WO2015078266A1

WO2015078266A1 - Apparatus, system and method for measuring pulse

Info

Publication number: WO2015078266A1
Application number: PCT/CN2014/090037
Authority: WO
Inventors: Wei Li; Guowei Zhang
Original assignee: Tencent Technology (Shenzhen) Company Limited
Priority date: 2013-11-28
Filing date: 2014-10-31
Publication date: 2015-06-04
Also published as: CN104665802B; CN104665802A; HK1206959A1

Abstract

A pulse measurement apparatus is provided. The apparatus includes a light source configured to irradiate human skin, where light intensity of the light source is adjusted through current strength. The apparatus also includes a photosensitive diode configured to receive light reflected from the human skin, where the photosensitive diode is one of a photosensitive element and a photosensitive receiving array containing multiple photosensitive elements. Further, the apparatus includes a conversion circuit configured to convert the reflected light received by the photosensitive diode to a voltage waveform and a processor configured to count a total number of pulses based on frequency domain of the voltage waveform converted by the conversion circuit.

Description

APPARATUS, SYSTEM AND METHOD FOR MEASURING PULSE

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority of Chinese Patent Application No. 201310628125.4, filed on November 28, 2013, the entire contents of which are incorporated by reference herein.

FIELD OF THE INVENTION

The present invention generally relates to the field of sensor technologies and, more particularly, to apparatuses, systems and methods for pulse measurement.

BACKGROUND

Human pulse measurement plays an important role in monitoring vital signs, and diagnosing and treating diseases. Existing pulse measurement methods mainly include a piezoelectric pulse measurement method, an infrared ray pulse measurement method, and an electrocardiography measurement method. In the piezoelectric pulse measurement method, a pulse measurement apparatus which is bound on human body converts pressure generated during pulse beats to electrical signals through a pressure sensor, thereby realizing pulse measurement. In the infrared ray pulse measurement method, a pulse measurement apparatus is clamped on a finger of a patient, and the pulse measurement apparatus measures the patent’s pulse rate through infrared ray. In the electrocardiography measurement method, several touch points are placed on several parts of the human body, and the pulse measurement apparatus obtains human vital sign parameters and converts the parameters to pulse parameters.

However, the above existing pulse measurement methods have relatively high requirements on a position relationship between the pulse measurement apparatus and the human body. Motion status (e.g., posture, motion) of the patient has stricter limitations. For example, when a strap is bound on an arm of a patient or a clip is clamped on a finger of the patient, if the patient does more vigorous exercise, the strap or the clip may be easily displaced or even fell off, affecting accuracy of the pulse measurement results. The existing pulse measurement methods are suitable for patients in bed, but are not suitable for healthy people’s continuous pulse measurement during daily activities.

The disclosed apparatuses, systems and methods are directed to solve one or more problems set forth above and other problems.

BRIEF SUMMARY OF THE DISCLOSURE

One aspect of the present disclosure includes a pulse measurement apparatus. The apparatus includes a light source configured to irradiate human skin, where light intensity of the light source is adjusted through current strength. The apparatus also includes a photosensitive diode configured to receive light reflected from the human skin, where the photosensitive diode is one of a photosensitive element and a photosensitive receiving array containing multiple photosensitive elements. Further, the apparatus includes a conversion circuit configured to convert the reflected light received by the photosensitive diode to a voltage waveform and a processor configured to count periodically a total number of pulses based on frequency domain of the voltage waveform converted by the conversion circuit.

Another aspect of the present disclosure includes a pulse measurement system. The system includes a pulse measurement apparatus configured to irradiate human skin by light that is emitted by a light source, receive light reflected from the human skin, convert the reflected light to a voltage waveform, count periodically a total number of pulses based on frequency domain of the converted voltage waveform and send a counting result to an application client terminal, where light intensity of the light source is adjusted through current strength. The system includes the application client terminal configured to receive the counting result sent from the pulse measurement apparatus and perform one of drawing a pulse graph in a human-machine interactive interface and reporting the counting result to a network server based on the counting result.

Another aspect of the present disclosure includes a pulse measurement method. The method includes irradiating human skin by light that is emitted by a light source, where light intensity of the light source is adjusted through current strength. The method also includes receiving light reflected from the human skin and converting the reflected light to a voltage waveform. Further, the method includes counting periodically a total number of pulses based on frequency domain of the converted voltage waveform.

Other aspects of the present disclosure can be understood by those skilled in the art in light of the description, the claims, and the drawings of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

To describe the technical solution of the embodiments of the present invention more clearly, drawings used in the description of the embodiments are introduced below. The drawings described below are merely exemplary embodiments of the present invention. For those skilled in the art, on the premise of no inventive effort being involved, other drawings may also be obtained according to these drawings and the descriptions included herein.

Figure 1 illustrates a structure schematic diagram of an exemplary pulse measurement apparatus consistent with the disclosed embodiments；

Figure 2 illustrates a schematic diagram of an exemplary voltage waveform consistent with the disclosed embodiments；

Figure 3 illustrates a structure schematic diagram of another exemplary pulse measurement apparatus consistent with the disclosed embodiments；

Figure 4 illustrates a structure schematic diagram of another exemplary pulse measurement apparatus consistent with the disclosed embodiments；

Figure 5 illustrates a structure schematic diagram of another exemplary pulse measurement apparatus consistent with the disclosed embodiments；

Figure 6 illustrates a schematic diagram of an exemplary frequency spectrum corresponding to a voltage waveform consistent with the disclosed embodiments；

Figure 7a and Figure 7b illustrate schematic diagrams of two different position relationships between a photosensitive diode and light-emitting diodes consistent with the disclosed embodiments；

Figure 8 illustrates a scenario diagram of an exemplary pulse measurement apparatus fixed on the top of a ceiling through a bolt consistent with the disclosed embodiments；

Figure 9 illustrates a scenario diagram of an exemplary pulse measurement apparatus fixed on a horizontal table through a bracket fixing part consistent with the disclosed embodiments；

Figure 10 illustrates a scenario diagram of an exemplary pulse measurement apparatus which is bound on a wrist of a human body through a strap type fixing part consistent with the disclosed embodiments；

Figure 11 illustrates a schematic diagram of an exemplary pulse measurement system consistent with the disclosed embodiments；

Figure 12 illustrates a schematic diagram of an exemplary interface on an application client terminal consistent with the disclosed embodiments；

Figure 13 illustrates a flow chart of an exemplary pulse measurement process consistent with the disclosed embodiments；

Figure 14 illustrates a flow chart of another exemplary pulse measurement process consistent with the disclosed embodiments；

Figure 15 illustrates a schematic diagram of an exemplary process for determining fundamental frequency consistent with the disclosed embodiments； and

Figure 16 illustrates a flow chart of another exemplary pulse measurement process consistent with the disclosed embodiments.

