CN114549684A - Improved mine radio wave perspective imaging reconstruction method based on discrete cosine transform and algebraic reconstruction algorithm - Google Patents
Improved mine radio wave perspective imaging reconstruction method based on discrete cosine transform and algebraic reconstruction algorithm Download PDFInfo
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Abstract
Aiming at the problem that an analytic algorithm cannot reconstruct projection data which are distributed unevenly in reconstruction of a mine radio wave perspective imaging image, the method comprises the steps of firstly detecting incident and received data of the coal rock electromagnetic wave and preprocessing the incident and received data; secondly, processing algorithm influence factors, namely selection of an iteration initial value and transformation of an electromagnetic wave angle; solving the magnetic field intensity based on the Maxwell equation again; then, resolving an algebraic iterative image reconstruction algorithm D-ART based on DCT (discrete cosine transform) transformation based on an ART (algebraic reconstruction algorithm) reconstruction algorithm; finally, reconstructing the coal rock by using a D-ART algorithm to obtain a reconstructed image; in summary, the invention provides an improved mine radio wave perspective imaging reconstruction method based on discrete cosine transform and an algebraic reconstruction algorithm.
Description
Technical Field
The invention relates to an improved mine radio wave perspective imaging reconstruction method based on discrete cosine transform and algebraic reconstruction algorithm, in particular to a solution for reconstruction of a transform image when an electromagnetic wave refraction angle cannot be determined, and belongs to the technical field of mine engineering geophysical prospecting.
Background
The traditional electromagnetic wave technology only needs to apply mine direct current electrical prospecting, mine transient electromagnetic prospecting, radio wave perspective, bottom penetrating radar and seismic prospecting methods to identify the fault structure of the coal rock. With the development of technology and years of effort, mine direct current electrical exploration and radio wave fluoroscopy make remarkable progress in theory, technology and exploration equipment.
In the invention, the coal rock fault is researched mainly by relying on a radio wave perspective method, when electromagnetic waves propagate in an underground rock stratum, due to the fact that various rocks and minerals have different electrical properties, the absorption of the electromagnetic wave energy is different to a certain extent, and the identification angles of different electromagnetic waves to the rock stratum are also different, so that the error problem in reconstruction of an electromagnetic wave radio perspective image is considered, a normal area and an abnormal area in a working surface can be fully defined by the tunnel radio wave perspective method through detection of hundreds of working surfaces, and in addition, in the reconstruction process of a radio wave perspective image, along with the condition of a fracture structure or a cavity, when the electromagnetic waves are refracted and reflected, the energy loss of the electromagnetic waves is caused, namely the attenuation amount. However, when the electromagnetic wave propagates in the underground rock formation, if there is a water-containing region, a trap column, a fault, a void or other uneven geological structure, the energy of the electromagnetic wave is absorbed by the water-containing region or completely shielded by the water-containing region, and then a signal significance abnormality and a perspective abnormality are generated.
As for the prior image reconstruction related algorithm, most scholars improve the image reconstruction related algorithm based on ART or SART, the problem of large linear iteration error is rarely considered, and the difference from the true value exists, so the method starts with the algorithm and transforms the ART result, thereby realizing the effect of reducing the error. In addition, in the reconstruction process, the condition that electromagnetic waves are not parallel beams can occur, the angle problem is considered at the moment, the Hough transformation is applied to improve the algorithm, so that the true value is achieved to the maximum extent, and the purpose of exploration and actual measurement of the rock stratum is achieved.
Disclosure of Invention
The invention provides a reconstruction method for improving mine radio wave perspective imaging based on discrete cosine transform and algebraic reconstruction algorithm, which improves the leak of the ART algorithm in large error to a great extent, so that the problem of image reconstruction in mine radio wave perspective can be more clearly understood, and the safety problem of a mine can be effectively enhanced.
