JP2012130391A - Heart rate detection device, method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heart rate detection device, a heart rate detection method, and a program for detecting the heart rate with high precision.SOLUTION: The heart rate detection device 100 has: a data acquisition part 1061 for acquiring a Doppler sensor output signal which has a frequency of a difference between frequency of an electromagnetic wave emitted to a subject M or a radiation wave Tx to be an ultrasonic wave and frequency of a reflection wave Rx which is obtained by reflection of the radiation wave M by the subject M; a time frequency analysis part 1062 for resolving the Doppler sensor output signal into component signals of a plurality of frequencies and analyzing time variation of each signal intensity about the plurality of component signals; an auto correlation analysis part 1063 for performing auto correlation analysis of each signal intensity about the plurality of component signals; and a heart rate detection part 1064 for selecting a component signal high in periodicity of a highest auto correlation function from among the plurality of component signals and detecting heart rate of the subject on the basis of the result of the auto correlation analysis of the selected component signal.

Description

  The present invention relates to a heart rate detection device, a heart rate detection method, and a program, and more particularly to a heart rate detection device, a heart rate detection method, and a program that detect a heart rate based on an output signal of a Doppler sensor.

  In recent years, research on a system for detecting a heart rate using a Doppler sensor has been advanced. The Doppler sensor outputs a Doppler sensor output signal having a difference frequency between the frequency of a radiated wave that is an electromagnetic wave or an ultrasonic wave radiated to the detection target and the frequency of the reflected wave reflected by the detection target. Therefore, the heart rate detection device using the Doppler sensor has an advantage that the heart rate can be detected without contacting the subject. For example, in Patent Document 1, the heart rate is detected from the frequency of the maximum amplitude in the waveform that has passed through a filter whose pass band is the frequency band (0.8 to 2.5 Hz) of the heart rate in the Doppler sensor output signal. An apparatus is disclosed.

JP 2000-83927 A

However, the Doppler sensor output signal includes not only the influence of the heartbeat but also the movement of the body due to respiration, the shaking of the body, and other environmental noises. For this reason, there is a problem that it is difficult to accurately extract the heart rate.
Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a new and improved heart rate detection device capable of detecting a heart rate with higher accuracy, It is to provide a heart rate detection method and program.

  In order to solve the above-described problem, according to an aspect of the present invention, the frequency of a radiated wave that is an electromagnetic wave or an ultrasonic wave radiated to a subject, and the frequency of a reflected wave reflected from the subject by the radiated wave. A data acquisition unit that acquires a Doppler sensor output signal having a difference frequency, and a time frequency that decomposes the Doppler sensor output signal into component signals at a plurality of frequencies, and analyzes a time variation of the signal intensity for each of the plurality of component signals. An analysis unit, an autocorrelation analysis unit for analyzing the autocorrelation of the signal intensity for each of the plurality of component signals, and selecting a component signal having the highest periodicity based on the autocorrelation function from the plurality of component signals, A heart rate detector that detects the heart rate of the subject based on the analysis result of the autocorrelation of the selected component signal, That, the heart rate detector is provided.

  According to this configuration, the Doppler sensor output signal can be divided into a plurality of component signals, and the heart rate can be detected based on the component signal having a high periodicity among the component signals. This makes it possible to detect a heart rate with higher accuracy than when analyzing the autocorrelation of the output signal of the Doppler sensor as it is without being decomposed.

  Moreover, you may further have a filter part which extracts the signal containing the frequency component according to the speed change of the said test subject's body movement resulting from the heartbeat from the said Doppler sensor output signal.

  Moreover, you may have further the filter part which removes the signal containing the frequency component according to the position change of the said test subject's body movement.

  The heart rate detector is a component having the highest periodicity based on the ratio between the value of the first peak having the largest amplitude and the value of the second peak having the second largest amplitude among the peaks of the autocorrelation function. A signal may be selected.

  The heart rate detection unit may detect the heart rate using the time of the first peak as a heartbeat interval.

