Patent Application
20060168607
The present invention contains subject matter related to Japanese Patent Application JP 2005-009617 filed in the Japanese Patent Office on Jan. 17, 2005, the entire contents of which being incorporated herein by reference.
1. Field of the Invention
The present invention relates to an objective-lens driving apparatus for use in an optical pickup that records and reproduces data in and from a data-recording medium such as an optical disc, said apparatus designed to drive an objective lens in three directions, i.e., focusing direction, tracking direction and tilt direction. The invention relates to an optical pick up and an optical disc apparatus, which use the objective-lens driving apparatus.
2. Description of the Related Art
Optical disc apparatuses are known, which record and reproduce data in and from a data-recording medium such as an optical disc. Any optical disc apparatus of this type has an optical pickup that is moved in the radial direction of an optical disc and applies a laser beam to the optical disc.
The optical pickup incorporates an objective-lens driving apparatus that drives the objective lens held by a movable unit. The apparatus moves the objective lens in the focusing direction, namely toward and away from the signal-recording surface of the optical disc, thus accomplishing the focusing adjustment. The apparatus moves the objective lens in the tracking direction, too, namely in the radial direction of the optical disc, thus achieving the tracking adjustment. Further, the apparatus moves the objective lens, thus adjusting the spot that the laser beam applied through the objective lens forms on the optical disc. Hence, the laser beam applied through the objective lens to the optical disc converges, forming a spot on the recording track of the optical disc.
Most objective-lens driving apparatuses for use in optical pickups perform the focusing adjustment and the tracking adjustment. In recent years, an objective-lens driving apparatus, such as a so-called three-axis actuator, has been developed. This apparatus not only performs the two-axis adjustment, i.e., focusing adjustment and tracking adjustment, but also tilts the movable unit to the signal-recording surface of the optical disc. The apparatus can therefore accomplish adjustment to compensate for the planer vibration or the like of the optical disc, which may occur while the disc is rotating. (See Jpn. Pat. Appln. Laid-Open Publication 2001-93177).
The objective-lens driving apparatus, such as three-axis actuator, can move the movable unit with respect to the fixed unit, in not only the focusing direction and tracking direction, but also the tilt direction. In the tilt direction, the movable unit can be rotated around an axis that corresponds to the tangential direction extending at right angles to the radial direction of the optical disc.
An objective-lens driving apparatus is known, which is shown in
As
As
In the objective-lens driving apparatus 101 shown in
The objective-lens driving apparatus 101 can not accomplish only focusing adjustment and tracking adjustment, but also performs adjustment to compensate for planer vibration, if any, of the optical disc. Thus, the apparatus 101 can make the laser-beam spot trace the recording track more accurately.
This objective-lens driving apparatus 101 is a magnetic circuit that includes the focusing coil 111 of voice-coil type wound around the axis extending in the focusing direction FCS, and the yoke 102 inserted in the focusing coil 111. The apparatus 101 inevitably has focusing-response characteristics including a prominent phase delay, because of inductance components. If the apparatus 101 is used in high-speed data-reproducing apparatuses, it may impose problems in achieving servo design for the data-reproducing apparatuses.
As
It is therefore desirable to provide an objective-lens driving apparatus, an optical pickup and an optical disc apparatus, in which the phase delay is small in focusing-response characteristic and no primary bending mode is excited in the movable unit when the unit receives a focusing thrust, and which therefore excel in resonance characteristic in high-frequency bands.
According to the present invention, there is provided an objective-lens driving apparatus which includes: a movable unit that has a lens holder holding an objective lens; a fixed unit that is spaced apart from the movable unit in a tangential direction intersecting at right angle to a focusing direction and tracking direction of the objective lens; elastic support members that connect the movable unit and the fixed unit to each other, support the movable unit, enabling the movable unit to move with respect to the fixed unit in the focusing direction and tracking direction and to incline in a tilt direction to a plane that is parallel to the tangential direction; a first magnet that has first to fourth segment regions facing the lens holder in the tangential direction, spaced from one another in the focusing direction and tracking direction and magnetized in the tangential direction; and a second magnet that is arranged, facing the first magnet in the tangential direction, and is magnetized in a direction opposite to a magnetization direction of the first magnet. The lens holder has: tracking coils that are provided at four positions, respectively, for generating drive forces acting in the tracking direction, respectively on the first and second segment regions of the first magnet, which are adjacent in the tracking direction, on the third and fourth segment regions of the first magnet, which are adjacent in the tracking direction, on those segment regions of the second magnet, which face the first and second segment regions, and on those segment regions of the second magnet, which face the third and fourth segment regions; focusing coils that are provided at four positions, respectively, for generating drive forces acting in the focusing direction, respectively on the first and third segment regions of the first magnet, which are adjacent in the focusing direction, on the second and fourth segment regions of the first magnet, which are adjacent in the focusing direction, on those segment regions of the second magnet, which face the first and third segment regions, and on those segment regions of the second magnet, which face the second and fourth segment regions; a first tilt coil that is wound around an axis extending in the focusing direction and generates drive forces acting in the tilt direction, respectively on the first and second segment regions of the first magnet, which are adjacent in the tracking direction, and on those segment regions of the second magnet, which face the first and second segment regions; and a second tilt coil that is wound around in a direction opposite to the winding direction of the first tilt coil, and generates drive forces acting in the tilt direction, respectively on the third and fourth segment regions of the first magnet, which are adjacent in the tracking direction, and on those segment regions of the second magnet, which face the third and fourth segment regions.
