阅读说明：本技术 基于双层图形透射成像的液面变形和形貌测量方法和系统 (Liquid level deformation and morphology measurement method and system based on double-layer graph transmission imaging ) 是由 刘战伟 黄耀 黄先富 吴东亮 钟梦林 李鲜 董慧敏 于 2021-06-22 设计创作，主要内容包括：本发明公开了一种基于双层图形透射成像的液面变形和形貌测量方法和系统,方法包括：提供图像采集设备；提供具有一定厚度的介质；液面静止时,利用图像获取方法通过图像采集设备对信息载体图形进行图像采集,得到液面静止时的信息载体图像；当液面发生形变时,利用图像获取方法对信息载体图形进行图像采集,得到液面形变后的信息载体畸变图像；求解上层信息载体图像各个时刻的全场位移矢量场与下层信息载体图像各个时刻的全场位移矢量场；求解液面各个时刻的液体高度数据。本发明通过记录液面静止时和液面变形后各时刻的双层信息载体图像,运用相关技术,可以实现对静态和动态液面形貌进行快速高精度地测量。(The invention discloses a liquid level deformation and morphology measurement method and system based on double-layer graph transmission imaging, wherein the method comprises the following steps: providing an image acquisition device; providing a medium having a thickness; when the liquid level is static, image acquisition is carried out on the information carrier graph through image acquisition equipment by using an image acquisition method to obtain an information carrier image when the liquid level is static; when the liquid level deforms, image acquisition is carried out on the information carrier graph by using an image acquisition method to obtain an information carrier distortion image after the liquid level deforms; solving a full-field displacement vector field of the upper information carrier image at each moment and a full-field displacement vector field of the lower information carrier image at each moment; and solving the liquid height data of the liquid level at each moment. The invention can realize the rapid and high-precision measurement of the appearance of the static and dynamic liquid level by recording the double-layer information carrier images at each moment when the liquid level is static and after the liquid level is deformed and applying the related technology.)

1. A liquid level deformation and morphology measurement method based on double-layer graph transmission imaging is characterized by comprising the following steps:

providing image acquisition equipment, arranging the image acquisition equipment on one side of a liquid surface, which is far away from the ground, wherein the image acquisition equipment is spaced from the liquid surface, and calibrating the image acquisition equipment;

providing a medium with a certain thickness, placing the medium at the bottom of the liquid level, and arranging an upper layer and a lower layer which are oppositely arranged in the direction vertical to the plane of the ground, wherein the upper layer and the lower layer are provided with information carrier patterns;

when the liquid level is static, acquiring an image of an information carrier by using an image acquisition method through the image acquisition equipment to obtain an information carrier image when the liquid level is static, wherein the image acquisition method comprises the steps of acquiring a double-layer information carrier image by using the image acquisition equipment, acquiring the image of an upper-layer information carrier image and the image of a lower-layer information carrier image into the same image, and dividing the image of the upper-layer information carrier image and the image of the lower-layer information carrier image into two images by using a geometric phase analysis technology or a color threshold extraction method to form an upper-layer information carrier reference image and a lower-layer information carrier reference image;

when the liquid level deforms, image acquisition is carried out on an information carrier graph by using the image acquisition method to obtain an information carrier distorted image after the liquid level deforms, wherein the information carrier distorted image comprises an upper information carrier distorted image and a lower information carrier distorted image;

taking an upper information carrier reference image and a lower information carrier reference image which are obtained when the liquid level is static as references, processing the upper information carrier distorted image and the lower information carrier distorted image to obtain displacement vector data in the direction of U, V in the plane at each moment of the upper information carrier image and the lower information carrier image, and solving a full-field displacement vector field at each moment of the upper information carrier image and a full-field displacement vector field at each moment of the lower information carrier image;

solving the liquid height data of the liquid level at each moment according to the full-field displacement vector field of the upper information carrier image and the full-field displacement vector field of the lower information carrier image according to the following method:

wherein S1 is the displacement in the full field of the upper information carrier image, S2 is the displacement in the full field of the lower information carrier image, d is the thickness between the upper layer and the lower layer of the medium, alpha is the included angle between the light ray of the corresponding position of the image collected by the image collecting device and the vertical direction, n1 is the refractive index of the liquid, and n2 is the refractive index of the medium.

2. A method for liquid level deformation and topography measurement based on two-layer pattern transmission imaging according to claim 1, wherein the information carrier pattern comprises stripes, speckles and lattice information.

3. The liquid level deformation and morphology measurement method based on double-layer graph transmission imaging according to claim 1, characterized in that digital moire technology, digital speckle technology or geometric phase analysis technology is adopted to process the distorted image of the upper information carrier and the distorted image of the lower information carrier to obtain displacement vector data of U, V directions in the plane at each moment of the distorted image of the upper information carrier and the distorted image of the lower information carrier.

