阅读说明：本技术 脉搏检测装置及脉搏检测方法 (Pulse detection device and pulse detection method ) 是由 池田拓磨 田中勇气 谷博之 于 2021-05-31 设计创作，主要内容包括：本发明提供一种能够实现稳定的脉搏检测的脉搏检测装置及脉搏检测方法。脉搏检测装置(101)具备：脉搏波检测部,其检测脉搏波,并输出表示检测到的上述脉搏波的脉搏波信号；阈值设定电路,其设定与上述脉搏波信号的振幅对应地随时间变化的阈值；以及比较器,其将上述脉搏波信号与上述阈值进行比较,并输出超过上述阈值的上述脉搏波信号作为表示脉搏的信息。(The invention provides a pulse detection device and a pulse detection method capable of realizing stable pulse detection. A pulse detection device (101) is provided with: a pulse wave detection unit that detects a pulse wave and outputs a pulse wave signal indicating the detected pulse wave; a threshold value setting circuit that sets a threshold value that changes with time in accordance with the amplitude of the pulse wave signal; and a comparator that compares the pulse wave signal with the threshold value and outputs the pulse wave signal exceeding the threshold value as information indicating a pulse wave.)

1. A pulse detection device is characterized by comprising:

a pulse wave detection unit that detects a pulse wave and outputs a pulse wave signal indicating the detected pulse wave;

a threshold value setting circuit that sets a threshold value that changes with time in accordance with the amplitude of the pulse wave signal; and

a comparator that compares the pulse wave signal with the threshold value and outputs the pulse wave signal exceeding the threshold value as information indicating a pulse.

2. The pulse detection device of claim 1,

further comprises a first constant multiplying circuit for multiplying a pulse wave signal representing the pulse wave by a constant having a value larger than 1,

the threshold setting circuit includes:

a sample hold circuit that holds a peak value of the pulse wave signal detected by the pulse wave detection unit; and

a time constant circuit for maintaining the peak value held by the sample-and-hold circuit for a certain period of time and outputting the peak value as a threshold value during the period,

the comparator compares the pulse wave signal multiplied by the constant by the first constant multiplying circuit with the threshold value output from the sample hold circuit.

3. The pulse detection device of claim 1,

the threshold setting circuit includes:

a sample hold circuit that holds a peak value of the pulse wave signal detected by the pulse wave detection unit;

a time constant circuit that maintains the peak value held by the sample-and-hold circuit for a certain time and outputs the peak value as a threshold value during the certain time; and

a second constant multiplying circuit that multiplies the threshold value output from the time constant circuit by a constant, and the constant is a value smaller than 1,

the comparator compares the pulse wave signal output from the pulse wave detection unit with a threshold value multiplied by a constant by the second constant multiplying circuit.

4. The pulse detection device of claim 1,

further comprises a first constant multiplying circuit for multiplying a pulse wave signal representing the pulse wave by a constant having a value larger than 1,

the threshold setting circuit includes:

a sample hold circuit that holds a peak value of the pulse wave signal detected by the pulse wave detection unit;

a time constant circuit that maintains the peak value held by the sample-and-hold circuit for a certain time and outputs the peak value as a threshold value during the certain time; and

a second constant multiplying circuit that multiplies the threshold value output from the time constant circuit by a constant, and the constant is a value smaller than 1,

the comparator compares the pulse wave signal multiplied by the constant by the first constant multiplying circuit with the threshold multiplied by the constant by the second constant multiplying circuit.

5. The pulse detection device according to any one of claims 2 to 4,

the constant voltage circuit sets a lower limit value of a threshold value output from the time constant circuit.

6. A pulse detection method, comprising:

detecting a pulse wave and outputting a pulse wave signal indicating the detected pulse wave;

setting a time-varying threshold value corresponding to the amplitude of the pulse wave signal; and

and comparing the pulse wave signal with the threshold value, and outputting the pulse wave signal exceeding the threshold value as information indicating a pulse.

7. The pulse detection method of claim 6, comprising:

a step of multiplying the pulse wave signal by a constant, the constant being a value greater than 1;

a step of holding a peak value of the pulse wave signal;

maintaining the held peak value for a predetermined time and outputting the peak value as a threshold value during the period; and

and comparing the pulse wave signal multiplied by the constant with a threshold value maintained for a certain time.

8. The pulse detection method of claim 6, comprising:

a step of holding a peak value of the pulse wave signal;

maintaining the held peak value for a predetermined time and outputting the peak value as a threshold value during the period;

a step of multiplying a threshold value maintained for a certain time by a constant, the constant being a value smaller than 1; and

and comparing the pulse wave signal with a threshold value multiplied by a constant.

