Muon detector, three-dimensional photographic imaging method, device and storage medium

Abstract

The application discloses a muon detector, a three-dimensional photographic imaging method and device and a storage medium, wherein the muon detector comprises three detection planes and a lead plate which are arranged in parallel in sequence, and three acquisition plates; the lead plate is arranged between the second detection plane and the third detection plane; the detection plane is composed of a three-prism-shaped scintillator and a corresponding photoelectric sensor; the photoelectric sensor is connected with the acquisition plate; and the acquisition plate is used for acquiring the number of muons passing through an object and the number of muons in the sky. The muon detector of the application adds a layer of lead plate between the three detection planes, which can effectively shield gamma particles in the air, reduce background noise interference and improve imaging accuracy.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of imaging technology, in particular to a muon detector, a three-dimensional photography imaging method, device and storage medium. BACKGROUND

[0002] Muons are particles with high penetration, and muon detection technology has been applied in many fields due to this characteristic, and muon imaging technology is one of the main technologies. Muon imaging technology can be divided into two categories: transmission imaging and scattering imaging. Scattering imaging, also known as tomographic imaging, is mainly used in nuclear material detection and non-destructive testing of cultural relics. Transmission imaging, also known as photography imaging, has been used in volcanology, mineral exploration and various other industrial and security applications, so the detector used for photography imaging has also attracted much attention. Muon detectors are generally divided into plastic scintillator detectors, gas detectors and nuclear emulsion detectors. Plastic scintillator detectors are easy to machine, have flexible structure design, stable performance, can adapt to different measurement and application occasions, and have low cost, so they can be used on a large scale. Plastic scintillator detectors are the current mainstream detectors, and photography imaging is currently the most important imaging method for large-scale objects.

[0003] However, when the detector collects muon information, other particles in the air will interfere, mainly including alpha particles, beta particles and gamma particles from cosmic ray decay, and the main interfering particles are gamma particles. The energy of gamma particles is low, so the gamma particles that interfere with the muon information collected by the detector are the gamma particles that directly contact the detector in the air, which can greatly affect the imaging accuracy and accuracy of the detector. If the number of detection planes of the detector is large, the cross-layer response method can be used to screen muons, but the number of detection plane layers of the existing photography imaging detector is small, only 2-3 layers, so the cross-layer response method cannot be used, which makes it difficult to shield cosmic rays. In addition, the ultimate goal of using muons to detect objects is to obtain the density structure information of the object. The current mature three-dimensional density structure imaging method is based on a tomographic imaging detector, but its imaging range does not exceed the detection area of the detector, so a large detector is required for imaging large objects, and therefore it is impossible to detect large-scale objects. The imaging range that can be obtained by the detector based on photography imaging can be much larger than the area of the detector itself, but the disadvantage is that a single detection system can only perform two-dimensional imaging, and two-dimensional imaging cannot completely obtain the density structure information of the object. Therefore, how to improve the reliability of obtaining the density structure information of the object and improve the imaging accuracy is a technical problem that needs to be solved.

[0004] The above content is only used to assist in understanding the technical solutions of the present application and does not represent an acknowledgement that the above content is prior art. SUMMARY

[0005] The application aims to provide a three-dimensional photographic imaging method, device, equipment and storage medium, and aims to solve the technical problems of low reliability of detector in obtaining object density structure information and low imaging accuracy in the prior art.

[0006] To achieve the above-mentioned purpose, the application provides a muon detector, which comprises three layers of detection planes and a lead plate arranged in parallel in sequence, and three acquisition plates.

[0007] The lead plate is arranged between the second layer of detection planes and the third layer of detection planes.

[0008] The detection planes are composed of three-prism-shaped scintillators and corresponding photoelectric sensors.

[0009] The photoelectric sensors are connected with the acquisition plates.

[0010] The acquisition plates are used to collect the number of muons passing through the object and the number of muons in the sky.

[0011] Preferably, the muon detector further comprises a shell and a rotatable base.

[0012] The three layers of detection planes and the lead plate are packaged in the shell, and the shell is made of light-proof aluminum packaging.

[0013] The shell is arranged on the rotatable base, and the rotatable base is rotated to adjust the muon detector to different angles to detect the object.

