Surface pressure measuring method and light and thin optical fiber pressure sensor thereof

Abstract

The invention provides a surface pressure measurement method and a light and thin type optical fiber pressure sensor thereof.The light and thin type optical fiber pressure sensor is prepared firstly, the light and thin type optical fiber pressure sensor and the surface of a shell to be measured are completely conformal, and during real-time measurement, after light is reflected on a total reflection prism, the angle is changed by 90 degrees, and then the light is emitted to a substrate and a diaphragm in sequence; and three beams of reflected light are formed on the lower surface of the substrate, the upper surface of the substrate and the lower surface of the diaphragm, a signal after interference of the three beams of reflected light enters spectrum detection equipment, and the measured pressure is obtained through spectrum demodulation. According to the invention, the sensor is installed by processing a groove in a surface to be measured or welding an auxiliary structure in the surface to be measured, the used optical fiber FP optical fiber pressure sensor enables a pressure diaphragm to be parallel to an optical fiber transmission direction finally through a special design, and the sensor is in a sheet-shaped trailing structure after being packaged. The device is very suitable for surface pressure measurement, is suitable for being integrated in a limited space, and has a good application prospect.

Description

Technical Field

[0001] This invention relates to the field of measurement and testing technology, specifically to a surface pressure measurement method and its thin and light fiber optic pressure sensor. Background Technology

[0002] Surface pressure measurement is of vital importance in high-end equipment manufacturing fields such as aerospace, automotive industry and high-speed train. It serves as a bridge between theoretical design, wind tunnel testing and actual performance, and directly determines the safety, economy and competitiveness of products.

[0003] Compared with traditional electronic sensors, fiber optic pressure sensors have the advantages of small size, light weight, fewer cables, strong resistance to electromagnetic interference, good electromagnetic isolation, inherent explosion-proof properties, long transmission distance, and strong environmental adaptability. They are very suitable for high-precision measurement in environments with strong electricity, strong magnetism, radiation, and extreme high and low temperatures. Currently, fiber optic pressure sensors are widely used in aerospace, nuclear industry, automotive industry, and intelligent transportation.

[0004] Commonly used intrinsic fiber optic pressure sensors (FP sensors) are mostly fiber optic with a diaphragm. Pressure changes cause deformation of the diaphragm, which in turn changes the cavity length of the FP sensor, resulting in changes in the interference signal output by the sensor. These sensors typically have a pressure-sensing diaphragm perpendicular to the fiber direction, and are often packaged as a cylindrical tail structure. Installation of this type of sensor usually requires drilling and threading or remote measurement via a pressure tube, affecting the accuracy of pressure measurement. Furthermore, their large size makes them unsuitable for integration into confined spaces. Summary of the Invention

[0005] This invention addresses the issue of large size in traditional fiber optic sensors by providing a surface pressure measurement method and a thin, lightweight fiber optic pressure sensor. The thin, lightweight fiber optic FP pressure sensor is mounted on the surface to be measured, allowing for conformal integration of the sensor with the surface, reducing the impact of sensor installation, and enabling more accurate pressure signal acquisition. Compared to traditional fiber optic sensors, it is small and lightweight, with side-mounted fiber optics, making it ideal for surface pressure measurement and showing great application potential.

