Analog device and method for detecting photoplethysmography based heart rate, blood oxygen and blood pressure monitoring devices

Abstract

The application provides a kind of for the analog device and method for the detection of photoplethysmography-based heart rate, blood oxygen and blood pressure monitoring equipment, it is related to the technical field of equipment inspection detection, it is applied to the test of the equipment using PPG (photoplethysmography) technical principle.The device comprises: photoelectric component module, ECG resistance network module, analog front end module, main control module, man-machine interaction module and power module.The analog device and method of the application can adapt to different types and configurations of PPG equipment, without replacing photoelectric components or adding or subtracting jigs, just need to place the measured equipment in a specific position, the simulation test of heart rate, blood oxygen, blood pressure monitoring equipment based on PPG principle can be realized.

Description

Technical Field

[0001] This invention relates to the technical field of equipment testing, and more particularly to a simulation device and method for testing heart rate, blood oxygen, and blood pressure monitoring devices based on photoplethysmography. Background Technology

[0002] Photoplethysmography (PPG) is an optical detection technique that uses the interaction of light with biological tissues to detect changes in blood volume in the cardiovascular system. Due to its non-invasive and low-cost characteristics, this technology is widely used in devices such as smartwatches and fitness trackers. PPG technology enables non-invasive, continuous, and convenient physiological monitoring, but it is also affected by factors such as motion artifacts, skin color, ambient light interference, and the tightness of the garment. Therefore, metrological calibration of reflective pulse oximeters and smart wearable devices that utilize the PPG principle is essential.

[0003] Heart rate detection is a fundamental application of PPG (Programmable Pixel Filter), its core principle being the detection of changes in blood volume. When a beam of light shines on the skin surface, it is absorbed and reflected by tissues such as skin, muscles, bones, and blood. Blood has a strong ability to absorb light of specific wavelengths. The blood volume in arteries changes instantaneously with the heartbeat, corresponding to changes in the intensity of light absorption. The sensor converts the received light signal into an electrical signal, forming a periodic waveform synchronized with the heartbeat (PPG waveform). By calculating the time interval between two adjacent peaks, the instantaneous heart rate can be obtained. The industry typically uses green light (500-600nm band) as the operating wavelength to achieve a better signal-to-noise ratio and resistance to motion interference.

[0004] Blood oxygenation measurement requires the use of two different wavelengths of light (usually red and infrared light), based on oxyhemoglobin (… The oxygen saturation level is calculated based on the differences in absorption characteristics of red light and deoxygenated hemoglobin (Hb) to different wavelengths of light. The device alternately emits red and infrared light and receives the intensity signals of each light after it passes through the tissue. The ratio of the AC component (pulsating part) to the DC component (constant tissue absorption part) of the two signals is calculated: R = (AC red light / DC red light) / (AC infrared light / DC infrared light). Utilizing the negative correlation between the R value and blood oxygen saturation, combined with clinical trial calibration data, the current blood oxygen saturation level is estimated. ).

[0005] Using PPG to measure blood pressure is currently a hot research and application topic, mainly based on the principles of pulse wave transit time (PTT) or pulse wave velocity (PWV). It requires combining ECG signals or waveform differences in pulse waves at specific distances with individual calibration results to achieve real-time monitoring of blood pressure fluctuation trends.

[0006] The PPG principle multi-physiological parameter simulation device is developed based on multi-parameter monitor detection equipment, reflective blood oxygen saturation simulator and other equipment. Its feature is the use of the PPG principle and the establishment of the relationship between ECG signal and PPG signals such as heart rate, blood oxygen, and blood pressure. It is used to generate simulated heart rate, blood oxygen, and blood pressure signals to verify the accuracy and reliability of PPG principle measurement equipment.

[0007] Existing patents and products utilizing optoelectronic technology primarily employ two technical approaches to achieve optical signal interfacing with external PPG (Polyoxymethylene) devices or smart wearable devices: 1) Using an optoelectronic module integrating multiple precisely positioned optical signal channels. This module constructs independent transmission paths through optical isolation components, allowing each channel to be aligned with the respective light source and photosensitive device on the probe of the device under test, effectively avoiding signal crosstalk. 2) Using a fixed optoelectronic module with specialized fixtures. Optical isolation is achieved by selectively blocking the light-emitting and light-receiving elements in specific device models. However, these technical solutions have significant limitations in practical applications. Specific adjustments are required for each optoelectronic layout of the PPG device being tested. When measuring physiological parameters such as heart rate, blood oxygen, or blood pressure, different types of optoelectronic components or fixtures typically need to be replaced.

