JP2017176263A - Apparatus and program for measuring biological information - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the electric power consumed at light emitting elements in measurement of multiple pieces of biological information.SOLUTION: A biological information measuring apparatus 10 includes a light emitting element LD1 and a light emitting element LD2 that emit light having mutually different wavelengths, and a light receiving element 3. The biological information measuring apparatus 10 controls the periods of light emission from the light emitting elements LD1 and LD2 such that the number of light emission from the light emitting element LD2 is smaller than the number of light emission from the light emitting element LD1 per unit time for the light emitting elements LD1 and LD2. The biological information measuring apparatus 10 measures multiple pieces of biological information based on a frequency spectrum with respect to the amount of light received at the light receiving element 3 from the light emitting element LD1 and on the respective amounts of light received at the light receiving element 3 from the light emitting element LD1 and the light emitting element LD2.SELECTED DRAWING: Figure 8

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 arranged on the substrate and irradiates a subject with a plurality of lights having different wavelengths so as to at least partially overlap each other, and on the substrate There is disclosed a self-luminous sensor device comprising: a light receiving unit that is disposed and 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 generates light having a first wavelength, a second light emitting element that generates light having a second wavelength, and the first and second light emitting elements are different from each other. A driving circuit that emits light at a time, and light from the first light emitting element that is transmitted through the living tissue when the living tissue is disposed at a position where the light of the first and second light emitting elements is irradiated Alternatively, the first light-receiving element arranged to receive the scattered light and the first light-receiving element and the first light-emitting element and the first light-emitting element so as to receive the light transmitted or scattered through the living tissue. A second light receiving element disposed at a predetermined distance from the one light receiving element, and blood of the living tissue based on an output of the second light receiving element by light from the first and second light emitting elements. Oxygen saturation calculation means for calculating the oxygen saturation in the A blood flow calculating means for calculating a blood flow velocity of the living tissue based on a cross-correlation function of outputs of the first and second light receiving elements by light from the first light emitting element; A flow measuring device is disclosed.

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

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

  In this case, even if it is possible to measure a plurality of pieces of biological information without alternately emitting light from the plurality of light emitting elements, the plurality of light emitting elements emit light alternately and drive control of the light emitting elements is continuously performed. More power is consumed than necessary for measuring information.

  An object of the present invention is to reduce the power consumed by a light emitting element when measuring a plurality of pieces of biological information, as compared with a case where a plurality of light emitting elements emit light alternately.

  In order to achieve the above object, the biological information measuring apparatus according to claim 1 includes a first light emitting element and a second light emitting element that irradiate light having different wavelengths, and the first light emitting element and the second light emitting element. The first light emitting element and the second light emitting element so that the number of light emission of the second light emitting element per unit time and the light receiving element that receives each irradiated light is smaller than the number of light emission of the first light emitting element. Control means for controlling the light emission period of the element, and measurement means for measuring a plurality of biological information from each of the light received by the light receiving element.

  According to a second aspect of the present invention, the control means includes: the first light emitting element and the second light emitting element so that the light emitting periods of the first light emitting element and the second light emitting element do not overlap. Control the light emission period.

  According to a third aspect of the present invention, the measuring means receives the frequency spectrum with respect to the amount of light received by the first light emitting element received by the light receiving element, and the light by the first light emitting element received by the light receiving element. The plurality of pieces of biological information are measured from the amount of received light and the amount of light received by the second light emitting element.

  According to a fourth aspect of the present invention, the measuring means is configured to receive the amount of light received during the light emission period of the first light emitting element and the light during the light emission period of the second light emitting element adjacent to the light emission period of the first light emitting element. The plurality of pieces of biological information are measured using a combination with the amount of received light.

  According to a fifth aspect of the present invention, the measuring means calculates the average value of the amount of light received in each of the light emitting periods of the first light emitting element included in the specific period, and receives the light in the light emitting period of the first light emitting element. The average value of the amount of light received in each light emission period of the second light emitting element adjacent to each light emission period of the first light emitting element included in the specific period is used as the light emission amount of the second light emitting element. The amount of light received during the period.

  According to a sixth aspect of the present invention, the measuring means measures the amount of light received from the light receiving element over a plurality of times during at least one of the light emitting period of the first light emitting element and the light emitting period of the second light emitting element. The acquired average value of the received light amounts is set as the received light amount in the light emission period in which the received light amount is acquired from the light receiving element over a plurality of times.

