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Claims  |
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What is claimed is:
1. An apparatus for effecting at least one of recording of information on
and reproducing of information from a recording medium, said apparatus
comprising:
a plurality of probes, arranged at positions respectively facing a
plurality of information blocks of the recording medium, for effecting at
least one of recording of information on and reproducing of information
from the information blocks of the recording medium;
displacement means for independently displacing each of said plurality of
probes at least in a direction parallel to a recording surface of the
medium;
detecting means for detecting deviation of each of said plurality of probes
in an in-surface direction of the recording medium relative to a
predetermined path on the recording medium;
tracking means for causing each of said plurality of probes to
independently perform tracking relative to the predetermined path on the
basis of the detected deviation, in order to compensate for the deviation;
and
recording and reproducing means comprising voltage application means for
applying voltage between said probes and the recording medium for
generating a tunnel current between said probes and the recording medium
to effect at least one of recording of information on and reproducing of
information from the recording medium.
2. An apparatus of claim 1, wherein the recording medium includes a
recording medium layer having an organic thin film.
3. An apparatus of claim 1, wherein said voltage application means
comprises means for applying a recording voltage as a recording pulse in
accordance with the information to be recorded.
4. An apparatus of claim 3, wherein said voltage application means
comprises means for independently applying voltage to each of said
plurality of probes for separately recording the information in each of
the blocks.
5. An apparatus of claim 1, further comprising current detecting means for
detecting current flowing between said plurality of probes and the
recording medium when voltage is applied by said voltage application
means, and wherein information is reproduced based on the detected
current.
6. An apparatus of claim 5, wherein the current detected by said current
detecting means is a tunnel current.
7. An apparatus of claim 5, wherein said current detecting means comprises
means for independently detecting current by each of said plurality of
probes, thereby reproducing the information separately from each of the
blocks.
8. An apparatus of claim 1, wherein said displacement means comprises means
for displacing each of said plurality of probes in three-dimensional
directions.
9. An apparatus of claim 8, wherein said displacement means comprises a
cantilever for supporting a respective probe at its upper end and means
for displacing said probe by deforming said cantilever in the
three-dimensional directions.
10. An apparatus of claim 9, wherein said cantilever has its longitudinal
direction in a direction parallel to the medium surface and its width
direction in a direction perpendicular to the medium surface.
11. An apparatus of claim 8, wherein said displacement means further
comprises a piezoelectric element.
12. An apparatus of claim 8, wherein said displacement means comprises
means for adjusting the space between said probes and the medium by
displacing said probes in a direction towards the medium, and means for
causing said probes to scan along a specified path in each of the blocks
by displacing said probes in a direction parallel to the medium surface.
13. A probe unit according to claim 8, wherein said displacement means
further comprises means for displacing said probe by utilizing a
piezoelectric effect and electrostatic power.
14. An apparatus of claim 1, wherein the predetermined path includes a
triangular wave path.
15. An apparatus of claim 1, wherein said tracking means performs the
tracking with a fine oscillation of the probe along the predetermined path
in a direction perpendicular to the direction of the predetermined path.
16. An apparatus of claim 1, wherein each of said probes and said
displacement means are formed by a micromechanic technique.
17. An apparatus of claim 1, wherein the predetermined path is formed by
reference marks provided in a plurality of locations on the recording
medium.
18. An apparatus for effecting at least one of recording of information on
and reproducing of information from a recording medium by using a probe,
said apparatus comprising:
a base plate;
a cantilever supported at both ends thereof in a direction of its width to
said base plate; and
a probe provided on said cantilever.
19. An apparatus according to claim 18, further comprising:
a fixed electrode provided on said base plate;
an opposite electrode provided on said cantilever at a position opposed to
said fixed electrode; and
displacing means for displacing said cantilever by applying a voltage
between said fixed electrode and said opposite electrode.
