Material identification method and material identification device

Abstract

The invention provides a material identification method, which comprises the steps that a target object is scanned in response to radiation rays, a plurality of detector modules of a radiation detector are used for detecting radiation ray signals, the detector modules are arranged at different positions, and ray signal channels are mutually independent; according to the radiation ray signal detected by each detector module, N ray indexes corresponding to the position where each detector module is located are calculated, and N is an integer larger than or equal to 1; and identifying the material of the target object according to the index values of each ray index at different positions. The invention further discloses a material recognition device.

Description

Technical Field

[0001] The present disclosure relates to the field of security inspection, backscattering, material identification or other fields, and more specifically, to a material identification method and a material identification device. Background Art

[0002] When radiation rays enter an object, some of them will undergo Compton scattering. During this process, the energy and flight direction of the radiation rays will change. Among them, the flight direction of some rays will change so much that they will return to the side where the radiation source is located. This type of ray is called backscattered ray, or backscatter for short.

[0003] In the related technology, the radiation detector can convert the detected rays into a large number of photons through a large area of ​​radiation-sensitive media, and then the photons are converted into electronic signals by a photoelectric conversion device. After amplification by the amplifier, the ADC (analog-to-digital converter) sampling technology is used to generate the corresponding digital signal sequence, and then the digital signal is processed based on the integral method (also called the current method) to obtain the backscatter scanning result.

[0004] When scanning one or more points of the target object, the transmitted radiation or scattered radiation from the same scanning point is detected by multiple positions of the radiation-sensitive medium of the radiation detector, and currently only the result of adding up the detection data of each position is used as the radiation signal of the same scanning point. A radiation image is obtained based on the radiation signal obtained based on the summation result, and then the radiation image is recognized to obtain the material recognition result.

[0005] In the process of realizing the inventive concept of the present disclosure, the inventors found that obtaining a radiation image based on a radiation signal obtained by summing up the detection data loses some information, which is not conducive to improving the accuracy of material identification. Summary of the invention

[0006] In view of the above problems, the present disclosure provides a material identification method and a material identification device.

[0007] According to a first aspect of the present disclosure, a material identification method is provided, comprising: in response to scanning a target object with radiation rays, detecting radiation ray signals using multiple detector modules of a radiation detector, wherein the multiple detector modules are arranged at different positions and the ray signal channels are independent of each other; calculating N ray indicators corresponding to the position of each detector module based on the radiation ray signals detected by each detector module, where N is an integer greater than or equal to 1; and identifying the material of the target object based on the indicator value of each ray indicator at different positions.

[0008] In some embodiments, the N ray indicators include a first ray indicator and a second ray indicator, and identifying the material of the target object according to the indicator value of each ray indicator at a different position includes: mapping the indicator values ​​of the first ray indicator and the second ray indicator at different positions in a coordinate system, wherein the vertical axis of the coordinate system corresponds to the first ray indicator and the horizontal axis of the coordinate system corresponds to the second ray indicator; and identifying the material of the target object according to the distribution of the first ray indicator and the second ray indicator in the coordinate system.

[0009] In some embodiments, in response to scanning the target object with radiation rays, detecting the radiation ray signals using multiple detector modules of the radiation detector includes: performing flying-spot scanning on the target object in response to the radiation source emitting radiation rays, and detecting the backscattered ray signals reflected by the target object using multiple detector modules.

[0010] In some embodiments, calculating N ray indices corresponding to the position of each detector module includes: for each ray index, calculating multiple index values ​​corresponding to the position of each detector module; wherein the multiple index values ​​correspond one-to-one to multiple point positions of flying spot scanning of the target object using radiation rays.

[0011] In some embodiments, before calculating the N ray indicators corresponding to the position of each detector module, the method also includes: allocating a corresponding location identifier according to the position of each detector module; wherein the N ray indicators corresponding to the position of each detector module are bound to the location identifier of the detector module.

[0012] In some embodiments, before calculating the N radiation indicators corresponding to the position of each detector module, the method also includes: performing energy threshold judgment on multiple groups of radiation signals to filter out radiation signals in different energy ranges from each group of radiation signals, wherein the multiple groups of radiation signals correspond one-to-one to multiple detector modules; and obtaining the number of radiation signals in different energy ranges in each group of radiation signals.

[0013] In some embodiments, calculating the N ray indices corresponding to the position of each detector module includes: for each group of ray signals, obtaining the target number of ray signals in the target energy range in different energy ranges; calculating the ratio of the target number to the total number of ray signals to obtain a first ray index, wherein the total number of ray signals is obtained based on the sum of the numbers of all ray signals in different energy ranges.

[0014] In some embodiments, calculating the N radiation indicators corresponding to the location of each detector module includes: calculating the ratio of the total number of radiation signals to the counting period to obtain a second radiation indicator, wherein the total number of radiation signals is obtained based on the sum of the numbers of all radiation signals under different energy ranges, and the counting period includes the period for obtaining the number.

[0015] In some embodiments, identifying the material of the target object according to the indicator value of each radiation indicator at different positions includes: matching the indicator value of each radiation indicator at different positions with indicator information of different materials, respectively, wherein the indicator information of different materials includes pre-calculated indicator values ​​of different materials at different positions; and identifying the material of the target object according to the matching result.

[0016] In some embodiments, a radiation source is used to emit radiation rays, and two radiation detectors are set on both sides of the radiation source; wherein, using multiple detector modules of the radiation detector to detect the radiation ray signal includes: using multiple detector modules of each radiation detector in the two radiation detectors to detect the radiation ray signal.

[0017] In some embodiments, the two radiation detectors distributed on both sides of the radiation source have different structures and each detects radiation ray signals from different areas of the corresponding target object. The structure of each radiation detector is determined according to the area of ​​the target object to be detected, and the detector structure includes the detection area of ​​each detector module in the multiple detector modules.

[0018] In some embodiments, before matching the indicator value of each radiation indicator at different positions with the indicator information of different materials, the method also includes: determining the indicator information of the material to be matched based on the respective structures of the two radiation detectors; wherein the indicator information of the material to be matched is calculated based on the radiation ray signals based on the material to be matched detected by two preset radiation detectors, and the two preset radiation detectors have a one-to-one correspondence with the two radiation detectors and have approximately the same structure.

[0019] Another aspect of an embodiment of the present disclosure provides a material identification device for executing a material identification method as described in any of the above items, the material identification device comprising: a radiation detector for scanning a target object in response to radiation rays, detecting radiation ray signals using multiple detector modules, the multiple detector modules being arranged at different positions and the ray signal channels being independent of each other; a processor, communicatively connected to the radiation detector, for performing the following operations: calculating N ray indicators corresponding to the position of each detector module based on the radiation ray signals detected by each detector module, where N is an integer greater than or equal to 1; and identifying the material of the target object based on the indicator value of each ray indicator at different positions.

[0020] One or more of the above embodiments have the following beneficial effects:

[0021] There are differences in the signals generated by detector modules at different positions in the radiation detector, and additional information can be obtained by comparing these differences. Multiple detector modules distributed at different positions use their own radiation signal channels to receive radiation rays after scanning the target object, and can independently calculate one or more radiation indicators corresponding to each position. By analyzing the distribution differences of the indicator values ​​of each radiation indicator at different positions, the material of the target object can be accurately identified. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above contents and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0023] Figure 1 The application scenario diagram of the backscatter detection device in the related art is schematically shown;

[0024] Figure 2 shows a sequence of events of rays incident on a backscatter detector according to an embodiment of the present disclosure;

[0025] Figure 3 A schematic diagram showing the change of the number of photons excited by a single ray over time according to an embodiment of the present disclosure is shown;

[0026] Figure 4 The figure shows the pulse electrical signal of signal accumulation and superposition in the related art;

[0027] Figure 5 A schematic diagram showing an application scenario of a backscatter detection device according to an embodiment of the present disclosure;

[0028] Figure 6 A schematic diagram of the layout of a radiation source and a backscatter detector according to an embodiment of the present disclosure is shown;

[0029] Figure 7 A schematic diagram showing the layout of a radiation source and a backscatter detector according to another embodiment of the present disclosure is shown;

[0030] Figure 8 A schematic diagram showing the layout of a radiation source and a backscatter detector according to yet another embodiment of the present disclosure is shown;

[0031] Fig. 9 A schematic diagram showing a comparison of response pulse waveforms of a fast decay crystal (GAGG) and a slow decay crystal (GOS) according to an embodiment of the present disclosure is shown;

[0032] Fig.10 A schematic diagram showing a waveform of a pulse electrical signal output by a detector module according to an embodiment of the present disclosure is shown;

[0033] Fig.11The following schematically shows an application scenario diagram of a material identification device according to an embodiment of the present disclosure;

[0034] Fig.12 A schematic diagram of data flow between a backscatter detector, an electronic device and a processor according to an embodiment of the present disclosure is shown;

[0035] Fig.13 A schematic diagram of backscatter detection of detector modules at different positions according to an embodiment of the present disclosure is shown;

[0036] Fig.14 The schematic diagram shows the energy spectra of backscattering of different materials at different positions after peak normalization;

[0037] Fig.15 Schematic diagram showing the relative amount of backscattered rays at different locations from different materials;

[0038] Fig.16 A schematic diagram of data flow between a backscatter detector, an electronic device and a processor according to another embodiment of the present disclosure is shown;

[0039] Fig.17 A schematic diagram of the waveform of a group of ray signals containing noise is schematically shown;

[0040] Fig.18 The energy spectra of backscattering of different materials at different positions are schematically shown;

[0041] Fig.19 The distribution diagram of the ray indicators of different materials in the coordinate system according to the embodiment of the present disclosure is schematically shown.