  According to a seventh aspect of the present invention, the measuring means measures biological information including at least one of a blood flow volume, a blood flow velocity, a blood volume, and an oxygen saturation level in the blood as the plurality of biological information.

  A biological information measurement program according to an eighth aspect causes a computer to function as the control means and the measurement means according to any one of the first to seventh aspects.

  According to invention of Claim 1, Claim 3, and Claim 8, when measuring several biological information, it is consumed with a light emitting element compared with the case where a several light emitting element is made to light-emit alternately. Electric power can be reduced.

  According to the second aspect of the present invention, biometric information can be measured with higher accuracy than those in which the light emission periods do not overlap.

  According to invention of Claim 4, compared with the case where the light reception amount in the light emission period which is not adjacent is combined, biometric information can be measured with a sufficient precision.

  According to the fifth aspect of the present invention, the biological information can be measured with higher accuracy than the case where the biological information is measured using the amount of received light in one specific light emission period.

  According to the sixth aspect of the present invention, biometric information can be measured with higher accuracy than when the amount of received light is acquired once during the light emission period.

  According to the seventh aspect of the invention, the measurement time can be shortened as compared with the case where a plurality of pieces of biological information are individually measured.

It is a schematic diagram which shows the example of a blood flow information and the measurement of the oxygen saturation in blood. It is a graph which shows an example of change of the amount of received light by reflected light from a living body. It is a schematic diagram with which it uses for description of the Doppler shift produced when a laser beam is irradiated to the blood vessel. It is a schematic diagram with which it uses for description of the speckle which arises when a blood vessel is irradiated with a laser beam. It is a graph which shows an example of the spectrum distribution with respect to the change of received light quantity. 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 amount of the light absorbed by the biological body. It is a figure which shows the structural example of a biometric information measuring apparatus. 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. It is a figure which shows the principal part structural example of the electric system of a biological information measuring device. It is a flowchart which shows an example of the flow of a biometric information measurement process. It is a timing chart which shows an example of the light emission timing of the light emitting element which irradiates IR light, and the light emitting element which irradiates red light, and the light reception timing by a light receiving element. It is a timing chart which shows an example of the light emission timing of the light emitting element which irradiates IR light, and the light emitting element which irradiates red light, and the light reception timing by a light receiving element. It is a timing chart which shows an example of the light emission timing of the light emitting element which irradiates IR light, and the light emitting element which irradiates red light, and the light reception timing by a light receiving element. It is a timing chart which shows an example of the light emission timing of the light emitting element which irradiates IR light, and the light emitting element which irradiates red light, and the light reception timing by a light receiving element.

  DETAILED DESCRIPTION Hereinafter, exemplary embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is provided to the component which an action or a function bears the same function through all the drawings, and the overlapping description is abbreviate | omitted.

  First, a method for measuring blood flow information and oxygen saturation in blood, which is an example of biological information related to blood, among biological information, will be described with reference to FIG.

  As shown in FIG. 1, blood flow information and blood oxygen saturation are stretched in the patient's body that is irradiated with light from the light emitting element 1 toward the patient's body (living body 8) and received by the light receiving element 3. It is measured using the intensity of light reflected or transmitted by the circulating artery 4, vein 5, capillary 6 or the like, that is, the amount of reflected or transmitted light received.

(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. 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 time, because this is influenced by three optical phenomena that appear when light is applied to the living body 8 including blood vessels. It is believed that there is.

  As a first optical phenomenon, a change in light absorption due to a change in the amount of blood existing in the blood vessel being measured due to pulsation can be considered. The blood contains blood cells such as red blood cells, and moves in blood vessels such as the capillaries 6, so that the number of blood cells moving in the blood vessels changes as the blood volume changes. May affect the amount of light received.

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

As shown in FIG. 3, for example, when a region including a capillary vessel 6, which is an example of a blood vessel, is irradiated from a light emitting element 1 with coherent light 40 having a frequency ω ₀ such as a laser beam, blood cells that move through the capillary vessel 6 are used. The scattered scattered light 42 causes a Doppler shift having a difference frequency Δω ₀ determined by the moving speed of blood cells. On the other hand, the frequency of the scattered light 42 scattered by a tissue such as skin (stationary tissue) that does not include a moving body such as a blood cell maintains the same frequency ω ₀ as the frequency of the irradiated laser light. Therefore, the frequency ω ₀ + Δω _{0 of} the laser light scattered by the blood vessel such as the capillary 6 interferes with the frequency ω _{0 of the} laser light scattered by the stationary tissue, and the beat signal having the difference frequency Δω ₀ is received by the light receiving element 3. And the amount of light received by the light receiving element 3 varies with time. Note that the difference frequency Δω ₀ of the beat signal observed by the light receiving element 3 depends on the moving speed of the blood cell, but is included in a range having an upper limit of about several tens of kHz.