4. A liquid level deformation and morphology measurement method based on double-layer graph transmission imaging according to claim 1, wherein the medium comprises transparent glass or transparent plastic, and the refractive index of the medium is equal to or different from that of the liquid.

5. A liquid level deformation and topography measurement method based on two-layer graphic transmission imaging as claimed in claim 1, characterized in that the full field displacement vector field at each moment of the upper information carrier image comprises the vector sum of the U, V in-plane direction displacement vector fields at each moment of the upper information carrier image, and the full field displacement vector field at each moment of the lower information carrier image comprises the vector sum of the U, V in-plane direction displacement vector fields at each moment of the lower information carrier image.

6. A liquid level deformation and morphology measurement system based on double-layer graph transmission imaging is characterized by comprising image acquisition equipment, a medium, an in-plane displacement vector processing module and a liquid level three-dimensional morphology processing module, wherein,

the medium has a certain thickness, is arranged at the bottom of the liquid level, and comprises an upper layer and a lower layer which are oppositely arranged in the direction vertical to the plane of the ground, and the upper layer and the lower layer are provided with information carrier patterns;

the image acquisition device is arranged on one side of the liquid surface, which is far away from the ground, has a gap with the liquid surface, is calibrated, is coupled with the in-plane displacement vector processing module, and is used for acquiring an image of an information carrier by using an image acquisition method when the liquid surface is static to obtain an image of the information carrier when the liquid surface is static, and the image acquisition method comprises the following steps: the image acquisition equipment acquires double-layer information carrier images, the images of the upper-layer information carrier image and the lower-layer information carrier image are acquired into the same image, and the image of the upper-layer information carrier image and the image of the lower-layer information carrier image are separated into two images by using a geometric phase analysis technology or a color threshold extraction method to form an upper-layer information carrier reference image and a lower-layer information carrier reference image; when the liquid level deforms, image acquisition is carried out on the information carrier graph to obtain an information carrier distorted image after the liquid level deforms, the information carrier distorted image comprises an upper information carrier distorted image and a lower information carrier distorted image, the upper information carrier distorted image and the lower information carrier distorted image are sent to the in-plane displacement vector processing module, when one information carrier distorted image is acquired, the instantaneous appearance of the liquid level at the acquisition moment is finally measured, and when a sequence information carrier distorted image which changes along with time is acquired, the appearance of the liquid level which changes along with time is finally measured;

the in-plane displacement vector processing module is respectively coupled with the image acquisition equipment and the liquid level three-dimensional morphology processing module, and is used for processing the upper information carrier distorted image and the lower information carrier distorted image to obtain U, V-direction displacement vector data in the plane at each moment of the upper information carrier image and the lower information carrier image by taking the upper information carrier reference image and the lower information carrier reference image obtained when the liquid level is static as references, solving a full-field displacement vector field at each moment of the upper information carrier image and a full-field displacement vector field at each moment of the lower information carrier image, and sending the full-field displacement vector fields to the liquid level three-dimensional morphology processing module;

the liquid level three-dimensional shape processing module is coupled with the in-plane displacement vector processing module and is used for receiving the data of the full-field displacement vector field of the upper information carrier image and the full-field displacement vector field of the lower information carrier image, which are sent by the in-plane displacement vector processing module, and solving the liquid level height according to the following method:

wherein S1 is the displacement in the full field of the upper information carrier image, S2 is the displacement in the full field of the lower information carrier image, d is the thickness between the upper layer and the lower layer of the medium, alpha is the included angle between the light ray of the corresponding position of the image collected by the image collecting device and the vertical direction, n1 is the refractive index of the liquid, and n2 is the refractive index of the medium.

7. A liquid level deformation and topography measurement system based on two-layer pattern transmission imaging according to claim 6, characterized in that the information carrier pattern comprises stripes, speckles and lattice information.

8. The liquid level deformation and morphology measurement system based on double-layer graph transmission imaging according to claim 6, wherein the in-plane displacement vector processing module processes the upper layer information carrier distorted image and the lower layer information carrier distorted image by using a digital moire technology, a digital speckle technology or a geometric phase analysis technology to obtain displacement vector data in an in-plane U, V direction of the upper layer information carrier image and the lower layer information carrier image at each moment.

9. A liquid level deformation and morphology measurement system based on double-layer graph transmission imaging according to claim 6, wherein the medium comprises transparent glass or transparent plastic, and the refractive index of the medium is equal to or different from that of the liquid.

