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

Abstract

An X-ray detection camera according to the present invention determines, on the basis of a signal from an object detection sensor that detects an object to be inspected irradiated with X-rays, whether or not a reset operation for performing voltage control on a detection unit so that charge is not collected by the detection unit can be executed, and performs the reset operation when the reset operation is possible.

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. WO2009 / 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 having: a determination unit that performs a determination process that determines whether a reset operation of controlling the voltage of the detection element in a manner that does not collect electric charge by the detection element can be performed; and a voltage control unit that controls the voltage source in a manner that performs the reset operation when the determination unit determines that the reset operation can be performed. The determination unit performs the determination process based on a signal from an object detection sensor that detects an object irradiated with radiation.

[0010] In a radiation detection device according to one embodiment of the present invention, it is determined whether a reset action can be performed to implement voltage control on a detection element in a manner that the detection element does not collect charge, based on a signal from an object detection sensor that detects an object irradiated with radiation. According to such a structure, it is determined whether a reset action can be performed in consideration of the detection result of the object by the object detection sensor. Thus, for example, a reset action can be performed at a time when there is no object, and voltage control on the detection element can be implemented in a manner that the detection element collects charge at a time when there is an object. As a result, the occurrence of a polarization phenomenon of the detection element can be suppressed, and in the case where radiation incident on 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 determine that a reset action can be performed when it is determined that the object is not detected based on a signal from the object detection sensor during the determination process. According to such a structure, a reset action can be performed at a time when the object does not exist, for example, when the object exists, the voltage of the detection element is controlled in such a way that the detection element collects charge. As a result, the occurrence of polarization in the detection element can be suppressed, and when the radiation incident on the radiation detection device passes through the object, the radiation can be detected more reliably.

[0012] (3) The radiation detection device described in (1) or (2) above may further include: a signal input unit that receives a signal input from the object detection sensor. With such a structure, the signal from the object detection sensor provided outside the radiation detection device can be reliably received, and control based on the signal can be appropriately performed.

[0013] (4) The radiation detection apparatus described in (1) or (2) above may further include an object detection sensor. With such a configuration, the above control can be appropriately performed based on a signal from the object detection sensor as an internal structure.

[0014] (5) In the radiation detection device described in (4) above, the object detection sensor may be provided on the same substrate as the detection element. With such a configuration, it is possible to suppress an increase in the size of the device.

[0015] (6) In the radiation detection apparatus described in (1) to (5) above, the determination unit may not perform determination processing until a prescribed period of time has passed, which is a period during which no reset operation is required, after the reset operation is performed, and may perform determination processing after the prescribed period has passed. According to such a structure, after the reset operation is performed, until the polarization phenomenon needs to be eliminated again in the radiation detection apparatus, it is possible to suppress the execution of a useless reset operation. As a result, the radiation detection apparatus can be operated more efficiently.

[0016] (7) In the radiation detection apparatus described in (1) to (6) above, the detection element operates based on the reference clock, and the determination unit 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 period has passed with better accuracy based on the reference clock. As a result, 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 apparatus.

[0017] (8) In the radiation detection device described in (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 (1) to (8) above; a light source that irradiates radiation; and a transport device that transports the object so that the object passes through an irradiation area of ​​the radiation. In such a radiation detection system, for example, when the transport device sequentially transports a plurality of objects, the radiation emitted from the light source passes through the object, and a reset operation can be performed when the object is not present, and a voltage control of the detection element can be performed in such a manner that the detection element collects charge when the object is present. As a result, the occurrence of polarization of the detection element can be suppressed, and when the radiation incident on the radiation detection device passes through the object, the radiation can be detected more reliably.

[0019] (10) The radiation detection system described in (9) above may further include an object detection sensor. With such a configuration, the above control can be appropriately performed based on a signal from the object detection sensor as an internal structure.

[0020] (11) A radiation detection method according to one aspect of the present invention includes: a voltage application step of directly converting incident radiation into electric charge and applying a bias voltage to a detection element that outputs the result of collecting electric charge for each of a plurality of pixel electrodes as camera image data; an acquisition step of acquiring a signal from an object detection sensor that detects an object irradiated with radiation; a determination step of determining 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 electric charge based on the signal from the object detection sensor; and a reset step of performing a reset action when it is determined in the determination step that the reset action can be performed. According to such a structure, for example, a reset action can be performed when there is no object, and a voltage control of the detection element can be performed in a manner that the detection element collects electric charge when there is an object. As a result, the occurrence of a polarization phenomenon of 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.

[0021] (12) 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 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 comprising: a determination unit that performs determination processing to determine whether a reset action of controlling the voltage of the detection element can be performed in a manner that the detection element does not collect electric charge; and a voltage control unit that controls the voltage source in a manner that the reset action is performed when the determination unit determines that the reset action can be performed; the determination unit performs determination processing based on sequence data that is repeated during a preset imaging period and a non-imaging period. According to such a structure, whether the reset action can be performed is determined in consideration of the sequence data that is repeated during a preset imaging period and a non-imaging period. Thus, for example, the reset action can be performed during the non-imaging period, and the voltage control of the detection element can be performed in a manner that the detection element collects electric charge during the imaging period. As a result, the occurrence of polarization phenomenon in the detection element can be suppressed, and when the radiation incident on the radiation detection device passes through the object, the radiation can be detected more reliably.