The technical scheme of the invention is as follows: the method comprises the steps of improving a mine radio wave perspective imaging reconstruction method based on discrete cosine transform and algebraic reconstruction algorithms, and firstly preprocessing coal rock electromagnetic wave detection incident and received data; secondly, processing algorithm influence factors, namely selection of an iteration initial value and transformation of an electromagnetic wave angle; solving the magnetic field intensity based on the Maxwell equation again; then, solving an algebraic iterative image reconstruction algorithm D-ART based on DCT transformation based on an ART reconstruction algorithm; and finally, performing reconstruction processing on the coal rock by using a D-ART algorithm to obtain a reconstructed image.
The method comprises the following specific steps:
step1, preprocessing the data of the detection, incidence and reception of the coal rock electromagnetic waves, determining the coal rock condition of the area where the mine is located, obtaining the data required by the algorithm according to the difference value before and after the radio waves penetrate the electromagnetic waves of the ore bed in the mine, and giving the image reconstruction ART algorithm prior ART thought and the mine actual condition;
firstly, assuming that the coal rock geological interference factors are few, the structure is simple, and circular isomers exist, in order to ensure the safety of coal rock industrial and mining, certain measures need to be taken to judge the isomer positions, and radio wave perspective is used at the momentThe method carries out gridding detection on the coal rock to obtain a matrix, and linear iteration can be carried out on a linear equation set by using the matrix as a coefficient matrix. As shown in FIG. 1, all operations of the present invention are based on the following scene images, i.e. the air intake lane and the return lane, which are shown by the section of the emissive site, i.e. a point emissive site 5, with a value of H0The receiving points are a group of 10 points 1-10, and the values are Hi(ii) a Conversely, the return airway can also be used as a transmitting area, and also as a point transmitting and 10 point receiving, and the variable of the isomer is expressed as F(x,y)Polar coordinate is represented as ri,j。
In the mine radio wave perspective, for the image reconstruction problem, many technical researches mainly include analytic algorithm image reconstruction and iterative algorithm image reconstruction, in the iterative algorithm, when projection data are insufficient and projection angle distribution is not uniform, the iterative algorithm can still solve the problem, and the ART algorithm in the iterative algorithm has the basic idea that an initial value is given to a reconstruction area and is generally zero, then obtained projection value residuals are uniformly back-projected along the ray direction one by one, the image is corrected until the requirement of iteration is met, and the iterative process can be ended. And the ART algorithm is used for solving a positive problem, namely predicting a projection value according to a previous gray value and a projection equation so as to obtain a calculated projection value, correcting an estimated value and further realizing solving of an inverse problem.
An algebraic iterative reconstruction Algorithm (ART) is the most commonly used reconstruction method in tomography because it has the advantages of high accuracy, strong noise immunity and high flexibility for tomographic reconstruction of a small number of projection angles. Its basic idea is to guess f from an initial value of f(0)Initially, the loop is projected into solution space using constraints, and the desired convergence condition, f, is reached at the k-th iteration(k)The iteration stops when the value is close enough to the true value f, the constraint condition has a realistic context for the coal petrography, and the boundary condition of the algorithm can be set appropriately.
Step2, firstly, giving a formula of an ART algorithm in an iterative reconstruction algorithm, and solving the field strength according to a Maxwell equation;
firstly, based on ART algorithm in reconstruction of mine radio wave perspective CT image, the following algorithm formula is given
Where k is the number of iterations, 1. ltoreq. i.ltoreq.N, λ is the relaxation factor (0. lamda. < 2)
As can be seen from the algorithmic formula, each equation is for xjIs corrected once, it can be more simply understood that the ith ray is used to correct each xjAfter the value is corrected, the (i +1) th ray is applied to each xjAnd (5) correcting the value until all the rays are finished, and finishing the first iteration.
