CN200947087Y - Energy spectrum-modulated device and material-identified equipment - Google Patents

Abstract

Disclosed are an energy spectrum modulation device and a material identification device, which can use X-rays of different energies to identify materials of substances in large and medium-sized objects such as sea freight and air containers. The energy spectrum modulation device includes: a rotating shaft; a first energy spectrum modulating component coupled with the rotating shaft; and a second energy spectrum modulating component coupled with the rotating shaft and/or the first energy spectrum modulating component. The utility model can be used in customs, ports, airports and other places to inspect large-scale container goods without opening the box.

Description

Energy spectrum modulation device and equipment for identifying materials

technical field

The utility model relates to radiation perspective imaging inspection of large objects, in particular to an energy spectrum modulation device and material identification equipment, which can identify material materials in large and medium-sized objects such as sea and air containers by using radiation of different energies.

technical background

Existing cargo inspection systems using radiation imaging generally allow single-energy rays to interact with the object to be inspected, and then detect the rays that penetrate the object to be inspected to obtain an image. This system can reflect changes in the shape and mass thickness of the inspected object, but it cannot identify the material.

The dual-energy detection method to distinguish the material properties of objects was proposed a long time ago, such as US Patent US5,044,002, and has been widely used in various fields in the low-energy segment, such as osteoporosis inspection, geological oil layer detection and small Substance material identification of the item. However, it has always been believed that in the high energy range (>1MeV), the small difference brought by the electron pair effect is not enough to realize the role of material identification, so the practicability is not very strong.

In the 1990s, U.S. Patent No. 5,524,133 proposed to use the angular distribution characteristics of Compton scattering and the isotropic characteristics generated by electron pairs to analyze the scattering components caused by the respective effects in X-rays after interacting with objects, so as to identify The atomic number of the substance that interacts with X-rays. In US5,524,133, high-energy X-rays are allowed to interact with an object and then interact with a target with a higher atomic number, and then place detectors at different angles of the target to detect Compton scattering and electron pair effects. However, it is very difficult to detect the scattering of X-rays after penetrating the material and interacting with the target, so the incident dose of X-rays is usually required to be very high. In addition, the signal-to-noise ratio of the detection signal is very low, because the detector array arranged at such an angle on the same horizontal plane is susceptible to interference from adjacent channels, these shortcomings seriously affect the determination of the atomic number of the substance, and the image quality is not good. Therefore, this method has not been practically applied since it was proposed in 1993.

Later, in US Pat. No. 6,069,936 and international application WO00/43760, X-rays generated by high-energy ray sources were used, and X-rays were filtered by specific materials to obtain another ray energy spectrum with higher energy. After the X-rays of the two energy spectra interact with the matter, detect the two penetrated X-rays, and determine the atomic number and material type of the matter by calculating the ratio of the two detection values.

In this method, when the X-rays of the two energy spectra interact with the object to be inspected, as the thickness of the object to be inspected gradually increases, the difference between the two energy spectra penetrating the object to be inspected will become smaller and smaller and converge rapidly. It will not be able to identify the material of the object to be inspected.

Utility model content

In view of the problems in the prior art, the utility model has been accomplished. The purpose of this utility model is to generate X-rays with obvious differences in the main energy levels of two beams of energy spectrum in the high-energy section (>1MeV), detect the penetrating radiation after the two beams interact with the same position of the material, and determine according to the two detection values The effective atomic number range of the substance, thereby enabling non-intrusive inspection of the item.

In one aspect of the present invention, an energy spectrum modulation device is proposed, comprising: a rotating shaft; a first energy spectrum modulating component coupled to the rotating shaft; and a second energy spectrum coupled to the rotating shaft and/or the first energy spectrum modulating component modulation components.

According to an embodiment of the present invention, the first energy spectrum modulation component includes at least one first blade; the second energy spectrum modulation component includes at least one second blade.

According to an embodiment of the present invention, the at least one first vane and the at least one second vane are alternately arranged.

According to an embodiment of the present invention, in the ray emitting direction, the mass thickness of the at least one first blade is smaller than or equal to the mass thickness of the at least one second blade.

