X-ray inspection device

Abstract

To provide an X-ray inspection device which can suppress the occurrence of false detection of foreign matter.SOLUTION: An X-ray inspection device 1 comprises a conveying unit 5, an X-ray irradiation unit 6, an X-ray detection unit 7, and a control unit 10 for inspecting whether or not foreign matter is included in an article A on the basis of an X-ray transmission image. The control unit 10 carries out first inspection of inspecting, using a prescribed threshold value, whether or not foreign matter having a lower X-ray attenuation rate than the article A is included in the article A, carries out a second inspection of inspecting, using a machine learning algorithm, whether or not foreign matter is included in the inside of the article A, and determines that foreign matter is included in the article A when foreign matter common to the respective inspection results of the first and second inspections is included in the article A.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an X-ray inspection apparatus.

Background Art

[0002] An X-ray inspection apparatus includes a conveyance unit that conveys an article, an X-ray irradiation unit that irradiates the article conveyed by the conveyance unit with X-rays, an X-ray detection unit that detects the X-rays transmitted through the article, and an inspection unit that generates an X-ray transmission image from the X-rays detected by the X-ray detection unit and inspects the article based on the X-ray transmission image (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an X-ray inspection apparatus, there is a demand for an inspection that determines a foreign object such as resin contained inside an article as an abnormality. When performing the inspection of the foreign object using a machine learning algorithm (trained model) in the X-ray inspection apparatus, it is difficult to distinguish between a cavity (void) formed inside the article and the foreign object, so there is a risk of determining a cavity that is not an abnormality as an abnormality and erroneously detecting a good product as a defective product. Further, when performing the inspection of the foreign object by image processing (energy analysis) in the X-ray inspection apparatus, if an attempt is made to increase the sensitivity, there is a risk of determining noise or the like as a foreign object and erroneously detecting a good product as a defective product.

[0005] One aspect of the present invention aims to provide an X-ray inspection apparatus capable of suppressing the occurrence of false detection of foreign objects.

Means for Solving the Problems

[0006] (1) An X-ray inspection apparatus according to one aspect of the present invention includes a conveyance unit that conveys an article, an X-ray irradiation unit that irradiates the article conveyed by the conveyance unit with X-rays, an X-ray detection unit that detects the X-rays irradiated by the X-ray irradiation unit and transmitted through the article, an X-ray transmission image generation unit that generates an X-ray transmission image based on the X-rays detected by the X-ray detection unit, and an inspection unit that inspects whether or not the article contains a foreign object based on the X-ray transmission image generated by the X-ray transmission image generation unit. The inspection unit performs a first inspection of inspecting whether or not the article contains a foreign object whose X-ray attenuation rate is lower than that of the article using a predetermined threshold value, and performs a second inspection of inspecting whether or not the article contains a foreign object inside the article using a machine learning algorithm. When the article contains a foreign object common to the inspection results of the first inspection and the second inspection, it is determined that the article contains a foreign object.

[0007] In the X-ray inspection apparatus according to one aspect of the present invention, when the article contains a foreign object common to the inspection results of the first inspection and the second inspection, the inspection unit determines that the article contains a foreign object. Thereby, in the X-ray inspection apparatus, by using the two inspection results, for example, even when a cavity is determined as a foreign object in the second inspection, if it is determined that the article does not contain a foreign object in the first inspection, it is not determined that the article contains a foreign object. Therefore, in the X-ray inspection apparatus, the occurrence of false detection of foreign objects can be suppressed.

[0008] (2) In the X-ray inspection apparatus of (1) above, when the inspection unit determines that the article contains a foreign object in at least one of the inspection results of the first inspection and the second inspection, the inspection unit may determine whether or not the article contains a foreign object based on the area occupied by the foreign object in the X-ray transmission image. In the first inspection, if the sensitivity is increased, the influence of minute noise becomes large and there is a risk of false detection. Therefore, the inspection unit determines whether or not the article contains a foreign object based on the area occupied by the foreign object in the X-ray transmission image. Thereby, in the X-ray inspection apparatus, minute noise can be excluded. Therefore, in the X-ray inspection apparatus, while improving the detection accuracy, the occurrence of false detection can be suppressed.

