Radiation inspection equipment and radiation inspection method

Abstract

We propose a radiation inspection device and method that can stably scan the entire object being inspected, even if a minute malfunction occurs in the pixel structure of the radiation sensor. [Solution] The radiation sensor is controlled so that the relative position between the radiation sensor and the object is shifted pixel by pixel according to a preset inspection trajectory.

Description

Technical Field

[0001] The present invention proposes a radiation inspection apparatus and a radiation inspection method using a radiation sensor composed of a CdTe-based compound semiconductor, in particular.

Background Art

[0002] Conventionally, as promising materials for radiation detection elements, CdTe-based compound semiconductors such as cadmium telluride (CdTe), cadmium selenium telluride (CdSeTe), cadmium zinc telluride (CdZnTe), and cadmium zinc selenium telluride (CdZnSeTe), which are II-VI group compound semiconductors, have been attracting attention.

[0003] Since these CdTe-based compound semiconductors are composed of elements with relatively large atomic numbers, they have high radiation detection efficiency and can make semiconductor detection elements small and high-performance. In addition, since CdTe-based compound semiconductors directly convert radiation into current, they are superior in detection efficiency and energy resolution compared to scintillator detectors with an indirect operating mechanism via luminescence typified by sodium iodide (NaI).

[0004] In addition, since CdTe-based compound semiconductors have a large bandgap and are less affected by heat, they can operate at room temperature. Compared to silicon-germanium (Si·Ge) detectors that require a cooling device to operate, the device can be miniaturized and has excellent field operability.

[0005] Such radiation detectors using CdTe-based compound semiconductors are suitable for detection applications using high-energy radiation because they have high sensitivity to radiation such as X-rays with high energy (for example, tube voltage exceeding 100 [KeV]) even when the object is difficult to penetrate X-rays and other radiations.

[0006] In fact, a radiation detector has been proposed in which a counter substrate having a photoelectric conversion semiconductor layer formed of a CdTe-based compound semiconductor and an active matrix substrate in which pixel electrodes are arranged in a two-dimensional matrix are electrically connected by conductive bumps (bump electrodes) (see Patent Document 1). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2015-165185 [Overview of the project] [Problems that the invention aims to solve]

[0008] Incidentally, while radiation detectors using such CdTe-based compound semiconductors require a uniform signal response across all detection regions, it is extremely difficult to manufacture all of the CdTe-based compound semiconductors that constitute the pixel structure of a radiation detector obtained by dicing a semiconductor wafer in a uniform manner.

[0009] Radiation detectors using CdTe-based compound semiconductors exhibit a so-called edge effect during actual use, where the sensitivity of the signal response gradually decreases or increases as one approaches the edge, resulting in a decrease in performance near the edge.

[0010] Edge effects occur due to distortions in the internal electric field near the edge or abnormally high surface leakage currents caused by defects resulting from improper dicing or surface stabilization. This leads to reduced detection performance near the edge, such as low charge collection efficiency or a low-energy tail structure in the photoelectric peak of the energy spectrum.

[0011] Furthermore, in radiation detectors using CdTe-based compound semiconductors, when a constant bias voltage is applied to the charged electrode during use, dark current flows and a polarization effect occurs. Dark current is a weak current that flows from the charged electrode to the current collector electrode due to the applied bias voltage, even when no radiation is incident. Polarization is a phenomenon in which the output of the detector gradually drifts when the bias voltage is continuously applied.

[0012] When such dark currents and polarization effects occur, the detection characteristics of each pixel in the radiation detector become unstable, resulting in variations in the output signal of each pixel for the same amount of incident X-ray flux (number of photons generated per unit time).

[0013] As a result, in radiation detectors, if the variation in the output signal becomes large and exceeds the acceptable range, that pixel will be treated as a defective pixel. In particular, if the effect of polarization is large, the output signal of each pixel may change during scanning to exceed the acceptable range, potentially increasing the number of defective pixels themselves.

[0014] Furthermore, when dark current or polarization effects occur, the dynamic range in which radiation intensity can be significantly detected becomes narrower. As a result, in response to incident radiation of high flux levels, a large number of so-called defective pixels may occur, such as pixels that produce no output, pixels with unstable output, or pixels that show abnormally high output values ​​compared to other pixels.

[0015] Thus, because it is difficult to manufacture all of the CdTe-based compound semiconductors that make up the pixel structure of a radiation detector uniformly, it is highly unlikely that a yield rate of 100% will be achieved during actual manufacturing. Even if a yield rate of 99% is achieved, it is still far from solving problems such as the loss of some lines in a band-like pattern in the pixel structure of the radiation detector, which would be unsuitable for industrial use.

