On-chip integrated heterodyne Doppler vibration meter and vibration measuring device

Abstract

The invention discloses an on-chip integrated heterodyne Doppler vibration meter and a vibration measuring device. The heterodyne Doppler vibration meter comprises a substrate; the first multi-mode interferometer, the frequency shifter, 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; 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 frequency 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 returned signal light beam enters a 90-degree mixer, a frequency shifter realizes frequency shift of the reference light beam, heterodyne interference of the signal light beam and the reference light beam is realized in the 90-degree mixer, and the heterodyne interference of the to-be-measured target is realized. In-phase components and quadrature components of the signals are obtained, complete phase and amplitude information is obtained, and vibration measurement of the to-be-measured target is achieved. The 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 technical field of interference measurement, and in particular to an on-chip integrated heterodyne Doppler vibrometer and a vibration measuring device. Background Art

[0002] Laser Doppler Vibrometer (LDV) is a measuring instrument that uses the laser Doppler effect and optical heterodyne interference 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 heterodyne Doppler vibrometer and a vibration measuring device, 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 heterodyne Doppler vibrometer, comprising:

[0006] substrate;

[0007] A first multimode interferometer, a frequency shifter, 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 multi-mode interferometer is coupled with the output end of the light source, the first output end of the first multi-mode interferometer is used to output a signal light beam to the target to be measured, the second output end of the first multi-mode interferometer is coupled with the input end of the frequency shifter, the output end of the frequency shifter is coupled with the input end of the second multi-mode interferometer, the first output end of the second multi-mode interferometer is coupled with the first input end of the third multi-mode interferometer, the second output end of the second multi-mode interferometer is coupled with the first input end of the fourth multi-mode interferometer, the first input end of the fifth multi-mode interferometer is used to receive the signal light beam returned by the target to be measured, the second input end of the fifth multi-mode interferometer is vacant, the first output end of the fifth multi-mode interferometer is coupled with the second input end of the third multi-mode interferometer, the second output end of the fifth multi-mode interferometer is coupled with the second input end of the fourth multi-mode interferometer, 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° 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 multimode interferometer to the frequency shifter, and is incident on the 90° mixer after being shifted by a preset frequency by the frequency shifter. The signal beam and the reference beam interfere in the 90° mixer, and an in-phase component and an orthogonal component are output.

[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 Doppler vibrometer device, comprising a light source, a circulator, the heterodyne Doppler vibrometer described above, and a processor;

[0019] The output beam of the light source is incident on the heterodyne Doppler vibrometer and is divided into a signal beam and a reference beam. The signal beam is output from the heterodyne Doppler vibrometer and 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 heterodyne Doppler vibrometer. The reference beam moves a preset frequency in the heterodyne Doppler vibrometer.

[0020] The signal light beam and the reference light beam interfere with each other in the heterodyne 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 heterodyne 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 heterodyne Doppler vibrometer.

[0022] The on-chip integrated heterodyne Doppler vibrometer provided by the embodiment of the present invention includes a substrate and a first multimode interferometer, a frequency shifter, 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 frequency shift of the reference beam is realized by the frequency shifter, the signal beam and the reference beam realize heterodyne 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 heterodyne Doppler vibrometer is integrated on the same chip, and has the advantages of small size, low power consumption and low cost.

[0023] 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

[0024] 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.

[0025] Figure 1 A structural block diagram of an on-chip integrated heterodyne Doppler vibrometer provided by an embodiment of the present invention;

[0026] Figure 2 It is a structural schematic diagram of a 90° mixer;

[0027] Figure 3 A schematic diagram of the structure of a frequency shifter provided by an embodiment of the present invention;

[0028] Figure 4 This is the waveform diagram of the sawtooth wave loaded on the frequency shifter;

[0029] Figure 5 A structural block diagram of another on-chip integrated heterodyne Doppler vibrometer provided by an embodiment of the present invention;

[0030] Figure 6 A structural block diagram of another on-chip integrated heterodyne Doppler vibrometer provided by an embodiment of the present invention;

[0031] Figure 7A structural block diagram of a Doppler vibration measuring device provided by an embodiment of the present invention;

[0032] Figure 8 A structural block diagram of another Doppler vibration measuring device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] 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.

