JP2009004025A - Lens actuator, optical pickup, and optical recording/playback device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens actuator which can be easily manufactured and wherein the highly accurate positioning of an objective lens and a diffraction element can be performed. <P>SOLUTION: The objective lens 2 and the diffraction element 3 are provided in a single lens holder 1 to be positioned and fixed so that the optical axis of the diffraction element 3 is inclined to the optical axis of the objective lens 2. Thereby, the highly accurate positioning of the objective lens 2 and the diffraction element 3 can be easily performed and optical disturbance caused by specular reflection can be further prevented. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention provides an alignment accuracy between a housing equipped with an objective lens for condensing a light beam on an optical recording medium, and a diffraction element that provides recording / reproducing compatibility with optical recording media of multiple types of standards. The present invention relates to a lens actuator that drives an objective lens in at least a focus direction and a tracking direction with respect to an optical recording medium, an optical pickup equipped with the lens actuator, and an optical recording / reproducing apparatus.

  7A to 7C are configuration diagrams of an optical pickup device equipped with a conventional objective lens actuator, where FIG. 7A is a front view, FIG. 7B is a side view, and FIG. 7C is a bottom view. .

  In FIG. 7, a lens holder 1 of a movable part is a housing that holds an objective lens 2 and a diffraction element 3 for focusing a light beam on an optical disk (not shown) to form a beam spot, and a driving coil for focusing 4 and a tracking drive coil 5 are attached, and are attached to the fixed base 7 via a support spring 6 serving as a suspension / coil feed line. A magnet 8 is attached to the fixed side base 7 which also serves as a back yoke of the magnetic circuit, and the drive coils 4 and 5 of the lens holder 1 are arranged in this magnetic field.

  In the above structure, the objective lens 2 and the diffractive element 3 are attached to the upper and lower sides of the lens holder 1, and the heat sink is mainly used to cancel the inertial moment of inertia between the objective lens 2 and the diffractive element 3 with respect to the entire lens holder 1. An inertia ballast 9 is also provided.

  However, in the conventional example, it is possible to increase the weight and rigidity of the movable part structure of the actuator equipped with the diffractive element and to prevent thermal damage to the diffractive element, but the diffractive element mounting accuracy and angle are not considered. If the objective lens and the diffractive element are completely coaxially mounted, there is a problem that specular reflection of the flat surface portion of the diffractive element generates flare as return light and generates a false signal.

  Regarding avoidance of the flare, Patent Document 1 provides an example for avoiding this problem, but there are problems with the function and reliability of the movable part structure described later.

In addition, anti-flare measures by oblique arrangement of diffractive elements have been proposed, and such an oblique arrangement, that is, a structure in which the diffractive element is inclined with respect to the optical axis of the objective lens has been proposed. This does not take into account the positioning accuracy in the state.
JP 2006-139874 A

  In general, an optical element that is a rotating body around an axis is provided with a cylindrical or columnar shaft portion on the outer shape in order to increase the ease of manufacture and mounting accuracy, and a round hole or a stepped round hole is formed on a member to which these are attached. Thus, positioning is performed by fitting the round hole and the shaft.

  When concentric diffractive elements are used as interchangeable elements, the following matters are necessary to satisfy the functions. First, it is necessary to position the optical axis of the objective lens and the optical axis of the diffractive element with high precision. Second, both surfaces of the compatible diffractive element have stepped steps, but each stepped end surface is flat. Therefore, the integral of the plane of each step is equivalent to the plane of the entire effective diameter, and in order to prevent flare due to regular reflection, it is necessary to slightly tilt the flat portion of each step from the vertical with respect to the lens optical axis. is there.

  In this case, the center of the diffractive element that should be positioned with high accuracy with respect to the lens optical axis is the approximate center of the surface on the objective lens side of both surfaces. In recent years, higher density BD (Blu-ray Disc standard) or HD (HD-DVD standard) optical pickups have been developed. For example, CD, DVD and BD, or CD, DVD There is a need for a three-wavelength compatible objective lens that is compatible with the HD and HD systems. In general, this type of objective lens has a configuration in which the objective lens body corrected for aberration with respect to the BD system or the HD system is provided with compatibility for the CD system and the DVD system by the diffraction element. The position and inclination with respect to the lens body, in particular, the shift eccentricity with respect to the objective lens body having a phase structure formed in the diffraction element, has a significant influence on the imaging characteristics of the CD system or DVD system on the long wavelength side.

