Radiation detection device, radiation detection system, and radiation detection method

Abstract

This X-ray detection camera is provided with: a radiation detection element that directly converts incident X-rays into charges and outputs, as X-ray image data, the results of charge collection for each of a plurality of third electrodes; a first bias power supply that applies a bias voltage to the radiation detection element; and a control unit. The control unit has: a determination unit that executes a determination process that, on the basis of the X-ray image data, determines whether or not a reset operation for performing voltage control on the radiation detection element so that charge is not collected by the radiation detection element can be executed; and a voltage control unit that controls the voltage source so as to execute the reset operation when the determination unit determines that the reset operation can be executed.

Description

Technical Field

[0001] One aspect of the present invention relates to a radiation detection device, a radiation detection system, and a radiation detection method. Background Art

[0002] Previously, there is a known radiation detection device for detecting radiation that passes through an object. In such a radiation detection device, for example, radiation that passes through an object is directly converted into electric charges by a direct conversion material of a detection element, and the electric charges are collected by a pixel electrode, thereby detecting radiation and obtaining a radiographic image. Here, in such a radiation detection device, if radiation is continuously irradiated to the detection element, polarization may occur in the detection element, resulting in degradation of the radiographic image. Therefore, it is sought to eliminate the polarization phenomenon in the detection element.

[0003] In the radiation detection device described in Patent Document 1, the HV (High Voltage) supplied from the HV power supply device to the radiation detection device is turned on and off at a predetermined cycle, thereby eliminating the polarization phenomenon in the radiation detection device.

[0004] In a pair of radiation detection devices described in Patent Document 2, when a self-bias power supply supplies a bias voltage to the radiation detection devices constituting one array, before a polarization phenomenon occurs in the radiation detection devices constituting one array, the supply end of the bias voltage is switched for the radiation detection devices constituting another array, thereby suppressing the occurrence of polarization phenomenon in the radiation detection devices.

[0005] In the plurality of radiation detection apparatuses described in Patent Document 3, bias voltages are applied so that bias application stop periods to the respective radiation detection apparatuses do not overlap with each other, thereby suppressing the occurrence of polarization phenomena simultaneously in the plurality of radiation detection apparatuses. Prior art literature Patent Literature

[0006] Patent Document 1: Japanese Patent Publication No. 2006-513406 Patent Document 2: Japanese Patent Application Publication No. 2008-304420 Patent Document 3: International Publication No. 2009 / 122665 Summary of the invention The problem the invention is intended to solve

[0007] In the above-mentioned radiation detection device, in order to eliminate the polarization phenomenon in the radiation detection device, the application of the bias voltage is stopped regardless of the external conditions of the radiation detection device. Therefore, if the timing of eliminating the polarization phenomenon of the detection element in the radiation detection device coincides with the timing of radiation incident on the radiation detection device passing through the object, there is a concern that the radiation detection device may not be able to detect the radiation passing through the object.

[0008] One aspect of the present invention is completed in view of the above-mentioned actual situation, and is about a radiation detection device, a radiation detection system and a radiation detection method that can suppress the occurrence of polarization phenomena in detection elements and more reliably detect the radiation when the radiation incident on the radiation detection device passes through an object. Technical means of solving problems

[0009] (1) A radiation detection device according to one embodiment of the present invention comprises: a detection element that directly converts incident radiation into electric charge and outputs the result of collecting the electric charge for each of a plurality of pixel electrodes as image data; a voltage source that applies a bias voltage to the detection element; and a control unit that is electrically connected to the detection element and the voltage source. The control unit comprises: a determination unit that performs a determination process that determines whether a reset operation of controlling the voltage of the detection element can be performed in a manner that the detection element does not collect electric charge based on the image data output from the detection element; and a voltage control unit that controls the voltage source in a manner that the reset operation is performed when the determination unit determines that the reset operation can be performed.

[0010] In a radiation detection device of one embodiment of the present invention, based on the camera image data output from the detection element, it is determined whether a reset action can be performed to control the voltage of the detection element in a manner that the detection element does not collect charges. According to such a structure, it is determined whether the reset action can be performed by considering the information shown in the camera image data output from the detection element, that is, the condition outside the radiation detection device. Thus, for example, it can be determined based on the camera image data whether the radiation incident to the radiation detection device passes through the object. Thus, for example, at the moment when the radiation incident to the radiation detection device does not pass through the object, the voltage source can perform a reset action, and at the moment when the radiation incident to the radiation detection device passes through the object, the voltage source can perform voltage control on the detection element in a manner that the detection element collects charges. As a result, the occurrence of polarization phenomenon of the detection element can be suppressed, and in the case where the radiation incident to the radiation detection device passes through the object, the radiation can be detected more reliably.

[0011] (2) In the radiation detection device described in (1) above, the determination unit may also determine that a reset action can be performed when it is determined based on the camera image data that the radiation has not passed through the object during the determination process. According to such a structure, a reset action can be performed by a voltage source at the moment when the radiation incident on the radiation detection device has not passed through the object, and a voltage control of the detection element can be performed by the voltage source in a manner that charges are collected by the detection element at the moment when the radiation incident on the radiation detection device has passed through the object. As a result, the occurrence of polarization in the detection element can be suppressed, and when the radiation incident on the radiation detection device has passed through the object, the radiation can be detected more reliably.

[0012] (3) In the radiation detection device described in (2) above, the determination unit may determine that the radiation has not passed through the object when the brightness value of the captured image data exceeds a predetermined threshold value during the determination process. With such a structure, it is possible to more accurately determine whether the radiation incident on the radiation detection device has passed through the object. Thus, the reset operation can be more reliably performed at the moment when the radiation incident on the radiation detection device has not passed through the object.

[0013] (4) In the radiation detection device described in (2) above, the determination unit may determine that the radiation has not passed through the object when the brightness value of the captured image data is lower than a predetermined threshold value during the determination process. According to such a structure, for example, when an object that shields or significantly absorbs radiation is arranged in a place where no object is arranged, it is possible to more reliably determine whether the radiation incident on the radiation detection device has passed through the object. Thus, for example, when the radiation incident on the radiation detection device has not passed through the object, the reset operation can be more reliably performed.

[0014] (5) In the radiation detection device described in (3) or (4) above, the detection element may also continuously output the camera image data. The determination unit may not perform the determination process until the amount of change in the brightness value between the plurality of camera image data continuously outputted from the detection element exceeds a prescribed threshold value after performing the reset action, and perform the determination process when the amount of change exceeds the prescribed threshold value. According to such a structure, after performing the reset action, the determination process is restarted after the imaging of the object of the radiation detection device is completed. Thus, after performing the reset action, the reset action can be suppressed until the polarization phenomenon needs to be eliminated again in the radiation detection device. As a result, the radiation detection device can be operated more efficiently.

[0015] (6) In the radiation detection apparatus described in any one of (2) to (4) above, the determination unit may not perform determination processing until a prescribed period of time has passed, which is a period during which the reset operation is not required, after the reset operation is performed, and may perform determination processing when the prescribed period has passed. According to such a structure, after the reset operation is performed, the reset operation can be suppressed until the polarization phenomenon needs to be eliminated again in the radiation detection apparatus. As a result, the radiation detection apparatus can be operated more efficiently.

[0016] (7) In the radiation detection device described in (6) above, the detection element may also operate based on a reference clock. The determination unit may also determine whether a predetermined period has elapsed by counting the reference clock. According to such a structure, whether a predetermined period has elapsed can be determined with greater accuracy based on the reference clock. Thus, after the reset operation is performed, the reset operation can be more reliably suppressed until the polarization phenomenon needs to be eliminated again in the radiation detection device.

[0017] (8) In the radiation detection device described in any one of (1) to (7) above, the reset operation may be either an operation of stopping the voltage application to the detection element or an operation of applying a reverse bias voltage to the detection element. With such a structure, the polarization phenomenon in the radiation detection device can be eliminated more reliably.

[0018] (9) A radiation detection system according to one embodiment of the present invention comprises: a radiation detection device as described in any one of (1) to (8) above; a light source that irradiates radiation; and a transport device that transports an object so that the object passes through an irradiation area of ​​the radiation.

[0019] In a radiation detection system of one embodiment of the present invention, radiation irradiated from a light source is incident on a detection element. An object transported by a transport device passes through an irradiation area of ​​the radiation. And, based on the camera image data output from the detection element, it is determined whether a reset action can be performed to control the voltage of the detection element in a manner that the detection element does not collect charges. According to such a structure, it is determined whether a reset action can be performed by considering the information shown in the camera image data output from the detection element, that is, the condition outside the radiation detection device. Thus, for example, by photographing the irradiation area of ​​the radiation through the detection element, it is possible to determine whether the radiation incident to the radiation detection device passes through the object based on the camera image data. Thus, for example, at the moment when the radiation incident to the radiation detection device does not pass through the object, the voltage source can perform a reset action, and at the moment when the radiation incident to the radiation detection device passes through the object, the voltage source can perform voltage control on the detection element in a manner that the detection element collects charges. As a result, the occurrence of a polarization phenomenon in the detection element can be suppressed, and when radiation incident on the radiation detection device passes through the object, the radiation can be detected more reliably.

[0020] (10) A radiation detection method according to one embodiment of the present invention comprises: a voltage application step of directly converting incident radiation into electric charges and applying a bias voltage to a detection element that outputs the result of collecting electric charges for each of a plurality of pixel electrodes as video image data; an acquisition step of acquiring video image data from the detection element; a determination step of determining whether a reset action of performing voltage control on the detection element without collecting electric charges by the detection element can be performed based on the video image data output from the detection element; and a reset step of performing the reset action if it is determined in the determination step that the reset action can be performed.

