Pulse wave signal processing device, biological information measuring device, and method for determining abnormal pressure.

Abstract

In the present invention, a pulse wave feature quantity calculation unit calculates a pulse wave feature quantity relating to the degree of steepness of a rise in a pulse wave measured using a photoelectric pulse wave sensor. A pressing force determination unit determines, on the basis of the value of the pulse wave feature quantity calculated by the pulse wave feature quantity calculation unit, whether or not a pressing force, which is the pressure at which the photoelectric pulse wave sensor is pressed against a site of measurement, falls within an appropriate range.

Description

Technical Field

[0001] The present invention relates to a pulse wave signal processing device, a biological information measuring device, and a pressing force abnormality determination method.

Background Art

[0002] As an index used for estimating a person's health condition, a pulse wave propagating in an artery is used. The pulse wave changes according to the change in blood flow volume at the measurement location. In wearable small electronic devices, a method of measuring a pulse wave using a photoelectric pulse wave sensor is convenient. For example, light is made incident from a light emitting element to a measurement site such as a finger, and the reflected light or transmitted light is detected by a light receiving element, and the change in blood flow volume is acquired as a pulse wave signal.

[0003] When the pressing force between the photoelectric pulse wave sensor and the measurement site deviates from the appropriate range, the amplitude of the detected pulse wave becomes small. Therefore, it is preferable to measure the pulse wave in a state where the photoelectric pulse wave sensor is brought into contact with the measurement site with an appropriate pressing force. In order to determine whether the pressing force is appropriate, a wristwatch-type pulse wave signal processing device incorporating a pressure sensor is known (Patent Document 1). This pulse wave signal processing device displays the current pressing force level detected by the pressure sensor on a display device. When the value of the pressing force is out of the appropriate range, the pulse wave signal processing device is vibrated to notify the user.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Conventional pulse wave signal processing devices are equipped with a pressure sensor to determine whether the pressing force is appropriate. As pulse wave signal processing devices become smaller, it can become difficult to mount the pressure sensor. Furthermore, because the mounting position of the pressure sensor differs from the mounting position of the light-emitting element or light-receiving element, even if the pressing force value at the pressure sensor's position is appropriate, it does not necessarily mean that the pressing force at the mounting position of the light-emitting element or light-receiving element is appropriate.

[0006] An object of the present invention is to provide a pulse wave signal processing device capable of determining whether the pressing force of a light-emitting element or a light-receiving element on a measurement point is within an appropriate range without using a pressure sensor. Another object of the present invention is to provide a biological information measurement device equipped with this pulse wave signal processing device. Yet another object of the present invention is to provide a pressing force abnormality determination method capable of determining whether the pressing force is within an appropriate range without using a pressure sensor. [Means for solving the problem]

[0007] According to one aspect of the present invention, With a photoplethysmography sensor Using light contained in the wavelength range of 600 nm to 950 nm A pulse wave feature calculation unit calculates pulse wave features related to the steepness of the rise of the measured pulse wave, Based on the value of the pulse wave feature calculated by the pulse wave feature calculation unit, the pressing force, which is the pressure applied when the photoelectric pulse wave sensor is pressed against the area to be measured, Isn't that excessive? A pressure determination unit that determines whether or not A pulse wave signal processing device equipped with [a specific feature] is provided.

[0008] According to another aspect of the present invention, The pulse wave signal processing device described above, The photoelectric pulse wave sensor measures the pulse wave of the area to be measured and inputs the measurement result to the pulse wave signal processing device. Equipped with, The photoplethysmography sensor provides a biological information measurement device that includes at least one light-emitting element and a light-receiving element that detects light reflected from the at least one light-emitting element at the measurement site or light transmitted through the measurement site.

[0009] According to yet another aspect of the present invention, The pulse wave features related to the steepness of the rise of the pulse wave measured by a photoelectric pulse wave sensor in contact with the area being measured are calculated. A method for determining whether the pressing force, which is the pressure applied when the photoelectric pulse wave sensor is pressed against the area to be measured, is abnormal is provided, based on the value of the pulse wave feature obtained by calculation. [Effects of the Invention]

[0010] The pressure is determined from pulse wave features related to the steepness of the rise of the pulse wave. Isn't that excessive? To determine whether or not it is present, there is no need to install a pressure sensor that directly measures the pressing force. Therefore, it is possible to miniaturize the device that comes into contact with the area being measured. Furthermore, the pressing force is Isn't that excessive? To determine whether or not, pulse waves are used, so the pressing force is not excessive Based on the determined pulse wave, highly reliable biometric information can be calculated. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a block diagram of a pulse wave signal processing device according to the first embodiment, and a schematic diagram of a biological information measurement device equipped with the pulse wave signal processing device. [Figure 2] Figure 2 is a graph showing examples of pulse waves, velocity pulse waves, and acceleration pulse waves. [Figure 3] Figure 3 is a graph showing an example of a pulse wave and an acceleration pulse wave. [Figure 4]FIG. 4A, FIG. 4B, FIG. 4C, and FIG. 4D are graphs showing the relationship between the values of the pulse wave characteristic quantities obtained from the pulse waves measured when the height from the heart to the measurement site (finger) is changed and the systolic blood pressure measured at the wrist, and when the vicinity of the elbow on the side where the finger as the measurement site is cooled to match the height of the chest. [Figure 5] FIG. 5 is a graph showing an example of the time change of the amount of light received by the light receiving element when near-infrared light is output from the light emitting element in a state where the photoelectric pulse wave sensor is in contact with the measurement site. [Figure 6] FIG. 6 is a graph showing the waveform shapes of the pulse waves for approximately one minute when the pressing force of the photoelectric pulse wave sensor on the measurement site is within the appropriate range and excessive. [Figure 7] FIG. 7 is a graph showing the time change of the elapsed time from the peak of the a-wave to the peak of the b-wave of the pulse wave shown in FIG. 5. [Figure 8] FIG. 12 is a graph showing the time change of the pulse wave characteristic quantity "1 / (VE0.5)" calculated from the pulse wave shown in FIG. 5. [Figure 9] FIG. 15 is a graph showing the time change of the pulse wave characteristic quantity "a / S" calculated from the pulse wave shown in FIG. 5. [Figure 10] FIG, 18 is a graph showing the time change of the pulse wave characteristic quantity "(a - b) / (a - d)" calculated from the pulse wave shown in FIG. 5. [Figure 11] FIG. 11 is a flowchart showing the procedure of the pressing force abnormality determination method according to the first embodiment. [Figure 12] FIG. 12 is a block diagram of the pulse wave signal processing device according to the second embodiment and a schematic diagram of the biological information measuring device including the pulse wave signal processing device. [Figure 13] FIG. 13 is a graph showing an example of the time change of the amount of light received by the light receiving element when near-infrared light and green light are respectively output from two light emitting elements in a state where the photoelectric pulse wave sensor is in contact with the measurement site. [Figure 14] FIG. 14 is a graph showing the waveform shapes of the pulse waves by green light for approximately one minute when the pressing force of the photoelectric pulse wave sensor on the measurement site is within the appropriate range and excessive. [Figure 15] Figure 15 is a graph showing the time change of the pulse wave feature "ab time" calculated from the pulse wave shown in Figure 13. [Figure 16] Figure 16 is a graph showing the time evolution of the pulse wave feature "1 / (VE0.5)" calculated from the pulse wave shown in Figure 13. [Figure 17] Figure 17 is a graph showing the time change of the pulse wave feature "a / S" calculated from the pulse wave shown in Figure 13. [Figure 18] Figure 18 is a graph showing the time evolution of the pulse wave feature "(ab) / (ad)" calculated from the pulse wave shown in Figure 13. [Figure 19] Figure 19 is a graph showing the pulse wave feature "ab time" calculated based on pulse waves obtained from multiple subjects. [Figure 20] Figure 20 is a graph showing the pulse wave feature value "1 / (VE0.5)" calculated based on pulse waves obtained from multiple subjects. [Figure 21] Figure 21 is a graph showing the pulse wave feature "a / S" calculated based on pulse waves obtained from multiple subjects. [Figure 22] Figure 22 is a graph showing the pulse wave feature coefficient "(ab) / (ad)" calculated based on pulse waves obtained from multiple subjects. [Figure 23] Figure 23 is a block diagram of a pulse wave signal processing device according to a modification of the second embodiment, and a schematic diagram of a biological information measurement device equipped with the pulse wave signal processing device. [Figure 24] Figure 24 shows a perspective view and a block diagram of a part of the biological information measurement device according to the third embodiment. [Modes for carrying out the invention]

