Patent Application
20110208032
The present invention relates to a detection device, detection method, vein sensing device, scanning probe microscope, distortion detection device and metal detection device that are based on a novel principle.
There is a conventional measurement device, proposed by the inventors, which non-invasively measures blood vessels and the like in a living body (see Patent Document 1). The measurement device emits from an emission electrode a quasi-static electric field that enables higher intensity to be obtained than an induction field at each distance corresponding to each of a plurality of frequencies and detects a change in the intensity of the quasi-static electric field of a frequency corresponding to the distance by means of a detection electrode to measure the state of blood vessels and the like.
Meanwhile, there has been a proposed proximity switch equipped with a magnetic field sensitive sensor (see Patent Document 2, for example). In the proximity switch, a magnetic flux-free area is formed by three poles with the same name between U-shaped leg members of a U-shaped permanent magnet having the vertical direction of magnetization. In the area, a sensor is attached that is sensitive to a magnetic field. Above the U-shaped leg members, a planar ferromagnetic trigger member that can come nearer is also provided on a plane parallel to a U-shaped base. As the trigger member comes closer to two poles of the U-shaped leg members, triggering takes place thanks to the offsetting of the magnetic flux-free area, enabling a switching signal of the sensor to be evaluated.
Moreover, it is known that a magnetic field sensitive sensor is disposed in a magnetic field-free area of a unique permanent magnet device (see Patent Document 3).
According to the techniques disclosed in Patent Documents 2 and 3, it is possible to detect an approaching ferromagnetic material that a conventional magnetic field sensitive sensor cannot detect. The principle is that the magnetic field sensitive sensor detects the change of the magnetic field-free area caused by the distortion of the magnetic field associated with the interaction between the magnetic field of the permanent magnet and the ferromagnetic material. However, nothing is disclosed or suggested by Patent Documents 2 and 3 about a detection device that uses an electrode that generates electric charges and an electric field detection element that detects an electric field.
It is know that each tissue of a living body is a dielectric material that has a different electric characteristic (permittivity and conductivity) as well as a different frequency characteristic (see Non-patent Documents 1, 2 and 3). With the use of the characteristics (the difference in electric characteristic between tissues), Impedance CT (Computed Tomography), a method of electrically detecting tissues, has been studied.
According to the knowledge of the inventors, for example, even a tiny fatty tissue between a blood vessel and the outer layer of a skin makes it impossible for the measurement device proposed in Patent Document 1 to obtain sensitivity. Thus, it is difficult to accurately measure the state of the blood vessel.
Therefore, the problem to be solved by the invention is to provide a detection device and a detection method that are based on a novel principle and able to detect blood vessels and other various targets with high sensitivity and accuracy.
Another problem to be solved by the invention is to provide a high-performance vein sensing device, scanning probe microscope, distortion detection device and metal detection device that use the above novel detection device.
After conducting a intense study to solve the above problems, the inventors have found the following technique to solve the above problems and come up with the invention: the technique of generating at least around one straight line m rotationally symmetric electric charges (m is an even number that is greater than or equal to 4) whose total amount of charge is substantially 0 and detecting an electric field on the straight line. The detection device and detection method based on the novel principle cannot be easily invented based on Patent Documents 2 and 3. The following describes the reasons.
The magnetic field and the electric field are different in that, in the magnetic field, there is no monopole, which corresponds to an electric charge in the electric field. However, both are equivalent to each other if a dipole, instead of a monopole, is used for formation. Accordingly, it seems possible to realize an electric field sensor based on a similar principle to the techniques disclosed in Patent Documents 2 and 3 by replacing the magnetic fields of the two conventional techniques disclosed in Patent Documents 2 and 3 with electric fields as well as magnetic dipoles with electric dipoles. However, in reality, the above is impossible for the following reasons. That is, as a result of the above replacement in the conventional technique, a wire used to obtain signals from an electric field sensitive sensor becomes an electrode, which has impact on the pole structure, leading to a loss of the symmetry. Therefore, an area where the electric field is zero is not formed; the electric field sensor is not realized. In other words, the structure of the magnetic field sensor and the structure of the electric field sensor are not compatible in terms of structure since the physical effects are different. When the above replacement is performed, three N-poles encircled by dotted lines in
That is, to solve the above problems, according to the first invention of the present invention, a detection device is characterized by comprising:
m electrodes that generate at least around one straight line m rotationally symmetric electric charges (m is an even number that is greater than or equal to 4) whose total amount of charge is substantially 0; and
at least one electric field detection element that detects an electric field on the straight line.