[0006] This invention provides a surface pressure measurement method, comprising the following steps: S1. Fabrication of a thin and light fiber optic pressure sensor: A groove structure is fabricated on a substrate using MEMS technology. The upper surface of a diaphragm is polished and then covered on the groove. The diaphragm and the groove are bonded together to form a fully solid-state vacuum pressure-free cavity. The upper end of a total reflection prism with a 45° reflective surface is connected to the bottom of the substrate, and the output end is connected to the collimator's output port. The collimator is located on the lower side of the fully solid-state vacuum pressure-free cavity. The collimator, substrate, and total reflection prism are fixed inside the housing. The optical fiber and spectral detection equipment are sequentially connected to the collimator's output end to obtain a thin and light fiber optic pressure sensor. The optical fiber is located on the side of the housing, and the diaphragm is parallel to the optical fiber's transmission direction. S2. When the thickness of the housing to be tested is ≥5mm, a mounting groove is processed on the surface of the housing to be tested. The thin and light fiber pressure sensor and the pigtail are embedded into the mounting groove, and then the gap is filled to make the thin and light fiber pressure sensor completely conformal with the surface of the housing to be tested. When the thickness of the housing to be tested is less than 5mm, a pressure-sensing hole is drilled on the surface of the housing to be tested. At the same time, a C-shaped recess is welded inside the mounting hole to form a mounting groove. The thin and light fiber optic pressure sensor is embedded in the mounting groove, the sensitive face is aligned with the pressure-sensing hole, and then it is fixed and sealed. Finally, the pigtail is fixed to the inner surface of the housing to be tested. S3. Real-time measurement: The light emitted by the spectral detection equipment enters the collimator through the optical fiber. After being collimated by the collimator, it enters the total internal reflection prism. After being reflected by the total internal reflection prism, the light changes angle by 90° and is directed to the substrate and the membrane in sequence. Three reflected beams are formed on the lower surface of the substrate, the upper surface of the substrate, and the lower surface of the membrane. The signal after the interference of the three reflected beams enters the spectral detection equipment again through the total internal reflection prism, collimator, and optical fiber. The measured pressure is obtained by spectral demodulation.

[0007] In a preferred embodiment of the surface pressure measurement method of the present invention, in step S2, after embedding the thin and light fiber optic pressure sensor and the pigtail into the mounting groove, the gap is filled with glue. After embedding the thin and light fiber optic pressure sensor into the mounting groove and aligning the sensitive surface with the pressure-sensing hole, use glue to fix and seal the thin and light fiber optic pressure sensor.

[0008] In a preferred embodiment of the surface pressure measurement method of the present invention, the spectral demodulation method in step S3 is as follows: the frequency value is obtained by performing a Fourier transform on the interference spectrum detected by the spectral detection device, the cavity length L0 is obtained based on the frequency value, and then the external pressure P is calculated. The reflected light signal E1 from the lower surface of the substrate is: ; The reflected light signal E2 from the upper surface of the substrate is: ; The reflected light signal E3 from the lower surface of the diaphragm is: ; Where R1 is the reflection coefficient of the lower surface of the substrate, R2 is the reflection coefficient of the upper surface of the substrate, R3 is the reflection coefficient of the lower surface of the diaphragm, φ0 is the phase difference, n0 is the refractive index of the substrate, n1 is the refractive index of air, E0 is the intensity of the light signal output by the spectral detection device, and λ is the operating wavelength. i Let L0 be the distance from the membrane to the bottom of the substrate groove, and L1 be the distance from the bottom surface of the substrate to the bottom of the groove.

[0009] The surface pressure measurement method described in this invention, as a preferred embodiment, ; in, I The intensity of the interference light signal detected by the spectral detection equipment.

[0010] The surface pressure measurement method described in this invention, as a preferred embodiment, ; Where µ is Poisson's ratio, E is elastic modulus, h is the effective thickness of the diaphragm, and r is the effective radius of the diaphragm.

[0011] The present invention provides a thin and light fiber optic pressure sensor, which includes a diaphragm sealed and connected above a groove in a substrate, a total internal reflection prism connected to the lower part of the substrate, a collimator, an optical fiber, and a spectral detection device sequentially connected to the output optical path of the 45° reflecting surface of the total internal reflection prism, and a housing connected to the outside of the substrate, the total internal reflection prism, and the collimator. The total internal reflection prism is connected to the bottom of the transparent mirror box, and the upper part of the transparent mirror box is a circular plane with the same radius as the base. The range and sensitivity of thin and light fiber optic pressure sensors can be adjusted by changing the thickness and size of the diaphragm.

[0012] The thin and light fiber optic pressure sensor described in this invention, as a preferred embodiment, has a measuring range of 6 MPa. Where φ0 is the diameter of the all-solid vacuum pressure-relief cavity and H1 is the thickness of the diaphragm.

[0013] The thin and light fiber optic pressure sensor described in this invention, as a preferred embodiment, has a diaphragm thickness of 0.28 mm and a diameter of 1.4 mm for the all-solid-state vacuum pressure-resistant cavity.

