JP2004177609A - Plastic lens and optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plastic lens, which can reduce burrs formed by cutting as much as possible and can be manufactured with a small number of manufacturing processes, and to provide an optical pickup device. <P>SOLUTION: The plastic lens 1 has a flange part 2 at the outer circumference of an optical surface and is manufactured by charging a resin in a metallic mold through a gate part 4. This plastic lens 1 is formed at an area of the part where the gate part 4 is provided with the metallic mold and has a plane 21 disposed inside a virtual outer circumferential surface 5. Further, a remaining part 42 where the cut gate part remains is formed on or inside the virtual outer circumferential surface. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to, for example, a plastic lens used in an optical disk device and the like, an optical pickup device equipped with the plastic lens, and a method of manufacturing the plastic lens.
[0002]
[Prior art]
2. Description of the Related Art In recent years, optical disk devices that record and reproduce various types of information on optical recording media such as CDs and DVDs have become widespread. This optical disk device includes an optical pickup device that reads information recorded on an optical recording medium. The optical pickup device includes a pickup lens for condensing light from a light source onto an optical recording medium.
[0003]
Since the pickup lens is a lens having a complicated shape such as an aspherical lens, a plastic such as a polyolefin resin or an acrylic resin is used. A case where such a plastic lens is formed by injection molding of a side gate method will be briefly described. First, a mold is created. The mold has a shape corresponding to the shape of the plastic lens. The mold is such that a circular shape is formed when viewed from the optical axis direction. In addition, the mold is provided with a gate portion that is a resin injection channel.
[0004]
Next, the mold is mounted on the injection molding machine, and the molten resin is poured from the gate. The poured resin is filled into the cavity of the mold. Then, after the resin is cooled and solidified, it is taken out of the mold. At this time, the removed plastic lens has a circular shape when viewed from the optical axis direction, and is further removed from the mold from a part of the outer periphery with the gate portion connected to the runner. Thereafter, the gate is cut, and the lens is removed from the runner. At this time, the gate portion is cut at a position closer to the lens surface, but it is inevitable that a part of the gate portion remains in manufacturing. If a part of the gate portion remains on the outer periphery, the plastic lens may not be stored in the holder when the lens is mounted on the lens holder, or may hinder the alignment.
[0005]
Conventionally, in order to prevent such an obstacle, a flange portion near the outer periphery where the gate portion is located has been cut together with the gate portion (for example, see Patent Document 1). FIG. 6 shows a top view of the plastic lens after cutting. The plastic lens 1 has an optical surface 3 functioning as a lens at the center. The flange 2 is provided on the outer periphery of the optical surface 3. The flange 2 is provided for attaching the plastic lens 1 to a lens holder or for protecting the lens surface. Before cutting, the gate portion 4 protrudes from the flange portion 2. By the cutting, the cutting portion 22 which is the flange portion 2 near the outer periphery where the gate portion 4 is located is also cut out together with the gate portion 4.
[0006]
Further, in order to prevent the above-described obstacle, a gate portion remaining on the outer periphery of the flange portion has been removed by polishing or the like.
[0007]
[Patent Document 1]
JP 2001-272501 A
[Problems to be solved by the invention]
According to the method of cutting the flange portion near the outer periphery where the gate portion is located together with the gate portion, chips are generated, and sharp cuts, so-called burrs, are generated on the cut surface. This burr has a problem that it becomes an obstacle when attaching the plastic lens to the lens holder.
[0009]
On the other hand, the method of removing the gate portion remaining on the outer periphery of the flange portion by polishing has a problem that the number of manufacturing steps increases. In addition, there is also a problem in that the plastic lens is damaged during the polishing process, and foreign matter is attached to the plastic lens, thereby deteriorating the performance. Furthermore, dust and the like generated during the polishing process must be removed. Furthermore, the stress applied to the plastic lens during polishing may affect the optical characteristics.
[0010]
The present invention has been made to solve such a problem, and can reduce the generation of burrs and chips caused by cutting as much as possible, and can produce a plastic lens and an optical lens that can be manufactured by a small number of manufacturing steps. It is an object to provide a pickup device.
