Imaging unit, radiation image acquisition system, and radiation image acquisition method

Abstract

The imaging unit comprises a housing having an incident window that passes radiation that has passed through an object, a scintillator having an input surface that inputs radiation that has passed through the incident window, and a line scan sensor having an imaging surface that captures scintillation light output from the input surface. The imaging unit further comprises a slit member disposed between the incident window and the scintillator and forming a slit that guides radiation that has passed through the incident window toward the input surface, and an equal magnification lens disposed between the scintillator and the line scan sensor and forming an image of scintillation light output from the input surface onto the imaging surface of the line scan sensor.

Description

Technology Field

[0001] The present disclosure relates to an imaging unit, a radiation image acquisition system, and a radiation image acquisition method. Background Technology

[0002] Conventionally, a radiation detection device is known that comprises a radiation source and a radiation detector, irradiates radiation onto an object being transported along a transport path placed between them, and converts the transmitted radiation into fluorescence (visible light) using a wavelength conversion member (see Patent Document 1). In this radiation detection device, the wavelength conversion member is supported by a support member provided in a housing. Radiation transmitted through the object passes through an opening formed in a shielding member and is incident on the wavelength conversion member. The fluorescence emitted by the fluorescent layer of the wavelength conversion member passes through a concentrator and is incident on the light receiving part of a photoelectric conversion element. The radiation detector generates and outputs a two-dimensional radiation image signal of the object. Prior art literature

[0003] Patent Document 1: Japanese Patent Publication No. 2018-141673 The problem to be solved

[0004] In the aforementioned conventional detector, radiation passing through the aperture tends to spread. Consequently, the radiation irradiation range at the input surface of the wavelength conversion member (the substrate layer of the wavelength conversion member in the detector) increases, resulting in low resolution. Furthermore, because the working distance is long, the sensitivity is low.

[0005] The present disclosure describes an imaging unit capable of improving resolution and sensitivity, a radiation image acquisition system, and a radiation image acquisition method. means of solving the problem

[0006] One aspect of the present disclosure is an imaging unit for acquiring a radiation image of an object being transported in a transport direction, comprising: a housing having an incident window that allows radiation transmitted through the object to pass through; a scintillator installed within the housing and having an input surface for inputting radiation that has passed through the incident window; a line scan sensor installed within the housing and having an imaging surface for imaging scintillation light output from the input surface; a slit member disposed between the incident window and the scintillator and forming a slit that guides radiation that has passed through the incident window toward the input surface; and an equal magnification lens disposed between the scintillator and the line scan sensor and forming an image of scintillation light output from the input surface on the imaging surface of the line scan sensor.

[0007] According to this imaging unit, radiation that has passed through an object passes through the incident window of the housing and enters the housing. A slit member inside the housing guides the radiation toward the input surface of the scintillator. At this time, the radiation irradiation area on the input surface of the scintillator is narrowed (i.e., limited) by the slit of the slit member. This allows for improved resolution. The equidistant lens used for imaging the scintillation light can improve sensitivity because it can shorten the working distance. The equidistant lens is positioned, for example, close to the input surface of the scintillator. Even in this case, the effect of scattered radiation is reduced because the radiation irradiation area is narrowed by the slit.

[0008] The slit member is positioned such that the slit is located in the direction normal to the input surface of the scintillator, and the equal magnification lens and line scan sensor may form an image of the scintillation light output in a direction inclined with respect to the normal direction of the input surface. In this case, it is easy to bring the equal magnification lens and line scan sensor close to the input surface. A desirable image is possible from the perspective of improving resolution and sensitivity.

[0009] The slit member may be positioned so that the slit extends obliquely with respect to the conveying direction. If the slit is oriented obliquely with respect to the conveying direction, the optical path of the radiation penetrating the object can be lengthened. As a result, the contrast of the acquired radiation image becomes high.

[0010] The slit member is positioned such that the slit is positioned at an angle with respect to the normal direction of the input surface of the scintillator, and the equal magnification lens and line scan sensor may form an image of the scintillation light output at an angle with respect to the normal direction of the input surface. In this case as well, it is easy to bring the equal magnification lens and line scan sensor close to the input surface.

[0011] The housing has another incident window that allows radiation transmitted through an object to pass through, and an imaging unit is disposed between the other incident window and a scintillator, and further comprises another slit member that forms another slit that guides the radiation passing through the other incident window toward an input surface, and the slit member and the other slit member may be arranged so that the slit and the other slit guide radiation in two different directions with respect to the input surface of the scintillator, respectively. Radiation images based on radiation guided (incident) from two different directions become different images based on the difference in angle. By doing so, various inspection precisions can be improved. For example, by using a mechanical shutter in combination, two types of images can be acquired in a single imaging step, thereby shortening the inspection time.

[0012] The imaging unit may further comprise a cover member that is detachably mounted to the housing while retaining a slit member. By preparing multiple types of combination parts of the cover member and the slit member retained by the cover member and appropriately exchanging them, the direction of incidence (angle of incidence) of radiation on the input surface of the scintillator can be easily changed. For example, by changing the direction of incidence of radiation and performing multiple imagings, various inspection precisions can be improved.

[0013] The slit member may be configured such that the width of the slit's return direction narrows as it approaches the input surface of the scintillator. In this case, since the entrance portion of the slit can be widened, the incident direction (angle of incidence) of radiation relative to the input surface of the scintillator can be changed, or radiation can be guided toward the input surface in multiple incident directions.

[0014] The slit member, equal magnification lens, and line scan sensor may be rotatable around an axis extending along the input surface within the housing. In this case, the direction of incidence (angle of incidence) of radiation with respect to the input surface of the scintillator can be easily changed. For example, by changing the direction of incidence of radiation and performing multiple imaging, various inspection precisions can be improved.

[0015] As another aspect of the present disclosure, a radiation image acquisition system for acquiring a radiation image of an object may be provided, comprising a radiation source that outputs radiation toward the object, a conveying device that conveys the object in a conveying direction and passes the radiation through it, and an imaging unit of any of the above installed such that the radiation source and the incident window are arranged on the same plane. According to this radiation acquisition system, resolution can be improved and sensitivity can also be improved through the above-described operation.

[0016] In a radiation image acquisition system, the slit members of the carrier device and the imaging unit may be arranged so that the slit extends obliquely with respect to the carrier direction. When the slit is oriented obliquely with respect to the carrier direction, the optical path of radiation penetrating the object can be lengthened. As a result, the contrast of the acquired radiation image becomes high.

[0017] Another aspect of the present disclosure is a method for acquiring a radiation image of an object, comprising: a radiation output process for outputting radiation toward an object being transported in a transport direction; a radiation introduction process for introducing radiation that has passed through the object into a housing through an incident window and guiding the radiation toward an input surface of a scintillator by means of a slit formed in the housing; a scintillation light output process for inputting the radiation that has passed through the slit into an input surface of a scintillator, converting the input radiation into scintillation light, and outputting the scintillation light from the input surface; a scintillation light imaging process for forming an image of the scintillation light output from the input surface onto an imaging surface of a line scan sensor by means of an equal magnification lens; and a scintillation light imaging process for capturing the scintillation light on the imaging surface of the line scan sensor.

[0018] According to this radiation image acquisition method, radiation transmitted through an object passes through the incident window of the housing and enters the housing. A slit member inside the housing guides the radiation toward the input surface of the scintillator. At this time, the slit in the slit member narrows (i.e., limits) the radiation irradiation area on the input surface of the scintillator. This improves resolution. The equal-magnification lens used in the scintillation optical imaging process can improve sensitivity because it can shorten the working distance. The equal-magnification lens is positioned, for example, close to the input surface of the scintillator. Even in such cases, the effect of scattered radiation is reduced because the radiation irradiation area is narrowed by the slit during the radiation introduction process.

