JP2007029388A - Biological signal detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biological signal detection device capable of detecting a biological signal without using a magnetic core, having a simple circuit and high sensitivity.
When a subject's back slightly moves due to, for example, heartbeat or breathing, it is transmitted to a conductive sheet. When the distance between the conductive sheet 52 and the coil 1 changes slightly, the stray capacitance existing between the conductive sheet 52 and the coil 1 changes slightly, and the oscillation frequency and oscillation amplitude of the detection unit 30 change slightly. When this change in oscillation amplitude is detected by the AM detector 33 and amplified by a factor of 100 by the operational amplifier 35, a biological signal such as heartbeat and respiration of the measurement subject is detected.
[Selection] Figure 1

Description

  The present invention relates to a biological signal detection apparatus that electrically detects biological signals such as respiration and heartbeat.

As a conventional biological signal detection device, there is one using a magnetic sensor as in Patent Document 1, for example. In this biological signal detection apparatus, the space between the magnetic sensor and the soft magnetic member is changed by the fine movement of the measurement subject by being installed under the bed where the measurement subject is resting, and the interval from the magnetic sensor By outputting a fine movement signal corresponding to the change, a biological signal such as a heart rate and a respiration rate of the measurement subject is detected.
JP 2002-45350 A

  However, the conventional biological signal detection apparatus uses a magnetic core, but has low sensitivity and requires many amplification stages. In addition, it has become difficult to make the product itself since the special core is not available recently.

  In addition, although there was one using fluctuations in oscillation frequency, it was necessary to use an fv converter (frequency-voltage converter), and the circuit was complicated and expensive, making it unsuitable for mass production.

  In view of the above problems, an object of the present invention is to provide a biological signal detection device that can detect a biological signal without using a magnetic core, has a simple circuit, and is highly sensitive.

  According to a first aspect of the present invention, in the biological signal detection apparatus including a detection unit that electrically detects a biological signal, the detection unit is configured by an LC oscillator using a detection coil.

  If it does in this way, the stray capacitance which exists between a human body and the coil 1 will change by the motion accompanying a to-be-measured person's biological activity, and the oscillation frequency and oscillation amplitude of LC oscillator which comprise a detection part will change. By monitoring the change, it is possible to easily detect a biological signal such as a heartbeat or a breathing pattern without attaching anything to the human body.

  In the biological signal detection apparatus according to the second aspect of the present invention, the output from the LC oscillator is AM-detected and amplified. The AM detection here is used in the same meaning as a general term as described in, for example, a textbook.

  In this way, the circuit can be simplified by AM detection of the output of the oscillator.

  In the biological signal detection apparatus according to claim 3 of the present invention, the detection coil is covered with a conductive sheet.

  If it does in this way, since the sweat which a to-be-measured person will prevent can adhere to a detection coil, the fall of the sensitivity at the time of long-time use can be prevented. Further, since the conductive sheet also moves due to the fine movement of the living body, the capacitance existing between the conductive sheet and the detection coil changes, and the oscillation frequency and oscillation amplitude change.

  In the biological signal detection apparatus according to claim 4 of the present invention, a crystal resonator is connected in series to the detection coil.

  In this way, by using a quartz resonator having a high Q for the detection unit, noise can be reduced and a biological signal having a clean waveform can be extracted. By connecting the detection coil and the crystal resonator in series, the detection coil can be used both for detecting a biological signal and for changing the frequency of the crystal resonator, and can further use amplitude fluctuation.

  In the biological signal detection apparatus according to claim 5 of the present invention, a plurality of the detection coils are provided and installed at a plurality of locations.

  If it does in this way, since detection of a living body signal will be attained by each of a plurality of detection coils, it will become possible to detect a living body signal without a problem even if a person to be measured changes its position by installing them at a plurality of locations. .

  According to the first aspect of the present invention, the circuit can be simplified by using the LC oscillator for the detection unit.

  According to the second aspect of the present invention, since the signal is extracted by AM detection, the circuit is simplified.

