CN114440781B - Gap sensor, gap measuring method and measuring device - Google Patents
Gap sensor, gap measuring method and measuring device Download PDFInfo
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- CN114440781B CN114440781B CN202210073673.4A CN202210073673A CN114440781B CN 114440781 B CN114440781 B CN 114440781B CN 202210073673 A CN202210073673 A CN 202210073673A CN 114440781 B CN114440781 B CN 114440781B
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Abstract
In order to solve the problems that a certain error is introduced to the effective right area of a capacitor plate when a capacitance method is adopted to measure gaps in the prior art and the capacitance measurement process is easy to be interfered by electromagnetic waves, the embodiment of the invention provides a gap sensor, a gap measurement method and a measurement device, which comprise the following steps: a 45 DEG reflecting mirror provided on one inner wall of the gap to change the direction of the light wave propagating to the 45 DEG reflecting mirror; and an optical fiber, the optical fiber end face being arranged on the one inner wall of the gap; the optical fiber end face is used for reflecting part of light of the light beam in the optical fiber back to the optical fiber to form a reference light wave, the optical fiber end face is used for enabling the other part of light of the light beam in the optical fiber to pass through the optical fiber end face and linearly propagate to the 45-degree reflecting mirror, so that the 45-degree reflecting mirror reflects the other part of light of the light beam to the other inner wall of the gap to form a detection light wave which is used for being reflected back to the optical fiber through the 45-degree reflecting mirror and is used for interfering with the reference light wave, and therefore distance from one inner wall of the gap to the other inner wall of the gap is measured. The embodiment of the invention avoids the defects that a certain error is introduced to the effective right-facing area of the capacitor plate when the gap measurement is carried out by adopting a capacitance method and the capacitance measurement process is easy to be subjected to electromagnetic interference.
Description
Technical Field
The invention relates to a gap sensor, a gap measuring method and a measuring device.
Background
In the design and manufacturing process of some high quality industrial products, it is often necessary to detect a sub-millimeter gap, the material constituting the gap is sometimes an insulator or a wire inconvenient for connecting an electric signal, and the space left for the sensor is limited and complicated. The current method that can partially meet the gap measurement needs is mainly the sheet capacitance method.
The sensor of the method consists of two metal sheets, and is respectively opposite to and fixed on two walls of a gap when being used for gap measurement, and is used as two polar plates of a capacitor. The capacitance is related to the geometry of the plates, the plate spacing, the positive area and the inter-plate medium.
Under normal conditions, the medium and the opposite area between the two polar plates are kept unchanged, the measured capacitance value and the gap value are in inverse proportion, and the gap size can be correspondingly calculated by detecting the capacitance value. Although this parallel plate capacitance method can give a gap between a parallel plate and a bipolar plate, there are several problems: firstly, the electrode plate itself has a certain thickness (generally about 0.4mm of the total thickness of two sheets) and a certain width (generally more than 5 mm), and has a certain difficulty in measuring smaller and narrower gaps; secondly, in the actual measurement process, when two wall surfaces of a gap are in lateral relative movement sometimes, a certain error is introduced into the effective right-facing area of the capacitor polar plate, so that the measurement accuracy is affected; finally, the accuracy of the capacitive gap measurement depends on the accuracy of the capacitive measurement, however the capacitive measurement process is susceptible to electromagnetic interference.
Disclosure of Invention
In order to solve the problems that a certain error is introduced to the effective right area of a capacitor plate when a capacitance method is adopted to measure gaps in the prior art and the capacitance measurement process is easy to be interfered by electromagnetic waves, the embodiment of the invention provides a gap sensor, a gap measurement method and a measurement device.
The embodiment of the invention is realized by the following technical scheme:
in a first aspect, an embodiment of the present invention provides a gap measurement sensor, including:
a 45 DEG reflecting mirror provided on one inner wall of the gap to change the direction of the light wave propagating to the 45 DEG reflecting mirror;
and an optical fiber, one end of which is arranged on the inner wall of the gap; the optical fiber is used for linearly transmitting the emitted light wave to the 45-degree reflecting mirror, so that the 45-degree reflecting mirror reflects the emitted light wave to the other inner wall of the gap to form a reflected light wave for being reflected back to the optical fiber through the 45-degree reflecting mirror, and the distance from one inner wall of the gap to the other inner wall of the gap is measured.
