Biometric information detection device

Abstract

To provide a biological information detection device enabling improvement of accuracy of biological information detection.SOLUTION: A biological information detection device 1 comprises: a transmission antenna 12 radiating a first radio wave toward an object person; a reflection member 13 reflecting the radio wave radiated from the transmission antenna 12 and having transmitted through the object person; and a receiving antenna 14 receiving the radio wave reflected by the reflection member 13 as a second radio wave. The biological information detection device 1 comprises: an input unit 21 acquiring a reception signal according to the second radio wave received by the receiving antenna 14; and a processing unit 24 calculating biological information on the basis of the reception signal acquired by the input unit 21. The first radio wave and the second radio wave have polarizations in directions different from each other. The receiving antenna 14 has higher reception sensitivity for the polarization of the second radio wave than that for the polarization of the first radio wave.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a biological information detection device that detects biological information of a subject. [Background technology]

[0002] Conventionally, radio wave transmission type biological information detection devices are known (see, for example, Patent Document 1). Patent Document 1 has a configuration in which radio waves radiated from a transmitting antenna toward a subject are received by a receiving antenna. The radio waves received by the receiving antenna fluctuate in accordance with the fluctuation of the subject's heart rate. Therefore, the heart rate of the subject can be calculated by observing the fluctuation of the radio waves received by the receiving antenna. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-153783 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional biometric information detection device, the components received by the receiving antenna include not only the transmitted waves that have passed through the subject's body, but also the direct waves received directly from the transmitting antenna and the body surface reflected waves that are diffracted and received on the surface of the subject's body. The transmitted waves include a heartbeat component that corresponds to the subject's heartbeat fluctuations, but the direct waves and body surface reflected waves do not include a heartbeat component. In other words, unlike the transmitted waves, the direct waves and body surface reflected waves become noise components that reduce the detection accuracy of biometric information. These were discovered after extensive research by the present inventors.

[0005] An object of the present disclosure is to provide a biological information detection device capable of improving the detection accuracy of biological information. [Means for solving the problem]

[0006] The invention described in claim 1 is A biological information detection device for detecting biological information of a subject, a transmitting antenna (12, 12A) that radiates a first radio wave toward the target person; A reflecting member (13, 13A, 13B) that reflects toward the target the radio waves that are radiated from the transmitting antenna and transmitted through the target; a receiving antenna (14, 14A) that receives the radio wave reflected by the reflecting member as a second radio wave; a signal acquiring unit (21) that acquires a reception signal corresponding to a second radio wave received by a receiving antenna when the first radio wave is radiated from a transmitting antenna; A calculation unit (24) that calculates biological information based on the received signal acquired by the signal acquisition unit, The first radio wave and the second radio wave are radio waves having polarizations in different directions from each other, The receiving antenna has a higher reception sensitivity for the polarized waves of the second radio wave than for the polarized waves of the first radio wave. And, The transmitting antenna (12A) emits a circularly polarized or elliptically polarized radio wave in a predetermined rotation direction as a first radio wave toward the target person, The reflecting member (13B) rotates the polarization direction of the first radio wave when reflecting the first radio wave radiated from the transmitting antenna so that the rotation direction of the second radio wave is opposite to the predetermined rotation direction. .

[0007] According to this, since the receiving antenna has a high reception sensitivity to the polarized waves of the second radio waves, the second radio waves that pass through the subject and contain components corresponding to the subject's biological information can be appropriately received by the receiving antenna. In addition, since the receiving antenna has a low reception sensitivity to the polarized waves of the first radio waves, reception of the first radio waves, which become noise components, by the receiving antenna is suppressed.

[0008] Therefore, according to the biological information detection device of the present disclosure, it is possible to improve the detection accuracy of the biological information compared to a case in which the receiving antenna receives the first radio wave and the second radio wave without distinguishing between them.

