JP4566154B2 - Optical pickup - Google Patents

Description

  The present invention relates to an optical pickup for recording / reproducing information with respect to a disc-shaped recording medium such as a digital versatile disc (DVD) or a compact disc (CD), and in particular, a lens holder on which an objective lens is mounted is conductive. The present invention relates to a moving coil type optical pickup that is elastically supported via a wire.

  In general, an optical pickup drives a light receiving / emitting unit in which a light emitting element such as a semiconductor laser and a light receiving element 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 driving means, a reflection mirror arranged in an 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 and a magnetic circuit section that generates a magnetic flux in a direction crossing these coils. In a moving coil type optical pickup, a focus coil and a tracking coil are mounted on a lens holder. The magnetic circuit unit is disposed on the base member of the actuator while being attached. The lens holder is elastically 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 tracking coil. Thus, when a drive current is supplied from the external drive circuit to the focus coil and tracking coil via the support substrate and each wire, the lens holder that holds the objective lens is driven in the focus direction and the tracking direction.

  In the optical pickup having such a general configuration, the light beam emitted from the light emitting element and reflected by the reflecting mirror is condensed on the recording surface of the disk by the objective lens, and the return light beam from the disk is the objective. Light is received by a light receiving element via a lens or a reflecting mirror. Here, in order to accurately record / reproduce the signal with respect to the recording surface of the disc, the optical axis of the objective lens positioned directly above the reflecting mirror is set perpendicular to the recording surface of the disc. For example, the actuator is mounted on the chassis using two adjustment screws, and the optical axis adjustment (skew adjustment) of the objective lens is performed by adjusting the tightening force of both adjustment screws. Yes.

Conventionally, in an optical pickup equipped with such a skew adjustment mechanism, a flexible wiring led out from a support substrate by securing a gap required for skew adjustment between the bottom surface of the actuator and the upper surface of the chassis. A technique is known in which the height dimension is reduced by drawing the substrate through the gap into the chassis (see, for example, Patent Document 1).
JP 2001-155364 A (page 3-4, FIG. 3)

  The prior art disclosed in Patent Document 1 can reduce the thickness of the optical pickup to a certain extent, but in order to achieve further reduction in the thickness of the optical pickup, a large opening is provided on the bottom surface of the chassis to release the movement of the actuator during skew adjustment. It is conceivable that the bottom surface of the actuator protrudes from the opening. When such a configuration is adopted, the height dimension can be shortened by overlapping the lower end portion of the actuator and the bottom surface of the chassis in the vertical direction within the opening, but the flexible wire drawn below the actuator Since there is a risk that the wiring board will loosen and protrude from the opening to the bottom side of the chassis, an additional process is required, for example, attaching the flexible wiring board to the bottom surface of the actuator using an adhesive sheet, which causes an increase in cost Will occur.

  The present invention has been made in view of the actual situation of the prior art, and an object of the present invention is to provide an optical pickup that can easily and reliably prevent the flexible wiring board led out from the bottom surface of the chassis from the support board. Is to provide.

The present invention has a structure in which an opening for projecting the actuator is provided on the bottom surface of the chassis to reduce the thickness, and a thin portion for supporting the flexible wiring board from below is formed on the auxiliary yoke fixed to the bottom surface of the actuator. did.

In the optical pickup according to the present invention, an opening through which the actuator protrudes is provided on the bottom surface of the chassis, and a thin portion for supporting the flexible wiring board from below is formed on the auxiliary yoke fixed to the bottom surface of the actuator. A wiring board attaching step is not required, and therefore, the protrusion of the flexible wiring board from the bottom surface of the chassis can be reliably prevented without any particular increase in cost.

The present invention includes an actuator provided with a lens holder for holding an objective lens and electromagnetic driving means for driving the lens holder, and a chassis on which the actuator, a light emitting / receiving element and an optical element are mounted. The means includes a focus coil and a tracking coil attached to the lens holder, and a magnetic circuit unit having a magnet and a yoke, and the lens holder is elastically attached to the support substrate via a conductive wire. In an optical pickup in which a flexible wiring board that is supported and led out from the support substrate is disposed between the actuator and the inner bottom portion of the chassis, the actuator includes an actuator base that holds the support substrate. And on the bottom of the actuator yoke Auxiliary yoke having wall portions are secured, the opening that臨出the actuator to the bottom of the chassis is provided, between the thin portion and the actuator base of the bottom surface of the auxiliary yoke exposed in the opening A gap for allowing the flexible wiring board to pass therethrough is formed.

