Abstract:
Disclosed is a method and a device for security-inspection of liquid articles with radiations, which relate to the field of radiation inspection technology. The method comprises steps of acquiring original environment information, emitting radiation beams to transmit the liquid articles, receiving the radiation beams transmitted through the liquid articles to form multi-angle projection data, computing a radiation absorption coefficient of the liquid articles to be detected by inverse operation of the multi-angle projection data, based on the initial environmental information and the uniformity of the liquid articles, and comparing the radiation absorption coefficients with the preset data to get the relevant information of the liquid articles. Comparing with the prior art, the present invention is not subjected to affection of cuter package of the liquid article, and is advantageous of high anti-jamming high accuracy, high safety and reliability, low cost and small size.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention is related to the field of radiation detection, and particularly, to the method and device for quick security-inspection of liquid articles with radiations. 
       BACKGROUND OF THE INVENTION 
       [0002]    Since 9•11 in U.S., security-inspection of aviation is becoming more and more emphasized. Besides traditional security-inspection of packs, security-inspection of the liquid articles carried by passengers is added. Accordingly, means and methods of a quick security-inspection of the liquid articles in packs are in dire need. 
         [0003]    Nowadays, there are four types of detection methods used in security-inspection of liquid articles, including the chemical method, the electromagnetic method, the neutron detection method and the radiation detection, method, as follows: 
         [0004]    1) The chemical method can be subdivided into the odor identification method, the ion scanning explosive detection method and the substance analysis. The odor identification in practical applications often fails to implement detection because of sealed and packaged conditions of liquid articles. The ion scanning explosive detection method is known for its high sensitivity, but with high false alarm rate, it suffers from the affection of background environment. The substance analysis is of high precision and high accuracy, but this method needs a certain period of time to analyze the sample, which cannot meet the demands of on-site quick detection. 
         [0005]    2) The electromagnetic method works in an active measurement manner. It distinguishes liquid articles from each other according to their dielectric constants in the electromagnetic field. The electromagnetic method is easily subjected to severe affection of metal packages or other thick material packages. As a result, the electromagnetic method is limited in case of complex package materials. 
         [0006]    3) The use of the neutron, detection method will leave residual radiation remaining in the detected liquid due to the effect of “neutron activation”. Furthermore, the radiation shielding is complicate true to neutrons&#39; strong perforation, and the apparatus has to take a large area, so the method is not suitable for application in the security-inspection systems of civil aviation. 
         [0007]    4) Currently, most of the security-inspection apparatuses of civil aviation are radiation apparatuses. In these apparatuses, the X-ray. 2D imaging technology and the three-dimensional CT technology are mostly adopted. These technologies, which are mainly used for security-inspection of packs, fail to accomplish the security-inspection of liquid articles in packs. 
         [0008]    The X-ray 2D imaging technology acquires two-dimensional projection images by integrating three-dimensional information of articles to be detected along X-ray&#39;s direction. These images show difference in the form of grayscale or pseudo-color, to give the operator a vivid display. However, the X-ray 2D imaging technology is in defect of one-dim.,.ensi.onal information of objects, so the detection of liquid articles is suffering from severe affection of shapes and size:; of the liquid articles. 
         [0009]    The three-dimensional CT technology is the extension and application of CT technology. The CT technology was applied in the diagnostics first, which was implemented by conducting a multi-angle projection of respective slices of an article. By using a computer to reconstruct the multi-angle projection data of respective slices, reconstructed images were obtained. The information of the different attenuation coefficients in the reconstructed images was displayed in the form of different grayscales, by which the inner differences of the articles were displayed. With the development of the CT technology, the industrial CT for the nondestructive inspection and the package CT for the security-inspection were put into use, with the goal remaining to be acquiring the slice images of the inner difference of articles. Therefore, with the traditional X-ray 3D imaging technology for thee liquid articles, only the slice images with no differences can be seen, 
         [0010]    Thus, it is difficult for the security-inspection devices of the CT type to gain popularity, for their high cost and bulkiness, as a result of the wide range of the articles that can be detected by them. 
