WO2013039241A1

WO2013039241A1 - Optical element and production method therefor

Info

Publication number: WO2013039241A1
Application number: PCT/JP2012/073748
Authority: WO
Inventors: 佐藤望; 澤上明; 菅忍
Original assignee: コニカミノルタアドバンストレイヤー株式会社
Priority date: 2011-09-16
Filing date: 2012-09-14
Publication date: 2013-03-21
Also published as: JPWO2013039241A1; CN103959381A

Abstract

The purpose of the present invention is to provide an optical element on which information related to a production jig and the like is recorded so as to be easily read out, and also provide a production method therefor. A flange (12) is provided with a character mark (M1) and a gate identification mark (M2), and as a result, information related to the production jig or the like used when producing a lens (10) can be directly identified according to the character mark (M1) and the like without using a replacement table or the like. This configuration enables enhanced identifiability and workability on the occasion of subsequent lens (10) management. Further, by providing the character mark (M1) and the like on the uppermost surface (TP1) on the optical disc side, said optical disc being an optical information recording medium, detection and identification of the character mark (M1) and the like becomes relatively easier.

Description

Optical element and manufacturing method thereof

The present invention relates to an optical element incorporated in an optical pickup device and a manufacturing method thereof, and more particularly to a resin optical element formed by injection molding and a manufacturing method thereof.

Conventionally, in an optical element incorporated in an optical pickup device or the like, marking is performed on the flange portion of the optical element, and historical information about the manufacturing equipment is obtained by the marking (specifically, which mold was manufactured once. In the case of molding a plurality of lenses, there is known a method for identifying which cavity in the mold was molded (for example, see Patent Document 1).

Patent Document 1 describes that hemispherical marking is formed on the lower surface of the flange portion having a step.

However, it is not easy to identify historical information about manufacturing jigs or the like with such a hemispherical convex marking alone, by increasing the number of markings or changing the relative position and angle between the markings. It is possible to identify necessary information. In this case, it is necessary to check the number of markings and the relative positions and angles of the markings in each optical element, which takes time for identification. That is, a replacement table or the like is required for identification, and the identification work becomes complicated, and the identification workability decreases.

Japanese Patent Laid-Open No. 11-16197

An object of the present invention is to provide an optical element recorded so that information on a manufacturing jig or the like can be easily read and a manufacturing method thereof.

In order to achieve such an object, an optical element according to the present invention is an optical element incorporated in an optical pickup device, which is formed of a resin, an optical function part, and a flange part formed around the optical function part. Convex character marking is provided on the uppermost surface of the flange portion on the optical information recording medium side. Here, the character marking is identification information having a character as a constituent element, and can also include a figure and a symbol.

According to the optical element described above, since the character marking is provided on the flange portion, it is possible to directly identify information on the manufacturing jig or the like when the optical element is manufactured without using a replacement table or the like by the character marking. This makes it possible to improve identification and workability in subsequent management. By making the character marking convex, a transfer surface can be provided by forming a depression corresponding to the character marking on the transfer surface of the mold, and the transfer surface can be easily processed. Further, by providing character marking on the uppermost surface on the optical information recording medium side, detection and recognition of character marking becomes relatively easy.

In a specific mode or aspect of the present invention, in the optical element, the height h of the convex character marking is 0.003 mm ≦ h ≦ 0.020 mm. By making the height of the character marking more than the above lower limit, the visibility of the character marking is secured, and by making the height of the character marking less than the above upper limit, the character marking and other information such as an optical information recording medium This prevents the members from colliding easily. When the optical element is an objective lens that is compatible with a plurality of types of optical information recording media, it is necessary to ensure WD (working distance) for all types of optical information recording media. In order to secure WD even for a substrate having a large substrate thickness such as (Compact Disc) (substrate thickness 1.2 mm), it is desirable that the height h of the character marking is 0.020 mm or less as described above. In addition, it is preferable that the height h of the character marking is 0.010 mm or less because WD can be secured more reliably.

In another aspect of the present invention, the component of the convex character marking is sized to fit within a square region having a side length of D, and the length D is 0.05 mm ≦ D ≦ 0.30 mm. It is. By making the square area containing the components of the character marking more than the above lower limit, the size of the character is increased to such an extent that transferability can be ensured, and the characters etc. are buried without being neatly transferred or crushed. Can be prevented. On the other hand, the space in the flange portion is easily secured by setting the square area that accommodates the components of the character marking to the upper limit or less.

In yet another aspect of the present invention, the flange portion further has a gate identification marking on the opposite side of the gate portion where the resin has been introduced. In this case, the position of the gate at the time of molding can be reliably identified.

In still another aspect of the present invention, the optical function unit includes a first optical surface and a second optical surface disposed on the optical information recording medium side of the first optical surface, and the optical information recording medium of the flange portion. The uppermost surface on the side protrudes from the uppermost surface of the second optical surface. When placing the optical element on a placement member such as a tray, the flange portion can serve as a guard so that the second optical surface does not contact the placement member even when the second optical surface faces downward. Therefore, the second optical surface is not damaged. This makes it possible to carry or store the second optical surface facing downward.