[0008] With the rapid development of smart wearable devices, the design of PPG (photoplethysmography) measurement components is constantly evolving towards multi-configuration, multi-wavelength, and multi-functional directions. Existing solutions face high implementation costs if they are to fully cover different types of devices under test. In addition, when the PPG optoelectronic layout becomes complex to a certain extent, existing technologies can hardly guarantee a reasonable layout of optoelectronic components, and cannot meet the basic design requirements such as the cross-sectional area of ​​the optical signal channel being larger than the emitting area of ​​the light source and the photosensitive area of ​​the photosensitive device, thus limiting their feasibility and effectiveness in supporting measurements with general PPG equipment. Summary of the Invention

[0009] To address the technical problem mentioned in the background section that typically requires replacing different types of optoelectronic components or fixtures, this invention provides a simulation device and method for detecting heart rate, blood oxygen, and blood pressure monitoring devices based on photoplethysmography (PPG). The device of this invention can simulate heart rate, blood oxygen saturation, and blood pressure signals, and is suitable for testing various devices employing PPG technology.

[0010] The technical means employed in this invention are as follows:

[0011] A simulation device for testing heart rate, blood oxygen, and blood pressure monitoring equipment based on photoplethysmography (PPG) is applied to the testing of equipment using PPG technology. The device includes: an optoelectronic component module, an ECG resistor network module, an analog front-end module, a main control module, a human-computer interaction module, and a power supply module. The system comprises a total internal reflection prism, a light-diffusing layer, a high-transmittance polarization layer, a photodiode array, a light-emitting diode array, an IV conversion circuit, and an interface circuit I. The high-transmittance polarization layer includes a first polarization layer and a second polarization layer with mutually perpendicular polarization directions. The optoelectronic module is centered on the total internal reflection prism. The light-diffusing layer is tightly fitted to one right-angled face of the prism, the first polarization layer is tightly fitted to the other right-angled face of the prism, and the second polarization layer is tightly fitted to the inclined surface of the prism. The photodiode array is located behind the first polarization layer, the IV conversion circuit is located behind the photodiode array, and the light-emitting diode array is located behind the second polarization layer. The photodiode array has a 4×4 array structure. The photodiode array includes four PIN photodiodes with different photosensitive ranges, with four of each PIN photodiode connected in parallel and connected to the corresponding four IV conversion circuits. The light-emitting diode array also has a 4×4 array structure. The light-emitting diode array includes four LEDs with different emission wavelengths, with four of each wavelength connected in series. The optoelectronic component module receives the pulsed light signal emitted by the PPG device under test and performs photoelectric signal conversion. The voltage comparator circuit in the analog front-end module identifies the wavelength type of the incident light and outputs the corresponding logic level. The main control module determines the wavelength of the incident light based on the logic level, controls the analog switch circuit in the analog front-end module to open the corresponding wavelength channel, and collects the photoelectric conversion value of the corresponding channel through the analog-to-digital converter circuit. The main control module dynamically adjusts the output amplitude of the digital-to-analog converter based on the set skin color type and the collected photoelectric conversion value. The digital-to-analog converter synchronously outputs ECG electrocardiogram signal, PPG light signal, and interference signal. The human-machine interaction module allows for parameter setting and display. The power supply module provides stable power to all the above modules.

[0012] Furthermore, the ECG resistor network module includes five output terminals: N, R, L, F, and V; wherein the N terminal is connected to the power supply analog ground through a fixed-value resistor, and the R, L, F, and V terminals are respectively connected to voltage divider attenuators; the voltage divider attenuator includes a digital potentiometer and a fixed-value resistor.

[0013] Furthermore, the analog front-end module includes: a voltage comparator circuit, an analog-to-digital converter circuit, a digital-to-analog converter circuit, a voltage-controlled constant current source circuit, and an analog switch circuit; the voltage comparator circuit compares the signal output by the IV conversion circuit with a reference voltage to generate a trigger signal; the analog-to-digital converter circuit performs analog-to-digital conversion on the corresponding channel according to the trigger signal; the digital-to-analog converter circuit includes: an ECG signal generation circuit, a PPG optical signal generation circuit, and an interference signal generation circuit; the operational amplifier adder converts the voltage signals output by the PPG optical signal generation circuit and the interference signal generation circuit into LED driving voltage signals; the voltage-controlled constant current source circuit converts the LED driving voltage signals into current signals to drive the light-emitting diode array.

[0014] Furthermore, the light-sensing ranges of the four different photosensitive PIN photodiodes are 400nm~1100nm, 380nm~750nm, 560nm~1100nm, and 840nm~1100nm, respectively.

[0015] Furthermore, the four different light-emitting wavelengths of the LEDs are green light 530nm, red light 660nm, first infrared light 820nm, and second infrared light 940nm. The main control module controls the analog switch circuit according to the identified incident light wavelength, and only turns on the switch channel corresponding to the incident light wavelength, so that the light-emitting diode array emits only light with the same wavelength as the incident light.

[0016] Furthermore, the LED driving circuit in the analog front-end module includes: an 8-channel digital-to-analog converter, an operational amplifier adder, and an analog switch; the output of every two digital-to-analog converters is connected to an operational amplifier adder, and each operational amplifier input is equipped with the analog switch. The main control module controls the opening and closing of the voltage-controlled constant current source circuit by controlling the on / off state of the analog switches.

