X-ray inspection device and calibration method therefor

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 an object to be inspected with X-rays and inspects the object based on the amount of transmitted X-rays, and a calibration method thereof. [Background technology]

[0002] An X-ray inspection device is a device that irradiates X-rays onto inspection items such as meat, fish, processed foods, and medicines that are transported sequentially at specified intervals on a transport path, and inspects the items for foreign matter or missing parts based on the amount of transmitted X-rays.

[0003] The X-ray inspection device is incorporated into an inspection line that performs inspections for foreign matter contamination and final weight inspections, for example, and performs inspections for foreign matter contamination, etc.

[0004] In an X-ray inspection system, X-rays with a width in a direction perpendicular to the transport direction are irradiated onto the transport path of the object being inspected. The X-rays that pass through the object are received by multiple sensor elements (pixels) arranged in a direction perpendicular to the transport direction of the object being inspected. Image information is obtained that shows the difference in the transmittance of the X-rays for each part of the object being inspected as shades of gray. Various processing steps are then performed on this image information to determine whether or not there is any foreign matter present, or whether any contents are missing or missing.

[0005] However, in this type of X-ray inspection device, the X-rays are emitted in a spreading manner in a direction perpendicular to the transport direction, and as a result, the intensity of the X-rays incident on each pixel is not uniform due to differences in the distance from the X-ray source to each pixel.

[0006] Patent document 1 describes an X-ray inspection device that uses a calibration member to change the X-ray incidence conditions common to all pixels to two or more types, and determines the calibration data necessary to make the image data of uniform density for each incidence condition changed by the calibration member. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6717784 Summary of the Invention [Problem to be solved by the invention]

[0008] However, with conventional X-ray inspection devices, there was a problem in that if any of the multiple pixels has a sensitivity that deviates significantly from the average sensitivity, the density of the image data could not be sufficiently calibrated.

[0009] The present invention has been made to solve such conventional problems, and has an object to provide an X-ray inspection device and a calibration method thereof that are capable of outputting abnormal pixel information for identifying abnormal pixels among multiple pixels that make up an X-ray detector. [Means for solving the problem]

[0010] In order to solve the above problem, an X-ray inspection apparatus according to the present invention is an X-ray inspection apparatus (1) comprising an X-ray generation source (20) that irradiates an inspection area with X-rays, and an X-ray detector (30) that detects 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 having a peak value 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 detects the number of the pulse signals that exceed a predetermined threshold voltage among the pulse signals output from the X-ray detection element, and the X-ray inspection apparatus further comprises a memory unit (56) that stores, for each pixel, a correspondence relationship between a value of a control parameter that changes the number of the pulse signals that exceed the threshold voltage and the number of the pulse signals detected by the pixel, and an abnormal pixel information output unit (57) that outputs abnormal pixel information for identifying an abnormal pixel based on the correspondence relationship read from the memory unit between the value of the control parameter and the number of the pulse signals detected by each pixel.

[0011] As a result, the X-ray inspection apparatus according to the present invention obtains a correspondence relationship between the value of the control parameter that changes the number of pulse signals exceeding a predetermined threshold voltage among pulse signals having peak 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 relationship between the value of the control parameter and the number of pulse signals detected by each pixel.

[0012] Also, an X-ray inspection apparatus according to the present invention is an X-ray inspection apparatus (1) including an X-ray generation source (20) that irradiates an inspection area with X-rays, an X-ray detector (30) that detects X-rays that have passed through the inspection area, a display unit (45) that displays various information, and an input / output unit (60) that can be connected to an external device (2), in which the X-ray detector includes an X-ray detection element (31) that outputs a pulse signal having a peak value 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 detects the number of the pulse signals that exceed a predetermined threshold voltage among the pulse signals output from the X-ray detection element, and a control parameter (46) that changes the number of the pulse signals that exceed the threshold voltage. and a control parameter control unit (55) which performs control to change the value of a meter, and the external device is configured to include a memory unit (56) which stores, for each pixel, a 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 the pulse signals detected by the pixel, and an abnormal pixel information output unit (57) which generates abnormal pixel information for identifying an abnormal pixel based on the correspondence between the value of the control parameter and the number of the pulse signals detected by each pixel which is read from the memory unit, and outputs the abnormal pixel information to the display unit via the input / output unit.

[0013] As a result, when the memory unit and abnormal pixel information output unit of the X-ray inspection apparatus of the present invention are provided in an external device, it is only necessary to connect the external device via the input / output unit when identifying abnormal pixels at the time of product shipment, thereby simplifying the main body of the apparatus.

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

[0015] In the X-ray inspection apparatus according to the present invention, the control parameter may be any one of the threshold voltage, a tube voltage of the X-ray generation source, or a type of a radiation quality variable object installed in the inspection region.

[0016] Furthermore, the X-ray inspection apparatus according to the present invention may further include a control parameter value specifying unit (58) for specifying, for each pixel, the threshold voltage, where the control parameter is the threshold voltage and the radiation quality variable element has a known absorption edge, the threshold voltage, read from the memory unit, at which a slope of the number of pulse signals detected by each pixel with respect to the control parameter changes discontinuously, and a calibration information output unit (59) for associating the threshold voltage specified by the control parameter value specifying unit with the known absorption edge and outputting the association as calibration information for each pixel.

