Method for measuring thickness distribution and refractive index dispersion curve of liquid film

Abstract

A method for measuring the thickness distribution and refractive index dispersion curve of a liquid film comprises the following steps: covering the liquid film on an SPR sensing module, irradiating a wide-spectrum linear polarization parallel light beam on the SPR sensing module and generating total reflection to obtain reflected light, and exciting an SPR mode and / or a PWR mode on the SPR sensing module by the wide-spectrum linear polarization parallel light beam through total reflection; information of the liquid film carried by the reflected light is received by the hyperspectral imager to obtain a hyperspectral image, and pixels in the hyperspectral image are in one-to-one correspondence with positions on the liquid film; determining at least three actually measured resonant wavelengths at a target position corresponding to the target pixel according to the hyperspectral image; obtaining the thickness of the liquid film at the target position and a refractive index dispersion curve of the liquid film according to the at least three actually measured resonance wavelengths at the target position; obtaining the thickness of the liquid film at other positions according to the refractive index dispersion curve of the liquid film at the target position and the actually measured resonance wavelength at each other position; and obtaining the thickness distribution of the liquid film according to the thicknesses of the liquid film at all positions.

Description

Technical Field

[0001] The invention relates to the field of precision detection, and in particular to a method for measuring the thickness distribution and refractive index dispersion curve of a liquid film. Background Art

[0002] Liquid films (referred to as liquid films) have important applications in many fields such as environmental protection, petrochemicals, chemical bionics, medicine and health, organic synthesis, analytical chemistry, and gas separation. Liquid films are widely used in mechanical seals and bearing lubrication, which can improve sealing, reduce friction, and extend the service life of mechanical devices; liquid films are also often used to protect solid surfaces from oxidation, improve the optical and mechanical properties of solid surfaces, and are used for waterproofing, heat insulation, and UV protection; liquid films have fast mass transfer rates and good molecular selectivity, and are often used for selective absorption and separation of gas molecules; liquid films play an important role in organisms. For example, tears form a uniform liquid film on the surface of the cornea, which reduces astigmatism and improves visual efficiency; liquid films also have important applications in the field of biochemical sensing. Using liquid films as sensitive films has the advantages of simple film formation, easy renewal, reusable substrates, and improved sensor selectivity. For example, using ionic liquid films as sensor sensitive films can achieve specific detection of heavy metal mercury ions. Liquid films are also an indispensable preliminary state in the process of preparing solid films by chemical methods, and are an important research object in the field of chemical film technology research. Thickness distribution and refractive index dispersion curve are two important parameters of liquid film. Accurate measurement of the thickness of liquid film and its two-dimensional distribution is helpful to establish a controllable preparation method of liquid film and optimize the performance of liquid film in different applications. Accurate measurement of the refractive index dispersion curve of liquid film can effectively evaluate the changes in optical properties and chemical composition of liquid film during use. The simultaneous measurement of the thickness distribution of liquid film and its refractive index dispersion curve will enable us to more comprehensively analyze and grasp the physical and chemical properties of liquid film during use.

[0003] Optical measurement methods have the advantages of being accurate, fast, non-destructive, and easy to implement, and are the main methods for measuring liquid film thickness and its refractive index. At present, optical instruments commonly used to measure the refractive index of liquids include ellipsometers, Abbe refractometers, optical waveguide sensors, and SPR sensors. These optical instruments are highly sensitive and can accurately measure the thickness or refractive index of liquid films, but they have a single function and are not suitable for simultaneously measuring the thickness and refractive index of liquid films, let alone the two-dimensional distribution of liquid film thickness and the refractive index dispersion curve of liquid films. In real life, there is a lack of advanced methods and tools that can simultaneously measure the thickness distribution of liquid films and their refractive index dispersion curves. Summary of the invention

[0004] In view of this, in order to solve the above problems, a method for measuring the thickness distribution and refractive index dispersion curve of a liquid film is proposed.

[0005] As one aspect of the present invention, a method for measuring the thickness distribution and refractive index dispersion curve of a liquid film is provided, wherein the method is implemented based on a hyperspectral SPR imaging device, wherein the hyperspectral SPR imaging device includes an SPR sensing module, and the method includes:

[0006] Covering the liquid film on the SPR sensor module;

[0007] A wide-spectrum linearly polarized parallel light beam is irradiated onto the SPR sensor module and totally reflected to obtain reflected light, wherein the wide-spectrum linearly polarized parallel light beam excites an SPR mode and / or a PWR mode on the SPR sensor module through total reflection, and the reflected light carries information of the liquid film through the interaction between the SPR mode and / or the PWR mode and the liquid film; wherein the reflected light is received by a hyperspectral imager to obtain a hyperspectral image, and pixels in the hyperspectral image correspond one-to-one to positions on the liquid film;

[0008] Determine, according to the hyperspectral image, at least three measured resonance wavelengths at a target position corresponding to a target pixel, wherein the measured resonance wavelengths at the target position are resonance wavelengths of an SPR mode and / or a PWR mode;

[0009] Obtaining a liquid film thickness at the target position and a refractive index dispersion curve of the liquid film according to at least three measured resonance wavelengths at the target position;

[0010] Obtaining the thickness of the liquid film at the other positions according to the refractive index dispersion curve of the liquid film and the measured resonance wavelength at each other position, wherein the other position is any position on the liquid film except the target position;

[0011] The thickness distribution of the liquid film is obtained according to the thickness of the liquid film at all positions of the liquid film.

[0012] According to an embodiment of the present invention, the SPR sensor module comprises a substrate and a metal film located on the substrate, the substrate is a prism, and the metal film is deposited on the bottom surface of the prism; or

[0013] The substrate is a combination of a prism and a transparent substrate in close contact with the bottom surface of the prism, and the metal film is deposited on the surface of the transparent substrate away from the prism;

[0014] The liquid film is disposed on the surface of the metal film;

[0015] The SPR mode is excited at the interface between the metal film and the substrate;

[0016] The PWR mode is excited within the liquid film.

[0017] According to an embodiment of the present invention, a covering layer is also formed on the liquid film;

[0018] Obtaining the thickness of the liquid film at the target position and the refractive index dispersion curve of the liquid film according to at least three measured resonant wavelengths at the target position, including:

[0019] The refractive index of the substrate, the refractive index and thickness of the metal film, and the refractive index of the cover layer above the liquid film are brought into the Fresnel reflection formula of the four-layer structure, and at least three measured resonance wavelengths of the liquid film at the target position are simulated and fitted to obtain a first relationship curve at each measured resonance wavelength at the target position, wherein the first relationship curve is a relationship curve between the refractive index of the liquid film and the thickness of the liquid film at the target position, and at least three measured resonance wavelengths correspond to at least three first curves;

[0020] According to the Cauchy dispersion formula and at least three first relationship curves of the liquid film at the target position, the thickness of the liquid film at the target position and the refractive index dispersion curve of the liquid film are obtained.

