JP2008192231A - Lens actuator, optical pickup device, and optical recording/reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To compose so that manufacture is easy and highly accurate positioning for a diffraction element can be performed by preventing occurrence of flare. <P>SOLUTION: A lens actuator is provided with a cylindrical hole part 1a in which a diffraction element 3 is a disk shape provided with an outer peripheral plane becoming an engagement shaft part 3b and a plane part 3c at an upper plane, and a lens holder 1 is provided with: a cylindrical hole part 1a which is extended on an inside plane by being tilted to an optical axis L of an objective lens 2 and the engagement shaft part 3b of the diffraction element 3 is inserted into; and a plane sloping surface part 1b abutting on the plane part 3c of the diffraction element 3 by being tilted to a virtual plane perpendicular to the optical axis L of the objective lens 2 in the cylindrical hole part 1a. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention includes a lens actuator that includes an objective lens that focuses a light beam on an optical recording medium, and that drives the objective lens in at least a focus direction and a tracking direction with respect to the optical information recording medium, and the lens The present invention relates to an optical pickup device equipped with an actuator and an optical recording and / or reproducing device.

In some optical pickup devices, there is a configuration including a diffraction element for providing compatibility with optical recording media of a plurality of types of standards for light sources having different wavelengths. In a lens unit in which a lens and a diffractive element are integrated, a configuration is described in which a diffractive element is provided on a support member so as to be inclined with respect to the optical axis of the objective lens in order to prevent the occurrence of flare from the diffractive element.
JP 2006-139874 A

  Patent Document 1 discloses a lens unit structure in which an objective lens and a diffractive element are adjusted and fixed to a support member, and the diffractive element is tilted and fixed. However, the diffractive element is tilted and attached with high accuracy. The method is not specifically disclosed.

  In general, an optical element serving as a rotating body around the optical axis is generally formed in a cylindrical shape or a columnar shape on the outer shape in order to increase the ease of manufacture and the mounting accuracy. Further, a round hole or a stepped round hole is formed in the member on the other side to which this is attached, and positioning is performed by fitting the hole and the shaft.

In addition, when a diffractive element having a concentric structure is used as a compatible element for a plurality of laser wavelengths, the following items (1) and (2) are required to satisfy the function.
(1) positioning the optical axis of the objective lens and the optical axis of the diffraction element with high precision;
(2) On the other hand, both surfaces of the compatible diffractive element have stepped steps, and each stepped end surface is a plane, so that the integration of the plane of each step is equivalent to the plane of the entire effective diameter. Tilting from the vertical to the optical axis of the lens to prevent flare due to specular reflection,
In this case, the center of the diffractive element to be positioned with high accuracy with respect to the lens optical axis is the center of the surface on the objective lens side of both surfaces of the diffractive element.

  In order to position the center of the inclined surface like the diffraction element with high accuracy, it is necessary to provide a holding hole inclined with respect to the holding hole of the objective lens in the housing. However, such a shape cannot be created with a normal mold structure when manufacturing with a resin mold. With a movable type that is tilted only partially, it is difficult to create a shape with high accuracy for such a lens unit or the like that requires a reduction in size and weight. That is, parts cannot be manufactured, or even if they can be manufactured, the accuracy required for assembly cannot be obtained.

  Further, when such a difficult-shaped member is used, there is a high possibility that a problem occurs in the basic function and reliability.

  Patent Document 1 describes a configuration example in which an objective lens and a diffractive element are incorporated in a support member. However, the use of such a dedicated support member leads to an increase in the size of a lens unit that is a movable housing. Further, since the mass of the balance weight with respect to the lens unit is also increased, the sensitivity is lowered or the higher order resonance frequency is easily lowered due to the increase in size and the mass.

  The object of the present invention is to solve the problems of the prior art, and is easy to manufacture, prevents the occurrence of flare, and performs a highly accurate positioning with respect to the diffraction element, an optical pickup device, and an optical type It is to provide a recording / reproducing apparatus.

  In order to achieve the above object, the invention described in claim 1 is directed to an objective lens for condensing a light beam on an optical recording medium and an optical recording medium of a plurality of types for a plurality of light sources having different wavelengths. A diffraction element for providing compatibility; and a lens actuator configured to drive the objective lens together with the lens holder in the focus direction and the tracking direction with respect to the optical recording medium. The diffraction surface of the element is inclined with respect to the optical axis of the objective lens, and the diffraction pattern center of the diffraction surface on the objective lens side of the diffraction element coincides with the optical axis of the objective lens. The element is installed in the lens holder, and with this configuration, the diffraction surface of the diffraction element is inclined rather than perpendicular to the objective lens. By mounting, the flare caused by surface reflection can be avoided, and the center of the diffraction pattern on the objective lens side of the diffractive element is made coincident with the optical axis of the objective lens, so that good optical characteristics with less aberration are obtained. be able to.