  For this reason, in the case of a diffractive element for a compatible optical system that uses a light source of three or more wavelengths that will be used in the future, positioning with a very high accuracy compared to the conventional wavelength selection or aperture limiting element of two wavelengths. The accuracy of several microns is required for the alignment of the diffraction element.

  By the way, in order to position the center of the inclined surface with high accuracy, the other member, for example, the lens holder 1 which is a movable housing in the lens actuator as shown in FIG. It is necessary to provide a hole. However, such a shape is an axis parallel to the optical axis of the objective lens. For example, when this hole is observed from the cross section taken along the line AA 'in FIG. 8A, it approximates an ellipse as shown in FIG. 8B. Is the projected shape. As a general theory, there is a plan to use a slide type or the like for the inclined cylindrical hole 1a (see FIG. 9B) for fitting the diffraction element 3. However, it is difficult to stably manufacture an actually small and compatible optical precision diameter hole in the upper part of the lens holder 1. That is, there are problems that the parts cannot be manufactured, the accuracy required for the assembly cannot be satisfied even if the parts can be manufactured, and the assembly work is difficult.

  In addition, when a member that creates a shape that is difficult to manufacture as described above is used, there is a high possibility that a problem in reliability occurs.

  In general, the diffractive element is a flat element. However, when such a flat element is mounted on an optical pickup, consideration for flare light is required. A part of the light beam traveling from the light source to the objective lens does not pass through the incident surface of each optical component and becomes specularly reflected light. When the diffractive element (aberration correction) is arranged perpendicular to the incident light (see FIG. 10), the specularly reflected light may overlap with the reflected light from the optical recording medium, that is, the signal light, resulting in noise light. is there. As a countermeasure, there is a method of slightly tilting the incident surface to the optical component. However, it is a basic premise that the optical axis of the objective lens body and the optical axis of the phase control element are kept parallel, and if both are inclined, the alignment accuracy is lowered.

  Furthermore, the material of the diffraction element may be glass, resin, or a glass resin substrate provided with a UV resin layer and the resin layer provided with a diffraction structure, but it is lighter than glass and can be molded. From the viewpoint of easy mass production, resin injection molding is desired. When the diffraction element is manufactured by injection molding, a draft gradient is required for taking it out of the mold. Without this draft, there is a problem that the molded part cannot be taken out, or distortion that adversely affects the optical characteristics at the time of taking out occurs.

  That is, when an injection molded part is assumed, it is clear that a draft angle is necessary in consideration of the influence on the optical characteristics due to removal from the mold and distortion. If a slip angle is given to the fitting shaft of the diffraction element, the diameters at the base and the tip are different, so that the looseness of the fitting becomes large and the positioning accuracy is deteriorated. Therefore, when a diffraction element having a drop gradient is assembled to the lens holder, it is difficult to satisfy the required mounting accuracy.

  Patent Document 1 shows an example in which a dedicated lens frame is provided as a built-in product, but the use of such a dedicated lens frame leads to an increase in the size of the movable housing, and the mass of the balance weight for these increases. Therefore, it is easy to cause a decrease in sensitivity due to an increase in size and an increase in mass, or a decrease in high-order resonance frequency. In particular, a lens built-in product using a lens frame with a large mass and a large moment of inertia should be fixed only by bonding. Has a great influence on the degradation of the higher-order resonance characteristics due to insufficient bonding rigidity.

  The present invention is directed to solving the above-described problems of the prior art. A lens actuator, an optical pickup device, and an objective lens and a diffractive element, which can be easily manufactured and can be positioned and adjusted with high accuracy, and An object is to provide an optical recording / reproducing apparatus.

