阅读说明：本技术 一种监测聚合物固化过程的非接触式高灵敏度光学传感系统及其方法 (Non-contact high-sensitivity optical sensing system and method for monitoring polymer curing process ) 是由 董博 白玉磊 谢胜利 于 2020-10-28 设计创作，主要内容包括：本发明公开了一种监测聚合物固化过程的非接触式高灵敏度光学传感系统及其方法,其中,方法采用光学干涉的方式通过探测样品臂反射光光程的变化量,实现聚合物固化过程的监测,该方法为非接触式测量方法,无需在聚合物试样内埋入探测器,即可实现固化过程的监测。此外,本发明的光学传感系统采用光纤结构,具有容易安装和使用的特点,可用于现场的在线监测。最后,本发明利用相位检测的方法实现光程差的测量,其灵敏度为纳米量级,测量灵敏度极高。(The invention discloses a non-contact high-sensitivity optical sensing system and a method for monitoring a polymer curing process, wherein the method adopts an optical interference mode to monitor the polymer curing process by detecting the variation of the optical path of reflected light of a sample arm. In addition, the optical sensing system adopts an optical fiber structure, has the characteristics of easy installation and use, and can be used for on-site on-line monitoring. Finally, the invention realizes the measurement of the optical path difference by using a phase detection method, and the sensitivity is in nanometer level, and the measurement sensitivity is extremely high.)

1. A non-contact, high sensitivity optical sensing system for monitoring a polymer curing process, comprising 50: 50, a fiber optic beam splitter (1), a broadband light source (2), a sample arm (3), a reference arm (4), a spectrometer (5) and a computer (6);

wherein the broadband light source (2) is illuminated through a 50: the 50 fiber beam splitter (1) is respectively connected with the sample arm (3) and the reference arm (4), and the spectrometer (5) is connected with the 50: 50 between the optical fiber beam splitter (1) and the computer (6);

the sample arm (3) includes a collimator lens L1 and a convex lens L2, the collimator lens L1 and the convex lens L2 being arranged in parallel along the irradiation direction of light and being spaced apart from each other; the polymer sample S was placed on the side of the convex lens L2 remote from the collimating lens L1;

the reference arm (4) comprises a collimating lens L3, a convex lens L4 and a reflector M, wherein the collimating lens L3, the convex lens L4 and the reflector M are sequentially arranged in parallel along the irradiation direction of light, and the collimating lens L3, the convex lens L4 and the reflector M are separated from each other;

the spectrometer (5) comprises a collimating lens L5, a convex lens L6, a diffraction grating G and a line camera;

the collimating lens L5 is perpendicular to the convex lens L6, the diffraction grating G is arranged between the collimating lens L5 and the convex lens L6, and is used for splitting the interference light emitted from the collimating lens L5 and enabling the split interference light to reach the convex lens L6 for focusing and imaging;

the linear array camera is arranged on one side, away from the diffraction grating G, of the convex lens L6 and used for collecting interference spectra;

and the computer (6) is connected with the linear array camera and is used for analyzing the interference spectrum acquired by the linear array camera, so that the curing process of the polymer sample S is monitored.

2. A method for use in a non-contact high sensitivity optical sensing system for monitoring the curing process of polymers as defined in claim 1, comprising the steps of:

s1, placing the polymer sample S on the side of the convex lens L2 far away from the collimating lens L1;

s2, light of the broadband light source is coupled to 50: 50 fiber beam splitters;

s3, from 50: 50% of light emitted from the 50-fiber beam splitter enters a sample arm and is used for illuminating the polymer sample S, and the other 50% of light enters a reference arm and is used as a reference;

s4, the reflected light of the front and back surfaces of the polymer sample S, and the reference light enter 50: interfering with each other to form interference after 50 optical fiber beam splitters, entering a spectrometer, and collecting by a linear array camera;

and S5, analyzing the interference spectrum collected by the linear array camera by the computer, and monitoring the curing process of the polymer sample S.

