JP5817362B2 - Signal processing device, pulse wave measuring device, and signal processing method - Google Patents

Description

  The present invention relates to a signal processing device, a pulse wave measurement device, and a signal processing method.

  A method of measuring a pulse wave of a living body based on a measurement value from a sensor that irradiates light to a measurement site such as a fingertip and receives light transmitted or reflected through the measurement site is known. In Patent Document 1 below, when measuring a pulse wave of a living body by such a method, artifacts due to body movements of the measurement subject such as movements, tremors, and coughs of the measurement subject are mixed in the measurement signal. In some cases, a method for separating a pulsation signal and an artifact signal from a measurement signal is disclosed. In the method of Patent Document 1, a stable period that is not affected by body movement and an artifact period that is affected by body movement are set in advance, and in each period, red light and infrared light are irradiated to the measurement site. A measurement signal corresponding to the amount of received light is acquired. Then, the norm ratio (φs) of the red light measurement signal to the infrared light measurement signal in the stable period and the norm ratio (φn) of the red light measurement signal to the infrared light measurement signal in the artifact period are expressed as red. The pulsation signal and the artifact signal in the artifact period are separated by using a separation matrix which is a transmission coefficient of the light pulsation signal and the artifact signal.

JP 2009-261458 A

By the way, as shown in FIG. 12, red light (wavelength: 620 nm) has a high extinction coefficient ratio of reduced hemoglobin (broken line) to oxyhemoglobin (solid line), and green light, infrared light, etc. are reduced hemoglobin to oxyhemoglobin. The extinction coefficient ratio of is low. That is, red light has higher sensitivity to reduced hemoglobin than infrared light and green light, and more light is absorbed. For example, when the measurement site is moved from the height of the heart to a lower position and the venous blood volume in the measurement site increases, the reduced hemoglobin increases, and the amplitude of the pulse wave signals of red light and green light is higher than before the movement. Decrease. In particular, since red light absorbs more light than green light, the amount of decrease in the amplitude of red light is greater than that of green light. That is, when the amount of venous blood at the measurement site increases, the amount of decrease in the amplitude of red light becomes larger than the amount of decrease in the amplitude of green light, and thus the norm ratio (φs, φn) changes. In the separation method, the norm ratio (φs, φn) causes an error in the calculated value of the norm ratio when the venous blood volume changes, so that a pulsation signal that appropriately reflects the state of the living body cannot be output.
The present invention provides a technique for outputting a pulsation signal that reflects the state of a living body to be measured even when the venous blood volume at a measurement site changes.

  The signal processing apparatus according to the present invention provides the living body in a first measurement period, which is a measurement period of a pulse wave of a living body, and in a second measurement period, which is affected by body movement of the living body from the first measurement period. A first measurement signal based on the amount of received light having received the first wavelength light transmitted or reflected, and a second measurement signal based on the amount of received light having the second wavelength light transmitted or reflected through the living body. An acquisition means for acquiring, a frequency band representing a predetermined pulsation from the first measurement signal and the second measurement signal in each of the first measurement period and the second measurement period acquired by the acquisition means; Extraction means for extracting each signal of the first frequency component and the second frequency component in a frequency band lower than the frequency band of the first frequency component, the first measurement period extracted by the extraction means, and the second The first lap of the measurement period According to the difference between the first coefficient and the second coefficient representing the correlation between the second measurement signal and the first measurement signal based on each signal sequence of several components and the second frequency component, the first coefficient and the second coefficient Separation processing for separating the first measurement signal in the second measurement period and the pulsation component and noise component included in the second measurement signal using the second coefficient, and the second measurement signal in the second measurement period And an output means for selectively performing the process of using the first frequency component as the pulsation component and outputting the pulsation component in the second measurement period. According to this configuration, it is possible to output a pulsation signal that reflects the state of the living body to be measured even when the venous blood volume at the measurement site changes.

‖Ｒ_ACpulse‖₂は第１測定期間の第１測定信号の第１周波数成分のノルムである。
‖Ｇ_ACpulse‖₂は第１測定期間の第２測定信号の第１周波数成分のノルムである。
‖Ｒ_DCpulse‖₂は第１測定期間の第１測定信号の第２周波数成分のノルムである。
‖Ｇ_DCpulse‖₂は第１測定期間の第２測定信号の第２周波数成分のノルムである。
‖Ｒ_{ACnoise(j-k:j+k)}‖₂は第２測定期間の第１測定信号の第１周波数成分のノルムである。
‖Ｇ_{ACnoise(j-k:j+k)}‖₂は第２測定期間の第２測定信号の第１周波数成分のノルムである。
‖Ｒ_{DCnoise(j-k:j+k)}‖₂は第２測定期間の第１測定信号の第２周波数成分のノルムである。
‖Ｇ_{DCnoise(j-k:j+k)}‖₂は第２測定期間の第２測定信号の第２周波数成分のノルムである。
この構成によれば、計測部位の静脈血量が変化しても、体動によるノイズが含まれている測定信号から脈動成分とノイズ成分とを分離する精度の低下を軽減することができる。 In the signal processing device according to the present invention, in the signal processing device, the output means uses the Euclidean norm ratio obtained by the following equation (1) as the first coefficient, and the Euclidean norm obtained by the following equation (2): When the ratio is the second coefficient, and the difference between the first coefficient and the second coefficient is within a predetermined threshold range, the first frequency of the second measurement signal in the second measurement period The process using the component as the pulsating component is performed, and when the component is out of the range of the threshold value, the separation process using the first coefficient and the second coefficient is performed.

