JP2008041117A - Optical pickup - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup capable of securing mechanical rigidity, without generating moments due to electromagnetic force, even if the center part of a movable body is thinned. <P>SOLUTION: This device is provided with a movable body 11, having a plurality of objective lenses 12 and 13 mounted on a thinned center 11A, a pair of coil blocks 20 disposed in both sides 11B of the movable body 11, two sets of magnets 31 disposed to sandwich the pair of coil blocks 20, a support member 15 for supporting both sides 11B of the movable body 11 to swingingly, and rising mirrors 32 and 33, arranged to face each other in the center 11A of the movable body 11. The coil block 20 includes a focus coil 21 for driving the movable body 11 in the focus direction F, and a track coil 22 arranged outside the focus coil 21 to drive the movable body 11 in a radial direction R, and a reinforcing member 11D is arranged in a beam shape in the lower surface of both sides 11B of the movable body 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus for recording / reproducing with respect to an optical disc, and more particularly to an optical pickup of the optical disc apparatus. More specifically, the present invention relates to an optical pickup equipped with a plurality of objective lenses so as to enable recording / reproduction of a plurality of types of optical disks having different optical characteristics.

  Various configurations have been devised as optical pickups for optical disc apparatuses for enabling recording / reproduction of a plurality of types of optical discs having different optical characteristics. In particular, with the advent of Blu-ray discs, which are high-density recording media, in addition to conventional red optical discs (CDs and DVDs), it is possible to record / reproduce blue optical discs (HD-DVDs and Blu-ray discs). There is a need for optical disk devices.

  In order to enable recording / reproduction of a plurality of types of optical disks having different optical characteristics using a single optical pickup, how to mount an objective lens on the optical pickup is a big problem. Two methods are considered as means for solving the problem. The first method is to mount one objective lens compatible with a plurality of types of optical disks having different optical characteristics. The second method is to mount a plurality of objective lenses corresponding to a plurality of types of optical disks.

  Next, the thickness of the objective lens corresponding to the main optical disk will be described with reference to FIG. What is indicated by reference numeral 101 in FIG. 6A is a compatible objective lens for DVD and CD. The thickness Ta of the compatible objective lens 101 is about 1.3 mm. Also, what is indicated by reference numeral 102 is a Blu-ray objective lens compatible with a Blu-ray disc. The thickness Tb of the Blu-ray objective lens 102 is about 2.5 mm. What is indicated by reference numeral 103 is a BD / DVD / CD compatible objective lens that can be used for DVD / CD and Blu-ray Disc. The thickness Tc of the BD / DVD / CD compatible objective lens 103 is about 4.5 mm. In the case where the objective lens alone has a thickness of 4.5 mm, the thickness of the slim drive (7 There is a problem that the thickness of the optical pickup becomes thicker than 3 mm).

  Therefore, from the viewpoint of thinning, the second method (a method of mounting a plurality of objective lenses) is considered to be an effective configuration of an optical pickup capable of recording / reproducing both a Blu-ray disc and a DVD / CD. Yes.

  By the way, as shown in FIG. 7, the optical pickup is mounted on a traverse unit 50 provided inside the optical disc apparatus A0. An optical disc D is loaded into the optical disc apparatus A0 so as to be inserted from the insertion port 51, and this optical disc D is supported by a spindle shaft (not shown). The traverse unit 50 is supported by a pair of rails 52 extending in the radial direction on the recording surface (the lower surface in FIG. 7) side of the optical disc D, and the drive unit 53 extends in the radial direction of the optical disc D along the rails 52. Is reciprocated. Here, the direction from the traverse unit 50 toward the optical disk, that is, the direction in which the optical pickup irradiates the optical disk D with the laser beam is the focus direction F, the moving direction of the traverse unit 50, that is, the radial direction of the optical disk D is the radial direction R, and the focus direction. A direction perpendicular to F and the radial direction, that is, a tangential direction of the optical disc D is defined as a tangential direction T.

  FIG. 8 is a perspective view showing an actuator for an optical pickup disclosed in Patent Document 1. As shown in FIG. The actuator 100 is mounted on the traverse unit 50 in FIG. 7 so that the two objective lenses are in the radial direction of the optical disc D. Therefore, the alignment direction of the two objective lenses is the radial direction R, the optical axis direction of the objective lenses is the focus direction F, and the direction orthogonal to the radial direction R and the focus direction F is the tangential direction T. The actuator 100 is configured such that objective lenses 112 and 113 corresponding to optical disks having different optical characteristics are mounted on one movable body 111 and the movable body 111 can be driven independently in the focus direction F and the radial direction R. 2 axis drive device. Such an actuator 100 can be applied to an optical pickup for recording / reproducing a plurality of optical disks having different optical characteristics.

