CN115523835A - Micro-scale measurement device and method based on three-core conical phase-shift fiber bragg grating - Google Patents

Abstract

A micro-scale measuring device and a method based on a three-core conical phase-shift fiber grating belong to the technical field of manufacturing and measuring of precision instruments; the device comprises a broadband light source, a spectrum analysis device, an optical circulator, a control computer, a multi-path optical switch and an external reference grating, wherein three single-mode fibers are respectively communicated with a tail fiber of a three-core tapered phase-shift fiber grating probe, and a light absorption material layer is coated on the surface of a spherical needle point of the probe; the method is characterized in that a computer is controlled to control a multi-path optical switch to switch an optical path, a spectrum analysis device is used for measuring the reflection spectrum of the fiber bragg grating respectively, and a differential data processing algorithm is utilized to realize three-dimensional micro-scale measurement without temperature coupling. The invention has the characteristics of smaller measurable size, no influence of part reflected light on axial measurement, high precision, no influence of shielding effect and long service life of the probe.

Description

Micro-scale measurement device and method based on three-core tapered phase-shifting fiber grating

technical field

The invention belongs to the technical field of precision instrument manufacture and measurement, and in particular relates to a micro-scale measurement device and method based on a three-core tapered phase-shifting fiber grating.

Background technique

With the continuous development of the aerospace industry, automobile industry, electronics industry and cutting-edge industries, the demand for precision and tiny parts has increased dramatically. Due to the limitation of the space scale and the shadowing effect of the tiny parts to be measured, as well as the influence of the measurement contact force, it is difficult to realize the precise measurement of the small parts, especially the measurement of the depth of the small inner cavity parts is difficult to improve, which has become a constraint to the development of the industry. "bottleneck". In order to achieve smaller size measurement and increase the measurement depth, the most widely used method is to use a slender probe to penetrate into the inner cavity of tiny parts for detection, and measure the tiny inner dimensions at different depths by aiming at the signal. Therefore, at present, the precise measurement of the size of tiny parts is mainly based on the coordinate measuring machine combined with the aiming and sending detection system with a slender probe. Since the development of the coordinate measuring machine technology has been relatively mature, it can provide precise three-dimensional space movement, so the aiming The detection method of the trigger probe becomes the key to the design of the detection system for small parts.

At present, the main means of measuring the size of tiny parts include the following methods:

1. Tan Jiubin and Cui Jiwen from Harbin Institute of Technology in China proposed a probe structure based on dual fiber coupling.

2. The US National Institute of Standards and Technology uses a probe with a single fiber optic rod combined with a micro-optical bead.

3. A new type of contact probe based on the bending hinge structure based on the principle of parallel kinematics developed by the Swiss Joint Metrology Office.

4. The FBG Bending-based micropore size measurement device and method proposed by Cui Jiwen and Yang Fuling of Harbin Institute of Technology, China.

5. The four-core fiber grating-based three-dimensional microscale measurement device and method proposed by Feng Kunpeng and Cui Jiwen of Harbin Institute of Technology, China.

In summary, in the current micro-size and coordinate detection methods, probes made of optical fibers have attracted widespread attention due to their small probe size, small measurement contact force, large measurement depth-to-diameter ratio, and high measurement accuracy. Its unique optical and mechanical properties realize the precise measurement of tiny dimensions at a certain depth through various methods. The three-dimensional micro-scale measurement device and method of four-core fiber grating have obvious technical advantages in the previous schemes, but there are still some problems:

1. It is difficult to further reduce the size of the probe tip to adapt to smaller size measurements.

2. In the contact measurement, the fiber grating in the probe is subjected to non-uniform strain, and the resulting spectral distortion will affect the measurement accuracy.

3. When the probe performs axial measurement, the optical signal in the probe will be emitted by the spherical tip of the probe and reflected by the surface of the part, and then coupled into the optical fiber to cause interference. There are multi-peak signals on the spectrum, which makes the probe signal unable to be demodulated, and high-precision axial measurement cannot be realized.

