A method, system, electronic device, and medium for extracting Brillouin radio frequency shift.

Abstract

This invention discloses a method, system, electronic device, and medium for extracting Brillouin scattering frequency shifts, relating to the field of Brillouin scattering frequency shift extraction. By denoising the Fabry-Perot etalon interference ring image, the ring signal is enhanced while suppressing noise. Subsequently, the Steger algorithm is used to extract the center line of the interference ring fringes, and then the least squares method is combined for circle fitting to obtain the radius of the required interference ring, thereby calculating the Brillouin scattering frequency shift. Since the center line of the ring reaches the sub-pixel level, and with the addition of the statistically based least squares method, the calculation accuracy of the Brillouin scattering frequency shift is improved.

Description

Technical Field

[0001] This invention relates to the field of Brillouin radio frequency migration extraction, and in particular to a Brillouin radio frequency migration extraction method, system, electronic device, and medium. Background Technology

[0002] Brillouin scattering lidar, as a novel type of frequency-modulated lidar, has significant application value in remote sensing of marine environmental parameters. In Brillouin scattering lidar, the frequency shift and linewidth of the Brillouin scattered light in the echo signal are measured using a Fabry-Perot etalon and a spectral array detector. This allows for the inversion of seawater physical parameters—temperature, salinity, sound velocity, etc.—achieving real-time measurement of physical parameters at a specific point in the water. Currently, there are three main methods for processing Fabry-Perot etalon interference ring images from Brillouin scattering lidar: First, the direct reading method, which selects a one-dimensional spectral intensity along a radius of the Fabry-Perot etalon interference pattern to directly measure the Brillouin scattering frequency shift. While relatively simple, this method suffers from significant accuracy issues: the positioning of interference fringes is only at the pixel level, and without noise processing, the results are easily affected by interference. Second, the circular-line interferometer optical system and cylindrical lens compression method. This method involves placing a 45-degree conical reflector or cylindrical lens behind the Fabry-Perot etalon to concentrate all the light intensity on the interference ring onto a single point. The first method effectively enhances weak signals and transforms two-dimensional interferograms into one-dimensional line spectra, simplifying subsequent data processing. However, this method requires the construction of more complex optical systems and generates additional optical system noise, thus limiting its accuracy. The second method is data folding, which is similar in principle to cylindrical lens compression, but differs in that it transforms two-dimensional interferograms into one-dimensional line spectra using image algorithms. This method uses multiple circular chords to determine the center of the interference rings. This method requires interference rings that are as complete as possible and have uniform linewidth, which places high demands on image quality and has limited automation, requiring manual image segmentation.

[0003] In summary, the aforementioned Brillouin dispersion radio frequency shift extraction method suffers from low accuracy. Summary of the Invention

[0004] The purpose of this invention is to provide a Brillouin radio frequency shift extraction method, system, electronic device, and medium to improve the accuracy of Brillouin radio frequency shift extraction.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A method for extracting Brillouin radio frequency shift includes:

[0007] Obtain the interference ring image of the Fabry-Perot etalon;

[0008] The interference ring image is denoised to obtain a denoised interference ring image;

[0009] The Steger algorithm is used to extract the center line of each interference ring in the denoised interference ring image to obtain a set of center lines; the interference ring is a first Rayleigh scattering interference ring, a Brillouin scattering interference ring, or a second Rayleigh scattering interference ring; the set of center lines includes the set of center lines of the first Rayleigh scattering interference ring, the set of center lines of the Brillouin scattering interference ring, and the set of center lines of the second Rayleigh scattering interference ring.

[0010] Based on the set of centerlines and the equation of the circle, the radius of the first Rayleigh scattering interference ring, the radius of the Brillouin scattering interference ring, and the radius of the second Rayleigh scattering interference ring are obtained by fitting using the least squares method.

[0011] The Brillouin scattering frequency shift in the echo signal of the Brillouin scattering lidar is calculated based on the radius of the first Rayleigh scattering interference ring, the radius of the Brillouin scattering interference ring, and the radius of the second Rayleigh scattering interference ring.

