JP5917977B2 - X-ray inspection equipment - Google Patents

Description

  The present invention synthesizes a plurality of transmission images captured with X-rays of different energies on an object to be inspected that is transported on a transport path, and uses the composite image to inspect foreign matter contamination, shape, etc. in the object to be inspected. It relates to an inspection device.

  Conventionally, it is obtained by irradiating X-rays to the inspection object for various inspections of inspection objects such as food (inspection of the presence of foreign matter such as metal, stone, glass, resin, bone, and cracks) A transparent image may be used. Further, in an inspection using a transmission image by X-rays, a plurality of transmission images obtained by irradiating the same inspection object with X-rays having different energies are combined to emphasize features in one composite image. Highly accurate inspection. For example, when foreign matter detection is performed in the presence / absence of foreign matter contamination, X-rays having different energies (Xs having different wavelength distributions) are controlled by controlling the tube voltage and tube current of the X-ray generator (X-ray tube) on the same inspection object. By combining a plurality of transmission images captured with a line), if there is a high-density foreign matter such as metal from a single composite image, this is detected, and if there is a low-density foreign matter such as resin, this is also detected. Inspection is possible.

  As a device that performs high-precision inspection using a plurality of transmission images, there is a foreign object detection device disclosed in Patent Document 1. This foreign object detection device detects two transmission data for the same object to be inspected with different X-ray energies, a converter for converting the transmission data into the thickness of the reference material, and the thickness of the reference material. It is the structure provided with the determination device which identifies a to-be-inspected object and a foreign material using two conversion data.

  According to this foreign object detection apparatus, the object to be inspected is irradiated with X-rays, and the detector detects two transmission data based on X-rays having different energy with respect to the same object to be inspected. The two transmission data detected by the detector depend on the composition and thickness of the transmitted material. The converter obtains the relationship between the thickness and the value of transmission data for a reference material having the same element as the object to be inspected, and converts the two transmission data obtained by the detector into the thickness of the reference material. . Since the two converted data are values converted into the thickness of the reference material for the same inspection object, they have the same value when they have the same elements. On the other hand, since the foreign substance has an element different from the reference substance, the two conversion data of the foreign substance have different values. Therefore, by comparing the two conversion data, the object to be inspected can be identified from the foreign matter. Note that the two conversion data can be compared by subtraction.

Japanese Patent Laid-Open No. 10-318943

  However, the foreign object detection device disclosed in Patent Document 1 has a configuration in which transmission data is obtained by each detector when the object to be transported passes through two detectors arranged side by side in the transport direction. Therefore, since the object to be inspected moves, there is a difference between the transmission data obtained by the first detector and the transmission data obtained by the second detector when the two transmission data are combined. Could have occurred. The composite data in which the deviation has occurred is inaccurate.

  Further, the inventors of the present application receive a problem of deviation of transmission data (transmission image), stop the object to be conveyed at a predetermined inspection position, and capture a transmission image at the common inspection position. We have devised to prevent misalignment of multiple transparent images. However, this has another problem that it takes time from the end of the previous imaging to the switching of the X-ray energy for the next imaging, which deteriorates the inspection efficiency and reduces the productivity. there were. The problem of such efficiency degradation is that it is difficult to suddenly increase the tube voltage in the energy subtraction process, but rather than that, because people judge from experience etc. whether energy has switched, This is because the time when the tube voltage will surely rise after the previous imaging is completed, that is, the next imaging is started after a time longer than the time when the energy is actually switched. there were.

  Therefore, the present invention has been made to solve the above-described problems, and an efficient composite image can be obtained in which an efficient inspection can be performed and productivity does not decrease and an inspection using a plurality of transmission images is free from deviation. An object of the present invention is to provide an X-ray inspection apparatus capable of performing reliable and accurate inspection.

