JPH11273134A - Information pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an information pickup device capable of improving the absolute value level of a signal by efficiently condensing scattered light owing to the interaction between a probe and a sample and reduced in its size. SOLUTION: In the information pickup device for obtaining the information of a sample 4 by condensing scattered light generated by the interaction between the sample 4 exposed to illumination light and the probe 3 arranged oppositely close to the sample 4 through an optical element 2, the probe 3 and the element 2 are unitedly formed and the oppositely close part of the element 2 to the sample 4 is formed as a plane part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording / reproducing technique, and more particularly to an information pickup apparatus capable of realizing high-resolution recording / reproducing by applying the principle of a near-field optical microscope.

[0002]

2. Description of the Related Art As a near-field optical microscope using a metal probe as a probe, "Near-field nano-optics-a new optical technique beyond the wavelength barrier" by Kawata (Parity Vol. 1)
2 No. 5 1997-05) is shown in the paper (Fig. 5 in the paper). That is,
A part of the scattered light is condensed using a detection lens with NA = 0.35 in the interaction between the metal probe and the sample exposed to the illumination light, and guided to a photomultiplier to obtain information on the sample. The size of the metal probe tip diameter and the distance between probe materials
A high resolution exceeding the resolution of the detection lens is realized at about one-tenth or less of the illumination wavelength.

[0003]

However, in the near-field optical microscope as described above, when the scattered light due to the interaction between the metal probe and the sample is detected and only a part of the scattered light is extracted, a high-resolution component is used. Can be extracted, but the absolute value of the signal level tends to be insufficient. Therefore, there are points to be improved, such as the necessity of a very expensive high-sensitivity sensor and shortage of S / N.

Therefore, the present invention solves the above-mentioned problems, and can improve the absolute value level of a signal by efficiently condensing scattered light due to the interaction between the probe samples. It is an object of the present invention to provide an information pickup device capable of performing the following.

[0005]

According to the present invention, in order to achieve the above object, an information pickup device is constructed as follows. That is, the information pickup device of the present invention collects, via the optical element, scattered light generated by the interaction between the sample exposed to the illumination light and the probe arranged close to and facing the sample. In an information pickup device for obtaining information on the sample,
The present invention is characterized in that the probe and the optical element are integrated, and a portion of the optical element facing / proximate to the sample is a flat portion. Further, the information pickup device of the present invention is characterized in that the sample is irradiated with the illumination light via the optical element. Further, the information pickup device of the present invention is characterized in that the optical element is formed of a hemispherical lens, and the probe is provided in a flat portion of the hemispherical lens or a cutout formed in the flat portion. I have. Further, the information pickup device of the present invention,
The optical element comprises a hemispherical lens, and the probe or fiber probe is surrounded by the hemispherical lens. Further, the information pickup device of the present invention is characterized in that the optical element is made of a glass flat plate having a diffraction portion.

[0006]

DETAILED DESCRIPTION OF THE INVENTION As described above, the present invention collects light scattered by the interaction between a sample exposed to illumination light and a probe arranged close to the sample via an optical element. In this case, a detection system is used in which an optical element having a flat portion facing and close to the sample and the probe are integrated. According to such a configuration of the present invention, the amount of condensed light is increased by one digit or more as compared with the conventional example, an improvement in the absolute value level of a signal can be expected, and the size of the device can be reduced. Becomes Further, in the present invention, by irradiating the sample via the above-described optical element, the optical element for collecting scattered light can be used as an illumination optical system, In addition to the improvement in the absolute value level of the signal, the size of the device can be further reduced.

[0007]

Embodiments of the present invention will be described below. Embodiment 1 FIG. 1 shows a schematic optical system of an information pickup apparatus according to Embodiment 1 of the present invention. The sample 4 is illuminated from the back side by the illumination light source 6 and the illumination lens 8. The illumination light is incident on the surface of the sample 4 so as to satisfy the total reflection condition, is totally reflected, is collected by the lens 9, and is received by the sensor 7 for monitoring the intensity of the illumination light. On the other hand, the scattered light due to the interaction between the metal probe 3 and the sample 4 integrated on the plane portion of the hemispherical lens 2 is condensed by the hemispherical lens 2 and the condensing lens 1 to detect information. Is received by the sensor 5. Thus, information on the surface of the sample 4 is detected by the output from the sensor 5.

