JP2022096139A - Biological information measurement device - Google Patents

Abstract

To provide a biological information measurement device capable of accurately detecting infrared light even when a distance from a detection element to a measurement object is as long as several meters.SOLUTION: A biological information measurement device 20 comprises: a pyroelectric sensor 30 which detects infrared light emitted by a subject B; a distance measuring sensor 40 which detects a distance L from the pyroelectric sensor 30 to the subject B; and an ambient temperature sensor 50 which detects an ambient temperature Tc of the subject B; and a control unit 60. The control unit 60 corrects a detected value of the pyroelectric sensor 30 on the basis of the distance L detected by the distance measuring sensor 40 and the ambient temperature Tc, and calculates biological information of the subject B.SELECTED DRAWING: Figure 1

Description

The present invention relates to a biological information measuring device.

As a technique for non-contactly detecting infrared rays emitted from an object to be measured and measuring the temperature of the object to be measured, an infrared radiation thermometer using a thermopile as a detection element is known (Patent Document 1). A thermopile consists of a large number of thermocouples connected in series or in parallel, and each thermocouple detects infrared rays emitted by an object to be measured to generate an electromotive force. Based on this electromotive force, the temperature of the object to be measured is measured.

Japanese Unexamined Patent Publication No. 2015-227880

An infrared radiation thermometer using a thermopile can measure temperature (body temperature), which is one of the biological information, in a non-contact manner, but it is practical unless the distance between the detection element (thermopile) and the object to be measured is several cm or less. Sufficient accuracy cannot be obtained. Further, if the temperature of the object to be measured is lower than the temperature of the detection element itself, the accuracy of temperature measurement is lowered. For example, in an environment where the ambient temperature exceeds 40 ° C, there is a problem that accurate temperature measurement is difficult when measuring the human body temperature.

The present invention has been completed based on the above circumstances, and is a biological information measuring device capable of highly accurate infrared detection even when the distance from the detection element to the object to be measured is as large as several meters. The purpose is to provide. Another object of the present invention is to provide a biological information measuring device capable of detecting infrared rays with high accuracy regardless of the temperature of the object to be measured and the ambient temperature.

The technique disclosed herein is a biometric information measuring device that non-contactly measures a subject's biometric information, that is, an electrocardiographic sensor that detects infrared rays emitted by the subject, and an electrocardiographic sensor to the subject. A distance measuring sensor for detecting a distance, a temperature sensor for detecting the ambient temperature of the subject, and a control unit are included, and the control unit is based on the distance detected by the distance measuring sensor and the ambient temperature. , The detection value of the charcoal sensor is corrected, and the biological information of the subject is calculated.

When the subject enters the detection range of the electrocardiographic sensor, the electromotive force of the electromotive force increases when the subject's temperature is higher than the ambient temperature, and conversely, the electromotive force decreases when the subject's temperature is lower than the ambient temperature. Furthermore, the amount of change in electromotive force depends on the temperature difference between the ambient temperature and the subject. Infrared rays are also attenuated depending on the propagating distance. Therefore, as the distance from the pyroelectric sensor to the subject increases, the amount of change in the electromotive force of the pyroelectric sensor also decreases.

In the biometric information measuring device having such a configuration, the electromotive force of the electromotive force sensor can be corrected by using the distance detected by the distance measuring sensor and the ambient temperature to remove the influence of the attenuation caused by the distance. can. This makes it possible to measure the subject's biological information contained in the infrared rays emitted by the subject in a non-contact manner and with high accuracy. Further, by using a pyroelectric sensor, it is possible to detect any change in the increase or decrease of the electromotive force. As a result, infrared rays emitted by the subject can be detected regardless of whether the ambient temperature or the temperature of the subject is high, so that the biological information of the subject can be calculated based on the electromotive force of the pyroelectric sensor.

Further, in the above configuration, the biological information may be the body temperature of the subject. The subject emits infrared rays from the surface according to the body temperature (surface temperature). By detecting the infrared rays with a pyroelectric sensor and making corrections based on the distance and the ambient temperature, the body temperature of the subject can be calculated in a non-contact manner.

Further, in the above configuration, the biological information may be a volume pulse wave of the subject. When the subject's heart beats, the blood flow in the blood vessels changes, and the volume of the blood vessels changes. The volume pulse wave, which is a change in the volume of a blood vessel, appears as a change in infrared rays emitted by the subject. The volumetric pulse wave of the subject can be calculated by detecting the infrared rays emitted by the subject with the pyroelectric sensor and making corrections based on the distance and the ambient temperature. In addition, blood pressure, heartbeat, and respiration can be calculated from the volume pulse wave.