[0022] (13) A radiation detection system according to one aspect of the present invention comprises: a radiation detection device as described in (12) above; a light source for irradiating radiation; and a stage for moving the light source and the detection element relative to an object, wherein the control unit controls the stage in such a manner that during imaging, the light source and the detection element move at a constant speed relative to the object, and during non-imaging, the light source and the detection element accelerate or decelerate relative to the object. According to such a structure, imaging can be appropriately performed by moving the light source and the detection element at a constant speed during imaging, and during non-imaging, the light source and the detection element can be accelerated or decelerated according to the situation, thereby effectively moving the light source, etc. Effects of the Invention

[0023] 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

[0024] Figure 1 This is a structural diagram of an X-ray inspection apparatus according to one embodiment. Figure 2 It is a structural diagram of an X-ray inspection camera. Figure 3 It is a diagram showing a radiation detection unit and a configuration example of a detection unit. Figure 4 It is a diagram showing a configuration example of an imaging sensor and a detection sensor. Figure 5 It is a block diagram showing the functional structure of the control unit. Figure 6 This is a diagram for explaining control corresponding to the distance between the inspection objects F. Figure 7 This is a diagram for explaining an example of a reset operation. Figure 8 Detailed description of the process performed by the X-ray inspection apparatus. Fig. 9 It is a diagram for explaining the problem of the X-ray camera of the comparative example. Fig.10 It is a diagram for explaining the problem of the X-ray camera of the comparative example. Fig.11 It is a structural diagram of an X-ray inspection apparatus according to a modified example. Fig.12 It is a structural diagram of an X-ray inspection apparatus according to a modified example. Fig.13 This is a diagram for explaining an example of a reset operation based on a signal from an external device. Fig.14 It is a diagram showing the sequence of the X-ray inspection apparatus according to a modification. Fig.15 It is a structural diagram of an X-ray inspection apparatus according to a modified example. Fig.16 It is a diagram for explaining the structure of the stage. Fig.17 This is a diagram for explaining a method of inspecting an object to be inspected. Fig.18 It is a graph showing the processing speed per hour in the X direction and the Y direction. Fig.19 It is a structural diagram of an X-ray inspection apparatus according to a modified example. Fig. 20 It is a structural diagram of an X-ray inspection apparatus according to a modified example. Fig.21 It is a structural diagram of an X-ray inspection apparatus according to a modified example. DETAILED DESCRIPTION

[0025] 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.

[0026] [Structure of X-ray Inspection Device] Figure 1 FIG. 1 is a structural diagram of an X-ray inspection apparatus 1A, which is a radiation detection system of the present embodiment. Figure 1As shown, the X-ray inspection apparatus 1A is an apparatus 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 (camera 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 apparatus 1A uses the X-ray image to perform foreign matter inspection, weight inspection, and product inspection, etc., with the object to be inspected F as an object. Examples of uses of the X-ray inspection apparatus 1A include food inspection, carry-on baggage inspection, substrate inspection, battery inspection, and material inspection. The X-ray inspection apparatus 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 100, a light source 7, an object detection sensor 8, 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.

[0027] 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.

[0028] The X-ray generator 3 is a device that irradiates (outputs) X-rays to the inspection object F as an X-ray source. The X-ray generator 3 is, for example, a point light source, and irradiates the 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 device 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 entire longitudinal direction of the inspection object F is irradiated with X-rays. 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.

[0029] The X-ray detection camera 100 detects at least the X-rays that have passed through the conveying unit 2 among the X-rays irradiated by the X-ray generator 3 to the conveying unit 2, and outputs an X-ray image based on the X-rays. The X-ray detection camera (radiation detection device) 100 is, for example, an X-ray flat panel sensor or an X-ray sensor camera, and includes a radiation detection unit (detection element) 20x (see FIG. 1 ) having at least one pixel line having a plurality of pixels arranged in a pixel arrangement direction. Figure 2 ). The radiation detection unit 20x is a direct conversion type radiation detection element that directly converts incident X-rays into electric charges. The X-ray detection camera 100 generates X-ray images based on the detected X-rays, and outputs the generated X-ray images to the control device 4. In addition, the radiation detection unit 20x of the X-ray detection camera 100 may be a one-dimensional sensor (single-line sensor) having a pixel line in a row, or a two-dimensional sensor having a plurality of pixel lines. As a two-dimensional sensor, it may also be an area scanning two-dimensional sensor. In addition, it may also be a line scanning two-dimensional sensor such as a multi-line sensor composed of a plurality of pixel lines or a TDI (Time Delay Integration) sensor.

[0030] The light source 7 irradiates (outputs) light for object detection to the object F to be inspected. The light source 7 may output light that can be detected by the object detection sensor 8, for example, it may output visible light, infrared light, or X-rays. The light source 7 is, for example, disposed above the conveyor 2. In addition, in the present embodiment, since the object detection sensor 8 detects the light output from the light source 7 and transmitted through the object F to be inspected, the light source 7 is disposed on the opposite side of the object detection sensor 8 relative to the object F (i.e., above the conveyor 2). However, when the object detection sensor 8 detects the light output from the light source 7 and reflected in the object F to be inspected, the light source 7 may be disposed below the conveyor 2 like the object detection sensor 8. In addition, the light source 7 and the object detection sensor 8 are not limited to the upper and lower directions, and may be disposed in the horizontal direction. When disposed in the horizontal direction, it may be in the width direction of the object F to be inspected (the direction intersecting the conveying direction TD), in the length direction of the object F to be inspected (the conveying direction TD), or in an inclined direction including the width direction and the length direction. In addition, a light-reflecting member such as a mirror may be disposed between the light source 7 and the object detection sensor 8. The light source 7 and the object detection sensor 8 may be integrated.

[0031] The object detection sensor 8 is a sensor for detecting the inspection object F. The object detection sensor 8 detects the inspection object F by detecting the light output from the light source 7. In the present embodiment, the object detection sensor 8 is described as detecting the light transmitted through the inspection object F, but the object detection sensor 8 may also detect the reflected light in the inspection object F. A specific configuration example of the object detection sensor 8 is described below.

[0032] 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 100. The control device 4 controls the X-ray detection camera 100 in a manner of repeatedly photographing in a prescribed detection cycle. When the radiation detection unit 20x of the X-ray detection camera 100 has a plurality of pixel lines, the control device 4 sets a prescribed detection cycle in a manner that can photograph X-rays that pass through the same area of ​​the inspection object F respectively through the plurality of pixel lines. The control device 4 generates an X-ray image based on the X-ray image output from the X-ray detection camera 100. For example, the control device 4 joins a row of image data output from the X-ray detection camera 100 to generate one X-ray image. In addition, the control device 4 may also generate one X-ray image by averaging or adding the output data from the X-ray detection camera 100. In addition, the control device 4 may be a device independently provided outside the X-ray detection camera 100, or may be integrated inside the X-ray detection camera 100.

