JP6920520B2 - Image acquisition system and image acquisition method - Google Patents

Description

The present disclosure relates to an image acquisition system and an image acquisition method.

Conventionally, there is known a device that acquires an X-ray image of an object by irradiating the transported object with X-rays, detecting the X-rays transmitted through the object, and performing TDI (time delay integration) control. (See Patent Documents 1 and 2). In the apparatus described in Patent Document 1, an object is conveyed by a belt conveyor. The X-ray sensor has a configuration in which a plurality of element rows including a plurality of detection elements arranged in a direction orthogonal to the transport direction are arranged in a plurality of stages in the transport direction. In the apparatus described in Patent Document 2, the container containing the sample (object) is moved in the X direction while the container is rotated. The TDI camera performs imaging synchronized with the transport speed of the sample. The angular velocity of the container is set to be equal to the ratio of the moving velocity in the TDI integration direction to the distance from the focal point of the X-ray source to the center of rotation.

Japanese Unexamined Patent Publication No. 2013-174545 JP-A-2017-53778

In the present disclosure, a device for irradiating an object rotated around a rotation axis with radiation and acquiring a radiation image using a camera capable of TDI control will be examined. In this device, the axis of rotation intersects the light receiving surface (or its extension surface) of the camera sensor. The velocity of the inner circumference of the object is different from the velocity of the outer circumference of the object. When TDI control is performed based on the velocity of the inner circumference, the acquired radiographic image can be blurred at the outer circumference. That is, if TDI control is performed based on the velocity of any portion of the object in the radial direction, the acquired radiographic image can be blurred in the other portion. As described above, the difference in velocity (peripheral velocity) due to the difference in radius makes it difficult to acquire a clear radiographic image by TDI control.

The present disclosure describes an image acquisition system and an image acquisition method capable of acquiring a clear radiographic image for any portion in the radial direction of an object.

In the image acquisition system according to one aspect of the present disclosure, a radiation source that outputs radiation toward an object, a rotating stage configured to rotate the object around a rotation axis, and radiation transmitted through the object are used. A radiation camera that has an input input surface and an image sensor that can control TDI (time delay integration), captures the input radiation and outputs image data, and an imaging surface of an object based on the image data. It is equipped with an image processing device that generates a radiation image, and the angle between the rotation axis of the rotating stage and the input surface of the radiation camera is such that the magnification at the inner circumference of the object is greater than the magnification at the outer periphery of the object. Set to be large, the radiation camera is configured to perform TDI control in the image sensor in synchronization with the rotational speed of the object by the rotating stage.

The image acquisition method according to another aspect of the present disclosure uses a rotating stage to rotate an object at a predetermined speed around the axis of rotation (rotation step) and from a radiation source toward the rotating object. An image of the input radiation is taken using a radiation camera having a step of outputting radiation (radiation output step), an input surface at which radiation transmitted through an object is input, and an image sensor capable of controlling TDI (time delay integration). And output the image data (radiation imaging step) and generate a radiation image on the imaging surface of the object based on the image data (image generation step), including the rotation axis of the rotating stage and the radiation camera. The angle formed by the input surface of the object is set so that the enlargement ratio at the inner peripheral portion of the object is larger than the enlargement ratio at the outer peripheral portion of the object. TDI control in the image sensor is performed in synchronization with the rotation speed.

According to the above-mentioned image acquisition system and image acquisition method, TDI control in the image sensor is performed in synchronization with the rotation speed of the object by the rotation stage. The speed of the inner peripheral portion (the portion closest to the rotation axis) of the imaging surface of the object is slower than the speed of the outer peripheral portion (the portion farthest from the rotation axis). An acute angle is formed between the rotation axis of the rotation stage and the input surface of the radiation camera. Therefore, the distance between the radiation source and the input surface portion where the radiation transmitted through the inner peripheral portion is input is longer than the distance between the radiation source and the input surface portion where the radiation transmitted through the outer peripheral portion is input. This means that the enlargement ratio at the inner peripheral portion is larger than the enlargement ratio at the outer peripheral portion. The transport speed adapted to a predetermined line speed in TDI control is inversely proportional to the enlargement ratio. According to the magnitude relationship of the enlargement ratio described above, the influence of the speed difference between the inner peripheral portion and the outer peripheral portion is alleviated. Further, the angle formed by the rotation axis of the rotation stage and the input surface of the radiation camera is set according to the FOD, which is the distance between the radiation source and the imaging surface in the object, so that the inner peripheral portion and the outer peripheral portion can be formed. In, the ratio of the magnification ratio becomes the reciprocal of the speed ratio, and the focus can be adjusted. As a result, it is possible to focus on any portion between the inner peripheral portion and the outer peripheral portion. Therefore, a clear radiographic image can be acquired for any portion in the radial direction of the object.

In some embodiments, the image acquisition system further comprises a stage movement control unit configured to move the rotating stage in the direction of the axis of rotation and move the object closer and further away from the radiation source. According to the stage movement control unit, the distance between the radiation source and the object can be adjusted. In other words, the image pickup surface based on the above-mentioned FOD can be set at an arbitrary position in the rotation axis direction (that is, the thickness direction) of the object. In this case, if the radiation source is immobile, the FOD can be considered constant. A radiographic image of an arbitrary position in the thickness direction of the object can be acquired.