[0017] Furthermore, the ECG signal generation circuit, the PPG optical signal generation circuit, and the interference signal generation circuit are all 16-bit digital-to-analog converters; and the digital-to-analog converters used by the ECG signal generation circuit, the PPG optical signal generation circuit, and the interference signal generation circuit are updated synchronously.

[0018] The present invention also includes a simulation method for detecting heart rate, blood oxygen, and blood pressure monitoring devices based on photoplethysmography, comprising the following steps: Step 1: Receive the pulsed light signal emitted by the PPG device under test through the optoelectronic component module, and perform photo-to-electric signal conversion; Step 2: Identify the incident light wavelength type and output the corresponding logic level through the voltage comparator circuit in the analog front-end module; Step 3: The main control module determines the incident light wavelength based on the logic level, controls the analog switch circuit to open the corresponding channel, and provides the corresponding channel's analog-to-digital conversion to acquire the photoelectric conversion value; Step 4: The main control module dynamically adjusts the output amplitude of the digital-to-analog converter based on the set skin color type and the collected photoelectric conversion value. Step 5: Synchronously output ECG electrocardiogram signal, PPG optical signal and interference signal through digital-to-analog converter, and display them by human-computer interaction module.

[0019] Compared with the prior art, the present invention has the following advantages: This invention proposes a simulation device and method for testing heart rate, blood oxygen, and blood pressure monitoring devices based on photoplethysmography (PPG). The device and method are adaptable to testing different types and configurations of PPG devices, requiring no replacement of photoelectric components or the addition or subtraction of fixtures. Simply placing the device under test in a specific location is sufficient to simulate the testing of PPG-based heart rate, blood oxygen, and blood pressure monitoring devices. This invention overcomes the shortcomings of traditional blood perfusion simulation methods, such as bulky devices and limited parameter adjustment ranges. It also solves the problems of frequent component replacements and narrow applicability of existing photoelectric simulation schemes, providing an effective technical approach for rapid and flexible testing of PPG functions.

[0020] This invention is applicable to the simulation testing of heart rate, blood oxygen, and blood pressure monitoring devices based on photoplethysmography (PPG). It is compatible with different types and configurations of PPG devices, allowing for flexible adjustment of various measured parameters without replacing photoelectric components or fixtures, enabling rapid measurement of the PPG device under test, and facilitating field application and deployment. Furthermore, calibration of each PPG parameter effectively ensures the accuracy and reliability of the PPG device measurement data.

[0021] This invention can be applied to manufacturers of smart wearable devices, medical device manufacturers, metrology and testing institutions, and medical institution equipment maintenance departments to carry out quality testing and calibration of the PPG devices being tested. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the system structure of the present invention.

[0024] Figure 2 This is a schematic diagram of the optoelectronic module structure of the present invention.

[0025] Figure 3 This is a schematic diagram showing the connection between the photodiode and the light-emitting diode of the present invention.

[0026] Figure 4 This is a schematic diagram of the ECG resistor network module structure of the present invention.

[0027] Figure 5 This is a schematic diagram of the simulated front-end module structure of the present invention.

[0028] Figure 6 This is a schematic diagram of the method flow of the present invention.

[0029] In the diagram: 1. Optoelectronic component module; 2. ECG resistor network module; 3. Analog front-end module; 4. Human-computer interaction module; 5. Main control module; 6. Power supply module; 7. Total internal reflection prism; 8. Light homogenizing layer; 9. First polarization layer; 10. Second polarization layer; 11. Photodiode array; 12. Light-emitting diode array; 13. IV conversion circuit; 14. Interface circuit I; 15. Voltage comparator circuit; 16. Analog-to-digital converter circuit; 17. 4-channel digital-to-analog converter; 18. Voltage-controlled constant current source circuit; 19. Operational amplifier adder circuit and analog switch circuit; 20. 8-channel digital-to-analog converter; 21. Interface circuit II; 22. Power supply voltage VCC; 23. Reference voltage VREF; 24. Photodiode output voltage PD-VOUT; 25. LED output current LED-I; 26. R, L, F, V terminals; 27. Digital potentiometer; 28. ECG signal output voltage ECG-VOUT; 29. ​​N terminal. Detailed Implementation

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0033] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0034] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0035] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0036] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0037] Example 1 like Figures 1-5 As shown, the present invention provides a simulation device for testing heart rate, blood oxygen and blood pressure monitoring devices based on photoplethysmography, applicable to the testing of devices using PPG technology principles, including: photoelectric component module 1, ECG resistor network module 2, analog front-end module 3, main control module 5, human-computer interaction module 4 and power supply module 6.

