X-ray inspection equipment
The X-ray inspection apparatus efficiently updates luminance conversion functions by combining pre-existing and new image data, addressing the time and data challenges of object variation, ensuring high-performance image correction.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- ISHIDA CO LTD
- Filing Date
- 2024-12-25
- Publication Date
- 2026-07-07
Smart Images
Figure 2026113252000001_ABST
Abstract
Description
Technical Field
[0001] It relates to an X-ray inspection apparatus.
Background Art
[0002] For example, as described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2012-73056), an X-ray is irradiated onto a conveyed inspection object, X-rays in the first and second energy bands that have passed through the inspection object are detected, and a first transmission image based on the detection result of the X-rays in the first energy band and a second transmission image based on the detection result of the X-rays in the second energy band are obtained. At least one of the first transmission image and the second transmission image is corrected based on a luminance conversion function (a luminance conversion table in Patent Document 1). After the correction, an X-ray inspection apparatus that inspects the inspection object based on a difference image obtained by performing subtraction processing using the first transmission image and the second transmission image is known.
[0003] The luminance conversion function is created by irradiating an X-ray onto the inspection object in the conveyance unit and performing the process of acquiring the first and second transmission images a plurality of times, and using the obtained plurality of first and second transmission images.
Summary of the Invention
Problems to be Solved by the Invention
[0004] The luminance conversion function may need to be reviewed for performance improvement. Also, when the inspection object is agricultural products or the like, even for the same type of inspection object, the inspection object may vary depending on the season and the place of origin, and in response to this, the luminance conversion function may need to be reviewed.
[0005] In this case, when creating a luminance conversion function from scratch, it is necessary to convey the inspection object in the conveyance unit again a plurality of times (for example, several hundred times) to obtain a transmission image, and it takes time to create the luminance conversion function.
[0006] In contrast, if, for example, the first and second transmission images used when the luminance conversion function was created in the previous instance are stored in the memory unit, the creation of the luminance conversion function can be completed in a relatively short time using the stored information and any additionally acquired first and second transmission images.
[0007] However, in this case, it is necessary to store a lot of information in the X-ray inspection device. In particular, if there are many different types of objects to be inspected, it is necessary to store a large amount of information in the X-ray inspection device. [Means for solving the problem]
[0008] An X-ray inspection apparatus according to a first aspect of the present invention comprises a transport unit, an X-ray source, a detection unit, a control unit, and a storage unit. The transport unit transports an object to be inspected. The X-ray source irradiates the object to be inspected with X-rays as it is transported by the transport unit. The detection unit detects X-rays of a first energy band and X-rays of a second energy band irradiated onto the object to be inspected. The control unit acquires a first transmission image based on the detection result of the X-rays of the first energy band and a second transmission image based on the detection result of the X-rays of the second energy band. The control unit corrects at least one of the first transmission image and the second transmission image based on a brightness conversion function, and after correction, inspects the object to be inspected based on a difference image obtained by performing subtraction processing using the first and second transmission images. The control unit acquires M first and second transmission images obtained by transporting the object to be inspected by the transport unit, and creates a first brightness conversion function as a brightness conversion function based on the acquired M first and second transmission images. The memory unit stores the first luminance conversion function. The control unit acquires N additional first and second transmission images obtained by transporting the object under inspection in the transport unit, and creates a second luminance conversion function based on the N additionally acquired first and second transmission images. The control unit combines the first luminance conversion function and the second luminance conversion function to create a third luminance conversion function as the luminance conversion function.
[0009] In the X-ray inspection device relating to the first aspect, a new brightness conversion function can be created in a relatively short time without having to store a large amount of data (image data or histogram data).
[0010] The X-ray inspection apparatus relating to the second perspective is the same as the X-ray inspection apparatus relating to the first perspective, and the control unit corrects at least one of the first and second brightness conversion functions based on the ratio of M sheets to N sheets when creating the third brightness conversion function.
[0011] In the X-ray inspection apparatus relating to the second aspect, the first and / or second brightness conversion function is corrected based on the amount of data used to create it, making it easier to obtain a third brightness conversion function with good performance.
[0012] The X-ray inspection device relating to the third viewpoint is an X-ray inspection device relating to the first or second viewpoint, where M is greater than N.
[0013] In X-ray inspection equipment related to the third perspective, a third brightness conversion function can be created in a relatively short time.
[0014] The X-ray inspection apparatus relating to the fourth viewpoint is an X-ray inspection apparatus relating to either the first viewpoint or the third viewpoint, wherein the object to be inspected used when creating the first brightness conversion function and the object to be inspected used when creating the second brightness conversion function are articles with the same characteristics.
[0015] In the X-ray inspection device relating to the fourth aspect, even if the first brightness conversion function is created with insufficient data, the brightness conversion function can be recreated in a relatively short time.
[0016] The X-ray inspection apparatus relating to the fifth viewpoint is an X-ray inspection apparatus relating to either the first viewpoint or the fourth viewpoint, wherein the object to be inspected used when creating the first brightness conversion function and the object to be inspected used when creating the second brightness conversion function differ in at least one of the following: shape, transport orientation, transport position, size, thickness, overlapping state of components, and composition of components.
[0017] In the X-ray inspection device relating to the fifth perspective, even if the first brightness conversion function is created with insufficient data types, the brightness conversion function can be recreated in a relatively short time.