‖R _ACpulse ‖ ₂ is the norm of the first frequency component of the first measurement signal of the first measurement period.
‖G _ACpulse ‖ ₂ is the norm of the first frequency component of the second measurement signal of the first measurement period.
‖R _DCpulse ‖ ₂ is the norm of the second frequency component of the first measurement signal of the first measurement period.
‖G _DCpulse ‖ ₂ is the norm of the second frequency component of the second measurement signal of the first measurement period.
_{‖R ACnoise (jk: j + k} ) || ₂ is the norm of the first frequency component of the first measurement signal of the second measurement period.
_{‖G ACnoise (jk: j + k} ) || ₂ is the norm of the first frequency component of the second measurement signal of the second measurement period.
_{‖R DCnoise (jk: j + k} ) || ₂ is the norm of the second frequency component of the first measurement signal of the second measurement period.
_{‖G DCnoise (jk: j + k} ) || ₂ is the norm of the second frequency component of the second measurement signal of the second measurement period.
According to this configuration, even if the venous blood volume at the measurement site changes, it is possible to reduce a decrease in accuracy in separating the pulsation component and the noise component from the measurement signal including noise due to body movement.

  The signal processing device according to the present invention is characterized in that, in the signal processing device, the light having the second wavelength has a smaller extinction coefficient of reduced hemoglobin with respect to oxyhemoglobin than the light having the first wavelength. And According to this configuration, it is possible to output a pulsation signal that is less affected by an increase in venous blood volume and more reflects the pulsation of the living body to be measured.

  Further, the pulse wave measuring device according to the present invention irradiates the living body with the light having the first wavelength, receives the light having the first wavelength that is transmitted or reflected through the living body, and the light according to the amount of received light. A first light receiving and emitting unit that outputs a first measurement signal; and irradiating the living body with light of the second wavelength, receiving light of the second wavelength that is transmitted or reflected through the living body, and according to the amount of received light A second light emitting / receiving unit that outputs the second measurement signal, and the first measurement signal and the second measurement signal output from the first light emitting / receiving unit and the second light receiving / emitting unit, And a signal processing device that outputs a pulsation component in two measurement periods. According to this configuration, it is possible to output a pulsation signal that reflects the state of the living body to be measured even when the venous blood volume at the measurement site changes.

  Further, the signal processing method according to the present invention includes a first measurement period for measuring a pulse wave of a living body to be measured, and a second measurement period that is affected by body movement of the living body more than the first measurement period. In the first measurement signal based on the amount of received light having received the first wavelength light transmitted or reflected through the living body, and the second based on the amount of received light having received the second wavelength light transmitted or reflected through the living body. An acquisition step of acquiring a measurement signal, and a predetermined pulsation from the first measurement signal and the second measurement signal in each of the first measurement period and the second measurement period acquired in the acquisition step. An extraction step of extracting signals of a first frequency component of a frequency band to be represented and a second frequency component of a frequency band lower than the frequency band of the first frequency component, respectively, and the first measurement period extracted by the extraction step When The difference between the first coefficient and the second coefficient representing the correlation between the second measurement signal and the first measurement signal based on the signal sequence of the first frequency component and the second frequency component in the second measurement period. Accordingly, a separation process that separates the first measurement signal and the pulsation component and the noise component included in the second measurement signal in the second measurement period using the first coefficient and the second coefficient, And a step of selectively performing the process of using the first frequency component of the second measurement signal in two measurement periods as the pulsation component, and outputting the pulsation component in the second measurement period. To do. According to this configuration, it is possible to output a pulsation signal that reflects the state of the living body to be measured even when the venous blood volume at the measurement site changes.

It is a figure showing the appearance of the pulse wave measuring device concerning an embodiment. It is a block diagram showing an example of composition of a pulse wave measuring device concerning an embodiment. It is a figure which shows the example of the hardware constitutions of the signal processing part in embodiment. It is a functional block diagram of a control part in an embodiment. It is a figure showing the measurement model of a pulsation signal and a noise signal in an embodiment. It is a figure showing the example of a waveform of AC component in an embodiment. It is a figure showing the example of a waveform of DC component in an embodiment. It is a figure showing the operation | movement flow of the pulse wave measuring device which concerns on embodiment. It is a figure showing the operation | movement flow of the pulse wave measuring device which concerns on embodiment. It is a figure which shows the waveform of the norm ratio by the conventional method, and the waveform of a pulsation signal. It is a figure which shows the waveform of the norm ratio by the method of embodiment, and the waveform of a pulsation signal. It is a figure showing the light absorption coefficient with respect to reduced hemoglobin and oxygenated hemoglobin.

<Configuration>
FIG. 1 is a diagram illustrating an appearance of a pulse wave measuring apparatus according to the present embodiment. As shown in FIG. 1A, for example, the pulse wave measuring device 1 is worn on the hand of a living body 2 to be measured. The pulse wave measuring device 1 is configured by connecting a device main body 10 attached to a wrist of a living body 2 and a pulse wave sensor 20 attached to a measurement site for measuring a pulse wave with a cable 30. In the present embodiment, the pulse wave sensor 20 is fixed to the palm side of the base of the index finger by a band 40 as shown in FIG. The apparatus main body 10 is provided with an operation switch 16 for operating the liquid crystal display 15 and the pulse wave measuring apparatus 1. Hereinafter, each component of the pulse wave measuring device 1 will be described in the order of the pulse wave sensor 20 and the device main body 10.

