JP6901753B2 - Measurement system and measurement method - Google Patents

Description

The present invention relates to a measuring system and a measuring method for measuring the movement of a measurement object by utilizing a change in capacitance.

Generally, in the medical field, a stethoscope, an electrocardiogram, a pulse wave sensor and the like are used as an inspection device for examining the activity of the heart. Since these sensors capture the activity of the heart one-dimensionally or two-dimensionally by sound, electric signal, etc., they are suitable for acquiring detailed information on the heart, for example, three-dimensional information on the heart. Not. Further, as other inspection equipment, CT scan, MRI, cardiac echo and the like are also used. These can capture the activity of the heart three-dimensionally using X-rays, magnetic fields, ultrasonic waves, etc., but they are very expensive and can only be measured while lying in bed. The inspection environment is limited.

On the other hand, the inventor of the present application has previously proposed a measurement system capable of detecting the movement of an organism, not limited to the human body (see Patent Document 1). This measurement system detects the presence of pests such as termites existing inside wood based on the change in capacitance, and is a minute change in capacitance due to the presence of the pest. Can also be detected by performing a specific process.

Japanese Unexamined Patent Publication No. 2016-138793

Since the activity of the heart in the human body also involves minute movements, the inventor of the present application has examined applying the measurement system described in Patent Document 1 to the activity of the heart. However, not only the heart but also various organs exist in the human body and are active at the same time as the heart. In the measurement system described in Patent Document 1, the movement of the heart cannot be distinguished from the movement of other organs and the like.

The present invention has been made in view of the above circumstances, and it is possible to measure the movement of a measurement object in a living body such as a human body by distinguishing it from other movements by utilizing a change in capacitance. It is an object of the present invention to provide a possible measurement system and measurement method.

The measurement system of the present invention
An oscillator circuit that has a resonance circuit that includes a capacitor,
A sensing element that includes a conductor placed near the living body and connected in parallel to the capacitor,
It is provided with a processing device that performs a process of extracting a frequency change in a frequency band corresponding to the movement of a measurement object in a living body from a change in the output frequency of the oscillation circuit.

According to the above measurement system, when the capacitance of the sensing element changes due to the movement of an organ or the like in the living body, the output frequency of the oscillation circuit changes accordingly. Then, the processing device performs a process of extracting the change in frequency in the frequency band corresponding to the movement of the object to be measured in the living body from the change in the output frequency of the oscillation circuit. Therefore, even if a plurality of organs or the like are active in the living body at the same time and the capacitance of the sensing element and the output frequency of the oscillation circuit are changed by these movements, the measurement target is selected from among the plurality of organs or the like. It is possible to identify and extract the change in frequency due to the movement of an organ or the like, and measure the movement of the object to be measured.
In the above, "extraction" includes not only a process of extracting a signal of a specific frequency band from a signal on which a plurality of frequencies are superimposed, but also a process of removing a signal other than the specific frequency band.

It is preferable that the processing device extracts the frequency change of the measurement target by the frequency analysis processing. However, the processing device may be one that extracts the frequency change of the object to be measured by a bandpass filter or the like.

The measurement system preferably includes a plurality of sets of the oscillation circuit and the sensing element.
In this case, it is possible to measure the movement of the object to be measured in the living body at a plurality of places.
Further, it is preferable that the processing device outputs the frequency changes due to the movement of the measurement object extracted from the changes in the output frequencies of the plurality of oscillation circuits in synchronization with each other.
With such a configuration, it is possible to grasp the movements occurring at a plurality of locations of the measurement object at the same time, and for example, it can be useful for three-dimensionally capturing the movements of the measurement object.

The processing device preferably extracts the change in frequency due to the heartbeat of the living body from the change in the output frequency of the oscillation circuit.
With such a configuration, it becomes possible to measure the movement of the heart and use it for diagnosis of heart disease and the like.

