JP2011253586A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small pickup having aberration correcting means that can correct various spherical aberrations, coma aberrations and astigmatism with low power consumption, and to provide a drive.SOLUTION: A variable focus lens actuator A1 can bend a transparent deformation film into a parabolic shape by applying a magnetic field, change the intensity distribution of transmitted light, and correct a spherical aberration. In addition, the variable focus lens actuator A1 can change a propagation direction of the transmitted light by tilting the transparent deformation film arbitrarily and correct a coma aberration and astigmatism.

Description

  The present invention relates to an optical disc apparatus using an aberration correction element such as a variable lens actuator that can change a lens surface and has an element having variable optical characteristics such as a variable focus lens and an aberration correction lens.

  In recent years, due to the increase in the amount of electronic information accompanying the spread of the Internet and the improvement in image quality, optical discs, which are one of the main information recording media, have been increasing in density. In order to increase the density, generally, the numerical aperture of the objective lens is increased, the condensed light spot size is reduced by shortening the wavelength, and the recording layer is multilayered.

  Optical discs collect light from a semiconductor laser through the substrate, so spherical aberration depends on the wavelength of the laser beam, the numerical aperture of the objective lens, and the thickness of the substrate (the distance between the disc incident surface and the recording layer, hereinafter referred to as the substrate thickness). Will occur. Since this spherical aberration is proportional to the fourth power of the numerical aperture of the objective lens, as the numerical aperture increases, the spherical aberration caused by the variation in the substrate thickness error increases rapidly. In addition, since the thickness of the substrate of the nearest recording layer and the farthest recording layer is several tens of micrometers (micrometers) when viewed from the laser beam incident side due to the multi-layered recording layer, normal recording / reproducing operation is realized. A mechanism for correcting the spherical aberration caused by these becomes essential.

  Further, glass, plastic, and the like have been studied as materials for the objective lens of the optical pickup. Plastic is superior to glass in terms of cost and mass productivity, and in recent years, plastic objective lenses have been used in many optical pickups. However, the plastic lens has a very large change in the refractive index with respect to the glass lens, and the spherical aberration caused by the change in temperature increases. Therefore, a mechanism for correcting spherical aberration caused by a temperature change is essential for a plastic objective lens.

  On the other hand, in the optical pickup, aberrations such as coma and astigmatism occur due to an inclination of the optical disk (disk tilt) with respect to the laser optical axis and an error in assembly of the optical pickup. Therefore, it is necessary to correct these aberrations.

  Spherical aberration is an aberration that is rotationally symmetric with respect to the optical axis. For example, by moving the lens of the optical pickup in the optical axis direction, or by providing the optical pickup with a variable focus lens and changing the focal length of the variable focus lens. Spherical aberration can be generated. On the other hand, coma and astigmatism are rotationally asymmetrical aberrations with respect to the optical axis. For example, by using a transmissive liquid crystal element and optimizing the voltage pattern applied to the liquid crystal element, coma and astigmatism are obtained. Point aberration can be generated.

  In the optical pickup described in Patent Document 1, a lens for correcting spherical aberration is moved in parallel to the optical axis direction by an actuator to generate spherical aberration having a sign opposite to that of spherical aberration due to fluctuation in substrate thickness. A technique for correcting spherical aberration due to variation in thickness error is disclosed.

  FIG. 15 is a diagram illustrating an example of an optical system of an optical pickup having a conventional aberration correction mechanism 223.

  Conventionally, in order to correct a change in spherical aberration due to a change in the position of the recording layer 211 of the optical disk 212 (a change in the position of the recording layer 211a and the recording layer 211b), the divergence angle of the laser beam from the laser light source 207 incident on the objective lens 209 has heretofore been This is performed by displacing the position of the lens 221 in the optical axis direction by using a uniaxial actuator using a motor 222.

  Further, the optical pickup described in Patent Document 2 discloses a technique for correcting spherical aberration by a signal from a detector using a transmissive liquid crystal element that generates a phase difference of light.

  In the optical pickup described in Patent Document 3, the spherical aberration is corrected by changing the intensity distribution pattern of the laser beam incident on the objective lens by bending the reflection surface of the reflection mirror that reflects the laser beam toward the objective lens in a parabolic shape. The technology is public.

  In Patent Document 4, in a liquid crystal aberration correction element having two transparent electrode surfaces, a transparent electrode pattern for correcting the coma in the radial direction of the optical disk on one side and the coma and astigmatism in the tangential direction of the optical disk on the other side. And a technique for correcting coma and astigmatism generated by an optical pickup by generating coma and astigmatism in a liquid crystal aberration correction element.

Japanese Patent Laid-Open No. 13-45067 JP-A-12-57616 JP 2006-155850 A JP 2005-122828 A

  However, in the example shown in Patent Document 1, an even larger spherical aberration SA1 occurs as the next-generation optical disk is multilayered, and therefore, a greater parallel movement in the optical axis direction of the lens is required for the correction. For example, when there are four or more layers, the lens may have to be moved in the optical axis direction z1 = several centimeters for correction. On the other hand, apart from the large spherical aberration SA1 caused by the multi-layered optical disc, the spherical aberration SA1 such as the spherical aberration generated in the objective lens (particularly, the plastic lens) due to the substrate thickness error fluctuation, the laser wavelength fluctuation, and the temperature fluctuation. Small spherical aberration SA2 also needs to be corrected. For this reason, for example, the lens may have to be moved in the optical axis direction in small steps of z2 = several tens of μm. Since the lens movement amount z and the spherical aberration SA to be corrected are in a substantially proportional relationship, the lens movement amounts z1 and z2 necessary for correcting the spherical aberration SA1 and SA2 cannot be designed independently. With this structure, it is difficult to achieve both the movement of a large lens of several centimeters and the movement of a small and highly accurate lens of several tens of micrometers. Further, in this structure, the spherical aberration correction mechanism is complicated and the installation space is increased. For this reason, there is a problem that it is difficult to secure a component arrangement space in an optical pickup in which downsizing and thinning are essential. Furthermore, it is difficult to correct coma and astigmatism with this structure.

  In addition, in order to correct the large spherical aberration SA1 in the example shown in Patent Document 2, the voltage applied to the liquid crystal element for generating the phase difference of light must be very large, and more electrodes are used. Since a pattern is required, it is not realistic.

  On the other hand, in the example shown in Patent Document 3, the number of drive electrodes for the variable mirror is small, and the functions of the spherical aberration correction actuator and the reflection mirror are combined. Since a large number of processes are required for manufacturing, the cost increases. In addition, there is a problem to be solved that the distance between the electrodes is different between the center and the end of the mirror due to the bending of the mirror, so that it is difficult to apply the deformation force uniformly to the mirror.

  Further, the liquid crystal element of Patent Document 4 can correct coma and astigmatism, but cannot simultaneously correct spherical aberration.

  In view of the above problems, an object of the present invention is to provide a variable focus lens actuator capable of correcting various spherical aberrations with low power consumption by small and simple control in a variable focus lens. Furthermore, in an optical pickup that must be reduced in size and thickness, large spherical aberration SA1 caused by the multi-layered optical disc, and error in the substrate thickness, laser wavelength variation, and temperature variation occur in the objective lens (especially plastic lens). In addition to correcting various spherical aberrations such as spherical aberration, which is smaller than the spherical aberration SA1, such as spherical aberration, coma aberration caused by an optical disc tilt (disc tilt) with respect to the optical axis or an error in assembling the optical pickup. Another object is to provide means for correcting astigmatism and the like at the same time.

  The optical pickup of the present invention includes a plurality of spherical aberration correction mechanisms, and the first spherical aberration correction mechanism corrects a large spherical aberration SA1 caused by multilayering of the optical disk. The second spherical aberration correction mechanism corrects a spherical aberration SA2, which is smaller than the spherical aberration SA1, such as a spherical aberration generated in the objective lens due to an error variation of the substrate thickness, a laser wavelength variation, or a temperature variation. At least one of the first or second spherical aberration correction mechanism further corrects a rotationally asymmetric wavefront aberration with respect to the optical axis of the lens, such as coma and astigmatism.

  The first or second spherical aberration correction mechanism for correcting the coma aberration and astigmatism is constituted by a variable focus lens actuator. The variable focus lens actuator includes: a lens member that refracts irradiated light; a magnetic force applying member that applies a bending force to the lens member by applying a magnetic field; An electromagnet structure that applies the magnetic field to the magnetic force applying member to bend the lens member into a desired shape.

  Alternatively, the first or second spherical aberration correction mechanism that corrects coma and astigmatism is configured by a transmissive liquid crystal element. The transmissive liquid crystal element has a plurality of transparent electrode surfaces, the first transparent electrode has an electrode pattern for correcting spherical aberration, and the second transparent electrode corrects coma and astigmatism. An electrode pattern is provided.

  The other spherical aberration correction mechanism is configured by, for example, a mechanism that translates the lens of the optical pickup in the optical axis direction by an actuator. Alternatively, the other spherical aberration correction mechanism is constituted by a deformable mirror device capable of deforming the mirror surface with respect to a predetermined position of the optical pickup.

  According to the present invention, it is possible to realize an optical pickup capable of correcting various spherical aberrations, coma aberrations, and astigmatisms by small and simple control of low power consumption.

