JP2008171485A - Objective lens drive unit and optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an objective lens drive unit mounted with a liquid crystal element, facilitating positioning of the liquid crystal element, and surely fix and arrange the liquid crystal element even after the positioning. <P>SOLUTION: A lens holder 18 provided to the objective lens drive unit 11 is provided with a first holding part 19 for holding an objective lens 9, and a second holding part 20 separate from the first holding part 19 and integrated with the first holding part 19 in assembling. The second holding part 20 is provided with a liquid crystal element 8 for correcting a wave front aberration, an FPC 24 for liquid crystal for controlling driving of the liquid crystal element 8, and a focus coil 22 wound around an optical axis. One end of each of wires 16a to 16e and 17a to 17e is fixed to a first printed circuit board 15, and the other end is attached to the second holding part 20. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical pickup device that reads and writes information by irradiating light onto an optical recording medium, and an objective lens driving device mounted on the optical pickup device.

  In recent years, optical recording media such as compact discs (hereinafter referred to as CDs) and digital versatile discs (hereinafter referred to as DVDs) have become widespread and are generally used. Then, in order to increase the amount of information in the optical recording medium, development related to the increase in capacity of the optical recording medium has been progressed. Has been put into practical use.

  When reading information from such an optical recording medium or writing information on the optical recording medium, an optical pickup device is used. As described above, in recent years, the capacity of optical recording media has been increased. However, as the capacity of optical recording media increases, it occurs when information is read from the optical recording medium using an optical pickup device. The effect of wavefront aberration (spherical aberration, coma aberration, astigmatism, etc.) is not negligible.

  In particular, spherical aberration becomes a problem due to manufacturing errors of the optical recording medium in an optical recording medium (for example, 0.1 mm for BD) having a thin transparent cover layer that protects the recording layer, such as BD. In recent years, an optical pickup device compatible with, for example, three types of optical recording media of BD / DVD / CD has been developed. In such an optical pickup device, a plurality of types of optical recording media having different transparent cover layer thicknesses have been developed. Since it is necessary to cope with it, generation of spherical aberration becomes a problem. In addition, coma aberration occurs when the optical recording medium is warped, for example, when the optical axis and the optical recording medium are tilted from a state orthogonal to the optical recording medium. The occurrence of this is particularly a problem with media.

  In order to correct such wavefront aberration, techniques for arranging a liquid crystal element in an optical system of an optical pickup device have been proposed in Patent Documents 1 to 5, for example. When a liquid crystal element is disposed in the optical system of the optical pickup device for the purpose of wavefront aberration correction, as shown in Patent Documents 2 to 5, for example, the liquid crystal element is placed on the lens holder of the objective lens driving device. In some cases, the lens is held together with the lens. This is because if the liquid crystal element is configured to move together with the objective lens, the optical axis of the liquid crystal element and the optical axis of the objective lens do not shift even when the objective lens moves in the tracking direction for servo control, for example. This is because unnecessary aberration does not occur and appropriate aberration correction can be easily performed.

When the liquid crystal element is mounted on the objective lens driving device, the number of wirings drawn from the liquid crystal element may be increased. Therefore, as shown in Patent Document 2, a liquid crystal for driving the liquid crystal element is used. It is convenient to arrange the drive circuit in the lens holder. In Patent Document 2, the liquid crystal driving circuit is configured by a driver IC and an FPC (Flexible Printed Circuit) capable of inputting a control signal or the like to the driver IC.
JP 2005-310327 A JP-A-2005-353208 Japanese Patent Laid-Open No. 2005-4826 JP 2004-265592 A JP 2003-303430 A

  However, the objective lens driving device disclosed in Patent Document 2 has the following drawbacks. In a configuration in which a liquid crystal element is mounted on a lens holder that holds an objective lens as disclosed in Patent Document 2, the liquid crystal element is positioned so that the optical axis of the objective lens and the optical axis of the liquid crystal element do not deviate from each other. It is necessary to bond the liquid crystal element to the lens holder. The details of this point are not described in Patent Document 2.