[0014] In a preferred embodiment of the thin and light fiber optic pressure sensor described in this invention, the diaphragm and the substrate are made of quartz or sapphire, and the diaphragm and the substrate are assembled by laser bonding. Single-mode optical fiber can be made of acrylate, polyimide, or metal coating, depending on the operating temperature. The casing is made of metal; The collimator, substrate, and total reflection prism are fixed inside the housing by adhesive bonding or glass powder welding.

[0015] The thin and light fiber optic pressure sensor of the present invention, as a preferred embodiment, has a thickness of less than or equal to 2 mm for the all-solid vacuum pressure-resistant cavity, a total thickness of less than or equal to 6 mm for the thin and light fiber optic pressure sensor, and an optical fiber output through the side of the housing. The thin and light fiber optic pressure sensor can be used for pressure measurement from 0 to 6 MPa.

[0016] The present invention has the following advantages: This invention proposes a surface pressure measurement method based on a fiber optic FP pressure sensor. The sensor can be installed by machining grooves on the surface to be measured or by welding auxiliary structures inside the surface to be measured. The fiber optic FP pressure sensor used is specially designed so that the pressure diaphragm is parallel to the fiber transmission direction. After encapsulation, the sensor takes the form of a sheet-like trailing structure, which is very suitable for surface pressure measurement and can be integrated into a limited space, showing great application prospects. Attached Figure Description

[0017] Figure 1 A three-dimensional view of a surface pressure measurement method and its thin and light fiber optic pressure sensor; Figure 2 This is a schematic diagram of a surface pressure measurement method and its thin and light fiber optic pressure sensor. Figure 3 A flowchart of a surface pressure measurement method; Figure 4 This is a schematic diagram of a surface pressure measurement method and a pressure-sensitive chip of a thin and light fiber optic pressure sensor subjected to stress. Figure 5 This is a schematic diagram of the optical path propagation in the pressure-sensitive chip of a surface pressure measurement method and its thin and light fiber optic pressure sensor. Figure 6 This is a schematic diagram of the pressure-sensitive chip structure of a surface pressure measurement method and its thin and light fiber optic pressure sensor. Figure 7 This is a schematic diagram showing the structural dimensions of the pressure-sensitive chip of a surface pressure measurement method and its thin and light fiber optic pressure sensor. Figure 8 The figure shows the simulation results of the pressure-sensing diaphragm deformation under 6MPa for a surface pressure measurement method and its thin and light fiber optic pressure sensor. Figure 9 This figure shows the simulation results of the pressure-sensing diaphragm under 6MPa for a surface pressure measurement method and its thin and light fiber optic pressure sensor.

[0018] Figure label: 1. Diaphragm; 2. Substrate; 3. Total internal reflection prism; 4. Optical fiber; 5. Collimator; 6. Housing; 7. Spectroscopic detection equipment. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Example 1

[0020] like Figures 1-3 As shown, a surface pressure measurement method and its thin and light fiber optic pressure sensor are disclosed. The sensor consists of a diaphragm 1, a substrate 2, a total reflection prism 3, an optical fiber 4, a collimator 5, and a housing 6. The cavity length between the diaphragm and the substrate and the thickness of the substrate 2 are calculated by detecting the reflection spectrum of the diaphragm using a spectral detection device 7, so as to achieve the purpose of simultaneous measurement of pressure and temperature. Furthermore, the accuracy of pressure measurement can be improved by temperature compensation.

[0021] The light emitted by the spectral detection device 7 enters the sensor through the optical fiber 4, is collimated by the collimator 5, and then enters the total internal reflection prism 3. After the light is reflected by the total internal reflection prism, the angle changes by 90° and enters the substrate 2 and the diaphragm 1, forming three reflected beams on the lower surface of the substrate, the upper surface of the substrate, and the lower surface of the diaphragm. The signal after the above light interference enters the spectral detection device again through the total internal reflection prism 3, the collimator 5, and the optical fiber 4, so as to achieve the purpose of characterizing the pressure measurement value through spectral demodulation.

