X-ray inspection apparatus and X-ray inspection method

Abstract

Provided are an X-ray inspection apparatus and an X-ray inspection method capable of continuously inspecting even long, sheet-like specimens while performing intensity correction. The apparatus comprises: an X-ray source; a specimen moving mechanism; an X-ray detection unit having a line sensor that detects X-rays transmitted through the specimen using pixels; an image storage unit that stores X-ray intensities; an intensity correction unit that corrects the X-ray intensities stored in the image storage unit; and a defect detection unit that detects the presence or absence of defects in the specimen. The intensity correction unit uses the X-ray intensity detected in an initial detection start area when X-ray detection begins in the specimen, or the X-ray intensity detected in the specimen before X-ray detection begins, as a reference intensity. The intensity correction unit corrects the X-ray intensity of pixels detected in an area after the detection start area based on a correction coefficient obtained by comparing the X-ray intensity detected after the detection start area with the reference intensity.

Description

Technical Field

[0001] The present invention relates to an X-ray inspection apparatus and an X-ray inspection method capable of detecting foreign matter and the like in a sample. Background Art

[0002] Typically, X-ray transmission inspection is used to detect tiny foreign matter such as metal in a long, sheet-like sample (inspection object). The sample is transported between an X-ray source and an X-ray detector using a conveyor belt or a roller-to-roller method, and the presence of foreign matter is determined based on the X-ray transmission image obtained by irradiating the sample with X-rays.

[0003] In X-ray inspection devices used for such X-ray transmission inspections, because inspection operations are performed continuously, temporal stability is required in the device's inspection capabilities. However, the X-ray intensity of the X-ray source and the sensitivity of the X-ray detector typically fluctuate over time. Furthermore, the detection intensity of the X-ray detector elements degrades due to X-ray irradiation, and this intensity degradation also varies between the elements of the X-ray detector. Furthermore, it is known that the X-ray intensity of the X-ray source also fluctuates with temperature increases. Consequently, there is a problem: immediately after data correction processing, the output of all elements, which was originally the same, shifts over time, causing the overall value to decrease, or causing output variations between elements, resulting in a reduction in the inspection device's detection capabilities. Consequently, inspection operations must be repeatedly interrupted to perform correction operations.

[0004] The line sensors and TDI (Time Delay Integration) sensors used in these X-ray detectors can affect detection accuracy due to fluctuations in the device environment (such as temperature fluctuations and phosphor brightness fluctuations). To ensure this detection accuracy, pixel X-ray intensity calibration must be performed regularly.

[0005] For example, Patent Document 1 discloses a method that includes a unit for determining whether X-rays are shielded by a sample and uses a section without a sample to perform a calibration operation without interrupting the inspection work.

[0006] Patent Document 2 describes a method for performing calibration without interrupting inspection work using signals from the boundary portions for a sample in which individual packaging portions for storing products and boundary portions are alternately arranged.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2001-4560

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2014-134457

[0011] The above-mentioned prior art suffers from the following issues. Specifically, when inspecting sheet-like specimens using a roll-to-roll method, periodic calibration operations are performed mid-inspection, allowing for stable inspection only up to the required length for intensity calibration. This makes continuous X-ray inspection for foreign matter on long sheets measuring several to tens of kilometers difficult. Furthermore, intensity calibration must be performed without a specimen present, which is difficult with sheet-like specimens, as the specimen is always present between the X-ray source and detector.

[0012] While the aforementioned existing Patent Documents 1 and 2 describe methods for performing intensity correction in sections without a sample and using signals from boundary sections (sections not requiring inspection), accurate correction may not be possible if the sections without a sample and the boundary sections (which are relatively short) are insufficiently captured. This is particularly difficult to apply with the aforementioned long, sheet-like samples, as they are continuously fed without interruption. Summary of the Invention

[0013] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an X-ray inspection apparatus and an X-ray inspection method capable of continuously inspecting a long sheet-like sample while performing intensity correction even when using a roll-to-roll method or the like.

[0014] In order to solve the above-mentioned problem, the present invention adopts the following structure. That is, the X-ray inspection device of the present invention is characterized in that it comprises: an X-ray source that irradiates a sample with X-rays; a sample moving mechanism that moves the sample in a specific direction when irradiated with the X-rays from the X-ray source; an X-ray detection unit that has a line sensor that is arranged on the side opposite to the X-ray source relative to the sample, and has a plurality of pixels arranged in a direction perpendicular to the specific direction, and detects the X-rays that have passed through the sample using the pixels; an image storage unit that stores the X-ray intensity detected by the pixels; and an intensity correction unit that performs the image storage. The X-ray intensity stored in the sample is corrected; and a defect detection unit detects whether there are defects in the sample based on the X-ray intensity, the intensity correction unit uses the X-ray intensity detected in the initial detection start area when the X-ray detection is started in the sample, or the X-ray intensity detected in the sample in advance before the X-ray detection is started as a reference intensity, and corrects the X-ray intensity of the pixel detected in the area after the detection start area based on a correction coefficient obtained by comparing the X-ray intensity detected after the detection start area with the reference intensity.