[0009] (3) In the X-ray inspection apparatus according to (1) or (2) above, the X-ray detection unit detects the X-rays in the first energy band that have passed through the article and the X-rays in the second energy band that have passed through the article, the X-ray transmission image generation unit generates an X-ray transmission image based on the X-rays in the first energy band and an X-ray transmission image based on the X-rays in the second energy band, and the inspection unit may determine whether or not the article contains a foreign object based on the difference image of the plurality of X-ray transmission images generated by the X-ray transmission image generation unit. In this configuration, since the difference image of the plurality of X-ray transmission images based on two different energy bands is used, foreign objects can be detected with higher accuracy.

[0010] (4) In the X-ray inspection apparatus according to any one of (1) to (3) above, the inspection unit may perform a second inspection using a learned model that has been machine-learned based on an image containing a foreign object whose X-ray attenuation rate is lower than that of the article. In this configuration, foreign objects such as resin present inside the article can be detected with high accuracy.

[0011] (5) In the X-ray inspection apparatus according to any one of (1) to (4) above, the foreign object may have a specific gravity smaller than that of the article. Foreign objects such as resin present inside the article (object to be inspected) have a specific gravity smaller than that of the article. In the X-ray inspection apparatus, with the above configuration, foreign objects such as resin present inside the article can be detected with high accuracy.

Advantages of the Invention

[0012] According to one aspect of the present invention, the occurrence of false detection of foreign objects can be suppressed.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Best Mode for Carrying Out the Invention

[0014] Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and duplicate descriptions are omitted.

[0015] As shown in FIG. 1, the X-ray inspection apparatus 1 includes an apparatus main body 2, support legs 3, a shield box 4, a conveyance unit 5, an X-ray irradiation unit 6, an X-ray detection unit 7, a display operation unit 8, and a control unit 10. In the present embodiment, for example, the X-ray inspection apparatus 1 inspects for foreign objects present inside an article A such as a soft candy. Examples of the foreign object include resin and the like.

[0016] The X-ray inspection apparatus 1 generates an X-ray transmission image of the article A while conveying the article A, and inspects (foreign object inclusion inspection) the article A based on the X-ray transmission image. The article A before inspection is carried into the X-ray inspection apparatus 1 by the carry-in conveyor 51. The article A after inspection is carried out of the X-ray inspection apparatus 1 by the carry-out conveyor 52. The article A determined to be a defective product by the X-ray inspection apparatus 1 is sorted out of the production line by a sorting device (not shown) disposed downstream of the carry-out conveyor 52. The article A determined to be a non-defective product by the X-ray inspection apparatus 1 passes through the sorting device as it is.

[0017] The apparatus main body 2 houses the control unit 10 and the like. The support legs 3 support the apparatus main body 2. The shield box 4 is provided on the apparatus main body 2. The shield box 4 prevents leakage of X-rays to the outside. Inside the shield box 4, an inspection area R where inspection of the article A by X-rays is carried out is provided. The shield box 4 is formed with a carry-in port 4a and a carry-out port 4b. The article A before inspection is carried into the inspection area R from the carry-in conveyor 51 through the carry-in port 4a. The article A after inspection is carried out from the inspection area R to the carry-out conveyor 52 through the carry-out port 4b. X-ray shielding curtains (not shown) for preventing leakage of X-rays are provided at each of the carry-in port 4a and the carry-out port 4b.

[0018] The conveying unit 5 is disposed within the shield box 4. The conveying unit 5 conveys the article A along the conveying direction D from the loading port 4a through the inspection area R to the unloading port 4b. The conveying unit 5 is, for example, a belt conveyor stretched between the loading port 4a and the unloading port 4b.

[0019] As shown in FIGS. 1 and 2, the X-ray irradiation unit 6 is disposed within the shield box 4. The X-ray irradiation unit 6 irradiates the article A conveyed by the conveying unit 5 with X-rays. The X-ray irradiation unit 6 has, for example, an X-ray tube that emits X-rays, and a collimator that spreads the X-rays emitted from the X-ray tube in a fan shape within a plane perpendicular to the conveying direction D.