According to one embodiment of the invention, said at least first vane is made of a high Z material.

According to an embodiment of the present invention, the at least one first vane is composed of at least one of Pb, W, U and Cu.

According to an embodiment of the invention, said at least one second vane consists of a low Z material.

According to an embodiment of the present invention, the at least one second blade is made of at least one of B, C, polyethylene and other hydrogen-rich organic materials.

The utility model also proposes a material identification device comprising the above-mentioned energy spectrum modulation device.

The equipment of the utility model is used to alternately generate two kinds of X-rays with different energy spectra, and the X-rays with obvious energy differences account for the main proportion of the energy spectra. This is beneficial to the identification of thicker objects to be inspected. In addition, the generated high and low energy X-rays are modulated by different absorbing materials to obtain a more optimized high and low energy ray energy spectrum, which further widens the difference in equivalent energy between the two beams of X-rays, thereby improving the identification of materials. Accuracy, especially for the detection of materials with small mass thickness.

In addition, the variable-gain detector adjusts the amplification gain for different single-pulse doses and ray energies of high and low-energy rays to obtain a larger dynamic range, which can further improve the detection effect of the same detector on rays with different energies, and improve the detection efficiency. effect and detection accuracy.

Description of drawings

Fig. 1 is a schematic diagram of the composition of a material identification system according to an embodiment of the present invention;

Fig. 2 is a cross-sectional view of an energy spectrum modulation device in the material identification system shown in Fig. 1;

Fig. 3 is a schematic diagram of the energy spectrum generated by the accelerator and a schematic diagram of the dual-energy spectrum obtained after modulation.

Fig. 4 has shown in the whole energy range, the function relation curve between radiation energy and material attribute and material mass thickness;

Fig. 5 is a flow chart of detecting and identifying materials using two beams of rays with different energies; and

Fig. 6 is a flowchart of a method for adjusting an image using different quality and thickness information.

Detailed ways

Embodiments of the utility model will be described in detail below with reference to the accompanying drawings.

Fig. 1 is a schematic diagram of a material identification system according to an embodiment of the present invention.

As shown in Figure 1, the material identification system according to the embodiment of the utility model includes a radio frequency linear accelerator 1, an energy spectrum modulation device 2, a synchronous control part 4 connected with the radio frequency linear accelerator 1 and the energy spectrum modulation device 2 through a line 3, the first A collimator 6A, a second collimator 6B, a third collimator 6C, a control part 9 connected to the energy spectrum modulation device 2 through a line 10, a detector 8 connected to the control part 9 through a line 11, a line through 12 A material identification and image processing part 13 connected to the detector 8 .

In this embodiment, two kinds of X-rays with different energies are alternately generated by the radio frequency linear accelerator 1, and they respectively act on the same object 7 to be inspected, and the X-rays that penetrate the object 7 to be inspected are detected by the detector 8, and then passed through The computer 13 analyzes and processes the detection results of the detector 8 to obtain the radiation image of the object to be inspected and realize the distinction of the material properties of the object to be inspected.

As shown in Figure 1, during operation, the synchronization control part 4 establishes a session 5 with the RF linear accelerator 1, and after confirming the status, the RF linear accelerator 1 will alternately generate Two types of X-rays with different energy levels. The energy spectrum 1P of the X-rays produced by the RF linear accelerator 1 has obvious energy differences, but it cannot meet the requirements of system applications. Therefore, it is necessary to perform energy spectrum modulation on the energy spectrum 1P to obtain high and low energy levels with a greater difference in energy levels. A ray spectrum.

Therefore, the radio frequency linear accelerator 1 can alternately generate X-rays of two different energy spectra according to the trigger signal, and the two energy spectra are respectively dominated by different energies. Since the X-rays generated by the accelerator have a relatively wide energy spectrum range, it is necessary to further increase the proportion of X-rays with required energy in the X-ray spectrum by means of energy spectrum modulation. According to the energy level of the X-rays generated by the radio frequency linear accelerator 1, different materials can be used for energy spectrum modulation, so as to obtain the energy spectrum most suitable for material and material resolution.