[0015] In this X-ray inspection apparatus, the intensity correction unit uses the X-ray intensity detected in the initial detection start region of the specimen S at the start of X-ray detection, or the X-ray intensity detected in the specimen before X-ray detection begins, as a reference intensity. The unit then corrects the X-ray intensity of pixels detected in the region after the detection start region based on a correction factor obtained by comparing the X-ray intensity detected after the detection start region with the reference intensity. This allows continuous inspection even for long, sheet-like specimens while performing intensity correction. Specifically, the X-ray intensity in the detection start region, where the X-ray detection unit is not yet affected by temperature fluctuations or other factors, or the X-ray intensity detected in the specimen beforehand, is set as the reference intensity, and subsequent X-ray intensities are corrected based on this reference intensity. This eliminates the need for calibration operations involving sections or boundaries without the specimen, enabling continuous, real-time inspection even for long, sheet-like specimens.

[0016] The X-ray inspection device of the second invention is characterized in that, based on the first invention, when the defect detection unit detects the defect, the intensity correction unit corrects the X-ray intensity detected in the defect detection area according to the following correction coefficient, wherein the correction coefficient is obtained by comparing the X-ray intensity detected in the area of ​​the sample where the defect is detected, i.e., the defect detection area, and the X-ray intensity detected in the area immediately before the defect detection area, i.e., the defect adjacent area.

[0017] Specifically, in this X-ray inspection apparatus, when a defect is detected by the defect detection unit, the intensity correction unit corrects the intensity detected in the defect detection area using a correction coefficient. The correction coefficient is obtained by comparing the X-ray intensity detected in the defect detection area, the area of ​​the specimen where the defect is detected, with the X-ray intensity detected in the defect adjacent area, an area immediately preceding the defect detection area. This allows for correction using an appropriate correction coefficient, avoiding defects such as foreign matter. Calculating the correction coefficient using the intensity detected in the defect area results in excessive fluctuations in X-ray intensity due to the defect, resulting in an inappropriate correction coefficient calculated for the defect detection area. Therefore, by calculating the correction coefficient using the X-ray intensity detected in an area adjacent to the defect detection area, i.e., an area without defects, appropriate correction can be performed even in the defect detection area.

[0018] A third aspect of the present invention is the X-ray inspection apparatus according to the first or second aspect, wherein the defect detection unit determines the presence or absence of the defect based on a change in the correction coefficient.

[0019] That is, in this X-ray inspection device, since the defect detection unit determines the presence or absence of defects based on the change of the correction coefficient, if the correction coefficient suddenly changes significantly by more than a certain value due to the presence of defects such as foreign matter, the presence or absence of defects such as foreign matter can be easily determined.

[0020] The X-ray inspection device of the fourth invention is characterized in that, based on any one of the first to third inventions, the X-ray detection unit includes a line sensor operation unit, which controls the accumulation and transfer of charges in the plurality of pixels along the specific direction, the line sensor operation unit divides the plurality of pixels into a plurality of blocks, performs the transfer on each of the blocks, and the intensity correction unit performs the correction of the pixels in the corresponding block based on the average value of the X-ray intensity calculated for each block.

[0021] That is, in this X-ray inspection apparatus, the intensity corrector corrects the pixels in the corresponding block based on the average value of the X-ray intensities calculated for each block. This reduces computational processing compared to correcting each pixel.

[0022] The X-ray inspection device of the fifth invention is characterized in that, based on any one of the first to fourth inventions, the X-ray detection unit has a TDI sensor, which has multiple columns of line sensors along the specific direction so that the pixels are arranged in a matrix, and the TDI sensor uses the pixels to detect the X-rays that have passed through the sample.

[0023] The X-ray inspection method of the sixth invention is characterized by comprising: an X-ray irradiation step of irradiating a sample with X-rays using an X-ray source; a sample movement step of continuously moving the sample in a specific direction while irradiating the sample with the X-rays from the X-ray source; an X-ray detection step of detecting the X-rays that have passed through the sample using pixels in an X-ray detection unit having a line sensor, wherein the line sensor is provided on a side opposite to the X-ray source with respect to the sample, and a plurality of the pixels are arranged in a direction perpendicular to the specific direction; an image storage step of storing the X-ray intensity detected by the pixels; and an intensity correction step. a step of correcting the stored X-ray intensity; and a defect detection step of detecting whether there are defects in the sample based on the X-ray intensity. In the intensity correction step, the X-ray intensity detected in the initial detection start area when the X-ray detection is started in the sample, or the X-ray intensity detected in the sample before the X-ray detection is started, is used as a reference intensity. The X-ray intensity of the pixel detected in the area after the detection start area is corrected based on a correction coefficient obtained by comparing the X-ray intensity detected after the detection start area with the reference intensity.