[0012] [First Embodiment] Referring to Figures 1 to 11, the pulse wave signal processing device, biological information measurement device, and pressing force abnormality determination method according to the first embodiment will be described.

[0013] Pulse waves are used to measure various types of biological information. For example, they are used to measure pulse rate and oxygen saturation. In addition, they are used to measure autonomic nervous system function based on fluctuations in pulse intervals, and to measure respiratory rate based on baseline fluctuations and fluctuations in pulse intervals of the pulse wave. Furthermore, techniques have been developed to estimate blood pressure from the waveform shape of the pulse wave. Pulse waves are classified into pressure pulse waves (piezoelectric pulse waves), which are measured using piezoelectric sensors, and volume pulse waves (photoelectric pulse waves), which are measured using photoelectric pulse wave sensors.

[0014] The pulse wave signal processing device according to the first embodiment is applicable to both piezoelectric pulse waves and photoelectric pulse waves. More information can be obtained from photoelectric pulse waves than from piezoelectric pulse waves. The following explanation will use photoelectric pulse waves as an example.

[0015] Figure 1 is a block diagram of the pulse wave signal processing device 30 according to the first embodiment, and a schematic diagram of a biological information measurement device equipped with the pulse wave signal processing device 30. The biological information measurement device includes the pulse wave signal processing device 30 and a photoelectric pulse wave sensor 50. The photoelectric pulse wave sensor 50 includes a light-emitting element 51 and a light-receiving element 53. The pulse wave signal processing device 30 includes a light-emitting control unit 31, a pulse wave feature calculation unit 32, a pressure determination unit 33, an abnormality notification unit 34, a control unit 35, and a pulse wave measurement unit 36.

[0016] The light-emitting element 51 and the light-receiving element 53 are used in contact with the user's body surface 70. The light-emitting element 51 emits measurement light toward the body surface 70. The emitted light is absorbed, reflected, or scattered (hereinafter sometimes simply referred to as "reflected") by the epidermal region 71, arterioles 72, and capillaries 73 within the body surface 70. A portion of the reflected light enters the light-receiving element 53.

[0017] Arterioles 72 are, for example, thin blood vessels with a diameter of 20 μm to 200 μm, and are located between arteries and capillaries 73. Multiple capillaries 73 branch off from arterioles 72. Capillaries 73 are, for example, thin blood vessels with a diameter of about 10 μm, and connect arteries and veins. Multiple capillaries 73 are distributed in a shallower region than the region where arterioles 72 are distributed. Note that the arrows shown in Figure 1 do not indicate the path of light propagation, but rather indicate that the light output from the light-emitting element 51 passes through the epidermal region 71, the region where capillaries 73 are distributed, and the region where arterioles are distributed before entering the photodetector 53.

[0018] The light-emitting element 51 outputs light for measurement under the control of the light-emitting control unit 31. A signal indicating the intensity of the light measured by the photodetector 53 is input to the pulse wave feature calculation unit 32. The signal indicating the intensity of the light detected by the photodetector 53 is called the "pulse wave signal". Arterial blood contains hemoglobin, and hemoglobin has the property of absorbing the light for measurement. Blood flow changes with the beating of the heart, and the amount of light absorbed changes in accordance with the change in blood flow. For this reason, the intensity of the pulse wave signal changes with the beating of the heart.

[0019] As the light-emitting element 51, for example, one that outputs light in the wavelength range from blue to near-infrared (wavelength range of 450 nm to 950 nm) is used. Examples of light-emitting elements 51 include light-emitting diodes (LEDs) and vertical-cavity surface-emitting lasers (VCSELs). Examples of light-receiving elements 53 include photodiodes (PDs) and phototransistors.

[0020] Light with wavelengths shorter than 450 nm can damage biological tissue. In the wavelength range longer than 950 nm, the absorbance of hemoglobin decreases. Therefore, it is preferable to use light in the wavelength range of 450 nm to 950 nm for acquiring pulse wave signals. Furthermore, an inexpensive Si photodiode can be used as the photodetector element 53 for detecting light in this wavelength range.

[0021] The control unit 35 controls the start and end of measurement, displays the measurement results, etc. The light emission control unit 31 controls the pulsed emission of the light-emitting element 51. For example, it causes the light-emitting element 51 to emit pulsed light at a predetermined frequency of 100 Hz to 1000 Hz.

[0022] The pulse wave measurement unit 36 ​​generates a pulse wave waveform (hereinafter sometimes simply referred to as "pulse wave") from the measurement result (pulse wave signal) input from the light-receiving element 53. For example, the pulse wave measurement unit 36 ​​generates a pulse wave by reading the measured value of light intensity from the light-receiving element 53 at a predetermined sampling rate in synchronization with the pulse emission of the light-emitting element 51.

[0023] The pulse wave feature calculation unit 32 calculates pulse wave features (hereinafter referred to as pulse wave features) from the pulse wave generated by the pulse wave measurement unit 36. For example, the pulse wave is separated into individual beats, and pulse wave features are obtained from the pulse wave of each beat.

[0024] Biological information such as pulse rate, oxygen saturation, respiratory rate, blood pressure in major arteries, blood pressure in capillaries and arterioles (peripheral blood pressure), blood flow rate, vascular resistance, degree of arteriosclerosis, blood glucose level, hemodynamics, and autonomic nervous system state are reflected in the pulse wave features. Therefore, this biological information can be estimated from the pulse wave features obtained by the pulse wave signal processing device 30. The pulse wave features obtained from pulse waves actually measured using the photoelectric pulse wave sensor 50 are easily affected by the pressure applied when the photoelectric pulse wave sensor 50 is pressed against the body. Therefore, when estimating various biological information from pulse wave features, the reliability of the estimation results decreases if the pressure is not within the appropriate range.

