Image processing method, image processing device, and program

Abstract

The present invention facilitates inspection of a sample in which a fine structure in a material has either or both of a radius vector direction and a radial direction component, or a sample having a circular shape and a nearly arcuate shape centering on a certain point. Provided is an image processing method for processing a Talbot image of a sample in which a fine structure in a material has either or both of a radius vector direction and a radial direction component, or a sample having a circular shape and a nearly arcuate shape centering on a certain point, the image processing method including a first step (step S3) for acquiring a polar coordinate origin, and a second step (step S4) for performing polar coordinate conversion on the basis of the polar coordinate origin.

Description

Image processing method, image processing device and program

[0001] The present invention relates to an image processing method, an image processing device, and a program.

[0002] Conventionally, inspections have been conducted on the state of resin flow that occurs during molding, such as for resin gears manufactured by injection molding. In such inspections, the state of resin flow is inspected between normal and abnormal locations, and between normal and abnormal lots. Furthermore, such inspections use X-ray Talbot-Lau interferometers, microfocus CT, and the like.

[0003] X-ray Talbot-Lau interferometry (Talbot photography), which utilizes the Talbot effect, is an excellent technique for globally understanding microstructures, such as fiber orientation in injection-molded products. The Talbot effect refers to the phenomenon in which coherent light passes through a first grating with slits at regular intervals, forming a lattice image at regular intervals in the direction of light propagation. This lattice image is called a self-image. The Talbot interferometer places a second grating at the position where the self-image is formed, and measures the resulting moiré fringes by slightly shifting the second grating. Since placing an object in front of the second grating disrupts the moiré, Talbot photography allows for the object to be placed in front of or behind the first grating, irradiate it with coherent X-rays, and then compute the resulting moiré fringe image to obtain a display image of the object. Compared to conventional X-ray transmission inspection systems and X-ray absorption CT, X-ray Talbot photography can simultaneously obtain multiple Talbot images, including absorption images, differential phase images, small-angle scattering images, and orientation analysis images. In particular, orientation angle images allow for confirmation of fiber orientation in a specific direction. Furthermore, Talbot CT imaging, which generates three-dimensional images (tomographic images), has also been developed as a three-dimensional extension of the Talbot imaging that generates the above-mentioned two-dimensional images. In Talbot CT imaging, the subject is rotated by a predetermined angle, and two-dimensional Talbot images taken at multiple angles in three dimensions are used to calculate the signal value of each voxel, thereby obtaining a three-dimensional Talbot image. While microfocus CT and other methods can also grasp the state of fibers, they take several hours to capture an image of an area of ​​a few millimeters, whereas an X-ray Talbot-Lau interferometer can capture an image of a large area of ​​about 100 mm in a short time of just a few minutes.

[0004] Patent Documents 1 and 2 describe a method of converting arc-shaped cartilage into a linear form by polar coordinate conversion of a medical image, which is a differential phase image obtained by Talbot photography, making it easier to examine the thickness of the cartilage.

[0005] JP 2017-225644 A JP 2015-104441 A

[0006] When inspecting samples whose microstructures have either or both radial and radial components, or samples whose shapes resemble circles or arcs centered on a certain point, it is difficult to compare and inspect areas located at similar positions around a certain point. To give a specific example, when inspecting parts containing radially arranged teeth, it is difficult to compare and inspect each individual feature. For example, when comparing the photographs of individual teeth in an injection-molded gear containing GF filler, secondary processing such as cutting out and rotating the tooth portion of the image is required. Furthermore, in injection molding, the gate position affects the resin flow and the resulting fiber orientation. From a molding technology perspective, it is desirable to visualize the orientation relative to the gate position. However, typical images do not always explicitly show the orientation relative to the gate position. Furthermore, some images obtained using Talbot photography have directional characteristics. In directional images, a certain direction in the image (e.g., the Y direction) is used as the reference, and the orientation, such as the orientation angle relative to that direction, is visualized. To understand the flow of the entire part, a bird's-eye view of the flow direction is available. However, when observing the flow relative to the local shape of teeth arranged in an arc, such as a gear, the flow direction at each tooth relative to the reference direction differs depending on the position of the tooth, so even if the flow situation at each tooth is the same, the values ​​on the image will not be the same depending on the orientation of the tooth, making mutual comparison difficult.In other words, for samples in which orientation characteristics appear along either or both the radial and radial directions, it is difficult to compare and inspect areas at similar positions around a certain point.

[0007] Furthermore, Patent Documents 1 and 2 describe polar coordinate conversion of medical images, which are differential phase images, but the polar coordinate conversion is simply performed based on an origin set at a certain location. Therefore, even if Patent Documents 1 and 2 are applied to radially arranged components, it does not necessarily make inspection easier.

[0008] Therefore, an object of the present invention is to facilitate the inspection of samples in which the microstructure within the material has either or both radial and radial components, or samples that have shapes that approximate circles and arcs centered on a point.

