CN117006956B - Method and system for measuring thickness of oil film on liquid surface - Google Patents
Method and system for measuring thickness of oil film on liquid surface Download PDFInfo
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- CN117006956B CN117006956B CN202311277192.6A CN202311277192A CN117006956B CN 117006956 B CN117006956 B CN 117006956B CN 202311277192 A CN202311277192 A CN 202311277192A CN 117006956 B CN117006956 B CN 117006956B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
- G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/20—Controlling water pollution; Waste water treatment
- Y02A20/204—Keeping clear the surface of open water from oil spills
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Abstract
本发明公开了一种液体表面的油膜厚度测量方法及系统，方法包括以下步骤：获取液体表面的油膜，以及油膜和液体之间形成的油液分界面；当有光信号入射时，油膜表面和油液分界面分别产生菲涅尔反射，并且油膜表面和油液分界面产生的菲涅尔反射光信号有一光程差；利用光程差以及反射回来的宽带光源干涉信号的特征，判断油膜表面和油液分界面不同位置反射回来的光信号，得到油膜厚度的光程；利用光程除以油品的折射率得到油膜的厚度。本发明利用干涉测量精度高以及白光干涉可以实现绝对物理量、绝对位置测量的特点，通过锯齿波驱动电压和多个管状压电陶瓷改变参考臂光纤的长度，实现对油膜上下表面的位置确定，最终实现油膜厚度的精确测量和信号解调。
The invention discloses a method and system for measuring the thickness of an oil film on a liquid surface. The method includes the following steps: obtaining the oil film on the liquid surface and the oil-liquid interface formed between the oil film and the liquid; when a light signal is incident, the oil film surface and The oil-liquid interface produces Fresnel reflections respectively, and the Fresnel reflected light signals generated by the oil film surface and the oil-liquid interface have an optical path difference; the optical path difference and the characteristics of the reflected broadband light source interference signal are used to determine the oil film surface. The optical signal reflected back from different positions of the oil interface is used to obtain the optical path of the oil film thickness; the optical path is divided by the refractive index of the oil to obtain the oil film thickness. This invention uses the characteristics of high interference measurement accuracy and white light interference to achieve absolute physical quantity and absolute position measurement. It changes the length of the reference arm optical fiber through sawtooth wave driving voltage and multiple tubular piezoelectric ceramics to determine the position of the upper and lower surfaces of the oil film. Finally, Achieve accurate measurement and signal demodulation of oil film thickness.
Description
Technical Field
The invention belongs to the technical field of optical fiber interferometry, and particularly relates to a method and a system for measuring the thickness of an oil film on the surface of a liquid.
Background
The oil film thickness of the liquid surface is an important parameter, and relates to practical application in many fields. The measurement of the thickness of the liquid surface oil film is an important and practical direction, and has important significance for scientific experiments of industrial production, petroleum exploration, life science and the like and monitoring of pollution of the water surface oil products in the marine aquaculture industry. With the continuous development of technology, the measurement method of the thickness of the liquid level oil film is also continuously developed and improved, and the currently commonly used measurement methods include a resistance method, a capacitance method, an ultrasonic method, a differential laser triangulation method, a laser-induced fluorescence method and the like. However, these conventional measurement methods have problems such as complicated and unstable sensors due to the necessity of liquid level isolation of electrodes of the electronic sensor, inaccurate measurement due to the change of capacitance when the oil film thickness is too small, and the like, and optical measurement methods have problems due to the necessity of optical path separation, the influence of fluorescent substances on stability and sensitivity, and contamination of samples. Therefore, the above-mentioned measuring methods for the thickness of the liquid surface oil film all have respective disadvantages, and the development of the optical fiber sensor opens up a new way for realizing the measuring method for the thickness of the liquid surface oil film.
The optical fiber sensing technology originates in the 70 th century, light is used as a medium in the optical fiber sensing technology, an optical signal emitted by a light source is transmitted to a target position through an optical fiber transmission medium, after interaction with a measured physical quantity, certain characteristics of the optical signal, such as light intensity, light frequency, light phase and the like, are changed, the changes are received by an optical receiver and then converted into an electric signal, and the electric signal is processed and analyzed to finally obtain the measured information, so that measurement and detection of various physical quantities, chemical quantities or biological quantities are realized. The optical fiber sensor has the advantages of light weight, small volume, high sensitivity, environmental interference resistance, corrosion resistance, good electrical insulation, remote transmission and the like. The optical fiber Michelson interference is one of the important, and the measuring method is used as a high-precision and high-sensitivity nondestructive measuring technology, covers the measurement in the fields of physics, engineering, chemistry, biology, medicine, environment, food and the like, plays an important role in the fields of high-precision detection, biomedicine, substance monitoring, environmental protection and the like, and can measure a plurality of physical quantities of small length, displacement, vibration, strain, temperature and the like of an object. In the oil film thickness measurement field of liquid level, the technology can realize the measurement of high precision and high stability of the oil film thickness of the liquid level, and the optical fiber Michelson interferometry can realize the advantages of non-contact, high precision, good stability and the like, and can not influence the measured oil.
