Multistage scanning imaging system and method based on diffraction imaging

Abstract

The invention provides a multistage scanning imaging system and method based on diffraction imaging, and relates to the technical field of radiation imaging. The system comprises a first transmission scanning stage and a second transmission scanning stage, the first transmission scanning stage comprises a first ray source and a first detection assembly, the first ray source is used for emitting a first ray for scanning an inspected object, and the first detection assembly is used for detecting a first transmission ray transmitted by the inspected object to generate a first detection signal; the signal processing device is configured to process the first detection signal to generate a transmission image, and obtain an object of interest in the inspected object according to the transmission image; the second diffraction scanning stage comprises a second ray source and a second detection assembly, the second ray source is used for emitting second rays for scanning the inspected object, and the second detection assembly is used for detecting scattered rays scattered by at least the interested object so as to generate a second detection signal; the signal processing device is configured to process the second detection signal to generate a diffraction image, and obtain material information of the object of interest according to the diffraction image.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of radiation scanning, and more particularly, to a multi-stage scanning imaging system and method based on diffraction imaging. BACKGROUND

[0002] X-ray diffraction (XRD) technology takes advantage of the wave characteristics of X-rays. The lattice structure of molecular order provides a natural diffraction grating. X-rays passing through the ordered molecular structure will achieve coherent reinforcement in a specific direction. Different molecular structures of objects are different, and the coherent superposition angle is also different, which is reflected in the different energy spectrum shapes. These energy spectrum shapes are like "fingerprints" and have very strong specificity, so the material resolution is very high, effectively making up for the shortcomings of transmission imaging. In the field of XRD scanning imaging, how to improve the utilization rate of X-rays and improve the spatial resolution is one of the continuous concerns of researchers.

[0003] It should be noted that the above information disclosed in this part is only for understanding the background of the inventive concept of the present disclosure, and therefore, the above information can include information that does not constitute prior art. SUMMARY

[0004] In view of at least one aspect of the above technical problems, embodiments of the present disclosure provide a multi-stage scanning imaging system based on diffraction imaging, comprising: a first transmission scanning stage comprising a first radiation source and a first detection assembly, the first radiation source being configured to emit first radiation for scanning an object under examination, and the first detection assembly being configured to detect first transmission radiation transmitted through the object under examination to generate a first detection signal; a signal processing device electrically connected to the first detection assembly, the signal processing device being configured to process the first detection signal to generate a transmission image, and to obtain an object of interest in the object under examination according to the transmission image; and a second diffraction scanning stage spaced apart from the first transmission scanning stage along a first direction, the second diffraction scanning stage comprising a second radiation source and a second detection assembly, the second radiation source being configured to emit second radiation for scanning the object under examination, and the second detection assembly being configured to detect scattered radiation scattered by at least the object of interest in the object under examination to generate a second detection signal, wherein the signal processing device is electrically connected to the second detection assembly, and the signal processing device is further configured to process the second detection signal to generate a diffraction image, and to obtain material information of the object of interest according to the diffraction image.

[0005] Exemplarily, the second detection assembly comprises at least one detection module, and each detection module comprises: an encoding plate configured to encode the scattered rays to form encoded scattered rays; a post-collimator configured to block rays scattered by the object under examination and having a first scattering angle greater than a preset scattering angle threshold; and a diffraction detector configured to detect the encoded scattered rays, wherein the encoded scattered rays are rays scattered by at least the object of interest in the object under examination and having a second scattering angle less than or equal to the preset scattering angle threshold.

[0006] Exemplarily, the second ray source and the second detection assembly are arranged on opposite sides of the object under examination along a second direction perpendicular to the first direction, and in the second direction, the encoding plate, the post-collimator and the diffraction detector are arranged in a direction away from the second ray source in sequence.

[0007] Exemplarily, the second detection assembly further comprises a transmission detector configured to detect second transmission rays transmitted by the object under examination to generate a third detection signal, and the signal processing device is further configured to: acquire attenuation characteristic information of at least the object of interest in the object under examination according to the third detection signal; and correct the second detection signal by using the attenuation characteristic information in the process of processing the second detection signal to generate a diffraction image.

[0008] Exemplarily, in the cone angle direction, the transmission detector is located on the path of the main beam of the second rays, and the detection module is offset relative to the path of the main beam of the second rays by a predetermined offset angle, and the predetermined offset angle is less than or equal to the preset scattering angle threshold.

[0009] Exemplarily, in the fan angle direction, the coverage range of the diffraction detector is consistent with the coverage range of the transmission detector.

[0010] Exemplarily, the second ray source comprises a target point for emitting rays, and the second detection assembly comprises a plurality of detection modules, and in the fan angle direction, the plurality of detection modules are arranged centripetally relative to the target point.

[0011] Exemplarily, in the fan angle direction, the plurality of detection modules are independently arranged, and the diffraction detectors of the plurality of detection modules respectively comprise detection surfaces, and for each of the plurality of detection modules, the connecting line of the detection surface and the target point is perpendicular to the detection surface.

[0012] Exemplarily, the rear collimator comprises collimating leaves, and two adjacent detection modules of the plurality of detection modules share a collimating leaf; and in the fan angle direction, the collimating leaves of the plurality of detection modules extend through the target point.

[0013] Exemplarily, the target point of the second radiation source and the detection module are movable along a third direction, and the third direction is perpendicular to the first direction and the second direction respectively; or the second detection assembly comprises a plurality of detection modules, the plurality of detection modules are arranged along the third direction, and the target point is movable along the third direction, and the third direction is perpendicular to the first direction and the second direction respectively; or the second detection assembly comprises a plurality of detection modules, the plurality of detection modules are arranged along the third direction, and the second radiation source comprises a plurality of target points, the plurality of target points are arranged along the third direction, and the third direction is perpendicular to the first direction and the second direction respectively.

[0014] Exemplarily, the second detection assembly comprises a plurality of rows of detection modules; in the cone angle direction, the plurality of rows of detection modules are arranged at intervals along the first direction; and / or in the cone angle direction, at least one row of detection modules and at least another row of detection modules are respectively located on two sides of the transmission detector.

[0015] Exemplarily, the diffraction detector of the detection module comprises a detection surface, and the second direction is perpendicular to the detection surface; or the diffraction detector of the detection module comprises a detection surface, and an extension line perpendicular to the detection surface and passing through the center of the detection surface passes through the object of interest.

[0016] Exemplarily, the second detection assembly comprises a plurality of transmission detectors and a plurality of diffraction detectors, in the cone angle direction, the plurality of transmission detectors are arranged at intervals, the plurality of diffraction detectors are arranged at intervals, and the plurality of transmission detectors and the plurality of diffraction detectors are arranged alternately.

[0017] Exemplarily, the rear collimator comprises a shielding cylinder, the encoding plate is located on the side of the shielding cylinder close to the second radiation source, and the diffraction detector is located on the side of the shielding cylinder away from the second radiation source.

[0018] Exemplarily, a plurality of first holes are formed in the encoding plate, the plurality of first holes are used for the scattered radiation to pass through, and the plurality of first holes form a predetermined first encoding pattern in a projection plane, and the projection plane is a plane determined by the intersection of the first direction and the third direction.

[0019] Exemplarily, the second diffraction scanning stage further comprises a front collimator, the front collimator comprises a plurality of second holes, the plurality of second holes are used for the second radiation to pass through, the plurality of second holes form a predetermined second encoding pattern in a projection plane, and the projection plane is a plane determined by the intersection of the first direction and the third direction.

[0020] In another aspect, a multi-stage scanning imaging method based on diffraction imaging is provided, comprising: scanning a subject object by using a first transmission scanning stage to obtain a transmission image of the subject object; obtaining an object of interest in the subject object based on the transmission image; performing diffraction scanning on at least the object of interest in the subject object by using a second diffraction scanning stage to obtain a diffraction image of the object of interest; obtaining material information of the object of interest based on the diffraction image of the object of interest; and determining the object of interest as a target object in response to the material information of the object of interest.