Next, means for solving the above problems will be described with reference to the drawings corresponding to the embodiments.
The X-ray inspection apparatus according to claim 1 according to the present invention combines a plurality of transmission images captured with X-rays of different energies onto the inspection object W transported on the transport path 2a, and uses the composite image. In the X-ray inspection apparatus 1 for inspecting the inspection object W,
Conveying means 2 for forming the conveying path 2a and conveying the inspection object W on the conveying path 2a in a predetermined conveying direction;
An X-ray generator 3 that irradiates the same inspection object W with X-rays of different energy in a predetermined inspection area on the transport path 2a;
Switching means 11 for switching the X-ray energy irradiated from the X-ray generator 3 by controlling the tube voltage and tube current of the X-ray generator (from the previous set value to the next set value);
X which consists of a plurality of X-ray detection elements 4a arranged in a plane so as to form the inspection area on the transport path 2a, detects X-rays transmitted through the inspection object W, and captures a transmission image A line detector 4;
Storage means 12 for storing a plurality of transmission images of the same object W imaged by the X-ray detector 4;
Control is performed so that the transport unit 2 is stopped when the inspection object W transported by the transport unit 2 is within the inspection area, and the transport unit 2 is operated when imaging by the X-ray detector 4 is completed. A conveyance control means 13;
Confirmation based on a table of stable times set according to the tube voltage and the tube current controlled by the switching means whether or not the energy of the X-rays irradiated from the X-ray generator 3 has been switched. Means 14;
It is characterized by having.

  According to the X-ray inspection apparatus of the first aspect of the present invention, the object to be inspected is imaged in a stationary state by controlling the operation of the means for conveying by the conveyance control means, so that the same object to be inspected can be obtained. No deviation occurs between a plurality of transmission images by X-rays having different energies. By using a composite image in which such deviation does not occur for inspection, high-accuracy inspection can be performed.

Further, the switching means controls the output of the tube voltage and tube current in the X-ray generator, whereby the X-ray wavelength distribution is changed, and X-rays having different energies are generated. Confirmation based on a table of stable times set according to the tube voltage and the tube current controlled by the switching means whether or not the energy of the X-rays irradiated from the X-ray generator has been switched is confirmed. By providing the means, whether or not the X-ray energy has been switched can be confirmed uniformly over the course of the stable time, and accurately grasped. As a result, it is possible to perform efficient inspection while suppressing loss of time required for switching energy, and productivity is not lowered.

It is the block diagram (schematic front view) which showed the X-ray inspection apparatus of this invention. It is a figure for demonstrating the relationship between the same to-be-inspected object and irradiation X-ray (tube voltage and tube current value), and the relationship between the to-be-inspected object and irradiation X-ray (tube voltage and tube current value) for every kind. . It is the figure which illustrated the confirmation table which (a)-(c) confirmation means has.

Embodiments of the present invention will be specifically described below with reference to the drawings.
In this embodiment, a plurality of transmission images captured with X-rays having different energies are combined with an object to be inspected that is transported on a transport path, and foreign matter contamination, shape, and the like in the object to be inspected using one composite image. An X-ray inspection apparatus for inspection. In this embodiment, the composite image is used to detect whether or not foreign objects such as metal, stone, glass, resin, and bone are mixed in an object to be inspected such as food (inspection for the presence of foreign objects).

  As shown in FIG. 1, the X-ray inspection apparatus 1 includes a transport unit 2, an X-ray generator 3, and an X-ray detector 4. The transport means 2 is a transport conveyor such as a belt conveyor, and is provided so as to penetrate a housing (not shown) having a shielding structure made of a radiation protection material. The transport conveyor 2 transports the inspection object W in a predetermined transport direction (the direction of the arrow in FIG. 1). At this time, the upper circulation surface of the transport conveyor 2 becomes the transport path 2a of the inspection object W.

  An X-ray generator 3 and an X-ray detector 4 are provided in the housing. The X-ray generator 3 is provided in the upper part in the housing. The X-ray detector 4 is provided between the upper circulation surface and the lower circulation surface of the conveyor 2. The X-ray generator 3 and the X-ray detector 4 are arranged to face each other with the conveyance path 2a interposed therebetween.

