JP2002092927A - Optical pickup device, method for manufacturing optical element, optical information recording medium and optical disk unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a noise light beam generated between a convex spherical lens and an optical information recording medium. SOLUTION: On a optical information recording medium D1 side of the convex spherical lens 10, an antireflection means 11 is provided. The reflectance of a light beam can be suppressed at a low level by the antireflection means 11, and a reflected light component is hardly generated in an air gap G1. Thereby, multiple-beam reflection is not generated, and the noise light beam generated between the convex spherical lens 10 and the optical information recording medium D1 can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an optical information recording medium,
An optical pickup device that irradiates a light spot on a recording surface of the optical information recording medium to optically record, reproduce, or erase information, a method of manufacturing an optical element provided in the optical pickup device, and the optical pickup device The present invention relates to an optical disk device provided with:

[0002]

2. Description of the Related Art An example of a conventional optical pickup device will be described with reference to FIG. As shown in FIG. 12, a conventional optical pickup device includes a semiconductor laser 101 as a laser light source, a collimator lens 102, a polarization beam splitter 103, a quarter-wave plate 104, an objective lens 105, and a condenser lens. 106 and a photodiode (hereinafter, referred to as PD) 107 are mainly configured. In such a configuration, the linearly polarized laser light emitted from the semiconductor laser 101 is
02 to be substantially parallel light, and the polarization beam splitter 1
The light is converted from linearly polarized light to circularly polarized light in an optical isolator constituted by the light receiving element 03 and the quarter-wave plate 104. The light converted into the circularly polarized light is condensed by the objective lens 105, and is irradiated in the form of a light spot on the recording surface of the optical disc D 'which is an optical information recording medium. The reflected light from the recording surface of the optical disk D 'follows a path opposite to the emitted light, passes through the objective lens 105, and is converted by the quarter-wave plate 104 into linearly polarized light whose polarization direction is rotated by 90 °. The light is reflected by the polarizing beam splitter 103 in the direction of the condenser lens 106. The light reflected by the polarization beam splitter 103 is condensed by the condenser lens 106 and is incident on the PD 107. The PD 107 detects an output amount of reflected light that changes according to a difference in reflectance caused by whether or not the recording surface of the optical disc D ′ has a mark. This allows
Detection of a servo signal (focus error signal, track error signal) and recording, reproduction, or erasure of a recording signal on the optical disk D ′ are performed. Although optical components for focus detection and track detection actually exist, description thereof will be omitted here.

[0003] In recent years, the density of optical discs as optical information recording media has been increasing. In order to perform recording and reproduction of such a high-density optical disk, a spot size w on the recording surface of the optical disk is required.
(W∝λ / sin θ ′) needs to be reduced. Here, θ ′ is the emission angle of the objective lens, and λ is the wavelength of the laser light. Further, the numerical aperture (NA) of the objective lens and the emission angle θ ′ of the objective lens have a relationship of NA = sin θ ′.

However, the spot size w on the recording surface of the optical disk D 'when the optical disk D' is irradiated by the optical pickup device as illustrated in FIG.
Can be obtained only with a size about the wavelength of laser light due to the diffraction limit of light. In order to further reduce the spot size w, it is conceivable to shorten the wavelength of the laser beam or increase the diameter of the objective lens 105 to increase the NA. However, it is not easy to develop a semiconductor laser that generates laser light having a shorter wavelength, and if an objective lens 105 having a large diameter is employed, the size of the apparatus becomes large and focus control and the like become difficult.

Therefore, as shown in FIG. 13, a convex spherical lens 10 such as a solid immersion lens (Solid Immersion Lens) is provided between the objective lens 105 and the optical disk D '.
An optical pickup device has been considered in which a recording surface of the optical disk D ′ is provided through the convex spherical lens 108 so as to effectively increase the NA and reduce the spot size w ( For example, JP-A-5-18
No. 9796). According to the configuration shown in FIG. 13, when light condensed by the objective lens 105 is incident on a hemispherical convex spherical lens 108 having a spherical incident surface side and a flat exit surface side, the incident light is It converges to the center of the plane on the exit surface side. If the distance between the convex spherical lens 108 and the recording surface of the optical disk D 'is equal to or less than the wavelength of the laser beam (for example, 100 nm or less), the convex spherical lens 108 is formed on the plane on the emission surface side of the convex spherical lens 108. The spot size w and the spot size formed on the recording surface of the optical disc D 'are substantially the same. Also, spot size w
Is proportional to the reciprocal of the refractive index of the convex spherical lens 108. Thus, assuming that the refractive index of the convex spherical lens 108 is n,
Since the spot size w becomes w∝λ / nsinθ ′, the same effect as when the NA is increased by n times is obtained, and a light spot with a smaller spot size w can be obtained.

[0006]

However, in the optical pickup device as described above, the optical disk D
When recording, reproducing, or erasing information with respect to the optical disk D ′, a parallel plate-shaped air gap is formed by the convex spherical lens 108 and the optical disk D ′. When the parallel plate-shaped air gap is formed, the light is reflected on each surface of the parallel plate to generate noise light due to repeated reflection, which adversely affects the recording, reproducing or erasing signals. is there.

An object of the present invention is to reduce generation of noise light generated between a convex spherical lens and an optical information recording medium.

An object of the present invention is to prevent a convex spherical lens from being damaged.

An object of the present invention is to remove a reflected light component in an air gap formed by a convex spherical lens and an optical information recording medium.

An object of the present invention is to prevent an optical information recording medium from being damaged.

[0011]

According to a first aspect of the present invention, there is provided an optical pickup device comprising a semiconductor via a substantially hemispherical convex spherical lens disposed with a predetermined air gap between the optical pickup device and an optical information recording medium. In an optical pickup device which irradiates a laser beam emitted from a laser as an optical spot on the optical information recording medium and optically records, reproduces or erases information on the optical information recording medium, the light of the convex spherical lens An anti-reflection means was provided on the information recording medium side.

Therefore, since the reflection factor of the light is kept low by the anti-reflection means, the reflected light component hardly occurs in the air gap, so that repeated reflection does not occur, thereby reducing the generation of noise light. It becomes possible to do.

