X-ray inspection apparatus and calibration method thereof

Abstract

To provide an X-ray inspection device that is able to output abnormal pixel information for specifying an abnormal pixel among a plurality of pixels constituting an X-ray detector, and to provide a calibration method therefor.SOLUTION: An X-ray inspection device 1 comprises: an X-ray detector 30 including an X-ray detection element configured to output a pulse signal of a peak value corresponding to energy of an X-ray having passed through an inspection region, and an X-ray detection unit composed of a plurality of pixels configured to detect the number of pulse signals exceeding a predetermined threshold voltage among the pulse signals output from the X-ray detection element; a storage unit 56 configured to store, for each of the pixels, a correspondence relation between a value of a control parameter for changing the number of the pulse signals exceeding the threshold voltage and the number of pulse signals detected by the pixels; and an abnormal pixel information output unit 57 configured to output abnormal pixel information for identifying an abnormal pixel, based on the correspondence relation, read from the storage unit 56, between the value of the control parameter and the number of the pulse signals detected by each of the pixels.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an X-ray inspection apparatus that irradiates a test object with X-rays and inspects the test object based on the amount of transmitted X-rays, and a calibration method therefor.

Background Art

[0002] An X-ray inspection apparatus irradiates test objects such as meat, fish, processed foods, and pharmaceuticals that are sequentially conveyed at predetermined intervals on a conveyance path with X-rays, and checks whether foreign substances are mixed in the test objects or whether there are shortages in the test objects based on the amount of transmitted X-rays of the irradiated X-rays.

[0003] An X-ray inspection apparatus is incorporated into an inspection line that performs inspections such as foreign substance mixing inspection and final weight inspection, and performs inspections such as foreign substance mixing inspection.

[0004] In an X-ray inspection apparatus, X-rays having a width in a direction orthogonal to the conveyance direction of the test object are irradiated, and the X-rays transmitted through the test object are received by a plurality of sensor elements (pixels) arranged in a direction orthogonal to the conveyance direction of the test object. Image information representing the difference in transmittance for each part of the test object with respect to the X-rays as shades of gray is obtained, and various processes are performed on this image information to determine the presence or absence of foreign substance mixing, the presence or absence of content loss, shortages, etc.

[0005] However, in such an X-ray inspection apparatus, since the X-rays are emitted so as to spread in a direction orthogonal to the conveyance direction, the intensity of the X-rays incident on each pixel becomes non-uniform due to the difference in the distance from the X-ray source to each pixel.

[0006] Patent Document 1 describes an X-ray inspection apparatus that uses a calibration member to change two or more X-ray incident conditions common to all pixels, and obtains calibration data necessary for the image data to have a uniform density for each incident condition changed by the calibration member.

Prior Art Documents

Patent Documents

[0007] [Patent Document 1] Patent No. 6717784 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, conventional X-ray inspection equipment had a problem in that it could not adequately calibrate the density of image data when some pixels deviated significantly from the average sensitivity.

[0009] The present invention has been made to solve the above-mentioned conventional problems, and aims to provide an X-ray inspection apparatus and a calibration method thereof that can output abnormal pixel information for identifying abnormal pixels among a plurality of pixels constituting an X-ray detector. [Means for solving the problem]

[0010] To solve the above problems, the X-ray inspection apparatus according to the present invention is an X-ray inspection apparatus (1) comprising an X-ray source (20) for irradiating an inspection area with X-rays and an X-ray detector (30) for detecting X-rays that have passed through the inspection area, wherein the X-ray detector includes an X-ray detection element (31) that outputs a pulse signal with a pulse height corresponding to the energy of the X-rays that have passed through the inspection area, and an X-ray detection unit (33) consisting of a plurality of pixels (32) that detect the number of pulse signals that exceed a predetermined threshold voltage from the pulse signals output from the X-ray detection element, and the X-ray inspection apparatus further comprises a storage unit (56) that stores for each pixel the correspondence between the value of a control parameter that changes the number of pulse signals that exceed the threshold voltage and the number of pulse signals detected by the pixel, and an abnormal pixel information output unit (57) that outputs abnormal pixel information for identifying abnormal pixels based on the correspondence between the value of the control parameter and the number of pulse signals detected by each pixel, which is read from the storage unit.

[0011] As a result, the X-ray inspection apparatus according to the present invention acquires the correspondence between the value of a control parameter that changes the number of pulse signals exceeding a predetermined threshold voltage among the pulse signals with pulse height values ​​corresponding to the energy of X-rays that have passed through the inspection area, and the number of pulse signals detected by each pixel of the X-ray detection unit. Furthermore, the X-ray inspection apparatus according to the present invention can output abnormal pixel information for identifying abnormal pixels based on the correspondence between the value of the control parameter and the number of pulse signals detected by each pixel.

[0012] Furthermore, the X-ray inspection apparatus according to the present invention is an X-ray inspection apparatus (1) comprising an X-ray source (20) for irradiating an inspection area with X-rays, an X-ray detector (30) for detecting X-rays that have passed through the inspection area, a display unit (45) for displaying various information, and an input / output unit (60) that can be connected to an external device (2), wherein the X-ray detector comprises an X-ray detection element (31) that outputs a pulse signal with a pulse height corresponding to the energy of the X-rays that have passed through the inspection area, an X-ray detection unit (33) consisting of a plurality of pixels (32) for detecting the number of pulse signals that exceed a predetermined threshold voltage among the pulse signals output from the X-ray detection element, and a control parameter for changing the number of pulse signals that exceed the threshold voltage The external device includes a control parameter control unit (55) that controls the change of the meter value, and the external device is configured to include a storage unit (56) that stores for each pixel the correspondence between the value of the control parameter controlled by the control parameter control unit, which is input via the input / output unit, and the number of pulse signals detected by the pixel, and an abnormal pixel information output unit (57) that generates abnormal pixel information for identifying abnormal pixels based on the correspondence between the value of the control parameter and the number of pulse signals detected by each pixel, which is read from the storage unit, and outputs the abnormal pixel information to the display unit via the input / output unit.

[0013] As a result, when the X-ray inspection apparatus according to the present invention has a storage unit and an abnormal pixel information output unit provided in an external device, the external device only needs to be connected via the input / output unit when identifying abnormal pixels at the time of product shipment, thus simplifying the main body of the apparatus.

[0014] Furthermore, in the X-ray inspection apparatus according to the present invention, the control parameter may be the threshold voltage or the tube voltage of the X-ray source.

[0015] Furthermore, in the X-ray inspection apparatus according to the present invention, the control parameter may be any of the threshold voltage, the tube voltage of the X-ray source, or the type of beam quality variable body installed in the inspection area.

[0016] Furthermore, the X-ray inspection apparatus according to the present invention may further include a control parameter value identification unit (58) that identifies a threshold voltage for each pixel such that the control parameter is the threshold voltage, the variable beam quality has a known absorption edge, and the slope of the number of pulse signals detected by each pixel read from the storage unit changes discontinuously with respect to the control parameter; and a calibration information output unit (59) that associates the threshold voltage identified by the control parameter value identification unit with the known absorption edge and outputs it as calibration information for each pixel.

[0017] With this configuration, the X-ray inspection apparatus according to the present invention can use a beam quality variable body having a known absorption edge to associate a threshold voltage in which the slope of the number of pulse signals detected by each pixel with respect to a control parameter changes discontinuously with respect to the known absorption edge, and output this as calibration information for each pixel.

[0018] Furthermore, the X-ray inspection apparatus according to the present invention may further include a control parameter value identification unit (58) that identifies the smallest threshold voltage for each pixel, where the control parameter is the threshold voltage, and read from the storage unit, such that the number of pulse signals detected by each pixel is less than a predetermined value; and a calibration information output unit (59) that associates the threshold voltage identified by the control parameter value identification unit with the tube voltage and outputs it as calibration information for each pixel.