  As a third optical phenomenon, the influence of speckle is considered.

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

  As already described, since the blood cell 7 moves in the blood vessel, the light scattering state in the blood cell 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 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 predetermined unit time T ₀ is cut out, and, for example, fast Fourier transform (Fast Fourier Transform) is performed on the data. : FFT), the spectral distribution for each frequency ω can be obtained. FIG. 5 shows an example of a graph 82 showing the spectrum distribution for each frequency ω in the unit time T ₀ . 5 represents the frequency ω, and the vertical axis represents the spectral intensity.

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

  In addition, since the blood flow volume is represented by the product of the blood volume and the blood flow velocity, it can be obtained from the calculation formula for the blood volume and the blood flow velocity. Blood flow volume, blood flow velocity, and blood volume are examples of blood flow information, and blood flow information is not limited to this.

FIG. 6 is an example of a graph 86 showing a change in blood flow per unit time T ₀ calculated. Note that 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 volume varies with time, but the variation tendency is classified into two types. For example, compared to the fluctuation range 88 of the blood flow rate in the interval T ₁ of the FIG. 6, the fluctuation range 90 of the blood flow in the interval T ₂ are large. This is because the change in the blood flow volume in the section T ₁ is mainly a change in the blood flow volume accompanying the movement of the pulse, whereas the change in the blood flow volume in the section T ₂ is a blood flow volume caused by causes such as congestion. It is thought that this is because of the change of.

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

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

  Further, looking at the breakdown of the change in light absorption in the living body 8, the light absorption amount mainly fluctuates by the artery 4, and the light absorption amount does not fluctuate compared to the artery 4 in other tissues including the vein 5 and the stationary tissue. It is known that the amount of fluctuation can be considered. This is because arterial blood pumped out of 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. . In FIG. 7, the range indicated by the arrow 94 indicates the amount of fluctuation of the light absorption corresponding to the change in the thickness of the artery 4.

In FIG. 7, assuming that the amount of received light at time t _a is I _a and the amount of received light at time t _b is I _b , the amount of change ΔA in the amount of light absorption due to the change in the thickness of the artery 4 can be _expressed by equation (1). Is done.

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

  On the other hand, hemoglobin (oxygenated hemoglobin) combined with oxygen flowing through the artery 4 easily absorbs light in an infrared (IR) region having a wavelength of about 880 nm, and hemoglobin (reduced hemoglobin) not bonded to oxygen. Is known to easily absorb light in the red region having a wavelength of around 665 nm. Furthermore, it is known that the oxygen saturation is proportional to the ratio of the amount of change ΔA in the amount of absorption at different wavelengths.

Therefore, compared to other wavelength combinations. Using infrared light (IR light) and red light, in which the difference in light absorption between oxidized hemoglobin and reduced hemoglobin is likely to appear, the amount of change ΔA _{IR in the} amount of light absorption when IR light is irradiated on the living body 8, and the red light By calculating the ratio of the amount of change ΔA _{Red in the} amount of light absorbed when the living body 8 is irradiated, the oxygen saturation S is calculated by the equation (2). In (2), k is a proportionality constant.

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

  That is, when calculating oxygen saturation in blood, a plurality of light emitting elements 1 that irradiate light of different wavelengths, specifically, a light emitting element 1 that irradiates IR light and a light emitting element 1 that irradiates red light, However, it is desirable to emit light so that the light emission periods do not overlap. Then, the reflected light or transmitted light from each light emitting element 1 is received by the light receiving element 3 and is obtained by modifying the expressions (1) and (2) or these expressions from the amount of light received at each light reception time point. The oxygen saturation is measured by calculating a known formula.

  As a well-known equation obtained by modifying the above equation (1), for example, the equation (1) may be developed and the amount of change ΔA in the amount of light absorption may be expressed as in equation (3).

(Equation 3)
ΔA = lnI _b −lnI _a (3)

  Further, the expression (1) can be modified as the expression (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 amount of change ΔA in the amount of light absorption.

(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 “light emitting element LD1”. The light emitting element 1 that emits red light is referred to as a “light emitting element LD2”. In addition, as an example, the light emitting element LD1 is used as the light emitting element 1 used for calculating blood flow, and the light emitting element LD1 and the light emitting element LD2 are used as light emitting element 1 used for calculating oxygen saturation in blood.

