X-ray inspection equipment

Abstract

The present invention provides an X-ray inspection device that exhibits excellent discrimination performance of X-ray transmission energy even with high doses of X-rays, and can sufficiently improve the accuracy of foreign object detection. [Solution] An X-ray inspection apparatus comprising: an X-ray irradiation unit 21 that irradiates an article W being transported with X-rays Bx; an X-ray detection unit 23 that detects X-rays using a photon counting method; image generation units 41, 42 that generate X-ray images Xia, Xib corresponding to the detection result based on the X-ray detection result by the X-ray detection unit 23; and inspection processing units 43, 44 that inspect the article based on the X-ray images Xia, Xib. The X-ray irradiation unit 21 has an X-ray source 22 that outputs white X-rays having a continuous spectrum, and physical filters 30; 130 that cut out a portion of the bandwidth of the white X-rays output by the X-ray source 21. The X-ray detection unit 23 detects X-rays from which the bandwidth unnecessary for image generation by the image generation units 41, 42 has been removed by the physical filter 30 using a photon counting method.

Description

[Technical Field]

[0001] The present invention relates to an X-ray inspection apparatus, and more particularly to an X-ray inspection apparatus that irradiates an article being transported with X-rays and inspects the article based on the X-ray transmission image. [Background technology]

[0002] In X-ray inspection equipment, generally, when X-rays are irradiated onto an object being transported within the inspection area and pass through the object, an image detection signal is output from an X-ray detection unit that detects the X-rays on the passing side, and the object is inspected using an X-ray inspection image generated based on this output signal.

[0003] In such X-ray inspection devices, in order to prevent X-rays from leaking outside the device, a collimator made of X-ray shielding material is placed in the irradiation path of the X-rays from the X-ray irradiation unit. By shaping the X-rays from the X-ray irradiation unit into a cone-shaped or fan-shaped beam using the collimator, measures are taken to prevent the X-ray irradiation area from becoming excessively wider than the detection area of ​​the X-ray detection unit.

[0004] Conventional X-ray inspection devices of this type are known to include, in addition to an item transport unit, an X-ray irradiation unit, a collimator, and an X-ray detection unit, a temperature measuring unit for measuring the temperature of the X-ray tube of the X-ray irradiation unit, a storage unit for storing position control data showing the relationship between the focal temperature of the X-ray tube and the amount of focal position shift, and a position control unit for moving at least one of the X-ray line sensors of the X-ray irradiation unit, collimator, and X-ray detection unit based on the temperature measured by the temperature measuring unit.

[0005] In this device, the position control unit performs position control to move at least one of the X-ray irradiation unit, collimator, and X-ray line sensors of the X-ray detection unit in order to counteract the movement of the focal point in the position adjustment data corresponding to the temperature of the X-ray tube measured by the temperature measurement unit (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2018-146554 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] In conventional X-ray inspection equipment as described above, even if the target in the X-ray tube (X-ray source) of the X-ray irradiation unit expands due to the ambient temperature and the passage of operating time, causing the target position to move from its initial position, the operation of the position control unit substantially cancels out the displacement of the target's focal position corresponding to that temperature based on the temperature of the X-ray tube measured by the temperature measurement unit. As a result, the slit width of the collimator can be kept to the required width, and the X-ray output of the X-ray irradiation unit can be suppressed. This effectively suppresses the diffusion of X-rays to both sides of the transport direction where the loading and unloading ports of goods are located, and the amount of X-ray leakage can be sufficiently reduced.

[0008] However, even with this optimization of the X-ray irradiation area, the X-rays irradiated onto the object from the X-ray irradiation unit contain spectral bands other than those necessary for X-ray inspection. Therefore, it was sometimes necessary to limit the X-ray output in order to sufficiently suppress the amount of X-ray leakage.

[0009] Furthermore, when using a photon-count type X-ray detector, if the X-ray flux incident on the X-ray detector is high, a pile-up phenomenon is likely to occur, where measurement pulse signals output from the X-ray detector's detection element array (sensor array) at close detection timings overlap, resulting in high-energy measurement pulses.

[0010] Therefore, when attempting to improve foreign object detection sensitivity by generating multiple transmission image data with different X-ray transmission energies based on the image detection signal from the X-ray detector, and then performing difference processing on these data to generate differential image data that amplifies the image influence due to the difference in material (transmittance) between the object and the foreign object mixed in it, there was an unresolved problem in that the discrimination performance of the X-ray transmission energy would decrease, preventing the acquisition of highly accurate differential image data and thus preventing sufficient improvement in foreign object detection accuracy. Furthermore, it was sometimes necessary to limit the X-ray output (dose) to prevent a decrease in energy discrimination performance.

[0011] Therefore, the present invention aims to provide an X-ray inspection device that excels in discriminating X-ray transmission energy even with high doses of X-rays and can sufficiently improve the accuracy of foreign object detection. [Means for solving the problem]

[0012] The X-ray inspection apparatus according to the present invention, in order to achieve the above objective, comprises: (1) an X-ray irradiation unit that irradiates an article being transported with X-rays; an X-ray detection unit that detects the X-rays using a photon counting method; an image generation unit that generates an X-ray image corresponding to the detection result based on the X-ray detection result by the X-ray detection unit; and an inspection processing unit that inspects the article based on the X-ray image, wherein the X-ray irradiation unit has an X-ray source that outputs white X-rays having a continuous spectrum and a physical filter that cuts a portion of the bandwidth of the white X-rays output by the X-ray source, and the X-ray detection unit detects the X-rays from which the bandwidth unnecessary for image generation in the image generation unit has been removed by the physical filter using the photon counting method.

[0013] With this configuration, in the X-ray inspection apparatus of the present invention, among the X-rays irradiated from the X-ray irradiation unit, X-rays in spectral bands unnecessary for inspection by the inspection processing unit, for example, X-rays in a low energy band to such an extent that they are absorbed by the article and do not reach the X-ray detection unit, will not be photon-counted even in ranges where the X-rays do not pass through the article or in thin portions of the article. This makes it possible to effectively suppress an increase in the X-ray flux incident on the X-ray detector, and to effectively suppress the occurrence of pile-up.