[0024] The X-ray inspection method of the seventh invention is characterized in that, based on the sixth invention, when the defect is detected in the defect detection step, in the intensity correction step, the X-ray intensity detected in the defect detection area is corrected according to the following correction coefficient, wherein the correction coefficient is obtained by comparing the X-ray intensity detected in the area of ​​the sample where the defect is detected, i.e., the defect detection area, and the X-ray intensity detected in the area immediately before the defect detection area, i.e., the defect adjacent area.

[0025] An X-ray inspection method according to an eighth invention is characterized in that, in addition to the sixth or seventh invention, the defect detection step determines the presence or absence of the defect based on a change in the correction coefficient.

[0026] The X-ray inspection method of the 9th invention is characterized in that, based on any one of the 6th to 8th inventions, the X-ray detection unit has a line sensor operation unit, which controls the accumulation and transfer of charges in the multiple pixels along the specific direction, and the line sensor operation unit divides the multiple pixels into multiple blocks, performs the transfer on each of the blocks, and in the intensity correction step, performs the correction of the pixels in the corresponding block based on the average value of the X-ray intensity calculated for each block.

[0027] The X-ray inspection method of the 10th invention is characterized in that, based on any one of the 6th to 9th inventions, the X-ray detection unit has a TDI sensor, which has a plurality of columns of line sensors along the specific direction so that the pixels are arranged in a matrix, and the TDI sensor uses the pixels to detect the X-rays that have passed through the sample.

[0028] Effects of the Invention

[0029] According to the present invention, the following effects are achieved.

[0030] That is, according to the X-ray inspection device and the X-ray inspection method of the present invention, the X-ray intensity of the initial detection start area when the detection starts in the sample, or the X-ray intensity detected in the sample before the X-ray detection starts, is used as the reference intensity. The X-ray intensity of the pixels detected in the area after the detection start area is corrected based on the correction coefficient obtained by comparing the X-ray intensity detected in the area after the detection start area with the reference intensity. Therefore, even long sheet samples can be inspected continuously in real time while performing intensity correction.

[0031] Therefore, in the X-ray inspection device and the X-ray inspection method of the present invention, even long samples such as the diaphragm of a lithium-ion battery or the diaphragm of a fuel cell, a gas diffusion layer, carbon paper, etc. can be inspected for foreign matter continuously and efficiently while maintaining high detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a diagram schematically showing the overall configuration of an X-ray inspection apparatus in this embodiment of the X-ray inspection apparatus and the X-ray inspection method according to the present invention.

[0033] Figure 2This is a plan view for explaining pixels and images (frames) of the TDI sensor in this embodiment.

[0034] Figure 3 1 and 2 are diagrams showing a reference image (a), a calculation image before correction (b), and a corrected image (c) in this embodiment.

[0035] Figure 4 Graphs showing a reference image (a) at 0 minutes (min), an image before correction (b) after 60 minutes, an image before correction (c) after 120 minutes, and their brightness curves (d) in this embodiment.

[0036] Figure 5 Graphs showing a corrected image (a) after 60 minutes, a corrected image (b) after 120 minutes, and their brightness curves (c) in this embodiment.

[0037] Figure 6 1 and 2 , which illustrate a reference image (a) at 0 minutes, an image before correction (b) 120 minutes after the presence of foreign matter, their brightness curves (c), and a defect-proximate image (d) in this embodiment.

[0038] Figure 7 Graphs showing a corrected image (a) and a brightness curve (b) after 120 minutes when a correction coefficient is calculated based on a defect detection region (image after 120 minutes) where foreign matter exists in this embodiment.

[0039] Figure 8 Graphs showing a corrected image (a) and its brightness curve (b) 120 minutes later when a correction coefficient is calculated based on an image of a defect adjacent region immediately before a defect detection region where a foreign object is present in this embodiment.

[0040] Description of labels

[0041] 1: X-ray inspection device; 2: X-ray source; 3: Sample moving mechanism; 4: X-ray detection unit; 4a: TDI sensor; 4g: Pixel; 4l: Line sensor; 5: Line sensor calculation unit; 6: Image storage unit; 8: Intensity correction unit; 9: Defect detection unit; B: Block; S: Sample; X: Defect; X1: X-ray; Y1: Specific direction DETAILED DESCRIPTION

[0042] Below, refer to Figures 1 to 8 An embodiment of the X-ray inspection apparatus and the X-ray inspection method according to the present invention will be described.