1 is a schematic diagram of an optical system of an optical pickup incorporating a variable mirror actuator of a variable focus lens device according to a first embodiment. (a) is a longitudinal sectional view in the axial direction illustrating the variable mirror actuator of the first embodiment, and (b) is a deformation film formed integrally with the reflection film and a magnetic body fixed to the deformation film. (a) It is the figure seen from the A direction of a figure. It is a figure which shows an example of the outline of the optical system of the optical pick-up incorporating the variable mirror actuator of 2nd Embodiment. (a) is the longitudinal cross-sectional view of the axial direction which illustrated the variable mirror actuator of 2nd Embodiment, (b) is the ring shape fixed to a deformation | transformation film | membrane formed integrally with a reflecting film, and a deformation | transformation film | membrane. It is the figure which looked at the magnetic body from the B direction of (a) figure. It is a longitudinal cross-sectional view of the axial direction which illustrated the variable mirror actuator of 3rd Embodiment. It is the longitudinal cross-sectional view of the axial direction which illustrated the variable mirror actuator of 4th Embodiment. (a) is a bottom view showing a reflector having a ring-shaped magnetic body, a deformation film, and a reflection film of the variable mirror actuator of the fifth embodiment, and (b) is a CC line in FIG. It is sectional drawing. (a) is a bottom view showing a reflector having a ring-shaped magnetic body, a deformation film, and a reflection film of the variable mirror actuator of the sixth embodiment, and (b) is a DD line in FIG. It is sectional drawing, (c) is the EE sectional view taken on the line of (a) figure. (a) is the longitudinal cross-sectional view of the variable mirror actuator of 7th Embodiment which illustrated the axial direction, (b) is the deformation | transformation film | membrane formed integrally with a reflection film from the F direction of (a) figure. It is a figure. (a) is the longitudinal cross-sectional view of the axial direction which illustrated the variable mirror actuator of 8th Embodiment, (b) is the deformation | transformation film | membrane formed integrally with a reflecting film, and the ring-shaped magnetic body fixed to this (A) is a diagram seen from the G direction of FIG. It is a bottom view which shows the reflector which has a ring-shaped magnetic body of the variable mirror actuator of 9th Embodiment, a deformation | transformation film | membrane, and a reflection film. It is a figure showing the displacement amount of the mirror with respect to the distance from the mirror center (center of the reflective film 27) at the time of applying a magnetic force to a ring-shaped magnetic body. It is a figure showing the deviation of the mirror (reflection film) surface shape and the ideal parabolic curve with respect to the distance from the mirror center (center of the reflection film). (a) is the longitudinal cross-sectional view of the axial direction which illustrated the variable mirror actuator of 10th Embodiment, (b) is the figure which looked at the holder and conducting wire of (a) from the H direction of (a) figure. is there. It is a figure which shows an example of the optical system of the optical pick-up which has the conventional aberration correction mechanism. 1 is an overall schematic diagram of an optical disc apparatus of the present invention. It is the schematic of an optical pick-up provided with the several spherical aberration correction mechanism of 9th Embodiment. It is the schematic which shows an example of the variable focus lens actuator of 9th Embodiment. It is the schematic of an optical pick-up provided with the several spherical aberration correction mechanism of 10th Embodiment. It is the schematic which shows an example of the variable mirror actuator of 10th Embodiment. It is a figure which shows the relationship between the substrate thickness error of an optical disk, and the spherical aberration which arises by it. It is a figure which shows the relationship between the deformation of the variable focus lens actuator of 1st Embodiment, and spherical aberration. CC sectional view taken on the line of variable focus lens actuator A1. It is a figure which shows the Example which correct | amends spherical aberration, a coma aberration, and / or astigmatism using a liquid crystal element.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 16 shows an example of the overall configuration of the optical disc apparatus according to the embodiment of the present invention.

  The optical disk device 100 includes an optical pickup H1 and a rotation motor, and the optical disk 32 is configured to be rotatable by the rotation motor.

  The optical pickup H1 plays a role of recording and / or reproducing digital information by irradiating the optical disk 32 with light. The reproduction light detected by the optical pickup H1 is converted into current / voltage (IV) and then input to the signal processing circuit. The signal processing circuit generates a reproduction signal and a servo signal and sends them to the controller.

  The controller controls the servo control circuit, the access control circuit, and the automatic position control means based on the servo signal. The automatic control means performs rotation control of the optical disk 32 by a rotary motor, the access control circuit performs position control of the optical pickup H1, and the servo control circuit performs position control of an objective lens of the optical pickup H1 described later. As a result, the light spot is positioned at an arbitrary position on the optical disk 32. The controller also controls the laser driver depending on whether playback or recording, and causes a laser included in an optical pickup H1 described later to emit light with an appropriate power / waveform.

  The optical disc apparatus 100 supports recording / reproduction of a multilayer optical disc having a plurality of recording layers, and the controller controls a spherical aberration correction mechanism, which will be described later, in order to correct spherical aberration that occurs according to the target layer. In addition, the controller controls an aberration correction mechanism, which will be described later, in order to correct coma and astigmatism caused by errors in the tilt of the optical disc (disc tilt) with respect to the optical axis and errors in the assembly of the optical pickup.

FIG. 21 is a diagram showing the relationship between the substrate thickness error of the optical disk and the amount of spherical aberration generated thereby when the NA of the objective lens is 0.85, that is, in Blu-ray Disc (BD). The objective lens of many BD optical pickups has a spherical aberration of 0 at a substrate thickness of 0.0875 mm, which is an intermediate position between the L0 layer (substrate thickness of 0.1 mm) and the L1 layer (substrate thickness of 0.075 mm) of the two-layer BD. However, when the recording layer position deviates from this thickness, spherical aberration as shown in FIG. 21 occurs. As described above, the amount of spherical aberration is substantially proportional to the substrate thickness error. For example, a very large spherical aberration of about 300 mλrms occurs in the recording layer shifted by 50 μm. As a result, the spots are not collected and the information on the optical disk cannot be read correctly. On the other hand, the spot on the optical disc cannot be correctly condensed due to spherical aberration generated in the objective lens due to fluctuations in the substrate thickness error, laser wavelength fluctuations, and temperature fluctuations. These spherical aberrations are small compared to the spherical aberration, but change during focusing on the recording layer in which the spherical aberration is corrected in a multilayer optical disc, so fine adjustment is necessary. . In addition, the optical pickup may intentionally shake the spherical aberration so as to maximize the reproduction signal intensity to search for a state in which the spherical aberration is optimally corrected. In this case, the spherical aberration can be finely adjusted. desirable.
<< First Embodiment >>
FIG. 1 shows an example of a schematic optical system of an optical pickup P1 incorporating a variable mirror actuator A1 of the variable focus lens device of the first embodiment.

  The variable mirror actuator A1 of the first embodiment arbitrarily corrects the reflecting surface of the reflecting mirror (reflecting film 17) that reflects the laser beam to enable spherical aberration correction.

  The optical pickup P1 includes an optical disc 12 on which a plurality of recording layers 11 (11a, 11b) to be attached to the optical pickup P1, a laser light source 7 that emits a laser beam that irradiates the recording layer 11 of the optical disc 12, and an optical disc. And a detector 1 for detecting the laser beam reflected by the twelve recording layers 11.

  The optical pickup P1 splits the laser beam from the laser light source 7 and the recording layer 11 of the optical disk 12 into the optical path of the laser beam from the laser light source 7 to the detector 1 through the recording layer 11 of the optical disk 12 by reflection and transmission. The laser beam from the polarization beam splitter 3 and the laser light source 7 reflected by the polarization beam splitter 3 is reflected toward the recording layer 11 of the optical disc 12 and the laser beam reflected by the recording layer 11 is reflected toward the detector 1. The variable mirror actuator A1 that performs the conversion, the quarter-wave plate 8 that converts linearly polarized light into circularly polarized light, and the objective lens that is moved in the optical axis direction by the lens actuator 10 and focuses the laser beam on the recording layer 11 of the optical disk 12. 9 and a condensing lens for condensing the laser beam reflected by the recording layer 11 on the detector 1. 2 is provided.

  In addition, between the laser light source 7 of the optical pickup P1 and the polarization beam splitter 3, a collimating lens 6 that makes the laser beam from the laser light source 7 parallel light and a grating that splits the laser beam collimated by the collimating lens 6 are used. And 5.

<Variable focus lens actuator A1>
FIG. 2A is an axial longitudinal sectional view illustrating the variable mirror actuator A1 of FIG. 1, and FIG. 2B is a deformation film 16 formed integrally with the reflective film 17 of the variable mirror actuator A1. 3 is a view of a ring-shaped magnetic body 18 fixed to the deformation film 16 as viewed from the direction A in FIG.

  In the variable mirror actuator A1, as shown in FIG. 1, the reflection film 17 that reflects the laser beam is made of a material that reflects the laser beam, for example, a metal such as aluminum or silver, a dielectric multilayer film containing SiO2, TiO2, or the like. Used to form a flat plate. As described above, the reflective film 17 may be a single-layer film such as a metal, or may be a multilayer reflective film using a dielectric or the like, and is not limited.

  Here, since the laser beam has a circular cross section and is incident on the reflection film 17 at an angle of 45 degrees, the reflection film 17 has the same circular shape as that before the reflection of the laser beam reflected by the reflection film 17. Are formed in an elliptical flat plate shape that is long in the laser beam traveling direction.

  As shown in FIG. 2, the reflective film 17 is laminated on one surface of an elliptical deformation film 16 having the same shape as the reflective film 17, such as a silicon substrate. Note that the deformable film 16 may be formed of a member other than a silicon substrate as long as it is a deformable member, and is not limited to a silicon substrate.

  On the other surface of the deformation film 16, a ring-shaped magnetic body 18 is laminated and fixed in order to bend the reflection film 17 into a parabolic shape that reflects the same laser beam as before reflection. The ring-shaped magnetic body 18 may be laminated and fixed on the reflective film.

  The ring-shaped magnetic body 18 is configured using a magnetic body. As shown in FIG. 1, in the ring-shaped magnetic body 18, the laser beam is incident on the reflection film 17 at an angle of 45 degrees, so that the laser beam reflected by the reflection film 17 has the same circular shape as before the reflection. Like the reflection film 17 and the deformation film 16, it is formed in an elliptical ring shape that is long in the traveling direction of the laser beam so as to have a transverse section. Since the ring-shaped magnetic body 18 does not hinder the deformation of the deformation film 16 due to its own rigidity, a low-rigidity structure is more desirable.

  The ring-shaped magnetic body 18 may be, for example, a composite material in which magnetic powder is dispersed in a photoresist, and is not limited as long as it is a material that receives a strong magnetic force by a magnetic field.

  In this way, a ring structure having a plurality of laminates in which the reflective film 17 is laminated on one surface of the deformation film 16 and the ring-shaped magnetic body 18 is laminated on the other surface of the deformation film 16 is described below. This is referred to as a reflector 17T (see FIG. 2).

  As shown in FIG. 2A, in the variable mirror actuator A1, the reflector 17T has an electromagnet D1 through a ring-shaped spacer 15 having an elliptical outer peripheral shape similar to that of the reflective film 17 and the deformation film 16. It is provided on the top.

  The spacer 15 is preferably a non-magnetic material such as resin, and may be formed integrally with the deformation film 16. The spacer 15 may be formed of a magnetic material as long as the performance of the variable mirror actuator A1 does not deteriorate.

  The electromagnet D1 includes a magnetic yoke 14 and a coil 13 wound around the yoke central portion 14c that forms the central portion thereof a plurality of times.

  The yoke 14 of the electromagnet D1 has an elliptical elliptical columnar yoke central portion 14c similar to the ring-shaped magnetic body 18, and a yoke peripheral portion 14s formed continuously on the lower outer periphery of the yoke central portion 14c. Yes. The yoke peripheral portion 14s has a U-shape with an axial cross section opened inward, and has an elliptical outer peripheral shape similar to the reflective film 17 and the deformation film 16 (see FIG. 2B). .