  According to a second aspect of the present invention, in the lens actuator of the first aspect, the diffractive element has a disk-like shape having an outer peripheral surface serving as a fitting shaft portion and a flat portion on the upper surface. A cylindrical hole in which an inner surface extends parallel to the optical axis of the lens and the fitting shaft of the diffraction element is inserted, and a virtual plane perpendicular to the optical axis of the objective lens in the cylindrical hole An inclined flat surface portion that inclines and contacts the flat surface portion of the diffractive element is formed, and the maximum width dimension of the maximum projected shape on the virtual plane perpendicular to the optical axis of the objective lens in the fitting shaft portion of the diffractive element is the lens holder. The diameter of the cylindrical hole portion is set so that the fitting shaft portion of the diffraction element is fitted to the cylindrical hole portion of the lens holder. Maximum projected shape on a virtual plane perpendicular to the optical axis of the objective lens The maximum width by which the diameter of the cylindrical bore of the lens holder, molding and precision out of the lens holder is facilitated, and also the positioning during installation of the diffractive element can be performed with ease and high accuracy.

  According to a third aspect of the present invention, in the lens actuator according to the second aspect, the diffraction pattern center of the diffractive surface on the objective lens side in the diffractive element tilted and attached to the lens holder coincides with the optical axis of the objective lens. The center of the cylindrical hole portion of the lens holder is shifted with respect to the optical axis of the objective lens. With this configuration, the center of the cylindrical hole portion is made parallel and decentered with the optical axis of the objective lens. By providing the holder, the lens holder can be easily molded and accurate, and positioning when attaching the diffraction element can be performed easily and with high precision.

  According to a fourth aspect of the present invention, in the lens actuator according to the first aspect, the diffractive element has a disk-like shape having an outer peripheral surface serving as a fitting shaft portion and a flat portion on the upper surface. A cylindrical hole in which an inner surface extends parallel to the optical axis of the lens and the fitting shaft of the diffraction element is inserted, and a virtual plane perpendicular to the optical axis of the objective lens in the cylindrical hole An inclined plane part that inclines and abuts the flat part of the diffractive element is formed, and the cylindrical hole part has a maximum projected circle on a virtual plane perpendicular to the optical axis of the objective lens in the fitting shaft part of the diffractive element. It is a long hole shape formed by stretching, and the center axis is set to be coaxial with the optical axis of the objective lens, and the fitting shaft portion of the diffraction element is fitted into the cylindrical hole portion of the lens holder, With this configuration, the objective lens at the fitting shaft portion of the tilted diffraction element By forming the cylindrical hole portion of the lens holder so as to have a long hole shape obtained by extending the maximum projected circle on a virtual plane perpendicular to the optical axis, the lens holder can be easily molded and accurate, and Positioning when attaching the diffraction element can be performed easily and with high accuracy.

  According to a fifth aspect of the present invention, in the lens actuator according to the fourth aspect, the diffraction pattern center of the diffractive surface on the objective lens side in the diffractive element tilted and attached to the lens holder coincides with the optical axis of the objective lens. In addition, the center of the long hole-shaped cylindrical hole of the lens holder is installed with being shifted with respect to the optical axis of the objective lens. With this configuration, the long hole shape of the cylindrical hole is centered on the objective lens. Since the lens holder is provided so as to be parallel and decentered with respect to the optical axis, the lens holder can be easily molded and accurate, and positioning when the diffraction element is attached can be performed easily and with high accuracy.

  According to a sixth aspect of the present invention, in the lens actuator according to the first aspect, the diffractive element has a disk-like shape having an outer peripheral surface serving as a fitting shaft portion and a flat portion on the upper surface. A cylindrical hole in which an inner surface extends parallel to the optical axis of the lens and the fitting shaft of the diffraction element is inserted, and a virtual plane perpendicular to the optical axis of the objective lens in the cylindrical hole An inclined flat surface portion that inclines and abuts the flat surface portion of the diffractive element is formed, and the cylindrical hole portion has a longest diameter projected on a virtual plane perpendicular to the optical axis of the objective lens in the fitting shaft portion of the diffractive element. The outer diameter of the diffractive element is an elliptical hole shape with a short diameter, and is set to be coaxial with the optical axis of the objective lens, and the fitting shaft of the diffractive element is fitted into the cylindrical hole of the lens holder. With this configuration, the fitting shaft part of the tilted diffraction element By forming the cylindrical hole portion of the lens holder so as to have an elliptical hole shape in which the maximum projected dimension on the virtual plane perpendicular to the optical axis of the objective lens is the major axis and the outer diameter dimension of the diffraction element is the minor axis, The lens holder can be easily molded and accurate, and positioning at the time of attaching the diffraction element can be performed easily and with high accuracy.