The method comprises the following specific operation steps:
to unknown quantity xjAssigned initial value
Calculating an estimate of the ith projection
Then calculating the error
Calculating a correction value for the jth unknown quantity
For xjCorrecting the value of (c):
then, k is applied to k +1, and the process is repeated until the whole projection process is completed.
Secondly, the radio wave perspective method is that a coal roadway with simple geological conditions and few interference factors is selected at first, 1-3 emission points are arranged, field intensity values of observation points of a distance transmitter are observed, then attenuation of electromagnetic waves is detected, the attenuation depends on the absorption of the coal seam to the electromagnetic waves, when the electromagnetic waves propagate in coal rocks, a part of electromagnetic energy is gradually absorbed and attenuated along with the increase of the distance, at the moment, beta represents an attenuation coefficient, and the specific formula is as follows:
in the formula, beta is the coal bed absorption coefficient (dB/m); h1Field intensity value (dB) of a No. 1 measuring point; h2Field intensity value (dB) of No. 2 measuring point; r is1The distance from the emission point to the No. 1 measuring point; r is2Is the distance from the emission point to the measurement point No. 2.
In summary, the attenuation absorption coefficient is related to the field strength and the distance, i.e. the attenuation of the electromagnetic wave is well described.
The calculation basis of the ART iterative algorithm is to solve a linear equation set, but after data exists, the problem of whether the equation has a solution needs to be considered, firstly, the judgment condition of the linear equation set is given below, a coefficient equation and a coefficient matrix of linear iteration can be obtained, and finally, the following equation AX is calculated as P, a is a coefficient matrix, whether the linear equation set has a solution is judged firstly, and then, a target function is established below, and the existence condition of the solution is applied:
J(X)＝||AX-P||2＝(AX-P)T(AX-P) (4)
the equation is an objective function of least squares, and the optimization of the function can be judged,
therefore, the partial derivatives are calculated,
the temperature of the molten steel is set to zero,
2ATAX-2ATP＝0 (6)
the optimal solution of the least square method can be obtained according to the formula,
X＝(ATA)-1ATP (7)
the above equation is mainly used for the classification and discussion of the linear equation group solution, and in the ART algorithm, a certain point is iterated for many times to reconstruct an image.
Step3, according to the iterative thought of the ART algorithm, firstly selecting an initial value, processing a coefficient matrix, controlling the ART algorithm to be converged forcibly, combining the ART algorithm and DCT transformation algorithm for research, and reducing the iterative error;
firstly, finding out factors for controlling ART algorithm convergence according to an iteration thought of the ART algorithm by Step3.1, wherein the factors mainly comprise selection of an initial value, design of an ART iteration formula, design of a coefficient matrix and design of an operation and iteration convergence criterion;
for the ART algebraic reconstruction algorithm, the iteration idea is indispensable, and the initial value condition is an important iteration condition, because the calculation amount of the ART algorithm is large, and the reconstruction speed is slow, different initial values can be selected to influence the convergence error, in addition, the iterative convergence criterion also influences the iteration result, and the treatment selection of the ART algorithm iteration is explained below.
Because the selection of the initial value, the design of the ART iterative formula, the design of the coefficient matrix and the design of the operation and iterative convergence criterion have great influence on the ART algorithm, the design of the ART iterative formula is that the existing iterative formula is used for the moment, the new selection is carried out on the initial value of the ART algorithm, and the random selection can be carried out on the coefficient matrix by selecting the radon function, so that the ART algebraic iteration can be carried out on different coefficient matrices. In addition, the design of the coefficient matrix is also greatly influenced, and the regularization of the coefficient matrix has a great influence on the iterative algorithm.
Derivation of this equation:
for the derivation of this equation, the reconstruction of the image by the ART algorithm may first be attributed to solving the following set of linear equations
Namely, it is
The value of X in this equation is solved.