According to a second aspect of the present invention, there is provided an optical pickup device having an optical element in which an objective lens and a substantially hemispherical convex spherical lens are integrally provided with their optical axes coincident with each other. Irradiating the optical information recording medium with a laser beam emitted from a semiconductor laser through the convex spherical lens arranged with a predetermined air gap as an optical spot,
In an optical pickup device for optically recording, reproducing or erasing information on the optical information recording medium, antireflection means is provided on the optical element side of the optical element.

Therefore, since the light reflectance is kept low by the anti-reflection means, the reflected light component hardly occurs in the air gap, so that repeated reflection does not occur, thereby reducing the generation of noise light. It becomes possible to do.

The third aspect of the present invention provides the first or second aspect.
In the optical pickup device described above, the anti-reflection means is formed of a material having excellent wear resistance.

Therefore, even if the convex spherical lens and the optical information recording medium are in contact with each other or dust adheres, it is possible to prevent the convex spherical lens from being damaged.

The invention described in claim 4 is the first to third aspects of the present invention.
In the optical pickup device according to any one of the above, the air gap is defined to have a width excluding an even multiple of a half wavelength of laser light emitted from the semiconductor laser.

Therefore, it is possible to suppress interference between the light reflected on the surface of the optical information recording medium and the light reflected on the convex spherical lens slightly existing in the air gap, thereby reducing the generation of noise light. Becomes possible. Note that the width excluding an even multiple of the half wavelength of the laser light is preferably an odd multiple of the half wavelength of the laser light.

The invention according to claim 5 provides the invention according to claims 1 to 4
In the optical pickup device according to any one of the above, the surface of the convex spherical lens disposed on the optical information recording medium side is a reflected light component on the convex spherical lens side and a reflected light component on the optical information recording medium side. Are formed such that the phase difference becomes an odd multiple of half the wavelength of the laser light emitted from the semiconductor laser for all incident angles.

Therefore, the surface reflected light from the convex spherical lens slightly existing in the air gap and the reflected light from the surface of the optical information recording medium cancel each other out due to the phase difference. It becomes possible to remove it reliably.

According to a sixth aspect of the present invention, there is provided a method of manufacturing an optical element, comprising: forming a concave portion having substantially the same shape as the shape of the convex spherical lens; A transparent material filling step of filling a refractive refractive transparent material, and after filling the high refractive transparent material, including a concave part closing step of closing the concave part with a thin plate having substantially the same refractive index as the high refractive transparent material, The curved surface of the convex spherical lens according to claim 5 is formed by bending the thin plate by expansion of a high refractive index transparent material.

Therefore, the curved surface of the convex spherical lens can be easily formed.

The optical information recording medium of the invention according to claim 7 is:
6. An optical information recording medium in which information is optically recorded, reproduced or erased by the optical pickup device according to claim 1, wherein an anti-reflection layer is provided on a surface of the medium located on the optical pickup device side. Have been.

Therefore, since the light reflectance is suppressed low by the anti-reflection layer, by using this optical information recording medium for an optical pickup device according to any one of claims 1 to 5, air Since almost no reflected light component is present in the gap, no repeated reflection occurs, so that it is possible to prevent noise light from being generated.

According to an eighth aspect of the present invention, in the optical information recording medium of the seventh aspect, the antireflection layer is formed of a material having excellent wear resistance.

Therefore, even if the convex spherical lens and the optical information recording medium should come into contact with each other or if dust adheres, it is possible to prevent the optical information recording medium from being damaged.

[0027] The optical disk apparatus according to the ninth aspect of the present invention provides:
2. A drive source for driving an optical information recording medium to rotate, and a seek source movable in a radial direction with respect to the optical information recording medium.
And an optical pickup device according to any one of (5) to (5).

Therefore, it is possible to provide an optical disk device having the same operation as the optical pickup device according to any one of the first to fifth aspects.

[0029]

FIG. 1 shows a first embodiment of the present invention.
This will be described with reference to FIG. The optical disk device according to the present embodiment generally includes a spindle motor (not shown) as a drive source for rotationally driving an ultra-high-density optical disk, which is an optical information recording medium having a very high recording density, and a rotational drive. And an optical pickup device for irradiating the recording layer of the optical disc with light for reproduction or recording.

Here, FIG. 1 is a configuration diagram schematically showing the optical pickup device 1, and FIG. 2 is a configuration diagram showing a part of it in an enlarged manner. As shown in FIG. 1, an optical pickup device 1 according to the present embodiment uses a laser beam (wavelength: λ) as a laser light source.
= 650 nm), a collimator lens 3, a polarizing beam splitter 4, a quarter-wave plate 5, an optical system 6, a condenser lens 7, and a photodiode (hereinafter, referred to as a light receiving element). 8 (referred to as PD). The optical system 6 roughly includes an objective lens 9
And a convex spherical lens 10 formed of a material having a high refractive index and having a hemispherical shape in which the incident surface side of the laser beam from the semiconductor laser 2 is spherical and the other surface is flat. The convex spherical lens 10 is disposed so that its plane portion faces the optical disc D1. Also,
The objective lens 9 and the convex spherical lens 10 are arranged such that their optical axes coincide. The convex spherical lens 10 has, for example, a refractive index n ₁ at a wavelength of 650 nm of 1.5.
It is formed of one transparent optical glass.

As shown in FIG. 2, an anti-reflection film 11 is applied to the flat portion (the optical disc D1 side) of the convex spherical lens 10. The antireflection film 11 has a refractive index n ₂
Is formed of a material that satisfies n ₂ = √n ₁ (n ₁ : refractive index of the convex spherical lens 10). In the present embodiment, MgF ₂ (refractive index n ₂ = 1.38) is used. Is formed. The thickness of the antireflection film 11 is set to λ / 4 (λ: wavelength of laser light). The reflectance of the antireflection film 11 is about 1 to 2%. Here, the antireflection film 11
This implements anti-reflection means.

Also, an optical disc D as an optical information recording medium
1, a transparent substrate (not shown), a reflective layer, a dielectric layer, a recording layer, a dielectric layer (not shown), a protective layer 12,
The anti-reflection layer 13 is sequentially laminated.