[0042] The reference numerals of the above drawings are as follows, where different application scenarios correspond to different embodiments:

[0043] 100, application scenario; 110, radiation source; 120, backscatter detector; 121, sensitive volume; 122, photoelectric converter; 130, electronic device; 140, target object; 150, network; 160, electronic device;

[0044] 500, application scenario; 510, radiation source; 520, backscatter detector; 521, detector module; 530, electronic device; 540, target object; 550, network; 560, electronic device;

[0045] 1100, application scenario; 1110, radiation source; 1120, backscatter detector; 1121, detector module; 1130, electronic device; 1131, processor; 1140, target object; 1150, network; 1160, electronic device.

[0046] It should be noted that, for the sake of clarity, in the drawings used to describe the embodiments of the present disclosure, the sizes of the overall / local structures or the overall / local areas may be enlarged or reduced, that is, these drawings are not drawn according to the actual scale. DETAILED DESCRIPTION

[0047] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0048] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0049] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0050] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted according to the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0051] Figure 1 The following diagram schematically shows an application scenario of a backscatter detection device in the related art.

[0052] When radiation rays enter an object, some of them will undergo Compton scattering. During this process, the energy and flight direction of the radiation rays will change. Among them, the flight direction of some rays will change so much that they will return to the side where the radiation source is located. This type of ray is called backscattered ray, or backscatter for short.

[0053] like Figure 1As shown, the application scenario 100 may include a backscatter detection device and a target object 140. The backscatter detection device may include one or more radiation sources 110, one or more backscatter detectors 120, an electronic device 160 and an electronic device 130.

[0054] Exemplarily, the radiation source 110 is configured to emit radiation rays to scan the target object 140 ; ​​the backscatter detector 120 and the radiation source 110 are located on the same side of the target object 140 , and the backscatter detector 120 is configured to receive radiation rays reflected by the target object 140 .

[0055] For example, the radiation source 110 may include an X-ray source, which may emit X-rays to scan the target object 140. The backscatter detector 120 may use its sensitive volume to convert the X-rays reflected by the target object 140 into photons, and then use the photoelectric converter 122 encapsulated therein to convert the photons into pulse electrical signals. The target object 140 may include an object, such as a vehicle, a container, a suitcase or other items in a security inspection scene, or various materials in a material analysis scene. The target object 140 may also include a human body, such as a person passing through a security inspection channel in a station, an airport or other public places. In some embodiments, the radiation source 110 may also include a gamma ray source or other ray source that may produce Compton scattering.

[0056] For example, the electronic device 160 may include devices such as an amplifier for amplifying the pulsed electrical signal output by the backscatter detector 120. The electronic device 130 may include one or more processors and a memory, the memory being used to store one or more programs, wherein when the one or more programs are executed by one or more processors, the one or more processors are enabled to perform data processing on the electronic signal. The radiation source 110, the backscatter detector 120, and the electronic device 160 may be communicatively connected to the electronic device 130 via the network 150 to transmit data. The network 150 may include various connection types, such as wired, wireless communication links, or fiber optic cables, etc. The backscatter detector 120 and the electronic device 160 may be communicatively connected to transmit the pulsed electrical signal.

[0057] For example, in combination Figure 1 The backscatter detection process of the target object 140 in the related art is described.

[0058] First, the radiation source 110 includes an X-ray source and a flying spot forming mechanism (not shown in the figure). The X-ray source emits X-rays, which are modulated by the flying spot forming mechanism to form a flying spot, and perform flying spot scanning on the target object 140 .

[0059] Then, the backscattered ray signal (eg, Figure 2The sequence of radiation events incident on the backscatter detector 120 shown in FIG. 1 ) enters the sensitive volume 121 of the backscatter detector 120. The sensitive volume 121 of the backscatter detector 120 refers to a region of the detector that can interact with incident radiation particles and generate photon signals, and the region may include a radiation-sensitive medium.

[0060] Figure 2 The horizontal axis is the time axis, t 21 ,t 22 ……t 29 Represents the scale on the horizontal axis. The time unit can be represented by nanoseconds (ns), microseconds (µs), milliseconds (ms) or seconds (s). Figure 2 The vertical axis is the energy axis, e 21 、e 22 ……e 28 Represents the scale on the vertical axis. Energy units can be joules or volts, etc. Figure 2 Each vertical line in the figure corresponds to a ray event. The horizontal axis coordinate of the bottom of the vertical line is the incident time point, and the vertical axis coordinate of the top of the vertical line is the ray energy.

[0061] Then, the sensitive volume 121 of the backscatter detector 120 absorbs the radiation through the radiation-sensitive medium and converts it into a large number of photons (ultraviolet-visible light range), generating Figure 3 A schematic diagram showing the change in the number of photons excited by a single ray (such as 1 ray event) over time according to an embodiment of the present disclosure is shown.

[0062] Figure 3 The horizontal axis is the time axis, t 31 ,t 32 ……t 37 Represents the scale on the horizontal axis. The time unit can be represented by nanoseconds (ns), microseconds (µs), milliseconds (ms) or seconds (s). Figure 3 The vertical axis is the signal axis, I 31 ,I 32 ……I 36 Represents the scale on the vertical axis, and its amplitude unit can be expressed using current, such as ampere (A), or using voltage, such as volt (V). Figure 3 The signal decay portion shown in is close to exponential decay.

[0063] Then, the photon stream is converted into an electronic signal in cooperation with the photoelectric converter 122 of the backscatter detector 120. The response time of the photoelectric converter 122 can be faster than the time of the photon pulse, and the corresponding pulse electrical signal of the single ray converted by it is also similar to Figure 3 .

[0064] When the radiation intensity (such as the radiation count rate) is high, the electronic signals generated by a series of radiation events will be stacked together and formed into a continuous pulse waveform using the photoelectric converter 122, such as Figure 4 The pulse electrical signal with signal stacking and superposition in the related art is shown. Figure 4 The pulse electrical signal output by the backscatter detector 120 when a large number of rays are incident is shown. Figure 2 There are multiple ray cases and their explanations. Figure 3 The result after convolution of the response waveform.

[0065] Figure 4 The horizontal axis is the time axis, t 41 ,t 42 ……t 49 Represents the scale on the horizontal axis. The time unit can be represented by nanoseconds (ns), microseconds (µs), milliseconds (ms) or seconds (s). Figure 4 The vertical axis is the signal axis, I 41 ,I 42 ……I 46 Represents the scale on the vertical axis, and its amplitude unit can be expressed using current, such as ampere (A), or using voltage, such as volt (V).

[0066] Then, the electronic signal (such as Figure 4 After the pulse electrical signal shown in the figure passes through the amplifier, the ADC can sample the pulse electrical signal output by the amplifier, and after sampling, a corresponding digital signal sequence is generated and transmitted to the electronic device 130 for processing.

[0067] In the related art, the sampling value of ADC includes the contribution of multiple ray signals, and the information of a single ray signal is lost, so it is impossible to obtain accurate information of different ray conditions, and different rays under the same ray conditions cannot be accurately distinguished. The inventors found that at least one of the reasons is that the detection area area (i.e., the detection area of ​​the sensitive volume) corresponding to a single ray transmission channel (such as a photoelectric converter channel) of the backscatter detector is too large. For example, a detection area area that is too large corresponds to a single photoelectric converter, and this single ray transmission channel will cause the processed ray signal count rate to be too high. The pulse electrical signal has a certain width, and under high count rate conditions, a large amount of signal accumulation and superposition will be generated (such as Figure 4 ), making it impossible to distinguish the signal of a single ray.

[0068] For example, for two different conditions of radiation: 1) energy 10keV (kiloelectron volts), count rate 2Mcps (million counts per second) and 2) energy 20keV, count rate 1 Mcps. The photon flux intensity generated by the accumulation of signals of the two radiation conditions is the same, so the results obtained after ADC sampling are also the same, and it is impossible to distinguish and obtain accurate information of radiation under different conditions.

[0069] Based on the problem that a large number of signals are piled up and superimposed, resulting in the loss of information of a single ray signal, the present disclosure provides Figure 5 The backscatter detection device shown can perform data processing based on an integral (also called current) detection principle, or can perform data processing based on a counting (also called pulse) detection principle.