Secondly, whether a linear equation set has a solution or not is considered, a unilateral data missing problem occurs in actual coal rock electromagnetic wave detection, the equation is not solved, forced convergence is considered to be performed on the equation at the moment, the ART algorithm stops iteration when the equation satisfies | delta i | ═ epsilon, and the epsilon at the moment is a specified error coefficient:
secondly, a maximum expectation method can be applied, which is actually a time-after-time iteration, and the SPSS software is applied, which mainly includes two steps: the first step is to solve the expected value of the missing data by using the existing information of the data; the second step is to make maximum likelihood estimates on the assumption that missing values are replaced, and iterate until convergence.
Step3.2: DCT transformation process
DCT transform is also called discrete cosine transform, and is used for compressing signals and image data, data after DCT transform are relatively concentrated, and the problem of large error of ART algorithm can be reduced to a great extent, and the two-dimensional DCT transform formula is as follows:
wherein:
the inverse transformation formula is as follows:
basically, there is more room to apply the inverse DCT transform in processing the image.
Step3.3: obtaining DCT according to Fourier transform deformation, and then using the DCT in an ART algorithm;
firstly, the algebraic iterative reconstruction algorithm is the most common reconstruction method in the tomography technology, and has high precision, strong noise resistance and high flexibility for the tomography reconstruction of a small number of projection angles.
The basic principle is that a linear equation set is solved based on the criterion of minimum norm, but a certain error exists in the iterative process, and the DCT is considered to be fused with the ART algorithm in consideration of the requirement of the algorithm on precision, so that the tomography reconstruction algorithm obtained by the DCT transformation based on algebraic iteration is realized. Therefore, the integration of the ART algorithm with DCT transformation is considered, and the specific process of the algorithm of the integration of DCT with ART is given below.
Two-dimensional fourier transform:
inverse transformation:
the two-dimensional Fourier transform has certain physical significance on the image, and data loss of different degrees caused by frequency on the images with different frequencies can be repaired.
The Fourier transform is needed for image reconstruction based on continuous data, so when projection data are insufficient or projection angle distribution is not uniform in coal rock detection, the problem cannot be solved by applying a transform domain, and other methods need to be considered when the data are discrete, so that an algebraic iteration problem needs to be considered.
Step3.4: and constructing an algorithm equation for improving the convergence rate of the ART algorithm. Judging what factors promote the convergence speed of the ART algorithm and have a better solution according to the Step 3.4; considering that the penetration of electromagnetic waves to a mine needs to consider the influence of an angle in the image reconstruction process of the mine, the angle influence is studied by Hough transformation; second, the perspective radiowave imaging is considered using the angle formed by the electromagnetic waves during reconstruction in combination with the DCT discrete cosine transform.
During radio wave perspective, point detection operation is carried out on the coal rock, so that the obtained data can form a matrix which can be used as a coefficient matrix of a linear equation set, the coefficient matrix is A, and the matrix is subjected to linear iteration to obtain a reconstructed image.
The invention has the beneficial effects that: the method effectively detects the attenuation abnormal value of the electromagnetic wave when the electromagnetic wave is detected on the coal rock through an image reconstruction algorithm, and judges the cause of the electromagnetic wave abnormality according to the parameters, including position, size and dielectric coefficient, of the reconstructed image, namely the abnormal condition existing in the coal rock, such as: the method is characterized in that a water-containing section, a collapse column, a fault, a cavity or other uneven geological structures are adopted to reduce personnel injury in the coal-rock industrial mine, for example, the water-containing section can cause coal-rock flooding, the fault can cause unsafe conditions of workers during operation, and the collapse column can easily cause collapse of the coal-rock, so that the abnormal conditions in the coal-rock can be judged by a scientific means.
Drawings
FIG. 1 is a diagram of a physical scenario of the present invention;
FIG. 2 is a flow chart of the present invention.
The specific implementation process comprises the following steps:
in order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. It should be noted that the embodiments and features of the embodiments in the present application may be arbitrarily combined with each other without conflict.