[0018] The X-ray inspection apparatus relating to the sixth viewpoint is an X-ray inspection apparatus relating to either the first viewpoint or the fifth viewpoint, and the control unit determines the value of N based on the value of M.
[0019] In the X-ray inspection apparatus relating to the sixth perspective, the control unit determines how much additional data is needed, thus preventing any excess or deficiency in the amount of additional data.
[0020] The X-ray inspection apparatus relating to the seventh viewpoint is an X-ray inspection apparatus relating to either the first viewpoint or the sixth viewpoint, and the memory unit stores the first brightness conversion function and the value of M in association. The control unit weights at least one of the first brightness conversion function and the second brightness conversion function based on the ratio of M sheets to N sheets, and after weighting, combines the first brightness conversion function and the second brightness conversion function to create a third brightness conversion function.
[0021] In the X-ray inspection apparatus relating to the seventh aspect, the brightness conversion function is weighted according to the amount of data used to create it, resulting in a high-performance third brightness conversion function.
[0022] The X-ray inspection apparatus relating to the eighth viewpoint is the X-ray inspection apparatus relating to the seventh viewpoint, and the memory unit stores the created third brightness conversion function in association with the sum of the values of M and N.
[0023] In the X-ray inspection device relating to the eighth aspect, when revising the brightness conversion function, a weighting system based on the amount of data used in its creation can be applied to obtain a brightness conversion function with good performance.
[0024] The X-ray inspection apparatus relating to the ninth viewpoint is an X-ray inspection apparatus relating to either the first viewpoint or the eighth viewpoint, wherein the memory unit stores the third brightness conversion function created by the control unit while maintaining the memory of the first brightness conversion function.
[0025] In the X-ray inspection apparatus according to the ninth aspect, even after creating the third luminance conversion function, by storing the first luminance conversion function in the storage unit, when the third luminance conversion function is inappropriate, the first luminance conversion function can be used again to recreate the third luminance conversion function.
[0026] The X-ray inspection apparatus according to the tenth aspect is an X-ray inspection apparatus according to any one of the first to ninth aspects, and further includes a display unit. The control unit creates a first difference image obtained using the first luminance conversion function and a second difference image obtained using the third luminance conversion function for the same first transmission image and second transmission image, and causes the display unit to display the first difference image and the second difference image.
[0027] In the X-ray inspection apparatus according to the tenth aspect, it is possible to easily grasp whether the performance of the luminance conversion function has been improved.
Advantages of the Invention
[0028] In the X-ray inspection apparatus of the present invention, it is possible to review the luminance conversion function in a relatively short time without storing a large amount of data (image data and histogram data) in the storage unit.
Brief Description of the Drawings
[0029] [Figure 1] It is an external perspective view of an X-ray inspection apparatus according to an embodiment of the present invention. [Figure 2] It is a simplified configuration diagram inside the housing of the X-ray inspection apparatus of FIG. 1. [Figure 3] It is an example of a graph conceptually showing the amount of transmitted X-rays detected by the line sensor of the X-ray inspection apparatus of FIG. 1. [Figure 4] It is a block diagram of the X-ray inspection apparatus of FIG. 1. [Figure 5] It is a flowchart of a method for creating a third luminance conversion function according to an example by the X-ray inspection apparatus of FIG. 1.
Modes for Carrying Out the Invention
[0030] An X-ray inspection apparatus according to one embodiment of the present invention will be described with reference to the drawings. Note that the following embodiments are specific examples of the present invention and do not limit the technical scope of the present invention.
[0031] (1) Overall overview The X-ray inspection device 10 is a device that inspects an item P based on multiple transmission images (multiple transmission images based on the detection results of X-rays in different energy bands) obtained by irradiating the item P with X-rays. Although not limited to the content of the inspection, the X-ray inspection device 10 performs foreign matter inspection to check for the presence or absence of foreign matter in the item P. In addition, the X-ray inspection device 10 performs foreign matter inspection on multiple types of items P (items P1, P2, ... Pk).
[0032] The X-ray inspection device 10 is incorporated into, for example, a food production line. For example, the items (food) P to be inspected are transported to the X-ray inspection device 10 from an upstream process. The X-ray inspection device 10 inspects the transported items P and classifies them as good or defective. The results of the foreign object inspection by the X-ray inspection device 10 are transmitted to a sorting mechanism (not shown) located downstream of the X-ray inspection device 10. Items P classified as good are sent to the next process (for example, a boxing process), and items P classified as defective are sent to, for example, a defective product collection container.
[0033] (2) Detailed explanation As shown in Figures 1 to 4, the X-ray inspection apparatus 10 mainly comprises a housing 11, a conveyor 12, an X-ray irradiator 13, a first line sensor 14 and a second line sensor 15, a display 30, and a controller 20.
[0034] (2-1) Cabinet The housing 11 is a shielded box that houses the conveyor 12, the X-ray irradiator 13, the first line sensor 14, the second line sensor 15, and the controller 20. A display 30 and various switches (not shown) are located on the upper front of the housing 11.
[0035] Openings 11a (see Figure 1) for loading and unloading articles P are formed on the upstream and downstream sides of the housing 11 in the conveying direction D (see Figure 2) of the conveyor 12.
