Biosignal measurement device and determination method

Abstract

To accurately determine whether a sensor part is detached from a user.SOLUTION: A biological signal measurement device for measuring a biological signal of a user includes: a sensor part being a sensor part which is attached to a user and includes a light emission part that emits light to a biological tissue of the user and a light reception part that generates a signal according to a light amount of reflected light or transmitted light of the light; a signal generation part that generates a pulse wave signal on the basis of the signal generated by the light reception part; an acquisition part that obtains a noise index representing a noise component of the pulse wave signal, a pulse wave index representing a pulse wave component of the pulse wave signal, and a DC index representing a DC component of the pulse wave signal; and a determination part that determines that the sensor part is detached from the user when a first ratio of the noise index to the pulse wave index and a second ratio of the noise index to the DC index satisfy a detection condition.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a biological signal measurement device and a determination method.

Background Art

[0002] Various devices are provided that measure biological signals by attaching sensors to users. When the sensor is detached from the user, the output from the sensor does not represent the biological information of the user. Therefore, a technique for determining whether the sensor is detached from the user is required. In Patent Document 1, it is proposed to provide a component such as a switch for detecting finger contact in the sensor. In Patent Document 2, it is proposed to detect whether the sensor is detached from the user by using the fluctuation of the DC component of the pulse wave. In Patent Document 3, it is proposed to detect whether the sensor is detached from the user based on the relationship between the pulse rate density and the signal intensity.

Prior Art Documents

Patent Documents

[0003] [[ID=2l]]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technique described in Patent Document 1, since determination is performed using components different from the sensor used for measuring biological signals, the cost increases. In the techniques described in Patent Documents 1 and 2, there are cases where it is not possible to accurately determine whether the sensor is detached from the user. Some aspects of the present invention aim to provide a technique for accurately determining whether the sensor used for measuring biological signals is detached from the user. [Means for solving the problem]

[0005] According to some embodiments, a biosignal measuring device for measuring a user's biosignals includes a sensor unit attached to the user, which includes a light-emitting unit that irradiates the user's biological tissue with light, and a light-receiving unit that generates a signal corresponding to the amount of reflected or transmitted light; a signal generation means that generates a pulse wave signal based on the signal generated by the light-receiving unit; an acquisition means that acquires a noise index representing the noise component of the pulse wave signal, a pulse wave index representing the pulse wave component of the pulse wave signal, and a DC index representing the DC component of the pulse wave signal; and a first ratio of the noise index to the pulse wave index. is greater than the first threshold, and The second ratio of the noise index to the DC index. This is greater than the second threshold. Detection conditions The condition is met. A biosignal measuring device is provided, which includes a determination means for determining that the sensor unit is detached from the user in certain cases. [Effects of the Invention]

[0006] According to some embodiments, it is possible to accurately determine whether the sensor unit is detached from the user. [Brief explanation of the drawing]

[0007] [Figure 1] A block diagram illustrating an example of the functional configuration of a biosignal measurement device according to an embodiment of the present invention. [Figure 2] A block diagram illustrating an example of the functional configuration of the signal processing unit shown in Figure 1. [Figure 3] A flowchart illustrating an example of the operation of the biosignal measurement device shown in Figure 1. [Figure 4] This diagram illustrates the method for acquiring indicators from the biosignal measurement device shown in Figure 1. [Figure 5] This diagram illustrates the method for acquiring indicators from the biosignal measurement device shown in Figure 1. [Modes for carrying out the invention]

[0008] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims, and not all combinations of features described in the embodiments are essential to the invention. Two or more of the features described in the embodiments may be combined in any way. Furthermore, identical or similar configurations will be given the same reference numeral, and redundant descriptions will be omitted.

[0009] Some embodiments of the present invention relate to a biosignal measuring device for measuring the biological signals of a user (e.g., a patient). The biological signals to be measured may be, for example, arterial blood oxygen saturation (SpO2). A biosignal measuring device for measuring SpO2 may also be called a pulse oximeter. In the following description, a pulse oximeter (hereinafter simply referred to as measuring device 100) will be used as an example. However, the present invention is applicable to any electronic device capable of acquiring changes in the intensity (light quantity) of light reflected by or transmitted through biological tissue as a pulse wave signal. Such electronic devices include medical devices such as biological information monitors, sleep evaluation devices, blood pressure monitors, and pulse wave meters. They also include, but are not limited to, general-purpose computer devices (smartphones, tablet terminals, media players, smartwatches, game consoles, etc.) capable of acquiring pulse wave signals via external sensors or networks.

