JP2011113588A - Optical element and optical pickup device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate such a risk that a thick periphery of an objective lens which often brings the objective lens into contact with an optical disk due to shocks or the like, which might break the objective lens and optical disk. <P>SOLUTION: A biconvex optical element made of glass materials includes: a lens having a first optical surface on which a light flux is incident, and a second optical surface from which the light flux is emitted; a periphery which is arranged at the periphery of the lens and has a protruded surface protruded at least partially from the second optical surface in the optical axis direction; and a sheet member which is formed on the protruded surface. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical element and an optical pickup device using the optical element.

  In recent years, high-density optical discs such as Blu-ray Disc (registered trademark; hereinafter also referred to as BD) optical pickup devices are also used in conventional optical discs such as CD (Compact Disc (registered trademark)), DVD ( Similar to an optical pickup device for an optical disk such as Digital Versatile Disc (registered trademark), there is a demand for thinning the entire device. The reduction in size and thickness of the optical pickup device contributes to the reduction in size and thickness of products equipped with this optical pickup device. Further, as the optical pickup device is reduced in size and thickness, the types of products on which the optical pickup device can be mounted increase. Therefore, due to the mass production effect of the optical pickup device and the optical member used therefor, the cost of the optical pickup device and the optical member used therefor can be reduced.

  An objective lens is one of the optical components having a large influence on the thickness of the optical pickup device. Due to the optical arrangement, the thickness of the objective lens affects the thickness of the optical pickup device. Therefore, it is necessary to reduce the thickness of the objective lens in order to reduce the thickness of the optical pickup device.

  In the case of an objective lens for BD, the lens thickness tends to be thick because correction of off-axis aberrations and the like is performed in a high NA range. The term “thick lens thickness” as used herein refers to the thickness on the lens axis when normalized by the focal length, and indicates that the thickness is thicker than a relatively low NA objective lens for CD and DVD. Here, the description will focus on a biconvex single lens that is superior in terms of optical performance and cost.

  In the lens design, since the objective lens optical surface on the light source side needs to bend the incident light largely, it is generally a high power surface and the amount of sag tends to increase.

  In addition, since the optical surface of the objective lens on the disk side also has a convex power, the lens thickness decreases toward the periphery. Here, the optical surface includes a refracting surface such as an aspherical surface, a diffractive surface, and a phase step surface.

  When the lens thickness is made as thin as possible, the edge thickness may not be secured in the vicinity of the lens effective diameter and the outer periphery thereof. As a result, cracking occurs when the lens is molded or when the lens is attached to the optical pickup.

  Therefore, a measure to prevent the lens from cracking can be considered by securing a certain edge thickness.

  For example, in Patent Documents 1, 2, and 3, a high NA objective lens includes a resin objective lens in which a region having a thicker thickness in the optical axis direction is provided on the outer peripheral portion than a thickness in the optical axis direction in an effective diameter region. It is disclosed.

JP 2007-334928 A JP 2007-334929 A JP 2007-334930 A

  FIG. 6 is a side view when the configuration of the above-mentioned patent document is applied to a glass lens.

  The optical element 80 is an example of an objective lens. In the optical element 80 to which the configuration disclosed in the above patent document is applied, the optical surface 81 and the outer peripheral surface 82 are connected by a discontinuous surface. The configuration as in the above-mentioned patent document has no problem in the case of a lens made of resin, but when applied to a lens made of glass, there arises a problem that a crack 83 occurs at the connection portion between the optical surface 81 and the outer peripheral surface 82. It was. Specifically, cracking occurred when the lens was molded or when the lens was attached to the optical pickup.

  Therefore, the configuration disclosed in the above patent document cannot be applied to a lens made of glass. The reason is considered to be caused by a difference between a resin lens construction method (for example, injection molding) and a glass lens construction method (for example, lens molding).

  Further, with respect to the purpose of increasing the thickness in the optical axis direction at the outer peripheral portion, the above-mentioned patent document also has a role of a collision preventing material with an optical disc by improving transferability and improving lens aberration performance.

  However, in such a configuration, the distance between the outer peripheral portion and the optical disk is reduced, and the objective lens and the optical disk are easily brought into contact with each other due to an impact or the like. As a result, the objective lens and the optical disk may be damaged. In the case of a lens made of a glass material, it is particularly easy to break.