3. The method of claim 2, wherein the step S4 is performed by the following steps:

s4-1, acquiring the interference spectrum by using a linear array camera:

in the above formula, I represents light intensity, k represents wave number, M represents the number of surfaces of the polymer sample S, j represents each surface, I_RAnd I_jRespectively showing the intensity of the reflected light from the reference surface and the jth surface of the polymer sample S, _jφ(t)＝φ_j0+2kΛ_j(t) represents the phase of the interference signal, φ_j0Representing the initial phase, Λ_j(t) represents an optical path difference between the reference surface reflected light and the jth surface reflected light, DC and AC being direct current components and self-coherent components, respectively;

s4-2, obtaining the positions of points A and B on the front and back surfaces of the polymer sample S according to the spectral characteristics of the interference spectrum;

s4-3, when the polymer sample S generates deformation/refractive index change in the curing process, the optical path difference change quantity delta lambda j (t) of the j-th surface is obtained from the phase difference of interference signals, namely

In the above formula, λ_cIs the central wavelength of the light source, t₀As an initial timing of curing of the polymer sample S, unwrap { } and diff { }]Respectively representing phase unwrapping and differential phase;

according to the law of refraction, the optical path differences corresponding to the front and back surfaces A and B of the polymer sample S are respectively expressed as:

in the above formula, Δ Λ₀Representing the variation of optical path difference caused by vibration and medium refractive index variation, epsilon representing strain, and n₀Denotes an initial refractive index, d denotes a distance of front and rear surfaces;

s4-4, obtainable according to equation (3):

in the above equation, the right side of the equation is a superposition of the refractive index change amount and the strain amount, and since the refractive index change amount and the strain amount are two indexes for monitoring the curing degree of the polymer sample S, α (t) after the superposition is defined asΔn(t)+n₀·ε(t)，Can be used as a new curing monitoring index to reflect the curing degree of the polymer sample S;

further, the curing rate of the curing process of the polymer sample S is expressed as follows, based on the relationship between the curing rate and the degree of curing:

in the above formula, δ t represents the time interval for collecting the interference spectra of two adjacent frames;

and S4-5, combining the measured optical path difference variation and the physical relationship described by the formulas (4) and (5), and finally obtaining a polymer sample S curing degree curve and a curing rate curve.

Technical Field

The invention relates to the technical field of curing monitoring, in particular to a non-contact high-sensitivity optical sensing system and a method for monitoring a polymer curing process.

Background

The polymer is also called macromolecule/high polymer, and is a common material widely applied to industrial production and daily life, such as consumable materials used in 3D printing, substrate materials of flexible electronic devices, composite materials adopted in aerospace aircrafts, dental resin used in tooth restoration, and the like.

During the preparation and shaping of the polymer, the polymer undergoes a transition from low molecular to high molecular, i.e. a curing process, which is usually accompanied by a change in physical state. Meanwhile, continuously changing mechanical and rheological properties have a crucial influence on the properties of polymeric materials and structures. Therefore, knowledge of the curing kinetics of polymers is of great importance for their production and use.

The curing of the polymer is a relatively complex process, the determination and calculation of the curing degree (or conversion rate) of the polymer has not been unified up to now, and the curing process is monitored by measuring certain physical quantities of the polymer (such as heat release, viscoelasticity, ion mobility, shrinkage strain, refractive index change and the like).

The currently popular curing monitoring methods mainly include the following methods:

1) differential scanning calorimetry: polymer curing is typically an exothermic process, and thus the total amount of exotherm from the curing process is constant for the same polymeric material. Therefore, the heat release of the tested sample is detected by differential scanning calorimetry, and the curing process of the polymer material can be effectively revealed.

2) Dynamic thermomechanical analysis: during the curing process of the polymer, the viscoelasticity of the polymer changes with the change of the curing degree, so the change amount can be used for reflecting the curing degree of the polymer. Therefore, the curing process of the polymer can also be revealed by measuring the elastic modulus of the tested sample by a dynamic thermomechanical analysis method and the relation of time.

3) Dielectric analysis method: during the curing process of the polymer, the ion mobility of the polymer gradually decreases with the increase of the curing degree, and finally stops. Therefore, the dielectric analysis method is adopted to measure the amplitude and phase change of the polymer material under the sinusoidal voltage, and the effective monitoring of the polymer curing process can be realized.

