JP2004191948A - Plastic lens and optical pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plastic lens to which marking for discriminating a manufacture tool, for example, is applied in an optimum condition, and an optical pickup device. <P>SOLUTION: The plastic lens 1 is equipped with a flange part 2 on the outer periphery of a lens surface. The flange surface 21 of the flange part 2 is formed higher than the lens surface. The flange surface 21 has a level difference part 20 and has the marking 3 injection-molded integrally on the marking surface of the level difference part 20. The highest part of the marking 3 is lower than the highest surface of the flange surface 21. Then, the marking 3 is provided to discriminate the manufacture tool, for example. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a plastic lens used for an optical element such as a camera and an optical disk device, and an optical pickup device equipped with the plastic lens.

  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 digital cameras, CDs, and DVDs have become widespread. For example, 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 on an optical recording medium.

  The pickup lens is generally manufactured by molding plastic such as polyolefin resin or acrylic resin, or glass. A plastic pickup lens is manufactured by injection molding or transfer molding using a molding die. For example, in injection molding, a pickup lens is manufactured by pouring a resin from a gate into a cavity in a mold and cooling the resin.

  On the other hand, this kind of plastic lens is mass-produced in order to reduce the unit price of the product. Therefore, a plurality of lenses are manufactured simultaneously using a molding die having a plurality of cavities. For example, a molding die having eight cavities is used, and eight lenses are manufactured at the same time. In this case, it is desirable to manufacture lenses having the same quality in each cavity, but in reality, the quality may vary. In addition, there may be a variation in manufacturing quality for each molding die and each molding machine.

  Incidentally, a technique for marking a plastic lens is disclosed in, for example, Patent Document 1. In this example, a coating film which becomes a mark by printing, coating or vapor deposition on one side of a flange portion for distinguishing a lens surface is used. It is provided. Therefore, since the lens and the marking are not made of the same material, in this method, when a lens is formed by injection molding, it is necessary to provide a marking forming step separately from the molding.

  On the other hand, in the technique disclosed in Patent Document 2, a convex or concave portion is provided on a flange surface to indicate a resin injection position. However, the production method and the molding die are not described at all, Since the mark is on the upper surface of the flange surface, the marking is likely to be scraped or stained when placed on a desk or by handling, and the information of the marking may not be transmitted well.

  Further, the marking disclosed in Patent Document 2 is for positioning the gate, and is not for identifying a lens or managing history in a production process. This is obvious from the fact that the marking disclosed in the document is provided only in one place, and individual lenses cannot be identified in a plurality of lenses.

Further, the convex marking in the configuration example shown in FIG. 5 of Patent Document 2 protrudes from the upper end of the flange surface by 0.1 to 0.5 mm. Therefore, there is a problem that the stability when the side having the convex portion is placed is inferior, and the convex-shaped marking comes into contact with another member and is scraped, so that the marking disappears. Foreign matter accumulates in the concave shape of such a size provided at the upper end of the flange and the visibility deteriorates. Therefore, a structure is desired in which the marking itself is visible separately from the flange surface and does not contact other members.
JP 2002-122711 A JP 2000-111709 A

  As described above, in the method of manufacturing a lens using a molding die, quality may vary among molding dies and cavities. Therefore, for quality control, manufacturing control, and for managing the history of the lens after being incorporated into the optical device, the lens itself has a marking for easily identifying a manufacturing jig or a manufacturing line such as a molding die or a cavity. Is desired. However, the lens is an optical component, and the marking cannot be formed in such a manner as to degrade the performance required for the optical component. For example, an optical function portion is formed at the center of the lens, but applying the optical function portion is not preferable because it impairs the optical function.

  Further, when the marking is broken by sliding with other members, not only is it difficult to visually recognize the marking itself, but also the damaged portion adheres to the optical function portion, resulting in deterioration of optical performance.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a lens and an optical pickup device in which marking is performed in an optimal mode.

  The lens according to the present invention is a plastic lens obtained by injection molding a resin material, comprising a flange portion on the outer periphery of the lens surface, and a flange surface on at least one side of the flange portion is formed higher than the lens surface. Having a part, the flange surface has a step part at least in part, and has a marking integrally formed on the marking surface of the step part, the highest part of the marking is the flange part of the flange surface It is characterized by being lower than the highest surface.