In still another aspect of the present invention, the optical function unit includes a first optical surface and a second optical surface disposed on the optical information recording medium side of the first optical surface, and is the uppermost surface of the second optical surface. This protrudes from the uppermost surface of the flange portion on the optical information recording medium side. In this case, the protrusion amount of the optical element on the side of the optical information recording medium can be suppressed to a functionally necessary minimum, and when the optical element is an objective lens, it becomes easy to secure WD for the flange portion.

In still another aspect of the present invention, the first optical surface has a larger curvature than the second optical surface. In this case, when the optical element is attached to the apparatus, the character marking can be formed on the second optical surface side instead of the first optical surface side which becomes the reference surface, so that the accuracy of attaching the optical element to the apparatus can be improved. it can.

In yet another aspect of the present invention, the relative position between the gate identification marking and the first character of the character marking is 90 °. In this case, when performing the groove processing corresponding to the character marking on the mold, the reproducibility and accuracy of the processing can be improved, and the reliability of the detection of the character marking can also be improved.

Still another aspect of the present invention has a mirror surface portion that generates reflected light that enables measurement of the inclination of the optical function portion, and the uppermost surface on the optical information recording medium side of the flange portion is on the outer periphery of the mirror surface portion. When measuring the inclination of the optical function part by the mirror surface part, it is possible to prevent the reflected light for measurement from being lowered. In addition, it is conventionally known to apply a hemispherical marking to the mirror surface, but in this case, it is considered that the intensity of the reflected light slightly decreases during the tilt measurement. In addition, in order to improve the distinguishability, when the character marking is used, the strength can be further reduced. Therefore, it is possible to prevent a decrease in reflected light by providing character markings on the outer periphery of the mirror surface portion for measuring inclination without providing character markings. Further, from the viewpoint of lens design, as the distance from the optical function section increases, it is easier to secure a space for marking characters. Furthermore, when marking is provided further away from the optical surface, the effect on the optical surface (optical function unit) can be further reduced when the groove corresponding to the character marking is processed in the mold.

In still another aspect of the present invention, the optical element is an objective lens arranged to face the optical information recording medium.

In still another aspect of the present invention, the optical element is a coupling lens disposed between a light source and an objective lens.

In yet another aspect of the present invention, the optical element is incorporated into an optical pickup device for a Blu-ray disc.

In order to achieve the above object, an optical element manufacturing method according to the present invention is a resin optical element manufacturing method in which an optical element incorporated in an optical pickup device is molded using an injection molding apparatus having a movable mold and a fixed mold. And a step of forming a character marking on the uppermost surface of the optical information recording medium side of the flange portion formed around the optical function portion of the optical element. The character marking is movable and fixed. It is formed by transferring one of the molds. Here, the character-like marking is identification information having a character, a figure, a symbol, or the like as a constituent element, and includes cases where only a figure or a symbol is used as a constituent element in addition to the character.

According to the above manufacturing method, since the letter-like marking is formed on the flange portion by transfer, the information regarding the mold parts and the arrangement of the optical element when the optical element is produced is read by using the letter-like marking. Therefore, it is possible to directly identify the information, and it is possible to improve identification and workability in the subsequent management. In addition, by providing the character marking on the uppermost surface on the optical information recording medium side, detection and recognition of the character marking becomes relatively easy.

In a specific aspect of the present invention, in the above-described optical element manufacturing method, the character-like marking is formed by a movable mold. When the first optical surface is deeper with a larger curvature than the second optical surface, for example, when the first optical surface is formed on the fixed mold side, there is no marking when the mold is opened to release the optical element from the fixed mold. The mold release resistance can be reduced with respect to one optical surface or the like. Further, when the optical element is protruded from the movable mold and the optical element is taken out, the second optical surface having a small release resistance can be protruded, so that the optical element is hardly deformed.

In another aspect of the present invention, the movable mold has a core part and a holding part that holds the core part from the periphery, and forms a letter-like marking by transferring the holding part. In this case, the character-shaped marking is formed by the holding portion, and when the shape corresponding to the character-shaped marking is formed in the movable mold, the influence on the core portion corresponding to the optical function portion may be reduced. it can. In addition, by using a split structure of the core part and the holding part, the optical part of the optical function part can be finely adjusted by rotating the core part.

In still another aspect of the present invention, the fixed mold has a core portion and a holding portion that holds the core portion from the periphery. By using a split structure of the core part and the holding part, it is possible to finely adjust the optical surface of the optical function part by rotating the core part.

It is a sectional side view explaining the shaping die for enforcing the manufacturing method of the optical element concerning a 1st embodiment. 2A is a cross-sectional view for explaining a mold space for molding an optical element, and FIG. 2B is a plan view of a transfer surface on the second mold side in FIG. 2A. 3A is a cross-sectional view of a lens that is an optical element, and FIG. 3B is an enlarged conceptual diagram viewed from the side of the character marking. FIG. 4A is a plan view seen from the first optical surface of the lens, and FIG. 4B is a plan view seen from the second optical surface of the lens. It is a conceptual diagram of the 1st optical path difference providing structure. It is a flowchart explaining the shaping | molding method using the shaping die shown in FIG. It is a conceptual diagram of a structure of an optical pick-up apparatus. It is a conceptual sectional view at the time of providing the 1st, 2nd, and 3rd optical path difference providing structure of a lens in a flat element. It is a figure explaining the optical element which concerns on 2nd 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 3rd Embodiment. It is a figure explaining the optical element which concerns on 4th Embodiment. It is a figure explaining the optical element which concerns on 5th Embodiment. 13A and 13B are diagrams illustrating a modification of the optical element shown in FIG. 3A and the like.