[0038] In a preferred embodiment, the optoelectronic component module 1 in this application includes: a total internal reflection prism 7, a light-diffusing layer 8, a first polarization layer 9, a second polarization layer 10, a photodiode array 11, a light-emitting diode array 12, an IV conversion circuit 13, and an interface circuit 114; the high-transmittance polarization layer includes: a first polarization layer 9 and a second polarization layer 10 with mutually perpendicular polarization directions; the optoelectronic component module is centered on the total internal reflection prism, with the light-diffusing layer tightly attached to one right-angled surface of the prism, the first polarization layer 9 tightly attached to the other right-angled surface of the total internal reflection prism 7, and the second polarization layer 10 tightly attached to the inclined surface of the total internal reflection prism 7; the photodiode array 11 is located after the first polarization layer 9, the IV conversion circuit is located after the photodiode array 11, and the light-emitting diode array is located after the second polarization layer 10; the photodiode array 11 is a 4×4 array structure; the photodiode array 11 includes: four types of PIN photodiodes with different photosensitive ranges (in this application, the four types of PIN photodiodes with different photosensitive ranges have different photosensitive...). The ranges are 400nm~1100nm, 380nm~750nm, 560nm~1100nm, and 840nm~1100nm, respectively. Using the same principle, the photosensitive diode's light-sensing range is not limited to these ranges; it only needs to generate different logic levels for different incident lights to distinguish them. Each type of photosensitive diode is connected in parallel and connected to its corresponding IV conversion channel. The LED array 12 is also a 4×4 array structure. The LED array 12 includes four different LEDs with different emission wavelengths (the four different emission wavelengths are green light 530nm, red light 660nm, first infrared light 820nm, and second infrared light 940nm). The main control module 5 controls the analog switch circuit according to the identified incident light wavelength, only opening the switch channel corresponding to the incident light wavelength, so that the LED array 12 only emits light with the same wavelength as the incident light. Each wavelength of LED is connected in series sequentially. Figure 3As shown, this invention provides a schematic diagram of photodiode and light-emitting diode (LED) connections. For the connection of four PIN photodiodes with different photosensitive ranges, the diagram uses an example of a PIN photodiode connection with one photosensitive range. The four PIN photodiodes with different photosensitive ranges use the same connection method. Four PIN photodiodes with a specific photosensitive range are connected in parallel, with one end of the parallel connection connected to a reference voltage VREF23. VREF23 provides a bias voltage for the four photodiodes. An IV conversion circuit 13, composed of an operational amplifier, resistors, and capacitors, converts the current output from the four parallel PIN photodiodes into a voltage, output as the photodiode output voltage PD-VOUT24. Similarly, for the connection of four LEDs with different emission wavelengths, the diagram uses an example of an LED connection with one emission wavelength. The four LEDs with different emission wavelengths use the same connection method. LEDs with a specific emission wavelength are connected in series, with one end connected to the supply voltage VCC22, and the other end connected to the LED output current LED-I25 and a voltage-controlled constant current drive circuit.

[0039] The photoelectric component module 1 receives the pulsed light signal emitted by the PPG device under test and performs photoelectric signal conversion. The voltage comparator circuit 15 in the analog front-end module 3 identifies the wavelength type of the incident light and outputs the corresponding logic level. The main control module 5 determines the wavelength of the incident light based on the logic level, controls the analog switch circuit in the analog front-end module 3 to open the corresponding wavelength channel, and collects the photoelectric conversion value of the corresponding channel through the analog-to-digital converter circuit 16. The main control module 5 dynamically adjusts the output amplitude of the 4-channel digital-to-analog converter 17 based on the set skin color type and the collected photoelectric conversion value. The 4-channel digital-to-analog converter 17 and the 8-channel digital-to-analog converter 20 synchronously output ECG electrocardiogram signal, PPG light signal and interference signal, which are displayed by the human-machine interaction module 4. The power supply module 6 provides stable power to the above modules.

[0040] In this application, the ECG resistor network module 2 attenuates the simulated ECG signal from the analog front end from the V level to the mV level and provides an accurate signal correspondence. For example... Figure 4The diagram shows the circuit structure of this module. The ECG resistor network module 2 has five output terminals: N, R, L, F, and V (N, R, L, F, and V are abbreviations for electrode leads in an electrocardiogram, representing different positions: L - left arm, R - right arm, N - right leg or right lower limb, F - left leg, and V - chest lead). Terminal N 29 is connected to the simulated ground of the power supply via a fixed-value resistor. For terminals R, L, F, and V 26, the circuit implementation consists of a voltage divider attenuator composed of a digital potentiometer 27 and a fixed resistor. Terminals R, L, F, and V 26 serve as corresponding output terminals. The ECG signal output voltage ECG-VOUT 28 is the simulated ECG signal (voltage signal, 4 outputs) output from the analog front-end module 3. Figure 4 (Illustrative diagram of channel 1). Digital potentiometer 27 is connected to the main control module 5 via an SPI digital bus. Besides being suitable for testing smartwatches, this invention can also be extended for ECG function testing in conventional electrocardiographs, monitors, and other devices, possessing excellent functional expandability and supporting simulation of multiple lead modes such as I, II, III, aVR, aVL, aVF, and V leads.

