WO2012111748A1

WO2012111748A1 - Method for manufacturing optical element, and optical element

Info

Publication number: WO2012111748A1
Application number: PCT/JP2012/053653
Authority: WO
Inventors: 山本省吾
Original assignee: コニカミノルタオプト株式会社
Priority date: 2011-02-16
Filing date: 2012-02-16
Publication date: 2012-08-23
Also published as: CN103370182A; CN103370182B; JPWO2012111748A1; JP5120525B2; JP2013037758A

Abstract

To provide a method for manufacturing an optical element capable of suppressing deformation and damage on an optical surface upon mold removal by pushing out a core section for mold release while maintaining the function of a flange end surface. [Solution] In the process of opening a mold, a lens (10) remains in a comparatively shallow second mold (42) for molding a second optical surface (OS2), and a gate portion GP provided in the lens (10) can be prevented from deformation in the process of pushing out after the second mold (42) is opened as well as in the following process of pushing out a mold. In addition, because a first mold (41) for molding a first optical surface (OS1) is one in which the lens (10) does not remain when the mold is opened, a flange section (12) formed by the first mold (41) has a small partial thickness. Therefore, a distance between a first transfer surface (S1) and a parting surface (PS1) is comparatively small, and consequently air can easily be removed from the first transfer surface (S1). As described above, a failure in the appearance of the lens (10) can be suppressed and a high-precision lens (10) can be manufactured.

Description

Optical element manufacturing method and optical element

The present invention relates to a method for manufacturing a resin-made optical element, and more particularly to a method for manufacturing an optical element with a runner using an injection molding apparatus, and an optical element manufactured by the method.

A method called injection molding is known as a method for manufacturing a resin lens, but it is necessary to project the resin lens to the outside when releasing the resin lens after shape transfer from the mold surface. As such a resin lens projecting process, for example, the optical lens transfer core mold part (hereinafter referred to as the core part) having a relatively large curvature is advanced so as to protrude from the surrounding mold part, thereby making the resin lens Is available (see, for example, Patent Document 1).

However, in the method of manufacturing an optical element as in Patent Document 1, in the case of a resin lens that has a large curvature and is deeply inserted into a mold surface, a runner portion or a sprue portion that extends from the resin lens after the resin lens protrusion process. When the molded product is taken out of the mold by holding it by the take-out device, the resin lens sticks to the core portion and the gate portion is bent. Such deformation of the gate part may cause minute deformation to the optical surface of the resin lens, or because the lens is tilted and released, an uneven release force is applied and the optical surface is minutely deformed. Sometimes. Therefore, as a result, a desired optical surface cannot be obtained, or the yield rate of the product is lowered. In particular, an objective lens for a BD (Blu-ray Disc) has a large curvature and a large amount of protrusion, so that the transfer surface of the core portion tends to be deep, and the lens portion size is required even though high shape accuracy is required for the lens portion. Is small. Therefore, the deformation of the gate portion tends to easily reach the optical surface, and it is desirable to reduce the deformation of the optical surface at the time of mold release. Also, if the lens is tilted and released due to deformation of the gate part, the optical surface of the lens may come into contact with the mold at the time of release, which may cause a crescent-shaped scratch on the optical surface of the lens. However, as a result, a desired optical surface cannot be obtained, or the yield rate of the product is lowered. Therefore, it is desirable to reduce scratches on the optical surface at the time of mold release.

Also, if the structure in the mold is different between the member that protrudes the lens part that is the product part and the member that protrudes the non-product part such as the runner, it is difficult to make the protrusion timing completely match, and the difference in the protrusion timing In some cases, the gate portion may be bent. If the gate portion is bent at the protruding stage, the gate portion is more likely to bend due to the lens sticking to the core portion at the time of subsequent removal.

Also, during molding, air venting and gas venting are performed from the parting surface that is the boundary of the mold. In order to increase the effect, a gap or an air vent of about 0.1 μm to 10 μm may be formed. In the method of manufacturing an optical element as in Patent Document 1, since the optical surface having a relatively large curvature is separated from the parting surface, air leakage and gas escape at the time of molding deteriorate, and the optical surface has a relatively large curvature. There is a possibility that appearance defects such as air accumulation and minute surface clouding may occur.

Here, in the step of taking out the resin lens, by installing a protruding pin on the flange portion on the optical surface side having a relatively large curvature and protruding the pin, and releasing the core portion before gripping with the extraction device It is considered that the problem that the gate part is bent is solved. However, in the case of pin protrusion, a protrusion burr (unnecessary minute protrusion) is generated on the mounting reference surface in the flange portion of the resin lens. Therefore, when the resin lens is attached to the lens holder, there arises a problem that the resin lens is tilted and coma aberration occurs. If the optical surface with a relatively large curvature is the fixed side of the mold, the optical surface with a relatively small curvature is the movable side of the mold, and the flange on the optical surface side with a relatively small curvature is protruded from the pin, the gate It is thought that the problem of bending of the part and the problem of air accumulation will be solved. However, when the optical surface side with a relatively small curvature is protruded from the pin, the area of the flange end surface (annular mirror surface portion) existing on the outer periphery of the optical surface with a relatively small curvature becomes small. The problem that detection becomes difficult arises.

Also, in both cases of core protrusion and pin protrusion, if the structure in the mold differs between the member that protrudes the optical element that is the product part and the member that protrudes the non-product part such as the runner, the protrusion timing is completely the same It becomes difficult to make it. If the projecting timing is different, the gate part will bend due to the difference in timing, but in the case of a BD pickup lens, the influence is transmitted to the optical function surface by the slight bending of the gate part. The aberration performance may not be obtained. In particular, in the case of a pin protrusion that protrudes a flange portion with a plurality of protrusion members, a plurality of protrusion members that protrude an optical element and a member that protrudes a runner portion increase the number of parts to be protruded, so that the timing of protrusion is further adjusted. It is difficult to cause the gate portion to bend more easily.

Japanese Patent Laid-Open No. 2002-200652

The present invention relates to a method for manufacturing an optical element capable of reducing deformation and scratches on an optical surface while maintaining the function of a flange end surface when a molded part is taken out by protruding a core part for mold release, and an optical manufactured by the method. An object is to provide an element.

