JP2008226292A - Objective lens actuator and information recording and playback device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an objective lens actuator having durability for higher-order resonance and reducing weight and thickness. <P>SOLUTION: The objective lens actuator is provided with a lens holder having four coil bobbins on which a coil is wound and fixing an objective lens, a pair of tracking coils wound diagonally on the coil bobbin, a pair of radial tilt coils wound diagonally on the coil bobbin at a position different from the tracking coils, a pair of focus coil wound in layers on each of radial tilt coils, a pair of tracking magnets arranged at a position facing the tracking coils, and a pair of focus magnets arranged at a position facing the focus coils, then, in each of the pair of focus coils and the pair of focus magnets, at least one of shape, size, mass, and arrangement position is asymmetry, while moment surrounding the radial tilt axis is balanced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an objective lens actuator and an information recording / reproducing apparatus, and more particularly to an objective lens actuator for driving an objective lens of an optical pickup in three axes and an information recording / reproducing apparatus incorporating the objective lens actuator.

  As is well known, in recent years, high-density recording technology of information has been promoted, and an optical disc having a recording capacity of 4.7 GB (Giga Byte) per layer on one side has been put into practical use.

  Examples of the optical disk include a CD (Compact Disk) -ROM (Read Only Memory), a DVD (Digital Versatile Disk) -ROM, a DVD-R (Recordable), a DVD-RW (Rewritable), a DVD-RAM (Random Access Memory), and the like. There are HD DVD (High Definition), BD (Blu-ray Disc) and the like.

  In an information recording / reproducing apparatus for an optical disc, information is recorded and reproduced by accurately focusing a laser beam on a specific position on the optical disc. This alignment is realized by controlling the relative position or the relative attitude angle between the objective lens for condensing the laser beam and the optical disk using an objective lens actuator.

  Specifically, position control called tracking control and focus control and attitude angle control called radial tilt control are performed using servo mechanisms.

  Tracking control is servo control that finely adjusts the position of the objective lens in the radial direction so that the focal point of the laser beam is always located at the center of a specific track of the optical disk. The focus control is servo control for controlling the separation distance between the objective lens and the optical disc so that the focal point of the laser beam is accurately positioned on the optical disc.

  With radial tilt control, even when the reflecting surface of the optical disc is slightly displaced from the plane perpendicular to the optical axis of the laser beam and tilted in the radial direction, the laser beam is always irradiated perpendicularly to the reflecting surface of the optical disc. In addition, the servo control controls the attitude angle of the objective lens in the radial direction of the optical disk.

  In general, the servo control is driven by electromagnetic force generated by a coil current and a permanent magnet magnetic flux. For this reason, the movable part to which the objective lens is mounted and the fixed part that supports the movable part are appropriately arranged so that the coil and the permanent magnet are adjacent to each other.

  The objective lens actuator also needs to follow an optical disk that rotates at high speed, and the servo control system is required to have high responsiveness. That is, a wide frequency band is required for the servo system.

  Patent Document 1 discloses an objective lens actuator for causing an objective lens to follow an optical disk rotating at high speed. However, since Patent Document 1 only discloses a configuration in which the objective lens is driven in the biaxial direction of the focus direction and the tracking direction, as today's high-precision objective lens actuator that requires control of the radial tilt direction, It is unsuitable for practical use.

  On the other hand, Patent Document 2 discloses an objective lens actuator that can drive the objective lens in the three-axis directions of the focus direction, the tracking direction, and the radial tilt direction, and achieves downsizing and high drive sensitivity. .

  In the optical disc apparatus, in order to increase the information transfer speed, it is necessary to increase the high-order resonance frequency of the movable part of the objective lens actuator in addition to increasing the thrust of the objective lens actuator. However, in Patent Document 2, since the structural rigidity of the movable part is small, there arises a disadvantage that the high-order resonance frequency cannot be increased.

For example, the performance of the objective lens actuator disclosed in Patent Document 2 is disclosed in Non-Patent Document 1, and according to this Non-Patent Document 1, a high-order resonance frequency is as low as about 20 kHz, and a recent objective lens actuator is disclosed. From the performance level, it can be seen that it is not suitable for practical use.
JP 63-259842 A US Patent Application Publication No. 2003/0016597 Junya Aso et al., “High Response Actuator with Tilt Function for 12.7mm Slim Optical Disc Drives”, ISOM / ODS (joint International Symposium on Optical Memory and Optical Data Storage) 2002, p.326-328

  Recently, the trend toward downsizing and thinning of information equipment incorporating an information recording / reproducing apparatus, such as a personal computer, has become more prominent. In response to this trend, demands for light weight, thinness, and high-density mounting are increasing for the information recording / reproducing apparatus or the objective lens actuator incorporated therein.

  On the other hand, in order to ensure the basic function and performance of the objective lens actuator, a balanced arrangement of coils and permanent magnets is necessary. In addition, it is indispensable to secure a mechanism for supporting the movable part on which the objective lens is mounted and a laser beam path. Under these constraints, how to achieve high-density mounting of the objective lens actuator is an important design issue.

  In addition, when the objective lens actuator is pursued to be lighter and thinner, the rigidity of the frame member constituting the objective lens actuator tends to decrease, but this works in a disadvantageous direction for higher-order resonance of the servo control system. . For this reason, it is also important to take measures to ensure the rigidity of the frame member while realizing a lighter and thinner thickness.

  The present invention has been made in view of the above circumstances, and achieves high-density mounting and light weight and thinness while ensuring the basic functions and performance of the objective lens actuator and the high-order resonance resistance of the servo control system. It is an object of the present invention to provide an objective lens actuator that can be used and an information recording / reproducing apparatus incorporating the same.