[0012] Optionally, the interference ring image is denoised to obtain a denoised interference ring image, specifically including:

[0013] The interference ring image is denoised using a multi-scale Fragi filter to obtain a denoised interference ring image.

[0014] Optionally, the Steger algorithm is used to extract the center line of each interference ring in the denoised interference ring image, resulting in a set of center lines, specifically including:

[0015] The first and second gradients of the denoised image are calculated using image convolution methods.

[0016] Based on the first-order gradient and the second-order gradient, the center line of each interference ring in the denoised interference ring image is extracted using the Steger algorithm to obtain a set of center lines.

[0017] Optionally, the Brillouin scattering frequency shift in the echo signal of the Brillouin scattering lidar is calculated based on the radius of the first Rayleigh scattering interference ring, the radius of the Brillouin scattering interference ring, and the radius of the second Rayleigh scattering interference ring, specifically including:

[0018] Using formula Calculate the Brillouin scattering frequency shift in the echo signal of a Brillouin scattering lidar; where v B For Brillouin dispersion radio frequency shift; r inside r represents the radius of the first Rayleigh scattering interference ring. middler represents the radius of the Brillouin scattering interference ring. outside The radius of the second Rayleigh scattering interference ring is indicated; FSR represents the free spectral range of the Fabry-Perot etalon.

[0019] A Brillouin radio frequency shift extraction system, comprising:

[0020] The image acquisition module is used to acquire the interference ring image of the Fabry-Perot etalon;

[0021] A denoising module is used to denoise the interference ring image to obtain a denoised interference ring image;

[0022] The centerline extraction module is used to extract the centerline of each interference ring in the denoised interference ring image using the Steger algorithm, thereby obtaining a set of centerlines; the interference ring is a first Rayleigh scattering interference ring, a Brillouin scattering interference ring, or a second Rayleigh scattering interference ring; the set of centerlines includes the set of centerlines of the first Rayleigh scattering interference ring, the set of centerlines of the Brillouin scattering interference ring, and the set of centerlines of the second Rayleigh scattering interference ring.

[0023] The fitting module is used to fit the first Rayleigh scattering interference ring radius, the Brillouin scattering interference ring radius, and the second Rayleigh scattering interference ring radius using the least squares method based on the set of center lines and the equation of the circle.

[0024] The frequency shift calculation module is used to calculate the Brillouin scattering frequency shift in the echo signal of the Brillouin scattering lidar based on the radius of the first Rayleigh scattering interference ring, the radius of the Brillouin scattering interference ring, and the radius of the second Rayleigh scattering interference ring.

[0025] An electronic device includes a memory and a processor, wherein the memory stores a computer program, and the processor runs the computer program to cause the electronic device to perform the Brillouin dispersion radio frequency shift extraction method described above.

[0026] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described Brillouin radio frequency shift extraction method.

[0027] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0028] The Brillouin scattering frequency shift extraction method of this invention enhances the ring signal and suppresses noise by denoising the Fabry-Perot etalon interference ring image. Then, the Steger algorithm is used to extract the center line of the interference ring fringes, and the least squares method is combined for circle fitting to obtain the radius of the desired interference ring, thereby calculating the Brillouin scattering frequency shift. Since the center line of the ring reaches the sub-pixel level, and the statistical least squares method is used, the calculation accuracy of the Brillouin scattering frequency shift is improved. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 The flowchart of the Brillouin radio frequency shift extraction method provided by the present invention is shown below.

[0031] Figure 2 This is a flowchart illustrating the Brillouin dispersion radio frequency shift extraction method of the present invention in a specific application.

[0032] Figure 3 The diagram shows the center line segment annotation of the interference ring image of the Fabry-Perot etalon. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] The purpose of this invention is to provide a Brillouin radio frequency shift extraction method, system, electronic device, and medium to improve the accuracy of Brillouin radio frequency shift extraction.

[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Example 1

[0037] like Figure 1 and Figure 2 As shown, the Brillouin radio frequency shift extraction method provided by the present invention includes:

[0038] Step 101: Acquire the interference ring image of the Fabry-Pérot etalon. In practical applications, the interference ring image of the Fabry-Pérot etalon is acquired as the initial image.