[0022] Diaphragm 1 and substrate 2 constitute a fiber optic FP pressure sensor MEMS pressure-sensitive chip. The materials of diaphragm 1 and substrate 2 can be quartz or sapphire. Substrate 2 is fabricated with a groove structure using MEMS technology. Diaphragm 1 and substrate 2 are assembled using laser bonding technology to form a fully solid-state vacuum pressure-resistant cavity. By adjusting the thickness and size of diaphragm 1, the range and sensitivity of the pressure sensor can be changed.

[0023] The upper surface of diaphragm 1 is roughened to prevent reflected light from forming on the upper surface.

[0024] One end of the total internal reflection prism 3 is connected to the substrate 2, and the other end is connected to the light outlet of the collimator 5. The total internal reflection prism 3 is designed with a 45° reflecting surface, which can realize the reversal of the light path.

[0025] Fiber 4 single-mode fiber can be coated with acrylate, polyimide, or metal depending on the operating temperature.

[0026] The operating wavelength range of collimator 5 needs to be compatible with the operating wavelength range of the fiber optic pressure sensor.

[0027] The housing 6 is used to protect and fix the various components, and the housing 6 is preferably made of a metal with a low coefficient of thermal expansion. The collimator 5, the substrate 2, and the total reflection prism 3 are fixed to the housing 6 by adhesive bonding or glass powder welding.

[0028] The spectral detection device 7 contains a light source suitable for the working wavelength of the fiber optic pressure sensor. It provides light to the sensor and detects its reflection spectrum to calculate the cavity length between the diaphragm and the substrate, thereby achieving the purpose of pressure measurement.

[0029] like Figure 3 As shown, this invention provides a surface pressure measurement method that allows a thin and light fiber optic pressure sensor to be mounted on the surface to be measured for surface pressure measurement. Includes the following steps: S1. Fabrication of a thin and light fiber optic pressure sensor; S2. For housings thicker than 5mm, a groove can be machined on the surface to embed the pressure sensor and fiber optic cable into the groove. Then, glue can be used to fill the gaps to make the sensor conform to the surface being measured, thus enabling accurate acquisition of surface pressure signals. For housings with thinner thickness, a hole is generally drilled on the surface, and a C-shaped recess is welded inside to form a groove. The sensor is then embedded in the groove, with the sensitive face aligned with the pressure-sensing hole. The sensor is then fixed in place with glue, ensuring a seal. Finally, the fiber optic cable is fixed to the inner surface of the housing. S3. Real-time measurement: The light emitted by the spectral detection equipment enters the collimator through the optical fiber. After being collimated by the collimator, it enters the total internal reflection prism. After being reflected by the total internal reflection prism, the light changes angle by 90° and is directed to the substrate and the membrane in sequence. Three reflected beams are formed on the lower surface of the substrate, the upper surface of the substrate, and the lower surface of the membrane. The signal after the interference of the three reflected beams enters the spectral detection equipment again through the total internal reflection prism, collimator, and optical fiber. The measured pressure is obtained by spectral demodulation.

[0030] like Figure 1 , 2 As shown, this invention proposes an optical fiber FP pressure sensor, which consists of a diaphragm 1, a substrate 2, a total reflection prism 3, an optical fiber 4, a collimator 5, and a housing 6. The cavity length between the diaphragm and the substrate and the thickness of the substrate 2 are calculated by detecting the reflection spectrum of the diaphragm using a spectral detection device 7, thereby achieving the purpose of simultaneous pressure and temperature measurement. Furthermore, the accuracy of pressure measurement can be improved through temperature compensation.

[0031] The light emitted by the spectral detection device 7 enters the sensor through the optical fiber 4, is collimated by the collimator 5, and then enters the total internal reflection prism 3. After the light is reflected by the total internal reflection prism, the angle changes by 90° and enters the substrate 2 and the diaphragm 1, forming three reflected beams on the lower surface of the substrate, the upper surface of the substrate, and the lower surface of the diaphragm. The signal after the above light interference enters the spectral detection device again through the total internal reflection prism 3, the collimator 5, and the optical fiber 4, so as to achieve the purpose of characterizing the pressure measurement value through spectral demodulation.

