JP4566155B2 - Optical pickup - Google Patents

Description

  The present invention relates to an optical pickup for recording / reproducing information on / from a disc-shaped recording medium such as a digital versatile disc (DVD) or a compact disc (CD), and more particularly, an objective is provided by a protective member attached to a lens holder. The present invention relates to an optical pickup that avoids contact between a lens and a disk-shaped recording medium.

  In general, an optical pickup drives a light receiving / emitting unit in which a light emitting unit such as a semiconductor laser and a light receiving unit such as a photodetector are integrally disposed, a lens holder that holds an objective lens, and the lens holder. It is roughly constituted by an actuator provided with electromagnetic drive means, a reflection mirror installed in the optical path between the light emitting / receiving unit and the objective lens, and a chassis on which these members are mounted. The electromagnetic driving means is composed of a focus coil and a tracking coil attached to the lens holder side, and a magnetic circuit part disposed on the actuator base side, and the focus coil and the tracking coil are generated in the magnetic circuit part. It is arranged so as to cross the magnetic flux. The lens holder is supported on a support substrate via a plurality of conductive wires, and the distal ends of the wires are connected to the terminals of the focus coil and the tracking coil, respectively. As a result, a drive current is supplied from the external drive circuit to the focus coil and the tracking coil via the support substrate and each wire.

  In the optical pickup having such a general configuration, a light beam emitted from a semiconductor laser or the like and reflected by a reflection mirror is irradiated onto a data track of the disk by an objective lens, and a return light beam from the disk is an object. Information is recorded / reproduced with respect to the disc by receiving light through a lens or a reflecting mirror, and at that time, the spot diameter of the light beam is set to the data track. Focus servo and tracking servo can be applied. That is, when an electric current is applied to the focus coil, an electromagnetic force is generated in a direction along the optical axis of the objective lens, so that the lens holder is driven in that direction to perform focus correction of the objective lens. Since an electromagnetic force is generated in a direction orthogonal to the optical axis, the lens holder is driven in that direction so that tracking correction of the objective lens can be performed.

Conventionally, in this type of optical pickup, particularly in an optical pickup in which the working distance between the surface of the objective lens and the disk is set narrower, the upper surface of the lens holder is closer to the disk than the surface of the objective lens. By attaching a protective member that protrudes toward the disc, if the lens holder moves excessively in the direction of the disc for any reason, the protective member is brought into contact with the disc before the objective lens, causing damage to the objective lens or disc. In order to prevent this, there is known (for example, see Patent Document 1). This protective member is composed of a single piece of silicon rubber, which is a soft elastic material, or a laminated body in which silicon rubber is integrated with a resin film. In either case, the protective member is fixed to the upper surface of the lens holder using an adhesive. It is like that.
Japanese Patent Laying-Open No. 2004-303383 (page 5-7, FIG. 3)

  In the conventional optical pickup disclosed in Patent Document 1, a protective member made of a single piece of silicon rubber or a laminate of silicon rubber and a resin film is adhered to the upper surface of the lens holder so as to protrude from the surface of the objective lens. Therefore, it is possible to prevent damage to the objective lens and the disk with a soft protective member, but since the silicon rubber and the resin film constituting the protective member are both materials having poor adhesion, the amount of adhesive is small. If it is insufficient, the protective member may be peeled off. Therefore, conventionally, the amount of adhesive used is increased to increase the adhesive strength of the protective member. However, if the amount of adhesive is too large, excess adhesive that protrudes from the lower surface of the protective member exceeds the side surface. There is a problem that the disk reaches the upper surface and the disc is damaged by the excess adhesive.

  The present invention has been made in view of the situation of the prior art as described above, and an object thereof is to provide an optical pickup capable of reliably avoiding contact between an objective lens and a disk-shaped recording medium. .

According to the present invention, a groove portion filled with an adhesive is formed on the upper surface of the lens holder, and the protective member is formed into a cross-sectional drum shape with a constricted central portion in the thickness direction. The constricted portion of the protective member is filled with the adhesive. By obtaining the anchor bolt effect, the protective member can be fixed to the lens holder with high adhesive strength using a small amount of adhesive.

