JPH11203708A - Optical recording and reproducing device and method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording/reproducing device having an excellent optical resolving power. SOLUTION: In an optical recording/reproducing device for performing the recording/reproduction of information in a recording medium 20 by using light from a light source 2, a semispherical lens 14 capable of generating an evanescent wave and an annular aperture 5 for shielding at least a part of a light beam passing through the semispherical lens 14 without contributing to the generation of the evanescent wave are provided on the optical path from the light source 2 to the recording medium 20. The annular aperture 5 shields the center of a laser beam passed through the semispherical lens 14 and forms the waveform of a hollow annular beam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus and method for recording / reproducing a signal on / from an optical disk by using a lens capable of generating an evanescent wave.

[0002]

2. Description of the Related Art In the field of information recording, various technological innovations for high-density recording have been observed today. In order to perform high-density recording on a limited area such as a recording medium, it is necessary to reduce the spot size of light emitted from a laser light source such as a semiconductor laser as much as possible. In order to satisfy such a demand, a technology for recording / reproducing using an extremely small spot formed through an evanescent wave has been developed.

[0003] This uses a lens capable of generating an evanescent wave (hereinafter, referred to as an "evanescent wave generating lens"), and converts an evanescent wave generated by total reflection of light in the evanescent wave generating lens. To use. Note that an evanescent wave generating lens positioned close to a recording medium is generally SIL
(Solid Immersion Lens). Since the evanescent wave generated by the evanescent wave generating lens exists as a minute light spot, the recording density of information on a recording medium such as an optical disk can be increased.

[0004]

However, even if light is incident on an evanescent wave generating lens in order to generate an evanescent wave, the evanescent wave generation efficiency is not always sufficient.

FIG. 24 is a conventional example showing a schematic configuration when a hemispherical lens is used as an evanescent wave generating lens. As shown in FIG. 1, light condensed by an objective lens 101 is perpendicularly incident on a curved surface of a hemispherical lens (an evanescent wave generating lens) 102, is condensed in the hemispherical lens 102, and is recorded on a recording medium 103. A light spot is formed on the recording surface by an evanescent wave.

FIG. 25 shows a schematic configuration of FIG. 24, in which the refractive index of the hemispherical lens 102 and the recording medium 103 is set to about 1.88, and the gap between the hemispherical lens 102 and the recording medium 103 is the wavelength of the incident light. FIG. 9 is a graph showing a normalized intensity distribution of a light spot when the incident angle of an end ray in the hemispherical lens 102 is set to about 57.6 ° at about 0.3 times. Where the horizontal axis of the graph is
Radial position (q /
λ).

As is apparent from FIG. 25, it can be understood that the formed light spot has a plurality of peaks in the radial direction on the recording surface of the recording medium 103. With respect to the maximum peak occurring at the center of the graph, the peaks occurring on both sides thereof are called side lobes and cause a reduction in optical resolution.

As described above, there is a problem that the optical resolution of the apparatus cannot be easily increased due to generation of side lobes. The present invention has been made in view of such a point, and an object of the present invention is to provide an optical recording / reproducing apparatus and an optical recording / reproducing method having excellent optical resolution.

[0009]

According to the present invention, there is provided an optical recording / reproducing apparatus for recording / reproducing information on / from a recording medium using light from a light source. A lens provided on the optical path and capable of generating an evanescent wave, and light blocking means for blocking at least a part of light passing through the lens capable of generating the evanescent wave without contributing to generation of the evanescent wave. It is characterized in that it is a device.

In addition, an objective lens for condensing light from the light source with respect to the lens capable of generating the evanescent wave can be provided in front of the lens capable of generating the evanescent wave.

Similarly, a meniscus lens can be provided before the lens capable of generating the evanescent wave and after the objective lens. Here, the light blocking means can be provided directly on the lens capable of generating the evanescent wave.

The light blocking means may be provided between the lens capable of generating the evanescent wave and the light source. Further, the light blocking means can be provided directly on the objective lens.