  In order to solve the above problem, according to another aspect of the present invention, a step of radiating a radiation wave, which is an electromagnetic wave or an ultrasonic wave, to a subject, and a reflected wave reflected by the subject from the radiation wave Detecting, obtaining a Doppler sensor output signal having a difference frequency between the frequency of the radiation wave and the frequency of the reflected wave, and decomposing the Doppler sensor output signal into component signals at a plurality of frequencies; Analyzing the time variation of the signal strength for each of the plurality of component signals; analyzing the autocorrelation of the signal strength for each of the plurality of component signals; and most autocorrelation function among the plurality of component signals Selecting a component signal having a high periodicity based on the analysis result of the autocorrelation of the selected component signal , And detecting the heart rate of the subject, the heart rate detection method is provided.

  In order to solve the above problem, according to another aspect of the present invention, a computer is used to radiate electromagnetic waves or ultrasonic waves radiated to a subject, and the radiated wave is reflected by the subject. A data acquisition unit that acquires a Doppler sensor output signal having a frequency that is different from the frequency of the reflected wave, and decomposes the Doppler sensor output signal into component signals at a plurality of frequencies, and each of the plurality of component signals has a signal strength time. A time-frequency analysis unit that analyzes fluctuations, an autocorrelation analysis unit that analyzes autocorrelation of signal strength for each of the plurality of component signals, and a component signal that has the highest periodicity of the autocorrelation function among the plurality of component signals And detecting a heart rate of the subject based on the autocorrelation analysis result of the selected component signal. Wherein the bets, the program to function as the heart rate detector is provided.

  As described above, according to the present invention, a heart rate with higher accuracy can be detected.

It is explanatory drawing for demonstrating the outline | summary of the heart rate detection apparatus which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of the heart rate detection apparatus which concerns on the same embodiment. It is a block diagram which shows the detailed structure of the heart rate extraction part 106 of the heart rate detection apparatus which concerns on the embodiment. It is a flowchart which shows an example of operation | movement of the heart rate detection apparatus which concerns on the same embodiment. It is a graph which shows an example of the signal which extracted the component containing the low frequency component depending on the heartbeat from the Doppler sensor output signal. It is a graph which shows an example of the signal which extracted the high frequency component depending on the heartbeat from the Doppler sensor output signal. It is a graph which shows the time change of the wavelet coefficient in 5 Hz. It is a graph which shows the time change of the wavelet coefficient in 10 Hz. It is a graph which shows the time change of the wavelet coefficient in 15 Hz. It is a graph which shows the time change of the wavelet coefficient in 20 Hz. It is a graph which shows the autocorrelation function of the wavelet coefficient of FIG. It is a graph which shows the autocorrelation function of the wavelet coefficient of FIG. It is a graph which shows the autocorrelation function of the wavelet coefficient of FIG. It is a graph which shows the autocorrelation function of the wavelet coefficient of FIG. It is explanatory drawing for demonstrating the evaluation function for evaluating periodicity. It is explanatory drawing for demonstrating the effect of the precision improvement by the embodiment.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

The description will be made in the following order.
1. Overview 2. Configuration 3. Example of operation Examples of effects

<1. Overview>
First, an outline of a heart rate detection device according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is an explanatory diagram for explaining an outline of a heartbeat detection device according to an embodiment of the present invention.

  As shown in FIG. 1, the heart rate detection device 100 according to the present embodiment radiates a radiated wave Tx near the chest of the subject M, and acquires a reflected wave Rx reflected by the radiated wave Tx on the subject M. Have This Doppler sensor outputs a Doppler sensor output signal having a difference frequency between the frequency of the radiation wave Tx and the frequency of the reflected wave Rx. The heart rate detection device 100 detects the heart rate of the subject M based on the analysis result of the Doppler sensor output signal.

  Since the heart rate detection apparatus 100 uses a radiation wave Tx that is an electromagnetic wave or an ultrasonic wave, the heart rate can be detected without contacting the subject M. For this reason, the heart rate detection device 100 is expected to be used in the health care field. For example, the heart rate detection device 100 can be used in a system for remotely monitoring the health state of an elderly person or the like.

