JP7795963B2 - X-ray inspection device and X-ray inspection method - Google Patents

Description

The present invention relates to an X-ray inspection device and X-ray inspection method that irradiates an inspection object with X-rays while transporting the object, and then detects the X-rays that have passed through the object to obtain an X-ray image, thereby inspecting the quality of the object.

For example, in the case of products in which the contents are placed through an opening in the packaging, the opening is sealed after the contents are placed in the packaging. At this time, the contents or foreign matter can get caught in the sealed area of the packaging, causing a poor seal, and products with such poor seals must be rejected as defective.

An example of an inspection device that inspects this type of product for seal defects is the X-ray inspection device disclosed in Patent Document 1 below. The X-ray inspection device disclosed in Patent Document 1 uses the outline area extracted from the X-ray transmission image as a reference, calculates the seal area based on preset seal information, and determines whether or not there is a seal defect using the shading level of the image within the seal area.

Japanese Patent Application Laid-Open No. 2005-024549

When inspecting for trapped contents or foreign objects in the sealed area using the X-ray inspection device disclosed in Patent Document 1 mentioned above, it is necessary to use low-energy X-rays so that the packaging material of the inspected item is visible in the X-ray transmission image. However, low-energy X-rays have low penetrating power and cannot be used to inspect thick items. Conversely, when inspecting thick items using high-energy X-rays, the packaging material does not appear in the X-ray transmission image, making it impossible to inspect for trapped contents.

In other words, when accurately inspecting thick contents with the X-ray inspection device disclosed in Patent Document 1, the contrast between the belt surface and the seal area cannot be obtained, and the outline area that serves as the reference for calculating the seal area cannot be extracted.

The present invention was made in consideration of the above-mentioned problems, and aims to provide an X-ray inspection device and X-ray inspection method that can inspect seals without compromising the inspection accuracy of even thick contents.

In order to achieve the above object, the X-ray inspection apparatus according to claim 1 of the present invention is an X-ray inspection apparatus 1 that irradiates an inspection object W, which has a rectangular content Wb in a plan view wrapped in a packaging material Wa, with X-rays while conveying the inspection object W on an upper running section 13 of a conveyor belt 11 wound around a plurality of conveyor rollers 12, 12 in a predetermined conveying direction A at a predetermined conveying speed , and inspects the quality of the inspection object using an X-ray image obtained by detecting the X-rays that have passed through the inspection object,
the object to be inspected has a sealed portion Wc at a leading end of the contents in the conveying direction where the packaging material is sealed;
a packaging material detection sensor 4 that is provided in the upstream running section near the detection position of the X-rays and detects the leading end of the seal portion in the conveying direction ;
a content region extraction means 22 for extracting a content region of the object to be inspected from the X-ray image;
a pseudo-seal width calculation means (23) for calculating a pseudo-seal width H based on setting information including the X-ray detection position in the conveying direction, the position of the packaging material detection sensor, and the conveying speed, the distance from the leading edge of the conveying direction to the outer edge of the leading edge of the content area ;
and a seal determining means 24b for determining that the contents have shifted toward the tip of the inspected object and that there is a seal defect when the pseudo seal width falls below a lower limit value.

The X-ray inspection apparatus according to claim 2 of the present invention is the X-ray inspection apparatus according to claim 1,
The packaging material detection sensor 4 is a color sensor.

The X-ray inspection method according to claim 3 of the present invention is an X-ray inspection method for inspecting the quality of an object W to be inspected, the object W having a rectangular content Wb in a plan view wrapped in a packaging material Wa, by irradiating the object W with X-rays while conveying the object W on an upper running section 13 of a conveyor belt 11 wound around a plurality of conveyor rollers 12, 12 at a predetermined conveying speed in a predetermined conveying direction A, and using an X-ray image obtained by detecting the X-rays that have passed through the object W to be inspected,
the object to be inspected has a sealed portion Wc at a leading end of the contents in the conveying direction where the packaging material is sealed;
detecting a leading end of the seal portion in the conveying direction by a packaging material detection sensor 4 in the vicinity of an upstream side of a detection position of the X-ray in the upper traveling section ;
extracting a content region of the object from the X-ray image;
calculating a distance from the leading edge of the conveying direction to an outer edge of the leading edge side of the content area as a pseudo seal width based on setting information including an X-ray detection position in the conveying direction, a position of the packaging material detection sensor, and the conveying speed ;
and determining that the contents have shifted toward the tip of the object to be inspected and that there is a seal defect when the pseudo seal width falls below a lower limit.

