WO2019064632A1 - Dispositif d'imagerie par rayons x et procédé de traitement d'image pour élément d'imagerie par rayons x - Google Patents

Dispositif d'imagerie par rayons x et procédé de traitement d'image pour élément d'imagerie par rayons x Download PDF

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WO2019064632A1
WO2019064632A1 PCT/JP2018/008420 JP2018008420W WO2019064632A1 WO 2019064632 A1 WO2019064632 A1 WO 2019064632A1 JP 2018008420 W JP2018008420 W JP 2018008420W WO 2019064632 A1 WO2019064632 A1 WO 2019064632A1
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light receiving
ray
pixel
receiving element
ray imaging
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PCT/JP2018/008420
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English (en)
Japanese (ja)
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桜井　健次
文洋 趙
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国立研究開発法人物質・材料研究機構
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Priority to JP2019544217A priority Critical patent/JPWO2019064632A1/ja
Publication of WO2019064632A1 publication Critical patent/WO2019064632A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/22—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material
    • G01N23/223—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material by irradiating the sample with X-rays or gamma-rays and by measuring X-ray fluorescence
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/24—Measuring radiation intensity with semiconductor detectors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/36—Measuring spectral distribution of X-rays or of nuclear radiation spectrometry

Definitions

  • the present invention relates to an X-ray imaging apparatus using a CCD imaging device, a CMOS imaging device or a semiconductor pixel radiation detector, and more specifically, a general purpose CCD imaging device for visible light or a CMOS imaging device, or a semiconductor pixel radiation detector
  • An X-ray imaging apparatus such as a fluorescent X-ray analyzer using the
  • the present invention also relates to an image processing method of an X-ray imaging device using a CCD imaging device, a CMOS imaging device, or a semiconductor pixel radiation detector.
  • Substances are composed of various elements, and their composition greatly affects their physical and chemical properties. For this reason, it is important to analyze the types and amounts of contained elements in order to understand substances and develop new materials. It is known that the type of an element is known from the energy of fluorescent X-rays emitted when the substance is irradiated with X-rays, and the amount is known from its intensity (Patent Documents 1 and 2). In order to perform this fluorescent X-ray analysis, a dedicated X-ray spectrometer and an X-ray detector are required together with the X-ray source.
  • Charge-coupled device (CCD) cameras usually have a very large active sensor area of more than 150 mm 2 .
  • Conventional CCD cameras are designed to record visible light images in a variety of applications, including scientific and industrial fields.
  • the quantum efficiency of the x-ray region is low due to the thin depletion of the CCD camera, but can also work in the x-ray wavelength region. Since the 1980's, advanced x-ray cameras such as pnCCD have been developed for astronomy. Since the thickness of the depletion layer is typically several hundred ⁇ m, the quantum efficiency of the X-ray region (1 to 10 keV) can be 90% or more.
  • the present invention solves the above-mentioned problems, and can separate X-ray energy information individually by processing the X-ray photon event occurring in a CCD image sensor, a CMOS image sensor or a semiconductor pixel radiation detector.
  • An object of the present invention is to provide an X-ray imaging apparatus capable of obtaining precise imaging pixel information.
  • Another object of the present invention is X-ray imaging suitable for utilizing a CCD imaging device or a CMOS imaging device designed for visible light wavelength, or a semiconductor pixel radiation detector as an imaging device of a large area X-ray spectrometer It is providing a device.
  • the X-ray imaging apparatus of the present invention is an X-ray imaging device (8) that receives an energy beam containing X-ray photons from an analysis object (5) as shown in, for example, FIG. 1 and FIG. 2A.
  • the X-ray imaging device has the two-dimensional arrangement of the unit light receiving devices (82) and the peripheral light receiving device (84) around the unit light receiving devices that causes charge sharing due to light reception of the X-ray photons.
  • An X-ray imaging device The light reception signal from the X-ray imaging device is read for each unit light receiving device, and an X-ray image of the analysis object captured according to the two-dimensional arrangement of the unit light receiving device in the X-ray imaging device An X-ray image generation circuit (10) to generate;
  • the X-ray image generation circuit 10 an effective event determination circuit (102) comparing the light reception signal read for each unit light receiving element and a first threshold value as a reference for recognizing an effective photon event; With respect to the peripheral light receiving element of the unit light receiving element recognized as an effective photon event by the effective event judging circuit, the light receiving signal read by the peripheral light receiving element is compared with a second threshold serving as a reference for recognizing noise.
  • a noise removing circuit (104) and a pixel for performing counting such that the pixel-by-pixel counter value of the X-ray image generating circuit (10) is incremented by 1 with respect to unit light receiving elements recognized as effective photon events without being removed by the noise removing circuit.
  • the peripheral light receiving element of the unit light receiving element recognized as a valid photon event and recognized by the valid event judging circuit (102) Isolated pixel extraction in which the light receiving signal of all the peripheral light receiving elements is compared with the first threshold and the unit light receiving element whose light receiving signal of all the peripheral light receiving elements is less than the first threshold is extracted as an isolated pixel
  • the noise removal circuit (104) has a circuit (103), and is a unit light receiving element recognized as a valid photon event and recognized by the valid event determination circuit (102), and the noise removal circuit (104) comprises the isolated pixel extraction circuit (103).
  • the peripheral light receiving element of the unit light receiving element extracted as an isolated pixel is characterized by comparing the light receiving signal read by the peripheral light receiving element with a second threshold value.
  • an X-ray imaging device (8) which receives an energy beam containing X-ray photons from an analysis object (5).
  • the X-ray imaging device has the two-dimensional arrangement of the unit light receiving devices (82) and the peripheral light receiving device (84) around the unit light receiving devices that causes charge sharing due to light reception of the X-ray photons.
  • An X-ray imaging device The light reception signal from the X-ray imaging device is read for each unit light receiving device, and an X-ray image of the analysis object captured according to the two-dimensional arrangement of the unit light receiving device in the X-ray imaging device And an X-ray image generation circuit (10) to generate The X-ray image generation circuit 10, an effective event determination circuit (102) comparing the light reception signal read for each unit light receiving element and a first threshold value as a reference for recognizing an effective photon event; With respect to the peripheral light receiving element of the unit light receiving element recognized as an effective photon event by the effective event judging circuit (102), the light receiving signal read by the peripheral light receiving element is compared with the first threshold value.
  • a charge division detection circuit (107) for detecting whether charge division has occurred between the unit light receiving element and the peripheral light receiving element; a unit light receiving element having charge division detected by the charge division detection circuit (107); Charge division processing circuit (108) for calculating median value, integral value and position information of peripheral light receiving elements for all light receiving elements exceeding the first threshold, and charge division processing circuit 108) counting the count value of the pixel-by-pixel counter corresponding to all the light receiving elements exceeding the first threshold value, using the median value, integral value and position information thereof calculated in 108). And an X-ray counter image generation circuit (108) for generating an X-ray image by the X-ray imaging device (8) based on the count value of the pixel-by-pixel counter circuit (106). It is characterized by
  • the X-ray imaging device (8) is a CCD imaging device, a CMOS imaging device, or a semiconductor pixel radiation detector.