In the optical pickup according to the present invention, the protective member for avoiding contact between the objective lens and the disc-shaped recording medium has a constricted drum shape having a narrowed central portion in the thickness direction, and this protective member is formed on the upper surface of the lens holder. Adhesive agent is filled in the constricted part protruding from the opening end of the groove part and the anchor bolt effect is obtained by placing it on the inner bottom surface of the groove part formed in the above, so that the adhesive strength is sufficiently high despite a small amount of adhesive Therefore, it is possible to solve the problem that the excess adhesive protrudes to the upper surface of the protective member and damages the disk.

The present invention includes an objective lens that converges a light beam on a disk-shaped recording medium, a lens holder that holds the objective lens, and an electromagnetic drive unit that corrects the lens holder in the optical axis direction of the objective lens, In the optical pickup in which a protective member for avoiding contact between the objective lens and the disc-shaped recording medium is fixed to the lens holder using an adhesive, a groove portion in which the adhesive is filled on the upper surface of the lens holder And the protective member has a constricted drum shape with a narrowed central portion in the thickness direction, and the protective member is placed on the inner bottom surface of the groove portion so that the constricted portion is an open end of the groove portion. And the adhesive is filled into the constricted portion.

In the optical pickup configured as described above, when the protective member is fixed to the inner bottom surface of the groove portion formed on the upper surface of the lens holder using an adhesive, the constricted portion of the protective member having a cross-sectional shape is formed as an opening of the groove portion. By projecting from the end and filling the constricted part with an adhesive to obtain the anchor bolt effect, it is possible to ensure a sufficiently high adhesive strength despite a small amount of adhesive. The problem that the agent protrudes to the upper surface of the protective member and damages the disk can be solved.

In the above configuration, the protective member may be a single elastic material made of silicon rubber or the like, but the protective member is formed of a laminated structure of an elastic member and a resin film integrated with each other. When the resin film is mounted on the lens holder, it is preferable that the protective member can be easily handled including during bonding work. In this case, a large number of protective members were removed from the sheet-like laminated structure by die cutting, and when this die cutting was performed from the elastic member side toward the resin film, the die was individually die cut. This is preferable because the dimension of the upper end portion of the subsequent elastic member is stabilized.

  In the above configuration, the material of the elastic member and the resin film constituting the laminated structure of the protective member is not particularly limited, but it is preferable that the elastic member is made of silicon rubber and the resin film is made of PET film.

  An embodiment will be described with reference to the drawings. FIG. 1 is a perspective view of the optical pickup according to the embodiment as viewed from above, FIG. 2 is a perspective view of the optical pickup as viewed from below, and FIG. FIG. 4 is a back view of the optical pickup, FIG. 5 is a perspective view of an actuator provided in the optical pickup, FIG. 6 is a plan view of the actuator, and FIG. 7 is a side view of the actuator. 8 is a perspective view showing the actuator with the back substrate removed, FIG. 9 is a cross-sectional view taken along the line AA in FIG. 6, FIG. 10 is a cross-sectional view taken along the line BB in FIG. FIG. 12 is a perspective view of an auxiliary yoke provided in the actuator, FIG. 13 is a cross-sectional view taken along the line DD of FIG. 6, and FIG. 14 is a type of a protective member provided in the actuator. Explanation showing the punching process It is.

  As shown in FIGS. 1 to 4, the optical pickup according to the present embodiment is assembled in a chassis 1 made of aluminum or the like, a light emitting / receiving unit 2 fixed to one side of the chassis 1, and the chassis 1. The actuator 3, the cover 4 that covers the optical components and the circuit board (both not shown) disposed in the chassis 1, and the flexible wiring board 5 that is led out of the chassis 1 from the circuit board. It is configured. The chassis 1 is reciprocated in the radial direction of the disk by a guide shaft (not shown), and a rectangular opening 1 a for projecting the actuator 3 is provided on the bottom surface of the chassis 1. The light emitting / receiving unit 2 is formed by unitizing a semiconductor laser and a photodetector, and the light receiving / emitting unit 2 is connected to an external drive circuit via a flexible wiring board 5.