[0032] In this embodiment, the fiber optic FP pressure sensor diaphragm 1 and substrate 2 constitute a fiber optic FP pressure sensor MEMS pressure-sensitive chip. The materials of diaphragm 1 and substrate 2 can be quartz. Substrate 2 is fabricated with a groove structure using MEMS technology. Diaphragm 1 and substrate 2 are assembled using laser bonding to form a fully solid-state vacuum pressure-sensitive cavity. By adjusting the thickness and dimensions of diaphragm 1, the range and sensitivity of the pressure sensor can be changed. Taking a fiber optic FP pressure sensor for measuring pressure from 0 to 6 MPa as an example, simulation calculations show a chip diameter of 2.4 mm, a chip thickness of 1.2 mm, a pressure-sensing cavity diameter of 1.2 mm, a diaphragm 1 thickness of 0.4 mm, and a cavity length of 0.05 mm.

[0033] The fiber 4 is a single-mode fiber, and the coating layer selected in this embodiment is polyimide.

[0034] After encapsulation, the sensor has a diameter of 7mm and a thickness of 5mm, and the optical fiber is output through the side of the housing 6.

[0035] The all-solid-state vacuum pressure-free cavity formed by diaphragm 1 and substrate 2 is the core component of the sensor. A groove structure is fabricated between diaphragm 1 and substrate 2 using MEMS technology. After welding, the vacuum cavity is formed to achieve pressure sensing. Its theoretical model is as follows: Figure 4 As shown.

[0036] The chip is kept under vacuum. Under the pressure difference between the inside and outside, the diaphragm is indented into the chip. At this time, the displacement L of the center of the diaphragm, that is, the change in the length of the vacuum cavity, is: (1) Where P is the external pressure, µ is Poisson's ratio, E is the elastic modulus, h is the effective thickness of the diaphragm, and r is the effective radius of the diaphragm.

[0037] like Figure 5 As shown in the figure, when an optical signal is incident on the chip, the bottom of the chip substrate, the upper surface of the groove, the lower surface of the diaphragm, and the upper surface of the diaphragm reflect the optical signal, respectively. The upper surface of the groove and the lower surface of the diaphragm constitute a vacuum intrigued fiber Fabry-Perot interferometer (EFPI) cavity. As the external pressure changes, the diaphragm deforms under pressure, causing a change in the length of the EFPI cavity. Pressure information is obtained by measuring the change in the EFPI cavity length.

[0038] The upper surface of the diaphragm is polished to induce diffuse reflection, thus negligible reflection of light E4 and reducing one interference event. Therefore, for the above dual EFPI cavity structure, the reflected light signals E1, E2, and E3 can be written as follows: (2) (3) (4) The intensity I of the output reflected interference light signal can be expressed as: (5) The pressure response change in the vacuum EFPI chamber is mainly related to the diaphragm parameters. Pressure response characteristics can be controlled by designing the structural dimensions of the pressure-sensitive chip. The basic structural model is as follows: Figure 6 As shown.

[0039] The main mechanism of the sensitive chip is based on the theory of small deflection deformation of thin plates. When the applied pressure is uniformly applied to the center surface of the thin plate, in order to ensure the linear deformation of the thin plate, the maximum deflection change of the thin plate should be less than 1 / 5 of the thickness of the thin plate. That is, the chip can be deformed by applying external pressure, which will cause the optical interference intensity to change, thereby demodulating the pressure change.

[0040] like Figure 7 The diagram shows the structural dimensions of a pressure-sensitive chip. In the diagram, R1 is the outer diameter of the pressure-sensitive chip, H1 is the overall thickness of the pressure-sensitive chip, L0 is the cavity length, R0 is the diameter of the pressure-sensing cavity, and H0 is the thickness of the pressure-sensing diaphragm.

[0041] According to technical specifications, the fiber optic pressure sensor size should not exceed 6mm. Furthermore, considering MEMS chip fabrication and packaging technologies, the outer diameter R1 and overall thickness H1 of the pressure-sensitive chip should be designed to match the sensor's package size requirements. Simultaneously, based on the demodulation requirements of the Fourier transform-based enhancement algorithm and taking into account the chip fabrication etching process, the cavity length L0 is selected to be approximately 0.05mm. In addition, to ensure the bonding strength of the sensitive chip, the width of the bonding area should not be less than 0.4mm. Therefore, the optimal range for the pressure-sensing cavity diameter R0 can be determined.