[0043] like Figure 1 and Figure 2As shown, the X-ray inspection device 1 of this embodiment includes: an X-ray source 2, which irradiates X-rays X1 to a sample S; a sample moving mechanism 3, which moves the sample S in a specific direction Y1 when irradiated with the X-rays X1 from the X-ray source 2; an X-ray detection unit 4, which has a line sensor 4l, which is arranged on the side opposite to the X-ray source 2 relative to the sample S, and has a plurality of pixels 4g arranged in a direction perpendicular to the specific direction Y1, and uses the pixels 4g to detect the X-rays X1 that has passed through the sample S; an image storage unit 6, which stores the X-ray intensity detected by the pixels 4g; an intensity correction unit 8, which corrects the X-ray intensity stored in the image storage unit 6; and a defect detection unit 9, which detects whether there is a defect X in the sample S based on the X-ray intensity.

[0044] In addition, the defect X is a foreign body, wrinkles, holes, etc.

[0045] The intensity correction unit 8 has the following functions: using the X-ray intensity detected in the initial detection start area when detection starts in the sample S, or the X-ray intensity detected in the sample S before the start of X-ray detection, as a reference intensity, and correcting the X-ray intensity of each pixel 4g detected in the area after the detection start area based on a correction coefficient obtained by comparing the X-ray intensity detected in the area after the detection start area with the reference intensity.

[0046] Furthermore, the intensity correction unit 8 has the function of correcting the X-ray intensity detected in the defect detection region, based on a correction coefficient obtained by comparing the X-ray intensity detected in the defect detection region, the region where the defect X is detected, with the X-ray intensity detected in the defect adjacent region, the region immediately preceding the defect detection region, when the defect detection unit 9 detects the defect X. Specifically, when a defect is detected, the correction coefficient for the defect detection region is calculated using the X-ray intensity detected in the defect adjacent region as a reference intensity for defect detection.

[0047] The defect detection unit 9 determines the presence or absence of a defect X based on the change in the correction coefficient. The X-ray detection unit 4 includes a TDI sensor 4a as an X-ray detector having a plurality of rows of line sensors 4l arranged in a matrix along a specific direction Y1, with pixels 4g arranged in a matrix. The pixels 4g detect X-rays X1 that have passed through the sample S; and a line sensor calculation unit 5 that controls the accumulation and transfer of charge in the plurality of pixels 4g along the specific direction Y1.

[0048] Furthermore, the X-ray inspection apparatus 1 of this embodiment includes a control unit C that controls the above-described units and a display unit 13 that displays information such as a transmission image.

[0049] The line sensor calculation unit 5 has a data transfer function of transferring the accumulated charge data obtained by the charge accumulation and transfer to the image storage unit 6 .

[0050] The line sensor calculation unit 5 is configured to divide the plurality of pixels 4 g into a plurality of blocks B and to transfer charge for each block B. In other words, the data transfer is performed for each block B.

[0051] The intensity correcting unit 8 is configured to correct the X-ray intensity of the pixel 4 g in the corresponding block B based on the average value of the X-ray intensity calculated for each block B.

[0052] like Figure 2 As shown, each block B is a so-called tap consisting of a plurality of line sensors 41 that are read out (transferred) at once by the line sensor calculation unit 5. Each block B is composed of, for example, 384 pixels × 1000 rows. The TDI sensor 4a of this embodiment is composed of a total of 16 blocks B arranged in a specific direction Y1.

[0053] The control unit C is a control computer composed of a CPU, etc. The control unit C includes a processing circuit, etc. The processing circuit performs image processing based on the signals (the data) input from the line sensor processing unit 5 and the intensity correction unit 8 to the image storage unit 6 to generate a transmission image, and then displays the image on the display unit 13.

[0054] The display unit 13 is a display device connected to the control unit C to display a contrast image and the like. The display unit 13 can display various information under the control of the control unit C. The display unit 13 can also display defects X such as foreign matter detected by the defect detection unit 9.

[0055] The X-ray source 2 is an X-ray tube capable of irradiating X-rays X1, which are emitted as primary X-rays from a window of beryllium foil or the like. The X-rays X1 are generated by thermal electrons generated from a filament (cathode) within the tube, accelerated by a voltage applied between the filament (cathode) and a target (anode), and collide with W (tungsten), Mo (molybdenum), Cr (chromium), etc. on the target.

[0056] The sample S is, for example, a strip of lithium-ion battery or fuel cell material, a gas diffusion layer, carbon paper, or a long sheet material used in medical systems. For example, if the sample S is an electrode sheet used in a lithium-ion secondary battery, the defect X that may be introduced into the sample may be, for example, Fe or SUS that may be introduced into the electrode as a defect.