  FIG. 2 is a block diagram showing the configuration of the pulse wave measuring device 1. The pulse wave sensor 20 includes a first light emitting / receiving unit 210, a second light emitting / receiving unit 220, and a driving unit 230. The first light emitting / receiving unit 210 is a light emitting element such as an LED (Light Emitting Diode) that emits light having a red light wavelength (an example of the first wavelength), and a light receiving element such as a photodiode that receives light having a red light wavelength. Device. The second light emitting / receiving unit 220 includes a light emitting element such as an LED that emits light having a wavelength of green light (an example of the second wavelength), and a light receiving element such as a photodiode that receives the light of green light. The light emitting element of the first light emitting / receiving unit 210 is configured to have a light emission peak wavelength of 525 nm, for example, and the light emitting element of the second light receiving / emitting unit 220 is configured to have a light emission peak wavelength of 620 nm, for example. The drive unit 220 includes a drive circuit that drives the light emitting elements of the first light emitting / receiving unit 210 and the second light emitting / receiving unit 220, and alternately switches the light emitting elements of the first light receiving / emitting unit 210 and the second light receiving / emitting unit 220. Make it emit light.

  In FIG. 1B, a portion of the pulse wave sensor 10 that is in contact with the measurement site (finger) is provided with a transmission plate (not shown) that transmits light, such as a glass plate, below the transmission plate. The first light emitting / receiving unit 210 and the second light emitting / receiving unit 220 are provided. The light emitting elements of the first light receiving and emitting unit 210 and the second light receiving and emitting unit 220 are fixed so that the direction of the transmission plate is the optical axis direction. The element is fixed so that the light receiving surface faces the direction of the transmission plate. The light emitted from each light emitting element is transmitted through the transmission plate and irradiated to the measurement site, and the light reflected from the measurement site is received by each light receiving device through the transmission plate, and a measurement signal corresponding to the amount of light received by each light receiving device. Is sent to the apparatus main body 10 via the cable 30. Hereinafter, a measurement signal indicating the amount of received light received by the first light receiving / emitting unit 210 is referred to as a first measurement signal, and a measurement signal indicating the amount of received light received by the second light receiving / emitting unit 220 is referred to as a second measurement signal.

  The apparatus main body 10 includes a control unit 110, a signal processing unit 120, a time measuring unit 130, a clock supply unit 140, a display unit 150, and an operation unit 160. The control unit 110 includes a CPU (Central Processing Unit), a memory (ROM (Read Only Memory), and a RAM (Random Access Memory)), and the CPU executes a control program stored in the ROM so that the control unit 110 The connected unit is controlled to perform an output process for outputting a pulsation component indicating the pulsation of the living body from the measurement signal detected by the pulse wave sensor 20. The details of the function of the control unit 110 will be described later.

  The signal processing unit 120 is an example of an acquisition unit and an extraction unit. The signal processing unit 120 acquires the first measurement signal and the second measurement signal output from the pulse wave sensor 20 via the cable 30, and a pulsation component (AC (Alternating Current) component) included in the waveform of each measurement signal. And a baseline fluctuation component (DC (Direct Current) component) included in the waveform of each measurement signal. The AC component represents a change in the amount of light reflected by arterial blood at the measurement site, that is, a heartbeat in the artery, and changes with time. The DC component represents the amount of light reflected by living tissue other than the artery and vein at the measurement site and venous blood, and has a sufficiently low frequency compared to the pulsation component. The AC component is an example of a first frequency component, and the DC component is an example of a second frequency component.

  Here, the hardware configuration of the signal processing unit 120 is shown in FIG. The signal processing unit 120 includes filters 121a and 121b that remove DC components from the first measurement signal and the second measurement signal, and an amplification circuit that amplifies the AC components extracted by the filters 121a and 121b with a predetermined gain. 122-1 and 122-2, and A / D conversion circuits 123-1 and 123-2 for A / D (Analog-Digital) conversion of the amplified signals of the AC components, respectively. In addition, the signal processing unit 120 converts each signal of the DC components extracted by the filters 124a and 124b and the filters 124a and 124b to remove the AC components included in the first measurement signal and the second measurement signal, respectively, from the A / D. A / D conversion circuits 123-3 and 123-4 for conversion are included. The filters 121a and 121b may be, for example, bandpass filters having a cutoff frequency of 1.7 Hz to 5 Hz representing the frequency of the pulsating component. The filters 124a and 124b may be moving average filters that extract a frequency lower than the pulsation frequency (for example, 1 Hz or less), or may be low-pass filters that remove the pulsation frequency band.

  The A / D conversion circuits 123-1 and 123-2 quantize the signals of the AC components of the first measurement signal and the second measurement signal at a predetermined sampling frequency, and the A / D conversion circuits 123-3 and 123. -4 quantizes each DC component signal of the first measurement signal and the second measurement signal at a predetermined sampling frequency. In the present embodiment, for example, the sampling frequency is 100 Hz, and quantization is performed with 10 bits.

  The clock unit 130 counts the clock signal from the clock supply unit 140 and clocks the time. The clock supply unit 140 includes an oscillation circuit and a frequency dividing circuit. The clock supply unit 140 supplies a reference clock signal to the control unit 110 by the oscillation circuit, and generates a time measuring clock signal for time measurement by the frequency dividing circuit to the control unit 110. Supply.

  The display unit 150 includes the liquid crystal display 15, and displays various images such as time information measured by the time measuring unit 130, a menu screen for measuring pulse waves, and measurement results under the control of the control unit 110. . The operation unit 160 includes an operation switch 16 and sends an operation signal indicating that the operation switch 16 has been operated to the control unit 110.

