Article inspection device

Abstract

To provide an article inspection device capable of performing an X-ray inspection rapidly and accurately even if the article is less than or equal to or more than the transmission limit thickness of X rays of low-energy components.SOLUTION: An article inspection device comprises: an X-ray detection section 23 for detecting X rays in a low-energy side and in a high-energy side each from among irradiated X rays within a predetermined energy range; an X-ray image generation section 31 for generating X-ray image data Xca in the low-energy side and X-ray image data Xcb in the high-energy side on the basis of luminance detection signals Lxa, Lxb detected here; and an output control section 30B for controlling X-ray output. The output control section 30B has transmission force control means 36b for increasing transmission force of X rays because of an increase in X-ray output from an X-ray irradiation section 21 according to articles at the time of inspection, and saturates detection luminance shown by the luminance detection signal Lxa at a low-energy side with the maximum luminance Vbs2 of a set gradation number in a region having a small transmission thickness below a transmission limit thickness Tna of X rays in a low-energy side in an article W at the time of an increase in the X-ray output.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an object inspection device, and more particularly to an object inspection device that acquires image data corresponding to the dose distribution of X-rays transmitted through a transported object by periodic detection operations of a line sensor type X-ray detector, and determines the quality state of the inspected object based on the image data. [Background technology]

[0002] In an article inspection device that inspects the quality of food and other articles, such as the presence or absence of contaminants, missing parts, and internal shape, an X-ray inspection method is known in which X-rays are irradiated onto the article being transported, the transmitted X-rays are detected by a line sensor's periodic scanning operation to obtain image data, and the quality of the article being inspected is determined based on the results of predetermined image processing of the image data.

[0003] In such an article inspection device, generally, the image data of transmitted X-rays that have passed through the object to be inspected is subjected to an inspection process in which logarithmic conversion is performed to convert the data into gradation density data that corresponds to the sensitivity of the human eye, image filtering is performed to reduce noise in order to determine the quality state of the object to be inspected, and image filtering is performed to emphasize the likelihood of a foreign object to prevent erroneous determination, as necessary, and further threshold processing is applied to determine whether or not a foreign object has been mixed in.

[0004] Conventional object inspection devices of this type include, for example, an X-ray detector into which X-rays that have passed through the object to be inspected are incident, with two sensor modules arranged above and below in the direction of X-ray transmission, making it possible to inspect the same location on the object to be inspected simultaneously (see, for example, Patent Document 1).

[0005] In this device, the upper sensor module uses a scintillator to convert X-rays into visible light, which is then reflected by a visible light reflector and output by a photodetector as X-ray transmission data corresponding to the amount of X-ray transmission.The lower sensor module uses an X-ray filter to attenuate the X-ray energy of a specified band component of X-rays, then uses a scintillator to convert the X-rays into visible light, after which the photodetector outputs the X-ray transmission data.

[0006] Therefore, the quality of the X-rays received by the upper and lower sensor modules can be differentiated by the presence or absence of an X-ray filter, making it possible to set the X-ray output and quality to be able to relatively easily detect metals with high X-ray absorption rates, while also being able to detect bones and shells, which have compositions and X-ray absorption rates roughly equivalent to those of processed foods. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-365368 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the above-mentioned X-ray inspection type article inspection device, an X-ray filter is placed between one of the upper and lower sensor modules and the X-ray source, and the quality of the X-rays incident on both sensor modules is made different, which makes it possible to detect a variety of foreign objects. However, when attempting to inspect articles such as food that are relatively large or packaged compared to the articles normally inspected, the X-ray intensity is significantly attenuated as it passes through the article, resulting in insufficient penetrating power and making it impossible to achieve sufficient inspection performance.

[0009] In contrast, in the case of loose items such as beans, where X-rays are transmitted and attenuated only near the surface of the conveyor belt, it is possible to set the X-ray irradiation conditions to a high X-ray intensity so that the output of the X-ray detector is saturated at the maximum detection brightness, making it possible to inspect even large items that are thick in the direction of X-ray transmission.

[0010] However, in this case, even if the object to be inspected is large overall, if there is a part or item that is transported while being located near the surface of the conveyor belt, the output of the X-ray detector will become saturated, and the entire object to be inspected cannot be inspected accurately.

[0011] Therefore, the present invention aims to provide an object inspection device that can perform X-ray inspection quickly and accurately on objects with a wide range of thicknesses, even if the thickness of the object in the X-ray transmission direction is greater than the transmission limit thickness of low-energy X-ray components, or if the object has an area with a transmission thickness greater than the transmission limit thickness. [Means for solving the problem]

[0012] (1) To achieve the above object, the article inspection device according to the present invention includes an X-ray irradiation unit that generates X-rays in a predetermined energy range using an X-ray tube and irradiates the X-rays onto an article inspection area into which an article is carried, an X-ray detection unit that has one scintillator that absorbs and emits X-rays on the low energy side of the predetermined energy range and another scintillator that absorbs and emits X-rays on the high energy side of the predetermined energy range, and has one and another groups of light-receiving elements attached to both scintillators, and an X-ray image data on the low energy side based on a first luminance detection signal from one group of light-receiving elements corresponding to the amount of X-rays on the low energy side and a second luminance detection signal from the other group of light-receiving elements corresponding to the amount of X-rays on the high energy side. and an output control unit that adjusts the tube voltage and tube current of the X-ray tube and controls the X-ray output of the X-ray irradiation unit in accordance with the item, wherein the output control unit has a penetration power control means that, during an inspection in which the type of the item is set, selectively increases the X-ray output from the X-ray irradiation unit to increase the penetrating power of the X-rays in accordance with the item, and when the X-ray output is increased in accordance with the item, for an area of ​​the item with a small penetration thickness that is below the penetration limit thickness of the low-energy X-rays, the detected brightness indicated by the first brightness detection signal in accordance with the X-ray dose on the low-energy side is saturated at the maximum brightness of a preset number of gradations.

[0013] With this configuration, when increasing the X-ray output for inspecting large objects, the present invention makes it possible to generate low-energy X-ray image data corresponding to the thickness in the X-ray transmission direction using at least the first brightness detection signal for regions with large transmission thicknesses equal to or greater than the low-energy X-ray transmission limit. Meanwhile, while some regions with small transmission thicknesses below the low-energy X-ray transmission limit become uninspectable due to saturation, these regions can still be inspected using high-energy X-rays that do not saturate even when the X-ray output is increased. Therefore, X-ray inspection is possible for a wide range of thicknesses in the X-ray transmission direction. As a result, even when the thicknesses of objects in the X-ray transmission direction vary significantly, effective brightness detection signals can be generated for each object thickness or thickness region, and accurate X-ray image data can be utilized to the fullest extent for the thicknesses in the corresponding X-ray transmission direction, enabling rapid and accurate X-ray inspection for a wide range of thicknesses in the X-ray transmission direction.

[0014] (2) In a preferred embodiment of the present invention, the X-ray image generating unit can be configured to generate the high-energy side X-ray image data for the small transmission thickness region of the object using at least the second brightness detection signal, and to generate the low-energy side X-ray image data for the large transmission thickness region of the low-energy side that is equal to or greater than the X-ray transmission limit thickness using at least the first brightness detection signal.

[0015] In this case, for an article or multiple regions thereof having significantly different thicknesses in the X-ray transmission direction, accurate X-ray image data can be generated by utilizing brightness detection signals effective for each article or thickness region. For example, if an article has multiple regions having significantly different thicknesses in the X-ray transmission direction, for regions with small transmission thicknesses, high-energy X-ray image data can be generated using a second brightness detection signal in which the detected X-ray dose is reduced due to attenuation when passing through one scintillator or due to an equivalent attenuation difference. For regions with large transmission thicknesses equal to or greater than the low-energy X-ray transmission limit, low-energy X-ray image data can be generated using a first brightness detection signal. Furthermore, by performing X-ray output increase / decrease control that can estimate and calculate the detected brightness indicated by the first brightness detection signal when it saturates at the maximum brightness of a preset number of gradations, it is possible to calculate an average brightness value, which is the average value of pixel values ​​corresponding to the transmitted X-ray dose on the high-energy and low-energy sides for each transmission thickness region, and accurately set the X-ray image density for each transmission thickness region. Therefore, even if an item is a loose item with a very small thickness in the X-ray transmission direction, or an item with a large size or packaging form with a very large thickness in the X-ray transmission direction, X-ray inspection of the item can be performed quickly and accurately.

[0016] (3) In a preferred embodiment of the present invention, the output control unit can be configured to increase the tube current of the X-ray tube to switch from low output mode to high output mode when the item being transported into the item inspection area has an area with a transmission thickness greater than the transmission limit thickness of the low-energy X-ray, thereby increasing the transmission power without changing the radiation quality of the X-rays irradiated from the X-ray irradiation unit.

[0017] In this case, when the detected brightness indicated by the second brightness detection signal saturates at the maximum brightness of the preset number of gradations, the brightness value can be easily estimated. Therefore, by manually or automatically switching modes, it is possible to selectively set the X-ray intensity and penetrating power higher than the X-ray output during normal product inspection.

[0018] (4) In a preferred embodiment of the present invention, the output control unit can be configured to have a thickness determination means for determining that an item being transported into the item inspection area has a transmission thickness equivalent to the transmission limit thickness of the low-energy X-rays when a predetermined number of detection brightness values ​​among a plurality of detection brightnesses corresponding to the first brightness detection signal from one of the photodetector groups are the smallest value.

[0019] In this case, automatic mode switching becomes possible. Note that the predetermined number of detected luminance values ​​among the plurality of detected luminance values ​​referred to here is a number that is necessary and sufficient to infer the existence of an area where the detected luminance value is the minimum value, even when taking into consideration noise and variations in the signal.

[0020] (5) In a preferred embodiment of the present invention, a type setting means is provided for setting the type of the article to be inspected, and the output control unit can be configured to selectively increase the X-ray output of the X-rays irradiated from the X-ray irradiation unit in accordance with the type of article set by the type setting means.

[0021] In this case, when a large product is selected for inspection, the thickness of which in the X-ray transmission direction exceeds the X-ray transmission limit thickness on the low-energy side, it is possible to easily and reliably switch to an automatic mode with higher output and higher penetration power than the X-ray intensity and penetration power used during normal product inspection.

[0022] (6) In a preferred embodiment of the present invention, the output control unit can be configured to set the range of detected brightness values ​​indicated by the second brightness detection signal in a region of a large transmission thickness equal to or greater than the transmission limit thickness of the low-energy X-ray to less than the maximum brightness when the transmission power of the X-ray is increased by the transmission power control means by increasing the X-ray output from the X-ray irradiation unit in accordance with the article.