[0042] According to (4-1), the key parameters affecting the mechanical response of the chip are the diaphragm thickness and diameter. The deformation Δz of the pressure-sensitive diaphragm is directly proportional to the fourth power of the effective radius a of the pressure-sensitive diaphragm 1, and inversely proportional to the third power of the diaphragm thickness h.

[0043] (4-1) According to the theory of small deflection deformation, the maximum deflection change of the pressure-sensitive diaphragm is at the center of the circle, which satisfies: (4-2) When the range is 6MPa, substituting into the above formula, we get:

[0044] When the diameter of the pressure-sensitive diaphragm is selected as φ0=1.2mm, the thickness of the pressure-sensitive diaphragm H0>66.1um.

[0045] When the maximum stress on the pressure-sensitive diaphragm exceeds the stress limit, the material will fracture, causing the sensor to fail. To meet safety principles, the formula for the maximum stress on the diaphragm can be used to derive: (4-3) When the range is 6MPa, substituting into the above formula, we get:

[0046] When the diameter of the pressure-sensitive diaphragm is selected as φ0=1.2mm, the thickness of the pressure-sensitive diaphragm is H0>38.4um.

[0047] Under the same pressure range, the thinner the pressure-sensitive diaphragm, the greater its deformation and the better its sensitivity. It's important to note that the diaphragm can be damaged during the fabrication of the sensitive chip due to factors such as wafer shape and thinning rate differences. In conventional designs, limited by process yield and wafer specifications, a diaphragm thickness of 40–600 μm is typically chosen.

[0048] Based on the size of the miniaturized sensitive cell and the difficulty of the bonding process, combined with demodulation requirements and packaging and testing requirements, the chip parameters are designed as shown in Table 1. Table 1 Chip Parameter Specifications

[0049] The chip structure design scheme was evaluated and verified using Comsol Multiphysics numerical simulation software. The chip parameters for a design range of 6 MPa are shown in Table 1, and the simulation results are as follows. Figure 8 , Figure 9 As shown, in this case, the diaphragm center displacement is 485 nm and the maximum stress is 24.7 MPa, which is also much smaller than the yield strength of quartz.

[0050] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method of surface pressure measurement, characterized by: It comprises the following steps: S1, preparing a light and thin optical fiber pressure sensor: a groove structure is processed on a substrate (2) by a MEMS process, the upper surface of a diaphragm (1) is polished and then covered on the groove, and the diaphragm (1) and the groove form a full solid vacuum absolute pressure cavity by bonding; a total reflection prism (3) with a 45° reflecting surface is connected to the bottom of the substrate (2) and the output end is connected to the light outlet of a collimator (5), the collimator (5) is located below the side of the full solid vacuum absolute pressure cavity, the collimator (5), the substrate (2) and the total reflection prism (3) are fixed in a shell (6), an optical fiber (4) and a spectrum detection device (7) are sequentially connected to the output end of the collimator (5), and the light and thin optical fiber pressure sensor is obtained, the optical fiber (4) is located on the side of the shell (6), and the diaphragm (1) is parallel to the transmission direction of the optical fiber (4); S2, when the thickness of a to-be-measured shell is greater than or equal to 5 mm, a mounting groove is processed on the surface of the to-be-measured shell, the light and thin optical fiber pressure sensor and a tail fiber are embedded into the mounting groove, and then the gap is filled to make the light and thin optical fiber pressure sensor completely conformal to the surface of the to-be-measured shell; when the thickness of the to-be-measured shell is less than 5 mm, a pressure sensing hole is obtained by punching the surface of the to-be-measured shell, a C-shaped concave table is welded in the mounting hole to form a mounting groove, the light and thin optical fiber pressure sensor is embedded into the mounting groove, the sensitive surface is aligned with the pressure sensing hole, and then the light and thin optical fiber pressure sensor is fixed and sealed, finally the tail fiber is fixed on the inner surface of the to-be-measured shell; S3, real-time measurement: the light emitted by the spectrum detection device (7) enters the collimator (5) through the optical fiber (4), is collimated by the collimator (5) and then enters the total reflection prism (3), the light is reflected on the total reflection prism (3) and the angle is changed by 90°, and then the light is sequentially shot to the substrate (2) and the diaphragm (1), three reflected lights are formed on the lower surface of the substrate, the upper surface of the substrate and the lower surface of the diaphragm, the signals of the three reflected lights after interference enter the spectrum detection device (7) through the total reflection prism (3), the collimator (5) and the optical fiber (4), and the measured pressure is obtained by spectrum demodulation.