  Next, functions of the control unit 110 will be described. FIG. 4 is a functional block diagram for realizing the output processing function of the control unit 110. The control unit 110 includes an output unit 110a. The output unit 110a is an example of an output unit. The output unit 110a uses a signal sequence of AC components (AC1, AC2) and DC components (DC1, DC2) extracted from the first measurement signal and the second measurement signal by the signal processing unit 120 and A / D-converted. Thus, the pulsation component and the noise component included in the AC component of the first measurement signal and the second measurement signal in the noise period (second measurement period) affected by body movement are separated, and the separated pulsation component is shown. The pulse wave data is displayed on the display unit 150. Specifically, the output unit 110a performs the first measurement signal and the second measurement signal in the noise period, and the first measurement in the stable period (first measurement period) that is hardly affected by body movement compared to the noise period. AC component in the stable period as a first coefficient and a second coefficient representing the correlation between the second measurement signal and the first measurement signal based on each signal sequence of the AC component and the DC component respectively extracted from the signal and the second measurement signal The norm ratio (φs) of the first measurement signal to the second measurement signal of each signal sequence of the DC component and the norm ratio of the first measurement signal to the second measurement signal of each signal sequence of the AC component and DC component in the noise period (Φn) is used to separate the pulsation component and the noise component included in the AC component of the noise period. Hereinafter, the separation method in the present embodiment will be described in more detail.

A measurement model of the first measurement signal (red light) and the second measurement signal (green light) is defined as shown in FIG. In FIG. 5, p is a pulsation signal indicating pulsation at time tn, and n is a noise signal indicating noise at time tn. G is a light receiving element of the second light receiving and emitting unit 220, that is, a terminal for green light (G), and R is a light receiving element of the first light receiving and emitting unit 210, that is, a terminal for red light (R). The pulsation signal p is transmitted to the G terminal with the transmission coefficient 1, and is transmitted to the R terminal with the transmission coefficient φs. The noise signal n is transmitted to the G terminal with the transmission coefficient 1, and is transmitted to the R terminal with the transmission coefficient φn. Accordingly, in this measurement model, φs at time tn is the ratio of the pulsation signal Gp (tn) transmitted to the G terminal at time tn and the pulsation signal Rp (tn) transmitted to the R terminal at time tn (φs = Rp (tn) / Gp (tn)). Φn at time tn is the ratio of the noise signal Gn (tn) transmitted to the G terminal at time tn and the noise signal Rp (tn) transmitted to the R terminal at time tn (φn = Rp (tn) / Gp (tn)). When p, n, G, and R are defined as vectors by extending from the measurement time tn to tn + k, φs is expressed by a norm ratio (Euclidean norm ratio) represented by the following equation (3). Incidentally, ‖Rpulse‖ ₂ represents the norm of a vector of the first measurement signal in the stable period, ‖Gpulse‖ ₂ shows a norm of a vector of the second measurement signal in the stable period.

On the other hand, if the noise period is regarded as a period k before and after k at a certain time point J (Jk: J + k), the norm ratio of the noise period using (2k + 1) norms including the time point J is expressed by the following formula ( 4). ‖R _{noise (Jk: J + k)} ‖ ₂ indicates the norm of the vector of the first measurement signal during the noise period, and ‖G _{noise (Jk: J + k)} ‖ ₂ indicates the second measurement during the noise period. The norm of the signal vector is shown.

  That is, φs is the norm ratio of the vector of the first measurement signal to the second measurement signal in the stable period, and φ (J) n is the norm ratio of the vector of the first measurement signal to the second measurement signal in the noise period. is there. The measurement model shown in FIG. 5 is expressed by the following equation (5). In order to separate the pulsation signal p and the noise signal n, an inverse matrix operation represented by the following equation (6) may be performed. The inverse matrix in Equation (6) is a separation matrix.

  In the conventional method, φs and φ (J) are obtained from Equations (3) and (4) using each signal obtained by reducing noise components to some extent from the first measurement signal and the second measurement signal, that is, a signal sequence of AC components. n is calculated. As described above, when the measurement site is moved from the height of the heart to a position lower than the heart to increase the venous blood volume of the measurement site, as shown in the waveforms of FIGS. The amplitude of the waveform of each AC component of green light is smaller than before the movement. In particular, the amount of decrease in the amplitude of red light is greater than that of green light due to the difference in sensitivity of red light and green light to reduced hemoglobin. Therefore, when φs and φ (J) n are calculated using the AC components of red light and green light during the stable period and noise period, the numerator (norm of the AC component of red light (first measurement signal)) decreases. The amount becomes larger than the denominator (the norm of the AC component of the green light (second measurement signal)), and φs and φ (J) n become smaller before and after the increase in venous blood volume.

  On the other hand, the DC component obtained by removing the AC component from the first measurement signal and the second measurement signal tends to increase as the venous blood volume increases. The reason will be described below. A photodiode, which is a light receiving element, has a characteristic that a resistance value increases in a state where light is not incident, and the amplitude of an output voltage tends to increase as more light is incident.

  FIG. 7 is a diagram illustrating output voltages in a state where no light is incident (dark state) and in a state where red light or green light is incident. As shown in this figure, in the dark state, the output voltage is always Vcc in both the period A and the period B. When red light or green light is incident, the period B is a light receiving element than the period A. Since the amount of received light is reduced, in the period B, the output voltage increases as the amount of light decreases. In other words, if the measurement site is moved to a position lower than the heart to increase the venous blood volume, the light receiving elements for red light and green light receive less light than before the movement, and the output voltage increases. . In particular, red light absorbs more light than green light, so the amount of red light received by the light receiving element is less than green light, and the increase in output voltage is red light than green light. Is bigger.