20. An apparatus for effecting at least one of recording of information on
and reproducing of information from a recording medium, said apparatus
comprising:
a probe, arranged at a position facing the recording medium, for effecting
at least one of recording of information on and reproducing of information
from the recording medium;
moving means for moving said probe in a direction of movement along a
predetermined path having a pattern preformed on the recording medium such
that the direction of movement periodically reverses direction;
detecting means for detecting deviation of said probe in an in-surface
direction of the recording medium relative to the predetermined path on
the recording medium;
tracking means for causing said probe to perform tracking relative to the
predetermined path on the basis of the detected deviation in order to
compensate for the deviation; and
recording and reproducing means comprising voltage application means for
applying voltage between said probe and the recording medium for
generating a tunnel current between said probe and the recording medium to
effect at least one of recording of information on and reproducing of
information from the recording medium along the specified path.
21. An apparatus of claim 20, wherein the recording medium includes a
recording medium layer having an organic thin film.
22. An apparatus for effecting at least one of recording of information on
and reproducing of information from a recording medium by using a probe
electrode, said apparatus comprising:
a base plate;
a cantilever supported at both ends thereof in a direction of its width to
said base plate;
a probe electrode provided on said cantilever; and
means for applying a voltage between said probe electrode and the recording
medium for generating a tunnel current between said probe and the
recording medium to effect at least one of recording of information on and
reproducing of information from the recording medium.
23. An apparatus according to claim 22, further comprising:
a fixed electrode provided on said base plate;
an opposite electrode provided on said cantilever at a position opposed to
said fixed electrode; and
displacing means for displacing said cantilever by applying a voltage
between said fixed electrode and said opposite electrode.
24. An apparatus according to claim 22, further comprising:
a piezoelectric element provided in said cantilever; and
deforming means for deforming said cantilever by applying current to said
piezoelectric element. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for recording and/or
reproducing information.
2. Related Background Art
Information which requires recording, such as computation information,
image information, etc., is on the increase at present, and a recorder
with a larger capacity has increasingly been in a great demand.
Further, with the evolution of the semiconductor process technique, the
miniaturization of a recorder unit is anticipated because the
microprocessor has been more miniaturized with a higher computational
capability. In order to satisfy such requirements, researches and
experiments have been carried on with the conventional techniques using
various methods, such as magnetic recording, semiconductor memory, optical
disc, etc., to implement the miniaturization of the recording area
(minimum recording area) for one bit, which is the minimum recording unit
in these methods.
For the magnetic recording, however, at least an area of several tens of
.mu.m is required as its minimum recording area for the magnetic recording
head to cause changes in the magnetic flux on a magnetic recording medium.
Because of this, the distance between the recording head and the recording
medium is restricted, making it difficult to control the distance at less
than approximately several hundred to several thousand angstroms. In the
optical disc, it is also difficult to reduce the beam diameter to a
dimension which is less than the optical wavelength to be applied; thus
requiring several .mu.m.sup.2 as its minimum recording area.
As a means to make the minimum recording area extremely small, there has
been proposed a recording and reproducing apparatus capable of providing a
minimum recording area of 10 nm.sup.2, in which a fine probe, chip, etc.
(hereinafter collectively referred to as a probe) for generating the
tunnel current for a recording medium is arranged to write recording
information by changing the work functions of the recording medium surface
with the tunnel current thus generated by the probe, which passes through
the recording medium, and to read information by detecting the changes in
the tunnel current between the probe and medium caused by the changes in
the work function as the result of writing a record on the recording
medium surface. For an apparatus such as this, there are some in which a
plurality of the aforesaid probes for recording and reproducing are
provided for the purpose of widening the recording area. The
implementation of this recording and reproducing in a wide area is
attempted by transporting a recording medium against the plurality of the
probes to allow the entire probes to scan the recording medium surface at
one time and perform the recording or reproducing by the tunnel current at
that juncture.
However, in an apparatus for recording and reproducing such as this, the
recording medium is transported at the time of scanning for recording or
reproducing by each of the probes, and the respective probes are fixedly
positioned with each other, or movably positioned only in the direction
perpendicular to the medium, which each of them face, to adjust the space
between the probe and medium. Therefore, in a case when each of the probes
is caused to scan for recording along the specified path on the recording
medium surface or to scan for reproducing the recorded information at each
location sequentially, it is impossible to control each scanning by the
respective probes. Consequently, there is a possibility that a recording
or reproducing error occurs for a probe or probes because one or plural
ones of the entire probes cannot scan along the specified path and
information sequence even if the entire scanning is precisely controlled.