It is preferable that the processing device extracts the change in frequency due to the respiration of the living body from the change in the output frequency of the oscillation circuit.
With such a configuration, it is possible to measure the movement of the lungs and the like and use it for diagnosis of respiratory diseases and the like. In addition, by measuring a plurality of movements between the heart and lungs, it is possible to grasp the relationship between the diseases of both.

It is preferable that the processing device extracts the frequency change due to the movement of a plurality of measurement objects from the output frequency change of the oscillation circuit.
With such a configuration, it becomes possible to grasp the relevance of diseases in a plurality of measurement objects.

It is preferable that a capacitor that blocks signals of a predetermined frequency or lower is connected in series with the sensing element.
With such a configuration, it is possible to block an input other than a change in the capacitance of the sensing element with respect to the oscillation circuit, for example, an input of an electric signal from the heart, and it is possible to suppress disturbance of the output of the oscillation circuit.

The measuring method of the present invention
A measurement method using an oscillation circuit having a resonance circuit including a capacitor and a sensor unit having a sensing element including a conductor connected in parallel to the capacitor.
The step of arranging the sensing element in the vicinity of the living body,
A step of detecting a frequency change of the oscillation circuit due to a change of the capacitance of the sensing element, and a process of detecting the frequency change of the oscillation circuit.
The process includes a process of extracting the frequency change of the frequency band corresponding to the movement of the object to be measured in the living body from the change of the output frequency of the oscillation circuit.

According to the present invention, the movement of a measurement object in a living body can be discriminated from other movements and measured by utilizing the change in capacitance.

It is a block diagram which shows an example of the capacitance measurement system which concerns on one Embodiment. It is a figure which shows an example of the schematic model of a heart and a sensing element. It is a graph which shows the relationship between the amount of change of capacitance and the amount of frequency change in an LC resonance circuit. It is a figure which compares and shows the graph which shows the frequency change of the heartbeat detected by the frequency detector, and the waveform of the heart sound by a stethoscope. (A) is a graph showing the frequency change detected by the frequency detector, (b) is a graph showing the frequency change due to the heartbeat extracted from the frequency change of (a), and (c) is the frequency change of (a). It is a graph which shows the frequency change by respiration extracted from. It is explanatory drawing which shows the appearance that a plurality of sensing elements were arranged corresponding to the object of measurement in a living body. It is a graph which shows the frequency change detected in a plurality of places of a living body.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an embodiment of a measurement system.
As shown in FIG. 1, the measurement system 1 includes a sensor unit 2 and a processing device 50. The sensor unit 2 includes an oscillation circuit 20 having an LC resonance circuit 21, a sensing element 10, a frequency converter 30, a frequency detector 40, and a transmitter 70. The processing device 50 includes a receiver 52.

The sensing element 10 has a plate-shaped electrode that is a conductor, and is connected to the LC resonance circuit 21. In the measurement system 1 of the present embodiment, the space around the sensing element 10 is set as the measurement target space. The sensing element 10 is used in a state of being brought close to the human body so that the human body (living body) enters the measurement target space. The sensing element 10 has a capacitance between the ground and the ground on the human body side. The capacitance of the sensing element 10 changes according to the movement of the measurement object X in the human body, for example, the movement of an organ. Then, the change in the capacitance of the sensing element 10 accompanying the movement of the measurement object X in the human body is reflected in the frequency of the signal output by the oscillation circuit 20.

FIG. 1 shows how the distance between the sensing element 10 and the heart changes due to the expansion and contraction of the heart as the measurement object X, and the capacitance (C ₀ , C _0' ) of the sensing element 10 changes accordingly. Shown. C ₀ is a capacitance when the heart is extended, C 0 _'is the capacitance of when the heart contracts.

The oscillation circuit 20 includes an LC resonance circuit 21 having a capacitor 22 and a coil 23, and an LC oscillator 24 connected to the LC resonance circuit 21. The sensing element 10 described above is connected in parallel with the capacitor 22. Therefore, the LC oscillator 24 oscillates at a resonance frequency corresponding to the capacitance of the sensing element 10. Therefore, when the capacitance of the sensing element 10 changes, the resonance frequency output from the LC oscillator 24 also changes according to the change.