In order to achieve the above object, an optical element manufacturing method according to the present invention is incorporated in an optical pickup device that records and / or reproduces information on an optical information recording medium, and has an aperture of 0.75 or more. Method of manufacturing an optical element using an injection molding apparatus having a first mold for molding the first optical surface of the first mold and a second mold for molding the second optical surface of the optical elements The second optical surface has a smaller curvature than the first optical surface, and the molten resin is injected into a mold space and a flow path space formed by the first mold and the second mold, thereby optical elements. And a molding step for molding the runner part, and a mold opening step for relatively opening the mold by moving the first mold and the second mold so as to leave the optical element in the second mold, The core part provided in the second mold is located on the first mold side with respect to the holding part that holds the core part from the periphery. The optical element is protruded toward the first mold side by moving the projection element, the projecting member provided on the second mold is moved to the first mold side, and the runner part is moved to the first mold side. A projecting step of projecting to the surface.

According to the method for manufacturing an optical element, when the second mold is moved away from the first mold in the mold opening process, the second optical surface has a small curvature and a relatively shallow surface depth. The optical element remains in the second mold (generally, a movable mold) for molding the mold, and the extrusion process after the mold opening by the core portion provided in the second mold and the subsequent molding by the take-out device It is possible to prevent the gate portion provided in the optical element from being deformed in the product removal step. This is because the second transfer surface that molds the second optical surface having a relatively small curvature is shallower than the first transfer surface that molds the first optical surface. This is because the sticking force becomes relatively small and the molded product can be easily removed from the core portion. Further, since the first mold for molding the first optical surface is a mold (generally, a fixed mold) in which no optical element remains when the mold is opened, a flange portion formed by the first mold This partial thickness is made smaller than when the optical element is left in the first mold. For this reason, the distance between the first transfer surface and the parting surface that is the contact surface between the first and second molds is reduced, and air and gas are easily released from the first transfer surface. As described above, appearance defects of the optical element can be reduced, and a highly accurate optical element can be manufactured. This is particularly effective in a lens having a relatively high thickness ratio p (thickness of the thickest part ÷ thickness of the thinnest part), such as an objective lens for a BD optical pickup device. In addition, it is possible to prevent the lens from being tilted and released due to the deformation of the gate, and the lens optical surface comes into contact with the mold during the release and the lens optical surface is not crescent-shaped. It becomes. Furthermore, due to the difference in the timing of projecting between the core part that projects the optical element and the projecting member that projects the runner part, it is easy to remove the molded product from the core part even if the gate part is bent at the time of ejection, When taking out, further bending of the gate portion can be prevented.

Further, since the optical element is released by protruding the core on the second optical surface side, it is possible to prevent the occurrence of burrs due to the protruding pins on the mounting reference surface of the optical element on the first optical surface side. When the lens is attached to the holder, it is possible to prevent a problem that the lens is inclined and coma is generated. Thereby, an optical element can be attached to an optical pick-up apparatus etc. with a sufficient precision. Furthermore, since the optical element is released from the core by protruding, a sufficient area of the end surface portion can be secured on the outer periphery (for example, the flange portion) of the optical surface. As a result, the light is reliably reflected at the end face with sufficient intensity, and the skew can be adjusted efficiently.

In addition, since the second transfer surface for forming the second optical surface having a relatively small curvature is shallower than the first transfer surface for forming the first optical surface, the second optical surface sticks to the second transfer surface of the core portion. Although the force is relatively small, it becomes easy to remove the molded product from the core part. On the other hand, the first optical surface having a larger curvature than the second optical surface is molded by the first mold (generally a fixed mold). Therefore, it is conceivable that the optical element sticks to the first mold side and tends to remain when the mold is opened. On the other hand, by making the volume of the flow path space provided on the second mold side larger than the volume of the flow path space provided on the first mold side, the optical element is arranged on the second mold side (general Can be easily left on the movable mold). However, in that case, the runner part molded in the flow path space is strongly attached to the second mold side. However, in the present invention, the second mold protrudes from the runner part to the first mold side. Since the member is provided, it is possible to release the runner part smoothly (smoothly).

Furthermore, by using the core protrusion, it is possible to reduce the number of parts for protrusion compared to the pin protrusion. Therefore, it is possible to more easily match the timing of projecting between the member that projects the optical element and the member that projects the runner portion, and it is possible to reduce gate bending at the time of ejection. As a result, it is possible to obtain a desired aberration even for a lens that requires high molding accuracy, such as a BD pickup lens.

In this specification, the core protrusion is a protrusion member having a transfer surface that molds the optical function surface of the optical element, and protrudes by bringing the transfer surface into contact with the optical function surface of the optical element. The term “projects” means that a flange portion provided on the outer periphery of the optical function portion of the optical element is projected by a plurality of projecting members.

In a specific mode or aspect of the present invention, in the projecting step, the timing at which the optical element is projected to the first mold side at the core portion is different from the timing at which the runner portion is projected to the first mold side by the projecting member. Here, the timing of projecting different means that there is a slight timing shift when projecting them almost simultaneously.
In both cases of core protrusion and pin protrusion, if the structure in the mold is different between the member that protrudes the optical element that is the product part and the member that protrudes the non-product part such as the runner, the protrusion timing must be completely matched Will be difficult. In the present invention, it is possible to make it easier to match the timing of projecting the optical element and the timing of projecting the runner portion than by projecting the pin by using the core projecting.

In another aspect of the present invention, the molding step forms a plurality of optical elements and a plurality of runner portions. When a plurality of optical elements and a plurality of runner parts are molded at a time, there are more parts for projecting the optical elements and the runner parts, and it becomes even more difficult to match the timings of the projections. In the present invention, by setting the core protrusion, the number of parts of the protruding member can be reduced as compared with the pin protrusion, so that the protrusion timing can be relatively matched.

In still another aspect of the present invention, the mold space is evacuated before the molding step in the method of manufacturing an optical element. In this case, the first transfer surface for forming the first optical surface having a relatively large curvature is also reliably filled with the molten resin, the transfer accuracy is improved, and the appearance of the optical element can be improved.

In still another aspect of the present invention, the optical element is a lens having an optical function part having a first optical surface and a second optical surface, and a flange part arranged around the optical function part. Has a gate portion formed in the outer peripheral edge of the flange portion in the molding process, and the lens outer diameter in the direction perpendicular to the lens optical axis of the lens is D, and the flange thickness in the direction parallel to the lens optical axis of the flange portion is T is the gate thickness in the direction parallel to the lens optical axis of the gate portion, H is the gate length in the direction perpendicular to the lens optical axis of the gate portion, and L is perpendicular to the lens optical axis of the gate portion. When the gate width in the direction is W, the following conditional expressions (1) to (3) are satisfied.
0.05D ≦ W ≦ 0.4D (1)
0.5T ≦ H ≦ T (2)
0.1 (mm) ≦ L ≦ 2.0 (mm) (3)
In this case, by satisfying the above conditional expressions (1) to (3), the element at the time of molding the optical element can be surely filled with the molten resin at the time of resin injection, and can provide an appropriate gate seal time, and Since the gate portion is less likely to be deformed in the ejecting step and the molded product taking-out step thereafter by the take-out device, it is possible to reliably prevent deformation of the optical function portion.

