JP2001076366A - Optical element for optical pickup and manufacture of optical element for optical pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To unnecessitate addition of a reflection preventing film coating process while lessening the spot size by using a solid immersion lens and moreover to relatively make difficult the generation of a total reflection even in the positional deviation of a laser. SOLUTION: This element is provided with a first substrate 3 in which the objective lens 1 condensing parallel light is provided, a second substrate 7 in which a solid immersion lens 2 whose optical axis coincides with that of the objective lens 1 is provided, and another solid immersion lens 4 which is formed in the inner part of the second substrate 7 and whose optical axis coincides with that of the objective lens 1 and the solid immersion lens 2. And, the first substrate 3 is integrated with the second substrate 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical element for an optical pickup for writing information on an optical disk or reading information written on the optical disk, and a method for manufacturing the optical element for an optical pickup.

[0002]

2. Description of the Related Art Information is written on or read from an optical disk by an element called an optical element for an optical pickup. FIG. 14 shows a schematic configuration of a general optical element for an optical pickup. The illustrated optical element for an optical pickup includes a semiconductor laser 141, a collimator lens 142, a polarization beam splitter 143, a quarter-wave plate 144, an objective lens 145, a condenser lens 146, and a photodiode 147. Note that the actual optical pickup optical element further includes optical components provided for focus detection and track detection, but is omitted in FIG. 14 for simplicity of description.

In the optical element for an optical pickup having such a configuration, the laser beam L is output from the semiconductor laser 141 in a direction parallel to the plane of the drawing. The laser light L passes through the collimator lens 142 and becomes parallel light, and further changes from linearly polarized light to circularly polarized light through the polarizing beam splitter 143 and the quarter-wave plate 144 (both are referred to as an optical isolator). Then, the light is condensed by the objective lens 145 and becomes a spot light S, which is applied to the optical disc 14. When the optical element for an optical pickup is used for writing on the optical disk 14, the spot light S forms a mark on a recording film on the optical disk 14.

On the other hand, when the optical pickup optical element is used for reading information from the optical disk 14, the position and shape of the mark on the optical disk 14 are recognized by the reflected light of the spot light S reflected on the optical disk 14. You.
At this time, when the reflected light of the spot light S is reflected on the optical disk 14, the turning direction of the circularly polarized light changes. And
After passing through the objective lens 145, the light becomes perpendicular to the paper surface by the 波長 wavelength plate 144, is reflected by the polarization beam splitter 143, is collected by the condenser lens 146, and is received by the photodiode 147.

[0005] In recent years, it has been required to form smaller-sized marks on optical discs in order to write information at a higher density, and to read formed smaller-sized marks. For this purpose, it is necessary to further reduce the spot size of the spot light S described above.

In the optical element for an optical pickup having the structure shown in FIG. 14, the e- ² intensity radius r ₂ of the spot light S is obtained by the following equation. 2r ₂ = kλ / NA (1) where k: a constant determined by the diameter of the objective lens 145 and the intensity distribution of the laser light L λ: the wavelength of the laser light L NA: the numerical aperture of the objective lens 145 (= n ₀ ( (Absolute refractive index of object space) · sin θ (sine of emission angle of objective lens 145)) From equation (1), the diameter (spot size) W of spot light S on optical disk 14 is determined by the conditions of objective lens 145 and optical disk 14. Is constant, it can be expressed as follows. W∝λ / sin θ Expression (2)

In order to further reduce the spot size W represented by the equation (2), the objective lens 145 and the optical disk 14
There is a technique in which a front lens (solid immersion lens) having a hemispherical shape is provided between the first lens and the second lens to increase the substantial numerical aperture of the objective lens. Such a technique is disclosed in, for example, JP-A-5-189796 and JP-A-8-315.
No. 404, Japanese Patent Application Laid-Open No. 9-243805, and the like.

FIG. 15 shows a configuration in which a solid immersion lens is provided between the objective lens 145 and the optical disk 14. FIG. 15A shows an example in which a hemispherical solid immersion lens 150 is used. FIG. 1, FIG.
FIG. 5B is a diagram showing an example using a super hemispherical solid immersion lens 151. Note that FIG.
In each of the configurations shown in (a) and (b), the solid immersion lens 150 and the interval between the solid immersion lens 151 and the optical disk 14 are arranged so as to be shorter than the wavelength of the laser light.

The spot size W 'obtained by the configuration shown in FIG. 15A is represented by the following equation (3), where n is the refractive index of the solid immersion lens 150. The spot size W ″ obtained by the configuration in FIG. 15B is different from the solid immersion lens 151.
If the refractive index of the solid immersion lens 151 is n ′, Snell's law is applied on the surface of the solid immersion lens 151, so that W ″ ∝λ / n ′ ² · sin θ ′ can be expressed by the following equation (4). Lens 150
It is possible to obtain a smaller spot size than using.

In the optical element for an optical pickup, the optical disk 14 and the bottom surfaces of the solid immersion lens 150 and the solid immersion lens 151 are arranged very close to each other, such as the wavelength of the laser beam L or less. For this reason, the spot size becomes substantially the same on the surface of the optical disk 14 and on the bottom surfaces of the solid immersion lens 150 and the solid immersion lens 151.