Specifically, the capacitance of the sensing element 10 when the heart is expanded is C ₀ , the capacitance of the sensing element 10 when the heart is contracted is C _0', and the capacitance of the capacitor 22 in the LC resonance circuit 21 is set to C 0'. the C, and inductance of the coil 23 is L, the output frequency of the LC oscillator 24 at the time of cardiac extend (resonance frequency) _{f r,} the output frequency of the LC oscillator 24 at the time of cardiac contraction (the resonant frequency) and f _{r '} Then, the change Δf of the output frequency of the LC oscillator 24 due to the expansion and contraction of the heart is expressed by the following equation.

Therefore, by detecting the amount of change in the output frequency of the LC oscillator 24, the amount of change ΔC in the capacitance of the sensing element 10 and the magnitude of the movement of the heart (amount of expansion and contraction) are measured based on the amount of change. Can be done.

FIG. 2 is a diagram showing an example of a schematic model of a heart and a sensing element. In the present embodiment, the electrodes of the sensing element 10 are a rectangular plate of 45 mm × 30 mm having a size smaller than that of the heart, set at a position separated from the surface of the human body by a predetermined distance (20 mm), and placed on the ground on the opposite side of the heart. It is assumed that there is a virtual electrode connected. _{The thicknesses of the heart walls C 1} , C ₃ , the blood C ₂ , the fat C ₄ , and the skin C ₅ in the heart when the heart is dilated and contracted are set as shown in FIG. Further, the dielectric constant ε of these elements and the dielectric constant ε of the air C ₆ are also set as shown in FIG. Under such a numerical setting, the change ΔC of the capacitance of the sensing element 10 due to the expansion and contraction of the heart is calculated to be about 40 fF.

FIG. 3 is a graph showing the relationship between the amount of change in capacitance and the amount of change in frequency in the LC resonance circuit. When the capacitance C and the inductance L of the capacitor and the coil of the LC resonance circuit are C = 1.8 pF and L = 1.5 nH, respectively, the change ΔC (about 40 fF) of the capacitance of the sensing element 10 obtained by calculation. ) And the change Δf of the resonance frequency in the LC resonance circuit are as shown in FIG. That is, when the capacitance of the sensing element 10 changes by about 40 fF, the change in the resonance frequency of the LC oscillation circuit becomes about 100 kHz.

The resonance frequency of the LC oscillator 24 is down-converted by the frequency converter 30, passed through the amplifier 34, and then detected by the frequency detector 40.
The frequency converter 30 converts the frequency by the superheterodyne method adopted in a general FM receiver. The frequency converter 30 includes a crystal oscillator 33, a local oscillator 32 connected to the crystal oscillator 33, and a mixer 31. The resonance frequency signal output from the LC oscillator 24 is input to the mixer 31 together with the specific frequency signal output from the local oscillator 32 connected to the crystal oscillator 33, and the frequency is converted. As a result, the resonance frequency (output frequency) of the LC oscillator 24 is down-converted.

In the measuring system 1, for example, the output frequency f _r in the steady state of the LC oscillator 24 (that does not consider the capacitance of the sensing element 10) is 98 MHz, the amount of change in the output frequency of the LC oscillator 24 caused by the expansion and contraction of the heart If Delta] f _r is 100Hz, as described above, the output frequency of the LC oscillator 24, the rate of change of the output frequency of the LC oscillator 24 by the 98 MHz ± 100kHz, and the heart expands and contracts is approximately 0.1%. On the other hand, when the output frequency of the LC oscillator 24 is down-converted by the frequency converter 30 in which the output frequency of the local oscillator 32 is 100 MHz, the output frequency of the frequency converter 30 becomes 2 MHz ± 100 kHz, which is the frequency due to the expansion and contraction of the heart. The rate of change of the output frequency of the converter 30 is about 5%. In this case, the rate of change of the output frequency is amplified about 50 times. Therefore, the frequency detector 40 that detects the output frequency of the frequency converter 30 can detect the change in the output frequency with high sensitivity and accuracy.