In still another aspect of the present invention, the following conditional expression (4) is satisfied, where t1 is the thickness of the flange portion formed by the first mold.
0 ≦ t1 <0.5T (4)
In this case, when the conditional expression (4) is satisfied, the optical element can be reliably left on the second mold side in the mold opening process.

In still another aspect of the present invention, when the first flange outer diameter on the first mold side of the lens flange portion is d1, and the second flange outer diameter on the second mold side is d2. The following conditional expression (5) is satisfied.
d1 <d2 (5)
In this case, since the conditional expression (5) is satisfied, a transfer surface corresponding to the outer diameter of the optical element can be formed with only the second mold alone, so that the outer diameter of the optical element is highly accurate. Can be maintained.

In still another aspect of the present invention, the parting surface that is a contact surface between the first mold and the second mold is more than the center of the flange thickness in the direction parallel to the lens optical axis of the flange portion. It is located on the first mold side in the direction parallel to the lens optical axis. In this case, the distance between the first transfer surface and the parting surface can be reduced, and air and gas can be easily released from the first transfer surface. Further, it is possible to easily leave the optical element on the second mold side.

In still another aspect of the present invention, the first mold includes a core part and a holding part that holds the core part, and the first optical surface of the optical function part is formed by the core part of the first mold. And forming an at least part of the first flange surface provided on the first optical surface side of the flange portion, and the outer peripheral portion of the tip portion facing the second mold of the core portion of the first mold is, An annular convex portion for forming an annular concave portion is provided between the first optical surface and the first flange surface. In this case, the flange space which forms a flange part can be enlarged, and the fluidity | liquidity of molten resin can be improved. Further, in this case, when the optical element contracts due to cooling in the first mold, the first optical part bites into the first core portion and becomes easy to adhere, but the first optical surface molded by the first mold is the second optical surface. By releasing the mold before the optical surface, it is possible to reliably prevent the mold release deformation and the like.

In still another aspect of the present invention, the optical element has a fine shape on the first optical surface. In this case, since the first optical surface has a fine shape, the first core portion and the first optical surface are easily brought into close contact with each other in the first mold, but the first optical surface is ahead of the second optical surface. By releasing the mold, it is possible to reliably prevent the mold release deformation and the like.
For example, there is a fine step on the optical surface with the larger curvature, such as a triple compatible lens that uses a common objective to interchange three types of optical disks: BD, DVD (digital versatile disk) and CD (compact disk). In the case of an optical element in which a diffractive structure is formed, even if the gate part is bent at the time of extraction and the optical element is tilted and released, the diffractive structure is not destroyed, and thus high light utilization efficiency. Can be obtained.

In yet another aspect of the present invention, the optical element has an on-axis lens thickness of d (mm) and a focal length of the optical element in a light beam having a wavelength of 500 nm or less is f (mm). .8 ≦ d / f ≦ 2.0. In this case, although the curvature of the first optical surface is large and the amount of protrusion is large, the appearance defect of the optical element can be reduced and a highly accurate optical element can be manufactured even for such an optical element.

In yet another aspect of the present invention, the optical element is an objective lens for an optical pickup device.

In still another aspect of the present invention, the optical element is an objective lens for an optical pickup device that records and / or reproduces information on three types of optical disks: BD, DVD, and CD. This is more useful in a triple compatible lens in which three types of optical disks of BD, DVD (digital versatile disk), and CD (compact disk), which require extremely high molding accuracy, are used with a common objective lens.
In this specification, BD means that information is recorded / reproduced by a light beam having a wavelength of about 390 to 415 nm and an objective lens having an NA of about 0.8 to 0.9, and the thickness of the protective substrate is 0.05 to It is a generic term for BD series optical discs of about 0.125 mm, and includes BD having only a single information recording layer, BD having two or more information recording layers, and the like. Further, in this specification, DVD is a general term for DVD series optical discs in which information is recorded / reproduced by an objective lens having an NA of about 0.60 to 0.67 and the thickness of the protective substrate is about 0.6 mm. Including DVD-ROM, DVD-Video, DVD-Audio, DVD-RAM, DVD-R, DVD-RW, DVD + R, DVD + RW, and the like. In this specification, CD is a general term for CD series optical discs in which information is recorded / reproduced by an objective lens having an NA of about 0.45 to 0.51 and the protective substrate has a thickness of about 1.2 mm. Including CD-ROM, CD-Audio, CD-Video, CD-R, CD-RW, and the like. As for the recording density, the recording density of BD is the highest, followed by the order of DVD and CD.

In still another aspect of the present invention, after the projecting step, a portion excluding the optical element of the molded product molded by the molding step is gripped, and the optical element is separated from the second mold. In this case, since the optical element is not gripped, it is possible to prevent scratches due to gripping from being attached to the optical element.

In order to solve the above-described problems, the optical element according to the present invention is obtained by manufacturing by the above-described optical element manufacturing method.

The optical element is a highly accurate optical element when manufactured by the manufacturing method described above. This is particularly effective in a lens having a relatively high thickness ratio p (thickness of the thickest part ÷ thickness of the thinnest part), such as an objective lens for a BD optical pickup device. Further, it is possible to prevent burrs caused by the protruding pins on the mounting reference surface of the optical element, and it is possible to attach the optical element to an optical pickup device or the like with high accuracy. Furthermore, a sufficient area of the end surface portion can be secured on the outer periphery (for example, the flange portion) of the optical surface, and the skew can be adjusted efficiently. In addition, the optical surface can be prevented from coming into contact with the mold when the optical element is tilted and released due to deformation of the gate portion, and the optical surface can be made an optical element having no scratch such as a crescent shape. Gate bending at the time of protrusion can be reduced, and a desired aberration performance can be satisfied even for a lens that requires high molding accuracy, such as a pickup lens for BD.