[0033] 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 unit 20x, 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 unit 20x (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 unit 20x. In this case, the individual periods may be set based on the deviation (delay time) of the detection period between specific multiple pixel lines according to 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 unit 20x (FDD).

[0034] 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.

[0035] [Structure of X-ray Inspection Camera] Figure 2 is a structural diagram of the X-ray detection camera 100. Figure 2 As shown, the X-ray detection camera 100 includes a detection unit 20 , a first bias power supply 30 (voltage source), a second bias power supply 40 , a control unit 50 , and an input / output interface 60 .

[0036] The detection unit 20 includes a radiation detection unit 20x, which 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 detection unit 20 continuously outputs the X-ray image data. The detection unit 20 is operated by the control unit 50 based on a reference clock (described later). The detection unit 20 includes 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 detection unit 20, 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.

[0037] The first electrode 23 is a bias electrode disposed on a surface on the opposite side of the semiconductor crystal 21 to the side opposite to the signal processing circuit 22. The first electrode 23 extends in the pixel arrangement direction, i.e., the X direction, and is integrally formed without being divided. The plurality of second electrodes 24 are pixel electrodes disposed on a surface on the side opposite to the signal processing circuit 22 in the semiconductor crystal 21, except for a portion (described later). The plurality of second electrodes 24 are arranged along the X direction. The plurality of third electrodes 25 are pixel electrodes disposed on a surface on the side opposite to the semiconductor crystal 21 in the signal processing circuit 22. 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.

[0038] 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) or cadmium zinc telluride (CdZnTe), thallium bromide (TlBr), etc. By applying a bias voltage to the semiconductor crystal 21 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.

[0039] 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 50. The signal processing circuit 22 continuously outputs the X-ray image data to the control unit 50. 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.

[0040] The first bias power supply 30 applies a bias voltage to the radiation detection section 20x of the detection section 20. 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 semiconductor crystal 21 via the first electrode 23 according to a control signal from the control section 50. The first bias power supply 30 applies a high voltage (HV: High Voltage) to the semiconductor crystal 21, for example. The first bias power supply 30 is configured to perform a reset operation (described later) on the semiconductor crystal 21. The second bias power supply 40 is electrically connected to the signal processing circuit 22 to provide a power source 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. The second bias power supply 40 may also be electrically connected to the photodiode 90 (described later) of the detection section 20y to provide a power source for the photodiode 90 to operate. Furthermore, the bias voltage (ON voltage value) applied by the first bias power supply 30 to the radiation detection section 20 x of the detection section 20 can also be set arbitrarily, and is, for example, -1000V.

[0041] The control unit 50 is electrically connected to the signal processing circuit 22 and the first bias power supply 30. The control unit 50 is composed of, for example, an FPGA (Field-Programmable Gate Array). The control unit 50 controls the detection unit 20 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 100. In addition, the control unit 50 may also control the detection unit 20 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 100. Through either of them, the control unit 50 outputs a control signal for operating the signal processing circuit 22 to the signal processing circuit 22. The control unit 50 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 100. For example, the control unit 50 outputs the X-ray image to the control device 4 via the input / output interface 60. The control unit 50 outputs a control signal for operating the first bias power supply 30 to the first bias power supply 30. The control unit 50 may also obtain a control signal from the control device 4 via the input / output interface 60. When the X-ray image data is information for generating an X-ray image, the control unit 50 generates an X-ray image based on the obtained X-ray image data.

[0042] Here, if Figure 2As shown in FIG. 1 , a part of the plurality of second electrodes 24 is connected to another photodetector (here, as an example, a photodiode 90) instead of the semiconductor crystal 21. The photodiode 90 detects light emitted from the light source 7. The second electrode 24 connected to the photodiode 90 is electrically connected to the signal processing circuit 22 via the third electrode 25. The signal processing circuit 22 outputs a signal corresponding to the detection result of the photodiode 90 to the control unit 50 based on the read electrical signal. Such a structure related to the output of the detection result of the photodiode 90 (the photodiode 90, the second electrode 24 connected to the photodiode 90, the third electrode 25 electrically connected to the second electrode 24, and the signal processing circuit 22) functions as a detection unit 20y related to the detection of the inspection object F. The case where the inspection object F is detected by the detection unit 20y is the case where the inspection object F exists in the irradiation area R3 of the X-ray generator 3. The detection unit 20y is an example of the object detection sensor 8 described above. In this case, the object detection sensor 8 is provided on the same substrate as the detection unit 20. In the detection unit 20, the structure related to the generation of X-ray image data is the radiation detection unit 20x, and the structure related to the detection of the inspection object F is the detection unit 20y. The radiation detection unit 20x and the detection unit 20y may have or not have sensitivity in the same wavelength and energy band. The light (signal) detected by the radiation detection unit 20x may be a reflected image or a transmitted image.

[0043] Figure 3 1 and 2 are diagrams showing configuration examples of the radiation detection section 20 x and the detection section 20 y (object detection sensor 8 ), and are diagrams showing them in plan view. Figure 3 In (a) to (e), the vertical direction of the paper is the conveying direction of the inspected object F. Figure 3 As shown in (a), the detection units 20y may be arranged in a row in the conveying direction with the radiation detection units 20x interposed therebetween. In this case, for example, the detection units 20y for detecting the inspection object F may be arranged in response to both forward and reverse conveyance of the inspection object F.