In order to arrange the solid immersion lens 150, the solid immersion lens 151 and the optical disk 14 close to each other, a structure called a flying head as shown in FIG. 16 is used. The flying head shown is a solid immersion lens 150
The suspension 160 is connected to the slider 161 to which is adhered, and the distance d between the bottom surface of the solid immersion lens 150 and the surface of the optical disk 14 can be set to about 100 nm by buoyancy when the optical disk 14 is rotated.

[0012]

However, in the above configuration, it is desirable to provide a glass member having a high refractive index in the material of the solid immersion lens in order to increase the effective numerical aperture and reduce the spot size. . However, using a glass member with a high refractive index
The difference between the refractive index of the glass member and the refractive index of air is increased. When the difference between the glass member and the refractive index of air increases,
There is a possibility that the reflectance on the surface of the solid immersion lens is increased and the light use efficiency is reduced.

For example, while a glass member having a refractive index of 1.5 in air has a reflectance of 4%, a glass member having a refractive index of 1.98 in air has a reflectance of 11%. Therefore, in a conventional optical element for an optical pickup using a solid immersion lens, it is necessary to coat an antireflection film on the surface of the solid immersion lens, and it is necessary to increase the number of steps of manufacturing the optical element for an optical pickup.

In the conventional optical element for an optical pickup, if the solid immersion lens has a super-hemispherical shape, when the mounting position with respect to the laser is deviated from a predetermined position, one of the laser beams passing through the objective lens is removed. The part may be totally reflected on the surface of the solid immersion lens. In such a case, not only the utilization efficiency of the laser light decreases, but also the spot size may increase due to an increase in aberration. Therefore, high precision has been required for attaching the optical element for optical pickup to the laser.

The present invention has been made in view of the above points, and it is not necessary to add an anti-reflection film coating step while reducing the spot size by using a solid immersion lens. It is another object of the present invention to provide an optical element for an optical pickup and a method of manufacturing the optical element for an optical pickup, which are less likely to cause total reflection.

[0016]

The above objects can be attained by the following means. That is, the invention according to claim 1 includes a first substrate provided with an objective lens for converging parallel light, a second substrate provided with a front lens having an optical axis coincident with the objective lens, and a second substrate provided with a first lens. The first substrate and the second substrate are integrated with each other, the first substrate and the second substrate having an objective lens and a front lens having the same optical axis as the front lens. It is characterized by the following.

With this configuration, the difference in the refractive index between the front lens provided on the second substrate and the surroundings is reduced, and light is reflected by the front lens provided on the second substrate. Rate can be reduced. Further, by providing the front lens on the first substrate, the angle of light incident on the front lens provided on the second substrate is increased, and the angle of view of the front lens provided on the second substrate is increased. Can be increased. Furthermore, by forming the objective lens on a separate substrate from the front lens and integrating them, the degree of freedom in the structure of the objective lens can be increased.

According to a second aspect of the present invention, the first substrate and the second substrate
The first substrate and the second substrate are integrated by being bonded to each other, and at least one of the first substrate and the second substrate has a bonding positioning unit indicating a bonding position.

With this configuration, the first substrate and the second substrate can be accurately positioned as designed.

According to a third aspect of the present invention, the first substrate and the second substrate
The board is integrated by laminating,
At least one of the first substrate and the second substrate is the first substrate.
And a spacing means for keeping a constant spacing after bonding the first substrate and the second substrate.

With this configuration, the distance between the first substrate and the second substrate after bonding can be accurately determined and maintained as designed.

According to a fourth aspect of the present invention, the first substrate and the second substrate
The board is integrated by laminating,
At least one of the first substrate and the second substrate has an adhesive groove for releasing the adhesive used for bonding.

With this configuration, the adhesive is uniformly applied inside the adhesive groove.

According to a fifth aspect of the present invention, there is further provided an optical path changing means for changing an optical path of the parallel light incident on the objective lens.

With this configuration, light incident on the objective lens can be selected from any direction.

According to a sixth aspect of the present invention, the objective lens has at least one convex surface.

With this configuration, the objective lens can efficiently collect light, and the degree of freedom in designing the objective lens is increased.

According to a seventh aspect of the present invention, there is provided a step of providing an objective lens for converging parallel light on the first substrate, and a step of forming a front lens having an optical axis coincident with the objective lens on the second substrate. Of the second substrate, a concave shape is formed on the back surface of the surface on which the front lens is formed, and the concave shape is embedded with a member having a higher refractive index than the front lens, whereby the objective lens, the front lens, A step of forming another front lens having the same axis, a step of integrating the first substrate and the second substrate,
It is characterized by including.

With this configuration, an optical element for an optical pickup can be manufactured using the same steps as those for manufacturing a semiconductor. By providing another front lens on the back surface of the surface on which the front lens is formed, the front lens and another front lens can be formed on one substrate.

The invention according to claim 8 is the step of providing an objective lens for converging parallel light on the first substrate and the step of forming a front lens having an optical axis coincident with the objective lens on the second substrate. Forming a concave shape on another substrate and embedding the concave shape with a member having a higher refractive index than the front lens to form another front lens whose optical axis coincides with the objective lens and the front lens. Bonding the back surface of the surface of the second substrate on which the front lens is formed, and the back surface of the surface of the other substrate on which the other front lens is formed; A step of further integrating the integrated second substrate and another substrate with the first substrate.