This invention makes it possible to inspect seals without compromising the accuracy of content inspection, even when the object being inspected has thick contents wrapped in packaging material.

1 is a block diagram of an X-ray inspection apparatus according to the present invention; 10 is an explanatory diagram for calculating the content area of an object to be inspected and the pseudo seal width at the leading end side in the conveying direction of the object to be inspected using the X-ray inspection device according to the present invention. FIG. 10 is a flowchart for performing a seal inspection using the X-ray inspection device according to the present invention. 10A and 10B are explanatory diagrams illustrating the case where the pseudo seal width is calculated on the front and rear sides of an object to be inspected in the transport width direction using the X-ray inspection device according to the present invention.

The following describes in detail the embodiments of the present invention, with reference to the accompanying drawings.

As shown in Figure 1, the X-ray inspection device 1 is generally configured with a conveying unit 2, driving means 3, packaging material detection sensor 4, X-ray generator 5, X-ray detector 6, setting input unit 7, signal processing unit 8, and display unit 9. It is incorporated, for example, into part of a conveying line, irradiates X-rays onto the object W to be inspected while conveying it, and detects the X-rays that have passed through the object W to obtain an X-ray image, which is used to inspect the quality of the object W (presence of foreign matter, presence of defective seals, etc.).

The object W to be inspected is a packaging material Wa containing contents Wb, including a container (tray), with the contents Wb having at least one straight side, the packaging material Wa sealed on one side of the contents Wb, and a sealed portion We on that side. Specifically, for example, this applies to a lunch box in which contents Wb, including a container (tray), are wrapped in transparent packaging material Wa. The object W to be inspected may be a lunch box containing the contents of a lunch box in a container (tray), or it may be a thick food product without a container (tray), such as cheese, wrapped in packaging. It is also preferable that the contents Wb be rectangular when viewed from above.

The transport unit 2 transports the test objects W sequentially at predetermined intervals in the transport direction A. For example, it is configured by a loop-shaped transport belt 11 wound around multiple transport rollers 12, and a conveyor supported on a housing (not shown) that can transport the test objects W sequentially in the transport direction A (rightward in Figure 1) using the upper running section 13 of the transport belt 11. The transport rollers 12 are driven to rotate by a motor serving as the drive means 3, and are controlled to achieve a predetermined transport speed.

The packaging material detection sensor 4 is composed of, for example, a distance sensor or a color sensor, and detects the outermost edge (outer edge) of the seal portion Wc of the packaging material Wa of the inspection object W as a specific position. When a distance sensor is used as the packaging material detection sensor 4, light from a light source (LED or laser diode) is irradiated onto the inspection object W, and the light reflected from the specific position on the inspection object W is received by a light receiving element, which converts the received reflected light into distance and outputs it. When a color sensor is used as the packaging material detection sensor 4, light from the light emitting unit is irradiated onto the inspection object W, and the light reflected from the specific position on the inspection object W is detected by the light receiving unit as the amount of received red, blue, and green light, respectively.

In addition, when the packaging material detection sensor 4 detects the front or rear side of the seal portion Wc of the packaging material Wa of the inspection item W in the transport width direction B (the side of the inspection item W), an area sensor that detects a specific position of the inspection item W within a predetermined area or an area camera that captures an image of the specific position of the inspection item W as a surface is used.

The specific position on the inspection object W is not limited to the outermost edge (outer end) of the seal portion Wc described above, but may also be a color mark attached to the seal portion Wc of the packaging material Wa or a colored seal portion Wc.

