On-chip integrated homodyne Doppler vibration meter, vibration measuring device and application

Abstract

The embodiment of the invention discloses an on-chip integrated homodyne Doppler vibration meter, a vibration measuring device and application. The homodyne Doppler vibration meter comprises a substrate; the first multi-mode interferometer, the second multi-mode interferometer, the third multi-mode interferometer, the fourth multi-mode interferometer and the fifth multi-mode interferometer are located on one side of the substrate, and the second multi-mode interferometer, the third multi-mode interferometer, the fourth multi-mode interferometer and the fifth multi-mode interferometer form a 90-degree mixer. An output light beam of a light source is divided into a signal light beam and a reference light beam through a first multi-mode interferometer, the signal light beam is transmitted to a to-be-measured target, the signal light beam returned by the to-be-measured target enters a 90-degree mixer, the signal light beam and the reference light beam achieve homodyne interference in the 90-degree mixer, and meanwhile an in-phase component and an orthogonal component of a signal are obtained; therefore, complete phase and amplitude information is obtained, and vibration measurement of the to-be-measured target is realized. The homodyne Doppler vibration meter is integrated on the same chip, and has the advantages of small size, low power consumption, low cost and the like.

Description

Technical Field

[0001] The present invention relates to the field of interference measurement technology, and in particular to an on-chip integrated homodyne Doppler vibrometer, a vibration measuring device and applications. Background Art

[0002] Laser Doppler Vibrometer (LDV) is a measuring instrument that uses the laser Doppler effect, interference and other principles to measure the vibration of an object. Compared with traditional sensors such as accelerometers, it has the advantages of long-distance measurement, non-contact, high spatial resolution, short measurement time, wide response bandwidth and high velocity resolution. It is widely used in model modal characteristic analysis, quality inspection, online control, structural flaw detection, health care and other fields.

[0003] However, the laser Doppler vibrometer in the prior art is relatively large in size, which is very limited for applications where space is limited. For example, when the LDV needs to be placed in the ear to measure the vibration of the eardrum, a very compact size is required; when multiple LDVs are used to measure the vibration distribution of a small surface, the size of each LDV should also be very small, and the LDV structure in the prior art is difficult to meet the requirements. Summary of the invention

[0004] The embodiment of the present invention provides an on-chip integrated homodyne Doppler vibrometer, a vibration measuring device and an application thereof, which reduces the size, power consumption and cost by integrating LDV on a chip.

[0005] According to one aspect of the present invention, there is provided an on-chip integrated homodyne Doppler vibrometer, comprising:

[0006] substrate;

[0007] A first multimode interferometer, a second multimode interferometer, a third multimode interferometer, a fourth multimode interferometer and a fifth multimode interferometer located on one side of the substrate, wherein the first multimode interferometer and the second multimode interferometer each include an input end and two output ends, and the third multimode interferometer, the fourth multimode interferometer and the fifth multimode interferometer each include two input ends and two output ends;

[0008] The input end of the first multimode interferometer is coupled with the output end of the light source, the first output end of the first multimode interferometer is used to output a signal light beam to the target to be measured, the second output end of the first multimode interferometer is coupled with the input end of the second multimode interferometer, the first output end of the second multimode interferometer is coupled with the first input end of the third multimode interferometer, the second output end of the second multimode interferometer is coupled with the first input end of the fourth multimode interferometer, the first input end of the fifth multimode interferometer is used to receive the signal light beam returned by the target to be measured, the second input end of the fifth multimode interferometer is vacant, the first output end of the fifth multimode interferometer is coupled with the second input end of the third multimode interferometer, the second output end of the fifth multimode interferometer is coupled with the second input end of the fourth multimode interferometer, and the second multimode interferometer, the third multimode interferometer, the fourth multimode interferometer and the fifth multimode interferometer form a 90° mixer.

[0009] Optionally, the output beam of the light source is incident on the first multi-mode interferometer, and is split into a signal beam and a reference beam by the first multi-mode interferometer;

[0010] The signal light beam is output from the first output end of the first multi-mode interferometer to the target to be measured, and the signal light beam including the vibration information of the target to be measured returned by the target to be measured is incident on the 90° mixer from the first input end of the fifth multi-mode interferometer;

[0011] The reference beam is output from the second output of the first multi-mode interferometer to the 90° mixer, and the signal beam and the reference beam interfere in the 90° mixer to output an in-phase component and an orthogonal component.