[0021] According to an embodiment of the present invention, obtaining the thickness of the liquid film at the other positions according to the refractive index dispersion curve of the liquid film and the measured resonance wavelength at each other position includes:

[0022] Using the hyperspectral image to obtain the measured resonance wavelength at the other positions;

[0023] determining the refractive index of the liquid film at the measured resonance wavelength at the other positions according to the refractive index dispersion curve of the liquid film;

[0024] The thickness of the liquid film at the other positions is obtained according to the refractive index of the liquid film at the other positions at the measured resonance wavelength and the Fresnel reflection formula of the four-layer structure.

[0025] According to an embodiment of the present invention, the Cauchy dispersion formula is expressed as follows:

[0026]

[0027] in, , As parameters, represents the refractive index of the liquid film at wavelength λ;

[0028] According to the Cauchy dispersion formula and at least three first relationship curves of the liquid film at the target position, the thickness of the liquid film at the target position and the refractive index dispersion curve of the liquid film are obtained, including:

[0029] According to the Cauchy dispersion formula and the at least three first relationship curves, at least two second relationship curves at the target position are obtained, wherein the second relationship curve is a relationship curve between the parameter b and the liquid film thickness at the target position, and all the second curves intersect at one point;

[0030] Obtaining the intersection of at least two second relationship curves to obtain the value of the parameter b and the thickness of the liquid film at the target position;

[0031] According to the value of the parameter b and the thickness of the liquid film at the target position, combined with any one of the at least three first relationship curves, the value of the parameter a is obtained; the values ​​of the parameter a and the parameter b are substituted into the Cauchy dispersion formula to obtain the refractive index dispersion curve of the liquid film.

[0032] According to an embodiment of the present invention, the Fresnel reflection formula of the four-layer structure is expressed as follows:

[0033] R = r 1234 ·r 1234 *

[0034]

[0035]

[0036]

[0037] Wherein, R represents the reflectivity of the four-layer structure consisting of the substrate, the metal film, the liquid film and the covering layer, wherein the substrate, the metal film, the liquid film and the covering layer are the first layer, the second layer, the third layer and the fourth layer from bottom to top, respectively, and r 1234 represents the reflection coefficient of the four-layer structure, r 1234 * Represents r 1234 The complex conjugate of , D2 is the thickness of the second layer, D3 is the thickness of the third layer, k2 and k3 represent the vertical components of the propagation constant of the broad spectrum linearly polarized parallel beam in the second layer and the third layer respectively; r 234 Represents the reflection coefficient of light in the three-layer structure consisting of the second, third, and fourth layers, r ij represents the interface reflection coefficient between the i-th layer and the j-th layer, i=1, 2 or 3, j=2, 3 or 4, λ is the wavelength of light in vacuum, n i represents the refractive index of the i-th layer at wavelength λ.

[0038] According to an embodiment of the present invention, the wide spectrum linearly polarized parallel light beam is s-polarized light or p-polarized light or other linearly polarized light that can be decomposed into an s-polarized component and a p-polarized component.

[0039] According to an embodiment of the present invention, when the wide spectrum linearly polarized parallel light beam is s-polarized light, r ij Obtained by the following formula:

[0040]

[0041] When the broad spectrum linearly polarized parallel light beam is p-polarized light, r ij Obtained by the following formula:

[0042]

[0043] Among them, θ i and θ j They represent the incident angle and refraction angle of the wide spectrum linear polarized light when it is incident from the i-th layer to the j-th layer, n j The refractive index of the jth layer, k i and k j They represent the vertical components of the propagation constants of light in the i-th and j-th layers respectively.

[0044] According to an embodiment of the present invention, the metal film does not fall off and does not change its physical and chemical properties after being covered by the liquid film; and the liquid film remains stable during the test time.

[0045] According to an embodiment of the present invention, the at least three measured resonance wavelengths at the target position are obtained through one hyperspectral imaging measurement or through multiple hyperspectral imaging measurements under different conditions.

[0046] The basic methods for measuring the thickness of the liquid film and the refractive index of the liquid film in the embodiments of the present invention are the surface plasmon resonance (SPR) sensing method and the plasma waveguide resonance (PWR) sensing method. SPR is a mature and highly sensitive biochemical sensing method. However, the detection depth of the SPR sensor is relatively small. In the visible light band, it can only detect a liquid film with a thickness of 300nm at most. As the thickness of the liquid film increases (from a few hundred nanometers to micrometers), a PWR mode will gradually be generated in the liquid film. Therefore, the PWR mode can be used to measure thicker (micrometer-level thickness) liquid films, and the SPR mode can be used to measure thinner (several nanometers to tens of nanometers thick) liquid films.

[0047] According to an embodiment of the present invention, the thickness and refractive index dispersion curve of the liquid film include multiple unknown quantities. Therefore, when the thickness distribution and refractive index dispersion curve of the liquid film are measured synchronously, multiple unknown quantities need to be determined, which requires the experiment to obtain at least three resonant wavelengths of the SPR mode and / or PWR mode at the target position corresponding to the target pixel in the hyperspectral image. For the target pixel, the three measured resonant wavelengths obtained can be used as known quantities to realize the measurement of the thickness of the liquid film and the refractive index color line curve at the target position. The thickness of the liquid film changes with the change of position, but the dispersion curve of the liquid film does not change with the change of position. The refractive index dispersion curve at the target position is the refractive index dispersion curve of the liquid film. Only one unknown quantity, namely the thickness, needs to be measured at each other position on the liquid film. Therefore, for other positions of the liquid film, the measured resonant wavelength and refractive index dispersion curve of the position can be used to realize the measurement of the thickness of the liquid film at the position. Therefore, the embodiment of the present invention can realize the simultaneous measurement of the thickness distribution of the liquid film and the refractive index dispersion curve of the liquid film. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present invention, but are not intended to limit the present invention.

[0049] Figure 1 The schematic diagram of the hyperspectral SPR imaging device provided by the embodiment of the present invention is shown;

[0050] Figure 2 A flow chart of a method for measuring the thickness distribution and refractive index dispersion curve of a liquid film provided by an embodiment of the present invention is shown;

[0051] Figure 3 A flow chart of a method for measuring the thickness distribution and refractive index dispersion curve of a liquid film according to another embodiment of the present invention is provided.

[0052] Figure 4A An experimental spectrum and a simulated spectrum of a target pixel on a hyperspectral image of a silicone oil film provided by an embodiment of the present invention are shown;

[0053] Figure 4B Shown by Figure 4A The two-dimensional distribution diagrams of the measured resonance wavelengths of the five PWR modes obtained;

[0054] Figure 4C Shown according to Figure 4A Three first curves are obtained from three of the obtained resonance wavelengths;

[0055] Figure 4D Shown according to Figure 4C The two second curves at the target position are obtained from the three first curves.