  In order to solve the above problems, an objective lens actuator according to the present invention is capable of performing a translational drive in the tracking direction, a translational drive in the focus direction, and a rotational drive about a radial tilt axis as described in claim 1. The actuator has an objective lens for condensing laser light on the information recording surface of the optical disc, a hollow substantially rectangular parallelepiped shape, and four coil bobbins for winding a coil on the side surface, and at the center of the upper surface A lens holder for fixing the objective lens, and a pair of tracking members that are wound diagonally around the coil bobbin disposed on the side surface of the lens holder with the objective lens interposed therebetween, and that translates the lens holder in a tracking direction. The radial coil is positioned at a position different from the tracking coil on the side surface of the coil and the lens holder. A pair of radial tilt coils wound diagonally around the coil bobbin across the objective lens so as to straddle the center axis, and rotationally drive the lens holder around a radial tilt axis, and above each of the radial tilt coils A pair of focus coils that are wound around the lens holder to translate the lens holder in the focus direction, a pair of tracking magnets disposed at positions facing each of the tracking coils, and each of the focus coils. A pair of focus magnets disposed at a position to be fixed, a fixed portion to which the tracking magnet and the focus magnet are fixed, one end is fixed to the fixed portion, and the other end is fixed to the lens holder, the lens holder A suspension wire that holds the air in a hollow state, and is disposed across the radial tilt axis. Each of the pair of focus coils and each of the pair of focus magnets has at least one of a shape, a dimension, a mass, and a disposition position that is asymmetric with respect to the radial tilt axis, and in the focus direction. It is characterized in that the moments about the radial tilt axis cancel each other and balance when driven in translation.

  In order to solve the above problems, an information recording / reproducing apparatus according to the present invention provides an optical pickup including an objective lens actuator and a drive control unit that controls driving of the objective lens actuator. And a reproduction processing unit that reproduces a signal output from the optical pickup, and a recording processing unit that modulates recording data and outputs the data as a laser control signal to the optical pickup, and the objective lens actuator includes: In an objective lens actuator capable of translational drive in the tracking direction, translational drive in the focus direction, and rotational drive around the radial tilt axis, an objective lens for condensing the laser beam on the information recording surface of the optical disc, and a hollow substantially rectangular parallelepiped shape None, with four coil bobbins for winding the coil on its side, and above A lens holder for fixing the objective lens in the center of the surface, and the lens holder wound diagonally around the coil bobbin disposed on the side surface of the lens holder with the objective lens interposed therebetween, and translationally driven in the tracking direction. A pair of tracking coils, and the lens holder wound diagonally around the coil bobbin with the objective lens sandwiched across the radial tilt axis at a position different from the tracking coil on the side surface of the lens holder. A pair of radial tilt coils that are driven to rotate about a radial tilt axis, a pair of focus coils that are wound on each of the radial tilt coils, and that drive the lens holder in translation in the focus direction; A pair of tracking magnets disposed at positions facing each other; A pair of focus magnets disposed at positions facing each of the coil coils, a fixed portion to which the tracking magnet and the focus magnet are fixed, one end fixed to the fixed portion, and the other end fixed to the lens holder Each of the pair of focus coils and each of the pair of focus magnets disposed across the radial tilt axis, each having a shape, a size, and a suspension wire that holds the lens holder in a hollow state. At least one of the mass and the arrangement position is asymmetric with respect to the radial tilt axis, and the moments around the radial tilt axis cancel each other and balance when driven in translation in the focus direction. It is characterized by that.

  According to the objective lens actuator and the information recording / reproducing apparatus of the present invention, the basic function and performance of the objective lens actuator and the high-order resonance resistance of the servo control system are ensured, and high-density mounting and light weight and thinning are achieved. Can be realized.

  Embodiments of an objective lens actuator and an information recording / reproducing apparatus according to the present invention will be described with reference to the accompanying drawings.

(1) Configuration and operation of information recording / reproducing apparatus The information recording / reproducing apparatus 100 according to the present embodiment includes, for example, a CD-R, CD-RW, DVD-R, DVD-RW, DVD-RAM, HD DVD-ROM, Information is recorded on and reproduced from an optical disc 200 such as HD DVD-R, HD DVD-RW, HD DVD-RAM, and BD (Blu-ray Disc).

  FIG. 1 is a diagram illustrating a configuration example of the information recording / reproducing apparatus 100.

  The information recording / reproducing apparatus 100 includes an optical pickup 50, a three-axis control unit 60 (drive control unit), a reproduction processing unit 70, and a recording processing unit 80.

  The optical pickup 50 irradiates the optical disc 200 with laser light for information recording and reproduction, converts the reflected light from the optical disc 200 into an electrical signal, and outputs it as a reproduction signal. As a semiconductor laser 51, a collimating lens 52, a PBS (polarizing beam splitter) 53, a diffraction grating and a quarter-wave plate 56, an objective lens 24, a condenser lens 54, and a photodetector 55. A rising mirror 205 (see FIG. 13 and the like) that changes the direction of the laser light may be provided between the PBS 53 and the diffraction grating and the quarter-wave plate 56.

  The optical pickup 50 also includes an objective lens actuator 10 to which the objective lens 24 and the diffraction grating / quarter wavelength plate 56 are attached. The objective lens 24, the diffraction grating and the quarter wavelength plate 56 are mounted by the objective lens actuator 10. Is controlled in three axes.

  The triaxial control unit 60 includes a focus error signal generation circuit 61, a focus control circuit 62, a tracking error signal generation circuit 63, a tracking control circuit 64, a radial tilt error signal generation circuit 65, and a radial tilt control circuit 66.

  Control signals generated by these circuits included in the three-axis control unit 60 are output to the objective lens actuator 10 to perform position control and attitude angle control of the objective lens 24. Specifically, focus control for controlling the separation distance between the objective lens and the optical disc so that the focal point of the laser beam is accurately positioned on the optical disc, and the focal point of the laser beam always at the center of a specific track of the optical disc. Tracking control to finely adjust the radial position of the objective lens, and even if the reflecting surface of the optical disk is slightly displaced from the plane perpendicular to the optical axis of the laser beam and tilted in the radial direction, the laser beam is reflected on the reflecting surface of the optical disk. Servo-controlled radial tilt control for controlling the attitude angle of the objective lens in the radial direction of the optical disc is performed so as to always irradiate vertically with respect to the optical disc.