[0016] This invention has been made in consideration of the above points, and aims to propose a radiation inspection device and radiation inspection method that can stably scan the entire object to be inspected even if a minute defect occurs in the pixel structure of the radiation sensor. [Means for solving the problem]

[0017] To solve these problems, the present invention provides a radiation inspection device comprising a radiation generating unit that irradiates radiation, and a radiation sensor in which radiation detection elements having a pixel structure made of a CdTe-based compound semiconductor are arranged in a grid with a predetermined aspect ratio, wherein the object to be inspected is located between the radiation generating unit and the radiation sensor, and the device provides a moving mechanism that moves the radiation sensor along either a first direction which is the longitudinal direction of the radiation sensor in its default position, or a second direction which is perpendicular to the first direction, or both, a control unit that controls the moving mechanism so that the relative position of the radiation sensor and the object is shifted in pixel units according to a preset inspection trajectory, and an image generation unit that generates an inspection image of the object by superimposing images sequentially captured by the radiation sensor at predetermined timings.

[0018] As a result, even if there are defects in each radiation detection element that makes up the radiation sensor, the radiation inspection device can reliably acquire inspection images of the object to be inspected by scanning and imaging the entire object at a pixel-by-pixel level.

[0019] Furthermore, in the present invention, when the image generation unit superimposes images sequentially captured by the radiation sensor at predetermined timings, it further includes a missing portion detection unit that detects missing portions present in the superimposed image. The control unit, based on the missing portions detected by the missing portion detection unit, redesigns the inspection trajectory by changing either the amount of displacement or the direction of displacement between the radiation sensor and the object, or both, based on the movement state of the radiation sensor a predetermined time earlier, and then provides feedback control to return the radiation sensor to the movement state.

[0020] As a result, in the radiation inspection apparatus, when scanning and imaging an object, based on inspection images at predetermined imaging timings, defective portions of the radiation sensor are detected, and feedback movement control is performed to avoid the defective portions, whereby the inspection image of the object can be efficiently scanned.

[0021] Furthermore, in the present invention, when defective portions in pixel units among the respective radiation detection elements constituting the radiation sensor are recognized in advance, the control unit sets an inspection trajectory based on the defective portions such that all the radiation detection elements excluding the defective portions cover the entire object in pixel units.

[0022] As a result, in the radiation inspection apparatus, when scanning and imaging an object, based on the information on the defective portions recognized in advance, feedback movement control is performed to avoid the defective portions, whereby the inspection image of the object can be efficiently scanned.

[0023] Also, in the present invention, the control unit sets an inspection trajectory such that the radiation sensor moves along a circular trajectory in pixel units.

[0024] As a result, in the radiation inspection apparatus, when scanning and imaging an object, due to the scanning operation along a circular trajectory that is continuous and does not cause an acceleration change, the burden on the moving mechanism unit that moves the radiation sensor can be reduced as much as possible.

[0025] Furthermore, in the present invention, the control unit controls the irradiation direction of the radiation generation unit while synchronizing with the movement of the radiation sensor by the moving mechanism unit so that radiation is always irradiated to each radiation detection element constituting the radiation sensor.

[0026] As a result, in the radiation inspection apparatus, even when the movement of the radiation sensor is relatively large, the radiation irradiated from the radiation generation unit can always be irradiated to the sensor region of the radiation sensor, and stable radiation inspection can be performed.

[0027] Furthermore, in the present invention, there are provided a radiation generation unit that irradiates radiation, and a radiation sensor in which radiation detection elements each having a pixel structure using a CdTe-based compound semiconductor are arranged in a lattice pattern with a predetermined aspect ratio. In a radiation inspection method for inspecting an object existing between the radiation generation unit and the radiation sensor, the method includes: a first step of moving the radiation sensor along either one or both of a first direction that is the longitudinal direction of the radiation sensor in the default position and a second direction perpendicular to the first direction; a second step of controlling the radiation sensor so as to be shifted in pixel units according to an inspection trajectory in which the relative position between the radiation sensor and the object is preset; and a third step of generating an inspection image of the object by superimposing images sequentially captured by the radiation sensor at a predetermined timing.

[0028] As a result, in the radiation inspection method, even when there are defective portions in each radiation detection element constituting the radiation sensor, an inspection image of the object can be stably acquired by scanning the entire object to be inspected over pixel units.

Effect of the Invention

[0029] According to the present invention, it is possible to realize a radiation inspection apparatus and a radiation inspection method capable of stably scanning the entire object to be inspected.

Brief Description of the Drawings

[0030] [[ID=!20]] [[ID=!21]] [Figure 1] It is a schematic diagram showing the configuration of a radiation inspection apparatus according to the present embodiment. [Figure 2] It is a conceptual diagram showing the configuration of each radiation detection element constituting the radiation sensor shown in FIG. 1. [Figure 3] It is a conceptual diagram showing the configuration of the radiation sensor shown in FIG. 1. [Figure 4] It is a conceptual diagram showing the configuration of the moving mechanism unit shown in FIG. 1. [Figure 5] Note: There seem to be some lines with "!" in the original text which might be a formatting error. I've translated the text as provided while keeping those lines as they are. If those are meant to be removed or corrected, please clarify.This is a conceptual diagram illustrating the operating state of the pantograph mechanism in the moving mechanism section. [Figure 6] Figure 5 is a conceptual diagram illustrating the pantograph mechanism. [Figure 7] This is a schematic diagram showing the configuration of a radiation inspection device according to another embodiment. [Modes for carrying out the invention]

[0031] An embodiment of the present invention will be described in detail below with reference to the drawings.

