JP3459463B2 - Pulse detection device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse detecting device. More specifically, the present invention relates to a pulse detection device capable of accurately measuring a pulse without being affected by exercise noise even during exercise.

[0002]

2. Description of the Related Art Conventionally, a device utilizing a light absorption characteristic of hemoglobin in blood by an optical sensor composed of a light emitting element and a light receiving element has been used to detect a pulse. Figure 5
FIG. 4 is a diagram illustrating a relationship between a path of light emitted from a light emitting element of an optical sensor and a light receiving element. This optical sensor is used for the subject 10
When it is attached to the pulse measurement site, the light from the light emitting element 2a penetrates into the subject through the opening 1a, and a part of the light is absorbed or proceeds to proceed. The reflected light is detected by the light receiving element 2b. Light is the amount of blood flow,
More precisely, the greater the amount of hemoglobin in the blood, the greater the amount that is absorbed, and the lower the light reflectance,
The signal detected by the light receiving element is also small. Therefore, the light receiving element detects a change in the amount of light absorption due to the amount of blood flow inside the measurement unit, specifically, a change in the light reflectance as a change in the received light amount, and this change in the received light amount is used as a pulse. Detect. When the pulse signal is detected, the time of the peak value of the signal is stored together with the time of the peak value of the next pulse signal, and the time difference is obtained. The pulse rate is obtained by taking the reciprocal of the time difference. Repeat this operation 3 to 10 times,
The average is displayed as the pulse rate.

In the pulse detecting device as described above, the pulse at rest can be accurately measured, but it is difficult to accurately measure the pulse at the time of exercise due to the influence of the noise signal due to exercise. That is, since the sensor itself including the light emitting element and the light receiving element moves due to the movement, noise corresponding to the vibration is introduced and is easily confused with the pulse signal. However, in recent years, from the aspect of health management, there is a demand for a pulse test during exercise such as when jogging. An example of a pulse measurement method that addresses the problem of noise signals due to this exercise is disclosed in Japanese Unexamined Patent Publication
No. 6-45633. This conventional pulse detection device is equipped with an optical sensor that detects only the noise signal due to exercise, in addition to the optical sensor that detects the original pulse signal that contains the noise signal due to exercise, and amplifies each detected signal to obtain the pulse rate. A method of detecting an amplified pulse signal is adopted by subtracting a signal obtained by amplifying only a noise signal due to exercise from a signal obtained by amplifying both a signal and a noise signal due to exercise.

[0004]

In the method of reducing the noise signal, the signal level is adjusted so that the amplification factor is changed so that the levels of the amplified signals output from the respective detection units are made equal to each other. Since it is not possible to match the output level of only the signal, it may not be possible to subtract only the noise signal and leave only the pulse signal.

[0005]

[0006]

It is an object of the present invention to solve the above problems and to provide a pulse detection device which has a high pulse detection accuracy not only at rest but also during exercise.

[0008]

A pulse detection device of the present invention comprises a pulse detection sensor consisting of a light emitting element and a light receiving element, a motion noise detection sensor, a peak detection signal from a pulse signal obtained from the pulse detection sensor, and a peak detection signal thereof. A means for obtaining time, a means for obtaining a peak detection signal from a motion noise signal obtained from the movement noise detection sensor and a time for obtaining the peak detection signal, and a peak detection signal for a pulse signal obtained at the time when the peak detection signal for movement noise is generated. It comprises means for removing the peak detection signal of the pulse signal and obtaining the cycle of the pulse signal from the remaining peak detection signal of the pulse signal, and means for obtaining the pulse rate from the cycle.

Further, means for checking whether or not noise due to exercise is detected by the signal obtained from the movement noise detecting sensor is provided, and when the noise due to exercise is not detected, the signal obtained from the pulse sensor immediately. Is provided with a means for determining the pulse rate,
It is preferable because it shortens the processing time.

[0010]

[0011]