[0056] Figure 5 shows the thickness distribution of the silicone oil film measured according to the implementation of the present invention;

[0057] Figure 6 shows a comparison between four experimental spectra extracted from other four pixels on the measured hyperspectral image of the silicone oil film and the corresponding simulation spectra according to an embodiment of the present invention;

[0058] Figure 7 shows the refractive index dispersion curve of the silicone oil film measured according to the implementation of the present invention;

[0059] Fig. 8A The experimental spectrum and the simulated spectrum extracted from the target pixel on the measured hyperspectral image of the glycerol film according to the embodiment of the present invention are shown;

[0060] Figure 8B Shown by Fig. 8A The two-dimensional distribution diagrams of the measured resonance wavelengths of the four PWR modes obtained;

[0061] Fig. 9A shows the refractive index dispersion curve of the glycerol film measured according to the implementation of the present invention;

[0062] Fig. 9B The thickness distribution of the dry oil film measured according to the present invention is shown.

[0063] Description of reference numerals:

[0064] 1- Linear polarizer;

[0065] 2-SPR sensor module;

[0066] 21 - base;

[0067] 211-Prism;

[0068] 212- glass substrate;

[0069] 22-Metal film;

[0070] 3-Liquid film;

[0071] 4- Broadband light source;

[0072] 5- Imaging lens;

[0073] 6-Hyperspectral imager;

[0074] 7- Covering layer. DETAILED DESCRIPTION

[0075] In order to make the purpose, technical scheme and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. However, the present invention can be implemented in different forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, providing these embodiments will make the invention thorough and complete and fully convey the scope of the present invention to those skilled in the art. In the accompanying drawings, for clarity, the sizes and relative sizes of layers and regions may be exaggerated, and the same reference numerals throughout represent the same elements.

[0076] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0077] Figure 1 The schematic diagram of the hyperspectral SPR imaging device is given.

[0078] like Figure 1 As shown, the hyperspectral SPR imaging device comprises: an SPR sensor module 2, a liquid film 3 is located on the SPR sensor module 2, a broadband light source 4 and a hyperspectral imager 6 are respectively arranged on both sides of the SPR sensor module 2, a linear polarizer 1 is placed between the broadband light source 4 and the SPR sensor module 2, and an imaging lens 5 is placed between the SPR sensor module 2 and the hyperspectral imager 6. The hyperspectral SPR imaging device is used to achieve the synchronous measurement of the thickness distribution of the liquid film 2 and the refractive index dispersion curve of the liquid film 2.

[0079] Figure 2 The flowchart of the method for measuring the thickness distribution and refractive index dispersion curve of a liquid film provided by an embodiment of the present invention is shown. Figure 1 and Figure 2 The method for measuring the thickness distribution and refractive index dispersion curve of the liquid film 3 includes operations S1 to S6.

[0080] Operation S1: Covering the liquid film 3 on the SPR sensor module.

[0081] Operation S2, irradiate the wide spectrum linear polarized parallel light beam onto the SPR sensor module 2 and obtain reflected light by total reflection, the wide spectrum linear polarized parallel light beam excites the SPR mode and / or PWR mode on the SPR sensor module 2 by total reflection, and the reflected light carries the information of the liquid film 3 through the interaction between the SPR mode and / or PWR mode and the liquid film 3. The wide spectrum linear polarized parallel light beam is obtained by passing through the linear polarizer 1 after being emitted by the broadband light source 4 of the hyperspectral SPR imaging device. Among them, the reflected light is received by the hyperspectral imager 6 after passing through the imaging lens 5 to obtain a hyperspectral image, and the pixels in the hyperspectral image correspond to the positions on the liquid film one by one.

[0082] Operation S3, determining at least three measured resonance wavelengths at a target position corresponding to a target pixel according to the hyperspectral image, wherein the measured resonance wavelength at the target position is a resonance wavelength of an SPR mode and / or a PWR mode. The target pixel is, for example, a pixel at the center point of the field of view of the hyperspectral imager 6 .

[0083] In operation S4 , a liquid film thickness at the target position and a refractive index dispersion curve of the liquid film are obtained according to at least three measured resonance wavelengths at the target position.

[0084] Operation S5 , obtaining the thickness of the liquid film at other positions according to the refractive index dispersion curve of the liquid film and the measured resonance wavelength of each other position, where the other position is any position on the liquid film except the target position.

[0085] In operation S6 , the distribution of the thickness of the liquid film is obtained according to the thickness of the liquid film at all positions on the liquid film 3 .

[0086] The basic methods for measuring the thickness of the liquid film and the refractive index of the liquid film in the embodiment of the present invention are the surface plasmon resonance (SPR) sensing method and the plasma waveguide resonance (PWR) sensing method. SPR is a mature and highly sensitive biochemical sensing method. However, the detection depth of the SPR sensor is relatively small. In the visible light band, it can only detect a liquid film with a thickness of 300nm at most. As the thickness of the liquid film increases (from a few hundred nanometers to micrometers), a PWR mode will gradually be generated in the liquid film. Therefore, the PWR mode can be used to measure thicker (micrometer-level thickness) liquid films, and the SPR mode can be used to measure thinner (several nanometers to tens of nanometers thick) liquid films. The embodiment of the present invention can realize surface plasmon resonance (SPR) and can also realize plasmon guided mode resonance (PWR). Therefore, the embodiment of the present invention can realize the detection of thinner (several nanometers to tens of nanometers) liquid films, and can also realize the detection of thinner (hundreds of nanometers to several micrometers) liquid films.

[0087] According to an embodiment of the present invention, the thickness and refractive index dispersion curve of the liquid film include multiple unknown quantities. Therefore, when the thickness distribution and refractive index dispersion curve of the liquid film are measured synchronously, multiple unknown quantities need to be determined, which requires the experiment to obtain at least three resonant wavelengths of the SPR mode and / or PWR mode at the target position corresponding to the target pixel in the hyperspectral image. For the target pixel, the three measured resonant wavelengths obtained can be used as known quantities to realize the measurement of the thickness and color line curve of the liquid film at the target position. The thickness of the liquid film changes with the change of position, but the dispersion curve of the liquid film does not change with the change of position. The refractive index dispersion curve at the target position is the refractive index dispersion curve of the liquid film. Only one unknown quantity, namely the thickness, needs to be measured at each other position on the liquid film. Therefore, for other positions of the liquid film, the measured resonant wavelength and refractive index dispersion curve of the position can be used to realize the measurement of the thickness of the liquid film at the position. Therefore, the embodiment of the present invention can realize the simultaneous measurement of the thickness distribution of the liquid film and the refractive index dispersion curve of the liquid film.

[0088] According to an embodiment of the present invention, the liquid constituting the liquid film 3 must be a stable and uniform liquid. The liquid film 3 is a thinner liquid film with a thickness range of 1-10 microns. The specific thickness range is related to the hyperspectral SPR imaging device. It is necessary to ensure that the PWR mode can be generated and at least three resonance peaks of the PWR mode are formed within the measured spectral range (400~10000 nm). The liquid film 3 can be prepared by natural diffusion method, spin coating method and other methods.