According to the present invention, there is also provided an optical pickup which includes a movable base that is moved in a radial direction of an optical disc placed on a disc table, and an objective-lens driving apparatus that is arranged on the movable table. The objective-lens driving apparatus is of the type described above.
According to the present invention, there is also provided an optical disc apparatus which includes a disc table on which an optical disc is to be placed, and an optical pickup which applies a laser beam through an objective lens to the optical disc placed on the disc table. The optical pickup has a movable base that is moved in a radial direction of an optical disc placed on a disc table, and an objective-lens driving apparatus that is arranged on the movable base. The objective-lens driving apparatus is of the type described above.
The objective-lens driving apparatus, optical pickup and optical disc apparatus according to the present invention can reduce the phase delay in focusing-response characteristic. This makes it easy to accomplish, for example, servo design for high-speed, data-recording/reproducing apparatuses. Further, the objective-lens driving apparatus, optical pickup and optical disc apparatus according to this invention can prevent the primary bending mode in the movable unit from being excited, by using focusing drive forces. Hence, they can acquire good resonance characteristics in high-frequency bands.
A data-recording/reproducing apparatus according to the present invention will be described, with reference to the accompanying drawings.
The data-recording/reproducing apparatus 1 can record and reproduce data signals in and from an optical disc 2. The optical disc 2, in and from which the apparatus 1 can record and reproduce data, is, for example, a compact disc (CD), a digital versatile disc (DVD), a recordable CD (CD-R), a recordable DVD (DVD-R), a rewritable CD (CD-RW), or a rewritable DVD (DVD-RW), a rewritable DVD (DVD+RW). Note that data can be recorded in the CD-R and the DVD-R and rewritten in the CD-RW, the DVD-RW and the DVD+RW. Alternatively, the optical disc 2 may be one in which data can be recorded at high density by applying laser beam emitted from a semiconductor laser and having a short wavelength of about 405 nm. Further, the optical disc 2 may be replaced by a magneto-optical disc or the like.
As
A chassis (not shown) is arranged in the housing 3. The chassis holds a spindle motor. A disc table 4 is secured to the shaft of the spindle motor.
Parallel guide rods 5 are secured to the chassis. The chassis supports a lead screw 6 that can be rotated by a feed motor (not shown).
The data-recording/reproducing apparatus 1 includes an optical pickup 7. As
A nut (not shown) is provided on the movable base 8 and set in screw engagement with the lead screw 6. When lead screw 6 is rotated by the feed motor, the nut moves in one direction or the other in accordance with the direction in which the lead screw 6 is rotated. The optical pickup 7 is therefore moved in the radial direction of the optical disc 2 placed on the disc table 4.
As shown in
The yoke base 10 is made of magnetic metal such as SPCC (cold-rolled steel), silicon steel or the like. As
First and second magnets 21 and 22 are secured, respectively to one side of the yoke part 10c and that side of the yoke part 10b which faces said one side of the yoke part 10c. The sides of the yoke parts 10b and 10c, to which the magnets 21 and 22 are secured, are opposed to the lens holder 15.
As shown in
In the first magnet 21, the first to fourth segment regions 31, 32, 33 and 34, which face the lens holder 15, namely first printed coil 39 and tilt coils 51 and 52 (later described), are shaped like substantially a square and spaced in the tracking direction TRK and focusing direction FCS. The first and fourth segment regions 31 and 34, which are located at two opposite corners, are S poles. The second and third segment regions 32 and 33, which are located at the other opposite corners, are N poles. The first magnet 21 is thus magnetized to have four magnetic poles. The region between the segment regions 31 to 34 is a non-magnetized segment region 21a.
The second magnet 22 is arranged, facing the first magnet 21 in the tangential direction TAN, and is magnetized in the direction opposite to the magnetization direction of the first magnet 21. That is, the second magnet 22 is opposed to the lens holder 15 in the tangential direction TAN and has fifth to eighth segment regions 35, 36, 37 and 38 that are spaced in the tracking direction TRK and focusing direction FCS and magnetized in the tangential direction TAN.
In the second magnet 22, the fifth to eighth segment regions 35, 36, 37 and 38, which face the lens holder 15, namely second printed coil 40 and first and second tilt coils 51 and 52 (later described), are shaped like substantially a square and spaced in the tracking direction TRK and focusing direction FCS. The fifth and eighth segment regions 35 and 38, which are located at two opposite corners, are S poles. The sixth and seventh segment regions 36 and 37, which are located at the other opposite corners, are N poles. The second magnet 22 is thus magnetized to have four magnetic poles. The region between the segment regions 35 to 38 is a non-magnetized segment region 22a.