  When positioning the liquid crystal element, if the FPC having an IC for controlling the liquid crystal element is already fixed to the lens holder, the movement of the liquid crystal element is restricted by the FPC when the liquid crystal element is moved, There is a problem that position adjustment becomes difficult. On the other hand, when the FPC is fixed to the lens holder after the positioning of the liquid crystal element, the positioning operation is easy to perform. However, depending on the arrangement of the liquid crystal element, the force received from the FPC after the FPC is bonded increases. There is a problem that the element is peeled off.

  In view of the above points, an object of the present invention is to drive an objective lens in which the position of the liquid crystal element can be easily adjusted and the liquid crystal element is securely fixed even after the position adjustment in an objective lens driving apparatus equipped with a liquid crystal element. Is to provide a device. Another object of the present invention is to provide an objective lens driving device capable of reducing the tilt of the objective lens while achieving the above object in an objective lens driving device equipped with a liquid crystal element. Furthermore, another object of the present invention is to provide an optical pickup device having a high reliability with respect to the quality of information recording and reading by providing an objective lens driving device that achieves the above object.

  To achieve the above object, the present invention provides a light source, an objective lens for condensing the light emitted from the light source on a recording surface of an optical recording medium, a lens holder for holding the objective lens, and one end portion. A rod-like elastic support member that is attached to the lens holder and supports the lens holder in a displaceable manner, and the rod-like elastic member that is fixed to the lens holder and formed of a conductive member. An optical pickup device comprising: an objective lens driving device comprising: a coil capable of supplying power via a support member; and a magnet that displaces the lens holder in a predetermined direction by an electromagnetic action in combination with the coil. The coil includes a focus coil wound around the optical axis so as to displace the lens holder in the optical axis direction. A first holding unit that holds the objective lens; and a second holding unit that is a separate part from the first holding unit and is integrated with the first holding unit during assembly. The unit holds a liquid crystal element that corrects wavefront aberration, a liquid crystal drive circuit that is capable of feeding power via the rod-like elastic support member and controls driving of the liquid crystal element, and the focus coil. The other end of the rod-like elastic support member is attached to the second holding part.

  In order to achieve the above object, the present invention provides an objective lens, a lens holder for holding the objective lens, one end attached to a fixed part, and the other end attached to the lens holder. A combination of the coil and the rod-like elastic support member that displaceably supports the coil, the coil that is fixed to the lens holder and that can be supplied with power through the rod-like elastic support member formed of a conductive member, and the coil And a magnet that displaces the lens holder in a predetermined direction by an action, wherein the lens holder is a first holding part that holds the objective lens, and is a separate part from the first holding part And a second holding part that is integrated with the first holding part at the time of assembly. The second holding part includes a liquid crystal element that corrects wavefront aberration, and the rod-like elastic support member. It is characterized by holding a liquid crystal driving circuit provided to be powered to control the driving of the liquid crystal element Te.

  According to the present invention, in the objective lens driving device configured as described above, the other end of the rod-like elastic support member is attached to the second holding portion.

  Further, the present invention provides the objective lens driving device having the above-described configuration, wherein the coil includes a focus coil wound around the optical axis so that the lens holder can be displaced in the optical axis direction. The focus coil is fixed to the two holding portions.

  Further, the present invention is an optical pickup device including the objective lens driving device configured as described above.

  According to the first configuration of the present invention, the second holding part that holds the liquid crystal element and the liquid crystal driving circuit that controls driving of the liquid crystal element is a separate part from the first holding part that holds the objective lens, and is assembled. The first holding part and the second holding part are integrated. For this reason, the position adjustment of the liquid crystal element to match the optical axis of the liquid crystal element and the optical axis of the objective lens can be performed by moving the second holding portion instead of moving only the liquid crystal element. For this reason, the adjustment of the liquid crystal element is not disturbed by the presence of the FPC (which constitutes a liquid crystal driving circuit) during the position adjustment of the liquid crystal element. Further, the possibility that the liquid crystal element is peeled off by a large force received from the FPC after the position adjustment can be reduced. That is, the position adjustment for aligning the optical axis of the liquid crystal element with the optical axis of the objective lens can be performed smoothly and the adhesive of the liquid crystal element can be prevented from being peeled off. Further, since the rod-like elastic support member formed of the conductive member is attached to the second holding part, the configuration for supplying power to the liquid crystal drive circuit attached to the second holding part does not become complicated, and the number of parts is small. it can.