DETAILED DESCRIPTION

In the following description, for purposes of illustration, many specific details are illustrated to provide a full understanding of one or more embodiments. However, obviously, those embodiments can also be implemented in the case of these specific details changed, replaced, or alternated. The followings, together with accompanying drawings, describe in detail certain embodiments of the present invention.

To realize accurate pulse measurement in the case of unrestricted motion of a user, a pulse measurement apparatus is provided. The apparatus measures human pulse (also known as heart rate, that is, the number of times a heart beats in one minute) through irradiating human body by a light source. The position relationship between the light source and the human body is not limited herein. Figure 1 illustrates a structure schematic diagram of an exemplary pulse measurement apparatus consistent with the disclosed embodiments. As shown in Figure 1, the apparatus may include power 10, a light source 11, a photosensitive diode 12, a conversion circuit 13, and a processor 14.

The light source 11 is configured to irradiate human skin. Specifically, the light emitted by the light source 11 irradiates the human skin. Light intensity of the light source 11 can be adjusted through current strength (also known as current intensity, that is, the magnitude of an electric current) . The value of the light intensity of the light source is not limited herein.

The photosensitive diode 12 is configured to receive the light reflected from the human skin. Specifically, the photosensitive diode 12 receives the light reflected from the human skin. After the human skin receives incident light emitted by the light source 11, human skin may absorb part of the light and reflect the remaining light. Because blood pressure changes periodically with the pulse, and the change of the blood pressure can cause the change of blood concentration in the human body (different blood concentrations have different light absorptivity) , so the light intensity of the reflected light received by the photosensitive diode 12 changes along with the pulse. In practical applications, the photosensitive diode 12 may be a photosensitive element or a photosensitive receiving array constituted by multiple photosensitive elements.

The conversion circuit 13 is configured to convert the reflected light received by the photosensitive diode 12 to a voltage waveform. Based on the light intensity change of the reflected light received by the photosensitive diode 12, the conversion circuit 13 implements a voltage signal conversion process. Figure 2 illustrates a schematic diagram of an exemplary voltage waveform consistent with the disclosed embodiments. As shown in Figure 2, because the process that the photosensitive diode 12 receives the reflected light is a continuous process, voltage signals obtained by the conversion circuit 13 are continuous voltage values. Therefore, a voltage waveform shown in an oscilloscope is a continuous voltage waveform.

The processor 14 is configured to count a total number of pulses based on the voltage waveform converted by the conversion circuit 13. After light intensity of the reflected light is converted to the voltage waveform, the processor 14 monitors the pulse beat based on frequency domain (e.g., peak in the frequency domain) of the voltage waveform, thereby counting the total number of pulses. The frequency domain refers to the analysis of mathematical functions or signals with respect to frequency. A frequency-domain graph shows how much of the signal lies within each given frequency band over a range of frequencies.

The pulse measurement apparatus can irradiate the human skin using the light source and receive the light reflected from the human skin. Then, the pulse measurement apparatus converts the reflected light to the voltage waveform. Finally, based on the converted voltage waveform, the pulse measurement apparatus can count the total number of pulses. Because the pulse measurement method based on the light irradiation does not need to limit human posture and movement, the pulse measurement can be performed when a user walks or moves. Comparing to existing technologies (e.g., a piezoelectric pulse measurement method, an infrared ray pulse measurement method, etc. ) , the accurate pulse measurement can be realized in the case of unrestricted motion of the user.

In addition, Figure 3 illustrates a structure schematic diagram of another exemplary pulse measurement apparatus consistent with the disclosed embodiments. As shown in Figure 3, in addition to the power 10, the light source 11, the photosensitive diode 12, the conversion circuit 13 and the processor 14 in Figure 1, the apparatus may also include a control circuit 31.

The control circuit 31 is configured to select initial current strength from a preset current strength selection range. To ensure that light intensity of the light which irradiates human skin is appropriate, and a voltage waveform is suitable for the pulse measurement, a current strength selection range can be preset. The initial current strength that activates the light source can be determined from the current strength selection range. Because the light intensity of the light source is affected by the type of the light source, device model, and ambient light intensity, those skilled in the art can set the current strength selection range based on an empirical value in a specific scenario and a specific device model.

There are no quantitative restrictions for setting the current strength selection range herein. After the current strength selection range is set, a current strength value can be randomly selected from the current strength selection range as the initial current strength. Based on experimental data, the initial current strength can also be determined using the current strength at a midpoint, a one-third point, or a quarter point of the current strength selection range as the initial current strength. The only requirement is that the initial current strength is selected from the current strength selection range, whereas the specific selection methods are not limited herein.

After the control circuit 31 selects the initial current strength, based on the light intensity activated by the initial current strength, the light source 11 irradiates the human skin. The current strength and the light intensity of the light source have a positive correlation. That is, the greater the current strength, the greater the light intensity of the light source； the smaller the current strength, the smaller the light intensity.

In addition, the pulse measurement apparatus does not limit posture and movement of the user. Therefore, when irradiating the human skin using the light source, to improve the accuracy of the pulse measurement, the effect of the user’s movement on the pulse measurement needs to be considered. Thus, based on the intensity of the reflected light received by the photosensitive diode 12, the light intensity of the light source 11 needs to be adjusted.