[0023] In this case, it is possible to expand the detection range of thickness in the X-ray transmission direction and to set the image density accurately.

[0024] (7) To achieve the above object, the article inspection method according to the present invention includes an X-ray irradiation step of irradiating an article inspection area into which an article is carried with X-rays by an X-ray irradiation unit that generates X-rays within a predetermined energy range using an X-ray tube; an X-ray detection step of receiving light from one scintillator that absorbs and emits low-energy X-rays among the X-rays that have passed through the article inspection area and from the other scintillator that absorbs and emits high-energy X-rays among the X-rays that have passed through the article inspection area, by an X-ray detection unit having corresponding one and other groups of light-receiving elements, thereby detecting the low-energy X-rays and the high-energy X-rays; and a first luminance detection signal corresponding to the amount of low-energy X-rays from the one group of light-receiving elements and the amount of high-energy X-rays from the other group of light-receiving elements. and an output control step of adjusting the tube voltage and tube current of the X-ray tube to control the X-ray output of the X-ray irradiation unit in accordance with the article, wherein in the output control step, when at least the article carried into the article inspection area has an area with a large transmission thickness equal to or greater than the low-energy X-ray transmission limit thickness, the X-ray output from the X-ray irradiation unit is increased to increase the penetrating power of the X-rays, and for areas of the article with a small transmission thickness below the low-energy X-ray transmission limit thickness, the detected brightness indicated by the first brightness detection signal in accordance with the low-energy X-ray dose is saturated at the maximum brightness of a preset number of gradations.

[0025] In this case, when the X-ray output is increased for the inspection of large objects, it is possible to generate low-energy X-ray image data corresponding to the thickness in the X-ray transmission direction using at least the first brightness detection signal for regions with a large transmission thickness equal to or greater than the low-energy X-ray transmission limit. Meanwhile, some regions with a small transmission thickness below the low-energy X-ray transmission limit become uninspectable due to saturation, but these regions can still be inspected using high-energy X-rays that do not saturate even when the X-ray output is increased. Therefore, X-ray inspection is possible for a wide range of thicknesses in the X-ray transmission direction. As a result, the object inspection method of the present invention enables rapid and accurate X-ray inspection of a wide range of thicknesses in the X-ray transmission direction, even when the thicknesses of objects in the X-ray transmission direction vary greatly, by generating brightness detection signals effective for each object thickness or thickness region and maximizing the use of accurate X-ray image data for the thickness in the corresponding X-ray transmission direction.

[0026] (8) In a preferred embodiment of the present invention, the type of the article to be inspected is set prior to the X-ray irradiation step, and the output control step can be configured to selectively control the X-ray intensity according to the type of the article so as to increase the penetrating power without changing the radiation quality of the X-rays irradiated from the X-ray irradiation unit.

[0027] In this case, when a large product is selected for inspection, the thickness of which in the X-ray transmission direction exceeds the X-ray transmission limit thickness on the low-energy side, it is possible to easily and reliably switch to an automatic mode with higher output and higher penetration power than the X-ray intensity and penetration power used during normal product inspection.

[0028] (9) In a preferred embodiment of the present invention, in the X-ray image generation step, the high-energy side X-ray image data is generated for the small-transmission-thickness region of the object using at least the second brightness detection signal, and the low-energy side X-ray image data is generated for the large-transmission-thickness region of the object using at least the first brightness detection signal.

[0029] In this case, for an article or multiple regions thereof having significantly different thicknesses in the X-ray transmission direction, accurate X-ray image data can be generated by utilizing brightness detection signals effective for each article or thickness region. For example, if an article has multiple regions having significantly different thicknesses in the X-ray transmission direction, low-energy X-ray image data can be generated for the regions with small transmission thickness using a first brightness detection signal, and high-energy X-ray image data can be generated for the regions with large transmission thickness using a second brightness detection signal, and then cut-out and synthesis can be performed. Alternatively, when the detected brightness indicated by the second brightness detection signal saturates at the maximum brightness of a preset number of gradations, X-ray output increase / decrease control can be performed to estimate and calculate that brightness value, thereby calculating the brightness average value, which is the average value of pixel values ​​corresponding to the transmitted X-ray dose on the high-energy and low-energy sides for each transmission thickness region, and setting the X-ray image density for each transmission thickness region. [Effects of the Invention]

[0030] According to the present invention, it is possible to provide an object inspection device that can perform X-ray inspection quickly and accurately on objects with a wide range of thicknesses, even if the thickness of the object in the X-ray transmission direction is greater than the transmission limit thickness of low-energy X-ray components, or if the object has an area where the transmission thickness is greater than the transmission limit thickness. [Brief explanation of the drawings]

[0031] [Figure 1] 1 is a schematic configuration diagram of an article inspection device according to an embodiment of the present invention; [Figure 2] 2 is a partially enlarged cross-sectional view of an X-ray detector in the article inspection device shown in FIG. 1. [Figure 3] 1. FIG. 4 is a partially enlarged cross-sectional view showing two other modified embodiments of the X-ray detector in the object inspection device shown in FIG. [Figure 4] 1A and 1B are diagrams showing a test piece used in an article inspection device according to one embodiment of the present invention, in which (a) is a top view and (b) is a side view. [Figure 5]1(a) is a detection characteristic diagram illustrating a case where, for the high-energy sensor module of the two sensor modules of a dual-energy type X-ray detector in an item inspection device according to one embodiment of the present invention, the detected brightness of all light-receiving elements is adjusted to the correction target value Vbs1 of the white reference minus the attenuation due to the upper scintillator (or X-ray filter) when the X-rays irradiated from the X-ray source are at a relatively low X-ray intensity, and a case where the detected brightness of all light-receiving elements is set to the maximum brightness Vbs2 near the saturation value, which is the white reference during inspection, minus the attenuation due to the upper scintillator, when the X-ray intensity is relatively high. In addition, (b) is a detection characteristic diagram illustrating a case where, for the lower energy sensor module of the two sensor modules of a dual energy type X-ray detector in an item inspection device according to one embodiment of the present invention, the detected brightness of all light receiving elements is aligned to the white reference correction target value Vbs2 that is not attenuated by the scintillator on the upper layer when the X-rays irradiated from the X-ray source are at a relatively low X-ray intensity, and a case where the detected brightness of all light receiving elements is saturated in an estimable manner when the X-ray intensity is relatively high. [Figure 6] This is an explanatory diagram of the detection characteristics after shading correction in the two upper and lower sensor modules of a dual-energy type X-ray detector in an item inspection device according to one embodiment of the present invention, where (a) shows an X-ray image in which the pixel values ​​are the detection values ​​of the high-energy sensor module onto which X-rays are incident after being attenuated (the X-ray amount is reduced) by the upper scintillator or X-ray filter, and (b) shows an X-ray image in which the pixel values ​​are the detection values ​​of the low-energy sensor module onto which X-rays are incident without being attenuated by other scintillators or X-ray filters. [Figure 7] The figures show examples of multiple display images based on the detection outputs of two sensor modules of a dual-energy type X-ray detector in an object inspection device according to one embodiment of the present invention, where (a) shows an average density image in which the pixel value is the brightness obtained by averaging the detection values ​​of the two sensor modules, and (b) shows a cut-out composite image in which a region P1 of small transmission thickness in which the pixel value is the detection value of the high-energy sensor module and a region P2 of large transmission thickness in which the pixel value is the detection value of the low-energy sensor module are combined. [Figure 8] 5 is a flowchart showing an outline of a procedure for setting the detection sensitivity of an X-ray detector in an article inspection device according to an embodiment of the present invention. [Figure 9] 3 is a flowchart showing an outline of a processing procedure during inspection in an article inspection device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0033] 1 to 9 show the configuration and operation of an article inspection device according to one embodiment of the present invention.

[0034] First, the configuration will be described.

[0035] The item inspection device 1 shown in Figure 1 is an X-ray inspection type device having an item conveying unit 10, an X-ray inspection unit 20, an inspection control unit 30, and an operation display unit 40, and forms part of an item inspection system that also has a sorting device, etc. (not shown) located downstream of the item conveying unit 10.

[0036] 1 (conveying direction), for example, a loop-shaped conveyor belt 11 is stretched between parallel rollers 12 and 13, and the object W on a conveying path 11a, which is the upper running section of the conveyor belt 11, is conveyed at a constant speed while passing through an inspection area Zx of the X-ray inspection unit 20. Here, the object conveyor 10 is a belt conveyor in which one of the rollers 12 or 13 is driven by a motor, and the conveying path 11a is flat, but the object W may be conveyed under pressure through a tubular conveying path, or the object W may pass through the inspection area Zx by its own weight.

[0037] The X-ray inspection unit 20 has an X-ray generator 21 and an X-ray detector 23 arranged across the conveying path 11a of the item conveying unit 10. The X-ray generator 21 and the X-ray detector 23 are arranged here, for example, to face each other and spaced apart above and below in the vertical direction, but they may also be arranged to be spaced apart both vertically and horizontally.

[0038] The X-ray generator 21 has an X-ray tube 22 inside a box 24 made of, for example, metal, and is configured so that the X-ray tube 22 is immersed in insulating oil (not shown) for cooling inside the box 24. The X-ray tube 22 causes electrons emitted from a filament on the cathode 22a side inside the envelope and focused by a focusing electrode to collide with a target on the anode 22b side facing the filament, causing X-rays within a predetermined energy range to be generated from the target.

[0039] The X-ray inspection unit 20 further includes one drive power supply circuit 25 and the other drive power supply circuit 26. One drive power supply circuit 25 applies a potential corresponding to a predetermined operating voltage to a focusing electrode (not referenced) on the cathode 22a side of the X-ray tube 22, and applies a predetermined lighting voltage that provides thermoelectron emission energy to a filament (not referenced) on the cathode 22a side. The other drive power supply circuit 26 applies a positive potential corresponding to a high-voltage operating anode voltage to the anode 22b of the X-ray tube 22. That is, one drive power supply circuit 25 is configured to include a so-called filament power supply circuit, and the other drive power supply circuit 26 is configured to include a high-voltage circuit that applies a high voltage between the filament of the X-ray tube 22 and the target.

[0040] The X-ray generator 21 is an X-ray irradiator that irradiates X-rays toward the inspection area Zx into which the inspection object W is carried along the transport path 11a of the inspection object W by the article transport unit 10, and in this embodiment has an X-ray tube 22 that irradiates X-rays downward from above vertically onto the inspection object W. However, the direction of irradiation of X-rays from the X-ray generator 21 is not limited to the downward direction and may be other directions.

