JP7264520B2 - Container inspection method and device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for inspecting a container to which a film such as a label is attached.

As a method for inspecting transparent labels attached to containers, the quality of transparent labels is inspected using the difference in the amount of reflected light in the ultraviolet region between a transparent label made of biaxially oriented polystyrene resin and a container made of polyethylene terephthalate resin. A technique has been proposed (see Patent Document 1, for example).

JP-A-2005-91338

With the above-described method, there is a case where the reliability of inspection cannot always be ensured because the difference in brightness required for inspection cannot be obtained between the label and other portions.

Accordingly, it is an object of the present invention to provide a method for inspecting a container, etc., capable of increasing the reliability of inspection by generating a sufficient difference in brightness between the defective portion and the other portions in the transparent portion of the film. aim.

A method for inspecting a container according to an aspect of the present invention includes a film having a transparent portion containing biaxially oriented polystyrene as a material attached thereto, and filled with a liquid containing colloidal particles that cause Tyndall phenomenon when irradiated with ultraviolet light. An inspection method for inspecting a container made of polyethylene terephthalate resin, comprising: a procedure of irradiating a target region including the transparent portion with the ultraviolet light from a lighting means to illuminate the target region; and the illuminated target region. and a step of determining the quality of the transparent portion based on the captured image of the target region, wherein the imaging step includes a step of capturing an image of the target region, wherein the imaging step includes a step of capturing an image of the ultraviolet light. is adjusted in the wavelength range of the incident light to the imaging means by filter means for limiting the wavelength range of the fluorescence generated by the irradiation of the ultraviolet light, and the image is captured.

A container inspection device according to an aspect of the present invention is equipped with a film having a transparent portion containing biaxially oriented polystyrene as a material, and is filled with a liquid containing colloidal particles that cause the Tyndall phenomenon when irradiated with ultraviolet light. An inspection apparatus for inspecting a container made of polyethylene terephthalate resin, comprising illumination means for illuminating the target area including the transparent portion with the ultraviolet light, and an image of the illuminated target area. and the wavelength of the light incident on the imaging means such that the passage of the wavelength range of the ultraviolet light is limited in comparison with the wavelength range of the fluorescence generated by the irradiation of the ultraviolet light. The apparatus includes filter means for adjusting a region, and determination means for determining whether the transparent portion is good or bad based on the captured image of the target area.

The figure which shows an example of the inspection apparatus of the container used by one form of this invention. The figure which shows the result of having measured the three-dimensional fluorescence spectrum when a sample piece made from a polyethylene terephthalate resin was irradiated with ultraviolet light. FIG. 4 is a diagram showing an example of the relationship between the spectral intensity of ultraviolet light that illuminates the bottle, the spectral intensity of fluorescence emission from the bottle, and the spectral sensitivity of the filter. The figure which shows an example of the spectral sensitivity of a camera. The figure which shows an example of the image obtained by the test|inspection method which concerns on one form. FIG. 5 is a diagram showing an example of processing an image obtained by an inspection method according to one embodiment;

One embodiment of the present invention will be described below with reference to the accompanying drawings. This embodiment is characterized by two points of view: selection of the wavelength range used for inspection and selection of the type of liquid to be filled in the container to be inspected. They will be described in order below.

[Configuration of inspection device]
First, referring to FIG. 1, a schematic configuration of a container inspection apparatus used in one embodiment of the present invention will be described. The inspection device 1 uses a bottle 2 made of polyethylene terephthalate resin as a container to be inspected. FIG. 1 shows a main part of the inspection device 1 in plan view along the axial direction of the bottle 2 . The bottle 2 is wrapped with a label (not shown) having a transparent portion at least partially. The label includes a biaxially oriented polystyrene resin as a material, at least in its transparent portion. The transparent portion here means transparent to visible light. Hereinafter, polyethylene terephthalate is sometimes abbreviated as "PET" and biaxially oriented polystyrene is sometimes abbreviated as "OPS". A bottle 2 to be inspected is filled with a liquid. The type of liquid (liquid type) will be described later.

