JP7254237B1 - Material classification method using X-ray device and X-ray - Google Patents

Abstract

Kind Code: A1 An X-ray apparatus that performs inspection using X-rays, and an X-ray apparatus capable of classifying materials constituting an inspection object while confirming the outer shape of the inspection object, and a material classification method using the X-ray apparatus. offer. An X-ray output unit that outputs X-rays with a predetermined output value and a predetermined number of detection elements are arranged one-dimensionally, and one detection element is defined as one pixel, and each pixel detects the X-rays. and an X-ray detection unit and a control unit for acquiring pixel information regarding a total energy amount indicating the magnitude of the energy of the entire X-ray and a high energy amount indicating the magnitude of energy equal to or greater than a predetermined value. The control unit irradiates the container moving on the conveyer with the X-ray, detects the X-ray transmitted through the container, and converts the pixel information corresponding to the X-ray to the X-ray. According to the pixel information obtained from the line detection unit, the rate of change of the attenuation coefficient of the object stored in the storage container is obtained, and the object is classified into a predetermined material. [Selection drawing] Fig. 1

Description

TECHNICAL FIELD The present invention relates to the configuration of an X-ray apparatus and a material classification method using the same, and more particularly to a technique effectively applied to baggage inspection such as hand luggage and parcels delivered to home.

2. Description of the Related Art X-ray devices are used to check objects stored in storage containers at baggage inspection sites such as airports. Usually, X-rays are irradiated to the storage container, and the transmitted X-rays are acquired to confirm the outline of the object.

In such an inspection, only the outer shape of the object can be known, and the mass of the object cannot be confirmed, so it is difficult to judge whether the object is dangerous.

As a background art of this technical field, there is a technique such as Patent Document 1, for example. In Patent Document 1, "X-rays are irradiated from an X-ray irradiation unit to an inspection object, transmitted X-rays that have passed through the inspection object are acquired by an X-ray detection unit, and the X-ray dose of the acquired transmitted X-rays is X-ray inspection apparatus for estimating the mass of an object to be inspected based on the above, and determining whether the estimated mass of the object to be inspected belongs to any mass class within a predetermined range set in advance.

JP 2010-145135 A

According to the technique of Patent Literature 1, when there is a single inspection target, the mass of the inspection target can be estimated.

However, when the material of the object to be inspected is unknown, or when a plurality of objects are mixed in the same storage container, the mass of each object cannot be estimated.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an X-ray apparatus for performing inspection using X-rays, which is capable of classifying materials constituting an inspection object while confirming the outer shape of the inspection object, and an apparatus using the same. The object is to provide a method for classifying materials that have been used.

In order to solve the above problems, the present invention arranges an X-ray output unit that outputs X-rays with a predetermined output value and a predetermined number of detection elements in a one-dimensional array, one detection element being one pixel, The X-rays are detected at each of the pixels, and pixel information regarding a total energy amount indicating the magnitude of the overall energy of the X-rays and a high energy amount indicating the magnitude of energy equal to or greater than a predetermined value is obtained. an X-ray detection unit for acquiring; detecting the transmitted X-rays transmitted through the storage container, acquiring the pixel information on the transmitted X-rays from the X-ray detection unit, and based on the pixel information , a high energy amount for the object stored in the storage container; The rate of change in the attenuation coefficient is calculated by dividing the attenuation coefficient of the total energy amount by the attenuation coefficient of the total energy amount . The rate of change of the attenuation coefficient of the object is obtained and clustered, and the boundary between each cluster is clarified by drawing a line between the clusters. It is characterized by being classified into any.

The present invention also provides a material classification method using X-rays, which comprises: (a) irradiating X-rays onto storage containers moving on a conveyer; (b) a high-energy attenuation coefficient for the object housed in the container based on the pixel information obtained in step (a); is divided by the attenuation coefficient of the total energy amount , and (c) the rate of change of the attenuation coefficient obtained in step (b) above , and the stage before operating the system, Prepare multiple combinations of the same size for the material sample to be classified, cluster by obtaining the rate of change of each attenuation coefficient, and draw a line between the clusters to clarify the boundaries between each cluster in advance. and classifying the object into one of the predetermined materials based on the prepared material classification cluster .

According to the present invention, there is provided an X-ray apparatus that performs inspection using X-rays, and an X-ray apparatus that can classify materials that constitute an inspection object while confirming the outer shape of the inspection object, and a material using the same. A classification method can be implemented.