[0021] In a radiation detection method of one embodiment of the present invention, in the determination step, based on the camera image data obtained in the acquisition step, it is determined whether a reset action can be performed to control the voltage of the detection element in a manner that the detection element does not collect charges. According to such a structure, it is determined whether the reset action can be performed by considering the information shown in the camera image data output from the detection element, that is, the condition outside the radiation detection device. Thus, for example, it can be determined based on the camera image data whether the radiation incident to the radiation detection device passes through the object. Thus, for example, at the moment when the radiation incident to the radiation detection device does not pass through the object, the voltage source can perform a reset action, and at the moment when the radiation incident to the radiation detection device passes through the object, the voltage source can perform voltage control on the detection element in a manner that the detection element collects charges. As a result, the generation of polarization in the detection element can be suppressed, and in the case where the radiation incident to the radiation detection device passes through the object, the radiation can be detected more reliably. Effects of the Invention

[0022] According to a radiation detection device, a radiation detection system, and a radiation detection method of one aspect of the present invention, the occurrence of polarization in a detection element can be suppressed, and when radiation incident on the radiation detection device passes through an object, the radiation can be detected more reliably. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a diagram showing the configuration of an X-ray inspection apparatus according to the first embodiment. Figure 2 It is a structural diagram of an X-ray inspection camera. Figure 3 It is a block diagram showing the functional structure of the control unit. Figure 4 It is a diagram for explaining the functions of the determination unit and the voltage control unit. Figure 5 This is a diagram for explaining the distance between objects to be inspected in an X-ray inspection apparatus. Figure 6 It is shown Figure 1Diagram of the X-ray irradiation range of the light source shown. Figure 7 This is a flowchart of an example of processing for executing the reset operation of the radiation detection method according to the first embodiment. Figure 8 This is a table explaining the problems of the X-ray detection camera of the comparative example. Fig. 9 It is a diagram for explaining the problem of the X-ray detection camera of the comparative example. Fig.10 It is a block diagram of an X-ray inspection apparatus according to a second embodiment. Fig.11 Yes Description Fig.10 A diagram showing the shape of the detected object. Fig.12 Yes Description Fig.10 A graph of the thickness of the detected object is shown. Fig.13 It is a diagram for explaining the functions of the determination unit and the voltage control unit. Fig.14 This is a diagram for explaining the distance between objects to be inspected in an X-ray inspection apparatus. Fig.15 It is a diagram for explaining the distance between inspection objects of a plurality of radiation detection elements according to a modified example. Fig.16 It is a diagram for explaining the operation of the X-ray detection camera according to the modification. Fig.17 It is a structural diagram of the X-ray inspection apparatus of the embodiment. DETAILED DESCRIPTION

[0024] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the same reference numerals are attached to the same or corresponding parts in each figure, and repeated description is omitted.

[0025] [First embodiment] [Structure of X-ray Inspection Device] Figure 1 FIG. 1 is a block diagram of an X-ray inspection apparatus 1A, which is a radiation detection system according to the first embodiment. Figure 1As shown, the X-ray inspection device 1A is a device that irradiates X-rays (radiation) to an object to be inspected (object) F transported in a transport direction TD, and obtains an X-ray image of the object to be inspected F based on the X-rays that pass through the object to be inspected F. The X-ray inspection device 1A uses the X-ray image to perform foreign matter inspection, weight inspection, and product inspection, etc. on the object to be inspected F. Examples of uses of the X-ray inspection device 1A include food inspection, carry-on baggage inspection, substrate inspection, battery inspection, and material inspection. The X-ray inspection device 1A includes a transport unit (transport device) 2 that transports the object to be inspected F, an X-ray generator (light source) 3 that irradiates X-rays, an X-ray detection camera 100A, a control device 4, and a shielding unit 5 that shields X-rays. In addition, the radiation of the present invention is not limited to X-rays, and also includes radiation other than X-rays such as gamma rays. In this embodiment, the radiation is described as X-rays.

[0026] The conveying unit 2 conveys the inspected object F in such a manner that the inspected object F passes through the irradiation area R3 irradiated with X-rays by the X-ray generator 3. The conveying unit 2 has a belt 2a on which the inspected object F is carried. In the conveying unit 2, the inspected object F is conveyed in the conveying direction TD at a predetermined conveying speed by the belt 2a moving in the conveying direction TD. A plurality of inspected objects F are placed on the belt 2a at predetermined intervals. Each inspected object F is sequentially conveyed to the irradiation area R3 by the movement of the belt 2a. In addition, as the inspected objects F conveyed in the conveying unit 2, for example, various items such as food such as meat, fish and shellfish, agricultural products, and snacks, rubber products such as tires, resin products, metal products, resource materials such as minerals, waste, and electronic components or electronic substrates are listed.

[0027] The X-ray generator 3 is a device for irradiating (outputting) X-rays. The X-ray generator 3 irradiates X-rays at least to the conveyor 2. Specifically, the X-ray generator 3 is, for example, a point light source, and irradiates X-rays by diffusing them in a certain irradiation direction (predetermined angle range). The X-ray generator 3 is arranged so that the irradiation direction is on the conveyor 2 side. The X-ray generator 3 is arranged above the conveyor 2 at a predetermined distance from the conveyor 2. The X-ray generator 3 is arranged so that the irradiation area R3 of the X-rays covers the entire width direction (direction intersecting the conveying direction TD) of the inspection object F. In the longitudinal direction (conveying direction TD) of the inspection object F, the X-ray generator 3 sets the predetermined division range in the longitudinal direction as the irradiation area R3. In the X-ray inspection apparatus 1A, the inspection object F is transported by the conveyor 2, and the inspection object F passes through the irradiation area R3 of the X-ray generator 3 as a whole, and the inspection object F is irradiated with X-rays in the longitudinal direction. In the X-ray generator 3, for example, the tube voltage and the tube current are set by the control device 4. The X-ray generator 3 irradiates the conveyor 2 with X-rays having a predetermined energy and radiation dose according to the set tube voltage and tube current.

[0028] The X-ray detection camera 100A detects at least the X-rays that pass through the conveying unit 2 among the X-rays irradiated by the X-ray generator 3 to the conveying unit 2, and outputs X-ray image data based on the X-rays. The X-ray detection camera (radiation detection device) 100A is, for example, an X-ray flat panel sensor or an X-ray sensor camera, and includes a radiation detection element (detection element) 10 having at least one column of pixel lines in which a plurality of pixels are arranged along a pixel arrangement direction. The radiation detection element 10 is a direct conversion type radiation detection element that directly converts incident X-rays into electric charges. The X-ray detection camera 100A generates X-ray image data based on the detected X-rays, and outputs the generated X-ray image data to the control device 4. In addition, the radiation detection element 10 of the X-ray detection camera 100A may be a one-dimensional sensor (single-line sensor) having a pixel line in one column, or may be a two-dimensional sensor having a plurality of pixel lines. As a two-dimensional sensor, a two-dimensional sensor of an area scanning method may also be used. Alternatively, a two-dimensional sensor of a line scan type such as a multi-line sensor composed of a plurality of pixel lines or a TDI (Time Delay Integration) sensor may be used.

[0029] The control device 4 is, for example, a computer such as a PC (Personal Computer). The control device 4 is electrically connected to the X-ray detection camera 100A. The control device 4 controls the X-ray detection camera 100A in a manner that repeatedly captures images in a predetermined detection cycle. When the radiation detection element 10 of the X-ray detection camera 100A has a plurality of pixel lines, the control device 4 sets a predetermined detection cycle in a manner that the X-rays of the plurality of pixel lines that respectively pass through the same area of ​​the inspection object F can be captured. The control device 4 generates an X-ray image based on the X-ray image data output from the X-ray detection camera 100A. For example, the control device 4 joins the X-ray image data of each pixel line output from the X-ray detection camera 100A to generate one X-ray image. In addition, the control device 4 may also generate one X-ray image by averaging or adding the X-ray image data of each pixel line output from the X-ray detection camera 100A. In addition, the control device 4 may be a device independently provided outside the X-ray detection camera 100A, or may be integrated inside the X-ray detection camera 100A.

[0030] In addition, the prescribed detection period may be set, for example, based on at least any one of the distance between multiple pixel lines of the radiation detection element 10, the distance between the X-ray generator 3 and the object F to be inspected on the conveying unit 2 (FOD (Focus Object Distance: source object distance)), and the distance between the X-ray generator 3 and the radiation detection element 10 (FDD (Focus Detector Distance: source sensor distance)). In addition, the prescribed detection period may be set individually based on the pixel width in a direction orthogonal to the pixel arrangement direction of the pixels constituting the pixel line of the radiation detection element 10. In this case, the deviation (delay time) of the detection period between specific multiple pixel lines may be set based on the distance between the multiple pixel lines, the conveying speed of the conveying unit 2, the distance between the X-ray generator 3 and the object F to be inspected on the conveying unit 2 (FOD), and the distance between the X-ray generator 3 and the radiation detection element 10 (FDD).