The inspection device 1 includes an image acquisition device 10 that acquires an image of a target area set on at least part of the bottle 2 . The target area may be set appropriately as long as it includes the transparent portion of the label. As an example, the entire bottle 2 may be set as the target area, or the target area may be set so as to be limited to the range where the label is wound. The image acquisition device 10 includes an illumination device 11 as an example of illumination means for illuminating a target area of the bottle 2, a camera 12 as an example of an imaging means for capturing an image of the illuminated target area, and light incident on the camera 12. and an optical filter 13 as an example of filter means for adjusting the wavelength band.

The illumination device 11 includes a pair of illuminators 11a. Each illuminator 11a irradiates a target area of the bottle 2 with ultraviolet light to illuminate the target area. The illuminators 11a are arranged so that their illumination directions are inclined with respect to the bottle 2 at a predetermined angle. A specific example of the wavelength range of the ultraviolet light emitted by the illuminator 11a will be described later. The camera 12 converts an optical image into an electrical image signal using, for example, an imaging device such as CCD or CMOS. The positional relationship between the illumination device 11 and the camera 12 is set so that the reflected light of the bottle 2 with respect to the illumination light from the illumination device 11 is incident. As an example, the illumination direction of the illuminator 11a is symmetrically tilted left and right with respect to the imaging direction of the camera 12 so that the reflected light of the bottle 2 with respect to the illumination light of the pair of illuminators 11a enters the camera 12. .

Bottle 2 may be stationary or may be moving. For example, the camera 12 may be installed in a beverage filling line, and the camera 12 may be caused to perform an imaging operation when the bottle 2 reaches the imaging range of the camera 12, thereby sequentially imaging the moving bottle 2. If the label of the bottle 2 extends in the circumferential direction wider than the field of view of the camera 12, the bottle 2 may be rotated around its centerline to capture an image of the unfolded label. The lighting device 11 may be lit all the time, or may be lit in synchronization with the imaging operation of the camera 12 . Filter 13 adjusts the wavelength range of incident light to camera 12 by restricting the passage of the wavelength range of ultraviolet light emitted from lighting device 11 . A specific example of the spectral characteristics of the filter 13 will be described later.

A processing unit 20 is provided in the inspection apparatus 1 in order to inspect the quality of the label of the bottle 2 based on the image captured by the camera 12 . The processing unit 20 is, for example, configured as a computer unit including a CPU and an internal storage device required for its operation. The processing unit 20 is provided with an image processing section 21 and an inspection section 22 . The image processing unit 21 and the inspection unit 22 may be provided as a logical device realized by combining, for example, the hardware of the processing unit 20 and a computer program as software, or may be provided by combining logic circuits such as LSIs. may be provided as a separate physical device.

The image processing unit 21 receives image signals output from the camera 12 and performs image processing suitable for inspection by the inspection unit 22 . For example, the image processing unit 21 may perform correction processing such as brightness and contrast of the image. The inspection unit 22 receives the image signal processed by the image processing unit 21 and processes the image signal according to a predetermined algorithm to determine whether the label is good or bad. Thereby, the inspection unit 22 functions as an example of a determination unit. The inspection algorithm uses the brightness difference in the image to determine whether the label is good or bad.

As means for outputting the inspection results in the inspection section 22, the processing unit 20 may be appropriately connected to a monitor 23 for displaying inspection results, a storage device 24 for storing inspection results, or the like. A printer may be connected as output means. Further, the processing unit 20 may be connected to various input means such as a keyboard and a pointing device for the operator of the inspection apparatus 1 to input appropriate instructions. In FIG. 1, the illustration of the input means is omitted.