  The DC component is obtained by removing the time change of the output voltage with the filters 124a and 124b. When the change of the DC component described above is applied to Equation (3) and Equation (4), it can be seen that φs and φ (J) n when the venous blood volume increases during the stable period and the noise period are relatively large. . Therefore, in the separation method of the present embodiment, the separation matrix is configured using the norm ratio of the AC component and the DC component that changes with changes in the venous blood volume, and the separation matrix is applied to Equation (6). Yes.

Specifically, a vector having the values of the AC components of red light (first measurement signal) and green light (second measurement signal) from measurement time tn to tn + k as elements is R _AC = (R _ACn R _{ACn +1} R _{ACn + 2} ... R _{ACn + k} ), each G _AC = (G _ACn G _{ACn + 1} G _{ACn + 2} ... G _{ACn + k} ), and red from the measurement time tn to tn + k R _DC = (R _DCn R _{DCn + 1} R _{DCn + 2} ... R _{DCn +} is a vector having elements of the DC component values of light (first measurement signal) and green light (second measurement signal) _{. k} ), G _DC = (G _DCn G _{DCn + 1} G _{DCn + 2} ... G _{DCn + k} ).

For each of the AC component vector and the DC component vector, the norm ratio of the red light (first measurement signal) vector to the green light (second measurement signal) is expressed by the following equations (7) and (8). Then, φ _{AC + DC} obtained by adding the norm ratios of the AC component and the DC component is obtained by the following equation (9). Note that equation (7), in equation (8), ‖R _AC ‖ ₂ shows a norm of a vector of the AC component of the first measurement signal, ‖G _AC ‖ ₂ vector of the AC component of the second measurement signal ‖R _DC ‖ ₂ represents the norm of the DC component vector of the first measurement signal, and ‖G _DC ‖ ₂ represents the norm of the DC component vector of the second measurement signal.

When the norm ratio between the stable period and the noise period is calculated by applying the expressions (3) and (4) to the expression (9), the norm ratios represented by the following expressions (10) and (11) are obtained. Incidentally, formula (10), in equation (11), ‖R _ACpulse ‖ ₂ norm of the AC component of the first measurement signal in the stable period, ‖G _ACpulse ‖ _2-norm of the AC component of the second measurement signal in the stable period , ‖R _DCpulse ‖ ₂ norm of the DC component of the first measurement signal in the stable period, ‖G _DCpulse ‖ ₂ is the norm of the DC component of the second measurement signal in the stable period. _{Further, ‖R ACnoise (jk: j +} k) || ₂ is the AC component of the first measurement signal in the noise period _{norm, ‖G ACnoise (jk: j +} k) || ₂ is AC of the second measurement signal in the noise period components of the _{norm, ‖R DCnoise (jk: j +} k) || ₂ is the DC component of the first measurement signal in the noise period _{norm, ‖G DCnoise (jk: j +} k) || ₂ is the second measurement signal in the noise period Is the norm of the DC component.

  Here, Expression (12) obtained by expanding the inverse matrix of Expression (6) is shown below.

  In the equation (12), when φ (J) n approaches the value of φs, the equation (12) diverges. When φ (J) n approaches the value of φs, it is considered that the measurement signal in the noise period is not affected by noise, and in this case, the separation processing according to Expression (12) is not performed. The AC component data of the green light (second measurement signal) is output as the pulsation component during that period. As described above, green light has a lower extinction coefficient for reduced hemoglobin than red light, and is considered to be less sensitive to venous blood. Therefore, it can be said that green light has a smaller noise component due to the increase in venous blood than red light, and well represents a pulsation signal.

  In the present embodiment, whether or not the norm ratio φ (J) n in the noise period is close to φs is determined by whether or not the norm ratio φ (J) n is within the threshold range defined by the lower limit coefficient m1 and the upper limit coefficient m2 based on φs. To do. That is, when φ (J) n in a certain noise period satisfies the condition of (m1 × φs) ≦ φ (J) n ≦ (m2 × φs), the norm ratio φ (J) n is close to φs. The data of the AC component of the second measurement signal in the noise period is determined as the pulsation component. On the other hand, if φ (J) n in a certain noise period does not satisfy the above condition, it is determined that the norm ratio φ (J) n is not close to φs, and the norm ratio obtained by the equation (10) is φs The norm ratio obtained by the above equation (11) is substituted into the equation (12) as φ (J) n, and the AC component of the first measurement signal and the second measurement signal measured in the noise period is used for the equation (12). 12), the pulsation signal (pulsation component) p and the noise signal (noise component) n are separated and the pulsation signal (pulsation component) p is output.

<Operation example>
Hereinafter, an operation example of the pulse wave measuring apparatus 1 according to the present embodiment will be described. 8 and 9 are diagrams showing an operation flow of the pulse wave measuring apparatus 1. FIG. In the following explanation, for convenience of explanation, the measurement subject moves the measurement site as a stable period so that the pulse wave is measured in a resting state so as not to be affected by the body movement of the measurement subject and the noise period. For example, a pulse wave is measured in a state in which the pulse wave is measured in advance under the influence of body motion, and the pulse wave is measured during the stable period, and then the pulse wave is measured during the noise period.