[0039] Step 102: Denoise the interference ring image to obtain a denoised interference ring image. In practical applications, a multi-scale Frangi filter is used to denoise the initial image.

[0040] Step 103: Use the Steger algorithm to extract the center line of each interference ring in the denoised interference ring image to obtain a set of center lines; the interference ring is a bright fringe in the shape of a ring in the denoised interference ring image, which contains multiple interference rings of different interference orders, namely the first Rayleigh scattering interference ring, the Brillouin scattering interference ring, and the second Rayleigh scattering interference ring; the set of center lines includes the center lines of all bright fringes.

[0041] In practical applications, centerline localization of the interference rings in the denoised initial image is achieved by first calculating the first-order gradient G' and second-order gradient G'" of the denoised initial image using image convolution. Then, the Steger algorithm is used to extract the centerline of each fringe (each interference ring) in the Fabry-Perot etalon interference ring image, achieving sub-pixel accuracy. Assuming there are n arcs in the Fabry-Perot etalon interference ring image, the centerlines in the denoised initial image can form a set U = {U1, U2, ..., U...}. n For a single set U i (i∈[1,n]), which includes the coordinates of each point on the center line, i.e., U i ={(x1,y1),(x2,y2),…,(x m ,y m )}, where each center line can be displayed on the image using numerical labels, such as Figure 3 As shown.

[0042] According to the frequency shift calculation formula The goal is to extract three distinct signals from an image: an inner-order Rayleigh scattering interference ring (first Rayleigh scattering interference ring), an outer-order Rayleigh scattering interference ring (second Rayleigh scattering interference ring), and a Brillouin scattering interference ring (the Brillouin scattering interference ring between the inner and outer order Rayleigh scattering interference rings of adjacent interference orders). Each signal has one or more center lines. By selecting the center lines corresponding to each signal, the set U of the inner-order Rayleigh scattering interference ring center lines can be formed. inside The set of central lines of the Brillouin scattering interference rings, U middle The set of center lines of the outer Rayleigh scattering interference rings U outsideFSR represents the free spectral range of the Fabry-Perot etalon, v B Represents Brillouin dispersion radio frequency shift, r j-1 ,r j ,r j 'Represents the inner Rayleigh scattering interference ring radius, outer Rayleigh scattering interference ring radius, and Brillouin scattering interference ring radius of adjacent orders, respectively.

[0043] As an optional implementation, step 103 specifically includes:

[0044] The first and second gradients of the denoised image are calculated using the image convolution method.

[0045] Based on the first-order gradient and the second-order gradient, the center line of each interference ring in the denoised interference ring image is extracted using the Steger algorithm, resulting in a set of center lines. The specific steps are as follows:

[0046] 1. Construct the Hessian matrix H at each pixel in the denoised interference ring image based on the first-order gradient and the second-order gradient, as shown in formula (1), where r xx r yy r xy The second-order gradients and mixed second-order gradients in the x-axis (horizontal axis) and y-axis (vertical axis) directions of the denoised interference ring image are given.

[0047]

[0048] 2. Calculate the eigenvector of matrix H at each pixel, and take the eigenvector corresponding to the largest eigenvalue, denoted as (n x ,n y ) T .

[0049] 3. Calculate the parameter δ and offset (Δx, Δy) at each pixel using formulas (2) and (3). Formula (2) x r y The first-order gradients in the x-axis and y-axis directions of the denoised interference ring image. If the condition is satisfied... This pixel becomes a candidate point, and its coordinates are represented by (x... o ,y o )express.

[0050]

[0051] (Δx,Δy)=(δn x ,δn y (3)

[0052] 4. Calculate the sub-pixel coordinates p of all the candidate points according to formula (4). e Then p e The final center point coordinates are determined according to a specific rule (the distance between adjacent points is less than the user-input value d (preset distance), and the tangent direction of adjacent points is (-n). y ,n x ) T The included angles are less than the user-input value θ (preset included angle) and are connected to form the set of centerlines.