  The actuator 100 described in Patent Document 1 has a structure in which a movable body 111 is supported on a base 130 via a holder 114. Two objective lenses 112 and 113 are mounted on the movable body 111 so as to be aligned in the radial direction R. In such an actuator 100, the movable body 111 is connected to the holder 114, and the movable body 111 is supported in such a manner that the movable body 111 can swing in the focus direction F and the radial direction R. The movable body 111 is moved in the focus direction F. A first magnetic circuit 150 for swinging and a second magnetic circuit 160 for swinging the movable body 111 in the radial direction R are included.

  The objective lenses 112 and 113 are arranged in such a way that the data recording / reproducing area of the high-density optical disc is positioned closer to the inner diameter side than the data recording / reproducing area of the low-density optical disc. It is installed so as to be positioned on the inner diameter side of the optical disk for the density optical disk.

  Each of the first and second magnetic circuits 150 and 160 is arranged in two sets so as to sandwich the objective lenses 112 and 113 along the tangential direction T. Each set of the first magnetic circuit 150 includes a focus magnet 151 and a focus coil 152, and each set of the second magnetic circuit 160 includes a track magnet 161 and a track coil 162. The focus magnet 151 and the track magnet 161 are made of permanent magnets, and the focus magnet 151 is provided outside the movable body 111 with respect to the track magnet 161. The focus coil 152 is provided between the movable body 111 and the focus magnet 151, and the track coil 162 is provided between the movable body 111 and the track magnet 161.

  An optical pickup using such an actuator 100 is necessarily constructed as shown in FIG. That is, below the actuator 100, the light source 140 that emits the laser light L, the collimator lens 141, the rising mirror 135 that guides the laser light L to the objective lenses 112 and 113, and the optical disk (not shown) are reflected back. A light detector 143 for detecting the amount of light of the received laser light L is installed. Between the light source 140 and the rising mirror 135, the laser light L from the light source 140 is transmitted and guided to the rising mirror 135, and the laser light L reflected and returned from the optical disk is guided to the photodetector 143. A half mirror 142 is provided.

  The laser light L emitted from the laser light source 140 passes through the half mirror 142, and then is guided to one of the objective lenses 112 and 113 via the rising mirror 135, and is recorded on the optical disk held by the disk rotation mechanism. The surface is irradiated. The laser light L reflected from the recording surface of the optical disk passes through the objective lenses 112 and 113 and the rising mirror 135 and is further guided to the photodetector 143 via the half mirror 142.

JP 2003-281758 A

  In the optical pickup using the actuator described in Patent Document 1 above, as shown in FIG. 9, it is necessary to install a rising mirror below the actuator. Components such as the rising mirror must be miniaturized.

  However, when the magnetic circuit is downsized, the drive performance in the focus direction or the radial direction is lowered, and problems such as an increase in power consumption and a decrease in tracking accuracy also occur, so there is a difficulty in downsizing the magnetic circuit. .

  In addition, the size of the rising mirror depends on the effective diameter of the objective lens. As an optical design condition, the width of the laser beam reflected by the rising mirror must be larger than the effective diameter of the objective lens. Therefore, it has been extremely difficult to reduce the size and thickness of the rising mirror.

  Therefore, it has been considered to make the thickness of the central portion of the movable body 111 where the objective lenses 112 and 113 are mounted thinner than the thickness of the magnetic circuits 150 and 160.

  FIG. 10 is a perspective view showing an optical pickup in which the central portion of the movable body is thinned. In the optical pickup 200, the movable body 211 has a central portion 211A on which the objective lenses 212 and 213 are mounted, and a side portion 211B that extends from the central portion 211A to both sides in the radial direction R and includes a coil block 220. The central portion 211A has a smaller thickness than the side portion 211B and is formed above the side portion 211B. In such a central portion 211A, the two objective lenses 212 and 213 are arranged so as to be aligned in the tangential direction T.