  According to a seventh aspect of the present invention, in the lens actuator according to the sixth aspect, the diffraction pattern center of the diffractive surface on the objective lens side in the diffractive element tilted and attached to the lens holder coincides with the optical axis of the objective lens. In addition, the center of the elliptical hole-shaped cylindrical hole portion of the lens holder is installed with being shifted with respect to the optical axis of the objective lens. With this configuration, the elliptical hole shape of the cylindrical hole portion is centered on the objective lens. Since the lens holder is provided so as to be parallel and decentered with respect to the optical axis, the lens holder can be easily molded and accurate, and positioning when the diffraction element is attached can be performed easily and with high accuracy.

  According to an eighth aspect of the present invention, in the lens actuator according to the second, fourth, or sixth aspect, the diffraction pattern center of the diffraction surface on the objective lens side of the diffraction element tilted and attached to the lens holder is on the optical axis of the objective lens. The position of the diffractive surface on the objective lens side of the diffractive element is set to be approximately the center of the cylindrical hole portion of the lens holder so as to coincide with the above. By setting the point as the center of the diffraction pattern on the objective lens side, the lens holder can be easily molded and accurate, and positioning when the diffraction element is attached can be performed easily and with high precision.

  The invention according to claim 9 includes an objective lens that focuses a light beam on the optical recording medium, a lens actuator that drives the objective lens in at least a focus direction and a tracking direction with respect to the optical recording medium, 9. An optical pickup device comprising means for obtaining optical information from a reflected beam from the optical recording medium, wherein the lens actuator according to claim 1 is mounted as the lens actuator. As a result, the installed lens actuator prevents flare caused by specular reflection on the diffractive surface of the diffractive element, and can be assembled easily and reliably, improving the performance of the player or drive equipped with the optical pickup device. can do.

  According to a tenth aspect of the present invention, there is provided an optical recording / reproducing apparatus that includes an optical pickup and optically records and / or reproduces information with respect to an optical recording medium. This pickup is equipped with a pickup device, and this configuration allows the optical pickup to be mounted easily and reliably while preventing flare caused by regular reflection on the diffraction surface of the diffraction element. It is possible to improve the performance of a player or drive equipped with a recording / reproducing apparatus.

  According to the lens actuator of the present invention, the diffractive surface of the diffractive element for providing compatibility with a plurality of types of optical recording media with respect to a plurality of light sources having different wavelengths is not perpendicular to the objective lens. By mounting it at an angle, flare due to surface reflection can be avoided and the center of the diffraction pattern on the objective lens side of the diffractive element coincides with the optical axis of the objective lens. Obtainable.

  Further, according to the optical pickup device or the optical recording / reproducing device of the present invention, the lens actuator according to the present invention is provided with the lens actuator according to the present invention, thereby improving the pickup characteristic, the recording characteristic, the reproducing characteristic, and the like.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  1A to 1C are configuration diagrams of an embodiment of an optical pickup device equipped with an objective lens actuator according to the present invention, where FIG. 1A is a front view, FIG. 1B is a side view, and FIG. Shows a bottom view.

  In FIG. 1, a lens holder 1 of a movable part holds an objective lens 2 for condensing a light beam on an optical disk (not shown) to form a beam spot, and holds a diffraction element 3 at a lower part as will be described later. A focusing drive coil 4 and a tracking drive coil 5 are attached to a support block 9 provided on a fixed base 7 via a support spring 6 serving as a suspension and coil feed line. It is attached. A magnet 8 is attached to the fixed base 7 as a back yoke of a magnetic circuit, and the drive coils 4 and 5 of the lens holder 1 are arranged in the magnetic field. The lens holder 1 is driven in the focus direction and the tracking direction by the electromagnetic action.

  2 to 10 are diagrams for explaining an embodiment of a lens actuator according to the present invention, and show a related configuration of an objective lens, a lens holder, and a diffraction element, which are the main parts of the lens actuator. .

  In the cross-sectional view of Embodiment 1 shown in FIG. 2, the objective lens 2 is fitted and fixed to the upper end portion of the lens holder 1, and the diffraction element 3 is fitted and fixed to the lower end portion of the lens holder 1. The fixing method of the objective lens 2 and the diffraction element 3 can be performed using materials, such as ultraviolet curable resin, for example. The diffractive element 3 is attached to the lens holder 1 in an inclined manner in order to prevent deterioration of the pickup signal due to the surface reflection flare.

  In this embodiment, the diffraction surface 3a of the diffraction element 3 is inclined with respect to the optical axis L of the objective lens 2, and the diffraction pattern center O of the diffraction surface 3a on the objective lens 2 side in the diffraction element 3 is the objective lens 2. The fitting shaft portion 3 b of the diffraction element 3 is fitted into the cylindrical hole portion 1 a of the lens holder 1 so as to substantially coincide with the optical axis L of the lens holder 1.