Further, the light blocking means can be provided between the objective lens and the light source. The light blocking means has a light blocking area variable function for changing a light blocking area. For this, for example, a liquid crystal shutter can be used.

Further, according to the present invention, in the optical recording / reproducing method for recording / reproducing information on / from a recording medium using the light from the light source, the step of blocking at least a part of the light from the light source and the step of not blocking An optical recording / reproducing method comprising: passing light through a lens capable of generating an evanescent wave; and irradiating a recording medium with light passing through the lens capable of generating an evanescent wave. I have.

According to the present invention described above, light that does not contribute to the generation of an evanescent wave is prevented from entering a lens capable of generating an evanescent wave. A recording / reproducing method is realized.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the overall configuration of an optical recording / reproducing apparatus according to the present invention. The optical recording / reproducing apparatus shown in FIG. 1 includes a light source 2 composed of a semiconductor laser, a collimator lens 4, an annular aperture (a diaphragm formed in an annular shape) 5, a condenser lens 6, and a pinhole portion 8.
, A collimator lens 10, an objective lens 12, and a hemispherical lens 14. Here, the hemispherical lens 14 corresponds to an evanescent wave generation lens, that is, an SIL. Then, light emitted from the hemispherical lens 14 is applied to the recording medium 20. The optical path of the laser beam is formed by these series of optical components.

The laser light on which the recording signal generated from the light source 2 is superimposed is shaped into parallel light by a collimator lens 4 and passes through an annular aperture (light blocking means) 5. This annular aperture 5 is, as shown in FIG.
It has an annular opening 5a. Therefore, the laser beam that has passed through the annular aperture 5 enters the condenser lens 6 in a hollow annular shape. The opening 5a of the annular aperture 5 and the objective lens 12 are set so that their optical central axes coincide.

The laser beam having passed through the condenser lens 6 enters the collimator lens 10 after passing through the pinhole 8, and is collimated by the collimator lens 10. This parallel light is transmitted through the objective lens 12 to the hemispherical lens 1.
4, a minute beam spot is formed on the bottom surface of the hemispherical lens 14. And this beam spot propagates through the air gap via evanescent waves,
Information is recorded on the recording layer through the surface of the recording medium 20.

Here, the hemispherical lens 14 utilizes a pressure generated by a fluid bearing action (air bearing) accompanying the rotation of the recording medium 20 so that the hemispherical lens 14 can face the recording medium 20 via a predetermined gap. It is configured. Note that the hemispherical lens 14 and the recording medium may be in contact with each other.

In FIG. 1, θm is a hemispherical lens 1
4 indicates the maximum incident angle of the laser beam, and θc indicates the critical angle in the hemispherical lens 14. Further, the pinhole portion 8 includes the condenser lens 6 and the collimator lens 10.
Are disposed at positions separated by the respective focal lengths f1 and f2. Therefore, the condenser lens 6 and the collimator lens 10 have a positional relationship separated by f1 + f2.

Then, the lens 1 for generating an evanescent wave
The distance between the recording medium 4 and the recording medium 20 is set close to, for example, 1/3 or less of the wavelength of the laser light used.
For example, a semiconductor blue laser (wavelength of about 400
When using (nm), the distance between the hemispherical lens 14 and the recording medium 20 is preferably set to 120 nm or less.

In the optical recording / reproducing apparatus of the present embodiment configured as described above, the size of the hollow annular light ring formed by the annular aperture 5 is represented by Δr,
Assuming that the size of the ring of the hollow circular light incident on the objective lens 12 is △ r ′ (see FIG. 1), the following relational expression holds.

[0023]

(Equation 1)

In this embodiment, the size △ r of the annular aperture 5 is set so that only the lens having an incident angle substantially equal to or larger than the critical angle θc enters the evanescent wave generating lens 14. This makes it possible to block most of the light that does not generate an evanescent wave and that is incident on the evanescent wave generation lens 14 from the objective lens 12. Needless to say, in the present invention, a necessary effect can be obtained only by providing a hollow annular stop in order to block light near the optical axis of the laser light.