[0032] (1) Configuration of the radiation inspection device according to this embodiment Figure 1 is a schematic diagram of the radiation inspection device 1 according to this embodiment. This radiation inspection device 1 includes a radiation generator 2 that emits radiation and a linear radiation sensor 3 for detecting the radiation emitted from the radiation generator 2.

[0033] This radiation sensor 3 uses multiple radiation detection elements as an imaging device to perform scanning imaging on an object to be inspected. As will be described later, the radiation sensor 3 is composed of radiation detection elements, each having a pixel structure made of a CdTe-based compound semiconductor, arranged in a grid pattern with a predetermined aspect ratio.

[0034] In addition to X-rays and gamma rays, other types of radiation include alpha rays and beta rays. However, X-rays and gamma rays are used because they have a high absorption rate when converting radiation into electrical signals.

[0035] In the radiation inspection device 1 shown in Figure 1, a base 4 is provided between the radiation generator 2 and the radiation sensor 3 so as to be movable in a predetermined scanning direction. An object to be inspected (for example, a person) is placed on its mounting surface 4A, and the base 4 can be controlled to move at a desired speed during inspection (within a range that satisfies an imaging timing of 2 to 5 [ms]).

[0036] The base 4 can be either a mobile electric trolley or a fixed belt conveyor; the point is that any configuration can be used as long as it can slide the object placed on the mounting surface in a predetermined scanning direction. Also, although the configuration of the base 4 in Figure 1 differs from the actual configuration, for illustrative purposes, the central part of the base 4 is intentionally cut out to expose the radiation sensor 3 and the moving mechanism 10.

[0037] The radiation inspection device 1 includes a moving mechanism 10 for moving the radiation sensor 3 in a desired direction, a control unit 11 for driving and controlling the moving mechanism 10, and an image generation unit 12 for generating an inspection image of the object based on the image captured from the radiation sensor 3.

[0038] The moving mechanism 10 is configured to allow the radiation sensor 3, which is positioned at a predetermined default position, to move freely in two dimensions (parallel to the scanning direction) in the forward, backward, left, and right directions relative to the object placed on the mounting surface 4A of the base 4, with respect to the default position.

[0039] The control unit 11 consists of an MCM (Multi-Chip Module) equipped with a CPU (Central Processing Unit) and memory, etc., to comprehensively control the entire device. It controls the sliding movement of the base 4 and controls the movement mechanism of the radiation sensor 3 so that the relative position between the radiation sensor 3 and the object is shifted pixel by pixel according to a preset inspection trajectory (pre-set for each radiation sensor).

[0040] The image generation unit 12 generates an inspection image of the object by superimposing images (usually at 60 fps) that are sequentially captured by the radiation sensor 3 at predetermined timings. The inspection image generated by the image generation unit 12 is then sent to the image display unit 13 for display.

[0041] In this way, the radiation inspection device 1 can scan the entire object to be inspected and acquire an inspection image of the object.

[0042] (2) Configuration of radiation detection element Figures 2(A) and (B) show the configuration of each radiation detection element 20 that constitutes the radiation sensor 3. The radiation detection element 20 consists of a rectangular flat substrate 21, a plurality of rectangular first electrode layers 22 arranged separately at equal intervals in two dimensions on one surface 21A of the substrate 21, and a second electrode layer 23 integrally formed on the other surface 21B of the substrate 21.

[0043] Specifically, the radiation detection element 20 has a rectangular flat substrate 21 that constitutes a p-type (first conductivity type) semiconductor layer 24 mainly made of a CdTe-based compound semiconductor. Multiple first electrode layers 22 are arranged in two dimensions at equal intervals on one side 21A of the substrate 21, and n-type (second conductivity type) semiconductor layers 25 made of a CdTe-based compound semiconductor are formed within the p-type semiconductor layer 24, facing the multiple first electrode layers 22, by doping technology.

[0044] In other words, the radiation detection element 20 has multiple pn junction structures on one side 21A of the substrate 21, in which an n-type semiconductor layer 25 is stacked on a p-type semiconductor layer 24 that extends across the entire substrate 21, and the pixel structure is formed such that the regions of the multiple pn junction structures each coincide with the region of the first electrode layer 22.

[0045] In the radiation detection element 20, the multiple first electrode layers 22 are bonded to the n-type semiconductor layer 25 that forms a pn junction structure on one side 21A of the substrate 21 that constitutes the p-type semiconductor layer 24. Therefore, they not only have the function of doping the p-type semiconductor material, which is the main material of the substrate 21, to form an n-type semiconductor, but also the function of electrodes connected to the n-type semiconductor layer 25. These first electrode layers 22 are made of, for example, indium (In).