[0031] The shielding part 5 prevents the X-rays emitted from the X-ray generator 3 from leaking to the outside of the X-ray inspection apparatus 1A. The shielding part 5 is provided so as to surround the irradiation area R3 of the X-ray generator 3. The shielding part 5 is provided with an inlet 5a and an outlet 5b for the conveying part 2 and the inspection object F conveyed by the conveying part 2 to pass through. The inlet 5a is formed on the upstream side of the irradiation area R3 of the X-ray generator 3 in the conveying part 2. The outlet 5b is formed on the downstream side of the irradiation area R3 of the X-ray generator 3 in the conveying part 2. In the X-ray inspection apparatus 1A, the inspection object F conveyed by the conveying part 2 passes through the inlet 5a, the irradiation area R3 of the X-ray generator 3, and the outlet 5b in sequence. The shielding screen 5c is provided between the irradiation area R3 and the inlet 5a and the outlet 5b so as to divide the irradiation area R3 from the inlet 5a and the outlet 5b, thereby preventing the X-rays from leaking to the outside of the X-ray inspection apparatus 1A.

[0032] [Structure of X-ray Inspection Camera] Figure 2 is a structural diagram of the X-ray detection camera 100A. Figure 2 As shown, the X-ray detection camera 100A includes a radiation detection element (detection element) 10 , a first bias power supply 30 (voltage source), a second bias power supply 40 , a control unit 50A, and an input / output interface 60 .

[0033] The radiation detection element 10 is a detection element that directly converts incident X-rays into electric charges, and outputs the result of collecting electric charges for each of a plurality of pixel electrodes as X-ray image data (camera image data). The radiation detection element 10 continuously outputs the X-ray image data. The radiation detection element 10 is operated by the control unit 50A based on a reference clock (described later). The radiation detection element 10 has a semiconductor crystal 21, a signal processing circuit 22, a first electrode 23, a plurality of second electrodes 24, and a plurality of third electrodes 25. In the following, in the radiation detection element 10, the direction in which the semiconductor crystal 21 and the signal processing circuit 22 extend is set as the X direction, and the direction in which the semiconductor crystal 21 and the signal processing circuit 22 are arranged is set as the Y direction.

[0034] The first electrode (bias electrode) 23 is provided on the surface of the semiconductor crystal 21 on the opposite side to the side facing the signal processing circuit 22. The first electrode 23 extends along the pixel arrangement direction, that is, the X direction, and is integrally formed without being divided. A plurality of second electrodes (pixel electrodes) 24 are provided on the surface of the semiconductor crystal 21 on the side facing the signal processing circuit 22. The plurality of second electrodes 24 are arranged along the X direction. A plurality of third electrodes (pixel electrodes) 25 are provided on the surface of the signal processing circuit 22 on the side facing the semiconductor crystal 21. The plurality of third electrodes 25 are arranged along the X direction. Each third electrode 25 corresponds to each second electrode 24 (arranged oppositely in the Y direction), and is electrically connected to the corresponding second electrode 24.

[0035] The semiconductor crystal 21 is a semiconductor crystal that directly converts incident X-rays into electric charges. The semiconductor crystal 21 is composed of semiconductor crystals such as cadmium telluride (CdTe), cadmium zinc telluride (CdZnTe) or thallium bromide (TlBr). By applying a bias voltage to the radiation detection element 10 from the first bias power supply 30, the electric charges generated in the semiconductor crystal 21 travel straight along the Y direction to the second electrode 24. As a result, the electric charges generated directly above each second electrode 24 reach the second electrode 24 located directly below it. The electric charges reaching the second electrode 24 are collected at the third electrode 25 corresponding to the second electrode 24.

[0036] The signal processing circuit 22 is, for example, an ASIC (Application Specific Integrated Circuit). The signal processing circuit 22 is electrically connected to the second electrode 24 via the third electrode 25. The signal processing circuit 22 is a circuit that reads the electrical signal between the first electrode 23 and the second electrode 24, and generates X-ray image data (camera image data) based on the read electrical signal. The signal processing circuit 22 collects electric charge for each of the plurality of third electrodes 25, and outputs the collected result as X-ray image data to the control unit 50A. The signal processing circuit 22 continuously outputs the X-ray image data to the control unit 50A. In addition, the X-ray image data is composed of a digital signal obtained by converting a voltage signal detected by the signal processing circuit 22. The X-ray image data may be the X-ray image itself, or may be information for generating an X-ray image.

[0037] The first bias power supply 30 applies a bias voltage to the radiation detection element 10. The first bias power supply 30 is electrically connected to the first electrode 23. The first bias power supply 30 applies a bias voltage to the radiation detection element 10 according to a control signal from the control unit 50A. The first bias power supply 30 applies a high voltage (HV: High Voltage) to the radiation detection element 10, for example. The first bias power supply 30 is configured in a manner to perform a reset operation (described later) on the radiation detection element 10. The second bias power supply 40 is electrically connected to the signal processing circuit 22 to provide power for the signal processing circuit 22 to operate. The second bias power supply 40 may also be a reference potential when the first bias power supply 30 applies a bias voltage. In addition, the bias voltage (ON voltage value) applied to the radiation detection element 10 by the first bias power supply 30 may also be arbitrarily set, for example, to -1000V.

[0038] The control unit 50A is electrically connected to the signal processing circuit 22 and the first bias power supply 30. The control unit 50A is composed of, for example, an FPGA (Field-Programmable Gate Array). The control unit 50A controls the radiation detection element 10 by controlling the signal processing circuit 22 and the first bias power supply 30 based on a reference clock input from the outside of the X-ray detection camera 100A. In addition, the control unit 50A can also control the radiation detection element 10 by controlling the signal processing circuit 22 and the first bias power supply 30 based on a reference clock generated inside the X-ray detection camera 100A. Through either of them, the control unit 50A outputs a control signal for operating the signal processing circuit 22 to the signal processing circuit 22. The control unit 50A obtains the X-ray image data output by the signal processing circuit 22, and outputs the X-ray image data to the outside of the X-ray detection camera 100A. For example, the control unit 50A outputs the X-ray image data to the control device 4 via the input / output interface 60. The control unit 50A outputs a control signal for operating the first bias power supply 30 to the first bias power supply 30. In addition, the control unit 50A may also obtain the control signal from the control device 4 via the input / output interface 60. In addition, when the X-ray image data is information for generating an X-ray image, the control unit 50A may also generate an X-ray image based on the obtained X-ray image data.

[0039] [Functional structure of control unit] Figure 3 is a block diagram showing the functional structure of the control unit 50A. Figure 3 As shown, the control unit 50A includes an acquisition unit 51, a determination unit 52A, and a voltage control unit 53. The following describes each functional unit of the control unit 50A in detail. The control unit 50A detects the brightness (background brightness) of the X-ray image data and controls the application of the high voltage (HV) of the first bias power supply 30 based on the detection result.

[0040] The acquisition unit 51 acquires a control signal for controlling the imaging of the X-ray detection camera 100A from the control device 4. The acquisition unit 51 outputs the acquired control signal to the signal processing circuit 22 or the first bias power supply 30. The acquisition unit 51 acquires X-ray image data from the signal processing circuit 22. The acquisition unit 51 outputs the X-ray image data to the determination unit 52A. In addition, when the X-ray image data is information for generating an X-ray image, the acquisition unit 51 may also generate an X-ray image based on the acquired X-ray image data, and output the generated X-ray image to the determination unit 52A. In addition, the acquisition unit 51 may also acquire a control signal generated inside the control unit 50A.

[0041] The determination unit 52A acquires the X-ray image data from the acquisition unit 51. The determination unit 52A performs determination processing for determining whether the reset operation can be performed in the radiation detection element 10 based on the acquired X-ray image data. That is, the determination unit 52A performs the above determination processing based on the X-ray image data output from the radiation detection element 10.

[0042] The reset action is an action for eliminating the internal electric field change of the so-called polarization phenomenon (Polarization) generated inside the semiconductor crystal 21 when the semiconductor crystal 21 is continuously irradiated with X-rays. Specifically, the reset action is an action of performing voltage control on the radiation detection element 10 in a manner that does not collect charge in the semiconductor crystal 21. For example, the reset action can be an action of stopping the voltage application to the radiation detection element 10 itself, or an action of applying a reverse bias voltage (a bias voltage opposite to the voltage normally applied) to the radiation detection element 10. In addition, the voltage (off voltage value) applied to the radiation detection element 10 when the first bias power supply 30 performs the reset action can also be arbitrarily set, for example, it can be 0V or 10V. In addition, the period for performing the reset action can be as long as the period required for the self-polarization phenomenon in the semiconductor crystal 21 to recover. The period for performing the reset action can also be a fixed value, for example, it can also be 1 millisecond. In addition, the period for performing the reset action can also be periodically (cyclically) changed. For example, 1 millisecond and 2 milliseconds can also be set as the period for alternating the reset action. Furthermore, since the signal processing circuit 22 cannot collect charges when performing the reset operation, it cannot generate X-ray image data.

[0043] Specifically, the determination unit 52A performs a determination process for determining whether the X-rays have penetrated the inspection object F based on the X-ray image data. More specifically, the determination unit 52A performs a determination process for determining whether the brightness value of the X-ray image data exceeds a predetermined threshold value. In the determination process, if the brightness value of the X-ray image data exceeds the predetermined threshold value, the determination unit 52A determines that the X-rays incident on the radiation detection element 10 have not penetrated the inspection object F. In the determination process, if the determination unit 52A determines that the X-rays have not penetrated the inspection object F based on the X-ray image data, it determines that the reset operation can be performed. The determination unit 52A outputs the result of the execution of the determination process to the voltage control unit 53. In addition, the case where "the X-rays (radiation) have not penetrated the inspection object F (object)" is the case where "the inspection object F does not exist in the irradiation region R3". In addition, the predetermined threshold value only needs to exceed the brightness of the X-ray image data when the inspection object F exists in the irradiation region R3. In addition, the predetermined threshold value may be lower than the brightness of the X-ray image data when the inspection object F does not exist in the irradiation region R3. The predetermined threshold value may also be preset in the control unit 50A.