[0017] With this configuration, the X-ray inspection apparatus according to the present invention can use a variable beam quality body having a known absorption edge to associate a threshold voltage, at which the slope of the number of pulse signals detected by each pixel with the control parameter changes discontinuously, with 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 specifying unit (58) for specifying, for each pixel, the minimum threshold voltage at which the number of pulse signals detected by each pixel is smaller than a predetermined value, the control parameter being the threshold voltage, read from the memory unit, and a calibration information output unit (59) for associating the threshold voltage specified by the control parameter value specifying unit with the tube voltage and outputting the association 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 is smaller than a predetermined value and substantially 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 specifying unit (58) that specifies, for each pixel, the maximum tube voltage at which the control parameter is the tube voltage and that has been read out from the memory unit, the number of pulse signals detected by each pixel is smaller than a predetermined value, and a calibration information output unit (59) that associates the tube voltage specified by the control parameter value specifying unit with the threshold voltage and outputs the association as calibration information for each pixel.

[0021] With this configuration, the X-ray inspection apparatus according to the present invention can associate the maximum tube voltage of the X-ray source at which the number of pulse signals detected by each pixel is smaller than a predetermined value and approximately zero with the threshold voltage, and output this as calibration information for each pixel.

[0022] Further, a calibration method according to the present invention provides a method for calibrating an X-ray inspection apparatus (1) including an X-ray generation source (20) that irradiates an inspection area with X-rays, and an X-ray detector (30) that detects X-rays that have passed through the inspection area, the X-ray detector including an X-ray detection element (31) that outputs a pulse signal having a peak value 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 detects the number of the pulse signals output from the X-ray detection element that exceed a predetermined threshold voltage, the method comprising the steps of irradiating the inspection area with X-rays (S1-4, S2-4, S3-5); The method may include an X-ray detection step (S1-5, S2-5, S3-6) of detecting X-rays, a storage step (S1-6, S2-6, S3-7) of storing in a storage unit (56) for each pixel a correspondence between a 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, and an abnormal pixel information output step (S1-9, S2-9, S3-11) of outputting abnormal pixel information for identifying an abnormal pixel based on the correspondence between the value of the control parameter and the number of the pulse signals detected by each pixel, read from the storage unit.

[0023] Further, a calibration method according to the present invention provides a method for calibrating an X-ray inspection apparatus (1) including an X-ray generation source (20) that irradiates an inspection area with X-rays, and an X-ray detector (30) that detects X-rays that have passed through the inspection area, the X-ray detector including an X-ray detection element (31) that outputs a pulse signal having a peak value 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 detects the number of the pulse signals output from the X-ray detection element that exceed a predetermined threshold voltage, the method comprising the steps of: placing a beam quality variable body (100) having a known absorption edge in the inspection area; irradiating the inspection area with X-rays; and detecting the X-rays that have passed through the inspection area. a control parameter value specifying step (S1-10) for specifying, for each pixel, the threshold voltage at which a slope of the number of pulse signals detected by each pixel with respect to the control parameter read from the storage unit changes discontinuously; and a calibration information output step (S1-11) for associating the threshold voltage specified by the control parameter value specifying step with the known absorption edge and outputting the result as calibration information for each pixel. Effect of the Invention

[0024] The present invention provides an X-ray inspection apparatus and a calibration method thereof that are capable of outputting abnormal pixel information for identifying an abnormal pixel among a plurality of pixels that constitute an X-ray detector. [Brief description of the drawings]

[0025] [Figure 1] 1 is a schematic configuration diagram of an X-ray inspection apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2 is an explanatory diagram showing the detection principle of the X-ray inspection apparatus of FIG. [Diagram 3]2(a) is a perspective view of a main part of an X-ray detector provided in the X-ray inspection apparatus of FIG. 1, and (b) is a side view of the main part of the X-ray detector. [Figure 4] Graph (a) is a graph that shows a schematic energy distribution of X-rays output from an X-ray generating source provided in the X-ray inspection apparatus of FIG. 1, graph (b) is a graph that shows a schematic pulse signal and threshold voltage input to each pulse detection circuit of the X-ray detector, and graph (c) is a graph that shows a schematic amount of X-ray detection obtained by sweeping the threshold voltage. [Diagram 5] Graph (a) is a graph that roughly shows the X-ray transmittance of PET resin, and graph (b) is a graph that roughly shows the X-ray transmittance of barium. [Figure 6] 1 is a graph showing roughly the energy distribution (dashed line) of X-rays output from an X-ray generating source and the energy distribution (solid line) of X-rays output from the X-ray generating source and transmitted through a barium-containing resin plate. [Figure 7] Graph (a) is a schematic graph showing the amount of X-ray detection when a barium-containing resin plate is not placed in the inspection area, and graph (b) is a schematic graph showing the amount of X-ray detection when a barium-containing resin plate is placed in the inspection area. [Figure 8] FIG. 11 is a schematic configuration diagram showing another configuration example of an X-ray inspection apparatus according to an embodiment of the present invention. [Figure 9] 2 is a flowchart (part 1) showing the process of a calibration method using the X-ray inspection apparatus of FIG. 1. [Figure 10] 10 is a graph showing a schematic relationship between the threshold voltage obtained by the processing of FIG. 9 and the amount of X-ray detection, where (a) shows the amount of X-ray detection when a barium-containing resin plate is placed in the inspection area, and (b) shows the amount of X-ray detection when a barium-containing resin plate is not placed in the inspection area. [Figure 11] 2 is a flowchart (part 2) showing the process of the calibration method using the X-ray inspection apparatus of FIG. 1. [Figure 12] 12 is a graph showing a schematic relationship between the tube voltage and the amount of detected X-rays obtained by the processing of FIG. 11. [Figure 13] 13 is a flowchart (part 3) showing the process of the calibration method using the X-ray inspection apparatus of FIG. [Figure 14] 14 is a graph showing a schematic relationship between the type of radiation quality variable object and the amount of detected X-rays obtained by the process of FIG. 13. [Figure 15] 2 shows an example of a table displayed on a display unit provided in the X-ray inspection apparatus of FIG. 1. [Figure 16] 1 shows an example of a graph displayed on a display unit. [Figure 17] 2 is a diagram for explaining a clustering technique performed by an abnormal pixel identifying unit included in the X-ray inspection apparatus of FIG. 1. FIG. [Figure 18] 10 is a graph for illustrating a method in which a control parameter value specifying unit included in the X-ray inspection apparatus of FIG. 1 specifies a threshold voltage corresponding to an absorption edge of a beam quality variable body. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