In the aspect of coal rock image identification, only a few coal petrography students and experts research the way of combining hole penetration and traditional mine radio electromagnetic wave perspective into images for the research of an image reconstruction method based on coal rocks; in the aspect of coal rock layered interface identification, the imaging speed and the imaging quality of an image are important indexes; generally, the higher and more elaborate the number of coal rock identification iterations, the longer the waste of time.
The traditional mine radio electromagnetic wave exploration is to invert the coal rock fault by using a common algebraic iterative algorithm through single detection data.
In order to solve the above problems, embodiments of the present invention provide an improved reconstruction method for mine radio wave fluoroscopic imaging based on discrete cosine transform and algebraic reconstruction algorithms.
First, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the invention implements a reconstruction method for improving mine radio wave perspective imaging based on discrete cosine transform and algebraic reconstruction algorithm, and firstly, preprocessing the data of the detection of the incident and received coal rock electromagnetic waves; secondly, processing algorithm influence factors, namely selection of an iteration initial value and transformation of an electromagnetic wave angle; solving the magnetic field intensity based on the Maxwell equation again; then, solving an algebraic iterative image reconstruction algorithm D-ART based on DCT transformation based on an ART reconstruction algorithm; and finally, performing reconstruction processing on the coal rock by using a D-ART algorithm to obtain a reconstructed image. The method comprises the following specific steps:
step1, preprocessing the data of the detection, incidence and reception of the coal rock electromagnetic waves, determining the coal rock condition of the area where the mine is located, obtaining data required by an ART algorithm according to the difference value before and after the radio waves penetrate the electromagnetic waves of the ore bed in the mine, and providing the image to reconstruct the prior ART idea and the mine actual condition of the ART algorithm;
firstly, assuming that coal rock geological interference factors are few and the structure is simple and a circular isomer exists, in order to ensure the safety of coal rock mining, a certain measure needs to be taken to judge the position of the isomer, at the moment, a radio wave perspective method is used for carrying out gridding detection on the coal rock, a matrix can be obtained, and the matrix is used as a coefficient matrix to carry out linear iteration on a linear equation set.
In the mine radio wave perspective, for the image reconstruction problem, many technical researches mainly include analytic algorithm image reconstruction and iterative algorithm image reconstruction, in the iterative algorithm, when projection data are insufficient and projection angle distribution is not uniform, the iterative algorithm can still solve the problem, and the ART algorithm in the iterative algorithm has the basic idea that an initial value is given to a reconstruction area and is generally zero, then obtained projection value residuals are uniformly back-projected along the ray direction one by one, the image is corrected until the requirement of iteration is met, and the iterative process can be ended. And the ART algorithm is used for solving a positive problem, namely predicting a projection value according to a previous gray value and a projection equation so as to obtain a calculated projection value, correcting an estimated value and further realizing solving of an inverse problem.
An algebraic iterative reconstruction Algorithm (ART) is the most commonly used reconstruction method in tomography because it has the advantages of high accuracy, strong noise immunity and high flexibility for tomographic reconstruction of a small number of projection angles. The basic idea is to guess f from an initial value of f(0)Initially, the loop is projected into solution space using constraints, and the desired convergence condition, f, is reached at the k-th iteration(k)The iteration stops when the value is close enough to the true value f, the constraint condition has a realistic context for the coal petrography, and the boundary condition of the algorithm can be set appropriately.
Step2, firstly, giving a formula of an ART algorithm in an iterative reconstruction algorithm, and solving the field strength according to a Maxwell equation;
firstly, based on ART algorithm in reconstruction of mine radio wave perspective CT image, the following algorithm formula is given
Where k is the number of iterations, 1. ltoreq. i.ltoreq.N, λ is the relaxation factor (0. lamda. < 2)
As can be seen from the algorithmic formula, each equation is for xjIs corrected once, it can be understood more simply that the ith ray is used to correct each xjAfter the value is corrected, the (i +1) th ray is applied to each xjAnd (5) correcting the value until all the rays are finished, and finishing the first iteration.