  The yoke 14 is formed of an iron core, ferrite, cobalt, or the like obtained by laminating a plurality of thin steel plates.

  The variable mirror actuator A1 of this configuration applies a current to the coil 13 of the electromagnet D1, thereby generating a strong magnetic field in the yoke 14 and attracting the ring-shaped magnetic body 18 of the reflector 17T, thereby FIG. As shown by the two-dot chain line, both the deformation film 16 and the reflection film 17 are bent in a parabolic shape. In this way, the divergence angle of the laser beam reflected by the reflection film 17 is controlled by bending the reflection film 17 into a parabolic shape suitable for aberration correction. Thereby, the spherical aberration of the laser beam generated by changing the position of the recording layer 11 to the position p1 of the recording layer 11a and the position p2 of the recording layer 11b shown in FIG. 1 is corrected.

  Here, the structure of the yoke 14 is more in the outer periphery outer region of the coil 13 shown in FIG. 2A than the configuration of the simple elliptical columnar yoke central portion 14c formed only inside the coil 13. A configuration in which concentric elliptical yoke peripheral portions 14 are connected and added is more desirable because the density of magnetic lines of force around the coil 13 is increased and the magnetic force acting on the ring-shaped magnetic body 18 can be further increased.

  For example, as shown in FIG. 2A, by forming the yoke peripheral upper portion 14s1 in the yoke peripheral portion 14s having a U-shaped cross section, the magnetic field formed around the coil 13 can be made higher density, and the ring-shaped magnetic A stronger magnetic force can be applied to the body 18.

  Needless to say, the yoke 14 may be composed of only the yoke central portion 14c.

  FIG. 22 is a diagram illustrating an example of the relationship between the deformation amount of the variable focus lens actuator of the first embodiment and spherical aberration. By changing the curvature of the substantially flat deformation film 16 in the state where there is no substrate thickness error as shown in FIG. 2 according to the change in the substrate thickness, it is possible to substantially cancel the spherical aberration caused by the substrate thickness error. In this example, for example, when the curvature is changed to 0.045 [1 / mm] with respect to a change in the substrate thickness of 50 μm, the spherical aberration that has occurred about 300 mλrms can be almost corrected.

<Reading of Record from Recording Layer 31 of Optical Disc 32>
Next, reading of the recording (signal) by the laser beam from the recording layer 11 of the optical disc 12 mounted on the optical pickup P1 will be described by taking reading from the recording layer 11b as an example.
The same applies to reading of a record (signal) from the recording layer 11a.

  As shown in FIG. 1, in order to read the pit recorded on the recording layer 11b of the optical disc 12 as an electric signal, the laser beam emitted from the laser light source 7 is collimated by the collimator lens 6 and passes through the grating 5; Reflected by the polarizing beam splitter 3 toward the variable mirror actuator A1. A part of the laser beam emitted from the laser light source 7 passes through the polarization beam splitter 3 and is received by the front monitor 4, and the emission intensity of the laser light source 7 is monitored.

  Then, the laser beam reflected by the polarizing beam splitter 3 is reflected by the reflecting film 17 of the variable mirror actuator A1, then passes through the ¼ wavelength plate 8, is converted into circularly polarized light, and is recorded by the objective lens 9 to the recording film 11b. The light is focused on and reflected from the recording film 11b. The laser beam reflected by the recording film 11b is transmitted again through the objective lens 9 and converted into collimated light, then transmitted through the quarter-wave plate 8 and converted into linearly polarized light, and is reflected by the reflective film 17 of the variable mirror actuator. Reflected toward the polarization beam splitter 3.

  The laser beam reflected by the reflection film 17 is transmitted through the polarization beam splitter 3, is condensed on the detector 1 by the condenser lens 2, and the amount of light incident on the detector 1 is converted into an electrical signal.

  At this time, in order to adjust the focal position of the laser beam of the objective lens 9 on the recording layer 11 (11a or 11b) of the optical disc 12, the objective calculated by the control circuit C1 based on the information of the laser beam received by the detector 1 is used. Based on a signal indicating the amount of movement of the lens 9, a driving current is passed from the lens driving circuit C2 to the lens actuator 10. Thereby, the lens actuator 10 translates or rotates the objective lens 9 with respect to the recording layer 11 of the optical disc 12 in the optical axis or in a direction perpendicular to the optical axis.

  Further, based on the information received by the detector 1, a current indicating the amount of deflection of the reflective film 17 calculated by the control circuit C1 is applied from the mirror drive circuit C3 to the coil 13 of the variable mirror actuator A1.

  As a result, the variable mirror actuator A1 generates a strong magnetic field at the center of the yoke 14 by the current flowing through the coil 13, and the ring-shaped magnetic body 18 of the reflector 17T is indicated by a two-dot chain line in FIG. So as to attract toward the electromagnet D1. Accordingly, the deformation film 16 and the reflection film 17 of the reflector 17T supported by the electromagnet D1 via the spacer 15 are bent in a parabolic shape.

In this way, by passing a current through the coil 13 of the variable mirror actuator A1, the reflective film 17 is bent into a desired parabolic shape, and the divergence angle of the laser beam reflected by the reflective film 17 is determined by the magnitude of the current of the coil 13. By controlling, the spherical aberration of the laser beam caused by the change of the position of the recording layer 11 to the position P1 (recording layer 11a) and the position P2 (recording layer 11b) is corrected.
<< Second Embodiment >>
Next, the variable mirror actuator A2 of the second embodiment will be described with reference to FIGS.

  FIG. 3 is a diagram illustrating an example of a schematic optical system of an optical pickup P2 incorporating the variable mirror actuator A2 of the second embodiment.

  FIG. 4A is an axial longitudinal sectional view illustrating the variable mirror actuator A2 of the second embodiment, and FIG. 4B is a deformation formed integrally with the reflective film 27 of the variable mirror actuator A2. FIG. 5 is a view of the ring-shaped magnetic body 28 fixed to the film 26 and the deformation film 26 as viewed from the direction B in FIG.

  The basic configuration of the optical pickup P2 of the second embodiment shown in FIG. 3 is the same as that of the optical pickup P1 (see FIG. 1) of the first embodiment, but the arrangement of the variable mirror actuator A1 of the first embodiment is the same. The variable mirror actuator A2 into which the laser beam is vertically incident is different. Accordingly, the variable mirror actuator A2 of the second embodiment is different from the configuration of the variable mirror actuator A1 of the first embodiment.

  Since the other configuration is the same as that of the variable mirror actuator A1 of the first embodiment, detailed description thereof is omitted.

  In FIGS. 3 and 4, the reference numerals of the constituent elements of the variable mirror actuator A <b> 2 are shown with reference numerals in the 20th order.

  Hereinafter, a structure different from the first embodiment of the optical pickup P2 of the second embodiment will be described in detail.

  The optical pickup P2 of the second embodiment differs from the optical system of the first embodiment shown in FIG. 1 in the optical system between the grating 5 and the objective lens 9.

  In the optical pickup P2 shown in FIG. 3, the laser beam emitted from the laser light source 7 and partially reflected by the beam splitter 19 is transmitted through the polarization beam splitter 3 and transmitted through the quarter-wave plate 8 to be circularly polarized. The The laser beam that has passed through the ¼ wavelength plate 8 is reflected by the reflection film 27 of the variable mirror actuator A 2, is again transmitted through the ¼ wavelength plate 8 to be linearly polarized, and is then converted into linearly polarized light by the polarization beam splitter 3. Is reflected toward the recording layer 11.

  The laser beam reflected by the polarization beam splitter 3 passes through the objective lens 9 and is collected, and is reflected by the recording film 11 (11a or 11b). The reflected laser beam is again transmitted through the objective lens 9 to become parallel light, reflected by the polarization beam splitter 3, and transmitted through the quarter-wave plate 8 to be circularly polarized. Then, the laser beam reflected again by the reflecting film 27 of the variable mirror actuator A 2 is transmitted through the quarter-wave plate 8 to be linearly polarized light, further passes through the polarizing beam splitter 3, and is irradiated toward the beam splitter 19. Then, a part of the light is transmitted and condensed on the detector 1 by the condenser lens 2.

  In the optical system of the optical pickup P2, the laser beam is incident / reflected perpendicularly to the reflection mirror 27 of the variable mirror actuator A2. Therefore, the laser beam applied to the reflection mirror 27 is circular.

  Therefore, the variable mirror actuator A2 of the second embodiment is obtained by forming the elliptical columnar variable mirror actuator A1 of the first embodiment into a cylindrical shape. The other configuration is the same as that of the variable mirror actuator A1 of the first embodiment.

  As shown in FIG. 4, in the variable mirror actuator A <b> 2 of the second embodiment, the reflective film 27 is formed in a circular flat plate shape, and the deformation film 26 is formed in a circular flat plate shape having the same shape as the reflective film 27. ing. The ring-shaped magnetic body 28 fixed to the deformation film 26 is formed in a circular ring shape. Thereby, as shown in FIG.4 (b), the reflector 27T is formed in the circular flat form.

  As shown in FIG. 4A, the reflector 27T is installed on the cylindrical electromagnet D2 via the deformable film 26 and a circular ring-shaped spacer 25 having the same outer peripheral shape as the reflective film 27. .

  The electromagnet D2 includes a circular cylindrical yoke central portion 24c similar to the ring-shaped magnetic body 28 and a U-shaped magnetic body periphery of the U-shaped magnetic body that is continuously formed on the outer periphery of the lower portion thereof and has an axially open cross section. A substantially cylindrical yoke 24 having a portion 24s is provided.

  A coil 23 is wound a plurality of times around a cylindrical yoke central portion 24c of the yoke 24 of the electromagnet D2.

  The dimension t in FIG. 4 (a) indicates the dimension of the gap between the ring-shaped magnetic body 28 and the yoke 24, and the dimension W1 in FIG. 4 (b) is a circular ring-shaped magnetic body. In FIG. 4B, the dimension W2 indicates the radial dimension of the inner diameter of the circular ring-shaped spacer 25.

  According to the variable mirror actuator A2 of the second embodiment, unlike the reflection film 17 of the elliptical mirror of FIG. 2 used in the variable mirror actuator A1 of the first embodiment, the reflection film 27 can be circular and the mirror size can be reduced. Is possible.