[0009] In order to solve the above problems, the image processing method of the present invention is an image processing method in which an information processing device processes Talbot images of a sample whose microstructure within the material has components in either or both of the radial and radial directions, or a sample whose shape is close to a circle or arc centered at a certain point, and includes: a first step of acquiring a polar coordinate origin; and a second step of performing polar coordinate transformation based on the polar coordinate origin.

[0010] The image processing device of the present invention is an image processing device that processes Talbot images of a sample whose microstructure within the material has components in either or both of the radial and radial directions, or a sample whose shape is close to a circle or arc centered on a certain point, and is equipped with: an acquisition unit that acquires the polar coordinate origin; and a conversion unit that performs polar coordinate conversion based on the polar coordinate origin.

[0011] Furthermore, the program of the present invention causes a computer of an image processing device that processes Talbot images of a sample whose microstructure within a material has components in either or both of the radial and radial directions, or a sample whose shape is close to a circle or arc centered at a certain point, to execute the following steps: a first step of acquiring the origin of polar coordinates; and a second step of performing polar coordinate transformation based on the origin of polar coordinates.

[0012] The present invention facilitates the inspection of samples in which the microstructure within the material has either or both radial and radial components, or has shapes that approximate circles and arcs centered at a point.

[0013] 1 is a schematic diagram showing an overall view of an X-ray Talbot imaging device. FIG. 2 is a block diagram showing the schematic configuration of an information processing device. FIG. 3 is a flowchart showing image processing. FIG. 4 is an example of a scattering intensity image. FIG. 5 is an example of an orientation angle image. FIG. 6 is a schematic diagram of fiber orientation. FIG. 7 is an example of a scattering intensity image and a guideline. FIG. 8 is an example of a scattering intensity image after polar coordinate transformation. FIG. 9 is an example of an orientation angle image after polar coordinate transformation and orientation angle correction. FIG. 10 is a schematic diagram of fiber orientation. FIG. 11 is an image of normalization. FIG. 12 is an image of normalization. FIG. 13 is an image of polar coordinate transformation and joining after region division. FIG. 14 is an image of tomographic orientation CT of a helical gear.

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, although the embodiments described below are subject to various technically preferable limitations for carrying out the present invention, the technical scope of the present invention is not limited to the following embodiments and illustrated examples.

[0015] In this embodiment, an image processing method using an information processing device 20 (image processing device) for processing a Talbot image of a subject H captured using an X-ray Talbot imaging device 10 will be described. The analysis system 1 shown in Fig. 1 includes the X-ray Talbot imaging device 10, a controller 19, and an information processing device 20. The X-ray Talbot imaging device 10 is connected to the information processing device 20 via the controller 19 and a communication network N. The communication network N may be a LAN (Local Area Network), a WAN (Wide Area Network), the Internet, or the like.

[0016] [Regarding the Subject] Here, we will explain the subject H. The subject H in this embodiment is a component (sample) whose microstructure in the material affects the performance of the component, and is a sample whose microstructure in the material has components in either the radial direction or the radial direction, or both, or a sample having a shape close to a circle or an arc centered at a certain point.

[0017] Specifically, the materials include fiber-reinforced plastics in general, resins in general, resins with added fillers in general, foam materials such as sponge, and casting materials such as aluminum die-cast. More specifically, known materials include CFRP (Carbon-Fiber-Reinforced Plastics), CFRTP (Carbon Fiber Reinforced Thermo Plastics), and FRP (Fiber-Reinforced Plastics) represented by GFRP (Glass-Fiber-Reinforced Plastics), which use carbon fiber or glass fiber as reinforcing fibers, and CMC (Ceramic Matrix Composites), which use ceramic fiber as a reinforcing material. In a broad sense, the term may also include composite materials made of multiple types of wood, such as plywood. Other examples include composite materials that do not contain fibers, such as MMC (Metal Matrix Composites), concrete, and reinforced concrete. Resins used in the materials include, but are not limited to, general-purpose plastics, engineering plastics, and super engineering plastics. Resins are often used as resin composites to which fillers with micro- or nano-sized structures are added to impart specific properties such as strength, and are used in plastic molded products. Fillers include organic materials, inorganic materials, magnetic materials, and metal materials. For example, when strength and rigidity are required in plastic molded products, composite materials using resins such as PPS, POM, PA, PC, and PP and fillers such as aramid fiber, talc, and cellulose fiber may be used. Furthermore, when the plastic molded product is a plastic mag, a composite material such as nylon as the resin and strontium ferrite or samarium cobalt as the filler may be used.

[0018] Examples of the microstructure include the orientation of fiber fillers such as carbon fiber (CF) and glass fiber (GF), the orientation of long fiber CF woven in a matrix, etc. Examples of the microstructure also include the orientation of flat fillers such as talc, the local distribution of fine particles, mixed or added fine bubbles, voids, welds (seams in resin flow), and blowholes (defective structures caused by fine bubbles that occur in aluminum castings).