[0010] Referring to the block diagram in Figure 1, an example of the functional configuration of a measuring device 100 according to some embodiments of the present invention will be described. The measuring device 100 may include each of the components shown in Figure 1. The measuring device 100 may also include components not shown in Figure 1, or may not include some of the components shown in Figure 1.

[0011] The sensor unit 110 includes a red light emitting unit 111 that emits red light, an infrared light emitting unit 112 that emits infrared light, and a light receiving unit 113 that outputs an electrical signal corresponding to the amount of light received. The sensor unit 110 is attached to the user of the measuring device 100 (hereinafter simply referred to as the user). The sensor unit 110 may be attached to the user by a clip, by tape, or by any other method.

[0012] The red light emitting unit 111 is positioned to irradiate the user's biological tissue 190 with light (red light) when the sensor unit 110 is attached to the user. The infrared light emitting unit 112 is positioned to irradiate the user's biological tissue 190 with light (infrared light) when the sensor unit 110 is attached to the user. The light receiving unit 113 is positioned to receive light that has been transmitted through the biological tissue 190 (transmitted light) or reflected light that has been reflected by the biological tissue 190 (reflected light) when the red light emitted by the red light emitting unit 111 and the infrared light emitted by the infrared light emitting unit 112 are attached to the user.

[0013] The red light-emitting section 111 and the infrared light-emitting section 112 may each be composed of an organic light-emitting diode (LED) or other light source. In the example shown in Figure 1, red light and infrared light are used. The red light may be, for example, light with a wavelength of 660 nm. The infrared light may be, for example, light with a wavelength of 900 nm. The sensor section 110 may include light-emitting sections that emit light of other wavelengths instead of the red light-emitting section 111 and the infrared light-emitting section 112. The absorbance of oxyhemoglobin at wavelengths λ1 and λ2 is a1 λ1 a1 λ2 The absorbance of reduced hemoglobin is a2 λ1 a2 λ2 Therefore, a1 λ1 and a1 λ2 a2 λ1 and a2 λ2 Any light source that generates light of any wavelengths λ1 and λ2 that are significantly different from each other may be used (for example, a combination of a red light source and an infrared or green light source).

[0014] In the case of a configuration for detecting the amount of transmitted light, a light receiving unit 113 is disposed at a position facing the red light emitting unit 111 and the infrared light emitting unit 112 with the biological tissue 190 of the measurement site (such as the earlobe or fingertip) interposed therebetween. Further, in the case of a configuration for detecting the amount of reflected light, the red light emitting unit 111, the infrared light emitting unit 112, and the light receiving unit 113 are disposed in close proximity to each other. Note that, regardless of whether the amount of transmitted light or the amount of reflected light is detected, the red light emitting unit 111 and the infrared light emitting unit 112 are disposed in close proximity to each other. Also, the light receiving unit 113 is disposed so as to receive the transmitted light or the reflected light of the light irradiated from the red light emitting unit 111 and the infrared light emitting unit 112 to the body surface under the same conditions (such as distance and angle).

[0015] The light receiving unit 113 receives the transmitted light or the reflected light of the light emitted by the red light emitting unit 111 and the infrared light emitting unit 112, and outputs an electrical signal corresponding to the amount of received light. The light receiving unit 113 may be a light receiving sensor having the wavelength of the transmitted light or the reflected light to be detected as the sensitivity wavelength, for example, a photodiode or a phototransistor.

[0016] The signal processing unit 140 generates a pulse wave signal by applying signal processing such as amplification, A / D conversion, and noise removal to the signal generated by the light receiving unit 113, and outputs this pulse wave signal to the control unit 130. The signal processing unit 140 generates a pulse wave signal for each of the red light and the infrared light.

[0017] The control unit 130 has, for example, a programmable processor, a non-volatile memory (ROM), and a volatile memory (RAM). The programmable processor realizes the functions of the measuring device 100 by reading the program stored in the ROM into the RAM and executing it to control each part of the measuring device 100. Note that at least a part of the operations of the control unit 130 may be realized by a hardware circuit such as a programmable logic array.

