JP2024077666A - Container inspection method and inspection device - Google Patents

Abstract

[Problem] To provide a container inspection method suitable for detecting adhesion of liquid to the outer surface of a container. [Solution] In an inspection method including the steps of illuminating an inspection area of a container with excitation light in a wavelength range in which the container fluoresces, and detecting adhesion of liquid in the inspection area based on the brightness difference of the fluorescence in the inspection area illuminated with the excitation light, the wavelength range of the excitation light is set to a wavelength range in which the intensity of the fluorescence in the liquid is relatively lower than the intensity of the fluorescence generated in the container, and in which the transmission of the excitation light through the liquid is restricted so that the brightness difference that should occur between the container and the liquid attached to the container does not disappear. [Selected Figure] Figure 8

Description

The present invention relates to a container inspection method and device for detecting adhesion of liquid to the outer surface of a container.

Liquids, such as the contents to be filled into a container, may adhere to the outside surface of the container for some reason. Conventionally, whether or not liquid is attached to the outside surface of a container is inspected by a worker touching the container with his or her hand to check for the presence or absence of liquid. Incidentally, a method for detecting the presence of liquid using the fluorescence phenomenon has been proposed for detecting oil leaks from parts of plant equipment, etc., in which pulsed light containing the absorption wavelength of oil is irradiated onto the parts, and the fluorescence emitted by the oil molecules excited by the irradiation is captured to detect oil leaks (see Patent Document 1).

Japanese Patent Application Laid-Open No. 10-311771

The technique of Patent Document 1 may be applicable to detecting liquid adhering to the outer surface of a container if the liquid has the property of fluorescing. However, if the container itself fluoresces, both the container and the liquid adhering to its outer surface will fluoresce, making it difficult to distinguish between the container and the liquid on its outer surface. If the container is filled with a fluorescent liquid as its contents, even if the fluorescence from the liquid can be detected, it may be difficult to determine whether the fluorescence is coming from inside or outside the container. In either case, the adhesion of the liquid cannot be detected correctly, which is an inconvenience.

Therefore, the present invention aims to provide a container inspection method suitable for detecting adhesion of liquid to the outer surface of a container.

A method for inspecting a container according to one aspect of the present invention is a method for inspecting a container for detecting adhesion of a liquid to the outer surface of the container, and includes the steps of illuminating an inspection area of the container with excitation light in a wavelength range in which the container fluoresces, and detecting adhesion of the liquid in the inspection area based on the brightness difference of the fluorescence in the inspection area illuminated with the excitation light, and the wavelength range of the excitation light is set to a wavelength range in which the intensity of the fluorescence in the liquid is relatively lower than the intensity of the fluorescence generated in the container, and the transmission of the excitation light in the liquid is limited so that the brightness difference that should occur between the container and the liquid attached to the container does not disappear.

A container inspection device according to one aspect of the present invention is a container inspection device for detecting adhesion of liquid to the outer surface of a container, and includes an illumination means for illuminating an inspection area of the container with excitation light in a wavelength range in which the container fluoresces, an imaging means for capturing an image reflecting the brightness difference of the fluorescence in the inspection area illuminated with the excitation light, and a detection means for detecting adhesion of the liquid in the inspection area based on the brightness difference of the fluorescence in the image, and the wavelength range of the excitation light by the illumination means is set to a wavelength range in which the intensity of the fluorescence in the liquid is relatively lower than the intensity of the fluorescence generated in the container, and the transmission through the liquid is limited to a range in which the brightness difference that should occur between the container and the liquid attached to the container does not disappear.

FIG. 13 is a diagram showing an example of the results of measuring a three-dimensional fluorescence spectrum of rapeseed oil. FIG. 13 is a diagram showing an example of the results of measuring three-dimensional fluorescence spectra for other rapeseed oils with different added components. FIG. 13 is a diagram showing an example of the results of measuring a three-dimensional fluorescence spectrum of soybean oil. FIG. 1 shows an example of the results of measuring a three-dimensional fluorescence spectrum of rice bran oil. FIG. 13 is a diagram showing an example of the results of measuring a three-dimensional fluorescence spectrum of safflower oil. FIG. 13 is a diagram showing an example of the results of measuring a three-dimensional fluorescence spectrum of sesame oil. FIG. 1 shows an example of the results of measuring a three-dimensional fluorescence spectrum of olive oil. FIG. 13 is a diagram showing an example of a result of measuring a three-dimensional fluorescence spectrum of a resin container. FIG. 13 is a diagram showing an example of the results of measuring the light transmittance of edible oil. FIG. 1 is a diagram showing one embodiment of a container inspection device. FIG. 11 is a diagram showing another embodiment of the container inspection device. FIG. 13 is a diagram showing a further embodiment of the container inspection device. FIG. 7 is a side view of the inspection device of FIG. 6 . FIG. 13 is a diagram showing an example of an image obtained in Test Example 1. FIG. 13 is a diagram showing an example of a further image obtained in Test Example 1. FIG. 13 is a diagram showing an example of an image obtained in Test Example 2. FIG. 11 is a diagram showing an example of an image obtained in a comparative example.