Particularly, in a recording and reproducing apparatus using the tunnel
current, there is a possibility that the recording and reproducing become
impossible because its minimum recording area is so narrow that even if
the thermal expansion of the recording medium and changes with the time
elapsed are small, the resultant changes in the recording position produce
a great affect, and if any one of the probes is adjusted to scan along the
specified path and information sequence, the other probes are caused to be
positioned apart entirely from the specified path and information
sequence.
SUMMARY OF THE INVENTION
For a recording apparatus and reproducing apparatus for carrying out a fine
recording by the utilization of the tunnel current, the present invention
is designed in consideration of the disadvantages of the conventional
examples mentioned above, and an object thereof is to provide a recording
apparatus and reproducing apparatus capable of performing the recording
and reproducing by the entire probes at accurate positions even when the
medium is deformed due to the thermal expansion, for example in the course
of recording or reproducing by a plurality of probes.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram showing the structure of a first embodiment
of a recording and reproducing apparatus according to the present
invention.
FIG. 2 is a perspective view schematically showing the recording and
reproducing head of the aforesaid apparatus.
FIGS. 3 and 4 are a plan view and a cross-sectional view respectively
showing a three-dimensional driving mechanism of the aforesaid apparatus.
FIG. 5 is a view illustrating the probe scanning path in the aforesaid
apparatus.
FIGS. 6A and 6B are views illustrating the principle of the tracking in the
aforesaid apparatus.
FIGS. 7A and 7B are flowcharts for the CPU control in the aforesaid
apparatus.
FIG. 8 is a view illustrating a control mechanism for the aforesaid
apparatus.
FIG. 9 is a perspective cross-sectional view showing the entire structure
of the aforesaid apparatus.
FIG. 10 is a view illustrating the scanning at the time of recording and
reproducing in the aforesaid apparatus.
FIGS. 11 and 12 are a plan view and a cross-sectional view respectively
showing the three-dimensional driving mechanism for a second embodiment of
a recording and reproducing apparatus according to the present invention.
FIG. 13 is a view illustrating a recording and reproducing chip unit of a
third embodiment of a recording and reproducing apparatus according to the
present invention, and
FIG. 14 is a view illustrating the displacement of a cantilever of the
aforesaid apparatus.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The recording medium used for an embodiment of a recording apparatus and
reproducing apparatus set forth below comprises a metal oxide
semiconductor organic thin film having a recording medium layer formed on
a conductive substrate electrode, the aforesaid recording medium layer
being capable of convexing the shape of its recording medium surface
(refer to Staufer, Appl. Phys. Letters. Vol. 51(4), 27, Jul. 1987, p.244)
or concaving it (refer to Heinzelmann, Appl. Phys. Letters, Vol. 53, 24,
Dec., 1988, P.2447) by the tunnel current generated by a tunnel current
generating probe, or comprises an organic thin film layer, etc. capable of
changing its electrical characteristic conductivity by the aforesaid
tunnel current. For the aforesaid organic film capable of changing its
electrical characteristic, a Langmuir-Blodgett's film is preferable (refer
to EP0272935 A2). More preferably, the aforesaid Langmuir-Blodgett's film
should have in its layer face a structure capable of presenting an
amorphous state or a second-dimensional crystalline state.
Also, the probe for generating the tunnel current used for a recording
apparatus and reproducing apparatus according to the present invention is
of such a structure that a cantilever provided with a displacement means
is formed by a micromechanic technique on a substrate having a
semiconductor layer, and at the leading end of the cantilever a probe is
mounted. As the displacement means mentioned above, such a means as a
piezoelectric effect, electrostatic power, etc. is employed, or
preferably, means by use of a bimorph is employed. Further, since the
probe is formed on the substrate having the semiconductor layer, it is
necessary to provide a recording and reproducing chip having a
semiconductor integrated circuit arranged in the vicinity of the probe,
which comprises a current amplifying circuit for amplifying the current
signals running from the probe for generating the tunnel current, a
circuit for converting current voltage, a driving circuit for driving the
aforesaid displacement means, and others.
