radiation detector

Abstract

This radiation detector comprises: a positioning member that has a through hole through which radiation passes; a scintillator that has an input surface to which the radiation, having passed through the through hole, is input, and converts the radiation into scintillation light; a sensor part that has a light-receiving surface for receiving the scintillation light converted by the scintillator, and detects the scintillation light; and a lens part that has lenses respectively forming images on the input surface of the scintillator and the light-receiving surface of the sensor part. The positioning member has a first positioning part that positions the scintillator by the input surface of the scintillator coming into contact therewith, and a second positioning part that positions the lens part by one end surface of the lens part coming into contact therewith.

Description

[Technical Field]

[0001] The present disclosure relates to radiation detectors. [Background technology]

[0002] A radiation detector is known that includes a phosphor that converts radiation into light and a sensor unit that detects the light from the phosphor (see, for example, Patent Document 1). Such a radiation detector is used in an inspection device or imaging device that includes a radiation source, and detects radiation that is irradiated from the radiation source onto an object and passes through the object. In the radiation detector described in Patent Document 1, the sensor unit is supported by a first support member, and the phosphor is supported by a second support member. The second support member is fitted into the first support member. The sensor unit is surrounded by the first support member and a protective member attached to the first support member. An opening is provided in the protective member, and light from the phosphor passes through the opening and enters the sensor unit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-191059 Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional radiation detector described above, the surface of the phosphor is inclined in both the +Z direction, where the radiation source is located, and the +X direction, where the sensor unit is located. By fixing the relative position between the first support member and the second support member, the relative position between the sensor unit supported by the first support member and the phosphor supported by the second support member is maintained. Incidentally, there can be various variations in the thickness of the phosphor (scintillator). In conventional radiation detectors, the surface position of the phosphor is determined by the position and height of the second support member. However, if the thickness of the phosphor changes, the surface position also changes accordingly.

[0005] As a result of a change in the position of the surface of the phosphor (i.e., the input surface through which radiation is input), the distance between the sensor unit and the surface of the phosphor may also change. If the distance between the sensor unit and the surface of the phosphor changes, for example, when a lens is disposed between the phosphor and the sensor unit, it may become difficult to form a desired image using the lens.

[0006] The present disclosure describes a radiation detector that can easily ensure the positional accuracy of the input surface of the scintillator, thereby maintaining a constant distance between the sensor portion and the input surface of the scintillator. [Means for solving the problem]

[0007] The constituent features of one aspect of the present disclosure are described as follows. [1] A positioning member having a through hole through which radiation passes; a scintillator having an input surface for inputting the radiation that has passed through the through hole and converting the radiation into scintillation light; a sensor unit having a light receiving surface that receives the scintillation light converted by the scintillator and detects the scintillation light; a lens unit having lenses that form images on the input surface of the scintillator and on the light receiving surface of the sensor unit, The positioning member has a first positioning portion that positions the scintillator by contacting the input surface of the scintillator, and a second positioning portion that positions the lens portion by contacting one end surface of the lens portion.

[0008] According to this radiation detector, a single positioning member positions the scintillator with a first positioning portion and positions the lens portion with a second positioning portion. Because the input surface of the scintillator contacts the first positioning portion, the positional accuracy of the input surface can be easily ensured even if, for example, the thickness of the scintillator changes. Therefore, the distance between the sensor portion and the input surface of the scintillator can be maintained constant. This configuration eliminates the need to consider the positional accuracy of different components, providing an advantage over conventional detectors. The distance between the input surface of the scintillator and one end face of the lens portion is also maintained constant, ensuring the accuracy of the focal length.

[0009] In some embodiments, the elements of the present disclosure may be written as follows: [2] The radiation detector according to [1], wherein the first positioning portion is in surface contact with the input surface of the scintillator. With this configuration, the orientation of the scintillator can be easily stabilized, and the positional accuracy of the input surface of the scintillator can be further improved.

[0010] [3] The radiation detector according to [1] or [2], wherein the second positioning portion is in surface contact with the one end surface of the lens portion. According to this configuration, the position of the lens portion can be fixed reliably and easily, and the positional accuracy of the lens portion is further improved.

[0011] [4] Further comprising a holding member for holding the lens unit and the sensor unit, The radiation detector according to any one of [1] to [3], wherein the holding member has a surface facing the side of the positioning member on which the second positioning portion is formed, and the one end face of the lens portion is exposed on the surface. According to this configuration, the relative positions of the sensor section, lens section, and scintillator are determined simply by assembling the positioning member to the holding member.

[0012] [5] The radiation detector according to [4], wherein the positioning member and the holding member are fixed with a gap between the side surface and the surface. This configuration makes it difficult for heat generated by the sensor unit to be transmitted to the positioning member. By protecting the positioning member from heat, the distance between the first positioning member and the second positioning member remains constant and is easy to maintain. Even if there is variation in the lens characteristics, the effects of that variation can be compensated for.

[0013] [6] The radiation detector according to any one of [1] to [5], wherein the positioning member has a recess that receives an edge of the scintillator. According to this configuration, the position of the scintillator can be easily fixed.