Specifically, after the conversion circuit 13 converts the reflected light to the voltage waveform, the processor 14 monitors whether the voltage waveform meets testing conditions. The testing conditions refer to light intensity conditions that can be used to measure the pulse after eliminating external interference. The testing conditions may include: a peak value and a valley value of the voltage waveform are in a preset voltage amplitude range, and a difference between the peak value and the valley value is greater than the preset voltage difference. That is, for the voltage waveform shown in Figure 2, the amplitude of the voltage cannot be greater than the preset voltage amplitude range.

Also, the amplitude of the voltage cannot be too small to affect the accuracy of the pulse measurement. If the voltage waveform meets the testing conditions, the pulse measurement can be performed. If the voltage waveform does not meet the testing conditions, the intensity of the light source11 needs to be adjusted through the control circuit 31 to obtain the adjusted current strength. When adjusting the intensity of the light source, the control circuit 31 adjusts the initial current strength according to preset current strength magnitude.

For example, the current strength is adjusted by 1mA, increasing or decreasing gradually the initial current strength. After the initial current strength is adjusted, based on the light intensity which is activated by the adjusted current strength selected by the control circuit 31, the light source 11 irradiates the human skin. Also, based on the reflected light newly received by the photosensitive diode 12, the conversion circuit 13 converts the reflected light to the voltage waveform again. Then, the processor 14 and the control circuit 31 monitor and adjust the new voltage waveform again, until the adjusted voltage waveform meets the testing conditions.

Further, after the voltage waveform meets the testing conditions, to eliminate the effect of noise spike on the pulse measurement, a noise frequency corresponding to the voltage waveform needs to be eliminated, such that the pulse measurement result can be more accurate. Figure 4 illustrates a structure schematic diagram of another exemplary pulse measurement apparatus consistent with the disclosed embodiments. As shown in Figure 4, in addition to the power 10, the light source 11, the photosensitive diode 12, the conversion circuit 13, the processor 14 and the control circuit 31 shown in Figure 3, the pulse measurement apparatus may also include a filter circuit 41.

The filter circuit 41 is configured to, after the processor 14 monitors that the voltage waveform meets the testing conditions, perform a band-pass filtering operation for the voltage waveform converted by the conversion circuit 13 based on a preset frequency bandwidth, where cutoff frequencies of the preset bandwidth are derived from the cutoff values of the preset pulse beats per minute.

It should be noted that a filter object is a frequency domain form of the voltage waveform, that is, the frequency values corresponding to the voltage waveform. When setting the preset frequency bandwidth, upper and lower cutoff frequencies of the preset frequency bandwidth can be derived based on the extreme limit of human pulse beats per minute in medicine. In general, the extreme limit of human pulse beats per minute is from 40 beats/minute to 220 beats/minute. That is, the upper and lower cutoff pulse beats per minute is 40 beats/minute and 220 beats/minutes, respectively. Then, the extreme limits of human pulse beats per minute are converted to frequency values, obtaining the upper and lower cutoff frequencies of the preset frequency bandwidth 0.67Hz and 3.67Hz. Therefore, the preset frequency bandwidth (0.67Hz to 3.67Hz) is obtained.

The purpose of setting the preset frequency bandwidth based on the pulse beats per minute is to eliminate disturbance frequency which does not meet patterns of the human pulse beats, thereby making subsequent processing results more accurate. For example, if a certain frequency (e.g., 1500Hz) generated by noise spike is not filtered, the pulse beats per minute measured in the subsequent step may be 1500Hz×60seconds＝90000 beats/minutes. The result is inconsistent with the laws of nature and the error is too large.

Figure 5 illustrates a structure schematic diagram of another exemplary pulse measurement apparatus consistent with the disclosed embodiments. As shown in Figure 5, the processor 14 may include a frequency domain conversion unit 51, a determination unit 52 and a data conversion unit 53.

The frequency domain conversion unit 51 is configured to convert a voltage waveform to frequency domain. The determination unit 52 is configured to determine the upper cutoff frequency of the frequency domain converted by the frequency domain conversion unit 51 as the fundamental frequency. The data conversion unit 53 is configured to convert the fundamental frequency determined by the determination unit 52 to pulse beats per minute.

After the band-pass filtering operation is performed for the voltage waveform, the remaining frequency values can be used to count the total number of pulses. Figure 6 illustrates a schematic diagram of an exemplary frequency spectrum corresponding to a voltage waveform consistent with the disclosed embodiments.

As shown in Figure 6, taking a voltage waveform as an example, the frequency domain conversion unit 51 converts the voltage waveform which meets band-pass filtering condition to frequency domain, obtaining a frequency spectrum constituted by continuous frequency values. Then, the determination unit 52 determines that the upper cutoff frequency of the frequency spectrum is used as the fundamental frequency. The data conversion unit 53 multiplies the fundamental frequency with 60 seconds to obtain pulse beats per minute.

Further, to save the power consumption, light emitting diodes (LEDs) may be used as the light source 11. In addition, the reflected light received by the photosensitive diode 12 may be reduced due to light scattering, thereby affecting the accuracy of the pulse measurement. To avoid this problem, the LEDs which are set around the photosensitive diode surround closely the photosensitive diode 12. Therefore, the reflected light that irradiates the human skin can be centralized on the surface of the photosensitive diode 12. In another implementation, the photosensitive diode 12 is set in the central part of the pulse measurement apparatus, 4 LEDs are set on the top, bottom, left and right of the photosensitive diode 12, respectively. Figure 7a and Figure 7b illustrate schematic diagrams of two different position relationships between a photosensitive diode and light emitting diodes consistent with the disclosed embodiments.

As shown in Figure 7a, a photosensitive diode is placed in the circular center and a plurality of LEDs are placed surrounding the center in a circular arrangement. As shown in Figure 7b, a photosensitive diode is placed in the rectangular center and a plurality of LEDs are placed surrounding the center in a rectangular arrangement. Other arrangements may also be used.

In addition, an irradiating direction of the light source 11 is set the same as the light receiving direction of the photosensitive diode 12. When counting total number of pulses, the direction of light source 11 and the photosensitive diode 12 are toward the human skin.