         [0011]    To sum up, for the quick detection of the liquid articles the chemical method, the electromagnetic method and the neutron detection method are not suitable for quick security-inspection. By using the X-ray 2D imaging technology and the three-dimensional CT technology, grayscale images or pseudo color images with contrast a:re acquired, but these images cannot work as sufficient evidence fear the security inspection of the liquid articles. 
       SUMMARY OF THE INVENTION 
       [0012]    In order to overcome the disadvantages in the existing technologies, an object of the invention is to provide a method as well as a device for security-inspection of liquid article using radiations, which can conduct a quick detection and get quantitative information of the liquid articles to be detected, without destroying the outer packages. 
         [0013]    On the first aspect of the invention, the invention provided a method for security-inspection of liquid articles with radiations, comprising the following steps: acquiring initial environmental information; emitting radiation beams to transmit through the liquid articles; receiving the radiation beams through the liquid articles to form multi-angle projection data; then based on the original environment information and the uniformity of the liquid articles, computing a radiation absorption coefficient of the liquid articles by an inverse operation of the multi-angle projection data; finally comparing the radiation absorption coefficient with the preset data to get the relevant information of the liquid articles. 
         [0014]    According to an embodiment of the invention, the original environment information comprises geometry boundary information of the liquid articles to be detected. 
         [0015]    According to an embodiment of the invention, the geometry boundary information was obtained by the radiogram technology or, the scan imaging technology. 
         [0016]    According to an embodiment of the invention, the liquid articles to be detected exhibit uniformity to radiations. 
         [0017]    On the other aspect of the invention, it provided a device for security-inspection of liquid articles with radiations, which comprises the following parts: a radiation source for emitting radiation beams; a carrier mechanism to carry the liquid articles to be detected so as to have the radiation beams transmit through; a detection and collection appliance to acquire both initial environmental information and the multi-angle projection data of the liquid articles; and a computer data processor. The processor comprises means of computing radiation absorption coefficients of the liquid articles by an inverse operation of the multi-angle projection data, constrained by the original environment information and the uniformity of the liquid articles, and also means of comparing the radiation absorption coefficient with the preset data to get the relevant information of the liquid articles. 
         [0018]    According to an embodiment of the invention, the radiation source is an X-ray machine (tube) or an isotope source 
         [0019]    According to an embodiment of the invention, there should be one or more radiation sources. 
         [0020]    According to an embodiment of the invention, the energy of the radiation source is adjustable. 
         [0021]    According to an embodiment of the invention, the detection and collection appliance is in the integral form of a detector and a data collector. 
         [0022]    According to an embodiment of the invention, the detector is a solid detector a liquid detector, a gas detector or a semiconductor detector According to an embodiment of the invention, there is one or more detectors. 
         [0023]    According to an embodiment of the invention, the detector is in a form of one-dimensional array or two-dimensional array. 
         [0024]    According to an embodiment of the invention, the detector has the energy switching function. 
         [0025]    According to an embodiment of the invention, the detector operates in the (current) integral mode or the pulse (counting) mode. 
         [0026]    According to an embodiment of the invention, the multi-angle projection data is obtained by rotating the liquid articles to be detected or rotating the radiation source with the detection and collection appliance. 
         [0027]    According to an embodiment of the invention, the multi-angle projection is obtained by increasing the amount of the projection angles or mounting the detector with an offset of ¼ size of a detector unit. 
         [0028]    According to an embodiment of the invention, the computer data processor conducts the comparison by adopting predetermined identification algorithm. 
         [0029]    According to an embodiment of the invention, the coordination of the radiation source, the detection and collection, appliance, the carrier mechanism and the computer data processor is controlled by the scan controller. 
         [0030]    The device of the invention is advantageous in taking small area, of high accuracy, high safety and reliability besides easy shielding. The present invention is adapted to the security-inspection or aviation fields and other important sites. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]    The features and advantages of the invention can be more clarified from the following detailed descriptions for the accompanying drawings. Wherein: 
           [0032]      FIG. 1  is a schematic diagram of a detection device according to an embodiment of the invention; 
           [0033]      FIG. 2  shows a structure diagram of the computer data processor in the inspection device of  FIG. 1 ; 
           [0034]      FIG. 3  shows a flow chart of the detection method according to an embodiment of the invention; and 
           [0035]      FIG. 4  shows a functional block diagram of the computer data processor in the inspection device of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0036]    The preferred embodiment of the invention will now be described more fully hereinafter with reference to the accompanying drawings. In the drawings the same reference numerals are used for denoting the same or similar components that are shown in different figures. For clarify, the detailed description of the known function and structure incorporated herein will be omitted, which would otherwise weaken the subject of the invention. 