In addition, the variable mirror actuator A2 can be manufactured in a columnar shape, so that it is easy to manufacture. Further, the control by the control circuit C1 and the mirror drive circuit C3 for deforming the reflective film 27 becomes easy. The ring-shaped magnetic body 28 may be laminated and fixed on the reflective film.
<< Third Embodiment >>
Next, the variable mirror actuator A3 of the third embodiment will be described with reference to FIG.

  FIG. 5 is a longitudinal sectional view in the axial direction illustrating the variable mirror actuator A3 of the third embodiment.

  The basic configuration of the optical pickup of the third embodiment is the same as that of the optical pickups P1 and P2 (see FIGS. 1 and 3) of the first and second embodiments, and the variable mirror actuator of the first and second embodiments. The shapes of the yokes 14 and 24 of A1 and A2 (see FIGS. 2A and 4A) are different.

  Since other configurations are the same as those of the variable mirror actuators A1 and A2 of the first and second embodiments, detailed description thereof is omitted.

  In FIG. 5, the reference numerals of the constituent elements of the variable mirror actuator A <b> 3 are shown with reference numerals in the thirtieth order.

  Hereinafter, the structure different from the yokes 14 and 24 of the variable mirror actuators A1 and A2 of the first and second embodiments will be described.

  The variable mirror actuator A3 of the third embodiment shown in FIG. 5 is the center of the yoke 34 on the inner diameter side of the coil 33 in the case of an elliptical columnar yoke 34 similar to the yoke 14 of the first embodiment (see FIG. 2). The portion is an elliptic columnar cavity 34k.

  On the other hand, in the case of a cylindrical yoke 34 similar to the yoke 24 of the second embodiment (see FIG. 4), the central portion of the yoke 34 on the inner diameter side of the coil 33 is a cylindrical cavity 34k.

As a result, the magnetic flux flowing in the yoke 34 on the inner diameter side of the coil 33 is concentrated by the yoke central portion 34 c inside the coil 33, and as a result, the magnetic flux density passing through the ring-shaped magnetic body 38 is increased. Therefore, there is an effect that the attractive force of the electromagnet D3 to the ring-shaped magnetic body 38 is improved.
<< Fourth Embodiment >>
Next, a variable mirror actuator A4 according to a fourth embodiment will be described with reference to FIG.

  FIG. 6 is an axial longitudinal sectional view illustrating the variable mirror actuator A4 of the fourth embodiment.

  The basic configuration of the optical pickup of the fourth embodiment is the same as that of the optical pickups P1 and P2 (see FIGS. 1 and 3) of the first and second embodiments, and the yoke 44a of the variable mirror actuator A4 shown in FIG. Is different from the shapes of the yokes 14 and 24 of the variable mirror actuators A1 and A2 of the first and second embodiments (see FIGS. 2A and 4A).

  Since other configurations are the same as those of the variable mirror actuators A1 and A2 of the first and second embodiments, detailed description thereof is omitted.

  In FIG. 6, the reference numerals of the respective constituent elements of the variable mirror actuator A4 are shown with reference numerals in the 40s.

  Hereinafter, the structure different from the yokes 14 and 24 of the variable mirror actuators A1 and A2 of the first and second embodiments will be described.

  The variable mirror actuator A4 of the fourth embodiment includes the elliptical or cylindrical yokes 14 and 24 of the first and second embodiments, and the yoke 44a on the inner peripheral portion of the coil 43 made of a magnetic material such as an iron core or ferrite. On the other hand, the outer peripheral portion of the coil 43 is constituted by a holder 44H of a structure made of another material such as resin.

  Here, a structure corresponding to the spacers 15 and 25 of the first and second embodiments (see FIGS. 2A and 4A) is integrally formed on the holder 44H, which is a separate structure from the yoke 44a. is doing.

  As a result, the positions of the yokes 14 and 24 of the variable mirror actuators A1 and A2 of the first and second embodiments can be configured as the yoke 44a and the holder 44H.

  Further, by using a material that can be easily processed for the holder 44H, the processing can be facilitated.

In addition, the holder 44H can be formed integrally with a base member that is a basic support member of the resin of the optical pickup, and the adaptability to the optical system is improved.
<< Fifth Embodiment >>
Next, a variable mirror actuator according to a fifth embodiment will be described with reference to FIG.

  FIG. 7A is a bottom view showing a reflector 57T having a ring-shaped magnetic body 58, a deformation film 56, and a reflection film 57 of the variable mirror actuator of the fifth embodiment (in the direction of arrow A in FIG. 2A). FIG. 7B is a cross-sectional view taken along the line CC of FIG. 7A.

  The basic configuration of the optical pickup of the fifth embodiment is the same as that of the optical pickups P1 and P2 (see FIGS. 1 and 3) of the first and second embodiments, and the deformation film 56 of the variable mirror actuator shown in FIG. Is different from the shapes of the deformation films 16 and 26 (see FIGS. 2 and 4) of the variable mirror actuators A1 and A2 of the first and second embodiments.

  Since other configurations are the same as those of the variable mirror actuators A1 and A2 of the first and second embodiments, detailed description thereof is omitted.

  In FIG. 7, the reference numerals of the constituent elements of the reflector 57T of the variable mirror actuator are shown with the reference numerals in the 50s.

  Hereinafter, a structure different from the deformation films 16 and 26 of the variable mirror actuators A1 and A2 of the first and second embodiments will be described.

  The deformable film 56 of the variable mirror actuator of the fifth embodiment shown in FIG. 7 is located on the outer periphery of the ring-shaped magnetic body 58 with respect to the deformable films 16 and 26 having a single film thickness of the first and second embodiments. In the region, concentrically thick regions 56a (56a1, 56a2, 56a3) and thin regions 56b (56b1, 56b2, 56b3, 56b4) are alternately and periodically formed.

  The ratio of the thick region 56a in each cycle of the thick region 56a and the thin region 56b of the deformation film 56 decreases as the distance from the center of the mirror, that is, the center of the reflective film 57 decreases. As the distance from the center of the reflection film 57 increases, the effective rigidity of the reflector 57T constituting the mirror decreases.

  Therefore, by optimizing the ratio of the thick region 56a in each cycle of the thick region 56a and the thin region 56b, the reflector 57T is made an ideal parabola by the magnetic force acting on the ring-shaped magnetic body 58. It can be transformed into a shape.

  In the fifth embodiment, the reflector 57T having the circular ring-shaped magnetic body 58, the deformation film 56, and the reflection film 57 has been described as an example, but the variable mirror actuator A1 of the first embodiment (FIG. 2). Of course, the present invention can be similarly applied to the reflector 17T having the elliptical ring-shaped magnetic body 18, the deformation film 16, and the reflection film 17, as shown in FIG.

Further, the ring-shaped magnetic body 58 may be laminated and fixed on the reflective film.
<< Sixth Embodiment >>
Next, the variable mirror actuator of 6th Embodiment is demonstrated using FIG.

  FIG. 8A is a bottom view of the reflector 67T having the ring-shaped magnetic body 68, the deformation film 66, and the reflection film 67 of the variable mirror actuator of the sixth embodiment (viewed in the direction of arrow A in FIG. 2A). 8 (b) is a sectional view taken along the line DD of FIG. 8 (a), and FIG. 8 (c) is a sectional view taken along the line EE of FIG. 8 (a).

  The basic configuration of the optical pickup of the sixth embodiment is the same as that of the optical pickups P1 and P2 (see FIGS. 1 and 3) of the first and second embodiments, and the deformation film 66 of the variable mirror actuator shown in FIG. Is different from the shapes of the deformation films 16 and 26 (see FIGS. 2A and 4A) of the variable mirror actuators A1 and A2 of the first and second embodiments.

  Since other configurations are the same as those of the variable mirror actuators A1 and A2 of the first and second embodiments, detailed description thereof is omitted.

  In FIG. 8, the reference numerals of the constituent elements of the reflector 67 </ b> T of the variable mirror actuator are shown with reference numerals in the 60s.

  Hereinafter, a structure different from the deformation films 16 and 26 of the variable mirror actuators A1 and A2 of the first and second embodiments will be described.

  The deformable film 66 of the variable mirror actuator of the sixth embodiment shown in FIG. 8 has a ring-like magnetic property compared to the deformable films 16 and 26 (see FIGS. 2 and 4) having a single film thickness of the first and second embodiments. In the outer peripheral outer region of the body 68, the thick region 66a is radially spread between the thin regions 66b. The thick region 66a is formed so that its width increases as it approaches the center of the deformation film 66, while its width decreases as it approaches the outer periphery.

  As a result, the effective rigidity of the reflector 67T forming the mirror decreases as the distance from the mirror center (center of the reflective film 67) increases.

  Therefore, by optimizing the structure in which the radially thick region 66a extends in the deformation film 66, the reflector 67T can be deformed into an ideal parabolic shape by the magnetic force acting on the ring-shaped magnetic body 68.

In the sixth embodiment, the reflector 67T having the circular ring-shaped magnetic body 68, the deformation film 66, and the reflection film 67 has been described as an example. However, the variable mirror actuator A1 of the first embodiment (FIG. 2). Of course, the present invention can be similarly applied to an elliptical reflector 17T having an elliptical ring-shaped magnetic body 18, a deformation film 16, and a reflective film 17, as shown in FIG.
<< Seventh Embodiment >>
Next, a variable mirror actuator A7 according to a seventh embodiment will be described with reference to FIG.

  FIG. 9A is an axial longitudinal sectional view illustrating the variable mirror actuator A7 of the seventh embodiment, and FIG. 9B is a deformation formed integrally with the reflective film 77 of the variable mirror actuator A7. It is the figure which looked at the film | membrane 76 from F direction of Fig.9 (a).

  The basic configuration of the optical pickup of the seventh embodiment is the same as that of the optical pickups P1 and P2 (see FIGS. 1 and 3) of the first and second embodiments, and the variable mirror actuator A7 shown in FIG. Are the shapes of the ring-shaped magnetic bodies 18 and 28 (see FIGS. 2A and 4A) of the variable mirror actuators A1 and A2 of the first and second embodiments and the mirror deformation principle (of the reflectors 17T and 27T). The deformation principle is different.

  Since other configurations are the same as those of the variable mirror actuators A1 and A2 of the first and second embodiments, detailed description thereof is omitted.

  Hereinafter, structures different from the ring-shaped magnetic bodies 18 and 28 of the variable mirror actuators A1 and A2 and the mirror deformation principle of the first and second embodiments (deformation principle of the reflectors 17T and 27T) will be described.

  In FIG. 9, the reference numerals of the constituent elements of the variable mirror actuator A <b> 7 are shown with reference numerals in the 70s.

