JP2013202077A - Pulse meter and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pulse meter and a program, etc., for determining a blood circulation state of a subject using a pulse wave sensor with less calculation amount and power consumption.SOLUTION: A pulse meter includes: a pulse wave detection part 10 having a pulse wave sensor 11 for outputting pulse wave sensor signals; a processing part 100 for performing processing to signals from the pulse wave detection part 10; and a reporting part 72 for reporting a processing result in the processing part 100. The processing part 100 determines the blood circulation state of a subject on the basis of change tendency information of the pulse wave sensor signals before cutting DC components, and the reporting part 72 reports determination result information of the blood circulation state in the reporting part 100.

Description

  The present invention relates to a pulse meter, a program, and the like.

  Conventionally, electronic devices such as a pulse meter have been widely used. A pulse meter is a device for detecting a pulsation derived from the heartbeat of a human body, for example, a signal derived from a heartbeat based on a signal from a pulse wave sensor attached to an arm, palm, finger, etc. Is a device for detecting

  For example, a photoelectric sensor is used as the pulse wave sensor. In this case, a method of detecting reflected light or transmitted light of the light irradiated on the living body with the photoelectric sensor can be considered. Depending on the blood flow in the blood vessel, the amount of light absorbed and reflected by the living body differs, so the sensor information (pulse wave sensor signal) detected by the photoelectric sensor is a signal corresponding to the blood flow, etc. By analyzing the signal, it is possible to obtain information on the beat.

  However, the blood flow rate decreases due to factors such as a decrease in temperature or a pressure on the blood flow measurement site (or a site closer to the heart). In that case, since the signal value to be acquired is decreased, the ratio of noise is relatively increased, and the SN state is deteriorated. Therefore, since the reliability of the pulsation information calculated from the signal also decreases, there is a possibility that the user's judgment may be mistaken if the pulsation information is notified as it is.

JP 2008-229199 A

  Patent Document 1 discloses a method for calculating the SN state of a pulse signal. In general, if the blood circulation state deteriorates, the tendency that the SN state also deteriorates is considered to be strong. Therefore, it is possible to determine that the blood circulation state is bad based on the bad SN state. Various correspondences are also possible.

  However, in Patent Document 1, frequency analysis (specifically, determination based on the baseline spectrum after FFT) is performed on the pulse signal to determine the SN state. Problems remain in terms of load and power consumption.

  According to some aspects of the present invention, it is possible to provide a pulse meter, a program, and the like that perform determination of a blood circulation state of a subject using a pulse wave sensor with a small amount of calculation and power consumption.

  One aspect of the present invention is a pulse wave detection unit having a pulse wave sensor that outputs a pulse wave sensor signal, a processing unit that processes a signal from the pulse wave detection unit, and a processing result in the processing unit A notification unit that notifies the blood flow state of the subject based on the change tendency information of the pulse wave sensor signal before the DC component cut, and the notification unit includes the processing unit This relates to a pulsometer for informing the blood circulation state determination result information.

  In one aspect of the present invention, the blood circulation state of the subject is determined based on the change tendency information of the pulse wave sensor signal before the DC component cut, and the determination result is notified by the notification unit. Therefore, it is possible to determine the blood circulation state with less calculation amount and power consumption than when performing frequency analysis such as FFT. Further, in order to notify the determination result, when the blood circulation state is bad, it is possible to notify the user that there is doubt about the reliability of information (for example, pulsation information acquired based on the pulse wave sensor signal). It becomes possible, and inappropriate judgment by the user can be suppressed.

  In one aspect of the present invention, the processing unit calculates a moving average or an integrated value of the pulse wave sensor signal before the DC component cut in a given period as an index value, and based on the calculated index value The change tendency information may be acquired.

  Thereby, it becomes possible to use a moving average or an integrated value as an index value for obtaining change trend information.

  In one aspect of the present invention, the processing unit is based on at least one of a period of body motion noise based on body movement of the subject, a period of breathing of the subject, and a pulsation period of the subject. The moving average or the integrated value of the pulse wave sensor signal before the DC component cut during the set given period may be calculated as the index value.

  As a result, it is possible to suppress the influence of body movement, respiration, and pulse, and to calculate appropriate index values and acquire change trend information.

  In the aspect of the invention, the processing unit may be configured to calculate the moving average or the pulse wave sensor signal before the DC component cut in the given period set as a period longer than the cycle of the respiration. The integrated value may be calculated as the index value.

  As a result, it is possible to suppress the influence of respiration and to calculate appropriate index values and acquire change tendency information.

  Moreover, in one aspect of the present invention, the processing unit acquires and acquires, as an index value, a signal obtained by performing filter processing using a low-pass filter on the pulse wave sensor signal before the DC component cut. The change tendency information may be acquired based on the index value.

  As a result, the pulse wave sensor signal before the DC component cut after the low-pass filter process can be used as an index value for acquiring change tendency information.

  In one aspect of the present invention, the low-pass filter has at least one of a frequency of body motion noise based on body motion of the subject, a frequency of breathing of the subject, and a frequency of pulsation of the subject. The filter processing in which the frequency set based on the frequency is set as the cut-off frequency may be performed.

  As a result, it is possible to suppress the influence of body movement, respiration, and pulse, and to calculate appropriate index values and acquire change trend information.

  In the aspect of the invention, the low-pass filter may perform the filtering process in which a frequency lower than the respiration frequency is set as the cutoff frequency.

  As a result, it is possible to suppress the influence of respiration and to calculate appropriate index values and acquire change tendency information.

  In one aspect of the present invention, the processing unit is configured to output a signal value of the pulse wave sensor signal before the DC component cut at a first timing and a second timing different from the first timing. Difference information of the signal value of the pulse wave sensor signal before the DC component cut may be calculated as an index value, and the change tendency information may be acquired based on the index value.

  Thereby, the difference information of the pulse wave sensor signal before the DC component cut at different timings can be used as an index value for obtaining change tendency information.

  In the aspect of the invention, the processing unit may receive information indicating that the pulse wave sensor signal before the DC component cut tends to decrease when the index value continuously decreases a given number of times. You may acquire as change tendency information and determine with the said blood circulation state being bad based on the acquired said change tendency information.

  This makes it possible to acquire change trend information based on the increase or decrease of the index value.

  In the aspect of the invention, the pulse wave detection unit includes a current / voltage conversion circuit that converts a current value, which is an output from the pulse wave sensor, into a voltage value, and the processing unit includes the current / voltage The pulse wave sensor signal before the DC component cut may be acquired based on the output signal of the conversion circuit.

  This makes it possible to obtain a signal by performing current / voltage conversion on the output of the pulse wave sensor.

  In the aspect of the invention, the current / voltage conversion circuit may include a first power supply node, a resistance element provided between the output nodes from which the output signal is output, the output node, and the second power supply. A bipolar transistor provided between the nodes and a photodiode provided between the first power supply node and the base of the transistor may be included.

  This makes it possible to realize a current / voltage conversion circuit with a specific configuration.

  In one aspect of the present invention, a temperature sensor that acquires temperature information is included, and the processing unit outputs the temperature information from the temperature sensor with respect to a signal corresponding to the output signal of the current / voltage conversion circuit. The pulse wave sensor signal before the DC component cut may be acquired by performing a temperature compensation process for canceling the fluctuation of the output signal according to the temperature change.

  This makes it possible to perform compensation processing based on the temperature information of the temperature characteristics of the current / voltage conversion circuit.

  Moreover, in one aspect of the present invention, it includes a temperature sensor that acquires temperature information, and the processing unit performs the blood circulation of the subject based on the change tendency information of the pulse wave sensor signal before the DC component cut. Determining the state, acquiring the temperature information at a timing corresponding to the acquisition timing of the determination result information of the blood circulation state, and the notification unit notifies the determination result information of the blood circulation state and the temperature information May be.

  Thereby, temperature information can be acquired in accordance with the determination of the blood circulation state.

  In one aspect of the present invention, when the processing unit determines that the blood circulation state of the subject is poor based on the change tendency information of the pulse wave sensor signal before the DC component cut, You may perform the process which makes the said temperature sensor an operation enable state.

  This makes it possible to determine the operating state of the temperature sensor based on the blood circulation state determination result information.

  In the aspect of the invention, the processing unit calculates pulsation information based on a pulse wave detection signal that is the pulse wave sensor signal after the DC component cut, and the notification unit Information may be notified.

  As a result, it is possible to calculate pulsation information based on the pulse wave detection signal and notify the information by the notification unit.