[0046] The second electrode layer 23 is formed by bonding it to the p-type semiconductor layer 24 from the other side 21B of the substrate 21, and functions as an electrode connected to the p-type semiconductor layer 24 on the other side 21B. This second electrode layer 23 is made of, for example, copper (Cu).

[0047] The radiation detection element 20 configured in this way operates as an imaging device capable of detecting radiation incident on each diode, which is composed of a p-type semiconductor layer 24 and an n-type semiconductor layer 25, by applying a reverse voltage between the first electrode layer 22 and the second electrode layer 23. In other words, the regions of the radiation detection element 20 corresponding to the n-type semiconductor layer 25 and the first electrode layer 22 form each pixel region.

[0048] In fact, the n-type semiconductor layer 25 formed on one surface 21A of the substrate 21 of the radiation detection element 20 has a size of, for example, 90 [μm] × 90 [μm], and the gap width between the n-type semiconductor layers 25 is set to 10 [μm].

[0049] Figure 3 shows the configuration of a radiation sensor 3, which is made up of multiple radiation detection elements 20. The radiation sensor 3 achieves a large sensor area (image detection surface) by arranging multiple radiation detection elements 20 in a grid pattern on a two-dimensional plane with a predetermined aspect ratio using tiling technology.

[0050] In fact, the radiation sensor 3 is configured such that, for example, multiple radiation detection elements 20 are arranged in a grid pattern with a predetermined aspect ratio (number of pixels: 2,048 x 32), and the overall sensor area is selected to have dimensions of 3.2 mm in height and 204.8 mm in width.

[0051] (3) Method for controlling the scanning of radiation sensors In practice, in the radiation inspection device 1, the control unit 11 controls the movement mechanism 10 to move the radiation sensor 3 with respect to the object to be inspected along either or both of the first direction (X direction), which is the longitudinal direction of the radiation sensor 3 in its default position, and the second direction (Y direction), which is perpendicular to the first direction.

[0052] In other words, in the radiation inspection device 1, the control unit 11 slides the base 4 on which the object is placed in the scanning direction (i.e., the second direction) and at the same time controls the movement mechanism 10 to move the radiation sensor 3 in a two-dimensional direction.

[0053] As shown in Figures 4(A) and (B), the moving mechanism 10 includes a sensor holding unit 30 for holding the radiation sensor 3, an X-direction drive unit 31 for moving the sensor holding unit 30 in the X direction, a Y-direction drive unit 32 for moving the sensor holding unit 30 in the Y direction, and a posture change drive unit 33 for rotating or swinging the sensor holding unit 30 to change the posture direction of the radiation sensor 3.

[0054] The X-direction drive unit 31 and the Y-direction drive unit 32 each have an X-direction actuator 40 and a Y-direction actuator 41, which serve as drive sources for driving the radiation sensor 3 in the X and Y directions, respectively, and the positional relationship between these actuators 40 and 41 is set so that they intersect with each other.

[0055] The X-direction actuator 40 and the Y-direction actuator 41 consist of stepping motors with encoders, and a slider 43 is engaged with a ball screw 42 formed on the output shaft thereof, so that the slider 43 can slide along a linear guide rail (not shown).

[0056] The attitude change drive unit 33 has an attitude change actuator 44 consisting of a stepping motor for supplying driving force to change the attitude of the radiation sensor 3, and the attitude change actuator 44 is fixed to the slider 43 of the X direction actuator 40.

[0057] The moving mechanism 10 is configured to move the radiation sensor 3 in two dimensions via a pantograph mechanism 50 that engages with the output shafts of the actuators 40, 41, and 44 of the X-direction drive unit 31, the Y-direction drive unit 32, and the attitude change drive unit 33, respectively.

[0058] One end of a roughly L-shaped lever 51 is fixed to the output shaft of the attitude change actuator 44, allowing it to rotate freely using the lever 51 as a pivot point. The other end of this lever 51 is fixed to the X-direction input link (first link) 60A of the pantograph mechanism 50, which will be described later. The slider of the Y-direction actuator is fixed to the Y-direction input link (second link) 60B of the pantograph mechanism.

[0059] Furthermore, the radiation sensor 3 is fixed to the sensor holding part 30 of the moving mechanism 10, and this sensor holding part 30 is engaged with the output link (seventh link) 60G of the pantograph mechanism 50.

[0060] In this way, the moving mechanism 10 engages the X-direction actuator 40, the Y-direction actuator 41, and the attitude change actuator 44 with the pantograph mechanism 50, thereby providing linear displacement in the X and Y directions, as well as linear displacement to change (rotate) the attitude of the radiation sensor (fixed to the 7th link 60G) 3.