Further, the gap measurement sensor includes:
a sheet provided with a groove along the length direction;
the 45-degree reflecting mirror is arranged in the groove, and one side of the 45-degree reflecting mirror is flush with one side of the sheet;
and one end of the optical fiber is arranged in the groove and is used for linearly transmitting the emitted light waves to the 45-degree reflecting mirror or linearly receiving the reflected light waves from the 45-degree reflecting mirror, and one side of the optical fiber is flush with one side of the sheet.
Further, the sheet is rectangular in structure.
Further, the sheet includes: a first sheet and a second sheet; the groove is formed between both sides of the first sheet and the second sheet which are close to each other.
Further, the thickness of the sensor is 80 mu m, and the transverse width is 0.9mm; wherein, the core diameter of the optical fiber is 9 mu m, and the cladding diameter of the optical fiber is 80 mu m; the thin sheet is a tantalum sheet with the thickness of 0.08mm and the specification of 0.4x1.5 mm; the thickness and width of the 45 mirror were 80 μm.
In a second aspect, an embodiment of the present invention provides a method for measuring a gap of the sensor, including:
transmitting an emission light wave emission instruction to control a light wave generation device to linearly propagate the emission light wave to a 45-degree reflecting mirror positioned on one inner wall of a gap through an optical fiber, so that the 45-degree reflecting mirror reflects the emission light wave to the other inner wall of the gap to form a reflected light wave for being reflected back to the optical fiber through the 45-degree reflecting mirror;
transmitting a frequency domain signal acquisition instruction to control a frequency domain signal acquisition device to acquire an emitted light wave and a reflected light wave, and completing interference and photoelectric conversion of the emitted light wave and the reflected light wave to obtain a frequency domain interference signal;
and (3) utilizing Fourier analysis to process the frequency domain interference signal to obtain the time difference between the emitted light wave and the reflected light wave, and calculating to obtain the distance between the reference reflecting surface of the 45-degree optical fiber end face and the other inner wall of the gap.
Further, the Fourier analysis is utilized to process the frequency domain interference signal to obtain the time difference between the emitted light wave and the reflected light wave, and the distance between the reference reflecting surface of the end face of the 45-degree optical fiber and the other inner wall of the gap is calculated; the distance d between the reference reflecting surface of the end face of the optical fiber and the other inner wall of the gap is calculated by using the following formula:
where τ is the time difference between the emitted and reflected light waves, c is the speed of light in vacuum, and n is the refractive index of the transmission medium.
In a third aspect, an embodiment of the present invention provides a gap measurement method, including:
executing the measuring method to measure the U-shaped piece with the gap height h to obtain the distance l between the reference reflecting surface of the 45-degree optical fiber end face in the U-shaped piece and the other inner wall of the standard gap piece 1 ；
The measuring method is executed to measure the gap value to be measured of the to-be-measured piece, and the distance l between the reference reflecting surface of the 45-degree optical fiber end face in the to-be-measured piece and the other inner wall of the standard gap piece is obtained 2 ；
Calculating a gap value g to be measured of the workpiece by using the following formula
g＝l 2 -l 1 +h。
In a fourth aspect, an embodiment of the present invention provides a gap measurement apparatus, including:
a broadband light source for generating broadband light waves;
the optical wave transmission device is used for receiving the broadband optical wave and transmitting the broadband optical wave to the optical fiber of the gap sensor;
the gap sensor is used for being connected with the light wave transmission device through an optical fiber;
the frequency domain signal acquisition instrument is used for acquiring emitted light waves and reflected light waves in the gap optical fiber to complete interference and photoelectric conversion of the emitted light waves and the reflected light waves, so as to obtain frequency domain interference signals;
and the computer is used for processing the frequency domain interference signals by utilizing Fourier analysis to obtain the time difference between the emitted light wave and the reflected light wave, and calculating the distance between the reference reflecting surface of the end face of the 45-degree optical fiber and the other inner wall of the gap.
Further, the optical wave transmission device includes:
the optical fiber circulator is used for receiving broadband light waves generated by the broadband light source;
and/or a multiplexing component for receiving the broadband light wave and transmitting the broadband light wave to an optical fiber of the gap sensor.