One embodiment of the present invention will now be described with reference to the accompanying drawings. In this embodiment of the inspection method, excitation light in a specific wavelength range is irradiated onto an inspection area of a container, and adhesion of liquid to the outer surface of the container is detected based on the brightness difference in the inspection area of the fluorescence generated in response to the irradiation. The wavelength range of the excitation light is selected according to the material of the container and the type of liquid whose adhesion to the outer surface of the container is to be detected. Below, the wavelength range of the excitation light will be described using an example in which the container is made of resin and the liquid is edible oil to be filled into the container as the content liquid.

Figures 1A to 1G show the results of measuring three-dimensional fluorescence spectra that show the relationship between the excitation light irradiated on each sample and the fluorescence that occurs in response to that irradiation, using seven types of edible oil selected as samples. In each figure, the vertical axis represents the wavelength range of the excitation light, and the horizontal axis represents the wavelength range of the fluorescence. The edible oil samples are: rapeseed oil A in Figure 1A, rapeseed oil B in Figure 1B, soybean oil in Figure 1C, rice oil in Figure 1D, safflower oil in Figure 1E, sesame oil in Figure 1F, and olive oil in Figure 1G. Rapeseed oil A and rapeseed oil B have in common that they are both made from rapeseed, but have different added ingredients.

According to Figures 1A to 1G, although the fluorescence characteristics differ depending on the type of edible oil, in all cases, fluorescence occurs when the excitation light is in the wavelength range of approximately 260 nm to 400 nm. In the examples of Figures 1A to 1E, the fluorescence wavelength range is approximately 400 nm, but in the example of sesame oil in Figure 1F and the example of olive oil in Figure 1G, fluorescence occurs in the wavelength range of approximately 320 nm. However, all examples have in common that the fluorescence intensity decreases when the excitation light is in the wavelength range of approximately 280 nm or less, and almost no fluorescence occurs in the wavelength range from around 260 nm to the shorter wavelength side.

Figure 2 shows the results of measuring a three-dimensional fluorescence spectrum in a container made of polyethylene terephthalate resin (hereinafter referred to as PET resin). The vertical axis is the wavelength range of the excitation light, and the horizontal axis is the wavelength range of the fluorescence. According to Figure 2, in a container made of PET resin, when the excitation light is in the wavelength range of approximately 200 nm to 400 nm, fluorescence in the wavelength range of approximately 360 nm to 420 nm is generated. The wavelength range of the excitation light that causes fluorescence in the container is wider on the short wavelength side compared to the wavelength range of the excitation light that causes fluorescence in edible oil. Such characteristics are similar for containers made of resins other than PET resin.

Next, the results of investigating the light transmission spectrum of each sample of edible oil used in Figures 1A to 1G are shown in Figure 3. In Figure 3, the vertical axis is the light transmittance, and the horizontal axis is the light wavelength range. As is clear from Figure 3, in the case of edible oil, the light transmittance clearly drops in the region on the short wavelength side, with the wavelength between approximately 320 nm and 400 nm as the boundary. Focusing on the wavelength range around 280 nm, the transmittance of soybean oil, rice oil, safflower oil, and sesame oil is almost 0%, the transmittance of rapeseed oil A and B is approximately 10% or less, and even olive oil, which has the highest transmittance, has a transmittance that drops to around 45%. As for olive oil, its transmittance starts to drop in the wavelength range around 320 nm, and maintains a transmittance of about 45% in the wavelength range of approximately 270 nm to 280 nm, but the transmittance drops again on the shorter wavelength side, reaching a transmittance of almost 0% around 250 nm.

