JP2011096311A - Lens driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens driving device which can effectively improve frequency characteristics with a simple configuration. <P>SOLUTION: The diameter (D3) of a head part Ba of a screw B with head is smaller than that of a head part SCb of an energizing screw SC, therefore, it does not contact the inner periphery of a first hole 21a of the first plate spring 21 and a through-hole of an adhesive layer 22. That is, since only the adhesive layer 22 exists between a base and the first plate screw 21, the frequency characteristics can be improved by its damping effect. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a lens driving device for an optical pickup device, and more particularly to a driving device having improved frequency characteristics.

  An optical pickup device capable of recording and / or reproducing information with respect to an optical disk represented by a CD or a DVD has been developed. In addition, an optical pickup device capable of recording / reproducing information on a Blu-ray Disc using a blue-violet semiconductor laser having a wavelength of about 400 nm is already on the market. Here, during recording and / or reproduction of information in the optical pickup device, a focusing operation for appropriately focusing the focused spot on the information recording surface of the optical disc with respect to the objective lens that forms the focused spot, A tracking operation that appropriately follows the track and an actuator that performs the tracking operation are provided. As an actuator, a holder that holds an objective lens is generally supported by a wire with respect to a base. However, in the case of wire support, since it is difficult to attach the wire in a balanced manner with respect to the center of gravity of the holder having the objective lens, it is difficult to maintain the tilt of the objective lens with respect to the incident light beam. There is a problem that a mechanism for driving the lens in the tilt direction is also required.

  On the other hand, in Patent Document 1, in order to improve the resonance characteristics, the deformed portion of the leaf spring body that supports the bobbin can be deformed in both the focusing direction and the tracking direction, and the leaf spring body fixing portions at both ends of the deformable portion. An optical pickup device in which a protrusion is extended in parallel to the deformed portion on each of the fixed portion-side adhesive portion and the movable portion-side adhesive portion, and a damping member having a width wider than that of the deformable portion is attached to the protruded portion. An actuator is disclosed.

JP 2000-306250 A

  However, in the technique of Patent Document 1, it is difficult to attach a thin plate spring body similar to a wire in a balanced manner with respect to the center of gravity of a holder having an objective lens. However, it is difficult to maintain the inclination, and there is a problem that the resonance suppression effect is insufficient only by pasting the damping material. On the other hand, if the holder that holds the objective lens is supported using a relatively wide leaf spring, it becomes possible to maintain the tilt of the objective lens with respect to the incident light beam, but another problem arises. found. Specifically, for example, when a holder that holds an objective lens is supported using a relatively light wire, such as a conventional general actuator, rolling vibration occurs in a low frequency band that does not affect the control system. However, when the holder that holds the objective lens is supported using a relatively wide leaf spring, the vibration mode changes and rolling vibration occurs in a band that affects the control system. It was found that there is a risk of occurrence.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a lens driving device capable of effectively improving frequency characteristics while having a simple configuration.

The lens driving device according to claim 1 is a lens driving device for an optical pickup device that focuses a light beam incident from a light source side onto an optical disc via an objective lens,
Base and
A holder that is movable relative to the base and holds the objective lens;
A leaf spring connecting the holder and the base;
An elastic layer integrated with the leaf spring;
The elastic layer is interposed between the leaf spring and the base, and the leaf spring and the base are not in direct contact with each other.

  According to the present invention, by supporting the holder using a leaf spring having a relatively high torsional rigidity instead of a wire, the tilt of the objective lens can be accurately maintained with respect to the incident light beam, and therefore tilt control is performed separately. There is no need to provide a mechanism, and a simpler configuration can be provided. On the other hand, if the holder that holds the objective lens is supported using a leaf spring, rolling vibration may occur in a band that affects the control system. In this case, the leaf spring and the base are in direct contact. Therefore, the elastic layer disposed between the base and the leaf spring exhibits an effective vibration damping effect, so that rolling vibration can be suppressed and the frequency characteristics of the lens driving device can be improved. In addition, since the elastic layer is integrated with the leaf spring, it can be easily assembled to the lens driving device.

  A lens driving device according to a second aspect is the lens driving device according to the first aspect, wherein the leaf spring is fixed to the base via a fixing member sandwiching the elastic layer with the leaf spring. It is characterized by.

  The lens driving device according to claim 3 is characterized in that, in the invention according to claim 2, the damping characteristic of the elastic layer can be adjusted by changing the thickness of the elastic layer.

  According to a fourth aspect of the present invention, in the lens driving device according to the second or third aspect, the elastic layer is a liquid material while maintaining a predetermined distance between the leaf spring and the fixing member. It is formed by solidifying after filling.