Compared with the prior art, the embodiment of the invention has the following advantages and beneficial effects:
according to the gap sensor, the gap measuring method and the measuring device, emitted light waves are transmitted to the 45-degree reflecting mirror through the straight line, so that the 45-degree reflecting mirror reflects the emitted light waves to the other inner wall of the gap to form reflected light waves for being reflected back to the optical fiber through the 45-degree reflecting mirror, the distance from one inner wall of the gap to the other inner wall of the gap is measured, and the defects that a certain error is caused by the effective dead area of a capacitor plate when the gap is measured by adopting a capacitance method in the prior art and electromagnetic interference is easily caused in the capacitance measuring process are avoided.
Drawings
In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings that are needed in the examples will be briefly described below, it being understood that the following drawings only illustrate some examples of the present invention and therefore should not be considered as limiting the scope, and that other related drawings may be obtained from these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram of a gap sensor.
FIG. 2 is a schematic diagram of a gap measurement device; wherein, the solid line is light wave signal transmission, and the dotted line is data transmission.
Fig. 3 is a schematic structural diagram of a U-shaped calibration fixture.
FIG. 4 is a schematic diagram of the placement position relationship between the gap sensor and the U-shaped calibration fixture.
Fig. 5 is a schematic diagram of a principle of a gap sensor for measuring the gap of a U-shaped calibration fixture.
Fig. 6 is a schematic diagram of the principle of the gap sensor for measuring the gap of the object to be measured.
Fig. 7 is a plot of raw frequency interference signals measured simultaneously for three gaps.
Fig. 8 is a signal plot of the signal of fig. 7 after fourier analysis.
Fig. 9 is a flow chart of a gap measurement method.
In the drawings, the reference numerals and corresponding part names:
in the figure: the device comprises a 101-optical fiber, a 102-first thin sheet, a 103-reference light reflecting surface, a 104-45-degree reflecting mirror, a 105-second thin sheet, a 201-broadband light source, a 202-optical fiber circulator, a 203-frequency domain signal acquisition instrument, a 204-computer, a 205-upper surface of a measured gap, a 206-miniature gap sensor, a 207-transmission optical fiber, a 208-lower surface of the measured gap, a 209-multiplexing assembly and a 301-U-shaped calibration tool.
Detailed Description
For the purpose of making apparent the objects, technical solutions and advantages of the present invention, the present invention will be further described in detail with reference to the following examples and the accompanying drawings, wherein the exemplary embodiments of the present invention and the descriptions thereof are for illustrating the present invention only and are not to be construed as limiting the present invention.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that: no such specific details are necessary to practice the invention. In other instances, well-known structures, circuits, materials, or methods have not been described in detail in order not to obscure the invention.
Throughout the specification, references to "one embodiment," "an embodiment," "one example," or "an example" mean: a particular feature, structure, or characteristic described in connection with the embodiment or example is included within at least one embodiment of the invention. Thus, the appearances of the phrases "in one embodiment," "in an example," or "in an example" in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combination and/or sub-combination in one or more embodiments or examples. Moreover, those of ordinary skill in the art will appreciate that the illustrations provided herein are for illustrative purposes and that the illustrations are not necessarily drawn to scale. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
In the description of the present invention, the terms "front", "rear", "left", "right", "upper", "lower", "vertical", "horizontal", "high", "low", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, merely to facilitate description of the present invention and simplify description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the scope of the present invention.
Examples
In order to solve the problems that a certain error is introduced to the effective right area of a capacitor plate when a capacitance method is adopted to measure gaps in the prior art and the capacitance measurement process is easy to be interfered by electromagnetic waves, the embodiment of the invention provides a gap sensor, a gap measurement method and a measurement device, and the gap sensor, the gap measurement method and the measurement device are shown by referring to figures 1-8.
