JP2007322344A - X-ray inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an X-ray inspection device capable of realizing a mass inspection and a shape inspection of an article in the same device. <P>SOLUTION: A mass estimation section 40 estimates the mass of an object 12 to be inspected based on an amount of transmission X-rays detected by an X-ray detector 8. A mass judgment section 41 judges the normality/abnormality of the mass of the object 12 based on data S1 input from the mass estimation section 40. An image creation section 42 creates an X-ray transmission image based on the amount of the transmission X-rays detected by the X-ray detector 8. A shape judgment section 43 judges the normality/abnormality of the shape of the object 12. A failure judgment section 44 judges the object 12 as a defective product when there is at least one abnormal result of respective judgment results by the mass judgment section 41 and by the shape judgment section 43. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an X-ray inspection apparatus, and more particularly to an X-ray inspection apparatus capable of estimating the mass of an inspection object by irradiating the inspection object with X-rays and detecting X-rays transmitted through the inspection object. .

  As a conventional technique for measuring the mass of an object to be measured using X-rays, Patent Document 1 below discloses that X-rays are irradiated to the object to be measured and transmitted X-rays transmitted through the object to be detected are detected. Based on the transmitted X-ray dose, the mass of the object to be measured is calculated from a predetermined formula for each predetermined unit transmission area, and the calculated mass for each unit transmission area is integrated over the entire transmission X-ray transmission area. An X-ray mass measuring apparatus is disclosed that calculates the total mass of the object to be measured.

JP 2002-296022 A

  However, according to the conventional X-ray mass measuring apparatus described above, the mass of the article can be measured, but no means for inspecting the shape of the article is taken. Therefore, as long as the mass of the article is within the target range, there is a problem that an article having a defective shape such as a crack or a chip is treated as a non-defective product. Here, if the inspection apparatus for shape inspection is provided separately from the X-ray mass measurement apparatus, the system is increased in size and the cost is increased.

  The present invention has been made to solve such a problem, and an object of the present invention is to obtain an X-ray inspection apparatus capable of realizing mass inspection and shape inspection of an article in the same apparatus.

  An X-ray inspection apparatus according to a first aspect of the invention detects an X-ray irradiation unit that irradiates an inspection target with X-rays, and X-rays that are irradiated from the X-ray irradiation unit and transmitted through the inspection target. X-ray detector, a mass estimator for estimating the mass of the inspection object based on the X-ray dose detected by the X-ray detector, and the normality of the mass of the inspection object estimated by the mass estimator / A mass determination unit that determines abnormality, an image creation unit that creates an X-ray transmission image based on the X-ray dose detected by the X-ray detection unit, and a shape of the inspection object based on the X-ray transmission image A shape determination unit that determines normal / abnormality of the image, and a defect determination unit that determines that the inspection object is a defective product when at least one of the determination results by the mass determination unit and the shape determination unit is abnormal With.

  The X-ray inspection apparatus according to the second invention is the X-ray inspection apparatus according to the first invention, and in particular, the mass estimation unit determines whether or not the plurality of inspection objects overlap based on the X-ray transmission image. It is determined, and an estimation condition for estimating the mass of the inspection object is changed according to the presence or absence of the overlap.

  The X-ray inspection apparatus according to a third aspect of the invention is the X-ray inspection apparatus according to the second aspect of the invention, particularly when the mass estimation unit determines that a plurality of the inspection objects are overlapped. The number of detected gradations of the X-ray dose detected by the line detection unit is increased.

  According to the X-ray inspection apparatus according to the first invention, the defect determination unit determines that the inspection object is a defective product when at least one of the determination results by the mass determination unit and the shape determination unit is abnormal. To do. Therefore, it is possible to avoid a situation in which an inspection object having an abnormal mass or shape is treated as a non-defective product. In addition, since the same apparatus is provided with the mass inspection function and the shape inspection function, the system can be reduced in size and cost as compared with the case where these inspections are performed by separate inspection apparatuses.