9. The pulse detection method of claim 6, comprising:

a step of multiplying the pulse wave signal by a constant, the constant being a value greater than 1;

a step of holding a peak value of the pulse wave signal;

maintaining the held peak value for a predetermined time and outputting the peak value as a threshold value during the period;

a step of multiplying a threshold value maintained for a certain time by a constant, the constant being a value smaller than 1; and

and comparing the pulse wave signal multiplied by the constant with a threshold value multiplied by the constant.

Technical Field

The present invention relates to a pulse detection device and a pulse detection method.

Background

In recent years, with the development of an aging society, the need for caring and monitoring people has been increased, and pulse detection by a wearable terminal has attracted much attention. In pulse detection using a wearable terminal, it is also important to ensure convenience, and therefore it is preferable to mount a small and lightweight battery.

Patent document 1 discloses a technique for realizing pulse detection while suppressing an increase in power consumption by using an analog circuit. The pulse wave detection device of patent document 1 includes a photoelectric pulse wave detection unit, an amplitude determination unit, a notification unit, and the like. The pulse wave signal detected by the photoelectric pulse wave detecting unit is input to the amplitude determining unit as an analog signal that oscillates around the base line voltage. The amplitude determination unit to which the analog signal is input shifts the baseline voltage of the analog signal to the ground level. The amplitude determination unit outputs an analog signal obtained by shifting the baseline voltage to the ground level to the notification unit. The notification unit generates a sound synchronized with the pulse at a timing when the amplitude of the pulse wave signal is equal to or greater than a predetermined threshold value.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2009-201801.

Disclosure of Invention

Problems to be solved by the invention

However, in the conventional technique of patent document 1, since the pulse wave signal is compared with the threshold value having a constant amplitude, the variation of the pulse wave signal due to the individual difference in pulse wave intensity, the installation position of the sensor, and other external factors is not taken into consideration, and therefore, there is room for improvement in realizing stable pulse wave detection.

The non-limiting embodiments of the present invention contribute to providing a pulse detection device and a pulse detection method that can realize stable pulse detection.

Means for solving the problems

A pulse detection device according to an embodiment of the present invention includes: a pulse wave detection unit that detects a pulse wave and outputs a pulse wave signal indicating the detected pulse wave; a threshold value setting circuit that sets a threshold value that changes with time in accordance with the amplitude of the pulse wave signal; and a comparator that compares the pulse wave signal with the threshold value and outputs the pulse wave signal exceeding the threshold value as information indicating a pulse wave.

The pulse detection method of one embodiment of the invention comprises the following steps: detecting a pulse wave and outputting a pulse wave signal indicating the detected pulse wave; setting a time-varying threshold value corresponding to the amplitude of the pulse wave signal; and comparing the pulse wave signal with the threshold value and outputting the pulse wave signal exceeding the threshold value as information indicating a pulse.

Effects of the invention

According to one embodiment of the present invention, a pulse detection device and a pulse detection method that can realize stable pulse detection can be constructed.

Further advantages and effects of an embodiment of the invention will be elucidated by the description and the drawings. The advantages and/or effects described above are provided by features disclosed in several embodiments, the description and the drawings, respectively, but not necessarily all features may be provided in order to obtain one or more advantages and/or effects of the same feature.

Drawings

Fig. 1 is a diagram showing a configuration example of a pulse wave detection device 101 according to an embodiment of the present invention.

Fig. 2 is a diagram showing a configuration example of the pulse detection circuit 103.

Fig. 3 is a diagram showing waveforms of pulse wave signal 201(V _ in) and signal 203(α × V _ in).

Fig. 4 is a diagram showing an example of the signal 203(α × V _ in), the threshold 206(V _ SH), and the threshold 208(β × V _ SH).

Fig. 5 shows the pulse wave signal 201(V _ in) and the threshold 1 having a constant amplitude.

Description of the reference numerals

1: threshold value

2: threshold setting circuit

101: pulse detection device

102: pulse wave detection unit

103: pulse detection circuit

201: pulse wave signal

202: first constant time circuit

203: signal

204: sample-and-hold circuit

205: time constant circuit

206: threshold value

207: second constant time circuit

208: threshold value

209: comparator with a comparator circuit

210: pulse output circuit

211: constant voltage circuit

212: pulse intensity output unit

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, the same reference numerals are given to components having substantially the same functions, and redundant description is omitted.

