JP2006190475A - Objective lens drive device of optical pickup - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To dispense with a coil and a magnet for adjusting the tilt of an objective lens. <P>SOLUTION: A magnetic circuit including at least one magnet 5 magnetized in 4 poles is formed. A coil unit 3 where focus coils 3fl and 3fr and tracking coils 3tu and 3td are mounted on the same plane in the magnetic gap 5g of the magnetic circuit is arranged, and current is supplied to each of the plurality of focus coils 3fl and 3fr within the coil unit 3 to carry out focus servo by the sum of driving forces of each. Moreover, a moment is generated around the center of gravity of a movable part by a difference of the driving forces to carry out adjusting of tilt of the objective lens 2 simultaneously. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an objective lens driving device for an optical pickup that constitutes an optical disc apparatus capable of optically reading information by projecting a light spot onto a recording medium on a disk.

  An optical pickup constituting an optical disk device is generally composed of an objective lens driving device having an objective lens and an optical system that transmits and receives light to and from the objective lens, and the objective lens driving device is mounted on a mounting base of the optical system block. It has an arranged structure. The objective lens driving device is composed of a movable part having an objective lens, a focus coil, and a tracking coil and a fixed part having a magnetic circuit. The movable part is partially surrounded by an elastic damper material such as a viscoelastic material. -It is supported from the fixed part by four held wires.

  In addition to driving the objective lens in the focus direction and tracking direction, an objective lens driving device for correcting coma aberration and astigmatism of the spot imaged on the disk is disclosed in JP-A-9-231595. Are known. As shown in FIGS. 7, 8, and 9, this conventional technique includes at least a pair of optical sensors 301 and 302 in the optical disk radial direction or tangential direction of the objective lens 103 on the optical disk facing surface of the lens holder 101. The coil 105 for correcting the tilt is provided on one side surface or both side surfaces of the lens holder 101 in the radial direction of the optical disk, and the coil 105 is used to correct the tilt on the yokes 113 and 114 facing the side surface of the lens holder 101. Corresponding to the arrangement, a pair of magnet members 106 and 107 having opposite polarities are provided, and the inclination of the optical disk 100 is detected based on the outputs of the optical sensors 301 and 302. The inclination detection angle, the collimator optical axis and the objective lens optical axis are detected. The coil 105 for correcting the inclination is driven by current based on the calculated value of the deviation from the magnet member 10 having the opposite polarity. Drives the side surface of the lens holder 101 by the electromagnetic interaction with the 107, tilt freely, servo-controls, it is characterized in.

  The pair of optical sensors 301 and 302 are attached to both sides of the objective lens 103 of the lens holder 101, and as shown in FIG. 8, ± first-order light 201 and 202 emitted from the optical head and diffracted by the optical disk groove. Is received. As shown in FIG. 10, the electric signals from the optical sensors 301 and 302 are amplified by the amplifiers 407 and 408 and differentially input to the differential amplifier 403. The inclination between the optical disc 100 and the lens holder 101 is calculated from the output of the differential amplifier 403.

  As shown in FIG. 10, from this inclination angle and the deviation between the optical axis of the objective lens and the collimator optical axis, the optimum lens inclination is preferably obtained by a preset unit 404 set in a ROM (read only memory), and the calculation of both is performed. Based on the result, the inclination correction coil 105 is driven via the phase compensation circuit 405 and the drive amplifier 406 for applying the servo.

  The lens holder 101 is provided with two slits 102 through which the yoke member 109 passes in the plane, the objective lens 103 is mounted at the center, and a pair of opposing side surfaces for tracking driving. A total of four square flat coils 104 are provided. In addition, a pair of rectangular flat coils are provided on the opposite side surfaces in the optical disc radial direction (R) as the coil 105 that performs inclination correction, and copper foil portions 115 and 116 are provided above and below the coil 105 that performs inclination correction. A printed circuit board (not shown) supported in this manner is attached.

