WO2013094173A1

WO2013094173A1 - Objective lens, optical pickup, optical disc device, mold for resin forming, and method for manufacturing objective lens

Info

Publication number: WO2013094173A1
Application number: PCT/JP2012/008044
Authority: WO
Inventors: 文朝山崎; 久敬戸田; 範晃寺原; 太田　武志
Original assignee: パナソニック株式会社
Priority date: 2011-12-22
Filing date: 2012-12-17
Publication date: 2013-06-27

Abstract

An objective lens provided with: a main body part having a first optical surface and a second optical surface opposite the first optical surface; and a flange part which is formed, integrally with the main body part, around the outer periphery of the main body part. The first optical surface is formed by a first mirror surface core which is inserted into a first body mold and rotatably supported. The second optical surface is formed by a second mirror surface core which is inserted into a second body mold and rotatably supported. The flange part has: an annular surface formed on the second-optical-surface side by the second body mold; a projected mark formed on the annular surface by an eject pin supported by the second body mold so as to be capable of advancing and retracting; and a marking part formed, by a machining mark from the second body mold, at a different position on the annular surface from that at which the projected mark is formed, the marking part indicating the direction of the astigmatism of the objective lens.

Description

Objective lens, optical pickup, optical disk device, resin molding die and objective lens manufacturing method

The present invention relates to an objective lens used for recording and / or reproducing information on an information recording medium, an optical pickup that includes the objective lens and optically records and / or reproduces information on the information recording medium, and the light The present invention relates to an optical disk device on which a pickup is mounted, a resin molding die for manufacturing the objective lens, and a method for manufacturing the objective lens.

With the practical use of blue-violet semiconductor lasers, Blu-ray Disc (hereinafter also referred to as optical disc) is a high-density and large-capacity information recording medium (hereinafter also referred to as an optical disc) that is the same size as CD (Compact Disc) and DVD (Digital Versatile Disc) Hereinafter, BD) has been put into practical use. BD uses a blue-violet laser light source that emits laser light having a wavelength of about 400 nm and an objective lens having a numerical aperture (hereinafter also referred to as NA) of about 0.85. An optical disc for recording or reproducing information on an information recording surface of 0.1 mm.

Generally, an objective lens made of a synthetic resin is used for an optical pickup for recording or reproducing an optical disk such as a CD or a DVD. Synthetic resin objective lenses have a lower specific gravity than glass objective lenses, reducing the burden on the objective lens actuator that drives the objective lens against optical disc surface deflection and eccentricity, and at higher speeds. It is also possible to follow. Moreover, since the objective lens made of synthetic resin can be mass-produced with high accuracy by injection molding, the cost of the objective lens can be reduced.

Therefore, in recent years, as a high NA (numerical aperture) objective lens used for an optical pickup for recording or reproducing a high-density optical disc such as a BD, a synthetic resin lens is often used.

Synthetic resin objective lenses may cause astigmatism due to the precision and molding conditions (mold temperature, resin temperature, and pressure conditions) of the resin molding mold, and in a pair of resin molding molds. It is known that coma aberration and the like occur due to a relative optical axis shift between the first surface and the second surface. Here, in order to suppress these aberrations, a high NA objective lens used for BD or the like requires stricter control of mold accuracy and molding conditions compared to conventional objective lenses for CD and DVD. It is done.

By the way, such an aberration affects the optical performance of the optical pickup when the objective lens is mounted on the optical pickup. Therefore, when the objective lens is mounted on the optical pickup, the inclination and mounting direction of the objective lens are adjusted. There is a need to. For this reason, the mark (marking part) which shows the direction of an aberration, etc. may be attached to the outer side of the optical surface of an objective lens.

The marking part can be formed by marking the edge part (flat part) one by one with an ink jet printer or the like after molding the objective lens, or by irradiating a resin molding die with an electron beam for rough surface processing. A method of transferring a rough surface portion, a convex shape or a concave shape mark to the edge portion of a molded lens by applying or forming a concave slow-thickness portion or a convex portion is known. By providing such a marking portion, the direction of aberration can be determined from the position of the marking portion.

Also, as another conventional marking method, there is a method disclosed in Patent Document 1 described below. FIG. 14 is a schematic view showing the shape of a conventional objective lens. The objective lens 201 includes an optical surface 202 serving as an optical function surface of the optical element, and an outer shape portion 203 integrally formed around the optical surface 202, and a trace 203b obtained by cutting the gate portion is formed on the outer shape portion 203. A marking portion 204 ("M105" in the figure) made up of a plurality of characters and symbols such as alphabets and the like is formed on the flat surface 203a of the outer shape portion 203 in the vicinity of the gate portion, remaining on the outer periphery. In this way, by forming the marking part 204 composed of characters or symbols, the marking part 204 having information such as the history of the molded part and the resin molding die can be reliably and simultaneously formed with the molded part. It can be easily formed.

As described above, when coma aberration or the like occurs due to relative optical axis misalignment between the first surface and the second surface in the pair of resin molding dies, the first surface and the second surface resin molding dies. It is known that the coma aberration can be adjusted by adjusting the relative optical axis by rotating the mold (specular core) in the barrel mold.

However, the conventional objective lens disclosed in Patent Document 1 and the like processes the edge portion (outside the optical function surface) of the mirror surface core to form a marking portion. Therefore, if the mirror surface core is rotated in the body mold, The relative positional relationship between the trunk mold and the marking portion changes, but no mention is made of the influence thereof.

In addition, for a high NA objective lens used for BD or the like, the formation of the marking portion itself causes an aberration. However, the shape of the marking portion suitable for such a high NA objective lens is not disclosed at all. Absent.

JP 2005-254660 A

The present invention has been made in view of solving such a conventional problem, and is based on the formation of a marking portion indicating the direction of astigmatism and the light generated by rotation of a resin molding die (mirror core). An object of the present invention is to provide a high NA synthetic resin objective lens that can achieve both axis adjustment (coma aberration correction).

An objective lens according to one aspect of the present invention is an objective lens that is molded using a resin molding die including a first barrel mold and a second barrel mold, and the objective lens has a numerical aperture NA of 0.7. A resinous objective lens as described above, having a first optical surface and a main body portion having a second optical surface facing the first optical surface, and an outer peripheral portion of the main body portion integrated with the main body portion. The first optical surface is formed by a first mirror core inserted into the first body mold and rotatably supported, and the second optical surface is Formed by a second specular core that is inserted into a second barrel mold and rotatably supported; and the flange portion is formed on the second optical surface side by the second barrel mold; and Formed on the annular surface by an eject pin supported so as to be able to move forward and backward in the second body mold Markings that are formed by the second cylinder-shaped processing marks at positions different from the positions where the protruding part marks are formed on the annular surface, and indicate the direction of astigmatism of the objective lens Part.

A resin molding die according to another aspect of the present invention is a resin molding die for manufacturing a resin objective lens having a numerical aperture NA of 0.7 or more, and the first optical element of the objective lens is a first mold. A first mirror core that forms a surface, a second mirror core that forms a second optical surface opposite to the first optical surface, and the first mirror core inserted with the first mirror core. A first barrel mold that is rotatably supported, a second mirror surface core inserted therein to rotatably support the second mirror core, and a second optical surface side circle of the flange portion of the objective lens A second body mold that forms an annular surface; and an eject pin that is supported by the second body mold so as to be able to advance and retreat. The eject pin forms a protrusion mark on the annular surface, and the second body mold. Is a position different from the position where the protruding portion trace is formed in the annular surface, By forming the Engineering traces, forming a marking unit for indicating the direction of the astigmatism of the objective lens.