[0014] In a preferred embodiment of the present invention, (2) the physical filter may be configured to be replaceably provided in the vicinity of the irradiation port of the X-ray irradiation unit.

[0015] With this arrangement, since the physical filter is replaceable in the vicinity of the irradiation port of the X-ray irradiation unit, it is possible to prevent X-rays in unnecessary spectral bands from being emitted from the X-ray irradiation unit, and the physical filter can be replaced according to the article.

[0016] In a preferred embodiment of the present invention, (3) the configuration may further comprise: a non-inspection band determination unit that determines, as an unnecessary spectrum, a partial band of the white X-rays that is unnecessary for the inspection of the article by the inspection processing unit; and a filter setting unit that switchably sets the physical filter corresponding to the unnecessary spectrum according to the determination result of the non-inspection band determination unit.

[0017] In this case, when the non-inspection band determination unit determines that a partial band unnecessary for the inspection of the article is an unnecessary spectrum, the physical filter corresponding to the unnecessary spectrum is switchably set according to the determination result.

[0018] In a preferred embodiment of the present invention, (4) the non-inspection band determination means may be configured to determine a band lower than the energy threshold at which the number of count values determined as unnecessary spectra is maximized as the unnecessary spectrum, when the energy threshold for determining as the unnecessary spectrum is changed to a plurality of different values within a predetermined variable range under a state where X-rays emitted from the X-ray irradiation unit and transmitted through a non-defective article are detected by the X-ray detection unit.

[0019] In this case, the energy threshold for determining as the unnecessary spectrum most suppresses the influence of the article, which is suitable for foreign matter detection.

[0020] In a preferred embodiment of the present invention, (5) a threshold storage unit is provided for storing the energy threshold for each product type of the article, the non-inspection band determination unit selectively sets any value of the energy thresholds stored in the threshold storage unit according to the product type of the article, and the filter setting unit may be configured to selectively set a physical filter corresponding to any of the energy thresholds selected and set by the non-inspection band determination unit according to the product type of the article.

[0021] This configuration enables selective setting of the physical filter corresponding to the unnecessary spectrum according to the product type of the article.

[0022] In a preferred embodiment of the present invention, (6) the filter setting means preferably has, as the physical filter, a plurality of filter elements different from each other in material and thickness in the X-ray transmission direction so as to be displaceable in a predetermined direction, and any one of the plurality of filter elements can be replaced in the vicinity of the irradiation port of the X-ray irradiation unit according to the product type of the article.

[0023] In this case, since any of the filter elements can be swapped with the vicinity of the irradiation port of the X-ray irradiation unit depending on the type of article, it is possible to cut out a certain frequency band that would result in unwanted spectra regardless of the type of article, thereby effectively suppressing an increase in the X-ray flux incident on the X-ray detector, and effectively suppressing the occurrence of pile-up during photon counting. [Effects of the Invention]

[0024] According to the present invention, it is possible to provide an X-ray inspection device that has excellent discrimination performance of X-ray transmission energy even with high doses of X-rays, and can sufficiently improve the accuracy of foreign object detection. [Brief explanation of the drawing]

[0025] [Figure 1] This is a schematic diagram of an X-ray inspection apparatus according to the first embodiment of the present invention. [Figure 2] This is a schematic diagram of the photon counting type X-ray detection unit in an X-ray inspection apparatus according to the first embodiment of the present invention. [Figure 3] This diagram illustrates the schematic arrangement of a collimator and a physical filter provided near the irradiation port of the X-ray irradiation section in an X-ray inspection apparatus according to the first embodiment of the present invention, where (a) is a top view of the collimator and physical filter in that arrangement, and (b) is a front cross-sectional view of the collimator and physical filter in that arrangement. [Figure 4] (a) is a graph showing the signal level waveform of the pulse signal with a peak value corresponding to the X-ray energy when X-ray detection using the photon counting method is performed without inserting a physical filter in the X-ray inspection apparatus according to the first embodiment of the present invention, including pulse signals where a pile-up phenomenon occurs. (b) is a graph showing the signal level waveform of the pulse signal with a peak value corresponding to the X-ray energy when X-ray detection using the photon counting method is performed with a physical filter inserted near the irradiation port of the X-ray irradiation unit. In each case, the vertical axis represents the pulse signal level and the horizontal axis represents the scan time. [Figure 5]This is a schematic diagram of an X-ray inspection apparatus according to a second embodiment of the present invention. [Figure 6] This is a perspective view of a physical filter in an X-ray inspection apparatus according to a second embodiment of the present invention, showing a slide-type physical filter unit in which multiple types of physical filters are arranged adjacently in a predetermined direction and integrated. [Figure 7] This diagram illustrates the schematic arrangement of a collimator and a physical filter provided near the irradiation port of the X-ray irradiation section in an X-ray inspection apparatus according to a second embodiment of the present invention, where (a) is a top view of the collimator in its arrangement, and (b) is a cross-sectional view taken along the line B7-B7 in (a). [Modes for carrying out the invention]

[0026] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

[0027] (First Embodiment) Figures 1 to 3 show an X-ray inspection apparatus according to the first embodiment of the present invention, and Figure 4 is an explanatory diagram of its main functions.

[0028] First, the configuration of this embodiment will be described.

[0029] As shown in Figure 1, the X-ray inspection apparatus 1 of this embodiment comprises a transport unit 10 for transporting the article W to be inspected, an X-ray imaging unit 20 for inspecting the article W while it is being transported by taking X-ray images, an inspection control unit 40 for controlling the transport unit 10 and the X-ray imaging unit 20, and a display operation unit 60 which is signal-connected to the inspection control unit 40 and is positioned near the X-ray imaging unit 20 for manual operation input.

[0030] The X-ray inspection device 1 irradiates the item W, which is being transported by the transport unit 10, with X-rays using the X-ray imaging unit 20, and generates image data corresponding to the transmitted X-ray dose distribution. Based on this image data, the device inspects the quality status of the item W. The quality status referred to here includes whether the item W meets the required quality and physical quantities as a product, such as the presence or absence of foreign matter, whether there are any missing parts, whether the shape, size, and storage condition of the contents are acceptable, and the distribution of density, thickness, volume, or mass.