[0041] The X-ray tube 22 is arranged, for example, with its axial direction oriented in a direction approximately parallel to the d1 direction, which is the predetermined transport direction. At the cathode 22a, a negative DC potential is applied to emit electrons from a filament that is lit at a high temperature and then the electrons are focused by a focusing electrode, while at the anode 22b, a positive DC potential is applied to the target, and the electrons from the filament are accelerated by a high voltage and collide with the target, generating X-rays within a predetermined energy range from the target.

[0042] The X-rays generated by the X-ray tube 22 are directed downward from an X-ray window 24a on the bottom side of the box body 24 toward the inspection area Zx into which the object W to be inspected is carried, and are emitted in the form of a fan beam that spreads in a line scanning direction perpendicular to the carrying direction. The anode of the X-ray tube 22 may be of a fixed type or a rotating type.

[0043] 2, the X-ray detector 23 is a dual-sensor X-ray detection unit having a low-energy side sensor module M1 having one scintillator 23a that absorbs and emits X-rays on the low-energy (long wavelength, low penetrating power) side of a predetermined energy range, and a high-energy side sensor module M2 having the other scintillator 23b that absorbs and emits X-rays on the high-energy (short wavelength, high penetrating power) side that remain after the low-energy X-rays are absorbed mainly by the one scintillator 23a of the predetermined energy range. The low-energy side sensor module M1 is arranged closer to the X-ray generator 21 than the high-energy side sensor module M2, in this case, on the upper side, in the direction d3 in FIG. 4, which is the X-ray irradiation direction (X-ray transmission direction).

[0044] That is, in both sensor modules M1 and M2, one scintillator 23a, which is located closer to the X-ray generator 21 than the other scintillator 23b, which has light-receiving sensitivity to higher-energy X-ray components, has the property of absorbing lower-energy X-ray components and emitting light. Therefore, within a predetermined X-ray energy range irradiated from the X-ray generator 21, the lower-energy X-ray components are mostly absorbed while passing through one scintillator 23a, generating scintillation light, and the remaining higher-energy X-ray components are mostly absorbed while passing through the other scintillator 23b, generating scintillation light.

[0045] Furthermore, one scintillator 23a is integrally mounted with one photodiode array 23c (one group of light-receiving elements), and the other scintillator 23b is integrally mounted with the other photodiode array 23d (the other group of light-receiving elements), and scintillation light from one scintillator 23a is received by light-receiving elements of N pixels adjacent to each other in the line scanning direction d2 to form one photodiode array 23c. Here, for example, if the width of each light-receiving element in the d1 direction of one photodiode array 23c is 1 mm, the gaps between the light-receiving elements are small enough to be ignored compared to the sensor width, and the width in the width direction (d2 direction in FIG. 4) of the transport path 11a along which the inspection object W is transported is 200 mm, then a line sensor having N=200 light-receiving elements will suffice.

[0046] Therefore, one photodiode array 23c has N charge-accumulation type light-receiving elements that receive scintillation light from one scintillator 23a, accumulates photocurrents generated simultaneously in each of the N light-receiving elements for a predetermined accumulation time, and outputs a brightness detection signal Lxa, which is a voltage signal, based on the charge corresponding to the product of the photocurrent and the accumulation time. Similarly, the other photodiode array 23d has N charge-accumulation type light-receiving elements that receive scintillation light from the other scintillator 23b, accumulates photocurrents generated in each of the N light-receiving elements for a predetermined accumulation time, and outputs a brightness detection signal Lxb, which is a voltage signal, based on the charge corresponding to the product of the photocurrent and the accumulation time.

[0047] Note that within the predetermined energy range, X-rays on the low energy side (relatively long wavelength components) that are absorbed by one scintillator 23a have a first energy region in which the X-ray energy is, for example, 20 keV to 40 keV. Also, X-rays on the high energy side (relatively short wavelength components) that are absorbed by the other scintillator 23b have a second energy region in which the X-ray energy is, for example, 50 keV to 70 keV. Here, it is assumed that X-rays in the first and second energy regions are absorbed by the one and other scintillators 23a, 23b, but the number of multiple energy regions (bands) that differ in high and low corresponding to the number of scintillators within the predetermined energy range is not limited to two, and may, of course, be three or more energy regions with different medians.

[0048] The low-energy sensor module M1 and the high-energy sensor module M2 of the X-ray detector 23 further include detection circuits 23e and 23f connected to the photodiode arrays 23c and 23d, respectively. Each of the detection circuits 23e and 23f incorporates an A / D converter and a clock generating circuit (not shown) to convert electrical signals from the N light-receiving elements of the first and second detectors into multi-level digital signals. Each of the detection circuits 23e and 23f also includes, for example, a parallel-to-serial converter (not shown) and a clock generating circuit that generates a parallel clock signal for parallel output of the multi-level digital signals from the A / D converter to the parallel-to-serial converter. The parallel-to-serial converter aligns the multi-level digital signals with the clock signal period and outputs brightness detection signals Lxa and Lxb (serial signals) as time-series voltage signals for two energy systems (high and low). This configuration reduces the influence of noise on the signal communication path and shortens the processing time in the inspection control unit 30. Of course, at least a part of the detection circuits 23e and 23f in the X-ray detector 23 may be included in a line image data generation unit 31 in the inspection control unit 30, which will be described later.

[0049] As shown in Figure 2, the X-ray detector 23 has a low-energy side sensor module M1 and a high-energy side sensor module M2 on the high-position side and low-position side, each having one scintillator 23a and the other scintillator 23b, and the low-energy side sensor module M1 absorbs the low-energy side X-ray components of the X-rays within a predetermined energy range from the X-ray generator 21, and allows only the high-energy side X-ray components to be incident on the high-energy side sensor module M2, but this is not limited to this.

[0050] 3(a), the X-ray detector 23 may be configured such that a low-energy side sensor module M1 having one scintillator 23a and a high-energy side sensor module M2 having the other scintillator 23b are arranged in parallel to each other and spaced apart from each other in the direction d1, which is the article conveying direction, and extending in the line scanning direction d2. In this case, a filter plate 23g made of a metal such as copper that absorbs low-energy X-ray components of X-rays within a predetermined energy range from the X-ray generator 21 is arranged above (on the X-ray generator 21 side) the high-energy side sensor module M2 having the other scintillator 23b, thereby allowing only high-energy X-ray components of X-rays irradiated from the common X-ray generator 21 to be incident on the high-energy side sensor module M2.

[0051] Furthermore, the X-ray detector 23 is not limited to the dual sensor type as shown in Fig. 2 or 3(a). That is, as shown in Fig. 3(b), the X-ray detector 23 may be one X-ray detector 23A having one scintillator 23a whose detection sensitivity range for X-ray energy corresponds to the detection sensitivity of the low-energy side sensor module M1 shown in Fig. 2 or 3(a), and another X-ray detector 23B having another scintillator 23b whose detection sensitivity range for X-ray energy corresponds to the detection sensitivity of the high-energy side sensor module M2 shown in Fig. 2 or 3(a), the two X-ray detectors being arranged in parallel to be spaced apart from each other in the direction d1, which is the article conveying direction, and extending in the line scanning direction d2. In this case, X-rays in a predetermined X-ray energy band may be emitted from a common X-ray generator 21 to both the one X-ray detector 23A and the other X-ray detector 23B, with the low-energy X-ray component incident on the one X-ray detector 23A and the high-energy X-ray component incident on the other X-ray detector 23B. Furthermore, although not shown, instead of the X-ray generator 21, one X-ray detector may be provided that emits X-rays in an X-ray energy band corresponding to the above-mentioned low-energy X-ray component toward the one X-ray detector 23A, and the other X-ray detector may be provided that emits X-rays in an X-ray energy band corresponding to the above-mentioned high-energy X-ray component toward the other X-ray detector 23B.

[0052] The inspection control unit 30 has a transport control function that controls the transport speed and transport interval of the items W by the transport belt 11 in the item transport unit 10, and an inspection control function that controls the X-ray irradiation intensity and irradiation period in the X-ray inspection unit 20, and controls the X-ray detection cycle and detection period for each item W in the X-ray detector 23 according to the transport speed of the items W. Note that the configuration of the transport control function unit is similar to that of a known unit, so detailed illustration thereof will be omitted.

[0053] As shown in Figure 1, the inspection control unit 30 is composed of an image generation block 30A that generates X-ray image data for inspection and display based on the brightness detection signals Lxa and Lxb from the X-ray detector 23, and a control block 30B that performs predetermined inspection control, display output control, etc. based on the X-ray transmission image data from the image generation block 30A.

[0054] The image generation block 30A has a line image data generation unit 31, an X-ray image data storage unit 32, and a display image generation unit 34, and the control block 30B has an image processing unit 33 that performs predetermined image processing and performs an inspection judgment function, a display control unit 35, and an inspection condition control unit 36.

[0055] Specifically, although the detailed configuration of the inspection control unit 30 is not shown, the hardware configuration includes, for example, a microcomputer having a CPU, ROM, RAM, and I / O interface, an auxiliary storage device that readably stores control programs for performing various functions in cooperation with the ROM, and a timer circuit, driver circuit, etc. In accordance with software such as the control program and setting information stored in the ROM, the CPU executes predetermined arithmetic processing while exchanging data with the RAM, etc., and also executes the control program. The hardware may also include an FPGA (Field Programmable Gate Array), a DSP (Digital Signal Processor), etc. The functions referred to here refer to the functions of each functional unit and means for X-ray output control, X-ray image data generation, inspection control, display output control, etc., as described below.

[0056] In the image generation block 30A, the line image data generation unit 31 converts both the luminance detection signals Lxa (first luminance detection signal) corresponding to the incidence and transmission absorption amount of low-energy X-rays from one sensor module M1 of the X-ray detector 23 and the luminance detection signal Lxb (second luminance detection signal) corresponding to the incidence and transmission absorption amount of high-energy X-rays from the high-energy sensor module M2 from serial digital signals into parallel digital signals corresponding to the number of gradations.

[0057] Here, the multi-tone digital signal converted into a parallel digital signal is line image data that indicates the amount of X-ray transmission at each pixel position for each line scan of the object W to be inspected as image density, and the line image data generation unit 31 is an X-ray image generation unit that generates low-energy X-ray image data Xca and high-energy X-ray image data Xcb corresponding to the distribution of X-ray transmission amounts accumulated during each line scan period as X-ray line image data of two components with different energies (wavelength, penetrating power) at high and low within a specified energy range.

[0058] The X-ray image data storage unit 32 has an image memory function that temporarily stores the low-energy side X-ray image data Xca and the high-energy side X-ray image data Xcb generated by the line image data generation unit 31 for each line scanning period. The X-ray image data storage unit 32 transfers the image data Xca and Xcb of the X-ray line images of the two components to the image processing unit 33 in the order in which the low-energy side Xca and the high-energy side Xcb X-ray image data are written from the line image data generation unit 31.