  According to the X-ray inspection apparatus according to the second invention, the mass estimation unit determines whether or not there is an overlap of a plurality of inspection objects based on the X-ray transmission image, and determines the inspection object according to the presence or absence of the overlap. The estimation condition for estimating the mass of is changed. In particular, when the object to be inspected is an article having a small thickness, there is a case where the overlap of a plurality of articles cannot be accurately determined depending on the method of detecting the film thickness of the article. On the other hand, in the X-ray inspection apparatus according to the second invention, since the overlap of articles is determined based on an X-ray transmission image that is a planar image, it is possible to determine the presence or absence of overlap of a plurality of articles with high accuracy. .

  According to the X-ray inspection apparatus according to the third invention, the mass estimation unit determines the number of detected gray levels of the X-ray dose detected by the X-ray detection unit when it is determined that a plurality of inspection objects overlap. Increase. By increasing the resolution by increasing the number of detected gradations, it is possible to more accurately grasp the overlap of a plurality of articles. Therefore, even when the inspection object is an article having a small thickness, it is possible to grasp the overlap of a plurality of articles by increasing the resolution, and to accurately perform mass estimation.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the element which attached | subjected the same code | symbol in different drawing shall show the same or corresponding element.

  FIG. 1 is a front view schematically showing an overall configuration of an X-ray inspection apparatus 1 according to an embodiment of the present invention. As shown in FIG. 1, the X-ray inspection apparatus 1 includes an upper housing 2, a shield box 3, and a lower housing 4. The upper housing 2 is provided with a monitor with a touch panel function, that is, a display / input unit 5. A belt conveyor 6 is disposed in the shield box 3. An X-ray irradiation unit 7 and an X-ray detection unit 8 are provided in the shield box 3 with the belt conveyor 6 interposed therebetween. The X-ray irradiation unit 7 irradiates the inspection object 12 such as food on the belt conveyor 6 with X-rays. The X-ray detection unit 8 detects X-rays irradiated from the X-ray irradiation unit 7 and transmitted through the inspection object 12. The shield box 3 has a function of preventing X-rays from leaking to the outside. A computer 9 for performing operation control and data processing of the X-ray inspection apparatus 1 is disposed in the lower housing 4.

  A belt conveyor 10 for carrying the inspection object 12 into the X-ray inspection apparatus 1 is provided on the upstream side of the belt conveyor 6. A belt conveyor 11 for carrying out the inspection object 12 after inspection from the X-ray inspection apparatus 1 is provided on the downstream side of the belt conveyor 6. Although not shown in FIG. 1, the belt conveyor 11 is provided with an arbitrary distribution mechanism 20 (see FIG. 3) for distributing non-defective products and defective products based on the inspection result by the X-ray inspection apparatus 1. It is installed.

  FIG. 2 is a perspective view showing an internal configuration of the shield box 3 shown in FIG. Above the belt conveyor 6, an X-ray irradiator (hereinafter referred to as “X-ray irradiator 7”) as the X-ray irradiator 7 is disposed. Below the belt conveyor 6, an X-ray line sensor (hereinafter referred to as “X-ray line sensor 8”) as the X-ray detection unit 8 is disposed. The X-ray line sensor 8 includes a plurality of X-ray detection elements 8a arranged in a straight line. The plurality of X-ray detection elements 8 a are arranged in parallel along the short side direction of the belt conveyor 6, that is, the direction perpendicular to the conveying direction of the inspection object 12 by the belt conveyor 6. As shown by hatching in FIG. 2, the X-ray irradiator 7 emits X-rays in a fan shape toward the X-ray line sensor 8.

  FIG. 3 is a block diagram showing a functional configuration of the X-ray inspection apparatus 1. The computer 9 includes a CPU 21 and a memory 22 such as a ROM or a RAM that can be referred to by the CPU 21. An X-ray irradiation unit 7, an X-ray detection unit 8, a display / input unit 5, and a distribution mechanism 20 are connected to the computer 9.

  FIG. 4 is a block diagram showing an inspection function by the computer 9. As shown in FIG. 4, the computer 9 includes a foreign substance inspection unit 30, a mass inspection unit 31, and a shape inspection unit 32. Each inspection function shown in FIG. 4 is realized by the CPU 21 executing the inspection program stored in the memory 22 shown in FIG.