[0019] With this configuration, the X-ray inspection apparatus according to the present invention can associate the minimum threshold voltage at which the number of pulse signals detected by each pixel becomes less than a predetermined value and nearly zero with the tube voltage of the X-ray source, and output this as calibration information for each pixel.

[0020] Furthermore, the X-ray inspection apparatus according to the present invention may further include a control parameter value identification unit (58) in which the control parameter is the tube voltage and identifies for each pixel the maximum tube voltage at which the number of pulse signals detected by each pixel, read from the storage unit, is less than a predetermined value, and a calibration information output unit (59) that associates the tube voltage identified by the control parameter value identification unit with the threshold voltage and outputs it as calibration information for each pixel.

[0021] With this configuration, the X-ray inspection apparatus according to the present invention can correlate the tube voltage and threshold voltage of the largest X-ray source where the number of pulse signals detected by each pixel is less than a predetermined value and close to zero, and output this as calibration information for each pixel.

[0022] Furthermore, the calibration method according to the present invention comprises an X-ray source (20) that irradiates an inspection area with X-rays, and an X-ray detector (30) that detects the X-rays that have passed through the inspection area, wherein the X-ray detector includes an X-ray detection element (31) that outputs a pulse signal with a pulse height corresponding to the energy of the X-rays that have passed through the inspection area, and an X-ray detection unit (33) consisting of a plurality of pixels (32) that detect the number of pulse signals that exceed a predetermined threshold voltage from the pulse signals output from the X-ray detection element, and the calibration method for an X-ray inspection apparatus (1) comprises the steps of irradiating the inspection area with X-rays (S1-4, S2-4, S3-5) and the X-rays that have passed through the inspection area The configuration may include: an X-ray detection step (S1-5, S2-5, S3-6) for detecting X-rays; a storage step (S1-6, S2-6, S3-7) for storing in a storage unit (56) for each pixel the correspondence between the value of a control parameter that changes the number of pulse signals exceeding the threshold voltage and the number of pulse signals detected by the pixel; and an abnormal pixel information output step (S1-9, S2-9, S3-11) for outputting abnormal pixel information to identify abnormal pixels based on the correspondence between the value of the control parameter and the number of pulse signals detected by each pixel, which is read from the storage unit.

[0023] Further, the calibration method according to the present invention includes an X-ray source (20) that irradiates an inspection area with X-rays, and an X-ray detector (30) that detects the X-rays that have passed through the inspection area. The X-ray detector includes an X-ray detection element (31) that outputs a pulse signal having a pulse height value corresponding to the energy of the X-rays that have passed through the inspection area, and a plurality of pixels (32) that detect the number of the pulse signals exceeding a predetermined threshold voltage among the pulse signals output from the X-ray detection element. In the calibration method of the X-ray inspection apparatus (1) including the X-ray detection unit (33), a step (S1-1) of installing a variable quality body (100) having a known absorption edge in the inspection area, a step (S1-4) of irradiating the inspection area with X-rays, an X-ray detection step (S1-5) of detecting the X-rays that have passed through the inspection area, a storage step (S1-6) of storing, for each pixel, the correspondence between the value of a control parameter that changes the number of the pulse signals exceeding the threshold voltage and the number of the pulse signals detected by the pixel in a storage unit (56), a control parameter value specifying step (S1-10) of specifying, for each pixel, the threshold voltage at which the slope of the number of the pulse signals detected by each pixel read from the storage unit with respect to the control parameter changes discontinuously, and a calibration information output step (S1-11) of associating the threshold voltage specified by the control parameter value specifying step with the known absorption edge and outputting the same as calibration information for each pixel may be included.

Advantages of the Invention

[0024] The present invention provides an X-ray inspection apparatus that can output abnormal pixel information for specifying abnormal pixels among a plurality of pixels constituting an X-ray detector, and a calibration method thereof.

Brief Description of the Drawings

[0025] [Figure 1] It is a schematic configuration diagram of an X-ray inspection apparatus according to an embodiment of the present invention. [Figure 2] It is an explanatory diagram showing the detection principle of the X-ray inspection apparatus of FIG. 1. [Figure 3](a) is a perspective view of the main part of the X-ray detector of the X-ray inspection apparatus shown in Figure 1, and (b) is a side view of the main part of the X-ray detector. [Figure 4] (a) is a graph that schematically shows the energy distribution of X-rays output from the X-ray source of the X-ray inspection apparatus in Figure 1, (b) is a graph that schematically shows the pulse signals and threshold voltages input to each pulse detection circuit of the X-ray detector, and (c) is a graph that schematically shows the X-ray detection amount obtained by sweeping the threshold voltage. [Figure 5] (a) is a graph that roughly shows the X-ray transmittance of PET resin, and (b) is a graph that roughly shows the X-ray transmittance of barium. [Figure 6] This graph schematically shows the energy distribution of X-rays emitted from an X-ray source (dashed line) and the energy distribution of X-rays emitted from the X-ray source and transmitted through a barium-containing resin plate (solid line). [Figure 7] (a) is a graph that roughly shows the amount of X-rays detected when no barium-containing resin plate is installed in the inspection area, and (b) is a graph that roughly shows the amount of X-rays detected when a barium-containing resin plate is installed in the inspection area. [Figure 8] This is a schematic diagram showing another example of the configuration of an X-ray inspection apparatus according to an embodiment of the present invention. [Figure 9] This is a flowchart (part 1) showing the calibration process using the X-ray inspection device shown in Figure 1. [Figure 10] The graph in Figure 9 schematically shows the correspondence between the threshold voltage obtained by the processing and the amount of X-rays detected. (a) shows the amount of X-rays detected when a barium-containing resin plate is installed in the inspection area, and (b) shows the amount of X-rays detected when a barium-containing resin plate is not installed in the inspection area. [Figure 11] This is a flowchart (part 2) showing the calibration method using the X-ray inspection device shown in Figure 1. [Figure 12] This graph schematically shows the correspondence between the tube voltage and the X-ray detection amount obtained by the processing shown in Figure 11. [Figure 13] This is a flowchart (part 3) showing the calibration process using the X-ray inspection device shown in Figure 1. [Figure 14] This graph schematically shows the correspondence between the type of beam quality variable obtained by the processing shown in Figure 13 and the amount of X-ray detected. [Figure 15] Figure 1 shows an example of a table displayed on the display unit of the X-ray inspection device. [Figure 16] An example of a graph displayed on the display unit is shown. [Figure 17] This figure illustrates the clustering method used by the abnormal pixel identification unit of the X-ray inspection device shown in Figure 1. [Figure 18] Figure 1 is a graph illustrating how the control parameter value identification unit of the X-ray inspection apparatus identifies the threshold voltage corresponding to the absorption edge of the beam quality variable body. [Modes for carrying out the invention]

[0026] Hereinafter, embodiments of the X-ray inspection apparatus and calibration method according to the present invention will be described with reference to the drawings.

[0027] As shown in Figure 1, the X-ray inspection apparatus 1 of this embodiment comprises a transport unit 10, an X-ray source 20, an X-ray detector 30, and a control unit 50 having a display unit 45 and an operation unit 46.

[0028] The conveying unit 10 is a belt conveyor that uses a loop-shaped conveying belt 11 wound around multiple conveying rollers 12 and 13 to sequentially convey the object to be inspected W, which is placed on the conveying surface 11a of the conveying belt 11, in the conveying direction Y, allowing it to pass through a predetermined inspection area. It is supported by a housing (not shown).

[0029] The conveyor belt 11 is made of a material that easily transmits X-rays (elements other than those with large atomic weights). When inspecting the object W to be inspected, the conveyor unit 10 controls the rotation of the drive motor to drive the conveyor belt at a conveying speed set in advance by the operation unit 46. As a result, the object W to be inspected, which is brought in from the entrance, is conveyed towards the exit side in the conveying direction Y shown in Figure 1 at the set conveying speed.