The convex spherical lens 10 and the optical disk D1
Is set to be equal to or less than the wavelength of the laser beam from the semiconductor laser 2, and a predetermined distance is provided between the antireflection film 11 of the convex spherical lens 10 and the antireflection layer 13 of the optical disc D1. An air gap G1 at intervals is provided.

In such a configuration, for example, during reproduction of the optical disc D1, the linearly polarized laser light emitted from the semiconductor laser 2 is converted into substantially parallel light by the collimator lens 3, and the polarization beam splitter 4 and the quarter-wave plate 5
Are converted from linearly polarized light to circularly polarized light in the optical isolator composed of The light converted into the circularly polarized light is transmitted to the optical system 6.
Convex lens 10 after being condensed by the objective lens 9
Incident on. The incident light is refracted greatly by being incident on the convex spherical lens 10 having a high refractive index, and converges as a minute light spot on a plane portion of the convex spherical lens 10. When the distance between the flat portion of the convex spherical lens 10 and the recording layer of the optical disk D1 is equal to or less than the wavelength of the laser light, the spot size of the light spot formed on the flat portion of the convex spherical lens 10 is reduced. The spot size of the light spot formed on the recording layer of the optical disc D1 is substantially the same. As a result, the laser light is converged as a light spot on the recording layer of the optical disk D1, and irradiates the mark recorded on the recording layer of the optical disk D1. Thereafter, the reflected light from the recording layer of the optical disk D1 follows the reverse path, passes through the objective lens 9, and is converted by the quarter-wave plate 5 into linearly polarized light whose polarization direction is rotated by 90 °. The light is reflected by the splitter 4 in the direction of the condenser lens 7. The light reflected by the polarization beam splitter 4 is condensed by the condenser lens 7 and is incident on the PD 8. PD
8 detects the output amount of the reflected laser light that changes according to the difference in the reflected light that occurs depending on whether or not a mark is formed on the recording layer of the optical disc D1, thereby detecting the optical disc D1.
Playback becomes possible.

Here, during reproduction of the optical disk D1 by the optical pickup device 1 as described above, a parallel plate-like shape is provided between the antireflection film 11 of the convex spherical lens 10 and the antireflection layer 13 of the optical disk D1. Air gap G1
Is formed. However, the antireflection film 1
1 and the antireflection layer 13, the reflectance of light is kept low, so that there is almost no reflected light component in the air gap G1 and there is no repeated reflection, so that almost no noise light is generated.

Next, a second embodiment of the present invention will be described with reference to FIGS. The same parts as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted (the same applies to the third, fourth, fifth, and sixth embodiments described later). The optical pickup device 20 of the present embodiment uses an optical system 21 instead of the optical system 6 of the optical pickup device 1 of the first embodiment, and replaces the optical disc D1 of the first embodiment. The difference is that the optical disc D2 is used.

FIG. 3 is an enlarged view showing a part of the optical pickup device 20. As shown in FIG. As shown in FIG.
Optical system 21 of optical pickup device 20 of the present embodiment
Is a semispherical objective lens 9 and a convex spherical lens 10 made of a material having a high refractive index, which is a hemispherical shape having a spherical surface on the incident surface side of the laser beam from the semiconductor laser 2 and a flat surface on the other side. , And is constituted. The convex spherical lens 10 is disposed so that its plane portion faces the optical disc D2. Further, the objective lens 9 and the convex spherical lens 10 are arranged such that their optical axes coincide with each other. The convex spherical lens 10 has a wavelength of 65, for example.
It is formed of a transparent optical glass having a refractive index n ₁ at 0 nm of 1.51.

In addition, two layers of protective films 22 and 23 are formed on the flat surface of the convex spherical lens 10 (on the optical disk D2 side). The protective films 22 and 23 are
Is n ₃ , the film thickness is d ₃ , the refractive index of the protective film 23 is n ₄ , and the film thickness is d ₄ , such that the relationship of n ₃ · d ₃ = n ₄ · d ₄ is satisfied. It is formed of a material. The relationship between the refractive index n ₃ and the protective film 23 refractive index of the protective film 22 and n ₄ is, n ₃ / n ₄ = √n _1: there is a (n ₁ refractive index of the convex spherical lens 10). Therefore, in the present embodiment, the protective film 22 is formed of CeO ₂ having a refractive index n ₃ of 2.2,
The protective film 23 is formed of a diamond-like carbon layer having a refractive index n ₄ of 1.8 and having excellent wear resistance. Since the wavelength λ of the laser beam is 650 nm, the thickness d ₃ of the protective film 22 is 293 nm, and the thickness d _{4 of the} protective film 23 is
Is 358 nm. Then, as shown in FIG. 4, the spectral reflectance of the convex spherical lens 10 on which such protective films 22 and 23 are formed is such that the wavelength λ of the laser light is 65.
It can be seen that at 0 nm, it is almost 0%. here,
Antireflection means is realized by the two protective films 22 and 23.

Also, an optical disc D as an optical information recording medium
2, a transparent layer (not shown), a reflective layer, a dielectric layer, a recording layer, a dielectric layer (not shown), a protective layer 12,
The anti-reflection layers 24 are sequentially laminated. The antireflection layer 24 is formed of a diamond-like carbon layer having excellent wear resistance.

The convex spherical lens 10 and the optical disk D2
Is set to be equal to or less than the wavelength of the laser light from the semiconductor laser 2, and a predetermined distance is provided between the protective film 23 of the convex spherical lens 10 and the antireflection layer 24 of the optical disk D2. The air gap G2 is provided.