[0031] The conveying unit 10 is a belt conveyor that winds a loop-shaped conveying belt 11 around a plurality of parallel conveying rollers 12a, 12b, 13a, 13b, and sequentially conveys articles W through an inspection area Zx on the conveying belt 11 in a predetermined conveying direction (hereinafter also referred to as conveying direction d1) indicated by arrow d1 in Figure 1, and is supported by a housing (not shown).

[0032] The X-ray imaging unit 20 includes an X-ray irradiation unit 21 (X-ray irradiation source) which incorporates an X-ray tube 22 and irradiates the X-rays generated by the X-ray tube 22 toward the inspection area Zx through which the item W passes, and an X-ray detector 23 (X-ray detection unit) which is positioned at a predetermined position in the transport direction d1 so as to face the X-ray irradiation unit 21 with the inspection area Zx in between, enabling imaging of the item W within the inspection area Zx using X-rays.

[0033] The X-ray irradiation unit 21 includes a power supply and drive circuit necessary to drive the X-ray tube 22, which acts as an X-ray source, as well as means for cooling the X-ray tube 22 and shielding the X-rays. The X-ray tube 22 generates X-rays of wavelength and intensity corresponding to its tube current and tube voltage.

[0034] Furthermore, the X-ray irradiation unit 21 is configured to irradiate the articles W in the inspection section Zx on the transport belt 11 with a fan-beam-shaped X-ray Bx directed vertically d3, which spreads in a line scanning direction d2 perpendicular to the transport direction d1 of the transport unit 10 (it may also be deflected). This X-ray irradiation unit 21 uses either a fixed-type target (anode) or a rotating-type target.

[0035] The X-ray imaging unit 20 is provided with two drive power supply circuits for the X-ray tube 22 of the X-ray irradiation unit 21: one drive power supply circuit 25 that applies a predetermined ignition voltage to the cathode 22a, and the other drive power supply circuit 26 that applies a positive potential corresponding to a high-voltage operating anode voltage to the anode 22b. Specifically, the one drive power supply circuit 25 includes a so-called filament power supply circuit, and the other drive power supply circuit 26 includes a high-voltage circuit that applies a high voltage between the filament of the X-ray tube 22 and the target.

[0036] The X-rays generated by the X-ray irradiation unit 21 are continuous-spectrum white X-rays containing multiple different wavelength regions. The energy of these X-rays needs to be set to a range suitable for inspecting the item W, and the tube voltage and tube current applied to the X-ray tube 22 can be variably controlled by the inspection control unit 40. Furthermore, the X-rays irradiated from the X-ray irradiation unit 21 and detected by the X-ray detector 23 are set to a predetermined beam quality (energy, wavelength) according to the type of item W.

[0037] In this embodiment, in particular, by using multiple types of X-rays with different beam qualities, so-called dual-energy or multi-energy X-ray images are generated. Then, by performing differential processing on X-ray images with different energy bands, differential image data is generated that greatly increases the image influence due to the difference in material (transmittance) between the article W and any foreign matter that may be mixed in, thereby improving the sensitivity for detecting abnormalities such as foreign matter.

[0038] As shown in Figure 2, the X-ray detector 23 has a one-dimensional X-ray line sensor 23L in which multiple sensor elements e1 to eN, each receiving X-rays and converting them into electrical signals, for example, N elements (where N is an integer greater than 1, for example, 256 × 8), are arranged in a line adjacent to each other in the line scanning direction d2. Here, the X-ray detector 23 is exemplified as a sensor array structure having a one-dimensional X-ray line sensor 23L, but it may also have a two-dimensional X-ray line sensor. Furthermore, the X-ray detector 23 may also be configured by joining together a predetermined number (k elements in the figure) of sensor element modules M1 to Mk (where k is an arbitrary natural number, for example, 8 modules) while arranging them in a line in the line scanning direction. In that case, each of the multiple sensor element modules M1 to Mk can have multiple sensor elements e1 to em (= N / k, for example, 256 elements) in each sensor element module Mi.

[0039] Specifically, the X-ray detector 23 is a photon detection type that uses a direct conversion type semiconductor element, such as a flat, layered cadmium telluride semiconductor (CdTe (Cadmium Telluride)), in the X-ray conversion portion which serves as each sensor element ei. Both sides of the semiconductor element have a face electrode, one side of which is a bias electrode, and the other side of which is a layer for arranging multiple pixel electrodes corresponding to multiple sensor elements e1 to eN. When X-rays from the X-ray irradiation unit 21 are incident on the semiconductor element of each sensor element ei of the X-ray detector 23, electrons and holes corresponding to the incident X-ray dose are generated between the face electrodes, and a pulse signal with a pulse height corresponding to the energy of the X-ray (photon) can be output to the inspection control unit 40.

[0040] The inspection control unit 40 has a transport control function that controls the transport speed Vc and transport interval of the articles W by the transport belt 11 in the transport unit 10, and an inspection control function that controls the X-ray irradiation intensity and irradiation period in the X-ray imaging unit 20, as well as the scanning period of the X-ray detector 23 and the detection period for each article W according to the transport speed Vc of the articles W. The configuration of the transport control function unit is assumed to be the same as known, and the inspection control function will be described below.

[0041] The inspection control unit 40, although its detailed overall configuration is not shown, has a hardware configuration that includes a processor having a CPU, ROM, RAM, and I / O interface (not shown), an auxiliary storage device that stores control programs for image processing, inspection judgment, and control functions in a readable format in cooperation with the ROM, and a timer circuit, etc. This hardware executes predetermined arithmetic processing and the control programs according to the software such as control programs and setting information stored in the ROM, while exchanging data with the CPU and RAM, etc., thereby enabling the execution of various functions. The hardware referred to here may include FPGA (Field Programmable Gate Array) and DSP (Digital Signal Processor), etc. Furthermore, the various functions referred to here are the functions of the means for generating the aforementioned X-ray transmission image data, predetermined inspection control, and display output control.

[0042] (Inspection and Control Unit) As shown in Figure 2, the inspection control unit 40 includes an image data generation unit 41, an image data storage unit 42, an image processing unit 43, and a pass / fail determination unit 44 as inspection control function units.