[0014] [7] Further comprising a support member fitted to the positioning member to support the scintillator, The radiation detector according to any one of [1] to [6], wherein the support member has a support surface facing an attachment surface on which the first positioning portion of the positioning member is formed, and the scintillator is sandwiched between the attachment surface and the support surface. According to this configuration, the scintillator can be reliably supported and fixed simply by fitting the support member into the positioning member.

[0015] [8] The radiation detector according to [7], wherein the support member is fixed to the positioning member so that the distance between the mounting surface and the support surface is adjustable. This configuration can be adapted to scintillators of any thickness. [Effects of the Invention]

[0016] According to some aspects of the present disclosure, the positional accuracy of the input surface of the scintillator can be easily ensured, thereby maintaining a constant distance between the sensor unit and the input surface of the scintillator. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view showing a radiation image acquisition system according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a diagram showing a schematic configuration of the radiation image acquisition system shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view showing the internal configuration of the radiation detector in FIG. [Figure 4] FIG. 4 is an enlarged cross-sectional view of a part of FIG. [Figure 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. 4, showing one end face of the lens portion exposed on the surface of the holding member. [Figure 6] FIG. 6 is a diagram illustrating a schematic configuration of a lens unit according to an example. [Figure 7] FIG. 7 is a perspective view showing the radiation detector of FIG. [Figure 8] FIG. 8 is a view showing a state in which the support member is removed from the positioning member. [Figure 9] FIG. 9 is a diagram showing a state in which the scintillator is removed from the positioning member. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate explanations will be omitted. Furthermore, each drawing is created for explanatory purposes and is drawn to particularly emphasize the portions to be described. Therefore, the dimensional proportions of each component in the drawings do not necessarily correspond to the actual ones.

[0019] As shown in FIGS. 1 and 2 , a radiographic image acquisition system 1 according to one embodiment is an apparatus for acquiring a radiographic image of an object A. The radiographic image acquisition system 1 is a non-destructive inspection system capable of inspecting the object A without disassembling or destroying it. The object A contains, for example, a substance made of light elements. The radiographic image acquisition system 1 is applicable, for example, to fields such as food inspection, battery inspection, and electronic component inspection. In the field of food inspection, for example, sealed containers and packaging are inspected for the presence or absence of foreign objects trapped inside. The radiographic image acquisition system 1 is particularly excellent in the ability to discriminate substances made of light elements. Examples of such substances include food scraps, hair, plastic, insects, and bones in meat. The radiographic image acquisition system 1 is applicable, for example, to in-line X-ray inspection.

[0020] The radiation image acquisition system 1 includes a radiation source 2 that outputs radiation such as white X-rays toward an object A, a conveying device 20 that conveys the object A in a predetermined conveying direction D, a scintillator 6 that generates scintillation light in response to input radiation that has passed through the object A conveyed by the conveying device 20, a line scan sensor (sensor unit) 3 that detects the scintillation light output from a radiation input surface 6a of the scintillator 6, and a computer 10 that controls several functions of the radiation image acquisition system 1 and creates radiation images. As described above, the radiation image acquisition system 1 is an X-ray imaging system that uses a scintillator surface observation method. The radiation image acquisition system 1 has excellent sensitivity to low-energy X-rays.

[0021] The radiation source 2 outputs a cone beam X-ray from its X-ray emission section. The radiation source 2 has a focal point 2a of the cone beam X-ray. The radiation source 2 may be, for example, a microfocus X-ray source or a millifocus X-ray source. The X-rays emitted from the radiation source 2 form a radiation flux. The radiation image acquisition system 1 is provided with a radiation source-side slit member 26 and a positioning member 70 (see FIG. 2 ), so that the X-rays in an irradiation region 12, narrowed to a limited portion of the X-rays in the output region where the radiation flux exists, are input to the input surface 6a of the scintillator 6. The irradiation region 12 extends in a triangular (or fan) shape toward the scintillator 6 in the housing 15 of the radiation detector 30.

[0022] The conveying device 20 has, for example, two belt conveyors 21, 21 that move along a circular orbit, and the object A is placed or held on the conveying surface 21a of the belt conveyor 21. The belt conveyor 21 is a conveying stage or a conveying unit. The conveying device 20 is equipped with a driving source (not shown) that drives each belt conveyor 21. The conveying device 20 is configured to convey the object A at a constant speed in a conveying direction D. In this embodiment, the conveying direction D is horizontal. Between the two belt conveyors 21, 21, a gap C that allows X-rays to pass is provided at a position corresponding to the above-mentioned irradiation area 12. The gap C has a small, constant length (width) in the conveying direction D and extends straight in a horizontal detection width direction perpendicular to the conveying direction D. The conveying timing and conveying speed of the object A in the conveying device 20 are preset and controlled by the control unit 10a of the computer 10. The belt conveyor 21 does not need to have the gap C through which X-rays pass, and the belt member of the belt conveyor 21 may be made of a radiolucent material. The conveying direction D shown in FIGS. 1 and 2 is parallel to the x-direction parallel to the paper surface shown in the figures. The detection width direction is parallel to the y-direction perpendicular to the paper surface shown in FIG. 2. The up-down direction is parallel to the z-direction parallel to the paper surface shown in FIG. 2.