  In view of the above problems, an object of the present invention is to provide an optical element that is unlikely to be cracked at the time of lens molding or lens mounting, and that is not easily damaged even when it comes into contact with an optical disk due to impact or the like.

  In order to achieve the above object, an optical element according to the present invention is a biconvex optical element made of a glass material, and includes a first optical surface on which a light beam enters and a second optical on which the incident light exits. And a lens part having a surface, an outer peripheral part provided on an outer periphery of the lens part, at least a part having a projecting surface projecting in the optical axis direction from the second optical surface, and the projecting surface. And a sheet member.

  According to the present invention, it is possible to provide a thin lens that is unlikely to be cracked at the time of lens molding or lens mounting and that is not easily damaged even when it comes into contact with an optical disk due to impact or the like.

1 is a side view showing a schematic configuration of an optical element according to Embodiment 1. FIG. A side view showing a schematic configuration of an optical element according to Embodiment 2. A side view showing a schematic configuration of an optical element according to Embodiment 3. Side view showing a schematic configuration of an optical element according to another embodiment. The figure which shows schematic structure of the optical pick-up apparatus which concerns on Embodiment 4. FIG. The side view which shows schematic structure of the optical element which adapted the structure of patent documents 1-3 to the glass lens

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the embodiments, components that perform similar operations or components that have similar functions are denoted by the same reference numerals, and description thereof may not be repeated.

(Embodiment 1)
FIG. 1 is a side view showing a schematic configuration of an optical element 10 according to the first embodiment.

  The optical element 10 according to the present embodiment is an objective lens made of a glass material. The optical element 10 is mounted on the optical pickup device 100 as shown in FIG. 5, for example, and focuses the laser beam on the information recording surface of the information recording medium 50.

  Here, the type of the information recording medium 50 is not particularly limited. The information recording medium 50 may be, for example, a CD (Compact Disc Rerecordable), a CD-RW (Compact Disk Read Only Memory), a CD-ROM (Compact Disk Read Only Memory), a DVD (Digit Discrete Memory), or a DVD (Digit Digital Memory). DVD-R (Digital Versatile Disc Recordable), DVD-RW (Digital Versatile Disc Rewriteable), DVD-ROM (Digital Versatile Disc Read Only Memory), DVD-ROM (Digital Versatile Disc Read Only Memory), DVD-ROM (Digital Versatile Disc Rewriteable Memory) EVD (Enhanced Versatile Disc), EVD-R (Enhanced Versatile Disc Recordable), EVD-RW (Enhanced Versatile Disc ReWritable), EVD-ROM (Enhanced Versatile Disc Read Only Memory), EVD-RAM (Enhanced Versatile Disk Random Access Memory) BD (Blu-ray Disc Read Only Memory), BD-R (Blu-ray Disc Recordable), BD-RW (Blu-ray Disc Rewritable), BD-ROM (Blu-ray Disc Read Only Memory), BD-RAM lu-ray Disc Random Access Memory), HD-DVD (High Definition Digital Versatile Disc), HD-DVD-R (High Definition Digital Versatile Disc Recordable), HD-DVD-RW (High Definition Digital Versatile Disc ReWritable), HD- DVD-ROM (High Definition Digital Versatile Disc Read Only Memory), HD-DVD-RAM (High Definition Digital Versatile Disc Access Memory, etc.) Disk (or more, all registered trademark) may be.

  Hereinafter, this embodiment will be described with reference to FIG.

  Laser light 60 having a wavelength of 408 nm emitted from a light source (not shown) is made into substantially parallel light by a collimating lens (not shown) or the like and enters the optical element 10. The optical element 10 is a single lens composed of two different aspherical surfaces made of a glass material and having a positive power. The laser beam 60 is incident on the aspherical first optical surface 21 and is emitted from the aspherical second optical surface 22. The emitted laser beam 60 is narrowed down by the optical element 10 and forms a good spot on the information recording surface of the information recording medium 50. Further, the laser beam 60 reflected on the information recording surface enters from the second optical surface 22, exits from the first optical surface 21, and again enters the collimating lens or the like as substantially parallel light, and a detector (not shown). )) And is detected as a signal.

  Hereinafter, the configuration and shape of the optical element 10 will be described in detail.

