JP2000033653A - Optical element and apparatus for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately produce an optical element. SOLUTION: An optical element 1 has a recessed part 1a provided to one surface thereof and a flat diffraction plane 4 having a diffraction lattice 3 is formed to the almost central part of the recessed part 1a and first and second bent surfaces 5a, 5b respectively inclined so as to become recessed parts are provided on both sides of the diffraction plane 4. In a mold for producing the optical element 1, a material is poured from a gate part 25 provided at a position not interfered with the mold member forming the first bent surface 5a or the second bent surface 5b to form the optical element 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an optical element and an optical element manufacturing apparatus, and more particularly to an optical element and an optical element manufacturing apparatus capable of manufacturing an optical element with high accuracy.

[0002]

2. Description of the Related Art In recent years, an optical recording medium represented by an optical disk has been widely used as a recording medium. When reproducing information recorded on the optical disk or recording information on the optical disk or the like, a general method is used. An optical pickup device is typically used. The optical pickup device outputs laser light from a laser diode to an optical disc or the like,
Reproduction is performed by detecting light reflected by the optical disk. Recently, miniaturization of the optical pickup device has been promoted, and a so-called integrated optical pickup device in which a laser diode as a light source and a photodiode as a light receiving portion are formed on one substrate may be used. The integrated optical pickup device and other optical pickup devices irradiate the optical disc with three spots of light in order to detect a tracking servo error during reproduction. These three spots are formed when laser light output from a laser diode is incident on a diffraction grating (grating).

FIG. 5 is a view showing an example of an optical element mounted as a part of the configuration of the integrated optical pickup device. The optical element 1 will be described with reference to FIG. The concave portion 1a is provided on the bottom surface of the optical element 1 in FIG.
Are formed, and the diffraction plane 4 and the refraction surfaces 5a and 5b are formed in the concave portion 1a. A diffraction grating 3 is formed on the diffraction plane 4, and a laser diode is arranged below the diffraction grating 3. As shown in FIG. 5B, the diffraction grating 3 diffracts the laser light output from the laser diode to form three spots of light.

[0004] Refraction surfaces 5 a and 5 b are formed on both sides of the diffraction grating 3, and the refraction surfaces 5 a and 5 b are inclined with respect to the diffraction plane 4. Therefore, the refraction surfaces 5a and 5b further form the recesses 5d and 5e in the recess 1a. The laser light is applied to the optical disk via the diffraction grating 3, and the return light is incident on the diffraction grating 2. The return light diffracted by the diffraction grating 2 is refracted by the refraction surfaces 5a and 5b and enters the photodiode. Information and the like on the optical disk are read based on the signal detected by the photodiode.

FIG. 6 is a system diagram showing an example of a conventional optical element manufacturing apparatus for manufacturing the optical element 1. The optical element manufacturing apparatus 6 will be described in detail with reference to FIG. The optical element manufacturing apparatus 6 shown in FIG.
Gate section 8, first mold 9a, second mold 9b, third mold 9
c. The first mold 9a and the second mold 9b have hollow portions in which the outer shape of the optical element is formed.
The mold 9a and the second mold 9b are joined to form the optical element 1. The second mold 9b has a hole, into which the third mold 9c is inserted. The third mold 9c is a mold that is integrally formed, and forms the concave portion 1a of the optical element 1. Therefore, the projections 9d and 9e for forming the recesses 5d and 5e are formed on the third mold 9c.

A gate 8 is formed on the joint surface between the first mold 9a and the second mold 9b, and the gate 8 is provided on the third mold 9c on the side of the protrusion 9d or 9e. ing. That is, the gate portion 8 is formed in the direction in which the refraction surfaces 5a and 5b are formed with respect to the diffraction plane 4 in FIG. The gate section 8 is connected to the resin supply section 7, and the material of the optical element 1 flows into the mold 9 from the resin supply section 7.

[0007]

The respective molds 9 as shown in FIG.
When an optical element is manufactured by injection molding using a, 9b, and 9c, the resin flows into the mold 9 over the refraction surface 5b of the third mold 9c. This resin flow is the third
After hitting the part 9e of the mold 9c, it flows over the part 9e to the part of the diffraction plane 5a. At this time, there is a case where the resin of the third mold 9c gets over the diffraction plane 5a while entraining air (air accumulation), and there is a problem that the shape of the optical element cannot be accurately transferred.