  The reproduction processing unit 70 performs reproduction processing on the signal output from the optical pickup 50, and includes a signal processing circuit 71 and a demodulation circuit 72.

  The recording processing unit 80 mainly records information on the optical disc 200, and includes a modulation circuit 81, a recording / reproduction control unit 82, and a laser control circuit 83.

  The operation of the information recording / reproducing apparatus 100 configured as described above will be described. First, the operation of recording information on the optical disc 200 will be described.

  The modulation circuit 81 of the recording processing unit 80 modulates recording information (data symbols) provided from a host, for example, a personal computer main body into a channel bit sequence based on a predetermined modulation method. The channel bit sequence corresponding to the recording information is input to the recording / reproducing control unit 82.

  The recording / reproducing control unit 82 receives a recording / reproducing instruction (in this case, a recording instruction) from the host. The recording / reproducing control unit 82 outputs a control signal to the triaxial control unit 60, and drives the objective lens actuator 10 so that the light beam is appropriately condensed at the target recording position. Further, the recording / reproducing control unit 82 supplies the channel bit sequence to the laser control circuit 83.

  The laser control circuit 83 converts the channel bit series into a laser drive waveform, and drives the semiconductor laser 51 in pulses. As a result, the semiconductor laser 51 generates a recording light beam corresponding to a desired bit sequence.

  The recording light beam generated by the semiconductor laser 51 is converted into parallel light by the collimator lens 52, enters the PBS 53, and passes therethrough. The light beam that has passed through the PBS 53 passes through the diffraction grating and the quarter-wave plate 56 and is focused on the information recording surface of the optical disc 200 by the objective lens 24.

  The focused light beam for recording can obtain the best light beam spot on the information recording surface of the optical disc 200 by focus control, tracking control, and radial tilt control by the triaxial control unit 60 and the objective lens actuator 10. Maintained in a state.

  Next, the reproduction of information from the optical disc 200 by the information recording / reproducing apparatus 100 will be described.

  The recording / reproducing control unit 82 receives a recording / reproducing instruction (in this case, a reproducing instruction) from the host. The recording / reproduction control unit 82 outputs a reproduction control signal to the laser control circuit 83 in accordance with a reproduction instruction from the host.

  The laser control circuit 83 drives the semiconductor laser 51 based on the reproduction control signal and generates a reproduction light beam. The reproduction light beam generated by the semiconductor laser 51 is converted into parallel light by the collimator lens 52, and enters and passes through the PBS 53. The light beam that has passed through the PBS 53 passes through the diffraction grating and the quarter-wave plate 56 and is focused on the information recording surface of the optical disc 200 by the objective lens 24.

  The condensed light beam for reproduction can obtain the best light beam spot on the information recording surface of the optical disc 200 by focus control, tracking control, and radial tilt control by the triaxial control unit 60 and the objective lens actuator 10. Maintained in a state.

  The reproduction light beam irradiated on the optical disc 200 is reflected by the reflective film or reflective recording film in the information recording surface. The reflected light passes through the objective lens 24 in the opposite direction to become parallel light again, passes through the diffraction grating and the quarter-wave plate 56, and then is reflected by the PBS 53 having a polarization perpendicular to the incident light.

  The light beam reflected by the PBS 53 becomes convergent light by the condenser lens 54 and enters the photodetector 55. The photodetector 55 is composed of, for example, a four-divided photodetector. The light beam incident on the photodetector 55 is photoelectrically converted into an electric signal and amplified. The amplified signal is equalized in the signal processing circuit 71 of the reproduction processing unit 70, binarized, and sent to the demodulation circuit 72. The demodulation circuit 72 performs a demodulation operation corresponding to a predetermined modulation method and outputs reproduced data.

  On the other hand, part of the electrical signal output from the photodetector 55 is input to the triaxial control unit 60, and a focus error signal is generated by the focus error signal generation circuit 61. Similarly, part of the electrical signal output from the photodetector 55 is input to the triaxial control unit 60, and a tracking error signal and a radial tilt error signal are generated by the tracking error signal generation circuit 63 and the radial tilt error circuit 66, respectively. Is done.

  The focus control circuit 62 controls the objective lens actuator 10 based on the focus error signal and controls the focus of the beam spot. The tracking control circuit 64 controls the objective lens actuator 10 based on the tracking error signal, and controls tracking of the beam spot. The radial tilt control circuit 66 controls the objective lens actuator 10 based on the radial tilt error signal and controls the radial tilt of the beam spot.

  As described above, the objective lens actuator 10 controls the position and the attitude angle of the objective lens 24 mounted on the objective lens actuator 10 based on the control signal from the triaxial control unit 60, and the position of the beam spot with respect to the optical disc 200. Is maintained to be optimal.

  Next, the structure and operation of the objective lens actuator 10 (first embodiment) will be described.

(2) Structure and operation of objective lens actuator (Part 1)
2 and 3 are perspective external views showing the entire structure of the objective lens actuator 10. FIG. 2 shows the direction in which the laser beam 204 is input (hereinafter, the direction in which the laser beam 204 is input is referred to as the front, and the opposite direction is referred to as the rear. The right side is referred to as the right side as viewed from the front, and the left side is referred to as the left side. 3 is a perspective view of the objective lens actuator 10 as viewed from the rear.

  The objective lens actuator 10 includes a movable part 34 including a lens holder 33 that holds the objective lens 24, with respect to the information recording surface of the optical disc 200, translational drive in the focus direction, translational drive in the tracking direction, and a radial tilt shaft 203. Each has a function of independently performing rotational driving around (in the radial tilt direction).

  In FIG. 2, the yoke base 35 formed in a flat plate shape is installed so as to be parallel to the information recording surface of the optical disc 200. A gel holder 36 having a substantially rectangular parallelepiped shape is installed on the rear side of the yoke base 35.