[First Embodiment]
A) Mold and Lens Hereinafter, the optical element and the optical element manufacturing method according to the 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 is a first die 41 that is a fixed die and a movable die. A second mold 42 is provided. 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. 2A, 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 function portions 11 in the center of the lens 10 shown enlarged in FIGS. 3A, 4A, and 4B. This is a portion for forming the second optical 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 FS or the fine shape 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, and S6 facing the flange space CV2 are the first, second, and third flange surfaces 12a of the lens 10 shown in an enlarged view in FIG. 3A and the like. , 12b, and 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. Although the details will be described later, a convex character marking M1 and a gate identification marking M2 are provided on the uppermost surface 2b of the second flange surface 12b of the flange portion 12 shown in FIG. 3A and the like. In order to form the character marking M1 and the gate identification marking M2, the sixth transfer surface S6 is provided with recesses MS1 and MS2, respectively. The flow path space FC has a runner part RS as a space for forming the runner part RP in the molded product MP shown in FIGS. 2A, 3A, etc., and the runner part RS is interposed via the gate part GS. It communicates with 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, 4A, 4B, etc., the lens 10 as the main body has an optical function part 11 having an optical function and an outer edge of the optical function part 11 radially outward as described above. And a substantially annular flange portion 12 provided. The lens 10 is an objective lens for a thick-type optical pickup device having a large protrusion on the first optical surface OS1 side. The lens 10 is a plastic lens. The plastic material in the present embodiment is, for example, a cycloolefin resin, and trade name APEL manufactured by Mitsui Chemicals, Inc., or trade name ZEONEX manufactured by Nippon Zeon Co., Ltd. can be used. 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 is satisfied.

In the optical function unit 11, the first optical surface OS1 has a fine structure FS (optical path difference providing structure including a plurality of steps) having a step of a diffractive structure in order to be compatible with multiple wavelengths. That is, the lens 10 is a three-wavelength compatible optical element corresponding to a short wavelength, high numerical aperture standard, a medium wavelength, medium numerical aperture standard, and a long wavelength, low numerical aperture standard. The fine structure FS provided on the optical surface OS1 has a shape that allows light collection in conformity with each wavelength. In the illustrated example of the single lens 10, in the illustrated example, a central region CN including the optical axis OA on the aspherical optical surface on the light source side, an intermediate region MD disposed around the center region CN, and a peripheral region disposed further around the center region CN. OT is formed concentrically around the optical axis OA. Although not shown, a first optical path difference providing structure is formed in the central region CN, and a second optical path difference providing structure is formed in the intermediate region MD. In addition, a third optical path difference providing structure is formed in the peripheral region OT. In the present embodiment, the third optical path difference providing structure is a blazed diffractive structure. The first optical path difference providing structure formed in the central region CN of the lens 10 is a structure in which the first basic structure and the second basic structure are overlaid as shown in FIG. The first basic structure makes the first-order diffracted light quantity of the first light beam (first wavelength; eg, 405 nm) that has passed through the first basic structure larger than any other order diffracted light quantity, and passes through the first basic structure. The first-order diffracted light quantity of the second light flux (second wavelength; for example, 658 nm) is made larger than any other order diffracted light quantity, and the third light flux (third wavelength; for example, 785 nm) that has passed through the first basic structure. ) Of the first order diffracted light amount is made larger than any other order diffracted light amount. At least the first basic structure provided in the vicinity of the optical axis OA of the central region CN has a step in a direction opposite to the optical axis OA. The second basic structure makes the second-order diffracted light quantity of the first light beam that has passed through the second basic structure larger than the diffracted light quantity of any other order, and the first-order of the second light beam that has passed through the second basic structure. The diffracted light quantity is made larger than any other order diffracted light quantity, and the first order diffracted light quantity of the third light flux that has passed through the second basic structure is made larger than any other order diffracted light quantity. In the second basic structure provided at least near the optical axis OA in the central region CN, the step is directed in the direction of the optical axis OA, and the wavelength of the incident light beam is longer in the first basic structure and the second basic structure. When this is changed, the spherical aberration changes in the direction of insufficient correction. For example, the lens 10 may be a lens corresponding only to a BD (Blu-ray） Disc) having a wavelength of 405 nm and a numerical aperture (NA) of 0.85.

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. Further, since the curvature of the first optical surface OS1 is extremely large, the lens 10 has a very large thickness at the center and a large thickness ratio p (thickness of the thickest portion ÷ thickness of the thinnest portion).

Although not shown, the first optical surface OS1 on the light source side of the lens 10 is provided with three layers of antireflection films. This antireflection film is provided using a vacuum deposition method. For example, SiO ₂ or ZrO ₂ is used as the material of the antireflection film on the first optical surface OS1. Further, the second optical surface OS2 on the optical disc side of the lens 10 is provided with a seven-layer antireflection film. The antireflection film is provided by using this vacuum deposition method. As a material of the antireflection film on the second optical surface OS2, for example, SiO ₂ , ZrO ₂ , a mixed material of SiO ₂ and Al ₂ O ₃ , or the like is used.