[0053] p e =(x o +Δx,y o +Δy) (4)

[0054] Step 104: Based on the set of centerlines and the equation of the circle, the radius of the first Rayleigh scattering interference ring, the radius of the Brillouin scattering interference ring, and the radius of the second Rayleigh scattering interference ring are obtained by fitting using the least squares method.

[0055] Step 105: Calculate the Brillouin scattering frequency shift in the echo signal of the Brillouin scattering lidar based on the radius of the first Rayleigh scattering interference ring, the radius of the Brillouin scattering interference ring, and the radius of the second Rayleigh scattering interference ring.

[0056] As an optional implementation, step 105 specifically includes:

[0057] Using formula Calculate the Brillouin scattering frequency shift in the echo signal of a Brillouin scattering lidar; where v B For Brillouin dispersion radio frequency shift; r inside r represents the radius of the first Rayleigh scattering interference ring. middle r represents the radius of the Brillouin scattering interference ring. outside The radius of the second Rayleigh scattering interference ring is indicated; FSR represents the free spectral range of the Fabry-Perot etalon.

[0058] In practical applications, the centerline set U is used respectively. inside U middle U outside Using the coordinates in the graph as the observed values, the least squares method is then used to fit the equation of the circle (xx). o ) 2 +(yy o ) 2 =r 2 After fitting, the center coordinates (x, y) of the inner-order Rayleigh scattering interference rings of adjacent orders can be obtained. o_inside ,y o_inside ) and radius r inside The coordinates of the center of the Brillouin scattering interference ring (xo_middle ,y o_middle ) and radius r middle The coordinates of the center of the outer Rayleigh scattering interference ring (x o_outside ,y o_outside ) and radius r outside ,at the same time The value is the Brillouin divergence frequency shift corresponding to the interferometric image of the Fabry-Perot etalon.

[0059] The purpose of this invention is to reduce image noise and improve the accuracy of converting measured images to Brillouin dispersion frequency shift. First, a multi-scale Frangi filter is used to denoise the Fabry-Perot etalon interference ring image, enhancing the ring signal while suppressing noise. Then, the Steger algorithm is used to extract the center line of the ring fringes, and the required ring parameters are obtained by fitting using the least squares method, thereby calculating the Brillouin dispersion frequency shift. Since the ring center line reaches the sub-pixel level, and with the statistical least squares method, the measurement accuracy is high. Furthermore, in the signal classification and filtering step, only the line segment labels need to be selected to classify the signal, reducing the complexity of processing the Fabry-Perot etalon interference ring image.

[0060] Example 2

[0061] To perform the method corresponding to Embodiment 1 above and achieve the corresponding functions and technical effects, a Brillouin radio frequency shift extraction system is provided below, comprising:

[0062] The image acquisition module is used to acquire the interference ring image of the Fabry-Perot etalon.

[0063] The denoising module is used to denoise the interference ring image to obtain a denoised interference ring image.

[0064] The centerline extraction module is used to extract the centerline of each interference ring in the denoised interference ring image using the Steger algorithm, thereby obtaining a set of centerlines; the interference ring is a first Rayleigh scattering interference ring, a Brillouin scattering interference ring, or a second Rayleigh scattering interference ring; the set of centerlines includes the set of centerlines of the first Rayleigh scattering interference ring, the set of centerlines of the Brillouin scattering interference ring, and the set of centerlines of the second Rayleigh scattering interference ring.

[0065] The fitting module is used to fit the first Rayleigh scattering interference ring radius, the Brillouin scattering interference ring radius, and the second Rayleigh scattering interference ring radius using the least squares method based on the set of center lines and the equation of the circle.

[0066] The frequency shift calculation module is used to calculate the Brillouin scattering frequency shift in the echo signal of the Brillouin scattering lidar based on the radius of the first Rayleigh scattering interference ring, the radius of the Brillouin scattering interference ring, and the radius of the second Rayleigh scattering interference ring.

[0067] Example 3

[0068] This embodiment provides an electronic device, including: a memory and a processor, wherein the memory is used to store a computer program, and the processor runs the computer program to enable the electronic device to perform the Brillouin radio frequency shift extraction method of Embodiment 1.

[0069] Example 4

[0070] This embodiment provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the Brillouin radio frequency shift extraction method of Embodiment 1.