  The gel holder 36 has openings 36a and 36b formed on both sides thereof. The opening 36a is filled with a gel agent for damping the three suspension wires 38a, 38b, and 38c. In the opening 36b, the three suspension wires 39a, 39b, The gel agent for giving damping to 39c is filled. A fixed end circuit board 37 is attached to the rear of the gel holder 36 (see FIG. 3). The fixed end circuit board 37 is connected to output terminals of a focus control circuit 62, a tracking control circuit 64, and a radial tilt control circuit 66 constituting the triaxial control unit 60, respectively.

  One end portions of three suspension wires 38a, 38b, and 38c, which are elastic linear bodies, are fixed to the fixed end circuit board 37 vertically in the focus direction at positions corresponding to the openings 36a of the gel holder 36. ing. These suspension wires 38 a, 38 b, 38 c are formed of a conductive material, and the other end passes through the opening 36 a of the gel holder 36, reaches almost the center of the yoke base 35, and is fixed to the movable portion 34. ing.

  Further, on the fixed-end circuit board 37, three suspension wires 39a, 39b, 39c (39b, 39c are hidden in FIGS. 2 and 3) at positions corresponding to the openings 36b of the gel holder 36. One end is fixed vertically in the focus direction. These suspension wires 39a, 39b, and 39c are formed of a conductive material, and the other ends of the suspension wires 39a, 39b, and 39c pass through the opening 36b of the gel holder 36, reach the substantially central portion of the yoke base 35, and are fixed to the movable portion 34. ing.

  The movable portion 34 is supported between the other end portions of the three suspension wires 38a, 38b, and 38c and the other end portions of the three suspension wires 39a, 39b, and 39c.

  FIG. 4 is an exploded perspective view showing the components of the objective lens actuator 10 in an exploded manner.

  As shown in FIG. 4, the movable portion 34 is formed in a substantially rectangular parallelepiped shape, and a lens holder 33 holding the objective lens 24 is attached to the upper surface in the drawing. A diffraction grating and a quarter-wave plate 56 (not shown) are disposed inside the lens holder 33.

  The other ends of the suspension wires 38 a, 38 b, 38 c are connected to the lens holder 33. Similarly, the other end portions of the suspension wires 39a, 39b, and 39c are connected to the lens holder 33. By these connections, the movable portion 34 is elastically supported in a hollow manner with respect to the yoke base 35, so that translational movement in the tracking direction and focus direction and rotation around the radial tilt shaft 203 are possible.

  The openings 36a and 36b of the gel holder 36 are filled with a viscoelastic material such as silicone gel, for example, so that the suspension wires 38a to 38c and 39a to 39c have high damping characteristics. Yes.

  5 is a perspective view seen from the front showing the positional relationship between the lens holder and each drive coil, and FIG. 6 is a perspective view seen from the rear showing the positional relationship between the lens holder and each drive coil. As shown in FIG. 5, the tracking coil 41a is wound around the tracking bobbin 92a on the right side of the front side wall of the movable portion 34, and the focus coil 42a and the radial tilt coil 43a are focused / radial on the left side. It is wound around a tilt bobbin 91a. Here, first, the radial tilt coil 43a is wound directly around the focus / radial tilt bobbin 91a, and then the focus coil 42a is wound around the radial tilt coil 43a.

  FIG. 6 is a perspective view of the movable part 34 as seen from the rear. As shown in FIG. 6, a focus coil 42b and a radial tilt coil 43b are wound around a focus / radial tilt bobbin 91b on the right side on the rear side wall of the movable portion 34, and a tracking coil 41b is tracking on the left side. It is wound around a bobbin 92b. Here, first, the radial tilt coil 43b is wound directly around the focus / radial tilt bobbin 91b, and then the focus coil 42b is wound around the radial tilt coil 43b.

  The coils 41a, 42a, 43a, 41b, 42b, 43b are electrically connected to suspension wires 38a, 38b, 38c, 39a, 39b, 39c (not shown), and are output from the triaxial control unit 60. The control current is supplied to the coils 41a to 43a and 41b to 43b via the fixed end circuit board 37 and the suspension wires 38a to 38c and 39a to 39c. In the present embodiment, the tracking coil 41a and the tracking coil 41b, the focus coil 42a and the focus coil 42b, and the radial tilt coil 43a and the radial tilt coil 43b are connected in series.

  The tracking magnets 44a and 44b and the focus magnets 45a and 45b are opposed to the yoke base 35 at diagonal positions with the objective lens 24 sandwiched between the tracking coils 41a and 41b and the focus coils 42a and 42b, respectively. Are arranged and fixed.

  As described above, each of the tracking coils 41 a and 41 b is wound around the diagonal position of the lens holder 33 with the position of the objective lens 24 as the center. Further, each of the focus coils 42a and 42b and each of the radial tilt coils 43a and 43b are wound around diagonal positions of the lens holder 33 opposite to the tracking coils 41a and 41b.

  7 and 8 are perspective views of the lens holder 33 provided with the tracking bobbins 92a and 92b and the focus / radial tilt bobbins 91a and 91b. 7 is a perspective view seen from the front, and FIG. 8 is a perspective view seen from the rear. FIG. 9 is a perspective view of only the coils 41a, 42a, 43a, 41b, 42b, and 43b in the present embodiment as viewed from the front.

  FIG. 10 is a diagram illustrating the positional relationship between each coil and a magnet disposed at a position facing the coil, including the polarity of the magnet.

  The tracking magnets 44a and 44b are formed by joining two magnets in the left-right direction so that the north pole and the south pole are adjacent to each other in the tracking direction (left-right direction in FIG. 10). As a result, a magnetic flux 202 is generated from the N pole of the left magnet to the S pole of the right magnet, and the tracking coils 41a and 41b are disposed in this magnetic flux. An electromagnetic force is generated between the magnetic flux and the current flowing through the tracking coils 41a and 41b, and translational driving in the tracking direction is performed on the lens holder 33 to which the tracking coils 41a and 41b are joined by the electromagnetic force. In this case, a current is passed through each of the tracking coils 41a and 41b arranged diagonally so that an electromagnetic force is generated in the same direction.