In the pulse detection device of the present invention, due to the influence of exercise, even if the output includes a motion noise signal when the pulse signal is detected, the motion signal noise can be reliably removed, and the pulse signal is more accurate. The pulse rate can be detected.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a pulse detecting device of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is an explanatory view of an embodiment of the pulse detecting device of the present invention. The sensor holder 1 is provided with a light emitting element 2a such as an infrared LED and a light receiving element 2b such as a photodiode and a phototransistor.
An opening 1a is provided on a surface of the sensor holder 1 to be attached to a human body so that light emitted from the light emitting element 2a can pass through and the light receiving element 2b can receive the light.
The light emitting element 2a and the light receiving element 2b constitute a sensor 2 for detecting a normal pulse signal, and the sensor 2 also picks up a noise signal due to exercise. Further, the sensor holder 1 has a light emitting element 3 made of the same material as described above.
The light receiving element 3a and the light receiving element 3b are arranged to face each other in a sealed space so as not to be affected by ambient light.
In the present embodiment, the light emitting element 3a is supported by the spring 5 and is formed so as to vibrate and move in position in response to the vibration caused by the movement. The light emitting element 3a and the light receiving element 3b detect a noise signal due to the movement. Make up three. The sensor holder 1 having the pulse detection sensor 2 and the motion noise detection sensor 3 attached thereto is attached to a belt 4, and is fixed to the measurement site such as the wrist or the chest by the belt 4. When the sensor holder 1 is attached to the measurement site, as described above, the light emitted from the light emitting element 2a reaches the subject, and the inside of the subject is partially absorbed and partially progressed while being reflected. To do. By detecting the reflected light by the light receiving element 2b, the blood volume increases during the pulse, and a larger amount of light than usual is absorbed by hemoglobin, and the reflected light decreases. Therefore, the pulse can be detected, but the sensor can be used during exercise. Also undergoes the same vibration, the positional relationship between the sensor and the blood vessel changes, noise due to ambient light enters periodically, and motion noise is also included as described above.

Next, the means for detecting the motion noise signal by the motion noise detection sensor 3 will be described with reference to FIG.

FIG. 1B is a sectional view taken along the line AA of FIG. The light emitting element 3a of the motion noise detection sensor 3 is provided in the sensor holder 1 via the spring 5, and the light receiving element 3b is provided in the sealed space so as to face the light emitting element 3a. With the movement, the light emitting element 3a vibrates by the spring 5, and the light emitting element 3 is arranged to face each other.
When the distance between a and the light receiving element 3b changes, the amount of light received by the light receiving element 3b changes. A noise signal due to movement is detected by this change in the amount of received light. The motion noise detection sensor 3 is not limited to such a configuration, and the light receiving element 3b may vibrate, or a housing that is a closed space may have a vibrating portion. Accordingly, the light receiving amount of the light receiving element 3b may be changed.

The process from the output of the sensor signal to the detection of the pulse will be described with reference to the schematic block diagram of the circuit shown in FIG. The pulse detection sensor 2 converts a change in the amount of received light accompanying a pulse signal and a noise signal due to exercise into an electric signal and outputs it. Since this signal further includes high frequency noise from the outside, a filter 6 is used to remove this noise.
Pass through. At this time, since the motion noise signal generated during exercise has a frequency similar to that of the pulse signal, it is not removed by the filter 6 and remains after passing through the filter 6.

After that, the signal output from the filter 6 is amplified by the amplifier 7 by about 40 to 120 dB and input to the microcomputer (hereinafter referred to as the microcomputer) 5 as the signal V ₁ .

On the other hand, the motion noise detection sensor 3 including the light emitting element 3a and the light receiving element 3b converts the change in the amount of received light during exercise into an electric signal and outputs it. This signal is
Since the noise signal generated by the circuit or other causes is included together with the noise signal caused by the motion, in order to remove the noise other than the signal caused by the motion, the filter 6 similar to the filter described above is passed. Next, the signal output through the filter 6 is output by the amplifier 7 in the range of 0 to 40d in the same manner as above.
The signal is amplified about B and input to the microcomputer 5 as a signal V ₂ .

Next, a means for obtaining a peak detection signal and its time for obtaining a pulse rate in the microcomputer 5 based on the signals V ₁ and V ₂ , means for removing a motion noise signal and obtaining a cycle of the pulse signal, A means for obtaining the pulse rate from the cycle will be described.

First, the procedure for detecting a pulse at rest will be described.

FIG. 3 shows an example of a pulse wave signal detected by the pulse detection sensor 2 at rest. The output signal of the sensor 2 is input to the microcomputer 5 as a signal V ₁ as shown in FIG. 3A via the filter 6 and the amplifier 7. Now, since it is at rest, the signal V ₁ does not include a noise signal due to exercise. Therefore, the signal V ₁ detects only the pulse wave signal. Next, the peak detection signal and its time are obtained, the instantaneous voltage value is read by the timer interrupt software for each reference time obtained by dividing the oscillation frequency of the oscillator 8 in the microcomputer 5, the peak value is detected, and the peak value is detected. The time of this peak value is stored as shown in b). Then, the time of the next peak value is similarly stored, and the pulse cycle is detected by obtaining the time Δt between the two peak values. This pulse cycle is stored in the memory as pulse data.

Next, the procedure for detecting the pulse cycle during exercise will be described.

FIG. 4 (a) shows an example of the signal detected by the pulse detection sensor 2 during exercise, and FIG. 4 (b) shows the peak detection signal of the signal of FIG. 4 (a), similar to FIG. 3 (b). Obtain by means. FIG. 4C shows a signal detected by the motion noise sensor 3 at this time, and FIG. 4D shows a peak detection signal of the motion noise.