[0025] The pressure determination unit 33 determines whether the pressure applied by the light-emitting element 51 and the light-receiving element 53 to the body surface 70 is appropriate, based on the pulse wave feature calculated by the pulse wave feature calculation unit 32. If the pressure value is outside the appropriate range (i.e., the pressure value is abnormal), the abnormality notification unit 34 notifies the user of the abnormal pressure. For example, the abnormal pressure is notified by sound, vibration, light, etc.

[0026] Next, we will describe pulse wave features that can be used to estimate biological information. Figure 2 is a graph showing an example of a pulse wave, velocity pulse wave, and acceleration pulse wave. The pulse wave feature calculation unit 32 performs first and second derivatives on the pulse wave. The waveforms obtained by first and second derivatives of the pulse wave are referred to as the velocity pulse wave and acceleration pulse wave, respectively. For example, the velocity pulse wave is obtained by numerically differentiating the intensity of the pulse wave, which is discretely distributed over time intervals corresponding to the sampling rate, over time intervals corresponding to the sampling rate. Furthermore, the acceleration pulse wave is obtained by numerically differentiating the magnitude of the velocity pulse wave.

[0027] In Figure 2, the horizontal axis represents time in seconds (s), the left vertical axis represents the magnitude of the velocity and acceleration pulse waves normalized to a maximum value of 1, and the right vertical axis represents the magnitude of the pulse wave in arbitrary units. The solid line, long dashed line, and short dashed line in the graph shown in Figure 2 represent the pulse wave, velocity pulse wave, and acceleration pulse wave, respectively. Generally, five peaks appear in the acceleration pulse wave within one beat. The first, second, third, fourth, and fifth peaks within one beat are called waves a, b, c, d, and e, respectively.

[0028] Figure 3 is a graph showing an example of a pulse wave and an acceleration pulse wave. The horizontal axis represents time, the left vertical axis represents the magnitude of the pulse wave in arbitrary units, and the right vertical axis represents the magnitude of the acceleration pulse wave in arbitrary units. Five divisions on the horizontal axis correspond to 0.2 seconds. The ratio of the pulse wave amplitude S to the peak value a of the a-wave of the acceleration pulse wave is denoted as "a / S". Note that the pulse wave amplitude S corresponds to the difference between the minimum and maximum values ​​after waveform correction so that the minimum values ​​of two consecutive pulse waves are the same magnitude.

[0029] Next, we will explain how to estimate blood pressure from pulse waves. In this specification, peripheral blood pressure refers to blood pressure in peripheral arterioles and capillaries. While the term "peripheral blood pressure" is sometimes used to mean blood pressure measured at the wrist or ankle with a cuff-type blood pressure monitor, blood pressure measured at the wrist or ankle is measured in a large artery (such as the radial artery) and differs from the blood pressure measured in arterioles and capillaries as defined herein. Blood pressure decreases as it progresses from large arteries to arterioles and then to capillaries. The degree to which blood pressure decreases varies depending on the measurement site, the user's vascular condition (e.g., arteriosclerosis), mental state (autonomic nervous system state), environment (temperature, noise, etc.), and type of clothing worn.

[0030] The following two assumptions are made regarding the characteristics of peripheral blood pressure. First, peripheral blood pressure has a positive correlation with blood pressure measured in the upper arm or wrist using a cuff-type blood pressure monitor, under conditions where the blood vessels are healthy and vascular resistance does not change. Second, cooling the vicinity of the measurement site to constrict blood vessels will decrease peripheral blood pressure. However, if peripheral blood vessels constrict and vascular resistance increases, blood pressure in the upper arm or wrist may increase.

[0031] The following three features are examples of pulse wave features that reflect the two characteristics mentioned above. • The reciprocal of the full width at half maximum (FMAX) of the first upward peak of the velocity pulse wave (hereinafter, FMAX will be denoted as VE0.5) ("1 / (VE0.5)"). The ratio of the amplitude S of the pulse wave to the peak value a of the a-wave of the acceleration pulse wave (hereinafter referred to as "a / S"). • The ratio of the difference between the peak values ​​of wave a and wave b of the acceleration pulse wave (ab) to the difference between the peak values ​​of wave a and wave d (ad) (hereinafter referred to as "(ab) / (ad)"). In this specification, these pulse wave characteristics will be referred to as "peripheral blood pressure indices."

[0032] The following features are pulse wave features that have characteristics similar to peripheral blood pressure indices. The reciprocal of the elapsed time from the peak of wave a to the peak of wave b (hereinafter referred to as "1 / (ab hours)").

[0033] Figures 4A, 4B, 4C, and 4D are graphs showing the relationship between pulse wave feature values ​​obtained from pulse waves measured when the height from the heart to the measurement site (finger) was changed, and when the measurement site was adjusted to chest height and the area near the elbow on the side with the finger was cooled, and systolic blood pressure measured at the wrist. Near-infrared light was used to measure the pulse waves. Near-infrared light penetrates not only the shallow region where capillaries 73 are distributed as shown in Figure 1, but also the deeper region where arterioles 72 are distributed. Therefore, the measured pulse waves reflect fluctuations in blood flow in both arterioles 72 and capillaries 73.

[0034] When using near-infrared light for measurement, the preferred range of the distance L1 (Figure 1) from the light-receiving element 53 to the light-emitting element 51 will be described. Here, distance L1 refers to the straight-line distance from the light-emitting point of the light-emitting element 51 to the light-receiving point of the light-receiving element 53. When distance L1 is short, the amount of light received from a very shallow region from the body surface 70 of the area to be measured becomes relatively stronger than the amount of light received from a deeper region. As a result, the influence of blood flow in the arterioles 72 becomes less likely to appear in the pulse wave. Conversely, when distance L1 is long, the amount of light received by the light-receiving element 53 decreases. In order to reflect the influence of blood flow in the arterioles 72 in the pulse wave and to ensure a sufficient amount of light received, it is preferable to set the distance L1 to 5 mm or more and 20 mm or less.

[0035] The horizontal axis of each graph from Figure 4A to Figure 4D represents systolic blood pressure at the wrist in units [mmHg]. The vertical axis of Figure 4A represents the pulse wave feature "1 / (VE0.5)" in units [s -1 The vertical axis of Figure 4B represents the pulse wave feature "a / S" in arbitrary units. The vertical axis of Figure 4C represents the pulse wave feature "(ab) / (ad)" in dimensionless units. The vertical axis of Figure 4D represents the pulse wave feature 1 / (ab time) in units [s -1 Represented by ].

[0036] In each graph, the measurement results for three subjects, A, B, and C, are shown using triangle, square, and circle symbols, respectively. The three hollow symbols shown for each subject represent the pulse wave feature values ​​obtained from pulse waves acquired with the height of the measurement site (finger) set to the height of the abdomen (navel), chest, and face, respectively. The pulse wave feature values ​​decrease in the order of the height of the measurement site: abdomen, chest, and face. The solid black symbols shown for each subject represent the pulse wave feature values ​​obtained from pulse waves acquired with the height of the measurement site set to chest height and the area near the elbow cooled.

[0037] Although there are differences among subjects, when the height of the measurement site is changed, each of the four pulse wave features generally shows a positive correlation with systolic blood pressure at the wrist.

