Cantilever beam type optical acoustic sensor with reverse interdigital structure

Abstract

The invention relates to the technical field of sensors, in particular to a cantilever beam type optical acoustic sensor with an inverse interdigital structure, which is characterized in that a diaphragm is processed to form an inverse interdigital-cantilever beam composite structure, a cantilever beam is fixed on the diaphragm through a fixed end, and a free end is suspended and used for reflecting an optical signal; the cantilever beam is formed by alternately distributing light-transmitting areas and supporting areas which are formed by two groups of parallel arrays, original diaphragm materials are reserved in the supporting areas, and the light-transmitting areas on the cantilever beam are of reverse interdigital structures; and the optical detection structure is used for emitting an optical signal, enabling the optical signal to irradiate the reflective surface of the free end of the reverse interdigital-cantilever beam composite structure for reflection, and receiving the optical signal reflected by the reflective surface. According to the inverse interdigital structure in the sensor, the enhancement of the pressure sensitivity of the sensor can be realized by adjusting the mass distribution of the fixed end of the cantilever beam, the resonant frequency of the inverse interdigital-cantilever beam composite structure can be effectively changed by adjusting the structural parameters of the inverse interdigital structure, and the enhancement of the sensitivity of the directional frequency is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, especially the fields of micro-vibration detection and acoustic detection, and particularly to a cantilever optical acoustic sensor with an inverse interdigital structure. Background Art

[0002] As a new sensing technology, optical acoustic sensors have shown significant application value in multiple fields in recent years. Compared with traditional piezoelectric and capacitive acoustic sensors, this technology has unique advantages in anti-electromagnetic interference and high sensitivity, and has been successfully applied in photoacoustic spectroscopy analysis, natural disaster warning, medical imaging diagnosis, industrial process monitoring and other scenarios, especially showing excellent performance in strong electromagnetic environments and complex working conditions.

[0003] According to the differences in modulation principles, optical acoustic sensors can be divided into five major technical branches: acousto-optic modulation type, interference type, intensity modulation type, wavelength modulation type, and polarization modulation type. Among them, the sensor system based on the Fabry-Perot cavity structure has become a current research hotspot due to its advantages of miniaturized design and ultra-high detection sensitivity. This special optical resonance structure can not only achieve accurate measurement of mechanical vibration in high-temperature environments, but also has breakthrough applications in fields such as environmental parameter monitoring, biomedical detection, and industrial non-destructive testing.

[0004] Optical acoustic sensors with a Fabry-Perot cavity as the main structure usually consist of a sensing diaphragm and an optical detection structure, and the most critical component is the sensing diaphragm. Among the selections of sensing diaphragms, the cantilever beam structure stands out with its high sensitivity, high linearity, and high reliability. The cantilever beam structure will vibrate under external pressure, and the sensitivity of the entire optical acoustic sensor directly depends on the amplitude of the cantilever beam structure. The larger this amplitude, the higher the sensitivity. In existing cantilever optical acoustic sensors, in order to increase the amplitude, the cantilever beam structure mostly adopts a simple hollow design. Although the simple hollow design reduces the stiffness and mass of the sensing diaphragm, it sacrifices the structural stability. There is a high demand in real life for a cantilever beam with high sensitivity and relatively stable structure, but this application demand has not been met yet. Summary of the Invention

[0005] To solve the above problems, the present invention proposes a cantilever optical acoustic sensor with an inverse interdigital structure to at least partially solve at least one of the above-mentioned technical problems.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] In the first technical solution, a cantilever optical acoustic sensor with an inverse interdigital structure is characterized by including

[0008] A diaphragm, on which an inverse interdigital-cantilever beam composite structure is formed by machining. The main body of the inverse interdigital-cantilever beam composite structure is a cantilever beam. The first end of the cantilever beam is a fixed end connected to the main body of the diaphragm, and the second end of the cantilever beam is a free end formed by machining. The cantilever beam is fixed on the diaphragm at the fixed end, and the free end is suspended for reflecting optical signals. The cantilever beam is composed of an alternating distribution of a light-transmitting area and a supporting area formed by two groups of parallel arrays. The supporting area retains the original diaphragm material, and the light-transmitting area on the cantilever beam is an inverse interdigital structure;

[0009] An optical detection structure, which is used to emit an optical signal and make the optical signal irradiate on the reflective surface of the inverse interdigital-cantilever beam composite structure for reflection, and receive the optical signal reflected by the reflective surface;

[0010] The inverse interdigital-cantilever beam composite structure induces an acoustic signal to generate mechanical vibration, and the mechanical vibration modulates the optical signal before it is received by the optical detection structure.