  On the other hand, the focus magnets 45a and 45b are formed by joining two magnets in the vertical direction so that the north pole and the south pole are adjacent to each other in the focus direction (vertical direction in FIG. 10). As a result, a magnetic flux 201 is generated from the N pole of the upper magnet to the S pole of the lower magnet, and the focus coils 42a and 42b and the radial tilt coils 43a and 43b are disposed in this magnetic flux. Electromagnetic force is generated between the magnetic flux and the currents flowing through the focus coils 42a and 42b and the radial tilt coils 43a and 43b.

  At this time, a current is passed through each of the focus coils 42a and 42b so that an electromagnetic force is generated in the same direction (upward or downward). As a result, translational drive in the focus direction can be performed by the resultant electromagnetic force generated in each of the focus coils 42a and 42b.

  On the other hand, a current is passed through each of the radial tilt coils 43a and 43b so that an electromagnetic force is generated in the opposite direction. As a result, it can be driven to rotate around the radial tilt shaft 203 between the radial tilt coils 43a and 43b.

  In addition, the direction of the magnetic pole of each magnet is not limited to that illustrated in FIG. 10, and a configuration in which the N pole and the S pole are interchanged is naturally possible. In this case, the current direction of the corresponding coil may be changed as appropriate.

  FIG. 11 is a plan view showing the positional relationship between the focus magnets 45a and 45b, the tracking magnets 44a and 44b, the focus coils 42a and 42b, the radial tilt coils 43a and 43b, and the tracking coils 41a and 41b. FIG. 11 also shows the radial tilt axis 203 and the light beam 204. Here, since the radial tilt coils 43a and 43b are respectively arranged inside the focus coils 42a and 42b, they are not visible in FIG. 11 which is a plan view.

  FIG. 12 is a plan view of the objective lens actuator 10 itself including components other than magnets and coils. Similarly, since the radial tilt coils 43a and 43b are respectively disposed inside the focus coils 42a and 42b, they are not visible in FIG. 12 which is a plan view.

  As shown in FIGS. 11 and 12, the shapes of a pair of focus magnets 45a and 45b, a pair of focus coils 42a and 42b, and a pair of radial tilt coils 43a and 43b, which are arranged diagonally across the objective lens 24, Dimensions and arrangement positions are different in each pair. That is, it is asymmetric with respect to the radial tilt axis 203 (Wa ≠ Wb, Da ≠ Db, etc.). Here, the radial tilt shaft 203 is a rotational axis in the radial tilt direction, and is also an axis that is symmetrical with respect to the six suspension wires 38a, 38b, 38c, 39a, 39b, and 39c.

  Assuming that there is no physical restriction on mounting, there is a form in which the shape, size, and arrangement position of a pair of magnets and coils arranged across the radial tilt axis 203 and the objective lens 24 are sandwiched are symmetrical. It is the most straightforward and balanced mechanically.

  However, if high-density mounting of the objective lens actuator 10 is pursued under various physical limitations, the shape, size, and arrangement position of the magnets and coils should be asymmetric with respect to the radial tilt axis 203. There is also.

  That is, in the present embodiment, as shown in FIGS. 11 and 12, the focus coil 42b, the radial tilt coil 43b, the tracking coil 41b wound around the rear side of the lens holder 33, the focus magnet 45b facing these, The tracking magnet 44b is disposed so as to approach the central radial tilt shaft 203 so as not to physically interfere with the six suspension wires.

  Conversely, the focus coil 42a, the radial tilt coil 43a, the tracking coil 41a wound around the front side of the lens holder 33, and the focus magnet 45a and the tracking magnet 44a facing these do not physically interfere with the light beam 204. Are arranged away from the radial tilt shaft 203.

  If the symmetry of the arrangement is pursued while the passage of the light beam 204 is secured, the distance between the suspension wires on both sides must be increased, resulting in the sacrifice of miniaturization and high density. Therefore, in the present embodiment, priority is given to miniaturization and high density, and this is separately compensated for dynamic imbalance.

  Specifically, when the same current is supplied to the pair of focus coils 42a and 42b and driven in the focus direction, the moment around the radial tilt axis 203 is prevented so that the objective lens 24 does not tilt in the radial tilt direction. The dimensions, shapes, and the like of the focus coils 42a and 42b and the focus magnets 45a and 45b are determined so as to be balanced.

  More specifically, for example, the dimensions of the focus coil 42b and the focus magnet 45b on the rear side are made larger than the focus coil 42a and the focus magnet 45a on the front side, and a larger electromagnetic force is generated on the rear side. The difference in distance from 203 (Da> Db) is compensated.

  Alternatively, the front-side focus coil 42a and the focus magnet 45a and the rear-side focus coil 42b and the focus magnet 45b have the same dimensions, and the current ratio passed through the focus coil 42a and the focus coil 42b is changed to increase the electromagnetic force on the rear side. May be generated to balance the moments about the radial tilt axis 203.

  In the objective lens actuator 10 configured as described above, when a current is supplied to the focus coils 42a and 42b, an electromagnetic force in the focus direction acts on both the focus coils 42a and 42b. By this electromagnetic force, the objective lens 24 mounted on the movable portion 34 is translated and driven in the focus direction (optical axis direction). At this time, the moments around the radial tilt axis 203 generated by the focus coil 42a and the focus coil 42b are opposite and equal to each other and cancel each other, and the objective lens 24 has a mechanism that does not tilt in the radial tilt direction.

  Regarding the rotational drive of the objective lens 24 in the radial tilt direction, for example, a control current is supplied to the radial tilt coil 43b so that an electromagnetic force in the positive optical axis direction is generated, and the radial tilt coil 43a is supplied. Supplies a control current so that an electromagnetic force in the negative optical axis direction is generated. In this way, the objective lens 24 mounted on the movable portion 34 can be driven to rotate about the radial tilt axis.