[0043] Here, the image data generation unit 41 and the image data storage unit 42 are image generation units that generate dual-energy or multi-energy X-ray images, such as the dual-energy X-ray images Xia and Xib described later, based on the X-ray detection results from the X-ray detector 23. The image processing unit 43 and the quality determination unit 44 are inspection processing units that inspect the article W based on the X-ray images Xia and Xib.

[0044] Specifically, the image data generation unit 41 sequentially acquires X-ray detection signals from each sensor element ei of the X-ray detector 23 at predetermined scanning cycles as image detection signals, and generates image data of an X-ray image corresponding to the transmission amount distribution of X-rays that have passed through the inspection area Zx. This image data generation unit 41 has multiple A / D conversion units 511 to 51 corresponding to multiple sensor elements e1 to eN.N , a plurality of peak value detection units 521 to 52 N , a plurality of region determination units 531 to 53 N , a plurality of region-specific accumulation units 541 to 54 N , and a plurality of transmitted image data output units 55.

[0045] The plurality of A / D conversion units 511 to 51 N are configured to capture, as the image detection signal Lx of the X-ray detector 23 (see FIG. 1), pulse signals of peak values corresponding to the energy of X-rays incident on the respective element regions from the plurality of sensor elements e1 to eN for each scanning cycle (scan time) of the X-ray line sensor 23L, and perform A / D conversion into pulse signal levels indicating the respective peak values (energies).

[0046] The plurality of peak value detection units 521 to 52 N are configured to perform differential processing on the data sequence input from, for example, the A / D conversion units 511 to 51 for each scanning cycle of the X-ray line sensor 23L, detect a zero-crossing timing when the differential value (signal slope) switches from a positive value equal to or greater than a predetermined value to a negative value equal to or less than a predetermined value, detect the data value at the zero-crossing timing as the peak value of the pulse signal, and output the same to the region determination units 531 to 53 N N .

[0047] The plurality of region determination units 531 to 53 N are configured to determine the energy band of X-rays incident on the respective element regions of the plurality of sensor elements e1 to eN based on the pulse signal levels respectively detected by the corresponding peak value detection units 521 to 52. N

[0048] The plurality of region-specific accumulation units 541 to 54 N are configured to execute processing of accumulating the pulse signal level values separately for a plurality of energy bands different in level during the scan time, while taking in the corresponding determination results from the plurality of region determination units 531 to 53 as the energy level values of X-rays incident on the plurality of sensor elements e1 to eN. N ​​​

[0049] The cumulative count here is the cumulative number of pulse signals output from each sensor element ei within the scan time that share the same energy band in which their peak value falls. By storing the cumulative counts for each energy band output for each scan time in parallel and chronologically in the image data memory, X-ray transmission image data for each element region corresponding to the transmitted X-ray energy incident on each sensor element ei within the scan time can be obtained. Furthermore, by dividing the pulse signal level value into two energy bands, HE and LE, using a predetermined threshold Lthp, and accumulating the pulse signal levels for each energy band, it becomes possible to create X-ray transmission image data Dpxh for the high-energy band HE and X-ray transmission image data Dpxh for the low-energy band LE.

[0050] Cumulative area by area 541~54 N The data obtained by accumulating the signal levels of pulse signals from multiple sensor elements e1 to eN is then input into the transmission image data output unit 55, which is associated with each element region of the multiple sensor elements e1 to eN, in order to obtain X-ray transmission image data Dpxh and Dpxl based on this data.

[0051] Then, the transparent image data output unit 55 has region-specific accumulation units 541-54 N The system is configured to sequentially write region-specific cumulative data, which is acquired and associated with multiple sensor element regions e1 to eN, to the image data storage unit 42.

[0052] The image data storage unit 42 stores and stores the X-ray image data Dpxh and Dpxl written by the transmission image data output unit 55 of the image data generation unit 41 during a predetermined inspection period corresponding to the transport direction length of the article W, thereby generating and storing dual-energy imaging data of the article W. The image data storage unit 42 has a data processing program and an image memory area that can perform the function of generating X-ray image data Xia and Xib corresponding to the dose distribution of X-rays transmitted through the article W as dual-energy imaging data of the article W, based on detection data of line scan images that are sequentially written while the line scan by the X-ray line sensor 23L of the X-ray detector 23 is repeated a predetermined number of times corresponding to the inspection period of the article W, and outputting these to the image processing unit 43.

[0053] The image processing unit 43 acquires dual-energy imaging data Xia and Xib of the item W from the image data storage unit 42 and performs image analysis processing such as preprocessing (including filtering) that allows extraction of image features from each, and feature measurement to determine the feature quantities of the extracted image features. The image processing unit 43 has a predetermined inspection algorithm pre-set and stored, which combines image processing filters and the like, in order to perform a predetermined item inspection based on the X-ray image data Xia and Xib acquired from the image data storage unit 42.

[0054] The image processing filter included in the inspection algorithm of the image processing unit 43 is a processing program for extracting image features necessary for a predetermined item inspection based on the X-ray image data Xia and Xib of the item W. If the inspection algorithm includes a filter for detecting foreign objects, for example, it has a feature extraction filter that performs edge detection processing to emphasize the contours of foreign objects in the item W, and emphasizes the edges of foreign objects by applying differential processing or the like to the neighboring region of the pixel of interest. Furthermore, the feature measurement of image features performed by the image processing unit 43 is a process that measures the amount of features necessary for the judgment process in the pass / fail judgment unit 44 by performing calculations on an image obtained by applying necessary preprocessing and image processing to one of the X-ray image data Xia and Xib of the item W or their difference image data acquired from the image data storage unit 42, for example, grayscale features, color features, shape features, etc.

[0055] The quality determination unit 44 performs a determination process to determine whether or not an item W is in a predetermined quality state based on the feature data extracted by the image processing unit 43. This determination process includes determining whether or not foreign objects are present, whether or not there are missing items, and whether the shape, size, or storage condition of the contents is acceptable. Based on the feature data extracted and measured by the image processing unit 43, the quality determination unit 44 detects feature shapes and foreign objects detected in the item W, and compares the area, contour length, and density sum of the detected object's feature quantities with predetermined judgment criteria (hereinafter referred to as predetermined judgment criteria). This allows the unit to perform a determination process to determine whether or not a local feature shape corresponding to a foreign object or defective part that satisfies the judgment conditions is included in the item W.