  According to the second configuration of the present invention, the second holding unit that holds the liquid crystal element and the liquid crystal driving circuit that controls driving of the liquid crystal element is a separate part from the first holding unit, and the first holding unit is assembled during assembly. The part and the second holding part are integrated. For this reason, the position adjustment of the liquid crystal element for aligning the optical axis of the liquid crystal element and the optical axis of the objective lens can be performed by moving the second holding unit instead of moving only the liquid crystal element. For this reason, the adjustment of the liquid crystal element is not disturbed by the presence of the FPC (which constitutes a liquid crystal driving circuit) during the position adjustment of the liquid crystal element. Further, the possibility that the liquid crystal element is peeled off by a large force received from the FPC after the position adjustment can be reduced. That is, the position adjustment for aligning the optical axis of the liquid crystal element with the optical axis of the objective lens can be performed smoothly, and the adhesion of the liquid crystal element can be prevented from being peeled off.

  Further, according to the third configuration of the present invention, in the objective lens driving device having the second configuration, the rod-like elastic support member formed of the conductive member is attached to the second holding portion. 2 The structure for supplying power to the liquid crystal drive circuit attached to the holding unit is not complicated.

  According to the fourth configuration of the present invention, in the objective lens driving device of the third configuration, the focus coil wound so as to surround the optical axis is attached to the second elastic holding member. Therefore, the drive center of the focus coil and the support center of the rod-like elastic support member are not shifted by adjusting the position of the liquid crystal element. Thereby, DC tilt of the objective lens can be suppressed. Further, by attaching the focus coil to the same part as the liquid crystal element, heat generated in the coil is easily transmitted to the liquid crystal, and the response speed of the liquid crystal can be improved.

    Further, according to the fifth configuration of the present invention, in the optical pickup device including the objective lens driving device having any one of the second to fourth configurations, adhesion peeling of the liquid crystal element mounted on the objective lens driving device occurs. Less likely. In addition, it is possible to suppress the DC tilt that occurs due to the position adjustment of the liquid crystal element. For this reason, it is possible to provide an optical pickup device having high reliability with respect to the quality of information recording and reading.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, embodiment shown here is an example and this invention is not limited to embodiment shown here.

  FIG. 1 is a schematic diagram showing a configuration of an optical system of an optical pickup device including the objective lens driving device of the present invention. In FIG. 1, reference numeral 1 denotes an optical pickup device that reads information recorded on a recording surface 30a of an optical disc 30 by irradiating an optical disc (optical recording medium) 30 with laser light and receiving reflected light. This is an apparatus that can write information on the recording surface 30a by irradiating the optical disc 30 with laser light. The optical pickup device 1 of this embodiment is compatible with three types of optical disks 30 of BD / DVD / CD.

  The optical system of the optical pickup device 1 includes a first light source 2, a second light source 3, a dichroic prism 4, a beam splitter 5, a collimator lens 6, a rising mirror 7, a liquid crystal element 8, and an objective lens. 9 and a photodetector 10 are provided. Details of each optical element will be described below.

  The first light source 2 is a two-wavelength compatible laser diode having two light emitting points so that laser light of two types of wavelengths can be emitted. The first light source 2 is used for a DVD having a wavelength of 780 nm and a DVD. And a laser beam having a wavelength of 650 nm. The second light source 3 is a laser diode that emits laser light with a single wavelength, and emits laser light with a wavelength of 405 nm band used for BD. Laser light emitted from the first light source 2 and the second light source 3 is sent to the dichroic prism 4.

  In this embodiment, the laser beam for CD and DVD is emitted using a laser diode for two wavelengths, but two laser diodes each emitting laser light of a single wavelength are used. It does not matter even if it uses and emits.