  In the case of rotational driving around the radial tilt axis, the radial tilt coil 43a and the radial tilt coil 43b generate moments in the same rotational direction, so there is no need to worry about the balance of the moments, and the two radial tilt coils 43a. 43b, the asymmetry of the size, shape, and arrangement position is not a significant problem.

  Similarly, in translational drive in the tracking direction, an electromagnetic force acts on the tracking coils 41a and 41b in the same direction (a direction orthogonal to the radial tilt shaft 203). For this reason, the asymmetry of the separation distance (arrangement position) of the two tracking coils 41a and 41b with respect to the radial tilt shaft 203 is not a significant problem. In the present embodiment, the tracking coils 41a and 41b are arranged so that a rotational moment around the radial tilt shaft 203 is not generated by the electromagnetic force generated by the tracking coils 41a and 41b.

  Note that the gap between the coils and the magnets facing each other is preferably as small as possible in order to efficiently generate electromagnetic force.

  As described above, in the present embodiment, high-density mounting is achieved while ensuring the passage of the light beam, and the asymmetry in the arrangement that accompanies this is allowed, while the shape of the coil and magnet is asymmetric. The balance as a moment including electromagnetic force is achieved, and a mechanical balance can be secured.

(3) Structure and operation of objective lens actuator (Part 2)
FIG. 13 is a perspective view showing a state where the movable portion 34 and the suspension wire are removed from the objective lens actuator 10.

  The base yoke 35 is provided with a lower opening 35a in the bottom wall and a front opening 35b in the front side wall.

  Below the base yoke 35, a raising mirror 205 disposed in an optical pickup (not shown) is disposed for guiding the light beam 204 to the objective lens 24, and a part thereof is a lower opening. It penetrates 35 a and enters the objective lens actuator 10.

  FIG. 14 is a diagram showing the positional relationship among the objective lens 24, the raising mirror 205, and the light beam 204.

  The light beam 204 input from the front of the objective lens actuator 10 is reflected by the rising mirror 205 and enters the objective lens 24 along the optical axis direction of the objective lens 24.

  FIGS. 15 and 16 are diagrams showing the positional relationship between the raising mirror 205 and the lens holder 33. The rising mirror 205 is configured to be accommodated in the lens holder 33 after passing through the lower opening 35 a of the base yoke 35. Further, in order to guide the light beam 204 to the rising mirror 205, a semicircular cutout 208 is formed on the front side wall of the lens holder 33. As described above, by accommodating a part of the rising mirror 205 in the lens holder 33, the objective lens actuator 10 and the optical pickup 50 can be integrally thinned.

  A reinforcing protrusion 209 is formed on the front side wall of the lens holder 33 at a position opposite to the semicircular cutout 208.

  17 and 18 are diagrams showing a detailed structure of the lens holder 33. FIG. FIG. 17 is a perspective view of the lens holder 33 as viewed from the front, and FIG. 18 is a perspective view of the lens holder 33 inverted upside down.

  The lens holder 33 is formed of a lightweight and highly rigid material such as an engineering plastic, for example, a liquid crystal polymer. The lens holder 33 has a substantially rectangular triple box-type hollow structure, and two holes 206a and 206b through which the magnetic yokes 207a and 207b pass are provided on both sides in the tracking direction across the objective lens 24.

  In order to reduce the thickness, a part of the rising mirror 205 is accommodated in the lens holder 33, and the front side wall of the lens holder 33 is guided to guide the light beam 204 to the rising mirror 205. Is provided with a semi-circular cutout 208.

  The reinforcing protrusion 209 is provided for the purpose of preventing the rigidity of the lens holder 33 in the radial tilt direction from being lowered due to the provision of the semicircular cutout 208.

  In order to achieve high-speed data transfer in the optical disc apparatus, it is essential to increase the higher order resonance frequency of the movable portion 34 in addition to the increase in thrust of the objective lens actuator 10, but the lens holder 33 having the above structure. By using, it is possible to significantly increase the high-order resonance frequency in the focus direction and the tracking direction.

  The objective lens actuator 10 described above can increase the thrust in the three axial directions, and the thrust of the focus coils 42a and 42b and the radial tilt coils 43a and 43b can be arbitrarily set by changing the thickness of each coil as appropriate. Can be set.

  Further, by optimizing the structure of the lens holder 33 and greatly increasing the rigidity, it is possible to realize an extremely high higher-order resonance frequency.

  As a result, it is possible to realize a high-performance, high-speed optical disc apparatus that can cope with high-speed data transfer and can suppress the tilt of the objective lens 24 in the radial tilt direction even when moving in the tracking direction. Furthermore, by adopting a structure in which a part of the rising mirror disposed in the optical pickup is disposed in the holding body, the ultra-thin objective lens actuator 10 that can be mounted on a notebook personal computer or the like can be realized.

(4) Second Embodiment FIG. 19 is a diagram showing a coil configuration according to the second embodiment of the present invention. In the second embodiment, the radial tilt coils 43a and 43b in the first embodiment are omitted, and the focus / radial tilt combined coils 46a and 46b and the tracking coils 41a and 41b are constituted by four coils. In this case, the focus radial tilt combined coils 46a and 46b are not connected in series, but are connected to the triaxial control unit 60 in parallel. The control of the focus direction can be realized by controlling the two focus radial tilt and use coils 46a and 46b by driving them in the same phase. Further, the control in the radial tilt direction can be realized by differentially driving and controlling the two focus radial tilt combined coils 46a and 46b.

  FIG. 20 is a perspective view showing the positional relationship between the magnet and each drive coil in the second embodiment. The focus radial tilt combined magnets 47a and 47b are formed by joining two magnets in the vertical direction so that the N pole and the S pole are adjacent to each other in the focus direction (vertical direction in FIG. 20). As a result, a magnetic flux 210 from the N pole of the upper magnet to the S pole of the lower magnet is generated, and the focus radial tilt combined coils 46a and 46b are disposed in this magnetic flux. An electromagnetic force is generated between the magnetic flux and the current flowing through the focus radial tilt combined coils 46a and 46b.