[0030] The transport unit 10 is not limited to a belt conveyor that transports the object to be inspected W horizontally at a constant speed. It can be any configuration that transports the object to be inspected W so that X-rays from the X-ray source 20 irradiate the object to be inspected W evenly, and the X-rays that pass through the object to be inspected W are detected by the X-ray detector 30. For example, it could be a configuration that uses the weight of the object to be inspected W to slide it down an incline, or a configuration that drops the object to be inspected W from above.

[0031] As shown in Figure 2, the X-ray source 20 irradiates the inspection area through which the object to be inspected W passes as it is transported along the transport path in the transport direction Y from the entrance to the exit. In the calibration mode described later, a beam quality variable body 100 is placed in the inspection area instead of the object to be inspected W.

[0032] The X-ray source 20 has a configuration in which a cylindrical X-ray tube 22 is immersed in insulating oil (not shown). Specifically, an electron beam from a filament 23 provided at the cathode of the X-ray tube 22 is irradiated onto a target 24 at the anode 25 to generate X-rays. The X-ray tube 22 is positioned so that its longitudinal direction is the transport direction Y of the object W to be inspected. The X-rays generated by the X-ray tube 22 are directed towards the X-ray detector 30 below the transport unit 10, and are irradiated in a roughly triangular screen shape through a slit (not shown) so as to cross the transport direction Y.

[0033] Next, the X-ray detector 30 of this embodiment, which detects X-rays that have passed through the inspection area, will be described.

[0034] Figure 3(a) is a perspective view of the main part of the X-ray detector 30 according to this embodiment, and Figure 3(b) is a side view of the main part. The X-ray detector 30 is composed of a photon detection type sensor, such as a CdTe semiconductor detector, and includes an X-ray detection element 31 and a pulse detection circuit array 33, as shown in Figures 3(a) and (b). The X-ray detection element 31 can be any material that outputs a pulse signal with a pulse height proportional to the energy of the incident X-rays that have passed through the inspection area, and is made of a semiconductor material such as cadmium telluride (CdTe).

[0035] The pulse detection circuit array 33 consists of multiple pulse detection circuits 321, 322, ..., 322 that detect the number of pulse signals exceeding a predetermined threshold voltage among the pulse signals output from the X-ray detection element 31. N For example, they are arranged in a straight line.

[0036] Here, N is the total number of pulse detection circuits 32. Each pulse detection circuit 32 constitutes one pixel. Specifically, the X-ray detector 30 is positioned below the transport surface 11a on which the object to be inspected W is transported, along the X direction perpendicular to the transport direction Y of the object to be inspected W (see Figure 2). The pulse detection circuit array 33 in this embodiment corresponds to the X-ray detection unit of the present invention.

[0037] Each pulse detection circuit 32 can be set to various threshold voltages by the control unit 50. The pulse height of the pulse signal input to the pulse detection circuit array 33 is proportional to the energy of the incident X-rays.

[0038] The physical quantities that represent the strength of X-rays are X-ray energy (wavelength) and intensity (number of photons). The energy of X-rays is expressed in units of [eV]. The energy of X-rays is determined by the tube voltage of the X-ray tube 22 and the material of the target 24 at the time of X-ray generation, and is generated with a continuous distribution. The intensity of X-rays is expressed in units of [cps] (number of photons per second). The intensity of X-rays changes with changes in the tube current of the X-ray tube 22, but the energy of the X-rays does not change.

[0039] In other words, the number of pulse signals per second that exceed the threshold voltage indicates the intensity of X-rays that exceeds the energy corresponding to the threshold voltage. Hereafter, the number of pulse signals per second that exceed the threshold voltage detected by each pulse detection circuit 32 will also be referred to as the "X-ray detection amount".

[0040] As the X-ray detector 30, a standard line sensor, a TDI (Time Delay Integration) type line sensor, or an area sensor can be used, as shown in Figures 3(a) and (b). If the X-ray detector 30 is a line sensor, the X-rays that have passed through the object W to be inspected within the inspection area can be detected by moving the object W to be inspected with the transport unit 10. If the X-ray detector 30 is an area sensor, the X-rays that have passed through the object W to be inspected within the inspection area can be detected by keeping the object W to be inspected stationary in the inspection area.

[0041] Figure 4(a) is a schematic graph showing the energy distribution of X-rays output from the X-ray source 20 when the tube voltage of the X-ray tube 22 is 60kV. Here, when the tube voltage of the X-ray tube 22 is x[kV], the maximum energy of the X-rays output from the X-ray source 20 is x[keV].

[0042] As shown in Figure 4(b), each pulse detection circuit 32 of the X-ray detector 30 receives pulse signals with various pulse height values ​​corresponding to the various energies of the X-rays output from the X-ray source 20 from the X-ray detection element 31.

[0043] Figure 4(c) is a schematic graph showing the X-ray detection amount obtained by sweeping the threshold voltage. Here, the threshold voltage is shown converted to X-ray energy [keV]. That is, the X-ray detection amount of each pulse detection circuit array 33 is proportional to the area under the energy corresponding to the threshold voltage in the X-ray energy distribution graph shown in Figure 4(a).

[0044] The variable beam quality body 100 is a resin plate that is placed in the inspection area in calibration mode instead of the object W under inspection mode. Here, calibration mode is an operation mode in which abnormal pixel information for identifying abnormal pixels and calibration information for performing energy calibration of pixels are acquired. Inspection mode is an operation mode in which a normal inspection is performed on the object W under inspection.

[0045] As the quality-changing body 100 that alters the energy (quality) of the X-rays output from the X-ray source 20, for example, a PET (polyethylene terephthalate) resin plate, a PVC (polyvinyl chloride) resin plate, or a barium-containing resin plate (for example, a barium sulfate-containing resin plate) can be used.

[0046] Figures 5(a) and (b) are schematic graphs showing the X-ray transmittance of PET resin and barium. As shown in Figure 5(a), higher energy X-rays penetrate PET resin more effectively. On the other hand, as shown in Figure 5(b), the overall trend is that higher energy X-rays penetrate barium more effectively, but the transmittance drops discontinuously at 37.4 keV. This is because barium has an absorption edge at 37.4 keV.

[0047] Barium-containing resin plates can be obtained by kneading barium sulfate into, for example, PET resin. The barium-containing resin plates obtained in this way exhibit X-ray transmission characteristics intermediate between those of PET resin and barium, and inherit the change in X-ray transmittance near the absorption edge of barium.

[0048] Elements that have an absorption edge around 30 keV include not only barium but also iodine and silver. Resin plates containing these elements can also be used as the variable beam quality 100 in this embodiment.

[0049] Figure 6 schematically shows the energy distribution of X-rays emitted from the X-ray source 20 (dashed line) and the energy distribution of X-rays emitted from the X-ray source 20 and transmitted through the barium-containing resin plate (solid line). As shown, the energy distribution of X-rays reaching the X-ray detector 30 is clearly different depending on whether or not the barium-containing resin plate is present.

[0050] Figure 7(a) is a graph that schematically shows the X-ray detection amount obtained by sweeping the threshold voltage set in each pulse detection circuit 32 when no barium-containing resin plate is installed in the inspection area between the X-ray source 20 and the X-ray detector 30. On the other hand, Figure 7(b) is a graph that schematically shows the X-ray detection amount obtained by sweeping the threshold voltage set in each pulse detection circuit 32 when a barium-containing resin plate, as a variable beam quality 100, is installed in the inspection area between the X-ray source 20 and the X-ray detector 30. In the graph of the X-ray detection amount in Figure 7(b), it can be seen that a discontinuous change appears in the slope of the X-ray detection amount with respect to the threshold voltage, which is one of the control parameters described later, reflecting the absorption edge of barium. The slope of the X-ray detection amount with respect to the control parameter refers to the ratio of the change in the X-ray detection amount to the small change in the control parameter, that is, the value obtained by first differentiating the X-ray detection amount with respect to the control parameter.