[0019] In the radiation output process, an object is conveyed multiple times in a conveying direction, and radiation is output from multiple different directions toward the object during the multiple conveyings. In the radiation introduction process, radiation is guided from multiple directions toward the input surface of a scintillator during the multiple conveyings. The radiation image acquisition method may further include an image processing process that performs image processing on multiple captured images obtained from the scintillation light imaging process. Radiation images based on radiation guided (incident) from multiple directions become different images based on the angle difference. By doing so, various inspection precisions can be improved. Effects of the invention

[0020] According to several aspects of the present disclosure, resolution can be improved, and sensitivity can also be improved. Brief explanation of the drawing

[0021] FIG. 1 is a perspective view showing a radiation image acquisition system according to one embodiment of the present disclosure. Figure 2 is a diagram showing the schematic configuration of the radiation image acquisition system shown in Figure 1. FIG. 3 is a cross-sectional view showing the internal configuration of the imaging unit in FIG. 1. Figure 4 is a diagram showing the arrangement of each part in the radiation image acquisition system of Figure 1. FIGS. 5(a) and FIGS. 5(b) are drawings showing the arrangement of each part in various modified examples of a radiation image acquisition system. Figures 6(a) and 6(b) are diagrams illustrating the difference in the angle of incidence of radiation on an object. Figures 7(a) to 7(c) are drawings showing the arrangement of each part in various modified examples of a radiation image acquisition system. FIGS. 8(a) and FIGS. 8(b) are drawings showing the internal configuration of various modified examples of a radiation image acquisition system. FIGS. 9(a) and FIGS. 9(b) are drawings showing the internal configuration of various modified examples of a radiation image acquisition system. FIGS. 10(a) to FIGS. 10(c) are drawings showing the sequence of inspection and imaging from multiple directions. FIG. 11 is a diagram showing the arrangement of each part in a modified example of a radiation image acquisition system. FIG. 12 is a diagram showing the arrangement of each part in a modified example of a radiation image acquisition system. FIG. 13 is a cross-sectional view showing an example of the internal configuration of an imaging unit corresponding to a modified example of FIG. 12. FIG. 14 is a cross-sectional view showing an enlarged portion of FIG. 13. FIG. 15 (a) and FIG. 15 (b) are drawings showing the difference in the irradiation area and the image formation area depending on the presence or absence of a slit member. Figure 16 is a table showing the measurement results of a radiation scattering test. Figures 17(a) to 17(c) are, respectively, radiation images obtained from imaging tests using samples. Figures 18 (a) and 18 (b) are radiation images obtained from imaging tests using samples, respectively. Specific details for implementing the invention

[0022] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In addition, in the description of the drawings, the same reference numerals are used for identical elements, and redundant descriptions are omitted. Furthermore, each drawing is prepared for illustrative purposes and is drawn to particularly emphasize the parts being described. Therefore, the dimensional ratios of each component in the drawings do not necessarily correspond to the actual ones.

[0023] As shown in FIGS. 1 and 2, a radiation image acquisition system (1) according to one embodiment is a device for acquiring a radiation image of an object (A). The radiation image acquisition system (1) is a non-destructive inspection system capable of inspecting the object (A) without disassembly or destruction. The object (A) contains, for example, a material composed of light elements. The radiation image acquisition system (1) is applied in fields such as, for example, food inspection, battery inspection, or inspection of electronic components. In the field of food inspection, for example, the presence or absence of foreign matter being entangled in sealed container packaging is inspected. The radiation image acquisition system (1) is particularly excellent in its ability to distinguish materials composed of light elements. Examples of such materials include food waste, hair, plastic, insects, meat bones, etc. The radiation image acquisition system (1) is applied, for example, to inline X-ray inspection.

[0024] The radiation image acquisition system (1) comprises a radiation source (2) that outputs radiation, such as white X-rays, toward an object (A), a transport device (20) that transports the object (A) in a predetermined transport direction (D), a scintillator (6) that generates scintillation light according to the input of radiation that has passed through the object (A) transported by the transport device (20), a line scan sensor (3) that detects scintillation light output from the radiation input surface (6a) of the scintillator (6), and a computer (10) that controls several functions of the radiation image acquisition system (1) and also creates a radiation image. Thus, the radiation image acquisition system (1) is an X-ray imaging system that observes the surface of a scintillator. The radiation image acquisition system (1) has excellent sensitivity to low-energy X-rays.

[0025] The radiation source (2) outputs cone-beam X-rays from the X-ray emission unit. The radiation source (2) has a focal point (2a) of the cone-beam X-rays. The radiation source (2) may be, for example, a micro-focus X-ray source or a milli-focus X-ray source. The X-rays emitted from the radiation source (2) form a radiation beam. In the radiation image acquisition system (1), by providing a source-side slit member (26) and a slit member (16) (see FIG. 2), X-rays within an irradiation area (12) that is narrowed to a limited portion of the X-rays within the output area where the radiation beam exists are input to the input surface (6a) of the scintillator (6). The irradiation area (12) extends in a triangular shape (or fan shape) toward the scintillator (6) within the housing (15) of the imaging unit (30).

[0026] The conveying device (20) has, for example, two belt conveyors (21, 21) that move along a circular track, and an object (A) is placed or maintained on the conveying surface (21a) of the belt conveyor (21). The belt conveyor (21) is a conveying stage or a conveying section. 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 the conveying direction (D). In this embodiment, the conveying direction (D) is a horizontal direction. Between the two belt conveyors (21, 21), a gap (C) through which X-rays pass is provided at a position corresponding to the above-mentioned irradiation area (12). The gap (C) has a slightly constant length (width) in the conveying direction (D) and extends straight in the detection width direction, which is horizontal and orthogonal to the conveying direction (D). The conveying timing or conveying speed of the object (A) in the conveying device (20) is pre-set and is controlled by the control unit (10a) of the computer (10). Additionally, the belt conveyor (21) does not need to have a gap (C) that allows X-rays to pass through, and the belt member of the belt conveyor (21) may be made of a radiation-transmitting material.

[0027] Additionally, the radiation image acquisition system (1) can accommodate all types of transport devices (20). For example, the transport direction (D) may be horizontal, but may also be inclined relative to the horizontal. The transport direction (D) may not be in the shape of a straight line, but may be, for example, in the shape of a curve. In that case, the transport direction (D) may be a tangent at the part of the transport path of the object (A) that overlaps with the irradiation area (12). The transport device (20) may not have a physical transport surface (21a). For example, the transport device (20) may transport the object (A) while it is levitating by air. In addition, the transport device (20) may transport the object (A) by releasing the object (A) into the air. In that case, the transport path of the object (A) may be, for example, in the shape of a parabola.

[0028] The conveying device (20) is not limited to a form having a belt conveyor (21). The conveying device (20) may, for example, have a roller conveyor including a plurality of rollers. Since the roller conveyor does not have a belt, the influence of the belt can be eliminated. The fact that a gap (slit-shaped opening) is formed between the rollers is also advantageous compared to a belt conveyor. By using a roller conveyor, X-ray attenuation caused by the belt is reduced. Considering the arrangement of the radiation source (2) and the arrangement of the irradiation area (12) (inclined irradiation) described later, the roller conveyor can be effectively utilized. The roller conveyor is a conveying means suitable for a radiation image acquisition system (1) where low-energy X-ray sensitivity is important. According to the form in which two or more belt conveyors are installed in the conveying direction as in this embodiment and X-rays are irradiated from the gap (C) between the belt conveyors, the influence of the belt can be eliminated while using the belt conveyor (21).

[0029] As shown in FIGS. 1 to 3, the radiation image acquisition system (1) is equipped with an imaging unit (30) installed to follow a conveying device (20). The imaging unit (30) is, for example, mounted on the conveying device (20) and fixed to the conveying device (20). The imaging unit (30) may be mounted on a stand other than the conveying device (20). The imaging unit (30) may be placed on a stand or the like. The imaging unit (30) is mounted 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 imaging unit (30) is positioned with a small gap from the conveying part so as not to interfere with the movement of the conveying part, such as a belt conveyor or a roller conveyor.

