JPH0798885A - Optical memory and its recording and reproduction method - Google Patents

Abstract

PURPOSE:To make an effective use of the characteristic using the photon STM and to enable more high-density recording and reproduction. CONSTITUTION:The projecting and recessing information of a medium 13 is recorded or reproduced by the evanescent light localized in the fine recessing and projecting parts while scanning a medium 13 by an optical probe. In the optical memory device using the photon scanning type tunnel microscope, plural optical probes 11 and 12 with the conical tip shape set to the dissimilar conical angles so that they have resolution reproducing series of recording recessed and projecting information strings 14 and 15 set in the range with dissimilar recording dimensions are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical memory device using a photon STM, a recording method and a reproducing method thereof.

[0002]

2. Description of the Related Art Generally, an optical memory device or the like is required to be capable of high density recording / reproducing.
It can be said that the current optical memory device is already reaching its limit in terms of high density recording / reproducing. This is the property of the wave of light that the resolution cannot be condensed in the region where the resolution is diffraction limit, that is, the wavelength shorter than λ / 2 with respect to the wavelength λ of the recording / reproducing light (laser light). by.

Therefore, under the present circumstances, in order to achieve higher density recording, there is no choice but to rely on a technique such as reducing the distance between pits or reducing the distance between tracks. If you try to increase the density of, the crosstalk will increase and playback will be impossible,
It will not be practical.

In this respect, in recent years, a photon STM (photon scanning tunneling microscope) having a resolution exceeding the diffraction limit has attracted attention, and its research has been actively conducted. For example, according to the description in “Electronic microscope in which the atom is visible-microscopic measurement / processing by Photon STM-” (p.381-384) in the May issue of the magazine “Electronics magazine”, Vol. Application to optical recording is also mentioned.

Here, the principle of the photon STM will be described with reference to the description in the above magazine and FIG. In general,
When an object is irradiated with light, scattered light includes light that propagates far and an electromagnetic field that is created only in the vicinity due to the interaction between polarizations induced in a substance by light irradiation, that is, light that does not propagate. To do. The latter light that does not propagate is so-called evanescent light.

As shown in FIG. 7, the intensity of such evanescent light becomes almost 0 when it is separated from the surface of the object (for example, the substrate 1) by the wavelength of the light, and has a spatial distribution equivalent to the surface shape of the substance. It is a thing. Reference numeral 2 is an equal ray indicating the intensity of evanescent light. The area where such evanescent light exists (hence the distance L from the surface of the substrate 1)
The evanescent light is scattered by the optical probe 3 having a sharp tip in a region where L << λ) to be converted into propagating light. At this time, the optical probe 3 is moved along the surface of the object 2
By scanning in a three-dimensional plane and measuring the measured intensity distribution (spatial distribution) of the evanescent light as a position function of the optical probe 3 via the photodetector 4, the three-dimensional shape of the object can be observed (reproduction). .

On the other hand, if the evanescent light is exuded from the tip of the optical probe 3 and the optical recording material is brought sufficiently closer to the optical probe 3 than the wavelength of the light, recording by the evanescent light is performed. Since the resolution in this case is determined by the tip shape of the optical probe 3, if the radius of curvature of the tip of the optical probe 3 is sharpened to the atomic size, it is possible to realize the resolution to see atoms and record the atomic size. Become.

Therefore, in detecting the unevenness of the minute object 5 by the optical probe 3, the wave function of the evanescent field between the minute object 5 and the tip of the optical probe 3 is localized to the same extent, and the overlapping of the wave functions is caused. When large, the evanescent light localized in the minute object 5 is efficiently converted into propagating light.

[0009]

However, even though such a photon STM can be used for ultra-high density recording of an optical memory, in practice, it is possible to make use of its characteristics and improve the method. Recording with less density and less crosstalk /
It is unknown whether it will be possible to regenerate it, and there is a current need for its development.

[0010]

According to a first aspect of the present invention, in regard to an optical memory device, the unevenness information of the medium is recorded or reproduced by evanescent light localized on the minute unevenness while scanning the medium surface with an optical probe. In the optical memory device using the photon scanning tunneling microscope, the different cone angles are set so as to have the resolution for reproducing only the series of recording concave / convex information strings set within the range of different recording dimensions. A plurality of optical probes having a conical tip shape are provided.