If only the laser beam having an incident angle equal to or larger than the critical angle θc of the hemispherical lens 14 is allowed to pass, the following result is obtained. That is, as in the case shown in FIG. 25, the refractive index between the hemispherical lens 14 and the recording medium 20 is set to about 1.88, and the gap between the hemispherical lens 14 and the recording medium 20 is set to about 0.3 times the wavelength. , The incident angle of the end ray in the hemispherical lens 14 is set to about 57.6 °. When the annular aperture 5 is provided in the optical path and the normalized intensity distribution of the light spot is measured, a waveform as shown in FIG. 3 is obtained. The horizontal axis in FIG.
3 shows a position (q / λ) in the radial direction within the recording surface.

Here, FIG. 3 and FIG. 25 will be compared. FIG.
In No. 5, a peak called a side lobe exists on both sides of the maximum peak generated at the center. On the other hand, in FIG. 3 in which the annular aperture 5 is provided,
It can be seen that the height of the side lobes generated on both sides of the maximum peak is greatly reduced.

Generally, in designing an optical system, a method of blocking light incident near the optical axis of a lens and permitting light to pass only in a peripheral portion of the lens is well known.
This is commonly referred to as "apodization". It is known that when this method is used, the half width of the maximum peak can be reduced, but the side lobes increase.

On the other hand, the method of the present invention is completely different from the above-mentioned annular illumination (apodization) in the phenomenon itself.
That is, in the present invention, by using the aperture such as the annular aperture 5, the laser light having an incident angle smaller than the critical angle θc can be cut off, so that the side lobe can be reduced. Therefore, the optical resolution of the device is greatly improved. Such effects can be obtained not only by using a hemispherical lens but also by using another general evanescent wave generating lens.

This will be described in more detail. Light condensed by the evanescent wave generating lens at an incident angle equal to or larger than the critical angle θc, that is, light in a hollow annular shape irradiated to a position separated from the optical axis is referred to as “external light”. Light near the optical axis is referred to as “internal light”.

FIG. 4 is a graph showing the intensity distribution characteristics of spots when external light transmits more to the recording medium side than internal light. FIG. 5 shows the same amount of external light and internal light transmitted to the recording medium side. Graph showing the intensity characteristics of the spot when
FIG. 6 is a graph showing the intensity distribution characteristics of a spot when internal light is transmitted to the recording medium side more than external light.

In order to minimize the influence of the internal light on the intensity distribution of the final light spot (internal light + external light) formed on the recording medium side, as shown in FIG. While minimizing the transmittance of
It is necessary to increase the transmittance of external light as much as possible. Factors that affect the transmittance in this case include the NA of the objective lens, the lens shape and the refractive index of the evanescent wave generating lens, the distance between the evanescent wave generating lens and the recording medium, and the refractive index of the surface film of the recording medium. (If there is no surface film, the refractive index of the recording medium itself).

Of course, according to the present invention, only a hollow annular stop is provided to block light near the optical axis of the laser light.
Irrespective of the relationship with the critical angle, the optical resolution of the device can be improved.

As described above, according to the present invention, light that does not contribute to the generation of evanescent waves is prevented from entering the hemispherical lens 14 (lens for generating evanescent waves). It is easy to improve.

Further, the present invention can be realized with a structure in which only the annular aperture 5, that is, a stop is provided in the optical path of the apparatus. Therefore, no major design change of the optical system is required, and there is no disadvantage in cost.

FIG. 7 shows a second embodiment of the optical recording / reproducing apparatus according to the present invention.
FIG. 8 is a diagram showing an overall configuration according to the embodiment, FIG. 8 is a schematic configuration diagram of an optical system constituting a part of an optical recording / reproducing apparatus according to the embodiment, and FIG. 9 is a plan view of an objective lens. . In the following embodiments, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted.