Although the air in the mold 9 needs to be discharged to the outside of each of the molds 9a, 9b and 9c in the injection molding, since the third mold 9c is integrally formed, the first mold 9a is formed. Air can be removed only from the joint surface between the first mold 9b and the second mold 9b. Therefore, there is a problem that air remaining on the diffraction plane 5a and the refraction planes 5b and 5c cannot be discharged. Further, since the gate portion 8 is provided in the direction of the arrow X1, that is, in a direction substantially parallel to the direction in which the refraction surface is formed with respect to the diffraction plane, when the resin flows from the gate portion 4 into the mold. The resin hits the third mold 9e. When this resin is applied, the position of the third mold 9c may be shifted, and there is a problem that the dimensions of the molded optical element 1 are shifted.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide an optical element manufacturing apparatus with high dimensional accuracy.

[0010]

According to the first aspect of the present invention, there is provided a flat diffraction element having a concave portion provided on one surface of an optical element and having a diffraction grating formed substantially at the center of the concave portion. An optical element having a plane and a first refraction surface and a second refraction surface which are respectively inclined so as to form a concave portion on both sides of the diffraction plane, wherein the first element is formed in a mold for manufacturing the optical element. This is achieved by an optical element formed by pouring a material from a gate portion provided at a position where there is no interference by the mold member forming the refractive surface or the second refractive surface.

According to the structure of the first aspect, the optical element is the first element.
It is formed by pouring a material from a gate portion provided at a position where no interference occurs with a mold member forming the refraction surface or the second refraction surface. Accordingly, the portion forming the first refraction surface or the second refraction surface does not obstruct the flow of the optical element material flowing into the gate portion. Therefore, it is possible to prevent the occurrence of air pockets in the optical element 1 and improve the dimensional accuracy.

[0012] According to a second aspect of the present invention, the above object is provided, in the configuration of the first aspect, the diffraction plane of the optical element,
This is achieved by an optical element in which the first refraction surface and the second refraction surface are formed by different molds. Claim 2
According to the configuration described above, by forming the diffraction plane, the first refraction surface, and the second refraction surface with different molds, the air in the mold, particularly the diffraction plane, the first refraction surface, and the air in the mold from the gap between the molds. Because the air accumulated on the second refraction surface can be removed,
The shape of the optical element can be accurately formed.

According to a third aspect of the present invention, the above object is achieved by the optical element material of the first aspect, wherein the optical element material is a plastic. According to the configuration of the third aspect, by using plastic as the material of the optical element, the optical element can be manufactured at low cost.

According to a fourth aspect of the present invention, there is provided a flat diffraction plane having a diffraction grating formed substantially at the center of a concave portion provided on one surface of an optical element; On both sides of the optical element manufacturing apparatus for manufacturing an optical element having a first refraction surface and a second refraction surface that are further inclined so as to form a concave portion, an internal space corresponding to the shape of the optical element is provided. A first mold and a second mold formed so as to be joined to each other, and the first mold and the first mold of the optical element.
Placed at a location corresponding to the plane, a diffraction plane mold corresponding to the diffraction plane, and disposed on both sides of the diffraction plane mold,
A third mold comprising a first refraction surface mold and a second refraction surface mold further projecting from the diffraction plane mold, and protruding portions of the first refraction surface mold and the second refraction surface mold This is achieved by an optical element manufacturing apparatus having a gate formed at a position where the material of the optical element is not interfered with, and through which a material of the optical element flows into the mold.

According to the configuration of claim 4, the optical element is the first element.
It is formed by pouring a material from a gate portion provided at a position where no interference occurs with a mold member forming the refraction surface or the second refraction surface. Thus, the portion of the third mold that forms the first refraction surface or the second refraction surface does not obstruct the flow of the optical element material flowing into the gate portion.
Therefore, it is possible to prevent so-called air pockets from occurring in the optical element 1 and improve dimensional accuracy.

According to a fifth aspect of the present invention, in the configuration of the fourth aspect, the diffraction plane mold, the first refraction surface mold, and the second refraction surface mold are respectively different molds. This is achieved by the optical elements formed. According to the configuration of claim 5, the diffraction plane mold, the first refraction plane mold, and the second
By forming the refraction surface molds with different molds, the air in the molds, especially the diffraction plane,
Since air trapped on the first refraction surface and the second refraction surface can be removed, the shape of the optical element can be accurately formed.

According to a sixth aspect of the present invention, the above object is achieved by an optical element in which the material of the optical element is plastic. According to the configuration of claim 6, by using plastic as the material of the optical element, the optical element can be manufactured at low cost.

