JP5558746B2 - X-ray image forming apparatus - Google Patents

Description

  The present invention relates to a low energy X-ray image forming apparatus.

  Conventionally, an apparatus for acquiring a transmission image of a subject using X-rays has been used. For example, Patent Document 1 below discloses an X-ray imaging apparatus that detects an X-ray transmitted through a subject by a CCD or the like and generates an X-ray image.

JP 2006-141729 A

  However, in the above conventional technique, since the X-ray is detected by the CCD, there is a problem that the CCD is deteriorated by the X-ray and cannot be used stably for a long time.

  Further, when a defect inspection of a packaging container or the like is performed, since the subject is thin, it is preferable to use low energy X-rays (soft X-rays) of less than 20 keV in order to obtain contrast. There is a problem that the X-ray image is noisy due to the influence of the printing ink layer formed on the surface and dust adhering to the surface of the subject.

  An object of the present invention is to provide a low-energy X-ray image forming apparatus capable of forming an X-ray image of a thin object with a low noise stably for a long time.

  In order to achieve the above object, the present invention provides a low energy X-ray image forming apparatus, a low energy X-ray irradiation means for irradiating a subject with a low energy X-ray of less than 20 keV, and a low energy that has passed through the subject. Electron amplifying means for generating electrons based on X-rays, amplifying the number of generated electrons, electron detecting means for detecting the number of electrons amplified by the electron amplifying means, and based on a detection result of the electron detecting means X-ray image forming means for forming an X-ray image of a subject.

  In the low energy X-ray image forming apparatus, the X-ray image forming unit obtains a difference between the standard X-ray image of the subject acquired in advance and the X-ray image of the subject, and the X-ray image is obtained from the difference value. It is characterized by forming.

  In the low energy X-ray image forming apparatus, the X-ray image forming unit detects the detection target substance from the detection result of the electron detection unit based on the X-ray absorption edge data of the detection target substance acquired in advance. The correction is performed to leave only the image of the detection target substance in the X-ray image.

  The low-energy X-ray image forming apparatus further includes a visible image capturing unit that captures a visible image of the subject, and the X-ray image forming unit captures the previously acquired standard visible image of the subject and the visible image capturing unit. A foreign object on the surface of the subject is detected from the visible image captured by the means, and the image of the surface foreign object is removed from the X-ray image.

  In the low energy X-ray image forming apparatus, the X-ray image forming unit removes the surface foreign matter from the X-ray image based on the attenuation amount of the low energy X-ray previously obtained for each size of the surface foreign matter. It is characterized by doing.

  The low-energy X-ray image forming apparatus further includes high-energy X-ray irradiation means for irradiating a subject with high-energy X-rays of 20 keV or higher, and the electronic amplification means, the electron detection means, and X-ray image formation Forming an X-ray image based on the high energy X-ray, and the high energy X-ray irradiation unit and the low energy X-ray irradiation unit irradiate the subject with X-rays from opposite directions. And

  According to the present invention, a low energy X-ray image can be formed stably for a long time. In addition, a low-energy X-ray image of a thin subject can be formed without noise such as printing ink or foreign matter.

It is a figure which shows the structural example of the low energy X-ray image forming apparatus concerning embodiment. It is a figure which shows the structural example of a gas electron amplifier and an electron detector. It is a figure which shows the example of the hardware constitutions of the computer which comprises X-ray image forming apparatus. 1 is a functional block diagram of an embodiment of an X-ray image forming apparatus. It is explanatory drawing of the example of correction | amendment operation | movement of an image correction part. FIG. 5 is a diagram illustrating an example of an X-ray absorption curve of a foreign object such as a metal when the object is present. It is explanatory drawing of the other example of correction | amendment operation | movement of an image correction part. It is a figure which shows the other structural example of the low energy X-ray image forming apparatus concerning embodiment.

  Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

  FIG. 1 shows a configuration example of a low energy X-ray image forming apparatus according to an embodiment. In FIG. 1, the low energy X-ray image forming apparatus includes an X-ray source 10, a gas electron amplifier 12, an electron detector 14, an X-ray image forming apparatus 16, and a visible image capturing apparatus 17. This low-energy X-ray image forming apparatus can be used to inspect the presence of cracks, foreign matters, etc. in the subject that is the target of the formation of the energy X-ray image, but the application is not limited thereto. Absent.

  The X-ray source 10 is a device that generates low energy X-rays of less than 20 keV and irradiates the subject 100, and a conventionally known X-ray irradiation device can be used.

  The gas electron amplifier 12 is a device that amplifies the number of electrons generated by X-rays transmitted through the subject 100. The gas electronic amplifier 12 includes a chamber filled with a predetermined detection gas and an electrode provided in the chamber for generating an electric field for accelerating the generated electrons, and X-rays are detected from the detection gas. Electrons generated in the chamber are amplified by charge multiplication by the electron avalanche effect. A configuration example of the gas electronic amplifier 12 will be described later.

  The electron detector 14 detects the number of electrons amplified by the gas electron amplifier 12. The electron detector 14 can be configured to detect the number of electrons amplified by a method of directly detecting charges or a method of detecting scintillation light.

  The X-ray image forming apparatus 16 is configured by an appropriate computer, and forms a low energy X-ray image (low energy X-ray transmission image) of the subject 100 based on the detection result of the number of electrons by the electron detector 14. .

  The visible image capturing device 17 is configured by an appropriate camera and captures a visible image (still image or moving image) of the subject 100. Image information of the subject 100 captured by the visible image capturing device 17 is output to the X-ray image forming device 16.

  Note that the subject 100 is a target on which an X-ray image is formed by the low energy X-ray image forming apparatus according to the embodiment, and inspection of internal defects, foreign matters, and the like are performed. For example, various packaging materials used for pharmaceuticals, cosmetics, foods, and the like can be given. These types of packaging materials include those commonly used such as laminated tubes, laminated film packaging, PTP packaging, SP packaging, and double-sided aluminum PTP packaging. Other packaging materials that can be inspected for defects, foreign matter, and the like by the present apparatus are included in the subject 100.

FIG. 2 shows a configuration example of the gas electron amplifier 12 and the electron detector 14. In FIG. 2, the gas electron amplifier 12 is configured such that a drift region 20 that generates primary electrons and an electron amplification plate 22 are disposed between a drift electrode 18 and an electron detector 14. The electronic amplifying plate 22 functions as a gas electronic amplifier that performs charge multiplication by an electron avalanche effect, and includes a plate-like insulating layer 24 and planar conductor layers 26 and 28 coated on both surfaces of the plate-like insulating layer 24. It consists of The electronic amplifying plate 22 is formed with a plurality of through holes 30 for focusing the electric field. The chamber 32 that accommodates these components is filled with a predetermined detection gas. As the detection gas, a combination of rare gas and quencher gas is generally used. Examples of the rare gas include He, Ne, Ar, and Xe. In addition, examples of the quencher gas include CO ₂ , CH ₄ , C ₂ H ₆ , and CF ₄ .

  In such a radiation detector, a predetermined voltage is applied from the power supply unit 34 to the conductor layers 26 and 28 and the drift electrode 18. As a result, an electric field for moving electrons from the drift electrode 18 toward the electron detector 14 is formed in the chamber 32 via the electron amplification plate 22. When radiation enters from the drift electrode 18 side in this state, primary electrons are generated by releasing electrons from atoms in the detection gas by photoelectric effect, Compton scattering, electron pair generation, or the like. The generated primary electrons ionize the detection gas in the drift region 20 between the drift electrode 18 and the electron amplifying plate 22, and the electrons generated at that time move toward the electron detector 14 by the electric field (two). Next electron). The secondary electrons approaching the electron amplification plate 22 are further accelerated by the electric field focused in the through hole 30 and avalanche amplification occurs. The excited charges generated thereby are collected by the electron detector 14 and a detection signal is output.