This not only confirms the external shape of the object to be inspected, but also classifies the material of the object to be inspected and estimates the mass of each material. can contribute to the prevention of

Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the whole X-ray apparatus outline|summary based on Example 1 of this invention. 2 is a perspective view showing a state of X-ray irradiation by the X-ray apparatus of FIG. 1; FIG. 2 is a diagram showing an X-ray irradiation section of the X-ray apparatus of FIG. 1; FIG. It is a figure which shows the method of memorize|storing the total energy amount and high energy amount of a transmitted X-ray in a memory|storage part. FIG. 4 is a diagram showing a method of arranging the rate of change of attenuation coefficients of each piece of pixel information; FIG. 10 is a diagram showing a method of material classification using material classification clusters; FIG. 4 is a diagram showing a method of arranging material classification information for each pixel in a storage area T1; FIG. 4 is a diagram showing a method of rearranging the normalized total energy for each material; It is a figure which shows the method of calculating a unit mass coefficient. It is a figure which shows the mass correlation coefficient setting curve for every material. FIG. 4 is a diagram showing an example of material classification clusters; It is a figure which shows the X-ray energy amount detection method by a photon counting method. It is a figure which shows the X-ray energy amount detection method by a scintillator method. It is a figure which shows the material classification method based on Example 2 of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in each drawing, the same configurations are denoted by the same reference numerals, and detailed descriptions of overlapping portions are omitted.

An X-ray apparatus according to a first embodiment of the present invention and a material classification method using the same will be described with reference to FIGS. 1 to 13. FIG.

First, the basic concept of the present invention will be described with reference to FIGS. 12 and 13. FIG.

The present invention acquires transmitted X-rays by irradiating a storage container with X-rays, acquires the total energy amount and high energy amount of transmitted X-rays in a unit time, and determines the attenuation coefficient and high energy amount with respect to the total energy amount. Calculate the attenuation coefficient for the amount of energy, divide the attenuation coefficient of the high energy amount by the attenuation coefficient of the total energy amount to calculate the rate of change of the attenuation coefficient, and estimate the material of the object based on the rate of change. .

X-rays, which are a type of electromagnetic wave, have the duality of wave action and particle action, like ordinary light. The present invention utilizes the function of particles. X-rays as particle beams have particles, ie X-ray photons. Each X-ray photon has energy. In the present invention, the amount of energy is defined as an aggregate of energy formed by aggregating a plurality of X-ray photons.

The following relational expression exists between the energy amount I0 of the X-rays irradiated to the object within a unit time and the energy amount I of the X-rays transmitted through the object obtained by irradiating the object with the X-rays. holds.

I = I0exp(-μx)
where μ is the attenuation coefficient and x is the thickness of the object.

Therefore, the attenuation coefficient can be calculated by the formula μ =- ln(I/I0)/x.

In addition, even if X-rays are emitted at a constant output value from an X-ray output unit that outputs X-rays, the energy possessed by each X-ray photon is not the same, and X-ray photons having large energy (high energy) and X-ray photons with small energy (low energy).

In the present invention, transmitted X-rays that have passed through an object are obtained by distinguishing between the total energy amount indicating the overall energy amount and the high energy amount indicating the total amount of X-ray photons having high energy, and the attenuation coefficient is calculated, and the rate of change thereof is calculated.

Furthermore, clusters are prepared in advance for classifying objects according to the change rate of the attenuation coefficient, and the material of the object is classified according to which cluster the actually calculated change rate belongs to.

Assuming that the attenuation coefficient of the total energy amount is μ1 and the attenuation coefficient of the high energy amount is μ2, the rate of change can be calculated by the following arithmetic expression. By clustering the rate of change, the material to which it belongs is determined.

Rate of change = ln(I2/I0)/ln(I1/I0)
Here, I1: total number of photons contained in transmitted X-rays, I2: number of high-energy photons contained in transmitted X-rays, and ln: natural logarithm.

A method of acquiring the total energy amount and the high energy amount from transmitted X-rays that have passed through an object will be described.

This method includes two methods, a photon counting method and a scintillator method.

First, the photon counting method will be explained. FIG. 12 shows an X-ray energy amount detection method based on the photon counting method. FIG. 12 shows an example of detection of X-ray photons 14 of transmitted X-rays by the X-ray detector 6 of the X-ray apparatus 1 of this embodiment, which will be described later with reference to FIG.

In this method, the X-ray photons 14 input to the X-ray detector 6 within a unit time are classified into high-energy and low-energy photons based on a predetermined threshold, and all X-ray photons are counted. The X-ray detector 6 is used, which calculates the total energy amount by counting X-ray photons having high energy, calculates the high energy amount, and outputs the total energy amount and the high energy amount.

Next, the scintillator method will be explained. FIG. 13 shows an X-ray energy amount detection method based on the scintillator method. FIG. 13 shows an example of detection of X-ray photons 14 of transmitted X-rays by the X-ray detector 6 of the X-ray apparatus 1 of this embodiment, which will be described later with reference to FIG.

In this method, the X-ray detection unit 6 is composed of two X-ray detection units, an X-ray detection unit 6a and an X-ray detection unit 6b, and a copper plate 15 is arranged in the middle position. X-ray photons with high energy pass through the copper plate 15 , but X-ray photons with low energy do not pass through the copper plate 15 . Therefore, the X-ray detection unit 6a outputs the total energy amount, and the X-ray detection unit 6b detects the X-rays transmitted through the copper plate 15, that is, X-ray photons with large energy and outputs the high energy amount.