According to the second aspect of the present invention, in the recording method of the optical memory device, while scanning the medium surface with the optical probe, the evanescent light is exuded from the tip of the optical probe to record the concave-convex information on the medium. In the recording method of the optical memory device using the photon scanning tunneling microscope, a plurality of conical tip-shaped optical probes each having a different cone angle are provided, and the optical probes are set within different recording dimension ranges. Each series of recording concave-convex information rows is separately formed on a separate row or mixed on the same row to form a record.

According to a third aspect of the present invention, there is provided a photon scanning method for reproducing an optical memory device, wherein the medium surface is scanned by an optical probe and the concave and convex information of the medium is reproduced by the evanescent light localized in the minute concave and convex. In a method of reproducing an optical memory device using a scanning tunneling microscope,
A plurality of conical tip-shaped optical probes set to different cone angles are provided, and each probe is set on a separate row or separately recorded on the same row, or set within the range of different recording dimensions. Each of the series of recorded concavo-convex information sequences thus recorded was reproduced by an optical probe having a resolution suitable for each recording dimension.

According to a fourth aspect of the present invention, in the recording method of the optical disk device, while scanning the surface of the medium with the optical probe, the evanescent light is exuded from the tip of the optical probe to record concave and convex information on the medium. In the recording method of the optical memory device using the photon scanning tunneling microscope, a plurality of conical tip-shaped optical probes each having a different cone angle are provided, and the concavo-convex information sequence for tracking and the concavo-convex information sequence are provided by these optical probes. A series of recording concave / convex information sequences set within a range of recording dimensions different from the above is formed.

According to a fifth aspect of the present invention, an optical memory utilizing a photon scanning tunneling microscope which reproduces the unevenness information of the medium by evanescent light localized on the minute unevenness while scanning the medium surface with an optical probe. In the reproducing method of the apparatus, a plurality of conical tip-shaped optical probes each set to a different cone angle are provided, and the tracking concavo-convex information sequence formed on the medium and a range of recording dimensions different from the concavo-convex information sequence are provided. The set of recording concave-convex information sequence and the set series of recording concave-convex information are reproduced by an optical probe having a resolution suitable for each recording dimension.

[0015]

In the optical memory device according to claim 1, the recording method of the optical memory device according to claim 2, or the reproducing method of the optical memory device according to claim 3, the optical probe has a fineness corresponding to its tip shape. Focusing on the point that it acts as a bandpass filter that selectively detects components, it has a plurality of optical probes with conical tip shapes set to different cone angles,
Since the resolution is such that only a series of unevenness information strings set within the range of different recording dimensions are reproduced, when viewed with each optical probe, the unevenness of the recording dimensions that does not match the resolution to be reproduced by itself. The information string is equivalent to being masked, so that a series of uneven information strings set within the range of different recording dimensions do not interfere with each other when recording / reproducing in close proximity to each other. By making full use of the characteristics of using a photon scanning tunneling microscope, it becomes possible to perform recording / reproduction with high density and little crosstalk.

Also, in the recording method of the optical memory device according to the fourth aspect or the reproducing method of the optical memory device according to the fifth aspect, since the plurality of optical probes having the conical tip shapes set at different cone angles are provided, Due to the difference in the resolution of these optical probes, a minute unevenness information sequence does not become difficult to detect by the tracking unevenness information sequence,
Recording / playback with less noise is possible.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. The present embodiment uses the photon STM described in FIG. 7, and the same portions as those shown in FIG. 7 are designated by the same reference numerals. The present embodiment is characterized in that a plurality of, for example, two optical probes 11 and 12 are provided. Here, these optical probes 11, 12
As shown in FIGS. 2 (a) and 2 (b), is a tip conical shape set to different cone angles and is set to have different resolutions. That is, according to the principle of the photon STM described above, as shown in FIGS. 2A and 2B, the tip shape of the optical probes 11 and 12, that is, the tip shape of the conical shape, is selected from the spatial frequencies of the unevenness of the object surface. It can be understood that it works as a bandpass filter that selectively detects a component having a fineness corresponding to the cone angle of, and it becomes possible to individually detect a series of concavo-convex information strings each having a different size (recording size). . Specifically, in the case of the optical probe 11 having a large cone angle, the optical probe 12 having a small cone angle has a resolution only for a micro object 5 having a large size. In this case, the resolution is set only for the small object 5 having a small size.