[0044] In addition, if Figure 3 As shown in (b), the detection unit 20y may be provided in one row relative to the radiation detection unit 20x in only one direction of the conveying direction. Figure 3 As shown in (c), the detection unit 20y may be set to only one pixel instead of one line. As a countermeasure for low line density, the detection unit 20y may be set to multiple sections, and TDI (Time Delay Integration) may be added. In addition, the position of the detection unit 20y may be as follows: Figure 3 As shown in (c), it can be an end, such as Figure 3As shown in (d), it may be the central part or any area. In addition, the detection part 20y may be adjacent to the radiation detection part 20x or may be separated from the radiation detection part 20x. Figure 3 As shown in (e) of FIG. 1 , a part of the radiation detection section 20x may be used together with the detection section 20y.

[0045] In addition, the structure of the object detection sensor 8 is not limited to the example of the detection unit 20y described above. The object detection sensor 8 may also be composed of a sensor different from the detection unit 20, namely, a detection sensor 80, rather than the pixels (detection unit 20y) in the detection unit 20 described above. The detection sensor 80 is a sensor that detects light emitted from the light source 7, and may be, for example, a camera equipped with a photoelectric sensor such as a photodiode. The detection sensor 80 may or may not have sensitivity at the same wavelength and energy band as the detection unit 20 (imaging sensor) related to the generation of X-ray image data. The light (signal) detected by the detection sensor 80 may be a reflected image or a transmitted image.

[0046] Figure 4 2 is a diagram showing a configuration example of the detection unit 20 and the detection sensor 80, which are imaging sensors, and is a diagram showing them from above. Figure 4 In FIG. 1 , the detection unit 20 is illustrated as an “imaging sensor”. Figure 4 In (a) to (d), the vertical direction of the paper is the conveying direction of the inspected object F. Figure 4 As shown in (a), the detection sensors 80 are arranged in a row in the conveying direction so as to sandwich the detection unit 20. In this case, for example, the detection sensors 80 for detecting the inspection object F can be arranged in response to both forward and reverse conveyance of the inspection object F.

[0047] In addition, if Figure 4 As shown in (b), the detection sensor 80 may be provided in one row only in one direction of the conveying direction relative to the detection unit 20. Figure 4 As shown in (c), the detection sensor 80 may be set to only one pixel instead of one line. As a countermeasure for low line quantity, the detection sensor 80 may be set to multiple segments, and TDI (Time Delay Integration) may be added. In addition, the position of the detection sensor 80 is as follows: Figure 4 As shown in (c), it can be an end, such as Figure 4 As shown in (d), it can also be the central part or any area. Figure 2 As shown, the description will be given by the detection unit 20y.

[0048] [Functional structure of control unit] Figure 5 is a block diagram showing the functional structure of the control unit 50. Figure 5As shown, the control unit 50 includes an acquisition unit 51, a determination unit 52, and a voltage control unit 53. Hereinafter, each functional unit of the control unit 50 will be described in detail. The control unit 50 determines the presence or absence of the inspection object F, and controls the application of the high voltage (HV) of the first bias power supply 30 according to the determination result.

[0049] The acquisition unit 51 acquires a control signal for controlling the imaging of the X-ray detection camera 100 from the control device 4. In addition, the acquisition unit 51 may also acquire a control signal generated by the control unit 50 based on a reference clock generated inside the X-ray detection camera 100. 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 to the control device 4. The acquisition unit 51 acquires a signal from the detection unit 20y constituting the object detection sensor 8 via the signal processing circuit 22. This signal is a signal corresponding to the detection result of the photodiode 90, and is a signal related to the detection of the object F to be inspected. The acquisition unit 51 outputs the signal from the detection unit 20y to the determination unit 52.

[0050] The determination unit 52 performs a predetermined determination process based on the signal from the detection unit 20y (the signal from the object detection sensor 8 that detects the inspection object F irradiated with X-rays) acquired by the acquisition unit 51. The determination process here is a process for determining whether the reset operation can be performed.

[0051] 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 detection unit 20 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 semiconductor crystal 21 itself, or an action of applying a reverse bias voltage (a bias voltage opposite to the voltage normally applied) to the semiconductor crystal 21. In addition, the voltage (off voltage value) applied to the detection unit 20 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, for example, a fixed value, for example, 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.

[0052] Specifically, the determination unit 52 determines whether the inspection object F exists in the irradiation area R3 of the X-ray generator 3 based on the signal from the detection unit 20y. The determination unit 52 determines whether the light is transmitted through the inspection object F or is light of background brightness that does not transmit through the inspection object F, based on the brightness of the light output from the light source 7 indicated by the signal from the detection unit 20y, for example. The determination unit 52 determines that the inspection object F exists in the irradiation area R3 of the X-ray generator 3 when the light output from the light source 7 transmits through the inspection object F. The determination unit 52 may also determine that the light output from the light source 7 transmits through the inspection object F (the inspection object F exists in the irradiation area R3 of the X-ray generator 3) when the brightness value indicated by the signal from the detection unit 20y does not exceed a predetermined threshold value.

[0053] In addition, for example, in the case of a structure in which a shading object or a marking is provided between multiple inspection objects F using the conveying section 2, since the brightness of light passing through the shading object etc. becomes smaller, the determination section 52 can also determine that the light output from the light source 7 passes through the inspection object F (there is an inspection object F in the irradiation area R3 of the X-ray generator 3) when the brightness value indicated by the signal from the detection section 20y does not exceed the prescribed threshold value.

[0054] The determination unit 52 may also determine that the reset action can be performed when it is determined that the inspection object F is not detected (the inspection object F does not exist in the irradiation area R3 of the X-ray generator 3) based on the signal from the detection unit 20y during the determination process. That is, the determination unit 52 determines that the reset action can be performed when the inspection object F does not exist and does not affect the imaging of the inspection object F. The determination unit 52 outputs the result of the execution of the determination process to the voltage control unit 53.

[0055] When the determination unit 52 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 52 performs a new determination process after the 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 52 may also determine whether a prescribed period has passed by counting the reference clock. In this case, the determination unit 52 may also start executing the determination process when it is determined that a prescribed period has passed.

[0056] The determination unit 52 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 52 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 is lower than a predetermined threshold value). By such flag management, control can be achieved in which a reset operation is not performed during a flag setting period.

