JP2003139901A - Optical lens, condenser lens, optical pickup and optical recording/reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical lens having high refractive index and low light absorbing characteristics in a UV wavelength region, to provide a condenser lens suitable for a near-field optical recording and reproducing method, to provide an optical pickup which can reduce the size of a condensed spot irradiating a recording medium and can deal with the requirement for high recording density and large capacity of a recording medium, and to provide an optical recording and reproducing device which is equipped with the optical pickup and can perform optical recording and reproducing with high recording density. SOLUTION: The condenser lens 13 is composed of one or more optical lenses 11, 12 including an optical lens 11 using an optical material selected from HfO2 , HfO2 -Y2 O3 , HfO2 -TiO2 , HfO2 -Sc2 O3 , HfO2 -Nd2 O3 , HfO2 -Ln2 O3 , Sc2 O3 , MgO, Y2 O3 , WO3 , Gd2 O3 , Eu2 O3 and Dy2 O3 . Thus, the optical pickup which uses light at 190 to 450 nm wavelength can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup having at least an optical lens, a condenser lens composed of a plurality of optical lenses, a light source for emitting light in the ultraviolet region, and a condenser lens composed of a plurality of optical lenses. The present invention relates to an optical recording / reproducing apparatus (including a magneto-optical recording / reproducing apparatus) provided with this optical pickup, and more specifically, it uses a material having a large refractive index of the optical lens in the ultraviolet light wavelength region and uses the numerical aperture of the optical lens. The optical lens, the condenser lens, the optical pickup, and the optical recording / reproducing apparatus (magneto-optical recording) suitable for a so-called near-field optical recording / reproducing system for recording / reproducing on / from an optical recording medium (including a magneto-optical recording medium). (Including playback device).

[0002]

2. Description of the Related Art Optical recording media (including magneto-optical recording media) typified by compact discs (CDs), mini discs (MDs) and digital video discs (DVDs) include music information, video information, data, programs and the like. Widely used as a storage medium. However, further enhancement of sound quality in music information, video information, data, programs, etc.,
Due to the demand for higher image quality, longer time, and larger capacity, an optical recording medium having a larger capacity (including a magneto-optical recording medium) and an optical recording / reproducing device (including a magneto-optical recording / reproducing device) for recording / reproducing the same have been developed. Is desired.

Therefore, in order to meet the above-mentioned requirements,
In an optical recording / reproducing device (including a magneto-optical recording / reproducing device), a light spot converged through a condenser lens by shortening the wavelength of a light source such as a semiconductor laser and increasing the numerical aperture of the condenser lens. The diameter is being reduced.

For example, as for a semiconductor laser, a GaN semiconductor laser whose oscillation wavelength has been shortened from the conventional 635 nm of a red laser to the 400 nm band is being put to practical use, and the diameter of a light spot is being reduced. .

For further shortening the wavelength, for example, a far-ultraviolet solid-state laser UW-1010 manufactured by Sony Corporation, which continuously oscillates a single wavelength light of 266 nm, has been released, and a further light spot The diameter is being reduced. In addition to the above, Nd: YAG laser double-wave laser (266 nm band) and diamond laser (235
nm band), GaN laser double wave laser (202 nm
Obi) is being researched and developed.

Further, for example, an optical lens having a large numerical aperture represented by a solid immersion lens (SIL) is used to realize a condensing lens having a numerical aperture of 1 or more, and the objective surface of this condensing lens is A so-called near-field optical recording / reproducing system has been studied in which recording / reproducing is performed by bringing the recording medium close to a distance of about the wavelength of a light source. In this near-field optical recording / reproducing system, it is important how the distance between the recording medium and the condenser lens is maintained in an optical contact state. Further, as the diameter of the light beam emitted from the light source and incident on the condenser lens becomes smaller, the distance between the recording medium and the condenser lens becomes very small, so that the condenser lens is greatly restricted in shape. Become.

Here, FIG. 12 shows a schematic configuration diagram of a main part of an optical pickup having the above-described condenser lens. Figure 1
As shown in FIG. 2, in this optical pickup, a super-hemispherical (first hemispherical shape is further added) first optical lens in order from the object side where the recording medium (optical recording medium or magneto-optical recording medium) 50 is present. 51 and second optical lens 52
A condenser lens 53 formed by arranging and is provided. Both the first optical lens 51 and the second optical lens 52 are formed of glass (SiO ₂ ) having a refractive index of n = 1.5. With this condenser lens 53, the light flux L can be converged and applied to the recording medium 50. Also,
The objective surface of the condenser lens 53, that is, the surface of the first optical lens 51 on the recording medium 50 side is close to the recording medium 50, and serves as the above-described near-field optical recording / reproducing type condenser lens 53.

The first semi-spherical optical lens 51 has a radius of curvature r, an index of refraction n, and a thickness t, where t = r (1 + 1 / n). I have a relationship. In this case, since the refractive index n = 1.5, t =
It becomes 1.667r. When the distance between the second optical lens 52 and the recording medium 50, which is determined by the numerical aperture of the second optical lens 52, is WD, t = r (1 + 1 / n)
It is necessary to satisfy the condition of = 1.667r <WD.

Therefore, in order to ensure the distance D between the first optical lens 51 and the second optical lens 52 suitably and easily, the radius of curvature r of the first optical lens 51 is as much as possible. It is necessary to select the material so that the material is formed small or the refractive index n thereof is as large as possible.

[0010]

However, the radius of curvature r of the first optical lens 51 cannot be reduced to about 1 mm or less due to the restriction of the assembling accuracy of the optical pickup. In the near-field optical recording / reproducing system, a condensing lens 53 is generally composed of a first optical lens 51 and a second optical lens 52 arranged in order from the object side.
Although a numerical aperture of 1 or more is realized by combining a plurality of optical lenses, the higher the numerical aperture, the higher the accuracy required for assembling the first optical lens 51 and the second optical lens 52, and the change in the environment. It is required to maintain this high accuracy. If the radius of curvature of the optical lens is too small, the two optical lenses 51, 5
Since the assembling accuracy of the condenser lens 53 composed of two cannot be increased, the curvature radius r of the first optical lens 51 cannot be reduced to about 1 mm or less.

Further, conventionally, glass has been used as a material for the optical lens.
I was using glass (SiO ₂) Is used
The refractive index n of the optical lens is limited to about 1.5 described above.
It was. Therefore, the thickness t of the first optical lens 51 is 1.6.
The limit is about 67 mm, and it is not possible to make it smaller than that.
could not.

On the other hand, in order to realize a high recording density in this near-field optical recording / reproducing system, as in the conventional optical recording / reproducing system, the emission wavelength of the light source is shortened and the numerical aperture of the condenser lens is increased. Due to the increase, it is necessary to reduce the size and area of the focused spot irradiated on the recording medium. Here, since the area of the condensing spot is semi-proportional to the square of the numerical aperture of the condensing lens, the numerical aperture of the condensing lens is increased in order to realize high density in the near-field optical recording / reproducing system. Is effective.