In addition, due to the different energy ranges of X-ray energy spectrum distribution, the suitable energy spectrum modulation materials are also different. For example, when the lower limit of the main energy range of a beam of X-ray energy spectrum distribution is higher than a certain higher energy threshold (such as ~3MeV), a low-Z material should be selected as the energy spectrum modulation material of the beam of X-rays, such as B , C, polyethylene and other hydrogen-rich organic materials, etc.

At the same time, in order to absorb the scattered components with lower energy in the rays, it is better to add a thinner high-Z material for energy spectrum modulation after the thicker low-Z material is used for energy spectrum modulation. When the lower limit of the main energy range of a beam of X-ray energy spectrum distribution is higher than a certain lower energy threshold (such as ~300keV), high-Z materials should be selected as the energy spectrum modulation material of the beam of X-rays, such as Pb, W , U, etc.; Z materials such as Cu can also be selected.

FIG. 2 is a top view of the energy spectrum modulation device 2 in the material identification system shown in FIG. 1 . As shown in Figure 2, the energy spectrum modulation device 2 includes a rotating shaft 201 coupled with a servo motor, a first energy spectrum modulating component 202 arranged on the rotating shaft 201, and a second energy spectrum modulating component coupled with the first energy spectrum modulating component 202 203 and a position detector (not shown).

Here, the first energy spectrum modulation component 202 is made of a high-Z material and is coupled with the rotating shaft 201 for energy spectrum modulation of low energy rays. As shown in FIG. 2 , the first energy spectrum modulation component 202 includes a plurality of spaced apart parts, which can be regarded as shorter blades. In this case, the first energy spectrum modulation component 202 can be coupled to the second energy spectrum modulation component 203 , and the second energy spectrum modulation component 203 is directly coupled to the rotating shaft 201 . However, as an alternative, the blades of the first energy spectrum modulation component 202 can be made into shapes similar to the blades of the second energy spectrum modulation component 203 as required, but the two have different mass thicknesses in the ray direction. In this way, the first energy spectrum modulation component 202 and the second energy spectrum modulation component 203 can be coupled on the rotating shaft 201 .

The second energy spectrum modulation component 203 is made of a low-Z material, such as a composite material such as polyethylene plus lead, and is made of one or more blades for energy spectrum modulation of high-energy rays. As shown in FIG. 2 , the mass thickness of the blades of the second energy spectrum modulation component 203 along the ray emitting direction is larger than the mass thickness of the blades of the first energy spectrum modulation component 202 .

In order to realize energy spectrum modulation, the blade rotates around the axis according to the set frequency. When the position detector detects that the blade turns to a fixed position, a trigger signal is generated as a synchronization signal, which is sent to the synchronization control through line 3 and line 10 respectively. The part 4 and the control part 9 control the synchronization between the radio frequency linear accelerator 1 and the detector 8 and the energy spectrum modulation device 2 respectively by the synchronization control part 4 and the control part 9 .

In this way, it can be ensured that all the high-energy spectrum rays generated by the radio frequency linear accelerator 1 interact with the blade material, that is, the modulation of the second energy spectrum modulation component 2, so that the low-energy spectrum is absorbed by the material on the shaft, that is, the first A modulation of the energy spectrum modulation component 1 .

As mentioned above, the material of the first energy spectrum modulation component 202 can be a high-Z material as the energy spectrum modulation material of the X-ray beam, such as Pb, W, U, etc.; a medium-Z material such as Cu can also be selected, and the second energy The material of the spectrum modulating component 203 can be a low-Z material as the energy spectrum modulating material of the beam of X-rays, such as B, C, polyethylene and other hydrogen-rich organic materials. As a result, a modulated energy spectrum 2P of high and low energy rays is obtained, in which the energy spectrum of two different energies is fully separated.

In addition, FIG. 3 is a schematic diagram of the energy spectrum generated by the accelerator and a schematic diagram of the dual-energy spectrum obtained after modulation. As shown in (A) of Figure 3, the energy spectrum before modulation is the normalized energy spectrum curves 301a and 301b produced by a dual-energy accelerator with a high energy of 9MeV and a low energy of 6MeV; as shown in Figure 3 (B), The energy spectra after energy spectrum modulation are energy spectrum curves 302a and 302b respectively. It can be seen from the figure that the difference between the two energy spectra is further widened.