[0011] In the first technical solution, preferably, the inverse interdigital-cantilever beam composite structure is made of stainless steel as the base material, and a cantilever beam and uniformly arranged inverse interdigital structures are formed by machining.

[0012] In the first technical solution, preferably, the inverse interdigital-cantilever beam composite structure and the diaphragm form a coplanar structure.

[0013] In the first technical solution, preferably, the inverse interdigital-cantilever beam composite structure and the diaphragm are an integral structure with the same material.

[0014] In the first technical solution, preferably, the irradiation area of the optical signal emitted by the optical detection structure on the reflective surface of the inverse interdigital-cantilever beam composite structure is the area with the largest vibration amplitude of the inverse interdigital-cantilever beam composite structure.

[0015] In the first technical solution, preferably, the optical detection structure includes

[0016] A quartz tube, on which a diaphragm is arranged at the first end;

[0017] A glass capillary tube, which is placed inside the quartz tube from the second end of the quartz tube;

[0018] A handheld protective bracket, which is installed at the tail end of the glass capillary tube;

[0019] A single-mode optical fiber, which passes through the handheld protective bracket and the glass capillary tube, and the light-emitting end and the light-receiving end of the single-mode optical fiber face the diaphragm direction.

[0020] In the first technical solution, preferably, the emitting end face of the single-mode optical fiber is opposite to the reflecting face of the inverse interdigital-cantilever composite structure and the distance therebetween is not greater than 500 μm.

[0021] In the first technical solution, preferably, the diaphragm thickness is 5 μm to 100 μm; the inverse interdigital structure is located on one side of the fixed end; the marked width of the light-transmitting area of the inverse interdigital structure is 20 μm to 60 μm, and the marked pitch is 100 μm to 300 μm.

[0022] In the first technical solution, preferably, the cantilever optical acoustic sensor with an inverse interdigital structure according to claim 7 is characterized in that: the cantilever optical acoustic sensor with an inverse interdigital structure serves as an acoustic sensing probe.

[0023] The beneficial effects of using the present invention are:

[0024] The cantilever optical acoustic sensor with an inverse interdigital structure proposed by the present invention is used for the diaphragm of the circular substrate frame for making this structure, the cantilever beam of this diaphragm, and the inverse interdigital structure prepared by processing technologies such as laser, MEMS, and micro-nano at the fixed end of the cantilever beam. The present invention also discloses the manufacturing method of this cantilever beam and its application in a non-intrinsic Fabry-Perot interferometric fiber optic acoustic wave sensor. The inverse interdigital structure is composed of two groups of parallel arrays, and a microstructure with alternating light-transmitting areas and supporting areas is formed by laser etching. The inverse interdigital structure can enhance the pressure sensitivity of the sensor by adjusting the mass distribution at the fixed end of the cantilever beam to reduce the stiffness and effective mass of the cantilever beam. At the same time, by adjusting the structural parameters of the inverse interdigital structure, the resonance frequency of the inverse interdigital-cantilever composite structure can be effectively changed to enhance the sensitivity of the directional frequency. The optical detection structure is used to emit an optical signal and make the optical signal irradiate and be reflected on this reflecting face, and receive the optical signal reflected by this reflecting face. The present invention creatively proposes a novel cantilever structure, which has a small volume, high sensitivity, and good durability, and has broad application prospects in fields such as deep water detection, photoacoustic spectroscopy gas detection, medical detection, and industrial equipment diagnosis. Description of the Drawings

[0025] Figure 1 It is a schematic structural diagram of a cantilever optical acoustic sensor with an inverse interdigital structure proposed by the present invention;

[0026] Figure 2 It is a top view of the diaphragm proposed by the present invention;

[0027] Figure 3 It is a top view of the inverse interdigital-cantilever composite structure proposed by the present invention;

[0028] Figure 4This is a schematic diagram of the illumination area of the light signal emitted by the optical detection structure proposed in the present invention on the reflective surface of the inverted interdigital-cantilever beam composite structure;

[0029] Figure 5 A top view of the inverted interdigitated-cantilever beam composite structure proposed by the present invention, wherein the free end thereof is circular;

[0030] Figure 6 A top view of a rectangular free end of the inverted interdigitated-cantilever beam composite structure proposed by the present invention;

[0031] Figure 7 This is the time domain response curve of a cantilever optical acoustic sensor with an inverse interdigital structure proposed in the present invention at 1000 Hz;

[0032] Figure 8 This is the frequency domain response curve of a cantilever beam optical acoustic sensor with an inverse interdigital structure proposed in the present invention at 1000 Hz.