In such a configuration, for example, during reproduction of the optical disk D2, the linearly polarized laser light emitted from the semiconductor laser 2 is converted into substantially parallel light by the collimator lens 3, and the polarization beam splitter 4 and the quarter-wave plate 5
Are converted from linearly polarized light to circularly polarized light in the optical isolator composed of The light converted into the circularly polarized light is transmitted through the optical system 2
The convex spherical lens 1 after being condensed by the objective lens 9
Incident at 0. The incident light is refracted greatly by being incident on the convex spherical lens 10 having a high refractive index, and converges as a minute light spot on a plane portion of the convex spherical lens 10. When the distance between the flat portion of the convex spherical lens 10 and the recording layer of the optical disc D2 is smaller than the wavelength of the laser beam, the spot size of the light spot formed on the flat portion of the convex spherical lens 10 is reduced. The spot size of the light spot formed on the recording layer of the optical disc D2 is substantially the same. Thereby, the laser light is converged as a light spot on the recording layer of the optical disk D2, and the optical disk D2
The mark recorded on the recording layer is irradiated. Thereafter, the reflected light from the recording layer of the optical disc D2 follows the reverse path, passes through the objective lens 9, and is converted by the quarter-wave plate 5 into linearly polarized light having its polarization direction rotated by 90 °. The light is reflected by the splitter 4 in the direction of the condenser lens 7. The light reflected by the polarization beam splitter 4 is condensed by the condenser lens 7 and is incident on the PD 8. PD
8 detects the output amount of the reflected laser light that changes according to the difference in the reflected light that occurs depending on whether or not there is a mark on the recording layer of the optical disk D2.
Playback becomes possible.

Here, during reproduction of the optical disk D2 by the optical pickup device 20 as described above, a parallel plate-shaped air is provided between the protective film 23 of the convex spherical lens 10 and the antireflection layer 24 of the optical disk D2. A gap G2 is formed. However, the protective films 22 and 2
3 is almost zero.
%, There is almost no reflected light component in the air gap G2, so that repeated reflection does not occur, so that noise light hardly occurs.

Since hard diamond-like carbon is used for the protective film 23 of the convex spherical lens 10 and the antireflection layer 24 of the optical disk D2, the convex spherical lens 10
Even if the optical disk D2 comes into contact with the optical disk D2,
Does not hurt.

Next, a third embodiment of the present invention will be described with reference to FIG. The optical pickup device 30 of the present embodiment is different from the optical pickup device 1 of the first embodiment in that an optical system 31 is used instead of the optical system 6 of the optical pickup device 1 of the first embodiment.

FIG. 5 is a configuration diagram showing a part of the optical pickup device 30 in an enlarged manner. As shown in FIG.
Optical system 31 of optical pickup device 30 of the present embodiment
Is roughly composed of an objective lens 9 and a convex spherical lens 32 having a substantially hemispherical shape and made of a material having a high refractive index. Unlike the convex spherical lens 10 described in the first embodiment, the convex spherical lens 32 on the side facing the optical disk D1 has a gentle curvature with a large radius of curvature. More specifically, this curved surface is a curved surface such that the phase difference between the surface reflected light component at the convex spherical lens 32 and the reflected light component at the surface of the optical disk D1 becomes an odd multiple of half a wavelength for all incident angles. Have been. At this time, the distance between the lowermost surface of the convex spherical lens 32 and the recording layer of the optical disc D1 is an odd multiple of a half wavelength of the laser light from the semiconductor laser 2. Further, the objective lens 9 and the convex spherical lens 32 are arranged such that their optical axes coincide with each other. The convex spherical lens 32
Is, for example, the refractive index n ₅ at a wavelength 650nm is formed by transparent optical glass 1.51.

In addition, an antireflection film 33 is applied to the curved surface portion (the optical disk D1 side) of the convex spherical lens 32. The antireflection film 33 is formed of a material whose refractive index n ₆ satisfies n ₆ = √n ₅ (n ₅ : refractive index of the convex spherical lens 32). ₂ (refractive index n ₂ = 1.38). The thickness of the antireflection film 33 is set to λ / 4 (λ: wavelength of laser light). The reflectance of the antireflection film 33 is about 1 to 2%. Here, the anti-reflection film 33
This implements anti-reflection means.

The antireflection film 33 of the convex spherical lens 32
An air gap G3 at a predetermined interval is provided between the optical disk D1 and the anti-reflection layer 13 of the optical disk D1.

In such a configuration, for example, during reproduction of the optical disk D1, the linearly polarized laser light emitted from the semiconductor laser 2 is converted into substantially parallel light by the collimator lens 3, and the polarized beam splitter 4 and the quarter-wave plate 5
Are converted from linearly polarized light to circularly polarized light in the optical isolator composed of The light converted into the circularly polarized light is transmitted to the optical system 3.
The convex spherical lens 3 after being focused by the first objective lens 9
2 is incident. The incident light is largely refracted by being incident on the convex spherical lens 32 having a high refractive index, and converges as a minute light spot on a plane portion of the convex spherical lens 32. If the distance between the flat portion of the convex spherical lens 32 and the recording layer of the optical disc D1 is smaller than the wavelength of the laser beam, the spot size of the light spot formed on the flat portion of the convex spherical lens 32 is reduced. The spot size of the light spot formed on the recording layer of the optical disc D1 is substantially the same. As a result, the laser light is converged as a light spot on the recording layer of the optical disc D1, and the optical disc D1
The mark recorded on the recording layer is irradiated. Thereafter, the reflected light from the recording layer of the optical disk D1 follows the reverse path, passes through the objective lens 9, and is converted by the quarter-wave plate 5 into linearly polarized light whose polarization direction is rotated by 90 °. The light is reflected by the splitter 4 in the direction of the condenser lens 7. The light reflected by the polarization beam splitter 4 is condensed by the condenser lens 7 and is incident on the PD 8. PD
8 detects the output amount of the reflected laser light that changes according to the difference in the reflected light that occurs depending on whether or not a mark is formed on the recording layer of the optical disc D1, thereby detecting the optical disc D1.
Playback becomes possible.

Here, during reproduction of the optical disk D1 by the optical pickup device 30 as described above, an air gap G3 is formed between the antireflection film 33 of the convex spherical lens 32 and the antireflection layer 13 of the optical disk D1. Will be formed. However, the light reflectance is suppressed low by the antireflection film 33 and the antireflection layer 13, and the phase difference between the slightly existing surface reflected light from the convex spherical lens 32 and the reflected light from the surface of the optical disk D 1. Therefore, the reflected light component hardly exists in the air gap G3, so that repeated reflection does not occur, so that noise light hardly occurs.