[0089] According to an embodiment of the present invention, the SPR sensor module 2 includes a substrate 21 and a metal film 22 located on the substrate 21. In the first embodiment, the first Kretschmann prism coupling structure is adopted, wherein the substrate 21 is a prism, the material of which can be glass, and the metal film 22 is deposited on the bottom surface of the glass prism. Figure 2As shown, the second Kretschmann prism coupling structure is adopted, wherein the substrate 21 is a combination of a prism 211 and a glass substrate 212 in close contact with the bottom surface of the prism 211. The metal film 21 is deposited on the surface of the glass substrate 212 away from the bottom surface of the prism 211, and the glass substrate 212 is in close contact with the bottom surface of the prism 211 through a high refractive index coupling liquid. The liquid film is arranged on the surface of the metal film 22, and the liquid film 3 is exposed to the outermost side. The thickness of the metal film is between 10nm and 100nm. When the metal film 22 is a gold film, the optimal thickness is 50nm. The parallel light beam with wide spectrum linear polarization passes through the substrate 21, and is totally reflected at the glass and metal interface of the SPR sensor module 2. The reflected light beam is emitted from the side of the prism 211, passes through the imaging lens 5, and is then received by the hyperspectral imager 6. The evanescent field generated by the total reflection penetrates the metal film 22 and excites the SPR mode at the interface between the metal film 22 and the substrate 21 and / or excites the PWR mode in the liquid film. Both the SPR mode and the PWR mode can interact with the liquid film, so that the reflected light carries the information of the liquid film 3 .

[0090] According to an embodiment of the present invention, Figure 1 When the SPR sensor module 2 in the embodiment is combined with a Kretschmann prism coupling structure, the broadband light source 4, such as a halogen tungsten lamp, emits broadband light that is converted into an s-polarized or p-polarized parallel light beam through a multimode quartz optical fiber, a prism 211, and a linear polarizer 1, and then incident on the prism at an angle θ, where the angle θ can be adjusted by rotating the device turntable. The broadband linearly polarized parallel light beam that enters the prism 211 is totally reflected at the interface between the glass substrate 212 and the metal film 22 of the SPR sensor module 2, and the reflected light is incident on the hyperspectral imager 6 through the imaging prism 5. The evanescent field generated by the total reflection can excite the PWR mode in the liquid film 3, or excite the SPR mode at the interface between the metal film 22 and the liquid film 3. When the evanescent field generated by the total reflection excites the PWR in the liquid film 3, the reflection spectrum will present multiple troughs, so that the wavelength corresponding to the trough in each pixel spectrum in the hyperspectral image recorded by the hyperspectral imager 6 is the resonant wavelength λ of the PWR mode. R In addition to the Kretschmann prism, those skilled in the art should be aware that the hyperspectral image of the liquid film can also be obtained by using an Otto prism coupling structure, which will not be described in detail here.

[0091] According to an embodiment of the present invention, when the liquid film 3 is very thin, the SPR mode can only be excited at the interface between the metal film 22 and the liquid film 3, and the PWR mode is gradually excited as the thickness of the liquid film increases. When only the SPR mode is excited at the interface between the metal film 22 and the liquid film 3, the target pixel of each high-light image can only obtain a resonant wavelength at a target position. Or when the liquid film thickness is not enough, although the PWR mode can be excited, each hyperspectral image can only be based on less than 3 resonant wavelengths of the target pixel.

[0092] A covering layer 7 is also formed on the liquid film 3. In order to obtain at least three measured resonance wavelengths at the target position corresponding to the target pixel, different hyperspectral images can be obtained by changing the test conditions, thereby obtaining the three resonance wavelengths at the target position. Changing the test conditions may include, for example, changing the material of the covering layer 7, or changing the polarization direction of the broad spectrum linear polarization parallel light beam.

[0093] For example, hyperspectral imaging can be performed on the reflected light under different (at least three) covering layers 7 to obtain at least three hyperspectral images, and at least three measured resonance wavelengths at the target position can be obtained based on the at least three hyperspectral images. For example, when the covering layers 7 on the liquid film 3 are air, water, and a solid plate with a flat and smooth surface, etc., hyperspectral imaging is performed on the reflected light to obtain a hyperspectral image corresponding to each covering layer 7, so as to obtain at least three measured resonance wavelengths at the target position based on the hyperspectral images corresponding to all covering layers 7.

[0094] According to an embodiment of the present invention, three resonance wavelengths at the target position can also be obtained by changing the polarization direction of the wide spectrum linear polarization parallel light beam and simultaneously changing the cover layer 7. Alternatively, the three resonance wavelengths at the target position can be obtained by only changing the polarization direction of the wide spectrum linear polarization parallel light beam. For example, the material of the cover layer 7 remains unchanged, and when the polarization directions of the wide spectrum linear polarization parallel light beam are different (S direction or P direction), the reflected light is subjected to hyperspectral imaging respectively to obtain a hyperspectral image corresponding to each polarization direction. Based on the hyperspectral images corresponding to each polarization direction under the condition of multiple cover layers 7, at least three measured resonance wavelengths at the target position can be obtained.

[0095] In either case, the at least three resonance wavelengths obtained can be used as known quantities to determine the refractive index dispersion curve and the thickness distribution.

[0096] According to an embodiment of the present invention, when the thickness of the liquid film 3 is large enough to support at least three PWR modes, a hyperspectral imaging measurement can obtain at least three resonant wavelengths at the target position. Therefore, a hyperspectral image obtained by imaging the reflected light once can be used to measure the liquid film.

[0097] According to an embodiment of the present invention, the PWR mode will generate multiple orders, each order corresponds to a resonance wavelength, and the resonance wavelength is related to the thickness of the liquid film and the refractive index dispersion curve of the liquid film. In the PWR mode, the resonance wavelengths of multiple orders at the target position of the liquid film (corresponding to PWR modes of different orders) can be used as multiple known quantities to simultaneously calculate the refractive index dispersion curve of the liquid film and the thickness at that position. When combined with a hyperspectral image, since the hyperspectral image can obtain the resonance spectrum of tens of thousands of pixels of the liquid film, the large number of resonance peaks of tens of thousands of pixels can solve the distribution of the thickness of the liquid film of the refractive index dispersion curve.

[0098] According to an embodiment of the present invention, operation S4, obtaining the liquid film thickness at the target position and the refractive index dispersion curve of the liquid film according to at least three measured resonance wavelengths at the target position, includes sub-operations S41 and S42.

[0099] In sub-operation S41, the refractive index of the substrate, the refractive index and thickness of the metal film, and the refractive index of the covering layer 7 above the liquid film are brought into the Fresnel reflection formula of the four-layer structure, and at least three measured resonance wavelengths of the liquid film at the target position are simulated and fitted to obtain a first relationship curve at each measured resonance wavelength at the target position, wherein the first relationship curve is a relationship curve between the refractive index of the liquid film and the thickness of the liquid film at the target position, and at least three measured resonance wavelengths correspond to at least three of the first curves.