[0038] Regarding the pulse wave features "1 / (VE0.5)", "a / S", and "(ab) / (ad)", cooling the elbow tends to decrease these features and increase systolic blood pressure. These trends are consistent with the characteristics of peripheral blood pressure described above. Note that the pulse wave feature "1 / (ab time)" may increase in some subjects when the elbow is cooled.

[0039] The pulse wave features "1 / (VE0.5)", "a / S", "(ab) / (ad)", and "1 / (ab time)" depend on the steepness of the pulse wave's rise. These features are less affected by the intensity of the pulse wave signal. Note that the peak values ​​a of wave a, b of wave b, d of wave d, and pulse wave amplitude S of the acceleration pulse wave, which are used to calculate the pulse wave features "a / S" and "(ab) / (ad)", each fluctuate with the intensity of the pulse wave signal, but by taking their ratios, the influence of intensity is almost eliminated.

[0040] Next, we will explain how to determine whether the pressing force is outside the appropriate range (i.e., whether it is abnormal).

[0041] Figure 5 is a graph showing an example of the time change in the amount of light received by the photodetector 53 when near-infrared light is output from the light-emitting element 51 with the photoplethysmography sensor 50 (Figure 1) in contact with the area to be measured. The horizontal axis represents time in units of [s], and the vertical axis represents the amount of light received on an arbitrary scale. A pulse wave is shown in which the amount of light received increases and decreases with each beat. The shape of a pulse wave is generally known to be a convex triangle that is raised upwards, but in Figure 5, the top and bottom are reversed, and a waveform with a convex triangle shape that is raised downwards is shown.

[0042] From 8s to 19s on the horizontal axis, the pressure applied by the photoelectric pulse wave sensor 50 to the measurement site was increased. It can be seen that when the pressure is increased, the average value of the received light increases, and the amplitude of the pulse wave decreases. The increase in the average value of the received light is due to the blood flow being obstructed by the excessive pressure.

[0043] Figure 6 is a graph showing the waveform shape of approximately one pulse for when the pressure applied by the photoelectric pulse wave sensor 50 to the measurement site is within the appropriate range and when it is excessive. The horizontal axis represents time, and the vertical axis represents the amount of light received. The thick solid and dashed lines in the graph represent the pulse waves when the pressure is within the appropriate range and when it is excessive, respectively. Note that the waveforms have been corrected so that the minimum values ​​and amplitudes of both are approximately equal. It can be seen that when the pressure is excessive, the rise of the pulse wave is steeper compared to when the pressure is normal. Thus, when the pressure is excessive, the waveform shape of the pulse wave changes. It is possible to determine whether the pressure is within the appropriate range or not by the change in the steepness of the rise of the pulse wave.

[0044] Figure 7 is a graph showing the time change of the elapsed time from the peak of wave a to the peak of wave b of the pulse wave shown in Figure 5 (hereinafter referred to as the pulse wave feature "ab time"). The horizontal axis represents time in units of [s], and the vertical axis represents the magnitude of the pulse wave feature "ab time" in units of [s]. It can be seen that the "ab time" is shorter during periods when the pressing force is excessive. By detecting this fluctuation in "ab time", it is possible to determine whether or not the pressing force is abnormal.

[0045] The pulse wave feature "ab time" is used to determine abnormal pressure. For example, a threshold can be set in advance, and if "ab time" is below the threshold, it can be determined that the pressure is abnormal. Alternatively, the reciprocal of the pulse wave feature "ab time" can be used to determine abnormal pressure; if the reciprocal of "ab time" is above the threshold, it can be determined that the pressure is abnormal.

[0046] Figures 8, 9, and 10 are graphs showing the time evolution of the pulse wave features "1 / (VE0.5)", "a / S", and "(ab) / (ad)", respectively, calculated from the pulse wave shown in Figure 5. The horizontal axis represents time in units of [s]. The vertical axis of Figure 8 represents the pulse wave feature "1 / (VE0.5)" in units of [s]. -1 The figures are represented as follows: the vertical axis in Figure 9 represents the pulse wave feature "a / S" in arbitrary units, and the vertical axis in Figure 10 represents the pulse wave feature "(ab) / (ad)" in dimensionless units. Both pulse wave features show that the pressure is greater during periods of excessive pressure compared to periods of appropriate pressure.

[0047] These pulse wave features are related to the steepness of the pulse wave's rise. The fact that these features increase during periods of excessive pressure can be explained as follows.

[0048] When pressure is applied to the skin, the capillaries are compressed, and blood flow is obstructed. As a result, blood stagnates in the arterioles, which are upstream of the capillaries, and the blood pressure in the arterioles rises. When near-infrared light is used as the light source for measurement, the effect of the rise in blood pressure in arterioles 72 is strongly expressed, and it is thought that these pulse wave characteristics used as peripheral blood pressure indicators will be enlarged.

[0049] When the pressing force becomes excessive, the pulse wave features "1 / (VE0.5)", "a / S", and "(ab) / (ad)" increase. For example, by setting a judgment threshold in advance, it is possible to determine that the pressing force is abnormal when these pulse wave features exceed the judgment threshold.

[0050] Figure 11 is a flowchart showing the procedure for determining abnormal pressure according to the first embodiment. Each step shown in Figure 11 is executed by the pulse wave feature calculation unit 32 (Figure 1).

[0051] First, the pulse wave feature calculation unit 32 (Figure 1) acquires the pulse wave signal from the light-receiving element 53 (Step S1). Then, the velocity pulse wave is obtained by first differentiating the pulse wave, and the acceleration pulse wave is obtained by second differentiating the pulse wave (Step S2). Based on the pulse wave, velocity pulse wave, and acceleration pulse wave, pulse wave features are calculated and stored for each heartbeat (Step S3). For example, at least one of the pulse wave features "ab time" shown in Figure 7, the pulse wave feature "1 / (VE0.5)" shown in Figure 8, the pulse wave feature "a / S" shown in Figure 9, and the pulse wave feature "(ab) / (ad)" shown in Figure 10 is calculated and stored.

[0052] Based on the calculated pulse wave features, it is determined whether the pressure is abnormal or not (step S4). For example, the pressure is determined whether it is abnormal or not by comparing the magnitude of the calculated pulse wave features with a determination threshold (step S4). Note that the pulse wave feature value may be the average value of the pulse wave feature values ​​calculated for each of the multiple heartbeats up to the present time over a certain period of time or the average value over a certain number of beats.

[0053] If the pressure value is normal, various biological information, such as blood pressure, is determined based on the pulse wave, velocity pulse wave, and acceleration pulse wave (step S5). In addition, it is possible to calculate the peak time of the waveform for each beat, calculate the peak time difference between beats to calculate the pulse rate for each beat, and determine autonomic nervous system function from the time-series data of the pulse rate using the maximum entropy method, etc. The procedure from step S1 to step S5 is repeated until the user performs the termination operation (step S7). If the pressure value is abnormal, the abnormality notification unit 34 (Figure 1) is activated to notify the user of the abnormality (step S6), and the process is terminated.

[0054] Next, we will describe the excellent effects of the first embodiment. In the first embodiment, if the pressing force is abnormal, the user is notified of the abnormality (step S6), so the user can know that the reliability of the calculated values ​​of various indicators related to biological information has decreased due to the abnormal pressing force value. Furthermore, the user can adjust the pressing force so that it becomes normal.