It is a sectional side view explaining the shaping die for enforcing the manufacturing method of the optical element concerning a 1st embodiment. It is a figure explaining the type | mold space for shape | molding an optical element. 3A is a cross-sectional view of a lens that is an optical element, and FIG. 3B is a plan view of the lens as viewed from the second optical surface. It is a figure explaining the comparative example of FIG. It is a flowchart explaining the shaping | molding method using the shaping die shown in FIG. 6A and 6B are conceptual diagrams illustrating the manufacturing process of the optical element. It is a figure explaining the modification of the type | mold space of FIG. 2, and the optical element of FIG. It is a figure explaining the type | mold space and optical element which are used with the manufacturing method of the optical element which concerns on 2nd Embodiment. It is a figure explaining the type | mold space of FIG. 8, and the modification of an optical element. It is a figure explaining another modification of the type | mold space of FIG. 8, and an optical element. It is a figure explaining the type | mold space and optical element which are used with the manufacturing method of the optical element which concerns on 3rd Embodiment. It is a figure explaining the type | mold space and optical element which are used with the manufacturing method of the optical element which concerns on 4th Embodiment. It is a figure explaining the modification of the type | mold space of FIG. 12, and an optical element. It is a figure explaining the type | mold space and optical element which are used with the manufacturing method of the optical element which concerns on 5th Embodiment. It is a figure explaining the type | mold space of FIG. 14, and the modification of an optical element. It is a figure explaining the type | mold space and optical element which are used with the manufacturing method of the optical element which concerns on 6th Embodiment.

[First Embodiment]
Hereinafter, an optical element manufacturing method according to a first embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, an injection molding apparatus 100 for carrying out the manufacturing method of the present embodiment includes a molding die 40, and the molding die 40 includes a first die 41 and a second die 42. With. Here, the 2nd metal mold | die 42 is driven by the opening / closing drive apparatus 79, and can be reciprocated to AB direction. The second mold 42 is moved toward the first mold 41, and both

molds

41 and 42 are mold-matched with the parting surfaces PS1 and PS2 and are clamped to partially expand in FIG. As shown, a mold space CV for molding the lens 10 as an optical element and a flow path space FC for supplying resin to the mold space CV are formed. A plurality of mold spaces CV and flow path spaces FC may be formed in the molding die 40.

As shown in FIG. 2, the mold space CV includes the main body space CV1 sandwiched between the first and second transfer surfaces S1 and S2, and the third, fourth, fifth, and sixth transfer surfaces S3, S4, and S5. , S6 and a flange space CV2 surrounded by S6. Here, the pair of opposing first and second transfer surfaces S1 and S2 facing the main body space CV1 are the first and second optical elements of the optical function unit 11 at the center of the lens 10 shown enlarged in FIGS. 3A and 3B. This is a portion for forming the surfaces OS1 and OS2. In this case, one first transfer surface S1 is deeper and larger in curvature than the other second transfer surface S2, and a fine uneven pattern for transferring the fine structure or fine shape FS of the first optical surface OS1. An FP is provided. On the other hand, the third, fourth, fifth, and sixth transfer surfaces S3, S4, S5, and S6 surrounding the flange space CV2 are portions for forming the flange portion 12 of the lens 10. Here, the third, fourth, and sixth transfer surfaces S3, S4, S6 facing the flange space CV2 are the first, second, and third flange surfaces of the lens 10 shown in an enlarged manner in FIGS. 3A and 3B. It is a part for forming 12a, 12b, 12c. The fifth transfer surface S5 facing the flange space CV2 is a portion for forming the outer peripheral side surface SS of the lens 10. In the first flange surface 12 a of the flange portion 12 shown in FIG. 3A, an annular recess u <b> 1 is provided on the outer edge adjacent to the outer peripheral side surface SS of the lens 10. The convex transfer surface S7 forming the concave portion u1 is adjusted when a spacer (not shown) is put on the bottom surface of the first core portion 64a described later in the first mold 41 in order to adjust the axial lens thickness d of the lens 10. To be a generation. As shown in FIG. 2, the convex transfer surface S7 is formed by projecting the end surface of the holding portion 64b beyond the end surface of the first core portion 64a. The flow path space FC has a runner portion RS as a space for forming the runner portion RP in the molded product MP shown in FIGS. 2, 3A, and 3B. The runner portion RS includes the gate portion GS. Via the mold space CV. The space of the gate portion GS forms a gate portion GP that connects the lens 10 and the runner portion RP in the molded product MP.

Of the molded product MP shown in FIGS. 3A and 3B, the lens 10 as the main body is made of resin, and as described above, the optical function unit 11 having an optical function and the outer edge of the optical function unit 11 in the radial direction. And a substantially annular flange portion 12 provided outside. The lens 10 is an objective lens for a thick optical pickup having a large protrusion on the first optical surface OS1 side. Specifically, the lens 10 enables reading or writing of optical information corresponding to a BD (Blu-ray Disc) having a wavelength of 405 nm and a numerical aperture (NA) of 0.85, for example. Here, the optical specification of the lens 10 is not limited to NA 0.85, and can correspond to various objective lens standards for optical pickups having NA of 0.75 or more, for example. The lens 10 has an on-axis lens thickness d (mm) and a focal length of the lens 10 in a light beam having a wavelength of 500 nm or less is f (mm). 2.0.

In the optical function unit 11, one first optical surface OS1 is disposed on the laser light source side, and protrudes larger than the other second optical surface OS2 disposed on the optical disk side which is an optical information recording medium. Is getting bigger. Furthermore, since the curvature of the first optical surface OS1 is extremely large, the lens 10 has a very large thickness at the center, and the thickness deviation ratio p (thickness of the thickest portion ÷ thickness of the thinnest portion) is high. The first optical surface OS1 is provided with a fine structure or fine shape FS that is a diffractive structure. The fine shape FS or the like is formed in a concentric annular zone. On the other hand, the second optical surface OS2 is a mirror surface having no diffractive structure.

The flange portion 12 has a first flange surface 12a extending in the direction perpendicular to the lens optical axis OA on the first optical surface OS1 side, and a second flange surface extending in the direction perpendicular to the lens optical axis OA on the second optical surface OS2 side. 12b and a third flange surface 12c. The third flange surface 12c is a mirror surface as an end surface for alignment. At the time of molding the lens 10, the gate portion GP is formed on a part of the outer peripheral side surface SS of the flange portion 12, but is removed by a finishing process after taking out from the molding die 40.

Hereinafter, the dimensions of the lens 10 and the mold space CV will be described. 2, 3A, and 3B, the size of the mold space CV corresponds to each element of the lens 10 and is substantially the same as the size of the lens 10. That is, when the molding shrinkage rate of the resin is α, the dimension of the lens 10 is (1−α) times the dimension of the mold space CV. Therefore, the dimension of the lens 10 will be described below.