  Another aspect of the present invention includes a pulse wave detection unit having a pulse wave sensor that outputs a pulse wave sensor signal, a processing unit that performs processing on a signal from the pulse wave detection unit, and processing in the processing unit The computer functions as an informing unit for informing the result, and the processing unit determines the blood circulation state of the subject based on the change tendency information of the pulse wave sensor signal before the DC component cut, and the informing unit The present invention relates to a program for informing the blood circulation state determination result information in the processing unit.

The basic structural example of the pulse meter of this embodiment. The structural example of the body movement noise reduction part using an adaptive filter. 3A to 3C show examples of a pulse wave detection signal, a body motion detection signal, and a waveform and a frequency spectrum of a signal after body motion noise reduction processing based on the pulse wave detection signal and the body motion detection signal. 4A and 4B show examples of a pulse meter. The detailed structural example of the pulse meter of this embodiment. The figure explaining the change tendency of the signal for blood circulation state determination. The other figure explaining the change tendency of the blood circulation state determination signal. An example of the configuration of a current / voltage conversion circuit. The flowchart explaining the process of this embodiment. The other flowchart explaining the process of this embodiment.

  Hereinafter, this embodiment will be described. In addition, this embodiment demonstrated below does not unduly limit the content of this invention described in the claim. In addition, all the configurations described in the present embodiment are not necessarily essential configuration requirements of the present invention.

1. Configuration Example of Pulse Meter First, a basic configuration example of a pulse meter (electronic device in a broad sense) of the present embodiment will be described with reference to FIG. FIG. 1 shows an example of a pulsometer. The configuration included in the pulsometer of the present embodiment may be simplified or omitted, or may not be an essential component in the pulsometer of the present embodiment. May be included.

  As shown in FIG. 1, the pulse meter of the present embodiment includes a pulse wave detection unit 10, a body motion detection unit 20, a processing unit 100, and a display unit 70. However, the pulse meter is not limited to the configuration shown in FIG. 1, and various modifications such as omission / change of some of these components or addition of other components are possible.

  The pulse wave detection unit 10 outputs a signal based on sensor information (pulse wave sensor signal) of the pulse wave sensor. The pulse wave detection unit 10 can include, for example, a pulse wave sensor 11, a filter processing unit 15, and an A / D conversion unit 16. However, the pulse wave detection unit 10 is not limited to the configuration of FIG. 1, and various components such as omitting some of these components or adding other components (for example, an amplification unit that amplifies a signal, etc.) are included. Variations are possible.

  The pulse wave sensor 11 is a sensor for detecting a pulse wave signal. For example, a photoelectric sensor can be considered. In addition, when using a photoelectric sensor as the pulse wave sensor 11, you may use the sensor comprised so that the signal component of external lights, such as sunlight, may be cut. This can be realized by, for example, a configuration in which a plurality of photodiodes are provided and difference information is obtained by feedback processing using these signals.

  The pulse wave sensor 11 is not limited to a photoelectric sensor, and may be a sensor using ultrasonic waves. In this case, the pulse wave sensor 11 has two piezoelectric elements. One of the piezoelectric elements is excited to transmit an ultrasonic wave into the living body, and the ultrasonic wave reflected by the blood flow of the living body is transmitted to the other. Received by the piezoelectric element. Since the frequency change occurs in the transmitted ultrasound and the received ultrasound due to the Doppler effect of blood flow, a signal corresponding to the blood flow can be obtained in this case as well, and pulsation information can be estimated. . Other sensors may be used as the pulse wave sensor 11.

  The filter processing unit 15 performs high-pass filter processing on the sensor information from the pulse wave sensor 11. Note that the cutoff frequency of the high-pass filter may be obtained from a typical pulse rate. For example, there are very few cases where the pulse rate of a normal person falls below 30 times per minute. In other words, since the frequency of the signal derived from the heartbeat is rarely 0.5 Hz or less, even if the information of the frequency band in this range is cut, the adverse effect on the signal to be acquired should be small. Therefore, about 0.5 Hz may be set as the cutoff frequency. Further, depending on the situation, a different cutoff frequency such as 1 Hz may be set. Furthermore, since it is possible to assume a typical upper limit value for the human pulse rate, the filter processing unit 15 may perform bandpass filter processing instead of high-pass filter processing. The cutoff frequency on the high frequency side can be set freely to some extent, but a value such as 4 Hz may be used.

  The A / D converter 16 performs A / D conversion processing and outputs a digital signal. The process in the filter processing unit 15 described above may be an analog filter process performed before the A / D conversion process, or a digital filter process performed after the A / D conversion process. .

  The body motion detection unit 20 outputs a signal (body motion detection signal) corresponding to the body motion based on the sensor information of various sensors. The body motion detection unit 20 can include, for example, an acceleration sensor 21, a pressure sensor 22, and an A / D conversion unit 26. However, the body motion detection unit 20 may include other sensors (for example, a gyro sensor), an amplification unit that amplifies a signal, and the like. Further, it is not necessary to provide a plurality of types of sensors, and a configuration including one type of sensor may be used.

  The processing unit 100 includes a signal processing unit 110 and a pulsation information calculation unit 120. However, the processing unit 100 is not limited to the configuration in FIG. 1, and various modifications such as omitting some of these components or adding other components are possible. The signal processing unit 110 performs signal processing on the output signal from the pulse wave detection unit and the output signal from the body motion detection unit.

  The signal processing unit 110 can include a pulse wave signal processing unit 111, a body motion signal processing unit 113, and a body motion noise reduction unit 115.

  The pulse wave signal processing unit 111 performs some signal processing on the signal from the pulse wave detection unit 10. Note that various signals based on the pulse wave sensor signal can be considered as the output from the pulse wave detector 10 indicated by D1 in FIG. For example, since calculation of pulsation information described later is often performed based on a pulse wave sensor signal (pulse wave detection signal) after the DC component cut, D1 includes a pulse wave sensor signal after high-pass filter processing. It is assumed that However, a signal that has not been subjected to filter processing may be output, or a pulse wave sensor signal after low-pass filter processing may be output depending on circumstances. When D1 includes a plurality of signals (for example, both the pulse wave sensor signal before the high-pass filter processing and the pulse wave sensor signal after the processing), the processing in the pulse wave signal processing unit 111 is included in D1. It may be performed for all of the signals, or may be performed for some of the signals. Various processing contents are also conceivable. For example, an equalizer process for the pulse wave detection signal may be performed, or another process may be performed.

  The body motion signal processing unit 113 performs various signal processes on the body motion detection signal from the body motion detection unit 20. Similar to D1, various signals can be considered as the output from the body motion detection unit 20 indicated by D2. For example, since the example of FIG. 1 includes the acceleration sensor 21 and the pressure sensor 22, the body motion detection signal of D2 includes an acceleration signal and a pressure signal. Since the body motion detection sensor may be another sensor such as a gyro sensor, D2 includes an output signal of a type corresponding to the type of sensor. The processing in the body motion signal processing unit 113 may be performed on all or part of the signals included in D2. For example, the signal included in D2 may be compared to perform a process of determining a signal used in the noise reduction process in the body motion noise reduction unit 115.

  In the processing in the pulse wave signal processing unit 111, a body motion detection signal may be used in accordance with the signal from the pulse wave detection unit. Similarly, in the processing in the body motion signal processing unit 113, a signal from the pulse wave detection unit 10 may be used in accordance with the body motion detection signal. In addition, a signal after a given process is performed in the pulse wave signal processing unit 111 on the output signal from the pulse wave detection unit 10 may be used for processing in the body motion signal processing unit 113. Or vice versa.

  The body motion noise reduction unit 115 performs a process of reducing noise (body motion noise) caused by body motion from the pulse wave detection signal using the body motion detection signal. A specific example of noise reduction processing using an adaptive filter is shown in FIG. The pulse wave sensor signal acquired from the pulse wave sensor 11 includes a component due to body movement in addition to a component due to heartbeat. The same applies to the pulse wave detection signal (pulse wave sensor signal after the DC component cut) used for the calculation of pulsation information. Of these, components useful for the calculation of pulsation information are components caused by heartbeats, and components caused by body movements hinder the calculation. Therefore, a signal (body motion detection signal) resulting from body motion is acquired using a body motion sensor, and a signal component correlated with the body motion detection signal (referred to as an estimated body motion noise component) is removed from the pulse wave detection signal. By doing so, body motion noise included in the pulse wave detection signal is reduced. However, even if the body motion noise in the pulse wave detection signal and the body motion detection signal from the body motion sensor are signals resulting from the same body motion, the signal level is not necessarily the same. Therefore, the estimated body motion noise component is calculated by performing filter processing in which the filter coefficient is adaptively determined for the body motion detection signal, and the difference between the pulse wave detection signal and the estimated body motion noise component is calculated. To do.