[0070] Figure 5 The application scenario diagram of the backscatter detection device according to the embodiment of the present disclosure is schematically shown. Figure 6 The schematic diagram of the layout of the radiation source and the backscatter detector according to the embodiment of the present disclosure is schematically shown.

[0071] like Figure 5 and Figure 6 As shown, the application scenario 500 according to this embodiment may include a backscatter detection device and a target object 540. The backscatter detection device may include one or more radiation sources 510, one or more backscatter detectors 520, an electronic device 560 and an electronic device 530.

[0072] In some embodiments, the radiation source 510 is configured to emit radiation rays to scan the target object 540; at least one backscatter detector 520 is distributed on at least one side of the radiation source 510 (such as at least one of the left side and the right side), each of which is configured to detect radiation ray signals, and the radiation ray signals include signals detected after the target object 540 is scanned by the radiation rays. For example, at least one backscatter detector 520 and the radiation source 510 are located on the same side of the target object 540, and the backscatter detector 520 is configured to receive radiation rays reflected by the target object 540. The backscatter detector 520 includes a plurality of detector modules 521 arranged at different positions and having independent radiation signal channels, and the radiation signal channel includes a channel for transmitting the detected radiation ray signals. At least two first detection modules have different detection area areas, and the respective detection area areas are respectively adapted to the respective target first count rates.

[0073] For example, the radiation source 510, the electronic device 530, the target object 540 and the network 550 of this embodiment can refer to the above description. Figure 1 The radiation source 510, the electronic device 530, the target object 540 and the network 550 are not described in detail here.

[0074] For example, the backscatter detector 520 can be a counting detector or an integrating detector. Each detector module 521 can receive the X-rays reflected by the target object 540, convert them into a photon stream, and then output a pulse electrical signal to the electronic device 560 via the corresponding ray signal channel. Multiple detector modules 521 can be regularly distributed at different positions to form a detector array, such as a single-row array or a multi-row array, or multiple detector modules 521 can be irregularly distributed at different positions. The above-mentioned different positions can be located in the same plane or in different planes, for example, distributed on the same curved surface.

[0075] Each detector module 521 includes a radiation-sensitive medium and a photoelectric converter device that are light-proof and encapsulated in a mechanical housing. Each detector module 521 uses its detection area to receive X-rays reflected by the target object 540. The detection area may include an area formed by the radiation-sensitive medium. Specifically, the X-rays interact with the radiation-sensitive medium and generate a certain number of photon streams with a specific decay time. The photon streams are absorbed by the photoelectric converter through the collection cavity and generate a pulse electrical signal. The collection cavity can be implemented by light guides, direct coupling of optical glue, etc.

[0076] Photoelectric conversion devices can have a signal amplification function (amplifying one electron to thousands to millions of electrons) to improve the signal-to-noise ratio. For example, the photoelectric conversion device can be a SiPM (silicon photomultiplier tube). The sensitive area size of SiPM is generally 4mm×4mm to 6mm×6mm to ensure sufficient light collection efficiency, and the number of microcells is generally not less than 3000 to ensure that the number of photons generated by high-energy rays (about 200keV) is within the linear response range of SiPM. The photoelectric conversion device can also be a PMT (photomultiplier tube), or an APD (avalanche photodiode) or HMPT (hybrid photomultiplier tube), etc.

[0077] The backscatter detector 520 includes a plurality of ray signal channels corresponding to a plurality of detector modules 521. Each ray signal channel can detect and record ray events independently and transmit photon signals and pulse electrical signals. Each ray signal channel corresponds to an independent signal transmission channel and can process the incident ray. For example, each detector module 521 has its own independent detection area and photoelectric conversion device.

[0078] For example, the count rate refers to the number of radiation counts recorded per unit time. The detection area of ​​the detector module 521 indicates the size of the detection area. The larger the detection area, the higher the count rate of the overall received radiation, and vice versa.

[0079] The target first count rate is used to indicate the maximum ray count theoretically recorded by the detector module 521 in a unit time. The target first count rate can be predetermined for each detector module 521. The detection area areas between the detector modules 521 can be the same or different, and the target first count rates between the detector modules 521 can also be the same or different. Any two modules with different detection area areas among the multiple detector modules 521 can both be referred to as the first detector modules 521.

[0080] The adaptation of the detection area of ​​the first detector module 521 to its target first count rate means that the detection area of ​​the detector module 521 can meet the design requirements of the target first count rate, for example, the maximum number of rays that can actually be recorded per unit time will not exceed the target first count rate.

[0081] According to the embodiment of the present disclosure, multiple detector modules 521 are distributed in different positions, and their ray signal channels are independent of each other, which can divide the entire detection area of ​​the backscatter detector 520 into multiple independent detection areas. Among them, at least two first detection modules have different detection area areas, and each first detection module is adapted to its respective target first count rate by combining its own detection area area and ray signal channel. Therefore, the detection area area corresponding to each ray signal channel is appropriate, so that the ray signal of the ray count rate within the target range can be received and processed, effectively overcoming the signal accumulation problem caused by the excessively high ray count rate, so that accurate information of a single ray can be obtained.

[0082] Furthermore, the detection areas of at least two first detection modules are different from each other, which can reduce the number of ray signal channels of the backscatter detector 520 as a whole, and reduce the cost and power consumption of photoelectric conversion devices and electronics.

[0083] In some embodiments, the detection area of ​​each first detection module is positively correlated with the distance from the first detection module to the ray beam, where the ray beam includes radiation rays emitted by the radiation source 510 to the target object 540 .

[0084] For example, at a position close to the X-ray beam emitted by the radiation source 510, the ray counting rate is relatively high and varies significantly with the spatial position. The first detection module at this position can use a smaller detection area to reduce the counting rate of a single module and reduce signal stacking. At a position far from the X-ray beam emitted by the radiation source 510, the ray counting rate is relatively low and does not vary significantly with the spatial position. The first detection module at this position can use a larger detection area.

[0085] Figure 6 Each rectangle in FIG corresponds to the detection area of ​​the detector module 521, and the radiation source 510 emits radiation rays from the ray emission area. Figure 6 The detector modules 521 - 1 and 521 - 2 filled with different patterns are both referred to as first detection modules. The distance between the detector module 521 - 1 and the ray beam along the first direction is d 51 The distance between the detector module 521-2 and the beam along the first direction is greater than d 51 D 52 The detection area of ​​the detector module 521 - 1 is smaller than the detection area of ​​the detector module 521 - 2 .

[0086] The distance between the ray beam along the first direction involved in the present disclosure is the distance between the right edge of the detection area along the first direction and the extension line of the ray beam emission area, and the extension line refers to the center line of the ray beam emission area extending along the second direction. Or, d 51 and d 52 It may also be the straight-line distance between the center of the detection area of ​​the detector module 521 - 1 and the center of the ray beam emission area of ​​the detector module 521 - 2 .

[0087] According to the embodiments of the present disclosure, the distance between the detector module 521 and the ray beam can be considered to reasonably determine the detection area of ​​each first detection module, so as to better adapt to the respective target first count rates.

[0088] In some embodiments, the plurality of detection modules further include at least two second detection modules, the detection regions of the at least two second detection modules are the same in area, and the distances of the at least two second detection modules from the ray beam along the first direction are less than or equal to the target threshold.

[0089] For example, in different regions of the X-ray beam emitted by the radiation source 510, the ray count rates are inconsistent, and multiple detector modules 521 with the same detection area area can be set in the same region, and multiple detector modules 521 with different detection area areas can be set in different regions. Any two detector modules 521 with the same detection area area can both be referred to as second detection modules. It can be understood that the first detection module and the second detection module are to more clearly illustrate the differences and similarities in the detection area area, and any detection module can be referred to as either the first detection module or the second detection module.

[0090] like Figure 6 As shown in the current figure, starting from the radiation source 510 and looking from right to left, the detector module 521-1 and the detector module 521-3 in the first column are both called second detection modules. 51 , the distances from the detector module 521-1 and the detector module 521-3 to the ray beam along the first direction are the same, both being d 51Furthermore, the distances from the detector modules 521 in each column to the ray beam along the first direction are the same, and the same target threshold can be set. Each column is regarded as an area, and the multiple detector modules 521 therein can have the same detection area.

[0091] According to an embodiment of the present disclosure, a plurality of second detection modules having the same detection area are provided, which can provide consistent detection performance when detecting radiation in the same area and improve detection reliability.

[0092] In some embodiments, at least two first detection modules are distributed along a first direction, and at least two second detection modules are distributed along a second direction (eg, Figure 6 distribution in the y direction.

[0093] like Figure 6 As shown, detector modules 521-1 and 521-2 are distributed along a first direction, and detector modules 521-1 and 521-3 are distributed along a second direction. The first direction is perpendicular to the second direction. Thus, different count rates near the beam can be considered and the detector modules can be arranged in a targeted manner.