White light interferometry is a low coherence measurement method. White light is a composite light, generally formed by mixing light with two wavelengths or three wavelengths, and is generally referred to as light with multiple colors, and any two of 3 primary colors are overlapped with each other to generate a secondary color, and 3 primary colors of blue, red and green are mixed according to a certain proportion to obtain the white light. The white light interferometry technology refers to white light not being the white light generally, but a light-emitting diode with spectral line width of tens of nanometers or even up to hundreds of nanometers is called white light, the white light with wide spectrum of the light-emitting diode is used as a light source of an optical fiber sensor, the optical fiber white light interferometry technology in the spectrum domain is realized, the coherence length of tens of micrometers is only caused by the wider spectral width of the light source, the interference envelope is very narrow, the absolute optical path difference of the optical fiber interferometer can be measured, the dynamic range is large, and the measurement accuracy is high. The basic principle is that the signal output by the broadband light source is injected into the optical fiber interferometer, the output spectrum of the interferometer is received by the spectrometer or oscilloscope at the output end according to the positions of the upper surface and the lower surface of the oil film, and the absolute optical path difference of the interferometer caused by the environmental parameters can be obtained by analyzing the spectrum characteristics of the output white light. The absolute optical path difference is obtained without a local receiving interferometer to scan the optical path difference, so that a sensing system does not need to use a mechanical scanning device, the volume and the weight of the system are reduced, the structure is compact, and the reliability is high. Therefore, a certain optical path difference is generated by utilizing the thickness of the oil film, and the optical path difference of the thickness of the oil film can be accurately and reliably measured by combining the optical fiber Michelson interference and white light interference technology. However, like white light interferometry study (2005) of oil film thickness and oil properties on water surface in Longzheng's thesis, a stepping motor is adopted to scan back and forth to drive a reflecting mirror to reflect light signals on the outer side of an optical fiber of a reference arm, and a vibration device is preferably additionally arranged on the reflecting mirror, so that the optical path matching of the reference arm and a sensing arm is realized to find the position of a white light interference peak value, the volume and the structure are large, the reflected light signals enter the optical fiber of the reference arm to be adjusted very inconvenient, the reliability is poor, the peak value searching of an interference spectrum also depends on the step length of the stepping motor, the more precise and the more expensive the stepping motor, the reference arm and the sensing arm are not well placed at the same position, and therefore, the measuring device is easily interfered by parameters such as the temperature of the environment, the reference arm in the literature is not just the optical fiber, but the air between the optical fiber end surface and the reflecting mirror on the stepping motor, and the reference arm is also easy to cause unstable system and increase of measurement errors.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method and a system for measuring the thickness of an oil film on the surface of a liquid, which utilize the characteristics of high interference measurement precision and white light interference to realize the measurement of absolute physical quantity and absolute position, and change the length of an optical fiber of a reference arm through sawtooth wave driving voltage and a plurality of tubular piezoelectric ceramics, thereby realizing the position determination of the upper surface and the lower surface of the oil film and finally realizing the accurate measurement of the thickness of the oil film and signal demodulation.
In order to achieve the above object, the present invention provides the following solutions:
the oil film thickness measuring method for the liquid surface comprises the following steps:
acquiring an oil film on the surface of liquid and an oil-liquid interface formed between the oil film and the liquid;
controlling incident light to irradiate an oil film on the surface of liquid so that the surface of the oil film and the oil-liquid interface respectively generate Fresnel reflection light signals;
judging the optical signals reflected from different positions of the oil film surface and the oil liquid interface by utilizing the optical path difference between the two Fresnel reflection optical signals and the characteristics of the reflected broadband light source interference signals, so as to obtain the optical path of the oil film thickness;
and determining the thickness of the oil film based on a preset relation between the optical path of the oil film thickness and the oil refractive index of the oil film.
