Radiation detector and radiation inspection device

Abstract

This radiation detector comprises: a shielding member having formed therein an opening through which radiation passes; a light conversion unit that has a scintillator including a side surface facing the opening in a Z-axis direction and a surface extending along the Z-axis direction and an X-axis direction intersecting the Z-axis direction; a light detection unit having a plurality of pixels arranged two-dimensionally along a plane facing the aforementioned surface; and a processing unit that is electrically connected to the plurality of pixels and processes output signals from the plurality of pixels. The plurality of pixels are arranged in a plurality of columns, each of the columns extending along the Z-axis direction.

Description

Radiation detector and radiation inspection apparatus

[0006]

[0001] The present disclosure relates to a radiation detector and a radiation inspection apparatus.

[0002] Patent Document 1 discloses a radiation inspection apparatus including two radiation detectors that detect radiation in different energy ranges. In the radiation detection apparatus disclosed in Patent Document 1, a first radiation detector that detects radiation in a first energy range and a second radiation detector that detects radiation in a second energy range different from the first energy range are arranged side by side in the radiation incident direction.

[0003] Japanese Patent Application Laid-Open No. 2013-57102

[0004] In the radiation inspection apparatus as described above, each radiation detector cannot detect radiation in a plurality of energy ranges. Therefore, for example, in order to detect radiation in a plurality of energy ranges, it is necessary to arrange a plurality of radiation detectors side by side in the radiation incident direction. However, since the scintillator and the pixels that detect light are stacked in the radiation incident direction in each radiation detector, there is a risk that the radiation detection apparatus will be enlarged when a plurality of radiation detectors are arranged side by side.

[0005] An object of the present disclosure is to provide a radiation detector and a radiation inspection apparatus that can detect radiation in a plurality of energy ranges while achieving miniaturization.

[0006] A radiation detector according to one aspect of the present disclosure is a radiation detector having: [1] a shielding member in which an opening through which radiation passes is formed, a side surface facing the opening in a first direction, and a surface along a second direction intersecting the first direction and the first direction, the light conversion unit having a first conversion member that converts the radiation into light; a light detection unit having a plurality of pixels two-dimensionally arranged along a plane facing the surface; and a processing unit electrically connected to the plurality of pixels and processing output signals from the plurality of pixels, wherein the plurality of pixels are each arranged in a plurality of columns along the first direction.

[0007] In the above-described radiation detector, the photodetector includes a plurality of pixels arranged two-dimensionally along a plane facing the surface of the first conversion member along the first and second directions. This allows for a higher density of pixels in the direction of radiation incidence compared to a configuration in which the conversion member and pixels are alternately stacked in the direction of radiation incidence (radiation traveling along the first direction) entering the side of the first conversion member from the opening of the shielding member, thereby enabling miniaturization of the radiation detector. Furthermore, the plurality of pixels are arranged in multiple rows along the first direction. That is, the plurality of pixels arranged in each row are aligned along the direction of radiation incidence (first direction), so it is possible to detect radiation in multiple energy ranges. Therefore, the above-described radiation detector can detect radiation in multiple energy ranges while achieving miniaturization.

[0008] A radiation detector in one aspect of the present disclosure may be [2] "the radiation detector according to [1] above, wherein the plurality of pixels are arranged in a matrix formed by a plurality of rows along the second direction and a plurality of columns, and the processing unit controls the exposure time of the plurality of pixels for each row included in the plurality of rows." In this case, for example, by controlling the exposure time to be shorter for pixels closer to the incident surface of radiation in the first conversion member (the side facing the opening of the shielding member) and longer for pixels further from the incident surface, the amount of signal detected by the pixels can be appropriately adjusted (for example, signal saturation can be suppressed), and a high dynamic range radiation transmission image can be obtained.

[0009] A radiation detector in one aspect of the present disclosure may be [3] "the radiation detector according to [1] or [2] above, wherein the plurality of pixels are arranged in a matrix formed by a plurality of rows along the second direction and a plurality of columns, and the processing unit controls the readout period of the output signals from the plurality of pixels for each row included in the plurality of rows." In this case, for example, by controlling the readout period to be larger for pixels in rows closer to the incident surface of radiation in the first conversion member (the side facing the opening of the shielding member), and by controlling the readout period to be smaller for pixels in rows farther from the incident surface, each of the plurality of rows can output an output signal in sync with each other, and a high-quality radiographic image can be obtained.

[0010] A radiation detector in one aspect of the present disclosure may be [4] "a radiation detector according to any one of [1] to [3] above, wherein the processing unit controls the number of target pixels among the plurality of pixels that are arranged in the first direction and whose output signals are added together, based on the position of the plurality of target pixels in the first direction." In this case, for example, a high-quality radiotransmission image can be obtained by adding output signals from more pixels that are farther from the radiation incident surface (the side facing the opening of the shielding member) in the first conversion member.

[0011] A radiation detector in one aspect of the present disclosure may be [5] "a radiation detector according to any one of [1] to [4] above, wherein the plurality of pixels are arranged in a matrix formed by a plurality of rows along the second direction and a plurality of columns, and the plurality of rows include a first row and a second row which is further away from the aperture than the first row in the first direction, and each of the plurality of second pixels arranged in the second row is larger than each of the plurality of first pixels arranged in the first row." In this case, for example, the signal amount of the output signal from pixels far from the incident surface of radiation in the first conversion member (the side facing the aperture of the shielding member) can be appropriately increased, and a high-quality radiographic image can be obtained.

[0012] A radiation detector in one aspect of the present disclosure may be [6] "the radiation detector according to any one of [1] to [5] above, wherein the plurality of pixels are arranged in a matrix formed by a plurality of rows along the second direction and a plurality of columns, the plurality of rows include a third row and a fourth row which is further away from the aperture than the third row in the first direction, the plurality of pixels include a plurality of third pixels arranged in the third row, and at least a portion of each of the plurality of third pixels does not face the surface in a third direction which intersects the first direction and the second direction." In this case, for example, the signal amount of the output signal from pixels close to the radiation incident surface (the side facing the aperture of the shielding member) in the first conversion member can be appropriately reduced, and a high-quality radiographic image can be obtained.

[0013] A radiation detector in one aspect of the present disclosure may be [7] "a radiation detector according to any one of [1] to [6] above, wherein the plurality of pixels are arranged in a matrix formed by a plurality of rows along the second direction and a plurality of columns, and the processing unit corrects the position information of the output signals from the plurality of pixels based on the magnification ratio in each of the plurality of rows." In this case, since the position information of the output signals is corrected based on the magnification ratio, a high-quality radiographic image can be obtained.

[0014] A radiation detector in one aspect of the present disclosure may be [8] "a radiation detector according to any one of [1] to [7] above, wherein the processing unit acquires a plurality of output signals corresponding to a plurality of energy ranges of radiation from the plurality of pixels for each of the plurality of columns, and the plurality of energy ranges are different for each of the columns included in the plurality of columns." In this case, the energy resolution in the plurality of pixels is improved, and by applying sparse modeling using, for example, compressed sensing technology, it is possible to reconstruct a signal with a larger signal amount from an output signal with a small signal amount. As a result, high-quality radiographic images can be obtained.

[0015] A radiation detector in one aspect of the present disclosure may be [9] "the radiation detector according to any one of [1] to [8] above, wherein the light conversion unit has a second conversion member that converts the radiation into light in a first direction, adjacent to the first conversion member, the second conversion member faces at least a portion of the plurality of pixels in a third direction intersecting the first and second directions, and the material of the first conversion member and the material of the second conversion member are different from each other." In this case, the degree of freedom in selecting the materials for the first conversion member and the second conversion member can be increased, and as a result, it becomes possible to realize a design that meets the required performance of the radiation detector.

[0016] A radiation detector in one aspect of the present disclosure may be

[10] "the radiation detector according to any one of [1] to [9] above, wherein the light conversion unit has a third conversion member that converts the radiation into light in a first direction, adjacent to the first conversion member, the third conversion member faces at least a portion of the plurality of pixels in a third direction that intersects the first and second directions, and the first conversion member and the third conversion member are optically separated from each other." In this case, crosstalk between the plurality of pixels (photodetectors) can be suppressed, and a high-quality radiation transmission image can be obtained.