Next, with reference to FIGS. 1 to 11, a specific device configuration of the X-ray device of this embodiment and a material classification method using the device will be described.

FIG. 1 shows an overall configuration diagram of an X-ray apparatus 1 of this embodiment. FIG. 1 shows a view (cross-sectional view) of the X-ray device 1 viewed from the lateral direction, the Z direction is a direction perpendicular to the floor surface on which the X-ray device 1 is installed, and the X direction indicates the conveying direction of the object 10 to be inspected.

As shown in FIG. 1, the X-ray apparatus 1 of the present embodiment includes, as main components, an apparatus main body 2, a measuring section 3 for measuring the mass of an inspection object 10, and the apparatus main body 2 and the measuring section 3. and a control unit 4 .

The apparatus main body 2 has an X-ray output section 5 for outputting X-rays, an X-ray detection section 6 for detecting X-rays, and an object detection section 7 for detecting the presence or absence of an object.

The apparatus main body 2 is arranged so that the conveyer 9 passes through the inside thereof, and the X-ray output from the X-ray output unit 5 is applied to the inspection object 10 carried into the apparatus main body 2 by the conveyer 9 . The X-ray detector 6 detects the transmitted X-rays that are irradiated with the rays 11 and pass through the inspection object 10 .

A shielding curtain 8 is installed in the penetrating portion of the carrying conveyor 9 of the apparatus main body 2 to prevent the X-rays 11 output from the X-ray output unit 5 from leaking to the outside of the apparatus main body 2 .

In the present invention, an X-ray output unit 5 for outputting X-rays with a predetermined output value and a predetermined number of detection elements are arranged in one dimension, and one detection element is regarded as one pixel, and X-rays 11 are directed to an object 10 to be inspected. An X-ray detection unit 6 that detects transmitted X-rays emitted and transmitted through each pixel and outputs the total energy amount and high energy amount of the transmitted X-rays as pixel information, and a measurement unit 3 that measures the mass of an object. , an object detection unit 7 for detecting the presence of the inspection object 10, and a control unit 4 for controlling the overall movement.

When a storage container containing an object (inspection object 10) moves on the transport conveyor 9, first, the mass of the storage container is measured by the measurement unit 3, and the measured value is transmitted to the control unit 4. . Further, when the storage container moves and enters the detection range of the object detection unit 7, the object detection unit 7 detects that the storage container has moved, and transmits a signal to the control unit 4 indicating that the storage container is present. When the control unit 4 acquires the signal indicating that the storage container is present, the control unit 4 transmits a command signal to the X-ray output unit 5 to output the X-rays 11, and furthermore, obtains the total energy amount and the high energy amount of the transmitted X-rays per unit time. Acquisition from the X-ray detection unit 6 and the processing necessary for material classification of the object (inspection object 10) stored in the storage container are started.

The material classification processing of the object (inspection object 10) in the control unit 4 will be described in detail.

FIG. 2 shows a diagram of irradiating the storage container 12 with X-rays 11 and detecting transmitted X-rays in a line shape, and FIG. 3 shows a diagram of acquiring the total energy amount and high energy amount of the transmitted X-rays.

The X-ray output unit 5 continuously emits the X-rays 11 from the starting end A to the terminal end B of the storage container 12 moving on the transport conveyor 9 . The X-ray detection unit 6 is arranged at a position facing the X-ray output unit 5 with the transportation conveyor 9 interposed therebetween, and detects transmitted X-rays that have passed through the object (inspection object 10).

The X-ray detection unit 6 detects transmitted X-rays on the line in one operation, but continuously detects transmitted X-rays while the storage container 12 is moving on the transport conveyor 9 . , the entire storage container 12 can be scanned two-dimensionally. As a result, each of the detection elements constituting the X-ray detection unit 6 is regarded as one pixel, and the pixel information (composed of the total energy amount and the high energy amount) output by each pixel is output to the control unit 4, and the control unit 4 can constitute a group of pixel information for two-dimensionally pixelating the entire storage container 12 based on these pixel information.

FIG. 4 shows a method of storing the total energy amount and high energy amount of transmitted X-rays in the storage unit. It is assumed that the storage unit is included in the control unit 4 .

The left diagram of FIG. 4 visualizes the pixel information group acquired by the X-ray detection unit 6 , and each square corresponds to one detection element 13 (that is, one pixel) of the X-ray detection unit 6 . C in the drawing indicates a range in which the X-ray output unit 5 outputs at one time and the transmitted X-ray can be detected by the X-ray detection unit 6 .

The right diagram in FIG. 4 visualizes how the first storage area T1 and the second storage area T2 are set in the storage unit based on the pixel information group in the left diagram. It corresponds to a storage area corresponding to each detection element of the line detection unit 6 . Specifically, the normalized total energy amount and the normalized high energy amount of transmitted X-rays are arranged in a storage area to generate image information as shown in the right figure.

