JP2010122103A - X-ray inspecting method and device - Google Patents

Abstract

An object of the present invention is to prevent a decrease in contrast of a foreign object image in an inspection object due to scattering of low energy X-rays, and to obtain a foreign object image having a good contrast for each of various inspection objects by a simple operation. An X-ray inspection method and apparatus capable of improving the detection performance of a foreign object can be provided.
When an object W is irradiated with X-rays from an X-ray generator 1, the presence or absence of a foreign substance in the object is determined from the X-ray space dose distribution transmitted through the object W. An X-ray filter F made of the same material as the material of the inspection object W or a material equivalent to the material of the inspection object W and the X-rays between the X-ray generator 1 and the inspection object W. By irradiating the object W, the object W is selectively irradiated with X-rays that are easily transmitted through the inspection object W (normal part) and that are not easily scattered in the inspection object W. And the reduction in the contrast of the foreign matter image due to the scattering of X-rays in the inspection object W is prevented.
[Selection] Figure 1

Description

  The present invention relates to an X-ray inspection method and apparatus for irradiating an inspection object with X-rays and inspecting the presence or absence of foreign matter in the inspection object from the spatial dose distribution of the transmitted X-rays. The present invention relates to an X-ray inspection method and apparatus capable of obtaining an image of a foreign object with good contrast with respect to each object and thus having excellent foreign object detection performance.

  An inspection apparatus using X-rays is known as an apparatus for inspecting whether or not foreign substances such as metals, bones, and stones are mixed in various foods and industrial products. In this type of inspection apparatus, an inspection object is transported by a conveyor, and a structure in which an X-ray generator and an X-ray detector are arranged to face each other on the way is usually used. The X-rays are fan-beam-shaped having a spread in a direction orthogonal to the conveying direction of the object to be inspected by a conveyor through slits, etc., and the X-ray detector is an X-ray line in which pixels are arranged in the X-ray spread direction. A sensor is used. According to this configuration, when the inspection object passes between the X-ray generator and the X-ray line sensor by the conveyor, the X-ray transmission data of the inspection object is sequentially collected one-dimensionally, and the inspection object is By completing the passage between the X-ray generator and the X-ray line sensor, two-dimensional X-ray transmission data of the inspection object, in other words, spatial dose distribution data of X-rays transmitted through the inspection object (X A fluoroscopic image).

  Such X-ray spatial dose distribution data is taken into the data processing unit and is used to determine the presence or absence of foreign matter in the inspection object. As a foreign object detection method, for example, if there is a part where the dose level decreases by a preset rate with respect to the dose of a normal part, a method of determining that there is a foreign object is employed.

  In the foreign matter inspection apparatus using X-rays as described above, the larger the difference or ratio between the X-ray dose transmitted through the normal part of the inspection object from the X-ray generator and the X-ray dose transmitted through the foreign matter, that is, the foreign matter. The greater the contrast of the image, the higher the foreign object detection performance.

  In general, the energy distribution of X-ray irradiation from the X-ray source is as illustrated in FIG. 4A, and the energy corresponding to the voltage (tube voltage) applied to the X-ray tube in the X-ray generator is maximized. As described above, X-rays having various energies are irradiated on the inspection object. Here, as is well known, low-energy X-rays are likely to scatter when passing through an object to be inspected, and the contrast of a foreign object image with respect to an image of a normal part is lowered.

  That is, as schematically shown in FIG. 5, when there is a foreign matter S such as tungsten having an extremely high X-ray attenuation rate in the inspection object W, the X-rays irradiated from the X-ray generator 51 are Although the X-rays do not reach the area A corresponding to the foreign matter S on the light receiving surface 52 of the X-ray detector due to the shielding by the foreign matter S in the inspected object W, the shadow should be inspected. Due to scattering of X-rays irradiated to other parts in the object W, some X-rays reach the region A as indicated by broken lines in the figure. As a result, the contrast between the image of the normal part of the object W to be inspected on the light receiving surface 52 of the X-ray detector and the image of the foreign matter S is lowered.