Next, a fourth embodiment of the present invention will be described with reference to FIGS. The optical pickup device 40 of the present embodiment is different in that an optical element 41 is used instead of the optical system 6 of the optical pickup device 1 of the first embodiment.

Here, FIG. 6 is a configuration diagram schematically showing the optical pickup device 40, and FIG. 7 is a configuration diagram showing a part thereof in an enlarged manner. As shown in FIG. 6, an optical pickup device 40 of the present embodiment includes a semiconductor laser 2 that emits laser light (wavelength: λ = 650 nm) as a laser light source, a collimator lens 3, a polarization beam splitter 4, /
A four-wavelength plate 5, an integrated optical pickup optical element (hereinafter referred to as an optical element) 41, a condenser lens 7, and a PD 8
It is mainly composed of

The optical element 41 is roughly formed of a material having a high refractive index, which is a hemispherical shape having a spherical surface on the incident surface side of the laser beam from the semiconductor laser 2 and a flat surface on the other side. The convex spherical lens 10 is disposed on the upper and lower surfaces of the transparent substrate 42, respectively. In this case, the objective lens 9 and the convex spherical lens 10 are arranged so that their optical axes coincide. The convex spherical lens 10 has a refractive index n ₁ at a wavelength of 650 nm, for example.
Is formed of 1.51 transparent optical glass.

In addition, as shown in FIG.
On the optical disk D1 side, an antireflection film 43 is applied. The antireflection film 43 is formed of a material whose refractive index n ₇ satisfies n ₇ = √n ₁ (n ₁ : refractive index of the convex spherical lens 10). ₂ (refractive index n ₂ = 1.38). Further, the thickness of the antireflection film 43 is set to λ / 4 (λ: wavelength of laser light). The reflectance of the antireflection film 43 is about 1 to 2%. Here, the anti-reflection film 43
This implements anti-reflection means.

The convex spherical lens 10 and the optical disk D1
Is set to be equal to or less than the wavelength of the laser beam from the semiconductor laser 2, and a predetermined distance is provided between the antireflection film 43 of the optical element 41 and the antireflection layer 13 of the optical disc D1. Is provided.

In such a configuration, for example, during reproduction of the optical disc D1, the linearly polarized laser light emitted from the semiconductor laser 2 is converted into substantially parallel light by the collimator lens 3, and the polarization beam splitter 4 and the quarter-wave plate 5
Are converted from linearly polarized light to circularly polarized light in the optical isolator composed of The light converted into the circularly polarized light is condensed by the objective lens 9 of the optical element 41 and then enters the convex spherical lens 10. The incident light is refracted greatly by being incident on the convex spherical lens 10 having a high refractive index, and converges as a minute light spot on a plane portion of the convex spherical lens 10. When the distance between the flat portion of the convex spherical lens 10 and the recording layer of the optical disk D1 is equal to or less than the wavelength of the laser light, the spot size of the light spot formed on the flat portion of the convex spherical lens 10 is reduced. , Optical disk D1
Is substantially the same as the spot size of the light spot formed on the recording layer. As a result, the laser light is emitted from the optical disc D1.
Converged as a light spot on the recording layer of the optical disc D
The mark recorded on one recording layer is irradiated. afterwards,
The reflected light from the recording layer of the optical disc D1 follows the reverse path, passes through the objective lens 9, and is converted by the quarter-wave plate 5 into linearly polarized light whose polarization direction is rotated by 90 °. Is reflected in the direction of the condenser lens 7. The light reflected by the polarization beam splitter 4 is condensed by the condenser lens 7 and is incident on the PD 8. PD
8 detects the output amount of the reflected laser light that changes according to the difference in the reflected light that occurs depending on whether or not a mark is formed on the recording layer of the optical disc D1, thereby detecting the optical disc D1.
Playback becomes possible.

Here, during reproduction of the optical disk D1 by the optical pickup device 40 as described above, a parallel plate-shaped air is placed between the antireflection film 43 of the optical element 41 and the antireflection layer 13 of the optical disk D1. A gap G4 is formed. However, the anti-reflection film 43
In addition, since the light reflectance is suppressed low by the antireflection layer 13, the reflected light component hardly exists in the air gap G4, so that repeated reflection does not occur, so that noise light hardly occurs.

Next, a fifth embodiment of the present invention will be described with reference to FIG. The optical pickup device 50 of the present embodiment uses an optical element 51 instead of the optical element 41 of the optical pickup device 40 of the fourth embodiment, and replaces the optical disk D1 of the fourth embodiment. The difference is that the optical disc D2 is used.

FIG. 8 is a configuration diagram showing a part of the optical pickup device 50 in an enlarged manner. As shown in FIG.
Optical element 51 of optical pickup device 50 of the present embodiment
Is a semispherical objective lens 9 and a convex spherical lens 10 made of a material having a high refractive index, which is a hemispherical shape having a spherical surface on the incident surface side of the laser beam from the semiconductor laser 2 and a flat surface on the other side. Are disposed on the upper and lower surfaces of the transparent substrate 42, respectively. In this case, the objective lens 9 and the convex spherical lens 10 are arranged so that their optical axes coincide. The convex spherical lens 10 is made of, for example, a transparent optical glass having a refractive index n ₈ of 1.62 at a wavelength of 650 nm.

In addition, two protective films 52 and 53 are formed on the optical element D2 side of the optical element 51. These protective films 52 and 53 have a refractive index of n ₉ ,
The thickness is d ₉ , the refractive index of the protective film 53 is n ₁₀ , and the thickness is d.
_When it is set to ₁₀ , it is formed of a material that satisfies the relationship of n ₉ · d ₉ = n ₁₀ · d ₁₀ . The refractive index n ₉ of the protective film 52 and the refractive index of the protective film 53 are set to n ₁₀
And n ₉ / n ₁₀ = √n ₈ (n ₈ : refractive index of the convex spherical lens 10). Therefore, in the present embodiment, the protective film 52 is formed of CeO ₂ having a refractive index n ₉ of 2.2,
Refractive index n ₁₀ forms a protective layer 53 by a diamond-like carbon layer of 1.8. Since the wavelength λ of the laser beam is 650 nm, the thickness d of the protective film 52 is
₉ 293 nm, the thickness d ₁₀ of the protective film 53 is a 358 nm. Then, similarly to the case shown in FIG. 4, the convex spherical lens 1 on which such protective films 52 and 53 are formed.
It can be seen that the spectral reflectance of 0 is almost 0% when the wavelength λ of the laser beam is 650 nm. Here, antireflection means is realized by the two protective films 52 and 53.