In the configuration in which the first optical lens 51 shown in FIG. 12 is a super-hemispherical optical lens, the numerical aperture NA of the near-field condenser lens 53 is NA = (numerical aperture of the second optical lens 52) × It is represented by (refractive index n of the first optical lens 51) × (refractive index n of the first optical lens 51). As described above, since glass (SiO ₂ ) is conventionally used as the material for the first and second optical lenses 51 and 52, the refractive index n of the first optical lens 51 is limited to about 1.5. there were. Therefore, for example, the second optical lens 52
When the numerical aperture is 0.45, the numerical aperture NA of the near-field condenser lens 53 is NA = 0.45 × 1.5 × 1.
5 = 1.0, and the numerical aperture NA could not be increased any further. Therefore, the conventional near-field condensing lens 53 made of a glass material has a limit in increasing the recording density.

Similarly, in the ultraviolet wavelength region,
Fluorinated compounds with low light absorption properties, eg Al
Even if a material such as F ₃ , BaF ₂ , MgF ₂ , or LiF ₂ is used, its refractive index is about 1.7 or less. For example, if the numerical aperture of the second optical lens is 0.45, it is a super hemisphere. Numerical aperture N of near-field condenser lens in case of optical lens
In the case of A, NA = 0.45 × 1.7 × 1.7 = 1.3, and the numerical aperture NA could not be further increased. Therefore, the near-field condensing lens using the conventional fluorinated compound has a limit in increasing the density.

In order to solve the above-mentioned problems, in the present invention, an optical lens having a high refractive index and a low light absorption characteristic in the ultraviolet wavelength region, and a near-field optical recording / reproducing system using this optical lens are suitable. Optical condensing lens, an optical pickup having the condensing lens, capable of reducing the condensing spot irradiated on the recording medium, and capable of coping with high recording density and large capacity of the recording medium. Further, the present invention provides an optical recording / reproducing apparatus equipped with this optical pickup and capable of performing optical recording / reproducing with high recording density.

[0016]

The optical lens of the present invention comprises:
HfO₂, HfO₂-Y₂O₃, HfO₂-TiO₂，
HfO₂-Sc₂O₃, HfO₂-Nd₂O₃, HfO
₂-Ln₂O₃, Sc ₂O₃, MgO, Y₂O₃, WO
₃, Gd₂O₃, Eu₂O₃, Dy₂O₃Chosen from
With an optical material, consisting of this optical material or this optical material
The material is the main component.

The condenser lens of the present invention is HfO.₂, HfO
₂-Y₂O₃, HfO₂-TiO₂, HfO₂-Sc₂
O₃, HfO₂-Nd₂O₃, HfO₂-Ln₂O₃，
Sc ₂O₃, MgO, Y₂O₃, WO₃, Gd₂O₃，
Eu₂O₃, Dy₂O₃Using an optical material selected from
It consists of this optical material or has this optical material as the main component
Composed of one or more optical lenses, including
It is what has been.

The optical pickup of the present invention is at least
A light spot is formed by converging the light source and the light emitted from this light source.
And a condenser lens that forms
Light with a wavelength in the range of 0 to 450 nm is emitted and
HfO₂, HfO₂-Y₂O₃, HfO₂-T
iO₂, HfO₂-Sc₂O₃, HfO₂-Nd
₂O ₃, HfO₂-Ln₂O₃, Sc₂O₃, MgO,
Y₂O₃, WO₃, Gd₂O ₃, Eu₂O₃, Dy₂O
₃Optical material selected from
Or 1 including an optical lens mainly composed of this optical material
It is composed of one or more optical lenses.

The optical recording / reproducing apparatus of the present invention has at least an optical
The light source and the light emitted from this light source are converged to form a light spot.
An optical pickup comprising a condenser lens to be formed
For recording and reproducing on a recording medium,
The light source emits light in the wavelength range of 190 to 450 nm.
Is emitted, and the condenser lens is HfO₂, HfO₂-Y
₂O ₃, HfO₂-TiO₂, HfO₂-Sc₂O₃，
HfO₂-Nd₂O₃, HfO₂-Ln₂O₃, Sc₂
O₃, MgO, Y₂O₃, WO₃, Gd₂O₃, Eu ₂
O₃, Dy₂O₃Using an optical material selected from
Optics consisting of or consisting of optical materials
Consists of one or more optical lenses, including lenses
It is a thing.

According to the configuration of the optical lens of the present invention described above
For example, HfO₂, HfO₂-Y₂O₃, HfO₂-TiO
₂, HfO₂-Sc₂O₃, HfO₂-Nd₂O₃, H
fO₂-Ln₂O₃, Sc₂O₃, MgO, Y₂O₃，
WO₃, Gd₂O₃, Eu₂O ₃, Dy₂O₃Choose from
Made of this optical material, or
Because it is composed mainly of optical materials,
The optical material has a high refractive index and high in the ultraviolet wavelength range
It has a high transmittance in the ultraviolet wavelength range because it has a transmittance.
It is possible to construct an optical lens having a folding rate and low absorption characteristics.
And become possible.

According to the configuration of the condensing lens of the present invention described above, since it is composed of one or more optical lenses including the optical lens of the present invention described above, the refractive index is high and the refractive index is low in the ultraviolet wavelength region. It becomes possible to configure a condenser lens having absorption characteristics, and the refractive index of the optical lens is high, so that the numerical aperture of the condenser lens is increased and the spot where the incident light is condensed by the condenser lens is increased. It can be reduced.

According to the configuration of the optical pickup of the present invention described above, since the condensing lens is composed of one or more optical lenses including the optical lens of the present invention described above, the light emitted from the light source 190 to It has a high refractive index and a high transmittance for light with a wavelength in the range of 450 nm. As a result, the light emitted from the light source is reduced as a light having a wavelength in the range of 190 to 450 nm, that is, an ultraviolet light wavelength region shorter than that of the conventional light source in the visible light region, and the condensed spot is reduced, and the refractive index of the optical lens is reduced. The high numerical aperture makes it possible to increase the numerical aperture of the condenser lens and further reduce the focal spot.

According to the configuration of the optical recording / reproducing apparatus of the present invention described above, the optical pickup of the present invention is provided, and the recording / reproducing is performed on the recording medium. It becomes possible to efficiently perform optical recording / reproducing with a high recording density.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to HfO ₂ , HfO ₂ −
_{Y 2 O 3, HfO 2 -TiO} 2, HfO 2 -Sc
_{2 O 3, HfO 2 -Nd 2} O 3, HfO 2 -Ln
₂ O ₃ , Sc ₂ O ₃ , MgO, Y ₂ O ₃ , WO ₃ , Gd
An optical lens comprising an optical material selected from ₂ O ₃ , Eu ₂ O ₃ , and Dy ₂ O ₃ or containing the optical material as a main component.