[0044] When the determination unit 52A performs a reset action through the voltage control unit 53, it may not perform a new determination process thereafter until a prescribed period has passed. In this case, the determination unit 52A performs a new determination process after a prescribed period has passed. The prescribed period is a period during which no reset action is required. The period during which no reset action is required is a period during which the above-mentioned polarization phenomenon is not a problem after the reset action. As described above, X-ray image data cannot be generated during the reset action. Therefore, it is preferable to perform the reset action within the minimum necessary limit. By appropriately setting and managing the period during which no reset action is required, X-ray image data can be generated more appropriately. The determination unit 52A may also determine whether a prescribed period has passed by counting the reference clock. In this case, the determination unit 52A may also start executing the determination process when it is determined that a prescribed period has passed.

[0045] The determination unit 52A may also manage a predetermined period (a period during which a reset operation is not required) by setting a flag. The flag here records that a reset operation has been performed. The determination unit 52A may, for example, set a flag (flag: 1) when a reset operation is performed, and may, for example, release the flag (flag: 0) when a new image of the inspection object F is started (when the brightness value of the X-ray image data is lower than a predetermined threshold value). By such flag management, control can be achieved in which a reset operation is not performed during the period during which the flag is set.

[0046] When the determination unit 52A determines that the reset operation can be performed, the voltage control unit 53 controls the first bias power supply 30 so as to perform the reset operation. In addition, an arbitrary delay time may be set between the determination process of the determination unit 52A and the execution of the reset operation by the voltage control unit 53. The delay time is, for example, the processing time in the X-ray detection camera 100A.

[0047] Reference Figure 4 In the example shown, the functions of the determination unit 52A and the voltage control unit 53 are described in more detail. Figure 4 (a) is a diagram showing a conveying unit 2 for conveying an inspection object F in a conveying direction TD, and a radiation detection element 10 provided on a surface of the conveying unit 2 opposite to a surface on the side facing the inspection object F. Figure 4 It is a diagram showing (b) the brightness value I of the X-ray image data generated by the radiation detection element 10 when each position P1 to P5 of the belt 2a in the conveying section 2 passes directly above the radiation detection element 10, (c) whether the bias voltage applied to the radiation detection element 10 by the first bias power supply 30 is turned on or off, and (d) the state of the flag. Figure 4 The vertical axes of (b) to (d) represent time, and indicate times T1 to T5 when the respective positions P1 to P5 of the belt 2 a pass directly above the radiation detection element 10 . Figure 4 The horizontal axis of (b) represents the brightness value I of the X-ray image data. Figure 4 In order to simplify the description, the width of the radiation detection element 10 along the transport direction TD is not considered.

[0048] As a premise, before the position P1 passes directly above the radiation detection element 10, the bias voltage is supplied to the radiation detection element 10 from the first bias power supply 30 (bias voltage: on), and the predetermined period (flag: 1) has not elapsed since the previous reset operation was performed. As described above, the determination unit 52A does not perform the determination of whether the brightness value I of the X-ray image data exceeds the predetermined threshold value I while the flag (flag: 1) is set. A Determination processing.

[0049] First, at time T1 when the position P1 passes directly above the radiation detection element 10 , the inspection object F1 starts passing directly above the radiation detection element 10 . Figure 4 In the example shown, at time T1, the brightness value of the X-ray image data decreases and falls below a predetermined threshold value I A In this case, the determination unit 52A determines that the predetermined period has passed and releases the flag (flag: 0). In addition, the flag release may be implemented based on information other than the change in the brightness value of the X-ray image data. For example, the predetermined period may also take into account the transport interval of the inspection object F1, so as to correspond to the time T1 when the position P1 passes directly above the radiation detection element 10 (the brightness value of the X-ray image data decreases and falls below the predetermined threshold value I). A The flag is set in a manner consistent with the time (the time at which the predetermined period of time has elapsed), and the flag is released at the time when the predetermined period of time has elapsed. The determination unit 52A periodically performs the determination process during the flag release period.

[0050] Next, at time T2 when position P2 passes directly above the radiation detection element 10, the object F1 ends passing directly above the radiation detection element 10. At this time, the brightness value I of the X-ray image data increases and exceeds a predetermined threshold value I A . Therefore, the determination unit 52A determines that the X-rays incident on the radiation detection element 10 have not passed through the inspection object F, and a reset action can be performed. The voltage control unit 53 controls the first bias power supply 30 in a manner that performs an action of stopping the application of voltage to the radiation detection element 10 (bias voltage: off), that is, a reset action. The determination unit 52A sets a flag (flag: 1) to record that the reset action has been performed. That is, the voltage control unit 53 disconnects the first bias power supply 30 at the moment when the brightness of the X-ray image data exceeds a prescribed threshold value detected by the determination unit 52A. In addition, for the timing of the determination processing of the determination unit 52A, an arbitrary delay time can be set before the moment when the voltage control unit 53 controls the first bias power supply 30 and performs the reset action.

[0051] Next, at time T3 when the position P3 passes directly above the radiation detection element 10, the voltage control unit 53 ends the reset operation and controls the first bias power supply 30 (bias voltage: on) so as to apply a bias voltage to the radiation detection element 10. That is, the voltage control unit 53 activates the first bias power supply 30 again.

[0052] Next, at time T4 when the position P4 passes directly above the radiation detection element 10 , the inspection object F2 starts passing directly above the radiation detection element 10 . Figure 4 In the example shown, at time T4, the brightness value of the X-ray image data decreases and falls below a predetermined threshold value I A In this case, the determination unit 52A clears the flag (flag: 0).

[0053] Finally, at time T5 when position P5 passes directly above the radiation detection element 10, the object F2 ends passing directly above the radiation detection element 10. At this time, the brightness value I of the X-ray image data increases and exceeds the predetermined threshold value I. A Therefore, the determination unit 52A determines that the reset operation can be performed, similarly to the time T2. The voltage control unit 53 controls the first bias power supply 30 so that the reset operation is performed. The determination unit 52A sets a flag (flag: 1) to record that the reset operation has been performed.

[0054] In addition, as a premise of control, the distance between the inspection objects F and the inspection objects F is greater than the sum of the width of the radiation detection element 10 along the conveying direction TD and the distance obtained by multiplying the time required for the reset operation by the conveying speed of the conveyor 2. The X-ray detection camera 100A may have only one radiation detection element 10. That is, in the X-ray detection camera 100A, only one row of sensors that expose X-rays may be provided.

[0055] Figure 5 It is a schematic diagram showing the conveying unit 2 that conveys the inspection targets F1 and F2. Figure 5 1 shows the moment when the inspection object F2 finishes passing directly above the radiation detection element 10 . Figure 5 In the example shown, the first bias power supply 30 in the radiation detection element 10 starts the reset operation. At this time, if the reset operation is not completed before the inspection object F1 starts to pass directly above the radiation detection element 10, the radiation detection element 10 cannot capture X-rays that pass through the inspection object F1. Therefore, the width W of the radiation detection element 10 along the conveying direction TD is separated between the inspection object F1 and the inspection object F2. A1 , and the distance D obtained by multiplying the time required for the reset operation by the transport speed of the transport unit 2 A1 The total distance is more than .

[0056] It should be noted that the determination region used for the determination process of the determination unit 52A only needs to include a part of the detection region where the radiation detection element 10 can detect X-rays. Figure 6 1 is a diagram showing the determination region R used in the determination process of the determination unit 52A. A Schematic diagram. Figure 6 As shown in (a), the determination area R A Alternatively, the entire detection region R (the entire field of view of the X-ray detection camera 100A) may be used. In this case, the determination region R A The brightness value of the determination area R A The maximum value of the overall brightness value can also be the determination area R A At least one of the minimum value, average value, and median value of the overall brightness value. Figure 6 As shown in (b), the determination area R A It may be a part of the detection area R (only a part of the field of view of the X-ray detection camera 100A). A The determination area R is specified in advance by at least one of the determination unit 52A, the control device 4, and the user. A It only needs to be a part of the detection area R, and therefore it may be composed of a plurality of mutually discontinuous areas.

[0057] In addition, the radiation detection element 10 has a width along the transport direction TD. In this case, the period from "the moment when the inspection object F starts to pass directly above the radiation detection element 10" to "the moment when the inspection object F ends to pass directly above the radiation detection element 10" is a period including the entire length along the transport direction TD of the radiation detection element 10 when the inspection object F transported in the transport direction TD is observed from the X-ray generator 3.

[0058] In addition, the determination unit 52A may determine whether to perform the determination process by the passage of the above-mentioned prescribed period and triggers other than flags. For example, the determination unit 52A may not perform the determination process until the amount of change in brightness value between a plurality of X-ray image data continuously output from the radiation detection element 10 exceeds a prescribed threshold value after performing the reset operation, and may perform the determination process when the amount of change in brightness value exceeds the prescribed threshold value. In addition, when the X-ray image data is information for generating an X-ray image, the determination unit 52A may perform the determination process on the amount of change in brightness value between X-ray images generated based on the X-ray image data.

[0059] In the first embodiment, the determination unit 52A may not perform determination processing before detecting a rising edge for the shift in the brightness value of the X-ray image data after the reset operation is performed, and may perform determination processing when a rising edge is detected. Alternatively, the determination unit 52A may perform determination processing when a falling edge is detected.