Further, in the above configuration, the biological information measuring device may include a cuff for compressing the blood vessel of the subject and a cuff pressure sensor for detecting a pressure pulse wave from the portion compressed by the cuff. By calibrating the volume pulse wave using the pressure pulse wave detected by the cuff pressure sensor, the blood pressure of the subject can be calculated with higher accuracy.

According to the technique disclosed herein, the electromotive force of the pyroelectric sensor can be corrected based on the distance and the ambient temperature, so that the biometric information can be measured non-contactly and with high accuracy. Further, regardless of whether the temperature of the subject or the ambient temperature is high, the electromotive force can be corrected to measure the biometric information in a non-contact manner and with high accuracy.

Block diagram of the temperature measuring device according to the first embodiment Overall perspective view of the temperature measuring device according to the first embodiment. Flow chart of temperature measurement and correction processing Graph showing the relationship between the distance L and the amount of change in electromotive force ΔVp Block diagram of the biological information measuring device according to the second embodiment Diagram showing blood pressure measurement by cuff Graph showing the relationship between the distance L and the volume pulse wave Pv1 The figure which shows the reference pulse wave area Flowchart of blood pressure calculation process Waveform diagram showing cuff pressure and pressure pulse wave

<Embodiment 1>
1. 1. Outline Description A temperature measuring device 20 (an example of a “biological information measuring device”) according to an embodiment of the present invention will be described with reference to FIGS. 1 to 4. In the first embodiment, the temperature measuring unit 10 using the temperature measuring device 20 having the configuration shown in the block diagram of FIG. 1 will be illustrated and described. The "temperature" here is the body temperature of the subject B as described later, and is an example of biological information. The temperature measuring unit 10 shown in FIG. 2 is a portable radiation thermometer. The temperature measurement unit 10 has a temperature measurement unit 11, a display unit 12, an operation unit 13, a measurement start switch 14, and a grip unit 15, respectively.

As shown in FIG. 2, the temperature measuring unit 10 includes a columnar grip portion 15 extending in the vertical direction and a temperature measuring portion 11 extending in the horizontal direction from the upper end of the grip portion 15, and has an L-shape as a whole. .. The grip portion 15 is a handle that is gripped by an operator who operates the temperature measuring unit 10 when measuring the body temperature Tb of the subject B. A measurement start switch 14 is provided on the grip portion 15. When the operator presses the measurement start switch 14, the detection of infrared rays and the like by each of the sensors 30 and the like, which will be described later, is started.

The display unit 12 includes a liquid crystal display panel and other display devices, and displays the body temperature of the subject B, which is the measurement result, the distance L to the subject B, and the like. The display unit 12 can also display a warning when the measurement result is higher or lower than an arbitrary threshold value input in advance, or when the power supply voltage for driving the temperature measuring unit is lowered.

The operation unit 13 is a switch for turning on / off the main power of the temperature measuring unit 10 and a switch used for other operations such as setting a threshold value.

The temperature measuring unit 11 has a built-in temperature measuring device 20 in such a posture that the measurement range of each sensor, which will be described later, faces the same horizontal direction as the extending direction of the temperature measuring unit 11. As shown in FIG. 1, the temperature measuring device 20 includes a pyroelectric sensor 30, a distance measuring sensor 40, an ambient temperature sensor 50, and a control unit 60.

The distance measuring sensor 40 is arranged toward the subject B along with the pyroelectric sensor 30 and the ambient temperature sensor 50, and is a transmission unit 41 that emits a laser beam and a reception unit that receives the laser beam reflected on the surface of the subject B. It has a part 42. The transmission unit 41 has a light source such as a laser diode inside thereof, and transmits a pulse laser emitted by the light source toward the subject B. The receiving unit 42 is a light receiving element such as a photodiode, receives the reflected wave reflected by the subject B, and measures the time difference from the transmission of the pulse laser to the reception. Then, by multiplying 1/2 of the time difference from the transmission of the pulse laser to the reception by the speed of light in consideration of the air temperature, the atmospheric pressure, and the humidity in the measurement environment, the distance L from the distance measurement sensor 40 to the subject B can be obtained. In this way, the distance measuring sensor 40 detects the distance L and outputs the detection result to the control unit 60.

Here, the measured value required for the correction process executed by the control unit 60 described later is the distance from the pyroelectric sensor 30 to the subject B, not the distance L from the distance measuring sensor 40 to the subject B. However, in the present embodiment, the pyroelectric sensors 30 are arranged side by side in the vicinity of the distance measuring sensor 40, and the distance between the two sensors can be said to be negligibly smaller than that of L. Therefore, the pyroelectric sensor 30 to the subject B There is no problem in treating the distance to L as L. However, it should be noted that if the distance between the two sensors is not negligible compared to the distance L, the positional relationship between the two sensors and the subject B must be considered.