[0100] In sub-operation S42, the thickness of the liquid film at the target position and the refractive index dispersion curve of the liquid film are obtained according to the Cauchy dispersion formula and at least three first relationship curves of the liquid film at the target position.

[0101] Cover layer 7 According to an embodiment of the present invention, the Cauchy dispersion curve is expressed as formula (1).

[0102] (1).

[0103] in, As parameters, It represents the refractive index of the liquid film at wavelength λ.

[0104] In sub-operation S42, the thickness of the liquid film at the target position and the refractive index dispersion curve of the liquid film are obtained according to the Cauchy dispersion formula and at least three first relationship curves of the liquid film at the target position, including sub-operations S421 to S423.

[0105] In sub-operation S421, at least two second relationship curves are obtained at the target position according to the Cauchy dispersion formula and at least three first relationship curves, where the second relationship curves are relationship curves between parameter b and the liquid film thickness at the target position. Since both parameter b and liquid film thickness are independent of wavelength (i.e., both parameter b and liquid film thickness are independent of wavelength), all (at least two) second relationship curves obtained at the target position are bound to intersect at one point.

[0106] Sub-operation S422, finding the intersection of at least two second relationship curves to obtain the value of parameter b and the liquid film thickness at the target position.

[0107] Sub-operation S423, according to the value of parameter b and the thickness of the liquid film at the target position, combined with any one of at least three first curves (relationship curves between the refractive index and the thickness of the liquid film at the target position), obtain the value of parameter a; substitute the values ​​of parameter a and parameter b into the Cauchy dispersion formula to obtain the refractive index dispersion curve of the liquid film 3. According to an embodiment of the present invention, when the refractive index dispersion curve of the liquid film 3 is determined using the Cauchy dispersion formula, there are two unknown parameters, namely parameter a and parameter b. At the target position of the liquid film 3, in addition to parameter a and parameter b, the thickness of the position needs to be measured. Therefore, three unknown quantities need to be measured. Therefore, when the refractive index dispersion curve of the liquid film 3 is obtained using the Cauchy dispersion formula, three resonance wavelengths at the target position need to be obtained. In order to improve the solution accuracy of parameter a and parameter b and the thickness of the liquid film at the target position, when determining at least three measured resonance wavelengths in a spectrum with more than three PWR resonance peaks, at least three measured resonance wavelengths are selected according to the principle of making the wavelength interval as large as possible.

[0108] The following is a detailed explanation of the measurement principle of the liquid film thickness distribution and the refractive index dispersion curve in combination with the Cauchy formula.

[0109] Take the use of the three measured resonant wavelengths of the target pixel to solve the thickness and refractive index dispersion curve at the target position as an example. The three measured resonant wavelengths of the target pixel are, for example, , and The refractive index of the substrate 21, the refractive index and thickness of the metal film 22, and the refractive index of the cover layer 7 above the liquid film are introduced into the Fresnel reflection formula of the four-layer structure, and each measured resonance wavelength of the liquid film 3 at the target position is simulated and fitted to obtain at least three first curves. That is, the first curve is Down The relationship between T and the second curve is Down The relationship between T and the third curve is Down Relationship with T. for The refractive index under for The refractive index under for The refractive index below.

[0110] According to formula (1),

[0111] (8)

[0112] (9)

[0113] (10)

[0114] According to (8)~(9), we can get:

[0115] (11)

[0116] According to (9) to (10), we can get:

[0117] (12)

[0118] Will Relationship with T, Relationship with T, Substitute the relationship between b and T into (11) and (12) respectively, and obtain two curves of the relationship between b and T. The intersection of the two curves of the relationship between b and T is the value of b and T. According to the Cauchy formula, a can be calculated. After determining a and b, the refractive index dispersion curve can be determined.

[0119] According to an embodiment of the present invention, in operation S5, the thickness of the liquid film at other positions is obtained according to the refractive index dispersion curve of the liquid film and the measured resonance wavelength of each other position, which can be divided into sub-operations S51 to S53.

[0120] In sub-operation S51, other measured resonance wavelengths at other positions are obtained using the measured hyperspectral image.

[0121] Sub-operation S52: determining the refractive index of the liquid film at other positions at the measured resonance wavelength according to the refractive index dispersion curve of the liquid film.

[0122] Sub-operation S53, obtaining the thickness of the liquid film at other positions according to the refractive index of the liquid film at other positions at the measured resonance wavelength and the Fresnel reflection formula of the four-layer structure.

[0123] According to an embodiment of the present invention, the Fresnel formula of the four-layer structure is expressed as formula (2) to formula (5).

[0124] R = r 1234 ·r 1234* (2)

[0125] (3)

[0126] (4)

[0127] (5)

[0128] Where R represents the reflectivity of the four-layer structure consisting of substrate, metal film, liquid film and covering layer. The substrate, metal film, liquid film and covering layer are the first layer, the second layer, the third layer and the fourth layer from bottom to top. 1234 represents the reflection coefficient of the four-layer structure, r 1234 * Represents r 1234 The complex conjugate of , D2 is the thickness of the second layer, D3 is the thickness of the third layer, k2 and k3 represent the vertical components of the propagation constant of the broad spectrum linearly polarized parallel beam in the second layer and the third layer respectively; r 234 Represents the reflection coefficient of light in the three-layer structure consisting of the second, third, and fourth layers, r ij represents the reflection coefficient of the interface between the i-th layer and the j-th layer, i=1, 2 or 3, j=2, 3 or 4, λ is the wavelength of light in vacuum, n i represents the refractive index of the i-th layer at wavelength λ.

[0129] The broad spectrum linearly polarized parallel light beam may be s-polarized light or p-polarized light or other linearly polarized light that can be decomposed into an s-polarized component and a p-polarized component.

[0130] When the broad spectrum linearly polarized parallel light beam is s-polarized light, r ij Obtained by the following formula: ij Obtained by formula (6).

[0131] (6)

[0132] When the broad spectrum linearly polarized parallel light beam is p-polarized light, r ij Obtained by the following formula. (7)

[0133] For other linearly polarized light, it can be decomposed into s polarization component and p polarization component, which can be calculated separately and then synthesized. i and θ j They represent the incident angle and refraction angle of light from the i-th layer to the j-th layer, respectively. j The single-wavelength refractive index of the jth layer, k i and k j They represent the vertical components of the propagation constants of light in the i-th and j-th layers respectively.

[0134] According to an embodiment of the present invention, the metal film 22 needs to be able to excite the SPR mode on its surface, and is usually gold, silver, aluminum or titanium.

[0135] When the metal film 22 is covered by the liquid film, it is required that it does not fall off, nor does it change its physical and chemical properties; the liquid film is required to remain stable within the test time.

[0136] The hyperspectral imager 6 may be, for example, a line scanning hyperspectral imager based on grating spectroscopy or a hyperspectral imager based on light source wavelength scanning.