[0014] Preferably, the three-dimensional photographic imaging method is applied to the muon detector as described above, and the method comprises:

[0015] The number of muons passing through the object and the number of muons in the sky collected by the muon detector are obtained.

[0016] The opacity of the object is calculated according to the number of muons passing through the object and the number of muons in the sky.

[0017] The density error is calculated according to the opacity, and the density of the object is calculated according to the density error.

[0018] It is compared whether the density error is less than the minimum error.

[0019] If the density error is less than the minimum error, the density of the object is output.

[0020] Preferably, the opacity of the object is calculated according to the number of muons passing through the object and the number of muons in the sky, and the method comprises:

[0021] The muon flux attenuation coefficient of the object passing through the object is calculated according to the number of muons passing through the object and the number of muons in the sky.

[0022] calculating a minimum passing energy through the object according to the muon flux attenuation coefficient;

[0023] calculating the opacity of the object according to the minimum passing energy.

[0024] Preferably, the calculating the density error according to the opacity comprises:

[0025] splitting the opacity into an independent opacity matrix;

[0026] voxel traversing the muons in the independent opacity matrix to obtain a voxel track;

[0027] calculating the density error according to the voxel track.

[0028] Preferably, before the voxel traversing the muons in the independent opacity matrix to obtain a voxel track, the method further comprises:

[0029] establishing a density structure model of the object and setting an initial density;

[0030] splitting the density structure model of the object to obtain a voxel matrix of the object;

[0031] Correspondingly, the voxel traversing the muons in the independent opacity matrix to obtain a voxel track specifically comprises:

[0032] voxel traversing the muons in the independent opacity matrix according to the voxel matrix to obtain a voxel track.

[0033] Preferably, the calculating the density of the object according to the density error comprises:

[0034] using a joint algebra reconstruction algorithm formula to obtain the density of the object through optimal solution approximation according to the density error; the joint algebra reconstruction algorithm formula is:

[0035]

[0036] wherein, represents the density after the jth iteration in the vth voxel, is the density error.

[0037] Preferably, before the obtaining the number of muons passing through the object and the number of muons in the sky collected by the muon detector, the method further comprises:

[0038] calculating the number of channels passed by the muons according to the signals collected by the acquisition plate in the muon detector;

[0039] judging whether the number of channels is a preset value;

[0040] If the number of channels is a preset value, the storage is combined as a muon event.

[0041] In addition, to achieve the above object, the application further provides a three-dimensional photographic imaging device, which comprises:

[0042] An acquisition module is configured to acquire the number of muons passing through the object and the number of muons in the sky collected by the muon detector;

[0043] A calculation module is configured to calculate the opacity of the object according to the number of muons passing through the object and the number of muons in the sky.

[0044] The calculation module is further configured to calculate the density error according to the opacity, and calculate the density of the object according to the density error.

[0045] The calculation module is further configured to compare whether the density error is less than a minimum error.

[0046] The calculation module is further configured to output the density of the object if the density error is less than the minimum error.

[0047] In addition, to achieve the above object, the application further provides a storage medium, which stores a three-dimensional photographic imaging program, and the three-dimensional photographic imaging program is executed by a processor to implement the steps of the three-dimensional photographic imaging method.

[0048] In the application, a new muon detector capable of shielding background noise and a three-dimensional imaging method combining multiple two-dimensional images are provided. The detector has three layers, and a lead plate is added between the detection planes, which can effectively shield γ particles in the air, reduce background noise interference and improve imaging accuracy. The three-dimensional imaging method can have a clearer understanding of the density structure information of the detected object, and increase the reliability of the detection result. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 It is a structure diagram of the muon detector of the hardware running environment involved in the embodiment scheme of the application;

[0050] Figure 2 It is a schematic diagram of different particle penetration ability in the muon detector embodiment of the application;

[0051] Figure 3 It is a flowchart of the first embodiment of the three-dimensional photographic imaging method of the application;

[0052] Figure 4 It is a muon event logical discrimination flowchart in the embodiment of the application;

[0053] Figure 5A schematic diagram of a twu coordinate system in an embodiment of the present application;

[0054] Figure 6 A muon particle source simulation diagram in an embodiment of the present application, Figure 6 (a) is a muon zenith angle distribution diagram, Figure 6 (b) is a muon energy spectrum distribution diagram;

[0055] Figure 7 A muon detection efficiency comparison diagram;

[0056] Figure 8 A gamma particle screening rate comparison diagram;

[0057] Figure 9 A structure block diagram of a first embodiment of the three-dimensional photographic imaging device of the present application.