4) Other monitoring methods are as follows: in addition to the mainstream methods described above, a series of new curing monitoring methods have been developed in recent years, including infrared spectroscopy using infrared absorption spectrum detection during curing, optical fiber sensing using refractive index change amount detection of materials, and shrinkage strain method using shrinkage strain measurement of polymers.

Although the existing method can realize monitoring of the curing process, various problems always exist in practical application, such as that differential scanning calorimetry and dynamic thermomechanical analysis can not realize on-line measurement, and the method is not suitable for industrial production and manufacturing; the dielectric analysis method is a contact measurement method, and the operation process is complex and cannot be applied to some practical application scenes. Therefore, in order to better monitor the polymer curing process, a new monitoring method with both on-line measurement and non-contact measurement capability needs to be developed.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a non-contact high-sensitivity optical sensing system which does not need to embed a detector in a polymer sample, is easy to install and convenient to use, can be used for on-site on-line monitoring and has extremely high measurement sensitivity for monitoring the curing process of a polymer.

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

a non-contact, high sensitivity optical sensing system for monitoring a polymer curing process, comprising 50: 50 optical fiber beam splitter, broadband light source, sample arm, reference arm, spectrometer and computer;

wherein the broadband light source passes through 50: the 50 fiber beam splitter is connected to the sample arm and the reference arm, respectively, and the spectrometer is connected to a 50: 50 fiber splitter and computer;

the sample arm includes a collimator lens L1 and a convex lens L2, the collimator lens L1 and the convex lens L2 being arranged in parallel along the irradiation direction of light and spaced apart from each other; the polymer sample S was placed on the side of the convex lens L2 remote from the collimating lens L1;

the reference arm comprises a collimating lens L3, a convex lens L4 and a reflector M, wherein the collimating lens L3, the convex lens L4 and the reflector M are sequentially arranged in parallel along the irradiation direction of light, and the collimating lens L3, the convex lens L4 and the reflector M are separated from one another;

the spectrometer comprises a collimating lens L5, a convex lens L6, a diffraction grating G and a line camera;

the collimating lens L5 is perpendicular to the convex lens L6, the diffraction grating G is arranged between the collimating lens L5 and the convex lens L6, and is used for splitting the interference light emitted from the collimating lens L5 and enabling the split interference light to reach the convex lens L6 for focusing and imaging;

the linear array camera is arranged on one side, away from the diffraction grating G, of the convex lens L6 and used for collecting interference spectra;

and the computer is connected with the linear array camera and is used for analyzing the interference spectrum acquired by the linear array camera, so that the solidification process of the polymer sample S is monitored.

To achieve the above object, the present invention further provides a method for monitoring a non-contact high-sensitivity optical sensing system of a polymer curing process, comprising the steps of:

s1, placing the polymer sample S on the side of the convex lens L2 far away from the collimating lens L1;

s2, light of the broadband light source is coupled to 50: 50 fiber beam splitters;

s3, from 50: 50% of light emitted from the 50-fiber beam splitter enters a sample arm and is used for illuminating the polymer sample S, and the other 50% of light enters a reference arm and is used as a reference;

s4, the reflected light of the front and back surfaces of the polymer sample S, and the reference light enter 50: interfering with each other to form interference after 50 optical fiber beam splitters, entering a spectrometer, and collecting by a linear array camera;

and S5, analyzing the interference spectrum collected by the linear array camera by the computer, and monitoring the curing process of the polymer sample S.