[0023] The radiological image acquisition system 1 can accommodate any type of conveying device 20. For example, the conveying direction D may be horizontal or may be inclined relative to the horizontal. The conveying direction D does not have to be linear, and may be, for example, curved. In this case, the conveying direction D may be a tangent to the conveying path of the object A at a portion that overlaps with the irradiation area 12. The conveying device 20 does not need to have a physical conveying surface 21a. For example, the conveying device 20 may convey the object A in a floating state using air. The conveying device 20 may also convey the object A by releasing it into the air. In this case, the conveying path of the object A may be, for example, parabolic.

[0024] The transport device 20 is not limited to a configuration having a belt conveyor 21. The transport device 20 may have, for example, a roller conveyor including multiple rollers. Because a roller conveyor does not have a belt, the influence of the belt can be eliminated. Another advantage over a belt conveyor is that gaps (slit-shaped openings) are formed between the rollers. Using a roller conveyor reduces X-ray attenuation caused by the belt. Considering the arrangement of the radiation source 2 and the arrangement of the irradiation area 12 (oblique irradiation), which will be described later, a roller conveyor can be effectively used. A roller conveyor is a transport means suitable for a radiological image acquisition system 1 in which sensitivity to low-energy X-rays is important. According to a configuration in which two or more belt conveyors are installed in the transport direction and X-rays are irradiated through the gap C between the belt conveyors, as in the present embodiment, the influence of the belt can be eliminated while using the belt conveyor 21.

[0025] As shown in FIGS. 1 to 3, the radiation image acquisition system 1 includes a radiation detector 30 installed along the conveying device 20. The radiation detector 30 is an imaging unit for capturing a radiation image of the object A. The radiation detector 30 is, for example, attached to the conveying device 20 and fixed to the conveying device 20. The radiation detector 30 may also be attached to a location other than the conveying device 20. The radiation detector 30 may also be placed on a stand or the like. The radiation detector 30 is attached so as not to interfere with the rotation of the belt conveyor 21. The same applies when the conveying device 20 is a roller conveyor. The radiation detector 30 is arranged with a certain gap from the conveying unit such as a belt conveyor or roller conveyor so as not to interfere with the movement of the conveying unit.

[0026] The radiation detector 30 has a rectangular parallelepiped housing 15. The housing 15 has a rectangular parallelepiped housing body 13 made of, for example, aluminum, and a lead cover 14 covering the outer surface (outer periphery) of the housing body 13. The housing body 13 houses each component of the radiation detector 30. The lead cover 14 shields radiation so that radiation outside the housing body 13 does not affect the internal space of the radiation detector 30. The lead cover 14 may be disposed on the outside or inside of the housing 15. Another cover may be attached to the outside of the lead cover 14. From the viewpoint of the strength and handling of lead, it is preferable that another material be attached to the outside of the lead. The cover may be made of a material other than lead, such as tungsten, iron, stainless steel, or copper. Furthermore, a rubber-like material or a sheet-like material in which a heavy metal such as tungsten is contained in rubber (resin) may be used.

[0027] The housing body 13 is made of a material that can block X-rays, for example. The housing body 13 may be made of iron, stainless steel, or the like. The housing body 13 may include a protective material, and lead, tungsten, or copper may be used as the protective material. Alternatively, a rubber-like material or a sheet-like material in which a heavy metal such as tungsten is contained in rubber (resin) may be used.

[0028] The upper wall 13a of the housing body 13 is disposed so as to face the conveying device 20. A top plate 14a of the lead cover 14 is attached to the top wall 13a at a distance from the top wall 13a. The top plate 14a is disposed parallel to the top wall 13a. An aluminum cover wall 13e is provided between the top wall 13a and the top plate 14a. The cover wall 13e may also be made of a metal such as stainless steel or iron.

[0029] The lead cover 14 covers the entire surface of the housing body 13 except for the bottom wall portion. (The illustration of the lead cover 14 is omitted except for the top plate portion 14a.) The top plate portion 14a of the lead cover 14 has an entrance window 14f formed therein, which allows X-rays that have passed through the object A to pass through. The entrance window 14f has a small, constant length (width) in the x direction and extends straight in the y direction. The length of the entrance window 14f in the x direction may be determined by the width of a slit formed by a first through-hole 74 (described later) or the width (thickness in the transport direction D) of the desired irradiation area 12.

[0030] Cover wall 13e and upper wall 13a have through holes 13g and 13f (see FIG. 3) formed in positions corresponding to entrance window 14f. Entrance window 14f of top plate 14a, through hole 13g of cover wall 13e, and through hole 13f of upper wall 13a are aligned in the thickness direction with a fixed length in the x direction, and form a first portion of a slit that is a passageway for radiation.

[0031] The radiation detector 30 is configured to capture an image of scintillation light output from the input surface 6a of the scintillator 6 in a direction inclined relative to the input surface 6a. The scintillator 6, the line scan sensor 3, and the equal-magnification lens (lens unit) 7 are installed within the housing 15. The equal-magnification lens 7 is disposed between the scintillator 6 and the line scan sensor 3. The radiation detector 30 has a structure for holding the scintillator 6, the line scan sensor 3, and the equal-magnification lens 7 in a predetermined positional relationship. In the radiation detector 30, a substrate and the like are arranged in a space extending in the x direction (transport direction D) from the position of the line scan sensor 3. The layout of the various components within the housing 15 can be changed depending on the application or installation location of the radiation detector, the desired surrounding layout, etc.

