JP2006040356A - Lens actuator, optical head, and optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an actuator which includes a simple configuration and is capable of saving power and using a spindle motor of great torque when mounted on an optical disk device. <P>SOLUTION: A permanent magnet 6a and a yoke 7a are disposed in an insertion hole formed at a lens holder 2, and a permanent magnet 6b and a yoke 7b are disposed in voids of leaf springs 4a, 4b. A yoke 7c is inserted and disposed in an insertion hole formed at a coil bobbin 21. A magnetic path is formed from the yokes 7a-7c, and magnetic flux leaking outside the actuator is reduced. The permanent magnet 6b, the coil bobbin 21, the permanent magnet 6a and the lens holder 2 (lens 1) are disposed in order in the lengthwise direction of the leaf springs 4a and 4b, so that when mounted on an optical disk device, a distance between the spindle motor and an optical axis of an objective lens can be shorted and the spindle motor of great torque is available. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical head for irradiating light for recording information on an optical information recording medium or reproducing information recorded on the optical information recording medium, and an optical disc apparatus including the same, The present invention relates to a technique for correcting aberration due to variation in the thickness of a light transmission layer of an optical information recording medium.

  In recent years, for example, in the field of recording or reproducing information using an optical information recording medium (optical disk) as a recording medium, a small-sized and large-capacity optical recording / reproducing apparatus has been developed. In order to realize a large capacity, the development of a reduction in the beam spot diameter by shortening the wavelength of the light emitted from the optical head and increasing the NA of the objective lens (NA: numerical aperture) is in progress.

  In general, an optical information recording medium has an information recording surface covered with a transparent light transmission layer, and light is irradiated through the light transmission layer during recording or reproduction. The light transmission layer may be a substrate on which an information recording surface is formed at the time of manufacturing an optical information recording medium, or may be a cover layer that protects the information recording surface after formation.

  When NA is increased, coma aberration is likely to occur due to an angle change between the objective lens and the substrate. Causes of this angle change include the warp of the optical information recording medium itself, the tilt of the spindle motor that rotates the optical information recording medium, and the tilt generated by the objective lens drive mechanism mounted on the optical head. It is difficult to increase the angle accuracy in accordance with the increase in NA.

  On the other hand, the objective lens is designed to form a beam spot with less spherical aberration on the information recording surface of the optical information recording medium when passing through a light transmitting layer having a specific optical thickness. If the thickness of the layer has an error with respect to the assumed optical thickness at the time of design, spherical aberration occurs. The spherical aberration due to the error in the thickness of the light transmission layer becomes very large as the NA increases, and the influence of the optical thickness error of the light transmission layer of the optical information recording medium cannot be ignored.

  The optical thickness is determined by the thickness and refractive index of the light transmission layer of the optical information recording medium through which light is transmitted. Even if the thickness of the light transmission layer of the optical information recording medium is different, the optical information recording medium It is assumed that the optical thicknesses are equal when the magnitudes of the spherical aberrations of the beam spots generated by passing through the light-transmitting layer match. Even when the recording layer is composed of a plurality of layers, the optical thickness is determined by the thickness and refractive index of each light-transmitting layer.

  An actuator using a leaf spring as shown in FIG. 15 is known as a method for correcting spherical aberration caused by a change in the thickness of the light transmission layer of the optical information recording medium (for example, Patent Document 1). FIG. 15 is a perspective view of an actuator using a leaf spring according to the prior art.

  As shown in FIG. 15, the actuator according to the conventional technique has a lens 1 for spherical aberration correction attached to a lens holder 2. A coil 3 is attached to the lens holder 2 by being wound in a direction in which the optical axis of the lens 1 is wound. The lens holder 2 is supported by one end of two parallel leaf springs 4a and 4b. One end of the two parallel leaf springs 4 a and 4 b is fixed by fixing members 9 and 10, and the other end is fixed to the lens holder 2. On the opposite side of the leaf springs 4a and 4b, a permanent magnet 6 is installed with a small distance from the coil 3. The permanent magnet 6 is attached to a yoke 7 made of a ferromagnetic material such as a steel plate, and the yoke 7 is attached to a base 8. Further, the permanent magnet 6 has an N pole on the side facing the coil 3 and is magnetized in the direction of arrow A in FIG.

  When a current is passed through the coil 3, the current passes through the magnetic field generated by the permanent magnet 6, and a Lorentz force is generated in the coil 3. Thereby, a force is applied to the lens holder 2 in the optical axis direction of the lens 1. Since the lens holder 2 is supported by the parallel leaf springs 4a and 4b, the leaf springs 4a and 4b are bent by the Lorentz force, and the lens holder 2 moves in the optical axis direction.

  This actuator is disposed between the objective lens of the optical recording / reproducing apparatus and the raising mirror, or between the raising mirror and the beam splitter. Then, the spherical aberration of light incident on the optical information recording medium from the objective lens is changed by moving the spherical aberration correcting lens 1 in the optical axis direction, and the optical thickness of the light transmission layer of the optical information recording medium is changed. It cancels out spherical aberration due to differences or errors.

  An advantage of using a leaf spring is that when a multilayer recording medium is used as the optical information recording medium, a response (operation) at the time of interlayer jump is fast. Further, it is advantageous when driving an optical information recording medium having a large optical thickness error distribution of the light transmission layer by feedback control.

JP 2003-45067 A (paragraphs [0026]-[0033], FIG. 4)

  However, according to the actuator shown in FIG. 15, the length of the coil 3 wound around the side surface of the lens holder 2 and the magnetic flux leaking out of the actuator can increase the magnetic flux density passing through the effective portion of the coil. It was not possible to improve the sensitivity. As a result, since the sensitivity is poor, it is necessary to increase the value of the current flowing through the coil, and there is a problem that power saving cannot be achieved.

  If the actuator according to the prior art shown in FIG. 15 is mounted on the optical recording / reproducing apparatus, for example, when the actuator according to the prior art is arranged between the beam splitter and the rising mirror, a space on the spindle motor side is required. Therefore, there is a problem that a spindle motor having a large torque necessary for high-speed recording / reproducing cannot be used.