  In order to achieve the above object, according to a first aspect of the present invention, an objective lens for condensing a light beam on an optical recording medium is provided in the casing, and the objective lens is mounted on the optical recording medium together with the casing. On the other hand, in a lens actuator that is driven at least in the focus direction and the tracking direction, a diffraction element for providing compatibility with optical recording media of a plurality of types with respect to a plurality of light sources having different wavelengths is used. The objective lens is characterized in that the surface is tilted with respect to the optical axis of the objective lens, and the diffraction pattern center of the objective lens side diffraction surface is substantially coincided with the optical axis of the objective lens and is installed in the housing. And diffractive element can be positioned and fixed in a single housing, thereby providing an actuator having a small and lightweight movable part. By attaching tilted with respect to the axis, it prevents optical disturbances caused by specular reflection, it is possible to obtain a good focusing spot.

  According to a second aspect of the present invention, in the lens actuator according to the first aspect, the casing has a cylindrical hole that is coaxial with the optical axis of the objective lens and has a cylindrical inner surface, and a plane perpendicular to the optical axis of the objective lens. An inclined surface is formed, and the diffraction element is formed with an axial shape having a side surface that is a cylinder coaxial with the optical axis of the diffraction element, and a plane perpendicular to the optical axis of the diffraction element. An axial shape is inserted, and the inclined surface of the housing and the flat surface of the diffractive element, and the cylindrical surface of the housing and the side surface of the diffractive element are in contact with each other, and the axial shape of the diffractive element is objective. It is characterized by satisfying the condition of “α = β” when the slope β is tapered toward the lens side and the intersection angle α between the optical axis of the objective lens and the inclined surface satisfies this condition. Get an actuator with moving parts and diffraction Child prevents optical disturbances caused by regular reflection by installing tilted with respect to the optical axis of the objective lens, and by positioning with high accuracy, it is possible to obtain a good focusing spot.

  According to a third aspect of the present invention, in the lens actuator according to the first aspect, the casing has a cylindrical hole that is coaxial with the optical axis of the objective lens and has a cylindrical inner surface, and a plane perpendicular to the optical axis of the objective lens. An inclined surface is formed, and the diffraction element is formed with an axial shape having a side surface that is a cylinder coaxial with the optical axis of the diffraction element, and a plane perpendicular to the optical axis of the diffraction element. Insert the shaft shape and incline by contacting the corner formed by the inclined surface of the housing and the plane of the diffraction element, and the corner formed by the cylindrical surface and the inclined surface of the housing, and the side of the diffraction element and the plane. When the axial shape of the diffractive element is a tapered cross section toward the objective lens side and the inclination β of the diffractive element and the crossing angle α between the optical axis of the objective lens and the inclined surface, “α> β (however, β <90 °) ”and satisfy this condition. A compact and lightweight actuator with a movable part is obtained, and the diffraction element is mounted tilted with respect to the optical axis of the objective lens to prevent optical disturbance due to regular reflection, and positioning is performed with high accuracy and good light collection. You can get a spot.

  According to a fourth aspect of the present invention, in the lens actuator according to the second or third aspect, the gradient in the tapered section toward the objective lens side in the axial shape of the diffractive element is a dropout necessary for injection molding for forming the diffractive element. Using the gradient, this configuration makes it possible to simplify the attachment of the diffractive element and perform high-accuracy positioning by using the draft gradient necessary for the injection molded part.

  According to a fifth aspect of the present invention, there is provided an objective lens for condensing a light beam on an optical recording medium, a lens actuator for driving the objective lens at least in a focus direction and a tracking direction with respect to the optical recording medium, and optical recording An optical pickup provided with means for obtaining optical information from a reflected beam from a medium, wherein the lens actuator according to any one of claims 1 to 4 is mounted as a lens actuator. By mounting a certain lens actuator, it is possible to pick up good and stable optical information that is easy to manufacture.

  According to a sixth aspect of the present invention, in an optical recording / reproducing apparatus that includes an optical pickup and optically records and / or reproduces information on an optical recording medium, the optical pickup according to the fifth aspect is used as the optical pickup. With this configuration, it is possible to record and / or reproduce optical information that is easy and easy to manufacture by mounting a reliable lens actuator.

  According to the lens actuator of the present invention, the objective lens and the diffractive element can be positioned and fixed to a single housing, respectively, and can be easily manufactured with high accuracy and have a small and lightweight movable part. An actuator can be provided, and an optical disturbance due to regular reflection can be prevented by attaching the diffractive element to the optical axis of the objective lens.