  The lens driving device according to claim 5 is the lens driving device according to any one of claims 1 to 4, wherein the holder holds a rising mirror for guiding the light beam emitted from the light source to the objective lens. It is characterized by.

  According to the present invention, it is possible to provide a lens driving device capable of effectively improving frequency characteristics while having a simple configuration.

1 is a perspective view of a lens driving device 10 for an optical pickup device according to an embodiment. 2A is a top view of the lens driving device 10, FIG. 2B is a IIB-IIB sectional view of the lens driving device 10, and FIG. 2C is a IIC-IIC sectional view of the lens driving device 10. It is a perspective view of leaf spring unit SU. It is a figure shown with the jig | tool JZ on the assumption that the leaf | plate spring unit SU was decomposed | disassembled in the state which the contact bonding layer 22 solidified. It is a figure which shows the process of manufacturing the leaf | plate spring unit SU. It is the figure which cut | disconnected the structure of FIG. 5 by the VI-VI line in the state which installed the 1st leaf | plate spring 21, and looked at the arrow direction. It is a figure which shows the simulation result which the present inventors performed, A solid line shows a gain and a dotted line shows a phase.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings. FIG. 1 is a perspective view of a lens driving device 10 for an optical pickup device according to the present embodiment. 2A is a top view of the lens driving device 10, FIG. 2B is a IIB-IIB sectional view of the lens driving device 10, and FIG. 2C is a IIC-IIC sectional view of the lens driving device 10. In FIG. 1, the arrow T direction is the tracking direction, and the arrow F direction is the focusing direction.

  The base 11 also serving as a yoke has an integral shape in which the lower ends of the pair of side plates 11a and 11a are connected by the bottom plate 11b. A magnet 12 having a yoke 12a attached to the back surface is disposed in a notch 11c formed in the center of the inside of each side plate 11a.

  The 1st holder 13 arrange | positioned in the base 11 non-contacting has a shape which connected the upper end of a pair of side plate 13a, 13a with the upper plate 13b while serving as a yoke. A rectangular opening 13c is formed in the center of the upper plate 13b. A magnet 14 having a yoke 14a attached to the back surface is disposed in a notch 13d formed on the inner side surface of each side plate 13a so as to face the opening 13c. A tracking coil 15 is disposed on the outer surface of each side plate 13 a so as to face the magnet 12.

  The end surface of the side plate 11a of the base 11 and the end surface of the side plate 13a of the first holder 13 are connected by a pair of parallel leaf spring units SU. The leaf spring unit SU will be described later.

  The second holder 16 disposed in a non-contact manner in the opening 13c of the first holder 13 holds a glass objective lens 17 in the central opening 16a. As shown in FIG. 2 (c), the upper plate 13b of the first holder 13 is an L-shaped plate that extends from one end (the rear side end in FIG. 1) downward to wrap around the side plate 13a. A rising mirror 18 is formed on the upper surface in the vicinity of the tip of the portion 13e that extends horizontally so as to face the objective lens 17.

  A focusing coil 19 (only one of them is shown in FIG. 1) is arranged on both side surfaces of the second holder 16 so as to face the magnet 14. The rectangular plate-like second leaf springs 20 and 20 parallel to the upper and lower sides are fixed to the upper surface and the lower surface of the upper plate 13b of the first holder 13 with screws B, and the other ends extend into the opening 13c. The second holder 16 is connected.

  Wiring for the tracking coil 15 and the focusing coil 19 can be routed through the leaf spring unit SU, and wiring for the focusing coil 19 can be routed via the second leaf spring 20.

  FIG. 3 is a perspective view of the leaf spring unit SU. The leaf spring unit SU is formed by stacking and joining a first leaf spring 21, an adhesive layer 22 as an elastic layer, and a fixing member 23. A rectangular plate-shaped fixing member 23 having the same width as the first plate spring 21 but a length of about 1/3 of the entire length is provided on one end side in the longitudinal direction of the first plate spring 21 having a rectangular plate shape. It is joined via a thin adhesive layer 22. The first leaf spring 21 has a pair of first holes 21 a and 21 a on the fixing member 23 side, and a pair of second holes 21 b having a smaller diameter than the first holes 21 a and 21 a on the side far from the fixing member 23. 21b. The fixing member 23 also has holes 23a and 23a having a smaller diameter than the first holes 21a and 21a corresponding to the first holes 21a and 21a of the first leaf spring 21. Hereinafter, a method for manufacturing the leaf spring unit SU will be described.