The first magnet 21 and the second magnet 22 are formed in the same shape and magnetized in opposite directions. That is, as
As shown in
A power-supplying substrate connected to a power-supply circuit (not shown) is secured to the relay substrate 18 that is attached to the back of the fixed unit 11. The power-supplying substrate is, for example, a flexible printed circuit board. The plurality of support members 16 are connected to the connecting lines provided on the power-supplying substrate, by the connecting parts 18a to 18f of the relay substrate 18. The support members 16 are arranged, each extending from the fixed unit 11 toward the movable unit 12 in the tangential direction TAN.
The movable unit 12 has the objective lens 14 and the lens holder 15. The lens holder 15 holds the objective lens 14.
As
As
That is, the first tracking coil 41 is arranged at a specific position, facing the first and second segment regions 31 and 32 of the first magnet 21. It generates a drive force acting the tracking direction TRK, from the magnetic field generated by the first and second segment regions 31 and 32 that are magnetized in the opposite directions, both being tangential direction TAN, and from the current flowing through the first tracking coil 41.
The second tracking coil 42 is arranged at a specific position, facing the third and fourth segment regions 33 and 34 of the first magnet 21. It generates a drive force acting the tracking direction TRK, from the magnetic field generated by the third and fourth segment regions 33 and 34 that are magnetized in the opposite directions, both being tangential direction TAN, and from the current flowing through the second tracking coil 42.
The third tracking coil 43 is arranged at a specific position, facing the fifth and sixth segment regions 35 and 36 of the second magnet 22. It generates a drive force acting the tracking direction TRK, from the magnetic field generated by the fifth and sixth segment regions 35 and 36 that are magnetized in the opposite directions, both being tangential direction TAN, and from the current flowing through the third tracking coil 43.
The fourth tracking coil 44 is arranged at a specific position, facing the seventh and eighth segment regions 37 and 38 of the second magnet 22. It generates a drive force acting the tracking direction TRK, from the magnetic field generated by the seventh and eighth segment regions 37 and 38 that are magnetized in the opposite directions, both being tangential direction TAN, and from the current flowing through the fourth tracking coil 44.
The first to fourth focusing coils 45, 46, 47 and 48 generate drive forces acting in the focusing direction FCS, for the first and third segment regions 31 and 33 of the first magnet 21 that are adjacent in the focusing direction FCS, for the second and fourth segment regions 32 and 34 of the first magnet 21 that are adjacent in the focusing direction FCS, for the segment regions 35 and 37 of the second magnet 22 that face the first and third segment regions 31 and 33, and for the segment regions 36 and 38 of the second magnet 22 that face the segment regions 32 and 34, respectively.
That is, the first focusing coil 45 is arranged at a specific position, facing the first and third segment regions 31 and 33 of the first magnet 21. It generates a drive force acting the focusing direction FCS, from the magnetic field generated by the first and third segment regions 31 and 33 that are magnetized in the opposite directions, both being tangential direction TAN, and from the current flowing through the first focusing coil 45.
The second focusing coil 46 is arranged at a specific position, facing the second and fourth segment regions 32 and 34 of the first magnet 21. It generates a drive force acting the focusing direction FCS, from the magnetic field generated by the second and fourth segment regions 32 and 34 that are magnetized in the opposite directions, both being tangential direction TAN, and from the current flowing through the second focusing coil 46.
The third focusing coil 47 is arranged at a specific position, facing the fifth and seventh segment regions 35 and 37 of the second magnet 22. It generates a drive force acting the focusing direction FCS, from the magnetic field generated by the fifth and seventh segment regions 35 and 37 that are magnetized in the opposite directions, both being tangential direction TAN, and from the current flowing through the third focusing coil 47.
The fourth focusing coil 48 is arranged at a specific position, facing the sixth and eighth segment regions 36 and 38 of the second magnet 22. It generates a drive force acting the focusing direction FCS, from the magnetic field generated by the sixth and eighth segment regions 36 and 38 that are magnetized in the opposite directions, both being tangential direction TAN, and from the current flowing through the fourth focusing coil 48.
The first to fourth tracking coils 41, 42, 43 and 44 are provided on the first printed coil 39. The first to fourth focusing coils 45, 46, 47 and 48 are provided on the second printed coil 40.
That is, the first and second printed coils 39 and 40 are arranged, respectively, on those surfaces of the first and second magnets 21 and 22 which oppose each other and which face the lens holder 15.
The first and second tracking coils 41 and 42 and the first and second focusing coils 45 and 46 are provided on the first printed coil 39 that opposes the first magnet 21. The third and fourth tracking coils 43 and 44 and the third and fourth focusing coils 47 and 48 are provided on the second printed coil 40 that opposes the second magnet 22.
In the objective-lens driving apparatus 9, the first to fourth focusing coils 45 to 48 generate drive forces acting in the focusing direction FCS, because of the open magnetic path defined by the first and second magnets 21 and 22. Therefore, the inductance imposes no influence, and the phase delay can be minimized. That is, in the objective-lens driving apparatus 9, since no yokes are inserted in the focusing coils as in the conventional objective-lens driving apparatus, a phase delay can be prevented, which may result from inductance that should be generated if yokes were inserted in the focusing coils.