[0018] The drive unit 120 drives the red light emitting unit 111 and the infrared light emitting unit 112 according to the amount of light emitted and the timing of light emission instructed by the control unit 130. The control unit 130 controls the timing of light emission so that the red light emitting unit 111 and the infrared light emitting unit 112 emit light alternately for predetermined periods of time, in order to detect the amount of transmitted or reflected light for two wavelengths using one light receiving unit 113.

[0019] Since the red light-emitting unit 111 and the infrared light-emitting unit 112 do not emit light simultaneously, strictly speaking, the acquisition timing of the red light pulse wave signal and the infrared light pulse wave signal are different. However, by setting the emission frequencies of the red light-emitting unit 111 and the infrared light-emitting unit 112 to be sufficiently higher than the frequency components of the pulse wave, these pulse wave signals can be treated as a group of measured values ​​sampled at the same timing.

[0020] The memory unit 150 is, for example, a non-volatile memory, or a removable storage medium such as a memory card. The control unit 130 stores pulse wave signals, SpO2 measurements, and other data in the memory unit 150, associating them with bibliographic information such as the date and time of measurement.

[0021] The display unit 160 is, for example, a liquid crystal display, and displays the SpO2 measurement value and the operating status and setting menu screen of the measuring device 100 according to the control of the control unit 130. The operation unit 170 includes buttons, switches, keys, etc., for the user to input instructions to the measuring device 100. If the display unit 160 is a touch display, the touch panel portion is included in the operation unit 170. The external interface (I / F) 180 is a communication interface for communicating with external devices by wired or wireless means.

[0022] Referring to the block diagram in Figure 2, an example of the functional configuration of the signal processing unit 140 will be specifically described. The signal processing unit 140 may include an analog-to-digital (AD) conversion unit 200, a pulse wave signal generation unit 210, and a low-pass filter 220. The AD conversion unit 200 samples the analog signal output from the light receiving unit 113 at a predetermined sampling frequency and converts it into a digital signal. As described above, the light receiving unit 113 outputs an analog signal corresponding to the amount of light received.

[0023] The pulse wave signal generation unit 210 generates a pulse wave signal based on the output from the AD conversion unit 200 (i.e., a digital signal representing the amount of light). The pulse wave signal generation unit 210 generates a pulse wave signal for red light and a pulse wave signal for infrared light, respectively. The pulse wave signal for red light generated by the pulse wave signal generation unit 210 is represented as the red light signal 211. The pulse wave signal for infrared light generated by the pulse wave signal generation unit 210 is represented as the infrared light signal 212.

[0024] The drive unit 120 may drive the red light emitting unit 111 and the infrared light emitting unit 112 to repeat the cycle of red light emission state, non-emission state, infrared light emission state, and non-emission state at a predetermined cycle. The red light emission state is when the red light emitting unit 111 emits red light and the infrared light emitting unit 112 does not emit light. The infrared light emission state is when the infrared light emitting unit 112 emits infrared light and the red light emitting unit 111 does not emit light. The non-emission state is when neither the red light emitting unit 111 nor the infrared light emitting unit 112 emits light.

[0025] The pulse wave signal generation unit 210 may generate a red light signal 211 by subtracting the signal generated by the light receiving unit 113 during the subsequent non-light emission state from the signal generated by the light receiving unit 113 during the red light emission state. The pulse wave signal generation unit 210 may generate a red light signal 211 each time the red light emission state is activated. The pulse wave signal generation unit 210 may generate an infrared light signal 212 by subtracting the signal generated by the light receiving unit 113 during the subsequent non-light emission state from the signal generated by the light receiving unit 113 during the infrared light emission state. The pulse wave signal generation unit 210 may generate an infrared light signal 212 each time the infrared light emission state is activated. The pulse wave signal generation unit 210 outputs the red light signal 211 and the infrared light signal 212 to the low-pass filter 220. Furthermore, the pulse wave signal generation unit 210 may output the infrared light signal 212 to the control unit 130. The pulse wave signal generation unit 210 may logarithmically transform the signal value of the pulse wave signal or normalize the amplitude value of the pulse wave signal.