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

[0028] The conveying section 10 is a belt conveyor that winds a loop-shaped conveying belt 11 around multiple conveying rollers 12, 13, and sequentially conveys inspection objects W to be inspected that are placed on the conveying surface 11a of the conveying belt 11 in a conveying direction Y to pass them through a specified inspection area, and is supported by a housing not shown.

[0029] The conveyor belt 11 is made of a material that easily transmits X-rays (an element other than an element with a large atomic weight). In the conveyor unit 10, when inspecting the inspection object W, the rotation of the drive motor is controlled to drive the conveyor belt so as to achieve a conveying speed that is set in advance by the operation unit 46. As a result, the inspection object W carried in from the carry-in entrance is conveyed in the conveying direction Y in FIG. 1 toward the carry-out exit at the set conveying speed.

[0030] The transport unit 10 is not limited to a belt conveyor that transports the object W to be inspected horizontally at a constant speed, but may be in any form that transports the object W to be inspected so that the X-rays from the X-ray generation source 20 are evenly irradiated onto the object W to be inspected, and the X-rays that have passed through the object W to be inspected are detected by the X-ray detector 30. For example, the transport unit 10 may be in a form that uses the weight of the object W to slide down a slope, or in a form that drops the object W from above.

[0031] 2, the X-ray source 20 irradiates an inspection area through which an object to be inspected W passes as it is transported on a transport path in a transport direction Y from an entrance to an exit. In a calibration mode to be 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 cylindrical X-ray tube 22 immersed in insulating oil (not shown). Specifically, an electron beam from a filament 23 provided on the cathode of the X-ray tube 22 is irradiated onto a target 24 of an anode 25 to generate X-rays. The X-ray tube 22 is arranged such that its longitudinal direction is the transport direction Y of the inspection object W. The X-rays generated by the X-ray tube 22 are irradiated toward the X-ray detector 30 below the transport unit 10 in a substantially triangular screen shape by a slit (not shown) so as to cross the transport direction Y.

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

[0034] Fig. 3(a) is a perspective view of the main part of an X-ray detector 30 according to this embodiment, and Fig. 3(b) is a side view of the main part. The X-ray detector 30 is composed of a photon detection 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 Figs. 3(a) and (b). The X-ray detection element 31 may be made of any material that outputs a pulse signal having a peak value proportional to the energy of X-rays that have passed through the inspection region and are incident thereon, and is made of a semiconductor material such as cadmium telluride (CdTe).

[0035] The pulse detection circuit array 33 includes a plurality of pulse detection circuits 321, 322, . . . , 32 which detect the number of pulse signals exceeding a predetermined threshold voltage among the pulse signals output from the X-ray detection element 31. N are arranged, for example, 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 disposed below the transport surface 11a along which the inspection object W is transported, along the X direction perpendicular to the transport direction Y of the inspection object W (see FIG. 2). The pulse detection circuit array 33 of this embodiment corresponds to the X-ray detection unit of the present invention.

[0037] Various threshold voltages can be set for each pulse detection circuit 32 by the control unit 50. The peak value 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 include their energy (wavelength) and intensity (number of photons). X-ray energy is expressed in units of eV. The energy of X-rays is determined by the tube voltage of the X-ray tube 22 at the time of generation of the X-rays and the material of the target 24, 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 X-rays does not change.

[0039] That is, the number of pulse signals exceeding the threshold voltage per second indicates the intensity of X-rays exceeding the energy corresponding to the threshold voltage. Hereinafter, the number of pulse signals exceeding the threshold voltage per second detected by each pulse detection circuit 32 is also referred to as the "X-ray detection amount."