[0057] In addition, the determination unit 52 may also 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 52 may not perform the determination process until the amount of change in the brightness value of the light output from the light source 7 indicated by the signal from the detection unit 20y exceeds the prescribed threshold value after performing the reset action, and perform the determination process when the amount of change in the brightness value exceeds the prescribed threshold value. The determination unit 52 may not perform the determination process until a rising edge is detected for the above-mentioned change in the brightness value after performing the reset action, and perform the determination process when a rising edge is detected. In addition, the determination unit 52 may perform the determination process when a falling edge is detected.

[0058] The rising edge is the portion of the graph where the luminance value rises sharply (increases) in the vertical axis and the time in the horizontal axis. In the rising edge, the change in the luminance value in a small time exceeds the specified threshold. The small time is a time that is sufficiently smaller than the time required for the object F to pass directly above the X-ray detection camera 100. The falling edge is the portion of the above graph where the luminance value drops sharply (decreases).

[0059] When the determination unit 52 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 processing of the determination unit 52 and the execution of the reset operation of the voltage control unit 53. The delay time is, for example, the processing time in the X-ray detection camera 100. The voltage control unit 53 controls the first bias power supply 30 only when the distance FD (refer to FIG. 1 ) between the inspection object F specified based on the signal from the detection unit 20y is less than 0. Figure 6 ) When the reset action time is sufficiently long, the first bias power supply 30 is controlled in such a manner as to execute the reset action.

[0060] In the X-ray detection camera 100, the reset operation and the imaging process may be controlled in an automatically linked manner. Figure 7 2 is a diagram showing an example of a reset operation in automatic linkage. The input trigger here is, for example, a trigger linked to the determination process completion. Figure 7As shown in (a), the reset action can also be controlled at the moment when the input trigger rises. In this case, when the reset action is completed, the X-ray image can be automatically taken to obtain an image with any number of lines. Figure 7 As shown in (b), an X-ray image may be captured at the time when the input trigger rises, and an image with an arbitrary number of lines may be obtained. In this case, a reset operation may be automatically performed immediately after the X-ray image is captured.

[0061] Figure 8 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 8 As shown, first, the voltage control unit 53 controls the first bias power supply 30 so as to apply a bias voltage to the detection unit 20 (step S1: voltage application step). Next, the acquisition unit 51 acquires a signal from the detection unit 20y constituting the object detection sensor 8 (step S2: acquisition step). Next, the determination unit 52 determines whether the inspection object F is detected (i.e., whether the reset operation can be performed) based on the signal from the detection unit 20y (step S3: determination step). When it is determined that the reset operation can be performed (step S3: YES), the voltage control unit 53 controls the first bias power supply 30 so as to perform the reset operation (step S4: reset step). When it is determined that the reset operation cannot be performed (step S3: NO), the process from step S2 is performed again.

[0062] In addition, in the above example, the reset action is performed by the voltage control unit 53 when the determination unit 52 determines that the inspection object F does not exist. However, for example, the first bias power supply 30 may be controlled by applying a high voltage by the voltage control unit 53 at the moment / period when the determination unit 52 determines that the inspection object F exists (the inspection object F is detected by the detection unit 20y), and the reset action may be appropriately performed during other periods.

[0063] 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 100, and the radiation detection method according to the first embodiment will be described.

[0064] 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 the X-ray image output by the radiation detection element to deteriorate.

[0065] In order to prevent the above-mentioned degradation of X-ray images, the radiation detection devices described in Patent Documents 1 to 3 temporarily cut off the voltage applied to the direct conversion radiation detection element to thereby recover the direct conversion radiation detection element from the polarization phenomenon.

[0066] In addition, in order to prevent the degradation of the X-ray image 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 images.

[0067] 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. Fig. 9 This is a table showing changes in the dead time ratio when the transport speed is changed. Fig. 9 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.

[0068] 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.

[0069] The second problem is that, in the X-ray detection camera of the comparative example, parallax between the added X-ray image groups occurs in an output image obtained by adding a plurality of X-ray images.

[0070] Generally, in an X-ray detection camera, while the object to be inspected passes through the camera's imaging area, each direct conversion type radiation detection element continuously outputs an X-ray image. These X-ray images are added together to generate an output image. At this time, at each position in the output image, the X-ray images from all the direct conversion type radiation detection elements are added together, so that no parallax is generated between the X-ray image groups after the addition process.

[0071] 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 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 images from some of the direct conversion type radiation detection elements are not added, so parallax between the X-ray image groups after the addition process occurs.

[0072] Fig.10 1 is a schematic diagram showing the inspection target object F transported on the transport unit 2000 . Fig.10 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 an X-ray image can be output. Fig.10 In (b), each line sensor 1001 to 1006 becomes insensitive. Fig.10 In the example shown, the front end Fa of the object F to be inspected is Fig.10 (a) is captured by line sensors 1001 and 1002. Fig.10 The rear end Fb of the object F is captured by the line sensor 1006 in (c). Fig.10 (c) is captured by line sensors 1004 to 1006. In this case, in the output image after the addition process, the line sensors at the output ends of the X-ray image after the addition process are different in the portion where the front end Fa is reflected and the portion where the rear end Fb is reflected. As a result, parallax between the X-ray image groups after the addition process is generated in the output image after the addition process.

[0073] In contrast to the above-mentioned comparative example, in the X-ray detection camera 100 of the first embodiment, based on the signal from the object detection sensor 8 that detects the inspection object F irradiated with X-rays, it is determined whether a reset operation can be performed to control the voltage of the detection unit 20 in a manner that the detection unit 20 does not collect charges. According to such a structure, it is determined whether the reset operation can be performed in consideration of the detection result of the inspection object F by the object detection sensor 8. Thus, for example, the reset operation can be performed at a time when the inspection object F does not exist, and the voltage control of the detection unit 20 can be implemented in a manner that the detection unit 20 collects charges at a time when the inspection object F exists. As a result, the occurrence of the polarization phenomenon of the detection unit 20 can be suppressed, and when the X-ray incident on the X-ray detection camera 100 passes through the inspection object F, the X-ray can be detected more reliably.

