JP2002000575A - Heart rate sensor and method of calculating heart rate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heart rate sensor capable of measuring heart rate during exercise continuously and stably, and a method of calculating the heart rate. SOLUTION: The heart rate sensor is provided with a light source 11 for emitting light to be irradiated over an organism 20, optical sensors 12 and 13 for receiving the light emitted from the light source 11 and passing through the organism 20, and a signal processing part 14 for calculating the heart rate based on the signal according to the received light by the sensors 12 and 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring a heart rate of a living body including a human, and a heart rate calculating method.

[0002]

2. Description of the Related Art Conventional devices for measuring heart rate include:
For example, it is disclosed in U.S. Pat. No. 5,299,570.

This measuring device includes a light source and an optical sensor. The measuring device is installed on the skin of a living body and detects light emitted from the light source, propagates in the living body, and reaches the optical sensor. By doing so, non-invasive measurement of biological information such as oxygen saturation and heart rate in blood is performed.

[0004]

However, the conventional measuring device has the following problems.

The amount of light emitted from the light source and propagated through the living body and reaches the optical sensor depends on the distance between the living body and the light source, the distance between the living body and the optical sensor, the distance between the light source and the optical sensor, and the amount of light. It changes greatly depending on the amount of blood present in the passage route.

Therefore, when a force is applied to the measuring device, the optical sensor sinks into the inside of the living body, and the distance between the optical sensor and the blood vessel in the living body changes, and in some cases, the amount of blood flowing through the blood vessel. However, there is a problem in that the measurement result is affected by a large change in the detected light amount.

Similarly, when light from another light source, such as sunlight or illumination light, is applied to the living body, the disturbance light propagates in the living body and reaches the optical sensor. Due to the change, there is a problem that an accurate heart rate cannot be measured.

For this reason, in the conventional apparatus, it is necessary to perform the measurement in a place that is not affected by disturbance light and in a resting state, and it is impossible to measure the heart rate continuously during exercise. .

In view of the above problems, an object of the present invention is to provide a heart rate sensor and a heart rate calculation method capable of continuously and stably measuring a heart rate during exercise.

[0010]

To solve the above problems, a heart rate sensor according to the present invention comprises a light source for emitting light for irradiating a living body, and at least two light sources for receiving light emitted from the light source and passing through the living body. And a signal processing unit for calculating a heart rate using signals corresponding to the light received by the at least two optical sensors.

The heart rate calculating method according to the present invention may further comprise a step of irradiating the living body with light, a step of receiving the light incident on the living body and passing through the living body with at least two optical sensors, and A step of calculating a heart rate using a signal corresponding to the received light.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.

(Embodiment 1) FIG. 1 is a sectional view showing a heartbeat sensor according to Embodiment 1 of the present invention. 11 is a light source, and 12 and 13 are optical sensors.

The light source 11 can be used without any particular limitation. Here, an LED having a wavelength of 950 nm is used. The optical sensors 12 and 13 are not particularly limited, but are preferably silicon photodiodes or solid-state imaging devices. Here, a silicon photodiode was used. Here, the optical sensors 12 and 13 may be provided on both sides of the light source 11 with the light source 11 as a center. In particular, it is preferable that the optical sensors 12 and 13 are arranged substantially symmetrically with respect to the light source 11. Also, the optical sensors 12, 13
The distance between the light source 11 and the light source 11 is preferably 2 mm or more. In the present embodiment, the light sensors 12 and 13 are
1 and the optical sensors 12 and 13
The distance between the light source 11 and the light source 11 was set to 2 mm or more.

Reference numeral 16 denotes a holding table for holding the light source 11 and the optical sensors 12 and 13.
3 and serves to keep the distance from the living body 20 to the light source 11 and the optical sensors 12 and 13 constant.

In this embodiment, the case where the holding table 16 is brought into close contact with the living body 20 will be described. However, the present invention is not limited to this, and the holding table 16 may be in non-contact with the living body 20. .