  More specifically, the diffractive element 3 has a disk-like shape having an outer peripheral surface serving as the fitting shaft portion 3b and a flat surface portion 3c on the upper surface side, and the lens holder 1 is positioned on the optical axis L of the objective lens 2. A cylindrical hole 1a that is inclined with respect to the inner surface and that is fitted with the fitting shaft 3b of the diffraction element 3, and a virtual axis perpendicular to the optical axis L of the objective lens 2 in the cylindrical hole 1a. It has an inclined flat surface portion 1 b that is inclined with respect to the surface and abuts against the flat surface portion 3 c of the diffraction element 3.

  As in the configuration of the first embodiment, by attaching the diffractive surface 3a of the diffractive element 3 so as to be inclined rather than perpendicular to the objective lens 2, flare due to surface reflection can be avoided, and the diffractive element 3 on the objective lens 2 side can be avoided. By making the diffraction pattern center O coincide with the optical axis L of the objective lens 2, it is possible to obtain good optical characteristics with less aberration.

  In the first embodiment, the lens holder 1 is formed with a cylindrical hole portion 1a that coincides with the fitting shaft portion 3b of the outer shape of the diffraction element 3 and has the same tilt axis L1 with respect to the optical axis L of the objective lens 2. In order to create the cylindrical hole 1a, for example, it is necessary to adopt a method of performing molding using a movable mold that is different only in the inclined hole portion. However, this method is expected to have a limitation on the structural dimensions.

  Therefore, in the embodiment described below, the lens holder 1 is not provided with the cylindrical hole portion 1a having the tilt axis L1 as in the first embodiment, but has a central axis parallel to the optical axis L of the objective lens 2. The lens holder 1 is formed with a cylindrical hole structure, and the optical axis L of the objective lens 2 and the diffraction pattern center O on the objective lens 2 side in the diffraction element 3 can be positioned with high accuracy.

  Here, in the diffractive element 3 having a general ring-shaped diffraction pattern, the entire structure is cylindrical in view of positioning by fitting to the lens holder 1 and ease of manufacture of the diffractive element 3 itself. As shown in FIG. 3, on the virtual plane S perpendicular to the optical axis L of the objective lens 2, a projection shape approximated to an ellipse or an ellipse is shown as shown in FIG.

  Therefore, in the second embodiment shown in FIG. 4, the cylindrical hole 1a having a cylindrical surface whose diameter is the maximum width dimension D of the projection shape of the diffraction element 3 shown in FIG. 2 is provided coaxially with the optical axis L. More specifically, the diffractive element 3 has a disk-like shape having an outer peripheral surface serving as the fitting shaft portion 3b and a flat surface portion 3c on the upper surface side, and the lens holder 1 is positioned on the optical axis L of the objective lens 2. A cylindrical hole 1a in which the inner side surface extends in parallel to and is inclined and the fitting shaft portion 3a of the diffraction element 3 is inserted, and is perpendicular to the optical axis L of the objective lens 2 in the cylindrical hole portion 1a. An inclined flat surface portion 1 b that is inclined with respect to the virtual surface S and abuts against the flat surface portion 3 c of the diffraction element 3 is provided.

  According to the second embodiment, the cylindrical hole portion 1a is a circular hole that is easy to process and does not have an inclined axis, so that there is no problem in forming the lens holder 1 and the inclined diffraction element 3 has a lens. By fitting the holder 1 to the inner diameter, high-accuracy positioning in the inclined side maximum width direction can be expected.

  However, there are two problems in the configuration of the second embodiment.

  Problem 1 is that the light of the objective lens 2 in the fitting shaft portion 3b of the diffractive element 3 tilted with respect to the optical axis L of the objective lens 2 by bringing the diffractive element 3 into contact with the inclined flat surface portion 1b of the lens holder 1. The maximum projection width in the direction of the axis L is a dimension between two points of the upper left corner a and the lower right corner b in FIG. As can be seen from FIG. 4, the diffraction element 3 rotates and tilts around the midpoint between the two projection maximum widths, and as a result, the midpoint becomes the objective lens 2 in the diffraction element 3. If it does not coincide with the diffraction pattern center O on the side, this decentration may increase the occurrence of aberrations.

  Problem 2 is that the cylindrical hole portion 1a of the lens holder 1 is a circular hole, and the entire circumference has the same diameter as the maximum width. Therefore, the diameter increases in the direction in which the maximum projection width does not change. In consideration of the effect of optical distortion, the fitting between the lens holder 1 and the lens holder 1 is a clearance fitting, so that a clearance tolerance margin is required, so that the positioning accuracy in the direction in which the maximum projection width does not change becomes strict.

  Embodiment 3 shown in FIG. 5 is a configuration example that addresses the problem 1, and a cylindrical hole 1a having a cylindrical surface whose diameter is the maximum width dimension D of the projection shape of the diffraction element 3 described in Embodiment 2. The center axis L2 of the lens holder 1 is not coaxial with the optical axis L of the objective lens 2 of the lens holder 1, but is translated and decentered.