[0021] Exemplarily, the method further comprises: kth transmission scanning: adjusting the scanning parameter of the first transmission scanning stage based on the material information of the object of interest obtained in the previous time, scanning the subject object by using the adjusted first transmission scanning stage, and obtaining the transmission image of the subject object for the kth time, wherein the transmission image obtained for the kth time is an image corrected based on the material information of the object of interest obtained in the previous time, and k is a positive integer greater than 1; kth transmission result obtaining: obtaining the object of interest in the subject object for the kth time according to the transmission image obtained for the kth time; kth diffraction scanning: adjusting the scanning parameter and the reconstruction position of the second diffraction scanning stage according to the object of interest obtained for the kth time, scanning the subject object by using the adjusted second diffraction scanning stage, and obtaining the diffraction image of the object of interest for the kth time; kth diffraction result obtaining: obtaining the material information of the object of interest for the kth time based on the diffraction image of the object of interest obtained for the kth time; and iteratively performing the kth transmission scanning, the kth transmission result obtaining, the kth diffraction scanning and the kth diffraction result obtaining as k increases until an iteration termination condition is met.

[0022] Exemplarily, the obtaining of the object of interest in the subject object based on the transmission image comprises: obtaining contour information of the object of interest in the subject object based on the transmission image; and the obtaining of the material information of the object of interest based on the diffraction image of the object of interest comprises: merging and averaging a plurality of voxels or pixels of the same material in the diffraction image based on the contour information of the object of interest; and obtaining the material information of the object of interest according to the average value. BRIEF DESCRIPTION OF DRAWINGS

[0023] The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of embodiments of the present disclosure taken in conjunction with the accompanying drawings, in which:

[0024] Figure 1 A schematic diagram schematically showing the projection relationship between a ray source, a subject object and a detector;

[0025] Figure 2 Structure diagram of a multi-stage scanning imaging system based on diffraction imaging according to some example embodiments of the present disclosure;

[0026] Figure 3 Workflow diagram of a multi-stage scanning imaging system based on diffraction imaging provided by embodiments of the present disclosure;

[0027] Figure 4A Cross-sectional diagram of a detection module provided by embodiments of the present disclosure;

[0028] Figure 4B Structure diagram of an encoding plate of a detection module provided by embodiments of the present disclosure;

[0029] Figure 5A Cross-sectional diagram of a first embodiment of a second diffraction scanning stage provided by embodiments of the present disclosure, taken along a cone angle main beam surface;

[0030] Figure 5B Cross-sectional diagram of a second embodiment of a second diffraction scanning stage provided by embodiments of the present disclosure, taken along a fan angle main beam surface;

[0031] Figure 5C Cross-sectional diagram of a third embodiment of a second diffraction scanning stage provided by embodiments of the present disclosure, taken along a fan angle main beam surface;

[0032] Figure 5D Cross-sectional diagram of a fourth embodiment of a second diffraction scanning stage provided by embodiments of the present disclosure, taken along a fan angle main beam surface;

[0033] Figure 5E Cross-sectional diagram of a fifth embodiment of a second diffraction scanning stage provided by embodiments of the present disclosure, taken along a fan angle main beam surface;

[0034] Figure 5F Cross-sectional diagram of a sixth embodiment of a second diffraction scanning stage provided by embodiments of the present disclosure, taken along a fan angle main beam surface;

[0035] Figure 5G Cross-sectional diagram of a seventh embodiment of a second diffraction scanning stage provided by embodiments of the present disclosure, taken along a cone angle main beam surface;

[0036] Figure 5H Cross-sectional diagram of an eighth embodiment of a second diffraction scanning stage provided by embodiments of the present disclosure, taken along a cone angle main beam surface;

[0037] Figure 5I Cross-sectional diagram of a ninth embodiment of a second diffraction scanning stage provided by embodiments of the present disclosure, taken along a cone angle main beam surface;

[0038] Figure 6is a schematic diagram of an encoding structure of a front collimator provided by an embodiment of the present disclosure;

[0039] Figure 7 is a schematic diagram of an arrangement of a first embodiment of a second ray source and a detection module of a second diffraction scanning stage provided by an embodiment of the present disclosure;

[0040] Figure 8 is a flowchart of a multi-stage scanning imaging method based on diffraction imaging provided by an embodiment of the present disclosure;

[0041] Figure 9 is a flowchart of another embodiment of a multi-stage scanning imaging method based on diffraction imaging provided by an embodiment of the present disclosure. DETAILED DESCRIPTION

[0042] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood, however, that the description is merely exemplary and is not intended to limit the scope of the present disclosure. In the following detailed description of the embodiments of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present disclosure. However, it would be apparent to those skilled in the art that the embodiments of the present disclosure can be practiced without these specific details. In other instances, well-known structures and methods are not described in detail in order to avoid obscuring the concepts of the present disclosure.

[0043] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the term "includes" and tautological expressions thereof, such as "including," means the inclusion of but not limited to, but also encompassing or additional items or components.

[0044] All terms used herein, including technical and scientific terms, have the same meanings as those generally understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having meanings that are consistent with the context of the present description, and should not be interpreted in an idealized or excessively formal manner.

[0045] In the case of using expressions similar to "at least one of A, B, and C, etc.", it should generally be interpreted to include at least one of each item enumerated, but not limited to, in addition to including each of the items listed individually, including combinations thereof, and / or the like.

[0046] It should be noted that, in this document, computed tomography (also referred to as CT) imaging refers to the process of using the analog signals received by a detector after a subject is tomographically scanned by a radiation source to form digital signals, using an electronic computer to calculate the attenuation coefficient of each pixel, and then reconstructing an image, so that the tomographic structure of each part of the subject can be displayed.

[0047] X-ray DR imaging (Digital Radiography) refers to a single-view, two-dimensional projection imaging technique. It uses X-rays to penetrate an object and then directly receives the transmitted signal by a digital detector and converts it into a digital image. Specifically, X-rays can pass through an object from one direction and be captured by a detector on the other side. Because different materials absorb X-rays to different extents, the resulting image is based on these differences. It should be understood that, in X-ray DR imaging, since all information is obtained from a single angle, a two-dimensional image is obtained, which can be referred to as a two-dimensional projection image in this document. In this two-dimensional projection image, the structures inside the object along the output direction of the rays are superimposed together.

[0048] X-ray diffraction (XRD) technology is based on the coherent scattering (i.e., Rayleigh scattering) signal generated when X-rays interact with matter to identify the molecular structure or crystal structure information of the object being inspected. For example, when a beam of X-rays is incident on a crystalline material with a periodic lattice arrangement, the incident photons will undergo elastic interaction with the electrons in the material, exciting the atoms and then de-exciting, releasing scattered photons with the same energy but different directions. Due to the highly ordered arrangement of atoms inside the crystal, these scattered photons will undergo constructive interference under certain geometric conditions, resulting in a significant increase in intensity in certain specific directions, which is the phenomenon of X-ray diffraction. Using this X-ray diffraction technique, material identification can be performed, and its application in imaging systems and imaging methods can be expressed as X-ray diffraction scanning imaging systems and methods.

[0049] Reference Figure 1 In an embodiment of the present disclosure, the radiation (e.g., X-rays) emitted by the radiation source 1 is incident on the object being inspected 6, for example, the X-rays are incident on a spatial position P1 in the object being inspected 6, the material at the spatial position P1 interacts with the incident X-rays, Rayleigh scattering occurs, and the scattered radiation is detected by the detector 2. The spatial point P1 on the object being inspected 6 is imaged to the image point P2 on the detector 2 by the radiation source 1. In forward projection (also referred to as forward projection), the voxel value of the spatial point on the object being inspected 6 is known, and the pixel value of the image point on the detector 2 is calculated. In back projection (also referred to as back projection), the pixel value of the image point on the detector 2 is known, and the voxel value of the spatial point on the object being inspected 6 is calculated.