[0057] The sample moving mechanism 3 includes: a motor (not shown) capable of moving relative to the TDI sensor 4a, for example, in the extension direction of the sample S; and at least a plurality of pairs of rollers 3a for unwinding and winding the strip-shaped sample S in the extension direction in a roll-to-roll manner, for example.

[0058] The TDI (Time Delay Integration) sensor 4a utilizes a CCD (Charge-Coupled Device) sensor, a CMOS (Complementary Metal Oxide Semiconductor) sensor, or a semiconductor sensor such as CdTe or Si. For example, the TDI sensor 4a is an X-ray detector having a plurality of pixels 4g (units, sensor elements) arranged in a direction perpendicular to and parallel to the direction of movement of the sample S (specific direction Y1). The TDI sensor 4a comprises a phosphor disposed on a detection surface; a fiber optic plate (FOP) comprising a plurality of optical fibers arranged in a two-dimensional pattern in rows and columns below the phosphor; and Si light-receiving elements disposed below the FOP. The TDI sensor 4a has a structure comprising multiple rows (plurality of lines) of line sensors 4l. For example, the TDI sensor 4a is constructed by arranging 200 to 1000 rows (stages) of unit line sensors 4l in the direction of transport of the sample S.

[0059] In the TDI sensor 4 a , a phosphor such as CsI (cesium iodide), GOS (gadolinium oxysulfide), or YAG (yttrium aluminum garnet) is used.

[0060] Furthermore, the TDI sensor 4 a performs charge accumulation and charge transfer for each block B of a plurality of pixels 4 g arranged along a specific direction Y1 .

[0061] The intensity correction unit 8 includes an intensity correction determination unit 10 for determining whether intensity correction is necessary, an intensity correction processing unit 11 for performing arithmetic processing for intensity correction, and a correction coefficient storage unit 12 for storing correction coefficients used during intensity correction.

[0062] The intensity correction determination unit 10 has the following functions: determining whether intensity correction is required based on the setting of whether intensity correction is performed sequentially or at regular intervals; and, when a defect X is detected by the defect detection unit 9, determining whether the X-ray intensity of the area adjacent to the defect is used as the X-ray intensity of the image before correction in order to calculate the correction coefficient.

[0063] Next, an X-ray inspection method using the X-ray inspection apparatus 1 according to this embodiment will be described.

[0064] The X-ray inspection method of this embodiment includes: an X-ray irradiation step, in which an X-ray source 2 is used to irradiate a sample S with X-rays X1; a sample movement step, in which the sample S is continuously moved in a specific direction when irradiated with the X-rays X1 from the X-ray source 2; an X-ray detection step, in which an X-ray detection unit 4 having a line sensor 4l is used to detect the X-rays X1 that has passed through the sample S using pixels 4g on the line sensor 4l, and the line sensor 4l is arranged on the side opposite to the X-ray source 2 relative to the sample S, and a plurality of pixels 4g are arranged in a direction perpendicular to the specific direction Y1; an image storage step, in which the intensity of the X-rays X1 detected by the pixels 4g is stored; an intensity correction step, in which the stored X-ray intensity is corrected; and a defect detection step, in which whether there is a defect X in the sample S is detected based on the corrected X-ray intensity.

[0065] In the above-mentioned intensity correction step, the X-ray intensity detected in the initial detection start area when the detection starts in the sample S, or the X-ray intensity detected in the sample S before the X-ray detection starts, is used as the reference intensity, and the X-ray intensity of the pixel 4g detected in the area after the detection start area is corrected according to the correction coefficient, and the correction coefficient is obtained by comparing the X-ray intensity detected in the area after the detection start area with the reference intensity.

[0066] Furthermore, when a defect X is detected in the defect detection step, the intensity correction step corrects the X-ray intensity detected in the defect detection area using a correction coefficient obtained by comparing the X-ray intensity detected in the defect detection area (the area where the defect X is detected) with the X-ray intensity detected in the defect adjacent area (the area immediately preceding the defect detection area) of the specimen S. Specifically, when a defect is detected, the correction coefficient for the defect detection area is calculated using the X-ray intensity detected in the defect adjacent area as a reference intensity for defect detection.

[0067] Furthermore, in the defect detection step, the presence or absence of the defect X is determined based on a threshold value of the X-ray intensity, or based on a change in the correction coefficient.

[0068] Furthermore, in the intensity correction step, the X-ray intensity in the pixel 4g in the corresponding block B is corrected based on the average value of the X-ray intensity calculated for each block B.

[0069] In the X-ray inspection method of the present embodiment described above, first, the sample S is moved by the sample moving mechanism 3 in a specific direction Y1 at a constant speed between the opposing X-ray source 2 and TDI sensor 4 a .

