ELECTRIC WAVE TYPE BIOSENSOR

Abstract

An electric wave type biosensor includes: an electromagnetic wave irradiation unit; and a reflected wave receiving unit which receives a reflected wave and obtains an I signal obtained by multiplying the irradiated electromagnetic wave signal and the received reflected signal, and a Q signal obtained by delaying the I signal only by a predetermined phase. The electric wave type biosensor further includes: a differentiation calculation unit which differentiates the I signal and the Q signal and calculates an I signal differential value and a Q signal differential value; and an angular velocity calculation unit which calculates an angular velocity of the I signal and the Q signal, based on the I signal and the Q signal and the I signal differential value and the Q signal differential value.

Claims

1. An electric wave type biosensor comprising: an electromagnetic wave irradiation unit which irradiates a body surface of a living body with an electromagnetic wave; a reflected wave receiving unit which receives a reflected wave obtained as the electromagnetic wave irradiated by the electromagnetic wave irradiation unit and then reflected on the body surface, and obtains an I signal obtained by multiplying the irradiated electromagnetic wave signal and the received reflected signal, and a Q signal obtained by delaying the I signal only by a predetermined phase; a differentiation calculation unit which differentiates the I signal and the Q signal which are obtained by the reflected wave receiving unit, and calculates an I signal differential value and a Q signal differential value; and an angular velocity calculation unit which calculates an angular velocity of the I signal and the Q signal, based on the I signal and the Q signal which are obtained by the reflected wave receiving unit and the I signal differential value and the Q signal differential value which are calculated by the differentiation calculation unit based on the I signal and the Q signal.

2. The electric wave type biosensor according to claim 1, further comprising: a bio-information extract unit which extracts bio-information of the living body based on the angular velocity calculated by the angular velocity calculation unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 is a schematic view in which an electric wave type biosensor according to a embodiment of the invention is installed in a vehicle interior of a vehicle;

[0017] FIG. 2 is a block diagram of the electric wave type biosensor of the embodiment of the invention;

[0018] FIG. 3 is a block diagram of a Doppler sensor in the electric wave type biosensor of the embodiment of the invention;

[0019] FIG. 4 is a schematic view illustrating a relationship of the Doppler sensor, a low pass filter and a band pass filter, and a microcomputer, in the electric wave type biosensor of the embodiment of the invention;

[0020] FIG. 5A is a graph illustrating an I signal and a Q signal which are obtained by a signal obtaining unit, FIG. 5B is a graph illustrating an I signal differential value and a Q signal differential value which are obtained by the signal obtaining unit, and FIG. 5C is a graph illustrating an angular velocity which is related to a heart rate calculated by an angular velocity calculation unit, in the electric wave type biosensor of the embodiment of the invention;

[0021] FIG. 6 is a graph illustrating the bio-information extracted by the electric wave type biosensor of the embodiment of the invention;

[0022] FIG. 7 is a flowchart illustrating a control in the electric wave type biosensor of the embodiment of the invention; and

[0023] FIG. 8 is a view for describing the angular velocity or the like on an I-Q coordinate plane.

DETAILED DESCRIPTION

[0024] In embodiments of the invention, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid obscuring the invention.

[0025] Hereinafter, an embodiment of the invention will be described with reference to the drawings. An electric wave type biosensor according to the embodiment of the invention irradiates a human body surface with an electromagnetic wave by using a Doppler sensor, obtains a differential value of an I signal and a Q signal of a reflected wave thereof, and accordingly, obtains the bio-information which is accompanied with fine movement included in the reflected wave.

[0026] An electric wave type biosensor 100 in the embodiment will be described with reference to FIGS. 1 to 4. The electric wave type biosensor 100 is installed in equipment having a surface which is directly or indirectly in contact with a part of the human body, and senses the bio-information of a user of the equipment. Here, the equipment (general term of tool, machinery, and machine) having a surface which is in contact with a part of the human body is specifically referred to as, for example, a chair or a sofa on which a human sits, a bed on which a human lies down, a body inspection equipment installed in a hospital, and a seat which is installed in a vehicle or an airplane and on which a human sits.

[0027] A surface which is in contact with a part of the human body is referred to as a seat surface or a backrest surface in a chair or the like, and a mattress upper surface in a bed. The surface may be directly or indirectly in contact with a part of the human body, or may indirectly come into contact with the human body as a human wears clothes. A part of the body is a buttock or a thigh on a seat surface of a chair or the like, and is generally referred to as the back in the backrest of a chair or the like or in a bed or the like. In the body inspection equipment, a part of the body may be any of arms and legs of a human.