Hereinafter, in conjunction with the accompanying drawings, the embodiments
of the present invention will be described.
FIG. 1 is a view schematically showing the structure of a first embodiment
of the recording and reproducing apparatus according to the present
invention, and FIG. 2 is a view schematically showing the recording and
reproducing head 100 employed for the apparatus thereof. On a recording
and reproducing chip 1, a plurality of three-dimensional driving
mechanisms 2 are configured in such a manner that each of them can
independently displace itself in the three axes (in FIG. 1, only one of
them is represented). At the leading end of each three-dimensional driving
mechanism 2, a probe 4 for generating the tunnel current is mounted. The
recording and reproducing head is constructed by a plurality of chips
arranged in parallel, so that the plural probes of the plural chips face
one recording medium at a time (in FIG. 1, only one of them is
illustrated).
In FIG. 3 and FIG. 4, a piezoelectric bimorph three-dimensional driving
mechanism is illustrated in detail as an example. FIG. 3 is its plan view
while FIG. 4 is its side view. The three-dimensional driving mechanism 2
is formed by anisotropic etching from the reverse side of the Si substrate
(100). The three-dimensional driving mechanism 2 comprises a piezoelectric
thin film 5 as means for displacing the probe, and a cantilever 3 having
the electrode 6, which drives the thin film. The piezoelectric thin film 5
is formed in two layers in the layer structure which sandwiches the
electrode 6 as shown in the side view in FIG. 4, and a set such as this is
arranged in two in series in the width direction (y direction) of the
cantilever 3 as shown in FIG. 3. The cantilever 3 is displaced in the x
direction by the balance of the expansion and contraction of the two
piezoelectric thin films 5 overlapped in the layer structure, and the
cantilever 3 is displaced in the y direction by the balance of the
expansion and contraction of the two piezoelectric thin films 5 in the
width direction. Also, the cantilever is displaced in the z direction by
the entire expansion and contraction of the four piezoelectric thin films.
Thus, the three-dimensional driving mechanism 2 drives the probe 4 in the
three dimensional directions, x, y, and z. A z axis driving controller 36
and an x, y axes driving controller 37, which will be described later,
control the driving of the cantilever 3 in the z direction and the x, y
directions respectively by varying the value of voltage applied to each of
the piezoelectric thin films 5 through the electrode 6 and the balance of
the respective voltage values.
Now, referring back to FIG. 1, reference numeral 21 designates a recording
medium for recording information and reference numeral 22 designates a
recording medium holder. As a recording medium, there are used not only a
medium such that Cr is deposited on quartz of 50 .ANG., for example, by a
vacuum evaporation method and, further thereon, Au is deposited for 300
.ANG. by the same method as a base electrode, on which SOAZ
(squarilium-bis-6-octyl-azulene) is stacked by an LB method in four layers
or the like, but also as in various recording media such as disclosed in
the EP0272935 A2 Publication.
Here, a data modulator 30 modulates recording data into signals adequate
for recording, and a recording voltage applicator 31 records the data on a
recording medium by applying a voltage between the recording medium 21 and
the probe 4 in accordance with the signals modulated by the data
modulator. When, for example, a writing voltage of a rectangle pulse
voltage of 3 volts high and 50 ns wide is applied by the recording voltage
applicator 31 while the probe 4 is allowed to approach the recording
medium 21 with a predetermined space, writing is executed because the
recording medium is caused to vary its electrical conductivity to generate
a portion which presents a different electrical resistance. Then, many
pieces of information are recorded two-dimensionally on the recording
medium 21 by applying the writing voltage in accordance with the
information to be written while maintaining the probe 4 constantly in the
z direction and at the same time, causing it to perform its relative
scanning in the x and y directions. Here, reference numeral 32 designates
a recording signal detector for detecting the current value of the tunnel
current running between the probe 4 and the recording medium 21 when the
voltage is applied therebetween, and reference numeral 33 designates a
data demodulator for demodulating the tunnel current signals detected by
the recording signal detector 32. In reproducing, a direct current voltage
of 200 mv, for example, which is lower than the recording voltage, is
applied between the probe 4 and the recording medium 21 while maintaining
the probe 4 and the recording medium 21 with a predetermined space. In
this condition, while the probe 4 is scanning along the recording bit
array on the recording medium 21, the tunnel current signals, which should
be detected by the use of the recording signal detector 32, respond to the
recording data signals. Therefore, by the use of a data demodulator 33, it
is possible to obtain the reproducing data signal by demodulating the
detected tunnel current signal which is output after a current voltage
conversion which is required.