[0030] The imaging unit (30) has a rectangular housing (15). The housing (15) has a rectangular housing body (13), made of, for example, aluminum, and a lead cover (14) that covers the outer surface (outer circumference) of the housing body (13). The housing body (13) accommodates each component of the imaging unit (30) in an internal space (15S). The lead cover (14) shields radiation so that radiation from outside the housing body (13) does not affect the internal space (15S) of the imaging unit (30). The lead cover (14) may be placed on the outside of the housing (15) or on the inside of the housing (15). Another cover may be mounted on the outside of the lead cover (14). From the perspective of the strength of the lead and handling, it is preferable that another material be mounted on the outside of the lead. The material of the cover may be a substance other than lead, and for example, tungsten, iron, stainless steel, copper, etc. may be used. In addition, a rubber-like material or a sheet-like material containing heavy metals such as tungsten in rubber (resin) may be used.

[0031] The housing body (13) is made of a material capable of shielding X-rays, for example. The housing body (13) may be made of iron or stainless steel, etc. The housing body (13) may include a protective material, and lead, tungsten, or copper may be used as the protective material. In addition, a rubber-shaped material or a sheet-shaped material containing heavy metals such as tungsten in rubber (resin) may be used. The housing body (13) includes an upper wall portion (13a) and a lower wall portion (13d) facing in the vertical direction, a pair of first side wall portions (13b) facing in the conveying direction (D), and a pair of second side wall portions (13c) facing in the horizontal detection width direction perpendicular to the conveying direction (D). The imaging unit (30) is made of a very small size in the conveying direction (D) of the housing body (13), so it is a compact device. The return direction (D) is parallel to the x direction parallel to the surface shown in the drawing. The detection width direction is parallel to the y direction perpendicular to the surface shown in the drawing. The up and down direction is parallel to the z direction parallel to the surface shown in the drawing.

[0032] The upper wall portion (13a) is positioned to face the conveying device (20). On the upper wall portion (13a), the top plate portion (14a) of the lead cover (14) is mounted at a distance from the upper wall portion (13a). The top plate portion (14a) is positioned parallel to the upper wall portion (13a). Between the upper wall portion (13a) and the top plate portion (14a), an aluminum support plate portion (13e) is provided to support the slit member (16) described later. Additionally, the support plate portion (13e) for supporting the slit member (16) may be made of a metal such as stainless steel or iron. On the outer surface of a pair of first side wall portions (13b), a pair of first side plates (14b) of the lead cover (14) are mounted. On the outer surface of a pair of second side wall portions (13c), a pair of second side plate portions (not shown) of a lead cover (14) are mounted. The lead cover (14) covers the entire surface of the housing body (13), excluding the bottom wall portion (13d). Also, in FIG. 1, the first side plate portion (14b) is omitted from the illustration.

[0033] An incident window (14f) is formed in the top plate portion (14a) of the lead cover (14) to allow X-rays that have passed through the object (A) to pass through. The incident window (14f) has a slightly constant length (width) in the x direction and extends straight in the y direction. The length of the incident window (14f) in the x direction may be determined by the width of the slit (S) of the slit member (16) described later or the width of the desired irradiation area (12) (thickness in the return direction (D)). The length of the incident window (14f) in the x direction is constant in the detection width direction (y direction) and the thickness direction (z direction) of the top plate portion (14a).

[0034] In the support plate portion (13e), a through hole (13g) (see FIG. 3) is formed at a position corresponding to the incident window (14f), having a certain length (width) in the x direction and extending straight in the y direction. A slit member (16) for defining an irradiation area (12) is disposed and fixed within this through hole (13g). The slit member (16) includes a first slit plate (17) and a second slit plate (18) facing each other with a slight certain gap in the x direction. The first slit plate (17) and the second slit plate (18) are, for example, made of copper. The gap between the first slit plate (17) and the second slit plate (18) is the width of the slit (S) formed by the slit member (16), and is, for example, equal to the length (width) in the x direction of the incident window (14f). The width of the slit (S) may differ slightly from the length (width) in the x-direction of the incident window (14f). With the upper portion (16a) of the slit member (16) inserted into the through hole (13g) of the support plate portion (13e), the upper portion (16a) is fixed to the support plate portion (13e). The support plate portion (13e) supports the slit member (16) so that the slit (S) is continuous with the incident window (14f). That is, the entrance end (Sa) of the slit (S) is directly connected to the incident window (14f) (for example, without leaving a gap). The y-direction ends of the first slit plate (17) and the second slit plate (18) may be open or closed by another copper plate, etc.

[0035] The slit member (16) is installed within the housing (15). The slit member (16) is positioned between the incident window (14f) and the scintillator (6). The slit member (16) is inserted into the opening (13f) formed in the upper wall portion (13a) and hangs down toward the internal space (15S). The slit member (16) extends to the vicinity of the input surface (6a) of the scintillator (6). The arrangement of the slit member (16) and the positional relationship between the slit member (16) and the scintillator (6) will be described later. Additionally, for example, when the top plate portion (14a) is not provided, the upper end of the slit member (16) may be exposed to the top surface of the housing (15) or may protrude upward from the housing (15). In that case, the upper part of the slit member (16) serves as an incoming window.

[0036] As shown in FIGS. 1 and 2, a source-side slit member (26) is provided for a radiation source (2) to regulate an irradiation area (12). The source-side slit member (26) has, for example, a pair of triangular copper plates. A pair of triangular copper plates face each other with a certain distance in the x-direction and form a slit. Both ends of the source-side slit member (26) in the y-direction are closed, for example, by another copper plate. In the radiation image acquisition system (1), each member is installed so that the focal point (2a) of the radiation source (2), the slit of the source-side slit member (26), the gap (C) of the carrier device (20), the incident window (14f), and the slit (S) of the slit member (16) are arranged on the same plane. These members restrict (limit) the X-ray irradiation area (12), and only some of the X-rays output from the radiation source (2) penetrate the object (A) and reach the input surface (6a) of the scintillator (6). The irradiation area (12) is a square pyramid-shaped area having a small thickness in the x-direction defined, for example, by the inner surface of the source-side slit member (26), the inner wall surface of the incident window (14f), and the inner wall surface of the slit member (16).

[0037] As shown in FIGS. 2 and 3, the slit member (16) guides X-rays that have passed through the incident window (14f) by means of the slit (S) toward the input surface (6a) of the scintillator (6). Scattering of X-rays in the internal space (15S) of the housing (15) is prevented by the slit member (16). The input surface (6a) of the scintillator (6) receives X-rays within the irradiation area (12) that have passed through the slit member (16). Furthermore, the "input surface (6a) of the scintillator (6)" refers only to the area that effectively acts on the output of the scintillation light. For example, among the entire rectangular input surface (6a), areas covered by the scintillator holder are not included in the "input surface (6a) of the scintillator (6)."

[0038] In the radiation image acquisition system (1), the imaging unit (30) is configured to capture scintillation light output from the input surface (6a) of the scintillator (6) in a direction inclined with respect to the input surface (6a). Inside the housing (15), the scintillator (6), the line scan sensor (3), and the equal magnification lens (7) are installed. Additionally, a shielding member (9) is mounted 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. The line scan sensor (3), the shielding member (9), and the equal magnification lens (7) are held in an internal space (15S) by a bracket, etc. (not shown).

[0039] The scintillator (6) is held, for example, in a scintillator holder (not shown) and is, for example, positioned horizontally. The scintillator (6) is a flat-plate wavelength conversion member. The scintillator (6) has a rectangular shape that is long in the detection width direction (y-direction) (see FIG. 1). The scintillator (6) is, for example, Gd2O2S:Tb, Gd2O2S:Pr, CsI:Tl, CdWO4, CaWO4, Gd2SiO5:Ce, Lu 0.4 Gd 1.6 SiO5, Bi4Ge3O 12 It is made of 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 based on the energy range of the radiation detected in the range of several μm to several mm. The scintillator (6) converts X-rays that have passed through the object (A) into visible light. X-rays of relatively low energy are converted to the input surface (6a) of the scintillator (6) and output from the input surface (6a).