         [0037]      FIG. 1  is a schematic diagram of the structures of an inspection device according to an embodiment of the invention. 
         [0038]    As shown in  FIG. 1 , the detection device according to the invention comprises a radiation source  10  for emitting radiations for detection, e.g. a X-ray machine or a isotope (X-ray or γ-ray source) source; a carrier mechanism  30 , which carries the liquid articles to be detected  20 , can rotate around axis Z thereof, and can ascend or descend to take the liquid articles  20  into the detection area, thereby the radiations emitted by the radiation source  10  can transmit through the liquid articles  20 ; a detection and collection appliance  40 , an integrated module of a detector and a data collector, which is used to detect the radiations transmitted through the liquid articles  20  to acquire analog signals, and convert the analog signals into digital signals, and hence output the scanning data of the liquid articles  20 ; a scan controller  50 , which controls each component of whole system so that they operate synchronously; and a computer data processor  60  for processing the, data collected by the data collector and outputting detection results. 
         [0039]    As shown in  FIG. 1 , the radiation source  10  is placed at one side of the carrier mechanism  30  carrying the liquid articles to be detected  20 , while the detection and collection appliance  40  is placed at the other side of the carrier mechanism  30 . The detection and collection appliance  40  comprises a detector and a data collector for acquiring the initial environmental information and the multi-angle projection data of the liquid articles  20 . The data collector has a signal amplifying and formation circuit, which operates under (current) integration mode or pulses (counting) mode. The detection and collection appliance  40  has its data output cable connected with the computer data processor  60  to store the collected data into a database. 
         [0040]      FIG. 2  shows a structure diagram of the computer data processor  60  of  FIG. 1 . As shown in  FIG. 2 , the data collected by the data collector are stored in the memory  61 . The configuration data and programs of the computer data processor are stored in the ROM (Read Only Memory)  62 . The RAM (Random Access Memory)  63  is used for temporarily storing various data during the operating procedure of the processor  66 . Besides, computer programs and a pre-created database are also stored in the memory  61  for data processing. The database stores various relevant parameters of known liquid articles, such as radiation absorption coefficient, density and etc, to compare with the radiation absorption coefficients of the liquid articles  20  computed by the processor  66 . There is an internal bus  64  that connects the memory  61 , the ROM  62 , the RAM  63 , the input device  65 , the processor  66  and the display den isle  67  together. 
         [0041]    After the user inputs operation commands through the input device  65  such as keyboards and mouse, the instruction code of the computer programs will instruct the processor  66  to perform predetermined data processing algorithm. After the processing results are obtained, they will be displayed on the display device  67  such as LCD, or redirected in the form of a hard copy. 
         [0042]      FIG. 3  shows the flow chart of a detection method according to an embodiment of the invention. As shown in  FIG. 3 , at step S 10 , the liquid articles to be detected  20  is placed on the carrier mechanism  30 . When an operator sends out the command of starting a scan, the scan controller  50  controls the radiation source  10  to emit radiations, and controls the carrier mechanism  30  to ascend and descend so as to enter the detection area constituted by the X-ray source  10  and the detector. At the same time, radiation beams are emitted from the radiation source  10  and transmit through the liquid articles to be detected  20 . The scan controller  50  controls the detection and collection appliance  40  to receive the radiations transmitted through the liquid articles  20 , to acquire initial environmental information of the liquid articles, such as the geometry boundary information, etc. The geometry boundary information can be obtained by the X-ray radiographic technique or by X-ray scan imaging technology. The X-ray scan imaging technology can adopt translating mode, rotating mode or spiral mode. 
         [0043]    Besides, in the above procedures, the obtained initial environmental information of the liquid articles to be detected  20  contains the size of package, the material of package, the volume ratio of package to liquid articles, and so on. These information and radiation absorption coefficients of various liquid articles can be pre-classified by using neural network recognition algorithm to form a database. In the real detection procedure, the detection of the liquid articles  20  is implemented by comparing the measured features with the features in the database. 