  The rising mirrors 232 and 233 are at least partially interposed between both side portions 211B of the movable body 211, that is, between the pair of coil blocks 220, and the central portion 211A of the movable body 211 is located above the both side portions 211B. Because of the position, it is as close as possible to the central portion 211A of the movable body 211. Thereby, the thickness of the optical pickup 200 is defined by the thickness of the holder 214 and the base 230, and the rising mirrors 232 and 233 do not increase the thickness of the optical pickup 200. Therefore, the rising mirrors 232 and 233 have a necessary and sufficient size so that the width of the laser beam is larger than the effective diameter of the objective lenses 212 and 213 as an optical design condition. The optical pickup 200 is reduced in size and thickness while having performance.

  However, since the central portion 211A of the movable body is thinned and formed above the side portion 211B, the center of gravity of the movable body 211 is positioned above. On the other hand, the movable body 211 is swung by the electromagnetic force generated between the current passed through the coil block 220 and the magnet 231, but the radial electromagnetic force generated in the track coil 222 is the focus direction F of the track coil 222. Therefore, a moment is generated in relation to the position of the center of gravity of the movable body 211 because the current is generated in any one of the energized portions 222A among the parallel energized portions in which currents flow in opposite directions. This moment causes a disadvantage that the movable body 211 can be swung also in the focus direction.

  FIG. 11 is a diagram illustrating a moment generated by the relationship between the electromagnetic force generated in the track coil 222 and the position of the center of gravity of the movable body, and is a diagram of the movable body 211 in FIG. 10 viewed from the tangential direction. The electromagnetic force F0 is broken down into a force F1 toward the center of gravity and a force F2 that generates a moment. Due to the moment generated by the force F2, the movable body 211 is rotated counterclockwise and is also swung in the focus direction. Therefore, the adjustment in the radial direction causes the inconvenience that the adjustment is not performed in the focus direction and the focus direction is not adjusted. Further, since the lens tilt occurs with respect to the disc, the recording / reproducing characteristics are deteriorated due to coma aberration.

  In addition, it is difficult to ensure sufficient mechanical rigidity by thinning the central portion 211A of the movable body, and since the deformation mode is generated from a low frequency when driven by passing current through the coils of the coil block, positioning accuracy is high. There is also a problem that it cannot be secured sufficiently.

  The present invention has been conceived under the circumstances described above. An object of the present invention is to provide an optical pickup capable of ensuring mechanical rigidity without generating a moment due to electromagnetic force even when the central portion of a movable body is thinned.

  In order to solve the above problems, the present invention takes the following technical means.

  The optical pickup according to claim 1 includes at least one objective lens, a plate-like holding portion that holds the objective lens, and a first direction parallel to the optical axis of the objective lens at both ends of the holding portion. A movable body having a substantially U-shaped cross section having extended side portions, and the movable body in the first direction and the second direction in which the two side portions orthogonal to the first direction are arranged. From a third direction perpendicular to the first and second directions, a support member that is displaceably supported and disposed at a position facing the objective lens in a space sandwiched between two sides of the movable body And a mirror for reflecting the light beam transmitted through the objective lens in the third direction and the two side portions of the movable body. A pair of coil blocks and placed facing the pair of coil blocks An optical pickup comprising a pair of magnets and a drive source for displacing the movable body in the first direction and the second direction, and the inner side surfaces of two side portions of the movable body It is characterized in that a reinforcing member for connecting both side portions is provided on.

  An optical pickup according to a second aspect is the optical pickup according to the first aspect, wherein two objective lenses are held side by side in the third direction in the holding portion of the movable body, and Two mirrors are arranged opposite to each objective lens in the space sandwiched between the two side portions, and the reinforcing member is a space sandwiched between the two side portions of the movable portion. It is provided in a space sandwiched between mirrors.

  An optical pickup according to a third aspect is the optical pickup according to the first or second aspect, wherein the reinforcing member is a plate-like member.

  An optical pickup according to a fourth aspect is the optical pickup according to the first or second aspect, wherein the reinforcing member is a rod-shaped member.

  The optical pickup according to claim 5 is the optical pickup according to claim 1 or 2, wherein the reinforcing member has a beam shape that connects both side portions at the front end surface instead of the inner side surface of the two side portions of the movable body. It is the member of this.