As indicated above, the first and third focusing coils 45 and 47 and the second and fourth focusing coils 46 and 48 are spaced apart in the tracking direction TRK in the objective-lens driving apparatus 9. Hence, it is possible to prevent the primary bending mode of the movable unit from being excited by the focusing drive forces. As
In the objective-lens driving apparatus 9, the first to fourth tracking coils and the first to fourth focusing coils are printed coils. They are not limited to printed coils, nonetheless. They may be, for example, coils that are wound around axes that extend in the tangential direction TAN.
The first and second tilt coils 51 and 52 are spaced apart in the focusing direction FCS. They have been formed by winding wires, are shaped like a hollow cylinder and have substantially the same size.
The first tilt coil 51 is wound around an axis that extends in the focusing direction FCS. It generates drive forces acting in the tilt direction TIL, for the segment regions 31 and 32 of the first magnet 21, which are adjacent in the tracking direction TRK, and for the segment regions 35 and 36 of the second magnet 22 which face the first and second segment regions 31 and 32, respectively.
That is, as shown in
The first tilt coil 51 has a side 54, which opposes not only the above-mentioned side 53 but also the second magnet 22. The side 54 is positioned, facing the fifth and sixth segment regions 35 and 36 of the second magnet 22. The first tilt coil 51 generates a drive force that acts in the tilt direction TIL, from the magnetic field generated by the fifth and sixth segment regions 35 and 36 magnetized in opposite directions, both being tangential direction TAN, and from the current flowing through the side 54 of the first tilt coil 51. To be more specific, a drive force may develop at that part of the side 53 of the first tilt coil 51, which faces the first segment region 31, acting in the direction TIL1 to move the lens holder away from the optical disc 2 in the focusing direction FCS as indicated above. Then, the current flows in one direction in that part of the side 54 of the first tilt coil 51, which faces the fifth segment region 35, and in the opposite direction in the side 53, though both directions being the tracking direction TRK. Since both the first region and the fifth region are S poles and the magnetic fields therefore extend in opposite directions, both being the tangential direction TAN, a drive force develops, which acts in the direction TIL1, moving the lens holder toward the optical disc 2 in the focusing direction FCS. At that part of the side 54 of the first tilt coil 51, which faces the sixth segment region 36, a drive force develops, which acts in the direction TIL1, moving the lens holder away from the optical disc 2 in the focusing direction FCS. This is because magnetic fields extending in the opposite directions are applied to those parts of the side 54 of the first tilt coil 51, which face the fifth and sixth segment regions 35 and 36, respectively.
The second tilt coil 52 is wound around an axis that extends in the focusing direction FCS, namely in the direction opposite to the winding direction of the first tilt coil 51. Therefore, the second tilt coil 52 generates a drive force that acts in the tilt direction TIL, at the third and fourth segment regions 33 and 34 of the first magnet 21, which are adjacent in the tracking direction TRK, and at the regions 37 and 38 of the second magnet 22, which oppose the third and fourth segment regions 33 and 34 of the first magnet 21.
That is, the second tilt coil 52 is wound, having a substantially rectangular cross section. It is so positioned that its side 55 opposes the first magnet 21 and faces the third and fourth segment regions 33 and 34 of the first magnet 21. The second tilt coil 52 therefore generates a drive force that acts in the tilt direction TIL, from the magnetic field generated by the third and fourth segment regions 33 and 34 magnetized in opposite directions, both being the tangential direction TAN, and from the current that flows in the side 55 of the second tilt coil 52. Then, a drive force may develop at that part of the side 53 of the first tilt coil 51, which faces the first segment region 31, acting in the direction TIL1 to move the lens holder away from the optical disc 2 in the focusing direction FCS as indicated above. To be more specific, the current flows in one direction in that part of the side 55 of the second tilt coil 52, which faces the third segment region 33, and in the opposite direction in the side 53, though both directions being the tracking direction TRK, because the second tilt coil 52 is wound in the direction opposite to the winding direction of the first tilt coil 52. Since the first region and the third region are an S pole and an N pole, respectively and the magnetic fields therefore extend in opposite directions, both being the tangential direction TAN, a drive force develops, which acts in the direction TIL1, moving the lens holder toward the optical disc 2 in the focusing direction FCS. At that part of the side 55 of the second tilt coil 52, which faces the fourth segment region 34, a drive force develops, which acts in the direction TIL1, moving the lens holder away from the optical disc 2 in the focusing direction FCS. This is because magnetic fields extending in the opposite directions are applied to those parts of the side 55 of the second tilt coil 52, which face the third and fourth regions 33 and 34, respectively.