  The dichroic prism 4 transmits the laser light emitted from the first light source 2 and reflects the laser light emitted from the second light source 3. The positions of the first light source 2 and the second light source 3 are adjusted so that the optical axes of the laser light after passing through the dichroic prism 4 are substantially the same. The laser light that has passed through the dichroic prism 4 is sent to the beam splitter 5.

  The beam splitter 5 reflects the laser beam emitted from the first light source 2 or the second light source 3 and guides it to the optical disc 30 side, and transmits the reflected light from the recording layer 30a of the optical disc 30 to the photodetector 10 side. Lead to. The laser light emitted from the first light source 2 or the second light source 3 and transmitted through the beam splitter 5 is sent to the collimating lens 6.

  The collimating lens 6 converts the laser light emitted from the light sources 2 and 3 into parallel light. Here, the parallel light refers to light in which all optical paths of the laser light emitted from the light sources 2 and 3 are substantially parallel to the optical axis. The parallel light transmitted through the collimating lens 6 is sent to the raising mirror 7.

  The raising mirror 7 reflects the laser beam sent from the collimating lens 6 so that the optical axis of the laser beam emitted from the light sources 2 and 3 is orthogonal to the recording surface 30 a of the optical disc 30. The laser light reflected by the rising mirror 7 is guided to the liquid crystal element 8.

  The liquid crystal element 8 has a function of correcting spherical aberration in the present embodiment. This is because the optical pickup device 1 of the present embodiment is compatible with three types of optical discs 30 of BD / DVD / CD having different thicknesses of the transparent cover layer 30b that protects the recording surface 30a, so that the generation of spherical aberration becomes a problem. This is because it is necessary to correct spherical aberration.

  FIG. 2 is a schematic cross-sectional view illustrating a configuration of the liquid crystal element 8 included in the optical pickup device 1. As shown in FIG. 2, the liquid crystal element 8 includes a liquid crystal 41, two transparent electrodes 42a and 42b that sandwich the liquid crystal 41, and glass substrates 43a and 43b that hold the transparent electrodes 42a and 42b.

  The transparent electrode 42a is a divided electrode divided into a plurality of concentric segments (not shown), and each segment can be fed independently. On the other hand, the transparent electrode 42b is a single common electrode without being divided. Therefore, by adjusting the potential applied to each segment of the transparent electrode 42a, the voltage applied between each segment and the transparent electrode 42b can be adjusted, and the alignment state of the liquid crystal 41 sandwiched therebetween can be adjusted. Become. Therefore, the spherical aberration can be corrected by adjusting the phase of the laser light passing through each segment.

  The configuration of the liquid crystal element 8 that corrects the spherical aberration is not limited to the configuration of the present embodiment, and can be changed as appropriate. For example, the transparent electrode 42b may be divided into a plurality of segments in the same manner as the transparent electrode 42a.

  The objective lens 9 condenses the laser light transmitted through the liquid crystal element 8 on the recording surface 30 a of the optical disk 30. The objective lens 9 is mounted on the objective lens driving device 11 together with the liquid crystal element 8, and the tracking direction is a direction parallel to the optical axis direction at the position of the objective lens 9 and a direction parallel to the radial direction of the optical disk 30. It is possible to move in the direction. Details of the configuration of the objective lens driving device 11 will be described later.

  The laser light reflected by the optical disk 30 passes through the objective lens 9 and the liquid crystal element 8, is reflected by the rising mirror 7, passes through the collimator lens 6 and the beam splitter 5 in this order, and is collected on the photodetector 10.

  The photodetector 10 converts the received optical information into an electrical signal and outputs it to, for example, an RF amplifier (not shown). The electric signal is used as a reproduction signal of data recorded on the recording surface 30a of the optical disc 30, a servo signal for performing focus control and tracking control, and the like. In some cases, it is used as feedback information related to the applied voltage applied to the liquid crystal element 8.

  Next, details of the objective lens driving device 11 included in the optical pickup device 1 will be described with reference to FIGS. 3 and 4. Here, FIG. 3 is a schematic perspective view showing the configuration of the objective lens driving device 11 of the present embodiment, and FIG. 4 is an exploded perspective view of the objective lens driving device 11 of the present embodiment.