  • the unit light receiving element (82) of the X-ray imaging element (8) has a two-dimensional area having a representative length of 1 to 10 ⁇ m as one pixel. It is good to do.
  • the first threshold is a value larger than background noise generated by each unit light receiving element (82) of the X-ray imaging element (8). Therefore, the value should be smaller than the energy level generated by the effective photon event.
  • the second threshold is a value larger than the background noise generated by each unit light receiving element (82) of the X-ray imaging element (8), and is a value smaller than the first threshold Good to have.
  • the peripheral light receiving element 84 is any of 3 ⁇ 3, 5 ⁇ 5 or 7 ⁇ 7 centered on the unit light receiving element (82) in which a photon event has occurred. It is good to have.
  • the energy level of the light receiving signal read for each unit light receiving element (82) of the X-ray image generation circuit (10) It is preferable to have an energy level determination circuit (105) for obtaining [10]
  • the pixel-by-pixel counter circuit of the X-ray image generation circuit (10) preferably corresponds to the energy level separated by the energy level determination circuit (105). It is good to be divided.
  • the pixel-by-pixel counter circuit of the X-ray image generation circuit (10) is an energy level of the light reception signal of the unit light receiving element (82) where a photon event occurred.
  • the energy levels of the light reception signals of the peripheral light reception elements (84) of the unit light reception element (82) may also be added.
  • the X-ray imaging apparatus of the present invention preferably further comprises an X-ray irradiation circuit that irradiates an energy beam containing X-rays to the object to be analyzed.
  • the X-ray imaging apparatus of the present invention further includes a pixel-by-pixel counter reset circuit that resets the pixel-by-pixel counter value of the X-ray image generation circuit (10).
  • the image processing method of the X-ray imaging device of the present invention is, for example, as shown in FIG. 5, FIG. 7A, and FIG. 7B, an X-ray imaging device that receives energy rays including X-ray photons from an analysis object.
  • An image processing method wherein the X-ray imaging device (8) has unit light receiving elements arranged in a two-dimensional arrangement, and the unit light receiving elements have a two-dimensional area which causes charge sharing by receiving the X-ray photons.
  • the light receiving signal read by the peripheral light receiving element is compared with the first threshold value, and the light receiving signals of all the peripheral light receiving elements are less than the first threshold value.
  • An isolated pixel extracting step (S200) for extracting a unit light receiving element as an isolated pixel, and the noise removing step (S300) is a unit light receiving element recognized as an effective photon event recognized in the effective event determining step (S100).
  • the light receiving signal of the unit light receiving element extracted as an isolated pixel in the isolated pixel extracting step (S200) is recognized as a light receiving signal read by the peripheral light receiving element and noise And comparing the second threshold value as a quasi.
  • a charge division processing step for calculating a median, an integral value, and position information thereof, and in the pixel-by-pixel counter step, the median, integral value calculated in the charge division processing step And the position information using, and performs counting to plus 1 the count value of the pixel-counter corresponding to all the light-receiving element exceeds the first threshold.
  • information on X-ray energy is obtained using a CCD imaging element, a CMOS imaging element or a semiconductor pixel radiation detector designed for visible light wavelength. Can be separated individually to obtain precise imaging pixel information.
  • a CCD imaging device, a CMOS imaging device, or a semiconductor pixel radiation detector can cope with a large-area X-ray spectrometer, the preconditions of spectral imaging can be established, and an X utilizing a CCD camera or a CMOS imaging device sufficiently. Line spectral imaging can be performed.
  • FIG. 2 is a block diagram of a configuration of a correction filtering circuit for isolated pixels, showing a first aspect of the present invention.
  • FIG. 7 is a block diagram of a correction filtering circuit for isolated pixels, which is a slight modification of the first aspect of the present invention.
  • FIG. 7 is a diagram specifically showing a method of obtaining X-ray energy (wavelength) from the brightness (charge amount) of the detected pixel, and particularly shows the X-ray imaging device and the distribution state of the charge amount.
  • FIG. 2 is a block diagram of a configuration of a correction filtering circuit for isolated pixels, showing a first aspect of the present invention.
  • FIG. 7 is a block diagram of a correction filtering circuit for isolated pixels, which is a slight modification of the first aspect of the present invention.
  • FIG. 7 is a diagram specifically showing a method of obtaining X-ray energy (wavelength) from the brightness (charge amount) of the detected pixel, and particularly shows the X-ray imaging device and the distribution state of the charge
  • FIG. 2 is a diagram specifically showing a method of obtaining X-ray energy (wavelength) from the brightness (charge amount) of a detected pixel, and particularly shows the charge amount and the count number. It is explanatory drawing about division (general charge division) of the electric charge which arose by the X-ray photon into several pixels. It is a flow chart explaining initial selection of a pixel which should be processed. It is a flowchart which shows the 1st type
  • FIG. 10 is a flow chart illustrating the strict threshold addition (second-order removal of the effect of charge division).
  • FIG. 17 illustrates the introduction of a strict threshold (secondary removal of the influence of charge division), showing the energy level of the threshold 120 for isolated pixel determination in the amount of charge.
  • FIG. 6 shows X-ray images by X-ray spectral energy using the method of strictly selecting and collecting the charges of isolated pixels (FIGS. 5 to 7B). It is an explanatory view showing a second type which is an object of the present invention and schematically showing a situation where charge division is the majority and no isolated pixel can be found. It is explanatory drawing of the calculation principle of the total charge amount including a surrounding pixel.
  • FIG. 6 is a block diagram of a correction filtering circuit for charge division, showing a second aspect of the present invention.
  • FIG. 10 shows X-ray images of different X-ray spectral energies using the method of correcting the influence of charge division (FIG. 9, 10) using the ratio of the median to the integral.
  • FIG. 10 is a block diagram of a configuration of a correction filtering circuit of a combined use type of isolated pixel and charge division showing a third aspect of the present invention. It is a principal part block diagram of the measuring apparatus for acquiring the X-ray image according to X-ray spectrum energy which shows the 2nd Example of this invention. It is explanatory drawing of the X-ray counter image by energy level produced
  • FIG. 1 is a schematic view of an X-ray analyzer showing an embodiment of the present invention.
  • the X-ray analyzer according to one embodiment of the present invention includes an X-ray tube 1, a crystal monochromator 2, a signal control mechanical shutter 3, a sample holder 4, a pinhole plate 6, and an X-ray camera 7.
  • the X-ray tube 1 is an electron tube for generating X-rays, and continuous X-rays are generated by colliding electrons generated by heating the filament (cathode) with a metal (target, anode) such as tungsten, molybdenum or copper. (Braking radiation) and characteristic X-rays are generated.