  According to such a configuration, the movable body equipped with a plurality of objective lenses, a pair of coil blocks, two sets of magnets, and a plurality of support members can be moved in a compact manner without functionally damaging the components. Even if the center of the body is thinned, the mechanical rigidity of the movable body is ensured by the reinforcing member, the resonance frequency can be increased, and the deformation mode is unlikely to occur. Further, the position of the center of gravity of the movable body is lowered by the weight of the reinforcing member, and no moment is generated even if electromagnetic force is generated in the track coil.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

  1 to 4 show a first embodiment of an optical pickup according to the present invention. The optical pickup A1 according to the present embodiment is equipped with two types of lenses corresponding to a plurality of optical discs (for example, Blu-ray disc, DVD, CD) having different optical characteristics, and optically records and reproduces the optical disc. Is for. The optical pickup A1 is mounted on the traverse unit 50 in FIG. 7 so that the two objective lenses are in the circumferential direction of the optical disc D. Therefore, the alignment direction of the two objective lenses is the tangential direction T, the optical axis direction of the objective lenses is the focus direction F, and the direction orthogonal to the tangential direction T and the focus direction F is the radial direction R.

  As shown in FIGS. 1 and 2, the optical pickup A1 includes a movable body 11, two objective lenses 12, 13, a holder 14, a plurality of support wires 15, two coil blocks 20, a base 30, and two pairs. And two sets of magnets 31 and two rising mirrors 32 and 33. One coil block 20 is composed of one focus coil 21 and two track coils 22. The movable body 11, the objective lenses 12, 13, the holder 14, the support wire 15, and the coil block 20 are configured as an upper assembly, and the base 30, the magnet 31, and the rising mirrors 32 and 33 are configured as a lower assembly. Yes. The upper assembly and the lower assembly are integrated by fixing the holder 14 and the base 30 to another substrate (not shown) or the like.

  The movable body 11 is mounted with objective lenses 12 and 13 and has a thinned central portion 11A, a side portion 11B having a coil block 20 extending from the central portion 11A to both sides in the radial direction R, and two parts. Reinforcing member 11D provided in a beam shape so as to connect the central position in the tangential direction of the lower surface of side portion 11B. The central portion 11A has a smaller thickness than the side portion 11B and is formed above the side portion 11B. In such a central portion 11A, the two objective lenses 12 and 13 are arranged so as to be aligned in the tangential direction T.

  The side portion 11B has a space penetrating in the focus direction F, and a part of the base 30 (hereinafter referred to as “magnetic core portion”) 30A is inserted into this space as a magnetic core. A focus coil 21 is formed on the entire inner wall surface of the side portion 11B, and track coils 22 are formed on both outer wall surfaces facing the tangential direction T. Further, a convex portion 11C is formed on the outer portion of the side portion 11B facing the radial direction R, and the tip of a support wire 15 extending in the tangential direction T is connected to the convex portion 11C. The base end of the support wire 15 is fixed to both end portions of the holder 14. Thereby, the movable body 11 can swing in the focus direction F and the radial direction R, but cannot swing in the tangential direction T, and is configured in a so-called biaxial drive system.

  The reinforcing member 11D is provided in order to ensure the mechanical rigidity of the movable body 11 having a thin central portion 11A, and to increase the resonance frequency to make it difficult to generate a deformation mode. 3A and 3B show a state in which a force is applied to the movable body 11 in the focus direction F when viewed from the tangential direction T in the case where there is no reinforcement member and in the case where there is a reinforcement member, respectively. It is a figure when analyzing by and displaying a mode animation. The calculated bending mode resonance frequency in the focus direction F was 7.8 kHz in the case of (a) and 16.7 kHz in the case of (b). When the reinforcing member is present, the bending mode resonance frequency is increased by two times or more as compared with the case without the reinforcing member, and the mechanical rigidity is improved. The reinforcing member 11D also serves as a balancer for adjusting the position of the center of gravity of the movable body 11 downward. That is, the reinforcing member 11D has a weight capable of adjusting the position of the center of gravity of the movable body 11 so that no moment is generated even when an electromagnetic force is generated in the track coil 22. The reinforcing member 11D may be integrally formed with the same material as the central part 11A and the side part 11B of the movable body, or a movable body such as metal for adjusting the center of gravity of the movable body 11. 11 may have a higher specific gravity than other parts. Further, the reinforcing member 11 </ b> D passes below between two raising mirrors 32 and 33, which will be described later, and is positioned so as not to contact the raising mirrors 32 and 33 even when the movable body 11 swings.