The ambient temperature sensor 50 is a temperature sensor using the thermistor 51. The thermistor 51 is made of a material having a characteristic that the resistance value changes in response to a temperature change. Since the resistance value of the thermistor 51 is uniquely determined from the temperature, the temperature of the thermistor can be obtained by measuring the resistance value of the thermistor 51. The thermistor 51 of the ambient temperature sensor 50 according to the present embodiment is arranged inside the temperature measuring unit 10 so as to be able to measure the temperature (ambient temperature Tc) of the space where the focal temperature sensor 30 exists. The ambient temperature sensor 50 outputs the measurement result, the ambient temperature Tc, to the control unit 60.

The pyroelectric sensor 30 is a passive sensor that generates an electromotive force by detecting infrared rays emitted by subject B, which is a heat source. The pyroelectric sensor 30 has a receiving unit 31 directed to the subject B and a main body unit 32. The receiving unit 31 is a Fresnel lens, which collects infrared rays emitted by an object in the measurement range R and causes them to be incident on a detection element (not shown) arranged in the main body unit 32. As the detection element, for example, ferroelectric ceramics such as PZT (lead zirconate titanate) are used. When the infrared rays reach the detection element, electric charges are induced on the surface of the detection element, and an electromotive force V0 corresponding to the amount of energy of the incident infrared rays is generated. The greater the energy of the incident infrared rays, the greater the electromotive force V0.

Since this electromotive force V0 is a very small value, the electromotive force V0 is amplified by a FET or the like (not shown) built in the main body 32, and the value output by the pyroelectric sensor 30 is the electromotive force Vp. The pyroelectric sensor 30 outputs the electromotive force Vp to the control unit 60.

The control unit 60 is a microcomputer and has a storage unit 61 and a calculation unit 62. The storage unit 61 temporarily stores the values output by the above-mentioned sensors (pyroelectric sensor 30, distance measuring sensor 40, ambient temperature sensor 50) and the operation contents input to the operation unit 13. The calculation unit 62 performs calculation processing based on these values and operation contents, and outputs the result to the display unit 12. The control unit 60 has at least "distance L from the pyroelectric sensor 30 to subject B", "ambient temperature Tc", and "electromotive force Vp of the pyroelectric sensor 30" which are detection values detected by each sensor. Entered. In the temperature measuring unit 10 according to the present embodiment, the control unit 60 performs correction based on these three values (L, Tc, Vp) to obtain the body temperature Tb of the subject B. Hereinafter, the principle of correction performed in the control unit 60 and a specific flow will be described.

2. 2. Principle of correction The pyroelectric sensor 30 is an infrared sensor that detects infrared rays incident on the receiving unit 31 and generates an electromotive force Vp proportional to the intensity of the infrared rays. Therefore, when the ambient temperature Tc of the pyroelectric sensor 30 is set, the electromotive force Vp changes when the subject B having a temperature Tb different from that of Tc enters the measurement range R. Next, the relationship between the ambient temperature Tc, the body temperature Tb, and the electromotive force Vp will be described.

The electromotive force Vp before starting the measurement of the body temperature Tb of the subject B, that is, when the temperature measured by the electromotive force sensor 30 is the same as the ambient temperature Tc, is defined as the reference electromotive force Vp0. The reference electromotive force Vp0 is a value proportional to the ambient temperature Tc. Further, the electromotive force after the subject B enters the measurement range R (that is, the electromotive force when the body temperature Tb of the subject B is measured) is defined as Vp1. The amount of change in electromotive force ΔVp is expressed by the following equation (1).
ΔVp = | Vp1-Vp0 | ... (1)

When the distance L is constant, even if the ambient temperature Tc takes different values within the range of 0 ° C to 50 ° C, the electromotive force sensor 30 that measures the body temperature Tb of the subject B has an electromotive force Vp1 proportional to the body temperature Tb. Occurs. That is, the electromotive force Vp1 when the infrared rays of the subject B are detected is hardly affected by the ambient temperature Tc and becomes a value proportional to the body temperature Tb. For example, when the distance L is constant and the body temperature Tb = 36 ° C., the electromotive force Vp1 of the pyroelectric sensor 30 has substantially the same value regardless of whether the ambient temperature Tc is 0 ° C. or 50 ° C.

From the above, when the ambient temperature Tc is lower than the body temperature Tb (Tc <Tb), the change amount ΔVp of the electromotive force of the electromotive force sensor 30 is proportional to the difference (Tb-Tc) between the body temperature Tb and the ambient temperature Tc. And rise. On the other hand, when the ambient temperature Tc is higher than the body temperature Tb (Tc> Tb), the change amount ΔVp of the electromotive force of the pyroelectric sensor 30 decreases in proportion to Tc—Tb. When the ambient temperature Tc and the body temperature Tb are the same, the electromotive force Vp does not change and ΔVp = 0.

