CN107468227B - A signal transmitter and PPG information collection device - Google Patents

Abstract

The invention discloses a signal transmitter, comprising a driving module and a light emitting device, an output end of the driving module is connected to an input end of the light emitting device; the driving module outputs current to the light emitting device; the light emitting device The emitting device emits an optical signal to the human skin at a preset incident angle, so that the optical signal enters the human blood vessel and carries PPG information and exits the human skin, wherein the optical signal corresponds to the output current of the driving module, The preset incident angle is greater than 13.8° and less than 15.5°. The invention also discloses a PPG information collection device including the above signal transmitter. The invention realizes that the PPG information can be collected in the thick fat part of the human body, so that people can collect the PPG information in a state of no perception, and detect abnormal physiological characteristics early.

Description

A signal transmitter and PPG information collection device

technical field

Embodiments of the present invention relate to the field of physiological signal detection, and in particular, to a signal transmitter and a PPG information collection device.

Background technique

Nowadays, people pay more and more attention to their own health status. The physiological parameters of the human body, such as heart rate and blood oxygen saturation, can reflect the health status of the human body. Photoplethysmographic pulse wave information (PPG information) can be used to obtain information such as heart rate and blood oxygen saturation of the human body. The absorption of light by muscles, fat layers, etc. remains constant throughout the blood circulation, while the blood volume changes pulsatilely under the action of the heart. When the heart contracts, the peripheral blood volume is large, the light absorption is large, and the detected light intensity When the heart is diastolic, the detected light intensity is large, so the light intensity received by the light receiver changes pulsatilely with the blood volume, and the light signal is converted into an electrical signal to obtain the volume pulse blood flow change, extracting to PPG information.

In the existing technologies for collecting human PPG information, since the optical signal will be absorbed and attenuated by the human body fat layer, the fingers or wrists with relatively weak fat layer are collected to prevent the received signal from being too weak. However, the acquisition of signals from these weak fat parts requires the use of specific structures and active human intervention. However, in the early stage of the disease, many patients have no abnormal response, and often do not actively collect physiological signals, thus delaying the treatment time.

SUMMARY OF THE INVENTION

The invention provides a signal transmitter and a PPG information collection device, so that PPG information can be collected in the thick fat part of the human body, so that people can collect PPG information without perception, and detect abnormal physiological characteristics early.

In a first aspect, an embodiment of the present invention provides a signal transmitter, including a driving module and a light emitting device, wherein an output end of the driving module is connected to an input end of the light emitting device;

The driving module outputs a current to the light emitting device; the light emitting device emits a light signal to the human skin at a preset incident angle, so that the light signal enters the human blood vessel and carries PPG information and exits the human skin, wherein , the optical signal corresponds to the output current of the driving module, and the preset incident angle is greater than 13.8° and less than 15.5°.

In a second aspect, an embodiment of the present invention provides a PPG information collection device, including a signal transmitter and a signal receiver;

The signal transmitter includes a driving module and a light emitting device, and the output end of the driving module is connected to the input end of the light emitting device;

The driving module outputs a current to the light emitting device; the light emitting device emits a light signal to the human skin at a preset incident angle, so that the light signal enters the human blood vessel and carries PPG information and exits the human skin, wherein , the optical signal corresponds to the output current of the driving module, and the preset incident angle is greater than 13.8° and less than 15.5°;

The signal receiver includes a light receiving device and a signal processing module, and the output end of the light receiving device is connected to the input end of the signal processing module;

The light receiving device is arranged adjacent to the light emitting device, receives the light signal emitted from the human skin, and converts the light signal into an electrical signal; the signal processing module receives and processes the electrical signal, Obtain the PPG information carried by the electrical signal.

In the embodiment of the present invention, an incident angle of greater than 13.8° and less than 15.5° emits an optical signal to the human skin. By establishing a transmission model of the optical signal in the fat part and experiments, it is found that the incident angle in this range will reduce the human body fat layer to the optical signal. The absorption attenuation of PPG can be carried out in the thick fat part of the human body, which solves the problem that the acquisition of PPG information in the weak fat part of the existing technology requires manual execution and delays the treatment time, so that people can collect PPG information without perception. , the effect of early detection of abnormal physiological characteristics.

Description of drawings

1 is a schematic structural diagram of a signal transmitter provided in Embodiment 1 of the present invention;

2 is a schematic diagram of optical signal transmission in the human body in Embodiment 1 of the present invention;

Fig. 3 is the relation curve of optical signal intensity and incident angle in the first embodiment of the present invention;

FIG. 4 is a schematic structural diagram of a PPG information collection device provided in Embodiment 2 of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, it should be noted that, for the convenience of description, the drawings only show some but not all structures related to the present invention.