[0040] 3(a) and 3(b), a standard line sensor, a time delay integration (TDI) type line sensor, an area sensor, or the like can be used as the X-ray detector 30. When the X-ray detector 30 is a line sensor, the X-rays that have passed through the object W in the inspection area can be detected by moving the object W by the transport unit 10. When the X-ray detector 30 is an area sensor, the X-rays that have passed through the object W in the inspection area can be detected by keeping the object W stationary in the inspection area.

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

[0042] As shown in FIG. 4(b), pulse signals of various peak values ​​corresponding to various energies of X-rays output from the X-ray source 20 are input from the X-ray detection elements 31 to each pulse detection circuit 32 of the X-ray detector 30.

[0043] Fig. 4(c) is a graph showing the amount of X-ray detection obtained by sweeping the threshold voltage. Here, the threshold voltage is shown converted into X-ray energy [keV]. That is, the amount of X-ray detection of each pulse detection circuit array 33 is proportional to the area of ​​the energy equivalent to the threshold voltage or more in the graph of the X-ray energy distribution as shown in Fig. 4(a).

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

[0045] As the beam quality variable body 100 that changes the energy (beam quality) of the X-rays output from the X-ray generating 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 graphs that show the schematic X-ray transmittance of PET resin and barium. As shown in Figure 5(a), the higher the energy of the X-ray, the better it penetrates PET resin. On the other hand, as shown in Figure 5(b), the overall tendency is that the higher the energy of the X-ray, the better it penetrates barium, 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 show 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] In addition to barium, elements having an absorption edge at around 30 keV include iodine, silver, etc. A resin plate containing these elements can also be used as the beam quality variable body 100 of this embodiment.

[0049] 6 shows a schematic diagram of the energy distribution (dashed line) of X-rays output from the X-ray generation source 20 and the energy distribution (solid line) of X-rays output from the X-ray generation source 20 and transmitted through a barium-containing resin plate. As such, the energy distribution of X-rays reaching the X-ray detector 30 clearly differs depending on whether or not a barium-containing resin plate is present.

[0050] FIG. 7(a) is a graph that shows the amount of detected X-rays obtained by sweeping the threshold voltage set in each pulse detection circuit 32 when a barium-containing resin plate is not installed in the inspection area between the X-ray generation source 20 and the X-ray detector 30. On the other hand, FIG. 7(b) is a graph that shows the amount of detected X-rays obtained by sweeping the threshold voltage set in each pulse detection circuit 32 when a barium-containing resin plate is installed as the radiation quality variable body 100 in the inspection area between the X-ray generation source 20 and the X-ray detector 30. In the graph of the amount of detected X-rays in FIG. 7(b), it can be seen that discontinuous changes appear in the slope of the amount of detected X-rays 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 amount of detected X-rays with respect to the control parameter refers to the ratio of the amount of change in the amount of detected X-rays to the minute amount of change in the control parameter, that is, the value obtained by first-order differentiation of the amount of detected X-rays with respect to the control parameter.

[0051] The control unit 50 controls the transport speed and transport interval of the inspection object 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 of the X-ray generation source 20, and controls the X-ray detection cycle and the detection period of the inspection object W in the X-ray detector 30 according to the transport speed of the inspection object W.

[0052] The control unit 50 also has a mode selection unit 51, an image data generation unit 52, a correction unit 53, a judgment unit 54, a control parameter control unit 55, a memory 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 operation mode of the X-ray inspection apparatus 1 between an inspection mode and a calibration mode. For example, the mode selection unit 51 is configured to select the operation mode of the X-ray inspection apparatus 1 in response to an operation input to the operation unit 46 by an operator.

[0054] The image data generating unit 52, the correcting unit 53, and the determining unit 54 are components that are mainly related to the inspection mode. The control parameter control unit 55, the memory unit 56, the abnormal pixel information output unit 57, the control parameter value specifying unit 58, and the calibration information output unit 59 are components that are mainly related to the calibration mode.

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

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

[0057] The judgment unit 54 performs a quality inspection to judge the presence or absence of foreign matter in the inspection object W based on the image data corrected by the correction unit 53 and a preset pass / fail judgment criterion, and judges the pass / fail of the inspection object W. For example, the judgment unit 54 executes image processing such as a filter for emphasizing foreign matter information and extracting it as a foreign matter extracted image on the image data corrected by the correction unit 53, and is able to detect the presence or absence of foreign matter mixed in the inspection object W. As a filter for emphasizing foreign matter information, for example, a feature extraction filter such as a differential filter (Roberts filter, Prewitt filter, Sobel filter) or a Laplacian filter is used. The judgment result by the judgment unit 54 is arranged to be displayed on the display unit 45.

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

[0059] 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 and the number of pulse signals detected by the pulse detection circuit array 33 (amount of X-ray detection).

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

[0061] The control parameter value specifying unit 58 specifies, for each pixel, a 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 specifying unit 58 specifies, for each pixel, a 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 is approximately 0. Alternatively, the control parameter value specifying unit 58 specifies, for each pixel, a 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 is approximately 0. Here, the term "approximately 0" is used because it is assumed that the X-ray detection amount may not be strictly 0 due to the influence of noise of the X-ray detector 30 or the like. For example, a certain threshold value ε can be set and it can be said that "X-ray detection amount<ε".