Therefore, in the case of an optical memory in which recording is performed by a concave / convex information string, a series of recording concave / convex information strings in which the recording dimension is set large is assigned to the optical probe 11, and a series of recording unevenness in which the recording dimension is set small. It will be appreciated that information strings can be assigned to the optical probe 12. Therefore, for example, as shown in FIG. 1, a series of recording concave-convex information rows 14 having a large recording dimension and a series of recording concave-convex information rows 15 having a small recording dimension are separately arranged on the medium 13. And the recording is alternately formed. In such recording, according to the principle of the photon STM described above, evanescent light is exuded from the respective tips of the optical probes 11 and 12 toward the medium 13 to record and form the recording unevenness information sequence 14 by the optical probe 11. Optical probe 1
The recording concave / convex information sequence 15 may be recorded and formed by 2. Then, when the optical probe 11 is assigned to the series of recording unevenness information sequence 14 and the optical probe 12 is assigned to the series of recording unevenness information sequence 15 so as to reproduce, these recording unevenness information sequences 14 and 15 are close to each other. However, in the optical probe 11, the recording unevenness information sequence 15 is equivalent to being masked, and only the recording unevenness information sequence 14 having a recording size suitable for its own resolution is detected and reproduced. Similarly, in the optical probe 12, the recording concave-convex information sequence 14 becomes equivalent to being masked, and only the recording concave-convex information sequence 15 having a recording size suitable for its own resolution is detected and reproduced. Therefore, the reproduction is performed without interference between the recording concave-convex information rows 14 and 15, and recording / reproducing with high density and less crosstalk can be performed.

Here, as an optical memory device using such a medium 13 and optical probes 11 and 12, for example,
It is configured as shown in FIG. First, the medium 13 is mounted on a support 16 such as a prism, and is three-dimensionally movably provided by an xy scanning device 18 and a z scanning device 19 controlled by a computer 17.
The laser light emitted from the semiconductor laser 20 to the medium 13 is collimated by the collimator lens 21, the mirror 22,
Irradiation is possible via the support 16.
Two optical probes 11 and 12 are arranged in close proximity to each other on the surface of the medium 13 corresponding to the irradiation position of the laser light. Further, a photodetector 23 for detecting scattered light guided in the optical probes 11 and 12 is provided and is configured to be taken into the lock-in amplifier 24. The lock-in amplifier 24 is connected to an AC power supply 25, and is set so as to take in a signal from the photodetector 23 to the computer 17 side at a predetermined cycle. Further, a control power supply 26 for generating a DC voltage for the semiconductor laser 20 based on the AC power supply 25 is provided, and a feedback control signal from the semiconductor laser control unit 28 is added via an adder 27 to obtain an optical output of the semiconductor laser 20. Is configured to be adjustable.

The wavelength of the laser light from the semiconductor laser 20 is 0.8 μm for a normal optical disk. Further, regarding the scanning control of the optical probes 11 and 12, the image processing by the lock-in amplifier 24, the technology such as STM and AFM as shown in Solid State Phys. Vol.28 No.3 1993,177 is used as it is. Has been. Also, the optical probes 11 and 12 having a predetermined cone angle
Is, for example, Jpn. J. Appl.Phys.Vol.31 (1992) p
It may be produced by the method shown in p.L1302-L1304.

When the shape of the SiO ₂ film (thin film having a thickness of about 20 nm) on the prism serving as the support 16 was measured using such an optical memory device, as shown in FIGS. It has been confirmed that the detection of the uneven information sequence having different resolutions has been achieved by the types of optical probes 11 and 12. The figure (a) shows the shape measurement result by the optical probe 11, and the figure (b) shows the shape measurement result by the optical probe 12.