  According to the third aspect of the present invention, the detection coil can be prevented from being contaminated and the detection sensitivity can be maintained.

  According to the fourth aspect of the present invention, it is possible to extract a biological signal having a clean waveform with reduced noise.

  According to the fifth aspect of the present invention, by installing a plurality of detection coils at a plurality of locations, it is possible to cope with a situation in which measurement is impossible due to the position of the subject being changed without incurring costs.

  Hereinafter, preferred embodiments of the biological signal detection apparatus of the present invention will be described with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the same location and description of a common part overlaps and it abbreviate | omits as much as possible.

  A circuit of the biological signal detection apparatus in the first embodiment is shown in FIG. In this embodiment, a Colpitts oscillation circuit is formed by the coil 1 as the detection coil, the FET 3 such as a JFET (junction field effect transistor), and the capacitors 2, 5 and 6 as the detection unit 30. The oscillation frequency is several MHz, and the frequency may be an appropriate value. Of course, for example, a MOS type FET or a bipolar transistor can be used as the FET 3. In the case of a bipolar transistor, the source corresponds to the emitter, the drain corresponds to the collector, and the gate corresponds to the base. Good. The same applies to the FET 14 described later. A specific connection of the detection unit 30 will be described. One end of the coil 1 is connected to the gate of the FET 3 via the capacitor 2, and the other end of the coil 1 is grounded (connected to the GND line). In addition to being connected to the capacitor 2, the gate of the FET 3 is grounded through a resistor 4. That is, the resistor 4 is connected in parallel to the series circuit of the coil 1 and the capacitor 2. The source of the FET 3 is grounded via a capacitor 5, and a capacitor 6 is connected between the gate and source of the FET 3. The drain of the FET 3 is connected to the power supply Vcc through the resistor 7 (connected to the Vcc line), and is grounded through the capacitor 8.

  The FET 3 serving as a detection signal output of the detection unit 30 is grounded via a series circuit of the inductance element 9 and the resistor 10 and one end of the capacitor 11 is connected to the source of the FET 3. An amplifying unit 31 composed of a peaking circuit (broadband amplifying circuit) for amplifying the detection signal is formed.

  A buffer unit 32 composed of a buffer circuit using a FET 14 such as a JFET is connected to the subsequent stage of the amplifying unit 31. The other end of the capacitor 11 constituting the amplifying unit 31 is connected to the gate of the FET 14. The gate of the FET 14 is connected to the power supply via the resistor 12 and is grounded via the resistor 13. That is, the gate of the FET 14 is biased by the divided voltage of the power source Vcc by the resistors 12 and 13, and the detection signal is inputted. The drain of the FET 14 is connected to the power source Vcc and grounded via the capacitor 15. The source of the FET 14 is grounded via the resistor 16.

  The source of the FET 14 serving as the output of the buffer unit 32 is connected to the AM detection unit 33 via the capacitor 17 for cutting the DC component. In the AM detector 33, a capacitor 17 is connected to a detection signal terminal Va via a diode 18 (capacitor 17 side is an anode and resistor 21 side is a cathode) and a resistor 21, and both ends of the resistor 21 are a capacitor 20 or a capacitor, respectively. It is formed by being grounded through 22. The AM detector 33 extracts an envelope (envelope) of the detection signal.

  As described above, in the circuit of FIG. 1, the detection signal output from the detection unit 30 is amplified by the amplification unit 31, passed through the buffer unit 32, and then AM detected by the AM detection unit 33 to obtain a low frequency signal. Yes. This is input to the inverting amplifier circuit of the operational amplifier 35 shown in FIG. 4 and amplified about 100 times. In FIG. 4, the non-inverting input terminal of the operational amplifier 35 is grounded, while the inverting input terminal is connected to the detection signal terminal Va via the resistor 36, and the output terminal of the operational amplifier 35 via the resistor 37; It is connected to an output terminal Vout for taking out the finally detected biological signal. A positive voltage Vcc and a negative voltage -Vdd are supplied to the power supply terminal of the operational amplifier 35, and bypass capacitors 38 and 39 are connected to these power supplies.