[0032] 3 and 4, the radiation detector 30 includes a holding member 60 that holds the equal-magnification lens 7 and the line scan sensor 3, a positioning member 70 that positions the scintillator 6, and a support member 80 that fits into the positioning member 70 and supports the scintillator 6. The holding member 60, positioning member 70, and support member 80 are attached to the housing main body 13 of the housing 15 and fixed in predetermined positions. The configurations of the scintillator 6, the line scan sensor 3, and the equal-magnification lens 7, as well as the configuration for holding each of these components, will be described below. Note that the positioning member 70 and support member 80 are not shown in FIG. 1.

[0033] The scintillator 6 is held by, for example, a scintillator holder (not shown) and is arranged, for example, horizontally. The scintillator 6 is a flat wavelength conversion member. The scintillator 6 has, for example, a substantially constant thickness. The scintillator 6 has a rectangular shape that is long in the detection width direction (y direction) (see FIGS. 1 and 9). The scintillator 6 is made of, for example, Gd2O2S:Tb, Gd2O2S:Pr, CsI:Tl, CdWO4, CaWO4, Gd2SiO5:Ce, Lu 0.4 Gd 1.6 SiO5, Bi4Ge3O 12, Lu2SiO5:Ce, Y2SiO5, YAlO3:Ce, Y2O2S:Tb, YTaO4:Tm, YAG:Ce, YAG:Pr, YGAG:Ce, YGAG:Pr, GAGG:Ce, etc. The thickness of the scintillator 6 is set to an appropriate value depending on the energy band of the radiation to be detected, ranging from several μm to several mm. The scintillator 6 converts X-rays that have passed through the object A into visible light (scintillation light). X-rays with relatively low energy are converted at the input surface 6a of the scintillator 6 and output from the input surface 6a.

[0034] The line scan sensor 3 captures images of the object A as it moves and outputs radiation image data, which is one-dimensional image data. The imaging section 31 of the line scan sensor 3 has an imaging surface 3a that captures the scintillation light output from the input surface 6a of the scintillator 6. This imaging surface 3a is a light-receiving surface that receives the scintillation light. The line scan sensor 3 is, for example, a general line sensor, a multi-line sensor, or an area image sensor capable of TDI (time delay integration) operation. The line scan sensor 3 is, for example, a CCD image sensor or a CMOS image sensor. The line scan sensor 3 has a configuration in which element rows, each of which has multiple light-receiving elements aligned in a pixel direction, are arranged in one or more columns in a column direction. In FIG. 2, the column direction is parallel to the Z direction. The line scan sensor 3 has a scan direction corresponding to the transport direction D of the object A and a line direction perpendicular to the scan direction. This line direction is the pixel direction, which is parallel to the y direction in FIG. 2. The scanning direction corresponds to the column direction described above, and is parallel to the z direction in Figure 2. In the case of an area image sensor that can be driven by TDI, the column direction is the same as the integration direction.

[0035] The line scan sensor 3 captures an image of the object A in accordance with the movement of the object A under the control of the control unit 10a. That is, the line scan sensor 3 captures an image on the imaging surface 3a in synchronization with the movement of the object A by the conveying device 20, and outputs radiation image data. This makes it possible to obtain a radiation image with a good S / N ratio. Note that, in order to synchronize the movement of the object A by the stage with the imaging by the line scan sensor, an encoder may be provided on the stage, and the line scan sensor 3 may be controlled by a signal from the encoder.

[0036] In this embodiment, the scintillator 6 is disposed such that, for example, the input surface 6a is inclined with respect to the transport direction D and is parallel to the line direction.

[0037] As shown in FIG. 3, the holding member 60 is housed inside the housing main body 13. The holding member 60 has a positioning portion 61 that serves as a guide. The holding member 60 holds the 1:1 lens 7 at the positioning portion 61 of the holding member 60 facing the scintillator 6. The holding member 60 also holds the line scan sensor 3 at a base end 65 opposite the positioning portion 61. The holding member 60 holds the 1:1 lens 7 so that, for example, one end surface 7a of the 1:1 lens 7 is perpendicular to the x-direction. The holding member 60 holds the line scan sensor 3 so that, for example, the imaging surface 3a of the imaging unit 31 is perpendicular to the x-direction. As shown in FIG. 4, the imaging unit 31 of the line scan sensor 3 is held by a main body 32 attached to a base 33. A portion of the base 33 and the main body 32 are fitted into the base end 65 of the holding member 60.

[0038] As shown in FIGS. 3 and 4 , the positioning member 70 is incorporated into the housing main body 13 at a position directly below the entrance window 14f. The positioning member 70 is made of a metal such as copper. The positioning member 70 has a first through-hole 74 through which radiation passes and a second through-hole 75 through which scintillation light converted by the scintillator 6 and output from the scintillator 6 passes. The first through-hole 74 is formed, for example, along the yz plane, and the second through-hole 75 is formed, for example, along the xy plane. The lengths of the first through-hole 74 and the second through-hole 75 in the y direction are longer than the length of the scintillator 6 in the y direction. The first through-hole 74 and the second through-hole 75 communicate with each other through a space extending in the y direction. The positioning member 70 has a mounting surface 77 that extends at an angle relative to the first through-hole 74, i.e., the radiation passage path. The mounting surface 77 is inclined, for example, at 45° relative to the xy plane. The scintillator 6 is pressed against the mounting surface 77 by a support member 80. A space where the first through-hole 74 and the second through-hole 75 intersect is open to this mounting surface 77. The input surface 6a of the scintillator 6 faces this opening 70d. By appropriately setting the tilt angle of the mounting surface 77, the angle of the input surface 6a relative to the radiation input to the input surface 6a and the angle of the input surface 6a relative to the imaging surface 3a are determined. The tilt angle (45°) of the mounting surface 77 described above is merely an example, and the mounting surface 77 may be tilted at another angle relative to the xy plane.