In this embodiment, the objective lens 1A is provided on the surface of the objective lens 12A or inside the objective lens 12A.
A concentric diaphragm 13 is provided coaxially with the optical axis of 2A (see FIG. 7).

Here, as the diaphragm 13, various members can be used as long as they are members that shield light without transmitting light. For example, there is a method in which the aperture 13 is formed by applying or vapor-depositing a material having a high light absorption coefficient such as black on the objective lens 12A.

By arranging the aperture 13 directly on the objective lens 12A in this manner, the light emitted from the light source is also blocked. Therefore, of the light that has reached the objective lens 12A, only the light that has reached the portion outside the stop 13 can pass through the objective lens 12A and enter the hemispherical lens 14.

The aperture 13 is preferably formed so as to have a diameter such that only light having a critical angle θc or more enters the hemispherical lens 14. However, the effects of the present invention can be expected if at least the laser beam can be shaped into a hollow ring shape.

FIG. 10 is a schematic configuration diagram of an optical system according to a third embodiment of the optical recording / reproducing apparatus of the present invention. Since the overall configuration of the apparatus according to the present embodiment is almost the same as that of FIG. 1, it is not shown.

In this embodiment, before the objective lens 12,
That is, a light source composed of a semiconductor laser or the like and the objective lens 1
2, a diaphragm member 11 as an optical component is provided.

Here, the aperture member 11 is configured to block the light near the optical axis among the light incident on the objective lens 12, similarly to the annular aperture 5 shown in FIG. Specifically, it is a liquid crystal shutter, and the aperture control unit 11
It is possible to control the ON / OFF of the shutter or the shutter area by the control signal from A.

Also in this embodiment, the objective lens 12
By blocking a part of the light incident on the hemispherical lens 14, light that does not contribute to the generation of the evanescent wave is prevented. Thus, as in the previous embodiment, almost no side lobes exist in the intensity distribution of the light spot, and the optical resolution of the apparatus can be easily improved.

The aperture member 1 according to the third embodiment is used.
1 is a lens in which a diaphragm is directly formed on a lens such as a hemispherical lens or an objective lens (for example, the second embodiment)
Unlike this, the aperture member 11 can be removed from the optical path as needed.

When a liquid crystal shutter is used as shown in FIG. 10, the shutter area can be changed according to an electric signal from the aperture control unit 11A. Therefore, the amount of aperture by the aperture member 11 can be freely changed. This makes it possible to relatively easily correct variations in characteristics of individual optical components, which are likely to occur when mass-producing the apparatus. Further, it becomes possible to finely adjust the aperture amount according to the type of the recording medium and the like.

Instead of providing the diaphragm member 11 at a stage preceding the objective lens 12, it is also possible to provide the diaphragm member 11 at a stage subsequent to the objective lens 12. FIG. 11 is a schematic configuration diagram of an optical system according to a fourth embodiment of the optical recording / reproducing apparatus of the present invention.

In this embodiment, a concentric stop is provided on the surface of the hemispherical lens or inside the hemispherical lens so as to be coaxial with the optical axis of the hemispherical lens. The aperture 13 here is formed so as to have a diameter such that only light having a critical angle θc or more enters the hemispherical lens 14A. Of course, the effects of the present invention can be expected if at least the laser beam can be shaped into a hollow ring.

Also in the present embodiment, light that does not contribute to the generation of evanescent waves can be prevented from passing through the hemispherical lens 14A, so that the optical resolution of the device can be easily improved as compared with the conventional case. .

FIG. 12 is a schematic structural view of an optical system according to a fifth embodiment of the optical recording / reproducing apparatus of the present invention. In this embodiment, the evanescent wave generation lens, ie, S
As the IL, a lens 15 having a shape closer to a sphere (hereinafter, referred to as an IL)
(Referred to simply as "spherical lens"). When the radius of curvature of the spherical surface of the spherical lens 15 is r and the refractive index is n, the center thickness of the spherical lens 15 is about r (1 + 1 / n).
The laser beam directed to a point on the optical axis about nr below the center of the spherical surface of the spherical lens 15 is refracted by the spherical surface and the spherical lens 1
The light is condensed at the center of the bottom surface of No. 5.