10. A liquid level deformation and topography measurement system based on dual layer graphic transmission imaging as claimed in claim 6 wherein the full field displacement vector field at each instant of the upper layer information carrier image comprises the vector sum of the U, V directional displacement vector fields in-plane at each instant of the upper layer information carrier image and the full field displacement vector field at each instant of the lower layer information carrier image comprises the vector sum of the U, V directional displacement vector fields in-plane at each instant of the lower layer information carrier image.

Technical Field

The invention relates to the field of optical measurement, in particular to a liquid level deformation and appearance measurement method and system based on double-layer graph transmission imaging.

Background

The deformation phenomenon generated by the disturbance of the free surface of the liquid has important scientific research value and practical engineering application. The phenomenon of solid floating represented by the floating of a water strider is the result of the combined action of gravity, buoyancy and surface tension, and how to quantitatively analyze the force exerted on the water strider by water during water striding has not been clearly concluded. The transmission and deformation of water waves under different excitations are important research directions in fluid mechanics, particularly in the field of aerospace, a large amount of carried liquid propellant inevitably shakes during a task, attitude instability of a spacecraft is easily caused, and therefore liquid shaking becomes an important research direction. Because the appearance of the liquid surface is directly related to buoyancy, surface tension, water waves, liquid shaking and the like, the characterization of the liquid surface deformation can obviously help the progress of related research directions.

The existing liquid level morphology measuring methods mainly comprise two types of methods: one is a transmission method and one is a reflection method. In the transmission method, the liquid level is measured by using a holographic shearing interference method (J.C.Wyant, Appl Opt, 1973; 12:2057-60) and a holographic interference method (K.D.Hinsch, Appl Opt, 1978; 17:3101-7) by using a K.D.Hinsch in J.Wyant and K.D.Hinsch, the deformation measurement sensitivity reaches the nanometer level, but the measurement range is small, and the liquid level deformation of millimeter and above can not be measured; the two-color lattice deflection method proposed by Thomui et al (Optics and Lasers in Engineering,2017,98:205-216) can measure the single-layer and double-layer liquid level deformation in the micrometer to millimeter magnitude, but is not suitable for the liquid level deformation with large slope; the transmission fringe method developed by Liu war Wei et al (Optics and Lasers in Engineering, 2012; 51 (2): 167-; the ray tracing method proposed by Qian et al (Proceedings of the IEEE conference on computer vision and pattern recognition.2017: 1269-. A.K. Asundi et al measured the three-dimensional topography of the dynamic liquid level by reflection (Huang L, A.K. Asundi et al, Opt Express, 2011; 12809-14), but the larger liquid level deformation caused the reflected light to exceed the camera field of view.

Therefore, how to reduce the iteration error, increase the measurement range, reduce the device manufacturing cost, and improve the measurement efficiency while ensuring the measurement sensitivity becomes an urgent problem to be solved.

Disclosure of Invention

In view of the above, the invention provides a liquid level deformation and morphology measurement method and system based on double-layer graph transmission imaging, so as to solve the problems that the existing liquid level morphology measurement method is difficult to realize high precision, high efficiency, economic device and simple operation at the same time.

On one hand, the invention discloses a liquid level deformation and morphology measuring method based on double-layer graph transmission imaging, which comprises the following steps:

providing image acquisition equipment, arranging the image acquisition equipment on one side of a liquid surface, which is far away from the ground, wherein the image acquisition equipment is spaced from the liquid surface, and calibrating the image acquisition equipment;

providing a medium with a certain thickness, placing the medium at the bottom of the liquid level, and arranging an upper layer and a lower layer which are oppositely arranged in the direction vertical to the plane of the ground, wherein the upper layer and the lower layer are provided with information carrier patterns;

when the liquid level is static, acquiring an image of an information carrier by using an image acquisition method through the image acquisition equipment to obtain an information carrier image when the liquid level is static, wherein the image acquisition method comprises the steps of acquiring a double-layer information carrier image by using the image acquisition equipment, acquiring the image of an upper-layer information carrier image and the image of a lower-layer information carrier image into the same image, and dividing the image of the upper-layer information carrier image and the image of the lower-layer information carrier image into two images by using a geometric phase analysis technology or a color threshold extraction method to form an upper-layer information carrier reference image and a lower-layer information carrier reference image;

when the liquid level deforms, image acquisition is carried out on an information carrier graph by using the image acquisition method to obtain an information carrier distorted image after the liquid level deforms, wherein the information carrier distorted image comprises an upper information carrier distorted image and a lower information carrier distorted image;

taking an upper information carrier reference image and a lower information carrier reference image which are obtained when the liquid level is static as references, processing the upper information carrier distorted image and the lower information carrier distorted image to obtain displacement vector data in the direction of U, V in the plane at each moment of the upper information carrier image and the lower information carrier image, and solving a full-field displacement vector field at each moment of the upper information carrier image and a full-field displacement vector field at each moment of the lower information carrier image;

solving the liquid height data of the liquid level at each moment according to the full-field displacement vector field of the upper information carrier image and the full-field displacement vector field of the lower information carrier image according to the following method:

wherein S1 is the displacement in the full field of the upper information carrier image, S2 is the displacement in the full field of the lower information carrier image, d is the thickness between the upper layer and the lower layer of the medium, alpha is the included angle between the light ray of the corresponding position of the image collected by the image collecting device and the vertical direction, n1 is the refractive index of the liquid, and n2 is the refractive index of the medium.