[0058] The implementation of the object of the present application, the functional characteristics and the advantages will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0059] It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0060] Reference Figure 1 , Figure 1 A structure schematic diagram of a muon detector involved in an embodiment scheme of the present application. A muon detector embodiment is proposed.

[0061] In the present embodiment, the muon detector comprises three layers of detection planes and a lead plate arranged in sequence and in parallel, and three acquisition plates;

[0062] The lead plate is arranged between the second layer of detection planes and the third layer of detection planes;

[0063] The detection plane is composed of a triangular prism-shaped scintillator and a corresponding photoelectric sensor;

[0064] The photoelectric sensor is connected with the acquisition plate;

[0065] The acquisition plate is used to acquire the number of muons passing through the object and the number of muons in the sky.

[0066] As Figure 1 shown, the structure of the muon detector: the detector uses three layers of detection planes, for example, each layer of detection plane has a detection area of 60cm*60cm, and the plane spacing of the three layers of detection planes is 30cm; the detection plane is composed of a triangular prism-shaped scintillator and a corresponding photoelectric detector; for example, each scintillator has a cross section of 50mm*25mm and a length of 60cm. A lead plate with a preset thickness is inserted between the second layer of detection planes and the third layer of detection planes, and the preset thickness is usually 5-10cm.

[0067] Further, in the embodiment, the muon detector further comprises a shell and a rotatable base;

[0068] The three-layer detection plane and the lead plate are packaged in the shell, and the shell is packaged by light-proof aluminum;

[0069] The shell is arranged on the rotatable base, and the rotatable base is rotated to adjust the muon detector at different angles to detect objects.

[0070] It should be noted that the shell of the muon detector is packaged by light-proof aluminum to prevent external light from entering the detector, and the detector is placed on the rotatable base, so that the angle can be adjusted according to different detection objects.

[0071] When the muon detector collects muon information, other particles in the air will interfere, mainly including alpha particles, beta particles and gamma particles generated by cosmic ray decay, and different particles have different penetration abilities, such as Figure 2 , Figure 2 is a schematic diagram of the penetration ability of different particles, and the main interference is caused by gamma particles, so the main shielding object is gamma particles, and a certain thickness of lead plate is arranged between the detection planes to shield the gamma particles. The first layer and the second layer of the detection plane are used to count the incident position and angle information of the muons, and the third layer of the detection plane behind the lead plate is used to count the number of collected muons, and the events responded by the three-layer detection plane at the same time are determined as muon events.

[0072] The muon detector is used to collect muon information at different angles, the flux attenuation coefficient at different angles is calculated after the number of muons and time information are obtained, the minimum energy of the muons passing through the object is calculated by using the flux attenuation coefficient, and then the opacity of the object is calculated to obtain the opacity image of the object at different angles; a physical model of the detected object is established and is divided into a plurality of voxels, and the initial density of the object is set. The path length of each muon in each voxel is calculated by using the established voxel model, and the iteration of the density is performed in combination with the opacity image and the initial density, and the optimal object density is obtained when the density error is less than the minimum error range.

[0073] Based on the hardware structure of the muon detector, an embodiment of the three-dimensional photographic imaging method is provided.

[0074] Referring to Figure 2 , Figure 2 is a flowchart of the first embodiment of the three-dimensional photographic imaging method, and the first embodiment of the three-dimensional photographic imaging method is applied to the muon detector in the above embodiment.

[0075] In the first embodiment, the three-dimensional photographic imaging method comprises the following steps:

[0076] Step S10: Obtain the number of muons passing through the object and the number of sky muons collected by the muon detector.