The convex spherical lens 10 and the optical disk D2
Is set to be equal to or less than the wavelength of the laser beam from the semiconductor laser 2, and between the protective film 53 of the optical element 51 and the antireflection layer 24 of the optical disc D2.
Air gaps G5 at predetermined intervals are provided.

In such a configuration, for example, during reproduction of the optical disk D2, the linearly polarized laser light emitted from the semiconductor laser 2 is converted into substantially parallel light by the collimator lens 3, and the polarization beam splitter 4 and the quarter-wave plate 5
Are converted from linearly polarized light to circularly polarized light in the optical isolator composed of The light converted into circularly polarized light is condensed by the objective lens 9 of the optical element 51 and then enters the convex spherical lens 10. The incident light is refracted greatly by being incident on the convex spherical lens 10 having a high refractive index, and converges as a minute light spot on a plane portion of the convex spherical lens 10. When the distance between the flat portion of the convex spherical lens 10 and the recording layer of the optical disc D2 is smaller than the wavelength of the laser beam, the spot size of the light spot formed on the flat portion of the convex spherical lens 10 is reduced. , Optical disk D2
Is substantially the same as the spot size of the light spot formed on the recording layer. As a result, the laser beam is
Converged as a light spot on the recording layer of the optical disc D
The mark recorded on the second recording layer is irradiated. afterwards,
The reflected light from the recording layer of the optical disc D2 follows the reverse path, passes through the objective lens 9, and is converted by the quarter-wave plate 5 into linearly polarized light whose polarization direction is rotated by 90 °. Is reflected in the direction of the condenser lens 7. The light reflected by the polarization beam splitter 4 is condensed by the condenser lens 7 and is incident on the PD 8. PD
8 detects the output amount of the reflected laser light that changes according to the difference in the reflected light that occurs depending on whether or not there is a mark on the recording layer of the optical disk D2.
Playback becomes possible.

When the optical disk D2 is reproduced by the optical pickup device 50 as described above, the protective film 53 of the optical element 51 and the anti-reflection layer 2 of the optical disk D2 are reproduced.
4, a parallel plate-shaped air gap G5 is formed. However, since the reflectance of the optical element 51 on which the protective films 52 and 53 are formed is almost 0%, there is almost no reflected light component in the air gap G5, and no repeated reflection occurs.
There is almost no noise light.

Since hard diamond-like carbon is used for the protective film 23 of the optical element 51 and the antireflection layer 24 of the optical disk D2, even if the optical element 51 comes into contact with the optical disk D2, , No scratches.

Next, a sixth embodiment of the present invention will be described with reference to FIGS. The optical pickup device 60 of the present embodiment is different from the optical pickup device 50 of the fifth embodiment in that an optical element 61 is used instead of the optical element 51 of the optical pickup device 50 of the fifth embodiment.

FIG. 9 is a configuration diagram showing a part of the optical pickup device 60 on an enlarged scale. As shown in FIG.
Optical element 61 of optical pickup device 60 of the present embodiment
Is constituted by arranging an objective lens 9 and a convex spherical lens 62 having a substantially hemispherical shape and having a high refractive index on the upper and lower surfaces of a transparent substrate 63, respectively. . In this case, the objective lens 9 and the convex spherical lens 62 are arranged such that their optical axes coincide. The side of the convex spherical lens 62 facing the optical disc D2 is the convex spherical lens 1 as described in the fifth embodiment.
Unlike 0, the curved surface has a large radius of curvature and is gentle. More specifically, this curved surface is a convex spherical lens 62
The surface is a curved surface such that the phase difference between the reflected light component on the optical disk D2 and the reflected light component on the surface of the optical disk D2 becomes an odd multiple of half a wavelength for all incident angles. At this time, the distance between the lowermost surface of the convex spherical lens 62 and the recording layer of the optical disk D2 is an odd multiple of half the wavelength of the laser light from the semiconductor laser 2. The convex spherical lens 62 has, for example, a wavelength of 6.
It is formed of a transparent optical glass having a refractive index n ₁₁ at 50 nm of 1.62.

In addition, a glass plate 64 is provided on the optical disk D2 side of the optical element 61. This glass plate 6
4 has a refractive index n ₁₂ at a wavelength of 650 nm.
1.62, which is almost the same as the refractive index n _{11 of the} second lens.

Here, a method of forming the convex spherical lens 62 and the glass plate 64 will be described with reference to FIG. First, as shown in FIG. 10A, a hemispherical concave portion 63a which is the shape of the convex spherical lens 62 is formed by etching the transparent substrate 63.

Next, as shown in FIG. 10B, after the concave portion 63a is filled with a resin-based adhesive X which is a high refractive index transparent material having a higher refractive index than the transparent substrate 63,
A glass plate 64 having a refractive index substantially the same as that of the high refractive transparent material is bonded. At this point,
The thickness of the glass plate 64 is larger than the designed thickness.

Thereafter, as shown in FIG. 10C, the glass plate 64 is polished so that the glass plate 64 has a designed thickness. In the present embodiment, the glass plate 64 is polished until the plate thickness becomes 20 μm.

Then, as shown in FIG. 10D, when the glass plate 64 is polished to a thickness of about 20 μm, the glass plate 64 also curves as the adhesive X expands. The curved surface as described above is formed. That is, the glass plate 64 is a thin plate. As described above, the convex spherical lens 62
Is formed.

On the glass plate 64, two protective films 65 and 66 are formed. In the present embodiment, the protective film 6 is made of MgF ₂ having a refractive index n ₁₂ of 1.38.
5 is formed, the refractive index n ₁₃ forms a protective layer 66 by a diamond-like carbon layer of 1.79. The thickness d ₁₂ of the protective film 65 is 116 nm, the thickness d ₁₃ of the protective film 66 is a 5 nm. Then, as shown in FIG. 11, the spectral reflectance of the convex spherical lens 62 on which such protective films 65 and 66 are formed is almost 0% when the wavelength λ of the laser beam is 650 nm. I understand. Here, antireflection means is realized by the two protective films 65 and 66.