  FIGS. 3A to 3C illustrate the above processing in terms of a frequency spectrum. FIG. 3A and the like show the time-varying waveform of the signal at the top and the frequency spectrum at the bottom. FIG. 3A shows a pulse wave detection signal before body motion noise reduction, and as shown in A1 and A2, two frequencies having large values appear in the spectrum. One of these is caused by heartbeat, and the other is caused by body movement. Note that although there are some frequencies that are higher than A1, they are not considered here because they are high frequency components corresponding to integer multiples of A1 and A2. Hereinafter, high-frequency components are also seen in FIGS. 3B and 3C, but are not considered here as well.

  On the other hand, FIG. 3B shows a body motion detection signal. If there is only one type of body motion that has caused the body motion detection signal, a frequency having a large value as shown in B1 is obtained. One appears. Here, the frequency of B1 corresponds to A2 in FIG. In such a case, the signal shown in FIG. 3C is obtained by taking the difference between the pulse wave detection signal and the estimated body motion noise component by the method shown in FIG. As apparent from the figure, pulse wave detection is performed by subtracting an estimated body motion noise component having a peak B1 due to body motion from a pulse wave detection signal having two peaks A1 and A2 due to heartbeat and body motion. The body motion component (corresponding to A2) in the signal is removed, and as a result, the peak C1 (frequency corresponds to A1) due to the heartbeat remains.

  It is guaranteed that the body motion noise included in the pulse wave detection signal corresponds to the body motion detection signal, and that the body motion detection signal does not contain a signal component that adversely affects the noise reduction processing. In such a situation, since it is not necessary to perform frequency analysis in the body motion noise reduction unit 115, the frequency spectrum shown in the lower part of FIGS. 3 (A) and 3 (B) may not be considered. However, depending on the type of sensor used to acquire the body motion detection signal, there may be a case where the above condition is not satisfied. In that case, for example, the body motion signal processing unit 113 may process the body motion detection signal so as to satisfy the above condition, or a body motion detection signal that does not satisfy the above condition may be processed. Etc. may be excluded from the output. Various methods for determining whether or not the above conditions are satisfied are conceivable. For example, a frequency spectrum obtained by frequency analysis as shown in the lower part of FIGS. 3A and 3B is used. May be.

  The pulsation information calculation unit 120 calculates pulsation information based on the input signal. The pulsation information may be a pulse rate value, for example. For example, the pulsation information calculation unit 120 obtains a spectrum by performing frequency analysis such as FFT on the pulse wave detection signal after the noise reduction processing in the body motion noise reduction unit 115 and obtains a representative frequency in the obtained spectrum. The processing may be performed with the heartbeat frequency as. In that case, a value obtained by multiplying the obtained frequency by 60 is a commonly used pulse rate (heart rate).

  Note that the pulsation information is not limited to the pulse rate, and may be, for example, information indicating the pulse rate (heartbeat frequency, cycle, etc.). Moreover, the information which represents the state of pulsation may be sufficient, for example, the value showing blood flow itself (or its fluctuation | variation) is good also as pulsation information. However, since the relationship between the blood flow rate and the signal value of the pulse wave sensor signal has individual differences for each user, when the blood flow rate or the like is used as pulsation information, correction processing is performed to deal with the individual differences. It is desirable.

  Also, it detects the timing at which a given value (upper peak, lower peak, or a value above a given threshold) appears on the time-varying waveform of the input pulse wave detection signal, and corresponds to the timing interval. The pulsation information may be calculated by obtaining the heartbeat period from the time to be performed. Alternatively, the pulsation information can be calculated by transforming the waveform of the pulse wave detection signal into a rectangular wave and using the rising edge of the rectangular wave. In this case, it is not necessary to perform frequency analysis, which is advantageous in terms of calculation amount and power consumption. However, in this method, since the signal value is used as it is without being converted to the frequency axis, it is necessary to prepare the waveform to some extent. Therefore, it is desirable to perform frequency analysis in a noisy situation or the like.

  The display unit 70 (output unit in a broad sense) is for displaying various display screens used for presenting the calculated pulsation information, and can be realized by, for example, a liquid crystal display or an organic EL display.

  Specific examples of the above-described pulse meter are shown in FIGS. 4 (A) and 4 (B). FIG. 4A shows an example of a wristwatch-type pulse meter. The base unit 400 including the pulse wave sensor 11 and the display unit 70 is attached to the left wrist 200 of the subject (user) by a holding mechanism 300 (for example, a band). FIG. 4B shows an example of a finger wearing type. A pulse wave sensor 11 is provided at the bottom of a ring-shaped guide 302 for insertion into the fingertip of the subject. However, in the case of FIG. 4B, since there is not enough space to provide the display unit 70, the display unit 70 (and a part corresponding to the processing unit 100 if necessary) is connected to the pulse wave sensor 11. It is assumed that it is provided on the other end side of the wired cable.

  The method of the present embodiment to be described later can be applied to any type of pulse wave meter, but is more preferably applied to a wristwatch type pulse meter (example in FIG. 4A). However, in the example of FIG. 4A, the pulse wave sensor 11 is attached to a portion where it is difficult to acquire a pulse wave sensor signal, such as the outside of the wrist (a portion in contact with the back cover surface of the wristwatch). For this reason, the amplitude of the pulse wave sensor signal output from the pulse wave sensor 11 tends to decrease as a whole. Therefore, it is desirable to perform processing related to accuracy of pulsation information by some method as in the present embodiment described later.

2. As described above, a method for acquiring information corresponding to the blood flow of a living body by using a photoelectric sensor, an ultrasonic sensor, or the like as the pulse wave sensor 11 is known. In these methods, when the blood flow rate is reduced due to some factor, the signal value corresponding to the blood flow rate is decreased, so that the ratio of noise in the entire signal is relatively increased. In that case, since it becomes difficult to separate a signal caused by blood flow from a noise signal, the reliability of information (for example, pulsation information) based on the signal of the pulse wave sensor 11 is reduced, and the information is transmitted to the user. May present problems if presented.

  In general, since it is considered that there is a correspondence between the decrease in blood flow and the deterioration of the SN state, the SN state is determined by some method, and various processes are performed when the SN state is determined to be bad. The above problem may be addressed. For example, when the SN state is bad, it is erroneous to the user by presenting information indicating that the presented information is not necessarily accurate because the SN state is bad as well as presenting pulsation information (displayed in a narrow sense) It can suppress making judgment.

  However, frequency analysis such as FFT has been widely used in the conventional SN state determination. Specifically, the SN state can be determined by performing conversion to the frequency axis by FFT and using the baseline spectrum ratio or the like. However, in general, frequency analysis requires a large amount of calculation, and processing load and power consumption become problems.

  Therefore, the present applicant proposes a method of determining the blood circulation state of the subject and appropriately notifying the user without performing frequency analysis such as FFT. Specifically, the blood circulation state is determined using change tendency information of the pulse wave sensor signal (hereinafter also referred to as a blood circulation state determination signal) before the DC component cut. Details of the change tendency information will be described later. By doing in this way, it becomes possible to determine the blood circulation state with a small amount of calculation and power consumption compared with the case of performing frequency analysis.

  In addition, if temperature decrease is a problem as a cause of deterioration of the blood circulation state, temperature measurement may be performed using a temperature sensor, and some processing may be performed when the measured temperature decreases. However, there is a problem that power consumption increases if temperature is constantly measured.

  In that respect, if the blood circulation state can be determined by the method of the present embodiment, an increase in power consumption by the temperature sensor can be reduced by performing temperature measurement when it is determined that the blood circulation state is bad. It becomes possible. In this embodiment, even if the temperature is lowered, there is no particular problem if the blood circulation state is not deteriorated, so it is sufficient to first determine the blood circulation state and perform temperature measurement only when the blood circulation state is bad. It is. However, as long as the output from the temperature sensor is used in other processing, the temperature sensor may be frequently enabled (always in a narrow sense).

  When a temperature sensor is used, it is possible to estimate whether or not the blood flow fluctuation factor is temperature. For example, when the blood circulation state is bad and the temperature is low, it can be estimated that the blood circulation state has deteriorated due to the temperature drop. Therefore, it is possible to notify the user not only that the blood circulation state has deteriorated but also the deterioration factor. In the case where temperature measurement is not performed, even when the deterioration of the blood circulation state is notified, since the cause of the deterioration cannot be specified, the actions that can be taken by the user who has been notified of the deterioration are limited. Specifically, what the user can do is to not use the corresponding pulsation information for judgment by the user (or reduce the importance in the judgment), etc. The technique for improving the blood circulation state itself is a factor that deteriorates the blood circulation state I can't decide unless I know. On the other hand, if it is specified that the deterioration of the blood circulation state is due to a decrease in temperature, when the user is informed of this, the user is not limited to the countermeasure at the time of notification that the unreliable information is not used. It is possible to take measures to improve the reliability of information acquired in the future, such as wearing warm clothes.