  Here, it is desirable to have a notch on the outer peripheral side surface of the flange portion.

  Further, it is preferable that at least the vicinity of the area where the marking is formed on the flange surface is a mirror surface.

  Further, it is preferable that the marking is a marking for identifying a manufacturing jig used for manufacturing the lens.

  According to the present invention, it is possible to provide a lens and an optical pickup device on which marking is performed in an optimal mode.

First Embodiment of the Invention
The lens according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2, taking a pickup lens as an example.

  FIG. 1A is a top view of the lens. FIG. 1B is a side view of the lens, and the left half shows a cross section. As shown in the figure, a flange 2 is formed on the outer periphery of the lens 1. The flange portion 2 has a flange surface 21 provided on the optical recording medium side in a state where the lens 1 is attached to the optical disk device and information is read from the optical recording medium. Hereinafter, for the sake of explanation, the optical recording medium side is referred to as the upper side 21 and the opposite side is referred to as the lower side 23. The flange portion 2 is located on the outer periphery of the optical function portion of the lens 1 and is formed in a belt shape over the entire periphery. In addition, the flange part 2 does not need to be continuous on the outer periphery, and may have a shape having a notch on a part of the outer periphery.

  As shown in FIG. 1B, the flange surface 21 has a portion that is higher than the upper surface of the optical function portion when viewed from the optical axis direction. Therefore, even when the lens 1 is placed on a desk or the like with the flange surface 21 side down during operation, the flange surface 21 contacts the desk, and the optical function unit does not contact the desk. Therefore, it is possible to avoid damage due to the optical function unit coming into contact with a desk or the like. Further, it is possible to avoid the damage caused by the optical recording medium coming into direct contact with the optical function unit after the lens 1 is attached to the optical disk device.

  The diameter of the lens (including the flange portion 2) according to this example is 5.8 mm. The vertical width of the flange 2 is 0.9 mm. Another example lens diameter is 3.8 mm.

  As shown in FIG. 1A, a step portion 20 is provided on the upper surface of the flange surface 21, and a manufacturing jig such as a molding die, a cavity, and an injection molding device is provided in that portion. Markings 3a and 3b for identification are provided at two places. The markings 3 a and 3 b are provided so as not to protrude from the uppermost surface of the flange surface 21. The markings 3a and 3b are formed integrally by providing a shape corresponding to the markings 3a and 3b on a mold portion facing the upper surface of the flange surface 21 during molding. The reason why the markings 3a and 3b are provided at two places is to make it possible to distinguish different lenses such as manufacturing jigs by making their relative positions different. For example, when cavities are identified by marking, markings are provided at different relative positions for each cavity. For example, in the case of the first cavity, the marking is arranged at a position where the angle formed by the line connecting the center of the lens and the position of each marking is 180 degrees. In the case of the second cavity, the markings are similarly arranged at different positions in the circumferential direction so as to be 120 degrees.

  The markings 3a and 3b are convex bodies having a shape such that a hemisphere protrudes. Although a concave body also functions as a marking, a convex body is preferable because a mold can be easily manufactured. The height of the markings 3a and 3b according to this example is 0.02 to 0.03 mm. When the markings 3a and 3b are formed in a hemispherical shape as described above, there is an advantage that manufacture using a mold is easy. The shape of the marking 3 itself is not limited to a hemispherical shape, but may be another shape such as a square shape or a cross shape, or may be a character such as an alphabet or a number. In this example, the markings 3a and 3b have the same shape, but may have different shapes. Three or more markings 3 may be provided. Further, if the marking is made different in a unit to be identified such as each cavity, only one marking may be used. If a mark indicating the gate position is present on the lens, it can be identified by the relative position between the marking indicating the gate position and the marking 3. Further, one lens may be provided with a marking capable of identifying the mold and the cavity. For example, the marking for identifying the mold is formed of two parallel convex portions, and the marking for identifying the cavity is formed of one convex portion, so that the two can be distinguished.