The flange portion 12 has a first flange surface 12a extending in a direction perpendicular to the optical axis OA on the first optical surface OS1 side, a second flange surface 12b extending in a direction perpendicular to the optical axis OA on the second optical surface OS2 side, And a third flange surface 12c. The third flange surface 12c extends adjacent to the second optical surface OS2, and serves as a mirror surface as an end surface for alignment. The second flange surface 12b is provided on the outer periphery of the third flange surface 12c. The flange portion 12 has a step structure b2 on the second flange surface 12b side. 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. 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. In the case of this embodiment, the gate part GP is cut in a straight line including a part of the flange part 12 in a direction perpendicular to the radial direction of the lens 10 extending to the gate part GP. This cut shape is usually called a D-cut shape.

The uppermost surface TP2 of the second optical surface OS2 protrudes from the uppermost surface TP1 of the step structure b2 of the second flange surface 12b on the optical disc side of the flange portion 12. Thereby, the protrusion amount of the lens 10 on the optical disk side can be suppressed to a functionally necessary minimum, and when the lens 10 is an objective lens, it becomes easy to secure WD for the flange portion 12.

As already described, convex character marking M1 and hemispherical gate identification marking M2 are provided on the uppermost surface TP1 of the step structure b2 of the second flange surface 12b. The character marking M1 is for identifying information relating to a manufacturing jig or the like when the lens 10 is manufactured. On the other hand, the gate identification marking M2 is for identifying the position of the gate part GP at the time of molding. The character marking M1 is provided at a position of 90 ° counterclockwise with respect to the gate part GP. The gate identification marking M2 is provided on the opposite side of the gate part GP. The relative position between the gate identification marking M2 and the first first character of the character marking M1 is 90 °. This is for improving the reproducibility and accuracy of processing and improving the detection reliability of the character marking M1 when the second die 42 is subjected to the groove processing corresponding to the character marking M1.

3A and 3B, the height h1 of the character marking M1 and the height h2 of the gate identification marking M2 are 0.003 mm or more and 0.020 mm or less, respectively. By making the heights h1 and h2 of the character marking M1 and the gate identification marking M2 equal to or higher than the lower limit, the visibility of the character marking M1 and the gate identification marking M2 is secured. Further, by making the heights h1 and h2 of the character marking M1 and the gate identification marking M2 equal to or less than the above upper limit, it is avoided that the character marking M1 and the gate identification marking M2 easily collide with other members such as an optical disk. is doing. When the lens 10 is an objective lens that is compatible with a plurality of types of optical information recording media, it is necessary to ensure a WD (working distance) for all types of optical information recording media. In order to secure a WD even for a substrate having a large thickness such as (substrate thickness 1.2 mm), the heights h1 and h2 of the character marking M1 and the gate identification marking M2 are set to 0.020 mm or less as described above. It is desirable. In order to ensure WD more reliably, it is more desirable that the heights h1 and h2 of the character marking M1 and the gate identification marking M2 be 0.010 mm or less.

As shown in FIG. 4B, the character marking M1 has, for example, constituent elements of four character parts J1, J2, J3, and J4. The character portions J1, J2, J3, and J4 are arranged on the arc of the second flange surface 12b in order from the character portion J1, which is the first character, starting from a position of 90 ° counterclockwise from the gate portion GP. . The character portions J1, J2, J3, and J4 are sized to fit within a square region having a side length D. Specifically, the length D is 0.05 mm or more and 0.30 mm or less. By setting the square area containing the character portions J1, J2, J3, and J4 to be equal to or higher than the lower limit, the size of the character portions J1, J2, J3, and J4 is increased to the extent that transferability can be ensured. , J3 and J4 can be prevented from being buried or crushed without being clearly transferred. On the other hand, the space in the flange portion 12 can be easily secured by setting the square area that accommodates the character portions J1, J2, J3, and J4 to be equal to or less than the above upper limit. Moreover, although it is preferable that the space | interval for each character is dense, since visibility becomes good, the space | interval of each character may open large.

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). 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. In addition, the end surface 64e of the holding portion 64b is formed with a concave portion to be the runner portion RP 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 that forms the mold space CV shown in FIG. 2A from the second mold 42, and a peripheral part 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 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 recess that should become the runner portion RP of the molded product MP shown in FIG. 3A.

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. Although there is a possibility, it can be solved by using a taper pin or a taper block for the template as disclosed in, for example, Japanese Utility Model Laid-Open No. 7-9945.

B) Lens Manufacturing Method FIG. 6 is a flowchart conceptually illustrating a method of manufacturing an optical element using the molding die 40 shown in FIG.

First, the 1st and 2nd metal mold | dies 41 and 42 are produced (step S11). Concave portions MS1 and MS2 for forming the character marking M1 and the gate identification marking M2 are formed on the convex transfer surface S22 of the holding portion 74b of the second mold 42. That is, the character marking M1 and the gate identification marking M2 are formed by the second mold 42 that is a movable type. The recesses MS1 and MS2 are processed by, for example, a laser marker, electric discharge machining, or the like. It should be noted that the processing with the laser marker is easy to recognize because the convex amount of the marking is small.