[0020] The X-ray detection unit 7 is a sensor 12 that detects electromagnetic waves. The X-ray detection unit 7 may be capable of detecting X-rays in a specific energy band, or may be capable of detecting X-rays by a photon counting method. The X-ray detection unit 7 may be a direct conversion type detection unit or an indirect conversion type detection unit. In the present embodiment, the X-ray detection unit 7 is a direct conversion type detection unit capable of detecting X-rays by a photon counting method, and includes, for example, a sensor (multi-energy sensor) that detects X-rays of each of a plurality of energy bands that penetrate the article A. The sensors are arranged, for example, at least in a direction (width direction) perpendicular to the conveying direction and the vertical direction of the conveying unit 5. The elements may be arranged not only in the width direction but also in the conveying direction. That is, the X-ray detection unit 7 may include a line sensor or may include a group of sensors arranged two-dimensionally. The sensor 12 is, for example, a photon detection type sensor such as a CdTe semiconductor detector.

[0021] As shown in FIG. 1, the display operation unit 8 is provided on the apparatus main body 2. The display operation unit 8 displays various information and accepts input of various conditions. The display operation unit 8 is, for example, a liquid crystal display, and displays an operation screen as a touch panel. In this case, the operator can input various conditions via the display operation unit 8.

[0022] The control unit 10 is arranged inside the apparatus main body 2. The control unit 10 controls the operations of each part of the X-ray inspection apparatus 1. The control unit 10 is composed of a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. The detection results of X-rays in the low energy band (first energy band) are input from the sensor 12 (see FIG. 2) of the X-ray detection unit 7 to the control unit 10, and at the same time, the detection results of X-rays in the high energy band (second energy band) are input from the sensor 12 (see FIG. 2) of the X-ray detection unit 7 to the control unit 10. The control unit 10 generates an X-ray transmission image based on the detection results. The control unit 10 functions as an X-ray transmission image generation unit that generates an X-ray transmission image based on the X-rays detected by the X-ray detection unit 7. Further, the control unit 10 functions as an inspection unit that inspects whether or not the article A contains a foreign object F (see FIG. 3(a), etc.) based on the X-ray transmission image.

[0023] The control unit 10 performs a first inspection and a second inspection to inspect whether or not the article A contains a foreign object F inside. The control unit 10 performs a first inspection using a predetermined threshold value to inspect whether or not the article A contains a foreign object F whose X-ray attenuation rate is lower than that of the article A. The control unit 10 performs a second inspection using a machine learning algorithm to inspect whether or not the article A contains a foreign object F inside. The control unit 10 determines that the article A contains a foreign object F when the foreign object F common to the respective inspection results of the first inspection and the second inspection is contained in the article A. The inside of the article A is a portion on the path through which X-rays pass between the front surface (the surface facing upward when being conveyed) and the back surface (the surface facing the conveying surface when being conveyed) of the article A.

[0024] [First Inspection] First, the first inspection in the control unit 10 will be described. The detection result of the X-ray detection unit 7 is input to the control unit 10. In the present embodiment, the detection results of the X-rays in the low energy band and the high energy band from the sensor 12 of the X-ray detection unit 7 are input to the control unit 10. The control unit 10 generates a plurality of X-ray transmission images based on the X-rays for each of the plurality of energy bands detected by the X-ray detection unit 7.

[0025] As shown in FIG. 3(a), the control unit 10 generates a first transmission image P1 as an X-ray transmission image based on the detection result of the X-rays in the low energy band. As shown in FIG. 3(b), the control unit 10 generates a second transmission image P2 as an X-ray transmission image based on the detection result of the X-rays in the high energy band. At least the article A and the background other than the article A are reflected in each of the first transmission image P1 and the second transmission image P2. As shown in an example in FIG. 3(a), the first transmission image P1 is darker overall compared to the second transmission image P2. On the other hand, as shown in an example in FIG. 3(b), the second transmission image P2 is brighter overall compared to the first transmission image P1. The comparison of the brightness between the first transmission image P1 and the second transmission image P2 corresponds to the comparison of the brightness of the article A displayed in the first transmission image P1 and the brightness of the article A displayed in the second transmission image P2.