An objective lens manufacturing method according to still another aspect of the present invention is a method of manufacturing an objective lens that uses a resin molding die to manufacture a resin objective lens having a numerical aperture NA of 0.7 or more, The resin molding die includes a first mirror core that forms a first optical surface of the objective lens, a second mirror core that forms a second optical surface facing the first optical surface, A first barrel type in which the first mirror core is inserted to rotatably support the first mirror core; and the second mirror core is inserted to rotatably support the second mirror core. A second body mold that forms an annular surface on the second optical surface side of the flange portion of the objective lens; and an eject pin that is supported by the second body mold so as to be able to advance and retreat, and using the eject pin. , Forming a protruding mark on the annular surface; and Using a barrel mold, a marking portion indicating the direction of astigmatism of the objective lens is formed by forming a processing mark at a position different from the position where the protruding portion mark is formed on the annular surface. Steps.

In the above objective lens, it is possible to achieve both the formation of the marking portion indicating the direction of astigmatism and the optical axis adjustment (coma aberration correction) by the rotation of the first and second mirror cores. Aberration performance superior to that of a lens can be obtained.

The objects, features and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings.

Sectional drawing and top view which show schematic shape of the objective lens made from a synthetic resin in Embodiment 1 of this invention The perspective view which shows schematic shape of the objective lens made from a synthetic resin in Embodiment 1 of this invention Sectional drawing which shows schematic structure of the metal mold | die for resin molding used when manufacturing the synthetic resin objective lens in Embodiment 1 of this invention by injection molding The figure which shows the position of the gate part and the marking part typically The top view which shows schematic shape of the objective lens made from another synthetic resin in Embodiment 1 of this invention The top view and sectional drawing which show typically the shape of the marking part of the objective lens in Embodiment 1 of this invention The figure which shows the other cross-sectional shape of a marking part typically Sectional drawing which shows schematic shape of the objective lens made from another synthetic resin in Embodiment 1 of this invention Sectional drawing which shows schematic structure of the metal mold | die for resin molding for manufacturing the objective lens shown in FIG. Schematic configuration diagram of an optical pickup according to Embodiment 2 of the present invention Schematic diagram for explaining the operation of the objective lens actuator of the optical pickup shown in FIG. The figure which shows schematic shape of the lens holder of the objective lens actuator shown in FIG. Schematic configuration diagram of an optical disc apparatus according to Embodiment 3 of the present invention. Schematic showing the shape of a conventional objective lens

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1A shows a cross-sectional view of a synthetic resin objective lens according to Embodiment 1 of the present invention, and FIG. 1B shows a plan view of the objective lens.

The objective lens 1 is an objective lens molded using a first barrel mold 10 and a second barrel mold 20 (see FIG. 3) described later, and is a resin objective lens having a numerical aperture NA of 0.7 or more. is there. The objective lens 1 includes a first lens surface (first optical surface) 1a on the light source side (laser light incident side) and a second optical disk side (side on which laser light is emitted) facing the first lens surface. A main body portion 2 having a lens surface (second optical surface) 1b and a peripheral flange portion 3 formed integrally with the main body portion 2 on the outer peripheral portion of the main body portion 2 are provided.

The first lens surface 1a and the second lens surface 1b have different spherical or aspherical surfaces (hereinafter collectively referred to as aspherical surfaces). The first lens surface 1a and / or the second lens surface 1b has a sawtooth shape or a step shape having a plurality of ring-shaped optical surfaces centered on the optical axis OA of the objective lens 1 on the base aspherical surface. The diffractive structure may be formed.

The peripheral flange portion 3 is secondly formed by an annular surface 3a formed on the first lens surface 1a side by a first mirror core 12 (see FIG. 3) to be described later and a second barrel mold 20 (see FIG. 3) to be described later. It has an annular surface 3b formed on the lens surface 1b side.

As described above, the objective lens 1 is integrally formed with the main body portion 2 having the first lens surface 1 a and the second lens surface 1 b and the peripheral flange portion 3. A plurality of protruding portion marks 5 and marking portions 7 are formed on the surface on the lens surface 1b side. The protruding portion mark 5 is formed on the annular surface 3b by an eject pin 27 (see FIG. 3) supported by the second body mold 20 so as to be able to advance and retreat. The marking part 7 is formed by a processing mark of the second barrel mold 20 at a position different from the position where the protruding part mark 5 is formed on the annular surface 3b, and indicates the direction of astigmatism of the objective lens 1.

The gate portion 6 indicated by a broken line in the drawing is formed by the inflow passage of the resin material when the objective lens 1 is molded. If the gate portion 6 remains largely, the objective lens 1 is mounted on the lens holder. In addition, it is necessary to “escape” the gate portion 6 on the lens holder. Further, the mounting direction of the objective lens 1 is limited to a direction in which the gate portion 6 and the “escape” of the lens holder coincide with each other. Therefore, it is desirable that the gate portion 6 is cut and removed after the objective lens 1 is molded.

FIG. 2 is a perspective view showing a schematic shape of the objective lens 1 of the present embodiment. The marking portion 7 is formed on the annular surface 3b of the peripheral flange portion 3 on the second lens surface 1b side, and, as will be described later, for example, in advance on a mold (second barrel die 20) for molding the objective lens 1. The processing trace formed by the cutting tool is added by transferring it to the objective lens 1 at the time of molding. Therefore, it is preferable that the marking part 7 is a convex part. Moreover, although the protrusion trace 5 is preferably a concave portion, it may be a convex portion. Moreover, as shown in the figure, the protruding portion trace 5 is preferably circular.

FIG. 3 is a cross-sectional view showing a schematic configuration of a resin molding die for manufacturing the objective lens 1 of the present embodiment. FIG. 3 (a) shows a state during molding (mold closed state), FIG. 3B shows a mold open state.

As shown in FIG. 3 (a), a pair of first body mold 10 and second body mold 20 that can be opened and closed by a parting line PL are respectively provided with a first core support hole 11 and a first core support hole 11 positioned on the same axis. A two-core support hole 21 is formed. A first mirror core 12 and a second mirror core 22 are inserted into the first core support hole 11 and the second core support hole 21, respectively, and are rotatably supported.

The first mirror core 12 has an outer diameter corresponding to the first core support hole 11, and a first optical functional surface 13 facing the parting line PL is formed at the tip. Similarly, the second mirror core 22 has an outer diameter corresponding to the second core support hole 21, and a second optical functional surface 23 facing the parting line PL is formed at the tip.

In the present embodiment, the radius of curvature of the first optical functional surface 13 is smaller than the radius of curvature of the second optical functional surface 23.

As described above, the first mirror surface core 12 and the second mirror surface core 22 are inserted into the first core support hole 11 and the second core support hole 21, respectively, and the first optical function surface 13 and the second optical function surface. 23, a molding space for the objective lens 1 is formed, and this molding space faces the parting line PL. The first core core 12 is inserted and fixed in the core support hole 11 of the first body mold 10, and the mirror core 22 is inserted and fixed in the core support hole 21 of the second body mold 20, thereby supporting the first core. The clearance between the hole diameter of the hole 11 and the outer diameter of the first mirror core 12 and the clearance between the hole diameter of the second core support hole 21 and the outer diameter of the second mirror core 22 can be minimized. Specifically, when the diameter of the first core support hole 11 (the diameter of the objective lens 1 to be molded) is about several mm, this clearance can be set to about 1 μm or less.