[0017] One aspect of the present disclosure is a radiation inspection device comprising

[11] "a transport unit for transporting an object to be inspected, an irradiation unit for irradiating the object to be inspected with radiation, and a radiation detector according to any one of [1] to

[10] above for detecting radiation that has passed through the object to be inspected." According to this radiation inspection device, for the reasons described above, it is possible to detect radiation in multiple energy ranges while miniaturizing the radiation detector.

[0018] This disclosure makes it possible to provide a radiation detector and a radiation detection device that can detect radiation in multiple energy ranges while being miniaturized.

[0019] Figure 1 is a perspective view showing a radiation inspection device according to the first embodiment. Figure 2 is a schematic diagram showing the configuration of the radiation inspection device shown in Figure 1. Figure 3 is a diagram showing the functional elements of the control device. Figure 4 is a diagram showing the configuration of the radiation detector shown in Figure 1. Figure 5 is a diagram showing the configuration of the radiation detector shown in Figure 1. Figure 6 is a diagram for explaining the magnification ratio in multiple rows composed of pixels. Figure 7 is a diagram showing the configuration of the radiation detector according to the second embodiment. Figure 8 is a diagram showing the configuration of the radiation detector according to the third embodiment. Figure 9 is a diagram showing the configuration of the radiation detector according to the fourth embodiment. Figure 10 is a schematic diagram showing the configuration of a radiation inspection device according to a modification of the fourth embodiment. Figure 11 is a diagram showing the configuration of the radiation detector according to the fifth embodiment. Figure 12 is a diagram showing the configuration of the radiation detector according to a modification of the fifth embodiment. Figure 13 is a schematic diagram showing the configuration of a radiation inspection device according to the sixth embodiment. Figure 14 is a diagram showing the configuration of the radiation detector according to the sixth embodiment. Figure 15 is a diagram showing the configuration of the radiation detector according to the seventh embodiment. Figure 16 is a diagram showing the configuration of the radiation detector according to a modification of the seventh embodiment.

[0020] Hereinafter, an example of this disclosure will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations are omitted. [First Embodiment] [Configuration of Radiation Inspection Apparatus]

[0021] Referring to Figures 1, 2, and 3, the configuration of the radiation inspection device 100 according to the first embodiment will be described. The radiation inspection device 100 is a device that irradiates an object to be inspected S with radiation from an irradiation unit 300 (radiation source) and detects the radiation that has passed through the object to be inspected S in multiple energy ranges. The radiation inspection device 100 performs, for example, inspection of foreign objects contained in the object to be inspected S or baggage inspection using a radiographic image. The radiation inspection device 100 comprises a radiation detector 1, a transport unit 200, an irradiation unit 300, and a control device 400. Hereinafter, the direction of radiation emission (the direction from the irradiation unit 3 toward the radiation detector 1) will be referred to as the Z-axis direction (first direction), one direction intersecting the Z-axis direction will be referred to as the X-axis direction (second direction), and the direction intersecting the Z-axis direction and the X-axis direction will be referred to as the Y-axis direction (third direction). In this example, the X-axis direction, Y-axis direction, and Z-axis direction are orthogonal to each other.

[0022] The radiation detector 1 detects radiation that has passed through the object S being inspected. The radiation detector 1 converts the radiation incident on the radiation detector 1 from the object S being inspected into light (scintillation light in this embodiment). The radiation detector 1 detects the converted scintillation light as an electrical signal using a photoreceiving element such as a photodiode. The electrical signal is used as measurement data for generating a radiation transmission image. The radiation detector 1 outputs the detected electrical signal (measurement data) to the control device 400. The detailed configuration of the radiation detector 1 will be described later.

[0023] The transport unit 200 transports the object to be inspected S. The transport unit 200 includes a belt section 201 on which the object to be inspected S is placed. The transport unit 200 transports the object to be inspected S in the transport direction at a predetermined transport speed by moving the belt section 201 in the transport direction (in this example, the Y-axis direction). The transport speed of the transport unit 200 can be changed by the transport control unit 202. The transport control unit 202 may also be able to change the height position (position in the Z-axis direction) of the belt section 201. By changing the height position of the belt section 201, the distance between the irradiation unit 300 and the object to be inspected S can be changed. The object to be inspected S may be, for example, food products such as meat, rubber products such as tires, luggage, cargo, resin products, metal products, resource materials such as minerals, waste for sorting or resource recovery (recycling), and electronic components.

[0024] The irradiation unit 300 is a radiation source that irradiates the object to be inspected S with radiation. The radiation emitted from the irradiation unit 300 may be, for example, X-rays. In this example, the irradiation unit 300 is a point light source and irradiates by diffusing radiation within a predetermined angular range. The irradiation unit 300 is positioned above the belt unit 201 at a predetermined distance from the belt unit 201 such that the direction of radiation irradiation is directed toward the belt unit 201 and the diffused radiation covers the entire width direction (X-axis direction) of the object to be inspected S. In the length direction (Y-axis direction) of the object to be inspected S, a predetermined division range in the length direction is defined as the radiation irradiation range. As the object to be inspected S is transported in the transport direction by the transport unit 200, radiation is irradiated over the entire length direction of the object to be inspected S.

[0025] The control device 400 is a computer device that controls various operations of the radiation detector 1. The control device 400 also processes output signals from the radiation detector 1. For example, the control device 400 generates a radiographic image of the object to be inspected S based on the measurement data output from the radiation detector 1, and generates inspection results for the object to be inspected S based on the radiographic image of the object to be inspected S. As shown in Figure 3, the control device 400 comprises a processing unit 401 and a control unit 402, which are composed of a processor, memory, storage, and communication device, a storage unit 403, which is a hard disk, an input unit 404, which is a mouse and keyboard, and a display unit 405, which is a display. The processing unit 401 processes various data by executing software (programs). The control device 400 is communicated with the radiation detector 1. [Radiation Detector Configuration]

[0026] The configuration of the radiation detector 1 according to this embodiment will be described in more detail with reference to Figures 4 and 5. Figures 4 and 5 are diagrams showing the configuration of the radiation detector 1. In Figure 5, the light conversion unit 30 of the radiation detector 1 is not shown. The radiation detector 1 comprises a shielding member 10, a substrate 20, a light conversion unit 30, a light detection unit 40, and a processing unit 50.

[0027] The shielding member 10 has a main body 11 that is impermeable to radiation (shielding). The main body 11 is a housing that accommodates the light conversion unit 30, the photodetection unit 40, and the processing unit 50. The main body 11 is made of, for example, lead. The main body 11 has an opening (slit) 12 through which radiation passes. The width of the opening in the X-axis direction is greater than the width of the opening in the Y-axis direction. The shielding member 10 is arranged such that the light conversion unit 30 faces the opening 12 in the Z-axis direction, and the substrate 20 and the photodetection unit 40 face the main body 11 (the part of the shielding member 10 other than the opening 12). As a result, radiation output from the irradiation unit 300 toward the light conversion unit 30 passes through the opening 12, and radiation output from the irradiation unit 300 toward the substrate 20 and the photodetection unit 40 is shielded by the shielding member 10.

[0028] The substrate 20 supports the light conversion unit 30, the light detection unit 40, and the processing unit 50. The substrate 20 is formed in a rectangular plate shape and is arranged perpendicular to the Y-axis direction. The light conversion unit 30, the light detection unit 40, and the processing unit 50 are arranged on one main surface of the substrate 20. The substrate 20 is fixed in the radiation detector 1.

[0029] The light conversion unit 30 converts radiation transmitted through the object S to be inspected into light (scintillation light in this embodiment). The light conversion unit 30 has a scintillator 31 (first conversion member), and the scintillator 31 converts radiation into scintillation light. The scintillator 31 may be formed of GOS:Pr (GOS doped with Pr) or GOS:Tb (GOS doped with Tb), or CSI:Tl (CSI doped with Tl). Any member that converts radiation into light can be used as the first conversion member, and for example, a phosphor may be used instead of a scintillator.

[0030] The scintillator 31 is formed in the shape of a rectangular plate (cuboid). The scintillator 31 includes a side surface 31a, a side surface 31b, a surface 31c, and a surface 31d. Side surface 31a faces the opening 12 of the shielding member 10 in the Z-axis direction. This allows radiation that has passed through the object to be inspected S to enter side surface 31a through the opening 12. Side surface 31b is located on the opposite side from side surface 31a in the Z-axis direction. Side surfaces 31a and 31b connect surfaces 31c and 31d to each other. Surface 31c is oriented along the X-axis and Z-axis directions and faces the light detection unit 40. Surface 31d is the surface opposite to surface 31c in the Y-axis direction and is oriented along the X-axis and Z-axis directions.

