White light interference type MEMS optical fiber displacement sensor

Abstract

The invention relates to a white light interference type MEMS optical fiber displacement sensor. The white light interference type MEMS optical fiber displacement sensor comprises a displacement component, an inner tube and a light source, wherein the inner tube is of a long-strip-shaped tubular structure; the outer sleeve is arranged on the outer surface of the inner pipe in a sleeving manner; the inner surface of the outer sleeve and the outer surface of the inner pipe are attached to form a relative displacement structure, and the central axis of the inner pipe coincides with the central axis of the outer sleeve. The sensing part is arranged to be close to the cable outlet end of the displacement part; the sensing component comprises a collimator and an MEMS optical chip, the collimator is arranged to be fixed to the outer sleeve, the MEMS optical chip is arranged to be fixed to the inner tube, the working end face of the collimator is parallel to the working end face of the MEMS optical chip, and when the collimator moves along the central axis direction along with the outer sleeve, the working end face of the MEMS optical chip is parallel to the working end face of the MEMS optical chip. The working end face of the collimator and the working end face of the MEMS optical chip are arranged to be perpendicular to each other relative to the central axis. According to the technical scheme, the measurement precision of the whole displacement sensor is improved through the design of the sensing component.

Description

Technical Field

[0001] The present application relates to the field of optical fiber sensing technology, and in particular to a white light interferometric MEMS optical fiber displacement sensor. Background Art

[0002] White light phase-shifting interferometry (PSI): Light within a specific wavelength range is emitted to the target surface and the reference surface, and optical interference will occur between the light reflected from the target surface and the light reflected from the reference surface. The phase between the light reflected from the target surface and the light reflected from the reference surface is related to the distance between the target surface and the reference surface. By using the phase measurement method, the phase difference of multiple interference fringes is obtained, and the distance between the target surface and the reference surface can be calculated. The target surface and the reference surface that constitute the optical interference are usually referred to as the two interference cavities of a white light interferometer. The distance in free space between the two interference cavities is the cavity length of the white light interferometer. Displacement measurement can be achieved by moving and changing the linear distance in space between the two interference cavities.

[0003] The displacement measurement using white light interferometer can reach the nanometer level in a small range (generally 0.5mm), and can reach the 0.1μm level in a range of 10mm. The principle of white light interferometer has been invented for a long time, but it is mostly used in industrial detection instruments and equipment, and is rarely used as a high-precision displacement sensor for structural monitoring or online monitoring of large industrial equipment. The main reasons are as follows: The dynamic measurement accuracy of white light interference is highly related to the quality of the interference spectrum (such as the symmetry and contrast of the interference spectrum, and the time domain stability of the interference spectrum). Only after the optical reflectivity of the two interferometer cavities is accurately set and the round-trip loss of the interference optical path is strictly controlled, can the reflected light of the target surface and the reference surface have extremely close light intensities, forming a high-quality dynamic interference spectrum. This also means that the two interferometer cavities of the displacement sensor must be fixed on an optical platform-level sliding guide rail that is strictly parallel and has good seismic resistance. This is an accuracy that cannot be met by existing high-precision linear bearing bushings (radial clearance is difficult to achieve sub-micron level), and it is not suitable as a guide structure component of the displacement sensor in terms of volume and cost. Because of this, white light interferometers are more often mounted on multi-degree-of-freedom high-precision displacement platforms to form high-precision detection instruments for geometric morphology measurement, with prices usually ranging from hundreds of thousands to millions of yuan.

[0004] However, the principle of white light phase-shifting interference has been invented for a long time, but there is a lack of strain or displacement measurement sensors using this principle in the industry. The main reasons are as follows: limitations of the phase measurement method. The principle of white light phase-shifting interference essentially has extremely high displacement measurement accuracy, but its accuracy also depends on the phase demodulation algorithm; it has high requirements for structural design. This technology has high requirements on the position and direction between the incident light, reference surface, and target surface. When the sensor is installed on the surface of the object to be measured, the sensor structure will produce strain or displacement with the object to be measured, and the vibration of the object to be measured and the humidity and water vapor in the environment can easily lead to optical interference failure.

[0005] Therefore, the prior art still needs to be improved and enhanced.

[0006] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the present application and for the convenience of understanding by those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art simply because they are described in the background technology section of the present application. Summary of the invention

[0007] In order to solve one or more of the above-mentioned technical problems, such as displacement measurement accuracy, the present disclosure provides a white light interferometric MEMS fiber optic displacement sensor, which aims to improve the white light interferometric collimation of the MEMS fiber optic displacement sensor through the design of core sensing components, thereby improving the measurement accuracy of the entire sensor.