[0137] Figure 3 A flow chart of a method for measuring the thickness distribution and refractive index dispersion curve of a liquid film according to another embodiment of the present invention is provided.

[0138] The following combination Figure 1 and Figure 3 The method of measuring the thickness distribution and refractive index dispersion curve of a liquid film according to the present invention is described in detail.

[0139] like Figure 1 As shown, the hyperspectral SPR imaging device comprises: an SPR sensor module 2, a liquid film 3 is located on the SPR sensor module 2, a broadband light source 4 and a hyperspectral imager 6 are respectively arranged on both sides of the SPR sensor module 2, a linear polarizer 1 is placed between the broadband light source 4 and the SPR sensor module 2, and an imaging lens 5 is placed between the SPR sensor module 2 and the hyperspectral imager 6. The hyperspectral SPR imaging device is used to achieve the synchronous measurement of the thickness distribution of the liquid film 2 and the refractive index dispersion curve of the liquid film 2.

[0140] like Figure 3 As shown, the method for measuring the thickness distribution and refractive index dispersion curve of the liquid film further comprises steps A to H. In step A, the liquid film 3 is covered on the SPR sensor module 2 .

[0141] Step B, irradiate the wide spectrum linear polarized parallel light beam onto the SPR sensor module 2 to cause total reflection, and obtain reflected light, the wide spectrum linear polarized parallel light beam excites the SPR mode and / or PWR mode on the SPR sensor module 2 through total reflection, and the reflected light carries the information of the liquid film 3 through the interaction between the SPR mode and / or PWR mode and the liquid film 3; the reflected light is received by the hyperspectral imager 6 to obtain a hyperspectral image, and the pixels in the hyperspectral image correspond to the positions on the liquid film 3 one by one. The wide spectrum linear polarized parallel light beam is obtained by passing through the linear polarizer 1 after being emitted by the broadband light source 4 of the hyperspectral SPR imaging device.

[0142] Step C, according to the hyperspectral image output by the hyperspectral imager 6, at least three measured resonant wavelengths at the target position corresponding to the target pixel are determined, and the measured resonant wavelength at the target position is the resonant wavelength of the SPR mode and / or the PWR mode. The target pixel is, for example, a pixel at the center point of the field of view of the hyperspectral imager 6. The at least three measured resonant wavelengths at the target position can be obtained by a single hyperspectral imaging measurement, or by multiple hyperspectral imaging measurements under different conditions.

[0143] Step D, bringing the refractive index of the substrate, the refractive index and thickness of the metal film, and the refractive index of the covering layer above the liquid film into the Fresnel reflection formula of the four-layer structure, performing simulation fitting on at least three measured resonant wavelengths of the liquid film at the target position, and obtaining at least three first relationship curves at the target position, where the first relationship curve is a relationship curve between the refractive index of the liquid film and the thickness of the liquid film at the target position, and each first curve corresponds one-to-one to each measured resonant wavelength.

[0144] Step E, according to the Cauchy dispersion formula n(λ) = a + bλ -2 At least three first relationship curves are obtained to obtain at least two second relationship curves at the target position, where the second relationship curve is a relationship curve between parameter b and the liquid film thickness at the target position, and then the intersection of at least two second relationship curves is obtained to obtain the value of parameter b and the liquid film thickness at the target position. Since parameter b and liquid film thickness do not depend on wavelength, multiple second relationship curves obtained at the same position will inevitably intersect at one point.

[0145] Step F, according to the obtained value of parameter b and the thickness of the liquid film at the target position, combined with any one of the at least three first relationship curves obtained, obtain the value of parameter a; substitute the values ​​of parameter a and parameter b into the Cauchy dispersion formula to obtain the refractive index dispersion curve of the liquid film. Since the liquid film at the target position and the liquid film at other positions are of the same material, the refractive index dispersion curve obtained by obtaining multiple first relationship curves and multiple second relationship curves at the target position is applicable to the entire liquid film 3.

[0146] Step G, determining the measured resonance wavelength at other positions based on the hyperspectral image output by the hyperspectral imager 6, and then determining the refractive index of the liquid film at the measured resonance wavelength at other positions based on the obtained refractive index dispersion curve of the liquid film, and then obtaining the liquid film thickness at other positions based on the refractive index of the liquid film at the measured resonance wavelength at other positions and the Fresnel reflection formula of the four-layer structure.

[0147] Step H, obtaining the thickness distribution of the liquid film according to the obtained thickness of the liquid film at all positions. Here, all positions include the target position and other positions except the target position.

[0148] The basic method for measuring the thickness distribution of the liquid film 3 and the refractive index dispersion curve of the liquid film 3 in the embodiment of the present invention is a hyperspectral surface plasmon resonance (SPR) imaging sensing method and a hyperspectral plasma waveguide resonance (PWR) imaging sensing method. SPR is a mature and highly sensitive biochemical sensing method. However, the detection depth of the SPR sensor is relatively small. In the visible light band, it can only detect a liquid film with a thickness of 300nm at most. As the thickness of the liquid film increases (from a few hundred nanometers to micrometers), a PWR mode will gradually be generated in the liquid film. Therefore, the PWR mode can be used to measure thicker (micrometer-level thickness) liquid films, and the SPR mode can be used to measure thinner (several nanometers to tens of nanometers thick) liquid films.

[0149] According to an embodiment of the present invention, the thickness and refractive index dispersion curve of the liquid film 3 include multiple unknown quantities. Therefore, when the thickness distribution and refractive index dispersion curve of the liquid film 3 are measured synchronously, multiple unknown quantities need to be determined, which requires the experiment to obtain at least three resonant wavelengths of the SPR mode and / or PWR mode at the target position corresponding to the target pixel in the hyperspectral image. For the target pixel, the three measured resonant wavelengths obtained can be used as known quantities to measure the thickness and color line curve at the target position. The thickness of the liquid film 3 changes with the change of position, but the dispersion curve of the liquid film 3 does not change with the change of position. The refractive index dispersion curve at the target position is the refractive index dispersion curve of the liquid film 3. Only one unknown quantity, namely the thickness, needs to be measured at each other position on the liquid film 3. Therefore, for other positions of the liquid film 3, the measured resonant wavelength and refractive index dispersion curve of the position can be used to measure the thickness of the liquid film at the position. Therefore, the embodiment of the present invention can achieve simultaneous measurement of the thickness distribution and refractive index dispersion curve of the liquid film 3.

[0150] To this end, the method for measuring the actual refractive index dispersion curve and thickness of the liquid film in this embodiment has been introduced. In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0151] The following examples 1 and 2 are listed to illustrate the actual measurement method of measuring the thickness distribution and refractive index dispersion curve of the liquid film. In these two examples, the broadband light source 14 includes a halogen tungsten lamp, a focusing lens and a linear polarizer 1. The metal film is also selected as a gold film, the thickness of the gold film is about 50 nm, and the hyperspectral SPR imaging sensor device uses a Kretschmann prism coupling structure. In Example 1, a silicone oil film is selected for detailed description, and in Example 2, a glycerol film is selected for detailed description.