[0060] The rising edge is a portion of the graph in which the vertical axis represents the brightness value and the horizontal axis represents the time, where the brightness value rises sharply (becomes larger). In the rising edge, the change in the brightness value in a small time exceeds a predetermined threshold. The small time is a time that is sufficiently smaller than the time required for the object F to pass directly above the radiation detection element 10. In addition, the falling edge described later is a portion of the above graph in which the brightness value drops sharply (becomes smaller).

[0061] Figure 4 In the example shown, the brightness value does not rise sharply during the period from when the determination unit 52A performs the reset operation at time T2 to before time T5, and therefore the determination process is not performed. When the brightness value I of the X-ray image data rises sharply at time T5, the determination unit 52A detects a rising edge in the shift of the brightness value of the X-ray image data and performs the determination process. In addition, when the brightness value I of the X-ray image data falls sharply at time T4, the determination unit 52A may detect a falling edge in the shift of the brightness value of the X-ray image data and perform the determination process. When the rising edge and the falling edge are detected, the above-mentioned flag management is not required.

[0062] In addition, the determination unit 52A determines that the brightness value I of the X-ray image data is lower than a predetermined threshold value I. A When the flag is released, the flag is released, but the present invention is not limited to this. For example, the determination unit 52A may also be lower than the threshold value I. A The flag is unset when the other thresholds are reached.

[0063] In addition, the determination unit 52A may always execute the determination process. In this case, the reset operation may be executed only when a predetermined period of time has passed during which the reset operation is unnecessary and the determination unit 52A determines that the reset operation is executable.

[0064] Figure 7 1 is a flowchart showing a process for executing a reset action of the radiation detection method performed by the X-ray inspection apparatus 1A. Figure 7As shown, first, the voltage control unit 53 controls the first bias power supply 30 in such a manner as to apply a bias voltage to the radiation detection element 10 (step S1: voltage application step). Next, the acquisition unit 51 acquires X-ray image data from the radiation detection element 10 (step S2: acquisition step). Next, the determination unit 52A determines whether the reset action can be performed based on the X-ray image data (step S3: determination step). When it is determined that the reset action can be performed (step S3: YES), the voltage control unit 53 controls the first bias power supply 30 in such a manner as to perform the reset action (step S4: reset step). When it is determined that the reset action cannot be performed (step S3: NO) and when the reset action is performed (step S4), the above-mentioned processing ends.

[0065] Hereinafter, the prior art and comparative examples will be described in detail, and the effects of the X-ray inspection apparatus 1A, the X-ray detection camera 100A, and the radiation detection method according to the first embodiment will be described.

[0066] Previously, CdTe and CdZnTe were used as materials for direct conversion radiation detection elements such as non-destructive counting detectors. Such direct conversion radiation detection elements can collect charges generated by conversion of X-rays to electrodes of a signal processing circuit by applying a high voltage (HV). However, in direct conversion radiation detection elements, if X-rays are continuously irradiated, changes in the internal electric field occur, which is called polarization, causing degradation of X-ray image data output from the radiation detection element.

[0067] In order to prevent the above-mentioned degradation of X-ray image data, in the radiation detection apparatuses described in Patent Documents 1 to 3, the voltage applied to the direct conversion type radiation detection element is temporarily stopped to allow the direct conversion type radiation detection element to recover from the self-polarization phenomenon.

[0068] In addition, in order to prevent the degradation of X-ray image data as described above, it is considered to periodically disconnect the applied voltage. For example, in the X-ray detection camera of the comparative example, it is considered to set the time obtained by multiplying the imaging cycle (line rate) of the multiple line sensors contained in the camera by the number of line sensors (number of segments) as one period, and periodically set the period during which the applied voltage to the direct conversion type radiation detection element is disconnected (hereinafter referred to as "insensitive time"). In addition, the insensitive time is the time until the polarization phenomenon of the direct conversion type radiation detection element is restored, and is therefore a certain length of time. In addition, during the insensitive time, the direct conversion type radiation detection element cannot output X-ray image data.

[0069] The X-ray detection camera of the comparative example has two problems. The first problem is that in the X-ray detection camera of the comparative example, the shorter the time (hereinafter referred to as "exposure time") for exposing the direct conversion type radiation detection element to X-rays, the higher the ratio of the insensitive time to the exposure time, i.e., the insensitive time ratio, increases, thereby causing the sensitivity of the direct conversion type radiation detection element to decrease. Figure 8 This is a table showing changes in the dead time ratio when the transport speed is changed. Figure 8 In the example shown, 60 lines with a pixel size of 100 μm are configured. If the conveying speed increases, the line rate increases and the exposure time per cycle decreases. At this time, since the length of the insensitive time is fixed, the insensitive time ratio increases. Since the image quality (SNR: Signal Noise Ratio) of the X-ray detection camera depends on the amount of X-rays captured, the increase in the insensitive time ratio leads to a decrease in the image quality of the X-ray detection camera.

[0070] In the X-ray camera of the comparative example, in order to suppress the degradation of the image quality of the X-ray detection camera caused by the reduction of the insensitive time ratio, it is considered to increase the dose of X-rays incident on the X-ray detection camera during the period when the X-ray detection camera is shooting. In this case, for example, a method of increasing the dose of X-rays irradiated per unit time is considered. However, if the limit of the dose that can be irradiated by the X-ray source, the allowable dose of the subject, and the dose leaked from the device are considered, then the increase in the dose has a limit. In addition, for example, consider shooting at a lower speed with the X-ray detection camera. However, this results in a reduction in the inspection speed of the object to be inspected, which impairs the convenience of the user.

[0071] The second problem is that, in the X-ray detection camera of the comparative example, parallax occurs between the X-ray image data groups after the addition process in an output image obtained by adding a plurality of X-ray image data.

[0072] Generally, in an X-ray detection camera, while the object to be inspected passes through the imaging area of ​​the camera, each direct conversion type radiation detection element continuously outputs X-ray image data. These X-ray image data are added together to generate an output image. At this time, the X-ray image data from all direct conversion type radiation detection elements are added together at each position in the output image, so that parallax does not occur between the X-ray image data groups after the addition process.

[0073] However, in the X-ray detection camera of the comparative example, since the applied voltage to each direct conversion type radiation detection element is periodically disconnected, a dead time is generated during the period when the object to be inspected passes through the camera's imaging area. Therefore, during this dead time, the above-mentioned addition process is performed in a state where the X-ray image data to be output by each direct conversion type radiation detection element is missing. At this time, at each position in the output image, the X-ray image data from a part of the direct conversion type radiation detection elements are not added, so parallax between the X-ray image data groups after the addition process occurs.

[0074] Fig. 9 1 is a schematic diagram showing the inspection target object F transported on the transport unit 2000 . Fig. 9 In (a) and (c), each line sensor 1001 to 1006 of the X-ray detection camera 1000 is exposed to X-rays and is in a state where it can output X-ray image data. Fig. 9 In (b), each line sensor 1001 to 1006 becomes insensitive. Fig. 9 In the example shown, the front end F of the object F to be inspected a exist Fig. 9 In (a), the line sensors 1001 and 1002 take pictures. Fig. 9 The rear end F of the object F to be inspected is photographed by the line sensor 1006 in (c). b exist Fig. 9 In (c), the front end F is captured by the line sensors 1004 to 1006. a The reflected part and the back end F b In the projected portion, the line sensors at the output ends of the added X-ray image data are different from each other. Thus, parallax between the added X-ray image data groups occurs in the output image after the addition process.

[0075] In contrast to the above-mentioned comparative example, in the X-ray detection camera 100A of the first embodiment, it is determined whether or not a reset operation can be performed to control the voltage of the radiation detection element 10 in a manner that the radiation detection element 10 does not collect charges, based on the X-ray image data output from the radiation detection element 10. According to such a configuration, it is determined whether or not a reset operation can be performed, taking into account information indicated by the X-ray image data output from the radiation detection element 10, that is, the external condition of the X-ray detection camera 100A. Thus, for example, it is possible to determine whether or not the X-ray incident to the X-ray detection camera 100A has passed through the inspection object F, based on the X-ray image data. Thus, for example, at the time when the X-ray incident to the X-ray detection camera 100A has not passed through the inspection object F, the first bias power supply 30 can perform a reset operation, and at the time when the X-ray incident to the X-ray detection camera 100A has passed through the inspection object F, the first bias power supply 30 can perform a voltage control on the radiation detection element 10 in a manner that the X-ray detection camera 100A collects charges. As a result, the occurrence of the polarization phenomenon of the radiation detection element 10 can be suppressed, and when the X-rays incident on the X-ray detection camera 100A pass through the inspection object F, the X-rays can be detected more reliably.

[0076] In this way, in the X-ray detection camera 100A, by appropriately controlling the on and off of the bias voltage application (high voltage reset), the generation of the insensitive time of the X-ray detection camera 100A during the inspection of the inspection object F can be suppressed, and high-sensitivity inspection can be achieved. In addition, the user's convenience can be maintained, and the image quality degradation of the X-ray image data output from the X-ray detection camera 100A can be suppressed. Furthermore, the structure of using the X-ray detection camera 100A is not as Fig. 9 As in the comparative example shown, the structure in which the video recording is cyclically disconnected and the video recording is continued at the moment when the X-rays pass through the inspected object F, thereby suppressing the parallax between the X-ray image data groups after the addition processing in one X-ray image in which multiple X-ray image data output from the X-ray detection camera 100A are added.