[0040] The line scan sensor (3) performs imaging in accordance with the movement of the object (A) and outputs radiation image data, which is one-dimensional image data. The line scan sensor (3) has an imaging surface (3a) that captures scintillation light output from the input surface (6a) of the scintillator (6). 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 Integral) driving. 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 a row of elements, in which a plurality of light-receiving elements are arranged in a row in the pixel direction, is arranged in one or multiple rows in the column direction corresponding to the movement direction of the object (A). The line scan sensor (3) has a scan direction corresponding to the transport direction (D) of the object (A) and a line direction orthogonal to the scan direction. This line direction is the pixel direction above and is parallel to the y direction in Fig. 2. Also, the scan direction corresponds to the column direction above and is parallel to the z direction in Fig. 2. In addition, in the case of an area image sensor capable of TDI driving, the column direction becomes the same direction as the integration direction.

[0041] The line scan sensor (3) captures the object (A) in accordance with the movement of the object (A) by the control unit (10a). That is, the line scan sensor (3) captures the object (A) on the imaging surface (3a) in synchronization with the movement of the object (A) by the transport device (20) and outputs radiation image data. By doing so, a radiation image with a good signal-to-noise ratio can be obtained. In addition, to synchronize the movement of the object (A) by the stage with the capture 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.

[0042] The scintillator (6) of the present embodiment is positioned so that the input surface (6a) is parallel to the return direction (D) and also parallel to the line direction. That is, the input surface (6a) of the scintillator (6) is parallel to the xy plane.

[0043] The equal magnification lens (7) is positioned between the scintillator (6) and the line scan sensor (3) and forms a scintillation light output from the input surface (6a) onto the imaging surface (3a) of the line scan sensor (3). The equal magnification lens (7) is a lens with a magnification of 1x and can be realized, for example, as a refractive index distribution type lens (GRIN lens), a rod lens, a rod lens array, etc. The focus of the equal magnification lens (7) is aligned with the input surface (6a) of the scintillator (6). Since the equal magnification lens (7) has a deep depth of field, the focus blur is small even when the phosphor is captured at an angle, and it acts advantageously in oblique imaging such as the present embodiment. In addition, the equal magnification lens (7) increases the degree of freedom in the combination of the arrangement of the radiation source (2), the object (A), and the line scan sensor (3).

[0044] The shielding member (9) is a radiation shielding member that transmits scintillation light generated from the scintillator (6) and concentrated by the equal-magnification lens (7), and shields X-rays. The shielding member (9) is, for example, lead-containing glass, or lead-free radiation shielding glass containing heavy elements such as Sr, Ba, Ti, B, W, Si, Gd, Zr, FOP (fiber optic plate), or radiation shielding resin. The shielding member (9) is mounted on the surface of the line scan sensor (3) (the surface of the protective resin). The shielding member (9) reduces the effect of scattered X-rays.

[0045] As shown in FIG. 3, in the imaging unit (30) of the radiation image acquisition system (1), the slit member (16) is positioned such that the slit (S) is positioned in the direction of the normal (B) of the input surface (6a) of the scintillator (6). The equal magnification lens (7), the shielding member (9), and the line scan sensor (3) are positioned in a direction inclined with respect to the direction of the normal (B) of 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 direction of the normal (B) of the input surface (6a) on the imaging surface (3a). The line scan sensor (3) captures the scintillation light output in a direction inclined with respect to the direction of the normal (B) of the input surface (6a).

[0046] The exit end (Sb) of the slit (S) formed by the slit member (16) is located close to the input surface (6a) of the scintillator (6). Additionally, the front end surface (7a) of the equal magnification lens (7) is located close to the input surface (6a) of the scintillator (6). In the imaging unit (30), each member is arranged so that the slit member (16) and the equal magnification lens (7) are located as close as possible to the input surface (6a) of the scintillator (6). The slit member (16) extends to a position close to the input surface (6a) of the scintillator (6) to such an extent that the imaging of the scintillation light by the line scan sensor (3) and the equal magnification lens (7) is not hindered. The distance from the exit end (Sb) of the slit (S) to the input surface (6a) of the scintillator (6) is preferably, for example, less than 20 mm. The distance from the exit end (Sb) of the slit (S) to the input surface (6a) of the scintillator (6) is better if it is shorter, and more preferably less than 5 mm. In addition, the bottoms of the two slit plates do not need to be aligned, and the distance from the scintillator may differ between the slit plate on the equal magnification lens (7) side (first slit plate) and the slit plate on the opposite side (second slit plate).

[0047] The equal-magnification lens (7) is positioned so as to be close to the irradiation area (12) (see (a) in FIG. 15) on the scintillator (6), to the extent that its front surface (7a) does not interfere with the scintillator (6) and the slit member (16).

[0048] The computer (10) has, for example, a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and an input / output interface. The computer (10) has a control unit (10a) (control processor) that controls a radiation source (2) and a line scan sensor (3), and an image processing unit (10b) (image processing processor) that creates a radiation image of an object (A) based on radiation image data output from the line scan sensor (3). The image processing unit (10b) inputs radiation image data and performs a predetermined processing, such as image processing, on the input radiation image data. A display device (11) is connected to the computer (10). The image processing unit (10b) outputs the created radiation image to the display device (11). The control unit (10a) controls the radiation source (2) based on values ​​of tube voltage or tube current of the radiation source (2) stored by user input, etc. The control unit (10a) controls the line scan sensor (3) based on the exposure time of the line scan sensor (3) stored by user input, etc. The control unit (10a) and the image processing unit (10b) may be different processors or the same processor. In addition, the computer (10) may be programmed to execute the functions of the control unit (10a) and the image processing unit (10b). In addition, the computer (10) may be composed of a microcomputer or an FPGA (Field-Programmable Gate Array).

[0049] Next, the operation of the radiation image acquisition system (1), that is, the method of acquiring a radiation image, will be explained. First, the object (A) is transported in the transport direction (D) using the transport device (20) (transport process). At the same time, radiation such as white X-rays is output from the radiation source (2) toward the object (A) (radiation output process). Next, the radiation that has passed through the object (A) is introduced into the housing (15) through the incident window (14f), and the radiation is guided toward the input surface (6a) of the scintillator (6) by the slit (S) formed inside the housing (15) (radiation introduction process). The radiation that has passed through the object (A) is input to the input surface (6a), and the radiation is converted into scintillation light by the scintillator (6), and the scintillation light is output from the input surface (6a) (scintillation light output process). Then, the scintillation light output from the input surface (6a) is formed on the imaging surface (3a) of the line scan sensor (3) by the equal magnification lens (7) (scintilation light forming process). Also, the scintillation light is captured on the imaging surface (3a) of the line scan sensor (3) (scintilation light capturing process). The line scan sensor (3) outputs the radiation image data obtained by the imaging to the image processing unit (10b) of the computer (10).

[0050] The image processing unit (10b) of the computer (10) inputs radiation image data and performs a predetermined process, such as image processing, on the input radiation image data to create a radiation image (image creation process). The image processing unit (10b) outputs the created radiation image to a display device (11). The display device (11) displays the radiation image output from the image processing unit (10b). Through the above process, a radiation image obtained by observing the surface of an object (A) is obtained.