[0019] Examples of samples having a shape close to a circle or arc with a certain point as the center include rotating shafts, bearings, circular gears, sector gears, rollers, and cams.

[0020] The subject H is manufactured by injection molding or the like. Other manufacturing methods include, for FRP (Fiber Reinforced Plastics), autoclave molding, RTM (Resin Transfer Molding), and SMC (Sheet Molding Compound) molding. Other manufacturing methods include casting and die casting for metals. In other words, the present invention is effective when applied to subject H manufactured by a molding method that generates a flow of molten resin or metal material during manufacturing, or to such molded products that have been subjected to secondary processing (cutting, drilling, grinding, polishing). In particular, the present invention is more effective when the subject H is a sample whose material microstructure has components in either or both the radial and radial directions.

[0021] [Regarding the X-ray Talbot Imaging Device] In this embodiment, the X-ray Talbot imaging device 10 uses a Talbot-Lau interferometer equipped with a source grating 12. Note that it is also possible to use an X-ray Talbot imaging device using a Talbot interferometer equipped only with a first grating 14 and a second grating 15, without the source grating 12. Furthermore, the X-ray Talbot imaging device 10 may be configured so that an imaging jig (not shown) for fixing the subject H in a predetermined orientation is provided on the subject table 13, and the subject H can be rotated three-dimensionally to perform Talbot CT imaging.

[0022] 1 is a schematic diagram showing an overall view of an X-ray Talbot imaging device 10. The X-ray Talbot imaging device 10 according to this embodiment includes an X-ray generator 11, a source grating 12, a subject table 13, a first grating 14, a second grating 15, an X-ray detector 16, a support 17, and a base 18. The grating directions of the source grating 12, the first grating 14, and the second grating 15 are the same.

[0023] With this X-ray Talbot imaging device 10, at least three types of images (two-dimensional images) can be reconstructed (referred to as reconstructed images) by capturing a moiré image Mo of a subject H at a predetermined position relative to the subject table 13 using a method based on the principles of fringe scanning and analyzing the moiré image Mo using a Fourier transform method. That is, these are three types of images: an absorption image (same as an ordinary X-ray absorption image) that visualizes the average component of the moiré fringes in the moiré image Mo, a differential phase image that visualizes the phase information of the moiré fringes, and a small-angle scattering image that visualizes the visibility of the moiré fringes.

[0024] Even more types of images can be generated by recombining the three types of reconstructed images described above. For example, small-angle scattering images taken at multiple (three or more) grating opposing angles are used, and after aligning the images, a sine wave is fitted to each pixel to extract fitting parameters. The sine wave graph is a graph in which the horizontal axis represents the relative angle α between the sample and the grating, and the vertical axis represents the small-angle scattering signal value of a certain pixel. The sine wave graph is expressed as in the following equation (1): The fitting parameters are the amplitude A, average B, and phase C of the sine wave in equation (1) above. The image showing the amplitude value for each pixel is called the orientation image, the image showing the average value for each pixel is called the scattering intensity image, and the image showing the phase for each pixel is called the orientation angle image. Note that the fitting method is not limited to sine waves. The orientation angle image provides the distribution of fiber orientation relative to the main direction. Hereinafter, the images generated by recombining the reconstructed images (orientation image, scattering intensity image, and orientation angle image) will be collectively referred to as the orientation analysis image.

[0025] Among the reconstructed images, the small-angle scattering image and the differential phase image also exhibit angular dependence on the lattice direction. Therefore, as described above, differential phase images or small-angle scattering images captured at multiple (three or more) lattice facing angles are used, and after aligning each image, a sine wave fitting is performed for each pixel to extract fitting parameters. As described above, the sine wave graph has the relative angle α between the sample and the lattice on the horizontal axis and the differential phase signal value or small-angle scattering signal value of a given pixel on the vertical axis. The sine wave graph is expressed as in Equation (1) above. For differential phase images, fitting is performed on the absolute value of the differential phase signal value of a given pixel, or the sign of A is inverted depending on θ. Using Equation (1) above, the differential phase signal value or small-angle scattering signal value of a pixel at a given relative angle α can be obtained.

[0026] The above describes Talbot radiography, which generates various two-dimensional images using a Talbot interferometer and a Talbot-Lau interferometer. Here, we will describe the acquisition of various three-dimensional images (tomographic images) using a Talbot-Lau interferometer. Talbot CT radiography is a three-dimensional extension of Talbot radiography, which generates various two-dimensional images. In Talbot CT radiography, a CT scanner is rotated by a predetermined angle (e.g., 1°) around the CT rotation axis to acquire Moiré fringe images covering 180° or 360°. These images are then processed using a fringe scanning method or a Fourier transform method to generate two-dimensional projection images (absorption images, small-angle scattering images, and differential phase images). Next, the signal values ​​of each voxel are calculated using the two-dimensional projection images (absorption tomographic images, small-angle scattering tomographic images, and phase tomographic images) corresponding to the two-dimensional projection images. In addition, the control unit 51 performs CT reconstruction and image processing using small-angle scattering images taken with the subject oriented in multiple directions relative to the CT rotation axis, thereby generating three-dimensional orientation analysis images (orientation degree tomographic image, orientation angle tomographic image, and scattering intensity image).