[0061] The pantograph mechanism 50 is a parallel crank mechanism in which multiple even-numbered sets of links 60 are symmetrically connected by rotational pairs k~s, and it provides displacement to the seventh link 60G for output via the first link 60A for X-direction input, the second link 60B for Y-direction input, and the third to sixth links 60C~60F which form a parallel four-bar (pantograph).

[0062] Furthermore, in this pantograph mechanism, the 8th to 10th links 60H to 60J are added by connecting to the 1st, 5th, 6th, and 7th links 60A, 60E, 60F, and 60G, respectively, to provide a function of maintaining a constant orientation for the 7th link, thereby adding two parallelogram loops.

[0063] In other words, in the pantograph mechanism 50, one end of the first link 60A for X-direction input is connected to one end of the third link 60C and one end of the fifth link 60E via a rotational pair p, and one end of the ninth link 60I is connected to the other end of the first link 60A via a rotational pair q.

[0064] One end of the second link 60B, which is for Y-direction input, is connected to one end of the fourth link 60D via a rotational pair k. One end of the sixth link 60F is connected to the other end of the fourth link 60D via a rotational pair m, and the other end of the third link 60C is connected to the vicinity of the front of one end of the fourth link 60D via a rotational pair l.

[0065] One end of the output seventh link 60G is connected to the other end of the sixth link 60F via a rotational pair o, and the other end of the fifth link 60E and one end of the eighth link 60H are connected to the vicinity of the front of one end of the sixth link 60F via a rotational pair n.

[0066] The other end of the seventh output link 60G is connected to one end of the tenth link 60J via a rotational pair s. The other end of the eighth link 60H is connected to the other end of the ninth link 60I and the other end of the tenth link 60J via a rotational pair r.

[0067] The rotational pair n connecting the other end of the fifth link 60E and one end of the eighth link 60H to the sixth link 60F is set at a predetermined position on the sixth link 60F such that the eighth link 60H remains parallel to the first link 60A for X-direction input and the seventh link 60G for X-direction output, regardless of whether or not there is input of driving force from the X-direction actuator 40, the Y-direction actuator 41 and the attitude change actuator 44.

[0068] Similarly, the rotational pair l connecting the other end of the third link 60C to the fourth link 60D is set at a predetermined position on the fourth link 60D such that the third link 60C remains parallel to the sixth link 60F, regardless of whether or not there is input of driving force from the X-direction actuator 40, the Y-direction actuator 41, and the attitude change actuator 44.

[0069] Furthermore, regardless of whether or not driving force is input from the X-direction actuator 40, the Y-direction actuator 41, and the attitude change actuator 44, the first isosceles triangle formed by the three points k, p, and l of the rotation pair is set to maintain similarity with the second isosceles triangle formed by the three points k, o, and m of the rotation pair. As a result, when no driving force is input from the attitude change actuator 44, the positions of the rotation pair k, p, the pivot point w of the approximately L-shaped lever 51 (the output axis of the attitude change actuator 44), and the rotation pair o are aligned in a straight line.

[0070] Thus, in addition to the first link 60A for X-direction input, the second link 60B for Y-direction input, and the seventh link 60G for output, the pantograph mechanism 50 has a substantially linear link and a rotational pair for combining and amplifying the linear displacements in the X and Y directions, as well as the rotational (oscillating) displacements input from the X-direction actuator 40, the Y-direction actuator 41, and the attitude change actuator 44, respectively, and outputting them to the seventh link 60G for output.

[0071] (3-1) Movement in the X direction (first direction) When moving the radiation sensor (effectively the seventh link 60G) 3 slightly in the first direction (X direction), the control unit 11 controls the X-direction drive unit 31 in the moving mechanism unit 10 to transmit the rotation of the output shaft of the X-direction actuator 40 to the slider 43 via the ball screw 42, while moving the first link 60A for the X-direction input of the pantograph mechanism 50 in the horizontal direction (X direction).

[0072] At this time, the control unit 11 energizes the Y-direction actuator 41 of the Y-direction drive unit 32 and the attitude change actuator 44 of the attitude change drive unit 33 to maintain a rotation angle of 0 degrees.

[0073] Here, the displacement of the rotational pair k in the Y direction is fixed by the excitation of the Y-direction actuator 41 of the Y-direction drive unit 32. Therefore, the displacement of the rotational pair p is amplified to the similarity ratio of △kpl:△kom, which is represented by the positions of the rotational pair k~s, and output to the rotational pair o, causing the rotational pair o to be displaced (moved).

[0074] As a result, the moving mechanism 10 can move the seventh link 60G for output in the X direction (first direction), thereby moving the sensor holder 30 and the radiation sensor 3, which are fixed to the seventh link 60G, in the same direction.

[0075] (3-2) Movement in the Y direction (second direction) When moving the radiation sensor (effectively the seventh link 60G) 3 slightly in the second direction (Y direction), the control unit 11 controls the Y-direction drive unit 32 in the moving mechanism unit 10 to transmit the rotation of the output shaft of the Y-direction actuator 41 to the slider 43 via the ball screw 42, while moving the second link 60B for the Y-direction input of the pantograph mechanism 50 in the vertical direction (Y direction).