  The foreign matter inspection unit 30 inspects whether or not foreign matter is mixed in the inspection object 12. The mass inspection unit 31 inspects whether or not the mass of the inspection object 12 is within the target range (within the allowable range). The shape inspection unit 32 inspects whether or not the inspection object 12 is cracked or chipped.

  First, the foreign substance inspection unit 30 will be described. With reference to FIG. 2, as described above, X-rays (transmitted X-rays) irradiated from X-ray irradiation unit 7 and transmitted through inspection object 12 are X-ray detection unit 8 having a plurality of X-ray detection elements 8a. Detected by. Here, when no foreign matter is mixed in the inspection object 12, the intensity distribution of transmitted X-rays detected by the plurality of X-ray detection elements 8a is substantially constant. On the other hand, when foreign matter is mixed in the inspection object 12, the amount of X-ray transmission decreases at the foreign matter mixed location, so the intensity distribution of the transmitted X-ray is negative corresponding to the foreign matter mixed location. A peak occurs. Therefore, whether or not foreign matter is mixed into the inspection object 12 can be inspected depending on whether or not a peak occurs in the intensity distribution of transmitted X-rays. The inspection object 12 determined to have foreign matter mixed therein is sorted as a defective product by the distribution mechanism 20 shown in FIG. 3 without being inspected by the mass inspection unit 31 and the shape inspection unit 32 described later. It is done.

  FIG. 5 is a block diagram illustrating functional configurations of the mass inspection unit 31 and the shape inspection unit 32 illustrated in FIG. 4. The mass inspection unit 31 includes a mass estimation unit 40 and a mass determination unit 41, and the shape inspection unit 32 includes an image creation unit 42 and a shape determination unit 43. The mass determination unit 41 and the shape determination unit 43 are connected to the defect determination unit 44.

The mass estimation unit 40 estimates the mass of the inspection object 12 based on the X-ray dose of transmitted X-rays detected by the X-ray detection unit 8 illustrated in FIG. 1, and outputs data S1 regarding the estimated mass M. Details are as follows. With reference to FIG. 2, the X-ray dose of transmitted X-rays irradiated from the X-ray irradiation unit 7 and transmitted through the inspection object 12 is detected by the X-ray detection unit 8. Specifically, each X-ray detecting elements 8a provided in the X-ray detector 8 detects the brightness I ₀ of the transmitted X-ray, respectively. Here, each X-ray detection element 8a detects the brightness I ₀ with the number of detection gradations of 256 gradations, for example, “255” is the highest luminance white and “0” is the lowest luminance black. . The mass estimation unit 40 shown in FIG. 5 inputs the detection value related to the brightness I ₀ from each X-ray detection element 8a, and based on the following formula (1) for estimating the mass, from the brightness I _0. The estimated mass m is calculated.

m = ct = −c / μ × ln (I / I ₀ ) = − αln (I / I ₀ ) (1)
Here, c is a coefficient for converting the thickness of the substance into mass, t is the thickness of the substance, I is the brightness when there is no substance, I ₀ is the brightness when passing through the substance, and μ is a line Absorption coefficient. In addition, α is a parameter given by c / μ, and an appropriate value is obtained in advance for each type of inspection object 12 by a prior inspection using a plurality of samples whose masses are known. Is stored in the memory 22 shown in FIG.

The mass estimation unit 40 converts the brightness I ₀ into the estimated mass m for each pixel (that is, each X-ray detection element 8a) based on the above equation (1). Then, while the inspection object 12 is conveyed by the belt conveyor 6, the detection of the brightness I ₀ by the X-ray detection element 8a and the conversion from the brightness I ₀ to the estimated mass m are repeatedly performed. Thereby, the estimated mass m corresponding to all the pixels of the inspection object 12 is obtained, and the total estimated mass M of the inspection object 12 is obtained by adding all these estimated masses m.