[0028] In the specification, the bio-information of the user is referred to as the size of the heart rate (pulse rate) or a pulse wave, or respiratory frequency or the size of respiration, and does not include cough or sneeze which generates movement of skin or muscle which does not come from the heart rate or respiration. The heart rate or the respiration generates fine movement on the body surface of the living body, and the electric wave type biosensor 100 detects the bio-information that is accompanied with the fine movement.

[0029] In the embodiment, a case where the electric wave type biosensor 100 is installed in an interior of a vehicle as illustrated in FIG. 1 will be described. The electric wave type biosensor 100 is installed in a backrest portion of a seat ST on which the driver or the like sits. Since the purpose of the electric wave type biosensor 100 is to sense the fine movement of the skin surface which is accompanied with the heart rate or respiration, a case where the electric wave type biosensor 100 is installed in the backrest portion which is a surface that is in contact with the back of the driver who does not have a relatively large movement is more preferable than a case where the electric wave type biosensor 100 senses the movement by irradiating a face or the like of the driver who has a large movement in a forward handle WL direction with an electric wave.

[0030] As illustrated in FIG. 2, the electric wave type biosensor 100 includes an electromagnetic wave irradiation unit 10 which irradiates the body surface of the living body with the electromagnetic wave; a reflected wave receiving unit 20 which obtains an I signal obtained by multiplying the signal of the irradiated electromagnetic wave and the received reflected signal, and a Q signal obtained by delaying the I signal by a predetermined phase, after the reflected wave obtained as the electromagnetic wave irradiated by the electromagnetic wave irradiation unit 10 is reflected on the body surface is received and wave detection or amplification is performed; and a control unit 60 which controls the electromagnetic wave irradiation unit 10. In addition, the electromagnetic wave irradiation unit 10 and the reflected wave receiving unit 20 configure a Doppler sensor DS.

[0031] FIG. 3 is a block diagram specifically illustrating the Doppler sensor DS. An oscillator 13 of the Doppler sensor DS oscillates at a predetermined frequency by a control of the control unit 60. In addition, a microwave band of the frequency is generally used, and there are many cases where the frequency is not particularly limited, but 24 GHz is generally used in a case of a use for obtaining the bio-information. The electromagnetic wave oscillated by the oscillator 13 is distributed by a distributor 12, and a measurement target TG is irradiated with one of the electromagnetic waves as an electromagnetic wave having a frequency f.sub.0 (for example, 24 GHz) from a transmission antenna 11.

[0032] The electromagnetic wave of the frequency f.sub.0 is reflected abutting against the measurement target TG having a movement, the frequency changes to frequency f.sub.r, and a receiving antenna 21 receives the reflected wave that becomes the frequency f.sub.r. In addition, the measurement target TG moves at a relative velocity v in a direction having an intersecting angle α with respect to directions of the transmission antenna 11 and the receiving antenna 21. Then, reflected wave frequency f.sub.r is acquired by the equation (1).

f.sub.r=f.sub.0±f.sub.d   (1)

[0033] A transmission wave frequency is f.sub.0, a Doppler frequency is f.sub.d=(2f.sub.0|v|/c.sub.0).Math.cos α, a light velocity is c.sub.0, a relative movement velocity of the measurement target is v, and an intersecting angle in the moving direction of the measurement target with respect to the transmission wave is α.

[0034] The reflected wave of the frequency f.sub.r received by the receiving antenna 21 is computed to be multiplied with the other electromagnetic wave (frequency f.sub.0) distributed by the distributor 12 in a mixer 22, and is output from an I signal output port IP which is a part of the reflected wave receiving unit 20 as the I signal including a base band component that is close to a DC region and a modulation component. In addition, the reflected wave which is a reflected wave of the frequency f.sub.r received by the receiving antenna 21 and of which a phase is shifted by π/2, is similarly computed to be multiplied with the other electromagnetic wave (frequency f.sub.0) distributed by the distributor 12 in the mixer 22, and is output from a Q signal output port QP which is a part of the reflected wave receiving unit 20 as the Q signal including the base band component that is close to the DC region and the modulation component.