[0076] At this time, the control unit 11 energizes the X-direction actuator 40 of the X-direction drive unit 31 and the attitude change actuator 44 of the attitude change drive unit 33 to maintain a rotation angle of 0 degrees.

[0077] Here, since the rotational pair p is fixed by the excitation of the X-direction actuator 40 of the X-direction drive unit 31, the displacement of the rotational pair k is amplified to the similarity ratio of △kpl:△opn, which is represented by the positions of the rotational pair k~s, as in the case of the X direction, and output to the rotational pair o, causing the rotational pair o to be displaced (moved).

[0078] As a result, the moving mechanism 10 can move the seventh link 60G for output in the Y direction (second direction), thereby moving the sensor holder 30 and the radiation sensor 3, which are fixed to the seventh link 60G, in the same direction.

[0079] (3-3) Movement in the XY direction (combined direction of the first and second directions) When moving the radiation sensor (essentially the seventh link 60G) 3 in a small amount of motion in a combined direction of the first direction (X direction) and the second direction (Y direction), the control unit 11 controls the X-direction drive unit 31 and the Y-direction drive unit 32 in the moving mechanism unit 10 individually or simultaneously to output a displacement that is a combination of the X-direction and Y-direction displacements to the seventh link 60G for the output of the pantograph mechanism 50 based on the X-direction and Y-direction inputs described above.

[0080] Furthermore, when driving in both the X and Y directions simultaneously, it is necessary to energize the attitude change actuator 44 to maintain a rotation angle of 0 degrees in order to keep the attitude of the pantograph mechanism 50 in its default state.

[0081] As a result, the moving mechanism 10 can move the seventh link 60G for output in a combined direction of the X direction (first direction) and the Y direction (second direction), thereby moving the sensor holder 30 and the radiation sensor 3 fixed to the seventh link 60G in the same direction.

[0082] (3-4) Movement in the direction of change of posture (rotation or swinging direction) When the radiation sensor (effectively the seventh link 60G) 3 is rotated or oscillated slightly, the control unit 11 controls the attitude change drive unit 33 in the moving mechanism unit 10 to rotate or oscillate the output shaft of the attitude control actuator 44, thereby applying rotational or oscillating displacement to the first link 60A for the X-direction input of the pantograph mechanism 50, with the lever 51 fixed to the output shaft having its pivot point w as the center of rotation.

[0083] In the moving mechanism 10, when the lever 51 applies an oscillation displacement to the first link 60A for X-direction input of the pantograph mechanism 50, the same angle of oscillation displacement is also output to the seventh link 60G for output.

[0084] Figure 5(B) shows an example where the lever 51 is swung α degrees (for example, 15 degrees) counterclockwise (leftward) with respect to the pivot point w, starting from the state in Figure 5(A). Figure 5(C) shows an example where the lever 51 is swung β degrees (for example, 15 degrees) clockwise (rightward) with respect to the pivot point w, starting from the state in Figure 5(A).

[0085] This will be explained using a conceptual diagram of the pantograph mechanism 50. Figures 6(A) to 6(C) correspond to the states in Figures 5(A) to 5(C), respectively. Figure 6(A) shows the positions of the rotational pairs k to s, as well as the position of the pivot point of the lever 50 (the output shaft of the attitude change actuator 44) as point w.

[0086] As shown in Figure 6(B), when point p is oscillated by an angle α around point w, triangle kpl deforms with point k as a fixed point. Then, triangle kom also deforms while maintaining its similar shape, and point o undergoes an amplified displacement in response to the displacement of point p. The displacement of point o is an oscillation of angle α.

[0087] In this case, points q, r, and s function passively as rotational counterparts that form two parallelogram loops (□pqrn, □osrn) added to maintain a constant orientation of the seventh link 60G. As shown in Figure 6(C), if point p is oscillated β degrees clockwise around point w, point o similarly oscillates β degrees clockwise around the virtual pivot point of the seventh link 60G.

[0088] As a result, the moving mechanism 10 can rotate or swing the output seventh link 60G in a desired direction, thereby rotating or swinging the sensor holder 30 and the radiation sensor 3, which are fixed to the seventh link 60G, in the same direction.

[0089] (4) Operation and effects of the radiation inspection apparatus according to this embodiment In the above configuration, if the radiation inspection device 1 has previously identified defective areas at the pixel level among the radiation detection elements 20 constituting the radiation sensor 3 before scanning and imaging the subject to be inspected with radiation, the control unit 11 sets the inspection trajectory based on the defective areas so that all radiation detection elements 20 excluding the defective areas cover the entire object at the pixel level.

[0090] Next, in the radiation inspection device 1, when scanning and imaging a subject with radiation, the control unit 11 controls the movement mechanism 10 so that the radiation sensor 3 is shifted in pixel units according to the set inspection trajectory, in accordance with the relative position between the radiation sensor 3 and the subject.

