JP2001154095A - Optical element, optical pickup device and recording/ reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high accuracy optical element, which is suitable to a close distance optical system, and is durable against heat, with little thermal influence, and which is not anisotropic, with less double refraction, and to provide an optical pickup device using the optical element, and to provide a recording/reproducing device equipped with the optical pickup device. SOLUTION: This optical element 1 is formed of thermosetting resin or photosetting resin, and the optical element 1 is provided with a 1st reflection surface 6, a 2nd reflection surface 4 and the high refraction area 7 of a plate part 5. The light reflected by the 2nd reflection surface is condensed to the high refraction area 7, and then the light oozing through the exit surface 7a of the high refraction area due to the close distance effect is used for the optical pickup. The optical pickup device includes the optical element 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element having a reflecting surface and suitable for a near-field optical system, an optical pickup device using the optical element, and a recording / reproducing apparatus provided with the optical pickup device. is there.

[0002]

2. Description of the Related Art In recent years, in order to increase the storage capacity in high-density optical recording, attempts have been made to reduce the spot size of laser light condensed for reading and writing on an optical disk and have been put to practical use. The most common way to do this is to shorten the wavelength of the light source. this is,
The spot radius called the Airy disk radius is expressed by the following equation (1). The spot size is reduced by shortening the wavelength, the size of the recording pit is reduced, and the pit density on the optical disk is increased. It is to let.

R = 0.61 · F · λ / n ≒ 1.22 · λ / (n · sin θ) = 1.22 · λ / NA (1) where, r: spot radius, λ: wavelength, θ: focal angle,
n: refractive index, NA: numerical aperture.

Therefore, conventionally, a compact disk (C
In D), the wavelength of the light source is 780 nm, whereas in the DVD capable of higher density recording, the wavelength of the light source is 650 nm.
When focusing on an optical disc with the same F-number objective lens, in the case of DVD,
Since the spot size becomes 1 / 1.2 of the CD and contributes to the recording density as an area ratio on the optical disk, the recording density increases by 1.2 ² = 1.44 times. Further, when the F-number is reduced, that is, when the light is focused using a bright objective lens, the spot size is reduced. That is, the brightness of the objective lens having an NA of 0.45 for CD use is 0.6 for NA for DVD use, and
Since the spot size becomes 1 / 1.33 times, this NA
The contribution to the recording density due to the increase is 1.77 times the CD. It can be seen that when combined with the above-described effect of shortening the wavelength, the recording density can be improved by 2.5 times or more.

Similarly, an objective lens that utilizes a near field is known as one that improves the recording density by shortening the wavelength of the focused spot light and simultaneously increasing the NA. For example, FIG. 9 shows Optics Design and
SIL (Solid Immersion) announced at Fabrication '98
Lens). As shown in FIG. 9, in this objective lens, the first surface 91 is a concave refraction surface, and gently diverges when a light beam from infinity is transmitted, but is reflected and folded by the plane of the second surface 92. Then, the light is suddenly condensed by the reflecting surface of the third surface 93, and is focused on the fourth surface 94, which is the exit surface, near the boundary surface with air. Most of the focal light is totally reflected because the optical medium constituting the objective lens has a higher refractive index than the air after emission, but the light is about a fraction of the wavelength with respect to the fourth surface S4. At the distance of, the light becomes light propagating on the fourth surface as an evanescent wave, and the light flux in the medium leaks into the air.
At this time, if the optical disc D is arranged so as to be close to the near field of 100 nm or less with respect to the fourth surface 94 so as to capture this miserable light, a collection of reading and writing on the optical disc at the wavelength in the medium is performed. Light spots can be connected.

In the above-described objective lens, the light beam condensed at the large converging angle θ on the third surface 93 becomes a large NA multiplied by the refractive index n of the medium, so that a very small spot size can be realized. The recording density can be dramatically increased. For example, the wavelength λ of the light source is 650 nm, the refractive index n of the medium of the objective lens is 1.8, and the converging angle θ is 6
If it is 0 °, the NA is 1.56, and the spot size is 1 / 2.6 times that of DVD. Therefore, the recording density is remarkably improved to 6.8 times, and is an objective lens suitable for an optical pickup optical system of an optical disk.