  One objective lens 12 is used, for example, for recording and reproduction of the first optical disk, and transmits the laser beam in the focus direction F and focuses it on the first optical disk. The other objective lens 13 also transmits laser light in the focus direction F. This objective lens 13 is used for recording and reproduction of a second optical disc having optical characteristics different from those of the first optical disc. The laser light having a wavelength different from that of the first optical disc is condensed on the second optical disc. Such first and second optical discs generally have different specifications regarding optical characteristics such as recording density and thickness, and specific types of disc include CD, DVD, HD-DVD, and Blu-ray disc. In the present embodiment, as an example, it is assumed that one objective lens 12 corresponds to a CD or DVD, and the other objective lens 13 corresponds to a Blu-ray disc.

  The holder 14 has the same thickness as the base 30 and is slightly larger in the radial direction R than the base 30. The proximal ends of the support wires 15 are fixed to both end portions of the holder 14 extending in the radial direction R. Such a holder 14 is installed so as to be placed at a predetermined interval in the tangential direction T with respect to the base 30, and the movable body 11 is held in a cantilever shape via the support wire 15. So as to overlap with the base 30. For this reason, a light guide hole 14 </ b> A is provided in the lower part of the holder 14 for allowing laser light traveling along the tangential direction T from a light source (not shown) to travel directly below the movable body 11.

  As described above, the support wire 15 is for supporting the movable body 11 in a cantilever shape, and a plurality of support wires 15 are provided on the outer convex portion 11C of one side portion 11B of the movable body 11. These support wires 15 also function as conductive wires for supplying power to the focus coil 21 and the track coil 22. Note that as many support wires 15 as necessary to drive the focus coil 21 and the track coil 22 are provided for one side 11B of the movable body 11, and three support wires 15 are provided on one side in FIGS. Although the wire 15 is shown, three or more support wires may be provided.

  The focus coil 21 has a posture in which the coil axis extends in the focus direction F, and is provided integrally with the side portion 11B of the movable body 11. The track coil 22 has a posture in which the coil axis extends in the tangential direction T, and is provided integrally with the side portion 11B of the movable body 11 so as to be located on both outer sides of the focus coil 21 in the tangential direction. In such a focus coil 21, the energized portion 21 </ b> A at a position overlapping the track coil 22 is easily affected by the magnetic field of the magnet 31, and the track coil 22 is a parallel energized portion where currents flow in opposite directions in the focus direction F. Among these, any one of the energized portions 22 </ b> A is easily subjected to the action of a magnetic field by the magnet 31. Therefore, when a vertical magnetic field acts on the energized portion 21A of the focus coil 21, the movable body 11 is swung in the focus direction F, and independently of this, the energized portion 22A of the track coil 22 is moved. The movable body 11 is swung in the radial direction R by the action of the vertical magnetic field.

  The base 30 has a magnet 31 fixed at a position sandwiching the magnetic core portion 30A in the tangential direction T, and rising mirrors 32 and 33 are fixed at the lower end portion thereof, and is raised between the magnetic core portion 30A and the magnet 31. The movable body 11 can be arranged above the mirrors 32 and 33. A cutout portion 30B is provided at the lower portion of the base 30 for allowing the laser light traveling along the tangential direction T from a light source (not shown) to proceed to the rising mirrors 32 and 33 as they are.

  The magnets 31 are generally fixed at the four corners of the base 30, and the two magnets 31 facing the tangential direction T across the magnetic core portion 30A form one set. The magnets 31 forming one set are installed so that the magnetic poles are opposite to each other along the tangential direction T. Specifically, for example, all the magnets 31 are N with respect to the magnetic core portion 30A. It is installed with the pole facing. Thus, when the two focus coils 21 are driven so that the current directions are the same around the axis in the focus direction F, the electromagnetic force in the same direction acts on the energized portions 21A of the focus coils 21, and the movable body 11 It is swung in the focus direction F as a whole. The amount of displacement at that time is controlled by adjusting the drive current for the focus coil 21. Further, when the track coils 22 are driven so that the current directions in the energized portions 22A of all the track coils 22 are the same as viewed from the corresponding magnets 31, electromagnetic forces in the same direction act on these energized portions 22A. The movable body 11 is swung in the radial direction R as a whole. The amount of displacement at that time is controlled by adjusting the drive current for the track coil 22. Since the center of gravity of the movable body 11 is adjusted by the reinforcing member 11D, no moment is generated by the electromagnetic force generated in the track coil.