The second tilt coil 52 is so positioned that its side 56, which faces the side 55 and the second magnet 22, opposes the second magnet 22 and faces the seventh and eighth segment regions 37 and 38 of the second magnet 22. The second tilt coil 52 therefore generates a drive force that acts in the tilt direction TIL, from the magnetic field generated by the seventh and eighth segment regions 37 and 38 magnetized in opposite directions, both being the tangential direction TAN, and from the current that flows in the side 56 of the second tilt coil 52. More specifically, a drive force may develop at that part of the side 53 of the first tilt coil 51, which faces the first segment region 31, acting in the direction TIL1 to move the lens holder away from the optical disc 2 in the focusing direction FCS as described above. Then, for the same reason described above, a drive force develops at that part of the side 56 of the second tilt coil 52, which faces the seventh segment region 37. The drive force acts in the direction TIL1, moving the lens holder toward the optical disc 2 in the focusing direction FCS. Further, a drive force develops at that part of the side 56 of the second tilt coil 52, which faces the eighth segment region 38. This drive force acts in the direction TIL1, moving the lens holder away from the optical disc 2 in the focusing direction FCS.
In the surface 15b of the lens holder 15 of the movable unit 12, which is perpendicular to the tracking direction TRK, a projection 24e is provided between the first tilt coil 51 and the second tilt coil 52, as is illustrated in
As shown in
The lens holder 15 has two surfaces 15a and 15b that are perpendicular to the tracking direction TRK. Projections 24a to 24c (i.e., some elastic support members 16) are provided on the surface 15a. Projections 24d to 24f (i.e., the remaining elastic support members 16) are provided on the surface 15b. The projections 24a to 24f are connected, at one end (i.e., end parts 17a to 17f) to the connecting parts 18a to 18f, respectively. The projections 24a to 24f are secured at the other end. Of the projections 24a to 24f, the one that lies middle in the focusing direction FCS, is used to invert the direction in which the wire is wound to form the first and second tilt coils 51 and 52. The lens holder 15 has two other projections 25a and 25b, both provided on the surface 15a that is perpendicular to the tracking direction TRK. The winding of the wire is started at the projection 25a and completed at the projection 25b.
To the elastic support members 16, drive currents for focusing adjustment, tracking adjustment and tilt adjustment are supplied from the power-supply circuit through the various connecting wires provided on the power-supplying substrate and through the connecting parts 18a to 18f provided on the relay substrate 18. Hence, two of the six elastic support members 16 serve to supply power the first to fourth focusing coils 45 to 48, other two serve to supply power to the first to fourth tracking coils 41 to 44, and the remaining two serve to supply power to the first and second tilt coils 51 and 52.
In the objective-lens driving apparatus 9 thus configured, drive currents may be supplied from the power-supply circuit to the first to fourth focusing coils 45 to 48, first to fourth tracking coils 41 to 44 and first and second tilt coils 51 and 52 through the power-supplying substrate, the relay substrate 18 and the elastic support members 16. When the drive currents are so supplied, the movable unit 12 is moved in the focusing direction FCS, the tracking direction TRK or the tilt direction TIL, in accordance with the relation between the directions of these drive currents and the directions of the magnetic fluxes generated by the first and second magnets 21 and 22 and yoke parts 10b and 10c.
As the movable unit 12 is moved in the focusing direction FCS, the tracking direction TRK or the tilt direction TIL, the elastic support members 16 are elastically deformed.
The lens holder 15 remains at the position neutral with respect to the focusing direction FCS as long as a drive current is supplied to none of the first to fourth focusing coils 45 to 48. The lens holder 15 remains at the position neutral with respect to the tracking direction TRK as long as a drive current is supplied to none of the first to fourth tracking coils 41 to 44. Further, the lens holder 15 remains at the position neutral with respect to the tilt direction TIL as long as a drive current is supplied to neither the first tilt coil 51 nor the second tilt coil 52.
In the optical disc apparatus 1 thus configured, the disc table 4 rotates as the spindle motor is driven. When the disc table 4 rotates, the optical disc 2 placed on the disc table 4 is rotated. At the same time, the optical pickup 7 is moved in the radial direction of the optical disc 2 and records or reproduces data in or from the optical disc 2.
During the data-recording process or the data-reproducing process, a drive current may be supplied to the first to fourth focusing coils 45 to 48. In this case, the movable unit 12 of the objective-lens driving apparatus 9 is moved in the focusing direction FCS (shown in
When a drive current is supplied to the first to fourth tracking coils 41 to 44, the movable unit 12 of the objective-lens driving apparatus 9 is moved in the tracking direction TRK (shown in
Moreover, when a drive current is supplied to the first and second tilt coils 51 and 52, the movable unit 12 of the objective-lens driving apparatus 9 is moved in the tilt direction TIL (shown in
As seen from
As seen from
As described above, the objective-lens driving apparatus 9 according to this invention uses an open circuit. Hence, a phase delay due to the inductance resulting from the yokes inserted in the focusing coils does not occur as in the conventional apparatus. The phase delay is therefore small, if any. This renders it easy to accomplish, for example, servo design for high-speed, data-recording/reproducing apparatuses.
The objective-lens driving apparatus 9 according to this invention has a plurality of focusing coils 45 to 48 that are spaced apart in the tracking direction TRK. Therefore, focusing drive forces do not excite the primary bending mode in the movable unit. This enables the apparatus 9 to acquire good resonance characteristic in high-frequency bands.