[0051] The control unit 50 controls the transport speed and transport interval of the object to be inspected W by the transport belt 11 in the transport unit 10. The control unit 50 also controls the X-ray irradiation intensity and irradiation period from the X-ray source 20, and controls the X-ray detection period and detection period of the object to be inspected W in the X-ray detector 30 according to the transport speed of the object to be inspected W.

[0052] The control unit 50 also includes a mode selection unit 51, an image data generation unit 52, a correction unit 53, a determination unit 54, a control parameter control unit 55, a storage unit 56, an abnormal pixel information output unit 57, a control parameter value identification unit 58, and a calibration information output unit 59.

[0053] The mode selection unit 51 switches the operating mode of the X-ray inspection device 1 between inspection mode and calibration mode. For example, the mode selection unit 51 selects the operating mode of the X-ray inspection device 1 in response to an operation input from the operator to the control unit 46.

[0054] The image data generation unit 52, correction unit 53, and determination unit 54 are mainly configurations related to the inspection mode. The control parameter control unit 55, storage unit 56, abnormal pixel information output unit 57, control parameter value identification unit 58, and calibration information output unit 59 are mainly configurations related to the calibration mode.

[0055] The image data generation unit 52 acquires the X-ray detection amount output from the X-ray detector 30 and threshold voltage information set by the control unit 50 at predetermined intervals, and generates image data of the object W for inspection for each different wavelength region, consisting of two-dimensional position information determined by the direction of passage of the object W and the direction of pixel arrangement, and the signal processing results for each position.

[0056] The correction unit 53 corrects the deviation of the image density characteristics from the ideal characteristics caused by the difference in distance from the X-ray source 20 to each pixel of the X-ray detector 30 for the image data generated by the image data generation unit 52, using a known method, for example, disclosed in Japanese Patent Publication No. 6717784.

[0057] The determination unit 54 performs a quality inspection to determine the presence or absence of foreign matter in the object W being inspected, based on the image data corrected by the correction unit 53 and a pre-set pass / fail judgment criterion, and determines whether the object W is good or bad. For example, the determination unit 54 performs image processing such as filtering on the image data corrected by the correction unit 53 to enhance foreign matter information and extract it as a foreign matter extraction image, thereby detecting the presence or absence of foreign matter mixed in the object W being inspected. As filters to enhance foreign matter information, for example, differential filters (Roberts filter, Prewitt filter, Sobel filter) and feature extraction filters such as Laplacian filters are used. The judgment result from the determination unit 54 is displayed on the display unit 45.

[0058] The control parameter control unit 55 is configured to control the value of a control parameter that changes the number of pulse signals exceeding the threshold voltage. For example, the control parameter is one of the following: the threshold voltage, the tube voltage of the X-ray tube 22, or the type of beam quality variable 100.

[0059] The memory unit 56 stores, for each pixel, the correspondence between the value of the control parameter controlled by the control parameter control unit 55 and the number of pulse signals (X-ray detection amount) detected by the pulse detection circuit array 33.

[0060] The abnormal pixel information output unit 57 generates abnormal pixel information to identify pixels that have output an abnormal X-ray detection amount (hereinafter also simply referred to as "abnormal pixels") based on the correspondence between the control parameter values ​​read from the storage unit 56 and the X-ray detection amount of each pixel, and outputs the generated abnormal pixel information to the storage unit 56 and the display unit 45.

[0061] The control parameter value identification unit 58 identifies, for each pixel, the threshold voltage at which the slope of the X-ray detection amount of each pixel read from the storage unit 56 with respect to the control parameter changes discontinuously. Alternatively, the control parameter value identification unit 58 identifies, for each pixel, the minimum threshold voltage at which the X-ray detection amount of each pixel read from the storage unit 56 becomes less than a predetermined threshold ε and approximately zero. Alternatively, the control parameter value identification unit 58 identifies, for each pixel, the maximum tube voltage at which the X-ray detection amount of each pixel read from the storage unit 56 becomes less than a predetermined threshold ε and approximately zero. Here, "approximately zero" is used because it is assumed that the X-ray detection amount may not be exactly zero due to the influence of noise in the X-ray detector 30, etc. For example, a certain threshold ε can be set and it can be said that "X-ray detection amount < ε".

[0062] The calibration information output unit 59 associates the threshold voltage identified by the control parameter value identification unit 58 with the known absorption edge of the wire quality variable body 100 and outputs it as calibration information for each pixel. Alternatively, the calibration information output unit 59 associates the threshold voltage identified by the control parameter value identification unit 58 with the tube voltage and outputs it as calibration information for each pixel. Alternatively, the calibration information output unit 59 associates the tube voltage identified by the control parameter value identification unit 58 with the threshold voltage and outputs it as calibration information for each pixel. For example, the calibration information output unit 59 outputs the calibration information to the storage unit 56 or the display unit 45.

[0063] Furthermore, the X-ray inspection apparatus 1 of this embodiment may include an input / output unit 60 that can be connected to an external device 2, as shown in Figure 8. The external device 2 includes the storage unit 56 and the abnormal pixel information output unit 57.

[0064] In other words, in the configuration shown in Figure 8, the storage unit 56 stores, for each pixel, the correspondence between the value of the control parameter controlled by the control parameter control unit 55, which is input via the input / output unit 60, and the X-ray detection amount of each pixel. The storage unit 56 also outputs the X-ray detection amount of each pixel to the control parameter value identification unit 58 via the input / output unit 60.

[0065] Furthermore, in the configuration shown in Figure 8, the abnormal pixel information output unit 57 generates abnormal pixel information for identifying abnormal pixels based on the correspondence between the control parameter values ​​read from the storage unit 56 and the X-ray detection amount of each pixel, and outputs the generated abnormal pixel information to the display unit 45 via the input / output unit 60.

[0066] <Method 1> Below, we will explain Method 1 for acquiring the X-ray detection amount in a configuration where the variable control parameter is the threshold voltage, referring to the flowchart in Figure 9.

[0067] First, the operator places the variable beam quality body 100, which has a known absorption edge such as a barium-containing resin plate, into the inspection area (step S1-1). Alternatively, instead of the operator placing the variable beam quality body 100 into the inspection area, a dedicated exchange mechanism (not shown) may be implemented in the X-ray inspection device 1. Furthermore, the variable beam quality body 100 may be transported to the inspection area by the transport unit 10. Alternatively, the variable beam quality body 100 may not be placed in the inspection area at all.

[0068] Next, the control parameter control unit 55 sets initial values ​​for various control parameters in response to the operator's input to the operation unit 46 (step S1-2). For example, in step S1-2, the tube voltage of the X-ray tube 22 is set to a predetermined value, and the threshold voltage of the X-ray detector 30 is set to E1.

[0069] Next, when the operator gives an input to the control unit 46 to instruct the start of measurement (Step S1-3: YES), the X-ray source 20 irradiates the inspection area with X-rays (Step S1-4).

[0070] Next, the X-ray detector 30 outputs the X-ray detection amount of the X-rays that have passed through the inspection area (X-ray detection step S1-5).

[0071] Next, the memory unit 56 stores the correspondence between the X-ray detection amount output from the X-ray detector 30 and the threshold voltage currently set as a variable control parameter for each pixel (storage step S1-6).

[0072] Next, if the operator has not given an input to the control unit 46 to indicate the end of the measurement (step S1-7: NO), the processes from step S1-8 onward are executed.

[0073] On the other hand, when the operator gives an input to the control unit 46 to indicate the end of the measurement (step S1-7: YES), the processes from step S1-9 onwards are executed.

