JP2008226302A - Objective lens and optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a low cost objective lens for an optical pickup device which has low resistance when being in contact with an optical disk and can secure a difference in height between the surface of the objective lens at an optical disk side and a contact part with high accuracy. <P>SOLUTION: In the objective lens having an optical function surface for forming an optical spot on an information recording surface of an optical disk and a flange part around the optical function surface, a plurality of bottomed holes for mounting a buffering member protruding from the optical function surface of the objective lens at an optical disk side are formed on the surface of the flange part at the optical disk side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an objective lens that focuses light on an information recording surface of an optical disc that is an optical recording medium to form a light spot, and an optical pickup device including the objective lens.

  Conventionally, as an optical disc as an optical recording medium, a compact disc (CD), a digital versatile disc (DVD), a high definition digital versatile disc (HD DVD), and a Blu-ray disc (BD) are known in order of storage capacity. To increase the capacity per optical disc, the light spot diameter is reduced by shortening the wavelength of the light source and increasing the numerical aperture of the objective lens, and the recording mark (pit) and track pitch on the optical disc. This is realized by reducing the size.

  In recent years, there has been a growing demand for smaller and thinner optical pickup devices. In response to such demands, the working distance, which is the axial distance between the optical disk surface and the final surface of the objective lens, is set to a small value. There are some which make the objective lens smaller and thinner by reducing the effective diameter while securing the number.

  Similarly, even in an objective lens with a large numerical aperture, if sufficient working distance is secured, the effective lens diameter increases, the lens mass increases, and the moment of inertia during focusing and tracking increases, resulting in responsiveness. Will get worse. For this reason, the working distance is set small, the effective diameter is reduced while ensuring the numerical aperture, and the increase in the mass of the objective lens is avoided.

  On the other hand, when the working distance is reduced, the objective lens inevitably approaches the optical disk that rotates at high speed, and the surface of the rotating optical disk is affected by an impact applied to a device such as a portable player incorporating the optical pickup device. When blurring occurs, the risk of contact between the objective lens surface and the optical disk surface increases. For this reason, when contacting the surface of the optical disc, a device in which a portion other than the objective lens surface is brought into contact has been proposed.

As a structure in which a portion other than the objective lens surface is brought into contact, a structure in which a buffer layer is laminated from the peripheral edge to the outer edge of the effective surface of the objective lens is known (see, for example, Patent Document 1). Moreover, what planted the molded object around the objective lens periphery of the frame body which assembles | assembles an objective lens is known (for example, refer patent document 2).
JP 2002-237071 A JP 2006-99814 A

  However, the device described in Patent Document 1 has a problem that since the area of the contact portion when it comes into contact with the optical disk is large, the resistance is large and the rotational speed is reduced.

  The optical disk system is rotationally controlled so that the linear velocity or angular velocity is constant, and if the rotational speed is reduced by contact resistance, the jitter value, which is one of the indicators of signal reproduction accuracy, is deteriorated. In addition, if the resistance is large, the wire may be damaged in the case where the frame with the objective lens assembled is held by a wire and focusing or tracking is performed. Furthermore, in the case of a CD / DVD doubled speed or a new HD DVD / BD, this problem becomes more serious because the linear velocity is higher.

  Moreover, the thing of the said patent document 2 fixes the objective lens and the molded object to be planted to a frame separately. For this reason, the frame is used as a reference, and the height difference between the apex of the molded object and the apex of the surface on the optical disk side of the objective lens varies due to the mounting error of the objective lens and the component error and mounting error of the molded body. However, there is a problem that the protruding amount is not stable.

  In view of the above problems, the present invention provides a low-cost objective lens for an optical pickup device that has a low resistance when it comes into contact with an optical disk and can accurately ensure a difference in height between the surface of the objective lens on the optical disk side and the contact portion. The object is to obtain an optical pickup device.

  The above object is achieved by the invention described below.

  1. An objective lens having an optical functional surface for forming a light spot on an information recording surface of an optical disc, and a flange portion around the optical functional surface, the optical disc of the objective lens on a surface of the flange portion on the optical disc side An objective lens having a plurality of bottomed holes for attaching a buffer member protruding from the optical function surface on the side.

  2. An objective lens having an optical functional surface for forming a light spot on an information recording surface of an optical disc and a flange portion around the optical functional surface, wherein a plurality of bottomed holes are formed on the optical disc side surface of the flange portion An objective lens, wherein a buffer member protruding from the optical functional surface on the optical disc side is attached to the bottomed hole.