[0039] The first through-hole 74 forms a second portion of the slit, which is a passageway for radiation, and cooperates with the first portion to guide the X-rays that have passed through the entrance window 14f toward the input surface 6a of the scintillator 6. The positioning member 70 prevents the X-rays from scattering in the internal space of the housing 15. The input surface 6a of the scintillator 6 inputs the X-rays (radiation) within the irradiation region 12 that have passed through the first through-hole 74 of the positioning member 70.

[0040] In the radiation image acquisition system 1, for example, a shielding member 9 is attached between the line scan sensor 3 and the equal-magnification lens 7. The line scan sensor 3, the shielding member 9, and the equal-magnification lens 7 are integrated together.

[0041] The shielding member 9 is a radiation-shielding member that transmits scintillation light generated by the scintillator 6 and focused by the 1:1 magnification lens 7 and blocks X-rays. The shielding member 9 is, for example, lead-containing glass, lead-free radiation-shielding glass containing heavy elements such as Sr, Ba, Ti, B, W, Si, Gd, and Zr, a fiber optic plate (FOP), or a radiation-shielding resin. The shielding member 9 is attached to the surface (surface of the protective resin) of the line scan sensor 3. The shielding member 9 reduces the effects of scattered X-rays. The shielding member 9 is, for example, a plate-shaped member provided on the line scan sensor 3, but may also be a block-shaped member provided across the space between the imaging surface 3 a of the line scan sensor 3 and the other end surface 7 c of the 1:1 magnification lens 7. That is, a gap may be formed between the shielding member 9 and the 1:1 magnification lens 7, or alternatively, no gap is required.

[0042] The equal-magnification lens 7 is disposed between the scintillator 6 and the line scan sensor 3 and forms an image of the scintillation light output from the input surface 6a on the imaging surface 3a of the line scan sensor 3. The equal-magnification lens 7 has a magnification of 1x and can be realized, for example, by a gradient index lens (GRIN lens), a rod lens, or a rod lens array. The equal-magnification lens 7 is focused on the input surface 6a of the scintillator 6. Because the equal-magnification lens 7 has a deep depth of field, there is little out-of-focus blur even when imaging a phosphor at an oblique angle, which is advantageous for oblique imaging such as that of this embodiment. Furthermore, the equal-magnification lens 7 increases the degree of freedom in the arrangement and combination of the radiation source 2, object A, and line scan sensor 3.

[0043] FIG. 6 is a diagram illustrating a schematic configuration of an example of an equal-magnification lens 7. As shown in FIG. 6, the equal-magnification lens 7 has a rectangular parallelepiped shape. The equal-magnification lens 7 has a structure in which, for example, a number of cylindrical lens bodies (lenses) 8 are arranged in a row and held by a lens holder 7b. The equal-magnification lens 7 has a total length W, a thickness T, and a lens length L2. Each lens body 8 has an aperture angle θ and a field of view radius R. The arrayed lens bodies 8 form images on the input surface 6a of the scintillator 6 and the imaging surface 3a of the line scan sensor 3, respectively. One end surface 7a and the other end surface 7c of the equal-magnification lens 7 in the direction of the lens length L2 are parallel to each other and form flat surfaces. Both end surfaces of the lens body 8 are exposed at the one end surface 7a and the other end surface 7c and are flush with both end surfaces of the lens holder 7b. In the equal-magnification lens 7, adjacent lens bodies 8 are arranged so that their images overlap. Because the lens bodies 8 are arranged in an array, there is no difference in brightness between the center and the edges of the array, and lens distortion does not occur at the edges. The working distance L1 on the one end face 7a side and the working distance L1 on the opposite side shown in Figure 6 correspond to the distance between the input surface 6a and the one end face 7a and the distance between the other end face 7c and the imaging surface 3a, respectively, shown in Figure 4. In other words, the conjugate length LC of the 1:1 lens 7 corresponds to the distance between the input surface 6a and the imaging surface 3a.

[0044] Returning to FIG. 4, in the radiation detector 30, the radiation passage path formed by the first through-holes 74 is arranged so as to be inclined with respect to the normal direction to the input surface 6a of the scintillator 6. The equal-magnification lens 7, shielding member 9, and line scan sensor 3 are arranged in a direction inclined with respect to the normal direction to the input surface 6a. The equal-magnification lens 7 forms an image of the scintillation light output in a direction inclined with respect to the normal direction of the input surface 6a on the imaging surface 3a. The line scan sensor 3 images the scintillation light output in a direction inclined with respect to the normal direction of the input surface 6a.