  In addition, according to the optical pickup device and the optical recording / reproducing apparatus according to the present invention, it is possible to perform good and stable optical recording / reproducing by mounting the lens actuator according to the present invention. .

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

  In the present embodiment, the configuration of the lens actuator in the optical pickup shown in FIG. 7 is excluded from the mounting structure of the objective lens 2 and the diffractive element 3 in the lens holder 1 that is a casing for holding the objective lens 2 and the diffractive element 3. Can be adopted.

  In the following description, components corresponding to the components described in FIG. 7 and having the same functions are denoted by the same reference numerals, detailed description thereof is omitted, and the main part of the lens actuator will be described.

  FIG. 1 is a partial cross-sectional view of a lens holder in a lens actuator of Embodiment 1 of the present invention. A lens holder 1 which is a housing has a hole having an effective beam diameter of an optical system in a central portion and an objective lens in an upper portion. 2 and a diffractive element 3 is provided below.

  This lens actuator is for an optical pickup, and the objective lens 2 collects a light beam on an optical disk (not shown) as an optical recording medium to form a beam spot. It functions to give compatibility to optical discs of three or more types of disc standards for light beams of three types of wavelengths (detailed later).

  In the first embodiment, in the conventional example of FIG. 9B described above, since the cylindrical hole 1a is formed to be inclined with respect to the optical axis L1 of the objective lens, it is difficult to create with high accuracy. On the other hand, in the first embodiment, the lens holder 1 is not provided with the inclined cylindrical hole as described above, but has a cylindrical hole 1a coaxial with the lens holder 1 as shown in FIG. Can be used for high-precision positioning.

  That is, the lens holder 1 is formed with a cylindrical hole 1a coaxial with the objective lens optical axis L1 and an inclined surface 1b inclined with respect to a plane perpendicular to the objective lens optical axis L1, and the diffraction element 3 is formed on the inclined surface 1b. Positioning is performed by contacting the flat surface 3b. For example, in order to form the cylindrical hole 1a and the inclined surface 1b in the lens holder 1 for this positioning, as shown in FIG. 2, the molds 10a and 10b are pulled up and down after molding by the molds 10a and 10b. The inclined surface 1b and the cylindrical surface 1c can be formed.

  The flat surface 3b and the side surface 3c of the diffraction element 3 are brought into contact with the inclined surface 1b and the cylindrical surface 1c of the lens holder 1, and the draft β of the diffraction element 3 is inclined with respect to the plane perpendicular to the objective lens optical axis L1 as shown in FIG. Positioning can be performed with high precision by equalizing the angle α of the surface.

  The outer shape of the diffractive element 3 and the plane of the diffractive element 3 do not have to be tapered as shown in FIG. Further, the shape of the lens holder 1 may not be limited to that shown in FIG.

  FIG. 3 is a partial cross-sectional view of the lens holder in the lens actuator according to the second embodiment of the present invention. The lens holder 1 has a hole having an effective beam diameter of the optical system at the center coaxial with the optical axis L1 of the objective lens. An inclined surface 1b having a certain cylindrical hole 1a and inclined with respect to a plane perpendicular to the objective lens optical axis L1 is formed. The flat surface 3b of the diffractive element 3 is brought into contact with the inclined surface 1b, and the positioning is performed by the side surface 3c that is the outer cylinder of the diffractive element 3 that is in contact with the cylindrical surface 1c of the cylindrical hole 1a of the lens holder 1.

  FIG. 4 is a partial cross-sectional view of the lens holder in the lens actuator according to the third embodiment of the present invention. In Embodiment 2 described above, the intersecting angle α between the inclined surface 1b located on the end surface of the lens holder 1 and the objective lens optical axis L1 is made to coincide with the draft angle β required for injection molding of the diffraction element 3, but the lens The intersecting angle α between the inclined surface 1b located on the end surface of the holder 1 and the objective lens optical axis L1 may be larger than the draft gradient β of the diffraction element 3, and this example will be described in the third embodiment.