  In the X-ray generator 3, an X-ray tube (not shown) that generates X-rays in a metal box is immersed in insulating oil, and irradiates the inspection object W conveyed by the conveyor 2 with X-rays. At this time, X-rays are irradiated radially from the X-ray generator 3 so that a range as indicated by a one-dot chain line in FIG. 1 is imaged. Here, the intensity of the X-ray generated by the X-ray tube changes in proportion to the current (tube current) flowing between the anode and the cathode of the X-ray tube, and the wavelength of the generated X-ray varies with the X-ray tube. In accordance with the voltage (tube voltage) applied between the anode and the cathode, the transmittance is reduced. That is, the quality (X-ray energy) of X-rays generated from the X-ray tube changes according to the tube current and tube voltage of the X-ray tube.

  The X-ray detector 4 includes a photodiode (not shown) and a plurality of X-ray detection elements 4a made of a scintillator provided on the photodiode. The X-ray detector 4 is an area sensor in which the X-ray detection elements 4a are arranged in a plane along the transport direction and the direction orthogonal to the transport direction. In addition, the area located immediately above the X-ray detector 4 on the transport path 2a is an inspection area where the inspection object W is imaged.

  The X-ray detector 4 captures a transmission image of X-rays transmitted through the inspection object W when the inspection object W is irradiated with X-rays from the X-ray generator 3 in the inspection area on the transport path 2a. Specifically, it is converted into an optical signal by the scintillator of the X-ray detection element 4a, and the optical signal is converted into an electric signal by the photodiode. Further, processing such as noise removal is performed, and a transmission image having a grayscale distribution is generated based on the X-ray transmission amount. As another X-ray detection example, a semiconductor such as cadmium telluride (CdTe) may be used to convert X-rays directly and efficiently into an electrical signal.

  In the X-ray inspection apparatus 1, the same inspection object W is imaged a plurality of times with X-rays having different energies, each transmission image is generated, and a plurality of transmission images are combined to form one composite Generate an image. The X-ray inspection apparatus 1 includes a control means 10 for reliably obtaining such a composite image.

  The control means 10 includes a switching means 11 that switches the X-ray energy irradiated from the X-ray generator 3 to a set value corresponding to the composition and shape of the inspection object W and other inspection conditions. In the switching means 11, the X-ray wavelength distribution is changed by controlling the tube voltage and tube current of the X-ray tube of the X-ray generator 3, and the X-ray energy irradiated from the X-ray generator 3 is changed. Can do.

  The control means 10 includes storage means 12 for sequentially storing inspection parameters for each product type that determines inspection conditions and the like, and a plurality of transmission images of the same inspection object W imaged by the X-ray detector 4.

  The control means 10 controls the conveyance conveyor 2 to stop when the inspection object W conveyed to the conveyance conveyor 2 falls within the inspection area, and to operate the conveyance conveyor 2 when imaging by the X-ray detector 4 is completed. A conveyance control means 13 is provided. Therefore, the inspection object W is imaged in a stationary state. As a result, no deviation occurs when the transparent images are combined, and an accurate combined image can be obtained. In addition, the conveyance control by the conveyance control means 13 becomes possible by controlling a drive unit such as a motor of the conveyance conveyor 2. Further, whether or not the inspection object W has been accommodated in the inspection area can be detected by detecting the passage of the inspection object W with a sensor provided on the transport path 2a.