Example 1

FIG. 1 is a schematic structural diagram of a signal transmitter according to Embodiment 1 of the present invention. The signal transmitter includes a driving module 11 and a light emitting device 12 . The output end of the driving module 11 is connected to the input end of the light emitting device 12 .

The driving module 11 outputs a current to the light emitting device 12; the light emitting device 12 emits a light signal to the human skin at a preset incident angle, so that the light signal enters the human blood vessel and carries PPG information and exits from the human skin, wherein the The optical signal corresponds to the output current of the driving module 11 , and the preset incident angle is greater than 13.8° and less than 15.5°.

According to the optical signal transmission model established based on physical optics theory and related experiments, it is found that the incident angle in this range will reduce the absorption attenuation of the optical signal by the human body fat layer. Preferably, the preset incident angle is 14.63°. Specifically, referring to FIG. 2, FIG. 2 is a schematic diagram of the transmission of optical signals in the human body in the first embodiment of the present invention. The optical signals pass through air, skin, and fat and finally enter the blood. Due to the different media in the inner and outer layers of the skin, gradient refraction will occur, and some of them are The human body absorbs the attenuation, partially reflects at the blood vessels, and then exits the human skin at an exit angle. Taking air as the first medium and the human body as the second medium, the equivalent refractive index ρ' of the second medium is related to the refractive index of the fat layer and blood vessels. Meanwhile, the incident angle determines the transmission distance of the light signal in fat and blood vessels, so the incident angle also affects the equivalent refractive index ρ' of the second medium. The inventor uses the theory of optical transmission and optical radiation to establish a transmission model of optical signals in the human body, and obtains the calculation formula of the equivalent refractive index ρ' of the second medium:

y为光信号在脂肪层中的折射率。根据上述公式，可计算得到当x＝14.63°时，第二介质的等效折射率ρ′最小，则在血管处被反射后出射的光信号强度最高。Among them, x is the incident angle of the light signal emitted by the light emitting device 12,

y is the refractive index of the optical signal in the fat layer. According to the above formula, it can be calculated that when x=14.63°, the equivalent refractive index ρ' of the second medium is the smallest, and the intensity of the light signal emitted after being reflected at the blood vessel is the highest.

如图2所示，α₁和α₂分别是光发射器件发射的立体角为ω的光信号照射到皮肤和脂肪层的交界边缘形成的入射角(平面角度)。建立直角坐标系，以n₁和n₂分别表示在皮肤和脂肪层中的光信号折射率，发现对应关系：Further deriving its mathematical expectation:

As shown in FIG. 2 , α ₁ and α ₂ are the incident angles (plane angles) formed by the light signal with solid angle ω emitted by the light emitting device irradiating the interface between the skin and the fat layer, respectively. A Cartesian coordinate system is established, and n ₁ and n ₂ are used to represent the refractive indices of light signals in the skin and fat layers, respectively, and the corresponding relationship is found:

On the basis of the above-mentioned correspondence, the simulation experiment was performed using matlab to obtain the relation curve between the optical signal intensity and the incident angle as shown in Figure 3. According to the results of the simulation experiments, when the incident angle is between 13.8° and 15.5°, the intensity of the outgoing light signal accounts for more than 80% of the maximum intensity of the outgoing light signal. Therefore, the preset incident angle greater than 13.8° and less than 15.5° can reduce the absorption attenuation of the light signal by the human body fat layer, so that the PPG information collection can be carried out in the thick fat part of the human body, and can be designed in various daily utensils. The structure of PPG information can be collected actively and deliberately. For example, preferably, the light emitting device can emit light signals to the human skin by touching the buttocks of the human body, that is, the light emitting device can be arranged on the toilet.

This embodiment also provides a preferred range of output current amplitudes of the driving module, so as to further improve the accuracy of collecting PPG information by using the signal transmitter provided in this embodiment. Specifically, the current amplitude cannot be too large or too small. If the current amplitude is too small, the outgoing optical signal will be too weak and difficult to identify; if the current amplitude is too large, the final signal may be distorted. For the human buttocks, the main factor that attenuates the light signal is fat content.