FIG. 4 is a diagram showing a comparison between a graph showing the frequency change of the heartbeat detected by the frequency detector 40 and the waveform of the heart sound by the stethoscope. However, the frequency change of the heartbeat and the heart sound are detected in a state where the breathing is stopped in order to eliminate the influence of the breathing.
From FIG. 4, it can be seen that the frequency change of the heartbeat detected by the frequency detector 40 obtains a waveform substantially synchronized with the heart sound detected by the stethoscope. Further, it can be seen that the frequency change of the heartbeat detected by the frequency detector 40 has a clear waveform as compared with the waveform of the heart sound by the stethoscope.

The transmitter 70 transmits information about the frequency change detected by the frequency detector 40. The receiver 52 is wirelessly connected to the transmitter 70 and receives the information transmitted from the transmitter 70. The processing device 50 is connected to the receiver 52, and performs predetermined processing on the information received by the receiver 52.

The processing device 50 performs a process of extracting the frequency change due to the movement of the heart from the frequency change detected by the frequency detector 40. Further, the processing device 50 performs a process of extracting not only the movement of the heart but also the movement of other organs and the like, for example, the change in frequency due to the movement of the lungs and the like accompanying respiration.
The processing device 50 is composed of, for example, a personal computer in which software for executing the above processing is installed. Then, the processing device 50 obtains the magnitude of the change for each frequency band by performing an analysis process of the frequency detected by the frequency detector 40, specifically, a fast Fourier transform (FFT) of the change of the frequency, and obtains the magnitude of the change for each frequency band. Extract frequency changes in the frequency band corresponding to other organs.

FIG. 5A is a graph showing the frequency change detected by the frequency detector 40. The processing device 50 performs FFT processing with the frequency change shown in FIG. 5 (a) as an input, and extracts the frequency change shown in FIGS. 5 (b) and 5 (c). 5 (b) is a graph showing the frequency change due to the heartbeat extracted from the frequency change of FIG. 5 (a), and FIG. 5 (c) is the frequency due to respiration extracted from the frequency change of FIG. 5 (a). It is a graph which shows the change. Heartbeat is in the frequency band around 1.0 Hz, and respiration is in the frequency band around 0.2 Hz.

By extracting the change in frequency of a specific object to be measured in the human body in this way, it is possible to measure the change in capacitance of the object to be measured, and by extension, the magnitude (deformation) of the movement of the object to be measured. Amount) can be measured. Therefore, even when various organs are active at the same time such as the human body, it is possible to suitably measure the movement of a specific measurement object.

In order to measure the change in capacitance and the amount of deformation of the object to be measured from the change in the frequency of the object to be measured, for example, the amount of change in frequency detected by the frequency detector 40, the capacitance and the object to be measured are measured. A table associated with the amount of deformation of is stored in advance in the storage unit of the processing device 50, and the amount of change in capacitance and measurement are performed by collating the detected frequency change of the measurement object with the table. The amount of deformation of the object can be obtained.

Since the processing device 50 can extract frequency changes for the movements of a plurality of measurement objects in the human body, it is possible to evaluate the relevance of the movements of the plurality of measurement objects. For example, it is possible to evaluate the relationship between heart disease and respiratory disease by sequentially extracting the changes in frequency due to heartbeat and respiration as described above.

As shown in FIG. 1, the oscillation circuit 20 includes a capacitor 25 as a high-pass filter between the sensing element 10 and the LC resonance circuit 21. The capacitor 25 is arranged in series with the sensing element 10. The capacitor 25 has a function of blocking the frequency of an electric signal (electrocardiogram) emitted from the heart, for example, a frequency of 100 kHz or less. The LC resonance circuit 21 preferably outputs a signal only under the influence of a change in the capacitance of the sensing element 10, and the electric signal input from the sensing element 10 becomes noise with respect to the output of the LC resonance circuit 21. Therefore, by blocking the electric signal from the heart by the capacitor 25, it is possible to suppress the disturbance of the output of the oscillation circuit 20 due to the electric signal.