[0041] Preferably, in this application, the analog front-end module 3 processes the output signal of the IV conversion circuit 13 output by the optoelectronic component module 1, and generates four corresponding analog-to-digital conversion trigger signals based on the four input signals through voltage comparison; it has a four-channel analog-to-digital converter, which triggers the corresponding channel digital-to-analog conversion process according to the analog-to-digital conversion trigger signals to realize the AD analog-to-digital conversion function, converts the analog optoelectronic conversion signal output by the optoelectronic component module 1 into a digital quantity, and outputs it to the main control module 5.

[0042] The analog front-end module 3 includes: a voltage comparator circuit 15, an analog-to-digital converter circuit 16, a digital-to-analog converter circuit, a voltage-controlled constant current source circuit 18, an operational amplifier adder circuit, and an analog switch circuit 19. The voltage comparator circuit 15 compares the signal output by the IV conversion circuit 13 with a reference voltage to generate a trigger signal. The analog-to-digital converter circuit 16 performs analog-to-digital conversion on the corresponding channel according to the trigger signal. The digital-to-analog converter circuit includes: an ECG signal generation circuit, an LED signal generation circuit, and an interference signal generation circuit. The operational amplifier adder converts the voltage signals output by the PPG optical signal generation circuit and the interference signal generation circuit into LED driving voltage signals. The voltage-controlled constant current source circuit 18 converts the LED driving voltage signals into current signals to drive the light-emitting diode array. In this application, the LED driving circuit in the analog front-end module 3 includes: an 8-channel digital-to-analog converter 20, an operational amplifier adder circuit and an analog switch circuit 19, and a voltage-controlled constant current source circuit 18; each pair of outputs of the 8-channel digital-to-analog converter 20 is connected to an operational amplifier adder, and each operational amplifier input terminal is provided with the analog switch. The main control module 5 controls the opening and closing of the voltage-controlled constant current source circuit 18 by controlling the on and off of the analog switches.

[0043] In a preferred embodiment, the ECG signal generating circuit, the PPG optical signal generating circuit, and the interference signal generating circuit are all 16-bit digital-to-analog converters; and the digital-to-analog converters used by the ECG signal generating circuit, the PPG optical signal generating circuit, and the interference signal generating circuit are updated synchronously.

[0044] When the voltage-controlled constant current source circuit 18 is turned off, the light-emitting diode array 12 in the optoelectronic component module 1 is extinguished. The output terminal of the voltage-controlled constant current source circuit 18 is connected to the light-emitting diode array 12 of the optoelectronic component module 1, providing it with driving current. It should be noted that the voltage-controlled constant current source circuit 18, the operational amplifier adder circuit, and the analog switch circuit 19 are independent 4-channel structures. The interface circuit II21 is connected to the main control module 5. The circuit 15 outputs a voltage signal to trigger the main control module 5 in an interrupt mode. It is connected to the main control module 5 through the SPI digital bus. The 4-channel digital-to-analog converter 17, the operational amplifier adder circuit, and the analog switch circuit 19 are triggered by the main control module 5 to synchronously update data.

[0045] In a preferred embodiment, the human-machine interface module 4 is connected to the main control module 5 and includes an OLED / LCD display, a rotary encoder, buttons, LEDs, and a buzzer. The display shows setting parameters and operating status; the rotary encoder and buttons are used to set the operating status and adjust analog parameters; the buzzer provides button operation prompts; and the LEDs display the simulated heartbeat signal. The main control module 5 is selected from 8-bit, 16-bit, or 32-bit models according to application requirements. This module internally stores simulated PPG, simulated ECG waveform data, and simulated interference signal waveform data, and can select the corresponding analog function based on the output signal of module 4. During operation, the main control module 5 reads the analog-to-digital conversion values ​​of the photoelectric conversion signal from the analog front-end module 3 and the output value of the voltage comparator. Based on this input information, it controls the 12 DA outputs of the 4-channel digital-to-analog converter 17 and the 8-channel digital-to-analog converter 20 in the analog front-end module 3, and simultaneously controls the on / off switching of the operational amplifier adder circuit and the analog switch in the analog switch circuit 19 to achieve coordinated operation of the overall system.

[0046] In this application, the power module 6 uses an LDO power chip to reduce interference and provides power at different voltages to the optoelectronic component module 1, the analog front-end module 3, and the main control module 5.