In the detection device, in an exemplary case, the signs of adjacent electric charges of the m electric charges are different (one is positively charged, and the other negatively charged); the absolute values of the m electric charges are equal to each other.
In the detection device, on the straight line that acts as a rotational axis of the m rotationally symmetric electric charges, the electric field E0 is 0 [V/m] due to the overlapping of the electric fields caused by the electric charges. In this case, an area where the electric field E0=0 [V/m] (point, line, surface) is referred as a unique area. When an area where E0≈0 [V/m] exists close to the area where E0=0 [V/m], the area where E0=0 [V/m] and the area where E0 is approximately equal to 0 [V/m] are collectively referred to as a unique area. To detect an electric field on a straight line means to detect an electric field of the unique area. In order to improve the sensitivity and accuracy of the detection, it is desirable to bring about a steep change in intensity of the electric field inside and outside the unique area. That is, when the change of the intensity of the electric field is directly measured, it is difficult to detect the change because the amount of change ΔE is small compared with E0 when the electric field E0 changes to E0+ΔE particularly if E0<<ΔE. Even if the change is amplified by an amplifier, it remains difficult to detect the change because the ratio of ΔE to E0 remains unchanged. If the electric field is detected in the unique area, it is possible to detect the change of the electric field with high accuracy and sensitivity because the detected intensity of the electric field is equivalent to the amount of change ΔE.
It is desirable that an electric field detection element and a wire extending outside from the electric field detection element be disposed on the straight line. The above means that the wire extending outside the electric field detection element is disposed on an equipotential surface. That is, since the electric field detection element and the wire extending outside from the electric field detection element are disposed on the equipotential surface, the rotational symmetry of m electric charges can be maintained.
In the detection device, by detecting that an electric field of the unique area changes in a way that does not satisfy E0=0 [V/m] or E0≈0 [V/m] for some reason, it is possible to detect the breaking of the rotational symmetry of the m electric charges.
The m electric charges are designed to make up, for example, a multipole or planar 2n-pole (n is an integer that is greater than or equal to 2) or to emerge at a vertex of a regular polyhedron or quasi-regular polyhedron. The multipole can be regarded as k dipoles (k is an integer greater than or equal to 2) that are disposed in such a way that the signs of electric charges of the adjacent dipoles are opposite to each other. For example, a quadrupole, octupole or the like can be cited as examples. The planar 2n-pole can be regarded as n dipoles arranged on a plane in such a way that the signs of electric charges of the adjacent dipoles are opposite to each other, for example, including a quadrupole, hexapole and octupole. The regular polyhedron may be a cube, which is used to generate an octupole. A quasi-regular polyhedron may be a truncated octahedron (The Truncated Octahedron), a rhombitruncated cuboctahedron (The Rhombitruncated cuboctahedron), or the like.
For example, in the quadrupole, the charge distribution has invariable two-fold rotational symmetry with respect to the rotation of 180 degrees around a straight line that is a rotational axis. There is only one straight line acting as a rotational axis. In this case, the straight line, or the straight line and an adjacent area, is a unique area. For the quadrupole, changes of an electric field inside and outside the unique area are steep in particular; the quadrupole is exceptionally excellent in the sensitivity and accuracy of detecting the breaking of the charge's rotational symmetry. Therefore, the quadrupole is highly desirable. In the octupole having a three-dimensional structure, the charge distribution has invariable two-fold rotational symmetry with respect to the rotation of 180 degrees around straight lines that are rotational axes. The straight lines acting as rotational axes are three straight lines that cross each other at right angles. In this case, the straight lines, or the straight lines and an adjacent area, are a unique area.