  Yoke portions 109 and 110 project from the actuator base 108, and constitute a substantially closed magnetic path for driving in the focus direction and the tracking direction via the magnets 111 and 112, respectively. Further, on both side surfaces of the actuator base 108, side yokes 113 and 114 for driving the lens holder tilt adjustment, which are U-shaped in plan, are provided. The side yokes 113 and 114 are provided with long magnets 106 and 107 having opposite polarities corresponding to the upper and lower sides of the coil 105 that performs inclination correction.

  In addition, square printed boards 117 and 118 are similarly attached to the actuator base 108 via copper foil portions 119 and 120. Then, phosphor bronze spring wires 121 are fixed by printed boards arranged at both ends of the spring wires 121 and relayed by four to support the lens holder 101 elastically (the spring wire 121 is fixed in a plan view of FIG. 9). reference).

  In FIG. 7, F indicates the focus axis of the moving system of the objective lens actuator, R indicates the tracking axis, and T indicates the optical disk tangent axis.

  Next, the tilt driving of the lens holder 101 in the prior art will be described with reference to FIG. 8. The current direction of the coil 105 that is provided on both side surfaces of the lens holder 101 in the radial direction of the optical disk and corrects left and right tilt is described. When the magnetic field directions of the left and right magnets 106 and 107 that are the same and are provided corresponding to the upper and lower sides of the coil 105 that performs inclination correction are symmetric, the electromagnetic drive of both coils is Fleming's left-hand rule. Therefore, the direction of the electromagnetic driving force differs between the left and right (see arrows F and F ′ in the figure). Accordingly, the center of gravity or the support center of the lens holder 101 is substantially the same point, but the lens holder 101 rotates around this point, and tilt correction with respect to the optical disc 100 can be performed.

JP-A-9-231595

  However, in this prior art, in order to correct the inclination of the objective lens, a coil 105 and magnets 106 and 107 for newly correcting the inclination must be installed separately from the tracking servo and focus servo coils and magnets. Therefore, there was a problem that the cost was increased. In this prior art, the coil 105 and the magnets 106 and 107 for correcting the tilt must be disposed on the side surface in the radial direction of the optical disc 100 of the lens holder 101 that holds the objective lens 103. There was a problem that the width and weight would increase.

  The present invention has been made for the purpose of solving such problems of the prior art.

  Means for solving the above problems will be described below with reference to FIG. 1 corresponding to one embodiment. The present invention is an objective lens driving device for an optical pickup that detects the tilt of an optical disc and adjusts the tilt of the objective lens based on the tilt signal of the optical disc, and includes a magnet including at least one magnet 5 magnetized in four poles. One circuit is formed, and the coil unit 3 having the focus coils 3fl and 3fr and the tracking coils 3tu and 3td mounted on the same plane is disposed in the magnetic gap 5g of the magnetic circuit. The focus coils 3fl and 3fr are respectively supplied with current, and focus servo is performed by the sum of the respective driving forces, and a moment is generated around the center of gravity of the movable part due to the difference in the driving forces to adjust the inclination of the objective lens 2. Are performed simultaneously.

  In the structure configured as described above, not only the focus servo but also the tilt adjustment of the objective lens 2 can be performed by the plurality of focus coils 3fl and 3fr, and a coil and a magnet for adjusting the tilt of the objective lens. Is unnecessary.

  Therefore, according to this invention, the effect that the increase in cost and the enlargement accompanying the inclination adjustment of an objective lens can be avoided is acquired.

  FIG. 1 is a perspective view showing an embodiment of the present invention. In FIG. 1, 1 is a lens holder, 2 is an objective lens, 3 is a coil unit, and 5 is a magnet.

  The lens holder 1 is made of a light metal having a high bending elastic modulus, for example, a magnesium alloy, or a resin made of carbon fiber. By using such a material, the lens holder 1 itself has a high flexural modulus and a high-order resonance frequency. Thereby, it is possible to cope with an increase in the speed of the optical disc apparatus.