Determination of the quality of the label by the inspection unit 22 utilizes the following characteristics. When the PET resin is irradiated with ultraviolet light, the PET resin emits fluorescent light. On the other hand, OPS resin has the property of absorbing ultraviolet light. Therefore, when the bottle 2 described above is irradiated with ultraviolet light, the bottle emits fluorescent light in the portion where the label is not present, and the intensity of the reflected light in the fluorescent wavelength region increases. On the other hand, since the OPS resin component absorbs ultraviolet light in the transparent portion of the label, the fluorescence intensity decreases. An image acquired by the camera 12 has a difference in brightness depending on the intensity of the fluorescence. If the transparent portion of the label is damaged due to tearing or the like, the damaged portion does not absorb the ultraviolet light and appears as a bright portion in the image. Therefore, if a bright portion derived from fluorescence appears in a portion where a label should originally exist, it can be determined that a defect has occurred.

The reflected light from the bottle 2 includes not only fluorescence generated by the bottle 2 but also ultraviolet light reflected on the label. When the ultraviolet light is incident on the camera 12, the obtained image is affected by the ultraviolet light, and the difference in brightness between the defective portion of the label and the other portion may be reduced. On the other hand, the wavelength range of the fluorescent light generated by the PET resin does not match the wavelength range of the irradiated ultraviolet light, and a deviation occurs between the two wavelength ranges. Therefore, the spectral characteristics of the filter 13 are set so that the wavelength range of the fluorescent light produced by the bottle 2 is passed, and the wavelength range of the ultraviolet light emitted from the illumination device 11 is restricted. As a result, the influence of reflected light on the bottle 2 can be suppressed, and the difference in brightness between the defective portion of the label and the other portion can be ensured.

It should be noted that the restriction on the incidence of ultraviolet light in the wavelength range may be any one that reduces the intensity of the incident light compared to the incidence of fluorescence in the wavelength range. Therefore, it includes not only a mode of completely blocking the incidence of ultraviolet light in the wavelength range, but also a mode of relatively reducing the amount of incident light. On the other hand, with respect to the wavelength range of fluorescence, it is sufficient if the amount of fluorescence required for inspection is incident on the camera 12 . The spectral characteristics of the filter 13 may be set so that the entire wavelength range of fluorescence passes through the filter 13 and is incident on the camera 12, and the incidence of a part of the fluorescence wavelength range on the camera 12 is restricted by the filter 13. may be For example, in the wavelength range of fluorescence, for a part of the wavelength range on the short wavelength side relatively close to the wavelength range of ultraviolet light as illumination light, the filter 13 restricts its passage, and the restricted wavelength range The spectral characteristics of the filter 13 may be set so that the fluorescence on the longer wavelength side passes through the filter 13 and enters the camera 12 .

[Selection of wavelength range]
Next, specific considerations regarding the selection of the ultraviolet light wavelength range and the like of the illumination device 11 will be described with reference to FIGS. 2 to 4. FIG. FIG. 2 shows the results of measuring the three-dimensional fluorescence spectrum when a sample piece of PET resin was irradiated with ultraviolet light. The vertical axis is the wavelength of the irradiated ultraviolet light, and the horizontal axis is the wavelength of fluorescence. The density of the contour lines in the figure indicates the fluorescence intensity, and the denser the contour, the higher the fluorescence intensity. According to FIG. 2, when the PET resin is irradiated with ultraviolet light around 365 nm, fluorescence with relatively high intensity is generated in the wavelength range of 380 to 430 nm.

FIG. 3 shows the relationship between the spectral intensity of the ultraviolet light that illuminates the bottle 2, the spectral intensity of fluorescence emitted from the bottle 2, and the spectral sensitivity of the filter 13. As shown in FIG. In FIG. 3, the horizontal axis indicates the wavelength, and the vertical axis indicates the spectral intensity of ultraviolet light and fluorescence, and the spectral sensitivity of the filter 13, respectively. As can be seen from FIG. 3, when the PET resin material is illuminated with ultraviolet light whose spectral intensity peaks around 365 nm, fluorescence occurs in the wavelength range of 380 nm to 430 nm. Although the distribution of spectral intensity of ultraviolet light and the distribution of spectral intensity of fluorescence partially overlap, if the wavelength range of ultraviolet light is in the range of 360 nm to 380 nm, the spectral characteristics of filter 13 are approximately 400 nm, preferably If it is set so as to allow light on the longer wavelength side from 420 nm to pass through and restrict the passage of the wavelength region on the shorter wavelength side, the fluorescence generated in the bottle 2 can be suppressed while suppressing the incidence of ultraviolet light on the camera 12. It can be made to enter the camera 12 efficiently.