With this configuration, an optical element for an optical pickup can be manufactured using the same steps as those for manufacturing a semiconductor. Further, by providing the front lens and the other front lens on different substrates, there is no restriction on the selection of the method of forming the front lens.

According to a ninth aspect of the present invention, the method further comprises the step of providing, on at least one of the first substrate and the second substrate, bonding positioning means for indicating a bonding position between the first substrate and the second substrate. It is characterized by including.

With this configuration, it is possible to manufacture an optical element for an optical pickup that can accurately position the first substrate and the second substrate as designed.

According to a tenth aspect of the present invention, in at least one of the first substrate and the second substrate, an interval holding means for keeping a constant interval after bonding the first substrate and the second substrate is provided. The method further includes the step of providing.

With this configuration, it is possible to manufacture an optical element for an optical pickup in which the distance between the first substrate and the second substrate after bonding can be accurately determined and maintained as designed. Can be.

The eleventh aspect of the present invention is characterized by further comprising the step of providing an adhesive groove for releasing the adhesive used for bonding on at least one of the first substrate and the second substrate. Things.

With this configuration, it is possible to manufacture an optical element for an optical pickup in which the adhesive is uniformly applied inside the adhesive groove.

The twelfth aspect of the present invention is characterized by further comprising a step of providing an optical path changing means for changing an optical path of the parallel light incident on the objective lens on the first substrate.

With this configuration, it becomes possible to manufacture an optical element for an optical pickup that can correct even if the light incident on the objective lens is shifted.

According to a thirteenth aspect of the present invention, the objective lens is
It has at least one convex surface.

With this configuration, the objective lens can efficiently condense light, and an optical element for an optical pickup with a high degree of freedom in designing the objective lens can be manufactured.

[0042]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 to 4 of the present invention will be described below. (Embodiment 1) FIG. 1 is a view for explaining one configuration of an optical element for an optical pickup according to Embodiment 1 of the present invention. The optical element for an optical pickup of FIG. 1 includes a first substrate 3 provided with an objective lens 1 for converging a laser beam L as a parallel light, and a solid lens which is a front lens whose optical axis coincides with that of the objective lens 1. A second substrate 7 provided with the immersion lens 2; and a solid immersion lens 4 which is another front lens formed inside the second substrate 7; And the substrate 7 are integrated.

In such a configuration, the solid immersion lens 2 functions as a solid immersion lens having the height of the second substrate 7 as well as the height of the solid immersion lens 2. Therefore, the solid immersion lens 4 is
Can be regarded as provided inside.

In the optical element for an optical pickup of FIG. 1, the first substrate 3 and the second substrate 7 are integrated by bonding. Then, both the first substrate 3 and the second substrate 7 have the spacing member 5 as spacing means for keeping the spacing after bonding the first substrate 3 and the second substrate 7 constant. ing. In the optical element for an optical pickup of the present invention, it is sufficient that the spacing member 5 is provided on at least one of the first substrate 3 and the second substrate 7.

The solid immersion lens 2 and the solid immersion lens 4 shown in FIG. 1 are both super hemispherical solid immersion lenses, and their optical axes (shown by broken lines in the figure) are the light of the objective lens 1. It is arranged so as to coincide with the axis (shown by a broken line in the figure). Also,
The solid immersion lens 2 and the solid immersion lens 4 are arranged such that the center of the solid immersion lens 2 is at a distance n ₁ × r from the original focal position of the objective lens 1.
₁ (indicated by A in the drawing), and the center of the solid immersion lens 4 is shifted from the original focal position of the solid immersion lens 2 by a distance n ₂ /
They are arranged so as to be separated by n ₁ × r ₂ (indicated by B in the figure). In such an arrangement, the distance is determined by the spacing member 5 and is stably maintained after bonding.

Further, the height of the solid immersion lens 2 is given by: r ₁ (1 + 1 / n ₁ ) −r ₂ (n ₂ / n ₁ −n ₁ / n ₂ ) (5) The height is expressed as r ₂ (1 + n ₁ / n ₂ ) (6). However, the above-mentioned characters are
The following numerical values shall be indicated. n ₁ : refractive index of the solid immersion lens 2 r ₁ : radius of the solid immersion lens 2 n ₂ : refractive index of the solid immersion lens 4 r ₂ : radius of the solid immersion lens 4

[0047] Incidentally, the spot size obtained by the objective lens and two solid immersion lens and the optical element for the optical pickup with an integrated, when the refractive index of the solid immersion lens and n _1, n _2, respectively, the refractive index n ₁ , N ₂ with the following relationship. That is, the spot size W ₁ obtained when all the solid immersion lenses are hemispherical can be expressed by the following equation: W ₁ Ｗλ / n ₂ · sin θ Further, as shown in FIG. 1, the spot size W ₂ in which two of the solid immersion lens is obtained when both are of super-hemispherical _{shape, W 2 αλ / (n 2} 2 / n 1) sinθ ... formula ( 8) can be expressed as

The spot light S thus formed
Writes information by forming a recording mark on the recording layer of the optical disc 14,
It is used to read information from the optical disc 14 on the basis of the reflected light. In reading this information, the optical disk 14
Is a phase change type, the magnitude of reflected light due to the difference in reflectance is used, and if the optical disk 14 is a magneto-optical recording type, polarized light is used.