[0009] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and specific components described in the embodiments described below. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram of a biological information detection device according to a first embodiment. [Diagram 2] FIG. 2 is an explanatory diagram for explaining a seat belt and the like. [Diagram 3] FIG. 2 is an explanatory diagram for explaining a transmitting antenna. [Figure 4] FIG. 4 is an explanatory diagram for explaining a reflective member. [Diagram 5] 10 is an explanatory diagram for explaining a change in radio waves caused by a reflective member; FIG. [Figure 6] FIG. 2 is an explanatory diagram for explaining characteristics of a receiving antenna. [Figure 7] 5 is a flowchart showing a flow of processing executed by an information control unit of the biological information detecting device according to the first embodiment. [Figure 8] FIG. 2 is an explanatory diagram for explaining a flow of processing of a received signal. [Figure 9] FIG. 2 is an explanatory diagram for explaining frequency characteristics of a received signal. [Figure 10] 10 is an explanatory diagram for explaining radio waves received by a receiving antenna in a comparative example. FIG. [Figure 11] FIG. 11 is an explanatory diagram for explaining frequency characteristics of a received signal in a comparative example. [Figure 12] FIG. 11 is an explanatory diagram for explaining a reflecting member according to a second embodiment. [Figure 13] FIG. 1 is a schematic enlarged view of a reflective member; [Figure 14] 10 is an explanatory diagram for explaining a change in radio waves in a reflective member. FIG. [Figure 15] FIG. 11 is a schematic configuration diagram of a biological information detection device according to a third embodiment. [Figure 16] 4 is an explanatory diagram for explaining a first radio wave radiated from a transmitting antenna. FIG. [Figure 17] 10 is an explanatory diagram for explaining a change in radio waves in a reflective member. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, the same reference numerals are used for parts that are the same as or equivalent to those described in the preceding embodiments, and the description thereof may be omitted. In addition, in the embodiments, when only a part of the components is described, the components described in the preceding embodiments can be applied to the other parts of the components. In the following embodiments, each embodiment can be partially combined with each other, even if not specifically stated, as long as it does not cause any trouble in combination.

[0012] (First embodiment) This embodiment will be described with reference to Fig. 1 to Fig. 11. In this embodiment, an example will be described in which the heart rate of one occupant P seated in a seat S of a vehicle is calculated as biometric information using the biometric information detection device 1 of the present disclosure. Note that the arrows with front / rear, left / right, and up / down directions shown in the drawings indicate the front / rear direction DR1, the left / right direction DR2, and the up / down direction DR3 when the occupant P is in the vehicle.

[0013] The vehicle is, for example, an autonomous vehicle equipped with an autonomous driving system. The autonomous driving system operates under the supervision of the driver when the autonomous driving system is below a certain index level (for example, below NHTSA's index level 3), and the driver is responsible for driving. On the other hand, it has been reported in many academic societies that the autonomous driving system reduces the psychological burden on the occupants P, including the driver, and reduces the level of awareness of the occupants P. For this reason, in recent years, development of a system that detects the level of awareness of the occupants P and displays a warning or the like in response to the result has been underway. When measuring biological information such as the heart rate and respiratory rate of the occupants P in order to detect the level of awareness of the occupants P, it is desirable to measure the biological information by a method that does not contact the body of the occupants P and does not restrain them, due to constraints such as "not interfering with driving" and "necessity of constant measurement."

[0014] Taking these factors into consideration, the biological information detection device 1 is configured as a radio wave transmission type device that detects the biological information of the occupant P based on the radio wave signal that has passed through the occupant P. The biological information detection device 1 treats the occupant P seated in the seat S of the vehicle as a subject, and calculates the heart rate of the subject as biological information.

[0015] 1, the seat S has a seat cushion SC that supports the lower body of the occupant P, a seat back SB that supports the upper body of the occupant P from behind, and a headrest HR that supports the head of the occupant P. When the occupant P is wearing the seat belt B, such as when the vehicle is traveling, the back of the occupant P comes into contact with the seat back SB.

[0016] As shown in Fig. 2, the seat belt B is a three-point type that has a shoulder belt BS that diagonally fastens the chest of the occupant P from the shoulder to the waist, and a waist belt BR that crosses the waist of the occupant P. When the occupant P is wearing the seat belt B, the chest of the occupant P is in close contact with the shoulder belt BS, and the waist of the occupant P is in close contact with the waist belt BR.

[0017] 1, the biological information detection device 1 includes a transmitter 11, a transmitting antenna 12, a reflecting member 13, a receiving antenna 14, a receiver 15, and an information control unit 20. The various components of the biological information detection device 1 are basically mounted on a vehicle, but some of them may be installed outside the vehicle.

[0018] The transmitter 11 outputs a transmission signal of a predetermined frequency (for example, a frequency in the 900 MHz band) to the transmission antenna 12. The transmission antenna 12 is disposed inside the seat back SB of the seat S. The transmission antenna 12 radiates a radio wave corresponding to the transmission signal from the transmitter 11 as a first radio wave toward the upper body of an occupant P seated in the seat S.