The angle of incidence of the laser light refracted by the spherical surface of the spherical lens 15 increases. Therefore, it becomes possible to design an optical system using an objective lens having a smaller NA. For example, even if the objective lens is displaced in the direction of its optical axis due to vibration or the like, and its relative position with respect to the recording medium 20 changes, the adverse optical effect can be suppressed if the NA of the objective lens is small.

FIG. 13 is a schematic configuration diagram of an optical system according to a sixth embodiment of the optical recording / reproducing apparatus of the present invention. In this embodiment, an aspheric lens 16 in which an evanescent generation lens and an objective lens are integrated is used. A stop 13 is formed on the aspherical lens 16 on the surface or inside of the lens so as to pass only laser light having an incident angle equal to or greater than the critical angle θc.

By providing such an aperture 13,
Light that does not contribute to the generation of the evanescent wave is prevented from transmitting through the aspheric lens 16. Thus, as in the previous embodiment, almost no side lobes exist in the intensity distribution of the light spot, and the optical resolution of the apparatus can be easily improved.

Further, since the number of optical elements can be reduced as compared with the above-described embodiments, the configuration of the optical system can be simplified and the manufacturing cost can be reduced. In each of the embodiments described above, the intensity distribution of light incident on the evanescent wave generating lens is adjusted by providing a stop or the like. On the other hand, by optimizing the optical refractive index of the surface film of the recording layer of the recording medium (or the recording medium itself when there is no film), it is possible to reduce the size of the spot of the laser beam. Become. Hereinafter, this will be described.

FIG. 14 is a schematic diagram of an optical system according to a seventh embodiment of the optical recording / reproducing apparatus of the present invention.
17 are graphs showing the relationship between the refractive index of the surface film of the recording medium and the transmittance of the air gap. The overall configuration of the device used in this embodiment is basically the same as that shown in FIGS.

In FIG. 14, the transmittance (internal transmittance) of the laser beam 31 whose incident angle in the spherical lens 15 is equal to or smaller than the critical angle θc to the recording medium 20 is I1, the spherical lens 1
Laser light 35 whose incident angle within 5 is equal to or greater than the critical angle θc
The transmittance of the recording medium 20 (external transmittance) is I2. The internal transmittance I1 and the external transmittance I2 are approximately represented by the following equations.

[0056]

(Equation 2) here

[0057]

(Equation 3) It is. Here, n0 is the refractive index of the spherical lens 15, n
2 is the refractive index of the surface film of the recording medium 20 (the recording medium itself when there is no film), θc is the critical angle of the laser light in the spherical lens 15, θm is the maximum incident angle of the laser light in the spherical lens 14, d Represents the distance between the bottom surface of the spherical lens 14 and the surface of the recording medium 20, and λ1 represents the wavelength of the laser in the air.

Now, n0 is 1.83 (thus θc is about 3
3.1 °), θm is about 66.2 °, d is 150 nm, λ
1 is 830 nm. Then, the relationship of the transmittance I1 to the refractive index n2, the relationship of the transmittance I2 to the refractive index n2, and the relationship of I2 / I1 to the refractive index n2 are expressed as shown in FIGS. 15, 16, and 17, respectively.

In this case, the refractive index n2 is equal to the external transmittance I2
Is larger than the refractive index (about 1.8) when the maximum value (see FIG. 16), and the refractive index when the ratio I2 / I1 between the external transmittance I2 and the internal transmittance I1 is the largest (approximately 2. 1). 17)
If it is smaller (see FIG. 17), the spot formed on the surface of the recording medium 20 can be made smaller.

FIG. 18 is a schematic configuration diagram of an optical system according to an eighth embodiment of the optical recording / reproducing apparatus of the present invention.
21 to 21 are graphs showing the relationship between the refractive index of the surface film of the recording medium and the transmittance of the air gap. The overall configuration of the device used in this embodiment is basically the same as that shown in FIGS.