The invention also provides a system for measuring the thickness of the oil film on the liquid surface, which is used for implementing the method for measuring the thickness of the oil film on the liquid surface and comprises the following steps: the device comprises a super-radiation light-emitting diode SLED light source, a 3dB optical fiber coupler, piezoelectric ceramics, a driving voltage device thereof, an optical fiber collimator, a detector, a data processing part thereof, a red light source, a wavelength division multiplexer and an area array CCD detector;
the super-radiation light-emitting diode SLED light source is used for generating SLED light signals;
the 3dB fiber coupler is used for dividing the SLED optical signal into two paths of optical signals with a power ratio of 1:1;
the optical fiber collimator is used for converting one path of coupled optical signals into parallel light and making the parallel light enter the liquid surface mixed with the oil film, and receiving the optical signals reflected by the oil film surface and the oil liquid interface;
the area array CCD detector is used for detecting and displaying red light signals reflected by the interface of the oil film surface and the oil liquid;
the piezoelectric ceramic is used for obtaining a maximum interference fringe peak value based on an optical signal reflected by an oil film surface and oil interface, obtaining an optical path corresponding to the oil film thickness based on the maximum interference fringe peak value, and obtaining the thickness of the oil film based on the optical path corresponding to the oil film thickness;
the piezoelectric ceramic driving voltage device is used for judging the surface position of an oil film and the interface position of oil liquid according to the spectral characteristics of interference fringes by utilizing the telescopic change of the reference arm optical fiber under the action of piezoelectric ceramic driving voltage;
the red light source is used for generating red light;
the wavelength division multiplexer is used for multiplexing the red light wavelength to the sensing arm optical fiber;
the optical fiber collimator is also used for receiving whether the optical signals reflected from the interface of the oil film surface and the oil liquid can enter the optical fiber collimator or not based on the wavelength of red light multiplexed onto the optical fiber of the sensing arm;
the detector and the data processing part thereof are used for receiving the other path of optical signals after coupling and converting the optical signals into electric signals.
Preferably, the piezoelectric ceramics are n tubular piezoelectric ceramics, n is more than or equal to 1, and the reference arm optical fibers are wound on the outer surfaces of the piezoelectric ceramics in sections respectively and fixed by optical cement;
the inner electrode and the outer electrode of the piezoelectric ceramic are connected with a controller of driving voltage, sawtooth wave voltage is applied through the controller, so that the piezoelectric ceramic generates radial telescopic displacement along with the voltage change of sawtooth waves, and the reference arm optical fiber wound on the outer surface stretches or shortens along with the stretching.
Preferably, two micrometers or other optical methods are used to measure radial displacement of the piezoelectric ceramic formed under different driving voltages, namely, the radius variation Δr of the piezoelectric ceramic, and based on the radius variation Δr, the circumference variation Δc of one circle of optical fiber winding is calculated, which comprises the following specific steps:
when the driving voltage is V1, the radius variation of the piezoelectric ceramic is measured to be delta r V1 Delta C V1 =2π×Δr V1 ；
Based on the circumference variation deltaC V1 And the number of windings N of the optical fiber, the relation Deltal=NxDeltaC between the elongation Deltal of the optical fiber wound on each piezoelectric ceramic and the sawtooth driving voltage V1 is obtained V1 Further, the elongation Δl=n×2pi×Δr of the optical fiber wound around each piezoelectric ceramic was obtained V1 。
Preferably, a certain driving voltage of the sawtooth wave corresponds to the elongation delta l of the optical fiber one by one, and after the elongation of the optical fiber is determined, the refractive index n of the fiber core of the optical fiber is calculated 1 The product of the elongation Deltal of the optical fiber and the corresponding optical path od 1 Specifically denoted od 1 =n 1 ×Δl。
Preferably, the process of obtaining the optical path corresponding to the oil film thickness based on the maximum interference fringe peak value includes:
in the process of increasing the driving voltage, the length of the reference arm optical fiber wound on the outer surface of the piezoelectric ceramic is lengthened, and then the optical path length of the reference arm optical fiber reaches the length L of the sensing arm optical fiber under a certain driving voltage Empty space Obtaining the maximum value of the interference pattern of the first large peak as the corresponding optical path, wherein L Empty space Is an optical fiber quasi-sensor armThe distance between the end face of the straight device and the upper surface of the oil film;
the driving voltage continues to increase, the reference arm optical fiber continues to be elongated by the piezoelectric ceramic, and when the driving voltage is increased, the optical path length corresponding to the amount that the reference arm optical fiber continues to be elongated is equal to the optical path length corresponding to the thickness of the oil film, so that the maximum value of the interference pattern of the second small peak value is obtained;
determining the corresponding optical path od of the oil film thickness by using the relation between the driving voltage of the maximum value of the two interference patterns at two moments and the driving voltage V of the piezoelectric ceramics and the optical fiber elongation delta l 2。
Preferably, the process of obtaining the thickness of the oil film based on the optical path corresponding to the thickness of the oil film includes:
according to the optical path od 2 And refractive index n of oil component 2 Calculate the oil film thickness h, h=od 2 /n 2 。
Preferably, the process of determining whether the optical signal reflected from the interface of the oil film surface and the oil liquid can enter the optical fiber collimator comprises the following steps:
coarse tuning with red color;
and fine adjustment is carried out according to the light intensity distribution of the red light signals received by the area array CCD detector and reflected from the interface between the oil film surface and the oil liquid, so that the reflected light signals enter the sensing arm optical fiber.