The second body mold 20 is formed with a flange forming portion 26 that communicates with a forming space formed by the first optical function surface 13 and the second optical function surface 23 so as to face the parting line PL. As is apparent from the shape of the objective lens 1 shown in FIGS. 1 and 2, the flange forming portion 26 corresponds to the annular surface 3 b on the second lens surface 1 b side of the peripheral flange portion 3 of the objective lens 1. .

The annular surface 3a on the first lens surface 1a side of the peripheral flange portion 3 of the objective lens 1 according to the present embodiment is formed by the first mirror core 12 as is apparent from FIG. It may be formed by a single body mold 10. However, since the annular surface 3a on the first lens surface 1a side of the peripheral flange portion 3 serves as a reference surface when the objective lens 1 is mounted on the optical pickup, it is formed with the same mold as the first optical function surface 13. It is preferred that That is, the annular surface 3 a on the first lens surface 1 a side of the peripheral flange portion 3 is preferably formed by the first mirror core 12. In this case, since the annular surface 3a on the first lens surface 1a side, which becomes a reference surface when the objective lens 1 is mounted on the optical pickup, can be formed with high precision, the objective lens 1 is attached to the optical pickup with high precision. Can be attached.

The flange molding portion 26 of the second body mold 20 forms an annular surface 3b on the second lens surface 1b side of the peripheral flange portion 3. The eject pin 27 is supported by the second body mold 20 so as to be able to advance and retreat, and forms a protruding mark 5 on the annular surface 3b of the peripheral flange portion 3 on the second lens surface 1b side. Specifically, in the flange forming portion 26, pin holes 28 into which eject pins 27 extending into the forming space are slidably inserted are formed at, for example, four locations on the circumference. Here, from the viewpoint of releasing while maintaining good moldability, it is preferable to arrange 2 to 8 eject pins 27.

The pin hole 28 extends in parallel with the second core support hole 21, and the eject pin 27 can be advanced and retracted in the axial direction by an eject pin drive section (not shown).

In addition, the position where the pin hole 28 is provided is the optical function surface side with a small effective diameter, that is, the objective lens of the present embodiment, of the two optical function surfaces of the first optical function surface 13 and the second optical function surface 23. 1 is preferably provided on the second optical function surface 23 side. By setting it as such a structure, a protrusion trace can be formed, keeping the external shape of the objective lens 1 including the peripheral flange part 3 small.

In the resin molding die of the present embodiment, the molding space formed by the first optical functional surface 13 and the second optical functional surface 23 facing the parting line PL in the second barrel die 20. A resin material injecting portion (not shown) communicating with is formed. The resin material injection portion serves as an inflow passage for the resin material when the objective lens 1 is molded, and the gate portion 6 is formed.

Molding by the resin molding die having the above configuration is performed by the first optical functional surface 13 and the second optical functional surface 23 from the resin material injection portion in a state where the first barrel die 10 and the second barrel die 20 are clamped. This is performed by injecting a resin material into the molding space. This resin material is heated and pressurized by the first mirror core 12 and the second mirror core 22, whereby the objective lens 1 is molded.

The first lens surface 1a of the objective lens 1 is formed by the first optical function surface 13 formed on the first mirror surface core 12, and the object lens 1 is formed by the second optical function surface 23 formed on the second mirror surface core 22. The second lens surface 1b is formed. Further, an annular surface 3b on the second lens surface 1b side of the peripheral flange portion 3 is formed by the flange forming portion 26 formed on the second body mold 20, and further, the eject pin 27 is used to form the second flange surface 3 of the peripheral flange portion 3. The protruding portion trace 5 is formed on the annular surface 3b on the two lens surface 1b side.

When the first barrel mold 10 and the second barrel mold 20 are opened after the injected resin material is cured, the objective lens 1 is attached to the second optical function surface 23 side. In this state, when the eject pin 27 is protruded to the molding space side of the flange forming portion 26 via the eject pin driving portion, the peripheral flange portion 3 of the objective lens 1 is protruded as shown in FIG. (2) The objective lens 1 is released from the optical function surface 23 and taken out.

As described above, the peripheral flange portion 3 is formed on the objective lens 1 and the peripheral flange portion 3 is pressed with the eject pin 27 to release the mold, thereby suppressing deformation (deterioration of surface accuracy) of the objective lens 1. . As in the objective lens 1 shown in FIG. 1, the circumferential position of the gate portion 6 and the circumferential position of the protruding portion trace 5 (that is, the protruding portion of the resin molding die) are different. Is preferred. In this case, as shown in FIG. 2, since the protruding portion trace 5 is a concave portion, the gate portion 6 is provided in the thick portion of the peripheral flange portion 3 in this way, so that the flow of the resin material As a result, the pressure loss is reduced and the optical function surface can be satisfactorily formed.

Next, the marking portion 7 of the objective lens 1 of the present embodiment will be described in detail.

The inventors of the present application have astigmatism caused by molding conditions (pressurizing conditions / heating conditions), etc., particularly for high NA objective lenses used in optical pickups for recording or reproducing high density optical disks such as BD. Has been found to be caused by the flow of resin during molding, that is, it has a relationship with the position of the gate portion in injection molding.

However, since the gate portion 6 is cut and removed after the objective lens 1 is molded for the above-described reason, there is no “mark” indicating the direction of astigmatism generated due to the flow of resin during molding. End up.

Therefore, in order to indicate the direction of astigmatism of the objective lens 1 from which the gate portion 6 has been removed, the inventor has conceived that “marking” in which the circumferential position is always constant with respect to the gate portion 6 is necessary.

In the mold for resin molding shown in FIG. 3, the flange molding portion 26 formed on the second barrel die 20 is preliminarily processed to have a concave shape corresponding to the marking portion 7 by a cutting tool. 2 is transferred to the objective lens 1 to form a convex marking portion 7 as shown in FIG.

By the way, coma aberration and the like occur due to the relative optical axis shift between the first optical functional surface 13 and the second optical functional surface 23. The first mirror core 12 and the second mirror core 22 are respectively connected to the first body. By rotating along the core support hole 11 of the mold 10 and the core support hole 21 of the second barrel mold 20, relative optical axis adjustment can be performed and coma aberration can be corrected.

Here, in the resin molding die for manufacturing the objective lens 1 according to the present embodiment, the flange molding portion 26 formed in the second barrel mold 20 is subjected to concave processing corresponding to the marking portion 7. Therefore, as described above, even when the optical axis is adjusted by rotating the first mirror core 12 and the second mirror core 22, the relative positional relationship between the gate portion 6 and the marking portion 7 in the objective lens 1 does not change. . Therefore, since the relationship between the direction of astigmatism generated due to the flow of resin during molding and the direction of the marking portion 7 is maintained, the marking portion 7 is used when the objective lens 1 is incorporated into the optical pickup. The astigmatism direction can be used as a mark when adjusting in a predetermined direction, for example, a direction in which the astigmatism due to another optical element of the optical pickup and the astigmatism of the objective lens 1 cancel each other.

That is, the objective lens 1 based on the configuration of the present embodiment has a marking indicating the direction of astigmatism (the marking portion 7 is connected to the annular surface 3b of the peripheral flange portion 3 while maintaining the relationship with the direction of astigmatism. And the optical axis adjustment (coma aberration correction) by the rotation of the mirror core (the first mirror core 12 and the second mirror core 22) can be made compatible. Better aberration performance.