  In the first embodiment, the focus coils 42a and 42b and the radial tilt coils 43a and 43b are arranged separately and independently. However, in the second embodiment, the focus coil and the radial tilt coil are combined. Two focus radial tilt combined coils 46a and 46b are opposed to the two focus radial tilt combined magnets 47a and 47b, respectively, and are arranged diagonally with the objective lens 24 interposed therebetween. In this case, the control of the focus direction can be realized by controlling the two focus radial tilt and use coils 46a and 46b in the same phase. Further, the control in the radial tilt direction can be realized by differentially driving and controlling the two focus radial tilt combined coils 46a and 46b.

  Note that the present invention is not limited to the above-described embodiments as they are, and can be embodied by variously modifying the constituent elements without departing from the scope of the invention in the implementation stage. For example, the direction of the magnetic poles of the various magnets is not limited to that illustrated, and a configuration in which the N pole and the S pole are interchanged is naturally possible. In this case, the current direction of the corresponding various coils can be appropriately changed. That's fine. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above-described embodiments. For example, some components may be deleted from all the components shown in the embodiment.

The block diagram which shows the structural example of one Embodiment of the information recording / reproducing apparatus which concerns on this invention. The external appearance perspective view seen from the front which shows the structural example of an objective-lens actuator. The external appearance perspective view seen from back which shows the example of composition of an objective lens actuator. The disassembled perspective view which shows the structural example of an objective-lens actuator. The perspective view seen from the front which shows the positional relationship of a lens holder and each drive coil. The perspective view seen from the back which shows the positional relationship of a lens holder and each drive coil. The perspective view of the lens holder seen from the front. The perspective view of the lens holder seen from back. The perspective view of the drive coil seen from the front. The perspective view explaining the positional relationship of a magnet and each drive coil. The top view explaining the positional relationship of a magnet and each drive coil. The top view of an objective lens actuator. The perspective view explaining arrangement | positioning of a raising mirror. The perspective view explaining the positional relationship of a raising mirror and an objective lens. The perspective view explaining the arrangement relationship of a lens holder and a raising mirror. The front view explaining the positional relationship of the semicircle-shaped notch of a lens holder and a reinforcement protrusion. The perspective view explaining the positional relationship of the semicircle-shaped notch of a lens holder and a reinforcement protrusion. The perspective view which looked at the structure of the lens holder from the bottom face side. The perspective view of the drive coil seen from the front in 2nd Embodiment. The perspective view which shows the positional relationship of the magnet in 2nd Embodiment, and each drive coil.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Objective lens actuator 24 Objective lens 33 Lens holder 34 Movable part 35 Yoke base 35a Lower opening 35b Front opening 36 Gel holder 37 Fixed end circuit board 38a, 38b, 38c Suspension wire 39a, 39b, 39c Suspension wire 41a, 41b Tracking coil 42a, 42b Focus coils 43a, 43b Radial tilt coils 44a, 44b Tracking magnets 45a, 45b Focus magnets 46a, 46b Focus radial tilt combined coils 47a, 47b Focus radial tilt combined magnets 50 Optical pickup 52 Collimating lens 60 Triaxial control unit 70 Reproduction processing unit 80 Recording processing units 91a, 91b Focus / radial tilt bobbins 92a, 92b Tracking bobbin 100 Information recording Raw device 200 the optical disk 203 radial tilt axis 204 light beam 205 raising mirror 206a, 206b holes 207a, 207b the magnetic yoke 208 semicircular notches 209 reinforcing projections

Claims (10)