Optionally, the information carrier pattern comprises stripes, speckles and lattice information.

Optionally, the distorted image of the upper information carrier and the distorted image of the lower information carrier are processed by using a digital moire technology, a digital speckle technology or a geometric phase analysis technology to obtain displacement vector data of U, V directions in the plane at each moment of the upper information carrier image and the lower information carrier image.

Optionally, the medium includes transparent glass or transparent plastic, and the refractive index of the medium is equal to or different from that of the liquid.

Optionally, the full-field displacement vector field of the upper information carrier image at each time instant comprises a vector sum of the in-plane U, V direction displacement vector fields of the upper information carrier image at each time instant, and the full-field displacement vector field of the lower information carrier image at each time instant comprises a vector sum of the in-plane U, V direction displacement vector fields of the lower information carrier image at each time instant.

On the other hand, the invention also discloses a liquid level deformation and morphology measuring system based on double-layer graph transmission imaging, which comprises image acquisition equipment, a medium, an in-plane displacement vector processing module and a liquid level three-dimensional morphology processing module, wherein,

the medium has a certain thickness, is arranged at the bottom of the liquid level, and comprises an upper layer and a lower layer which are oppositely arranged in the direction vertical to the plane of the ground, and the upper layer and the lower layer are provided with information carrier patterns;

the image acquisition device is arranged on one side of the liquid surface, which is far away from the ground, has a gap with the liquid surface, is calibrated, is coupled with the in-plane displacement vector processing module, and is used for acquiring an image of an information carrier by using an image acquisition method when the liquid surface is static to obtain an image of the information carrier when the liquid surface is static, and the image acquisition method comprises the following steps: the image acquisition equipment acquires double-layer information carrier images, the images of the upper-layer information carrier image and the lower-layer information carrier image are acquired into the same image, and the image of the upper-layer information carrier image and the image of the lower-layer information carrier image are separated into two images by using a geometric phase analysis technology or a color threshold extraction method to form an upper-layer information carrier reference image and a lower-layer information carrier reference image; when the liquid level deforms, image acquisition is carried out on the information carrier graph to obtain an information carrier distorted image after the liquid level deforms, the information carrier distorted image comprises an upper information carrier distorted image and a lower information carrier distorted image, the upper information carrier distorted image and the lower information carrier distorted image are sent to the in-plane displacement vector processing module, when one information carrier distorted image is acquired, the instantaneous appearance of the liquid level at the acquisition moment is finally measured, and when a sequence information carrier distorted image which changes along with time is acquired, the appearance of the liquid level which changes along with time is finally measured;

the in-plane displacement vector processing module is respectively coupled with the image acquisition equipment and the liquid level three-dimensional morphology processing module, and is used for processing the upper information carrier distorted image and the lower information carrier distorted image to obtain U, V-direction displacement vector data in the plane at each moment of the upper information carrier image and the lower information carrier image by taking the upper information carrier reference image and the lower information carrier reference image obtained when the liquid level is static as references, solving a full-field displacement vector field at each moment of the upper information carrier image and a full-field displacement vector field at each moment of the lower information carrier image, and sending the full-field displacement vector fields to the liquid level three-dimensional morphology processing module;

the liquid level three-dimensional shape processing module is coupled with the in-plane displacement vector processing module and is used for receiving the data of the full-field displacement vector field of the upper information carrier image and the full-field displacement vector field of the lower information carrier image, which are sent by the in-plane displacement vector processing module, and solving the liquid level height according to the following method:

wherein S1 is the displacement in the full field of the upper information carrier image, S2 is the displacement in the full field of the lower information carrier image, d is the thickness between the upper layer and the lower layer of the medium, alpha is the included angle between the light ray of the corresponding position of the image collected by the image collecting device and the vertical direction, n1 is the refractive index of the liquid, and n2 is the refractive index of the medium.

Optionally, the information carrier pattern comprises stripes, speckles and lattice information.

