JP2018155643A - X-ray detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray detector for detecting foreign matter from an inspection object and the spectrum of foreign matter, and a method for analyzing a spectrum simply at so high speed as can be used in-line that is installed in the X-ray detector.SOLUTION: The X-ray detector includes a multi-energy sensor unit with which X-ray energy irradiated from an X-ray source can be spectralized for each pixel, with the X-ray energy having passed through an object under inspection is obtained as a spectrum on the basis of the X-ray data by the multi-energy sensor and the spectral data obtained from the multi-energy sensor approximated by a quadratic function, whereby the feature quantities of an inspection object and foreign matter are efficiently extracted.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an X-ray inspection apparatus that detects foreign matter contained in an inspection object by irradiating the inspection object with X-rays.

  There is a growing need for difficult-to-detect foreign materials, such as detecting bones in chicken and detecting foreign materials in cereals.

  In view of this, efforts have been made to enable detection of difficult-to-detect foreign substances using a dual energy sensor (see, for example, Patent Document 1). This sensor uses two types of sensors having different energy characteristics to simultaneously image an object to be inspected, and can obtain two images having different contrasts. A technique for eliminating the influence of the object to be inspected by performing differential processing on these two images and extracting only foreign matters is called energy subtraction.

  In foreign matter detection, ideally, if the X-ray absorption spectrum itself of the object to be inspected and the foreign matter can be obtained, the elements contained therein can be analyzed. Can be determined.

  Therefore, it is conceivable to obtain an energy spectrum of transmitted X-rays using a multi-energy sensor with energy resolution. Unlike the combination of an S sensor that detects low energy X-rays and an H sensor that detects high energy X-rays, this sensor is characterized by the ability to collect X-ray spectra for each pixel. By comparing the spectra of the sensors, it is possible to determine whether the pixel being inspected is an inspection object or a foreign object.

For example, in a multi-energy sensor manufactured by MultiX, each pixel having a 0.8 mm pitch generates 64 levels of energy spectrum. If the object to be inspected is a square having a side of 300 mm, data of 375 pixels × 375 pixels × 64 levels can be obtained.

Patent No. 5616182

  The big obstacle in the analysis of this data is the large amount of data. Usually, the dual energy sensor is about 0.4 mm pixel, and in the above example, the data amount is 750 pixels × 750 pixels × 2 steps, and the multi energy sensor is (375/750) × (375/750) × (64/2). ) = 8 times the amount of data. If the data processing time is a normal CPU, the dual energy sensor is about 100 ms, and even if the processing is simplified, the multi-energy sensor requires about 800 ms, which is eight times as much.

  The time allowed for in-line inspection of a general food is (500 mm-300 mm) / (30 m / min) = 400 ms when the distance from the X-ray irradiation unit to the sorting apparatus is 500 mm and the inspection speed is 30 m / min. Therefore, it will not be in time for the above 800 ms.

  If the inspection object flows at intervals of 400 mm, the interval of the inspection object is 100 mm, and 100 mm / (30 m / min) = 200 ms, and the calculation process of the previous inspection object is not finished. The next calculation will start and correct inspection will be impossible.

  Therefore, the problem to be solved by the present invention is to provide a new X-ray inspection apparatus capable of performing an inspection in a processing time that does not cause a practical problem when a multi-energy sensor is used.

  The energy spectrum of X-rays usually shows a generally convex spectrum. When X-rays are incident on the inspection object, the X-rays are absorbed according to the elements contained in the inspection object, so that the spectrum of the transmitted X-rays changes from the incident X-ray spectrum. The absorption spectrum of X-rays is unique to the element, and an element having a larger atomic number Z has a characteristic of absorbing lower energy X-rays. Conversely, an element with a small Z has a relatively low absorption of low energy X-rays.