  Hereinafter, a specific configuration and an operation of the detection unit 30 when a circuit having the above configuration is actually used as a biological signal detection device will be described.

  FIG. 5 shows a cross section when the biological signal detection device is placed on a bed. The coil 1 has a spider web shape called a spider coil. In this embodiment, the diameter of the coil 1 is approximately 3 cm, embedded in a 1.5 cm thick polystyrene plate 51 together with the circuit board 53 on which the circuit shown in FIGS. Then, a thin conductive sheet 52 was covered and a blanket or the like was laid thereon. When detecting a biological signal, it is preferable that a portion having as much movement as possible, such as the heart of the measurement subject, be placed on the coil 1.

  If the measurement subject's back slightly moves due to, for example, heartbeat or breathing, it is transmitted to the conductive sheet 52. When the distance between the conductive sheet 52 and the coil 1 changes slightly, the stray capacitance existing between the conductive sheet 52 and the coil 1 changes slightly, and the oscillation frequency and oscillation amplitude of the detection unit 30 change slightly. When the change in the oscillation amplitude is detected by the AM detection unit 33 and amplified by a factor of 100 by the operational amplifier 35, a biological signal such as heartbeat and respiration of the measurement subject is detected as shown in FIG. Of course, even if there is no conductive sheet 52, stray capacitance is generated between the human body and the coil 1, and a biological signal can be detected. However, the conductive sheet 52 is inserted between the human body of the person to be measured and the coil 1. Thus, the biological signal can be detected stably, and the sweat generated by the person to be measured can be cut off, so that it can be operated stably for a long time without worrying about a decrease in detection sensitivity due to the sweat being attached to the coil 1. it can.

  As described above, in this embodiment, in the biological signal detection apparatus including the detection unit 30 that electrically detects the biological signal, the detection unit 30 is configured by an LC oscillator using the coil 1 as a detection coil. .

  In this way, the stray capacitance existing between the human body and the coil 1 changes due to the movement of the measurement subject due to the biological activity, and consequently the oscillation frequency and oscillation amplitude of the LC oscillator constituting the detection unit 30 change. . By monitoring the change, it is possible to easily detect a biological signal such as a heartbeat or a breathing pattern without attaching anything to the human body. As described above, the circuit can be simplified by using the LC oscillator for the detection unit 30.

  In the biological signal detection apparatus of this embodiment, the AM detection unit 33 AM-detects and amplifies the output from the detection unit 30 formed of an LC oscillator.

  In this way, the circuit can be simplified by AM detection of the output of the oscillator.

  Furthermore, in the biological signal detection device of this embodiment, the coil 1 is covered with the conductive sheet 52.

  If it does in this way, since the sweat which a to-be-measured person emits can prevent adhering to the coil 1, the fall of the sensitivity at the time of long-time use can be prevented. Therefore, it is possible to prevent the coil 1 from being soiled and maintain detection sensitivity. Further, since the conductive sheet 52 also moves due to the fine movement of the living body, the capacitance existing between the conductive sheet 52 and the coil 1 changes, and the oscillation frequency and oscillation amplitude change.

  FIG. 2 shows a circuit of the biological signal detection apparatus in the second embodiment. In the second embodiment, the detection unit 30 uses a series circuit of a crystal resonator 40, a variable capacitor 41 (which may be fixed), and the coil 1 instead of the coil 1 alone. Other configurations are the same as those in the first embodiment. In the case of the first embodiment, since only the coil 1 is used, the Q (resonance sharpness) of the circuit is not high. Therefore, it is unstable, and the oscillation frequency and oscillation amplitude slightly change even without external action. This may appear as noise and clean recording may not be possible. As a countermeasure against this, the detection unit 30 of the present embodiment uses a quartz resonator 40 having a high Q. However, since the crystal unit 40 is highly stable, the frequency does not normally move. Therefore, the coil 1 is inserted in series so that the frequency moves. Further, the coil 1 is also used for detecting a biological signal. The biological signal detection apparatus according to the present embodiment is characterized in that the coil 1 is used for both the biological signal detection and the frequency fluctuation of the crystal unit 40, and further uses the amplitude fluctuation. is there.