  In many cases, the optical recording / reproducing apparatus is limited in the thickness direction perpendicular to the optical information recording medium, and the thickness of the optical head and the spindle motor is limited. For this reason, when this actuator is disposed between the rising mirror and the beam splitter, it is desirable to install the actuator with the longitudinal direction of the actuator being a horizontal direction on the optical information recording medium.

  In addition, even if this actuator is located between the objective lens and the rising mirror due to the space inside the optical recording / reproducing apparatus, the arrangement of each device, or the design of the optical head itself, the objective lens actuator located in the immediate vicinity of the optical axis It is desirable to reduce the thickness of the optical head by arranging the actuator so that the longitudinal direction of the actuator is the radial direction of the optical information recording medium.

  Therefore, when the conventional actuator is mounted on the optical recording / reproducing apparatus, the permanent magnet 6 and the yoke 7 are installed on the tip side of the actuator, so that the permanent axis is closer to the rotation axis side of the optical information recording medium than the optical axis of the objective lens. The magnet 6 and the yoke 7 need to be arranged. Therefore, in order to provide a space for arranging the permanent magnet 6 and the like, the diameter of the spindle motor must be reduced by the amount of the permanent magnet 6 and the yoke 7.

  A spindle motor generally has a larger torque as its volume increases. When the torque of the spindle motor is increased, the time until the target rotational speed is reached is shortened. In general, the rotational speed can be increased, which is advantageous for speeding up recording and reproduction of the optical recording / reproducing apparatus. However, when the actuator according to the prior art is used in an optical recording / reproducing apparatus, it is necessary to reduce the diameter of the spindle motor by the amount of the permanent magnet 6 and the yoke 7, and the volume is reduced by that amount in combination with the thickness limitation described above. Since a spindle motor must be used, it is difficult to speed up recording and reproduction.

  The present invention solves the above-described problems, and provides an actuator that has a simple configuration, has a higher sensitivity than conventional actuators, and can save power.

  Another object of the present invention is to provide an actuator that does not impair the space for the spindle motor when mounted on an optical recording / reproducing apparatus. By mounting the actuator of the present invention, a spindle motor having a larger torque can be used for the space compared to the case of mounting a conventional actuator, and information can be recorded and reproduced at high speed. It is an object of the present invention to provide an optical head capable of recording and an optical recording / reproducing apparatus including the optical head.

  The invention according to claim 1 is installed in a light source, an objective lens that focuses light emitted from the light source on an information recording surface of an optical information recording medium, and an optical path between the light source and the objective lens. A lens actuator that moves the lens in the optical path direction, one end of which is fixed to a fixed portion and the other end is movable in the optical path direction. A leaf spring, a movable member extending in the longitudinal direction from the other end of the leaf spring, the lens and the coil being installed, and a magnet and a magnet installed so as to sandwich the coil from the inside and outside of the coil And an actuator for a lens.

  According to a second aspect of the present invention, in the lens actuator according to the first aspect, the magnets are disposed outside the coil at a predetermined interval and on opposite sides of the coil. The magnetic material comprises at least two magnet members, and the magnetic material is installed inside the coil so as to sandwich the coil from the inside and outside of the coil with at least one of the magnet members. It is characterized by that.

  When a current is passed through the coil, the current passes through the magnetic field generated by the magnet, and a Lorentz force is generated in the coil. Magnetic flux emitted from the magnet (a plurality of magnet members) passes through the coil. Since a magnetic material is installed in the coil, the magnetic flux that has passed through the coil is received by the magnetic material. As described above, since the magnetic material is disposed so as to receive the magnetic flux passing through the effective portion of the coil, the magnetic flux leaking out of the actuator can be reduced. As a result, the density of the magnetic flux passing through the effective portion of the coil can be increased, so that the sensitivity can be improved and the movable range of the leaf spring can be expanded with a small current. As a result, power saving can be achieved.

  In addition, there is one aspect of the leakage flux reduction as follows. In the coil, the surface (side) opposite to the surface facing the magnet is opposite to the Lorentz force generated on the “facing surface (side)” by the magnetic field lines passing through the “facing surface (side)”. Directional Lorentz force is generated. Although the magnitude of this force is smaller than that of the “opposing surface (side)”, it is a factor that lowers the sensitivity of the actuator. Therefore, by providing a magnetic material between the surface (side) facing the magnet and the opposite surface (side) in the coil, the magnetic flux leakage that affects the opposite surface (side) is greatly reduced. can do. For this reason, by installing a magnetic material that receives magnetic flux passing through the coil, the sensitivity of the actuator can be improved, and as a result, power saving can be achieved. That is, the movable range of the actuator can be expanded even with a small current.

  A third aspect of the present invention is the lens actuator according to the first or second aspect, wherein the coil and the magnet are located between the fixed portion and the lens. It is characterized by being.

  A fourth aspect of the present invention is the lens actuator according to the third aspect, wherein the magnet is disposed between the coil and the lens or between the coil and the fixing portion. It is characterized by this.

  In this invention, the coil is not wound so as to include the lens, and the coil is installed on the movable member at a predetermined distance from the lens. In addition, the movable member extends in the longitudinal direction of the leaf spring, and the coil and the magnet (a plurality of magnet members) are installed between the fixed portion and the lens, so that the lens is installed on the distal end side of the actuator. It will be.

  Therefore, when the actuator according to the present invention is mounted on an optical recording / reproducing apparatus, the diameter of the spindle motor can be increased compared to the case where a conventional actuator is mounted, and a spindle motor having a large torque can be used. . This is because a lens is installed on the tip side of the actuator, and it is necessary to dispose a magnet as in the prior art on the rotation axis side of the optical information recording medium with respect to the optical axis of the objective lens in the optical recording / reproducing apparatus. Because there is no. Therefore, the diameter of the spindle motor can be increased by the space for the arrangement. This effect can be obtained not only when the actuator of the present invention is arranged between the beam splitter and the raising mirror but also when the actuator is arranged between the raising mirror and the objective lens.

  In addition, since the magnet is disposed between the coil and the lens or between the coil and the fixed portion, the magnet is disposed in the longitudinal direction of the leaf spring. The length in the short direction is not increased. Furthermore, even when a plurality of magnet members are arranged, the thickness of the actuator (length in the short direction) is larger than that of a conventional actuator because the magnet members are sandwiched from the longitudinal direction of the leaf spring. Never become.

