JP2000011406A - Optical pick-up - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a wire fixed with adhesion from coming off by attenuating an unwanted resonance, especially, suppressing unwanted resonance in the tangential direction. SOLUTION: This optical pick-up is provided with a lens holder 11 containing an object lens 15, an actuator base 12 supporting this lens holder 11 via plural wires 13, and an electromagnetic drive mechanism 14 driving the lens holder 11 in one of the directions of focusing and tracking at least, and a soft elastic adhesive, of which young's modulus is from 60 to 150 kgf/cm2, is applied to at least either of the joint parts of the wires 13 with the lens holder 11 or the actuator base 12, to fixedly bond the wire 13 with elasticity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup suitable for an optical disk apparatus using an optical disk such as a magneto-optical disk, and in particular, a movable member including an objective lens is elastically supported by a fixed member via a wire. About optical pickups.

[0002]

2. Description of the Related Art In general, an optical pickup is mounted on an optical disk device and reciprocates, mounted on the carriage, and emits and receives a light emitting element and a light receiving element. And a lens actuator having a movable objective lens so that the light can be accurately incident on the lens. The lens actuator of the optical pickup includes a lens holder that holds the objective lens, a fixing member that elastically supports the lens holder via four wires, and an electromagnetic drive mechanism that drives the lens holder in a focusing direction or a tracking direction. And so on. As described above, in the optical pickup in which the lens holder is elastically supported on the fixed member via the wire, there are six resonance frequencies which are naturally determined by the mass and inertia moment of the lens holder and the spring constant of the wire. Of these, the focus direction and the tracking direction
The drive of the lens actuator is controlled using the resonance of the two parallel movements. In order to attenuate or block other unnecessary resonances, a method using a leaf spring instead of a wire or a method of surrounding the end of the wire with a damper agent has been adopted.

[0003] An optical pickup using a band-shaped leaf spring instead of a wire, as described in Japanese Patent Application Laid-Open No. Hei 9-16996, has a portion of the leaf spring formed with a stretchable portion punched in a crank shape. Thus, the leaf spring has a spring property in a tangential direction orthogonal to the tracking axis. When both ends of a leaf spring having a telescopic portion that expands and contracts in the tangential direction are fixed to a lens holder and a fixing member, yawing (rotational resonance around the focus axis) and pitching (rotational resonance around the tracking axis) do not cause a problem in the lens actuator. Since the band is shifted to the band, unnecessary vibration such as yawing and pitching can be reduced, and unnecessary resonance in the tangential direction can also be attenuated.

[0004]

According to such an optical pickup, unnecessary vibration such as yawing and pitching can be reduced, and there is an advantage that focus servo and tracking servo are stabilized. However, the spring characteristics in the tangential direction of the leaf spring are determined by the elastic portion having a complicated shape, and it is very difficult to process such an elastic portion into a fine leaf spring. Formed on each of the leaf springs,
Since it is necessary to make the spring characteristics of each leaf spring in the tangential direction uniform, extremely high processing accuracy is required for the processing of the leaf spring including the expansion and contraction portion, which has been a major factor leading to an increase in cost. Therefore, the applicant has proposed an improved optical pickup 50 in which a wire is surrounded by a damper agent without using such a leaf spring (Japanese Patent Application No. 10-61336).
issue).

FIG. 12 shows an improved optical pickup 50.
It is a perspective view of. As shown in FIG. 12, the optical pickup 50 includes a lens holder 51 made of a synthetic resin, an actuator base 52 made of a synthetic resin, four wires 53 for elastically supporting the lens holder 51 on the actuator base 52, An electromagnetic drive mechanism 54 for driving the lens holder 51 in the focus direction and the tracking direction is provided. An objective lens 55 is mounted on the lens holder 51, and two mounting portions 51a are formed on each side surface of the lens holder 51, that is, four mounting portions 51a. A projection 52a is formed at the center of the back surface of the actuator base 52,
The left and right sides of the projection 52a are stepped portions 52b. Further, a total of four cutouts 52c are formed, two on each side surface of the actuator base 52, and these cutouts 52c are continuous with the step 52b on the back surface of the actuator base 52.