To further reduce the limitation on the motion of the user, the apparatus may also include a fixing part. The fixing part is configured to fix the apparatus on a position which is a predetermined distance apart from the human skin. The fixing part can be a bolted fixing part, a bracket fixing part, a magnetic fixing part, an adhesive fixing part, an inlaid fixing part, or a strap type fixing part. There are no limitations on the type of the fixing part.

Figure 8 illustrates a scenario diagram of an exemplary pulse measurement apparatus fixed on the top of a ceiling through a bolt consistent with the disclosed embodiments. As shown in Figure 8, a user’s pulses are measured when the user moves in a room. The fixing part is a bolted fixing part. The pulse measurement apparatus is fixed on the top of a ceiling through the bolt. The light source 11 and the photosensitive diode 12 are set face down, forming a three-dimensional irradiation area. When the user moves in the irradiation area, the pulse measurement apparatus can measure the user’s pulses in real time.

Figure 9 illustrates a scenario diagram of an exemplary pulse measurement apparatus fixed on a horizontal table through a bracket fixing part consistent with the disclosed embodiments. As shown in Figure 9, a user’s pulses are measured when the user moves in open air. The fixing part is a bracket fixing part. The pulse measurement apparatus is fixed on a horizontal table. The light source 11 and the photosensitive diode 12 are set to face human body, forming a three-dimensional irradiation area. When the user moves in the irradiation area, the pulse measurement apparatus can measure the user’s pulses in real time.

Figure 10 illustrates a scenario diagram of an exemplary pulse measurement apparatus which is bound on a wrist of a human body through a strap type fixing part consistent with the disclosed embodiments. As shown in Figure 10, the fixing part is a strap type fixing part and the pulse measurement apparatus is bound on human body (e.g., wrist) using the strap type fixing part. The motion of a user is not limited herein. The light source 11 and the photosensitive diode 12 are set to face human body, forming a certain irradiation area. The distance between the human body and the surface of the light source 11 and the photosensitive diode 12 is controlled in the range of -5mm to +10mm, where the negative value refers to a situation that the surface of the light source 11 and the photosensitive diode 12 extrudes the human skin. The pulse measurement apparatus can measure the user’s pulses in real time when the user moves. The user’s motion area is not limited herein.

Figure 11 illustrates a schematic diagram of an exemplary pulse measurement system consistent with the disclosed embodiments. The pulse measurement system is configured to process, display and transmit a pulse measurement result. As shown in Figure 11, the pulse measurement system may include a pulse measurement apparatus 111 and a client terminal 112. The pulse measurement apparatus can be any one of the pulse measurement apparatuses shown in Figure 1, and Figure 3 to Figure 10.

The pulse measurement apparatus 111 is configured to irradiate human skin, receive light reflected from the human skin and convert the reflected light to a voltage waveform. The pulse measurement apparatus 111 is also configured to count a total number of pulses based on the voltage waveform and send a counting result to the client terminal 112.

Specifically, the pulse measurement apparatus 111 sends the counting result to the client terminal 112 through a wire or wireless transmission mode. The wireless transmission mode includes, but is not limited to, mobile communication network transmission, wireless fidelity (WI-FI) transmission, Bluetooth transmission, infrared transmission, and so on.

The client terminal 112 is configured to receive the counting result sent from the pulse measurement apparatus 111, and draw a pulse graph in a human-machine interactive interface or send the counting result to a network server based on the counting result.

The pulse measurement apparatus 111 keeps counting the user’s pulses. The client terminal 112 receives the pulse counting result in real time through a data transmission path established between the client terminal 112 and the pulse measurement apparatus 111, and draws the pulse graph in the human-machine interactive interface for the user based on the counting result. Or the pulse measurement apparatus 111 sends the obtained counting result to a network server, such that the server can analyze sample data.

In one application scenario, a mobile phone is installed a “health index” application. A user wears a pulse measuring type health watch on his/her wrist. The pulse measuring type health watch counts the user’s pulses in real time, and sends a counting result to the mobile client terminal. Figure 12 illustrates a schematic diagram of an exemplary interface on an application client consistent with the disclosed embodiments.

As shown in Figure 12, the mobile terminal draws a heart rate waveform in real time on an interface of the “health index” application based on the counting result, and displays in real time the user’s pulses per minute on the upper right of the interface. At the same time, the mobile client terminal sends the received counting result and the user’s current motion status (e.g., static, walking, running, etc. ) to a network server, such that the network server can evaluate and analyze the user’s physical fitness based on the counting result in combination with the user’s motion status. In addition, the network server also stores the counting result as the sample data, such that the network server can perform a health trend analysis for a target population based on the pulse counting results of a large number of mobile phone’s users.

Figure 13 illustrates a flow chart of an exemplary pulse measurement process consistent with the disclosed embodiments. A pulse measurement apparatus can be any one of the pulse measurement shown in Figure 1, and Figure 3 to Figure 10. As shown in Figure 13, the pulse measurement process may include the following steps.

Step 1301: the pulse measurement apparatus irradiates human skin.

Specifically, the pulse measurement apparatus irradiates the human skin through light-emitting diodes (LEDs) , providing a source of the reflected light.

Step 1302: the pulse measurement apparatus receives the light reflected from the human skin.

Specifically, the pulse measurement apparatus receives the light reflected from the human skin through a photosensitive diode. In practical applications, the photosensitive diode may be a light sensor or a photosensitive receiving array constituted by multiple light sensors.

Step 1303: the pulse measurement apparatus converts the reflected light to a voltage waveform.

Specifically, the pulse measurement apparatus converts the reflected light to a frequency spectrum which is constituted by continuous frequency values. The frequency spectrum is presented as a voltage waveform in an oscilloscope. The converted voltage waveform is shown in Figure 2.

Step 1304: the pulse measurement apparatus counts a total number of pulses based on the voltage waveform.

After the voltage waveform is formed, the pulse measurement apparatus finds a characteristic frequency of the frequency spectrum corresponding to the voltage waveform. Based on the value of the characteristic frequency, the pulses per minute are counted. The value of the characteristic frequency is a frequency value representing the target beat law, e.g., a maximum frequency of the frequency spectrum.