Next, the first and

second molds

41 and 42 are attached to the injection molding apparatus 100, the opening / closing drive unit 79 is operated, and the second mold 42 is relatively advanced toward the first mold 41. Mold closing is started (step S12). 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 S13).

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 S14). 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 at a necessary pressure (step S15). 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 S16).

Next, the opening / closing drive device 79 is operated to perform mold opening for relatively moving the second mold 42 backward (step S17). As the second mold 42 moves backward, the first mold 41 and the second mold 42 are separated from each other. As a result, 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 advance / retreat 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 S18). As a result, the molded product MP is released. At this time, the lens 10 is completely pushed out of the holding portion 74b.

In this state, a take-out device (not shown) is operated to separate the molded product MP from the second mold 42 and carry it out (step S19). 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 part of the outer periphery of the lens 10.

C) Optical Pickup Device Hereinafter, the configuration of the optical pickup device PU1 incorporating the lens 10 will be described with reference to FIG. Such an optical pickup device PU1 can be mounted on an optical information recording / reproducing device. Here, the lens 10 is an objective lens capable of appropriately recording and / or reproducing information on, for example, BD, DVD (Digital Versatile Disc), and CD which are different optical disks.

The optical pickup device PU1 emits light when recording / reproducing information with respect to the lens 10, the λ / 4 wavelength plate QWP, the collimating lens COL, the polarization beam splitter BS, the dichroic prism DP, and the BD. A first semiconductor laser LD1 (first light source) that emits a laser beam (first beam) of λ1 = 405 nm, a laser beam (second laser beam) emitted when information is recorded / reproduced with respect to a DVD (second laser beam of wavelength λ2 = 660 nm) A second semiconductor laser LD2 (second light source) that emits a light beam) and a third semiconductor that emits a laser light beam (third light beam) having a wavelength of λ3 = 785 nm that is emitted when information is recorded / reproduced with respect to the CD. It has a laser unit LDP integrated with a laser LD3, a sensor lens SEN, and a light receiving element PD as a photodetector.

The divergent light beam of the first light beam (λ1 = 405 nm) emitted from the blue-violet semiconductor laser LD1 passes through the dichroic prism DP, passes through the polarization beam splitter BS, and then passes through the collimating lens COL as shown by the solid line. The light is converted into parallel light, converted from linearly polarized light into circularly polarized light by the λ / 4 wavelength plate QWP, and the diameter of the light flux is regulated by a diaphragm (not shown) and is incident on the lens 10. Here, the light beam condensed by the central region, the intermediate region, and the peripheral region of the lens 10 becomes a spot formed on the information recording surface RL1 of the BD via the protective substrate PL1.

The reflected light beam modulated by the information pits on the information recording surface RL1 is transmitted again through the lens 10 and a diaphragm (not shown), converted from circularly polarized light to linearly polarized light by the λ / 4 wavelength plate QWP, and converged by the collimating lens COL. The light beam is reflected by the polarization beam splitter BS, and converges on the light receiving surface of the light receiving element PD via the sensor lens SEN. Then, the information recorded on the BD can be read by using the output signal of the light receiving element PD to focus or track the lens 10 by the biaxial actuator AC1. Here, when the wavelength fluctuation occurs in the first light flux or when recording / reproducing of a BD having a plurality of information recording layers, the spherical aberration generated due to the wavelength fluctuation or different information recording layers is changed in magnification. The collimating lens COL as a means is changed in the direction of the optical axis OA, and can be corrected by changing the divergence angle or the convergence angle of the light beam incident on the lens 10.

The divergent light beam of the second light beam (λ2 = 660 nm) emitted from the semiconductor laser LD2 of the laser unit LDP is reflected by the dichroic prism DP as shown by the dotted line, passes through the polarization beam splitter BS, the collimating lens COL, and λ The light is converted from linearly polarized light to circularly polarized light by the / 4 wavelength plate QWP and enters the lens 10. Here, the light beam condensed by the central region and the intermediate region of the lens 10 (the light beam that has passed through the peripheral region is flared and forms a spot peripheral portion) is transmitted through the protective substrate PL2 to the information recording surface of the DVD. It becomes a spot formed on RL2, and forms the center of the spot.

The reflected light beam modulated by the information pits on the information recording surface RL2 passes through the lens 10 again, is converted from circularly polarized light to linearly polarized light by the λ / 4 wavelength plate QWP, and is converted into a convergent light beam by the collimating lens COL. The light is reflected by the beam splitter BS and converges on the light receiving surface of the light receiving element PD via the sensor lens SEN. And the information recorded on DVD can be read using the output signal of light receiving element PD.

The divergent light beam of the third light beam (λ3 = 785 nm) emitted from the semiconductor laser LD3 of the laser unit LDP is reflected by the dichroic prism DP, as shown by the one-dot chain line, and passes through the polarization beam splitter BS and the collimating lens COL. The light is converted from linearly polarized light to circularly polarized light by the λ / 4 wave plate QWP and enters the lens 10. Here, the light beam condensed by the central region of the lens 10 (the light beam that has passed through the intermediate region and the peripheral region is flared and forms a spot peripheral part) is passed through the protective substrate PL3, and the information recording surface of the CD It becomes a spot formed on RL3.