[0027] It is also possible to perform image processing such as filtering, clarification, and contour extraction on the reconstructed image, orientation analysis image, 3D CT image, and 3D orientation analysis image, as well as image processing for combining two or more types of images. Hereinafter, such processed images are referred to as secondary images.

[0028] Hereinafter, the term "Talbot photography" will refer to not only the photography of the moiré image Mo, but also the generation of the above-mentioned reconstructed image, orientation analysis image, 3D CT image, 3D orientation analysis image, and secondary image. Also, hereinafter, the reconstructed image, orientation analysis image, 3D CT image, 3D orientation analysis image, and secondary image will be collectively referred to as "Talbot image."

[0029] The fringe scanning method is a method in which one of multiple gratings is moved in the direction of the slit period by 1 / M of the grating slit period (M is a positive integer, M>2 for absorption images, and M>3 for differential phase images and small-angle scattering images) and then a moiré image Mo is captured M times, and reconstruction is performed using the captured image to obtain a high-resolution reconstructed image.

[0030] The Fourier transform method is a method in which, in the presence of a subject, one moiré image Mo is captured using an X-ray Talbot imaging device, and then, in image processing, the moiré image Mo is subjected to a Fourier transform or the like to reconstruct and generate an image such as a differential phase image.

[0031] The configuration of other parts of the X-ray Talbot imaging device 10 according to this embodiment will be described. This embodiment is a so-called vertical type, in which the X-ray generator 11, source grating 12, subject table 13, first grating 14, second grating 15, and X-ray detector 16 are arranged in this order in the z direction, which is the direction of gravity. That is, in this embodiment, the z direction is the irradiation direction of X-rays from the X-ray generator 11.

[0032] The X-ray generator 11 includes an X-ray source 11a, such as a Coolidge X-ray source or a rotating anode X-ray source, which are widely used in medical settings. Other X-ray sources may also be used. The X-ray generator 11 of this embodiment irradiates X-rays in a cone beam shape from a focal point. That is, as shown in FIG. 1 , the X-rays are irradiated so that they spread out as they move away from the X-ray generator 11, with the X-ray irradiation axis Ca coinciding with the z direction as the central axis (i.e., the X-ray irradiation range).

[0033] In this embodiment, the controller 19 (see FIG. 1) is configured by a computer having a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), an input / output interface, etc., all of which are not shown, connected to a bus. The controller 19 is also provided with appropriate means and devices, such as input means including an operation unit, output means, storage means, and communication means, all of which are not shown.

[0034] The controller 19 performs overall control of the X-ray Talbot imaging device 10. That is, for example, the controller 19 is connected to the X-ray generator 11, and is capable of setting the tube voltage, tube current, irradiation time, etc. of the X-ray source 11a.

[0035] [Regarding the Information Processing Device] In this embodiment, a general-purpose computer device (control PC) is used as the information processing device 20 that executes various processes. However, this is not limited to this, and some of the functions of the information processing device 20 may be provided on a network so that each process can be executed by exchanging data via communication. As shown in Figure 2, the information processing device 20 includes a control unit 21, an operation unit 22, a communication unit 23, a storage unit 24, and a display unit 25.

[0036] The control unit 21 is composed of a CPU (Central Processing Unit), RAM (Random Access Memory), etc. The CPU of the control unit 21 reads out various programs stored in the storage unit 24, loads them into the RAM, and executes various processes (e.g., image processing, which will be described later) in accordance with the loaded programs, thereby controlling the operation of each unit of the information processing device 20. The control unit 21 functions as an acquisition unit that acquires the polar coordinate origin. The control unit 21 functions as a conversion unit that performs polar coordinate conversion based on the polar coordinate origin.

[0037] The operation unit 22 is a keyboard equipped with cursor keys, numeric input keys, various function keys, etc., a pointing device such as a mouse, a touch panel laminated on the surface of the display unit 25, etc. The operation unit 22 is configured to be operable by an operator, and outputs various signals to the control unit 21 based on operations performed by the operator.

[0038] The communication unit 23 is capable of transmitting and receiving various signals and various data to and from other devices connected via the communication network N.

[0039] The storage unit 24 is configured by a non-volatile semiconductor memory, a hard disk, or the like, and stores various programs executed by the control unit 21, parameters required for executing the programs, various data (for example, Talbot images), and the like.