[0019] The reflecting member 13 is disposed on the opposite side of the occupant P from the transmitting antenna 12. The reflecting member 13 is disposed facing the transmitting antenna 12 with the occupant P seated in the seat S in between. The reflecting member 13 is configured as a reflecting antenna that reflects radio waves emitted from the outside in the direction of incidence of the radio waves. The reflecting member 13 of this embodiment reflects, toward the occupant P, the radio waves that are emitted from the transmitting antenna 12 and transmitted through the occupant P. Specifically, as shown in FIG. 2, the reflecting member 13 is disposed on the shoulder belt BS of the seat belt B. As a result, when the occupant P fastens the seat belt B, the reflecting member 13 comes into close contact with the body of the occupant P via the clothes of the occupant P.

[0020] The receiving antenna 14 receives the radio wave reflected by the reflecting member 13 as a second radio wave. The second radio wave is a reflected wave reflected by the reflecting member 13 toward the occupant P. The receiving antenna 14 is disposed inside the seat back SB of the seat S, similar to the transmitting antenna 12. That is, the receiving antenna 14 and the transmitting antenna 12 are disposed on the opposite side of the reflecting member 13 with respect to the occupant P. The receiving antenna 14 receives radio waves that are radiated from the transmitting antenna 12 and transmitted through the occupant P, and are reflected by the reflecting member 13 and transmitted through the occupant P again. In FIG. 1, the receiving antenna 14 and the transmitting antenna 12 are disposed apart from each other, but the receiving antenna 14 and the transmitting antenna 12 may be disposed close to each other.

[0021] The receiver 15 amplifies and outputs the radio signal received by the receiving antenna 14. Specifically, the receiver 15 amplifies the radio signal received by the receiving antenna 14 and outputs it to the information control unit 20 as a biological signal P1.

[0022] The information control unit 20 calculates the heart rate of the occupant P based on the biological signal P1 acquired from the receiver 15. The information control unit 20 includes an input unit 21, a storage unit 22, an output unit 23, and a processing unit .

[0023] The input unit 21 is a signal acquisition unit that acquires a reception signal corresponding to radio waves received by the receiving antenna 14 when the radio waves are radiated from the transmitting antenna 12. The input unit 21 outputs the biosignal P1, which is an analog signal input from the receiver 15, to the processing unit 24 as a digital signal.

[0024] The storage unit 22 includes a RAM, a ROM, a writable non-volatile storage medium, etc. The RAM, the ROM, and the writable non-volatile storage medium constituting the storage unit 22 are all non-transient substantial storage media.

[0025] The output unit 23 outputs the signal input from the processing unit 24 to a device external to the information control unit 20. The external device to which the signal is output may be, for example, an in-vehicle navigation device that provides route guidance or the like, an in-vehicle data communication module that communicates with the outside of the vehicle, or a mobile communication terminal carried by the occupant P.

[0026] The processing unit 24 is a device that executes processing according to a program recorded in the ROM of the storage unit 22 or a writable non-volatile storage medium. The processing unit 24 in this embodiment uses the RAM of the storage unit 22 as a working area. The processing unit 24 functions as a calculation unit that calculates bioinformation based on the reception signal acquired by the input unit 21.

[0027] Here, the transmitted waves that have passed through the body of the occupant P contain a heartbeat component that corresponds to the fluctuation of the heartbeat of the occupant P, but the radio waves that have not passed through the body of the occupant P do not contain the heartbeat component. In other words, unlike the transmitted waves, the radio waves that have not passed through the body of the occupant P become noise components that reduce the detection accuracy of the biological information. The radio waves that have not passed through the body of the occupant P include the direct wave W1 traveling from the transmitting antenna 12 to the receiving antenna 14 and the body surface reflected wave W2 that is diffracted by the surface of the body of the occupant P and travels to the receiving antenna 14.

[0028] For example, when the intensity of the first radio wave radiated by the transmitting antenna 12 is “E0” and the angle between the polarization plane of the first radio wave and the polarization plane of the second radio wave is “θ”, the receiving intensity E of the first radio wave received by the receiving antenna 14 can be expressed by the following mathematical formula F1.

[0029] E = E0 × cosθ (F1) As shown in formula F1, the reception intensity E of the first radio wave is "E0" when "θ=0" and is "0" when "θ=π / 2". Therefore, if the polarization of the first radio wave radiated by the transmitting antenna 12 can be rotated by "π / 2" using the reflecting member 13, the reception intensity E of the first radio wave at the receiving antenna 14 can be made "0". In other words, if the polarization of the first radio wave radiated by the transmitting antenna 12 can be rotated by "π / 2" using the reflecting member 13, the receiving antenna 14 can receive the radio waves that have passed through the body of the occupant P without receiving the first radio wave that becomes noise.