Also, in such an optical element for an optical pickup, a fine structure is provided on the bottom side of the solid immersion lens 4 so that the optical element can be stably floated when used by being attached to the flying head shown in FIG. It can be provided.

The optical element for an optical pickup configured as described above forms a spot light as follows.
That is, the collimated parallel laser light L enters the objective lens 1 and is condensed, travels toward the solid immersion lens 2, and is refracted on the surface of the solid immersion lens 2. Then, due to this refraction, the light enters the surface of the solid immersion lens 4 at a larger angle,
Here, the light is irradiated onto the optical disk 14 as spot light S while being further refracted.

The spot light S is refracted by the super hemispherical solid immersion lens 4 at a substantially high refractive index, and has a large angle of view θ by the solid immersion lens 2. Therefore, the spot size of the spot light S becomes smaller.

According to the optical element for an optical pickup having such a configuration, since the solid immersion lens 4 is provided inside the second substrate 7, the reflectance on the surface of the solid immersion lens 4 is reduced. Therefore, even if a glass member having a large refractive index is used as the solid immersion lens 4, the light use efficiency does not decrease. Further, at this time, as a material of the solid immersion lens 2 that functions to increase the angle of view θ, it is not necessary to use a member having a particularly high refractive index, so that there is no problem in reducing the light use efficiency of the solid immersion lens 2. .

Accordingly, the optical element for an optical pickup according to the first embodiment can be provided with a solid immersion lens to reduce a small spot size, and can also prevent a decrease in light use efficiency.

Next, a method of manufacturing the optical element for an optical pickup according to the present invention will be described with reference to the configuration shown in FIG. In the method of manufacturing the optical element for an optical pickup according to the first embodiment, the step of providing the objective lens 1 for converging parallel light on the first substrate 3 and the optical axis of the objective lens 1 coincide with the second substrate 7. A step of forming the solid immersion lens 2 and forming a concave shape on the back surface of the surface of the second substrate 7 on which the solid immersion lens 2 is formed; The method includes a step of forming the solid immersion lens 4 by embedding a shape, and a step of integrating the first substrate 3 and the second substrate 7.

Such a process will be described below with reference to FIGS. 2 to 5, FIG. 2 is a diagram for explaining a process of forming a mask pattern for forming the solid immersion lens 2, and FIG. 3 is an etching process for forming the solid immersion lens 2. FIG. 4 is a view for explaining a step of forming a mask pattern for forming the solid immersion lens 4, and FIG. 5 is a view for explaining an etching step for forming the solid immersion lens 4. FIG. It should be noted that the step of providing the objective lens 1 on the first substrate 3 is omitted because any known method may be used.

In the process shown in FIG. 2, first, a photoresist 21 (for example, OFPR-800: positive type resist, OMR-85, manufactured by Tokyo Ohka Co., Ltd.) is applied as a photosensitive material on the second substrate 7 which is a transparent glass member. Negative resist) is applied (a) and irradiated with light to form a resist pattern 2
2 is formed (b). Then, heat and pressure are applied to the resist pattern 22 to form a convex mask 23 having a convex shape (c). Incidentally, as the photosensitive material, a photosensitive dry film may be used instead of the photoresist.

Next, as shown in FIG. 3, the second substrate 7 is dry-etched using the convex mask 23 as a mask. Since the second substrate 7 is a glass member, CF ₄ or O ₂ may be used as the gas for the dry etching, and an inert gas such as Ar may be mixed as necessary. The dry etching method includes reactive ion etching (RIE) and electron cyclotron resonance etching (E
(A). And
After the etching, the convex mask 23 is removed by ashing, and the solid immersion lens 2 is completed (b).

Although not shown, the spacing member 5 on the same surface as the solid immersion lens 2 shown in FIG. 1 also etches the second substrate 7 simultaneously with the solid immersion lens 2 in this step. Can be formed.

Next, as shown in FIG. 4, a photoresist 21 is applied to the surface opposite to the surface of the second substrate 7 on which the solid immersion lens 2 is formed (a), and the photoresist 21 is irradiated with light to form a photoresist. 21 is a concave mask 4 having a spherical bottom.
1 (b). Such a concave mask 41 having a spherical bottom has a structure in which the photoresist 21 is shaded,
Alternatively, it can be formed by using a material that has a function of diffusing light.

Next, as shown in FIG. 5, the second substrate 7 is dry-etched using the photoresist 21 having the concave mask 41 as a mask. As the gas for the dry etching, CF ₄ and O ₂ may be used similarly to the etching at the time of forming the solid immersion lens 2, and an inert gas such as Ar may be mixed as necessary. In addition, as a method of dry etching, reactive ion etching (RIE),
A method such as electron cyclotron resonance etching (ECR) is used (a). After this etching,
A concave portion 52 is formed on the second substrate 7 (b).

Next, a material (high-refractive-index material) having a higher refractive index than the second substrate 7 is embedded in the concave portion 52 to complete the solid immersion lens 4 (c). During the etching process on the second substrate 7, the surface on which the solid immersion lens 2 is provided is:
The solid immersion lens 2 is fixed with wax or the like so as not to be damaged.

After the above steps, the first substrate 3 provided with the objective lens 1 and the spacing member 5 and the second substrate 7 are integrated by bonding the spacing members 5 together. . The spacing member 5 of the first substrate 3
Is formed in advance by a photolithography mask forming step and a dry etching step, similarly to the spacing member 5 provided on the second substrate 7.