Next, the relationship between the electromotive force Vp and the distance L will be described. In the temperature measuring unit 10 according to the present embodiment, the distance from the pyroelectric sensor 30 to the subject B is measured by the distance measuring sensor 40 and is set as the distance L. Since the infrared rays received by the pyroelectric sensor 30 are attenuated as the distance L from the subject B, which is a heat source, increases, the electromotive force Vp of the pyroelectric sensor 30 varies depending on the value of the distance L. Therefore, in order to obtain the body temperature Tb of the subject B from the change amount ΔVp of the electromotive force Vp, it is necessary to make a correction in consideration of the influence of the attenuation based on the distance L.

Here, the standard electromotive force E excluding the influence of attenuation is specified. The standard electromotive force E is an electromotive force Vp measured when the distance between the electromotive force sensor 30 and the object to be measured is 0, and is a value proportional to the temperature T. The attenuation factor is a function of distance f (L). If the standard electromotive force E when the temperature of the object to be measured is T and the distance L is 0 is multiplied by the attenuation factor f (L) as the effect of attenuation, the electromotive force Vp after attenuation can be obtained. The relationship of is expressed by the equation (2). Equation (2') is a modification of equation (2).
Vp = E × f (L) ... (2)
f (L) = Vp / E ... (2')

Before measuring the body temperature Tb, that is, the standard electromotive force when measuring the ambient temperature Tc is E0, the standard electromotive force when measuring the body temperature Tb is E1, and the amount of change in the standard electromotive force ΔE = E1-E0. And. Equation (3) is obtained from equation (1) and equation (2'). Equation (3') is a modification of equation (3).
f (L) = ΔVp / ΔE ... (3)
ΔE = ΔVp / f (L) ... (3')

FIG. 4 shows a graph obtained by experimentally obtaining a damping factor f (L), where the horizontal axis is the distance L [cm] and the vertical axis is the damping factor f (L) = ΔVp / ΔE. The body temperature Tb is constant, ΔE and ΔVp when the ambient temperature Tc and the distance L are changed are obtained experimentally, and a plurality of (L, ΔVp / ΔE) are plotted to obtain the curve A1.

The curve A2 is a curve obtained by approximating the damping factor f (L) as a function of the distance L based on the curve A1. The approximate expression of the attenuation factor f (L) is expressed by the expression (4) with K as a constant. Equation (4) is an approximation that can approximate f (L) with sufficient accuracy when the distance L changes in the range of 15 cm to 300 cm and when the ambient temperature Tc changes in the range of 0 ° C to 50 ° C. It is an expression.
f ( ^L ) = KL ... (4)

Hereinafter, a correction process for calculating the standard electromotive force E by removing the influence of the distance L from the change amount ΔVp of the electromotive force Vp using the damping factor f (L) will be described. This correction process is performed by the calculation unit 62.

As described above, the standard electromotive force E is the electromotive force Vp when the distance L is 0. In the pyroelectric sensor 30 of the present embodiment, assuming that the temperature of the object to be measured is T [° C.], the relationship between the standard electromotive force E and the temperature T is expressed by the following equation (5). The modified equation (5) is the equation (5'). Since the standard electromotive force E is a value uniquely determined by the temperature T of the object to be measured, the temperature T of the object to be measured, that is, the body temperature Tb of the subject B can be obtained from the standard electromotive force E using the equation (5'). Can be calculated.
E = 0.5 + 0.01 × T ... (5)
T = (E-0.5) x 100 ... (5')

For example, when the standard electromotive force E is 0.76 V, the temperature T of the object to be measured is 26 ° C. according to the equation (5'). Further, when the temperature T of the object to be measured is 40 ° C., the standard electromotive force E is 0.90 [v] according to the equation (5). The reference electromotive force Vp0, which is the electromotive force of the pyroelectric sensor 30 when the ambient temperature Tc, is equal to the standard electromotive force E0 obtained by substituting the ambient temperature Tc into the equation (5) (Vp0 = E0).

The standard electromotive force Eb when the body temperature Tb of the subject B separated by a distance L is expressed by the equation (6) with an initial value of E0 and a change amount of ΔE. Using equations (3') and (4), equation (6) can be transformed into equation (7) when Tc <Tb. Equation (7') is expressed by replacing ΔVp in equation (7) with Vp1-Vp0.
Eb = ΔE + E0 ... (6)
Eb = (ΔVp × ^KL ) + Vp0 ... (7)
Eb = (Vp1-Vp0) × ^KL + Vp0 ... (7')