[0050] It should be understood that scattered photons undergo constructive interference under specific geometric conditions, resulting in significantly enhanced diffraction peaks in certain directions. (Refer to reference...) Figure 1 In XRD-based diffraction imaging systems, diffraction behavior follows Bragg's law, mathematically expressed as: 2d sin(θ / 2) = nλ, where d represents the interplanar spacing of the crystal, θ is the angle between the incident and scattered X-rays (i.e., the scattering angle), λ is the wavelength of the incident X-ray, and n is any positive integer. This formula indicates that for a given crystalline material, the interplanar spacing d is fixed. Therefore, only when the wavelength λ of the incident X-ray and the scattering angle θ satisfy the above relationship will a distinct diffraction peak be observed on the detector. Different substances possess different combinations of interplanar spacings due to their unique crystal structures, thus producing their own unique diffraction patterns. These patterns are like the "fingerprint" or "DNA" of a substance, possessing extremely high specificity and distinguishability.

[0051] Therefore, in an XRD-based diffraction imaging system, the voxel value of a spatial point on the object under inspection 6 can be obtained from the pixel value of the image point on the detector 2 through the image reconstruction algorithm. Moreover, based on different diffraction peak information, the material composition at the spatial point on the object under inspection 6 can also be identified.

[0052] In practical applications, Bragg's formula can be combined with the photon energy formula E = hc / λ to obtain an expression with energy E and scattering angle θ as variables. Based on this, X-ray diffraction detection technology can be divided into two main modes: Angular dispersive X-ray diffraction (ADXRD) and Energy dispersive X-ray diffraction (EDXRD). Angular dispersive X-ray diffraction uses a monochromatic light source and measures the light intensity at different angles after illuminating an object, thus obtaining an angle-intensity spectrum. According to Bragg's formula, with a fixed energy, the displacement and angle are in one-to-one correspondence, so the displacement-intensity spectrum can be calculated. Angular dispersive X-ray diffraction measures light intensity, so an energy integrating detector can meet the requirements. Energy dispersive X-ray diffraction uses a continuous spectrum light source and measures the energy-intensity distribution at a specific angle. Similarly, when the angle is fixed, energy and displacement are in one-to-one correspondence, so the displacement-intensity spectrum can be calculated. The difference between EDXRD and ADXRD lies in their scanning time. EDXRD has a shorter scan time, allowing the diffraction energy spectrum of the scanned object to be obtained in a single exposure. This results in higher requirements for the detector, necessitating the use of an energy spectrum detector. ADXRD, on the other hand, can utilize an energy integration detector. The disadvantages of EDXRD include lower energy resolution and higher noise levels in the measured diffraction spectrum. ADXRD is more commonly used in laboratory research, while EDXRD is frequently used in security inspections.

[0053] However, the inventors discovered through research that although XRD technology exists, its application in existing security inspection technologies still presents numerous problems. On one hand, while traditional security CT scans can provide three-dimensional tomographic images of objects, they are based on the principle of dual-energy X-ray transmission and primarily rely on the correlation between the ratio of high and low energy attenuation coefficients and the atomic number to determine the effective atomic number and electron density of an object. Because the constituent elements (C, H, O, N) of many addictive substances and explosive materials are very similar to those of everyday safe items, their effective atomic numbers and electron densities are extremely similar, making it difficult for existing technologies to accurately distinguish between everyday items and contraband, thus increasing the difficulty of detection.

[0054] On the other hand, while XRD technology compensates for the shortcomings of transmission imaging by utilizing molecular fingerprint features, it detects scattered signals, which are extremely weak compared to the main transmission beam. To obtain effective spatial resolution, existing technologies typically employ long collimators (such as pinhole or slit collimators) to strictly confine the X-rays. This approach results in a single pixel acquiring only a very small amount of X-ray signal within a single time period, leading to extremely low X-ray utilization. This directly results in poor system signal-to-noise ratio, limited energy resolution, and excessively long exposure time required to obtain a resolvable energy spectrum, failing to meet the high-throughput requirements for rapid scanning of luggage and parcels in practical security inspection scenarios.

[0055] To address at least one aspect of the aforementioned problems, embodiments of this disclosure provide a multi-level scanning imaging system and method based on diffraction imaging. The embodiments of this disclosure will be described in detail below using an imaging system for objects such as luggage and inspected objects as an example. It should be understood that the embodiments of this disclosure are not limited to imaging scenarios for objects such as luggage and inspected objects; they can be applied to various scanning imaging scenarios. For example, they can be applied to scanning imaging scenarios involving various different inspection objects, including but not limited to vehicle scanning imaging, luggage / inspected object scanning imaging, human or animal scanning imaging, organ / tissue scanning imaging, small object scanning imaging, and large object scanning imaging such as containers. It should be noted that the description of scanning imaging scenarios herein is not exhaustive, and the exemplary descriptions below should not be construed as limiting the scope of protection of this disclosure.

[0056] Reference Figure 2The diffraction imaging system according to embodiments of this disclosure may include multiple scanning stages (e.g., first scanning stage A, second scanning stage B, ...), a transport mechanism 8, a control device 7, and a signal processing device 5. For example, the scanning stage may include an X-ray source and a detection component. To achieve comprehensive detection of the object 6 under inspection, the scanning stages are typically arranged sequentially at intervals along the transport direction of the transport mechanism 8 (e.g., the z-axis direction shown in the figure), thereby forming a multi-stage inspection channel. Each scanning stage can be configured independently in physical structure. For example, the scanning stage may include an X-ray source and a transmission detection component for acquiring the transmission attenuation image of the object; or, the scanning stage may also include an X-ray source and a diffraction detection component for acquiring the scattering and diffraction signal of the object. In some embodiments, the first scanning stage A and the second scanning stage B may be configured as the same type of scanning module to increase the sampling rate, or they may be configured as different types of scanning modules to obtain complementary physical information. The transport mechanism 8 is used to carry the object 6 under inspection and, driven by the control device 7, sequentially feeds the object 6 under inspection into the scanning areas of the first scanning stage A and the second scanning stage B along a predetermined direction (the positive z-axis direction shown by the arrow in the figure). Control device 7 is electrically connected to the conveying mechanism 8, the first scanning stage A, and the second scanning stage B, respectively, to achieve overall coordinated control of the system. Control device 7 can control the beam emission timing of the X-ray source in each scanning stage and the data acquisition window of the detection components based on the operating speed or position sensor feedback signal of the conveying mechanism 8, ensuring that scanning is triggered when the object under inspection 6 reaches the corresponding position. Signal processing device 5 is electrically connected to the detection components of each scanning stage (such as the first scanning stage A and the second scanning stage B). When the system operates in conjunction, when the object under inspection 6 passes through the first scanning stage A, the first detection signal generated by the first scanning stage A is transmitted to signal processing device 5; subsequently, when the object under inspection 6 continues to move and passes through the second scanning stage B, the second detection signal generated by the second scanning stage B is also transmitted to signal processing device 5. Signal processing device 5 is configured to process, reconstruct, or fuse multiple sets of received detection signals. This multi-level scanning architecture design allows the system to acquire multi-dimensional information (such as density information, atomic number information, or crystal structure information) of the object under inspection 6 in a single conveying process, thereby providing richer data support for subsequent material identification and hazardous material determination.

[0057] It should be noted that, for ease of description, this paper establishes a coordinate system xyz based on a first direction z, a second direction x, and a third direction y. For example, the first direction z can be parallel to the direction of motion of the object being inspected. Figure 2 The left and right directions; the third direction y can be parallel to the emission direction of the rays in a scan level, that is, the direction from the ray source to the detector, for example. Figure 2The vertical direction; the second direction x can intersect with the third direction y and the first direction z respectively, for example. Figure 2 The forward and backward directions in the coordinate system, for example, any two of the first direction z, the second direction x, and the third direction y, are perpendicular to each other. It should be understood that the coordinate system xyz established based on the first direction z, the second direction x, and the third direction y is for ease of description only and is not intended to limit the embodiments of this disclosure. Based on the definition of the coordinate system xyz, for ease of description, fan angles and cone angles can also be established. In this document, a fan angle refers to the angle subtended by the X-ray beam emitted from the X-ray source in the plane (i.e., the xy plane) defined by the second direction x and the third direction y. Accordingly, the fan angle direction refers to the direction in which the X-ray beam spreads in the xy plane, corresponding to the width direction of the object being inspected or the cross-sectional coverage of the scanning channel. A cone angle refers to the angle subtended by the X-ray beam emitted from the X-ray source in the plane (i.e., the yz plane) defined by the first direction z and the third direction y. Accordingly, the cone angle direction refers to the direction in which the X-ray beam spreads in the yz plane, corresponding to the direction of movement of the object being inspected or the longitudinal coverage of the scanning channel. It should be understood that the above definitions of angle and direction are intended to clearly describe the spatial arrangement of the detection components and their geometric relationship with the scanned cross section of the object being inspected, so as to enable those skilled in the art to understand the technical solution.