The X-ray generator 5 uses a known X-ray tube to generate X-rays with a wavelength and intensity corresponding to the tube current and tube voltage, and is capable of irradiating the object W to be inspected on the conveyor belt 11 with fan-shaped X-rays that pass through the X-ray window in the enclosure and are perpendicular to the conveying direction A of the conveyor unit 2.

The tube current and tube voltage of the X-ray tube of the X-ray generator 5 should be adjusted according to the material and size (particularly the dimensions in the direction of X-ray transmission) of the object W to be inspected. For new types, the setting values are determined or selected so that appropriate contrast is obtained by test imaging using the object W or sample.

The X-ray detector 6 is composed of an X-ray line sensor in which detection elements, such as a scintillator phosphor and a photodiode or charge-coupled device, are arranged in an array at a predetermined pitch in the width direction B of the conveyor 2, and are designed to detect X-rays at a predetermined resolution. It is placed at a predetermined position in the conveyor direction A corresponding to the position where X-rays are irradiated from the X-ray generator 5.

The X-ray detector 6 detects X-rays emitted from the X-ray generator 5 and transmitted through the object W or sample for each predetermined transmission area corresponding to the detection element, converts the X-rays into an electrical signal corresponding to the amount of transmitted X-rays, and outputs an X-ray detection signal for each transmission area.

Then, one line of X-ray image data is accumulated for each scan from the X-ray detector 6 (X-ray line sensor), which consists of multiple detection elements arranged in a line in the main scanning direction (y direction: width direction of the transport path) perpendicular to the transport direction A, and is stored as an X-ray image in the memory means 21 (described later) of the signal processing unit 8.

Here, the scanning period T (scanning speed [repetition rate]) of the X-ray detector 6 is set so that the unit dimension in the transport direction A (x direction) and the unit dimension in the main scanning direction (y direction) roughly match, depending on the transport speed. As a result, the distance between adjacent elements of the X-ray detector 6 (X-ray line sensor) becomes the length per pixel in the X-ray image.

The X-ray detector 6 may be a photon-counting type X-ray detector that can simultaneously acquire images of multiple energies.

The setting input unit 7 is composed of multiple keys and switches operated by the user to enter various settings and instructions related to the inspection and display of the object W. More specifically, the setting input unit 7 sets the X-ray image data acquisition settings, such as the tube current and tube voltage of the X-ray tube of the X-ray generator 5, the scan speed of the X-ray detector 6, and the transport speed of the transport unit 2, as well as the threshold for extracting the contents Wb of the object W and the allowable seal width range that serves as the basis for determining seal defects in the seal portion Wc of the object W. The setting input unit 7 also allows the setting of detection limit values that serve as the basis for determining whether or not the object W contains foreign matter or whether or not the contents Wb are missing when performing multiple inspections of the contents Wb of the object W. These detection limit values are set appropriately depending on the type of object W and the type of foreign matter to be detected.

The signal processing unit 8 is configured with a memory means 21, a content area extraction means 22, a pseudo-seal width calculation means 23, and a quality determination unit 24.

The storage means 21 stores the state of the packaging material detection sensor 4 at the time X-ray image data is acquired from the X-ray detector 6 (X-ray line sensor), linked to the X-ray image data. This allows the level of the packaging material detection sensor 4 to correspond to the x- and y-coordinates on the X-ray image, with the conveyance direction A as the x-axis and the conveyance width direction B as the y-axis. This data linking is performed based on the mounting position of the packaging material detection sensor 4, the X-ray detection position, and the conveyance speed, which are set in the setting input unit 7. Furthermore, the X-ray image data has density levels that correspond to grayscale values that are lighter the greater the amount of transmission.

The content area extraction means 22 uses the threshold value set in the setting input unit 7 to extract X-ray image data with a density level exceeding the threshold value from the X-ray image data stored in the storage means 21 as a content area corresponding to the content Wb of the object W to be inspected.