Here, high energy X-rays are less scattered, and the contrast between the image of the normal part and the image of the foreign matter is increased. In anticipation of such an effect, there is a case where an X-ray filter is inserted between the X-ray generator and the X-ray detector to cut low energy X-rays (see, for example, Patent Document 1). .
JP 2006-38761 A

  By the way, if a metal is used as the X-ray filter, it is possible to cut up to a high energy X-ray as illustrated in FIG. 4B, and using a resin or the like is high as illustrated in FIG. 4C. Low energy X-rays can be cut without cutting energy X-rays.

  From the viewpoint of preventing scattering, it is sufficient to use an X-ray filter that transmits only X-rays with as high energy as possible. In that case, foreign matter may also be transmitted, and thus X with high energy is unavoidably transmitted. However, there is a problem that selection of an appropriate X-ray filter is not easy.

  The present invention has been made in view of such circumstances, and prevents a decrease in the contrast of an image of a foreign object in an inspection object due to scattering of low energy X-rays. It is an object of the present invention to provide an X-ray inspection method and an X-ray inspection apparatus capable of obtaining a foreign object image having a good contrast for each of the above.

  In order to solve the above-mentioned problems, the X-ray inspection method of the present invention irradiates an inspection object with X-rays from an X-ray generator, and inspects the X-ray from the spatial dose distribution of the X-ray transmitted through the inspection object. In the X-ray inspection method for determining the presence or absence of foreign matter in an object, between the X-ray generator and the object to be inspected, the same material as the material of the object to be inspected, or the material and X-ray of the object to be inspected On the other hand, an X-ray filter made of an equivalent substance is interposed, and X-rays transmitted through the X-ray filter are irradiated to the object to be inspected (claim 1).

  Here, in the X-ray inspection method of the present invention, a configuration using the same product itself as the inspection object (Claim 2) can be adopted as the X-ray filter.

  In the X-ray inspection method of the present invention, when the object to be inspected is a non-homogeneous product, such as a curry roux, etc., a configuration in which the product is homogenized is used as an X-ray filter (Claim 3). You can also

  On the other hand, the X-ray inspection apparatus of the present invention is an apparatus for realizing the above-described method of the present invention, and includes an X-ray generator for irradiating the inspection object with X-rays and an X-ray transmitted through the inspection object. In an X-ray inspection apparatus provided with an X-ray detector to be detected and a discriminating means for determining the presence or absence of foreign matter in the inspection object based on the output of the X-ray detector, the X-ray generator and the inspection object In the meantime, it is characterized by comprising a filter substance holding means for holding any substance in an exchangeable manner as an X-ray filter (Claim 4).

  Here, in the X-ray inspection apparatus of the present invention, the filter substance holding means forms a casing as a whole and has a predetermined height in the X-ray irradiation direction, and a bottom portion of the inner space of the frame. The structure (Claim 5) provided with the bottom body which plugs up can be employ | adopted suitably.

  The present invention comprises an X-ray filter made of the same material as the inspection object before the inspection object, or a substance equivalent to the inspection object for X-rays. By transmitting through the X-ray filter, it is possible to use X-rays that are easily transmitted through the object to be inspected (normal site) and that are in an energy region where scattering is difficult to occur.

  That is, from the viewpoint of preventing scattering in the inspection object, it is sufficient to use an X-ray filter that transmits only high-energy X-rays using metals as a filter. Therefore, the contrast may be lowered depending on the material of the object to be inspected and the material of the foreign material. As a result, the following materials are desirable for the X-ray filter.