Optionally, the in-plane displacement vector processing module processes the distorted image of the upper information carrier and the distorted image of the lower information carrier by using a digital moire technology, a digital speckle technology or a geometric phase analysis technology to obtain displacement vector data of U, V directions in the plane at each time of the distorted image of the upper information carrier and the distorted image of the lower information carrier.

Optionally, the medium includes transparent glass or transparent plastic, and the refractive index of the medium is equal to or different from that of the liquid.

Optionally, the full-field displacement vector field of the upper information carrier image at each time instant comprises a vector sum of the in-plane U, V direction displacement vector fields of the upper information carrier image at each time instant, and the full-field displacement vector field of the lower information carrier image at each time instant comprises a vector sum of the in-plane U, V direction displacement vector fields of the lower information carrier image at each time instant.

Compared with the prior art, the liquid level deformation and morphology measurement method and system based on double-layer graph transmission imaging provided by the invention at least realize the following beneficial effects:

1) according to the invention, by recording the double-layer information carrier images at each moment when the liquid level is static and after the liquid level is deformed, the appearance of the static and dynamic liquid levels can be rapidly and accurately measured by using the related technology;

2) according to the invention, by analyzing the optical relationship between the image distortion and the liquid level height of the upper and lower layers of information carriers, the measurement range is effectively improved, and the measurement sensitivity is improved;

3) the invention measures the distortion of the light reflected by the upper and lower layers of information carrier patterns after the light transmits out of the deformed liquid level, and can comprehensively obtain the liquid level morphology change chart by combining the given spacing distance between the upper and lower layers of information carrier patterns.

4) The invention only needs to use a single image acquisition device, and the device is simple and economical.

Of course, it is not necessary for any product in which the present invention is practiced to achieve all of the above-described technical effects simultaneously.

Other features of the present invention and advantages thereof will become apparent from the following detailed description of exemplary embodiments thereof, which proceeds with reference to the accompanying drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention.

FIG. 1 is a flowchart of a method for measuring a three-dimensional profile of a liquid level according to a first embodiment of the present invention;

FIG. 2 is a schematic diagram of a liquid level three-dimensional topography measurement method according to an embodiment of the present invention;

fig. 3 is a double-layer information carrier image obtained by the image acquisition method of the present invention;

fig. 4 is an upper information carrier image obtained by color threshold extraction;

fig. 5 is a lower information carrier image obtained by means of a color threshold extraction method;

FIG. 6 is yet another dual-layer information carrier image obtained by the image acquisition method of the present invention;

fig. 7 and 8 are upper information carrier images obtained using a geometric phase analysis technique;

fig. 9 and 10 are images of an underlying information carrier obtained using a geometric phase analysis technique;

fig. 11 is a structural block diagram of a liquid level three-dimensional topography measurement system according to a second embodiment of the present invention.

Detailed Description

Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that: the relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.

The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate.

In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.

The first embodiment is as follows:

with reference to fig. 1, the present invention provides a flow chart of a liquid level deformation and topography measurement method based on double-layer graph transmission imaging, which comprises the following steps:

step 101: providing image acquisition equipment, arranging the image acquisition equipment on one side of the liquid level far away from the ground, and calibrating the image acquisition equipment, wherein the image acquisition equipment is spaced from the liquid level;

in connection with fig. 2, the acquisition of the image of each layer of the information carrier may be realized by a CCD (charge-coupled Device, i.e. image sensor) camera and/or an image acquisition Device that functions to convert the image into a digital signal. An image acquisition device (such as a CCD camera) is placed directly above the water bath.

Step 102: providing a medium with a certain thickness, placing the medium at the bottom of a liquid level, and arranging an upper layer and a lower layer which are oppositely arranged in a direction vertical to a plane where the ground is located, wherein the upper layer and the lower layer are provided with information carrier patterns;

in some alternative embodiments, the medium comprises transparent glass or transparent plastic, and the refractive index of the medium and the refractive index of the liquid may or may not be equal.

Referring to fig. 2, in practical application, each layer of information carrier pattern is placed at the bottom of the outside of a glass water tank containing a proper amount of transparent liquid. In this case the information carrier pattern is in this way placed at the bottom or below the liquid level, and the law of refraction of light, snell's law, can be applied.

The information carrier pattern is: fringes, speckles, lattices, etc. can analyze the pattern of the in-plane displacement according to the distortion.