Here, in the resin molding die (second barrel mold 20), the concave processing trace for forming the marking portion 7 of the objective lens 1 is circumferential with respect to the gate portion 6 as shown in FIG. It is preferable to form in a direction of approximately 180 ° in the direction.

For example, as in the objective lens shown in FIG. 4A, when the marking portion 7a is formed in the vicinity of the gate portion 6 (approximately 0 ° in the circumferential direction), in the vicinity of the resin material injection portion of the resin molding die. A concave processing mark is formed. In this case, the flow of the resin at the time of injection molding deteriorates due to the marking portion 7a, which becomes a cause of occurrence of molding defects and the like. 4B, when the marking portion 7b is formed at a position such as approximately 90 ° in the circumferential direction (counterclockwise) with respect to the gate portion 6, the objective portion shown in FIG. Since the objective lens 1 has an asymmetric shape with respect to the straight line xx connecting the optical axis with the lens 1, it causes generation of coma aberration and the like.

Therefore, the marking portion 7 of the objective lens 1 is preferably formed within a range of 180 ± 10 ° in the circumferential direction with respect to the gate portion 6, and is approximately 180 ° in the circumferential direction with respect to the gate portion 6. More preferably, it is formed at a position. In this case, the generation of astigmatism due to molding defects or the like can be suppressed, and the generation of coma aberration can be suppressed.

Further, it is more preferable that the protrusion mark 5 is arranged symmetrically with respect to a straight line xx connecting the optical axis OA of the objective lens 1 and the center of the gate part 6. In this case, the occurrence of coma aberration can be suppressed. For example, when the four protruding portion traces 5 shown in FIG. 1 are formed, the protruding portions are located at positions of approximately 45 °, 135 °, 225 °, and 315 ° in the circumferential direction (clockwise) with respect to the gate portion 6. It is preferable to form the marks 5.

Further, in another objective lens 1 ′ of the present embodiment shown in FIG. 5, when two protruding portion marks 5 ′ are formed, that is, a pin hole into which an eject pin is inserted is a resin molding die. , The arrangement of the gate portion 6 ′, the two protruding portion traces 5 ′, and the marking portion 7 ′ is as shown in FIG. The protruding portion marks 5 ′ are formed at positions of approximately 90 ° and 270 ° in the circumferential direction (clockwise) with respect to the gate portion 6, and approximately 180 in the circumferential direction (clockwise) with respect to the gate portion 6. It is preferable to form the marking portion 7 ′ at a position of °.

By the way, when forming a processing mark on a resin mold and transferring the processing mark to an objective lens to add a marking portion, the visibility of the marking portion is very important. That is, in the case of a marking portion with low visibility, equipment such as a microscope is required to incorporate the objective lens into the optical pickup, which increases the number of work steps and increases the cost of the optical pickup.

FIG. 6 is a diagram schematically showing the shape of the marking portion 7 formed on the objective lens 1 of the present embodiment. 6A is a plan view of the marking portion 7, FIG. 6B is a cross-sectional view of the marking portion 7 along the center line AA, and FIG. 6C is along the center line BB. A cross-sectional view of the marking portion 7 is shown. In FIG. 6, the direction of the center line AA is the radial direction of the objective lens 1 (optical disk), and the direction of the center line BB is the circumferential direction of the objective lens 1 (optical disk).

As shown in FIGS. 1 and 6A, the marking portion 7 applied to the objective lens 1 of the present embodiment is more radial than the circumferential direction of the objective lens 1 when viewed from the upper surface of the objective lens 1. Has a long, substantially oval shape. Specifically, the marking portion 7 has an oval shape having a length L in the radial direction, a width W in the circumferential direction, and a height H, and the length L is at least twice the width W. preferable. By making such an oval shape, it becomes easy to distinguish from the circular protruding portion trace 5, and the width in the circumferential direction can be reduced while ensuring the visibility of the marking portion 7. As a result, the angle adjustment (rotational adjustment in the circumferential direction) of the objective lens 1 can be performed with higher accuracy.

Further, as shown in FIGS. 6B and 6C, the cross-sectional shape of the marking portion 7 is a convex lens shape. As a result of examining various cross-sectional shapes, the inventors of the present application have such a shape, and when viewed from the upper surface of the objective lens 1, the lens action (refractive action) of the marking part 7 causes the marking part 7 to We found that visibility improved dramatically.

Note that the cross-sectional shape of the marking portion 7 is not particularly limited to the above example, and may be other shapes. FIG. 7 is a cross-sectional view of the marking portion along the center line BB schematically showing another cross-sectional shape of the marking portion. Even if the side wall of the marking portion 7 ′ is inclined as in the example shown in FIG. 7, it is possible to improve visibility by refraction. In this case, the inclination angle α of the side wall 71 is preferably 20 ° or more and 50 ° or less in view of the balance between the workability of the processing marks on the mold and the visibility of the marking portion 7 ′.

In addition, when the size of the marking portion 7 is increased, the influence on the aberration of the objective lens 1 cannot be ignored, which may affect the optical performance. Therefore, as a result of intensive studies on the size of the marking portion 7, the inventors of the present application, as a dimension of the marking portion 7 that does not affect the optical performance while ensuring the visibility, The length L in the radial direction is preferably in the range of 0.2 mm or more and 0.5 mm or less, more preferably in the range of 0.25 mm or more and 0.45 mm or less, and the circumferential direction of the marking portion 7 Is preferably in the range of 0.05 mm or more and 0.25 mm or less, more preferably in the range of 0.08 mm or more and 0.15 mm or less, and the height H of the marking portion 7 is 0. It was found that it was preferably in the range of 0.003 mm or more and 0.025 mm or less, and more preferably in the range of 0.005 mm or more and 0.020 mm or less.

Further, the surface roughness is changed between the marking portion 7 and its peripheral portion (annular surface 3b on the second lens surface 1b side of the peripheral flange portion 3), that is, the surface roughness of the marking portion 7 is changed to the peripheral flange portion 3. By making the surface roughness different from the surface roughness, the visibility of the marking portion 7 can be further improved. Specifically, the surface roughness of the concave processing trace corresponding to the marking portion 7 is different from the flange forming portion 26 of the mold corresponding to the annular surface 3b on the second lens surface 1b side of the peripheral flange portion 3. By making it smaller than this part, the surface roughness of the marking part 7 can be made smaller than the surface roughness of the peripheral flange part 3. In this case, it is possible to achieve improvement in visibility due to the lens action of the marking portion 7 and suppression of mold processing costs.

By the way, when the objective lens is mounted on the optical pickup, the measurement laser light is irradiated from the optical disk side (the second lens surface 1b side of the objective lens 1) of the objective lens, and the objective is determined from the angle of the reflected light of the measurement laser light. In general, the inclination of the lens is detected and the relative inclination between the optical pickup and the objective lens is adjusted.

For example, in the objective lens 1 shown in FIG. 1, an annular reflection plane 1c perpendicular to the optical axis OA can be used as the reflection surface of the measurement laser beam. Here, it is important that the reflection plane 1c is located on the outer peripheral side of the second lens surface 1b and is formed of the same mold as the mold that forms the second lens surface 1b. That is, the reflection plane 1c is not formed by the second body mold 20 that forms the peripheral flange portion 3, but by the second mirror core 22 that forms the second lens surface 1b that determines the optical performance of the objective lens 1. It is guaranteed to be perpendicular to the optical axis OA.