[0094] Figure 7 The schematic diagram of the layout of a radiation source 510 and a backscatter detector 520 according to another embodiment of the present disclosure is schematically shown.

[0095] In some embodiments, two backscatter detectors 520 with the same structure may be symmetrically arranged on both sides (eg, left and right sides) of the radiation source 510. Figure 7 As shown, the two backscatter detectors 520 may have a symmetrical and identical detector module 521 structure, and the backscatter detector structure includes the detection area of ​​each detector module in the plurality of detector modules. For example, two detector modules 521 with the same left and right sides to the radiation source 510 may have the same detection area.

[0096] According to the embodiments of the present disclosure, by symmetrically arranging two identical backscatter detectors 520 on both sides of the radiation source 510, more abundant backscatter data can be detected, thereby improving detection accuracy.

[0097] Figure 8 The schematic diagram of the layout of a radiation source 510 and a backscatter detector 520 according to yet another embodiment of the present disclosure is schematically shown. Figure 8 Each rectangle in may correspond to a detection area of ​​the detector module 521 .

[0098] In some embodiments, backscatter detectors 520 may be provided on two or more sides of the radiation source 510. The distances between the backscatter detectors 520 and the radiation source 510 on any two sides may be the same or different, and the structures of the detector modules 521 of the backscatter detectors 520 on any two sides may be the same or different. The distance between the backscatter detectors 520 and the radiation source 510 on each side and the structure of the detector modules 521 may be determined based on a specific region on the target object 540 to be detected. For example, different regions on the target object 540 have different structures and materials, and Compton scattering distributions are also different, so the structure of the corresponding backscatter detector 520 may be determined based on the characteristics of each region.

[0099] like Figure 8 As shown, two backscatter detectors 520 are arranged on both sides of the radiation source 510. The detector modules 521 of the two backscatter detectors 520 have different structures and each detects radiation signals of different regions of the corresponding target object. For example, the number and arrangement of the multiple detector modules 521 are different, and the detection region shape, detection region size, and detection region area of ​​the detector modules 521 are not completely consistent.

[0100] According to the embodiments of the present disclosure, the backscatter detector 520 on each side can detect a specific area on the target object 540, thereby improving the detection accuracy.

[0101] In some embodiments, the detection area of ​​at least one detector module 521 among the multiple detector modules 521 of the backscatter detector 520 is adjustable. For example, the detection area of ​​the first detector module 521, the second detector module 521 or other detector modules 521 is adjustable. For example, a retractable shielding window is configured for each detector module 521 by mechanical adjustment. The material of the shielding window can shield radiation, and the size of the detection area where each detector module 521 can receive radiation signals can be adjusted by changing the size of the window.

[0102] According to the embodiments of the present disclosure, the adjustability of the detection region area enables the detector module 521 to adapt to different target objects 540, different counting rates, different positions, etc., with higher flexibility.

[0103] In some embodiments, the detection region area of ​​each detector module 521 in the at least one detector module 521 is adjusted according to the difference between the detected actual count rate and the target first count rate.

[0104] For example, if the actual count rate is lower than the target first count rate by a certain value, such as a difference of more than 20%, the count rate can be increased by increasing the detection area, and vice versa, the detection area can be reduced to avoid overlap. This can improve the accuracy and efficiency of the detected data. The detection area area changes within a certain range, in which case a constant target first count rate can be maintained.

[0105] In some embodiments, Figure 8 Two backscatter detectors 520 are shown distributed on both sides of the radiation source 510 , and the structure of each backscatter detector 520 is determined according to the area of ​​the target object 540 to be detected.

[0106] For example, if there is more Compton scattering on one side of the target object 540, resulting in a higher count rate on that side, then the detection area of ​​the detector corresponding to the detector module 521 for detecting that side can be adjusted to be smaller. On the contrary, if there is less Compton scattering on the other side, resulting in a lower count rate, the detection area of ​​the detector corresponding to the detector module 521 for detecting that side can be increased. This can more effectively meet the detection needs of different locations.

[0107] It should be noted that the arrangement of the multiple detector modules 521 in the backscatter detector 520 of the embodiment of the present disclosure, as well as the shape and detection area of ​​each detector module 521 are not limited to Figure 6 , Figure 7 and Figure 8 As shown, it can be flexibly adjusted within the scope of the inventive concept of the present disclosure.

[0108] In some embodiments, the detection region area of ​​each detector module 521 is predetermined based on its target second count rate per unit area and the target pulse width of a single radiation signal.

[0109] The target second count rate is used to indicate the maximum ray count recorded in the detection area per unit area per unit time. Unlike the target second count rate, the target first count rate is the maximum ray count recorded in the entire detection area per unit time. For example, the unit area is per square centimeter and the unit time is 1 second, which is only an example.

[0110] A single ray signal is obtained through a single ray event, e.g. Figure 3 The target pulse width is used to indicate the pulse width of the pulse waveform of a single ray signal when signal accumulation does not occur. Different detector modules 521 may have the same or different target second count rates.

[0111] It can be understood that the ray count recorded in the detection region per unit area per unit time affects the ray count of the entire detection region, and the pulse width of a single ray signal affects whether the pulse waveforms of multiple ray signals are stacked.

[0112] According to the embodiments of the present disclosure, a suitable detection region area can be determined based on the target second count rate per unit area and the target pulse width of a single ray signal, thereby effectively preventing signal accumulation and superposition.

[0113] The decay time and afterglow effect of the radiation-sensitive medium affect the pulse width of a single radiation signal. For example, some existing technical solutions use materials with long decay times such as CsI, GOS, and BaFCl as radiation-sensitive media, which results in a larger signal pulse width (e.g. Figure 3 As shown in the figure), it is also easy to produce signal accumulation and superposition; in addition, materials such as CsI have a more obvious afterglow effect, that is, the first incident ray signal will continue to generate photon signals, thereby affecting the identification of the later incident ray signals.

[0114] In some embodiments, the detection area of ​​each detector module 521 includes a radiation-sensitive medium, which is configured to interact with radiation rays reflected by the target object 540 to generate radiation photons; wherein the decay time of the radiation photons is less than or equal to the first target time, and / or the duration of the afterglow effect is less than or equal to the second target time.

[0115] After receiving radiation exposure, Figure 3 The photons generated by the radiation-sensitive medium shown will decay in two steps. The first step is to decay rapidly from the peak output to a lower value. This process is called decay. The attenuation gradient at this value has essentially changed to a lower decay rate. The second step continues to decay at this lower decay rate. This low-intensity decay is generally a longer decay, and the decaying luminescence at this time is called afterglow. For example, it can be defined as 1% to 2% below the peak value (only as an example). For example, the initial rapid decay time is called the decay time, such as from the peak value to the moment 1 / e of its peak value. The natural constant e is the base of the natural logarithm. The duration of the afterglow effect in the disclosed embodiment can be calculated based on the time from the peak value to decay to 1000ppm (0.1% to 0.2%).

[0116] Exemplarily, the first target time and the second target time are used to constrain multiple ray signals from signal accumulation and superposition. For example, by testing various materials of ray-sensitive media, materials with short decay time and small afterglow effect can be selected for testing and evaluation to see whether multiple ray signals can be constrained from signal accumulation and superposition. For example, the first target time can be 200 nanoseconds, and the second target time can be 10 milliseconds, which is only an example.

[0117] Fig. 9 The figure schematically shows a comparison diagram of the response pulse waveforms of a fast decay crystal (GAGG) and a slow decay crystal (GOS) according to an embodiment of the present disclosure.

[0118] Fig. 9 The horizontal axis is the time axis, t 91 ,t 92 ……t 97 Represents the scale on the horizontal axis. The time unit can be represented by nanoseconds (ns), microseconds (µs), milliseconds (ms) or seconds (s). Fig. 9 The vertical axis is the signal axis, I 91 ,I 92 ……I 96 Represents the scale on the vertical axis, and its amplitude unit can be expressed in current, such as ampere (A), or voltage, such as volt (V). GAGG is gadolinium aluminum gallium garnet, and GOS is gadolinium oxysulfide crystal.

[0119] like Fig. 9 As shown, the response pulse waveform of GAGG has a shorter decay time and a smaller afterglow effect than the response pulse waveform of GOS. By defining the first target time and the second target time, multiple ray signals can be constrained from signal accumulation and superposition. Therefore, GAGG can be selected as the material of the ray-sensitive medium.

[0120] It should be noted that, in some embodiments, fast-attenuation crystals such as BGO (bismuth germanate), LYSO (lutetium yttrium silicate) or plastic scintillators may also be selected as the material of the radiation-sensitive medium, but the present disclosure is not limited thereto.

[0121] In some embodiments, the target second count rate per unit area of ​​each detector module 521 is predetermined according to its relative position to the radiation beam, for example, the target second count rate is predetermined according to the distance from the radiation beam and at different positions of the radiation beam.

[0122] In some embodiments, the target second count rate per unit area of ​​each detector module 521 is negatively correlated with its distance from the radiation beam along the first direction.