As already described, in the measurement of the blood flow rate, the difference frequency Δω ₀ of the beat signal observed by the light receiving element 3 is included in a range having an upper limit of about several tens of kHz, and therefore at least twice the difference frequency Δω ₀ . It is necessary to cause the light emitting element LD1 to emit light at the above frequency and to acquire the reflected light from the light emitting element LD1 by the light receiving element 3.

  Therefore, when considered in combination with the measurement of oxygen saturation in blood, for example, after adjusting the light emission frequency of the light emitting element LD2 to the light emission frequency of the light emitting element LD1, the light emitting periods of the light emitting elements LD1 and LD2 are partially emitted. The light emitting elements LD1 and LD2 emit light alternately so that the light emitting periods do not overlap, and the light receiving element 3 obtains the amount of light received for each light emitting period of the light emitting elements LD1 and LD2. Then, the oxygen saturation in the blood is measured.

  However, when measuring oxygen saturation in the blood, it is known that the measurement frequency of the amount of received light is about 30 Hz to about 1000 Hz. Therefore, the light emission frequency of the light emitting element LD2 is about 30 Hz to about 1000 Hz. It is. In other words, it is not necessary to cause the light emitting element LD2 to emit light in accordance with the light emitting frequency of the light emitting element LD1, and the light emitting frequency of the light emitting element LD2 may be lower than the light emitting frequency of the light emitting element LD1.

  Hereinafter, a biological information measuring device that measures a plurality of biological information with less power than that consumed when the light emitting elements LD1 and LD2 emit light alternately will be described.

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

  As shown in FIG. 8, the biological information measuring apparatus 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 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 period and the light emission period of the light emitting element LD1 and the light emitting element LD2 to the driving circuit 14 including a power supply circuit that supplies driving power to the light emitting element LD1 and the light emitting element LD2.

  When receiving the control signal from the control unit 12, the driving circuit 14 supplies driving power to the light emitting element LD1 and the light emitting element LD2 according to the light emission cycle and the light emitting period instructed by the control signal, and the light emitting element LD1 and the light emitting element LD2 are supplied. Drive.

  The amplifier circuit 16 amplifies a voltage corresponding to the intensity of light received by the light receiving element 3 to a voltage level defined as an input voltage range of the A / D conversion circuit 18. Here, as an example, the light receiving element 3 is an element that outputs a voltage according to the intensity of received light, but the light receiving element 3 may output a current according to the intensity of received light, In this case, the amplifier circuit 16 amplifies the current output from the light receiving element 3 to the current level defined as the input current range of the A / D conversion circuit 18.

  The A / D conversion circuit 18 receives the voltage amplified by the amplifier circuit 16 as an input, converts the received light amount of the light receiving element 3 represented by the magnitude of the voltage into a numerical value, and outputs it.

  The measurement unit 20 calculates the spectral distribution for each frequency ω by performing an FFT process on the amount of light received by the light emitting element LD1 using the amount of light received by the A / D conversion circuit 18 as an input. The blood flow rate is measured by integrating the product of the frequency ω and the spectral intensity at the frequency ω with respect to the frequency ω.

In addition, the measurement unit 20 receives the light reception amount quantified by the A / D conversion circuit 18 and manages the light reception amounts of light emitted by the light emitting element LD1 and the light emitting element LD2 in time series. Then, the measuring unit 20 calculates the change amount 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 according to the equation (1), and the light absorption amount with respect to the change amount ΔA _IR of the light absorption amount. The oxygen saturation is measured by calculating the ratio of the change amount ΔA _Red in accordance with the equation (2).

  FIG. 9 shows an arrangement example of the light emitting element LD 1, the light emitting element LD 2, and the light receiving element 3 in the biological information measuring apparatus 10. As shown in FIG. 9, the light emitting element LD 1, the light emitting element LD 2, 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 light from the light emitting element LD1 and the light emitting element 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 LD <b> 1, the light emitting element LD <b> 2, 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 light from the light emitting element LD1 and the light emitting element LD2 that have passed through the living body 8.

  Here, as an example, the light-emitting element LD1 and the light-emitting element LD2 are described as both surface-emitting laser elements. However, the present invention is not limited to this, and may be edge-emitting laser elements.