[0034] 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.

[0035] 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 heterodyne 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 heterodyne Doppler vibrometer, including: a substrate; a first multimode interferometer, a frequency shifter, 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, the second output end of the first multimode interferometer is coupled to the input end of the frequency shifter, and the third multimode interferometer, the fourth multimode interferometer and the fifth multimode interferometer each including two input ends and two output ends. The output end of the frequency converter is coupled with the input end of the second multi-mode interferometer, the first output end of the second multi-mode interferometer is coupled with the first input end of the third multi-mode interferometer, the second output end of the second multi-mode interferometer is coupled with the first input end of the fourth multi-mode interferometer, the first input end of the fifth multi-mode interferometer is used to receive the signal light beam returned by the target to be measured, the second input end of the fifth multi-mode interferometer is vacant, the first output end of the fifth multi-mode interferometer is coupled with the second input end of the third multi-mode interferometer, the second output end of the fifth multi-mode interferometer is coupled with the second input end of the fourth multi-mode interferometer, 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° mixer.

[0036] Among them, the on-chip integrated heterodyne 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 already 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.

[0037] Figure 1 A structural block diagram of an on-chip integrated heterodyne Doppler vibrometer provided by an embodiment of the present invention, see Figure 1 The heterodyne Doppler vibrometer 10 integrated on the chip includes a first multimode interferometer 1, a frequency shifter 2, a second multimode interferometer 3, a third multimode interferometer 4, a fourth multimode interferometer 5 and a fifth multimode interferometer 6. The first multimode interferometer 1 and the second multimode interferometer 3 each include an input end and two output ends, and the third multimode interferometer 4, the fourth multimode interferometer 5 and the fifth multimode interferometer 6 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 7, the first output end of the first multimode interferometer 1 is used to output a signal beam to a target 8 to be measured, the second output end of the first multimode interferometer 1 is coupled to the input end of the frequency shifter 2, and the output end of the frequency shifter 2 is coupled to the second multimode interferometer 1. The input end of the second multimode interferometer 3 is coupled, the first output end of the second multimode interferometer 3 is coupled with the first input end of the third multimode interferometer 4, the second output end of the second multimode interferometer 3 is coupled with the first input end of the fourth multimode interferometer 5, the first input end of the fifth multimode interferometer 6 is used to receive the signal light beam returned by the target 8 to be measured, the second input end of the fifth multimode interferometer 6 is vacant, the first output end of the fifth multimode interferometer 6 is coupled with the second input end of the third multimode interferometer 4, the second output end of the fifth multimode interferometer 6 is coupled with the second input end of the fourth multimode interferometer 5, and the second multimode interferometer 3, the third multimode interferometer 4, the fourth multimode interferometer 5 and the fifth multimode interferometer 6 form a 90° mixer.

[0038] 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.

[0039] In this embodiment, two 1×2 MMIs (a first multimode interferometer 1 and a second multimode interferometer 3) and three 2×2 MMIs (a third multimode interferometer 4, a fourth multimode interferometer 5 and a fifth multimode interferometer 6) are used. Figure 2 This is a schematic diagram of the 90° mixer structure. Figure 2, wherein the second multimode interferometer 3, the third multimode interferometer 4, the fourth multimode interferometer 5 and the fifth multimode interferometer 6 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 3) 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.

[0040] 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.

[0041] (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.

[0042] (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.

[0043] (4) Achieve efficient digital signal processing: The I and Q signals generated by the 90° mixer facilitate subsequent digital signal processing (DSP).

[0044] Figure 3 A schematic diagram of the structure of a frequency shifter provided by an embodiment of the present invention, Figure 4 For the sawtooth wave waveform loaded on the frequency shifter, refer to Figure 3 and Figure 4 The structure of the frequency shifter on a silicon photonic chip based on sawtooth wave modulation is a doped silicon waveguide. The laser is coupled in from one end and output from the other end. The phase of the optical signal is changed by adjusting the refractive index of the silicon waveguide to produce a periodic sawtooth wave change of 0 to 2π. The output optical signal will shift in frequency, and the frequency shift is the frequency of the applied sawtooth wave. In theory, the change in frequency can be observed through an optical spectrometer.