  For example, if chicken is the object to be inspected, chicken is generally an aggregate of organic matter, and therefore contains a large amount of elements with small Z such as hydrogen, carbon, oxygen, etc. Many elements with large Z such as phosphorus and phosphorus are contained. Therefore, X-ray absorption only by chicken does not absorb very low energy X-rays, and the transmitted X-ray spectrum is biased toward a relatively low energy side. Conversely, foreign substances such as bones absorb a large amount of low energy X-rays, so that the spectrum of transmitted X-rays is biased toward the high energy side.

  Therefore, the X-ray inspection apparatus according to the first invention detects an X-ray source for irradiating the inspection object with X-rays, and X-rays in a plurality of different energy bands included in the inspection object to detect energy for each pixel. A multi-energy sensor that outputs a spectrum; and a comparison unit that compares energy spectra of each pixel of the obtained object to be inspected, wherein the comparison unit is a pixel having an energy spectrum different from the energy spectrum of other pixels It is determined that there is a foreign object.

  In the X-ray inspection apparatus according to the second invention, when the difference between the energy spectrum of the target pixel and the energy spectrum of another pixel exceeds the reference, the comparison unit of the first invention has a foreign object on the target pixel. It is judged that there is

  Further, in the X-ray inspection apparatus according to the third invention, the comparison unit of the second invention obtains a peak value of the energy spectrum of each pixel, and a difference between the obtained peak values of each pixel exceeds a reference value In addition, it is determined that there is a foreign object in the target pixel of the energy spectrum.

  In the X-ray inspection apparatus according to the fourth aspect of the invention, the reference value of the third aspect of the invention is a difference in peak value of each energy spectrum between a pixel in a region without a foreign substance and a pixel in a region with a foreign substance.

  Furthermore, an X-ray inspection apparatus according to a fifth aspect of the present invention detects an X-ray source that irradiates an X-ray to the inspection object, and X-rays in a plurality of different energy bands included in the inspection object, and energy for each pixel. A multi-energy sensor that outputs a spectrum; and a comparison unit that compares each obtained energy spectrum with a predetermined energy spectrum, wherein the comparison unit determines whether there is a difference between the compared energy spectrum and the predetermined energy spectrum. Thus, it is determined whether or not there is a foreign object in the pixel of the compared energy spectrum.

  In the X-ray inspection apparatus according to the sixth invention, the predetermined energy spectrum of the fifth invention is an energy spectrum of a pixel in a region where a foreign substance exists.

  In the X-ray inspection apparatus according to the seventh invention, the predetermined energy spectrum of the fifth invention is an energy spectrum of a pixel in a region where the inspection object exists.

  In the X-ray inspection apparatus according to an eighth aspect of the invention, the comparison unit according to the fifth to seventh aspects obtains the peak value of the energy spectrum of each pixel and compares the obtained peak value with a predetermined peak value. .

  In the X-ray inspection apparatus according to the ninth invention, the comparison unit according to the fifth to eighth inventions obtains the peak value from a quadratic curve approximated to an energy spectrum.

  In the X-ray inspection apparatus according to a tenth aspect of the invention, the comparison unit according to the fifth to eighth aspects obtains the peak value from the second derivative of the energy spectrum.

  When the above inventions are outlined, the energy spectrum of X-rays generally has an upwardly convex shape. Therefore, for comparison, for example, the peak value of an energy spectrum is searched for and the peak value is different from that of the other. Foreign matter can be detected by examining how much it differs from the peak value of the energy spectrum. How much difference is determined by adding foreign matter to the object to be inspected, and obtaining the peak value of each pixel in the region without foreign matter and the pixel in the region with foreign matter in advance. It can be confirmed whether it is permitted. There is also a method for obtaining a quadratic curve approximated to an energy spectrum as a method for easily searching for a peak value. Ideally, the obtained spectrum should be approximated by the least-squares method. However, as described above, the in-line inspection device for foods has a short time allowed for calculation, so it represents three points. To obtain a quadratic function.