[0123] For example, at a position close to the X-ray beam emitted by the radiation source 510, the ray counting rate is high, and the target second counting rate per unit area of ​​the detector module 521 at this position can be high; at a position far from the X-ray beam emitted by the radiation source 510, the ray counting rate is low, and the target second counting rate per unit area of ​​the detector module 521 at this position can be low; refer to Figure 7 The farther the detector module 521 is from the radiation source 510 along the first direction, the lower the target second count rate per unit area, and vice versa. Thus, the set target second count rate distribution is consistent with the actual detection environment, improving the detection accuracy.

[0124] In some embodiments, the detection area of ​​each detector module 521 is predetermined based on its target second count rate per unit area and the target pulse width of a single radiation signal, including: multiplying the target second count rate per unit area of ​​each detector module 521 and the target pulse width of a single radiation signal to obtain a first value; and determining the detection area based on the inverse of the first value.

[0125] The calculation process of the detection area S is derived below.

[0126] The count rate of a single ray signal channel of each detector module 521 (ie, the target first count rate) satisfies Formula 1:

[0127] Formula 1

[0128] in, is the target first count rate, w is the target pulse width of a single ray signal, for example, it is the minimum pulse width allowed without signal accumulation and superposition. 1 represents 1 second.

[0129] The target first count rate is the target second count rate per unit area r unit The product of the detection area S is:

[0130] Formula 2

[0131] Combining Formula 1 and Formula 2, we can eliminate get:

[0132] Formula 3

[0133] in, is a first value, and the detection region area S is less than or equal to the reciprocal of the first value.

[0134] In some embodiments, determining the detection area based on the reciprocal of the first value includes: multiplying the reciprocal of the first value by a safety factor to determine the detection area, wherein the value of the safety factor is less than 1. The safety factor values ​​of different detector modules 521 may be the same or different, so as to adjust the count rate of the detector module 521 in a targeted manner.

[0135] Based on formula 3, the insurance coefficient is introduced to obtain:

[0136] Formula 4

[0137] Wherein, k is the insurance weight, and the reciprocal of k is the insurance coefficient. For example, the value of k is greater than or equal to 2 and less than or equal to 10.

[0138] Fig.10 The figure schematically shows a waveform diagram of a pulse electrical signal output by a detector module according to an embodiment of the present disclosure.

[0139] Fig.10 The horizontal axis is the time axis, t 101 ,t 102 ……t 109 Represents the scale on the horizontal axis. The time unit can be represented by nanoseconds (ns), microseconds (µs), milliseconds (ms) or seconds (s). Fig.10 The vertical axis is the signal axis, I 101 ,I 102 ……I 106 Represents the scale on the vertical axis, and its amplitude unit can be expressed using current, such as ampere (A), or using voltage, such as volt (V).

[0140] Referring to Formula 4, for example, the target second count rate per unit area is 10kcps / cm 2 , the target pulse width w of a single ray signal is 1 μs, and the detection area S is 100 cm 2 ,like Fig.10 , most of the pulse signals did not accumulate.

[0141] According to the embodiments of the present disclosure, by introducing a safety factor, the size of the detection area can be controlled, and the ray counting rate of a single ray signal channel can be further controlled to avoid signal accumulation and superposition.

[0142] When scanning one or more points of the target object, the transmitted radiation or scattered radiation from the same scanning point is detected by multiple positions of the radiation-sensitive medium of the backscatter detector, and currently only the result of adding up the detection data of each position is used as the radiation signal of the same scanning point. A radiation image is obtained based on the radiation signal obtained based on the summation result, and then the radiation image is identified to obtain the material identification result.

[0143] Based on the sum of the detection data, a radiation signal is obtained, and then the radiation image is obtained by processing the radiation signal, which loses some information and is not conducive to improving the accuracy of material recognition.

[0144] Fig.11 The following schematically shows an application scenario diagram of a material identification device according to an embodiment of the present disclosure. Fig.12 The figure schematically shows a data flow diagram among a backscatter detector, an electronic device and a processor according to an embodiment of the present disclosure.

[0145] It should be noted that in the embodiments of the material identification device or the material identification method, a radiation detector including a plurality of detector modules may be used, and the radiation detector may be arranged on the same side of the target object as a backscatter detector with the radiation source, or may be arranged on opposite sides of the target object with the radiation source as a transmission detector. It is understood that when the radiation detector is used as a backscatter detector, it may have an adaptive structure, size, detection parameters, etc. with the backscatter scanning scene. When the radiation detector is used as a transmission detector, it may have an adaptive structure, detection parameters, etc. with the transmission scanning scene.

[0146] The following example takes the radiation detector as preferably a backscatter detector.

[0147] like Fig.11 As shown, the application scenario 1100 according to this embodiment may include a backscatter detection device and a target object 1140. The backscatter detection device may include one or more radiation sources 1110, one or more backscatter detectors 1120, an electronic device 1160 and an electronic device 1130.

[0148] For example, the radiation source 1110, the electronic device 1130, the target object 1140 and the network 1150 of this embodiment can refer to the above description. Figure 1 The radiation source 1110, the electronic device 1130, the target object 1140 and the network 1150 are not described in detail here.

[0149] In some embodiments, the backscatter detector 1120 may be the backscatter detector 520 described above, and one or more embodiments of the backscatter detector 520 described above may be applied to the backscatter detector 1120. For example, at a position close to the X-ray beam emitted by the radiation source 510, the ray count rate is high and varies significantly with the spatial position, and the detection module at this position may use a smaller detection area; at a position far from the X-ray beam emitted by the radiation source 510, the ray count rate is low and does not vary significantly with the spatial position, and the first detection module at this position may use a larger detection area. It can be seen that while reducing the number of ray signal channels, accurate spatial distribution information of ray indicators can also be obtained.

[0150] In other embodiments, the backscatter detector 1120 is not limited to the backscatter detector 520 described above. For example, it may include a plurality of detector modules 1121 arranged at different positions, wherein the detection area of ​​each detector module 1121 may be the same or different, and the radiation signal channels of each detector module 1121 may be independent of each other or multiplexed. This embodiment is not specifically limited as long as the position of each detector can be identified.

[0151] In some embodiments, the backscatter detector 1120 is used to scan the target object 1140 in response to radiation rays, and detects radiation ray signals using multiple detector modules 1121, where the multiple detector modules 1121 are arranged at different positions and the ray signal channels are independent of each other.

[0152] Reference Fig.11 and Fig.12 , the processor 1131 is configured to perform operation S1201~operation S1202. Fig.12 The middle dotted line is used to represent the corresponding position relationship.

[0153] In operation S1201, based on the radiation ray signal detected by each detector module 1121, N ray indices corresponding to the position of each detector module 1121 are calculated, where N is an integer greater than or equal to 1; in operation S1202, the material of the target object is identified based on the indicator value of each ray indicator at different positions.

[0154] In the backscattering scenario, the ray events are random, and their energy and the time interval between two events conform to a certain statistical distribution. When the same X-ray beam is incident on objects with different properties (material composition, surface density, etc.), the statistical distribution characteristics of the rays in the backscattering scenario will also change, which is reflected in the following three aspects:

[0155] 1) Quantity: Lighter materials or materials with higher surface density have a higher probability of scattering. 2) Energy: Different materials have different backscattering energy spectrum distributions, which are related to surface density. 3) Angular distribution: Backscattering in different directions has different quantity and energy distributions.

[0156] The basic principle of backscatter detection technology is to use a backscatter detector to measure the values ​​and changes of the above three statistical features or their combination, and infer the material information and changes of the target object. The signal characteristics corresponding to the above three statistical features in the detector are:

[0157] 1) Count rate, which reflects the number of backscattered rays. 2) Pulse height, which reflects the energy of backscattered rays. 3) Detector spatial position, which reflects the angular distribution information of backscattered rays.

[0158] Fig.13 The diagram schematically shows a backscatter detection diagram of the detector modules at different positions according to an embodiment of the present disclosure.

[0159] Combination Fig.13 For example, the statistical characteristics of backscatter generated by two common objects, iron plate (hereinafter referred to as Fe, 5mm thick, representing heavy materials such as metal) and polyethylene block (hereinafter referred to as PE, 10cm thick, representing light materials such as plastic) when irradiated by a 200kVp X-ray machine are compared. The detector module 1121 may include a detector module P1 and a detector module P2. In FIG13 , the detector module P1 represents the detector pixel closer to the X-ray beam, and the detector module P2 represents the detector pixel farther away.

[0160] Fig.14 The figure schematically shows the energy spectra of backscattering of different materials at different positions after peak normalization. Fig.14 The horizontal axis is the energy axis, e 141 、e 142 ……e 149 Represents the scale on the horizontal axis, and the energy unit can be keV.

[0161] Reference Fig.14 ,For the energy information, the energy spectrum peak of Fe is several tens of keV higher than the energy spectrum peak of PE; and for the energy spectra at different positions, the energy spectrum peak at the detector module P2 (far away from the X-ray beam) is higher.