[0056] In this embodiment, the X-ray inspection apparatus 1 irradiates the inspection area Zx into which the article W is brought in with X-rays Bx from the X-ray irradiation unit 21 of the X-ray imaging unit 20, and detects the X-rays passing through the inspection area Zx with an X-ray detector 23 having N sensor elements e1 to eN. Based on the image detection signal Lx from the X-ray detector 23, imaging data Dpxh and Dpxl of the article W are generated, and the inspection control unit 40 performs inspection control to inspect the article W using these image data and predetermined judgment criteria that have been set in advance.

[0057] (Partial cut of the X-ray irradiation band) In this embodiment, the X-ray tube 22 of the X-ray irradiation unit 21 is an X-ray source that outputs white X-rays having a continuous spectrum, and the X-ray irradiation unit 21 is detachably provided with a physical filter 30 that cuts off a portion of the bandwidth of the white X-rays generated and output by the X-ray tube 22 before irradiation, so that it can be replaced depending on the item W.

[0058] This physical filter 30 has a filter plate 31 that cuts out a portion of the low-energy band LE, which is part of the total energy band of white X-rays emitted from the X-ray irradiation unit 21 and is lower than a predetermined threshold level Lthp as shown in Figure 4(a), in particular the low-energy band (long wavelength band) of X-rays that are absorbed while passing through the article W due to the product effect of the article W.

[0059] As shown in Figure 3, guide ribs 35a and 35b are provided on both ends of the filter plate 31 of the physical filter 30, and these guide ribs 35a and 35b are slidably attached to the left and right guide rails 36a and 36b in the front-rear direction. This allows the physical filter 30 to move between a mounting position near the irradiation port 24a of the X-ray irradiation unit 21 (preferably above the collimator) and a detachable position that moves from the mounting position to the front or back side of the X-ray inspection device 1. Multiple types of physical filters with different filter characteristics are prepared and interchangeable, allowing the filter characteristics to be changed according to the item W and the inspection content.

[0060] The material of the filter plate 31 of the physical filter 30 can be a metal that does not easily deteriorate, such as aluminum, copper, or iron. By changing the thickness and material of the filter plate 31 through replacement, any unwanted X-ray spectra that do not effectively contribute to the inspection can be cut out.

[0061] Furthermore, in order to determine spectral bands that are not required for inspection, the inspection control unit 40 may be equipped with an inspection condition setting unit 45 to determine the appropriate type of physical filter, thickness, tube voltage, tube current, and a determination threshold (hereinafter simply referred to as the energy threshold) for whether or not photon counting is required in the energy band effective for inspection, based on the X-ray transmission image of the item W. In this case, for example, the correlation between the count value and the energy threshold during X-ray irradiation and photon counting of the item W to be inspected can be taken, and the energy threshold just before the count value for each item W starts to decrease when the energy threshold is increased (the decrease in the count value due to the threshold change begins) can be determined as the maximum energy of the unnecessary X-ray spectrum. This value can then be set in the inspection condition setting unit 45 as the determination threshold for whether or not photon counting is required in the energy band, i.e., the non-inspection band determination threshold Thc (see Figure 4(b); hereinafter simply referred to as the determination threshold Thc), which is the lower limit of the energy band effective for inspection. Furthermore, the inspection condition setting unit 45 can set the tube voltage and tube current of the X-ray tube 22 of the X-ray irradiation unit 21 to set the upper limit of the energy band effective for the inspection and the required X-ray image density range.

[0062] Furthermore, in addition to the inspection condition setting unit 45, the inspection control unit 40 is provided with a non-inspection band determination means 46 that determines a portion of the white X-ray band that is unnecessary for X-ray inspection of the item W based on a determination threshold Thc, and according to the determination result of the non-inspection band determination means 46, the type of physical filter 30 corresponding to the unnecessary spectrum and the request for its insertion are displayed on the display operation unit 60 in the form of a pop-up display or the like, and the filter settings by the inspection condition setting unit 45 and setting requests related to other inspection conditions can also be output.

[0063] Furthermore, the inspection control unit 40 is provided with a threshold storage means 47 that stores a determination threshold Thc for each type of item W, which determines whether or not the energy band is subject to photon counting (i.e., whether or not it is an uninspected band). The uninspected band determination means 46 selects and sets one of the energy threshold Thc values ​​stored in the threshold storage means 47 according to the type of item W. The inspection condition setting unit 45, which is a filter setting means, compares one of the energy thresholds selected and set by the uninspected band determination means 46 according to the type of item W with the cut state of unwanted spectra by the physical filter 30, which is determined by detecting X-rays transmitted through the physical filter 30 using a photon counting method. The inspection condition setting unit 45 determines whether or not the energy threshold to be set according to the type of item W and the physical filter 30 are a corresponding effective combination (i.e., whether or not the filter is installed in a state suitable for inspection). If they do not correspond, the type of physical filter 30 corresponding to the unwanted spectra is displayed on the display operation unit 60, and the inspection condition setting unit 45 is enabled to set filters and other inspection conditions.

[0064] More specifically, the physical filter 30 can be configured to set the material and thickness of the filter plate 31 so as a threshold for determining whether or not an energy band is subject to photon counting. For example, in Figure 4(a), it can cut out relatively long wavelength bands where the pulse signal level (low energy) is half (1 / 2) or less of the predetermined threshold level Lthp in the low-energy band LE that is below the predetermined high / low energy band determination threshold level Lthp.

[0065] As shown in Figures 1 to 3, in the X-ray irradiation path from the X-ray irradiation unit 21 to the X-ray detector 23, collimators 27A and 27B, each formed of an X-ray shielding material, are provided to limit the irradiation range of the X-rays from the X-ray irradiation unit 21 to the vicinity of the detection range of the X-ray detector 23 and to prevent X-rays from leaking outside the X-ray inspection apparatus 1 (outside the apparatus).