  The optical element 10 is made of a glass material. The glass material used for the optical element 10 can be appropriately selected according to the characteristics required for the optical element 10. The glass transition point of the glass material is, for example, 400 degrees or more.

  The optical element 10 includes a lens portion 20, an outer peripheral portion 30 provided on the outer periphery of the lens portion 20, and a sheet member 90. The lens unit 20 includes a first optical surface 21 and a second optical surface 22. The outer peripheral portion 30 has a first outer peripheral surface 31 and a second outer peripheral surface 32. The second outer peripheral surface has a protruding surface 33 at least partially protruding in the optical axis direction from the second optical surface 22, and an intermediate surface 34 provided on the optical axis side of the protruding surface 33. The sheet member 90 is formed on the protruding surface 33.

  The lens unit 20 is formed so that the thickness in the optical axis direction becomes thinner from the optical axis 70 in the radial direction. That is, the distance between the first optical surface 21 and the second optical surface 22 decreases as the distance from the optical axis 70 increases in the radial direction. Here, in the present specification, a portion of the first optical surface 21 that is closest to the second optical surface 22 side is defined as an end portion of the first optical surface 21. Further, a portion of the second optical surface 22 that is closest to the first optical surface 21 is defined as an end portion of the second optical surface 22.

  The outer peripheral portion 30 formed outside the lens portion 20 is formed so that the thickness in the optical axis direction increases as the distance from the optical axis 70 increases.

  The first optical surface 21 is a convex surface having an optical function. Here, the optical function refers to a function for producing optical characteristics required for the optical element 10.

  The second optical surface 22 is a convex surface having an optical function. The second optical surface 22 is disposed at a position facing the first optical surface.

  Each of the first optical surface 21 and the second optical surface 22 has a region corresponding to an optical effective diameter that is a diameter when actual laser light passes. The optical effective diameter of the first optical surface 21 is the length of a line segment connecting the intersections of the laser beam 60 and the first optical surface 21. The optical effective diameter of the second optical surface 22 is the length of a line segment connecting the intersections of the second optical surface 22 and the laser beam 60.

  The first outer peripheral surface 31 is provided on the first optical surface 21 side. The first outer peripheral surface 31 is provided on the outer periphery of the first optical surface 21.

  The second outer peripheral surface 32 is provided on the second optical surface 22 side. The second outer peripheral surface 32 is provided on the outer periphery of the second optical surface 22. The second outer peripheral surface 32 has a protruding surface 33 at least partially protruding in the optical axis direction from the second optical surface 22. In the present embodiment, the entire protruding surface 33 protrudes in the optical axis direction from the second optical surface 22. The projecting surface 33 is formed perpendicular to the optical axis. With such a configuration, the thickness of the outer peripheral portion 30 can be ensured.

  A coating film (not shown) may be formed on the surfaces of the lens unit 20 and the outer peripheral unit 30. The coating film is a film having a function generally used for lenses and the like. For example, the coating film is a film having functions such as antireflection and durability improvement. As a material for the coating film, a material generally employed for realizing the above-described function can be used. The film thickness of the sheet member 90 is appropriately set according to the required optical design and function. The film thickness of the sheet member 90 is, for example, about several hundred nm to several μm.

  A sheet member 90 is formed on the protruding surface 33. As the sheet member 90, for example, a resin adhesive tape, an ultraviolet curable resin, or the like may be used. The thickness of the sheet member 90 is appropriately set. The thickness of the sheet member 90 may be about 10 μm, for example.

  In the present embodiment, the sheet member 90 serves as a buffer material for the optical element 10. Therefore, even when the optical element 10 and the information recording medium 50 come into contact with each other due to vibration or impact when the optical element 10 is attached to an optical pickup device or the like, the optical element 10 and the information recording medium 50 are not easily damaged.

  The sheet member 90 may be formed on the entire surface of the protruding surface 33, or may be formed at a plurality of locations with a predetermined interval. If the sheet member 90 is formed on the entire surface of the protruding surface 33, the possibility of preventing the optical element 10 and the information recording medium 50 from being damaged increases. Further, even if the sheet member 90 is formed on the protruding surface 33 with a predetermined interval, the sheet member 90 is located closest to the optical disc, so that an area where the sheet member 90 is not formed is the same as the information recording medium 50. The possibility of contact is reduced. Therefore, the optical element 10 and the information recording medium 50 are not easily damaged. In addition, since the sheet members formed with a predetermined interval are marks, it can be used for alignment when the optical element 10 is attached.