[0040] The display unit 25 is configured with a monitor such as an LCD (Liquid Crystal Display), and displays various screens and the like in accordance with instructions of a display signal input from the control unit 21 .

[0041] [Image Processing] Image processing of the Talbot image in the information processing device 20 will be described with reference to Fig. 3. Image processing starts when the control unit 21 receives a signal to start image processing input by the user using the operation unit 22. It is assumed that the Talbot image has been sent from the X-ray Talbot imaging device 10 to the information processing device 20 and has already been stored in the storage unit 24 before the image processing starts.

[0042] First, the control unit 21 acquires a Talbot image from the storage unit 24 (step S1). Next, the control unit 21 displays the Talbot image on the display unit 25 (step S2). In this embodiment, the scattering intensity image P1 shown in Fig. 4 or the orientation angle image P2 shown in Fig. 5 is acquired by Talbot imaging of the subject H, which is a gear manufactured by injection molding.

[0043] Here, the scattering intensity image P1 shown in Fig. 4 will be described. The gate GT is the gate location in injection molding that appears in the scattering intensity image P1. The weld line WL is the weld line that occurred during injection molding that appears in the scattering intensity image P1.

[0044] Next, the orientation angle image P2 shown in Figure 5 will be described. By referring to the image P3 showing the orientation corresponding to the color of each pixel in the orientation angle image P2, the orientation angle of the fiber at that pixel is shown. As shown in the image P3 showing the orientation, the orientation angle is defined as 0° in the upward direction of the paper (the Y direction in the XY coordinate system). Figure 6 is a schematic diagram SD1 that visualizes the fiber orientation for each specified region using line directions. By checking the orientation angle image P2 and the image P3 showing the orientation shown in Figure 5, the user can read the fiber orientation as shown in Figure 6.

[0045] Next, the user uses the operation unit 22 to specify the origin of polar coordinates on the Talbot image displayed on the display unit 25. The control unit 21 specifies the origin of polar coordinates on the Talbot image (step S3; first process). For example, the user may use the operation unit 22 to select an arbitrary position with a cursor. Alternatively, for example, the control unit 21 may perform a Hough transform on the Talbot image to detect arcs at multiple locations, and display the centers of the arcs as candidate points for selection on the display unit 25, allowing the user to select from the candidate points. The origin of polar coordinates may be set not only near the center of the subject H, but also at the position of the gate GT of the subject H.

[0046] An example of how the user can specify the origin of the polar coordinate system will now be described with reference to Figure 7. The user can easily specify the origin of the polar coordinate system O by moving the guide line G1 displayed on the display unit 25 and aligning it with the subject H displayed in the scattering intensity image P1.

[0047] After specifying the polar coordinate origin O, the range in the Talbot image to be converted to polar coordinates may be specified. An example of how the user specifies the range to be converted to polar coordinates will be described with reference to FIG. 8 . The user specifies the range to be converted to polar coordinates by moving the start guideline G2 and the end guideline G3. The user can also specify the direction of rotation from the start guideline G2 to the end guideline G3. If the rotation direction is specified as clockwise rotation, the larger area between the start guideline G2 and the end guideline G3 is specified as the range to be converted to polar coordinates. If the rotation direction is specified as counterclockwise rotation, the smaller area between the start guideline G2 and the end guideline G3 is specified as the range to be converted to polar coordinates.

[0048] Next, the control unit 21 converts the Talbot image into polar coordinates (step S4; second process). Next, the control unit 21 displays the polar coordinate converted Talbot image on the display unit 25 (step S5; third process). The formula for converting the XY coordinate system I(x, y) into the polar coordinate system I(γ, θ) is shown below. 9 is a scattering intensity image P4 after polar coordinate conversion. The gate GT and weld line WL are also converted and appear in the scattering intensity image P4. In this way, the teeth of the object H, which is a gear, are aligned side by side, making inspection easier.

[0049] Next, the control unit 21 determines whether the Talbot image has directionality (step S6). If it is determined that the Talbot image has directionality (step S6; YES), the control unit 21 advances image processing to step S7. If it is determined that the Talbot image does not have directionality (step S6; NO), the control unit 21 advances image processing to step S9. A Talbot image having directionality means that the value of each pixel in the Talbot image is set based on a certain direction. In other words, a Talbot image having directionality refers to a small-angle scattering image, a differential phase image, or an orientation angle image.