  A fifth aspect of the present invention is the lens actuator according to any one of the first to fourth aspects, wherein the leaf spring has a U-shaped portion or a hollow shape portion, and the magnet Is installed through a U-shaped portion or a hollow shape portion of the leaf spring.

  The invention described in claim 6 receives a light source, an objective lens for condensing the light emitted from the light source on the information recording surface of the optical information recording medium, and the light reflected by the optical information recording medium. A light receiving element, a lens installed in an optical path between the light source and the objective lens, and an actuator for the lens according to any one of claims 1 to 5, which moves the lens in the optical path direction. It is an optical head characterized by having.

  The light emitted from the light source is transmitted through the lens and then condensed on the information recording surface of the optical information recording medium by the objective lens. At this time, by moving the lens on the optical axis by the lens actuator, the spherical aberration generated in the lens is adjusted to cancel the aberration generated in the optical information recording medium.

  According to a seventh aspect of the present invention, there is provided the optical head according to the sixth aspect, a calculating means for calculating a servo signal in response to a signal output from the optical head, and an actuator for the lens based on the servo signal. And an optical disc apparatus characterized by comprising:

  According to the lens actuator of the first aspect, since the magnetic material is disposed in the coil, the leakage amount of the magnetic flux can be reduced. As a result, it is possible to obtain greater sensitivity as compared with the conventional actuator, and the movable range of the leaf spring can be expanded even with a small current, so that power saving can be achieved. Moreover, it has a simple structure compared with the actuator of the prior art, and can be easily manufactured as compared with the conventional actuator.

  Further, according to the lens actuator of the second aspect, since a plurality of magnet members are used, higher sensitivity can be obtained. Furthermore, since the magnet member is arranged so as to sandwich the coil, the lens can be moved substantially parallel to the optical axis direction. As a result, it is possible to suppress the occurrence of aberrations such as coma and astigmatism that can occur with movement, so that the thickness of the light transmission layer of the optical information recording medium can be reduced without generating other aberrations. It becomes possible to generate a beam spot in which the spherical aberration caused by the fluctuation is well corrected.

  According to the lens actuator of the third aspect, in addition to the above effect, it is not necessary to provide a space for arranging the magnet between the objective lens and the spindle motor in the optical recording / reproducing apparatus. Compared with the case where a conventional actuator is mounted, the diameter of the spindle motor can be increased by that amount of space, and a spindle motor having a large torque can be used. As a result, information can be recorded and reproduced at high speed.

  According to the lens actuator of the fourth aspect, the thickness is the same as the thickness of the conventional actuator, and the above effect can be obtained while maintaining the thinness.

  Moreover, according to the actuator for lenses of Claim 5, since a leaf | plate spring has a U-shaped part or a hollow shape part, compared with a leaf | plate spring which does not have a U-shaped part etc. The spring constant of the spring can be reduced. As a result, the sensitivity of the actuator is further improved and the movable range can be expanded.

  Further, according to the optical head described in claim 6 and the optical disk device described in claim 7, it is possible to save power by mounting the actuator of the present invention, and also when mounting a conventional actuator. In comparison, since the diameter of the spindle motor can be increased, it is possible to increase the speed of recording and reproduction by using a spindle motor having a large torque. Furthermore, since the thickness of the conventional actuator is maintained, the above-described effects can be achieved without increasing the thickness of the optical disk device.

  Hereinafter, an actuator for a lens according to an embodiment of the present invention will be described with reference to FIGS.

[First Embodiment]
The configuration and operation of the lens actuator according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view of the actuator according to the first embodiment. FIG. 2 is a top view of the actuator according to the first embodiment. FIG. 3 is a side view of the actuator according to the first embodiment. FIG. 4 is a perspective view of an actuator with an auxiliary yoke.

(Constitution)
As shown in FIGS. 1 to 3, the actuator according to the first embodiment includes a lens 1 for spherical aberration correction that is fixed inside a lens holder 2 with a resin. A coil bobbin 21 is provided at one end of the lens holder 2. The lens holder 2 and the coil bobbin 21 are made of light non-conductive PPS (polyphenylene sulfide), liquid crystal polymer, or the like. The coil bobbin 21 may be formed integrally with the lens holder 2. The lens holder 2 and the coil bobbin 21 correspond to the “movable member” of the present invention.

  The coil 3 is wound and attached to the coil bobbin 21 so as to include a straight line parallel to the optical axis of the lens 1. The coil 3 is made of enameled copper clad aluminum wire or the like. The coil bobbin 21 is sandwiched between plate springs 4a and 4b that are parallel to each other in the vertical direction (Z direction), and is supported at one end in the longitudinal direction of the plate springs 4a and 4b.

  One end of the parallel leaf springs 4 a and 4 b opposite to the end supporting the coil bobbin 21 is fixed by the fixing member 5. At this time, the parallel leaf springs 4a and 4b are fixed with resin so as to sandwich the coil bobbin 21 and the fixing member 5 from above and below. Moreover, the parallel leaf | plate springs 4a and 4b have the hollow structure from which the inside was removed. Since the holes are hollowed out, the spring constants of the leaf springs 4a and 4b are smaller than in the state where the holes are not hollowed out. As a result, even when the same voltage is applied, the sensitivity is improved and the movable range is widened compared to a leaf spring that is not hollowed out.

  Note that the coil bobbin 21 can be supported by sandwiching the coil bobbin 21 from above and below by only four leaf springs without using the leaf springs 4a and 4b having the hollow structure. However, it is difficult to assemble the four thin leaf springs in parallel so as not to be distorted or bent. If a leaf spring having a hollow structure is used as in the actuator according to the present embodiment, it becomes easy to assemble, and further, the leaf springs 4a and 4b move together to function, so that the stability of the shape is increased. .

  In addition to the hollow plate spring, for example, a plate spring having a U-shape when viewed from the Z-axis direction may be used.

  Further, the fixing member 5 is made of PPS, liquid crystal polymer, or the like that is not conductive and lightweight. Since the fixing member 5 is fixed to the base 8, the parallel leaf springs 4 a and 4 b are attached to the base 8 via the fixing member 5.