[0033] Figure 9 This is a stress analysis diagram of the inverted interdigitated-cantilever beam composite structure proposed in the present invention.

[0034] In the above drawings, the meanings of the reference numerals are as follows:

[0035] 1-diaphragm, 2-quartz tube, 3-glass capillary, 4-handheld protective bracket, 5-single-mode optical fiber, 6-fixed end, 7-inverse interdigital structure array, 8-free end, 9-inverse interdigital-cantilever beam composite structure, 10-irradiation area. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of this technical solution more clear, the following technical solution is further described in detail in conjunction with specific implementation methods. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of this technical solution.

[0037] In order to solve the problem in the prior art that the stability and sensitivity of the sensing diaphragm 1 of the cantilever beam optical acoustic sensor cannot be taken into account at the same time, the present invention proposes a cantilever beam optical acoustic sensor with an inverse interdigital structure.

[0038] like Figure 1 As shown, this embodiment proposes a cantilever beam optical acoustic sensor with an inverted interdigital structure, wherein the optical detection structure includes a quartz tube 2, a glass capillary 3, a handheld protective bracket 4 and a single-mode optical fiber 5. The optical detection structure is used to emit a light signal and make the light signal irradiate the reflective surface of the inverted interdigital-cantilever beam composite structure 9 for reflection, and receive the light signal reflected by the reflective surface.

[0039] Specifically, the optical detection structure is a Fabry - Perot interference detection structure. The single - mode optical fiber 5 is inserted into the quartz tube 2 through the glass capillary 3. The end face of the single - mode optical fiber 5 is located below the reflective surface of the inverse interdigital - cantilever beam composite structure 9 and then fixed. After the end face of the single - mode optical fiber 5 is cut, it is arranged in a non - sealed cavity, so that the end face is opposite to the reflective surface of the inverse interdigital - cantilever beam composite structure 9 and the distance therebetween is not greater than 500 μm. The single - mode optical fiber 5 and the reflective surface of the inverse interdigital - cantilever beam composite structure 9 form an interference cavity of the Fabry - Perot interference detection structure. The optical signal emitted by the single - mode optical fiber 5 will be incident on Figure 3 the maximum amplitude region of the inverse interdigital - cantilever beam composite structure 9 as shown, and then return to the optical fiber. It should be noted here that the reflected light will deviate slightly from the incident path, but since the amplitude is still very small, the reflected light can still be received by the single - mode optical fiber 5.

[0040] As Figures 2 - 4 shown, in this embodiment, the inverse interdigital - cantilever beam composite structure 9 is formed on the diaphragm 1. The main body of the inverse interdigital - cantilever beam composite structure 9 is a cantilever beam. The first end of the cantilever beam is a fixed end 6 connected to the main body of the diaphragm 1, and the second end of the cantilever beam is a free end 8 formed by processing. The cantilever beam is fixed on the diaphragm 1 by the fixed end 6, and the free end 8 is suspended for reflecting optical signals. The cantilever beam is composed of an alternating distribution of a light - transmitting area and a supporting area formed by two groups of parallel arrays. The supporting area retains the original material of the diaphragm 1, and the light - transmitting area on the cantilever beam is an inverse interdigital structure.

[0041] The inverse interdigital - cantilever beam composite structure 9 is the core component of this sensor. The inverse interdigital - cantilever beam composite structure 9 senses the acoustic signal and generates mechanical vibration, and the mechanical vibration modulates the optical signal before it is received by the optical detection structure. The inverse interdigital - cantilever beam composite structure 9 of this embodiment includes a fixed end 6, an inverse interdigital structure array 7, and a free end 8. Among them, the inverse interdigital - cantilever beam composite structure 9 is connected to the main body of the diaphragm 1 through the fixed end 6; as Figure 1 shown, the optical detection structure of this embodiment emits an optical signal through the single - mode optical fiber 5 and makes the optical signal irradiate on Figure 3 the irradiation area 10 and receives the reflected optical signal; thus, the mechanical vibration generated by the inverse interdigital - cantilever beam composite structure 9 sensing the acoustic signal can modulate the optical signal before the optical signal is received by the optical detection structure.

[0042] The following will separately describe each component of the optical acoustic sensor of this embodiment in detail.