The gap sensor, the gap measuring method and the measuring device are designed based on the spectrum interference principle, and the specific deduction process is as follows:
two beams of broadband light wave signals with correlation are adopted to be subjected to interference detection through a frequency domain signal acquisition instrument, and light waves with different frequency components are respectively subjected to interference superposition, so that interference fringes with alternate brightness and darkness are finally formed on a frequency domain (the reciprocal domain of wavelength). The theoretical derivation is shown below:
with interference-participating reference-wave and detection-wave signals E ref (t) and E prb (t) are respectively
E ref (t)＝E 0 exp(i2πf 0 t+iφ r ) (1)
Wherein E is ref (t) and E prb (t) is the complex amplitude, f 0 For the frequency (ratio of light velocity to wavelength) of a certain light wave component, τ is the transmission time difference of two light wave signals, φ r And phi p Is the initial phase of the two light waves, and R is the relative coefficient of the reflected detection light (namely the ratio of the detection light to the reference light intensity) of the detected target.
In a frequency domain signal acquisition instrument (which scans light intensity at equally spaced wavelengths, unlike a spectrometer), two broadband light waves are dispersed into a plurality of frequencies, each frequency component comprising E ref (t) and E prb (t) the two complex amplitudes are coupled to one photoelectric conversion element at the same time. Because the photoelectric conversion process is square rate detection, the square of the sum of (1) and (2) can be obtained 0 The spectral intensity of the component interference field is as follows:
where η is a constant coefficient including factors such as photoelectric conversion efficiency. Photoelectric conversion element in frequency domain signal acquisition instrumentThe part cannot respond to f on the order of hundred terahertz 0 And higher frequency time-varying signals, so that their average value 0 is output, and thus the last three terms of equation (3) can be omitted and rewritten as:
from the formula (4), the intensity of the frequency domain interference field is not only related to the reflectivity R and the initial phase angle phi of the light wave signal r 、φ p The frequency f of the light wave and the transmission time difference tau are related, and the transmission time difference tau is the period of the interference signal. Thus, the frequency domain interference field intensity distribution acquired by the spectrometer can be written as:
in which I 0 (f) For the spectral distribution function of the reference broadband light wave, Δφ is the initial phase difference between the reference light wave and the probe light wave, and in general, the influence of chromatic dispersion can be ignored, i.e., Δφ is a constant.
Carrying out Fourier analysis on the frequency domain interference signal in the formula (5), so as to obtain the transmission time difference tau of two light waves, and further calculating the distance d between the reference light reflecting surface and the measured surface as follows:
where c is the speed of light in vacuum and n is the refractive index of the transmission medium.
When the principle is applied to gap measurement, one surface of the gap is a measured surface and is used for reflecting detection light waves, the other surface of the gap is stuck with a gap sensor, and the reference light reflecting surface is an end surface of an optical fiber in the gap sensor.
Based on this, in a first aspect, an embodiment of the present invention provides a gap sensor, as shown in fig. 1, including: a 45 DEG reflecting mirror provided on one inner wall of the gap to change the direction of the light wave propagating to the 45 DEG reflecting mirror; and an optical fiber 101 having one end for being provided to the one inner wall of the gap; the optical fiber is used for linearly transmitting the emitted light wave to the 45-degree reflecting mirror, so that the 45-degree reflecting mirror reflects the emitted light wave to the other inner wall of the gap to form a reflected light wave for being reflected back to the optical fiber through the 45-degree reflecting mirror, and the distance from one inner wall of the gap to the other inner wall of the gap is measured.
Therefore, the embodiment of the invention transmits the emitted light wave to the 45-degree reflecting mirror through straight line, so that the 45-degree reflecting mirror reflects the emitted light wave to the other inner wall of the gap to form the reflected light wave for reflecting the reflected light wave back to the optical fiber through the 45-degree reflecting mirror, thereby realizing the measurement of the distance from one inner wall of the gap to the other inner wall of the gap, and avoiding the defects that a certain error is introduced to the effective dead area of the capacitor plate and the capacitance measurement process is easy to be affected by electromagnetic interference when the capacitance method is adopted for measuring the gap in the prior art.
Optionally, the gap measurement sensor includes: a sheet provided with a groove along the length direction; the 45-degree reflecting mirror is arranged in the groove, and one side of the 45-degree reflecting mirror is flush with one side of the sheet; and one end of the optical fiber is arranged in the groove and is used for linearly transmitting the emitted light waves to the 45-degree reflecting mirror or linearly receiving the reflected light waves from the 45-degree reflecting mirror, and one side of the optical fiber is flush with one side of the sheet.
Further, the sheet is rectangular in structure.