  The actuator 3 is an objective lens driving device. As shown in FIGS. 5 to 10, the actuator 3 elastically supports the lens holder 7 made of a synthetic resin to which the objective lens 6 is attached and the lens holder 7. Four wires 8, a synthetic resin support member 9 through which the proximal end side of each wire 8 is inserted, a back substrate 10 fixed to the surface of the support member 9 on the side opposite to the lens holder 7, and a support member 9 includes a base member (actuator base) 11 on which 9 is mounted and fixed.

  A focus coil 12 and a tracking coil 13 are wound around the lens holder 7, and as is apparent from FIG. 6, the focus coil 12 and the tracking coil 13 are arranged on the base member 11 side. The magnetic path is crossing. The base member 11 also serves as a yoke, and the magnet 14 is fixed to a pair of upright portions 11a that are bent at a right angle upward from the bottom surface of the base member 11. The magnet 14 and the yoke (base member 11) constitute a magnetic circuit unit, and the magnetic circuit unit, the focus coil 12 and the tracking coil 13 constitute an electromagnetic drive means for driving the lens holder 7. The yoke is provided with a top yoke 15 and an auxiliary yoke 16, and the top yoke 15 is disposed above the one standing portion 11a and the focus coil 12 so as to reduce the leakage magnetic flux on the upper surface of the yoke. The auxiliary yoke 16 is disposed under the upright portions 11a, and the auxiliary yoke 16 supplements a portion where the magnetic flux on the bottom surface of the yoke is likely to be saturated. The auxiliary yoke 16 is formed by pressing a metal plate such as iron. As shown in FIG. 12, the auxiliary yoke 16 has a fixed portion 16a and a thin portion (support portion) 16b. The fixed portion 16a is formed by bending a metal plate, which is a raw material, into an L shape, and the fixed portion 16a is fixed to the lower portion of one upright portion 11a and the bottom surface of the base member 11. The thin-walled portion 16b is obtained by partially reducing the thickness of a metal plate that is a raw material, and the thin-walled portion 16b is connected to the magnetic path of the magnet 14 along the bottom surface of the base member 11 from opposite ends of the fixed portion 16a. It extends in the orthogonal direction. That is, the fixed portion 16a of the auxiliary yoke 16 is in close contact with the bottom surface of the base member 11 that also serves as the yoke, but both thin portions 16b are separated from the bottom surface of the base member 11, and the base member 11 and a flexible wiring board 21 described later. As shown in FIG. 11, a gap S is formed between the bottom surface of the base member 11 and the thin portion 16b.

  The base member 11 is formed with an arm portion 11b having a hemispherical protrusion. The arm portion 11b is supported by the leaf spring 17 so as to be swingable, and two adjusting screws 18 are provided. The base member 11 is fixed to the chassis 1 in a state where the optical axis of the objective lens 6 is adjusted by screwing the base member 11 from below the chassis 1. In other words, in order to accurately record / reproduce signals with respect to the recording surface of the disc, the optical axis of the objective lens 6 positioned immediately above the reflecting mirror is set perpendicular to the recording surface of the disc. Therefore, when the actuator 3 is attached to the chassis 1, the optical axis of the objective lens 6 (skew adjustment) can be adjusted by adjusting the tightening force of the adjusting screw 18. Since the opening 1a for escaping the movement of the base member 11 during the skew adjustment is provided on the bottom surface of the chassis 1, the optical pickup of the optical pickup is overlapped by the vertical overlap of the lower portion of the base member 11 in the opening 1a. The height is reduced.

  The wires 8 are made of a conductive metal material, and a total of four wires 8 are attached to the left and right side portions of the lens holder 7, two on each side. As shown in FIG. 5, when the dimension between the two wires 8 opposed in the vertical direction is the vertical pitch P1, and the dimension between the two wires 8 opposed in the horizontal direction is the horizontal pitch P2, the vertical pitch P1 is It is set much smaller than the left-right direction pitch P2. Both ends of the focus coil 12 and the tracking coil 13 are connected to one end (free end) of each wire 8, and the other end (base end) of each wire 8 is a space formed in the support member 9. It penetrates 9a and protrudes to the back side. As shown in FIG. 8, on the back side of the support member 9, stepped surfaces 9c are formed on both left and right sides with a central convex portion 9b interposed therebetween, and these stepped surfaces 9c communicate with the open end of the space 9a. Thus, a recess 9d extending in the left-right direction is formed. The recess 9d crosses between the two upper and lower wires 8 projecting from the open end of the space 9a and reaches the side edge of the support member 9. The left and right step surfaces 9c are respectively 2 in the vertical direction by the recess 9d. It is divided. The support member 9 is fixed with the inner bottom surface of the base member 11 as an attachment surface, but the lower end portion of the step surface 9c protrudes downward from the attachment surface (see FIG. 10).