  In this way, if the amount of eccentricity is set from the positional relationship between the projection maximum width obtained from the fitting shaft portion 3b of the diffraction element 3 and the tilt angle and the diffraction pattern center O, the effect of the second embodiment can be enjoyed. The diffraction pattern center O on the objective lens 2 side can be aligned with the optical axis L of the objective lens 2.

  The fourth embodiment illustrated in FIG. 6 is a configuration example that addresses the problem 1 in the second embodiment. Between the two points having the maximum projection width as described above in the fitting shaft portion 3b of the diffraction element 3 tilted with respect to the optical axis L of the objective lens 2 by being brought into contact with the inclined flat surface portion 1b of the lens holder 1. By disposing the diffractive surface 3a on the objective lens 2 side of the diffractive element 3 on a plane passing through the midpoint (between a and b), the diffractive element on the objective lens 1 side can be enjoyed while enjoying the effects of the second embodiment. 3 can be aligned with the optical axis L of the objective lens 2.

  Embodiment 5 shown in FIG. 7 is a configuration example that addresses the problem 2 in Embodiment 2, and in the non-tilting direction of the cylindrical hole 1a of the lens holder 1 of Embodiment 2, the fitting shaft portion of the diffraction element 3 In order to eliminate an assembly error due to a gap generated between the objective lens 2b and the optical axis L of the objective lens 2 when tilted with respect to a virtual plane perpendicular to the optical axis L, as shown in the end view along line AA in FIG. The elongated hole shape formed by extending the outer shape of the diffraction element 3 in accordance with the maximum projected circle on the virtual plane (direction A in FIG. 8) is the hole shape (longitudinal dimension) of the cylindrical hole portion 1a of the lens holder 1. M). By adopting this shape, there is no gap between the cylindrical hole portion 1a and the fitting shaft portion 3b in the non-inclined direction (direction orthogonal to the A direction), and in the inclined direction, the cylindrical hole portion 1a is the same as in the second embodiment. Will be obtained.

  The sixth embodiment shown in FIG. 9 is an application of the configuration example to cope with the problem 1 of the second embodiment in the fifth embodiment. The central axis L2 of the long cylindrical hole 1a is The diffraction pattern center O on the objective lens 2 side is easily aligned with the optical axis L of the objective lens 2 by providing the lens holder 1 so that it is not coaxial with the optical axis L of the objective lens 2 but is translated and decentered. be able to.

  The seventh embodiment shown in FIG. 10 is an application of the configuration example to cope with the problem 1 of the second embodiment in the fifth embodiment, and is between two points (between a and b) having the maximum projection width as described above. By arranging the diffraction surface 3a on the objective lens 2 side of the diffraction element 3 on a plane passing through the middle point of the diffraction pattern 3, the diffraction pattern center O of the diffraction element 3 on the objective lens 1 side is obtained while enjoying the effects of the second embodiment. Can be aligned with the optical axis L of the objective lens 2.

  In Embodiment 5, the hole shape of the cylindrical hole portion 1a of the lens holder 1 is a long hole shape. However, the hole shape of the cylindrical hole portion 1a is the objective lens 2 in the fitting shaft portion 3b of the diffraction element 3. It is also conceivable to form an elliptical hole shape in which the maximum projected dimension on a virtual plane perpendicular to the optical axis L is the major axis and the outer diameter dimension of the diffraction element 3 is the minor axis. Also in this case, the center axis of the elliptical hole shape of the cylindrical hole portion 1a is set to be coaxial with the optical axis L of the objective lens 1.

  Further, even if the hole shape of the cylindrical hole portion 1a of the lens holder 1 is changed to the elliptical hole shape as described above, the central axis of the elliptical hole-shaped cylindrical hole portion 1a is set to be the same as that of the lens holder 1 as in the sixth embodiment. Instead of being coaxial with the optical axis of the objective lens 2, it is provided in the lens holder 1 so as to be translated and decentered, or in the same manner as in the seventh embodiment, on a plane passing through the midpoint between the two points that becomes the maximum projection width. By arranging the diffractive surface 3a on the objective lens 2 side in the diffractive element 3, the problems 1 and 2 can be dealt with.

  FIG. 11 is a schematic configuration diagram of an optical pickup apparatus equipped with an objective lens actuator according to an embodiment of the present invention. In a single objective lens 2, three types of optical recording media (BD system, (DVD system, CD system) 20a, 20b, and 20c are compatible optical pickups for recording or reproducing with different numerical apertures: NA.

  The substrate thicknesses of the BD, DVD, and CD optical recording media 20a, 20b, and 20c are 0.1 mm, 0.6 mm, and 1.2 mm, respectively, and the BD, DVD, and CD optical recording media. The numerical apertures (NA) corresponding to 20a, 20b, and 20c are NA0.85, NA0.65, and NA0.50, respectively, and the wavelengths λ1, λ2, and λ3 of the first, second, and third light sources are respectively λ1 = 395 to 415 nm, λ2 = 650 to 670 nm, and λ3 = 770 to 805 nm.