[0012] Optionally, it further includes a first photodetector and a second photodetector, wherein the first photodetector is used to receive output signals from two output ends of the third multi-mode interferometer, and the second photodetector is used to receive output signals from two output ends of the fourth multi-mode interferometer.

[0013] Optionally, both the first photodetector and the second photodetector are balanced photodetectors.

[0014] Optionally, a first edge coupler is further included, wherein an input end of the first edge coupler is coupled to a first output end of the first multi-mode interferometer, and an output end of the first edge coupler is used to output the signal light beam.

[0015] Optionally, a second edge coupler is further included, wherein the input end of the second edge coupler is used to receive the signal light beam returned by the target to be measured, and the output end of the second edge coupler is coupled to the first input end of the fifth multi-mode interferometer.

[0016] Optionally, the first multi-mode interferometer, the second multi-mode interferometer, the third multi-mode interferometer, the fourth multi-mode interferometer and the fifth multi-mode interferometer are connected through an optical waveguide located on one side of the substrate.

[0017] Optionally, the optical waveguide is a silicon waveguide.

[0018] According to another aspect of the present invention, there is provided a homodyne Doppler vibrometer device, comprising a light source, a circulator, the above-mentioned homodyne Doppler vibrometer and a processor;

[0019] The output beam of the light source is incident on the homodyne Doppler vibrometer and is divided into a signal beam and a reference beam. The signal beam is output from the homodyne Doppler vibrometer and is incident on the first end of the circulator, and is output from the second end of the circulator to the target to be measured. The signal beam returned by the target to be measured is incident from the second end of the circulator, emitted from the third end of the circulator and coupled into the homodyne Doppler vibrometer.

[0020] The signal light beam and the reference light beam interfere with each other in the homodyne Doppler vibrometer, and the processor determines the vibration information of the target to be measured according to the interference signal.

[0021] Optionally, it also includes a first optical fiber array and a second optical fiber array, the first optical fiber array is used to transmit the signal light beam output by the homodyne Doppler vibrometer to the first end of the circulator, and the second optical fiber array is used to transmit the signal light beam output by the third end of the circulator to the homodyne Doppler vibrometer.

[0022] According to another aspect of the present invention, there is provided an application of the above-mentioned homodyne Doppler vibrometer, wherein the homodyne Doppler vibrometer is used to implement cardiac pump function assessment, heartbeat monitoring, heart sound monitoring or respiratory parameter monitoring.

[0023] The on-chip integrated homodyne Doppler vibrometer provided by the embodiment of the present invention includes a substrate and a first multimode interferometer, a second multimode interferometer, a third multimode interferometer, a fourth multimode interferometer and a fifth multimode interferometer located on one side of the substrate, wherein the second multimode interferometer, the third multimode interferometer, the fourth multimode interferometer and the fifth multimode interferometer form a 90° mixer. The output beam of the light source is divided into a signal beam and a reference beam by the first multimode interferometer, the signal beam is transmitted to the target to be measured, the signal beam returned by the target to be measured is incident on the 90° mixer, the signal beam and the reference beam realize homodyne interference in the 90° mixer, and the in-phase component and the orthogonal component of the signal are obtained at the same time, thereby obtaining complete phase and amplitude information, and realizing vibration measurement of the target to be measured. The homodyne Doppler vibrometer is integrated on the same chip, and has the advantages of small size, low power consumption, and low cost.

[0024] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 A structural block diagram of an on-chip integrated homodyne Doppler vibrometer provided by an embodiment of the present invention;

[0027] Figure 2 It is a structural schematic diagram of a 90° mixer;

[0028] Figure 3 A structural block diagram of another on-chip integrated homodyne Doppler vibrometer provided by an embodiment of the present invention;

[0029] Figure 4 A structural block diagram of another on-chip integrated homodyne Doppler vibrometer provided by an embodiment of the present invention;

[0030] Figure 5 A structural block diagram of a homodyne Doppler vibration measuring device provided by an embodiment of the present invention;

