Gap optical fiber sensing unit

Abstract

The invention discloses a gap optical fiber sensing unit which comprises an optical fiber, a sensor probe and a reflective film. The substrate, the optical fiber mounting groove, the adhesive isolation groove and the 45-degree reflecting surface in the sensor probe are integrally formed, so that the sensor probe is convenient to process and high in engineering degree, the components in the sensor probe are free of adhesives, the structure is more stable, the mounting angle deviation of the optical fiber and the 45-degree reflecting surface and the alignment deviation of the optical fiber and the 45-degree reflecting surface are avoided, and the sensor probe is more stable in structure. The precision of the whole sensing unit is higher, and the precision of a 135-degree angle between the axial direction of the optical fiber and the reflecting surface is ensured; according to the invention, the 45-degree reflecting surface and the reflecting film both adopt long-strip-shaped structures, so that the transverse reflecting area can be increased, and the fault tolerance of the transverse deflection angle during the installation of the optical fiber is improved. And the overall shape of the structure can be changed and processed according to the structure condition of the measured surface, so that various structures such as a plane, a curved surface and a rough surface can be measured.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber sensing equipment, and in particular to a gap optical fiber sensing unit. Background Art

[0002] There are usually gap structures of hundreds of microns in precision equipment. The test of the absolute value and relative change of the gap is of great significance in engineering. The most widely used gap test methods are mainly based on four test technologies: eddy current displacement test technology, differential displacement meter test technology, film capacitor displacement test technology and optical fiber displacement test technology. The test systems of the first three test technologies are mainly composed of general data acquisition devices and sensors. The following mainly describes the differences in sensors in gap test applications.

[0003] (1) The eddy current displacement test uses the eddy current effect and is a non-contact measurement. The distance between the target plate and the detection coil is measured by the alternating magnetic field generated by the high-frequency alternating current. When measuring the gap, the installation diagram of the eddy current sensor 101 is as follows: Figure 1 As shown, it is necessary to process a threaded hole on one side of the gap structure for installation, and paste the eddy current sheet 102 on the other side surface. The minimum size of the sensor is Φ3mm×25mm.

[0004] (2) The differential displacement meter is based on the principle of linear variable differential transformer (LVDT). It senses the movement of the target through a metal probe, thereby changing the mutual inductance voltage between the coil structures inside the sensor. This technology is currently more commonly used in environmental testing. The sensor size reaches Φ15mm and the probe is about 1mm. The installation method of the differential displacement meter 103 is similar to that of the eddy current sensor. It is necessary to process a through hole as the activity space of the probe 104, and at the same time install it on the outer surface of the gap structure through screws, such as Figure 2 shown.

[0005] (3) The thin film capacitive displacement sensor is based on the principle of capacitive displacement sensing. When the distance between the capacitor plates changes under the condition of a constant medium, the capacitance value changes accordingly. The physical form of the capacitive displacement sensor is two thin-film electrodes. When in use, a groove structure needs to be processed on the surface of the gap structure. Electrode 105 and electrode 2 106 are installed on both sides of the gap structure, such as Figure 3 As shown, its thickness is 0.2 mm and its width is about 10 mm.

[0006] (4) If Figure 4As shown, the test system of the optical fiber displacement test technology is usually composed of an optical fiber probe, a modulated optical path, a light source and an optical signal demodulation unit. The light beam is emitted to the measured surface through the optical fiber probe 107, returns to the probe with the distance information of the measured surface, is transmitted to the modulated optical path to cause interference and other effects, and finally the optical signal demodulation unit analyzes the displacement signal. The optical fiber displacement test technology has the advantages of small size, high measurement accuracy and strong anti-interference ability, and is an excellent solution for solving the internal parameter testing in a small space.

[0007] At present, there are official products for optical fiber displacement measurement abroad. The optical fiber displacement test system of Germany's attocube can match the Φ1.2mm probe probe and can be installed in a pin-type manner similar to the eddy current displacement sensor, such as Figure 3 There are similar products in China, but the domestic fiber optic displacement test system can directly match the bare optical fiber as a probe for displacement measurement, and its probe diameter can reach 125μm; although it can directly penetrate into the narrow gap, its measurement direction is the optical fiber axis, so it is impossible to directly measure the gap.