The wire 53 is made of an extremely fine metal wire of about several tens μm, has a straight portion 53b and a flexible portion 53c extending substantially perpendicularly to each other via a bent portion 53a, and has an overall L-shape. Formed in. Each wire 53
Is disposed between the lens holder 51 and the actuator base 52, and the tip of the linear portion 53b is fixed to the mounting portion 51a of the lens holder 51 with an adhesive 56,
The rear end of the flexible portion 53c is fixed on the protrusion 52a of the actuator base 52 with an adhesive 57. This allows
The straight portion 53b extends in the tangential direction shown in FIG. 12, and the flexible portion 53c is converted into a substantially right angle direction by the bent portion 53a and extends in the tracking direction.
Further, since the fixed end of the flexible portion 53c is bonded to the protruding portion 52a, the depth of the step portion 52b is located between the flexible portion 53c at the portion extending from the fixed end to the bent portion 53a and the back surface of the actuator base 52. A gap corresponding to the dimension is secured, and the gap (step 52b) and the cutout 52c are filled with a damper (not shown) made of an ultraviolet curable resin.

Although the details of the electromagnetic drive mechanism 54 are not shown, a focus coil and a tracking coil, and a magnetic circuit (magnet and yoke) for generating a magnetic flux in a direction intersecting the direction of the current flowing through these coils. ).

[0008] Such an improved optical pickup 50
Then, the lens holder 51 is driven in the focusing direction of the objective lens 55 by the current flowing through the focus coil of the electromagnetic drive mechanism 54, and the lens holder 51 is driven in the tracking direction of the objective lens 55 by the current flowing through the tracking coil. At this time, a step 52b is provided between the flexible portion 53c of the wire 53 and the back surface of the actuator 52.
12, a portion from the fixed end of the flexible portion 53c to the bent portion 53a can be deformed in the axial direction of the straight portion 53b, that is, in the tangential direction shown in FIG. Unnecessary resonance is reduced. Even in the improved optical pickup 50, the wire 53 must be bent into an L shape in order to reduce unnecessary resonance. On the other hand, in recent years, high performance of drive control of the lens holder 51 has been required for DVDs, MDs, and the like, and it has been necessary to further reduce the influence of unnecessary resonance in the tangential direction, particularly in a high resonance frequency band.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical pickup which attenuates unnecessary resonance and suppresses unnecessary resonance in the tangential direction without adding any complicated mechanical mechanism. Is to do.

[0010]

As a first means for solving the above problems, a movable member including an objective lens, a fixed member supporting the movable member via a plurality of wires, and a movable member are provided. An electromagnetic drive mechanism for driving in at least one of a focus direction and a tracking direction, wherein at least one of the movable member and the fixed member has a Young's modulus of 60 at the joint with the wire.
To 150 kgf / cm ² by applying a soft elastic adhesive and fixing the wire to the movable member or the fixed member.

Further, as a second solution, a groove for disposing a wire is formed on at least one of the movable member and the fixed member, and irregularities are formed on a contact surface of the groove with the wire.

Further, as a third solution, the depth of the unevenness of the groove is 5 μm or more.

As a fourth solution, a groove for disposing a wire is formed on at least one of the movable member and the fixed member, and irregularities are formed on the side surface of the wire in the groove.

Further, as a fifth solution, the depth of the irregularities of the wire is 1 μm or more and 4 μm or less.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical pickup 1 according to the present invention will be described.
Embodiment 0 will be described with reference to the drawings. As shown in FIG. 1, a lens actuator constituting the optical pickup 10 includes a lens holder 11 made of a synthetic resin as a movable member, an actuator base 12 made of a synthetic resin as a fixed member, and an actuator base 12 made of a lens holder. And an electromagnetic drive mechanism 14 for driving the lens holder 11 in the focusing direction and the tracking direction. The lens holder 11 includes a cylindrical lens holding portion 16 for holding the objective lens 15 and a rectangular yoke holding portion 17 integrated with a cylindrical part of the lens holding portion 16. On the opposite side surface 18 of the yoke holding portion 17,
Two V-shaped mounting portions 11a are formed side by side in the height direction (vertical direction in the figure).

The actuator base 12 is formed in a substantially rectangular shape, and has opposed side wall surfaces 19 and the side wall surfaces 19.
, A front wall surface 21 (in the figure, the front side) and a front wall surface 21 (a rear side in the figure), and a top plate surface 22 and a bottom plate surface 23. An overhang 19a is formed to project in parallel with. Also,
On each side wall surface 19, four grooves 19b are formed two by two in parallel with the top plate surface 22, and a substantially V-shaped notch 12a and a substantially U-shaped recess 12b are formed in each groove 19b. It is formed continuously. Then, the lens holder 11
17a of the yoke holding portion 17 (the front surface in the figure)
And the front wall surface 21 of the actuator base 12 are opposed to each other at a predetermined interval.