FIG. 2 shows an enlarged view of the vicinity of the hemispherical lens 2 (first example of a probe optical element integrated element).
The metal probe 3 is provided so as to be joined to the hemispherical lens 2 at a position substantially along the optical axis on the plane. The tip of the metal probe 3 has a size of about 1/10 or less of the illumination wavelength. Since the illumination light is totally reflected, near-field light, which is non-propagating light, exists in the region from the sample surface to about one quarter of the wavelength. The distance between the tip of the metal probe 3 and the surface of the sample 4 is maintained at the same distance as the size of the tip by shear force control, and the resolution of the metal probe 3 is about the size of the tip of the metal probe 3. Interaction between the tip and the sample 4 exposed to the illumination light and having the near-field light described above causes scattered light. As shown in FIG. 3, the light scattered from the vicinity of the tip of the metal probe 3 is ± 9 around the optical axis.
Light of less than 0 ° can enter the hemispherical lens 2. That is, assuming that the tip of the metal probe 3 is almost in contact with the sample 4, almost all of the scattered light from the tip of the metal probe 3 toward the hemispherical lens 2 enters the hemispherical lens 2.

Here, assuming that the length of the metal probe 3 is h and the radius of the plane portion / effective portion of the hemispherical lens 2 is a, | θ1 | <cot ⁻¹ (h / a), and h / a Can be quite small. The angle in the hemispherical lens 2 is θ2 = sin ⁻¹ (sin θ1 / n) n; the refractive index in the hemispherical lens. Since it is sufficiently short compared to the thickness (or the radius of curvature of the spherical surface) of the lens shape 2, the light beam emitted almost perpendicularly to the spherical surface and traveling toward the condenser lens 1 is a light beam of NA ≒ sin θ2.

Therefore, the condenser lens 1 is set to NA ≒ sin θ2
By doing so, almost all the light scattered within ± θ1 can be collected. Specifically, h / a <0.01, n ≒ 1.
8. By setting the NA of the condenser lens 1 to 0.56,
Light of approximately | θ1 | <89 ° is given by h / a <0.1, n ≒
1.8, by setting the NA of the condenser lens 1 to 0.55, light of approximately | θ1 | <84 ° is converted to h / a <0.2, n
By setting ≒ 1.8 and NA = 0.54 of the condenser lens 1, it is possible to condense light of approximately | θ1 | <78 °.

Thus, the scattered light can be collected with almost no loss. Here, if the thickness of the hemispherical lens 2 in the optical axis direction is thicker than in the case of a hemisphere, the ray of θ1 is θ
Can exit the sphere at an angle less than 2
It is possible to use a condenser lens having a smaller A, and the limitation on the size of the apparatus is relaxed. Thus, the amount of condensed light can be secured, and the absolute value level of the signal can be improved.

[Embodiment 2] FIG. 4 is a schematic diagram showing an optical system according to Embodiment 2 of the present invention, in which the light-converging optical system is also used as an illumination optical system. The light from the light source 11 is irradiated to the sample 4 by the condenser lens 1 and the hemispherical lens 2, and the light reflected from the sample 4 is scattered by the interaction between the metal probe 3 joined to the hemispherical lens 2 and the sample 4. The light is condensed by the condensing lens 1 via the hemispherical lens, separated and deflected by the beam splitter 13, and guided to the sensor 12. In this case, the reflected light from the sample 4 is low-resolution light and becomes background light. Therefore, high resolution is realized by separation by a filter.

In this case, the sample 4 is used as an optical disk by adding a diffraction grating, a wave plate, a Wollaston prism, and the like to the optical system and holding the hemispherical lens 2 using a floating head technology such as a hard disk. It is also possible. In this case, high resolution is realized by separation by a frequency filter. When the diffraction grating is disposed between the light source 11 and the beam splitter 13, an image spot is generated in a portion other than the metal probe 3. At this spot, scattered light due to the interaction between the metal probe 3 and the sample 4 does not occur, but can be used as track guide light by a known technique. Further, a Wollaston prism is placed between the beam splitter 13 and the sensor 12, and the sensor 12
Is a sensor comprising at least two light receiving areas, the sample 4 can be made a magneto-optical disk. In the present embodiment, the whole can be made compact as compared with the previous embodiment.