[0055] In the first embodiment, since information is obtained from the pulse wave to determine whether the pressing force is abnormal or not, there is no need to mount a pressure sensor for measuring the pressing force in the bio-information measurement device. This makes it possible to miniaturize and reduce the cost of the bio-information measurement device.

[0056] Another method for determining whether the pressing force is abnormal without using a pressure sensor is to determine whether the pressing force is abnormal based on the absolute value of the amount of light received by the light-receiving element 53 (Figure 1). However, the absolute value of the amount of light received fluctuates depending on the blood circulation status of the area being measured. For example, poor blood circulation increases the amount of light received. Furthermore, the absolute value of the amount of light received also fluctuates depending on the area being measured. For example, the ventral side of the distal phalanx of the finger has a higher blood vessel density than the dorsal side of the finger, the middle phalanx, the proximal phalanx, the back of the hand, and the wrist. The absolute value of the amount of light received fluctuates depending on the blood vessel density of the area being measured. In addition, the absolute value of the amount of light received also fluctuates depending on the skin color. For example, if the skin is dark due to a lot of melanin, the amount of light received decreases.

[0057] Thus, since the absolute value of the amount of light received is affected by various factors other than the pressing force, the accuracy of the determination decreases when the method of determining whether the pressing force is abnormal or not is based on the absolute value of the amount of light received. In the first embodiment, since the absolute value of the amount of light received is not used to determine whether the pressing force is normal or not, it is possible to eliminate the influence of various factors that affect the intensity of the light-receiving material and maintain a high level of determination accuracy.

[0058] Next, a modified example of the first embodiment will be described. In the first embodiment, at least one of the pulse wave features "ab time", "1 / (VE0.5)", "a / S", and "(ab) / (ad)", which are affected by the steepness of the rise of the pulse wave, is used to determine whether the pressing force is abnormal or not. However, other pulse wave features that are affected by the steepness of the rise of the pulse wave may also be used. It is preferable to use a pulse wave feature that is less affected by fluctuations in the absolute value of the amount of light received by the photodetector 53.

[0059] In the first embodiment, the measurement of pulse wave characteristics using near-infrared light is used to determine abnormalities in pressing force. However, light in other wavelength ranges in which the pulse wave characteristics change when the pressing force is excessive may be used as the measurement light. In addition to near-infrared light, red light may also be used. For example, light included in the wavelength range of 600 nm to 950 nm may be used as the measurement light.

[0060] In the first embodiment, if it is determined in step S4 (Figure 11) that the pressing force is abnormal, the user is notified of the abnormal pressing force in step S6 (Figure 11). In addition, various biometric information calculated from the pulse wave, such as pulse wave frequency, oxygen saturation, autonomic nerve function, respiratory rate, blood pressure, vascular resistance, blood flow rate, peripheral blood pressure index, hemodynamics, and blood glucose level, may be displayed, and the user may be notified that the reliability of these measured values ​​is low because the pressing force is abnormal. Furthermore, it is advisable to notify the user to reduce the pressing force.

[0061] Since frequent notifications of these conditions can be annoying to users, it may be better to not send notifications normally, and only send a notification if excessive pressure persists for a long period, such as several hours or more, to alert users to the abnormal pressure.

[0062] [Second Example] Next, with reference to Figures 12 to 22, the pulse wave signal processing device, biometric information measuring device, and pressure abnormality determination method according to the second embodiment will be described. Hereinafter, the configurations common to the pulse wave signal processing device, biometric information measuring device, and pressure abnormality determination method according to the first embodiment, which were described with reference to Figures 1 to 11, will be omitted from the explanation.

[0063] Figure 12 is a block diagram of the pulse wave signal processing device 30 according to the second embodiment, and a schematic diagram of a bio-information measurement device equipped with the pulse wave signal processing device 30. In the bio-information measurement device according to the first embodiment (Figure 1), the photoelectric pulse wave sensor 50 includes one light-emitting element 51 and one light-receiving element 53. In contrast, the photoelectric pulse wave sensor 50 of the bio-information measurement device according to the second embodiment includes another light-emitting element 52 in addition to the light-emitting element 51.

[0064] The two light-emitting elements 51 and 52 emit light of different wavelengths. For example, one light-emitting element 51 emits near-infrared light with a wavelength of 850 nm to 950 nm, while the other light-emitting element 52 emits green light with a wavelength of 500 nm to 550 nm. Alternatively, light-emitting element 52 may emit light with wavelengths ranging from blue to yellow-green. The light-emitting element 52 is positioned closer to the light-receiving element 53 than the light-receiving element 51. The distance from the light-receiving element 53 to the light-emitting element 52 is denoted as L2. Near-infrared light is absorbed less by living organisms than green light. Therefore, it penetrates deeper into living tissue.

[0065] Therefore, when near-infrared light is used as the light source for measurement, fluctuations in blood flow in arterioles 72 distributed in deeper regions are largely reflected in the pulse wave. When green light is used as the light source for measurement, the light does not penetrate to the deeper regions where arterioles 72 are distributed, so fluctuations in blood flow in capillaries 73 distributed in shallower regions are largely reflected in the pulse wave, while fluctuations in blood flow in arterioles 72 are not easily reflected in the pulse wave. The arrows from the light-emitting element 51 to the light-receiving element 53 shown in Figure 12 represent that information regarding the blood flow of arterioles 72 is reflected in the amount of light received by the light-receiving element 53. The arrows from the light-emitting element 52 to the light-receiving element 53 represent that information regarding the blood flow of capillaries 73 is reflected in the amount of light received by the light-receiving element 53, while information regarding the blood flow of arterioles 72 is not substantially reflected in the amount of light received by the light-receiving element 53.

[0066] The distance L1 is preferably 5 mm to 20 mm, as described in the first embodiment. The distance L2 is preferably 1 mm to 3 mm in order to efficiently acquire information from areas shallow to the body surface 70.

[0067] The light emission control unit 31 causes the two light-emitting elements 51 and 52 to emit light at different times. The pulse wave measurement unit 36 ​​synchronizes the timing of receiving the light intensity signal from the light-receiving element 53 with the timing of the light emission of the light-emitting elements 51 and 52, thereby separating and acquiring the pulse wave using near-infrared light and the pulse wave using green light.

[0068] Figure 13 is a graph showing an example of the time change in the amount of light received by the light-receiving element 53 when the photoplethysmography sensor 50 is in contact with the area to be measured and near-infrared light and green light are output from the light-emitting elements 51 and 52, respectively. The horizontal axis represents time in units of [s], and the vertical axis represents the amount of light received on an arbitrary scale. The thick solid and dashed lines in the graph shown in Figure 13 represent the time change in the amount of light received (photoplethysmography) when near-infrared light and green light are used as the light source for measurement, respectively. The photoplethysmography when near-infrared light is used as the light source for measurement is the same as the photoplethysmography shown in Figure 5.

[0069] During the period when the pressure applied by the photoelectric pulse wave sensor 50 to the measurement site was excessive, it was observed that, similar to the pulse wave obtained with near-infrared light, the average value of the received light increased and the amplitude of the pulse wave decreased. The increase in the average value of the received light is due to the blood flow being obstructed by the excessive pressure.