[0077] In the X-ray detection camera 100A of the first embodiment, when the determination unit 52A determines that the X-rays have not passed through the inspection object F based on the X-ray image data during the determination process, it determines that the reset operation can be performed. According to such a configuration, when the X-rays incident to the X-ray detection camera 100A have not passed through the inspection object F, the reset operation is performed by the first bias power supply 30, and when the X-rays incident to the X-ray detection camera 100A have passed through the inspection object F, the voltage of the radiation detection element 10 can be controlled by the first bias power supply 30 in such a manner that the X-ray detection camera 100A collects the charge. As a result, the occurrence of the polarization phenomenon of the radiation detection element 10 can be suppressed, and when the X-rays incident to the X-ray detection camera 100A have passed through the inspection object F, the X-rays can be detected more reliably.

[0078] In the X-ray detection camera 100A of the first embodiment, when the brightness value of the X-ray image data exceeds a predetermined threshold value during the determination process, the determination unit 52A determines that the X-rays have not passed through the inspection object F. According to such a configuration, it is possible to more reliably determine whether the X-rays incident to the X-ray detection camera 100A have passed through the inspection object F. Thus, at the moment when the X-rays incident to the X-ray detection camera 100A have not passed through the inspection object F, the reset operation can be more reliably performed.

[0079] In the X-ray detection camera 100A of the first embodiment, the radiation detection element 10 continuously outputs X-ray image data. The determination unit 52A may not perform determination processing until the amount of change in brightness value between a plurality of X-ray image data continuously outputted from the radiation detection element 10 exceeds a predetermined threshold value after performing a reset operation, and may perform determination processing when the amount of change exceeds the predetermined threshold value. According to such a structure, after performing a reset operation, the determination processing is restarted after the imaging of the inspection object F by the X-ray detection camera 100A ends. In the first embodiment, after performing a reset operation, the determination unit 52A performs determination processing when a rising edge is detected in the shift of brightness value of the X-ray image data. Thus, after performing a reset operation, the reset operation can be suppressed until the polarization phenomenon needs to be eliminated again in the X-ray detection camera 100A. As a result, the X-ray detection camera 100A can be operated more efficiently.

[0080] In the X-ray detection camera 100A of the first embodiment, the determination unit 52A does not perform determination processing until a predetermined period, which is a period during which the reset operation is not required, has passed after the reset operation is performed, and performs determination processing when the predetermined period has passed. According to such a configuration, the reset operation can be suppressed from being performed until the depolarization phenomenon is required again in the X-ray detection camera 100A after the reset operation is performed. As a result, the X-ray detection camera 100A can be operated more efficiently.

[0081] In the X-ray detection camera 100A of the first embodiment, the radiation detection element 10 operates based on the reference clock. The determination unit 52A can also determine whether a predetermined period has passed by counting the reference clock. According to such a structure, it is possible to determine whether a predetermined time has passed with better accuracy based on the reference clock. Thus, after the reset action is performed, until the polarization phenomenon needs to be eliminated again in the X-ray detection camera 100A, the reset action can be more reliably suppressed.

[0082] In the X-ray detection camera 100A of the first embodiment, the reset operation is either an operation of stopping the voltage application to the radiation detection element 10 or an operation of applying a reverse bias voltage to the radiation detection element 10. With such a configuration, the polarization phenomenon in the X-ray detection camera 100A can be eliminated more reliably.

[0083] In the X-ray inspection device 1A of the first embodiment, the X-rays irradiated from the X-ray generator 3 are incident on the radiation detection element 10. The inspection object F transported by the transport unit 2 passes through the irradiation area R3 of the X-rays. And, based on the X-ray image data output from the radiation detection element 10, it is determined whether a reset operation of performing voltage control on the radiation detection element 10 in a manner that the radiation detection element 10 does not collect charges can be performed. According to such a structure, it is determined whether the reset operation can be performed in consideration of the information shown in the X-ray image data output from the radiation detection element 10, that is, the external condition of the X-ray detection camera 100A. Thus, for example, since the irradiation area R3 of the X-rays is photographed by the radiation detection element 10, it is possible to determine whether the X-rays have passed through the inspection object F based on the X-ray image data. Thus, for example, when the X-ray incident to the X-ray detection camera 100A does not pass through the inspection object F, the first bias power supply 30 can perform a reset operation, and when the X-ray incident to the X-ray detection camera 100A passes through the inspection object F, the first bias power supply 30 can perform voltage control on the radiation detection element 10 in such a manner that charges are collected by the radiation detection element 10. As a result, the generation of polarization of the radiation detection element 10 can be suppressed, and when the X-ray incident to the radiation detection element 10 passes through the inspection object F, the X-ray can be detected more reliably.

[0084] In the radiation detection method of the first embodiment, in the determination step, it is determined whether a reset operation can be performed to control the voltage of the radiation detection element 10 in a manner that the radiation detection element 10 does not collect charges, based on the X-ray image acquired in the acquisition step. According to such a configuration, it is determined whether the reset operation can be performed, taking into account information indicated by the X-ray image data output from the radiation detection element 10, that is, the external condition of the X-ray detection camera 100A. Thus, for example, it can be determined based on the X-ray image data whether the X-ray incident to the X-ray detection camera 100A has passed through the inspection object F. Thus, for example, at the time when the X-ray incident to the X-ray detection camera 100A has not passed through the inspection object F, the first bias power supply 30 can perform the reset operation, and at the time when the X-ray incident to the X-ray detection camera 100A has passed through the inspection object F, the first bias power supply 30 can perform the voltage control of the radiation detection element 10 in a manner that the radiation detection element 10 collects charges. As a result, the occurrence of the polarization phenomenon of the radiation detection element 10 can be suppressed, and when the X-rays incident on the radiation detection element 10 pass through the inspection object F, the X-rays can be detected more reliably.

[0085] [Second embodiment] [Structure of X-ray Inspection Device] Fig.10 1B is a block diagram showing an X-ray inspection apparatus 1B according to the second embodiment. Fig.10 As shown, the X-ray inspection apparatus 1B of the second embodiment is different from the X-ray inspection apparatus 1A of the first embodiment in that an X-ray detection camera 100B is provided instead of the X-ray detection camera 100A. The X-ray detection camera 100B is different from the X-ray detection camera 100A in that a control unit 50B is provided. The X-ray inspection apparatus 1B of the second embodiment is different from the X-ray inspection apparatus 1A of the first embodiment in that an inspection object M is arranged between a plurality of inspection objects F.

[0086] The detection object M is arranged at a place where the inspection object F is not arranged. The detection object M is, for example, a light-reducing object that absorbs (dims) X-rays more obviously than a shielding object that shields X-rays and the inspection object F. The detection object M is, for example, made of lead, tungsten, iron, steel, etc. The detection object M only needs to be arranged in a manner that a part of the detection area where X-rays can be detected includes a part of the detection object M.

[0087] Fig.11 is a schematic diagram showing an example of the shape of the detection object M. The detection object M only needs to be arranged within the range that can be photographed by the X-ray detection camera 100B. Fig.11As shown in (a), it may also extend to the entire detection area R (the entire field of view of the X-ray detection camera 100B). That is, the detection object M may also extend to the entire width of the conveying section 2 along a direction intersecting the conveying direction TD. In this case, the brightness value of the detection object M in the X-ray image data may be, for example, the maximum brightness value of the entire detection object M, or at least any one of the minimum, average, and central values ​​of the brightness value of the entire detection object M. The detection object M may also be arranged in a part of the detection area R, such as Fig.11 As shown in (b), the detection object M may be arranged on one side of the conveying unit 2 in the direction intersecting the conveying direction TD. Furthermore, the detection object M may be composed of a plurality of mutually discontinuous parts.

[0088] In addition, the thickness of the object M is not particularly limited. Specifically, in the present embodiment, the X-ray generator 3 is a point light source, and the X-rays are obliquely incident on the object M. Here, when the object has a thickness, the X-ray transmission length of the entire object is not uniform. In this case, even if the thickness of the object is uniform, the brightness of the object in the X-ray image varies for each part of the object. Fig.12 In the example shown, at the end of the detection object M having thickness, the X-ray transmission length is shorter than that of the central part of the detection object M, resulting in different brightness between the end and the central part of the detection object M in the X-ray image. Therefore, the thickness of the detection object M is preferably thinner than 50 mm. In addition, the detection object M may also be thicker than 0.1 mm. In addition, in the case where the detection object M is a shielding object, the required thickness of the detection object M is different depending on the material and density of the detection object M. The influence on the thickness of the detection object M is also different depending on the light source, the X-ray detection camera and the optical system of the object to be inspected. Based on the above, the thickness of the detection object M is preferably a thickness that fully exerts the shielding ability and is as thin as possible.

[0089] [Structure of X-ray Inspection Camera] like Figure 2 As shown, the X-ray detection camera 100B is different from the X-ray detection camera 100A in that it has a control unit 50B instead of the control unit 50A. Figure 3 2 is a block diagram showing the functional structure of the control unit 50B. The control unit 50B is different from the control unit 50A in that the control unit 50B has a determination unit 52B instead of the determination unit 52A. The control unit 50B detects a specific object in the X-ray image data and controls the application of the high voltage (HV) of the first bias power supply 30 according to the detection result. Specifically, the control unit 50B turns off the first bias power supply 30 at the time when the detection object M is detected in the X-ray image data.

[0090] The determination unit 52B, unlike the determination unit 52A, performs a determination process for determining whether the brightness value of the X-ray image data is lower than a predetermined threshold value. In the determination process, the determination unit 52B determines that the X-rays incident on the radiation detection element 10 have not passed through the inspection object F when the brightness value of the X-ray image data is lower than the predetermined threshold value. In addition, the determination unit 52B outputs the determination result to the voltage control unit 53. In the second embodiment, the predetermined threshold value only needs to be lower than the brightness of the X-ray image data when the inspection object F exists in the irradiation region R3 and higher than the brightness of the X-ray image data when the inspection object M exists in the irradiation region R3.