[0031] Figure 6 A structural block diagram of another homodyne Doppler vibration measuring device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0033] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0034] Traditional LDVs have the disadvantages of large size, high power consumption and high production cost, and cannot be applied in some scenarios with limited measurement space. For example, for device size, when the LDV needs to be placed in the ear to measure the vibration of the eardrum, a very compact size is required. When multiple LDVs are used to measure the vibration distribution of a small surface, the size of each LDV should also be very small. For power consumption, power consumption may come from different components of the LDV, including laser sources, photodetectors, demodulation electronics, thermostats, and other auxiliary components. For homodyne LDVs, the conventionally used acousto-optic modulator (AOM) may consume a lot of power (up to several watts). For production cost, unlike the parameters mentioned above, production cost is a commercial consideration for LDV systems. Customers require high-performance equipment and low-priced products. In an embodiment of the present invention, the volume is reduced and the production cost is reduced by integrating the LDV on a chip, and the power consumption compared to traditional LDV devices may be greatly reduced by replacing the AOM with low-power components. Based on this, an embodiment of the present invention provides an on-chip integrated homodyne Doppler vibrometer, including: a substrate; a first multimode interferometer, a second multimode interferometer, a third multimode interferometer, a fourth multimode interferometer, and a fifth multimode interferometer located on one side of the substrate, the first multimode interferometer and the second multimode interferometer each including an input end and two output ends, the third multimode interferometer, the fourth multimode interferometer, and the fifth multimode interferometer each including two input ends and two output ends; the input end of the first multimode interferometer is coupled to the output end of the light source, the first output end of the first multimode interferometer is used to output a signal light beam to a target to be measured, and the second output end of the first multimode interferometer is coupled to the second multimode The input ends of the interferometers are coupled, the first output end of the second multimode interferometer is coupled with the first input end of the third multimode interferometer, the second output end of the second multimode interferometer is coupled with the first input end of the fourth multimode interferometer, the first input end of the fifth multimode interferometer is used to receive a signal light beam returned by the target to be measured, the second input end of the fifth multimode interferometer is vacant, the first output end of the fifth multimode interferometer is coupled with the second input end of the third multimode interferometer, the second output end of the fifth multimode interferometer is coupled with the second input end of the fourth multimode interferometer, and the second multimode interferometer, the third multimode interferometer, the fourth multimode interferometer and the fifth multimode interferometer form a 90° mixer.

[0035] Among them, the on-chip integrated homodyne Doppler vibrometer provided by the embodiment of the present invention can be formed based on a silicon photonic chip, and the substrate can be selected from silicon dioxide. The reasons for the low cost of silicon photonic chips mainly include the following points: mature manufacturing process: silicon-based semiconductor manufacturing process is very mature and widely used in the electronics industry. Silicon photonic chips can be mass-produced using the existing semiconductor manufacturing infrastructure, reducing production costs. High integration: Silicon photonic chips can integrate multiple optical and electronic functions on one chip, reducing the number of components and assembly steps required, thereby reducing the cost of the overall system. Low material cost: Silicon is an abundant and inexpensive material. Compared with other optical materials (such as gallium arsenide or indium phosphide), the cost of silicon is much lower. This makes it more economical to mass-produce silicon photonic chips. Mass production advantages: Silicon photonic chips can be mass-produced using mass production technology in the semiconductor industry. This scale effect can significantly reduce the production cost of each chip. Compatibility: Silicon photonic chips are compatible with existing CMOS manufacturing processes and can be seamlessly integrated with electronic circuits. This reduces the cost of developing new processes and equipment while improving production efficiency. Reduced packaging and assembly costs: By integrating more functionality on a chip, the complexity and cost of packaging and assembly can be reduced. This helps reduce the manufacturing cost of the entire system.

[0036] Figure 1 A structural block diagram of an on-chip integrated homodyne Doppler vibrometer provided by an embodiment of the present invention, refer to Figure 1 The homodyne Doppler vibrometer 10 integrated on the chip includes: a first multimode interferometer 1, a second multimode interferometer 2, a third multimode interferometer 3, a fourth multimode interferometer 4 and a fifth multimode interferometer 5. The first multimode interferometer 1 and the second multimode interferometer 2 each include an input end and two output ends, and the third multimode interferometer 3, the fourth multimode interferometer 4 and the fifth multimode interferometer 5 each include two input ends and two output ends; the input end of the first multimode interferometer 1 is coupled to the output end of the light source 6, the first output end of the first multimode interferometer 1 is used to output a signal beam to the target 7 to be measured, and the second output end of the first multimode interferometer 1 is coupled to the input end of the second multimode interferometer 2. The first output end of the second multimode interferometer 2 is coupled to the first input end of the third multimode interferometer 3, the second output end of the second multimode interferometer 2 is coupled to the first input end of the fourth multimode interferometer 4, the first input end of the fifth multimode interferometer 5 is used to receive the signal light beam returned by the target 7 to be measured, the second input end of the fifth multimode interferometer 5 is vacant, the first output end of the fifth multimode interferometer 5 is coupled to the second input end of the third multimode interferometer 3, the second output end of the fifth multimode interferometer 5 is coupled to the second input end of the fourth multimode interferometer 4, and the second multimode interferometer 2, the third multimode interferometer 3, the fourth multimode interferometer 4 and the fifth multimode interferometer 5 form a 90° mixer.