The convex spherical lens 62 and the optical disk D2
Is set to be equal to or less than the wavelength of the laser light from the semiconductor laser 2, and between the protective film 66 of the optical element 61 and the antireflection layer 24 of the optical disk D2.
Air gaps G6 are provided at predetermined intervals.

In such a configuration, for example, during reproduction of the optical disk D2, the linearly polarized laser light emitted from the semiconductor laser 2 is converted into substantially parallel light by the collimator lens 3, and the polarization beam splitter 4 and the quarter-wave plate 5
Are converted from linearly polarized light to circularly polarized light in the optical isolator composed of The light converted into circularly polarized light is condensed by the objective lens 9 of the optical element 61 and then enters the convex spherical lens 62. The incident light is refracted greatly by being incident on the convex spherical lens 62 having a high refractive index, and converges as a minute light spot on a plane portion of the convex spherical lens 62. When the distance between the flat portion of the convex spherical lens 62 and the recording layer of the optical disc D2 is equal to or less than the wavelength of the laser beam, the spot size of the light spot formed on the flat portion of the convex spherical lens 62 is reduced. , Optical disk D2
Is substantially the same as the spot size of the light spot formed on the recording layer. As a result, the laser light is emitted from the optical disc D2.
Converged as a light spot on the recording layer of the optical disc D
The mark recorded on the second recording layer is irradiated. afterwards,
The reflected light from the recording layer of the optical disc D2 follows the reverse path, passes through the objective lens 9, and is converted by the quarter-wave plate 5 into linearly polarized light whose polarization direction is rotated by 90 °. Is reflected in the direction of the condenser lens 7. The light reflected by the polarization beam splitter 4 is condensed by the condenser lens 7 and is incident on the PD 8. PD
8 detects the output amount of the reflected laser light that changes according to the difference in the reflected light that occurs depending on whether or not there is a mark on the recording layer of the optical disk D2.
Playback becomes possible.

When the optical disc D2 is reproduced by the optical pickup device 60 as described above, the protective film 66 of the optical element 61 and the antireflection layer 2 of the optical disc D2 are reproduced.
4, a parallel plate-shaped air gap G6 is formed. However, the reflectance of the optical element 61 on which the protective films 65 and 66 are formed is almost 0%, and the light reflected on the surface of the slightly convex spherical lens 62 and the light reflected on the surface of the optical disk D2 are different. Since they cancel each other out due to the phase difference, there is almost no reflected light component in the air gap G6, and there is no repeated reflection, so that almost no noise light is generated.

Also, since hard diamond-like carbon is used for the protective film 66 of the optical element 61 and the antireflection layer 24 of the optical disk D2, even if the optical element 61 and the optical disk D2 come into contact with each other, , No scratches.

In each of the embodiments, the optical disc (optical information recording medium) has a reflective layer, a dielectric layer, a recording layer, a dielectric layer, a protective layer, and an anti-reflection layer sequentially laminated on a transparent substrate. Although the arrangement is provided, the invention is not limited to this, and optical information recording media having various layer configurations can be applied.

[0077]

According to the optical pickup device of the first aspect of the present invention, the semiconductor laser is separated from the semiconductor laser via the substantially hemispherical convex spherical lens disposed with a predetermined air gap between the optical pickup device and the optical information recording medium. In an optical pickup device that irradiates the emitted laser light onto the optical information recording medium as a light spot and optically records, reproduces or erases information on the optical information recording medium, the optical information recording of the convex spherical lens is performed. By providing the anti-reflection means on the medium side, the reflectance of light can be suppressed low by the anti-reflection means, and almost no reflected light component can be generated in the air gap. Does not occur,
Generation of noise light can be reduced.

According to the optical pickup device of the second aspect of the present invention, there is provided an optical element in which an objective lens and a substantially hemispherical convex spherical lens are provided integrally with their optical axes aligned. A laser beam emitted from a semiconductor laser is radiated as a light spot on the optical information recording medium via the convex spherical lens disposed with a predetermined air gap therebetween, and information is recorded on the optical information recording medium. In an optical pickup device that performs reproduction or erasure optically, by providing an anti-reflection means on the optical information recording medium side of the optical element, it is possible to suppress the light reflectance by the anti-reflection means, Since almost no reflected light component is generated in the air gap, repeated reflection does not occur, and generation of noise light can be reduced.

According to a third aspect of the present invention, in the optical pickup device of the first or second aspect, the anti-reflection means is made of a material having excellent wear resistance, for example, a convex spherical surface. Even if the lens and the optical information recording medium should come into contact with each other or if dust adheres to the lens, it is possible to prevent the convex spherical lens from being damaged.

According to a fourth aspect of the present invention, in the optical pickup device according to any one of the first to third aspects, the air gap is an even multiple of a half wavelength of laser light emitted from the semiconductor laser. By defining the width to be excluded, interference between the surface reflected light of the convex spherical lens slightly existing in the air gap and the reflected light of the surface of the optical information recording medium can be suppressed, and the generation of noise light can be suppressed. Can be reduced. Note that the width excluding an even multiple of the half wavelength of the laser light is preferably an odd multiple of the half wavelength of the laser light.

According to a fifth aspect of the present invention, in the optical pickup device according to any one of the first to fourth aspects, the surface of the convex spherical lens disposed on the optical information recording medium side is the convex spherical surface. A curved surface such that the phase difference between the reflected light component on the lens side and the reflected light component on the optical information recording medium side is an odd multiple of half the wavelength of the laser light emitted from the semiconductor laser for all incident angles. Since the light reflected by the convex spherical lens slightly existing in the air gap and the light reflected by the surface of the optical information recording medium are canceled by the phase difference, the reflected light in the air gap is formed. Components can be reliably removed.

