JP6711071B2 - Biological information measuring device and biological information measuring program - Google Patents

Description

The present invention relates to a biological information measuring device and a biological information measuring program.

In Patent Document 1, a substrate, an irradiation unit that is disposed on the substrate, and irradiates a plurality of lights having different wavelengths so as to at least partially overlap with each other on a subject, and the irradiation unit on the substrate. Disclosed is a self-luminous sensor device, comprising: a light-receiving unit that is arranged and that detects light from the subject caused by the plurality of irradiated light, for each wavelength.

In Patent Document 2, a first light emitting element that emits light of a first wavelength, a second light emitting element that emits light of a second wavelength, and the first and second light emitting elements are different from each other. And a drive circuit that emits light at a certain time, and the light from the first light emitting element that is transmitted through the body tissue when the living tissue is arranged at a position where the light of the first and second light emitting elements is irradiated. Alternatively, a first light-receiving element arranged to receive scattered light, and the first light-receiving element for receiving the light from the first and second light-emitting elements that has been transmitted or scattered through the biological tissue. Blood of the biological tissue based on the outputs of the second light receiving element arranged at a position separated from the first light receiving element by a predetermined distance and the light from the first and second light emitting elements. Flow rate of blood of the biological tissue based on a cross-correlation function of the outputs of the first and second light receiving elements by the light from the first light emitting element An oxygen saturation and blood flow measuring device including a blood flow calculating means for calculating

Japanese Patent No. 4475601 JP, 7-265284, A

When measuring multiple biological information such as oxygen saturation in blood and blood flow information, multiple light emitting elements that emit light of different wavelengths are alternately emitted toward the living body, and the light transmitted or reflected by the living body is received. A method of measuring biological information from a change in amount may be used.

In this case, as the light emitting element, for example, when using a light emitting element that irradiates coherent light such as laser light, due to Doppler shift, for example, with the frequency of light reflected by moving biological tissue like blood cells in blood vessels and A situation occurs in which the frequency of light reflected from a stationary living tissue that does not move like skin does not match the frequency of light. Then, the lights reflected by the living body contain high-frequency components due to the interference of lights having different frequencies. The high-frequency component contained in the reflected light is used, for example, to measure the blood flow rate.

However, the high-frequency component contained in the reflected light is not necessarily information necessary for measuring other biological information, and may be one of the factors that deteriorate the measurement accuracy of biological information as a noise component in some cases. is there. Therefore, when measuring biometric information that does not require high frequency components, necessary biometric information has been acquired using a plurality of devices.

It is an object of the present invention to accurately measure a plurality of pieces of biometric information with one device even when a light receiving signal from a light receiving element contains a noise component.

In order to achieve the above object, the biological information measuring apparatus according to claim 1 is a light of a wavelength different from the first emitting element and the first light emitting element which irradiates the coherent light, and not the coherent light A second light emitting element that emits light, receives each light emitted from the first light emitting element and the second light emitting element, and outputs a light reception signal corresponding to the received light amount of each light. A light receiving element and the light receiving signal correspond to a first light receiving signal corresponding to a light receiving amount of light emitted from the first light emitting element and a light receiving amount of light emitted from the second light emitting element. separating means for separating the second light receiving signal, and a filter for removing noise components of the first light receiving signal and the first light receiving signal before the noise component is removed by said filter, said filter Measurement means for measuring a plurality of biological information using the first received light signal from which the noise component has been removed by the above and the second received light signal from which the noise component has not been removed by the filter.

According to a second aspect of the present invention, the measuring means includes a frequency spectrum of the first light receiving signal before the noise component is removed by the filter, and the first light receiving signal from which the noise component is removed by the filter. And the rate of change of the second received light signal in which the noise component has not been removed by the filter, with respect to the change of.

In the invention according to claim 3, the measuring means measures biological information including a blood flow rate or a blood flow velocity and oxygen saturation in blood as the plurality of biological information, and the oxygen saturation in the blood is measured. when measuring degrees, with respect to a change in the first light receiving signal which the noise component is divided by the filter, using the rate of change of the second light receiving signal noise component is not removed by the filter.

In the invention according to claim 4, the measuring means measures biological information including a blood flow rate or a blood flow velocity and oxygen saturation in blood as the plurality of biological information, and the blood flow rate or the blood flow. When measuring the velocity, the frequency spectrum of the first received light signal before the noise component is removed by the filter is used.