In some embodiments, the image acquisition system further comprises an angle adjuster configured to hold the rotating stage or radiation camera and adjust the angle between the rotating axis of the rotating stage and the input surface of the radiation camera. In this case, the angle adjusting unit can adjust the angle formed by the rotation axis of the rotation stage and the input surface of the radiation camera to an appropriate angle according to the FOD.

In some aspects of the image acquisition system, the angle adjuster inputs the rotation axis of the rotating stage and the radiation camera so that the magnification at the inner circumference of the object is greater than the magnification at the outer circumference of the object. It is configured to adjust the angle between the surface and the surface.

In some aspects of the image acquisition system, the angle adjuster holds the radiation camera such that the input surface of the radiation camera is tilted with respect to the axis of rotation. In this case, the posture of the radiation camera can be adjusted, and the angle formed by the rotation axis of the rotating stage and the input surface of the radiation camera can be adjusted to an appropriate angle according to the FOD.

In some aspects of the image acquisition system, the angle adjuster holds the rotating stage so that the axis of rotation is tilted with respect to the input surface of the radiation camera. In this case, the posture of the rotating stage can be adjusted, and the angle formed by the rotating axis of the rotating stage and the input surface of the radiation camera can be adjusted to an appropriate angle according to the FOD.

In some aspects of the image acquisition system, the radiation camera comprises a scintillator having an input surface, and the image sensor captures the scintillation light emitted by the scintillator in response to the input of radiation. In this case, a clear radiographic image of the object can be obtained.

In some aspects of the image acquisition system, the image sensor is a direct transform radiation image sensor with an input surface. In this case, a clear radiographic image of the object can be obtained.

In some embodiments, the image acquisition method further comprises controlling the rotation stage to move in the direction of the axis of rotation and moving the object closer to or further from the radiation source (movement step). According to this step, the distance between the radiation source and the object can be adjusted. In other words, the image pickup surface based on the above-mentioned FOD can be set at an arbitrary position in the rotation axis direction (that is, the thickness direction) of the object. In this case, if the radiation source is immobile, the FOD can be considered constant. A radiographic image of an arbitrary position in the thickness direction of the object can be acquired.

In some embodiments, the image acquisition method further comprises a step (adjustment step) of adjusting the angle between the rotation axis of the rotation stage and the input surface of the radiation camera by rotating the rotation stage or the radiation camera. In this case, the angle formed by the rotation axis of the rotation stage and the input surface of the radiation camera can be adjusted to an appropriate angle according to the FOD by the step of adjusting the angle.

In some aspects of the image acquisition method, in the adjustment step, the rotation axis of the rotating stage and the input surface of the radiation camera are such that the magnification at the inner circumference of the object is greater than the magnification at the outer circumference of the object. Adjust the angle between the camera and the camera.

In some aspects of the image acquisition method, in the adjustment step, the radiation camera is rotated so that the input surface of the radiation camera is tilted with respect to the rotation axis. In this case, the posture of the radiation camera can be adjusted, and the angle formed by the rotation axis of the rotating stage and the input surface of the radiation camera can be adjusted to an appropriate angle according to the FOD.

In some aspects of the image acquisition method, in the adjustment step, the rotation stage is rotated so that the rotation axis is tilted with respect to the input surface of the radiation camera. In this case, the posture of the rotating stage can be adjusted, and the angle formed by the rotating axis of the rotating stage and the input surface of the radiation camera can be adjusted to an appropriate angle according to the FOD.

In some aspects of the image acquisition method, the radiation camera comprises a scintillator having an input surface, and in the radiation imaging step, the scintillation light emitted by the scintillator in response to the input of radiation is imaged. In this case, a clear radiographic image of the object can be obtained.

In some aspects of the image acquisition method, the image sensor is a direct conversion radiation image sensor having an input surface. In this case, a clear radiographic image of the object can be obtained.

According to some aspects of the present disclosure, a clear radiographic image can be obtained for any portion of the object in the radial direction.

It is a figure which shows the schematic structure of the image acquisition apparatus which concerns on 1st Embodiment of this disclosure. It is a figure for demonstrating the positional relationship between a radiation source, an object, and a radiation camera in the image acquisition apparatus of FIG. It is a figure for demonstrating the tilt of FOR, FDD, and a radiation camera in the image acquisition apparatus of FIG. It is a figure for demonstrating the velocity of the inner peripheral part and the velocity of the outer peripheral part of a rotating object. 5 (a) to 5 (d) are views showing the movement of the imaging surface by the stage movement control unit. It is a flow chart which shows the procedure of the image acquisition method by the image acquisition apparatus of FIG. It is a figure which shows the schematic structure of the modification of 1st Embodiment. It is a figure which shows the schematic structure of the image acquisition apparatus which concerns on 2nd Embodiment of this disclosure. It is a flow chart which shows the procedure of the image acquisition method by the image acquisition apparatus of FIG. It is a figure which shows the schematic structure of the image acquisition apparatus which concerns on 3rd Embodiment of this disclosure. It is a figure for demonstrating the positional relationship between a radiation source, an object, and a radiation camera in the image acquisition apparatus of FIG. It is a figure for demonstrating each condition of a simulation. It is a figure which shows the simulation result which concerns on the comparative example 1. FIG. It is a figure which shows the simulation result which concerns on the comparative example 2. It is a figure which shows the simulation result which concerns on Example.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate description will be omitted. In addition, each drawing is created for the purpose of explanation, and is drawn so as to particularly emphasize the target part of the explanation. Therefore, the dimensional ratio of each member in the drawing does not always match the actual one.