[0008] In a first aspect of the present disclosure, a white light interferometric MEMS optical fiber displacement sensor is proposed, the MEMS optical fiber displacement sensor comprising: a displacement component, comprising an inner tube and an outer tube, the inner tube being configured as an elongated tubular structure; the outer tube being arranged to be sleeved on the outer surface of the inner tube; the inner surface of the outer tube abuts against the outer surface of the inner tube to form a relatively displaceable structure, and the central axis of the inner tube coincides with the central axis of the outer tube; a sensing component, arranged to be close to the cable outlet end of the displacement component; the sensing component comprising a collimator and a MEMS optical chip, the collimator being arranged to be fixed on the outer tube, the MEMS optical chip being arranged to be fixed on the inner tube, the working end face of the collimator being parallel to the working end face of the MEMS optical chip, and when the collimator moves along the direction of the central axis with the outer tube, the working end face of the collimator and the working end face of the MEMS optical chip are arranged to be perpendicular to the central axis. Furthermore, the MEMS fiber optic displacement sensor also includes: a fixing component, which includes a cable-outlet end support seat and a tail-end support seat, and the cable-outlet end support seat and the tail-end support seat are respectively used to fix the MEMS fiber optic displacement sensor on the two end points of the object to be measured through the corresponding cable-outlet end mounting seat and the tail-end mounting seat. When the object to be measured is stretched and deformed, the two end points undergo displacement changes, which are transmitted to the cable-outlet end support seat and the tail-end support seat through the cable-outlet end mounting seat and the tail-end mounting seat, and then transmitted to the outer tube and the inner tube, thereby causing the distance of the interference cavity between the working end face of the collimator and the working end face of the MEMS optical chip to change, and then the displacement is measured through white light interference.

[0009] Furthermore, in some embodiments, the MEMS optical chip is configured to be fixedly connected to the inner tube via a chip fixing seat; the chip fixing seat is disposed at an end of the inner tube close to the cable outlet end of the displacement component; the MEMS optical chip is configured to be fixed on the chip fixing seat, and the working end face of the MEMS optical chip faces the direction of the cable outlet end of the displacement component.

[0010] Furthermore, in some embodiments, part of the chip holder is configured to extend into the interior of the inner tube and be fixedly connected to the inner tube; the remaining part of the chip holder is configured to extend out of the inner tube and remain inside the outer tube.

[0011] Furthermore, in some embodiments, the collimator is configured to be fixedly connected to the outer sleeve via a connecting sleeve; the connecting sleeve is configured to cover the outer surface of the collimator; a portion of the connecting sleeve is configured to extend into the interior of the outer sleeve and be fixedly connected to the inner surface of the outer sleeve, and the working end face of the collimator faces the working end face of the MEMS optical chip.

[0012] Furthermore, in some embodiments, the remaining portion of the connecting sleeve is configured to extend out of the outer sleeve and is covered with a cable outlet support seat, and the cable outlet support seat is configured to cover the outer surface of a section of the outer sleeve near the cable outlet end near one end of the outer sleeve.

[0013] Furthermore, in some embodiments, a section of the outer surface of the connecting sleeve is provided with an external thread, and a section of the inner surface of the cable outlet support seat is provided with an internal thread, so that the connecting sleeve and the cable outlet support seat form a threaded fixed connection relationship through the cooperation of the external thread and the internal thread.

[0014] Furthermore, in some embodiments, the fixed connection between the outer sleeve and the connecting sleeve is glue bonding; the fixed connection between the outer sleeve and the cable outlet end support seat is glue bonding.

[0015] Furthermore, in some embodiments, the other end away from the cable outlet end of the displacement component is configured as a tail end, and the inner tube is configured at the tail end to extend out of the outer sleeve and be covered and fixedly connected by a tail end support seat.

[0016] Further, in some embodiments, near the tail end of the above-mentioned displacement component and the above-mentioned inner tube is arranged inside the above-mentioned outer tube, a guide groove along the direction of the central axis is arranged on the side wall of the above-mentioned outer tube, and a guide pin is arranged on the outer side wall of the above-mentioned inner tube; when the above-mentioned outer tube and the above-mentioned inner tube move relative to each other, the above-mentioned guide pin moves in the above-mentioned guide groove along the direction of the central axis to limit the movement of the above-mentioned outer tube and the inner tube along the direction of the above-mentioned central axis.

[0017] Furthermore, in some embodiments, the MEMS optical fiber displacement sensor also includes: an elastic sealing dust cover, which is arranged near the tail end of the above-mentioned displacement component; the above-mentioned elastic sealing dust cover is arranged to cover the outer sleeve section with the above-mentioned guide groove, and continuously covers from the above-mentioned outer sleeve section to part of the above-mentioned tail end support seat.

[0018] Further, in some embodiments, the outer sleeve and the inner tube are configured to be composed of carbon fiber; or the elastic sealing dust cover is configured to be composed of rubber; or the cable outlet end support seat and the support seat are configured to be composed of metal.

[0019] Furthermore, in some embodiments, the white light reflectivity of the working end surface of the collimator and the white light reflectivity of the working end surface of the MEMS optical chip are set to be the same or similar.

[0020] The beneficial effects of the present disclosure are:

[0021] 1) In some embodiments, the displacement component is arranged as a relative displacement structure in which an inner tube and an outer tube are nested, wherein the central axis of the inner tube coincides with the central axis of the outer tube, so that the relative movement of the inner tube and the outer tube is limited to the direction along the central axis, and the movement in the non-central axis direction is minimized, so that the white light interference structure is more stable when measuring displacement; further, the sensing component is arranged at the cable outlet, so that the white light interference cavity formed by the collimator and the MEMS optical chip can focus on sensing the displacement along the axial direction and be affected as little as possible by the non-axial offset (especially when the tail end support seat undergoes non-axial offset), thereby improving the stability of the sensing function of the white light interference cavity, and then improving the accuracy of the entire white light interference MEMS fiber optic displacement sensor.