This embodiment is different from the first embodiment in that a hemispherical lens 14 is used instead of a spherical lens as an evanescent wave generating lens. Also in FIG. 18, the laser beam 3 whose incident angle in the hemispherical lens 14 is equal to or smaller than the critical angle θc
1 is the transmittance (internal transmittance) to the recording medium 20, and I2 is the transmittance (external transmittance) of the laser light 35 whose incident angle in the hemispherical lens 16 is equal to or more than the critical angle θc to the recording medium 20. And The internal transmittance I1 and the external transmittance I2 are approximately represented by the following equations.

[0062]

(Equation 4) here

[0063]

(Equation 5) It is. Here, n0 is the refractive index of the hemispherical lens 14, n
2 is the refractive index of the surface film of the recording medium 20 (the recording medium itself if there is no film), θc is the critical angle of the laser light in the hemispherical lens 14, θm is the maximum incident angle of the laser light in the hemispherical lens 14, d Represents the distance between the bottom surface of the hemispherical lens 16 and the surface of the recording medium 20, and λ1 represents the wavelength of the laser in the air.

Now, n0 is 1.83 (thus θc is about 3
3.1 °), θm is about 66.2 °, d is 150 nm, λ
1 is 830 nm. Then, the relationship of the transmittance I1 to the refractive index n2, the relationship of the transmittance I2 to the refractive index n2, and the relationship of I2 / I1 to the refractive index n2 are expressed as shown in FIGS. 19, 20, and 21, respectively.

In this case, the refractive index n2 is equal to the external transmittance I2
Is larger than the refractive index (about 1.93) at the time when the maximum (see FIG. 20), and the refractive index (= ∞) when the ratio I2 / I1 between the external transmittance I2 and the internal transmittance I1 becomes the maximum. If it is smaller than that (see FIG. 21), that is, if it is 1.93 or more, it becomes possible to reduce the spot formed on the surface of the recording medium 20.

FIG. 22 is a schematic configuration diagram of an optical system according to a ninth embodiment of the optical recording / reproducing apparatus of the present invention. In the apparatus shown in FIG. 1, a prism 18 is provided between two objective lenses 12 and a recording medium 20, and an evanescent wave generated on the bottom surface of the prism 18 is used. That is, 2
By combining the objective lenses 12 and the prism 18, the function of an evanescent wave generation lens is provided. One objective lens has a role of converging the parallel light and focusing on the bottom surface of the prism, and the other objective lens has a role of converting the light reflected on the bottom surface of the prism or the recording medium into parallel light.

In the case of this embodiment, as shown in FIG.
All or almost all of the incident laser light 30 is condensed at an incident angle equal to or greater than the critical angle θc. Therefore, the bottom surface of the prism 18 is located in the near field (approximately 1/3 or less of the wavelength of light) of the surface of the recording medium 20, and the refractive index of the surface film of the recording medium 20 (or the recording medium itself when there is no film) is reduced. If it is a normal value (approximately 1.5 to 2.5), the transmittance I2 of the laser beam 35 incident on the prism 18 at an incident angle equal to or larger than the critical angle θc to the recording medium 20
(I2 / I1) of the transmittance I1 of the laser beam 31 incident on the prism 10 at an incident angle equal to or less than the critical angle θc to the recording medium 20 is a surface film of the recording medium 20 (when there is no film). Is a large value regardless of the refractive index of the recording medium itself). Of course, components such as the aperture are unnecessary.

Therefore, if the refractive index is appropriately set according to the miniaturization of the light spot formed on the recording medium 20, the laser beam 3 applied to the recording medium via the evanescent wave
5 can be set to a large value.