  Both ends of the coil 3 are temporarily fixed to the upper and lower surfaces of the coil bobbin 21 with resin and then fixed to the parallel leaf springs 4a and 4b with solder. In this way, the coil 3 is connected to the parallel leaf springs 4 a and 4 b, and the parallel leaf springs 4 a and 4 b are used as electrodes, so that a current flows through the coil 3.

  The coil bobbin 21 is formed with an insertion hole for inserting a yoke so as to be parallel to the optical axis direction of the lens 1. Further, another insertion hole is formed in the lens holder 2 between the lens 1 and the insertion hole of the coil bobbin 21.

  In the insertion hole formed in the lens holder 2, a permanent magnet 6a and a yoke 7a are installed. Further, a permanent magnet 6b and a yoke 7b that are paired with the permanent magnet 6a are disposed in the hollow portions of the leaf springs 4a and 4b. Accordingly, the coil bobbin 21 is sandwiched between the permanent magnet 6a and the permanent magnet 6b from the longitudinal direction (Y direction) of the leaf springs 4a and 4b. The permanent magnet 6a and the permanent magnet 6b correspond to the “magnet member” of the present invention. In addition, the permanent magnet 6a and the permanent magnet 6b are arranged so that the distance between the coil bobbin 21 and the permanent magnet 6a is equal to the distance between the coil bobbin 21 and the permanent magnet 6b. Further, the permanent magnet 6a and the permanent magnet 6b are arranged so that the same pole, for example, the N pole faces each other, and are magnetized in the facing direction (the direction of arrow A) as shown in FIGS. Furthermore, the magnetic force of the permanent magnet 6a is equal to the magnetic force of the permanent magnet 6b.

  A yoke 7a is attached to the back surface of the permanent magnet 6a, a yoke 7b is attached to the back surface of the permanent magnet 6b, and the yokes 7a and 7b are attached to the base 8. A yoke 7 c is inserted into the insertion hole formed in the coil bobbin 21. The yoke 7c is also attached to the base 8. Each permanent magnet is fixed to each yoke with resin. For the yokes 7a to 7c, soft steel, wrought iron or the like, which is a soft magnetic material, is used. Thus, by using a magnetic material, a magnetic path is formed between the permanent magnets 6a and 6b and the yokes 7a to 7c, and leakage of magnetic flux generated from the permanent magnets 6a and 6b to the outside of the actuator is reduced. Can do.

  In addition, the yoke 7c is installed in the coil bobbin 21, that is, in the coil 3, and the magnetic flux emitted from the permanent magnets 6a and 6b and passing through the coil 3 is received by the yoke 7c, thereby leaking the magnetic flux outside the actuator. Further reduction can be achieved. Thereby, since the magnetic flux density which passes the coil 3 can be raised, the sensitivity as an actuator becomes good and it becomes possible to extend the movable range of a leaf | plate spring even if it is little electric current. As a result, power saving can be achieved. The base 8 may be a magnetic material.

  In the present embodiment, the two permanent magnets 6a and 6b are used. However, even if only one of them is installed, the leakage magnetic flux can be reduced. That is, even when only the permanent magnet 6a (or the permanent magnet 6b) is used, the magnetic flux passing through the coil 3 is received by the yoke 7c, so that the leakage magnetic flux can be reduced as compared with the conventional actuator. In addition, when two permanent magnets 6a and 6b are used as in the present embodiment, the magnetic force is increased as compared with the case of one, so that sensitivity is further improved.

  Further, any or all of the yokes 7a to 7c and the base 8 may be integrated. That is, any or all of the yokes 7a to 7c and the base 8 may be integrally manufactured from the same metal plate. As a result, the number of parts constituting the actuator can be reduced, and the manufacturing cost can be reduced.

  Moreover, when another yoke is installed on the yokes 7a to 7c, there is an effect of further reducing the leakage magnetic flux and increasing the density of the magnetic flux passing through the coil 3. For example, by installing the auxiliary yoke 7d on the yokes 7a to 7c as shown in FIG. 4, it is possible to reduce the leakage of magnetic flux from the permanent magnets 6a and 6b to the outside of the actuator. Since the auxiliary yoke 7d can increase the density of magnetic flux passing through the coil 3, sensitivity as an actuator is further improved, and power saving can be achieved.

(Function and effect)
When the actuator according to the present embodiment is mounted on the optical recording / reproducing apparatus, the diameter of the spindle motor can be increased as compared with the case where a conventional actuator is mounted, so that a spindle motor having a large torque can be used. . This effect will be described with reference to FIGS. FIG. 5 is a top view of the vicinity of the optical information recording medium of the optical recording / reproducing apparatus, and FIG. 6 is a side view thereof. 5 and 6 are diagrams in the case where an actuator is disposed between the beam splitter and the rising mirror.

  As shown in FIGS. 5 and 6, light emitted from a light source (not shown) passes through a diffraction element (not shown) and a beam splitter 19, and further passes through a spherical aberration correction expander (not shown). . The expander for correcting spherical aberration is composed of a convex lens and a concave lens. By moving one of them in the optical axis direction, the spherical aberration of light incident on the optical information recording medium 23 from the objective lens 22 is changed, and optical information is obtained. The spherical aberration that occurs in the recording medium 23 can be canceled out. In this embodiment, the convex lens is mounted on the actuator and moved. Then, the light that has passed through the spherical aberration correcting expander is reflected by the rising mirror 20 in the direction of the optical information recording medium (X direction), passes through the objective lens 22, and is condensed on the optical information recording medium 23. . The objective lens 22 shown in FIGS. 5 and 6 is arranged at the innermost position where the optical information recording medium 23 can be recorded.

  According to the actuator according to the present embodiment, the permanent magnet 6b, the coil 3, the permanent magnet 6a, and the lens 1 are arranged in this order in the longitudinal direction of the leaf springs 4a and 4b, and the lens 1 is arranged at the tip of the lens holder 2. Thus, when mounted on the optical recording / reproducing apparatus, the portion occupied by the optical head component on the side of the spindle motor 49 can be made the same level as the objective lens 22 and the rising mirror 20. As a result, a spindle motor having a diameter close to the innermost track of the optical information recording medium can be used. This effect will be described in detail with reference to FIG.