Compared with the prior art, the invention has the beneficial effects that:
the invention does not need a stepping motor, a vibrating mirror and a reference light signal, the reference light signal is reflected at the tail end of the optical fiber, the reflection of the tail end can be realized by using the Fresnel reflection of the end face of the optical fiber and the air, and the device is simple and reliable and has low cost.
According to the invention, the white light interference technology, the optical fiber Michelson interference technology and the piezoelectric ceramic are fully utilized to change the elongation and shortening of the reference arm optical fiber, so that the positioning of the oil film surface position and the positioning of the oil liquid interface position are realized, the one-to-one correspondence between the piezoelectric ceramic driving voltage and the elongation of the reference arm optical fiber is utilized to easily determine how much the corresponding driving voltage reference arm optical fiber changes, the optical path difference corresponding to the oil film thickness is further determined according to the corresponding piezoelectric ceramic driving voltage, finally the oil film thickness can be obtained by utilizing the optical path difference and the refractive index of the oil product component, and the accurate and absolute measurement of the oil film thickness is realized. In addition, the reference arm does not need a complex mechanical scanning device, so that the reference arm optical fiber and the sensing arm optical fiber can be basically placed at the same position, environmental parameters such as temperature and the like can be prevented from interfering with the measuring device, and the error is smaller and the precision is higher in the overall design.
The liquid level oil film thickness measuring device provided by the invention does not depend on other precise instruments and mechanical scanning mechanisms, has simple structure and low maintenance cost, realizes the measurement and signal demodulation of the liquid level oil film thickness by using an optical fiber Michelson interference technology, a white light interferometry technology and tubular piezoelectric ceramics, and has the characteristics of simple and quick optical path adjustment, safe and reliable measurement, simple signal demodulation method, low cost, high precision and the like.
Drawings
In order to more clearly illustrate the technical solutions of the present invention, the drawings that are needed in the embodiments are briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic block diagram of an oil film thickness measurement system for a liquid surface in accordance with an embodiment of the present invention;
FIG. 2 is a schematic diagram of interference spectrum generated by the optical signals reflected by the upper and lower surfaces of the oil film and the reference arm in the embodiment of the invention;
FIG. 3 is a diagram showing the variation of the driving voltage of the sawtooth wave with time according to the embodiment of the present invention;
fig. 4 is a front view of the outgoing light direction of the fiber collimator in the embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
Example 1
The invention provides a method for measuring the thickness of an oil film on the surface of a liquid, which comprises the following steps: the liquid surface is polluted by certain oil to form an oil film and floats on the surface, an interface is formed between the oil film and the liquid, the oil film interface generates Fresnel reflection for optical signals, the oil film surface also generates Fresnel reflection for incident optical signals, the Fresnel reflection optical signals generated by the oil film surface and the oil film interface have an optical path difference, the optical signals reflected at different positions are judged by utilizing the optical path difference and the characteristics of reflected broadband light source interference signals, the optical path of the oil film thickness is finally obtained, and the optical path is further divided by the refractive index of the oil product to obtain the thickness of the oil film.