  In the variable mirror actuator A7 of the seventh embodiment, for example, a magnetic ring 78 corresponding to the ring-shaped magnetic body 18 shown in FIG. 2 is not fixed to the deformation film 76.

  Then, as shown in FIG. 9A, a thick cylindrical short cylindrical magnetic ring 78 and a magnetic ring 78 are formed in a cylindrical groove 74m formed around the coil 73 in the yoke 74 of the electromagnet D7. A structure having a compression coil spring 78s that presses upward is disposed.

  Due to this structure, the short cylindrical magnetic ring 78 receives an upward pressing force from the compression coil spring 78s during the steady state when no current is flowing through the coil 73 of the electromagnet D7 (upper part of FIG. 9A). The deformation film 76 and the reflection film 77 are deformed into a shape close to a parabolic shape (see the solid line in FIG. 9A).

  From this steady state, when a current is applied to the coil 73 of the electromagnet D7, the magnetic field generated in the yoke 74 around the coil 73 is transmitted through the magnetic ring 78, and the magnetic ring 78 is drawn in a direction approaching the electromagnet D7. Since the upward pressing force of the body ring 78 is weakened, the deformation film 76 and the reflection film 77 are restored to a shape close to a flat plate shape (see the two-dot chain line in FIG. 9A).

  On the other hand, when the applied current to the coil 73 is reduced, the magnetic field generated in the yoke 74 around the coil 73 is weakened, the magnetic force in the direction approaching the electromagnet D7 received by the magnetic ring 78 is weakened, and the compression coil spring 78s is moved upward. Upon receiving the elastic force, the magnetic ring 78 pushes the deformation film 76 and the reflection film 77 upward (upward in FIG. 9A).

  As described above, the elastic force of the compression coil spring 78 s causes the ring-shaped magnetic ring 78 to contact the deformation film 76 in a ring shape, and drives the variable mirror actuator A 7 to apply a current to the coil 73 of the electromagnet D 7. The deformation film 76 can be flexed freely as in the first embodiment, and the reflection film 77 can have a desired parabolic shape.

In the seventh embodiment, the case where the variable mirror actuator A7 has a cylindrical shape has been described as an example. However, as in the first embodiment, the case where the variable mirror actuator A7 has an elliptical column shape (see FIG. 2) is also applicable. Of course there is.
<< Eighth Embodiment >>
Next, a variable mirror actuator A8 according to an eighth embodiment will be described with reference to FIG.

  FIG. 10A is an axial longitudinal sectional view illustrating the configuration of the variable mirror actuator A8 of the eighth embodiment, and FIG. 10B is formed integrally with the reflective film 87 of the variable mirror actuator A8. FIG. 11 is a view of a deformable film 86 and a ring-shaped good conductor 88 fixed thereto, as viewed from the G direction in FIG.

  The basic configuration of the optical pickup of the eighth embodiment shown in FIG. 10 is the same as that of the optical pickups P1 and P2 (see FIGS. 1 and 3) of the first and second embodiments.

  The basic configuration of the variable mirror actuator A8 of the eighth embodiment is similar to the variable mirror actuators A1 and A2 of the first and second embodiments, but the variable mirror actuators A1 and A2 of the first and second embodiments The driving principle of the mirrors (reflection films 17 and 27) is different.

  Since other configurations are the same as those of the variable mirror actuators A1 and A2 of the first and second embodiments, detailed description thereof is omitted.

  In FIG. 10, the reference numerals of the respective constituent elements of the variable mirror actuator A8 are shown with reference numerals in the 80s.

  Hereinafter, a structure in which the variable mirror actuators A1 and A2 of the first and second embodiments of the variable mirror actuator A8 of the eighth embodiment and the mirrors (reflection films 17 and 27) drive principle are different will be described.

  In the variable mirror actuator A8 of the eighth embodiment, a ring-shaped good conductor 88 such as gold is used instead of the ring-shaped magnetic body fixed to the deformable film 86 integrated with the reflective film 87 (FIG. 10B). Reference). The ring-shaped good conductor 88 is arranged in the outer region of the outer peripheral surface 84a of the yoke 84 facing the inner periphery of the coil 83 of the electromagnet D8.

  Then, the ring-shaped spacer exemplified in the first and second embodiments is eliminated between the reflector 87T and the yoke 84, the yoke outer peripheral portion 84g is formed to extend to the spacer region, and the reflector 87T is formed on the yoke outer peripheral portion 84g. Is fixed.

  The variable mirror actuator A8 of this configuration is arranged outside the outer peripheral surface 84a of the yoke 84 by passing a drive current through the coil 83 of the electromagnet D8 and changing the magnetic flux in the yoke 84 by electromagnetic induction. A change in magnetic flux passing through the ring of the ring-shaped good conductor 88 shown in b) occurs. Along with this, an induced current is induced in the ring-shaped good conductor 88 in the ring circulation direction, a magnetic field is generated that cancels the magnetic flux transmitted through the ring of the good conductor 88, and repels the magnetic field generated from the coil 83. The force acts on the ring-shaped good conductor 88.

  Thereby, the deformation | transformation film | membrane 86 can be bent to a suitable parabolic shape similarly to 1st, 2nd embodiment.

  Note that the drive waveform of the current applied to the coil 83 does not change the magnetic field and does not act on the good conductor 88 in constant current drive. Further, in the case of linear sine curve current driving, the force acting on the good conductor 88 is canceled out, and a phenomenon occurs in which the movement of the good conductor 88 is hindered.

  Therefore, it is desirable that the current applied to the coil 83 be a non-linear driving waveform such as a triangular wave or a sine half wave that can move the good conductor 88 well.

In the eighth embodiment, the case where the variable mirror actuator A8 has a cylindrical shape has been described as an example. However, as in the first embodiment, the present invention can be similarly applied to an elliptic cylinder shape. is there.
<< Ninth Embodiment >>
Next, the variable mirror actuator of 9th Embodiment is demonstrated using FIG.

  FIG. 11 is a bottom view showing the reflector 97T having the ring-shaped magnetic body 98, the deformation film 96, and the reflection film 97 of the variable mirror actuator of the ninth embodiment (corresponding to the view in the direction of arrow A in FIG. 2A). ).

  The basic configuration of the optical pickup (not shown) of the ninth embodiment is the same as that of the optical pickups P1 and P2 (see FIGS. 1 and 2) of the first and second embodiments.

  The reflector 97T of the variable mirror actuator of the ninth embodiment is different from the mirror shape (the shapes of the reflectors 17T and 27T) of the variable mirror actuators A1 and A2 of the first and second embodiments.

  Since other configurations are the same as those of the variable mirror actuators A1 and A2 of the first and second embodiments, detailed description thereof is omitted.

  In FIG. 11, the reference numerals of the components of the reflector 97 </ b> T are denoted by reference numerals in the 90s.

  Hereinafter, a structure different from the reflectors 17T and 27T of the variable mirror actuators A1 and A2 of the first and second embodiments will be described.

  In the reflector 27T, which is a variable mirror in the second embodiment, as shown in FIG. 4, a ring-shaped magnetic body 28 is fixed on a circular reflective film 27 having a single film thickness and a deformation film 26. . The magnetic force generated by the coil 23 and the yoke 24 disposed below the reflector 27T, which is a variable mirror, causes an attractive force toward the yoke 24 on the ring-shaped magnetic body 28, and the reflector 27T forming the mirror at this time The amount of displacement of the mirror at each distance from the center (the center of the reflective film 27) is represented by a solid line L3 in FIG.

  FIG. 12 is a diagram showing the amount of displacement of the mirror (reflection film 27) with respect to the distance from the mirror center (center of the reflection film 27) when a magnetic force is applied to the ring-shaped magnetic body 28 of the second embodiment. Yes, the deformation of the mirror surface shape of the second embodiment is represented by a solid line (L3), while the ideal parabolic curve of the mirror surface shape that ideally reflects the laser beam is represented by a broken line (L4).

  According to FIG. 12, in the structure of the second embodiment, the deformation of the mirror is within the inner circumference of the ring-shaped magnetic body 28 (left of the ring inner circumference position W1 in FIG. 12). Consistency with the object curve L4 is high, and the outer peripheral edge 27e (see FIG. 12) of the outer periphery of the ring-shaped magnetic body 28 (the area from the ring inner periphery W1 to the right and the mirror end position W2 in FIG. 4), gradually deviates from an ideal parabolic ideal parabolic curve L4.

  For highly accurate spherical aberration correction, the difference between the ideal parabolic ideal parabolic curve L4 and the mirror surface shape L3 of the mirror (reflection film 27) needs to be on the order of nanometers or less.

  On the other hand, in order to mount the variable mirror actuator A2 on the optical pickup P2 (see FIG. 3), the variable mirror actuator A2 needs to be reduced in size by several micrometers square, so that it is disposed below the reflector 27T forming the variable mirror. Due to the magnetic field generated by the coil 23 and the yoke 24, the attractive force acting on the ring-shaped magnetic body 28 becomes very weak.

  On the other hand, the deformation film 26 and the reflective film 27 have a larger section modulus and improved rigidity with downsizing, and therefore generally the distance between the ring inner peripheral position W1 and the mirror end position W2 shown in FIG. The rigidity of the outer circumferential outer region of the ring-shaped magnetic body 28 (see FIG. 4B) needs to be effectively reduced. That is, the deformation and the reduction in rigidity of the deformation film 26 and the reflection film 27 of the variable mirror actuator A2 are contradictory phenomena.

  Therefore, in the reflector 97T of the ninth embodiment shown in FIG. 11, the gaps 99 are periodically and periodically formed in the outer peripheral outer regions 96s and 97s of the ring-shaped magnetic body 98 of the deformation film 96 and the reflection film 97. Yes. Since the rigidity of the outer peripheral outer regions 96s and 97s of the ring-shaped magnetic body 98 is effectively reduced by increasing the ratio of the region D2 as the gap 99 per period D1 in the outer peripheral regions 96s and 97s, it is variable. The deformation film 96 and the reflection film 97 of the mirror actuator can be both reduced in size and reduced in rigidity.

  Note that the deformation of the deformation film 96 and the reflection film 97 in the ninth embodiment is different in rigidity in the cross section of the beam structure portion L1 and the gap portion L2 shown in FIG. As shown in FIG. 13, the deviation between the mirror surface shape at the position and the ideal parabolic curve is different from the ideal parabolic curve line (0.0 line on the horizontal axis) as the distance from the center of the mirror increases. Deviation in conflicting directions.