[0051] According to the imaging unit (30), radiation image acquisition system (1), and radiation image acquisition method of the present embodiment, radiation transmitted through an object (A) passes through the incident window (14f) of the housing (15) and enters the housing (15). The slit member (16) inside the housing (15) guides the radiation toward the input surface (6a) of the scintillator (6). At this time, the radiation irradiation area (12) on the input surface (6a) of the scintillator (6) is narrowed (i.e., limited) by the slit (S) of the slit member (16). FIG. 15 (a) shows the irradiation area (12) when the slit member (16) is provided, and FIG. 15 (b) shows the irradiation area (12) when the slit member (16) is not present. As is evident from FIG. 15 (a) and FIG. 15 (b), the irradiation area (12) on the input surface (6a) of the scintillator (6) is limited to a narrower area by providing a slit member (16). Accordingly, the imaging area formed by the equal magnification lens (7) also becomes a narrow area, similar to the irradiation area (12) shown in FIG. 15 (a). When the radiation irradiation area (12) on the input surface (6a) of the scintillator (6) is wide, the fluorescence emitted on the scintillator (6) cross-talks (mixes with each other), causing a decrease in resolution. Additionally, a decrease in resolution occurs due to the influence of scattered rays, etc. When the radiation irradiation area (12) is narrowed, the decrease in resolution caused by cross-talk or scattered rays can be prevented. Therefore, by narrowing the irradiation area (12) in this way, the resolution can be improved. The equal magnification lens (7) used in the scintillation optical imaging process can improve sensitivity because it can shorten the working distance. The equal magnification lens (7) is positioned close to the input surface (6a) of the scintillator (6). Even in such a case, the radiation irradiation area (12) is narrowed by the slit (S) in the radiation introduction process, so the effect of scattered radiation is reduced.The slit member (16) also has the effect of preventing radiation exposure from the line scan sensor (3) or the equal magnification lens (7). In the imaging unit (30), the unit is made compact by the installation of the slit member (16) and the application of the equal magnification lens (7).

[0052] As shown in FIG. 4, the slit member (16) is positioned such that the slit (S) is located in the direction of the normal (B) of the input surface (6a) of the scintillator (6), and the equal magnification lens (7) and line scan sensor (3) form an image of the scintillation light output in a direction inclined with respect to the direction of the normal (B) of the input surface (6a). This configuration makes it easy to bring the equal magnification lens (7) and the line scan sensor (3) close to the input surface (6a). A desirable image is possible in terms of improving resolution and sensitivity.

[0053] In addition, since the shielding member (9) is mounted on the line scan sensor (3), the effect of suppressing scattered X-rays is achieved. FIG. 16 is a table showing the measurement results of a radiation scattering test. In this test, a lead cover (14) was installed around the housing body (13), including the vicinity of the incident window (14f). The number of scattered X-ray pixels was measured in Examples 1 and 2, which provided a copper plate slit section having the same configuration as the slit member (16), and in a comparative example without a copper plate slit section. As shown in FIG. 16, in Examples 1 and 2, the ratio of scattered X-rays was suppressed to a lower level compared to the comparative example, confirming the X-ray scattering reduction effect by the copper plate slit section. In addition, a difference in the ratio of scattered X-rays was confirmed in Example 1, which provided the shielding member (9), and Example 2, which did not have the shielding member (9). It was confirmed that by providing the shielding member (9), the ratio of scattered X-rays is suppressed to a lower level.

[0054] The radiation image acquisition system and imaging unit of the present disclosure may take various modified forms in addition to the forms shown in FIGS. 2 to 4. The modified forms of the present disclosure will be described below with reference to each drawing. In addition, although the shielding member (9) is omitted in the following description, the shielding member (9) may be provided in any modified form, just like the imaging unit (30).

[0055] For example, as shown in FIG. 5(a), the slit member (16) may be positioned so that the slit (S) extends obliquely with respect to the conveying direction (D). In this radiation image acquisition system (1A) and imaging unit (30A), the slit member (16) is positioned so that the slit (S) is positioned in a direction inclined with respect to the normal (B) of the input surface (6a) of the scintillator (6), and the equal magnification lens (7) and line scan sensor (3) form an image of the scintillation light output in the direction of the normal (B) of the input surface (6a). As shown in FIG. 6(a) and FIG. 6(b), by making the slit (S) obliquely with respect to the conveying direction (D), the optical path of the radiation penetrating the object (A) can be extended. When a certain thickness (thickness in a direction perpendicular to the conveying surface (21a)) is assumed for the object (A), the optical path length (Lb) shown in FIG. 6 (b) is longer than the optical path length (La) shown in FIG. 6 (a). As a result, the contrast of the acquired radiation image is increased.

[0056] Additionally, as shown in FIG. 5(b), the slit member (16) may be positioned so that the slit (S) extends obliquely with respect to the conveying direction (D). In this radiation image acquisition system (1B) and imaging unit (30B), the slit member (16) is positioned so that the slit (S) is positioned in a direction inclined with respect to the normal (B) of the input surface (6a) of the scintillator (6), and the equal magnification lens (7) and line scan sensor (3) also form an image of the scintillation light output in a direction inclined with respect to the normal (B) of the input surface (6a). In this case as well, the contrast of the acquired radiation image is increased.

[0057] FIGS. 17(a) to FIGS. 17(c) are, respectively, test results for whether foreign matter (F) (hair, etc.) is entangled in the bag portion of a plastic bag packaging snacks. As shown in the image of FIG. 17(a), when the slit member (16) was not provided, the foreign matter (F) could not be seen. However, as shown in the image of FIG. 17(b), when the slit member (16) was provided and perpendicular incidence of X-rays as shown in FIG. 4 was performed, the foreign matter (F) was confirmed. Additionally, as shown in the image of FIG. 17(c), when the slit member (16) was provided and oblique incidence of X-rays as shown in FIG. 5 was performed, the foreign matter (F) was confirmed. In addition, in the images of FIG. 17 (b) and FIG. 17 (c), the contrast in the images was clear by lowering the tube voltage of the radiation source (2) to 25 kV and raising the tube current to 25 mA (in FIG. 17 (a), 100 kV and 15 mA, respectively).

[0058] FIGS. 18(a) and FIGS. 18(b) are test results for testing whether foreign matter is curled into the sealing portion of a plastic bag used to package snacks. As shown in the image of FIG. 18(a), when a slit member (16) is provided and X-rays are incident perpendicularly as shown in FIG. 4, a large packaging bag (P1) and a small packaging bag (P2) contained inside it (the candy inside is visible as black) were confirmed. Additionally, as shown in the image of FIG. 18(b), when a slit member (16) is provided and X-rays are incident obliquely as shown in FIG. 5, the large packaging bag (P1), the small packaging bag (P2) contained inside it, and additionally, the unevenness of the sealing portion (P3) of the large packaging bag (P1) were confirmed.

[0059] As shown in FIG. 7(a), the slit member (16) may be positioned so that the slit (S) extends obliquely with respect to the conveying direction (D). In this radiation image acquisition system (1C) and imaging unit (30C), the conveying direction (D) is inclined with respect to the input surface (6a) of the scintillator (6). The slit member (16) is positioned so that the slit (S) is located in the direction of the normal (B) of the input surface (6a) of the scintillator (6), and the equal magnification lens (7) and line scan sensor (3) form an image of the scintillation light output in a direction inclined with respect to the normal (B) of the input surface (6a). Even in this case, the contrast of the acquired radiation image is increased. In the radiation image acquisition system (1D) and imaging unit (30D) shown in FIG. 7(b), unlike the radiation image acquisition system (1C) and imaging unit (30C), the direction of the transport surface (21a) is not changed, and the direction of the radiation source (2) and the imaging unit (30D) is inclined. In other respects, it is the same as the radiation image acquisition system (1C) and imaging unit (30C). Also, in the radiation image acquisition system (1E) and imaging unit (30E) shown in FIG. 7(c), only the orientation of the object (A) on the transport surface (21a) is inclined.

[0060] As shown in FIG. 8(a), the slit member (16) may be configured such that the width of the slit (S) in the return direction (D) narrows as it approaches the input surface (6a) of the scintillator (6). In this radiation image acquisition system (1F) and imaging unit (30F), the opening of the slit member (16) is widened by a pair of tapered first slit plates (17) and second slit plates (18), thereby enabling vertical and oblique incidence of X-rays through a single housing (15). Additionally, an angle indicator (40) may be installed within the housing (15) to easily visualize the angle of oblique incidence. The equal magnification lens (7) and line scan sensor (3) form an image of the scintillation light output in an oblique direction relative to the normal (B) of the input surface (6a). In this way, the entrance portion of the slit (S) can be widened, thereby changing the incident direction (incident angle) of radiation to the input surface (6a) of the scintillator (6), or guiding radiation to the input surface (6a) in multiple incident directions. For oblique incidence of X-rays, another incident window (14g) may be formed in the housing (15), for example, to allow radiation that has passed through the object (A) to pass through. The incident window (14g) may be formed in accordance with the arrangement of the second slit plate (18) (the oblique surface defining the slit (S)). An opening and closing mechanism may be provided to appropriately open and close the incident windows (14f, 14g). The opening and closing mechanism may operate in accordance with the imaging timing by the line scan sensor (3).