  When measuring the blood flow in the measurement unit 20, as described above, a laser element that easily generates a beat signal compared to other light is used for the light emitting element LD1 in order to use the spectral distribution of the amount of light received by the beat signal. It is preferable to use it.

However, even if the light emitted from the light emitting element LD2 is not laser light, the change amount ΔA _Red of the light absorption amount of the light emitting element LD2 is calculated, and therefore, the light emitting element LD2 includes a light-emitting diode (LED). ) Or organic light-emitting diode (OLED) may be used.

  Next, with reference to FIG. 11, the principal part structure of the electric system of the biological information measuring device 10 which concerns on this Embodiment is demonstrated.

  As shown in FIG. 11, the biological information measuring apparatus 10 according to the present embodiment includes a light-emitting element LD1 and a control unit that controls the light-emission period and light-emission period of the light-emitting element LD2, and the blood flow volume and blood in the living body 8. A CPU (Central Processing Unit) 30 is provided as an example of a measuring means for measuring oxygen saturation. The biological information measuring apparatus 10 includes a ROM (Read Only Memory) 32 in which various programs and various parameters are stored in advance, and a RAM (Random Access Memory) 34 used as a work area when the CPU 30 executes the various programs. Is provided.

  The CPU 30, ROM 32, and RAM 32 are connected to each other via an internal bus 36 of the biological information measuring apparatus 10, and further, the internal bus 36 includes a light emitting element LD 1, a light emitting element LD 2, a light receiving element 3, an amplifier circuit 16, and an A / D. Conversion circuits 18 are connected to each other.

  The CPU 30 has a built-in timer that measures the elapsed time from the specified time.

  Next, the operation of the biological information measuring device 10 will be described with reference to FIG.

  FIG. 12 is a flowchart illustrating an example of the flow of a biological information measurement process executed by the CPU 30 when the CPU 30 receives an instruction to start measurement of biological information. A program (biological information measurement program) for defining the biological information measurement process is installed in advance in the ROM 32, for example. Note that at the start of the biological information measurement program, it is assumed that both the light emitting element LD1 and the light emitting element LD2 are in a light emission stop state in which laser light is not irradiated.

  First, in step S <b> 10, the CPU 30 resets two timers, timer A and timer B, built in the CPU 30. Here, resetting the timer means stopping the measurement by the timer and starting to newly measure the elapsed time from the time when the timer is stopped.

In step S20, CPU 30 determines whether or Reset the timer A has elapsed time T ₃ or more in step S10. The time T ₃ is a parameter stored in advance in a predetermined area of the ROM 32, for example, and determines the time from the light emission period of the light emitting element LD1 to the next light emission period, that is, the light emission stop period of the light emitting element LD1.

  Since the light emitting element LD1 is used for blood flow measurement, it is set to a cycle corresponding to a frequency in a range with an upper limit of about several tens of kHz.

Determination processing in step S20 is in the negative determination is, CPU 30 may repeatedly performs the processes of steps S20, timer A waits until the elapsed time T ₃ or more. On the other hand, if the determination is affirmative, the process proceeds to step S30.

  In step S30, the CPU 30 resets the timer A.

  In step S40, the CPU 30 notifies the drive circuit 14 of a light emission start instruction that instructs the light emission element LD1 to start light emission. When the drive circuit 14 receives the light emission start instruction, the drive circuit 14 supplies drive power to the light emitting element LD1 and irradiates the laser light from the light emitting element LD1.

  In step S50, the CPU 30 acquires the amount of light received by the light emitting element LD1 received by the light receiving element 3 during the light emitting period of the light emitting element LD1 from the A / D conversion circuit 18, and stores it in a predetermined area of the RAM 34, for example. .

In step S60, CPU 30 determines whether or Reset the timer A has elapsed time T ₄ or more in step S20. The time T ₄ is a parameter stored in advance in a predetermined area of the ROM 32, for example, and determines the time from when the light emitting element LD1 emits light until it stops emitting light, that is, the light emitting period of the light emitting element LD1.

Determination processing in step S60 is in the negative determination is, CPU 30 may repeatedly performs the processes of steps S60, timer A waits until the elapsed time T ₄ or higher. On the other hand, if the determination is affirmative, the process proceeds to step S70.

  In step S70, the CPU 30 notifies the drive circuit 14 of a light emission stop instruction that instructs the light emission element LD1 to stop light emission. When receiving the light emission stop instruction, the drive circuit 14 stops the supply of drive power to the light emitting element LD1, and stops the irradiation of the laser light by the light emitting element LD1. Further, the CPU 30 resets the timer A.