In the objective-lens driving apparatus 9 according to this invention, the first and second tilt coils 51 and 52 can be wound together, not separately, around the lens holder 15. This helps to simplify the structure of the apparatus and lowers the manufacturing cost of the apparatus.
The objective-lens driving apparatus 9 according to this invention has first and second magnets 21 and 22 that have the same shape. They differ only in that they are magnetized in opposite directions. Thus, the apparatus 9 can be readily mass-produced, which serves to lower the manufacturing cost of the apparatus 9.
The first and second magnets 21 and 22 incorporated in the objective-lens driving apparatus 9 described above are integrally formed by means of four-pole magnetization. The present invention is not limited to this. For example, two magnets spaced apart, substantially in the tracking direction TRK, may be two-pole magnetized and may then be combined together.
If this is the case, the first magnet 61 is prepared by arranging third and fourth magnets 63 and 64 in the tracking direction TRK and combining them together, as is illustrated in
The third and fourth magnets 63 and 64 are arranged, with their magnetization axes oriented in the tangential direction TAN and their segment regions arranged in the focusing direction FCS. Further, they are so arranged that the segment regions of one magnet are magnetized in the direction opposite to the magnetization direction of the segment regions of the other magnet.
That is, the third magnet 63 includes ninth and tenth segment regions 71 and 72 that are arranged in a plane facing the lens holder 15, spaced apart in the focusing direction FCS and magnetized in the tangential direction TAN. The ninth segment region 71 makes an S pole, and the tenth segment region 72 makes an N pole. As indicated above, the third magnet 63 is two-pole magnetized. The region between the segment regions 71 and 72 is a non-magnetized segment region 63a.
The fourth magnet 64 includes eleventh and twelfth segment regions 73 and 74 that are arranged in a plane facing the lens holder 15, spaced apart in the focusing direction FCS and magnetized in the tangential direction TAN. The eleventh segment region 73 makes an N pole, and the twelfth segment region 74 makes an S pole. As mentioned above, the fourth magnet 64 is two-pole magnetized. The region between the segment regions 73 and 74 is a non-magnetized segment region 64a.
The third and fourth magnets 63 and 64 are so arranged that the ninth and tenth segment regions 71 and 72 align in the focusing direction FCS and the eleventh and twelfth segment regions 73 and 74 align in the focusing direction FCS, too. The ninth segment region 71 of the third magnet 63 is so arranged that it is magnetized in the direction opposite to the magnetization direction of the eleventh segment region 73 of the fourth magnet 64, which is arranged adjacent in the tracking direction TRK. The first magnet 61 is thereby formed as is illustrated in
The ninth and tenth segment regions 71 and 72 of the third magnet 63 and the eleventh and twelfth segment regions 73 and 74 of the fourth magnet 64 function as first to fourth segment regions of the first magnet 61. Like the first magnet 21, the third and fourth magnets 63 and 64 generate magnetic fields that provide drive forces for moving the lens holder in the focusing direction FCS, tracking direction TRK and tilt direction TIL, jointly with the currents that flow through the focusing coils, tracking coils and tilt coils.
The fifth and sixth magnets 65 and 66 are arranged in the tangential direction TAN in which they are magnetized. Further, they are so arranged that their segment regions are aligned in the focusing direction FCS. In addition, they are so arranged that one of them have its segment regions magnetized in the direction opposite to the magnetization direction of those of the other magnet that is adjacent to the first-mentioned magnet in the tracking direction TRK.
That is, the fifth magnet 65 has thirteenth and fourteenth segment regions 75 and 76 that face the lens holder 15 in the tangential direction TAN, are spaced apart in the focusing direction FCS and are magnetized in the tangential direction TAN. Here, the thirteenth segment region 75 is an S pole, and the fourteenth segment region 76 is an N pole. As noted above, the fifth magnet 65 is two-pole magnetized. The region between the segment regions 75 and 76 is a non-magnetized segment region 65a.
The sixth magnet 66 has fifteenth and sixteenth segment regions 77 and 78 that face the lens holder 15 in the tangential direction TAN, are spaced apart in the focusing direction FCS and are magnetized in the tangential direction TAN. Here, the fifteenth segment region 77 is an N pole, and the sixteenth segment region 78 is an S pole. As noted above, the sixth magnet 66 is two-pole magnetized. The region between the segment regions 77 and 78 is a non-magnetized segment region 66a.
The fifth and sixth magnets 65 and 66 are so arranged that the thirteenth and fourteenth segment regions 75 and 76 and the fifteenth and sixteenth segment regions 77 and 78 are aligned in the focusing direction FCS. The thirteenth segment region 75 of the fifth magnet 65 is arranged and jointed to the fifteenth segment region 77 of the sixth magnet 66 adjacent in the tracking direction TRK, so that the segment regions 75 and 77 are magnetized in opposite directions. Thus, the fifth and sixth magnets 65 and 66 constitute the second magnet 62. In this state, the fourteenth segment region 76 of the fifth magnet 65 is magnetized in the direction opposite to the magnetization direction of the sixteenth segment region 78 of the sixth magnet 66, which is arranged adjacent in the tracking direction TRK. The fifth and sixth magnets 65 and 66 may be jointed together with adhesive or the like. The may otherwise be jointed by virtue of magnetic force only.