[0050] Next, the control unit 21 corrects the direction angle of the Talbot image (step S7; fourth process). Next, the control unit 21 displays the Talbot image with the direction angle corrected on the display unit 25 (step S8; fifth process). For example, as shown in the orientation angle image P2 and the image P3 indicating the orientation shown in FIG. 5, the upward direction of the paper surface is defined as 0°. However, the orientation angle image P2 was converted to polar coordinates in step S4, and the polar coordinate-converted orientation angle image and the image P3 indicating the orientation do not correspond. Therefore, the orientation angle of the polar coordinate-converted orientation angle image must be converted from XY coordinates to polar coordinates. Specifically, the radial direction from the origin of the polar coordinates is set to 0°, and the orientation direction relative to the radial direction is obtained, thereby correcting (converting) the orientation angle. The image shown in FIG. 10 is the orientation angle image P5 after polar coordinate conversion and orientation angle correction. The orientation angle image P5 corresponds to the image P6 indicating the orientation, with the orientation angle corrected. FIG. 11 is a schematic diagram SD2 that visualizes the fiber orientation for each specified region using line directions. By checking the orientation angle image P5 and the orientation image P6 shown in FIG. 10, the user can interpret the fiber orientation as shown in FIG. 11. The horizontal alignment of the teeth of the subject H, which is a gear, facilitates inspection. Furthermore, the fiber orientation, as indicated by the arrows in the figure, is easily recognized. Furthermore, when performing polar coordinate transformation to interpolate signal values ​​between pixels, it is desirable to use nearest-neighbor interpolation rather than linear, polynomial, or spline interpolation, especially for orientation angle images, because the angle values ​​are periodic.

[0051] Here, we will further explain in detail the method for correcting the signal values ​​of small-angle scattering images and differential phase images. As described above, it is assumed that small-angle scattering images and differential phase images are fitted using the following equation (1). Note that, as described above, in the differential phase image, fitting is performed on the absolute value of the differential phase signal value of a certain pixel, or the sign of A is inverted depending on θ. Here, if α0 is the relative angle when the image to be corrected was captured, when the pixel of interest in the original image is converted to polar coordinates θ, the signal value after correction can be corrected as shown in the following equation (2) for the signal value I(α0). Note that δ is an offset (constant value) for changing the reference during conversion. Furthermore, by applying the following two types of correction, the radial direction (I r The radial direction (I c The signal components of (1) can also be explicitly separated and extracted into two components as shown in the following equations (3) and (4). Furthermore, for small-angle scattering images and differential phase images, nearest neighbor interpolation or the like can be applied as a method for interpolating signal values ​​between pixels when polar coordinate transformation is performed, rather than linear interpolation, polynomial interpolation, or spline interpolation.

[0052] Next, the user uses the operation unit 22 to input whether or not normalization of the polar coordinate converted Talbot image is required. The control unit 21 determines whether or not normalization is required (step S9). If normalization is required (step S9; YES), the control unit 21 proceeds to step S10 for image processing. If normalization is not required (step S9; NO), the control unit 21 ends the image processing.

[0053] Next, the control unit 21 normalizes the polar coordinate converted Talbot image (step S10; sixth process). Next, the control unit 21 displays the normalized Talbot image on the display unit 25 (step S11; seventh process). Here, normalization of the Talbot image after polar coordinate conversion will be described. When the Talbot image is polar coordinate converted, the distance from the polar coordinate origin to the periphery (edge) of the object H is not necessarily constant. As a result, in the Talbot image after polar coordinate conversion, the portion corresponding to the periphery of the object H is not located at a constant position in a certain direction (for example, the r direction, which is the upward direction of the paper). Therefore, in the Talbot image after polar coordinate conversion, the portion corresponding to the periphery of the object H is corrected (normalized) so that it is located at a constant position in a certain direction. This facilitates inspection. Specifically, if the polar coordinate origin is set to a gate, the flow direction can be explicitly analyzed in the arc direction and the radial direction.

[0054] Normalization will be described in detail with reference to FIG. 12. FIG. 12 shows an image I1 of a Talbot image, an image I2 after polar coordinate conversion, and an image I3 after normalization. Note that the subject H is shown as a circle for simplification. As shown in image I1, the origin O of the polar coordinates is not at the center of the subject H. Therefore, the distance from the origin O of the polar coordinates to the periphery of the subject H is not constant, as indicated by the arrow. Therefore, the value of the radial direction r is not constant, as in image I2. Therefore, the control unit 21 normalizes the value of the radial direction r to make it constant, thereby correcting it as in image I3.

[0055] 12 has been described using a circular subject H, but the present invention is not limited to this. For example, the subject H may be rectangular, as shown in Fig. 13. As in Fig. 12, Fig. 13 also shows an image I4 of a Talbot image, an image I5 after polar coordinate conversion, and an image I6 after normalization.

[0056] (Other) With regard to the order of the steps of the image processing described above, steps S4-5 and S6-8 may be reversed.