[0062] The calibration information output unit 59 is configured to associate the threshold voltage specified by the control parameter value specifying unit 58 with the known absorption edge of the radiation quality variable body 100, and output the associated information as calibration information for each pixel. Alternatively, the calibration information output unit 59 is configured to associate the threshold voltage specified by the control parameter value specifying unit 58 with the tube voltage, and output the associated information as calibration information for each pixel. Alternatively, the calibration information output unit 59 is configured to associate the tube voltage specified by the control parameter value specifying unit 58 with the threshold voltage, and output the associated information 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] 8, the X-ray inspection apparatus 1 of the present embodiment may include an input / output unit 60 connectable to an external device 2. The external device 2 includes the storage unit 56 and the abnormal pixel information output unit 57 described above.

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

[0065] In addition, in the configuration of FIG. 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 ​​and the X-ray detection amounts of each pixel read from the memory unit 56, and outputs the generated abnormal pixel information to the display unit 45 via the input / output unit 60.

[0066] <Method 1> Hereinafter, a first method for acquiring the amount of detected X-rays in a configuration in which the variable control parameter is a threshold voltage will be described with reference to the flow chart of FIG.

[0067] First, an operator places the beam quality variable body 100 having a known absorption edge, such as a barium-containing resin plate, in the inspection area (step S1-1). Note that the beam quality variable body 100 may be placed in the inspection area by a dedicated replacement mechanism (not shown) mounted in the X-ray inspection apparatus 1, instead of being placed in the inspection area by an operator. The beam quality variable body 100 may be transported by the transport unit 10 and placed in the inspection area. Alternatively, the beam quality variable body 100 does not have to be placed in the inspection area.

[0068] Next, the control parameter control unit 55 sets initial values ​​for various control parameters in response to an operation input by the operator 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 performs an operation input to the operation unit 46 to instruct the start of measurement (step S1-3: YES), the X-ray generation source 20 irradiates the inspection area with X-rays (step S1-4).

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

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

[0072] Next, if the operator has not performed an operational input to the operation unit 46 to instruct the end of the measurement (step S1-7: NO), the process proceeds to step S1-8 and subsequent steps.

[0073] On the other hand, when the operator performs an operational input to the operation unit 46 to instruct the end of the measurement (step S1-7: YES), the process proceeds to step S1-9 and thereafter.

[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), and then the processes from step S1-4 onwards are executed again.

[0075] In step S1-9, the abnormal pixel information output unit 57 outputs abnormal pixel information for identifying abnormal pixels that have output abnormal X-ray detection amounts, based on the correspondence between the control parameter values ​​and the X-ray detection amounts of each pixel read from the memory unit 56 (abnormal pixel information output step S1-9).

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

[0077] By the process shown in the flowchart of Fig. 9, the correspondence between the threshold voltage and the amount of detected X-rays as shown in Fig. 10(a) and (b) is obtained for each pixel. Fig. 10(a) shows the measurement result of the amount of detected X-rays when the beam quality variable body 100 is placed in the inspection area. On the other hand, Fig. 10(b) shows the measurement result of the amount of detected X-rays when the beam quality variable body 100 is not placed in the inspection area. Here, the amount of detected X-rays obtained when the threshold voltage is E1 is M1, and the amount of detected X-rays obtained when the threshold voltage is E2 is M2. In the above process, the number of threshold voltages set in the X-ray detector 30 is 1 or more, and the more the better.

[0078] <Method 2> Hereinafter, a second method for acquiring the amount of detected X-rays in a configuration in which the variable control parameter is the tube voltage will be described with reference to the flowchart of FIG.

[0079] First, an operator places the beam quality variable body 100 having a known absorption edge, such as a barium-containing resin plate, in the inspection area (step S2-1). Note that the beam quality variable body 100 may be placed in the inspection area by a dedicated replacement mechanism (not shown) mounted in the X-ray inspection apparatus 1, instead of being placed in the inspection area by an operator. The beam quality variable body 100 may be transported by the transport unit 10 and placed in the inspection area. Alternatively, the beam quality variable body 100 does not have 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 an operation input by the operator to the operation unit 46 (step S2-2). For example, in step S2-2, the threshold voltage of 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 performs an operational input to the operation unit 46 to instruct the start of measurement (step S2-3: YES), the X-ray generation source 20 irradiates the inspection area with X-rays (step S2-4).

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

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

[0084] Next, if the operator has not performed an operational input to the operation unit 46 to instruct the end of the measurement (step S2-7: NO), the process proceeds to step S2-8 and subsequent steps.

[0085] On the other hand, when the operator performs an operational input to the operation unit 46 to instruct the end of the measurement (step S2-7: YES), the process proceeds to step S2-9 and thereafter.

[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 processing after step S2-4 is 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 the respective pixels (abnormal pixel information output step S2-9).

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

[0089] By the processing 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 corresponds 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 or the like of the X-ray detector 30. 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 processing is 1 or more, and the larger the number, the more desirable.

[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 with reference to the flowchart of FIG. 13.

[0091] 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, an operator places the resin board 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 board s1 in the inspection area. Alternatively, the control parameter control unit 55 may control the transport unit 10 to transport and place the resin board s1 in the inspection area.

