JP3317519B2 - Optical system drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system driving apparatus used for an optical information recording / reproducing apparatus for optically recording and reproducing data.

[0002]

2. Description of the Related Art An optical system driving apparatus includes means for supporting an objective lens for irradiating a light spot on a recording medium in a focusing direction parallel to the optical axis and a tracking direction orthogonal to the focusing direction so as to be displaceable. There are provided means for driving in the focusing direction and the tracking direction. Various such optical system driving devices have been proposed so far. For example, as shown in FIG.
In the apparatus disclosed in Japanese Patent No. 261827 (conventional example 1), an objective lens 101 is mounted on one end of a holder 100, and a focusing coil 102 and a tracking coil 103 are provided on the other end. Further, in this conventional example, there is a possibility that torsional resonance may occur when performing the focusing control. Therefore, the balancer 104 is provided in the holder 100 so that the position of the center of gravity of the movable portion and the point of application of the driving force coincide with each other.

Further, Japanese Patent Application Laid-Open No. 2-56 shown in FIGS.
Japanese Unexamined Patent Publication No. 736 (conventional example 2) discloses a driving force generating mechanism (plan view) and an optical pickup having the same (perspective view). In FIG. 8, reference numeral 105 denotes a frame portion;
Is a focus coil, 107 and 108 are tracking coils, 109 is an inner yoke, 110 is an outer yoke, and 112 is a magnet. In a state where a magnetic field is formed in the direction of the arrow M, the current flows through the focus coil 106 to move the focus coil 106, and accordingly, the frame having the objective lens moves. On the other hand, a magnetic field is also formed in the direction of arrow M on the tracking coils 107 and 108, and the forces of F1 and F2 are generated and combined to act. Then, since all force components other than the tracking direction are canceled, the frame is controlled in the tracking direction.

FIG. 9 is a perspective view of an optical pickup.
The ends of two support rods 114, 115, and 116 are elastically connected to the side of the support 113 at the upper part and at the two lower parts. A moving frame 117 is elastically connected to the other end of the support rod. The moving frame 117 is provided with an objective lens 118 and a driving force generating mechanism 119.

[0005] In addition, FIG.
In the device disclosed in Japanese Patent Publication No. 2 (Conventional Example 3), a drive coil 122 is fixed to a lens holder 121 supported by a frame 120 so as to be freely displaceable. A magnetic circuit 125 for applying a magnetic field to the drive coil is fixed to the frame, and a current is applied to the drive coil to drive the objective lens 123 according to a control signal.

[0006]

SUMMARY OF THE INVENTION Among the above, conventional example 1
Has an objective lens 101 provided at the end of the movable part.
When the movable portion resonates, it resonates in a mode having a node near the center of gravity of the movable portion. When the objective lens 101 is in the vicinity of the center of gravity of the movable part, even if resonance occurs, it is also a node of resonance, so that it is not much affected by resonance. However, in the configuration in which the objective lens 101 is provided at the end of the movable portion as in this conventional example, the size and thickness of the optical system driving device can be reduced, but the objective lens 101 is separated from the resonance node. Therefore, when resonance occurs, there is a problem that it is affected by the resonance.

Therefore, it is basically necessary to match the drive point of the movable part with the center of gravity so that resonance does not occur.
Therefore, in this conventional example, the objective lens 1 having a large mass is used.
The balancer 104 is provided on the opposite side of the “01”. However, providing the balancer 104 causes an increase in the mass of the movable part and an increase in the size of the movable part, and the addition of the balancer 104 causes a disadvantage that the cost is increased and a disadvantage in the work process is caused.

Next, in Conventional Example 2, one magnetic circuit is used to reduce the size of the optical system driving device, a driving force generating mechanism 119 is provided at the end of the movable portion, and an objective lens 118 is provided at the opposite end. Because of this configuration, the objective lens 118 is greatly affected by resonance (FIG. 9). FIG. 8 shows the driving force generating mechanism 119 in FIG. 9. In the focus driving, the magnetic flux is generated on the side A between the magnet 112 and the yoke 109 of the focus coil 106 and the side B adjacent thereto. , C and does not act on the side D opposite to the yoke 109. Therefore, since the focus driving point is near the side A, the driving point is an end of the movable part and does not coincide with the center of gravity of the movable part, so that resonance occurs. On the other hand, when trying to match the drive point with the center of gravity in order to prevent resonance, it is necessary to extend the movable portion on the opposite side of the objective lens with respect to the drive point and provide a balancer, which is the same as in the conventional example. Failure occurs.