However, this objective lens is based on a catadioptric reflective optical system if the folding of the second surface 92 is eliminated, and the first surface 91 contributes to the reduction of aberration as an optical surface. And the third surface 93 as a reflection surface. For this reason, it is difficult to realize sufficient aberration correction.

An objective lens used for an optical pickup in a recording / reproducing apparatus is easily affected by heat from other parts of the apparatus, which may cause a problem in heat durability. Yes, it is necessary to cope with the effects of this heat. Nevertheless, there is a demand for an optical element having high optical precision and low birefringence without anisotropy.

[0009]

SUMMARY OF THE INVENTION A first object of the present invention is suitable for a near-field optical system, is durable to heat, has little heat influence, has no anisotropy and has high optical precision. An object of the present invention is to provide an optical element having a small birefringence, an optical pickup device using the optical element, and a recording / reproducing apparatus including the optical pickup device.

A second object of the present invention is to provide an optical element suitable for a near-field optical system and capable of sufficiently correcting aberrations, an optical pickup device using the optical element, and recording / reproducing provided with the optical pickup device. It is to provide a device.

[0011]

In order to achieve the above object, an optical element according to the present invention is characterized by being formed of a thermosetting resin or a photocurable resin, and having a reflecting surface formed at least partially. I do.

According to this optical element, since it is formed from a thermosetting resin or a photocurable resin, it is less affected by heat as compared with a thermoplastic resin, and can achieve durability against heat, It is possible to realize an optical element having high optical precision with little anisotropy and little birefringence. Further, since the reflection surface is formed, an optical element suitable for a near-field optical system using the reflection surface can be provided.
Further, since molding can be performed at a lower temperature, it is advantageous in terms of manufacturing cost.

In this specification, the term "reflective surface" refers to a surface that reflects 50% or more (preferably 90% or more) of light incident on the reflective surface.

A thermosetting resin is a resin having a reticulated structure which is hardly re-softened by heating once it is cured. Examples include, but are not limited to, methacrylate-based resins, styrene-based resins, urethane-based resins, and the like. As specific examples of preferred thermosetting resins,
There are UV1000, 2000, 3000 manufactured by Mitsubishi Chemical, MR-6, -7 manufactured by Mitsui Chemical, and Desolite manufactured by Nippon Synthetic Rubber.

The photocurable resin is a resin having a property of starting curing by irradiating ultraviolet rays, and generally, the curing speed is accelerated by applying heat. Therefore, even with the same monomer resin, a thermosetting resin and a photocurable resin can be separately formed by selecting a polymerization initiator. Specific examples of the photocurable resin material include UV1000, 2000, 3000 of Mitsubishi Chemical Corporation, Kayarad of Nippon Kayaku Co., Ltd., and MR-6, -7 of Mitsui Chemicals, Inc.
There are two or three by optimizing the UV irradiation intensity.
It can be cured in about a minute.

An incident surface on which light from the outside is incident;
An emission surface for emitting light to the outside, and the reflection surface is configured to collect light incident from the incident surface on the emission surface, so that the collected light seeps from the emission surface. Thus, an optical element suitable for the near-field optical system can be obtained.

Further, the reflection surface has at least a first reflection surface and a second reflection surface, the first reflection surface reflects incident light, and the second reflection surface reflects the first light. The light reflected by the reflection surface may be configured to be condensed on the emission surface.

Further, another optical element according to the present invention has a near-field effect on an exit surface where light from the outside enters from an incident surface and emits light to the outside, and is formed of a thermosetting resin or a photocurable resin. , And includes a reflective surface.

According to this optical element, since it is formed from a thermosetting resin or a photocurable resin, it is less affected by heat as compared with a thermoplastic resin, and can realize durability against heat, It is possible to provide an optical element having optically high precision near-field effect with little anisotropy and little birefringence. Further, since the reflection surface is formed, an optical element suitable for a near-field optical system using the reflection surface can be provided.

Further, the first reflecting surface may be formed in a planar shape or a curved shape, and the second reflecting surface may be formed in a curved shape such that light is condensed on the emission surface. Can be.

Further, by forming the region including the emission surface or the region including the vicinity of the emission surface from a material having a higher refractive index than other portions, light condensed in this region bleeds from the emission surface. The optical element which comes out and is suitable for the near-field optical system can be obtained.