[0035] The electric wave type biosensor 100 further includes a low pass filter 80 and a band pass filter 90 into which the I signal output from the I signal output port IP and the Q signal output from the Q signal output port QP by the reflected wave receiving unit 20 are input; and a signal obtaining unit 30 which obtains a signal which will be described later from each of the low pass filter 80 and the band pass filter 90. The low pass filter 80 is an arbitrary filter which removes noise of a high-frequency component and allows only the base band component to pass through in the I signal and the Q signal output by the I signal output port IP and the Q signal output port QP, and outputs signals (I and Q) that are the smoothed I signal and Q signal. In addition, since the purpose of the electric wave type biosensor 100 is to obtain the bio-information, such as heart rate or respiration, the low pass filter 80 is a filter which allows a heart rate of approximately 1 Hz or respiration of approximately 0.3 Hz to pass, and for example, is a filter which removes the heart rate or respiration which is equal to or greater than 10 Hz.

[0036] The band pass filter 90 is an embodiment of a differentiation calculation unit for obtaining differential values (ΔI and ΔQ) of each signal by removing a DC component from the I signal and the Q signal which are output by the I signal output port IP and the Q signal output port QP. In addition, the differential values (ΔI and ΔQ) obtained by the band pass filter 90 are linear approximate values, and the differentiation calculation unit is not limited to the band pass filter 90, and may be a unit which differentiates the I signal and the Q signal and calculates an I signal differential value ΔI and a Q signal differential value ΔQ.

[0037] The signal obtaining unit 30 receives the I signal and the Q signal of which the high-frequency component is removed by the low pass filter 80, and the I signal differential value ΔI which is a differential value of the I signal from the band pass filter 90 and the Q signal differential value ΔQ which is a differential value of the Q signal. In addition, from the viewpoint of a physical configuration, as illustrated in FIG. 4, the I signal output from the I signal output port IP of the Doppler sensor DS is input into the low pass filter 80, and the I signal of which the high-frequency component is removed by the low pass filter 80 is input into an I port of an AD port of a microcomputer MC which is the signal obtaining unit 30. In addition, the I signal output from the I signal output port IP is input into the band pass filter 90, and the I signal of which the DC component is removed by the band pass filter 90 is input into a ΔI port of the AD port of the microcomputer MC which is the signal obtaining unit 30 as the I signal differential value ΔI.

[0038] In addition, the Q signal output from the Q signal output port QP of the Doppler sensor DS is input into the low pass filter 80, and Q signal of which the high-frequency component is removed by the low pass filter 80 is input into a Q port of the AD port of the microcomputer MC which is the signal obtaining unit 30. In addition, the Q signal output from the Q signal output port QP is input into the band pass filter 90, and the Q signal of which the DC component is removed by the band pass filter 90 is input into a ΔQ port of the AD port of the microcomputer MC which is the signal obtaining unit 30 as the Q signal differential value ΔQ. In addition, the microcomputer MC may include the above-described control unit 60, an angular velocity calculation unit 40 which will be described later, a bio-information extract unit 50, and an external output unit 70. In addition, each of the AD ports is connected to an AD converter, and is a port which converts an analog signal into a digital signal.

[0039] The electric wave type biosensor 100 further includes the angular velocity calculation unit 40 which calculates the angular velocity of the I signal and the Q signal, based on the I signal and the Q signal which are obtained by the reflected wave receiving unit 20 and the I signal differential value ΔI and the Q signal differential value ΔQ which are calculated by the differentiation calculation unit 90 based on the I signal and the Q signal. As will be described in the following, the angular velocity calculation unit 40 acquires an angular velocity ω of the I signal and the Q signal based on the I signal, the Q signal, the I signal differential value ΔI, and the Q signal differential value ΔQ.

[0040] A transmission wave x.sub.s(t) of the frequency f.sub.0 in accordance with time t, which is transmitted by the transmission antenna 11 of the Doppler sensor DS, is expressed by the equation (2).

x.sub.s(t)=A.sub.s cos(ω.sub.st)   (2)

[0041] A transmission wave amplitude is A.sub.s, and a transmission wave angular velocity is ω.sub.s=2πf.sub.0.

[0042] In addition, a reflected wave x.sub.r(t) of the frequency f.sub.r in accordance with time t, which is received by the receiving antenna 21 of the Doppler sensor DS, is expressed by the equation (3).

x.sub.r(t)=A.sub.r cos([ω.sub.s±ω.sub.d]t+φ)   (3)

[0043] A receiving wave amplitude is A.sub.r, a Doppler angular velocity is ω.sub.d=2πf.sub.d, and a phase which depends on a distance to the measurement target is φ.