The measurement system 1 can include a plurality of sensor units 2. Then, the sensing element 10 can be brought close to a plurality of points on the human body, and the movement of the object to be measured such as the heart can be measured at the plurality of points at the same time. In FIG. 6, the sensing elements 10 are arranged at four locations on the front, back, left, and right of the measurement object X in the human body, and the capacitances C _{0a to} C _0d , C _{0'a accompanying the movement of the measurement object X are shown.} An example of detecting a change of ~ C _{0'd as} a change of the output frequency of each sensor unit 2 is shown. Further, FIG. 7 shows a change in the output frequency in each sensor unit 2. From FIG. 7, it can be seen that the change in the output frequency is suitably detected in all the sensor units 2 in response to the movement of the object X to be measured.

The processing device 50 converts the change in the output frequency detected by each sensor unit 2 into the change in the capacitance of the sensing element 10, and further converts the change in the capacitance of the sensing element 10 into the magnitude of the movement of the measurement object X in the direction facing the sensing element 10. It is converted into (the amount of deformation of the object X to be measured), and these are synchronized and output. By using the deformation amount of the measurement object X obtained in this way, for example, in order to deform the three-dimensional image of the measurement object X in real time or ex post facto and grasp the movement of the measurement object three-dimensionally. Can be useful. In the plurality of sensor units 2, the crystal oscillator 33 and the local oscillator 32 may be shared with each other, and at least a plurality of sets of the sensing element 10 and the oscillation circuit 20 may be provided.

In the measurement system 1, the sensor unit 2 and the processing device 50 are wirelessly connected via the transmitter 70 and the receiver 52, but both may be connected by wire. However, it is more preferable that the sensor unit 2 and the processing device 50 are wirelessly connected because the presence of the wire may affect the change in the capacitance of the sensing element 10. Further, by wirelessly connecting the sensor unit 2 and the processing device 50, only the sensor unit 2 can be easily carried, the degree of freedom in selecting the measurement environment is increased, and the measurement environment can be easily changed.

The sensing element 10 is used by arranging it in the vicinity of the human body. For example, the sensing element 10 is used in a state of being separated from the human body and its clothes (non-contact state). Therefore, the measurement system 1 of the present embodiment can measure the movement of the measurement object X, for example, the expansion / contraction of the heart, in a non-invasive manner. Further, since the movement of the measurement object X can be measured from above the clothes, the degree of freedom of the measurement environment can be further increased. For example, a sensing element is attached to the backrest or seat belt of a vehicle such as an automobile, the driver sits on the seat, and the sensing element is placed near the human body by wearing the seat belt. It is also possible to measure the movement of the heart and the like. In this case, the measurement result can be used to prevent the occurrence of an accident caused by, for example, poor physical condition of the driver.

The present invention is not limited to the above embodiment, and the design can be appropriately changed within the scope of the invention described in the claims.
In the measurement system of the above embodiment, an LC resonance circuit is used as the resonance circuit including the capacitor, but the present invention is not limited to this, and for example, an RC resonance circuit can also be used.

The capacitor 25 constituting the high-pass filter is not limited to between the sensing element 10 and the LC oscillator 24, and may be connected in series with the sensing element 10.
The processing device 50 has extracted the frequency change of a specific measurement object by frequency analysis such as FFT processing, but the frequency change of the specific measurement object may be extracted by using a bandpass filter.

The present invention can be applied to living organisms other than the human body.