[0030] Taking the above into consideration, in the biological information detection device 1, the first radio wave radiated by the transmitting antenna 12 and the second radio wave received by the receiving antenna 14 are radio waves having polarized waves in different directions. The receiving antenna 14 has a higher reception sensitivity for the polarized wave of the second radio wave than for the polarized wave of the first radio wave. The transmitting antenna 12, the reflecting member 13, and the receiving antenna 14 of this embodiment will be described below with reference to Figs. 2 to 6.

[0031] As shown in Fig. 3, the transmitting antenna 12 radiates a radio wave having a planar polarization plane as a first radio wave toward the occupant P. Specifically, the transmitting antenna 12 is configured as a dipole antenna in which elements that emit radio waves are arranged vertically along the up-down direction DR3. The transmitting antenna 12 radiates a vertically polarized wave VP that oscillates in a vertical plane toward the occupant P.

[0032] Here, in this specification, "radio waves having a planar polarization plane" refers to radio waves whose polarization plane is substantially within one plane. Examples of "radio waves having a planar polarization plane" include those having linear polarization such as horizontal polarization HP and vertical polarization VP. Note that horizontal polarization HP is a linear polarization in which the vibration direction of the electric field is approximately horizontal to the ground. Vertical polarization VP is a linear polarization in which the vibration direction of the electric field is approximately perpendicular to the ground.

[0033] The reflecting member 13 not only reflects the first radio wave radiated from the transmitting antenna 12 and transmitted through the occupant P, but also rotates the polarization plane of the first radio wave when reflecting the first radio wave. Specifically, the reflecting member 13 rotates the polarization direction of the first radio wave when reflecting the first radio wave radiated from the transmitting antenna 12 so that the polarization plane of the first radio wave and the polarization plane of the second radio wave that is the reflected wave intersect in a manner that is closer to orthogonal than orthogonal or parallel. The reflecting member 13 is disposed in an inclined position with respect to the transmitting antenna 12 so that the first radio wave radiated from the transmitting antenna 12 can be rotated when it is reflected.

[0034] 2 and 4, the reflecting member 13 is configured as a dipole reflecting antenna disposed at a predetermined inclination angle α with respect to the vertical direction DR3, which is the extension direction of the transmitting antenna 12. The reflecting member 13 in this embodiment is fixed to the shoulder belt BS. The reflecting member 13 extends obliquely from the shoulder to the waist together with the shoulder belt BS.

[0035] Here, the inclination angle α is set to an angle greater than "0" so that the polarization direction of the first radio wave can be rotated. The inclination angle α is set to an angle less than "π / 2" so that the first radio wave can be reflected. For example, the inclination angle α is set within an angle range of "π / 6" to "π / 3". It is preferable that the inclination angle α is set within an angle range of "π / 4"±"π / 18" in consideration of the direction of polarization after reflection and the loss associated with reflection. Note that the inclination angle α is a guideline for installing the reflecting member 13, and it is preferable to actually adjust it to an optimal angle taking into account the detection accuracy of biological information.

[0036] The reflecting member 13 configured in this manner rotates the polarization direction of the first radio wave when reflecting the first radio wave so that the polarization plane of the first radio wave and the polarization plane of the reflected wave are orthogonal or closer to orthogonal than parallel. For example, as shown in Fig. 5, the reflecting member 13 rotates the polarization direction of the first radio wave so that the reflected wave is closer to a horizontally polarized wave HP than a vertically polarized wave VP. Note that the closer to orthogonal than parallel aspect can be interpreted as, for example, an aspect in which the angle between the polarization plane of the first radio wave and the polarization plane of the reflected second radio wave is within the range of "π / 4" to "π / 2".

[0037] The receiving antenna 14 receives the radio waves reflected by the reflecting member 13 as second radio waves. The receiving antenna 14 is disposed inside the seat back SB of the seat S, similar to the transmitting antenna 12. The receiving antenna 14 receives, among the radio waves radiated from the transmitting antenna 12 and transmitted through the occupant P, the radio waves reflected by the reflecting member 13 and transmitted through the occupant P again.

[0038] The receiving antenna 14 is configured to be able to receive a second radio wave having a polarization direction different from that of the first radio wave, and the receiving sensitivity of the polarization of the second radio wave is higher than that of the polarization of the first radio wave. That is, the receiving antenna 14 is configured to suppress the reception of a vertically polarized wave VP and promote the reception of a horizontally polarized wave HP, for example. The receiving antenna 14 is configured, for example, as shown in FIG. 6, as a dipole antenna capable of receiving a horizontally polarized wave HP that oscillates in a horizontal plane.