As shown in FIGS. 3A and 3B, the dimension of the lens 10 is such that the lens outer diameter in the direction perpendicular to the lens optical axis OA of the lens 10 is D, and the flange thickness of the flange portion 12 in the direction parallel to the lens optical axis OA is as follows. Is T, the gate thickness of the gate portion GP in the direction parallel to the lens optical axis OA is H, the gate length of the gate portion GP in the direction perpendicular to the lens optical axis OA is L, and the lens light of the gate portion GP When the gate width in the direction perpendicular to the axis OA is W, the following conditional expressions (1) to (3) are satisfied.
0.05D ≦ W ≦ 0.4D (1)
0.5T ≦ H ≦ T (2)
0.1 (mm) ≦ L ≦ 2.0 (mm) (3)

The lens 10 that satisfies the conditional expressions (1) to (3) can be reliably filled with the molten resin at the time of resin injection in the resin injection step (step S14) described later and provided with an appropriate gate seal time. In addition, the gate part GP is not easily deformed in the projecting process (step S17) and the molded product taking process (step S18), and the deformation of the gate part GP is difficult to reach the optical function part 11. Therefore, the deformation of the gate part GP is ensured. Can be prevented. Note that the shape of the gate portion GP is not particularly limited as long as the conditional expressions (1) to (3) are satisfied, and may be a rectangular parallelepiped, for example.

When the flange thickness of the lens 10 in the direction parallel to the lens optical axis OA is T and the partial thickness formed by the first mold 41 on the fixed side of the flange portion 12 is t1, the following Conditional expression (4)
0 ≦ t1 <0.5T (4)
Meet. More preferably, the following conditional expression (4a)
0 ≦ t1 <0.2T (4a)
Shall be satisfied. In addition, when the partial thickness formed by the movable second mold 42 in the flange portion 12 is t2, the partial thickness t2 is 0.5T so as to correspond to the conditional expression (4). ≦ t2 ≦ T.

In the present embodiment, as shown in FIG. 2, the parting surfaces PS1 and PS2 which are contact surfaces of the first mold 41 and the second mold 42 are in a direction parallel to the lens optical axis OA of the flange portion 12. It is located closer to the first mold 41 in the direction parallel to the lens optical axis OA than the center of the flange thickness T. As a result, the distance between the first transfer surface S1 of the first mold 41 and the parting surface PS1 is shortened, and air and gas can easily escape from the first transfer surface S1.

By satisfying the conditional expression (4), the lens 10 can be reliably left on the second mold 42 side on the movable side in the mold opening process.

In the flange portion 12 of the lens 10, when the outer diameter on the first flange surface 12a side is d1, and the outer diameter on the second flange surface 12b side is d2, the following conditional expression (5)
d1 <d2 (5)
Meet. More preferably, the following conditional expression (5a)
d1 <d2-0.010 (mm) (5a)
Shall be satisfied.

By satisfying the conditional expression (5), it is possible to form the fourth transfer surface S4 corresponding to the lens outer diameter D of the lens 10 using only the second mold 42 alone. Can be maintained with high accuracy. On the other hand, when d1 = d2, the lens outer diameter D of the lens 10 is generated when a misalignment (deviation between the lens optical axis OA and the axis AX) occurs between the first mold 41 side and the second mold 42 side, for example. Becomes d3 (see FIG. 4), and as a result, d3> d2 which is larger than the desired lens outer diameter D (= d2). Therefore, the lens outer diameter D changes depending on the misalignment amount, and the outer diameter of the fourth transfer surface S4 corresponding to the second flange surface 12b of the second mold 42 is used in order to make the lens outer diameter D with high accuracy. Even if (equivalent to d2) is made accurately, it becomes meaningless. Further, if d1> d2, even if the outer diameter (corresponding to d1) of the third transfer surface S3 of the first mold 41 is made with high accuracy, the thickness of the flange portion 12 is the first mold 41 side with respect to d1. Therefore, when the lens 10 is attached to a holder or the like, the lens 10 becomes loose and cannot be positioned with high accuracy.

Returning to FIG. 1, the first mold 41 on the fixed side includes a first core part 64 a as a central part that forms the mold space CV shown in FIG. 2 from the first mold 41, and the periphery of the first core part 64 a. A holding part 64b as a peripheral part provided in the base plate and a receiving plate 64c for supporting the first core part 64a and the holding part 64b from the back are provided. Here, the first core portion 64a is incorporated in a through hole 64g formed in the holding portion 64b and fixed with a bolt (not shown). In addition, the end surface 64e of the holding portion 64b is formed with a concave portion to be the runner portion RS of the molded product MP shown in FIG.

The second mold 42 on the movable side includes a second core part 74a as a central part for forming the mold space CV shown in FIG. 2 from the second mold 42, and peripheral parts provided around the second core part 74a. Holding part 74b, a receiving plate 74c that supports the second core part 74a and the holding part 74b from behind, a projecting member 74p for protruding and releasing the runner part RP of the molded product MP, and the second core part The

movable rods

75 and 76 that push the 74a and the projecting member 74p from the back, and the advance / retreat mechanism 78 that moves the

movable rods

75 and 76 forward and backward in the axis AX direction are provided.

The second core portion 74a is incorporated in a through hole 74g formed in the holding portion 74b so as to be movable back and forth along the axis AX direction. The projecting member 74p is also incorporated in a through hole 74h formed in the holding portion 74b so as to be movable back and forth along the axis AX direction. Here, the 2nd core part 74a is urged | biased back by the force more than fixed by the spring 74s. That is, the second core portion 74a is driven by the moving movable rod 75 to move forward and moves forward to the first mold 41 side, and automatically retracts according to the spring 74s that expands as the movable rod 75 moves backward. Return to. Further, the protruding member 74p is driven by the movable rod 76 to advance toward the first mold 41 side, and when the mold is closed, an external force by a holding portion 64b on the first mold 41 side, which will be described later, or resin at the time of resin inflow Retreats by pressure and returns to the original position. Similarly to the second core portion 74a, the protruding member 74p may be automatically retracted and returned to its original position by using a spring. In addition, the end surface 74e of the holding portion 74b is formed with a concave portion to be the runner portion RS of the molded product MP shown in FIG.

Note that when the first optical surface OS1 having a relatively large curvature is formed by a fixed mold, the optical surface is likely to be deformed due to an axial deviation when the first and

second molds

41 and 42 are opened. There is a possibility, but it can be solved by using a taper pin or a taper block for the template as disclosed in Japanese Utility Model Laid-Open No. 7-9945.

FIG. 5 is a flowchart conceptually illustrating a method for manufacturing an optical element using the molding die 40 shown in FIG.