  A connecting portion between the second optical surface 22 and the second outer peripheral surface 32 is formed as a concave curved surface 41. The curved surface 41 is formed by continuously connecting the end of the second optical surface 22 and the end of the second outer peripheral surface 32. In other words, the second optical surface 22 and the second outer peripheral surface 32 are smoothly connected.

  With such a configuration, it is possible to prevent cracks that have occurred in conventional optical elements.

  In the conventional optical element, the connection portion between the optical surface and the outer peripheral surface is formed as a discontinuous surface. For this reason, it is considered that stress was concentrated on the connecting portion during lens molding or lens mounting, and cracking occurred. Moreover, since this connection part is the part where the thickness in the optical axis direction is the thinnest, it is considered that the connection part was particularly easily broken.

  On the other hand, in the present embodiment, the connection portion between the second optical surface 22 and the second outer peripheral surface 32 is formed by a curved surface 41. In other words, the end of the second optical surface 22 and the end of the second outer peripheral surface 32 are connected continuously. In other words, the second optical surface 22 and the second outer peripheral surface 32 are smoothly connected. Therefore, it is considered that the stress concentration generated in the conventional optical element is relaxed and cracking is prevented.

  Since the optical element 10 according to the present embodiment has the above-described configuration, it is difficult for cracks to occur during lens molding. Therefore, the optical element 10 can be molded stably.

  Further, the optical element 10 has a sufficient thickness of the outer peripheral portion 30, and the connecting portion where the thickness in the optical axis direction is the smallest is also formed by the curved surface 41. For this reason, it is possible to prevent cracking when the optical pickup device is attached.

  Further, the radius of curvature of the curved surface 41 is formed to be smaller than the radius of curvature of the second optical surface 22. With such a configuration, the second outer peripheral surface 32 starts to protrude in the optical axis direction at a position closer to the optical axis. As a result, a thick portion of the outer peripheral portion 30 can be secured widely. Therefore, it is possible to further prevent cracking when mounting the optical pickup device.

  The curved surface 41 is preferably formed closer to the optical axis than the connection portion between the first optical surface 21 and the first outer peripheral surface 31. If the curved surface 41 and the connecting portion are located on the same axis parallel to the optical axis, or if the curved surface 41 is further away from the optical axis than the connecting portion, the lens portion 20 and the outer peripheral portion 30 The connecting portion becomes very thin and the portion is easily broken. On the other hand, by forming the curved surface 41 at a position closer to the optical axis than the connection portion, it becomes easy to ensure the thickness of the connection portion. By adopting such a configuration, it becomes easier to prevent cracks during molding of the lens and cracks when attached to the optical pickup device.

  Next, a method for manufacturing the optical element 10 will be described.

  First, a glass material is placed between an upper die and a lower die that have been finely processed into a desired shape. As the glass material, for example, VC79 (glass transition point 516 ° C., yield point 553 ° C.) of Sumita Optical Glass can be used.

  In this embodiment, the upper and lower mold members are mainly composed of tungsten carbide and are covered with a platinum-based alloy protective film. The same member as the upper and lower molds was used for the barrel mold for sliding the upper and lower molds. Hereinafter, the upper mold, the lower mold, and the body mold may be collectively referred to as a mold.

  Next, the mold on which the glass material is placed is placed in a molding apparatus. The molding apparatus includes a preheating process, a pressing process, and a cooling process, and sequentially feeds the molds with an arm or the like. The molding temperature in the pressing step is set to, for example, 580 ° C. in consideration of the characteristics of the glass material. The die that has undergone the pressing step is cooled in the cooling step, and then further cooled by a cooling plate. When the die temperature becomes 200 ° C. or lower, the die is taken out from the molding apparatus. A glass material is shape | molded in the shape of the optical element 10 through such a process.

  Next, the optical element 10 is manufactured by sticking a resin adhesive tape on the protruding surface 33.

  In the present embodiment, the optical element 10 is composed of two aspheric surfaces, but is not limited thereto. For example, it may be a spherical surface, or may be a diffractive surface or a phase step surface as shown in FIG.