[0022] 2) Further, in some embodiments, the displacement measurement of the object to be measured is achieved by changing the stretching conditions of the fixed cable-outlet mounting seat and the tail-end mounting seat to be measured; further, by fixedly connecting the collimator to the outer sleeve, fixedly connecting the MEMS optical chip to the inner tube, and combining the relative displacement of the outer sleeve and the inner tube (which is stretched during actual use, causing the cable-outlet mounting seat and the tail-end mounting seat to move relative to each other), a white light interference cavity is formed between the working end face of the collimator and the working end face of the MEMS optical chip, thereby achieving precision measurement of displacement by the white light interference MEMS fiber optic displacement sensor.

[0023] 3) Further, in some embodiments, by providing a connecting sleeve, the internal collimator can be fixedly connected to the outer sleeve and the cable outlet mounting seat, so that the object to be measured at the cable outlet mounting seat can be directly associated with the internal collimator; accordingly, by providing a fixed connection between the tail end mounting seat and the inner tube, the object to be measured at the tail end mounting seat can be directly associated with the inner tube inside, and then associated with the MEMS optical chip through the chip fixing seat; therefore, when the white light interference cavity formed by the working end face of the collimator and the working end face of the MEMS optical chip changes (for example, when stretched), the white light interference MEMS optical fiber displacement sensor can achieve accurate measurement of displacement.

[0024] 4) Further, in some embodiments, at the tail end near the displacement component, a guide groove along the central axis is provided on the side wall of the outer sleeve, and a guide pin is provided on the outer side wall of the inner tube at the corresponding position; the guide pin can move along the central axis in the guide groove; thereby limiting the movement of the outer sleeve and the inner tube to only along the central axis. Further, the guide groove can be symmetrically arranged on the other side wall of the outer sleeve relative to the central axis, and the other outer side wall of the inner tube is correspondingly provided with a guide pin (also symmetrically arranged relative to the central axis); this avoids the generation of offset or rotation outside the direction of the non-central axis due to the guide constraint at only one end, and further, it can also share the torque and improve the life of the device.

[0025] 5) Furthermore, in some embodiments, an elastic sealing dust cover is provided near the tail end of the displacement component, so that it covers the outer sleeve section with the guide groove, the outer surface of the inner tube that may be exposed, and part of the outer surface of the tail end support seat, so as to play a dust-proof sealing role without affecting the measurement function, thereby improving the life of the device and the working state of the device during operation, and then improving the measurement accuracy of the displacement sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and other features, advantages and aspects of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings, in which: Figure 1A schematic diagram of a white light interferometric MEMS optical fiber displacement sensor according to an embodiment of the present disclosure is shown; Figure 2 An enlarged schematic diagram of a white light interferometric MEMS optical fiber displacement sensor near a cable outlet end according to an embodiment of the present disclosure is shown; Figure 3 An enlarged schematic diagram of a white light interferometric MEMS optical fiber displacement sensor near the tail end according to an embodiment of the present disclosure is shown; Figure 4 A schematic diagram of another white light interferometric MEMS fiber optic displacement sensor according to an embodiment of the present disclosure is shown; Figure 5 A schematic diagram showing a white light interferometric MEMS fiber optic displacement sensor according to an embodiment of the present disclosure being assembled on a mounting base; Figure 6 Another schematic diagram showing a white light interferometric MEMS fiber optic displacement sensor mounted on a mounting base according to an embodiment of the present disclosure; Figure 7 A schematic diagram of a white light interference process according to an embodiment of the present disclosure is shown; and In the various drawings, the same or corresponding reference numerals denote the same or corresponding parts. DETAILED DESCRIPTION

[0027] Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be construed as being limited to the embodiments described herein. On the contrary, these embodiments are provided to provide a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are only for exemplary purposes and are not intended to limit the scope of protection of the present disclosure.

[0028] In the description of the embodiments of the present disclosure, the term "including" and similar terms should be understood as open inclusion, that is, "including but not limited to". The term "based on" should be understood as "based at least in part on". The term "one embodiment" or "the embodiment" should be understood as "at least one embodiment". The terms "first", "second", etc. may refer to different or the same objects. Other explicit and implicit definitions may also be included below.

[0029] Generally, strain sensors are used to monitor the strain of objects. Strain sensors are fixed to the surface of the object being measured by glue, welding, bolts, etc. The fixed points are usually located at the two end points of the sensor (assuming they are points A and B). The distance between the two fixed points is commonly known as the gauge length of the sensor. When strain occurs on the surface of the object being measured, the strain can be transmitted to the strain sensor body through the two fixed points, causing the output signal of the internal components of the sensor to change, thereby achieving strain measurement. The strain is calculated by dividing the change in the distance between the two fixed points by the distance between the two fixed points, that is, △L / L (△L is the change in the distance between points A and B, and L is the distance between points A and B), so strain sensors can essentially measure displacement. However, general displacement sensors and strain sensors are usually not interchangeable, mainly due to the limitations of measurement technology. For example, the vibrating wire measurement technology has a strain gauge product range of 3000 microstrains. Calculated based on a gauge length of 100mm, the maximum displacement it measures is 0.45mm, and the measurement accuracy is ±0.5%, or ±2.25μm. The displacement gauge measurement range is calculated based on 12.5mm, with an accuracy of ±0.1%, or ±12.5μm. In short, when vibrating wire technology is used in different fields (strain measurement field, displacement measurement field), its measurement accuracy is different. The main reason is that the vibrating wire itself has a limited measurement range and can only measure tiny displacements (generally not more than 0.5mm). Over-stretching the vibrating wire will cause it to fail and be damaged. When it is necessary to measure a larger displacement, an additional range amplification mechanism is required. The introduction of this type of structure will cause a decrease in measurement accuracy. Correspondingly, other strain measurement products also have the same defects, such as strain gauges or displacement gauges based on measurement principles such as electronic strain gauges and fiber gratings. Furthermore, white light phase-shifting interferometry (PSI) is to emit light within a specific wavelength range to the target surface and the reference surface, and light interference will occur between the reflected light from the target surface and the reflected light from the reference surface. The phase between the reflected light from the target surface and the reflected light from the reference surface is related to the distance between the target surface and the reference surface. By using the phase measurement method, the phase difference of multiple interference fringes can be obtained to calculate the distance between the target surface and the reference surface. This technology can be used to measure displacements within a small range (generally 0.5 mm) to the nanometer level, and within a range of 10 mm to the 0.1 μm level. Compared with the above-mentioned vibrating wire, resistance strain gauge, and fiber Bragg grating strain measurement principles, both the measurement accuracy and the measurement range have been greatly improved.