[ embodiment ]

< example of configuration of pulse wave detection device 101 >

Fig. 1 is a diagram showing a configuration example of a pulse wave detection device 101 according to an embodiment of the present invention. The pulse wave detection device 101 includes a pulse wave detection unit 102 and a pulse wave detection circuit 103.

The pulse wave detection unit 102 is a photoelectric sensor, a piezoelectric sensor, or the like used in proximity to a human body. The pulse wave detection unit 102 is attached to, for example, an arm of a person, and detects a pulse wave of the person.

The pulse wave detection circuit 103 is an analog circuit that detects a pulse wave based on a signal indicating the pulse wave detected by the pulse wave detection unit 102.

< pulse detection Circuit 103>

Next, a configuration example of the pulse detection circuit 103 will be described with reference to fig. 2. Fig. 2 shows an example of the configuration of the pulse detection circuit 103.

The pulse detection circuit 103 includes a first constant multiplying circuit 202, a sample-and-hold circuit 204, a time constant circuit 205, a second constant multiplying circuit 207, a comparator 209, a pulse output circuit 210, a constant voltage circuit 211, and a pulse intensity output unit 212. The sample-and-hold circuit 204, the time constant circuit 205, the second constant multiplying circuit 207, and the constant voltage circuit 211 constitute a threshold setting circuit 2. The threshold setting circuit 2 is an analog circuit that sets thresholds (a threshold 206(V _ SH) and a threshold 208(β × V _ SH)) that change over time in accordance with the amplitude of the pulse wave signal 201(V _ in).

< first constant multiplying circuit 202>

The pulse wave signal 201(V _ in), which is a signal indicating the pulse wave detected by the pulse wave detecting unit 102, is input to the first constant multiplying circuit 202. The first constant multiplying circuit 202 multiplies the input pulse wave signal 201(V _ in) by a coefficient α (for example, 1.1 to 3.0) larger than 1 to generate an amplified signal 203(α × V _ in) and outputs the amplified signal to the comparator 209.

< sample-and-hold Circuit 204>

The pulse wave signal 201(V _ in) is input to the sample-and-hold circuit 204, and the sample-and-hold circuit 204 generates a signal that holds the peak value of the pulse wave signal 201(V _ in), and outputs the signal to the time constant circuit 205.

< time constant Circuit 205>

The time constant circuit 205 holds the input signal for a certain period of time with a specific time constant, and outputs the signal input to the time constant circuit 205 to the second constant multiplying circuit 207 as information indicating the threshold value 206(V _ SH).

< second constant multiplying circuit 207>

The second constant multiplying circuit 207 multiplies the input threshold 206(V _ SH) by a coefficient β smaller than 1 (for example, 0.1 to 0.9) to generate a threshold 208(β × V _ SH) after attenuation, and outputs the threshold to the comparator 209.

< comparator 209>

The signal 203(α × V _ in) and the threshold 208(β × V _ SH) are input to the comparator 209, and the comparator 209 outputs the signal 203(α × V _ in) exceeding the threshold 208(β × V _ SH) to the pulse output circuit 210 as information indicating a pulse.

< pulse output Circuit 210>

The pulse output circuit 210 generates a sound corresponding to the pulse from, for example, a speaker based on the input information indicating the pulse, and displays the pulse on a display by visualizing the pulse.

< constant voltage Circuit 211>

The constant voltage circuit 211 is a circuit for setting the lower limit value of the voltage of the threshold 206(V _ SH) maintained by the time constant circuit 205. An output terminal of the constant voltage circuit 211 is connected to an output terminal of the time constant circuit 205 via a diode. The output voltage of the constant voltage circuit 211 is applied to the output terminal of the time constant circuit 205, so that the threshold value 206(V _ SH) is maintained at a predetermined value even when the output (the threshold value 206(V _ SH)) of the time constant circuit 205 is small.

Thus, for example, even when the amplitude of the pulse wave signal 201(V _ in) is small because the pulse wave detection unit 102 is provided at a site in the body where pulse waves are difficult to detect, it is possible to suppress the threshold value 206(V _ SH) from being buried in noise or the like, and to perform stable pulse wave detection.

< pulse intensity output unit 212>

The pulse intensity output unit 212 has a function of outputting the intensity of the pulse detected by the comparator 209. The pulse intensity output unit 212 may be, for example, a sound generating unit such as a buzzer or a speaker that generates a sound corresponding to the pulse intensity, or a display screen that displays an image corresponding to the pulse intensity.