[0058] like Figure 3 As shown, in embodiments of this disclosure, the diffraction imaging system may include at least two scanning stages, such as a first scanning stage A and a second scanning stage B, with different scanning stages capable of scanning the object 6 under inspection from different perspectives. Figure 2In this context, A and B can represent the principal beam planes in the fan-angle directions of two scanning stages, respectively. That is, in the embodiments of this disclosure, a multi-stage scanning imaging system based on diffraction imaging is proposed. This system includes: a first transmission scanning stage (e.g., first scanning stage A), comprising a first X-ray source and a first detection component. The first X-ray source is used to emit a first X-ray to scan an object 6 under inspection, and the first detection component is used to detect the first transmitted X-ray transmitted through the object 6 under inspection to generate a first detection signal; a signal processing device 5, electrically connected to the first detection component, configured to: process the first detection signal to generate a transmission image, and obtain an object of interest in the object 6 under inspection based on the transmission image; and a second diffraction stage. The scanning stage (e.g., the first scanning stage B), the second diffraction scanning stage, and the first transmission scanning stage are arranged at intervals along a first direction z. The second diffraction scanning stage includes a second X-ray source 10 and a second detection component 30. The second X-ray source 10 is used to emit a second X-ray to scan the object under inspection 6. The second detection component 30 is used to detect scattered X-rays scattered by at least the object of interest in the object under inspection 6 to generate a second detection signal. The signal processing device 5 is electrically connected to the second detection component 30. The signal processing device 5 is further configured to process the second detection signal to generate a diffraction image and obtain material information of the object of interest based on the diffraction image.

[0059] Specifically, firstly, while single XRD imaging systems can provide molecular structure information of matter using the wave characteristics and lattice diffraction principles of X-rays with extremely high specificity, they detect scattered signals, which are significantly weaker and have higher background noise compared to the transmitted main beam. Obtaining a sufficiently clear and resolvable diffraction spectrum typically requires a long signal integration time. Relying solely on the XRD system for omnidirectional blind or gridded scanning of the entire object being inspected would result in excessively long overall inspection times, failing to meet the high-throughput and rapid inspection requirements of security checkpoints such as airports and train stations. Furthermore, while traditional transmission imaging (such as CT) offers fast scanning speeds, it relies solely on effective atomic number and electron density for identification, making it difficult to accurately distinguish between contraband such as drugs and explosives and everyday organic matter with similar atomic numbers, resulting in high false alarm and false negative rates. The multi-level scanning imaging system based on diffraction imaging employs a cascaded collaborative mode of "first-level transmission security inspection + second-level diffraction security inspection." First, the first transmission scanning level (such as a CT scan) performs a rapid three-dimensional tomographic scan of the object being inspected (6), generating a high-resolution transmission image. Based on the density and atomic number information in this transmission image, it quickly screens and locates the "object of interest" (POI) and its spatial coordinates for suspected contraband. When the object being inspected (6) is transmitted to the second diffraction scanning level, based on the previously located spatial coordinates, the second X-ray source (10) and the second detection component (30) are controlled to perform focused scanning or sampling only on the local area where the PPO is located. This method avoids unnecessary full diffraction scanning of the entire object being inspected (6), thus significantly shortening the XRD detection time. Through this hierarchical processing, while ensuring the overall security inspection pass rate, the high specificity of XRD's "fingerprint" recognition capability allows for precise re-inspection of difficult areas in the transmission imaging, achieving a complementary advantage of "rapid detection and location" and "precise detection and characterization," effectively solving the problem of difficulty in achieving both efficiency and accuracy in existing technologies.

[0060] In some exemplary embodiments, multiple first transmission scanning stages and / or multiple second diffraction scanning stages with different scanning angles can be arranged at intervals along the first direction z, that is, the multiple first transmission scanning stages and / or multiple second diffraction scanning stages are positioned differently in the first direction z. For example, the first transmission scanning stages and multiple second diffraction scanning stages can be arranged at intervals along the first direction z, and the object 6 being inspected can move along the first direction z.

[0061] It should be noted that, in the illustrated example, one first transmission scanning stage and one second diffraction scanning stage are shown. The multi-level scanning imaging system based on diffraction imaging provided in this disclosure embodiment may include more than one first transmission scanning stage, that is, more than two first transmission scanning stages. Each first transmission scanning stage can scan the object 6 under inspection from different viewing angles to obtain first detection signals obtained from different viewing angles. The multi-level scanning imaging system based on diffraction imaging provided in this disclosure embodiment may include more than one second diffraction scanning stage, that is, more than two second diffraction scanning stages. Each second diffraction scanning stage can scan the object 6 under inspection from different viewing angles to obtain second detection signals obtained from different viewing angles.

[0062] In the following description, for ease of description, the first transmission scan stage and the second diffraction scan stage will be described as a first transmission scan stage and a second diffraction scan stage. It should be understood that this description is merely illustrative of embodiments of the present disclosure and is not intended to limit the embodiments of the present disclosure.

[0063] Reference Figure 4A As shown, in some exemplary embodiments, the second detection component 30 includes at least one detection module 300, which includes: an encoding plate 310 for encoding scattered rays to form encoded scattered rays; a post-collimator 340 for blocking rays scattered by the object under inspection 6 with a first scattering angle, wherein the first scattering angle is greater than a preset scattering angle threshold; and a diffraction detector 330 for detecting the encoded scattered rays, wherein the encoded scattered rays are rays scattered by at least one object of interest in the object under inspection 6 with a second scattering angle, wherein the second scattering angle is less than or equal to a preset scattering angle threshold. In some specific embodiments, the detection module 300 adopts a combination structure of "encoding plate 310 + post-collimator 340 + diffraction detector 330" to solve the problem of insufficient throughput in traditional pinhole imaging; refer to the attached figure. Figure 4BAs shown, the encoding plate 310 is not a completely transparent or completely opaque plate, but rather a plate of shielding material with high X-ray absorption (i.e., the white background in the figure, such as a lead or tungsten plate) with multiple tiny through-holes (i.e., the black dotted areas in the figure) formed according to specific mathematical rules (such as a MURA array or a random array). These black dotted through-holes allow scattered rays in specific directions to pass through, while the white background blocks the rays. In this way, the scattered signal from the object of interest is not directly projected onto the diffraction detector 330, but is modulated by the encoding plate 310 to form an encoded projection carrying spatial and spectral information of the object. The post-collimator 340 acts as a field stop, strictly limiting the angle range of X-rays entering the detection module 300. It filters out large-angle background scattering noise, ensuring that only small-angle diffracted rays carrying effective material information, typically with scattering angles within 10 degrees, reach the subsequent diffraction detector 330. This provides a clean physical environment for high signal-to-noise ratio signal acquisition. The post-collimator 340 can be located between the object under inspection 6 and the diffraction detector 330, adjacent to or integrated into the incident surface of the diffraction detector 330. The post-collimator 340 may include multiple collimators 341, for example, thin sheets of high-absorbing material (e.g., lead or tungsten sheets), forming a honeycomb or multi-slit structure, allowing only X-rays with incident directions within a preset scattering angle threshold range to pass through. The diffraction detector 330 receives the coded scattered rays filtered by the post-collimator 340 and converts them into a processable electrical signal. The diffraction detector 330 can be an energy-resolved photon counting detector, such as a pixelated array made of semiconductor materials such as cadmium zinc telluride (CZT), mercury cadmium telluride (HgI2), or silicon drift detector (SDD). Such detectors can not only record the spatial position information of incident photons, but also accurately measure the energy of each photon, thereby outputting a diffraction energy spectrum in intensity-energy form.