  The optimal combination of these three points depends on the characteristics of the inspection object and foreign matter, the structure of the apparatus, and the setting conditions. For example, in the inspection of bones in chicken, when the tube voltage is set to 100 kV with a tungsten target tube with a beryllium window, it is best to select three energy bands of 26 keV, 40 keV, and 76 keV. I know. These can be obtained in advance by using chicken and bone samples and selecting the three points with the highest peak energy.

In order to select these three points appropriately, for example, when bone detection in chicken is performed as an example, as a pre-setup, a sample of bone to be detected is attached to chicken and a multi-energy sensor is used. Get multi-energy images. Since this multi-energy sensor detects a plurality of energy bands included in the transmitted X-rays of the inspection object and outputs an energy spectrum for each pixel, energy of three points of a quadratic function characterizing the energy spectrum of a certain pixel Let the coordinates be ε ₁ , ε ₂ , ε ₃ .

When the pixel of the obtained image is represented by (x, y), energy is ε, and X-ray intensity is represented by I (x, y, ε), (ε ₁ , I ₀ (x, y, ε ₁ )), ( ε ₂ , I ₀ (x, y, ε ₂ )), (ε ₃ , I ₀ (x, y, ε ₃ ))
If I ₀ (x, y, ε) = a (x, y) ε ² + b (x, y) ε + c (x, y), Equation 1 is obtained, and by transforming into Equation 2, I ₀ (x, y, ε) can be obtained.

In the previous setup, the chicken-only pixel and the bone-attached pixel were known and were determined by Equation 2 with (x _A , y _A ), (x _B , y _B ) as the respective pixels. When the energy coordinates of the vertices of the quadratic function are obtained using Equation 3 below, Equation 4 is obtained.

When examining bone in chicken as a foreign object, the most easily detected bone is the energy band where the difference in energy spectrum between chicken and bone is the largest. Using the above results, Equation 5 This is the largest case. What is necessary is just to obtain such energy combinations ε ₁ , ε ₂ , ε _3. For this purpose, Equation 5 is obtained for all combinations of ε ₁ , ε ₂ , ε ₃ , and ε ₁ , ε is maximized. ₂ and ε ₃ may be used.

If ε ₁ , ε ₂ , and ε ₃ are obtained in advance learning, when actually inspecting a foreign substance, after calculating Equation 2 at an arbitrary coordinate (x, y), the energy coordinate is used. If a certain numerical formula 6 is imaged as a gray value, the foreign matter part will be lifted.

  Since this method is an algebraic operation using a quadratic curve, the calculation time is significantly faster than detecting foreign matter by successive comparison of energy spectra.

For simplicity of explanation, (x _A , y _A ), (x _B , y _B ) are shown here, but these are expanded to a range with an area and averaged gray value Alternatively, the maximum value, minimum value, or median value of the gray values in the region may be used.

According to the invention, an energy spectrum for each pixel in a plurality of different energy bands included in the object to be inspected is obtained using the multi-energy sensor, and the obtained energy spectrum is compared for each pixel. Since it is determined that there is a foreign substance in a pixel having an energy spectrum different from the energy spectrum, a more accurate inspection can be performed.
Further, if the peak values of the energy spectra are compared with each other instead of the successive comparison between the energy spectra, the calculation speed can be improved. Further, if the peak value of the quadratic curve is obtained in advance by obtaining the energy coordinates of the three points of the quadratic function, the calculation speed can be further improved.

The external view of a X-ray foreign material detection apparatus. The schematic diagram of a X-ray foreign material inspection apparatus. Imaging of inspection object by line sensor unit. Imaging of the inspection object imaged by the line sensor unit. The block diagram of a X-ray inspection apparatus. The block diagram of a line sensor unit. Data for each pixel of the line sensor unit. Data after calibration of the line sensor unit. An image of the sum of all energy data for each pixel of chicken and bone. 64 energy slice images. Graph of energy spectrum at a certain pixel. The energy spectrum approximated by the least square method is indicated by a broken line. Approximate the energy spectrum of chicken with a quadratic function passing through ε ₁ = 20 keV, ε ₂ = 40 keV, ε ₃ = 60 keV, and obtained the energy coordinates of the vertices. Approximate the energy spectrum of the bone with a quadratic function that passes through ε ₁ = 20 keV, ε ₂ = 40 keV, ε ₃ = 60 keV, and obtained the energy coordinates of the vertices. Approximation with a quadratic function that passes through ε ₁ = 26 keV, ε ₂ = 40 keV, and ε ₃ = 76 keV, and the result is an image with the energy coordinates of the vertices as gray values. An example of an image where chicken and bones are not sufficiently separated.