As shown in FIGS. 1 and 2, the image acquisition system 1 is a device for acquiring a radiographic image of the object 20. The object 20 includes, for example, a cylindrical wheel portion 22 centered on the rotation axis L and a roll portion 21 wound around the wheel portion 22. An annular boundary surface 23 is formed between the wheel portion 22 and the roll portion 21. The image acquisition system 1 may be configured so that the wheel portion 22 is not included in the radiographic image. That is, the image acquisition system 1 may be configured to acquire a radiographic image of only the roll portion 21. The roll portion 21 is, for example, a chip capacitor wound in a roll shape. The roll portion 21 may be a separator or the like wound in a roll shape. The object 20 may be a disc or the like without the wheel portion 22. In that case, the object 20 has a rotation axis L. When the image acquisition system 1 is used for inspecting the object 20, the roll unit 21 is a portion to be inspected, that is, an inspection unit.

The image acquisition system 1 acquires a radiation image on an imaging surface of the roll unit 21 at a predetermined position in the thickness direction, that is, in the rotation axis L direction. In other words, the image acquisition system 1 acquires a radiation image focused on the imaging surface of the roll unit 21. By acquiring a radiographic image, the image acquisition system 1 can detect, for example, a foreign substance or a defect that may exist in the roll portion 21 of the object 20. The image acquisition system 1 detects, for example, an object made of polyamide fiber or polyolefin fiber, split type composite fiber, single fiber, or core-sheath type composite fiber, and a foreign substance made of metal that may exist in the object. It is possible.

The image acquisition system 1 includes a radiation generator 3 that generates radiation such as white X-rays. The radiation generator 3 has a radiation source 2 that outputs radiation toward the object 20. The radiation source 2 emits (outputs) cone beam X-rays from the X-ray emitting portion. The radiation source 2 may be, for example, a microfocus X-ray source or a millifocus X-ray source. The X-rays emitted from the radiation source 2 form a radiation bundle 2a. The region where the radiation bundle 2a exists is the emission region of the radiation source 2. The shape or structure of the X-ray emitting portion may be devised so that the wheel portion 22 of the object 20 is not included in the radiographic image. The radiation source 2 is configured so that the tube voltage and the tube current can be adjusted.

The image acquisition system 1 inputs the rotation stage 6 configured to hold the object 20 and rotate the object 20 around the rotation axis L, and the radiation output from the radiation source 2 and passed through the object 20. It is provided with a radiation camera 4 for taking an image. The rotary stage 6 may include, for example, a motor driven by power supply, a gear portion connected to the motor, and a stage body rotated via the gear portion. The rotating stage 6 rotates the stage body at a constant speed, for example. The rotation speed of the rotation stage 6 can be adjusted as appropriate.

The radiation camera 4 includes, for example, an input surface 11a into which radiation that has passed through the object 20 is input, a scintillator 11 that generates scintillation light in response to the input of radiation, and a FOP that transmits scintillation light generated by the scintillator 11. It includes a (Fiber Optic Plate) 12 and an image sensor 13 including a light receiving surface 13a into which scintillation light transmitted through the FOP 12 is input, and images the scintillation light and outputs image data. The radiation camera 4 is, for example, an indirect conversion type camera in which a FOP 12 with a scintillator 11 is coupled to an image sensor 13. The radiation camera 4 indirectly captures the radiation input to the input surface 11a of the scintillator 11 and outputs the image data.

The scintillator 11 is a plate-shaped (for example, flat plate-shaped) wavelength conversion member. The scintillator 11 converts the radiation transmitted through the object 20 and input to the input surface 11a into scintillation light. Radiation with relatively low energy is converted on the input surface 11a side and emitted (output) from the input surface 11a. Radiation of relatively high energy is converted on the back surface of the scintillator 11 and emitted (output) from the back surface.

The FOP 12 is a plate-shaped (for example, flat plate-shaped) optical device. The FOP12 is made of, for example, glass fiber, and transmits scintillation light or the like with high efficiency. FOP12 shields radiation such as white X-rays.

The image sensor 13 is an area image sensor capable of TDI (time delay integration) drive. The image sensor 13 is, for example, a CCD area image sensor. The image sensor 13 has a configuration in which a plurality of element rows in which a plurality of CCDs are arranged in a row in the pixel direction are arranged in a plurality of stages in the integration direction corresponding to the moving direction of the object 20. The integration direction is a direction orthogonal to the pixel direction and corresponds to the direction perpendicular to the paper surface in FIGS. 1 and 3. The image sensor 13 is controlled by the timing control unit 16 described later so as to perform charge transfer according to the speed (peripheral speed) of the object 20. That is, the image sensor 13 transfers the electric charge on the light receiving surface 13a in synchronization with the rotation speed of the object 20 by the rotation stage 6. This makes it possible to obtain a radiographic image having a good S / N ratio.

The image sensor 13 may be a CMOS area image sensor capable of driving TDI (time delay integration). Further, the image sensor 13 may be a CCD-CMOS image sensor capable of TDI (time delay integration) drive. For example, the CCD-CMOS image sensor is an image sensor described in Japanese Patent Application Laid-Open No. 2013-098420 or Japanese Patent Application Laid-Open No. 2013-098853. It should be noted that being "TDI driveable" is synonymous with being "TDI controllable".