[0162] Fig.15 The relative amount of backscattered rays at different locations from different materials is shown schematically. Fig.15 The vertical axis is the quantity axis, n 151 、n 152 ……n 159 Represents the scale on the vertical axis.

[0163] Reference Fig.15 ,For the ray quantity information, at the same detection position, the relative number of rays at PE is greater than that of rays at Fe; while for the relative number of rays at different positions, the relative number of rays at P1 (close to the X-ray beam) is greater.

[0164] Combination Figure 11~Figure 15 In operation S1201, the processor 1131 can calculate N radiation indicators at the location of each detector module 1121 based on the count rate characteristics and pulse height characteristics detected by each detector module 1121. In operation S1202, N radiation indicators can be obtained at each location, so that the material of the target object 1140 can be identified through the distribution of each indicator in space.

[0165] Therefore, material identification and a better signal-to-noise ratio can be achieved by improving the resolution of the energy, count rate, and position of the rays.

[0166] According to an embodiment of the present disclosure, there are differences in the signals generated by the detector modules at different positions in the backscatter detector, and additional information can be obtained by comparing these differences. Multiple detector modules 1121 distributed at different positions use their own ray signal channels to receive the radiation reflected by the target object 1140. By each detector module 1121 receiving the radiation reflected by the target object 1140, one or more ray indicators corresponding to each position can be independently calculated. By analyzing the spatial distribution differences of the indicator values ​​of each ray indicator at different positions, the material of the target object 1140 can be accurately identified.

[0167] Compared with the method of identifying materials using backscatter images, identifying materials by using the spatial distribution differences of each ray indicator at different locations provides a different dimensional identification method, which can serve as an effective supplement to backscatter image identification. When using the spatial distribution of ray indicators to identify materials independently, it can also have high identification accuracy and efficiency.

[0168] Fig.16 The figure schematically shows a data flow diagram among a backscatter detector, an electronic device and a processor according to another embodiment of the present disclosure.

[0169] like Fig.16 As shown, the electronic device includes an amplifier, a threshold comparator, a counter, and a channel encoder. In some embodiments, the threshold comparator is used to perform energy threshold judgment on multiple groups of ray signals to filter out ray signals in different energy ranges from each group of ray signals, wherein each group of ray signals is obtained based on the radiation rays received by the corresponding detector module 1121; the counter is connected to the processor 1131 in communication, and the counter is used to obtain the number of ray signals in different energy ranges in each group of ray signals.

[0170] It can be understood that different energy ranges refer to multiple energy ranges, and the threshold comparator is used to filter out complete or partial ray signals from these energy ranges. When filtering partial ray signals, it means that the unselected remaining part of each group of ray signals does not fall within any energy range set by the threshold comparator.

[0171] Generally, the pulse electrical signal directly output by the photoelectric conversion device is difficult to be directly transmitted to the remote processor 1131 for further processing. Therefore, near the output end of the photoelectric conversion device, the amplifier amplifies the signal and then transmits it to the remote processor 1131, so as to improve the signal-to-noise ratio after transmission. The signal decay time designed by the amplifier can be slightly less than the decay time of the radiation-sensitive medium, or equivalent to it (such as 200 ns to 1μs), because too small decay time will cause the signal-to-noise ratio of the amplified signal to be insufficient, while too large decay time will cause serious signal accumulation and exceed the normal working range of the subsequent signal processing circuit.

[0172] The threshold comparator is used to receive the pulse electrical signal amplified by the amplifier. The threshold comparator determines the energy of the signal and generates a corresponding trigger signal. The counter records the number of trigger signals per unit time, thereby obtaining the energy and counting rate information of the ray, and combines it with the channel coding containing the position information, and transmits it to the processor 1131 for data analysis after packaging.

[0173] Reference Fig.16 The threshold comparator may include a high energy threshold comparator and a low energy threshold comparator, which are connected to the high energy counter and the low energy counter respectively. The function of the threshold comparison is to realize pulse energy discrimination, that is, to screen out the ray signals in different energy ranges.

[0174] In the related art, the signal output by the detector photoelectric conversion device is a pile-up signal, and the ADC (analog-to-digital converter) is generally used to directly sample the amplitude of the signal. This method is relatively simple and mature, but the relative fluctuation of the amplitude is large when the counting rate is relatively low and the radiation energy is relatively low, resulting in a poor signal-to-noise ratio.

[0175] In this embodiment, for example, for an X-ray machine of about 200 kVp, two energy ranges can be set. The high energy threshold comparator screens the ray signals in the high energy range, and the low energy threshold comparator screens the ray signals in the low energy range. The low energy range is used to eliminate the background signal and interference signal caused by the noise of the photoelectric conversion device to improve the signal-to-noise ratio, for example, it can be set to 5 keV to 10 keV (corresponding voltage level). The high energy range is used to screen the signal of high energy rays, and can be set to 70 keV to 100 keV.

[0176] When a ray signal passes through the threshold comparator, a specific waveform is generated as a trigger signal for counting. Fig.17 A waveform diagram of a group of ray signals containing noise is schematically shown, wherein the signal waveform shown has multiple low-energy ray events and multiple high-energy ray events.

[0177] Fig.17 The horizontal axis is the time axis, t 171 ,t 172 ……t 179 Represents the scale on the horizontal axis. The time unit can be represented by nanoseconds (ns), microseconds (µs), milliseconds (ms) or seconds (s). Fig.17 The vertical axis is the signal axis, V 171 、V 172 ……V 177 Represents the scale on the vertical axis, and its amplitude unit can be expressed using voltage, such as volts (V), or using current, such as amperes (A). Fig.17 The two dotted lines in the middle level are the low threshold and the high threshold, which are used to divide the low energy range and the high energy range, such as 5keV for the low threshold and 70keV for the high threshold.

[0178] Fig.18 The energy spectra of backscattering of different materials at different positions are schematically shown. Fig.18 The pulse waveform shown is not normalized and contains both energy spectrum and count rate information. Fig.18 , choosing the appropriate energy range can distinguish the high and low energy components in the energy spectra of Fe and PE.

[0179] Fig.18 The horizontal axis is the energy axis, e 181 、e 182 ……e 189 Represents the scale on the horizontal axis. Energy units can be joules or volts, etc. Fig.18 The vertical axis is the quantity axis, n 181 、n 182 ……n 189 Represents the scale on the vertical axis. Fig.18 The two vertical dashed lines in the middle are the low threshold and the high threshold respectively.

[0180] It should be noted that the threshold comparator is not limited to the high energy threshold comparator and the low energy threshold comparator, and one or more threshold comparators may be provided. Similarly, one or more counters may also be provided.

[0181] For example, refer to Fig.16, the electronic device may also include at least one of a low-pass filter, a shaping amplifier and a time discriminator. For example, a low-pass filter (e.g., a bandwidth of 10MHz to 100MHz) is added before the high-energy threshold comparator and the low-energy threshold comparator to suppress interference signals and single photons or crosstalk signals; a shaping amplifier is added before the high-energy threshold comparator and the low-energy threshold comparator to reduce the pulse width, thereby increasing the upper limit of the counting rate; a holding time discriminator is added between each pair of threshold comparators and counters, that is, only signals that pass the threshold comparator and remain for more than a certain period of time can be sent to the counter, so as to exclude false cases caused by fluctuations in the signal attenuation process.

[0182] In some implementations, the processor 1131 is further configured to assign a corresponding location identifier according to the location of each detector module 1121; wherein the N radiation indicators corresponding to the location of each detector module 1121 are bound to the location identifier of the detector module 1121, for example, the binding operation is performed by the processor 1131.

[0183] Exemplarily, the channel encoder is used to generate a unique channel code for each detector module 1121, which can map the position of the detector module 1121, that is, the spatial distribution information of the ray. The processor 1131 can assign a corresponding position identifier based on the channel code of each detector module 1121, such as Fig.18 As shown, location identifier_1, location identifier_2, ..., location identifier_N-1 and location identifier_N respectively have corresponding detector modules 1121.

[0184] For example, the channel encoder may include a multi-channel data acquisition card. The multi-channel data acquisition card can be used to simultaneously acquire signals from multiple channels, with the front end of each channel connected to the photoelectric converter of each detector module 1121, and the back end of each channel connected to the amplifier, forming a ray signal channel of each detector module 1121 to transmit pulse electrical signals.

[0185] According to an embodiment of the present disclosure, binding a position identifier to the radiation index at each position can help track and associate the output data of the detector module 1121, which can be helpful in accurately obtaining the spatial distribution of the radiation index and facilitating material identification based on the spatial distribution of the radiation index.

[0186] In some embodiments, calculating the N ray indices corresponding to the position of each detector module 1121 in operation S1201 includes: for each group of ray signals, obtaining the target number of ray signals in the target energy range in different energy ranges; calculating the ratio of the target number to the total number of ray signals to obtain a first ray index, wherein the total number of ray signals is obtained based on the sum of the numbers of all ray signals in different energy ranges.