Contents of the invention

The purpose of the present invention is to overcome the disadvantages of low resolution and single measured dimension in the prior art method for measuring the size of tiny parts, and to provide a device and method suitable for three-dimensional microscale measurement of tiny parts. The invention adopts a tapered three-core fiber grating to form a probe structure, and sets a π/2 phase shift point at the center of each fiber grating in the probe, and at the same time designs a light-absorbing coating on the spherical needle tip of the probe. The probe in the invention can reduce the size of the probe tip through the design of the tapered structure, and then measure smaller parts without affecting the sensitivity; the stress non-uniformity of the fiber grating in the tapered probe is further enhanced, and through the design The phase shift point can introduce a very narrow central concave fine spectral structure in the spectrum of the fiber grating, and the fine spectral structure will not be distorted and deformed during the measurement, which can improve the measurement accuracy; the optical absorption coating on the probe ball tip layer, which can effectively absorb the residual optical signal of the probe, and avoid interference during axial measurement of the probe, thereby achieving high-precision axial measurement.

The working principle of the present invention is that after the end of the three-core tapered phase-shift fiber grating probe is affected by the touch displacement, the stress causes the parameters of the fiber grating to change, and then the central wavelength of the reflection spectrum changes accordingly. To switch the channel for measuring fiber gratings to obtain the central wavelength information of the concave fine spectral structure in the corresponding reflection spectrum and then perform differential data processing on it, which reduces the influence of temperature fluctuations on the measurement results and greatly improves the adaptability of the device to the environment , so as to realize a brand-new temperature uncoupled three-dimensional microscale measurement.

The technical solution of the present invention is: a micro-scale measurement device based on a three-core tapered phase-shifting fiber grating, including a broadband light source, a spectrum analysis device, an optical ring device, a control computer, a multi-channel optical switch and an external reference grating, the The broadband light source and the spectrum analyzer are respectively connected to the optical circulator, and the optical circulator is connected to the multi-channel optical switch, the multi-channel optical switch and the control computer, the control computer and the spectrum analyzer, and the multi-channel optical switch to the external reference grating to form a path. It is characterized in that three single-mode optical fibers respectively connect the multi-channel optical switch with the tail fiber of the three-core tapered phase-shifting fiber grating probe, and the probe holder is fixedly installed with the three-core tapered phase-shifting fiber grating probe (the end with a larger diameter, the The tail fiber of the three-core tapered phase-shifting fiber grating probe described above is connected to three tapered phase-shifting fiber gratings in the three-core tapered phase-shifting fiber grating probe to form a path, and the end of the three-core tapered phase-shifting fiber grating probe with a smaller diameter has The spherical needle tip is coated with a layer of light-absorbing material on the surface of the spherical needle tip.

A three-dimensional micro-scale measurement method based on a three-core tapered phase-shifting fiber grating, characterized in that during the measurement process, a multi-channel optical switch switches different optical paths under the control of a control computer, and uses a spectrum analysis device to measure the three-core tapered phase shift respectively The reflection spectra of the three tapered phase-shifting fiber gratings inside the fiber grating probe and the external reference grating. In data processing, the center wavelength offset of the reflection spectrum of the external reference grating is used as the temperature drift information, which is compared with the three-core tapered phase-shifting fiber grating probe respectively. The central wavelength of the concave fine spectral structure in the reflection spectrum of the two groups of fiber gratings in the needle is processed by differential data to obtain the wavelength offset only affected by the displacement, and then the geometric relationship of the three fiber gratings inside the three-core tapered phase-shifting fiber grating probe is used , obtain axial and radial contact displacements without temperature coupling, and realize three-dimensional micro-scale measurement without temperature coupling.

The advantages of the present invention are:

1. The three-dimensional micro-scale measurement device and method based on the three-core tapered phase-shifting fiber grating has the characteristics of high precision, small contact force, no damage to the surface of the measured part, and long service life of the probe.

2. The optical detection signal is only transmitted inside the fiber grating, and the contact in space is converted into the change of the central wavelength of the reflection spectrum. When measuring micro-scale parts, it is not affected by the shadowing effect of the parts. The measurement depth-to-diameter ratio can reach 100:1, satisfying The requirements for micro-scale measurement of microstructures with large aspect ratio are fulfilled.

3. The three-dimensional micro-scale measurement method based on the three-core tapered phase-shifting fiber grating enables the probe to have two-dimensional radial uncoupled sensing capabilities, and the two sets of orthogonal fiber gratings in the probe can respectively measure the touching displacement in this direction , which realizes radial and orthogonal hit decoupling.

4. The three-dimensional micro-scale measurement method based on the three-core tapered phase-shifting fiber grating can simultaneously realize radial and axial coupling-free measurement, simplify the steps of micro-scale measurement, and improve the efficiency of micro-scale measurement.