In this case, a high refractive index region may be provided by disposing the lens in a region including the exit surface or a region including the vicinity of the exit surface.

In this case, the boundary surface between the material having a high refractive index and the material having a low refractive index is formed to be a substantially spherical surface having a center substantially at the center of the light exit surface, so that an optical element suitable for a near-field optical system can be obtained. it can.

In the above-described optical element, the reflection surface may be a back mirror or a front mirror.

Here, the surface mirror refers to a reflecting mirror having a configuration in which a light beam enters the reflecting surface from outside the medium constituting the reflecting surface and reflects to the outside of the medium at a reflection angle equal to the incident angle. Further, the back mirror refers to a reflecting mirror in which a light beam enters from the medium constituting the reflection surface, reflects the light beam at a reflection angle equal to the incident angle, and returns the light beam to the medium.

Further, it is preferable that the reflection surface is formed of a material different from that of the optical element body. This allows, for example,
It is possible to correct the aberration of the light incident on the boundary surfaces having different refractive indexes. Note that the different materials are materials whose refractive indexes are different from each other at least.

Further, another optical element according to the present invention has a reflecting surface formed at least in part from a material different from that of the optical element main body, wherein the reflecting surface has a first reflecting surface and a second reflecting surface. Wherein the first reflecting surface reflects the incident light, the second reflecting surface condenses at least a part of the light from the first reflecting surface on an emitting surface, and the first reflecting surface At least one of the surface and the second reflecting surface is formed inside the optical element body.

According to this optical element, an efficient optical element can be realized by obtaining a reflective surface having a large reflectance by using a reflective surface formed of a material different from that of the optical element body. Also, the first
The reflection surface and the second reflection surface are formed inside the optical element body, so that an optical element suitable for the near-field optical system can be obtained.

Further, the reflecting surface is a surface mirror, and a hemispherical lens having a high refractive index is disposed near the light emitting surface or in a light transmitting portion including a part of the light emitting surface, so that the surface inside the optical element main body is formed. Since the light is condensed in the air by the reflecting surface which is a mirror, the NA can be increased to one or more.

Further, by arranging a lens on the incident surface on which light from the outside enters, the light beam enters the lens, passes through the two optical surfaces, is reflected by the reflecting surface, and can be optically corrected for aberration. Since there are three surfaces, the distribution of aberration correction and the degree of freedom in optical design are expanded, and it becomes easy to secure good optical performance.

The optical element as described above is suitable for a near-field optical system using light leaching from an exit surface.

Therefore, an optical pickup device can be constructed by using the above-described optical element as an objective lens, and in particular, light leaching from the exit surface can be used for the optical pickup, and the spot size of the light can be reduced. An optical pickup device including a near-field optical system that can realize a large recording density can be configured.

Further, an optical pickup device of the present invention includes a light source, the above-described optical element for condensing light from the light source on an information recording medium, and a light receiving element for receiving light from the information recording medium. The closest distance between the optical element and the information recording medium is λ / 2 (λ: wavelength of the light source) or less.

According to this optical pickup device, a near-field optical system is constituted by the above-described optical elements, and light incident from a light source and leaching from an exit surface is used for an optical pickup, thereby reducing the spot size of the light. It is possible to configure an optical pickup device that can be reduced in size and realize a large recording density.

In this case, in order to use a large amount of near-field light, the closest distance is more preferably λ / 4 or less.

Further, the above-mentioned optical pickup device is provided,
A recording / reproducing apparatus capable of recording and / or reproducing at least one of audio and images can be configured.

[0037]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of an optical element showing an embodiment of the present invention.

As shown in FIG. 1, the optical element 1 has a concave lens portion 2 having a concave surface 2a into which light from the outside enters and a concave surface 2b from which the light exits, an optical element main body 3, and a flat plate portion 5.
A hollow portion 8 formed therein so as to be surrounded by the concave lens portion 2, the optical element body 3, and the flat plate portion 5, and a first reflecting surface 6 formed flat on the outer peripheral side of the flat plate portion 5. And light from the first reflecting surface 6 formed on the inner surface of the cavity 8
Reflection surface 4 for reflecting light so as to converge toward the center of
And a high refraction region 7 formed in the central portion 9 of the flat plate portion 5
And

Since the optical element body 3 is made of a thermosetting resin or a photocurable resin and is translucent, the concave lens portion 2 can be integrally formed. Also, since the material of the optical element is a thermosetting resin or a photocurable resin,
Compared with a thermoplastic resin, the influence of heat is small and durability against heat can be realized, and an optical element having no optical anisotropy, low birefringence and high optical precision can be realized. Further, since molding can be performed at a lower temperature, it is advantageous in terms of manufacturing cost.