  FIG. 13 is a diagram showing the deviation between the mirror (reflective film 97) surface shape and the ideal parabolic curve with respect to the distance from the mirror center (center of the reflective film 97). The mirror surface shape of FIG. The deviation (0.0) line from the parabola curve indicates a line having no deviation between the mirror surface shape and the ideal parabola curve, that is, a line representing the ideal parabola curve.

Therefore, the distance W3 between the gap 99 in the outer circumferential outer region of the ring-shaped magnetic body 98 shown in FIG. 11 and the ring-shaped magnetic body 98, the number of beam structures L1, the size and number of the gap 99 in the gap L2. Etc. are optimally designed, without increasing the distance between the ring inner circumferential position W1 and the mirror end position W2, which is an edge that substantially forms a mirror, and the region within the inner circumference of the ring-shaped magnetic body 98 and It can be made to coincide with an ideal parabola-shaped ideal parabolic curve with high accuracy in a region from the inner periphery / outside of the ring-shaped magnetic body 98 to the mirror end position W2.
<< Tenth Embodiment >>
Next, a variable mirror actuator A10 according to a tenth embodiment will be described with reference to FIG.

  FIG. 14A is a longitudinal sectional view in the axial direction illustrating the variable mirror actuator A10 of the tenth embodiment, and FIG. 14B shows the holder 130 and the conductive wire 128 shown in FIG. It is the figure seen from the H direction of (a).

  The basic configuration of the optical pickup (not shown) of the tenth embodiment is the same as that of the optical pickups P1 and P2 (see FIGS. 1 and 2) of the first and second embodiments, and FIG. A variable mirror actuator A10 shown in the figure has a different configuration from the yokes 14 and 24 and the coils 13 and 23 of the variable mirror actuators A1 and A2 of the first and second embodiments.

  Since other configurations are the same as those of the variable mirror actuators A1 and A2 of the first and second embodiments, detailed description thereof is omitted.

  In FIG. 14, the reference numerals of the constituent elements of the variable mirror actuator A10 are shown with reference numerals in the 100s.

  Hereinafter, a structure different from the variable mirror actuators A1 and A2 of the first and second embodiments will be described.

  The holder 130 of the variable mirror actuator A10 of the tenth embodiment shown in FIG. 14 is formed with a short cylindrical recess 130o in the upper center portion, and is formed in a short cylindrical shape using resin or the like. And the conducting wire 128 for applying the attractive force by a magnetic field to the ring-shaped magnetic body 108 of the reflector 107T is spirally arranged in the recess 130o of the holder 130.

  The variable mirror actuator A10 of this configuration generates a magnetic field that applies an attractive force to the ring-shaped magnetic body 108 by applying a current to the conducting wire 128 that is spirally arranged in the recess 130o in the holder 130, and this magnetic field causes the ring to ring. The magnetic film 108 is attracted toward the conducting wire 128, whereby the deformable film 106 and the reflective film 107 to which the ring-shaped magnetic material 108 is fixed are deformed into a parabolic shape that approximates an ideal parabola.

  According to the tenth embodiment, since the conducting wire 128 is a flat winding, the structure of the holder 130 and the conducting wire 128 can be made thin, and as a result, the entire variable mirror actuator A10 can be made thinner than the first and second embodiments. is there.

  Further, the shape of the holder 130 of the variable mirror actuator A10 can be simplified, the productivity can be improved, and the production cost can be reduced.

In the tenth embodiment, the case where the spiral conductive wire 128 is formed in a planar shape is exemplified. However, if a magnetic field that causes an attractive force to deform the reflective film 107 into an ideal parabola can be generated, the spiral conductive wire is formed. 128 may be formed with unevenness. The ring-shaped magnetic body 108 may be laminated and fixed on the reflective film.
<Effect>
According to the first to tenth embodiments, the circular or elliptical ring-shaped magnetic bodies 18,..., 68 fixed to the deformable films 16,. 88, when a driving force is applied to the ring-shaped magnetic bodies 98, 108 from the electromagnets D1,..., D10, circular or elliptical ring-shaped magnetic bodies 18,. The ring-shaped force distribution of the body ring 78, the good conductor 88, and the ring-shaped magnetic bodies 98 and 108 acts.

  As a result, the ring-shaped magnetic bodies 18,..., 68, the magnetic body ring 78, the good conductor 88, the deformed films 16,. It can be formed into a curved shape.

  Further, in this structure, the bending amounts from the centers of the ring-shaped magnetic bodies 18,..., 68, the magnetic ring 78, the good conductor 88, and the ring-shaped magnetic bodies 98 and 108 are the same concentrically or concentrically.

  Therefore, even if the deformable film 16,..., 106 and the reflective film 17,... 107 are bent and deformed, the ring-shaped magnetic bodies 18,. The distance between the magnetic bodies 98 and 108 and the electromagnets D1,..., D10 is the same everywhere in the ring shape, and the force that makes the stress distribution uniform in the deformable films 16,. Can be granted.

  Further, the forces acting on the ring-shaped magnetic bodies 18,..., 68, the magnetic ring 78, the good conductor 88, and the ring-shaped magnetic bodies 98, 108 depend on the current value for driving the electromagnets D1,. By controlling the drive current value, spherical aberration can be corrected in multiple stages.

  In the first to tenth embodiments, since the laser beam from the laser light source 7 has a circular cross section, the case where the reflection film 17 or the like is circular or elliptical is exemplified. If the laser beam is circular, the reflective film 17 and the like need not necessarily be circular or elliptical. Further, if the cross section of the laser beam from the laser light source 7 is a shape other than a circle, the shape of the reflective film 17 and the like need not be a circle or an ellipse. In the handling of the optical system and the like, the cross section of the laser beam from the laser light source 7 is preferably circular, so that the shape of the reflection film 17 and the like is most preferably circular and is preferably elliptical.

  Further, in the first to tenth embodiments, the ring-shaped magnetic bodies 18, ..., 68, the magnetic ring 78, and the ring-shaped magnetic bodies 98, 108 that are continuous in a ring shape are exemplified, but the reflective film 17, ..., If 77, 97, and 107 can be formed in an ideal parabolic curve shape, the ring-shaped magnetic bodies 18,..., 68, the magnetic ring 78, and the ring-shaped magnetic bodies 98 and 108 are not necessarily continuous in a ring shape. Good.

  In the first to tenth embodiments, the case where the deformation films 16,... 106 are provided is illustrated, but the strength of the reflection films 17, 107 can be formed to a predetermined value or more. , 67, 87,..., 107 can be joined with ring-shaped magnetic bodies 18,..., 68, good conductor 88, and ring-shaped magnetic bodies 98 and 108, respectively, and the magnetic ring 78 can be in contact with the reflective film 76. If the reflection film 76 can be pressed by the compression coil spring 78s, the deformation films 16,... 106 need not be provided.

Moreover, although each structure was demonstrated separately in 1st-10th embodiment, you may comprise combining the structure of 1st-10th embodiment suitably.
<< Eleventh Embodiment >>
FIG. 17 shows an example of a schematic optical system of an optical pickup P3 incorporating the variable focus lens actuator A1 of the variable focus lens device of this embodiment and the movable lens actuator B of the movable lens device. In the description of FIG. 17, portions overlapping with those of the first embodiment are omitted.

  The variable focus lens actuator A1 according to the eleventh embodiment arbitrarily corrects both incident and transmissive surfaces of a lens through which a laser beam is transmitted, thereby enabling correction of spherical aberration, coma and / or astigmatism. The movable lens actuator B moves the lens position in the optical axis direction and enables correction of spherical aberration.

  The optical pickup P3 splits the laser beam from the laser light source 27 and the recording layer 31 of the optical disk 32 into a light path of the laser beam from the laser light source 27 to the detector 21 through the recording layer 31 of the optical disk 32 by reflection and transmission. A polarizing beam splitter 23, a movable lens actuator B that transmits the laser beam from the laser light source 27 reflected by the polarizing beam splitter 23 in the direction of the reflecting mirror 33 and converts the divergence angle of the laser beam, a variable focus lens actuator A1, A mirror 33 that reflects the laser beam transmitted through the variable focus lens actuator A1 toward the recording layer 31 of the optical disc 32 and reflects the laser beam reflected from the recording layer 31 toward the detector 21, and linearly polarized light into circularly polarized light. A quarter-wave plate 28 to be converted and a lens array An objective lens 29 that condenses the laser beam onto the recording layer 31 of the optical disk 32 that is moved in the optical axis direction by the actuator 30 and a condensing lens that condenses the laser beam reflected by the recording layer 31 onto the detector 21. 22.

<Variable focus lens actuator A1>
FIG. 18A is a cross-sectional view in the axial direction illustrating the variable focus lens actuator A1, and FIG. 18B is a cross-sectional view taken along line EE of the variable focus lens actuator A1. In the description of FIG. 15, portions overlapping with the first embodiment are omitted.

The variable focus lens actuator A1 will be described with reference to FIGS. 18 (a) and 18 (b). The laser beam having a circular cross section passes through the transparent deformation film 11a, passes through the transparent liquid 5 such as matching oil, and is refracted and condensed by the transparent deformation film 11b.
The transparent liquid 5 is sealed between the upper transparent deformable film 11a and the lower transparent deformable film 11b via a spacer, and the lens region P2 is filled with the entire region transparent liquid 5, and the lens region P2 associated with the lens curvature change. The reservoir region P3 (FIG. 23) that stores the transparent liquid 5 that compensates for the change in volume is partially filled with the gas 4, and the gas 4 is compressed and expanded as the transparent liquid 5 in the reservoir region P3 increases or decreases. The transparent liquid 5 in the reservoir region P3 can be increased or decreased.

  On the surface of the upper transparent deformation film 11a, a ring-shaped magnetic body 36 is fixed to arbitrarily tilt the transparent deformation film 11a. The upper transparent deformation film 11a is fixed to the yoke 34 of the electromagnet D3 via the spacer 7.

  The spacer 7 is preferably a non-magnetic material such as resin, and may be formed integrally with the transparent deformation film 11a. The spacer 7 may be formed of a magnetic material as long as the performance of the variable focus lens actuator A1 does not deteriorate.

  The electromagnet D3 includes a magnetic yoke 34 and a coil 35 wound around the yoke 34 a plurality of times.

  The yoke 34 is formed of a steel core, ferrite, cobalt, or the like.

  By allowing different currents to flow through the four coils 35a, 35b, 35c, and 35d, it is possible to arbitrarily tilt the incident surface according to the intensity distribution of the magnetic fields applied to the four yokes 34a, 34b, 34c, and 34d. The number of yokes 34 and coils 35 need not be four, and the same effect can be obtained with three yokes.