The thirteenth and fourteenth segment regions 75 and 76 of the fifth magnet 65 and the fifteenth and sixteenth segment regions 77 and 78 of the sixth magnet 66 serve as the fifth to eighth segment regions of the second magnet 62. As in the second magnet 22 described above, they generate not only currents to supply to the focusing coils, tracking coils and tilt coils, but also magnetic fields that provide drive forces acting in the focusing direction FCS, tracking direction TRK and tilt direction TIL.
An objective-lens driving apparatus according to this invention, which includes such first and second magnets 61 and 62 as described above, has an open magnetic path, like the objective-lens driving apparatus 9 that has been described. In the apparatus, phase delays do not develop from the inductance resulting from the yokes that are inserted in the focusing coils as in the conventional apparatus. Phase delay, if any, can therefore be reduced. It is therefore easy to accomplish, for example, servo design for high-speed, data-recording/reproducing apparatuses. Moreover, since a plurality of focusing coils are spaced apart in the tracking direction TRK, focusing drive forces do not excite the primary bending mode in the movable unit. The objective-lens driving apparatus can therefore acquire good resonance characteristic in high-frequency bands.
In the objective-lens driving apparatus that has the first and second magnets 61 and 62, the third to sixth magnets 63 to 66 are identical. The apparatus can therefore be readily mass-produced, which helps to lower the manufacturing cost of the objective-lens driving apparatus.
Furthermore, in the objective-lens driving apparatus including the first and second magnets 61 and 62, neither the border region between the third and fourth magnets 63 and 64 nor the border region between the fifth and sixth magnets 65 and 66 is a non-magnetized segment region. This can enhance the tracking sensitivity.
The first and second magnets incorporated in the objective-lens driving apparatus 9 may be each composed of two magnets that are two-pole magnetized and spaced apart in the focusing direction FCS.
As shown in
The seventh and eighth magnets 83 and 84 are arranged, with their magnetization axes oriented in the tangential direction TAN and their segment regions arranged in the tracking direction TRK. Further, they are so arranged that the segment regions of one magnet are magnetized in the direction opposite to the magnetization direction of those of the other magnet.
That is, the seventh magnet 83 includes seventeenth and eighteenth segment regions 91 and 92 that are arranged in a plane facing the lens holder 15 in the tangential direction TAN, spaced apart in the tracking direction TRK and magnetized in the tangential direction TAN. Here, the seventeenth segment region 91 makes an S pole, and the eighteenth segment region 92 makes an N pole. As indicated above, the seventh magnet 83 is two-pole magnetized. The region between the segment regions 91 and 92 is a non-magnetized segment region 83a.
The eighth magnet 84 includes nineteenth and twentieth segment regions 93 and 94 that are arranged in a plane facing the lens holder 15 in the tangential direction TAN, spaced apart in the tracking direction TRK and magnetized in the tangential direction TAN. Here, the nineteenth segment region 93 makes an N pole, and the twentieth segment region 94 makes an S pole. As mentioned above, the eighth magnet 84 is two-pole magnetized. The region between the segment regions 93 and 94 is a non-magnetized segment region 84a.
The seventh and eighth magnets 83 and 84 are so arranged that the seventeenth and eighteenth segment regions 91 and 92 align in the tracking direction TRK and the nineteenth and twentieth segment regions 93 and 94 align in the tracking direction TRK, too. The seventeenth segment region 91 of the seventh magnet 83 is so arranged that it is magnetized in the direction opposite to the magnetization direction of the nineteenth segment region 93 of the eighteenth magnet 84, which is arranged adjacent in the focusing direction FCS. The first magnet 81 is thereby formed as shown in
The seventeenth and eighteenth segment regions 91 and 92 of the seventh magnet 83 and the nineteenth and twentieth segment regions 93 and 94 of the eighth magnet 84 serve as the first to fourth segment regions of the first magnet 81. As in the first magnet 21 described above, they generate not only currents to supply to the focusing coils, tracking coils and tilt coils, but also magnetic fields that provide drive forces acting in the focusing direction FCS, tracking direction TRK and tilt direction TIL.
The ninth and tenth magnets 85 and 86 are arranged in the tangential direction TAN in which they are magnetized. Further, they are so arranged that their segment regions are aligned in the tracking direction TRK In addition, they are so arranged that one of them have its segment regions magnetized in the direction opposite to the magnetization direction of the segment regions of the other magnet that is adjacent to the first-mentioned magnet in the focusing direction FCS.
That is, the ninth magnet 85 has twenty-first and twenty-second segment regions 95 and 96 that face the lens holder 15 in the tangential direction TAN, are spaced apart in the tracking direction TRK and are magnetized in the tangential direction TAN. Here, the twenty-first segment region 95 is an S pole, and the twenty-second segment region 96 is an N pole. As noted above, the ninth magnet 85 is two-pole magnetized. The region between the segment regions 95 and 96 is a non-magnetized segment region 85a.