  The mass determination unit 41 determines normality / abnormality of the mass of the inspection object 12 based on the data S1 input from the mass estimation unit 40, and outputs data S2 regarding the determination result. Specifically, the upper limit value and the lower limit value of the target mass range (allowable range) are preset for each type of the inspection object 12 and stored in the memory 22 shown in FIG. The mass determination unit 41 compares the estimated mass M represented by the data S1 with the upper limit value and the lower limit value. When the estimated mass M is equal to or lower than the upper limit value and equal to or higher than the lower limit value, the inspection object 12 Is determined to be normal. On the other hand, when the estimated mass M is larger than the upper limit value or smaller than the lower limit value, it is determined that the mass of the inspection object 12 is abnormal.

The image creation unit 42 creates an X-ray transmission image based on the X-ray transmission X-ray amount detected by the X-ray detection unit 8 shown in FIG. 1, and outputs image data S3 related to the X-ray transmission image. Specifically, as described above, each X-ray detection element 8a included in the X-ray detection unit 8 detects 256 gradations, for example, white having the highest luminance is “255” and black having the lowest luminance is “0”. The brightness I ₀ is detected by the number of gradations. Thereby, image data of the inspection object 12 corresponding to one line is created. Then, while the inspection object 12 by the belt conveyor 6 is conveyed, it detects the brightness I ₀ by each X-ray detecting elements 8a are repeatedly executed for each line. Thereby, the brightness I ₀ of all the pixels of the inspection object 12 is obtained, respectively, and an X-ray transmission image (image data S3) of the entire inspection object 12 is created.

  The shape determination unit 43 determines normality / abnormality of the shape of the inspection object 12 based on the image data S3 input from the image creation unit 42, and outputs data S4 regarding the determination result. As an example, data relating to the upper limit value and lower limit value of the perimeter of a non-defective product is stored in advance in the memory 22 shown in FIG. Then, the shape determination unit 43 extracts edges from the X-ray transmission image of the inspection object 12 represented by the image data S3, and compares the total length of the extracted edges with the above upper limit value and lower limit value. The shape determination unit 43 determines that the shape of the inspection object 12 is normal when the total edge length is equal to or lower than the upper limit value and equal to or higher than the lower limit value. When it is smaller than the lower limit value, it is determined that the shape of the inspection object 12 is abnormal. For example, when the inspection object 12 is cracked, the total length of the edges becomes long, so that the inspection object 12 having the cracks is found by making the total length of the edges larger than the above upper limit value. Can do.

  As another example, data relating to the upper limit value and lower limit value of the upper area of the non-defective product is stored in advance in the memory 22 shown in FIG. And the shape determination part 43 calculates | requires the upper area of the test target object 12 from the X-ray transmission image represented by image data S3, and compares the calculated | required upper area value with said upper limit and lower limit. The shape determination unit 43 determines that the shape of the inspection object 12 is normal when the value of the upper area is equal to or lower than the upper limit value and equal to or higher than the lower limit value. When it is smaller than the lower limit value, it is determined that the shape of the inspection object 12 is abnormal. For example, when the inspection object 12 is chipped, the upper area is reduced. Therefore, the inspection object 12 having the chipping can be found by making the upper area value smaller than the lower limit value. .

  As yet another example, image data of a template image related to the contour shape of a good product is stored in advance in the memory 22 shown in FIG. And the shape determination part 43 performs the template matching process using said template image in the X-ray transmissive image of the test target object 12 represented by image data S3. When the similarity between the inspection object 12 and the template image is equal to or higher than a predetermined level, the shape determination unit 43 determines that the shape of the inspection object 12 is normal, and the similarity is lower than the predetermined level. In this case, it is determined that the shape of the inspection object 12 is abnormal. For example, when the inspection object 12 is cracked or chipped, the difference from the contour shape of a non-defective product becomes large. 12 can be found.

  The defect determination unit 44 inputs data S2 (mass normal / abnormal) from the mass determination unit 41 and data S4 (shape normal / abnormal) from the shape determination unit 43. And based on data S2 and S4, when at least one of each determination result by the mass determination part 41 and the shape determination part 43 is abnormal, it determines with the test target object 12 being inferior goods. In other words, the defect determination unit 44 determines that the inspection object 12 is a non-defective product when both of the determination results by the mass determination unit 41 and the shape determination unit 43 are normal. The determination result by the defect determination unit 44 is displayed on the display / input unit 5 shown in FIG. Further, the inspection object 12 determined to be non-defective is distributed as non-defective by the sorting mechanism 20 shown in FIG. On the other hand, the inspection object 12 determined as a defective product is distributed as a defective product by the distribution mechanism 20.