[0047] Example 2 like Figure 6 As shown, the present invention also includes a simulation method for detecting heart rate, blood oxygen, and blood pressure monitoring devices based on photoplethysmography, comprising the following steps: Step 1: Receive the pulsed light signal emitted by the PPG device under test through the optoelectronic component module 1, and perform photo-to-electric signal conversion; Step 2: Identify the incident light wavelength type and output the corresponding logic level through the voltage comparator circuit 15 in the analog front-end module 3; Step 3: The main control module 5 determines the wavelength of the incident light based on the logic level, controls the analog switch circuit to open the corresponding channel, and provides the corresponding channel's analog-to-digital conversion acquisition photoelectric conversion value; Step 4: The main control module 5 dynamically adjusts the output amplitude of the digital-to-analog converter based on the set skin color type and the collected photoelectric conversion value. Step 5: Synchronously output ECG electrocardiogram signal, PPG optical signal and interference signal through digital-to-analog converter, and display them by human-computer interaction module 4.

[0048] Example 3 This invention is based on the principles of photoelectric technology. Taking four commonly used light sources with different wavelengths in current smart wearable devices as examples, these include: green light (530nm), red light (660nm), infrared light (820nm), and infrared light (940nm). Other wavelengths can be used or new wavelengths can be added as needed. Specifically, 530nm green light is mainly used for heart rate measurement based on the PPG principle; 660nm red light, 820nm infrared light, and 940nm infrared light are suitable for detecting reflective blood oxygen saturation. Furthermore, by combining ECG measurement with PPG heart rate waveform analysis, blood pressure measurement (PTT, PWV) based on the principles of pulse wave conduction time and pulse wave velocity can be achieved.

[0049] The optoelectronic component module 1 adopts a 4×4 photodiode array structure, containing four types of PIN photodiodes with different light-sensing ranges. Each type corresponds to four photodiodes connected in parallel. The light-sensing ranges of the four photodiodes are: (400~1100) nm (① photodiode), (380~750) nm (② photodiode), (560~1100) nm (③ photodiode), and (840~1100) nm (④ photodiode). By combining and configuring these photodiodes with different light-sensing ranges, selective reception of light of different operating wavelengths can be achieved, thus avoiding the use of optical filters. Alternatively, a single-sensing-range (400~1100) nm photodiode can be used in conjunction with different bandpass optical filters to achieve selective reception of 530nm, 660nm red light, 820nm infrared light, and 940nm infrared light. Both of these technical approaches can also be implemented through compromise designs and combinations based on actual needs.

[0050] The optoelectronic module 1 employs a 4×4 LED array 12, containing four different emission wavelengths of LEDs: green (530nm), red (660nm), infrared (820nm), and infrared (940nm). LEDs of each wavelength are connected in series. There is a good linear relationship between the luminous intensity of the LEDs and the driving current (this invention satisfies this requirement at relatively low driving currents). This characteristic is utilized to control the luminous intensity of the LEDs by controlling the driving current. The driving current-luminous flux characteristic of the optoelectronic module 1 is calibrated using a standard photometer and the driving current-luminous flux characteristic curve from the LED's instruction manual.

[0051] Two identical optoelectronic modules are used, with their uniform light layer 8 bonded together. The LED array 12 of one module is driven by a controlled current source. By adjusting the relative angle between the two modules, the output voltage of the other module after IV conversion reaches its maximum value. Experiments were conducted at four operating wavelengths: 530nm, 660nm, 820nm, and 940nm. The correspondence between the LED driving current and the IV conversion output voltage at each wavelength was established and normalized.

[0052] When measuring heart rate, blood oxygen, etc., the PPG principle device under test emits light of various wavelengths in the form of pulses. Depending on the structure of the device under test, it may have one wavelength or multiple wavelengths of light. When 530nm light is incident on optoelectronic module 1, ① the output of photodiode + IV conversion circuit 13 triggers the corresponding voltage comparator circuit 15 (hereinafter referred to as ①, the rest are similar) to output a high level, ② output a high level, ③ output a low level, and ④ output a low level (voltage comparator logic potential: 1100); when 660nm light is incident on optoelectronic module 1, ① output a high level, ② output a low level, ③ output a high level, and ④ output a low level (voltage comparator logic potential: 1110); when 820nm light is incident on optoelectronic module 1, ① output a high level, ② output a low level, ③ output a low level, and ④ output a low level (voltage comparator logic potential: 1010); when 940nm light is incident on optoelectronic module 1, ① output a high level, ② output a low level, ③ output a low level, and ④ output a low level (voltage comparator logic potential: 1011). When there is no light, the voltage comparator logic potential is 0000.

[0053] Based on the logic level output by the voltage comparator, the main control module 5 determines whether the current incident light wavelength is 530nm, 660nm, 820nm, or 940nm, and initiates analog-to-digital conversion for the corresponding channel to ensure that the photoelectric conversion value of the corresponding channel is acquired during the incident light operation. When the photoelectric component module 1 receives an optical signal, the main control module 5 controls the analog switching circuit in the analog front-end module 3 to only open the switching channel corresponding to the incident light wavelength, while closing the other channels, so that the LED array in module 1 emits only light with the same wavelength as the incident light.