[0008] In conclusion, eddy current displacement testing technology, differential displacement meter testing technology, and thin film capacitor displacement testing technology all require the processing of mounting holes to perform gap measurements, which destroys the integrity of the product being tested and makes it impossible to directly reach into the gap for measurement.

[0009] Tao Tianjiong and others from the China Academy of Engineering Physics proposed an invention patent with publication number CN202210073673, "A gap sensor, gap measurement method and measurement device". In this patent, the main structure of the sensor is composed of three small thin sheets, which are bonded with glue.

[0010] The above technical solution has the following disadvantages: 1. The traditional technology sensor is large in size and cannot directly penetrate into the tiny gap for measurement. The sensor installation hole is processed in vain, which destroys the integrity of the measured product; 2. The 45° reflector structure proposed in the existing similar patents can achieve good light path reflection on a macro scale, but due to the small size of the overall structure, the structure may have the following practical processing and engineering application problems: (1) The sensor body is a structure made of three thin sheets, which has extremely high requirements for bonding technology (micrometer-level bonding process operation is required). After bonding, the overall strength of the structure is not high and it is easy to be damaged; (2) The 45° reflector surface is very small. When splicing with adhesives, there may be bonding errors, resulting in deviations in the installation angle of the 45° reflector. Therefore, the sensor has low tolerance for incident light angles. (3) It cannot adapt to different measured surfaces in engineering applications, including curved surfaces, rough surfaces, etc. The curved surface will cause the sensor to be unable to fit completely and the light beam will be obliquely incident. The rough surface will cause the sensor's transmitted light beam to be severely scattered on the measured surface. Both of these will cause the received light signal to be weak, ultimately affecting the effectiveness of optical signal sensing.

[0011] Therefore, it is necessary to develop a gap optical fiber sensing unit to solve the above problems. Summary of the invention

[0012] The purpose of the present invention is to design a gap optical fiber sensing unit in order to solve the above problems.

[0013] The present invention achieves the above-mentioned purpose through the following technical solutions: A gap optical fiber sensing unit, comprising: optical fiber; The sensor probe comprises a substrate, the bottom of which is mounted on the inner surface of the gap structure part 2, the substrate is provided with an optical fiber installation groove matching the size of the optical fiber and a long strip-shaped 45° reflection surface, the middle of the optical fiber is installed in the optical fiber installation groove, and the axial posture is fixed; the 45° reflection surface is at an angle of 45° relative to the plane of the substrate, one end of the optical fiber is close to and aligned with the 45° reflection surface, and the angle between the optical fiber axis and the 45° reflection surface is 135°; Reflective film; the reflective film is installed on the inner surface of the gap structure member 1, and the reflective film is placed directly above the 45° reflective surface.

[0014] Preferably, the optical fiber installation groove is formed as a V-shaped groove or a U-shaped groove.

[0015] Preferably, the optical fiber is glued into the optical fiber installation groove.

[0016] Furthermore, an adhesive isolation groove is provided on the substrate, and the adhesive isolation groove is provided between the optical fiber installation groove and the 45° reflecting surface; the substrate, the 45° reflecting surface, the optical fiber installation groove, and the adhesive isolation groove are integrally formed.

[0017] Preferably, the width of the reflective film is greater than the horizontal width of the 45° reflective surface, and the length of the reflective film is greater than the length of the 45° reflective surface.

[0018] The beneficial effects of the present invention are: The substrate, optical fiber installation groove, adhesive isolation groove, and 45° reflective surface in the sensor probe of the present invention are integrally formed, which is convenient for processing and has a high degree of engineering. Each component in the sensor probe does not need to use adhesives, and the structure is more stable. There will be no installation angle deviation of the optical fiber and the 45° reflective surface, and there will be no alignment deviation of the optical fiber and the 45° reflective surface, so that the entire sensing unit has higher accuracy and ensures the accuracy of the 135° angle between the optical fiber axis and the reflective surface. The 45° reflective surface and reflective film of the present invention are both in the form of long strips, which can increase the lateral reflective area and improve the tolerance of the lateral deflection angle when installing the optical fiber. The present invention can also change and process the overall shape of the structure according to the surface structure to be measured, and realize the measurement of various structures such as planes, curved surfaces, and rough surfaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the existing technical application structure Figure 1 ; Figure 2 Schematic diagram of the existing technical application structure Figure 2 ; Figure 3 Schematic diagram of the existing technical application structure Figure 3 ; Figure 4 Schematic diagram of the existing technical application structure Figure 4 ; Figure 5 It is a structural schematic diagram of the present invention; Figure 6 A top view of the sensor probe of the present invention; Figure 7 It is a front view of the sensor probe in the present invention; Figure 8 It is a right side view of the sensor probe in the present invention; Fig. 9 This is the optical path diagram of the present invention.