[0187] For example, the target energy range is a high energy range, and the total number of ray signals is the sum of the high energy counts (i.e., the target number) in the high energy range and the low energy counts in the low energy range. The first ray index may be the proportion of high energy counts, as shown in Formula 5:

[0188] Formula 5

[0189] Where NLE is the low energy count (corresponding to Fig.18 The area between the two dashed lines in the figure), NHE is the high energy count (corresponding to Fig.18 ER is the ratio of high-energy counts. A high ER means more high-energy components in the energy spectrum (higher average energy of the rays), whereas a low ER means more low-energy components (lower average energy of the rays).

[0190] In some embodiments, calculating the N radiation indicators corresponding to the position of each detector module 1121 in operation S1201 includes: for each group of radiation signals, calculating the ratio of the total number of radiation signals to the counting period of the counter to obtain a second radiation indicator, wherein the total number of radiation signals is obtained based on the sum of the numbers of all radiation signals under different energy ranges, and the counting period includes the period for obtaining the number of radiation signals.

[0191] The second ray index may be a ray counting rate, as shown in Formula 6 below:

[0192] Formula 6

[0193] Where CR represents the radiation count rate, N HE is high energy count, N LE is the low energy count, T is the counting period of the counter. The total number of ray signals is the sum of the high energy count and the low energy count.

[0194] It should be noted that the energy range can be flexibly set according to the needs, so the calculation method of the first ray index and the second ray index is not limited to the above formula 5 and formula 6. In addition, the N ray indexes disclosed in the present invention are not limited to the first ray index and the second ray index, and there may be other ray indexes, such as scattering angle, detection efficiency, attenuation coefficient, etc.

[0195] In some embodiments, in operation S1202, identifying the material of the target object 1140 according to the indicator value of each ray indicator at a different position includes: mapping the indicator values ​​of the first ray indicator and the second ray indicator at different positions in a coordinate system, wherein the vertical axis of the coordinate system corresponds to the first ray indicator and the horizontal axis of the coordinate system corresponds to the second ray indicator; and identifying the material of the target object 1140 according to the distribution of the first ray indicator and the second ray indicator in the coordinate system.

[0196] In some embodiments, the radiation source 1110 of the backscatter detection device is configured to perform a flying spot scan on the target object 1140, wherein calculating N radiation indices corresponding to the position of each detector module 1121 includes: for each radiation index, a plurality of index values ​​corresponding to the position of each detector module 1121, wherein the plurality of index values ​​correspond one-to-one to the plurality of point positions of the flying spot scan.

[0197] Fig.19 The distribution diagram of the ray indicators of different materials in the coordinate system according to the embodiment of the present disclosure is schematically shown. Fig.19 The vertical axis is the high energy count ratio (ER), p 191 、p 192 …… 196 is the vertical axis scale, the unit can be percentage. The horizontal axis is the ray count rate (CR), c 191 、c 192 ……c 196 is the horizontal axis scale, the unit can be counts per second (cps).

[0198] Take the various radiation indicators of Fe detected at the detector module P1 as an example. Fig.19 The mark in is "○". Each "○" corresponds to a point position on the flying spot scanning target object. The vertical axis coordinate of each "○" is the index value of the first ray index, and the horizontal axis coordinate is the index value of the second ray index, that is, each "○" can fuse the information of multiple ray indexes. All "○"s are all the first ray indexes and all the second ray indexes corresponding to the position of the detector module P1. The Fe at the position of the detector module P2, the PE at the position of the detector module P1, and the Fe at the position of the detector module P2 are the same, and will not be repeated here.

[0199] like Fig.19 , the first ray index and the second ray index of different materials have different spatial distributions. For example, the various ray indexes of Fe detected at the position of the detector module P1 (see the mark "○") and the various ray indexes of PE detected at the position of the detector module P1 (see the mark "□") are two clusters of marks distributed at different positions in the coordinate system. For example, the various ray indexes of Fe detected at the position of the detector module P1 (see the mark "○") and the various ray indexes of Fe detected at the position of the detector module P2 (see the mark "●") are two clusters of marks distributed at different positions in the coordinate system. Through preliminary experimental tests, the above information of the objects of different materials and volumes can be stored as feature data in the database. When the equipment is running, the material information closest to the actual data can be found through appropriate algorithms (table lookup, fitting, pattern matching, neural network, etc.), thereby realizing the ability to identify substances.

[0200] For example, forming Fig.19The image shown is input into the pre-trained neural network model to output the predicted material. The neural network model can be trained using samples of different materials and volumes. Each sample includes similar Fig.19 Images shown along with material labels.

[0201] According to the embodiments of the present disclosure, by mapping to a coordinate system, the spatial distribution of each ray index can be clearly reflected, and more information can be provided to distinguish different materials.

[0202] It should be noted that the present disclosure is not limited to Fig.19 The two-dimensional coordinate system shown can also be mapped to a coordinate system of more dimensions, for example, when more ray indices are calculated.

[0203] In some embodiments, in operation S1202, the indicator value of each ray indicator at different positions is matched with the indicator information of different materials, wherein the indicator information of different materials includes the pre-calculated indicator values ​​at different positions; the material of the target object 1140 is identified based on the matching result.

[0204] For example, the information on the indicators of different materials includes the following: Fig.11 The backscatter detection device shown detects various materials and obtains a set of index values. The index value of each ray index at different positions can be obtained by experiment or calculation, such as multiple index values ​​at the same position. Matching refers to the process of comparing the index value of each ray index at different positions with the index information of known materials.

[0205] For example, you can get Fig.19 The Fe-related markers in the image shown are then matched with the images of the index information of each material in the database pre-mapped in the same coordinate system, such as calculating the similarity. Alternatively, the difference in the index value of the same ray index in the same position can be directly compared.

[0206] According to an embodiment of the present disclosure, the accuracy of material identification is improved by matching the actual value of the ray index with the index information of different materials in a pre-calculated database.

[0207] In some embodiments, during the material identification process, the Fig.11 , and refer to Figure 7 and Figure 8, using a radiation source 1110 to emit radiation rays, and setting two backscatter detectors 1120 on both sides of the radiation source 1110; wherein, using multiple detector modules 1121 of the backscatter detector 1120 to detect radiation ray signals includes: using multiple detector modules 1121 of each backscatter detector 1120 in the two backscatter detectors 1120 to detect radiation ray signals.

[0208] According to the embodiments of the present disclosure, more radiation signals can be detected by using two backscatter detectors 1120, and more information for material identification can be obtained. For example, not only are there differences in the distribution of radiation signals detected by detector modules 1121 at different positions on the same backscatter detector 1120, but there are also differences in the distribution of radiation signals between the two backscatter detectors 1120.

[0209] In some embodiments, the two backscatter detectors 1120 distributed on both sides of the radiation source 1110 may have the same or different structures, and each detects radiation ray signals corresponding to different regions of the target object 1140. In the case of different structures, the structure of each backscatter detector 1120 is determined according to the region of the target object 1140 to be detected, and the detector structure includes the detection region area of ​​each detector module 1121 in the plurality of detector modules 1121.

[0210] For example, different regions on the target object 1140 have different structures and materials, and Compton scattering distributions are also different, so the corresponding backscatter detector 1120 structure can be determined according to the characteristics of each region. For example, the number and arrangement of multiple detector modules 1121 are different, and the detection area shape, detection area size, and detection area area of ​​the detector module 1121 are not completely consistent.

[0211] According to the embodiments of the present disclosure, the backscatter detector 1120 on each side can detect a specific area on the target object 1140, thereby improving the detection accuracy and material identification accuracy.

[0212] In some embodiments, before matching the index value of each radiation index at different positions with the index information of different materials respectively, it also includes: determining the index information of the material to be matched based on the respective structures of the two backscatter detectors 1120; wherein the index information of the material to be matched is calculated based on the radiation ray signal based on the material to be matched detected by two preset backscatter detectors, and the two preset backscatter detectors have a one-to-one correspondence with the two backscatter detectors 1120 and have approximately the same structure.

[0213] It can be understood that the detector area of ​​each detector module 1121 is adapted to the target first count rate to a certain extent, so as to avoid the stacking phenomenon, have a better signal-to-noise ratio, more accurate detection, and more accurate index values ​​of the calculated radiation index. Therefore, the different structures of the backscatter detector 1120 affect the calculation results of the radiation index of the same scanning point to a certain extent.

[0214] For example, each material can be identified in advance through simulation tests. Two preset backscatter detectors can be set on both sides of the preset radiation source, and the preferred structures of the two preset backscatter detectors can be determined according to the characteristics of different areas of the target material. Then, radiation scanning, radiation detection, and radiation index calculation steps are performed. On the basis of being able to accurately identify the target material based on the distribution of radiation indicators, relevant information (such as radiation parameters, radiation indicators, detector structure, etc.) is stored in the database. Taking the detector structure as an example, each detector module in each preset detector has a corresponding position code, and the position code is stored in a mapping manner with the detector area area and bound to the identified material.