[0031] The light detection unit 40 detects scintillation light emitted from the light conversion unit 30. The light detection unit 40 has a plurality of pixels 41. Each pixel 41 is composed of, for example, a light-receiving element capable of detecting scintillation light. The light-receiving element may be a photodiode made of silicon, or a photodiode made of a compound semiconductor such as InGaAs or CdTe.

[0032] Each pixel 41 is formed in a rectangular shape in a planar view. In this example, each pixel 41 is formed in a square shape having the same shape as the others. The shape of the pixels 41 is not limited. Multiple pixels 41 are arranged two-dimensionally along a plane (virtual plane) opposite the surface 31c. Multiple pixels 41 are each arranged in multiple rows along the X-axis direction. Multiple pixels 41 are each arranged in multiple columns along the Z-axis direction. That is, multiple pixels 41 are arranged in a matrix formed by multiple rows and multiple columns.

[0033] In this example, N pixels 41 (where N is an integer greater than or equal to 2) are arranged in a row along the X-axis so that they are adjacent to each other. M pixels 41 (where M is an integer greater than or equal to 2) are arranged along the Z-axis so that they are adjacent to each other. The A-th pixel 41 (where A is any integer between 1 and M) of the row of N pixels is aligned along the X-axis. That is, in the light detection unit 40, M × N pixels 41 are arranged in a matrix. Hereinafter, a row in which multiple pixels 41 are arranged will be simply referred to as a "row," and a column in which multiple pixels 41 are arranged will be simply referred to as a "column." Two adjacent pixels 41 in the Z-axis direction are far apart from each other. The distance between two adjacent pixels 41 in the Z-axis direction is smaller than the width of a single pixel 41 in the Z-axis direction.

[0034] Multiple rows composed of multiple pixels 41 contain M rows. The M rows may be described as row R1, row R2, row R3, ..., row RM, in order from the row closest to the aperture 12. Multiple columns composed of multiple pixels 41 contain N columns. The N columns may be described as column C1, column C2, column C3, ..., column CN, in order from one side in the X-axis direction of the light detection unit 40.

[0035] Multiple pixels 41 overlap with the scintillator 31 in the Y-axis direction. In this example, the entirety of each pixel 41 overlaps with the scintillator 31. When viewed from the Y-axis direction, the scintillator 31 extends across the entire region where the multiple pixels 41 are arranged. Each pixel 41 is positioned so that its light-receiving surface faces the surface 31c of the scintillator 31. The pixels 41 convert the scintillation light emitted from the scintillator 31 into an electrical signal. The pixels 41 output the converted electrical signal as an output signal to the processing unit 50.

[0036] The processing unit 50 is electrically connected to the plurality of pixels 41 and the control device 400. The processing unit 50 is configured to include, for example, a circuit (such as a signal readout circuit). The processing unit 50 processes the output signals from the plurality of pixels 41. The processing of the processing unit 50 may, for example, read (acquire) an electrical signal from the pixels 41 as an output signal and transmit the output signal to the control device 400. In this embodiment, the processing unit 50 acquires an output signal from each pixel 41. The processing unit 50 may perform processing such as noise removal or amplification on the output signals from the pixels 41 before transmitting the output signal to the control device 400.

[0037] The processing unit 50 performs processing to control multiple pixels 41 (for example, various operations and settings of the pixels 41). The processing unit 50 may perform processing based on instructions from the control unit 402 of the control device 400. For example, the control unit 402 of the control device 400 may transmit an instruction signal for control to the pixels 41 to the processing unit 50, and the processing unit 50 may control the pixels 41 based on the instruction signal. The processing unit 50 controls, for example, the exposure time, sensor gain, readout period, etc., of the multiple pixels 41. The processing unit 50 may be composed of, for example, an FPGA, ASIC, microcontroller, etc. [Operation of the radiation inspection device]

[0038] Next, the operation of the radiation inspection device 100, that is, the process of acquiring a radiographic image of the object to be inspected S, will be explained. First, the object to be inspected S is placed on the belt section 201 of the transport section 200, and the transport section 200 moves the object to be inspected S in the transport direction (Y-axis direction). In this state, the irradiation section 300 irradiates the object to be inspected S with radiation. The radiation that has passed through the object to be inspected S passes through the opening 12 of the shielding member 10 and enters the side surface 31a of the scintillator 31. The radiation travels through the scintillator 31 from side surface 31a to side surface 31b.

[0039] The scintillator 31 generates scintillation light upon the incidence of radiation (converts radiation into scintillation light). At this time, the distance the radiation travels through the scintillator 31 depends on the energy of the radiation. Specifically, the higher the energy, the further the radiation reaches from the side surface 31a. In other words, radiation with higher energy is converted into scintillation light at a position farther from the side surface 31a, while radiation with lower energy is converted into scintillation light at a position closer to the side surface 31a.

[0040] Scintillation light emitted from the scintillator 31 enters the photodetector 40 from the surface 31c of the scintillator 31. The scintillation light is detected (received) by a plurality of pixels 41 of the photodetector 40. At this time, pixels 41 located in rows further away from the side surface 31a of the scintillator 31 (the opening 12 of the shielding member 10) detect scintillation light corresponding to radiation in a higher energy range. For example, the scintillation light detected by the pixel 41 located in row RM corresponds to scintillation light in a higher energy range than the scintillation light detected by the pixel 41 located in row R1.

[0041] Each pixel 41 in each column detects scintillation light corresponding to radiation in multiple energy ranges. Multiple pixels 41 arranged along the Z-axis in each column each detect scintillation light corresponding to radiation in different energy ranges. In this example, the number of detectable energy ranges is equal to the number of pixels 41 in each column. That is, multiple pixels 41 detect scintillation light corresponding to M energy ranges of radiation. Each pixel 41 outputs an electrical signal corresponding to the detected scintillation light as an output signal to the processing unit 50. In other words, the processing unit 50 reads the output signal from the pixel 41. The processing unit 50 transmits the acquired output signal to the control device 400. The processing unit 401 of the control device 400 processes the received output signal to generate a radiographic image. The display unit 405 of the control device 400 displays the generated radiographic image.

[0042] Next, the operation of the processing unit 50 will be described in more detail. In this embodiment, the processing unit 50 controls the exposure time of multiple pixels 41. Exposure time is the time during which an output signal is output from the pixel 41 (the length of time during which the processing unit 50 reads out the output signal). In this example, the processing unit 50 controls the exposure time of multiple pixels 41 row by row. More specifically, the processing unit 50 controls the exposure time of the pixels 41 such that the exposure time becomes shorter for rows closer to the side surface 31a of the scintillator 31 (the opening 12 of the shielding member 10) in the Z-axis direction. For example, the processing unit 50 controls the exposure time of the pixels 41 such that the exposure time of row R1 is shorter than the exposure time of row R2. In other words, the processing unit 50 controls the exposure time of the pixels 41 such that the exposure time becomes longer for rows further away from the side surface 31a of the scintillator 31 (the opening 12 of the shielding member 10) in the Z-axis direction.

[0043] The processing unit 50 may stop the exposure (readout of the output signal from the pixel 41) of the pixels 41 arranged in each row, triggered by the fact that the exposure time has reached the threshold value set for each row. The threshold value of the exposure time may be set by the user of the radiation inspection apparatus 100 or the like. Specifically, the user may input or select the threshold value using the input unit 404 of the control device 400, and the input or selected threshold value may be transmitted to the processing unit 50 of the radiation detector 1 and used. The threshold value of the exposure time may be set based on, for example, the exposure amount of each row in actual measurement using a phantom, or may be set based on inspection conditions such as an inspection recipe.

[0044] The processing unit 50 may perform a process of performing exposure a plurality of times and calculating the average value of the plurality of output signals acquired in each exposure. For example, in the pixel 41 with a short exposure time set, the processing unit 50 may intermittently (dividedly) acquire the output signal a plurality of times and calculate the average value of the plurality of acquired output signals. In this case, the processing unit 50 may transmit the calculated average value to the control device 400 as the value of the final output signal.