< pulse wave detection action >

Next, the pulse detection operation of the pulse detection circuit 103 will be described. The pulse wave signal 201(V _ in) detected by the pulse wave detecting unit 102 is input to the first constant multiplying circuit 202 and the sample hold circuit 204, respectively.

The pulse wave signal 201(V _ in) input to the first constant multiplying circuit 202 is multiplied by a coefficient α larger than 1 to generate a signal 203(α × V _ in) in which the pulse wave signal 201(V _ in) is amplified. The signal 203(α × V _ in) is input to the comparator 209. A specific example of the waveform of the signal 203(α × V _ in) will be described later.

The peak value of the pulse wave signal 201(V _ in) input to the sample-and-hold circuit 204 is held by the sample-and-hold circuit 204 and maintained for a certain time by the time constant circuit 205. Thereby, the threshold 206(V _ SH) is generated and input to the second constant multiplying circuit 207. The threshold value 208(β × V _ SH) after attenuating the threshold value 206(V _ SH) is generated by multiplying the threshold value 206(V _ SH) input to the second constant multiplying circuit 207 by a coefficient β smaller than 1.

The comparator 209, to which the signal 203(α × V _ in) and the threshold 208(β × V _ SH) are input, detects the signal 203(α × V _ in) exceeding the threshold 208(β × V _ SH) as a pulse.

Here, in order to detect a pulse, it is necessary to satisfy a relationship of signal 203(α × V _ in) > threshold 208(β × V _ SH), and for this reason, it is necessary to satisfy a relationship of coefficient α > coefficient β.

Referring to fig. 3, a waveform of the pulse wave signal 201(V _ in) before being multiplied by the coefficient α and a waveform of the signal 203(α × V _ in) after being multiplied by the coefficient α will be described.

Fig. 3 is a diagram showing waveforms of pulse wave signal 201(V _ in) and signal 203(α × V _ in). In the left diagram of fig. 3, a signal 203(α × V _ in) generated when a pulse wave signal 201(V _ in) having a large amplitude is detected is shown. In the right diagram of fig. 3, a signal 203(α × V _ in) generated when a pulse wave signal 201(V _ in) having a small amplitude is detected is shown.

As shown in fig. 3, the waveform of the signal 203(α × V _ in) has a shape similar to the waveform of the pulse wave signal 201(V _ in) regardless of whether the amplitude of the pulse wave signal 201(V _ in) is large or small.

Next, referring to fig. 4, waveforms of the signal 203(α × V _ in), the threshold 206(V _ SH), and the threshold 208(β × V _ SH) will be described.

Fig. 4 is a diagram showing an example of the signal 203(α × V _ in), the threshold 206(V _ SH), and the threshold 208(β × V _ SH).

The left part of fig. 4 shows waveforms of a signal 203(α × V _ in), a threshold 206(V _ SH), and a threshold 208(β × V _ SH) generated when a pulse wave signal 201(V _ in) having a large amplitude is detected.

The right part of fig. 4 shows waveforms of a signal 203(α × V _ in), a threshold 206(V _ SH), and a threshold 208(β × V _ SH) generated when the pulse wave signal 201(V _ in) having a small amplitude is detected.

As shown in fig. 4, the magnitudes of the threshold 206(V _ SH) and the threshold 208(β × V _ SH) vary with time in accordance with the magnitude of the pulse, i.e., the amplitude of the signal 203(α × V _ in).

In contrast, in the conventional pulse wave detection device, a threshold value having a constant amplitude is used. This threshold value is explained with reference to fig. 5. Fig. 5 shows the pulse wave signal 201(V _ in) and the threshold 1 having a constant amplitude.

The left part of fig. 5 shows a pulse wave signal 201(V _ in) having a large amplitude and a threshold value 1 having a constant amplitude. In the case of such a pulse wave signal 201 having a large amplitude, the peak value of the pulse wave signal 201 exceeds the threshold value 1, and therefore stable pulse detection can be performed.

The right part of fig. 5 shows a pulse wave signal 201(V _ in) having a small amplitude and a threshold value 1 having a constant amplitude. In the case of such a pulse wave signal 201 having a small amplitude, the peak value of the pulse wave signal 201 does not exceed the threshold value 1, and thus it is difficult to perform stable pulse detection.

The pulse wave detection device 101 according to the present embodiment is configured to set a threshold 208(β × V _ SH) that changes with time in accordance with the amplitude of each of the pulse wave signal 201(V _ in) and the signal 203(α × V _ in). Therefore, even when the amplitude of the pulse wave signal 201(V _ in) is small, stable pulse detection can be performed by using the time-varying threshold 208.