  Moreover, in this embodiment, although the sheet | seat member 90 is formed only on the protrusion surface 33, it is not restricted to this. For example, as shown in FIG. 4, a UV curable resin or the like may be formed on the aspherical surface of the second optical surface 22, a diffraction step, a phase step, or the like. In this case, the resin layer formed on the second optical surface 22 may have an optical function. That is, a laminated diffractive optical element in which a resin lens is laminated on a glass lens may be used.

(Embodiment 2)
FIG. 2 is a side view showing a schematic configuration of the optical element 11 according to the second embodiment.

  The optical element 11 according to the second embodiment is different from the optical element 10 according to the first embodiment in that the outer peripheral portion 30 further has a curved surface 42.

  In the present embodiment, a connecting portion between the protruding surface 33 and the intermediate surface 34 is formed as a convex curved surface 42. The curved surface 42 is formed by continuously connecting the end of the protruding surface 33 and the end of the intermediate surface 34. In other words, the protruding surface 33 and the intermediate surface 34 are smoothly connected. That is, in the optical element 11 according to Embodiment 2, the center from the optical axis center of the second optical surface 22 to the outermost peripheral end portion of the second outer peripheral surface 32 is a continuous surface.

  With such a configuration, it is possible to prevent not only the crack of the connection portion between the second optical surface 22 and the second outer peripheral surface 32 but also the crack of the connection portion between the protruding surface 33 and the intermediate surface 34. As a result, cracks during lens molding are further less likely to occur. Therefore, the optical element 11 can be molded more stably.

  The curvature radius of the curved surface 42 is preferably formed to be larger than the curvature radius of the curved surface 41. With such a configuration, processing of the mold corresponding to the outer peripheral portion 30 is facilitated. As a result, productivity in lens molding can be improved.

(Embodiment 3)
FIG. 3 is a side view showing a schematic configuration of the optical element 12 according to the third embodiment.

  The optical element 12 according to the third embodiment is different from the optical elements according to the other embodiments in that a connecting portion between the first optical surface 21 and the first outer peripheral surface 31 is formed as a curved surface 43.

  The curved surface 43 is formed in a concave shape.

  The curved surface 43 is formed by continuously connecting the end portion of the first optical surface 21 and the end portion of the first outer peripheral surface 31. In other words, the first optical surface 21 and the first outer peripheral surface 31 are smoothly connected. That is, the optical element 12 according to Embodiment 3 is a surface having continuity from the center of the optical axis of the first optical surface 21 to the outermost peripheral end portion of the first outer peripheral surface 31.

  With such a configuration, it is possible to prevent not only the crack on the second optical surface side but also the crack at the connection portion between the first optical surface 21 and the first outer peripheral surface 31. As a result, cracks during lens molding are further less likely to occur. Therefore, the optical element 12 can be molded more stably.

  The curved surface 41 is preferably formed at a position closer to the optical axis than the curved surface 43. If the curved surface 41 and the curved surface 43 are located on an axis parallel to the optical axis, or if the curved surface 41 is farther from the optical axis than the curved surface 43, the connecting portion between the lens portion 20 and the outer peripheral portion 30 is It becomes very thin and the part becomes easy to break. On the other hand, by forming the curved surface 41 at a position closer to the optical axis than the curved surface 43, it becomes easy to ensure the thickness of the connection portion. By adopting such a configuration, it becomes easier to prevent cracks during molding of the lens and cracks when attached to the optical pickup device.

(Embodiment 4)
FIG. 5 is a diagram illustrating a schematic configuration of the optical pickup device according to the fourth embodiment.

  The optical pickup device 100 according to the present embodiment includes the thin optical element described in the first to third embodiments. Thereby, a thin optical pickup device capable of performing stable recording and reproduction can be realized.

  An optical pickup device 100 according to this embodiment includes a light source 101, a beam shaping lens 104, a beam splitter 105, a collimator lens 102, a rising mirror 107, an objective lens 103, a detection lens 108, and a detector 109. With.