[Embodiment 3] Next, as Embodiment 3 of the present invention, a modified example relating to an integrated structure of a probe and an optical element will be described. FIG. 5 is a view showing a configuration example 2 in which a cutout 22 for joining a metal probe to a hemispherical lens 21 is provided as a configuration example 2 different from the above configuration example relating to the integrated configuration of the probe and the optical element. It is. By providing the notch 22, the tip of the metal probe 3, the flat part of the hemispherical lens 2, and the sample 4 can be brought closer to each other, and the value of θ1 becomes closer to 90 degrees, so that a wider range of scattered light Can be collected. This embodiment can be applied to the first and second embodiments.

FIG. 6 is a view showing a hemispherical lens 23 formed so as to surround a metal probe 24 as a third configuration example different from the above-mentioned configuration example regarding the integrated configuration of the probe and the optical element. In this case, a fiber probe can be used instead of the metal probe 24. This embodiment is also applicable to the first and second embodiments. In the case of a fiber probe, light can be supplied to the sample through the fiber probe. In this case, the illumination light is emitted from the hemispherical lens 23.
, Which is a modification of the second embodiment. FIG. 7 shows a glass plate 25 with a diffractive portion having a diffractive portion 26 in place of a spherical portion spherical surface of a hemispherical lens as a configuration example 4 different from the above-described configuration example regarding the integrated configuration of the probe and the optical element. FIG. Originally, when the light is emitted from a plane, the light emitted at a high NA as shown by the dotted line in the drawing can be directed to the condenser lens at a desired angle by the diffraction unit 26, and the light beam incident on the condenser lens at the desired NA You can do it. This embodiment is also applicable to the first and second embodiments.

[0016]

As described above, according to the present invention, the light scattered by the interaction between the sample exposed to the illumination light and the probe arranged close to the sample is transmitted through the optical element. In an information pickup device for collecting light, an optical element having a plane portion facing / adjacent to the sample and the above-mentioned probe are integrally formed to efficiently collect scattered light due to interaction between the probe and sample. As a result, the absolute value level of the signal can be improved, and the size of the device can be reduced. Further, in the present invention, by irradiating the sample via the above-described optical element, the optical element for collecting scattered light can be used as an illumination optical system, In addition to the improvement in the absolute value level of the signal, the size of the device can be further reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic optical system of an information pickup device according to the present invention.

FIG. 2 is an enlarged view of the vicinity of a hemispherical lens integrated with a probe according to a first embodiment of the present invention.

FIG. 3 is a diagram for explaining the operation of the present invention.

FIG. 4 is a diagram illustrating a configuration of a second exemplary embodiment of the present invention.

FIG. 5 is a diagram showing another configuration example in which the probe and the optical element according to the third embodiment of the present invention are integrated.

FIG. 6 is a diagram showing another configuration example in which the probe and the optical element according to the third embodiment of the present invention are integrated.

FIG. 7 is a diagram showing another configuration example in which the probe and the optical element according to the third embodiment of the present invention are integrated.

[Explanation of symbols]

 1: condensing lens 2, 21, 23: hemispherical lens 3, 24: metal probe 4: sample 5, 7, 12: sensor 6, 11: light source 25: glass plate with diffraction part

Claims (5)

[Claims] 1. An information processing apparatus according to claim 1, wherein scattered light generated by an interaction between a sample exposed to the illumination light and a probe arranged close to and opposed to the sample is condensed through an optical element to obtain information on the sample. An information pickup device to be obtained, wherein the probe and the optical element are integrated, and a portion of the optical element facing / proximate to the sample is a flat portion. 2. The information pickup device according to claim 1, wherein the illumination light is applied to the sample via the optical element. 3. The optical element according to claim 1, wherein the optical element comprises a hemispherical lens, and the probe is provided in a flat portion or a cutout formed in the flat portion of the hemispherical lens. The information pickup device according to claim 2. 4. The information pickup device according to claim 1, wherein the optical element is formed of a hemispherical lens, and the probe or the fiber probe is surrounded by the hemispherical lens. 5. The information pickup device according to claim 1, wherein the optical element is formed of a flat glass plate having a diffraction portion.