For example, the detection device can detect: (1) a change of the position of at least one electrode among m electrodes; (2) a change of the amount of charge (voltage) of electric changes that emerge on at least one electrode among the m electrodes; and (3) an electric charge (including a charged conductor) or object (which is made of a conductor or dielectric) outside the m electrodes. That is, in the case of (1), when the position of at least one electrode changes for some reason, the rotational symmetry of the m electric charges breaks. Therefore, the electric field on the straight line, which is the rotational axis of the m electric charges, changes in a way that does not satisfy E0=0 [V/m] or E0≈0 [V/m]. In the case of (2), when the amount of charge of electric charges that emerge on at least one electrode changes for some reason, the rotational symmetry of the m electric charges breaks. Therefore, the electric field on the straight line, which is the rotational axis of the m electric charges, changes in a way that does not satisfy E0=0 [V/m] or E0≈0 [V/m]. In the case of (3), if there is an electric charge or object (which is made of a conductor or dielectric) outside the m electrodes, the rotational symmetry of the m electric charges breaks due to the effects of the electric charge or object. Therefore, the electric field on the straight line, which is the rotational axis of the m electric charges, changes in a way that does not satisfy E0=0 [V/m] or E0≈0 [V/m].
The electric charges of the m electrodes may be those caused by applying an alternating voltage to the above electrodes or be static electric charges. In particular, when m electric charges are generated by applying a sine-wave alternating voltage to the m electrodes, it is desirable that d<<λ/2π, where λ represents the length of the sine wave and d represents the length of a dipole that makes up the m electric charges. Thanks to the condition, in an electric field caused by the m electric charges, a quasi-static electric field becomes dominant.
The shape of the m electrodes can be selected when necessary. In general, the m electrodes are point electrodes or planar electrodes. In terms of detection sensitivity and accuracy, it is preferable that the m electrodes be square planar electrodes. When the m electrodes are regarded as one basic unit, the detection device may use only one basic unit or a matrix array electrode where a plurality of basic units are arranged in one-dimensional or two-dimensional array.
The principle and configuration of how the electric field detection element detects do not matter. However, in general, a detection electrode is used. The election electrode may consist of a single electrode. However, in order to improve detection sensitivity and accuracy, it is desirable that the detection electrode be of a dipole type, for example, with a pair of electrodes positioned close to each other. In this case, the difference in potential between the dipole-type electrodes is measured, and the potential difference is amplified by an amplifier or the like when necessary. Thus, it is possible to detect an electric field. The detection electrode may be made by disposing two dipole-type electrodes in such a way that the electrodes cross each other at right angles. An electro-optic crystal may be used for the electric field detection element: it is possible to detect an electric field because of an electro-optic effect, which refers to a change of refractive index caused by the electric field. In this case, for example, a laser beam having a constant polarization plane is emitted to the electro-optic crystal. Then, the polarization plane of the laser beam that has passed through the electro-optic crystal is detected. Subsequently, the change of the refractive index is measured from the rotation angle of the polarization plane. Then, an electric field is detected from the change of the refractive index. Various electro-optic crystals can be used.
The detection device can be used for various apparatuses, devices, systems, microscopes and the like that are used in detecting electric charges on the basis of the detection of the electric field, detecting a conductor or dielectric, detecting a change of the position of an object, or doing other processes.
According to the second invention, a detection device is characterized in that
m rotationally symmetric electric charges (m is an even number that is greater than or equal to 4) whose total amount of charge is substantially 0 are generated at least around one straight line, and an electric field on the straight line is detected.
According to the third invention, a detection method is characterized in that
m rotationally symmetric electric charges (m is an even number that is greater than or equal to 4) whose total amount of charge is substantially 0 are generated at least around one straight line, and an electric field on the straight line is detected.
According to the fourth invention, a detection device that detects a to-be-detected target or a change of the state of the to-be-detected target is characterized by comprising:
a plurality of electric field applying means for applying electric fields to the to-be-detected target;
electric field detection means for detecting an electric field of a detection area adjacent to the to-be-detected target; and
processing means for detecting a change of the electric field of the detection area detected by the electric field detection means and detecting the to-be-detected target or a change of the state of the to-be-detected target, wherein
when the to-be-detected target is not adjacent to the detection area or is in a predetermined state, a plurality of the electric field applying means applies electric fields in such a way that the electric fields applied from a plurality of the electric field applying means diminish each other and an electric field adjacent to the detection area and the electric field detection means comes to substantially 0.
Here, in an exemplary case, the number of the electric field applying means is m (m is an even number that is greater than or equal to 4). The detection area means an area where the electric field detection means detects an electric field.