As shown in Figure 2, the pseudo seal width calculation means 23 calculates the difference in x-coordinate between the coordinate at which the packaging material detection sensor 4 detects the leading edge of the packaging material Wa of the inspection item W and the coordinate at which the leading edge of the content area corresponding to the content Wb of the inspection item W, extracted by the content area extraction means 22, in the conveying direction A. This x-coordinate difference corresponds to the time from the detection by the packaging material detection sensor 4 to the acquisition of X-ray image data by the X-ray detector 6 (X-ray line sensor). This time is converted into a distance based on the mounting position of the packaging material detection sensor 4, the X-ray detection position, and the conveying speed, and the value calculated is the pseudo seal width H.

In the above explanation, the specific position of the seal portion Wc of the object W to be inspected for determining the pseudo seal width H is the leading edge in the transport direction A, but it may also be the trailing edge of the seal portion Wc of the object W to be inspected for in the transport direction A. Furthermore, as will be explained later, the specific position of the seal portion Wc of the object W to be inspected for determining the pseudo seal width H may also be the rear or front side in the transport width direction B (side of the object W to be inspected).

The quality determination unit 24 determines the quality of the inspection item W and is equipped with a contents determination means 24a and a seal determination means 24b.

The contents determination means 24a performs a process to determine the quality state of the contents Wb of the inspection item W (e.g., determining whether or not there are foreign objects or missing items) based on the X-ray image of the contents area.

The seal portion determination means 24b determines whether the pseudo seal width H calculated by the pseudo seal width calculation means 23 is within the allowable range of the length (number of pixels) set in the setting input unit 7. If the pseudo seal width H is within the allowable range, it is determined to be OK, and if the pseudo seal width H is outside the allowable range, it is determined to be a defective seal.

The display unit 9 is composed of various display devices, such as LCDs, and displays and outputs the judgment results from the quality judgment unit 24. The display unit 9 also displays X-ray inspection images of the inspection object W that are extracted for inspection and display from the X-ray images stored in the storage means 21.

Next, the operation of calculating the pseudo seal width H of the object W to be inspected and performing a seal inspection using the X-ray inspection device 1 configured as described above will be described with reference to the flowchart in Figure 3. Here, we will explain an example in which the object W to be inspected is transported in the transport direction A so that the seal portion Wc of the object W to be inspected is positioned at the front and rear of the transport unit 2 in the transport direction A, and the pseudo seal width at the leading end of the object W to be inspected in the transport direction A is calculated to perform a seal inspection.

When the inspection object W is transported in the transport direction A by the transport unit 2, the packaging material detection sensor 4 detects a specific position of the seal portion Wc of the inspection object W (ST1). Specifically, the packaging material detection sensor 4 detects the leading edge of the seal portion Wc of the packaging material Wa of the inspection object W as the specific position of the seal portion Wc.

Next, the content region of the object W to be inspected is extracted by the content region extraction means 22 of the signal processing unit 8 (ST2). Specifically, the content region extraction means 22 extracts X-ray image data with a density level exceeding a threshold from the X-ray image data stored in the storage means 21 as a content region corresponding to the content Wb of the object W to be inspected.

Next, the pseudo seal width calculation means 23 of the signal processing unit 8 calculates the pseudo seal width of the inspection item W (ST3). Specifically, the pseudo seal width calculation means 23 calculates the difference in x-coordinate between the coordinate at which the packaging material detection sensor 4 detects the leading edge of the seal portion Wc of the packaging material Wa of the inspection item W and the coordinate at which the leading edge in the conveying direction A of the content area corresponding to the content Wb of the inspection item W extracted by the content area extraction means 22. This x-coordinate difference corresponds to the time from the detection timing by the packaging material detection sensor 4 to the acquisition timing of X-ray image data by the X-ray detector 6, so this time is converted into a distance based on the mounting position of the packaging material detection sensor 4, the X-ray detection position, and the conveying speed to calculate the pseudo seal width H.