[0074] In this way, in the X-ray detection camera 100, 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 100 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 of the X-ray image output from the X-ray detection camera 100 can be suppressed. Furthermore, the structure of the X-ray detection camera 100 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 groups after the addition processing in one image in which multiple X-ray images output from the X-ray detection camera 100 are added together.

[0075] In the X-ray detection camera 100 of the present embodiment, the determination unit 52 may determine that a reset operation can be performed when it is determined that the inspection object F is not detected based on the signal from the object detection sensor 8 during the determination process. According to such a structure, a reset operation is performed at a time when the inspection object F does not exist, for example, the voltage control of the detection unit 20 can be performed in a manner such that the detection unit 20 collects charges at a time when the inspection object F exists. As a result, the generation of a polarization phenomenon of the detection unit 20 can be suppressed, and when the X-ray incident on the X-ray detection camera 100 passes through the inspection object F, the X-ray can be detected more reliably.

[0076] The X-ray detection camera 100 of the present embodiment includes the object detection sensor 8. With such a configuration, the above-described control can be appropriately performed based on a signal from the object detection sensor 8 as an internal structure.

[0077] In the X-ray detection camera 100, the object detection sensor 8 is provided on the same substrate as the detection unit 20 (see Figure 2 ). According to such a structure, it is possible to suppress the enlargement of the device.

[0078] In the X-ray detection camera 100, the determination unit 52 may 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 may perform determination processing after the predetermined period has passed. According to such a structure, it is possible to suppress the execution of useless reset operations until the depolarization phenomenon is required again in the X-ray detection camera 100 after the reset operation is performed. As a result, the X-ray detection camera 100 can be operated more efficiently.

[0079] In the X-ray detection camera 100, the detection unit 20 operates based on the reference clock, and the determination unit 52 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 more accurately based on the reference clock. As a result, after the reset action is performed, until the polarization phenomenon needs to be eliminated again in the X-ray detection camera 100, the reset action can be more reliably suppressed.

[0080] In the X-ray detection camera 100, the reset operation may be either an operation of stopping the voltage applied to the detection unit 20 or an operation of applying a reverse bias voltage to the detection unit 20. With such a configuration, the polarization phenomenon in the X-ray detection camera 100 can be eliminated more reliably.

[0081] The X-ray inspection apparatus 1A of the present embodiment includes: the X-ray detection camera 100 described above; an X-ray generator 3 that irradiates X-rays; and a conveyor 2 that conveys the inspection object F so that the inspection object F passes through the irradiation area R3 of the X-rays. In such an X-ray inspection apparatus 1A, for example, by configuring the X-rays emitted from the X-ray generator 3 to pass through the inspection object F when the conveyor 2 sequentially conveys a plurality of inspection objects F, for example, a reset operation can be performed when the inspection object F is not present, and a voltage control can be performed on the detection unit 20 so that the charge is collected by the detection unit 20 when the inspection object F is present. As a result, the occurrence of a polarization phenomenon in the detection unit 20 can be suppressed, and when the X-rays incident on the X-ray detection camera 100 pass through the inspection object F, the X-rays can be detected more reliably.

[0082] [Example of variation] As mentioned above, although the X-ray inspection apparatus 1A including the X-ray detection camera 100 of the embodiment has been described, the present invention is not limited to this, and various modifications can be applied.

[0083] Fig.111 is a structural diagram of an X-ray inspection apparatus 1B of a modified example. In the X-ray inspection apparatus 1B, the structure of the conveying unit 2B (conveying device) for conveying the inspection object F is different from that of the above-mentioned X-ray inspection apparatus 1A. Specifically, the conveying unit 2B is divided and formed in a manner that does not exist on the line connecting the light source 7 and the object detection sensor 8 (in a manner that does not form a gap). In particular, when visible light or infrared light is emitted from the light source 7, that is, when the inspection object F is detected by a transmission image, by forming it in a manner that the conveying unit 2B does not exist on the line connecting the light source 7 and the object detection sensor 8, it is possible to detect the inspection object F with high accuracy without being affected by the conveying unit 2B.

[0084] Fig.12 1 is a structural diagram of an X-ray inspection device 1C of a variation. In the X-ray inspection device 1C, the object F to be inspected is detected by a detection sensor 88 (an example of an object detection sensor 8) provided outside the X-ray detection camera 100, and the above-mentioned determination process is performed based on an external signal from the detection sensor 88. In this case, the control unit 50 of the X-ray inspection device 1C functions as a signal input unit that receives an input of an external signal from the detection sensor 88. And, the control unit 50 performs the above-mentioned determination process based on the external signal. According to such a structure, the signal from the object detection sensor 8 provided outside the X-ray detection camera 100 can be reliably received, and control based on the signal can be appropriately implemented.

[0085] Fig.12 In the example shown, a plurality of light sources 77 are provided for irradiating the inspected object F with light for object detection. Furthermore, a plurality of detection sensors 88 are provided as sensors for detecting light emitted from the light source 77. The plurality of detection sensors 88 are arranged near the conveying path of the inspected object F. The detection sensor 88 may be, for example, a camera equipped with a photoelectric sensor such as a photodiode. The light (signal) detected by the detection sensor 80 may be a reflected image or a transmitted image. The light detected by the detection sensor 88 may be visible light, infrared light or an X-ray image. The detection sensor 88 may also be composed of a weight sensor, a magnetic sensor, a laser sensor, an electric wave sensor, an ultrasonic sensor, a contact sensor, etc. other than a photoelectric sensor. In addition, as a structure for obtaining an external signal from a sensor arranged outside, a structure for obtaining an external signal from a machine such as a weight checker, a central control machine (sequence generator), etc. may also be adopted.