[0045] Returning to FIG. 4 , the positioning member 70 has a locking plate portion 79 that contacts the side surface of the housing body 13, and a main body portion 70a that is disposed within the housing body 13. A first through-hole 74 and a second through-hole 75 are formed in the main body portion 70a. A rectangular recess 70c, for example, is formed in the main body portion 70a, and the positioning portion 61 of the holding member 60 is fitted into this recess 70c. In this way, the holding member 60 is fitted into and fixed within the housing body 13 with respect to the positioning member 70 that is fixed to the housing body 13.

[0046] The positioning member 70 has a first positioning portion 71 that positions the scintillator 6 by contacting the input surface 6a of the scintillator 6. The first positioning portion 71 is formed as part of the mounting surface 77 and has a flat surface. The first positioning portion 71 comes into surface contact with, for example, the input surface 6a of the scintillator 6.

[0047] The support member 80 fitted to the positioning member 70 supports the scintillator 6. The support member 80 has a support surface 82 facing the mounting surface 77 on which the first positioning portion 71 is formed. The inclination angle of the support surface 82 is equal to the inclination angle of the mounting surface 77, and therefore the support surface 82 is parallel to the mounting surface 77. The mounting surface 77 and the support surface 82 both have flat surfaces, for example. The support member 80 holds the scintillator 6 between the mounting surface 77 and the support surface 82. The support member 80 is fixed to the positioning member 70 with an appropriate fixing means such as a screw or a bolt so that a gap 89 between the mounting surface 77 and the support surface 82 (the distance in the normal direction of the support surface 82) can be adjusted. The size of the gap 89 is constant, for example, in the extension direction of the gap 89 (a direction along an inclined plane (a plane parallel to the mounting surface 77) including the y-axis).

[0048] More specifically, as shown in FIG. 8, the positioning member 70 has a pair of side plate portions 73, 73 arranged at both ends in the y direction, and the support member 80 is fitted between the side plate portions 73, 73.

[0049] The positioning member 70 has a second positioning portion 72 that positions the imaging surface 3a by contacting one end surface 7a of the 1:1 magnification lens 7. The second positioning portion 72 is formed as part of the side surface 76 that faces the holding member 60, and has a flat surface. The second positioning portion 72 comes into surface contact with, for example, one end surface 7a of the 1:1 magnification lens 7.

[0050] More specifically, the holding member 60 has a surface 62 facing a side surface 76 on which the second positioning portion 72 is formed, and a gap 69 is formed between the side surface 76 and the surface 62, which are two parallel surfaces. The gap 69 is formed along the yz plane and is constant, for example, throughout. The positioning member 70 and the holding member 60 are fixed with the gap 69. As shown in FIG. 5, one end surface 7a of the 1:1 magnification lens 7 is exposed at the surface 62. As shown in FIG. 4, the one end surface 7a of the 1:1 magnification lens 7 protrudes from the surface 62 and abuts against the side surface 76 of the positioning member 70. The protruding length of the one end surface 7a is equal to the width of the gap 69.

[0051] With the above-described configuration, the positioning member 70 positions the scintillator 6 and also the equal-magnification lens 7.

[0052] 4, 8, and 9, the mounting structure (mounting method) of the scintillator 6 to the positioning member 70 will be described. The positioning member 70 has an L-shaped recess 78 that receives the edge 6c of the scintillator 6 at the lower end of the mounting surface 77 (the end opposite the first through-hole 74). The recess 78 extends in the y direction and is formed over the entire area in the y direction (see FIG. 9). When the scintillator 6 is pressed against the mounting surface 77 and the edge 6c of the scintillator 6 fits into the recess 78, the orientation of the scintillator 6 is stabilized (see FIG. 8). In this state, the input surface 6a of the scintillator 6 faces an opening 70d formed by the intersection of the first through-hole 74 and the second through-hole 75. As shown in FIG. 8, the back surface 6b of the scintillator 6 is exposed. Thereafter, support member 80 is attached to positioning member 70 (see FIG. 7), and support member 80 is fixed by an appropriate fixing means, thereby fixing scintillator 6. As shown in FIG. 4, support member 80 supports scintillator 6 with support surface 82 in contact with back surface 6b of scintillator 6. A gap 89 equal to the thickness of scintillator 6 is formed between positioning member 70 and support member 80.

[0053] The recess 78 has, for example, a flat surface. The surface of the recess 78 may be perpendicular to the inclined surface (the surface parallel to the mounting surface 77). The height of the surface of the recess 78 (the depth of the recess 78; the length in a direction perpendicular to the y direction) may be approximately equal to the thickness of the scintillator 6 or may be smaller than the thickness of the scintillator 6. If the height (depth) is smaller than the thickness of the scintillator 6, the end face of the scintillator 6 abutting the recess 78 protrudes from the recess 78. The thicker the scintillator 6, the larger the gap 89. Depending on the thickness of the scintillator 6, the position of the support member 80 may vary in the x direction (move parallel), and the support member 80 may be fixed at an appropriate position. The depth of the recess 78 defines the minimum size of the gap 89. In order to securely hold the scintillator 6 without giving any play to the scintillator 6, the depth of the recess 78 is equal to or smaller than the thickness of the thinnest scintillator 6 that can be set in the radiation detector 30. The recess 78 is a notch or receiving surface formed in the positioning member 70 that receives part or all of the end face of the scintillator 6 (at least part in the thickness direction).