  Hereinafter, after describing a system configuration example of a pulse meter, a blood circulation state determination process using a blood circulation state determination signal (pulse wave sensor signal before DC component cut) will be described. Thereafter, the control in the notification control unit will be described, and finally the details of the processing of the present embodiment will be described using a flowchart.

3. System Configuration Example FIG. 5 shows a system configuration example of the pulse meter according to the present embodiment. The pulse meter includes a pulse wave detection unit 10, a body motion detection unit 20, a temperature sensor 30, a processing unit 100, and a notification unit 72. However, the pulse meter is not limited to the configuration of FIG. 5, and various modifications such as omitting some of these components or adding other components are possible. For example, in this embodiment, it is not essential to reduce body movement noise, and the body movement detection unit 20 and the body movement noise reduction unit 115 of the processing unit 100 may be omitted.

  The pulse wave detection unit 10 includes a pulse wave sensor 11, a current / voltage conversion circuit 12, a filter processing unit 15, and A / D conversion units 16-1 and 16-2. However, the pulse wave detection unit 10 is not limited to the configuration in FIG. 5, and various modifications such as omitting some of these components or adding other components are possible.

  The pulse wave sensor 11 uses a photoelectric sensor or the like as described above with reference to FIG. Specifically, the photoelectric sensor is a photodiode or the like, and its output becomes a current value, so that it is converted into a voltage value by the current / voltage conversion circuit 12. In this embodiment, the filter processing unit 15 is realized by a high-pass filter that performs high-pass filter processing. In the present embodiment, the pulse wave detection unit 10 includes an A / D conversion unit 16-1 and an A / D conversion unit 16-2, and converts each input analog signal into a digital signal and outputs the digital signal.

  As shown in FIG. 5, the pulse wave sensor 11 is connected to a current / voltage conversion circuit 12. The current / voltage conversion circuit 12 is connected to the filter processing unit 15 and the A / D conversion unit 16-2. The filter processing unit 15 is connected to the A / D conversion unit 16-1. The A / D conversion unit 16-1 is connected to the body movement noise reduction unit 115, and the A / D conversion unit 16-2 is connected to a blood circulation state determination unit 117 described later. That is, the pulse wave sensor signal (pulse wave detection signal, AC component of the pulse wave sensor signal) after the DC component cut is output from the A / D conversion unit 16-1 to the body motion noise reduction unit 115. The pulse wave sensor signal (blood circulation state determination signal) before the DC component cut is output from the / D conversion unit 16-2 to the blood circulation state determination unit 117. Since the output signal to the blood circulation state determination unit 117 only needs to include the DC component of the pulse wave sensor signal, a filter processing unit that performs low-pass filter processing enters before the A / D conversion unit 16-2. It may be configured. In addition, various modifications can be made to the connection of each unit included in the pulse wave detection unit 10.

  The body motion detection unit 20 includes an acceleration sensor 21 and an A / D conversion unit 26. The acceleration sensor 21 is connected to the A / D conversion unit 26, and the A / D conversion unit 26 is connected to the body movement noise reduction unit 115. The body motion detection unit 20 only needs to have a sensor for detecting body motion, and the acceleration sensor 21 may be changed to another sensor, or may have a plurality of sensors.

  The temperature sensor 30 acquires temperature information and outputs it to the notification control unit 130. Further, when performing the process of compensating the temperature characteristic of the current / voltage conversion circuit 12 based on the temperature information, the temperature information is output to a temperature compensation processing unit (not shown in FIG. 5) that performs the process. May be. In this case, since the target of the temperature compensation processing is a signal from the pulse wave detection unit 10, a first temperature compensation processing unit is provided between the A / D conversion unit 16-1 and the body motion noise reduction unit 115, A second temperature compensation processing unit may be provided between the A / D conversion unit 16-2 and the blood circulation state determination unit 117. Further, the temperature compensation processing unit need not be divided into two, and may be combined into one.

  The processing unit 100 includes a signal processing unit 110, a pulsation information calculation unit 120, and a notification control unit 130. The signal processing unit 110 includes a body motion noise reduction unit 115 and a blood circulation state determination unit 117. However, the processing unit 100 and the signal processing unit 110 are not limited to the configuration in FIG. 5, and some of these components (for example, the body motion noise reduction unit 115) are omitted or other components are added. Various modifications of the above are possible.

  The blood circulation state determination unit 117 may be included in the pulse wave signal processing unit 111 in FIG. The blood circulation state determination unit 117 performs a blood circulation state determination process based on the blood circulation state determination signal output from the A / D conversion unit 16-2. A specific method will be described later. The determination result of the blood circulation state is output to the notification control unit 130 and the temperature sensor 30 as necessary.

  The body motion noise reduction unit 115 performs body motion noise reduction processing on the pulse wave detection signal from the A / D conversion unit 16-1 based on the body motion detection signal from the body motion detection unit 20. The processing content of the body motion noise reduction unit 115 is the same as that described above with reference to FIG. The processing in the pulsation information calculation unit 120 is also as described above.

  The notification control unit 130 performs control for notification by the notification unit 72. For example, the pulsation information from the pulsation information calculation unit 120 may be controlled to be constantly notified (displayed in a narrow sense). Then, when a determination result indicating that the blood circulation state is bad is received from the blood circulation state determination unit 117, control is performed to notify that together with the pulsation information at the corresponding timing. In addition, when acquiring temperature information from the temperature sensor 30, it is notified that the blood circulation is deteriorated due to low temperature together with the pulsation information of the corresponding timing on the condition that the blood circulation state is bad and the temperature is low. Control may be performed.

  The notification unit 72 notifies the user of various types of information according to the control content in the notification control unit 130. Although it limited to the display part 70 in FIG. 1, the alerting | reporting method in the alerting | reporting part 72 in FIG. 5 is not limited to a display. A display using the display unit 70 may be used, or a lamp such as an LED may be turned on or blinked. Further, notification by voice or other sounds may be used. In addition, the notification unit 72 can use various notification methods that the user can recognize.

4). Blood Circulation State Determination Based on Change Trend Information Next, blood circulation state determination processing using a blood circulation state determination signal (pulse wave sensor signal before DC component cut) will be described. As described above, the blood circulation state determination signal used in the blood circulation state determination unit 117 may be a signal obtained by removing the AC component (high frequency component) from the pulse wave sensor signal because the DC component does not have to be cut. Good.

  When the blood circulation state is good, the blood flow volume increases, so the amount of irradiation light absorbed increases. Therefore, the reflected light (or transmitted light) incident on the pulse wave sensor 11 becomes weak, and when a photodiode is used as the pulse wave sensor 11, the value of the output current of the photodiode becomes small. On the other hand, if the blood circulation state is bad, the amount of absorbed light is reduced by reducing the blood flow volume, and the reflected light (or transmitted light) becomes strong, so that the output current value of the photodiode increases. Since the difference according to the blood circulation state is reflected in the blood circulation state determination signal of the present embodiment, it is possible to determine the blood circulation state based on the blood circulation state determination signal.

As an example, a conversion process using the current / voltage conversion circuit shown in FIG. 8 is performed on the output current of the photodiode, and the converted voltage signal (or a signal based thereon) is used as a blood circulation state determination signal. Consider the case. In this case, when the output current of the photodiode and i _PD, since the voltage after conversion is represented by the formula (2) described later, the voltage value as the i _PD is large is small, the voltage value as the i _PD is small is large Become. That is, if the blood circulation state is good, the value of the blood circulation state determination signal increases, and if the blood circulation state is bad, the value of the blood circulation state determination signal decreases. Therefore, the blood circulation state may be determined from these differences.

  However, although the blood circulation state determination signal is a signal corresponding to the blood circulation state (blood flow rate in a narrow sense), individual differences or the like occur in the signal level. For example, a person with relatively dark skin has better light absorption in the skin than a person with white skin. Therefore, even if the actual blood flow is the same, a person with dark skin has better absorption of the irradiated light in the skin than a white person, and the reflected light (or transmitted light) becomes weaker, resulting in a pulse wave. The signal level of the sensor signal (here, the pulse wave sensor 11 is a photoelectric sensor) increases. Therefore, the blood circulation state determination process is performed based on the change tendency information, not the value of the blood circulation state determination signal itself.