  FIG. 2 shows an enlarged sectional view of the vicinity of the flange portion 2 of the lens 1. Here, when the marking 3 is attached to the highest surface of the horizontal flange surface 21 in the optical axis direction, the contact between the marking 3 and the optical recording medium when the lens 1 is mounted on the optical pickup device when the lens 1 is mounted on the optical pickup device. As a result, the minute markings 3 may be damaged and cannot be confirmed. In addition, there is a possibility that the shaving of the marking 3 may cause a problem that plastic dust is generated. Therefore, in order to solve such inconvenience, the flange surface has a step portion at least in part, and the marking 3 is configured so that the upper end thereof is lower than the highest portion of the flange surface 21. In the embodiment of the present invention, the flange surface has a step in the circumferential direction, and the marking 3 on the step is configured so that the upper end thereof is lower than the highest portion of the flange surface 21. . With such a configuration, the marking 3 does not protrude from the flange surface 21 and the possibility of breakage due to sliding contact or the like can be reduced.

  The surface 211 of the flange surface 21 that is lower than the flange surface in the optical axis direction, particularly in the stepped portion where the marking 3b is provided, is referred to as a marking surface. The marking surface 211 is preferably less than 100 μm from the highest surface of the flange surface 21, more preferably less than 50 μm, in order to easily release the molded product from the mold. Further, the height of the marking surface may be higher or lower than the height of the lens surface.

The flange surface 21 including the marking surface 211 is mirror-finished by a corresponding die polishing process. Since the mirror-finished area has a higher light reflectance than the non-mirror-finished area, the difference in brightness between the marking 3 part and the other part becomes large. Therefore, there is an advantage that the visibility of the marking 3 is improved. Note that the entire area of the flange surface 21 may be a mirror surface, but it is sufficient if at least the vicinity of the region where the marking is formed is a mirror surface. When the marking is provided on the marking surface, the ratio M / W of the width (M) of the marking bottom portion to the width (W) of the marking surface is preferably 2 or more and 10 or less, more preferably 2.5 or more and 5 or less. .
It is preferable that the marking surface 211 be provided with the highest portion of the flange surface on the outer periphery of the marking surface 211 and not extend to the outer peripheral portion of the lens so that the adhesive or the like does not flow and the marking becomes difficult to see.

  From the viewpoint of preventing damage due to sliding contact, it is conceivable to dispose the marking 3 on an area other than the optical function part, for example, on the outermost peripheral area of the lens surface, instead of the flange surface 21. However, in the case of such a configuration, there is a problem that the marking 3 is hardly visible behind the flange portion 2. Further, in order to obtain a large effective diameter, that is, a wider optical function portion, it is not preferable to provide the marking 3 on the lens surface. Therefore, in the embodiment of the present invention, the marking 3 is provided on the flange 2. In the embodiment of the present invention, since the marking 3 is provided on the flange surface 21, the marking 3 can be visually observed even when the lens 1 is mounted on the optical disk device.

  Note that, in the embodiment of the present invention, as shown in FIG. 2, the portions where the minimum thickness of the lens on the upper side and the lower side are different from each other are not matched. That is, the boundary Q between the flange surface 23 and the lens surface is located outside the boundary P between the flange surface 21 and the lens surface. By adopting such a shape, even when the thickness of the entire lens is reduced and the thickness of the flange portion is also reduced, a marking surface having a sufficient width can be secured.

Embodiment 2 of the invention
The lens according to the second embodiment differs from the lens according to the first embodiment in the shape of the flange portion. The other points are the same as in the first embodiment of the present invention, and the description is omitted.

  FIG. 3 is an enlarged sectional view of a flange portion of the lens according to the second embodiment of the present invention. As shown in the figure, a concave portion is provided on the flange surface, and the bottom surface of the concave portion is used as a marking surface. The bottom surface of the concave portion is also a step portion lower than the high surface of the flange surface 21. Although the marking surface 211 extends to the inner peripheral portion of the flange portion, a high surface of the flange surface 21 is formed on the inner peripheral side similarly to the outer peripheral side as shown in FIG. 3, and the marking surface 211 is sandwiched between the flange surfaces 21. In this case, the height of the two flange surfaces 21 does not need to be the same.