[0043] The material used in the inverse interdigital-cantilever composite structure 9 has elasticity. In different embodiments, the material used in the inverse interdigital-cantilever composite structure 9 is made of a single material such as silicon, metal, organic polymer, etc.; or is made of a multi-layer material or composite material made of a silicon-metal bilayer material, a silicon-organic polymer bilayer material, or a metal-organic polymer bilayer material. The thickness of the inverse interdigital-cantilever composite structure 9 is between 5 μm and 100 μm, and the specific thickness is determined by the material and actual requirements.

[0044] It should be noted that, as Figure 2 shown, the reflective surface of the inverse interdigital-cantilever composite structure 9 is marked into a regularly arranged inverse interdigital structure, and the unmarked area forms a dendritic support skeleton. The inverse interdigital structure can achieve a directional enhancement of the sound pressure sensitivity by adjusting the mass distribution, reducing the stiffness and the effective mass. At the same time, by adjusting the structural parameters of the inverse interdigital structure, the resonance frequency of the inverse interdigital-cantilever composite structure 9 can be effectively changed, realizing a sensitivity enhancement of the directional frequency.

[0045] Specifically, the thickness of the diaphragm 1 is 5 μm to 100 μm. The inverse interdigital structure array 7 is close to the fixed end 6 side, the marking width is 20 μm to 60 μm, and the marking pitch is 100 μm to 300 μm. The inverse interdigital-cantilever composite structure 9 is composed of an alternating distribution of a light-transmitting area and a support area formed by two groups of inverse interdigital structure arrays 7. The light-transmitting area part is etched through the diaphragm 1 by laser, and the support area retains the original diaphragm 1 material.

[0046] In this embodiment, the inverse interdigital-cantilever composite structure 9 and the diaphragm 1 are an integral structure with the same material, which is beneficial to the stability of the structure.

[0047] In this embodiment, the optical detection structure is a Fabry-Perot interference detection structure. The single-mode optical fiber 5 is inserted into the quartz tube 2 through the glass capillary 3. The end face of the single-mode optical fiber 5 is located below the reflective surface of the inverse interdigital-cantilever composite structure 9 and then fixed. The end face of the single-mode optical fiber 5 is cut and arranged in a non-closed cavity, so that the end face is opposite to the reflective surface of the inverse interdigital-cantilever composite structure 9 and the distance is not greater than 500 μm. The single-mode optical fiber 5 and the reflective surface of the inverse interdigital-cantilever composite structure 9 form an interference cavity of the Fabry-Perot interference detection structure. The optical signal emitted by the single-mode optical fiber 5 will be incident on the irradiation area 10 of the inverse interdigital-cantilever composite structure 9 as Figure 3 shown, that is, the maximum amplitude area, and then return to the optical fiber. It should be noted here that the reflected light will deviate slightly from the incident path, but since the amplitude is still very small, the reflected light can still be received by the single-mode optical fiber 5.

[0048] The sensing mechanism of this exemplary embodiment of the present invention is as follows: an external acoustic signal acts on the inverted interdigital-cantilever composite structure 9, causing it to elastically deform under the influence of the acoustic pressure. Compared to other conventional structures, this structure adjusts its mass distribution, reducing stiffness and effective mass. This allows the cantilever structure to generate a larger amplitude, resulting in a more dramatic change in the Fabry-Perot cavity length, thereby increasing the sensitivity of the optical acoustic sensor.

[0049] As an optional embodiment, in some embodiments, the inverse interdigitated-cantilever beam composite structure 9 may be appropriately modified.

[0050] The inverse interdigitated-cantilever beam composite structure 9 forms a coplanar structure with the diaphragm 1: preferably, the inverse interdigitated-cantilever beam composite structure 9 and the diaphragm 1 are an integral structure made of the same material; preferably, the inverse interdigitated-cantilever beam composite structure 9 is fixed to the diaphragm 1 by bonding or gluing.

[0051] The inverse interdigitated-cantilever beam composite structure 9 can also form a non-coplanar structure with the diaphragm 1: preferably, the inverse interdigitated-cantilever beam composite structure 9 and the diaphragm 1 are an integral structure made of the same material; preferably, the inverse interdigitated-cantilever beam composite structure 9 is fixed to the diaphragm 1 by bonding or gluing.

[0052] The material used in the inverse interdigitated-cantilever beam composite structure 9 is elastic; preferably, the material is made of a single material, preferably silicon, metal or organic polymer; preferably, the material is made of a multilayer material or a composite material, preferably a silicon-metal double-layer material, a silicon-organic polymer double-layer material or a metal-organic polymer double-layer material; the free end 8 of the inverse interdigitated-cantilever beam composite structure 9 can be circular or polygonal.