[0064] like Figure 5AAs shown, in some exemplary embodiments, the second X-ray source 10 and the second detection assembly 30 are positioned on opposite sides of the object to be inspected along a second direction y, which is perpendicular to the first direction z. Along the second direction y, the encoding plate 310, the rear collimator 340, and the diffraction detector 330 are arranged sequentially away from the second X-ray source 10. In some specific embodiments, this arrangement along the second direction y constructs a forward diffraction imaging optical path based on transmission geometry. The second X-ray source 10 is located on one side of the object 6 to be inspected, while the second detection assembly 30 is located on the other side. Along this path, X-rays first penetrate the object 6 to be inspected and are scattered, with the resulting scattered rays continuing to propagate forward. At this point, the internal arrangement logic of the second detection assembly 30 is crucial: the scattered rays first reach the encoding plate 310 at the very front for spatial modulation; the modulated rays pass through the region of the rear collimator 340 in the middle (during which stray light is absorbed); finally, the filtered and modulated "encoded scattered rays" are projected onto the detection surface 311 of the diffraction detector 330 located at the very back. This physical sequence of "source-object-encoding-tube-detection" ensures that the diffraction detector 330 receives the transmission direction signal after it has been scattered by the object being inspected 6, taking advantage of the strong forward scattering signal. It also provides the necessary magnification and geometric space for the encoding projection, thus guaranteeing the physical realization of the imaging system.

[0065] In some exemplary embodiments, the rear collimator 340 includes a shielding cylinder 320, an encoding plate 310 located on the side of the shielding cylinder 320 closer to the second X-ray source 10, and a diffraction detector 330 located on the side of the shielding cylinder 320 away from the second X-ray source 10. In some specific embodiments, to further enhance the system's anti-interference capability, the detection module 300 is structurally designed as a closed component similar to a "dark box." Figure 4A The cross-sectional structure of the detection module 300 shown is illustrated. The shielding cylinder 320, made of heavy metal materials such as lead or tungsten, forms the sidewall of the detection module 300 (i.e., the solid part of the rear collimator 340). The encoding plate 310 is installed at the entrance window (front end) of the shielding cylinder 320, while the diffraction detector 330 is encapsulated at the bottom (rear end) of the shielding cylinder 320. Thus, the encoding plate 310 and the sidewall of the shielding cylinder 320 together form a closed electromagnetic and radiation shielding space. Physically, this structure can completely isolate stray scattered rays from the environment and secondary scattered rays generated by the non-interest areas (i.e., outside the field of view) of the inspected object 6. This means that the diffraction detector 330 cannot "see" any area except for the through-hole of the encoding plate 310, thereby minimizing background noise and improving the signal-to-noise ratio (SNR) of weak diffraction signals, which plays a crucial role in detecting the weak diffraction peaks generated by contraband.

[0066] In some exemplary embodiments, the encoding plate 310 has a plurality of first holes 3111 for allowing scattered rays to pass through. The plurality of first holes 3111 form a predetermined first encoding pattern in a projection plane, which is a plane defined by the intersection of a first direction z and a third direction x. In some specific embodiments, refer again to the attached diagram. Figure 4B These scattered black holes (first holes 3111) on the plate are not random, but form a predetermined first coded pattern. This pattern design introduces a computational imaging mechanism. In conventional pinhole imaging, to achieve high resolution, the pinhole must be reduced in size, but this leads to a sharp decrease in light throughput (i.e., a weak signal). However, the first coded pattern in this embodiment, such as an improved uniform redundant array MURA, allows up to 50% light transmission, resulting in a higher number of photons reaching the diffraction detector 330 compared to conventional pinholes. Although the diffraction detector 330 receives an aliased image of multiple holes, since the first coded pattern is pre-defined and known, the signal processing device 5 can "decode" the detected signal using mathematical algorithms (such as correlation decoding or iterative reconstruction) to accurately reconstruct the high-resolution diffraction energy spectrum of the object under inspection 6. Therefore, this structure achieves both "high throughput" and "high resolution" at the physical level.

[0067] In some exemplary embodiments, the second diffraction scanning stage further includes a pre-collimator 20, such as Figure 6 As shown, the precollimator 20 includes a plurality of second holes 21 for the passage of a second ray. These second holes 21 form a predetermined second coding pattern in the projection plane, which is the plane defined by the intersection of a first direction z and a third direction x. In some specific embodiments, in addition to coding at the detector end, this embodiment also introduces a coding mechanism at the light source end. (Refer to the attached diagram.) Figure 6 As shown, a precollimator 20 is placed between the X-ray source and the object 6 being inspected. Multiple second apertures 21 on the precollimator 20 form a predetermined second coding pattern (e.g., random coding or multi-slit coding). This structure transforms a traditional single-point or single-slit light source into a "structured illumination" light source. Structurally, this allows multiple beams of X-rays to simultaneously illuminate different parts of the object 6 being inspected, or to form an illumination field of a specific shape. On the one hand, it significantly improves the utilization rate of the X-rays emitted by the X-ray source and reduces the wasted energy from the collimator. On the other hand, through optomechanical coding, a larger measurement range (i.e., an increased field of view) can be covered in a single exposure, and through subsequent joint solving algorithms, scattered signals from different illumination positions can be distinguished, achieving rapid imaging under a large field of view, suitable for security inspection scenarios requiring full-coverage scanning of large luggage.

[0068] like Figure 5AAs shown, the second detection component 30 may further include a transmission detector 31, which is used to detect the second transmitted rays transmitted through the object 6 under inspection to generate a third detection signal. The signal processing device 5 is further configured to: acquire attenuation characteristic information of at least the object of interest in the object 6 under inspection based on the third detection signal; and correct the second detection signal using the attenuation characteristic information during the process of processing the second detection signal to generate a diffraction image. In some specific embodiments, the correction process is used to solve the problem of quantifying X-ray diffraction. When X-rays penetrate the object 6 under inspection and reach the diffracting interior, and during the process of the diffracted rays penetrating the object again to reach the detector, the ray energy is absorbed by the object material and attenuated (i.e., self-absorption effect). This attenuation is closely related to the thickness and density of the object along the path. If no correction is made, it will lead to distortion of the intensity of the reconstructed diffraction spectrum. For example, the signal of contraband located inside the object 6 under inspection will appear very weak due to excessive attenuation. Therefore, the third detection signal acquired in real time by the transmission detector 31 is introduced, which directly reflects the total attenuation of the rays after passing through the object. Signal processing device 5 uses the third detection signal to construct an "attenuation distribution map" or "attenuation feature information" of the object 6 being inspected. In the algorithm for reconstructing the diffraction image, the original diffraction signal of each voxel is calculated with the attenuation factor corresponding to that location to compensate for energy loss caused by path absorption. This correction mechanism can restore the true diffraction intensity of the object of interest, obtaining consistent and accurate material identification results regardless of whether the object of interest is located on the surface of a package or deeply buried in thick clothing.

[0069] For example, in the cone angle direction, the transmission detector 31 is located on the path of the main beam of the second ray, and the detection module 300 is deviated from the path of the main beam of the second ray at a predetermined deviation angle, which is less than or equal to a preset scattering angle threshold. In some specific embodiments, the cone angle direction corresponds to the yz plane, that is, the longitudinal section along the direction of movement (Z-axis) of the object 6 being inspected. Refer to the appendix. Figure 5AAs shown in the geometric relationship, the transmission detector 31 is placed on the straight line of the second ray emitted by the second ray source 10 to capture directly transmitted photons that have not been scattered. The encoding plate 310, the post-collimator 340, and the diffraction detector 330, responsible for collecting diffraction signals, are not located on the main beam path of this second ray, but rather form an angle with it—a predetermined deviation angle. By deviating the diffraction detector 330 from the main beam, the high-intensity transmission main beam is prevented from directly irradiating the highly sensitive diffraction detector 330, thus preventing saturation or damage to the diffraction detector 330, and also achieving physical separation of the transmitted and scattered signals. Secondly, the deviation angle is limited to "less than or equal to a preset scattering angle threshold" (e.g., within 10 degrees) because the diffraction peaks of most contraband crystal structure features are mainly concentrated in small-angle regions; if the deviation angle is too large, these crucial fingerprint features cannot be captured. Therefore, this small deviation design, which is close to the main beam of the second ray but avoids it, ensures detection safety while improving the efficiency of effective signal acquisition.