[0045] The processing unit 50 may control the sensor gain corresponding to the plurality of pixels 41. That is, the processing unit 50 may adjust the degree of amplification of the output signal from the pixel 41. In this example, the processing unit 50 controls the sensor gain corresponding to the plurality of pixels 41 for each row. More specifically, the processing unit 50 controls the sensor gain so that the degree of amplification becomes smaller for the rows closer to the side surface 31a (opening 12 of the shielding member 10) of the scintillator 31 in the Z-axis direction. For example, the processing unit 50 controls the sensor gain corresponding to the pixel 41 so that the sensor gain corresponding to the output signal from the pixel 41 arranged in row R1 is smaller than the sensor gain corresponding to the output signal from the pixel 41 arranged in row R2 (so that the degree of amplification becomes smaller). In other words, the processing unit 50 controls the sensor gain so that the degree of amplification becomes larger for the rows farther from the side surface 31a (opening 12 of the shielding member 10) of the scintillator 31 in the Z-axis direction.

[0046] In this embodiment, the processing unit 50 controls the readout period (line period) of the output signals from multiple pixels 41. The readout period of the output signals is the time interval between the output signals being output from the pixels 41 (the processing unit 50 reading out the output signals). In other words, the readout period of the output signals means the time interval from when the processing unit 50 acquires an output signal from a pixel 41 until it acquires the next output signal. In this example, the processing unit 50 controls the readout period of the output signals row by row. More specifically, the processing unit 50 controls the readout period so that the readout period is larger (the time interval is larger) for rows that are closer to the side surface 31a of the scintillator 31 (the opening 12 of the shielding member 10) in the Z-axis direction. For example, the processing unit 50 controls the readout period of the output signals from multiple pixels 41 so that the readout period corresponding to row R1 is larger than the readout period corresponding to row R2. In other words, the processing unit 50 controls the readout period so that the readout period is smaller (the time interval is smaller) for rows that are further from the side surface 31a of the scintillator 31 (the opening 12 of the shielding member 10) in the Z-axis direction.

[0047] The readout cycle may be set based on the magnification factor for each row. Specifically, first, the magnification factor for each row is calculated. If D1 is the distance along the Z-axis from the irradiation unit 300 (radiation source) to the object to be inspected S, and D2 is the distance along the Z-axis from the irradiation unit 300 to the pixel center of the pixel 41 placed in the target row, then the magnification factor for the target row is calculated as D2 / D1 (D2 divided by D1). The further the row is from the irradiation unit 300 (the larger the distance D2), the greater the magnification factor. Next, the readout speed (line speed) for each row is calculated. If V1 (m / min) is the speed in the transport direction of the object to be inspected S (in this embodiment, the Y-axis direction), then the readout speed V2 (m / min) is calculated as V1 (m / min) × magnification factor (D2 / D1). Subsequently, based on the readout speed for each row, the readout cycle is set so that each of the multiple rows outputs an output signal (the processing unit 50 reads it out) in sync with each other (at the same timing). The setting of the readout period described above may be performed by the processing unit 50 or by the control unit 402 of the control device 400.

[0048] The processing unit 50 corrects the position information of the output signals from the plurality of pixels 41 based on the magnification ratios in each of the plurality of rows. As described above, since the magnification ratios in each of the plurality of rows are different from each other, the sizes of the radiation images of the inspection object S in each row are also different from each other. In FIG. 6, the radiation irradiated from the irradiation unit 300 is indicated by a dashed line. As shown in FIG. 6, among the irradiated radiation, the radiation that has passed through column C3 in row R1 has passed through column C2 in row R4. Therefore, when dealing with the output signals of the pixels 41 without considering the magnification ratio (for example, when treating the output signals from a plurality of pixels 41 arranged in the same column as signals corresponding to the radiation that has passed through the same position in the inspection object S), there is a risk of blurring, displacement, virtual images, etc. occurring in the acquired radiation transmission image. In order to reduce such blurring and the like, the processing unit 50 corrects the position information of the output signals from the plurality of pixels 41 based on the magnification ratios in each of the plurality of rows.

[0049] Let's explain in more detail the difference in magnification between rows of pixels 41. For example, let D1 be the distance along the Z-axis from the irradiation unit 300 (radiation source) to the object S being inspected. Let D2(p1) be the distance along the Z-axis from the irradiation unit 300 to the pixel center of a pixel 41 located in row R1, let D2(p2) be the distance along the Z-axis from the irradiation unit 300 to the pixel center of a pixel 41 located in row R2, and let D2(p10) be the distance along the Z-axis from the irradiation unit 300 to the pixel center of a pixel 41 located in row R10. In this case, the magnification in row R1 is D2(p1) / D1, the magnification in row R2 is D2(p2) / D1, and the magnification in row R10 is D2(p10) / D1. The magnification ratio differs between row R1 and row R10 by D2(p10) / D2(p1), and between row R2 and row R10 by D2(p10) / D2(p2). The processing unit 50 applies a correction value to correct the position information to the output signal (signal brightness value) obtained from each row, and corrects the distortion between each row. The processing unit 50 may also apply correction processing to each pixel 41 arranged along the radiation incidence direction according to the digital summation range and the physical pixel size. For example, using row R10 as the reference, the processing unit 50 corrects the magnification ratio so that the radiation image corresponding to the output signal obtained in row R1 is D2(p10) / D2(p1). Similarly, the processing unit 50 corrects the magnification ratio so that the radiation image corresponding to the output signal obtained in row R2 is D2(p10) / D2(p2).

[0050] The following describes a specific method for magnification correction (magnification correction). First, the processing unit 50 sets a reference pixel for each row. If the pixels 41 for each row are located directly below the irradiation unit 300, which is the radiation source (at a position where they overlap in the Z-axis direction), the processing unit 50 may set those pixels 41 as reference pixels. Alternatively, the processing unit 50 may determine the corresponding pixels 41 for each row based on the radiation image of the object to be inspected S and set them as reference pixels. For example, first, a phantom for magnification correction (including a chart, reference sample, etc.) may be imaged, and the corresponding pixels for each row may be determined based on the phantom image. In this case, if the phantom image for each row consists of one pixel, that one pixel may be determined as the corresponding pixel and set as the reference pixel. If the phantom image for each row consists of multiple pixels, the corresponding pixels may be determined based on information such as the center or edge of the phantom image and set as the reference pixel.

[0051] The processing unit 50 performs magnification correction centered on the reference pixel. Examples of correction methods include the method described in Japanese Patent Application Publication No. 2011-64642. For example, simple interpolation, first-order interpolation, second-order interpolation, spline interpolation, or Lagrangian interpolation may be applied. The brightness value of the corrected pixel is obtained by generating one corrected pixel from two adjacent pixels. The brightness value IL(y) of the corrected pixel may be set to satisfy the formula IL(y) = γ(α × L(x) + β × L(x+1)) based on the signal values ​​L(x) and L(x+1) of the two pixels before correction, pixel correction coefficients α and β, and brightness adjustment coefficient γ.

[0052] As a magnification correction, decimation or reduction processing may be applied. For example, with respect to row R1, the processing unit 50 performs magnification correction so that the radiation image corresponding to the output signal obtained in row R2 is D2(p1) / D2(p2) times. With respect to row R1, the processing unit 50 performs magnification correction so that the radiation image corresponding to the output signal obtained in row R10 is D2(p10) / D2(p1) times. As for decimation processing, simple decimation, averaging decimation, additive decimation, minimum filter decimation, or maximum filter decimation can be applied. The processing applied to the correction is not limited to one of the magnification, decimation, and reduction processing, but two or more arbitrary processing may be combined. For example, the processing unit 50 may perform magnification and reduction processing in combination. It is preferable that the difference in magnification of each row be as small as possible.

[0053] The correction processing by the processing unit 50 will be further explained using specific numerical values. The shape of each pixel 41 when viewed from the Y-axis direction is square, and the pitch between pixels 41 (the distance between the centers of adjacent pixels 41 in the X-axis direction and the Z-axis direction) is 1 mm. The distance along the Z-axis from the irradiation unit 300 to the object to be inspected S is 100 mm, and the distance from the radiation source to the center of the pixel 41 located in row R1 is 110 mm. In this case, the magnification in row R1 is 1.1. The distance from the radiation source to the center of the pixel 41 located in row R2 is 111 mm. In this case, the magnification in row R2 is 1.11. The distance from the radiation source to the center of the pixel 41 located in row R10 is 119 mm. In this case, the magnification in row R10 is 1.19.