When Tc> Tb, the standard electromotive force Eb is obtained by using the formula (8) instead of the above formula (7). A coefficient (1.2) is added as a difference from the equation (7), which is a coefficient derived from an empirical value in order to improve the accuracy of the approximation. Equation (8') is expressed by replacing ΔVp in equation (8) with Vp1-Vp0.
Eb = ΔVp × ^KL × 1.2 + Vp0 ... (8)
Eb = (Vp1-Vp0) x ^KL x 1.2 + Vp0 ... (8')

Hereinafter, the description will be given based on the equation (7') used in the case of Tc <Tb. Since the electromotive force Vp1 is the output value of the focusing sensor 30 at the time of subject B measurement and the distance L is the output value of the distance measuring sensor 40, it is a value detected by the sensor of the temperature measuring device 20 respectively. Further, the constant K is an empirical value obtained by an experiment in advance, and is a known value. The reference electromotive force Vp0 is the standard electromotive force E0 when the ambient temperature Tc, and E0 can be calculated from the ambient temperature Tc measured by the ambient temperature sensor 50 and the equation (5).

By substituting the measured values (Vp1, L), the calculated values (Vp0), and the constant K by each sensor into the equation (7'), the standard electromotive force Eb when the body temperature Tb of the subject B is measured can be calculated. Then, the standard electromotive force Eb is substituted into E in the equation (5'), and finally the body temperature Tb is calculated. Even when Tc> Tb, the standard electromotive force Eb and the body temperature Tb can be calculated using the formulas (8') and (5').

3. 3. Flow chart FIG. 3 is a measurement flow when the body temperature Tb of the subject B is measured in a non-contact manner using the temperature measuring unit 10 according to the present embodiment, and is composed of a total of eight steps of steps S10 to S17. This measurement flow is stored in the control unit 60, and S11 and subsequent steps are sequentially executed by turning on the measurement start switch 14 (S10) as a trigger.

The operator grips the grip portion 15 of the temperature measuring unit 10 and turns the temperature measuring portion 11 toward the subject B so that the exposed skin portion (for example, the head) of the subject B falls within the measurement range R. In this state, the measurement start switch 14 is pressed (S10).

Then, a signal to start the measurement flow after S11 arrives from the measurement start switch 14 toward the control unit 60. Then, the control unit 60 causes the distance measuring sensor 40 to start measuring the distance L from the pyroelectric sensor 30 to the subject B.

The distance measuring sensor 40 emits a pulse laser from the light source of the transmitting unit 41 toward the subject B. The receiving unit 42 receives the pulsed laser reflected on the surface of the subject B. The distance measuring sensor 40 calculates the distance L based on the time difference from the transmission of the pulse laser to the reception and the value of the speed of light, and transmits the result to the control unit 60 (S11).

Next, the control unit 60 causes the ambient temperature sensor 50 to measure the ambient temperature Tc. The ambient temperature sensor 50 detects the ambient temperature Tc based on the resistance value of the thermistor 51, and transmits the result to the control unit 60 (S12).

Next, the control unit 60 calculates the standard electromotive force E0 as the standard electromotive force E at the temperature Tc based on the ambient temperature Tc and the equation (5). Since the standard electromotive force E0 is equal to the electromotive force of the pyroelectric sensor 30 (reference electromotive force Vp0) when the temperature of the pyroelectric sensor 30 is the ambient temperature Tc, it can be obtained from the known characteristics of the pyroelectric sensor 30. It can be done (S13).

Next, the control unit 60 causes the pyroelectric sensor 30 to detect the infrared rays emitted by the subject B. An electromotive force Vp1 proportional to the intensity of the detected infrared rays is generated in the pyroelectric sensor 30. The pyroelectric sensor 30 outputs the electromotive force Vp1 to the control unit 60 (S14).

At this point, the values of the distance L, the ambient temperature Tc, the standard electromotive force E0 (reference electromotive force Vp0), and the electromotive force Vp1 of the electromotive force sensor 30 are input to the control unit 60, and the storage unit 61 has input the respective values. I remember these values.

Next, the control unit 60 compares the reference electromotive force Vp0 with the electromotive force Vp1 which is the output of the pyroelectric sensor 30 (S15).

When Vp0 <Vp1 (S15: YES), the control unit 60 substitutes the measured value (distance L, electromotive force Vp1) and the calculated value (reference electromotive force Vp0) into the equation (7') to obtain the standard electromotive force Eb. calculate. Next, the standard electromotive force Eb is substituted into the equation (5') to calculate the body temperature Tb (S16).

When Vp0> Vp1 (S15: NO), the control unit 60 substitutes the measured value (distance L, electromotive force Vp1) and the calculated value (reference electromotive force Vp0) into the equation (8') to obtain the standard electromotive force Eb. calculate. Next, the standard electromotive force Eb is substituted into the equation (5') to calculate the body temperature Tb (S17).