First, the opening / closing drive device 79 is operated, and the mold closing is started by moving the second mold 42 relatively forward toward the first mold 41 (step S11). Note that the surfaces of both

molds

41 and 42 are heated to a temperature suitable for molding.

By continuing the closing operation of the opening / closing drive device 79, the first mold 41 and the second mold 42 are moved to the mold contact position where they are in contact with each other, the mold closing is completed, and the opening / closing drive device 79 is further closed. By continuing, the mold clamping which clamps the 1st metal mold | die 41 and the 2nd metal mold | die 42 with required pressure is performed (step S12).

Next, a vacuum device (not shown) is operated to evacuate the mold space CV between the clamped first mold 41 and the second mold 42 (step S13). As a result, the mold space CV is appropriately decompressed, and the molten resin is reliably filled into the first transfer surface S1 having a relatively large curvature.

Next, an injection device (not shown) is operated to inject the molten resin into the mold space CV with a necessary pressure (step S14). The injection device maintains the resin pressure in the mold space CV.

After the molten resin is introduced into the mold space CV, the molten resin in the mold space CV is gradually cooled by heat dissipation, so that the molten resin is solidified with the cooling and waits for completion of molding (step S15).

Next, the opening / closing drive device 79 is operated to perform mold opening for relatively moving the second mold 42 backward (step S16). As the second mold 42 moves backward, the first mold 41 and the second mold 42 are separated from each other. As a result, as shown in FIG. 6A, the molded product MP, that is, the lens 10 remains on the second mold 42 side. That is, the lens 10 is released from the first mold 41 while being held so as to be embedded in the movable second mold 42.

Next, the advancing / retreating mechanism 78 is operated, and the molded product MP remaining in the second mold 42 is ejected to the first mold 41 side by the movable rods 75 and 76 (step S17). Thereby, as shown to FIG. 6B, mold release of the molded product MP is performed. At this time, the lens 10 is completely pushed out of the holding portion 74b.

In this state, the unillustrated unloading device is operated to separate the molded product MP from the second mold 42 and carry it out (step S18). When transporting the molded product MP, the portion of the molded product MP excluding the lens 10 is gripped. At this time, since the curvature of the second optical surface OS2 of the lens 10 is small and the surface depth is relatively shallow, the sticking force of the second optical surface OS2 to the second transfer surface S2 of the second core portion 74a is relatively small. Therefore, since the molded product MP can be easily removed from the second core portion 74a, it is possible to prevent a biased force from being applied to a part of the outer periphery of the lens 10.

According to the optical element manufacturing method of the present embodiment described above, when the second mold 42 is moved away from the first mold 41 in the mold opening process (step S16), the relatively shallow first step is performed. 2 The lens 10 is left in the second mold 42 for molding the optical surface OS2, and the protruding process after the mold opening by the second core portion 74a of the second mold 42 (step S17) and the molded product taking-out process by the taking-out device In (Step S18), the gate portion GP provided in the lens 10 can be prevented from being deformed. This is because the second transfer surface S2 for forming the second optical surface OS2 having a relatively small curvature is shallower than the first transfer surface S1 for forming the first optical surface OS1, and the second transfer surface of the second core portion 74a. This is because the sticking force of the second optical surface OS2 to S2 becomes relatively small and the molded product MP can be easily detached from the second core portion 74a. Further, in order to make the first mold 41 for molding the first optical surface OS1 a mold in which the lens 10 does not remain when the mold is opened, the partial thickness t1 of the flange portion 12 formed by the first mold 41 is set to the first thickness 41. Compared with the case where the lens 10 is left in one mold 41, the size is reduced. For this reason, the distance between the first transfer surface S1 and the parting surface PS1 becomes relatively short, and air and gas easily escape from the first transfer surface S1. By the above, the appearance defect of the lens 10 can be reduced and the highly accurate lens 10 can be manufactured. This is particularly effective in a lens having a relatively high thickness ratio p (thickness of the thickest part ÷ thickness of the thinnest part), such as an objective lens for a BD optical pickup device.
Further, since the second transfer surface S2 for forming the second optical surface OS2 having a relatively small curvature is shallower than the first transfer surface S1 for forming the first optical surface OS1, the second transfer surface S2 of the second core portion 74a. Although the sticking force of the second optical surface OS2 to the surface becomes relatively small and the lens 10 can be easily detached from the second core portion 74a, the first optical surface OS1 having a larger curvature than the second optical surface OS2 is provided on the first optical surface OS1. Since the molding is performed with the single mold 41, it is conceivable that the lens 10 sticks to the first mold 41 side and easily remains when the mold is opened. On the other hand, the lens 10 can be easily left on the second mold 42 side by increasing the volume of the flow path space FC provided on the second mold 42 side. However, in that case, the runner portion RP formed in the flow path space FC is strongly attached to the second mold 42 side, but the runner portion RP protrudes from the second mold 42 to the first mold 41 side. Since the member 74p is provided, the runner part RP can be released smoothly.
Furthermore, the lens 10 is tilted and released due to the deformation of the gate portion GP, and the first optical surface OS1 of the lens 10 contacts the mold during the release, and the first optical surface OS1 of the lens 10 has a crescent-shaped scratch. Can be prevented. Further, even if the gate portion GP is bent at the time of protrusion due to a difference in timing of protrusion between the second core portion 74a that protrudes the lens 10 and the protruding member 74p that protrudes the runner portion RP, the lens 10 is removed from the second core portion 74a. Since it is easy to remove, further bending of the gate portion GP can be prevented during subsequent removal.
Furthermore, by using the core protrusion, it is possible to reduce the number of parts for protrusion compared to the pin protrusion. Therefore, it is possible to more easily match the timing of projection between the second core portion 74a that projects the lens 10 and the projecting member 74p that projects the runner portion RP, and the bending of the gate portion GP at the time of projection can be reduced. As a result, it is possible to obtain a desired aberration even for the lens 10 that requires high molding accuracy, such as a BD pickup lens.

In addition, since the lens 10 is released by the core protrusion, it is possible to prevent a burr at the time of pin protrusion from occurring on the mounting reference surface of the lens 10. Thereby, the lens 10 can be accurately attached to the optical pickup device or the like. Furthermore, since the lens 10 is released by protruding the core, a sufficient area of the end surface portion can be secured on the outer periphery (for example, the flange portion 12) of the optical surface. As a result, the light is reliably reflected at the end face with sufficient intensity, and the skew can be adjusted efficiently.