However, the first embodiment is not limited to the configuration shown in FIG. 5. For example, instead of the step of fixing the solid immersion lens 2 with wax or the like to form the solid immersion lens 4, A concave portion 52 is formed on another substrate (not shown) different from both the first substrate 3 and the second substrate 7, and the concave portion 52 is embedded with a member having a higher refractive index than the solid immersion lens 2. Thereby forming the solid immersion lens 4, the back surface of the surface of the second substrate 7 on which the solid immersion lens 2 is formed, and the back surface of the other substrate on which the solid immersion lens 4 is formed And a step of further integrating the integrated second substrate 7 and the other substrate and the first substrate 3 with each other. Unishi and may be.

Next, FIGS. 6A, 6B and 6C show another example of a method of manufacturing the optical element for an optical pickup according to the first embodiment. The manufacturing method shown in FIG. 6 is a manufacturing method in which the spacing member 5 is not provided, and shows a method of manufacturing an optical element for an optical pickup configured by directly bonding substrates.

In this method of manufacturing an optical element for an optical pickup, first, a solid immersion lens 62 is formed on a substrate 61 as a first substrate by using the steps shown in FIGS. At this time, in the configuration of FIG. 6, it is assumed that the high refractive material embedded in forming the solid immersion lens 62 is left on the substrate 61 as a layer 68 having a predetermined thickness. Next, in order to obtain lens performance, a flat plate 63 as a second substrate is disposed on the solid immersion lens 62 and fixed by bonding or the like.

The flat plate 63 is a member having the same or similar refractive index as the high refractive index material embedded for manufacturing the solid immersion lens 62. Shall be designed to satisfy the condition of Further, the thickness of the flat plate 63 may be set to a desired value by polishing after bonding to the substrate. Further, a resin material having an effect of bonding the flat plate 63 to the high refractive index material of the solid immersion lens 62 may be used. In this case, a resin material having a high transmittance with respect to the wavelength of the laser beam used in the optical element for an optical pickup is selected.

Subsequently, a solid immersion lens 64 is formed on the flat plate 63 by using the steps shown in FIGS. Then, the flat plate 65 is arranged on the formed solid immersion lens 64. Then, the objective lens 66 is provided on the lower surface of the substrate 61. In the configuration of FIG. 6,
The prism 6 is provided on the surface of the substrate 61 on which the objective lens 66 is provided.
7 was provided. At this time, the prism 67 is fixed to the substrate 61 by an adhesive having a high transmittance with respect to the wavelength of the laser light L.

The solid immersion lens 62,
As another method for forming the flat plate 63, a high-refractive-index material is embedded in the concave portion 62a of the solid immersion lens 62 or the concave portion 64a of the solid immersion lens 64 by sputtering, and after etching back and flattening. In some cases, a high refractive index material is left in the concave portions 62a and 64a, or a flat plate made of the same material as the material used as the sputtering target is bonded.

The sputtering target was LaF ₂ (having a refractive index of 1.7 at a wavelength of 768.2 nm).
335), SFSI (refractive index at wavelength 768.2 nm: 1.8927), Si (wavelength 1.
The refractive index at 33 μm is 3.5011, and ZnSe (the refractive index at a wavelength of 656.3 nm is 2.578).

The objective lens 66 has a substrate 66a and a substrate 6 provided with the solid immersion lenses 62 and 64.
1. Grooves for bonding the flat plate 63 can also be formed by combining photolithography and etching in the above-described steps. In addition, a metal film can be used as the etching mask without using a photosensitive resin.

According to the structure shown in FIG. 6, the solid immersion lens 62 is also provided inside the substrate 61 in addition to the solid immersion lens 64. Therefore, when the solid immersion lens 62 is made of a material having a high refractive index, Also, the reflectance of the solid immersion lens 62 does not increase. For this reason, a spot light with a smaller spot size can be realized by using a member having a high refractive index for both the solid immersion lens 62 and the solid immersion lens 64.

According to the optical pickup optical element of the first embodiment described above, the solid immersion lens for condensing the spot light is provided inside the substrate, so that a material having a high refractive index is used for the solid immersion lens. However, the reflectance does not increase and the light use efficiency does not decrease. Further, by providing the solid immersion lens between the objective lens and the solid immersion, the angle of view of the solid immersion lens forming the spot light is increased, and the spot size of the spot light can be further reduced.

Further, according to the optical element for an optical pickup of the first embodiment, by bonding the first substrate and the second substrate via the spacing member, the distance between the objective lens and the solid immersion lens can be improved. Is stably maintained, and the characteristics of the optical element for an optical pickup can be stabilized.

Further, the first embodiment of the present invention is not limited to the configuration shown in FIG. That is, the configuration of the solid immersion lens is not limited to the super-hemispherical shape as shown in FIG. 1, and any of the super-hemispherical shape and the hemispherical shape may be used in combination according to a desired numerical aperture. Also, the shape of the objective lens may have at least one convex surface, and the upper surface shown in FIG. 1 is not limited to the convex shape.

FIGS. 7 to 10 show other structural examples of the optical element for an optical pickup according to the first embodiment. The configuration shown in FIGS. 7 to 10 is substantially the same as the configuration shown in FIG. 1. Therefore, the same reference numerals are given to the same members, and the description thereof will be partially omitted.