[0054] When row R10 is used as the reference, the processing unit 50 performs magnification correction so that the radiation image corresponding to the output signal obtained in row R1 becomes 1.19 / 1.1 = 1.082 times. When row R10 is used as the reference, the processing unit 50 performs magnification correction so that the radiation image corresponding to the output signal obtained in row R2 becomes 1.19 / 1.11 = 1.072 times. Furthermore, when row R1 is used as the reference, the processing unit 50 performs reduction processing so that the radiation image corresponding to the output signal obtained in row R2 becomes 0.99 times. When row R1 is used as the reference, the processing unit 50 performs reduction processing so that the radiation image corresponding to the output signal obtained in row R10 becomes 0.92 times. The above-described method for magnification correction is just one example, and other methods may be used. The processing unit 50 may perform the above correction processing based on instructions from the control unit 402 of the control device 400. The processing unit 50 transmits the position information of the corrected output signal to the control device 400 along with the output signal. The processing unit 401 of the control device 400 processes the output signal based on the received position information and generates a radiographic image. [Operation and Effects]

[0055] In the radiation detector 1 and radiation inspection device 100, the photodetector 40 includes a plurality of pixels 41 arranged two-dimensionally along a plane facing the surface 31c of the scintillator 31. This allows for a higher density of pixels 41 in the direction of radiation incidence compared to a configuration in which the scintillator and pixels are alternately stacked in the direction of radiation incidence (radiation traveling along the Z-axis), thereby enabling miniaturization of the radiation detector 1. Furthermore, the plurality of pixels 41 are arranged in a plurality of rows along the Z-axis. That is, the plurality of pixels 41 arranged in each row are aligned along the direction of radiation incidence (Z-axis), so radiation of multiple energy ranges can be detected. Therefore, the radiation detector 1 can detect radiation of multiple energy ranges while achieving miniaturization.

[0056] Multiple pixels 41 are arranged in a matrix, each consisting of multiple rows aligned along the X-axis and multiple columns aligned along the Z-axis. The processing unit 50 controls the exposure time of each row of pixels 41. This allows for, for example, shortening the exposure time of pixels 41 closer to the radiation incident surface in the scintillator 31 (the side surface 31a facing the opening 12 of the shielding member 10) and lengthening the exposure time of pixels 41 further from the incident surface. This appropriately adjusts the signal amount detected by the pixels 41 (for example, suppressing signal saturation), enabling the acquisition of a high dynamic range radiographic image.

[0057] The processing unit 50 controls the readout period of the output signals from multiple pixels 41 row by row. For example, by controlling the readout period so that the pixels 41 in rows closer to the radiation incident surface (the side surface 31a facing the opening 12 of the shielding member 10) in the scintillator 31 are read more frequently, and the readout period so that the pixels 41 in rows further from the incident surface are read less frequently, each of the multiple rows can output output signals in sync with each other, thereby enabling the acquisition of high-quality radiographic images.

[0058] The processing unit 50 corrects the position information of the output signals from multiple pixels 41 based on the magnification ratio in each of the multiple rows. As a result, the position information of the output signals is corrected based on the magnification ratio, making it possible to obtain high-quality radiographic images. [Second Embodiment]

[0059] Referring to Figure 7, the radiation inspection apparatus 100 and radiation detector 1 according to the second embodiment will be described. Below, the differences between the radiation inspection apparatus 100 and radiation detector 1 according to the second embodiment will be mainly described, and common points may be omitted from the explanation. In this embodiment, the processing unit 50 adds the output signals from a plurality of pixels 41 arranged in the Z-axis direction. A plurality of pixels 41 arranged in the Z-axis direction whose output signals are added together are called target pixels. The processing unit 50 controls the number of target pixels based on the position of the target pixels in the Z-axis direction.

[0060] More specifically, the processing unit 50 controls the number of target pixels so that the further the position of the target pixel in the Z-axis direction is from the side surface 31a of the scintillator 31 (the opening 12 of the shielding member 10), the greater the number of target pixels. In the example shown in Figure 7, the processing unit 50 acquires the output signal from the pixel 41 located in row R1 in each column without adding it to the output signals from other pixels 41, acquires the output signals from two pixels 41 located in rows R2 and R3 by adding them together, and acquires the output signals from three pixels 41 located in rows R4 to R6 by adding them together. Thereafter, the processing unit 50 increases the number of pixels 41 (target pixels) whose output signals are added up to row RM, and acquires the output signals from the target pixels by adding them together. The processing unit 50 acquires the output signal with the target pixels as one channel.

[0061] The processing unit 50 controls the number of multiple pixels 41 (target pixels) whose output signals are added together, based on the positions of the multiple target pixels in the Z-axis direction. This allows for the acquisition of high-quality radiographic images by adding output signals from more pixels 41 that are further from the radiation incident surface in the scintillator 31 (the side surface 31a facing the opening 12 of the shielding member 10) (pixels 41 with smaller output signal amounts). [Third Embodiment]

[0062] Referring to Figure 8, the radiation inspection apparatus 100 and radiation detector 1 according to the third embodiment will be described. Below, the differences from the radiation inspection apparatus 100 and radiation detector 1 according to the third embodiment will be mainly described, and common points may be omitted from the explanation. In this embodiment, the plurality of rows include a first row and a second row which is further away from the opening 12 of the shielding member 10 than the first row in the Z-axis direction. Each of the plurality of pixels 41 (plural second pixels) arranged in the second row is larger than each of the plurality of pixels 41 (plural first pixels) arranged in the first row.

[0063] In this embodiment, row R1 is the first row, and row R2, which is further away from the opening 12 of the shielding member 10 than row R1 in the Z-axis direction, is the second row. Each of the plurality of pixels 41 arranged in row R2 is larger than each of the plurality of pixels 41 arranged in row R1. The size of a pixel 41 is the area of ​​the pixel 41 when viewed from the Y-axis direction (viewed from the light-receiving surface side). The size of the pixels 41 arranged in the second row may be twice or more, three or more, or four or more times the size of the pixels 41 arranged in the first row.

[0064] In this embodiment, the plurality of rows include row R1 (first row) and row R2 (second row), which is further away from the opening 12 of the shielding member 10 than row R1 in the Z-axis direction. Each of the plurality of pixels 41 (second pixels) arranged in row R2 is larger than each of the plurality of pixels 41 (first pixels) arranged in row R1. This makes it possible to appropriately increase the signal amount of the output signal from pixels 41 that are far from the radiation incident surface (the side surface 31a facing the opening 12 of the shielding member 10) in the scintillator 31, and to obtain a high-quality radiographic image. [Fourth Embodiment]

[0065] Referring to Figure 9, the radiation inspection apparatus 100 and radiation detector 1 according to the fourth embodiment will be described. Below, the differences between the radiation inspection apparatus 100 and radiation detector 1 according to the fourth embodiment will be mainly described, and common points may be omitted from the description. In this embodiment, the plurality of rows include a third row and a fourth row which is further away from the opening 12 of the shielding member 10 than the third row in the Z-axis direction. At least a portion of each of the plurality of pixels 41 (plural third pixels) arranged in the third row does not face the surface 31c of the scintillator 31 in the Y-axis direction. The entirety of each of the plurality of pixels 41 (plural fourth pixels) arranged in the fourth row faces the surface 31c in the Y-axis direction.

[0066] In this embodiment, row R1, which is closest to the opening 12 of the shielding member 10, is the third row, and row R2, which is further away from the opening 12 of the shielding member 10 than row R1 in the Z-axis direction, is the fourth row. At least a portion of each of the multiple pixels 41 (multiple third pixels) arranged in row R1 does not face the surface 31c of the scintillator 31 in the Y-axis direction. In this example, when viewed from the Y-axis direction, half of the region of the pixels 41 arranged in row R1 that is closest to the opening 12 of the shielding member 10 does not face the surface 31c. When viewed from the Y-axis direction, the pixel centers of the pixels 41 arranged in row R1 coincide with the side surface 31a of the scintillator 31. The entirety of each of the multiple pixels 41 (multiple fourth pixels) arranged in row R2 faces the surface 31c in the Y-axis direction.

[0067] In this embodiment, the plurality of rows include row R1 (third row) and row R2 (fourth row), which is further away from the opening 12 of the shielding member 10 than row R1 in the Z-axis direction. At least a portion of each of the plurality of pixels 41 (third pixels) arranged in row R1 does not face the surface 31c of the scintillator 31 in the Y-axis direction. This makes it possible to appropriately reduce the signal amount of the output signal from pixels 41 that are close to the incident surface of radiation in the scintillator 31 (the side surface 31a facing the opening 12 of the shielding member 10), and to obtain a high-quality radiographic image.