Further, the sheet includes: a first sheet 102 and a second sheet 105; the groove is formed between both sides of the first sheet and the second sheet which are close to each other.
Alternatively, referring to FIG. 1, the fiber 101 with the coating removed is tightly sandwiched between two sheets, with the middle fiber end face being the reference light reflecting surface 103, coated with a reflective film with a return loss of 30 dB. Opposite the reference light reflecting surface 103 is a micro 45 degree mirror 104, which is used to reflect the light wave in a direction perpendicular to the first sheet 102, and has a width equal to the diameter of the optical fiber, a height equal to the thickness of the sheet, and a length of about 1/3 of the length of the sheet. The thin sheet is fixed with the optical fiber 101 and the 45-degree reflecting mirror 104 through glue.
For a more compact design, facilitating the use of smaller gap measurements, optionally the sensor is a miniature gap sensor; the thickness of the sensor is 80 mu m, and the transverse width is 0.9mm; wherein, the core diameter of the optical fiber is 9 mu m, and the cladding diameter of the optical fiber is 80 mu m; the thin sheet is a tantalum sheet with the thickness of 0.08mm and the specification of 0.4x1.5 mm; the thickness and width of the 45 mirror were 80 μm.
Specifically, the optical fiber of the optical fiber gap sensor adopts a single-mode optical fiber with the core diameter of 9 mu m, the cladding diameter of 80 mu m and the working center wavelength of 1550 nm; the bracket material is a tantalum sheet with the thickness of 0.08mm, and is manufactured into a 0.4X1.5 mm microchip by adopting a femtosecond laser processing technology; the reflector adopts micro 45-degree reflector with thickness and width of 80 μm. The optical fiber, the bracket and the reflector are tightly attached, and are fixed by using glue, so that the thickness of the manufactured sensor is about 80 mu m, and the transverse width is about 0.9mm.
Therefore, the embodiment of the invention adopts the optical fiber structural design, the thickness of the sensor can be reduced to the optical fiber diameter level (less than 0.1 mm), the transverse dimension can be reduced to below 1mm, and the sensor is very suitable for small-gap measurement in a limited space. The light beam of the sensor directly irradiates the gap surface, and the reflected light is used for measurement, so that the problem of dead area does not exist. The measuring device adopts the spectrum interference technology, and the light beam on the system link is entirely transmitted in the optical fiber, so that the electromagnetic interference is not easy to happen.
In a second aspect, an embodiment of the present invention provides a method for measuring a gap of a sensor, where an execution body may be a server, and referring to fig. 9, including:
s101, transmitting an emission light wave emission instruction to control a light wave generating device to linearly transmit the emission light wave to a 45-degree reflecting mirror positioned on one inner wall of a gap through an optical fiber, so that the 45-degree reflecting mirror reflects the emission light wave to the other inner wall of the gap to form a reflection light wave for being reflected back to the optical fiber through the 45-degree reflecting mirror;
s102, sending a frequency domain signal acquisition instruction to control a frequency domain signal acquisition device to acquire an emitted light wave and a reflected light wave, and completing interference and photoelectric conversion of the emitted light wave and the reflected light wave to obtain a frequency domain interference signal;
s103, utilizing Fourier analysis to process the frequency domain interference signals to obtain the time difference between the emitted light waves and the reflected light waves, and calculating to obtain the distance between the reference reflecting surface of the 45-degree optical fiber end face and the other inner wall of the gap.
Further, the Fourier analysis is utilized to process the frequency domain interference signal to obtain the time difference between the emitted light wave and the reflected light wave, and the distance between the reference reflecting surface of the end face of the 45-degree optical fiber and the other inner wall of the gap is calculated; the distance d between the reference reflecting surface of the end face of the optical fiber and the other inner wall of the gap is calculated by using the following formula:
where τ is the time difference between the emitted and reflected light waves, c is the speed of light in vacuum, and n is the refractive index of the transmission medium.
The principle is referred to above in the relevant content, and this will not be repeated.