[0074] In step S1-8, the control parameter control unit 55 sets the threshold voltage, which is a variable control parameter, to a new value (step S1-8). Then, the processing from step S1-4 onwards is executed again.

[0075] In step S1-9, the abnormal pixel information output unit 57 outputs abnormal pixel information to identify the abnormal pixel that output an abnormal X-ray detection amount, based on the correspondence between the control parameter value read from the storage unit 56 and the X-ray detection amount of each pixel (abnormal pixel information output step S1-9).

[0076] The processing in steps S1-10 and S1-11 will be described later.

[0077] The process shown in the flowchart of Figure 9 allows for the determination of the relationship between the threshold voltage and the detected X-ray amount for each pixel, as shown in Figures 10(a) and (b). Figure 10(a) shows the measurement results of the detected X-ray amount when the variable beam quality 100 is installed in the inspection area. On the other hand, Figure 10(b) shows the measurement results of the detected X-ray amount when the variable beam quality 100 is not installed in the inspection area. Here, the detected X-ray amount obtained when the threshold voltage is E1 is assumed to be M1, and the detected X-ray amount obtained when the threshold voltage is E2 is assumed to be M2. In the above process, the number of threshold voltages set for the X-ray detector 30 should be 1 or more, and a larger number is preferable.

[0078] <Method 2> Below, we will explain Method 2 for acquiring the X-ray detection amount in a configuration where the variable control parameter is the tube voltage, referring to the flowchart in Figure 11.

[0079] First, the operator places the variable beam quality body 100, which has a known absorption edge such as a barium-containing resin plate, into the inspection area (step S2-1). Alternatively, instead of the operator placing the variable beam quality body 100 into the inspection area, a dedicated exchange mechanism (not shown) may be implemented in the X-ray inspection device 1. Furthermore, the variable beam quality body 100 may be transported to the inspection area by the transport unit 10. Alternatively, the variable beam quality body 100 does not need to be placed in the inspection area.

[0080] Next, the control parameter control unit 55 sets initial values ​​for various control parameters in response to the operator's input to the operation unit 46 (step S2-2). For example, in step S2-2, the threshold voltage for each pixel is set to a predetermined value, and the tube voltage of the X-ray tube 22 is set to V1.

[0081] Next, when the operator gives an input to the control unit 46 to instruct the start of measurement (Step S2-3: YES), the X-ray source 20 irradiates the inspection area with X-rays (Step S2-4).

[0082] Next, the X-ray detector 30 outputs the X-ray detection amount of the X-rays that have passed through the inspection area (X-ray detection step S2-5).

[0083] Next, the memory unit 56 stores the correspondence between the X-ray detection amount output from the X-ray detector 30 and the tube voltage currently set as a variable control parameter for each pixel (storage step S2-6).

[0084] Next, if the operator has not given an input to the control unit 46 to indicate the end of the measurement (step S2-7: NO), the processes from step S2-8 onward are executed.

[0085] On the other hand, when the operator gives an input to the control unit 46 to indicate the end of the measurement (step S2-7: YES), the processes from step S2-9 onwards are executed.

[0086] In step S2-8, the control parameter control unit 55 sets the tube voltage, which is a variable control parameter, to a new value (step S2-8). Then, the processes after step S2-4 are executed again.

[0087] In step S2-9, the abnormal pixel information output unit 57 outputs abnormal pixel information for specifying abnormal pixels that output abnormal X-ray detection amounts based on the correspondence between the values of the control parameters read from the storage unit 56 and the X-ray detection amounts of each pixel (abnormal pixel information output step S2-9).

[0088] The processes of steps S2-10 and S2-11 will be described later.

[0089] By the process shown in the flowchart of FIG. 11, the correspondence between the tube voltage and the X-ray detection amount as shown in FIG. 12 is obtained for each pixel. Here, it is assumed that the X-ray detection amount obtained when the tube voltage is V1 is M1, and the X-ray detection amount obtained when the tube voltage is V2 is M2. Note that when the tube voltage is x [kV], the maximum energy generated from the X-ray tube 22 is x [keV]. Therefore, when the threshold voltage is equivalent to y [keV] and x <y is satisfied, the X-ray detection amount becomes smaller than a predetermined threshold value ε and is almost 0. Here, the term "almost 0" is assumed because the X-ray detection amount may not become exactly 0 due to the influence of noise in the X-ray detector 30 or the like. For example, a certain threshold value ε is determined, and it can be said that "X-ray detection amount <ε". The number of tube voltages set for the X-ray tube 22 in the above process is 1 or more, and the more the better.

[0090] <Method 3> Hereinafter, Method 3 for obtaining the X-ray detection amount in a configuration where the variable control parameter is the type of the quality variable body 100 will be described while referring to the flowchart of FIG. 13.

[0091] [[ID=2l]] First, the control parameter control unit 55 displays, on the display unit 45, a message prompting the operator to install the quality variable body 100 (resin plate s1) in the inspection area (step S3-1).

[0092] Next, the operator places the resin plate s1 in the inspection area (step S3-2). Alternatively, the control parameter control unit 55 may control a dedicated exchange mechanism (not shown) mounted on the X-ray inspection device 1 to place the resin plate s1 in the inspection area. Alternatively, the control parameter control unit 55 may control the transport unit 10 to transport and place the resin plate s1 in the inspection area.

[0093] Next, the control parameter control unit 55 sets initial values ​​for various control parameters in response to the operator's input to the operation unit 46 (step S3-3). In step S3-3, the threshold voltage of each pixel and the tube voltage of the X-ray tube 22 are set to predetermined values.

[0094] Next, when the operator gives an input to the control unit 46 to instruct the start of measurement (step S3-4: YES), the X-ray source 20 irradiates the inspection area with X-rays (step S3-5).

[0095] Next, the X-ray detector 30 outputs the X-ray detection amount of the X-rays that have passed through the inspection area (X-ray detection step S3-6).

[0096] Next, the memory unit 56 stores, pixel by pixel, the correspondence between the X-ray detection amount output from the X-ray detector 30 and the type of beam quality variable body 100 currently set as a variable control parameter (storage step S3-7).

[0097] Next, if the operator has not given an input to the control unit 46 to indicate the end of the measurement (step S3-8: NO), the processes from step S3-9 onward are executed.

[0098] On the other hand, when the operator gives an input to the control unit 46 to indicate the end of the measurement (step S3-8: YES), the process in step S3-11 is executed.

[0099] In step S3-9, the control parameter control unit 55 displays a message on the display unit 45 prompting the operator to change the type of the variable control parameter, which is the wire quality variable body 100, that is, to install a new resin plate in the inspection area (step S3-9).

[0100] Next, the operator removes the resin plate currently installed in the inspection area and installs a new resin plate in the inspection area (step S3-10). Alternatively, the control parameter control unit 55 may control a dedicated replacement mechanism (not shown) implemented in the X-ray inspection device 1 to remove the resin plate currently installed in the inspection area and install a new resin plate in the inspection area. Alternatively, the control parameter control unit 55 may control the transport unit 10 to transport the resin plate currently installed in the inspection area out of the inspection area and transport and install the new resin plate in the inspection area. Then, the process from step S3-5 onwards is executed again.

[0101] In step S3-11, the abnormal pixel information output unit 57 outputs abnormal pixel information to identify the abnormal pixel that output an abnormal X-ray detection amount, based on the correspondence between the control parameter value read from the storage unit 56 and the X-ray detection amount of each pixel (abnormal pixel information output step S3-11).