The present invention is based on HfO ₂ , HfO ₂ -Y
_{2 O 3, HfO 2 -TiO 2} , HfO 2 -Sc 2 O 3,
_{HfO 2 -Nd 2 O 3, HfO} 2 -Ln 2 O 3, Sc 2
O ₃ , MgO, Y ₂ O ₃ , WO ₃ , Gd ₂ O ₃ , Eu ₂
A condensing lens comprising an optical material selected from O ₃ and Dy ₂ O ₃ and composed of one or more optical lenses including an optical lens made of this optical material or having the optical material as a main component. .

The present invention also provides the above condensing lens,
An optical lens made of an optical material or containing an optical material as a main component and another optical lens are arranged with their optical axes aligned.

The present invention is an optical pickup comprising at least a light source and a condenser lens for converging the light emitted from the light source to form a light spot, and the light source has a range of 190 to 450 nm. The light of the wavelength is emitted,
The condenser lenses are HfO ₂ , HfO ₂ -Y ₂ O ₃ , and HfO.
_{2 -TiO 2, HfO 2 -Sc 2} O 3, HfO 2 -Nd
₂ O ₃ , HfO ₂ -Ln ₂ O ₃ , Sc ₂ O ₃ , MgO,
_{Y 2 O 3, WO 3,} Gd 2 O 3, Eu 2 O 3, Dy 2 O
Using an optical material selected from ₃ , including an optical lens made of this optical material or containing this optical material as a main component 1
The optical pickup is composed of one or more optical lenses.

Further, according to the present invention, in the above optical pickup, an optical lens made of an optical material or containing an optical material as a main component has an absorption coefficient of 2.0 cm ^-1 or less for light emitted from a light source.

In the present invention, in the above optical pickup, the light source is composed of a GaN semiconductor laser.

Further, according to the present invention, in the above optical pickup, the light source is a Nd: YAG laser double wave laser, Ga.
It is composed of any one of a double-wave laser of N laser, Ar gas laser, and diamond laser.

According to the present invention, in the above optical pickup, an optical lens made of an optical material or containing an optical material as a main component and another optical lens are arranged in order from the object side and are arranged with their optical axes aligned. It constitutes an optical lens.

The present invention comprises an optical pickup having at least a light source and a condenser lens for converging light emitted from the light source to form a light spot, and an optical pickup for recording / reproducing on / from a recording medium. a recording and reproducing apparatus, light having a wavelength in the range of 190~450nm is emitted by a light source, a condenser _{lens, HfO 2, HfO 2 -Y 2} O 3, H
_{fO 2 -TiO 2, HfO 2 -Sc} 2 O 3, HfO 2 -
_{Nd 2 O 3, HfO 2 -Ln} 2 O 3, Sc 2 O 3, Mg
O, Y ₂ O ₃ , WO ₃ , Gd ₂ O ₃ , Eu ₂ O ₃ , Dy
An optical recording / reproducing apparatus comprising an optical material selected from ₂ O ₃ and one or more optical lenses including an optical lens made of this optical material or having the optical material as a main component.

According to the present invention, in the above-mentioned optical recording / reproducing apparatus, an optical lens made of an optical material or containing an optical material as a main component has an absorption coefficient of 2.
The configuration is 0 cm ^-1 or less.

In the present invention, in the above optical recording / reproducing apparatus, the light source is composed of a GaN semiconductor laser.

In the optical recording / reproducing apparatus of the present invention, the light source is a Nd: YAG laser double-wave laser or GaN.
It is composed of any of a laser double-wave laser, an Ar gas laser, and a diamond laser.

According to the present invention, in the above optical recording / reproducing apparatus, an optical lens made of an optical material or containing an optical material as a main component and another optical lens are arranged in order from the object side so that their optical axes coincide with each other. To form a condenser lens.

First, a description will be given of a specific embodiment of the present invention.
Prior to this, an outline of the present invention will be described. In the present invention
Is HfO₂, HfO₂-Y₂O₃, HfO₂-TiO
₂, HfO₂-Sc₂O₃, HfO₂-Nd₂O₃, H
fO₂-Ln₂O₃, Sc₂O ₃, MgO, Y₂O₃，
WO₃, Gd₂O₃, Eu₂O₃, Dy₂O₃Choose from
Made of this optical material, or
An optical lens whose main component is an optical material is used. That is, optics
The lens contains other ingredients besides the selected optical material
Good. Below, consists of this selected optical material or optical
An optical lens whose main component is a high refractive index optical material
Optical lens. Of these, HfO ₂-Y
₂O₃, HfO₂-TiO₂, HfO₂-Sc₂O₃，
HfO₂-Nd₂O₃, HfO₂-Ln₂O₃Each optical
The material is HfO₂To increase refractive index or transmittance
Y for big₂O₃, TiO₂, Sc₂O₃, Nd₂O
₃, Ln₂O₃With the addition of (lanthanoid oxide)
is there. The above optical materials have general chemical formulas.
Not only stoichiometric composition but other composition
Including those that are It also contains trace impurities
Including things.

Preferably, the optical lens made of the high refractive index optical material is made of a single crystal of the optical material. As a result, there is no grain boundary such as a polycrystalline material and no striae such as a glass material, and therefore, there is an advantage that scattering or absorption of incident light does not occur.

Further, since the crystal structure of HfO ₂ is cubic, it has optical isotropy in which the refractive index is constant in all directions regardless of the crystal axis. Similarly, Sc ₂ O ₃ , Mg
O, Y ₂ O ₃ , WO ₃ , Gd ₂ O ₃ , Eu ₂ O ₃ , Dy
_Since the crystal structure of each optical material of ₂ O ₃ is also a cubic crystal or a structure conforming to a cubic crystal (in the case of WO ₃ ), optical isotropy in which the refractive index is constant in all directions regardless of the crystal axis have. Therefore, when manufacturing an optical lens made of a high refractive index optical material, cutting, processing, without worrying about the crystal axis direction,
Polishing can be performed. Therefore, it is possible to process the glass material at a cost comparable to that of the glass material.

Further, the optical material constituting the optical lens made of the high refractive index optical material is vapor deposition, sputtering, electron beam vapor deposition, pulling method (CZ method), Bernoulli method, floating zone method (FZ).
Method), Bridgman method, flux method, top seed method (TSSG method), solvent transfer floating zone method (TSFZ method),
Laser annealing method, thermal crystallization (solid phase growth) method, chemical vapor deposition (Chemical Vapor Deposition)
n: CVD) method, plasma CVD method or the like.