As shown in FIG. 4, in order to simplify and handle all pixel information within a certain range, an air portion indicating the energy amount of a portion where no object (inspection object 10) exists in the storage container 12, that is, an air portion. With the energy set to the maximum value of 1, the pixel information of the pixels constituting the transmitted X-ray transmitted through the object (inspection object 10) is scaled, and the normalized total energy amount and the normalized high energy amount are obtained for each pixel information. , set a first storage area T1 and a second storage area T2 in the storage unit, store the normalized total energy amount in T1 in a two-dimensional array, and store the normalized high energy amount in T2 It is stored in a two-dimensional array.

One (X, Y) coordinate of the storage areas T1 and T2 corresponds to one pixel, and the grid indicated as the origin in the left figure is the starting point of the linear X-ray detection unit 6, and the last opposing grid. is the end of the X-ray detection unit 6, and the X-axis direction increases from the starting point toward the end. Also, the Y coordinate increases in the direction indicated as the Y-axis direction in the left figure, that is, the direction opposite to the direction in which the container 12 moves on the transport conveyor 9 .

FIG. 5 shows a method of arranging the rate of change of the attenuation coefficient of each pixel information.

Next, the control unit 4 calculates the change rate of the attenuation coefficient from each pixel information. As already mentioned, by dividing the attenuation coefficient of the normalized high energy amount of each pixel information by the attenuation coefficient of the normalized total energy amount, the rate of change of the attenuation coefficient of each pixel information can be calculated. . That is, the change rate of the attenuation coefficient of the pixel information at the k-th coordinate in the X-axis direction and the k-th coordinate in the Y-axis direction (xk, yk) is obtained by setting the attenuation coefficient of the normalized high energy amount to μ2 (xk, yk), Assuming that the attenuation coefficient of the normalized total energy amount is μ1(xk, yk), the rate of change of the attenuation coefficient can be calculated by the following arithmetic expression.

Change rate of attenuation coefficient = μ2(xk,yk)/μ1(xk,yk)
As shown in FIG. 5, the rates of change of these attenuation coefficients are arranged at the corresponding (X, Y) coordinates in the third storage area T3 set in the storage unit. In this state, the materials can be distinguished by referring to the corresponding (X, Y) coordinates in the storage area T3 for each pixel belonging to the storage areas T1 and T2.

The attenuation coefficient for each normalized total energy amount in the storage area T1 is μ1, the attenuation coefficient for each normalized high energy amount in the storage area T2 is μ2, and the rate of change is calculated and stored in the third storage area T3 Remember. Substances are distinguished by calculating the rate of change of each attenuation coefficient by the so-called dual energy method.

Next, each distinguished material, that is, whether each pixel to which the storage region T1 belongs belongs to the first material indicating the material group of heavy metals, belongs to the second material indicating the material group of light metals, or Determine whether the material belongs to the third material indicating the material group of resin.

FIG. 6 shows a method of material classification using material classification clusters.

The right figure of FIG. 6 is plotted on a two-dimensional XY plane, with the X axis representing the normalized total energy amount of the pixel information belonging to T1, and the Y axis representing the rate of change of the attenuation coefficient corresponding to each pixel information. .

Plot the normalized total energy amount T1 (xk, yk) stored in the storage area T1 on the horizontal axis and the rate of change T3 (xk, yk) of the attenuation coefficient stored in the storage area T3 on the vertical axis. , to cluster each pixel.

Incidentally, as indicated by broken lines in the right diagram of FIG. 6, in the material classification cluster, boundaries for classifying the first material, the second material, and the third material are described in advance. By this processing, it is possible to determine whether each pixel belonging to the storage area T1 belongs to the first material, the second material, or the third material.

FIG. 7 shows a method of arranging the material classification information for each pixel in the storage area T1.

As shown in FIG. 7, the material classification information for each pixel in the storage area T1 is arranged in the fourth storage area T4 set in the storage unit.

The material classification cluster is set as follows.

This process must be performed and prepared before actually classifying the material of the object (inspection object 10). As will be described later with reference to FIG. 11, a plurality (eg, 9 samples) of heavy metals (eg, iron), light metals (eg, aluminum), and resin are prepared as samples. Each shape is preferably a square column or a cylinder. The top and bottom areas of all samples are the same, but the height is varied.

X-rays are irradiated from the X-ray output unit 5 to these samples, and respective pixel information is acquired through the X-ray detection unit 6 . For these pieces of pixel information, change rates of attenuation coefficients of the normalized total energy amount and the normalized high energy amount are calculated. Then, the storage areas T1 and T3 described above are created in the storage unit. Further, as shown in the right diagram of FIG. 6, the values in the storage area T1 are plotted on the X axis and the values in the storage area T3 are plotted on the Y axis in a two-dimensional space.