Considering the above three-dimensional fluorescence spectrum and transmission spectrum, in order to detect the adhesion of edible oil to the outer surface of a container, the wavelength range of the excitation light may be set as follows. First, the wavelength range capable of making the container fluoresce is wider toward the short wavelength side than the wavelength range capable of making the edible oil fluoresce. Focusing on this property, the wavelength range of the excitation light is set so that the container can be made to fluoresce and the intensity of the fluorescence in the edible oil is relatively lower than the intensity of the fluorescence generated in the container. That is, if the first requirement is that the wavelength range is capable of making the container fluoresce and the second requirement is that the wavelength range is that the intensity of the fluorescence in the edible oil is relatively lower than the intensity of the fluorescence generated in the container, the wavelength range of the excitation light is set to satisfy both the first and second requirements. This makes it possible to suppress the fluorescence of the edible oil attached to the outer surface of the container compared to that of the container while making the container fluoresce, and to generate a brightness difference in the fluorescence between the container and the edible oil. The greater the brightness difference between the container and the edible oil, the more advantageous it is for detecting adhesion of edible oil. Therefore, it is preferable that the wavelength range of the excitation light is one in which the edible oil does not fluoresce, or, even if it does fluoresce, the intensity of the fluorescence is clearly lower than the intensity of the fluorescence generated in the container.

On the other hand, even if the fluorescence in the edible oil is suppressed, when the excitation light passes through the edible oil attached to the outer surface of the container, the excitation light reaches the container behind the edible oil, generating fluorescence, which passes through the edible oil and is released to the outside. In this case, the fluorescence generated behind the edible oil is observed from the outside, and as a result, the difference in brightness between the container and the edible oil may be lost, making it difficult to distinguish between the two. In order to avoid such inconvenience, it is necessary to select an excitation light in a wavelength range in which the edible oil itself acts as a means for restricting the transmission of the excitation light. Specifically, it is sufficient to select an excitation light in a wavelength range in which the transmission of the excitation light in the edible oil is restricted so that the difference in brightness that should occur between the container and the edible oil does not disappear. In the following, the third requirement is that the wavelength range is one in which such a restricting effect occurs. Note that the disappearance of the difference in brightness here is not limited to the case where the difference in brightness is completely lost, but includes the concept of the difference in brightness being reduced to an unrecognizable level.

When the wavelength range of the excitation light satisfies the third requirement in addition to the first and second requirements, a contrast in fluorescence is generated between the container and the edible oil adhering to its outer surface, and the adhesion of edible oil to the outer surface of the container can be detected using this contrast as a clue. In order to generate a contrast between the container and the edible oil, it is advantageous to have a lower transmittance of the edible oil in the selected wavelength range. However, the transmittance of the excitation light through the edible oil does not need to be completely 0%. For example, if the transmittance of the edible oil in the wavelength range of the excitation light is at least 50% or less, preferably 30% or less, it may be possible to suppress the effect of the fluorescent emission of the container behind the edible oil on the contrast between the container and the edible oil.

Next, the wavelength ranges that satisfy the above-mentioned first, second and third requirements will be considered using the examples of Figures 1A to 1G and Figure 2. According to the example of Figure 2, it can be confirmed that in a resin container, if the excitation light is in the wavelength range of approximately 200 nm to 400 nm, fluorescence will be emitted. Therefore, if the wavelength range of the excitation light is set to 400 nm or less, the first requirement will be satisfied. On the other hand, according to the three-dimensional fluorescence spectrum of Figures 1A to 1G, if the wavelength range of the excitation light is 260 nm or less, the edible oil will hardly emit fluorescence. However, if the wavelength range of the excitation light is 280 nm or less, the intensity of the fluorescence is relatively low, and it is understood that the fluorescence emission of the edible oil can be suppressed to a degree that ensures a brightness difference between the container and the edible oil. Therefore, in order for the wavelength range of the excitation light to satisfy the second requirement, it is sufficient to set the wavelength range of the excitation light to 280 nm or less. Next, according to the light transmission spectrum of Figure 3, the transmittance of edible oil drops to 50% or less regardless of the type if it is approximately 280 nm or less, and if it is 260 nm or less, the transmittance drops to 30% or less. Therefore, it is believed that the third requirement is met regardless of the type of edible oil if the wavelength range of the excitation light is at least 280 nm or less, preferably 260 nm or less. Taking all of the above into consideration, in order to meet all of the first, second and third requirements, the wavelength range of the excitation light should be set to 280 nm or less, preferably 260 nm or less. Such a wavelength range is included in the wavelength range of ultraviolet light.

The lower limit of the wavelength range of the excitation light can be set appropriately as long as the first requirement is satisfied. According to FIG. 2, in a resin container, fluorescence occurs in a wavelength range of 200 nm or more. Since the wavelength range of 200 nm or less is a range called vacuum ultraviolet, in practice, the lower limit of the wavelength range of the excitation light may be set to 200 nm. Illumination light sources in the ultraviolet range that are relatively easily available on the market are 222 nm, 265 nm, and 280 nm. Illumination light sources in any wavelength range may be selected as a light source for irradiating excitation light. In particular, ultraviolet light of 222 nm is a wavelength that has been attracting attention in recent years as sterilizing ultraviolet light that has almost no effect on the human body, and is a light source for which technology development as sterilizing light is actively being carried out. Considering such a background, using ultraviolet light with a wavelength of 222 nm as excitation light can be a promising option. However, according to the above consideration, illumination light sources in the wavelength range of 265 nm or 280 nm may also be selected.