The pulse measurement apparatus can irradiate the human skin using the light source and receive the light reflected from the human skin. Then, the reflected light is converted to the voltage waveform. Further, based on the converted voltage waveform, the total number of pulses can be counted. In general, blood pressure changes periodically with the pulse, and the change of the blood pressure can cause the change of blood concentration in the human body. The different blood concentrations have different light absorptivity.

Therefore, the pressure change during pulse beats can be monitored by measuring the light intensity of the reflected light, further measuring and counting the total number of pulses. Because the pulse measurement method based on light irradiation does not need to limit human posture and movement, the pulse measurement can be performed when a user walks or moves. Comparing to existing technologies (e.g., a piezoelectric pulse measurement, an infrared ray pulse measurement, etc. ) , the accurate pulse measurement can be realized in the case of unrestricted motion of a user.

Figure 14 illustrates a flow chart of another exemplary pulse measurement process consistent with the disclosed embodiments. As shown in Figure 14, the process may include the following steps.

Step 1401: initial current strength is selected from a preset current strength selection range.

To ensure the accuracy of pulse measurement, at the beginning, a light intensity range of a light which can be used to get accurate pulse measurement results needs to be set in advance. However, the light intensity is determined by the current strength that activates the light. Therefore, a preset current strength selection range needs to be set in advance. Testers can set the current strength selection range based on empirical values in external environment and a specific device model of the apparatus. For example, when the model of a LED is Everlight 23-21/GHC-YR2T1/2A and the model of a photosensitive diode is Everlight PD70-01B/TR7, the current strength selection range is set between 3mA to 16 mA.

After the current strength selection range is set, a current strength value can be randomly selected from the current strength selection range as the initial current strength. The initial current strength can also be determined based on experimental data, using current strength at a midpoint, a one-third point, or a quarter point of the current strength selection range as the initial current strength. The only requirement is that the initial current strength is selected from the current strength selection range, whereas the specific selection methods are not limited herein. For example, a current strength selected randomly by the apparatus may be 10mA.

Step 1402: the light source irradiates human skin. Specifically, the pulse measurement apparatus applies 10mA current to the LED, such that the LED activates a light which has a corresponding light intensity to irradiate the human skin.

Step 1403: the pulse measurement apparatus receives the light reflected from the human skin. The implementation in Step 1403 may be the same as Step 1302 shown in Figure 13, which is not repeated herein.

Step 1404: the pulse measurement apparatus converts the reflected light to a voltage waveform. The implementation in Step 1404 may be the same as Step 1303 shown in Figure 13, which is not repeated herein.

Step 1405: the pulse measurement apparatus monitors whether the voltage waveform meets testing conditions.

In order not to affect pulse measurement results when the relative position between the human skin and the pulse measurement apparatus changes, the initial current strength can be adjusted through monitoring the voltage waveform at the beginning of the pulse measurement, thereby changing the light intensity and making the voltage waveform meeting the testing conditions. Thus, external interference on the pulse measurement results can be eliminated.

Specifically, after the voltage waveform is formed, the pulse measurement apparatus monitors a few initial continuous voltage waveforms to judge whether the voltage waveforms meet the testing conditions. The testing conditions may include: a peak value and a valley value of the voltage waveform are in the preset voltage amplitude range, and a difference between the peak value and the valley value is greater than the difference of the preset voltage value. If the voltage waveform does not meet the testing conditions, the process goes to Step 1406； if the voltage waveform meets the testing conditions, the process goes to Step 1407.

For example, for the model of the apparatus described in Step 1401, the appropriate testing conditions include: the preset voltage amplitude range is 0V to 3.3V, and the preset voltage difference is 0.5V. When the initial current strength 10mA is selected in Step 1401, if the peak value of the voltage waveform is 3.9V and the valley value of the voltage waveform is 0.6V, the voltage waveform does not meet the testing conditions because the peak value 3.9V is greater than the upper limit 3.3V； if the peak value of the voltage waveform is 2.9V and the valley value of the voltage waveform is 2.7V, the voltage waveform still does not meet the testing conditions because the difference between the peak value and the valley value 0.2V is less than the difference of the preset voltage value 0.5V.

Step 1406: the initial current strength is adjusted based on the preset current strength magnitude.

Specifically, if the peak value and/or the valley value of the voltage waveform exceed the preset voltage amplitude range, the initial current strength is decreased based on the preset current strength magnitude； if the difference between the peak value and the valley value is equal to or less than the preset voltage difference, the initial current strength is increased based on the preset current strength magnitude. For example, when a peak value is 3.9V and a valley value is 0.6V, because the peak value is greater than the upper limit 3.3V, the initial current strength needs to be decreased； when the peak value is 2.9V and the valley value is 2.7V, because a difference between the peak value and the valley value (2.9V-2.7V＝0.2V) is less than 0.5V, the initial current strength needs to be increased.

When adjusting the initial current strength, the initial current strength can be adjusted gradually based on the preset current strength magnitude. For example, the current strength is increased or decreased 1mA each time. Then, Step 1402 to Step 1405 are repeated, it is judged whether the voltage waveform generated based on the adjusted current strength meets the testing conditions. If the voltage waveform does not meet the testing conditions, the process goes to Step 1406 and the current strength is increased or decreased 1mA again. The current strength is adjusted until the voltage waveform meets the testing conditions.

Because the user is always in a motion status, the distance between the human body and the pulse measurement apparatus changes frequently. In order not to affect the accuracy of the pulse measurement results, the pulse measurement apparatus can monitor the voltage waveform constantly during the whole pulse measurement process. When detecting that the voltage waveform does not meet the testing conditions, the current strength is adjusted timely.

Step 1407: based on preset frequency bandwidth, the band-pass filtering operation is performed for the voltage waveform.