A. X-rays in an energy band that pass well through the material of the object to be inspected and hardly pass through the foreign matter to be detected pass.
B. The X-rays in the energy band scattered by the material of the inspection object are cut.
More specifically, when it is desired to detect iron scrap as foreign matter in the aluminum die cast, the X-ray filter is preferably aluminum, and when it is desired to detect bone in meat, the X-ray filter is good. . This is because if the material of the object to be inspected is used as the X-ray filter, the energy of the X-ray transmitted through the X-ray filter and irradiated to the object to be inspected is the X-ray in the energy band transmitted through the material of the object to be inspected. Therefore, X-rays in an energy band that increases and therefore passes well through the inspected object. Moreover, it is not an unnecessarily high energy band, and is an energy band in which the transmission of foreign matter different from the material of the object to be inspected can be suppressed as much as possible.

  In addition, the energy band in which scattering is increased due to the material of the inspection object passes through the X-ray filter of the same material as the inspection object, and the energy band that is highly scattered in the inspection object is irradiated to the inspection object. The spatial intensity distribution of the X-rays transmitted through the object to be inspected becomes high in the contrast of the foreign object image, and the foreign object detection performance is good.

  In the present invention, the X-ray filter may be made of the same material as the material of the object to be inspected, or may be made of a material equivalent to the X-ray.

  Then, as in the invention according to claim 2, the same product itself as the object to be inspected can be used as an X-ray filter, and when the product is not homogeneous, the food product as in the invention according to claim 3 is used. Can be used as an X-ray filter that is homogenized by a mixer or the like. Such an X-ray filter can reliably satisfy the above-described A and B, and at the same time, Selection can be made easily and reliably.

  And the X-ray inspection apparatus of this invention is an apparatus for implement | achieving the X-ray inspection method of the above-mentioned this invention, Comprising: An arbitrary substance is X-ray-filtered between an X-ray generator and an X-ray detector. The structure provided with the holding | maintenance means for hold | maintaining so that replacement | exchange is possible as follows. As the holding means, as in the invention according to claim 5, the housing according to claims 2 and 3 can be easily realized by forming a housing with a frame and a bottom as a whole. .

  According to the present invention, it is possible to easily and surely use an optimum X-ray filter according to the material of the object to be inspected, and to always irradiate X-rays having appropriate energy according to the object to be inspected. As a result of increasing the contrast of the foreign object image with respect to each of the materials to be inspected, the foreign object detection performance can be improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing the overall configuration of the embodiment of the present invention, and is a view excluding covers.

  The X-ray generator 1 and the X-ray line sensor 2 are disposed to face each other, and a conveyor 3 for conveying the inspection object W is disposed therebetween. The X-ray generator 1 is irradiated in the direction of the X-ray line sensor 2 as a fan beam-like X-ray through the slit 1a. The X-ray line sensor 2 is arranged so that a plurality of elements are arranged in the fan beam-shaped X-ray spreading direction. In FIG. 1, a plurality of elements are arranged in a direction perpendicular to the paper surface. The inspection object W is conveyed by the conveyor 3 at a constant speed in a direction perpendicular to the fan beam-shaped X-ray spreading direction (the right direction indicated by an arrow in FIG. 1).

  The output of the X-ray line sensor 2, that is, the one-dimensional dose distribution of incident X-rays is always taken into the data processing unit 4. A photoelectric sensor 5 is disposed upstream of the pair of the X-ray generator 1 and the X-ray detector 2 in the conveyance direction of the inspection object W by the conveyor 3, and the data processing unit 4 The arrival of the inspection object W is recognized by the output, and thereby a two-dimensional X-ray fluoroscopic image of the inspection object W is constructed from the one-dimensional dose distribution output from the X-ray line sensor 2.

  The data processing unit 4 mainly includes a computer and its peripheral devices, and a touch panel type monitor / operation unit 6 is connected to the data processing unit 4. An X-ray fluoroscopic image of the inspection object W is displayed on the monitor / operation unit 6, and various commands can be given to the apparatus or various settings can be made by operating the monitor / operation unit 6. it can.