  The flange surface 21 is preferably perpendicular to the optical axis direction, but may be an inclined surface.

  Here, a method of manufacturing a lens having the above-described structure by injection molding will be briefly described.

  First, a mold is created. The mold has a shape corresponding to the shape of the molded product. Particularly, the mold used in the embodiment of the present invention has a shape such that a marking is formed on the flange surface 21.

  Next, the mold is mounted on the injection molding machine. Thereafter, in the injection molding machine, the resin is poured into the cavity in the mold from the gate. Then, a lens is manufactured by cooling the resin poured into the cavity.

  As described above, the lens according to the embodiment of the present invention is provided with a marking for identifying a manufacturing jig such as a cavity number or a mold number in an optimal mode. The same effect as in the embodiment can be obtained.

Embodiment 3 of the Invention
The lens according to the third embodiment differs from the lens according to the first embodiment in the position of the marking. The other points are the same as in the first embodiment of the present invention, and the description is omitted.

  FIG. 4 is an enlarged sectional view of a flange portion of the lens according to the third embodiment of the present invention. As shown in the figure, the marking 3 b is a hemispherically protruding projection, and is provided on the flange surface 21. The marking 3b is formed such that its upper end is lower than the highest surface of the flange surface 21. In the lens according to the third embodiment of the present invention, the step portion 20 is provided in a region outside the flange surface 21.

  As described above, the lens according to the third embodiment of the present invention is provided with a marking for identifying a manufacturing jig such as a cavity or a molding die in an optimal mode. The same effect as described above can be obtained.

Embodiment 4 of the Invention
The lens according to the fourth embodiment of the invention is different from the lens according to the first embodiment in the shape of the outer peripheral side surface of the flange portion. The other points are the same as in the first embodiment of the present invention, and the description is omitted.

  FIG. 5 is an enlarged sectional view of a flange portion of a lens according to a fourth embodiment of the present invention, particularly showing a state where the lens is fixed to a pickup holder of an optical pickup device. As shown in the figure, a cutout portion 221 is formed on the outer peripheral side surface of the flange portion 2 of the lens. The notch 221 is formed so as to cut out a part of the upper end of the outer peripheral side surface of the flange 2. The cutout portion 221 is provided over the entire circumference of the flange portion 2, but does not necessarily need to be provided over the entire circumference.

  The pickup holder 4 has a shape such that it contacts the lower flange portion 23 and the flange side portion 22. Specifically, it has a mounting portion 41 on which the lower flange portion 23 is mounted, and a convex portion 42 protruding upward outside the mounting portion 41.

  The bottom of the notch 221 is formed to be substantially the same height as the top of the protrusion 42 of the pickup holder 4. That is, the height H of the convex portion 42 is formed so as to be substantially the same as the distance from the lower flange portion 23 at the bottom of the cutout portion 221.

  When fixing the lens 1 to the pickup holder 4, it is common to use an adhesive. However, by providing the cutout 221 as described above, the cutout 221 is filled with the adhesive liquid. Function as Therefore, it is possible to prevent the adhesive from flowing into the area where the marking 3b is provided, and to erase the marking 3b.

Embodiment 5 of the Invention
The lens according to the fifth embodiment of the present invention has the same shape as the lens according to the first embodiment of the present invention, and a part of a mold is nested in the manufacturing process. The other points are the same as in the first embodiment of the present invention, and the description is omitted.

FIG. 6 is a side view of the lens according to the fifth embodiment of the present invention, and nests 51 and 52 are also shown. As shown in the figure, molds for forming a portion including the optical function part of the lens 1 are nested 51 and 52. The molds for the other flange portions 2 are formed by molds 53 and 54 that are separate from the nests 51 and 52. The surface on which the marking is not provided may be an integral type in which the mold 54 and the insert 52 are integrated without using the insert 52.
As will be understood from the description, the optical function part means the diameter of the light beam actually passing through the lens, and the diameter differs depending on the application. For example, NA is 0.45 for a CD, 0.60 for a DVD, and 0.85 for a Blu-ray, and is located on the inner peripheral side of the lens surface diameter.