[0011]
[Means for Solving the Problems]
The plastic lens according to the present invention has a flange portion (for example, the flange portion 2 according to the embodiment of the present invention) on the outer circumference of the optical surface, and a molding die has a gate portion (for example, according to the embodiment of the present invention). A plastic lens manufactured by pouring a resin through the gate portion 4), which is formed by the molding die in a region where the gate portion is provided, and is formed on a virtual outer peripheral surface (for example, of the present invention). The surface (for example, the flat surface 21 or the curved surface 23 according to the embodiment of the present invention) which is located inside the virtual outer peripheral surface 5) according to the embodiment, and the same or inner side as the virtual outer peripheral surface are cut. And a remaining portion where the gate portion remains (for example, the remaining portion 42 according to the embodiment of the present invention). In such a configuration, since the cut surface is only the gate portion, burrs generated by cutting are small, and generation of chips and the like are small. Further, since the remaining portion of the gate portion is the same as or inside the virtual outer peripheral surface, there is no need to remove it by polishing, so that the manufacturing process can be simplified.
[0012]
The surface formed by the molding die is preferably a flat surface. In this case, it does not hinder the cutting of the gate portion, and the manufacturing becomes easy.
[0013]
It is further preferable that the remaining portion is left so as to be substantially in contact with the virtual outer peripheral surface. With such a configuration, rattling when attaching the plastic lens to the lens holder can be reduced.
[0014]
Further, the cutting shape of the remaining portion may be an arc. With such a configuration, it is possible to further reduce backlash when attaching the pickup lens to the lens holder.
[0015]
The plastic lens according to the preferred embodiment is mounted on an optical pickup device.
[0016]
On the other hand, the method of manufacturing a plastic lens according to the present invention includes a first step of pouring a resin into a molding die through a gate portion, a second step of removing solidified resin, and a second step of cutting and removing the gate portion. A plastic lens manufacturing method comprising the steps of: forming a surface located inside a virtual outer peripheral surface in a region where the gate portion is provided in the first step; In the third step, the gate portion is cut such that the cut gate portion remains at the same or inside the virtual outer peripheral surface using a molding die having an appropriate shape. According to such a method, since the cut surface is only the gate portion, a plastic lens with less burrs generated by cutting can be manufactured by fewer manufacturing steps.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
[0018]
First Embodiment of the Invention
First Embodiment A plastic lens according to a first embodiment of the present invention will be described with reference to FIG. The plastic lens of this example is a pickup lens used in an optical disc device. This pickup lens is manufactured by injection molding using a polyolefin resin or an acrylic resin.
[0019]
FIG. 1 shows a top view and a side view of the pickup lens. As shown in the figure, a flange 2 is formed on the outer periphery of the pickup lens 1. When the pickup lens 1 is attached to the optical disk device and information is read from the optical recording medium, the flange portion 2 has the surface 2a positioned on the optical recording medium side. In the following description, the optical recording medium side (surface 2a side) is described as the upper side, and the opposite side (surface 2b side) is described as the lower side. The flange portion 2 is located on the outer periphery of the optical surface, which is the optical function portion of the pickup lens 1, and is formed in a belt shape over the entire periphery.
[0020]
As shown in FIG. 1, the upper surface of the flange portion 2 is formed to be higher than the upper surface of the optical surface 3a. Therefore, even when the pickup lens 1 is placed on a desk or the like with the flange portion 2a side down during the operation, the flange portion 2 contacts the desk, and the optical surface 3a does not contact the desk. Therefore, damage due to the optical surface 3a coming into contact with a desk or the like can be avoided. Further, it is possible to avoid damage caused by the optical recording medium coming into direct contact with the optical surface 3a after attaching the pickup lens 1 to the optical disk device.
[0021]
The diameter of the pickup lens 1 (including the flange portion 2) according to this example is 5.8 mm. The vertical width of the flange 2 is 0.9 mm. The diameter of the pickup lens 1 according to another example is 3.8 mm.
[0022]
As shown in FIG. 1, a flat surface 21 is formed on a part of the outer periphery of the pickup lens 1 according to the embodiment of the present invention. The plane 21 is located inside the virtual outer peripheral surface 5 and has a shape in which a part of the circular pickup lens 1 is cut off. Here, the virtual outer peripheral surface 5 refers to an outer peripheral surface when the pickup lens 1 is formed to be circular when viewed from the optical axis direction. The plane 21 is not formed by cutting afterwards, but has a shape such that the molding die itself produces the plane 21, and is formed based on the shape of the molding die. Since the flat surface 21 has a structure formed by injection molding, the surface thereof has no burrs and has a smooth surface.