[0037] Among them, the multimode interferometer (MMI) is a functional device based on multimode waveguides, which can be integrated on silicon photonic chips and is an optical waveguide that can support multiple propagation modes. The principle is: in this waveguide, different modes have different propagation constants. Mode excitation and propagation: When the light signal enters the multimode waveguide, multiple modes in it are excited. These modes propagate at different speeds in the waveguide, so the relative phase changes with the propagation distance. Interference effect: Due to the phase difference of different modes, they interfere at a specific position, forming constructive or destructive interference of light intensity. By precisely designing the length and width of the waveguide, the coherent recombination of these modes at the waveguide outlet or specific position can be controlled. Self-imaging effect: In a multimode waveguide, due to the interference effect, the light field distribution of the input surface can be replicated (reproduced) at a specific position of the waveguide (called the self-imaging point). This feature allows MMI to be used as a power divider (such as a 1×N power divider). Output design: The output end of the MMI is designed to have multiple ports, and the optical signal can be distributed at these ports in a predetermined ratio. For example, it can be designed to distribute a single input optical signal equally or unequally to multiple output ports.

[0038] In this embodiment, two 1×2 MMIs (a first multimode interferometer 1 and a second multimode interferometer 2) and three 2×2 MMIs (a third multimode interferometer 3, a fourth multimode interferometer 4 and a fifth multimode interferometer 5) are used. Figure 2 This is a schematic diagram of the 90° mixer structure. Figure 2, wherein the second multimode interferometer 2, the third multimode interferometer 3, the fourth multimode interferometer 4 and the fifth multimode interferometer 5 form a 90° mixer, and the working principle of the 90° mixer is as follows: Input signal distribution: The first MMI (the second multimode interferometer 2) of the optical 90° mixer is used to divide the input signal into two paths, and usually the two signals have the same power. Phase adjustment: One of the signals is phase-adjusted by another MMI, usually adding a 90° phase delay to achieve orthogonality with the other signal. Mixing operation: The adjusted two signals each enter the other two MMIs. In these MMIs, one signal may be mixed with a local oscillator signal (Local Oscillator, LO), and this LO signal provides the necessary phase reference for controlling the phase of the output signal. Output generation: Finally, through the action of these four MMIs, two signals with a phase difference of 90° are output. These two signals are usually represented as I (In-phase, in-phase) and Q (Quadrature, orthogonal) components, which can be directly used for orthogonal demodulation or other signal processing applications. 90° mixer design considerations include: Waveguide dimensions and design: The design of the MMI (such as width, length, and refractive index) must be precisely controlled to ensure correct mode excitation and interference, thereby achieving accurate phase and power distribution. Phase stability: In order to keep the phase relationship of the output signal stable, it is necessary to ensure that the MMI structure is insensitive to changes in temperature and manufacturing processes. Integration and compatibility: When designing an MMI mixer, it is necessary to consider its integration with other optical components, including light sources, detectors, and other light processing devices.

[0039] The functions of a 90° mixer include: (1) Removing DC offset and low-frequency noise: A 90° mixer can help remove DC offset and low-frequency noise, thereby improving the signal-to-noise ratio of the signal. This is because the I and Q components of the signal can be separated in the frequency domain, making it easier to process and analyze.

[0040] (2) Complete acquisition of phase and amplitude information: By using a 90° mixer, the I and Q components of the signal can be acquired simultaneously, thereby obtaining complete phase and amplitude information. This is very important for accurate measurement and analysis, especially in applications that require accurate phase information, such as laser Doppler velocimeters and radar systems.

[0041] (3) Improve system sensitivity: In coherent detection, the 90° mixer can improve the sensitivity of the system because it can convert all phase information of the input signal into an easily processable baseband signal, thus enabling the system to detect weaker signals.

[0042] (4) Achieve efficient digital signal processing: The I and Q signals generated by the 90° mixer facilitate subsequent digital signal processing (DSP).