[0045] according to E in =E0×e jωt , Can get The waveguide that forms the frequency shifter on a silicon photonic chip generally adopts a ridge waveguide structure. Electrodes are made on both sides of the waveguide. The sawtooth wave electrical signal generated by the arbitrary waveform generator is loaded on the electrodes, so that the refractive index of the waveguide also undergoes sawtooth modulation. The frequency shifter on a silicon photonic chip has two working modes: (1) Forward bias: The refractive index is changed by injecting carriers to increase the carrier concentration in the waveguide. The efficiency is extremely high and the device size is short (<1mm). Limited by the carrier lifetime, the frequency shift range is short 0~50MHZ. (2) Reverse bias: The refractive index is changed by depleting carriers to reduce the carrier concentration in the waveguide. The efficiency is low and the device is relatively long (3mm). Using the plasma dispersion effect, the frequency shift range is as long as 0-1GHz. In principle, the on-chip frequency shifter shifts the frequency of the local oscillator light. For example, the local oscillator light with a frequency of xMHz is shifted by 50MHz (x+50) after the frequency shifter. Another signal light (with the same frequency of xMHz as the local oscillator light) is reflected by the object and has a shift of 10MHz (x±10, the sign depends on the direction of movement). Then the beat frequency of the two is 40MHz or 60MHz, which can be used to determine the direction of movement of the target to be measured. If there is no frequency shifter, there is no positive or negative sign on the spectrum, and the direction of movement of the target to be measured cannot be determined. When using a 90° mixer, there is no frequency shift, but the positive and negative frequencies are spread out on the spectrum, and the positive and negative frequencies, that is, the direction of movement of the target to be measured, can also be obtained.

[0046] Optional, continue to refer to Figure 1, the output beam of the light source 7 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 8 to be measured, and the signal beam including the vibration information of the target to be measured returned by the target 8 to be measured is incident on the 90° mixer from the first input end of the fifth multimode interferometer 6; the reference beam is output from the second output of the first multimode interferometer 1 to the frequency shifter 2, and is incident on the 90° mixer after being shifted by a preset frequency by the frequency shifter 2, the signal beam and the reference beam interfere in the 90° mixer, and output an in-phase component and an orthogonal component.

[0047] Optionally, the first multimode interferometer 1, the second multimode interferometer 3, the third multimode interferometer 4, the fourth multimode interferometer 5 and the fifth multimode interferometer 6 are connected via an optical waveguide located on one side of the substrate. Optionally, the optical waveguide is a silicon waveguide.

[0048] 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 frequency shift of the reference beam is realized by a frequency shifter, the signal beam and the reference beam realize heterodyne interference in the 90° mixer, and the in-phase component and 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 heterodyne Doppler vibrometer is integrated on the same chip, and has the advantages of small size, low power consumption, and low cost.

[0049] Figure 5 A structural block diagram of another on-chip integrated heterodyne Doppler vibrometer provided by an embodiment of the present invention is shown in FIG. Figure 5 Optionally, the heterodyne Doppler vibrometer also includes a first photodetector 9 and a second photodetector 11, the first photodetector 9 is used to receive output signals from two output ends of the third multimode interferometer 4, and the second photodetector 11 is used to receive output signals from two output ends of the fourth multimode interferometer 5.

[0050] The first photodetector 9 and the second photodetector 11 are used to convert the optical signal into an electrical signal, and obtain the vibration information of the target 8 to be measured according to the electrical signal. The first photodetector 9 and the second photodetector 11 can also be integrated on a chip to reduce the volume. Optionally, the first photodetector 9 and the second photodetector 11 are both balanced photodetectors.

[0051] Figure 6 A structural block diagram of another on-chip integrated heterodyne Doppler vibrometer provided by an embodiment of the present invention is shown in FIG. Figure 6Optionally, the heterodyne Doppler vibrometer further includes a first edge coupler 12, an input end of the first edge coupler 12 is coupled to a first output end of the first multimode interferometer 1, and an output end of the first edge coupler 12 is used to output a signal light beam.

[0052] Optional, continue to refer to Figure 6 The heterodyne Doppler vibrometer also includes a second edge coupler 13 , an input end of the second edge coupler 13 is used to receive a signal light beam returned by the target 8 to be measured, and an output end of the second edge coupler 13 is coupled to a first input end of the fifth multimode interferometer 5 .