Further, although the conventional technique uses an a/D converter (analog-digital converter) having relatively large power consumption, the pulse wave detection device 101 of the present embodiment includes analog circuits such as the comparator 209 and the sample-and-hold circuit 204, and thus can perform stable pulse wave detection while suppressing an increase in power consumption.

Further, since an increase in power consumption can be suppressed, the pulse detector 101 of the present embodiment can be combined with a small and lightweight battery. Therefore, by applying the pulse wave detection device 101 of the present embodiment to a wearable device using a piezoelectric sensor or the like, a small and lightweight wearable device capable of pulse wave detection can be realized.

It should be understood that, for example, the following modes also belong to the technical scope of the present invention.

(1) The pulse detection device is provided with: a pulse wave detection unit that detects a pulse wave and outputs a pulse wave signal indicating the detected pulse wave; a threshold value setting circuit that sets a threshold value that changes with time in accordance with the amplitude of the pulse wave signal; and a comparator that compares the pulse wave signal with the threshold value and outputs the pulse wave signal exceeding the threshold value as information indicating a pulse wave.

(2) The pulse wave detection device further includes a first constant multiplying circuit that multiplies a pulse wave signal indicating the pulse wave by a constant, the constant being a value greater than 1, and the threshold setting circuit includes: a sample hold circuit for holding a peak value of the pulse wave signal detected by the pulse wave detection unit; and a time constant circuit that maintains the peak value held by the sample-and-hold circuit for a predetermined time and outputs the peak value as a threshold value during the time, wherein the comparator compares the pulse wave signal multiplied by a constant by the first constant multiplying circuit with the threshold value output from the sample-and-hold circuit.

(3) The threshold setting circuit includes: a sample hold circuit for holding a peak value of the pulse wave signal detected by the pulse wave detection unit; a time constant circuit that maintains the peak value held by the sample-and-hold circuit for a predetermined time and outputs the peak value as a threshold value during the time; and a second constant multiplying circuit that multiplies a constant by a threshold value output from the time constant circuit, the constant being a value smaller than 1, wherein the comparator compares the pulse wave signal output from the pulse wave detecting unit with the threshold value multiplied by the constant by the second constant multiplying circuit.

(4) The pulse wave detection device further includes a first constant multiplying circuit that multiplies a pulse wave signal indicating the pulse wave by a constant, the constant being a value greater than 1, and the threshold setting circuit includes: a sample hold circuit for holding a peak value of the pulse wave signal detected by the pulse wave detection unit; a time constant circuit that maintains the peak value held by the sample-and-hold circuit for a predetermined time and outputs the peak value as a threshold value during the time; and a second constant multiplying circuit that multiplies the threshold value output from the time constant circuit by a constant, the constant being a value smaller than 1, wherein the comparator compares the pulse wave signal multiplied by the constant by the first constant multiplying circuit with the threshold value multiplied by the constant by the second constant multiplying circuit.

(5) The pulse detection device further includes a constant voltage circuit that sets a lower limit value of the threshold value output from the time constant circuit.

(6) The pulse detection method comprises the following steps: detecting a pulse wave and outputting a pulse wave signal indicating the detected pulse wave; setting a time-varying threshold value corresponding to the amplitude of the pulse wave signal; and comparing the pulse wave signal with the threshold value, and outputting the pulse wave signal exceeding the threshold value as information indicating a pulse.

(7) The pulse detection method comprises the following steps: multiplying the pulse wave signal by a constant, the constant being a value greater than 1; a step of holding a peak value of the pulse wave signal; maintaining the held peak value for a predetermined time and outputting the peak value as a threshold value during the period; and a step of comparing the pulse wave signal multiplied by the constant with a threshold value maintained for a certain time.

(8) The pulse detection method comprises the following steps: a step of holding a peak value of the pulse wave signal; maintaining the held peak value for a predetermined time and outputting the peak value as a threshold value during the period; a step of multiplying a threshold value maintained for a certain time by a constant, the constant being a value smaller than 1; and comparing the pulse wave signal with a threshold value multiplied by a constant.

(9) The pulse detection method comprises the following steps: multiplying the pulse wave signal by a constant, the constant being a value greater than 1; a step of holding a peak value of the pulse wave signal; maintaining the held peak value for a predetermined time and outputting the peak value as a threshold value during the period; a step of multiplying a threshold value maintained for a certain time by a constant, the constant being a value smaller than 1; and comparing the pulse wave signal multiplied by the constant with a threshold value multiplied by the constant.

Industrial applicability

One embodiment of the present invention is suitable for use in a pulse detection device.