The effective diameter D2 of the second lens surface 1b is smaller than the effective diameter D1 of the first lens surface 1a, and the diameter D3 on the outer peripheral side of the reflection plane 1c is larger than the effective diameter D1 of the first lens surface 1a. Larger is preferred. In this case, since the measurement laser beam can be sufficiently reflected by the reflection plane 1c, the inclination of the objective lens 1 is detected from the angle of the reflected light of the measurement laser beam, and the optical pickup and the objective lens 1 are The relative inclination can be adjusted with high accuracy.

On the other hand, when the reflection plane 1c and the first lens surface 1a are close to each other, the flow of the resin during molding may deteriorate, and the flatness of the reflection plane 1c may deteriorate. If the flatness of the reflection plane 1c deteriorates, the reflected light of the measurement laser beam cannot be obtained normally, and the tilt of the objective lens cannot be detected. Therefore, as described below, it is preferable to provide a step portion between the second lens surface 1b and the reflection plane 1c so that the reflection plane 1c and the first lens surface 1a do not approach each other.

FIG. 8 is a cross-sectional view showing a schematic shape of another objective lens made of synthetic resin according to Embodiment 1 of the present invention. The objective lens 1 ″ shown in FIG. 8 is different from the objective lens 1 shown in FIG. 1 in that a step 1d is provided between the second lens surface 1b and the reflection plane 1c. These are the same as those of the objective lens 1 shown in FIG.

In the objective lens 1 ″ shown in FIG. 8, the peripheral flange portion 3 has a step portion 1d formed inside the annular surface 3b on the second lens surface 1b side, and is an annular surface on the upper side of the step portion 1d. A certain reflection plane 1c and the first lens surface 1a are configured not to be close to each other, and the effective diameter D2 of the second lens surface 1b is set to be smaller than the effective diameter D1 of the first lens surface 1a. In addition, the diameter D4 on the outer peripheral side of the step portion 1d (reflection plane 1c) is set to be larger than the effective diameter D1 of the first lens surface 1a.

In this case, the stepped portion 1d sufficiently separates the reflection plane 1c and the first lens surface 1a, and the flow of resin during molding becomes smooth, so that the flatness of the reflection plane 1c can be improved. As a result, the measurement laser beam can be accurately reflected by the reflection plane 1c, so that the inclination of the objective lens 1 "is accurately detected from the angle of the reflected light of the measurement laser beam, and the optical pickup and the objective lens 1 are detected. The relative inclination with “can be adjusted with high accuracy.

9 is a cross-sectional view showing a schematic configuration of a resin molding die for manufacturing the objective lens 1 ″ shown in FIG. 8. The resin molding die shown in FIG. 9 is the resin molding die shown in FIG. The difference from the mold is that instead of the second mirror core 22, a second mirror core 22 ′ having an annular recess 22 a for forming a step 1 d on the objective lens 1 ″ is used. Since the other points are the same as those of the resin molding die shown in FIG. 3, detailed description thereof is omitted.

As shown in FIG. 9, the second mirror core 22 ′ has an annular recess 22a on the outer peripheral side of the second optical functional surface 23, and the annular recess 22a is filled with resin, so that the objective lens 1 ″ is provided. In this way, even when the reflection plane 1c formed by the step 1d is shaped as shown in Fig. 8, the step 1d (reflection plane 1c) is the object of the objective. The reflection plane 1c is formed by the same mold as the second optical functional surface 23 that forms the second lens surface 1b that determines the optical performance of the lens 1 ", that is, the second mirror core 22", so that the reflection plane 1c is optical axis. It is guaranteed to be perpendicular to OA.

As described above, in the present embodiment, for example, when viewed from the upper surface of the objective lens 1, an elliptical shape having a longer radial direction than the circumferential direction of the objective lens 1 and a cross-section having a convex lens shape or a side wall inclined shape. Although the marking portion 7 has been described, the present invention is not limited to the marking portion having such a shape.

For example, the shape of the marking portion when viewed from the upper surface of the objective lens 1 is not limited to an oval shape whose radial direction is longer than the circumferential direction, and may be an astigmatic shape such as a circle, a triangle, or an arrow. The excellent effect that it is possible to achieve both the formation of the marking portion indicating the direction of aberration and the optical axis adjustment (coma aberration correction) by the rotation of the mirror core is not impaired.

Also, a marking portion formed by irradiating an electron beam to a flange molding portion formed on a body mold of a resin molding die to perform a rough surface processing, and transferring the processing marks at the time of molding. However, it is possible to achieve both the formation of the marking part indicating the direction of astigmatism and the optical axis adjustment (coma aberration correction) by rotating the mirror core, which is an excellent effect that cannot be obtained with conventional objective lenses. Needless to say.

(Embodiment 2)
FIG. 10 is a schematic configuration diagram of the optical pickup according to the present embodiment.

In FIG. 10, an optical pickup 100 includes an objective lens 1, a blue-violet laser light source 101, a polarizing beam splitter 102, a quarter wavelength plate 103, a collimating lens 104, a mirror 105, an objective lens actuator 109, a red laser light source 111, a flat beam. A splitter 113, a detection lens 122, and a light receiving element 123 are provided. The objective lens 1 is the objective lens shown in Embodiment 1, and BD60 or DVD70 is used as an information recording medium.

First, the operation of the optical pickup 100 when recording or reproducing the BD 60 will be described. The blue-violet laser light having a wavelength of about 405 nm emitted from the blue-violet laser light source 101 enters the polarization beam splitter 102 as S-polarized light. The laser light reflected by the polarization beam splitter 102 is converted into circularly polarized light by the quarter wavelength plate 103, then converted into substantially parallel light by the collimator lens 104, reflected by the mirror 105, and bent. The blue-violet laser light reflected by the mirror 105 is converged as a light spot on the information recording surface of the BD 60 by the objective lens 1.

The blue-violet laser light reflected on the information recording surface of the BD 60 is transmitted through the objective lens 1 again, reflected by the mirror 105, transmitted through the collimator lens 104, and then converted into linearly polarized light different from the forward path by the quarter wavelength plate 103. Converted. The blue-violet laser light converted into linearly polarized light is incident on and transmitted through the polarization beam splitter 102 and the flat beam splitter 113 as P-polarized light, and is guided to the light receiving element 123 via the detection lens 122. The laser light detected by the light receiving element 123 is calculated after being photoelectrically converted, and generates a focus error signal for following the surface blur of the BD 60 and a tracking error signal for following the eccentricity of the BD 60.

Next, the operation of the optical pickup 100 when recording or reproducing the DVD 70 will be described. The red laser light having a wavelength of about 660 nm emitted from the red laser light source 111 is incident on the flat plate beam splitter 113 as S-polarized light, reflected, and transmitted through the polarizing beam splitter 102. The red laser light transmitted through the polarization beam splitter 102 is converted into circularly polarized light by the quarter wavelength plate 103, then converted into substantially parallel light by the collimator lens 104, reflected by the mirror 105, and bent. The red laser light reflected by the mirror 105 is converged as a light spot on the information recording surface of the DVD 70 by the objective lens 1.