  4 and 5 are diagrams showing a process of manufacturing the leaf spring unit SU, and FIG. 6 is a cross-sectional view taken along line VI-VI with the first leaf spring 21 installed in the state shown in FIG. It is the figure seen in the direction. In FIG. 4, the jig JZ used for manufacturing the leaf spring unit SU has a housing shape as a whole, and is made of a material to which an adhesive layer resin described later is difficult to stick. A shallow groove JZa having a width W substantially equal to that of the first leaf spring 21 on the upper surface of the jig JZ, a deeper rectangular recess JZb formed in the shallow groove JZa, and two screws formed on the bottom surface of the recess JZb A hole JZc (see FIG. 6) is formed. A chamfered portion C may be formed between the shallow groove JZa and the recess JZb. The inner shape of the recess JZb substantially matches the outer shape of the fixing member 23. An urging screw SC can be screwed into the screw hole JZc having the same diameter D1 as the hole 23a of the fixing member 23. The urging screw SC includes a screw portion SCa that is screwed into the screw hole JZc, and a head SCb that is larger in diameter than the screw portion SCa and has the same diameter D2 (> D1) as the first hole 21a of the first leaf spring 21. And have.

  When manufacturing the leaf spring unit SU, the fixing member 23 is first placed in the recess JZb of the jig JZ with the biasing screw SC removed from the screw hole JZc, and then the threaded portion of the biasing screw SC. When SCa is screwed into the screw hole JZc, the head SCb comes into contact with the upper surface of the fixing member 23 and further screwing is prevented. In this state, the fixing member 23 is fixed in the recess JZb by the biasing screw SC. The thickness h of the fixing member 23 is smaller than the depth Δ from the bottom surface of the shallow groove JZa to the bottom surface of the recess JZb (Δ> h).

  Thereafter, the first plate spring 21 is placed in the shallow groove JZa so that the first hole 21a of the first plate spring 21 is inserted into the head SCb of the biasing screw SC. In such a state, a gap (Δ−h) as a predetermined value is formed between the fixing member 23 and the first leaf spring 21. Therefore, a liquid resin agent (for example, acryl-modified silicone resin: Shore hardness 42A, elongation at break 220%) is poured into the gap from the side of the jig JZ, and is solidified with time. As a result, the adhesive layer 22 is formed in close contact and integral between the first leaf spring 21 and the fixing member 23. At this time, referring to FIG. 4, since the head SCb of the biasing screw SC passes through the adhesive layer 22, a through hole 22a having an inner diameter D2 is formed at the time of solidification. Thereafter, the urging screw SC is loosened and removed, and the integrated joint is removed from the jig JZ, whereby the leaf spring unit SU is formed. At this time, by projecting a pin or the like inserted into the through hole JZd formed in the jig JZ, the first leaf spring 21 can be pushed from the back surface, and the leaf spring unit SU can be easily removed.

  As shown in FIG. 3, one end of the leaf spring unit SU formed in this way is fixed to the base 11 via a head screw B inserted into the first holes 21a and 21a. That is, when the screw portion Bb of the head-attached screw B is screwed into a screw hole (not shown) of the base 11, the head Ba presses the periphery of the hole 23 a of the fixing member 23. B and the fixing member 23 are fixed to the base 11 and integrated. Further, the other end of the leaf spring unit SU is fixed to the first holder 13 by a similar screw B inserted through the second holes 21b and 21b. Thus, the first holder 13 is supported to be displaceable with respect to the base 11 via the leaf spring unit SU. Since the lens driving device 10 has a comparatively small configuration and its parts are small, the first plate spring 21, the adhesive layer 22, and the fixing member 23 are integrally assembled as the plate spring unit SU, so that the assembly is possible. It becomes easy.

  Here, the outer diameter D3 of the head Ba of the screw with head B is smaller than the inner diameter D2 of the first hole 21a of the first leaf spring 21 and the through hole 22a of the adhesive layer 22 (D3 <D2). Yes.

  Accordingly, as apparent with reference to the dotted line in FIG. 6, the head Ba of the head screw B has a smaller diameter (D3) than the head SCb of the biasing screw SC. In a state of being fixed to the base 11 via the part-attached screw B, the inner periphery of the first hole 21 a of the first leaf spring 21 and the through hole 22 a of the adhesive layer 22 is not contacted. That is, since only the adhesive layer 22 exists between the base 11 and the first leaf spring 21, the frequency characteristics can be improved without hindering the damping effect. Although the attenuation characteristic of the adhesive layer 22 also changes depending on the thickness thereof, according to the present embodiment, the thickness h of the fixing member 23 assembled to the jig JZ is changed to change the attenuation characteristic on the jig JZ. Since the gap (Δ−h) between the one leaf spring 21 and the fixing member 23 can be set to an arbitrary value, the attenuation characteristic can be adjusted by changing the thickness of the adhesive layer 22.