The tenth magnet 86 has twenty-third and twenty-fourth segment regions 97 and 98 that face the lens holder 15 in the tangential direction TAN, are spaced apart in the tracking direction TRK and are magnetized in the tangential direction TAN Here, the twenty-third segment region 97 is an N pole, and the twenty-fourth segment region 98 is an S pole. As noted above, the tenth magnet 86 is two-pole magnetized. The region between the segment regions 97 and 98 is a non-magnetized segment region 86a.
The ninth and tenth magnets 85 and 86 are so arranged that the twenty-first and twenty-second segment regions 95 and 96 align in the tracking direction TRK and the twenty-third and twenty-fourth segment regions 97 and 98 align in the tracking direction TRK, too. The twenty-first segment region 95 of the ninth magnet 85 is so arranged that it is magnetized in the direction opposite to the magnetization direction of the twenty-third segment region 97 of the tenth magnet 86, which is arranged adjacent in the focusing direction FCS. The second magnet 82 is thereby formed. In this state, the twenty-second segment region 96 of the ninth magnet 85 is magnetized in the direction opposite to the magnetization direction of the twenty-fourth segment region 98 of the tenth magnet 86, which is arranged adjacent in the focusing direction FCS. The ninth and tenth magnets 85 and 86 may be jointed together with adhesive or the like. Alternatively, they may be jointed by virtue of magnetic force only.
The twenty-first and twenty-second segment regions 95 and 96 of the ninth magnet 85 and the twenty-third and twenty-fourth segment regions 97 and 98 of the tenth magnet 86 serve as the fifth to eighth segment regions of the second magnet 82. As in the second magnet 22 described above, they generate not only currents to supply to the focusing coils, tracking coils and tilt coils, but also magnetic fields that provide drive forces acting in the focusing direction FCS, tracking direction TRK and tilt direction TIL.
An objective-lens driving apparatus according to this invention, which includes such first and second magnets 81 and 82 as described above, has an open magnetic path, like the objective-lens driving apparatus 9 that has been described. In the apparatus, phase delays do not develop from the inductance resulting from the yokes that are inserted in the focusing coils as in the conventional apparatus. Phase delay, if any, can therefore be reduced. It is therefore easy to accomplish, for example, servo design for high-speed, data-recording/reproducing apparatuses. Moreover, since a plurality of focusing coils are spaced apart in the tracking direction TRK, focusing drive forces do not excite the primary bending mode in the movable unit. The objective-lens driving apparatus can therefore acquire good resonance characteristic in high-frequency bands.
In the objective-lens driving apparatus that has the first and second magnets 81 and 82, the seventh to tenth magnets 83 to 86 are identical. The apparatus can therefore be readily mass-produced, which helps to lower the manufacturing cost of the objective-lens driving apparatus.
Furthermore, in the objective-lens driving apparatus including the first and second magnets 81 and 82, neither the border region between the seventh and eighth magnets 83 and 84 nor the border region between the ninth and tenth magnets 85 and 86 is a non-magnetized segment region. This can enhance the tracking sensitivity.
The first and second magnets incorporated in the objective-lens driving apparatus 9 may be each composed of four magnets spaced apart in both the tracking direction TRK and the focusing direction FCS. Namely, each of the first and second magnets is composed of four magnets having the same shape. The apparatus 9 can therefore be readily mass-produced, which helps to lower the manufacturing cost of the apparatus 9.
The optical pickup 7 according to this invention has the objective-lens driving apparatus 9 described above. Hence, the optical pickup 7 can perform three-axis adjustment. That is, the apparatus 9 can perform focusing adjustment, tracking adjustment and tilt adjustment, making the laser-beam spot accurately trace the recording track. In addition, the phase delay, i.e., one focusing-response characteristic, can be reduced. Servo design for high-speed, data-recording/reproducing apparatuses can therefore be easily accomplished. Moreover, the focusing drive forces do not excite the primary bending mode in the movable unit. Therefore, the optical pickup 7 can acquire good resonance characteristic in high-frequency bands and can be manufactured at low cost.
The data-recording/reproducing apparatus 1 according to this invention has the objective-lens driving apparatus 9 described above. The apparatus 1 can therefore record and reproduce data at high efficiency, because the apparatus 9 can perform three-axis adjustment. That is, the apparatus 9 can perform focusing adjustment, tracking adjustment and tilt adjustment, making the laser-beam spot accurately trace the recording track. In addition, the phase delay, i.e., one focusing-response characteristic, can be reduced. Servo design for high-speed, data-recording/reproducing apparatuses can therefore be easily accomplished. Moreover, the focusing drive forces do not excite the primary bending mode in the movable unit. Therefore, the data-recording/reproducing apparatus 1 can acquire good resonance characteristic in high-frequency bands and can be manufactured at low cost.
It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-009617 | Jan 2005 | JP | national |