  The optical pickup shown in FIG. 11 has a semiconductor laser 21, a collimating lens 22, a polarizing beam splitter 23, a wavelength selective beam splitter 24, a deflecting prism 25, a quarter wavelength plate 26, and an aberration with respect to the BD optical recording medium 20a. It comprises a correction element (diffraction element) 3, an objective lens 2, a detection lens 27, and a light receiving element. The center wavelength of the semiconductor laser 21 as the first light source is 405 nm, and the numerical aperture (NA) of the objective lens 2 is 0.85. The objective lens 2 and the aberration correction element (diffraction element) 3 constituting the objective lens actuator 11 are provided in a single lens holder 1 as in the configurations of the embodiments shown in FIGS. The substrate thickness of the BD optical recording medium 20a is 0.1 mm.

  The light emitted from the semiconductor laser 21 is made into substantially parallel light by the collimator lens 22. The light that has passed through the collimating lens 22 enters the polarization beam splitter 23 and is deflected by the deflecting prism 25. Then, the light is converted into circularly polarized light by the quarter-wave plate 26 and condensed on the BD optical recording medium 20a via the aberration correction element 3 and the objective lens 2, whereby information is recorded and reproduced. The reflected light from the BD optical recording medium 20a passes through the quarter-wave plate 26 and is then converted into linearly polarized light that is orthogonal to the polarization direction of the outgoing light. Separated and deflected and guided onto the light receiving element 28 by the detection lens 27, a reproduction signal, a focus error signal, and a track error signal are detected and become drive control signals for the drive coils 4 and 5.

  The present optical pickup includes a two-wavelength laser unit 30 that generates a laser beam for the DVD optical recording medium 20b and a laser beam for the CD optical recording medium 20c. Light can be emitted.

  The light emitted from the DVD semiconductor laser 30a having a center wavelength of 660 nm with respect to the DVD optical recording medium 20b is deflected by the deflecting prism 25 via the collimating lens 31 and the wavelength selective beam splitter 24. Then, the light is condensed on the DVD optical recording medium 20 b via the quarter-wave plate 26, the aberration correction element 3, and the objective lens 2. The DVD-type optical recording medium 20b has a substrate thickness of 0.6 mm and a numerical aperture (NA) of 0.65. The switching of NA is limited by the aberration correction element 3. Then, the reflected light from the DVD optical recording medium 20b passes through the objective lens 2 and the quarter wavelength plate 26, then is deflected by the wavelength selective beam splitter 24, and separated from the incident light by the hologram element 32 to be separated from the DVD system. Guided on the light receiving element 30b, a reproduction signal, a focus error signal, and a track error signal are detected.

  Further, the light emitted from the CD semiconductor laser 33 a having a center wavelength of 785 nm with respect to the CD optical recording medium 20 c is deflected by the deflecting prism 25 through the collimating lens 31 and the wavelength selective beam splitter 24. Then, the light is condensed on the CD optical recording medium 20 c via the quarter-wave plate 26, the aberration correction element 3, and the objective lens 2. The substrate thickness of the CD optical recording medium 20c is 1.2 mm, and the numerical aperture (NA) of the objective lens 2 is 0.50. The switching of NA is limited by the aberration correction element 3. Then, the reflected light from the CD optical recording medium 20c passes through the objective lens 2 and the quarter wavelength plate 26, is then deflected by the wavelength selective beam splitter 24, and is separated from the incident light by the hologram element 32 to be separated from the CD system. Guided on the light receiving element 33b, a reproduction signal, a focus error signal, and a track error signal are detected.

  FIG. 12 is a block diagram showing a schematic configuration of an optical recording / reproducing apparatus equipped with the optical pickup device having the configuration of the embodiment according to the present invention. Of the reproducing, recording and erasing of information with respect to the optical recording medium, An apparatus that performs at least one.

  In the present embodiment, an optical pickup 41 corresponding to the optical pickup device shown in FIG. 11 is provided. A spindle motor 47 that rotationally drives the optical recording medium 20, an optical pickup 41 that is used for recording and reproducing information signals, and a feed motor 42 that moves the optical pickup 41 to the inner and outer circumferences of the optical recording medium 20. A modulation / demodulation circuit 44 that performs predetermined modulation and demodulation processing, a servo control circuit 43 that performs servo control of the optical pickup 41, and a system controller 46 that performs overall control of the optical information processing apparatus.

  The spindle motor 47 is driven and controlled by the servo control circuit 43 and is driven to rotate at a predetermined rotational speed. That is, the optical recording medium 20 to be recorded and reproduced is chucked on the drive shaft of the spindle motor 48 and is driven and controlled by the servo control circuit 43. The spindle motor 47 is rotationally driven at a predetermined rotational speed.