In the invention according to claim 5, the filter is a low-pass filter.

According to the first and second aspects of the present invention, even when the light receiving signal from the light receiving element includes a noise component, it is possible to accurately measure a plurality of biological information by one device. ..

According to the invention described in claim 3, it is possible to improve the measurement accuracy of the oxygen saturation level in the blood, as compared with the case where the received light signal including the noise component is used.

According to the invention described in claim 4, it is possible to improve the measurement accuracy of the blood flow rate or the blood flow velocity as compared with the case of using the received light signal including the noise component.

According to the fifth aspect of the present invention, the accuracy of measuring the oxygen saturation level in blood can be improved as compared with the case of using a high-pass filter that removes lower frequency components.

It is a schematic diagram which shows the measurement example of blood flow information and the oxygen saturation in blood. 7 is a graph showing an example of changes in the amount of received light due to reflected light from a living body. FIG. 6 is a schematic diagram for explaining a Doppler shift that occurs when a blood vessel is irradiated with laser light. It is a schematic diagram with which explanation of speckle which occurs when a blood vessel is irradiated with laser light is explained. It is a graph which shows an example of spectrum distribution with respect to change of the amount of received light. It is a graph which shows an example of a change of blood flow. It is a graph which shows an example of the change of the light absorption of the light absorbed by the living body. It is a figure which shows the structural example of a biological information measuring device. It is a figure which shows the example of arrangement|positioning of a light emitting element and a light receiving element. It is a figure which shows the example of arrangement|positioning of a light emitting element and a light receiving element. 7 is a timing chart showing an example of light emission timings of a light emitting element that emits IR light and a light emitting element that emits red light, and light reception timings by a light receiving element. It is a figure which shows an example of the output waveform accompanying the change of the cutoff frequency of LPF.

Embodiments for carrying out the present invention will be described below in detail with reference to the drawings. It should be noted that components having the same functions or functions have the same reference numerals throughout the drawings, and redundant description will be omitted.

First, with reference to FIG. 1, a method of measuring blood flow information and blood oxygen saturation, which is one example of biological information regarding blood among biological information, will be described.

As shown in FIG. 1, the blood flow information and the oxygen saturation level in the blood are measured in the patient's body by receiving light from the light emitting element 1 toward the patient's body (living body 8) and receiving the light by the light receiving element 3. The intensity of light reflected or transmitted by the circulated arteries 4, veins 5, capillaries 6 and the like, that is, the amount of received reflected or transmitted light is measured.

(Measurement of blood flow information)
FIG. 2 is an example of a graph 80 showing the amount of reflected light received by the light receiving element 3. The horizontal axis of the graph 80 in FIG. 2 represents the passage of time, and the vertical axis represents the output of the light receiving element 3, that is, the amount of light received by the light receiving element 3.

As shown in FIG. 2, the amount of light received by the light receiving element 3 changes with the passage of time, but this is because it is affected by the three optical phenomena that appear when the light is applied to the living body 8 including blood vessels. It is believed that there is.

The first optical phenomenon is considered to be a change in absorption of light due to a change in the amount of blood existing in the blood vessel being measured due to pulsation. Blood contains, for example, blood cells such as red blood cells and moves in blood vessels such as capillaries 6. Therefore, the number of blood cells moving in the blood vessels changes due to a change in blood volume, and the light receiving element 3 May affect the amount of received light.

As the second optical phenomenon, the influence of Doppler shift is considered.

As shown in FIG. 3, when coherent light 40 having a frequency ω ₀ , such as laser light, is irradiated from the light emitting element 1 to a region including the capillaries 6 as an example of blood vessels, blood cells that move in the capillaries 6 are generated. The scattered light 42 thus scattered causes a Doppler shift having a difference frequency Δω ₀ determined by the moving velocity of blood cells. On the other hand, the frequency of the scattered light 42 scattered by a tissue (stationary tissue) such as skin that does not include a moving body such as blood cells maintains the same frequency ω ₀ as the frequency of the emitted laser light. Therefore, the frequency ω ₀ + _{Δω 0} of the laser light scattered by the blood vessels 6 such capillary, and the frequency omega ₀ of the laser light scattered by stationary tissue will interfere with each other, the beat signal receiving element 3 having a difference frequency [Delta] [omega ₀ And the amount of light received by the light receiving element 3 changes with the passage of time. The difference frequency Δω ₀ of the beat signal observed by the light receiving element 3 depends on the moving speed of the blood cells, but is included in the range with an upper limit of about several tens kHz.