  As described above, the focus coil 21 and the magnet 31 function as a magnetic circuit for focusing control, and the track coil 22 and the magnet 31 function as a magnetic circuit for tracking control. Each magnet 31 is shared for focusing control and tracking control. These magnetic circuits constitute an actuator by being combined with the movable body 11, the holder 14, the support wire 15, and the base 30. With such a configuration, the optical pickup A1 can be reduced in size and thickness while providing necessary and sufficient electromagnetic performance.

  The rising mirrors 32 and 33 are fixed to the inside of the base 30 and are disposed so as to face the central portion 11A of the movable body 11 so that the reflecting surfaces are inclined with respect to the corresponding objective lenses 12 and 13, respectively. Yes. Further, the raising mirrors 32 and 33 are arranged with a gap enough to pass the reinforcing member 11D therebetween. When the gap between the objective lenses 11 and 12 is narrow or when the thickness of the reinforcing member 11D in the tangential direction T is large, it is possible to move the reinforcing member 11D when there is not enough space to pass the reinforcing member 11D. The body 11 is manufactured separately from the body 11, and the movable body 11 is combined with the base 30, and then the reinforcing member 11D is attached to the movable body 11.

  The raising mirrors 32 and 33 are located at positions facing the light guide hole 14 </ b> A of the holder 14 and the notch 30 </ b> B of the base 30 in the tangential direction T. One raising mirror 32 is disposed so as to reflect the laser light traveling in one direction along the tangential direction T upward and to guide the laser light to the objective lens 12. The other raising mirror 33 has a reflecting surface opposite to the reflecting surface of the raising mirror 32. The raising mirror 33 is directed in the opposite direction along the tangential direction T. The laser beam that has traveled is arranged so as to reflect upward and guide the laser beam to the objective lens 13. Since the reinforcing member 11D is located between the raising mirrors 32 and 33, that is, on the side opposite to the reflecting surface, it does not block the laser beam.

  As shown in FIG. 4, the optical pickup A1 is incorporated in an optical disk device (not shown) together with other optical components such as laser light sources 40A and 40B, collimator lenses 41A and 41B, beam splitters 42A and 42B, and photodetectors 43A and 43B. It is. The optical disc D is arranged so that the recording surface faces the optical pickup A1 while being supported by a spindle shaft (not shown) along the focus direction F, and the optical disc D is rotated around the spindle shaft at high speed during recording and reproduction. . Although not shown in FIG. 4, the radial direction R is a direction penetrating the paper surface. The optical disk device is provided with optical components for more efficiently entering laser light to the objective lenses 12 and 13, or for efficiently guiding the reflected light from the optical disk D to the photodetectors 43A and 43B. However, these are not shown in the figure.

  For example, in FIG. 4, when the laser light source 40A arranged on the left side in the tangential direction T emits laser light L1, the laser light L1 travels rightward in the tangential direction T and passes through the collimator lens 41A and the beam splitter 42A. At the same time, the light passes through the light guide hole 14A of the holder 14 and the cutout portion 30B on the left side of the base 30, and enters the left raising mirror 32 as it is. Then, the laser beam L 1 is reflected upward in the focus direction F by the reflecting surface of the rising mirror 32, and finally irradiated to the optical disc D through the objective lens 12. On the other hand, when the laser light source 40B disposed on the right side of the tangential direction T emits laser light L2, the laser light L2 travels leftward in the tangential direction T and passes through the collimator lens 41B and the beam splitter 42B. It passes through the notch 30B on the right side of the base 30 and enters the right raising mirror 33 as it is. Then, the laser beam L2 is reflected upward in the focus direction F by the reflecting surface of the rising mirror 33, and finally irradiated onto the recording surface of the optical disc D through the objective lens 13.

  As an actual operation, when the optical disc D is loaded in the optical disc apparatus, the laser beams L1 and L2 are simultaneously output from both laser light sources 40A and 40B, and these laser beams L1 and L2 are irradiated onto the recording surface of the optical disc D. And reflected at each irradiation position. The reflected laser beams L1 and L2 are transmitted through the corresponding objective lenses 12 and 13 downward in the focus direction F, and travel in the opposite direction to that described above to reach the beam splitters 42A and 42B. The light is reflected by the splitters 42A and 42B and guided to the photodetectors 43A and 43B.