  3. The objective lens according to 1 or 2, wherein the bottomed hole has a constant inner diameter in the depth direction, or is formed so that the inner diameter decreases as the depth proceeds.

  4). The objective lens according to any one of claims 1 to 3, wherein the bottomed holes are formed at equal angular intervals around the optical axis of the optical functional surface on the optical disc side.

5. When the number of the buffer members is N and the number of the bottomed holes is M,
N ≦ M
The objective lens according to any one of 2 to 4, wherein:

  6). The objective lens according to any one of 2 to 5, wherein at least a tip of the buffer member is formed in a spherical shape.

  7. The objective lens according to any one of 2 to 6, wherein the buffer member is formed by attaching a buffer material to a base material.

  8). The objective lens according to any one of 2 to 6, wherein the buffer member is formed by applying a buffer material to a base material.

  9. An optical pickup device comprising a light source and the objective lens according to any one of 1 to 8.

  According to the present invention, there is obtained an objective lens and an optical pickup device for an optical pickup device that have a low resistance when contacted with an optical disc and can ensure a difference in height between the surface of the objective lens on the optical disc side and the contact portion with high accuracy. It becomes possible.

  Hereinafter, the present invention will be described in detail with reference to embodiments, but the present invention is not limited thereto.

  FIG. 1 is a perspective view showing an example of an optical pickup device 100 having an objective lens 1 according to the present embodiment. The figure shows an example in which an objective lens is assembled to a holder supported by a wire.

  As shown in the figure, the optical pickup device 100 includes an optical system unit 30, a reflecting member 40, and a holder 20 in which the objective lens 1 is assembled. Although not shown, the optical disk is located above the objective lens 1.

  The optical system unit 30 includes a laser light source that emits laser light to the objective lens 1, a light receiving unit that receives light returned from the optical disk, and optical members that form these optical paths. The reflection member 40 causes the light beam emitted from the optical system unit 30 to enter the objective lens 1 and guides the reflected light from the optical disk to the optical system unit 30.

  The holder 20 is supported by four flexible wires 26 extending from the support member 27, and the wire 26 is used as a suspension within a predetermined range in the optical axis O direction (focusing direction) and in the direction orthogonal to the optical axis O (tracking direction). It is possible to move. In some cases, it is tilted with respect to the optical axis to correct coma.

  Although not shown, the holder 20 includes a magnetic circuit including a focus driving coil, a tracking driving coil, a magnet, an outer yoke, and an inner yoke. By supplying power to the focus driving coil and the tracking driving coil, the holder 20 can swing in the optical axis direction (focusing direction), the optical axis orthogonal direction (tracking direction), and the tilting direction of the objective lens 1. Yes. In addition, power is supplied to these coils via a wire 26.

  Further, although not shown, a moving mechanism for moving the optical system unit 30, the reflecting member 40, and the holder 20 integrally in the radial direction of the optical disc is provided.

  FIG. 2 is a diagram schematically showing a configuration of the optical pickup device 100 including the objective lens 1 according to the present embodiment. Hereinafter, a case where information recorded on an optical disk is reproduced will be described as an example.

  An optical pickup device 100 shown in FIG. 1 has a semiconductor laser 31 that emits a light beam having a predetermined wavelength in an optical system unit 30. The emission wavelength is, for example, 785 nm if the optical disk to be used is CD, 655 nm if it is DVD, and 405 nm if it is HD DVD or BD.

  The light beam emitted from the semiconductor laser 31 passes through the polarization beam splitter 32, is converted into a parallel light beam by the collimator lens 33, and is then circularly polarized by the quarter wavelength plate 34. This parallel light beam is focused by the stop S, and is focused on the information recording surface 61b by the objective lens 1 via the transparent substrate 61a which is a protective layer of the optical disc 61, and is made into a light spot.

  The light beam modulated and reflected by the pits recorded on the information recording surface 61b passes through the objective lens 1 and the stop S again. Next, the ¼ wavelength plate 34 makes a linear polarization state, passes through the collimator lens 33, enters the polarization beam splitter 32, and is reflected there. The reflected light beam is given astigmatism by the cylindrical lenses 35 and 36 and is incident on the photodetector 37, and a read signal of information recorded on the optical disc 61 is obtained using the output signal.