  The objective lens driving device 11 includes a base 12, permanent magnets 13a and 13b, a gel holder 14, a first printed circuit board 15, wires 16a to 16e, 17a to 17e, a lens holder 18, and tracking coils 21a to 21d. And a focus coil 22, a second printed circuit board 23, and an FPC (Flexible Printed Circuit) 24 for liquid crystal.

  The base 12 is formed of a metal having ferromagnetism, and a through hole 12c through which the laser light emitted from the light sources 2 and 3 (see FIG. 1) passes is formed at the approximate center. A lens holder 12, which will be described in detail later, is disposed on the through hole 12c. On the base 12, a pair of permanent magnets 13 a and 13 b are provided so as to face each other with a predetermined interval so as to sandwich the lens holder 18. The permanent magnets 13 a and 13 b are fixed in a state of being magnetically integrated with the base 12 by being magnetically attached to the protruding pieces 12 a and 12 b whose outer surfaces are bent from the base 12.

  On the base 12, a gel holder 14 of a resin molded product such as polycarbonate is fixedly arranged on the outer surface side of the projecting piece 12b on which one permanent magnet 13b is magnetically attached. When viewed from the lens holder 18 side, the gel holder 14 is formed with through holes 14a and 14b on the left and right.

  The through holes 14a and 14b are filled with a gel material mainly composed of silicon. Here, the gel material is obtained by injecting a low-viscosity gel material (sol) into each of the through holes 14a and 14b of the gel holder 14 and then curing the gel material by ultraviolet irradiation for a predetermined time. The gel holder 14 configured as described above plays a role of attenuating and suppressing vibration generated in the wires 16a to 16e and 17a to 17e by the gel material in accordance with driving of the lens holder 14 described later.

  Further, a first printed circuit board 15 is erected on the base 12 adjacent to the outer surface side of the gel holder 14. The first printed circuit board 15 is connected to a main FPC (not shown) that controls the optical pickup device 1, and controls the electrical system of the objective lens driving device 11 by a signal from the main FPC. One end of each of the conductive wires 16a to 16e and 17a to 17e is connected to the first printed circuit board 15 by soldering at five locations in the vertical direction on both the left and right sides.

  The soldered wires 16a to 16e are inserted into the through-hole 14a of the gel holder 14, and the wires 17a to 17e are inserted into the through-hole 14b of the gel holder 14, and the other end is attached to the lens holder 18. . Accordingly, the lens holder 18 is supported by the wires 16a to 16e and 17a to 17e so as to be swingable with respect to the base 12.

  Next, details of the lens holder 18 provided in the objective lens driving device 11 will be described. The lens holder 18 includes a first holding unit 19 that holds the objective lens 9 and a second holding unit 20 that holds the liquid crystal element 8. The 1st holding | maintenance part 19 and the 2nd holding | maintenance part 20 are independent parts, and are integrated at the time of an assembly. As described above, the first holding part 19 and the second holding part 20 are separate parts when the optical axis deviation between the objective lens 9 and the liquid crystal element 8 is adjusted. This is because the entire second holding unit 20 that holds the liquid crystal element 8 is moved instead of being moved so that the optical axis deviation can be adjusted. When the position adjustment is performed, the first holding unit 19 and the second holding unit 20 are fixed and integrated by, for example, adhesion.

  The first holding part 19 is formed with a substantially circular through hole 19a at a substantially central part thereof, and holds the objective lens 9 at this part. Two tracking coils 21a and 21b are provided on the side wall of the first holding unit 19 facing the permanent magnet 13a, and two tracking coils 21c and 21d are provided on the side wall of the first holding unit 19 facing the permanent magnet 13b. Each is fixed with an adhesive or the like. The tracking coils 21a to 21d are connected by a single line as a whole.

  The tracking coil 21a and the tracking coil 21c, and the tracking coil 21b and the tracking coil 21d are arranged symmetrically. Moreover, each tracking coil 21a-21d is fixed to the 1st holding | maintenance part 19 so that only the half may overlap with permanent magnet 13a, 13b when it sees from each permanent magnet 13a, 13b side. .