  The Doppler sensor is a sensor that uses a phenomenon (Doppler effect) in which the frequency of the reflected wave Rx shifts in proportion to the moving speed of the object (here, the subject M). However, the Doppler sensor output signal acquired here includes not only the influence due to the heartbeat to be detected, but also, for example, body movement due to breathing, body shaking, and other environmental noise. In order to detect a heart rate with high accuracy, it is important to remove the influence on the Doppler sensor output signal due to factors other than the heartbeat and detect a frequency shift due to the heartbeat.

When the subject M is moved, the Doppler sensor output signal V _d, which is observed from the Doppler sensor is expressed by the following equation.

The amplitude _Kd depends on the displacement of the body movement of the subject M. Further, the frequency f _d depends on the speed of the body movement of the subject M. When the one-minute heart rate is 60, the subject M's body movement occurs in a cycle of 1 second. For this reason, the Doppler sensor output signal also includes a component that depends on the change in the amplitude _Kd caused by this movement. However, the signal having a period of about 1 second tends to include the influence of breathing and the influence of shaking of the body. For this reason, it has been difficult to accurately detect the heart rate.

Therefore, the heart rate detection apparatus 100 according to the present embodiment is not a frequency component corresponding to the displacement movement of the body caused by the heartbeat, the speed of magnitude by movement of the body, i.e. the frequency component that depends on the magnitude variation of f _d Observe. At this time, the frequency of a signal containing a component depending on the magnitude variation of f _d is there are individual differences. Further, when the body orientation relative positions and the radiation wave Tx emitted of the same person at a be radiated wave Tx is different, the frequency of a signal containing a component depending on the magnitude variation of f _d, and the magnitude of the amplitude of the signal It is different. For this reason, the heart rate detection device 100 selects a component signal with the highest periodicity from a plurality of component signals obtained by decomposing the Doppler sensor output signal into a plurality of frequency components, and uses the selected component signal to select a heart rate. Perform number detection.

  An example of the functional configuration and operation for realizing the function of the heart rate detection device 100 will be described below.

<2. Configuration>
Here, an example of a functional configuration of the heart rate detection device 100 according to the present embodiment will be described with reference to FIGS. 2 and 3. FIG. 2 is a block diagram showing the configuration of the heart rate detection device according to the present embodiment. FIG. 3 is a block diagram showing a detailed configuration of the heart rate extraction unit 106 of the heart rate detection device according to the present embodiment.

  A heart rate detection device 100 includes a Doppler sensor 101, an amplifier 102, an analog filter 103, an A / D (Analog / Digital) converter 104, a digital filter 105, a heart rate extraction unit 106, and a heart rate display unit. 107.

As described above, the Doppler sensor 101 is a sensor that uses a phenomenon (Doppler effect) in which the frequency of the reflected wave Rx shifts in proportion to the moving speed of the object (here, the subject M). The Doppler sensor 101 detects a reflected wave Rx obtained by reflecting the radiation wave Tx to the subject M. The Doppler sensor 101 outputs a Doppler sensor output signal having a frequency _f d ₌ f t -f _r of the difference between the frequency _{f t} of the radiation wave Tx frequency _{f r} of the reflected wave Rx. The voltage Vd of the Doppler sensor output signal is expressed by the following Equation 1 as described above.

Here, the amplitude _Kd is a value that depends on the radio wave reception intensity, and the radio wave reception intensity _Pr generally follows a radar equation expressed by the following Equation 2. Here, P _t is the transmission power, G _t is the transmission antenna gain, σ is the scattering cross section at the location, A _r is the effective aperture area of the reception antenna, and R is the distance between the sensor and the recognition target.

  The radiation wave Tx used here may be an electromagnetic wave or an ultrasonic wave. As the Doppler sensor 101, a general Doppler sensor module may be used. Then, the Doppler sensor 101 inputs the acquired Doppler sensor output signal to the amplifier 102.