The image acquisition system 1 displays an image processing device 10 that generates a radiation image on the imaging surface P of the object 20 and a radiation image generated by the image processing device 10 based on the image data output from the radiation camera 4. A display device 15 for controlling the image and a timing control unit 16 for controlling the imaging timing of the radiation camera 4 are provided.

The image processing device 10 is composed of, for example, a computer having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output interface, and the like. The image processing device 10 may have an image processing processor that creates a radiation image of the object 20 based on the radiation image data output from the radiation camera 4. The image processing processor inputs, for example, radiation image data, and executes a predetermined process such as image processing on the input radiation image data. The image processor outputs the created radiation image to the display device.

As the display device 15, a known display can be used. An input device (not shown) may be connected to the image processing device 10. The input device can be, for example, a keyboard, a mouse, or the like. The user can input various parameters such as the thickness of the object 20, the position of the boundary surface 23 on the object 20, and the position of the imaging surface P by using the input device.

The timing control unit 16 is composed of, for example, a computer having a CPU, a ROM, a RAM, an input / output interface, and the like. The timing control unit 16 may have a control processor that controls the imaging timing in the radiation camera 4. The control processor controls the radiation camera 4 and the rotation stage 6 based on, for example, the thickness of the object 20 stored by the user's input or the like, the position of the boundary surface 23 on the object 20, or the position of the imaging surface P. .. The image processing device 10 and the timing control unit 16 may be configured as a program executed by a single computer, or may be configured as individually provided units.

The image acquisition system 1 further controls (movement control) a stage elevator 7 for raising and lowering the rotary stage 6 in the direction of the rotation axis L, and a stage elevator 7 for raising and lowering the rotary stage 6. A unit (stage movement control unit) 17 is provided. As the stage elevator 7, a known elevator can be used. The stage elevator 7 may include, for example, a ball screw and a motor (drive source) arranged on the rotation axis L and penetrating the rotation stage 6 and the object 20. The stage elevator 7 is not limited to the screw type, and may be a telescopic type elevator using, for example, a hydraulic pressure as a drive source.

The stage elevating control unit 17 is composed of, for example, a computer having a CPU, ROM, RAM, an input / output interface, and the like. The stage elevating control unit 17 may have a control processor that controls the movement of the rotation stage 6 in the rotation axis L direction. The control processor controls the stage elevator 7 based on, for example, the thickness of the object 20 stored by the user's input or the like, or the position of the imaging surface P. The stage elevator control unit 17 controls the stage elevator 7 to bring the object 20 closer to or further from the radiation source 2. That is, the stage elevating control unit 17 is configured to move the object 20 closer to and further from the radiation source 2.

Each configuration of the image acquisition system 1 described above may be housed in a housing (not shown) and fixed in the housing. Further, each of the above configurations may be assembled on a base, for example, without being housed in the housing. All or at least one of the radiation source 2, the radiation camera 4, and the rotating stage 6 may be movable so that their relative positional relationship with each other can be adjusted. The image processing device 10 may be housed in a housing or may be installed outside the housing. All or at least one of the image processing device 10, the display device 15, the timing control unit 16, and the stage elevating control unit 17 is installed at a location away from the location where the radiation source 2, the radiation camera 4, and the rotary stage 6 are provided. May be done. The control by the image processing device 10, the timing control unit 16, and the stage elevating control unit 17 may be remote control using wireless communication.

Subsequently, the arrangement and positional relationship of the radiation source 2, the rotating stage 6, and the radiation camera 4 will be described. As shown in FIGS. 1 and 2, the rotating stage 6 is installed, for example, between the radiation source 2 and the radiation camera 4. More specifically, the rotation stage 6 is provided at a position such that the rotation axis L of the rotation stage 6 passes by the side of the radiation source 2. As a result, the boundary surface 23 of the object 20 is located directly below the radiation source 2. In other words, the radiation generator 3 and the rotation stage 6 are arranged so that the extension surface of the boundary surface 23 (in the present embodiment, the cylindrical surface centered on the rotation axis L) passes through the radiation source 2. The emission region of the radiation source 2 includes or passes through the roll portion 21. The radiation camera 4 is arranged so that the radiation transmitted through the roll portion 21 of the object 20 is input to the input surface 11a of the radiation camera 4 (see FIG. 2). In other words, the input surface 11a of the radiation camera 4 is provided so as to include a virtual plane including the radiation source 2 and the rotation axis L.

In the present embodiment, the radiation camera 4 is installed so as to be inclined so that its input surface 11a forms an acute angle with respect to the rotation axis L of the rotation stage 6. As a result, in the obtained radiographic image, the influence of the speed difference between the inner peripheral portion and the outer peripheral portion of the roll portion 21 is alleviated (details will be described later). In the present specification, the terms "inner circumference", "outer circumference", "radius" and "diameter direction" are used with reference to the rotation axis L.

Further, in the present embodiment, not only the radiation camera 4 is tilted, but also the angle (the acute angle described above) formed by the rotation axis L and the input surface 11a of the radiation camera 4 is the imaging surface P in the radiation source 2 and the object 20. It is set according to the FOD (Focus-Object Distance), which is the distance to and from. Hereinafter, a detailed description will be given with reference to FIGS. 3 and 4.