When recording and forming the recording concave-convex information string of different recording dimensions on the medium 13, the recording is not limited to that shown in FIG. 2, and for example, as shown in FIG. The concavo-convex information sequence 29 and the recording concavo-convex information sequence 30 having a small recording size are mixed on the same column to allow the optical probe 11,
It is also possible to record and form by 12 and reproduce by the optical probes 11 and 12.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, the tracking unevenness information sequence 31 and the recording unevenness information sequence 32 are provided as two optical probes 1.
It is formed so as to have a recording size that can be separated by 1 and 12. Specifically, the tracking concavo-convex information sequence 31 has a recording dimension that matches the resolution of the optical probe 11, and the recording concavo-convex information sequence 32 has a recording dimension that conforms to the resolution of the optical probe 12.

That is, even if these concavo-convex information sequences 31 and 32 are close to each other, the optical concavo-convex information sequence 3 is recorded in the optical probe 11.
2 is equivalent to being masked, and the tracking concave-convex information sequence 3 of the recording size that matches the resolution of the self
Only 1 is detected and reproduced and used for tracking control.
Similarly, in the optical probe 12, the tracking concave-convex information string 31 is equivalent to being masked, and only the recording concave-convex information string 32 having a recording dimension suitable for its own resolution is detected and reproduced.

Therefore, according to the present embodiment, it becomes possible to accurately detect and reproduce the minute recording unevenness information sequence 32 without making it difficult to detect by the tracking unevenness information sequence 31. In addition, the tracking unevenness information sequence 3
Since accurate tracking control is maintained even if the interval between 1 and 32 is made as small as possible, high density recording with less noise becomes possible.

[0026]

The present invention is configured as described above, and according to the first aspect of the present invention, in the optical memory device, the evanescent light localized on the minute unevenness while scanning the medium surface with the optical probe is used. In an optical memory device using a photon scanning tunneling microscope that records or reproduces unevenness information of a medium, it is necessary to have a resolution for reproducing only each series of unevenness information rows set within a range of different recording dimensions. According to the invention of claim 2, a plurality of optical probes each having a conical tip shape, each of which is set to a different cone angle, are provided on the medium surface, while scanning the medium surface with the optical probes. Of an optical memory device using a photon scanning tunneling microscope, in which evanescent light is exuded from the tip to record concave-convex information on the medium. In recording method, a plurality of the optical probe tip cone which is set to different cone angle,
Each of the series of recording concave-convex information columns set within the range of different recording dimensions by these optical probes is separated into separate columns, or is recorded on the same column in a mixed manner. According to the third aspect of the present invention, in the reproducing method of the optical memory device, the photon scanning type in which the unevenness information of the medium is reproduced by the evanescent light localized on the minute unevenness while scanning the surface of the medium with the optical probe. In a method of reproducing an optical memory device using a tunnel microscope, a plurality of optical probes each having a conical tip shape set at different cone angles are provided, and each probe is separated on a separate row or mixed on the same row. A series of recording concave / convex information strings set within the range of different recording dimensions formed by recording are reproduced by an optical probe having a resolution suitable for each recording dimension. , By having a plurality of conical tip-shaped optical probes set at different cone angles, and having a resolution capable of reproducing only each series of uneven information rows set within the range of different recording dimensions. When viewed with an individual optical probe, the unevenness information sequence of the recording dimension that does not match the resolution to be reproduced by itself becomes equivalent to being masked, and therefore each of the information set in the range of different recording dimensions is different. A series of concavo-convex information lines will not interfere even if they are brought close to each other for recording / reproduction, and by utilizing the features of the photon scanning tunnel microscope to the maximum, recording / reproduction with high density and less crosstalk can be achieved. Can be done.