[0059] The X-ray image data storage unit 32 is also configured to output, at a predetermined readout period, image data Xia and Xib, which are acquired during a predetermined number of line scans and show the inspection object W as transmission images of X-rays with two different high and low energy (wavelength) components, to the display image generation unit 34. The predetermined readout period referred to here is a time equivalent to a period for generating successive display images of each inspection object W, which is set according to the length of each inspection object W in the conveying direction and the conveying speed, based on the timing of the inspection object W being carried into the article conveying unit 10, which is detected by the article detection sensor 27, for example.

[0060] In the control block 30B, the image processing unit 33 has two functions: a thickness determination means 33a that performs a predetermined thickness calculation process based on the low-energy X-ray image data Xca and the high-energy X-ray image data Xcb input from the X-ray image data storage unit 32, thereby performing a thickness determination function for each line scan of the object to be inspected W; and an inspection determination means 33b that performs a predetermined image processing based on the image data Xca, Xcb input from the X-ray image data storage unit 32, thereby performing an inspection determination function to determine a predetermined quality state of the object to be inspected W.

[0061] If thickness determination information has already been set as part of the product type information for the object W to be inspected, the thickness determination means 33a is configured to determine, based on the thickness determination information, whether the object W to be inspected has a portion that is equal to or greater than the transmission limit thickness Tna of X-rays of the lower energy wavelength component (hereinafter simply referred to as lower energy X-rays) of the X-rays within a predetermined energy range irradiated from the X-ray generator 21.

[0062] The information for determining thickness referred to here is mainly information indicating whether the object W to be inspected is large and whether high-energy X-rays with greater penetrating power are required. Specifically, for example, it is information A1 (see Figure 1) indicating that the pixel region is one in which the X-ray equivalent thickness τ (=α·t) corresponding to the linear absorption coefficient α and thickness t of each part of the object W to be inspected, i.e., the thickness equivalent to the density value of the X-ray image, is less than the penetration limit thickness Tna of low-energy X-rays, or information A2 indicating that the pixel region is one in which the penetration limit thickness Tna of low-energy X-rays is equal to or greater than the penetration limit thickness Tna of low-energy X-rays.

[0063] Furthermore, if thickness determination information has not already been set as part of the type information for the object W to be inspected, the thickness determination means 33a registers thickness determination information A1 or A2 in response to manual input, for example, when registering the type, or calculates the X-ray equivalent thickness τ in each pixel region of the object W to generate thickness determination information A1 or A2 indicating whether or not it is equal to or greater than the low-energy X-ray penetration limit thickness Tna, and includes this information as part of the type information.

[0064] In this case, the thickness determination means 33a performs the following thickness calculation process based on, for example, the Beer-Lambert law (see paragraphs 0054 to 0061 of JP 2006-300887 A), and performs a thickness determination function of determining, for each line scan of the object W, whether the X-ray equivalent thickness τ corresponding to the linear absorption coefficient α and thickness t in each pixel region of the object W is equal to or greater than the low-energy X-ray penetration limit thickness Tna.

[0065] That is, the phenomenon in which X-rays, which are photon beams, are irradiated onto the object W to be inspected, and N0 photons of a predetermined energy are reduced to N by passing through the object W (thickness t, linear absorption coefficient α) and the conveyor belt 11 (thickness t0, linear absorption coefficient α0), can be approximated by the following equation [1] according to the Beer-Lambert law. N=N0exp(-α·t-α0·t0) ···[1] In the X-ray fan beam optical system employed in this embodiment, the amount of light received I for each pixel in the range of the focal elevation angle (90°-θ) of the X-ray detector 23, which is made of, for example, a scintillator-type CCD line sensor, is a value corresponding to the X-ray irradiation intensity in each transmission region, I(θ)={1 / (1+tan 2 θ)}·I(0°) ···〔2〕 However, normally, light receiving sensitivity correction is performed to adjust the detection sensitivity of the X-ray detector 23 so that the amount of light received I(θ) is flat and at maximum brightness (white reference) on the conveyor belt surface (background image area) before the article is loaded. For example, as shown in Figure 5(a), shading correction is performed to align the output of all sensor elements of the X-ray detector 23 to the white reference value (maximum brightness) for the amount of light received I(θ) on the conveyor belt surface before the article is loaded.

[0066] Therefore, the amount of light received I0 on the belt surface (background) before the article is carried in after the light receiving sensitivity correction becomes a constant value corresponding to approximately N0exp(-α0·t0), and the amount of light received I' in each transmission area, which is no longer dependent on the angle θ due to the light receiving sensitivity correction of the X-ray detector 23, can be calculated using the following equation [3]. I'=I0exp(-α·t) ···[3] Here, α·t is a value that directly indicates the amount of X-ray absorption by the material through which the X-rays pass before leaving the X-ray generator 21 and being detected by the X-ray detector 23. By correlating this with the density value of the X-ray absorption image, it is possible to create an image in which the density value is greater for materials with higher X-ray absorption rates or areas with greater thickness in the X-ray transmission direction.

[0067] Therefore, using the above-mentioned light receiving amounts I' and I0, α·t is the X-ray equivalent thickness τ in each transmission area of ​​the workpiece, and γ is the correction index value corresponding to the X-ray intensity (penetration power) that attenuates exponentially while passing through a material, the image density value J(τ) of the X-ray transmission image can be expressed by the following equation [4]. J(τ)=(α t) γ ={ln(I0)-ln(I´)} γ [4] In this case, the correction index value γ may be 1, but if the correction index value γ is set within a certain range, for example, close to 1.3, the image density value J(τ) will show good linearity with respect to the thickness t for many foods.

[0068] The thickness determination means 33a may perform a thickness determination function for each line scan of the inspection object W to generate thickness determination information A1 or A2 indicating whether the thickness is equal to or greater than the low-energy X-ray penetration limit thickness Tna, and may determine that the inspection object W carried into the article inspection region Zx has a penetration thickness equivalent to the low-energy X-ray penetration limit thickness Tna when a predetermined number or more of a plurality of (e.g., N) detected luminance values ​​corresponding to the first luminance detection signal Lxa from one of the photodiode arrays 23c are minimum values. The predetermined number here is a number that is necessary and sufficient to infer the existence of a region where the detected luminance values ​​have minimum values, even taking into account signal noise and variations.

[0069] The inspection and determination means 33b uses the X-ray image data Xca and Xcb of the low-energy component stored in the X-ray image data storage unit 32, and performs image processing for determination using a predetermined image processing algorithm on each of the X-ray image data Xca and Xcb after processing, in accordance with the previously set and stored determination processing conditions and the conditions additionally set by the condition setting means 36. It also performs a difference process known as an energy subtraction process, for example, between the processed X-ray image data Xca and Xcb, and determines the presence or absence of defects such as foreign matter or bone in the inspection object W based on the transmission image data obtained as a result of this difference process (hereinafter simply referred to as a difference image). Note that the predetermined image processing algorithm here is, for example, a combination of a plurality of image processing filters and image processing for feature extraction.

[0070] When performing the above-mentioned differential processing, for example, among X-rays in a plurality of energy (wavelength) regions, X-rays in a wavelength region on the low energy side are less likely to pass through defective parts such as foreign matter and bone, while X-rays in a wavelength region on the high energy side are relatively more likely to pass through defective parts such as foreign matter and bone. Therefore, in the differential image, it is possible to obtain transmission image data in which defective parts such as foreign matter and bone are emphasized compared to an image of the product influence that shows the inspection object W itself, and this improves the judgment accuracy of the inspection and judgment means 33b that judges whether or not the inspection object W has defective parts due to the inclusion of foreign matter or remaining bone.

[0071] On the other hand, during normal inspection of an item, the display image generation unit 34 of the image generation block 30A calculates the average pixel density values ​​corresponding to both of the X-ray image data Xia and Xib (first and second brightness detection signals) of two different energy components, high and low, for each line scanning period, as shown in Figure 7(a), to create a display image.

[0072] Furthermore, when setting to perform sensitivity correction or the like for the X-ray detector 23, the display image generation unit 34 creates a cutout composite image based on the X-ray image data Xia and Xib of the low-energy and high-energy components from the X-ray image data storage unit 32 and the thickness determination information A1 or A2 from the image processing unit 33, as shown in Fig. 7(b), in which the high-energy X-ray image data Xib based on the second luminance detection signal Lxb is used for the region P1 where the penetration thickness is small, that is, below the low-energy X-ray penetration limit thickness Tna, and the low-energy X-ray image data Xia based on the first luminance detection signal Lxa is used for the region P2 where the penetration thickness is large, that is, equal to or greater than the low-energy X-ray penetration limit thickness Tna. Note that the details of the procedure for creating such a display image will be described later, but this is made possible by the X-ray output control for improving inspection accuracy as follows.

[0073] 1 and 2, X-rays emitted from the X-ray generator 21 in a predetermined wavelength range including high and low energy components are attenuated as they pass through the low-energy sensor module M1, particularly one of the scintillators 23a, resulting in a reduced X-ray dose, before entering the high-energy sensor module M2. The dual-energy X-ray detector 23 improves inspection accuracy by using X-ray images in two energy bands, high and low, corresponding to the difference in X-ray intensity due to the attenuation described above. Therefore, we consider a system that can switch between high and low X-ray output (X-ray intensity) from the X-ray generator 21 so that the X-ray irradiation intensity from the X-ray generator 21 for large inspection objects W is increased by the attenuation difference. In this case, for the low-energy side sensor module M1, which does not suffer from attenuation of X-ray intensity due to one scintillator 23a or the metal filter plate 23g (X-ray filter shown in Figure 3(a)), the detection range can be set so that the detected value is saturated at the maximum brightness Vbs2 when the X-ray output is small enough to be suitable for a normal inspection object size, and for the high-energy side sensor module M2, which suffers from the above-mentioned attenuation, the detection range can be set so that the detected value becomes the maximum brightness Vbs2 when the X-ray output is large enough to be applied to a large inspection object W. Therefore, the detection sensitivity of the X-ray detector 23 can be set to be compatible with a large inspection object W, and by creating a display image during inspection as shown in Figures 7(a) and (b), it is possible to output a display image corresponding to the detection sensitivity setting.