1: Measurement system 10: Sensing element 20: Oscillation circuit 21: LC resonance circuit 22: Capacitor 25: Capacitor 50: Processing device X: Object to be measured

Claims (8)

It is a measurement system that distinguishes and measures the movement of objects to be measured in the body, including the heart, from the movements of other organs.
An oscillator circuit having a plurality of sets of sensing elements including conductors arranged in the vicinity of the living body and resonance circuits including capacitors connected in parallel to the sensing elements.
When the plurality of sensing elements are arranged at a plurality of locations near the living body, the frequency change of the output frequency of each of the plurality of oscillation circuits is changed to the frequency change of the frequency band corresponding to the movement of the object to be measured in the living body. A measurement system including a processing device that performs a process of extracting a frequency change corresponding to a movement in a direction corresponding to each of the plurality of sensing elements. Each of the plurality of oscillation circuits has an oscillator that oscillates at a resonance frequency corresponding to the capacitance of the sensing element by being connected to the resonance circuit.
A frequency converter that down-converts the output frequency from the oscillator,
Frequency detection that detects a frequency change of the output frequency down-converted in the frequency converter due to a change in the capacitance due to a change in the distance between the sensing element and the measurement object including at least the heart. With a vessel,
The measurement system according to claim 1, wherein the processing device extracts a frequency change corresponding to a movement in a direction corresponding to each of the plurality of sensing elements from the frequency change detected by the frequency detector. The measurement system according to claim 1 or 2, wherein the processing device outputs frequency changes corresponding to movements of measurement objects extracted from changes in output frequencies of the plurality of oscillation circuits in synchronization with each other. It is a measurement system that distinguishes and measures the movement of objects to be measured in the body, including the heart, from the movements of other organs.
A sensing element containing a conductor, which is arranged in the vicinity of the living body,
A resonance circuit including a capacitor connected in parallel to the sensing element, and an oscillation circuit having an oscillator connected to the resonance circuit to oscillate at a resonance frequency corresponding to the capacitance of the sensing element.
A frequency converter that down-converts the output frequency from the oscillator,
Frequency detection that detects a frequency change of the output frequency down-converted in the frequency converter due to a change in the capacitance due to a change in the distance between the sensing element and the measurement object including at least the heart. With a vessel
A measurement system including a processing device that performs a process of extracting a frequency change in a frequency band corresponding to the movement of a measurement object including at least the heart from the frequency change detected by the frequency detector. The measurement system according to any one of claims 1 to 4, wherein the processing device extracts frequency changes corresponding to the movements of a plurality of the measurement objects from the frequency changes. The measurement system according to any one of claims 1 to 5, wherein a capacitor that cuts off a signal having a predetermined frequency or less is connected in series with the sensing element. Using a sensor unit having a plurality of sets of sensing elements including conductors and an oscillating circuit having a resonance circuit including a capacitor connected in parallel to the sensing elements, at least the movement of an object to be measured in a living body including the heart can be measured. , A measurement method that distinguishes and measures the movement of other organs.
A step of arranging a plurality of the sensing elements at a plurality of locations near the living body,
The step of detecting the frequency change of the oscillation circuit due to the change of the capacitance of each of the plurality of sensing elements, and
From the change in the output frequency of the oscillation circuit, the frequency change in the frequency band corresponding to the movement of the object to be measured in the living body and the frequency change corresponding to the movement in the direction corresponding to each of the plurality of sensing elements is extracted. A measuring method including a step of performing a process. It has a sensing element including a conductor, a resonance circuit including a capacitor connected in parallel to the sensing element, and an oscillator that oscillates at a resonance frequency corresponding to the capacitance of the sensing element by being connected to the resonance circuit. Using a sensor unit having an oscillation circuit, a frequency converter that down-converts the output frequency from the oscillator, and a frequency detector connected to the frequency converter, an object to be measured in a living body including at least the heart is used. It is a measurement method that distinguishes movement from the movement of other organs and measures it.
The step of arranging the sensing element in the vicinity of the living body,
The process of down-converting the output frequency from the oscillator,
The frequency change of the oscillation circuit due to the change of the capacitance due to the change of the distance between the sensing element and the measurement object including at least the heart of the output frequency down-converted in the frequency converter. Detection process and
A measurement method including a step of extracting a frequency change in a frequency band corresponding to the movement of a measurement object including at least the heart from a change in the output frequency of the oscillation circuit.

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