  The lens holder 1 is formed with two notches 1a in the tracking direction T. The objective lens mounting portion 1b that holds the objective lens 2 is formed to have a uniform thickness.

  The cutout portion 1a has a reinforcing insulating protective film (not shown) formed on the surface thereof. This is because a light metal having a high bending elastic modulus used for the lens holder 1, such as a magnesium alloy or a resin of carbon fiber, has a high conductivity, so that the insulating property of the coil unit 3 attached to the notch 1a is high. This is to ensure When a reinforcing insulating protective film is not formed on the surface of the cutout portion 1a of the lens holder 1, a reinforcing insulating protective film (not shown) is formed on the portion of the coil unit 3 attached to the cutout portion 1a. To ensure the insulation of the coil unit 3.

  The coil unit 3 is formed by stacking a required number of printed circuit boards 3p formed by stacking two tracking coils 3tu, 3td and two focus coils 3fl, 3fr.

  The above is the case where the focus coils 3fl and 3fr and the tracking coils 3tu and 3td are formed on the printed circuit board 3p. However, even if the focus coils 3fl and 3fr and the tracking coils 3tu and 3td are individually formed on the two printed circuit boards. Good.

  The coil unit 3 is fixed to the lens holder 1 by being inserted into and bonded to the notch 1a. Six V grooves 3v are formed at both ends of the tracking direction T of the coil unit 3, and one ends of the six conductive elastic bodies 4 are fixed to the V grooves 3v by solder 3h. The conductive elastic bodies 4 as lead wires are 6 in total, 2 × 2 4 for driving the focus coil and 2 for driving the tracking coil.

  In order to elastically support the lens holder 1 that is a movable part, four conductive elastic bodies 4 are sufficient. Therefore, when the conductive elastic body 4 is composed of four pieces, any one of the coils is used. Connects lead wires (not shown).

  As shown in FIG. 2, the magnet 5 is magnetized in two poles in the tracking T direction and arranged in two stages in the upper and lower directions in the focus F direction, and is magnetized in four poles. It is glued to. In this case, when the coil unit 3 is disposed in the magnetic gap 5g at the movable neutral position of the movable portion supported in a cantilevered manner so as to be movable by the conductive elastic body 4, that is, at its own weight position in the focus direction F, FIG. 2, the two tracking coils 3tu and 3td are arranged up and down, that is, in the first and second quadrants of the magnet 5, and in the third and fourth quadrants, and the two coils 3tu and 3td are arranged. Tracking servo is performed by supplying optimum upper and lower currents Iu and Id for correcting a tracking error output from the control circuit unit. As shown in FIG. 3, two focus coils 3fl and 3fr are arranged on the left and right, that is, in the first quadrant and the fourth quadrant and in the second quadrant and the third quadrant of the magnet 5, and both coils 3fl. The optimum left and right currents I1 and Ir for simultaneously correcting the focus error and tilt error output from the control circuit unit at 3 fr are supplied to perform focus servo and tilt servo.

  The coil unit 3 is disposed in the magnetic gap 5g, and the other end of the conductive elastic body 4 passes through the wire base 8 and is fixed to the base substrate 9 with solder. Thereby, the focus coils 3fl and 3fr and the tracking coils 3tu and 3td attached to the coil unit 3 are arranged in the magnetic gap 5g, and the movable part including the lens holder 1 for holding the objective lens 2 is magnetized. 5, a fixed part constituted by a yoke base 6, a yoke 7, a wire base 8 and a base substrate 9 is supported in a cantilevered manner so as to be movable.

  The tilt detection of the optical disk is performed by separately preparing a tilt detection sensor or by using a reproduction signal of an optical pickup.