  The variable focus lens actuator A1 of this configuration applies a current to the coil 35 of the electromagnet D3, thereby generating a strong magnetic field in the yoke 34 and attracting the ring-shaped magnetic body 36 of the transparent deformable film 11a, whereby the reservoir region P3. The inner transparent liquid 5 gradually flows into the lens region P2, and the amount of deflection of the transparent deformation film 11a increases accordingly. The deformation force of the transparent deformation film 11a and the force acting on the ring-shaped magnetic body 36 are balanced, and a certain amount of deflection is maintained after reaching the target deflection amount. By changing the current applied to the coils 35a, 35b, 35c, 35d of the electromagnet D3, the transparent deformation film 11a is arbitrarily tilted, and the laser beam transmitted through the transparent deformation film 11a depends on the amount of deflection of the transparent deformation film 11a. A change in the direction of travel occurs. The amount of deflection of the transparent deformation film 11a depends on the current value applied to the coils 35a, 35b, 35c, and 35d, and is controlled to be deformed into a shape suitable for correcting coma and astigmatism.

  On the other hand, the lower transparent deformation film 11b has the same function and configuration as the variable focus lens actuator A1 of the first embodiment, and a description thereof will be omitted.

  The correction amount of the spherical aberration due to the deformation of the transparent deformation film 11b depends on the convergence / divergence degree of the light beam incident on the variable focus lens actuator A1 and the deformation amount. The large spherical aberration SA1 caused by the multilayering of the optical disk due to the deformation of the transparent deformation film 11b may be corrected, and the spherical aberration such as the spherical aberration generated in the objective lens due to the fluctuation of the substrate thickness, the fluctuation of the wavelength of the laser, and the fluctuation of the temperature. A spherical aberration SA2 that is smaller than the aberration SA1 may be corrected.

<Moving lens actuator B>
The movable lens actuator B uses, for example, a stepping motor as a drive source, attaches a lead screw formed with a spiral groove to the shaft of the stepping motor, and supports a lens holder on which a lens is mounted in the groove of the lead screw. The lead screw is rotated by driving the stepping motor, and the lens supported in the groove of the lead screw is linearly moved in the optical axis direction. The amount of lens movement can be controlled by the number of steps of the stepping motor. This stepping motor has a step of about 10 μm, for example, and the amount of correction of spherical aberration per step can be designed according to the focal length of the lens and the magnification of the optical system. From the relationship of magnification, the correction amount of spherical aberration per step is approximately proportional to the square of f, where f is the focal length of the lens to be moved. Can correct the large spherical aberration SA1. In addition, it is possible to correct the small spherical aberration SA2 with high accuracy by moving the long focus lens.

<Reading of Record from Recording Layer 31 of Optical Disc 32>
Next, reading of the recording (signal) by the laser beam from the recording layer 31 of the optical disc 32 mounted on the optical pickup H1 will be described by taking reading from the recording layer 31b as an example. The same applies to reading of a record (signal) from the recording layer 31a.

  As shown in FIG. 17, in order to read the pit recorded on the recording layer 31 b of the optical disc 32 as an electric signal, the laser beam emitted from the laser light source 27 is collimated by the collimating lens 26 and passes through the grating 25. The light is reflected by the polarization beam splitter 23 toward the movable lens actuator B and the variable focus lens actuator A1.

  Then, the laser beam reflected by the polarization beam splitter 23 is transmitted through the movable lens actuator B and the variable focus lens actuator A1, the divergence angle is adjusted, reflected by the reflecting mirror 33, and then transmitted through the quarter wavelength plate 28. Then, the light is converted into circularly polarized light, collected on the recording film 31b by the objective lens 29, and reflected from the recording film 31b. The laser beam reflected by the recording film 31b is transmitted again through the objective lens 29 and converted into collimated light, then transmitted through the quarter-wave plate 28, converted into linearly polarized light, and reflected by the reflection mirror 33. After the divergence angle is adjusted by the variable focus lens actuator A1 and the movable lens actuator B, the light is transmitted toward the polarization beam splitter 23.

  The laser beam that has passed through the polarization beam splitter 23 is condensed on the detector 21 by the condenser lens 22, and the amount of light incident on the detector 21 is converted into an electrical signal.

  Based on information received by the detector 21 and based on a signal indicating the amount of deflection of the transparent deformable films 11a and 11b of the variable focus lens actuator A1 calculated by the control circuit C1, a current is supplied from the mirror drive circuit C3 to the variable focus lens actuator A1. Applied to the coils 9 and 35. Further, a current is applied to the coil of the movable lens actuator B from the lens driving circuit C2 based on a signal indicating the movement amount of the movable lens actuator B calculated by the control circuit C1.

  As a result, the variable focus lens actuator A1 generates a strong magnetic field in the central portion of the yoke 10 by the current flowing through the coil 9, and the ring-shaped magnetic body 8 of the transparent deformable film 11b is electromagnet as shown by the broken line in FIG. Attract towards D1. Accordingly, the deformation film 11b supported by the electromagnet D1 via the spacer 7 bends in a parabolic shape. Further, a strong magnetic field is generated in the central portion of the yoke 34 by the current flowing through the coil 35, and the ring-shaped magnetic body 36 of the transparent deformation film 11a is attracted toward the electromagnet D3 as indicated by a broken line in FIG. Along with this, the deformation film 11a supported by the electromagnet D3 via the spacer 7 is inclined.

  In this way, by passing a current through the coil 9 of the variable focus lens actuator A1, the transparent deformable film 11b is bent into a desired parabolic shape, and the divergence angle of the laser beam transmitted through the transparent deformable film 11b is set to the current of the coil 9. The spherical aberration of the laser beam generated by changing the position of the recording layer 31 between the recording layer 31a and the recording layer 31b is corrected. In addition, by passing an electric current through the coil 35 of the variable focus lens actuator A1, the transparent deformation film 11a is tilted to a desired shape, and the traveling direction of the laser beam transmitted through the transparent deformation film 11a is controlled by the magnitude of the current of the coil 35. Then, coma aberration and astigmatism caused by errors in the tilt of the optical disk with respect to the optical axis (disk tilt) and errors in the assembly of the optical pickup are corrected.

  Furthermore, the lens is driven in the optical axis direction by passing a current through the coil of the movable lens actuator B, the divergence angle of the laser beam transmitted through the lens is controlled, and the position of the recording layer 31 is the position of the recording layer 31. The spherical aberration of the laser beam caused by changing to the recording layer 31a and the recording layer 31b is corrected.

  The spherical aberration to be corrected by the varifocal lens A1 and the movable lens actuator B is generated in the objective lens due to a large spherical aberration SA1 caused by the multilayering of the optical disc, error in the substrate thickness, laser wavelength variation, and temperature variation. A spherical aberration SA2, which is smaller than the spherical aberration SA1, such as a spherical aberration, is separated.

  Here, the movable lens actuator B and the deformation film 11b correct spherical aberration, and the deformation film 11a corrects astigmatism and coma aberration. Therefore, these combinations are as shown in Tables 1 and 2.

In the case of a non-multi-layer recording medium, it is not necessary to correct the large spherical aberration SA1 in the first place, so the small spherical aberration SA2 and astigmatism / coma aberration are corrected.

  In the above, a variable focus lens that changes the surface shape of the deformation film by using the transparent liquid 5 is used. However, the present invention is not limited to this, and the entire lens is liquid and changes its shape depending on the surface tension. Is also possible. In the above description, the term “deformable film” is used for the sake of convenience.

  In this embodiment, electromagnetic force is used as a method for deforming the mirror. However, for example, electrostatic attraction may be used. The mirror can be deformed by generating an electrostatic attractive force between the opposing electrodes formed by providing a gap between the deforming mirror part and the fixed part.

In the present embodiment, an example in which a variable focus lens is used for correcting spherical aberration, coma aberration, and / or astigmatism has been shown. However, for example, a liquid crystal element may be used. In this case, the liquid crystal element has a plurality of transparent electrode surfaces, the first transparent electrode has an electrode pattern for correcting spherical aberration, and the second transparent electrode corrects coma and astigmatism. An electrode pattern is provided. This first transparent electrode corrects large spherical aberration SA1 or small spherical aberration SA2. FIG. 24 shows an example of the structure of the liquid crystal element. 24A is a cross-sectional view of the liquid crystal element, FIG. 24B is an example of the electrode pattern of the first transparent electrode, and FIG. 24A is the second transparent electrode when correcting the coma aberration. An example of an electrode pattern is shown. As shown in FIG. 24A, in the liquid crystal element, a liquid crystal layer made of liquid crystal is formed between two transparent substrates. Since the first transparent electrode corrects spherical aberration, a concentric electrode pattern is formed as shown in FIG. 24B, and the electrode pattern is formed so as to generate wavefront aberration opposite in sign to the spherical aberration to be corrected. is doing. Further, the second transparent electrode is formed with an electrode pattern as shown in FIG. 24C, and the electrode pattern is formed so as to generate a wavefront aberration having a sign opposite to that of the aberration wavefront to be corrected.
<< Twelfth Embodiment >>
In the eleventh embodiment, the movable lens actuator B is used for correcting the spherical aberration, but a variable mirror actuator may be used instead. FIG. 19 shows an example of a schematic optical system of an optical pickup H1 in which a variable mirror actuator A3 of a variable mirror device is incorporated instead of the movable lens actuator B. In addition, in the description of FIG. 19, portions overlapping with those of the eleventh embodiment are omitted.

  The movable mirror actuator A3 of the variable mirror device deforms the reflecting mirror surface on which the laser light is incident, and enables correction of spherical aberration.

  The optical pickup P3 splits the laser beam from the laser light source 27 and the recording layer 31 of the optical disk 32 into a light path of the laser beam from the laser light source 27 to the detector 21 through the recording layer 31 of the optical disk 32 by reflection and transmission. The polarizing beam splitter 23, the variable focus lens actuator A1 that transmits the laser beam from the laser light source 27 reflected by the polarizing beam splitter 23 in the direction of the reflecting mirror 33 and converts the divergence angle of the laser beam, and the lens actuator A1. The reflected laser beam is reflected toward the recording layer 31 of the optical disc 32, and the variable mirror actuator A3 that reflects the laser beam reflected from the recording layer 31 toward the detector 21, and 1/4 that converts linearly polarized light into circularly polarized light. Wave plate 28 and lens actuator 30 An objective lens 29 that is further moved in the optical axis direction and condenses the laser beam onto the recording layer 31 of the optical disc 32; and a condensing lens 22 that condenses the laser beam reflected by the recording layer 31 onto the detector 21; It has.