[0070] In the fan-angle direction, the coverage area of ​​the diffraction detector 330 of the second detection component 30 is consistent with the coverage area of ​​the transmission detector 31. The fan-angle direction corresponds to the xy-plane, i.e., the width direction of the cross-section of the object 6 being inspected. This consistency in coverage ensures spatial alignment of the data. If the field of view (FOV) of the diffraction detector 330 of the second detection component 30 is smaller than that of the transmission detector 31, objects located at the edge of the field of view will have transmission data but lack diffraction data, resulting in unidentifiable objects. Conversely, if the diffraction field of view is larger than the transmission field of view, the diffraction data in the edge region will lack corresponding attenuation correction information. Therefore, the consistency of their coverage ensures that objects of interest at any lateral position within the scanning channel can simultaneously obtain both "transmission attenuation data" and "diffraction energy spectrum data," guaranteeing accurate detection without blind spots throughout the entire channel.

[0071] In some exemplary embodiments, the second radiation source 10 includes a target point for emitting radiation; the second detection assembly 30 includes a plurality of detection modules 300, which are arranged centripetally relative to the target point in a fan-shaped direction. In some specific embodiments, centripetal arrangement means that in the fan-shaped plane (xy plane), all detection modules 300 are not arranged in parallel, but rather in a fan-shaped distribution, and the central axis of each module, when extended backward, converges to the target point of the radiation source. This geometric layout is as follows: Figure 7As shown, geometric parallax and non-uniformity are eliminated. Regardless of whether the detector module 300 is located at the center or edge of the array, the rays enter the encoder plate 310 and collimator in a "normal incidence" manner. This ensures that all modules have a consistent effective aperture and angular resolution, avoids encoding pattern distortion or collimator obstruction caused by oblique ray incidence, and thus ensures consistent imaging quality across the entire scanning channel width.

[0072] In some embodiments, in the fan-angle direction, multiple detection modules 300 are independently arranged, and the diffraction detectors 330 of the multiple detection modules 300 each include a detection surface 311; for each of the multiple detection modules 300, the line connecting the detection surface 311 and the target point is perpendicular to the detection surface 311; in some specific embodiments, refer to the attached... Figure 7 The normal to the detection surface 311 of each independent detection module 300 is precisely pointed to the target point, which means that the incident X-rays always enter perpendicular to the detection surface 311. In physical detection, perpendicular incidence can minimize the oblique path penetration of the rays inside the detector crystal, avoiding "pixel blurring" or "position uncertainty" caused by oblique incidence, thereby improving the spatial positioning accuracy and energy response uniformity of the detector.

[0073] In some embodiments, the rear collimator 340 includes a collimator 341, and two adjacent detection modules 300 among the plurality of detection modules 300 share the collimator 341; in the fan-angle direction, the collimator 341 of the plurality of detection modules 300 extends through the target point; in some specific embodiments, refer to the appendix Figure 5B The collimating plates 341 effectively form the partition walls between the detection modules 300. Instead of manufacturing a separate shell for each detection module 300, adjacent detection modules 300 share this tungsten or lead partition wall. Geometrically, these shared collimating plates 341 are arranged radially, with their extension lines all passing through the X-ray source target. This design eliminates the physical gaps between adjacent detection modules 300, improving the fill factor and X-ray utilization of the detector array. Secondly, these collimating plates 341 pointing towards the target form a large field-of-view fan-beam grid, which not only serves as a supporting structure but also effectively absorbs lateral scattered stray information, further improving the overall signal-to-noise ratio of the system.

[0074] In some exemplary embodiments, reference is made to the appendix. Figure 5C As shown, both the target point and the detection module 300 of the second radiation source 10 can move along a third direction x, which is perpendicular to the first direction z and the second direction y, respectively; or, referring to the appendix Figure 5DAs shown, the second detection component 30 includes multiple detection modules 300, which are arranged along a third direction x. The target point can move along the third direction x, which is perpendicular to the first direction z and the second direction y, respectively; or, refer to the attached diagram. Figure 5E As shown, the second detection component 30 includes multiple detection modules 300 arranged along a third direction x. The second radiation source 10 includes multiple target points arranged along a third direction x, which is perpendicular to the first direction z and the second direction y. Exemplarily, a moving scan can be used; after the first transmission scan stage determines the specific X-coordinate of the object of interest, the second radiation source 10 and its corresponding detection modules 300 are driven to synchronously translate along the third direction x, moving to the location of the object of interest for fixed-point scanning. Exemplarily, a multi-target source array scan can be used; refer to the attached diagram. Figure 5F As shown, the second detection component 30 covers the entire channel width in the third direction x, while the second radiation source 10 is composed of multiple independent target points arranged along the third direction x; depending on the position of the object of interest, only one or several target points at the corresponding position can be controlled to emit beams.

[0075] like Figure 5G As shown, in some exemplary embodiments, the second detection component 30 includes multiple rows of detection modules 300; in the cone angle direction, the multiple rows of detection modules 300 are arranged at intervals along the first direction z; and / or, in the cone angle direction, at least one row of detection modules 300 and at least another row of detection modules 300 are respectively located on both sides of the transmission detector 31. In some specific embodiments, the multiple rows of detection modules 300 are arranged in the cone angle direction, which means that when the conveyor belt carries the object 6 to be inspected through the scanning area, the same part of the object 6 to be inspected will pass through the first row, the second row... the Nth row of detection modules 300 in sequence. The weak diffraction signals collected by the multiple rows of detectors can be superimposed by "time delay integration" or simple signal accumulation techniques. This "multi-layer scanning" increases the statistics of effective photons and improves the signal-to-noise ratio by a factor of two without reducing the conveyor belt speed. Exemplarily, the detection modules 300 can also be symmetrically distributed on the front and rear sides of the transmission detector 31 (main beam plane). This dual-sided arrangement not only balances the mechanical structure, but also allows for simultaneous data acquisition using different cone angles (such as forward +5 degrees and backward -5 degrees), further enriching the detection dimensions of the crystal structure.

[0076] like Figure 5A , Figure 5G and Figure 5HAs shown, in some exemplary embodiments, the diffraction detector 330 of the detection module 300 includes a detection surface 311, which is perpendicular to the second direction y; or, the diffraction detector 330 of the detection module 300 includes a detection surface 311, and an extension line perpendicular to the detection surface 311 and passing through the center of the detection surface 311 passes through the object of interest. In some specific embodiments, the orientation setting of the detector directly affects the reception efficiency and geometric distortion of the diffracted rays. For example, referring to... Figure 5G The detector surface 311 is perpendicular to the second direction y, meaning the detector is placed horizontally. This layout allows for compact devices, enabling the detector module 300 to be mounted close to the top or bottom of the transport channel, saving space. Exemplarily, the diffraction detector 330 rotates in the yz plane so that the normal to the detector surface 311 points directly at the object of interest. This "object-facing" orientation ensures that scattered rays from the object are incident on the detector crystal surface at a near-perpendicular angle, minimizing pixel blurring caused by oblique incidence, thereby guaranteeing high energy resolution and spatial positioning accuracy of the diffraction spectrum.