According to FIG. 2, it is possible to obtain more fluorescence by setting the wavelength region of the ultraviolet light to have a peak around 320 nm. However, in that case, the wavelength range of fluorescence also shifts to the short wavelength side. As shown in FIG. 4, the spectral sensitivity of a general camera used for capturing images in the visible light range is highest near 550 nm. The sensitivity of the camera is substantially lost near 1000 nm on the long wavelength side and near 400 nm on the short wavelength side. Therefore, if the wavelength range of ultraviolet light is set around 320 nm, the wavelength range of fluorescence may deviate from the wavelength range in which the camera 12 exhibits sufficient spectral sensitivity. Therefore, it is preferable to set the ultraviolet light emitted from the illumination device 11 within the range of 360 nm to 380 nm as described above.

[Selection of liquid type]
The intensity of fluorescence generated when the bottle 2 filled with liquid is irradiated with ultraviolet light is affected by the liquid type. Table 1 shows the results of measurement of the average luminance and relative luminance of fluorescence measured when bottles 2 are filled with various liquids and irradiated with ultraviolet light. The relative luminance is a ratio when the average luminance when filled with water is set to 1. The illumination conditions of ultraviolet light and the measurement conditions of brightness are the same for each liquid type.

Comparing the brightness and darkness of the image when the bottle 2 is imaged after being filled with various types of liquids, when the milk beverages 1 and 2 are filled, the necessary and sufficient brightness and darkness can be obtained to determine the missing portion of the label. It was confirmed that Milk drinks 1 and 2 are both drinks containing colloidal particles with a diameter of 30 to 300 nm. In this type of liquid, the irradiation of ultraviolet light causes the Tyndall phenomenon, and under the influence of this phenomenon, the bottle 2 efficiently emits fluorescent light. Therefore, the container to be inspected is preferably a container filled with a liquid containing colloidal particles that causes the Tyndall phenomenon when irradiated with ultraviolet light. More preferably, the inspection method of the present embodiment can be applied to a container filled with a liquid of a liquid type that provides a relative luminance that is 5.6 times or more the average luminance obtained when filled with water. desirable.

In the above embodiment, the transparent portion of the label wrapped around the PET bottle is used as the target for quality determination, but the transparent portion may be on the film attached to the PET resin container. The transparent portion is not limited to the example in which only the OPS resin is used as the material. For example, even when a hybrid material in which OPS resin and PET resin are combined is used as the material of the transparent portion, the quality thereof may be determined according to the present invention.

[Experimental example]
An example of an image obtained using the inspection apparatus 1 of FIG. 1 is shown in FIG. 5 together with a comparative example. In (a) of the same figure, a PET bottle with an OPS resin label wrapped around the entire circumference is irradiated with ultraviolet light in the wavelength range described above, and the wavelength range of the incident light is adjusted by the filter having the spectral characteristics described above. It is an example of the obtained image. For the label, a pseudo defect was generated by partially cutting it into a rectangular shape. Milk drink 1 in Table 1 was filled in a PET bottle. FIG. 1(b) is an image obtained when the same PET bottle is illuminated with white light instead of ultraviolet light, and FIG. is an image obtained when photographing a PET bottle. In the image of FIG. 4A, it can be confirmed that a rectangular defect image corresponding to the pseudo defect appears as a bright portion. On the other hand, in FIG. 4B, the entire bottle is displayed brightly, making it difficult to confirm the portion corresponding to the pseudo defect. A defect image can be confirmed in FIG. 4C as in FIG. Those bright areas are the images corresponding to the light sources of the illumination device. If such a bright portion appears, there is a possibility that it will be erroneously determined as defective even though there is no defect. Although some images corresponding to the light source can be seen in FIG. 11(a), the brightness is clearly lower than that in FIG. 11(c) and can be identified as defects by image processing.