4. Explanation of effects Thermopile is often used as a detection element for thermometers (radiation thermometers) that measure temperature in a non-contact manner, such as for measuring human body temperature. The thermopile connects a large number of thermocouples in series or in parallel, calculates the body temperature of the subject based on the thermoelectromotive force of each thermocouple and the ambient temperature, and outputs the result.

However, although the thermometer using the thermopile is non-contact, practically sufficient accuracy cannot be obtained unless the distance between the detection element and the subject is brought close to about several cm. Further, when the temperature of the detection element is higher than the temperature of the object to be measured, there is a problem that the measurement cannot be performed. This means that body temperature cannot be measured in an environment where the ambient temperature is higher than the body temperature.

In the temperature measuring unit 10 according to the present embodiment, a pyroelectric sensor 30 is used as a detection element for detecting infrared rays. The pyroelectric sensor 30 detects infrared rays emitted by a heat source located several meters away and generates an electromotive force proportional to the intensity of the infrared rays. In the configuration of the present embodiment, even if the distance L from the detection element (pyroelectric sensor 30) to the subject B is 250 cm or more, the pyroelectric sensor 30 can detect the infrared rays emitted by the subject B. Then, by performing correction using the ambient temperature Tc and the distance L based on the electromotive force Vp1 generated in the pyroelectric sensor 30, sufficient accuracy can be obtained in the measurement of the body temperature Tb.

Further, in the configuration of the present embodiment, correction is performed using different calculation formulas (see formula (7') or formula (8')) depending on whether the ambient temperature Tc is lower or higher than the body temperature Tb. Thereby, the body temperature Tb can be calculated with high accuracy in either case. In the configuration of the present embodiment, if the ambient temperature Tc is in the range of 0 ° C. to 50 ° C., the body temperature Tb can be calculated with practically sufficient accuracy.

<Embodiment 2>
The biological information measuring device 120 according to the second embodiment calculates the volume pulse wave Pv based on the fluctuation of the electromotive force Vp1 of the pyroelectric sensor 30 that has detected the infrared rays emitted by the subject B. Further, the blood pressure of the subject B is calculated from the volume pulse wave Pv.

When the heart of subject B contracts, blood is pumped into the arteries and the pressure in the blood vessels changes. The change in pressure in the blood vessels becomes a wave and propagates toward the direction away from the heart. This wave is a pulse wave. The volume change of the blood vessel caused by the pulse wave is the volume pulse wave Pv.

The infrared rays emitted by the subject B fluctuate with the volume pulse wave Pv of the subject B. Therefore, the biological information measuring device 120 according to the second embodiment can detect the fluctuation of the volume pulse wave Pv1 of the subject B from the time change of the electromotive force Vp1 of the pyroelectric sensor 30. Further, since the volume pulse wave Pv is closely related to the blood pressure, heartbeat, and respiration of the subject B, these various biological information of the subject B can be detected from the time change of the volume pulse wave Pv1. Hereinafter, a case where the blood pressure of the subject B is calculated using the biological information measuring device 120 will be described as an example.

As shown in FIG. 5, the biological information measuring device 120 according to the second embodiment is different in that it has a cuff 70 in addition to the temperature measuring device 20 of the first embodiment. Further, the biological information measuring device 120 is different from the temperature measuring device 20 in the correction process executed by the calculation unit 162.

The cuff 70 is used to measure a reference blood pressure value (absolute value), and as shown in FIG. 6, it can be attached to the upper arm BA of the subject B and has a rubber bag inside. The rubber bag is connected to a pump 71 for supplying air, and the blood vessels are compressed by supplying and exhausting air to the rubber bag. Further, a cuff pressure sensor 72 for detecting air fluctuations in the rubber bag is incorporated in the cuff 70, and a detection signal output from the cuff pressure sensor 72 that presses the blood vessel (hereinafter, “pressure pulse wave Pw”). ") Is input to the control unit 60 by wired or wireless communication in a state where a predetermined frequency component (noise component) is cut.

The pyroelectric sensor 30 detects the infrared rays emitted by the subject B and generates an electromotive force Vp1. The electromotive force Vp1 input to the control unit 60 is converted into a volume pulse wave Pv1 by the calculation unit 162. As shown in FIG. 8, the actual electromotive force Vp1 when the volumetric pulse wave Pv1 is measured has a value alternately fluctuating on the plus side and the minus side with each heartbeat of the subject B. The reciprocal of the time t0 required for one heart rate is the heart rate of subject B. In the curve B1 of FIG. 7, the volume pulse wave Pv1 obtained from the potential difference between the peak and the valley within one heartbeat time t0 is plotted.