[0054] Incident light of different wavelengths generates corresponding analog voltages in the optoelectronic component module 1, which are the result of photoelectric conversion. These analog signals are then sent to the analog-to-digital converter (ADC) in the analog front-end module 3 for digitization processing. This ADC is a 4-channel, 12-bit quantization precision ADC. Based on this, and combined with the correspondence between the driving current of the light-emitting diode at each wavelength and its I-V conversion output voltage (which has been normalized), the reference amplitude value of the 8-channel DAC output controlled by the 8-channel digital-to-analog converter 20 in the analog front-end module 3 is determined.

[0055] The 12-channel DAC circuit and voltage-controlled constant current source circuit 18 in the control analog front-end module 3 are existing technologies and will not be described in detail. The input signals of the main control module 5 include two types: the input trigger signal generated by the 4-channel voltage comparator circuit 15 of the control analog front-end module 3, and the 4-channel ADC conversion signal from the same module. The input trigger signal of the voltage comparator is used to identify the wavelength type of the incident light, thereby triggering the main control module 5 to control the 4-channel ADC in the analog front-end module 3 to start the photoelectric conversion data acquisition of the corresponding channel. The output of the main control module 5 includes control signals for the analog switches of the analog front-end module 3, and signals for controlling the synchronous output of the 12-channel DAC. The above constitutes the hardware layer required to implement this invention. Based on the hardware structure, this invention also requires software support to realize the PPG simulation function. This software is implemented on the main control module 5, specifically using C language programming, and all related calculations, processing, and operations in the program are performed digitally.

[0056] In the implementation process, it is necessary to simulate human skin color, blood oxygen value, blood oxygen curve type, pulse amplitude, heart rate, blood pressure, and interference (such as ambient light, respiratory interference, etc.). All of the above parameters can be set through the invention's human-machine interface. The physical interface between the invention and the PPG device under test includes optical signals and ECG electrical signals. The simulation functions are all implemented by modulating these two signals. To simulate the differences in light absorption and reflection characteristics of different skin colors, the invention adopts the Fitzpatrick Skin Type standard, classifying skin color into six levels from Type I to Type VI, corresponding to very light skin to dark brown / black skin. Among them, Type I skin has a stronger ability to reflect light, while Type VI skin has a weaker ability to reflect light. The skin color setting affects all optical signal simulations of the invention. Based on the set skin color type and combined with the photoelectric conversion ADC value collected by the simulation front-end module 3, the invention dynamically adjusts the output amplitude of the DAC in the simulation front-end module 3, thereby enabling the invention's device to adapt to PPG devices with different light intensities.

[0057] To precisely control the output of the 12 DAC signals, the main control module 5 uses an internal timer to generate interrupts at fixed time intervals, continuously updating the data of each channel. Of the 12 DAC channels, 4 are used to generate ECG (electrocardiogram) signals, 4 are used to generate PPG (photoplethysmography) signals, and the remaining 4 are used to generate interference signals. The ECG-related DAC data updates and the PPG-related DAC data updates are kept in phase to ensure signal waveform consistency. The time difference between the peak value of the ECG signal's R-wave and the peak value of the PPG signal is the pulse wave conduction time (PTT), which is a configurable parameter.

[0058] For ECG and blood oxygenation signal data, referencing existing medical databases, and for PPG devices with specific unknown R-curve types, this invention can import a quadratic polynomial-based formula generated from Webster's linear empirical calibration to fit the blood oxygenation R-value curve, achieving fitting of a single R-curve over a relatively large range. value.

[0059] Example 4 The hardware and software functions of this invention support the playback of real human PPG heart rate, blood oxygen, and blood pressure measurement data, and can be used for the development and teaching of PPG principle devices. This invention can also simulate transmissive blood oxygenation by replacing the transmissive photoelectric module.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A simulation device for detecting heart rate, blood oxygen, and blood pressure monitoring equipment based on photoplethysmography, applied to the testing of equipment employing PPG technology, characterized in that, include: Optoelectronic component module, ECG resistor network module, analog front-end module, main control module, human-machine interaction module, and power supply module; The optoelectronic component module includes: a total internal reflection prism, a light-diffusing layer, a high-transmittance polarization layer, a photodiode array, a light-emitting diode array, an IV conversion circuit, and an interface circuit I. The high-transmittance polarization layer includes: a first polarization layer and a second polarization layer with mutually perpendicular polarization directions. The optoelectronic component module is centered on the total internal reflection prism. The light-diffusing layer is tightly attached to one right-angled surface of the prism, the first polarization layer is tightly attached to the other right-angled surface of the prism, and the second polarization layer is tightly attached to the inclined surface of the prism. The photodiode array is located behind the first polarization layer, the IV conversion circuit is located behind the photodiode array, and the light-emitting diode array is located behind the second polarization layer. The photodiode array has a 4×4 array structure. The photodiode array includes: four PIN photodiodes with different photosensitive ranges, with four of each PIN photodiode connected in parallel and connected to the corresponding four IV conversion circuits. The light-emitting diode array also has a 4×4 array structure. The light-emitting diode array includes: four LEDs with different emission wavelengths, with four of each wavelength connected in series. The optoelectronic component module receives the pulsed light signal emitted by the PPG device under test and performs photoelectric signal conversion. The voltage comparator circuit in the analog front-end module identifies the wavelength type of the incident light and outputs the corresponding logic level. The main control module determines the wavelength of the incident light based on the logic level, controls the analog switch circuit in the analog front-end module to open the corresponding wavelength channel, and collects the photoelectric conversion value of the corresponding channel through the analog-to-digital converter circuit. The main control module dynamically adjusts the output amplitude of the digital-to-analog converter based on the set skin color type and the collected photoelectric conversion value. The digital-to-analog converter synchronously outputs ECG electrocardiogram signal, PPG light signal, and interference signal. The human-machine interaction module allows for parameter setting and display. The power supply module provides stable power to all the above modules.