Preferred examples of the thermosetting resin include UV 1000, 2000, 300 manufactured by Mitsubishi Chemical Corporation.
0, MR-6, -7 manufactured by Mitsui Chemicals, and Desolite manufactured by Nippon Synthetic Rubber.

Preferred examples of the photocurable resin include UV1000, 2000, 3000 manufactured by Mitsubishi Chemical Corporation.
And Kayarad manufactured by Nippon Kayaku, MR-6,-manufactured by Mitsui Chemicals
7 and the like. In the case of photocurable resin, a part of the molding die is made of a material such as glass that transmits ultraviolet light, and after filling the molding resin with a liquid resin at room temperature, it is cured by irradiating it with ultraviolet light. The element can be shaped.

The flat plate portion 5 is made of a light-transmitting material such as a glass plate, and has a first reflection surface 6 formed on the outer periphery of the central portion 9. The second reflecting surface 4 is formed with a curvature such that light is focused toward the center of the flat plate portion 5. The first reflection surface 6 and the second reflection surface 4 can be formed, for example, by a vapor deposition method using a silver material, and at least 50% or more of the light incident on each of the reflection surfaces 6, 4 is reflected. I have. The reflectance is more preferably 90% or more. The flat plate portion 5 can be fixed to the optical element main body 3 at its outer periphery by bonding or the like. Note that the optical element body 3 refers to the entire portion including the concave lens portion 2 and the second reflection surface 4 in FIG.

The high-refractive-index region 7 having a refractive index n formed near the center 9 of the flat plate portion 5 has a higher refractive index than the translucent material of the flat plate portion 5. And is formed in a substantially hemispherical shape by ion exchange, doping, or the like. The high refraction region 7 may not be made of a thermosetting material.

According to the optical element shown in FIG. 1, substantially parallel light enters from the concave surface 2a of the lens unit 2 and emerges from the concave surface 2b so as to diffuse around the optical axis p from the concave surface 2b. The diffused light is reflected by the first reflecting surface 6 of the flat portion 5, and the reflected light is further reflected by the second reflecting surface 4 toward the vicinity of the center of the flat portion 5, and is reflected near the center of the flat portion 5. get together. Then, the collected light enters the high refractive region 7 formed in the vicinity of the center 9 of the flat plate portion 5 and exits from the exit surface 7a. At this time, λ / 2 (λ
Near-field light having a wavelength of λ / n in the range of the distance of (light wavelength). The exuded light can be used for an optical pickup, for example, as shown in FIG. 2 described later. The use within the range of the distance of λ / 4 is more effective because the intensity of the near-field light decreases exponentially with the distance from the emission surface 7a.

As described above, in the embodiment of FIG.
The reflection surface 6 and the second reflection surface 4 are surface mirrors, but since the light passes through the lens portion 2, the optical element body 3 constituting the second reflection surface 4 and the like must be light-transmissive. Is preferred. In the case of such a front surface mirror, unlike the case of the back surface mirror as shown in FIG.
And then exits to the outside. In other words, there are three more free surfaces that transmit through the two optical surfaces (2a, 2b), are reflected by the second reflecting surface 4, and can optically correct aberration, and are one more than in the case of the back mirror. This is preferable because aberration can be corrected and good optical performance can be easily secured. For example, in the case of a backside mirror, aberration correction was performed on two free surfaces, so that only spherical aberration and coma for off-axis incident light could be corrected. Astigmatism can also be improved satisfactorily.

In the optical element having the above-described configuration of the surface mirror, since the incident light is condensed by the surface mirror in the air, the NA does not increase to 1 or more.
Since the high refraction region 7 is provided, the NA can be increased by the refractive index of the material constituting the high refraction region 7. For example,
The refractive index of the high refraction region 7 is set to 2.4 (SiO ₃ ) or 2.8.
(TiO ₂ ), the NA was 0.86 (θ = 60 °) when there was no high-refractive area 7.
2.1 and 2.4. Therefore, light with a small spot diameter can be obtained, and when used in an optical pickup device, high-density recording of 4.4 times or 5.8 times becomes possible.