With reference to FIG. 3, _{the calculation of the FDD out on} the outer peripheral portion and the inclination θ of the radiation camera 4 _{suitable for the FDD in on the inner peripheral side will be described.} Here, the FDD (Focus-Detector Distance) is the distance between the radiation source 2 and the input surface 11a of the radiation camera 4, and the subscripts "in" and "out" are the "inner circumference" and "outer circumference", respectively. Means. First, when the radiation camera 4 which is a TDI camera is driven at an arbitrary line speed, the transport speed adapted to the line speed is inversely proportional to the X-ray geometric magnification (that is, the magnification). The enlargement ratio Min _{in the inner peripheral portion and the enlargement ratio M out} in the outer peripheral portion are represented by the following equations (1) and (2).

Here, if the relationship of the following equation (3) is established, the focus is achieved on both the inner peripheral portion and the outer peripheral portion.

Equation (5) is derived from equations (1), (2) and (3), and the relational expression (4) (see FIG. 4) between the angular velocity ω and the tangential velocity v.

If the radiation camera 4 is tilted to adjust the FDD so as to satisfy this equation (5), the focus is achieved on both the inner peripheral portion and the outer peripheral portion. The equation (4) is derived from the following equations (6) and (7) (see also FIG. 4). The FOD can be adjusted by changing the ratio of the line speed of the radiation camera 4 to the rotation speed of the rotation stage 6.

Subsequently, when the winding thickness w of the roll is determined as in the equation (8), _{the FDD out in} the outer peripheral portion _{and the inclination θ of the radiation camera 4 suitable for the FDD in in the} inner peripheral portion are obtained by the following equation (8). It is calculated as 9) to (11). It can be said that the inclination θ is the angle formed by the plane perpendicular to the rotation axis L and the input surface 11a of the radiation camera 4.

As described above, in the present embodiment, the angle β formed by the rotation axis L and the input surface 11a of the radiation camera 4 is the distance between the radiation source 2 and the imaging surface P in the object 20 FOD (Focus-Object Distance). ) Is set according to. It is clear that the relationship is angle β = π / 2-angle θ. Basically, when the enlargement ratio increases n times, the moving speed of the image on the image sensor 13 also increases n times, so that the TDI control speed (charge transfer speed) also increases n times. Considering a realistic enlargement ratio, the inclination angle θ needs to be 20 ° to 30 °.

Subsequently, the operation of the image acquisition system 1, that is, the method of acquiring a radiographic image will be described with reference to FIGS. 5 and 6. First, an object 20 such as a chip capacitor wound in a roll shape is attached to the rotary stage 6 and held by the rotary stage 6. Next, as shown in FIG. 6, the FOD is determined (step S01). FOD can be determined based on the desired magnification.

Next, the stage elevating control unit 17 drives the stage elevator 7 in accordance with the FOD to move the rotary stage 6 in the rotation axis L direction (step S02 (movement step)). Next, using the rotation stage 6, the object 20 is rotated at a predetermined speed around the rotation axis L (step S03 (rotation step)). Next, an irradiation line is output and irradiated from the radiation source 2 toward the rotating object 20 (step S04 (radiation output step)). The radiation transmitted through the roll portion 21 of the object 20 is input to the input surface 11a.

Next, the radiation camera 4 performs TDI control in the image sensor 13 in synchronization with the rotation speed of the object 20 by the rotation stage 6 (step S05). That is, the image sensor 13 is driven at a speed synchronized with the rotation speed of the roll. Then, the radiation camera 4 images the imaging surface (step S06) and outputs the image data (step S07) (steps S05 to S07 (radiation imaging step)). The image processing device 10 inputs the image data output from the radiation camera 4 to generate a radiation image on the imaging surface P of the object 20 (step S08 (image generation step)).

Through the above series of processes, a radiation image of the imaging surface P is acquired. According to the image acquisition system 1 and the image acquisition method of the present embodiment, the TDI control in the image sensor 13 is performed in synchronization with the rotation speed of the object 20 by the rotation stage 6. Of the imaging surface P of the object 20, the speed of the inner peripheral portion (the portion closest to the rotation axis) is slower than the speed of the outer peripheral portion (the portion farthest from the rotation axis). An acute angle β is formed between the rotation axis L of the rotation stage 6 and the input surface 11a of the radiation camera 4. _{Therefore, the distance FDD in} between the radiation source 2 and the portion of the input surface 11a where the radiation transmitted through the inner peripheral portion is input is the distance between the radiation source 2 and the portion of the input surface 11a where the radiation transmitted through the outer peripheral portion is input. Distance _{longer than FDD out} (see Figure 3). This means that the enlargement ratio at the inner peripheral portion is larger than the enlargement ratio at the outer peripheral portion (see equations (1) and (2)). The transport speed adapted to a predetermined line speed in TDI control is inversely proportional to the enlargement ratio. According to the magnitude relationship of the enlargement ratio described above, the influence of the speed difference between the inner peripheral portion and the outer peripheral portion is alleviated. Further, the angle formed by the rotation axis L of the rotation stage 6 and the input surface 11a of the radiation camera 4 is set according to the FOD which is the distance between the radiation source 2 and the imaging surface P in the object 20. In the inner peripheral portion and the outer peripheral portion, the ratio of the enlargement ratio becomes the reciprocal of the speed ratio, and the focus can be adjusted. As a result, it is possible to focus on any portion between the inner peripheral portion and the outer peripheral portion. Therefore, a clear radiographic image can be acquired for any portion of the object 20 in the radial direction.