The light source 11 emits light, and the optical sensor 1
This is a signal processing unit for calculating a heart rate using the signals obtained from 2 and 13. A display unit 15 displays the heart rate calculated by the signal processing unit 14. The signal processing unit 14 and the display unit 15 are provided in the display device 18, and are connected to the holding table 16 via the cable 17. In the present embodiment, the holding table 16 and the display device 18 are connected via the cable 17, but the holding table 16 and the display device 18 may transmit and receive information wirelessly by transmitting / receiving means. And the display device 18 may be integrated.

Light emitted from the light source 11 is irradiated onto the living body 20 and diffuses while scattering inside the living body 20.
Some of the light scattered inside the living body 20 and passed through the blood vessels 19 reaches the optical sensors 12 and 13. Optical sensor 12, 1
The light that has reached No. 3 is converted into a signal corresponding to the intensity in the signal processing unit 14, and the sum or average value of the two signals is calculated.

The flow rate of blood flowing in the blood vessel 19 changes in accordance with the pulse of the heart, but the detection signals of the optical sensors 12 and 13 change periodically due to a change in absorbance accompanying a change in blood flow rate. The heart rate is calculated based on the periodic change of the detection signal.

According to the present embodiment, a stable and stable heart rate can be detected even during exercise.
Hereinafter, the principle will be described.

Here, when the holding base 16 is slightly touching the living body 20 and there is almost no pressing force against the living body 20, the left end of the holding base 16, that is, the upper part of the optical sensor 12 during the exercise is located. A case where some force is applied will be described as an example. At this time, when the left end of the holding table 16 is pressed against the living body 20, the left end of the holding table 16 slightly sinks into the living body 20, and the right end (the optical sensor 13 side) of the holding table 16 reacts as a reaction. It is assumed that it is farther away and slightly floating. That is, a case where a rotational movement about the light source 11 occurs will be described.

When no force is applied to the upper part of the optical sensor 12, the blood flow rate is stable and the optical sensor 1
Since the distance between the blood vessels 2 and 13 and the blood vessel 19 is constant, the heart rate can be detected stably.

However, when a force is applied to the upper part of the optical sensor 12, the optical sensor 12 comes into close contact with the living body 20 and the blood vessel 19
Approach. Thereby, the living body 20 is
More light passing through is detected.

On the other hand, since the optical sensor 13 is arranged substantially symmetrically with respect to the light source 11 with respect to the optical sensor 12, the optical sensor 13 moves in a direction away from the blood vessel 19, so that the detection signal obtained by the optical sensor 13 is obtained. The amount decreases.

Therefore, the optical sensor 12 and the optical sensor 1
By calculating the sum or average value of the signals of the optical sensors 1,
2 can be compensated for by the decrease in the signal that occurred simultaneously in the optical sensor 13, and when a force is applied to one side of the heart rate sensor during exercise, the signal intensity of the optical sensor suddenly changes. Can be measured stably even when the occurrence of

If the change in the signal strength is slow, it is possible to make electrical correction to stabilize the heartbeat detection. It is very difficult to control it.

(Embodiment 2) FIG. 2 is a sectional view of a heart rate sensor according to Embodiment 2 of the present invention, from which a display device is omitted. As the light source 21 and the optical sensors 22 and 23, those similar to those in the first embodiment were used.

In general, it is known that light applied to a living body propagates while scattering inside the living body, and a part of the light is emitted from the surface again.

Further, it is known that the light detected by the optical sensor 22 contains a large amount of light that has entered the depth direction of the living body by a length corresponding to about a half of the distance between the light source 21 and the optical sensor 22. Have been. Therefore, in the optical sensor 23, the optical sensor 22
It is possible to detect light that has penetrated to a deeper part of the living body as compared with the case of FIG.

The present embodiment utilizes such a principle, and the distance between the optical sensor 22 and the light source 21 is 2 mm.
Hereinafter, the distance between the optical sensor 23 and the light source 21 is set to a value larger than 2 mm.

By setting the distance between the optical sensor 22 and the light source 21 to 2 mm or less, the component of the signal detected by the optical sensor 22 includes a large amount of light transmitted on the surface of the living body 20. A signal with a small change in light absorbance due to a change in flow can be detected.