  FIG. 3 shows an example of a hardware configuration of a computer constituting the X-ray image forming apparatus 16. 3, the X-ray image forming apparatus 16 includes a central processing unit (for example, a CPU such as a microprocessor can be used) 36, a random access memory (RAM) 38, a read only memory (ROM) 40, and an input device 42. , A display device 44, a communication device 46, and a storage device 48, and these components are connected to each other by a bus 50. The input device 42, the display device 44, the communication device 46, and the storage device 48 are connected to the bus 50 via the input / output interfaces 52, respectively.

  The CPU 36 controls the operation of each unit described later based on a control program stored in the RAM 38 or the ROM 40. The RAM 38 mainly functions as a work area for the CPU 36, and the ROM 40 stores a control program such as BIOS and other data used by the CPU 36.

  The input device 42 includes a keyboard, a pointing device, a touch panel, and the like, and is used by a user to input operation instructions and the like.

  The display device 44 is configured by a liquid crystal display or the like, and displays an X-ray image, a visible image, or the like of the subject 100.

  The communication device 46 includes a USB (Universal Serial Bus) port, a network port, and other appropriate interfaces, and is used by the CPU 36 to exchange data with an external device via communication means such as a network.

  The storage device 48 is a magnetic storage device such as a hard disk, and stores various data necessary for processing to be described later. As the storage device 48, a digital versatile disk (DVD), a compact disk (CD), a magneto-optical disk (MO), a flexible disk (FD), a magnetic tape, an electric erasure and rewritable can be used instead of a hard disk. A read-only memory (EEPROM), flash memory or the like may be used.

  FIG. 4 shows a functional block diagram of an embodiment of the X-ray image forming apparatus 16. 4, the X-ray image forming apparatus 16 includes a detection information acquisition unit 54, an X-ray image formation unit 56, a standard image acquisition unit 58, a difference calculation unit 60, an absorption edge detection unit 62, an image correction unit 64, and a visible image acquisition. The unit 66 and the attenuation amount data acquisition unit 68 are included, and these functions are realized by, for example, the CPU 36 and a program for controlling the processing operation of the CPU 36.

  The detection information acquisition unit 54 acquires information on the number of electrons detected by the electron detector 14 via the communication device 46. This information can be obtained by connecting the electron detector 14 shown in FIG. 2 with, for example, a USB.

  The X-ray image forming unit 56 forms a low energy X-ray image (low energy X-ray transmission image) of the subject 100 based on the information on the number of electrons acquired by the detection information acquiring unit 54. In this case, the X-ray image can be formed by a method such as determining the density (pixel value) of the image according to the number of electrons, but the method of forming the X-ray image is not limited to this. The low energy X-ray image formed by the X-ray image forming unit 56 is displayed on the display device 44.

  The standard image acquisition unit 58 acquires standard X-ray image data of the subject 100 stored in the storage device 48 in advance. The standard X-ray image is a low-energy X-ray image of the subject 100 having no defects such as cracks or foreign matter (dust) inside and no foreign matter attached to the surface. However, when printing using ink or the like is performed on the subject 100, it is a low-energy X-ray image acquired in a state where the printing exists.

  The difference calculation unit 60 calculates the difference between the low energy X-ray image formed by the X-ray image forming unit 56 and the standard X-ray image acquired by the standard image acquisition unit 58. The calculation result is output to the image correction unit 64 to correct the X-ray image.

  The absorption edge detection unit 62 detects an X-ray absorption edge of a metal or other foreign substance existing inside the subject 100. In this case, the X-ray source 10 is configured to perform X-ray irradiation while continuously changing the intensity of energy in the energy range near the absorption edge of the foreign substance that is the detection target substance. The absorption edge detector 62 monitors the transition of the number of electrons detected by the electron detector 14 in the energy range, and detects the absorption edge from the change in the X-ray absorption rate or transmittance. In this case, by storing the absorption edge data of each substance that becomes a foreign substance in the storage device 48, the absorption edge detection unit 62 specifies the type of the foreign substance from the detected energy (absorption peak position) of the absorption edge. It is good also as a structure. In this example, the X-ray absorption edge data is stored in advance in the storage device 48 for each detection target substance, and the energy level of the low-energy X-ray irradiated from the X-ray source 10 based on this data. It is set as the structure which controls this.