[0066] The collimators 27A and 27B are formed and positioned to shape the X-ray Bx beam from the X-ray irradiation unit 21 into a cone-shaped or fan-shaped beam using their respective slits 27s1 and 27s2, thereby allowing X-rays that can be incident on the X-ray line sensor 23L of the X-ray detector 23 to pass through the irradiation area, while blocking X-rays that would otherwise fall outside the detection area of ​​the X-ray line sensor 23L.

[0067] In each figure, the filter plate 31 of the physical filter 30 is positioned between the collimators 27A and 27B, and the left and right guide rails 36a and 36b are shown as X-ray shielding material. However, it goes without saying that the arrangement is not limited to this configuration, and there may be only one collimator 27A or 27B, and the filter plate 31 of the physical filter 30 may be positioned closer to the X-ray irradiation unit 21 than the collimator 27A.

[0068] In either configuration, the X-ray detector 23 detects X-rays using a photon counting method, after the X-rays have had unnecessary bandwidths removed by the physical filter 30 for image generation in the image generation unit, which consists of the image data generation unit 41 and the image data storage unit 42. Therefore, when the image data generation unit 41 and the image data storage unit 42, which constitute the image generation unit, generate X-ray images Xia and Xib corresponding to the imaging results at the X-ray detector 23, the X-rays incident on the X-ray detector 23 have low-energy bandwidths cut off even in the range where they do not pass through the item W, to the extent that they would be absorbed while passing through the item W due to the product influence of the item W. This does not adversely affect the imaging results, and the multiple A / D conversion units 511 to 51 of the image data generation unit 41 N Therefore, the unwanted pulse signals captured at each scanning cycle of the X-ray line sensor 23L can be reduced. N This makes it possible to suppress unnecessary wave height detection processing.

[0069] On the other hand, for X-rays within the energy band effective for inspection that pass through the article W and are detected by the X-ray detector 23, multiple pulse height detection units 521-52N Based on the pulse signal levels detected by each of these, multiple region determination units 531-53 N This allows for accurate determination of the transmitted X-ray energy band.

[0070] In Figure 1, the transport unit 10 is shown as a transport path extending from the inlet to the outlet of the article W to the X-ray inspection device 1, with the upper section 11a of the loop-shaped transport belt 11 being represented. However, the transport belt 11 may be divided into an upstream and downstream side in the article transport direction, with the irradiation position of the X-ray beam Bx from the X-ray irradiation unit 21 to the X-ray detector 23 in between, and the X-ray beam Bx from the X-ray irradiation unit 21 incident on the X-ray detector 23 between these upstream and downstream transport belts. In that case, it is also conceivable to use a polyimide film or the like as the resin cover on the upper surface of the X-ray detector 23 into which the X-rays are incident to suppress thermal effects from direct irradiation.

[0071] Next, I will explain the mechanism of action.

[0072] In the X-ray inspection apparatus of this embodiment configured as described above, X-rays in spectral bands that are unnecessary for inspection by the inspection control unit 40, such as X-rays in the low-energy band that are absorbed by the object W and do not reach the X-ray detector 23, are not photon counted even in areas that do not penetrate the object W or in thin parts of the object W. This effectively suppresses an increase in the X-ray flux incident on the X-ray detector 23.

[0073] As a result, conventionally, a pile-up phenomenon occurs where the signal levels of two pulse signals P1a and P1b in the low-energy band LE, which are counted at close timings, are counted together and perceived as the pulse signal P1 in the high-energy band HE, as is the case with the leftmost pulse signal P1 in Figure 4(a). In this embodiment, however, in the low-energy band LE, where the X-ray flux incident on the X-ray detector 23 tends to increase, photon counts of approximately the signal level of pulse signal P1b are not counted together. Therefore, as shown in Figure 4(b), the occurrence of the pile-up phenomenon can be effectively suppressed.

[0074] Furthermore, in this embodiment, the physical filter 30 is removably provided near the irradiation port 24a of the X-ray irradiation unit 21, so that unwanted X-rays in the spectral band can be effectively prevented from being irradiated from the X-ray irradiation unit 21, and the physical filter 30 can be replaced according to the type of article W and the degree of product influence.

[0075] Furthermore, in this embodiment, the inspection control unit 40 has a non-inspection band determination means 46 that determines a portion of the white X-ray band that is unnecessary for X-ray inspection of the item W as an unnecessary spectrum, and an inspection condition setting unit 45 that acts as a filter setting means to set a physical filter corresponding to the unnecessary spectrum in a switchable manner according to the determination result of the non-inspection band determination means 46. Therefore, when the non-inspection band determination means 46 determines that a portion of the band that is unnecessary for inspection of the item W is an unnecessary spectrum, the physical filter 30 corresponding to the unnecessary spectrum can be appropriately attached, detached, or replaced according to the determination result.

[0076] In addition, in this embodiment, the non-inspection band determination means 46 sets an energy threshold Thc for determining unwanted spectra when X-rays detected by the photon counting method are determined to be unwanted spectra, and is equipped with a physical filter 30 corresponding to the set value Thc. The energy threshold Thc is set when, under conditions in which X-rays irradiated from the X-ray irradiation unit 21 and transmitted through a good product W or a substitute masterpiece are detected by the X-ray detector 23, the energy threshold for determining unwanted spectra is changed, for example, increased, within a predetermined variable range. The threshold just before the decrease in count values ​​due to the threshold increase begins is determined to be the maximum energy of the unwanted X-ray spectrum, and the threshold Thc is set to the threshold when the number of count values ​​determined to be unwanted spectra is maximized. Therefore, the energy threshold Thc for determining unwanted spectra minimizes the influence of the product W, making it suitable for foreign object detection.

[0077] Furthermore, in this embodiment, a threshold storage means 47 is provided for storing an energy threshold Thc for each type of article W. A non-inspection bandwidth determination means 46 selects and sets one of the energy threshold values ​​stored in the threshold storage means 47 according to the type of article W. An inspection condition setting unit 45, which is a filter setting means, determines whether or not the physical filter 30 corresponding to the new type of article W is installed when switching articles W, and can display an output to the display operation unit 60 indicating that a change in the inspection condition setting is necessary. Therefore, the energy threshold Thc according to the type of article W and the corresponding physical filter 30 can be set to conditions that are more effective for X-ray inspection of the article W.