  The second holding portion 20 is formed with a hole 20a having a substantially rectangular shape in plan view so as to hold the liquid crystal element 8 formed in a substantially rectangular shape in plan view. Further, the through hole 20b is formed so that laser light can pass through. Is formed. Wire attachment portions 20c and 20d for attaching the wires 16a to 16e and the wires 17a to 17e are formed on the outer surface of the second holding portion 20, respectively, so that one ends of the wires 16a to 16e and 17a to 17e are formed. Is attached to the second holding part 20.

  The second printed circuit board 23 is fixed to the surface of the second holding part 20 where the wire attachment part 20c is formed. Electrode portions (not shown) provided on the second printed circuit board 23 are connected to the wires 16a to 16e by soldering, and the second printed circuit board 23 is connected to the first printed circuit via the wires 16a to 16e. It is electrically connected to the substrate 15. The second printed circuit board 23 is connected to the lead lines of the tracking coils 21a to 21d connected by a single line as a whole, and to the lead line of the focus coil 24 described later in detail. For this reason, the second printed circuit board 23 serves to electrically connect the first printed circuit board 15 to the tracking coils 21a to 21d and the focus coil 22.

  In the configuration of the present embodiment, since it is only necessary to connect a power supply line to both ends of the tracking coils 21a to 21d and the focus coil 22 as a whole, out of the wires 16a to 16e. One of these is not used for power supply. However, in order to balance left and right, it is set to five. In addition, since the second printed circuit board 23 of the present embodiment does not include an IC, the lead lines of the tracking coils 21a to 21d and the lead lines of the focus coil 22 may be provided without providing the second printed circuit board 23 in some cases. May be directly connected to the wires 16a to 16e (exactly, only four of them are used).

  A part of the liquid crystal FPC 24 having an IC for controlling the driving of the liquid crystal element 8 is fixed to the surface of the second holding portion 20 where the wire attachment portion 20d is formed. And the electrode part (not shown) formed in this part and wires 17a-17e are connected by soldering. As a result, the liquid crystal FPC 24 is electrically connected to the first printed circuit board 15.

  In this embodiment, the liquid crystal FPC 24 and the wires 17a to 17e are directly connected by soldering. However, a separate printed circuit board is provided between the wires 17a to 17e and the liquid crystal FPC 24, and the printed circuit board is printed. The liquid crystal FPC 24 and the wires 17a to 17e may be electrically connected through a circuit board. However, as in the present embodiment, it is preferable to directly connect the liquid crystal FPC 24 and the wires 17a to 17e by soldering in order to reduce the number of components.

  In addition, a part of the liquid crystal FPC 24 is connected to the transparent electrodes 42 a and 42 b (see FIG. 2) constituting the liquid crystal element 8 so that power can be supplied to the liquid crystal element 8. Other portions of the liquid crystal FPC 24 are accommodated inside the second holding portion 20 and are bonded and fixed as necessary so that the force applied to the liquid crystal element 8 is reduced.

  In the present embodiment, the liquid crystal FPC 24 is provided on the lens holder 18 side for the following reason, for example. That is, the number of wirings for supplying power to the transparent electrodes 42a and 42b of the liquid crystal element 8 is, for example, 10 or more. For this reason, if an IC for controlling the liquid crystal element 8 is provided at the position of the first printed circuit board 15, for example, the number of wires used for power feeding becomes large, and the lens holder 18 cannot be driven appropriately. Therefore, the liquid crystal FPC 24 is provided in the lens holder 18 so that the number of wires does not become excessive.

  The reason why the liquid crystal FPC 24 is attached to the second holding unit 20 is to facilitate the position adjusting operation of the liquid crystal element 8 and to prevent the liquid crystal element 8 adhered and fixed to the lens holder 18 from being peeled off. That is, for example, if the liquid crystal FPC 24 is disposed at a position away from the first holding unit 19 or the like, the liquid crystal FPC 24 may be constrained and adjustment of the liquid crystal element 8 becomes difficult, or the liquid crystal element 8 may be attached to the lens holder 18. After bonding, the liquid crystal element 8 is peeled off due to excessive force applied to the liquid crystal element 8 from the liquid crystal FPC 24. For this reason, the liquid crystal FPC 24 is attached to the second holding unit 20 to prevent the liquid crystal element 8 from being peeled off and the workability of the liquid crystal element 8 to be adjusted.