  The image correcting unit 64 corrects the low energy X-ray image formed by the X-ray image forming unit 56. For example, based on the calculation result of the difference received from the difference calculation unit 60, noise (image of the printing ink layer) of the printing ink layer existing on the low energy X-ray image is removed, and the low energy inside the subject 100 is removed. Correction to X-ray image is performed. Further, the image correction unit 64 performs correction to leave only the image of the detection target substance on the low energy X-ray image based on the data of the absorption end of the detection target substance detected by the absorption end detection unit 62. Further, the image correction unit 64 detects surface foreign matter existing on the surface of the subject 100 based on the visible image information of the subject 100 acquired by the visible image acquisition unit 66, removes the surface foreign matter from the low energy X-ray image, Correction is performed to obtain a low-energy X-ray image inside the subject 100. In the visible image, only the surface foreign matter existing on the surface of the subject 100 is shown, and the foreign matter inside the subject 100 is not shown. Therefore, the foreign matter existing in the visible image can be determined as the surface foreign matter. Further, the image correction unit 64 performs correction based on the attenuation amount data of the foreign matter acquired by the attenuation amount data acquisition unit 68, assuming that there is no X-ray attenuation corresponding to the surface foreign matter on the low energy X-ray image. This correction can be performed by a method such as adding the number of electrons corresponding to the attenuation amount to the information on the number of electrons acquired by the detection information acquisition unit 54. Thereby, a surface foreign material can be removed from a low energy X-ray image. An example of the operation of the image correction unit 64 will be described later.

  The visible image acquisition unit 66 acquires visible image information of the subject 100 captured by the visible image capturing device 17. The acquired visible image information is output to the image correction unit 64. Note that the visible image acquired by the visible image acquisition unit 66 is also preferably displayed on the display device 44.

  The attenuation amount data acquisition unit 68 acquires from the storage device 48 the low energy X-ray attenuation amount data obtained in advance for each size of the foreign matter existing on the surface of the subject 100 and stored in the storage device 48. The acquired attenuation amount data is output to the image correction unit 64. Whether or not a foreign object exists on the surface of the subject 100 is detected from the visible image information of the subject 100.

  5A, 5B, 5C, 5D, and 5E are explanatory diagrams of examples of the correction operation of the image correction unit 64. FIG. This example is an example of a correction operation when a printing ink layer is present on the surface of the subject 100.

  FIG. 5A is a standard X-ray image of the subject 100 acquired by the standard image acquisition unit 58. The letter “A” is printed on the surface of the subject 100. FIG. 5B is a cross-sectional view of the subject 100. In FIG. 5B, the ink layer A that forms the letter “A” exists on the surface of the subject 100, and there is no defect such as a crack or foreign matter inside the subject 100.

  On the other hand, FIG. 5C is a low energy X-ray image of the subject 100 formed by the X-ray image forming unit 56. In this low-energy X-ray image, an image of printing (ink layer) of the letter “A” on the surface of the subject 100 and an image of the foreign object α existing inside the subject 100 are shown. FIG. 5D is a cross-sectional view of the subject 100, and shows that the ink layer A that forms the letter “A” exists on the surface of the subject 100, and foreign matter exists inside the subject 100. .

  The difference calculation unit 60 calculates the difference between the standard X-ray image shown in FIG. 5A and the low energy X-ray image shown in FIG. As a result, the ink layer image of the letter “A”, which is a common part between the standard X-ray image and the low-energy X-ray image, is removed. The image correction unit 64 corrects the low energy X-ray image to an image obtained by removing the image of the printing ink layer of the character “A” based on the difference calculation result. Thereby, a low energy X-ray image inside the subject 100 shown in FIG. 5E is formed. As a result, the low-energy X-ray image forming apparatus according to the embodiment can detect defects and foreign matters inside the subject.

  FIG. 6 shows an example of an X-ray absorption curve of a foreign object such as metal when the object 100 is present. In FIG. 6, the horizontal axis is the energy of low energy X-rays irradiated from the X-ray source 10 to the subject 100, and as described above, the energy in the energy range near the known absorption edge of the foreign substance that is the detection target substance. The strength changes continuously. The vertical axis represents the transmittance of the subject 100 of X-rays.