[0044] In addition, a signal which is computed to be multiplied by inputting the transmission wave and the reflected wave into the mixer 22, is expressed by the equation (4).

x.sub.s(t)x.sub.r(t)=A.sub.sA.sub.r cos(ω.sub.st)cos([ω.sub.s+ω.sub.d]t+φ)=(A.sub.sA.sub.r/2){cos(ω.sub.dt+φ)+cos([2ω.sub.s+ω.sub.d]t+φ)}  (4)

[0045] In a case where the high-frequency component is removed by the low pass filter 80, the modulation component of a second member in the equation (4) is removed. Then, I(t) which is the I signal after extracting the Doppler frequency component by the low pass filter 80 is expressed by the equation (5).

I(t)=(A.sub.sA.sub.r/2)cos(ω.sub.dt+φ)   (5)

[0046] In addition, Q(t) which is the Q signal obtained by delaying the phase by π/2 from the I signal is expressed by the equation (6).

Q(t)=(A.sub.sA.sub.r/2)cos(ω.sub.dt+φ−π/2)   (6)

[0047] The I signal represented by the equation (5) and the Q signal represented by the equation (6) are input into the signal obtaining unit 30.

[0048] In addition, since the I signal differential value ΔI is ΔI≈dI/dt, and the Q signal differential value ΔQ is ΔQ≈dQ/dt, when each of the equation (5) and the equation (6) is differentiated by the time t, the I signal differential value ΔI and the Q signal differential value ΔQ can be calculated.

[0049] In addition, the angular velocity ω on the I-Q coordinate plane as illustrated in FIG. 7 is ω=dθ/dt.

[0050] In addition, since θ=arctan(I−I.sub.offset)/(Q−Q.sub.offset) when I.sub.offset can be expressed by a constant defined by an installation condition of the electric wave type biosensor, and Q.sub.offset can be expressed by a constant defined by an installation condition of the electric wave type biosensor, the angular velocity ω can be expressed by Expression 1 as follows:

[00001]$\begin{array}{cc}\omega \approx \frac{\left(t-t_{\mathrm{offset}}\right)\times \Delta .Math..Math.Q-\left(Q-Q_{\mathrm{offset}}\right)\times \Delta .Math..Math.I}{{\left(I-I_{\mathrm{offset}}\right)}^2+{\left(Q-Q_{\mathrm{offset}}\right)}^2}& \left(\mathrm{Expression}.Math..Math.1\right)\end{array}$

[0051] In addition, the size of a circle in FIG. 8 indicates the size of receiving strength in the receiving antenna 21 of the reflected wave, and fluctuates according to a state (distance, inclination of the reflected surface, reflectivity, or the like) of the surface of the living body which is the measurement target TG. In a case where the distance between the Doppler sensor DS and the surface of the living body is d, and a displacement amount Δd of the distance d is expressed by the equation (7).

Δd=λ.Math.Δθ/4π  (7)

[0052] λ is a wavelength (for example, 12.5 mm in a case where the frequency is 24 GHz) of the transmission wave.

[0053] For example, there is a case where the displacement amount Δd increases when an upper half of the body of the driver largely moves, and the phase of θ becomes unclear. In addition, both of the movement of the surface of the living body generated by the heart rate or respiration and the movement of the surface of the living body generated by another large action of the human, are included in the movement of the surface of the living body, but it is difficult to detect the fine movement of the surface of the living body only by using the I signal/Q signal output by the Doppler sensor DS. For example, when the upper half of the body of the driver largely moves, the strength of the reflected wave largely fluctuates to be superior to the fine movement, such as the heart rate, and the fine movement of the surface of the living body cannot be detected.

[0054] Here, in the embodiment of the invention, since the movement of the surface of the living body caused by the large action of the human is substantially zero within an extremely short period of time, it is possible to extract the movement of the surface of the living body caused by the heart rate or respiration by considering the I signal differential value ΔI and the Q signal differential value ΔQ. In addition, it is possible to accurately detect the bio-information which is accompanied with the fine movement on the body surface, such as heart rate or respiratory frequency, by calculating the angular velocity ω on an I signal and Q signal coordinate plane that is a change of a phase based on the above-described (Expression 1) not to be disturbed by the change in a state of the surface of the living body, such as the distance or the inclination of the reflected surface.