  The photodetectors 43A and 43B detect the light amounts of the laser beams L1 and L2 reflected by the recording surface of the optical disc D and the diffraction pattern. A disc discrimination circuit (not shown) determines the type of the optical disc D based on the output signals from the photodetectors 43A and 43B. As a result of the determination, if it is determined that the currently loaded optical disk D is not recordable / reproducible, the output of the laser light from the laser light sources 40A and 40B is stopped as a reading error.

  On the other hand, for example, when a CD optical disc D is loaded, it is determined that the optical disc D is an appropriate CD, and only the left objective lens 12 and the rising mirror 32 and the left optical components 40A to 43A are used. Thus, recording / reproduction with respect to the optical disc D is performed. Similarly, when an optical disc D such as a Blu-ray disc is loaded, it is determined that the optical disc D is an appropriate Blu-ray disc, the right objective lens 13 and the rising mirror 33, and the right optical components 40B to 43B. Recording / reproduction with respect to the optical disc D is performed using only

  At the time of recording / reproducing with respect to the optical disc D, a focusing error detection process and a tracking error detection process are performed by the photodetectors 43A and 43B, and when a focusing error is detected, focusing control is performed by making full use of the focus coil 21. . When a tracking error is detected, tracking control is performed using the track coil 22. Such focusing control and tracking control are realized by feedback control.

  Therefore, according to the optical pickup A1 of the present embodiment, the central portion 11A of the movable body is made thin in order to keep the size of the optical pickup A1 thin and small as a whole, but the mechanical rigidity of the movable body 11 is increased by the reinforcing member 11D. Since it is ensured and the resonance frequency is increased to make it difficult for the deformation mode to occur, even when the movable body 11 is driven, the positioning accuracy cannot be sufficiently ensured. Further, since the position of the center of gravity of the movable body 11 is adjusted by the reinforcing member 11D, no moment is generated even if electromagnetic force is generated in the track coil.

  In the above embodiment, the reinforcing member 11D is provided in a beam shape on the lower surface of the two side portions 11B. However, the reinforcing member 11D may be provided in a rod shape on the inner side surface of the two side portions 11B, or a rising mirror. When the space | interval of 32 and 33 is wide enough, as shown in FIG. 5, you may provide in plate shape on the inner surface of the two side parts 11B. In addition, when the reinforcing member is provided in a plate shape, the rigidity of the movable body 11 can be further increased, but the reinforcing member 11D is always positioned between the two rising mirrors, and assembling error is absorbed. Therefore, in order to avoid contact between the rising mirror and the reinforcing member 11D, a gap of at least 0.3 mm is required between the rising mirrors 32 and 33 and the reinforcing member 11D.

  Moreover, although the case where the two objective lenses are arranged in the tangential direction T has been described in the above embodiment, the two objective lenses may be arranged in the radial direction R. In addition, in the case where there is one objective lens, as long as the raising mirror can be disposed so as not to contact the reinforcing member, three or more objective lenses may be mounted.

  Regarding the above embodiment, the following additional notes are disclosed.

(Appendix 1)
At least one objective lens;
A movable body having a substantially U-shaped cross section having a flat plate-shaped holding portion for holding the objective lens and side portions extending in a first direction parallel to the optical axis of the objective lens at both ends of the holding portion,
A support member that displaceably supports the movable body in the first direction and a second direction in which the two side portions orthogonal to the first direction are disposed;
A light beam from a third direction orthogonal to the first and second directions is arranged in a position opposed to the objective lens in a space sandwiched between two sides of the movable body in the first direction. A mirror that reflects and transmits the objective lens and reflects the light beam transmitted through the objective lens in the third direction;
The movable body includes a pair of coil blocks provided on two side portions of the movable body and a pair of magnets arranged to face the pair of coil blocks, and the movable body is moved in the first direction and the second direction. A drive source that is displaced to
An optical pickup comprising:
An optical pickup comprising a reinforcing member for connecting both side portions to the inner side surface of two side portions of the movable body.

(Appendix 2)
Two objective lenses are held side by side in the third direction on the holding portion of the movable body, and two objective lenses are opposed to each objective lens in a space between the two side portions of the movable portion. Mirror is placed,
The optical pickup according to appendix 1, wherein the reinforcing member is provided in a space sandwiched between two side portions of the movable portion and sandwiched between the two mirrors.