[0026] The control unit 10 performs image processing including subtraction processing on the first transmission image P1 and the second transmission image P2 to generate a difference image that extracts the difference between the first transmission image P1 and the second transmission image P2. For example, the control unit 10 performs a difference process of adjusting the luminance values (shading values) of the portions corresponding to the article A between the first transmission image P1 and the second transmission image P2 and calculating the difference in the luminance values of these respective pixels, and obtains a difference image processed so that the difference between the luminance value of the pixel corresponding to the foreign object F and the luminance value of the pixel not corresponding to the foreign object F becomes large. Here, the control unit 10 may perform image processing on at least one of the first transmission image P1 and the second transmission image P2 using an image processing algorithm.

[0027] The image processing algorithm is composed of one image processing filter or a combination of multiple image processing filters. The image processing algorithm can be obtained from the outside via a network such as the Internet. The image processing algorithm can also be obtained from an external storage medium such as a USB memory or a removable hard disk. The image processing algorithm can be automatically generated from a plurality of image processing filters based on the specifications or inspection conditions of the X-ray inspection apparatus 1 by adopting a genetic algorithm (GA = Genetic Algorithms), which is a method applying the mechanisms of heredity and evolution in the biological world. The image processing algorithm can also be appropriately set by the user via the display operation unit 8.

[0028] Figure 4 is a graph schematically showing an example of the luminance distribution of the difference image. In Figure 4, the vertical axis corresponds to luminance, and the horizontal axis corresponds to the position along the conveyance direction D (each pixel of the difference image). The control unit 10 performs an inspection regarding the presence or absence of the foreign object F included in the article A based on the generated difference image. The control unit 10 detects the foreign object F based on the luminance distribution in the difference image. The control unit 10 detects a first foreign object having a higher specific gravity (heavier) than the article A using a first threshold value, and detects a second foreign object having a lower specific gravity (lighter) than the article A using a second threshold value different from the first threshold value. Specifically, the control unit 10 detects the first foreign object when there is a luminance value greater than the first threshold value in the luminance distribution of the difference image. The control unit 10 detects the second foreign object when there is a luminance value smaller than the second threshold value in the luminance distribution of the difference image.

[0029] As shown in FIG. 4, the first threshold value is a luminance value greater than the reference luminance value, which is the luminance value corresponding to article A. The reference luminance value is, for example, 0 and also corresponds to the background of the difference image. The first threshold value is a foreign object determination threshold value for determining the presence or absence of a first foreign object. The second threshold value is a foreign object determination threshold value for determining the presence or absence of a second foreign object. The second threshold value is a luminance value smaller than the reference luminance value. The first threshold value and the second threshold value can be set individually via the display operation unit 8. The first threshold value and the second threshold value may be appropriately set by tests or the like according to the properties of article A. For example, the absolute value of the first threshold value may be larger than the absolute value of the second threshold value.

[0030] The first foreign object is, for example, metal or the like present inside article A and is composed of an element heavier than the elements of article A. The first foreign object corresponds to, for example, a brightly lit portion in the difference image. The second foreign object is, for example, plastic resin or the like present inside article A and is composed of an element lighter than the elements of article A. The second foreign object corresponds to, for example, a darkly lit portion in the difference image.

[0031] In the example shown in FIG. 4, in the luminance distribution of the difference image, the luminance value is greater than the first threshold value (that is, there is a significantly bright portion in the difference image), and it can be determined that the first foreign object is included therein. Also, in the luminance distribution of the difference image, the luminance value is smaller than the second threshold value (that is, there is a significantly dark portion in the difference image), and it can be determined that the second foreign object is included therein. In the case where the luminance value is less than or equal to the first threshold value and greater than or equal to the second threshold value in the luminance distribution of the difference image (that is, when the brightness of the difference image is the same as the background brightness), it can be determined that there is no foreign object there.

[0032] [Second Inspection] Next, the second inspection will be described. The control unit 10 determines whether or not the article A contains the foreign object F using the learned model. The learned model is a learned model that has been machine-learned based on an image containing the foreign object F whose X-ray attenuation rate is lower than that of the article A. The learned model can also be obtained from an external storage medium such as a USB memory or a removable hard disk. The control unit 10 inputs, for example, the second transmission image P2 into the learned model and determines whether or not the article A contains the foreign object F. The control unit 10 stores the inspection result of the foreign object F in the storage unit.