  When recording and reproducing information signals to and from the optical recording medium 20, the optical pickup 41 irradiates laser light onto the optical recording medium 20 that is rotationally driven and detects the reflected light as described above. The optical pickup 41 is connected to the modulation / demodulation circuit 44. When recording an information signal, a signal input from the external circuit 45 and subjected to a predetermined modulation process by the modulation / demodulation circuit 44 is supplied to the optical pickup 41. Based on the signal supplied from the modulation / demodulation circuit 44, the optical pickup 41 irradiates the optical recording medium 20 with laser light that has undergone light intensity modulation. Further, when reproducing the information signal, the optical pickup 41 irradiates the rotationally driven optical recording medium 20 with a laser beam having a constant output, and a reproduction signal is generated from the return light. The reproduction signal is supplied to the modem circuit 44.

  The optical pickup 41 is also connected to the servo control circuit 43. Then, as described above, the focus servo signal and the tracking servo signal are generated from the return light reflected and returned by the rotationally driven optical recording medium 20 at the time of recording / reproducing the information signal. It is supplied to the control circuit 43.

  The modem circuit 44 is connected to the system controller 46 and the external circuit 45. When recording an information signal on the optical recording medium 20, the modulation / demodulation circuit 44 receives a signal to be recorded on the optical recording medium 20 from the external circuit 45 under the control of the system controller 46. Apply modulation processing.

  The signal modulated by the modem circuit 44 is supplied to the optical pickup 41. Further, when reproducing the information signal from the optical recording medium 20, the modem circuit 44 receives the reproduction signal reproduced from the optical recording medium 20 from the optical pickup 41 under the control of the system controller 46. Predetermined demodulation processing. The signal demodulated by the modem circuit 44 is output from the modem circuit 44 to the external circuit 45.

  The feed motor 42 is for moving the optical pickup 41 to a predetermined position in the radial direction of the optical recording medium 20 when recording and reproducing the information signal, and based on a control signal from the servo control circuit 43. Driven. That is, the feed motor 42 is connected to the servo control circuit 43 and is controlled by the servo control circuit 43.

  The servo control circuit 43 controls the feed motor 42 so that the optical pickup 41 is moved to a predetermined position facing the optical recording medium 20 under the control of the system controller 46. The servo control circuit 43 is also connected to the spindle motor 47, and controls the operation of the spindle motor 47 under the control of the system controller 46. That is, the servo control circuit 43 controls the spindle motor 47 so that the optical recording medium 20 is rotationally driven at a predetermined rotational speed when recording and reproducing information signals with respect to the optical recording medium 20.

  Further, as a method for determining the type of the optical recording medium, a tracking servo signal or a focus servo signal may be used.

  By providing the optical recording / reproducing apparatus for recording and reproducing on a plurality of types of optical recording media with the optical pickup device of the present invention, the quality of recording and reproducing information on optical recording media having different substrate thicknesses can be improved. Can be increased.

  The present invention is applied to a lens actuator that drives an objective lens that focuses a beam on various optical recording media such as a CD system and a DVD system, various optical pickup devices that include the lens actuator, and optical recording / reproducing devices. be able to.

(A)-(c) is a block diagram of embodiment of the optical pick-up apparatus carrying the objective lens actuator based on this invention, (a) is a front view, (b) is a side view, (c) is a bottom face. Figure Sectional drawing which shows the relevant structure of the principal part in Embodiment 1 of the lens actuator which concerns on this invention. Explanatory drawing of the projection shape on the virtual surface of the diffraction element in this embodiment Sectional drawing which shows the relevant structure of the principal part in Embodiment 2 of the lens actuator which concerns on this invention. Sectional drawing which shows the relevant structure of the principal part in Embodiment 3 of the lens actuator which concerns on this invention. Sectional drawing which shows the relevant structure of the principal part in Embodiment 4 of the lens actuator which concerns on this invention. Sectional drawing which shows the relevant structure of the principal part in Embodiment 5 of the lens actuator which concerns on this invention. AA line end view in FIG. Sectional drawing which shows the relevant structure of the principal part in Embodiment 6 of the lens actuator which concerns on this invention. Sectional drawing which shows the relevant structure of the principal part in Embodiment 7 of the lens actuator which concerns on this invention. 1 is a schematic configuration diagram of an optical pickup device equipped with an objective lens actuator according to an embodiment of the present invention. 1 is a block diagram showing a schematic configuration of an optical recording / reproducing apparatus equipped with an optical pickup device having a configuration according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lens holder 1a Cylindrical hole 1b of lens holder Inclined plane part 2 of lens holder Objective lens 3 Diffraction element 3a Diffraction surface 3b of diffraction element Fitting shaft part 3c Diffraction element plane part 4, 5 Drive coil 8 Magnet 9 Support block D Maximum dimension width L of projection shape of diffraction element Optical axis O of objective lens O Diffraction pattern center S of diffraction element Virtual plane