[0215] It should be noted that the materials involved in the present disclosure may include raw materials, and may also include items of the same category as the target object. For example, if the target object is a luggage of a specific model of brand A, then the "materials" may include luggage of a specific model of brand A.

[0216] During the scanning of the target object 1140, the detection area of ​​each detector module 1121 in each backscatter detector 1120 is adjusted according to the difference between the detected actual count rate and the target first count rate. After the adjustment, the steps of radiation scanning, radiation detection, and radiation index calculation are performed. Then, the mapping relationship between the position code of each detector module of each backscatter detector 1120 and the detector area is obtained, and one or more materials bound with the same or similar mapping relationship are retrieved in the database. Then, the index value of each radiation index at different positions is matched with the index information of the retrieved material.

[0217] For example, the detector structures being substantially the same may mean that there are a certain number of detector regions with the same position codes, and the difference in area is within a certain range.

[0218] According to the embodiments of the present disclosure, a multi-stage identification method of first screening the detector structure and then performing index matching can reduce the matching workload and improve the accuracy of material identification.

[0219] In some embodiments, a radiation detection method is also provided, which includes: causing a radiation source to emit radiation rays to scan a target object, and causing each backscatter detector of at least one backscatter detector to detect a radiation ray signal, wherein the radiation ray signal includes a signal detected after the target object is scanned by the radiation rays.

[0220] It should be noted that for the parts not mentioned in the radiation detection method of this embodiment, reference can be made to the above Figure 5~Figure 10 The corresponding backscatter detection device is understood in each embodiment. That is, the radiation detection method of this embodiment includes using the above-described Figure 5~Figure 10 The steps of each component of the backscatter detection device correspond to the following. Moreover, the implementation methods, technical problems solved, functions realized, and technical effects achieved are the same or similar to the implementation methods, technical problems solved, functions realized, and technical effects achieved of the corresponding components in some embodiments of the device, and will not be repeated here.

[0221] In some embodiments, a material identification method is also provided, which includes: in response to scanning a target object with radiation rays, detecting radiation ray signals using multiple detector modules of a backscatter detector, wherein the multiple detector modules are arranged at different positions and the ray signal channels are independent of each other; calculating N ray indicators corresponding to the position of each detector module based on the radiation ray signals detected by each detector module, where N is an integer greater than or equal to 1; and identifying the material of the target object based on the indicator value of each ray indicator at different positions.

[0222] Exemplarily, the material identification method of this embodiment can perform radiation detection through the above-mentioned radiation detection method, and then the processor executes the steps of calculating radiation indicators and identifying materials. Alternatively, the material identification method of this embodiment can perform backscatter detection through a radiation detection method that already exists in the relevant technology or will be disclosed in the future, and then the processor executes the steps of calculating radiation indicators and identifying materials.

[0223] It should be noted that for the parts not mentioned in the material identification method of this embodiment, reference can be made to the above Figure 11~Figure 19 The material identification method of this embodiment includes using the material identification method described above to identify the material of the device. Figure 11~Figure 19 The steps of each component of the corresponding material identification device. In addition, the implementation methods, technical problems solved, functions realized, and technical effects achieved are the same or similar to the implementation methods, data processing flows, technical problems solved, functions realized, and technical effects achieved of the corresponding components in some embodiments of the device, and are not repeated here.

[0224] According to the embodiments of the present disclosure, it is possible to achieve material resolution and improve the signal-to-noise ratio of radiation detection by acquiring information such as the energy, count rate, and spatial distribution carried by backscattered X-rays.

[0225] It will be appreciated by those skilled in the art that the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways, even if such combinations and / or combinations are not explicitly described in the present disclosure. In particular, the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways without departing from the spirit and teachings of the present disclosure. All of these combinations and / or combinations fall within the scope of the present disclosure.

[0226] The embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes and are not intended to limit the scope of the present disclosure. Although the embodiments are described above separately, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. The scope of the present disclosure is defined by the attached claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A material identification method, comprising: In response to the radiation ray scanning the target object, the radiation ray signal is detected by using a plurality of detector modules of the radiation detector, wherein the plurality of detector modules are arranged at different positions and the radiation signal channels are independent of each other; According to the radiation ray signal detected by each detector module, N ray indicators corresponding to the position of each detector module are calculated, where N is an integer greater than or equal to 1; The material of the target object is identified according to the indicator value of each of the ray indicators at different positions.

2. The method according to claim 1, characterized in that The N ray indicators include a first ray indicator and a second ray indicator, and identifying the material of the target object according to the indicator value of each ray indicator at different positions includes: Mapping the index values ​​of the first ray index and the second ray index at different positions in a coordinate system, wherein the vertical axis of the coordinate system corresponds to the first ray index, and the horizontal axis of the coordinate system corresponds to the second ray index; The material of the target object is identified according to the distribution of the first ray index and the second ray index in the coordinate system.

3. The method according to claim 1, characterized in that In response to scanning the target object with radiation, detecting the radiation signal using a plurality of detector modules of the radiation detector comprises: In response to the radiation source emitting radiation rays, a flying spot scan is performed on the target object, and the plurality of detector modules are used to detect backscattered ray signals reflected by the target object.

4. The method according to claim 3, characterized in that The calculating of the N ray indices corresponding to the position of each detector module comprises: For each of the ray indicators, a plurality of indicator values ​​corresponding to the position of each detector module are calculated; The plurality of index values ​​correspond one-to-one to the plurality of point positions of the flying spot scanning.

5. The method according to claim 1, characterized in that Before calculating the N ray indices corresponding to the position of each detector module, the method further includes: Allocating a corresponding location identifier according to the location of each detector module; Among them, the N ray indicators corresponding to the position of each detector module are bound to the position identifier of the detector module.

6. The method according to any one of claims 1 to 5, characterized in that Before calculating the N ray indices corresponding to the position of each detector module, the method further includes: Performing energy threshold judgment on the multiple groups of ray signals to filter out ray signals in different energy ranges from each group of ray signals, wherein the multiple groups of ray signals correspond one-to-one to the multiple detector modules; The number of ray signals in different energy ranges in each group of ray signals is obtained.

7. The method according to claim 6, characterized in that The calculating of the N ray indices corresponding to the position of each detector module comprises: for each group of ray signals, Acquire the target quantity of the ray signal under the target energy range in the different energy ranges; The ratio of the target quantity to the total ray signal quantity is calculated to obtain a first ray index, wherein the total ray signal quantity is obtained according to the sum of the quantities of all ray signals in the different energy ranges.

8. The method according to claim 6, characterized in that The calculating of the N ray indices corresponding to the position of each detector module comprises: for each group of ray signals, The ratio of the total number of ray signals to the counting period is calculated to obtain a second ray index, wherein the total number of ray signals is obtained according to the sum of the numbers of all ray signals in the different energy ranges, and the counting period includes a period for obtaining the number.

9. The method according to any one of claims 1 to 5, 7 and 8, characterized in that: The identifying the material of the target object according to the indicator value of each of the ray indicators at different positions includes: Matching the index value of each of the ray indexes at different positions with the index information of different materials respectively, wherein the index information of different materials includes the index values ​​of the different materials at different positions obtained in advance; The material of the target object is identified according to the matching result.

10. The material identification method according to claim 9, characterized in that: Using a radiation source to emit the radiation rays, and arranging two radiation detectors on both sides of the radiation source; Wherein, the detecting of radiation ray signals by using a plurality of detector modules of the radiation detector comprises: The radiation ray signals are detected using a plurality of detector modules of each of the two radiation detectors.

11. The material identification method according to claim 10, characterized in that: The two radiation detectors distributed on both sides of the radiation source have different structures and each detects radiation ray signals corresponding to different areas of the target object. The structure of each radiation detector is determined according to the area of ​​the target object to be detected, and the structure includes the detection area of ​​each detector module in the plurality of detector modules.

12. The material identification method according to claim 11, characterized in that: Before matching the index value of each of the radiation indexes at different positions with the index information of different materials respectively, the method further includes: Determining index information of the material to be matched based on the respective structures of the two radiation detectors; The index information of the material to be matched is calculated based on radiation ray signals detected by two preset radiation detectors based on the material to be matched, and the two preset radiation detectors have a one-to-one correspondence with the two radiation detectors and have substantially the same structure.

13. A material identification device, used to execute the material identification method according to any one of claims 1 to 12, the material identification device comprising: A radiation detector, for scanning a target object in response to radiation rays, detecting radiation ray signals using a plurality of detector modules, wherein the plurality of detector modules are arranged at different positions and the radiation signal channels are independent of each other; A processor is connected to the radiation detector for performing the following operations: According to the radiation ray signal detected by each detector module, N ray indicators corresponding to the position of each detector module are calculated, where N is an integer greater than or equal to 1; The material of the target object is identified according to the indicator value of each of the ray indicators at different positions.

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