In FIG. 7, the curve obtained by plotting the volume pulse wave Pv1 measured by the experiment with the horizontal axis as the distance L is the curve B1. As the distance L increases, the detected volume pulse wave Pv1 gradually attenuates. The curve of the approximate expression created based on the curve B1 is the curve B2. The approximate expression is as follows, where the influence of the attenuation due to the distance L is excluded, that is, the volumetric pulse wave Pv1 at the distance 0 is the standard volumetric pulse wave Pv0, and the attenuation rate is the function g (L) of the distance L. It is represented by (9).
Pv1 = Pv0 × g (L) ... (9)

Further, the attenuation factor g (L) is expressed by the equation (10) with Kv as a constant.
g (L) = Kv ^−L ... (10)

Assuming that the standard volumetric pulse wave when the influence of the attenuation caused by the distance L is excluded is Pv0, the standard volumetric pulse wave Pv0 when Tc <Tb can be calculated by using the equation (11).
Pv0 = Pv1 × Kv ^L ... (11)

However, when Tc> Tb, the standard volume pulse wave Pv0 is calculated using the equation (12). The coefficient (1.2), which is different from the equation (11), is a coefficient obtained from empirical values in order to improve the accuracy of correction.
Pv0 = Pv1 x Kv ^L x 1.2 ... (12)

Here, the volume pulse wave Pv1 is a value calculated from the electromotive force Vp1 of the focusing sensor 30, and the distance L is an output value of the distance measuring sensor 40, so both are values calculated or detected by the biological information measuring device 120. Further, the constant Kv is a known value obtained in advance by an experiment. Therefore, the calculation unit 162 can calculate the standard volumetric pulse wave Pv0 excluding the influence of attenuation from the measured value Pv1 by executing the correction process of the equation (11) or the equation (12).

Next, the blood pressure calculation process for calculating the blood pressure Pp of the subject B from the standard volume pulse wave Pv0 will be described with reference to the flowchart shown in FIG. The blood pressure calculation process is a process executed by the calculation unit 162 in parallel with the calculation of the standard volume pulse wave Pv0 described above.

In the blood pressure value calculation process, first, calibration is performed when measuring the blood pressure value.

In the calibration, first, the pressure pulse wave Pw is input from the cuff pressure sensor 72 to the calculation unit 162 (S20). The calculation unit 162 calculates the reference systolic blood pressure value Ps, diastolic blood pressure value Pd, and mean blood pressure value Pm based on the pressure pulse wave Pw and the cuff pressure Pc shown in FIG. 10 (S21). The systolic blood pressure value Ps and the diastolic blood pressure value Pd may be directly set by omitting the above steps.

On the other hand, using the volumetric pulse wave Pv1 detected by the focal pulse sensor 30 at the same time as the measurement time of the pressure pulse wave Pw, the standard volumetric pulse wave Pv0 corrected by the calculation unit 162 is assumed to be the reference pulse wave. (S22), as shown in FIG. 8, the integrated value of the change in blood flow volume within one heartbeat time t0 is obtained as the reference pulse wave area Vo (S23).

Then, the mean blood pressure coefficient, the ratio between the systolic blood pressure value and the mean blood pressure value, and the ratio between the diastolic blood pressure value and the mean blood pressure value are calculated as calibration values according to the following equations (13) to (15) (S24). .. Here, the mean blood pressure coefficient is M, the ratio of the systolic blood pressure value to the mean blood pressure value is N, and the ratio of the diastolic blood pressure value to the mean blood pressure value is O. Further, Pm is the mean blood pressure, Ps is the systolic blood pressure, Pd is the diastolic blood pressure, and Vo is the reference pulse wave area.

M = Vo / Pm ... (13)
N = Ps / Pm ... (14)
O = Pd / Pm ... (15)
When the calibration values (M, N, O) are obtained as described above, the main measurement of the blood pressure value is performed.

In this measurement, the pyroelectric sensor 30 receives the infrared rays emitted by the subject B and generates an electromotive force Vp1. Then, the value of the standard volumetric pulse wave Pv0 obtained through the correction process is input to the calculation unit 162 over time (S25).

Then, the calculation unit 162 calculates the pulse wave area Von, which is the integrated value of one heartbeat time of the input standard volume pulse wave Pv0, and uses the following formula based on the pulse wave area of one heartbeat and the mean blood pressure coefficient M. From (16), the mean blood pressure Pmn of one heartbeat (hereinafter referred to as “1 beat mean blood pressure”) is calculated (S26).
Pmn = Von / M ... (16)

Further, when the 1-beat mean blood pressure is calculated, the formula (17) and the formula are based on the ratio of the systolic blood pressure value to the mean blood pressure value, the ratio of the diastolic blood pressure value to the mean blood pressure value, and the 1-beat mean blood pressure. The maximum blood pressure value Psn and the minimum blood pressure value Pdn are calculated from (18) (S18).