(Embodiment)
Hereinafter, an X-ray inspection apparatus 100 according to an embodiment of the present invention will be described with reference to the drawings. The X-ray inspection apparatus 100 according to the present embodiment is an X-ray inspection apparatus that inspects an object to be inspected 600 such as food (for example, a plurality of sausages in a bag) as shown in FIGS. The sensor unit mainly includes a transport unit 500 that transports the inspection object 600, an X-ray source 200 that irradiates the inspection object 600 with X-rays, and a sensor that detects X-rays irradiated from the X-ray source 200. 300 and the image processing unit 400 of FIG. FIG. 5 shows a configuration block diagram of the X-ray inspection apparatus.

  The X-ray inspection apparatus 100 is mainly used for detecting foreign matters mixed in food. It is a mechanism that is installed in a food production site, etc., and observes the inside of food using X-ray fluoroscopic images, and detects X-ray images by visual inspection or analysis to detect mixed foreign matter.

  In the X-ray inspection apparatus 100, X-rays are irradiated while the inspection object 600 is conveyed by the conveyance unit 500, and the X-rays transmitted through the inspection object 600 are sequentially received by the line sensor unit 300. The received data is converted into digital data by an electronic board (not shown) inside the line sensor unit 300 and transferred to the image processing unit 400. The image processing unit 400 inspects whether there is a foreign object inside the inspection object 600 of the two-dimensional transmission X-ray image. The result is displayed on the display MT in FIG. 1, and the operator can know the presence or absence of a foreign object. At the same time, the location of foreign matter is displayed on the X-ray image of the object to be inspected.

(Transport section)
The transport unit 500 is provided to transport the inspection object 600 into the inspection room. The transport unit 500 can use various transport mechanisms such as a belt conveyor, a top chain conveyor, and a rotary table. The most common type is a belt conveyor type, and a resin-made conveyor belt 510 is attached between pulleys before and after the conveyor unit 500. In order to prevent X-rays from leaking, a strip-shaped curtain 550 made of resin mixed with heavy metal is attached to the entrance / exit of the examination room in FIG.

(X-ray source)
The X-ray source 200 irradiates the inspection object 600 transported to the inspection position by the transport unit 500 with X-rays. The X-rays emitted from the X-ray source 200 include X-rays in various energy bands from low energy (long wavelength) to high energy (short wavelength). Although described as “low energy” and “high energy”, “high” and “low” are relatively “high” and “low” among a plurality of energy bands irradiated from the X-ray source 200. It does not indicate a specific range. The same applies hereinafter.

(Multi energy sensor unit)
The multi-energy sensor unit 300 includes a wide range of X-rays emitted from the X-ray source 200 of FIG. 2 from high-energy X-rays to low-energy X-rays. The multi-energy sensor unit 300 detects X-rays in these different energy bands, and is a sensor with high energy resolution. In addition, the sensor unit 300 is a line sensor type in which pixels are arranged in a line, and as shown in FIG. 4, the inspection object 600 conveyed by the conveyance unit 500 is imaged for each line. It is input and synthesized into a two-dimensional image. Furthermore, the multi-energy sensor unit 300 includes a light receiving unit 350 and a control unit 360, and includes an external input interface 370 that can be controlled from the outside, and an external output interface 380 that is used for data output and the like. The control unit 360 analyzes the X-rays of a plurality of energy bands detected by the light receiving unit 350, so that an energy spectrum for each pixel is output.