Example two
As shown in fig. 1, the invention further provides a system for measuring the thickness of an oil film on a liquid surface, wherein the system for measuring the thickness of the oil film on the liquid surface is used for implementing the method for measuring the thickness of the oil film on the liquid surface according to the first embodiment, and the system for measuring the thickness of the oil film on the liquid surface is composed of a superluminescent diode (SLED) light source, a 3dB optical fiber coupler, piezoelectric ceramics and a driving voltage device thereof, an optical fiber collimator, a detector and a data processing part thereof, a red light source and a wavelength division multiplexer;
the optical signals emitted by the light source respectively enter the reference arm and the sensing arm optical fiber through the optical fiber coupler in a power ratio of 1:1, the tail end of the sensing arm optical fiber is provided with an optical fiber collimator for emitting parallel light and conveniently receiving the optical signals reflected by the oil film surface and the oil liquid interface, the diameter of the cross section of the optical fiber collimator is 1.8-5mm, the end face of the tail end of the reference arm optical fiber is cut flat and perpendicular to the optical fiber axis (a reflecting film can be plated if necessary) for reflecting the optical signals, the optical fiber of the reference arm is 1-5cm shorter than the sum of the optical fiber of the sensing arm and the optical fiber collimator, the number of piezoelectric ceramics on the reference arm can be 1, the number of piezoelectric ceramics can be n, and the optical fiber is wound on the n piezoelectric ceramics for obtaining larger elongation of the reference arm optical fiber, so that the maximum interference fringe peak value (when the corresponding reference optical path is equal to the sensing optical path); in addition, a wavelength division multiplexer of 630nm red light wavelength and SLED wavelength of the sensing light source is arranged on the sensing arm, the red light wavelength is multiplexed to the sensing arm optical fiber through the wavelength division multiplexer and then output from the optical fiber collimator, and whether the reflected light signal can enter the optical fiber collimator or not is judged, so that the position of the optical fiber collimator is conveniently adjusted. The sensing light source adopts a broad-spectrum super-radiation light-emitting diode SLED, the coherence of the broad-spectrum light-emitting diode is very low, and fringes have a maximum value when interference occurs, so that absolute measurement can be realized, the oil film surface position and the oil liquid interface position can be accurately judged according to the spectral characteristics of the interference fringes by utilizing the telescopic change of the reference arm optical fiber under the action of the piezoelectric ceramic driving voltage, and therefore, the interference spectrum peak value corresponding to the oil film surface position and the oil liquid interface position can be converted into the driving voltage of the piezoelectric ceramic to be represented. Because of the adoption of SLED, the interference spectrum of the reference arm optical fiber, which comprises the oil film surface position and the oil liquid interface position in the complete change process, is shown in figure 2, and the envelope of the reference arm optical fiber is similar to the spectrum of the light source, and has the maximum value.
In this embodiment, the optical fiber segments of the reference arm are respectively wound around the outer surfaces of the tubular piezoelectric ceramics, and are fixed with optical cement. The inner electrode and the outer electrode of the tubular piezoelectric ceramic are connected with a controller of driving voltage, and sawtooth wave voltage is applied by the controller, so that the tubular piezoelectric ceramic generates radial telescopic displacement along with the voltage change of the sawtooth wave, and the optical fiber wound on the outer surface stretches or shortens along with the elongation, so that one driving voltage of the sawtooth waveThe pressure corresponds to the elongation delta l of the optical fiber one by one, and after the elongation is determined, the refractive index n of the fiber core of the optical fiber is calculated 1 The product of the elongation Deltal and the optical path od 1 Specifically denoted od 1 =n 1 x.DELTA.l. The driving voltage of the sawtooth wave is shown in fig. 3.
In this embodiment, two micrometers or other optical methods are used to measure the radial displacement of the piezoelectric ceramic formed under different driving voltages, that is, the radius variation Δr of the tubular piezoelectric ceramic, and then calculate the circumference variation Δc of one winding of the optical fiber, for example: when the driving voltage is V1, the radius variation of the piezoelectric ceramic is measured to be delta r V1 Delta C V1 =2π×Δr V1 The method comprises the steps of carrying out a first treatment on the surface of the The elongation Δl of the optical fiber wound on each piezoelectric ceramic is obtained from the number of turns N of the optical fiber wound (Δl=n×Δc V ) Relationship with the sawtooth driving voltage V, therefore, when the driving voltage is V1, Δl=n×2pi×Δr V1 。
In the embodiment, the position of the optical fiber collimator is adjusted by utilizing the red light path, so that the end face of the optical fiber collimator is basically parallel to the oil film surface, and the collimator can receive more optical signals reflected by the interface of the oil film surface and the oil liquid; an area array CCD detector is arranged at the end face of the collimator, the CCD surface is basically consistent with the end face of the optical fiber collimator, the front view of the outgoing light direction of the optical fiber collimator is opposite to that shown in figure 4, the side length is 4-6 times of the diameter of the optical fiber collimator, and the optical fiber collimator is arranged at the center position; and determining whether the light signal is reflected back to the collimator, firstly, roughly adjusting the color of red light, and then finely adjusting the light intensity distribution received by the CCD detector, so that the reflected light signal can better enter the sensing arm optical fiber. After the adjustment, if the surface of the liquid has no oil film, the measuring device can only