Next, in Conventional Example 3, an objective lens 123 is provided at the end of the movable portion, and a magnetic circuit 125 symmetrical on the XZ plane is provided near the center of gravity of the center of the lens holder 121.
Since the magnetic circuit is symmetric, the driving point is at the center and coincides with the center of gravity, so that no resonance occurs. However, in this case, since the center of the magnetic circuit 125 is made to coincide with the center of gravity of the movable portion, the lens holder 121 on the opposite side to the objective lens 123 does not need to be large enough to balance the mass of the objective lens 123. Not be. Further, since two magnetic circuits having two magnetic gaps whose main magnetic field directions are opposite to each other on the XZ plane must be provided, there is a problem that the weight of the movable portion increases and the size of the movable portion increases.

The present invention has been proposed to solve the above-mentioned disadvantages of the prior art, and has as its object to provide a compact, inexpensive optical system driving device having excellent characteristics without resonance.

In order to achieve the above object, the present invention provides an optical element for irradiating a light spot on a recording medium surface, and a first coil for moving the optical element in a direction substantially perpendicular to the recording medium surface. And a second coil for moving in a substantially horizontal direction with respect to the recording medium surface;
A magnetic circuit composed of a magnet and a yoke that applies a magnetic flux to the coil, a movable body provided with the optical element and the first and second coils, and a movable body substantially perpendicular to a recording medium surface. In an optical system driving device including a supporting means for supporting a movable member in a substantially horizontal direction, a side of the first coil located in a magnetic gap formed by the magnet and the yoke, and a side of the first coil facing the side of the first coil. A notch is formed in a part of the yoke so that the magnetic flux also extends to the sides, thereby forming a magnetic circuit, and driving forces opposite to each other are generated on the two coil sides. The second coil, which is arranged between an optical element and the first coil and substantially coincides with the center of gravity of the movable body, and is arranged so as to apply a magnetic flux from the magnet; A driving force is generated on each of two coil sides extending in the focus direction, and a driving point by the resultant force is substantially coincident with the center of gravity of the movable body between the optical element and the second coil. The optical system driving device was constructed as described above.

[0012]

In this way, a part of the yoke is cut out to generate a driving force on two opposing sides of the first coil, so that the driving point by the resultant force coincides with the center of gravity of the movable part, and A driving force is generated on each of two coil sides extending in the focus direction of the coil, and a driving point by the resultant force is made to coincide with a center of gravity of the movable portion. Can be. In addition, since a configuration for balancing is not required, a small and inexpensive optical system driving device can be obtained.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. 1 to 4 show a first embodiment of the present invention. FIG. 1 is a perspective view, FIG. 2 is an exploded perspective view,
FIG. 3 is a plan view, and FIG. 4 is an explanatory view (plan view) of a magnetic field.
In FIG. 2, a base 1 has a yoke 2a formed by pressing.
The yokes 2b and 2c are formed so as to face each other, and a rising portion 3 is formed at a position away from these yokes in the Y (-) direction. Although the number of yokes 2b and 2c is usually one, they are separated into two via a notch 4 at the center in the X direction.

A magnet 5 is bonded and fixed to the yoke 2a on a surface 51. A spacer 6 made of plastic is fixed between the magnet 5 and the base 1 to position the magnet 5 in the Z direction. ing. Further, a wire receiver 7 and a substrate 8 are fixed to the rising portion 3 so as to sandwich the rising portion 3 in the Y direction. One end 9 ′ of four wires 9 a to 9 d extending in the Y direction is provided on substrate 8.
a to 9'd are fixed by soldering, and the other end 9 "a to
9 "d denotes through holes 10a, 10b,
After penetrating 10c and 10d, respectively, they are soldered and fixed to substrates 11a and 11b fixed to the X direction side. The four wires 9a to 9d pass through the holes of the wire receiver 7, respectively, and pass through the rubbers 12a to 12d bonded and fixed to the holes of the wire receiver 7.

A focus coil 13 is adhesively fixed to an opening in the center of the holder 10 so that one side crosses between the magnet 5 and the yokes 2b and 2c. In a portion where the focus coil 13 crosses between the magnet 5 and the yokes 2b and 2c, two tracking coils 14 are provided.
a and 14b are stuck. Note that the focus coil 13 and the tracking coils 14a and 14b
It is electrically connected to four wires 9a to 9d via 1a and 11b. An objective lens 15 is fixed to an upper end of the holder 10 in the Y (-) direction.

Next, the operation of the embodiment constructed as described above will be described below. The laser light emitted from the optical block of the main body (not shown) passes through the opening 1a of the base 1 in FIG.
It is irradiated as a beam spot on a recording medium (not shown). The reflected light from the recording medium is again transmitted to the objective lens 15.
And returns to the optical block and is received by a photodetector (not shown), thereby detecting a focus error, a tracking error, and a recording signal.