  The change trend information represents information indicating whether the trend is decreasing, increasing, or neither. Various methods for acquiring the change tendency information from the blood circulation state determination signal are conceivable. Here, the index value is acquired based on the blood circulation state determination signal, and the change tendency information is acquired based on the increase or decrease of the index value.

  Hereinafter, three specific examples of index values for acquiring change trend information will be described. Although it is sufficient to use any one of the following index values, this does not prevent the use of a plurality of index values.

  As the first index value, a moving average or integrated value of the blood circulation state determination signal is used. Specifically, a given index value calculation period is set, and a moving average or an integrated value may be calculated for the signal value of the blood circulation state determination signal in the set index value calculation period. The moving average may be a simple moving average or a weighted moving average. Also, when using the integrated value, it is not limited to simply adding all the values, but may be added after multiplying the signal value of each blood circulation state determination signal by a weighting factor. Good.

  A specific example in the case of using the time variation waveform of the blood circulation state determination signal and the moving average as the index value is shown in FIGS. In FIG. 6, vertical movement occurs in a short span, but the moving average that is the index value is consistently decreasing, and it can be seen that the blood circulation state determination signal tends to decrease. On the other hand, similarly in FIG. 7, since the moving average is consistently increasing, it can be understood that the blood circulation state determination signal tends to increase. If the blood circulation state determination signal is in a decreasing tendency, it is determined that the blood circulation state is bad, and if it is in an increasing tendency, it is determined that the blood circulation state is good. There are various methods for obtaining the change trend from the index value. For example, when the index value decreases (increases) continuously for a certain number of times (for example, 5 times), it is determined that the change trend is decreasing (increase trend). do it. This is the same when other index values are used.

  The problem here is the setting of the length of the index value calculation period. As shown in FIG. 6, if the AC component is not removed from the pulse wave sensor signal, the value of the blood circulation state determination signal also fluctuates at a period corresponding to the period of the pulse. In addition, the blood circulation state determination signal may fluctuate due to breathing or other body movements, and the period in this case is generally longer than the pulse. In other words, it can be easily understood from FIG. 6 that the tendency is decreasing, but the signal value of the blood circulation state determination signal in a short span (for example, a pulse or a period shorter than one cycle of breathing or body movement) is There is a possibility of taking a large value locally. In that case, even if the blood circulation state determination signal as shown in FIG. 6 is acquired, there is a possibility that the index value is not continuously decreased, and there may be a case where it cannot be determined that the index value is decreasing.

  Therefore, the length of the above-described index value calculation period may be set to a period that can suppress the influence of fluctuations caused by pulse, respiration, and body movement. Specifically, a period corresponding to one cycle of the pulse may be set if the influence of fluctuation due to the pulse is suppressed. Even during this period, the blood circulation state determination signal locally takes a large value and a small value due to the pulse, but they cancel each other to some extent in the calculation process of the moving average or integrated value. The impact can be suppressed. Further, this period is not limited to the length of one cycle, and may be a longer period, in which case it is not limited to an integral multiple of one cycle. When the index value calculation period consists of a period that is an integral multiple of one cycle and a period that is shorter than one cycle, there is a possibility that the effect of canceling fluctuations caused by pulses may be low in a period that is shorter than one cycle. This is because the ratio to the calculated index value is limited because the ratio of the entire value calculation period is small (at least less than 50%).

  The same applies to the case where the influence of fluctuation due to breathing or other fluctuation due to body movement is suppressed, and a period longer than one cycle of the fluctuation to be suppressed may be set as the index value calculation period. From the above, the length of the index value calculation period is subject to the number of conditions according to the type of variation to be suppressed. May be set as the index value calculation period. For example, as shown in FIG. 6, when it is necessary to suppress the influence of the pulse and respiration, and the respiration cycle is longer than the respiration cycle, a period longer than one respiration cycle is set as the index value calculation period. Will be set.

  If it is a pulse or respiration, the range that the cycle can take is determined to some extent from the biological characteristics of the subject, so the maximum value or a sufficiently large value for the maximum value is set and set. An index value calculation period corresponding to the value may be set. In addition, when considering fluctuations caused by body motion, the cycle varies greatly depending on the type of body motion, and the types of exercise of the user are various. However, since the fluctuation period caused by body movement is also known to some extent in a typical range, the index value calculation period can be set based on the typical range. For example, the index value calculation period may be set to about 10 seconds.

  That is, even if it is unknown whether the blood circulation state determination signal is affected by the pulse, respiration, or body movement, it is possible to deal with many cases by always setting an index value calculation period of about 10 seconds. . However, the length of the index value calculation period may be changed dynamically. For example, in the embodiment in which the body motion detection unit 20 acquires the body motion detection signal, the body motion noise period is detected from the body motion detection signal, and the length of the index value calculation period is set based on the detected period. May be.

  In addition, the advantage of extending the index value calculation period has been described above. However, if the index value calculation period is excessively long, the calculation amount for calculating the index value increases or the actual blood circulation state determination signal increases (decreases). ) There is a concern that a time lag may occur in the reflection of the change trend information (and the index value) even if the trend changes from a tendency to a decrease (increase). Therefore, an upper limit may be set for the length of the index value calculation period in consideration of these effects.

  Next, the second index value will be described. As the second index value, a signal obtained by subjecting the blood circulation state determination signal to low-pass filter processing is used. The reason why the low-pass filter is used here is to suppress the influence of fluctuation due to the pulse, respiration, body movement, etc., as in the first method. Here, the fluctuation to suppress the influence on the blood circulation state determination is a frequency having a higher frequency than the fluctuation to be detected as the change tendency information. That is, the cut-off frequency of the low-pass filter used for the low-pass filter process is a frequency corresponding to the frequency of fluctuation to be suppressed. It has been described that in the first method, many cases can be dealt with if a period of about 10 seconds is taken into consideration. Therefore, in the second method, about 0.1 Hz, which is a frequency corresponding to a period of about 10 seconds, may be set as the cutoff frequency of the low-pass filter. In addition, in the same way as the setting method of the index value calculation period can be considered in the first method, various settings can be made for the cutoff frequency of the low-pass filter. The lowest frequency may be set as a reference.

  The blood circulation state determination signal after the low-pass filter processing is acquired with the same frequency (for example, 16 Hz) as the blood circulation state determination signal. It is good also as an index value by picking up.

  Next, the third index value will be described. As the third index value, a difference value between the signal value of the blood circulation state determination signal at the first timing and the signal value of the blood circulation state determination signal at the second timing different from the first timing is used. . In the following description, it is assumed that the difference value is an index value corresponding to the first timing. In this case, the second timing is more temporally than the first timing in view of the fact that the index value should be calculated as soon as possible after obtaining the signal value at the first timing if the processing is highly real-time. It is the previous timing. In a narrow sense, the second timing may be an acquisition start timing of the pulse wave sensor signal. However, the second timing may be later in time than the first timing as long as data is accumulated and processing is performed later.

  When the third index value is used, it is sufficient to obtain the difference value between the two signal values, so that the processing is easier than when the first and second index values are used.

5. Control by Notification Control Unit Next, control by the notification control unit 130 will be described. The notification control unit 130 acquires the pulsation information from the pulsation information calculation unit 120 and the blood circulation state determination result information at the timing corresponding to the pulsation information from the blood circulation state determination unit 117.

  Various notification control methods are conceivable. For example, when it is determined that the blood circulation state is good, control for notifying the pulsation information (for example, pulse rate) is performed, and when it is determined that the blood circulation state is bad. The control for notifying that the blood circulation state is bad together with the pulsation information may be performed. The notification of the pulse rate can be displayed by a display unit. Further, the notification that the blood circulation state is bad may be one that displays a sentence, an icon, or the like, may be lighting or blinking of an LED or the like, or may be a technique such as emitting a warning sound. Good.

  In addition, when it determines with a blood circulation state being good, you may perform control which alert | reports that a blood circulation state is good together with pulsation information.

  Further, when temperature information is acquired from the temperature sensor 30, the notification control may be different depending on whether the temperature is low. This is because when the temperature is low and the blood circulation state is bad, it can be assumed that the deterioration factor of the blood circulation state is low temperature, and the information is significant for the user.

  Consider a specific example in the embodiment in which the temperature sensor 30 is enabled when the blood circulation state is poor. When it is determined that the blood circulation state is good, the control may be performed to notify only the pulsation information, or the control may be performed to notify that the blood circulation state is good together with the pulsation information. Good.