[0020] Legend: 1-gap structure part 1; 2-sensor probe; 21, substrate; 22, optical fiber installation groove; 23, adhesive isolation groove; 24, 45° reflecting surface; 3-optical fiber; 4-gap structure part 2; 5-reflective film; 101-eddy current sensor; 102-eddy current sheet; 103-differential displacement meter; 104-probe; 105-electrode 1; 106-electrode 2; 107-optical fiber probe. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0024] In the description of the present invention, it should be understood that the terms "upper", "lower", "inside", "outside", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use, or are directions or positional relationships commonly understood by those skilled in the art. These directions or positional relationships are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0025] Furthermore, the terms “first”, “second”, etc. are merely used for distinguishing descriptions and should not be understood as indicating or implying relative importance.

[0026] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms such as "setting" and "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings.

[0028] like Figure 5-9 As shown, a gap optical fiber sensing unit comprises: Optical fiber 3; optical fiber 3 is optical fiber 3 without coating layer (size not exceeding Φ125μm); The sensor probe 2 comprises a substrate 21, the bottom of which is adhered to the inner surface of the gap structure member 24 by adhesive, and the substrate 21 is provided with an optical fiber installation groove 22 matching the size of the optical fiber 3 and a long 45° reflection surface 24, the middle part of the optical fiber 3 is adhered in the optical fiber installation groove 22 by glue, and the axial posture is fixed; the 45° reflection surface 24 is at an angle of 45° relative to the plane of the substrate 21, one end of the optical fiber 3 is close to and aligned with the 45° reflection surface 24, and the angle between the axis of the optical fiber 3 and the 45° reflection surface 24 is 135°; an adhesive isolation groove 23 is also provided on the substrate 21, and the adhesive isolation groove 23 is arranged between the optical fiber installation groove 22 and the 45° reflection surface 24; the substrate, the 45° reflection surface, the optical fiber installation groove, and the adhesive isolation groove are integrally formed.

[0029] The reflective film 5 is adhered to the inner surface of the gap structure member 1 by an adhesive, and the reflective film 5 is placed directly above the 45° reflective surface 24.

[0030] In some embodiments, the optical fiber installation groove 22 is formed as a V-shaped groove or a U-shaped groove.

[0031] In some embodiments, the width of the reflective film 5 is greater than the horizontal width of the 45° reflective surface 24 , and the length of the reflective film 5 is greater than the length of the 45° reflective surface 24 .

[0032] In the present invention, the sensor probe 2 is a flat structure. When the gap optical fiber sensing unit is working, light of a specific wavelength is transmitted to the sensor probe 2 through the optical fiber 3, emitted vertically by the sensor probe 2, and returned to the sensor probe 2 after being reflected by the reflective film 5. The returned light signal carries the gap information and is finally transmitted back to the back-end instrument through the optical fiber 3 to complete the acquisition of the gap signal.

[0033] The substrate 21 is an ultra-thin rectangular parallelepiped (length: ≤5mm, width: ≤3mm, thickness: ≤200μm, the structural dimensions can be adjusted according to actual needs); the 45° reflective surface 24 is used to reflect the light emitted from the end face of the optical fiber 3 to the vertical direction of the substrate 21, and at the same time reflect the vertically incident light into the optical fiber 3. The long strip reflective surface design can increase the lateral reflective area and improve the tolerance of the lateral deflection angle when the optical fiber 3 is installed.