  FIG. 7 is a diagram showing a simulation result performed by the present inventors. FIG. 7A shows frequency characteristics of a lens driving device in which the first leaf spring is directly fixed to the base without using an adhesive layer. FIG. 7B shows frequency characteristics of the lens driving device in which the first leaf spring is fixed to the base via the adhesive layer. When the adhesive layer is not used, as shown in FIG. 7A, resonance occurs around 800 Hz as a band that affects the control system (due to rolling vibration around the axis orthogonal to the focusing direction (F) and the tracking direction (T). However, when an adhesive layer is used as in this embodiment, resonance in the same band disappears as shown in FIG. Therefore, the effect of the present invention was confirmed.

  Next, operations of the optical pickup device and the lens driving device according to the present embodiment will be described. In FIG. 1, when a light beam having a predetermined wavelength is emitted from a light source (not shown) along the optical axis X, the light beam enters from between the side plates 13a and 13a of the first holder 13, and FIG. ), The light is reflected by the rising mirror 18 and condensed on the information recording surface of the optical disc OD via the objective lens 17. The reflected light from the information recording surface passes through the objective lens 17 again, is reflected by the rising mirror 18, and enters a photodetector (not shown). Based on the signal from the photodetector, power is supplied to the tracking coil 15 by a control device (not shown), the first holder 13 is displaced in the tracking direction T, and power is supplied to the focusing coil 19. The second holder 16 is displaced in the focusing direction F for each objective lens 17.

  According to the present embodiment, the objective lens 17 is made of glass, and the first holder 13 has the rising mirror 18, and the mass of the entire first holder 13 is relatively large. By supporting the first leaf spring 21 of the leaf spring unit SU having a high height, a tilt adjustment mechanism can be made unnecessary. However, if the first holder 13 is simply supported by the first leaf spring 21, rolling vibration around the axis perpendicular to the focusing direction (F) and the tracking direction (T) becomes a problem (FIG. 7 (a)). However, the damping function of the adhesive layer 22 in the leaf spring unit SU can suppress rolling vibration (see FIG. 7B) and provide good frequency characteristics.

  In the above-described embodiment, the first holder 13 is supported by the leaf spring unit SU with respect to the base 11, but the second holder 16 with respect to the first holder 13 and a similar leaf spring unit are provided. It may be used and supported. In such a case, it goes without saying that the first holder 13 corresponds to the base.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be modified or improved as appropriate. For example, the lens driving device of the present invention can be applied to a holographic type optical pickup device.

DESCRIPTION OF SYMBOLS 10 Lens drive device 11 Base 11a Side plate 11b Bottom plate 11c Notch 12 Magnet 12a Yoke 13 1st holder 13a Side plate 13b Upper plate 13c Opening 13d Notch 13e Plate part 14 Magnet 14a Yoke 15 Tracking coil 16 Holder 17a Opening lens 17 Mirror 19 Focusing coil 21a 1st hole 21b 2nd hole 22 Adhesive layer 22a Through hole 23 Fixing member 23a Hole B Screw with head Ba Head Bb Screw part C Chamfer JZ Jig Jja Shallow groove JZb Recess JZc Hole OD Optical disk SC Energizing screw SCa Screw part SCb Head SU Leaf spring unit

Claims (5)

A lens driving device for an optical pickup device for condensing a light beam incident from a light source side onto an optical disc through an objective lens,
Base and
A holder that is movable relative to the base and holds the objective lens;
A leaf spring connecting the holder and the base;
An elastic layer integrated with the leaf spring;
The lens driving device, wherein the elastic layer is interposed between the leaf spring and the base, and the leaf spring and the base are not in direct contact with each other.   The lens driving device according to claim 1, wherein the leaf spring is fixed to the base via a fixing member that sandwiches the elastic layer with the leaf spring.   The lens driving device according to claim 2, wherein a damping characteristic of the elastic layer can be adjusted by changing a thickness of the elastic layer.   The elastic layer is formed by solidifying after filling a liquid material between the leaf spring and the fixing member while maintaining a predetermined value between the leaf spring and the fixing member. The lens drive device described in 1.   The lens driving device according to claim 1, wherein the holder holds a rising mirror for guiding a light beam emitted from the light source to the objective lens.

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