2. The simulation device for detecting heart rate, blood oxygen, and blood pressure monitoring equipment based on photoplethysmography according to claim 1, characterized in that, The ECG resistor network module includes five output terminals: N, R, L, F, and V. The N terminal is connected to the power supply analog ground through a fixed-value resistor, and the R, L, F, and V terminals are respectively connected to voltage divider attenuators. The voltage divider attenuator includes a digital potentiometer and a fixed-value resistor.

3. The simulation device for detecting heart rate, blood oxygen, and blood pressure monitoring equipment based on photoplethysmography according to claim 1, characterized in that, The analog front-end module includes: a voltage comparator circuit, an analog-to-digital converter circuit, a digital-to-analog converter circuit, a voltage-controlled constant current source circuit, an operational amplifier adder, and an analog switch circuit; the voltage comparator circuit compares the signal output by the IV conversion circuit with a reference voltage to generate a trigger signal; the analog-to-digital converter circuit performs analog-to-digital conversion on the corresponding channel according to the trigger signal; the digital-to-analog converter circuit includes: an ECG signal generation circuit, a PPG optical signal generation circuit, and an interference signal generation circuit; the operational amplifier adder converts the voltage signals output by the PPG optical signal generation circuit and the interference signal generation circuit into LED driving voltage signals; the voltage-controlled constant current source circuit converts the output LED driving voltage signals into current signals to drive the light-emitting diode array.

4. The simulation device for detecting heart rate, blood oxygen, and blood pressure monitoring equipment based on photoplethysmography according to claim 1, characterized in that, The four PIN photodiodes with different photosensitive ranges have photosensitive ranges of 400nm~1100nm, 380nm~750nm, 560nm~1100nm, and 840nm~1100nm, respectively.

5. A simulation device for detecting heart rate, blood oxygen, and blood pressure monitoring equipment based on photoplethysmography, as described in claim 1, characterized in that, The four different light-emitting wavelengths of the LEDs are green light (530nm), red light (660nm), first infrared light (820nm), and second infrared light (940nm). The main control module controls the analog switch circuit according to the identified incident light wavelength, and only turns on the switch channel corresponding to the incident light wavelength, so that the light-emitting diode array emits only light with the same wavelength as the incident light.

6. The simulation device for detecting heart rate, blood oxygen, and blood pressure monitoring equipment based on photoplethysmography according to claim 1, characterized in that, The LED driving circuit in the analog front-end module includes: an 8-channel digital-to-analog converter, an operational amplifier adder, and an analog switch; the output of every two digital-to-analog converters is connected to an operational amplifier adder, and each operational amplifier input is equipped with the analog switch. The main control module controls the opening and closing of the voltage-controlled constant current source circuit by controlling the on and off of the analog switches.

7. A simulation device for detecting heart rate, blood oxygen, and blood pressure monitoring equipment based on photoplethysmography, as described in claim 3, characterized in that, The ECG signal generation circuit, the PPG optical signal generation circuit, and the interference signal generation circuit are all 16-bit digital-to-analog converters; and the digital-to-analog converters used by the ECG signal generation circuit, the PPG optical signal generation circuit, and the interference signal generation circuit are updated synchronously.

8. A simulation method for detecting heart rate, blood oxygen, and blood pressure monitoring devices based on photoplethysmography, using the apparatus described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Receive the pulsed light signal emitted by the PPG device under test through the optoelectronic component module, and perform photo-to-electric signal conversion; Step 2: Identify the incident light wavelength type and output the corresponding logic level through the voltage comparator circuit in the analog front-end module; Step 3: The main control module determines the incident light wavelength based on the logic level, controls the analog switch circuit to open the corresponding channel, and provides the corresponding channel's analog-to-digital conversion to acquire the photoelectric conversion value; Step 4: The main control module dynamically adjusts the output amplitude of the digital-to-analog converter based on the set skin color type and the collected photoelectric conversion value. Step 5: Synchronously output ECG electrocardiogram signal, PPG optical signal and interference signal through digital-to-analog converter, and set and display them by human-computer interaction module.

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