According to the fourth aspect of the present invention, regarding the recording method of the optical disk device, while scanning the medium surface with the optical probe, the evanescent light is exuded from the tip of the optical probe to record the concave-convex information on the medium. In the recording method of the optical memory device using the photon scanning tunneling microscope as described above, a plurality of conical tip-shaped optical probes set at different cone angles are provided, and the concavo-convex information sequence for tracking and this concavo-convex pattern are provided by these optical probes. According to the invention of claim 5, a series of recording concave-convex information rows set within a range of recording dimensions different from the information row is formed, and the fine unevenness is locally formed while scanning the medium surface with the optical probe. Optical memory device using a photon scanning tunneling microscope for reproducing uneven information of the medium by existing evanescent light In the reproducing method, a plurality of conical tip-shaped optical probes each having a different cone angle are provided, and the tracking concave-convex information sequence formed on the medium and a recording dimension different from the concave-convex information sequence are set. Since a series of recorded concave-convex information sequence and the optical probe having a resolution suitable for each recording dimension are reproduced, by again having a plurality of optical probes each having a conical tip shape set to different cone angles, Due to the difference in resolution of these optical probes, a minute unevenness information sequence does not become difficult to detect by the tracking unevenness information sequence, and the distance between the tracking unevenness information sequence is narrowed to achieve high density, Recording / playback with less noise can be performed.

[Brief description of drawings]

FIG. 1 is a perspective view schematically showing a state of a recording concave-convex information string having different recording dimensions according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing an operation of an optical probe having different cone angles.

FIG. 3 is a block diagram showing a configuration example of an optical disc device.

FIG. 4 is a characteristic diagram showing the reproduction result.

FIG. 5 is a perspective view schematically showing a state of a recording unevenness information row having different recording dimensions as a modification.

FIG. 6 is a perspective view schematically showing a state of an unevenness information string showing a second embodiment of the present invention.

FIG. 7 is a schematic diagram for explaining the principle of photon STM.

[Explanation of symbols]

 11, 12 Optical probe 13 Medium 14, 15 Recording unevenness information sequence 29, 30 Recording unevenness information sequence 31 Tracking unevenness information sequence 32 Recording unevenness information sequence

Claims (5)

[Claims] 1. An optical memory device using a photon scanning tunneling microscope, which records or reproduces unevenness information of the medium by evanescent light localized on minute unevenness while scanning the medium surface with an optical probe, It is characterized in that a plurality of conical tip-shaped optical probes each having a different cone angle are provided so as to have a resolution for reproducing only a series of recording concave / convex information sequences set within a range of different recording dimensions. Optical memory device. 2. A recording of an optical memory device using a photon scanning tunneling microscope, which scans the surface of a medium with an optical probe to allow evanescent light to seep out from the tip of the optical probe to record concave-convex information on the medium. In the method, a plurality of optical probes each having a conical tip shape set at different cone angles are provided, and a series of recording concave-convex information sequences set within the range of different recording dimensions by the optical probes are respectively separated. A recording method of an optical memory device, characterized in that recording is formed separately on a column or mixed on the same column. 3. A reproducing method of an optical memory device using a photon scanning tunneling microscope, which reproduces unevenness information of the medium by evanescent light localized on minute unevenness while scanning the medium surface with an optical probe, A plurality of conical tip-shaped optical probes set to different cone angles are provided, and each probe is set on a separate row or separately recorded on the same row, or set within the range of different recording dimensions. A reproducing method of an optical memory device, wherein each of the series of recorded concave-convex information sequences thus reproduced is reproduced by an optical probe having a resolution suitable for each recording dimension. 4. A recording of an optical memory device using a photon scanning tunneling microscope in which while scanning a medium surface with an optical probe, evanescent light is exuded from the tip of the optical probe to record concave-convex information on the medium. In the method, a plurality of conical tip-shaped optical probes each set to a different cone angle are provided, and a series of irregularities information for tracking and a series of recording dimensions different from the irregularities information sequence are set by these optical probes. A recording method of an optical memory device, characterized in that a recording unevenness information sequence is formed. 5. A reproducing method of an optical memory device using a photon scanning tunneling microscope, wherein the uneven information of the medium is reproduced by evanescent light localized on minute unevenness while scanning the surface of the medium with an optical probe, A plurality of conical tip-shaped optical probes each set to a different cone angle are provided, and a series of recording unevenness information for tracking formed on the medium and a range of recording dimensions different from this unevenness information sequence are recorded. A reproducing method of an optical memory device, wherein the unevenness information string and the unevenness information string are reproduced by an optical probe having a resolution suitable for each recording dimension.