[0036] (2-2) Conveyor The conveyor 12 is an example of a conveying section that transports an item P as the object to be transported. The conveyor 12 is positioned to pass through both openings 11a of the housing 11.
[0037] (2-3)X-ray irradiator The X-ray irradiator 13 is an example of an X-ray source. The X-ray irradiator 13 irradiates X-rays onto the item P being transported by the conveyor 12. As shown in Figure 2, the X-ray irradiator 13 is positioned above the conveyor 12. The X-ray irradiator 13 irradiates X-rays into a fan-shaped irradiation range Y toward the line sensors 14 and 15 positioned below the conveyor 12. As shown in Figure 2, the irradiation range Y of the X-ray irradiator 13 extends perpendicular to the transport surface of the conveyor 12 and spreads in a direction perpendicular to the transport direction D of the conveyor 12 (the width direction of the conveyor belt 12).
[0038] (2-4) Line Sensor Line sensors 14 and 15 are examples of detection units. Line sensors 14 and 15 detect X-rays irradiated from the X-ray irradiator 13 that have passed through the item P and the conveyor belt 12. The first line sensor 14 and the second line sensor 15 are sensors that detect X-rays of different energy bands (wavelengths). The first line sensor 14 detects X-rays in the first energy band (low energy band with relatively long wavelengths), and the second line sensor 15 detects X-rays in the second energy band (high energy band with relatively short wavelengths).
[0039] In this embodiment, as shown in Figure 2, the second line sensor 15 is arranged vertically below the first line sensor 14. Of the X-rays irradiated from the X-ray irradiator 13, X-rays in the first energy band are detected by the first line sensor 14. Of the X-rays that have passed through the first line sensor 14, the intermediate energy band (X-rays in the energy band between the high energy band and the low energy band) is removed by a filter (not shown) placed between the first line sensor 14 and the second line sensor 15. X-rays in the second energy band that have passed through the filter are detected by the second line sensor 15. The first line sensor 14 is mainly composed of a large number of X-ray detection elements 14a (see Figure 2). The second line sensor 15 is mainly composed of a large number of X-ray detection elements 15a (see Figure 2). The X-ray detection elements 14a and 15a are installed horizontally and in a straight line in a direction perpendicular to the conveying direction D of the conveyor 12. Line sensors 14 and 15 detect the amount of X-rays transmitted through the item P or conveyor 12 (transmitted X-ray dose) for X-rays in their respective target energy bands, and output an X-ray transmission signal based on the transmitted X-ray dose (intensity of transmitted X-rays). The brightness (luminance) of the first transmission image, described later, is determined based on the X-ray transmission signal output by the first line sensor 14, and the brightness of the second transmission image, described later, is determined based on the X-ray transmission signal output by the second line sensor 15. In the transmission images (first and second transmission images), areas with a high transmitted X-ray dose are displayed brightly, and areas with a low transmitted X-ray dose are displayed darkly.
[0040] Figure 3 is a graph showing an example of the transmitted X-ray quantity detected by the X-ray detection elements 14a and 15a. Because there are two line sensors 14 and 15 detecting X-rays in different energy bands, a graph of the detection result of the first line sensor 14 (solid line G1) and a graph of the detection result of the second line sensor 15 (dashed line G2) can be obtained. In the graph in Figure 3, the horizontal axis corresponds to the position of each X-ray detection element 14a and 15a (position in the width direction of the conveyor belt 12), and the vertical axis shows the transmitted X-ray quantity (detected amount) detected by the X-ray detection elements 14a and 15a. It is not always necessary to provide two line sensors; for example, a single direct-conversion type line sensor capable of detecting X-rays using a photon counting method may be used. A direct-conversion type line sensor is, for example, a multi-energy sensor that detects X-rays in multiple energy ranges passing through an object, and includes photon detection type sensors such as CdTe semiconductor detectors. In this line sensor, for example, electron-hole pairs are generated when X-ray photons arrive. The generation of this electron-hole pair allows for the detection of energy (photon energy).
[0041] (2-5) Display The display 30 is a liquid crystal display with touch panel functionality. The display 30 is electrically connected to the controller 20 and exchanges signals with the controller 20.
[0042] The display 30 functions as both a display unit and an input unit. The display 30 displays, for example, transparent images or the results of foreign object inspection. The display 30 also accepts various settings and information input from the operator.
[0043] (2-6) Controller As shown in Figure 4, the controller 20 is electrically connected to the conveyor 12, the X-ray irradiator 13, the first line sensor 14, the second line sensor 15, and the display 30.
[0044] The controller 20 controls the operation of each part of the X-ray inspection device 10. The controller 20 also performs foreign object inspection based on the detection results of the X-ray transmission amount from the line sensors 14 and 15.
[0045] The controller 20 mainly comprises a processor including a CPU, auxiliary storage devices such as ROM, RAM, and flash memory, a display control circuit that controls the data display on the display 30, a key input circuit that captures key input data entered by the operator via the display 30, and a communication port that enables connection to external devices and networks such as LANs. As shown in Figure 5, the controller 20 functions as a storage unit 21 and a control unit 22.