[0152] Example 1

[0153] In the method for measuring the thickness distribution of the liquid film and the actual refractive index dispersion curve of this example, the liquid film 3 is a silicone oil film prepared by spin coating on a glass substrate sputtered with a 50nm gold film. The method for measuring the refractive index dispersion curve and thickness distribution of the silicone oil film in this example includes:

[0154] The hyperspectral image of the silicone oil film was obtained using a hyperspectral SPR imaging device.

[0155] First, fix the glass substrate as a whole on the spin coating platform, and drip an appropriate amount of silicone oil in the center of the substrate. Set the spin coating platform speed to 2000rpm, spin coating for 120s, and obtain a spin-coated silicone oil film. Then, fix the substrate with spin-coated silicone oil to the bottom surface of the glass prism, and the upper surface of the silicone oil is exposed to the air, that is, the corresponding cover layer is air at this time.

[0156] Secondly, the linear polarizer 1 is adjusted to make the incident broad spectrum linear polarization parallel light beam p-polarized light, and the hyperspectral imager 6 is used to record the hyperspectral images of the reflected light of the p-polarized light on the SPR resonance module 2 when the incident angle is 50°.

[0157] Figure 4A The experimental spectrum and the simulated spectrum of the target pixel on the highlight image formed by the silicone oil film provided by the embodiment of the present invention are shown;

[0158] like Figure 4A As shown, the spectrum of the target pixel point obtained when the incident angle of the p-polarized light is 50°, and the simulation result of the spectrum at the target pixel point. The spectrum of the target pixel point includes the measured resonance wavelengths of multiple measured SPR modes and / or PWR modes, and the measured resonance wavelength is the same as the simulated resonance wavelength.

[0159] Five measured resonant wavelengths (or simulated resonant wavelengths) of the measured SPR mode and / or PWR mode that are less affected by the spectrum of the broadband light source 14 are selected for fitting. The five resonant wavelengths are resonant wavelength No. 1, resonant wavelength No. 2, resonant wavelength No. 3, resonant wavelength No. 4, and resonant wavelength No. 5. Figure 4A The five more obvious resonance wavelengths (measured resonance wavelengths or simulated resonance wavelengths) λ of this pixel can be determined R They are 527.7 nm, 563.9 nm, 606.9 nm, 655.7 nm, and 714.0 nm respectively. After the five measured resonance wavelengths (or simulated resonance wavelengths) of the pixel are determined, a two-dimensional distribution diagram of the measured resonance wavelengths of the five measured SPR modes and / or PWR modes can be drawn. Figure 4B Shown by Figure 4A The obtained two-dimensional distribution diagrams of the measured resonance wavelengths of the five SPR modes and / or PWR modes.

[0160] According to the five measured resonance wavelengths at the target position (the center of the hyperspectral image), the thickness at the center and the refractive index dispersion curve of the liquid film are obtained. Under the premise of knowing the resonance wavelength, the thickness is scanned and a series of refractive indices can be obtained through Fresnel formula fitting.

[0161] Figure 4C Shown according to Figure 4A Three first curves are obtained from three of the obtained resonance wavelengths.

[0162] like Figure 4C As shown, due to Figure 4A The refractive index-thickness simulation curves at the target position drawn by the obtained resonance wavelength No. 3, resonance wavelength No. 4, and resonance wavelength No. 5. Since the resonance wavelength No. 3, resonance wavelength No. 4, and resonance wavelength No. 5 are different, the refractive indices corresponding to the three resonance peaks are not the same, so the three first curves have no intersection. However, the refractive indices corresponding to the three resonance peaks conform to the Cauchy dispersion formula. According to formulas (11) and (12), the refractive index of the liquid film can be converted into the parameter b of the Cauchy dispersion formula, thereby drawing the refractive index parameter b-thickness curve.

[0163] Figure 4D Shown according to Figure 4C The two second curves at the target position are obtained from the three first curves.

[0164] like Figure 4D As shown, according to formula (11) ~ formula (12), according to Figure 4C The two refractive index parameter-thickness curves (two second curves) obtained from the refractive index-thickness simulation curves at the 3rd resonance wavelength, the 4th resonance wavelength, and the 5th resonance wavelength. Under this experimental condition, since the thickness of the liquid film at this target position is fixed with the refractive index parameter, the intersection of the two refractive index parameter-thickness curves intuitively depicts the method of solving the initial thickness of the pixel point at the target position. The initial thickness of the liquid film at the target position can be obtained from the position of the intersection. nm.

[0165] Figure 5 The thickness distribution of the silicone oil film provided according to the embodiment of the present invention is shown.

[0166] like Figure 5 As shown, the thickness of the silicone oil film is distributed in the range of 3900-4100 nm.

[0167] Figure 6 The figure shows the comparison between the simulated spectra and the experimental spectra obtained by the other four pixels on the hyperspectral image formed by the silicone oil film provided by the embodiment of the present invention.

[0168] like Figure 6As shown, the comparison between the simulated spectrum and the experimental spectrum obtained by its four pixels is as follows Figure 5 As shown in parts (a), (b), (c) and (d), the simulated resonance wavelengths obtained by simulating the spectra of the other four pixels (except the target pixel) are in good agreement with the measured resonance wavelengths of the SPR mode and / or PWR mode. Figure 7 As shown, the dispersion curve obtained in this example is .

[0169] Example 2

[0170] The difference from Example 1 is that the liquid film in this example is a glycerol film. This embodiment measures the hyperspectral SPR image of the glycerol film when the incident angle of a broad spectrum linearly polarized parallel beam in the p-polarization direction is 52°. Since the glycerol film is thinner than the silicone oil film in Example 1 and has fewer PWR resonance orders, only four resonance wavelengths are selected for each pixel for fitting, and a resonance wavelength distribution diagram is drawn.

[0171] Fig. 8A The experimental spectrum and the simulated spectrum of the target pixel on the hyperspectral image formed by the glycerol film provided according to the embodiment of the present invention are shown.

[0172] like Fig. 8A As shown, the resonance wavelength of the central pixel (target pixel) is still preferentially fitted. The preliminary fitting results are as follows Fig. 8A The four resonance wavelengths are 500.1 nm, 566.8 nm, 631.1 nm, and 729.7 nm. The single-wavelength refractive index of this pixel is obtained by preliminary fitting. , the thickness at the target position nm. Figure 8B Shown by Fig. 8A The obtained two-dimensional distribution diagrams of the measured resonance wavelengths of the four SPR modes and / or PWR modes.

[0173] The refractive index dispersion curve of the glycerol film is shown in Fig. 9A As shown in Figure 2, the thickness distribution of the glycerol film is as follows: Fig. 9B As shown, the dispersion curve in this example is .