[0033] [Foreign Object Judgment] When the control unit 10 determines that the article A contains the foreign object F (second foreign object) common to the inspection result of the first inspection and the inspection result of the second inspection, the control unit 10 determines that the article A contains the foreign object F. When the control unit 10 determines that the article A contains the foreign object F in at least one of the inspection results of the first inspection and the second inspection, the control unit 10 determines whether or not the article A contains the foreign object F based on the area occupied by the foreign object F in the X-ray transmission image. The threshold value may be appropriately set by a test or the like according to the properties (size, etc.) of the foreign object F. In the present embodiment, the control unit 10 determines that the article A contains the foreign object F when the foreign object F common to the inspection result of the first inspection and the inspection result of the second inspection is contained in the article A and the area of the foreign object F is equal to or greater than the threshold value.

[0034] After determining the foreign object detection, the control unit 10 causes the display operation unit 8 to display the inspection result. For example, an inspection result image and an inspection result of "OK (good product)" or "NG (defective product)" are displayed on the display operation unit 8. In the display operation unit 8, the area including the foreign object F is surrounded and displayed. Further, when the control unit 10 determines that the article A contains the foreign object F, the control unit 10 outputs an instruction signal for instructing the sorting device to sort the article A.

[0035] As described above, in the X-ray inspection apparatus 1 according to the present embodiment, when the control unit 10 determines that the foreign object F common to the inspection results of the first inspection and the second inspection is included in the article A, it determines that the foreign object F is included in the article A. Thus, in the X-ray inspection apparatus 1, by using the two inspection results, for example, even when a cavity is determined as the foreign object F in the second inspection, if it is determined that the foreign object F is not included in the first inspection, it is not determined that the foreign object F is included in the article A. Therefore, in the X-ray inspection apparatus 1, the occurrence of false detection of the foreign object F can be suppressed.

[0036] In the X-ray inspection apparatus 1 according to the present embodiment, when the control unit 10 determines that the foreign object F is included in the article A in at least one of the inspection results of the first inspection and the second inspection, it determines whether the foreign object F is included in the article A based on the area occupied by the foreign object F in the X-ray transmission image. In the first inspection, if the sensitivity is increased, the influence of minute noise becomes large, and there is a risk of false detection. Therefore, the control unit 10 determines whether the foreign object F is included in the article A based on the area occupied by the foreign object F in the X-ray transmission image. Thereby, in the X-ray inspection apparatus 1, minute noise can be excluded. Therefore, in the X-ray inspection apparatus 1, while improving the detection accuracy, the occurrence of false detection can be suppressed.

[0037] In the X-ray inspection apparatus 1 according to the present embodiment, the X-ray detection unit 7 detects X-rays in a high energy band that has passed through the article A and X-rays in a low energy band that has passed through the article A. The control unit 10 generates a first transmission image P1 based on the X-rays in the high energy band and a second transmission image P2 based on the X-rays in the low energy band. The control unit 10 determines whether the foreign object F is included in the article A based on the difference image between the first transmission image P1 and the second transmission image P2. In this configuration, since the difference image of a plurality of X-ray transmission images based on two different energy bands is used, the foreign object F can be detected with higher accuracy.

[0038] In the X-ray inspection apparatus 1 according to the present embodiment, the control unit 10 performs a second inspection using a learned model that has been machine-learned based on an image including a foreign object F whose X-ray attenuation rate is lower than that of the article A. With this configuration, it is possible to accurately detect a foreign object F such as resin present inside the article A.

[0039] As described above, the embodiments of the present invention have been described. However, the present invention is not necessarily limited to the above-described embodiments, and various modifications can be made without departing from the gist thereof.

[0040] In the above embodiment, the X-ray detection unit 7 is configured to detect X-rays in two bands, but is not limited thereto. For example, the X-ray detection unit 7 may be configured to detect X-rays in three or more bands. In this case, the X-ray detection unit 7 may determine the presence or absence of a foreign object included in the article A using X-rays in three or more bands.