Further, by installing the optical sensor 23 at a position where the distance from the light source 21 is larger than 2 mm, the light detected by the optical sensor 23 contains more light propagating inside the living body 20 than the optical sensor 22. Therefore, the optical sensor 23 can detect a signal having a large change in light absorbance due to a change in blood flow. The light reaching the optical sensors 22 and 23 is converted into a signal corresponding to the intensity in the signal processing unit, and the quotient or difference between the two signals is calculated.

According to the present embodiment, the heart rate can be stably measured even when a force is applied to the heart rate sensor in the vertical direction. Hereinafter, the principle will be described for a case where a quotient of two signals is used.

When an external force 25 is applied to the holding table 24 from the vertical direction, the detection signal intensity changes abruptly due to a change in the distance between the optical sensors 22 and 23 and the blood vessel 19, and the blood flow changes when the holder is too pressed. By doing so, it is conceivable that the amount of light absorbed changes and the intensity of the detection signal changes abruptly. In the conventional method, it is greatly affected by such a change, and accurate heart rate detection has been difficult.

When an external force 25 is applied to the holding table 24 from the vertical direction and the light source 21 and the optical sensors 22 and 23 approach the blood vessel 19 and the amount of light detected by the optical sensor 23 changes, the amount of light of the optical sensor 22 also changes. Changes to

Now, it is assumed that the signal of the optical sensor 22 changes by a times and the signal of the optical sensor 23 changes by b times. Before the external force 25 is applied, the quotient X of the signal of the optical sensor 23 and the signal of the optical sensor 22
Is

[0037]

(Equation 1)

The heart rate is calculated based on the value. On the other hand, the quotient Y of the signal of the optical sensor 23 and the signal of the optical sensor 22 when the external force 25 is applied is

[0039]

(Equation 2)

## EQU2 ## Since a is approximately a ≒ b,

[0041]

(Equation 3)

## EQU2 ## and the same value as the original signal, so that the change in signal intensity can be suppressed.

Therefore, by obtaining the heart rate based on the quotient of the signals from the two optical sensors, the effect of suppressing the effect of the sudden increase and decrease of the light propagating in the living body due to the external force from the vertical direction is exhibited. be able to. Here, the same effect can be obtained by using the difference between the signals of the two optical sensors.

Further, according to the present embodiment, the influence of disturbance light such as sunlight and illumination light on the living body can be reduced.

Here, the disturbance light 26 entering the living body 20
The light also propagates while being scattered inside the living body 20 like the light from the light source 21, but a part of the light enters the optical sensors 22 and 23. Since the two optical sensors 22 and 23 are affected by the disturbance light 26, the optical sensors 22 and 23 as in the present embodiment are used.
By using the quotient or difference of the signals in the above, a sharp change in the signal intensity can be greatly suppressed, and a more accurate heart rate can be stably obtained. Here, the distance between the optical sensor 22 and the optical sensor 23 is preferably within 3 mm.
In this case, the influence of the disturbance light on the optical sensor 22 and the optical sensor 23 is substantially the same, so that the influence of the disturbance light can be further reduced.

(Embodiment 3) FIG. 3 is a sectional view of the heart rate sensor according to Embodiment 3 of the present invention, from which the display device is omitted. 31 is a light source, 32 and 33 are irradiation light measurement optical sensors provided within 2 mm from the light source 31 for mainly measuring light propagating in the living body, and 34 and 35 are light sources 31 Is a heart rate signal measuring optical sensor provided at a distance greater than 2 mm for detecting light propagating inside the living body and detecting a pulsation signal of blood. The same light source and light sensor as those in Embodiment 1 were used.

In this embodiment, the signals detected by the irradiation light measuring optical sensor 32 and the irradiation light measuring optical sensor 33 are averaged, and the heart rate signal measuring optical sensor 34 and the heart rate signal measuring optical sensor 35 are averaged. The detected signals are averaged. Instead, the sum may be calculated, or the average value or the sum may be calculated after weighting the detection value of each optical sensor.

When the respective average values are determined, the quotient Z of the average value of the irradiation light measurement optical sensor and the average value of the heartbeat signal measurement optical sensor is determined. Where Z is

[0049]

(Equation 4)

Is represented by According to this equation, for example, an external force is applied to the upper part of the heartbeat signal measurement optical sensor 34 or the heartbeat signal measurement optical sensor 35 during exercise, causing a bias in the pressing force, and the detection values of the respective optical sensors change. in case of,

[0051]

(Equation 5)

According to the above item, the effect of suppressing increase / decrease of the signal of each sensor can be exhibited.