Here, the image acquisition method may further include a step of controlling the movement of the rotation stage 6 in the direction of the rotation axis L and moving the object 20 closer to or further from the radiation source 2. For example, after the above-mentioned steps S01 to S08 are completed, the object 20 may be moved in the rotation axis L direction (step S02). As shown in FIG. 5A, in the first image generation, the imaging surface P is set near the lower surface of the roll portion 21. Therefore, as shown in FIG. 5B, the rotation stage 6 is lowered by the amount corresponding to 1/4 (1 / n: n is a natural number) of the thickness in the rotation axis L direction. As a result, the imaging surface P can be moved from the lower surface of the roll portion 21 to about 1/4 of the thickness, and a clear radiographic image of the imaging surface P can be obtained. Similarly, as shown in FIGS. 5 (c) and 5 (d), the position of the imaging surface P can be raised stepwise by lowering the rotation stage 6.

According to this step, the distance between the radiation source 2 and the object 20 can be adjusted. In other words, the imaging surface P based on the above-mentioned FOD can be set at an arbitrary position in the rotation axis L direction (that is, the thickness direction) of the object 20. In this case, if the radiation source 2 is immobile, the FOD can be regarded as constant. A radiographic image of an arbitrary position in the thickness direction of the object 20 can be acquired.

According to the radiation camera 4 having the scintillator 11 having the input surface 11a and the image sensor 13 for capturing the scintillation light emitted by the scintillator 11 in response to the input of radiation, it is possible to acquire a clear radiation image of the object 20. can.

In the image acquisition method using the image acquisition system 1, for example, the image processing device 10 and the timing control are performed so that the above steps S02 to S08 are automatically performed when the first parameters (FOD, etc.) are input. The unit 16, the stage elevating control unit 17, and the display device 15 may be set. Further, after acquiring one radiation image for a certain imaging surface P, the stage elevating control unit 17 may move 1 / n to acquire a radiation image for the next imaging surface P. By acquiring radiographic images at such different positions in the thickness direction, it is possible to feed back, for example, information on the found foreign matter (position information in the radial direction or the thickness direction) to the manufacturing process.

A modified example of the first embodiment will be described with reference to FIG. 7. As shown in FIG. 7, the stage elevator 7 and the stage elevating control unit 17 are omitted, and instead, an image provided with a mechanism for elevating (moving in the rotation axis L direction) the radiation generator 3 (radiation source 2). Acquisition system 1A may be provided. In FIG. 7, the elevating mechanism of the radiation generator 3 is not shown. Further, the illustration of the image processing device 10, the display device 15, and the timing control unit 16 is also omitted (this point is the same in FIGS. 10 and 11 below).

Even with such an image acquisition system 1A, the inclination θ of the radiation camera 4 according to the FOD can be calculated by the following equation (12).

Subsequently, the image acquisition system 1B according to the second embodiment will be described with reference to FIGS. 8 and 9. The image acquisition system 1B differs from the image acquisition system 1 of the first embodiment in that the stage elevating machine 7 and the stage elevating control unit 17 are omitted, and instead, the radiation camera 4 is rotated to rotate the image acquisition system 1B. This is a point provided with a rotation mechanism 18 and an angle adjusting unit 19 configured to adjust the angle formed by the rotation axis L of the stage 6 and the input surface 11a of the radiation camera 4. The rotating mechanism 18 includes a rotating shaft 18a connected to the radiation camera 4, and has a motor, gears, and the like (not shown) to rotate the radiation camera 4. The rotating mechanism 18 holds the radiation camera 4 so that the input surface 11a of the radiation camera 4 is tilted with respect to the rotation axis L. The rotation shaft 18a of the rotation mechanism 18 may be perpendicular to the virtual plane including the rotation axis L and the radiation source 2.

As shown in FIG. 9, the difference between the image acquisition method using the image acquisition system 1B and the image acquisition method using the image acquisition system 1 is that the FDD is determined prior to the determination of the FOD (step S01). (Step S10), the point at which the object 20 is installed according to the FDD (step S11), and thereafter the FOD is determined (step S01), and then the inclination angle θ is based on the FDD, the FOD, and the winding thickness w. Is calculated (see step S12, equations (11) and (12)), and the rotation mechanism 18 is controlled by the angle adjusting unit 19 so as to have the tilt angle θ, and the angle of the radiation camera 4 is adjusted (step S13 (adjustment). Step)) The point. The stage movement (step S02, see FIG. 6) in the image acquisition system 1 is not performed.

The image acquisition system 1B also exerts the same actions and effects as those of the image acquisition systems 1 and 1A described above. Further, by the step of adjusting the angle, the angle formed by the rotation axis L of the rotation stage 6 and the input surface 11a of the radiation camera 4 can be adjusted to an appropriate angle according to the FOD.

Further, in the step of adjusting the angle, the angle formed by the rotation axis L of the rotation stage 6 and the input surface 11a of the radiation camera 4 is set according to the FOD which is the distance between the radiation source 2 and the imaging surface P in the object 20. Since it is adjusted, it is possible to focus on any FOD.

Further, in the step of adjusting the angle, since the radiation camera 4 is rotated so that the input surface 11a of the radiation camera 4 is tilted with respect to the rotation axis L, the posture of the radiation camera 4 is adjusted and the rotation axis of the rotation stage 6 is adjusted. The angle formed by L and the input surface 11a of the radiation camera 4 can be adjusted to an appropriate angle according to the FOD.