[0026] The low-pass filter 220 is a filter for removing high-frequency noise contained in the pulse wave signal. The high-frequency noise removed by the low-pass filter 220 may be noise originating from the commercial power supply, for example, noise with a frequency higher than the commercial power supply frequency (50Hz or 60Hz). The low-pass filter 220 generates a red light signal 221 by filtering the red light signal 211. The low-pass filter 220 generates an infrared light signal 222 by filtering the infrared light signal 212. The low-pass filter 220 outputs the generated red light signal 221 and infrared light signal 222 to the control unit 130. The low-pass filter 220 may filter the pulse wave signal by, for example, taking a moving average of the pulse wave signal.

[0027] The control unit 130 can acquire (calculate) biological information such as pulse rate and SpO2 by applying known methods to the red light signal 221 and the infrared light signal 222. For example, the control unit 130 first extracts the red light signal 221 and the infrared light signal 222 into one-beat intervals under predetermined conditions. Then, for each one-beat interval, the control unit 130 detects the peak value (the maximum value in the interval where the amplitude value is positive) and its position, and the bottom value (the minimum value in the interval where the amplitude value is negative) and its position for at least one of the signals.

[0028] The control unit 130 calculates the instantaneous pulse rate (beats / minute) by using the time difference between the peak (or bottom) positions of two adjacent beat intervals as the period of one beat. The control unit 130 also calculates the maximum amplitude values ​​of the red light signal 221 and the infrared light signal 222 from the difference between the peak and bottom values, and calculates the ratio R = maximum amplitude value of red light signal 221 / maximum amplitude value of infrared light signal 222. The control unit 130 can determine the SpO2 for each beat by referring to a table that converts the ratio R to SpO2, for example, which is pre-stored in ROM. Note that the pulse rate and SpO2 may be displayed using a moving average value calculated over a predetermined number of consecutive beats.

[0029] Referring to the flowchart in Figure 3, an example of a method for determining whether the sensor unit 110 is detached from the user will be described. Each step of the method in Figure 3 may be performed by a programmable processor loading a program stored in ROM into RAM and executing it. Alternatively, some or all of the steps of the method in Figure 3 may be performed by hardware circuits such as a programmable logic array.

[0030] In S301, the control unit 130 acquires the infrared light signal 212 and the infrared light signal 222 and stores them for subsequent processing. These signals may be stored in RAM or in the storage unit 150.

[0031] In S302, the control unit 130 uses the stored infrared light signals 212 and 222 to acquire a noise index, a pulse wave index, and a DC index. The noise index is an index that represents the noise component of the pulse wave signal. The control unit 130 may acquire the noise index using infrared light signal 212 (i.e., the pulse wave signal obtained for infrared light before filtering) or using infrared light signal 222 (i.e., the pulse wave signal obtained for infrared light after filtering). The noise index may represent noise components originating from the commercial power supply, and may, for example, components with a frequency of 50Hz or higher than the commercial power supply frequency (50Hz or 60Hz).

[0032] The pulse wave index is an index that represents the pulse wave component of the pulse wave signal. The control unit 130 may acquire the pulse wave index using the infrared light signal 212 or using the infrared light signal 222. The DC index is an index that represents the DC component of the pulse wave signal. The control unit 130 may acquire the DC index using the infrared light signal 212 or using the infrared light signal 222.

[0033] Referring to the graph in Figure 4, specific examples of methods for acquiring noise index, pulse wave index, and DC index will be explained. Figure 4(a) is a graph with time on the horizontal axis and the value of the infrared light signal 212 acquired at each time while the sensor unit 110 is not separated from the user on the vertical axis. Figures 4(b) and (c) are graphs with time on the horizontal axis and the value of the infrared light signal 222 acquired at each time while the sensor unit 110 is not separated from the user on the vertical axis. Since the infrared light signal 222 is a signal obtained by applying a low-pass filter to the infrared light signal 212, the graphs in Figures 4(b) and (c) are smoother than the graph in Figure 4(a).

[0034] As shown in Figure 4(a), the noise index may be a value based on the range 402 of the infrared light signal 212 during period 401. Range is a term used in statistical analysis and represents the difference between the maximum and minimum values ​​of the observed values. That is, range 402 represents the difference between the maximum and minimum values ​​of the infrared light signal 212 during period 401.

[0035] The period 401 may be long enough to include one or more cycles of high-frequency noise (for example, power supply noise with a frequency of 50 Hz or 60 Hz). If the period 401 is too short, it cannot include one cycle of high-frequency noise. On the other hand, if the period 401 is too long, it will include pulse wave components. Therefore, for example, the period 401 may be long between 20 ms and 100 ms.