[0070] Next, the sample S is irradiated with X-rays X1 from the X-ray source 2 , and the transmitted X-rays that have passed through the sample S and the defect X are detected by the TDI sensor 4 a .

[0071] At this time, although the sample moving mechanism 3 starts to move the sample S in the specific direction Y1, Figure 2 When the image (frame) of the TDI sensor 4a shown in FIG. 1 is started, the X-ray intensity of the image of all blocks B (1 to 16) of the TDI sensor 4a initially sent to the line sensor calculation unit 5 is used as the reference intensity of the detection start area. Figure 3 The image shown in (a) is stored in the image storage unit 6 and is also stored by the image storage unit 7.

[0072] In addition, instead of the reference intensity of the detection start area, the X-ray intensity detected in the sample S before starting X-ray detection may be stored in the image storage unit 6 and saved in the image storage unit 7 as the reference intensity.

[0073] In the detection start region, no change in X-ray intensity occurs in the TDI sensor 4a. Figure 3 As shown in (a), an image with the same X-ray intensity is obtained in all blocks B.

[0074] After the detection start area, the X-ray intensity is sequentially detected by the TDI sensor 4 a as the sample S moves, and a correction coefficient is calculated sequentially or at regular intervals to perform image correction.

[0075] For example, Figure 3 As shown in (b), when the X-ray intensity (X-ray intensity of the image before correction) obtained by the TDI sensor 4a after the above-mentioned detection start area changes, the correction coefficient is calculated based on the X-ray intensity of the image before correction and the reference intensity obtained in the detection start area or the reference intensity obtained in advance.

[0076] In the figure, the X-ray intensity of the image of each block B is indicated by the shades of gray scale, and the brighter the gray scale, the higher the X-ray intensity.

[0077] The correction coefficient is calculated for each block B according to the following equation (1).

[0078] The correction coefficient is calculated based on the average value of the X-ray intensity calculated for each block B. Specifically, the intensity correction unit 8 pre-calculates the average X-ray intensity of all pixels 4g in each block B and uses this average value for the calculations in the following equations (1) and (2). Furthermore, the X-ray intensity of the pixel 4g is pre-corrected for brightness by the line sensor calculation unit 5 or the intensity correction unit 8. In other words, the reference intensity is the X-ray intensity of the image after brightness correction.

[0079] Next, the X-ray intensity of the corrected image is calculated using the obtained correction coefficient according to the following formula (2).

[0080] Formula (1): Correction coefficient = reference intensity (average value) ÷ X-ray intensity (average value) of the image before correction

[0081] Formula (2): X-ray intensity of each pixel in the corrected image = X-ray intensity of each pixel in the uncorrected image × correction coefficient

[0082] For example, if the intensity correction determination unit 10 is set to perform intensity correction every 60 minutes, Figure 4 As shown in (a), the X-ray intensity in the detection start area at 0 minutes after the start of detection is stored as the reference intensity. Figure 4 As shown in (b) and (c), when the X-ray intensity of the pre-correction image is obtained 60 minutes after the start of detection and 120 minutes after the start of detection, as shown in (b) and (c), Figure 4 As shown in (d), a brightness curve is obtained for each X-ray intensity.

[0083] According to these brightness curves, the X-ray intensity changes relative to the X-ray intensity of the detection start area at 0 minutes after the start of detection (baseline intensity), and the brightness of each block B becomes lower as time passes, such as after 60 minutes and 120 minutes.

[0084] Therefore, in this embodiment, the intensity correction processing unit 11 performs the calculation processing of the above equations (1) and (2) to correct the X-ray intensity of the pre-correction image after 60 minutes and 120 minutes, as shown in FIG. Figure 5 As shown in (a) and (b), the X-ray intensity of the corrected image is obtained. Figure 5 As shown in (c), for example, the brightness curve of the X-ray intensity in the corrected image after 60 minutes is a brightness curve in which fluctuation is suppressed similarly to the brightness curve of the reference intensity.

[0085] On the other hand, relative to Figure 6 The baseline intensity of the detection start area shown in (a) is as follows: Figure 6As shown in (b) of FIG. 1 , a case will be described in which the defect detection unit 9 detects a defect X in an image before correction that is to be subjected to intensity correction 120 minutes after the start of detection.

[0086] In addition, the image storage unit 6 and the image saving unit 7 successively store and save images.

[0087] Furthermore, the intensity correction processing unit 11 successively calculates correction coefficients based on the above-mentioned equations (1) and (2), and stores and saves these values ​​in the correction coefficient storage unit 12. When the change in the correction coefficient exceeds a certain amount and occurs suddenly, the defect detection unit 9 determines that a defect X exists in the region. In other words, although the X-ray intensity of the pixel 4a gradually changes over time due to temperature fluctuations, etc., if it suddenly and dramatically changes, it is considered that a defect X such as a foreign object exists.