In step S80, CPU 30 determines whether this time has elapsed since the reset timer B in step S10 time T ₅ or more. The time T ₅ is a parameter stored in advance in a predetermined area of the ROM 32, for example, and determines the light emission stop period of the light emitting element LD2. The time T ₅ is set to be longer than the time T ₃ . Specifically, it corresponds to the measurement frequency of the amount of light received from each of the light emitting element LD1 and the light emitting element LD2, which is used when measuring oxygen saturation in blood, that is, a frequency of about 30 Hz to about 1000 Hz. it may be set time T ₅ in accordance with the cycle of.

By setting the time T _{5 in} this way, as will be described below, the light emission period from when the light emitting element LD2 emits light until the next light emission is set longer than the light emission period of the light emitting element LD1.

Determination processing in step S80 is shifted to the step S20 in the case of negative determination, CPU 30, by repeating the process of step S20～S80, during light emission stop period of the light emitting element LD2, the light emitting elements LD1 time T ₃ each The process of emitting light over time T ₄ is repeatedly executed.

  On the other hand, if the determination process in step S80 is affirmative, the process proceeds to step S90.

  In subsequent steps S90 to S130, the light emission start operation and the light emission stop operation are performed on the light emitting element LD2 in the same manner as the light emitting element LD1 shown in steps S30 to S70.

  That is, in step S90, the CPU 30 resets the timer B.

  In step S100, the CPU 30 notifies the drive circuit 14 of a light emission start instruction that instructs the light emission element LD2 to start light emission. When the drive circuit 14 receives the light emission start instruction, the drive circuit 14 supplies drive power to the light emitting element LD2, and irradiates the laser light from the light emitting element LD2.

  In step S110, the CPU 30 acquires the amount of light received by the light emitting element LD2 received by the light receiving element 3 during the light emitting period of the light emitting element LD2 from the A / D conversion circuit 18, and stores it in a predetermined area of the RAM 34, for example. .

In step S120, CPU 30 determines whether or Reset the timer B has elapsed time T ₆ or more in step S90. The time T ₆ is a parameter stored in advance in a predetermined area of the ROM 32, for example, and determines the light emission period of the light emitting element LD2. The time T ₆ is set to be equal to or shorter than the time T ₃ for setting the length of the light emission stop period of the light emitting element LD1.

Determination processing in step S120 is the case of a negative determination, CPU 30 is repeatedly performs the processes of steps S120, timer B waits until the elapsed time T ₆ or more. On the other hand, if the determination is affirmative, the process proceeds to step S130.

  In step S130, the CPU 30 notifies the drive circuit 14 of a light emission stop instruction for instructing the light emission element LD2 to stop light emission. When receiving the light emission stop instruction, the drive circuit 14 stops the supply of drive power to the light emitting element LD2, and stops the irradiation of the laser light by the light emitting element LD2. Further, the CPU 30 resets the timer B.

  In step S140, the CPU 30 performs FFT processing on the time-series data of the light reception amount of the light emitting element LD1 acquired in step S50 according to the blood flow measurement method described above, and calculates the spectrum distribution for each frequency ω. The blood flow is measured by integrating the spectral distribution with respect to all frequencies ω.

  In step S150, the CPU 30 uses, for example, the RAM 34 to calculate the received light amount of the light emitting element LD1 acquired in step S50 and the received light amount of the light emitting element LD2 acquired in step S110, according to the method for measuring the oxygen saturation in blood. Is stored in a predetermined area. Then, the CPU 30 calculates the expression (1) and (2) or a known expression obtained by modifying these expressions using the time series data of the amount of received light, so that the oxygen saturation level in the blood is calculated. Measure.

  In step S160, the CPU 30 determines whether or not an end instruction for ending the measurement of biometric information has been received. If the determination process is negative, the process proceeds to step S20, and steps S20 to S160 are repeatedly executed until an end instruction is received, thereby continuously measuring the blood flow volume and the oxygen saturation.

  FIG. 13 is an example of a timing chart showing the light emission timings of the light emitting element LD1 and the light emitting element LD2 when the biological information measurement program of FIG. 12 is executed.

As shown in FIG. 13, in the light emitting element LD1, a light emission stop period having a length of time T ₃ and a light emission period having a length of time T ₄ appear repeatedly. Further, the light emitting element LD2, the light emission stop period having a length of time T _5, although the light emitting period is repeatedly appear with a length of time T _6, emit emission stop period of the light emitting element LD2 of the light emitting element LD1 By setting it longer than the stop period, a situation where the light emitting element LD2 emits light every light emission stop period of the light emitting element LD1 is avoided.