  When the blood circulation state is bad, the temperature sensor 30 is set in an operation enable state, and temperature information is acquired from the temperature sensor 30. When it is determined that the temperature is low based on the temperature information, control is performed to notify that the blood circulation state is bad and the temperature is low together with the pulsation information. The fact that the blood circulation state is bad and the low temperature may be notified by separate sentences or icons, or a single sentence or icon or the like (warning sound etc.) indicating that the blood circulation state is bad due to the low temperature. Including). When it is determined that the temperature is not low, control is performed to notify that the blood circulation state is bad together with the pulsation information as in the above example. In addition, when it is not low temperature, you may alert | report that it is not low-temperature together with the blood circulation state being bad. In that case, the blood circulation state may be informed in one piece of information that the blood circulation state is bad but not due to temperature.

6). Details of Processing Details of processing according to this embodiment will be described with reference to a flowchart. In the following, the index value used for acquiring the change tendency information of the blood circulation state determination signal is not particularly limited, and any of the above-described index values may be used.

  FIG. 9 shows a flowchart for explaining the processing of this embodiment. When this processing is started, first, a pulse wave sensor signal (blood circulation state determination signal) before the DC component cut and a pulse wave sensor signal (pulse wave detection signal) after the DC component cut are acquired (S101, S102). . Then, change tendency information ΔDC of the blood circulation state determination signal is acquired (S103). Specifically, in S103, any one of the first to third index values described above is calculated, and it is determined whether or not the calculated index value is continuously decreasing.

  It is determined whether or not ΔDC is decreasing (S104). If it is decreasing, it is determined that the blood circulation state is bad (S105), and a blood flow flag indicating that is turned ON (S106). On the other hand, if it is determined in S104 that there is no tendency to decrease, it is determined that the blood circulation state is good (S107), and the blood flow flag is turned OFF (S108).

  After the processing of S106 or S108, pulsation information (here, the pulse rate) is calculated based on the pulse wave detection signal acquired in S102 (S109), and the pulse rate and the blood flow flag at the corresponding timing are stored ( S110). Then, it is determined whether or not the blood flow flag is ON or OFF (S111). If it is ON, the blood flow is bad, so that the fact is notified (S112) and the pulse rate is displayed (S113). ). On the other hand, if the blood flow flag is OFF in S111, the process proceeds to S113 without performing S112, and the pulse rate may be displayed.

  Further, as described above, the notification control may be performed using the temperature information from the temperature sensor 30 together. FIG. 10 shows a flowchart for explaining the processing in this case. Since S201 to S213 (excluding S212) in this process are the same as S101 to S113 (excluding S112) in FIG. 9, detailed description may be omitted.

  If it is determined in S204 that ΔDC is decreasing, it is determined that the blood circulation state is poor (S205), the blood flow flag is turned on (S206), and temperature information from the temperature sensor 30 is acquired (S206). S214). Then, based on the acquired temperature information, it is determined whether or not the temperature is low (specifically, a comparison process between the temperature value and the threshold value) (S215). If the temperature is low, the low temperature flag is turned on. (S216) If the temperature is not low, the low temperature flag is turned off (S217).

  On the other hand, if it is determined in S204 that there is no tendency to decrease, it is determined that the blood circulation state is good (S207), and the blood flow flag is turned OFF (S208). In this case, since the temperature information is not acquired in the first place, it is not determined that the temperature is low, and the process proceeds to S217 to turn off the low temperature flag. With the above processing, three combinations of (ON, ON), (ON, OFF), and (OFF, OFF) are obtained as combinations of the blood flow flag and the low temperature flag.

  Thereafter, the pulse rate is calculated (S209), and the blood flow flag and the low temperature flag at the corresponding timing are stored together with the calculated pulse rate (S210). Then, notification control is performed according to the flag. Specifically, first, it is determined whether the blood flow flag is ON (S211). If it is OFF, the process proceeds to S213 as in FIG. 9, and the pulse rate is displayed without any other notification. . If the blood flow flag is ON in S211, it is determined whether or not the low temperature flag is ON (S218). If it is ON, it is notified that the blood circulation state is bad due to the low temperature (S219). If there is, the fact that the blood circulation state is bad is notified (S220). In S220, as described above, not only that the blood circulation state is bad, but also that it is not due to low temperature may be notified. Since the process proceeds to S213 after the process of S219 or S220, the pulse rate corresponding to the blood circulation state to be notified is displayed.

  In the above embodiment, as shown in FIG. 5, the pulse meter processes the pulse wave detection unit 10 having the pulse wave sensor 11 that outputs the pulse wave sensor signal and the signal from the pulse wave detection unit 10. And a notification unit 72 that notifies the processing result of the processing unit 100. Then, the processing unit 100 determines the blood circulation state of the subject based on the change tendency information of the pulse wave sensor signal before the DC component cut. The notification unit 72 notifies the blood circulation state determination result information in the processing unit 100.

  Here, the pulse wave sensor signal corresponds to the output of the pulse wave sensor 11 and is a current value corresponding to the amount of incident light if the pulse wave sensor 11 is a photoelectric sensor such as a photodiode. The change trend information is information indicating whether the blood circulation state determination signal is increasing, decreasing, or neither, as described above.

  Thereby, it is possible to determine the blood circulation state of the subject based on the pulse wave sensor signal before the DC component cut, and to notify the user of the determination result information (for example, information indicating good or bad blood circulation). become. When the blood circulation state is poor, the ratio of noise to the entire signal increases relatively, so the reliability of the signal (eg, pulse information such as the pulse rate) acquired based on the pulse wave sensor signal decreases. However, it is possible to notify the user of this and call attention. At this time, the determination is made based on the pulse wave sensor signal before the DC component cut, and the frequency analysis processing such as FFT is not performed on the pulse wave sensor signal (or the pulse wave detection signal obtained by cutting the DC component). The amount of calculation and power consumption can be reduced compared to the case of performing frequency analysis or the like.

  In addition, the processing unit 100 may calculate a moving average or integrated value of the pulse wave sensor signal before the DC component cut in a given period as an index value, and acquire change trend information based on the calculated index value. .

  Thereby, it is possible to use a moving average or an integrated value as an index value for obtaining change trend information. As is apparent from FIGS. 6 and 7, even if the blood circulation state determination signal has a decreasing tendency (increasing tendency) in the long span, the value repeatedly increases and decreases due to various factors in the short span. Therefore, even if the signal value of the blood circulation state determination signal is used as it is, it is difficult to obtain accurate change tendency information due to the influence of various fluctuation factors. On the other hand, if it is a moving average or integrated value, it is possible to suppress the effects of fluctuations in a short span by appropriately setting the period to be calculated, so accurate change trend information can be acquired. is there. When using the integrated value, the calculation amount is small because no division is required unlike the moving average. On the other hand, when using a moving average, normalization by division is possible even if the given period to be calculated or the number of samples in the period changes, so the given period etc. can be flexibly set. It can be set (for example, dynamically changed).

  In addition, the processing unit 100 is configured to perform a given period set based on at least one of a period of body movement noise based on body movement of the subject, a period of breathing of the subject, and a pulsation period of the subject. The moving average or integrated value of the pulse wave sensor signal before the DC component cut may be calculated as the index value. For example, in a given period set as a period longer than the respiration cycle, the moving average or integrated value of the pulse wave sensor signal before the DC component cut may be calculated as the index value.

  As a result, a period set based on at least one cycle of body motion noise, respiration, and pulse can be set as a period for which a moving average or integrated value is to be calculated. As shown in FIG. 6, the change in the value that is desired to be captured as the change tendency information in this embodiment is in a long span, but the blood circulation state determination signal increases or decreases in a shorter span due to various fluctuation factors. Therefore, it becomes a problem. However, if the fluctuation period of a signal value in a short span is taken as a unit of the fluctuation period, both the timing when the signal value increases and the timing when the signal value increases when the signal value when there is no fluctuation factor is used as a reference. It is assumed to include. Therefore, by calculating the moving average or integrated value over one period, the increase or decrease of the value within the period can be smoothed. In other words, by setting the given period based on at least one cycle of body movement, breathing, and pulse, which can be considered as a fluctuation factor, the influence on the index value (and change trend information) due to fluctuation in a short span Can be suppressed. Specifically, the moving average or the integrated value may be calculated in a period longer than the breathing cycle that seems to have the longest cycle.

  Note that the fluctuation factors of the blood circulation state determination signal are not limited to those described above. Therefore, when the value of the blood circulation state determination signal fluctuates due to first to Nth fluctuation factors having first to Nth fluctuation cycles (N is an integer equal to or greater than 1), the processing unit 100 , The moving average or the integrated value of the pulse wave sensor signal before the DC component cut in the given period set as a period equal to or longer than the longest period among the first to Nth fluctuation periods. The index value may be calculated.