[0030] However, in white light interferometry, due to the limitations of the phase measurement method, the principle of white light phase-shifting interferometry essentially has extremely high displacement measurement accuracy, but its accuracy has high requirements on structural design. This technology has high requirements on the position and direction between the incident light, reference surface, and target surface. When the sensor is installed on the surface of the object to be measured, the sensor structure produces strain or displacement with the object to be measured, and the vibration of the object to be measured and the humidity and water vapor in the environment can easily lead to optical interferometry failure.

[0031] In order to solve at least one of the above problems, as well as one or more of other potential problems, an exemplary embodiment of the present disclosure proposes a white light interferometric MEMS optical fiber displacement sensor, which includes a displacement component, a sensing component, and a fixing component. Specifically, the following is expanded in conjunction with the accompanying drawings. It should be noted that the so-called "cable outlet end" in the embodiments of the present disclosure refers to an end close to the optical fiber or optical cable or optical cable fixing seat, and the "tail end" refers to the other end relative to the cable outlet end.

[0032] Figure 1A schematic diagram of a white light interferometric MEMS fiber optic displacement sensor according to an embodiment of the present disclosure is shown. In this exemplary embodiment, the white light interferometric MEMS fiber displacement sensor 100 includes: a displacement component 110, and the displacement component 110 includes an inner tube 112 and an outer tube 114, wherein the inner tube 112 is configured as an elongated tubular structure, or in other embodiments, can be configured as a hollow structure with side walls; the outer tube 114 is configured to be sleeved on the outer surface of the inner tube 112; the double-layer tube structure thus forms an inner surface of the outer tube 114 and an outer surface of the inner tube 112 in contact with each other and form a relatively displaceable structure, further, the inner tube 112 is configured as a tube body structure with a circular cross-section, and the center axis of the tube body structure passes through the center of the cross-section circle, similarly, the cross-section of the outer tube 114 is also circular, and similarly there is a central axis, thus, the central axis of the inner tube 112 is configured to coincide with the central axis of the outer tube 114, so that the inner surface of the outer tube 114 and the outer surface of the inner tube 112 can be more closely contacted, and the circular cross-section tube structure of both is also easy to process, produce and assemble. Furthermore, the sensing component 120 is arranged at an end portion (for example, the cable outlet end) close to the displacement component 110; the sensing component 120 further includes a core collimator 122 and a MEMS optical chip 124, wherein the collimator 122 is arranged to be fixed on the outer sleeve 114, the MEMS optical chip 124 is arranged to be fixed on the inner tube 112, and the working end face of the collimator 122 (that is, the end face of the outgoing light) is parallel to the working end face of the MEMS optical chip 124 (that is, the plane that is directly opposite to the working end face of the collimator 122 and cooperates with it to form a white light interference area, and the plane is used to reflect the white light from the working end face of the collimator 122; being parallel to each other can more effectively form a white light interference cavity area), and when the collimator 122 moves along the above-mentioned central axis direction with the outer sleeve 114, the working end face of the collimator 122 and the working end face of the MEMS optical chip 124 are arranged to be perpendicular to the central axis (correspondingly, the two are also in a parallel state). Furthermore, the white light interferometry MEMS fiber optic displacement sensor 100 also includes a fixed component, which includes two support seats respectively arranged at the cable outlet end and the tail end of the white light interferometry MEMS fiber optic displacement sensor 100, such as the cable outlet end support seat 132 and the tail end support seat 134 shown in the figure (corresponding to the cable outlet end mounting seat 132-1 and the tail end mounting seat 134-1 connected to the object to be measured). It should be understood that the cable outlet end is close to the optical cable, and generally the optical fiber cable will be connected to the collimator 122, and the tail end is the other end relative to the cable outlet end.The sensing component 120 is arranged at one end portion close to the displacement component 110, especially at the cable outlet end, so as to reduce the arrangement length of the optical fiber or optical cable inside the MEMS optical fiber displacement sensor. When the MEMS optical fiber displacement sensor measures displacement, generally, the cable outlet end support seat 132 and the tail end support seat 134 (the displacement of the cable outlet end mounting seat 132-1 and the tail end mounting seat 134-1 transmitted by the measured object) undergo relative movement, generally when the displacement is away from each other, the most ideal movement is that the displacement is also carried out along the above-mentioned central axis direction (two-dimensional direction). However, in actual situations, the displacement between the two points will deviate from the third dimension direction of the central axis direction, for example, upward, then the sensing component 120 will produce a torsional force and torsional offset of the tail end support seat 134 relative to the cable outlet end support seat 132, thereby easily destroying the structure in which the working end face of the collimator 122 is parallel to the working end face of the MEMS optical chip 124, thereby affecting the white light interference cavity structure formed therein, and then affecting the measurement robustness and accuracy of the MEMS optical fiber displacement sensor. Therefore, in a preferred embodiment, the sensing component 120 is arranged near the cable outlet support seat 132, so that when a non-central axis direction offset occurs between the inner tube 112 (arranged to be fixed to the tail end support seat 134) and the outer sleeve 114 (arranged to be fixed to the cable outlet support seat 132), the sensing component 120 is as little affected as possible by the offset. Preferably, the other end away from the cable outlet end of the displacement component 110 is arranged as the tail end, and the inner tube 112 is arranged at the tail end to extend out of the outer sleeve 114 and be covered and fixedly connected by the tail end support seat 134.