Although the lens portion 2 on which the light beam first enters is a concave surface, it may be a convex surface. The optical surface shape does not matter, and the power on this surface may be positive or negative. If the power composed of this incident surface and the immediately following exit surface is positive, the transmitted light will be reflected by the next reflection surface and collected once before reaching the surface mirror in order to obtain a divergent light beam. .

Next, an optical pickup optical system and an optical pickup device including the optical element of FIG. 1 will be described with reference to FIG.

An optical pickup device 20 shown in FIG. 2 comprises an optical pickup optical system 21, a light source 22 composed of a laser diode, and a light receiving sensor 23 composed of a photodiode.
, And is configured to read information from the optical disk 10 by light from the light source 22. The optical pickup device 20 includes an auto-servo mechanism (not shown) so that the optical pickup device 20 can automatically move in the horizontal direction of FIG. 2 with respect to the optical disk 10, and automatically moves in the vertical direction of FIG. An auto tracking servo mechanism (not shown) is provided.

The optical pickup optical system 21 includes a diffraction grating 24 for diffracting a laser beam from a light source 22 and a diffraction grating 24.
A beam splitter 25 that reflects light from the optical disk 6 toward the optical disk 10 and transmits light from the optical disk 6 toward the light receiving sensor 23, a collimator lens 26 that converts the light reflected by the beam splitter 25 into parallel light, and a collimator lens The parallel light from the optical disk 26 enters the optical disk 10
And an optical element 1 for focusing light. Optical disk 10
Is arranged very close to the emission surface 7a of the optical element 1, and the distance between the optical disk 10 and the emission surface 7a of the optical element 1 is preferably λ / 2, where λ is the wavelength of the light source 22, and λ / 4 is more preferred.

According to the optical pickup device 20 shown in FIG.
The laser light from the light source 22 is diffracted by the diffraction grating 24, reflected by the beam splitter 25, converted into parallel light by the collimator lens 26, and then enters the optical element 1 from the lens unit 2. This incident light is applied to the flat plate portion 5 as described with reference to FIG.
, And is incident on the high refraction region 7 and exits from the exit surface 7a. At this time, light oozes within a range of a distance of λ / 2 from the emission surface 7a due to the near-field effect. The light due to the near-field effect is irradiated onto the rotating optical disk 10, the light is reflected from the optical disk 10, and the reflected light follows the reverse path, passes through the beam splitter 25, and is received by the light receiving sensor 23. By converting the intensity of the light into an electric signal, the information recorded on the optical disk 10 can be read. Similarly, information can be written and recorded on an optical disk.

In this case, in the optical element 1, the free surfaces that can optically correct aberrations are the concave surfaces 2 a and 2 b of the lens unit 2.
And the second reflecting surface 4, sufficient aberration correction is possible, and good optical performance can be secured. Therefore,
When applied to the optical pickup device 20 as shown in FIG.
This is preferable because accurate reading and writing can be performed. In addition, light having a small spot diameter can be obtained by the optical element 1, and high-density recording can be performed.

Next, a modification of the optical element shown in FIG. 1 will be described with reference to FIG. The optical element 11 shown in FIG. 6 has a hole shape obtained by hollowing out the vicinity 9 of the center of the flat plate portion 5 instead of the high refraction region 7 in FIG. 1, and is arranged so that the hemispherical lens 17 is embedded in the hole portion 9a. It was done. The periphery of the upper portion of the hole 9a is cut out in a chamfered shape to form a notch 9b, and the reflected light from the second reflecting surface 4 is not obstructed by the flat plate portion 5 and is sufficiently formed on the spherical surface of the hemispherical lens 17. To be incident on. The hemispherical lens 17 is arranged so that its emission surface 17a is flush with the outer surface 5a of the flat plate portion 5, but may be arranged so that the emission surface 17a protrudes from the outer surface 5a. Further, the hemispherical lens 17 is preferably formed from a high refractive index material. Further, the flat plate portion 5 does not necessarily need to be made of a translucent material, and may be a non-translucent material.