[0046] (2-6-1) Storage section The memory unit 21 is composed of ROM, RAM, auxiliary devices, etc., and stores various programs executed by the processor, which functions as the control unit 22, and various settings for controlling each part of the X-ray inspection device 10. The memory unit 21 also stores data transmitted from the line sensors 14 and 15, and calculated values based on this data. The memory unit 21 includes a brightness conversion function storage area 21a. Brightness conversion functions, which will be described later, are stored in the brightness conversion function storage area 21a. Note that different brightness conversion functions are stored in the brightness conversion function storage area 21a for each object to be handled (items P1, P2, ..., Pk). In addition, multiple brightness conversion functions may be stored in the brightness conversion function storage area 21a for each object (items P1, P2, ..., Pk). The information stored in the brightness conversion function storage area 21a will be explained together in the description of the creation unit 22d, which will be described later.
[0047] (2-6-2) Control Unit The processor, acting as the control unit 22, functions as a first image generation unit 22a, a second image generation unit 22b, an inspection unit 22c, and a creation unit 22d.
[0048] (2-6-2-1) Image generation unit The first image generation unit 22a generates a first transmission image (low-energy transmission image) based on the amount of transmitted X-rays in the first energy band detected by the first line sensor 14. The second image generation unit 22b generates a second transmission image (low-energy transmission image) based on the amount of transmitted X-rays in the second energy band detected by the second line sensor 15. Specifically, the first image generation unit 22a acquires X-ray transmission signals corresponding to the intensity of X-rays transmitted through the object P, etc., output from each X-ray detection element 14a of the first line sensor 14 at fine time intervals, and generates a first transmission image based on the acquired X-ray transmission signals. The first image generation unit 22a generates a first transmission image by concatenating the data on the intensity of X-rays obtained from each X-ray detection element 14a at fine time intervals in a matrix in a time series. The second image generation unit 22b is the same as the first image generation unit 22a except that it uses the X-ray transmission signals output from each X-ray detection element 15a of the second line sensor 15, so a detailed explanation is omitted.
[0049] (2-6-2-2) Inspection Department The inspection unit 22c determines whether or not foreign matter is present in the item P based on the first and second transmission images. Specifically, the inspection unit 22c performs the following processing: When the inspection unit 22c acquires the first and second transmission images of the item P to be inspected, it corrects the brightness of the second transmission image using the brightness conversion function for that item P stored in the brightness conversion function storage area 21a. The brightness conversion function will be described later. In fact, the inspection unit 22c also performs processing such as sizing the first and second transmission images (see Patent Document 1 (JP 2012-73056)), but this will not be explained here. Next, the inspection unit 22c performs subtraction processing using the first transmission image and the second transmission image corrected by the brightness conversion function (referred to as the corrected second transmission image) to generate a difference image. Subtraction processing is a process that takes the difference between the brightness of each pixel (referred to as the first pixel) in the first transmission image and the brightness of the corresponding pixel (referred to as the second pixel) in the corrected second transmission image (based on the X-rays that passed through the item P and conveyor 12 at the position corresponding to each first pixel). Subtraction processing here is a process of dividing one of the brightness values of each first pixel and the brightness value of the corresponding second pixel by the other. The difference image is an image in which pixels have brightness values based on the difference value (division value) between each first pixel and its corresponding second pixel. If there is no foreign matter mixed in the item P, the brightness values of each pixel in the difference image will be approximately the same value (brightness value indicating the background). If there is foreign matter mixed in the item P, a difference will occur between the brightness value of the first transmission image and the brightness value of the corrected second transmission image at the position corresponding to the foreign matter. The inspection unit 22c inspects for the presence of foreign matter in the item P based on the difference in the difference image due to the presence or absence of foreign matter. The inspection results from the inspection unit 22c are displayed on the display 30. The inspection results from the inspection unit 22c are also transmitted to, for example, a sorting mechanism located downstream of the X-ray inspection device 10.
[0050] (2-6-2-3) Luminance Conversion Function Creation Section The creation unit 22d creates a brightness conversion function for each object (for each item P1, P2, ..., Pk). As described above, the brightness conversion function is information used by the inspection unit 22c to correct the brightness of each pixel in the second transmission image. Alternatively, or in addition to the brightness conversion function, the inspection unit 22c may use information to correct the brightness of each pixel in the first transmission image.
[0051] First, let's explain the luminance conversion function. As mentioned above, the inspection unit 22c performs foreign object inspection of item P based on the difference image obtained by subtraction processing between the first transmission image and the corrected second transmission image. Subtraction processing, simply put, is the process of roughly eliminating the presence of item P from the difference image (erasing item P). To achieve this, if item P does not contain foreign objects, it is required that the luminance value of each first pixel in the first transmission image, which was used to determine the luminance of each pixel in the region of item P in the difference image, and the luminance value of the second pixel in the corrected second transmission image corresponding to each first pixel, be approximately the same. Normally, there is a difference between the absorption rate of the first energy band and the absorption rate of the second energy band of item P, so the luminance conversion function is a function that makes the luminance of each first pixel and the luminance of the second pixel corresponding to each first pixel approximately the same. The creation unit 22d has two types of creation modes for the luminance conversion function. Here, one creation mode is called the new creation mode, and the other creation mode is called the synthesis mode. The New Creation mode is used to create a luminance conversion function from the first and second transparency images of a newly acquired item P. The Synthesis mode is used to create a new luminance conversion function by combining multiple previously created luminance conversion functions.