Further, the specific process of step S4 is as follows:

s4-1, acquiring the interference spectrum by using a linear array camera:

in the above formula, I represents light intensity, k represents wave number, M represents the number of surfaces of the polymer sample S, j represents each surface, I_RAnd I_jRespectively showing the reference plane and the jth surface of the polymer sample SThe intensity of the reflected light of (a), _jφ(t)＝φ_j0+2kΛ_j(t) represents the phase of the interference signal, φ_j0Representing the initial phase, Λ_j(t) represents an optical path difference between the reference surface reflected light and the jth surface reflected light, DC and AC being direct current components and self-coherent components, respectively;

s4-2, obtaining the positions of points A and B on the front and back surfaces of the polymer sample S according to the spectral characteristics of the interference spectrum;

s4-3, when the polymer sample S generates deformation/refractive index change in the curing process, the optical path difference change quantity delta lambda j (t) of the j-th surface is obtained from the phase difference of interference signals, namely

In the above formula, λ_cIs the central wavelength of the light source, t₀As an initial timing of curing of the polymer sample S, unwrap { } and diff { }]Respectively representing phase unwrapping and differential phase;

according to the law of refraction, the optical path differences corresponding to the front and back surfaces A and B of the polymer sample S are respectively expressed as:

in the above formula, Δ Λ₀Representing the variation of optical path difference caused by vibration and medium refractive index variation, epsilon representing strain, and n₀Denotes an initial refractive index, d denotes a distance of front and rear surfaces;

s4-4, obtainable according to equation (3):

in the above equation, the right side of the equation is a superposition of the refractive index change amount and the strain amount, and since the refractive index change amount and the strain amount are two indexes for monitoring the curing degree of the polymer sample S, α (t) after the superposition is defined asΔn(t)+n₀ε (t), which can be used as a new curing monitoring index to reflect the curing degree of the polymer sample S;

further, the curing rate of the curing process of the polymer sample S is expressed as follows, based on the relationship between the curing rate and the degree of curing:

in the above formula, δ t represents the time interval for collecting the interference spectra of two adjacent frames;

and S4-5, combining the measured optical path difference variation and the physical relationship described by the formulas (4) and (5), and finally obtaining a polymer sample S curing degree curve and a curing rate curve.

Compared with the prior art, the principle and the advantages of the scheme are as follows:

the scheme adopts an optical interference mode to realize the monitoring of the curing process of the polymer by detecting the variation of the optical path of the reflected light of the sample arm, and the method is a non-contact measurement method, and can realize the monitoring of the curing process without embedding a detector in a polymer sample. In addition, the optical sensing system of the scheme adopts an optical fiber structure, has the characteristics of easy installation and use, and can be used for on-site on-line monitoring. Finally, the scheme realizes the measurement of the optical path difference by using a phase detection method, and the sensitivity is in the nanometer level and is extremely high.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the services required for the embodiments or the technical solutions in the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a schematic structural diagram of a non-contact high-sensitivity optical sensing system for monitoring a polymer curing process according to the present invention;

FIG. 2 is a schematic diagram of the spectral characteristics of an interference spectrum;

FIG. 3 is a diagram showing the amount of change in optical path difference between the front and rear surfaces of a polymer sample S;

FIG. 4 is a graph showing the change of the S-cure degree curve and the S-cure rate curve of a polymer specimen.

Detailed Description

The invention will be further illustrated with reference to specific examples:

as shown in fig. 1, a non-contact high-sensitivity optical sensing system for monitoring a polymer curing process (with a depth resolution of 7.5 μm, a depth range of 3mm, and a monitoring rate of 8kfps) according to an embodiment of the present invention includes 50: 50 optical fiber beam splitter 1, broadband light source 2, sample arm 3, reference arm 4, spectrometer 5 and computer 6;

wherein, the broadband light source 2 passes through 50: the 50 fiber beam splitter 1 is connected to the sample arm 3 and the reference arm 4, respectively, and the spectrometer 5 is connected to the 50: 50 between the fiber splitter 1 and the computer 6;

the sample arm 3 includes a collimator lens L1 and a convex lens L2, the collimator lens L1 and the convex lens L2 being arranged in parallel along the irradiation direction of light and being spaced apart from each other; the polymer sample S was placed on the side of the convex lens L2 remote from the collimating lens L1;

the reference arm 4 comprises a collimating lens L3, a convex lens L4 and a reflector M, wherein the collimating lens L3, the convex lens L4 and the reflector M are sequentially arranged in parallel along the irradiation direction of light, and the collimating lens L3, the convex lens L4 and the reflector M are separated from each other;

the spectrometer 5 comprises a collimating lens L5, a convex lens L6, a diffraction grating G and a line camera;

the collimating lens L5 is perpendicular to the convex lens L6, the diffraction grating G is arranged between the collimating lens L5 and the convex lens L6, and is used for splitting the interference light emitted from the collimating lens L5 and enabling the split interference light to reach the convex lens L6 for focusing and imaging;

the linear array camera is arranged on one side of the convex lens L6 far away from the diffraction grating G and is used for collecting interference spectra;

and the computer 6 is connected with the linear array camera and is used for analyzing the interference spectrum acquired by the linear array camera, so that the solidification process of the polymer sample S is monitored.