         [0044]    Thereafter, at step S 20 , the carrier mechanism  30  rotates under the control of the scan controller  50 . When the carrier mechanism,  30  reaches the first angle, radiations will be emitted from the radiation source  10  to transmit through the liquid articles to be detected  20 . The detection and to collection appliance  40  receives the transmitted radiations to obtain the projection data of the first angle, which is denoted as a 1×N dimensional vector g 1  and stored in the memory  61  of the computer data processor  60 , wherein N is the number of the detection units of one row in the detector. 
         [0045]    At step S 20 ′, the carrier mechanism  30  continues rotating under the control of the scan controller  50 . When the carrier mechanism  30  reaches the second angle, radiations will be emitted from the radiation source  10  to transmit through the liquid article  20 . The detection and collection appliance  40  receives the transmitted radiations to obtain the projection data of the second angle, which is denoted as 1×N dimensional vector g 2  and stored in the memory  61  of the computer data processor  60 . 
         [0046]    The above steps are repeated in this manner. In step S 20 ″, the carrier mechanism  30  continues rotating under the control of the scan controller  50 . When the carrier mechanism  30  reaches the M th  angle, the projection data for M th  angle is obtained, which is denoted as 1×N dimensional vector g M  and stored in the memory  61  of the computer data processor  60 . After the above scan procedure, the multi-angle projection data of the liquid articles  20  is obtained, which is denoted as an M×N dimensional vector g. Thereby, the multi-angle projection data of the liquid article to be detected  20  can be sequentially acquired for one slice. 
         [0047]    Herein, in order to increase multi-angle projection data, the amount of angle projection can be increased during the scanning, or the detector is mounted with an offset of ¼ size of one detection unit of the detector. 
         [0048]    Suppose that the linear attenuating coefficient (the absorption coefficient) of the liquid article to be detected  20  is expressed as an I-dimensional vector f, wherein I is the dimension of discretized pixels of the liquid article. Based on the interaction between X-ray and substance, according to the Bill&#39;s Law, we can get: 
         [0000]        g   1 =exp(− H   1   f ) 
         [0000]        g   2 =exp(− H   2   f ) 
         [0000]        g   M =exp(−H M   f )   (1) 
         [0000]    Wherein the H 1 , . . . , H M  each represents an N×I system matrix, whose element H nj  reflects the contribution of the discrete pixel j in the object image under the corresponding angle, to the signal collected by the n th  detector. H 1  . . . H M  each is a single sparse matrix, which is determined by practical design of the scanning system. For example, these matrices can be determined by pre-computing and then being stored in the memory  61 , or through a real time computation according to the temporal system parameters. Thus, the linear attenuating coefficient information of the liquid articles can be obtained through the inverse operation with regard to the formula (1). 
         [0049]    The inverse operation is an inverse process of normal operation. The process of normal operation is that the original signal emitted by radiation source attenuates when transmitting through the liquid articles  20  and the detector receives the attenuated radiation signal. Accordingly, an inverse operation is to compute the information of radiation attenuation by the liquid articles on the basis of the signal received by the detector. 
         [0050]    However, during the detection procedure of liquid articles, because the inverse operation is an ill-conditioned problem, other information needs to be incorporated, e.g. the geometry boundary information of the liquid articles to be detected  20 , which is obtained at the former step S 10 , so as to improve the validity and stability of the solution. 
         [0051]    At step S 30 , the boundary condition and uniformity condition for the inverse operation are set on the basis of the initial environmental information obtained in step S 10 , which contains the geometry boundary information of the liquid article  20 . The space shape of the liquid articles can be expressed as a bounded function. The geometry boundary information of the liquid articles  20  can be determined by the above X-ray radiographic technology or X-ray scan imaging technology, thereby the valid active region Ω can be defined, which is f i =0, for i∉Ω. The introduction of the boundary condition can speed up the solution, and to some extent ameliorate its ill-condition. Secondly, as the target object of the detection system is the liquid part, the scanned object can be divided into two parts, i.e. the liquid region Ω 1  and the non-liquid region Ω n . For the uniformity of the liquid part, f i =smooth function, for iεΩ 1 , will be lo obtained. The smooth function is characterized by that both the whole variance in the liquid region Ω 1  and the local fluctuation in the non-liquid region Ω n  are limited,. The use of the liquid articles uniformity greatly optimizes the extraction of the liquid article information, and improves the robustness of the system. 