[0034] The optical fiber installation groove 22 is used for installing the optical fiber 3 (size ≤ Φ125μm), and the optical fiber 3 is glued to the bottom of the groove. The end face of the optical fiber 3 is located near the 45° reflection surface 24 (the center distance with the 45° reflection surface 24 is adjusted according to actual needs) but does not contact the 45° reflection surface 24. The design of the optical fiber installation groove 22 ensures the glue bonding area.

[0035] The adhesive isolation groove 23 is used to isolate the adhesive and the 45° reflective surface 24. In this patent, the optical fiber 3 is mainly fixed by the optical fiber installation groove 22. Due to surface tension, the adhesive usually diffuses along the optical fiber installation groove 22, which may contaminate the 45° reflective surface 24 and affect the signal-to-noise ratio of the measured optical signal. The design of the adhesive isolation groove 23 can effectively buffer the diffusion of glue to the 45° reflective surface 24, thereby ensuring the cleanliness of the 45° reflective surface 24 and ensuring its reflective performance.

[0036] The function of the reflective film 5 is to correct the reflective performance of the measured surface, so as to ensure the intensity of the light signal reflected to the sensor probe 2. Since the light emitted from the end face of the optical fiber 3 usually diverges at a certain angle, the roughness of the measured surface is poor, and the measured light signal is diffusely reflected. The intensity of the light signal returning to the end face of the optical fiber 3 is sharply weakened, resulting in a decrease in the signal-to-noise ratio of the measured light signal. The longer the measurement distance, the weaker the light signal, which seriously affects the effective measurement range. Pasting the reflective film 5 on the measured surface can ensure the reflective performance, and can ensure the consistency between the actual application and the calibration test, thereby improving the engineering practicality of the entire test probe. The specific shape and material of the reflective film 5 can be selected according to actual needs. For example, in high and low temperature environments, metal high-temperature welding glue can be used to paste 10μm thick tin foil to ensure signal stability in high and low temperature environments; in normal temperature environments, 3M regressive reflective film can be used to widen the relative angle range of the gap structure and ensure the range at the same time.

[0037] The sensor probe 2 is made of an integrated design and an integrated molding process, so the structure can be designed accordingly according to the shape of the installation surface. Taking a curved surface as an example, the main structure of the sensor probe 2 is designed according to the curvature of the curved surface to achieve matching installation. Therefore, this application can cope with displacement tests on different installation surfaces.

[0038] The sensing unit designed by this patent has strong environmental adaptability. According to the material of the reflective film 5 used, stable measurement can be achieved in a wide temperature range environment. The use of the regressive reflective film 5 can achieve the measurement of non-parallel displacement. This patent has the advantage of small size, with a maximum height of no more than 200μm, and is suitable for gap measurement in a small space.

[0039] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A gap optical fiber sensing unit, characterized in that: include: optical fiber; Sensor probe; The sensor probe includes a substrate, the bottom of which is mounted on the inner surface of the gap structure part 2, and the substrate is provided with an optical fiber installation groove matching the size of the optical fiber and a long strip of 45° reflective surface, the middle of the optical fiber is installed in the optical fiber installation groove, and the axial posture is fixed; the 45° reflective surface is at an angle of 45° relative to the plane of the substrate, one end of the optical fiber is close to and aligned with the 45° reflective surface, and the angle between the optical fiber axis and the 45° reflective surface is 135°; Reflective film; the reflective film is installed on the inner surface of the gap structure member 1, and the reflective film is placed directly above the 45° reflective surface.

2. A gap optical fiber sensing unit according to claim 1, characterized in that: The optical fiber installation groove is formed as a V-shaped groove or a U-shaped groove.

3. A gap optical fiber sensing unit according to claim 2, characterized in that: The optical fiber is glued into the optical fiber installation groove.

4. A gap optical fiber sensing unit according to claim 3, characterized in that: An adhesive isolation groove is also provided on the substrate, and the adhesive isolation groove is provided between the optical fiber installation groove and the 45° reflecting surface; the substrate, the 45° reflecting surface, the optical fiber installation groove, and the adhesive isolation groove are integrally formed.

5. A gap optical fiber sensing unit according to claim 1, characterized in that: The width of the reflective film is greater than the horizontal width of the 45° reflective surface, and the length of the reflective film is greater than the length of the 45° reflective surface.

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