In the above description, an example is given in which the container is made of resin and the liquid to be detected for adhesion to its outer surface is edible oil. However, the combination of the container material and the type of liquid may be changed as appropriate as long as a wavelength range that satisfies all of the above-mentioned first, second, and third requirements can be selected. A container can be a candidate for the selection of a container that satisfies the first requirement if it has the property of emitting fluorescence at least in a specific wavelength range. A liquid does not necessarily have to have the property of emitting fluorescence. A liquid that does not emit fluorescence in any range, or that emits fluorescence but whose intensity is sufficiently lower than that of the container, can also be a candidate for the selection of a liquid that satisfies the second requirement. On the other hand, the light transmission characteristics of the liquid must have a transmission characteristic that allows a wavelength range that satisfies the third requirement to be selected in at least a part of the wavelength range that satisfies the first and second requirements. In the above example, if a wavelength range that satisfies the first and second requirements is selected, the third requirement will also be satisfied as a result. However, the sufficiency of the third requirement is not necessarily subordinate to the sufficiency of the first and second requirements. For example, if the third requirement is not met in a portion of the wavelength range that satisfies the first and second requirements, it is necessary to further narrow down the wavelength range of the excitation light by the third requirement.

In the above, the transmittance of the container to the excitation light was not considered. However, in a container made of PET resin, the transmittance decreases from around 360 nm to the short wavelength side, and the transmittance is almost 0% in the wavelength range of approximately 320 nm or less. In a container made of a resin other than PET resin, for example, a container made of polyethylene resin (hereinafter referred to as PE resin), the transmittance also decreases to almost 0% in the wavelength range of approximately 320 nm or less. Therefore, if the wavelength range of the excitation light is set to 280 nm or less as described above, the excitation light cannot pass through the container, and the excitation light is also prevented from entering the container. In this case, even if a substance that emits fluorescence in response to excitation light in the selected wavelength range is contained in the container, the diffused fluorescent light generated by the substance inside the container passes through the liquid attached to the container, and the difference in brightness between the container and the edible oil attached to its outer surface is not impaired as a result.

However, depending on the wavelength range of the excitation light, it is possible that the fluorescence generated within the container may impair the contrast between the container and the liquid adhering to its outer surface. In such a case, the wavelength range of the excitation light may be selected by further emphasizing that the wavelength range of the excitation light must be a wavelength range in which the transmission of the excitation light through the container is limited so that the contrast between the container and the edible oil adhering to its outer surface is not lost, as a fourth requirement that the wavelength range of the excitation light must satisfy. The concept of loss of contrast here includes not only cases in which the contrast is completely lost, but also cases in which the contrast is reduced to an unrecognizable degree. In addition, in cases in which the container is filled with edible oil, the second requirement selects excitation light in a wavelength range in which the fluorescence of the edible oil is suppressed. Therefore, even if the excitation light passes through the container and reaches the edible oil inside, there is no risk that the edible oil on the outer surface of the container and the edible oil inside the container will be difficult to distinguish due to the influence of the fluorescence generated by the edible oil inside.

Next, with reference to Figures 4 to 7, an example of an inspection device for detecting adhesion of liquid using the above-mentioned technique will be described. Figure 4 shows an example of an inspection device. The inspection device 1 is configured for the purpose of detecting adhesion of liquid to the outer surface of a bottle 2, which is an example of a container. The inspection device 1 includes an image acquisition unit 10 that acquires an image of the bottle 2, and a processing unit 20 that processes the acquired image to detect adhesion of liquid to the outer surface of the container.

The bottle 2 is, for example, hollow and cylindrical or polyhedral in shape, made of PET resin. However, the container is not limited to the bottle 2 made of PET resin. The container may be made of various materials as long as it has the property of emitting fluorescence when irradiated with excitation light. For example, containers made of other resin materials such as PE resin, PP (polypropylene) resin, COP (cycloolefin polymer) resin, glass, etc. may be targeted. The liquid to be detected for adhesion to the outer surface of the bottle 2 may be, for example, edible oil to be filled into the bottle 2 as the liquid content. However, the type of liquid may also be changed as appropriate as long as it satisfies the second and third requirements described above.