[0086] Fig.13 This is a diagram for explaining an example of a reset operation based on an external signal from an external device (here, the detection sensor 88). Fig.13 In FIG. 1 , the horizontal axis represents time, and the vertical axis represents the state of the input trigger. The input trigger here is, for example, a trigger based on an external signal and a trigger that is linked to the completion of the determination process. Fig.13As shown in (a), a reset operation may be performed at the moment when the input trigger rises, and exposure (X-ray image capture) may be automatically performed when the reset operation is completed to obtain an image with any number of lines. In this case, the level and polarity ("P" or "N") of the input trigger are not particularly limited.

[0087] In addition, if Fig.13 As shown in (b), an arbitrary delay time may be set for the input trigger inside the X-ray detection camera 100, and then the reset action may be performed. Such a delay time may also be set by considering using an external signal from an external device, that is, the detection sensor 88, for example.

[0088] In addition, if Fig.13 As shown in (c), the reset action and exposure (X-ray image capture) can also be performed according to the high (High) / low (Low) period of the input trigger. Fig.13 In the example shown in (c), the reset operation is performed while the input trigger is high, and the exposure (X-ray image capture) is performed while the input trigger is low.

[0089] In addition, if Fig.13 As shown in (d) of FIG. 1 , the rising edge of the input trigger can also be detected, and after the rising edge is detected, the reset action is performed for a specified period of time. Fig.13 In the graph shown, the portion where the input trigger rises sharply (becomes larger). In the rising edge, the change in the input trigger within a small period of time exceeds the specified threshold. In addition, the reset action period may not be set to a certain value, for example, it may be set based on a table of preset reset action time cycles. For example, in the case where there is a period of continuous conveyance of the inspected object F and a period of discontinuous conveyance, control such as obtaining a longer reset action time (stable reset) may be implemented during the period of discontinuity of the inspected object F.

[0090] Fig.14 1 is a diagram showing a sequence of an X-ray inspection apparatus according to a modification. In the X-ray inspection apparatus according to this modification, the determination unit 52 of the control unit 50 executes determination processing based on repetition of imaging periods and non-imaging periods set in advance, that is, sequence data. Fig.14 This shows the sequence of imaging and high voltage control. Fig.14 , the horizontal axis is time. Fig.14 The "shooting" of the shooting sequence indicates the shooting period, and the "stop etc." indicates the non-shooting period. If such a shooting sequence is preset, the control unit 50 can easily and appropriately perform the reset operation by obtaining the information of the shooting sequence. Fig.14 As shown, a high voltage control sequence is set corresponding to the imaging sequence. During the imaging period, the first bias power supply 30 applies a high voltage to the semiconductor crystal 21 . During the non-imaging period, the first bias power supply 30 performs a reset operation on the semiconductor crystal 21 .

[0091] Fig.15 This is a block diagram of an X-ray inspection apparatus 1D that performs determination processing based on sequential data. Fig.15 As shown, the X-ray inspection apparatus 1D includes an X-ray generator 3, an X-ray detection camera 100, and a conveyor 2D. In the X-ray inspection apparatus 1D, an inspection object F placed on the conveyor 2D is irradiated with X-rays along an irradiation line 500. Fig.15 In the example shown, a refracted irradiation line 500 is set for the inspection object F.

[0092] Fig.16 1 is a diagram for explaining the structure of the stage 150. The X-ray inspection apparatus 1D includes the stage 150 for moving the X-ray generator 3 and the X-ray detection camera 100 relative to the inspection object F. The stage 150 includes an arm for clamping both the X-ray generator 3 and the X-ray detection camera 100. In the X-ray inspection apparatus 1D, the stage 150 is controlled by the control unit 50 to perform X-ray irradiation on the inspection object F along the above-mentioned folded irradiation line 500.

[0093] Fig.17 The diagram is a diagram for explaining a method of inspecting an object F using the X-ray inspection apparatus 1D. Fig.18 It is a figure which shows the moving speed per hour in the X direction and the Y direction in this inspection method. Fig.17 In the figure, the dotted line portion represents the video recording period, the solid line portion represents the reset period, and 0 represents the reset start time.

[0094] Fig.17 (a) is an example of setting a folded irradiation line 500 for a rectangular object F to be inspected when viewed from above. The control unit 50 controls the stage 150 as follows: during imaging, the X-ray generator 3 and the X-ray detection camera 100 move in the X direction, and during non-imaging (reset period), the X-ray generator 3 and the X-ray detection camera 100 move in the Y direction. Fig.18 As shown in FIG. 1 , the movement in the X direction is maintained at a constant speed during a predetermined period. That is, the control unit 50 controls the stage 150 in the following manner: during the imaging period, the X-ray generator 3 and the X-ray detection camera 100 move in the X direction at a constant speed relative to the inspection object F. Fig.18As shown, the movement in the Y direction is performed in a manner of first accelerating (accelerating relative to the object F to be inspected) and then decelerating (decelerating relative to the object F to be inspected). That is, the control unit 50 controls the stage 150 in a manner that the X-ray generator 3 and the X-ray detection camera 100 accelerate or decelerate during the non-imaging period. In addition, the stage 150 only needs to be able to move the X-ray generator 3 and the X-ray detection camera 100 relative to the object F to be inspected. For example, it may be a structure as follows: the stage 150 fixes the position of the X-ray generator 3 and the X-ray detection camera 100, and the object F to be inspected is moved by some method, thereby, the X-ray generator 3 and the X-ray detection camera 100 move relative to the object F to be inspected.

[0095] Fig.17 In the example shown in (a), if the X-ray generator 3 and the X-ray detection camera 100 first move in the X direction during imaging and start resetting during non-imaging, then move in the Y direction; if they then turn back during imaging and move in the -X direction and start resetting during non-imaging, then move in the Y direction; if they then turn back during imaging and move in the X direction and start resetting during non-imaging, then move in the Y direction; if they then turn back during imaging and move in the -X direction and start resetting during non-imaging, then move in the Y direction; finally, they move in the X direction during imaging.