If a focus error is detected, 2
An electric current is applied to the focus coil 13 via the wires. Then, since the holder 10 is supported by the four wires 9a to 9d so as to be movable in the vertical direction (focus direction) and the radial direction (tracking direction) with respect to the recording medium surface, the holder 10 is moved in the focus direction. The Rukoto. On the other hand, when a tracking error is detected, a current flows through the tracking coils 14a and 14b via two wires other than the two wires. Then, since the holder 10 is supported by the four wires 9a to 9d, it is moved in the tracking direction.

The holder 10 and the objective lens 15 attached thereto are subjected to focus control and tracking control. When the holder 10 moves in the focus direction in the Z (-) direction, the holder 10 comes into contact with the spacer 6. Since the spacer 6 is made of plastic, the contact sound can be made smaller than that of the spacer 6 which hits the metal base 1. For this reason, the surface where the spacer 6 contacts the magnet 5 is configured to be larger than the contact surface of the magnet 5.

Next, the driving points of the apparatus will be described with reference to FIG. In this figure, the strength and direction of the magnetic field at each coil position are indicated by arrows. Note that the configuration of the magnetic circuit is such that a line 16 passing through the center point in the X
, Only the range of 1/2 is shown.
The magnet 5 and the yoke 2 of the focus coil 13
A strong magnetic field acts on the side 13a crossing between b and 2c,
Due to the Y-direction component of this magnetic field, a force of magnitude Fa is received in the focus direction. On the other hand, the yoke 2 is also provided on the opposite side 13b of the focus coil 13 across the yokes 2b and 2c.
The magnetic flux 50 passes through the notch 4 between b and 2c, and a magnetic field acts. The force of the magnitude Fb is received in the focus direction by the Y-direction component of the magnetic field.

The direction of the magnetic field acting on the side 13b of the focus coil 13 is the same as that of the side 13a, but the direction of the current is opposite, so that the direction of the force Fb is opposite to Fa. The relationship of the magnitudes of the forces is Fa> Fb. At the point 17 where a: b = Fb: Fa when these two forces are combined, the magnitude F
The force of a-Fb acts. Thereby, usually the side 13a
A nearby driving point can be moved to a point 17 on the objective lens 15 side.

In order to prevent unnecessary resonance of the apparatus, it is necessary that the center of gravity and the drive point of the movable portion constituted by the holder 10 and the components attached thereto coincide with the drive point. In this regard, in this embodiment, since the driving point 17 approaches the position of the objective lens 15 which is large in mass among the components constituting the movable portion, it is easy to make the center of gravity of the movable portion substantially coincide with the driving point. Since there is no need to provide a large size or a large holder, the size and weight of the movable portion can be reduced.

In this embodiment, the yoke is divided into 2b and 2c, and the acting force is Fa-Fb, so that the driving force of the movable part is reduced. However, as described above, the movable part is reduced in size and weight. As a result, the reduction in driving force can be sufficiently compensated. Note that the tracking coils 14a, 14b
, The sides 14a-1, 14a-2, 14b-1, and 14b-2 receiving the driving force in the same manner as the focus coil 13.
Needless to say, the resultant force of the forces acting on the driving point is set to the point 17 so as to substantially coincide with the driving point.

FIGS. 5 and 6 show a second embodiment of the present invention, and are an exploded perspective view and a plan view. Parts corresponding to those in the first embodiment are denoted by the same reference numerals. In the first embodiment, the magnet 5 is adhered and fixed to the yoke 2a, but in the present embodiment, one magnet is attached to the separated yokes 2b, 2c.
The two magnets 5 are bonded and fixed. The base 1 and the magnet 5 are used to position the magnet 5.
This is the same as the first embodiment in that a spacer 6 is provided between them.

A focus coil 13 is bonded and fixed to the opening of the holder 10 so as to wind the magnet 5 and the yokes 2b and 2c. Further, two tracking coils 14a and 14b are adhered and fixed to the outside of the focus coil 13 on the yoke 2a side. The other configuration is the same as that of the first embodiment, and the description is omitted.

Next, the driving point position of this embodiment will be described with reference to FIG. Magnet 5 of focus coil 13
A strong magnetic field acts on the side 13a between the armature and the yoke 2a, and receives a force of magnitude Fa in the focus direction by the Y-direction component of the magnetic field. The yoke 2 is also provided on the opposite side 13b of the focus coil 13 across the yokes 2b and 2c.
The magnetic flux passes through the notch 4 between b and 2c, and the magnetic field spreads. The side 13b receives a force of the magnitude Fb by the Y-direction component of the magnetic field.