In addition, in 1st Embodiment, as shown in FIG. 7, you may provide the level | step difference structure b1 in the 1st flange surface 12a of the flange part 12. As shown in FIG. In the step structure b <b> 1, the step on the center side of the lens 10 is higher toward the laser light source side than the step on the outside of the lens 10. On the outside of the first core portion 64a of the first mold 41, a step-shaped convex transfer surface S21 for forming the step structure b1 is provided.

When the lens 10 has the stepped structure b1, even if a burr due to the boundary between the first core portion 64a and the holding portion 64b occurs on the first flange surface 12a side, the burr is not attached when the lens 10 is attached to a lens holder or the like. It can be stored in a space formed between the holder or the like and the step structure b1. Thereby, the lens 10 can be accurately attached to a holder or the like.

[Second Embodiment]
Hereinafter, a method for manufacturing an optical element according to the second embodiment will be described. Note that the optical element manufacturing method according to the second embodiment is a modification of the first embodiment, and parts that are not particularly described are the same as those in the first embodiment.

As shown in FIG. 8, the lens 10 has a step structure b2 on the second flange surface 12b side of the flange portion 12. In the step structure b <b> 2, the step on the outside of the lens 10 is higher toward the information recording medium side than the step on the center side of the lens 10. On the inner side of the holding portion 74b of the second mold 42, a step-shaped convex transfer surface S22 for forming the step structure b2 is provided.

Since the lens 10 has the step structure b2, even if a burr due to the boundary between the second core portion 74a and the holding portion 74b occurs on the second flange surface 12b side, the burr is stored in the space formed by the step structure b2. Can do. Thereby, it is possible to prevent the distance (WD: working distance) between the information recording medium and the lens 10 from being changed due to the variation of the burr length during molding.

In addition, in 2nd Embodiment, as shown in FIG. 9, you may provide the level | step difference structure b1 demonstrated in 1st Embodiment in the 1st flange surface 12a of the flange part 12. As shown in FIG.

Further, in the second embodiment, like the step structure b3 shown in FIG. 10, the step on the center side of the lens 10 of the step structure b3 is higher toward the information recording medium side than the step on the outside of the lens 10. Also good. In this case, a step-shaped convex transfer surface S23 for forming the step structure b3 is provided outside the second core portion 74a of the second mold 42. The convex transfer surface S23 of the second core portion 74a is deeper from the parting surface PS2 than the fourth transfer surface S4 of the holding portion 74b. In addition, in FIG. 10, it is good also as a structure which does not provide the level | step difference structure b1 in the 1st flange surface 12a of the flange part 12. As shown in FIG.

[Third Embodiment]
Hereinafter, a method for manufacturing an optical element according to the third embodiment will be described. Note that the optical element manufacturing method according to the third embodiment is a modification of the first embodiment, and parts not specifically described are the same as those in the first embodiment.

As shown in FIG. 11, the lens 10 has a recess m1 between the optical function part 11 and the flange part 12. That is, the boundary between the optical function part 11 and the flange part 12 on the laser light source side has a circularly depressed shape. At the boundary between the first transfer surface S1 and the third transfer surface S3 of the first core portion 64a of the first mold 41, a convex transfer surface S24 is formed as a surface constituting an annular convex portion for forming the concave portion m1. Is provided. The convex transfer surface S24 is shallower from the parting surface PS1 than the third transfer surface S3.

By providing the convex transfer surface S24 that forms the recess m1, the flange space CV2 that forms the flange 12 can be widened, and the fluidity of the molten resin can be improved.

In the third embodiment, the step structure b1 described in the first and second embodiments may be provided on the first flange surface 12a of the flange portion 12.

[Fourth Embodiment]
Hereinafter, a method for manufacturing an optical element according to the fourth embodiment will be described. Note that the optical element manufacturing method according to the fourth embodiment is a modification of the second and third embodiments, and parts not specifically described are the same as those of the second and third embodiments. .

As shown in FIG. 12, the leading end surface of the first core portion 64a is a first transfer surface S1 for forming a first optical surface OS1 of the lens 10 at a main portion. Therefore, the holding portion 64b having the third transfer surface S3 is arranged around the first core portion 64a having the first transfer surface S1, so that the outer edge portion of the first core portion 64a is connected to the main body space CV1 and the flange space. It is in a state of biting into the boundary with CV2.

Since the outer edge portion of the first core portion 64a has a structure that easily bites between the first optical surface OS1 of the lens 10 and the first flange surface 12a, the molten resin filled in the mold space CV is completely solidified. Then, the lens 10 becomes difficult to release from the first mold 41 due to the shrinkage of the resin, which causes a poor appearance. Therefore, by making the first mold 41 a fixed mold that does not leave the lens 10 when the mold is opened, the lens 10 can be reliably removed from the first mold 41 while maintaining a good appearance before the molten resin is completely solidified. Can be released.

In addition, in 4th Embodiment, it is good also as a structure which does not provide the level | step difference structure b2 in the 2nd flange surface 12b side of the flange part 12 like 1st Embodiment. In the fourth embodiment, the step structure b1 described in the first and second embodiments may be provided on the first flange surface 12a of the flange portion 12.

Further, as shown in FIG. 13, a stepped structure b4 may be provided on the first flange surface 12a side of the flange portion 12. In the step structure b <b> 4, the step on the outside of the lens 10 is higher toward the laser light source side than the step on the center side of the lens 10. On the inner side of the holding portion 64b of the first mold 41, a step-like convex transfer surface S25 for forming the step structure b4 is provided. Thus, even if a burr due to the boundary between the first core portion 64a and the holding portion 64b occurs on the first flange surface 12a side, when the lens 10 is attached to the lens holder or the like, the burr is placed between the holder and the step structure b4. Can be accommodated in the space formed. Thereby, the lens 10 can be accurately attached to a holder or the like.

[Fifth Embodiment]
Hereinafter, a method for manufacturing an optical element according to the fifth embodiment will be described. Note that the optical element manufacturing method according to the fifth embodiment is a modification of the first embodiment, and parts not specifically described are the same as those in the first embodiment.

As shown in FIG. 14, the 1st metal mold | die 41 has a structure which is not divided | segmented into the 1st core part 64a and the holding | maintenance part 64b. That is, the first mold 41 has a mold part 64d in which the first core part 64a and the holding part 64b described in the first embodiment are integrated, and the first part of the lens 10 is formed by the mold part 64d. The optical surface OS1 and the first flange surface 12a are formed.

In addition, in 5th Embodiment, as shown in FIG. 15, it is more preferable that the taper TP is provided in the outer edge by the side of the 1st flange surface 12a of the flange part 12, ie, the side surface of the recessed part u1. The first mold 41 is provided with an inclined transfer surface S26 for forming a taper TP outside the third transfer surface S3 of the mold part 64d.