  In FIG. 8, when the control unit 110 of the pulse wave measuring device 1 accepts an operation for measuring a pulse wave via the operation unit 160 (step S10: YES), the pulse wave sensor 20 and the first light emitting / receiving unit 210 The red light and the green light reflected from the measurement part are respectively irradiated by irradiating the measurement part to which the pulse wave sensor 20 is alternately mounted from the two light receiving and emitting units 220 with a constant time interval. The first measurement signal and the second measurement signal corresponding to the received light amount are transmitted to the control unit 110 (step S11). If control unit 110 does not accept an operation for measuring a pulse wave via operation unit 160 (step S10: NO), control unit 110 waits until the operation is performed.

  In the signal processing unit 120, the control unit 110 acquires the first measurement signal and the second measurement signal transmitted from the pulse wave sensor 20, and obtains an AC component and a DC component from the first measurement signal and the second measurement signal. Extract each one. Then, in the signal processing unit 120, the control unit 110 amplifies and A / D-converts each AC component signal of the extracted first measurement signal and second measurement signal, and extracts the first measurement signal and the first measurement signal. The signals of the DC components of the two measurement signals are A / D converted, and the A / D converted AC components and DC component data are stored in the RAM in time series (step S12).

  The control unit 110 reads consecutive n pieces of data from the AC component and DC component data of the first measurement signal and the second measurement signal stored in the RAM, and the second AC component and DC component are read with respect to the second data. The norm ratio of the first measurement signal to the measurement signal is obtained by the equations (7) and (8), and the norm ratio (φs) in the stable period is obtained by adding the norm ratios of the AC component and the DC component by the equation (10). And the obtained norm ratio φs is stored in the RAM (step S13).

  Next, in FIG. 9, the control unit 110 also performs the processes of steps S <b> 10, S <b> 11, and S <b> 12 described above for the noise period, and the AC component and DC component of the first measurement signal and the second measurement signal stored in the RAM. 2k + 1 pieces of continuous data are read out from the data at time t = J as the base point, and the norm ratio (φ (J) n) at time J is obtained by equation (11) (step S24).

  When the norm ratio φ (J) n is within a predetermined threshold range (m1 × φs ≦ φ (J) n ≦ m2 × φs) based on the norm ratio (φs) of the stable period, the control unit 110 (Step S25: YES), the AC component data of the second measurement signal at time J is output as a pulsation component (step S26).

  On the other hand, when the norm ratio φ (J) n is not within a predetermined threshold range based on the norm ratio φs (m1 × φs ≦ φ (J) n ≦ m2 × φs), the control unit 110 (step S25: NO), the norm ratio φs and the norm ratio φ (J) n, and the values of the AC components of the first measurement signal and the second measurement signal at time J are substituted into equation (12) for calculation. A pulsation component and a noise component are separated from the first measurement signal and the second measurement signal at t = J. And the control part 110 outputs the data of the separated pulsation component as a pulsation component in the time J (step S27). If the instruction to end the measurement of the pulse wave in the noise period is not made via the operation unit 160 (step S28: NO), the control unit 110 increments the value of time t by 1 (step S29), and the first When the processing from step S24 described above is performed on the measurement signal and the second measurement signal and an instruction to end the pulse wave measurement in the noise period is given via the operation unit 160 (step 28: YES), the pulse wave End the measurement.

  FIGS. 10A and 10B are waveform diagrams of the respective norm ratios and the output results of the pulsation signal when the norm ratios (φs, φ (J) n) between the stable period and the noise period are calculated using only the AC component. It is a figure which shows the wave form diagram showing. 11A and 11B show a waveform diagram of each norm ratio and a waveform diagram of a pulsation signal when the norm ratios (φs, φ (J) n) are calculated by the method of the above-described embodiment. FIG. 10 and 11, the period A (0 to 20 sec) is a period during which a pulse wave is measured at the position of the heart at the measurement site, and the period B (20 to 50 sec) is the measurement site at the heart height. This was a period in which the pulse wave was measured by moving to a lower position, and the measurement was performed in a resting state so that noise due to body movement did not occur in any period. Moreover, in FIG. 10A and FIG. 11A, the broken line represents the norm ratio φs calculated by the equation (10) using the first measurement signal and the second measurement signal for 10 seconds from the start of measurement, The shaded portion indicates the threshold range of φs where the lower limit coefficient m1 = 0.8 and the upper limit coefficient m2 = 1.2. The solid line represents φ (J) n calculated by the equation (11) using the first measurement signal and the second measurement signal measured in the periods A and B. In this example, the solid line The width is 2 s (k = 100 when the sampling frequency is 100 Hz).

  As shown in FIGS. 10 (a) and 11 (a), the period A is a position where the measurement site is at the height of the heart and there is almost no influence of body movement, so the norm ratios φs and φ (J ) N is a close value, and a stable pulsation signal is output as shown in FIGS. 10 (b) and 11 (b). In FIG. 10 (a) and FIG. 11 (a), φ (J) n rises once under the influence of body movement due to movement in the vicinity of 20 seconds when the measurement site is moved to a position lower than the heart, and then falls. Yes. Since the measurement is performed in a resting state after moving the measurement site, the pulse wave should be stable as in the period A even if the venous blood volume changes after the measurement site is moved.