Further, in the present invention, the condenser lens is composed of one or more optical lenses including the above-mentioned optical lenses made of the high refractive index optical material. That is, a condensing lens having any one of the following configurations A to C is configured. A. Condensing lens B. consisting of one optical lens made of high refractive index optical material. Condensing lens C. combining a plurality of optical lenses made of high refractive index optical material. A condensing lens in which an optical lens made of a high refractive index optical material and an optical lens made of another material are combined. Incidentally, in the configuration of C, the high refractive index optical is the most objective side, that is, the most recording medium side of the plurality of optical lenses. Place an optical lens made of material.

Further, in the present invention, the light source is set to 190 to
A light source that emits light with a wavelength in the range of 450 nm is used. That is, the wavelength in the conventional visible light region (for example, 635n
A light source that emits light of a shorter wavelength than the light source that emits light of m) is used. As such a light source, for example, Ga
In addition to the N semiconductor laser, a Nd: YAG laser double-wave laser, a GaN laser double-wave laser, an Ar gas laser, a diamond laser, and the like can be given. Then, an optical pickup is configured by including at least this light source and the above-mentioned condenser lens.

As a result, the wavelength of the light emitted from the light source can be shortened, and the condensed spot by the condenser lens can be reduced. In addition, since the above selected high refractive index optical material has a high refractive index with respect to light having a wavelength in the range of 190 to 450 nm, and has a high refractive index as compared with conventional glass or fluoride, It is possible to increase the numerical aperture of the optical lens. The condensing spot can also be reduced by increasing the numerical aperture of the condensing lens, so that it is possible to cope with the high recording density together with the shortening of the wavelength of the light source.

When HfO ₂ is adopted as the selected high refractive index optical material, the refractive index of the optical lens can be increased to 2.0 or more, and the wavelength of 19
Excellent light transmittance (light transmittance) for light with a wavelength longer than 0 nm. Similarly, when HfO ₂ —Y ₂ O ₃ is adopted, the refractive index of the optical lens becomes 1.8 or more, and the wavelength of 25
Excellent light transmittance (light transmittance) at wavelengths longer than 0 nm. H
When fO ₂ —TiO ₂ is adopted, the refractive index of the optical lens is 2.15 or more, and the light transmittance (light transmittance) is excellent at a wavelength longer than 350 nm. HfO ₂ -Sc ₂ O
_{When 3} is used, the refractive index of the optical lens is 1.75.
Therefore, the light transmittance (light transmittance) is excellent at a wavelength longer than 300 nm. When HfO ₂ —Nd ₂ O ₃ is adopted, the refractive index of the optical lens becomes 1.80 or more, and the wavelength of 3
Excellent light transmittance (light transmittance) at wavelengths longer than 50 nm.
When HfO ₂ -Ln ₂ O ₃ is adopted, the refractive index of the optical lens is 1.90 or more, and the light transmittance (light transmittance) is excellent at a wavelength longer than 250 nm. When Sc ₂ O ₃ is used, the refractive index of the optical lens is 1.85 or more, and the light transmittance (light transmittance) is excellent at a wavelength longer than 250 nm. When MgO is used, the refractive index of the optical lens is 1.71 or more, and the light transmittance (light transmittance) is excellent at a wavelength longer than 190 nm. When Y ₂ O ₃ is used, the refractive index of the optical lens becomes 1.75 or more, and the light transmittance (light transmittance) at a wavelength longer than 300 nm.
Is excellent. When WO ₃ is used, the refractive index of the optical lens is 2.0 or more, and the light transmittance (light transmittance) is excellent at a wavelength longer than 280 nm. When Gd ₂ O ₃ is adopted, the refractive index of the optical lens becomes 1.88 or more,
Excellent light transmittance (light transmittance) at wavelengths longer than 350 nm. When Eu ₂ O ₃ is used, the refractive index of the optical lens is 1.9 or more, and the light transmittance (light transmittance) is excellent at a wavelength longer than 350 nm. When Dy ₂ O ₃ is adopted, the refractive index of the optical lens becomes 1.86 or more,
Excellent light transmittance (light transmittance) at wavelengths longer than 300 nm.

Further, an optical lens made of a high refractive index optical material using the above-mentioned selected optical material is the above-mentioned 190-45.
Excellent light transmittance (light transmittance) for light having a wavelength within the range of 0 nm. In the present invention, the light (19) emitted from the light source of the optical lens made of the high refractive index optical material
The absorption coefficient for light having a wavelength in the range of 0 to 450 nm) is set to 2.0 cm ^-1 or less. Thereby, the loss of light due to the optical lens made of the high refractive index optical material is reduced, and the efficiency of optical recording / reproducing can be improved. It is preferable that the absorption coefficient is small, and preferably the absorption coefficient is set to 0.1 cm ^-1 or less so that there is almost no loss due to the optical lens. When the absorption coefficient is 0.1 cm ^-1 , the internal transmittance can be 95% or more with an optical lens having a thickness of 5 mm.

By the way, for each optical material,
The refractive index for light with a wavelength in the range of 450 nm is almost constant regardless of the crystal, but the absorption coefficient for light with a wavelength in the range of 190 to 450 nm may differ for each crystal.

Therefore, it is desirable to control the composition and manufacturing conditions of the optical lens made of the high refractive index optical material so that the absorption coefficient is 2.0 cm ^-1 or less. For example, the absorption coefficient can be reduced to 2.0 cm ^-1 or less by controlling and optimizing the oxygen defect concentration and the composition ratio. The oxygen defect concentration can be adjusted by changing the heat treatment time in an oxygen atmosphere after growing the single crystal.

Since each of the above-mentioned optical materials has a high refractive index, the numerical aperture of the condenser lens can be increased (for example, 1.5 or more) as described above, and the condenser lens can be downsized and Thinning is possible. As a result, it can be mounted on an optical pickup device, an optical recording / reproducing device or the like at a relatively low cost.

Further, the optical axes of the optical lens made of the high refractive index optical material and the other optical lens (the optical lens made of the high refractive index optical material or the optical lens made of another material) are aligned in order from the object side. In the case of the above-mentioned configuration B or C in which the condenser lens is configured by a plurality of optical lenses including an optical lens made of a high-refractive-index optical material, the diameter of the light beam incident on the condenser lens is Can be small. This is because an optical lens made of a high-refractive-index optical material arranged on the objective side has a high refractive index, so that the apertures of other optical lenses required to realize the same numerical aperture (for example, 2.0) of the condenser lens. This is because the number can be reduced, and the radius of curvature of the other optical lens can be reduced. If the radius of curvature is small, even if the diameter of the incident light beam is small, a sufficient distance from other optical lenses to the recording medium is secured, and high assembly accuracy is achieved in a condensing lens composed of multiple optical lenses. can do. Since the diameter of the light beam incident on the condenser lens can be reduced in this way, the condenser lens that is controlled and driven in the focusing direction and the tracking direction of the optical recording medium can be made compact and lightweight. It is possible to improve the servo characteristics such as focusing servo, tracking servo, and seek time.