  Also in the third embodiment, the lens holder 1 is formed with a cylindrical hole 1a that is coaxial with the objective lens optical axis L1 and an inclined surface 1b that is inclined with respect to a plane perpendicular to the objective lens optical axis L1. The flat surface 3b of the diffractive element 3 is brought into contact with 1b, and further, the corner 1d of the lens holder 1 (formed by the inclined surface 1b and the cylindrical surface 1c) and the corner 3d of the diffractive element 3 (the flat surface 3b and the side surface 3c). Positioning) is performed.

  FIG. 5 is a schematic configuration diagram of an optical pickup equipped with the objective lens actuator according to each of the embodiments of the present invention. In the single objective lens 38, three types of optical recording media using different light source wavelengths are shown. This is a compatible optical pickup that records or reproduces (BD system, DVD system, CD system) with different numerical apertures: NA.

  The substrate thicknesses of the BD, DVD, and CD optical recording media 39a, 39b, and 39c are 0.1 mm, 0.6 mm, and 1.2 mm, respectively, and the BD, DVD, and CD optical recording media. It corresponds to 39a, 39b, 39c. The numerical apertures (NA) 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 λ1 = 395 to 415 nm and λ2 =, respectively. 650 to 670 nm, λ3 = 770 to 805 nm.

  The optical pickup shown in FIG. 5 has a semiconductor laser 31, a collimator lens 32, a polarization beam splitter 33, a wavelength selective beam splitter 34, a deflection prism 35, a quarter wavelength plate 36, an aberration with respect to the BD optical recording medium 39a. It comprises a correction element (diffraction element) 37, an objective lens 38, a detection lens 40, and a light receiving element 42. The center wavelength of the semiconductor laser 31 as the first light source is 405 nm, and the numerical aperture (NA) of the objective lens 38 is 0.85. The aberration correction element (diffraction element) 37 and the objective lens 38 are provided in a single lens holder 1 as in the configuration of the embodiment. The substrate thickness of the BD optical recording medium 39a is 0.1 mm.

  The light emitted from the semiconductor laser 31 is made into substantially parallel light by the collimator lens 32. The light that has passed through the collimating lens 32 enters the polarization beam splitter 33 and is deflected by the deflecting prism 35. Then, the light is converted into circularly polarized light by the quarter wavelength plate 36 and condensed on the BD optical recording medium 39a via the aberration correction element 37 and the objective lens 38, whereby information is recorded and reproduced. The reflected light from the BD optical recording medium 39a passes through the quarter-wave plate 36 and is then converted into linearly polarized light that is orthogonal to the polarization direction of the outgoing light. Separated and deflected, the light is guided onto the light receiving element 42 by the detection lens 40, and a reproduction signal, a focus error signal, and a track error signal are detected.

  This optical pickup has a two-wavelength laser unit 50 that generates laser light for the DVD optical recording medium 39b and laser light for the CD optical recording medium 39c, that is, the wavelengths are different from each other. Laser light can be emitted.

  Further, the light emitted from the DVD semiconductor laser 43a having a center wavelength of 660 nm is deflected by the deflecting prism 35 through the collimating lens 45 and the wavelength selective beam splitter 34 with respect to the DVD optical recording medium 39b. Then, the light is condensed on the DVD optical recording medium 39b via the quarter-wave plate 36, the aberration correction element 37, and the objective lens 38. The DVD optical recording medium 39b 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 37. Then, the reflected light from the DVD optical recording medium 39b passes through the objective lens 38 and the quarter wavelength plate 36, then is deflected by the wavelength selective beam splitter 34, separated from the incident light by the hologram element 44, and separated from the DVD system. Guided on the light receiving element 43b, a reproduction signal, a focus error signal, and a track error signal are detected.

  Further, the light emitted from the CD semiconductor laser 46 a having a center wavelength of 785 nm with respect to the CD optical recording medium 39 c is deflected by the deflecting prism 35 through the collimating lens 45 and the wavelength selective beam splitter 34. Then, the light is condensed on the CD optical recording medium 39 c via the quarter-wave plate 36, the aberration correction element 37, and the objective lens 38. The substrate thickness of the CD optical recording medium 39c is 1.2 mm, and the numerical aperture (NA) of the objective lens is 0.50. The switching of NA is limited by the aberration correction element 37. Then, the reflected light from the CD optical recording medium 39c passes through the objective lens 38 and the quarter wavelength plate 36, then is deflected by the wavelength selective beam splitter 34, and separated from the incident light by the hologram element 44 to be separated from the CD system. Guided on the light receiving element 46b, a reproduction signal, a focus error signal, and a track error signal are detected.