[0033] Furthermore, the above-mentioned MEMS fiber optic displacement sensor 100 also includes a fixing component, which includes a cable-outlet end support seat 132 and a tail-end support seat 134. The cable-outlet end support seat 132 and the tail-end support seat 134 are respectively used to fix the MEMS fiber optic displacement sensor 100 on the two end points of the object to be measured through the corresponding cable-outlet end mounting seat 132-1 and the tail-end mounting seat 134-1. When the object to be measured is stretched and deformed, the two end points undergo displacement changes, which are transmitted to the cable-outlet end support seat 132 and the tail-end support seat 134 through the cable-outlet end mounting seat 132-1 and the tail-end mounting seat 134-1, and then transmitted to the outer tube 114 and the inner tube 112, thereby causing the distance of the interference cavity between the working end face of the collimator 122 and the working end face of the MEMS optical chip 124 to change, and then the displacement is measured through white light interference.

[0034] Furthermore, the cable outlet of the MEMS optical fiber displacement sensor will be described in more detail below.

[0035] Figure 2 The embodiment according to the present disclosure is shown Figure 1A magnified schematic diagram of a white light interferometric MEMS fiber displacement sensor near the cable outlet. In the illustrated embodiment, the MEMS optical chip 124 of the MEMS fiber displacement sensor 100 is configured to be fixedly connected to the inner tube 112 through a chip holder 125; the chip holder 125 is disposed at one end of the inner tube 112 near the cable outlet end of the displacement component; the MEMS optical chip 124 is configured to be fixed to the chip holder 125, and to keep the working end face of the MEMS optical chip 124 facing the direction of the cable outlet end of the displacement component 110 (i.e., facing the working end face of the collimator 122). Furthermore, as shown in the illustrated embodiment, part of the chip holder 125 is configured to extend into the interior of the inner tube 112 and be fixedly connected to the inner tube 112; the remaining part of the chip holder 125 is configured to extend out of the inner tube 112 and remain in the interior of the outer sleeve 114. In this way, the MEMS optical chip 124 can be configured to be displaced relative to the central axis direction of the inner tube 112 as the inner tube 112 is displaced. Furthermore, in the illustrated embodiment, the collimator 122 is configured to be fixedly connected to the outer sleeve 114 through the connecting sleeve 126; the connecting sleeve 126 is configured to cover the outer surface of the collimator 122 (the connecting sleeve 126 is thus fixedly connected to the collimator 122); a portion of the connecting sleeve 126 is configured to extend into the interior of the outer sleeve 114 and to be fixedly connected to the inner surface of the outer sleeve 114, so that the collimator 122 is configured to be displaced relative to the central axis direction of the outer sleeve 114 along with the displacement of the outer sleeve 114, and the working end face of the collimator 122 is kept facing the working end face of the MEMS optical chip 124. Further, the remaining portion of the connecting sleeve 126 is configured to extend out of the outer sleeve 114, and a portion of the remaining portion of the connecting sleeve 126 is covered with a cable outlet support seat 132, and the cable outlet support seat 132 is configured to cover the outer surface of a section of the outer sleeve 114 near the cable outlet end near the outer sleeve 114.

[0036] More preferably, a section of the outer surface of the connecting sleeve 126 is provided with an external thread, and a section of the inner surface of the cable outlet support seat 132 is provided with an internal thread, so that the connecting sleeve 126 and the cable outlet support seat 132 form a threaded fixed connection relationship through the external thread and the internal thread. Thus, the assembly of the MEMS optical fiber displacement sensor 100 in this section is facilitated. Further, as Figure 2 As shown, the optical signal of the collimator 122 is input and output through the optical cable 140, and the optical cable 140 is fixed by the optical cable fixing seat 142 on the left side of the sensor.

[0037] Preferably, the fixed connection between the outer sleeve 114 and the connecting sleeve 126 is glue bonding; the fixed connection between the outer sleeve 114 and the cable outlet end support seat 132 is glue bonding.

[0038] Furthermore, the tail end of the MEMS optical fiber displacement sensor will be described in more detail below.