[0039] Next, the operation of the biological information detection device 1 will be described. The transmitter 11 outputs a transmission signal of a predetermined frequency to the transmitting antenna 12. The transmitting antenna 12 radiates radio waves corresponding to the transmission signal from the transmitter 11 toward the occupant P seated in the seat S. Specifically, the transmitting antenna 12 radiates a vertically polarized wave VP as a first radio wave toward the occupant P. A part of the first radio wave transmitted from the transmitting antenna 12 passes through the occupant P seated in the seat S.

[0040] The body of the occupant P functions as a dielectric with respect to the radio waves. Therefore, when the radio waves pass through the body of the occupant P, a dielectric loss occurs in the electric field strength of the radio waves. Among the parts of the body of the occupant P, the heart H changes shape as it expands and contracts. Therefore, in the radio waves that pass through the heart H and reach the reflecting member 13, a dielectric loss occurs in the electric field strength and changes according to the heartbeat of the heart H.

[0041] The first radio wave that has passed through the occupant P is reflected by the reflecting member 13. At this time, the reflecting member 13 rotates the polarization direction of the first radio wave. After the radio wave reflected by the reflecting member 13 passes through the body of the occupant P, the horizontally polarized wave HP component of the radio wave is received by the receiving antenna 14 as the second radio wave. The intensity of the signal received by the receiving antenna 14 in this manner includes a component that changes periodically according to the heartbeat of the heart H. Therefore, the level of the electrical signal output from the receiving antenna 14 to the receiver 15 when the receiving antenna 14 receives the radio wave from the transmitting antenna 12 includes a component that changes according to the heartbeat of the heart H.

[0042] Hereinafter, the flow of the process executed by the processing unit 24 of the information control unit 20 will be described with reference to Fig. 7, Fig. 8, and Fig. 9. The process shown in Fig. 7 is executed by the information control unit 20 periodically or irregularly when an occupant P is seated in a seat S of the vehicle.

[0043] As shown in Fig. 7, in step S100, when radio waves are transmitted from the transmitting antenna 12, the processing unit 24 acquires, via the receiver 15, a time waveform of a received signal received by the receiving antenna 14. The time waveform of a received signal is a time change in the signal strength of the received signal. For example, the time waveform is as shown in the upper part of Fig. 8. This time waveform includes not only components that are correlated with the heartbeat, but also components that are unrelated to the heartbeat.

[0044] Next, in step S110, the processing unit 24 performs a filter process to remove noise components contained in the received signal. For example, the processing unit 24 removes the noise components contained in the received signal using a filter that passes a frequency band of components that have a correlation with the heart rate. As a result, for example, a time waveform shown in the middle part of FIG. 8 is obtained.

[0045] Next, in step S120, the processing unit 24 performs a Fourier transform on the time waveform obtained in step S110 to calculate the frequency characteristics of the received signal. The frequency characteristics are characteristics that indicate the relationship between frequency and intensity. As a result, for example, the frequency characteristics shown in the lower part of Fig. 8 are obtained. In the lower part of Fig. 8, the horizontal axis indicates frequency and the vertical axis indicates signal intensity.

[0046] Next, the processing unit 24 proceeds to step S130 and identifies a peak intensity SP that has a correlation with the heartbeat in the frequency characteristics. For example, as shown in Fig. 9, the processing unit 24 identifies the peak intensity SP that has the largest intensity in the frequency characteristics as the intensity that has a correlation with the heartbeat. Then, the processing unit 24 extracts the identified peak intensity SP and the frequency corresponding to the peak intensity SP as a component that has a correlation with the heartbeat.

[0047] Next, the processing unit 24 proceeds to step S140 and calculates the heart rate from the components having a correlation with the heart rate extracted in step S130. Specifically, the processing unit 24 obtains the heart rate expressed in bmp units by multiplying the value, which is expressed in Hz units, of the frequency corresponding to the peak strength SP in the frequency characteristics of the received signal by 60. bpm is an abbreviation of beats per minute, and is a unit that expresses the number of heart beats per minute. For example, if the frequency Hz corresponding to the peak strength SP is 1 Hz, the heart rate is multiplied by 60 to obtain 60 bpm.

[0048] Next, in step S150, the processing unit 24 outputs the heart rate calculated in step S140 from the output unit 23 to a device external to the biological information detecting device 1. The processing unit 24 may be configured to output the heart rate to a driver status monitor DSM that detects the wakefulness, etc. of the occupant P based on the heart rate of the occupant P, for example.