receive the pattern of one interference fringe peak value in fig. 2 no matter how the driving voltage of the piezoelectric ceramic is adjusted; when an oil film exists on the liquid surface, the sawtooth wave driving voltage is increased from 0 volt, and the oil liquid interface is larger than the optical path length of an optical signal reflected by the oil film surface, so that a first interference pattern and a second interference pattern of the received signal firstly appear, and the specific process is as follows: during the driving voltage increaseThe length of the reference arm optical fiber wound on the outer surface of the piezoelectric ceramic is gradually lengthened, and then the optical path length of the reference arm reaches the length L of the sensing arm optical fiber under a certain driving voltage Empty space The interference pattern has a maximum value, as the corresponding optical path, that is: the driving voltage at this time corresponds to the maximum value one by one, wherein L Empty space Is the distance between the end face of the optical fiber collimator on the sensing arm and the upper surface of the oil film, as shown in fig. 1; as the drive voltage continues to increase, the reference arm fiber continues to be elongated by the piezoelectric ceramic, and when a certain drive voltage is increased, the optical path length corresponding to the amount of the continued elongation is equal to the optical path length corresponding to the oil film thickness, and the interference pattern of the second small peak in fig. 2 appears and has a maximum value, that is, the drive voltage at this time corresponds to the maximum value of the small peak pattern one by one. Therefore, when the small peak interference pattern maximum occurs, the corresponding optical path od of the oil film thickness can be determined by using the drive voltage at two times of the two interference pattern maxima and the relation between the drive voltage V of the piezoelectric ceramic and the optical fiber elongation Deltal 2 I.e. od 2 =od 1 Further according to the optical path od 2 And refractive index n of oil component 2 Calculate the oil film thickness h, h=od 2 /n 2 . If the first interference pattern and the maximum value are not present in the case that the driving voltage of the first piezoelectric ceramic increases to the maximum value, the driving voltage of the second piezoelectric ceramic is maintained constant and then increases from 0V, the length of the reference arm optical fiber wound around the outer surface of the second piezoelectric ceramic is gradually lengthened during the increase of the driving voltage, and then the total optical path length of the reference arm optical fiber reaches the length L of the sensing arm optical fiber under the driving voltage of the first and second piezoelectric ceramics Empty space The corresponding optical path is the same, and the interference pattern has the maximum value; as the drive voltage continues to increase, the reference arm fiber continues to be elongated by the piezoelectric ceramic, if the second small peak interference pattern does not appear when the drive voltage of the second piezoelectric ceramic increases to a maximum value, the drive voltage of the second piezoelectric ceramic is kept at the maximum value, then the drive voltage of the third piezoelectric ceramic increases from 0 volt, and during the increase of the drive voltage, the fiber is wound outside the third piezoelectric ceramicThe length of the reference arm fiber on the surface continues to be gradually lengthened, and then the total optical path length of the reference arm fiber reaches the length L of the sensing arm fiber under the driving voltage of the first, the second and the third piezoceramics Empty space And the optical path length corresponding to the sum of the oil film thickness is the same, the interference pattern with the second small peak value is generated and has the maximum value, the optical path length corresponding to the oil film thickness can be obtained by utilizing the driving voltage value at the moment of the maximum value of the two interference patterns according to the one-to-one correspondence relation between the driving voltage of each piezoelectric ceramic and the elongation of the optical fiber of the reference arm, and the oil film thickness is calculated according to the optical path length and the refractive index of the oil product component. And in the process of searching the driving voltage corresponding to the maximum value of the interference pattern, if the driving voltage of the ith piezoelectric ceramic is completely applied and the interference pattern and the maximum value thereof do not appear, keeping the driving voltage of the ith piezoelectric ceramic unchanged, then gradually increasing the driving voltage of the (i+1) th piezoelectric ceramic from 0 volt until the interference pattern and the maximum value thereof appear, wherein the optical path corresponding to the elongation of the reference arm optical fiber between the driving voltages at the moment of the maximum values of the two interference patterns is the optical path corresponding to the thickness of the oil film, and the thickness of the oil film can be obtained according to the optical path and the refractive index of the oil product component.
In this embodiment, the reference arm optical fiber has n tubular piezoelectric ceramics, m bundle optical fibers are wound on the surface of the piezoelectric ceramics, when the thickness of the square film of the optical fiber coupler of 3dB is measured along the sensor arm optical fiber, the influence of parameters such as temperature of the external environment on the optical fiber is almost the same, and the sensor arm optical fiber is wound m bundles respectively at the corresponding positions of the piezoelectric ceramics and the same diameter of the reference arm m bundle optical fiber to form n m bundle optical fibers, so that the reference arm optical fiber and the sensor arm optical fiber have lengths which are almost the same in space. Under the conditions that the space length is almost different and m bundles of optical fibers are wound at the same position, the reference arm optical fiber and the sensing arm optical fiber are placed in the same environment, so that the measuring device can avoid interference of other parameters of external environments such as temperature and the like on oil film thickness measurement, reduce errors of a measuring method and improve accuracy.