[0074] That is, in this embodiment, when switching to high X-ray output to inspect a large object W, the low-energy side sensor module M1 inspects the large-thickness region of the object W, and the high-energy side sensor module M2 inspects the small-thickness region of the object W. In this manner, even if an X-ray dose sufficient to saturate the X-ray detection output of the low-energy side sensor module M1 is applied to the irradiation range in a belt surface state without the object W, the X-rays reaching the high-energy side sensor module M2 are reduced by a certain amount by one of the scintillators 23a and the metal filter plate 23g (X-ray filter). Therefore, even in the small-thickness region close to the belt surface state, the X-ray detection output does not saturate, and good inspection can be performed. Therefore, for example, for X-rays transmitted through the small-thickness region P1 of the test piece DPH close to the belt surface state, the X-ray dose is set so that the detection signal output of the high-energy side sensor module M2 is near the saturation value, i.e., the maximum brightness Vbs2. As a result, it becomes possible to irradiate a large, thick object W to be inspected with the maximum amount of X-rays, thereby improving inspection performance.

[0075] The display control unit 35 executes predetermined display control processing by taking in an OK / NG signal, which is the judgment result from the inspection judgment means 33b of the image processing unit 33 (and further a judgment difference image Xsc in response to a display request), candidate image data for the display image Xip, which is image data generated by the display image generation unit 34, such as image data for the display image Xav obtained by calculating, for each pixel, the average of pixel density values ​​corresponding to the X-ray image data Xia and Xib of the two high and low energy components described above, or image data for the cut-out composite image Xct described above, and display control conditions set by the condition setting means 36 in response to a request operation input from the operation means 42, for example, an operation for selecting the type of the inspection object W. The display control unit 35 then causes the display means 41 to display the X-ray inspection results and the display image Xip of the inspection object W, which is the inspection target, in a display format set by the condition setting means 36 in response to the type and other inspection conditions.

[0076] The inspection condition control unit 36 ​​controls the tube current and tube voltage of the X-ray tube 22 of the X-ray generator 21 and performs sensitivity correction of the X-ray detector 23, while also having the function of setting a measurement period, which is the period for capturing detection signals for each work W from the X-ray detector 23 to the X-ray image generation unit 31, in accordance with the work detection signal of the work detection sensor 27.

[0077] In addition, the inspection condition control unit 36, in cooperation with one drive power supply circuit 25 and the other drive power supply circuit 26, is capable of switching the output of the X-rays generated and irradiated by the X-ray generator 21 (X-ray intensity; tube voltage x tube current of the X-ray tube 22) between multiple output values ​​of different magnitudes.

[0078] Specifically, the filament power supply circuit formed by one of the drive power supply circuits 25 has an inverter circuit and a high-frequency transformer controlled by a current control circuit, and the inverter circuit performs a switching operation of the power supply voltage, thereby enabling current output control according to the current-on time ratio. Also, the high-voltage circuit formed by the other drive power supply circuit 26 can control voltage output according to the type of the object W to be inspected by its voltage control circuit.

[0079] Furthermore, the inspection condition control unit 36 ​​has a setting means 36a that sets and stores the target current value in the current control circuit of one drive power supply circuit 25 and the target voltage value in the voltage control circuit of the other drive power supply circuit 26, and an adjustment means 36b that adjusts the control gains of the current control circuit of one drive power supply circuit 25 and the voltage control circuit of the other drive power supply circuit 26 so that they become the target current value and the target voltage value set by the setting means 36a.

[0080] Then, according to the inspection conditions set in the inspection condition control unit 36, the X-ray output of the X-ray generator 21 (tube voltage x tube current of the X-ray tube 22) can be switched between two large and small output values ​​Pxh1 and Pxh2, as shown in FIG. 5, for example, and when setting to perform sensitivity correction of the X-ray detector 23, etc., it is controlled to the relatively small X-ray output Pxh1, and when inspecting the object W to be inspected, it is controlled to the relatively larger of the two large and small X-ray output values ​​Pxh2, which can be variably set depending on the type of object W to be inspected.

[0081] Here, the relatively smaller X-ray output Pxh1 of the two large and small X-ray outputs is set to, for example, 80 kV × 1 mA, and the relatively larger X-ray output value Pxh2 of the two large and small X-ray output values ​​is set to, for example, 80 kV × 2 mA. That is, in this embodiment, the X-ray output Pxh2 during inspection is twice as large as the X-ray output Pxh1 during setting.

[0082] The inspection condition control unit 36, together with one drive power circuit 25 and the other drive power circuit 26, further has the function of a penetration power control means that, when the object W to be inspected carried into the inspection area Zx has an area P2 with a large penetration thickness equal to or greater than the low-energy X-ray penetration limit thickness Tna, increases the tube current of the X-ray tube 22 so as to switch the output (tube voltage x tube current) of the X-ray generator 21 of the X-ray inspection unit 20 from a low-output mode in which the output is an X-ray output Pxh1 to an X-ray output Pxh2 that is greater than the X-ray output Pxh1, thereby increasing the penetration power without changing the radiation quality of the X-rays irradiated from the X-ray generator 21.

[0083] The inspection condition control unit 36, which serves as the penetration power control means, sets the image data generation conditions in the X-ray image generation unit 31, i.e., the conditions for converting the first and second luminance detection signals Lxa and Lxb into parallel digital signals according to the number of gradations, as shading correction conditions, and makes them different depending on whether the X-ray output mode of the X-ray generator 21 is a low output mode or a high output mode.

[0084] Specifically, as shown in Figure 5(a), the inspection condition control unit 36 ​​changes the output (tube current x tube voltage) of the X-ray tube 22 to a high output mode to change the X-ray output Pxh2 during inspection, and when inspecting an object W to increase the penetrating power of the X-rays, the high-energy side sensor module M2, which absorbs the high-energy X-ray components and detects the amount of X-rays among the X-rays in a predetermined energy range irradiated at high output (high X-ray intensity) from the X-ray generator 21, has its detection brightness range indicated by its second brightness detection signal Lxb set to be equal to or less than the maximum brightness Vbs2. That is, in the high-energy side sensor module M2 that detects high-energy X-rays, when the output of the X-ray tube 22 increases to the X-ray output Pxh2 during inspection, when high-intensity X-rays that have simply passed through the belt surface before the inspection object W is carried in are incident on the X-ray detector 23, the incident X-rays pass through the low-energy side sensor module M1 and then enter the high-energy side sensor module M2, so the brightness of the X-ray image corresponding to the detection signal output of the high-energy side sensor module M2 becomes the maximum brightness Vbs2. Then, when the inspection object W is carried in the inspection area, the detection signal output of the high-energy side sensor module M2 becomes a detection value of brightness corresponding to the X-ray dose after attenuation (weakening) in accordance with the X-ray equivalent thickness τ of the inspection object W.

[0085] Furthermore, as shown at the bottom of the figure, when the output of the X-ray tube 22 is set to the X-ray output Pxh1 in low output mode in cooperation with one drive power supply circuit 25 and the other drive power supply circuit 26, the inspection condition control unit 36, in cooperation with the X-ray image generation unit 31, performs shading correction for the high-energy side sensor module M2, which detects the high-energy X-ray components of the X-rays within a specified energy range irradiated from the X-ray generator 21 at an output (X-ray intensity) of approximately 50% of that in high output mode, to align the output of all light receiving elements of the photodiode array 23d to an output value equivalent to a specified brightness Vbs1 at approximately the low-energy X-ray penetration limit thickness Tna.

[0086] On the other hand, as shown in Figure 5(b), for the low-energy side sensor module M1 which detects the low-energy side X-ray components among the X-rays in a predetermined energy range irradiated from the X-ray generator 21, during shading correction in which the inspection condition control unit 36 ​​sets the output of the X-ray tube 22 to the X-ray output Pxh1 in low output mode, when X-rays that have only passed through the belt surface before the inspection object W is brought in are incident on the X-ray detector 23, the incident X-rays are incident on the low-energy side sensor module M1 without being attenuated by other scintillators or X-ray filters, and therefore the detection brightness range indicated by its first brightness detection signal Lxa is set to a range covering the entire range below the maximum brightness Vbs2. That is, even when the output of the X-ray tube 22 has not been increased to the X-ray output Pxh2 and is set to an X-ray output Pxh1 that is about 50% of that in the high-output mode, the low-energy side sensor module M1 that detects low-energy X-rays reaches a maximum luminance Vbs2 that is about the same as the detection luminance of the high-energy side sensor module M2 that detects high-energy X-rays when X-rays that have simply passed through the belt surface before the inspection object W is carried in are incident on the X-ray detector 23. Therefore, when the output of the X-ray tube 22 is increased to the X-ray output Pxh2, the detection luminance of the low-energy side sensor module M1 remains saturated at the maximum luminance Vbs2, and the true value of the luminance cannot be determined from the second luminance detection signal Lxb.

[0087] That is, during inspection when the output of the X-ray tube 22 is the X-ray output Pxh2 in high output mode, the object W to be inspected is less than the X-ray equivalent thickness τ corresponding to the low-energy X-ray penetration limit thickness Tna, so the first brightness detection signal Lxa of the low-energy side sensor module M1 that detects the low-energy X-rays becomes saturated. However, the second brightness detection signal Lxb of the high-energy side sensor module M2 that detects the high-energy X-rays shows the maximum brightness Vbs2 in the area where X-rays that have only passed through the belt surface before the object W to be inspected are incident, and in the area where the object W to be inspected has an X-ray equivalent thickness τ that exceeds the low-energy X-ray penetration limit thickness Tna, a brightness detection signal corresponding to the amount of X-ray detection after attenuation according to the X-ray equivalent thickness τ of the object W to be inspected is output.

[0088] Therefore, during inspection when the X-ray generator 21 is in high-output mode and the X-ray intensity is high enough to be suitable for a large inspection object W, when a test piece DPH, which is a dual-energy X-ray attenuation evaluation model with different thicknesses as shown in Figure 4, is carried into the inspection area Zx, the irradiation intensity of the X-rays from the X-ray generator 21 is increased more than usual by the attenuation difference mentioned above, but the second brightness detection value Lxb from the high-energy side sensor module M2, which detects the X-rays after attenuation has occurred in one of the scintillators 23a (or X-ray filter) of the low-energy side sensor module M1, will have a relatively low and good image density (high brightness) for the high-energy side X-ray image data Xib based on the second brightness detection signal Lxb in the small transmission thickness region P1 of the test piece DPH that is below the low-energy side X-ray transmission limit thickness Tna. On the other hand, in the region P2 where the penetration thickness is large, equal to or greater than the low-energy X-ray penetration limit thickness Tna, the high-energy X-ray image data Xib based on the second brightness detection signal Lxb has a relatively high image density (minimum brightness). Therefore, based on the second brightness detection signal Lxb at this time, a high-energy X-ray detected image Xib as shown in FIG. 6(a) can be obtained.