  The central portion of the back substrate 10 is bonded and fixed to the flat surface of the convex portion 9b of the support member 9, and both end portions in the longitudinal direction of the back substrate 10 are opposed to the step surface 9c of the support member 9 through the gap g. It is an end. The back substrate 10 is a laminated substrate in which four conductive plate patterns made of elastic metal thin plates are arranged in parallel with each other in a non-contact manner, and both surfaces of the four conductive plate patterns are sandwiched between heat-resistant insulating cover films. In addition, small holes 10a are formed in a total of four locations (four corners) in the upper and lower portions of the free end portion of the back substrate 10, respectively. Around each small hole 10a, a land portion 10b in which a part of the conductor plate pattern is exposed is formed, and the base end portion of each wire 8 penetrates the small hole 10a of the back substrate 10 and the land portion 10b. It is soldered to. As shown in FIG. 10, the space 9 a of the support member 9 is filled with a gel-like damper agent 19, and this damper agent 19 exerts a viscous resistance against the radial displacement of each wire 8. It is like that. The gap g between the stepped surface 9 c of the support member 9 and the back substrate 10 is also filled with a gel-like damper agent 20, and this damper agent 20 provides a viscous resistance against the longitudinal displacement of each wire 8. It comes to work. Here, since the concave portion 9d extending in the left-right direction is formed on the stepped surface 9c, the back substrate 10 and the concave portion 9d face each other with a wide gap G, and the damper agent 20 is sufficiently larger than the gap G. In a narrow gap g. Note that the damper agent 20 can be filled only in the gap g between the back substrate 10 and the stepped surface 9c by using a dispenser or the like, but the damper agent 20 is also filled in the gap G between the back substrate 10 and the recess 9d. May be.

  A connecting terminal portion 10c is formed at the lower end of the center of the back substrate 10 so that the conductive plate patterns protrude outward, and a lead flexible wiring substrate 21 is connected to the connecting terminal portion 10c. The flexible wiring board 21 is connected to the above-described flexible wiring board 5 through the lower side of the actuator 3 exposed from the opening 1a of the chassis 1, and the flexible wiring board 21, the rear substrate 10 and the wires 8 are connected from an external drive circuit. A drive current is supplied to the focus coil 12 and the tracking coil 13 through the vias. The flexible wiring board 5 and the flexible wiring board 21 may be integrated, and the flexible wiring board 21 and the back substrate 10 may be integrated. As shown in FIGS. 2 and 4, a part of the flexible wiring board 21 is inserted in a gap S (see FIG. 11) formed between the bottom surface of the base member 11 and the thin portion 16 b of the auxiliary yoke 16. As a result, loosening of the flexible wiring board 21 is prevented.

  A pair of protective members 22 are attached to the upper surface of the lens holder 7 with the objective lens 6 interposed therebetween, and these protective members 22 protrude upward from the surface of the objective lens 6. Even if the distance fluctuates excessively in the direction of the disk, the protective member 22 comes into contact with the disk before the objective lens 6. As shown in FIG. 13, the protection member 22 is positioned by a groove portion 7a formed on the upper surface of the lens holder 7, and is adhesively fixed to a predetermined position of the lens holder 7 by an adhesive 23 filled in the groove portion 7a. . The protective member 22 is formed of a laminated structure in which a silicon rubber 25 is integrated on a PET (polyethylene terephthalate) film 24, and the lower PET film 24 is placed on the inner bottom surface of the groove 7a. The upper silicon rubber 25 is formed in a drum shape with a constricted center in the thickness direction of the cylindrical body, and the silicon rubber 25 has a degree that the middle portion of the constricted portion 25a protrudes upward across the opening end of the groove portion 7a. It has a thickness. Therefore, when the adhesive 23 is filled up to the vicinity of the opening end of the groove 7a, it enters the constricted portion 25a of the silicon rubber 25, and the anchor bolt effect of the adhesive 23 entering the constricted portion 25a causes a small amount of the adhesive 23 to be formed. Nevertheless, the protection member 22 can be fixed to the lens holder 7 with sufficiently high adhesive strength.