The reflected light beam modulated by the information pits on the information recording surface RL3 passes through the lens 10 again, is converted from circularly polarized light to linearly polarized light by the λ / 4 wave plate QWP, and is converted into a convergent light beam by the collimating lens COL. The light is reflected by the beam splitter BS and converges on the light receiving surface of the light receiving element PD via the sensor lens SEN. And the information recorded on CD can be read using the output signal of light receiving element PD.

According to the optical element and the optical element manufacturing method of the present embodiment described above, since the character marking M1 and the gate identification marking M2 are provided on the flange portion 12, the manufacturing jig when the lens 10 is manufactured, and the like. The information can be directly identified without using a replacement table or the like by the character marking M1 or the like. Thereby, the discriminability and workability can be enhanced in the subsequent management of the lens 10. In addition, by making the character markings M1 and the gate identification markings M2 convex, transfer is performed by forming depressions (recesses MS1, MS2) corresponding to the character markings M1 and the like on the convex transfer surface S22 of the second mold 42. A surface can be provided, and the transfer surface can be easily processed. Further, by providing the character marking M1 and the like on the uppermost surface TP1 on the optical disc side which is an optical information recording medium, detection and recognition of the character marking M1 and the like becomes relatively easy.

Further, when the inclination of the optical function unit 11 is measured by the mirror surface part, the inclination of the optical function part 11 is provided on the outer periphery of the third flange surface 12c, which is the mirror surface part, of the uppermost surface TP1 of the flange part 12. , It is possible to prevent a decrease in reflected light for measurement. Further, the third flange surface 12c for measuring the inclination is not provided with the character marking M1 or the like, but is provided with the character marking M1 or the like on the outer periphery thereof, thereby making it possible to prevent the reflected light from being lowered. Further, from the viewpoint of lens design, the further away from the optical function unit 11, the easier it is to secure a space for attaching the character marking M1 and the like. Further, when the character marking M1 or the like is provided further away from the second optical surface OS2, when the groove corresponding to the character marking M1 or the like is processed in the second mold 42, the second optical surface OS2 (the optical function unit 11) is processed. ) Can be reduced.

[Example 1]
Hereinafter, examples of the optical surface of the lens 10 according to the above-described embodiment will be described. In the following (including the lens data in the table), a power of 10 (for example, 2.5 × 10 ⁻³ ) may be expressed using E (for example, 2.5 × E−3). Further, the optical surface of the objective lens is formed as an aspherical surface that is symmetric about the optical axis OA and is defined by a mathematical formula obtained by substituting the coefficients shown in Table 1 into Formula 1.

[Equation 1]

Here, X (h) is an axis in the optical axis direction (with the light traveling direction being positive), κ is a conical coefficient, Ai is an aspherical coefficient, h is a height from the optical axis, and r is a paraxial radius of curvature. It is.

Further, in the case of the embodiment using the diffractive structure, the optical path difference given to the light flux of each wavelength by the diffractive structure is defined by an equation in which the coefficient shown in the table is substituted into the optical path difference function of Formula 2. .

[Equation 2]

Here, h is the height from the optical axis, λ is the wavelength of the incident light beam, m is the diffraction order, and B _2i is the coefficient of the optical path difference function.

The first optical path difference providing structure of the lens 10 of the first embodiment will be described with reference to FIG. 5 (FIG. 5 is a conceptual diagram different from the actual shape of the first embodiment). In the first optical path difference providing structure of Example 1, the (1/1/1) blaze is added to the second basic structure BS2 that is a (2/1/1) blaze-type diffraction structure in the entire central region. The optical path difference providing structure is formed by superimposing the first basic structure BS1, which is a diffractive structure of the mold. Further, the step of the second foundation structure BS2 faces the direction of the optical axis OA, and the step of the first foundation structure BS1 faces the direction opposite to the optical axis OA. Furthermore, the average pitch of the first foundation structure BS1 is smaller than the average pitch of the second foundation structure BS2, and the number of steps facing the direction opposite to the optical axis OA of the first foundation structure is the second foundation structure BS2. More than the number of steps facing the direction of the optical axis OA of the structure. In the first basic structure BS1 and the second basic structure BS2, when the wavelength of the incident light beam is changed to be longer, the spherical aberration is changed in the direction of insufficient correction.

In addition, the second optical path difference providing structure of Example 1 has a structure in which the third basic structure that is the same as the first basic structure and the fourth basic structure that is the same as the second basic structure are overlapped in the entire intermediate region. It has become. The step of the third foundation structure faces in the opposite direction to the optical axis OA, and the step of the fourth foundation structure faces the optical axis OA. In the third foundation structure and the fourth foundation structure, when the third foundation structure changes so that the wavelength of the incident light beam becomes longer, the spherical aberration changes in the overcorrection direction, and the fourth foundation structure enters. If the wavelength of the light beam is changed so as to be longer, the spherical aberration changes to be undercorrected.