         [0052]    It is to be noted that the liquid articles having uniformity denotes those solutions, suspending liquids or emulsions that absorb the radiations uniformly. For example, in the above sense, the milk and the porridge etc are also liquid articles of uniformity, namely, the uniformity of these liquid articles will be exhibited when they absorb the radiation. 
         [0053]    Therefore, at step S 40 , with the geometry boundary condition of the liquid articles  20  being the boundary condition and the uniformity of the liquid articles being the condition of convergence, using the above formula (1), the computer data processor  60  computes to get the radiation absorption coefficient of the liquid article  20 . The valid radiation absorption coefficient of the liquid articles then can be worked out on the basis of the obtained statistical characteristics of the pixels within the region Ω 1 . 
         [0054]    Thereafter, at step S 50 , the computer data processor  60  outputs the relevant information of the liquid article to be detected  20 , by comparing the computed radiation absorption coefficient with those of the known liquids in the database. For example, the radiation absorption coefficient of alcohol is −280, if the detected result for an unknown liquid article falls into the range of −270 to −290, this unknown liquid article in all probability is alcohol. Afterwards, the identification information of the detected liquid article will be shown on the display device  67  or directly printed out. 
         [0055]    At the above step S 40 , the Bayesian method can be adopted to compute the radiation absorption coefficient of the liquid article  20  with the geometry boundary information and the uniformity as conditions. Also the non-statistical method can be adopted, wherein first solve the above formula (1) to obtain a preliminary radiation absorption coefficient, then after optimizing using the boundary condition and uniformity, estimate the linear attenuation coefficient of the liquid article  20  on the basis of distribution of f i , for i εΩ 1 , to improve the vialidity and the stability of the computation. The computation of the radiation absorption coefficient with the Bayesian method and the non-statistical method will be described below as examples. 
         [0056]    [An example of computation of the linear absorption coefficient of liquid article with the Bayesian method] 
         [0057]    1. Determine the target function: 
         [0000]      Φ( f )=Φ 1 ( g;f )+λ P ( f )   (2) 
         [0000]    Wherein Φ 1 (g;f) is a likelihood function determined by the noise characteristics of the collected data, P(f) is the metric of the uniformity for f 1 εΩ 1 , e.g. P(f)=−variance(f)| rεΩ , λ is a regulation parameter preset empirically; 
         [0058]    2. Solve {circumflex over (f)} arg max[Φ(f)] using the numerical optimization method. During the process of solution, keep f i =0, for i∉Ω; 
         [0059]    3. Calculate the probability distribution p(μ liquid ) of fεΩ 1  to get the linear absorption coefficient of the liquid article, e.g. 
         [0000]      μ liquid =mean( f )| fεΩ     1   , or μ liquid =arg max( p ( f ))| fεΩ     1   . 
         [0060]    [An example of computation of the linear absorption coefficient of liquid article with the non-statistic method] 
         [0061]    1. Acquire a preliminary estimate of the radiation absorption coefficient f by an analytic method, e.g. filter-back-projection reconstructing method or ART method; 
         [0062]    2. Compute the uniformity of f i εΩ 1    
         [0063]    a) If the preset uniformity demand is satisfied, say, the local variance is lower than a certain threshold, then acquire the absorption coefficient of the liquid article on the basis of the statistical characteristics of fεΩ 1  such as μ liquid =mean(f)| fεΩ     1   . 
         [0064]    b) If the uniformity demand is not satisfied, then conduct a boundary condition processing and a smoothing processing with regard to the radiation absorption coefficient f to acquire f′. Compare the orthographic projection of the processed f′ with the collected data g, analyze the difference between again to reconstruct and modify f, and then return step  2 . 
         [0065]    During the implementation of the non-statistical method, the operational speed and precision can be adjusted by setting different uniformity demands. In some extreme cases, the absorption coefficient of liquid article can be obtained just by one step, without iteration. 