(Control device)
The control device controls the entire X-ray inspection apparatus 100 including the X-ray source 200, the conveyance unit 500, the sensor unit 300, and other devices, and processes the data obtained from the sensor unit 300 to detect foreign matter, which will be described later. The comparison unit 400 is provided. The comparison unit 400 is configured by a computer, and processes data sent from the sensor unit 300 by executing a built-in program, and stores an energy spectrum for each pixel. Subsequently, the stored energy spectrum is compared for each pixel to check whether the energy spectrum of the target pixel is different from that of other pixels. If the energy spectrum is different, there is a foreign object in the target pixel. Is determined. When a foreign object is detected, the part is displayed on the display 910 or a warning is issued by the buzzer 920 to notify the operator of the detection of the foreign object.

(Generation of images using a multi-energy sensor)
(Imaging settings)
When the X-ray is irradiated, the inspection object 600 is transferred by the transfer unit 500, and an image is picked up by the line sensor unit 300 (FIG. 6), a shutter is set for each time required to move one pixel of the inspection object 600. Then, the object 600 is imaged in a strip shape as shown in FIG. Then, the image on the line is transferred as data to the control device. For example, if the length in the transport direction is 1 mm and the transport speed is 30 m / min, the shutter time is
The following formula 1 is obtained.

(Advance preparation)
Next, as pre-preparation for imaging with the multi-energy sensor 300, calibration is performed so that uniform data can be obtained correctly when there is no object 600 to be inspected. For example, since there is some X-ray absorber even if there is no object to be inspected, such as the conveyor belt 510 of the belt conveyor, the cover 370 of the line sensor unit 300, etc., these effects are examined. In addition, since the line sensor itself also varies in sensitivity depending on the pixels, it is also meaningful to measure these simultaneously.

(Setting the dynamic range of the multi-energy sensor)
In the above-described background correction in a normal line sensor, only the brightness is adjusted for each pixel. However, since the multi-energy sensor 300 collects the spectrum for each pixel, the spectrum needs to be corrected. This method will be specifically described below.

For example, consider the case where X-rays with tube voltage V (kV) are irradiated. Let I _D (V, z, ε) be data from the line sensor unit in the energy band ε to ε + Δε of the pixel z when there is no inspection object and no X-rays are irradiated. On the other hand, data from the line sensor unit 300 in the energy band ε to ε + Δε of the pixel z in a state where there is no inspection object and X-rays are irradiated is defined as I _B (V, z, ε). As a major premise, measurement cannot be performed if the light receiving capacity of the sensor overflows, so the tube current value is adjusted so that I _B (V, z, ε) does not exceed the specified value of the line sensor unit 300. There is a need to. For example, the tube current value is reduced so that the maximum value of I _B (V, z, ε) is 90% of the measurement capacity of the line sensor unit.

In the multi-energy sensor 300, the energy from the X-ray source 200 is also spectrumd, but the total energy reaching each pixel from the X-ray source 200 is considered to be constant, and the sum of I _B (V, z, ε) with respect to ε. Is assumed to be constant, so I _B (V, z) = Σ _ε I _B (V, z, ε) is made uniform. Then, an output is obtained as shown in FIG. 7 due to the positional relationship of the line sensor unit 300 and the variation of each pixel.

In such a state where there is variation for each pixel, the subsequent processing becomes complicated, so that calibration is performed so as to be uniform. In other words, I _B (V, z) and I _D (V, z) are constant as shown in FIG. A transformation I ′ (V, z) = aI (V, z) in which Equation 2 which is a straight line representing ξ on the horizontal axis in FIG. 7 is identical to Equation 3 of the straight line representing FIG. ) + b is obtained, and Equations 4 and 5 are obtained.

  Once the calibration parameters a and b are obtained in this way, the raw data from the line sensor unit 300 is converted and used as I ′ (V, z) = aI (V, z) + b. To do. This setting of the dynamic range is effective for a certain tube voltage V (kV). When the tube voltage is changed to V ′ (kV), it is necessary to set the calibration again.