The optimal high and low energy rays modulated by the energy spectrum modulation device 2 interact with the object 7 after being collimated by the first and second collimators 6A and 6B. As shown in FIG. 1 , the inspected object 7 moves toward a fixed path and a fixed direction perpendicular to the radiation plane. The rays passing through the object 7 to be inspected are collected by the detector 8 after passing through the third collimator 6C. The detector 8 realizes the collection of high and low energy data according to the synchronous signal of the control system 9 , such as the transmission intensity value after the radiation sees through the object. In addition, the detector 8 can change its gain multiple according to the external trigger signal, thereby changing the dynamic range of the detector 8 to more accurately obtain the signal values of the two kinds of energies after the radiation interacts with the matter, so that the two kinds of energies can be accurately distinguished The difference between the radiation and matter after the action. For example, in the case of radiation with different energies, the detector 8 has different gain factors.

The output data signal of the detector 8 is transmitted to the material identification and image processing part 13 through the line 12 . As mentioned above, what the detector 8 detects is a high-energy detection value HEL and a low-energy detection value LEL. By substituting the detected high-energy detection value HEL and low-energy detection value LEL into the classification function, the effective atomic number range of the material in the object to be detected is determined, thereby determining the material properties of the substance.

Here, the process of obtaining the classification function is to use two kinds of dual-energy systems for materials with known atomic numbers (such as polyethylene representing organic substances, aluminum representing light metals, iron representing inorganic substances, and lead representing heavy metals, etc.). Energy rays scan different mass thicknesses to obtain a series of collection values. Calculate the two function values for the high and low energy signals collected each time. For example, find In(HEL/HEL0) from high-energy or low-energy signals, and find a*{In(LEL/LEL0)-In(HEL/HEL0)} from high- and low-energy signals, where a is a coefficient, and HEL0 and LEL0 are predetermined references The detection value, and then according to the statistical value of the two function values, the fitting function of the material is fitted, as shown in Figure 4.

Then, according to statistical methods (such as K-means, leader clustering, vector machine), the classification curve is obtained from the fitting function. For example, the variance statistics are performed on the fitting function value, and then the fitting curve is moved by the corresponding variance value according to the required optimal classification standard. When identifying unknown materials, according to the two function values of the detection value, and calculate the classification function value of the detection value, and then compare with the classification function value to obtain the effective atomic number range of the material, and then determine the material properties of the object.

Fig. 5 is a flow chart of detecting materials using two beams of different energy rays to identify materials.

As shown in Figure 5, in step S110, the RF linear accelerator 1 can alternately generate X-rays of two different energy spectra according to the trigger signal, for example, the first X-ray has a first energy spectrum, and the second X-ray has a second energy spectrum .

Then, in step S120, use the energy spectrum modulation device 2 shown above to perform energy spectrum modulation on X-rays with different energy spectra, for example, under the control of the synchronization signal, the first energy spectrum modulation component 202 performs energy spectrum modulation on the first X-ray. spectrum modulation, and the second energy spectrum modulation component 203 performs energy spectrum modulation on the second X-ray.

Next, in step S130 , the modulated X-rays pass through the first and second collimators 6A and 6B, irradiate the object 7 to be inspected, and interact with the object 7 to be inspected.

In step S140 , the detector 8 realizes the collection of high and low energy data according to the synchronization signal of the control system 9 . Here, the detector 8 can change its gain multiple according to the external trigger signal, thereby changing the dynamic range of the detector 8, so as to more accurately obtain the signal values after the two energy rays interact with the matter.

In step S150 , the high and low energy imaging signals detected by the detector 8 are sent to the material identification and image processing part 13 . In the material identification and image processing section 13, it is judged whether the transmitted signal is a high-energy imaging signal or a low-energy imaging signal.

In step S160 and step S170, the high-energy X-ray imaging signal and the low-energy imaging signal are respectively processed.

In step S180, according to the two function values of high energy and low energy, calculate the classification function value of the detection value, and then compare with the classification function value to obtain the effective atomic number range of the material, and then determine the material property of the object.