The configuration shown in FIG. 7 is substantially the same as the configuration shown in FIG. 1, and differs from the configuration shown in FIG. 1 only in that the objective lens 71 has a downwardly convex shape. The configuration shown in FIG. 8 is substantially the same as the configuration shown in FIG. 1 except that it has an objective lens 1 and an objective lens 71 and has an objective lens having a convex shape on both sides as a whole. This is different from the configuration of FIG. Further, the configuration shown in FIG. 9 is different from the configuration shown in FIG. 1 only in that the objective lens 91 is provided inside the first substrate and the spacing member 92 is provided only on the second substrate 7 side. Configuration. Note that such an objective lens 91 can be manufactured by the steps shown in FIGS. In the configuration shown in FIG. 10, the spacing member 92 is provided only on the second substrate 7 side, and the lower surface of the first substrate 101 has a meniscus shape.

(Embodiment 2) Next, Embodiment 2 of the present invention will be described. FIG. 11 is a diagram for explaining Embodiment 2 of the present invention. However, in FIG.
10 are denoted by the same reference numerals, and the description thereof will be partially omitted. In the configuration shown in FIG. 11, a prism 67 that is an optical path changing unit that changes the optical path of the laser light L incident on the objective lens 91 is provided on the upper surface of the first substrate 3.

The present inventors have found that the configuration shown in FIG. 11 and a conventional general optical pickup optical element have a light utilization efficiency and a maximum angle at which laser light does not cause total reflection on the surface of the solid immersion lens. And the following results were obtained. Light utilization efficiency Condition: Refractive index of first substrate including solid immersion lens 2: 1.5 Refractive index of solid immersion lens 4: 1.98 Light utilization efficiency (light incident perpendicular to optical element for optical pickup) The conventional optical element for optical pickup: 62.7% The optical element for optical pickup having the configuration of FIG. 11: 70.1% The optical element for optical pickup according to the first embodiment is also described as follows. If an anti-reflection film is provided on the surface of the solid immersion lens 2 facing the objective lens, it goes without saying that the utilization efficiency is further improved.

Maximum value of incident angle at which laser light L does not cause total reflection 30.3 degrees in a conventional optical pickup optical element, FIG.
The optical element for optical pickup No. 1 had an angle of 41.8 degrees. That is, the optical element for an optical pickup in FIG. 11 can increase the incident angle from the objective lens to the solid immersion lens.

(Embodiment 3) Next, Embodiment 3 of the present invention will be described. FIGS. 12A and 12B are views for explaining the optical element for an optical pickup according to the third embodiment, and FIG. 12A is a cross section of the optical element for the optical pickup according to the third embodiment. FIG. 2B is a top view of the configuration shown in FIG. In FIG. 12, the same members as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof will be partially omitted.

The optical element for an optical pickup according to the third embodiment is integrated by bonding the first substrate 3 and the second substrate 7, and both the first substrate 3 and the second substrate 7 It is configured to have a positioning portion 120 which is a bonding positioning means indicating a bonding position. In addition, the positioning part 120 is not limited to the thing which both the 1st board | substrate 3 and the 2nd board | substrate 7 have like FIG. 12, and at least one of the 1st board | substrate 3 and the 2nd board | substrate 7 is used. Should just have.

Four positioning units 120 according to the third embodiment are provided at equal intervals on the circumference of a circle concentric with the objective lens 1 and the objective lens 71. And each positioning part 1
20 is an upper positioning part 120a and a lower positioning part 120b
And the upper positioning portion 120a is a concave groove 1 along the spherical surface.
21a, and the lower positioning portion 120b has a rectangular groove 12
1b. The groove 121a and the groove 121b are
By sandwiching the microsphere 121, the upper positioning portion 12
0a and the lower positioning portion 120b can be accurately aligned and integrated. The microspheres 121 are required to be dimensionally and accurately designed and have no variation. An existing member that can be used as the microsphere 121 is, for example, a liquid crystal spacer.

According to such a configuration, the first substrate 3 and the second substrate 7 are accurately aligned and integrated, and the solid immersion lens 2 provided on the first substrate 3 is formed.
Then, the position of the solid immersion lens 4 provided on the second substrate 7 and the distance between the solid immersion lens 4 and the space can be accurately adjusted as designed.

Note that the positioning means of the present invention is not limited to the above-described configuration. For example, the positioning means may provide alignment marks used in a semiconductor process on the surfaces of the first substrate 3 and the second substrate 7. When the alignment marks are used as positioning means, the first substrate 3 and the second substrate 7 are positioned and integrated while checking the alignment marks with a microscope or the like. According to such a configuration, the first substrate 3 and the second substrate 7 can be positioned on the order of μm.

Further, the positioning means of the present invention may be such that grooves of concave and convex engaging with each other are formed on the first substrate 3 and the second substrate 7 by photolithography and etching. According to such a configuration, the positioning means can be formed relatively easily, and the configuration and manufacturing process of the optical element for an optical pickup can be simplified.