[0053] In this embodiment, by testing Figure 1 The time domain and frequency domain response curves of the cantilever optical acoustic sensor with an inverse interdigital structure at 1000 Hz are obtained.

[0054] First, the experiment was made Figure 1An optical acoustic sensor of cantilever beam type with inverse interdigital structure as shown. The stainless steel diaphragm 1 is bonded to a hollow quartz tube 2 with an outer diameter of 10 mm and an inner diameter of 6 mm through ultraviolet adhesive. At the other end of the quartz tube 2, a glass capillary 3 is used for optical fiber alignment and fixed with a handheld protective bracket 4. Then, a single-mode optical fiber 5 is inserted into the quartz insert to form a Fabry-Perot interference cavity between the end face of the optical fiber and the reflective surface of the inverse interdigital-cantilever composite structure 9. All the above connection steps use ultraviolet adhesive. The diaphragm 1 with the inverse interdigital-cantilever composite structure 9 is fabricated by a laser marking machine, and the thickness of the inverse interdigital-cantilever composite structure 9 is 15 μm. The rectangular structure has a length of 2.35 mm and a width of 1.6 mm. The inverse interdigital structure array 7 is 60.3 mm away from the fixed end, the slit spacing inside the inverse interdigital structure array 7 is 0.15 mm, and the distance between two groups of inverse interdigital structure arrays 7 is 0.15 mm. As Figure 5 , Figure 6 shown, in other embodiments, the cantilever beam can be rectangular or a non-standard beam structure of T-shaped. An interference cavity of the Fabry-Perot interference detection structure is formed by the end face of the single-mode optical fiber 5 and the reflective surface of the inverse interdigital-cantilever composite structure 9. The obtained interference cavity length information is converted into an electrical signal by a photodetector, and information storage and output are performed by a computer electrically connected thereto. A loudspeaker is placed 50 cm away from the diaphragm 1 to emit a sound wave of 1000 Hz, and the time-domain and frequency-domain response curves of the optical acoustic sensor of cantilever beam type with inverse interdigital structure at 1000 Hz obtained from the experiment are recorded and output by the computer.

[0055] Figure 7 The time-domain response curve of the optical acoustic sensor of cantilever beam type with inverse interdigital structure measured by the experiment is given. It can be seen from the figure that under the sound wave with basically constant sound pressure, the inverse interdigital-cantilever composite structure 9 vibrates uniformly, indicating the excellent reliability of an optical acoustic sensor of cantilever beam type with inverse interdigital structure designed by the present invention.

[0056] Figure 8 The frequency-domain response curve of the optical acoustic sensor of cantilever beam type with inverse interdigital structure measured by the experiment is given. It can be seen from the figure that a large sharp peak appears at the frequency corresponding to 1000 Hz, indicating that an optical acoustic sensor of cantilever beam type with inverse interdigital structure designed by the present invention has good selectivity for sound.

[0057] As Figure 9 shown, the interdigital-cantilever composite structure 9 will disperse the stress received by the cantilever beam to the break points of the interdigital structure in space. Due to the dispersion of the break points, the stress received by the cantilever beam will not be concentrated in a small area over a large range, making the structure more stable.

[0058] A cantilever beam structure based on an inverse interdigital structure and a sensor incorporating the same are proposed by the present invention. It relates to fields such as optical measurement, MEMS devices, pressure / force sensing, and piezoelectric signal conversion. The sensor includes: a circular substrate frame for fabricating the structure, a cantilever beam connected to the substrate frame, and an inverse interdigital structure prepared by processing technologies such as laser, MEMS, and micro-nano at the fixed end 6 of the cantilever beam. The present invention also discloses a method for fabricating the cantilever beam and its application in a non-intrinsic Fabry-Perot interferometric fiber optic acoustic wave sensor. The inverse interdigital structure is composed of two groups of parallel arrays, and a microstructure with alternating light-transmitting areas and support areas is formed by laser etching. The inverse interdigital structure can enhance the pressure sensitivity of the sensor by adjusting the mass distribution at the fixed end 6 of the cantilever beam, reducing the stiffness and effective mass of the cantilever beam. At the same time, by adjusting the structural parameters of the inverse interdigital structure, the resonance frequency of the inverse interdigital-cantilever beam composite structure 9 can be effectively changed, achieving enhanced sensitivity in the directional frequency. The optical detection structure is used to emit an optical signal and irradiate the optical signal onto the reflective surface for reflection, and to receive the optical signal reflected by the reflective surface. The sensor, with its small size, high sensitivity, and good durability, has broad application prospects in fields such as deep water detection, photoacoustic spectroscopy gas detection, medical detection, and industrial equipment diagnosis.