[0049] Here, when the receiving antenna 14 is configured to be able to receive polarized waves of the first radio wave, as shown in FIG. 10, the components received by the receiving antenna 14 include a direct wave W1 directly received from the transmitting antenna 12 and a body surface reflected wave W2 diffracted and received on the surface of the body of the occupant P. In this case, the frequency characteristics of the received signal change due to the direct wave W1 and the body surface reflected wave W2. For example, as shown in FIG. 11, the frequency characteristics of the received signal include a peak NP due to the direct wave W1 and the body surface reflected wave W2 in addition to the peak intensity SP having a correlation with the heartbeat. In this way, if a peak other than the peak intensity SP having a correlation with the heartbeat appears in the frequency characteristics of the received signal, there is a risk that the other peak will be erroneously detected as an intensity having a correlation with the heartbeat.

[0050] In contrast, in the biological information detection device 1 of this embodiment, the first radio wave radiated by the transmitting antenna 12 and the second radio wave received by the receiving antenna 14 are radio waves having polarized waves in different directions. The receiving antenna 14 has a higher reception sensitivity for the polarized wave of the second radio wave than for the polarized wave of the first radio wave.

[0051] According to this, the receiving sensitivity of the receiving antenna 14 to the polarized waves of the second radio waves is high, so that the second radio waves that pass through the occupant P and contain components corresponding to the biological information of the occupant P can be appropriately received by the receiving antenna 14. In addition, the receiving sensitivity of the receiving antenna 14 to the polarized waves of the first radio waves is low, so reception of the first radio waves, which become noise components, by the receiving antenna 14 (i.e., self-interference) is suppressed.

[0052] Therefore, according to the biological information detection device 1 of this embodiment, it is possible to improve the detection accuracy of the biological information compared to a case in which the receiving antenna 14 receives the first radio wave and the second radio wave without distinguishing between them.

[0053] Moreover, according to this embodiment, the following effects can be obtained.

[0054] (1) The transmitting antenna 12 radiates radio waves having a planar polarization plane as the first radio waves toward the occupant P. The reflecting member 13 rotates the polarization direction of the first radio waves when reflecting the first radio waves radiated from the transmitting antenna 12 so that the polarization plane of the first radio waves and the polarization plane of the second radio waves intersect in a manner that is closer to orthogonal than orthogonal or parallel. In this manner, if the reflecting member 13 is configured to rotate the polarization direction of the first radio waves at "π / 2" or in a manner close to "π / 2", it becomes easier for the receiving antenna 14 to appropriately distinguish between the first radio waves and the second radio waves, thereby improving the detection accuracy of the biological information.

[0055] (2) Here, unlike the present embodiment, if the transmitting antenna 12 and the receiving antenna 14 are positioned opposite each other with the target person in between, there is a risk that the receiving antenna 14 will receive not only the radio waves that have passed through the body of the occupant P, but also the radio waves that have been diffracted by the surface of the body of the occupant P.

[0056] In contrast, in the biological information detection device 1 of this embodiment, the transmitting antenna 12 and the receiving antenna 14 are arranged on the opposite side of the reflecting member 13 with respect to the occupant P. With such an arrangement, the radio waves diffracted by the body surface of the occupant P are difficult to receive by the receiving antenna 14 unless they are reflected by the reflecting member 13. Therefore, it is possible to suppress reception of the radio waves diffracted by the body surface of the occupant P by the receiving antenna 14, thereby improving the detection accuracy of the biological information.

[0057] (Modification of the first embodiment) As in the first embodiment, it would be ideal if the vertically polarized wave VP could be completely rotated to the horizontally polarized wave HP by the reflecting member 13, but in reality, this may be difficult. In this case, if a receiving antenna 14 that simply receives the horizontally polarized wave HP is used, there is a concern that the efficiency may decrease. For this reason, it is desirable to adopt an antenna for the receiving antenna 14 that can receive radio waves having a polarization plane at the most efficient angle, taking into consideration the strength of the radio waves directly input from the transmitting antenna 12 to the receiving antenna 14 and the strength of the radio waves reflected by the reflecting member 13 and input. This also applies to the following embodiments.

[0058] In the first embodiment, dipole antennas are exemplified as the transmitting antenna 12 and the receiving antenna 14, but antennas other than dipole antennas may be adopted as the transmitting antenna 12 and the receiving antenna 14. This also applies to the following embodiments.

[0059] In the first embodiment, the transmitting antenna 12 is exemplified as one that radiates a vertically polarized wave VP oscillating in a vertical plane toward the occupant P, but the transmitting antenna 12 is not limited to this. The transmitting antenna 12 may be configured to radiate a horizontally polarized wave HP oscillating in a horizontal plane toward the occupant P. In this case, the receiving antenna 14 may be configured to suppress reception of the horizontally polarized wave HP and promote reception of the vertically polarized wave VP. This also applies to the following embodiments.