[0043] Optional, continue to refer to Figure 1 The output beam of the light source 6 is incident on the first multimode interferometer 1, and is split into a signal beam a and a reference beam b by the first multimode interferometer 1; the signal beam a is output from the first output end of the first multimode interferometer 1 to the target 7 to be measured, and the signal beam including the vibration information of the target to be measured returned by the target 7 to be measured is incident on the 90° mixer from the first input end of the fifth multimode interferometer 5; the reference beam is output from the second output end of the first multimode interferometer 1 to the 90° mixer, and the signal beam and the reference beam interfere in the 90° mixer to output an in-phase component and an orthogonal component.

[0044] Optionally, the first multimode interferometer 1, the second multimode interferometer 2, the third multimode interferometer 3, the fourth multimode interferometer 4 and the fifth multimode interferometer 5 are connected via an optical waveguide located on one side of the substrate. Optionally, the optical waveguide is a silicon waveguide.

[0045] The technical solution of the embodiment of the present invention is to divide the output beam of the light source into a signal beam and a reference beam through a first multimode interferometer, the signal beam is transmitted to the target to be measured, the signal beam returned by the target to be measured is incident on a 90° mixer, the signal beam and the reference beam realize homodyne interference in the 90° mixer, and simultaneously obtain the in-phase component and orthogonal component of the signal, thereby obtaining complete phase and amplitude information, and realizing vibration measurement of the target to be measured. The homodyne Doppler vibrometer is integrated on the same chip, and has the advantages of small size, low power consumption, and low cost.

[0046] Figure 3 A structural block diagram of another on-chip integrated homodyne Doppler vibrometer provided in an embodiment of the present invention is shown in FIG. Figure 3 Optionally, the homodyne Doppler vibrometer also includes a first photodetector 8 and a second photodetector 9, the first photodetector 8 is used to receive output signals from two output ends of the third multimode interferometer 3, and the second photodetector 9 is used to receive output signals from two output ends of the fourth multimode interferometer 4.

[0047] The first photodetector 8 and the second photodetector 9 are used to convert the optical signal into an electrical signal, and obtain the vibration information of the target 7 according to the electrical signal. The first photodetector 8 and the second photodetector 9 can also be integrated on a chip to reduce the volume. Optionally, the first photodetector 8 and the second photodetector 9 are both balanced photodetectors.

[0048] Figure 4 A structural block diagram of another on-chip integrated homodyne Doppler vibrometer provided in an embodiment of the present invention is shown in FIG. Figure 4Optionally, the homodyne Doppler vibrometer further includes a first edge coupler 11, an input end of the first edge coupler 11 is coupled to a first output end of the first multimode interferometer 1, and an output end of the first edge coupler 11 is used to output a signal light beam.

[0049] Optional, continue to refer to Figure 4 The homodyne Doppler vibrometer also includes a second edge coupler 12 , the input end of the second edge coupler 12 is used to receive the signal light beam returned by the target 7 to be measured, and the output end of the second edge coupler 12 is coupled to the first input end of the fifth multimode interferometer 5 .

[0050] Setting an edge coupler can improve the beam quality and enhance the performance of the homodyne Doppler vibrometer.

[0051] Figure 5 A structural block diagram of a homodyne Doppler vibration measuring device provided by an embodiment of the present invention, referring to Figure 5 The homodyne Doppler vibrometer device includes a light source 6, a circulator 13, any one of the homodyne Doppler vibrometers 10 provided in the above embodiments, and a processor 14; the output light beam of the light source 6 (which may be a laser, but is not a limitation of the embodiments of the present invention) is incident on the homodyne Doppler vibrometer 10 and is divided into a signal light beam and a reference light beam; the signal light beam is output from the homodyne Doppler vibrometer 10 and is incident on the first end of the circulator 13, and is output from the second end of the circulator 13 to the target 7 to be measured; the signal light beam returned by the target 7 to be measured is incident from the second end of the circulator 13, and is emitted from the third end of the circulator 13 and coupled into the homodyne Doppler vibrometer 10; the signal light beam and the reference light beam interfere in the homodyne Doppler vibrometer 10, and the processor 14 determines the vibration information of the target 7 to be measured according to the interference signal.

[0052] The homodyne Doppler vibrometer device provided in the embodiment of the present invention includes the homodyne Doppler vibrometer provided in the above embodiment, and has the same or corresponding technical effects as the homodyne Doppler vibrometer, which will not be described in detail here.