  In the actuator according to this embodiment, since the lens 1 is installed at the tip of the actuator, the distance between the spindle motor 49 and the objective lens 22 is shortened as shown in FIG. Since the permanent magnet 6 a is installed between the lens holder 2 and the coil bobbin 21, it is not necessary to provide a space for arranging the permanent magnet 6 a between the objective lens 22 and the spindle motor 49. Therefore, the spindle motor 49 having a diameter closer to the innermost track of the optical information recording medium than that of the prior art can be disposed by the space. As a result, the diameter of the spindle motor 49 can be increased as compared with the conventional actuator. As a result, the rotational speed of the spindle motor can be increased, the rotational torque is large, and the target rotational speed is reached quickly, so that the recording and reproduction of information can be speeded up.

  Further, since the permanent magnets 6a and 6b are arranged in the longitudinal direction (Y direction) of the actuator, the same thickness as that of the conventional actuator can be maintained. As a result, as shown in FIG. 6, it is possible to maintain the thickness of the optical recording / reproducing apparatus. That is, it is possible to achieve effects such as high sensitivity while maintaining the thickness of the conventional actuator (optical recording / reproducing apparatus).

  Next, the mechanism of driving the actuator will be described with reference to FIGS. In order to use this actuator, a lead wire or the like is fixed to the end of the parallel leaf springs 4a and 4b on the fixing member 5 side with solder or the like and connected to the electric circuit board. Then, a current is applied to the coil 3 by applying a voltage to the parallel leaf springs 4a and 4b. For example, as shown in FIG. The current flowing in the coil 3 passes through the magnetic field generated by the permanent magnet 6a and the permanent magnet 6b, thereby generating a Lorentz force in the coil 3.

  Here, the direction and magnitude of the Lorentz force generated in the coil 3 will be described. As shown in FIGS. 1 and 3, Lorentz force acts on the permanent magnet 6 a side of the coil 3 in a direction away from the base 8 (in the direction of arrow Z <b> 1). A Lorentz force also acts on the permanent magnet 6b side of the coil 3 in the direction away from the base 8 (the direction of the arrow Z1). Thus, the Lorentz force acts on the permanent magnets 6a and 6b side of the coil 3 in the same direction (the direction of the arrow Z1). Further, since the permanent magnets 6a and 6b are arranged so that the distance between the coil 3 and the permanent magnet 6a is equal to the distance between the coil 3 and the permanent magnet 6b, Will generate the same amount of Lorentz force.

  Further, the magnetic lines of force that acted effectively on the coil 3 by emitting the permanent magnets 6a and 6b reach the yoke 7c. Since the yoke 7c is all magnetically coupled as a magnetic material via the yoke 7a and the yoke 7b and the base 8, a magnetic circuit with very little leakage magnetic flux is formed thereby.

  Since the coil bobbin 21 (lens holder 2) is supported by parallel leaf springs 4a and 4b, the leaf springs 4a and 4b are bent by the Lorentz force, and the lens holder 2 moves in the optical axis direction. Since the same Lorentz force is applied to the two sides of the coil 3, the lens holder 2 moves in the optical axis direction while being parallel to the optical axis of the lens 1. That is, since the Lorentz force having the same magnitude is generated on both sides of the coil bobbin 21 in the same direction (the direction of the arrow Z1), the magnitudes of the moments are equal and the moments can be balanced. As a result, the bending shape of the leaf spring 4a and the bending shape of the leaf spring 4b become the same, and the lens holder 2 moves up and down while maintaining a parallel state with respect to the optical axis.

  Accordingly, since the lens holder 2 is not easily tilted with the movement in the optical axis direction and the angle is not shifted with respect to the optical axis, the occurrence of coma and astigmatism can be suppressed.

  As described above, the spherical aberration generated in the optical information recording medium is changed by moving the spherical aberration correcting lens 1 in the optical axis direction, thereby changing the spherical aberration of the light incident on the optical information recording medium from the objective lens. It is possible to cancel and generate a beam spot with less aberration on the optical information recording medium. Then, by applying the same Lorentz force to the two sides of the lens holder 2, the lens holder 2 can be moved in parallel with the optical axis. This makes it possible to suppress the occurrence of other aberrations such as coma and astigmatism, and to generate a beam spot with less aberration on the optical information recording medium without causing other aberrations. It becomes possible.

[Second Embodiment]
As a second embodiment, the configuration and operation of the optical system of the optical head including the actuator of the present invention and the optical recording / reproducing apparatus including the same will be described with reference to FIGS. FIG. 7 is a side view showing the optical system of the optical recording / reproducing apparatus according to the second embodiment, and FIG. 8 is a top view showing the optical system of the optical recording / reproducing apparatus according to the second embodiment.

  As shown in FIGS. 7 and 8, the light emitted from the light source 16 enters the diffraction grating 17, and is divided into three beams for generating a tracking error signal in the diffraction grating 17. The light that has passed through the diffraction grating 17 is incident on the collimating lens 18 to become parallel light, and is incident on the beam splitter 19 as P-polarized light. The beam splitter 19 transmits about 90% of P-polarized light and reflects about 10%.

  The light transmitted through the beam splitter 19 is corrected for spherical aberration by a spherical aberration correcting expander 29 and enters the rising mirror 20. The expander 29 for correcting spherical aberration includes a concave lens spherical aberration correcting lens 29a and a convex lens spherical aberration correcting lens 29b. By moving one of them in the optical axis direction, optical information is transmitted from the objective lens 22. By changing the spherical aberration of the light incident on the recording medium 23, it is possible to cancel the spherical aberration generated in the optical information recording medium. In the present embodiment, a spherical aberration correcting lens 29b, which is a convex lens, is mounted on the actuator 31 and moved in the optical axis direction. The actuator 31 corresponds to the actuator of the present invention.

  The light incident on the rising mirror 20 has its optical path bent by the rising mirror 20 and is incident on the quarter-wave plate 21. The light beam is circularly polarized when passing through the quarter-wave plate 21 and enters the objective lens 22.

  In the objective lens 22, the light is focused and condensed on an information recording track on the information recording surface of the optical information recording medium 23. The objective lens 22 is mounted on an objective lens actuator 24 that can move at least in the focusing direction and the tracking direction with respect to the optical information recording medium 23.