  As described above, in the biological signal detection device of this embodiment, the crystal unit 40 is connected in series to the coil 1.

  In this way, by using the quartz resonator 40 having a high Q for the detection unit 30, noise can be reduced and a biological signal having a clean waveform can be extracted. By connecting the coil 1 and the crystal unit 40 in series, the coil 1 can be used both for detecting a biological signal and for changing the frequency of the crystal unit 40, and can further use amplitude variation.

  FIG. 3 shows a circuit of the biological signal detection apparatus in the third embodiment. In the third embodiment, a coil 42 is further connected in series to the coil 1 of the second embodiment. For example, the person to be measured may change the position to the left or right of the bed, for example, by turning over when the person to be measured is sleeping on the bed 50. At this time, if there is only one detection coil (for example, coil 1), the human body may be separated from the detection coil, and the biological signal of the measurement subject may not be detected. Therefore, it is conceivable to install a plurality of detection circuits, but this is expensive. However, it is possible to detect a biological signal by installing a plurality of detection coils only in the detection unit 30 and connecting them in series or in parallel. If only the detection coil is added, the cost increase is small. By providing a plurality of detection coils of the coils 1 and 42 in the detection unit 30, it becomes possible to detect a biological signal without any problem even if the measurement subject changes the position on the bed 50 from side to side.

  As described above, in the biological signal detection device of this embodiment, a plurality of detection coils such as the coils 1 and 42 are provided and installed at a plurality of locations.

  In this way, since the biological signals can be detected by each of the plurality of coils 1 and 42, the biological signals can be detected without any problem even if the measurement subject changes the position by installing them at a plurality of locations. become. Therefore, by installing a plurality of detection coils at a plurality of locations, it is possible to cope with a situation in which measurement is impossible due to the person to be measured changing the position without incurring costs.

  FIG. 7 shows a circuit of the biological signal detection apparatus in the fourth embodiment. In the fourth embodiment, two buffer units 32 and thereafter are provided in parallel, one of the AM detectors 33a uses a capacitor 17a having a value suitable for heartbeat detection, and the other AM detector 33b detects respiration. A capacitor 17b having an appropriate value is used. That is, by providing a plurality of AM detection units 33 in which the value of the capacitor 17 and thus the frequency band to be subjected to AM detection are changed in parallel, a plurality of different biological signals can be detected simultaneously.

  A specific circuit configuration will be described below. The configurations of the detection unit 30 and the amplification unit 31 are the same as those of the circuit of the first embodiment shown in FIG. The output of the amplifying unit 31 is connected to the buffer units 32a and 32b. The buffer unit 32a and the AM detecting unit 33a, and the buffer unit 32b and the AM detecting unit 33b thereafter have the values of the capacitors 17a and 17b described above. Except for the difference, the circuit configuration is substantially the same. Therefore, the buffer unit 32a and the AM detection unit 33a will be mainly described, and description of the buffer unit 32b and the AM detection unit 33b will be omitted as much as possible.

  A buffer unit 32a composed of a buffer circuit using the FET 14 is connected to the subsequent stage of the amplifier unit 31. The other end of the capacitor 11 constituting the amplifying unit 31 is connected to the gate of the FET 14. In the figure, the capacitor 11 is a capacitor in which two capacitors are connected in parallel. The gate of the FET 14 is grounded via a resistor 45. The drain of the FET 14 is connected to the power source Vcc through a resistor 46 and grounded through a capacitor 15. The source of the FET 14 is grounded via the resistor 16.

  The source of the FET 14 serving as the output of the buffer unit 32a is connected to the AM detection unit 33a via a capacitor 17a having a value suitable for heartbeat detection. In the AM detector 33a, the capacitor 17a is connected to the heartbeat detection signal terminal Vh via the diode 18 (the capacitor 17a side is an anode and the resistor 21 side is a cathode) and the resistor 21, and both ends of the resistor 21 are the capacitor 20 or It is formed by being grounded via a parallel circuit of a capacitor 22 and a resistor 47. On the other hand, the source of the FET 14 serving as the output of the buffer unit 32b is connected to the AM detection unit 33b via a capacitor 17b having a value suitable for respiration detection. The output of the AM detection unit 33b is a respiration detection signal terminal Vb.