[0036] The end of period 401 may be the current time Tc (i.e., the time when S302 is executed), or it may be an earlier time. The closer the end of period 401 is to the current time Tc, the better the judgment accuracy of S304 and S305 described below. The noise index may be the range 402 itself, or it may be another value obtained based on the range 402 (for example, the square or twice the range 402).

[0037] The noise index may be a value based on the average value of the range 402 of the infrared light signal 212 over multiple periods 401. The value based on the average value may be the average value itself or other values ​​obtained based on the average value. The multiple periods 401 may be consecutive periods. Each of the multiple periods 401 may be of the same length. For example, the control unit 130 may define multiple periods by dividing the period n seconds prior to the current time Tc (e.g., 1 ≤ n ≤ 6), and the noise index may be the average value of the range 402 of the infrared light signal 212 for each of the multiple periods.

[0038] As shown in Figure 4(b), the pulse wave index may be a value based on the range 412 of the infrared light signal 222 during period 411. The range 412 represents the difference between the maximum and minimum values ​​of the infrared light signal 222 during period 411.

[0039] Period 411 may be long enough to include one or more pulse wave cycles. If period 411 is too short, it may not be able to include one pulse wave cycle. On the other hand, if period 411 is too long, the responsiveness may decrease. Therefore, for example, period 411 may be long enough to be between 3 seconds and 10 seconds. Period 411 is longer than period 401.

[0040] The end of period 411 may be the current time Tc (i.e., the time when S302 is executed), or it may be an earlier time. The closer the end of period 411 is to the current time Tc, the better the accuracy of the determinations in S304 and S305 described below. The pulse wave index may be the range 412 itself, or it may be another value obtained based on the range 412 (for example, the square or twice the range 412).

[0041] In the example shown in Figure 4(b), the control unit 130 acquires the pulse wave index using the infrared light signal 222 after applying a low-pass filter. This reduces the influence of noise components on the pulse wave index. Alternatively, the control unit 130 may acquire the pulse wave index using the infrared light signal 212 before applying the low-pass filter, instead of the infrared light signal 222.

[0042] As shown in Figure 4(c), the DC index may be a value based on a representative value 422 of the infrared light signal 222 during period 421. The representative value 422 may be the minimum value, as shown in the example in Figure 4(c), or it may be the maximum value, mean value, median value, etc.

[0043] The period 421 can be of any length. If the period 421 is too long, the responsiveness may decrease. For example, the period 421 may be 250 milliseconds or longer and 10 seconds or shorter. The period 421 is longer than the period 401.

[0044] The end of period 421 may be the current time Tc (i.e., the time when S302 is executed), or it may be an earlier time. The closer the end of period 421 is to the current time Tc, the better the accuracy of the determinations in S304 and S305 described below. The DC index may be the representative value 422 itself, or it may be another value obtained based on the representative value 422 (for example, the square or twice the representative value 422).

[0045] In the example shown in Figure 4(c), the control unit 130 obtains the DC index using the infrared light signal 222 after applying a low-pass filter. This reduces the influence of noise components on the DC index. Alternatively, the control unit 130 may obtain the DC index using the infrared light signal 212 before applying the low-pass filter, instead of the infrared light signal 222.

[0046] In S303, the control unit 130 determines whether the noise index, pulse wave index, and DC index satisfy the detection conditions. The detection conditions are the conditions for detecting that the sensor unit 110 is detached from the user. If the control unit 130 determines that the noise index, pulse wave index, and DC index satisfy the detection conditions (YES in S303), it proceeds to S304 and determines that the sensor unit 110 is detached from the user (i.e., not attached). If the control unit 130 determines that the noise index, pulse wave index, and DC index do not satisfy the detection conditions (NO in S303), it proceeds to S305 and determines that the sensor unit 110 is not detached from the user (i.e., attached).

[0047] The detection conditions will be explained in detail. The detection conditions may be based on, for example, the ratio of the noise index to the pulse wave index and the ratio of the noise index to the DC index. In the following explanation, the ratio of the noise index to the pulse wave index (i.e., the value obtained by dividing the noise index by the pulse wave index) will be referred to as the pulse wave ratio. The ratio of the noise index to the DC index (i.e., the value obtained by dividing the noise index by the DC index) will be referred to as the DC ratio.