As the third optical phenomenon, the influence of speckle can be considered.

As shown in FIG. 4, when the blood cell 7 such as red blood cells moving in the blood vessel in the direction of the arrow 44 from the light emitting element 1 is irradiated with the coherent light 40 such as the laser light, the laser light hit the blood cell 7 Is scattered in various directions. Since the scattered lights have different phases, they randomly interfere with each other. This produces a random spotted light intensity distribution. The light intensity distribution pattern formed in this manner is called a "speckle pattern".

As described above, since the blood cells 7 move in the blood vessel, the light scattering state in the blood cells 7 changes, and the speckle pattern changes with the passage of time. Therefore, the amount of light received by the light receiving element 3 changes with the passage of time.

Next, an example of how to obtain blood flow information will be described. When the amount of light received by the light receiving element 3 with the passage of time shown in FIG. 2 is obtained, data included in a range of a predetermined unit time T ₀ is cut out and, for example, fast Fourier transform (Fast Fourier Transform) is performed on the data. :FFT) to obtain the spectral distribution for each frequency ω. FIG. 5 shows an example of the graph 82 showing the spectrum distribution for each frequency ω in the unit time T ₀ . The horizontal axis of the graph 82 in FIG. 5 represents the frequency ω and the vertical axis represents the spectrum intensity.

Here, the blood volume is proportional to a value obtained by normalizing the area of the power spectrum represented by the shaded area 84 surrounded by the horizontal axis and the vertical axis of the graph 82 by the total light amount. Further, since the blood flow velocity is proportional to the frequency average value of the power spectrum represented by the graph 82, the value obtained by integrating the product of the frequency ω and the power spectrum at the frequency ω with respect to the frequency ω is divided by the area of the shaded area 84. Proportional to.

Since the blood flow rate is represented by the product of the blood volume and the blood flow rate, it can be obtained from the above equation for calculating the blood volume and the blood flow rate. The blood flow rate, blood flow velocity, and blood volume are examples of blood flow information, and the blood flow information is not limited to this.

FIG. 6 is an example of a graph 86 showing changes in the calculated blood flow rate per unit time T ₀ . The horizontal axis of the graph 86 in FIG. 6 represents time and the vertical axis represents blood flow.

As shown in FIG. 6, the blood flow varies with time, but the tendency of the variation is classified into two types. For example, the fluctuation range 90 of the blood flow rate in the section T ₂ is larger than the fluctuation range 90 of the blood flow rate in the section T ₁ of FIG. This is because the change in the blood flow rate in the section T ₁ is mainly the change in the blood flow rate associated with the movement of the pulse, whereas the change in the blood flow rate in the section T ₂ is the blood flow rate associated with the cause such as congestion. It is thought that this is because it shows the change of.

(Measurement of oxygen saturation)
Next, the measurement of oxygen saturation in blood will be described. The oxygen saturation in blood is an index showing how much hemoglobin in blood is bound to oxygen, and symptoms such as anemia are more likely to occur as the oxygen saturation in blood decreases.

FIG. 7 is a conceptual diagram showing a change in the amount of light absorbed by the living body 8, for example. As shown in FIG. 7, the amount of light absorbed in the living body 8 tends to change with the passage of time.

Further, looking at the details of the fluctuation of the light absorption in the living body 8, the light absorption changes mainly by the artery 4, and the light absorption does not change in other tissues including the vein 5 and the quiescent tissue as compared with the artery 4. It is known that the amount of fluctuation is recognizable. This is because the arterial blood pumped from the heart moves in the blood vessel with a pulse wave, so that the artery 4 expands and contracts with time along the cross-sectional direction of the artery 4, and the thickness of the artery 4 changes. .. Note that, in FIG. 7, the range indicated by the arrow 94 indicates the variation amount of the light absorption amount corresponding to the variation of the thickness of the artery 4.