  A tilt error signal and a focus error signal obtained by using a reproduction signal from the tilt detection sensor or the optical pickup are input to the control circuit unit shown in FIG. 4, and a focus error for energizing the focus coils 3f1 and 3fr shown in FIG. In addition, optimal left and right currents I1 and Ir that simultaneously correct the tilt error are calculated and output from the control circuit unit. The objective lens drive device to be controlled performs focus servo by a force that moves in the focus direction F by the sum of the left and right drive forces F1 and Fr shown in FIG. 5A generated by the left and right currents I1 and Ir. Tilt servo is performed by the moment M = F1 × d−Fr × d generated around the center of gravity G due to the difference between the left and right driving forces F1 and Fr. d is a separation distance between the center of gravity G of the lens holder 1 and the focus coils 3f1 and 3fr.

  FIG. 5B is a diagram in the case where Fr is generated in the opposite direction to F1, unlike FIG. 5A. At this time, the force to move in the focus direction F is F1 + (− Fr ) And the tilt is Fl × d − (− Fr × d). In any case, focus servo is performed with a function of (F1 + Fr), and tilt servo is performed with a function of (F1-Fr).

  The left and right focus coils 3fl and 3fr can adjust the tilt of the objective lens 2 as well as the focus servo. Therefore, a coil and a magnet for adjusting the tilt of the objective lens 2 are unnecessary. Therefore, the number of parts is small, the inclination of the objective lens 2 can be adjusted at a low cost, and the entire objective lens driving device can be reduced in size.

  If the tracking coils 3tu and 3td are energized, a driving force in the same direction in the tracking direction T is generated in both the coils 3tu and 3td, and the objective lens 2 is moved in the tracking direction T corresponding to the eccentricity of the recording medium. Can do.

  By inserting and adhering the coil unit 3 to the notch 1a of the lens holder 1, only one magnetic gap 5g is sufficient. Therefore, this also reduces the number of components, makes it possible to adjust the inclination of the objective lens 2 at a low cost, and to reduce the size of the entire objective lens driving device.

  Note that each of the tracking coils 3tu and 3td may be constituted by one. Since currents are separately supplied to the upper and lower tracking coils 3tu and 3td, they are not connected in series but are independent systems.

  The above is the case where the focus coils 3fl and 3fr and the tracking coils 3tu and 3td are stacked on the printed board 3p, but the focus coils 3fl and 3fr and the tracking coils 3tu and 3td are individually formed on the two printed boards. May be.

  In the above, tilt servo is performed by the left and right focus coils 3fl and 3fr. Although not shown, the upper and lower two arranged in the first quadrant and the second quadrant and the third quadrant and the fourth quadrant of the magnet 5 are shown. The upper and lower optimum currents Iu and Id that simultaneously correct the tracking error and tilt error output from the control circuit section are supplied to the tracking coils 3tu and 3td, and moved in the tracking direction T by the sum of the upper and lower driving forces Fu and Fd. The tracking servo may be performed by the force to be applied, and the tilt servo may be performed by the moment generated around the center of gravity G due to the difference between the upper and lower driving forces Fu and Fd.

  The above is a case where the notch 1a is formed in the center of the lens holder 1, the coil unit 3 is inserted and bonded, and one magnetic gap 5g is formed. As shown, the lens holder 1 has two slits 11 through which the magnet 5 and the yoke 7 pass in the plane, the objective lens 2 is mounted at the center, and a pair perpendicular to the tracking direction T. Two support pieces 12 to which one end of the conductive elastic body 4 is fixed are vertically provided on the side surfaces of the conductive elastic body 4, and the coil unit 3 is bonded and fixed to a pair of side surfaces parallel to the tracking direction T. In addition, even if two magnetic gaps 5g are formed and tilt adjustment of the objective lens 2, that is, tilt servo is performed using the focus coil 3f or the tracking coil 3t, The effect of the like can be obtained.

  Even when two magnetic gaps 5g are formed, the coil unit 3 is formed by stacking a plurality of printed boards on which the focus coil 3f and the tracking coil 3t are individually mounted, or on which the focus coil and the tracking coil are mounted. It is formed by stacking a plurality of printed circuit boards.