The above embodiments are merely illustrative of the preferred embodiments of the present invention, and the scope of the present invention is not limited thereto, but various modifications and improvements made by those skilled in the art to which the present invention pertains are made without departing from the spirit of the present invention, and all modifications and improvements fall within the scope of the present invention as defined in the appended claims.
Claims (7)
1. An oil film thickness measurement system for a liquid surface, comprising: the device comprises a super-radiation light-emitting diode SLED light source, a 3dB optical fiber coupler, piezoelectric ceramics, a driving voltage device thereof, an optical fiber collimator, a detector, a data processing part thereof, a red light source, a wavelength division multiplexer and an area array CCD detector;
the super-radiation light-emitting diode SLED light source is used for generating SLED light signals;
the 3dB fiber coupler is used for dividing the SLED optical signal into two paths of optical signals with a power ratio of 1:1;
the optical fiber collimator is used for converting one path of coupled optical signals into parallel light and making the parallel light enter the liquid surface mixed with the oil film, and receiving the optical signals reflected by the oil film surface and the oil liquid interface;
the area array CCD detector is used for detecting and displaying red light signals reflected by the interface of the oil film surface and the oil liquid;
the piezoelectric ceramic is used for obtaining a maximum interference fringe peak value based on an optical signal reflected by an oil film surface and oil interface, obtaining an optical path corresponding to the oil film thickness based on the maximum interference fringe peak value, and obtaining the thickness of the oil film based on the optical path corresponding to the oil film thickness;
the piezoelectric ceramic driving voltage device is used for judging the surface position of an oil film and the interface position of oil liquid according to the spectral characteristics of interference fringes by utilizing the telescopic change of the reference arm optical fiber under the action of piezoelectric ceramic driving voltage;
the red light source is used for generating red light;
the wavelength division multiplexer is used for multiplexing the red light wavelength to the sensing arm optical fiber;
the optical fiber collimator is also used for receiving whether the optical signals reflected from the interface of the oil film surface and the oil liquid can enter the optical fiber collimator or not based on the wavelength of red light multiplexed onto the optical fiber of the sensing arm;
the detector and the data processing part thereof are used for receiving the other path of coupled optical signals and converting the optical signals into electric signals;
the implementation method of the system comprises the following steps: acquiring an oil film on the surface of liquid and an oil-liquid interface formed between the oil film and the liquid;
controlling incident light to irradiate an oil film on the surface of liquid so that the surface of the oil film and the oil-liquid interface respectively generate Fresnel reflection light signals;
judging the optical signals reflected from different positions of the oil film surface and the oil liquid interface by utilizing the optical path difference between the two Fresnel reflection optical signals and the characteristics of the reflected broadband light source interference signals, so as to obtain the optical path of the oil film thickness;
and determining the thickness of the oil film based on a preset relation between the optical path of the oil film thickness and the oil refractive index of the oil film.
2. The system for measuring the thickness of an oil film on the surface of a liquid according to claim 1, wherein the piezoelectric ceramics are n tubular piezoelectric ceramics, n is larger than or equal to 1, and reference arm optical fibers are wound on the outer surfaces of the piezoelectric ceramics respectively in sections and fixed by optical cement;
the inner electrode and the outer electrode of the piezoelectric ceramic are connected with a controller of driving voltage, sawtooth wave voltage is applied through the controller, so that the piezoelectric ceramic generates radial telescopic displacement along with the voltage change of sawtooth waves, and the reference arm optical fiber wound on the outer surface stretches or shortens along with the stretching.