According to the fifth invention, a vein sensing device is characterized by using a detection device including:
m electrodes that generate at least around one straight line m rotationally symmetric electric charges (m is an even number that is greater than or equal to 4) whose total amount of charge is substantially 0; and
at least one electric field detection element that detects an electric field on the straight line.
According to the sixth invention, a scanning probe microscope is characterized by using a detection device including:
m electrodes that generate at least around one straight line m rotationally symmetric electric charges (m is an even number that is greater than or equal to 4) whose total amount of charge is substantially 0; and
at least one electric field detection element that detects an electric field on the straight line.
In this case, the scanning probe microscopes (SPM) include an atom force microscope (AFM), a scanning tunneling microscope (STM), and the like.
According to the seventh invention, a distortion detection device is characterized by using a detection device including:
m electrodes that generate at least around one straight line m rotationally symmetric electric charges (m is an even number that is greater than or equal to 4) whose total amount of charge is substantially 0; and
at least one electric field detection element that detects an electric field on the straight line.
According to the eighth invention, a metal detection device is characterized by using a detection device including:
m electrodes that generate at least around one straight line m rotationally symmetric electric charges (m is an even number that is greater than or equal to 4) whose total amount of charge is substantially 0; and
at least one electric field detection element that detects an electric field on the straight line.
According to the second to eighth inventions, what has been described for the first invention is similarly true as long as the second to eight inventions go against the characteristic thereof.
According to the invention having the above configuration, the electric field E0 is equal to 0 [V/m] or approximately equal to 0 [V/m] on the straight line, which is the rotational axis of the m electric charges and in the adjacent unique area. Therefore, the electric field is maintained when the rotational symmetry of the m electric charges is kept. When the rotational symmetry of the m electric charges breaks for some reason, the electric field of the unique area changes in a way that does not satisfy E0=0 [V/m] or E0≈0 [V/m]. Moreover, the electric field detection element and the wire thereof are provided on the straight line, which is a rotational axis. Therefore, the wire does not affect the rotational symmetry of the m electric charges. That is, the rotational symmetry of the m electric charges is maintained. Therefore, the wire does not affect the detection capability. Moreover, it is possible for the detection device and method to obtain sufficiently large sensitivity even when fat tissue exists between the outer layer of a skin and a blood vessel. Therefore, it is possible to detect blood vessels with high sensitivity and accuracy.
According to the present invention, it is possible to realize a detection device that is based on a novel principle and able to detect blood vessels and other various targets with high sensitivity and accuracy. It is also possible to realize a high-performance vein sensing device, scanning probe microscope, distortion detection device and metal detection device that use the above detection device.
The following describes an embodiment of the present invention with reference to the accompanying drawings.
What is first described is a specific example of the configuration of electrodes used in generating m electric charges in a detection device of the present invention as well as an specific example of a unique area generated by the m electric charges.
In order to obtain a quadrupole, four electrodes are disposed at the vertexes of a square. The same voltage is applied to the electrodes on a diagonal of the square. The voltage whose polarity is inverted against the voltage is applied to the electrodes on the other diagonal. The applied voltage is a direct-current or alternating voltage.
When a direct-current voltage is applied, the electrodes on one diagonal are charged with +Q [C], and the electrodes on the other diagonal with −Q [C].
When an alternating current is applied, for example, a sine-wave voltage is applied to electrodes on one diagonal. A sine-wave voltage whose phase has been shifted by 180 degrees from the above sine-wave voltage is applied to the electrodes on the other diagonal.
According to the present invention, to apply a direct-current voltage to the electrodes in principle means to apply an alternating voltage to the electrodes. Therefore, what is described hereinafter is a model where a static electric charge is changed by applying a direct-current voltage to the electrodes.
When absolute values of electric charges of all the four electrodes are equal to each other, a unique area emerges exactly at the center of the four electrodes.
It is clear from
(2) Planar 2n-Pole
A planar 2n-pole is made by generalizing the above quadrupole on a plane. The planar 2n-pole is a structure where electric charges are disposed at the positions corresponding to the vertexes of a shape having equal sides and 2n corners (a square, an equilateral hexagon, an equilateral octagon or the like) so that the adjacent electrodes have opposite polarities. In this case, the central portion of the shape having equal sides and 2n corners turn out to be a unique area.