In a third aspect, an embodiment of the present invention provides a gap measurement method, including:
executing the measuring method to measure the U-shaped piece with the gap height h to obtain the distance l between the reference reflecting surface of the 45-degree optical fiber end face in the U-shaped piece and the other inner wall of the standard gap piece 1 ；
The measuring method is executed to measure the gap value to be measured of the to-be-measured piece, and the distance l between the reference reflecting surface of the 45-degree optical fiber end face in the to-be-measured piece and the other inner wall of the standard gap piece is obtained 2 ；
Calculating a gap value g to be measured of the workpiece by using the following formula
g＝l 2 -l 1 +h。
The principle is referred to the following clearance measuring device content, which is not repeated.
In a fourth aspect, an embodiment of the present invention provides a gap measurement apparatus, as shown in fig. 2, including:
a broadband light source for generating broadband light waves;
the optical wave transmission device is used for receiving the broadband optical wave and transmitting the broadband optical wave to the optical fiber of the gap sensor;
the gap sensor is used for being connected with the light wave transmission device through an optical fiber;
the frequency domain signal acquisition instrument is used for acquiring emitted light waves and reflected light waves in the gap optical fiber to complete interference and photoelectric conversion of the emitted light waves and the reflected light waves, so as to obtain frequency domain interference signals;
and the computer is used for processing the frequency domain interference signals by utilizing Fourier analysis to obtain the time difference between the emitted light wave and the reflected light wave, and calculating the distance between the reference reflecting surface of the end face of the 45-degree optical fiber and the other inner wall of the gap.
Further, the optical wave transmission device includes:
the optical fiber circulator is used for receiving broadband light waves generated by the broadband light source;
and/or a multiplexing component for receiving the broadband light wave and transmitting the broadband light wave to an optical fiber of the gap sensor.
Referring to fig. 2, a broadband light wave generated by a broadband light source 201 is input from a 1 port of an optical fiber circulator 202, and a light wave output from a 2 port enters a multiplexing component 209 (which functions as beam splitting and combining or frequency splitting, and can be connected to a plurality of sensors to measure a plurality of gaps simultaneously), and output light thereof is sent to a micro gap sensor 206 by a transmission optical fiber 207. The miniature gap sensor 206 is glued to the lower surface 208 of the gap being measured. The micro gap sensor 206 collects the reflected reference light wave and detection light wave signals through the reflection of the upper surface 205 of the measured gap to the reference light wave and detection light wave signals, the reflected reference light wave and detection light wave signals are reversely input into the 2 ports of the optical fiber circulator 202 through the transmission optical fiber 207 and the multiplexing component 209 in sequence, and then output to the frequency domain signal acquisition instrument 203 from the 3 ports, so that interference, photoelectric conversion and acquisition of the reference light wave and the detection light wave are completed. The frequency domain interference signal of the frequency domain signal acquisition instrument is acquired through the computer 204, then the frequency domain interference signal is subjected to Fourier analysis to obtain a transmission time difference, and further distance information between the reference light reflecting surface and the measured surface is obtained through calculation.
Optionally, the broadband light source selects a single-mode optical fiber of a C band to couple out a spontaneous emission light source (ASE), and the power is 200mW; the optical fiber circulator is a 1550nm single-mode optical fiber circulator, the optical sweep frequency range of the frequency domain signal acquisition instrument is 191.25-196.12THz, and the sampling rate is 312.5MHz; the transmission optical fiber is a common single-mode optical fiber working at 1550nm wave band; the multiplexing component adopts a 1X 3 optical fiber coupler to split and combine beams; the gaps to be measured are three gaps with different values, and the reference light reflecting surfaces of the miniature optical fiber gap sensor are arranged at different positions so as to avoid influence on gap interpretation caused by the fact that peak values are close to each other and coincide when signals are subjected to Fourier analysis. Since the distance was calculated by using the formula (6) under the test in air, the vacuum light velocity c was 2.998 ×108m/s and the air refractive index n was 1.0003.
Optionally, the gap measurement is implemented by two steps of sensor calibration and formal measurement.
Calibrating a sensor: the micro gap sensor 206 is tightly attached to the lower surface of the measured gap by using glue, and the glue between the sensor and the lower surface of the measured gap has a certain thickness, so that calibration subtraction is required. The specific operation is to cover the upper surface of the sensor (refer to figure 4) with a U-shaped calibration tool 301 (U-shaped part) with the inner height h for calibration to obtain the distance l from the reference light reflecting surface of the sensor to the inner top surface of the calibration tool 1 (refer to fig. 5) for calculation of the gap to be measured;
formally measuring: after the calibration tool is taken out, the upper surface of the measured gap is installed in place, the gap is formally measured, and the distance l between the sensor reference light reflecting surface and the upper surface of the measured gap is obtained 2 (refer to FIG. 6).