  A focus coil 22 wound around the optical axis of the objective lens 9 is fixed to the second holding unit 20 with an adhesive or the like along the inner surface of the second holding unit 20. The reason why the focus coil 22 is fixed to the second holding unit 20 in the objective lens driving device 11 will be described with reference to FIG. FIG. 5 is an explanatory diagram for explaining the relationship between the drive center of the focus coil (focus drive center) and the support center of the wire that supports the lens holder.

  FIG. 5A shows a state where the focus coil 22 is fixed to the first holding portion 19 (not shown in FIG. 5). When adjusting the position by moving the second holding unit 20 in order to align the optical axes of the objective lens 9 and the liquid crystal element 8, the drive center of the focus coil 22 (focus drive center) and the support of the wires 16a to 16e and 17a to 17e are supported. Since the position is adjusted independently of the center, the focus drive center and the support center may not match. When the focus drive center and the support center deviate, the lens holder 18 rotates due to the generation of moment, and a DC tilt occurs.

  On the other hand, when the focus coil 22 is provided on the second holding unit 20 side as in the present embodiment, even if the second holding unit 20 is moved to align the optical axes of the objective lens 9 and the liquid crystal element 8, The focus drive center and the support center do not deviate (state shown in FIG. 5B). Therefore, the DC tilt can be reduced. Since the second holding unit 20 is not moved in the vertical direction (focus direction) for adjusting the position of the liquid crystal element 8, the driving centers of the tracking coils 21a to 21d and the wires 16a to 16e and 17a to The support center of 17e is not shifted by adjusting the position of the liquid crystal element 8.

  The operation of the objective lens driving device 11 configured as described above will be described. When a current is supplied from the first printed circuit board 15 to, for example, the tracking coils 21a to 21d via the wires 16a and 16b, the lens holder 18 is caused by an electromagnetic action with a magnetic field formed by the permanent magnets 13a and 13b. A force in the tracking direction T (see FIG. 3) is applied to the. For this reason, the movement of the lens holder 18 in the tracking direction T can be controlled by controlling the direction and magnitude of the current flowing by the first printed circuit board 15.

  Further, when a current is supplied from the first printed circuit board 15 to the focus coil 22 through, for example, the wires 16c and 16d, the lens holder 18 is caused by an electromagnetic action with a magnetic field formed by the permanent magnets 13a and 13b. A force in the focus direction F (see FIG. 3) is applied to the lens. For this reason, the movement of the lens holder 18 in the focus direction F can be controlled by controlling the direction and magnitude of the current flowing through the first printed circuit board 15.

  Further, when a signal is sent from the first printed circuit board 15 to the liquid crystal FPC 24 via the wires 17a to 17e, the liquid crystal FPC 24 controls a voltage applied to the transparent electrodes 42a and 42b of the liquid crystal element. Thereby, the liquid crystal element 8 corrects the spherical aberration generated in the optical pickup device 1.

  The objective lens driving device 11 of the present embodiment is an example, and is not limited to the configuration of the present embodiment, and various modifications can be made without departing from the object of the present invention. For example, in the present embodiment, the tracking coils 21a to 21d are fixed to the first holding part 19, but the tracking coils 21a to 21d may be provided on the second holding part 20 side. In addition, the lens holder 18 is composed of two parts, the first holding part 19 and the second holding part 20, but may be constituted by three or more parts. Furthermore, the objective lens driving device 11 of the present embodiment is configured to displace the lens holder 18 only in the focus direction F and the tracking direction T. However, for example, a configuration in which the lens holder 18 can be tilted may be used.