  The light source 101 emits a laser beam 110 having a wavelength corresponding to the type of the information recording medium 106. In the present embodiment, the laser light 110 emitted from the light source 101 is divergent light. For example, when the information recording medium 106 is BD (registered trademark), the light source 101 emits laser light having a wavelength of 378 to 438 nm (may be less than 420 nm). On the other hand, when the information recording medium 106 is a DVD (registered trademark), the light source 101 emits laser light having a wavelength of 630 to 690 nm. When the information recording medium 106 is a CD (registered trademark), the light source 101 emits laser light having a wavelength of 750 to 810 nm. Further, for example, when the optical pickup device is for focusing laser light on three types of optical discs of CD, DVD, and BD, the light source 101 corresponds to the type of the optical disc arranged with respect to the optical pickup device. The light of wavelength is selectively emitted.

  The beam shaping lens 104 is a lens that shapes the laser light emitted from the light source 101 into a desired shape. The beam shaping lens 104 is disposed in front of the light source 101. Laser light shaped by the beam shaping lens 104 enters the beam splitter 105.

  The beam splitter 105 is an optical element that transmits light in one deflection direction and reflects light in the deflection direction orthogonal thereto. The beam splitter 105 reflects the beam shaped by the beam shaping lens 104 toward the collimating lens 102. The laser beam reflected by the information recording medium 106 passes through the beam splitter 105 and enters the detector 109.

  The collimating lens 102 is an optical element that emits light that has entered the collimating lens 102 as substantially parallel light. The substantially parallel light means light in which the laser beam does not spread and the diameter of the laser beam does not change even when the light travels. The collimating lens 102 may be configured by a single lens or may be configured by a plurality of lenses.

  The rising mirror 107 is an optical element that reflects the laser light that has been collimated by the collimator lens 102 in a direction perpendicular to the recording surface of the information recording medium 106. The laser beam reflected by the rising mirror 107 enters the objective lens 103.

  The objective lens 103 is a lens that condenses the laser light emitted from the light source 101 on the recording surface of the information recording medium 106. In the present embodiment, the objective lens 103 is configured by only one lens, but is not limited thereto. If necessary, it may be configured with one or a plurality of other optical elements such as a phase correction element and a beam expander lens.

  The NA of the objective lens 103 is not particularly limited, but may be, for example, 0.8 or more, particularly when the optical pickup device focuses laser light on BD (registered trademark) or the like. preferable.

  The laser beam focused on the information recording surface of the information recording medium 106 by the objective lens 103 is reflected by the information recording surface. Then, the laser light reflected by the information recording surface passes through the objective lens 103, the rising mirror 107, the collimator lens 102, and the beam splitter 105 again, and is incident on the detector 109 by the detection lens 108. .

  In the present embodiment, the collimator lens 102 has a function as an aberration correction element, and is positioned at a reference position between the beam splitter 105 and the objective lens 103. The collimating lens 102 is configured to be displaceable on the optical axis AX from the reference position. Furthermore, in the present embodiment, the objective lens 103 is configured such that substantially parallel light is incident on the objective lens 103 when the collimating lens 102 as an aberration correction element is located at the reference position.

  Here, the objective lens 103 has the same shape as the optical element 10 shown in FIG. That is, the objective lens 103 is a biconvex lens made of a glass material. The objective lens 103 is a so-called aspherical lens.

  Hereinafter, the surface shape of the exit surface side of the objective lens 103 will be described in detail. Here, the surface on the exit surface side corresponds to the surface constituted by the second optical surface and the second outer peripheral surface of the above-described first to third embodiments.

  The exit surface of the objective lens 103 is a convex aspherical surface having a positive power within the effective diameter. Then, the lens thickness in the optical axis direction becomes thinner as going from the optical axis in the radial direction. That is, the sag amount on the exit surface decreases. Here, the sag amount represents the amount of displacement in the direction of the optical axis when a plane that passes through the intersection of the exit surface and the optical axis and is perpendicular to the optical axis is used as a reference plane. The sign of the sag amount on the exit surface is negative on the light source side and positive on the information recording medium side.

  In the outer peripheral region exceeding the effective diameter, the outer peripheral surface is connected to the outer peripheral surface by a curved surface different from the aspherical surface of the effective inner diameter region, and the lens thickness increases in the optical axis direction. That is, the sag amount on the exit surface decreases from the optical axis to the effective diameter, but reverses and increases in the vicinity of the effective diameter. Then, when a part of the outer peripheral surface protrudes in the optical axis direction from the optical surface, the sag amount is reversed to plus. By setting it as such a shape, the crack at the time of lens shaping | molding can be prevented, and lens shaping | molding can be performed easily. Further, it is possible to prevent cracking when the objective lens 103 is attached to a lens holder (not shown).