[0174] It can be seen from the above technical scheme that the equipment used in the method of the present invention for measuring the refractive index dispersion curve and thickness distribution of the liquid film is low in cost and simple to operate. The theory involved in the simulation fitting is also not complicated. In addition, the refractive index dispersion curve and thickness distribution of the liquid film can be obtained simultaneously, which is of great practical significance for quickly and accurately obtaining multiple parameters of various types of liquid films at the same time.

[0175] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for measuring the thickness distribution and refractive index dispersion curve of a liquid film, the method being implemented based on a hyperspectral SPR imaging device, the hyperspectral SPR imaging device comprising an SPR sensor module, the method comprising: Covering the liquid film on the SPR sensor module; A wide-spectrum linearly polarized parallel light beam is irradiated onto the SPR sensor module and totally reflected to obtain reflected light, wherein the wide-spectrum linearly polarized parallel light beam excites an SPR mode and / or a PWR mode on the SPR sensor module through total reflection, and the reflected light carries information of the liquid film through the interaction between the SPR mode and / or the PWR mode and the liquid film; wherein the reflected light is received by a hyperspectral imager to obtain a hyperspectral image, and pixels in the hyperspectral image correspond one-to-one to positions on the liquid film; Determine, according to the hyperspectral image, at least three measured resonance wavelengths at a target position corresponding to a target pixel, wherein the measured resonance wavelengths at the target position are resonance wavelengths of an SPR mode and / or a PWR mode; Obtaining a liquid film thickness at the target position and a refractive index dispersion curve of the liquid film according to at least three measured resonance wavelengths at the target position; Obtaining the thickness of the liquid film at the other positions according to the refractive index dispersion curve of the liquid film and the measured resonance wavelength at each other position, wherein the other position is any position on the liquid film except the target position; The thickness distribution of the liquid film is obtained according to the thickness of the liquid film at all positions of the liquid film.

2. The method according to claim 1, wherein: The SPR sensor module comprises a substrate and a metal film on the substrate, wherein the substrate is a prism, and the metal film is deposited on the bottom surface of the prism; or The substrate is a combination of a prism and a transparent substrate in close contact with the bottom surface of the prism, and the metal film is deposited on the surface of the transparent substrate away from the prism; The liquid film is disposed on the surface of the metal film; The SPR mode is excited at the interface between the metal film and the substrate; The PWR mode is excited within the liquid film.

3. The method according to claim 1, wherein: A covering layer is also formed on the liquid film; Obtaining the thickness of the liquid film at the target position and the refractive index dispersion curve of the liquid film according to at least three measured resonant wavelengths at the target position, including: The refractive index of the substrate, the refractive index and thickness of the metal film, and the refractive index of the cover layer above the liquid film are brought into the Fresnel reflection formula of the four-layer structure, and at least three measured resonance wavelengths of the liquid film at the target position are simulated and fitted to obtain a first relationship curve at each measured resonance wavelength at the target position, wherein the first relationship curve is a relationship curve between the refractive index of the liquid film and the thickness of the liquid film at the target position, and at least three measured resonance wavelengths correspond to at least three first curves; According to the Cauchy dispersion formula and at least three first relationship curves of the liquid film at the target position, the thickness of the liquid film at the target position and the refractive index dispersion curve of the liquid film are obtained.

4. The method according to claim 3, wherein: According to the refractive index dispersion curve of the liquid film and the measured resonance wavelength at each other position, the thickness of the liquid film at the other position is obtained, including: Using the hyperspectral image, obtaining the measured resonance wavelength at the other positions; determining the refractive index of the liquid film at the measured resonance wavelength at the other positions according to the refractive index dispersion curve of the liquid film; The thickness of the liquid film at the other positions is obtained according to the refractive index of the liquid film at the other positions at the measured resonance wavelength and the Fresnel reflection formula of the four-layer structure.

5. The method according to claim 3, wherein: The Cauchy dispersion formula is expressed as follows: in, , As parameters, represents the refractive index of the liquid film at wavelength λ; According to the Cauchy dispersion formula and at least three first relationship curves of the liquid film at the target position, the thickness of the liquid film at the target position and the refractive index dispersion curve of the liquid film are obtained, including: According to the Cauchy dispersion formula and the at least three first relationship curves, at least two second relationship curves at the target position are obtained, wherein the second relationship curve is a relationship curve between the parameter b and the liquid film thickness at the target position, and all the second curves intersect at one point; Obtaining the intersection of at least two second relationship curves to obtain the value of the parameter b and the thickness of the liquid film at the target position; According to the value of the parameter b and the thickness of the liquid film at the target position, combined with any one of the at least three first relationship curves, the value of the parameter a is obtained; the values ​​of the parameter a and the parameter b are substituted into the Cauchy dispersion formula to obtain the refractive index dispersion curve of the liquid film.

6. The method according to claim 3, wherein: The Fresnel reflection formula of the four-layer structure is expressed as follows: R= r 1234 ·r 1234 * Wherein, R represents the reflectivity of the four-layer structure consisting of the substrate, the metal film, the liquid film and the covering layer, wherein the substrate, the metal film, the liquid film and the covering layer are the first layer, the second layer, the third layer and the fourth layer from bottom to top, respectively, and r 1234 represents the reflection coefficient of the four-layer structure, r 1234 * Represents r 1234 The complex conjugate of , D2 is the thickness of the second layer, D3 is the thickness of the third layer, k2 and k3 represent the vertical components of the propagation constant of the broad spectrum linearly polarized parallel beam in the second layer and the third layer respectively; r 234 Represents the reflection coefficient of light in the three-layer structure consisting of the second, third, and fourth layers, r ij represents the reflection coefficient of the interface between the i-th layer and the j-th layer, i=1, 2 or 3, j=2, 3 or 4, λ is the wavelength of light in vacuum, n i represents the refractive index of the i-th layer at wavelength λ.

7. The method according to claim 1, wherein: The wide spectrum linearly polarized parallel light beam is s-polarized light or p-polarized light or other linearly polarized light that can be decomposed into an s-polarized component and a p-polarized component.

8. The method according to claim 7, wherein: When the broad spectrum linearly polarized parallel light beam is s-polarized light, r ij Obtained by the following formula: When the broad spectrum linearly polarized parallel light beam is p-polarized light, r ij Obtained by the following formula: Among them, θ i and θ j They represent the incident angle and refraction angle of the wide spectrum linear polarized light when it is incident from the i-th layer to the j-th layer, n j The refractive index of the jth layer, k i and k j They represent the vertical components of the propagation constants of light in the i-th and j-th layers respectively.

9. The method according to claim 1, wherein: The metal film does not fall off and does not change its physical and chemical properties after being covered by the liquid film; and the liquid film remains stable during the test time.

10. The method according to claim 1, wherein: The at least three measured resonance wavelengths at the target position are obtained through one hyperspectral imaging measurement or through multiple hyperspectral imaging measurements under different conditions.

Images