In an objective lens actuator capable of translational drive in the tracking direction, translational drive in the focus direction, and rotational drive around the radial tilt axis,
An objective lens that focuses the laser beam on the information recording surface of the optical disc;
A lens holder that has a hollow substantially rectangular parallelepiped shape, has four coil bobbins for winding a coil on its side surface, and fixes the objective lens to the center of the upper surface thereof;
A pair of tracking coils that are wound diagonally around the coil bobbin disposed on the side surface of the lens holder with the objective lens interposed therebetween, and that translate the lens holder in the tracking direction;
The lens holder, which is wound around the coil bobbin diagonally across the objective lens so as to straddle the radial tilt axis at a position different from the tracking coil on the side surface of the lens holder, is driven to rotate around the radial tilt axis A pair of radial tilt coils to
A pair of focus coils wound around each of the radial tilt coils and driving the lens holder in translation in the focus direction;
A pair of tracking magnets disposed at positions facing each of the tracking coils;
A pair of focus magnets disposed at positions facing each of the focus coils;
A fixed portion to which the tracking magnet and the focus magnet are fixed;
One end is fixed to the fixing portion, the other end is fixed to the lens holder, and the suspension wire that holds the lens holder in a hollow state,
With
Each of the pair of focus coils and each of the pair of focus magnets disposed across the radial tilt axis has at least one of a shape, a size, a mass, and an arrangement position with respect to the radial tilt axis. An objective lens actuator characterized by being configured so that the moments around the radial tilt axis cancel each other and balance when driven in translation in the focus direction.   Each of the pair of focus coils disposed across the radial tilt axis is configured such that moments around the radial tilt axis cancel each other and balance when the same current is supplied to the pair of focus coils. The objective lens actuator according to claim 1.   The lens holder houses a part of a rising mirror that guides laser light input / output from a direction orthogonal to the optical axis of the objective lens onto the optical axis, and is placed in front of one of the side walls of the lens holder. 2. The objective lens actuator according to claim 1, wherein the objective lens actuator is formed so as to have a substantially semicircular notch through which laser light to be written out is passed.   The objective lens actuator according to claim 3, wherein the lens holder has a reinforcing protrusion formed on the side wall at a position opposite to the substantially semicircular cutout. In an objective lens actuator capable of translational drive in the tracking direction, translational drive in the focus direction, and rotational drive around the radial tilt axis,
An objective lens that focuses the laser beam on the information recording surface of the optical disc;
A lens holder that has a hollow substantially rectangular parallelepiped shape, has four coil bobbins for winding a coil on its side surface, and fixes the objective lens at the center of the upper surface thereof;
A pair of tracking coils that are wound diagonally around the coil bobbin disposed on the side surface of the lens holder with the objective lens interposed therebetween, and that translate the lens holder in the tracking direction;
The lens holder, which is wound around the coil bobbin diagonally across the objective lens so as to straddle the radial tilt axis at a position different from the tracking coil on the side surface of the lens holder, is driven to rotate around the radial tilt axis Then, a pair of focus radial tilt combined coils that are driven in translation in the focus direction,
A pair of tracking magnets disposed at positions facing each of the tracking coils;
A pair of focus radial tilt combined magnets disposed at positions facing each of the focus radial tilt combined coils;
A fixed portion to which the tracking magnet and the focus radial tilt combined magnet are fixed;
One end is fixed to the fixing portion, the other end is fixed to the lens holder, and the suspension wire that holds the lens holder in a hollow state,
With
Each of the pair of focus radial tilt combined coils and each of the pair of focus radial tilt combined magnets disposed across the radial tilt axis has at least one of a shape, a dimension, a mass, and a disposition position as described above. An objective lens actuator characterized by being asymmetric with respect to the radial tilt axis and configured so that moments about the radial tilt axis cancel each other and balance when driven in translation in the focus direction. An optical pickup comprising an objective lens actuator;
A drive controller for controlling the drive of the objective lens actuator;
A reproduction processing unit for reproducing the signal output from the optical pickup;
A recording processing unit that modulates recording data and outputs the modulated data to the optical pickup as a laser control signal;
The objective lens actuator is
In an objective lens actuator capable of translational drive in the tracking direction, translational drive in the focus direction, and rotational drive around the radial tilt axis,
An objective lens that focuses the laser beam on the information recording surface of the optical disc;
A lens holder that has a hollow substantially rectangular parallelepiped shape, has four coil bobbins for winding a coil on its side surface, and fixes the objective lens at the center of the upper surface thereof;
A pair of tracking coils that are wound diagonally around the coil bobbin disposed on the side surface of the lens holder with the objective lens interposed therebetween, and that translate the lens holder in the tracking direction;
The lens holder, which is wound around the coil bobbin diagonally across the objective lens so as to straddle the radial tilt axis at a position different from the tracking coil on the side surface of the lens holder, is driven to rotate around the radial tilt axis A pair of radial tilt coils to
A pair of focus coils wound around each of the radial tilt coils and driving the lens holder in translation in the focus direction;
A pair of tracking magnets disposed at positions facing each of the tracking coils;
A pair of focus magnets disposed at positions facing each of the focus coils;
A fixed portion to which the tracking magnet and the focus magnet are fixed;
One end is fixed to the fixing portion, the other end is fixed to the lens holder, and the suspension wire that holds the lens holder in a hollow state,
With
Each of the pair of focus coils and each of the pair of focus magnets arranged across the radial tilt axis has at least one of shape, size, mass, and arrangement position with respect to the radial tilt axis. An information recording / reproducing apparatus configured to be asymmetric and configured so that moments about the radial tilt axis cancel each other and balance when driven in translation in the focus direction.   Each of the pair of focus coils disposed across the radial tilt axis is configured such that moments around the radial tilt axis cancel each other and balance when the same current is supplied to the pair of focus coils. The information recording / reproducing apparatus according to claim 6.   The lens holder houses a part of a rising mirror that guides laser light input / output from a direction orthogonal to the optical axis of the objective lens onto the optical axis, and is placed in front of one of the side walls of the lens holder. 7. The information recording / reproducing apparatus according to claim 6, wherein the information recording / reproducing apparatus is formed so as to have a substantially semicircular notch through which laser light to be written out is passed.   9. The information recording / reproducing apparatus according to claim 8, wherein the lens holder has a reinforcing protrusion formed on the side wall at a position opposite to the substantially semicircular cutout. An optical pickup comprising an objective lens actuator;
A drive controller for controlling the drive of the objective lens actuator;
A reproduction processing unit for reproducing the signal output from the optical pickup;
A recording processing unit that modulates recording data and outputs the modulated data to the optical pickup as a laser control signal;
The objective lens actuator is
In an objective lens actuator capable of translational drive in the tracking direction, translational drive in the focus direction, and rotational drive around the radial tilt axis,
An objective lens that focuses the laser beam on the information recording surface of the optical disc;
A lens holder that has a hollow substantially rectangular parallelepiped shape, has four coil bobbins for winding a coil on its side surface, and fixes the objective lens at the center of the upper surface thereof;
A pair of tracking coils that are wound diagonally around the coil bobbin disposed on the side surface of the lens holder with the objective lens interposed therebetween, and that translate the lens holder in the tracking direction;
The lens holder, which is wound around the coil bobbin diagonally across the objective lens so as to straddle the radial tilt axis at a position different from the tracking coil on the side surface of the lens holder, is driven to rotate around the radial tilt axis Then, a pair of focus radial tilt combined coils that are driven in translation in the focus direction,
A pair of tracking magnets disposed at positions facing each of the tracking coils;
A pair of focus radial tilt combined magnets disposed at positions facing each of the focus radial tilt combined coils;
A fixed portion to which the tracking magnet and the focus radial tilt combined magnet are fixed;
One end is fixed to the fixing portion, the other end is fixed to the lens holder, and the suspension wire that holds the lens holder in a hollow state,
With
Each of the pair of focus radial tilt combined coils and each of the pair of focus radial tilt combined magnets disposed across the radial tilt axis has at least one of a shape, a dimension, a mass, and a disposition position as described above. An information recording / reproducing apparatus configured to be asymmetric with respect to the radial tilt axis and configured to cancel and balance the moments about the radial tilt axis when driven in translation in the focus direction.

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