  • the monochromator 2 is also called a monochromator, and is a device for taking out only light of a specific wavelength from the light dispersed by a dispersion element such as a diffraction grating or a prism with a slit.
  • the monochromator includes, for example, an entrance slit, a collimator mirror, a dispersive element (diffraction grating or prism), a focusing mirror, and an exit slit.
  • graphite (002), 2d 6.72 ⁇ is used.
  • a curved graphite spectroscope (monochromator) is installed at a position in front of a detector to remove a diffraction line due to a CuK ⁇ ray.
  • a thin Ni foil filter may be used instead of the monochromator.
  • the signal control mechanical shutter 3 physically moves the shutter curtain, and in fact, it is necessary to block incident X-rays from being incident on the sample. Therefore, while using the same mechanism as the mechanical shutter for visible light, one using a material that can absorb X-rays and a thickness can be used, and UNIBLITZ (registered trademark) can be used, for example.
  • the necessity of the mechanical shutter is determined by the magnitude relationship between the actual imaging time and the time required to transfer the image. In the CCD sensor shown in Example 1 to be described later, the readout transfer time of one frame is affected, and the effective imaging time is different between the pixel at the beginning of reading and the pixel at the end of reading. In order to prevent this, it is necessary to stop the X-ray with a mechanical shutter. On the other hand, in the CMOS sensor of the second embodiment, since the readout is quick, the measurement is performed without using the mechanical shutter depending on the imaging time.
  • the sample holder 4 holds a sample 5 to be subjected to X-ray spectral analysis, and has, for example, a sample stage.
  • the sample 5 is a target of X-ray spectral analysis, and includes various test objects such as a metal material, an inorganic material, an organic material, and a biomaterial.
  • pinhole plates are used very often in XRF imaging.
  • the pinhole plate 6 is also referred to as a micro pinhole collimator and is used in the case of XRF imaging measurement.
  • the pinhole plate 6 is removed in non-imaging XRF spectrum measurement.
  • the X-ray camera 7 is provided with an imaging sensor 8.
  • the imaging sensor 8 is a two-dimensional semiconductor sensor, and for example, a CCD, a CMOS, or an X-ray pixel detector in which an element structure is specially formed is used.
  • the imaging sensor 8 has unit light receiving elements of a two-dimensional arrangement according to the number of pixels. For example, in the case where the number of pixels is 1,000,000, 1000 unit light receiving elements are two-dimensionally arranged in the vertical x horizontal directions. For example, when the imaging sensor 8 is 10 mm ⁇ 10 mm, each unit light receiving element has a size of 10 ⁇ m ⁇ 10 ⁇ m.
  • a CCD 47-10 which is a CCD sensor manufactured by e2V can be used.
  • the beam size at the sample position is about 1 mm (H), 5 mm (V).
  • the cooler 9 is used when the imaging sensor 8 is used in an X-ray application.
  • the cooling of the cooler 9 is generally electronic cooling by a Peltier element, but its exhaust heat needs to be removed by air cooling or water cooling.
  • air cooling a fan is used as the cooler 9.
  • water cooling the cooler 9 requires circulating cooling water.
  • FIG. 1 schematically shows the case of water cooling.
  • the cooling temperature is as wide as -50 ° C to 5 ° C depending on the sensor. Below 0 ° C., it is general to evacuate the area around the sensor to avoid freezing and the like.
  • a cooled CCD is used at -30.degree. C.
  • a CMOS camera is used at 5.degree.
  • the X-ray beam 101 a indicates that the X-ray generated by the X-ray tube 1 is irradiated to the sample 5 through the monochromator 2.
  • the X-ray beam 101a spreads horizontally on the sample 5, and the typical irradiation area is 10 mm ⁇ 5 mm.
  • Primary X-ray intensity is greater than 10 8 counts / sec.
  • the X-ray beam 101 b indicates one of the X-rays reflected on the sample 5 that passes through the pinhole plate 6 and the CCD sensor 7.
  • the operation of the device thus configured will now be described.
  • the X-ray beam 101 a strikes the sample at a low angle, the X-ray beam 101 a spreads horizontally on the sample 5.
  • a signal-controlled mechanical shutter 3 is placed in the beam path from the x-ray tube 1 to the sample 5.
  • the mechanical shutter 3 is open and allows the X-ray beam 101a to pass.
  • the mechanical shutter 3 is closed to shut off the X-ray beam 101a to avoid contamination on the camera image.
  • the X-ray beam 101 b reflected on the sample 5 is narrowed by the pinhole plate 6 and reaches the X-ray camera 7.
  • the centers of the sample holder 4, the pinhole plate 6, and the CCD sensor 7 are aligned.
  • the X-ray camera 7 can be moved back and forth in the optical axis direction, and may be provided with a position adjustment mechanism which can also be moved in a planar direction perpendicular to the optical axis.
  • the pixel detection signal received by the imaging sensor 8 is converted into an image signal by the X-ray image generation circuit 10.
  • FIG. 2A is a configuration block diagram of a correction filtering circuit for isolated pixels, showing the first aspect of the present invention.
  • the X-ray imaging device 8 receives energy beams including X-ray photons from the object to be analyzed 4 and has unit light receiving devices 82 in a two-dimensional arrangement.
  • a peripheral light receiving element 84 is generated around the unit light receiving element 82 to cause charge sharing due to the reception of the X-ray photon.
  • the peripheral light receiving element 84 may be any of 3 ⁇ 3, 5 ⁇ 5 or 7 ⁇ 7 centered on the unit light receiving element 82 in which the photon event has occurred.
  • the X-ray image generation circuit 10 reads the light reception signal from the X-ray imaging device 8 for each unit light receiving device, and picks up an image according to the two-dimensional arrangement of the unit light receiving device in the X-ray imaging device. It is generated as an X-ray image of the analyte.
  • the X-ray image generation circuit 10 includes an effective event determination circuit 102, an isolated pixel extraction circuit 103, a noise removal circuit 104, an energy level determination circuit 105, a pixel-by-pixel counter circuit 106, and an X-ray counter image generation circuit 109.
  • the components of the X-ray image generation circuit 10 may use hardware electronic circuits such as application specific integrated circuits for each of the components or may realize functions by computer software. FIG.
  • FIG. 2B shows a slight modification of the first aspect of the invention of FIG. 2A.
  • the pixel-by-pixel counter reset circuit 106 a is added below the pixel-by-pixel counter circuit 106.
  • the other configurations are the same, and thus redundant description will be omitted.
  • counting is performed to add 1 to the count value of the pixel-by-pixel counter corresponding to all light receiving elements exceeding the first threshold, but when the pixel to be measured is completed, the pixel-by-pixel counter
  • the pixel-by-pixel counter is reset by the reset circuit 106 a to end the pixel-by-pixel processing, and the X-ray counter image generation circuit 109 generates an image.