[0023]
When taken out of the mold, the gate portion 4 protrudes from the plane 21 and is connected to the runner 6. Thereafter, the gate portion 4 is cut and removed. Cutting includes cutting with a blade, pressing, cutting with a laser, cutting with heat, and the like. The cutting is performed so that the cut surface 41 of the gate portion 4 is the same as or inside the virtual outer peripheral surface 5, that is, the center of the lens. That is, although a part of the gate portion remains due to the cutting, the remaining portion 42 is the same as the virtual outer peripheral surface 5 or is included inside the virtual outer peripheral surface 5.
[0024]
If the flat portion 21 is large, rattling occurs when the pickup lens 1 is mounted on the lens holder, depending on the shape of the lens supporting portion of the holder. For this reason, it is preferable that the length of the plane portion 21 (the length in the horizontal direction with respect to the main plane of the lens) be 0.2 mm to 2.5 mm.
[0025]
As described above, in the plastic lens according to the first embodiment of the present invention, injection molding is performed so that a part of the plastic lens becomes a flat surface, and the gate portion extending from the flat surface is cut at the same or inside the virtual outer peripheral surface 5. Therefore, the burr of the cut portion is limited to only the region of the gate portion, and the remaining portion of the gate portion after cutting is the same as or inside the virtual outer peripheral surface 5, so that it is not necessary to remove This has the effect of not hindering attachment to the lens holder.
[0026]
Embodiment 2 of the invention
A plastic lens according to a second embodiment of the present invention will be described with reference to FIG. The plastic lens of this example is a pickup lens used in an optical disc device. FIG. 2A is a top view showing a state where the pickup lens is attached to the lens holder. FIG. 2B is an enlarged view in which the vicinity of the gate unit 4 is enlarged.
[0027]
The pickup lens 1 according to the second embodiment of the present invention has the same configuration as the pickup lens according to the first embodiment of the present invention, but is cut so that the cut surface 41 of the gate portion 4 is close to the virtual outer peripheral surface 5. ing.
[0028]
The reason for such a configuration will be described in detail. The pickup lens 1 may be supported at four points by a lens holder 7 as shown in FIG. In such a case, if the flat portion 21 of the pickup lens 1 and the support portion of the lens holder are located at positions facing each other, the pickup lens 1 is moved between the support portion holding the pickup lens 1 on the opposite side to the support portion. The degree of freedom of movement increases. That is, rattling of the pickup lens 1 increases. The backlash increases by the length of a shown in FIG. When the backlash of the pickup lens 1 increases in this way, it becomes difficult to fix the pickup lens 1 to the center of the lens holder 1.
[0029]
Therefore, in the second embodiment of the present invention, as shown in FIG. 2B, the cut surface 41 of the gate portion 4 is cut so as to be closer to the virtual outer peripheral surface 5. With such a configuration, the play of the pickup lens 1 with respect to the lens holder 7 can be reduced, and the pickup lens 1 can be securely fixed to the center of the lens holder 7.
[0030]
If the cut surface 41 is arranged so as not to face the supporting portion of the lens holder 7, such a rattling problem can be prevented. However, in order to adjust the optical characteristics, it is necessary to rotate the pickup lens 1 and adjust the mounting direction. Therefore, the pickup lens 1 may need to be fixed at a position where the cut surface 41 faces the support of the lens holder 7.
[0031]
Embodiment 3 of the Invention
Third Embodiment A plastic lens according to a third embodiment of the present invention will be described with reference to FIG. The plastic lens of this example is a pickup lens used in an optical disc device. FIG. 3 is a top view showing the vicinity of the gate portion of the pickup lens.
[0032]
The pickup lens 1 according to the third embodiment of the present invention has the same configuration as the pickup lens according to the first embodiment of the present invention, but the cut surface 41 of the gate portion 4 has a curved surface along the virtual outer peripheral surface 5. are doing. That is, the cut surface 41 is formed in an arc shape. With such a configuration, rattling when the pickup lens 1 is attached to the lens holder 7 can be reduced, and the pickup lens 1 can be securely fixed to the center of the lens holder 7. The gate 4 may be cut by shearing with a blade, pressing, cutting by laser, cutting by heat, or the like. When cutting with a blade, it is preferable to use a blade that has been previously processed into a curved shape.