In FIG. 7, if the amount of light received at time t _a is I _a and the amount of light received at time t _b is I _b , the amount of change ΔA in the amount of absorbed light due to the change in the thickness of the artery 4 is expressed by equation (1). To be done.

(Equation 1)
ΔA=ln(I _b /I _a )... (1)

On the other hand, hemoglobin (oxygenated hemoglobin) that is bound to oxygen flowing through the artery 4 is particularly apt to absorb light in the infrared (IR) region having a wavelength around 880 nm, and hemoglobin that is not bound to oxygen (reduced hemoglobin). Is known to be particularly easy to absorb light in the red region having a wavelength around 665 nm. Further, it is known that the oxygen saturation has a proportional relationship with the ratio of the change amount ΔA of the absorption amount at different wavelengths.

Therefore, compared to other wavelength combinations. By using infrared light (IR light) and red light where the difference in the absorption amount between oxyhemoglobin and reduced hemoglobin tends to appear, the change amount ΔA _IR of the absorption amount when the living body 8 is irradiated with the IR light and the red light The oxygen saturation S is calculated by the equation (2) by calculating the ratio with the change amount ΔA _Red of the absorption amount when the living body 8 is irradiated. Note that in (2), k is a proportional constant.

(Equation 2)
S=k(ΔA _Red /ΔA _IR )・・・(2)

That is, when calculating the oxygen saturation in blood, a plurality of light emitting elements 1 that emit light of different wavelengths, specifically, a light emitting element 1 that emits IR light and a light emitting element 1 that emits red light. The light emitting periods may partially overlap with each other, but it is preferable to emit light so that the light emitting periods do not overlap. Then, the reflected light or the transmitted light from each light emitting element 1 is received by the light receiving element 3, and the expressions (1) and (2) are obtained from the received light amount at each light receiving time, or these expressions are modified. The oxygen saturation is measured by calculating a known formula.

As a known formula obtained by modifying the above formula (1), for example, the formula (1) may be developed to express the change amount ΔA of the light absorption amount as the formula (3).

(Equation 3)
ΔA=lnI _b −lnI _a (3)

Further, the equation (1) can be transformed into the equation (4).

(Equation 4)
ΔA=ln(I _b /I _a )=ln(1+(I _b −I _a )/I _a )... (4)

Usually, because it is _{(I b -I a) «I a} , ln order to _{(I b / I a) ≒} (I b -I a) / I a is satisfied, instead of equation (1), light Equation (5) may be used as the change amount ΔA of the light absorption amount.

(Equation 5)
ΔA≈(I _b -I _a )/I _a (5)

When it is necessary to distinguish between the light emitting element 1 that emits IR light and the light emitting element 1 that emits red light, the light emitting element 1 that emits IR light is hereinafter referred to as a “light emitting element LD1”. The light emitting element 1 that emits red light is referred to as a “light emitting element LD2”. Further, as an example, the light emitting element LD1 is used as the light emitting element 1 used for calculating the blood flow rate, and the light emitting elements LD1 and LD2 are used as the light emitting element 1 used for calculating the oxygen saturation level in blood.

Further, when measuring the oxygen saturation level in blood, it is known that a measurement frequency of the amount of received light of about 30 Hz to 1000 Hz is sufficient. Therefore, a light emission frequency indicating the number of blinks of the light emitting element LD2 per second. Also, about 30 Hz to 1000 Hz is sufficient. Therefore, from the viewpoint of the power consumption of the light emitting element LD2, it is preferable that the light emitting frequency of the light emitting element LD2 is lower than the light emitting frequency of the light emitting element LD1, but the light emitting frequency of the light emitting element LD2 is adjusted to the light emitting frequency of the light emitting element LD1. Alternatively, the light emitting element LD1 and the light emitting element LD2 may be caused to emit light alternately.

As described above, the blood flow rate is measured by utilizing the change in the amount of light received by the light receiving element 3 due to the influence of the beat signal and the like, while the measurement of the oxygen saturation level in blood is affected by the influence of the beat signal and the like. The resulting change in the amount of light received by the light receiving element 3 acts as a noise component.

Therefore, hereinafter, a biological information measuring device that accurately measures a plurality of biological information even when the light receiving signal from the light receiving element 3 includes a frequency fluctuation component such as a beat signal will be described.