  In the present embodiment, the liquid crystal element 8 mounted on the objective lens driving device 11 is configured to correct spherical aberration. However, the present invention is not limited to this, and the liquid crystal element 8 has coma aberration, astigmatism, and the like. The present invention can also be applied to other wavefront aberrations.

  In addition, in this embodiment, the optical pickup device 1 is configured to be compatible with BD / DVD / CD, but is not limited to this configuration, and the objective lens driving device of the present invention can be widely applied to the optical pickup device. Needless to say.

  According to the present invention, in an objective lens driving device in which a liquid crystal element is mounted together with an objective lens, adjustment work at the time of assembly is easy, and the liquid crystal element is not peeled off after assembly. Therefore, it is useful when applied to an optical pickup device.

These are the schematic which shows the structure of the optical system of the optical pick-up apparatus in this embodiment. These are schematic sectional drawing which shows the structure of the liquid crystal element with which the optical pick-up apparatus of this embodiment is provided. These are the schematic perspective views which show the structure of the objective lens drive device with which the optical pick-up apparatus of this embodiment is provided. These are the exploded perspective views of the objective lens drive device with which the optical pick-up apparatus of this embodiment is provided. These are explanatory drawings for demonstrating the relationship between the drive center of a focus coil, and the support center of the wire which supports a lens holder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical pick-up apparatus 2 1st light source 3 2nd light source 8 Liquid crystal element 9 Objective lens 11 Objective lens drive device 13a, 13b Permanent magnet 16a-16e Wire (bar-shaped elastic support member)
17a-17e wire (bar-shaped elastic support member)
DESCRIPTION OF SYMBOLS 18 Lens holder 19 1st holding | maintenance part 20 2nd holding | maintenance part 21a-21d Tracking coil 22 Focus coil 24 FPC (liquid crystal drive circuit) for liquid crystals

Claims (5)

A light source;
An objective lens for condensing the light emitted from the light source on the recording surface of the optical recording medium;
A lens holder that holds the objective lens, a rod-like elastic support member that has one end attached to a fixed portion and the other end attached to the lens holder, and supports the lens holder in a displaceable manner, and the lens holder A coil that can be supplied with power via the rod-like elastic support member that is fixed to the rod-shaped elastic support member, and a magnet that displaces the lens holder in a predetermined direction by an electromagnetic action in combination with the coil. An objective lens driving device comprising:
In an optical pickup device comprising:
The coil includes a focus coil wound around the optical axis so that the lens holder can be displaced in the optical axis direction,
The lens holder includes a first holding unit that holds the objective lens, and a second holding unit that is a separate part from the first holding unit and is integrated with the first holding unit when assembled. ,
The second holding unit includes: a liquid crystal element that corrects wavefront aberration; a liquid crystal drive circuit that is provided so as to be able to supply power via the rod-shaped elastic support member; and controls the driving of the liquid crystal element; and the focus coil. Hold and
2. The optical pickup device according to claim 1, wherein the other end of the rod-like elastic support member is attached to the second holding part. An objective lens;
A lens holder for holding the objective lens;
A rod-like elastic support member that has one end attached to a fixed portion and the other end attached to the lens holder, and supports the lens holder so that it can be displaced;
A coil that is fixed to the lens holder and can be fed via the rod-like elastic support member formed of a conductive member;
A magnet that displaces the lens holder in a predetermined direction by an electromagnetic action in combination with the coil;
In an objective lens driving device comprising:
The lens holder includes a first holding unit that holds the objective lens, and a second holding unit that is a separate part from the first holding unit and is integrated with the first holding unit when assembled. ,
The second holding unit holds a liquid crystal element that corrects wavefront aberration, and a liquid crystal driving circuit that is provided so as to be able to supply power via the rod-like elastic support member and controls driving of the liquid crystal element. An objective lens driving device.   The objective lens driving device according to claim 2, wherein the other end of the rod-like elastic support member is attached to the second holding portion. The coil includes a focus coil wound around the optical axis so that the lens holder can be displaced in the optical axis direction,
The objective lens driving device according to claim 3, wherein the focus coil is fixed to the two holding portions.   An optical pickup device comprising the objective lens driving device according to claim 2.