[0096] Fig.17 (b) shows an example of setting the refracted irradiation line 500 for the inspection object F which is missing the upper right part of the rectangle and has a stepped shape. Fig.17 As shown in (b) of FIG. 1 , for the inspection object F of such a shape, the inspection object F does not exist in the step portion, so the step portion is controlled so as to become a reset period.

[0097] According to the X-ray inspection apparatus 1D, a reset operation can be performed during a non-imaging period, and during an imaging period, voltage control of the detection element can be performed in a manner such that charges are collected by the X-ray detection camera 100. As a result, the occurrence of a polarization phenomenon of the X-ray detection camera 100 can be suppressed, and when X-rays pass through the inspection object F, the X-rays can be detected more reliably.

[0098] In addition, according to the above structure, the X-ray generator 3 and the X-ray detection camera 100 are moved at a certain speed during the imaging, so that the imaging is properly implemented, and during the non-imaging period, the X-ray generator 3 and the X-ray detection camera 100 are accelerated or decelerated according to the situation, so that the X-ray generator 3 and the X-ray detection camera 100 can be effectively moved.

[0099] Fig.19 : is a structural diagram of an X-ray inspection device of a variation. For example, Fig.19In the X-ray inspection device 1E shown in (a), the X-ray generator 3 irradiates the rotating inspection object F with X-rays, and controls the X-ray detection camera 100 so as to perform a reset operation and image capture at each predetermined angle. Fig.19 In the X-ray inspection apparatus 1F shown in (b) of FIG. 1 , a section T1 in which the inspection object F is not transported is periodically set, and the reset operation is performed during the period corresponding to the section.

[0100] Fig. 20 1G is a block diagram of an X-ray inspection apparatus according to a modified example. In the X-ray inspection apparatus 1G, the control unit 50 of the X-ray detection camera 100G outputs an output signal for stopping the imaging-related operation of the X-ray inspection apparatus 1G to the conveyor 2, the X-ray generator 3, and the control device 4 when the voltage control unit 53 performs a reset operation.

[0101] Specifically, the control unit 50 may output an output signal for controlling the transport unit 2 to the outside of the X-ray detection camera 100, 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 50 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 4. In this case, the control unit 50 may output an output signal requesting the transport of the transport unit 2 to be stopped to the control device 4 when the first bias power supply 30 performs the reset operation. And, the control device 4 receives the output signal and stops the transport of the transport unit 2.

[0102] In addition, the control unit 50 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 100, specifically, the X-ray generator 3, when performing a reset operation through the first bias power supply 30. The control unit 50 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 50 may also stop the output signal when performing a reset operation through the first bias power supply 30. Furthermore, the control unit 50 may also send an output signal requesting to stop the X-ray irradiation of the X-ray generator 3 to the control device 4. In this case, the control device 4 receives the request and controls the X-ray generator 3 in a manner in which the X-ray irradiation is stopped.

[0103] Fig.211 is a structural diagram of an X-ray inspection device 1H of a variation. In addition to the structure of the X-ray inspection device 1G described above, the X-ray inspection device 1H is provided with a baffle 600. The baffle 600 is a structure that is disposed directly below the X-ray generator 3 and adjusts the radiation amount of X-rays by opening and closing. In the X-ray inspection device 1H, the control unit 50 outputs an output signal instructing the baffle 600 to open and close. In addition, the control unit 50 outputs an output signal for stopping the X-ray irradiation of the X-ray generator 3 to the X-ray generator 3. According to such a structure, the opening and closing of the baffle 600 and the irradiation of X-rays from the X-ray generator 3 can be adjusted through the control of the control unit 50, thereby reducing the radiation amount of X-rays. By reducing the radiation amount of X-rays, the progression of polarization can be suppressed. Explanation of symbols

[0104] 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H…X-ray inspection device (radiation detection system); 2, 2B, 2D…conveying section (conveying device); 3…X-ray generator (light source); 8…object detection sensor; 20x…radiation detection section (detection element); 30…first bias power supply (voltage source); 50…control section; 52…determination section; 53…voltage control section; 100…X-ray detection camera (radiation detection device); 150…stage; F…inspected object (object).

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 a determination process for determining whether a reset operation of performing voltage control on the detection element in a manner that the charge is not collected by the detection element can be performed; and a voltage control unit that controls the voltage source so as to execute the reset action when the determination unit determines that the reset action can be executed, The determination unit executes the determination process based on a signal from an object detection sensor that detects an object irradiated with the radiation.

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 that the object is not detected based on the signal from the object detection sensor in the determination process.

3. The radiation detection device according to claim 1 or 2, wherein: The device further includes a signal input unit that receives a signal input from the object detection sensor.

4. The radiation detection device according to claim 1 or 2, wherein: The device further comprises: the object detection sensor.

5. The radiation detection device according to claim 4, wherein: The object detection sensor is provided on the same substrate as the detection element.

6. The radiation detection device according to claim 1 or 2, 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 or 2, 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 or 2; 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. The radiation detection system according to claim 9, wherein: The device further comprises: the object detection sensor.

11. A radiation detection method, wherein: Include: 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 a signal from an object detection sensor that detects an object irradiated with the radiation; a determination step of determining whether a reset operation of controlling the voltage of the detection element in a manner that the charge is not collected by the detection element can be performed based on a signal from the object detection sensor; and A resetting step of executing the resetting action if it is determined in the determining step that the resetting action can be executed.

12. 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 a determination process for determining whether a reset operation of performing voltage control on the detection element in a manner that the charge is not collected by the detection element can be performed; and a voltage control unit that controls the voltage source so as to execute the reset action when the determination unit determines that the reset action can be executed, The determination unit executes the determination process based on sequence data that is repetition of preset imaging periods and non-imaging periods.

13. A radiation detection system, wherein: have: The radiation detection device according to claim 12; a light source that irradiates the radiation; and a stage for moving the light source and the detection element relative to the object, The control unit controls the stage in the following manner: During the imaging period, the light source and the detection element move at a constant speed relative to the object, and during the non-imaging period, the light source and the detection element accelerate or decelerate relative to the object.

Images