Psn = Pmn × N ... (17)
Pdn = Pmn × O ... (18)

Then, the control unit 60 performs a blood pressure check for collating the calculated blood pressure value with the blood pressure reference value (the range of the blood pressure value obtained by normal measurement (for example, 50 to 140 mmHg)) (S28), and the calculated blood pressure value. Is within the blood pressure reference value, it is determined that "measurement is normal" (S28: YES), and the transition of the blood pressure value, which is the calculation processing result, is displayed on the display unit 12 (S29). On the other hand, when it is outside the blood pressure reference value, it is determined that "there is an error in the measurement" (S28: NO), and the process returns to the step of calculating the systolic blood pressure / diastolic blood pressure (S21) to calculate the blood pressure value again.

As described above, according to the present embodiment, in the blood pressure value calculation process, the pressure pulse wave Pw is measured in advance for the subject B by the cuff pressure sensor 72, and the standard volumetric pulse wave calculated by the correction process of the calculation unit 162 is performed. By obtaining the calibration value from Pv0 and using the calibration data for the standard volumetric pulse wave Pv0 calculated over time, the finally calculated blood pressure value can be converted into an absolute value. As a result, blood pressure can be continuously measured by a non-contact means called a pyroelectric sensor 30 without repressurizing with the cuff 70.

<Other embodiments>
The present invention is not limited to the embodiments described in the above description and drawings, and for example, the following embodiments are also included in the technical scope of the present invention, and further, within the scope not deviating from the gist other than the following. It can be changed in various ways.

(1) In each of the above-described embodiments, a thermistor is used as the ambient temperature sensor, but a thermocouple, a thermopile, a resistance temperature detector, or the like may be used in addition to the thermistor.

(2) In each of the above-described embodiments, the distance measuring sensor uses a pulsed laser as an example, but instead of the pulsed laser, a sensor that measures the distance using infrared rays, visible light, sound waves, or ultrasonic waves is used. May be good.

(3) In the above-mentioned second embodiment, the blood pressure of the subject was first measured using a cuff, and the absolute value of the blood pressure was calculated by performing calibration based on the measured value. However, if the absolute value of blood pressure is not always necessary, for example, for childcare for sick children or for watching over in nursing care facilities, and it is sufficient to monitor only relative changes, it is not necessary to perform calibration first. .. Therefore, in such an application, it is not necessary to detect the pressure pulse wave using a cuff at the beginning, and only the non-contact measurement needs to be performed. This can reduce the burden on medical / long-term care workers.

(4) In the second embodiment described above, the electromotive force Vp1 of the pyroelectric sensor 30 is first converted into a volumetric pulse wave Pv1, and then correction is performed to exclude the influence of attenuation due to the distance L to calculate the standard volumetric pulse wave Pv0. .. However, the correction excluding the influence of the attenuation due to the distance L may be performed directly on the electromotive force Vp1 as shown in the first embodiment. In this case, the standard electromotive force E is calculated from the electromotive force Vp1 of the pyroelectric sensor 30, and then the standard electromotive force E is converted into the standard volume pulse wave Pv0.

10 ... temperature measurement unit, 11 ... temperature measurement unit, 12 ... display unit, 13 ... operation unit, 14 ... measurement start switch, 15 ... grip unit, 20 ... temperature measurement device, 30 ... charcoal sensor, 31 ... receiver unit, 32 ... Main body, 40 ... Distance measurement sensor, 41 ... Transmitter, 42 ... Receiver, 50 ... Ambient temperature sensor, 51 ... Thermistor, 60 ... Control unit, B ... Subject, Vp1 ... Electromotive force, R ... Measurement range, Tb ... Subject's body temperature, Tc ... Ambient temperature

Claims (4)

A pyroelectric sensor that detects infrared rays emitted by the subject, which is a biological information measuring device that measures the biological information of the subject in a non-contact manner.
A distance measuring sensor that detects the distance from the pyroelectric sensor to the subject,
An ambient temperature sensor that detects the ambient temperature of the subject, and
Including the control unit
The control unit is a biometric information measuring device that calculates biometric information of a subject by correcting the detection value of the pyroelectric sensor based on the distance detected by the ranging sensor and the ambient temperature. The biometric information measuring device according to claim 1.
The biological information is a biological information measuring device which is the body temperature of the subject. The biometric information measuring device according to claim 1 or 2.
The biological information is a biological information measuring device which is a volume pulse wave of the subject. The biometric information measuring device according to claim 3.
A cuff for compressing the blood vessels of the subject,
A cuff pressure sensor that detects a pressure pulse wave from a portion compressed by the cuff, and the like.
A biological information measuring device that calculates the blood pressure of the subject based on the pressure pulse wave obtained from the cuff pressure sensor and the volumetric pulse wave.

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