In the X-ray inspection apparatus 1, the X-ray energy irradiated to the same inspection object W is changed to change the features for each transmission image, and one composite image is obtained by combining these transmission images. High-precision inspection with enhanced features is possible. In the X-ray inspection apparatus 1, for example, imaging is performed three times with X-rays whose energy is changed, and as shown in FIG. Value where high-density foreign matter such as metal appears clearly in the transmitted image, second value where low-density foreign matter such as resin appears clearly, and third time value where X-ray opaque material such as glass appears clearly Switch to. As a result, all these foreign substances appear from the image obtained by combining the three transmission images. In this embodiment, the tube voltage is set in the range of 10 to 100 kV, and the tube current is set in the range of 0.1 to 10 mA according to the inspection conditions. Also, as shown in FIG. 2, by creating a plurality of patterns (three patterns in this embodiment) of combinations of such tube voltage and tube current values for each type, composition and shape (especially thickness) Thus, the configuration is such that three transmission images with different characteristics are taken for the different inspection objects W for each of the types P ₁ , P ₂ , and P ₃ . Specifically, for the type P ₁ , an image is taken using the X-ray set to the tube voltage X ₁ kV and the tube current x ₁ mA at the first time, and the tube voltage Y ₁ kV and the tube current y ₁ at the second time. Imaging is performed using X-rays set to mA and X-rays of tube voltage Z ₁ kV and tube current z ₁ mA for the third time. Similarly, as for the product P ₂ and the product P ₃ , as shown in the figure, the tube voltages X ₂ , Y ₂ , Z ₂ kV, tube currents x ₂ , y ₂ , z ₂ mA are shown in the figure. Imaging is performed using X-rays composed of the combination of X-rays, tube voltages X ₃ , Y ₃ , Z ₃ kV, and tube currents x ₃ , y ₃ , z ₃ mA.

  Further, the control means 10 includes confirmation means 14 for confirming whether or not the energy of the X-rays irradiated from the X-ray generator 3 has been switched from the previous set value to the next set value. As confirmation items by the confirmation means 14, the time taken for the X-ray output from the X-ray generator 3 to be stabilized (increase or decrease) after the tube voltage and tube current values are changed to desired set values, There is a density check of a transmission image.

  When the confirmation item by the confirmation unit 14 is a density check of a transmission image, for example, the edge of the inspection area perpendicular to the conveyance direction as shown by the oblique lines in FIG. 1 or the end of the inspection area along the conveyance direction This can be realized by using the X-ray detection element 4a at the edge, that is, the position that receives X-rays but is not involved in the inspection, for the density check. The confirmation means 14 switches the X-ray energy to a desired set value when the average density of the plurality of X-ray detection elements 4a in the position that receives this X-ray but is not involved in the inspection reaches a predetermined density. Judge that it has changed.

  If the confirmation item by the confirmation unit 14 is the time taken for the X-ray output from the X-ray generator 3 to be stabilized after the tube voltage and tube current values are changed to the next set values, the confirmation unit 14 can be realized by having a reference confirmation table. In this case, the confirmation unit 14 confirms based on the confirmation table that the energy of the X-rays emitted from the X-ray generator 3 has been switched to a desired set value. As the confirmation table, the tube voltage and tube current as shown in FIGS. 3A to 3C are changed from a certain set value to a certain set value, and the X-ray output from the X-ray generator 3 is stabilized. There are those created by actually measuring the time taken for each.

FIG. 3A shows a table of stabilization times when the tube voltage for changing the X-ray wavelength distribution is switched. In FIG. 3A, for example, the stabilization time when switching from the tube voltage V ₁ to V ₂ is S ₁₂ , and the stabilization time when switching from V ₂ to V ₃ is S ₂₃ . The stabilization time when switching from tube voltage V ₂ to V ₁ is S ₂₁ , and the stabilization time when switching from V ₃ to V ₂ is S ₃₂ . The confirmation unit 14 uses this table to determine that the X-ray energy has been switched to the desired set value when the corresponding stable time has elapsed since the switching unit 11 switched to the set value.