The conversion by the calibration may be set electronically by a gain circuit / offset circuit, or digitized data may be digitally calculated by a control device. For example, if the dynamic range of the line sensor unit is 12 bits, it is determined as I _D0 = 500 and I _B0 = 3500 with a margin.

(Imaging the inspection object)
The data transferred from the line sensor unit 300 is sequentially stored by the memory inside the control device, and after the inspection object 600 passes, that is, this imaging continues until reaching a preset imaging length L. . The length L is set longer than the inspected object 600 with a margin according to variations in the inspected object 600, the size of the buffer in the imaging process, and the like. In this manner, the data stored in the memory is connected to generate an image of the inspection object 600.

(Inspection image display)
Since the data of the multi-energy sensor 300 has a spectrum for each pixel, the above imaging result displays, for example, the sum of all the spectra for each pixel, and recognizes the image of the inspection object to the operator. This is displayed on the display 910. This is for easy display for the operator. In actuality, each pixel holds an energy spectrum, and the spectrum data is stored in a memory.

  FIG. 9 shows a connected image obtained by summing up the total energy for each pixel. Note that the dynamic range is adjusted for each energy for each pixel so that the background is uniform using data measured in advance.

For example, if the performance of the multi-energy sensor 300 can collect data by dividing the energy band into 64 steps every 2 keV from 20 keV to 148 keV, 64 energy slice images can be obtained. FIG. 10 shows 64 energy slice images, and each image corresponds to a respective energy band ε _k (k = 0, 1, 2,..., 63). In the figure, they are arranged in the order of k = 0, 1, 2,. The calibration described above is performed in advance.

  A process for detecting a foreign object from the image acquired by the multi-energy sensor unit 300 using the comparison unit 400 of the control device will be described using a specific example.

  As a preliminary setup, a chicken and a bone sample to be detected are attached to the inside or the surface thereof, and a multi-energy image of the chicken is obtained. As an example, an energy spectrum in a certain pixel is shown in FIG.

  Extracting bone from chicken is possible if the entire energy spectrum can be compared for each pixel, but this requires a huge amount of calculations and is not applicable to an in-line inspection device.

  Therefore, by approximating the energy spectrum with a quadratic function and using the energy coordinates of the vertex of the quadratic function as a feature amount, bones are extracted from the chicken with fewer calculations.

  When the energy spectrum is approximated by a least square method using a quadratic function, a broken line in FIG. 12 is obtained. Here, since the X / ray intensity is low in the region where the energy is high, the S / N is reduced due to the lack of statistical data. Therefore, the calculation is performed in the region of 70 keV or less, excluding the calculation of the least square method.

  However, this least-squares method is also a method with a large amount of calculation. In the case of further simplification, since the quadratic function can be obtained if three points are known, an appropriate three points are selected and these three points are selected. Find the quadratic function that passes. For example, FIG. 13 shows a quadratic function based on the least square method and a quadratic function passing through three points of ε_1 = 20 keV, ε_2 = 40 keV, and ε_3 = 60 keV. It can be seen that very similar shapes can be obtained. Therefore, it is only necessary to determine three points at which bones are most easily extracted from chicken by prior setup, and this determination method will be described below.

Chicken meat is composed of elements with a relatively small atomic number, and the X-ray spectrum transmitted through it tends to be biased to the left, but foreign substances such as bones are composed of elements with relatively large atomic numbers such as calcium and phosphorus. Therefore, the X-ray spectrum transmitted therethrough tends to be biased to the right side. In other words, the energy coordinates of the vertices are good indicators of how the spectrum is biased. When the energy spectra of the chicken and bone pixels shown in FIGS. 13 and 14 are expressed by a quadratic function passing through ε ₁ = 20 keV, ε ₂ = 40 keV, and ε ₃ = 60 keV, the energy coordinates of the vertices are 34. 6 keV and 36.0 keV, it can be seen that the bone is certainly biased toward the high energy side.