When the signal V ₁ is input to the microcomputer 5, it is checked whether or not the motion noise signal is input at the same time by determining whether or not the signal V ₂ from the motion noise sensor is input. If V ₂ is not input, the signal V ₁ is determined to be the pulse signal itself, and the pulse cycle is calculated from the difference from the previously input pulse time stored in the memory. When the signal V ₂ is input, the period Δt ₁₂ between A _{0 and} A ₁ must be detected in order to show the accurate pulse period. Where A ₀ −
When the period Δt ₁₁ between B ₁ is detected as a pulse, an erroneous pulse period is detected because the signal B ₁ is a noise signal.

Therefore, the following means can be adopted in the present invention as means for obtaining the period Δt ₁₂ between A _{0 and} A ₁ .

First, as a first means, the pulse rate is continuously measured from the pulse rate detected in a stationary state before the exercise is started. Generally, the pulse rate does not change rapidly even when the exercise is started, and it tends to gradually increase. Using this, the pulse rate obtained from the period Δt ₁₁ between A _{0 and} B ₁ and the pulse rate obtained from the period Δt ₁₂ between A _{0 and} A ₁ are calculated. Discard it as noise or use a signal of data that is close to the data at rest. After that, by adopting the data ± 5 times / minute or the data closest to the immediately preceding data, the correct pulse signal is always grasped.

Since this work stores the previous pulse rate in the microcomputer, it can be easily obtained by simply comparing Δt obtained by the subtraction with the previous data, and can be easily obtained by the calculating means of the microcomputer. .

Further is allowed to link time axis of the time signal V ₁ axis and the signal V ₂ as the second means, for the time t _1, t ₂ of the peak detection signal of the signal V ₂ is a motion noise signal , Of the peak detection signal V ₁ at times t ₁ and t
_The signal generated in ₂ (corresponding to B ₁ and B ₂ in FIG. 4B) can be removed as a motion noise signal.

That is, in the first method, the interval Δt between each peak detection signal is obtained, and the signal opened more than a certain range depending on the pulse rate obtained from the cycle of the previous measurement is discarded as noise. The second method is to obtain the period. The second method is to obtain the time of occurrence of the motion noise from the data of the motion noise signal, remove the signal data in the pulse detection signal that coincides with the time of occurrence as the signal of the motion noise, and The period is obtained from the data.

By combining these methods,
The reliability is further improved.

After that, new data is added to the past data in the memory. The data of about 3 to 10 times are averaged and displayed as a pulse.

[0032]

According to the pulse detection device of the present invention, the noise signal and the pulse signal are discriminated from the signal including the noise signal generated in the pulse signal due to the influence of exercise, so that the pulse signal is not only at rest but also during exercise. A highly reliable pulse detection device with high pulse detection accuracy can be obtained.

[Brief description of drawings]

FIG. 1 is a plan view and a sectional view showing an embodiment of a pulse detection device of the present invention.

FIG. 2 is a circuit block diagram of a pulse detection device of the present invention.

FIG. 3 is a graph showing an example of a pulse wave signal detected at rest.

FIG. 4 is a graph showing an example of a pulse wave signal and a motion noise signal detected during exercise.

FIG. 5 is an explanatory diagram of a relationship between a light path projected from a conventional light emitting element and a light receiving element.

[Explanation of symbols]

2 pulse detection sensor 2a light emitting element 2b Light receiving element 3 Motion noise detection sensor 3a light emitting element 3b Light receiving element 5 springs

Continuation of the front page (56) Reference JP-A-1-153139 (JP, A) JP-A-1-288230 (JP, A) JP-A-52-125372 (JP, A) JP-A-62-213727 (JP , A) Actual Kaihei 3-129107 (JP, U) Actual Kaihei 3-15502 (JP, U) Special Tables 5-506802 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) A61B 5/0245

Claims (2)

(57) [Claims] 1. A pulse detection sensor comprising a light emitting element and a light receiving element, a motion noise detection sensor, a means for obtaining a peak detection signal and its time from a pulse signal obtained from the pulse detection sensor, and a motion noise detection sensor. Gills
The peak detection signal and its time from the motion noise signal
And a motion noise peak detection signal is generated.
The peak detection signal of the pulse signal obtained during
A pulse detection device comprising: means for determining the cycle of the pulse signal from the peak detection signal of the remaining pulse signal, which is removed from the peak detection signal of the signal; and means for determining the pulse rate from the cycle. 2. A means for checking whether or not noise due to exercise is detected by the signal obtained from the movement noise detection sensor is provided, and when the noise due to exercise is not detected, the signal obtained from the pulse sensor immediately. The pulse detecting device according to claim 1, further comprising means for obtaining a pulse rate.