  • the valid event judging circuit 102 compares the light reception signal read for each unit light receiving element 82 with a first threshold value which is a reference for recognizing a valid photon event.
  • the first threshold is a value larger than the background noise generated in each unit light receiving element 82 of the X-ray imaging element 8 and smaller than the energy level generated in the effective photon event.
  • the first threshold is also called Lower Limit of Discrimination, and is used not only for CCD and CMOS sensors but also for signal processing circuits of any radiation detector. The purpose is to remove the kind of noise or dark current of the detector or the signal processing circuit that is also recognized when X-rays are not incident.
  • the signal is recognized only when the signal level is higher than the first threshold value, and the value of the luminance value (the brightness of the image, which corresponds to the charge amount generated by the X-ray) seen in the pixel is considered.
  • this luminance value corresponds to the information of X-ray energy, and in the aspect of elemental analysis, the information of elements.
  • the isolated pixel extraction circuit 103 detects the light receiving signal read by the peripheral light receiving element and the first threshold value for the peripheral light receiving element 84 of the unit light receiving element 82 recognized as an effective photon event by the effective event judging circuit 102. And the unit light receiving element 82 in which the light reception signals of all the peripheral light receiving elements 84 are equal to or less than the first threshold value is extracted as an isolated pixel.
  • the noise removing circuit 104 uses the light receiving signal read by the peripheral light receiving element 84 for the peripheral light receiving element 84 of the unit light receiving element 82 recognized as a valid photon event by the valid event judging circuit 102 and a reference for recognizing as noise. And a second threshold value.
  • the second threshold is a value larger than the background noise generated in each unit light receiving element 82 of the X-ray imaging device 8 and is a value smaller than the first threshold.
  • the energy level determination circuit 105 is also called a spectral circuit, and obtains the energy level of the light reception signal read from each unit light receiving element 82 of the X-ray image generation circuit 10.
  • the energy level is set, for example, to a value corresponding to an element to be analyzed, for example, a metal element such as calcium or chromium.
  • the energy level may have a region defined by the upper limit value and the lower limit value.
  • the pixel-by-pixel counter circuit 106 counts the pixel-by-pixel counter value of the X-ray image generation circuit 10 by 1 for unit light-receiving elements 82 that are not removed by the noise removal circuit 104 and are recognized as valid photon events.
  • the pixel-by-pixel counter circuit 106 is preferably divided according to the energy level separated by the energy level determination circuit 105, and the energy level of the light reception signal of the unit light receiving element 82 where a photon event has occurred.
  • the energy levels of the light reception signals of the peripheral light reception elements 84 of the unit light reception element 82 may also be added.
  • the X-ray counter image generation circuit 109 generates an X-ray image by the X-ray imaging device 8 based on the count value of the pixel-by-pixel counter circuit 106.
  • FIG. 16 is an explanatory diagram of an X-ray counter image by energy level generated by the X-ray counter image generation circuit, where (A1) is an element A image, (A2) is an element B image, and (A3) is an element C An image, (A4) represents an element D image, (B1) represents a region P spectrum, (B2) represents a region Q spectrum, and (B3) represents a region R spectrum.
  • the level of the brightness (charge amount I) of the (X, Y) pixel is in the range of X-ray photon energy corresponding to the element A ( AL ⁇ I ⁇ A H ) ,
  • the count of the (X, Y) position of the image of the A element is +1.
  • the count of the (X, Y) position of the image of the B element is incremented by 1 with respect to the X-ray photon energy range (B L ⁇ I ⁇ B H ) corresponding to the element B .
  • the count of the (X, Y) position of the image of the C element is incremented by 1 with respect to the X-ray photon energy range (C L ⁇ I ⁇ C H ) corresponding to the element C .
  • the count of the (X, Y) position of the D element image is incremented by +1. .
  • the photon event is displayed at the position of coordinate (X, Y) on FIG. 16 (A2). According to the region P spectrum shown in FIG.
  • X-ray photon energy E by the level of the brightness (charge amount I) of each pixel can be found for the (X, Y) region (or the entire region). That is, since the X-ray spectrum in the (X, Y) region is known, the count of the energy E of the spectrum of the region P spectral region is incremented by 1.
  • the region Q spectrum shown in FIG. 16 (B2) and the region R spectrum shown in FIG. 16 (B3) are also similar to the region P spectrum shown in FIG. 16 (B1).
  • the location of the brightness (charge amount) of the pixel corresponding to the photon event is +1 in the region Q spectrum in FIG. 16 (B2).
  • FIGS. 3A and 3B specifically show a method of obtaining X-ray energy (wavelength) from the brightness (charge amount) of the detected pixel
  • FIG. 3A shows the X-ray imaging device and the distribution state of the charge amount
  • FIG. 3B shows the charge amount and the count number.
  • the unit light receiving elements 110 are unit light receiving elements of the X-ray imaging element, and are two-dimensionally arranged.
  • the first threshold 112 is a value larger than background noise generated by the unit light receiving element 110 and smaller than an energy level generated by an effective photon event.
  • the noise equivalent signal 111 is such that the brightness (charge amount) of the pixel detected by the unit light receiving element 110 is lower than the first threshold 112.
  • the effective photon event signal 113 is such that the brightness (charge amount) of the pixel detected by the unit light receiving element 110 is higher than the first threshold 112.
  • the horizontal axis indicates the charge amount
  • the vertical axis indicates the count number.
  • the first threshold 115 is a threshold sufficiently larger than the amount of charge 117 at the level of dark current seen with or without X-ray irradiation.
  • the effective photon event signal 116 is a signal with a larger amount of charge than the first threshold 115, and can be summed to obtain information on the charge generated by the X-ray.
  • the amount of charge at the level of the dark current has a median value 118 of the dark current and has a noise width 119 with respect to the upper limit value of the actual dark current.
  • the imaging under the single photon counting condition is, in other words, imaging that is repeatedly and continuously performed imaging in a very short imaging time.
  • the imaging time is increased, the accumulated image becomes clear, but the meaning is that a large number of charges are accumulated in one pixel.
  • the imaging time is increased, the information of individual X-ray photons can not be known anymore, by which X-ray of X-ray photon energy produces the charge.
  • the X-ray energy can be determined by calculating the charge amount back.
  • FIG. 4 is an explanatory diagram of division of charge generated by X-ray photons into a plurality of pixels (general charge division, charge sharing).
  • an ordinary radiation detector semiconductor detector
  • the total charge amount 125 is shortened for a short time, as described in FIGS. 3A and 3B.
  • Energy analysis 122 can be measured.
  • the X-ray imaging device 124 is composed of a large number of unit image elements 123, the charge generated by one X-ray photon 121 does not necessarily go to one device.
  • FIG. 5 is a flowchart illustrating initial selection of pixels to be processed.
  • the initial selection (S100) of the pixel to be processed corresponds to the operation of the valid event determination circuit 102 of the X-ray image generation circuit 10.