[0068] Next, a modified example of the fourth embodiment will be described with reference to Figure 10. The radiation detector 1 according to this modified example further comprises a substrate 25, a photodetector 45, and a processing unit 55. The substrate 25 supports the photodetector 45 and the processing unit 55. The configuration of the substrate 25 is the same as that of the substrate 20. The main surface of the substrate 25 on which the photodetector 45 is located faces the main surface of the substrate 20 on which the photodetector 40 is located in the Y-axis direction. Between the substrate 25 and the substrate 20, the photodetector 45, the photoconversion unit 30, and the photodetector 40 are arranged in this order from the substrate 25 side.

[0069] The configuration of the photodetector 45 is the same as that of the photodetector 40. The multiple pixels of the photodetector 45 face the surface 31d of the scintillator 31 in the Y-axis direction. The entirety of each of the multiple pixels of the photodetector 45 faces (overlaps with) the surface 31d. Of the scintillation light generated in the scintillator 31, the scintillation light emitted from the surface 31d is detected by the multiple pixels of the photodetector 45. In the Z-axis direction, the positions of the photodetector 40 and the photodetector 45 are different from each other. Specifically, the photodetector 40 is located closer to the opening 12 of the shielding member 10 than the photodetector 45. In this example, the photodetectors 40 and 45 are arranged such that the position of each row of the photodetector 40 is offset from the position of the corresponding row in the photodetector 45 by a distance equal to half the width along the Z-axis direction of a single pixel (half a pixel). The processing unit 55 is electrically connected to the multiple pixels of the light detection unit 45 and the control device 400. The processing unit 55 is configured to include, for example, a circuit (such as a signal readout circuit). The processing unit 55 processes the output signals from the multiple pixels of the light detection unit 45. The configuration of the processing unit 55 is the same as that of the processing unit 50.

[0070] In this modified example, the radiation detector 1 includes a photodetector 45. Multiple pixels of the photodetector 45 face the surface 31d of the scintillator 31 in the Y-axis direction. This allows for more efficient detection of scintillation light emitted from the scintillator 31. Furthermore, in the Z-axis direction, the positions of the photodetector 40 and the photodetector 45 are different. This allows the photodetector 40 and the photodetector 45 to detect radiation in different energy ranges. As a result, the energy resolution is improved, and high-quality radiation transmission images can be obtained. [Fifth Embodiment]

[0071] Referring to Figure 11, the radiation inspection apparatus 100 and radiation detector 1 according to the fifth embodiment will be described. Below, the differences from the radiation inspection apparatus 100 and radiation detector 1 according to the first embodiment will be mainly described, and common points may be omitted from the explanation. In the first embodiment, the number, shape, and position in the Z-axis direction of the pixels 41 in each column are the same. Therefore, the energy range of the radiation detected in each column is the same. That is, multiple output signals corresponding to multiple radiation with the same energy range are acquired in multiple columns. For example, the multiple energy ranges corresponding to the multiple output signals acquired from column C1 are the same as the multiple energy ranges corresponding to the multiple output signals acquired from column C2.

[0072] In contrast, in this embodiment, the energy ranges of the radiation detected in each column are different from each other. That is, for each column, multiple output signals corresponding to radiation in multiple energy ranges that are different from each other are acquired. For example, the multiple energy ranges corresponding to the multiple output signals acquired from column C1 are different from the multiple energy ranges corresponding to the multiple output signals acquired from column C2. The configuration for detecting radiation in different energy ranges for each column will be described below.

[0073] The radiation detector 1 according to this embodiment further includes a filter 70. The filter 70 is positioned between the irradiation unit 300 and the light conversion unit 30 (scintillator 31). The filter 70 selectively transmits radiation within a specific energy range. That is, the filter 70 controls the energy spectrum of the radiation reaching the light conversion unit 30. The filter 70 may be made of, for example, copper.

[0074] The filter 70 is positioned in the Z-axis direction so as to overlap with some of the columns but not with the other columns. The columns onto which the filter 70 overlaps may be set randomly. The filter 70 has multiple apertures 71 formed therein. The parts of the filter 70 where apertures 71 are not formed overlap with the columns, and the parts where apertures 71 are formed do not overlap with the columns. For example, in the example shown in Figure 11, the filter 70 is positioned in the Z-axis direction so as to overlap with columns C1 and C2 but not with column C3. A portion of the radiation within a certain energy range from the radiation irradiated from the irradiation unit 300 is blocked by the filter 70. Therefore, the energy range of the radiation incident on the columns that overlap with the filter 70 is different from the energy range of the radiation incident on the columns that do not overlap with the filter 70.

[0075] In the radiation detector 1 according to this embodiment, the shape (length along the Z-axis) and position (position of the pixel center in the Z-axis direction) of the pixels 41 in each row are different from each other. For example, in row C1, pixels 411a, 412a, and 413a are arranged in that order from the side closest to the opening 12 of the shielding member 10. In row C2, pixels 411b, 412b, and 413b are arranged in that order from the side closest to the opening 12 of the shielding member 10. Pixels 411a, 412a, 413a, 411b, 412b, and 413b are all pixels 41.

[0076] The shape of pixel 411a is smaller than that of pixel 411b. Also, in the Z-axis direction, the pixel center of pixel 411a is located closer to the aperture 12 than the pixel center of pixel 411b. Similarly, the shapes and positions of pixels 412a and 412b, and pixels 413a and 413b, are different from each other. By appropriately combining the arrangement of the filter 70 and the adjustment of the shape and position of the pixels 41 as described above, the processing unit 50 can acquire multiple output signals from the pixels 41 corresponding to radiation of multiple different energy ranges for each row.

[0077] When a configuration is adopted to detect radiation in different energy ranges for each column as described above, the energy resolution improves, but the signal amount in each energy range decreases. Therefore, the processing unit 50 applies sparse modeling using compressed sensing technology to reconstruct a signal with a larger (desired) signal amount from an output signal with a small signal amount.

[0078] In this embodiment, the processing unit 50 acquires multiple output signals corresponding to multiple energy ranges of radiation from multiple pixels 41 in each of the multiple columns. The multiple energy ranges are different for each column. This improves the energy resolution of the multiple pixels 41, and by applying sparse modeling using, for example, compressed sensing technology, it is possible to reconstruct a signal with a larger signal amount from an output signal with a small signal amount. As a result, high-quality radiographic images can be obtained.

[0079] Next, a modified example of the fifth embodiment will be described. In this embodiment, the processing unit 50 may acquire multiple output signals corresponding to radiation of different energy ranges from the pixels 41 for each column by controlling the summation range of the output signals in each column. In the example shown in Figure 12, there are 7 rows. In column C1, pixels 411a, 412a, 413a, 414a, 415a, 416a, and 417a are arranged in this order from the side closest to the opening 12 of the shielding member 10. In column C2, pixels 411b, 412b, 413b, 414b, 415b, 416b, and 417b are arranged in this order from the side closest to the opening 12.

[0080] The processing unit 50 acquires the output signal from pixel 411a without adding it to the output signals from other pixels 41, acquires the output signals from pixels 412a to 415a by adding them together, and acquires the output signals from pixels 416a and 417a by adding them together. In other words, the processing unit 50 acquires the output signals by treating pixels 412a to 415a as one channel and pixels 416a and 417a as one channel.

[0081] The processing unit 50 acquires the output signals of pixels 411b and 412b by adding them together, acquires the output signal from pixel 413b without adding it to the output signals from other pixels 41, and acquires the output signals from pixels 414b to 417b by adding them together. In other words, the processing unit 50 acquires the output signals of pixels 411b and 412b as one channel, and pixels 414b to 417b as another channel. In this way, the processing unit 50 adds the output signals of pixels 41 at different positions and in different numbers in each column. By controlling the pixels 41 whose output signals are added, the processing unit 50 can acquire multiple output signals from pixels 41 corresponding to radiation in multiple different energy ranges for each column. [Sixth Embodiment]

[0082] Referring to Figures 13 and 14, the radiation inspection apparatus 100 and radiation detector 1 according to the sixth embodiment will be described. Hereinafter, the differences between the radiation inspection apparatus 100 and radiation detector 1 according to the sixth embodiment will be mainly described, and common points may be omitted from the explanation. In this embodiment, the light conversion unit 30 has a scintillator 32 (second conversion member) aligned with the scintillator 31 in the Z-axis direction. The scintillator 32 faces at least a portion of the plurality of pixels 41 in the Y-axis direction. Any member that converts radiation to light can be used as the second conversion member; for example, a phosphor may be used instead of a scintillator.