  Further, a change in the amount of light due to a change in the shape of the spot and a change in position on the photodetector 37 is detected to perform focus detection and track detection. Based on this detection, the objective lens 1 is moved in the optical axis direction so that the light beam from the semiconductor laser 31 is imaged on the information recording surface 61b of the optical disk 61 by an actuator (not shown), and the light beam from the semiconductor laser 31 is The objective lens 1 is moved in a direction perpendicular to the optical axis so as to form an image on a predetermined track.

  In the above description, an example of an optical pickup device corresponding to one type of optical disc has been described. However, an optical pickup device that includes a plurality of types of laser light sources and is compatible with a plurality of types of optical discs may be used. In this case, it is preferable to use an objective lens that can be shared for a plurality of types of optical discs in terms of downsizing and cost reduction of the optical pickup device.

  FIG. 3 is a diagram illustrating an example of the objective lens 1 according to the present embodiment. 2A is a plan view of the objective lens 1 viewed from the optical disk side, and FIG. 2B is a side sectional view taken along line AA shown in FIG.

  As shown in the figure, the objective lens 1 has an optical function surface 1a having a large curvature facing the light source side and an optical function surface 1b having a small curvature facing the optical disc side. A flange portion 1f is formed around the optical function surfaces 1a and 1b.

  On the surface of the flange portion 1f on the optical disk side, bottomed holes 1h having small diameters are formed integrally with the optical axis O on the optical function surface 1b side at intervals of 45 degrees.

  FIG. 4 is a view showing a state where the buffer member 2 is attached to the objective lens 1 shown in FIG. 2A is a plan view of the objective lens 1 viewed from the optical disk side, and FIG. 2B is a side sectional view taken along line AA shown in FIG.

  As shown in the figure, the cushioning member so that the bottomed hole 1h formed in the flange portion 1f protrudes in the optical axis direction from the optical function surface 1b by d in the four positions in increments of 90 degrees. 2 is attached.

  FIG. 5 is a diagram showing another example of the objective lens 1 according to the present embodiment. 2A is a plan view of the objective lens 1 viewed from the optical disk side, and FIG. 2B is a side sectional view taken along line AA shown in FIG.

  Similarly, the objective lens 1 has an optical function surface 1a having a large curvature facing the light source side and an optical function surface 1b having a small curvature facing the optical disc side. A flange portion 1f is formed around the optical function surfaces 1a and 1b.

  On the surface of the flange portion 1f on the optical disc side, bottomed holes 1h having small diameters are formed integrally with the optical axis O on the optical function surface 1b side at intervals of 60 degrees.

  FIG. 6 is a view showing a state in which the buffer member 2 is attached to the objective lens 1 shown in FIG. 2A is a plan view of the objective lens 1 viewed from the optical disk side, and FIG. 2B is a side sectional view taken along line AA shown in FIG.

  As shown in the figure, the cushioning member so that the bottomed hole 1h formed in the flange portion 1f protrudes from the optical function surface 1b in the direction of the optical axis by d in three places in increments of 120 degrees. 2 is attached.

  As shown in FIGS. 3 to 6, it is preferable to form a larger number of bottomed holes 1 h than the number of buffer members 2 to be attached. By doing in this way, the attachment position or the attachment number of the buffer member 2 can be suitably selected according to a condition.

  In addition, by forming the number of bottomed holes more than the number of buffer members, the objective lens can be reduced in weight, the moment of inertia during focusing and tracking can be reduced, and the responsiveness should be improved. Can do.

  In addition, although the formation of the bottomed hole has been described with the intervals of 45 degrees and 60 degrees, the present invention is not limited to this. Good.

  The objective lens according to the above embodiment is preferably made of plastic and formed by injection molding. In particular, in the molding of the objective lens as shown in FIGS. 3 and 5 above, the position of the gate formed at the time of injection molding is such that the side surface of the flange portion 1f avoids the bottomed hole 1h. It is preferable to form a mold.

  FIG. 7 is an enlarged cross-sectional view showing a shape example of the bottomed hole 1h.

  FIG. 5A shows a bottomed hole 1h formed in the flange portion 1f with a constant inner diameter in the depth direction. The thin shaft portion formed in the buffer member 2 is fixed by being pressed into or inserted into the bottomed hole 1h.

  FIG. 4B shows a surface in which a surface that is one step lower than the surface on the optical disc side of the flange portion 1f is formed, and a bottomed hole 1h having a constant inner diameter in the depth direction is formed on this lower surface. The thin shaft portion formed in the buffer member 2 is fixed by being pressed into or inserted into the bottomed hole 1h.