[0033]
Further, it is possible to make the width of the gate portion close to the width of the flat portion 21. By increasing the width of the gate portion, moldability is improved, and the stability of quality can be increased.
[0034]
Embodiment 4 of the Invention
Fourth Embodiment A plastic lens according to a fourth embodiment of the present invention will be described with reference to FIG. The plastic lens of this example is a pickup lens used in an optical disc device. FIG. 4 is a top view showing the vicinity of the gate portion of the pickup lens.
[0035]
The pickup lens 1 according to the fourth embodiment of the present invention has the same configuration as the pickup lens according to the first embodiment of the present invention, except that a curved surface 23 is formed on a part of the outer periphery of the pickup lens 1 instead of the flat surface 21. are doing. The curved surface 23 is located inside the virtual outer peripheral surface 5. The curved surface 23 is not formed by cutting afterwards, but has a shape such that the molding die itself produces the curved surface 23, and is formed based on the shape of the molding die. Since the curved surface 23 has a structure formed by injection molding, the surface thereof has no burrs and has a smooth surface.
[0036]
Note that the curved surface 23 does not need to be a curved surface that changes evenly over the entire region, and may be partially flat. For example, the vicinity of the gate portion 4 may be a flat surface, and the vicinity of the outer periphery of the flange portion 2 may be a curved surface.
[0037]
In the example shown in FIG. 4, as in the first and second embodiments of the invention, it is cut in a straight line, but as in the third embodiment of the invention, it is cut along the virtual outer peripheral surface 5. You may cut so that it may become a curved surface.
[0038]
Embodiment 5 of the Invention
Embodiment 5 of the present invention relates to an optical pickup device equipped with the pickup lens according to Embodiments 1 to 4 of the present invention.
[0039]
FIG. 5 shows a configuration of an optical pickup device 8 on which the pickup lens 1 is mounted. The pickup lens 1 is fixed at four points by a pickup holder 7. The flange portion 2 of the pickup lens 1 and the pickup holder 7 are fixed by an adhesive.
[0040]
【The invention's effect】
According to the present invention, it is possible to provide a plastic lens and an optical pickup device in which burrs generated by cutting can be reduced as much as possible and can be manufactured by a small number of manufacturing steps.
[Brief description of the drawings]
FIG. 1 is a top view and a side view of a plastic lens according to the present invention.
FIG. 2 is a top view and a side view of the plastic lens according to the present invention.
FIG. 3 is an enlarged view showing the vicinity of a gate portion of the pickup lens according to the present invention.
FIG. 4 is an enlarged view showing the vicinity of a gate portion of the pickup lens according to the present invention.
FIG. 5 is a diagram showing an optical pickup device according to the present invention.
FIG. 6 is a top view showing a conventional pickup lens.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Pickup lens 2 Flange part 3 Optical surface 4 Gate part 5 Virtual outer peripheral surface 6 Runner 7 Lens holder 8 Optical pickup device

Claims (6)

A plastic lens having a flange portion on the outer periphery of the optical surface and manufactured by pouring a resin into a molding die through a gate portion,
A surface formed by the molding die in a region of a portion where the gate portion is provided, and a surface located inside the virtual outer peripheral surface,
A plastic lens having a remaining portion in which the cut gate portion remains, which is the same as or inside the virtual outer peripheral surface. The plastic lens according to claim 1, wherein the surface formed by the molding die is a flat surface. The plastic lens according to claim 1, wherein the remaining portion is left so as to substantially contact the virtual outer peripheral surface. 2. The plastic lens according to claim 1, wherein a cut shape of the remaining portion is an arc shape. An optical pickup device equipped with the plastic lens according to claim 1. A first step of pouring a resin into a molding die through a gate portion;
A second step of removing the solidified resin;
A third step of cutting and removing the gate portion, the method comprising the steps of:
In the first step, a molding die having a shape such that a surface located inside the virtual outer peripheral surface is formed in a region where the gate portion is provided,
In the third step, a method of manufacturing a plastic lens in which a gate portion is cut such that the cut gate portion remains on or inside the virtual outer peripheral surface.

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