Thus, a quadratic function is obtained with the energy coordinates of the above three points as ε ₁ , ε ₂ , and ε ₃ , and the energy coordinates of the vertexes are swept for all combinations of ε ₁ , ε ₂ , and ε ₃ , What is necessary is just to make it the difference of the peak value of a chicken and a bone large. The image where the difference between the peak values of chicken and bone was the largest was ε ₁ = 26 keV, ε ₂ = 40 keV, and ε ₃ = 76 keV. FIG. 15 shows the result, and it can be seen that only bones are extracted from this figure. FIG. 16 shows an example when the energy ε ₁ , ε ₂ , ε ₃ is not set correctly as a reference for comparison. It can be seen that the bone is not sufficiently detected.

  In FIG. 15 and FIG. 16, the outside of the inspection object (chicken) is a noisy area, but it can be easily removed by masking only the part without chicken beforehand. In the present specification, an image in a state where no mask is set is described for the sake of explanation.

(Modification)
As described above, in the embodiment, the quadratic curve is used for the approximation of the energy spectrum. However, a cubic curve, an exponential function, a logarithmic function, a trigonometric function, or other similar functions, or a combination thereof can be used. Depending on the performance of the installed computer, approximation with more advanced functions is possible.

DESCRIPTION OF SYMBOLS 100 X-ray inspection apparatus 200 X-ray source 300 Line sensor unit 350 Light receiving part 400 of a line sensor unit Image processing part 500 of the control apparatus of an X-ray inspection apparatus Conveyance part 600 of an X-ray inspection apparatus

Claims (10)

An X-ray source for irradiating the inspection object with X-rays;
A multi-energy sensor that detects X-rays of a plurality of different energy bands included in the inspection object and outputs an energy spectrum for each pixel;
A comparison unit for comparing the energy spectrum of each pixel of the obtained inspection object;
With
The X-ray inspection apparatus according to claim 1, wherein the comparison unit determines that there is a foreign substance in a pixel having an energy spectrum different from that of another pixel.   The comparison unit according to claim 1, wherein when the difference between the energy spectrum of the target pixel and the energy spectrum of another pixel exceeds a reference, the comparison unit determines that there is a foreign object in the target pixel. X-ray inspection equipment.   The comparison unit obtains the peak value of the energy spectrum of each pixel, and determines that there is a foreign object in the pixel of the target energy spectrum when the difference between the obtained peak values of each pixel exceeds a reference value. The X-ray inspection apparatus according to claim 2.   The X-ray inspection apparatus according to claim 3, wherein the reference value is a difference in peak value of each energy spectrum between a pixel in a region having no foreign matter and a pixel in a region having a foreign matter. An X-ray source for irradiating the inspection object with X-rays;
A multi-energy sensor that detects X-rays of a plurality of different energy bands included in the inspection object and outputs an energy spectrum for each pixel;
A comparison unit for comparing each obtained energy spectrum with a predetermined energy spectrum;
With
The X-ray inspection apparatus, wherein the comparison unit determines whether there is a foreign object in a pixel of the compared energy spectrum based on whether there is a difference between the compared energy spectrum and the predetermined energy spectrum.   The X-ray inspection apparatus according to claim 5, wherein the predetermined energy spectrum is an energy spectrum of a pixel in a region where foreign matter exists.   The X-ray inspection apparatus according to claim 5, wherein the predetermined energy spectrum is an energy spectrum of a pixel in a region where an inspection object exists.   The X-ray inspection apparatus according to claim 5, wherein the comparison unit obtains a peak value of an energy spectrum of each pixel and compares the obtained peak value with a predetermined peak value. .   The X-ray inspection apparatus according to claim 5, wherein the comparison unit obtains the peak value from a quadratic curve approximated to an energy spectrum.   The X-ray inspection apparatus according to claim 5, wherein the comparison unit obtains the peak value from a second-order derivative of an energy spectrum.