[0070] Figure 14 is a graph showing the waveform shape of the pulse wave for approximately one beat using green light, when the pressing force of the photoelectric pulse wave sensor 50 on the measurement site is within the appropriate range and when it is excessive. The horizontal axis represents time, and the vertical axis represents the amount of light received. The thick solid and dashed lines in the graph show the pulse wave waveform when the pressing force is within the appropriate range and when it is excessive, respectively. It can be seen that the change in the pulse wave due to pressing force fluctuations using green light is smaller than the change in the pulse wave due to pressing force fluctuations using near-infrared light (Figure 6). For example, the difference in the steepness of the rise of the waveform between the case where the pressing force is appropriate and the case where it is excessive is smaller than when near-infrared light is used.

[0071] Figure 15 is a graph showing the time change of the pulse wave feature "ab time" calculated from the pulse wave shown in Figure 13. The horizontal axis represents time in units of [s], and the vertical axis represents the pulse wave feature "ab time" in units of [s]. The thick solid and dashed lines in the graph of Figure 15 represent the "ab time" calculated based on pulse waves using near-infrared light and green light, respectively. Unlike the "ab time" calculated based on pulse waves using near-infrared light, the "ab time" calculated based on pulse waves using green light does not show a significant change when the pressing force is excessive.

[0072] Figures 16, 17, and 18 are graphs showing the time evolution of the pulse wave features "1 / (VE0.5)", "a / S", and "(ab) / (ad)", respectively, calculated from the pulse wave shown in Figure 13. The horizontal axis represents time in units of [s]. The vertical axis of Figure 16 represents the pulse wave feature "1 / (VE0.5)" in units of [s]. -1 The graphs are represented as follows: the vertical axis in Figure 17 represents the pulse wave feature "a / S" in arbitrary units, and the vertical axis in Figure 18 represents the pulse wave feature "(ab) / (ad)" in dimensionless units. The thick solid and dashed lines in the graphs of Figures 16, 17, and 18 represent the pulse wave features calculated based on pulse waves using near-infrared light and green light, respectively. These pulse wave features calculated based on pulse waves using green light do not show a significant change even when the pressing force is excessive, compared to the pulse wave features calculated based on pulse waves using near-infrared light. This is because, as shown in Figure 14, the change in the pulse wave waveform when the pressing force is excessive is small.

[0073] The reason why a significant change is observed in the pulse wave features calculated based on pulse waves using near-infrared light when excessive pressure is applied, while no significant change is observed in the pulse wave features calculated based on pulse waves using green light, can be explained as follows.

[0074] When the pressure applied to the skin increases, the capillaries 73 (Figure 12) are compressed, and blood flow is obstructed. As a result, blood accumulates in the arterioles 72 (Figure 12), which are upstream of the capillaries 73, and the blood pressure in the arterioles 72 increases. When near-infrared light is used as the light source for measurement, it is thought that the increase in blood pressure in the arterioles 72 is reflected in the pulse wave, resulting in a larger pulse wave characteristic value.

[0075] When green light is used as the light source for measurement, the increase in blood pressure within the arterioles 72 is hardly reflected in the pulse wave, and the change in blood pressure within the capillaries 73 is mainly reflected in the pulse wave. When capillaries 73 are compressed by excessive pressure, vascular resistance increases and blood flow decreases. Since blood pressure depends on the product of blood flow and vascular resistance, no significant change is observed in the blood pressure within the capillaries 73. For this reason, it is thought that no significant change is observed in the pulse wave characteristics when green light is used as the light source for measurement.

[0076] As shown in Figures 15, 16, 17, and 18, when the pressing force is excessive, the pulse wave features obtained by near-infrared light change significantly, but no significant change is observed in the pulse wave features obtained by green light. In other words, when the pressing force is excessive, the difference between the pulse wave features obtained by near-infrared light and the pulse wave features obtained by green light becomes larger compared to when the pressing force is within the appropriate range. The pressing force determination unit 33 (Figure 12) compares the pulse wave features obtained by near-infrared light and the pulse wave features obtained by green light, and determines whether the pressing force is abnormal or not based on the comparison result of the two.

[0077] Figures 19, 20, 21, and 22 are graphs showing pulse wave features "ab time," "1 / (VE0.5)," "a / S," and "(ab) / (ad)," respectively, calculated based on pulse waves obtained from multiple subjects. The horizontal axis of each graph represents pulse wave features calculated based on pulse waves using green light, and the vertical axis represents pulse wave features calculated based on pulse waves using infrared light. Hollow circles indicate pulse wave features based on pulse waves obtained when the pressing force is within an appropriate range, while solid black circles indicate pulse wave features based on pulse waves obtained when the pressing force is excessive.

[0078] Figure 19 shows that while some subjects had nearly the same pulse wave feature "ab time" when using near-infrared light and when using green light, many subjects had a shorter pulse wave feature "ab time" when using near-infrared light than when using green light. Furthermore, in cases of excessive pressure, all subjects in which excessive pressure was confirmed had a pulse wave feature "ab time" of 0.06 s or less when using near-infrared light. Therefore, the pulse wave feature "ab time" measured using near-infrared light is subject-independent and can be considered a preferable indicator for determining abnormal pressure.

[0079] Figure 20 shows that while some subjects had nearly identical pulse wave features "1 / (VE0.5)" when using near-infrared light and green light, many subjects had a larger pulse wave feature "1 / (VE0.5)" with near-infrared light than with green light. In cases of excessive pressure, some subjects had a larger pulse wave feature "1 / (VE0.5)" with near-infrared light than with green light, but subjects with nearly identical values ​​were also observed.

[0080] The pulse wave feature "a / S" shown in Figure 21 and the pulse wave feature "(ab) / (ad)" shown in Figure 22 also show a similar distribution to the pulse wave feature "1 / (VE0.5)" shown in Figure 19. The distribution of the features shown in Figures 19, 20, and 22 can be explained as follows.

[0081] When the pressing force is excessive, the capillaries 73 are compressed, obstructing blood flow, causing blood to pool in the arterioles 72 upstream. This increases the blood pressure in the arterioles 72, and the pulse wave features "1 / (VE0.5)", "a / S", and "(ab) / (ad)" measured by near-infrared light become larger. At this time, no significant changes in these pulse wave features are observed with green light. Subjects whose pulse wave features measured by near-infrared light are larger than those measured by green light when the pressing force is excessive are thought to be in this state.

[0082] If the pressing force becomes excessive, arteriole 72 will also be compressed, and blood flow will be obstructed. As a result, the difference between the pulse wave features obtained by near-infrared light and the pulse wave features obtained by green light will decrease. Subjects in whom the pulse wave features obtained by near-infrared light and the pulse wave features obtained by green light are approximately the same in magnitude when the pressing force becomes excessive are thought to be in this state.

[0083] From the above analysis, it can be seen that the pulse wave features "1 / (VE0.5)", "a / S", and "(ab) / (ad)" are effective in determining when the pressure applied is excessive within a certain range.

[0084] In particular, the pulse wave feature "ab time" using near-infrared light, as shown in Figure 19, is smaller in all subjects when the pressure is excessive than when the pressure is within the appropriate range. Therefore, by setting a judgment threshold, it is possible to determine that the pressure is excessive when the measured value of the pulse wave feature "ab time" falls below the judgment threshold. Alternatively, an estimation formula may be created in advance such that the degree of excessive pressure increases as the pulse wave feature "ab time" shortens, and the degree of excessive pressure can be estimated from the measured value of the pulse wave feature "ab time".