The sharpness of the unique areas at the central portions of the quadrupole, the hexapole and the octupole is evaluated.
It is clear from
As shown in
As l becomes smaller relative to the distance r from each vertex of the polygon to the unique area, the electric fields caused by two electric charges diminish each other, resulting in the smaller electric field strength of the unique area. That is, as l increases, the strength of the electric field of the unique area becomes larger. Specifically, when electric charges are disposed on the vertexes of a square, the strength of the electric field of the unique area grows to a maximum.
In order to obtain a three-dimensional octupole, eight electrodes are disposed at the vertexes of a cube.
When the absolute values of all the electric charges of the eight electrodes are equal to each other, a unique area emerges right at the center of the eight electrodes, i.e. the center of the cube.
It is clear from
If all the faces of a regular polyhedron or quasi-regular polyhedron are in a shape having 2n corners, a multipole can be made by applying electric charges to the vertexes of each face in such a way that the adjacent polarities are inverted. In this case, a rotationally symmetric figure emerges with a normal line of the center of each face serving as an axis. That is, the multipole is made so that the normal line of the center of each face serves as a unique area. The above configuration is made possible only by a cube among regular polyhedrons. The above configuration corresponds to the above octupole.
The above configuration is made possible by a truncated octahedron, a rhombitruncated cuboctahedron and the like among quasi-regular polyhedrons.
Based on the above assumption, embodiments of the present invention will be described.
As shown in
Suppose that a to-be-detected target 21 is beneath the electrodes 11 and 12 as shown in
In this case, in detecting the to-be-detected target 21, the difference in electric characteristic (permittivity and conductivity) between the to-be-detected target 21 and the surrounding space is used. Specifically, for example, the to-be-detected target 21 is a conductor in the atmosphere, a dielectric in the atmosphere (it is easy to detect a dielectric whose permittivity is larger than the permittivity of the atmosphere), the blood in the fat (the blood is higher in electric conductivity than the fat), or the like.
If the to-be-detected target 21 is in the shape of a rod or line (For example, the to-be-detected target 21 is a vein), it is preferable that not only the electric field strength but also an electric field vector to be detected be taken into account. The following explains such a case.
If the rod- or line-shaped to-be-detected target 21 is positioned beneath two out of the four electrodes 11 to 14, the component of the electric field that emerges is in the same direction as that of the to-be-detected target 21 (longitudinal direction). For example, as shown in
In the detection device, the arrangement of the electrodes 11 to 14, the shape of the electrodes 11 to 14, and the distance from the electrodes 11 to 14 to the to-be-detected target 21 correlate with the amount of detection (electric field strength). Accordingly, the following describes the results of formulation based on an electromagnetic simulation for the above.
The conditions of the simulation are as follows.
Simulation software: EEM-FDM by Information and Mathematical Science Laboratory Inc.
Calculation method: Maxwell's equations calculated by the finite-difference frequency-domain
Calculation range: x: −0.04 to 0.04 m, y: −0.06 to 0.06 m, z: −0.05 to 0.05 m
Mesh size: 0.002 m
Frequency: 1 MHz, Amplitude: 1V
The following shows formulation items
a. The horizontal position of a to-be-detected target—the electric field strength of a unique area
b. The depth of a to-be-detected target—the electric field strength of a unique area
c. The size of a to-be-detected target—the electric field strength of a unique area
d. The distance between electrodes—the depth of detection
e. The length of an electrode—the depth of detection
f. The size of a tip of an electrode—the depth of detection
The above will be described one by one.
a. The horizontal position of a to-be-detected target—the electric field strength of a unique area
b. The depth of a to-be-detected target—the electric field strength of a central point
c. The size of a to-be-detected target—the electric field strength of a unique area
d. The distance between electrodes—the depth of detection
e. The length of an electrode—the depth of detection
f. The size of a tip of an electrode—the depth of detection
The summary of the above is: the electric field strength of the unique area is dependent on the horizontal position and depth of the to-be-detected target. The sensitivity for changes in the horizontal position is significantly high. The amount of detection becomes smaller for the to-be-detected target positioned at depth. When the electrode is a plate, it is possible to detect the to-be-detected target positioned at depth as the area of the plate gets larger.
The following describes what the detection device detects.