The electromagnetic drive mechanism 14 is made of a U-shaped yoke 24 made of a metal magnetic material integrated with the yoke holding portion 17 and the same metal magnetic material attached and fixed so as to cover both ends of the yoke 24. A back yoke 25, a magnet 26 attached and fixed inside the yoke 24, and a substantially cylindrical coil attached to and fixed to the projecting portion 19 a of the actuator base 12 so as to face the magnet 26 and cross the yoke 24. 27 (a focus coil and a tracking coil (not shown)), thereby having one magnetic circuit.

The wire 13 is made of an extremely fine metal wire of about several tens of μm. One end 13 a of the wire 13 engages with the mounting portion (groove) 11 a of the lens holder 11, and the other end 13 a
b engages with the notch 12a through the recess 12b of the actuator base 12. The lens holder 11 is movably supported by the wire 13.

Next, the attachment of the wire 13 will be described with reference to FIG. FIG. 2 is a perspective view schematically showing the optical pickup 10 shown in FIG. As shown in FIG. 2, the mounting portion 1 is an engagement portion of the wire 13.
A wire 13 is engaged with the notch 1a and the notch 12a, and is firmly fixed to the mounting portion 11a with an ultraviolet curing adhesive 40, and a soft elastic adhesive 41 is attached to the notch 12a.
And elastically fixed. As the soft elastic adhesive 41, a urethane acrylate resin or a silicone elastic adhesive, which is a UV-curable resin, is used. Thus, each wire 13 bridges the lens holder 11 and the actuator base 12 at a predetermined interval. Further, a damper agent 45 is applied (filled) to the concave portion 12b, and a silicon gel damping material is used for the damper agent. Here, a damper agent having a Young's modulus of about 0.3 kgf / cm ² is used. This is mainly for attenuating the resonance of the lens holder 11 in the tracking direction and the focus direction.

In the optical pickup constructed as described above, the lens holder 11 is driven in the focusing direction of the objective lens 15 by the current flowing through the focus coil of the electromagnetic drive mechanism 14, and the lens holder 11 is moved by the current flowing through the tracking coil. It is driven in 15 tracking directions. At this time, since the wire 13 is disposed in the notch portion 12a via the soft elastic adhesive 41, a high frequency band in the tangential direction (longitudinal vibration mode of the four wires 13), such as yawing and pitching, is unnecessary. Resonance is reduced.

Next, in order to explain the damping action (damping action) of the optical pickup 10 of the present invention, a generally known one-degree-of-freedom system model of vibration will be described first.
FIG. 3 is a diagram showing a one-degree-of-freedom model of this vibration.
As shown in FIG. 3, a weight 31 having a mass m is suspended from a fixed top plate 30 via a spring member 32. The attenuator 33 is provided in parallel with the spring member 32, and the top plate 30 and the weight 3
1 to attenuate the vibration of the spring member 32. In the one-degree-of-freedom model configured as described above, the resonance value Mp can be expressed by the following equation.

Mp = 1 / (2 · ζ√ (1-ζ ² ) (1) Further, the damping ratio coefficient ζ in this equation can be expressed by the following equation: ζ = c / 2√ (mk) (2) where c is the viscous damping coefficient of the attenuator 33, m is the mass of the weight 31, and k is the spring constant of the spring member 32.

Next, in the one-degree-of-freedom model, the relationship between the damping ratio coefficient ζ and the resonance value Mp when the weight 31 is forcibly vibrated is shown in Table 1 below.

[0024]

[Table 1]

As shown in Table 1, as the damping ratio coefficient ζ increases, the resonance value Mp decreases. For example, the above (2)
From the equation, the mass m of the weight 31 and the spring constant k of the spring member 32 are set to certain values, and the viscous damping coefficient c of the damper 33 is obtained.
Is increased, the braking force is greatly affected, so that the damping ratio coefficient ζ increases from the above equation (2), and the resonance value Mp of the entire model decreases from the equation (1). Here, when the damping ratio coefficient 十分 is sufficiently smaller than the numerical value 1, √ of the equation (1) is obtained.
(1-ζ ² ) is approximated to Numerical Value 1, and the resonance value Mp changes in a substantially inversely proportional relationship with the damping ratio coefficient ζ. FIG. 4 shows the relationship between the damping ratio coefficient ζ and the resonance value Mp (Table 1).
Is shown in the graph.

Next, a case where the above-described one-degree-of-freedom model is applied to the optical pickup 10 of the present invention will be described. Table 2
Is the relationship between the damping ratio coefficient ζ and the resonance value Mp when the one-degree-of-freedom model is applied to the forced vibration of the rotating system, that is, when yawing, which is one of the unnecessary resonances of the movable member constituting the lens actuator, occurs. It is shown.