[0041] In the above embodiment, as the X-ray detection unit 7, a form of a so-called photon counting type sensor has been described as an example. However, the X-ray detection unit 7 may include a first line sensor and a second line sensor. The first line sensor and the second line sensor are each composed of X-ray detection elements (not shown) arranged one-dimensionally along a horizontal direction perpendicular to the conveyance direction D. The first line sensor detects X-rays in a low energy band that have passed through the article A and the conveyance belt of the conveyance unit 5. The second line sensor detects X-rays in a high energy band that have passed through the article A, the conveyance belt of the conveyance unit 5, and the first line sensor. Further, the X-ray detection unit 7 may have a configuration including one line sensor, or may use another sensor.

[0042] In the above embodiment, a form has been described as an example in which a first transmission image P1 and a second transmission image P2 are generated, and based on a difference image obtained by extracting the difference between the first transmission image P1 and the second transmission image P2, it is determined whether or not the article A contains a foreign object F. However, in a configuration that does not detect X-rays in a plurality of energy bands, it may be determined whether or not the article A contains a foreign object F based on the X-ray transmission image.

[0043] In the above embodiment, for the purpose of inspecting a foreign object F whose X-ray attenuation rate is lower than that of the article A, in the second inspection, a form using a learned model that has been machine-learned based on an image including the foreign object F whose X-ray attenuation rate is lower than that of the article A was described as an example. However, the learned model is not limited to this. For example, in the second inspection, a learned model that has been machine-learned based on an image including a foreign object F whose X-ray attenuation rate is higher than that of the article A may be used. When using this learned model, a metal or the like can be detected as the foreign object F. Specifically, when a foreign object F (first foreign object) common to the inspection result of the first inspection and the inspection result of the second inspection is included in the article A, it is determined that the article A contains the foreign object F.

[0044] In the above embodiment, the X-ray inspection apparatus 1 has the control unit 10, but it is not limited to this. For example, at least some functions of the control unit 10 may be implemented in an external control device (such as a laptop PC, a tablet, a server, etc.) capable of wired communication or wired communication with the X-ray inspection apparatus 1. Each configuration in the above embodiment or the above modification example can be arbitrarily applied to each configuration in other embodiments or other modification examples.

Explanation of Reference Numerals

[0045] 1...X-ray inspection apparatus, 5...transport unit, 6...X-ray irradiation unit, 7...X-ray detection unit, 10...control unit (X-ray transmission image generation unit, inspection unit), A...article, F...foreign object.

Claims

1. A conveying unit for conveying an article; An X-ray irradiation unit that irradiates the article conveyed by the conveying unit with X-rays; An X-ray detection unit that detects the X-rays that have passed through the article after being irradiated by the X-ray irradiation unit; An X-ray transmission image generation unit that generates an X-ray transmission image based on the X-rays detected by the X-ray detection unit; An inspection unit that inspects whether the article contains a foreign object based on the X-ray transmission image generated by the X-ray transmission image generation unit, comprising: The inspection unit: Performs a first inspection using a predetermined threshold value to inspect whether the article contains a foreign object whose X-ray attenuation rate is lower than that of the article; Performs a second inspection using a machine learning algorithm to inspect whether the article contains a foreign object inside the article; An X-ray inspection apparatus that determines that the article contains the foreign object when the foreign object common to the inspection results of the first inspection and the second inspection is included in the article.

2. When the inspection unit determines that the article contains the foreign object in at least one of the inspection results of the first inspection and the second inspection, the inspection unit determines whether the article contains a foreign object based on the area occupied by the foreign object in the X-ray transmission image. The X-ray inspection apparatus according to claim 1.

3. The X-ray detection unit detects the X-rays in a first energy band that have passed through the article and the X-rays in a second energy band that have passed through the article; The X-ray transmission image generation unit generates an X-ray transmission image based on the X-rays in the first energy band and an X-ray transmission image based on the X-rays in the second energy band; The inspection unit determines whether the article contains a foreign object based on a difference image of a plurality of the X-ray transmission images generated by the X-ray transmission image generation unit. The X-ray inspection apparatus according to claim 1 or 2.

4. The inspection unit performs the second inspection using a learned model that has been machine-learned based on an image containing a foreign object whose X-ray attenuation rate is lower than that of the article. The X-ray inspection apparatus according to claim 1 or 2.

5. The foreign object has a specific gravity smaller than that of the article. The X-ray inspection apparatus according to claim 1 or 2.

Images