(Appendix 3)
3. The optical pickup according to appendix 1 or 2, wherein the reinforcing member is a plate-like member.

(Appendix 4)
The optical pickup according to appendix 1 or 2, wherein the reinforcing member is a rod-shaped member.

(Appendix 5)
3. The optical pickup according to appendix 1 or 2, wherein the reinforcing member is a beam-shaped member that connects both side portions at the front end surface instead of the inner side surface of the two side portions of the movable body.

(Appendix 6)
The coil block has a focus coil for driving the movable body in the first direction with the coil axis extending in the first direction, and a coil coil extending in the third direction. The optical pickup according to any one of appendices 1 to 5, further comprising a track coil that is provided outside the focus coil and drives the movable body in the second direction.

(Appendix 7)
A holder for holding the movable body in a cantilever shape via the plurality of support members is provided, and this holder is used for advancing laser light to the rising mirror along a third direction. The optical pickup according to any one of appendices 1 to 6, wherein a light guide hole is provided.

(Appendix 8)
An optical disc apparatus comprising the optical pickup according to any one of appendices 1 to 7.

  According to the present invention, the optical pickup can be reduced in size and thickness by thinning the central portion of the movable body while ensuring the mechanical rigidity. Further, by applying such an optical pickup, the entire optical disc apparatus can be reduced. Small and thin can be realized.

1 is an exploded perspective view showing an embodiment of an optical pickup according to the present invention. It is a whole perspective view of the optical pick-up shown in FIG. It is a figure which shows the characteristic comparison of the movable body by the presence or absence of a reinforcement member. It is sectional drawing which follows the II line | wire of FIG. It is a disassembled perspective view which shows other embodiment of the optical pick-up based on this invention. It is explanatory drawing for demonstrating the thickness of the objective lens corresponding to various optical disks. It is a side view which shows the optical disk device incorporating an optical pick-up. It is a perspective view which shows the actuator for optical pick-ups which concerns on a prior art. It is sectional drawing which follows the II-II line of FIG. It is a disassembled perspective view which shows the optical pick-up based on a prior art. It is a figure for demonstrating the moment which generate | occur | produces in the movable body of the optical pick-up concerning a prior art.

Explanation of symbols

A1 to A2 Optical pickup F Focus direction (first direction)
R radial direction (second direction)
T Tangential direction (third direction)
L1, L2 Laser light 11 Movable body 11A Central part (holding part) of movable body
11B Side of movable body 11D, E Reinforcement member 12, 13 Objective lens 14 Holder 14A Light guide hole 15 Support wire (support member)
20 Coil block 21 Focus coil 22 Track coil 31 Magnet 32, 33 Raising mirror

Claims (5)

At least one objective lens;
A movable body having a substantially U-shaped cross section having a flat plate-shaped holding portion for holding the objective lens and side portions extending in a first direction parallel to the optical axis of the objective lens at both ends of the holding portion,
A support member that displaceably supports the movable body in the first direction and a second direction in which the two side portions orthogonal to the first direction are disposed;
A light beam from a third direction orthogonal to the first and second directions is arranged in a position opposed to the objective lens in a space sandwiched between two sides of the movable body in the first direction. A mirror that reflects and transmits the objective lens and reflects the light beam transmitted through the objective lens in the third direction;
The movable body includes a pair of coil blocks provided on two sides of the movable body and a pair of magnets arranged to face the pair of coil blocks, and the movable body is moved in the first direction and the second direction. A drive source that is displaced in the direction;
An optical pickup comprising
An optical pickup comprising a reinforcing member for connecting both side portions to the inner side surface of two side portions of the movable body. Two objective lenses are held side by side in the third direction on the holding portion of the movable body, and two objective lenses are opposed to each objective lens in a space between the two side portions of the movable portion. Mirror is placed,
2. The optical pickup according to claim 1, wherein the reinforcing member is provided in a space sandwiched between two side portions of the movable portion and sandwiched between the two mirrors. .   The optical pickup according to claim 1, wherein the reinforcing member is a plate-like member.   The optical pickup according to claim 1, wherein the reinforcing member is a rod-shaped member.   3. The optical pickup according to claim 1, wherein the reinforcing member is a beam-shaped member that connects both side portions at the front end surface instead of the inner side surfaces of the two side portions of the movable body.

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