<Variable mirror actuator A3>
FIG. 20 is a longitudinal sectional view in the axial direction illustrating the variable mirror actuator of FIG.

  In the variable mirror actuator A3, as shown in FIG. 19, the reflective film 37 that reflects the laser beam is made of a material that reflects the laser beam, for example, a metal such as aluminum or silver, a dielectric multilayer film containing SiO2, TiO2, or the like. Used to form a flat plate. As described above, the reflective film 37 may be a single-layer film such as a metal, or may be a multilayer reflective film using a dielectric or the like, and is not limited.

  Here, since the laser beam has a circular cross section and is incident on the reflection film 37 at an angle of 45 degrees, the reflection film 37 has the same circular shape as that before the reflection of the laser beam reflected by the reflection film 37. Are formed in an elliptical flat plate shape that is long in the laser beam traveling direction.

  As shown in FIG. 20, the reflective film 37 is laminated on one surface of an elliptical deformation film 38 having the same shape as the reflective film 37, such as a silicon substrate. The deformable film 38 may be formed of a material other than a silicon substrate as long as it is a deformable member, and is not limited to a silicon substrate.

  On the other surface of the deformation film 38, a ring-shaped magnetic body 40 is laminated and fixed in order to bend the reflection film 37 into a parabolic shape so as to reflect the same laser beam as before the reflection. The ring-shaped magnetic body 40 may be laminated and fixed on the reflective film.

  The ring-shaped magnetic body 40 is configured using a magnetic body. As shown in FIG. 19, in the ring-shaped magnetic body 40, since the laser beam is incident on the reflection film 37 at an angle of 45 degrees, the laser beam reflected by the reflection film 37 has the same circular shape as before the reflection. Like the reflection film 37 and the deformation film 38, it is formed in an elliptical ring shape that is long in the traveling direction of the laser beam so as to have a cross section. Since the ring-shaped magnetic body 40 does not hinder the deformation of the deformation film 16 due to its own rigidity, a low-rigidity structure is more desirable.

  The ring-shaped magnetic body 40 may be, for example, a composite material in which magnetic powder is dispersed in a photoresist, and is not limited as long as the material receives a strong magnetic force by a magnetic field.

  Thus, a ring structure having a plurality of laminates in which the reflective film 37 is laminated on one surface of the deformation film 38 and the ring-shaped magnetic body 40 is laminated on the other surface of the deformation film 38, This is referred to as a reflector 37T (see FIG. 20).

  As shown in FIG. 20, in the variable mirror actuator A3, the reflector 37T is placed on the electromagnet D4 via a ring-shaped spacer 39 having an elliptical outer peripheral shape similar to the reflective film 37 and the deformation film 38. Is provided.

  The spacer 39 is preferably a non-magnetic material such as resin, and may be formed integrally with the deformation film 38. The spacer 39 may be formed of a magnetic material as long as the performance of the variable mirror actuator A3 does not deteriorate.

  The electromagnet D4 includes a magnetic yoke 42 and a coil 41 that is wound a plurality of times around a yoke central portion 42c that forms the central portion thereof.

  The yoke 42 of the electromagnet D4 has an elliptical elliptical columnar yoke central portion 42c similar to the ring-shaped magnetic body 40, and a yoke peripheral portion 42s formed continuously on the lower outer periphery of the yoke central portion 42c. Yes. The yoke peripheral portion 42 s has a U-shape with an axial section opened inward, and has an elliptical outer peripheral shape similar to the reflective film 37 and the deformation film 38.

  The yoke 42 is formed of an iron core, ferrite, cobalt, or the like obtained by laminating a plurality of thin steel plates.

  The variable mirror actuator A3 of this configuration applies a current to the coil 41 of the electromagnet D4, thereby generating a strong magnetic field in the yoke 42 and attracting the ring-shaped magnetic body 40 of the reflector 37T, thereby causing the dotted line in FIG. As shown, the deformation film 38 and the reflection film 37 are both bent in a parabolic shape. In this way, the divergence angle of the laser beam reflected by the reflection film 37 is controlled by bending the reflection film 37 into a parabolic shape suitable for aberration correction. Thereby, the spherical aberration of the laser beam generated when the position of the recording layer 31 is changed to the position p1 of the recording layer 31a and the position p2 of the recording layer 31b shown in FIG. 19 is corrected.

  Here, the structure of the yoke 42 is a concentric elliptical shape in the outer peripheral area of the coil 41 shown in FIG. 20 rather than the simple elliptical columnar yoke central portion 42c formed only inside the coil 41. The configuration in which the yoke peripheral portion 42 is connected and added is more desirable because the density of magnetic lines of force around the coil 41 is increased and the magnetic force acting on the ring-shaped magnetic body 40 can be increased.

  For example, as shown in FIG. 20, by forming the yoke peripheral upper portion 42 s 1 in the yoke peripheral portion 42 s having a U-shaped cross section, the magnetic field formed around the coil 41 can be made higher density, and the ring-shaped magnetic body 40 is formed. , Can give a stronger magnetic force.

  Needless to say, the yoke 42 may be composed of only the yoke central portion 42c.

<Reading of Record from Recording Layer 31 of Optical Disc 32>
Next, reading of the recording (signal) by the laser beam from the recording layer 31 of the optical disc 32 mounted on the optical pickup H1 will be described by taking reading from the recording layer 31b as an example. The same applies to reading of a record (signal) from the recording layer 31a.

  As shown in FIG. 19, in order to read the pit recorded on the recording layer 31 b of the optical disc 32 as an electric signal, the laser beam emitted from the laser light source 27 is collimated by the collimator lens 26 and passes through the grating 25. The light is reflected by the polarization beam splitter 23 toward the variable focus lens actuator A1.

  Then, the laser beam reflected by the polarization beam splitter 23 is transmitted through the variable focus lens actuator A1, adjusted for the divergence angle, reflected by the variable mirror actuator A3, and then transmitted through the quarter wavelength plate 28 to be circularly polarized. The light is converted, collected by the objective lens 29 on the recording film 31b, and reflected from the recording film 31b. The laser beam reflected by the recording film 31b is transmitted again through the objective lens 29 and converted into collimated light, then transmitted through the quarter-wave plate 28, converted into linearly polarized light, and reflected by the variable mirror actuator A3. Thereafter, the divergence angle is adjusted by the variable focus lens actuator A 1, and then transmitted toward the polarization beam splitter 23.

  The laser beam that has passed through the polarization beam splitter 23 is condensed on the detector 21 by the condenser lens 22, and the amount of light incident on the detector 21 is converted into an electrical signal.

  Based on the information received by the detector 21, based on a signal indicating the deformation amount of the variable mirror actuator A3 calculated by the control circuit C1, a current is applied from the mirror drive circuit C3 to the coil 40 of the variable mirror actuator A3.

  Thereby, the variable mirror actuator A3 generates a strong magnetic field in the central portion of the yoke 42 by the current flowing through the coil 41, and the ring-shaped magnetic body 40 of the reflector 37T is moved to the electromagnet D4 as shown by the dotted line in FIG. Attract towards. Accordingly, the deformation film 38 and the reflection film 37 of the reflector 37T supported by the electromagnet D4 via the spacer 39 are bent in a parabolic shape.

  In this way, by passing a current through the coil 41 of the variable mirror actuator A3, the reflecting film 37 is bent into a desired parabolic shape, and the divergence angle of the laser beam reflected by the reflecting film 37 is determined by the magnitude of the current of the coil 41. By controlling, the spherical aberration of the laser beam caused by the change of the position of the recording layer 31 to the position P1 (recording layer 31a) and the position P2 (recording layer 31b) is corrected. This spherical aberration may be used for correcting the large spherical aberration SA1 or for correcting the small spherical aberration SA2.

13, 23, 33, 43, 73, 83 Coil 14, 24, 34, 44, 54, 64, 74, 84 Yoke 16, 26, 36, 46, 56, 66, 76, 86, 96, 106 (Variable structure member)
17, 27, 37, 47, 57, 67, 77, 97, 107 Reflective film (reflective member)
18, 28, 38, 48, 58, 68, 98, 108 Ring-shaped magnetic body (magnetic force imparting member)
34k cavity (hole)
44H Holder 56a1, 56a2, 56a3 Thick region (concave structure)
56b1, 56b2, 56b3, 56b4 Thin area (concave structure)
66a Thick region (rib structure)
78 Magnetic ring (magnetic force imparting member)
78s compression coil spring (pressing member)
88 Good conductor (magnetic force imparting member)
99 Air gap (opening)
128 Conductor A1-A10 Variable mirror actuator D1-D10 Electromagnet (electromagnet structure)
37, reflection film 38, deformation film 100, optical disk device H1, optical pickup

Claims (8)

A light source;
A variable focus lens actuator provided in an optical path for irradiating light from the light source to an optical information recording medium having a recording layer;
The variable focus lens actuator includes a first deforming member that corrects at least one of coma and astigmatism by changing its shape, and a second deformation that corrects spherical aberration by changing its shape. An optical disc apparatus comprising a member. And a movable lens actuator for moving the lens in the optical path,
2. The optical disk device according to claim 1, wherein spherical aberration is corrected by the movable lens actuator. In addition, the optical path has a variable mirror actuator in which the shape of the reflecting member is variable,
2. The optical disk apparatus according to claim 1, wherein spherical aberration is corrected by the variable mirror actuator. A light source;
A variable focus lens actuator provided in an optical path for irradiating light from the light source to an optical information recording medium having a recording layer;
The variable focus lens actuator includes:
A first deformation member;
A first magnetic field application member that changes the shape of the first deformation member;
A second deformable member;
A second magnetic field application member that changes the shape of the second deformation member;
An optical disc apparatus comprising: Correcting at least one of coma and astigmatism by the first deformable member;
5. The optical disk apparatus according to claim 4, wherein spherical aberration is corrected by the second deformable member. 5. The optical disk apparatus according to claim 4, further comprising spherical aberration correcting means in the optical path. The spherical aberration correction means corrects the first spherical aberration,
7. The optical disc apparatus according to claim 6, wherein the second deforming member corrects a second spherical aberration smaller than the first spherical aberration. A light source;
A liquid crystal element provided in an optical path for irradiating light from the light source to an optical information recording medium having a recording layer;
The optical disk device, wherein the liquid crystal element includes a first electrode pattern for correcting spherical aberration, and a second electrode pattern for correcting at least one of coma and astigmatism.

Images