[0018]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Note that the embodiments described below are preferred specific examples of the present invention,
Although various technically preferable limits are given, the scope of the present invention is not limited to these modes unless otherwise specified in the following description.

FIG. 1 is a view showing an example of the optical element of the present invention. The optical element 1 will be described with reference to FIG. The optical element 1 is a lens mounted on an integrated optical pickup device, and is formed in a substantially trapezoidal shape. The optical element 1 includes diffraction gratings 2 and 3, a diffraction plane 4, and refraction surfaces 5a and 5a.
b, a gate section 6 and the like. The diffraction grating 2 is formed on the upper surface of the optical element 1. The diffraction grating 2 diffracts the return light from the optical disk to form three spots of light.
A concave portion 1a is formed on the bottom surface of the optical element 1, and a diffraction grating 3 is formed at the center. A laser diode is arranged below the diffraction grating 3, and laser light emitted from the laser diode is diffracted by the diffraction grating 3,
Light of three spots is formed.

FIG. 2 is an enlarged sectional view of the lower portion of the optical element 1. The diffraction plane 4 and the refraction grating surfaces 5a and 5b will be described in detail with reference to FIGS. The diffraction plane 4 is formed almost flat in the center of the concave portion 1a, and the diffraction grating 3 is formed almost in the center of the diffraction plane 4.
A first refraction surface 5a and a second refraction surface 5b on both sides of the diffraction plane 4
Are formed. First refraction surface 5a and second refraction surface 5b
Are inclined with respect to the diffraction plane 4 by an angle θ, and further concave portions 5c and 5d are formed in the concave portion 1a. The refracting surfaces 5a and 5b refract the return light diffracted into three spots by the diffraction grating 2 and output the refracted light to a photodetector of an optical pickup (not shown).

FIG. 3 is a sectional view showing a preferred embodiment of the optical element manufacturing apparatus of the present invention. The optical element manufacturing apparatus will be described in detail with reference to FIG. The lens manufacturing apparatus 10 of FIG. 3 includes a mold 20, a resin supply unit 30, and the like. The mold 20 includes a first mold 21, a second mold 22,
The third mold 23 is formed. The mold 20 is held by a base material (not shown). Each of the first mold 21 and the second mold 22 has a hollow portion in which the outer shape of the optical element 1 is formed, and is held movably in the arrow Z direction.

FIG. 4 is a cross-sectional view of a portion around the third mold 23. The third mold 23 will be described in detail with reference to FIGS. The third mold 23 shown in FIG. 3 and FIG.
Forming a concave portion 1a of the optical element 1 shown in FIG.
It is inserted into the through hole 22 a of the second mold 22. The third mold 23 includes a diffraction plane mold 23a, a refraction plane mold 23b, and 23.
c. Refraction surface molds 23b and 23c are arranged on both sides of the diffraction plane mold 23a.
3a and the refraction surface molds 23b and 23c
A diffraction plane 5a and refraction planes 5b and 5c are formed. Therefore, the refraction surface dies 23b and 23c are formed with the projections 23d and 23e in order to form the recesses 5c and 5d in the recess 1a in FIG.
Are formed.

Next, referring to FIG. 3 and FIG.
Will be described in detail. 3 is formed on the joint surface between the first mold 21 and the second mold 22, and when the material of the optical element 1 flows, the refraction surface molds 23b, 2b.
3c is provided at a position that does not interfere with the projections 23d and 23e. That is, the gate portion 25 is provided in the diffraction plane mold 2.
It is formed on a side D2 substantially perpendicular to the direction D1 where the refraction surface dies 23b and 23c are formed with respect to 3a.

The gate section 25 is connected to a resin supply section 30, and the resin supply section 30 contains a resin as a material of an optical element. The resin contained in the gate 25
The resin is injected into the space in the mold 20 by hydraulic pressure or the like via the. This resin is, for example, plastic, and the optical element 1 of FIG. 1 can be produced at low cost by using plastic.

Next, a method for manufacturing the optical element 1 using the lens manufacturing apparatus 10 will be described in detail with reference to FIGS. First, the first mold 21, the second mold 22, and the third mold 23 are combined and the resin supply unit 30 and the gate unit 2 are combined.
5 is supplied with resin. At this time, since the gate portion 25 of FIG. 4 is formed at a position where the gate portion 25 does not interfere with the protrusions 23d and 23e, the flow of the resin is not interrupted.
Therefore, the flow of the resin becomes smooth, and the occurrence of air pools due to entrainment of air can be prevented.