其中φ_e为辐射通量，Ω为辐射立体角。根据能量守恒定律得到入射信号辐射强度U_e≈U_f+U_c，其中U_f为反射信号强度，U_c为在脂肪层传输吸收的信号强度。显然，光信号在空气传输的阻抗

光信号在臀部脂肪层的阻抗

其中，F为电流算子，是衡量在特定的光电转换比例下，输出电流所对应的光信号与介质阻抗之间的关系。The formula for calculating the radiation intensity of the optical signal is:

where φ _e is the radiation flux and Ω is the radiation solid angle. According to the law of conservation of energy, the radiation intensity of the incident signal U _e ≈ U _f +U _c is obtained, where U _f is the reflected signal intensity, and U _c is the signal intensity transmitted and absorbed in the fat layer. Obviously, the impedance of optical signal transmission in air

Impedance of optical signals in the fat layer of the buttocks

Among them, F is the current operator, which measures the relationship between the optical signal corresponding to the output current and the medium impedance under a specific photoelectric conversion ratio.

经过上述入射信号辐射强度U_e的公式及入射光信号、发射光信号和传输光信号之间的关系，进一步推导可得到：

该公式说明了光信号的衰减程度与脂肪阻抗有关。在设计信号发射器时，根据信号发射器驱动模块的光电转换参数，通过该公式可以推导最利于采集PPG信息的状态下，人体脂肪层阻抗与所需驱动电流幅值之间的函数关系。现有技术普遍采用AFE4400集成模拟前端芯片作为驱动模块的前端芯片，根据该函数关系和可测得的人体臀部脂肪层阻抗，可获得采用AFE4400集成模拟前端芯片的驱动模块的最佳输出电流为8.3mA。进一步地，经过实验验证，当采用AFE4400集成模拟前端芯片的驱动模块的输出电流大于7.5mA且小于9.5mA时，出射光信号强度为相同入射角度下最大出射光信号强度的90％以上。Define p as the ratio of the reflected voltage V _{reflected light signal} (the voltage corresponding to the reflected light signal at a specific photoelectric conversion ratio) to the incident voltage V _{incident light signal} (the voltage corresponding to the incident light signal at a specific photoelectric conversion ratio). Then V _{incident optical signal} =V _{reflected optical signal} +V _{transmitted optical signal} , I _{incident optical signal} =I _{reflected optical signal} +I _{transmitted optical signal} , and

Through the above formula of the incident signal radiation intensity U _e and the relationship between the incident optical signal, the emitted optical signal and the transmitted optical signal, further deduction can be obtained:

This formula states that the attenuation of the optical signal is related to the fat impedance. When designing the signal transmitter, according to the photoelectric conversion parameters of the driver module of the signal transmitter, this formula can be used to deduce the functional relationship between the impedance of the human body fat layer and the required driving current amplitude in the state that is most conducive to collecting PPG information. In the prior art, the AFE4400 integrated analog front-end chip is generally used as the front-end chip of the driver module. According to this functional relationship and the measurable impedance of the fat layer of the human body, the optimal output current of the driver module using the AFE4400 integrated analog front-end chip can be obtained as 8.3 mA. Further, through experimental verification, when the output current of the driver module using the AFE4400 integrated analog front-end chip is greater than 7.5mA and less than 9.5mA, the outgoing light signal intensity is more than 90% of the maximum outgoing light signal intensity at the same incident angle.

On the basis of the above technical solution, the signal transmitter is preferably a dual-band transmitter. Dual-band PPG information is required when testing blood oxygen saturation.

The technical solution of this embodiment is to establish the transmission model of the optical signal in the fat area, and to control the intensity of the outgoing optical signal by using the optimal incident angle obtained from the experiment and the output current of the driving module, so as to reduce the absorption attenuation of the optical signal by the human body fat layer, so that the The PPG information collection can be carried out in the thick fat part of the human body, which solves the problem that the existing technology needs to actively perform the PPG information collection in the weak fat part, which will delay the treatment time, and realize that people can collect the PPG information in a state of no perception, and early detection of physiological characteristics Unusual effect.

Embodiment 2

FIG. 2 is a PPG information collection device provided by Embodiment 2 of the present invention. The PPG information collection device 30 includes a signal transmitter 10 and a signal receiver 20;

The signal transmitter 10 includes a driving module 11 and a light emitting device 12, and the output end of the driving module is connected to the input end of the light emitting device. The driving module 11 outputs a current to the light emitting device 12; the light emitting device 12 emits a light signal to the human skin at a preset incident angle, so that the light signal enters the human blood vessel and carries PPG information and exits from the human skin, wherein the The optical signal corresponds to the output current of the driving module 11 , and the preset incident angle is greater than 13.8° and less than 15.5°.