Thereby, clusters of heavy metals, light metals, and resins can be formed. In order to clarify each cluster area more clearly, a line connects the midpoints of plotted points of heavy metal and light metal, and the midpoints of plotted points of light metal and resin are connected with a line. Also, by increasing the number of samples, it is possible to form clusters with higher accuracy.

Next, the mass of each object (inspection object 10) classified into three types of materials is estimated. Note that the mass is simply estimated, and the mass of the storage container 12 is ignored.

Here, since the mass of each object (inspection object 10) cannot be directly estimated, a unit mass coefficient (M) common to the whole, that is, common to each object (inspection object 10) Set the mass coefficient per pixel to be used.

The unit mass coefficient (M) is the total number of pixels of the entire object (Σ the first material by the sum of the number of pixels (Gh(k)) of the second material (Gl(k)) and Σ the number of pixels of the third material (Ga(k))). k indicates the normalized total energy amount.

A specific description will be given with reference to FIG. FIG. 8 shows a method of rearranging the normalized total energy for each material.

First, as shown in FIG. 8, based on the material classification information arranged in the storage area T4, the (X, Y) coordinates arranged in the storage area T1 are assigned to the first material, the second material, and the third material. Classifying and arranging the normalized total energy amount arranged at each (X, Y) coordinate belonging to the first material in the storage area T1 in the fifth storage area T5 set in the storage unit, The normalized total energy amounts arranged at the respective (X, Y) coordinates belonging to the second material in the storage area T1 are arranged in the sixth storage area T6 set in the storage unit, and stored in the storage area T1. The normalized total energy amounts arranged at the respective (X, Y) coordinates belonging to the third material are arranged in the seventh storage area T7 set in the storage section.

That is, the material information in the storage area T4 is applied to the information in the storage area T1, and the information is classified according to material and stored in separate storage areas. This is because the objects are stored in separate storage areas for each classified material, so that the material can be manipulated independently for each material.

One pixel of the X-ray detector 6 corresponds to one (X, Y) coordinate of the storage area in which pixel information is arranged. Therefore, the number of pixels can be calculated by counting the (X, Y) coordinates of interest in the storage area. Therefore, the number of pixels classified into the first material counts the number of coordinates belonging to the storage area T5, the number of pixels classified into the second material counts the number of coordinates belonging to the storage area T6, and the number of pixels classified into the third material counts the number of coordinates belonging to the storage area T6. The number of pixels classified into can be calculated by counting the number of coordinates belonging to the storage area T7.

FIG. 9 shows a method of calculating the unit mass factor.

From these pieces of information, the unit mass coefficient (M) can be calculated by the following arithmetic expression as shown in FIG.

Unit mass coefficient (M) = (mass of object) / (exclusive area of first material + exclusive area of second material + exclusive area of third material)
Here, the area occupied by the first material: the number of (X, Y) coordinates belonging to the storage area T5, the area occupied by the second material: the number of (X, Y) coordinates belonging to the storage area T6, the area of the third material Occupied area: The number of (X, Y) coordinates belonging to the storage area T7.

Next, the mass correlation coefficient of the first material (mh(k)) and the mass correlation coefficient of the second material (ml(k )), and the mass correlation coefficient (ma(k)) of the third material to estimate the mass of the first material, the mass of the second material, and the mass of the third material. do. Note that k indicates the normalized total energy amount as well as the unit mass coefficient (M).

FIG. 10 shows a mass correlation coefficient setting curve for each material.

As shown in FIG. 10, the mass correlation coefficient indicates the mass distribution of each material at the same normalized total energy amount. It shows how much distributed capacity the second material and the third material have in the entire mass.

Using these parameters, the mass of each material can be estimated by the following equation.

[Mass estimation formula (1)]
Estimated mass of the first material = M x Σ (Gh(k) x mh(k)) (1)
Σ(Gh(k)×mh(k)) corresponds to the following formula, and the product of the number of pixels Gh(k) corresponding to each normalized total number of photons and the mass correlation coefficient mh(k) is It is the total.

Gh(0.1)×mh(0.2)＋Gh(0.2)×mh(0.2)＋・・・＋Gh(k)×mh(k)
[Mass estimation formula (2)]
Estimated mass of the second material = M × Σ (Gl(k) × ml(k)) (2)
Σ(Gl(k)×ml(k)) corresponds to the following formula, and the product of the number of pixels Gl(k) corresponding to each normalized total number of photons and the mass correlation coefficient ml(k) is It is the total.

Gl(0.1)×ml(0.2)＋Gl(0.2)×ml(0.2)＋・・・＋Gl(k)×ml(k)
[Mass estimation formula (3)]
Estimated mass of the third material = M×Σ(Ga(k)×ma(k)) (3)
Σ(Ga(k)×ma(k)) corresponds to the following formula, and the product of the number of pixels Ga(k) corresponding to each normalized total number of photons and the mass correlation coefficient ma(k) is It is the total.