[0088] When the defect detection unit 9 determines that there is a defect X in the image before correction, Figure 6 As shown in (c), the brightness curve of the X-ray intensity in the image before correction (defect detection area) varies greatly in the block B where the defect X exists, and the brightness decreases relative to the reference intensity of the detection start area. Figure 6 The baseline strength shown in (a) and Figure 6 When the X-ray intensity of the defect detection area having the defect X shown in (b) is calculated in the same manner as above, the correction coefficient is calculated as follows: Figure 7 As shown in (a), only the block B with defect X is overcorrected, as shown in Figure 7 As shown in (b), the corrected image has an abnormal brightness curve in the block B portion where the defect X exists. In particular, when there is a defect X such as a large foreign object, this excessive correction becomes noticeable.

[0089] Therefore, in this embodiment, based on the signal from the defect detection unit 9 that detects the defect X, as shown in FIG. Figure 6 As shown in (d), the intensity correction determination unit 10 transmits the X-ray intensity in the area immediately before the defect detection area where the defect X is detected, that is, the defect adjacent area, that is, the area adjacent to 120 minutes as a correction image (pre-correction image) to the intensity correction processing unit 11. The intensity correction processing unit 11 uses the X-ray intensity in the defect adjacent area and the reference intensity to calculate the correction coefficient and perform intensity correction.

[0090] Thus, in the presence of a defect X, when intensity correction is performed using the X-ray intensity of the defect-adjacent region without the defect X, as shown in FIG. Figure 8 As shown in (a), the block B with the defect X is also properly corrected in the same manner as the other blocks B, as shown in FIG. Figure 8As shown in (b), a brightness curve is obtained in which only the intensity of the portion of the defect X is locally reduced.

[0091] Thus, in the X-ray inspection apparatus 1 of the present embodiment, the intensity correction unit 8 uses the X-ray intensity detected in the initial detection start area when the detection starts in the sample S, or the X-ray intensity detected in the sample S before the X-ray detection starts, as the reference intensity, and corrects the X-ray intensity of the pixel 4g detected in the area after the detection start area based on the correction coefficient obtained by comparing the X-ray intensity detected after the detection start area with the reference intensity. Therefore, even a long sheet sample S can be continuously inspected while performing intensity correction.

[0092] That is, by setting the X-ray intensity of the detection start area where the temperature change of the X-ray detection unit 4 has not yet produced an influence, or the X-ray intensity detected in the sample in advance as the reference intensity, the X-ray intensity obtained thereafter is corrected according to the reference intensity. Thus, when performing the correction operation, there is no need for intervals and boundaries without samples, and even a long sample S can be inspected continuously for a long time in real time.

[0093] In addition, when the defect detection unit 9 detects a defect X, the intensity correction unit 8 corrects the intensity detected in the defect detection area based on the correction coefficient. The correction coefficient is obtained by comparing the X-ray intensity detected in the area of ​​the sample S where the defect X is detected, that is, the defect detection area, and the X-ray intensity detected in the area immediately before the defect detection area, that is, the defect adjacent area. Therefore, the part of the defect X such as foreign matter can be avoided and correction can be performed using an appropriate correction coefficient.

[0094] When the correction coefficient is calculated using the intensity detected in the defect X portion, the X-ray intensity fluctuates too much due to the defect X, and the correction coefficient calculated in the defect detection area is inappropriate. Therefore, by calculating the correction coefficient using the X-ray intensity detected in the area immediately before the defect detection area, that is, the defect adjacent area without defects, the defect detection area can also be properly corrected.

[0095] Furthermore, since the defect detection unit 9 determines the presence of defects based on changes in the correction coefficient, the presence of defects X such as foreign matter can be easily determined if the correction coefficient suddenly changes significantly by more than a certain value due to the presence of defects X such as foreign matter.

[0096] Furthermore, the intensity corrector 8 corrects the X-ray intensity in the pixel 4g in the corresponding block B based on the average value of the X-ray intensity calculated for each block B. This reduces the computational processing compared to correcting each pixel 4g.