[0089] On the other hand, when the X-ray generator 21 is in high-power mode and the X-ray intensity is high enough to be suitable for a large object W to be inspected, the first brightness detection value Lxa from the low-energy sensor module M1, which detects low-energy X-ray components, saturates at the maximum brightness Vbs2 in the small-thickness region P1 of the test piece DPH, which is below the low-energy X-ray penetration limit thickness Tna. Therefore, as shown by the imaginary line in Figure 6(b), the image density becomes equivalent to the image density of the background image. For the large-thickness region P2, which is equal to or exceeds the low-energy X-ray penetration limit thickness Tna, the low-energy X-ray image data Xia based on the first brightness detection signal Lxa has an X-ray intensity high enough to be suitable for a large object W to be inspected, and the image density corresponds to the brightness detection value obtained after the X-rays, which are incident without attenuation by other scintillators or X-ray filters, are attenuated according to the sufficiently large X-ray equivalent thickness τ of the large-thickness region P2. Therefore, the X-ray image Xia is obtained based on the first brightness detection signal Lxa at this time, as shown in Figure 6(b).

[0090] In this case, in the low-energy side sensor module M1, if we consider the brightness value Vbs3 as the brightness detection value that should actually be detected in excess of the maximum brightness Vbs2 for the small transmission thickness region P1, which remains saturated at the maximum brightness Vbs2 even in high-output mode, the brightness value Vbs3 can be calculated using the following equation (1) based on the brightness value Vbs2 at the time of shading correction and the current increase ratio (It2 / It1; for example, 2) from the tube current It1 at the time of setting to the tube current It2 at the time of inspection. Vbs3=Vbs2×(It2 / It1)...[1] To explain an example of the procedure for the correction process, including the calculation of such brightness value Vbs3, the inspection condition control unit 36 ​​automatically determines the tube voltage of the X-ray tube 22 to a predetermined tube voltage, for example, 80 kV, during initial setup, for example, when a master work is transported. Then, when low-energy X-ray components of X-rays within a predetermined energy range from the X-ray generator 21 are incident on one scintillator 23a of the low-energy side sensor module M1 of the X-ray detector 23, the inspection condition control unit 36 ​​performs shading correction to adjust the output of all sensor elements of the low-energy side sensor module M1 to an output value (voltage value) equivalent to the maximum brightness Vbs2 at approximately the low-energy X-ray penetration limit thickness Tna. The inspection condition control unit 36 ​​also sets a tube current of the X-ray tube 22 suitable for this correction, for example, 1 mA, and sets the output of the X-ray generator 21 in low-output mode to the X-ray output Pxh1.

[0091] Furthermore, at this time, among the X-rays in a predetermined energy range from the X-ray generator 21, after passing through the belt surface before the inspection object W is carried in, a part of the X-rays is absorbed and attenuated by the low-energy side sensor module M1, and the high-energy side X-ray component is incident on the high-energy side sensor module M2 of the X-ray detector 23. At this time, as shown in Fig. 5(a), shading correction is performed so that the outputs of all sensor elements of the high-energy side sensor module M2 are aligned to a predetermined brightness Vbs1.

[0092] During this shading correction, the luminance value Vbs1 of the correction target that serves as the white reference during setting for the high-energy side sensor module M2 that detects high-energy X-rays is, for example, 2047 in 12-bit gradation (Vbs1=4095 / 2), and the luminance value Vbs2 of the correction target that serves as the white reference during setting for the low-energy side sensor module M1 that detects low-energy X-rays is, for example, the maximum luminance of 4095 in 12-bit gradation (Vbs2=4095). Therefore, during setting, the belt surface luminance values ​​of the low-energy side sensor module M1 and the high-energy side sensor module M2 are slightly different from each other, but during inspection, each becomes a constant belt surface luminance value that is equivalent to the luminance value of the background.

[0093] During an inspection, as described above, when the output (tube current × tube voltage) of the X-ray tube 22 is changed to the X-ray output Pxh2 during inspection, the current is increased, for example, from the setting tube current It1 to the inspection tube current It2. The increase ratio at this time is, for example, 2 times. Furthermore, during this inspection, if the object W is in a region below the low-energy X-ray penetration limit thickness Tna, the line image data generation unit 31 generates line image data Xca having an image density with a predetermined number of gradations corresponding to the detection value of the second luminance detection value Lxb, which is below the maximum luminance Vbs2. On the other hand, if the object W is in a region beyond the low-energy X-ray penetration limit thickness Tna, the line image data generation unit 31 generates line image data Xca having an image density with a predetermined number of gradations corresponding to the detection value of the first luminance detection value Lxa, which is below the maximum luminance Vbs2. Alternatively, without dividing the thickness into regions, the line image data generating unit 31 generates line image data (unsigned) having an image density of a predetermined number of gradations based on the detection value of the second brightness detection value Lxb that is equal to or less than the maximum brightness Vbs2 and the detection value of the first brightness detection value Lxa that is equal to or less than the maximum brightness Vbs2, or a brightness value Vbs3 that is calculated separately and corresponds to the first brightness detection value Lxa.

[0094] Furthermore, when the first brightness detection value Lxa from the low-energy side sensor module M1 saturates at the maximum brightness Vbs2, the actual brightness value Vbs3 is calculated using the above-mentioned formula [1] based on the brightness value Vbs2 at the time of shading correction and the current increase ratio from the tube current It1 at the time of setting to the tube current It2 at the time of examination. That is, in this embodiment, when the detected brightness indicated by the first brightness detection signal Lxa saturates at the maximum brightness Vbs2 of the preset number of gradations, the brightness value Vbs3 that should actually be detected at that time is estimated and calculated using the above-mentioned formula [1] that uses the current increase ratio from the tube current It1 at the time of setting to the tube current It2 at the time of examination.

[0095] By employing the high-output mode of the X-ray generator 21 and varying the shading correction conditions as described above, it is possible to effectively detect the X-ray penetration thickness τ of the region P1, which has a small penetration thickness below the low-energy X-ray penetration limit thickness Tna, using the second brightness detection signal Lxb of the high-energy side sensor module M2, onto which X-rays enter the X-ray detector 23 and are attenuated by one of the scintillators 23a and the X-ray filter. Furthermore, it is possible to effectively detect the X-ray penetration thickness τ of the region P2, which has a large penetration thickness equal to or greater than the low-energy X-ray penetration limit thickness Tna, using the first brightness detection signal Lxa from the low-energy side sensor module M1 of the X-ray detector 23. Therefore, regardless of whether the inspection object W is large or not, the X-ray image generation unit 31 can generate accurate X-ray image data Xca, Xcb, etc., using the effective brightness detection signals Lxa and Lxb within a practical range of the X-ray equivalent thickness τ.

[0096] The thickness determination means 33a of the image processing unit 33 may be configured to determine that the object W to be inspected brought into the inspection area Zx has a transmission thickness equivalent to the transmission limit thickness Tna of low-energy X-rays when a predetermined number of detection brightness values ​​among the multiple detection brightnesses corresponding to the first brightness detection signal Lxa from the photodiode array 23c of the low-energy side sensor module M1 are the minimum value (e.g., 0), as shown in Figure 4.

[0097] Furthermore, during inspection, as described above, the display image generating unit 34 calculates, for each pixel, the average pixel density values ​​of the X-ray image data Xia and Xib of the two energy components, high and low, of the X-rays in a predetermined energy range from the X-ray generator 21, and generates a display image as an average density image as shown in Fig. 7(a). When setting to perform shading correction or the like, it can generate a cut-out composite image as shown in Fig. 7(b) by using the high-energy X-ray image data Xib for the small penetration thickness region P1 and the low-energy X-ray image data Xia for the large penetration thickness region P2. Therefore, in this embodiment, for the small penetration thickness region P1 of the inspection object W, high-energy X-ray image data Xcb is generated using at least the second brightness detection signal Lxb, and for the large penetration thickness region P2, low-energy X-ray image data Xca is generated using at least the first brightness detection signal Lxa.

[0098] 7(a), when the density-also displayed image Xav is used as the display image during inspection, the region P1 of the test piece DPH where the transmission thickness is small, which is below the low-energy X-ray transmission limit thickness Tna, has an averaged relatively low image density (high brightness), while the region P2 where the transmission thickness is large has an averaged relatively high image density. Therefore, the X-ray image density can be accurately set for each of the small-thickness region P1 and the large-thickness region P2.

[0099] On the other hand, as shown in Figure 7(b), when the cut-out composite image Xct is used as the display image at the time of setting, the small transmission thickness region P1 of the test piece DPH has a low image density (high brightness) according to the second brightness detection value Lxb from the high-energy side sensor module M2 that detects the high-energy side X-ray component, while the large transmission thickness region P2 has an image density corresponding to the first brightness detection signal Lxa that corresponds to the X-ray amount attenuated according to the large X-ray equivalent thickness τ. Therefore, each set sensitivity can be accurately displayed.

[0100] The setting means 36a of the inspection condition control unit 36 ​​is a type setting means for setting the type of the object W to be inspected (type number "001" in FIG. 1), and the adjustment means 36b of the inspection condition control unit 36, which is an output control unit, may be configured to selectively increase the X-ray output from the X-ray generator 21 from the output level of the low-output mode to the output level of the high-output mode in accordance with the type of the object W set by the type setting means. Even in this case, the inspection condition control unit 36 ​​functions as a penetration power control means for selectively increasing the penetration power of the X-rays irradiated from the X-ray generator 21 in accordance with the object W, without changing the radiation quality, during inspection when the type of the object W is set by a selection input from the operation means 42. When the X-ray output is increased, in a small penetration thickness region P1 of the object W, which is below the penetration limit thickness Tna of the low-energy X-rays, the detection brightness indicated by the first brightness detection signal Lxa corresponding to the low-energy X-ray dose can be saturated at the maximum brightness Vbs2 of the preset number of gradations.

[0101] If the density values ​​do not saturate when the density values ​​of the X-ray image data Xia and Xib of X-rays in multiple energy ranges are added together, the display image generation unit 34 may generate a total X-ray image Xte (transmission image data of X-rays in a specified energy range) as one candidate for the display image Xip.

[0102] The operation display unit 40 is a touch panel display device configured with, for example, an LCD (Liquid Crystal Display) or the like, and has both the function of display means 41 and the function of operation means 42 (operation input means).

[0103] The function of the display means 41 is to display on the display screen various information required in relation to X-ray inspection, such as the operating status and setting information of the article inspection device 1. The function of the operation means 42 is to perform various touch panel operations, such as selecting a display screen, switching the operating mode between inspection mode, setting mode, or another mode, and inputting the setting of various parameters in the setting mode, and is a function to input required information in response to user operation input.

[0104] This operation display unit 40 is not limited to a touch panel integrated into the item inspection device 1, but may also be provided in the form of a portable tablet-type information terminal, or may be additionally installed in the form of a display and operation panel separate from the touch panel integrated into the item inspection device 1.