[0077] like Figure 5I As shown, in some exemplary embodiments, the second detection component 30 includes multiple transmission detectors 31 and multiple diffraction detectors 330. In the cone angle direction, the multiple transmission detectors 31 are arranged at intervals, the multiple diffraction detectors 330 are arranged at intervals, and the multiple transmission detectors 31 and multiple diffraction detectors 330 are arranged alternately. In some specific embodiments, it is not limited to a single transmission main beam, but can form a "multi-slit" collimation similar to a venetian blind structure in the first direction z. The arrays of transmission detectors 31 and diffraction detectors 330 are alternately interleaved in the first direction z (e.g., transmission-diffraction-transmission-diffraction...). This alternating arrangement allows for parallel operation using X-ray fans generated by multiple slits. Each slit can generate a set of transmission data and corresponding scattering data. This high-density hybrid array design essentially reuses the scanning channel in space, multiplying the amount of information acquired per unit time, greatly improving the scanning throughput of the security inspection system, and is suitable for large logistics or checked baggage security inspection scenarios with extremely high detection speed requirements.

[0078] This disclosure provides a multi-level scanning imaging method based on diffraction imaging, such as... Figure 8 As shown, the multi-level scanning imaging method based on diffraction imaging may include steps S100 to S500.

[0079] Step S100 is the first-level transmission scanning step. In this step, the object 6 under inspection is scanned using the first transmission scanning level to obtain a transmission image of the object 6 under inspection.

[0080] Step S200 is the object of interest localization step, in which the object of interest in the inspected object 6 is obtained based on the transmission image.

[0081] Step S300 is the second-stage diffraction scanning step. In this step, at least the object of interest in the object being inspected 6 is diffracted using the second diffraction scanning stage to obtain the diffraction image of the object of interest.

[0082] Step S400 is the material information acquisition step, in which the material information of the object of interest is acquired based on the diffraction image of the object of interest;

[0083] Step S500 is the target determination step, in which the object of interest is determined as the target object in response to the material information of the object of interest.

[0084] It is understood that a portion of the multi-stage scanning imaging method based on diffraction imaging can be executed by the control device 7, and another portion can be executed by the signal processing device 5. For example, steps S100 and S300 can be executed by the control device 7, which can control the X-ray sources and detectors of the first transmission scanning stage and the second diffraction scanning stage to perform the corresponding scanning steps; steps S200, S400, and S500 can be executed by the signal processing device 5. That is, the relevant functions and steps executed by the signal processor 130 can be included as part of the multi-stage scanning imaging method based on diffraction imaging. For the sake of brevity, these will not be elaborated further here.

[0085] For example, refer to Figure 9 The multi-level scanning imaging method based on diffraction imaging may also include steps S1100 to S1500.

[0086] Step S1100 is the k-th transmission scan: Based on the material information of the object of interest obtained in the previous scan, the scanning parameters of the first transmission scan level are adjusted, and the object 6 under inspection is scanned using the adjusted first transmission scan level. The transmission image of the object 6 under inspection is obtained for the k-th scan. The transmission image obtained for the k-th scan is a corrected image based on the material information of the object of interest obtained in the previous scan, and k is a positive integer greater than 1.

[0087] Step S1200 is to obtain the k-th transmission result: Based on the transmission image obtained in the k-th transmission, the object of interest in the inspected object 6 is obtained in the k-th transmission.

[0088] Step S1300 is the k-th diffraction scan: Based on the object of interest obtained in the k-th scan, adjust the scanning parameters and reconstruction position of the second diffraction scan level, and use the adjusted second diffraction scan level to scan the object 6 under inspection, and obtain the diffraction image of the object of interest in the k-th scan.

[0089] Step S1400 is to obtain the result of the k-th diffraction: based on the diffraction image of the object of interest obtained in the k-th diffraction, the material information of the object of interest is obtained in the k-th diffraction; and

[0090] Step S1500: As k increases, iteratively execute the kth transmission scan, the kth transmission result acquisition, the kth diffraction scan, and the kth diffraction result acquisition until the iteration termination condition is met.

[0091] It should be understood that steps S1100 to S1500 achieve dynamic optimization of detection accuracy by establishing a "bidirectional feedback loop" between the primary transmission system and the secondary diffraction system. Specifically, this is a collaborative iterative process of "CT guiding XRD, XRD feeding back to CT": First, regarding "XRD feeding back to CT" (corresponding to step S1100), after the XRD system determines the specific composition of the object of interest (e.g., determining it to be a liquid or metal of a specific density) through energy spectrum analysis, this material composition information is fed back to the primary transmission system. The transmission imaging system utilizes this prior knowledge to correct beam hardening artifacts or modify the calculation model of the attenuation coefficient for that region, thereby generating a clearer, more accurate k-th transmission image, and thus obtaining more precise object contour and position information. Second, regarding "CT guiding XRD" (corresponding to step S1300), based on the more precise spatial position and geometry provided by the k-th transmission image (i.e., the updated object of interest information), the control device 7 can fine-tune the parameters of the secondary diffraction scan stage. For example, based on the exact depth and location of the object, the "reconstruction focus plane" of the coded imaging can be adjusted to precisely align with the center of the object; or based on the size of the object, the collimator opening or integration time of the scan can be adjusted. This iterative cycle of "transmission-diffraction-correction-retransmission-rediffraction" allows the two subsystems to correct each other's errors until a preset detection accuracy (e.g., a material identification confidence level greater than 95%) or an upper limit on the number of iterations (i.e., the iteration termination condition) is reached. Thus, even in extreme cases of complex occlusion or mixed materials, extremely high detection accuracy can still be achieved.

[0092] For example, Figure 9 A flowchart illustrating a multi-level scanning imaging method based on diffraction imaging, provided for embodiments of this disclosure. (Refer to...) Figure 9In step S400, obtaining the object of interest (OPI) in the inspected object 6 based on the transmission image includes: obtaining the contour information of the OPI in the inspected object 6 based on the transmission image. Obtaining the material information of the OPI based on the diffraction image of the OPI includes: merging multiple voxels or pixels of the same material in the diffraction image and calculating the average value based on the contour information of the OPI; obtaining the material information of the OPI based on the average value.

[0093] It should be understood that in the XRD imaging system and method, based on the detection data acquired by the detector, an image reconstruction algorithm can be used to reconstruct at least the object of interest of the object under inspection 6. The reconstruction process is essentially a process of solving the following linear equation (1), that is, given the imaging system matrix A and the detection signal b (i.e., projection data), the internal structure x of the object under inspection 6 is solved.

[0094] ,

[0095] Where x is the three-dimensional voxel vector to be reconstructed, and each element in the vector represents the feature information of the object 6 under inspection at that voxel; b is the detection signal acquired by the detector under the scanning view; A is the imaging system matrix (or projection matrix), and each element in matrix A is used to describe the influence weight of each voxel of the object 6 under inspection on each detection signal.

[0096] In some exemplary embodiments, the second detection component 30 includes multiple diffraction detectors 330. For the detection signals obtained by the diffraction detectors 330 from different viewpoints, the detection signals from all viewpoints can be put into the same equation (1) for iterative solution. During the solution process, the data weight along the ray direction can be reduced.

[0097] For example, the object being examined, 6, is discretized into a three-dimensional voxel mesh, x. For each energy i at each scanning viewpoint, the contribution weight aij of each voxel j to the diffraction detection signal at that viewpoint is calculated. For example, the weight aij can be determined by at least the following factors: whether the geometric path satisfies the Bragg condition, the absorption attenuation of the incident path and the diffraction path, the spatial resolvability of the voxel at that viewpoint, etc. The above-mentioned contribution weight aij is used to construct the above-mentioned imaging system matrix A. The detection signals at all views are merged to construct a detection signal vector b with a higher dimension. The constructed imaging system matrix A and the detection signal vector b are substituted into equation (1), and the reconstructed image is solved by iterative solution.

[0098] In this embodiment, a multi-view joint solution framework is established, integrating the detection signals from all diffraction detectors 330 into a unified linear equation. In this way, the phase concentration or presence of each voxel within the examined object 6 is no longer determined solely by a single, potentially noisy, detection signal, but rather by redundant observations from multiple independent perspectives. This data fusion mechanism has a noise suppression effect: random noise, which is uncorrelated across different perspectives, is weakened through joint optimization; while the true material signal remains consistent across all relevant perspectives, thus being effectively enhanced. The final result is a higher signal-to-noise ratio in the reconstructed diffraction spectrum, significantly improving the accuracy and robustness of material identification.