According to a sixth aspect of the present invention, there is provided a concave part forming step of forming a concave part having substantially the same shape as that of the convex spherical lens, and the concave part formed in the concave part forming step is formed by the concave part forming step. A transparent material filling step of filling the transparent material with high refractive index, and a step of closing the concave portion with a thin plate having substantially the same refractive index as that of the transparent material with high refractive index after filling the transparent material with high refractive index. The curved surface of the convex spherical lens can be easily formed by forming the curved surface of the convex spherical lens according to claim 5 by curving the thin plate by expansion of the highly refractive transparent material.

According to a seventh aspect of the present invention, there is provided an optical information recording medium in which information is optically recorded, reproduced, or erased by the optical pickup device according to any one of the first to fifth aspects. An anti-reflection layer is provided on the surface of the medium located on the side of the optical pickup device, so that the reflectance of light is suppressed low by the anti-reflection layer. By using the optical pickup device according to any one of 1 to 5, almost no reflected light component is present in the air gap, so that repeated reflection does not occur and noise light can be prevented from being generated.

According to an eighth aspect of the present invention, in the optical information recording medium according to the seventh aspect, the antireflection layer is formed of a material having excellent wear resistance, so that, for example, a convex spherical lens Even if the optical information recording medium comes into contact with the optical information recording medium or dust adheres to the optical information recording medium, it is possible to prevent the optical information recording medium from being damaged.

According to the ninth aspect of the present invention, there is provided an optical disk apparatus according to any one of the first to fifth aspects, wherein a drive source for rotating and driving the optical information recording medium and a seek movable in the radial direction with respect to the optical information recording medium. By providing the optical pickup device according to any one of the first to fifth aspects, it is possible to provide an optical disk device having the same operation and effect as the optical pickup device according to any one of the first to fifth aspects.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing an optical pickup device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing an enlarged part of the configuration.

FIG. 3 is a configuration diagram showing an enlarged part of an optical pickup device according to a second embodiment of the present invention.

FIG. 4 is a graph showing the relationship between the wavelength of laser light and the reflectance of a convex spherical lens.

FIG. 5 is a configuration diagram showing an enlarged part of an optical pickup device according to a third embodiment of the present invention.

FIG. 6 is a configuration diagram schematically showing an optical pickup device according to a fourth embodiment of the present invention.

FIG. 7 is a configuration diagram showing a part of the configuration in an enlarged manner.

FIG. 8 is a configuration diagram showing an enlarged part of an optical pickup device according to a fifth embodiment of the present invention.

FIG. 9 is a configuration diagram showing an enlarged part of an optical pickup device according to a sixth embodiment of the present invention.

FIG. 10 is an explanatory diagram showing a method of forming a convex spherical lens and a glass plate.

FIG. 11 is a graph showing the relationship between the wavelength of laser light and the reflectance of a convex spherical lens.

FIG. 12 is a configuration diagram schematically showing an example of a conventional optical pickup device.

FIG. 13 is a configuration diagram showing an enlarged part of an optical pickup device including a conventional convex spherical lens.

[Explanation of symbols]

1, 20, 30, 40, 50, 60 Optical Pickup Device 2 Semiconductor Laser 9 Objective Lens 10, 32, 62 Convex Spherical Lens 13, 24 Antireflection Layer 41, 51, 61 Optical Element 63a Depression 64 Thin Plate D1, D2 Optical Disk G1 ~ G6 Air gap X High refraction transparent material

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 7/22 G11B 7/24 538J 7/24 538 G02B 1/10 A F-term (Reference) 2H087 KA13 2K009 AA02 CC06 DD03 5D029 MA21 5D119 AA11 AA22 AA31 AA32 AA43 BA01 CA06 DA01 DA05 EB02 JA44 JA64 JA65 JB02 JB03 JC03 NA05

Claims (9)

[Claims] 1. A laser beam emitted from a semiconductor laser via a substantially hemispherical convex spherical lens arranged with a predetermined air gap between the optical information recording medium and a light spot on the optical information recording medium. In the optical pickup device for optically recording, reproducing or erasing information on the optical information recording medium, anti-reflection means is provided on the optical information recording medium side of the convex spherical lens. Optical pickup device. 2. An optical element in which an objective lens and a substantially hemispherical convex spherical lens are integrally provided with their optical axes aligned, and are arranged with a predetermined air gap between the optical element and the optical information recording medium. An optical pickup device that irradiates a laser beam emitted from a semiconductor laser via the convex spherical lens onto the optical information recording medium as a light spot, and optically records, reproduces, or erases information on the optical information recording medium. 3. The optical pickup device according to claim 1, wherein an antireflection unit is provided on the optical information recording medium side of the optical element. 3. The optical pickup device according to claim 1, wherein the anti-reflection means is formed of a material having excellent wear resistance. 4. The light according to claim 1, wherein the air gap is defined to have a width excluding an even multiple of a half wavelength of laser light emitted from the semiconductor laser. Pickup device. 5. The surface of the convex spherical lens disposed on the optical information recording medium side has a phase difference between a reflected light component on the convex spherical lens side and a reflected light component on the optical information recording medium. The optical pickup device according to any one of claims 1 to 4, wherein the optical pickup device is formed on a curved surface so as to be an odd multiple of a half wavelength of laser light emitted from the semiconductor laser with respect to an incident angle. 6. A concave part forming step of forming a concave part having substantially the same shape as the convex spherical lens, a transparent material filling step of filling the concave part formed by the concave part forming step with a high refractive transparent material. After filling the high refractive transparent material, a concave portion closing step of closing the concave portion with a thin plate having substantially the same refractive index as the high refractive transparent material, wherein the thin plate is curved by expansion of the high refractive transparent material. A method for manufacturing an optical element, comprising forming a curved surface of the convex spherical lens according to claim 5. 7. An optical information recording medium on which information is optically recorded, reproduced, or erased by the optical pickup device according to claim 1, wherein a surface of the medium located on the optical pickup device side is provided. An optical information recording medium provided with an anti-reflection layer. 8. The optical information recording medium according to claim 7, wherein the antireflection layer is formed of a material having excellent wear resistance. 9. A drive source for rotationally driving an optical information recording medium, and the optical pickup device according to claim 1 which is capable of moving in a seek direction in the radial direction with respect to the optical information recording medium. An optical disc device characterized by the above-mentioned.