  • the input data is a value recorded in all the pixels (unit light receiving elements) of the X-ray imaging device (S102).
  • the pixels (the unit light receiving elements 82) exceeding the first threshold (the lowest threshold) are sorted and counted (S104).
  • a histogram of charge amount (X-ray spectrum) is obtained (S106).
  • FIG. 6 shows a first type targeted by the present invention, and is a flow chart for explaining sorting of isolated pixels (first-order removal of the influence of charge division).
  • the selection of isolated pixels (S200) corresponds to the operation of the isolated pixel extraction circuit 103 of the X-ray image generation circuit 10.
  • the input image data is an X-ray image obtained by subtracting the background seen even when there is no X-ray (S202).
  • isolated pixels are selected (S204). That is, the peripheral pixels (peripheral light receiving element 84) of the pixel (unit light receiving element 82) for which a valid signal is recognized are checked to confirm that any peripheral pixels are equal to or less than the minimum threshold.
  • the output data is a histogram (X-ray spectrum) of the charge amount indicating the position of the isolated pixel and the charge amount (S206). That is, it is determined whether the pixel is an isolated pixel, and only the isolated pixel is selected. In this way, the influence of division of charge into multiple pixels in the X-ray spectrum is removed from the charge amount histogram.
  • X-ray spectrum X-ray spectrum
  • FIGS. 7A and 7B illustrate the introduction of a strict threshold (secondary removal of the influence of charge division), and FIG. 7A is a flowchart, and FIG. 7B is an energy of the threshold 120 for isolated pixel determination in charge amount. It shows the level.
  • the strict threshold addition (S300) corresponds to the operation of the noise removal circuit 104 of the X-ray image generation circuit 10.
  • the input image data is the position and charge amount of the isolated pixel (S302).
  • a threshold for isolated pixel determination (second threshold 120 shown in FIG. 7B) having a value smaller than the normally adopted minimum threshold is applied to pixels in the peripheral portion, and even one of the peripheral pixels is used. If there is something beyond this, the charge collection is regarded as incomplete and excluded (S304).
  • the output data is a histogram of charge (X-ray spectrum) indicating the position of the isolated pixel and the amount of charge, and the noise that is determined to be an incomplete charge collection noise due to the influence of charge division is removed.
  • the obtained data is obtained (S306).
  • the effective event determination circuit 102 and the isolated pixel extraction circuit 103 first search for an isolated pixel for determination.
  • the isolated pixel found has a luminance value larger than the first threshold, and eight pixels around the isolated pixel are smaller than the first threshold It is a matter of course from the definition of isolated pixels that the luminance value is obtained.
  • the noise removing circuit 104 imposes a more severe restriction on the peripheral eight pixels. It is a feature of the first type of the present invention.
  • the peripheral light receiving element 84 is adopted as an isolated pixel having eight effective peripheral pixels if it is smaller than the first threshold value but smaller than the more severe second threshold value, and if not applicable. , Charge division of the second type.
  • the (X, Y) pixel is a counter, and one is added to a specific point to brighten that point. Since the pixel-by-pixel counter in this case is in a position where it only needs to exceed the first threshold, it ignores the energy of the X-rays and gives an image incorporating all the X-ray spectra.
  • the energy level determination circuit 105 is used to determine whether the luminance value of the pixel is in the range corresponding to the specific X-ray energy. For example, in a CCD camera equipped with a 16-bit A / D converter, the brightness of a pixel of an image is expressed by an integer value between 0 and 65535.
  • the first threshold value Assuming that the brightness of the dark current level is 250, it is customary to set the first threshold value to, for example, 300 arbitrary values. Also, the second threshold is set, for example, between 250 and 300. Most X-ray signals have a level corresponding to an energy level much higher than the first threshold, and even a single photon has a value of, for example, about 800. At this time, the difference between X-ray energy and whether it was 600 or 800 is in the range of the characteristic value according to the element usually composed. Therefore, when creating an image of a specific element using the energy level determination circuit 105, for example, the setting is made to be 750 or more and 820 or less, and the luminance value is so at point (X, Y).
  • the (X, Y) point of the image of the element is added to 1. That is, when measuring, the image is only one image, but the image corresponding to the counter may be prepared and used independently for the number of elements to be focused and the type of X-ray energy focused on. it can.
  • FIG. 8 shows an X-ray image by X-ray spectral energy using the method of strictly selecting and collecting charges of isolated pixels (FIGS. 5 to 7 B), using the setup of FIG. There is.
  • FIG. 8 shows pinhole XRF imaging obtained at a spatial resolution of 20 ⁇ m
  • FIG. 8 (a) shows a photograph of the inspection object, and the observation area is indicated by a dashed square.
  • FIG. 8 (b) shows the obtained XRF spectrum.
  • the imaging results of Ca in the substrate and Cr of the black pattern are shown in FIGS. 8 (c) and 8 (d), respectively. Cr bars at 20 ⁇ m intervals are clearly distinguished.
  • the X-ray tube 1 is a sealed X-ray tube, and a copper target (TOSHIBA A26L-Cu, 1.5 kW) is used.
  • Characteristic X-rays generated from the copper target include K ⁇ rays of about 1.54 ⁇ and K ⁇ rays of 1.38 ⁇ .
  • the K ⁇ line is a mixture of the K ⁇ 1 line with a peak wavelength of 1.5406 ⁇ and the K ⁇ 2 line with 1.5444 ⁇ at an intensity ratio of 2: 1, but since the two peaks are in close proximity, a standard powder diffractometer The specification is to detect both without distinguishing them.
  • a tungsten foil having a thickness of 20 ⁇ m to 50 ⁇ m and a hole of 5 ⁇ m to 100 ⁇ m in diameter is used by a UV laser. Having a spatial resolution of more than 20 ⁇ m can be visualized directly, for example by testing a standard resolution target. Because pinholes have advantages such as low cost, easy adjustment, and energy dependence, obtaining high spatial resolution with pinholes is important to expand the application of full field of view XRF imaging.
  • the X-ray camera 7 is combined with the collimator of the micro pinhole plate 6 for full field of view XRF imaging to achieve a spatial resolution better than 20 ⁇ m. This result can be directly visualized without mathematical expression or model fitting.
  • the test object is a black chromium pattern coated on a transparent glass substrate [Fig. 8 (a)].
  • the thickness of the chromium layer is 1000 ⁇ .
  • the chrome bars are distributed equidistantly at 1 mm intervals, and the individual widths are equal to the respective intervals.
  • the numbers above indicate the number of bars in each group.
  • the distance from the target to the pinhole is 2 mm, so the magnification for pinhole imaging is 7.
  • the observation area is 1.9 mm ⁇ 1.9 mm, and is shown by the dashed square in FIG. 8 (a).
  • the separation of the central observed bar is 20 ⁇ m.
  • the spectrum can identify calcium and chromium peaks.
  • calcium is inferred from the glass substrate.