  Further, the processing unit 100 acquires, as an index value, a signal obtained by performing a filtering process using a low-pass filter on the pulse wave sensor signal before the DC component cut, and changes trend information based on the acquired index value. You may get it.

  Thereby, it becomes possible to acquire change tendency information using the blood circulation state determination signal after the low-pass filter processing as an index value. In this case as well, there is no change in the increase / decrease of the value in a short span, but they have a higher frequency than the change of the value to be acquired as the change trend information. Therefore, by using a low-pass filter having an appropriate cut-off frequency, it is possible to suppress the influence due to fluctuations in a short span, so that accurate change trend information can be acquired. Note that a plurality of timings for performing the low-pass filter processing (or connection positions of filter processing units for performing the processing) are conceivable. For example, a filter processing unit 15-2 that performs low-pass filter processing (analog filter processing) may be provided between the current / voltage conversion circuit of the pulse wave detection unit 10 of FIG. 5 and the A / D conversion unit 16-2. . Alternatively, low-pass filter processing (digital filter processing) is performed on the signal processing unit 110 (for example, between the A / D conversion unit 16-2 and the blood circulation state determination unit 117 or inside the blood circulation state determination unit 117) of the processing unit 100. A filter processing unit may be provided.

  The low-pass filter uses a frequency set based on at least one of a frequency of body motion noise based on body motion of the subject, a frequency of breathing of the subject, and a frequency of pulsation of the subject as a cutoff frequency. Also good. For example, a frequency lower than the breathing frequency may be set as the cutoff frequency.

  Here, the cut-off frequency of the low-pass filter refers to a frequency at which the filter output value of a signal having a frequency exceeding the cut-off frequency becomes somewhat smaller than the filter output value of a signal having a frequency included in the passband. The degree of decrease of the signal value can be variously considered. For example, a frequency at which the ratio of the signal value to the filter output value in the pass band is ½ is set as the cutoff frequency.

  Thereby, even when a low-pass filter is used, it is possible to suppress the influence on the index value (and change tendency information) due to various fluctuation factors. Since the fluctuation frequency of the fluctuation factor exceeds the cutoff frequency, signals corresponding to fluctuations in those short spans are sufficiently attenuated. Specific fluctuation factors are as described above, and body movement, respiration, pulse, and the like may be considered. And since it is considered that the frequency of respiration is often the lowest among them, a frequency lower than the frequency of respiration may be set as the cut-off frequency.

  In this case as well, the fluctuation factors of the blood circulation state determination signal are not limited to those described above. Therefore, when the value of the blood circulation state determination signal fluctuates due to first to Nth fluctuation factors having first to Nth fluctuation frequencies (N is an integer equal to or greater than 1), the low-pass filter A frequency equal to or lower than the lowest frequency among the first to Nth fluctuation frequencies may be set as the cutoff frequency.

  The processing unit 100 also includes a signal value of the pulse wave sensor signal before the DC component cut at the first timing and a pulse wave sensor signal before the DC component cut at the second timing different from the first timing. The difference information of the signal value may be calculated as an index value, and the change tendency information may be acquired based on the index value.

  Thereby, it becomes possible to acquire change tendency information using difference information (for example, difference values) of signal values at two different timings of the blood circulation state determination signal as an index value. Here, the first timing is the acquisition timing of the latest blood circulation state determination signal in a narrow sense, and the second timing is the acquisition start timing of the blood circulation state determination signal, but is not limited thereto. is not. In this method, since a binary difference value may be obtained, it is possible to reduce the amount of calculation in the index value calculation process as compared with a moving average, integrated value calculation process, low pass filter process, and the like.

  Further, the processing unit 100 acquires, as change trend information, information indicating that the pulse wave sensor signal before the DC component cut is decreasing when the index value continuously decreases a given number of times, and acquires the acquired change trend. It may be determined that the blood circulation state is bad based on the information.

  Thereby, it becomes possible to acquire change tendency information based on the index value. Here, for example, information that the index value at a certain timing is smaller than the index value at the previous timing is continuously decreasing for a given number of times (such as 5 times). To get. However, the method of acquiring the change trend information from the index value is not limited to this. For example, it is determined x times whether the adjacent index values have increased or decreased, and even if y is decreased and z times (z = xy) is increased, y is greater than z When it is considered to be sufficiently large, it may be determined that the trend is decreasing. Further, the increase / decrease determination between a plurality of index values is not limited to that performed between adjacent index values. In addition, the method of acquiring change tendency information from the index value can be variously modified.

  Further, the pulse wave detection unit 10 may include a current / voltage conversion circuit 12 that converts a current value output from the pulse wave sensor 11 into a voltage value. Then, the processing unit 100 acquires a pulse wave sensor signal before the DC component cut based on the output signal of the current / voltage conversion circuit 12. Specifically, the current / voltage conversion circuit 12 includes a first power supply node, a resistance element (R) provided between an output node from which an output signal is output, and an output node and a second power supply node. And a bipolar transistor provided between the first power supply node and the base of the transistor.

  This makes it possible to convert a current value, which is an output of the pulse wave sensor 11 (for example, a photoelectric sensor and in a narrow sense, a photodiode) into a voltage value. Here, the current / voltage conversion circuit 12 is, for example, the circuit shown in FIG. In this case, the first power supply node is a node for supplying a power supply voltage, and the second power supply node is a node corresponding to the ground. However, the first and second power supply nodes are not limited to those shown in FIG.

  Further, the pulse meter may include a temperature sensor 30 that acquires temperature information, as shown in FIG. Then, the processing unit 100 performs a temperature compensation process for canceling the fluctuation of the output signal according to the temperature change on the signal corresponding to the output signal of the current / voltage conversion circuit 12 based on the temperature information from the temperature sensor. You may go. Then, the signal after the temperature compensation process is acquired as the pulse wave sensor signal before the DC component cut.

As a result, the temperature characteristics of the current / voltage conversion circuit 12 can be compensated. For example, considering the circuit of FIG. 8, the voltage value _{VDC as} an output signal satisfies the following expression (1) and the following expression (2) obtained by modifying the expression.

_{V DC = V C -i c R} ····· (1)
_{V DC = V C -i PD h} fe R ····· (2)
Here, considering the biological characteristics of the subject, blood circulation is good at high temperatures, and blood circulation is poor at low temperatures. When the blood circulation is good, absorption of irradiation light in the living body is improved, and reflected light (or transmitted light) is reduced, i _PD is reduced, and the value of _VDC is increased from the above equation (2). Conversely, when blood circulation is poor, the value of _VDC decreases. That, _{V DC} is large if a high temperature, tends if low _{V DC} is small.

However, given the circuit characteristics of the current-voltage conversion circuit 12 of FIG. 8, the h _fe of the transistor decreases at low temperatures, because tends to increase at high temperature, the result V _DC is significant at low temperatures as at elevated temperatures V _DC becomes smaller. That is, the circuit has a temperature characteristic opposite to that of the living body, and there is a risk that the temperature characteristic of the living body that is originally desired to be detected using the blood circulation state determination signal is canceled. Therefore, here, the processing for compensating the temperature characteristics of the circuit is performed, so that the characteristics of the living body easily appear in the blood circulation state determination signal, and the blood circulation state is accurately determined. Specifically, since the temperature characteristic of the transistor (particularly the temperature characteristic of h _fe ) is known in advance, the processing unit 100 may perform a correction process on the signal value based on the temperature information from the temperature sensor 30.

  However, the temperature compensation processing is not limited to that performed by the processing unit 100, and for example, the temperature compensation is performed in a circuit by providing the resistance R or the like in FIG. 8 with a temperature characteristic opposite to that of the transistor. Also good.

In the case of using a current-voltage conversion circuit of FIG. 8, as _{V DC i PD} is large, as described above becomes _{small, V DC} increases as _{i PD} is small. However, depending on the configuration of the current-voltage conversion circuit, i _PD larger the V _DC increases, it is possible to more V _DC is i _PD is small to have a characteristic that decreases. In that case, if the blood circulation state is good, V _DC (and the value of the blood circulation state determination signal) decreases, and if the blood circulation state is bad, V _DC increases. That is, depending on the configuration of the current / voltage conversion circuit or the like, the relationship between the quality of the blood circulation state and the magnitude of the value of the blood circulation state determination signal may be reversed from that described above. Therefore, in the blood circulation state determination unit 117, it is necessary to change the determination conditions and the like according to the configuration of the current / voltage conversion circuit and the like.