[0053] Setting an edge coupler can improve the beam quality and enhance the performance of the heterodyne Doppler vibrometer.

[0054] Figure 7 A structural block diagram of a Doppler vibration measuring device provided by an embodiment of the present invention, referring to Figure 7 The Doppler vibrometer device includes a light source 7, a circulator 14, any one of the heterodyne Doppler vibrometers 10 provided in the above embodiments, and a processor 15; the output light beam of the light source 7 (which may be a laser, but is not a limitation of the embodiments of the present invention) is incident on the heterodyne Doppler vibrometer 10 and is divided into a signal light beam and a reference light beam; the signal light beam is output from the heterodyne Doppler vibrometer 10 and is incident on the first end of the circulator 14, and is output from the second end of the circulator 14 to the target 8 to be measured; the signal light beam returned by the target 8 to be measured is incident from the second end of the circulator 14, and is emitted from the third end of the circulator 14 and coupled into the heterodyne Doppler vibrometer 10; the reference light beam moves at a preset frequency in the heterodyne Doppler vibrometer 10; the signal light beam and the reference light beam interfere with each other in the heterodyne Doppler vibrometer 10, and the processor 15 determines the vibration information of the target 8 to be measured according to the interference signal.

[0055] The Doppler vibration measuring device provided in the embodiment of the present invention includes the heterodyne Doppler vibration measuring instrument provided in the above embodiment, and has the same or corresponding technical effects as the heterodyne Doppler vibration measuring instrument, which will not be described in detail here.

[0056] Figure 8 A structural block diagram of another Doppler vibration measuring device provided by an embodiment of the present invention is shown in FIG. Figure 8 Optionally, the Doppler vibrometer device also includes a first optical fiber array 16 and a second optical fiber array 17, the first optical fiber array 16 is used to transmit the signal light beam output by the heterodyne Doppler vibrometer 10 to the first end of the circulator 14, and the second optical fiber array 17 is used to transmit the signal light beam output by the third end of the circulator 14 to the heterodyne Doppler vibrometer 10.

[0057] By providing the first optical fiber array 16 and the second optical fiber array 17, the light beam can be transmitted in the optical fiber, thereby reducing light loss and helping to improve system performance.

[0058] 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 heterodyne Doppler vibrometer, characterized in that: include: substrate; A first multimode interferometer, a frequency shifter, 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 multi-mode interferometer is coupled with the output end of the light source, the first output end of the first multi-mode interferometer is used to output a signal light beam to the target to be measured, the second output end of the first multi-mode interferometer is coupled with the input end of the frequency shifter, the output end of the frequency shifter is coupled with the input end of the second multi-mode interferometer, the first output end of the second multi-mode interferometer is coupled with the first input end of the third multi-mode interferometer, the second output end of the second multi-mode interferometer is coupled with the first input end of the fourth multi-mode interferometer, the first input end of the fifth multi-mode interferometer is used to receive the signal light beam returned by the target to be measured, the second input end of the fifth multi-mode interferometer is vacant, the first output end of the fifth multi-mode interferometer is coupled with the second input end of the third multi-mode interferometer, the second output end of the fifth multi-mode interferometer is coupled with the second input end of the fourth multi-mode interferometer, 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° mixer.

2. The on-chip integrated heterodyne 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 multimode interferometer to the frequency shifter, and is incident on the 90° mixer after being shifted by a preset frequency by the frequency shifter. The signal beam and the reference beam interfere in the 90° mixer, and an in-phase component and an orthogonal component are output.

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

9. A Doppler vibration measuring device, characterized in that: It comprises a light source, a circulator, a heterodyne 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 heterodyne Doppler vibrometer and is divided into a signal beam and a reference beam. The signal beam is output from the heterodyne Doppler vibrometer and 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 heterodyne Doppler vibrometer. The reference beam moves a preset frequency in the heterodyne Doppler vibrometer. The signal light beam and the reference light beam interfere with each other in the heterodyne Doppler vibrometer, and the processor determines vibration information of the target to be measured according to the interference signal.

10. The 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 heterodyne 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 heterodyne Doppler vibrometer.

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