[0055] FIG. 5A is a graph illustrating the I signal and the Q signal which are obtained by the signal obtaining unit 30, and illustrates a time-series change of each signal of which the high-frequency component is removed while passing through the low pass filter 80 from the signal obtained from the surface of the living body. In addition, FIG. 5B is a graph illustrating the I signal differential value ΔI and the Q signal differential value ΔQ which are output by the band pass filter 90 (differentiation calculation unit), and illustrates the time-series change of each signal of which only the frequency of the heart rate component is allowed to pass through the band pass filter 90. In addition, the amplitude of the I signal differential value ΔI and the Q signal differential value ΔQ fluctuates according to the position of θ, but the case of the drawing indicates a case where θ is positioned to be near an I axis on the I-Q coordinate plane in which the I signal differential value ΔI relatively largely fluctuates.

[0056] In addition, FIG. 5C illustrates the time-series change of the angular velocity ω related to the heart rate calculated by the angular velocity calculation unit 40 in accordance with the (Expression 1), based on the I signal and the Q signal which are illustrated in FIG. 5A and the I signal differential value ΔI and the Q signal differential value ΔQ which are illustrated in FIG. 5B. As illustrated in FIG. 5C, only the heart rate is clearly illustrated by periodical peaks of the graph. In this manner, it is possible to provide the electric wave type biosensor 100 which accurately detects the fine movement by irradiating the surface of the human body with the electromagnetic wave, and by detecting the bio-information which is accompanied with the fine movement, such as the heart rate frequency or the respiratory frequency, based on the angular velocity on the coordinate plane of the I signal and the Q signal of the reflected wave.

[0057] In addition, as a modification of the embodiment, the electric wave type biosensor 100 can further include the bio-information extract unit 50 which extracts the bio-information of the living body based on the angular velocity ω calculated by the angular velocity calculation unit 40. The bio-information extract unit 50 extracts the bio-information based on the characteristics of the bio-information to be extracted. For example, FIG. 6 is a graph of the bio-information illustrated by the angular velocity ω output by the angular velocity calculation unit 40. In the case of FIG. 6, the frequency component which passed through the band pass filter 90 in the previous stage is also allowed to pass not only the frequency of the heart rate component but also the frequency component of respiration. In the case, the angular velocity ω output by the angular velocity calculation unit 40 is obtained by synthesizing two of the periodical component of respiration and the periodical component of heart rate.

[0058] In this manner, in a case where the angular velocity ω obtained by synthesizing two of the periodical component of respiration and the periodical component of heart rate is input to the bio-information extract unit 50, the bio-information extract unit 50 can extract the heart rate or the respiratory frequency or the strengths from the heights of each of the peaks by comparing the period of general respiration or heart rate. In this manner, by irradiating the human body surface with the electromagnetic wave, by obtaining a plural pieces of bio-information based on the angular velocity on the coordinate plane of the I signal and the Q signal of the reflected wave, and by extracting a specific bio-information based on the frequency component, such as general heart rate or respiratory frequency, it is possible to obtain various pieces of bio-information at the same time.

[0059] In addition, the electric wave type biosensor 100 further includes the external output unit 70 for outputting the bio-information to the external mechanism which uses the bio-information illustrated by the angular velocity ω calculated by the angular velocity calculation unit 40 or the bio-information extracted by the bio-information extract unit 50.

[0060] FIG. 7 is a flowchart illustrating a control in the electric wave type biosensor 100. In addition, S in the flowchart indicates steps. In S100, each of the AD ports which is the signal obtaining unit 30 of the electric wave type biosensor 100 obtains the I signal and the Q signal which passed through the low pass filter 80 and the I signal differential value ΔI and the Q signal differential value ΔQ which passed through the band pass filter 90. In S102, the angular velocity calculation unit 40 calculates the angular velocity ω based on the above-described (Expression 1), from the I signal, the Q signal, the I signal differential value ΔI, and the Q signal differential value ΔQ, which are obtained by the signal obtaining unit 30, and the offset values defined by the installation condition of the electric wave type biosensor 100.

[0061] In S104, the bio-information extract unit 50 extracts the bio-information to be extracted from the angular velocity ω calculated by the angular velocity calculation unit 40 by signal processing. In addition, in S106, the external output unit 70 outputs the extracted bio-information to the external mechanism.

[0062] In addition, the invention is not limited to the exemplified embodiment, and can be realized according to a configuration within a range that does not depart from the contents described in each of the claims. In other words, the invention is illustrated in the drawings mainly particularly regarding the specific embodiment, and is described, but without departing from the technical idea and the range of object, those skilled in the art can add various deformations in the number of components and other specific configurations, with respect to the above-described embodiment.

[0063] While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.