[0039] Figure 3 The embodiment according to the present disclosure is shown Figure 1 A magnified schematic diagram of the white light interferometric MEMS fiber optic displacement sensor near the tail end. In this illustrated embodiment, near the tail end of the displacement component 110 and the inner tube 112 is disposed inside the outer tube 114, a guide groove 114-1 along the central axis direction is disposed on the side wall of the outer tube 114, and a guide pin 112-1 is disposed on the outer side wall of the inner tube 112; when the outer tube 114 and the inner tube 112 move relative to each other, the relative movement of the outer tube 114 and the inner tube 112 is limited along the central axis direction by the guide pin 112-1 moving in the guide groove 114-1 along the central axis direction.

[0040] Furthermore, a more preferred solution of the MEMS optical fiber displacement sensor will be described in more detail below.

[0041] Figure 4 A schematic diagram of another white light interferometric MEMS fiber displacement sensor according to an embodiment of the present disclosure is shown. In the illustrated embodiment, the MEMS fiber displacement sensor further includes: an elastic sealing dust cover 150, and the elastic sealing dust cover 150 is arranged near the tail end of the displacement component 110; and the elastic sealing dust cover 150 is arranged to cover the outer sleeve section with the guide groove 114-1, and continuously cover the outer sleeve section to part of the tail end support seat 134. Therefore, when the inner tube 112 and the outer sleeve 114 move relative to each other, and the inner tube 112 is exposed outside the outer sleeve 114 at the tail end, the elastic sealing dust cover 150 can be provided to achieve effective dustproof and sealing effects. In some embodiments, near the tail end of the MEMS fiber displacement sensor, there is a relative sliding opening between the outer sleeve 114 and the inner tube 112 (the outer surface of the inner tube 112 is exposed), and an elastic sealing dust cover 150 is arranged to prevent dust, water vapor and other impurities from entering the matching gap between the outer sleeve 114 and the inner tube 112.

[0042] In addition, it should be understood that the outer sleeve 114 and the inner tube 112 can be made of carbon fiber; the carbon fiber double sleeve structure has high matching accuracy and self-lubricating properties. When the outer sleeve and the inner tube composed of carbon fiber slide relative to each other, the sliding resistance is small, and due to the high matching accuracy of the two and the long embedded length of the inner tube, the stability of the white light phase-shifting interference can be guaranteed when the two slide relative to each other. And the carbon fiber double sleeve structure has good toughness and light weight. Its body resonant frequency is low. When the sensor is in a vibration environment, the carbon fiber double sleeve structure can avoid the failure of white light phase-shifting interference in a vibration environment. At the same time, when the surface of the object to be measured is slightly bent and twisted, given the high toughness, self-lubricating property of the carbon fiber tube and the long embedded length of the inner tube, the stability of the white light phase-shifting interference of the sensor in such an environment can also be improved. And the carbon fiber double sleeve structure is more compact and uses fewer parts.

[0043] Furthermore, the cable-outlet support base 132 and the tail-end support base 134 are configured to be made of metal to enhance their structural rigidity.

[0044] Furthermore, the following combination Figures 1 to 6The structure and assembly principle of the white light interferometric MEMS fiber displacement sensor in some embodiments of the present disclosure are explained. In some embodiments, the external structure of the body of the MEMS fiber displacement sensor is composed of metal fixing seats (cable end support seat 132, tail end support seat 134) at both ends of the displacement sensor, and an outer sleeve 114 and an inner tube 112 located between the two; wherein the cable end support seat 132 and the outer sleeve 114 are fixed together by a connecting sleeve 126, and the outer sleeve 114 is bonded to the connecting sleeve 126 by glue, and then the two are fixed together on the cable end support seat 132, and the connection method is that the outer thread of the outer ring of the connecting sleeve 126 is matched with the inner thread in the inner hole of the cable end support seat 132, and the part of the outer sleeve 114 inserted into the cable end support seat 132 is also connected by glue, and the composite fixing method of thread and glue ensures the reliable connection and coaxiality of the three. The inner tube 112 and the tail end support seat 134 are connected together by glue. The cable-outlet mounting base 132-1 and the tail-end mounting base 134-1 at both ends of the MEMS optical fiber displacement sensor (the cable-outlet support base 132 is fixed to the surface of the object to be measured through the cable-outlet mounting base 132-1, and the tail-end support base 134 is fixed to the surface of the object to be measured through the tail-end mounting base 134-1. When the surface of the object to be measured is strained, the strain will cause the distance between the cable-outlet mounting base 132-1 and the tail-end mounting base 134-1 (i.e., the cable-outlet support base 132 and the tail-end support base 134) at both ends of the sensor to change, from This causes relative sliding between the outer sleeve 114 and the inner tube 112. A collimator 122 is fixed in the inner hole of the connecting sleeve 126, and the two are connected by welding. A chip holder 125 is fixed on the left side of the inner tube 112, and a MEMS optical chip 124 is fixed on the end face of the chip holder 125. Between the collimator and the MEMS optical chip 124 is an interference cavity for white light phase-shifting interference. The collimator 122 is integrated with the outer sleeve 114, and the MEMS optical chip 124 is connected to the inner tube 112. 12 is integrated with the outer tube 114 and the inner tube 112. When relative sliding occurs between the outer tube 114 and the inner tube 112, the length of the interference cavity between the collimator 122 and the MEMS optical chip 124 will change. The change in cavity length can be calculated by phase demodulation technology, thereby obtaining the change in distance between the cable-outlet mounting seat 132-1 and the tail-end mounting seat 134-1 (i.e., the cable-outlet support seat 132 and the tail-end support seat 134) at both ends of the sensor. A guide pin 112-1 (for example, In the embodiment of the present invention, a guide groove 114-1 (e.g., a waist-shaped hole) is provided at a corresponding position of the outer sleeve 114. When relative sliding occurs between the outer sleeve 114 and the inner tube 112, the guide pin 112-1 can slide in the guide groove 114-1 of the outer sleeve 114. This structure allows relative sliding between the outer sleeve 114 and the inner tube 112 (double sleeve structure) and avoids relative rotation between the outer sleeve 114 and the inner tube 112, thereby improving the stability of white light phase-shifting interference.