  The amplifier 102 has a function of amplifying the Doppler sensor output signal input from the Doppler sensor 101. As the amplifier 102, a general amplifier circuit may be used. At this time, the amplification factor of the amplifier 102 is determined so that the amplitude of the Doppler sensor output signal after passing through the analog filter 103 and the digital filter 105 becomes an amplitude suitable for observation. The amplifier 102 inputs the Doppler sensor output signal after the amplification process to the analog filter 103.

  The analog filter 103 is a filter that removes a frequency component having a large influence due to noise or the like from the Doppler sensor output signal input from the amplifier 102 and extracts a frequency component including the influence of the heartbeat. It should be noted that by removing frequency components that are greatly affected by noise or the like, frequency components resulting from movement displacement due to heartbeats are also removed. The analog filter 103 may be any one of a low-pass filter, a high-pass filter, a band-pass filter, and the like, for example. Alternatively, the analog filter 103 may be used in combination with a low-pass filter, a high-pass filter, a band-pass filter, or the like. The analog filter 103 inputs the Doppler sensor output signal after the filtering process to the A / D converter 104.

  The A / D converter 104 has a function of converting a Doppler sensor output signal that is an analog signal input from the analog filter 103 into a digital signal. The A / D converter 104 inputs the Doppler sensor output signal converted into the digital signal to the digital filter 105.

  The digital filter 105 is a filter that performs a filtering process on the Doppler sensor output signal digitized by the A / D converter 104. The digital filter 105 has a function of removing frequency components that could not be removed by the analog filter 103. The digital filter 105 inputs the Doppler sensor output signal after the filtering process to the heart rate extraction unit 106.

  The heart rate extraction unit 106 has a function of extracting a heart rate based on the input Doppler sensor output signal. Referring to FIG. 3, the heart rate extraction unit 106 decomposes the acquired Doppler sensor output signal into component signals at a plurality of frequencies by wavelet transform, and acquires the signal of the component signal. Mainly functions as a wavelet analysis unit 1062 that analyzes temporal fluctuations in intensity, an autocorrelation analysis unit 1063 that analyzes autocorrelation of wavelet coefficients, and a heart rate detection unit 1064 that detects a heart rate based on the analysis result of autocorrelation To do.

  Here, the wavelet analysis unit 1062 is an example of a time-frequency analysis unit that decomposes the Doppler sensor output signal acquired by the data acquisition unit into component signals at a plurality of frequencies and analyzes signal signal temporal fluctuations for the component signals. The wavelet analysis unit 1062 uses wavelet transform to decompose the Doppler sensor output signal into component signals at a plurality of pseudo frequencies. In the present embodiment, wavelet analysis is performed for pseudo frequencies of 5 Hz, 10 Hz, 15 Hz, and 20 Hz.

  In addition, the autocorrelation analysis unit 1063 extracts a peak from the autocorrelation function of each component signal after the wavelet transform, and selects a component signal having the highest periodicity from a plurality of component signals based on the extracted peak. The heart rate detector 1064 detects the heart rate using the component signal selected by the autocorrelation analyzer.

  The heart rate display unit 107 has a function of displaying heart rate information extracted by the heart rate extraction unit 106. The heart rate display unit 107 may include, for example, a display screen generation unit that generates a display screen including information on the heart rate extracted by the heart rate extraction unit 106, and a display device that displays the generated display screen. The display device may be a display device such as a liquid crystal display (LCD) device, an OLED (Organic Light Emitting Diode) device, a CRT (Cathode Ray Tube) display device, and a lamp. When the display device is a lamp, the lamp may blink at the same interval as the heart rate based on the heart rate extracted by the heart rate extraction unit 106, for example.

  Heretofore, an example of the function of the heart rate detection device 100 according to the present embodiment has been shown. Each component described above may be configured using a general-purpose member or circuit, or may be configured by hardware specialized for the function of each component. Further, the function of each component is determined by a ROM (Read Only Memory), a RAM (Random Access Memory), or the like that stores a control program that describes a processing procedure in which an arithmetic unit such as a CPU (Central Processing Unit) realizes these functions. Alternatively, the control program may be read from the storage medium, and the program may be interpreted and executed. Therefore, it is possible to appropriately change the configuration to be used according to the technical level at the time of carrying out the present embodiment.