  FIG. 6 is a block diagram showing a schematic configuration of an optical recording / reproducing apparatus equipped with the optical pickup having the configuration of the embodiment according to the present invention. At least one of reproducing, recording, and erasing information on an optical recording medium is shown. A device that does one.

  In the present embodiment, an optical pickup 51 corresponding to the optical pickup shown in FIG. 5 is provided. A spindle motor 58 that rotationally drives the optical recording medium 39, an optical pickup 51 that is used to record and reproduce information signals, and a feed motor 52 that moves the optical pickup 51 to the inner and outer circumferences of the optical recording medium 39. A modulation / demodulation circuit 54 that performs predetermined modulation and demodulation processing, a servo control circuit 53 that performs servo control of the optical pickup 51, and a system controller 56 that controls the entire optical information processing apparatus.

  The spindle motor 58 is driven and controlled by the servo control circuit 53, and is driven to rotate at a predetermined rotational speed. That is, the optical recording medium 39 to be recorded and reproduced is chucked on the drive shaft of the spindle motor 58 and is driven and controlled by the servo control circuit 53. The spindle motor 58 is rotationally driven at a predetermined rotational speed.

  When recording and reproducing information signals to and from the optical recording medium 39, the optical pickup 51 irradiates the optical recording medium 39 that is rotationally driven with laser light and detects the reflected light. This optical pickup 51 is connected to a modem circuit 54. When recording the information signal, a signal input from the external circuit 55 and subjected to a predetermined modulation process by the modulation / demodulation circuit 54 is supplied to the optical pickup 51. The optical pickup 51 irradiates the optical recording medium 39 with laser light that has been subjected to light intensity modulation, based on the signal supplied from the modulation / demodulation circuit 54. Further, when reproducing the information signal, the optical pickup 51 irradiates the rotationally driven optical recording medium 39 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 54.

  The optical pickup 51 is also connected to the servo control circuit 53. 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 39 at the time of recording / reproducing the information signal. It is supplied to the control circuit 53.

  The modem circuit 54 is connected to the system controller 56 and the external circuit 55. When recording an information signal on the optical recording medium 39, the modem circuit 54 receives a signal to be recorded on the optical recording medium 39 from the external circuit 55 under the control of the system controller 56. Apply modulation processing.

  The signal modulated by the modem circuit 54 is supplied to the optical pickup 51. Further, when reproducing the information signal from the optical recording medium 39, the modulation / demodulation circuit 54 receives the reproduction signal reproduced from the optical recording medium 39 from the optical pickup 51 under the control of the system controller 56. Predetermined demodulation processing. Then, the signal demodulated by the modem circuit 54 is output from the modem circuit 54 to the external circuit 55.

  The feed motor 52 is for moving the optical pickup 51 to a predetermined position in the radial direction of the optical recording medium 39 when recording and reproducing the information signal, and based on a control signal from the servo control circuit 53. Driven. That is, the feed motor 52 is connected to the servo control circuit 53 and controlled by the servo control circuit 53.

  The servo control circuit 53 controls the feed motor 52 so that the optical pickup 51 is moved to a predetermined position facing the optical recording medium 39 under the control of the system controller 56. The servo control circuit 53 is also connected to the spindle motor 58 and controls the operation of the spindle motor 58 under the control of the system controller 56. That is, the servo control circuit 53 controls the spindle motor 58 so that the optical recording medium 39 is rotationally driven at a predetermined rotational speed when information signals are recorded and reproduced on the optical recording medium 39.

  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 of the present invention in an optical recording / reproducing apparatus that performs recording and reproducing processing on a plurality of types of optical recording media, the accuracy of quality of recording and reproducing information on optical recording media having different substrate thicknesses is improved. be able to.

  The present invention relates to a lens actuator that drives an objective lens that focuses a beam on various optical recording media such as a BD system, an HD system, a CD system, and a DVD system, various optical pickups that include the lens actuator, optical recording / recording It can be applied to a playback device.