FIG. 8 is a diagram showing a configuration example of the biological information measuring device 10 according to the present embodiment.

As shown in FIG. 8, the biological information measuring device 10 includes a control unit 12, a drive circuit 14, an amplification circuit 16, an A/D (Analog/Digital) conversion circuit 18, a measurement unit 20, a signal separation circuit 22, a low-pass filter ( A low pass filter (LPF) 24, a light emitting element LD1, a light emitting element LD2, and a light receiving element 3.

The control unit 12 outputs a control signal for controlling the light emission cycle and the light emission period of the light emitting elements LD1 and LD2 to the drive circuit 14 including a power supply circuit that supplies drive power to the light emitting elements LD1 and LD2.

When the drive circuit 14 receives the control signal from the control unit 12, the drive circuit 14 supplies drive power to the light emitting element LD1 and the light emitting element LD2 in accordance with the light emitting cycle and the light emitting period instructed by the control signal, and the light emitting element LD1 and the light emitting element LD2. To drive.

Here, FIG. 9 shows an arrangement example of the light emitting element LD1, the light emitting element LD2, and the light receiving element 3 in the biological information measuring device 10. As shown in FIG. 9, the light emitting element LD1, the light emitting element LD2, and the light receiving element 3 are arranged side by side toward one surface of the living body 8. In this case, the light receiving element 3 receives the light of the light emitting elements LD1 and LD2 reflected by the living body 8.

However, the arrangement of the light emitting element LD1, the light emitting element LD2, and the light receiving element 3 is not limited to the arrangement example of FIG. For example, as shown in FIG. 10, the light emitting element LD1 and the light emitting element LD2 and the light receiving element 3 may be arranged at positions facing each other with the living body 8 interposed therebetween. In this case, the light receiving element 3 receives the light of the light emitting elements LD1 and LD2 that have passed through the living body 8.

Note that, here, as an example, the light emitting element LD1 and the light emitting element LD2 are both described as being surface emitting laser elements, but the invention is not limited to this and may be edge emitting laser elements.

When measuring the blood flow rate in the measurement unit 20, it is preferable to use a laser element that is more likely to generate a beat signal than the other light, as the light emitting element LD1 because the spectral distribution of the amount of received light by the beat signal is used.

However, even if the light emitted from the light emitting element LD2 is not a laser beam, the change amount ΔA _Red of the amount of light absorbed by the light emitting element LD2 is calculated, so that the light emitting element LD2 includes a light-emitting diode (LED). ) Or an organic light-emitting diode (OLED) may be used.

The amplifier circuit 16 converts a current corresponding to the intensity of light received by the light receiving element 3 into a voltage, and then amplifies it to a voltage level defined as an input voltage range of the A/D conversion circuit 18. In other words, the amplifier circuit 16 amplifies the light receiving signal output from the light receiving element 3. Here, as an example, the light receiving element 3 will be described as an element that outputs a current corresponding to the intensity of the received light as a light receiving signal, but the light receiving element 3 generates a voltage corresponding to the intensity of the received light. You may output as a light reception signal.

The A/D conversion circuit 18 receives the received light signal amplified by the amplifier circuit 16 as an input, and outputs a received light signal that is a numerical value of the amount of received light of the light receiving element 3 represented by the received light signal.

When the signal separation circuit 22 receives the digitized light-receiving signal of the light-receiving element 3 from the A/D conversion circuit 18, the received light-receiving signal is represented as a data string of the amount of light received by the light-emitting element LD1. The light receiving signal 46 by the light emitting element LD2 and the light receiving signal 48 by the light emitting element LD2 represented as a data string of the amount of light received by the light emitting element LD2 are separated. Whether the received light amount of the received light signal received from the A/D conversion circuit 18 is included in the received light signal 46 or the received light signal 48 depends on, for example, the light emitting period and the light emitting period of the light emitting elements LD1 and LD2. Can be determined.

The signal separation circuit 22 outputs the light receiving signal 46 from the light emitting element LD1 to the measuring unit 20, while outputting the light receiving signal 46 from the light emitting element LD1 and the light receiving signal 48 from the light emitting element LD2 to the LPF 24.