The signal receiver 20 includes a light receiving device 21 and a signal processing module 20 . The output end of the light receiving device 21 is connected to the input end of the signal processing module 22 . The light receiving device 21 is arranged adjacent to the light emitting device 12, receives the light signal emitted from the human skin, and converts the light signal into an electrical signal; the signal processing module 22 receives and processes the electrical signal to obtain the PPG information carried by the electrical signal.

During specific implementation, the processing of the electrical signal by the signal processing module 22 includes filtering and amplification. Further, the signal processing module includes a 50Hz power frequency notch filter. Specifically, the signal processing module 22 first filters out the noise brought by the environment in the electrical signal, and amplifies the originally weak signal, and then uses the 50Hz power frequency software built in the microprocessor to trap The wave filter filters out the power frequency interference brought by the human body and converts the analog electrical signal into a digital electrical signal.

Further, the signal processing module 22 also includes a communication module, and the communication module transmits the processed electrical signal carrying the PPG information to the external display terminal for preview and reference analysis by the guardian, and obtains the physiological characteristics to be detected, such as heart rate and blood pressure. oxygen saturation, etc.

In the technical solution of this embodiment, the light signal is emitted to the human skin at an incident angle greater than 13.8° and less than 15.5°. Through establishing a transmission model of the light signal in the fat part and experiments, it is found that the incident angle in this range will reduce the body fat layer. The absorption and attenuation of the optical signal enables PPG information collection to be carried out in the thick fat part of the human body, solving the problem that the acquisition of PPG information in the weak fat part in the existing technology requires manual execution, which will delay the treatment time, and realize that people can be in a state of no perception. The effect of collecting PPG information and early detection of abnormal physiological characteristics.

It should be noted that, those skilled in the art can combine and combine different embodiments or examples and features of different embodiments or examples described in this specification under the condition of not contradicting each other.

Note that the above are only preferred embodiments of the present invention and applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and can also include more other equivalent embodiments without departing from the concept of the present invention. The scope is determined by the scope of the appended claims.

Claims (10)

1. a signal transmitter, is characterized in that, comprises drive module and light emission device, the output end of described drive module is connected with the input end of described light emission device; The driving module outputs a current to the light emitting device; the light emitting device emits a light signal to the human skin at a preset incident angle, so that the light signal enters the human blood vessel and carries PPG information and exits the human skin, wherein , the optical signal corresponds to the output current of the driving module, and the preset incident angle is greater than 13.8° and less than 15.5°; The PPG information is collected at the thick fat part of the human body. 2 . The signal transmitter of claim 1 , wherein the preset incident angle is 14.63°. 3 . 3 . The signal transmitter according to claim 1 or 2 , wherein the light emitting device is arranged on the toilet; and the light emitting device emits light signals to the human skin by touching the buttocks of the human body. 4 . 4. The signal transmitter according to claim 3, wherein the driving module comprises an AFE4400 integrated analog front-end chip. 5 . The signal transmitter of claim 4 , wherein the output current of the driving module is greater than 7.5 mA and less than 9.5 mA. 6 . 6 . The signal transmitter of claim 4 , wherein the output current of the driving module is 8.3 mA. 7 . 7. The signal transmitter according to claim 1 or 2, wherein the signal transmitter is a dual-band transmitter. 8. A PPG information collection device, characterized in that, comprising a signal transmitter and a signal receiver; The signal transmitter includes a driving module and a light emitting device, and the output end of the driving module is connected to the input end of the light emitting device; The driving module outputs a current to the light emitting device; the light emitting device emits a light signal to the human skin at a preset incident angle, so that the light signal enters the human blood vessel and carries PPG information and exits the human skin, wherein , the optical signal corresponds to the output current of the driving module, the preset incident angle is greater than 13.8° and less than 15.5°; the PPG information is collected in the thick fat part of the human body; The signal receiver includes a light receiving device and a signal processing module, and the output end of the light receiving device is connected to the input end of the signal processing module; The light receiving device is arranged adjacent to the light emitting device, receives the light signal emitted from the human skin, and converts the light signal into an electrical signal; the signal processing module receives and processes the electrical signal, Obtain the PPG information carried by the electrical signal. 9 . The PPG information collection device according to claim 8 , wherein the processing of the electrical signal by the signal processing module includes filtering and amplification. 10 . 10 . The PPG information collection device according to claim 9 , wherein the signal processing module comprises a 50Hz power frequency notch filter. 11 .

Images