The method comprises the following specific operation steps:
to unknown quantity xjAssigning an initial value
Calculating an estimate of the ith projection
Then calculating the error
Calculating a correction value for the jth unknown quantity
For xjCorrecting the value of (c):
then, k is applied to k +1, and the process is repeated until the whole projection process is completed.
Secondly, the radio wave perspective method is that a coal roadway with simple geological conditions and few interference factors is selected at first, 1-3 emission points are arranged, field intensity values of observation points of a distance transmitter are observed, then attenuation of electromagnetic waves is detected, the attenuation depends on the absorption of the coal seam to the electromagnetic waves, when the electromagnetic waves propagate in coal rocks, a part of electromagnetic energy is gradually absorbed and attenuated along with the increase of the distance, at the moment, beta represents an attenuation coefficient, and the specific formula is as follows:
in the formula, beta is the coal bed absorption coefficient (dB/m); h1Field intensity value (dB) of a No. 1 measuring point; h2Field intensity value (dB) of No. 2 measuring point; r is1The distance from the emission point to the No. 1 measuring point; r is2Is the distance from the emission point to measurement point No. 2.
In summary, the attenuation absorption coefficient is related to the field strength and the distance, i.e. the attenuation of the electromagnetic wave is well described.
The calculation basis of the ART iterative algorithm is to solve a linear equation set, but after data exists, the problem of whether the equation has a solution needs to be considered, firstly, the judgment condition of the linear equation set is given below, a coefficient equation and a coefficient matrix of linear iteration can be obtained, and finally, the following equation AX is calculated as P, a is a coefficient matrix, and whether the linear equation set has a solution is judged firstly, and a target function is established below (mainly using the existence condition of the solution in an advanced algebra):
J(X)＝||AX-P||2＝(AX-P)T(AX-P) (19)
the equation is an objective function of least squares, and the optimization of the function can be judged,
therefore, the partial derivatives are calculated,
so that the number of the carbon atoms is zero,
2ATAX-2ATP＝0 (21)
the optimal solution of the least square method can be obtained according to the formula,
X＝(ATA)-1ATP (22)
the above equation is mainly used for the classification and discussion of the linear equation group solution, and in the ART algorithm, a certain point is mainly iterated for many times to reconstruct an image.
Step3, according to the iterative thought of the ART algorithm, firstly selecting an initial value, processing a coefficient matrix, controlling the ART algorithm to be converged forcibly, combining the ART algorithm and DCT transformation algorithm for research, and reducing the iterative error;
firstly, finding out factors for controlling ART algorithm convergence according to an iteration thought of the ART algorithm by Step3.1, wherein the factors mainly comprise selection of an initial value, design of an ART iteration formula, design of a coefficient matrix and design of an operation and iteration convergence criterion;
for the ART algebraic reconstruction algorithm, the iteration idea is indispensable, and the initial value condition is an important iteration condition, because the calculation amount of the ART algorithm is large, the reconstruction speed is slow, different initial values can be selected to influence the convergence error, in addition, the iterative convergence criterion also influences the iteration result, and the treatment selection of the ART algorithm iteration is explained below.
Because the selection of the initial value, the design of the ART iterative formula, the design of the coefficient matrix and the design of the operation and iterative convergence criterion have great influence on the ART algorithm, the design of the ART iterative formula is that the existing iterative formula is used for the moment, the new selection is carried out on the initial value of the ART algorithm, and the random selection can be carried out on the coefficient matrix by selecting the radon function, so that the ART algebraic iteration can be carried out on different coefficient matrices. In addition, the design of the coefficient matrix is also greatly influenced, and the regularization of the coefficient matrix has a great influence on the iterative algorithm.
Derivation of this equation:
for the derivation of this equation, the reconstruction of the image by the ART algorithm can first be attributed to the solution of the following system of linear equations
Namely, it is
The value of X in this equation is solved.