[0078] (Second Embodiment) Figures 5 to 7 show an X-ray inspection apparatus 2 according to a second embodiment of the present invention.

[0079] Since this embodiment has the same or similar configuration as the first embodiment, redundant explanations of these identical or similar configurations and their functions will be omitted in Figures 5 to 7, using the corresponding reference numerals for the components shown in Figures 1 to 3. The differences will be explained below.

[0080] As shown in Figures 5 and 6, in this embodiment, the X-ray irradiation unit 21 of the X-ray imaging unit 20 is detachably provided with a physical filter 130 that cuts out a portion of the bandwidth of the white X-rays generated and output by the X-ray tube 22.

[0081] This physical filter 130 divides the entire energy band of white X-rays emitted from the X-ray irradiation unit 21 into a band HE above a predetermined threshold level Lthp shown in Figure 4(a) and a band LE below a predetermined threshold level Lthp, similar to the physical filter 30 of the first embodiment. It has multiple types of filter plates, for example, four types 131, 132, 133, and 134, which cut off a portion of the low-energy band included in the low-energy band LE, particularly X-rays in relatively long wavelength bands that are absorbed while passing through the article W due to the product influence of the article W, into different subbands (see Figure 6).

[0082] As shown in Figures 6 and 7, a pair of guide ribs 135a and 135b are provided at both ends of the filter plates 131 to 134, extending in the transport direction d1 while protruding on both sides in the line scanning direction d2. These guide ribs 135a and 135b are supported by a pair of front and rear guide rails 136a and 136b so as to be able to reciprocate and slide in a direction parallel to the transport direction d1. As a result, the physical filter 130 allows any one of the filter plates 131 to 134 to be moved between a mounting position near the irradiation port 24a of the X-ray irradiation unit 21 and separate retraction positions at a predetermined distance from the mounting position in the transport direction. By preparing multiple types of filter plates 131 to 134 with different filter characteristics, the filter characteristics can be automatically switched according to the item W and the inspection content.

[0083] The materials of the various filter plates 131-134 can be appropriately selected according to the item W and its inspection requirements, and are not particularly limited. For example, as shown in Figure 6, the material of filter plate 131 is, for example, an aluminum plate of a predetermined thickness; the material of filter plate 132 is, for example, an aluminum plate with a greater thickness than filter plate 131; the material of filter plate 133 is, for example, an iron plate with a greater thickness than filter plate 132; and the material of filter plate 134 is, for example, a copper plate with a greater thickness than filter plate 133.

[0084] In this embodiment, in order to determine spectral bands that are unnecessary for inspection, the control unit 140 that receives the image detection signal Lx from the X-ray detector 23 is equipped with an inspection control unit 40 similar to that in the first embodiment, and it incorporates an inspection condition setting unit 45, a non-inspection band determination means 46, and a threshold storage means 47. The control unit 140 has hardware and software similar to the inspection control unit 40 of the first embodiment, but it also has the following configuration in order to variably control the irradiation conditions of the X-ray irradiation unit 21.

[0085] In other words, the control unit 140 is equipped with an irradiation condition control unit 150 in addition to the inspection control unit 40 similar to that of the first embodiment. Based on the control output of the inspection control unit 40, the irradiation condition control unit 150 variably sets the determination threshold Thc (non-inspection band determination threshold) determined by the non-inspection band determination means 46 according to the type of item W, one of the filter plates 131 to 134 of the physical filter 130 suitable for that determination threshold Thc, and the tube voltage and tube current of the X-ray tube 22 of the X-ray irradiation unit 21.

[0086] Specifically, the irradiation condition control unit 150 is a functional unit that determines the appropriate type of physical filter, thickness, tube voltage, tube current, and energy threshold for whether or not photon counting is required from the X-ray transmission image of the object W, and has hardware and software corresponding to that function.

[0087] The irradiation condition control unit 150, for example, correlates the count value with the energy threshold when X-ray irradiation and photon counting are performed on the item W. When the energy threshold is increased, the unit determines the energy threshold just before the count value for each item W begins to decrease (when the decrease in the count value due to the threshold change begins) as the maximum energy of the unnecessary X-ray spectrum. The inspection condition setting unit 45 then sets this threshold as the determination threshold Thc, which is the determination threshold (lower limit of the energy band effective for inspection) for determining whether or not the energy band is suitable for photon counting. The unit then allows the selection of filter plates 131 to 134 of the physical filter 130 that are suitable for this determination threshold Thc.

[0088] Furthermore, the irradiation condition control unit 150 can control the tube voltage and tube current of the X-ray tube 22 of the X-ray irradiation unit 21 by controlling one drive power supply circuit 25 and the other drive power supply circuit 26 of the X-ray imaging unit 20, and can also position any one of the filter plates 131 to 134 of the physical filter 130 near the irradiation port 24a of the X-ray irradiation unit 21 via a linear actuator 155 such as a linear stepping motor (which may include a mechanism for converting rotational motion into linear motion). The functions of the inspection condition setting unit 45, the non-inspection band determination means 46, and the threshold storage means 47 in the inspection control unit 40 are as described above.

[0089] In this embodiment as well, similar to the first embodiment, X-rays in spectral bands that are unnecessary for inspection by the inspection control unit 40, such as X-rays in the low-energy band that are absorbed by the object W and do not reach the X-ray detector 23, are not photon counted even in areas that do not penetrate the object W or in thin parts of the object W. This effectively suppresses the increase in the X-ray flux incident on the X-ray detector 23.

[0090] As a result, conventionally, as described in the first embodiment, a pile-up phenomenon occurs where the signal levels of two pulse signals P1a and P1b in the low-energy band LE, which are counted at close timings, are counted together and perceived as the pulse signal P1 in the high-energy band HE, as shown in the pulse signal P1 on the far left of Figure 4(a). However, in this embodiment, the signal level of pulse signal P1b is generally below the energy threshold Thc corresponding to the type of item W, so it is not counted together with pulse signal P1a, and the pile-up phenomenon can be effectively suppressed as shown in Figure 4(b).