Ga(0.1)×ma(0.2)＋Ga(0.2)×ma(0.2)＋・・・＋Ga(k)×ma(k)
Here, M: unit mass coefficient, Gh(k), Gl(k), Ga(k): the number of pixels of the first material corresponding to the normalized total energy amount, the number of pixels of the second material, and the number of pixels of the second material, and The number of pixels of the three materials, mh(k), ml(k), ma(k): the mass correlation coefficient of the first material corresponding to the normalized total energy amount, the mass correlation coefficient of the second material, and the mass correlation coefficient of the third material.

The unit mass coefficient (M) and the mass correlation coefficient of each material corresponding to the normalized total energy (k) (the mass correlation coefficient of the first material mh(k), the mass correlation coefficient of the second material The process of setting the number ml(k) and the mass correlation coefficient ma(k) of the third material will be described. The processing from step 1 to step 10 below is performed in order. These processes also need to be performed and prepared before actually classifying the material of the object.

[Step 1]
FIG. 11 shows an example of material classification clusters. As shown in FIG. 11, a plurality of first material samples, second material samples, and third material samples (nine each in FIG. 11) are prepared. The sample used when preparing the material classification cluster can be used.

In addition, prepare a two-dimensional XY plane in which the X-axis is the normalized total energy amount (k) and the Y-axis is the mass correlation coefficient m(k) corresponding to the normalized total energy amount (k), and the two-dimensional Temporary mass phases for the mass correlation coefficient mh(k) for the first material, the mass correlation coefficient ml(k) for the second material, and the mass correlation coefficient ma(k) for the third material are plotted on the XY plane. Set the correlation coefficient curve. This temporary mass correlation coefficient curve is set as an initial value and may be linear. Correct it so that it becomes an actual curve by adjusting from the subsequent steps.

[Step 2]
From the samples prepared in the process of step 1, select one each of the first material sample, the second material sample, and the third material sample having the same height, and three samples The combination is grouped, and the mass of the entire group is measured by the measurement unit 3 and acquired by the control unit 4 .

[Step 3]
One group is selected in descending order of height from among the groups grouped in the processing of step 2.

[Step 4]
A command signal is transmitted from the control unit 4 to the X-ray output unit 5 for the group selected in the process of step 3, and the entire group is scanned while the X-ray output unit 5 outputs X-rays. (A sample of the first material, a sample of the second material, and a sample of the third material belonging to the group are simultaneously irradiated with X-rays.)
[Step 5]
During scanning in the process of step 4, the X-ray detector 6 detects transmitted X-rays that have passed through each sample in the group, and the pixel information of each pixel output from the X-ray detector 6 is to obtain.

[Step 6]
Based on the number of pixels of each of the first material sample, the second material sample, and the third material sample obtained by the process of step 5, and the pixel information of each pixel, the normalized total number of photons , and set a temporary value for each mass correlation coefficient.

here,
Normalized total energy of the first material: kh
Normalized total energy of the second material: kl
Normalized total energy of the third material: ka
Number of pixels of the first material corresponding to kh Gh (kh)
Number of pixels of the second material corresponding to kl Gl(kl)
Number of pixels Ga(ka) of the third material corresponding to ka
mass correlation coefficient mh(kh) of the first material corresponding to kh
mass correlation coefficient ml(kl) of the second material corresponding to kl
Mass correlation coefficient ma(ka) of the third material corresponding to ka
and

[Step 7]
Calculate the unit mass modulus (M). The mass of the entire target group measured in the process of step 2 is the number of pixels of the sample of the first material, the number of pixels of the sample of the second material, and the number of pixels of the sample of the third material calculated in the process of step 6. (the number of pixels in the entire target group).

Unit mass coefficient (M) = mass of the entire target group / number of pixels of the entire target group [Step 8]
The unit mass coefficient (M) obtained in the process of step 7, the number of pixels Gh (kh) of the first material in the normalized energy amount (kh) of the first material obtained in the process of step 6, and the mass correlation mh (kh), the number of pixels Gl (kl) of the second material in the normalized total energy amount (kl) of the second material, the mass correlation coefficient ml (kl), and the normalization of the third material Substitute the number of pixels Ga (ka) of the third material in the total energy (ka) and the mass correlation coefficient ma (ka) into the following formula to calculate the virtual mass, which is the calculated mass of the entire target group. do.

Temporary mass＝M×(Gh(kh)×mh(kh)+Gl(kl)×ml(kl)＋Ga(ka)×ma(ka))
Since the actual mass of the entire target group was measured in step 2,
Adjust mh, ml, and ma so that temporary mass = actual mass of the entire target group, and determine the plot position on the mass correlation coefficient setting curve for each normalized total photon number kh, kl, and ka .

[Step 9]
The other samples are also sequentially processed in steps 3 to 7 to determine plot positions on the mass correlation coefficient setting curve for each normalized total photon number. This allows setting the mass correlation coefficient for the prepared sample.

[Step 10]
After determining the plotted positions on the mass correlation coefficient setting curve for each normalized total photon number for all samples, numerical interpolation is performed between each point to form a gentle curve.