Step 103: when the liquid level is static, image acquisition is carried out on an information carrier graph through image acquisition equipment by using an image acquisition method to obtain an information carrier image when the liquid level is static, the image acquisition method comprises the steps that the image acquisition equipment acquires a double-layer information carrier image, the images of an upper-layer information carrier graph and a lower-layer information carrier graph are acquired into the same image, the image of the upper-layer information carrier graph and the image of the lower-layer information carrier graph are divided into two images by using a geometric phase analysis technology or a color threshold extraction method to form an upper-layer information carrier reference image and a lower-layer information carrier reference image;

when the image acquisition method is used, the upper and lower information carrier images can be separated into two images by controlling the different colors of the upper and lower information carrier images and realizing color threshold extraction through programming, so that the upper information carrier image and the lower information carrier image are formed. Or the upper layer information carrier image and the lower layer information carrier image are separated into two images by controlling the difference of the phase distribution of the upper layer information carrier image and the lower layer information carrier image through a geometric phase analysis technology to form the upper layer information carrier image and the lower layer information carrier image.

In particular, with reference to fig. 3 to 10, fig. 3 shows a two-layer information carrier image, and both the upper layer information carrier image and the lower layer information carrier image are captured in fig. 3, at which time the upper layer information carrier image and the lower layer information carrier image can be separated by color threshold extraction to obtain two images, fig. 4 and 5, i.e. the upper layer information carrier image and the lower layer information carrier image; it is of course also possible to use a geometric phase analysis technique, in fig. 6 a captured image of a dual-layer information carrier, in which case the images of the upper information carrier pattern and the lower information carrier pattern are both captured in fig. 6, in which case the images of the upper information carrier pattern and the lower information carrier pattern can be separated by means of the geometric phase analysis technique to obtain two images, fig. 7 and 8 are phase diagrams for the upper information carrier image in two directions, and fig. 9 and 10 are phase diagrams for the lower information carrier image in two directions.

Step 104: when the liquid level deforms, image acquisition is carried out on an information carrier graph by using an image acquisition method to obtain an information carrier distorted image after the liquid level deforms, wherein the information carrier distorted image comprises an upper information carrier distorted image and a lower information carrier distorted image;

of course, the image obtaining method herein may refer to the method in step 103, and is not described herein again.

The information carrier distortion image is an image which is acquired by image acquisition equipment after an effective light source is reflected out of the liquid surface by the information carrier graph at the bottom of the liquid surface (water) after the liquid surface is deformed.

Step 105: taking an upper information carrier reference image and a lower information carrier reference image which are obtained when the liquid level is static as references, processing the upper information carrier distorted image and the lower information carrier distorted image to obtain U, V-direction displacement vector data in the plane at each moment of the upper information carrier image and the lower information carrier image, and solving a full-field displacement vector field at each moment of the upper information carrier image and a full-field displacement vector field at each moment of the lower information carrier image;

the distortion in each layer information carrier image is processed using the correlation technique to obtain displacement vector data of the in-plane U, V direction at each time on each layer information carrier image. The UV direction is the same (parallel) as the XY coordinate axis, but is used to refer to 'U, V' in field theory.

In this embodiment, after the liquid level is deformed, the light reflected by each layer of information carrier pattern will be shifted in transmission angle through the deformed region of the liquid level, so that distortion phenomenon (for example, a certain region in the information carrier image will extend or contract towards a certain side of the image) will occur in the collected each layer of information carrier image, so that the displacement vector field data in the direction of U, V in the plane of the distorted each layer of information carrier image can be obtained by applying the correlation technique to the distorted information carrier image according to the distortion direction, and further the full-field displacement vector field of each layer of information carrier image can be obtained.

Optionally, the distorted image of the upper information carrier and the distorted image of the lower information carrier are processed by using a digital moire technology, a digital speckle technology or a geometric phase analysis technology to obtain displacement vector data of the upper information carrier image and the lower information carrier image in the in-plane U, V direction at each moment.

Digital moire technology: the basic element of all moire measurement techniques is a grating. Moire fringes generated by overlapping two groups of grid lines can move macroscopically along with the slight change of the geometric shapes of the grid lines, and the moire method is used for analyzing the displacement field of an object by measuring the movement amount of the fringes. The grid lines are carriers of object deformation information, so that the deformation information of the object can be conveniently and quickly extracted by selecting the appropriate grid lines. The reference grid lines in the moire method may be actual geometric grid lines or computer-generated digital grid lines, and the type of the grid lines is usually selected according to the type of the problem to be analyzed and the convenience of the analysis. The digital moire technology adopts digital grid superposition, the generation of moire fringes is different from the generation of the traditional moire technology which is realized by optical superposition of two groups of grid lines, and the digital deformation grid line graph is subjected to binarization and then is subjected to logic operation with a binary reference grid generated by a computer to simulate the geometric moire formed by the superposition of the grid lines.