The resin supply section 30 continues to supply the resin until the mold 20 is completely filled. At this time, the first mold 2
1 and the second mold 22, the second mold 22 and the third mold 2
3 and diffraction plane mold 23a and refraction plane mold 23
The air in the mold 20 is evacuated from the joint surfaces b and 23c. Diffraction plane mold 23a and refraction plane mold 23b, 23
By allowing air to be evacuated also from the joint surface of c, the diffraction plane 5a and the refraction surface 5
Air pools at b and 5c can be reliably removed. Then, after the resin in the mold 20 is solidified, the optical element 1 is completed.

According to the above embodiment, the resin is
Since the gate portion 25 is provided so that the refractive surface molds 23b and 23c do not hinder the flow of the resin when flowing into the optical element 1, the optical element 1 can be provided with high accuracy. In addition, by forming the third mold 23 into a split structure, the air at the time of injecting the resin escapes from between the third molds 23, so that a shape defect due to the air can be prevented. Therefore, the yield is improved by improving the moldability of the optical element 1 and the optical element 1 is improved.
Cost can be reduced. Further, the third mold 2
By dividing the structure of FIG.
Since the mold 3a can be planarized and a mold processing process utilizing a semiconductor process can be used, the mold 20 can be manufactured at low cost.

[0028]

As described above, according to the present invention,
An optical element manufacturing apparatus for manufacturing an optical element having good dimensional accuracy can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a preferred embodiment of an optical element of the present invention.

FIG. 2 is a cross-sectional view showing a peripheral portion of a concave portion in the optical element of the present invention.

FIG. 3 is a cutaway perspective view showing a preferred embodiment of the optical element manufacturing apparatus of the present invention.

FIG. 4 is a cross-sectional view illustrating a portion around a third mold in the optical element manufacturing apparatus of the present invention.

FIG. 5 is a diagram showing an optical element constituting the optical pickup.

FIG. 6 is a sectional view showing an example of a conventional optical element manufacturing apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical element, 3 ... Diffraction grating, 5a ... Diffraction plane, 5b, 5c ... Refractive surface, 10 ... Optical element manufacturing apparatus, 20 ... Mold, 21 ... 1st mold, 22 ・
..Second mold, 23 ... third mold, 23a ... diffraction plane forming mold, 23b, 23c ... refractive surface forming mold,
25: gate section, 30: resin supply section.

 ──────────────────────────────────────────────────の Continued on the front page F term (reference) 2H042 AA03 AA05 AA20 AA31 2H049 AA02 AA04 AA14 AA31 AA43 AA51 AA57 AA63 4F202 AA00 AH33 AH73 CA11 CB01 CK06 4F213 AA00 AH33 AH73 WA05 WB01WC01

Claims (6)

[Claims] A concave portion is provided on one surface of an optical element, and a flat diffraction plane having a diffraction grating formed substantially at the center of the concave portion, and further concave portions on both sides of the diffraction plane so as to form a concave portion. An optical element having an inclined first refraction surface and a second refraction surface, which is not interfered by a mold member forming the first refraction surface or the second refraction surface in a mold for manufacturing the optical element. An optical element formed by pouring a material from a gate portion provided at a position. 2. The diffraction plane of the optical element, the first
The optical element according to claim 1, wherein the refracting surface and the second refracting surface are formed by different molds, respectively. 3. The optical element according to claim 1, wherein the material of the optical element is plastic. 4. A concave portion is provided on one surface of an optical element, and a flat diffraction plane having a diffraction grating formed substantially at the center of the concave portion, and a concave portion on both sides of the diffraction plane so as to form a concave portion. An optical element manufacturing apparatus for manufacturing an optical element having an inclined first refracting surface and a second refracting surface, comprising: a first metal formed so as to be connectable to each other so as to have an internal space corresponding to the shape of the optical element; A mold and a second mold; a diffraction plane mold disposed at a location corresponding to the one surface of the optical element; a diffraction plane mold corresponding to the diffraction plane; and a diffraction plane mold disposed at both sides of the diffraction plane mold. A third refracting surface mold and a second refracting surface mold further protruding from the mold.
A mold, and a gate portion formed at a position where the mold does not interfere with the first refraction surface mold and the second refraction surface mold, for flowing a material of the optical element into the mold. Optical element manufacturing apparatus. 5. The optical element manufacturing apparatus according to claim 4, wherein the diffraction plane mold, the first refraction surface mold, and the second refraction surface mold are divided. 6. The optical element manufacturing apparatus according to claim 4, wherein the material of the optical element is plastic.