  In this case, the measurement unit 20 emits light including the light receiving amount of the light emitting element LD2 acquired at the light receiving point 96B and the light receiving point 96B among the light receiving points 96 representing the respective acquisition timings of the light receiving amounts of the light emitting elements LD1 and LD2. Oxygen saturation in blood using the light receiving amount of the light emitting element LD1 at either the light receiving point 96A or the light receiving point 96B obtained during the light emitting period of the element LD2 and the light emitting period of the light emitting element LD1 adjacent along the time axis. Measure the degree.

  This is because, when measuring oxygen saturation in blood, the measurement accuracy tends to be higher when the amount of light received by the light emitting element LD1 and the amount of light received by the light emitting element LD2 are as close as possible in time. is there. In the following, the fact that the light receiving point 96 is as close as possible in time may be simply referred to as “the light receiving point 96 is close”.

  In the flowchart of the biological information measurement program shown in FIG. 12, the length of the light emission stop period of the light emitting element LD2 is fixed, but may be variable.

14, in the case where the time T ₅ and time T ₇ for defining the light emission stop period of the light emitting element LD2 is set to different values, which is an example of a timing chart showing the emission timing of the light emitting elements LD1 and the light-emitting element LD2. Even in this case, the measurement unit 20 receives the received light amount of the light emitting element LD1 at the light receiving point 96A, the received light amount of the light emitting element LD2 at the light receiving point 96B, which is an example of the light receiving point 96 close to the light receiving point 96A, and the received light. The blood oxygen saturation is measured using the amount of light received by the light emitting element LD1 at the point 96C and the amount of light received by the light emitting element LD2 at the light receiving point 96D, which is an example of the light receiving point 96 close to the light receiving point 96C.

  Further, for example, an average value of the light receiving amount of each light receiving point 96 in a plurality of light emitting periods included in a specific period among the light emitting periods of the light emitting element LD1 may be used as the light receiving amount in the light emitting period of the light emitting element LD1. Further, among the light emission periods of the light emitting element LD2, the average value of the light reception amount of each light receiving point 96 in a plurality of light emission periods included in the specific period may be used as the light reception amount in the light emission period of the light emitting element LD2.

For example, as shown in FIG. 15, the measurement unit 20 uses the average value of the amounts of light received at the light receiving points 96A and 96C in the respective light emitting periods included in the specific period T _LD1 among the light emitting periods of the light emitting element LD1. Is calculated. In addition, the measurement unit 20 calculates an average value of the amounts of light received at the light receiving points 96B and 96D in each light emitting period included in the specific period T _LD2 among the light emitting periods of the light emitting element LD2. Then, the measurement unit 20 measures the oxygen saturation level in the blood using the average value of the respective received light amounts of the light receiving points 96A and 96C and the average value of the received light amounts of the light receiving points 96B and 96D. .

  Further, as shown in FIG. 16, the measuring unit 20 provides a plurality of light receiving points 96 in the light emitting period of the light emitting element LD1 and the light emitting period of the light emitting element LD2, acquires the amount of light received at each light receiving point 96, and acquires each received light received. The average value of the received light amount at the point 96 may be used as the received light amount in the light emission period of the light emitting element LD1 and the light emitting element LD2, respectively. That is, the average value of the respective received light amounts at the light receiving point 96A and the light receiving point 96C is set as the received light amount in the light emitting period of the light emitting element LD1, and the average value of the respective received light amounts at the light receiving point 96B and the light receiving point 96D is emitted from the light emitting element LD2. The amount of light received during the period.

  Note that FIG. 16 shows an example in which a plurality of light receiving points 96 are provided for each light emitting period of the light emitting element LD1 and the light emitting element LD2 and the amount of light received at the light receiving point 96 is averaged. It is not limited to this. For example, a plurality of light receiving points 96 may be provided only for either one of the light emitting elements LD1 and LD2.

  That is, the received light amount data of the light emitting element LD1 and the light emitting element LD2 used for the measurement is not limited to the number of data described in FIG. 14, and may have a plurality of light emitting periods in a specific period as shown in FIG. As shown in FIG. 16, a plurality of light receiving points 96 may be provided in the light emitting period of the light emitting element LD1 and the light emitting period of the light emitting element LD2.