[0052] <New creation mode> The new creation mode is used, for example, when a luminance conversion function does not exist for a certain item P (here, the symbol of the item in the luminance conversion function is referred to as "Pα"), or when a luminance conversion function is stored in the storage unit 21 for item Pα, but it needs to be revised. In the new creation mode, the creation unit 22d creates a luminance conversion function using, for example, the method for creating a luminance conversion table described in Patent Document 1 (Japanese Patent Application Publication No. 2012-73056). An overview is provided below.
[0053] If no luminance conversion function exists for an item Pα (i.e., the luminance conversion function for item Pα is not stored in the storage unit 21), the item Pα, which is known to be free of foreign matter, is transported on the conveyor 12 multiple times (for example, M times (where M is a positive integer)). The value of M may be a predetermined value, or it may be determined as appropriate by the worker performing the task of creating the luminance conversion function. The same item Pα may be transported on the conveyor 12 multiple times, or different items of the same type Pα may be transported multiple times. If the items Pα are not uniform and there are individual differences, it is preferable that items Pα with different shapes, sizes, thicknesses, overlapping states of components, and component compositions (weight ratios of each component) are transported on the conveyor 12. Furthermore, it is preferable that the item Pα is transported on the conveyor 12 with changes in transport posture and transport position (the position of the item P on the conveyor 12 belt in the width direction).
[0054] Furthermore, a luminance conversion function (referred to as the existing luminance conversion function) for item Pα is stored in the memory unit 21. However, if it is desired to revise the existing luminance conversion function, item Pα, which is known to be free of foreign matter, is transported on the conveyor 12 multiple times (for example, N times (where N is a positive integer)). Preferably, N is a value smaller than M. The value of N may be a predetermined value, or it may be determined as appropriate by the worker performing the task of creating the luminance conversion function. Alternatively, the control unit 22 may determine the value of N based on the number of first and second transmission images (value of M) used to create the first luminance conversion function. Although not limited to this, for example, the control unit 22 may determine the value of N as 1 / 5 of the value of M and request the worker via the display 30 to transport item Pα on the conveyor 12 N times. The value of N may be determined, for example, statistically.
[0055] If an existing brightness conversion function is stored in the memory unit 21, the conveyor 12 may transport, for example, an item Pα with the same characteristics (substantially identical) as the item Pα used when creating the existing brightness conversion function. Furthermore, if the items Pα are not uniform and there are individual differences, the conveyor 12 may transport an item P that differs from the item Pα used when creating the existing brightness conversion function in terms of shape, size, thickness, overlapping state of components, composition of components (weight ratio of each component), etc. For example, if a foreign object inspection for a thick item Pα is causing false detections, the conveyor 12 may transport a thick item Pα. In addition, the conveyor 12 may transport the item Pα with a different transport posture and transport position (the position of the item Pα in the width direction of the conveyor belt 12) than when the existing brightness conversion function was created.
[0056] In new creation mode, the creation unit 22d receives detection results from line sensors 14 and 15 each time item Pα is transported on the conveyor 12 in the manner described above, and based on the detection results, acquires a first transmission image based on the detection results of X-rays in the first energy band and a second transmission image based on the detection results of X-rays in the second energy band. The creation unit 22d acquires M first and second transmission images if no brightness conversion function exists for item Pα, and N first and second transmission images if an existing brightness conversion function for item Pα is stored in the storage unit 21.
[0057] Next, the creation unit 22d uses data from multiple first transmission images to create a histogram of the first energy band showing the luminance distribution of multiple first transmission images, and uses data from multiple second transmission images to create a histogram of the second energy band showing the luminance distribution of multiple second transmission images. Furthermore, the control unit 22 integrates the histogram of the first energy band to calculate the histogram integral curve for the first energy band, and integrates the histogram of the second energy band to calculate the histogram integral curve for the second energy band. Then, the control unit 22 compares the histogram integral curve for the first energy band and the histogram integral curve for the second energy band to create a luminance conversion function that matches or approximates the histogram integral curve for the first energy band. Specifically, the luminance conversion function is obtained by finding the luminance conversion ratio I2 / I1 for each luminance such that the integrated value I2 of the histogram integral curve for the second energy band matches the integrated value I1 of the histogram integral curve for the first energy band. A more detailed method for creating a luminance conversion function is described in Patent Document 1 (Japanese Patent Application Publication No. 2012-73056).
[0058] The creation unit 22d stores the luminance conversion function created in the new creation mode in the luminance conversion function storage area 21a of the storage unit 21, associating it with the information of the number of first and second transparent images used during creation. The luminance conversion function is a table that associates the luminance values of the second transparent image with the multiplier values multiplied by the luminance values of the second transparent image to match the luminance values of each pixel in the second transparent image with the luminance values of the corresponding pixels in the first transparent image. However, the format of the luminance conversion function is not limited as long as it indicates what value to correct the luminance of each pixel in the second transparent image to.
[0059] <Composition Mode> The synthesis mode is a mode for creating a brightness conversion function used when it becomes necessary to revise the brightness conversion function for item Pα. A revision of the brightness conversion function becomes necessary, for example, when the creation unit 22d generates a difference image and the item Pα is not properly erased in the difference image (for example, specifically when a false detection occurs in foreign object inspection). Another reason for revising the brightness conversion function is, for example, when item Pα is an agricultural product, and even for the same type of item Pα, the characteristics of item Pα change depending on the season or place of origin.