FIG. 23 is a schematic structural view of an optical system according to a tenth embodiment of the optical recording / reproducing apparatus of the present invention. The device shown in the figure has a configuration in which a meniscus lens 19 is provided between an objective lens 12 and a spherical lens 15, laser light is condensed by the objective lens 12 and the meniscus lens 19, and evanescent light is generated by the spherical lens 15. It has become. On the surface of the meniscus lens 19 or inside the meniscus lens 19, an aperture 13 for blocking laser light near the optical axis of the meniscus lens 19 is provided.

Here, the objective lens 12, the spherical lens 15 and the meniscus lens 19 are arranged so as to satisfy aplanatic conditions in order to minimize optical aberrations.

Here, the incident angle of the end ray of the laser beam immediately after passing through the objective lens 12 is θ1, and the incident angle of the end ray of the laser beam immediately after passing through the meniscus lens 19 is θ.
2. Assuming that the incident angle of the end ray of the laser light in the spherical lens 15 is θ3, the refractive index of the meniscus lens 19 is n1, and the refractive index of the spherical lens 15 is n2, the following equation is established.

[0072]

(Equation 6)

As is apparent from the above equation, the NA of light that enters the spherical lens 15 via the meniscus lens 19 is
Numerical aperture NA 'when no meniscus lens 19 is arranged
(= Sin θ1) becomes n1 times. In the case of the present embodiment, as shown in FIG. 23, the distance between the meniscus lens 19 and the spherical lens 15 is kept constant by the holding member 21. Therefore, the NA of the objective lens 2 can be changed without changing the incident angle of the end ray of the laser light in the spherical lens 15.
Is equivalent to reducing.

The lower the NA of the objective lens 12, the deeper the focal depth of the objective lens 12. Therefore, the spot diameter of light on the bottom surface of the spherical lens 15 does not easily change with the change in the distance between the objective lens 12 and the spherical lens 15.
That is, when the meniscus lens 19 is provided, the influence of the displacement of the objective lens 12 on the resolution of recording and reproduction is reduced.

It goes without saying that the present invention can be implemented in various modifications without departing from the spirit thereof. For example, as the diaphragm 4 of the present invention, various members can be used as long as the member blocks light without transmitting light. As described above, this is a method of forming the stop 4 by applying or vapor-depositing a material having a high light absorptivity such as black on the objective lens 1a. Also,
By treating the surface of the lens in a satin shape, light is diffusely reflected, and of course, it is possible to provide a function of a diaphragm.

The present invention also relates to an optical recording / reproducing
It also includes a master recording device for manufacturing a master of an optical disc such as a D-ROM. In this case, a photoresist is used as a recording medium.

[0077]

As described above, according to the present invention, an optical recording / reproducing apparatus having excellent optical resolution is realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing an entire configuration of an optical recording / reproducing apparatus according to a first embodiment of the present invention.

FIG. 2 is a plan view of an annular aperture according to the first embodiment.

FIG. 3 is a graph showing a normalized intensity distribution of a light spot according to the present invention.

FIG. 4 is a graph showing intensity distribution characteristics of spots when external light transmits more to the recording medium than internal light.

FIG. 5 is a graph showing intensity characteristics of spots when the same amount of external light and internal light are transmitted to the recording medium.

FIG. 6 is a graph showing intensity distribution characteristics of spots when external light transmits more to the recording medium than internal light.

FIG. 7 is a diagram showing an overall configuration according to a second embodiment of the optical recording / reproducing apparatus of the present invention.

FIG. 8 is a schematic configuration diagram of an optical system forming a part of the optical recording / reproducing apparatus according to the embodiment.

FIG. 9 is a plan view of an objective lens according to a second embodiment.

FIG. 10 is a schematic configuration diagram of an optical system according to a third embodiment of the optical recording / reproducing apparatus of the present invention.

FIG. 11 is a schematic configuration diagram of an optical system according to a fourth embodiment of the optical recording / reproducing apparatus of the present invention.

FIG. 12 is a schematic configuration diagram of an optical system according to a fifth embodiment of the optical recording / reproducing apparatus of the present invention.