Here, reference numeral 34 designates a detector for detecting the height
of a probe. This detector 34 receives the detected signal from the
recording signal detector 32 and processes the remaining signal after the
high-frequency oscillating components due to the presence of an
information bit have been cut, and issues an instruction signal to a z
axis driving controller 36 in order to control the vertical movement of
the probe 4 so that the value of this remaining signal becomes constant.
Hence, a substantially constant space can be maintained between the probe
4 and the medium 21.
Reference numeral 35 designates a track detector. The track detector 35
detects the deviation of the probe 4 from the path, along which the data
should be recorded, or from the bit array of the recorded data
(hereinafter, they are referred to as a track) when the probe 4 performs
the relative scanning on the recording medium 21. One example of this
detection is given below.
The x, y axes driving controller 37 drives the probe 4 to scan roughly
along the contour of the track in accordance with an instruction from a
CPU 50 which will be described later. At this juncture, the probe 4 is
caused to oscillate in a width less than the bit width as well as at a
frequency lower than the bit generating frequency in the bit array
direction and the direction perpendicular thereto within the track. The
movement of the probe 4 at that time will be shown in FIG. 5. In FIG. 5,
reference numerals 18, 19, and 20 designate a track, an information bit,
and the scanning path of the probe 4, respectively. Here, there is shown
in FIG. 6A, the amplitude of the tunnel current signal generated by the
probe 4 when passing through the bits each at the track width direction
position of the probe. Now, since the amplitude of the generated signal
varies in accordance with the track width direction position of the probe
4 in this fashion, a modulated component in response to the frequency of
the width direction oscillation is added to the tunnel current signal
detected by the probe 4 which performs the track scanning while
oscillating in the track width direction. Here, there is shown in FIG. 6B,
each of the detected signals when the center of this width direction
oscillation is respectively at the positions in the track width direction,
4b, 4c, and 4d. In this respect, reference numeral 4a designates an
oscillating waveform of the width direction oscillation of the probe 4
when these signals are generated, i.e., the waveform of the control signal
in the track width direction provided for the three-dimensional driving
mechanism. The signals shown in FIG. 6B with reference marks 4b, 4c, and
4d are formed by the collections of signals generated at each time the
probe 4 passes through each of the bits. However, since each of the
signals is extremely fine and is in a great number, the signals are simply
represented only by an envelope in FIG. 6B.
As shown in FIG. 6B, the amplitudes of the detected signal change its
envelope representing the signals 4b, 4c, and 4d of FIG. 6B in accordance
with the positions indicated by arrows with the corresponding reference
marks in FIG. 6A. Therefore, if the envelope signals are drawn by the
full-wave rectification, the signals become those of 4b', 4c', and
4d'shown in FIG. 6B. In other words, against the oscillating waveform 4a
of the probe 4, its envelope signal is as small as the signal 4c'when the
probe 4 is located just above the calibrations as indicated by arrow 4c.
If the probe is deviated upwards as indicated by arrow 4b, the phase is
shifted 180.degree. to the oscillating waveform 4a, and the amplitude also
becomes large. If the probe is deviated downwards as indicated by arrow
4d, the phase becomes equivalent to the oscillating waveform 4a and the
amplitude also becomes large. Accordingly, it is possible to obtain a
signal proportional to the deviation from the center of the track by
performing the phase detection o | | |