[0060] If the brightness conversion function needs to be revised, and a new brightness conversion function is created from scratch in new creation mode, it will be necessary to transport the object to be inspected on the conveyor belt 12 hundreds of times again to acquire the first and second transmission images. In particular, if there are individual differences in the item Pα, and the shape, size, thickness, overlapping state of components, composition of components (weight ratio of each component), etc. differ from one item to another, a very large number of first and second transmission images may be required.
[0061] In contrast, in synthesis mode, the creation unit 22d utilizes a luminance conversion function created based on, for example, M first and second transmission images, which has the advantage of reducing the time required to create the luminance conversion function. Furthermore, the size of the luminance conversion function data is considerably smaller than the size of the data for the first and second transmission images used to create the luminance conversion function, as well as the size of the histogram data for the first and second transmission images. Therefore, the size of the data that needs to be stored in the storage unit 21 for execution of synthesis mode is considerably smaller than the size of the data that needs to be stored when creating the luminance conversion function in new creation mode, which is an advantage.
[0062] An example of a method for creating a luminance conversion function using such a synthesis mode will be explained with reference to the flowchart in Figure 5.
[0063] For example, if the creation unit 22d needs to revise the brightness conversion function, it will switch to a new creation mode to obtain new data, transport the item P on the conveyor belt 12, and acquire N additional first and second transparency images (the item P is transported on the conveyor belt 12 N times, and the first and second transparency images are acquired each time) (step S1).
[0064] Next, the creation unit 22d creates a luminance conversion function (hereinafter referred to as the second luminance conversion function) based on the N additionally acquired first and second transmission images (step S2).
[0065] Subsequently, the creation unit 22d, using the synthesis mode, synthesizes the previously used luminance conversion function (hereinafter referred to as the first luminance conversion function) with the second luminance conversion function created based on N first and second transmission images to create a new luminance conversion function (hereinafter referred to as the third luminance conversion function). Here, the first luminance conversion function is a luminance conversion function stored in the luminance conversion function storage area 21a of the storage unit 21, created based on M first and second transmission images (for example, the luminance conversion function initially created for item Pα). Note that the first luminance conversion function used for synthesis does not have to be the luminance conversion function initially created for item Pα; it may be a luminance conversion function that has already been revised (the luminance conversion function created in the synthesis mode last time).
[0066] Then, in synthesis mode, the creation unit 22d corrects at least one of the first luminance conversion function and the second luminance conversion function based on the ratio of M sheets to N sheets (step S3), and then synthesizes the first luminance conversion function and the second luminance conversion function to create a third luminance conversion function (step S4).
[0067] The processes in steps S3 and S4 will be explained with specific examples.
[0068] For example, suppose the first luminance conversion function is a luminance conversion function created based on 500 first and second transmission images, and the information is that the luminance value An (n=1~a) of a pixel in the second transmission image is multiplied by Xn (n=1~a). Suppose the second luminance conversion function is a luminance conversion function created based on 100 first and second transmission images, and the information is that the luminance value An (n=1~a) of a pixel in the second transmission image is multiplied by Yn (n=1~a).
[0069] In this example, the ratio of M sheets to N sheets is 5:1, and the first luminance conversion function is created based on five times the data of the second luminance conversion function.
[0070] The creation unit 22d corrects the first luminance conversion function based on the ratio of M images to N images. Specifically, the creation unit 22d multiplies the first luminance conversion function by M / N (5 times). Then, the creation unit 22d generates information as the third luminance conversion function that multiplies the luminance value An (n=1~a) of the pixels in the second transmission image by ((Xn × 5 (=500 / 100) + Yn) ÷ 6 (n=1~a). The reason for dividing by 6 here is that simply multiplying the first luminance conversion function by 5 and adding the second luminance conversion function would result in a value that is too large.
[0071] In other words, in steps S3 and S4, the creation unit 22d weights at least one of the first and second luminance conversion functions based on the ratio (5:1) of the value of M to the value of N, and after weighting, combines the first and second luminance conversion functions to create a third luminance conversion function. By using this creation method, when reviewing the luminance conversion function, it is possible to create a third luminance conversion function with good performance (where the image of object Pα is easily erased from the difference image) based on M+N (600) first and second transparency images by acquiring only N (100 in this case) first and second transparency images.
[0072] When the creation unit 22d creates the third luminance conversion function in the manner described above, it associates the created third luminance conversion function with the sum of the values of M and N, and stores it in the luminance conversion function storage area 21a of the storage unit 21 as a luminance conversion function for item Pα (step S5).