[0060] The reflective member 13 is exemplified as being fixed to the shoulder belt BS of the seat belt B, but is not limited thereto. The reflective member 13 may be fixed, for example, to an instrument panel in front of the occupant P. This also applies to the following embodiments.

[0061] Second embodiment Next, a second embodiment will be described with reference to Fig. 12 to Fig. 14. In this embodiment, differences from the first embodiment will be mainly described. In this embodiment, an example in which the reflecting member 13A is configured by a reflecting antenna having a metamaterial structure will be described.

[0062] As shown in Fig. 12, the reflecting member 13A has a structure in which a plurality of metallic microelements 131 are periodically arranged, and the microelements 131 rotate and reflect the polarization direction of the incident radio waves. The reflecting member 13A is formed into a plate-like shape by periodically arranging the microelements 131 shown in Fig. 13. Each of the microelements 131 has a rectangular lattice frame that is inclined with respect to the up-down direction DR3 and the left-right direction DR2.

[0063] The reflecting member 13A thus configured can change the resonance characteristics and rotate the polarization plane of the input radio wave by adjusting the vertical dimension Lu, horizontal dimension Lv, width dimension Ld, and tilt angle β of the lattice frame of the microscopic element 131. According to experiments by the inventors, it has been found that when the reflecting member 13A of this embodiment is used, the polarization can be rotated with a high efficiency of 90% or more. For example, as shown in FIG. 14, the vertically polarized wave VP transmitted from the transmitting antenna 12 can be rotated to the horizontally polarized wave HP with high efficiency. Note that when the reflecting member 13 of the first embodiment is used, the polarization can be rotated with an efficiency of about 25%.

[0064] The rest is the same as in the first embodiment. The biological information detection device 1 of this embodiment can obtain the same effects as in the first embodiment, which are achieved by a configuration common to the first embodiment or an equivalent configuration.

[0065] Moreover, according to this embodiment, the following effects can be obtained.

[0066] (1) Reflecting member 13A has a structure in which a plurality of metallic microelements 131 are periodically arranged, and reflects incident radio waves by rotating the polarization direction of the radio waves using the plurality of microelements 131. In this way, if reflecting member 13A reflects radio waves by rotating the polarization direction of the radio waves using the plurality of microelements 131, the polarization direction can be rotated with high efficiency.

[0067] Third embodiment Next, a third embodiment will be described with reference to Figures 15 to 17. In this embodiment, differences from the first embodiment will be mainly described.

[0068] The transmitting antenna 12A shown in Fig. 15 radiates a circularly polarized wave or an elliptical polarized wave in a predetermined rotation direction as a first radio wave toward the occupant P. "Circularly polarized wave" and "elliptically polarized wave" are polarized waves in which a plane containing the traveling direction of the radio wave and the vibration direction of its electric field rotates. The transmitting antenna 12A of this embodiment radiates a right-handed circularly polarized wave RP as shown in Fig. 16. Note that the transmitting antenna 12A may be configured to radiate a right-handed elliptical polarized wave.

[0069] The reflecting member 13B rotates the polarization direction of the first radio wave when reflecting the first radio wave emitted from the transmitting antenna 12 so that the rotation direction of the second radio wave input to the receiving antenna 14 is opposite to the predetermined rotation direction of the first radio wave.

[0070] Here, circularly polarized waves and elliptically polarized waves have the characteristic that the rotation direction is reversed when reflected by a metal surface. For this reason, in this embodiment, a metal member having at least a surface portion that faces the transmitting antenna 12 across the occupant P and is made of metal is used as the reflecting member 13B. Such a reflecting member 13B can be realized, for example, by attaching a metal plate to the seat belt B.

[0071] The receiving antenna 14A receives a circularly polarized or elliptical polarized radio wave that is opposite to the predetermined rotation direction of the first radio wave. As shown in Fig. 17, the receiving antenna 14A receives a counterclockwise circularly polarized wave LP. The receiving antenna 14A may also be configured to receive a counterclockwise elliptical polarized wave.

[0072] The rest is the same as in the first embodiment. The biological information detection device 1 of this embodiment can obtain the same effects as in the first embodiment, which are achieved by a configuration common to the first embodiment or an equivalent configuration.

[0073] Moreover, according to this embodiment, the following effects can be obtained.

[0074] (1) The biological information detection device 1 of this embodiment is configured to reverse the rotation direction of the first radio wave radiated from the transmitting antenna 12A by the reflecting member 13B. In this manner, if the configuration is such that the rotation direction of the first radio wave is reversed by the reflecting member 13B, it becomes easier for the receiving antenna 14A to appropriately distinguish between the first radio wave and the second radio wave, thereby improving the detection accuracy of the biological information.