The third optical path difference providing structure of Example 1 is composed of only the fifth basic structure. In the fifth basic structure, the second-order diffracted light amount of the first light beam that has passed through the fifth basic structure is made larger than the diffracted light amount of any other order, and the first-order diffraction of the second light beam that has passed through the fifth basic structure. It is a blaze-type diffractive structure in which the amount of light is larger than any other order of diffracted light, and the first order diffracted light of the third light beam that has passed through the fifth basic structure is larger than any other order of diffracted light.

Table 1 shows the lens data of Example 1. In Table 1, “ri” represents the radius of curvature, and “di” represents the distance from the next surface. “Ni” indicates the refractive index of the lens material.

[Table 1]

Furthermore, the actual shape of the objective lens was designed based on the lens data of Example 1. The actual shape data is shown in Tables 2 and 3. By substituting the data shown in Tables 2 and 3 into the equation shown in Equation 3, the actual shape data of each annular zone can be obtained.

[Equation 3]

H represents the height from the optical axis in the direction perpendicular to the optical axis. Ai represents an aspheric coefficient.

[Table 2]

[Table 3]

As can be seen from Tables 2 and 3, in this example, the first zone to the 104th zone is the central region, the 105th zone to the 160th zone is the middle zone, and the 161th zone. To the 181st ring zone is the peripheral region.

Furthermore, FIG. 8 shows a conceptual cross-sectional view in the case where the first optical path difference providing structure, the second optical path difference providing structure, and the third optical path difference providing structure of Example 1 are provided in a flat element. Actually, the step surface of the optical path difference providing structure is inclined with respect to the optical axis OA, but in FIG. 8, it is arranged as a direction parallel to the optical axis OA for convenience. The central region where the first optical path difference providing structure is provided is the region indicated by CN, the intermediate region where the second optical path difference providing structure is provided is the region indicated by MD, and the third optical path difference providing structure The peripheral area provided with is an area indicated by OT.

Next, the antireflection film of Example 1 will be described. The first optical surface OS1 on the laser light source side of the lens 10 is provided with a three-layer antireflection film shown in Table 4 below. The antireflection film is provided using a vacuum deposition method.

[Table 4]

The second optical surface OS2 on the optical disc side of the lens 10 is provided with a seven-layer antireflection film shown in Table 3 below. The antireflection film is provided using a vacuum deposition method. Note that L5 in Table 5 is a mixed material of SiO ₂ and Al ₂ O ₃ and has a mixing ratio of SiO ₂ : Al ₂ O ₃ = 90 to 99: 1 to 10.

[Table 5]

Hereinafter, examples of dimensions and the like of the lens 10 according to the above-described embodiment will be described.
The outer diameter g1 of the lens 10 shown in FIG. 3A is 5 mm, and the on-axis thickness g2 of the optical function unit 11 is 2.67 mm. The surface depth g3 of the first optical surface OS1 of the lens 10 is 1.930 mm, the surface diameter g4 of the first optical surface OS1 is 4.015 mm, and the effective diameter g5 of the first optical surface OS1 is 3. It is 850 mm. The surface depth g6 of the second optical surface OS2 of the lens 10 is 0.087 mm, the surface diameter g7 of the second optical surface OS2 is 3.033 mm, and the effective diameter g8 of the second optical surface OS2 is 2. It is 851 mm. Here, the surface diameter refers to the diameter of the optical surface, and the effective diameter refers to the diameter of the portion of the optical surface through which the light beam passes. The thickness g9 of the flange portion 12 of the lens 10 parallel to the optical axis OA direction is 0.77 mm, the width g10 of the first flange surface 12a in the lens radial direction is 0.985 mm, and the second flange surface 12b. The lens width g11 in the lens radial direction is 1.967 mm. The thickness g12 of the thinnest portion of the flange portion 12 is 0.653 mm, and the distance g13 from the uppermost surface TP1 of the second flange surface 12b to the uppermost surface TP2 of the second optical surface OS2 is 0.03 mm. Yes. The width g14 of the alignment end face 12c is 0.082 mm. The heights h1 and h2 of the character marking M1 and the gate identification marking M2 are 0.010 mm. As shown in FIG. 4B, the length D of one side of the square area of the character portions J1, J2, J3, and J4, which are components of the character marking M1, is 0.15 mm. The gate cut amount d1 is 0.14 mm. Note that the gate cut amount d1 is the length in the gate axis direction of a portion of the flange portion 12 cut away perpendicularly to the gate axis direction extending to the gate portion GP when viewed from the optical axis OA direction.

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

As shown in FIG. 9, the top surface TP1 of the step structure b2 of the second flange surface 12b on the optical disc side of the flange portion 12 protrudes from the top surface TP2 of the second optical surface OS2. Since the second flange surface 12b protrudes from the uppermost surface TP2 of the second optical surface OS2, when the lens 10 is placed on a placement member such as a tray, the second optical surface OS2 is placed downward. However, the flange portion 12 serves as a guard so that the second optical surface OS2 does not contact the mounting member, and the second optical surface OS2 is not damaged.

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

As shown in FIG. 10, in the present embodiment, the first and

second molds

41 and 42 in the first embodiment are arranged in reverse. That is, the first mold 41 is a movable mold, and the second mold 42 is a fixed mold.