[0093] Next, the control parameter control unit 55 sets initial values ​​for various control parameters in response to an operation input by the operator 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 each set to a predetermined value.

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

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

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

[0097] Next, if the operator has not performed an operational input to the operation unit 46 to instruct the end of the measurement (step S3-8: NO), the process proceeds to step S3-9 and subsequent steps.

[0098] On the other hand, when the operator performs an operational input to the operation unit 46 to instruct the end of the measurement (step S3-8: YES), the process of step S3-11 is executed.

[0099] In step S3-9, the control parameter control unit 55 displays a message on the display unit 45 urging the operator to change the type of the beam quality variable body 100, which is a variable control parameter, i.e., to place a new resin plate in the examination area (step S3-9).

[0100] Next, the operator removes the resin plate currently placed in the inspection area and places 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 placed in the inspection area and place 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 placed in the inspection area out of the inspection area and transport the new resin plate to the inspection area and place it there. Then, the processes from step S3-5 onwards are executed again.

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

[0102] By the process shown in the flowchart of Fig. 13, the correspondence between the type of the radiation quality variable body 100 and the amount of detected X-rays as shown in Fig. 14 is obtained for each pixel. Here, the amounts of detected X-rays obtained when the types of the radiation quality variable body 100 are resin plates s1, s2, s3, and s4 are M1, M2, M3, and M4, respectively. As an example, the resin plate s1 is a barium-containing resin plate, the resin plate s2 is a relatively thick PET resin plate, the resin plate s3 is a relatively thin PET resin plate, and the resin plate s4 is a PVC resin plate. In the above process, the number of types of radiation quality variable body 100 placed in the examination area is 1 or more, and the more the better.

[0103] An example of a method for identifying an abnormal pixel by the abnormal pixel information output unit 57 will be described below.

[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 on the display unit 45 as abnormal pixel information, allowing an operator to identify abnormal pixels by visual judgment.

[0105] Fig. 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 Fig. 15 show, for each pixel, the correspondence between a state (e.g., a threshold voltage of 1 or more) corresponding to the value of a certain variable control parameter and the measured amount of detected X-rays.

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

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

[0108] For example, the automatic judgment criterion is a representative value obtained from the amount of X-ray detection of all pixels in each state. As shown in the judgment results in the right column of the table in Fig. 15, the representative value of all pixels can be, for example, the average value of the amount of X-ray detection 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 that has the largest difference from the average value, or a pixel that outputs an X-ray detection amount whose difference from the average value is equal to or greater than a predetermined threshold value, as an abnormal pixel.

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

[0111] 15, the amount of detected X-rays at pixel 3 deviates from the average value by 15 or more. Therefore, when the predetermined threshold value is 15, the abnormal pixel identifying unit 57a identifies pixel 3 as an abnormal pixel.

[0112] The automatic judgment standard may be set to any value by the operator using the operation unit 46.

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

[0114] The machine learning performed by the abnormal pixel identifying unit 57a is based on a clustering method such as a self-organizing map, a density-based spatial clustering of applications with noise (DBSCAN) method, or a t-distributed stochastic neighbor embedding (t-SNE) method. A clustering method is a method for classifying data in a feature space based on the distance (or similarity) between data. The machine learning performed by the abnormal pixel identifying unit 57a is not limited to these clustering methods, and may be based on a method using a classifier such as a support vector machine or a random forest.

[0115] Fig. 17 is a diagram for explaining the clustering technique by the abnormal pixel identifying unit 57a. For example, in the example shown in Fig. 15, the data of the X-ray detection amount of pixels 1, 2, and 4 belong to cluster 1, and the data of the X-ray detection amount of pixel 3 belongs to cluster 2. In this manner, clusters to which a large number of data belong and clusters to which a small number of data belong are determined. For example, the abnormal pixel identifying unit 57a determines that a pixel corresponding to the data of the X-ray detection amount belonging to a large cluster is a normal pixel, and that a pixel corresponding to the data of the X-ray detection amount belonging to a small cluster is an abnormal pixel.

[0116] As described above, by the abnormal pixel information output unit 57 outputting the abnormal pixel information, it is possible to encourage the operator to take an action such as setting the X-ray detector 30 not to use the abnormal pixel.

[0117] Hereinafter, the operations of the control parameter value specifying unit 58 and the calibration information output unit 59 for acquiring calibration information for performing energy calibration of pixels will be described.

[0118] First, a configuration in which a variable control parameter is a threshold voltage and a beam quality variable body 100 having an absorption edge is used will be described.

[0119] As shown in the graph in Figure 18, the discontinuous change in transmittance due to the influence of the absorption edge appears not only in the graph of the amount of X-ray detection versus the threshold voltage, but also in its first and second derivatives. At the absorption edge, the first derivative of the amount of X-ray detection becomes discontinuous, and the value of the second derivative of the amount of X-ray detection becomes a prominently large value. Therefore, if an appropriate threshold value θ is determined, 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 differentiates the X-ray detection amount twice with respect to the threshold voltage, and uses the threshold value θ as described above to identify, for each pixel, the threshold voltage at which the slope of the X-ray detection amount for each pixel read out from the memory unit 56 relative to the control parameter changes discontinuously.