[0057] The control unit 21 may also perform a comparative analysis of the repetitive shape of the subject H in the Talbot image after polar coordinate conversion. The repetitive shape of the subject H may be, for example, the teeth of a gear (subject H). Specifically, in steps S5, S8, and S11, the control unit 21 sets a region of interest (ROI) of a certain size for each repetitive shape in the Talbot image after polar coordinate conversion, and performs an analysis for each ROI, thereby performing a repetitive analysis of similar shapes in the horizontal direction (polar coordinate θ direction). The ROI may be set automatically by the control unit 21 through image analysis, or manually by the user using the operation unit 22. The control unit 21 may display the distribution of orientation angles for each ROI on the display unit 25. The control unit 21 may also display, on the display unit 25, the difference between each ROI and a reference image created by, for example, obtaining an average / median value from multiple ROIs. The control unit 21 may acquire the frequency of occurrence for each ROI of the orientation angle arbitrarily set by the user, and display a bar graph or the like for each ROI on the display unit 25. This makes it easier to determine abnormal locations relative to other locations in a repetitive shape.

[0058] Furthermore, the control unit 21 may store settings including the polar coordinate origin, the polar coordinate start and end points, and the rotation direction in the storage unit 24. Then, in step S4, the control unit 21 may perform polar coordinate conversion within a set range based on the stored settings. This eliminates the need for the user to set similar settings.

[0059] As shown in FIG. 14 , the control unit 21 may also divide the Talbot image (step 8), perform polar coordinate conversion on each divided Talbot image, and combine the images after polar coordinate conversion (step 9). Note that angle correction and normalization may be performed as needed. Here, the division and combination will be explained using FIG. 14 . The original Talbot image I7 is divided at the dashed-dotted line, as in Talbot image I8, and each image is subjected to polar coordinate conversion to obtain polar coordinate-converted Talbot images I9 and I10. By combining these images, a combined polar coordinate-converted Talbot image I11 is obtained. The user selects the division position on the Talbot image using the operation unit 22. In this way, even if the curvature of the object H is not constant, such as a cam, the polar coordinate-converted Talbot images are combined into a single image, facilitating inspection.

[0060] The present invention is also applicable when the subject H is a helical gear. A method for applying the present invention will be specifically described using FIG. 15 . The left side of FIG. 15 is a side view of the helical gear HG, and the right side of FIG. 15 is a front view of the helical gear HG. First, the control unit 21 acquires a reference axis A passing near the center of the helical gear HG. Next, the control unit 21 performs Talbot CT imaging on planes L1, L2, and L3 orthogonal to the reference axis A to obtain 3D CT images and 3D orientation analysis images in three orthogonal coordinate systems. Next, in step S3, the control unit 21 sets the intersection with the reference axis A as the origin of polar coordinates in the 3D CT images and 3D orientation analysis images. Next, in step S4, the control unit 21 aligns the positions of the identical tooth portions in polar coordinates by changing the 0-degree position of the polar coordinates using the twist angle of the helical gear HG and the acquired positions in the reference axis A direction of the 3D CT images and 3D orientation analysis images. Then, the control unit 21 performs polar coordinate conversion. This allows comparison of the same tooth. In addition, the control unit 21 may stack the three aligned polar coordinate system 3D CT images and 3D orientation analysis images, and reconstruct them as volume data.

[0061] (Effects) As described above, the image processing method is an image processing method in which an information processing device processes Talbot images of a sample whose internal microstructure has components in either or both of the radial and radial directions, or a sample whose shape resembles a circle or an arc centered on a certain point. The image processing method includes a first step (step S3) of acquiring the polar coordinate origin, and a second step (step S4) of performing polar coordinate transformation based on the polar coordinate origin. This facilitates the inspection of samples whose internal microstructure has components in either or both of the radial and radial directions, or a sample whose shape resembles a circle or an arc centered on a certain point. For example, if the subject is a gear, it is easy to compare and visually confirm the signal values ​​of Talbot images of multiple gear teeth. Furthermore, if the subject has a functional shape to be observed at the edge, the above comparison of any shape is facilitated.

[0062] The image processing device (information processing device 20) processes Talbot images of samples whose internal microstructures have components in either or both of the radial and radial directions, or samples whose shapes resemble circles and arcs centered on a certain point. The image processing device includes an acquisition unit (control unit 21) that acquires the origin of polar coordinates, and a conversion unit (control unit 21) that performs polar coordinate conversion based on the origin of polar coordinates. This facilitates the inspection of samples whose internal microstructures have components in either or both of the radial and radial directions, or samples whose shapes resemble circles and arcs centered on a certain point.

[0063] The program also causes a computer in an image processing device (information processing device 20) that processes Talbot images of samples whose internal microstructures have components in either or both of the radial and radial directions, or samples whose shapes approximate circles and arcs with a certain point at their center, to execute a first step (step S3) of acquiring the origin of polar coordinates, and a second step (step S4) of performing polar coordinate transformation based on the origin of polar coordinates. This facilitates the inspection of samples whose internal microstructures have components in either or both of the radial and radial directions, or samples whose shapes approximate circles and arcs with a certain point at their center.

[0064] The embodiment of the present invention has been described above, but the description of the above embodiment is a preferred example of the present invention, and the present invention is not limited to this.