  In the above, the magnetic gap 5g is formed by facing two magnets 5 bonded to the yoke 7 on the yoke base 6 as shown in FIGS. It may be configured that the magnet 5 and the yoke 7 are opposed to each other. Furthermore, the yoke 7 which opposes may be omitted, and the space from the N pole to the S pole may be used as the magnetic gap 5g.

It is a disassembled perspective view which shows one Embodiment of this invention. FIG. 6 is a layout diagram showing a positional relationship between a magnet magnetized with four poles and a tracking coil at a self-weight position in a focus direction. FIG. 5 is an arrangement diagram showing a positional relationship between a magnet magnetized with four poles and a focus coil at a self-weight position in a focus direction. It is a block diagram which shows the circuit structure of the focus servo and tilt servo in one Embodiment of this invention. FIGS. 4A and 4B are explanatory diagrams of a focus servo and a tilt servo according to an embodiment of the present invention. FIG. 5A shows a case where a driving force in the same direction is generated, and FIG. It is a disassembled perspective view which shows the other form of implementation of this invention. It is a disassembled perspective view of a prior art. It is explanatory drawing in the inclination correction drive in a prior art. It is a top view of the actuator of a prior art. It is a block diagram which shows the structure of the circuit which performs the tilt servo in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lens holder 2 Objective lens 3 Coil unit 3fl Focus coil 3fr Focus coil 3t Tracking coil 5 Magnet

Claims (4)

In an objective lens driving device of an optical pickup that detects the tilt of an optical disc and adjusts the tilt of the objective lens based on an optical disc tilt signal, at least one magnetic circuit including a magnet magnetized in four poles, And forming a coil unit in which the focus coil and the tracking coil are mounted on the same plane in the magnetic gap of the magnetic circuit, and supplying current to each of the plurality of focus coils in the coil unit, respectively. An objective lens driving device for an optical pickup that performs focus servo by the sum of the driving forces and simultaneously adjusts the tilt of the objective lens by generating a moment around the center of gravity of the movable part due to the difference in driving force In an objective lens driving device of an optical pickup that detects the tilt of an optical disc and adjusts the tilt of the objective lens based on an optical disc tilt signal, at least one magnetic circuit including a magnet magnetized in four poles, Forming a coil unit in which a focus coil and a tracking coil are mounted on the same plane in the magnetic gap of the magnetic circuit, and supplying a current to each of the plurality of tracking coils in the coil unit, respectively. An objective lens driving device for an optical pickup, which performs tracking servo by the sum of the driving forces and simultaneously adjusts the tilt of the objective lens by generating a moment around the center of gravity of the movable part due to the difference in driving force In an objective lens driving device for an optical pickup that detects the tilt of an optical disk and adjusts the tilt of the objective lens based on the tilt signal of the optical disk, at least one magnetic circuit including at least one magnet magnetized with four poles, And forming a coil unit in which the focus coil and the tracking coil are mounted on the same plane in the magnetic gap of the magnetic circuit, and supplying current to each of the plurality of focus coils in the coil unit, respectively. An objective lens driving device for an optical pickup that performs focus servo by the sum of the driving forces and simultaneously adjusts the tilt of the objective lens by generating a moment around the center of gravity of the movable part due to the difference in driving force In an objective lens driving device for an optical pickup that detects the tilt of an optical disk and adjusts the tilt of the objective lens based on the tilt signal of the optical disk, at least one magnetic circuit including at least one magnet magnetized with four poles, Forming a coil unit in which a focus coil and a tracking coil are mounted on the same plane in the magnetic gap of the magnetic circuit, and supplying a current to each of the plurality of tracking coils in the coil unit, respectively. An objective lens driving device for an optical pickup, which performs tracking servo by the sum of the driving forces and simultaneously adjusts the tilt of the objective lens by generating a moment around the center of gravity of the movable part due to the difference in driving force

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