[0077] In this specific implementation, the execution entity is the muon detector. The position of the muon is calculated by measuring the energy deposition of the muon as it passes through the first and second detection planes, and the angle at which the muon enters the detector is calculated. After the muon passes through the third detection plane, the muon is then... Figure 4 The logic shown indicates that muon events are stored and transmitted after a certain determination. Placing a lead plate between the second and third detection planes does not interfere with the calculation of muon positions and incident angles. This also means that adding a lead plate, while shielding gamma particles, does not affect the accuracy of the final density calculation and imaging precision. A triangular prism scintillator acts as a channel. The muon detector outputs information such as the position, time, energy, and quantity of muons hitting the scintillator, as well as the number of muons passing through the object and the number of muons in the sky collected by the muon detector.

[0078] Furthermore, prior to step S10, the procedure also includes:

[0079] The number of channels through which the muons pass is calculated based on the signals collected by the acquisition board in the muon detector.

[0080] Determine whether the number of channels is a preset value;

[0081] If the number of channels is a preset value, they are merged and stored as a muon event.

[0082] It should be noted that the preset value is 6. In order to improve imaging efficiency, before step S10, the number of channels through which the muon passes is calculated to determine whether it is a muon event. Since the muon detector has three layers and the number of channels through each layer is 2, when the number of channels is 6, it is identified as a muon event, and it is then merged and stored as a muon event before continuing to execute the subsequent step S10.

[0083] Step S20: Calculate the opacity of the object based on the number of muons passing through the object and the number of sky muons.

[0084] Understandably, the key to calculating the density of an object in a three-dimensional density imaging method lies in the object's opacity and the track information of muons passing through the object. The density is solved using these two parts, and the core formula is Equation (1):

[0085]

[0086] In the formula, O is the object opacity vector matrix, which is composed of opacity matrices obtained from different angles; ρ is the density of the object to be measured; and A is the track matrix of the muon passing through the object.

[0087] Further, the step S20 comprises:

[0088] According to the number of muons passing through the object and the number of muons in the sky, the flux attenuation coefficient of muons passing through the object is calculated;

[0089] According to the flux attenuation coefficient of muons, the minimum passing energy of muons passing through the object is calculated;

[0090] According to the minimum passing energy, the opacity of the object is calculated.

[0091] It should be noted that ③ single angle opacity: the opacity of the object is related to the flux attenuation coefficient of muons passing through the object, which is expressed as formula (2):

[0092]

[0093] In the formula, the actual flux attenuation coefficient is N exp , N out and N in are the number of muons collected by the detector and the number of muons in the sky, T out and T in are the time of the detector collecting muons passing through the city wall and collecting open sky muons.

[0094] The minimum energy E min of muons passing through the object is calculated by the theoretical flux attenuation coefficient from formula (3):

[0095]

[0096]

[0097] In the formula, φ is the muon energy spectrum, expressed as formula (4), η is the position resolution of the detector, and in actual calculation, N prd =N exp to get the minimum energy E min value.

[0098] After calculating the minimum energy E min of muons passing through the object, the opacity of the object is calculated by formula (5), which is as follows:

[0099]

[0100] In the formula, o is the opacity of muons passing through the object, E v =0.10566 GeV is the rest mass of muons.

[0101] The energy average loss rate is calculated as formula (6):

[0102]

[0103] where a and b are functions of the material properties through which the mesons propagate, a represents the ionization-induced energy loss, and b represents the nuclear interaction and pair production, and in the range of energy less than 100 GeV, a = 2.0 MeV cm 2 / g and b = 3.5 x 10 -6 cm 2 / g can be used in numerical calculation. Therefore, the energy loss rate is usually set as a constant, 2.0 MeV cm 2 / g.

[0104] The object opacity can be calculated by the measured muon flux attenuation coefficient through equations (2) to (6).

[0105] Step S30: calculating the density error according to the opacity, and calculating the density of the object according to the density error.

[0106] It is to be noted that ② muon voxel track:

[0107] After the above process, assuming that M sets of two-dimensional radiographic images are taken, the equation as shown in equation (7) is obtained on the basis of equation (1), and each matrix element in the O matrix is the opacity data obtained from the two-dimensional images:

[0108]

[0109] 1) The area where the object to be measured is located is divided into a plurality of (N v ) independent volumes, each independent volume is referred to as a voxel, and each voxel is used as a storage unit to store the initial density of the object and the track information when the muon passes through;

[0110] 2) Each two-dimensional radiographic image is divided into a plurality of independent area measurement values, and the image is divided in the following manner: according to the coordinate position of the muon impact and according to the tangent value of the impact angle of the muon. Each two-dimensional image obtains n m =n x x n y x n tw x n wu independent measurement values, in short, each independent area image contains the position information and angle information of the muon. The impact angle is the angle of the muon projected on the tw and uw plane. As shown in Figure 5 , Figure 5 is a schematic diagram of the twu coordinate system.