Secondly, whether a linear equation set has a solution or not is considered, a unilateral data missing problem occurs in actual coal rock electromagnetic wave detection, the equation is not solved, forced convergence of the equation needs to be considered at this time, the ART algorithm stops iteration when | Δ i | ═ |, and epsilon at this time is a specified error coefficient:
again, the maximum expectation method can be applied, which is actually a one-time iteration, where the SPSS software is applied, and there are two main steps: the first step is to utilize the existing information of the data to solve the expected value of the missing data; the second step is to make maximum likelihood estimates on the assumption that missing values are replaced, and iterate until convergence.
Step3.2: DCT transformation process
DCT transform is also called discrete cosine transform, and is used for compressing signals and image data, data after DCT transform are relatively concentrated, and the problem of large error of ART algorithm can be reduced to a great extent, and the two-dimensional DCT transform formula is as follows:
wherein:
the inverse transformation formula is as follows:
basically, there is more room for applying the inverse DCT transform in processing an image.
Step3.3: obtaining DCT according to Fourier transform deformation, and then using the DCT in an ART algorithm;
firstly, the algebraic iterative reconstruction algorithm is the most common reconstruction method in the tomography technology, and has high precision, strong noise resistance and high flexibility for the tomography reconstruction of a small number of projection angles.
The basic principle of the method is that a linear equation set is solved based on the minimum norm criterion, but certain errors exist in the iterative process, and the DCT is considered to be fused with the ART algorithm in consideration of the requirement of the algorithm on precision, so that the tomography reconstruction algorithm obtained by the DCT based on algebraic iteration is realized. Therefore, the integration of the ART algorithm with DCT transformation is considered, and the specific process of the algorithm of the integration of DCT with ART is given below.
Two-dimensional fourier transform:
inverse transformation:
the two-dimensional Fourier transform has certain physical significance on the image, and data loss of different degrees caused by frequency on images with different frequencies can be repaired.
The Fourier transform is needed for image reconstruction based on continuous data, so when projection data are insufficient or projection angle distribution is not uniform in coal rock detection, the problem cannot be solved by applying a transform domain, and other methods need to be considered when the data are discrete, so that an algebraic iteration problem needs to be considered.
Step3.4: and constructing an algorithm equation for improving the convergence rate of the ART algorithm. Judging what factors promote the convergence speed of the ART algorithm and have a better solution according to the Step 3.4; considering that the penetration of electromagnetic waves to a mine needs to consider the influence of an angle in the image reconstruction process of the mine, the angle influence is considered to be studied by carrying out Hough transformation; second, the perspective radiowave imaging is considered using the angle formed by the electromagnetic waves during reconstruction in combination with the DCT discrete cosine transform.
During radio wave perspective, point detection operation is carried out on the coal rock, so that the obtained data can form a matrix which can be used as a coefficient matrix of a linear equation set, the coefficient matrix is A, and the matrix is subjected to linear iteration to obtain a reconstructed image.
While the present invention has been described in detail with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge of those skilled in the art.
Claims (5)
1. The improved mine radio wave perspective imaging reconstruction method based on discrete cosine transform and algebraic reconstruction algorithm is characterized in that: firstly, preprocessing the data of the detection, incidence and reception of the coal rock electromagnetic waves; secondly, processing algorithm influence factors, namely selection of an iteration initial value and transformation of an electromagnetic wave angle; solving the magnetic field intensity based on the Maxwell equation again; then, solving an algebraic iterative image reconstruction algorithm D-ART based on DCT transformation based on an ART reconstruction algorithm; and finally, performing reconstruction processing on the coal rock by using a D-ART algorithm to obtain a reconstructed image.