[0091] At that time, the control unit 11 controls the irradiation direction of the radiation generator (radiation generating unit) 2 in synchronization with the movement of the radiation sensor 3 by the moving mechanism 10, so that radiation is always irradiated to each radiation detection element 20 that constitutes the radiation sensor 3.

[0092] The control unit 11 then controls the image generation unit 12 to superimpose images sequentially captured by the radiation sensor 3 at predetermined timings (2 to 5 ms) to generate an inspection image of the object.

[0093] As a result, even if there are defects in each of the radiation detection elements 20 that make up the radiation sensor 3, the radiation inspection device 1 can stably acquire an inspection image of the object to be inspected by scanning and imaging the entire object at a pixel-by-pixel level.

[0094] In particular, the radiation inspection device 1 can efficiently scan an inspection image of an object by using feedback movement control to avoid defective areas based on information about defective areas that have been recognized in advance when scanning an object.

[0095] (5) Other embodiments In this embodiment, the description concerns a case where the control unit 11 pre-sets the inspection trajectory of the radiation sensor 3 for each radiation sensor 3 when scanning using radiation in the radiation inspection device 1. However, the present invention is not limited to this, and the inspection trajectory may be set while detecting missing parts at the pixel level based on the captured image of the object during scanning.

[0096] In the radiation inspection apparatus 70 shown in Figure 7, where the corresponding parts in Figure 1 are denoted by the same reference numerals, a missing area detection unit 71 is provided, which is connected to the control unit 11 and the image generation unit 12. This missing area detection unit 71 detects the image obtained from the image generation unit 12 in accordance with the control of the control unit 11.

[0097] In other words, the missing area detection unit 71 detects missing areas in the superimposed image when the image generation unit 12 superimposes images sequentially captured by the radiation sensor 3 at predetermined timings. Specifically, the missing area detection unit 71 determines that the electrode corresponding to the pixel is a missing area if the data (grayscale value) obtained from the radiation detection element 20 on a pixel-by-pixel basis is below a predetermined threshold.

[0098] Based on the missing portion detected by the missing portion detection unit 71, the control unit 11 redesigns the inspection trajectory by changing either the amount of displacement or the direction of displacement between the radiation sensor 3 and the object, or both, based on the movement state of the radiation sensor 3 a predetermined time prior, and then provides feedback control to the movement mechanism unit 10 to return the radiation sensor 3 to the movement state.

[0099] As a result, when scanning an object, the radiation inspection device 70 can efficiently scan the inspection image of the object by detecting defective areas of the radiation sensor 3 based on the inspection image at predetermined imaging timings and performing feedback movement control to avoid those defective areas. This is particularly effective when defective areas at the pixel level among the radiation detection elements 20 constituting the radiation sensor 3 have not been recognized in advance.

[0100] In this embodiment, we have described a case in which the moving mechanism 10 for moving the radiation sensor 3 in two dimensions (X direction, Y direction, XY combined direction, and rotation or swing direction for changing posture) in the radiation inspection device 1, 70 is configured with the pantograph mechanism 50 described above. However, the present invention is not limited to this, and essentially, as long as the radiation sensor can be moved minutely at a relatively high speed in two dimensions, a pantograph mechanism with an arc notch, other parallel link mechanisms, or various other mechanisms capable of similar minute movements in two dimensions may be applied.

[0101] In practical terms, when moving the radiation sensor 3 a small distance, it is desirable to use the pantograph mechanism 50 described above to amplify the displacement and perform high-speed control. When moving the radiation sensor 3 a large distance, it is desirable to use, for example, a rotary actuator to control its movement while maintaining synchronization in a circular orbit.

[0102] If the radiation sensor 3 is set to move in a circular orbit on a pixel-by-pixel basis, then when scanning an object, the scanning motion will be a continuous circular orbit that does not cause changes in acceleration, thus minimizing the burden on the moving mechanism 10 that moves the radiation sensor 3.

[0103] Furthermore, although this embodiment describes the case where the radiation generator 2 in the radiation inspection device 1, 70 is fixed, the present invention is not limited to this, and the control unit 11 may control the irradiation direction of the radiation generator 2 in synchronization with the moving mechanism 10 so that radiation is always irradiated to each radiation detection element constituting the radiation sensor 3.

[0104] As a result, in the radiation inspection device 1, 70, even when the movement of the radiation sensor 3 is relatively large, the radiation emitted from the radiation generator 2 can always be directed onto the sensor area of ​​the radiation sensor 3, making it possible to perform stable radiation inspections.