[0061] As shown in FIG. 8(b), the slit member (16), the equal magnification lens (7), and the line scan sensor (3) may be rotatable around an axis (L) extending along the input surface (6a) within the housing (15). In this radiation image acquisition system (1G) and imaging unit (30G), after fixing the angle formed between the irradiation area (12) of the radiation source (2) and the optical axis (E) of the line scan sensor (3), the angle with respect to these input surfaces (6a) can be easily changed. Therefore, a rotation mechanism (50) capable of rotatable the equal magnification lens (7) and the line scan sensor (3) around the axis (L) is provided. That is, the incident direction (incident angle) of radiation with respect to the input surface (6a) of the scintillator (6) can be easily changed. For example, by changing the incident direction of radiation and performing multiple imagings, the precision of various inspections can be improved.

[0062] As shown in FIG. 9(a), the imaging unit (30H) may further be provided with a cover member (43) that is detachably mounted to the housing while retaining the slit member (16). In this radiation image acquisition system (1H) and imaging unit (30H), the slit member (16) is fixed to an L-shaped cover member (43) such that the slit (S) faces in the direction of the normal (B) of the input surface (6a). By mounting the replacement unit (45H), which is integrated with these, to the housing (15), imaging similar to that shown in FIG. 4 becomes possible. Meanwhile, as shown in FIG. 9(b), the imaging unit (30J) may further be provided with a cover member (44) that is detachably mounted to the housing while retaining the slit member (16). In this radiation image acquisition system (1J) and imaging unit (30J), a slit member (16) is fixed to an L-shaped cover member (44) so ​​that the slit (S) faces in a direction inclined with respect to the normal (B) of the input surface (6a). By mounting an integrated exchange unit (45J) to the housing (15), imaging such as that shown in FIG. 5 (b) becomes possible. In this way, by preparing multiple types of combination parts of the cover member and the slit member (16) held in the cover member and exchanging them appropriately, the direction of incidence (angle of incidence) of radiation on the input surface (6a) of the scintillator (6) can be easily changed. For example, by changing the direction of incidence of radiation and performing multiple imagings, the precision of various inspections can be improved.

[0063] Alternatively, as shown in FIGS. 10 (a) to FIGS. 10 (c), imaging may be performed by combining a radiation image acquisition system (1K) and an imaging unit (30K) arranged in the same manner as FIG. 4, a radiation image acquisition system (1L) and an imaging unit (30L) arranged in the same manner as FIG. 5 (a), and a radiation image acquisition system (1M) and an imaging unit (30M) in which the arrangement of the slit member (16) is symmetric with respect to the normal (B) of the input surface (6a) with respect to the radiation image acquisition system (1L) and the imaging unit (30L). That is, in the radiation output process, the object (A) is transported multiple times in the transport direction (D), and in the said multiple transports, radiation is output from multiple different directions toward the object (A), and in the radiation introduction process, radiation may be guided from multiple directions toward the input surface (6a) of the scintillator (6) in the multiple transports. In that case, the radiation image acquisition method may further include an image processing process that performs image processing on a plurality of captured images obtained from a scintillation light imaging process. Radiation images based on radiation guided (incident) from multiple directions become different images based on the difference in angles. By doing this, various inspection precision can be improved. By making many combinations, imaging such as CT imaging is also possible. The tube voltage may be changed with a different radiation source (2, 2A).

[0064] Additionally, as shown in FIG. 11, the housing (15) may further have another incident window (14g) that passes radiation that has passed through an object (A), and an imaging unit (30N) may be positioned between the other incident window (14g) and the scintillator (6), and may further have another slit member (16A) that forms another slit (SA) that guides radiation that has passed through the other incident window (14g) toward the input surface (6a). The slit member (16) and the other slit member (16A) are positioned so that the slit (S) and the other slit (SA) guide radiation from two different directions, respectively, toward the input surface (6a) of the scintillator (6). The radiation image based on the radiation guided (incident) from the two different directions becomes a different image based on the angle. By doing so, various inspection precision can be improved. For example, by using a mechanical shutter (41, 42) made of lead plate or the like, two types of images can be acquired in a single shot, thereby shortening the inspection time. For example, the mechanical shutter (41, 42) and the shutter of the line scan sensor (3) may be synchronized. An opening and closing mechanism for opening and closing the incident window (14f, 14g) may be provided, and this opening and closing mechanism may operate in accordance with the opening and closing timing of the mechanical shutter (41, 42) (the imaging timing by the line scan sensor (3)). By making many combinations, imaging such as CT imaging is also possible. The tube voltage may be changed using a different radiation source (2, 2A).

[0065] Additionally, as shown in FIG. 12, the scintillator (6) may be positioned obliquely within the housing (15). In this radiation image acquisition system (1P) and imaging unit (30P), the slit member (16) is positioned such that the slit (S) is positioned in a direction inclined with respect to the normal (B) of the input surface (6a) of the scintillator (6), and the equal magnification lens (7) and line scan sensor (3) also form an image of the scintillation light output in a direction inclined with respect to the normal (B) of the input surface (6a). With this configuration, it is easy to bring the equal magnification lens (7) and line scan sensor (3) close to the input surface (6a).

[0066] As explained above, it can be seen that the images differ between X-ray incidence by normal and oblique incidence. There are things that can be observed and things that cannot be observed with normal incidence, and things that can be observed and things that cannot be observed with oblique incidence. Furthermore, even with oblique incidence, if the angle (direction) of X-ray incidence on the object (A) is different, the image also changes. By processing these images, the precision of various inspections is improved. As shown in the various modified forms above, the combination of normal and oblique incidence can realize nearly infinite types of combinations by taking all forms.

[0067] Referring to FIGS. 13 and 14, a specific configuration example of an imaging unit (30R) is described, in which radiation is incident from a direction inclined with respect to the input surface (6a) of a scintillator (6), and an equal-magnification lens (7) and a line scan sensor (3) form an image of the scintillation light output in a direction inclined with respect to the input surface (6a). FIG. 13 is a cross-sectional view showing an example of the internal configuration of the imaging unit (30R). FIG. 14 is a cross-sectional view showing an enlarged portion of FIG. 13. The imaging unit (30R) shown in FIG. 13 has the same configuration as the imaging unit (30P) shown in FIG. 12 with respect to the arrangement of the incident window (14f), the scintillator (6), the radiation incident on the scintillator (6), the equal-magnification lens (7), and the line scan sensor (3).

[0068] The imaging unit (30R) is configured to capture scintillation light output from the input surface (6a) of the scintillator (6) in a direction inclined with respect to the input surface (6a). Inside the housing (15), the scintillator (6), the line scan sensor (3), and the equal magnification lens (7) are installed. The equal magnification lens (7) is positioned between the scintillator (6) and the line scan sensor (3). The imaging unit (30R) has a structure for maintaining the scintillator (6), the line scan sensor (3), and the equal magnification lens (7) in a predetermined positional relationship.

[0069] As shown in FIGS. 13 and 14, the imaging unit (30R) comprises a holding member (60) for holding a magnification lens (7) and a line scan sensor (3), a positioning member (70) for positioning a scintillator (6), and a supporting member (80) fitted into the positioning member (70) to support the scintillator (6). The holding member (60), the positioning member (70), and the supporting member (80) are mounted on the housing body (13) of the housing (15) and fixed at a predetermined position. Below, the configuration of the scintillator (6), the line scan sensor (3), and the magnification lens (7), and the configuration for holding each of these parts will be described.