  Then, the heartbeat signal output from the heartbeat detection signal terminal Vh and the respiratory signal output from the respiration detection signal terminal Vb are each amplified by about 100 times by the operational amplifier 35 shown in FIG. Biological signals indicating the heartbeat and respiration of the person can be detected simultaneously. FIG. 8 is a waveform diagram showing a respiration waveform 50 and a heartbeat waveform 51 as the detection result. In the figure, the signal before passing through the filter is observed. In the figure of (a), the respiration waveform 50 greatly fluctuates according to the measurement subject's respiration, and the amplitude of the heartbeat waveform 51 greatly changes according to the measurement subject's heartbeat. On the other hand, FIG. 6B shows the detection result when the measurement subject holds his / her breath, and it can be seen that a large fluctuation disappears from the respiratory waveform 50 by holding his / her breath.

  The present invention is not limited to the above embodiments, and can be modified without departing from the spirit of the present invention. In each of the above embodiments, the Colpitts oscillation circuit having one coil 1 has been described, but various oscillation circuits such as a Hartley circuit can be used. In the Hartley circuit, two coils are used. In this case, either one of the coils may be used for detection, or each of the two coils may be used for detection. Further, the coil 1 can be installed in various modes, and it goes without saying that the coil 1 can be directly attached to the person to be measured using, for example, a band or the like. In the operational amplifier circuit of FIG. 4, a signal is applied from the inverting input terminal (minus input terminal), but an input signal may be applied from the non-inverting input terminal (plus terminal). Further, the amplification degree can be changed as necessary. It goes without saying that a desired respiratory waveform or heartbeat waveform can be more clearly extracted by passing the detected signal or the detected amplified signal through a low-pass filter or a high-pass filter.

  In an aging society, management of the health status of the elderly has become a problem. It can be used when monitoring the patient's condition from a remote location in home medical care, etc., and it is not necessary to attach anything to the living body, and it can detect biological signals such as respiration and heartbeat by simply lying down on the bed. The point is a feature.

It is a circuit diagram which shows the circuit structure around the detection part of the biosignal detection apparatus in 1st Example of this invention. It is a circuit diagram which shows the circuit structure around the detection part of the biosignal detection apparatus in 2nd Example of this invention. It is a circuit diagram which shows the circuit structure around the detection part of the biosignal detection apparatus in 3rd Example of this invention. It is a circuit diagram which shows the inverting amplifier circuit which comprises the biological signal detection apparatus in the 1st-3rd Example of this invention. It is explanatory drawing which shows the usage condition of the biosignal detection apparatus of this invention. It is a wave form diagram showing the biological signal detected by the biological signal detection apparatus in the 1st-3rd Example of this invention. It is a circuit diagram which shows the circuit structure around the detection part of the biosignal detection apparatus in 4th Example of this invention. It is a wave form diagram showing the biosignal detected by the biosignal detection apparatus in 4th Example of this invention.

Explanation of symbols

1 Coil (Detection coil)
30 detector
40 crystal unit
42 Coil (Detection coil)
52 Conductive sheet

Claims (5)

The biological signal detection apparatus provided with the detection part which detects a biological signal electrically, The said detection part was comprised from LC oscillator using the detection coil, The biological signal detection apparatus characterized by the above-mentioned. The biological signal detection apparatus according to claim 1, wherein the output from the LC oscillator is subjected to AM detection and amplified. The biological signal detection device according to claim 1, wherein the detection coil is covered with a conductive sheet. The biological signal detection device according to claim 1, wherein a crystal resonator is connected in series to the detection coil. The biological signal detection device according to any one of claims 1 to 4, wherein a plurality of the detection coils are provided and installed at a plurality of locations.

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