According to the optical element 11 shown in FIG. 6, substantially parallel light enters from the concave surface 2a of the lens unit 2 and emerges from the concave surface 2b so as to diffuse around the optical axis p from the concave surface 2b.
The diffused light is reflected by the first reflecting surface 6 of the plane portion 5,
This reflected light is further reflected by the second reflection surface 4 toward the vicinity of the center of the flat plate portion 5 and gathers near the center of the flat plate portion 5. Then, the collected light enters the hemispherical lens 17 and exits from the exit surface 17a. At this time, near-field light having a wavelength of λ / n (refractive index of the hemispherical lens 17) oozes within a range of λ / 2 (λ is the wavelength of the light source) from the emission surface 7a due to the near-field effect. The exuded light can be used for an optical pickup, for example, as shown in FIG. The use within the range of the distance of λ / 4 is more effective because the intensity of the near-field light decreases exponentially with the distance from the emission surface 7a.

Next, another optical element will be described with reference to FIG. The optical element shown in FIG. 3 is an objective lens having a reflective surface formed as a back mirror and formed of a translucent thermosetting resin or photocurable resin.

The optical element 31 shown in FIG. 3 has a concave surface 32 formed around the optical axis p, and a first planar reflecting surface formed on the bottom 35 so that light from the concave surface 32 is incident and reflected. 3
4 and a second reflecting surface 3 formed around the concave surface 32 and reflecting light from the first reflecting surface 34 toward the center of the bottom 35.
3 and a high refraction region 36 formed near the center of the bottom 35
And The second reflection surface 33 is formed with a curvature such that light is focused on the high refraction region 36. Further, a flange portion 37 is formed so as to protrude from the outer periphery of the optical element 31 in a direction substantially perpendicular to the optical axis p, and this flange portion 37 is used when attaching the optical element to an optical pickup device.

The optical element 31 is formed integrally from a thermosetting resin or a photocurable resin by molding, and is translucent. The first and second reflecting surfaces 34 and 33 are formed as back mirrors, and the second reflecting surface 33 has a curvature such that incident light is reflected toward the center of the bottom 35. The high refractive region 36 near the center of the bottom 35 is formed to have a higher refractive index than the resin material of the optical element, and is buried near the center of the bottom 35, for example, embedded by sputtering, vapor deposition, ion exchange,
It is formed in a substantially hemispherical shape by doping or the like.

According to the optical element 31, substantially parallel light from the upper side of the figure enters the optical element 31 so as to enter from the concave surface 32 and diffuse around the optical axis p. The light is reflected by the reflecting surface 34 and the reflected light is
3, the light is further reflected toward the vicinity of the center of the bottom 35,
Are focused and incident on the high refraction region 36 of FIG. Then, the collected light exits from the exit surface 36a of the high refractive region 36 to the outside. At this time, light oozes within a range of λ / 2 (λ is the wavelength of light) from the exit surface 36a due to the near-field effect. The exuded light can be used for an optical pickup of an optical information recording medium, for example, as described above.

Further, since the optical element 31 is formed of a thermosetting resin or a photocurable resin, the optical element 31 is less affected by heat as compared with a thermoplastic resin, and can realize durability against heat, It is possible to realize an optical element having high optical precision with little anisotropy and little birefringence. Further, since molding can be performed at a lower temperature, it is advantageous in terms of manufacturing cost. In addition, since it has durability against heat, FIG.
Used in an optical pickup device such as
Even if, for example, heat-generating electric components or electronic components such as a CPU are arranged around the device, thermal deformation is small and is preferable.

Next, a modification of FIG. 3 will be described with reference to FIG. The optical element 39 shown in FIG. 4 is obtained by forming the first reflecting surface 34 of the optical element 31 shown in FIG. 3 into a second reflecting surface 38 having a curvature. According to the optical element 39, the number of free surfaces that can optically correct aberration is three, which is one more than in FIG. 3, so that sufficient aberration correction is possible, and good optical performance is easily ensured, which is preferable. .