[0065] In the above description, examples have been given in which a hard disk or a semiconductor nonvolatile memory is used as a computer-readable medium for the program according to the present invention, but the present invention is not limited to these examples. Other computer-readable media may also be used, such as a portable recording medium such as a CD-ROM.

[0066] In addition, the detailed configuration and operation of each device can be modified as appropriate without departing from the spirit of the invention.

[0067] The present disclosure can be used in an image processing method, an image processing device, and a program.

[0068] REFERENCE SIGNS LIST 1 Analysis system 10 X-ray Talbot imaging device 11 X-ray generator 19 Controller 20 Information processing device (image processing device) 21 Control unit (acquisition unit, conversion unit) 22 Operation unit 23 Communication unit 24 Storage unit 25 Display unit H Subject

Claims

1. An image processing method in which an information processing device processes Talbot images of a sample whose internal microstructure has components in either or both of the radial and radial directions, or a sample whose shape is close to a circle or arc with a certain point as its center, comprising: a first step of acquiring the origin of polar coordinates; and a second step of performing polar coordinate transformation based on the origin of polar coordinates.

2. The image processing method according to claim 1, further comprising a third step of displaying the Talbot image after the polar coordinate conversion on a display unit.

3. The image processing method according to claim 1, wherein the Talbot image is a small-angle scattering image, a differential phase image, and an orientation angle image, and further comprising a fourth step of correcting the signal values ​​of the small-angle scattering image, the differential phase image, and the orientation angle image based on polar coordinates, with the radial direction as the reference.

4. The image processing method according to claim 3, further comprising a fifth step of displaying the corrected image on a display unit.

5. The image processing method according to claim 1, wherein in the first step, the origin of the polar coordinates selected by the user is acquired.

6. An image processing method according to claim 5, wherein in the first step, concentric circles serving as a guide are displayed on the display unit when the user selects the origin of the polar coordinates.

7. An image processing method as described in claim 1, wherein in the first step, when the user selects the range to be converted into polar coordinates, either the start point, end point, or rotation direction of the polar coordinates is displayed on the display unit, and in the second step, polar coordinate conversion is performed on the range selected by the user.

8. An image processing method as described in claim 1, wherein in the first step, a range is set by referring to the previous settings including the polar coordinate origin, the polar coordinate start point and end point, and the rotation direction, and in the second step, a polar coordinate conversion of the set range is performed.

9. The image processing method according to claim 1, wherein the origin of the polar coordinates is the gate position during molding.

10. The image processing method according to claim 1, further comprising a sixth step of normalizing the polar coordinate transformed image.

11. The image processing method according to claim 10, further comprising a seventh step of displaying the normalized image on a display unit.

12. The image processing method according to claim 2, wherein in the third step, the Talbot image after the polar coordinate transformation is displayed so that similar shapes having periodicity can be compared.

13. The image processing method according to claim 4, wherein in the fifth step, the corrected image is displayed so that similar shapes having periodicity can be compared.

14. An image processing method according to claim 11, wherein in the seventh step, the normalized image is displayed so that similar shapes having periodicity can be compared.

15. The image processing method according to claim 1, wherein the Talbot image is a three-dimensional CT image and a three-dimensional orientation analysis image acquired in a direction perpendicular to an axis relative to the three-dimensional shape of the sample in a tomographic orientation CT analysis, and wherein in the first step, the polar coordinate origins of the three-dimensional CT image and the three-dimensional orientation analysis image are acquired as points intersecting with the axis.

16. An image processing method according to claim 15, wherein the sample is a helical gear, the Talbot images are 3D CT images and 3D orientation analysis images acquired at multiple locations in the axial direction of the three-dimensional shape of the sample in the tomographic orientation CT analysis, and in the second step, the reference for the starting point of the polar coordinates can be changed at the location where the helical gear twist angle and the Talbot image were acquired.

17. An image processing method according to claim 1 or claim 2, comprising: an eighth step of dividing a Talbot image into regions; and a ninth step of performing the polar coordinate transformation individually on a plurality of regions and then combining the transformation results.

18. The image processing method according to claim 1, wherein the material is a fiber-reinforced resin material or a resin material to which a filler is added.

19. An image processing device that processes Talbot images of a sample whose microstructure within the material has components in either or both of the radial and radial directions, or a sample whose shape is close to a circle or arc centered on a certain point, comprising: an acquisition unit that acquires the origin of polar coordinates; and a conversion unit that performs polar coordinate conversion based on the origin of polar coordinates.

20. A program that causes a computer in an image processing device that processes Talbot images of a sample whose microstructure within the material has components in either or both of the radial and radial directions, or a sample whose shape is close to a circle or arc centered on a certain point, to execute the following steps: a first step of acquiring the polar coordinate origin; and a second step of performing polar coordinate transformation based on the polar coordinate origin.

Images