  The light reflected by the information recording surface of the optical information recording medium 23 passes through the objective lens 22 and is converted into linearly polarized light in the direction orthogonal to the forward path to the quarter wavelength plate 21 in the quarter wavelength plate 21. Then, it is reflected by the rising mirror 20 and enters the beam splitter 19 as S-polarized light. The beam splitter 19 reflects S-polarized light by about 100%. The reflected light is focused at the convex lens 25, and astigmatism for generating a focus error signal is given to the anamorphic lens 26. Thereafter, the light enters the light receiving element 27 and is converted into an electric signal in the light receiving portion of the light receiving element 27.

  This electric signal is sent to a modulation / demodulation circuit (not shown), where it is demodulated and output to the outside as an information signal. By this operation, the information signal recorded on the optical information recording medium 23 is reproduced.

  Note that about 10% of the light reflected by the beam splitter 19 in the forward optical system enters the front monitor light receiving element 28. Then, the light receiving unit of the front monitor light receiving element 28 converts it into an electrical signal for output monitoring of the light source 16, and the electrical signal is used for feedback control of the output of the light source 16.

  The actuator of the present invention may be provided in an optical recording / reproducing apparatus for a multilayer recording medium that uses a multilayer recording medium as the optical information recording medium 23. In this optical recording / reproducing apparatus for a multilayer recording medium, in addition to the functions of the optical recording / reproducing apparatus described above, a focus jump function for moving the imaging position of the objective lens included in the optical head to another layer, and a spherical surface A spherical aberration correction function for performing aberration correction is provided. For example, in the case of a two-layer optical information recording medium, when switching the reproduction position from the first layer to the second layer, the focus jump function changes the imaging position of the objective lens included in the optical head from the first layer to the second layer. Move to. Also, when the focal point is on the second layer, the optical path length of the light passing through the medium becomes thicker than that of the first layer, so that a larger spherical aberration correction is required than the single layer optical information recording medium, and the spherical aberration correction The function corrects the spherical aberration.

[Third Embodiment]
As a third embodiment, the configuration and operation of the optical system of the optical head including the actuator of the present invention and another optical recording / reproducing apparatus including the actuator will be described with reference to FIGS. 9 and 10. FIG. FIG. 9 is a side view showing an optical system of an optical head and an optical recording / reproducing apparatus according to the third embodiment, and FIG. 10 is a top view showing an optical system of the optical head and the optical recording / reproducing apparatus according to the third embodiment. FIG.

  As shown in FIGS. 9 and 10, the light emitted from the light source 16 passes through the diffraction grating 17, the collimating lens 18, and the beam splitter 19 and enters the rising mirror 20 as in the above-described embodiment. .

  The light that has passed through the beam splitter 19 passes through the collimator lens 30 and enters the rising mirror 20. The light is made substantially parallel light by the collimator lens 30, and further, the collimator lens 30 is moved in the optical axis direction by the actuator 31, so that the amount of spherical aberration in the entire optical system is variable. As described above, in the present embodiment, the spherical aberration can be corrected by moving the collimating lens 30. As a result, the number of optical elements can be reduced, and the manufacturing cost can be reduced.

  The light incident on the rising mirror 20 is incident on the quarter-wave plate 21 with its optical path bent by the rising mirror 20. When passing through the quarter-wave plate 21, the light is circularly polarized and enters the objective lens 22.

  In the objective lens 22, the light is focused and condensed on an information recording track on the information recording surface of the optical information recording medium 23. The objective lens 22 is mounted on an objective lens actuator 24 that can move at least in the focusing direction and the tracking direction with respect to the optical information recording medium 23.

  The light reflected by the information recording surface of the optical information recording medium 23 passes through the objective lens 22 and is converted into linearly polarized light in the direction orthogonal to the forward path to the quarter wavelength plate 21 in the quarter wavelength plate 21. Then, the light is reflected by the rising mirror 20 and enters the collimating lens 30. The collimating lens 30 produces focused light, and the anamorphic lens 26 is provided with astigmatism for generating a focus error signal. Thereafter, the light enters the light receiving element 27 and is converted into an electric signal in the light receiving portion of the light receiving element 27.

  Note that about 10% of the light reflected by the beam splitter 19 in the forward optical system enters the front monitor light receiving element 28. Then, the light receiving unit of the front monitor light receiving element 28 converts it into an electrical signal for output monitoring of the light source 16, and the electrical signal is used for feedback control of the output of the light source 16.

  As described above, by moving the collimating lens to enable correction of spherical aberration, the optical head can be reduced in size, so that the optical recording / reproducing apparatus can be reduced in size. In such a case, for the purpose of downsizing, the collimating lens 30 is brought as close as possible to the raising mirror 20 and the objective lens 22 which are optical elements closest to the center of the spindle motor, as in this embodiment. The fact that the drive system including the magnetic circuit of the actuator 31 is integrated in one direction with respect to the collimating lens 30 is very effective for miniaturization because the size of the spindle motor is not limited.

In the second and third embodiments described above, a spherical aberration correction lens is arranged between the beam splitter 19 and the rising mirror 20, but the space inside the optical recording / reproducing apparatus, the arrangement of each device, or Depending on the design of the optical head itself, the spherical aberration correcting lens actuator may be disposed between the objective lens and the rising mirror. In a fourth embodiment to be described next, an optical recording / reproducing apparatus having this configuration will be described.
[Fourth Embodiment]
As a fourth embodiment, the configuration and operation of the optical system of the optical head including the actuator of the present invention and the optical recording / reproducing apparatus including the optical head will be described with reference to FIGS. FIG. 11 is a side view showing the optical system of the optical recording / reproducing apparatus according to the fourth embodiment, and FIG. 12 is a top view showing the optical system of the optical recording / reproducing apparatus according to the fourth embodiment.

  As shown in FIGS. 11 and 12, the light emitted from the light source 16 passes through the diffraction grating 17, the collimating lens 18, and the beam splitter 19 and enters the rising mirror 20 as in the above-described embodiment. .