Therefore, according to the present invention, it is possible to provide an optical pickup and an optical recording / reproducing apparatus which can cope with the shortening of the wavelength of the light source (for example, the wavelength of 190 to 420 nm) and the densification / capacity increase of the recording medium. .

The optical pickup of the present invention includes a read-only device for performing only reproduction, a record-only device for performing only recording, and a recording / reproducing device for performing both recording and reproduction. Further, the optical pickup of the present invention includes one that performs magneto-optical recording / reproducing with respect to a magneto-optical recording medium, and has a configuration in which a magneto-optical recording system and a near-field optical reproducing system are combined, for example, a magnetic coil or the like in a part of the optical pickup Including those that incorporate. Further, the optical recording / reproducing apparatus of the present invention includes a reproduction-only apparatus for performing only reproduction, a recording-only apparatus for performing recording only, and a recording / reproduction apparatus capable of performing both recording and reproduction.

According to the present invention, as in the structure shown in FIG. 12, for example, a condenser lens composed of a first optical lens and a second optical lens arranged in order from the objective side is held. The present invention can be applied to an optical pickup adopting a so-called near-field optical recording / reproducing system, and an optical recording / reproducing apparatus equipped with this optical pickup. Less than,
A case where the present invention is applied to this configuration will be described as a specific embodiment of the optical pickup according to the present invention.

FIG. 1 shows a schematic configuration diagram of a main part of an optical pickup as an embodiment of the present invention. Further, FIG. 2 shows one form of the configuration of an optical system that constitutes the optical pickup shown in FIG.

As shown in FIGS. 1 and 2, a light source (not shown) such as a semiconductor laser and a condenser lens 13 for condensing the light flux L on a recording medium (optical recording medium or magneto-optical recording medium) 30.
And the first beam splitter 14 for separating the light flux L1 emitted from the light source and the light flux L2 reflected by the recording medium 30.
And the second beam splitter 15 for splitting the light flux L2 reflected by the recording medium 30 into two light fluxes, thereby forming an optical pickup.

The light source is configured to emit light having a wavelength within the range of 190 to 450 nm. The condenser lens 13 is formed by arranging the first optical lens 11 and the second optical lens 12 in order from the recording medium 30 side so that their optical axes coincide with each other.

When the recording medium 30 is, for example, a disk-shaped medium, the recording medium 30 is mounted on a spindle motor (not shown) so that the recording medium 30 is rotated at a predetermined rotation speed. Although the first optical lens 11 and the recording medium 30 are not actually in contact with each other, the distance between the optical lens 11 and the recording medium 30 is sufficiently small compared to the thickness t of the optical lens 11. (For example, on the order of tens of thousands), it is drawn as in contact with each other in FIGS. 1 and 2. The same applies to the following figures.

In the optical pickup of the present embodiment, at least the first optical lens 11 on the recording medium 30 side of the condenser lens 13 is made of the above-mentioned optical lens made of the high refractive index optical material (the above-mentioned optical material). Or an optical lens whose main component is the optical material).
The material of the second optical lens 12 is not particularly limited, and may be any of the lenses made of the high refractive index optical material, the glass lens, the plastic lens, and the lenses made of other materials described above.

Next, the light path and the action of each component in the optical pickup shown in FIGS. 1 and 2 will be described. The forward light emitted from a light source such as a semiconductor laser is
It is converted into parallel light by a collimator lens (not shown). Then, the light flux L1 of the outward light passes through the first beam splitter 14 and is condensed on the information recording surface of the recording medium 30 via the condenser lens 13. The return light reflected by the information recording surface is transmitted through the condenser lens 13 again and
Is reflected by the beam splitter 14 and becomes a light beam L2, which is incident on the second beam splitter 15. The return light (light flux L3) reflected by the second beam splitter 15 is
The light is focused on a tracking photodetector (not shown), and a tracking error signal is detected. The backward light (light flux L4) that has passed through the second beam splitter 15 is focused on a focusing photodetector (not shown), and a focusing error signal, a reproduction pit signal, and the like are detected.

Further, the optical pickup shown in FIGS. 1 and 2 is provided with means for controlling and driving the condenser lens 13 in the tracking direction and the focusing direction. Examples of this means include a biaxial actuator used in a general optical pickup, a slider used in a magnetic head and the like. These condenser lenses 1
The form of the control driving means of No. 3 is shown below.

FIG. 3 shows a schematic configuration diagram when a biaxial actuator is adopted as the control driving means of the condenser lens 13 shown in FIGS. 1 and 2. As shown in FIG. 3, a biaxial actuator 16 including a coil 17 for controlling and driving the focusing lens 13 in the tracking direction (for tracking) and a coil 18 for controlling and driving the focusing lens 13 in the focusing direction (for focusing). The condenser lens 13 (11, 12) is fixed to the.

The biaxial actuator 16 is further constructed so that the distance between the recording medium 30 and the first optical lens 11 can be controlled. For example, by monitoring the amount of returning light and feeding back the distance information, the distance between the first lens 11 and the recording medium 30 can be kept constant, and
It is possible to avoid the collision between the lens 11 and the recording medium 30. Further, the biaxial actuator 16 monitors the amount of returning light and feeds back position information,
By driving the tracking coil 17, the condenser lens 1
3 can be moved in the tracking direction to move the focused spot to a desired recording track.

Next, the condenser lens 1 shown in FIG. 1 and FIG.
FIG. 4 shows a schematic configuration diagram when a slider is used as the control driving means of No. 3. As shown in FIG. 4, the condenser lens 1 is attached to the slider 21 controlled and driven in the tracking direction.
3 (11, 12) are fixed. This slider 21
Is supported by a movable optical unit (not shown) that moves in the tracking direction via an elastic body, for example, a gimbal 22 that has elasticity only in the surface contact direction of the recording medium 30. The movable optical unit is controllably driven in the tracking direction by a control drive unit composed of a linear motor or the like. Then, a gas flow generated with the rotation of the recording medium 30 flows between the recording medium 30 and the slider 21, and a gas thin film is formed which balances the pressing force of the gimbal 22 which is an elastic body toward the recording medium 30 side. The slider 21 is configured to fly above the recording medium 30 while maintaining a constant distance, for example, a distance of 50 nm. That is, when the recording medium 30 is rotated at a predetermined number of revolutions to reproduce information from the recording medium 30 or record information on the recording medium 30, the condenser lens 1
The distance between the first optical lens 11 and the recording medium 30 forming the third optical disc 3 is kept substantially constant by the slider 21.