[0111] 3) The element in [a] is defined as a k,v , and the element expression is as follows:

[0112]

[0113] where m k is the number of muons in the kth independent area; d is the distance of the lth muon in the kth independent area to pass through voxel v. In short, this element refers to the average value of the path of muons in each independent area to pass through 1 voxel.

[0114] Further, in the embodiment, the calculating the density of the object according to the density error comprises:

[0115] using a joint algebra reconstruction algorithm formula to obtain the density of the object by optimal solution approximation according to the density error; the joint algebra reconstruction algorithm formula is:

[0116]

[0117] wherein, denotes the density after the jth iteration in the vth voxel, is the density error.

[0118] 3. Density solving method:

[0119] In formula (7), the ρ to be inverted is the solution of this set of equations. However, there is a problem in solving this set of equations: usually, the number of inputs is less than the number of unknowns, that is, the sum N m of independent measurements provided by all two-dimensional images is less than the number N v of voxels of the object, so an iterative method needs to be used to solve this problem, and here a joint algebra reconstruction algorithm is used to obtain the required ρ by optimal solution approximation, and the solving method is as follows:

[0120]

[0121] In formula (9), the correction value denotes the density after the jth iteration in the vth voxel.

[0122] Further, in the embodiment, the step S30 comprises:

[0123] splitting the opacity into an independent opacity matrix;

[0124] performing voxel traversal on the muons in the independent opacity matrix to obtain a voxel track;

[0125] calculating a density error according to the voxel track.

[0126] It should be understood that the calculation method of in formula (9) is shown in formula (10):

[0127]

[0128] In formula (10), A is the opacity matrix corresponding to the density vector of the mth group of photographic images in the j-1th iteration, and the calculation formula is shown in formula 3.11; A m,v is the track of the mth group of photographic images at the vth voxel; and wm is a weighting factor considering the statistical accuracy of the mth measurement, and the weight is taken as the square root of the number of muons in the current voxel measurement.

[0129]

[0130] Briefly, the density iteration method is to determine the correction value of the same voxel by using the error of all rays passing through the same voxel at different projection angles.

[0131] The three-dimensional density reconstruction of the detected object can be completed through the above three parts.

[0132] Step S40: comparing whether the density error is less than the minimum error.

[0133] Step S50: if the density error is less than the minimum error, outputting the density of the object.

[0134] In a specific implementation, the density calculation of the object is to obtain the required density by optimal solution approximation through the joint algebra reconstruction algorithm, so that the calculated density is evaluated in the iteration calculation process, and when the density error is less than the minimum error, the obtained density is determined as the optimal solution. If the density error is greater than or equal to the minimum error, the density is updated through the joint algebra reconstruction algorithm.

[0135] In order to verify the performance difference between the muon detector structure of the application and the traditional detector structure, GEANT4 is used to evaluate the performance of the following three detector structures, which are three-layer detection planes containing lead plates, three-layer detection planes without lead plates and traditional two-layer detection planes. The muon detection efficiency, muon rejection rate and gamma particle rejection rate of the three detector structures are compared.

[0136] The calculation formula of the detection efficiency σ is formula (12)

[0137]

[0138] In the formula, N p1 and N p3 respectively represent the number of muons detected by the first layer detection plane and the number of muons detected by the third layer detection plane.

[0139] In order to ensure that the muon screening rate is closer to the real effect, the zenith angle distribution and the energy spectrum of muons are simulated and used, the simulation results are shown in Figure 6 The average value of the zenith angle of muons is 38.23°, and the average energy of muons is 3.99 GeV. Figure 6 The muon particle source simulation diagram is shown in Figure 6 (a) is a muon zenith angle distribution diagram, Figure 6 (b) is a muon energy spectrum distribution diagram.