[0073] Furthermore, it is preferable that the first luminance conversion function, which has been previously associated with the value of M and stored in the luminance conversion function storage area 21a of the storage unit 21, remains stored in the storage unit 21 without being erased for at least a predetermined period. Also, when the creation unit 22d creates the third luminance conversion function in the manner described above, the second luminance conversion function may also be stored in the luminance conversion function storage area 21a of the storage unit 21 as a luminance conversion function for item Pα, as shown in step S6. In this way, by storing the first luminance conversion function and the second luminance conversion function in the storage unit 21, even if the amount of data of the transparent image used to create the second luminance conversion function is small, or if the performance of the third luminance conversion function is not as good as that of the first luminance conversion function, the third luminance conversion function can be created again using the first and second luminance conversion functions. When the third luminance conversion function is created, the control unit 22 (particularly the inspection unit 22c) may create a first difference image obtained using the first luminance conversion function (the luminance conversion function used until now) and a second difference image obtained using the newly created third luminance conversion function for the same first and second transmission images, and display the first and second difference images on the display 30. The first and second difference images may be displayed side by side on the same screen, or they may be displayed in response to operations on the display 30. With this configuration, the operator reviewing the luminance conversion function can understand whether the third luminance conversion function has improved performance compared to the first luminance conversion function. In this configuration, the operator may be able to select whether or not to use the third luminance conversion function from the touch panel display 30 in the future. If the decision is made not to use it, the third luminance conversion function may be recreated again using the creation unit 22d. Furthermore, if the operator agrees to use the created third luminance conversion function, the control unit 22 may erase the first and second luminance conversion functions from the storage unit 21 to reduce the amount of data. In addition, the storage unit 21 may retain all or part of the luminance conversion functions created for item Pα (for example, excluding luminance conversion functions that clearly do not provide the desired performance) without erasing them.
[0074] Furthermore, the creation unit 22d may create not just one, but multiple third luminance conversion functions (using different second luminance conversion functions) for the item Pα, and store all of them in the storage unit 21. Then, for example, an operator may determine which luminance conversion function to use for the inspection unit 22c based on the difference image of each third luminance conversion function displayed on the display 30. The third luminance conversion functions that were not selected may be deleted from the storage unit 21 or retained in the storage unit 21.
[0075] (3) Features The X-ray inspection apparatus 10 includes a conveyor 12 as an example of a transport unit, an X-ray irradiator 13 as an example of an X-ray source, line sensors 14 and 15 as examples of detection units, a control unit 22, and a storage unit 21. The conveyor 12 transports an item P. The X-ray irradiator 13 irradiates the item P being transported by the conveyor 12 with X-rays. The line sensors 14 and 15 detect X-rays of a first energy band and X-rays of a second energy band irradiated onto the item P. The control unit 22 acquires a first transmission image based on the detection result of the X-rays of the first energy band and a second transmission image based on the detection result of the X-rays of the second energy band. The control unit 22 corrects at least one of the first and second transmission images based on a brightness conversion function, and after correction, inspects the item P based on a difference image obtained by performing subtraction processing using the first and second transmission images. The control unit 22 acquires M first and second transparent images obtained by transporting the item P on the conveyor belt 12, and creates a first brightness conversion function as a brightness conversion function based on the acquired M first and second transparent images. The storage unit 21 stores the first brightness conversion function. The control unit 22 acquires N additional first and second transparent images obtained by transporting the item P on the conveyor belt 12, and creates a second brightness conversion function based on the additional N first and second transparent images. The control unit 22 combines the first brightness conversion function and the second brightness conversion function to create a third brightness conversion function as a brightness conversion function.
[0076] In the X-ray inspection device 10, a third brightness conversion function is created by combining a pre-existing first brightness conversion function with a second brightness conversion function created based on additionally acquired first and second transmission images. Therefore, a new brightness conversion function can be created in a relatively short time without having to store a large amount of data (image data or histogram data of the transmission images).
[0077] In the X-ray inspection apparatus 10, the control unit 22 corrects at least one of the first and second brightness conversion functions based on the ratio of M images to N images when creating the third brightness conversion function. With this configuration, the first and / or second brightness conversion functions are corrected based on the amount of data used for creation, making it easier to obtain a third brightness conversion function with good performance. It is preferable that the value of M is greater than the value of N. In this case, a relatively small number of additional transmission images can be acquired, so the third brightness conversion function can be created in a relatively short time. In addition, in the X-ray inspection apparatus 10, the control unit 22 may determine the value of N based on the value of M. With this configuration, it is possible to suppress an excess or deficiency in the amount of additional data.
[0078] In the X-ray inspection apparatus 10, the item P used when creating the first brightness conversion function and the item P used when creating the second brightness conversion function may be items with the same characteristics. With this configuration, missing data can be supplemented and the third brightness conversion function can be created in a relatively short time. Furthermore, in the X-ray inspection apparatus 10, the item P used when creating the first brightness conversion function and the item P used when creating the second brightness conversion function may differ in at least one of the following: shape, transport orientation, transport position, size, thickness, overlapping state of components, and composition of components. With this configuration, missing data can be supplemented and the third brightness conversion function can be created in a relatively short time.
[0079] In the X-ray inspection apparatus 10, the memory unit 21 stores the first brightness conversion function and the value of M in association. The control unit 22 weights at least one of the first brightness conversion function and the second brightness conversion function based on the ratio of M sheets to N sheets, and after weighting, combines the first brightness conversion function and the second brightness conversion function to create a third brightness conversion function. Here, a third brightness conversion function with good performance is obtained.
[0080] In the X-ray inspection apparatus 10, the memory unit 21 may store the created third brightness conversion function in association with the sum of the values of M and N. With this configuration, when reviewing the brightness conversion function (when reviewing the third brightness conversion function), a high-performance brightness conversion function can be obtained by weighting it according to the amount of data used in its creation. Alternatively, in the X-ray inspection apparatus 10, the memory unit 21 may store the third brightness conversion function created by the control unit 22 while maintaining the memory of the first brightness conversion function (for at least a predetermined period). With this configuration, if the third brightness conversion function is not appropriate (if the data used to create the second brightness conversion function is not appropriate), the brightness conversion function can be reviewed again using the first brightness conversion function (the third brightness conversion function can be recreated).