Specifically, when detecting that the voltage waveform meets the testing conditions, the band-pass filtering operation is performed for the voltage waveform. The purpose of Step 1407 is, on the basis of that the external interference is eliminated in Step 1406, to further eliminate the noise frequency generated due to device noise, such that the frequency values of the human pulse beats can be filtered. The cutoff frequencies of the preset bandwidth are derived from the cutoff values of the preset pulse beats per minute. As previously mentioned, the extreme limit of human pulse beats per minute is from 40 beats/minute to 220 beats/minute. That is, the upper and lower cutoff pulse beats per minute is 40 beats/minute and 220 beats/minutes, respectively. The corresponding upper frequency and lower cutoff frequency of the preset frequency bandwidth are 0.67Hz and 3.6Hz, respectively. The frequency range between 0.67Hz and 3.6Hz can be used as the preset frequency bandwidth (0.67Hz to 3.67Hz) to perform the band-pass filtering operation for the voltage waveform. If the frequency value of the voltage waveform exceeds the preset frequency bandwidth, it is considered that the frequency value is not the frequency generated by the human pulse, and the frequency needs to be discarded through the band-pass filtering operation. For example, if the upper cutoff frequency of the frequency spectrum corresponding to the voltage waveform is 4.5Hz, because 4.5Hz exceeds the frequency bandwidth (0.67Hz to 3.67Hz) , the frequency value 4.5Hz needs to be discarded.

To improve the accuracy of filtering the human pulse, a relative small preset frequency bandwidth can be selected when performing the band-pass filtering operation. If the voltage waveform does not meet the testing conditions, the preset frequency bandwidth is amplified based on the frequency bandwidth adjusting magnitude, and the voltage waveform is performed the second filtering operation based on the adjusted frequency bandwidth range until the voltage waveform meets the testing conditions or the voltage waveform is discarded. For example, at the beginning, the frequency bandwidth 0.92Hz to 3Hz corresponding to the pulse beats 55 beats/minute to 180 beats/minute is selected to perform the band-pass filtering operation for the voltage waveform. If the filtered voltage waveform does not meet the testing conditions, the frequency bandwidth is further amplified.

Further, the frequency bandwidth 0.83Hz to 3.3Hz corresponding to the pulse beats 50 beats/minute to 200 beats/minute is selected to perform the second band-pass filtering operation for the voltage waveform. If the filtered voltage waveform still does not meet the testing conditions, the frequency bandwidth is further amplified. The frequency bandwidth 0.67Hz to 3.67Hz corresponding to the pulse beats 40 beats/minute to 220 beats/minute is selected to perform band-pass filtering operation for the voltage waveform again. If the filtered voltage waveform meets the testing conditions, the process goes to Step1408. If the filtered voltage waveform still does not meet the testing conditions, the voltage waveform is discarded.

In practical applications, the frequency bandwidth used in the first band-pass filtering process can also be decreased to the frequency bandwidth corresponding to the pulse beats 60 beats/minute to 170 beats/minute. It even can be the frequency bandwidth corresponding to the pulse beats 70 beats/minute to 150 beats/minute. There is no limitation on selecting the frequency bandwidth used in the first band-pass filtering process.

During the band-pass filtering process, the testing conditions for determining whether the filtered voltage waveform is qualified may include any one condition or the combination of at least two conditions.

a. the mean square error of time intervals between any two adjacent voltage waveforms is less than a first preset threshold value.

In practical applications, the first preset threshold value can be set as 10％ of the mean of the time intervals. For example, when the time intervals are 1 second, 2 seconds, 3 seconds, 4 seconds and 5 seconds, respectively, the mean of the time intervals is 3 seconds. The first preset threshold value is obtained by 3×10％＝ 0.3 seconds, and the mean square error is 1.41 seconds. Because the mean square error is greater than the first preset threshold value, the time interval of the voltage waveform does not meet the testing conditions.

b. the mean square error of peak values of various voltage waveforms is less than the second preset threshold value, and the mean square error of valley values of various voltage waveforms is less than the third preset threshold value.

In practical applications, the second preset threshold value can be set as 15％ of the mean peak value, and the third threshold value can be set as 15％ of the mean valley value. For example, it is assumed that the mean peak value of 10 continuous voltage waveforms is 2.5V, the second preset threshold value is 0.375V, and the mean square error is 0.4V. Because the mean square error is greater than the second preset threshold value, the voltage waveform does not meet the testing conditions. For another example, it is assumed that the mean valley value of 10 continuous voltage waveforms is 1V, the third preset threshold value is 0.15V, and the mean square error is 0.1V. Because the mean square error is less than the third preset threshold value, the voltage waveform meets the testing conditions.

c. the upper cutoff frequency of the frequency domain corresponding to the voltage waveform is in the preset frequency bandwidth.

For a voltage waveform, the maximum frequency value of the frequency domain corresponding to the voltage waveform is the upper cutoff frequency of the frequency domain. If the upper cutoff frequency of the frequency domain is within the range of 0.67Hz to 3.67Hz (that is, the frequency range corresponding to pulse beats per minute from 40 beats/minute to 220 beats/minute) , it is considered that the voltage waveform meets the testing conditions.

The above testing conditions a, b, and c provide the basis for filtering the voltage waveform from 3 aspects, including a waveform interval, a waveform amplitude, and the upper cutoff frequency of the waveform frequency, respectively, such that the forms of the filtered voltage waveform are similar, according with the laws of normal human pulse beat and suitable for the subsequent pulse counting.

Step 1408: the voltage waveform is converted to frequency domain.

When the band-pass filtered voltage waveform meets the testing conditions, the pulse can be measured based on the voltage waveform. Specifically, the voltage waveform is converted to frequency domain spectrum, where the spectrum is constituted by continuous frequency values. Taking a voltage waveform as an example (as shown in Figure 15) , the horizontal axis is a time axis and the vertical axis is a frequency axis.

Step 1409: the upper cutoff frequency of the frequency domain corresponding to the voltage waveform is determined as the fundamental frequency.

For example, in the voltage waveform spectrum shown in Figure 15, the upper cutoff frequency of the frequency domain 2.6Hz is determined as the fundamental frequency.

Because the voltage waveform is generated continuously, the converted spectrum may include spectrum corresponding to multiple continuous voltage waveforms. When determining the upper cutoff frequency of the frequency domain, the basis for defining the frequency domain is a sampling frequency of the pulse measurement apparatus. For example, if the pulse measurement apparatus determines the fundamental frequency every 500ms, the frequency domain is a spectrum constituted by all the frequencies between the previous sampling time point and the current sampling time. The pulse measurement apparatus finds the upper cutoff frequency from the spectrum corresponding to the time interval between two sampling time points, and determines the obtained frequency as the fundamental frequency.