By providing the first mold 41 with the taper TP, the lens 10 can be easily removed from the first mold 41, and the lens 10 can be easily left in the second mold 42 on the movable side when the mold is opened.

[Sixth Embodiment]
Hereinafter, a method for manufacturing an optical element according to the sixth embodiment will be described. Note that the optical element manufacturing method according to the sixth embodiment is a modification of the first embodiment, and parts that are not particularly described are the same as those in the first embodiment.

As shown in FIG. 16, the partial thickness t1 formed by the first mold 41 in the flange portion 12 of the lens 10 is t1 = 0. That is, the flange thickness T of the lens 10 is equal to the partial thickness t2 formed by the second mold 42 in the flange portion 12. Thereby, air becomes easier to escape from the first transfer surface S1. Further, since the lens 10 is easily removed from the first mold 41, the lens 10 can be easily left in the movable second mold 42 when the mold is opened.

As mentioned above, although this invention was demonstrated according to embodiment, this invention is not limited to the said embodiment. For example, the mold closing process can be performed by fixing the second mold 42 and making the first mold 41 movable. In this case, a projection mechanism for the lens 10 is provided on the second mold 42 side where the lens 10 remains.

In the above embodiment, the lens 10 is an objective lens for an optical pickup. However, a small lens having a similar shape and a large central thickness can also be manufactured by the same method as in this embodiment. Deformation and scratches can be reduced, and a case where the required accuracy is high can be dealt with.

In the above embodiment, the return force of the core portion 64a is given by the spring, but the core portion 64a can be returned by means other than the spring.

In the above embodiment, the outer peripheral side surface SS of the lens 10 is a cylindrical surface, but the outer peripheral side surface SS may not be symmetrical to the lens optical axis OA. That is, the outer peripheral side surface SS may be a substantially prismatic surface, or a surface obtained by combining a cylindrical surface and a prismatic surface. Further, a slight taper can be formed on the outer peripheral side surface SS, and a slight taper can also be formed on the fifth transfer surface S5 of the holding portion 74b.

In the above embodiment, the optical surface of the lens 10 may be smooth without providing the fine shape FS or the like on the optical surface.

In the above embodiment, after the first and

second molds

41 and 42 are clamped, evacuation is performed (step S13), but the mold space CV is reliably filled with the molten resin, and the transfer accuracy is maintained. For example, it is not necessary to perform evacuation.

Claims

A first mold for forming a first optical surface of an optical element that is incorporated in an optical pickup device that records and / or reproduces information on an optical information recording medium, and has a numerical aperture of 0.75 or more; A method of manufacturing an optical element using an injection molding apparatus having a second mold for molding a second optical surface of the optical elements,
The second optical surface has a smaller curvature than the first optical surface,
A molding step of molding the optical element and the runner part by injecting a molten resin into a mold space and a flow path space formed by the first mold and the second mold;
A mold opening step of opening the mold by relatively moving the first mold and the second mold so as to leave the optical element in the second mold;
The core part provided in the second mold is moved relatively to the first mold side with respect to the holding part that holds the core part from the periphery, and the optical element is moved to the first mold. Projecting to the mold side, moving the projecting member provided on the second mold to the first mold side, and projecting the runner part to the first mold side; and
An optical element manufacturing method comprising:
In the projecting step, the timing of projecting the optical element to the first mold side at the core portion and the timing of projecting the runner portion to the first mold side from the projecting member are different. The manufacturing method of the optical element of Claim 1.
The method for manufacturing an optical element according to claim 1, wherein the molding step forms a plurality of the optical elements and a plurality of the runner portions.
2. The method of manufacturing an optical element according to claim 1, wherein the mold space is evacuated before the molding step.
The optical element is a lens having an optical function part having the first optical surface and the second optical surface, and a flange part arranged around the optical function part,
The optical element has a gate portion formed in the molding step on an outer peripheral edge of the flange portion,
A lens outer diameter in a direction perpendicular to the lens optical axis of the lens is D, a flange thickness of the flange portion in a direction parallel to the lens optical axis is T, and a direction parallel to the lens optical axis of the gate portion When the gate thickness in the direction perpendicular to the lens optical axis of the gate portion is L and the gate width in the direction perpendicular to the lens optical axis of the gate portion is W, The optical element manufacturing method according to claim 1, wherein the following conditional expression is satisfied.
0.05D ≦ W ≦ 0.4D
0.5T ≦ H ≦ T
0.1 (mm) ≦ L ≦ 2.0 (mm)
6. The method of manufacturing an optical element according to claim 5, wherein the following conditional expression is satisfied when a thickness of the flange portion formed by the first mold is t1.
0 ≦ t1 <0.5T
Of the flange portions of the lens, when the first flange outer diameter on the first mold side is d1, and the second flange outer diameter on the second mold side is d2, the following conditional expression The method of manufacturing an optical element according to claim 5, wherein:
d1 <d2
The parting surface, which is the contact surface between the first mold and the second mold, is closer to the lens optical axis than the center of the flange thickness of the flange portion in the direction parallel to the lens optical axis. 6. The method of manufacturing an optical element according to claim 5, wherein the optical element is located on the first mold side in a parallel direction.
The first mold has a core part and a holding part for holding the core part,
The core portion of the first mold forms at least a part of the first optical surface of the optical function portion and a first flange surface provided on the first optical surface side of the flange portion,
An outer peripheral portion of a tip portion of the core portion of the first die facing the second die is formed with an annular recess between the first optical surface and the first flange surface. The method for manufacturing an optical element according to claim 5, further comprising an annular convex portion.
2. The method of manufacturing an optical element according to claim 1, wherein the optical element has a fine shape on the first optical surface.
The optical element has an axial lens thickness of d (mm), and 0.8 ≦ d / f when the focal length of the optical element in a light beam having a wavelength of 500 nm or less is f (mm). 2. The method of manufacturing an optical element according to claim 1, wherein ≦ 2.0.
The method of manufacturing an optical element according to claim 1, wherein the optical element is an objective lens for an optical pickup device.
2. The optical element according to claim 1, wherein the optical element is an objective lens for an optical pickup device that records and / or reproduces information on three types of optical disks of BD, DVD, and CD. Production method.
2. The method according to claim 1, wherein after the projecting step, a portion excluding the optical element of the molded product molded by the molding step is gripped, and the optical element is separated from the second mold. Of manufacturing the optical element.
An optical element manufactured by the method for manufacturing an optical element according to claim 1.