As an example, the bottle 2 is held in an upright state with its mouth facing up and its axis AX aligned vertically. The image acquisition unit 10 includes an illumination device 11 as an example of illumination means for illuminating at least the inspection range of the bottle 2 with excitation light in a predetermined wavelength range, and an imaging device 12 as an example of imaging means for imaging the bottle 2. The wavelength range of the excitation light irradiated by the illumination device 11 is set to a wavelength range that satisfies the above-mentioned first requirement, second requirement, and third requirement. Furthermore, the wavelength range of the excitation light may be set to satisfy the fourth requirement. The illumination device 11 includes a plurality of illuminators 11a arranged symmetrically on either side of the imaging optical axis Lp of the bottle 2 by the imaging device 12. The number of illuminators 11a may be changed as appropriate. The illumination device 11 may be configured with a single illuminator 11a.

The imaging device 12 is equipped with a camera 13 that captures the inspection range of the bottle 2 illuminated by the lighting device 11. The optical axis of the camera 13 corresponds to the imaging optical axis Lp of the imaging device 12. The camera 13 converts the optical image of the bottle 2 into an electrical image signal using an imaging element such as a CCD or CMOS. The camera 13 must be set to a wavelength range of the imaging target so that it can capture an image that reflects the brightness difference of the fluorescence generated in the bottle 2 in response to the illumination by the lighting device 11. For example, as shown in FIG. 2, in a resin container, fluorescence in a wavelength range of approximately 360 nm to 420 nm is generated in response to irradiation with excitation light in a wavelength range of 200 nm to 400 nm, so it is sufficient for the camera 13 to have sensitivity in at least a part of the wavelength range of 360 nm to 420 nm. Commercially available cameras for the visible light range have sensitivity in the vicinity of 400 nm, and in some cases, up to a wavelength range slightly shorter than that. Therefore, a camera for the visible light range can be used. Since the excitation light may be reflected on the bottle 2 and enter the camera 13, the imaging device 12 may further include a filter that blocks reflected light of the excitation light from entering the camera 13. However, as described above, the wavelength range of the excitation light is expected to be set to a short wavelength range of 280 nm or less, and the camera 13 often has no sensitivity to this wavelength range. Therefore, even if the filter is omitted, there is no risk that the brightness difference of the image captured by the camera 13 will be impaired by the influence of reflected light, and it is not necessary to provide a filter.

The inspection range of the bottle 2 may be the whole bottle 2 or a part of it. That is, the inspection range may be changed as appropriate, and the configuration and lighting direction of the lighting device 11 may also be changed as appropriate to match the inspection range of the bottle 2. FIG. 4 shows an example in which the shoulder of the bottle 2 is set as the inspection range, and the camera 13 is arranged to image the bottle 2 from vertically above with its imaging optical axis Lp aligned with the axis line AX of the bottle 2. The lighting device 11 is arranged to illuminate the shoulder of the bottle 2 from diagonally above with multiple illuminators 11a arranged symmetrically around the imaging optical axis Lp. In FIG. 5, the camera 13 is arranged in the same manner as in FIG. 4, while the lighting device 11 is arranged to illuminate the shoulder of the bottle 2 from diagonally above with one or more illuminators 11a arranged on one side of the imaging optical axis Lp. The example in FIG. 5 is applicable when only a portion of the shoulder of the bottle 2 is to be inspected, but it is also possible to capture an image of the entire circumference of the shoulder of the bottle 2 as the inspection range by rotating the bottle 2 about its axis AX or by rotating the lighting device 11 about the axis AX.

6 and 7 show an example in which the camera 13 is arranged to capture an image of the bottle 2 from its side, and the lighting device 11 is arranged with multiple illuminators 11a arranged symmetrically on either side of the imaging optical axis Lp of the camera 13. In this arrangement, an image can be captured by including at least a part of the body of the bottle 2 in the inspection range. The shoulder and neck of the bottle 2 can also be included in the inspection range. By rotating the bottle 2 around the axis AX, or by rotating the illuminators 11a and the camera 13 around the axis AX, it is possible to capture an image of the entire circumference of the bottle 2 as an inspection range. Furthermore, although not shown, it is also possible to capture an image of the bottom of the bottle 2 and detect the adhesion of liquid to the bottom by arranging the camera 13 to capture an image of the bottle 2 from below and arranging the lighting device 11 to illuminate the bottom of the bottle 2 from an oblique direction. The lighting device 11 may be constantly lit or may be lit in a pulsed manner at a predetermined cycle.