Table 2 shows the results of measuring the average brightness of pseudo-defects and other normal portions by filling various liquids into the PET bottles used in the experimental examples. Samples A to M differ only in liquid type. Also, the average luminance ratio in Table 2 indicates the ratio of the average luminance of the pseudo defect when the average luminance of the normal portion is set to 1. The liquids filled in Samples A to M are all milk beverages containing colloidal particles with a diameter of 30 to 300 nm. It is.

As is clear from the results in Table 2, it was confirmed that the average brightness of pseudo defects was clearly higher than that of normal portions in all samples, and that the difference could be used to clearly distinguish defects. FIG. 6 shows an example of image processing obtained by photographing sample M in Table 2. In FIG. FIG. 1(a) is an original image before image processing, and FIG. 1(b) is an image obtained by binarizing the original image. As in the example of FIG. 5(a), some bright portions corresponding to the light source of the illumination device appear in the original image of (a), and the image after binarization is also affected by the bright portions to some extent. or remain. FIG. 6C shows an image obtained by applying a process of removing isolated white pixels in the image as noise. It can be confirmed that the bright part corresponding to the light source is not recognized in the image after noise removal. Therefore, by using the noise-removed image, it is possible to accurately determine the quality of the transparent portion of the label.

Various aspects of the present invention derived from each of the embodiments and modifications described above are described below. In the following description, in order to facilitate understanding of each aspect of the present invention, the corresponding components illustrated in the accompanying drawings are added in parentheses, but the present invention is thereby limited to the illustrated form. not something.

A method for inspecting a container according to an aspect of the present invention includes a film having a transparent portion containing biaxially oriented polystyrene as a material attached thereto, and filled with a liquid containing colloidal particles that cause Tyndall phenomenon when irradiated with ultraviolet light. An inspection method for inspecting a container (2) made of polyethylene terephthalate resin, comprising a procedure of irradiating a target region including the transparent portion with the ultraviolet light from illumination means (11) to illuminate the target region; The imaging step includes a step of capturing an image of the illuminated target region by imaging means (12), and a step of determining the quality of the transparent portion based on the captured image of the target region. and adjusting the wavelength range of incident light to the imaging means by filter means (13) for restricting the passage of the wavelength range of the ultraviolet light in comparison with the wavelength range of the fluorescence generated by the irradiation of the ultraviolet light. to pick up the image.

A container inspection device according to an aspect of the present invention is equipped with a film having a transparent portion containing biaxially oriented polystyrene as a material, and is filled with a liquid containing colloidal particles that cause the Tyndall phenomenon when irradiated with ultraviolet light. An inspection apparatus (1) for inspecting a container (2) made of polyethylene terephthalate resin, comprising illumination means (11) for illuminating the target region including the transparent portion by irradiating the target region with the ultraviolet light. an imaging means (12) for capturing an image of said illuminated target area, such that the passage of the wavelength range of said ultraviolet light is restricted in comparison with the wavelength range of said fluorescence produced by irradiation with said ultraviolet light. and filter means (13) for adjusting the wavelength range of light incident on the imaging means, and discrimination means (22) for discriminating the quality of the transparent portion based on the captured image of the target region. It is prepared.