Digital speckle techniques: digital Image Correlation (DIC), also called Digital speckle correlation, is a method of obtaining deformation information of a region of interest by correlating two Digital images before and after deformation. The basic principle is to grid the region of interest in the pre-deformation image, and treat each sub-region as rigid motion. And then, for each sub-region, performing correlation calculation according to a predefined correlation function by a certain search method, and searching a region with the maximum cross-correlation coefficient with the sub-region in the deformed image, namely the position of the sub-region after deformation, so as to obtain the displacement of the sub-region. And calculating all the sub-regions to obtain the deformation information of the whole field.

Geometric phase analysis technique: the method comprises the steps of carrying out Fourier transformation on lattice images before and after deformation, selecting two nonlinear vectors, carrying out inverse Fourier transformation, obtaining phase information of the lattice images before and after deformation, subtracting the phase information before deformation from the phase information after deformation to obtain a phase difference, and obtaining a strain field and a displacement field according to the relation between the phase difference and strain and displacement.

The full-field displacement vector field at each instant of the upper information carrier image comprises the vector sum of the in-plane U, V-direction displacement vector fields at each instant of the upper information carrier image and the full-field displacement vector field at each instant of the lower information carrier image comprises the vector sum of the in-plane U, V-direction displacement vector fields at each instant of the lower information carrier image.

Step 106: solving the liquid height data of the liquid level at each moment according to the full-field displacement vector field of the upper information carrier image and the full-field displacement vector field of the lower information carrier image according to the following method:

wherein S1 is the displacement in the whole field of the upper information carrier image, S2 is the displacement in the whole field of the lower information carrier image, d is the thickness between the upper layer and the lower layer of the medium, alpha is the included angle between the light ray of the corresponding position of the image collected by the image collecting device and the vertical direction, n1 is the refractive index of the liquid, and n2 is the refractive index of the medium.

It will be appreciated that the image capture device will experience different degrees of refraction in image capture of the information carrier patterns on the upper and lower layers of the medium due to the different indices of refraction of the medium, the liquid and the air, and that the full in-plane displacement S1 of the upper information carrier image is not equal to the full in-plane displacement S2 of the lower information carrier image due to the thickness between the upper and lower layers of the medium.

Furthermore, the height distribution of the liquid level is obtained by solving according to the full-field displacement vector field, and a functional relation between the height of the liquid level and the displacement of each layer of information carrier image plane needs to be established. Specifically, as shown in fig. 2, in the cross-sectional optical path diagrams before and after the deformation of the liquid surface, the distance H between the liquid surface at a certain point and the upper information carrier pattern satisfies the above formula, and it is needless to say that the deformation and the shape of the liquid surface at each point on the liquid surface can be understood by calculating the height H.

Example two:

with reference to fig. 11, the present embodiment provides a liquid level deformation and topography measurement system based on two-layer graph transmission imaging, which includes an image acquisition device 201, a medium 205, an in-plane displacement vector processing module 202, and a liquid level three-dimensional topography processing module 203.

The medium 205 has a certain thickness, is set up in the bottom of the liquid level, in the direction perpendicular to the level of ground, the medium 205 includes upper strata and lower floor that relatively sets up, upper strata and lower floor have information carrier figure;

the image acquisition device 201 is arranged on one side of the liquid level far away from the ground, the image acquisition device 201 is spaced from the liquid level, the image acquisition device 201 is calibrated, and is coupled with the in-plane displacement vector processing module 202 and used for acquiring an image of an information carrier by using an image acquisition method when the liquid level is static to obtain an image of the information carrier when the liquid level is static, and the image acquisition method comprises the following steps: the method comprises the steps that an image acquisition device acquires double-layer information carrier images, images of an upper-layer information carrier image and an image of a lower-layer information carrier image are acquired into the same image, the image of the upper-layer information carrier image and the image of the lower-layer information carrier image are separated into two images by utilizing a geometric phase analysis technology or a color threshold extraction method, and an upper-layer information carrier reference image and a lower-layer information carrier reference image are formed; when the liquid level is deformed, image acquisition is carried out on the information carrier graph to obtain an information carrier distorted image after the liquid level is deformed, the information carrier distorted image comprises an upper information carrier distorted image and a lower information carrier distorted image and is sent to the in-plane displacement vector processing module 202, when one information carrier distorted image is acquired, the instantaneous appearance of the liquid level at the acquisition moment is finally measured, and when a sequence information carrier distorted image which changes along with time is acquired, the appearance of the liquid level which changes along with time is finally measured;

the in-plane displacement vector processing module 202 is coupled to the image acquisition device 201 and the liquid level three-dimensional topography processing module 203, and is configured to process the upper layer information carrier distorted image and the lower layer information carrier distorted image to obtain displacement vector data in the in-plane U, V direction at each time of the upper layer information carrier image and the lower layer information carrier image, with the upper layer information carrier reference image and the lower layer information carrier reference image obtained when the liquid level is static as a reference, solve a full-field displacement vector field at each time of the upper layer information carrier image and a full-field displacement vector field at each time of the lower layer information carrier image, and send the displacement vector fields to the liquid level three-dimensional topography processing module 203;