The red laser light reflected on the information recording surface of the DVD 70 is transmitted again through the objective lens 1, reflected by the mirror 105, transmitted through the collimator lens 104, and then converted into linearly polarized light different from the forward path by the quarter wavelength plate 103. Converted. The red laser light converted into the linearly polarized light is incident on and transmitted through the polarization beam splitter 102 and the plate beam splitter 113 as P-polarized light, and is guided to the light receiving element 123 via the detection lens 122. The laser beam detected by the light receiving element 123 is calculated after being photoelectrically converted, and generates a focus error signal for following the surface blur of the DVD 70 and a tracking error signal for following the eccentricity of the DVD 70.

As described above, the objective lens 1 according to the present embodiment is the objective lens shown in the first embodiment, and is used to record or reproduce information on the violet laser beam and the DVD 70 for recording or reproducing information on the BD 60. Are provided with a diffraction structure for condensing each red laser beam as a minute light spot by utilizing the difference in wavelength.

FIG. 11 is a schematic diagram for explaining the operation of the objective lens actuator 109 shown in FIG. As shown in FIG. 11, the objective lens actuator 109 supports the lens holder 109a by a plurality of suspension wires 109b, and a light spot is applied to the information track of the rotating BD 60 or DVD 70 by the focus error signal and the tracking error signal. Is driven in the biaxial directions (focus direction Fo and tracking direction Tr). The structure of the objective lens actuator 109 may be a structure in which the objective lens 1 can be tilted in the radial direction of the optical disc in addition to the displacement in the focus direction Fo and the tracking direction Tr.

The optical pickup 100 of the present embodiment includes the objective lens 1 shown in the first embodiment. Since the objective lens 1 has the marking portion 7 formed on the annular surface 3b of the peripheral flange portion 3 on the second lens surface 1b side, the optical axis adjustment (coma aberration correction) is performed by rotating the mirror core in the resin molding die. ) And an objective lens with good aberration performance can be obtained.

Further, when the objective lens 1 is incorporated in the optical pickup 100, the astigmatism direction of the objective lens 1 can be adjusted to a predetermined direction using the marking portion 7 as a mark. For example, astigmatism due to astigmatism between the blue-violet laser light source 101 and the red laser light source 111, astigmatism generated in the polarization beam splitter 102, the quarter-wave plate 103, the collimating lens 104, the mirror 105, and the like, and the objective lens It is possible to adjust the angle of the objective lens 1 (rotational adjustment in the circumferential direction) in the direction in which the astigmatism of 1 cancels out. Therefore, the performance of the optical pickup 100 can be improved, and the BD 60 and the DVD 70 can be recorded or reproduced satisfactorily.

Here, when the objective lens 1 is incorporated into the optical pickup 100, the marking portion 7 can be easily aligned in a predetermined direction by using a plurality of angle target portions formed radially on the lens holder 109a.

FIG. 12 is a diagram showing a schematic shape of the lens holder 109a of the objective lens actuator 109 shown in FIG. The angle target portion 109c is a step portion formed radially around the seating surface (the surface on which the objective lens 1 is mounted) of the lens holder 109a. The angle target portion 109c is formed of a notch, a groove, a protrusion, or the like, and is a concave portion or a convex portion that forms a step with the periphery of the angle target portion 109c, and a plurality (for example, six in this example) are provided. Note that the angle target portions 109c are not necessarily arranged at equal intervals. For example, if the direction is clear, such as the radial direction Rd of the optical pickup (radial direction of the optical disc (BD60 or DVD 70)) and the tangential direction Tn (tangential direction of the optical disc), the angle target portion in that direction is omitted. Also good.

In addition, depending on the shape of the lens holder, the spacer (protector) for preventing the objective lens from colliding with the optical disk, the arrangement of the adhesive reservoir area for preventing the adhesive from flowing out, etc. It may be difficult to form. For example, FIG. 12 shows a case where six angle target portions 109c with an interval of 30 ° are provided. That is, in the circumferential direction (clockwise direction), six angle target portions 109c are formed in directions of 30 °, 60 °, 120 °, 240 °, 300 °, and 360 °, and the radial direction Rd ( The angle target portions in the direction of 0 °, 180 °) and the tangential direction (90 °, 270 °) are omitted.

In the above case, the angle target portion 109c is provided in the vicinity of the spacer (protector) 109d for preventing the objective lens 1 from colliding with the optical disc and the adhesive reservoir region 109e for preventing the adhesive from flowing out. Although not formed, it is sufficient to align the marking portion 7 of the objective lens 1 in a predetermined direction.

As described above, the optical pickup 100 according to the present embodiment uses the plurality of angle target portions 109c formed radially on the lens holder 109a and the marking portion 7 of the objective lens 1 having excellent visibility. Since the angle adjustment (rotational adjustment in the circumferential direction) of the objective lens 1 is facilitated, no equipment such as a microscope is required, and the number of work steps can be reduced and the cost of the optical pickup can be reduced.

Note that the optical pickup includes a two-wavelength light source that emits red laser light and infrared laser light instead of the red laser light source 111, and the objective lens 1 is a blue-violet laser light for recording or reproducing information on the BD. Diffraction for condensing red laser light for recording or reproducing information on DVD and infrared laser light for recording or reproducing information on CD using a wavelength difference as a small light spot, respectively. When the structure is provided, each of BD, DVD, and CD can be recorded or reproduced satisfactorily.

Further, the optical pickup includes a blue-violet laser light source that emits at least blue-violet laser light, and the objective lens 1 condenses the blue-violet laser light for recording or reproducing information as a minute light spot only on the BD. Needless to say, even in this case, it is possible to record or reproduce BDs satisfactorily.

(Embodiment 3)
FIG. 13 is a schematic configuration diagram of the optical disc apparatus according to the present embodiment. An optical disc apparatus 300 shown in FIG. 13 includes an optical disc driving unit 301, a control unit 302, and an optical pickup 100 therein.

The optical disk drive unit 301 includes a motor for rotationally driving the BD 60 (or DVD 70), and has a function of rotationally driving the BD 60 (or DVD 70). The optical pickup 100 is the optical pickup described in the second embodiment. The control unit 302 has a function of driving and controlling the optical disc driving unit 301 and the optical pickup 100, a function of performing signal processing of a control signal and an information signal received by the optical pickup 100, and an information signal to the optical disc apparatus 300. Has a function of interfacing with the outside of the inside.

Since the optical disc apparatus 300 is equipped with the optical pickup described in the second embodiment, the BD 60 and the DVD 70 can be recorded or reproduced satisfactorily.

In addition, the optical disc apparatus 300 is mounted with an optical pickup including an objective lens used as a compatible objective lens for a BD using a blue-violet laser beam, a DVD using a red laser beam, and a CD using an infrared laser beam. Thus, each of BD, DVD, and CD can be recorded or reproduced satisfactorily.

The aspects of the present invention will be described from the above embodiments as follows. That is, an objective lens according to an aspect of the present invention is an objective lens that is molded using a resin molding die including a first barrel mold and a second barrel mold, and the objective lens has a numerical aperture NA. 0.7 or more objective lens made of resin, having a first optical surface and a second optical surface facing the first optical surface, and the main body on the outer periphery of the main body And the first optical surface is formed by a first specular core that is inserted into the first body mold and is rotatably supported, and the second optical surface. Is formed by a second mirror core that is inserted into the second barrel mold and is rotatably supported, and the flange portion is an annular surface formed on the second optical surface side by the second barrel mold. And the ring by an eject pin supported by the second body mold so as to freely advance and retract. Astigmatism direction of the objective lens formed by the second cylinder mold processing mark at a position different from the position where the protrusion mark is formed on the annular surface and the protrusion mark formed on the surface And a marking portion.