Partial sectional drawing of the lens holder in the lens actuator of Embodiment 1 of this invention The figure explaining the inclined surface formation of the lens holder of this Embodiment 1. Partial sectional drawing of the lens holder in the lens actuator of Embodiment 2 of this invention Partial sectional drawing of the lens holder in the lens actuator of Embodiment 3 of this invention Schematic configuration diagram of an optical pickup device equipped with the objective lens actuator having the configuration of each embodiment according to the present invention. 1 is a block diagram showing a schematic configuration of an optical recording / reproducing apparatus equipped with an optical pickup according to an embodiment of the present invention. (A)-(c) is a block diagram of the optical pick-up which mounted the conventional objective lens actuator, (a) is a front view, (b) is a side view, (c) is a bottom view. (A) of a conventional optical pickup is a cross-sectional view, and (b) is a diagram showing a projection shape of a diffraction element viewed from a cross-section taken along line A-A 'of (a). (A) of a conventional optical pickup is a cross-sectional view, and (b) is a view showing an inclined cylindrical hole. Sectional view in which diffraction elements of a conventional optical pickup are arranged vertically

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lens holder 1a Cylindrical hole 1b Slope 1c Cylindrical surface 1d Corner | angular part 2,38 Objective lens 3,37 Diffraction element (aberration correction element)
3b Flat surface 3c Side surface 3d Corners 39, 39a, 39b, 39c Optical recording medium 51 Optical pickup

Claims (6)

In a lens actuator for providing an objective lens for condensing a light beam to an optical recording medium in a housing, and driving the objective lens together with the housing in at least a focus direction and a tracking direction with respect to the optical recording medium,
A diffractive element for providing compatibility with optical recording media of a plurality of types for a plurality of light sources having different wavelengths, a diffractive surface of the diffractive element being inclined with respect to the optical axis of the objective lens, and the objective lens A lens actuator characterized in that the center of the diffraction pattern of the side diffractive surface is set in the casing so as to substantially coincide with the optical axis of the objective lens. The casing is formed with a cylindrical hole that is coaxial with the optical axis of the objective lens and whose inner surface is a cylindrical surface, and an inclined surface that is inclined with respect to a plane perpendicular to the optical axis of the objective lens,
The diffractive element is formed with an axial shape having a side surface that is a cylinder coaxial with the diffractive element optical axis, and a plane perpendicular to the diffractive element optical axis,
The axial shape of the diffraction element is inserted into the cylindrical hole of the casing, and the inclined surface of the casing and the plane of the diffraction element, and the cylindrical surface of the casing and the side surface of the diffraction element are in contact with each other. To be positioned and
When the axial shape of the diffractive element is a tapered cross-section toward the objective lens side and an angle of intersection α between the objective lens optical axis and the inclined surface, the condition of “α = β” is satisfied. The lens actuator according to claim 1. The casing is formed with a cylindrical hole that is coaxial with the optical axis of the objective lens and whose inner surface is a cylindrical surface, and an inclined surface that is inclined with respect to a plane perpendicular to the optical axis of the objective lens,
The diffractive element is formed with an axial shape having a side surface that is a cylinder coaxial with the diffractive element optical axis, and a plane perpendicular to the diffractive element optical axis,
Inserting the axial shape of the diffractive element into the cylindrical hole of the casing, the diffractive element formed by the inclined surface of the casing and the plane of the diffractive element, and the corner formed by the cylindrical surface and the inclined surface of the casing It is structured to be inclined and positioned by abutting the corner formed by the side surface and the plane,
When the axial shape of the diffractive element has a slope β in a tapered section toward the objective lens side and an intersection angle α between the optical axis of the objective lens and the inclined surface, “α> β (where β <90 The lens actuator according to claim 1, wherein the condition “°)” is satisfied.   4. The lens actuator according to claim 2, wherein the gradient in the taper section toward the objective lens in the axial shape of the diffraction element uses a draft gradient necessary for injection molding for forming the diffraction element. . 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 provided with means for obtaining optical information,
An optical pickup comprising the lens actuator according to claim 1 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 according to claim 5 mounted as the optical pickup.

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