[0085] Next, we will describe the excellent effects of the second embodiment. In the second embodiment, the measurement values ​​of pulse wave features using near-infrared light and the measurement values ​​of pulse wave features using green light are compared to determine abnormalities in pressing force, thereby improving the accuracy of the determination.

[0086] Next, a biological information measurement device according to a modified example of the second embodiment will be described with reference to Figure 23. Figure 23 is a block diagram of a pulse wave signal processing device according to a modification of the second embodiment, and a schematic diagram of a bio-information measurement device equipped with the pulse wave signal processing device. In the second embodiment (Figure 12), light output from two light-emitting elements 51 and 52 that output light of different wavelengths and reflected from the measurement site is detected by one photodetector 53. In contrast, in the modification shown in Figure 23, the photoelectric pulse wave sensor 50 includes two photodetectors 53 and 54. Light output from one light-emitting element 51 and reflected from the measurement site is detected by one photodetector 53, and light output from the other light-emitting element 52 and reflected from the measurement site is detected by the other photodetector 54.

[0087] An optical filter is placed on the light-receiving surface of one of the light-receiving elements 53 to transmit light output from the light-emitting element 51 and block light in other wavelength ranges. An optical filter is placed on the light-receiving surface of the other light-receiving element 54 to transmit light output from the light-emitting element 52 and block light in other wavelength ranges.

[0088] The preferred ranges for the distance L1 from the light-receiving element 53 to the light-emitting element 51, and the preferred ranges for the distance L2 from the light-receiving element 54 to the light-emitting element 52, are the same as the preferred ranges for distances L1 and L2 in the biological information measurement device according to the second embodiment (Figure 12).

[0089] As shown in this modified example, multiple light-receiving elements 53 and 54 may be arranged for each of the multiple light-emitting elements 51 and 52. In this modified example, it is not necessary to stagger the light emission timing of the two light-emitting elements 51 and 52; they may be kept emitting light continuously, or the two light-emitting elements 51 and 52 may be pulsed at a constant frequency independently.

[0090] [Third Embodiment] Next, a third embodiment of the bio-information measurement device will be described with reference to Figure 24. The following description will omit details of components common to the pulse wave signal processing device and bio-information measurement device of the second embodiment, which were described with reference to Figures 12 to 22.

[0091] Figure 24 is a perspective view of a part of the biological information measurement device according to the third embodiment and a block diagram of the pulse wave signal processing device 30. Two light-emitting elements 51 and 52, and one light-receiving element 53 are attached to the inner surface of an annular attachment member 60. The attachment member 60 is used by being worn on the user's finger. Multiple sizes of the attachment member 60 are available to suit the thickness of the user's finger. When the attachment member 60 is worn on the finger, the light-emitting elements 51 and 52 emit light toward the finger. The light-receiving element 53 is mounted at a position where light reflected from inside the finger enters. The attachment member 60 further incorporates a light emission control unit 31, a pulse wave measurement unit 36, and a communication unit 55. The light emission control unit 31, the pulse wave measurement unit 36, and the communication unit 55 may be configured as a single integrated circuit. The attachment member 60 and the light-emitting elements 51 and 52, the light-receiving element 53, the light emission control unit 31, the pulse wave measurement unit 36, and the communication unit 55 attached thereto are collectively referred to as the "ring device 61".

[0092] The functions of the pulse wave signal processing device 30 are realized by a ring device 61, a portable information terminal 62, and a server 63. For example, a smartphone, tablet, or notebook computer can be used as the information terminal 62. The information terminal 62 includes a communication unit 37, a control unit 35, and an anomaly notification unit 34. The server 63 includes a communication unit 38, a pulse wave feature calculation unit 32, and a pressure determination unit 33.

[0093] Data communication takes place between the communication unit 55 of the ring device 61 and the communication unit 37 of the information terminal 62, and between the communication unit 37 of the information terminal 62 and the communication unit 38 of the server 63. For communication between the ring device 61 and the information terminal 62, for example, various standards of short-range wireless communication methods are used. For communication between the information terminal 62 and the server 63, a communication network such as the Internet is used.

[0094] The light emission control unit 31 controls the pulse emission of light-emitting elements 51 and 52. The pulse wave measurement unit 36 ​​reads the signal from the light-receiving element 53. For example, the light emission control unit 31 of the ring device 61 receives a command from the control unit 35 of the information terminal 62 and causes the light-emitting elements 51 and 52 to emit light based on the received command. The pulse wave measurement unit 36 ​​reads the intensity signal of the light received from the light-receiving element 53 and transmits it to the server 63 via the information terminal 62. The pulse wave feature calculation unit 32 and the pressure determination unit 33 of the server 63 calculate pulse wave features based on the pulse wave, similar to the pulse wave signal processing device 30 according to the second embodiment (Figure 12), and determine whether the pressure is abnormal or not.

[0095] The pressure determination unit 33 transmits the determination result to the control unit 35 of the information terminal 62. When the control unit 35 receives a determination result indicating that the pressure is abnormal, it controls the abnormality notification unit 34 to notify the user that the pressure is abnormal.

[0096] If the ring size is too large, a gap will form between the photoelectric pulse wave sensor 50 and the skin, making it impossible to stably measure the pulse wave signal. If the ring size is too small, the pressure applied by the photoelectric pulse wave sensor 50 to the skin will be excessive, reducing the reliability of the biometric information estimation results. Next, a method for selecting an appropriate ring device 61 from several sizes of ring devices 61 will be described.

[0097] First, the user attaches multiple ring devices 61 of different sizes in sequence and operates the photoelectric pulse wave sensor 50 and the pulse wave signal processing device 30. It is recommended to select a ring device 61 that is slightly larger than the size of the ring device 61 used when excessive pressure is detected, for example, one or two sizes larger, as the optimal size ring device 61. By selecting a size one or two sizes larger than the size used when excessive pressure is detected, it is possible to avoid selecting an inappropriately sized ring device 61.

[0098] Next, we will describe the excellent effects of the third embodiment. Because the epidermis of the fingers is relatively thin, they are suitable for acquiring pulse waves using the photoelectric pulse wave sensor 50. Also, because the capillary pathways are less complex than those of the face, the values ​​of the pulse wave features tend to be more stable. Therefore, the reliability of various biological information obtained from the pulse wave is increased. Furthermore, when using the biological information measurement device continuously or intermittently, an excellent effect is obtained in that the ring device 61 is worn on the finger for a long time with minimal discomfort or unease.

[0099] If the size of the ring device 61 is not appropriate, it may not be possible to measure the pulse wave stably, or the reliability of the biometric information estimation results may decrease. In the third embodiment, it is possible to select a ring device 61 of an appropriate size from a plurality of ring devices 61 of different sizes. By selecting a ring device 61 of an appropriate size, it becomes possible to measure the pulse wave stably and improve the reliability of the biometric information estimation results.