Subsequently, the image acquisition system 1C according to the third embodiment will be described with reference to FIGS. 10 and 11. The image acquisition system 1C differs from the image acquisition system 1 of the first embodiment in that the stage elevating device 7 and the stage elevating control unit 17 are omitted, and the extension surface of the boundary surface 23 does not pass through the radiation source 2. Radiation so that the point where the rotating stage 6 and the object 20 are tilted and the edge (optical axis) of the radiation bundle 2a corresponding to the inner peripheral portion of the imaging surface P are orthogonal to the input surface 11a of the radiation camera 4. This is the point where the camera 4 is arranged.

The same can be said for the image acquisition system 1C as in the above equations (1) to (5), and the inclination angle θ of the object 20 is calculated by the following equation (13). In the image acquisition system 1C, it is clear that the angle β formed by the rotation axis L and the input surface 11a has a relationship of angle β = π / 2-angle θ.

The same mechanism as the rotation mechanism 18 and the angle adjusting unit 19 in the image acquisition system 1B described above may be applied to the rotation stage 6 of the image acquisition system 1C. In this case, the posture of the rotating stage 6 can be adjusted, and the angle formed by the rotating axis L of the rotating stage 6 and the input surface 11a of the radiation camera 4 can be adjusted to an appropriate angle according to the FOD.

Although the embodiments of the present disclosure have been described above, the present invention is not limited to the above embodiments. For example, in the above embodiment, the case where the radiation camera 4 is an indirect conversion type camera in which the FOP 12 with the scintillator 11 is coupled to the image sensor 13 has been described, but the radiation camera is not limited to this mode. For example, an indirect conversion type radiation camera in which the FOP 12 is omitted and the scintillator 11 is coupled to the image sensor 13 may be adopted. In this case as well, the input surface 11a of the scintillator 11 is the input surface of the radiation camera and serves as a reference for the above-mentioned angle. Further, a direct conversion type radiation camera composed of only the image sensor 13 may be adopted. In this case, the light receiving surface 13a of the image sensor 13 is the input surface of the radiation camera and serves as a reference for the above-mentioned angle. Even in a direct conversion type radiation camera, TDI control by the image sensor 13 is possible. Further, a direct conversion type radiation camera in which the FOP is coupled to the image sensor 13 may be adopted. In this case, the surface of the FOP is the input surface of the radiation camera and serves as a reference for the above-mentioned angle. Even when these direct conversion type radiation image sensors are used, a clear radiation image of an object can be acquired.

Further, the angle formed by the rotation axis L of the rotation stage 6 and the input surface 11a of the radiation camera 4 may be set according to the FOD, and agrees with the above equations (11), (12), and (13). You don't have to. It is possible to obtain a clear radiographic image for any portion in the radial direction even if the angle is slightly different from the above equations (11), (12), and (13). Further, the image acquisition system is not limited to the mode in which the rotating stage 6 or the radiation camera 4 can rotate, and the rotating stage 6 or the radiation camera 4 is fixed at an angle "set according to the FOD", and the angle is adjusted thereafter. An image acquisition system in which is disabled may be provided as an aspect of the present invention.

Further, a configuration in which the angles of both the rotating stage 6 and the radiation camera 4 can be adjusted may be adopted. When tilting the rotating stage 6, it is necessary to tilt the radiation camera 4 more.

An image acquisition system in which any two or more of the plurality of embodiments described above are combined may be provided. For example, tilting of the radiation camera in the image acquisition system 1 and raising / lowering the rotation stage 6, raising / lowering the radiation generator 3 in the image acquisition system 1A, rotation (angle adjustment) of the radiation camera 4 in the image acquisition system 1B, and image acquisition. An image acquisition system in which any two or more of the inclinations of the rotation stage 6 and the object 20 in the system 1C are combined may be provided.

(Test example)
A simulation was performed to verify the effect of the image acquisition system 1 according to the first embodiment. It is assumed that the radius of the inner peripheral portion is r _in = 120 mm and the radius of the outer peripheral portion is r _out = 150 mm. As shown in FIG. 12, the speed ratio of the foreign matter 2 (indicated by the reference numeral F2) located in the center in the winding thickness direction is 1. It is 125 times, and the speed ratio of the foreign matter 3 (indicated by reference numeral F3) located on the outer peripheral portion is 1.25.

As Comparative Example 1, the simulation was performed under the condition that the radiation camera 4 is not tilted, that is, the input surface 11a of the radiation camera 4 is orthogonal to the rotation axis L in the image acquisition system 1. Further, as Comparative Example 2, the radiation camera 4 was tilted, and the input surface 11a of the radiation camera 4 formed an acute angle with respect to the rotation axis L, but the simulation was performed under the condition of about half of the appropriate angle according to the FOD. In Comparative Examples 1 and 2, the TDI transfer speed was set so as to match the transport speed of the foreign matter 1 in the inner peripheral portion. In the embodiment, the simulation was performed under the condition that the input surface 11a of the radiation camera 4 formed an acute angle with respect to the rotation axis L and the angle was appropriate according to the FOD. The tilt angle in the examples was about 34 °, and the tilt angle in the comparative example 2 was about 17 °. The simulation conditions were FDD: 300 mm and FOD: 100 mm. The simulation results of Comparative Example 1, Comparative Example 2, and Examples are shown in FIGS. 13, 14 and 15, respectively. In each figure, the transport direction D is also shown.