Next, FIG. 7 shows an optical pickup device using the optical element shown in FIG. The optical pickup device shown in FIG. 7 has an optical element 31 shown in FIG. 3 instead of the optical element 1 shown in FIG. The optical element 31 is fixed to the apparatus by a flange 37 in a direction substantially perpendicular to the optical axis p. In the optical element 31, the light incident from the optical system 21 exits from the exit surface 36a to the outside as described above.
Light exudes within a distance of 2. The light due to the near-field effect is irradiated onto the rotating optical disk 10, and information can be read from the optical disk 10 in the same manner as in the case of FIG. It is more effective to use within the range of the distance of λ / 4. Further, as described above, since the light has a small spot diameter, high-density recording becomes possible when used in an optical pickup device.

Next, still another optical element will be described with reference to FIG. The optical element shown in FIG. 5 is configured such that the reflection surface is formed as a parabolic back surface mirror, is formed of a translucent thermosetting resin or photocurable resin, and allows light to enter from the side. It is.

In the optical element 41 shown in FIG. 5, light incident substantially parallel from the side surface 42 is reflected by a parabolically-shaped reflecting surface 43 of the back mirror. It is configured to gather in the refraction region 45. The high refraction region 45 near the bottom surface 44 is formed at a substantially focal point of a parabolic shape of the reflection surface 43. Optical element 41
Is formed of a thermosetting resin or a photocurable resin by integral molding and is translucent. The high refractive region 45 near the bottom surface 44 is formed to have a higher refractive index than the resin material of the optical element, and is formed in a substantially hemispherical shape by, for example, embedding, ion exchange, doping, or the like near the bottom surface 44.

According to the optical element 41, substantially parallel light from the right side of the drawing enters from the side surface 42 and is reflected by the reflection surface 43, and the reflected light is collected in the high refractive region 45 near the bottom surface 44. Then, the collected light exits from the exit surface 45a of the high refraction region 45 to the outside. At this time, the light seeps within a range of λ / 2 (λ is the wavelength of light) from the exit surface 45a due to the near-field effect. The exuded light can be used for an optical pickup of an optical information recording medium, for example, as described above.

The incident surface 42 may be an optically transmissive surface having a curvature, or may be used as a toric surface or the like for correcting aberrations such as off-axis characteristics.

Further, since the optical element 41 is formed of a thermosetting resin or a photo-setting resin, the optical element 41 is less affected by heat as compared with the case of using a thermoplastic resin, and can realize durability against heat, and can realize optical durability. It is possible to realize an optical element having high optical precision with little anisotropy and little birefringence. Further, since molding can be performed at a lower temperature, it is advantageous in terms of manufacturing cost. In addition, since it has durability against heat, FIG.
Used in an optical pickup device such as
Even if, for example, an electric component or an electronic component that generates heat, such as a CPU, is arranged around the device, thermal deformation is small, which is preferable.

Next, FIG. 8 shows an optical pickup device using the optical element shown in FIG. The optical pickup device of FIG. 8 has an optical element 41 of FIG. 5 instead of the optical element 1 of the device of FIG. This optical element 41
In this case, the light incident from the optical system 21 exits from the exit surface 45a to the outside as described above. At this time, the light seeps within a range of λ / 2 from the exit surface 45a due to the near-field effect. The optical disk 10 in which light due to this near-field effect is rotating
The optical disk 10 is irradiated on the optical disk 10 in the same manner as in FIG.
Information can be read from. It is more effective to use within the range of the distance of λ / 4. Further, as described above, since the light has a small spot diameter, high-density recording becomes possible when used in an optical pickup device. Further, FIG. 8 includes an auto-tracking servo mechanism that automatically moves in the horizontal direction of the figure, and an auto-servo mechanism that automatically moves in the vertical direction of the figure.

[0068]

According to the present invention, an optical element which is suitable for a near-field optical system, has durability against heat, has little heat influence, has no anisotropy, has high optical precision and has low birefringence, An optical pickup device using this optical element and a recording / reproducing device provided with the optical pickup device can be provided.

Further, it is possible to provide an optical element suitable for the near-field optical system and capable of sufficiently correcting aberrations, an optical pickup device using the optical element, and a recording / reproducing apparatus including the optical pickup device.

[Brief description of the drawings]

FIG. 1 is a sectional view of an optical element according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing an optical pickup optical system and an optical pickup device including the optical system according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view of another modified optical element according to the embodiment of the present invention.

FIG. 4 is a sectional view showing a modification of the optical element of FIG. 3;

FIG. 5 is a cross-sectional view of an optical element of still another modification according to the embodiment of the present invention.