[0099] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram or flowchart, and combinations of blocks in a block diagram or flowchart, may be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0100] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A multi-level scanning imaging system based on diffraction imaging, characterized in that, include: The first transmission scanning stage includes a first radiation source and a first detection component. The first radiation source is used to emit a first radiation to scan the object being inspected, and the first detection component is used to detect the first transmission radiation transmitted through the object being inspected to generate a first detection signal. A signal processing device electrically connected to the first detection component, the signal processing device being configured to: process the first detection signal to generate a transmission image, and obtain an object of interest in the object being inspected based on the transmission image; as well as The second diffraction scanning stage, which is arranged at intervals along a first direction with the first transmission scanning stage, includes a second X-ray source and a second detection component. The second X-ray source emits a second X-ray to scan the object under inspection, and the second detection component detects scattered X-rays scattered by at least the object of interest within the object under inspection to generate a second detection signal. The signal processing device is electrically connected to the second detection component, and the signal processing device is further configured to: process the second detection signal to generate a diffraction image, and obtain material information of the object of interest based on the diffraction image.

2. The system according to claim 1, wherein, The second detection component includes at least one detection module, and at least one detection module includes: An encoding board, the encoding board being used to encode the scattered rays to form encoded scattered rays; A rear collimator, the rear collimator being used to block rays scattered by the object being inspected at a first scattering angle, wherein the first scattering angle is greater than a preset scattering angle threshold; and A diffraction detector is used to detect the coded scattered rays, wherein the coded scattered rays are rays scattered by at least the object of interest in the object being inspected and have a second scattering angle, the second scattering angle being less than or equal to a preset scattering angle threshold.

3. The system according to claim 2, wherein, The second radiation source and the second detection component are arranged on opposite sides of the object to be inspected along a second direction, which is perpendicular to the first direction; In the second direction, the encoding plate, the rear collimator, and the diffraction detector are arranged in a direction that moves away from the second ray source in sequence.

4. The system according to claim 2 or 3, wherein, The second detection component further includes a transmission detector for detecting a second transmitted ray transmitted through the object being inspected, in order to generate a third detection signal; The signal processing device is further configured to: acquire attenuation feature information of at least the object of interest in the object being inspected based on the third detection signal; and correct the second detection signal using the attenuation feature information during the process of processing the second detection signal to generate a diffraction image.

5. The system according to claim 4, wherein, In the cone angle direction, the transmission detector is located on the path of the main beam of the second ray, and the detection module is deviated from the path of the main beam of the second ray by a predetermined deviation angle, which is less than or equal to a preset scattering angle threshold.

6. The system according to claim 5, wherein, In the sector direction, the coverage area of ​​the diffraction detector is the same as the coverage area of ​​the transmission detector.

7. The system according to any one of claims 2-3 and 5-6, wherein, The second radiation source includes a target for emitting radiation; The second detection component includes multiple detection modules, which are arranged centripetally relative to the target point in the fan-angle direction.

8. The system according to claim 7, wherein, In the sector direction, the plurality of detection modules are arranged independently of each other, and the diffraction detectors of the plurality of detection modules each include a detection surface; for each of the plurality of detection modules, the line connecting the detection surface and the target point is perpendicular to the detection surface.

9. The system according to any one of claims 2-3 and 5-6, wherein, The rear collimator includes a collimating plate, and two adjacent detection modules among the plurality of detection modules share the collimating plate; In the fan-angle direction, the collimation plates of the plurality of detection modules extend through the target point.

10. The system according to any one of claims 2-3 and 5-6, wherein, Both the target point of the second radiation source and the detection module can move along a third direction, which is perpendicular to the first and second directions, respectively; or, The second detection component includes multiple detection modules arranged along a third direction, and the target point is movable along this third direction, which is perpendicular to both the first and second directions; or, The second detection component includes multiple detection modules arranged along a third direction, and the second radiation source includes multiple target points arranged along a third direction, which is perpendicular to the first direction and the second direction, respectively.

11. The system according to any one of claims 2-3 and 5-6, wherein, The second detection component includes a multi-row detection module; In the cone angle direction, the multiple rows of detection modules are arranged at intervals along the first direction; and / or, In the cone angle direction, at least one row of detection modules and at least another row of detection modules are located on both sides of the transmission detector.

12. The system according to any one of claims 2-3 and 5-6, wherein, The diffraction detector of the detection module includes a detection surface, which is perpendicular to the second direction; or, The diffraction detector of the detection module includes a detection surface, and an extension line perpendicular to the detection surface and passing through the center of the detection surface passes through the object of interest.

13. The system according to any one of claims 2-3 and 5-6, wherein, The second detection component includes multiple transmission detectors and multiple diffraction detectors. In the cone angle direction, the multiple transmission detectors are arranged at intervals, the multiple diffraction detectors are arranged at intervals, and the multiple transmission detectors and the multiple diffraction detectors are arranged alternately.

14. The system according to any one of claims 2-3 and 5-6, wherein, The rear collimator includes a shielding tube, the encoding plate is located on the side of the shielding tube closer to the second radiation source, and the diffraction detector is located on the side of the shielding tube away from the second radiation source.

15. The system according to any one of claims 2-3 and 5-6, wherein, The coding plate has a plurality of first holes for the scattered rays to pass through. The plurality of first holes form a predetermined first coding pattern in the projection plane, which is a plane defined by the intersection of the first direction and the third direction.

16. The system according to any one of claims 2-3 and 5-6, wherein, The second diffraction scanning stage further includes a precollimator, which includes a plurality of second holes for the passage of the second ray. The plurality of second holes form a predetermined second coding pattern in a projection plane, which is a plane defined by the intersection of the first direction and the third direction.

17. A multi-level scanning imaging method based on diffraction imaging, characterized in that, include: The object under inspection is scanned using the first transmission scanning stage to obtain a transmission image of the object under inspection; The object of interest in the inspected object is obtained based on the transmission image; The second diffraction scanning stage is used to perform diffraction scanning on at least the object of interest in the object being inspected, and to obtain a diffraction image of the object of interest. Obtain material information of the object of interest based on the diffraction image of the object of interest; as well as In response to the material information of the object of interest, the object of interest is determined to be the target object.

18. The method according to claim 17, wherein, The method further includes: The k-th transmission scan: Based on the material information of the object of interest obtained in the previous scan, the scanning parameters of the first transmission scan level are adjusted, and the object under inspection is scanned using the adjusted first transmission scan level. The transmission image of the object under inspection is obtained in the k-th scan, wherein the transmission image obtained in the k-th scan is a corrected image based on the material information of the object of interest obtained in the previous scan, and k is a positive integer greater than 1. The k-th transmission result is obtained: Based on the transmission image obtained in the k-th transmission, the object of interest in the inspected object is obtained in the k-th transmission. k-th diffraction scan: Based on the object of interest obtained in the k-th scan, adjust the scanning parameters and reconstruction position of the second diffraction scan level, and use the adjusted second diffraction scan level to scan the object under inspection, and obtain the diffraction image of the object of interest in the k-th scan. Acquisition of the k-th diffraction result: Based on the diffraction image of the object of interest acquired in the k-th diffraction, the material information of the object of interest is acquired in the k-th diffraction; and As k increases, the k-th transmission scan, the acquisition of the k-th transmission result, the k-th diffraction scan, and the acquisition of the k-th diffraction result are executed iteratively until the iteration termination condition is met.

19. The method of claim 17, wherein, The step of obtaining the object of interest in the inspected object based on the transmission image includes: obtaining the contour information of the object of interest in the inspected object based on the transmission image; The step of obtaining the material information of the object of interest based on the diffraction image of the object of interest includes: merging and averaging multiple voxels or pixels of the same material in the diffraction image based on the contour information of the object of interest; and obtaining the material information of the object of interest based on the average value.

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