5. A mutual-reference differential compensation system is designed inside the probe, combined with a three-dimensional micro-scale measurement method based on a three-core tapered phase-shifting fiber grating, which eliminates the impact of ambient temperature changes on measurement and greatly improves the sensor's adaptability to the environment It can go deep into the space and environment where traditional measurement tools cannot work normally to perform precise measurement, such as narrow semi-enclosed spaces and flammable and explosive environments, and is also suitable for industrial on-site measurement.

6. The sensitivity of the tapered structure probe is close to that of the cylindrical structure probe with the same diameter at the larger end of the cone, but the three-core tapered phase-shift fiber grating probe can measure smaller size parts.

7. By designing the phase shift point in the probe and measuring the fine spectral structure generated by it, the spectral distortion caused by the non-uniform spectrum in the tapered probe can be avoided, thereby improving the size measurement accuracy.

8. The spherical tip of the three-core tapered phase-shifting fiber grating probe is coated with light-absorbing material to prevent the optical signal in the probe from being emitted by the spherical tip of the probe and reflected by the surface of the part when the probe performs axial measurement. , and then coupled into the optical fiber, interference occurs, thereby improving the reliability and accuracy of axial measurement.

Description of drawings

Figure 1 is a schematic diagram of the structure of a three-dimensional microscale measurement device based on a three-core fiber grating;

In the figure: 1. Broadband light source, 2. Spectral analysis device, 3. Optical circulator, 4. Control computer, 5. Multi-channel optical switch, 6. Single-mode fiber, 7. External reference grating, 8. Three-core tapered phase Fiber grating probe pigtail, 9. probe holder, 10. three-core tapered phase-shifting fiber grating probe, 11. spherical needle tip, 12. light-absorbing material layer.

Fig. 2 is the sectional view of A-A among Fig. 1;

Among the figure: 13. The tapered phase-shifting fiber grating 1, 14. The tapered phase-shifting fiber grating forming the three-core tapered phase-shifting fiber grating probe 2, 15. The three-core tapered phase-shifting fiber grating forming the probe Tapered phase-shifting fiber grating 3 for shifting fiber grating probes.

Fig. 3 is an enlarged cross-sectional view of the three-core fiber grating probe in Fig. 1 .

Among the figure: 16. The tapered phase-shifting fiber grating 1, 17. The tapered phase-shifting fiber Bragg grating forming the three-core tapered phase-shifting fiber grating probe 2, 18. The three-core tapered phase-shifting fiber grating forming the probe Tapered phase-shifting fiber grating 3 for shifting fiber grating probes.

Fig. 4 is a schematic diagram of the fine spectral structure of the reflection spectrum distortion and the depression produced by the phase shift point under the non-uniform strain of the tapered phase shifting fiber.

In the figure: 19. The reflection spectrum of the three-core tapered phase-shifting fiber Bragg grating probe before the action of the displacement sensing signal, 20. The fine spectral structure of the depression in the reflection spectrum of the three-core tapered phase-shifting fiber Bragg grating probe, 21. The action of the displacement sensing signal The final taper is the reflection spectrum of the 1 (cylindrical) probe, 22. The taper after the displacement sensing signal is the reflection spectrum of the 1.2 probe, 23. The taper after the displacement sensing signal is the reflection spectrum of the 1.5 probe, 24. The taper after the action of the displacement sensing signal is the reflection spectrum of the 2 probe.

Fig. 5 is the spectrum of the coherent signal interference of the reflected signal of the part collected by the spectral analysis device during the axial measurement when the spherical tip of the probe has no light-absorbing coating.

detailed description

Below in conjunction with accompanying drawing, specific embodiment of the present invention is described in further detail:

A micro-scale measurement device based on a three-core tapered phase-shifting fiber grating, including a broadband light source 1, a spectrum analysis device 2, an optical ring device 3, a control computer 4, a multi-channel optical switch (5) and an external reference grating 7, the The broadband light source 1 and the spectrum analyzer 2 are respectively connected to the optical ring device 3, the optical circulator 3 is connected to the multi-channel optical switch 5, the multi-channel optical switch 5 is connected to the control computer 4, the control computer 4 is connected to the spectrum analyzer 2, and the multi-channel optical switch 5 is connected with an external reference grating 7 to form a path, which is characterized in that three single-mode optical fibers 6 respectively connect the multi-channel optical switch 5 with the three-core tapered phase-shifting fiber Bragg grating probe pigtail 8, and the probe holder 9 is fixed with three cores One end with a larger diameter of the tapered phase-shifting fiber grating probe 10, the three-core tapered phase-shifting fiber grating probe pigtail 8 is connected with three tapered phase-shifting fiber gratings in the three-core tapered phase-shifting fiber grating probe 10 to form In the channel, the end of the three-core tapered phase-shift fiber grating probe 10 with a smaller diameter has a spherical needle tip 11, and the surface of the spherical needle tip 11 is coated with a light-absorbing material layer 12.