  The divisions of the nests 51 and 52 and other parts may be located between the outermost periphery of the optical function part of the lens and the innermost periphery of the marking surface. More preferably, the division between the nests 51 and 52 and the other portions is preferably the innermost peripheral portion of the flange portion 2. The first reason is that when the resin cures at the boundary between the nests 51 and 52 and other parts, even if burrs that are sharp projections occur, the burrs exceed the step portions provided separately. If not, there is no problem. Second, if the nests 51 and 52 and the other part are located in the thin portion at the boundary between the flange surface 21 and the lens surface, it becomes difficult to mirror-process the flange surface 21.

  A portion functioning as a marking is provided in a portion of the separate mold 53 facing the upper surface 21 of the flange portion, and this portion is formed as a marking 3b on the flange surface by injection molding.

  As described above, the part corresponding to the optical function part is mainly used as the nest 51 because the marking provided on the upper surface of the flange is also integrally formed. This is because it is desirable that the nested portion of only the optical function portion can be appropriately rotated about the optical axis without moving the nested portion of the flange portion for marking the cavity number as a marking. It is not necessary to provide a portion functioning as a marking on the flange portion each time in another integral mold, as in the case where the optical function portion is formed by a single mold.

For example, if the lens manufactured once with the nested portion installed at a predetermined position does not have good performance, the nest is rotated and manufactured again, and the nesting position is adjusted until the performance is improved.
Note that, in the present embodiment, two or more members may be used as mold members for forming parts other than the optical function part.

  In the present invention, the marking is provided not on the optical function part but on the other part. However, this is particularly suitable for a manufacturing method in which the part corresponding to the optical function part is nested 51. That is, at the position corresponding to the marking of the mold, when processing into a shape such that the marking is formed, the die 53 to be processed is separate from the nest 51 forming the optical function part, This is because the possibility of damaging the nest 51 can be reduced.

Embodiment 6 of the Invention
Embodiment 6 of the present invention relates to an optical pickup device equipped with the lens according to Embodiments 1 to 7 of the present invention.

  FIG. 7 shows a configuration of an optical pickup device 100 on which the lens 1 is mounted. The lens 1 is fixed at four points by a pickup holder 4. In particular, the flange portion 2 of the lens 1 and the pickup holder 4 are fixed with an adhesive.

  When the lens 1 is mounted on the optical pickup device 100 in this manner, the marking provided on the flange portion 2 can be visually observed or observed with a magnifying glass. For a lens having a predetermined defect, it is possible to manage the history of a manufacturing jig, a mold, a manufacturing line, a manufacturing place, a producer, and the like using the marking as a clue.

Other embodiments.
As the shape of the lens of the present invention, for example, a lens having a meniscus shape in which one surface is convex and the other surface is concave can be used.

It is a figure showing a top view and a side view of a lens concerning the present invention. It is an expanded sectional view of the flange part of the lens concerning the present invention. It is an expanded sectional view of the flange part of the lens concerning the present invention. It is an expanded sectional view of the flange part of the lens concerning the present invention. It is an expanded sectional view of the flange part of the lens concerning the present invention. It is sectional drawing which shows the mode of manufacture of the lens concerning this invention. FIG. 2 is a diagram showing an optical pickup device according to the present invention.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Lens 2 Flange part 3 Marking 4 Pickup holder 100 Optical pickup device

Claims (5)

  A plastic lens obtained by injection molding a resin material, including a flange portion on the outer periphery of the lens surface, at least one side of the flange portion of the flange surface has a portion formed higher than the lens surface, The flange surface has a step portion at least in part, and has a marking integrally formed on the marking surface of the step portion, and the highest portion of the marking is lower than the highest surface of the flange surface. A plastic lens.   The plastic lens according to claim 1, further comprising a notch on an outer peripheral side surface of the flange.   The plastic lens according to claim 1, wherein at least the vicinity of the area of the flange surface where the marking is formed is a mirror surface.   The plastic lens according to claim 1, wherein the marking is a marking for identifying a manufacturing jig used for manufacturing the lens. An optical pickup device equipped with the lens according to claim 1.

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