Dynamic information storage or retrieval – Specific detail of information handling portion of system – Electrical modification or sensing of storage medium
Reexamination Certificate
2001-04-19
2003-05-13
Huber, Paul W. (Department: 2653)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Electrical modification or sensing of storage medium
C369S044140, C369S283000
Reexamination Certificate
active
06563782
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a U.S. national state application of copending International Application Ser. No. PCT/JP99/04892, filed Sep. 8, 1999, and claiming a priority date of Sep. 17, 1998, and published in a non-English language.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a medium for recording information reproducible by utilizing near-field light and an information reproducing apparatus and an information recording and reproducing apparatus for reproducing information recorded in the information recording medium at a high density, particularly to an information recording medium and an information reproducing apparatus capable of providing a reproduced signal having a large intensity and an information recording and reproducing apparatus having high reliability and capable of carrying out high-speed recording.
2. Background Information
A number of present information reproducing apparatus carry out information reproduction on a magnetic disk or an optical disk as an information recording medium. In particular, a CD, which is one of optical disks enabling information recording at a high density and mass production at low cost, is widely utilized as a medium for recording information having a large capacity. The CD is formed with pits having a size of a wavelength of laser beam used in reproduction and a depth of about a quarter of the wavelength on its surface to thereby enable a reading operation utilizing an interference phenomenon of light.
In reading recorded information from an optical disk represented by CD, generally, there is utilized a lens optical system used in an optical microscope. Hence, when information recording density is increased by reducing the size or the track pitch of a pit, due to a problem of a diffraction limit of light, the system runs into a wall that a spot size of laser beam cannot be made a half wavelength or smaller and an information recording unit cannot be constituted by a size smaller than the wavelength of laser beam.
Further, not only in an optical disk but also in a magneto-optical disk recording information by a magneto-optical recording system and a phase change recording system, recording and reproduction of information at a high density is realized by a very small spot of laser beam and therefore, the information recording density is restricted by the diameter of the spot provided by focusing laser beam.
Hence, in order to break though the restriction by the diffraction limit, there has been proposed an information reproducing apparatus using an optical head provided with a very small aperture having a diameter equal to or smaller than the wavelength of laser beam utilized for reproduction, for example, about 1/10 of the wavelength and utilizing near-field light (including both of near-field light and far-field light) generated at the very small aperture portion.
Inherently, there is provided a near-field microscope using a probe having the above-described very small aperture as an apparatus of utilizing near-field light and the near-field microscope is utilized for observation of a very small surface structure of a sample. As one of near-field light utilizing systems in a near-field microscope, there is provided a system (illumination mode) in which a distance between a very small aperture of a probe and a surface of a sample is reduced to a degree of a diameter of the very small aperture of the probe and propagated light is introduced via the probe and toward the very small aperture of the probe, thereby, near-field light is generated at the very small aperture. In this case, scattered light produced by an interaction between the generated near-field light and the surface of the sample, is detected by a scattered light detecting system by being accompanied by intensity or phase reflected with a fine structure of the surf ace of the sample and there is enabled observation having a high resolution which cannot be realized by a conventional optical microscope.
Further, as another system of a near-field microscope utilizing near-field light, there is provided a system in which near-field light is localized at the surface of a sample by irradiating propagated light toward a sample and a very small aperture of a probe is made proximate to the surface of the sample up to a degree of the diameter of the very small aperture of the probe (collection mode). In this case, scattered light produced by interaction between the localized near-field light and the very small aperture of the probe, is introduced to a scattered light detecting system via the very small aperture of the probe by being accompanied by the intensity or phase reflected with a fine structure of the surface of the sample to thereby achieve observation having a high resolution.
Information reproducing apparatus utilizing the above-described near-field light, utilizes these observation systems in the near-field microscope and by utilizing the near-field light, information reproduction of an information recording medium recorded with information at a higher density can be carried out.
In such an information reproducing apparatus, as a probe for reproducing information, there is particularly proposed use of a planer probe without a sharpened front end.
FIG. 14
is a view showing a conventional planer probe utilizing near-field light and an information recording medium. In
FIG. 14
, a planer probe
101
is formed with an aperture having an inverse pyramid structure on a planer substrate and particularly, an apex portion of the aperture is penetrated by a very small aperture
102
having a diameter of several tens nanometers. According to the planer probe
101
, near-field light
107
is generated at a vicinity of the very small aperture
102
by irradiating laser beam
106
toward the very small aperture
102
.
The near-field light
107
is scattered by a data mark
105
particularly showing strong interaction between the near-field light and the data mark and produces propagated light
108
at an information recording medium
104
. The propagated light
108
is introduced to a light receiving element
103
provided at a vicinity of the very small aperture
102
of the planer probe
101
and is detected as a reproduced signal.
As described above, the planer probe is constructed by a constitution in which both of the very small aperture
102
for generating the near-field light
107
and the light receiving element
103
for detecting the propagated light
108
scattered from the data mark
105
, are arranged on a side of a surface of the information recording medium
104
(reflection mode) and therefore, downsizing of an information reproducing apparatus can be achieved, further, the planer probe can be formed by using the semiconductor fabrication technology and accordingly, mass production having high reproducibility is realized and the planer probe is pertinently used as an optical head of the information reproducing apparatus utilizing the near-field light.
Further, high density information recording can be carried out also by changing a state, for example, a crystal state of the surface of the information recording medium by interaction between the near-field light generated from the probe and the information recording medium.
However, in using the planer probe
101
, in order to provide the propagated light
108
scattered from the data mark
105
, since the propagated light
108
is defined as light having a wavelength of several 100 nm, it is necessary to make a distance “a” from the data mark
105
or the very small aperture
106
to the light receiving element
103
equal to or larger than the wavelength. In this case, a clearance “d” between the very small aperture
102
and the information recording medium
104
is generally provided with a value equal to or smaller than 100 nm in order to achieve sufficiently large interaction between the near-field light
107
generated at the very small aperture
102
and the data mark
105
on the information recording medium
104
. Therefore, in the c
Chiba Norio
Kasama Nobuyuki
Kato Kenji
Maeda Hidetaka
Mitsuoka Yasuyuki
Adams & Wilks
Huber Paul W.
Seiko Instruments Inc.
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