[0091] In the second embodiment, when the inspection object M is a shielding object that shields X-rays, the determination unit 52B performs a determination process of determining whether the brightness value of the X-ray image data is below a predetermined threshold value. In the determination process, the determination unit 52B determines that the X-rays incident on the radiation detection element 10 have not passed through the inspection object F when the brightness value of the X-ray image data is below a predetermined threshold value.

[0092] The determination unit 52B performs a new determination process when a predetermined period has passed, similarly to the determination unit 52A. For example, the determination unit 52B can also manage the predetermined period by setting a flag, similarly to the determination unit 52A. However, the determination unit 52B is different from the determination unit 52A in that, for example, when the imaging of the detection object M is completed (when the brightness value of the X-ray image data exceeds a predetermined threshold value), the flag is released (flag: 0).

[0093] Reference Fig.13 In the example shown, the functions of the determination unit 52B and the voltage control unit 53 are described in more detail. Fig.13 (a) is a diagram showing a conveying unit 2 for conveying an inspection object F in a conveying direction TD, and a radiation detection element 10 provided on a surface of the conveying unit 2 opposite to a surface on the side facing the inspection object F. Fig.13 It is a diagram showing (b) the brightness value I of the X-ray image data generated by the radiation detection element 10 when each position Q1 to Q6 of the belt 2a in the conveying section 2 passes directly above the radiation detection element 10, (c) the bias voltage applied to the radiation detection element 10 by the first bias power supply 30 is turned on or off, and (d) a specified period after the reset action is performed. Fig.13 The vertical axes of (b) to (d) represent time, and indicate times t1 to t6 when the respective positions Q1 to Q6 of the belt 2 a pass directly above the radiation detection element 10 . Fig.13 The horizontal axis of (b) represents the brightness value I of the X-ray image data. Fig.13 In order to simplify the description, the width of the radiation detection element 10 along the transport direction TD is not considered.

[0094] As a premise, before the position Q1 passes directly above the radiation detection element 10, the bias voltage is supplied from the first bias power supply 30 to the radiation detection element 10 (bias voltage: on). At this time, a predetermined period has passed since the previous reset operation was performed (flag: 0). As described above, the determination unit 52 periodically performs the determination of whether the brightness value I of the X-ray image data is lower than the predetermined threshold value I during the flag release period (flag: 0). B Determination processing.

[0095] First, at time t1 when position Q1 passes directly above the radiation detection element 10, the object F1 starts to pass directly above the radiation detection element 10. At this time, the brightness value of the X-ray image data decreases. Next, at time t2 when position Q2 passes directly above the radiation detection element 10, the object F1 ends passing directly above the radiation detection element 10. At this time, the brightness value of the X-ray image data increases.

[0096] Next, at time t3 when position Q3 passes directly above the radiation detection element 10, the object M begins to pass directly above the radiation detection element 10. At this time, the brightness value of the X-ray image data becomes significantly smaller and falls below a predetermined threshold value I B Therefore, the determination unit 52B determines that the X-rays incident on the radiation detection element 10 have not passed through the inspection object F, and the reset operation can be performed. The voltage control unit 53 controls the first bias power supply 30 in such a manner as to perform an operation of stopping the application of voltage to the radiation detection element 10 (bias voltage: off), i.e., a reset operation. The determination unit 52A sets a flag (flag: 1) recording that the reset operation has been performed. The determination unit 52B does not perform the determination process while the flag is set (flag: 1).

[0097] Next, at time t4 when the position Q4 passes directly above the radiation detection element 10 , the voltage control unit 53 ends the reset operation and controls the first bias power supply 30 so as to apply a bias voltage to the radiation detection element 10 (bias voltage: on).

[0098] Finally, at time t5 when the position Q5 passes directly above the radiation detection element 10 , the object M ends passing directly above the radiation detection element 10 . Fig.13 In the example shown, at time t5, the brightness value of the X-ray image data increases and exceeds a predetermined threshold value I B In this case, the determination unit 52B determines that the predetermined period has elapsed, and releases the flag (flag: 0).

[0099] Furthermore, as a premise, the downstream end of the inspection object M is spaced from the inspection object F by a distance greater than the sum of the width of the radiation detection element 10 in the transport direction TD and the distance obtained by multiplying the time required for the reset operation by the transport speed of the transport unit 2 . Fig.14 It is a schematic diagram showing the conveying unit 2 that conveys the inspection targets F1 and F2. Fig.14 1 shows the moment when the object M passes directly above the radiation detection element 10 and is detected by the radiation detection element 10 . Fig.14 In the example shown, the first bias power supply 30 starts the reset operation in the radiation detection element 10. At this time, if the reset operation is not completed before the inspection object F1 starts to pass directly above the radiation detection element 10, the X-ray detection camera 100B cannot capture X-rays that pass through the inspection object F1. Therefore, the width W of the radiation detection element 10 along the conveying direction TD is separated from the downstream end of the inspection object M and the inspection object F1. B1 , and the distance D obtained by multiplying the time required for the reset operation by the transport speed of the transport unit 2 B1 The total distance is more than .

[0100] In addition, the detection object M only needs to be detectable by the radiation detection element 10, so Fig.11 As shown in (c), it may be an object of a characteristic shape, for example, a cross, a rod, a triangle, a square, a circle, etc. In this case, the determination unit 52B performs a determination process of determining whether the detection object M is detected in the X-ray image data. In the determination process, the determination unit 52B determines that the X-ray incident on the radiation detection element 10 does not pass through the inspection object F when the detection object M is detected in the X-ray image data.

[0101] In addition, the period from “the moment when the detection object M starts to pass directly above the radiation detection element 10” to “the moment when the detection object M finishes passing directly above the radiation detection element 10” is the entire period including the length along the transport direction TD of the radiation detection element 10 when observing the detection object M transported in the transport direction TD from the X-ray generator 3.

[0102] In the second embodiment, the determination unit 52B may not perform the determination process until a falling edge is detected for the shift in the brightness value of the X-ray image data after the reset operation is performed, and may perform the determination process when a falling edge is detected. Fig.13In the example shown, the determination unit 52B does not perform determination processing because the brightness value does not drop sharply after the determination unit 52B performs the reset operation at time t3 until the object F2 begins to pass directly above the radiation detection element 10. In addition, the determination unit 52B may detect a falling edge in the shift of the brightness value of the X-ray image data and perform determination processing when the brightness value I of the X-ray image data drops sharply when another object M located upstream of the object M begins to pass directly above the radiation detection element 10. In addition, the determination unit 52B may detect a rising edge in the shift of the brightness value of the X-ray image data and perform determination processing when the brightness value I of the X-ray image data rises sharply at time T5.

[0103] In addition, the determination unit 52B determines that the brightness value I of the X-ray image data exceeds a predetermined threshold value I. B For example, the determination unit 52B may also remove the flag when the threshold value I is exceeded. B The flag is unset when the other thresholds are reached.

[0104] In the X-ray inspection device 1B, the X-ray detection camera 100B and the radiation detection method of the second embodiment, as in the first embodiment, the occurrence of polarization phenomenon of the radiation detection element 10 can be suppressed, and when the X-rays incident on the radiation detection element 10 pass through the inspection object F, the X-rays can be detected more reliably.

[0105] Furthermore, in the second embodiment, when the brightness value of the X-ray image data is lower than a predetermined threshold value during the determination process, the determination unit 52B determines that the X-rays have not penetrated the inspection object F. According to such a configuration, when the inspection object M that shields or significantly absorbs X-rays is arranged in a place where the inspection object F is not arranged, it is possible to more reliably determine whether the X-rays incident on the X-ray detection camera 100B have penetrated the inspection object F. As a result, at the moment when the X-rays incident on the X-ray detection camera 100B have not penetrated the inspection object F, the reset operation can be more reliably performed.

[0106] In the X-ray detection camera 100B of the second embodiment, the radiation detection element 10 continuously outputs X-ray image data. The determination unit 52B may not perform determination processing until the amount of change in brightness value between a plurality of X-ray image data continuously outputted from the radiation detection element 10 exceeds a predetermined threshold value after performing a reset action, and may perform determination processing when the amount of change exceeds the predetermined threshold value. According to such a structure, after performing a reset action, the determination processing is restarted after the imaging of the inspection object F by the X-ray detection camera 100B ends. In the second embodiment, after performing a reset action, the determination unit 52B performs determination processing when a rising edge is detected in the shift of brightness value of the X-ray image data. Thus, after performing a reset action, the reset action can be suppressed until the polarization phenomenon needs to be eliminated again in the X-ray detection camera 100B. As a result, the X-ray detection camera 100B can be operated more efficiently.

[0107] Such an X-ray inspection apparatus 1B also exhibits the same operational effects as those of the first embodiment.

[0108] [Example of variation] Although the X-ray inspection apparatuses according to the first embodiment and the second embodiment have been described above, the present invention is not limited thereto, and various modifications are applicable.

[0109] In the first embodiment described above, the X-ray image data detected by the X-ray detection camera 100A may be output to the control device 4, and the addition process may be performed in the control device 4. In this way, when the X-ray image data output from the X-ray detection camera 100A is data for each line, the separation distance between the plurality of objects to be inspected F may be set to be greater than the sum of the width of each pixel line of the radiation detection element 10 and the distance obtained by multiplying the time required for the reset operation by the transport speed of the transport unit 2. In this regard, for example, in the case of a structure in which the TDI (Time Delay Integration) addition result is output from a plurality of radiation detection elements to the control unit, the distance between the objects to be inspected may be set by further considering the time it takes for the objects to be inspected to pass through all the radiation detection elements.