  Now, a filter holding member 10 for accommodating the X-ray filter F is provided between the slit 1a and the conveyor 3, and the X-ray from the X-ray generator 1 passes through the slit 1a to form a fan beam. Then, the object W is irradiated after passing through the X-ray filter F.

  As shown below, the filter holding member 10 is replaceably provided in the apparatus. FIG. 2 is a perspective view showing a specific example of an arrangement position of the filter holding member 10 for holding the X-ray filter F. Here, although not shown in FIG. 1, in order to minimize leakage of X-rays from the X-ray generator 1, the periphery of the X-ray generator 1, the slit 1 a, and the X-ray filter 10. Are provided with covers for X-ray protection.

  That is, the space between the X-ray generator 1 and the slit 1 a is covered with the X-ray protective cover 20, and the lower part of the slit 1 a is covered with the X-ray irradiation cylinder 21 until reaching the conveyor 3. The filter holding member 10 is disposed in the X-ray irradiation tube 21.

  The X-ray irradiation cylinder 21 is provided with a slit 1 a on the upper surface thereof, and the lower side thereof extends in a cylindrical shape downward and reaches the upper surface of the conveyor 3. The filter holding member 10 is fixedly disposed at a specified position in the X-ray irradiation tube 21. For example, a holding mechanism such as a rail is provided in the X-ray irradiation tube 21, and the filter holding member 10 is placed at a specified position on the holding mechanism and is fixed by an appropriate fixing mechanism. The X-ray irradiation tube 21 is provided with a filter exchange door 21a that can be opened and closed as indicated by an arrow in a portion that can be accessed by an operator (for example, a surface facing the front). The filter replacement door 21a is provided with an interlock mechanism that opens only when the X-ray from the X-ray generator 1 is OFF. When the filter replacement door 21a is open, X-rays are irradiated. An interlock circuit is provided to prevent this.

  The filter holding member 10 is for holding a filter substance of an arbitrary material such as the same product as the object to be inspected W, and its configuration example is shown in FIG.

  The filter holding member 10 in this example forms a casing as a whole so as to accommodate the substance constituting the X-ray filter F, and includes a frame 11 having a predetermined height in the X-ray irradiation direction, It is constituted by a film-like bottom body 12 that closes the bottom of the inner space of the frame body 11. As the material of the bottom body 11, a material that is strong and less deteriorated by X-rays and transmits X-rays well, such as a polyimide film, is used.

  The size of the frame 11 (the direction perpendicular to the X-ray irradiation direction and the length in the X-ray spreading direction) is the distance between the focal point of the X-ray generator 1 and the X-ray filter F, and X-ray generation X-rays reaching the X-ray line sensor 2 with a ÷ b × c or more, where b is the distance between the focal point of the device 1 and the X-ray line sensor 2 and c is the X-ray irradiation range on the X-ray line sensor 2 Are all transmitted through the X-ray filter F in the filter holding member 10.

  In such a filter holding member 10, the substance which comprises the X-ray filter F is accommodated equally. As the X-ray filter F, it is desirable to use the product itself as the inspection object W, or to homogenize the product as the inspection object W when the product as the inspection object W is not homogeneous. That is, for example, if the inspection object W is a mixture of a plurality of materials, such as curry roux, for example, it is assumed that each material has been subjected to, for example, a mixer process so that each material spreads uniformly. If there are irregularities in the line transmission direction, this is assumed to be a plate. In addition, the material of the same material as the product that is the inspection object W may be used instead of the product itself.

  Here, in the case of using a perishable or liquid material such as food as the X-ray filter F, after accommodating it in the filter holding member 10, the top surface is made of a film similar to the bottom body 12. You may cover and enclose the whole. In this case, there is an advantage that a change with time can be reduced and liquid leakage does not occur when the X-ray filter is replaced or when the apparatus is vibrated, and the handling becomes easy.