[0054] Returning to FIG. 2 , the computer 10 includes, for example, a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and an input / output interface. The computer 10 includes a control unit 10a (control processor) that controls the radiation source 2 and the line scan sensor 3, and an image processing unit 10b (image processor) that creates a radiographic image of the object A based on the radiographic image data output from the line scan sensor 3. The image processing unit 10b receives the radiographic image data and performs predetermined processing, such as image processing, on the received radiographic image data. A display device 11 is connected to the computer 10. The image processing unit 10b outputs the created radiographic image to the display device 11. The control unit 10a controls the radiation source 2 based on values ​​of the tube voltage and tube current of the radiation source 2 that are stored based on user input or the like. The control unit 10a controls the line scan sensor 3 based on the exposure time of the line scan sensor 3 that are stored based on user input or the like. The control unit 10a and the image processing unit 10b may be separate processors or may be the same processor. The computer 10 may be programmed to execute the functions of the control unit 10a and the image processing unit 10b. The computer 10 may be configured with a microcomputer or an FPGA (Field-Programmable Gate Array).

[0055] Next, the operation of the radiation image acquisition system 1, i.e., the method for acquiring a radiation image, will be described. First, the object A is transported in the transport direction D using the transport device 20 (transport step). At the same time, radiation such as white X-rays is output from the radiation source 2 toward the object A (radiation output step). Next, the radiation that has passed through the object A is made to enter the housing 15 through the entrance window 14f and is guided toward the input surface 6a of the scintillator 6 via a slit formed in the housing 15 (radiation introduction step). The radiation that has passed through the object A is input to the input surface 6a, where it is converted into scintillation light by the scintillator 6, and the scintillation light is output from the input surface 6a (scintillation light output step). The scintillation light output from the input surface 6a is then imaged on the imaging surface 3a of the line scan sensor 3 by the 1:1 lens 7 (scintillation light imaging step). Furthermore, the scintillation light is imaged on the imaging surface 3a of the line scan sensor 3 (scintillation light imaging step). The line scan sensor 3 outputs radiation image data obtained by imaging to the image processing unit 10b of the computer 10.

[0056] The image processing unit 10b of the computer 10 receives the radiation image data and performs predetermined processing such as image processing on the received radiation image data to create a radiation image (image creation step). The image processing unit 10b outputs the created radiation image to the display device 11. The display device 11 displays the radiation image output from the image processing unit 10b. Through the above steps, a radiation image obtained by observing the surface of the object A is obtained.

[0057] According to the radiation detector 30 of this embodiment, the positioning member 70, which is a single member, positions the scintillator 6 using the first positioning portion 71 and positions the 1:1 lens 7 using the second positioning portion 72. Because the scintillator 6 a contacts the first positioning portion 71, the positional accuracy of the input surface 6 a can be easily ensured even if the thickness of the scintillator 6 changes, for example. Therefore, the distance between the line scan sensor 3 and the input surface 6 a of the scintillator 6 can be maintained constant. This configuration eliminates the need to consider the positional accuracy of different components, providing an advantage over conventional detectors. The distance between the input surface 6 a of the scintillator 6 and one end surface 7 a of the 1:1 lens 7 is also maintained constant, ensuring the accuracy of the focal length (working distance L1 shown in FIG. 6 ).

[0058] In conventional radiation detectors, focal adjustment was necessary whenever the thickness of the scintillator varied. However, in the radiation detector 30 of this embodiment, the input surface 6a of the scintillator 6 is fixed by contacting the positioning member 70 with the scintillator 6. Furthermore, the distance between the input surface 6a and one end surface 7a of the 1:1 lens 7 and the distance between the other end surface 7c of the 1:1 lens 7 and the imaging surface 3a are automatically fixed, eliminating the need for such frequent adjustment of the focal length. Regardless of the thickness of the scintillator 6, the input surface 6a of the scintillator 6 can be easily brought close to one end surface 7a of the 1:1 lens 7. Because the 1:1 lens 7, which is a rod lens array, has a shallow depth of field, the positional accuracy of the input surface 6a of the scintillator 6 is extremely important. However, the radiation detector 30 allows for appropriate detection of scintillation light emitted from the input surface 6a.

[0059] The first positioning portion 71 is in surface contact with the input surface 6a of the scintillator 6, and therefore can easily stabilize the attitude of the scintillator 6. The positional accuracy of the input surface 6a of the scintillator 6 is further improved.

[0060] The second positioning portion 72 comes into surface contact with one end surface 7a of the 1:1 magnification lens 7, so that the position of the 1:1 magnification lens 7 can be reliably and easily fixed. The positional accuracy of the 1:1 magnification lens 7 is further improved.

[0061] Furthermore, simply by assembling the positioning member 70 to the holding member 60, the relative positions of the line scan sensor 3, the equal-magnification lens 7, and the scintillator 6 are determined.

[0062] Because the positioning member 70 and the holding member 60 are fixed with a gap 69 between them, heat generated by the line scan sensor 3 is less likely to be transmitted to the positioning member 70. By protecting the positioning member 70 from heat, the distance between the first positioning portion 71 and the second positioning portion 72 remains constant and is easily maintained. Even if there is variation in the characteristics of each lens body 8, the effects of this variation can be compensated for.