In step S190, in order to obtain a clear image of the inspected object, multiple images obtained after scanning the inspected object with X-rays with different energies may be fused to obtain a scanned image with better quality.

As we all know, high-energy rays have strong penetrating power to objects, and the detection data obtained after penetrating objects with large mass and thickness are more accurate, so the grayscale image with large mass and thickness is clearer. But in China, high-energy rays will get a blurred grayscale image when distinguishing the thickness of a thin mass, and it is easy to lose detailed information. And this shortcoming is exactly what the grayscale image obtained after the low-energy rays penetrate the matter can make up for it.

Fig. 6 is a flowchart of a method for adjusting an image using different quality and thickness information. The image fusion process uses the different attenuation characteristics of high and low energy rays on different mass thicknesses of objects, and obtains clear images in a wide range of mass thicknesses through the fusion of the two detection values.

In steps S191 and S192, determine the material properties of the inspected object, for example, whether the mass thickness of the inspected object 7 is thick or thin. Here, according to the attenuation of the ray, determine the approximate range of the mass thickness of the material, that is, when the attenuation is very serious, such as less than a predetermined threshold, it is considered to be a high-quality thickness material, and when the attenuation is small, such as greater than a predetermined threshold, it is considered to be low Quality thickness material.

In step S193, for materials with a small mass and thickness, a smaller weight factor, such as 30%, is assigned to the high-energy data; a larger weight factor, such as 70%, is assigned to the low-energy data.

In step S194, for materials with a large mass and thickness, a larger weight factor, such as 70%, is assigned to high-energy data; a smaller weight factor, such as 30%, is assigned to low-energy data.

Then, in step S195, the high-energy image and the low-energy image are synthesized according to the weight factors given above, so as to obtain a final clear image.

Therefore, the utility model proposes to compare the detection values obtained after the interaction between X-rays of different energies and matter with their corresponding predetermined thresholds, and assign different weight factors to high-energy and low-energy data, thereby synthesizing the obtained The grayscale information of the final image.

Although the detected images have different image characteristics after the radiation interacts with objects of different mass thicknesses, after processing by the above method, in the process of detecting scanned objects, the quality and thickness of the inspected objects differ greatly. , and a very clear grayscale image can also be obtained.

The above is only a specific embodiment of the utility model, but the scope of protection of the utility model is not limited thereto, anyone familiar with the technology can easily think of the transformation within the technical scope disclosed in the utility model Or replacement, all should be covered within the scope of the present utility model. Therefore, the protection scope of the present utility model should be based on the protection scope of the claims.

Claims (9)

1. An energy spectrum modulation device, characterized in that, comprising: shaft; a first energy spectrum modulating component coupled to the rotating shaft; and A second energy spectrum modulation component coupled to the rotating shaft and/or the first energy spectrum modulation component. 2. The energy spectrum modulation device according to claim 1, wherein the first energy spectrum modulation component comprises at least one first blade; the second energy spectrum modulation component comprises at least one second blade. 3. The energy spectrum modulation device according to claim 2, wherein the at least one first blade and the at least one second blade are arranged alternately. 4. The energy spectrum modulation device according to claim 2, characterized in that, in the radiation emission direction, the mass thickness of the at least one first blade is smaller than or equal to the mass thickness of the at least one second blade. 5. The energy spectrum modulation device according to claim 2, wherein the at least first blade is made of a high-Z material. 6. The energy spectrum modulation device according to claim 5, wherein the at least one first blade is composed of at least one of Pb, W, U and Cu. 7. The energy spectrum modulation device according to claim 2, wherein the at least one second blade is made of a low-Z material. 8. The energy spectrum modulation device according to claim 7, wherein the at least one second blade is made of at least one of B, C, polyethylene and other hydrogen-rich organic materials. 9. A material identification device comprising an energy spectrum modulation device, characterized in that the material identification device comprises: shaft; a first energy spectrum modulating component coupled to the rotating shaft; and A second energy spectrum modulation component coupled to the rotating shaft and/or the first energy spectrum modulation component.

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