  • the glass substrate may contain other elements such as silicon and sodium. Since the fluorescent X-ray is strongly absorbed by the CCD window material, it can not be detected this time.
  • the calcium image [FIG. 8 (c)] and the chromium image [FIG. 8 (d)] are drawn by the signals in the regions (regions of interest) of each peak.
  • the XRF intensity distribution is homogeneous, indicating that calcium is uniformly distributed in the glass substrate.
  • the surface-coated chromium pattern does not leave a shadow on the calcium image, since the chromium layer is so thin as 1000 ⁇ thick.
  • the X-ray transmission of CaK ⁇ and K ⁇ is higher than 99.99%.
  • Chromium images can clearly distinguish chromium bars with a separation of 20 ⁇ m, indicating that the spatial resolution is better than 20 ⁇ m.
  • two black vertical lines are observed. They are due to linearly arranged dead pixels on the CCD sensor chip and do not affect the signals of other pixels.
  • the e2V CCD sensor used as the imaging sensor 8 in the first embodiment it takes 4 to 5 seconds to read and transfer one frame (a catalog data reading speed of 0.25 frame / second). Assuming that X-rays have been received for 4 to 5 seconds, there is a difference in effective imaging time between the reading start pixel and the reading end pixel, and the reading end pixel is the reading start pixel. As compared to the image, it took 4 to 5 seconds extra. In order to prevent this, it is necessary to stop the X-ray with a mechanical shutter. Some CCD sensors have a built-in mechanism for temporarily storing charge information to avoid such problems.
  • the temporary storage mechanism is such that an area of the same size as the area used for imaging is provided next to it, transferred at a speed on the order of microseconds (referred to as frame transfer), and then read out.
  • the area that is the transfer destination of the frame transfer is outside the opening of the X-ray window in order to shield the X-ray from hitting.
  • FIG. 9 shows a second type of object of the present invention, and is an explanatory view schematically showing a situation where charge division is the majority and isolated pixels can not be found.
  • the unit light receiving elements 155 are unit light receiving elements of the X-ray imaging element 156 and are two-dimensionally arranged.
  • the lowest threshold is also applied to one or more pixels around it (see FIG. A charge above the first threshold 115) shown in 3B is observed.
  • the charge division is remarkable, and the charge corresponding to the energy of the X-ray photon 151 is divided into a plurality of pixels.
  • the amount of charge generated by the X-ray photons 151 can be regarded as the sum of the peripheral portions of the largest unit light receiving element 152, for example, 25 pixels of 5 ⁇ 5.
  • the total charge amount for 25 pixels is equivalent to one pixel of the light receiving element 152.
  • FIG. 10 is an explanatory diagram of a method of determining what form of charge division should be numerically adopted in the situation shown in FIG.
  • the charges generated by the x-ray photons are distributed not only in one isolated pixel but in the periphery. That is, it extends around the largest unit light receiving element 161 (x, y: for example, about 5 pixels square).
  • the sum of the charge amounts in the wide area pixels gives information on the charge amount generated by the X-ray photon, that is, the energy of the X-ray.
  • the X-ray detection position should be regarded as 161 points.
  • FIG. 11 is a block diagram of a correction filtering circuit for charge division, showing a second aspect of the present invention. Note that, in FIG. 11, the same reference numerals are given to components having the same function as those of FIG. 2A, and the description will be omitted.
  • the X-ray image generation circuit 20 includes an effective event determination circuit 102, an energy level determination circuit 105, a pixel-by-pixel counter circuit 106, a charge division detection circuit 107, an X-ray counter image generation circuit 108, and an X-ray counter image generation circuit 109.
  • the charge division detection circuit 107 detects the light receiving signal read by the peripheral light receiving element 84 for the peripheral light receiving element 84 of the unit light receiving element 82 recognized as being recognized as a valid photon event by the effective event judging circuit 102; The threshold is compared to detect whether charge division occurs between the unit light receiving element 82 and the peripheral light receiving element 84.
  • the charge division processing circuit 108 calculates the median value of all light receiving elements exceeding the first threshold value for the unit light receiving element 82 and the peripheral light receiving element 84 in which charge division has occurred and detected by the charge division detection circuit 107. , Integral value and its position information are calculated.
  • the X-ray counter image generation circuit 109 generates an X-ray image by the X-ray imaging device 8 based on the count value of the pixel-by-pixel counter circuit 106.
  • the pixel-by-pixel counter circuit 106 uses the median, integral value, and position information thereof calculated by the charge division processing circuit 108. Then, counting is performed such that the count value of the pixel-by-pixel counter corresponding to all the light receiving elements exceeding the first threshold value is incremented by one.
  • FIG. 12 is an explanatory diagram of the sorting process of the pixel information in the case where the charge division is remarkable.
  • the sorting process of pixel information (S400) in the case where the charge division is remarkable corresponds to the operation of the charge division detection circuit 107 and the X-ray counter image generation circuit 108 of the X-ray image generation circuit 10.
  • the input image data exceeds the lowest threshold (first threshold 115 shown in FIG. 3B) for determining X-ray incidence / detection itself.
  • Position information of the center value, the integral value, and the pixel for which the center value is given (S402).
  • the ratio of the median value to the integral value is extracted and sorted out in a specified range (S404).
  • a histogram X-ray spectrum
  • an X-ray image showing the distribution and charge amount of pixels of specific X-ray energy are obtained (S406).
  • a histogram X-ray spectrum
  • the distribution can be given as an image for the X-ray energy or an X-ray energy range having a certain width.
  • the ratio of the median to the integral value is determined, and it is determined that the form of charge division that can be restored is effective only when it falls within a certain range.
  • 5 ⁇ 5 is empirically effective as the range of pixels for calculating the integral value, it is not limited to this, and depending on the size and structure of the pixel of the sensor, it may take a narrow range or a wider range. It may be valid.
  • a range in which the ratio of the median to the integral value is preferred is referred to as an appropriate range of the ratio
  • the lower limit of the appropriate range of the ratio is referred to as an appropriate lower limit of the ratio.
  • the upper limit of is called the appropriate upper limit of the ratio.
  • an appropriate range of pixels for which an integral value is calculated is referred to as an integration appropriate range.
  • an integration appropriate range is empirically effective when the ratio of the median to the integral is between 40% and 50%, it is not limited thereto, and it may be further different depending on the size and structure of the pixel of the sensor. Taking a range may be effective.
  • the X-ray irradiation position and the X-ray energy can be simultaneously recorded.
  • the data can be used to obtain an x-ray spectrum or an x-ray image group corresponding to any x-ray energy appearing in the spectrum.
  • the charge division detection circuit 107, the charge division processing circuit 108, and the pixel-by-pixel counter circuit 106 cooperate with the energy level determination circuit 105 in accordance with a CMOS camera in which it is difficult to find isolated pixels.
  • the operation of will be described.