  A computer program for realizing each function of the heart rate detection device 100 according to the present embodiment as described above can be produced and installed in a personal computer or the like. In addition, a computer-readable recording medium storing such a computer program can be provided. The recording medium is, for example, a magnetic disk, an optical disk, a magneto-optical disk, a flash memory, or the like. Further, the above computer program may be distributed via a network, for example, without using a recording medium.

<3. Operation>
Next, the operation of the heart rate detection device 100 according to the present embodiment will be described with reference to FIGS. FIG. 4 is a flowchart showing an example of the operation of the heart rate detection device according to the present embodiment. FIG. 5 is a graph showing an example of the Doppler sensor output signal. FIG. 6 is a graph showing an example of a signal obtained by extracting a high frequency component from the Doppler sensor output signal of FIG. FIG. 7 is a graph showing the time change of the wavelet coefficient at 5 Hz. FIG. 8 is a graph showing the time change of the wavelet coefficient at 10 Hz. FIG. 9 is a graph showing the time change of the wavelet coefficient at 15 Hz. FIG. 10 is a graph showing the time change of the wavelet coefficient at 20 Hz. FIG. 11 is a graph showing the autocorrelation function of the wavelet coefficients of FIG. FIG. 12 is a graph showing the autocorrelation function of the wavelet coefficients of FIG. FIG. 13 is a graph showing the autocorrelation function of the wavelet coefficients of FIG. FIG. 14 is a graph showing the autocorrelation function of the wavelet coefficients of FIG.

  First, referring to FIG. 4, an example of the operation of the heart rate detection device 100 according to the present embodiment is shown. The operations shown here are mainly 1. 1. First stage of acquiring a Doppler sensor output signal and extracting a high frequency component including the influence of heartbeat (S101 to S105); 2. a second stage of extracting component signals at a plurality of frequencies (S107); The third stage (S109 to S115) for detecting the heart rate based on the autocorrelation function of the component signal is divided into three.

  First, the first stage will be described. The installation position of the heart rate detection device 100 or the position of the subject M is adjusted so that the radiation direction of the radiation wave Tx radiated from the Doppler sensor of the heart rate detection device 100 is the direction of the subject M. Then, the heart rate detection device 100 radiates a radiation wave Tx near the chest of the subject M (S101). At this time, it is preferable that the radiation position of the radiation wave Tx is a part where it is easy to observe the influence of the motion to be detected. In the present embodiment, since the influence of the heartbeat is easily observed in the vicinity of the chest, a radiation wave Tx is emitted to the chest. In addition, when the subject M moves less during observation, the heart rate detection accuracy increases.

  The Doppler sensor 101 has a difference frequency fd between the frequency ft of the radiated wave Tx and the frequency fr of the reflected wave Rx based on the radiated wave Tx and the reflected wave Rx reflected by the subject M. A Doppler sensor output signal is output (S103). The Doppler sensor output signal output at this time includes, for example, as shown in FIG. 5, signal intensity fluctuation due to respiration and signal intensity fluctuation due to heartbeat. FIG. 5 shows the waveform after the power supply noise is cut after the Doppler sensor output signal output from the Doppler sensor 101 is amplified by the amplifier 102.

  Next, the heart rate detection apparatus 100 performs various signal processing on the acquired Doppler sensor output signal using the amplifier 102, the analog filter 103, the A / D converter 104, and the digital filter 105 (S105). The filtering processing performed here is performed in order to extract frequency components due to changes in the speed of body movement caused by heartbeats, excluding components unrelated to heartbeat effects such as environmental noise, body shake, and breathing. . In the present embodiment, frequency components corresponding to changes in the body position due to heartbeats are also excluded from the Doppler sensor output signal. The frequency component corresponding to the position change of the body due to the heartbeat has a cycle of a heartbeat interval of about 1 second. Such a frequency component tends to overlap with a frequency component generated by body shake or the like. For this reason, in this embodiment, signals having a frequency higher than this are extracted except for signals having a period of about 1 second.