  As described above, according to the biological information measuring apparatus 10 according to the present embodiment, a part of the light emission periods of the light emitting element LD1 and the light emitting element LD2 may overlap. The light emitting element LD1 and the light emitting element LD2 are controlled such that the number of times of light emission of the light emitting element LD2 is smaller than the number of times of light emission of the light emitting element LD1.

  Accordingly, the light emission period of the light emitting element LD1 and the light emitting element LD2 are set to be the same, and the blood flow volume and oxygen saturation in the blood are reduced with less power than that consumed when the light emitting elements LD1 and LD2 emit light alternately. The degree is measured.

  In addition, the biological information measuring device 10 is applied to the measurement of the blood flow velocity in addition to the blood flow 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, the pulse rate is measured from the change in the amount of light received by the light receiving element 3. Moreover, an acceleration pulse wave is measured by differentiating twice the waveform obtained by measuring the change of the pulse rate in time series. The acceleration pulse wave is used for estimating blood vessel age or diagnosing arteriosclerosis.

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

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

  In the embodiment, as an example, the form in which the processing in the control unit 12 and the measurement unit 20 is realized by software has been described. However, the same processing as the flowchart shown in FIG. 12 may be processed by hardware. Good. In this case, the processing speed can be increased as compared with the case where the processing in the control unit 12 and the measurement unit 20 is realized by software.

  In the embodiment, the biological information measurement program is installed in the ROM 32. However, the present invention is not limited to this. The biological information measurement program according to the present invention can also be provided in a form recorded on a computer-readable recording medium. For example, the biological information measurement program according to the present invention is provided in a form recorded in a portable recording medium such as a CD (Compact Disc) -ROM, a DVD (Digital Versatile) -ROM, or a USB (Universal Serial Bus) memory. Is also possible. The biological information measurement program according to the present invention can be provided in a form recorded in a semiconductor memory such as a flash memory.

1, 2 ... Light emitting element (LD)
DESCRIPTION OF SYMBOLS 3 ... Light receiving element 4 ... Artery 5 ... Vein 6 ... Capillary blood vessel 7 ... Blood cell 8 ... Living body 10 ... Living body information measuring device 12 ... Control part 14 ... Drive circuit 16 ... amplifier circuit 18 ... conversion circuit 20 ... measurement unit 30 ... CPU
96 (96A, 96B, 96C, 96D) ... light receiving point

Claims (8)

A first light emitting element and a second light emitting element that irradiate light having different wavelengths;
A light receiving element that receives each light emitted from the first light emitting element and the second light emitting element;
Control means for controlling the light emission periods of the first light emitting element and the second light emitting element so that the number of times of light emission of the second light emitting element per unit time is less than the number of times of light emission of the first light emitting element;
Measuring means for measuring a plurality of biological information from each of the light received by the light receiving element;
A biological information measuring device comprising: The biological information measurement according to claim 1, wherein the control unit controls a light emission period of the first light emitting element and the second light emitting element so that light emission periods of the first light emitting element and the second light emitting element do not overlap. apparatus. The measuring means receives the frequency spectrum with respect to the amount of light received by the first light emitting element received by the light receiving element, and the amount of light received by the first light emitting element and the second light emission received by the light receiving element. The biological information measuring apparatus according to claim 1, wherein the biological information is measured from an amount of light received by the element. The measuring means uses a combination of a light receiving amount of the first light emitting element during a light emitting period and a light receiving amount of the second light emitting element adjacent to the light emitting period of the first light emitting element. The biological information measuring device according to claim 1, wherein the biological information is measured. The measuring means sets an average value of the amount of light received in each of the light emitting periods of the first light emitting element included in the specific period as the amount of light received in the light emitting period of the first light emitting element, and in the specific period The average value of the amount of light received in each light emission period of the second light emitting element adjacent to each of the light emission periods of the first light emitting element included is the amount of light received in the light emission period of the second light emitting element. The biological information measuring device according to claim 4. The measuring means acquires the amount of light received from the light receiving element over a plurality of times during at least one of the light emitting period of the first light emitting element and the light emitting period of the second light emitting element. The biological information measuring device according to claim 4 or 5, wherein an average value of the amount is set as a light reception amount in a light emission period in which the light reception amount is acquired from the light receiving element over a plurality of times. The measurement means measures biological information including at least one of blood flow volume, blood flow velocity, blood volume, and oxygen saturation in blood as the plurality of biological information. The biological information measuring device according to item 1.   A biological information measurement program for causing a computer to function as the control unit and the measurement unit according to any one of claims 1 to 7.

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