  Further, the pulse meter may include a temperature sensor 30 that acquires temperature information, as shown in FIG. The processing unit 100 determines the blood circulation state of the subject based on the change tendency information of the pulse wave sensor signal before the DC component cut, and the temperature at a timing corresponding to the acquisition timing of the blood circulation state determination result information. Information may be acquired. The notification unit 72 notifies the blood circulation state determination result information and the temperature information.

  As a result, it is possible to determine the blood circulation state, acquire temperature information at a timing corresponding to the acquisition timing of the determination result information (same timing in a narrow sense), and notify both of them. Therefore, since the blood circulation state and temperature information can be displayed together, if the blood circulation state is poor, the blood flow state deterioration factor, such as whether the cause is a decrease in temperature or something else, is entered. Announcement becomes possible. Note that the temperature information does not necessarily need to be notified. For example, when the blood circulation state is good, the fact is notified and the temperature information may not be notified.

  In addition, the processing unit 100 performs a process of setting the temperature sensor 30 to an operation enabled state when it is determined that the blood circulation state of the subject is bad based on the change tendency information of the pulse wave sensor signal before the DC component cut. May be.

  As a result, the temperature sensor 30 can be set in an operation enable state as necessary, so that power consumption by the temperature sensor 30 can be reduced. Since the temperature sensor 30 here is assumed to be used for estimating the deterioration factor of the blood circulation state (unless the temperature compensation of the current / voltage conversion circuit 12 described above is taken into consideration), if the blood circulation state is good It is not necessary to forcibly acquire temperature information. Therefore, in this case, the temperature sensor 30 is not set in the operation enable state.

  Further, the processing unit 100 calculates pulsation information based on a pulse wave detection signal that is a pulse wave sensor signal after the DC component cut. And the alerting | reporting part 72 may alert | report pulsation information.

  Accordingly, it is possible to notify the blood circulation state determination result information described above, or, in some cases, temperature information, in accordance with the notification of the pulsation information. The pulsation information such as the pulse rate is very useful for grasping the state of the subject. Therefore, it becomes a big problem when information far from the actual situation is output. Since the determination of the blood circulation state described above in the present embodiment is to detect that the reliability of the pulsation information may be low, a warning is given to the user by informing that when the blood circulation state is bad. It becomes possible to emit.

  Note that the pulse meter or the like of the present embodiment may realize part or most of the processing by a program. In this case, the pulse meter or the like of the present embodiment is realized by a processor such as a CPU executing a program. Specifically, a program stored in the information storage medium is read, and a processor such as a CPU executes the read program. Here, the information storage medium (computer-readable medium) stores programs, data, and the like, and functions as an optical disk (DVD, CD, etc.), HDD (hard disk drive), or memory (card type). It can be realized by memory, ROM, etc. A processor such as a CPU performs various processes according to the present embodiment based on a program (data) stored in the information storage medium. That is, in the information storage medium, a program for causing a computer (an apparatus including an operation unit, a processing unit, a storage unit, and an output unit) to function as each unit of the present embodiment (a program for causing the computer to execute processing of each unit) Is memorized.

  Although the present embodiment has been described in detail as described above, it will be easily understood by those skilled in the art that many modifications can be made without departing from the novel matters and effects of the present invention. Accordingly, all such modifications are intended to be included in the scope of the present invention. For example, a term described at least once together with a different term having a broader meaning or the same meaning in the specification or the drawings can be replaced with the different term in any part of the specification or the drawings. Further, the configuration and operation of the pulse meter and the like are not limited to those described in this embodiment, and various modifications can be made.

10 pulse wave detection unit, 11 pulse wave sensor, 12 current / voltage conversion circuit,
15 filter processing unit, 16 A / D conversion unit, 20 body motion detection unit,
21 acceleration sensor, 22 pressure sensor, 26 A / D converter,
30 temperature sensor, 70 display unit, 72 notification unit, 100 processing unit,
110 signal processing unit, 111 pulse wave signal processing unit, 113 body motion signal processing unit,
115 body movement noise reduction unit, 117 blood circulation state determination unit,
120 pulsation information calculation unit, 130 notification control unit, 200 left wrist, 300 holding mechanism,
302 guide, 400 base

Claims (16)

A pulse wave detector having a pulse wave sensor for outputting a pulse wave sensor signal;
A processing unit that performs processing on a signal from the pulse wave detection unit;
An informing unit for informing a processing result in the processing unit;
Including
The processor is
Based on the change tendency information of the pulse wave sensor signal before the DC component cut, determine the blood circulation state of the subject,
The notification unit
The pulsometer characterized by notifying the blood circulation state determination result information in the processing unit. In claim 1,
The processor is
Calculating a moving average or integrated value of the pulse wave sensor signal before the DC component cut in a given period as an index value, and acquiring the change tendency information based on the calculated index value Total. In claim 2,
The processor is
The DC component cut in the given period set based on at least one of a period of body motion noise based on body movement of the subject, a period of breathing of the subject, and a pulsation period of the subject The pulse meter, wherein the moving average or the integrated value of the previous pulse wave sensor signal is calculated as the index value. In claim 3,
The processor is
The moving average or the integrated value of the pulse wave sensor signal before the DC component cut in the given period set as a period longer than the cycle of the breath is calculated as the index value. And a pulse meter. In claim 1,
The processor is
A signal obtained by performing a filtering process using a low-pass filter on the pulse wave sensor signal before the DC component cut is acquired as an index value, and the change tendency information is acquired based on the acquired index value. A pulse meter characterized by In claim 5,
The low pass filter is
The frequency set based on at least one of the frequency of body motion noise based on the body motion of the subject, the frequency of breathing of the subject, and the frequency of pulsation of the subject is set as a cutoff frequency A pulse meter characterized by performing filtering. In claim 6,
The low pass filter is
The pulsometer characterized by performing the filtering process in which a frequency lower than the frequency of the breathing is set as the cutoff frequency. In claim 1,
The processor is
The signal value of the pulse wave sensor signal before the DC component cut at the first timing and the signal value of the pulse wave sensor signal before the DC component cut at the second timing different from the first timing The difference information is calculated as an index value, and the change tendency information is acquired based on the index value. In any of claims 2 to 8,
The processor is
When the index value decreases continuously a given number of times, information indicating that the pulse wave sensor signal before the DC component cut is in a decreasing tendency is acquired as the change tendency information, and the acquired change tendency information is A pulse meter characterized by determining that the blood circulation state is poor based on the pulse rate. In any one of Claims 1 thru | or 9,
The pulse wave detector
A current / voltage conversion circuit that converts a current value, which is an output from the pulse wave sensor, into a voltage value;
The processor is
A pulse meter, wherein the pulse wave sensor signal before the DC component cut is acquired based on an output signal of the current / voltage conversion circuit. In claim 10,
The current / voltage conversion circuit is:
A resistance element provided between a first power supply node and an output node from which the output signal is output;
A bipolar transistor provided between the output node and a second power supply node;
A photodiode provided between the first power supply node and a base of the transistor;
A pulse meter characterized by including. In claim 10 or 11,
Including a temperature sensor to get temperature information,
The processor is
For the signal corresponding to the output signal of the current / voltage conversion circuit, based on the temperature information from the temperature sensor, performing a temperature compensation process to cancel the fluctuation of the output signal according to a temperature change, A pulse meter that acquires the pulse wave sensor signal before the DC component cut. In any one of Claims 1 thru | or 11,
Including a temperature sensor to get temperature information,
The processor is
The blood circulation state of the subject is determined based on the change tendency information of the pulse wave sensor signal before the DC component cut, and the timing at a timing corresponding to the acquisition timing of the determination result information of the blood circulation state Get temperature information,
The notification unit
The pulsometer characterized by notifying the determination result information and the temperature information of the blood circulation state. In claim 13,
The processor is
When the blood circulation state of the subject is determined to be poor based on the change tendency information of the pulse wave sensor signal before the DC component cut, a process of setting the temperature sensor to an operation enabled state is performed. Characteristic pulse meter. In any one of Claims 1 thru | or 14.
The processor is
Based on the pulse wave detection signal that is the pulse wave sensor signal after the DC component cut, pulsation information is calculated,
The notification unit
The pulsometer characterized by notifying the pulsation information. A pulse wave detector having a pulse wave sensor for outputting a pulse wave sensor signal;
A processing unit that performs processing on a signal from the pulse wave detection unit;
As an informing unit for informing a processing result in the processing unit,
Make the computer work,
The processor is
Based on the change tendency information of the pulse wave sensor signal before the DC component cut, determine the blood circulation state of the subject,
The notification unit
A program for notifying determination result information of the blood circulation state in the processing unit.

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