[0053] Figure 6 A structural block diagram of another homodyne Doppler vibration measuring device provided by an embodiment of the present invention is shown in FIG. Figure 6 Optionally, the homodyne Doppler vibrometer device also includes a first optical fiber array 15 and a second optical fiber array 16, the first optical fiber array 15 is used to transmit the signal light beam output by the homodyne Doppler vibrometer 10 to the first end of the circulator 13, and the second optical fiber array 16 is used to transmit the signal light beam output by the third end of the circulator 13 to the homodyne Doppler vibrometer 10.

[0054] By providing the first optical fiber array 15 and the second optical fiber array 16, the light beam can be transmitted in the optical fiber, thereby reducing light loss and helping to improve system performance.

[0055] An embodiment of the present invention further provides an application of the homodyne Doppler vibration measuring device provided in the above embodiment, and the homodyne Doppler vibration measuring device is used to implement cardiac pump function evaluation, heartbeat monitoring, heart sound monitoring or respiratory parameter monitoring.

[0056] Among them, for the application of cardiac pump function assessment, current cardiac function assessment methods mostly rely on invasive or contact techniques, such as electrocardiogram (ECG) and cardiac catheterization. Although these methods are effective, they have problems such as patient discomfort, infection risk and high cost. Therefore, there is an urgent need for a new technology that is safe, non-invasive, contact-free and can quickly assess cardiac pump function. Laser Doppler vibrometer technology is a non-invasive, non-contact technology that uses a laser beam to detect tiny vibration changes on the surface of tissue to assess cardiac pump parameters.

[0057] The specific test process is: using the homodyne Doppler vibrometer provided by the embodiment of the present invention to perform measurements under different pacing configurations, including biventricular pacing (BiV), left ventricular pacing (LV), right ventricular pacing (RV) and no pacing. Atrioventricular sequential pacing (DDD mode) is used for signal recording, and the AV delay of pacing is similar to the patient's original setting. Baseline measurements are performed under atrial pacing (AAI mode), before and after each measurement. All pacing settings are higher than the patient's own sinus rhythm by more than 10 beats per minute to exclude the influence of spontaneous heart rate changes. Each recording lasts 20 to 30 seconds, including the process of switching from DDD mode to AAI mode or from AAI mode back to DDD mode. Each patient serves as his own control, and the study ends automatically after completing the measurement protocol. By analyzing the signal after 10Hz to 100Hz bandpass filtering, the amplitude changes of the laser Doppler vibrometer signal in the pacing on and off states are compared. Under different pacing modes, the amplitude changes of the two channels are averaged and compared. The results showed that the amplitude during ventricular pacing was significantly higher than the baseline state (AAI mode). Among them, the amplitude increase was the largest under biventricular pacing (BiV). The changes in the amplitude of the laser Doppler vibrometer signal in different modes can be used to characterize the effect of the pacemaker.

[0058] For heartbeat monitoring applications, it is suitable for contactless real-time monitoring of cardiac activity in clinical environments. Mechanical activity during breathing is monitored by detecting vibrations on the skin surface. Laser Doppler vibrometer technology can extract important parameters such as respiratory rate and ventilation volume by measuring surface vibration signals at locations such as the chest or neck. Electrocardiogram (ECG) is the traditional standard for heart monitoring, which records the electrical activity of the heart through electrodes in contact with the skin. However, with the development of technology, laser Doppler vibrometer technology is used to record the mechanical activity (vibration) of the heart and generate a vibrometer cardiogram (VCG). Unlike ECG, VCG directly reflects the mechanical activity of the heart and is particularly suitable for scenarios that require contactless monitoring. By accurately recording and analyzing the patient's surface vibration signals, the heart rate can be estimated in real time, which is particularly suitable for the diagnosis of cardiac abnormalities such as atrial fibrillation.

[0059] In specific implementation, the homodyne Doppler vibrometer is aimed at the patient's chest, and the surface vibration data is collected by a laser beam; then the vibration signal is filtered, and a bandpass filter (0.75Hz~2Hz) is used to remove breathing and other interference signals and separate the heartbeat signal; the heartbeat frequency is analyzed by fast Fourier transform (FFT) or autocorrelation function (ACF) to monitor the heart rhythm (atrial fibrillation and other problems). It has the following advantages: non-invasive and contactless, avoiding the electrode contact problem in traditional electrocardiograms; real-time monitoring, especially suitable for the diagnosis of diseases such as atrial fibrillation and arrhythmia; accurate heartbeat frequency calculation, and signal processing algorithms effectively remove interference.