The illumination light for the bottle 2 in the environment in which the image acquisition unit 10 is installed may include ambient light in the visible range, for example, natural light, so long as the bottle 2 is illuminated mainly by excitation light from the lighting device 11 and an image reflecting the brightness contrast of the fluorescence generated in the bottle 2 is captured by the camera 13. In other words, the ambient light may be blocked and the bottle 2 may be illuminated only by excitation light from the lighting device 11, or some ambient light may be allowed to enter the bottle 2 as long as it does not substantially affect the image reflecting the brightness contrast of the fluorescence. Alternatively, a filter may be used to remove the effects of visible light that is unnecessary for capturing an image reflecting the brightness contrast of the fluorescence from the image captured by the camera 13.

Returning to FIG. 4, the processing unit 20 of the inspection device 1 will be described. Although the processing unit 20 is omitted in FIGS. 5 to 7, the processing unit 20 is provided in the examples of FIGS. 5 to 7 as in FIG. 4. The processing unit 20 detects the adhesion of liquid in the inspection range of the bottle 2 based on the difference in brightness of the fluorescence in the image captured by the image acquisition unit 10. As an example, the processing unit 20 is configured using a computer unit including a CPU and an internal storage device required for its operation. The processing unit 20 is provided with an image adjustment unit 21 and a detection unit 22. The image adjustment unit 21 and the detection unit 22 are provided as logical devices realized by, for example, a combination of the computer hardware of the processing unit 20 and an inspection program PG, which is an example of a computer program as software. However, at least a part of the processing unit 20 may be configured as a physical device combining logic circuits such as an LSI. 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 device 1 to input appropriate instructions. The input means are omitted from FIG. 1.

The image adjustment unit 21 receives the image signal output from the camera 13, and performs image processing suitable for the inspection by the detection unit 22, thereby adjusting the image captured by the camera 13 to an image suitable for the processing by the detection unit 22. For example, the image adjustment unit 21 may perform correction processing such as correction of the brightness and contrast of the image. The detection unit 22 receives the image signal processed by the image adjustment unit 21, and detects the adhesion of liquid within the inspection range of the bottle 2. Thereby, the detection unit 22 functions as an example of a detection means, and the processing corresponds to an example of a procedure for detecting an object.

The process of the detection unit 22 detects the adhesion of liquid based on the difference in brightness of the fluorescence in the inspection range. That is, when the inspection range is illuminated with excitation light in a wavelength range that satisfies the above-mentioned first to third requirements, and further satisfies the fourth requirement as necessary, the intensity of the fluorescence in the area where the liquid is attached will be relatively low compared to the intensity of the fluorescence generated in other areas of the container. Therefore, if the process of the detection unit 22 is configured to determine whether or not a dark area corresponding to the adhesion of liquid appears in the image captured by the camera 13, and to determine that the adhesion of liquid has been detected if such a dark area is present, it will be possible to detect the adhesion of liquid based on the difference in brightness in the image.

The processing of the detection unit 22 may be appropriately configured as long as it includes processing for detecting the adhesion of liquid to the outer surface of the container based on the brightness difference of the fluorescence in the image. For example, the detection unit 22 may be configured to prepare an image of a normal bottle 2 with no liquid attached as a reference image, and detect the adhesion of liquid by calculating the difference between the image of the inspection range actually captured and the reference image. The processing of the detection unit 22 may include at least a part of the content of detecting the adhesion of liquid. The detection unit 22 may be configured to determine the presence or absence of adhesion of liquid, but is not necessarily limited to this. For example, the processing of the detection unit 22 may be configured to further determine the position of the area where the liquid is attached, the area of the area, etc. If the thickness of the liquid attached to the outer surface of the container is reflected in the brightness of the dark part itself in the image, the physical quantity such as the thickness of the liquid or the amount of adhesion may be further estimated using the brightness of the dark part as a clue.

When the detection unit 22 detects the adhesion of liquid, the processing unit 20 may display the fact as an inspection result on the monitor 23 or store it in the storage device 24. The inspection result may include information such as the position of the area where the liquid is attached and the area of the attached liquid. When the content liquid to be filled into the bottle 2 is attached to the outer surface of the bottle 2, the content liquid may have splashed outside the bottle 2 during the process of filling the bottle 2 with the content liquid, or the content liquid may have leaked from the bottle 2. The processing unit 20 may determine that the bottle 2 on which the adhesion of the content liquid is detected is an abnormal product and output the determination result as the inspection result, and in that case, may also notify of a defect in the filling process or a possibility of liquid leakage from the bottle 2. The output means of the inspection result is not limited to the monitor 23 and the storage device 24, and a printer may be connected as the output means.