[0071] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0072] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for extracting Brillouin radio frequency shift, characterized in that, include: Obtain the interference ring image of the Fabry-Perot etalon; The interference ring image is denoised to obtain a denoised interference ring image; The Steger algorithm is used to extract the center line of each interference ring in the denoised interference ring image, resulting in a set of center lines; the interference rings include a first Rayleigh scattering interference ring, a Brillouin scattering interference ring, and a second Rayleigh scattering interference ring; the set of center lines includes the set of center lines of the first Rayleigh scattering interference ring, the set of center lines of the Brillouin scattering interference ring, and the set of center lines of the second Rayleigh scattering interference ring. Based on the set of centerlines and the equation of the circle, the radius of the first Rayleigh scattering interference ring, the radius of the Brillouin scattering interference ring, and the radius of the second Rayleigh scattering interference ring are obtained by fitting using the least squares method. The Brillouin scattering frequency shift in the echo signal of the Brillouin scattering lidar is calculated based on the radius of the first Rayleigh scattering interference ring, the radius of the Brillouin scattering interference ring, and the radius of the second Rayleigh scattering interference ring.

2. The Brillouin radio frequency shift extraction method according to claim 1, characterized in that, The interference ring image is denoised to obtain a denoised interference ring image, specifically including: The interference ring image is denoised using a multi-scale Fragi filter to obtain a denoised interference ring image.

3. The Brillouin radio frequency shift extraction method according to claim 1, characterized in that, The Steger algorithm is used to extract the center line of each interference ring in the denoised interference ring image, resulting in a set of center lines, specifically including: The first and second gradients of the denoised image are calculated using image convolution methods. Based on the first-order gradient and the second-order gradient, the center line of each interference ring in the denoised interference ring image is extracted using the Steger algorithm to obtain a set of center lines.

4. The Brillouin dispersion radio frequency shift extraction method according to claim 1, characterized in that, Based on the radius of the first Rayleigh scattering interference ring, the radius of the Brillouin scattering interference ring, and the radius of the second Rayleigh scattering interference ring, the Brillouin scattering frequency shift in the echo signal of the Brillouin scattering lidar is calculated, specifically including: Using formula Calculate the Brillouin scattering frequency shift in the echo signal of a Brillouin scattering lidar; where v B For Brillouin dispersion radio frequency shift; r inside r represents the radius of the first Rayleigh scattering interference ring. middle r represents the radius of the Brillouin scattering interference ring. outside The radius of the second Rayleigh scattering interference ring is indicated; FSR represents the free spectral range of the Fabry-Perot etalon.

5. A Brillouin radio frequency shift extraction system, characterized in that, include: The image acquisition module is used to acquire interference ring images of the Fabry-Perot etalon; A denoising module is used to denoise the interference ring image to obtain a denoised interference ring image; The centerline extraction module is used to extract the centerline of each interference ring in the denoised interference ring image using the Steger algorithm, thereby obtaining a set of centerlines; the interference rings include a first Rayleigh scattering interference ring, a Brillouin scattering interference ring, and a second Rayleigh scattering interference ring; the set of centerlines includes the set of centerlines of the first Rayleigh scattering interference ring, the set of centerlines of the Brillouin scattering interference ring, and the set of centerlines of the second Rayleigh scattering interference ring. The fitting module is used to fit the first Rayleigh scattering interference ring radius, the Brillouin scattering interference ring radius, and the second Rayleigh scattering interference ring radius using the least squares method based on the set of center lines and the equation of the circle. The frequency shift calculation module is used to calculate the Brillouin scattering frequency shift in the echo signal of the Brillouin scattering lidar based on the radius of the first Rayleigh scattering interference ring, the radius of the Brillouin scattering interference ring, and the radius of the second Rayleigh scattering interference ring.

6. An electronic device, characterized in that, include: A memory and a processor, the memory being used to store a computer program, the processor running the computer program to cause the electronic device to perform the Brillouin dispersion radio frequency shift extraction method according to any one of claims 1-4.

7. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the Brillouin dispersion radio frequency shift extraction method according to any one of claims 1-4.

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