[0070] As shown in FIG. 13, the holding member (60) is housed inside the housing body (13). The holding member (60) has a positioning part (61) that serves as a guide. Additionally, the holding member (60) holds the equal magnification lens (7) at the positioning part (61) of the holding member (60) facing the scintillator (6). Additionally, the holding member (60) holds the line scan sensor (3) at the base part (65) on the opposite side from the positioning part (61). The holding member (60) holds the equal magnification lens (7) such that, for example, the front end surface (one end surface) (7a) of the equal magnification lens (7) is orthogonal to the x direction. The holding member (60) holds the line scan sensor (3) such that, for example, the imaging surface (3a) of the imaging part (31) is orthogonal to the x direction. As shown in FIG. 14, the imaging portion (31) of the line scan sensor (3) is maintained on the main body portion (32) mounted on the base portion (33). A part of the base portion (33) and the main body portion (32) are fitted into the base portion (65) of the retaining member (60).

[0071] As shown in FIGS. 13 and 14, a positioning member (70) is assembled to a housing body (13) at a position directly below an incident window (14f). The positioning member (70) is made of a metal, for example, 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 length in the y direction of the first through hole (74) and the second through hole (75) is longer than the length in the y direction of the scintillator (6). The first through hole (74) and the second through hole (75) are connected in space extending in the y direction. The positioning member (70) has a mounting surface (77) that is inclined with respect to the first through hole (74), that is, the path of the radiation. The mounting surface (77) is inclined, for example, at 45˚ with respect to the xy plane. A 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 opened in this mounting surface (77). The input surface (6a) of the scintillator (6) faces this opening (70d). By appropriately setting the inclination angle of the mounting surface (77), the angle of the input surface (6a) with respect to the radiation input to the input surface (6a), and the angle of the input surface (6a) with respect to the imaging surface (3a) are determined. The inclination angle (45˚) of the mounting surface (77) described above is merely an example, and the mounting surface (77) may be inclined at a different angle with respect to the xy plane.

[0072] The first through hole (74) forms a slit that serves as a path for radiation passage. The incident window (14f) of the top plate (14a), the through hole (13g) of the support plate (13e), and the opening (13f) of the upper wall (13a) are arranged in the z-direction with a constant length in the x-direction. The first through hole (74) is arranged in a straight line with the incident window (14f), the through hole (13g), and the opening (13f). The first through hole (74) guides the X-rays passing through the incident window (14f) toward the input surface (6a) of the scintillator (6). Scattering of X-rays within the internal space of the housing (15) is prevented by the positioning member (70). The input surface (6a) of the scintillator (6) inputs X-rays (radiation) within the irradiation area (12) (see FIG. 12) that has passed through the first through hole (74) of the positioning member (70).

[0073] Although the equal magnification lens (7) has a known configuration, the important feature parts of the imaging unit (30R) will be described below. The equal magnification lens (7) has a rectangular shape. The equal magnification lens (7) has a structure in which a plurality of cylindrical lens bodies (lenses) (8), for example, arranged in a row, are held by a lens holding part (7b). By the lens bodies (8) arranged in an array shape, the equal magnification lens (7) forms an image on the input surface (6a) of the scintillator (6) and the imaging surface (3a) of the line scan sensor (3), respectively. The front end surface (7a) and the base end surface (other end surface) (7c) of the equal magnification lens (7) in the lens length direction are parallel to each other and each form a flat surface. Both end surfaces of the lens bodies (8) are exposed to the front end surface (7a) and the base end surface (7c) and are planes with both end surfaces of the lens holding part (7b). In the equal magnification lens (7), adjacent lens bodies (8) are arranged to overlap images. Since the lens bodies (8) are arranged in an array shape, there is no difference in brightness between the center and the end of the array, and no lens distortion occurs at the end. In the equal magnification lens (7), the operating distance on the front end surface (7a) side and the operating distance on the opposite side correspond to the distance between the input surface (6a) and the front end surface (7a) shown in FIG. 14, and the distance between the base end surface (7c) and the imaging surface (3a), respectively. That is, the conjugate length of the equal magnification lens (7) corresponds to the distance between the input surface (6a) and the imaging surface (3a).

[0074] Returning to FIG. 14, in the imaging unit (30R), the path of radiation formed by the first through hole (74) is arranged to be inclined with respect to the normal direction of the input surface (6a) of the scintillator (6). The equal magnification lens (7), the shielding member (9), and the line scan sensor (3) are arranged in a direction inclined with respect to the normal direction of 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) captures the scintillation light output in a direction inclined with respect to the normal direction of the input surface (6a).

[0075] 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 (3a) of the line scan sensor (3) and the base surface (7c) of the equal magnification lens (7). That is, a gap may be formed between the shielding member (9) and the equal magnification lens (7), but a gap may not exist.

[0076] The positioning member (70) has a catch plate portion (79) that contacts the side of the housing body (13) and a main body portion (70a) 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). The main body portion (70a) is a slit member that is disposed between the incident window (14f) and the scintillator (6) and forms a slit that guides radiation passing through the incident window (14f) toward the input surface (6a). For example, a rectangular concave portion (70c) is formed in the main body portion (70a), and a positioning portion (61) of the retaining member (60) is fitted into this concave portion (70c). In this way, the retaining member (60) is fitted and fixed within the housing body (13) in the positioning member (70) which is fixed to the housing body (13).

[0077] The positioning member (70) has a first positioning part (71) that positions the scintillator (6) by contacting the input surface (6a) of the scintillator (6). The first positioning part (71) is formed as part of the mounting surface (77) described above and has a flat surface. The first positioning part (71) makes surface contact with, for example, the input surface (6a) of the scintillator (6).

[0078] A support member (80) fitted into a positioning member (70) supports a scintillator (6). The support member (80) has a support surface (82) facing a mounting surface (77) on which a first positioning member (71) is formed. The inclination angle of the support surface (82) is the same as the inclination angle of the mounting surface (77), and thus the support surface (82) is parallel to the mounting surface (77). 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 a suitable fixing means, such as a screw or a screw, so that the gap (89) (distance in the normal direction of the support surface (82)) between the mounting surface (77) and the support surface (82) can be adjusted.

[0079] The positioning member (70) has a second positioning part (72) that positions the imaging surface (3a) by contacting the front end surface (7a) of the equal magnification lens (7). The second positioning part (72) is formed as part of the side surface (76) facing the holding member (60) and has a flat surface. The second positioning part (72) is in surface contact with, for example, the front end surface (7a) of the equal magnification lens (7).

[0080] According to the imaging unit (30R), a single positioning member (70) positions the scintillator (6) by the first positioning part (71) and positions the equal magnification lens (7) by the second positioning part (72). Since the input surface (6a) of the scintillator (6) contacts the first positioning part (71), the positional precision of the input surface (6a) can be easily secured even if, for example, the thickness of the scintillator (6) changes. Therefore, the distance between the line scan sensor (3) and the input surface (6a) of the scintillator (6) can be maintained constant. This configuration eliminates the need to consider the positional precision of other members, thereby providing an advantage over conventional detectors. The distance between the input surface (6a) of the scintillator (6) and the front surface (7a) of the equal magnification lens (7) is also maintained constant, thereby ensuring the precision of the focal length (the operating distance of the equal magnification lens (7)).

[0081] In the imaging unit (30R), the main body (70a) of the positioning member (70) forms a slit to guide radiation to the scintillator (6). There is no need to separately provide the above-mentioned slit member (16) (first slit plate (17) and second slit plate (18)). That is, the slit is formed by the positioning member (70) which positions the input surface (6a) of the scintillator (6) and the leading surface (7a) of the equal magnification lens (7). A second through hole (75), which is the optical path of the scintillation light, is also formed. In addition, a holding member (60) that holds the line scan sensor (3) is fitted into the positioning member (70) and positioned. By this, the same arrangement as the imaging unit (30P) shown in FIG. 12 can be realized simply and easily.