  FIG. 2C shows a bottomed hole 1h formed in the flange portion 1f so that the inner diameter decreases as it proceeds in the depth direction. The tip of the thin shaft portion formed in the buffer member 2 is pressed into the bottomed hole 1h and fixed.

  In addition, after press-fitting, further adhesion may be performed.

  FIG. 8 is a diagram illustrating a shape example of the buffer member 2.

  FIG. 2A shows a hemispherical head portion excluding the thin shaft portion of the buffer member 2. FIG. 2B shows a cylindrical tip formed by rounding it into a sphere. FIG. 3C shows a conical tip formed by rounding it into a sphere. Thus, the shock absorbing member 2 can reduce the damage of the optical disk when it comes into contact with the optical disk by making the tip spherical. In particular, regardless of the manner of contact with the optical disc, the contact becomes point contact, and the influence on the optical disc can be minimized.

  In addition, at least the front end of the buffer member 2 is preferably formed using a material having good sliding characteristics in order to suppress the influence on the optical disk at the time of contact. For example, an ultraviolet curable paint or adhesive, an ultraviolet curable resin, a rubber-based or cellulose-based resin, a fluororesin (for example, Teflon (registered trademark)), or the like may be formed by painting. Alternatively, these may be formed separately according to the shape of the tip of the buffer member 2 and attached to the tip.

  As described above, an objective lens having a plurality of bottomed holes for attaching a buffer member protruding from the optical functional surface on the optical disk side to the surface on the optical disk side of the flange portion, and using the bottomed holes By using an objective lens to which a buffer member protruding from the optical function surface on the optical disk side is attached, it is possible to accurately ensure the difference in height between the optical function surface on the optical disk side of the objective lens and the contact portion of the buffer member. it can.

  Further, by forming the shape of the mounting portion of the buffer member on the objective lens side in accordance with the buffer member, only one type of buffer member can be applied to various types of objective lenses, and a low-cost objective lens can be obtained. it can.

  Furthermore, by selectively attaching the buffer member to the bottomed hole, the contact portion can be formed with the minimum number of buffer members, and the resistance when contacting the optical disk can be reduced, which has an effect on the optical disk. Can be minimized.

It is a perspective view which shows an example of the optical pick-up apparatus which has the objective lens which concerns on this Embodiment. It is a figure which shows schematically the structure of the optical pick-up apparatus provided with the objective lens which concerns on this Embodiment. It is a figure which shows the example of the objective lens which concerns on this Embodiment. It is a figure which shows the state which attached the buffer member to the objective lens shown in FIG. It is a figure which shows the other example of the objective lens which concerns on this Embodiment. It is a figure which shows the state which attached the buffer member to the objective lens shown in FIG. It is an expanded sectional view which shows the example of a shape of a bottomed hole. It is a figure which shows the example of a shape of a buffer member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Objective lens 1f Flange part 1h Bottomed hole 2 Buffer member 20 Holder 30 Optical system unit 40 Reflective member 61 Optical disk 100 Optical pick-up apparatus

Claims (9)

An objective lens having an optical functional surface for forming a light spot on the information recording surface of an optical disc, and a flange portion around the optical functional surface,
An objective lens, wherein a plurality of bottomed holes for attaching a buffer member protruding from the optical function surface of the objective lens on the optical disc side are formed on the surface of the flange portion on the optical disc side. An objective lens having an optical functional surface for forming a light spot on the information recording surface of an optical disc, and a flange portion around the optical functional surface,
A plurality of bottomed holes are formed on the surface of the flange portion on the optical disk side,
An objective lens, wherein a buffer member protruding from the optical functional surface on the optical disc side is attached to the bottomed hole. 3. The objective lens according to claim 1, wherein the bottomed hole has a constant inner diameter in the depth direction, or is formed such that the inner diameter decreases as the depth advances. The objective lens according to any one of claims 1 to 3, wherein the bottomed holes are formed at equiangular intervals around an optical axis of an optical functional surface on the optical disc side. When the number of the buffer members is N and the number of the bottomed holes is M,
N ≦ M
The objective lens according to any one of claims 2 to 4, wherein The objective lens according to claim 2, wherein at least a tip of the buffer member is formed in a spherical shape. The objective lens according to claim 2, wherein the buffer member is formed by attaching a buffer material to a base material. The objective lens according to claim 2, wherein the buffer member is formed by applying a buffer material to a base material. An optical pickup device comprising a light source and the objective lens according to claim 1.

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