  However, as shown in FIG. 10 (a), the norm ratio φ (J) n calculated only by the AC component falls below the threshold range of φs due to the increase in venous blood volume. For this reason, it is determined that it is affected by noise due to body movement, separation processing is performed, and the pulsation signal in period B does not have a stable waveform as shown in FIG. On the other hand, φ (J) n in FIG. 11A is calculated using an AC component and a DC component. Therefore, even if the venous blood volume increases after movement of the measurement site, before and after movement. The difference in norm ratio φ (J) n is reduced and falls within the threshold range of norm ratio φs. As a result, as the pulsation signal in the period within the threshold range of the norm ratio φs, an AC component signal of green light (second measurement signal) is output, and a waveform with a stable pulse wave is obtained as in the period A. Yes.

  As described above, by outputting the pulsation signal by the method of the above-described embodiment, the change in norm ratio accompanying the change in venous blood volume is suppressed and the venous blood is compared with the case where the norm ratio is calculated using only the AC component. Noise due to an increase in volume and noise due to body movement are distinguished, and a pulsation signal that well represents the state of the measurement subject can be output.

<Modification>
The present invention is not limited to the above-described embodiment, and may be carried out by being modified as follows. Further, the following modifications may be combined.

(1) In the above-described embodiment, the pulse wave measurement device 1 including the pulse wave sensor 20 that can be attached to and detached from the measurement subject and the main body device 10 has been described. However, the first measurement signal and the second measurement signal are acquired. As long as the signal processing device has the functions of the signal processing unit 120 and the control unit 110 of the main body device 10, the configuration of the main body device 10 is not limited. For example, when a device such as a PC or a portable information terminal is used as the signal processing device, the first measurement signal and the second measurement signal output from the pulse wave sensor 20 are connected to the pulse wave sensor 20 by wired or wireless communication. May be obtained. The signal processing device reads the waveform data of the first measurement signal and the second measurement signal from the storage device in which the waveform data of the first measurement signal and the second measurement signal measured by the pulse wave sensor 20 is stored in advance. The first measurement signal and the second measurement signal may be acquired.

(2) In the above-described embodiment, an example using a light emitting element that emits red light and green light, respectively, has been described. The combination is not limited to this as long as the extinction coefficients for reduced hemoglobin and oxidized hemoglobin are different. In this case, the AC component of the light measurement signal whose extinction coefficient for reduced hemoglobin is lower or similar to that of oxyhemoglobin is output as a pulsating component.

(3) In the above-described embodiment, the example in which the period for measuring the pulse wave is provided as the stable period and the norm ratio φs is calculated using the measurement result of the stable period has been described. The norm ratio φs based on the measurement result measured in advance in a quiet state so as not to be received may be stored in the pulse wave measuring device 1 in advance. In this case, the pulse wave measuring apparatus 1 is configured to include a storage unit that stores the calculated norm ratio φs.

(4) In the above-described embodiment, the example in which the light reflected by the measurement site is received by the first light receiving and emitting unit 210 and the second light receiving and emitting unit 220 has been described. However, the light transmitted through the measurement site is received. It may be configured.

(5) In the above-described embodiment, the example in which the pulse wave sensor 20 is mounted using the index finger as the measurement site has been described. However, the measurement site may be a biological site such as the back of the hand, the wrist, the back of the foot, or the earlobe. It is not limited to this.

(6) In the above-described embodiment, the example in which the norm ratios φs and φ (J) n using the Euclidean norm are applied as the coefficients representing the correlation between the second measurement signal and the first measurement signal has been described. The norm ratios φs and φ (J) n may be calculated using the maximum norms of the AC and DC components of the first measurement signal and the second measurement signal in the noise period.

  DESCRIPTION OF SYMBOLS 1 ... Pulse wave measuring device, 10 ... Main body device, 15 ... Liquid crystal display, 16 ... Operation switch, 20 ... Pulse wave sensor, 30 ... Cable, 40 ... Band, DESCRIPTION OF SYMBOLS 110 ... Control part, 110a ... Output part, 120 ... Signal processing part, 121a, 121b, 124a, 124b ... Filter, 122-1, 122-2 ... Amplification circuit, 123-1 , 123-2, 123-3, 123-4 ... A / D conversion circuit, 130 ... timer, 140 ... clock supply unit, 150 ... display unit, 160 ... operation unit, 210: first light emitting / receiving unit, 220: second light emitting / receiving unit, 230: driving unit

Claims (9)

A first measurement signal based on a received light amount of light having a first wavelength transmitted through or reflected by the living body in a first measurement period and a second measurement period, which are measurement periods of a pulse wave of the living body; and obtaining means for obtaining a second measurement signal based on the received light amount of the received light to light of the second wavelength reflected by the transmitted or the biological the biological,
From the first measuring signal in the second measurement period before and Symbol first measurement period and a second measurement signal, a signal of the first frequency component, a second frequency of the lower frequency band than the frequency band of the first frequency component extraction means to extract the component of the signal,
Wherein the first measurement period extracted by the extracting means and the second signal of the first frequency component in the measurement period and the second frequency component of the signal and the based-out the second measurement signal and the first measurement signal The first coefficient and the second coefficient representing the correlation between the first coefficient and the second coefficient are calculated, and the second measurement period is calculated using the first coefficient and the second coefficient according to the difference between the first coefficient and the second coefficient. Separation processing for separating a pulsation component and a noise component included in the first measurement signal and the second measurement signal, and the first frequency component of the second measurement signal in the second measurement period as the pulsation component And an output means for selectively outputting the pulsating component in the second measurement period. And the output means, and the first coefficient value obtained by the following equation (1), the signal processing according to the value obtained by the following formula (2) in claim 1, characterized in that the said second coefficient apparatus.