[0102] The process shown in the flowchart of Figure 13 allows for the acquisition of a correspondence between the type of beam quality variable 100 and the X-ray detection amount for each pixel, as shown in Figure 14. Here, the X-ray detection amounts obtained when the type of beam quality variable 100 is resin plate s1, s2, s3, and s4 are assumed to be M1, M2, M3, and M4, respectively. As an example, resin plate s1 is a barium-containing resin plate, resin plate s2 is a relatively thick PET resin plate, resin plate s3 is a relatively thin PET resin plate, and resin plate s4 is a PVC resin plate. In the above process, the number of types of beam quality variable 100 installed in the inspection area should be one or more, and a larger number is preferable.

[0103] The following describes an example of how the abnormal pixel information output unit 57 identifies abnormal pixels.

[0104] The abnormal pixel information output unit 57 displays, for example, a table or graph showing the measurement results of the X-ray detection amount obtained by the X-ray detector 30 as abnormal pixel information on the display unit 45, enabling the operator to identify abnormal pixels by visual inspection.

[0105] Figure 15 shows an example of a table displayed on the display unit 45 by the abnormal pixel information output unit 57. The measurement results shown in the left column of the table in Figure 15 show the correspondence between the state corresponding to a certain variable control parameter value (for example, a threshold voltage of 1 or more) and the measured X-ray detection amount for each pixel.

[0106] Figure 16 shows an example of a graph displayed on the display unit 45 by the abnormal pixel information output unit 57. Figure 16 shows the measurement results of the X-ray detection amount of multiple pixels when the variable control parameter is the threshold voltage. From this graph, it can be visually confirmed that the measurement result of the X-ray detection amount of pixel 3 is abnormal.

[0107] Alternatively, the abnormal pixel information output unit 57 may include an abnormal pixel identification unit 57a that automatically identifies abnormal pixels, and output the number and location of the abnormal pixel identified by the abnormal pixel identification unit 57a as abnormal pixel information. For example, the abnormal pixel identification unit 57a automatically identifies abnormal pixels based on an automatic determination criterion for each state corresponding to a certain variable control parameter value.

[0108] For example, the automatic judgment criterion is a representative value obtained from the X-ray detection amount of all pixels in each state. As shown in the judgment results in the right column of the table in Figure 15, the representative value of all pixels can be, for example, the average value of the X-ray detection amount obtained in each state.

[0109] In this case, the abnormal pixel identification unit 57a identifies, for example, a pixel that outputs an X-ray detection amount with the largest difference from the average value, or a pixel that outputs an X-ray detection amount whose difference from the average value is greater than or equal to a predetermined threshold, as an abnormal pixel.

[0110] For example, in all states 1 to 6 shown in Figure 15, it can be seen that the X-ray detection amount of pixel 3 deviates the most from the average value. Therefore, the abnormal pixel identification unit 57a identifies pixel 3 as an abnormal pixel.

[0111] Furthermore, for example, in all states 1 to 6 shown in Figure 15, it can be seen that the X-ray detection amount of pixel 3 deviates by 15 or more from the average value. Therefore, if the predetermined threshold is 15, the abnormal pixel identification unit 57a identifies pixel 3 as an abnormal pixel.

[0112] Furthermore, the automatic judgment criteria may be set to any value by the operator using the control unit 46.

[0113] Alternatively, the abnormal pixel identification unit 57a may prepare a vector for each pixel that summarizes the X-ray detection amounts for all states corresponding to a certain variable control parameter value, and automatically classify abnormal pixels and normal pixels using machine learning.

[0114] The machine learning performed by the anomaly pixel identification unit 57a is based on clustering methods such as self-organizing maps, DBSCAN (Density-Based Spatial Clustering of Applications with Noise), and t-SNE (t-distributed Stochastic Neighbor Embedding). Clustering methods are techniques that classify data in a feature space based on the distance (or similarity) between data. Furthermore, the machine learning performed by the anomaly pixel identification unit 57a is not limited to these clustering methods, but may also be based on methods using classifiers such as support vector machines or random forests.

[0115] Figure 17 is a diagram illustrating the clustering method used by the abnormal pixel identification unit 57a. For example, in the example shown in Figure 15, the X-ray detection data of pixels 1, 2, and 4 belong to cluster 1, and the X-ray detection data of pixel 3 belongs to cluster 2. In this way, clusters with a large number of data points and clusters with a small number of data points are determined. For example, the abnormal pixel identification unit 57a determines that pixels corresponding to X-ray detection data belonging to a large cluster are normal pixels, and pixels corresponding to X-ray detection data belonging to a small cluster are abnormal pixels.

[0116] As described above, by outputting abnormal pixel information from the abnormal pixel information output unit 57, it is possible to prompt the operator to take action, for example, by setting the X-ray detector 30 not to use abnormal pixels.

[0117] The operation of the control parameter value identification unit 58 and the calibration information output unit 59, which acquire calibration information for performing pixel energy calibration, will be described below.

[0118] First, we will describe a configuration in which the variable control parameter is the threshold voltage and a wire quality variable body 100 having an absorption edge is used.

[0119] As shown in the graph in Figure 18, the discontinuous change in transmittance due to the absorption edge is reflected not only in the graph of the X-ray detection amount against the threshold voltage, but also in its first and second derivatives. At the absorption edge, the first derivative of the X-ray detection amount becomes discontinuous, and the value of the second derivative of the X-ray detection amount becomes a significantly large value. Therefore, by setting an appropriate threshold θ, for example, the threshold voltage at which the second derivative value > θ can be identified in correspondence with the absorption edge (e.g., 37.4 keV).

[0120] Therefore, the control parameter value identification unit 58 takes the second derivative of the X-ray detection amount with respect to the threshold voltage and uses the threshold θ described above to identify, for each pixel, the threshold voltage at which the slope of the X-ray detection amount of each pixel read from the storage unit 56 with respect to the control parameter changes discontinuously.

[0121] The following describes a calibration method for acquiring calibration information using a configuration in which the variable control parameter is the threshold voltage and a variable-quality beam element 100 having an absorption edge is used, again referring to the flowchart in Figure 9.

[0122] In step S1-10, the control parameter value identification unit 58 identifies, for each pixel, the threshold voltage at which the slope of the X-ray detection amount of each pixel read from the storage unit 56 with respect to the control parameter changes discontinuously (control parameter value identification step S1-10).

[0123] Next, the calibration information output unit 59 outputs calibration information by associating the threshold voltage identified in the control parameter value identification step S1-10 with a known absorption edge (calibration information output step S1-11).

[0124] On the other hand, for a calibration method in which the variable control parameter is the threshold voltage and calibration information is acquired in a configuration that does not use the wire quality variable body 100, the processing of the control parameter value identification step S1-10 and the calibration information output step S1-11 is as follows.

[0125] As shown in FIG. 10(b), the control parameter value specifying unit 58 specifies, for each pixel, the minimum threshold voltage at which the X-ray detection amount of each pixel read from the storage unit 56 becomes smaller than a predetermined threshold value ε and substantially zero (control parameter value specifying step S1-10). Thereby, the correspondence between the threshold voltage and the energy of the X-ray can be obtained. Here, the term "substantially zero" is assumed because the X-ray detection amount may not become exactly zero due to the influence of noise in the X-ray detector 30 or the like. For example, a certain threshold value ε is determined, and it can be said that "X-ray detection amount < ε". When the tube voltage is x [kV], the maximum energy generated from the X-ray tube 22 is x [keV]. Therefore, when the threshold voltage corresponds to y [keV] and x < y is satisfied, the X-ray detection amount becomes substantially zero.

[0126] Next, the calibration information output unit 59 associates the threshold voltage specified by the control parameter value specifying unit 58 with the tube voltage and outputs it as calibration information for each pixel (calibration information output step S1-11).

[0127] Furthermore, a calibration method for obtaining calibration information in a configuration where the variable control parameter is the tube voltage will be described again while referring to the flowchart of FIG. 11.