[0083] In this example, scintillator 31 faces a pixel 41 located in row R1 in the Y-axis direction, and scintillator 32 faces a pixel 41 located in other rows (rows R2 to RM) in the Y-axis direction. The width (maximum width) of scintillator 31 in the Z-axis direction is approximately equal to the width of a single pixel 41 in the Z-axis direction, and is smaller than the width (maximum width) of scintillator 32 in the Z-axis direction. The width (maximum width) of scintillator 31 in the X-axis direction is equal to the width (maximum width) of scintillator 32 in the X-axis direction.

[0084] The scintillator 32 is formed in the shape of a rectangular plate (cuboid). The scintillator 32 includes a side surface 32a, a side surface 32b, a surface 32c, and a surface 32d. Side surface 32a faces the opening 12 of the shielding member 10 via the scintillator 31 in the Z-axis direction. This allows radiation that has passed through the scintillator 31 to enter side surface 32a. The scintillator 32 is positioned such that side surface 32a is in contact with side surface 31b of the scintillator 31. Side surface 32b is located on the opposite side from side surface 32a in the Z-axis direction. Side surfaces 32a and 32b connect surfaces 32c and 32d to each other. Surface 32c is oriented along the X-axis and Z-axis directions and faces the photodetector 40. Surface 32d is the surface opposite to surface 32c in the Y-axis direction and is oriented along the X-axis and Z-axis directions.

[0085] The materials of scintillator 31 and scintillator 32 are different from each other. When we say that the materials of scintillator 31 and scintillator 32 are different from each other, we mean that they are different in terms of type or ratio. When we say that the materials of scintillator 31 and scintillator 32 are different in terms of type, it means that one of the materials of scintillator 31 or scintillator 32 contains at least one material that is not included in the other. Furthermore, when we say that the materials of scintillator 31 and scintillator 32 are different in terms of ratio, it means that the ratio of the materials contained in scintillator 31 is different from the ratio of the materials contained in scintillator 32. In other words, even if the materials of scintillator 31 and scintillator 32 are composed of materials of the same type, if the ratios of the materials are different, then the materials of scintillator 31 and scintillator 32 can be said to be different from each other. Because the materials of scintillator 31 and scintillator 32 are different from each other, scintillator 31 and scintillator 32 have different properties (e.g., luminescence efficiency, absorption efficiency, etc.).

[0086] The material of the scintillator 31 closest to the opening 12 of the shielding member 10 may be a material with relatively low conversion efficiency from radiation to scintillation light (for example, low luminescence efficiency or absorption efficiency). This can suppress saturation of the signal amount of the output signal in row R1 on the radiation incident side. The material of the scintillator 31 may be, for example, GOS:Pr. The scintillator 31 may also be a scintillator for soft X-rays (YGAG:Ce), etc. The material of the scintillator 32 may be a material with higher conversion efficiency from radiation to scintillation light compared to the material of the scintillator 31. The material of the scintillator 32 may be, for example, GOS:Tb or CSI:Tl. The doping agents contained in the materials of the scintillator 31 and the scintillator 32 are not limited to Tb, Pr, Ce, and Tl, but may also be Eu, etc.

[0087] If the material of scintillator 31 and scintillator 32 are both mixtures of scintillator material (a substance that absorbs radiation and converts it into scintillation light) and binder resin, the ratio of scintillator material to binder resin in the material of scintillator 31 may differ from the ratio in scintillator 32. For example, the proportion of binder resin in the material of scintillator 31 may be higher than that in the material of scintillator 32 (the density of the scintillator material may be relatively lower).

[0088] The materials for scintillator 31 and scintillator 32 may each contain a light-shielding material that blocks scintillation light. The proportion of the light-shielding material may be higher in the material for scintillator 31 compared to the material for scintillator 32. The light-shielding rate of the light-shielding material for scintillation light may be, for example, 80% or more. The materials for scintillator 31 and scintillator 32 may each contain a light-absorbing material that absorbs scintillation light. The proportion of the light-absorbing material may be higher in the material for scintillator 31 compared to the material for scintillator 32. The absorption rate of the light-absorbing material for scintillation light may be, for example, 80% or more.

[0089] In this embodiment, the light conversion unit 30 has a scintillator 32 that is aligned with the scintillator 31 in the Z-axis direction. The scintillator 32 faces at least a portion of the plurality of pixels 41 in the Y-axis direction. The scintillator 31 and the scintillator 32 are made of different materials. This increases the degree of freedom in material selection for the scintillator 31 and the scintillator 32, and as a result, it becomes possible to realize a design that meets the required performance of the radiation detector 1. For example, by making the material of the scintillator 31 that is close to the aperture 12 of the shielding member 10 a material that has a lower conversion efficiency from radiation to scintillation light compared to the material of the scintillator 32, it is possible to suppress the saturation of the signal amount of the output signal in the radiation incident row R1. [Seventh Embodiment]

[0090] Referring to Figure 15, the radiation inspection apparatus 100 and radiation detector 1 according to the seventh embodiment will be described. Hereinafter, the differences between the radiation inspection apparatus 100 and radiation detector 1 according to the seventh embodiment will be mainly described, and common points may be omitted from the explanation. In this embodiment, the light conversion unit 30 includes, in addition to the scintillator 31, a scintillator 33 (third conversion member), a scintillator 34, and a scintillator 35. Any member that converts radiation to light can be used as the third conversion member; for example, a phosphor may be used instead of a scintillator. In this case, not only the scintillator 33 (third conversion member), but also the scintillators 34 and 35 may be replaced with other conversion members (such as phosphors). The scintillators 31, 33, 34, and 35 are arranged in this order from the side closest to the opening 12 of the shielding member 10 in the Z-axis direction.

[0091] In the example shown in Figure 15, there are 7 rows. In this example, scintillator 31 faces a pixel 41 located in row R1 in the Y-axis direction, scintillator 33 faces a pixel 41 located in row R3 in the Y-axis direction, scintillator 34 faces a pixel 41 located in row R5 in the Y-axis direction, and scintillator 35 faces a pixel 41 located in row R7 in the Y-axis direction. None of the scintillators face the pixels 41 located in rows R2, R4, and R6 in the Y-axis direction.

[0092] The width (maximum width) of scintillator 31 in the Z-axis direction is approximately equal to the width of a single pixel 41 in the Z-axis direction, and is equal to the respective widths (maximum widths) of scintillators 33, 34, and 35 in the Z-axis direction. The respective widths (maximum widths) of scintillators 31, 33, 34, and 35 in the X-axis direction are equal to each other.

[0093] Each of the scintillators 33 to 35 is formed in a rectangular parallelepiped shape. Scintillator 33 includes side 33a and side 33b. Side 33a faces the opening 12 of the shielding member 10 via scintillator 31 in the Z-axis direction. This allows radiation that has passed through scintillator 31 to enter side 33a. Side 33b is located on the opposite side from side 33a in the Z-axis direction. Scintillator 34 includes side 34a and side 34b. Side 34a faces the opening 12 of the shielding member 10 via scintillators 31 and 33 in the Z-axis direction. This allows radiation that has passed through scintillators 31 and 33 to enter side 34a. Side 34b is located on the opposite side from side 34a in the Z-axis direction. Scintillator 35 includes side 35a and side 35b. Side surface 35a faces the opening 12 of the shielding member 10 via scintillators 31, 33, and 34 in the Z-axis direction. This allows radiation that has passed through scintillator 31 to enter side surface 35a. Side surface 35b is located on the opposite side from side surface 35a in the Z-axis direction.

[0094] Multiple scintillators 31, 33, 34, and 35 are optically separated from each other. Optical separation of multiple scintillators means that there is a structure between the multiple scintillators that prevents the propagation of scintillation light. For example, if there is a reflective member (e.g., a reflective film) that reflects scintillation light, or a light-shielding member (e.g., a light-shielding film) that blocks scintillation light, between the multiple scintillators, the multiple scintillators are optically separated from each other. Also, if there is space between the multiple scintillators (they are physically separated), the propagation of scintillation light from one scintillator to another is hindered by the space (reflection occurs between the scintillator and the space), so the multiple scintillators can be said to be optically separated from each other.