The optical sensing system specifically works as follows:

s1, placing the polymer sample S on the side of the convex lens L2 far away from the collimating lens L1;

s2, the light of broadband light source 2 is coupled to 50: 50 a fiber beam splitter 1;

s3, from 50: 50% of light emitted from the 50-fiber beam splitter 1 enters the sample arm 3 to illuminate the polymer sample S (in the process, the collimating lens L1 performs collimation, and the convex lens L2 performs focusing), and the other 50% of light enters the reference arm 4 to be used as reference (in the process, the collimating lens L3 performs collimation, the convex lens L4 performs focusing, and the mirror M performs reflection);

s4, the reflected light of the front and back surfaces of the polymer sample S, and the reference light enter 50: 50, interfering with each other to form interference after the optical fiber beam splitter 1, entering a spectrometer 5, and collecting by a linear array camera;

s5, the computer 6 analyzes the interference spectrum collected by the linear array camera and monitors the curing process of the polymer sample S.

The specific curing process of polymer sample S was monitored as follows:

s4-1, acquiring the interference spectrum by using a linear array camera:

in the above formula, I represents light intensity, k represents wave number, M represents the number of surfaces of the polymer sample S, j represents each surface, I_RAnd I_jRespectively showing the intensity of the reflected light from the reference surface and the jth surface of the polymer sample S, _jφ(t)＝φ_j0+2kΛ_j(t) represents the phase of the interference signal, φ_j0Representing the initial phase, Λ_j(t) represents an optical path difference between the reference surface reflected light and the jth surface reflected light, DC and AC being direct current components and self-coherent components, respectively;

s4-2, obtaining the positions of points A and B on the front and back surfaces of the polymer sample S according to the spectral characteristics of the interference spectrum (shown in FIG. 2);

s4-3, when the polymer sample S generates deformation/refractive index change in the curing process, the variation quantity delta lambda j (t) of the optical path difference of the j-th surface is obtained from the phase difference of interference signals (shown in figure 3), namely

In the above formula, λ_cIs the central wavelength of the light source, t₀As an initial timing of curing of the polymer sample S, unwrap { } and diff { }]Respectively representing phase unwrapping and differential phase;

according to the law of refraction, the optical path differences corresponding to the front and back surfaces A and B of the polymer sample S are respectively expressed as:

in the above formula, Δ Λ₀Representing the variation of optical path difference caused by vibration and medium refractive index variation, epsilon representing strain, and n₀Denotes an initial refractive index, d denotes a distance of front and rear surfaces;

s4-4, obtainable according to equation (3):

in the above equation, the right side of the equation is a superposition of the refractive index change amount and the strain amount, and since the refractive index change amount and the strain amount are two indexes for monitoring the curing degree of the polymer sample S, α (t) after the superposition is defined asΔn(t)+n₀ε (t), which can be used as a new curing monitoring index to reflect the curing degree of the polymer sample S;

further, the curing rate of the curing process of the polymer sample S is expressed as follows, based on the relationship between the curing rate and the degree of curing:

in the above formula, δ t represents the time interval for collecting the interference spectra of two adjacent frames;

s4-5, combining the measured optical path difference variation and the physical relationship described by the formulas (4) and (5), finally obtaining a curing degree curve and a curing rate curve of the polymer sample S, wherein the normalized result is shown in FIG. 4.

The above-mentioned embodiments are merely preferred embodiments of the present invention, and the scope of the present invention is not limited thereto, so that variations based on the shape and principle of the present invention should be covered within the scope of the present invention.