[0105] Next, an embodiment of an article inspection method according to the present invention that can be implemented using the apparatus configured as described above will be described.

[0106] In this embodiment, first, the setting process shown in FIG. 8 is executed, and first, the article conveyor conditions, the tube voltage of the X-ray tube 22, etc. are set by the above-mentioned automatic setting sequence (step S11).

[0107] Next, under the X-ray output Pxh1 in low output mode, the shading correction as described above is performed on the first brightness detection signal Lxa from the low-energy side sensor module M1 that detects the low-energy X-ray component of the X-rays in the specified energy range and the second brightness detection signal Lxb from the high-energy side sensor module M2 that detects the high-energy X-ray component so that they align with the respective correction target values ​​Vbs2, Vbs1, and the brightness values ​​Vbs2, Vbs1 that serve as the white reference at the time of setting are set (step S12).

[0108] Next, the estimated brightness Vbs3 when the X-ray output (tube voltage x tube current) of the X-ray tube 22 is increased from the X-ray output Pxh1 at the time of setting, which is the low X-ray output mode, to the X-ray output Phx2 at the time of inspection, which is the high X-ray output mode, is calculated using the above-mentioned formula (1) (step S13).

[0109] After such setting processing, at the start of the inspection when the type of the object W to be inspected and the inspection conditions are switched, shading correction for each energy component as described above is performed under the low-output mode X-ray output Pxh1 according to the set type so that it aligns with the respective correction target values ​​Vbs1, Vbs2, and the brightness values ​​Vb1, Vbs2 that serve as the white reference at the time of setting can be set again, or the X-ray output (tube voltage x tube current) of the X-ray tube 22 can be increased to the X-ray output Phx2 during the inspection without changing the radiation quality by increasing the tube current. Here, the inspection control processing will be described assuming that the processing required during the inspection is performed.

[0110] As shown in FIG. 9, in the inspection control process, first, inspection conditions that have been set and stored in advance according to the set product type are selected, and various corresponding control parameters are set (step S21).

[0111] Next, depending on the set type, it is determined whether or not the object to be inspected W has an area with a large penetration thickness exceeding the low-energy X-ray penetration limit thickness Tna (step S22), and if an area with a large penetration thickness is found (YES in step S22), the tube current is increased as a large object inspection mode and the output is switched to the X-ray output Phx2 of the high X-ray output mode (step S23; output control step). This increases the penetrating power of the X-rays without changing the radiation quality of the X-rays irradiated from the X-ray generator 21.

[0112] Next, the article inspection begins. First, the X-ray generator 21, which generates X-rays in a predetermined energy range using the X-ray tube 22, irradiates the inspection area Zx into which the inspection object W is carried (step S24; X-ray irradiation stage).

[0113] Next, the X-ray detection unit 23 having corresponding photodiode arrays 23c, 23d is caused to receive light from one scintillator 23a, which absorbs and emits low-energy X-rays among the X-rays that have passed through the inspection area Zx, and the other scintillator 23b, which absorbs and emits high-energy X-rays among the X-rays that have passed through the inspection area Zx, and detects the low-energy X-rays and high-energy X-rays (step S25; X-ray detection stage).

[0114] Next, based on the first luminance detection signal Lxa and the second luminance detection signal Lxb from the one and other photodiode arrays 23c, 23d, the line image data generation unit 31 generates low-energy X-ray image data Xca and high-energy X-ray image data Xcb, and transfers these data from the X-ray image data storage unit 32 to the image processing unit 33, which then executes a predetermined inspection and judgment process. At the same time, image data Xia and Xib, which show the object W as X-ray transmission images of two different energy components, high and low, are output from the X-ray image data storage unit 32 to the display image generation unit 34, and the average value of pixel density values ​​corresponding to the X-ray image data Xia and Xib is calculated for each pixel to generate a display image as shown in Figure 7(a) (step S26; X-ray image generation stage).

[0115] In the object inspection method of this embodiment, during the output control stage, when the object W to be inspected that is brought into the inspection area Zx has at least a region P2 with a large transmission thickness that is equal to or greater than the transmission limit thickness Tna of the low-energy X-rays, the penetrating power of the X-rays irradiated from the X-ray generator 21 is selectively increased, and in the region P1 of the object W with a small transmission thickness that is below the transmission limit thickness Tna of the low-energy X-rays, the detection brightness indicated by the first brightness detection signal Lxa of the low-energy side sensor module M1 is saturated at the maximum brightness Vbs2 of the preset number of gradations.

[0116] In addition, the type of the object W to be inspected is set prior to the X-ray irradiation stage, and in the output control stage, the X-ray intensity is controlled so as to selectively increase the penetrating power without changing the radiation quality of the X-rays irradiated from the X-ray generator 21 according to the type of object W to be inspected.

[0117] Furthermore, in the X-ray image generation stage, low-energy X-ray image data Xia is generated for the large transmission thickness region P2 of the object W using at least the first brightness detection signal Lxa, and high-energy X-ray image data Xib is generated for the small transmission thickness region P1 using at least the second brightness detection signal Lxb, thereby calculating the average pixel density values ​​corresponding to both of these image data Xia and Xib, or generating an image for display by combining cut-out images using low-energy X-ray image data Xia based on the first brightness detection signal Lxa for the large transmission thickness region P2 and high-energy X-ray image data Xib based on the second brightness detection signal Lxb for the small transmission thickness region P1.

[0118] Next, the operation will be described.

[0119] In this embodiment configured as described above, even if the thickness of the object W in the X-ray transmission direction varies greatly as the aforementioned X-ray equivalent thickness τ (=α·t), effective brightness detection signals Lxa, Lxb are generated to generate accurate X-ray image data Xia, Xib, and by making maximum use of these, it becomes possible to quickly and accurately inspect large foods, etc.

[0120] That is, in this embodiment, when the X-ray output of the X-ray generator 21 is increased to increase the penetrating power of the X-rays for inspecting large items, it is possible to generate low-energy X-ray image data Xia corresponding to the thickness in the X-ray transmission direction using at least the first brightness detection signal Lxa for areas such as the large-penetration-thickness region P2, which is equal to or greater than the low-energy X-ray penetration limit thickness Tna. Meanwhile, while some areas, such as the small-penetration-thickness region P1, which is below the low-energy X-ray penetration limit thickness Tna, cannot be inspected due to saturation, these areas can still be inspected with high-energy X-rays that do not saturate even when the X-ray output is increased. Therefore, X-ray inspection is possible for a wide range of thicknesses in the X-ray transmission direction. As a result, it is possible to provide an item inspection device 1 that can quickly and accurately inspect large foods and the like.

[0121] In this embodiment, the line image data generating unit 31, which is an X-ray image generating unit, generates low-energy X-ray image data Xia for the large X-ray transmission thickness region P2 using at least the first luminance detection signal Lxa, and generates high-energy X-ray image data Xib for the small X-ray transmission thickness region P1 using at least the second luminance detection signal Lxb. Therefore, when the thickness of the object W to be inspected in the X-ray transmission direction varies greatly, accurate X-ray image data Xia and Xib can be generated using the luminance detection signals Lxa and LXb that are effective for each thickness or thickness region, enabling the generation of a display image by the aforementioned luminance average calculation or cut-out synthesis. Therefore, X-ray inspection of an object can be performed quickly and accurately, regardless of whether the object is loose and very thin in the X-ray transmission direction or whether the object is very large in size or packaged.

[0122] Furthermore, in this embodiment, when the object to be inspected W brought into the inspection area Zx has an area P2 with a large penetration thickness equal to or greater than the low-energy X-ray penetration limit thickness Tna, the tube current of the X-ray tube 22 is increased to switch from low-power mode to high-power mode, thereby increasing the penetration power of the X-rays irradiated from the X-ray generating unit 21, so that manual or automatic mode switching makes it possible to selectively switch to high penetration power.

[0123] In addition, in this embodiment, the image processing unit 33 has a thickness determination means 33a that determines that the object W to be inspected brought into the inspection area Zx has a transmission thickness equivalent to the low-energy side X-ray transmission limit thickness Tna when a predetermined number of detection brightness values ​​among multiple detection brightnesses corresponding to the first brightness detection signal Lxa from the photodiode array 23c of the low-energy side sensor module M1 are the minimum value, thereby making it possible to automatically switch between high and low X-ray output modes.

[0124] In this embodiment, the setting means 36a of the inspection condition control unit 36 ​​serves as a type setting means for setting the type of the inspection object W to be inspected, and the X-ray output of the X-rays irradiated from the X-ray generator 21 can be selectively increased in accordance with the type of the inspection object W set by the type setting means. Therefore, when a type of large object to be inspected, whose thickness in the X-ray transmission direction is equal to or greater than the low-energy X-ray transmission limit thickness Tna, is set, automatic mode switching can be performed quickly and accurately to X-ray intensity and penetrating power higher than those used in normal product inspection.

[0125] Furthermore, in this embodiment, the control block 30B, which controls the image processing unit 33 and the inspection condition control unit 36 ​​to cooperate with each other, functions as an output control unit, and when the inspection condition control unit 36, which is a penetration power control means, increases the penetration power of the X-rays irradiated from the X-ray irradiation unit in accordance with the object to be inspected W, the range of detected brightness values ​​indicated by the first brightness detection signal Lxa in the large penetration thickness region P2 is set to less than the maximum brightness Vbs2. Therefore, it is possible to achieve both an expansion of the detection range of the thickness in the X-ray transmission direction and accurate image density setting.

[0126] Furthermore, in the article inspection method of this embodiment, during the output control stage, when the inspection object W carried into the inspection region Zx has at least a region P2 with a large penetration thickness equal to or greater than the low-energy X-ray penetration limit thickness Tna, the penetrating power of the X-rays irradiated from the X-ray generator 21 is increased, and the detected brightness indicated by the first brightness detection signal Lxa is saturated at the maximum brightness Vbs2 of the preset number of gradations in a region P1 of the inspection object W with a small penetration thickness below the low-energy X-ray penetration limit thickness Tna. Therefore, in the article inspection method of this embodiment, when the X-ray output is increased to increase the penetrating power of the X-rays for the inspection of a large inspection object W, it becomes possible to generate low-energy X-ray image data for the region P2 with a large penetration thickness equal to or greater than the low-energy X-ray penetration limit thickness Tna, etc., using at least the first brightness detection signal Lxa. As a result, when the thickness of the object W to be inspected varies greatly in the X-ray transmission direction, by generating brightness detection signals Lxa and / or Lxb that are effective for each thickness or thickness region and making maximum use of accurate X-ray image data Xia and Xib for each corresponding thickness, it becomes possible to perform product inspection that can quickly and accurately inspect foods and other items that are large in size or packaging.