  In the example of FIG. 6, an X-ray absorption curve of a printing ink layer (denoted as C) and an X-ray absorption curve of iron (denoted as Fe) that is a foreign substance are shown. As shown in FIG. 6, iron has an absorption edge AE, but the ink layer has no absorption edge. Therefore, the absorption edge detection unit 62 can detect the presence of foreign matter from the position of the absorption edge AE. The image correction unit 64 can determine from the absorption edge data detected by the absorption edge detection unit 62 that the object 100 includes foreign matter in addition to the ink layer. Therefore, the image correction unit 64 performs correction for removing the image of the ink layer while leaving only the foreign object image in the low energy X-ray image. In this case, since the position of the foreign matter can be determined as the position where the low energy X-ray was irradiated when the absorption edge appeared, the ink from the low energy X-ray image including the images of both the ink layer and the foreign matter can be used. Only the image of the layer can be removed. In addition, since the kind of foreign material can be determined from the peak value of the absorption edge or the like, it can be determined whether or not the image left in the low energy X-ray image is a foreign material image. By this correction, a low energy X-ray image inside the subject 100 can be formed, and defects and foreign matters inside the subject can be detected.

  FIGS. 7A, 7B, 7C, and 7D are explanatory diagrams of other examples of the correction operation of the image correction unit 64. FIG. This example is an example of a correction operation when a foreign object is present on the surface of the subject 100.

  FIG. 7A is a low-energy X-ray image of the subject 100 formed by the X-ray image forming unit 56. This low energy X-ray image includes an image of the foreign object α existing inside the subject 100 and an image of the foreign matter β present on the surface of the subject 100. FIG. 7B is a cross-sectional view of the subject 100, and shows that the foreign object α exists inside the subject 100 and the foreign object β exists on the surface of the subject 100.

  On the other hand, FIG. 7C shows visible image information of the subject 100 captured by the visible image capturing device 17. The visible image information includes an image of the foreign matter β present on the surface of the subject 100, but does not show the foreign matter α inside the subject 100. Therefore, the image correction unit 64 determines that the foreign matter β shown in the visible image information is a surface foreign matter existing on the surface of the subject 100, and corrects it to an image obtained by removing the image of the foreign matter β from the low energy X-ray image. . Thus, a low energy X-ray image inside the subject 100 shown in FIG. 7D is formed. As a result, the low-energy X-ray image forming apparatus according to the embodiment can detect defects and foreign matters inside the subject.

  In order to remove the image of the foreign matter β from the low energy X-ray image, the image correction unit 64 obtains the position and size of the foreign matter β in the visible image information, for example, and the low energy X corresponding to the position and size. The pixel value of the image of the region in the line image is corrected to a value when there is no attenuation by the X-ray foreign matter. Alternatively, the attenuation amount data acquisition unit 68 uses the low energy X-ray attenuation amount data acquired from the storage device 48, obtains the attenuation amount based on the foreign matter β determined to be a surface foreign matter from the visible image information, and corresponds to this attenuation amount. This may be performed by adding the number of electrons to be added to the information on the number of electrons acquired by the detection information acquisition unit 54.

  FIG. 8 shows another configuration example of the low-energy X-ray image forming apparatus according to the embodiment, and the same elements as those in FIG. In FIG. 8, a high energy X-ray source 70 that irradiates the subject 100 with high energy X-rays of 20 keV or higher is added to the configuration of FIG. 1, and the subject 100 is irradiated with the high energy X-ray source 70. The transmitted high-energy X-ray is detected by the electron detector 74 via the gas electron amplifier 72. The gas electron amplifier 72 and the electron detector 74 have the same configuration as that of the gas electron amplifier 12 and the electron detector 14. The gas electron amplifier 72 and the electron detector 74 convert X-rays into an electron flow and then amplify them. The intensity is detected.