In the optical pickup configured in this way, not only can the thickness be reduced by providing an opening for the actuator to protrude from the bottom surface of the chassis, but the flexible wiring board is supported from below by an auxiliary yoke fixed to the bottom surface of the actuator. Since the thin-walled portion is formed, the step of attaching the flexible wiring board to the actuator is not required, and therefore, the protrusion of the flexible wiring board from the bottom of the chassis can be reliably prevented without any particular increase in cost. In addition, the auxiliary yoke, which is required to supplement the yoke's saturation magnetic flux, can also be used as a loosening prevention member for the flexible wiring board. In addition to preventing protrusion from the bottom surface, the flexible wiring substrate can be moved in the state of the actuator alone by passing the flexible wiring substrate through the gap between the thin portion of the auxiliary yoke and the bottom surface of the actuator base. Since it can be held to some extent, it is easy to handle the actuator as a part.

  In the above configuration, it is preferable that the actuator base also serves as the yoke because the number of parts can be reduced.

  Further, in the above configuration, the auxiliary yoke has a fixed portion fixed to the bottom surface of the yoke and a pair of thin portions extending outward from opposite opposite ends of the fixed portion. It is preferable that the extending direction of the thin portion and the direction of the magnetic flux generated by the magnet are substantially orthogonal since the saturation magnetic flux of the yoke is complemented in a balanced manner by the auxiliary yoke.

  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 of 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 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 substrate having a laminate structure 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 free end portion of the back substrate 10, two in the upper and lower portions. 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 void 9 a of the support member 9 is filled with a gel-like damper agent 19, and the damper agent 19 acts on the radial resistance of each wire 8 in the radial direction. It is like that. Further, the gap g between the stepped surface 9c 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 has 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 obtained, but also excessive damping is not applied at the time of yawing operation in which the displacement amount of the left and right ends of the back substrate 10 is large, and an increase in the resonance frequency during the 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.

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 1a Opening 2 Light receiving / emitting unit 3 Actuator 5 Flexible wiring board 6 Objective lens 7 Lens holder 8 Wire 9 Support member 10 Back board (support board)
11 Base member ( Yoke, Actuator base )
11a Standing portion 11b Arm portion 12 Focus coil 13 Tracking coil 14 Magnet 15 Top yoke 16 Auxiliary yoke 16a Fixed portion 16b Thin portion 17 Leaf spring 18 Adjustment screw 21 Flexible wiring board S Gap

Claims (3)

An actuator provided with a lens holder for holding an objective lens and electromagnetic driving means for driving the lens holder; and a chassis on which the actuator, a light emitting / receiving element and an optical element are mounted, and the electromagnetic driving means includes: A focus coil and a tracking coil attached to the lens holder, and a magnetic circuit unit having a magnet and a yoke, and the lens holder is elastically supported on a support substrate via a conductive wire. In the optical pickup in which the flexible wiring substrate led out from the support substrate is disposed between the actuator and the inner bottom portion of the chassis,
The actuator includes an actuator base for holding the support substrate, and an auxiliary yoke having a thin portion is fixed to the bottom surface of the yoke of the actuator, and an opening for projecting the actuator is provided on the bottom surface of the chassis. The optical pickup is characterized in that a gap through which the flexible wiring board passes is formed between the thin portion of the auxiliary yoke exposed in the opening and the bottom surface of the actuator base . 2. The optical pickup according to claim 1 , wherein the actuator base also serves as the yoke. 3. The auxiliary yoke according to claim 1 , wherein the auxiliary yoke has a fixed portion fixed to the bottom surface of the yoke, and a pair of the thin portions extending outward from opposite ends of the fixed portion. The optical pickup is characterized in that the extending direction of these thin portions and the direction of the magnetic flux generated by the magnet are substantially orthogonal.

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