[0059] In this embodiment, an optical acoustic sensor is also proposed to be used as an acoustic sensing probe. The optical acoustic sensor further includes a photodetector for converting the optical signal received by the optical detection structure of the optical acoustic sensing element into an electrical signal for output.

[0060] It should be noted that in the description of the present invention, unless otherwise specified, the meaning of "a plurality of" is two or more; the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation to the present invention. In addition, terms such as "first", "second", "third", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. At the same time, in the description of the present invention, unless otherwise clearly specified and limited, the terms "connected" and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0061] The above content is only a preferred embodiment of the present invention. For those of ordinary skill in the art, many changes can be made in the specific implementation manners and application scopes according to the idea of the present technical content. As long as these changes do not depart from the concept of the present invention, they all fall within the protection scope of this patent.

Claims

1. A cantilever optical acoustic sensor with an inverse interdigital structure, characterized in that: including a diaphragm, on which an inverse interdigital-cantilever composite structure is formed by machining. The main body of the inverse interdigital-cantilever composite structure is a cantilever beam. The first end of the cantilever beam is a fixed end connected to the main body of the diaphragm, and the second end of the cantilever beam is a free end formed by machining. The cantilever beam is fixed on the diaphragm by the fixed end, and the free end is suspended for reflecting optical signals. The cantilever beam is composed of an alternating distribution of a light-transmitting area and a support area formed by two groups of parallel arrays. The support area retains the original diaphragm material, and the light-transmitting area on the cantilever beam is an inverse interdigital structure; an optical detection structure, which is used to emit an optical signal and make the optical signal irradiate on the reflective surface of the inverse interdigital-cantilever composite structure for reflection, and receive the optical signal reflected by the reflective surface; under the action of an external acoustic signal, the inverse interdigital-cantilever composite structure generates mechanical vibration, and the mechanical vibration modulates the optical signal before it is received by the optical detection structure.

2. The cantilever optical acoustic sensor with an inverse interdigital structure according to claim 1, characterized in that: The inverse interdigital-cantilever composite structure uses stainless steel material as the base material, and a cantilever beam and uniformly arranged inverse interdigital structures are formed by machining.

3. The cantilever optical acoustic sensor with an inverse interdigital structure according to claim 1, wherein: The inverse interdigital-cantilever composite structure and the diaphragm form a coplanar structure.

4. The cantilever optical acoustic sensor with an inverse interdigital structure according to claim 1, characterized in that: The inverse interdigital-cantilever composite structure and the diaphragm are an integral structure with the same material.

5. The cantilever optical acoustic sensor with an inverse interdigital structure according to claim 1, characterized in that: The irradiation area of the optical signal emitted by the optical detection structure on the reflective surface of the inverse interdigital-cantilever composite structure is the area with the largest vibration amplitude of the inverse interdigital-cantilever composite structure.

6. The cantilever optical acoustic sensor with an inverse interdigital structure according to claim 1, characterized in that: The optical detection structure includes a quartz tube, with a diaphragm provided at the first end of the quartz tube; a glass capillary tube, which is placed inside the quartz tube from the second end of the quartz tube; a handheld protective bracket, which is installed at the tail end of the glass capillary tube; a single-mode optical fiber, which passes through the handheld protective bracket and the glass capillary tube, and the light-emitting end and the receiving end of the single-mode optical fiber face the direction of the diaphragm.

7. The cantilever optical acoustic sensor with an inverse interdigital structure according to claim 6, wherein: The emission end face of the single-mode optical fiber is opposite to the reflective surface of the inverse interdigital-cantilever composite structure and the distance therebetween is not greater than 500 μm.

8. The cantilever optical acoustic sensor with an inverse interdigital structure according to claim 6, characterized in that: The thickness of the diaphragm is 5 μm to 100 μm; the inverse interdigital structure is located on the side of the fixed end; the marked width of the light-transmitting area of the inverse interdigital structure is 20 μm to 60 μm, and the marked spacing is 100 μm to 300 μm.

9. The cantilever optical acoustic sensor with an inverse interdigital structure according to claim 6, characterized in that: The cantilever beam type optical acoustic sensor with an inverse interdigital structure is used as an acoustic sensing probe.

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