  As shown in FIG. 14, a large number of protective members 22 are removed by punching out a large sheet-like laminated structure 26 in which a PET film 26a and a silicon rubber 26b are integrated with a punch 27, At that time, the punch 27 is punched from the upper end surface of the silicon rubber 26b toward the PET film 26a. If a large number of individual protective members (PET film 24 and silicon rubber 25) 22 are taken out in this way, the upper end dimension of the die-cut silicon rubber 25 is stabilized depending on the diameter of the punch 27. A large number of protective members 22 with little variation in dimensions can be obtained.

  In the optical pickup configured as described above, the light beam emitted from the semiconductor laser of the light receiving and emitting unit 2 and reflected by the reflecting mirror (not shown) is converged by the objective lens 6 and irradiated onto the data track of the disk. Information is recorded / reproduced, and at that time, a focus servo and a tracking servo for controlling the spot diameter of the light beam with respect to the data track are applied. That is, when a drive current is supplied from the external drive circuit to the focus coil 12 via the flexible wiring substrate 21, the back substrate 10, and each wire 8, electromagnetic force is generated in the direction along the optical axis of the objective lens 6. Then, the lens holder 7 is driven in that direction, and the focus correction of the objective lens 6 can be performed. Similarly, when a drive current is supplied to the tracking coil 13, an electromagnetic force is generated in a direction perpendicular to the optical axis of the objective lens 6, so that the lens holder 7 is driven in that direction to track the objective lens 6. Correction can be made.

  During the correction operation of the objective lens 6, each wire 8 bends and deforms while compressing the damper agent 19 filled in the space 9 a of the support member 9. The radial displacement of each wire 8 accompanying this bending deformation. On the other hand, since the damper agent 19 exhibits viscous resistance, unnecessary resonance acting in the radial direction of each wire 8 is attenuated. Further, the free end portion of the back substrate 10 facing the step surface 9c of the support member 9 is elastically deformed following the bending deformation of each wire 8, and the gap g between the step surface 9c and the back substrate 10 is filled. Since the damper agent 20 is compressed and unnecessary resonance acting in the length direction of each wire 8 is attenuated, the optical axis of the objective lens 6 is rotated in the left-right direction around the optical axis during a pitching operation in which the optical axis is tilted in the front-rear direction. The high-order resonance frequency during the yawing operation can be lowered to a low region that does not affect the servo band of the focus correction operation or tracking correction operation.

  In the objective lens driving device of the optical pickup according to the present embodiment, the recess 9d that extends to the side edge across the two upper and lower wires 8 on the step surface 9c of the support member 9 that faces the free end of the rear substrate 10. Since the gap g filled with the damper agent 20 is narrower at both the upper and lower ends than the center portion by the recess 9d, it is effective at the time of the pitching operation in which the displacement amount of the upper and lower ends of the back substrate 10 is large. Not only can damping be achieved, but excessive damping is not applied more than necessary during yawing operation in which the amount of displacement of the left and right ends of the back substrate 10 is large, and an increase in resonance frequency during yawing operation can be minimized. . Further, the lower end portion of the stepped surface 9c of the support member 9 is protruded downward from the mounting surface to the base member 11, and the up-down direction of the wire 8 is within a space limited to the up-down direction on the back side of the support member 9. Since the pitch can be maximized, damping can be applied more effectively during the pitching operation.