[0081] In the X-ray inspection apparatus 10, the control unit 22 may create a first difference image obtained using a first brightness conversion function and a second difference image obtained using a third brightness conversion function for the same first and second transmission images, and display the first and second difference images on the display 30. With this configuration, the operator can easily understand whether the performance of the brightness conversion function has been improved by reviewing the brightness conversion function.
[0082] (4) Variations The following are modifications of the above embodiment. These modifications may be combined with other modifications to the extent that they do not contradict each other.
[0083] (4-1) Variation A In the above embodiment, when creating the third luminance conversion function, the first luminance conversion function and the second luminance conversion function are corrected (weighted) based on the ratio of M images (the number of first and second transmission images used to create the first luminance conversion function) to N images (the number of first and second transmission images used to create the second luminance conversion function). However, the method of creating the third luminance conversion function by the creation unit 22d is not limited to this method. For example, when reviewing the luminance conversion function, the factor that contributes most to improving the performance of the luminance conversion function may not be the number of transmission images used to create the luminance conversion function to be synthesized, but rather that the transmission images used to create the luminance conversion function to be synthesized were recently acquired. For example, if the object under inspection is an agricultural product whose characteristics change relatively large depending on the season, the newly generated second luminance conversion function may contribute more to improving the performance of the luminance conversion function than the first luminance conversion function that has been used until now. In such cases, the creation unit 22d may increase the weighting of the second luminance conversion function, and after weighting, combine the first luminance conversion function and the weighted second luminance conversion function to create a third luminance conversion function.
[0084] (4-2) Modification B In the above embodiment, the creation unit 22d combines two luminance conversion functions in the combination mode, but is not limited to this, and may combine three or more luminance conversion functions in the combination mode. [Explanation of symbols]
[0085] 10 X-ray inspection equipment 12. Conveyor (transport section) 13 X-ray irradiator (X-ray source) 14. First line sensor (detection unit) 15. Second line sensor (detection unit) 21 Memory section 22 Control Unit 30. Display (display unit, notification unit) P Article (object to be inspected) [Prior art documents] [Patent Documents]
[0086] [Patent Document 1] Japanese Patent Publication No. 2012-73056
Claims
1. A transport unit that transports the object to be inspected, An X-ray source that irradiates the object to be inspected, which is being transported by the transport unit, A detection unit for detecting X-rays in a first energy band and X-rays in a second energy band irradiated onto the object to be inspected, A control unit that acquires a first transmission image based on the detection results of X-rays in the first energy band and a second transmission image based on the detection results of X-rays in the second energy band, corrects at least one of the first transmission image and the second transmission image based on a brightness conversion function, and then performs subtraction processing using the first transmission image and the second transmission image to inspect the object under inspection based on the difference image obtained, Memory unit and, Equipped with, The control unit acquires M first and second transmission images by transporting the object to be inspected in the transport unit, and creates a first luminance conversion function as the luminance conversion function based on the M acquired first and second transmission images. The memory unit stores the first brightness conversion function, The control unit, The first and second transmission images, which are acquired by transporting the object to be inspected by the transport unit, are further acquired by N additional images, and a second luminance conversion function is created based on the N additionally acquired first and second transmission images. A third luminance conversion function is created by combining the first luminance conversion function and the second luminance conversion function. X-ray inspection equipment.
2. When creating the third brightness conversion function, the control unit corrects at least one of the first brightness conversion function and the second brightness conversion function based on the ratio of M sheets to N sheets. The X-ray inspection apparatus according to claim 1.
3. The above M is greater than the above N. The X-ray inspection apparatus according to claim 1 or 2.
4. The object under inspection used when creating the first luminance conversion function and the object under inspection used when creating the second luminance conversion function are articles with the same characteristics. The X-ray inspection apparatus according to claim 1 or 2.
5. The object under inspection used when creating the first luminance conversion function and the object under inspection used when creating the second luminance conversion function differ in at least one of the following: shape, transport orientation, transport position, size, thickness, overlapping state of components, and composition of components. The X-ray inspection apparatus according to claim 1 or 2.
6. The control unit determines the value of N based on the value of M. The X-ray inspection apparatus according to claim 1 or 2.
7. The storage unit stores the first brightness conversion function and the value of M in association with each other. The control unit weights at least one of the first luminance conversion function and the second luminance conversion function based on the ratio of the value of M and the value of N, and after weighting, combines the first luminance conversion function and the second luminance conversion function to create the third luminance conversion function. The X-ray inspection apparatus according to claim 1.
8. The storage unit stores the created third brightness conversion function in association with the sum of the value of M and the value of N. The X-ray inspection apparatus according to claim 7.
9. The memory unit maintains the memory of the first brightness conversion function while storing the third brightness conversion function created by the control unit. The X-ray inspection apparatus according to claim 1 or 2.
10. It also includes a display unit, The control unit creates a first difference image obtained using the first brightness conversion function and a second difference image obtained using the third brightness conversion function for the same first and second transparency images, and causes the display unit to display the first difference image and the second difference image. The X-ray inspection apparatus according to claim 1 or 2.