As can be seen from fig. 3, in the actual measurement process, the distance l=l from the inner top surface of the calibration tool to the upper top surface of the measured gap 2 -l 1 Then the gap value g to be measured can be expressed as
g＝l 2 -l 1 +h (7)
Optionally, in the experiment, the device and the gap measuring method provided by the embodiment of the invention are used, the three gap sensors are calibrated by using a U-shaped tool with the height h of the inner top surface of 1mm, and the calibration value l is obtained 1 1.321mm, 1.208mm and 1.105mm respectively. For three roomsThe raw frequency interference signal of the slot simultaneous measurement is shown in fig. 7. As shown in fig. 8, the reflection efficiency of the third gap surface is far higher than that of the first two gaps, so the signal component intensity is far higher than that of the first two gaps. These three gap measurement readings l 2 0.512 mm, 0.765mm and 1.075mm, respectively, the gaps g are calculated to be 0.191mm, 0.557mm and 0.970mm, respectively, according to the foregoing equation (7).
In summary, the embodiment of the invention develops the miniature optical fiber gap sensor and the measuring device based on the spectrum interference principle, and realizes the measurement of the micro gap in the limited space.
Therefore, the embodiment of the invention has the advantage that the all-fiber miniature gap sensor and the measuring device are developed by utilizing the spectrum interference principle. The miniature gap sensor adopting the optical fiber structural design has small size (the minimum thickness is smaller than 0.1mm, and the transverse width is smaller than 1 mm), and is very suitable for measuring the miniature gap (0.1 mm to several millimeters) in a limited space. The measuring device consists of optical fiber devices, and signals are transmitted through the optical fibers, so that the measuring device has very strong electromagnetic interference resistance. The multiplexing component is matched with the arrangement of the distance between the reference light reflecting surfaces in the sensor, so that simultaneous measurement of a plurality of target gaps can be realized. And the signals are read through a Fourier analysis method, the gap value to be measured is obtained, the sensitivity degree to signal noise is low, and then the absolute gap measurement with micron-scale precision is realized. Therefore, the miniature gap sensor provided by the embodiment of the invention has the advantages of small size, compact system structure, convenience in operation and strong environmental adaptability, and has a pushing effect on the detection of the limited space gap in the development test of related industrial products.
The foregoing description of the embodiments has been provided for the purpose of illustrating the general principles of the invention, and is not meant to limit the scope of the invention, but to limit the invention to the particular embodiments, and any modifications, equivalents, improvements, etc. that fall within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (9)
1. A gap measurement sensor, comprising:
a 45 DEG reflecting mirror provided on one inner wall of the gap to change the direction of the light wave propagating to the 45 DEG reflecting mirror;
and an optical fiber, the optical fiber end face being arranged on the one inner wall of the gap; the optical fiber end face is used for reflecting part of light of the light beam in the optical fiber back to the optical fiber to form a reference light wave, the optical fiber end face is used for enabling the other part of light of the light beam in the optical fiber to pass through the optical fiber end face and linearly propagate to the 45-degree reflecting mirror, so that the 45-degree reflecting mirror reflects the other part of light of the light beam to the other inner wall of the gap to form a detection light wave which is used for reflecting the light beam back to the optical fiber through the 45-degree reflecting mirror and is used for interfering with the reference light wave, and therefore measurement of the distance from one inner wall of the gap to the other inner wall of the gap is achieved;
further comprises: a sheet; the thin sheet is provided with a groove along the length direction; the 45-degree reflecting mirror is arranged in the groove, and one side of the 45-degree reflecting mirror is flush with one side of the sheet; the optical fiber end face at one end of the optical fiber is arranged in the groove, and one side of the optical fiber is flush with one side of the sheet.
2. The gap measurement sensor of claim 1, wherein the sheet is rectangular in configuration.
3. The gap measurement sensor according to claim 1 or 2, characterized in that the sheet comprises: a first sheet and a second sheet; the groove is formed between both sides of the first sheet and the second sheet which are close to each other.