  In the present embodiment, the case where the collimator lens 102 is used as an aberration correction element has been described as an example. However, the aberration correction element may be a single beam expander lens disposed between the collimator lens and the objective lens, or You may comprise by a beam expander lens and a collimating lens. Further, a liquid crystal lens, a liquid lens, or the like may be used as the aberration correction element.

  Further, in the present embodiment, the optical element such as a lens other than the objective lens may be configured by only a refractive surface having substantially only a refractive action, and other elements such as a diffraction surface and a phase step surface. It may have an optical function surface.

  The optical pickup device 100 may further include an element that does not substantially affect the transmitted wavefront aberration between the light source 101 and the information recording medium 106.

  In the present embodiment, the BD optical system has been described, but an actuator (not shown) on which the objective lens 103 is mounted is further provided with an objective lens so that DVD, CD, etc. can be recorded and reproduced by the same optical pickup device. A so-called two-lens configuration may be used.

  The objective lens according to the present invention can obtain a lens shape that can be stably manufactured even if it is a thin objective lens. Therefore, a CD (Compact Disc), a DVD (Digital Versatile Disc), and a BD (Blu- For example, information devices such as computers, video devices, and audio devices that perform recording and reproduction on various information recording media such as ray discs, EVDs (Enhanced Versatile Discs), and HD-DVDs (High Definition Digital Versatile Discs) Etc. are useful.

DESCRIPTION OF SYMBOLS 10, 11, 12 Optical element 20 Lens part 21 1st optical surface 22 2nd optical surface 30 Outer peripheral part 31 1st outer peripheral surface 32 2nd outer peripheral surface 33 Projection surface 34 Intermediate | middle surface 41, 42, 43 Curved surface 50 Information recording medium 60 Laser beam 70 Optical axis 80 Optical element 81 Optical surface 82 Outer peripheral surface 83 Crack 90 Sheet member 100 Optical pickup device 101 Light source 102 Collimating lens 103 Objective lens 104 Beam shaping lens 105 Beam splitter 106 Information recording medium 107 Rising mirror 108 Detection lens 109 Detector 110 Laser light

Claims (12)

A biconvex optical element made of a glass material,
A lens unit having a first optical surface on which a light beam is incident and a second optical surface from which the incident light is emitted;
An outer peripheral portion provided on the outer periphery of the lens portion, and having a projecting surface at least a portion projecting in the optical axis direction from the second optical surface;
A sheet member formed on the protruding surface;
An optical element comprising: The sheet member on the protruding surface is a resin adhesive tape,
The optical element according to claim 1. The sheet member is formed at a plurality of locations at a predetermined interval on the protruding surface.
The optical element according to claim 1. The outer periphery is
A first outer peripheral surface provided on the first optical surface side;
A second outer peripheral surface provided on the second optical surface side,
A connecting portion between the second optical surface and the second outer peripheral surface forms a curved surface;
The optical element according to claim 1. The curved surface connecting the second optical surface and the second outer peripheral surface is a concave surface.
The optical element according to claim 4. The radius of curvature of the curved surface is smaller than the radius of curvature of the second optical surface;
The optical element according to claim 4. The second outer peripheral surface further has an intermediate surface provided closer to the optical axis than the protruding surface,
A connecting portion between the projecting surface and the intermediate surface forms a curved surface;
The optical element according to claim 4. The curved surface connecting the projecting surface and the intermediate surface is a convex surface.
The optical element according to claim 7. A curvature radius of a curved surface connecting the projecting surface and the intermediate surface is larger than a curvature radius of a curved surface connecting the second optical surface and the second outer peripheral surface;
The optical element according to claim 7. A connecting portion between the first optical surface and the first outer peripheral surface is formed as a curved surface;
The optical element according to claim 3. The position of the curved surface connecting the second optical surface and the second outer peripheral surface is closer to the optical axis than the position of the curved surface connecting the first optical surface and the first outer peripheral surface.
The optical element according to claim 10. An optical pickup device comprising the optical element according to claim 1.

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