[0027]

[Table 2]

As shown in Table 2, the moment of inertia I around the Z axis (the optical axis direction of the objective lens 15) of the center of gravity of the movable member is shown.
Is constant and 1.6 × 10 ⁻⁸ [kg · m ² ]. The rotation spring constant κ indicates the spring constant of the wire 13 when rotating about the Z-axis of the center of gravity of the movable member. The rotation spring constant κ indicates the position of the lens holder 11 from where it is attached to the wire 13 (the joint of the notch 12a). This is a value obtained by dividing the product of the distance to the X axis (the tangential direction of the objective lens 15) and the spring constant k of the wire by the rotation angle for displacement. Further, assuming the attenuator 33, that is, the viscous damping coefficient c of the soft elastic adhesive 41, the above equation (2) can be expressed by the following equation.

Ζ = c / 2√ (l · κ) (3)

From the equations (3) and (1), the resonance value Mp, that is, the yawing value of the lens actuator is obtained as shown in Table 2. Here, Table 3 shows the relationship among various adhesives used as the soft elastic adhesive 41 in the optical pickup 10, their Young's modulus (E), and rotation spring constant κ.

[0031]

[Table 3]

Next, a simulation was attempted on the optical pickup 10 in order to determine the frequency response characteristics of the lens actuator. 5 to 8, the horizontal axis represents the frequency f [Hz], and the vertical axis represents the amplitude M (Magnitude) [d
B] and phase φ (Phase) [degree] are shown, respectively, and adhesive samples A, B, C, and D in Table 3 are shown.
5, 6, 7, and 8 respectively correspond to the frequency response characteristics of the lens actuator when using. In FIG. 8, at 2 kHz, the phase change amount is 20 [degre].
e], but in FIG. 5, it can be seen that the amount of phase change is reduced to about 5 [degree], and unnecessary resonance is reduced.

Next, a modified example of the embodiment of the present invention will be described below. FIG. 9 is a partially enlarged perspective view showing a joint portion between a part of the lens holder 11 and the actuator base 12 of the optical pickup and the wire 13. Other parts (not shown) are the same as those of the optical pickup 10 described above. As shown in FIG. 9, one end 13a of a metal wire 13 is attached and fixed to a V-shaped attachment portion 11a of a lens holder 11 made of resin.
The other end 13 b of the wire 13 is attached and fixed to a notch 12 a of the actuator base 12.
Then, the mounting portion 11a and the notch portion 12a are
It is fixed to the joint with the wire 13 using a soft elastic adhesive 41. In the optical pickup configured as described above,
There is no concave portion 12b coated (filled) with the above damper agent, and is fixed to the joint between the mounting portion 11a and the wire 13 using a soft elastic adhesive 41 instead of the ultraviolet curing adhesive 40. Therefore, the labor for forming the concave portion 12b in the actuator base 12 can be omitted, and the operation can be further simplified. Further, from the results of the above-described simulation and actual measurement, when a soft elastic bonding member having a Young's modulus of 100 [kgf · cm ² ] is used, an optimal material having no or suppressed side resonance is obtained.

Next, a modified example of the wire 13 in the embodiment of the present invention will be described. As shown in FIG. 11, the wire 13 is a round and long metal wire made of a metal member. A gentle unevenness is formed on the side surface of the wire 13, and the height (t _pp ) of the unevenness on the side surface is 1 to 4 μm. In addition, the unevenness is provided at intervals (l) of approximately 200 μm. The wire 13 thus formed
Is attached to the mounting portion 11a and fixed with the soft elastic adhesive 41, the side surface of the wire 13 is made rough in an uneven shape, so that the bonding strength and the pulling force between the soft elastic adhesive 41 and the wire 13 can be increased. it can. The wire 13
May be provided in a spiral shape, instead of a side surface having regular irregularities in the longitudinal direction.

Next, the lens holder 1 will be described with reference to FIG.
A modified example of the first mounting portion 11a will be described. As shown in FIG. 10A, a concave portion 11b having a size substantially equal to the diameter of the wire 13 is provided at the deepest portion of the mounting portion 11a.
Is formed in the thickness direction, and the inner wall of the recess 11b is formed in an uneven surface. This uneven surface has a peak value (h _pp ) of 5 to 15 μm, and the optimum value is 10 μm. As shown in FIG. 10B, a wire 13 is arranged and engaged with the recessed portion 11b, and attached and fixed with an adhesive. Therefore, the movement of the lens holder 11 in the tracking direction or the focus direction causes the wire 13 to move.
In this case, the adhesive strength between the concave portion 11b and the soft elastic adhesive 41 can be increased with respect to the pulling force. Although the concave portion 11b is formed in the mounting portion 11a of the lens holder 11,
It may be formed in the notch 12a of the actuator base 12, or may be formed in both of them. As described above, the optical pickup 10 of the present invention is not limited to the structure described above.