FIG. 6 is a sectional view showing a modification of the optical element of FIG. 1;

7 is a diagram schematically illustrating an optical pickup optical system including the optical element of FIG. 3 and an optical pickup device including the optical system.

8 is a diagram schematically illustrating an optical pickup optical system including the optical element of FIG. 5 and an optical pickup device including the optical system.

FIG. 9 is a cross-sectional view of a conventional optical element.

[Explanation of symbols]

1, 11, 31, 39, 41 Optical element 2 Lens portion 2a, 2b, 32 Concave surface 6, 34, 38 First reflective surface 4, 33 Second reflective surface 7, 36, 45 High refraction region 17 Hemispherical lens 7a, 36a, 45a, 17a Emission surface 43 Reflection surface 20 Optical pickup device 21 Optical pickup optical system 22 Light source 23 Light receiving sensor 26 Collimator lens

Claims (21)

[Claims] 1. An optical element comprising a thermosetting resin or a photocurable resin, wherein at least a part thereof has a reflection surface. 2. An imaging device according to claim 1, further comprising an incident surface on which light from the outside is incident, and an exit surface for emitting light to the outside, wherein said reflecting surface focuses light incident from said incident surface on said exit surface. The optical element according to claim 1, wherein: 3. The reflection surface includes at least a first reflection surface and a second reflection surface, wherein the first reflection surface reflects incident light, and wherein the second reflection surface includes the first reflection surface. The optical element according to claim 1, wherein the light reflected by the reflection surface is focused on the emission surface. 4. An outgoing surface through which light from the outside enters from an incident surface and emits light to the outside, has a near-field effect, is formed of a thermosetting resin or a photocurable resin, and includes a reflecting surface. An optical element characterized by the above. 5. The optical element according to claim 1, wherein the reflecting surface or the first reflecting surface is formed in a planar shape. 6. The optical element according to claim 1, wherein the reflection surface or the first reflection surface is formed in a curved shape. 7. The optical element according to claim 1, wherein the reflection surface or the second reflection surface is formed in a curved shape such that light is converged on the emission surface. 8. The optical element according to claim 2, wherein the region including the emission surface is made of a material having a higher refractive index than other portions. 9. The optical element according to claim 2, wherein a region including the vicinity of the emission surface is made of a material having a high refractive index. 10. The optical element according to claim 7, wherein a boundary surface between the material having a high refractive index and the material having a low refractive index is a substantially spherical surface having a center substantially at the center of the emission surface. 11. A mirror according to claim 1, wherein at least one of said reflecting surface, said first reflecting surface and said second reflecting surface is a back mirror.
The optical element according to any one of the above. 12. The apparatus according to claim 1, wherein at least one of said reflection surface, said first reflection surface and said second reflection surface is a surface mirror.
The optical element according to any one of the above. 13. The optical element according to claim 1, wherein the reflection surface is formed of a material different from that of the optical element body. 14. A reflection surface formed at least in part from a material different from that of the optical element main body, wherein the reflection surface includes a first reflection surface and a second reflection surface, and wherein the first reflection surface is provided. Reflects the incident light, the second reflecting surface condenses at least a part of the light from the first reflecting surface on an emitting surface, and optically couples the first and second reflecting surfaces. An optical element formed inside an element body. 15. The optical element according to claim 14, wherein the reflection surface is a surface mirror, and a hemispherical lens having a high refractive index is arranged near a light exit surface or a light transmitting portion including a part of the light exit surface. 16. The optical element according to claim 14, wherein a lens is arranged on an incident surface on which light from the outside enters. 17. The optical element according to claim 1, wherein the optical element is used for a near-field optical system. 18. An optical pickup device comprising the optical element according to claim 1 as an objective lens. 19. A light source, and condensing light from the light source on an information recording medium.
18. An optical element according to claim 17, further comprising: a light receiving element that receives light from the information recording medium, wherein a closest distance between the optical element and the information recording medium is λ /
2 (λ: wavelength of the light source) or less. 20. The optical pickup device according to claim 19, wherein the closest distance is λ / 4 or less. 21. A recording / reproducing apparatus comprising the optical pickup device according to claim 19, wherein at least one of recording and reproduction of at least one of sound and image is possible.