What is described first is the case where changes in the positions of the electrodes 11 to 14 are detected by the detection device.
Suppose that the electric charges have moved as the positions of some of the electrodes 11 to 14 have changed. The following looks at the case where the electrodes 11 and 12 have moved by about 0.001 [m] to the left in
It is clear from
E=0 [V/m] with x=0 [m] in the case where the positions of the electrodes 11 and 12 have not changed; or
E=36.1 [V/m] with x=0 [m] in the case where the positions of the electrodes 11 and 12 have changed to the left.
In this case, a portion of the unique area where the electric field strength equals 0 moves to the left (the negative direction of x) by 0.001/2=0.0005 [m]. However, since the change of the electric field around the unique area is steep, the amount of detection of the electric field is large. In general, when two of the electrodes move only by a in the direction parallel to that of the x-axis, the unique area moves by a/2. It is clear from the graphs of
The following describes the case where the detection device detects changes in the amounts of charges of the electrodes 11 to 14.
Suppose that the electric charges, +1 [C] and −1 [C], of the electrodes 11 and 12 have doubled to +2 [C] and −2 [C].
The following describes the case in which the detection device detects that other electric charges approach the electrodes 11 to 14.
In this case, the electric field strength of the quadrupole and the electric field strength of the electric charges approaching the electrodes 11 to 14 overlap each other. Detection takes place at a position where the electric field becomes 0 as a result of overlapping.
The following describes the frequency of a voltage applied to the electrodes 11 to 14.
In the detection device, a unique area is electrostatically determined by the electric charges of the electrodes 11 to 14. The electrodes 11 to 14 may be charged with electrostatic charges (in the case of a direct current). The sine-wave voltage with a frequency of d<<λ/2π is applied to the electrodes 11 to 14: the wavelength λ of the sine-wave voltage is sufficiently longer than the to-be-detected target 21 or the detection section, i.e. the distance between the electrodes 11 and 12 or between the electrodes 13 and 14, or in other wards the length d of the dipole.
The following describes a specific example of an electric field detection method by the detection electrode 20.
In the case of
As described above, according to the detection device of the first embodiment, to detect the electric field, the detection electrode 20 is provided in the unique area of the quadrupole caused by the electric charges that emerge at the electrodes 11 to 14. Therefore, it is possible to detect the to-be-detected target 21 with high sensitivity and accuracy. The detection device can be used in such detection processes as detecting changes in the positions of the electrodes 11 to 14, detecting changes in the amount of charge of the electrodes 11 to 14, or detecting that other electric charges approach the electrodes 11 to 14.
The following describes a detection device according to a second embodiment of the present invention.
In the detection device, instead of the detection electrode 20 of the detection device of the first embodiment, a detection element that uses electro-optic crystal detects the components Ex and Ey of the electric field vector.
The other ends of the optical fibers 37 and 38 are connected to an optical detection system.
The following describes a method of detecting the components Ex and Ey of the electric field vector by a detection element that uses the electro-optic crystal.
As shown in
If the permittivity of the optical fibers 37, 38, 42 and 48 is different from that of the surrounding area (which is for example an atmosphere), there is a fear that the existence of the optical fibers 37, 38, 42 and 48 could have an effect on the electric field at the detection position. However, the refractive index of the optical fibers 37, 38, 42 and 48 is about 1.1 to 1.5. Accordingly, the relative permittivity c r is approximately equal to 1.2 to 2.5, which is close to the permittivity of the atmosphere (with a relative permittivity of 1). Therefore, the effect of the optical fibers 37, 38, 42 and 48 on the electric field is smaller than the effect of a wire, which is a problem with an electrical detection method, on the electric field.
Except for the above, the second embodiment is the same as the first embodiment.
According to the second embodiment, the same effects as those of the first embodiment can be obtained.
The following describes a vein sensing device according to a third embodiment of the present invention.
The vein sensing device uses a detection device of a quadrupole type of the first embodiment shown in
Since the to-be-detected target 21 is a rod-shaped vein, it is preferable that not only electric field strength but also a to-be-detected electric field vector be taken into consideration. When the vein lies in the x-axis direction, the component Ex of the x-direction electric field vector is not 0 [V/m]. When the vein lies in the y-axis direction, the component Ey of the y-direction electric field vector is not 0 [V/m]. That is, it is possible to detect the direction of the vein thanks to the direction of the electric field vector. To detect the electric field, for example, the detection electrode 20 shown in
The following proves, with an electromagnetic simulation, that it is possible to detect a vein using a quadrupole electrode for a skin model that is made up of a numerical phantom.