the liquid level three-dimensional topography processing module 203 is coupled to the in-plane displacement vector processing module 202, and is configured to receive full-field displacement vector field data of the upper information carrier image and full-field displacement vector field data of the lower information carrier image sent by the in-plane displacement vector processing module 202, and solve the liquid level height according to the following method:

where S1 is the full-field in-plane displacement of the upper information carrier image, S2 is the full-field in-plane displacement of the lower information carrier image, d is the thickness between the upper layer and the lower layer of the medium 205, α is the angle between the light ray at the position corresponding to the image acquired by the image acquisition device 201 and the vertical direction, n1 is the refractive index of the liquid 204, and n2 is the refractive index of the medium 205.

Optionally, the information carrier pattern comprises stripes, speckles and lattice information.

Optionally, the in-plane displacement vector processing module 202 processes the distorted image of the upper information carrier and the distorted image of the lower information carrier by using a digital moire technique, a digital speckle technique, or a geometric phase analysis technique to obtain displacement vector data of U, V directions in the plane at each time of the upper information carrier image and the lower information carrier image.

Optionally, the medium 205 comprises transparent glass or transparent plastic, and the refractive index of the medium 205 is not equal to the refractive index of the liquid 204.

Optionally, the full-field displacement vector field at each time instant of the upper information carrier image comprises a vector sum of the in-plane U, V direction displacement vector fields at each time instant of the upper information carrier image, and the full-field displacement vector field at each time instant of the lower information carrier image comprises a vector sum of the in-plane U, V direction displacement vector fields at each time instant of the lower information carrier image.

In this embodiment, each layer of information carrier image is an image acquired by an image acquisition device, where each layer of information carrier image is a water bottom layer of information carrier image, and an effective light source is reflected by the information carrier image to exit a liquid level, where the information carrier image includes a pattern with a specific gray gradient, such as a stripe, a speckle, and a dot matrix. The acquisition of the image of the information carrier can be effected by means of a CCD camera and/or an image acquisition device which converts the image into a digital signal. In practical application, the double-layer information carrier graph is placed at the bottom of the outer surface of a glass water tank containing a proper amount of transparent liquid. An image acquisition device (such as a CCD camera) is placed directly above the water bath.

Further, the image capturing module 201 may be a CCD camera and/or an image capturing device that converts an image into a digital signal function.

Optionally, the in-plane displacement vector processing module 202 may be: and the in-plane displacement vector processing module is composed of a CPU, a GPU and/or a chip with a data processing function.

Optionally, the liquid level three-dimensional topography processing 203 may be: and the liquid level three-dimensional shape processing module is composed of a CPU, a GPU and/or a chip with a data processing function.

In this embodiment, each layer of information carrier image is an image acquired by an image acquisition device, where each layer of information carrier image is a water bottom layer of information carrier image, and an effective light source is reflected by the information carrier image to exit a liquid level, where the information carrier image includes a pattern with a specific gray gradient, such as a stripe, a speckle, and a dot matrix. The acquisition of the image of the information carrier can be effected by means of a CCD camera and/or an image acquisition device which converts the image into a digital signal. In practical application, the double-layer information carrier graph is placed at the bottom of the outer surface of a glass water tank containing a proper amount of transparent liquid. An image acquisition device (such as a CCD camera) is placed directly above the water bath.

Further, the dual-layer information carrier image capturing module 201 may be a CCD camera and/or an image capturing device that converts images into digital signals.

According to the embodiment, the liquid level deformation and morphology measurement method and system based on double-layer graph transmission imaging provided by the invention at least realize the following beneficial effects:

1) according to the invention, by recording the double-layer information carrier images at each moment when the liquid level is static and after the liquid level is deformed, the appearance of the static and dynamic liquid levels can be rapidly and accurately measured by using the related technology;

2) according to the invention, by analyzing the optical relationship between the image distortion and the liquid level height of the upper and lower layers of information carriers, the measurement range is effectively improved, and the measurement sensitivity is improved;

3) the invention measures the distortion of the light reflected by the upper and lower layers of information carrier patterns after the light transmits out of the deformed liquid level, and can comprehensively obtain the liquid level morphology change chart by combining the given spacing distance between the upper and lower layers of information carrier patterns.

4) The invention only needs to use a single image acquisition device, and the device is simple and economical.

Although some specific embodiments of the present invention have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustrative purposes only and are not intended to limit the scope of the present invention. It will be appreciated by those skilled in the art that modifications may be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.