With the X-ray apparatus of this embodiment and the method of classifying materials using the X-ray apparatus described above, it is possible to classify the materials constituting the inspection object while confirming the outer shape of the inspection object.

An X-ray apparatus according to a second embodiment of the present invention and a material classification method using the same will be described with reference to FIG. FIG. 14 is a diagram showing the material classification method of this embodiment. In this embodiment, an example will be described in which a dangerous object contained in a suitcase or the like is detected at a baggage inspection site such as an airport.

Generally, in baggage inspection, which is one of the security inspections, X-rays are irradiated on the baggage passing through the inspection device, and the security inspector visually detects dangerous items based on the image that has been clarified by image processing. there is

Security inspectors need to look at these X-ray images and perform quick and accurate inspections in a row, but customer satisfaction decreases when careful inspections cause congestion. The physical and mental burden on security inspectors increases.

Therefore, in this embodiment, the X-ray apparatus 1 is provided with a function of selecting a specific inspection object 10 from a plurality of objects stored in a storage container (suitcase 16). This function of selecting a specific object to be inspected 10 is, for example, a security inspector using an input device such as a mouse of a personal computer while viewing an X-ray image on a monitor to frame an object for which safety is a concern. It is realized by enclosing with a line.

The control unit 4 of the X-ray apparatus 1 applies the material classification method and the weight estimation method described in the first embodiment to the selected specific inspection object 10, based on the pixel information of the selected inspection object 10. to determine the rate of change of the attenuation coefficient of the selected inspection object 10, and the plurality of materials that constitute the selected inspection object 10 are each selected from predetermined materials (for example, the first material, the second material, and the third material). material).

Based on the classification, the mass of each material is estimated, and based on the estimated mass of each material, it is determined whether or not the selected inspection object 10 is a dangerous material.

As a result, it is possible to assist in determining whether the object to be inspected is dangerous or not, thereby contributing to the prevention of crimes and the like.

In addition, the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations. In addition, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Moreover, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

DESCRIPTION OF SYMBOLS 1... X-ray apparatus, 2... Apparatus main body, 3... Measurement part, 4... Control part, 5... X-ray output part, 6, 6a, 6b... X-ray detection part, 7... Object detection part, 8... Shielding curtain , 9... Conveyor for transportation, 10... Object to be inspected, 11... X-ray, 12... Storage container, 13... X-ray detection element (of X-ray detection unit 6), 14... X-ray photon, 15... Copper plate, 16... Suit Case, A... starting end of storage container, B... end of storage container, C... transmitted X-ray detection range, T, T1 to T7... storage area.

Claims (13)