According to the above aspect, while the container emits fluorescent light when irradiated with ultraviolet light, at least part of the ultraviolet light is absorbed in the portion covered with the transparent portion of the film, thereby suppressing fluorescent light emission. If the container itself is exposed due to a defect such as a break in the transparent portion, the absorption of ultraviolet light is impaired at the defect and the intensity of fluorescence emission increases. In addition, when the liquid filled in the container contains colloidal particles that cause the Tyndall phenomenon when irradiated with ultraviolet light, the container efficiently emits fluorescent light under the influence of the colloidal particles. Therefore, in an image where the transparent portion of the film has a defective portion, a clear difference in brightness occurs between the defective portion and the other portions. Therefore, it is possible to accurately determine whether or not there is a defective portion, thereby enhancing the reliability of the inspection.

In the above aspect, the illuminating means irradiates ultraviolet light showing a peak in a wavelength range of 360 to 380 nm to illuminate the container, and the filter means captures the image with respect to a wavelength range shorter than 400 nm. The wavelength range of said incident light may be adjusted so that its incidence on the means is restricted. In addition, the brightness of the fluorescence emission of the container illuminated by the illumination procedure is 5.6 times or more the average brightness of the fluorescence generated when the container is filled with water and irradiated with the ultraviolet light. may be filled in the container as the liquid. If the wavelength range of ultraviolet light and the characteristics of the filter means are set as described above, or if the type of liquid is set as described above, the contrast difference corresponding to the presence or absence of defects in the transparent portion of the film will appear more reliably. can be made

1 inspection device 2 bottle (container)
10 image acquisition device 11 illumination device (illumination means)
12 camera (imaging means)
13 filter (filter means)
20 processing unit 22 inspection unit (discrimination means)

Claims (5)

An inspection method for inspecting a container made of polyethylene terephthalate resin, to which a film having a transparent part containing biaxially oriented polystyrene is attached and filled with a liquid containing colloidal particles in which Tyndall phenomenon occurs when irradiated with ultraviolet light and
a step of irradiating the target region including the transparent portion with the ultraviolet light from the illumination means to illuminate the target region;
a procedure for capturing an image of the illuminated target area by an image capturing means;
a procedure for determining whether the transparent portion is good or bad based on the captured image of the target area;
including
In the imaging procedure, the wavelength range of incident light to the imaging means is reduced by filter means for limiting passage of the wavelength range of the ultraviolet light in comparison with the wavelength range of fluorescence generated by the irradiation of the ultraviolet light. A method of inspecting a container that adjusts and captures the image. In the step of illuminating, the illuminating means irradiates ultraviolet light showing a peak in a wavelength range of 360 to 380 nm to illuminate the container, and in the step of imaging, the filter means uses the filter means to a wavelength shorter than 400 nm. 2. The container inspection method according to claim 1, wherein the wavelength range of said incident light is adjusted so that the incident light to said imaging means is limited with respect to the wavelength range of . The brightness of the fluorescence emission of the container illuminated by the illumination procedure is 5.6 times or more the average brightness of the fluorescence generated when the container is filled with water and irradiated with the ultraviolet light. 3. The container inspection method according to claim 1, wherein the liquid is filled in the container as the liquid. An inspection device for inspecting a container made of polyethylene terephthalate resin, on which a film having a transparent part containing biaxially oriented polystyrene is mounted and filled with a liquid containing colloidal particles that causes the Tyndall phenomenon when irradiated with ultraviolet light. and
illuminating means for irradiating a target region including the transparent portion with the ultraviolet light to illuminate the target region;
imaging means for capturing an image of the illuminated target area;
filter means for adjusting the wavelength range of the incident light to the imaging means so that the passage of the wavelength range of the ultraviolet light is restricted in comparison with the wavelength range of fluorescence generated by the irradiation of the ultraviolet light; ,
and a determining means for determining whether the transparent portion is good or bad based on the captured image of the target area. The illumination means illuminates the container with ultraviolet light showing a peak in a wavelength range of 360 to 380 nm,
5. The container inspection apparatus according to claim 4, wherein the filter means adjusts the wavelength range of the incident light so that the incident light to the imaging means is limited in a wavelength range shorter than 400 nm.

Images