  The light transmitted through the beam splitter 19 has its optical path bent by the rising mirror 20, the spherical aberration is corrected by the spherical aberration correcting expander 29, and is incident on the quarter wavelength plate 21. When passing through the quarter-wave plate 21, the light is circularly polarized and enters the objective lens 22. The expander 29 for correcting spherical aberration includes a spherical aberration correcting lens 29a and a spherical aberration correcting lens 29b. Here, the spherical aberration correcting lens 29a is mounted on the actuator 31 of the spherical aberration correcting lens. The actuator 31 corresponds to the actuator of the present invention.

  In response to an instruction signal from a control unit (not shown), the actuator 31 moves the spherical aberration correcting lens 29 a in the optical axis direction so that the spherical aberration is canceled on the information recording surface of the optical information recording medium 23.

  The light is condensed on the information recording track of the optical information recording medium 23 by the objective lens 22. By passing through the spherical aberration correcting lenses 29a and 29b and the objective lens 22, the spherical aberration is canceled and condensed on the information recording surface.

  The light reflected by the information recording surface of the optical information recording medium 23 passes through the objective lens 22 and is converted into linearly polarized light in the direction orthogonal to the forward path to the quarter wavelength plate 21 in the quarter wavelength plate 21. Then, it is reflected by the rising mirror 20 and enters the beam splitter 19 as S-polarized light. The beam splitter 19 reflects S-polarized light by about 100%. The reflected light is focused at the convex lens 25, and astigmatism for generating a focus error signal is given to the anamorphic lens 26. Thereafter, the light enters the light receiving element 27 and is converted into an electric signal in the light receiving portion of the light receiving element 27.

  This electric signal is sent to a modulation / demodulation circuit (not shown), where it is demodulated and output to the outside as an information signal. By this operation, the information signal recorded on the optical information recording medium 23 is reproduced.

  Note that about 10% of the light reflected by the beam splitter 19 in the forward optical system enters the front monitor light receiving element 28. Then, the light receiving unit of the front monitor light receiving element 28 converts it into an electrical signal for output monitoring of the light source 16, and the electrical signal is used for feedback control of the output of the light source 16.

  As described above, when the spherical aberration correction lens is arranged between the rising mirror 20 and the objective lens 22, the spherical aberration correction lens is also centered on the spindle motor in the same manner as the rising mirror 20 and the objective lens 22. Is the closest optical element. According to the present embodiment, since the drive system including the magnetic circuit of the actuator 31 is integrated in one direction with respect to the spherical aberration correction lens, it is easy to design an optical head that does not limit the size of the spindle motor.

  By using the actuator of the present invention, the diameter of the spindle motor can be increased as compared with the case where a conventional actuator is mounted, so that a spindle motor having a large torque can be used. Further, it is possible to reduce power consumption by reducing magnetic flux leaking from the actuator.

  Next, a case where the actuator according to the present embodiment is disposed between the raising mirror 20 and the objective lens 22 will be described with reference to FIG. FIG. 13 is a side view of the vicinity of the optical information recording medium of the optical recording / reproducing apparatus.

  In FIG. 13, light emitted from a light source (not shown) passes through a diffraction element and a beam splitter (both not shown) and is reflected by the rising mirror 20 in the direction of the optical information recording medium (X direction). Then, the light passes through the lens 1 and the objective lens 22 and is condensed on the optical information recording medium 23. Even in such an arrangement, the distance between the spindle motor 49 and the objective lens 22 can be made closer. As a result, the diameter of the spindle motor 49 can be increased compared to the case where a conventional actuator is mounted. As a result, the rotational speed of the spindle motor can be increased, the rotational torque is large, and the target rotational speed is reached quickly, so that the recording and reproduction of information can be speeded up.

  Further, according to the actuator according to the present embodiment, as described above, the magnetic flux leaking out of the actuator can be reduced and the magnetic flux acting on the coil can be concentrated, so that sensitivity is improved and power saving is achieved. It becomes possible.

  On the other hand, when an actuator as shown in FIG. 15 is used, in order to obtain the same effect as when the actuator according to this embodiment is mounted, the actuator is not arranged so as to be long in the X direction in the figure. must not. However, in this direction, the optical axis of the raising mirror 20 to the objective lens 22 is sandwiched, one side is an objective lens actuator, and the other side is mounted with electric circuit components such as an LD driver, an operational amplifier, and an FPC connector provided on the optical head. Therefore, it is difficult to arrange the actuators avoiding these.

  Even if an actuator arranged so that a permanent magnet is sandwiched from the short side direction (X direction) is used, the mechanism of the objective lens actuator is usually preferably close to the optical axis of the rising mirror 20 to the objective lens 22. Magnets and yokes hinder this.

  After all, in this embodiment, the space is free in the Y direction, and is only in one direction on the opposite side of the spindle motor with the optical axis of the raising mirror 20 to the objective lens 22 interposed therebetween. Therefore, the actuator of this embodiment in which the mechanical systems such as the magnetic circuit and the leaf spring are all arranged in one direction with respect to the lens is very effective.

[Fifth Embodiment]
As a fifth embodiment, a configuration of an optical recording / reproducing apparatus including the actuator of the present invention will be described with reference to FIG. FIG. 14 is a block diagram showing a schematic configuration of an optical recording / reproducing apparatus according to the fifth embodiment.

  The optical recording / reproducing apparatus 40 according to the present embodiment records information on the optical information recording medium 23 chucked by the spindle motor 49 by chucking means (not shown), or records information from the optical information recording medium 23. Play back. The optical head 41 is provided in a chassis (not shown) provided with a slider mechanism, and can be moved in the radial direction of the optical information recording medium 23 by a coarse motion motor 48. Further, the optical head 41 includes a position sensor that detects the position of the movable portion of the actuator of the present invention.

  The electric signal output from the optical head 41 is input to the signal calculation unit 42, and the signal calculation unit 42 calculates and amplifies the electric signal. The signal calculation unit 42 may be mounted on the optical head 41. The controller 43 includes a focus servo tracking circuit, a tracking servo tracking circuit, and a laser control circuit, and controls operations of the optical head 41 and the spindle motor 49. These circuits are not physical circuits but may be software executed in the controller 43. Based on the electrical signal from the optical head 41, the controller 43 calculates servo signals such as a focus error signal and tracking error signal in addition to the data reproduction signal. The controller 43 corresponds to “calculation means” of the present invention. A part of the controller 43 may be mounted on the optical head 41.