Further, when the change in the tube voltage is large, as shown in FIG. 3B, it is more preferable to adopt a table configuration in which the change in the tube current is taken into consideration for one tube voltage switching. FIG. 3B shows the stabilization time for each amount of change in tube current when the tube voltage V ₅ shown in FIG. 3A is switched to V ₂ . In FIG. 3B, for example, the stabilization time when switching from the tube current I ₁ to I ₂ is S ₅₂₁ , and the stabilization time when switching from I ₁ to I ₃ is S ₅₂₂ . The stabilization time when switching from the tube current I ₂ to I ₁ is S ₅₂₁ , and the stabilization time when switching from I ₃ to I ₂ is S ₅₂₂ . Furthermore, if there is no change in tube current becomes S _52. Incidentally, the horizontal line in FIG. 3 (b), X-rays from the X-ray generator 3 at tube voltage V ₅ tube current I ₄ is shown that can not be output.

  FIG. 3C shows a configuration example of a confirmation table in the case where a part of the table considering the tube current as shown in FIG. 3B is included. As shown in FIG. 3C, this table has a table configuration in which the change in the tube voltage in the shaded portion takes into account the change in the tube current, and there is no change in the tube current in the change in the tube voltage in the blank portion. The table structure of the stable time corresponding only to the change of the tube voltage is adopted. With such a configuration, an optimized table having only necessary information can be obtained.

  Although the confirmation table obtained through the density check of the transmission image and the actual measurement has been described as the confirmation unit 14 so far, the inspection area is inspected when setting the inspection parameter for setting the inspection condition of the inspection object W. In the absence of an object, the switching stabilization time is measured by changing the tube voltage and the tube current, the switching stabilization time together with the tube voltage and the tube current is stored in the storage means 12 as an inspection parameter, and the switching of the inspection parameter is performed. You may make it confirm with the confirmation means 14 using stable time. Note that the measurement in this case is the time from when the tube voltage and tube current are changed until the average concentration of the plurality of X-ray detection elements 4a reaches a predetermined concentration, and can be performed regardless of the inspection position. it can.

  According to the above-described embodiment, by imaging the inspection object W to be conveyed while controlling the operation of the conveyance conveyor 2 by the conveyance control means 13, X of different energy with respect to the same inspection object W is obtained. No deviation occurs between the three transmission images by the lines. By using one composite image in which such a deviation does not occur for inspection, high-precision inspection can be performed.

  Moreover, by providing the confirmation means 14, it can be grasped | ascertained correctly whether the energy of X-ray switched. As a result, it is possible to perform efficient inspection while suppressing loss of time required for switching energy, and productivity is not lowered.

  Furthermore, by having it in the confirmation table, it is possible to uniformly confirm whether or not the X-ray energy has been switched.

DESCRIPTION OF SYMBOLS 1 ... X-ray inspection apparatus 2 ... Conveyance means (conveyor)
2a ... conveying path 3 ... X-ray generator 4 ... X-ray detector 4a ... X-ray detecting element 11 ... switching means 12 ... storage means 13 ... conveying control means 14 ... confirming means W ... inspection object

Claims (1)

X-ray inspection in which a plurality of transmission images captured with X-rays having different energies are combined with the inspection object W transported on the transport path (2a), and the inspection object (W) is inspected using the composite image. In device (1):
Transport means (2) for forming the transport path and transporting the inspection object on the transport path in a predetermined transport direction;
An X-ray generator (3) for irradiating the same inspection object W with X-rays of different energy in a predetermined inspection area on the conveyance path;
Switching means (11) for switching the X-ray energy irradiated from the X-ray generator by controlling the tube voltage and tube current of the X-ray generator ;
X-rays comprising a plurality of X-ray detection elements (4a) arranged in a plane so as to form the inspection area on the conveyance path, and detecting X-rays transmitted through the inspection object and capturing a transmission image A detector (4);
Storage means (12) for storing a plurality of transmission images of the same object imaged by the X-ray detector;
A conveyance control means (13) for controlling the conveyance means to stop when the inspection object conveyed to the conveyance means falls within the inspection area and to operate the conveyance means when imaging by the X-ray detector is completed. )When,
Confirming means for confirming whether or not the energy of the X-rays irradiated from the X-ray generator has been switched based on a table of stabilization times set in accordance with the tube voltage and the tube current controlled by the switching means. (14) and
An X-ray inspection apparatus comprising:

Images