In this objective lens, the first optical surface is formed by a first specular core that is inserted into the first body mold and is rotatably supported, and the second optical surface is inserted into the second body mold. Since it is formed by the second mirror core that is rotatably supported, the optical axis adjustment (coma aberration correction) can be easily performed by the rotation of the first and second mirror cores. In addition, the flange portion has an annular surface formed on the second optical surface side by the second body mold, and a protruding portion trace is formed on the annular surface by the eject pin that is supported by the second body mold so as to freely advance and retract. At the same time, the marking portion indicating the direction of astigmatism of the objective lens is formed by the second barrel-shaped processing mark at a position different from the position where the protruding part mark is formed on the annular surface. The marking portion can be formed at a predetermined position while maintaining the relationship with the direction of astigmatism without being affected by the optical axis adjustment due to the rotation of the second specular core, and A marking part can be easily visually recognized by contrast.

As a result, it is possible to achieve both the formation of the marking portion indicating the direction of astigmatism and the optical axis adjustment (coma aberration correction) by the rotation of the first and second specular cores. Excellent aberration performance can be obtained. Furthermore, in an objective lens made of a synthetic resin having a high NA, it is possible to provide an excellent objective lens that has a small effect on the aberration due to the formation of the marking portion and has improved the visibility of the marking portion.

The marking portion is preferably formed within a range of 180 ± 10 ° in the circumferential direction with respect to the gate portion formed by the inflow passage of the resin material when the objective lens is molded. In this case, the generation of astigmatism due to molding defects or the like can be suppressed, and the generation of coma aberration can be suppressed.

It is preferable that the protrusion traces include a plurality of protrusion traces arranged symmetrically with respect to a straight line connecting the optical axis of the objective lens and the gate portion. In this case, the occurrence of coma aberration can be suppressed.

It is preferable that the flange portion has an annular surface formed on the first optical surface side by the first mirror surface core. In this case, since the annular surface on the first optical surface side serving as a reference surface when the objective lens is mounted on the optical pickup can be formed with high accuracy, the objective lens can be attached to the optical pickup with high accuracy. it can.

The flange portion may have an annular surface formed on the first optical surface side by the first body mold. In this case, the first optical surface can be formed with higher accuracy by the first mirror core.

The effective diameter of the second optical surface is smaller than the effective diameter of the first optical surface, and the flange portion has a stepped portion formed inside the annular surface on the second optical surface side. Preferably, the outer diameter of the stepped portion is larger than the effective diameter of the first optical surface.

In this case, the annular portion on the second optical surface side and the first optical surface are sufficiently separated by the step portion, and the flow of the resin during molding becomes smooth. The flatness of the annular surface can be improved. As a result, the measurement laser beam can be accurately reflected using the annular surface on the second optical surface side as a reflection plane, so that the inclination of the objective lens can be accurately determined from the angle of the reflected light of the measurement laser beam. Thus, the relative inclination between the optical pickup and the objective lens can be adjusted with high accuracy.

It is preferable that the marking part is a convex part formed by transferring a processing mark formed by cutting the second body mold. In this case, the marking portion can be easily formed, and the protruding portion trace is usually a recess, so that the contrast with the protruding portion trace becomes clearer and the marking portion visibility is further improved. Can do.

The cross-sectional shape of the convex portion is preferably a convex lens shape. In this case, when viewed from the upper surface of the objective lens, the visibility of the marking portion can be dramatically improved by the lens action (refractive action) of the marking portion.

The side wall of the marking part may be inclined. Also in this case, the visibility of the marking portion can be dramatically improved by the refractive action.

The inclination angle of the side wall of the marking part is preferably 20 ° or more and 50 ° or less. In this case, it is possible to achieve a balance between the processability of the processing marks on the mold and the visibility of the marking portion.

The surface roughness of the marking portion is preferably different from the surface roughness of the flange portion. In this case, the visibility of the marking portion can be further improved.

The surface roughness of the marking part is preferably smaller than the surface roughness of the flange part. In this case, it is possible to improve the visibility of the marking portion and suppress the mold processing cost.

The marking portion may be formed by transferring a rough surface process formed by irradiating the second body mold with an electron beam. Also in this case, it is possible to achieve both the formation of the marking portion indicating the direction of astigmatism and the optical axis adjustment (coma aberration correction) by the rotation of the first and second mirror cores.

The shape of the marking portion is preferably a substantially oval shape in which the length in the circumferential direction of the objective lens is shorter than the length in the radial direction of the objective lens. In this case, it is usually easy to distinguish from the circular protrusion mark, and the width in the circumferential direction can be reduced while ensuring the visibility of the marking part. (Rotational adjustment in the circumferential direction) can be performed.

The length of the marking portion in the radial direction of the objective lens is L (mm), the width of the marking portion in the circumferential direction of the objective lens is W (mm), and the height of the marking portion from the flange portion is When H (mm), the marking portion preferably satisfies the following formula:
0.2 ≦ L ≦ 0.5
0.05 ≦ W ≦ 0.25
0.003 ≦ H ≦ 0.025
Moreover, it is more preferable that the marking portion satisfies the following formula.

0.25 ≦ L ≦ 0.45
0.08 ≦ W ≦ 0.15
0.005 ≦ H ≦ 0.020

In these cases, it is possible to easily form a marking portion that does not affect the optical performance while ensuring visibility.

An optical pickup according to another aspect of the present invention includes a light source that emits laser light, at least the objective lens that converges the laser light on an information recording surface of the information recording medium, and a laser reflected by the information recording medium. A light receiving portion for receiving light.

This optical pickup uses the above-mentioned objective lens, so that BD or the like can be recorded or reproduced satisfactorily.

The optical pickup further includes an actuator for driving a lens holder on which the objective lens is mounted in at least two axial directions, and a radial step portion around the seat surface of the lens holder with the optical axis of the objective lens as a center. It is preferable that a plurality of is formed.

In this case, it is easy to adjust the angle of the objective lens (rotational adjustment in the circumferential direction) by using a plurality of step portions formed radially on the lens holder and the marking portion of the objective lens having excellent visibility. This eliminates the need for equipment such as a microscope, thereby reducing the number of work steps and reducing the cost of the optical pickup.

An optical disc apparatus according to another aspect of the present invention includes the above optical pickup, a motor for rotationally driving an information recording medium, and a control unit that controls the optical pickup and the motor.

In this optical disk apparatus, since the above objective lens is used, BD or the like can be recorded or reproduced satisfactorily.

A resin molding die according to another aspect of the present invention is a resin molding die for manufacturing a resin objective lens having a numerical aperture NA of 0.7 or more, wherein the first mold of the objective lens is used. A first mirror core that forms an optical surface; a second mirror core that forms a second optical surface facing the first optical surface; and the first mirror core inserted with the first mirror core. A first body mold that rotatably supports the second mirror surface core, and the second mirror surface core is rotatably supported by the second optical surface side of the flange portion of the objective lens. A second body mold that forms an annular surface; and an eject pin that is supported by the second body mold so as to be able to move forward and backward. The eject pin forms a protruding mark on the annular surface, and the second body The mold is at a position different from the position where the protruding portion trace is formed on the annular surface, By forming the Engineering traces, forming a marking unit for indicating the direction of the astigmatism of the objective lens.