The direction of the magnetic field acting on the side 13b of the focus coil 13 is the same as that of the side 13a, but the direction of the current is opposite, so that the direction of the force Fb is opposite to Fa. The relationship of the magnitudes of the forces is Fa> Fb. When these two forces are combined, a force of magnitude Fa-Fb acts on a point 17 where a: b = Fb: Fa, as in the first embodiment. As a result, the driving point which is normally near the side 13a is
Side point 17 can be moved. Also in this embodiment, since the driving point 17 approaches the position of the objective lens 15 which is large in mass among the components constituting the movable portion, it is easy to make the center of gravity of the movable portion substantially coincide with the driving point. Needless to say, the tracking coils 14a and 14b also have a resultant force of the forces acting on the sides 14a and 14b at the point 17 in consideration of the leakage magnetic flux so as to substantially coincide with the driving point. The other operations are the same as those in the first embodiment, and the description is omitted.

In this embodiment, the magnet 5 is bonded and fixed to the yokes 2b and 2c farther from the objective lens 15, so that the tracking coil 14 is compared with the first embodiment.
a, 14b and the focus coil 13 can be brought closer to the objective lens 15 side. By bringing them closer to each other, it becomes easier to make the center of gravity of the movable part coincide with the drive point, and the movable part can be reduced in size.

[0028]

As described above, according to the present invention, a notch is formed in a part of one magnetic circuit including a magnet and a yoke, and an optical element (for example, an objective lens) is substantially perpendicular to a recording medium surface. The first coil (for example, a focus coil) for moving in the opposite direction generates driving forces in opposite directions to each other, and a driving point due to the resultant force is moved between the optical element and the first coil. In addition to the configuration in which the center of gravity of the movable portion is substantially coincident with the center of gravity of the movable portion, the two coils extending in the focus direction of a second coil (for example, a tracking coil) for moving the optical element in a substantially horizontal direction with respect to the recording medium surface. A driving force is generated on each of the coil sides, and a driving point due to the resultant force is made substantially coincident with a center of gravity of the movable portion between the optical element and the second coil. Therefore, an optical system driving device having excellent characteristics with suppressed resonance can be obtained. In addition, by setting a drive point between the optical element, which is a main component forming the movable portion, and the first and second coils, it becomes easy to match the drive point with the center of gravity. Therefore, it is possible to provide a small and inexpensive optical system driving device without complicating the device or increasing the size of the device for balancing.

[Brief description of the drawings]

FIG. 1 is a perspective view of an apparatus according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view of the first embodiment.

FIG. 3 is a plan view of the first embodiment.

FIG. 4 is an explanatory diagram showing a state of a magnetic field in the first embodiment.

FIG. 5 is an exploded perspective view of an apparatus according to a second embodiment of the present invention.

FIG. 6 is a plan view of a second embodiment.

FIG. 7 is a perspective view showing Conventional Example 1.

FIG. 8 is a sectional view showing Conventional Example 2.

FIG. 9 is a perspective view showing Conventional Example 2.

FIG. 10 is a plan view showing a third conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base 2a, 2b, 2c Yoke 3 Rising part 4 Notch 5 Magnet 7 Wire receiver 8 Substrate 9a-9d Wire 10 Holder 11a, 11b Substrate 12a-12d Rubber 13 Focus coil 14a, 14b Tracking coil 15 Objective lens

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 7/09 G11B 7/095

Claims (1)

(57) [Claims] An optical element for irradiating a light spot on a recording medium surface, a first coil for moving the optical element in a direction substantially perpendicular to the recording medium surface, and a substantially horizontal direction with respect to the recording medium surface. A second coil for moving in the direction, a magnetic circuit including a magnet and a yoke for applying a magnetic flux to the first and second coils, the optical element, and the first and second coils. An optical system driving device comprising: a movable body; and a support unit that supports the movable body so as to be movable in a substantially vertical direction and a substantially horizontal direction with respect to a recording medium surface. And a notch is formed in a part of the yoke so that the magnetic flux also reaches the side of the first coil located on the side of the first coil and the side opposite to the side of the coil, thereby forming a magnetic circuit. A driving force is generated in directions opposite to each other, and a driving point based on the resultant force is configured to be substantially coincident with the center of gravity of the movable body between the optical element and the first coil. A driving force is generated on each of two coil sides extending in the focus direction of the second coil arranged so as to apply a magnetic flux, and a driving point due to a resultant force between the two coil sides is moved between the optical element and the second coil. An optical system driving device, wherein the optical system driving device is configured so as to substantially coincide with the center of gravity of the movable body.