As shown in FIG. 13, when the radiation camera 4 is not tilted, the radiation image of the foreign matter 1 is clear, but the speeds of the foreign matter 2 and 3 do not match, so that the image looks blurred in the transport direction D. , The contrast has deteriorated. Further, as shown in FIG. 14, even when the radiation camera 4 is tilted but the angle is not appropriate, the images of the foreign objects 2 and 3 are blurred in the transport direction D because the speeds do not match. The contrast has deteriorated.

As shown in FIG. 15, when the radiation camera 4 was tilted and an appropriate angle was set according to the FOD, the speed difference (velocity ratio) was absorbed and the object could be photographed at all positions in the radial direction without blurring. ..

1 ... Image acquisition system, 2 ... Radiation source, 3 ... Radiation generator, 4 ... Radiation camera, 6 ... Rotating stage, 7 ... Stage lifter, 10 ... Image processing device, 11 ... Scintillator, 11a ... Input surface, 13 ... Image Sensor, 13a ... Light receiving surface, 15 ... Display device, 16 ... Timing control unit, 17 ... Stage elevating control unit (stage movement control unit), 20 ... Object, 21 ... Roll unit, 22 ... Wheel unit, 23 ... Boundary surface , L ... Rotation axis, P ... Imaging surface.

Claims (16)

A radiation source that outputs radiation toward an object,
A rotating stage configured to rotate the object around the axis of rotation,
A radiation camera having an input surface into which the radiation transmitted through the object is input and an image sensor capable of controlling TDI (time delay integration), and an image sensor that captures the input radiation and outputs image data.
An image processing device that generates a radiographic image on the imaging surface of the object based on the image data is provided.
The angle formed by the rotation axis of the rotation stage and the input surface of the radiation camera is set so that the enlargement ratio in the inner peripheral portion of the object is larger than the enlargement ratio in the outer peripheral portion of the object.
The radiation camera is an image acquisition system configured to perform TDI control in the image sensor in synchronization with the rotation speed of the object by the rotation stage. The image acquisition system according to claim 1, further comprising a stage movement control unit configured to move the rotating stage in the direction of the rotation axis and move the object closer to and further from the radiation source. 1 or 2 further comprising an angle adjusting unit configured to hold the rotating stage or the radiation camera and adjust the angle formed by the rotating axis of the rotating stage and the input surface of the radiation camera. Image acquisition system described in. In the angle adjusting unit, the rotation axis of the rotation stage and the input surface of the radiation camera are arranged so that the enlargement ratio in the inner peripheral portion of the object is larger than the enlargement ratio in the outer peripheral portion of the object. The image acquisition system according to claim 3, which is configured to adjust the angle of formation. The image acquisition system according to claim 3 or 4, wherein the angle adjusting unit holds the radiation camera so that the input surface of the radiation camera is tilted with respect to the rotation axis. The image acquisition system according to claim 3 or 4, wherein the angle adjusting unit holds the rotation stage so that the rotation axis is tilted with respect to the input surface of the radiation camera. The image according to any one of claims 1 to 6, wherein the radiation camera includes a scintillator having the input surface, and the image sensor captures scintillation light emitted by the scintillator in response to the input of the radiation. Acquisition system. The image acquisition system according to any one of claims 1 to 6, wherein the image sensor is a direct conversion type radiation image sensor having the input surface. A rotation step that uses a rotation stage to rotate an object at a predetermined speed around the rotation axis,
A radiation output step that outputs radiation from a radiation source toward the rotating object,
Radiation imaging that captures the input radiation and outputs image data using a radiation camera having an input surface into which the radiation transmitted through the object is input and an image sensor capable of controlling TDI (time delay integration). Steps and
Including an image generation step of generating a radiographic image on the imaging surface of the object based on the image data.
The angle formed by the rotation axis of the rotation stage and the input surface of the radiation camera is set so that the enlargement ratio in the inner peripheral portion of the object is larger than the enlargement ratio in the outer peripheral portion of the object.
In the radiation imaging step, an image acquisition method in which TDI control in the image sensor is performed in synchronization with the rotation speed of the object by the rotation stage. The image acquisition method according to claim 9, further comprising a moving step of controlling the movement of the rotation stage in the direction of the rotation axis to bring the object closer to or further away from the radiation source. 9. Image acquisition method. In the adjustment step, the rotation axis of the rotation stage and the input surface of the radiation camera are formed so that the enlargement ratio in the inner peripheral portion of the object is larger than the enlargement ratio in the outer peripheral portion of the object. The image acquisition method according to claim 11, wherein the angle is adjusted. The image acquisition method according to claim 11 or 12, wherein in the adjustment step, the radiation camera is rotated so that the input surface of the radiation camera is tilted with respect to the rotation axis. The image acquisition method according to claim 11 or 12, wherein in the adjustment step, the rotation stage is rotated so that the rotation axis is tilted with respect to the input surface of the radiation camera. The radiation camera includes a scintillator having the input surface, and in the radiation imaging step, the scintillation light emitted by the scintillator in response to the input of the radiation is imaged, according to any one of claims 9 to 14. Image acquisition method. The image acquisition method according to any one of claims 9 to 14, wherein the image sensor is a direct conversion type radiation image sensor having the input surface.

Images