Step 1410: the fundamental frequency is converted to pulses per minute to obtain a pulse rate.

For example, if the fundamental frequency is 2.6Hz, the pulses per minute can be obtained by multiplying 2.6Hz by 60 seconds (2.6*60＝ 156 beats/minute) .

The pulse measurement apparatus counts the total number of pulses periodically according to a preset unit interval. The unit interval is used as a unit of measurement of time and represents a definite predetermined time interval. The total number of pulses is counted by using the voltage waveforms collected within the time interval which is N times of the preset unit interval before the counting time point, where N is a positive integer. For example, when a pulse measurement apparatus outputs pulses per minute every other second, the pulses per minute is calculated and obtained based on the voltage waveforms in the previous 8 seconds. In addition, when the pulse measurement apparatus outputs the pulses per minute every time, the pulse measurement apparatus can also output synchronously a mean pulses per minute calculated based on cumulative pulses per minute.

To further improve the accuracy of the pulse measurement, after determining the fundamental frequency in Step 1409, the pulse measurement apparatus can also perform windowing amplification for neighborhood of the fundamental frequency based on a wavelet operator. Then, Step 1410 is performed, that is, the fundamental frequency is converted to pulses per minute to obtain a pulse rate, improving the accuracy of the calculation through refining data granularity.

In another application scenario, the pulse measurement apparatus sends the pulse counting result to an application client terminal through a transmission mode such as WI-FI, Bluetooth, and so on. Based on the pulse counting result, the application client terminal draws a pulse graph on a user-machine interface, or sends the pulse counting result to a network server. For example, a pulse graph drawn on the application client terminal is shown in Figure 12, and the pulse measurement apparatus updates the pulses per minute every second.

In addition to measure the user’s pulses through irradiating the user’s skin by the LEDs without limiting the user’s movement, the pulse measurement method can also adjust the current strength that activates the LEDs through a waveform feedback approach during the light source irradiates the user’s skin, thereby eliminating the effect of external interference on the voltage waveform and ensuring the accuracy of the counting result. Then, based on a normal pulse range of the human body, the voltage waveform is filtered, eliminating the effect of noise spike on the pulse measurement, further improving the accuracy of the counting result. Further, before calculating the target pulses per minute based on the fundamental frequency, the pulse measurement method can also perform windowing amplification for the neighborhood of the fundamental frequency based on a wavelet operator, improving the accuracy of the calculation through refining data granularity.

Figure 16 illustrates a flow chart of another exemplary pulse measurement process consistent with the disclosed embodiments. As shown in Figure 16, after a user wears a pulse measurement apparatus, the pulse measurement apparatus is started to work. Then, transmitting power of LEDs is initialized and a certain power of light is issued. The light source irradiates the user’s skin, and a photosensitive diode receives the light reflected from the user’s skin. The intensity of the reflected light changes along with the change of blood concentration in the user’s skin. A processor in the pulse measurement apparatus judges the light intensity range of the reflected light, and adjusts the transmitting power of the LEDs.

After several adjustments, the intensity of the reflected light is basically stabilized in a measurable range. Then, a band-pass filtering operation is performed for signals to obtain a prototype of a pulse waveform. Further, a second band-pass filtering operation is performed to eliminate noises, making the heart rate stable and measurable.

Finally, digital signals are outputted through a Bluetooth mode in real time to a mobile phone or other related devices for storing and subsequently processing the digital signals. By using the pulse measurement apparatus, the pulse is measured and the digital signals are transmitted in real time. The pulse measurement apparatus together with the related application software can realize functions such as recording health index, early warning, and so on. For example, a pulse measurement apparatus can monitor the number of daily premature beat of a patient, providing the patient with timely warning when the premature beat exacerbates.

Those skilled in the art should understand that all or part of the steps in the above method may be executed by relevant hardware instructed by a program, and the program may be stored in a computer-readable storage medium such as a removable hard disk, a read-only memory (ROM) , a random access memory (RAM) , a magnetic disk, an optical disk, and so on.

The embodiments disclosed herein are exemplary only. Other applications, advantages, alternations, modifications, or equivalents to the disclosed embodiments are obvious to those skilled in the art and are intended to be encompassed within the scope of the present disclosure.

INDUSTRIAL APPLICABILITY AND ADVANTAGEOUS EFFECTS

Without limiting the scope of any claim and/or the specification, examples of industrial applicability and certain advantageous effects of the disclosed embodiments are listed for illustrative purposes. Various alternations, modifications, or equivalents to the technical solutions of the disclosed embodiments can be obvious to those skilled in the art and can be included in this disclosure.

By using the disclosed apparatuses, methods and systems for pulse measurement, the pulse measurement apparatus can irradiate human skin using a light source and receive light reflected from the human skin. Then, the reflected light is converted to the voltage waveform. Finally, based on the converted voltage waveform, a total number of pulses can be counted. The disclosed apparatuses, methods and systems can be used in a variety of indoor and outdoor scenarios, eliminating the effect of external interference and ensuring the accuracy of a counting result.