The thickness of the light-absorbing material layer 12 coated on the spherical needle tip 11 is not greater than 20 microns.

The material of the light-absorbing material layer 12 coated on the spherical tip 11 can be gold nanoparticles or copper sulfide nanoparticles or tungsten oxide nanoparticles or indium tin oxide nanoparticles or aluminum-doped zinc oxide nanoparticles or antimony-doped dioxide Tin nanoparticles, polypyrrole nanoparticles or cesium tungstate nanoparticles or graphene or single-wall and multi-wall carbon tubes or carbon-containing light-absorbing inks or dye light-absorbing inks, but not limited to the above-mentioned light-absorbing materials.

The three-core tapered phase-shifting fiber grating probe 10 is composed of three tapered phase-shifting fiber gratings whose size error is less than 10%, and the three tapered phase-shifting fiber gratings are arranged in an equilateral triangle array.

The structure of the three-core tapered phase-shift fiber grating probe 10 can be formed by self-assembly of three tapered phase-shift fiber gratings in low-viscosity ultraviolet glue.

The phase shift points of the three tapered phase-shifting fiber gratings in the three-core tapered phase-shifting fiber grating probe 10 are located at the center of the length of the tapered phase-shifting fiber gratings, and the phase shift amount is π/2.

A three-dimensional micro-scale measurement method based on a three-core tapered phase-shifting fiber grating, characterized in that during the measurement process, a multi-channel optical switch 5 switches different optical paths under the control of a control computer 4, and uses a spectrum analysis device 2 to measure the three cores respectively The reflection spectrum of the three tapered phase-shifting fiber gratings inside the tapered phase-shifting fiber grating probe 10 and the external reference grating 7, during data processing, using the center wavelength offset of the reflection spectrum of the external reference grating 7 as temperature drift information, Respectively perform differential data processing with the central wavelength of the concave fine spectral structure in the two groups of fiber grating reflection spectra in the three-core tapered phase-shift fiber grating probe 10 to obtain the wavelength offset only affected by the displacement, and then use the three-core tapered phase shift The geometric relationship of the three fiber gratings inside the fiber grating probe 10 can obtain the axial and radial touching displacement without temperature coupling, and realize the three-dimensional micro-scale measurement without temperature coupling.

Working process of the present invention is as follows:

The broadband light generated by the broadband light source 1 enters the multi-channel optical switch 5 through the optical circulator 3, and the multi-channel optical switch 5 is under the control of the control computer 4, and the spectrum analysis device 2 respectively measures the Reflection spectra of three tapered phase-shifting fiber gratings and an external reference grating 7. When the three-core tapered phase-shift fiber grating probe 10 touches the part to be tested, the central wavelength of the concave fine spectral structure in the reflection spectrum of the fiber grating in the three-core tapered phase-shift fiber grating probe 10 will change. In data processing, the center wavelength offset of the reflection spectrum of the external reference grating 7 is used as the temperature drift information, which is compared with the center wavelength of the concave fine spectral structure in the two groups of fiber grating reflection spectra in the three-core tapered phase-shift fiber grating probe 10 respectively. The differential data processing obtains the wavelength offset only affected by the displacement, and then uses the geometric relationship of the three fiber gratings inside the three-core tapered phase-shifting fiber grating probe 10 to obtain the axial and radial contact displacement without temperature coupling.

Combining the radial and axial contact displacement information, the three-dimensional micro-scale measurement of parts is finally realized.

The technical innovations and beneficial technical effects of the micro-scale measuring device and method based on the three-core tapered phase-shifting fiber grating are: the tapered probe structure design is adopted, and its sensitivity is the same as that of a cylindrical structure probe with the same diameter at the larger end of the tapered structure. The needle is similar, but the measurable size of the tapered probe is smaller, which can break through the measurement problems of microholes, microgrooves and other parts below 100 microns. By setting the phase shift point in the fiber grating and measuring the fine spectral structure generated by it, the spectral distortion caused by the non-uniform spectrum in the tapered probe can be avoided, thereby improving the measurement accuracy of the size. The spherical tip of the probe is coated with a light-absorbing material to prevent the optical signal in the probe from being emitted by the spherical tip of the probe and reflected by the surface of the part when the probe performs axial measurement, and then coupled into the optical fiber to cause interference. Thereby improving the axial measurement reliability and precision.