The LPF 24 has a frequency component equal to or higher than a predetermined cutoff frequency fc with respect to a frequency component included in a change in the received light signal 46 by the light emitting element LD1 and a frequency component included in a change in the received light signal 48 by the light emitting element LD2. Is attenuated and then output to the measuring unit 20. Here, the frequency component higher than the cutoff frequency fc will be referred to as “high frequency component”. Although a specific setting value of the cutoff frequency fc will be described later, it is preferable to set the cutoff frequency fc to a frequency of about 10 Hz or less.

The measurement unit 20 includes a blood flow rate measurement unit 20A and an oxygen saturation measurement unit 20B, and the light reception signal 46 from the light emitting element LD1 output from the signal separation circuit 22 is input to the blood flow rate measurement unit 20A. Further, the light receiving signal 46 from the light emitting element LD1 and the light receiving signal 48 from the light emitting element LD2 output from the LPF 24 are input to the oxygen saturation measuring section 20B.

When receiving the light reception signal 46 from the light emitting element LD1, the blood flow measurement unit 20A performs FFT processing on the light reception signal 46 to calculate the spectrum distribution for each frequency ω, and calculates the product of the frequency ω and the spectrum intensity at the frequency ω. Is integrated with respect to the frequency ω to measure the blood flow.

Further, when the oxygen saturation measuring section 20B receives the light reception signal 46 from the light emitting element LD1 and the light reception signal 48 from the light emitting element LD2 from which the high frequency components have been removed by the LPF 24, the variation ΔA _IR of the light absorption amount of the light emitting element LD1. , And the change amount ΔA _Red of the light absorption amount of the light emitting element LD2 is calculated according to the formula (1), and the ratio of the change amount ΔA _Red of the light absorption amount to the change amount ΔA _IR of the light absorption amount is calculated according to the formula (2), Measure oxygen saturation. The oxygen saturation measuring unit 20B may measure the oxygen saturation in blood by calculating a known formula obtained by modifying the formulas (1) and (2).

As already described, since the difference frequency Δω ₀ of the beat signal included in the light reception signal 46 of the light emitting element LD1 is included in the range with the upper limit of about several tens kHz, the LPF 24 removes the noise component due to the beat signal. It The LPF 24 also removes the noise component due to the beat signal included in the received light signal 48 from the received light signal 48 of the light emitting element LD2. Therefore, the oxygen saturation measuring section 20B can measure the oxygen saturation in blood by using the light receiving signal 46 and the light receiving signal 48 from which the noise component due to the beat signal is removed.

When an LED or an OLED is used for the light emitting element LD2, the light emitted by the light emitting element LD2 does not become coherent light, and thus the light reception signal 48 from the light emitting element LD2 hardly contains a beat signal. Therefore, in this case, the signal separation circuit 22 may directly output the received light signal 48 to the oxygen saturation measuring section 20B without outputting it to the LPF 24.

Also in the blood flow volume calculation unit 20A, a frequency component higher than the difference frequency Δω ₀ of the beat signal may act as a noise component when measuring the blood flow volume. Therefore, another LPF having a cutoff frequency fc of about several tens of kHz, which is different from the LPF 24, may be provided between the signal separation circuit 22 and the blood flow measurement unit 20A.

Further, as the frequency component approaches DC, the correlation with the measurement accuracy of the blood flow rate tends to decrease. Therefore, instead of the another LPF, a band for passing a frequency component of several Hz to several tens kHz is passed. A pass filter may be provided between the signal separation circuit 22 and the blood flow measuring unit 20A to remove a direct current component of less than several Hz and a frequency component of more than several tens of kHz from the received light signal 46.

In this case, the measurement accuracy of the blood flow in the biological information measuring device 10 is improved as compared with the case where the separate LPF or bandpass filter is not provided.

As an example, as shown in FIG. 11, FIG. 12 shows an output waveform example of the light reception signal 46 from the light emitting element LD1 in the LPF 24 when the light emitting element LD1 and the light emitting element LD2 emit light alternately in the same cycle. Note that, in FIG. 11, a plurality of points 96 indicate light receiving points 96 by the light receiving element 3.

The output waveform of the received light signal 46 shown in FIG. 12 shows the output waveform when the cutoff frequencies fc of the LPF 24 are set to 5 Hz, 10 Hz, 200 Hz, and FULL, respectively. Here, the cutoff frequency fc being FULL means that the cutoff frequency is infinite, that is, the received light signal 46 input to the LPF 24 is output as it is.

