which is a direction perpendicular to the disk-shaped recording medium, and a tracking direction, which is a radial direction of the disk-shaped recording medium;

a focusing coil that is fixed to the lens holder and drives the lens holder in the focusing direction;

a tracking coil that is fixed to the lens holder and drives the lens holder in the tracking direction;

an actuator base that holds one end of the support mechanism; and

a magnet that is held on the actuator base and disposed at a position opposing the focusing coil and/or the tracking coil, and also applies a magnetic field to the focusing coil and/or the tracking coil,

a first gap and a second gap are formed between the lens holder and the objective lens,

when the disk-shaped recording medium rotates clockwise, and in an xy plane in which the center of the objective lens is defined as an origin, the tracking direction is defined as an y axis, and the tangential direction of tracks of the disk-shaped recording medium is defined as an x axis, a center side of the disk-shaped recording medium is defined as a positive direction for the y axis, a direction obtained by rotating the positive direction of the y axis clockwise through 90° is defined as a positive direction for the x axis, and four regions obtained by dividing the xy plane by the x axis and the y axis are defined as a first quadrant, a second quadrant, a third quadrant, and a fourth quadrant in the counterclockwise direction, the first gap is positioned at least in the first quadrant, and the second gap is positioned at least in the third quadrant,

a center of the first gap is positioned on a straight line obtained by rotating a positive-direction portion of the x axis counterclockwise through 30°, and

a center of the second gap is positioned on a straight line obtained by rotating a positive-direction portion of the x axis counterclockwise through 210°.

2. The optical pickup device according to claim 1 , wherein the first gap is positioned within a range from ±30° to ±60° centered on the straight line obtained by rotating the positive-direction portion of the x axis counterclockwise through 30°, and the second gap is positioned within a range from ±30° to ±60° centered on the straight line obtained by rotating the positive-direction portion of the x axis counterclockwise through 210°.

3. The optical pickup device according to claim 1 , wherein

the objective lens is fixed to a first fixed section and a second fixed section of the lens holder; and

the first fixed section is positioned at least in the second quadrant, and the second fixed section is positioned at least in the fourth quadrant.

4. The optical pickup device according to claim 3 , wherein

the lens holder has a first lens protector and a second lens protector that prevent the objective lens and the disk-shaped recording medium from coming into contact with each other; and

the first lens protector is positioned in the first quadrant, and the second lens protector is positioned in the third quadrant.

5. The optical pickup device according to claim 1 , wherein the tracking coil includes:

a first tracking coil fixed to a center of one side surface of the lens holder perpendicular to the x axis; and

a second tracking coil fixed to a center of the other side surface of the lens holder perpendicular to the x axis.

6. The optical pickup device according to claim 5 , wherein the focusing coil includes:

a first focusing coil fixed to a portion of one side surface of the lens holder perpendicular to the x axis, the portion being positioned in the first quadrant; and

a second focusing coil fixed to a portion of the other side surface of the lens holder perpendicular to the x axis, the portion being positioned in the third quadrant.

7. The optical pickup device according to claim 6 , wherein

the magnet includes:

a first magnet that has a magnetizing boundary surface on the x axis, applies magnetic fields in the opposite directions to two sides of the first tracking coil that are substantially parallel to the optical axis of the objective lens, and applies a magnetic field to a side that is closer to the disk-shaped recording medium, from among the two sides of the first focusing coil that are substantially parallel to the y axis; and

a second magnet that has a magnetizing boundary surface on the x axis, applies magnetic fields in the opposite directions to two sides of the second tracking coil that are substantially parallel to the optical axis of the objective lens, and applies a magnetic field to a side that is closer to the disk-shaped recording medium, from among the two sides of the second focusing coil that are substantially parallel to the y axis.

8. The optical pickup device according to claim 5 , wherein

the focusing coil includes:

a first focusing coil fixed to a portion of one side surface of the lens holder perpendicular to the x axis, the portion being positioned in the first quadrant;

a second focusing coil fixed to a portion of the other side surface of the lens holder perpendicular to the x axis, the portion being positioned in the second quadrant;

a third focusing coil fixed to a portion of the other side surface of the lens holder, the portion being positioned in the third quadrant; and

a fourth focusing coil fixed to a portion of the one side surface of the lens holder, the portion being positioned in the fourth quadrant.

9. The optical pickup device according to claim 8 , wherein

the magnet includes:

a first magnet that has a magnetizing boundary surface on the x axis, applies magnetic fields in the opposite directions to two sides of the first tracking coil that are substantially parallel to the optical axis of the objective lens, and applies a magnetic field to a side that is closer to the disk-shaped recording medium, from among the two sides of the first focusing coil that are substantially parallel to the y axis, and to a side that is closer to the disk-shaped recording medium, from among the two sides of the fourth focusing coil that are substantially parallel to the y axis; and

a second magnet that has a magnetizing boundary surface on the x axis, applies magnetic fields in the opposite directions to two sides of the second tracking coil that are substantially parallel to the optical axis of the objective lens, and applies a magnetic field to a side that is closer to the disk-shaped recording medium, from among the two sides of the second focusing coil that are substantially parallel to the y axis, and to a side that is closer to the disk-shaped recording medium, from among the two sides of the third focusing coil that are substantially parallel to the y axis.

10. The optical pickup device according to claim 1 , wherein the objective lens includes a resin lens formed by resin molding.

11. The optical pickup device according to claim 1 , wherein the objective lens is a multiple-wavelength compatible objective lens corresponding to a plurality of wavelengths including at least a wavelength of about 405 nm.

12. The optical pickup device according to claim 11 , wherein the multiple-wavelength compatible objective lens is a three-wavelength compatible objective lens corresponding to three wavelengths including a wavelength of about 660 nm and a wavelength of about 780 nm in addition to a wavelength of about 405 nm.

13. The optical pickup device according to claim 1 , wherein the dimension from a lower surface of the optical base to the disk-shaped recording medium is equal to or less than 11 mm.

14. An optical information device comprising:

the optical pickup device according to claim 1 ;

a motor that rotates the disk-shaped recording medium; and

a control unit that controls the motor and the optical pickup device on the basis of a signal obtained from the optical pickup device.

15. An information processing device comprising:

the optical information device according to claim 14 ; and

an information processing unit that processes information recorded on the optical information device and/or information reproduced from the optical information device.