Even when an external force is applied to the upper portion of the light source 31 from the vertical direction and the light amount detected by the heartbeat signal measurement optical sensor 34 and the heartbeat signal measurement optical sensor 35 is uniformly reduced, the irradiation light measurement is performed. Since the amount of light reaching the optical sensor 32 for illumination and the optical sensor for irradiation light measurement 33 is similarly reduced,
By using Z, a sudden change in the detected light amount can be suppressed.

Also, when disturbance light such as sunlight or illumination light enters, all of the optical sensors are affected by the influence and the signal intensity increases. Changes can be suppressed.

In the present embodiment, an example using a quotient has been described. However, the present invention is not limited to this, and a similar effect can be obtained by obtaining a difference.

Here, as shown in the plan view of FIG.
It is preferable that the irradiation light measuring optical sensor 42 is provided concentrically with the light source 41 as the center, and the heartbeat signal measuring optical sensor 43 is further provided concentrically with the light source 41 as the center. In this way, by obtaining the heart rate based on the quotient or difference of the signals obtained by the irradiation light measurement optical sensor 42 and the heartbeat signal measurement optical sensor 43, external forces from various angular directions act. Even in such a case, the effect of suppressing those effects can be obtained.

[0057]

According to the present invention, even when an external force is applied to the heart rate sensor or when disturbance light is irradiated, the effects can be suppressed. It becomes possible to measure stably.

[Brief description of the drawings]

FIG. 1 is a sectional view of a heart rate sensor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view excluding a display device of a heart rate sensor according to another embodiment of the present invention.

FIG. 3 is a sectional view of a heart rate sensor according to still another embodiment of the present invention, excluding a display device.

FIG. 4 is a plan view showing an arrangement of a light source and an optical sensor of a heart rate sensor according to still another embodiment of the present invention.

[Explanation of symbols]

 11, 21, 31, 41 Light source 12, 13, 22, 23 Optical sensor 32, 33, 42 Illumination light measuring optical sensor 34, 35, 43 Heart rate signal measuring optical sensor 14 Signal processing unit 15 Display unit 16, 24, 36 holding table 17 cable 18 display device 19 blood vessel 20 living body 25 external force 26 disturbance light

Claims (8)

[Claims] 1. A light source for emitting light for irradiating a living body,
At least two optical sensors for receiving light emitted from the light source and passing through the living body, and signal processing means for calculating a heart rate using signals corresponding to the light received by the at least two optical sensors. Characteristic heart rate sensor. 2. The heart rate sensor according to claim 1, further comprising two optical sensors provided on both sides of the light source with the light source as a center. 3. The distance between the two light sensors and the light source is 2 m.
The heart rate sensor according to claim 2, wherein the heart rate sensor is larger than m. 4. A step of irradiating the living body with light, a step of receiving light incident on the living body and passing through the living body with at least two optical sensors, and using a signal corresponding to the light received by the at least two optical sensors. A heart rate calculation method, comprising: 5. A heart rate using the heart rate sensor according to claim 2 or 3, wherein a heart rate is calculated using a sum or an average value of signals corresponding to light received by the two optical sensors. Calculation method. 6. An irradiation light measuring optical sensor provided at a position within a distance of 2 mm from a light source, and a heartbeat signal measuring optical sensor provided at a position greater than 2 mm from the light source. The heart rate sensor according to claim 1, wherein: 7. An irradiation light measuring optical sensor is provided around the light source in a substantially concentric shape, and a heartbeat signal measuring optical sensor is provided in a substantially concentric shape outside the irradiation light measuring optical sensor. The heart rate sensor according to claim 6, wherein: 8. A quotient or a difference between a signal corresponding to light received by the irradiation light measurement optical sensor and a signal corresponding to light received by the heartbeat signal measurement optical sensor, using the heart rate sensor according to claim 6. A heart rate calculation method, wherein the heart rate is calculated by using the following.