[0127] Furthermore, in this embodiment, the type of the object W to be inspected is set prior to the X-ray irradiation stage, and in the output control stage, control is performed to selectively increase the penetrating power of the X-rays irradiated from the X-ray generator 21 depending on the type of object W to be inspected, thereby enabling quick and accurate automatic mode switching.

[0128] Additionally, in this embodiment, in the X-ray image generation stage, low-energy X-ray image data Xia is generated for the large-thickness region P2 of the object W using at least the first luminance detection signal Lxa, and high-energy X-ray image data Xib is generated for the small-thickness region P1 using at least the second luminance detection signal Lxb. Therefore, when the thickness of the object W in the X-ray transmission direction varies, accurate X-ray image data Xia or Xib can be generated by utilizing the luminance detection signal Lxa or Lxb effective for each thickness or thickness region. Therefore, for example, the average value (average luminance) of pixel values ​​corresponding to the transmitted X-ray dose on the high-energy side and the low-energy side for each transmission thickness region can be calculated to set the X-ray image density for each transmission thickness region P1, P2, or the first luminance detection signal Lxa can be used for the large-thickness region P2 and the second luminance detection signal Lxb can be used for the small-thickness region P1 to perform cutout and synthesis.

[0129] Thus, according to this embodiment, an object inspection device 1 can be provided that is capable of performing X-ray inspection quickly and accurately over a wide range of thicknesses in the X-ray transmission direction, even if the thickness in the X-ray transmission direction is greater than the transmission limit thickness Tna of low-energy X-rays, or if there is a region P2 where the transmission thickness is greater than the transmission limit thickness Tna.

[0130] In the above-described embodiment, the X-ray detector 23 is an indirect conversion type having scintillators 23a and 23b, but in the modified form shown in Figures 3(a) and 3(b), it may also be a direct conversion type, for example, a photon counting type X-ray detector.

[0131] As described above, the object inspection device of the present invention provides an object inspection device that can quickly and accurately perform X-ray inspection on objects with a wide range of thicknesses, even if the thickness of the object in the X-ray transmission direction is greater than the transmission limit thickness of low-energy X-rays, has an area where the transmission thickness is greater than the transmission limit thickness, or is less than the transmission limit thickness of low-energy X-rays.The present invention is useful for object inspection devices in general that obtain image data corresponding to the dose distribution of X-rays that have passed through a transported object by periodic detection operations of a line sensor-type X-ray detector, and judge the quality condition of the object based on the image data. [Explanation of symbols]

[0132] 1. Item inspection equipment 10. Item transport section 11 Conveyor belt 11a Transport path 12,13 Laura 20 X-ray Inspection Department 21 X-ray generator (X-ray irradiation unit) 22 X-ray tube 22a cathode 22b Anode 23 X-ray detector (X-ray detection part) 23a Scintillator (one scintillator) 23A One of the X-ray detectors (low-energy X-ray detector) 23b Scintillator (other scintillator) 23B The other X-ray detector (X-ray detection part on the high energy side) 23c Photodiode array (one group of light receiving elements) 23d Photodiode array (the other photodetector group) 23e, 23f detection circuit 23g metal filter plate 24 Box body 24a X-ray window 25,26 Drive power supply circuit 27 Work detection sensor 27 Item detection sensor 30 Inspection control section 30A Image Generation Block 30B Control block (output control section) 31 Line image data generation unit (X-ray image generation unit) 32 X-ray image data storage unit 33 Image processing section 33a Thickness determination means 33b Testing and Judging Means 34 Display image generation section 35 Display control unit 36 Inspection condition control section 36a Setting means (condition setting means) 36b Adjustment means (transmittance control means) 40 Operation display section 41 Display means 42 Operating means A1 information (information on pixel area that is less than the transmission limit thickness) A2 information (information on pixel area with thickness greater than the transmission limit) d1 direction (transport direction) d2 Line scan direction d3 X-ray irradiation direction Tube current at It1 setting It2 Tube current during examination Lxa First luminance detection signal Lxb Second luminance detection signal M1 Low-energy side sensor module (sensor module for detecting low-energy side components, one of the sensor modules) M2 High-energy side sensor module (sensor module for detecting high-energy components, other sensor module) P1 Small transmission thickness area P2 Large transmission thickness area Pxh1 X-ray output (output value, X-ray output at time of setting, X-ray output in low output mode) Pxh2 X-ray output (output value, X-ray output during inspection, X-ray output in high-power mode) T1 Thickness in the X-ray transmission direction (transmission thickness, thickness less than the transmission limit thickness of low-energy X-rays) T2 Thickness in the direction of X-ray transmission (transmission thickness, thickness greater than the transmission limit thickness of low-energy X-rays) Tna: Thickness limit of X-rays (thickness limit of X-rays at low energy) Vbs1 correction target value Vbs2 luminance value (maximum luminance, correction target value) Vbs3 luminance value (estimated luminance at saturation) Xb X-rays (X-rays within a specific energy range) Xia X-ray image data (low-energy X-ray image data) Xib X-ray image data (high-energy X-ray image data) Xca image data (low-energy X-ray image data) Xcb image data (high-energy X-ray image data) Zx Item Inspection Area

Claims

1. an X-ray irradiation unit (21) that generates X-rays (Xb) within a predetermined energy range using an X-ray tube (22) and irradiates the X-rays onto an article inspection area (Zx) into which an article (W) is carried; an X-ray detection unit (23) having one scintillator (23a) that absorbs and emits X-rays on the low energy side of the predetermined energy range, and another scintillator (23b) that absorbs and emits X-rays on the high energy side of the predetermined energy range, and having one and the other groups of light-receiving elements (23c, 23d) attached to both scintillators; an X-ray image generating unit (31) that generates X-ray image data (Xca) on the low energy side and X-ray image data (Xcb) on the high energy side based on a first luminance detection signal (Lxa) corresponding to the X-ray dose on the low energy side from one of the light receiving element groups and a second luminance detection signal (Lxb) corresponding to the X-ray dose on the high energy side from the other of the light receiving element groups; an output control unit (30B) that adjusts a tube voltage and a tube current of the X-ray tube and controls an X-ray output of the X-ray irradiation unit in accordance with the article, The output control unit a penetrating power control means (36b) for selectively increasing the penetrating power of the X-rays by increasing the X-ray output from the X-ray irradiation unit in accordance with the object during an inspection in which the type of the object is set; An object inspection device characterized in that, when the X-ray output is increased in accordance with the object, for a region (P1) of the object where the transmission thickness is small and is below the transmission limit thickness (Tna) of the low-energy X-ray, the detection brightness indicated by the first brightness detection signal in accordance with the transmission amount of the low-energy X-ray is saturated at a maximum brightness (Vbs2) of a preset number of gradations.

2. The object inspection device described in claim 1, characterized in that the X-ray image generation unit generates the high-energy side X-ray image data for the small transmission thickness area of ​​the object using at least the second brightness detection signal, and generates the low-energy side X-ray image data for the large transmission thickness area (P2) that is equal to or greater than the X-ray transmission limit thickness on the low-energy side using at least the first brightness detection signal.

3. The object inspection device described in claim 1 or 2, characterized in that when an object brought into the object inspection area has an area with a transmission thickness greater than the low-energy X-ray transmission limit thickness, the output control unit increases the tube current of the X-ray tube to switch from low-output mode to high-output mode, thereby increasing the penetration power without changing the radiation quality of the X-rays irradiated from the X-ray irradiation unit.

4. The output control unit is characterized in that it has a thickness determination means (33a) that determines that an item being transported into the item inspection area has a transmission thickness equivalent to the transmission limit thickness of the low-energy X-rays when a predetermined number of detection brightness values ​​among the multiple detection brightnesses corresponding to the first brightness detection signal from one of the photodetector groups are the minimum value.

5. a product type setting means (36a) for setting the product type of the product to be inspected; 4. The object inspection method according to claim 3, wherein the output control unit selectively increases the X-ray output of the X-rays irradiated from the X-ray irradiation unit depending on the type of object set by the type setting means.

6. The object inspection device described in claim 1 or 2, characterized in that when the output control unit increases the X-ray penetration power by increasing the X-ray output from the X-ray irradiation unit in accordance with the object using the penetration power control means, the output control unit sets the range of detected brightness values ​​indicated by the second brightness detection signal in the area of ​​transmission thickness greater than or equal to the low-energy X-ray penetration limit thickness to be less than the maximum brightness.

7. an X-ray irradiation step (S24) in which an X-ray irradiation unit (21) generates X-rays (Xb) within a predetermined energy range using an X-ray tube (22) and irradiates the X-rays onto an article inspection area (Zx) into which an article (W) is carried; an X-ray detection step (S25) in which an X-ray detection unit (23) having corresponding groups of light-receiving elements (23c, 23d) receives light from one scintillator (23a) that absorbs and emits low-energy X-rays among the X-rays that have passed through the article inspection area, and another scintillator (23b) that absorbs and emits high-energy X-rays among the X-rays that have passed through the article inspection area, and detects the low-energy X-rays and the high-energy X-rays; an X-ray image generating step (S26) of generating X-ray image data (Xca) on the low energy side and X-ray image data (Xcb) on the high energy side based on a first luminance detection signal (Lxa) corresponding to the X-ray dose on the low energy side from one of the light receiving element groups and a second luminance detection signal (Lxb) corresponding to the X-ray dose on the high energy side from the other light receiving element group; an output control step (S23) of adjusting a tube voltage and a tube current of the X-ray tube to control an X-ray output of the X-ray irradiation unit according to the article, In the output control step, when at least the article being transported into the article inspection area has a large transmission thickness region (P2) that is equal to or greater than the low-energy side X-ray transmission limit thickness, the X-ray output from the X-ray irradiation unit is increased to increase the X-ray transmission power, and for a small transmission thickness region (P1) of the article that is below the low-energy side X-ray transmission limit thickness (Tna), the detection brightness indicated by the first brightness detection signal corresponding to the low-energy side X-ray dose is saturated at a maximum brightness (Vbs2) of a preset number of gradations.

8. Prior to the X-ray irradiation step, the type of the article to be inspected is set (S21), 8. The object inspection method according to claim 7, wherein the output control step selectively controls the X-ray intensity depending on the type of the object so as to increase the penetrating power without changing the radiation quality of the X-rays irradiated from the X-ray irradiation unit.

9. An object inspection method as described in claim 7 or 8, characterized in that in the X-ray image generation step, the high-energy side X-ray image data is generated for the small transmission thickness area of ​​the object using at least the second brightness detection signal, and the low-energy side X-ray image data is generated for the large transmission thickness area using at least the first brightness detection signal.

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