It should be noted that the condenser lens 13 is used for the optical pickup and, if necessary, for the surface deflection of the recording medium 30.
2-axis actuator 16 or slider 2 for fixing
As a means for correcting the remaining focus error component followed by 1 and the error component generated during the assembly process of the condenser lens 13 (11, 12), two optical lenses 11,
A relay lens that can be corrected by changing the interval of 12 may be inserted between the first beam splitter 14 and the second optical lens 12. Also, FIG.
When the first optical lens 11 and the second optical lens 12 are fixed to the slider 21 as shown in FIG. 5, the remaining focus error component followed by the slider 21 and the error generated during the assembling process of the condenser lens are performed. As a means for correcting the component, of the two optical lenses constituting the condenser lens 13, the first optical lens 11 is fixed to the slider 21, while the second optical lens 12 is the first optical lens such as a piezoelectric element. For example, the optical lens 11 may be configured to be movable in the optical axis direction.

In the case of an optical recording / reproducing apparatus (structure similar to a stack type recording medium adopted in a magnetic recording / reproducing apparatus such as a hard disk drive), the spindle motor has means for mounting a plurality of optical recording media. , Fig. 5
It is preferable that the slider 21 is further provided with a mirror 23 that bends the optical axis by approximately 90 degrees, as shown in FIG. With such a configuration, the distance between the optical recording media of the optical recording / reproducing apparatus can be reduced, and as a result, the optical recording / reproducing apparatus can be made smaller and thinner.

Next, the shape of the first optical lens 11 will be described. The shape of the first optical lens 11 is not limited to the super-hemispherical shape shown in FIGS. 1 to 5, and other shapes can be adopted. Hereinafter, a form in which the shape of the first optical lens 11 is changed will be shown.

FIG. 6 shows a case where a hemispherical optical lens 11A is adopted as the first optical lens 11. At this time, the thickness of the lens matches the radius of curvature r. Further, FIG. 7 shows a case where the same super-hemispherical optical lens 11B as in FIG. 1 is adopted as the first lens 11. In addition to the hemisphere, a part of the upper half of the sphere is added by a thickness of r / n. At this time, the thickness of the lens is r (1 + 1 / n). In these cases, the objective surface facing the recording medium 30 is a flat surface, and the surface opposite to the objective surface is a convex spherical surface. In addition, the biaxial actuator 1
6 or fixed to the slider 21.

Next, FIG. 8 shows the hemispherical shape shown in FIG.
The case where the optical lens 11C having a shape in which the objective surface is processed into a conical shape is adopted is shown. Further, FIG. 9 shows a case where an optical lens 11D having a shape obtained by processing the objective surface into a conical shape is adopted from the super hemisphere shown in FIG. In the near-field optical recording / reproducing method, since the distance between the recording medium 30 and the first optical lens 11 is very close to several tens of nm, the objective surface is processed into a conical shape in this way. , Recording medium 30 or first optical lens 11
The tolerance for the inclination of can be expanded.

Further, when the recording medium 30 is a magneto-optical recording medium in the near field optical recording / reproducing system, a magnetic field is required at the time of recording and / or reproducing. In this case, as shown in FIG. 10 or 11, magnetic field applying means such as a magnetic coil 25 may be attached to a part of the objective surface of the first optical lens 11. FIG. 10 shows a case where the objective surface of the hemispherical optical lens 11E is processed so that the vicinity of the center is left and the magnetic coil 25 is provided. Figure 1
1 shows a case in which the objective surface of the super-hemispherical optical lens 11F is processed to leave the vicinity of the center and the magnetic coil 25 is provided.

Subsequently, various characteristics of the above-mentioned high refractive index optical material were examined.

(Example 1 / Comparative Example 1) As Example 1, H
A fO ₂ material was used, and a SiO ₂ material was prepared as Comparative Example 1. The wavelength dependence of the refractive index of Example 1 and Comparative Example 1 is shown in comparison with FIG. FIG. 13 shows 190 nm
The wavelength range from ˜800 nm is shown.

From FIG. 13, the HfO ₂ material of Example 1 was
The refractive index exceeds 1.9 in all wavelength ranges from 190 nm to 800 nm, and the value is 265 nm.
It can be seen that it reaches 2.1 or higher in the vicinity. On the other hand, the SiO ₂ material of Comparative Example 1 has a refractive index of about 1.5 in the entire wavelength range from 190 nm to 800 nm, and the value near the wavelength of 265 nm is 1.50.

Furthermore, FIG. 14 shows the wavelength dependence of the absorption coefficient of the HfO ₂ material of Example 1. From FIG. 14, the absorption coefficient of the HfO ₂ material of Example 1 is
It is found that all of the values are 0.1 cm ^-1 or less on the long wavelength side from nm, the light transmittance (light transmittance) is excellent, and the optical efficiency of recording / reproducing with respect to the optical power from the light source can be increased. .

Further, for Example 1 and Comparative Example 1, the refractive index at a wavelength of 265 nm was measured, and based on this refractive index, the materials of Example 1 and Comparative Example 1 were used for the first optical lens, respectively. This first optical lens and numerical aperture of 0.
The numerical aperture of the condensing lens when the condensing lenses 13 and 53 of the forms shown in FIGS. 1 and 12 were assembled by combining 45 second optical lenses was calculated. Table 1 shows the refractive index and the numerical aperture of the condenser lens. Further, an optical material obtained by adding other materials to the HfO _2, HfO ₂ -Y
_{2 O 3, HfO 2 -TiO 2} , HfO 2 -Sc 2 O 3,
Table 1 also shows the refractive index and the numerical aperture of the condenser lens when HfO ₂ —Nd ₂ O ₃ and HfO ₂ —Ln ₂ O ₃ are respectively used as the material of the optical lens.

[0074]

[Table 1]

As is clear from Table 1, conventional SiO 2₂
Compared to the material, HfO₂, HfO ₂-Y₂O₃, Hf
O₂-TiO₂, HfO₂-Sc₂O₃, HfO₂-N
d₂O₃, HfO₂-Ln₂O₃And the refractive index of
The numerical aperture of a condenser lens made of material is clear
It turns out to be great.

The area of the light spot condensed by the condenser lens can be reduced in inverse proportion to the square of the numerical aperture of the condenser lens. Therefore, it is understood that HfO ₂ can realize an optical pickup device capable of recording / reproducing an optical recording medium having a density 2.0 times higher than that of SiO ₂ .

(Examples 2 to 8) W as Example 2
The O ₃ material, a Sc ₂ O ₃ material as Example 3, the MgO material as Example 4, a Y ₂ O ₃ material as Example 5, the Gd ₂ O ₃ material as Example 6, as in Example 7 Eu ₂ O ₃ material, Dy ₂ O ₃ material as Example 8
I prepared each.