[0060] For heart sound monitoring applications, it is suitable for real-time monitoring of heart valve activity and other heart sound characteristics. Traditional heart sound monitoring records heart sounds through a stethoscope or microphone, which has contact limitations and is not suitable for some patients. Laser Doppler vibrometer technology can capture cardiac mechanical activity signals without contact and extract heart sound signals through signal processing. This method provides a more convenient and accurate means of heart sound monitoring, which is particularly suitable for contactless clinical monitoring. The present invention provides a non-invasive heart sound monitoring method based on laser Doppler vibrometer technology, which extracts heart sound information, including the sound of heart valve closing, by recording tiny vibration signals on the patient's skin surface. This method is particularly suitable for the detection of abnormal heart valve function.

[0061] In specific implementation, the homodyne Doppler vibration measuring device is aimed at the patient's chest, and the mechanical vibration signal of the chest is collected through the laser beam; then the vibration signal is processed using a low-pass filter to remove high-frequency interference and extract the signal related to the heart sound; and then the peak detection algorithm is used to analyze the intensity and timing of the heart sound signal to monitor the heart valve activity. It has the following advantages: non-invasive and non-contact, suitable for special situations where it is impossible to contact the patient; provides accurate heart sound information, especially suitable for the detection of heart valve diseases; efficient signal processing algorithm, can detect and analyze heart sounds in real time.

[0062] For respiratory parameter monitoring applications, traditional respiratory monitoring methods mainly rely on contact devices, such as respiratory belts, flow sensors or electrodes, which require direct contact with the patient's skin, which is inconvenient and has the risk of infection. Especially in emergency medical situations, patients may not be able to perform contact measurements due to injuries or infections. Therefore, an efficient, safe and contactless respiratory monitoring technology is urgently needed.

[0063] Laser Doppler vibrometry is a non-contact technology that monitors mechanical activity during breathing by detecting vibrations on the skin surface. Laser Doppler vibrometry can extract important parameters such as respiratory rate and ventilation volume by measuring surface vibration signals at locations such as the chest or neck.

[0064] The embodiment of the present invention provides an application of a homodyne Doppler vibrometer in contactless respiratory monitoring. Through laser Doppler vibrometer technology, respiratory parameters such as respiratory rate, respiratory rhythm and ventilation volume can be monitored in real time. It is particularly suitable for scenarios requiring non-invasive and contactless monitoring, such as intensive care, emergency or motion monitoring.

[0065] In specific implementation, the homodyne Doppler vibrometer is first aimed at the chest or neck of the patient, and the surface vibration data is collected contactlessly by a laser beam; then the collected vibration signal is filtered to separate the respiratory signal, and a bandpass filter is used to remove high-frequency interference such as heartbeat; the respiratory frequency is calculated using the fast Fourier transform (FFT) or autocorrelation function (ACF) method, and the ventilation volume is calculated by integration. In signal processing, in order to reduce distortion, a linear phase finite impulse response (FIR) filter is used, and the cutoff frequency of the filter is set to 0.6Hz to ensure that the respiratory signal is separated from the heartbeat signal. By integrating the respiratory signal, the displacement of the chest or abdomen during breathing is calculated to evaluate the ventilation volume.

[0066] The present invention is suitable for neonatal intensive care, respiratory monitoring of elderly patients, sports status monitoring of athletes, and contactless respiratory monitoring in emergency and workplace environments.

[0067] Advantages: Non-invasive and non-contact: completely non-contact, avoiding patient discomfort and infection risks; Real-time monitoring: real-time monitoring of respiratory rate and ventilation volume, convenient for doctors or nurses to evaluate the patient's respiratory condition at any time; High signal quality: through advanced filtering and signal processing technology, it can effectively improve the accuracy and reliability of the signal.