[0110] Fig.15 It is a schematic diagram showing the conveying unit 2 that conveys the inspection targets F1 and F2. Fig.15 1 shows the moment when the inspection object F2 has finished passing directly above all the radiation detection elements 70. Each radiation detection element 70 here has the same structure as the above-mentioned radiation detection element 10 and the like. Fig.15In the example shown, the determination process starts and the reset operation starts when imaging is completed in all radiation detection elements 70. At this time, if the reset operation is not completed before the inspection object F1 starts to pass through the upstream radiation detection element 70, the radiation detection element 70 cannot capture X-rays that pass through the inspection object F1.

[0111] Therefore, the distance between the inspection objects F1 and F2 is set to a distance greater than the sum of the result obtained by multiplying the reset action time by the transport speed of the transport unit 2 and the number of segments of the radiation detection element 70 (added number of segments) by the width of each radiation detection element 70. Fig.15 In the example shown, the distance between the inspection object F1 and the inspection object F2 is set to the sum of the widths W of all the radiation detection elements 70 along the conveying direction TD. A2 , and the distance D obtained by multiplying the time required for the reset operation by the transport speed of the transport unit 2 A2 The total distance is more than .

[0112] In addition, in the X-ray detection cameras 100A and 100B, the reset operation and the imaging process are controlled so as to be automatically linked. Fig.16 1 is a diagram showing an example of the relationship between an input trigger input to an X-ray detection camera and the operation of the X-ray detection camera. In addition, the input trigger here is, for example, a trigger linked to the completion of the determination process. Fig.16 As shown in (a), the control can also be performed by performing a reset action at the moment when the input trigger rises. In this case, it is also possible to automatically perform imaging when the reset action is completed and obtain X-ray image data of any number of lines. In addition, as Fig.16 As shown in (b), imaging can be performed at the time when the input trigger rises to obtain X-ray image data of an arbitrary number of lines. In this case, the reset operation can be automatically performed immediately after the X-ray image data is obtained.

[0113] Alternatively, the time for which the bias voltage is applied to the radiation detection element 10 is counted, and the reset operation is performed only when the time exceeds a certain value. In this case, the time for which the bias voltage is applied to the radiation detection element may be counted while irradiating X-rays.

[0114] In addition, in the first embodiment and the like, whether to perform the reset action is determined based on the brightness value of the X-ray image data, but the present invention is not limited thereto. In addition, the cycle and time of performing the reset action can also be set arbitrarily. Specifically, the cycle and time of performing the reset action can also be set based on conditions such as the tube voltage and tube current of the X-ray generator 3. In addition, the cycle and time of performing the reset action can also be set based on conditions such as the distance between the inspection object F and the X-ray detection camera 100A, and the type of the inspection object F.

[0115] Furthermore, in the above-described first embodiment and the like, the X-ray detection camera 100A is electrically connected only to the control device 4 , but the present invention is not limited to this. Fig.17 1 is a block diagram showing an X-ray inspection apparatus 1D of a modified example. The X-ray inspection apparatus 1D includes a conveying unit 2, an X-ray generator 3, an X-ray detection camera 100A, a control device 4D, and a shielding unit 5. In the X-ray inspection apparatus 1D of this modified example, the X-ray detection camera 100A is electrically connected to the conveying unit 2, the X-ray generator 3, and the control device 4D, respectively.

[0116] In the X-ray inspection device 1D of the variation, the control unit 50A of the X-ray detection camera 100A outputs an output signal for stopping the imaging-related actions of the X-ray inspection device 1D to the transport unit 2, the X-ray generator 3 and the control device 4D when performing a reset action through the voltage control unit 53.

[0117] Specifically, the control unit 50A may output an output signal for controlling the transport unit 2 to the outside of the X-ray detection camera 100A, specifically, the transport unit 2, in a manner of stopping the transport when the first bias power supply 30 performs the reset operation. In addition, the control unit 50A may stop the transport of the transport unit 2 by stopping the output signal (level drive trigger) output when the transport unit 2 performs the transport. Furthermore, the transport unit 2 may be controlled by the control device 4D. In this case, the control unit 50A outputs an output signal requesting the transport of the transport unit 2 to be stopped to the control device 4D when the first bias power supply 30 performs the reset operation. And the control device 4D receives the output signal and stops the transport of the transport unit 2.

[0118] In addition, the control unit 50A may also output an output signal for stopping the X-ray irradiation of the X-ray generator 3 to the outside of the X-ray detection camera 100A, specifically, to the X-ray generator 3, when performing a reset operation through the first bias power supply 30. The control unit 50A may also output an output signal (light source drive trigger) in a manner in which the X-ray generator 3 irradiates X-rays. In this case, the control unit 50A may also stop the output signal when performing a reset operation through the first bias power supply 30. Furthermore, the control unit 50A may also send an output signal requesting to stop the X-ray irradiation of the X-ray generator 3 to the control device 4D. In this case, the control device 4D receives the request and controls the X-ray generator 3 in a manner in which the X-ray irradiation is stopped.

[0119] In the X-ray inspection device 1D of the variation, it is determined whether a reset action can be performed to control the voltage of the radiation detection element 10 in a manner that the radiation detection element 10 does not collect charge, based on the X-ray image data output from the radiation detection element 10. And, in the case where the reset action can be performed, the reset action is performed after an output signal for stopping the action related to the imaging of the X-ray detection camera 100A is output to an external device. According to such a structure, in the case where the reset action is performed at the moment when the X-ray incident to the X-ray detection camera 100A does not pass through the inspection object F, the action of the external device related to the imaging of the inspection object F is stopped. At this time, for example, at least one of the conveyance of the inspection object F and the X-ray irradiation of the X-ray generator 3 is stopped. As a result, the reset action can be completed more reliably during the period when the X-ray incident to the X-ray detection camera 100A does not pass through the inspection object F. As a result, the occurrence of polarization phenomenon in the radiation detection element 10 can be suppressed, and when X-rays incident on the X-ray detection camera 100A do not pass through the inspection object F, the X-rays can be detected more reliably. Explanation of symbols

[0120] 1A, 1B, 1D…X-ray inspection device (radiation detection system); 2…conveying unit (conveying unit); 3…X-ray generator (light source); 100A, 100B…X-ray detection camera (radiation detection device); 10, 70…radiation detection element (detection element); 24…second electrode (pixel electrode); 25…third electrode (pixel electrode); 30…first bias power supply (voltage source); 50A, 50B…control unit; 52A, 52B…determination unit; 53…voltage control unit; F, F1, F2…inspected object (object); I…brightness value; I A ,I B …threshold; R3: irradiated area.

Claims

1. A radiation detection device, wherein: have: a detection element that directly converts incident radiation into electric charges and outputs a result of collecting the electric charges for each of a plurality of pixel electrodes as image pickup image data; a voltage source for applying a bias voltage to the detection element; and a control unit electrically connected to the detection element and the voltage source, The control unit has: a determination section that performs determination processing for determining whether a reset operation of performing voltage control on the detection element in a manner that the detection element does not collect the charge can be performed based on the captured image data output from the detection element; and A voltage control unit controls the voltage source so as to execute the reset operation when the determination unit determines that the reset operation can be executed.

2. The radiation detection device according to claim 1, wherein: The determination unit determines that the reset operation can be performed when it is determined based on the captured image data that the radiation has not penetrated the object in the determination process.

3. The radiation detection device according to claim 2, wherein: The determination unit determines that the radiation has not passed through the object when the brightness value of the captured image data exceeds a predetermined threshold value in the determination process.

4. The radiation detection device according to claim 2, wherein: The determination unit determines that the radiation has not passed through the object when the brightness value of the captured image data is lower than a predetermined threshold value in the determination process.

5. The radiation detection device according to claim 3 or 4, wherein: The detection element continuously outputs the camera image data. After executing the reset action, the determination unit does not perform the determination processing until the amount of change in the brightness value between the plurality of camera image data continuously output from the detection element exceeds a prescribed threshold value, and executes the determination processing when the amount of change exceeds the prescribed threshold value.

6. The radiation detection device according to any one of claims 2 to 4, wherein: The determination unit does not perform the determination process until a predetermined period of time, which is a period during which the reset operation is unnecessary, has elapsed after the reset operation is performed, and performs the determination process when the predetermined period of time has elapsed.

7. The radiation detection device according to claim 6, wherein: The detection element operates based on a reference clock. The determination unit determines whether the predetermined period has elapsed by counting the reference clock.

8. The radiation detection device according to claim 1, wherein: The reset operation is either an operation of stopping application of a voltage to the detection element or an operation of applying a reverse bias voltage to the detection element.

9. A radiation detection system, wherein: have: The radiation detection device according to claim 1; a light source that irradiates the radiation; and A transport device transports the object so that the object passes through an irradiation area of ​​the radiation.

10. A radiation detection method, wherein: have: a voltage applying step of directly converting incident radiation into electric charges and applying a bias voltage to a detection element that outputs a result of collecting the electric charges for each of a plurality of pixel electrodes as image pickup image data; An acquisition step of acquiring the camera image data from the detection element; a determination step of determining whether a reset operation of controlling the voltage of the detection element in a manner that the detection element does not collect the charge can be performed based on the captured image data output from the detection element; and A resetting step of executing the resetting action if it is determined in the determining step that the resetting action can be executed.

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