By using this resin molding die, it is possible to achieve both the formation of the marking portion indicating the direction of astigmatism and the optical axis adjustment (coma aberration correction) by the rotation of the first and second mirror cores, An objective lens having aberration performance superior to that of a conventional objective lens can be manufactured.

An objective lens manufacturing method according to another aspect of the present invention is a method of manufacturing an objective lens that uses a resin molding die to manufacture a resin objective lens having a numerical aperture NA of 0.7 or more, The resin molding die includes a first mirror core that forms a first optical surface of the objective lens, a second mirror core that forms a second optical surface facing the first optical surface, A first barrel type in which the first mirror core is inserted to rotatably support the first mirror core; and the second mirror core is inserted to rotatably support the second mirror core. A second body mold that forms an annular surface on the second optical surface side of the flange portion of the objective lens; and an eject pin that is supported by the second body mold so as to be able to advance and retreat, and using the eject pin. , A step of forming protrusion marks on the annular surface, and the second body mold And forming a marking portion indicating the direction of astigmatism of the objective lens by forming a processing mark at a position different from the position where the protrusion mark is formed on the annular surface. Including.

This objective lens manufacturing method makes it possible to achieve both the formation of the marking portion indicating the direction of astigmatism and the optical axis adjustment (coma aberration correction) by rotating the first and second mirror cores. An objective lens having aberration performance superior to that of the lens can be manufactured.

The objective lens according to the present invention can achieve both the formation of the marking portion indicating the direction of astigmatism and the correction of coma aberration by adjusting the optical axis by rotating the resin molding die (mirror core). It has excellent performance and is useful as an objective lens with a high NA used for an optical pickup for recording or reproducing a high density optical disk such as a BD. In addition, an optical pickup and an optical disc apparatus using the objective lens are useful because they can record or reproduce BD and the like satisfactorily.

Claims

An objective lens molded using a resin molding die having a first barrel mold and a second barrel mold,
The objective lens is a resin objective lens having a numerical aperture NA of 0.7 or more,
A main body having a first optical surface and a second optical surface facing the first optical surface;
A flange portion formed integrally with the main body portion on the outer peripheral portion of the main body portion;
The first optical surface is formed by a first mirror core that is inserted into the first body mold and supported rotatably.
The second optical surface is formed by a second specular core that is inserted into the second barrel mold and supported rotatably.
The flange portion is
An annular surface formed on the second optical surface side by the second body mold;
A protrusion mark formed on the annular surface by an eject pin supported by the second body mold so as to freely advance and retract;
A marking portion formed by the second barrel-shaped processing mark at a position different from the position where the protrusion mark is formed on the annular surface, and indicating a direction of astigmatism of the objective lens. A characteristic objective lens.
The marking portion is formed within a range of 180 ± 10 ° in a circumferential direction with respect to a gate portion formed by an inflow passage of a resin material when the objective lens is molded. The objective lens according to 1.
3. The objective lens according to claim 2, wherein the protrusion trace includes a plurality of protrusion traces arranged symmetrically with respect to a straight line connecting the optical axis of the objective lens and the gate portion.
4. The objective lens according to claim 1, wherein the flange portion has an annular surface formed on the first optical surface side by the first mirror core.
The objective lens according to any one of claims 1 to 3, wherein the flange portion has an annular surface formed on the first optical surface side by the first body mold.
The effective diameter of the second optical surface is smaller than the effective diameter of the first optical surface,
The flange portion has a step portion formed inside the annular surface on the second optical surface side,
6. The objective lens according to claim 1, wherein a diameter of an outer peripheral side of the step portion is larger than an effective diameter of the first optical surface.
The objective lens according to any one of claims 1 to 6, wherein the marking portion is a convex portion formed by transferring a machining mark formed by cutting the second body mold. .
The objective lens according to claim 7, wherein a cross-sectional shape of the convex portion is a convex lens shape.
The objective lens according to claim 7, wherein a side wall of the marking portion is inclined.
The objective lens according to claim 9, wherein an inclination angle of a side wall of the marking portion is 20 ° or more and 50 ° or less.
The objective lens according to claim 7, wherein the surface roughness of the marking portion is different from the surface roughness of the flange portion.
The objective lens according to claim 11, wherein the surface roughness of the marking portion is smaller than the surface roughness of the flange portion.
2. The objective lens according to claim 1, wherein the marking portion is formed by transferring a rough surface process formed by irradiating the second body mold with an electron beam.
The shape of the marking portion is a substantially oval shape in which the length in the circumferential direction of the objective lens is shorter than the length in the radial direction of the objective lens. Objective lens described in 1.
The length of the marking portion in the radial direction of the objective lens is L (mm), the width of the marking portion in the circumferential direction of the objective lens is W (mm), and the height of the marking portion from the flange portion is The objective lens according to claim 14, wherein when H (mm) is satisfied, the marking portion satisfies the following expression.
0.2 ≦ L ≦ 0.5
0.05 ≦ W ≦ 0.25
0.003 ≦ H ≦ 0.025
The objective lens according to claim 15, wherein the marking portion satisfies the following expression.
0.25 ≦ L ≦ 0.45
0.08 ≦ W ≦ 0.15
0.005 ≦ H ≦ 0.020
A light source that emits laser light;
An objective lens according to any one of claims 1 to 16, wherein at least the laser beam is converged on an information recording surface of an information recording medium;
An optical pickup comprising: a light receiving portion that receives the laser light reflected by the information recording medium.
An actuator for driving the lens holder on which the objective lens is mounted in at least two axial directions;
The optical pickup according to claim 17, wherein a plurality of radial step portions around the optical axis of the objective lens are formed around a seating surface of the lens holder.
An optical pickup according to claim 17 or 18,
A motor for rotationally driving the information recording medium;
An optical disc apparatus comprising: a control unit that controls the optical pickup and the motor.
A resin molding die for producing a resin objective lens having a numerical aperture NA of 0.7 or more,
A first specular core forming a first optical surface of the objective lens;
A second specular core forming a second optical surface facing the first optical surface;
A first body mold in which the first mirror core is inserted and rotatably supports the first mirror core;
A second barrel mold in which the second mirror core is inserted, rotatably supports the second mirror core, and forms an annular surface on the second optical surface side of the flange portion of the objective lens;
An eject pin supported by the second body mold so as to freely advance and retract,
The eject pin forms a protruding mark on the annular surface,
The second barrel mold forms a marking portion indicating the direction of astigmatism of the objective lens by forming a processing mark at a position different from the position where the protruding portion mark is formed on the annular surface. A mold for resin molding characterized by the above.
An objective lens manufacturing method for manufacturing a resin objective lens having a numerical aperture NA of 0.7 or more using a resin molding die,
The resin mold is
A first specular core forming a first optical surface of the objective lens;
A second specular core forming a second optical surface facing the first optical surface;
A first body mold in which the first mirror core is inserted and rotatably supports the first mirror core;
A second barrel mold in which the second mirror core is inserted, rotatably supports the second mirror core, and forms an annular surface on the second optical surface side of the flange portion of the objective lens;
An eject pin supported by the second body mold so as to freely advance and retract,
Using the eject pin to form a protruding mark on the annular surface;
A marking portion that indicates the direction of astigmatism of the objective lens by forming a processing mark at a position different from the position at which the protrusion mark is formed on the annular surface using the second body mold. Forming an objective lens.