3. The system for measuring the thickness of an oil film on the surface of a liquid according to claim 2, wherein two micrometers or other optical methods are used to measure radial displacement of the piezoelectric ceramic formed under different driving voltages, namely, the radius change Δr of the piezoelectric ceramic, and the circumference change Δc of one circle of optical fiber winding is calculated based on the radius change Δr, which comprises the following steps:
when the driving voltage is V1, the radius variation of the piezoelectric ceramic is measured to be delta r V1 Delta C V1 =2π×Δr V1 ；
Based on the circumference variation deltaC V1 And the number of windings N of the optical fiber, the relation Deltal=NxDeltaC between the elongation Deltal of the optical fiber wound on each piezoelectric ceramic and the sawtooth driving voltage V1 is obtained V1 Further, the elongation Δl=n×2pi×Δr of the optical fiber wound around each piezoelectric ceramic was obtained V1 。
4. The system for measuring the thickness of an oil film on a liquid surface according to claim 3, wherein a certain driving voltage of the sawtooth wave corresponds to the elongation Δl of the optical fiber one by one, and after the elongation of the optical fiber is determined, the refractive index n of the core of the optical fiber is calculated 1 The product of the elongation Deltal of the optical fiber and the corresponding optical path od 1 Specifically denoted od 1 =n 1 ×Δl。
5. The system for measuring the oil film thickness of a liquid surface according to claim 4, wherein the process of obtaining the optical path length corresponding to the oil film thickness based on the maximum interference fringe peak value comprises:
in the process of increasing the driving voltage, the length of the reference arm optical fiber wound on the outer surface of the piezoelectric ceramic is lengthened, and then the optical path length of the reference arm optical fiber reaches the length L of the sensing arm optical fiber under a certain driving voltage Empty space Obtaining the maximum value of the interference pattern of the first large peak as the corresponding optical path, wherein L Empty space The distance from the end face of the optical fiber collimator on the sensing arm to the upper surface of the oil film;
the driving voltage continues to increase, the reference arm optical fiber continues to be elongated by the piezoelectric ceramic, and when the driving voltage is increased, the optical path length corresponding to the amount that the reference arm optical fiber continues to be elongated is equal to the optical path length corresponding to the thickness of the oil film, so that the maximum value of the interference pattern of the second small peak value is obtained;
drive voltage at two moments using maximum values of two interference patterns and piezoelectric ceramicThe relation between the driving voltage V and the optical fiber elongation Deltal, and the corresponding optical path od of the oil film thickness is determined 2。
6. The system for measuring the thickness of an oil film on a liquid surface according to claim 5, wherein the process of obtaining the thickness of the oil film based on the optical path corresponding to the thickness of the oil film comprises:
according to the optical path od 2 And refractive index n of oil component 2 Calculate the oil film thickness h, h=od 2 /n 2 。
7. The system of claim 1, wherein determining whether the optical signal reflected from the oil film surface and oil interface can enter the fiber collimator comprises:
coarse tuning with red color;
and fine adjustment is carried out according to the light intensity distribution of the red light signals received by the area array CCD detector and reflected from the interface between the oil film surface and the oil liquid, so that the reflected light signals enter the sensing arm optical fiber.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102636197A (en) * | 2012-05-09 | 2012-08-15 | 南开大学 | Cascade acoustic microstructure optical fiber long cycle grating interferometer |
| CN108981596A (en) * | 2018-08-31 | 2018-12-11 | 天津大学 | The embedded optical fiber frequency domain interferometer measuration system of wind tunnel test oil film thickness and method |
| CN109000839A (en) * | 2018-05-29 | 2018-12-14 | 东华大学 | A kind of mattress pressure testing system based on 3D printing Yu low coherence interference technology |
| CN113607658A (en) * | 2021-08-05 | 2021-11-05 | 大连海事大学 | A method for obtaining oil film attenuation coefficient based on oil film gray value |
| CN113866124A (en) * | 2021-09-26 | 2021-12-31 | 岭南师范学院 | A SPR Differential Intensity Modulation Sensor |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| US6847453B2 (en) * | 2001-11-05 | 2005-01-25 | Optiphase, Inc. | All fiber autocorrelator |
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- 2023-10-07 CN CN202311277192.6A patent/CN117006956B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102636197A (en) * | 2012-05-09 | 2012-08-15 | 南开大学 | Cascade acoustic microstructure optical fiber long cycle grating interferometer |
| CN109000839A (en) * | 2018-05-29 | 2018-12-14 | 东华大学 | A kind of mattress pressure testing system based on 3D printing Yu low coherence interference technology |
| CN108981596A (en) * | 2018-08-31 | 2018-12-11 | 天津大学 | The embedded optical fiber frequency domain interferometer measuration system of wind tunnel test oil film thickness and method |
| CN113607658A (en) * | 2021-08-05 | 2021-11-05 | 大连海事大学 | A method for obtaining oil film attenuation coefficient based on oil film gray value |
| CN113866124A (en) * | 2021-09-26 | 2021-12-31 | 岭南师范学院 | A SPR Differential Intensity Modulation Sensor |
Non-Patent Citations (1)
| Title |
|---|
| 利用光纤干涉仪测量滑动轴承润滑油膜厚度;陈玉平;河南科学;第34卷(第6期);第856-860页 * |
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