The same sine-wave voltage is applied to two electrodes on one diagonal of a square. The sine-wave voltage whose phase has been shifted by 180 degrees from the above sine-wave voltage is applied to two electrodes on the other diagonal.
The frequency is selected so that as for the electrical characteristics of a living body, the electric conductivity of blood is higher than the electric conductivity of other tissues. According to the simulation, calculation is conducted with a frequency of 1 MHz.
The conditions of the simulation are as follows.
Simulation software: EEM-FDM by Information and Mathematical Science Laboratory Inc.
Calculation method: Maxwell's equations calculated by the finite-difference frequency-domain
Calculation range: x: −4 mm to 4 mm, y: −3 mm to 3 mm, z: −5 mm to 5 mm
Mesh size: 0.0002 m
Frequency: 1 MHz, Amplitude: 1V
Living-body phantom: a living-body phantom shown in
The formulation items are as follows:
a. The horizontal position of a vein—the electric field strength of a unique area
b. The depth of a vein—the electric field strength of a unique area
c. The size of a vein—the electric field strength of a unique area
d. The distance between electrodes—the depth of detection
e. The length of an electrode—the depth of detection
f. The size of a tip of an electrode—the depth of detection
The above will be described one by one.
a. The horizontal position of a vein—the electric field strength of a unique area
b. The depth of a vein—the electric field strength of a unique area
c. The size of a vein—the electric field strength of a unique area
d. The distance between electrodes—the depth of detection
e. The length of an electrode—the depth of detection
The following is a summary of the above. The depth of a vein (blood) around the outer layer of a skin inside a living body is dependent on the horizontal position and depth of the vein. In the horizontal direction, the sensitivity to positional changes is significantly high; the amount of detection is smaller for a target positioned at depth. It is found that it is possible to dramatically improve the amount of detection with the use of a method of increasing the area of the plate of the electrode tip portion or a method of narrowing the distance between electrodes.
According to the vein sensing device of the third embodiment, it is possible to non-invasively detect a vein inside a living body with high sensitivity and accuracy from above the outer layer of the skin. It is possible to accurately detect the pattern of the vein. For example, the vein sensing device can be applied to the case where the vein sensing device is put on an arm vein to detect the pattern of the vein for the purpose of vein personal authentication.
As a conventional method to detect a vein pattern inside a living body from above the outer layer of the skin, there is an impedance measurement method. However, the following are the problems with the impedance measurement method: varying and unstable impedance depending on how the electrode is put on the skin; perspiration that affects the impedance measurement method; unclear differences between a vein and any parts other than the vein; the electromotive force caused by two kinds of electrodes (metal) put on the skin as the electrodes come in contact with, which gives rise to noise during the impedance measurement process. On the other hand, the vein sensing device of the third embodiment does not have such problems. Table 2 shows a comparison of the detection method of the present method and the detection method of the impedance measurement method.
The following describes a vein sensing device according to a fourth embodiment of the present invention.
As shown in
With the use of the matrix array electrode shown in
The conditions of the simulation are as follows.
Simulation software: EEM-FDM by Information and Mathematical Science Laboratory Inc.
Calculation method: Maxwell's equations calculated by the finite-difference frequency-domain
Calculation range: x: −0.003 to 0.031 m, y: −0.003 to 0.031 m, z: −0.05 to 0.05 m
Mesh size: 0.002 m
Frequency: 1 MHz, Amplitude: 1V
Living-body phantom: a living-body phantom shown in
The electrical characteristics are shown in Table 1.
The number of electrodes 61 arranged comes to 14×14=196.
The use of the matrix array electrode helps to improve both the horizontal resolution and the depth-direction detection performance. The reasons will be described below.
As described above, as for the detection performance of the quadrupole-type electrode, it is possible to detect a deeper vein as the area of the electrode is increased. However, as the area of the electrode increases, the planar resolution decreases. Accordingly, a plurality of electrodes in the matrix array electrode are regarded as a group to which the same electric signals (voltage) are applied. In this manner, the electrodes are apparently regarded as one large electrode. In this case, an atomic unit, which is one basic unit, and a group of the basic units are the same in configuration. Therefore, the configuration is referred to as a fractal structure.