‖RACpulse‖ ₂ is a norm of a first frequency component of the first measurement signal of the first measurement period.
‖GACpulse‖ ₂ is a norm of a first frequency component of the second measurement signal of the first measurement period.
‖RDCpulse‖ ₂ is a norm of a second frequency component of the first measurement signal of the first measurement period.
‖GDCpulse‖ ₂ is a norm of a second frequency component of the second measurement signal of the first measurement period.
‖RACnoise (jk: j + k) || ₂ is the norm of the first frequency component of the first measurement signal of the second measurement period.
‖GACnoise (jk: j + k) || ₂ is the norm of the first frequency component of the second measurement signal of the second measurement period.
‖RDCnoise (jk: j + k) || ₂ is the norm of the second frequency component of the first measurement signal of the second measurement period.
‖GDCnoise (jk: j + k) || ₂ is the norm of the second frequency component of the second measurement signal of the second measurement period.   When the difference between the first coefficient and the second coefficient is within a predetermined threshold range, the process using the first frequency component of the second measurement signal in the second measurement period as the pulsation component 3. The signal processing apparatus according to claim 2, wherein the separation processing using the first coefficient and the second coefficient is performed when the value is outside the range of the threshold value. 4. The light of the second wavelength, the signal processing according to any one of claims 1 to 3, wherein the absorption coefficient of reduced hemoglobin with respect to oxygenated hemoglobin than the light of the first wavelength is small apparatus. The said light of the first wavelength is irradiated to the living body, receiving the first light of a wavelength reflected by the transmitted or the biological the biological, and outputs the first measurement signal corresponding to the received light amount 1 light emitting and receiving unit;
The second light having a wavelength of irradiating the living body, and receiving the second light of the wavelength reflected by the transmitted or the biological the biological, and outputs the second measurement signal corresponding to the amount of received light Two light emitting and receiving parts;
Using the first measurement signal and the second measurement signal outputted from the first light receiving and emitting unit and the second light receiving and emitting unit, according to claim 1 from 4 outputting the ripple component in the second measurement period A pulse wave measuring device comprising: the signal processing device according to any one of the above. A first measurement period for measuring the pulse wave of the measurement target living body, in a second measurement period that is affected by the body movement of the living body, first wavelength reflected by the transmitted or the biological the biological an obtaining step of obtaining a second measurement signal based on the first measurement signal, and a light receiving amount of receiving light of the second wavelength reflected by the transmitted or the biological the biological based on the amount of received light and receiving light,
From the first measurement signal before Symbol first measurement period and the second measurement period and a second measurement signal, a signal of the first frequency component, a second frequency of the lower frequency band than the frequency band of the first frequency component An extraction step for extracting component signals;
Signal and the second frequency component of the signal and based-out the second measurement signal to said first measuring signal of the first frequency component in the first measurement period and the second measurement period extracted by the extraction step The first coefficient and the second coefficient representing the correlation between the first coefficient and the second coefficient are calculated, and the second measurement period is calculated using the first coefficient and the second coefficient according to the difference between the first coefficient and the second coefficient. Separation processing for separating a pulsation component and a noise component included in the first measurement signal and the second measurement signal, and the first frequency component of the second measurement signal in the second measurement period as the pulsation component And a step of outputting the pulsation component in the second measurement period selectively. Light having a first wavelength transmitted through the living body or reflected by the living body in a first measuring period, which is a measurement period of the pulse wave of the living body, and in a second measuring period, which is affected by body movement of the living body An acquisition means for acquiring a first measurement signal based on the amount of received light received and a second measurement signal based on the amount of received light having received the second wavelength light transmitted through or reflected by the living body;
From the first measurement signal and the second measurement signal in the first measurement period and the second measurement period, a signal of a first frequency component and a second frequency component in a frequency band lower than the frequency band of the first frequency component Extracting means for extracting the signal of
Wherein the first measurement period extracted by the extracting means and the second measurement period the second measuring signal based on a signal before SL signal and the second frequency component of the first frequency component that put on the first measurement signal The first coefficient and the second coefficient representing the correlation with each other are calculated, and the first measurement signal and the second measurement signal in the second measurement period are calculated using the first coefficient and the second coefficient. A signal processing apparatus comprising: a separation unit that separates a pulsation component and a noise component contained therein. The separating means sets a value obtained by adding each value of the first frequency component and the second frequency component of the first measurement signal to the second measurement signal in the first measurement period as the first coefficient, and The value obtained by adding each value of the first frequency component and the second frequency component of the first measurement signal with respect to the second measurement signal in two measurement periods is used as the second coefficient. Signal processing equipment. Light having a first wavelength transmitted through the living body or reflected by the living body in a first measuring period, which is a measurement period of the pulse wave of the living body, and in a second measuring period, which is affected by body movement of the living body Obtaining a first measurement signal based on the amount of received light received, and a second measurement signal based on the amount of received light having received the second wavelength of light transmitted through or reflected by the living body;
From the first measurement signal and the second measurement signal in the first measurement period and the second measurement period, a signal of a first frequency component and a second frequency component in a frequency band lower than the frequency band of the first frequency component An extraction step for extracting the signal of
Correlation between the second measurement signal and the first measurement signal based on the first frequency component signal and the second frequency component signal of the first measurement period and the second measurement period extracted by the extraction step. The first coefficient and the second coefficient representing the pulsation component and noise included in the first measurement signal and the second measurement signal in the second measurement period are calculated using the first coefficient and the second coefficient. Separating step to separate the components and
A signal processing method characterized by comprising:

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