[0075] (Modification of the third embodiment) The biological information detection device 1 may be configured such that the transmitting antenna 12A emits left-handed circularly polarized waves LP or elliptical polarized waves, and the receiving antenna 14A receives right-handed circularly polarized waves RP or elliptical polarized waves. The reflecting member 13B may be configured as an antenna that inverts radio waves instead of reflecting them on the surface of a metal plate.

[0076] (Other embodiments) Representative embodiments of the present disclosure have been described above, but the present disclosure is not limited to the above-described embodiments and can be modified in various ways, for example, as described below.

[0077] Although the example has been given in which the transmitting antenna 12 and the receiving antenna 14 are disposed on the opposite side of the reflecting member 13 with respect to the occupant P, the biological information detection device 1 is not limited to this. In the biological information detection device 1, the receiving antenna 14 may be disposed on the opposite side of the transmitting antenna 12 with respect to the occupant P, similar to the reflecting member 13, as long as the receiving antenna 14 can detect the second radio wave.

[0078] In the above embodiment, the heart rate is calculated as the biological information, but the biological information detection device 1 may be configured to calculate biological information other than the heart rate (for example, respiratory rate, pulse rate).

[0079] In the above embodiment, an example in which the biometric information detection device 1 of the present disclosure is applied to a vehicle equipped with an automatic driving system has been described, but the application target of the biometric information detection device 1 is not limited thereto. The biometric information detection device 1 can also be applied to a vehicle not equipped with an automatic driving system. For example, the biometric information detection device 1 may be arranged such that the transmitting antenna 12, the receiving antenna 14, and the reflecting member 13 are arranged in the left-right direction DR2 with the occupant P in between. The biometric information detection device 1 may be configured to calculate biometric information of not only the driver but also other occupants P. In addition, the biometric information detection device 1 may be used not only for calculating the biometric information of the occupant P of the vehicle, but also for calculating the biometric information of a person outside the vehicle (for example, inside a building).

[0080] In the above-described embodiments, it goes without saying that the elements constituting the embodiments are not necessarily essential, except in cases where it is particularly expressly stated that they are essential or where they are clearly considered to be essential in principle.

[0081] In the above-described embodiments, when numerical values ​​such as the number, values, amounts, ranges, etc. of components of the embodiments are mentioned, they are not limited to the specific numbers unless it is specifically stated as required or unless it is clearly limited to a specific number in principle.

[0082] In the above-described embodiments, when referring to the shapes, positional relationships, etc. of components, etc., there is no limitation to those shapes, positional relationships, etc., unless specifically stated or in principle limited to a specific shape, positional relationship, etc.

[0083] The control unit and the method of the present disclosure may be implemented in a special-purpose computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. The control unit and the method of the present disclosure may be implemented in a special-purpose computer provided by configuring a processor with one or more dedicated hardware logic circuits. The control unit and the method of the present disclosure may be implemented in one or more special-purpose computers configured with a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. The computer program may also be stored in a computer-readable non-transitory tangible recording medium as instructions executed by a computer. [Explanation of symbols]

[0084] 1 Biometric information detection device 12, 12A Transmitting Antenna 13, 13A, 13B Reflective member 14, 14A Receiving antenna 21 Input section (signal acquisition section) 24 Processing section (calculation section)

Claims

1. A biological information detection device for detecting biological information of a subject, A transmitting antenna (12, 12A) that radiates a first radio wave toward the target person; A reflecting member (13, 13A, 13B) that reflects toward the target the radio waves that are radiated from the transmitting antenna and transmitted through the target; a receiving antenna (14, 14A) that receives the radio wave reflected by the reflecting member as a second radio wave; a signal acquisition unit (21) that acquires a reception signal corresponding to the second radio wave received by the receiving antenna when the first radio wave is radiated from the transmitting antenna; A calculation unit (24) that calculates the biological information based on the received signal acquired by the signal acquisition unit, the first radio wave and the second radio wave are radio waves having polarizations in different directions, the receiving antenna has a higher receiving sensitivity for the polarized wave of the second radio wave than for the polarized wave of the first radio wave, The transmitting antenna (12A) emits, as the first radio wave, a circularly polarized wave or an elliptically polarized wave in a predetermined rotation direction toward the target person, A biometric information detection device in which the reflecting member (13B) rotates the polarization direction of the first radio wave when reflecting the first radio wave emitted from the transmitting antenna so that the rotation direction of the second radio wave is opposite to the specified rotation direction.

2. The biological information detection device according to claim 1 , wherein the transmitting antenna and the receiving antenna are disposed on an opposite side of the subject from the reflecting member.

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