[0121] Hereinafter, a calibration method for acquiring calibration information in a configuration using a radiation quality variable body 100 having an absorption edge, in which the variable control parameter is a threshold voltage, will be described with reference to the flowchart of FIG.

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

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

[0124] On the other hand, in a calibration method in which the variable control parameter is a threshold voltage and calibration information is obtained in a configuration that does not use the beam quality variable body 100, the processing of the control parameter value determination 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 or the like of the X-ray detector 30. 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 with reference 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 or the like of the X-ray detector 30. 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, by the calibration information output unit 59 outputting calibration information for performing pixel energy calibration, it is possible to prompt an operator to take action such as adjusting the gain of an abnormal pixel of the X-ray detector 30.

[0131] The accuracy of the correspondence between the X-ray energy and the threshold voltage by the tube voltage depends on the accuracy of the tube voltage. Therefore, it is considered that the correspondence between the X-ray energy and the threshold voltage by using the beam quality variable body 100 having an absorption edge is more accurate than the correspondence between the X-ray energy and the threshold voltage by the tube voltage.

[0132] The control unit 50 is configured with a control device such as a computer including, for example, a central processing unit (CPU), a graphics processing unit (GPU), a field programmable gate array (FPGA), a read only memory (ROM), a random access memory (RAM), and a hard disk drive (HDD). For example, the control unit 50 can configure at least a part of the mode selection unit 51, the image data generation unit 52, the correction unit 53, the determination unit 54, the control parameter control unit 55, the abnormal pixel information output unit 57, the control parameter value identification unit 58, and the calibration information output unit 59 in software by executing a predetermined program by the CPU or the GPU. The above programs are stored in the ROM or the HDD in advance. Alternatively, the above programs may be provided or distributed in a state in which they are recorded in a computer-readable recording medium such as a compact disc or a DVD in an installable or executable format. Alternatively, the above programs may be stored in a computer connected to a network such as the Internet, and provided or distributed by downloading 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 a display control signal from the control unit 50. The display unit 45 may have an operation function of the operation unit 46 such as soft keys on the display screen.

[0134] Operation unit 46 is for receiving operation input by an operator, and is composed of a user interface such as keys, push buttons, switches, and soft keys on the display screen of display unit 45 provided on the main body of X-ray inspection apparatus 1.

[0135] For example, an operator can input operations into the operation unit 46 to select the operating mode of the X-ray inspection apparatus 1 in the mode selection unit 51, and input information required for a series of inspections, including information on the object W to be inspected (e.g., product name, etc.) (e.g., the conveying speed of the conveying unit 10, the total number of objects W to be inspected, a judgment threshold for determining whether the object W is good or bad, etc.).

[0136] As described above, the X-ray inspection apparatus 1 according to this embodiment obtains the correspondence between the value of the control parameter that changes the number of pulse signals exceeding a predetermined threshold voltage among pulse signals having peak values ​​corresponding to the energy of X-rays that have passed through the inspection area, 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 an abnormal pixel, 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 where the memory unit 56 and the abnormal pixel information output unit 57 are provided in the external device 2, the X-ray inspection apparatus 1 of this embodiment only needs to connect to the external device 2 via the input / output unit 60 when identifying abnormal pixels at the time of product shipment, thereby simplifying the apparatus body.

[0138] Furthermore, the X-ray inspection apparatus 1 according to this embodiment can use the beam quality variable body 100 having a known absorption edge to associate a threshold voltage, at which the slope of the X-ray detection amount of each pixel with the control parameter changes 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 associate the minimum threshold voltage at which the amount of X-ray detection for each pixel is smaller than a predetermined threshold value ε and is substantially 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 output as calibration information for each pixel an association between the maximum tube voltage of the X-ray tube 22 at which the amount of X-ray detection for each pixel is smaller than a predetermined threshold value ε and substantially zero and the threshold voltage.

[0141] That is, 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 substances that pose safety problems. [Explanation of symbols]

[0142] 1 X-ray inspection equipment 2 External device 20 X-ray Source 22 X-ray tube 23 Filament 24 Target 25 Anode 30 X-ray detector 31 X-ray detector 32,321,322,...,32 N Pulse detection circuit (pixel) 33 Pulse detection circuit array (X-ray detection section) 45 Display section 46 Control section 50 Control section 55 Control parameter control section 56 Memory section 57 Abnormal pixel information output section 57a Abnormal pixel identification section 58 Control parameter value specification unit 59 Calibration information output section 60 Input / output section 100 Radiation quality variable body W Inspection item

Claims

1. an X-ray generating source (20) for irradiating an examination area with X-rays; An X-ray inspection device (1) including an X-ray detector (30) for detecting 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 with a peak value 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 the pulse signals exceeding a predetermined threshold voltage among the pulse signals output from the X-ray detection elements; The X-ray inspection apparatus includes: a memory unit (56) that stores, for each pixel, a correspondence between a value of a control parameter that changes the number of the pulse signals that exceed the threshold voltage and the number of the pulse signals detected by the pixel; an abnormal pixel information output unit (57) that outputs abnormal pixel information for identifying an abnormal pixel based on the correspondence between the value of the control parameter and the number of the pulse signals detected by each of the pixels, read from the memory unit.