First, FIG. 15A shows the wavelength dependence of the refractive index of the WO ₃ material of Example 2. For comparison, FIG. 15B shows the wavelength dependence of the refractive index of the SiO ₂ material of Comparative Example 1 described above.
Shown in. From FIG. 15A, the WO ₃ material of Example 2 has a wavelength range of 190 nm to 800 nm in all wavelength ranges.
The refractive index exceeds 2.0, and the value reaches 2.3 at a wavelength near 400 nm. On the other hand, from FIG. 15B, the SiO ₂ material of Comparative Example 1 has a refractive index of about 1.5 and a value of 400 nm at a wavelength of 1.47 in the entire wavelength range from 190 nm to 800 nm.

For each of Examples 2 to 8 and Comparative Example 1, the refractive index at a wavelength of 400 nm was measured, and the first optical lens was compared with Examples 2 to 8 based on this refractive index. Each of the materials of Example 1 is used to combine the first optical lens with the second optical lens having a numerical aperture of 0.45 to form the condenser lenses 13 and 53 having the configurations shown in FIGS. The numerical aperture of the condenser lens when assembled was calculated. Table 2 shows the refractive index and the numerical aperture of the condenser lens.

[0080]

[Table 2]

As is clear from Table 2, conventional SiO₂
Compared to materials, WO₃, Sc₂O ₃, MgO, Y₂O
₃, Gd₂O₃, Eu₂O₃, Dy₂O₃Of each material
Folding rate and of the condensing lens made using these materials
The numerical aperture is obviously SiO₂Greater than material.

The area of the light spot condensed by the condenser lens can be reduced in inverse proportion to the square of the numerical aperture of the condenser lens. Therefore, if the wavelength of the light emitted from the light source of the optical recording / reproducing apparatus is set to a wavelength of 390 nm to 420 nm of the GaN semiconductor laser, for example, WO ₃ has a density 2.4 times higher than that of SiO _2. An optical pickup device capable of recording / reproducing on / from an optical recording medium can be realized. Further, for example, Sc ₂ O ₃ as compared to SiO _2,
It is possible to realize an optical pickup device capable of recording / reproducing an optical recording medium having a density as high as 1.5 times.

Next, in the structure of the optical pickup shown in FIG. 1, the two lenses of the condenser lens 13, that is, the first optical lens 11 and the second optical lens 12 are both set to the wavelength of 2.
Consider a case in which near field recording / reproduction is performed by forming HfO ₂ having a refractive index of 2.12 with respect to 65 nm and maintaining the distance between the first optical lens 11 and the recording medium 30 at 40 nm, for example. The first optical lens 11 is formed of a super hemispherical solid immersion lens (SIL). At this time, assuming that the numerical aperture of the second optical lens 12 is 0.45, from Table 1, the numerical aperture NA of the condenser lens 13 is 2.03. Then, the second optical lens 1
2 is WD, the thickness of the first optical lens 11 is t, and the radius of curvature of the convex spherical surface of the first optical lens 11 is r, t = r (1 + 1 / n ) =
It is necessary to satisfy the condition of 1.472r <WD. This condition is relaxed as compared with the case where the first optical lens is made of a glass (SiO ₂ ) material (1.667r <WD), and the distance WD between the second optical lens 12 and the recording medium 30 is WD.
Can be secured with a margin.

By the way, in the configuration of the near-field optical recording / reproducing optical pickup shown in FIGS. 1 and 12, the first semi-spherical optical lenses 11 and 51 are made of the above-mentioned HfO ₂ material of the first embodiment. SiO of Comparative Example 1
₂ Compare the case of using (glass) material. And
Regarding Example 1 and Comparative Example 1, the refractive index at a wavelength of 265 nm and the thickness t = r of the first optical lenses 11 and 51.
Table 3 compares the numerical values of the element (1 + 1 / n) related to (1 + 1 / n).

[0085]

[Table 3]

As shown in Table 3, the numerical value of (1 + 1 / n) is 1.472 in the case of Example 1 and 1.667 in the case of Comparative Example 1. As can be seen from this comparison, since the HfO _{2 of} Example 1 has a large refractive index (2.12), the thickness t of the first optical lens 11 is set to that of the glass (SiO ₂ ) of Comparative Example 1. Can be reduced by about 12%. That is, it is understood that near-field recording / reproduction can be realized by the super hemispherical lens at a thickness closer to that of the hemispherical lens.

Therefore, as shown in FIG. 1, the distance WD between the second optical lens 12 and the recording medium 30 can be sufficiently secured, and the diameter of the light flux L incident on the second optical lens 12 can be ensured. Can easily be small. As a result, the first optical lens 11 can be made thin, and
Since the diameters of the first optical lens 11 and the second optical lens 12 can be reduced, the weight of the first and second optical lenses 11 and 12 can be reduced, and the first and second optical lenses 11 and 12 can be reduced. The condensing lens 13 can be made lighter. Therefore, since the weight of the condenser lens 13 that is controlled and driven in the focus direction and the tracking direction of the recording medium 30 is small, it is possible to improve the servo characteristics such as focus servo, tracking servo, and seek time. It is possible to reduce the size and thickness of the pickup and the optical recording / reproducing device.

The present invention is not limited to the above-mentioned embodiments, and various other configurations can be adopted without departing from the gist of the present invention.

[0089]

According to the present invention described above, the refractive index of the optical lens can be increased in the ultraviolet wavelength region. Further, according to the present invention, it is possible to increase the numerical aperture of the condenser lens and easily obtain a compact and lightweight condenser lens. Therefore, as compared with the case of using a condensing lens formed of a conventional glass material, the recording density can be significantly improved, and the optical pickup that enables recording and reproduction of a recording medium having a high recording density and a large capacity. And an optical recording / reproducing apparatus can be realized.

Further, when a condenser lens is constructed by arranging an optical lens made of the above-mentioned optical material or containing the optical material as a main component and another optical lens in order from the objective side with their optical axes aligned, It is possible to reduce the diameter of the light beam incident on the optical lens. This makes it possible to reduce the size and weight of the condenser lens that is controlled and driven in the focusing direction and the tracking direction of the recording medium, and improve the servo characteristics such as focus servo, tracking servo, and seek time. Become.

Therefore, according to the present invention, it is possible to provide an optical pickup device and an optical recording / reproducing device that are compatible with a light source of a shorter wavelength, which is expected as the density and capacity of an optical recording medium will be increased in the future. .

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a main part of an optical pickup according to an embodiment of the present invention.

FIG. 2 is a diagram showing one form of an optical system of the optical pickup of FIG.

FIG. 3 is a schematic configuration diagram in which a biaxial actuator is adopted as a control driving unit of the condenser lens of FIGS. 1 and 2.

FIG. 4 is a schematic configuration diagram in which a slider is used as a control drive unit of the condenser lens of FIGS. 1 and 2.

FIG. 5 is a schematic configuration diagram when a slider is provided with a mirror.

FIG. 6 is a diagram showing one form of a shape of a first optical lens.