  As described above, according to the X-ray inspection apparatus 1 according to the present embodiment, the defect determination unit 44 is inspected when at least one of the determination results by the mass determination unit 41 and the shape determination unit 43 is abnormal. It is determined that the item 12 is defective. Accordingly, it is possible to avoid a situation in which the inspection object 12 having an abnormal shape even if the mass is normal and the inspection object 12 having an abnormal mass even if the shape is normal are treated as non-defective products. In addition, since the same apparatus is provided with the mass inspection function and the shape inspection function, the system can be reduced in size and cost as compared with the case where these inspections are performed by separate inspection apparatuses.

  Hereinafter, a countermeasure when the inspection object is a thin article or food will be described. 6 and 7 are side views showing an example of the inspection object. 6 and 7 show an example in which two thin articles 51a and 51b are placed on the tray 50 as inspection objects. In FIG. 6, the articles 51a and 51b are placed side by side at desired locations on the tray 50. In FIG. 7, the articles 51a and 51b partially overlap each other.

FIG. 8 is a top view of the articles 51a and 51b as viewed from above corresponding to FIG. FIG. 9 shows an X-ray transmission image 60 corresponding to FIG. In the above example, the X-ray detection element 8a included in the X-ray detection unit 8 detects the brightness I ₀ of the transmitted X-ray with the number of detection gradations of 256 gradations. Here, when the thickness of the articles 51a and 51b is thin, most of the X-rays irradiated from the X-ray irradiation unit 7 pass through the articles 51a and 51b. Therefore, in the detected number of gradations of about 256 gradations, whether the articles 51a and 51b are arranged as shown in FIG. 6 or the articles 51a and 51b are overlapped as shown in FIGS. There is no significant difference in the brightness I ₀ of transmitted X-rays detected by the detection element 8a. As a result, it is difficult to distinguish the brightness _{I 0} of the article 51a, 51b overlap whether the transmitted X-rays, in the X-ray image 60 shown in FIG. 9, the overlap of the article 51a, 51b clear Is not appearing. As described above, the mass estimation unit 40 shown in FIG. 5 calculates the estimated mass m using the equation (1) with the transmitted X-ray brightness I ₀ as a parameter, but the overlapping of the articles 51a and 51b is bright. Since I ₀ cannot be detected, the calculation error of the estimated mass m increases as a result.

  Therefore, in the X-ray inspection apparatus 1 according to the present embodiment, the shape determination unit 43 shown in FIG. 5 detects whether or not the articles 51a and 51b overlap. Specifically, it is as follows.

  With reference to FIG. 5, first, the image creating unit 42 creates the X-ray transmission image 60 shown in FIG. 9 in a state where the number of detected gradations of the X-ray detection element 8a is set to 256 gradations. The image data S3 of the X-ray transmission image 60 is input to the shape determination unit 43. The shape determination unit 43 extracts the edges of the X-ray transmission image 60, and determines that the articles 51a and 51b overlap when the total length of the extracted edges is larger than a predetermined threshold value. This predetermined threshold value is set to a value larger than the upper limit value of the perimeter length of the non-defective product, and is stored in advance in the memory 22 shown in FIG. As another example, the shape determination unit 43 calculates the upper area of the X-ray transmission image 60, and determines that the articles 51a and 51b overlap when the calculated upper area value is larger than a predetermined threshold value. To do. This predetermined threshold value is set to a value larger than the upper limit value of the upper area of the non-defective product, and is stored in advance in the memory 22 shown in FIG.

  When it is determined that the articles 51a and 51b do not overlap, the above-described mass inspection and shape inspection are continued. Referring to FIG. 5, on the other hand, when it is determined that the articles 51a and 51b are overlapped, the number of detected gradations of the X-ray detection element 8a is changed to, for example, 512 gradations according to a command from the shape determining unit 43. In addition, a signal S5 to that effect is input from the shape determination unit 43 to the mass estimation unit 40. Then, after the number of detected gradations is changed to 512 gradations, the inspection object is re-inspected.