[0097] In addition, the technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

Claims

1. An X-ray inspection device, characterized in that: The X-ray inspection device comprises: An X-ray source that irradiates the sample with X-rays; a sample moving mechanism that moves the sample in a specific direction when the sample is irradiated with the X-rays from the X-ray source; an X-ray detection unit including a line sensor disposed on a side of the sample opposite to the X-ray source, the line sensor having a plurality of pixels arranged in a direction perpendicular to the specific direction, and detecting the X-rays that have passed through the sample using the pixels; an image storage unit for storing X-ray intensities detected by the pixels; an intensity correction unit that corrects the X-ray intensity stored in the image storage unit; as well as a defect detection unit, which detects whether there are defects in the sample based on the X-ray intensity, The sample is in the form of a long sheet without any part that does not need to be inspected. The sample moving mechanism allows the sample to be continuously supplied and moved without interruption. The intensity correction unit uses the X-ray intensity detected in the initial detection start area when the detection of X-rays in the sample is started, or the X-ray intensity detected in the sample before the detection of X-rays is started, as a reference intensity, and corrects the X-ray intensity of the pixel detected in the area after the detection start area based on a correction coefficient obtained by comparing the X-ray intensity detected after the detection start area with the reference intensity. The defect detection unit determines the presence or absence of the defect based on a change in the correction coefficient.

2. The X-ray inspection apparatus according to claim 1, wherein When the defect detection unit detects the defect, the intensity correction unit corrects the X-ray intensity detected in the defect detection area according to the following correction coefficient, wherein the correction coefficient is obtained by comparing the X-ray intensity detected in the area of ​​the sample where the defect is detected, i.e., the defect detection area, and the X-ray intensity detected in the area immediately before the defect detection area, i.e., the defect adjacent area.

3. The X-ray inspection apparatus according to claim 1 or 2, characterized in that The X-ray detection unit includes a line sensor calculation unit that controls the accumulation and transfer of charges in the plurality of pixels along the specific direction. The line sensor operation unit divides the plurality of pixels into a plurality of blocks and performs the transfer for each of the blocks. The intensity correction unit performs the correction of the pixels in the corresponding block based on the average value of the X-ray intensities calculated for each block.

4. The X-ray inspection apparatus according to claim 1 or 2, characterized in that The X-ray detection unit includes a time delay integration sensor having a plurality of lines of line sensors arranged in a matrix along the specific direction, and detecting the X-rays transmitted through the sample using the pixels.

5. The X-ray inspection apparatus according to claim 3, wherein The X-ray detection unit includes a time delay integration sensor having a plurality of lines of line sensors arranged in a matrix along the specific direction, and detecting the X-rays transmitted through the sample using the pixels.

6. An X-ray inspection method, characterized in that: The X-ray inspection method has the following features: An X-ray irradiation step of irradiating the sample with X-rays using an X-ray source; a sample moving step of continuously moving the sample in a specific direction while irradiating the sample with the X-rays from the X-ray source; An X-ray detection step of detecting the X-rays transmitted through the sample using pixels in an X-ray detection unit including a line sensor, wherein the line sensor is provided on a side of the sample opposite to the X-ray source and has a plurality of pixels arranged in a direction perpendicular to the specific direction; an image storing step of storing the X-ray intensity detected by the pixels; an intensity correction step of correcting the stored X-ray intensity; and Defect detection step, detecting whether there are defects in the sample based on the X-ray intensity, The sample is in the form of a long sheet without any part that does not need to be inspected. In the sample moving step, the sample is continuously supplied and moved without interruption, In the intensity correction step, the X-ray intensity detected in the initial detection start area when the X-ray detection is started in the sample, or the X-ray intensity detected in the sample before the X-ray detection is started, is used as a reference intensity. The X-ray intensity of the pixel detected in the area after the detection start area is corrected based on a correction coefficient obtained by comparing the X-ray intensity detected after the detection start area with the reference intensity. In the defect detection step, the presence or absence of the defect is determined based on a change in the correction coefficient.

7. The X-ray inspection method according to claim 6, wherein: When the defect is detected in the defect detection step, in the intensity correction step, the X-ray intensity detected in the defect detection area is corrected according to the following correction coefficient, wherein the correction coefficient is obtained by comparing the X-ray intensity detected in the area of ​​the sample where the defect is detected, i.e., the defect detection area, and the X-ray intensity detected in the area immediately before the defect detection area, i.e., the defect adjacent area.

8. The X-ray inspection method according to claim 6 or 7, characterized in that: The X-ray detection unit includes a line sensor calculation unit that controls the accumulation and transfer of charges in the plurality of pixels along the specific direction. The line sensor operation unit divides the plurality of pixels into a plurality of blocks and performs the transfer for each of the blocks. In the intensity correction step, the pixels in the corresponding block are corrected based on an average value of the X-ray intensities calculated for each block.

9. The X-ray inspection method according to claim 6 or 7, characterized in that: The X-ray detection unit includes a time delay integration sensor having a plurality of lines of line sensors arranged in a matrix along the specific direction, and detecting the X-rays transmitted through the sample using the pixels.

10. The X-ray inspection method according to claim 8, wherein: The X-ray detection unit includes a time delay integration sensor having a plurality of lines of line sensors arranged in a matrix along the specific direction, and detecting the X-rays transmitted through the sample using the pixels.

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