[0068] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An on-chip integrated homodyne Doppler vibrometer, characterized in that: include: substrate; A first multimode interferometer, a second multimode interferometer, a third multimode interferometer, a fourth multimode interferometer and a fifth multimode interferometer located on one side of the substrate, wherein the first multimode interferometer and the second multimode interferometer each include an input end and two output ends, and the third multimode interferometer, the fourth multimode interferometer and the fifth multimode interferometer each include two input ends and two output ends; The input end of the first multimode interferometer is coupled with the output end of the light source, the first output end of the first multimode interferometer is used to output a signal light beam to the target to be measured, the second output end of the first multimode interferometer is coupled with the input end of the second multimode interferometer, the first output end of the second multimode interferometer is coupled with the first input end of the third multimode interferometer, the second output end of the second multimode interferometer is coupled with the first input end of the fourth multimode interferometer, the first input end of the fifth multimode interferometer is used to receive the signal light beam returned by the target to be measured, the second input end of the fifth multimode interferometer is vacant, the first output end of the fifth multimode interferometer is coupled with the second input end of the third multimode interferometer, the second output end of the fifth multimode interferometer is coupled with the second input end of the fourth multimode interferometer, and the second multimode interferometer, the third multimode interferometer, the fourth multimode interferometer and the fifth multimode interferometer form a 90° mixer.

2. The on-chip integrated homodyne Doppler vibrometer according to claim 1, characterized in that: The output beam of the light source is incident on the first multi-mode interferometer, and is split into a signal beam and a reference beam by the first multi-mode interferometer; The signal light beam is output from the first output end of the first multi-mode interferometer to the target to be measured, and the signal light beam including the vibration information of the target to be measured returned by the target to be measured is incident on the 90° mixer from the first input end of the fifth multi-mode interferometer; The reference beam is output from the second output of the first multi-mode interferometer to the 90° mixer, and the signal beam and the reference beam interfere in the 90° mixer to output an in-phase component and an orthogonal component.

3. The on-chip integrated homodyne Doppler vibrometer according to claim 2, characterized in that: It also includes a first photodetector and a second photodetector, wherein the first photodetector is used to receive output signals from two output ends of the third multi-mode interferometer, and the second photodetector is used to receive output signals from two output ends of the fourth multi-mode interferometer.

4. The on-chip integrated homodyne Doppler vibrometer according to claim 3, characterized in that: The first photodetector and the second photodetector are both balanced photodetectors.

5. The on-chip integrated homodyne Doppler vibrometer according to claim 1, characterized in that: It also includes a first edge coupler, wherein the input end of the first edge coupler is coupled to the first output end of the first multi-mode interferometer, and the output end of the first edge coupler is used to output the signal light beam.

6. The on-chip integrated homodyne Doppler vibrometer according to claim 1, characterized in that: It also includes a second edge coupler, the input end of the second edge coupler is used to receive the signal light beam returned by the target to be measured, and the output end of the second edge coupler is coupled to the first input end of the fifth multi-mode interferometer.

7. The on-chip integrated homodyne Doppler vibrometer according to claim 1, characterized in that: The first multi-mode interferometer, the second multi-mode interferometer, the third multi-mode interferometer, the fourth multi-mode interferometer and the fifth multi-mode interferometer are connected through an optical waveguide located at one side of the substrate.

8. The on-chip integrated homodyne Doppler vibrometer according to claim 7, characterized in that: The optical waveguide is a silicon waveguide.

9. A homodyne Doppler vibration measuring device, characterized in that: It comprises a light source, a circulator, a homodyne Doppler vibrometer as claimed in any one of claims 1 to 8, and a processor; The output beam of the light source is incident on the homodyne Doppler vibrometer and is divided into a signal beam and a reference beam. The signal beam is output from the homodyne Doppler vibrometer and is incident on the first end of the circulator, and is output from the second end of the circulator to the target to be measured. The signal beam returned by the target to be measured is incident from the second end of the circulator, emitted from the third end of the circulator and coupled into the homodyne Doppler vibrometer. The signal light beam and the reference light beam interfere with each other in the homodyne Doppler vibrometer, and the processor determines the vibration information of the target to be measured according to the interference signal.

10. The homodyne Doppler vibration measuring device according to claim 9, characterized in that: It also includes a first optical fiber array and a second optical fiber array, the first optical fiber array is used to transmit the signal light beam output by the homodyne Doppler vibrometer to the first end of the circulator, and the second optical fiber array is used to transmit the signal light beam output by the third end of the circulator to the homodyne Doppler vibrometer.

11. An application of the homodyne Doppler vibration measuring device according to claim 9 or 10, characterized in that: The homodyne Doppler vibration measuring device is used to realize cardiac pump function evaluation, heartbeat monitoring, heart sound monitoring or respiratory parameter monitoring.

Images