[0105] Furthermore, although this embodiment describes a case where a base 4 provided between the radiation generator 2 and the radiation sensor 3 is moved in a predetermined scanning direction, the present invention is not limited to this. The base 4 may be fixed and the object placed on it may be moved, and the radiation generator 2 and the radiation sensor 3 may be moved together in this scanning direction, while the radiation sensor 3 is moved minutely in a two-dimensional direction, and the direction of radiation irradiation from the radiation generator 2 may also be made to follow. [Explanation of Symbols]

[0106] 1, 70...Radiation inspection device, 2...Radiation generator (radiation generating unit), 3...Radiation sensor, 4...Base, 10...Moving mechanism unit, 11...Control unit, 12...Image generation unit, 13...Image display unit, 20...Radiation detection element, 21...Substrate, 22...First electrode layer, 23...Second electrode layer, 24...p-type semiconductor layer, 25...n-type semiconductor layer, 30...Sensor holding unit, 31...X-direction drive unit, 32...Y-direction drive unit, 33...Attitude change drive unit, 40...X-direction actuator, 41...Y-direction actuator, 42...Ball screw, 43...Slider, 44...Attitude change actuator, 50...Pantograph mechanism, 51...Lever, 60A~60J...1st~10th links, 71...Missing part detection unit, k~s...Rotational pair, w...Pivot point.

Claims

1. A radiation inspection device comprising a radiation generating unit that irradiates radiation and a radiation sensor in which radiation detection elements having a pixel structure made of a CdTe-based compound semiconductor are arranged in a grid with a predetermined aspect ratio, wherein the object to be inspected is located between the radiation generating unit and the radiation sensor, A moving mechanism that moves the radiation sensor along either a first direction which is the longitudinal direction of the radiation sensor in its default position, or a second direction which is perpendicular to the first direction, or both of the above, The control unit controls the movement mechanism of the radiation sensor so that the relative position between the radiation sensor and the object is shifted in pixel units according to a preset inspection trajectory. An image generation unit generates an inspection image of the object by superimposing images sequentially captured at predetermined timings by the radiation sensor. A radiation inspection device characterized by being equipped with the following features.

2. When the image generation unit superimposes images sequentially captured by the radiation sensor at predetermined timings, it further includes a missing portion detection unit that detects missing portions present in the superimposed image. The control unit, based on the missing portion detected by the missing portion detection unit, redesigns the inspection trajectory by changing either the amount of displacement or the direction of displacement between the radiation sensor and the object, or both, based on the movement state of the radiation sensor a predetermined time prior, and then provides feedback control to the movement mechanism to return the radiation sensor to the movement state. The radiation inspection apparatus according to feature 1.

3. If a defective area at the pixel level is known in advance among the radiation detection elements constituting the radiation sensor, the control unit sets the inspection trajectory based on the defective area so that all radiation detection elements excluding the defective area cover the entire object at the pixel level. The radiation inspection apparatus according to feature 1.

4. The control unit sets the inspection trajectory so that the radiation sensor moves in a circular orbit for each pixel. A radiation inspection apparatus according to any one of claims 1 to 3.

5. The control unit controls the irradiation direction of the radiation generation unit in synchronization with the movement of the radiation sensor by the moving mechanism, so that the radiation is always irradiated onto each of the radiation detection elements constituting the radiation sensor. A radiation inspection apparatus according to any one of claims 1 to 3.

6. A radiation inspection method comprising a radiation generating unit that irradiates radiation and a radiation sensor in which radiation detection elements having a pixel structure made of a CdTe-based compound semiconductor are arranged in a grid with a predetermined aspect ratio, wherein the object to be inspected is located between the radiation generating unit and the radiation sensor, The first step is to move the radiation sensor along either or both of the first direction which is the longitudinal direction of the radiation sensor in its default position and the second direction which is perpendicular to the first direction, The second step involves controlling the radiation sensor so that the relative position between the radiation sensor and the object is shifted in pixel units according to a preset inspection trajectory. A third step involves superimposing images sequentially captured at predetermined timings by the radiation sensor to generate an inspection image of the object. A radiation inspection method characterized by comprising the following:

7. The third step further includes a fourth step of detecting missing portions in the superimposed image when superimposing images sequentially captured by the radiation sensor at predetermined timings, In the second step, based on the missing portion detected in the fourth step, the inspection trajectory is redesigned by changing either the amount of displacement or the direction of displacement of the relative position between the radiation sensor and the object, or both, based on the movement state of the radiation sensor a predetermined time prior, and then feedback control is performed to return the radiation sensor to the movement state. The radiation inspection method according to feature 6.

8. If a defective area at the pixel level is known in advance among the radiation detection elements constituting the radiation sensor, in the second step, the inspection trajectory is set based on the defective area so that all the radiation detection elements excluding the defective area cover the entire object at the pixel level. The radiation inspection method according to feature 6.

9. In the second step, the inspection trajectory is set so that the radiation sensor moves in a circular orbit for each pixel. The radiation inspection method according to any one of claims 6 to 8, characterized by the following:

10. A fifth step involves controlling the irradiation direction of the radiation generating unit in synchronization with the movement of the radiation sensor in the first step, so that each of the radiation detection elements constituting the radiation sensor is always irradiated with the radiation. A radiation inspection method according to any one of claims 6 to 8, characterized by comprising:

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