[0045] In order to facilitate installation and application, further, guide grooves are provided at both ends of the MEMS optical fiber displacement sensor (cable end support seat 132, tail end support seat 134), and corresponding positions of the mounting support (cable end mounting seat 132-1 and tail end mounting seat 134-1) are also designed with card slots. When the MEMS optical fiber displacement sensor is installed on the mounting support (cable end mounting seat 132-1 and tail end mounting seat 134-1), the guide grooves can facilitate the installation of the sensor and the control of the gauge length, such as Figure 5-6 shown.

[0046] Furthermore, in some embodiments, a G-Lens collimator (G-Lens, Gradient-index lens) is used in the MEMS fiber optic displacement sensor, and the optical fiber and the metal sleeve are connected by optical glue, and the optical fiber is coupled to the G-Lens collimator. Therefore, it is difficult to achieve absolute perpendicularity between the output light of the G-Lens collimator and the output end face (this is because the G-Lens collimator embeds the optical fiber in a G-Lens lens with a diameter of 1.8 mm or larger, and after coupling, it is encapsulated in the metal sleeve by glue, so there are many components, and the output light in the optical fiber is easy to form an angle with the output end face). Therefore, when the output end face of the collimator is coupled with the MEMS chip (reflection surface) to form an interference cavity, the output end face and the reflection surface form an angle, causing the entire interference optical path to be sensitive to angles. When the angle of either end of the MEMS chip or the collimator changes, the interference optical path is prone to instability. Preferably, in the embodiments of the present disclosure, a Grin (Graded-Index Lens) fiber collimator is used to weld the optical fiber to the Grin fiber, so that the Grin fiber and the single-mode fiber are integrated (the Grin collimator is made by fusing a section of self-focusing optical fiber to the optical fiber, has few components, and the light is directly transmitted in the optical fiber, and the output end face is the end face of the optical fiber). Compared with the G-Lens collimator, the Grin fiber collimator has fewer connection points and a simpler configuration; in addition, the G-Lens collimator has more assembly parts and more connection points, so the overall tolerance error is larger and the output angle is larger. Correspondingly, the use of a Grin fiber collimator can make the interference cavity formed by the light output end face and the emission surface have almost no angle or a very small angle (for example, in some embodiments, the Grin collimator makes the output light angle close to 0, thereby improving the consistency of the reflectivity in the interference cavity and making the white light interference cavity more stable). The interference cavity is insensitive to angles and is more stable. This is because the Grin fiber collimator is welded to the optical fiber, making the working end face of the collimator easier to be vertical (that is, the working end face of the collimator and the working end face of the MEMS optical chip in some of the above embodiments are set to be perpendicular to the central axis). The more parallel the two surfaces forming the interference cavity are, the smaller the change in the refractive index of the incident light is, and the more stable the parameters of the entire interference cavity are, and the lower the impact of the angle change brought by the external structure on the interference cavity is. Therefore, the interference cavity is insensitive to angles and is more stable.Furthermore, with respect to the transmittance of the Grin fiber collimator itself, in order to ensure that a reliable white light interference cavity is formed between the working end face of the Grin fiber collimator and the working end face of the MEMS chip, it is necessary to coat the working end face of the Grin fiber collimator and the corresponding working end face of the MEMS chip with a corresponding reflective film, so that the reflectivity between the two end faces forming the white light interference cavity is close to or equal; accordingly, in order to ensure that white light passes through the Grin fiber collimator and is emitted from its working end face, a transmission film is also coated on the working end face of the Grin fiber collimator to ensure that sufficient white light can be emitted from the working end face of the Grin fiber collimator to the MEMS chip. In the white light interference cavity formed as described above; in some embodiments, the reflectivity and transmittance of the MEMS chip are set, and the reflectivity of the coating on its working end face (i.e., the reflection surface) can be set to about 4%~20% according to use (too high reflectivity will drown out the interference signal), and keep it consistent with the reflectivity of the Grin collimator, so that the light intensity of the interference cavity is more stable (the reflectivity is proportional to the light intensity); at the same time, in order to allow white light to enter the interference cavity, it is necessary to ensure that the transmittance of the coating on the reverse side (i.e., the transmission surface) of the working end face of the MEMS chip is greater than 99%, so that the light transmitted through the front side will no longer be reflected back to interfere with the signal of the interference cavity, all for the purpose of making the optical cavity more stable.

[0047] Further, the white light path is described according to the attached drawings, such as Figure 7 As shown. Figure 7 In the figure, white light 129-1 is transmitted through the optical fiber 129, and enters the collimator 122 through the vertical connection surface (welding surface) between the optical fiber and the Grin optical fiber collimator, and then is emitted from the collimator 122 through the working end surface 122-1 (white light emitting end surface) of the collimator 122, and is emitted to the working end surface 124-1 (white light reflecting surface) of the MEMS optical chip 124. It should be understood that a white light interference cavity is formed between the working end surface 122-1 (white light emitting end surface) of the collimator 122 and the working end surface 124-1 (white light reflecting surface) of the MEMS optical chip 124, and ensuring the verticality between the working end surface 122-1 of the collimator 122 and the working end surface 124-1 of the MEMS optical chip 124 is very important for the measurement accuracy and stability of the MEMS optical fiber displacement sensor.