Claims (10)

An objective lens for condensing a light beam on an optical recording medium and a diffractive element for providing compatibility with optical recording media of various types for a plurality of light sources having different wavelengths are installed opposite to the lens holder. A lens actuator configured to drive the objective lens together with the lens holder in the focus direction and the tracking direction with respect to the optical recording medium,
The diffractive surface of the diffractive element is inclined with respect to the optical axis of the objective lens, and the diffraction pattern center of the diffractive surface of the diffractive element on the objective lens side coincides with the optical axis of the objective lens. A lens actuator, wherein the diffraction element is installed in the lens holder.   The diffraction element has a disc-like shape having an outer peripheral surface serving as a fitting shaft portion and a flat portion on the upper surface, and an inner surface extends in parallel to the optical axis of the objective lens on the lens holder. And a cylindrical hole portion into which the fitting shaft portion of the diffractive element is inserted, and an inclined surface with respect to a virtual plane perpendicular to the optical axis of the objective lens in the cylindrical hole portion. A maximum width dimension of a maximum projection shape on a virtual plane perpendicular to the optical axis of the objective lens in the fitting shaft portion of the diffraction element is formed in the cylindrical hole portion of the lens holder. 2. The lens actuator according to claim 1, wherein the lens actuator is set to have a diameter, and the fitting shaft portion of the diffraction element is fitted into the cylindrical hole portion of the lens holder.   The center of the cylindrical hole portion of the lens holder is aligned with the center of the diffraction pattern of the diffractive surface on the objective lens side of the diffractive element that is inclined and attached to the lens holder on the optical axis of the objective lens. The lens actuator according to claim 2, wherein the lens actuator is installed to be shifted with respect to the optical axis of the objective lens.   The diffraction element has a disc-like shape having an outer peripheral surface serving as a fitting shaft portion and a flat portion on the upper surface, and an inner surface extends in parallel to the optical axis of the objective lens on the lens holder. And a cylindrical hole portion into which the fitting shaft portion of the diffractive element is inserted, and an inclined surface with respect to a virtual plane perpendicular to the optical axis of the objective lens in the cylindrical hole portion. An elongated flat surface formed by extending a circular projection with a maximum projection on a virtual plane perpendicular to the optical axis of the objective lens in the fitting shaft portion of the diffraction element. 2. The shape is set so that the central axis is coaxial with the optical axis of the objective lens, and the fitting shaft portion of the diffraction element is fitted into the cylindrical hole portion of the lens holder. Lens actuator.   The elongated cylindrical hole portion of the lens holder so that the diffraction pattern center of the diffraction surface on the objective lens side of the diffraction element inclined and attached to the lens holder coincides with the optical axis of the objective lens The lens actuator according to claim 4, wherein the center of the lens is installed with being shifted with respect to the optical axis of the objective lens.   The diffraction element has a disc-like shape having an outer peripheral surface serving as a fitting shaft portion and a flat portion on the upper surface, and an inner surface extends in parallel to the optical axis of the objective lens on the lens holder. And a cylindrical hole portion into which the fitting shaft portion of the diffractive element is inserted, and an inclined surface with respect to a virtual plane perpendicular to the optical axis of the objective lens in the cylindrical hole portion. And the cylindrical hole portion has a longest projection maximum dimension on a virtual plane perpendicular to the optical axis of the objective lens in the fitting shaft portion of the diffraction element, and the outside of the diffraction element. The elliptical hole shape having a short diameter is set so as to be coaxial with the optical axis of the objective lens, and the fitting shaft portion of the diffraction element is fitted into the cylindrical hole portion of the lens holder. The lens actuator according to claim 1.   The cylindrical hole portion of the elliptical hole shape of the lens holder so that the diffraction pattern center of the diffraction surface on the objective lens side in the diffraction element inclined and attached to the lens holder coincides with the optical axis of the objective lens The lens actuator according to claim 6, wherein the center of the lens is installed with being shifted with respect to the optical axis of the objective lens.   The diffractive surface of the diffractive surface on the objective lens side of the diffractive element is aligned such that the center of the diffractive pattern of the diffractive surface on the objective lens side of the diffractive element attached to the lens holder is inclined and coincides with the optical axis of the objective lens. 7. The lens actuator according to claim 2, wherein the position is set at a substantially center of the cylindrical hole portion of the lens holder. From an objective lens for condensing a light beam to the optical recording medium, a lens actuator for driving the objective lens in at least a focus direction and a tracking direction with respect to the optical recording medium, and a reflected beam from the optical recording medium In an optical pickup device provided with means for obtaining optical information,
9. An optical pickup device comprising the lens actuator according to claim 1 mounted as the lens actuator. In an optical recording / reproducing apparatus that includes an optical pickup and optically records and / or reproduces information on an optical recording medium,
An optical recording / reproducing apparatus comprising the optical pickup device according to claim 9 as the optical pickup.

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