[0091] Furthermore, in this embodiment, the control unit 140 activates the inspection condition setting unit 45, which acts as a filter setting means to enable switching of physical filters corresponding to unwanted spectra, according to the determination result of the non-inspection bandwidth determination means 46 of the inspection control unit 40. Therefore, when the non-inspection bandwidth determination means 46 determines that a portion of the bandwidth that is unnecessary for the inspection of the item W is an unwanted spectrum, the irradiation condition control unit 150 is activated according to the determination result to automatically select one of the multiple types of filter plates 131 to 134 of the physical filter 130 that corresponds to the unwanted spectrum, and can be positioned and placed near the irradiation port 24a of the X-ray irradiation unit 21 via the linear actuator 155.

[0092] Therefore, it becomes possible to select and set the physical filter 130 to correspond to unwanted spectra according to the type of item W. Regardless of the type of item W, a certain bandwidth of unwanted spectra can be cut, effectively suppressing the increase in X-ray flux incident on the X-ray detector 23 during photon counting-based X-ray detection, and effectively suppressing the occurrence of pile-up during photon counting.

[0093] As a result, even when a large dose of X-rays is irradiated by the X-ray irradiation unit 21, we can provide an X-ray inspection device 2 that has excellent discrimination performance for X-ray transmission energy and can sufficiently improve the accuracy of foreign object detection.

[0094] It goes without saying that the shapes and sizes of the collimators 27A and 27B and filters 30 and 130, as well as the number of different types of filter elements, as exemplified in each of the embodiments described above, are all arbitrary.

[0095] As described above, the present invention provides an X-ray inspection device that excels in discriminating X-ray transmission energy even with high doses of X-rays and can sufficiently improve the accuracy of foreign object detection. The present invention is useful for X-ray inspection devices in general that irradiate transported articles with X-rays and inspect the articles based on X-ray transmission images. [Explanation of symbols]

[0096] 1;2 X-ray inspection equipment 10 Conveying section 11. Conveyor belt 11a Upper running section 12a, 12b, 13a, 13b Conveyor rollers 20 X-ray imaging section 21 X-ray irradiation section (X-ray irradiation source) 22. X-ray tube (X-ray generator) 22a cathode 22b Anode 23. X-ray detector (X-ray detection unit) 23L X-ray line sensor 24 tanks 24a Irradiation port (irradiation window) 25 One of the drive power supply circuits (cathode side drive power supply circuit) 26 The other drive power supply circuit (anode side drive power supply circuit) 27A, 27B collimator 27s1, 27s2 Slit 30 Physical Filters 31 Filter plate (filter element) 35a, 35b Guide ribs 36a, 36b Guide rails 40 Inspection Control Unit 41 Image Data Generation Unit 42 Image data storage unit 43 Image Processing Unit 44. Quality Determination Unit 45. Inspection condition setting unit (filter setting means) 46 Non-inspection bandwidth determination means 47 Threshold storage means 511~51 N A / D conversion unit 521~52 N Wave height detection unit 531~53 N Area determination section 541~54 N Cumulative section by area 55 Transparent Image Data Output Unit 60 Display operation section 130 Physical Filters 131, 132, 133, 134 Filter plates (filter elements) 135a, 135b Guide Ribs 136a, 136b Guide rails 140 Control Unit 150 Irradiation Condition Control Unit 155 Linear Actuator d1 Conveying direction d2 Line scanning direction d3 Vertical direction Dpxh, Dpxl X-ray transmission image data (imaging data, image data) e1~eN Sensor element HE High energy side energy band LE (Low Energy Band) P1 pulse signal P1a, P1b pulse signals Thc decision threshold (energy threshold, non-test bandwidth decision threshold) Xia,Xib X-ray image data (image data) W Goods

Claims

1. An X-ray irradiation unit (21) that irradiates the transported item (W) with X-rays (Bx), An X-ray detection unit (23) that detects the aforementioned X-rays using a photon counting method, Image generation units (41, 42) generate X-ray images (Xia, Xib) corresponding to the detection results based on the X-ray detection results by the X-ray detection unit, An X-ray inspection apparatus comprising an inspection processing unit (43, 44) that inspects the article based on the X-ray image, The X-ray irradiation unit includes an X-ray source (22) that outputs white X-rays having a continuous spectrum, and a physical filter (30; 130) that cuts out a portion of the bandwidth of the white X-rays output by the X-ray source. The X-ray detection unit is characterized by detecting X-rays, from which bandwidths unnecessary for image generation in the image generation unit have been removed by the physical filter, using the photon counting method.

2. The X-ray inspection apparatus according to claim 1, characterized in that the physical filter is provided in a replaceable manner near the irradiation port (24a) of the X-ray irradiation unit.

3. Non-inspection band determination means (46) that determines a portion of the white X-ray band that is unnecessary for inspection of the article in the inspection processing unit as an unnecessary spectrum, The X-ray inspection apparatus according to claim 1 or 2, further comprising: filter setting means (45) that can switch a physical filter corresponding to the unwanted spectrum according to the determination result of the non-inspection band determination means.

4. The X-ray inspection apparatus according to claim 3, wherein the non-inspection band determination means, under the condition that X-rays irradiated from the X-ray irradiation unit and transmitted through a good product are detected by the X-ray detection unit, changes the energy threshold for determining the unwanted spectrum to a plurality of different values ​​within a predetermined variable range, and determines a band lower than the energy threshold at which the number of count values ​​determined to be unwanted spectrum is maximized as an unwanted spectrum.

5. A threshold storage means (47) is provided for storing the energy threshold for each type of article. The non-inspection bandwidth determination means selects and sets one of the energy threshold values ​​stored in the threshold storage means according to the type of article, The X-ray inspection apparatus according to claim 4, characterized in that the filter setting means selects and sets a physical filter corresponding to one of the energy thresholds selected and set by the non-inspection band determination means according to the type of article.

6. The X-ray inspection apparatus according to claim 3, wherein the filter setting means has a plurality of filter elements (131, 132, 133, 134) as the physical filter, which are displaceable in a predetermined direction and have different materials and thicknesses in the X-ray transmission direction, and any of the plurality of filter elements can be replaced near the irradiation port of the X-ray irradiation unit depending on the type of article.

Images