2. The improved mine radio wave perspective imaging reconstruction method based on discrete cosine transform and algebraic reconstruction algorithm is characterized in that: the method comprises the following specific steps:
step1, preprocessing the data of the detection, incidence and reception of the coal rock electromagnetic waves, determining the coal rock condition of the area where the mine is located, obtaining data required by a reconstruction algorithm according to the difference value before and after the radio waves penetrate the electromagnetic waves of the ore bed in the mine, and giving the prior ART thought of an image algebraic reconstruction algorithm ART and the mine actual condition;
step2, firstly, giving a formula of an ART algorithm in an iterative reconstruction algorithm, and solving the electromagnetic wave field intensity according to a Maxwell equation;
step3, according to the iterative thought of the ART algorithm, firstly selecting an initial value, processing a coefficient matrix, controlling ART convergence factors, correcting an image, and combining the ART algorithm with DCT transformation to reduce iterative errors.
3. The improved reconstruction method for mine radio wave perspective imaging based on discrete cosine transform and algebraic reconstruction algorithm as claimed in claim 1, wherein: in Step 1: the ART prior ART idea is to give an initial value to a reconstruction region, then to back-project the obtained projected value residuals uniformly along the ray direction one by one, and to correct the image until the iteration requirement is met, and then to end the iteration.
4. The improved reconstruction method for mine radio wave perspective imaging based on discrete cosine transform and algebraic reconstruction algorithm as claimed in claim 1, characterized in that: the ART algorithm formula and the electromagnetic wave field strength included in Step2 are as follows:
based on an ART algorithm in the reconstruction of a mine radio wave perspective CT image, the following algorithm formula is given:
where k is the number of iterations, i is greater than or equal to 1 and less than or equal to N, and λ is the relaxation factor (0 < λ < 2);
as can be seen from the algorithmic formula, each equation is for xjIs corrected once, it can be understood that the ith ray is used to correct each xjAfter the value is corrected, the (i +1) th ray is applied to each xjCorrecting the value until all rays are finished, and finishing the first iteration;
the method comprises the following specific operation steps:
to unknown quantity xjAssigning an initial value
Calculating an estimate of the ith projection
Then calculating the error
Calculating a correction value for the jth unknown quantity
For xjCorrecting the value of (c):
then, repeating the process by using k as k +1 to know that the whole projection process is finished;
and observing the field intensity value of each observation point of the distance transmitter, and then detecting the attenuation quantity of the electromagnetic wave.
5. The improved reconstruction method for mine radio wave fluoroscopy imaging based on discrete cosine transform and algebraic reconstruction algorithm as claimed in claim 1, wherein: the Step3 comprises the following concrete steps:
step3.1, finding out factors for controlling the convergence of the ART algorithm according to the iterative thought of the ART algorithm, wherein the factors comprise the selection of an initial value, the design of an ART iterative formula, the design of a coefficient matrix and the design of an operation and iterative convergence criterion;
carrying out new selection on the initial value of the ART algorithm, selecting a radon function to randomly select a coefficient matrix, and adopting forced convergence for a convergence criterion;
step3.2, DCT transformation;
DCT transform is also called discrete cosine transform, is used for compressing signal and image data, and the data after DCT transform is relatively concentrated, so that the problem of large error of ART algorithm can be reduced;
step3.3, DCT transformation algorithm based on algebraic iteration: obtaining DCT according to Fourier transformation deformation, and then using the DCT in an ART algorithm;
fusing DCT and ART algorithm to realize the chromatography reconstruction algorithm obtained by DCT transformation based on algebraic iteration; hence consider using the DCT transform in conjunction with the ART algorithm;
step3.4, considering that the penetration of electromagnetic waves to the mine needs to consider the influence of angles in the image reconstruction process of the mine, carrying out Hough transformation research, and combining the angles formed by the electromagnetic waves in the reconstruction process with DCT discrete cosine transformation to carry out perspective imaging on the radio waves; after the image is reconstructed, how to mark the region with potential safety hazard in the reconstructed image, the image is subjected to gridding processing.
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