  FIG. 6 shows a signal after the Doppler sensor output signal is amplified by the amplifier 102 and then passed through a high-pass filter having a cutoff frequency of 2 Hz and a low-pass filter having a cutoff frequency of 20 Hz. The low frequency signal components present in FIG. 5 are cut.

  Next, the second stage will be described. The heart rate extraction unit 106 analyzes the component signal decomposed into each frequency component using the Doppler sensor output signal that has been subjected to various types of signal processing by the first stage processing. Specifically, the data acquisition unit 1061 acquires the Doppler sensor output signal input from the digital filter 105. Then, the wavelet analysis unit 1062 performs continuous wavelet transform on the acquired Doppler sensor output signal, decomposes it into component signals of each pseudo frequency, and analyzes them.

  By the first stage processing, the main noise component and the like are removed from the Doppler sensor output signal, and the Doppler sensor output signal becomes a signal including the frequency component due to the influence of the speed change of the body movement due to the heartbeat. However, the Doppler sensor output signal may also contain a frequency component due to the influence of body movement that becomes noise. Further, there are individual differences in the height of the frequency component and the magnitude of the amplitude due to the influence of the speed change of the body movement due to the heartbeat. Furthermore, even in the same subject M, if the position of the body with respect to the position where the radiation wave Tx of the Doppler sensor is emitted or the radiation direction of the radiation wave Tx is different, the frequency component due to the influence of the speed change of the body movement due to the heartbeat The frequency height and amplitude are different. Thus, the frequency of the frequency component due to the influence of the speed change of the body movement due to the heartbeat varies depending on the subject M and the sensing environment of the Doppler sensor. For this reason, the heart rate detection apparatus 100 according to the present embodiment decomposes a signal including a frequency component due to an influence of a speed change of a body movement caused by a heartbeat into a plurality of frequency components. Specifically, the wavelet analysis unit 1062 decomposes the Doppler sensor output signal including the frequency component due to the influence of the speed change of the body motion due to the heartbeat into component signals at a plurality of pseudo frequencies by continuous wavelet transform (S107). 7 to 10 show wavelet coefficients at pseudo frequencies of 5 Hz, 10 Hz, 15 Hz, and 20 Hz when continuous wavelet transform is performed on the Doppler sensor output signal. The wavelet coefficient is a value proportional to the signal strength.

  Next, the third stage will be described. According to the second stage, the Doppler sensor output signal including the frequency component due to the influence of the speed change of the body movement due to the heartbeat was decomposed into component signals at a plurality of frequencies. The third stage is a stage in which a component signal including periodic amplitude fluctuations due to the influence of a change in the speed of body movement due to a heartbeat is selected from the plurality of component signals, and a heart rate is detected from the selected component signal. is there.

  In general, the amplitude depending on breathing or shaking of the body is larger than the amplitude of the output signal of the Doppler sensor depending on the movement of the body due to the heartbeat. For this reason, it may be difficult to clearly extract the heartbeat period from the autocorrelation of the original signal. For this reason, in the present embodiment, by obtaining the wavelet coefficients in the plurality of pseudo frequencies obtained in the second stage and taking the autocorrelation function in each frequency component, the frequency with low periodicity and large amplitude is obtained. The influence of the components can be separated.

  Generally, there is an upper limit and a lower limit in the time interval of a human heartbeat. For this reason, the autocorrelation analysis unit 1063 obtains an autocorrelation function within the range between the upper limit and the lower limit as shown in FIGS. 11 to 14 (S109). In the present embodiment, the one having the highest periodicity is selected from these autocorrelation functions, and the heart rate is detected based on the selected autocorrelation function. For example, the ratio of the value of the largest peak and the second largest peak of the autocorrelation function is used here for determining the periodicity.