[Fourth Embodiment]
The optical element according to the fourth embodiment will be described below. The optical element according to the fourth 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. 11, in the lens 10, the gate part GP is cut so as to go around the local part of the flange part 12. This cut shape is usually called a U-cut shape.

[Fifth Embodiment]
The optical element according to the fifth embodiment will be described below. The optical element according to the fifth embodiment is a modification of the fourth embodiment, and parts that are not particularly described are the same as those in the fourth embodiment.

As shown in FIG. 12, in the lens 10, a part of the flange portion 12 near the gate portion GP is cut along the outer periphery thereof. Further, the gate portion GP is cut so as to go around the local portion of the flange portion 12.

Hereinafter, dimensions and the like of the lens 10 shown in FIG. 12 will be described. In the lens 10, for example, the gate cut amount d1 is 0.2 mm, the arc cut amount d2 is 0.08 mm or less, and the total cut range d3 is 1.2 mm or more and 2 mm or less. The gate cut amount d1 is the length in the gate axis direction extending from the outer diameter of the lens 10 to the deepest portion of the flange portion 12 as viewed from the optical axis OA direction. The arc cut amount d2 is the length in the gate axis direction of the portion of the flange portion 12 cut away along the outer periphery thereof. Further, the total cut range d3 is a length in a direction perpendicular to the gate axis direction of a portion obtained by cutting a part of the flange portion 12 along the outer periphery thereof.

As mentioned above, although this invention was demonstrated according to embodiment, this invention is not limited to the said embodiment. For example, it is not necessary to arrange the first mold 41 and the second mold 42 horizontally, and it may be a vertical mold in which the first mold 41 and the second mold 42 are arranged vertically. .

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 have a shape symmetrical to the 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 microstructure FS or the like on the optical surface.

In the above embodiment, the lens 10 may be a coupling lens disposed between the laser light source and the objective lens.

In the above embodiment, the character marking M1 is composed only of characters, but may be a combination of characters, figures, symbols, and the like. Moreover, only a figure and a symbol are good also as a component as a character-like marking.

In the above embodiment, the constituent elements of the character marking M1 are the four character portions J1, J2, J3, and J4, but the number of constituent elements may be changed as appropriate. In addition, the shapes of the character marking M1 and the gate identification marking M2 can be changed as appropriate. For example, the gate identification marking M2 is not limited to a hemispherical shape but may be a convex line shape. Specifically, as shown in FIGS. 13A and 13B, a convex three-line shape can be used.

Claims

An optical element incorporated in an optical pickup device,
Formed of resin,
An optical function part, and a flange part formed around the optical function part,
An optical element provided with convex character markings on the uppermost surface of the flange portion on the optical information recording medium side.
The optical element according to claim 1, wherein a height h of the convex character marking is 0.003 mm ≦ h ≦ 0.020 mm.
The component of the convex character marking is sized to fit within a square region having a side length of D,
The optical element according to claim 1, wherein the length D is 0.05 mm ≦ D ≦ 0.30 mm.
The optical element according to claim 1, wherein the flange portion further has a gate identification marking on the opposite side of the gate portion which is a resin introduction trace.
The optical function unit has a first optical surface and a second optical surface arranged on the optical information recording medium side of the first optical surface,
The optical element according to claim 1, wherein an uppermost surface of the flange portion on the optical information recording medium side protrudes from an uppermost surface of the second optical surface.
The optical function unit has a first optical surface and a second optical surface arranged on the optical information recording medium side of the first optical surface,
The optical element according to claim 1, wherein an uppermost surface of the second optical surface protrudes from an uppermost surface on the optical information recording medium side of the flange portion.
The optical element according to claim 5, wherein the first optical surface has a larger curvature than the second optical surface.
The optical element according to claim 1, wherein a relative position between the gate identification marking and the first character of the character marking is 90 °.
A mirror surface portion that generates reflected light that enables measurement of the inclination of the optical function portion;
The optical element according to claim 1, wherein an uppermost surface of the flange portion on the optical information recording medium side is on an outer periphery of the mirror surface portion.
The optical element according to claim 1, wherein the optical element is an objective lens disposed to face the optical information recording medium.
The optical element according to claim 1, which is a coupling lens disposed between the light source and the objective lens.
The optical element according to claim 1, which is incorporated in an optical pickup device for a Blu-ray disc.
A method for producing a resin-made optical element for molding an optical element incorporated in an optical pickup device using an injection molding apparatus having a movable mold and a fixed mold,
Forming a letter-like marking on the uppermost surface of the optical information recording medium side of the flange portion formed around the optical function portion of the optical element;
The method of manufacturing an optical element, wherein the character marking is formed by transferring one of the movable mold and the fixed mold.
The method of manufacturing an optical element according to claim 13, wherein the character-like marking is formed by the movable mold.
The movable mold has a core part and a holding part that holds the core part from the surroundings,
The method of manufacturing an optical element of an optical element according to claim 13, wherein the character-like marking is formed by transferring the holding part.
14. The method of manufacturing an optical element according to claim 13, wherein the fixed mold includes a core part and a holding part that holds the core part from the periphery.