Next, the seal determination means 24b of the signal processing unit 8 determines the seal of the object W to be inspected (ST4). Specifically, the seal determination means 24b can set the OK/NG criteria for the seal Wec of the object W to any predetermined range using upper and lower limit values, and determines whether the pseudo seal width H is within the predetermined range. That is, if the pseudo seal width H is within the predetermined range, it is determined to be OK, and if it is outside the predetermined range, it is determined to be NG. More specifically, if the pseudo seal width H is outside the predetermined range and exceeds the upper limit, the container (tray) has shifted backward and there is a seal defect on the rear side of the object W to be inspected. If the pseudo seal width H is below the lower limit, the container (tray) has shifted forward and there is a seal defect on the front side of the object W to be inspected, and the object is determined to be NG and sorted.

In the above-described embodiment, the pseudo seal width at the leading end of the inspection object W in the transport direction A is calculated by the X-ray inspection device 1. However, as shown in Figure 4(a), the pseudo seal width at the rear or front end of the inspection object W in the transport width direction B may also be calculated by the X-ray inspection device 1.

In this case, the area sensor serving as the packaging material detection sensor 4 is positioned on the entrance side of the conveying section 2 in the conveying direction A, as shown by the dotted line in Figure 4(a). The front edge of the conveyor belt 11 of the conveyor in the conveying section 2 in the conveying width direction B is set as the reference line L, and the level from the area sensor (packaging material detection sensor 4) is converted into a distance from the reference line L at the scanning interval of the X-ray line sensor (X-ray detector 6), and a value is maintained.

In addition, the storage means 21 of the X-ray inspection device 1 stores the converted value acquired by the area sensor (packaging material detection sensor 4) in association with the X-ray image data at the timing when X-ray image data is acquired from the X-ray line sensor (X-ray detector 6). This allows the converted value acquired by the area sensor (packaging material detection sensor 4) to correspond to the x and y coordinates on the X-ray image, with the conveying direction A as the x-axis and the conveying width direction B as the y-axis.

The pseudo seal width calculation means 23 of the X-ray inspection device 1 then converts the distance from the front edge of the content area to the reference line L, calculates the difference from this converted value obtained by the area sensor (packaging material detection sensor 4) over the length (D) of the content area in the conveying direction A, and calculates the average or maximum value as the pseudo seal width H, as shown in Figure 4(b).

In the X-ray inspection device 1 shown in Figure 1, when the inspection object W is transported by the transport unit 2, the inspection object W is not always transported straight along the transport direction A, and one side of the contents or seal of the inspection object may be tilted relative to the transport direction A or the transport width direction B. For this reason, tilt correction is performed as described below.

If the contents or one side of the sealed portion of the object W to be inspected is tilted relative to the conveying direction A, the tilt angles of the contents Wb and one side of the sealed portion We of the object W to the conveying direction A (X-axis) are calculated, and the tilt of the contents Wb and one side of the sealed portion We of the object W is individually corrected to cancel out each calculated tilt angle.

In addition, if the contents or one side of the sealed portion of the object W to be inspected is tilted relative to the conveying width direction B, the tilt angles of the contents Wb and one side of the sealed portion Wc of the object W to the conveying width direction B (Y axis) are calculated, and the tilt of the contents Wb and one side of the sealed portion Wc of the object W to be inspected is individually corrected to cancel out the calculated tilt angles.

As described above, according to this embodiment, a specific position of the seal portion Wc of the inspection object W being transported along the transport direction A is detected, the content area of the inspection object W is extracted from the X-ray image, the distance from the specific position to the outer edge of one side of the content area is calculated as the pseudo seal width H, and if the calculated pseudo seal width H is outside a specified range, it is determined that the seal is defective. This makes it possible to inspect the seal without compromising the inspection accuracy of the contents, even for inspection objects with thick contents wrapped in packaging material.

Furthermore, it is possible to simultaneously inspect the contents of thick objects and inspect the objects for seal defects, two contradictory inspections. Similarly, by adopting this embodiment for dual-energy X-rays, it is possible to simultaneously detect hard and soft foreign objects and inspect for seal defects.