FIG. 7 is a diagram showing one form of a shape of a first optical lens.

FIG. 8 is a diagram showing one form of the shape of the first optical lens.

FIG. 9 is a diagram showing an example of the shape of the first optical lens.

FIG. 10 is a diagram showing an example of the shape of the first optical lens.

FIG. 11 is a diagram showing an example of the shape of the first optical lens.

FIG. 12 is a schematic configuration diagram of a main part of an optical pickup including a near-field optical recording type condenser lens.

13 is a diagram comparing the wavelength dependence of the refractive index of Example 1 and Comparative Example 1. FIG.

FIG. 14 is a diagram showing the wavelength dependence of the absorption coefficient of Example 1.

15A is a diagram showing wavelength dependence of a refractive index in Example A. FIG. B is a diagram showing the wavelength dependence of the refractive index of Comparative Example 1. FIG.

[Explanation of symbols]

11 first optical lens, 12 second optical lens, 1
3 condensing lens, 162 axis actuator, 21 slider, 22 gimbal, 23 mirror, 25 magnetic coil, 30 recording medium (optical recording medium or magneto-optical recording medium)

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) G11B 7/125 G11B 7/125 A 7/135 7/135 A // C03C 10/02 C03C 10/02 F term (reference) ) 2H087 KA13 LA01 NA04 PA02 PA17 PB02 QA02 QA05 QA14 QA21 QA33 QA41 UA01 UA02 4G062 AA04 AA11 BB07 DA01 DA01 DB01 DD01 DE01 DF01 FE01 F01 FE01 FA01 FE01 FA01 FA01 FE01 FA01 EF01 FA01 EF01 FA01 FE01 FA01 EF01 EF01 FA01 FA01 EF01 FE01 FA01 EF01 EF01 FA01 FE01 FA01 EF01 FE01 FA01 EF01 FA01 EF01 FE01 FA01 EF01 FA01 FE01 FA01 FE01 FA01 FE01 FA01 FE01 FA01 EF01 FL01 FL02 GA01 GA10 GB01 GC01 GD01 GE01 HH01 HH03 HH05 HH07 HH08 HH09 HH11 HH13 HH15 HH17 HH18 HH20 JJ01 JJ03 JJ05 JJ07 JJ10 KK01 KK02 KK03 KK04 KK05 KK06 KK07 KK08 KK10 MM02 NN02 5D119 AA01 AA11 AA22 BB05 CA06 EB02 FA03 FA04 FA05 JA29 JA44 JB02 MA06 5D789 AA01 AA11 AA22 BB05 CA06 CA21 CA22 CA23 EB02 FA03 FA04 FA05 JA29 JA44 JB02 MA06

Claims (13)

[Claims] 1. HfO ₂ , HfO ₂ —Y ₂ O ₃ , HfO
_{2 -TiO 2, HfO 2 -Sc 2} O 3, HfO 2 -Nd
₂ O ₃ , HfO ₂ -Ln ₂ O ₃ , Sc ₂ O ₃ , MgO,
_{Y 2 O 3, WO 3,} Gd 2 O 3, Eu 2 O 3, Dy 2 O
An optical lens comprising an optical material selected from ₃ and consisting of or containing the optical material as a main component. 2. HfO ₂ , HfO ₂ —Y ₂ O ₃ , HfO
_{2 -TiO 2, HfO 2 -Sc 2} O 3, HfO 2 -Nd
₂ O ₃ , HfO ₂ -Ln ₂ O ₃ , Sc ₂ O ₃ , MgO,
_{Y 2 O 3, WO 3,} Gd 2 O 3, Eu 2 O 3, Dy 2 O
_A condenser lens comprising an optical material selected from ₃ and one or more optical lenses including an optical lens made of the optical material or having the optical material as a main component. 3. An optical lens made of the optical material or containing the optical material as a main component, and another optical lens are arranged so that their optical axes are aligned with each other. The condenser lens described in. 4. At least a light source and light emitted from the light source
And a condenser lens that converges the light to form a light spot.
An optical pickup consisting of With the above light source, the wavelength within the range of 190 to 450 nm
Light is emitted, The condenser lens is HfO₂, HfO₂-Y₂O₃, H
fO₂-TiO₂, HfO₂-Sc₂O₃, HfO₂−
Nd₂O₃, HfO₂-Ln₂O₃, Sc₂O ₃, Mg
O, Y₂O₃, WO₃, Gd₂O₃, Eu₂O₃, Dy
₂O₃From the optical material using an optical material selected from
1. Comprising or including an optical lens mainly composed of the optical material
One or more optical lenses
Optical pickup. 5. The optical lens made of the optical material or containing the optical material as a main component has an absorption coefficient of 2.0 cm ⁻¹ or less for light emitted from the light source. The optical pickup according to item 4. 6. The optical pickup according to claim 4, wherein the light source is a GaN semiconductor laser. 7. The optical pickup according to claim 4, wherein the light source is composed of any one of a Nd: YAG double-wave laser, a GaN double-wave laser, an Ar gas laser, and a diamond laser. . 8. The condensing lens is configured such that, in order from the object side, the optical lens made of the optical material or containing the optical material as a main component and another optical lens are arranged with their optical axes aligned with each other. The optical pickup according to claim 4, wherein the optical pickup is provided. 9. At least a light source and light emitted from the light source
And a condenser lens that converges the light to form a light spot.
Equipped with an optical pickup, It is an optical recording / reproducing device that performs recording / reproduction on a recording medium.
hand, With the above light source, the wavelength within the range of 190 to 450 nm
Light is emitted, The condenser lens is HfO₂, HfO₂-Y₂O₃, H
fO₂-TiO₂, HfO₂-Sc₂O₃, HfO₂−
Nd₂O₃, HfO₂-Ln₂O₃, Sc₂O ₃, Mg
O, Y₂O₃, WO₃, Gd₂O₃, Eu₂O₃, Dy
₂O₃From the optical material using an optical material selected from
1. Comprising or including an optical lens mainly composed of the optical material
One or more optical lenses
Optical recording / reproducing device. 10. The optical lens made of the optical material or containing the optical material as a main component has an absorption coefficient of 2.0 cm ⁻¹ or less for light emitted from the light source. 9. The optical recording / reproducing apparatus according to item 9. 11. The optical recording / reproducing apparatus according to claim 9, wherein the light source is composed of a GaN semiconductor laser. 12. The optical recording according to claim 9, wherein the light source is composed of any one of a Nd: YAG double wave laser, a GaN double wave laser, an Ar gas laser and a diamond laser. Playback device. 13. An optical lens made of the optical material or containing the optical material as a main component, in order from the object side,
The optical recording / reproducing apparatus according to claim 9, wherein the condensing lens is configured by arranging the optical axes of the other optical lenses so as to match each other.