[0140] The effects of the three schemes are compared as follows, Figure 7 The muon detection efficiency comparison diagram is shown in Figure 8 The gamma particle screening rate comparison diagram is shown in Figure 7 and Figure 8 In the table, 1 represents a 3-layer detection plane detector containing a lead plate; 2 represents a 3-layer detection plane detector without a lead plate, and 3 represents a 2-layer detection plane detector.

[0141] Table 1 Comparison table of performance of detectors with different structures

[0142] Number of detection planes 3 layers (with lead plate) 3 layers 2 layers Muon detection efficiency 50.8％ 51.1％ 71.4％ Muon rejection rate 0.02％ 0 0 Gamma survival rate 1.57％ 72.12％ 88.32％

[0143] According to the comparison results, the muon detection efficiency of the traditional two-layer detection plane structure is about 70%, and the use of a 3-layer detection plane will reduce the detection efficiency to about 50% to some extent; however, the gamma particle screening rate of the two-layer detection plane is only 12%, and the gamma particle screening rate of the three-layer detection plane with a lead plate can reach more than 98%, which indicates that the structure can greatly improve the gamma particle screening rate while not greatly reducing the muon detection efficiency, is very effective in shielding gamma particles, and greatly reduces the influence of background noise interference on imaging accuracy.

[0144] In the embodiment, a new muon detector capable of shielding background noise and a three-dimensional imaging method of combining multiple two-dimensional images are provided. The detector has three layers, and a lead plate is added between the detection planes, which can effectively shield gamma particles in the air, reduce background noise interference, and improve imaging accuracy; the three-dimensional imaging method can have a clearer understanding of the density structure information of the detected object, and increase the reliability of the detection result.

[0145] In addition, an embodiment of the present application also provides a storage medium, and the storage medium stores a three-dimensional photographic imaging program. When the three-dimensional photographic imaging program is executed by a processor, the steps of the three-dimensional photographic imaging method described above are implemented.

[0146] In addition, with reference to Figure 9 , an embodiment of the present application also provides a three-dimensional photographic imaging device, which comprises:

[0147] An acquisition module 10 is configured to acquire the number of muons passing through the object and the number of muons in the sky collected by the muon detector;

[0148] A calculation module 20 is configured to calculate the opacity of the object according to the number of muons passing through the object and the number of muons in the sky.

[0149] The calculation module 20 is further configured to calculate the density error according to the opacity, and calculate the density of the object according to the density error.

[0150] The calculation module 20 is further configured to compare whether the density error is less than a minimum error.

[0151] The calculation module 20 is further configured to output the density of the object if the density error is less than the minimum error.

[0152] Other embodiments or specific implementations of the three-dimensional photographic imaging device described in the present application can refer to the above-mentioned method embodiments, which will not be described here.

[0153] It should be noted that in this paper, the term "includes", "contains" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or system including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or includes elements inherent to such process, method, article or system. Without more limitations, the element defined by the statement "includes a" does not exclude the presence of another identical element in the process, method, article or system including the element.

[0154] The above-mentioned embodiment numbers of the present application are only for description, and do not represent the advantages and disadvantages of the embodiments. In the unit claims of several devices, several of these devices can be embodied by the same hardware item. The use of the words first, second, and third does not represent any order, and these words can be interpreted as identifiers.

[0155] Through the above description of the embodiments, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be realized by software and the necessary general hardware platform, of course, they can also be realized by hardware, but in many cases, the former is a better embodiment. Based on such understanding, the technical solutions of the present application can be embodied in the form of a software product, which is stored in a storage medium (such as a magnetic disk, an optical disk), and includes a plurality of instructions for making a terminal device (which can be a mobile phone, a computer, or a network device, etc.) execute the methods described in the embodiments of the present application.

[0156] The above merely describes the preferred embodiments of the present application, and is not intended to limit the patent scope of the present application, and any equivalent structure or equivalent process conversion, or direct or indirect application in other related technical fields, which are made by using the content of the present application specification and drawings, are also included in the patent protection scope of the present application.