[0128] In step S2-10, as shown in FIG. 12, the control parameter value specifying unit 58 specifies, for each pixel, the maximum tube voltage at which the X-ray detection amount of each pixel read from the storage unit 56 becomes smaller than a predetermined threshold value ε and substantially zero (control parameter value specifying step S2-10). Thereby, the correspondence between the threshold voltage and the energy of the X-ray can be obtained. Here, the term "substantially zero" is assumed because the X-ray detection amount may not become exactly zero due to the influence of noise in the X-ray detector 30 or the like. For example, a certain threshold value ε is determined, and it can be said that "X-ray detection amount < ε".

[0129] Next, the calibration information output unit 59 associates the tube voltage specified by the control parameter value specifying unit 58 with the threshold voltage and outputs it as calibration information for each pixel (calibration information output step S2-11).

[0130] As described above, the calibration information output unit 59 outputs calibration information for performing pixel energy calibration, which prompts the operator to take actions such as adjusting the gain of abnormal pixels in the X-ray detector 30.

[0131] Furthermore, the accuracy of the correspondence between X-ray energy and threshold voltage using the tube voltage depends on the accuracy of the tube voltage. For this reason, it is considered that using a variable beam quality body 100 with an absorption edge to match X-ray energy and threshold voltage is more accurate than matching X-ray energy and threshold voltage using the tube voltage.

[0132] The control unit 50 is composed of a control device such as a computer, which includes, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an FPGA (Field Programmable Gate Array), a ROM (Read Only Memory), a RAM (Random Access Memory), and an HDD (Hard Disk Drive). For example, the control unit 50 can configure at least a part of the mode selection unit 51, image data generation unit 52, correction unit 53, determination unit 54, control parameter control unit 55, abnormal pixel information output unit 57, control parameter value identification unit 58, and calibration information output unit 59 in software by executing a predetermined program by the CPU or GPU. The above program is pre-stored in the ROM or HDD. Alternatively, the above program may be provided or distributed in an installable or executable format recorded on a computer-readable recording medium such as a compact disc or DVD. Alternatively, the above program may be stored on a computer connected to a network such as the Internet and provided or distributed by download via the network.

[0133] The display unit 45 is composed of a display device such as an LCD (Liquid Crystal Display) or a CRT (Cathode Ray Tube), and displays various information such as abnormal pixel information, various judgment results, and measurement results based on display control signals from the control unit 50. The display unit 45 may also have operating functions of the operation unit 46, such as soft keys on the display screen.

[0134] The operation unit 46 is for receiving operation input from the operator and consists of a user interface such as keys, push buttons, switches, and soft keys on the display screen of the display unit 45, which are provided on the main body of the X-ray inspection device 1.

[0135] For example, by inputting operations into the control unit 46, the operator can select the operating mode of the X-ray inspection device 1 in the mode selection unit 51, or input information necessary for a series of inspections, including information about the object to be inspected W (e.g., product name), such as the transport speed of the transport unit 10, the total number of objects to be inspected W, and the judgment threshold for determining whether the object to be inspected W is good or bad.

[0136] As described above, the X-ray inspection apparatus 1 according to this embodiment acquires the correspondence between the value of a control parameter that changes the number of pulse signals with pulse height values ​​corresponding to the energy of X-rays that have passed through the inspection area that exceed a predetermined threshold voltage, and the amount of X-rays detected by each pixel of the pulse detection circuit array 33. Furthermore, the X-ray inspection apparatus 1 according to this embodiment can output abnormal pixel information for identifying abnormal pixels based on the correspondence between the value of the control parameter and the amount of X-rays detected by each pixel.

[0137] Furthermore, in the case of the X-ray inspection apparatus 1 according to this embodiment, if the storage unit 56 and the abnormal pixel information output unit 57 are provided in an external device 2, the external device 2 only needs to be connected via the input / output unit 60 when identifying abnormal pixels at the time of product shipment, thus simplifying the main body of the apparatus.

[0138] Furthermore, the X-ray inspection apparatus 1 according to this embodiment can use a variable beam quality body 100 having a known absorption edge to associate the threshold voltage, which causes the slope of the X-ray detection amount of each pixel with respect to the control parameter to change discontinuously, with the known absorption edge, and output this as calibration information for each pixel.

[0139] Furthermore, the X-ray inspection apparatus 1 according to this embodiment can correlate the minimum threshold voltage at which the X-ray detection amount of each pixel becomes less than a predetermined threshold ε and nearly zero with the tube voltage of the X-ray tube 22, and output this as calibration information for each pixel.

[0140] Furthermore, the X-ray inspection apparatus 1 according to this embodiment can correlate the tube voltage of the X-ray tube 22 with the threshold voltage at which the X-ray detection amount of each pixel is small enough to be nearly zero (below a predetermined threshold ε) and output this as calibration information for each pixel.

[0141] In other words, the X-ray inspection apparatus 1 according to this embodiment can output calibration information for performing energy calibration of each pixel of the X-ray detector 30 without using radioactive materials that pose safety problems. [Explanation of symbols]

[0142] 1. X-ray inspection device 2 External device 20 X-ray sources 22 X-ray tube 23 Filaments 24 Targets 25 Anode 30 X-ray detectors 31 X-ray detection element 32,321,322,···,32 N Pulse detection circuit (pixel) 33. Pulse detection circuit array (X-ray detection unit) 45 Display section 46 Control section 50 Control Unit 55 Control parameter control unit 56 Memory section 57 Abnormal Pixel Information Output Unit 57a Abnormal pixel identification section 58 Control parameter value identification unit 59 Calibration Information Output Unit 60 Input / output section 100 Radiation quality variable body W: Object under inspection

Claims

1. An X-ray source (20) that irradiates the examination area with X-rays, An X-ray inspection apparatus (1) comprising an X-ray detector (30) for detecting X-rays that have passed through the inspection area, The aforementioned X-ray detector is An X-ray detection element (31) that outputs a pulse signal with a pulse height corresponding to the energy of the X-rays that have passed through the inspection area, The X-ray detection unit (33) includes a plurality of pixels (32) that detect the number of pulse signals exceeding a predetermined threshold voltage among the pulse signals output from the X-ray detection element, The threshold voltage, the tube voltage of the X-ray source, or the type of beam quality variable installed in the inspection area is used as a control parameter to change the number of pulse signals exceeding the threshold voltage. The aforementioned X-ray inspection apparatus, A storage unit (56) stores for each pixel the correspondence between the value of the control parameter and the number of pulse signals detected by the pixel, An abnormal pixel information output unit (57) outputs abnormal pixel information for identifying abnormal pixels based on the correspondence between the value of the control parameter read from the storage unit and the number of pulse signals detected by each pixel, Control parameter value identification unit (58), The system further includes a calibration information output unit (59), When the control parameter is the threshold voltage and the variable-quality beam has a known absorption edge, the control parameter value identification unit identifies the threshold voltage for each pixel at which the slope of the number of pulse signals detected by each pixel with respect to the control parameter changes discontinuously, and the calibration information output unit associates the threshold voltage identified by the control parameter value identification unit with the known absorption edge and outputs it as calibration information for each pixel. or X-ray inspection apparatus, characterized in that, when the control parameter is the tube voltage, the control parameter value identification unit identifies the maximum tube voltage for each pixel that reads from the storage unit such that the number of pulse signals detected by each pixel is less than a predetermined value, and the calibration information output unit associates the tube voltage identified by the control parameter value identification unit with the threshold voltage and outputs it as calibration information for each pixel.