When the matrix array electrode having such a fractal structure is used for detection, scanning is for example performed in the following manner.
Scanning of the matrix array electrode is performed several times. In the first scanning process, the four electrodes 61 encircled by dotted lines in
As described above, according to the vein sensing device of the fourth embodiment, the large electrode is formed by the electrical switching of the matrix array electrode. The planar-direction resolution is designed to be dependant on the distance between the electrodes 61 of one basic unit. It is possible to scan with the above resolution. Therefore, in the vein sensing device, it is possible to obtain the depth-direction detection performance that matches that of the physically large electrode. Since scanning is possible on a per-one-basic-unit-electrode basis, it is possible to obtain a high horizontal resolution, which cannot be obtained by a simply large electrode.
Incidentally, in the example shown in
The following describes a scanning probe microscope according to a fifth embodiment of the present invention.
As shown in
The operation of the scanning probe microscope will be described. As shown in
According to the fifth embodiment, it is possible to realize the scanning probe microscope based on a novel principle. Unlike a conventional atom force microscope, a structure for moving a sample in the horizontal direction is not required in the scanning probe microscope. It is unnecessary to use a cantilever that mechanically operates. Since the scanning probe microscope works in a non-contact manner, the sample is not damaged and there are no other effects on the sample. It is possible to accurately scan the uneven surface of the sample at high speed.
The following describes a distortion detection device according to a sixth embodiment of the present invention.
The distortion detection device detects the distortion of a structure such as a building and of land by detecting a change in the position of a multipole electrode through a change in the electric field strength of a unique area.
In the distortion detection device, if the building 81 is not distorted, the electric field of the unique area is 0 [V/m]. However, if the positions of the electrodes 11 to 14 change as the building 81 is distorted, the electric field detected by the detection electrode 20 does not satisfy 0 [V/m]. Therefore, it is possible to predict the distortion of the building 81 thanks to the change of the electric field.
According to the sixth embodiment, it is possible to realize the distortion detection device based on a novel principle.
The following describes a metal detection device according to a seventh embodiment of the present invention.
As shown in
When an object whose conductivity is different or an object whose permittivity is different comes closer to the detection electrode 20, the metal detection device detects the object. Specifically, the to-be-detected object 21 is, for example, a buried metal object around the surface of the earth, an object that is different in electric characteristic from the ground, a metal object embedded in a wall, or the like.
The operation of the metal detection device will be described.
An operator uses a hand to grab the handle 92 and moves the metal detection device along the surface of the ground in the horizontal direction. At this time, above an uniform object, electric charges that occur on the electrodes 11 to 14, i.e. the electric fields caused by the quadrupole, are balanced relative to the electrodes 11 to 14. The electric field strength is 0 [V/m] at the center of the electrodes 11 to 14. If a metal object or an object whose electric characteristic is different exists away from the center of the electrodes 11 to 14, the balance of the electric fields caused by the electric charges of the electrodes 11 to 14 is lost. The detection electrode 20 positioned at the center detects an electric field other than the one that is 0 [V/m]. The change of the electric field enables metal to be detected.
The electric-field detection of the detection electrode 20 can be carried out with the use of the same detection system, which is shown in
According to a seventh embodiment, it is possible to realize the metal detection device based on a novel principle.
The following describes a scanning probe microscope according to an eighth embodiment of the present invention.
As shown in
According to the scanning probe microscope, since the detection device does not touch the surface of the sample, the sample is not damaged. Moreover, since the scanning probe microscope does not use a cantilever that mechanically operates like a conventional atom force microscope, it is possible to accurately scan the uneven surface of the sample at high speed.
According to the eighth embodiment, it is possible to realize the scanning probe microscope based on a novel principle.
The above has provided a detailed description of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Various modifications may be made based on the technical ideas of the present invention.
For example, the numeric values, structures, arrangements, shapes and the like described in the above embodiments are just examples. Therefore, different numeric values, structures, arrangements, shapes and the like may be used when necessary.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2008/066146 | 9/2/2008 | WO | 00 | 5/13/2011 |