[0048] It should be understood that the MEMS fiber optic displacement sensor in each embodiment of the present disclosure adopts a two-point displacement measurement technology path to measure the deformation (displacement) within the two points, i.e. the gauge length. Therefore, the installation area and the requirements for the installation surface are greatly reduced, and the surface of the object to be measured does not need to be polished finely, and the measurement can be achieved as long as it can be firmly bonded.

[0049] The embodiments of the present disclosure have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

[0050] The above description is only an optional embodiment of the present disclosure and is not intended to limit the present disclosure. For those skilled in the art, the present disclosure may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A white light interferometric MEMS optical fiber displacement sensor, characterized in that: include: The displacement component comprises an inner tube and an outer tube, wherein the inner tube is configured as an elongated tubular structure; the outer tube is configured to be sleeved on the outer surface of the inner tube; the inner surface of the outer tube abuts against the outer surface of the inner tube to form a relatively displaceable structure, and the central axis of the inner tube coincides with the central axis of the outer tube; A sensing component is arranged to be close to the cable outlet end of the displacement component; the sensing component comprises a collimator and a MEMS optical chip, the collimator is arranged to be fixed on the outer sleeve, the MEMS optical chip is arranged to be fixed on the inner tube, the working end face of the collimator is parallel to the working end face of the MEMS optical chip, and when the collimator moves along the central axis direction with the outer sleeve, the working end face of the collimator and the working end face of the MEMS optical chip are arranged to be perpendicular to the central axis.

2. The MEMS optical fiber displacement sensor according to claim 1, characterized in that: The MEMS optical chip is configured to be fixedly connected to the inner tube via a chip fixing seat; the chip fixing seat is arranged at an end of the inner tube close to the cable outlet end of the displacement component; the MEMS optical chip is configured to be fixed on the chip fixing seat, and the working end face of the MEMS optical chip faces the direction of the cable outlet end of the displacement component.

3. The MEMS optical fiber displacement sensor according to claim 2, characterized in that: Part of the chip mounting base is configured to extend into the interior of the inner tube and be fixedly connected to the inner tube; the remaining part of the chip mounting base is configured to extend out of the inner tube and still be inside the outer tube.

4. The MEMS optical fiber displacement sensor according to claim 1, characterized in that: The collimator is configured to be fixedly connected to the outer sleeve via a connecting sleeve; the connecting sleeve is configured to cover the outer surface of the collimator; a portion of the connecting sleeve is configured to extend into the interior of the outer sleeve and be fixedly connected to the inner surface of the outer sleeve, and the working end face of the collimator faces the working end face of the MEMS optical chip.

5. The MEMS optical fiber displacement sensor according to claim 4, characterized in that: The remaining portion of the connecting sleeve is configured to extend out of the outer sleeve and is covered with a cable outlet support seat, and the cable outlet support seat is configured to cover the outer surface of a section of the outer sleeve close to the cable outlet end near one end of the outer sleeve.

6. The MEMS optical fiber displacement sensor according to claim 5, characterized in that: A section of the outer surface of the connecting sleeve is provided with an external thread, and a section of the inner surface of the cable outlet support seat is provided with an internal thread, so that the connecting sleeve and the cable outlet support seat form a threaded fixed connection relationship through the cooperation of the external thread and the internal thread.

7. The MEMS optical fiber displacement sensor according to claim 5, characterized in that: The fixed connection between the outer sleeve and the connecting sleeve is glue bonding; the fixed connection between the outer sleeve and the cable outlet end support seat is glue bonding.

8. The MEMS optical fiber displacement sensor according to claim 1, characterized in that: The other end away from the cable outlet end of the displacement component is arranged as a tail end, and the inner tube is arranged at the tail end to extend out of the outer sleeve and be covered and fixedly connected by a tail end support seat.

9. The MEMS optical fiber displacement sensor according to claim 8, characterized in that: At the tail end near the displacement component and the inner tube is arranged inside the outer tube, a guide groove along the center axis direction is arranged on the side wall of the outer tube, and a guide pin is arranged on the outer side wall of the inner tube; when the outer tube and the inner tube move relative to each other, the guide pin moves in the guide groove along the center axis direction to limit the movement of the outer tube and the inner tube along the center axis direction.

10. The MEMS optical fiber displacement sensor according to claim 9, characterized in that: Also includes: An elastic sealing dust cover is arranged near the tail end of the displacement component; the elastic sealing dust cover is arranged to cover the outer sleeve section with the guide groove, and continuously covers from the outer sleeve section to part of the tail end support seat.

11. The MEMS optical fiber displacement sensor according to claim 10, characterized in that: The outer tube and the inner tube are configured to be composed of carbon fibers; or The elastic sealing dust cover is configured to be made of rubber; or The cable outlet end support seat and the tail end support seat are configured to be made of metal.

12. The MEMS optical fiber displacement sensor according to claim 1, characterized in that: The white light reflectivity of the working end surface of the collimator and the white light reflectivity of the working end surface of the MEMS optical chip are set to be the same or similar.

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