2. An X-ray source (20) that irradiates an inspection area with X-rays, An X-ray inspection apparatus (1) comprising an X-ray detector (30) for detecting X-rays that have passed through the inspection area, The aforementioned X-ray detector is An X-ray detection element (31) that outputs a pulse signal with a pulse height corresponding to the energy of the X-rays that have passed through the inspection area, The X-ray detection unit (33) includes a plurality of pixels (32) that detect the number of pulse signals exceeding a predetermined threshold voltage among the pulse signals output from the X-ray detection element, The threshold voltage or the tube voltage of the X-ray source is used as a control parameter to change the number of pulse signals that exceed the threshold voltage. The aforementioned X-ray inspection apparatus, A storage unit (56) stores for each pixel the correspondence between the value of the control parameter and the number of pulse signals detected by the pixel, An abnormal pixel information output unit (57) outputs abnormal pixel information for identifying abnormal pixels based on the correspondence between the value of the control parameter read from the storage unit and the number of pulse signals detected by each pixel, Control parameter value identification unit (58), The system further includes a calibration information output unit (59), When the control parameter is the threshold voltage, the control parameter value identification unit identifies the smallest threshold voltage for each pixel that results in a number of pulse signals detected by each pixel being less than a predetermined value, read from the storage unit, and the calibration information output unit associates the threshold voltage identified by the control parameter value identification unit with the tube voltage and outputs it as calibration information for each pixel. or X-ray inspection apparatus, characterized in that, when the control parameter is the tube voltage, the control parameter value identification unit identifies the maximum tube voltage for each pixel that reads from the storage unit such that the number of pulse signals detected by each pixel is less than a predetermined value, and the calibration information output unit associates the tube voltage identified by the control parameter value identification unit with the threshold voltage and outputs it as calibration information for each pixel.

3. The X-ray inspection apparatus according to claim 1, wherein the variable beam material is a polyethylene terephthalate resin plate or a polyvinyl chloride resin plate.

4. The X-ray inspection apparatus according to claim 1, wherein the variable beam quality is a resin plate containing barium, iodine, or silver, which is an element having an absorption edge around 30 keV.

5. An X-ray inspection system comprising: an external device (2); an X-ray source (20) for irradiating an inspection area with X-rays; an X-ray detector (30) for detecting X-rays that have passed through the inspection area; a display unit (45) for displaying various information; an input / output unit (60) connectable to the external device; a control parameter value identification unit (58); and a calibration information output unit (59), The aforementioned X-ray detector is An X-ray detection element (31) that outputs a pulse signal with a pulse height corresponding to the energy of the X-rays that have passed through the inspection area, An X-ray detection unit (33) consisting of a plurality of pixels (32) that detect the number of pulse signals exceeding a predetermined threshold voltage among the pulse signals output from the X-ray detection element, The control parameter control unit (55) includes a control parameter control unit that performs control to change the value of a control parameter that changes the number of pulse signals that exceed the threshold voltage, The control parameter is one of the threshold voltage, the tube voltage of the X-ray source, or the type of beam quality variable installed in the inspection area. The external device is, A storage unit (56) stores for each pixel the correspondence between the value of the control parameter controlled by the control parameter control unit, which is input via the input / output unit, and the number of pulse signals detected by the pixel. The system includes an abnormal pixel information output unit (57) that generates abnormal pixel information for identifying abnormal pixels based on the correspondence between the value of the control parameter read from the storage unit and the number of pulse signals detected by each pixel, and outputs the abnormal pixel information to the display unit via the input / output unit. When the control parameter is the threshold voltage and the variable-quality beam has a known absorption edge, the control parameter value identification unit identifies the threshold voltage for each pixel at which the slope of the number of pulse signals detected by each pixel with respect to the control parameter changes discontinuously, and the calibration information output unit associates the threshold voltage identified by the control parameter value identification unit with the known absorption edge and outputs it as calibration information for each pixel. or An X-ray inspection system characterized in that, when the control parameter is the tube voltage, the control parameter value identification unit identifies the maximum tube voltage for each pixel that reads from the storage unit such that the number of pulse signals detected by each pixel is less than a predetermined value, and the calibration information output unit associates the tube voltage identified by the control parameter value identification unit with the threshold voltage and outputs it as calibration information for each pixel.

6. An X-ray inspection system comprising: an external device (2); an X-ray source (20) for irradiating an inspection area with X-rays; an X-ray detector (30) for detecting X-rays that have passed through the inspection area; a display unit (45) for displaying various information; an input / output unit (60) connectable to the external device; a control parameter value identification unit (58); and a calibration information output unit (59), The aforementioned X-ray detector is An X-ray detection element (31) that outputs a pulse signal with a pulse height corresponding to the energy of the X-rays that have passed through the inspection area, An X-ray detection unit (33) consisting of a plurality of pixels (32) that detect the number of pulse signals exceeding a predetermined threshold voltage among the pulse signals output from the X-ray detection element, The control parameter control unit (55) includes a control parameter control unit that performs control to change the value of a control parameter that changes the number of pulse signals that exceed the threshold voltage, The control parameter is the threshold voltage or the tube voltage of the X-ray source. The external device is, A storage unit (56) stores for each pixel the correspondence between the value of the control parameter controlled by the control parameter control unit, which is input via the input / output unit, and the number of pulse signals detected by the pixel. The system includes an abnormal pixel information output unit (57) that generates abnormal pixel information for identifying abnormal pixels based on the correspondence between the value of the control parameter read from the storage unit and the number of pulse signals detected by each pixel, and outputs the abnormal pixel information to the display unit via the input / output unit. When the control parameter is the threshold voltage, the control parameter value identification unit identifies the smallest threshold voltage for each pixel that results in a number of pulse signals detected by each pixel being less than a predetermined value, read from the storage unit, and the calibration information output unit associates the threshold voltage identified by the control parameter value identification unit with the tube voltage and outputs it as calibration information for each pixel. or An X-ray inspection system characterized in that, when the control parameter is the tube voltage, the control parameter value identification unit identifies the maximum tube voltage for each pixel that reads from the storage unit such that the number of pulse signals detected by each pixel is less than a predetermined value, and the calibration information output unit associates the tube voltage identified by the control parameter value identification unit with the threshold voltage and outputs it as calibration information for each pixel.

7. An X-ray source (20) that irradiates an inspection area with X-rays, The system includes an X-ray detector (30) for detecting X-rays that have passed through the inspection area, The aforementioned X-ray detector is An X-ray detection element (31) that outputs a pulse signal with a pulse height corresponding to the energy of the X-rays that have passed through the inspection area, A calibration method for an X-ray inspection apparatus (1) including an X-ray detection unit (33) consisting of a plurality of pixels (32) that detect the number of pulse signals exceeding a predetermined threshold voltage among the pulse signals output from the X-ray detection element, Step (S1-1) involves installing a beam quality variable having a known absorption edge in the inspection area, The steps include setting the initial value of the threshold voltage (S1-2), The steps include irradiating the aforementioned inspection area with X-rays (S1-4), X-ray detection step (S1-5) for detecting X-rays that have passed through the inspection area, A storage step (S1-6) is performed to store in the storage unit (56) for each pixel the correspondence between the threshold voltage value and the number of pulse signals detected by the pixel, The steps include setting the threshold voltage to a new value (S1-8), An abnormal pixel information output step (S1-9) outputs abnormal pixel information for identifying abnormal pixels based on the correspondence between the threshold voltage value read from the storage unit and the number of pulse signals detected by each of the pixels, A control parameter value identification step (S1-10) is performed to identify, for each pixel, the threshold voltage at which the slope of the number of pulse signals detected by each pixel, read from the storage unit, changes discontinuously. A calibration method characterized by including a calibration information output step (S1-11) which associates the identified threshold voltage with the known absorption edge and outputs it as calibration information for each of the pixels.

8. The calibration method according to claim 7, wherein the wire quality variable is a polyethylene terephthalate resin plate or a polyvinyl chloride resin plate.

9. The calibration method according to claim 7, wherein the variable beam quality is a resin plate containing barium, iodine, or silver, which is an element having an absorption edge around 30 keV.

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