As shown in FIG. 15, the autocorrelation function generally has a plurality of peaks. The peak having the largest amplitude is called the first peak, and the peak having the second largest amplitude is called the second peak. At this time, the autocorrelation analysis unit 1063 performs periodicity evaluation using the ratio between the first peak and the second peak as an evaluation function (S111), and the body correlation due to the heartbeat is selected from the autocorrelation functions for a plurality of component signals. The autocorrelation function of the component signal that contains the most frequency component due to the influence of the speed change of the motion is selected. That is, the evaluation function is expressed as follows.
Evaluation function = (magnitude of first peak amplitude) / (magnitude of second peak amplitude)

  Here, the heart rate detection unit 1064 is based on the autocorrelation function of the wavelet coefficient having the highest pseudo function of the evaluation function selected by the autocorrelation analysis unit 1063, and the time of the first peak of the selected autocorrelation function. Is a heartbeat interval (S113). For example, in the examples of FIGS. 11 to 14, the evaluation values of the evaluation functions at the pseudo frequencies of 5 Hz, 10 Hz, 15 Hz, and 20 Hz are 1.40, 2.03, 2.84, and 3.36, respectively. . That is, the heart rate is obtained using the autocorrelation function at 20 Hz, which has the highest evaluation value. If there is only one peak of the autocorrelation function, it may be an autocorrelation function of a signal component in a low pseudo frequency band including the influence of body shake. For this reason, the autocorrelation function of the wavelet coefficient at the pseudo frequency is not subject to evaluation. The heart rate detection unit 1064 obtains the heart rate per unit time (for example, 1 minute) using the peak time of the autocorrelation function as the heart rate interval (S115). The heart rate detection unit 1064 inputs the obtained heart rate information to the heart rate display unit 107. The heart rate display unit 107 provides heart rate information based on the input information.

<4. Examples of effects>
As described above, according to the heart rate detection device 100 according to the present embodiment, noise components are removed from the acquired Doppler sensor output signal by filtering, and further decomposed into component signals at a plurality of pseudo frequencies. Then, the component signal having the highest periodicity is selected from the plurality of component signals, including the frequency component due to the speed change of the body movement due to the heartbeat. The heart rate detection device 100 extracts a heartbeat interval based on the peak value of the autocorrelation function of the selected component signal. The heart rate detecting device 100 can detect the heart rate per unit time from the heart rate interval.

  The Doppler sensor output signal before decomposition into a plurality of component signals may include a frequency component due to noise other than the influence due to heartbeat, for example, the influence of body shake. Here, the frequency component due to the influence of body shake or the like generally has a larger amplitude than the influence due to the heartbeat. For this reason, even if the autocorrelation of the Doppler sensor output signal is obtained, it may be difficult to detect periodicity due to the influence of noise. Further, the height of the frequency component and the magnitude of the amplitude due to the influence of the speed change of the body movement due to the heartbeat vary depending on individual differences and the sensing environment. Therefore, in this embodiment, the Doppler sensor output signal is decomposed into component signals at each frequency, and the autocorrelation is analyzed for each component signal. In addition, a component signal having a high periodicity including the influence of the heartbeat is selected from the plurality of component signals, and the heart rate is detected based on the peak value of the autocorrelation function of the selected component signal. With this configuration, the heart rate detection device 100 can provide more accurate heart rate information.

  In addition, the experimental result verified about the precision of heart rate detection is shown in FIG. Here, the accuracy of the heart rate detected in the present embodiment and the accuracy of the heart rate detected under the conditions of the comparative example are shown for three subjects. In the comparative example, a method of detecting the heart rate from the autocorrelation function of the output signal of the Doppler sensor after performing amplification processing to an appropriate amplitude was used. The error rate indicates the error rate with respect to the actual heart rate value obtained from the pulse wave meter for each of the present embodiment and the comparative example. From FIG. 16, the accuracy of the heart rate detected by using the method of the present embodiment is higher than the heart rate detected by the method of the comparative example for all of the subject A, the subject B, and the subject C. I understand.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

  For example, in the above embodiment, a device for detecting a heartbeat has been described, but the present invention is not limited to such an example. For example, other biological information such as breathing, poverty, tremor, and muscle sound may be measured. Needless to say, by changing parameters such as the frequency of the passband of the filter, the filter can be widely applied to detection of periodicity.

  In the above embodiment, the obtained heart rate is provided as it is, but the present invention is not limited to this example. For example, various techniques for improving accuracy such as reducing the influence of abnormal values by taking the median value of the heart rate during a predetermined period may be used.