2. A method of surface pressure measurement according to claim 1, characterized in that: In step S2, after the light and thin optical fiber pressure sensor and the tail fiber are embedded into the mounting groove, the gap is filled with glue; after the light and thin optical fiber pressure sensor is embedded into the mounting groove and the sensitive surface is aligned with the pressure sensing hole, the light and thin optical fiber pressure sensor is fixed and sealed with glue.

3. The method of claim 1, wherein: In step S3, the method of spectrum demodulation is: the frequency value is obtained by Fourier transform of the interference spectrum detected by the spectrum detection device (7), then the cavity length L0 is obtained according to the frequency value, and then the external applied pressure P is calculated; the reflected light signal E1 of the lower surface of the substrate is: ； the reflected light signal E2 of the upper surface of the substrate is: ； the reflected light signal E3 of the lower surface of the diaphragm is: ； wherein R1 is the reflection coefficient of the lower surface of the substrate, R2 is the reflection coefficient of the upper surface of the substrate, R3 is the reflection coefficient of the lower surface of the film, φ0 is the phase difference, n0 is the refractive index of the substrate, n1 is the refractive index of air, E0 is the intensity of the light signal output by the optical spectrum detection device (7), and λ is the working wavelength, i is the imaginary part, L0 is the distance from the film (1) to the bottom of the groove of the substrate (2), and L1 is the distance from the bottom surface of the substrate (2) to the bottom of the groove.

4. The surface pressure measurement method according to claim 3, characterized in that: ； wherein I is the intensity of the interference light signal detected by the optical spectrum detection device (7).

5. The surface pressure measurement method of claim 4, wherein: wherein µ is Poisson's ratio, E is the modulus of elasticity, h is the effective thickness of the diaphragm (1), and r is the effective radius of the diaphragm (1). ； The light and thin optical fiber pressure sensor comprises the diaphragm (1) sealedly connected above the groove of the base (2), the total reflection prism (3) connected to the lower part of the base (2), the collimator (5), the optical fiber (4) and the spectrum detection device (7) connected in sequence to the 45° reflection surface output light path of the total reflection prism (3), and the shell (6) connected to the outside of the base (2), the total reflection prism (3) and the collimator (5).

6. The thin and light optical fiber pressure sensor according to any one of claims 1-5, characterized in that: The total reflection prism (3) is connected to the bottom of the transparent mirror box, and the upper part of the transparent mirror box is a circular plane with the same radius as the base (2). The range and sensitivity of the light and thin optical fiber pressure sensor can be adjusted by adjusting the thickness and size of the diaphragm (1). The thickness of the diaphragm (1) is 0.28 mm, and the diameter of the all-solid-state vacuum absolute pressure cavity is 1.4 mm.

7. The thin optical fiber pressure sensor of claim 6, wherein: When the range of the equivalent is 6 MPa, where φ0 is the diameter of the all-solid-state vacuum absolute pressure chamber, and H1 is the thickness of the diaphragm (1).

8. The thin optical fiber pressure sensor according to claim 7, wherein: The diaphragm (1) and the base (2) are made of quartz or sapphire, and are assembled by laser bonding.

9. The thin optical fiber pressure sensor of claim 6, wherein: The optical fiber (4) is a single-mode optical fiber, and the material can be selected from acrylate, polyimide or metal coating according to the use temperature. The shell (6) is made of metal. The collimator (5), the base (2) and the total reflection prism (3) are fixed in the shell (6) by gluing or glass powder welding. The thickness of the all-solid-state vacuum absolute pressure cavity is less than or equal to 2 mm, the total thickness of the light and thin optical fiber pressure sensor is less than or equal to 6 mm, the optical fiber (4) is output through the side of the shell (6), and the light and thin optical fiber pressure sensor can be used for 0-6 MPa pressure measurement.

10. The thin optical fiber pressure sensor of claim 6, wherein: ​

Images