[0063] The recess 78 formed in the positioning member 70 allows the position of the scintillator 6 to be easily fixed.

[0064] Furthermore, the scintillator 6 can be reliably supported and fixed simply by fitting the support member 80 into the positioning member 70. For example, if the scintillator 6 deteriorates, the scintillator 6 can be easily replaced.

[0065] Since the support member 80 is fixed so that the spacing 89 is adjustable, it can accommodate scintillators of any thickness.

[0066] Although the embodiments of the present disclosure have been described above, the present invention is not limited to the above embodiments. For example, in the above embodiments, a configuration has been described in which the first positioning portion is in surface contact with the input surface of the scintillator. However, the first positioning portion may include three or more protrusions, and the input surface of the scintillator may be in contact with these protrusions. In this case, the tips of the protrusions define a predetermined positioning plane for determining the position of the input surface of the scintillator. The tips of the protrusions (portions that support the scintillator) may each be point-like, linear, or of any planar shape. Alternatively, any of these shapes may be combined.

[0067] In the above embodiment, the second positioning portion is in surface contact with one end face of the lens portion. However, the second positioning portion may include three or more protrusions, and the one end face of the lens portion may be in contact with these protrusions. In this case, the tips of the protrusions define a predetermined positioning plane for determining the position of the one end face of the lens portion. The tips of the protrusions (portions that support the lens portion) may each be dot-shaped, linear, or of any planar shape. Alternatively, any of these shapes may be combined.

[0068] The configuration of the holding member can be changed as appropriate. For example, the part that holds the lens unit and the part that holds the sensor unit may be separate. The holding member as in the above embodiment may be omitted, and the lens unit and / or the sensor unit may be fixed inside the housing using other appropriate holding means (such as a bracket).

[0069] The shape of the recessed portion can be changed as appropriate. The positioning member need not be provided with a recessed portion. A configuration may be adopted in which the scintillator contacts one flat surface formed on the positioning member, and the edge of the scintillator contacts another flat surface intersecting the flat surface. That is, although the recessed portion in the above embodiment has three flat surfaces, the positioning member may have only two flat surfaces that contact the scintillator.

[0070] The support member may be omitted. In that case, a mounting structure may be employed in which the scintillator is fixed simply by being fitted into the positioning member, or a separate fixture may be attached to fix the scintillator to the support member.

[0071] The slit, which is a passageway for radiation, may be formed by a member separate from the positioning member 70. The holding member 60 may not be fitted into the positioning member 70, but may be fixed to another portion within the housing 15. [Industrial Applicability]

[0072] According to some aspects of the present disclosure, the positional accuracy of the input surface of the scintillator can be easily ensured, thereby maintaining a constant distance between the sensor unit and the input surface of the scintillator. [Explanation of symbols]

[0073] 1...radiation image acquisition system, 3...line scan sensor (sensor unit), 3a...imaging surface, 6...scintillator, 6a...input surface, 7...equal magnification lens (lens unit), 7a...one end surface, 8...lens body (lens), 15...housing, 20...conveying device, 30...radiation detector, 60...holding member, 62...surface, 69...gap, 70...positioning member, 71...first positioning portion, 72...second positioning portion, 74...first through hole, 75...second through hole, 76...side surface, 77...mounting surface, 78...recessed portion, 80...support member, 82...support surface, 89...spacing.

Claims

1. a positioning member having a through hole through which radiation passes; a scintillator having an input surface for inputting the radiation that has passed through the through hole and converting the radiation into scintillation light; a sensor unit having a light receiving surface that receives the scintillation light converted by the scintillator and detects the scintillation light; a lens unit having lenses that form images on the input surface of the scintillator and on the light receiving surface of the sensor unit, The positioning member has a first positioning portion that positions the scintillator by contacting the input surface of the scintillator, and a second positioning portion that positions the lens portion by contacting one end surface of the lens portion.

2. The radiation detector according to claim 1 , wherein the first positioning portion is in surface contact with the input surface of the scintillator.

3. The radiation detector according to claim 1 , wherein the second positioning portion is in surface contact with the one end surface of the lens portion.

4. the first positioning portion is in surface contact with the input surface of the scintillator; The radiation detector according to claim 1 , wherein the second positioning portion is in surface contact with the one end surface of the lens portion.

5. a holding member for holding the lens unit and the sensor unit; 5. The radiation detector according to claim 1, wherein the holding member has a surface facing a side surface of the positioning member on which the second positioning portion is formed, and the one end face of the lens portion is exposed on the surface.

6. The radiation detector according to claim 5 , wherein the positioning member and the holding member are fixed with a gap between the side surface and the surface.

7. 5. The radiation detector according to claim 1, wherein the positioning member has a recess that receives an edge of the scintillator.

8. a support member fitted to the positioning member to support the scintillator; The radiation detector according to any one of claims 1 to 4, wherein the support member has a support surface facing an attachment surface on which the first positioning portion of the positioning member is formed, and the scintillator is sandwiched between the attachment surface and the support surface.

9. The radiation detector according to claim 8 , wherein the support member is fixed to the positioning member such that a distance between the attachment surface and the support surface is adjustable.

Images