Claims

A pulse measurement apparatus, comprising:

a light source configured to irradiate human skin of a user, wherein light intensity of the light source is adjusted through strength of a current to the light source；

a photosensitive diode configured to receive light reflected from the human skin, wherein the photosensitive diode is one of a photosensitive element and a photosensitive receiving array constituted by multiple photosensitive elements；

a conversion circuit configured to convert the reflected light received by the photosensitive diode to a voltage waveform； and

a processor configured to, based on frequency domain of the voltage waveform converted by the conversion circuit, count periodically a total number of pulses.
The apparatus according to claim 1, further including:

a control circuit configured to select initial current strength from a preset current strength selection range,

wherein the light source is configured to, based on light intensity activated by the initial current strength selected by the control circuit, irradiate the human skin.
The apparatus according to claim 2, wherein:

the processor is configured to, after the conversion circuit converts the reflected light to the voltage waveform, monitor whether the voltage waveform meets testing conditions, wherein the testing conditions include whether a peak value and a valley value of the voltage waveform are in a preset voltage amplitude range and whether a difference between the peak value and the valley value is greater than a preset voltage difference；

the control circuit is configured to, when the processor detects that the voltage wave does not meet the testing conditions, adjust the initial current strength according to a preset current strength magnitude to obtain the adjusted current strength； and

the light source is configured to, based on the light intensity activated by the adjusted current strength selected by the control circuit, irradiate the human skin.
The apparatus according to claim 3, further including:

a filter circuit configured to, after the processor detects that the voltage waveform meets the testing conditions, perform a band-pass filtering operation for the voltage waveform converted by the conversion circuit based on preset frequency bandwidth, wherein cutoff frequencies of the preset frequency bandwidth are derived from cutoff values of preset pulses per minute.
The apparatus according to claim 1, wherein the processor further includes:

a frequency domain conversion unit configured to convert the voltage waveform to the frequency domain；

a determination unit configured to determine an upper cutoff frequency of the frequency domain converted by the frequency domain conversion unit as a fundamental frequency； and

a data conversion unit configured to convert the fundamental frequency determined by the determination unit to pulses per minute.
The apparatus according to claim 1, wherein:

the light source is light emitting diodes (LEDs) ； and

the LEDs which are set around the photosensitive diode surround closely the photosensitive diode.
The apparatus according to claim 5, wherein:

an irradiating direction of the light source is same as a light receiving direction of the photosensitive diode； and

the irradiating direction of the light source and the light receiving direction of the photosensitive diode are toward the human skin.
The apparatus according to claim 7, further including:

a fixing part configured to fix the pulse measurement apparatus on a position which is a predetermined distance apart from the human skin.
The apparatus according to claim 8, wherein:

the fixing part is a strap type fixing part； and

the strap type fixing part is configured to bind the pulse measurement apparatus on human body.
A pulse measurement system, comprising:

an application client terminal； and

a pulse measurement apparatus configured to:

irradiate human skin by light that is emitted by a light source, wherein light intensity of the light source is adjusted through current strength；

receive light reflected from the human skin；

convert the reflected light to a voltage waveform；

count periodically a total number of pulses based on frequency domain of the converted voltage waveform； and

send a counting result to the application client terminal,

wherein the application client terminal is configured to:

receive the counting result sent from the pulse measurement apparatus； and

based on the counting result, perform one of drawing a pulse graph in a human-machine interactive interface and reporting the counting result to a network server.
A pulse measurement method, comprising:

irradiating human skin by light that is emitted by a light source, wherein light intensity of the light source is adjusted through current strength；

receiving light reflected from the human skin；

converting the reflected light to a voltage waveform； and

based on frequency domain of the converted voltage waveform, counting periodically a total number of pulses.
The method according to claim 11, wherein irradiating human skin by light that is emitted by a light source further includes:

selecting initial current strength from a preset current strength selection range； and

based on the light intensity activated by the initial current strength, irradiating the human skin.
The method according to claim 12, after converting the reflected light to the voltage waveform, further including:

monitoring whether the voltage waveform meets testing conditions, wherein the testing conditions include whether a peak value and a valley value of the voltage waveform are in a preset voltage amplitude range and whether a difference between the peak value and the valley value is greater than a preset voltage difference；

when the voltage waveform does not meet the testing conditions, adjusting the initial current strength according to a preset current strength magnitude to obtain the adjusted current strength； and

based on the light intensity activated by the adjusted current strength, irradiating the human skin.
The method according to claim 13, wherein adjusting the initial current strength according to a preset current strength magnitude further includes:

when at least one of the peak value and the valley value of the voltage waveform exceeds the preset voltage amplitude range, decreasing the initial current strength based on the preset current strength magnitude； and

when the difference between the peak value and the valley value is not more than the preset voltage difference, increasing the initial current strength based on the preset current strength magnitude.
The method according to claim 13, when the voltage waveform meets the testing conditions, further including:

based on a preset frequency bandwidth, performing a band-pass filtering operation for the voltage waveform, wherein cutoff frequencies of the preset bandwidth are derived from cutoff values of preset pulses per minute.
The method according to claim 15, after performing a band-pass filtering operation for the voltage waveform based on a preset frequency bandwidth, further including:

determining whether the voltage waveform meets the testing conditions to obtain a determination result, wherein the testing conditions include at least one of the following conditions:

mean square error of time intervals between any two adjacent voltage waveforms is less than a first preset threshold value；

the mean square error of peak values of various voltage waveforms is less than a second preset threshold value, and the mean square error of valley values of various voltage waveforms is less than a third preset threshold value； and

an upper cutoff frequency of the frequency domain corresponding to the voltage waveform is in the preset frequency bandwidth；

when the voltage waveform does not meet the testing conditions, amplifying the preset frequency bandwidth based on a frequency bandwidth adjusting magnitude to obtain adjusted frequency bandwidth； and

based on the adjusted frequency bandwidth, performing a second band-pass filtering operation for the voltage waveform.
The method according to claim 11, wherein counting periodically a total number of pulses based on the voltage waveform further includes:

converting the voltage waveform to the frequency domain；

determining the upper cutoff frequency of the frequency domain as a fundamental frequency； and

converting the fundamental frequency to pulses per minute.
The method according to claim 17, wherein converting the fundamental frequency to pulses per minute further includes:

based on a wavelet operator, performing windowing amplification for neighborhood of the fundamental frequency； and

converting the amplified fundamental frequency to the pulses per minute.
The method according to claim 11, wherein counting periodically a total number of pulses based on the voltage waveform further includes:

based on a preset unit interval, counting periodically the total number of pulses； and

counting periodically the total number of pulses by using the collected voltage waveforms within a time interval which is N times of the preset unit interval before a counting time point, wherein N is a positive integer.
The method according to claim 19, after counting periodically a total number of pulses based on the voltage waveform, further including:

sending the counting result to an application client terminal in real time, such that the application client terminal performs one of drawing a pulse graph on a human-machine interactive interface and sending the counting result to a network server.