4. A gap measuring sensor according to claim 3, characterized in that the sensor has a thickness of 80 μm and a lateral width of 0.9mm; wherein, the core diameter of the optical fiber is 9 mu m, and the cladding diameter of the optical fiber is 80 mu m; the thin sheet is a tantalum sheet with the thickness of 0.08mm and the specification of 0.4x1.5 mm; the thickness and width of the 45 mirror were 80 μm.
5. A gap measurement method based on the sensor of any one of claims 1-4, comprising:
transmitting a reference light wave transmitting instruction to control a light wave generating device to transmit a light beam into an optical fiber, so that part of light of the light beam in the optical fiber is reflected back to the optical fiber from the end face of the optical fiber to form a reference light wave, and the other part of light of the light beam in the optical fiber is transmitted through the end face of the optical fiber and linearly transmitted to a 45-degree reflecting mirror, so that the 45-degree reflecting mirror reflects the other part of light of the light beam to the other inner wall of a gap to form a detection light wave which is used for being reflected back to the optical fiber through the 45-degree reflecting mirror and is used for interfering with the reference light wave;
transmitting a frequency domain signal acquisition instruction to control a frequency domain signal acquisition device to acquire a reference light wave and a detection light wave, and completing interference and photoelectric conversion of the reference light wave and the detection light wave to obtain a frequency domain interference signal;
and (3) utilizing Fourier analysis to process the frequency domain interference signal to obtain the time difference between the reference light wave and the detection light wave, and calculating to obtain the distance between the end face of the optical fiber and the other inner wall of the gap.
6. The gap measurement method of claim 5, wherein a time difference between the reference light wave and the detected light wave is obtained by fourier analysis processing of the frequency domain interference signal, and a distance between the end face of the optical fiber and the other inner wall of the gap is calculated; comprises calculating the distance between the end face of the optical fiber and the other inner wall of the gap by using the following formulad：
Where τ is the time difference between the reference and probe light waves, c is the speed of light in vacuum, and n is the refractive index of the transmission medium.
7. A gap measurement method, comprising:
performing the measurement method of claim 5 or 6 to measure the U-shaped standard part with the height h of the inner top surface to obtain the distance between the end surface of the optical fiber in the U-shaped standard part and the inner top surface of the U-shaped standard partl 1 ；
Execution ofThe measurement method of claim 5 or 6, wherein the distance between the end face of the optical fiber in the measurement member and the other inner wall of the measurement member is obtained by measuring the measurement gap value of the measurement memberl 2 ；
Calculating a gap value g to be measured of the workpiece by using the following formula
g=l 2 -l 1 +h。
8. A gap measuring device, comprising:
a broadband light source for generating broadband light waves;
a light wave transmitting means for receiving the broadband light wave and transmitting the broadband light wave to the optical fiber of the gap measuring sensor according to any one of claims 1 to 4, and receiving and transmitting the reference light wave and the probe light wave returned from the optical fiber of the gap measuring sensor;
the gap measurement sensor of any one of claims 1-4 for connection to an optical wave transmission device via an optical fiber;
the frequency domain signal acquisition instrument is used for acquiring reference light waves and detection light waves in the gap optical fiber so as to complete interference and photoelectric conversion of the reference light waves and the detection light waves and obtain frequency domain interference signals;
and the computer is used for processing the frequency domain interference signal by utilizing Fourier analysis to obtain the time difference between the reference light wave and the detection light wave, and calculating the distance between the end face of the optical fiber and the other inner wall of the gap.
9. The gap measurement device of claim 8 wherein the optical wave transmission device comprises:
the optical fiber circulator is used for receiving the broadband light wave generated by the broadband light source, and receiving and transmitting the reflected reference light wave and the reflected detection light wave;
and a multiplexing assembly for receiving, distributing and transmitting the broadband light waves to the optical fiber of the gap measurement sensor of any one of claims 1-4, and receiving and transmitting reference and probe light waves returned from the optical fiber of the gap measurement sensor.
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| DE19514852C2 (en) * | 1995-04-26 | 1997-07-03 | Deutsche Forsch Luft Raumfahrt | Method and arrangement for acceleration and vibration measurement |
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