(Embodiment 4) Next, Embodiment 4 of the present invention will be described. FIGS. 13A and 13B are views for explaining the optical element for an optical pickup according to the fourth embodiment, and FIG. 13A is a cross section of the optical element for the optical pickup according to the fourth embodiment. FIG. 2B is a top view of the configuration shown in FIG. In FIG. 13, the same members as those shown in FIGS. 1 and 12 are denoted by the same reference numerals,
The description is partially omitted.

The optical element for an optical pickup according to the fourth embodiment is integrated by bonding a first substrate and the second substrate. The positioning portions 120 provided on both the first substrate 3 and the second substrate 7 are provided.
In addition, an adhesive groove 130 for releasing the adhesive a used for bonding is provided.

The positioning portion 120 provided with the adhesive groove 130 is not limited to the one provided in both the first substrate 3 and the second substrate 7 as shown in FIG. It is only necessary that at least one of the substrate 3 and the second substrate 7 has this. In addition, the adhesive groove 130 is provided in the positioning portion 12.
However, the present invention is not limited to the configuration provided at 0, and may be provided at any position on the first substrate 3 and the second substrate 7 as long as they are bonded together.

Also in the fourth embodiment, the positioning portion 12
Four 0s are provided at equal intervals on the circumference of a circle concentric with the objective lens 1 and the objective lens 71. Embodiment 4
In the figure, an adhesive groove 130 is provided along the concentric circle. The adhesive groove 130 of the fourth embodiment is
30a, so that the adhesive a used for bonding the first substrate 3 and the second substrate 7 can be released.

The first having such an adhesive groove 130
When bonding the first substrate 3 and the second substrate, the adhesive a is sufficiently poured into the adhesive groove 130 in advance, and the first substrate 3 and the second substrate 7 are combined and pressure is applied. At this time, the adhesive a overflowing from the adhesive groove 130 is applied to the extending portion 13 of the adhesive groove 130 at the end of the positioning portion 120.
The first substrate 3 and the second substrate 7 are extruded through Oa. After removing the extruded adhesive a, the adhesive a to which the first substrate 3 and the second substrate 7 are bonded is subjected to a curing treatment, and the first substrate 3 and the second substrate 7 are bonded to each other. Is completed.

According to such a configuration, since the adhesive a spreads evenly in the bonding groove 130 and can be uniformly shrunk when cured, the first substrate 3 and the second substrate 7 are shifted after bonding. Nothing. Therefore, in the configuration of the fourth embodiment, the first substrate 3 and the second substrate 7 can be accurately bonded at the determined position without displacement.

The adhesive groove 130 of the present invention is not limited to the structure of the fourth embodiment. For example, the adhesive groove 130 is not limited to a single, substantially circular shape, and may be double or triple. Also, the first
Any other shape may be used as long as the shape spreads evenly between the substrate 3 and the second substrate 7 and the shrinkage during curing becomes uniform.

[0093]

The present invention described above has the following effects. That is, the invention described in claim 1 is:
The reflectance of light at the front lens can be reduced, and the light utilization efficiency of the optical element for an optical pickup can be prevented from being reduced by providing the front lens. Further, by increasing the angle of view of the front lens provided on the second substrate, the spot size of the spot light can be further reduced. Further, the degree of freedom in the structure of the objective lens can be increased, and an optical element for an optical pickup with small aberration can be configured.

According to the second and ninth aspects of the present invention, the first substrate and the second substrate can be accurately positioned as designed, and the manufacturing tolerance of the optical element for an optical pickup can be reduced.

The invention according to claim 3 and claim 10 is as follows:
The distance between the first substrate and the second substrate after bonding can be accurately determined and maintained as designed, and the manufacturing tolerance of the optical element for an optical pickup can be reduced.

The invention according to claim 4 and claim 11 is as follows:
The adhesive is uniformly applied, and the substrates are not displaced from each other at the time of bonding, so that the manufacturing tolerance of the optical element for an optical pickup can be reduced.

The invention according to claim 5 and claim 12 is as follows:
The allowable range of the incident angle of light for obtaining the spot diameter as designed is widened, and the degree of freedom of the configuration of the entire optical element for an optical pickup can be widened.

The invention according to claim 6 and claim 13 is as follows:
The objective lens can efficiently condense light, and the degree of freedom in designing the objective lens is increased, so that the degree of freedom in the configuration of the entire optical element for an optical pickup can be increased.

According to the seventh aspect of the invention, the same steps as those for manufacturing a semiconductor can be used, and an optical element for an optical pickup can be manufactured with relatively high accuracy and at low cost. Further, the front lens and the other front lens can be formed on one substrate, and it is not necessary to add a bonding step.

According to the eighth aspect of the present invention, the same steps as those for manufacturing a semiconductor can be used, and an optical element for an optical pickup can be manufactured with relatively high accuracy and at low cost. Further, there is no restriction on the formation of the front lens, and the degree of freedom in the method of manufacturing the optical element for an optical pickup can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining one configuration of an optical element for an optical pickup according to a first embodiment of the present invention.

FIG. 2 is a view showing a step of manufacturing the configuration shown in FIG. 1 and illustrating a step of forming a mask pattern for forming a solid immersion lens.

FIG. 3 is a view showing a step of manufacturing the configuration shown in FIG. 1, and is a view for explaining an etching step for the mask shown in FIG. 2;

FIG. 4 is a view showing a step of manufacturing the configuration shown in FIG. 1 and illustrating a step of forming a mask pattern for forming another solid immersion lens.