  • the charge division detection circuit 107 and the charge division processing circuit 108 perform verification on all pixels at each image read out to obtain a median and an integral value, and determine that only when the ratio is within the predetermined range, it is valid. It is carried out. That is, it is interpreted that the total charge amount corresponding to the integral value is originally at the (X, Y) point giving the median value, and the reading is replaced.
  • the charge division processing circuit 108 cooperates with the energy level determination circuit 105 to determine whether or not the integral value is in a range corresponding to the specific X-ray energy.
  • the brightness of a pixel of an image is represented by an integer value between 0 and 65535. Assuming that the brightness of the dark current level is 250, it is customary to set the first threshold value to, for example, 300 arbitrary values.
  • Most X-ray signals have a level corresponding to an energy level much higher than the first threshold, and even a single photon has a value of, for example, about 800. At this time, the difference between X-ray energy and whether it was 600 or 800 is in the range of the characteristic value according to the element usually composed.
  • FIG. 13 shows an X-ray image by X-ray spectral energy using the method of correcting the influence of charge division (FIG. 9, 10) using the ratio of the median to the integral value. It uses a setup.
  • Fig. 13 shows a photograph and an X-ray fluorescence spectrum of the ceramic plate obtained by the same sCMOS camera
  • Fig. 13 (a) is a photograph of the front of the ceramic plate
  • Fig. 13 (b) is its X-ray fluorescence spectrum
  • FIG. 13 (c) is a photograph of the back side
  • FIG. 13 (d) is its spectrum. Photographs and X-ray fluorescence spectra are obtained with the same sCMOS camera. This is an embodiment using a method (FIGS. 9 and 10) of correcting the influence of charge division using the ratio of the median to the integral.
  • a visible light digital camera can measure the XRF spectrum of a sample, it can also analyze the composition of elements in the sample. For example, a ceramic plate with a white base (FIG. 13c, back) and a blue pattern (FIG. 13a, front) is tested.
  • the two photographs of FIGS. 13a and 13c are taken by the sCMOS camera before removing the optical lens system and the transparent glass cover. Since the camera does not have a color filter, the picture is monochrome.
  • the XRF spectra of the front Figure 13b
  • the back Figure 13d
  • the primary x-ray beam is a monochromatic copper K ⁇ ray.
  • the exposure time of one image is 100 ms.
  • the accumulation time is 30 minutes.
  • all peaks are identified, so the corresponding elements can be identified as well.
  • the elemental compositions of the front and back sides are very similar, it can be seen that cobalt appears only on the front and shows the relationship between cobalt and ceramic blue.
  • sCMOS cameras are used in the same way as other existing x-ray detectors.
  • concentrations of the elements in the sample can be used for quantitative XRF analysis by using experimentally obtained calibration curves or by using so-called reference free analysis based on X-ray fundamental parameters.
  • reference free analysis based on X-ray fundamental parameters can be used for quantitative XRF analysis by using experimentally obtained calibration curves or by using so-called reference free analysis based on X-ray fundamental parameters.
  • the use of sCMOS cameras is valuable in that it can be applied to the analysis of trace elements, especially when combined with total reflection geometry.
  • FIG. 14 is a configuration block diagram of a correction filtering circuit of a combined use type of an isolated pixel and charge division showing a third aspect of the present invention.
  • the X-ray image generation circuit 30 includes an effective event determination circuit 102, an isolated pixel extraction circuit 103, a noise removal circuit 104, an energy level determination circuit 105, a pixel-by-pixel counter circuit 106, a charge division detection circuit 107, and an X-ray counter image generation circuit. And an X-ray counter image generation circuit 109.
  • the correction filtering circuit for isolated pixel shown in FIG. 2A and the correction filtering circuit for charge division of FIG. Therefore, it is possible to properly cope with an event captured by an imaging sensor in which an isolated pixel and charge division coexist.
  • FIG. 15 is a block diagram of a main part of a measurement apparatus for obtaining an X-ray image by X-ray spectral energy according to a second embodiment of the present invention.
  • the X-ray analyzer according to the second embodiment of the present invention comprises a sample holder 204, a sample 205, an imaging sensor 208, and an X-ray beam guide 212.
  • the components corresponding to the X-ray tube 1, the crystal monochromator 2 and the signal control mechanical shutter 3 shown in FIG. 1 are not shown in FIG.
  • the X-ray beam guide 212 guides only the parallel component of the fluorescent X-ray as the X-ray beam 201 to the imaging sensor 208.
  • the present invention it is clear how to avoid charge division and correction of charge division, and it becomes possible to manufacture with a smaller element size than the present, and in CCD sensors and CMOS sensors designed for visible light, It enables x-ray imaging with energy discrimination. Furthermore, although the case where a CCD imaging device or a CMOS imaging device designed for visible light wavelength is used as an X-ray imaging device is shown as an embodiment of the present invention, the present invention is not limited to these. The present invention can also be applied to the case where a semiconductor pixel radiation detector specially manufactured for performing energy discrimination X-ray imaging is used as an X-ray imaging device.
  • FIG. 17 shows how to use the first threshold and the second threshold in filtering.
  • the first threshold is used to check the intensity of one light receiving element (pixel) to recognize a valid photon event.
  • the second threshold which is smaller than the first threshold, has surrounding pixels to ensure that there is no leakage current to avoid tailing on the low energy side of the peak. Used to check the Only the first threshold is used to remove the noise equivalent signal. Then, using the second threshold value, it is confirmed that the peripheral light receiving element has not caused the photon event (see S304 in FIG. 7A).
  • the functions of the components of the X-ray image generation circuit 10 or 20 can be realized by computer software. For example, in FIG. 18, after data is received by the computer via the interface and processed by software, necessary data is stored. About the principal part structure of the measuring apparatus for acquiring the X-ray image according to X-ray spectrum energy, since it is the same as that of the thing of FIG. 1, the overlapping description is abbreviate
  • the image data processed by the computer 54 is stored in a data storage 54 such as a hard disk, for example.
  • Lines 62, 64, 66, and 68 for transmitting control signals to the component parts 42, 43, and 47 of the apparatus and detection signals from the respective parts are temporarily connected to the interface 52 and can be captured by the computer 54.
  • the computer 54 sequentially fetches data from each part, performs processing, and transmits necessary instructions to each part.
  • the processed image data is stored in the data storage 54 either collectively or sequentially while performing the measurement.
  • the A / D converter can be placed on the camera side or on the camera controller.
  • the computer can receive the A / D converted image itself. More specifically, the computer can receive data of 1024 ⁇ 1024, and one pixel of 16 bits (65,536 tones).
  • the type may be diagnosed by paying attention to the shape distribution of the group.
  • Various diagnostic methods have been studied, but as a method with the highest degree of certainty and the quickest judgment, it is to use the quantitative relationship between the total charge amount and the central charge amount as an index. I understand.
  • the dispersed ones can be collected and summed.