In this re-examination, the X-ray detection element 8a sets the transmitted X-ray brightness I ₀ with the number of detected gradations of 512 gradations, with white having the highest luminance being “511” and black having the lowest luminance being “0”. To detect. Further, the mass estimation unit 40 shown in FIG. 5 inputs a detection value related to the brightness I ₀ of 512 gradations from the X-ray detection element 8a, and the brightness of 512 gradations based on the above equation (1). It calculates the estimated mass m from I _0. Thereafter, the estimated mass M of the entire inspection object is calculated by summing the estimated mass m of all pixels.

  As described above, according to the X-ray inspection apparatus 1 according to the present embodiment, when the mass estimation unit 40 determines that the articles 51a and 51b overlap, the number of detected gradations of the X-ray detection element 8a. Increase. By increasing the number of detected gradations and increasing the resolution, it is possible to more accurately grasp the overlap between the articles 51a and 51b. Therefore, even when the inspection object is the thin articles 51a and 51b, the overlap of the articles 51a and 51b can be grasped by increasing the resolution, and mass estimation can be accurately performed.

  In addition, the image creation unit 42 generates an X-ray transmission image based on the X-ray amount of the transmission X-ray detected by the X-ray detection unit 8 having the X-ray detection element 8a in which the number of detection gradations is set to 512 gradations. create. FIG. 10 is a diagram showing an X-ray transmission image 61 created by the image creation unit 42 in the reexamination, corresponding to FIG. In the X-ray transmission image 61, it is possible to clearly distinguish a portion where the articles 51a and 51b overlap and a portion where they do not overlap.

It is a front view which shows typically the whole structure of the X-ray inspection apparatus which concerns on embodiment of this invention. It is a perspective view which shows the internal structure of the shield box shown in FIG. It is a block diagram which shows the function structure of a X-ray inspection apparatus. It is a block diagram which shows the test | inspection function by a computer. It is a block diagram which shows the function structure of the mass inspection part and shape inspection part which were shown in FIG. It is a side view which shows an example of a test target object. It is a side view which shows an example of a test target object. FIG. 8 is a top view of the article viewed from above corresponding to FIG. 7. It is a figure which shows the X-ray transmissive image corresponding to FIG. FIG. 9 is a diagram corresponding to FIG. 8 and showing an X-ray transmission image created by an image creation unit in reexamination.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 X-ray inspection apparatus 7 X-ray irradiation part 8 X-ray detection part 9 Computer 12 Inspection object 31 Mass inspection part 32 Shape inspection part 40 Mass estimation part 41 Mass determination part 42 Image creation part 43 Shape determination part 44 Defect determination part 51a 51b Goods

Claims (3)

An X-ray irradiation unit for irradiating the inspection object with X-rays;
An X-ray detection unit that detects X-rays irradiated from the X-ray irradiation unit and transmitted through the inspection object;
A mass estimation unit that estimates the mass of the inspection object based on the X-ray dose detected by the X-ray detection unit;
A mass determination unit that determines normality / abnormality of the mass of the inspection object estimated by the mass estimation unit;
An image creation unit for creating an X-ray transmission image based on the X-ray dose detected by the X-ray detection unit;
A shape determination unit for determining normality / abnormality of the shape of the inspection object based on the X-ray transmission image;
An X-ray inspection apparatus comprising: a defect determination unit that determines that the inspection object is a defective product when at least one of the determination results by the mass determination unit and the shape determination unit is abnormal.   The mass estimation unit determines whether or not a plurality of the inspection objects overlap based on the X-ray transmission image, and sets an estimation condition for estimating the mass of the inspection object according to the presence or absence of the overlap. The X-ray inspection apparatus according to claim 1 to be changed.   3. The X according to claim 2, wherein the mass estimation unit increases the number of detected gradations of the X-ray dose detected by the X-ray detection unit when it is determined that a plurality of the inspection objects overlap. Line inspection device.

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