  Further, in the optical pickup according to the present embodiment, the thickness is reduced by providing the opening 1a for projecting the actuator 3 on the bottom surface of the chassis 1, and the component parts of the magnetic circuit unit provided in the actuator 3 are provided. The auxiliary yoke 16 having the thin portion 16b is fixed to the bottom surface of the yoke (base member 11), and the flexible wiring substrate 21 is led out from the back substrate 10 to the gap S defined between the thin portion 16b and the bottom surface of the yoke. Part of the auxiliary yoke 16 required to supplement the saturation magnetic flux of the yoke can also be used as a loosening prevention member for the flexible wiring board 21, and therefore the opening of the flexible wiring board 21 can be used. It is possible to reliably prevent the protrusion from 1a without any particular increase in cost.

  Furthermore, in the optical pickup according to the present embodiment, as a protective member 22 for avoiding contact between the objective lens 6 and the disk, a silicone rubber 25 having a drum shape in cross section having a constricted portion 25a whose central portion in the thickness direction is narrowed. Using a laminated structure integrated on the PET film 24, the PET film 24 is placed on the inner bottom surface of the groove portion 7a formed on the upper surface of the lens holder 7, and the central portion of the constricted portion 25a of the silicon rubber 25 is formed in the groove portion. Since the groove portion 7a is filled with the adhesive 23 so as to enter the constricted portion 25a while projecting upward across the opening end of the adhesive 7a, the adhesive 23 entering the constricted portion 25a of the silicon rubber 25 is provided. The anchor bolt effect secures the protective member 22 to the lens holder 7 with a sufficiently high adhesive strength in spite of a small amount of the adhesive 23. It can be, can reliably prevent damaging the disc adhesive 23 of surplus protruding to the upper surface of the protective member 22.

  In the above embodiment, the moving coil type optical pickup in which the focus coil and the tracking coil are attached to the lens holder side that holds the objective lens has been described. However, the magnetic circuit unit is attached to the lens holder side. The present invention can also be applied to a moving magnet type optical pickup.

It is the perspective view which looked at the optical pick-up concerning the example of the present invention from the upper part. It is the perspective view which looked at this optical pick-up from the lower part. It is a top view of the optical pickup. It is a back view of the optical pickup. It is a perspective view of an actuator provided in the optical pickup. It is a top view of the actuator. It is a side view of the actuator. It is a perspective view which removes a back substrate from this actuator and shows. It is sectional drawing which follows the AA line of FIG. It is sectional drawing which follows the BB line of FIG. It is sectional drawing which follows the CC line of FIG. It is a perspective view of the auxiliary yoke with which this actuator is equipped. It is sectional drawing which follows the DD line | wire of FIG. It is explanatory drawing which shows the die cutting process of the protection member with which this actuator is equipped.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chassis 2 Light receiving / emitting unit 3 Actuator 6 Objective lens 7 Lens holder 7a Groove part 8 Wire 9 Support member 10 Back substrate 11 Base member 12 Focus coil 13 Tracking coil 14 Magnet 22 Protection member 23 Adhesive 24 PET film (resin film)
25 Silicon rubber (elastic member)
25a Constricted part 26 Sheet-like laminated structure 27 Punch

Claims (4)

An objective lens for converging a light beam on a disc-shaped recording medium; a lens holder for holding the objective lens; and an electromagnetic driving means for correcting the lens holder in the optical axis direction of the objective lens. In an optical pickup in which a protective member that avoids contact between the objective lens and the disc-shaped recording medium is fixed using an adhesive,
A groove portion filled with the adhesive is formed on the upper surface of the lens holder, and the protective member has a constricted drum shape with a narrowed central portion in the thickness direction. The protective member is an inner bottom surface of the groove portion. An optical pickup characterized in that the constricted portion protrudes from the opening end of the groove portion, and the adhesive is filled in the constricted portion. 2. The structure according to claim 1 , wherein the protective member is formed of a laminated structure of an elastic member and a resin film integrated with each other, the constriction is formed on the elastic member, and the resin film is mounted on the lens holder. An optical pickup characterized by being placed. 3. The method according to claim 2 , wherein a large number of the protective members are removed from the sheet-like laminated structure by die cutting, and the die cutting is performed from the elastic member side toward the resin film. An optical pickup characterized by that. 4. The optical pickup according to claim 3 , wherein the elastic member is made of silicon rubber and the resin film is made of a PET film.

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