FIG. 13 is a schematic configuration diagram of an optical system according to a sixth embodiment of the optical recording / reproducing apparatus of the present invention.

FIG. 14 is a schematic configuration diagram of an optical system according to a seventh embodiment of the optical recording / reproducing apparatus of the present invention.

FIG. 15 is a graph showing the relationship between the refractive index of the surface film of the recording medium and the internal transmittance of the air gap.

FIG. 16 is a graph showing the relationship between the refractive index of the surface film of the recording medium and the external transmittance of the air gap.

FIG. 17 is a graph showing the relationship between the refractive index of the surface film of the recording medium and the external transmittance / internal transmittance of the air gap.

FIG. 18 is a schematic configuration diagram of an optical system according to an eighth embodiment of the optical recording / reproducing apparatus of the present invention.

FIG. 19 is a graph showing the relationship between the refractive index of the surface film of the recording medium and the internal transmittance of the air gap.

FIG. 20 is a graph showing the relationship between the refractive index of the surface film of the recording medium and the external transmittance of the air gap.

FIG. 21 is a graph showing the relationship between the refractive index of the surface film of the recording medium and the external transmittance / internal transmittance of the air gap.

FIG. 22 is a schematic configuration diagram of an optical system according to a ninth embodiment of the optical recording / reproducing apparatus of the present invention.

FIG. 23 is a schematic configuration diagram of an optical system according to a tenth embodiment of the optical recording / reproducing apparatus of the present invention.

FIG. 24 is a conventional example showing a schematic configuration when a hemispherical lens is used as a lens for generating an evanescent wave.

FIG. 25 is a graph showing a normalized intensity distribution of a light spot in the related art.

[Explanation of symbols]

Reference Signs List 2 light source 5 annular aperture (light blocking means) 11 aperture member (light blocking means) 12, 12A objective lens 13 aperture (light blocking means) 14, 14A hemispheric lens (lens for generating evanescent waves) 15 spherical lens (for generating evanescent waves) Lens) 16 Aspherical lens (lens for generating evanescent wave) 19 Meniscus lens 20 Recording medium

Claims (10)

[Claims] An optical recording / reproducing apparatus for recording / reproducing information on / from a recording medium by using light from a light source, comprising: a lens provided on an optical path from the light source to the recording medium, capable of generating an evanescent wave; An optical recording / reproducing apparatus, comprising: light blocking means for blocking at least a part of light passing through a lens capable of generating the evanescent wave without contributing to generation of the evanescent wave. 2. An objective lens for converging light from the light source to a lens capable of generating the evanescent wave is provided at a stage preceding the lens capable of generating the evanescent wave. Item 2. The optical recording / reproducing apparatus according to Item 1. 3. The optical recording / recording apparatus according to claim 1, wherein a meniscus lens is provided in front of the lens capable of generating the evanescent wave and downstream of the objective lens.
Playback device. 4. The optical recording / reproducing apparatus according to claim 1, wherein said light blocking means is provided directly on a lens capable of generating said evanescent wave. 5. An optical recording / reproducing apparatus according to claim 1, wherein said light blocking means is provided between a lens capable of generating said evanescent wave and said light source. 6. The optical recording / reproducing apparatus according to claim 1, wherein said light blocking means is provided directly on said objective lens. 7. An optical recording / reproducing apparatus according to claim 1, wherein said light blocking means is provided between said objective lens and said light source. 8. An optical recording / reproducing apparatus according to claim 1, wherein said light blocking means has a light blocking area variable function for changing a light blocking area. 9. An optical recording / reproducing apparatus according to claim 8, wherein said light blocking means is a liquid crystal shutter. 10. An optical recording / reproducing method for recording / reproducing information on / from a recording medium using light from a light source, wherein at least a part of the light from the light source is blocked, and the light not blocked is evanescently transmitted. An optical recording / reproducing method, comprising: a step of passing a wave through a lens capable of generating a wave; and a step of irradiating a recording medium with light passing through a lens capable of generating an evanescent wave.