  A characteristic point in FIG. 8 is that the low-energy X-ray source 10 and the high-energy X-ray source 70 irradiate the subject 100 with X-rays from opposite directions that are parallel to each other. Thereby, the interference phenomenon in which the X-rays emitted from the mutual X-ray sources 10 and 70 are detected by the other electron detectors 74 and 14 can be avoided. As a result, the distance between the mutual X-ray sources 10 and 70 and the mutual electron detectors 74 and 14 can be reduced, and the apparatus can be miniaturized.

  Further, in the example shown in FIG. 8, by irradiating the subject 100 with high energy X-rays of 20 keV or higher, low energy of less than 20 keV such as a thick portion of the subject 100 and a material portion that hardly transmits X-rays. It is possible to inspect parts that are difficult to observe with X-rays.

  10 X-ray source, 12 Gas electron amplifier, 14 Electron detector, 16 X-ray image forming device, 17 Visible image photographing device, 18 Drift electrode, 20 Drift region, 22 Electronic amplification plate, 24 Plate-like insulating layer, 26, 28 Conductor layer, 30 through hole, 32 chamber, 34 power supply, 36 CPU, 38 RAM, 40 ROM, 42 input device, 44 display device, 46 communication device, 48 storage device, 50 bus, 52 input / output interface, 54 detection information Acquisition unit, 56 X-ray image forming unit, 58 Standard image acquisition unit, 60 Difference calculation unit, 62 Absorption edge detection unit, 64 Image correction unit, 66 Visible image acquisition unit, 68 Attenuation data acquisition unit, 70 High energy X-ray Source, 72 Gas electronic amplifier, 74 Electron detector, 100 Subject.

Claims (5)

X-ray irradiation means for irradiating a subject with low energy X-rays of less than 20 keV ;
Electron amplifying means for generating electrons based on the low energy X-rays passing through the subject and amplifying the number of generated electrons;
An electron detection means for detecting the number of electrons amplified by the electron amplification means;
X-ray image forming means for forming an X-ray image of the subject based on the detection result of the electronic detection means;
Visible image capturing means for capturing a visible image of the subject;
With
The X-ray image forming unit detects a foreign matter on the surface of the subject from the standard visible image of the subject acquired in advance and the visible image taken by the visible image photographing unit, and removes the image of the surface foreign matter from the X-ray image. An X-ray image forming apparatus.   2. The X-ray image forming apparatus according to claim 1, wherein the X-ray image forming unit obtains a difference between the standard X-ray image of the subject acquired in advance and the X-ray image of the subject, and uses the difference value to obtain an X-ray image. Forming an X-ray image forming apparatus. The X-ray image forming apparatus according to claim 1 or 2,
The X-ray irradiation means performs X-ray irradiation while continuously changing the intensity of energy in the energy range near the absorption edge of the detection target substance,
An absorption edge detection unit for monitoring the transition of the number of electrons detected by the electron detection means in the energy range and detecting the detection target substance by detecting an absorption edge from a change in the absorption rate or transmittance of X-rays; Prepared,
The X-ray image forming unit detects the detection target substance from the detection result of the absorption end detection unit based on the X-ray absorption end data of the detection target substance acquired in advance, and the X-ray image shows the detection target substance. An X-ray image forming apparatus, wherein correction is performed to leave only an image.   4. The X-ray image forming apparatus according to claim 1, wherein the X-ray image forming unit is configured to generate an X-ray image based on an X-ray attenuation obtained in advance for each size of the surface foreign matter. An X-ray image forming apparatus, wherein the surface foreign matter is removed from the X-ray image forming apparatus. High X-ray imaging apparatus according to any one of claims 1 to 4, further, the high-energy X-ray irradiation means for irradiating the above high-energy X-ray 20keV to the subject, it has passed through the subject An electron amplifying unit that generates electrons based on the energy X-rays and amplifies the number of generated electrons, and forms an X-ray image based on the high-energy X-rays by the electron detecting unit and the X-ray image forming unit. An X-ray image forming apparatus, wherein the high energy X-ray irradiation unit and the X- ray irradiation unit irradiate the subject with X-rays from opposite directions.

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