2. an X-ray generating source (20) for irradiating an examination area with X-rays; an X-ray detector (30) for detecting X-rays passing through the examination area; A display unit (45) for displaying various information; An X-ray inspection device (1) comprising an input / output unit (60) connectable to an external device (2), The X-ray detector includes: an X-ray detection element (31) that outputs a pulse signal with a peak value corresponding to the energy of the X-rays that have passed through the inspection area; an X-ray detection unit (33) including a plurality of pixels (32) for detecting the number of pulse signals exceeding a predetermined threshold voltage among the pulse signals output from the X-ray detection elements; A control parameter control unit (55) that performs control to change a value of a control parameter that changes the number of the pulse signals exceeding the threshold voltage, The external device is a storage unit (56) that stores, for each pixel, a 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 the pulse signals detected by the pixel; an abnormal pixel information output unit (57) that generates abnormal pixel information for identifying an abnormal pixel based on the correspondence between the value of the control parameter and the number of the pulse signals detected by each of the pixels, read from the memory unit, and outputs the abnormal pixel information to the display unit via the input / output unit.

3. 3. The X-ray inspection apparatus according to claim 1, wherein the control parameter is the threshold voltage or a tube voltage of the X-ray generation source.

4. 3. The X-ray inspection apparatus according to claim 1, wherein the control parameter is any one of the threshold voltage, a tube voltage of the X-ray generation source, and a type of a radiation quality variable body installed in the inspection region.

5. the control parameter is the threshold voltage; the radiation quality variable body has a known absorption edge; a control parameter value specifying unit (58) that specifies, for each pixel, the threshold voltage at which a slope of the number of the pulse signals detected by each pixel with respect to the control parameter changes discontinuously, the threshold voltage being read from the storage unit; 5. The X-ray inspection apparatus according to claim 4, further comprising: 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 the association as calibration information for each of the pixels.

6. the control parameter is the threshold voltage; a control parameter value specifying unit (58) that specifies, for each pixel, a minimum threshold voltage at which the number of the pulse signals detected by each pixel is smaller than a predetermined value, read from the storage unit; 4. The X-ray inspection apparatus according to claim 3, further comprising a calibration information output unit (59) that associates the threshold voltage and the tube voltage identified by the control parameter value identification unit and outputs the association as calibration information for each of the pixels.

7. the control parameter is the tube voltage, a control parameter value specifying unit (58) that specifies, for each pixel, a maximum tube voltage at which the number of the pulse signals detected by each pixel is smaller than a predetermined value, the maximum tube voltage being read from the storage unit; 4. The X-ray inspection apparatus according to claim 3, further comprising: a calibration information output unit (59) that associates the tube voltage and the threshold voltage specified by the control parameter value specifying unit and outputs the association as calibration information for each of the pixels.

8. the control parameter is the tube voltage, a control parameter value specifying unit (58) that specifies, for each pixel, a maximum tube voltage at which the number of the pulse signals detected by each pixel is smaller than a predetermined value, the maximum tube voltage being read from the storage unit; 5. The X-ray inspection apparatus according to claim 4, further comprising a calibration information output unit (59) that associates the tube voltage and the threshold voltage specified by the control parameter value specifying unit and outputs the association as calibration information for each of the pixels.

9. an X-ray generating source (20) for irradiating an examination area with X-rays; an X-ray detector (30) for detecting 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 with a peak value corresponding to the energy of the X-rays that have passed through the inspection area; an X-ray detection unit (33) including a plurality of pixels (32) for detecting the number of the pulse signals output from the X-ray detection elements that exceed a predetermined threshold voltage, A step of irradiating the inspection area with X-rays (S1-4, S2-4, S3-5); an X-ray detection step (S1-5, S2-5, S3-6) for detecting X-rays that have passed through the inspection area; a storage step (S1-6, S2-6, S3-7) of storing in a storage unit (56) for each pixel a correspondence relationship between a 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; and an abnormal pixel information output step (S1-9, S2-9, S3-11) of outputting abnormal pixel information for identifying an abnormal pixel based on the correspondence between the value of the control parameter read from the storage unit and the number of the pulse signals detected by each of the pixels.

10. an X-ray generating source (20) for irradiating an examination area with X-rays; an X-ray detector (30) for detecting 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 with a peak value corresponding to the energy of the X-rays that have passed through the inspection area; an X-ray detection unit (33) including a plurality of pixels (32) for detecting the number of the pulse signals output from the X-ray detection elements that exceed a predetermined threshold voltage, A step (S1-1) of placing a beam quality variable body (100) having a known absorption edge in the examination area; A step (S1-4) of irradiating the inspection area with X-rays; an X-ray detection step (S1-5) of detecting X-rays that have passed through the inspection area; a storage step (S1-6) of storing in a storage unit (56) for each pixel a correspondence relationship between a 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; a control parameter value specifying step (S1-10) of specifying, for each pixel, the threshold voltage at which a slope of the number of 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 identified by the control parameter value identification step with the known absorption edge and outputting the result as calibration information for each pixel.

Images