[0095] In this example, the light conversion unit 30 has light-shielding films 81, 82, and 83. The light-shielding rate of the light-shielding films against scintillation light may be, for example, 80% or more. Light-shielding film 81 is formed on the side surface 31b of scintillator 31. That is, it is placed between scintillator 31 and scintillator 33. Scintillator 31 and scintillator 33 are optically separated from each other by light-shielding film 81. Light-shielding film 82 is formed on the side surface 33b of scintillator 33. That is, it is placed between scintillator 33 and scintillator 34. Scintillator 33 and scintillator 34 are optically separated from each other by light-shielding film 82. Light-shielding film 83 is formed on the side surface 34b of scintillator 34. That is, it is placed between scintillator 34 and scintillator 35. Scintillator 34 and scintillator 35 are optically separated from each other by light-shielding film 83.

[0096] Multiple scintillators 31, 33, 34, and 35 are arranged spaced apart from each other in the Z-axis direction. Scintillator 33 has a side surface 33a spaced apart from the side surface 31b of scintillator 31. Scintillators 31 and 33 are optically separated from each other by the space between them. Scintillator 34 has a side surface 34a spaced apart from the side surface 33b of scintillator 33. Scintillators 33 and 34 are optically separated from each other by the space between them. Scintillator 35 has a side surface 35a spaced apart from the side surface 34b of scintillator 34. Scintillators 34 and 35 are optically separated from each other by the space between them.

[0097] The light conversion unit 30 has a scintillator 33 that is aligned with the scintillator 31 in the Z-axis direction. The scintillator 33 faces at least some of the multiple pixels 41 in the Y-axis direction. The scintillators 31 and 33 are optically separated from each other. This suppresses crosstalk between the multiple pixels 41 (photodetectors), making it possible to acquire high-quality radiotransmission images.

[0098] Next, a modified example of the seventh embodiment will be described with reference to Figure 16. In each of the embodiments described above, the distance between two adjacent pixels 41 in the Z-axis direction is smaller than the width of a single pixel 41 in the Z-axis direction. In contrast, in the modified example shown in Figure 16, the distance D10 between two adjacent pixels 41 in the Z-axis direction is greater than or equal to the width of a single pixel 41 in the Z-axis direction. That is, the distance between adjacent rows in the Z-axis direction is greater than or equal to the width of a single pixel 41 in the Z-axis direction. By increasing the distance between two adjacent pixels 41 in the Z-axis direction in this way (for example, making it greater than or equal to the width of a single pixel 41 in the Z-axis direction), crosstalk between multiple pixels 41 (photodetectors) can be suppressed, and high-quality radiographic images can be obtained.

[0099] This disclosure is not limited to the embodiments described above. Modifications of the embodiments described above will be described below. In the following description, the differences from the embodiments described above will be mainly explained, and common points may be omitted from the explanation. For example, in the embodiments described above, two adjacent pixels 41 in the Z-axis direction may be in contact with each other. That is, two adjacent pixels 41 in the Z-axis direction do not have to be spaced apart from each other. The distance between two adjacent pixels 41 in the Z-axis direction may be greater than or equal to the width of one pixel 41 in the Z-axis direction, or it may be greater than or equal to twice the width of one pixel 41 in the Z-axis direction.

[0100] In the third embodiment, the first row may be any row from among a plurality of rows. For example, in the example shown in Figure 8, any one of rows R2 to RM-1 may be the first row. The second row may be any row that is further away from the opening 12 of the shielding member 10 than the first row in the Z-axis direction, and does not have to be a row adjacent to the first row in the Z-axis direction. For example, when row R1 is the first row, the second row may be any one of rows R3 to RM.

[0101] In the fourth embodiment, the third row may be any row from among a plurality of rows. For example, in the example shown in Figure 9, any one of rows R2 to RM-1 may be the third row. The fourth row may be any row that is further away from the opening 12 of the shielding member 10 than the third row in the Z-axis direction, and does not have to be a row adjacent to the third row in the Z-axis direction. For example, when row R1 is the third row, the fourth row may be any one of rows R3 to RM. The row corresponding to the first row in the third embodiment and the row corresponding to the third row in the fourth embodiment may be the same or different from each other. The row corresponding to the second row in the third embodiment and the row corresponding to the fourth row in the fourth embodiment may be the same or different from each other.

[0102] 1...Radiation detector, C1-CM...Rows, R1-RM...Plant, 10...Shielding member, 12...Aperture, 30...Light conversion unit, 31...Scintillator (first conversion member), 31a...Side, 31c...Surface, 32...Scintillator (second conversion member), 33...Scintillator (third conversion member), 40...Light detection unit, 41...Pixel, 50...Processing unit, 100...Radiation inspection device, 200...Transport unit, 300...Irradiation unit, S...Object to be inspected.

Claims

1. A radiation detector comprising: a shielding member having an opening through which radiation passes; a first conversion member having a side surface facing the opening in a first direction and a surface along the first direction and a second direction intersecting the first direction, which converts the radiation into light; a photodetector having a plurality of pixels arranged two-dimensionally along a plane facing the surface; and a processing unit electrically connected to the plurality of pixels and processing output signals from the plurality of pixels, wherein the plurality of pixels are each arranged in a plurality of rows along the first direction.

2. The radiation detector according to claim 1, wherein the plurality of pixels are arranged in a matrix formed by a plurality of rows along the second direction and a plurality of columns, and the processing unit controls the exposure time of the plurality of pixels for each row included in the plurality of rows.

3. The radiation detector according to claim 1 or 2, wherein the plurality of pixels are arranged in a matrix formed by a plurality of rows along the second direction and a plurality of columns, and the processing unit controls the readout period of the output signals from the plurality of pixels for each row included in the plurality of rows.

4. The radiation detector according to any one of claims 1 to 3, wherein the processing unit controls the number of target pixels among the plurality of pixels that are arranged in the first direction and whose output signals are added together, based on the positions of the plurality of target pixels in the first direction.

5. The radiation detector according to any one of claims 1 to 4, wherein the plurality of pixels are arranged in a matrix formed by a plurality of rows along the second direction and a plurality of columns, the plurality of rows include a first row and a second row which is further away from the aperture than the first row in the first direction, and each of the plurality of second pixels arranged in the second row is larger than each of the plurality of first pixels arranged in the first row.

6. The radiation detector according to any one of claims 1 to 5, wherein the plurality of pixels are arranged in a matrix formed by a plurality of rows along the second direction and a plurality of columns, the plurality of rows include a third row and a fourth row which is further away from the aperture than the third row in the first direction, the plurality of pixels include a plurality of third pixels arranged in the third row, and at least a portion of each of the plurality of third pixels does not face the surface in a third direction intersecting the first and second directions.

7. The radiation detector according to any one of claims 1 to 6, wherein the plurality of pixels are arranged in a matrix formed by a plurality of rows along the second direction and a plurality of columns, and the processing unit corrects the position information of the output signals from the plurality of pixels based on the magnification ratio in each of the plurality of rows.

8. The radiation detector according to any one of claims 1 to 7, wherein the processing unit acquires a plurality of output signals corresponding to a plurality of energy ranges of radiation from the plurality of pixels in each of the plurality of columns, and the plurality of energy ranges are different for each column included in the plurality of columns.

9. The light conversion unit has a second conversion member that converts the radiation into light in the first direction, adjacent to the first conversion member, the second conversion member faces at least a portion of the plurality of pixels in a third direction intersecting the first and second directions, and the materials of the first conversion member and the second conversion member are different from each other, the radiation detector according to any one of claims 1 to 8.

10. The light conversion unit has a third conversion member that converts the radiation into light in the first direction, adjacent to the first conversion member, the third conversion member faces at least a portion of the plurality of pixels in the third direction intersecting the first and second directions, and the first conversion member and the third conversion member are optically separated from each other, the radiation detector according to any one of claims 1 to 9.

11. A radiation inspection apparatus comprising: a transport unit for transporting an object to be inspected; an irradiation unit for irradiating the object to be inspected with radiation; and a radiation detector according to any one of claims 1 to 10 for detecting radiation that has passed through the object to be inspected.

Images