  The data reproduction signal is subjected to waveform equalization and waveform shaping by a digital signal processing circuit (not shown), and then converted to an analog signal by a D / A converter (not shown) and output. When recording information, the recording data is converted into a laser drive signal by the laser controller circuit in the controller 43, and the laser drive signal is supplied to the optical head 41 by the laser drive circuit 44 to record the data.

  The actuator drive circuit 45 performs focus position control and tracking position control of the objective lens of the optical head 41 in response to a focus error signal, a tracking error signal, and the like. Further, the position of the actuator for the spherical aberration correction lens is controlled. The actuator drive circuit 45 corresponds to “control means” of the present invention. The actuator drive circuit 45 may be mounted on the optical head 41. The spindle motor drive circuit 47 drives the spindle motor 49 to control the rotation of the optical information recording medium 23, and the coarse motion motor drive circuit 46 drives the coarse motion motor 48 to record the optical head 41 in the optical information recording. The medium 23 is moved in the radial direction. The laser drive circuit 44 supplies a laser drive signal to the optical head 41 and controls the output of the light source of the optical head 41. The laser drive circuit 44 may be mounted on the optical head 41. By mounting the actuator according to the first embodiment, it is not necessary to provide a space for arranging the permanent magnet 6 and the like inside the objective lens. The diameter can be increased. As a result, the rotational speed of the spindle motor can be increased, the rotational torque is large, and the target rotational speed is reached quickly, so that information can be recorded and reproduced at high speed.

  Furthermore, the optical recording / reproducing apparatus 40 of this embodiment has a CPU for controlling the entire apparatus, a memory, an interface for transmitting / receiving signals to / from the outside, and the like.

  The position sensor detects the position of the lens holder 2, and the detected signal is input to the signal calculation unit 42 and compared with a target position signal stored in advance in a memory (not shown), and the lens is positioned at the target position. A signal is output to the actuator drive circuit 45 so as to move the holder 2. The actuator drive circuit 45 receives the signal from the controller 43 and adjusts the amount of current that should flow through the coil 3 attached to the lens holder 2. Then, a current is passed through the coil 3 so as to keep the lens holder 2 at the target position, and feedback control is performed.

  Although described as an optical recording / reproducing apparatus, an optical reproducing apparatus that exclusively reproduces an optical signal may be used. The “optical disk apparatus” in the present invention includes an optical recording / reproducing apparatus, an optical reproducing apparatus, an optical recording / reproducing apparatus for a multilayer recording medium, and an optical reproducing apparatus for a multilayer recording medium.

It is a perspective view of the actuator for lenses concerning a 1st embodiment of this invention. It is a top view of the actuator for lenses concerning a 1st embodiment of this invention. It is a side view of the actuator for lenses concerning a 1st embodiment of this invention. It is a perspective view of the actuator for lenses with an auxiliary yoke concerning a 1st embodiment of this invention. FIG. 2 is a top view of the vicinity of an optical information recording medium of an optical recording / reproducing apparatus. FIG. 3 is a side view of the vicinity of an optical information recording medium of an optical recording / reproducing apparatus. It is a side view which shows the optical system of the optical recording / reproducing apparatus concerning 2nd Embodiment of this invention. It is a top view which shows the optical system of the optical recording / reproducing apparatus concerning 2nd Embodiment of this invention. It is a side view which shows the optical system of the optical recording / reproducing apparatus concerning the 3rd Embodiment of this invention. It is a top view which shows the optical system of the optical recording / reproducing apparatus concerning the 3rd Embodiment of this invention. It is a side view which shows the optical system of the optical recording / reproducing apparatus based on 4th Embodiment of this invention. It is a top view which shows the optical system of the optical recording / reproducing apparatus concerning the 4th Embodiment of this invention. FIG. 3 is a side view of the vicinity of an optical information recording medium of an optical recording / reproducing apparatus. It is a block diagram which shows schematic structure of the optical recording / reproducing apparatus which concerns on 6th Embodiment of this invention. It is a perspective view which shows schematic structure of the actuator for lenses concerning a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lens 2 Lens holder 3 Coil 4a, 4b Leaf spring 5 Fixing member 6a, 6b Permanent magnet 7a, 7b, 7c Yoke 8 Base 21 Coil bobbin

Claims (7)

A light source;
An objective lens for condensing the light emitted from the light source on the information recording surface of the optical information recording medium;
A lens installed in an optical path between the light source and the objective lens;
An actuator for a lens that moves the lens in the optical path direction.
A leaf spring having one end fixed to the fixed portion and the other end allowed to move in the optical path direction;
A movable member extending in the longitudinal direction from the other end of the leaf spring, and the lens and the coil are installed;
A magnet and a magnetic material installed so as to sandwich the coil from the inside and outside of the coil;
An actuator for a lens, comprising: The magnet is composed of at least two magnet members installed on the outer side of the coil at predetermined intervals and on opposite sides of the coil,
The said magnetic material is installed inside the said coil so that the said coil may be pinched | interposed from the inner side and the outer side of the said coil by the at least 1 magnet member among the said magnet members. 2. An actuator for a lens according to 1.   3. The lens actuator according to claim 1, wherein the coil and the magnet are located between the fixed portion and the lens. 4.   The said magnet is installed between the said coil and the said lens, or between the said coil and the said fixing | fixed part, The actuator for lenses of Claim 3 characterized by the above-mentioned.   The said leaf | plate spring has a U-shaped part or a hollow shape part, and the said magnet is installed through the U-shaped part or the hollow shape part of the said leaf spring. Item 5. The actuator for a lens according to any one of Items 4. A light source;
An objective lens for condensing the light emitted from the light source on the information recording surface of the optical information recording medium;
A light receiving element for receiving light reflected by the optical information recording medium;
A lens installed in an optical path between the light source and the objective lens;
The lens actuator according to any one of claims 1 to 5, wherein the lens is moved in the optical path direction;
An optical head comprising: An optical head according to claim 6;
Calculating means for calculating a servo signal in response to a signal output from the optical head;
Control means for controlling the actuator for the lens based on the servo signal;
An optical disc apparatus comprising:

Images