[0048] Referring to the graph in Figure 5, the noise index, pulse wave index, and DC index when the sensor unit 110 is detached from the user will be explained. Figure 5(a) is a graph with time on the horizontal axis and the values ​​of the infrared light signal 212 acquired at each time while the sensor unit 110 is detached from the user on the vertical axis. Figures 5(b) and (c) are graphs with time on the horizontal axis and the values ​​of the infrared light signal 222 acquired at each time while the sensor unit 110 is detached from the user on the vertical axis.

[0049] As shown in Figure 5(a), when the sensor unit 110 is detached from the user, the noise index may be a value based on the range 501 of the infrared light signal 212 during period 401. The range 501 when the sensor unit 110 is detached from the user may be similar in magnitude to the range 402 when the sensor unit 110 is not detached from the user.

[0050] As shown in Figure 5(b), when the sensor unit 110 is detached from the user, the pulse wave index may be a value based on the range 511 of the infrared light signal 222 during period 411. The range 511 when the sensor unit 110 is detached from the user may be significantly smaller than the range 412 when the sensor unit 110 is not detached from the user. Therefore, the ratio to pulse wave may become significantly larger when the sensor unit 110 is detached from the user. Thus, the detection condition may include the ratio to pulse wave being greater than a predetermined threshold. This threshold may be determined in advance by the manufacturer of the measuring device 100, for example, and stored in the memory unit 150, etc., before the start of the operation shown in Figure 3.

[0051] As shown in Figure 5(c), when the sensor unit 110 is detached from the user, the DC index may be a value based on a representative value 521 of the infrared light signal 222 during period 421. The representative value 521 when the sensor unit 110 is detached from the user may be significantly smaller than the representative value 422 when the sensor unit 110 is not detached from the user. Therefore, the ratio to DC may become significantly larger when the sensor unit 110 is detached from the user. Thus, the detection condition may include the ratio to DC being greater than a predetermined threshold. This threshold may be determined in advance by the manufacturer of the measuring device 100, for example, and stored in the memory unit 150, etc., before the start of the operation shown in Figure 3. The threshold used for the ratio to pulse wave and the threshold used for the ratio to DC may be different values ​​or the same value.

[0052] The control unit 130 may use a combination of conditions relating to the pulse wave ratio (for example, the pulse wave ratio being greater than a threshold) and conditions relating to the DC ratio (for example, the DC ratio being greater than a threshold). For example, the detection condition may satisfy at least one of the conditions relating to the pulse wave ratio and the conditions relating to the DC ratio. This allows the control unit 130 to detect that the sensor unit 110 is separated from the user even if one of the conditions is not met, as long as the other condition is met.

[0053] The detection conditions may include the value obtained from the pulse wave ratio and the DC ratio satisfying a predetermined condition. For example, the detection conditions may include the product of the pulse wave ratio and the DC ratio being greater than a predetermined threshold. In this case, even if one of the pulse wave ratio and the DC ratio does not change significantly, the detection condition is satisfied if the other of the pulse wave ratio and the DC ratio becomes significantly larger.

[0054] In S306, the control unit 130 stores the determination results from S304 and S305. The determination results may be stored in the storage unit 150. For example, the control unit 130 may store the determination result (i.e., whether the sensor unit 110 is detached from the user or not) along with the date and time the determination was made. Alternatively, the control unit 130 may store the date and time when the mounting state of the sensor unit 110 changed (for example, the date and time when the sensor unit 110 was not detached from the user in the previous determination, but was detached from the user in the new determination).

[0055] In S307, the control unit 130 determines whether to terminate the process shown in Figure 3. If the control unit 130 determines that the process shown in Figure 3 should be terminated (YES in S307), it terminates the process; otherwise (NO in S307), it returns to S301 and repeats steps S301 to S307. For example, the control unit 130 may determine to terminate the process shown in Figure 3 in response to instructions from the user or when the timer expires.

[0056] According to the method described above, the measuring device 100 can determine whether the sensor unit 110 is detached from the user using the signal obtained from the light receiving unit 113, which is used to measure biological signals, without requiring any additional sensors. Furthermore, the measuring device 100 can accurately determine whether the sensor unit 110 is detached from the user by using the ratio to pulse wave and the ratio to DC.