As shown in FIG. 12, as the cutoff frequency fc becomes lower, the noise component is removed from the output waveform of the received light signal 46, and the waveform becomes smoother. In this case, even if the cutoff frequency fc is 200 Hz, it is possible to confirm that the received light signal 46 still contains a noise component. Therefore, the cutoff frequency fc is preferably about 5 Hz or more and about 10 Hz or less. I understand.

As described above, according to the biological information measuring device 10 according to the present embodiment, the oxygen saturation level in blood is measured using the light reception signal of the light emitting element 1 after passing through the LPF 24. Therefore, when measuring the biological information, even if the beat signal generated by the interference of the coherent light emitted from the light emitting element 1 acts as a noise component, the LPF 24 removes the noise component, and therefore, Biological information can be measured with high accuracy.

The biological information measuring device 10 is also applied to the measurement of the blood flow velocity in addition to the blood flow rate as already described. Further, as shown in FIG. 7, since the amount of light received by the light receiving element 3 changes according to the pulsation of the artery 4, the pulse rate is measured from the change in the amount of light received by the light receiving element 3. Further, the photoelectric pulse wave is measured by differentiating twice the waveform obtained by measuring the change in pulse rate in time series. The photoelectric pulse wave is used for estimating the age of blood vessels, diagnosing arteriosclerosis, and the like.

In addition, the biological information measuring device 10 is not limited to the contents described here, but can be used for measuring other biological information.

Although the present invention has been described above using the embodiment, the present invention is not limited to the scope described in the embodiment. Various modifications and improvements can be added to the embodiments without departing from the scope of the present invention, and the embodiments to which the modifications or improvements are added are also included in the technical scope of the present invention. For example, the order of processing may be changed without departing from the scope of the present invention.

Further, each process of the biological information measuring device 10 shown in FIG. 8 may use any form of software or hardware, or a combination of software and hardware.

1, 2... Light emitting device (LD)
3... Light receiving element 4... Artery 5... Vein 6... Capillaries 7... Blood cells 8... Living body 10... Biological information measuring device 12... Control unit 14...・Drive circuit 16・・・Amplifying circuit 18・・・Conversion circuit 20・・・Measuring section 22・・・Signal separation circuit 24・・・LPF
96... Receiving point

Claims (5)

A first light emitting element which emits coherent light and a second light emitting element which emits light having a wavelength different from that of the first light emitting element and which is not coherent light ;
A light receiving element that receives each light emitted from the first light emitting element and the second light emitting element, and outputs a light receiving signal corresponding to the light receiving amount of each light;
The received light signal is a first received light signal corresponding to the received light amount of the light emitted from the first light emitting element, and a second received light signal corresponding to the received light amount of the light emitted from the second light emitting element. A signal and a separating means for separating into
A filter for removing noise components of the first light receiving signal,
The first received light signal before the noise component is removed by the filter, the first received light signal where the noise component is removed by the filter, and the second received signal where the noise component is not removed by the filter. A light receiving signal, and a measuring unit that measures a plurality of biological information using the received light signal,
A biological information measuring device equipped with. The measuring means measures the frequency spectrum of the first light receiving signal before the noise component is removed by the filter and the noise by the filter with respect to the change of the first light receiving signal from which the noise component is removed by the filter. The biological information measuring device according to claim 1, wherein the plurality of biological information is measured using a rate of change of the second received light signal in which a component is not removed. The measuring means, as the plurality of biological information, measuring biological information including blood flow rate or blood flow velocity, and oxygen saturation in blood, when measuring the oxygen saturation in blood, to changes in the first light receiving signal which the noise component is divided by the filter, according to claim 1 or claim 2, wherein using the rate of change of the second light receiving signal noise component is not removed by the filter Biological information measuring device. The measuring means, as the plurality of biometric information, in the case of measuring the blood flow or blood flow velocity, and blood oxygen saturation, and measures biological information including, the blood flow or blood flow velocity, the The biological information measuring device according to claim 1 or 2 , wherein a frequency spectrum of the first received light signal before a noise component is removed by a filter is used. The biological information measuring device according to any one of claims 1 to 4, wherein the filter is a low-pass filter.

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