Next, using the image acquisition unit 10 of the inspection device 1 of this embodiment, an image of a container with liquid attached was actually taken, and the results of a test to see whether or not a difference in brightness of the fluorescence appeared in the obtained image will be described along with the following test examples 1 and 2 and a comparative example.

(Test Example 1)
First, the effect of selecting ultraviolet light with a wavelength of 222 nm as the excitation light was confirmed. The illumination and imaging conditions were as follows. In Test Example 1, a PET resin bottle, a PE resin bottle, and a glass bottle were selected as containers. Of the edible oil samples used in the measurements of Figures 1A to 1G, rapeseed oil A, sesame oil, and olive oil were targeted as liquids. The containers were filled with the samples and sealed with caps. The inspection range of the container was set to the shoulder, and the sample edible oil was attached to a part of it. The imaging direction was vertically downward.
Illumination conditions Four Care222 illuminators manufactured by Ushio Inc. were used as illuminators, and these illuminators were arranged at equal intervals around the axis of the bottle as shown in Fig. 4. The illuminators irradiate ultraviolet light with a peak wavelength of 222 nm, with an upper limit wavelength of 250 nm or less. The depression angle of each illuminator, i.e., the angle at which the central axis of the illumination light is tilted downward with respect to the horizontal plane, was set to approximately 20°, and the distance from the light-emitting surface of each illuminator to the shoulder of the bottle was set to approximately 80 mm. The excitation light was continuously irradiated.
Imaging conditions ID2MB-CLKTS2 manufactured by Idjour Co., Ltd. was used as the camera, and the camera was placed vertically downward on the axis of the bottle as shown in FIG. 4. The camera is a monochrome camera with a resolution of 2 million pixels using a CMOS sensor. The camera lens is TC1614-3MP manufactured by Kenko Tokina Co., Ltd., with a focal length of 16 mm, and was used with an aperture of 1.4. The shutter speed is 1/30, the imaging distance of the camera is approximately 230 mm, and the imaging range is approximately 160 mm x 85 mm. In addition, a bandpass filter BP550 manufactured by Midwest Optical Systems, Inc. (abbreviated as MidOpt), a US corporation, was attached to the lens to limit the incidence of light in the wavelength range of approximately 400 nm or less into the camera. In addition, in the images shown below, the areas corresponding to the caps attached to each container are processed to be dark areas. In addition, the images in each figure are cropped somewhat left and right relative to the camera's imaging range in order to exclude areas other than the container.

The images obtained in Test Example 1 are shown in Figures 8 and 9. Figure 8 shows examples of images obtained when a PET resin container was selected, with (a) showing rapeseed oil A, (b) showing sesame oil, and (c) showing olive oil. In each image, it can be seen that dark areas have appeared in region X. These dark areas roughly correspond to the areas where the sample edible oil was applied.

9 shows examples of images obtained when a PE resin container and a glass bottle are selected as the container instead of a PET resin container, and rapeseed oil A is selected as the liquid, with (a) showing the case of a PE resin container and (b) showing the case of a glass bottle. The lighting conditions and imaging conditions are the same as those in the example of FIG. 8, and the container is filled with the sample and sealed. As is clear from these figures, it can be confirmed that in both the PE resin container and the glass bottle, a dark area indicating adhesion of edible oil appears in region X. Also, according to FIG. 9(b), it can be confirmed that the present invention can detect adhesion of liquid even in containers made of materials other than resin, because a dark area indicating adhesion of edible oil appears in region X not only in the resin container but also in the glass bottle.

(Test Example 2)
Next, the effect of selecting the wavelength of 280 nm, which was given as an example above as a guideline, as the wavelength of the excitation light was confirmed. The lighting and imaging conditions were as follows. In Test Example 1, a bottle made of PET resin was selected as the container. Of the edible oil samples used in the measurements of Figures 1A to 1G, rapeseed oil A, sesame oil, and olive oil were targeted as the liquids. The container was filled with the sample and sealed with a cap.
Illumination conditions: Two KTDBA-43_18UV-280 illuminators manufactured by Raymac Co., Ltd. were used, and these illuminators were placed on one side of the axis of the bottle as shown in Figure 5. The illuminators irradiate ultraviolet light with a peak wavelength of 280 nm, with a lower limit wavelength of 250 nm or more. The depression angle of each illuminator was set to approximately 15°, and the distance from the light-emitting surface of each illuminator to the shoulder of the bottle was set to approximately 40 mm. The excitation light was pulsed at a constant frequency.
Imaging Conditions The shutter speed was changed to 1/250 compared to Test Example 1, and the rest was set to the same as Test Example 1.