Claims

1. A three-dimensional photographic imaging method applied to a muon detector, characterized in that, The muon detector comprises: three parallel detection planes and a lead plate, as well as three acquisition plates; The lead plate is positioned between the second and third detection planes. The detection plane is composed of a triangular prism scintillator and a corresponding photoelectric sensor; The photoelectric sensor is connected to the acquisition board; The acquisition board is used to collect the number of muons passing through the object and the number of muons in the sky; The three-dimensional photographic imaging method includes: Obtain the number of muons passing through the object and the number of muons in the sky collected by the muon detector; The opacity of the object is calculated based on the number of muons passing through the object and the number of muons in the sky; Calculate the density error based on the opacity, and calculate the density of the object based on the density error; Compare whether the density error is less than the minimum error; If the density error is less than the minimum error, then the density of the object is output; The step of calculating the density error based on the opacity includes: The opacity is split into independent opacity matrices; Voxel traversal is performed on the muons in the independent opacity matrix to obtain voxel tracks; The density error is calculated based on the voxel tracks.

2. The three-dimensional photographic imaging method as described in claim 1, characterized in that, The muon detector also includes a housing and a rotatable base; The three-layer detection plane and lead plate are encapsulated within the housing, which is made of light-proof aluminum. The outer casing is mounted on the rotatable base, which rotates to allow the muon detector to adjust to different angles to detect objects.

3. The three-dimensional photographic imaging method as described in claim 2, characterized in that, The calculation of the object's opacity based on the number of muons passing through the object and the number of sky muons includes: Calculate the muon flux attenuation coefficient passing through the object based on the number of muons passing through the object and the number of muons in the sky; Calculate the minimum energy required to pass through an object based on the muon flux attenuation coefficient. The opacity of the object is calculated based on the minimum energy required to pass through it.

4. The three-dimensional photographic imaging method as described in claim 1, characterized in that, Before performing voxel traversal on the muons in the independent opacity matrix to obtain voxel tracks, the method further includes: Establish a density structure model of the object and set the initial density; The object density structure model is decomposed to obtain the object's voxel matrix; Accordingly, the step of performing voxel traversal on the muons in the independent opacity matrix to obtain voxel tracks specifically includes: Based on the voxel matrix, voxel traversal is performed on the muons in the independent opacity matrix to obtain voxel tracks.

5. The three-dimensional photographic imaging method as described in claim 1, characterized in that, The step of calculating the density of the object based on the density error includes: Based on the density error, the density of the object is approximated by the optimal solution using the joint algebraic reconstruction algorithm formula; the joint algebraic reconstruction algorithm formula is: ； in, This represents the density after the j-th iteration in the v-th voxel. The density error is mentioned above.

6. The three-dimensional photographic imaging method according to any one of claims 1 to 5, characterized in that, Before obtaining the number of muons passing through objects and the number of sky muons collected by the muon detector, the method further includes: The number of channels through which the muons pass is calculated based on the signals collected by the acquisition board in the muon detector. Determine whether the number of channels is a preset value; If the number of channels is a preset value, they are merged and stored as a muon event.

7. A three-dimensional photographic imaging device, applied to a muon detector, characterized in that, The muon detector comprises: three parallel detection planes and a lead plate, as well as three acquisition plates; The lead plate is positioned between the second and third detection planes. The detection plane is composed of a triangular prism scintillator and a corresponding photoelectric sensor; The photoelectric sensor is connected to the acquisition board; The acquisition board is used to collect the number of muons passing through the object and the number of muons in the sky; The three-dimensional photographic imaging device includes: The acquisition module is used to acquire the number of muons passing through the object and the number of muons in the sky collected by the muon detector; A calculation module is used to calculate the opacity of an object based on the number of muons passing through the object and the number of sky muons; The calculation module is also used to calculate the density error based on the opacity, and to calculate the density of the object based on the density error; The calculation module is also used to compare whether the density error is less than the minimum error; The calculation module is also used to output the density of the object if the density error is less than the minimum error; The calculation module is further configured to split the opacity into independent opacity matrices; perform voxel traversal on the muons in the independent opacity matrices to obtain voxel tracks; and calculate the density error based on the voxel tracks.

8. A muon detector, characterized in that, The muon detector stores a three-dimensional photography imaging program, which, when executed by a processor, implements the steps of the three-dimensional photography imaging method as described in any one of claims 1 to 6.

9. A storage medium, characterized in that, The storage medium stores a three-dimensional photographic imaging program, which, when executed by a processor, implements the steps of the three-dimensional photographic imaging method as described in any one of claims 1 to 6.

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