         [0066]    Besides, at the above step S 10 , if the liquid article  20  is of a sandwiched structure or layered e.g. it has two layers. The geometry boundary information of these two layers can be obtained using the above method, respectively, then conduct the same subsequent procedures with regard to the liquid article of the respective layers, and finally output the identification information of the two types of liquid articles, which serves as the ultimate identification information of the detected liquid article  20 . 
         [0067]    For example, in the case of a two-layer liquid article, the liquid article region comprises the first liquid article region Ω 1A  and the second liquid article region Ω 1B . The linear attenuation coefficient of the first liquid article region Ω 1A  is denoted as f A , the linear attenuation coefficient of the second liquid article region Ω 1B  is denoted as f B . Then f A =smooth function 1, for AεΩ 1A , f B =smooth function 2, for BεΩ 1B . 
         [0068]    Thus, the above-described step S 10 ˜S 50  are conducted with regard to the first liquid article region Ω 1A  and the second liquid article region Ω 1B , respectively As mentioned above, based on the information such as the i of package, the material of package, the size ratio of the package to the liquid article, making use of the recognition algorithms such as the ANM (Artificial Neural Network), SVM (Support Vector Machine), BNN (Bayesian Neural Network), a classification table for the known various liquid articles can be established and stored into a database. As stated above, at steps S 10  and S 40 , after acquiring the initial environmental information as well as the radiation absorption coefficient of the liquid article  20 , the classification of the liquid article  20  in the database can hence be determined with the same neural network recognition algorithm, thereby the identification information of the liquid article  20  can be obtained. 
         [0069]    In this embodiment of the invention, the scanning is implemented by rotating the detected liquid article  20 . By means of scanning, both the volume and the cost of the device are reduced. However, another manner of scanning, that the detected liquid article  20  stays still while the radiation source  10  with the detection and collection appliance  40  rotates, can also be adopted. 
         [0070]    Besides, the radiation source  10  may comprise one or more X-ray machines, as well as one or more isotope sources, and the radiation energy of the X-ray machines is adjustable. In the case that the radiation source  10  comprises a plurality of X-ray machines or isotope sources, there may be the same number of detectors as the X-ray machines or isotope sources, and these X-ray machines or isotope sources are set correspondingly. Herein, the detectors may be gas collectors, liquid detectors, solid detectors or semiconductor detectors, and may have an energy switching function. Besides, the detectors can work under the mode of one-dimensional array or two-dimensional arrays, i.e. the line array detector or the area array detector. 
         [0071]    The computation procedure of the radiation absorption coefficient and the acquiring procedure of the identification information of the detected liquid article  20  are described above in the form that the computer data processor  60  runs the programs containing the predetermined data processing algorithm. However, the computer data processor  60  may be embodied in other forms.  FIG. 4  is a functional block diagram of the computer data processor  60  of the inspection device of  FIG. 1 . 
         [0072]    As shown in  FIG. 4 , as another example of the computer data processor, this computer data processor  60 ′ comprises the following: a data memory  71 , which stores the original environment information and the multi-angle projection data and etc, such as the system matrices H 1 , . . . , H M  to describe the system property; the database  74 , which stores the absorption coefficients of various liquid articles or other characteristic information, as well as a database of the classification table of various liquid articles to be used for the comparison of the checking procedure; an absorption coefficient calculation unit  72 , which calculates the radiation absorption coefficient of the detected liquid article  20  based on formula (1), under the condition of uniformity of the liquid article, on the basis of the initial environmental information stored in the data memory  71  such as the geometry boundary information of liquid article, and the multi-angle projection data; a comparison unit  73 , which compares the radiation coefficient of the liquid article  20  computed by the absorption coefficient computing unit  72  with those stored beforehand to determine the useful identification information of the liquid article  20 ; a output unit  75  such as a display or other output device, for presenting the identification information acquired by the comparison unit  73  to the operator. 
         [0073]    Although exemplary embodiments of the present invention have been described hereinabove, it should be clear to those skilled in the field that any variations and/or modifications of the basic inventive concepts will still fall within the scope of the present invention, as defined in the appended claims.