[0057] In the example described above, the control unit 130 uses infrared light signals 212 and 222 to determine whether the sensor unit 110 is separated from the user. Alternatively, or in addition to this, the control unit 130 may use red light signals 211 and 221 to determine whether the sensor unit 110 is separated from the user. Generally, infrared light is less affected by variations in blood oxygen concentration than red light, so higher determination accuracy can be obtained by using infrared light signals 212 and 222.

[0058] The biosignal measurement device according to the present invention can also be implemented as a program (application software) that enables the operation of the drive unit 120, control unit 130, and signal processing unit 140 described above on a general-purpose information processing device such as a personal computer, which is generally available. Therefore, such a program and a storage medium that stores the program (such as an optical storage medium like a CD-ROM or DVD-ROM, a magnetic storage medium like a magnetic disk, or a semiconductor memory card) also constitute the present invention. Some or all of the drive unit 120, control unit 130, and signal processing unit 140 may be implemented by a dedicated circuit instead of being implemented as a program.

[0059] The invention is not limited to the embodiments described above, and various modifications and changes are possible within the scope of the gist of the invention. [Explanation of Symbols]

[0060] 110...Sensor unit, 111...Red light emitting unit, 112...Infrared light emitting unit, 113...Light receiving unit, 120...Drive unit, 130...Control unit, 140...Signal processing unit

Claims

1. A biosignal measuring device for measuring a user's biosignals, A sensor unit to be attached to the user, comprising a light-emitting unit that irradiates light onto the user's biological tissue, and a light-receiving unit that generates a signal corresponding to the amount of reflected or transmitted light, A signal generation means that generates a pulse wave signal based on the signal generated by the light receiving unit, An acquisition means for acquiring a noise index representing the noise component of the pulse wave signal, a pulse wave index representing the pulse wave component of the pulse wave signal, and a DC index representing the DC component of the pulse wave signal. A biosignal measuring device comprising: determination means for determining that the sensor unit is separated from the user when the detection conditions are met such that a first ratio of the noise index to the pulse wave index is greater than a first threshold, and a second ratio of the noise index to the DC index is greater than a second threshold.

2. The noise index is a value based on the range of the pulse wave signal during the first period, The pulse wave index is a value based on the range of the pulse wave signal or the signal obtained by applying a low-pass filter to the pulse wave signal over a second period that is longer than the first period. The DC index is a value based on a representative value of the pulse wave signal or the signal obtained by applying a low-pass filter to the pulse wave signal during a third period. The first period described above has a length of 20 milliseconds or more and 100 milliseconds or less. The second period described above has a length that includes one or more pulse wave cycles, The biosignal measuring device according to claim 1, wherein the third period is longer than the first period.

3. The biosignal measuring device according to claim 2, wherein the DC index is a value based on the minimum value of the signal obtained by applying a low-pass filter to the pulse wave signal during the third period.

4. The biosignal measuring device according to claim 3, wherein the noise index is a value based on the average value of the range of the pulse wave signal over a plurality of first periods.

5. The second period is 3 seconds or more and 10 seconds or less in length. The biosignal measuring device according to claim 2, wherein the third period is 250 milliseconds or longer and 10 seconds or less in length.

6. The biosignal measuring device according to claim 1, wherein the acquisition means acquires the noise index, the pulse wave index, and the DC index from a pulse wave signal generated based on the amount of reflected or transmitted infrared light irradiated onto the user's biological tissue.

7. A method performed by a computer to determine whether a sensor unit, which includes a light-emitting unit that irradiates light onto the user's biological tissue and a light-receiving unit that generates a signal corresponding to the amount of reflected or transmitted light, is detached from the user, A signal generation step that generates a pulse wave signal based on the signal generated by the light receiving unit, An acquisition step to acquire a noise index representing the noise component of the pulse wave signal, a pulse wave index representing the pulse wave component of the pulse wave signal, and a DC index representing the DC component of the pulse wave signal. A method comprising: a determination step of determining that the sensor unit is detached from the user when the detection conditions are met such that the first ratio of the noise index to the pulse wave index is greater than a first threshold, and the second ratio of the noise index to the DC index is greater than a second threshold.

8. A program for causing a computer to function as at least a determination means for a biosignal measuring device according to any one of claims 1 to 6.

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