  As described above, by using the X-ray filter F as a product to be inspected W itself, a homogenized product thereof, or a substance made of the same material as the inspected object W, X transmitted through the X-ray filter F is used. The X-rays scattered by the X-ray filter F scatter the X-rays scattered by the inspection object W as the energy band that passes through the inspection object W increases. There are fewer factors that reduce In addition, the X-rays irradiated to the inspection object W are not only in an unnecessarily high energy band, and therefore, much of the X-rays are blocked by the foreign matter S, and this also reduces the contrast of the foreign matter image. There is no. The X-ray filter F for obtaining the optimum X-ray for the inspection of the inspection object W is a product itself that is the inspection object W or a homogenized product thereof, and further, Since it is only necessary to store the same material in the filter holding member 10, the selection is easy, and there is no mistake in the selection, and the foreign object detection performance with high accuracy is always obtained even if the inspection object W changes variously. It can be demonstrated.

  Note that the X-ray filter F is not limited to the above-described product which is the inspection object W, or a homogenized product thereof, or the same material as the inspection object W. An equivalent material can also be used.

  Further, in the above embodiment, the X-ray is shaped into a fan beam, and an X-ray line sensor in which elements are arranged in the X-ray spreading direction is used as an X-ray detector. Although the present invention is not limited to this, the present invention is not limited to this, and an apparatus having a configuration in which a cone beam-shaped X-ray and a two-dimensional X-ray detector are used and an object to be inspected is positioned therebetween. Of course, it can also be applied.

It is a schematic diagram showing the whole structure of embodiment of this invention, and is a figure which excludes covers. It is a principal part perspective view which shows the specific example of the arrangement | positioning position of the filter holding member 10 in embodiment of this invention. It is a figure which shows the structural example of the filter holding member 10 in embodiment of this invention. It is explanatory drawing of general energy distribution of X-ray, (A) is a conceptual graph showing energy distribution of X-rays output from an X-ray source, (B) is a case where a metal is used as an X-ray filter. A conceptual graph showing energy distribution of X-rays transmitted through the X-ray filter, (C) is a conceptual graph showing energy distribution of X-rays transmitted through the X-ray filter when resin or the like is used as the X-ray filter. It is a simple graph. It is a figure which illustrates typically the reason for which the contrast of a foreign material image falls by the X-ray scattering in a to-be-inspected object.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 X-ray generator 1a Slit 2 X-ray line sensor 3 Conveyor 4 Data processing part 5 Photoelectric sensor 6 Monitor and operation part 10 Filter holding member 11 Frame body 12 Bottom body 20 X-ray protective cover 21 X-ray irradiation cylinder 21a Filter exchange door F X-ray filter W Inspection object

Claims (5)

In an X-ray inspection method for irradiating an inspection object with X-rays from an X-ray generator and determining the presence or absence of foreign matter in the inspection object from an air dose distribution of X-rays transmitted through the inspection object.
Between the X-ray generator and the object to be inspected, an X-ray filter made of the same material as the material of the object to be inspected or a material equivalent to the material of the object to be inspected and X-ray is interposed, An X-ray inspection method characterized by irradiating an inspection object with X-rays transmitted through an X-ray filter.   2. The X-ray inspection method according to claim 1, wherein the same product itself as the object to be inspected is used as the X-ray filter.   2. The X-ray inspection method according to claim 1, wherein when the object to be inspected is a non-homogeneous product, a homogenized product is used as an X-ray filter. An X-ray generator that irradiates the inspection object with X-rays, an X-ray detector that detects X-rays transmitted through the inspection object, and the presence or absence of foreign matter in the inspection object based on the output of the X-ray detector In the X-ray inspection apparatus provided with the discriminating means for discriminating
An X-ray inspection apparatus comprising a filter substance holding means for holding an arbitrary substance as an X-ray filter in an exchangeable manner between the X-ray generator and the object to be inspected.   The filter substance holding means comprises a frame having a casing as a whole and having a predetermined height in the X-ray irradiation direction, and a bottom that closes the bottom of the inner space of the frame. X-ray inspection equipment.

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