an X-ray output unit that outputs X-rays with a predetermined output value;
A total energy amount indicating the magnitude of the overall energy of the X-rays by arranging a predetermined number of detection elements in a one-dimensional manner and detecting the X-rays at each of the pixels, with each detection element as one pixel. and an X-ray detection unit that acquires pixel information about a high energy amount indicating a magnitude of energy equal to or greater than a predetermined value;
a control unit;
The control unit
The X-ray output unit is instructed to irradiate the storage container moving on the conveyer with the X-ray, and the transmitted X-ray transmitted through the storage container is detected to detect the pixel corresponding to the transmitted X-ray. obtaining information from the X-ray detection unit;
obtaining a rate of change of the attenuation coefficient calculated by dividing the attenuation coefficient of the high energy amount with respect to the object stored in the storage container by the attenuation coefficient of the total energy amount based on the pixel information;
In the stage before operating the system, prepare multiple combinations of the same size for the material samples to be classified, cluster them by obtaining the rate of change of each attenuation coefficient, and draw a line between the clusters. An X-ray apparatus characterized by classifying the object into one of the predetermined materials by referring to material classification clusters prepared in advance by clarifying boundaries . An X-ray apparatus according to claim 1, wherein
An X-ray apparatus, wherein the X-ray output unit irradiates the X-rays from the leading end to the trailing end of the storage container moving on the carrying conveyor. An X-ray apparatus according to claim 2,
The predetermined material is a first material, a second material different from the first material, and a third material different from the first material and the second material. An X-ray device characterized by: An X-ray apparatus according to claim 3,
The control unit acquires the pixel information of the entire storage container by scanning the X-ray detection unit from the start end to the end end,
air part energy indicating an energy amount of an air portion where the object does not exist with respect to the total energy amount and the high energy amount included in each of the pixel information corresponding to the transmitted X-rays transmitted through the object; calculating the normalized total energy content and the normalized high energy content by scaling the amounts to a maximum value of 1;
Setting a first storage area T1 and a second storage area T2 in the storage unit,
two-dimensionally arranging the normalized total energy amount in the T1 to generate first image information of the object;
An X-ray apparatus characterized by generating second image information of the object by two-dimensionally arranging the normalized high energy amounts in the T2. An X-ray apparatus according to claim 4,
The control unit
Calculate a first attenuation coefficient indicating an attenuation coefficient corresponding to the normalized total energy amount arranged at each (X, Y) coordinate of the T1;
calculating a second attenuation coefficient indicating an attenuation coefficient corresponding to the normalized high energy amount arranged at the (X, Y) coordinates of each of the T2;
Each said second attenuation coefficient is divided by said first attenuation coefficient for the corresponding (X,Y) coordinate to calculate said rate of change of said normalized high energy dose relative to said respective normalized total energy dose. and arranged in a third storage area T3 set in the storage unit. An X-ray apparatus according to claim 5,
The control unit
The information that the numerical values arranged at the (X, Y) coordinates of the T1 are the X coordinates and the numerical values arranged at the (X, Y) coordinates of the T3 are the Y coordinates are normalized. Clustering is performed by material classification clusters showing the correlation between the total energy amount and the rate of change of the attenuation coefficient, and each (X, Y) coordinate is assigned to any one of the first material, the second material, and the third material. belong to or classify
arranging the material classification information as the first material, the second material, and the third material at the (X, Y) coordinates corresponding to T4 indicating the fourth storage area set in the storage unit; An X-ray device characterized by: An X-ray apparatus according to claim 6,
The control unit
Based on the material classification information arranged in the T4, each (X, Y) coordinate arranged in the T1 is classified into the first material, the second material, and the third material,
arranging the normalized total energy amount arranged at each (X, Y) coordinate belonging to the first material in T5 indicating a fifth storage area set in the storage unit;
arranging the normalized total energy amount arranged in each (X, Y) coordinate belonging to the second material in T6 indicating the sixth storage area set in the storage unit;
The X characterized in that the normalized total energy amount arranged in each (X, Y) coordinate belonging to the third material is arranged in T7 indicating the seventh storage area set in the storage unit. line device. An X-ray apparatus according to claim 7,
The control unit
In T5, counting the number of (X, Y) coordinates having the same normalized total energy amount (k) to calculate the first pixel number Gh(k);
In T6, counting the number of (X, Y) coordinates having the same normalized total energy amount (k) to calculate a second pixel number Gl(k);
In T7, counting the number of (X, Y) coordinates having the same normalized total energy amount (k) to calculate a third pixel number Ga(k);
The mass of the object is divided by the sum of the first pixel number group, the second pixel number group, and the third pixel number group to obtain the first material, the second material, and the first material. An X-ray apparatus characterized by calculating a unit mass coefficient (M) common to three materials. An X-ray apparatus according to claim 8,
The control unit uses a mass correlation coefficient setting curve to determine the mass correlation coefficient mh(k ), ml(k) and ma(k) (where k is the number of normalized photons). An X-ray device according to claim 9,
According to the following arithmetic expressions (1) to (3), the control unit
Mass of the first material = M(Gh(0.1)mh(0.1)+Gh(0.2)mh(0.2)+・・・+Gh(k)mh(k))・・・(1)
Mass of second material = M(Gl(0.1)ml(0.1)+Gl(0.2)ml(0.2)+・・・+Gl(k)ml(k))・・・(2)
Mass of the third material = M(Ga(0.1)ma(0.1)+Ga(0.2)ma(0.2)+・・・+Ga(k)ma(k))・・・(3)
An X-ray apparatus characterized by estimating the mass of the first material, the mass of the second material, and the mass of the third material of the object. An X-ray apparatus according to claim 1, wherein
The X-ray device includes a measurement unit,
a storage container sensor arranged at a rear position of the transport conveyor from the measurement unit,
measuring the mass of the storage container by the measuring unit;
When the storage container sensor detects the storage container after the mass of the storage container is measured by the measurement unit, the control unit transmits a command signal to the X-ray output unit to start the X-ray irradiation. An X-ray apparatus characterized by: An X-ray apparatus according to claim 1, wherein
The X-ray device has a function of selecting a specific object from a plurality of objects stored in the storage container,
The control unit obtains a change rate of an attenuation coefficient of the selected target based on the pixel information of the selected target,
An X-ray apparatus characterized by classifying a plurality of materials constituting the selected object into one of the predetermined materials. A material classification method using X-rays,
(a) a step of irradiating X-rays onto a storage container moving on a carrying conveyor, and detecting transmitted X-rays transmitted through the storage container to acquire pixel information for the transmitted X-rays;
(b) Based on the pixel information acquired in step (a), the attenuation coefficient is calculated by dividing the attenuation coefficient of the high energy amount for the object stored in the storage container by the attenuation coefficient of the total energy amount. determining a rate of change ;
(c) The change rate of the attenuation coefficient obtained in step (b) above, and the change in the attenuation coefficient of each of the material samples to be classified in the stage before operating the system, by preparing a plurality of combinations of the same size The object is classified into one of the predetermined materials based on material classification clusters prepared in advance by performing clustering by obtaining the ratio and further clarifying the boundaries between each cluster by drawing lines between the clusters. a step;
A material classification method characterized by having

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