  • the position and energy it is equivalent to the center of distribution of the dispersed charge or simply the pixel with the largest amount of charge being the detection position, and the total charge occurring there It can be considered easy.
  • this is not always the case.
  • electronic circuits for readout and the like are wired to every pixel. These are close to the places where X-rays enter and generate charges. As such, the charge distribution across pixels resulting from charge splitting may be in different patterns.
  • the ratio of the median to the sum is less than a predetermined value (specified value 1) (for example, 40%) is the occurrence of intense dissipation (something on the wall between pixels or wiring It is considered to be the cause of The amount of charge lost is so large that it is impossible to obtain information on the energy of X-rays that have already entered, and such inclusion may result in strange spectra being obtained. If the ratio between the median value and the sum value is larger than the prescribed value (for example, 50%), the total amount of charge lost is not large, but an abnormality occurs in the process of charge division It is considered to be a thing. Therefore, these are excluded.
  • a predetermined value for example, 40%
  • the specified value 1 and the specified value 2 described above are defined based on a large amount of experimental data, but the conditions on the detector side such as a CMOS element and the observation target side such as light to be detected and electromagnetic waves such as X-ray If the measurement conditions such as temperature and humidity are constant, the same value is obtained even if measurement is performed at different times and places. Therefore, the prescribed value 1 and the prescribed value 2 can be obtained for each of these conditions, and can be generalized as the standard value 1 and the standard value 2 under the conditions. From the above, it is preferable that the reference value is 1 or more such that severe dissipation does not occur. Further, it is preferable that the reference value is 2 or less so as not to cause an abnormality in the process of charge division.
  • an image obtained by correcting and converting information of X-ray energy (element) into a final state that can be easily extracted from the obtained original image is obtained.
  • the image looks like the original image you get an image that looks dark or not, so you hardly know what it is.
  • every pixel is completely isolated, and there may be differences in the brightness among the individual pixels that are bright in the dark.
  • the brightness of all the pixels of this image is checked, and those close to a specific brightness level are detected by comparison. If that is the case, at that (X, Y) point, the energy X-ray is determined to have one count, and the energy is added to the image counter.
  • the brightness of the image corresponds to energy (wavelength of light), not intensity (brightness of light).
  • the amount of charge generated corresponding to the energy of X-rays For example, for the X-ray of 6400 eV and the X-ray of 3200 eV, even if the same one photon enters, the charge generation amount differs by 2 times.
  • a threshold is generally set and used to distinguish a signal from electrical noise or the like.
  • a threshold is called a lower level discriminator (LLD).
  • LLD lower level discriminator
  • Such a threshold is also used in the embodiments of the present invention.
  • the determination that the pixel obtaining the signal is isolated is that the charge amount is above LLD for all pixels It becomes possible by checking whether it is.
  • information is acquired using only such an image that looks like only noise appears (referred to as “single photon counting mode”).
  • the charge amount corresponds to the brightness of the pixel.
  • the LLD used at this time may be a standard that is clearly brighter than noise. Since the values do not have to be strictly selected, they can be set for each of various measurements in consideration of the measurement conditions, the type of image to be obtained, and the like.
  • the newly introduced threshold is considered to be much closer to the noise level than LLD.
  • signal processing using such thresholds is not known. This is because it is determined that the signal is a clear signal distinguished from noise if it is LLD or more, and it is considered sufficient to look at only such a signal.
  • the second threshold which has been introduced, may be used to scrutinize the surrounding pixels, once for a pixel of interest once considered as isolated. Then, once the surrounding pixels that have been regarded as zero are examined again, if they exude a little next to the target pixel, even if it is a pixel that has once been regarded as isolated, it is isolated.
  • the idea is to exclude from the pixels that you This is because if the brightness of an isolated pixel is regarded as the total charge amount, and if a slight amount of bleeding is overlooked when determining the energy of the X-ray, then the energy of the X-ray may be underestimated. It is.
  • almost perfect X-rays are obtained in the case where it is recognized that one isolated pixel has a charge (in the case where the frequency of charge division is not so high, the case where the pixel size is relatively large, etc.) The effect that a spectrum is obtained can be recognized.
  • the X-ray imaging apparatus of the present invention it is possible to process X-ray photon events occurring in a CCD imaging device or a CMOS imaging device designed for visible light wavelength or a semiconductor pixel radiation detector.
  • Line energy information can be separated individually, and precise imaging pixel information can be obtained.
  • the signal processing of a digital camera detects (1) a light signal including X-rays and converts it into an electric signal (charge) and stores it (sensor), (2) it is stored for each pixel of the sensor
  • the process includes reading out the charge amount (readout circuit, A / D converter), (3) displaying the read-out as an image, or storing it as electronic data.
  • Each of these steps may be branched into further steps. There may also be detailed processes with certain features.
  • Reference Signs List 1 X-ray tube 2 crystal monochromator 3 signal control mechanical shutter 4 204 sample holder 5 205 sample 6 imaging optical system (pinhole plate) 7 X-ray camera (CCD camera, CMOS camera) 8, 208 Image sensor (two-dimensional semiconductor sensor) 82 unit light receiving element 84 peripheral light receiving element 9 cooling circuit 10, 20, 30 X-ray image generating circuit 101a, 101b X-ray beam 102 effective event judging circuit 103 isolated pixel extracting circuit 104 noise removing circuit 105 energy level judging circuit 106 pixel by pixel Counter circuit 107 Charge division detection circuit 108 Charge division processing circuit 109 X-ray counter image generation circuit 11 X-ray image display device 112, 115 First threshold 120 Second threshold

Abstract

L'invention concerne un dispositif d'imagerie par rayons X dans lequel un élément d'imagerie à dispositif de couplage de charge (CCD), un élément d'imagerie à semi-conducteur complémentaire à l'oxyde de métal (CMOS), ou un détecteur de rayonnement à pixels semi-conducteurs conçu pour une utilisation dans la longueur d'onde de la lumière visible est approprié pour être utilisé en tant qu'élément d'imagerie d'un spectromètre à rayons X de grande surface. L'élément d'imagerie par rayons X pour recevoir des rayons énergétiques comprenant des photons de rayons X provenant d'un objet à analyser comprend des éléments de réception de lumière unitaires dans une configuration bidimensionnelle. Les éléments de réception de lumière unitaires ont une région bidimensionnelle permettant un partage de charge par réception des photons de rayons X. Un circuit de génération d'image en rayons X, avec lequel des signaux de réception de lumière provenant de l'élément d'imagerie par rayons X sont lus pour chacun des éléments de réception de lumière unitaires, compare les signaux de réception de lumière lus provenant de chacun des éléments de réception de lumière unitaires avec une première valeur seuil servant de critère de reconnaissance comme un événement de photon effectif et une seconde valeur seuil servant de critère de reconnaissance comme un bruit, et utilise les signaux qui effacent les première et seconde valeurs seuil comme événements de photons de rayons X efficaces pour générer une image de rayons X.
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