[0100] Next, a modified example of the third embodiment will be described. Some or all of the functions of the server 63 may be implemented by the information terminal 62. Alternatively, some of the functions of the information terminal 62 may be implemented by the ring device 61. For example, the functions of the abnormality notification unit 34 may be implemented by the ring device 61. For example, a vibration generator may be mounted on the mounting member 60, and when it is determined that the pressing force is abnormal, the vibration generator may be activated to vibrate the mounting member 60.

[0101] The pressure determination unit 33, as described in the second embodiment, should have a function to estimate the degree of excessive pressure from the measured value of the pulse wave feature "ab time" (Figure 19) and notify the user of the degree of excessive pressure, based on an estimation formula that is created in advance such that the degree of excessive pressure increases as the pulse wave feature "ab time" (Figure 19) becomes shorter. When the ring device 61 is worn, the pressure increases when the finger is bent and decreases when the finger is straightened. The abnormality notification unit 34 instructs the user to bend or straighten their finger.

[0102] The pressure determination unit 33 determines whether the size of the ring device 61 is appropriate based on the change in the degree of excessive pressure when the user extends and bends their finger, and the abnormality notification unit 34 notifies the user of the determination result. This makes it possible to select a ring device 61 of the appropriate size accurately in a simple manner.

[0103] Next, other modifications of the third embodiment will be described. The ring device 61 of the biometric information measurement device according to the third embodiment is worn on the finger, but a device that is worn on a part of the body other than the finger may be used instead of the ring device 61. For example, it may be a wearable device that is worn on the wrist, neck, face, ear, etc. Furthermore, the biometric information measurement device does not necessarily have to be wearable, and may be a device that measures biometric information by pressing a finger against the photoelectric pulse wave sensor 50 as needed. For example, the biometric information measurement device may be a portable device such as a smartphone, or a fixed-installation device.

[0104] In portable or fixed-installation biometric information measurement devices, it is preferable that the pulse wave signal processing device 30 determines whether the pressing force is within the appropriate range when the user brings the area to be measured into contact with the photoelectric pulse wave sensor 50. If the photoelectric pulse wave sensor part of the biometric information measurement device is a wearable device, it is preferable that the pulse wave signal processing device 30 determines whether the pressing force is within the appropriate range when the wearable device is worn. For example, if the wearable device is a wristband or watch type device worn on the wrist, the pulse wave is measured when it is worn, and if it is determined that the pressing force is abnormal, the abnormality notification unit 34 should notify the user to loosen the belt.

[0105] The embodiments described above are illustrative, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible. Similar effects and benefits from similar configurations in multiple embodiments will not be mentioned sequentially for each embodiment. Furthermore, the present invention is not limited to the embodiments described above. For example, it will be obvious to those skilled in the art that various modifications, improvements, and combinations are possible. [Explanation of Symbols]

[0106] 30 Pulse wave signal processing device 31 Light emission control unit 32 Pulse wave feature calculation unit 33 Pressure detection unit 34 Abnormality notification section 35 Control Unit 36. Pulse wave measurement section 37, 38 Communications Department 50 Photoplethysmography Sensor 51, 52 Light-emitting element 53, 54 Photodetector 55 Communications Department 56 Control Unit 60 Mounting component 61 Ring device 62 Information terminals 63 servers 70 Body surface 71 Epidermal area 72 arterioles 73 Capillaries

Claims

1. A pulse wave feature calculation unit calculates pulse wave feature quantities related to the steepness of the rise of a pulse wave measured using light in the wavelength range of 600 nm to 950 nm by a photoelectric pulse wave sensor. A pressure determination unit determines whether the pressing force, which is the pressure applied when the photoelectric pulse wave sensor is pressed against the area to be measured, is excessive, based on the value of the pulse wave feature calculated by the pulse wave feature calculation unit. A pulse wave signal processing device equipped with the following features.

2. The pulse wave signal processing device according to claim 1, wherein the pulse wave feature quantity includes information regarding the time difference between the peak of wave a and the peak of wave b of an acceleration pulse wave obtained by second-order differentiation of the pulse wave.

3. The pulse wave signal processing device according to claim 1 or 2, which includes information regarding the width of the first peak appearing within one beat of a velocity pulse wave obtained by first differentiating the pulse wave.

4. The pulse wave signal processing device according to claim 1 or 2, wherein the pulse wave feature quantity includes information relating to the ratio of the peak value of the a-wave of the acceleration pulse wave obtained by second-order differentiation of the pulse wave to the amplitude of the pulse wave.

5. The pulse wave signal processing apparatus according to claim 1 or 2, wherein the pulse wave feature quantity includes information relating to the ratio of the difference between the peak value of wave a and the peak value of wave b of the acceleration pulse wave obtained by second-order differentiation of the pulse wave, and the difference between the peak value of wave a and the peak value of wave d.

6. Furthermore, the pulse wave signal processing device according to claim 1 or 2, further comprising an abnormality notification unit that notifies the user that the pressing force is abnormal when the pressing force determination unit determines that the pressing force is excessive.

7. A pulse wave signal processing device according to claim 1 or 2, The photoelectric pulse wave sensor measures the pulse wave of the area to be measured and inputs the measurement result to the pulse wave signal processing device. Equipped with, The photoplethysmography sensor is a biological information measurement device that includes at least one light-emitting element and a light-receiving element that detects light reflected from the at least one light-emitting element at the measurement site or light transmitted through the measurement site.

8. The biological information measuring device according to claim 7, wherein the at least one light-emitting element includes a first light-emitting element that emits light in the wavelength range from red to near-infrared.

9. The bio-information measuring device according to claim 8, wherein the light-receiving element detects light reflected from the part to be measured, and the distance between the first light-emitting element and the light-receiving element is 5 mm or more and 20 mm or less.

10. The at least one light-emitting element includes two light-emitting elements that emit light of different wavelengths, The pressure determination unit calculates pulse wave feature quantities related to the steepness of the rising edge of the two pulse waves measured using the light output from each of the two light-emitting elements, The bio-information measuring device according to claim 7, wherein the pressure determination unit compares the values ​​of two pulse wave feature quantities obtained from two pulse waves measured using light output from each of the two light-emitting elements, and determines whether or not the pressure is excessive based on the comparison result.

11. The biological information measuring device according to claim 10, wherein one of the two light-emitting elements includes a second light-emitting element that emits light in the wavelength range from blue to yellow-green.

12. The bio-information measuring device according to claim 11, wherein the light-receiving element detects light reflected from the part to be measured, and the distance between the second light-emitting element and the light-receiving element is 1 mm or more and 3 mm or less.

13. Furthermore, it includes a mounting component that is attached to the finger. The bio-information measuring device according to claim 7, wherein the at least one light-emitting element and the light-receiving element are attached to the mounting member, and when the mounting member is attached to a finger, the at least one light-emitting element emits light toward the finger, and the light reflected inside the finger is incident on the light-receiving element.

14. The biological information measuring device according to claim 13, wherein the pressing determination unit has a function of determining whether or not the size of the mounting member is too small based on the pressing force.

15. A photoelectric pulse wave sensor in contact with the area to be measured calculates pulse wave features related to the steepness of the rise of the pulse wave measured using light in the wavelength range of 600 nm to 950 nm. A method for determining whether the pressing force, which is the pressure applied when the photoelectric pulse wave sensor is pressed against the area to be measured, is excessive, based on the value of the pulse wave feature obtained by calculation.

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