In addition, this eliminates the need for measures such as compensation for the severe temperature effects that are unique to X-rays, simplifying on-site operations.

Furthermore, if the specific position of the seal portion Wc of the inspection object W detected by the packaging material detection sensor 4 is colored, using a color sensor as the packaging material detection sensor 4 makes it possible to stably detect the specific position (for example, the leading or trailing edge in the conveying direction A, or the rear or front side in the conveying width direction B) even if the seal portion is unstable and the distance between the sensor and the seal portion changes.

The above describes the best mode for the X-ray inspection device and X-ray inspection method according to the present invention, but the present invention is not limited to the description and drawings of this mode. In other words, all other modes, embodiments, and operational techniques that are conceived by those skilled in the art based on this mode are naturally included within the scope of the present invention.

REFERENCE SIGNS LIST 1 X-ray inspection device 2 Conveying section 3 Driving means 4 Packaging material detection sensor 5 X-ray generator 6 X-ray detector 7 Setting input section 8 Signal processing section 9 Display section 11 Conveying belt 12 Conveying roller 13 Upward running section 21 Memory means 22 Content area extraction means 23 Pseudo seal width calculation means 24 Quality determination section 24a Content determination means 24b Seal portion determination means W Inspected item Wa Packaging material Wb Contents Wc Seal portion A Conveying direction B Conveying width direction H Pseudo seal width L Reference line

Claims (3)

An X-ray inspection device (1) for inspecting the quality of an object (W) to be inspected, the object (W) having a rectangular content (Wb) in a plan view wrapped in a packaging material (Wa), is irradiated with X-rays while being conveyed in a predetermined conveying direction (A) at a predetermined conveying speed through an upper running section (13) of a conveying belt (11) wound around a plurality of conveying rollers (12, 12 ), and the quality of the object to be inspected is inspected using an X-ray image obtained by detecting the X-rays that have passed through the object,
the object to be inspected has a sealed portion (Wc) at the leading end side of the contents in the conveying direction where a packaging material is sealed,
a packaging material detection sensor (4) provided in the upstream running section near the detection position of the X-rays and detecting the leading edge of the seal portion in the conveying direction ;
a content region extraction means (22) for extracting a content region of the object to be inspected from the X-ray image;
a pseudo seal width calculation means ( 23) for calculating a distance from the leading edge of the conveying direction to an outer edge of the leading edge side of the content area as a pseudo seal width (H) based on setting information including an X-ray detection position in the conveying direction, a position of the packaging material detection sensor, and the conveying speed;
and a seal determination means (24b) that determines that the contents have shifted toward the tip of the inspected object and that there is a seal defect when the pseudo seal width falls below a lower limit value. The X-ray inspection device according to claim 1, characterized in that the packaging material detection sensor (4) is a color sensor. An X-ray inspection method for inspecting the quality of an object (W) to be inspected, the object (W) having a rectangular content (Wb) in a plan view wrapped in a packaging material (Wa), by irradiating the object with X-rays while conveying the object through an upper running section (13) of a conveyor belt (11) wound around a plurality of conveyor rollers (12, 12) in a predetermined conveying direction (A) at a predetermined conveying speed, and using an X-ray image obtained by detecting the X-rays that have passed through the object,
the object to be inspected has a sealed portion (Wc) at the leading end side of the contents in the conveying direction where a packaging material is sealed,
a step of detecting a leading end of the seal portion in the conveying direction by a packaging material detection sensor (4) in the vicinity of an upstream side of a detection position of the X-ray in the upper traveling section ;
extracting a content region of the object from the X-ray image;
calculating a distance from the leading edge of the conveying direction to an outer edge of the leading edge side of the content area as a pseudo seal width based on setting information including an X-ray detection position in the conveying direction, a position of the packaging material detection sensor, and the conveying speed ;
and determining that the contents have shifted toward the tip of the object to be inspected and that there is a seal defect when the pseudo seal width is below a lower limit value.