[0036]

A movable member including an objective lens, a fixed member that supports the movable member via a plurality of wires, and an electromagnetic drive mechanism that drives the movable member in at least one of a focus direction and a tracking direction. The movable member or the fixed member has a Young's modulus of 60 to 150 kg at a joint portion with the wire at least one of the movable member and the fixed member
By applying a soft elastic adhesive of f / cm ² and fixing the wire to the movable member or the fixed member, the wire has a simple structure, and the elastic action (damping action) of the soft elastic adhesive causes the wire to move. Elastic deformation (damping) is possible in the tangential direction, which is the length direction, so that unnecessary resonance can be attenuated. It is not simply elastically deformed in the length direction but elastically deformed in the length direction while maintaining the adhesive strength.

Further, a groove for disposing a wire is formed on at least one of the movable member and the fixed member.
Due to the formation of the irregularities on the contact surface with the wire, the adhesive flows into the gaps of the irregularities, it is possible to sufficiently secure the bonding area, and to improve the retaining strength against the pulling force due to the movement of the movable member. Can be.

Further, a groove for disposing a wire is formed in at least one of the movable member and the fixed member.
By forming the unevenness on the side surface in the groove, the adhesive flows into the gap of the unevenness, it is possible to sufficiently secure the bonding area, and it is possible to improve the retaining strength against the removal force accompanying the movement of the movable member. it can.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an optical pickup according to an embodiment of the present invention.

FIG. 2 is a perspective view schematically showing an optical pickup of the present invention.

FIG. 3 is a diagram showing a one-degree-of-freedom model of vibration.

FIG. 4 is a diagram illustrating a relationship between a damping ratio coefficient and a resonance value of a one-degree-of-freedom model.

FIG. 5 is a diagram showing vibration characteristics (adhesive sample A) obtained by simulating the lens actuator of the optical pickup of the present invention.

FIG. 6 is a diagram illustrating vibration characteristics (adhesive sample B) obtained by simulating the lens actuator of the optical pickup of the present invention.

FIG. 7 is a diagram showing vibration characteristics (adhesive sample C) obtained by simulating the lens actuator of the optical pickup of the present invention.

FIG. 8 is a diagram showing vibration characteristics (adhesive sample D) obtained by simulating the lens actuator of the optical pickup of the present invention.

FIG. 9 is a partially enlarged perspective view showing a joint between a lens holder, an actuator base, and a wire, which is a modification of the embodiment of the present invention.

FIG. 10A is a plan view showing a modified example of the mounting portion of the present invention, and FIG. 10B is a perspective view thereof.

FIG. 11 is a perspective view showing a modification of the wire of the present invention.

FIG. 12 is a perspective view of an improved optical pickup.

[Explanation of symbols]

 Reference Signs List 11 movable member (lens holder) 12 fixing member (actuator base) 13 wire 14 electromagnetic drive mechanism 15 objective lens 19b groove 41 soft elastic adhesive

Claims (5)

[Claims] 1. A movable member including an objective lens, a fixed member that supports the movable member via a plurality of wires, and an electromagnetic drive mechanism that drives the movable member in at least one of a focus direction and a tracking direction. In at least one of the movable member or the fixed member, the Young's modulus is 60 to 1 at a joint portion with the wire.
An optical pickup, wherein a soft elastic adhesive of 50 kgf / cm ² is applied, and the wire is fixed to the movable member or the fixed member. 2. The device according to claim 1, wherein a groove for disposing the wire is formed on at least one of the movable member and the fixed member, and irregularities are formed on a contact surface of the groove with the wire. Optical pickup. 3. The unevenness of the groove has a depth dimension of 5 μm.
3. The optical pickup according to claim 2, wherein the distance is at least m. 4. The device according to claim 1, wherein at least one of said movable member and said fixed member is provided with a groove for disposing said wire, and irregularities are formed on a side surface of said wire in said groove. Optical pickup. 5. The unevenness of the wire has a depth dimension of 1
The optical pickup according to claim 4, wherein the optical pickup is not less than 4 µm.