  Moreover, in the said embodiment, although the component signal with high periodicity was selected based on the ratio of the value of the 1st peak of an autocorrelation function, and the value of a 2nd peak, this invention is not limited to this example. For example, the component signal may be selected based on the ratio between the value of the first peak in the range of the heartbeat interval and the value when the time of the autocorrelation function is zero. In addition, a method for evaluating the periodicity of the autocorrelation function may be used.

  In this specification, the steps described in the flowcharts are executed in parallel or individually even if they are not necessarily processed in time series, as well as processes performed in time series in the described order. Including processing to be performed. Further, it goes without saying that the order can be appropriately changed even in the steps processed in time series.

DESCRIPTION OF SYMBOLS 100 Heart rate detection apparatus 101 Doppler sensor 102 Amplifier 103 Analog filter 104 A / D converter 105 Digital filter 106 Heart rate extraction part 107 Heart rate display part

Claims (7)

A data acquisition unit that acquires a Doppler sensor output signal having a frequency that is a difference between a frequency of a radiation wave that is an electromagnetic wave or an ultrasonic wave radiated to a subject and a frequency of a reflected wave that is reflected by the subject;
A time frequency analysis unit for decomposing the Doppler sensor output signal into component signals at a plurality of frequencies and analyzing a time variation of the signal intensity for each of the plurality of component signals;
An autocorrelation analyzer for analyzing the autocorrelation of the signal strength for each of the plurality of component signals;
A heart rate that selects a component signal having the highest periodicity from the plurality of component signals based on an autocorrelation function, and detects a heart rate of the subject based on an analysis result of the autocorrelation of the selected component signals A detection unit;
A heart rate detection device comprising: A filter unit that extracts, from the Doppler sensor output signal, a signal including a frequency component corresponding to a change in speed of the body motion of the subject caused by a heartbeat;
The heart rate detection device according to claim 1, further comprising: A filter unit for removing, from the Doppler sensor output signal, a signal including a frequency component corresponding to a change in position of the subject's body movement caused by a heartbeat;
The heart rate detection device according to claim 1, further comprising:   The heart rate detection unit obtains a component signal having the highest periodicity based on a ratio between the value of the first peak having the largest amplitude and the value of the second peak having the second largest amplitude among the peaks of the autocorrelation function. The heart rate detection device according to any one of claims 1 to 3, which is selected.   The heart rate detection device according to claim 4, wherein the heart rate detection unit detects the heart rate with the time of the first peak as a heart rate interval. Emitting a radiation wave, which is an electromagnetic wave or an ultrasonic wave, to a subject;
Detecting the reflected wave reflected by the subject by the radiation wave;
Obtaining a Doppler sensor output signal having a frequency difference between the frequency of the radiated wave and the frequency of the reflected wave;
Decomposing the Doppler sensor output signal into component signals at a plurality of frequencies;
Analyzing signal intensity temporal variation for each of the plurality of component signals;
Analyzing the autocorrelation of the signal strength for each of the plurality of component signals;
Selecting a component signal having the highest autocorrelation function periodicity from among the plurality of component signals;
Detecting the heart rate of the subject based on the analysis result of the autocorrelation of the selected component signal;
A method for detecting a heart rate, comprising: Computer
A data acquisition unit that acquires a Doppler sensor output signal having a frequency that is a difference between a frequency of a radiation wave that is an electromagnetic wave or an ultrasonic wave radiated to a subject and a frequency of a reflected wave that is reflected by the subject;
A time frequency analysis unit for decomposing the Doppler sensor output signal into component signals at a plurality of frequencies and analyzing a time variation of the signal intensity for each of the plurality of component signals;
An autocorrelation analyzer for analyzing the autocorrelation of the signal strength for each of the plurality of component signals;
A heart rate detector that selects a component signal having the highest periodicity of the autocorrelation function from the plurality of component signals and detects the heart rate of the subject based on the analysis result of the autocorrelation of the selected component signal When,
A program for functioning as a heart rate detection device.

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