[0082] In addition, in the imaging unit (30R) shown in FIG. 13, a substrate, etc. is placed within a space extending in the x direction (transport direction (D)) from the position of the line scan sensor (3), but even in such an imaging unit (30R), the size of the housing body (13) in the Z direction can be reduced. Furthermore, depending on the application location or installation location of the imaging unit, or the required surrounding layout, the layout of various components within the housing (15) can be changed.

[0083] Additionally, for the various embodiments described above (imaging units (30, 30A~30H, 30J~30N, 30P)) shown in FIGS. 1 to 12, a structure using at least one of the positioning member (70), the support member (80), and the holding member (60), that is, a structure similar to that of the imaging unit (30R), may be applied. When the positioning member (70) is used, the main body part (70a) of the positioning member (70) may form a slit to guide radiation to the scintillator (6). In that case, the slit member (16) may be omitted.

[0084] The explanation regarding various modified forms continues. For example, the range in which the slit member (16) is provided may be smaller than the above embodiment, or it may be a part of the range from the incident window (14f) to the input surface (6a) of the scintillator (6).

[0085] The material used for the slit member (16) is not limited to a copper plate, but may be, for example, aluminum, stainless steel, iron, lead, etc. In the slit member (16), a copper foil may be attached to the surface of aluminum, iron, stainless steel, or lead, or a copper plate may be attached, or the surface of the plate material may be covered with copper. In addition, the slit member (16) may be formed from multiple materials. The same can be said regarding the source-side slit member (26). In addition, the source-side slit member (26) may be omitted. Copper has the characteristic that it is difficult to generate scattered rays, so using copper is advantageous in terms of reducing scattered rays and the noise reduction of the sensor accordingly.

[0086] The shielding member (9) may be omitted. In that case, a magnification lens is directly mounted to the line scan sensor (3). In addition, in the above embodiment, the scintillation light emitted from the input surface (6a) of the scintillator (6) is captured, but in addition to this, the scintillation light emitted from the opposite side of the input surface (6a) of the scintillator (6) may also be captured. In this case, the scintillator (6) may be composed of multiple scintillators, and a member that blocks the scintillation light may be placed between the multiple scintillators.

[0087] [Industrial Applicability]

[0088] According to several aspects of the present disclosure, resolution can be improved and sensitivity can also be improved. Explanation of the symbols

[0089] 1: Radiation imaging acquisition system 3: Line scan sensor 3a: Imaging surface 6: Scintillator 6a: Input surface 7: Isomagnification lens 9: Shielding member 13: Housing body 14: Lead cover 14f: Entry Window 14g: Other entrance window 15: Housing 16: Slit member 16A: Other slit member 17: First slit plate 18: Second slit plate 20: Return device 21a: Return surface 30: Imaging unit 26: Seaman-side slit member 70: Positioning member (slit member) B: Normal (of the scintillator's input surface) C: Gap D: Return direction E: Optical axis (of the line scan sensor) S: Slit SA: Another slit

Claims

Claim 1 An imaging unit for acquiring a radiation image of an object being transported in a transport direction, comprising: a housing having an incident window that allows radiation transmitted through the object to pass through; a scintillator installed within the housing and having an input surface for inputting the radiation that has passed through the incident window; a line scan sensor installed within the housing and having an imaging surface for capturing scintillation light output from the input surface; a slit member disposed between the incident window and the scintillator and forming a slit that guides the radiation that has passed through the incident window toward the input surface; and an equal magnification lens disposed between the scintillator and the line scan sensor and forming an image of the scintillation light output from the input surface onto the imaging surface of the line scan sensor. Claim 2 In claim 1, the slit member is positioned such that the slit is located in the normal direction of the input surface of the scintillator, and the equal magnification lens and the line scan sensor are an imaging unit that forms and captures the scintillation light output in a direction inclined with respect to the normal direction of the input surface. Claim 3 In claim 1, the slit member is an imaging unit arranged such that the slit extends obliquely with respect to the conveying direction. Claim 4 In claim 1, the slit member is arranged such that the slit is positioned in a direction inclined with respect to the normal direction of the input surface of the scintillator, and the equal magnification lens and the line scan sensor are an imaging unit that forms and captures the scintillation light output in a direction inclined with respect to the normal direction of the input surface. Claim 5 An imaging unit according to any one of claims 1 to 4, wherein the housing has another incident window that passes radiation that has penetrated the object, and the imaging unit further comprises another slit member disposed between the other incident window and the scintillator and forming another slit that guides the radiation that has passed through the other incident window toward the input surface, and the slit member and the other slit member are disposed such that the slit and the other slit guide the radiation in two different directions, respectively, with respect to the input surface of the scintillator. Claim 6 An imaging unit according to any one of claims 1 to 4, further comprising a cover member that retains the slit member and is detachably mounted to the housing. Claim 7 An imaging unit according to any one of claims 1 to 4, wherein the slit member is configured such that the width of the conveying direction of the slit becomes narrower as it approaches the input surface of the scintillator. Claim 8 An imaging unit according to any one of claims 1 to 4, wherein the slit member, the equal magnification lens, and the line scan sensor are rotatable around an axis extending along the input surface within the housing. Claim 9 A radiation image acquisition system for acquiring a radiation image of an object, comprising: a radiation source that outputs the radiation toward the object; a conveying device that conveys the object in the conveying direction and passes the radiation through it; and an imaging unit described in any one of claims 1 to 4 installed such that the radiation source and the incident window are arranged on the same plane. Claim 10 A radiation image acquisition system for acquiring a radiation image of an object, comprising: a radiation source that outputs the radiation toward the object; a conveying device that conveys the object in the conveying direction and passes the radiation through it; and an imaging unit as described in claim 5 installed such that the radiation source and the incident window are arranged on the same plane. Claim 11 A radiation image acquisition system for acquiring a radiation image of an object, comprising: a radiation source that outputs the radiation toward the object; a conveying device that conveys the object in the conveying direction and passes the radiation through it; and an imaging unit as described in claim 6 installed such that the radiation source and the incident window are arranged on the same plane. Claim 12 A radiation image acquisition system for acquiring a radiation image of an object, comprising: a radiation source that outputs the radiation toward the object; a conveying device that conveys the object in the conveying direction and passes the radiation through it; and an imaging unit as described in claim 7 installed such that the radiation source and the incident window are arranged on the same plane. Claim 13 A radiation image acquisition system for acquiring a radiation image of an object, comprising: a radiation source that outputs the radiation toward the object; a conveying device that conveys the object in the conveying direction and passes the radiation through it; and an imaging unit as described in claim 8 installed such that the radiation source and the incident window are arranged on the same plane. Claim 14 A radiation image acquisition system according to claim 9, wherein the slit member of the conveying device and the imaging unit is arranged such that the slit extends obliquely with respect to the conveying direction. Claim 15 A radiation image acquisition system according to claim 10, wherein the slit member of the conveying device and the imaging unit is arranged such that the slit extends obliquely with respect to the conveying direction. Claim 16 A radiation image acquisition system according to claim 11, wherein the slit member of the conveying device and the imaging unit is arranged such that the slit extends obliquely with respect to the conveying direction. Claim 17 A radiation image acquisition system according to claim 12, wherein the slit member of the conveying device and the imaging unit is arranged such that the slit extends obliquely with respect to the conveying direction. Claim 18 A radiation image acquisition system according to claim 13, wherein the slit member of the conveying device and the imaging unit is arranged such that the slit extends obliquely with respect to the conveying direction. Claim 19 A method for acquiring a radiation image of an object, comprising: a radiation output process for outputting radiation toward the object being transported in a transport direction; a radiation introduction process for introducing the radiation that has passed through the object into a housing through an incident window and guiding the radiation toward an input surface of a scintillator by means of a slit formed in the housing; a scintillation light output process for inputting the radiation that has passed through the slit into an input surface of a scintillator, converting the input radiation into scintillation light, and outputting the scintillation light from the input surface; a scintillation light imaging process for forming an image of the scintillation light output from the input surface onto an imaging surface of a line scan sensor by means of an equal magnification lens; and a scintillation light imaging process for capturing the scintillation light on the imaging surface of the line scan sensor.

Images