5 is a view showing a step of manufacturing the configuration shown in FIG. 1, and is a view for explaining an etching step performed on the mask pattern shown in FIG. 4;

FIG. 6 is a diagram illustrating another example of the method for manufacturing the optical element for an optical pickup according to the first embodiment.

FIG. 7 is a diagram illustrating another configuration example of the optical element for an optical pickup according to the first embodiment;

FIG. 8 is a diagram illustrating another configuration example of the optical element for an optical pickup according to the first embodiment;

FIG. 9 is a diagram illustrating another configuration example of the optical element for an optical pickup according to the first embodiment;

FIG. 10 is a diagram illustrating another configuration example of the optical element for an optical pickup according to the first embodiment;

FIG. 11 is a view for explaining an optical element for an optical pickup according to a second embodiment of the present invention.

FIG. 12 is a view for explaining an optical element for an optical pickup according to a third embodiment of the present invention.

FIG. 13 is a view for explaining an optical element for an optical pickup according to a fourth embodiment of the present invention.

FIG. 14 is a diagram showing a schematic configuration of a general optical element for an optical pickup.

FIG. 15 is a diagram showing a general configuration in which a solid immersion lens is provided between an objective lens and an optical disk.

FIG. 16 is a diagram showing a configuration of a general flying head.

[Explanation of symbols]

 1, 71, 91 Objective lens 2, 4, 62, 64 Solid immersion lens 3 First substrate 5, 92 Spacing member 7 Second substrate 14 Optical disk 21 Photo resist 22 Resist pattern 23 Convex mask 41 Concave mask 52 Concave shape Unit 61 Substrate (first substrate) 63 Flat plate (second substrate) 67 Prism 120 Positioning unit 121 Microsphere 121a, 121b Concave groove 130 Adhesive groove 130a Extension unit

Claims (13)

[Claims] 1. A first substrate provided with an objective lens for converging parallel light, a second substrate provided with a front lens having an optical axis coincident with the objective lens, and the second substrate And another front lens having an optical axis coinciding with the objective lens and the front lens, wherein the first substrate and the second substrate are integrated with each other. An optical element for an optical pickup, comprising: 2. The first substrate and the second substrate,
2. The optical pickup optical device according to claim 1, wherein the first substrate and the second substrate are integrated by being attached to each other, and at least one of the first substrate and the second substrate has an attachment positioning unit indicating an attachment position. element. 3. The first substrate and the second substrate,
The first substrate and the second substrate are integrated by being attached to each other, and at least one of the first substrate and the second substrate
2. The optical element for an optical pickup according to claim 1, further comprising a spacing unit that keeps a constant spacing after bonding the first substrate and the second substrate. 4. The first substrate and the second substrate,
The integrated substrate is bonded by bonding, and at least one of the first substrate and the second substrate has an adhesive groove for releasing an adhesive used for bonding. 3. The optical element for an optical pickup according to any one of 3. 5. The apparatus according to claim 1, further comprising an optical path changing means for changing an optical path of the parallel light incident on the objective lens on the first substrate. Optical element for optical pickup. 6. The optical element for an optical pickup according to claim 1, wherein the objective lens has at least one convex surface. 7. A step of providing an objective lens for converging parallel light on a first substrate; a step of forming a front lens having an optical axis coincident with the objective lens on a second substrate; Of the substrate, a concave shape is formed on the back surface of the surface on which the front lens is formed, and the objective lens and the front lens are formed by embedding the concave shape with a member having a higher refractive index than the front lens. A method of manufacturing an optical element for an optical pickup, comprising: a step of forming another front lens having the same optical axis; and a step of integrating the first substrate and the second substrate. . 8. A step of providing an objective lens for converging parallel light on a first substrate; a step of forming a front lens having an optical axis coincident with the objective lens on a second substrate; Forming a concave shape, forming another front lens whose optical axis matches the objective lens and the front lens by embedding the concave shape with a member having a higher refractive index than the front lens, A step of bonding the back surface of the second substrate on which the front lens is formed and the back surface of the other substrate on which the other front lens is formed, to integrate them. And a step of further integrating the integrated second substrate and the other substrate with the first substrate. A method for manufacturing an optical element for an optical pickup, comprising: 9. The method according to claim 1, further comprising the step of providing, on at least one of the first substrate and the second substrate, bonding positioning means for indicating a bonding position between the first substrate and the second substrate. 9. The method according to claim 7, wherein
5. The method for producing an optical element for an optical pickup according to item 1. 10. The method according to claim 1, further comprising the step of providing at least one of the first substrate and the second substrate with an interval maintaining means for maintaining a constant interval after bonding the first substrate and the second substrate. 10. The method according to claim 7, wherein
The method for producing an optical element for an optical pickup according to any one of the above. 11. The method according to claim 7, further comprising the step of providing at least one of the first substrate and the second substrate with an adhesive groove for releasing an adhesive used for bonding. 11. The method for manufacturing an optical element for an optical pickup according to any one of items 10. 12. The method according to claim 7, further comprising a step of providing an optical path changing unit on the first substrate for changing an optical path of parallel light incident on the objective lens. 5. The method for producing an optical element for an optical pickup according to item 1. 13. The method of manufacturing an optical element for an optical pickup according to claim 7, wherein the objective lens has at least one convex surface.