Claims (7)

1. The utility model provides a microscale measuring device based on three-core toper phase shift fiber grating, includes broadband light source (1), spectral analysis device (2), light circulator (3), control computer (4), multichannel photoswitch (5) and outside reference grating (7), broadband light source (1) and spectral analysis appearance (2) are connected with light circulator (3) respectively, and light circulator (3) and multichannel photoswitch (5), multichannel photoswitch (5) and control computer (4), control computer (4) and spectral analysis appearance (2), multichannel photoswitch (5) are connected with outside reference grating (7) and are formed the route, its characterized in that three single mode fiber (6) are respectively with multichannel photoswitch (5) and three-core toper phase shift fiber grating probe tail fiber (8) intercommunication, the probe holder (9) admittedly is equipped with the great one end of three-core toper phase shift fiber grating probe (10) diameter, three-core toper phase shift fiber grating probe tail fiber grating (8) and the toper phase shift fiber grating probe (10) in the ball-shaped light absorption grating probe (11) that the needle point is connected has the ball-shaped light absorption grating material layer (11), three-shaped pyramid phase shift fiber grating probe (10) are connected with the ball-shaped material layer.

2. The micro-scale measurement device based on the three-core tapered phase-shifting fiber grating of claim 1, wherein: the thickness of a light absorption material layer (12) coated on a spherical needle tip (11) of the three-core conical phase-shift fiber grating probe (10) is not more than 20 micrometers.

3. The micro-scale measurement device based on the three-core tapered phase-shifting fiber grating of claim 1, wherein: the material of the light absorption material layer (12) coated on the spherical needle tip (11) of the three-core conical phase-shift fiber grating probe (10) can be gold nanoparticles, copper sulfide nanoparticles, tungsten oxide nanoparticles, indium tin oxide nanoparticles, aluminum-doped zinc oxide nanoparticles, antimony-doped tin dioxide nanoparticles, polypyrrole nanoparticles, cesium tungstate nanoparticles, graphene, single-wall and multi-wall carbon tubes, carbon-containing ink or dye light absorption ink, but is not limited to the light absorption material.

4. The micro-scale measurement device based on the three-core tapered phase-shifting fiber grating of claim 1, wherein: the three-core conical phase-shift fiber grating probe (10) is composed of three conical phase-shift fiber gratings with the size error smaller than 10%, and the three conical phase-shift fiber gratings are arranged in an equilateral triangle array.

5. The micro-scale measurement device based on the three-core tapered phase-shifting fiber grating according to claim 1, characterized in that: the structure of the three-core tapered phase-shift fiber grating probe (10) can be formed by three tapered phase-shift fiber gratings through self-assembly action in low-viscosity ultraviolet glue.

6. The micro-scale measurement device based on the three-core tapered phase-shifting fiber grating according to claim 1, characterized in that: the phase shift points of three conical phase shift fiber gratings in the three-core conical phase shift fiber grating probe (10) are all positioned in the center of the length of the conical phase shift fiber grating for shifting, and the phase shift amount is pi/2.

7. A three-dimensional micro-scale measurement method based on a three-core tapered phase-shift fiber grating is characterized in that in the measurement process, a multi-path optical switch (5) switches different optical paths under the control of a control computer (4), a spectrum analysis device (2) is used for respectively measuring the reflection spectrums of the three tapered phase-shift fiber gratings and an external reference grating (7) in a three-core tapered phase-shift fiber grating probe (10), in the data processing, the central wavelength offset of the reflection spectrum of the external reference grating (7) is used as temperature drift information, the central wavelength offset and the central wavelength of a concave fine spectrum structure in the two groups of fiber grating reflection spectrums in the three-core tapered phase-shift fiber grating probe (10) are respectively subjected to differential data processing to obtain the wavelength offset only affected by displacement, then the geometric relation of the three fiber gratings in the three-core tapered phase-shift fiber grating probe (10) is used for obtaining axial and radial touch displacement without temperature coupling, and three-dimensional micro-scale measurement without temperature coupling is realized.

Images