Examples of images obtained in Test Example 2 are shown in Figure 10. Figure 10(a) shows the case of rapeseed oil A, (b) shows the case of sesame oil, and (c) shows the case of olive oil. In all images, it can be seen that dark areas indicating adhesion of edible oil appear in region X. According to Figure 3, for olive oil, the light transmittance in the wavelength range around 280 nm is higher than other edible oils, being approximately 45%, but even in this case, dark areas appear as shown in Figure 10(c), so it can be seen that excitation light with a wavelength of 280 nm can be selected as excitation light capable of detecting adhesion of edible oil.

Comparative Example
For comparison with Test Examples 1 and 2, the effect of selecting a wavelength of 365 nm as the wavelength of excitation light was confirmed. The container and liquid used in the comparative example were the same as those in Test Example 1. The illumination and imaging conditions were as follows.
Illumination conditions One Kyoto Denki Co., Ltd. KDUV-L110-4236A illuminator was used, and the illuminator was placed on one side of the axis of the bottle as shown in Figure 5. The illuminator irradiates ultraviolet light with a peak wavelength of 365 nm. The depression angle of the illuminator was set to approximately 10°, and the distance from the light-emitting surface of the illuminator to the shoulder of the bottle was set to approximately 80 mm. The excitation light was pulsed at a constant frequency.
Imaging Conditions The shutter speed was changed to 1/1000 in comparison with Test Example 1, and the rest was set to the same as Test Example 1.

An example of an image obtained in the comparative example is shown in FIG. 11. FIG. 11(a) shows the case of rapeseed oil A, FIG. 11(b) shows the case of sesame oil, and FIG. 11(c) shows the case of olive oil. In all images, no dark areas indicating the adhesion of liquid appear in the bright areas corresponding to the fluorescence of the container. When the excitation light is in the wavelength range of about 365 nm, as is clear from FIG. 1A, FIG. 1F, and FIG. 1G, all of the sample rapeseed oil A, sesame oil, and olive oil emit fluorescence, and as is clear from FIG. 3, the transmittance of rapeseed oil A and olive oil is almost 100%, and even sesame oil, which has the lowest transmittance, shows a transmittance of about 60%. Therefore, it is considered that the wavelength range of the excitation light does not satisfy at least one of the above-mentioned second and third requirements, and the difference in brightness is lost due to the fluorescence of the edible oil or the fluorescence of the container behind the edible oil.

The present invention is not limited to the above-mentioned embodiment, and may be embodied in an appropriate modified or altered form. For example, the combination of container and liquid can be appropriately selected as long as a wavelength range that satisfies the first to third requirements, and further the fourth requirement if necessary, can be found. To the extent that there is a need to inspect the adhesion of liquid to the outer surface of a container, the present invention is applicable as a method and device for detecting the adhesion of liquid to the outer surface of a container, regardless of whether the container is filled with the liquid content.

In the above embodiment, the imaging device 12 including the camera 13 is used as the imaging means, but the imaging means is not necessarily limited to the example using a camera. In the inspection of the present invention, if data showing the brightness difference between the container and the liquid attached to its outer surface can be obtained, it is possible to detect the adhesion of the liquid based on the brightness difference of the fluorescence shown in the data. Therefore, data reflecting the brightness difference of the fluorescence may be obtained using various sensors that output detection signals according to the intensity of the fluorescence to be detected, and the adhesion of the liquid may be detected based on the brightness difference of the fluorescence in the obtained data. For example, data showing the brightness difference of the fluorescence in the inspection range may be obtained using a light intensity sensor having a two-dimensional planar detection range. Alternatively, data showing the brightness difference of the fluorescence in the inspection range may be obtained by scanning the inspection range with a one-dimensional light intensity sensor (line sensor). The data obtained in this way is substantially equivalent to the image data obtained by the camera 13 of the above embodiment in that it has a signal intensity showing the brightness difference of the fluorescence. Therefore, such data is also included in the concept of "image" in the present invention, and various sensors for obtaining such data are also included in the concept of "imaging means" in the present invention.

Various aspects of the present invention derived from each of the above-mentioned embodiments and modifications are described below. In the following description, the corresponding components shown in the attached drawings are noted in parentheses to facilitate understanding of each aspect of the present invention, but this does not limit the present invention to the illustrated forms.

A method for inspecting a container according to one aspect of the present invention is a method for inspecting a container (2) for detecting adhesion of a liquid to the outer surface thereof, and includes the steps of illuminating an inspection area of the container with excitation light in a wavelength range in which the container fluoresces, and detecting adhesion of the liquid in the inspection area based on the brightness difference of the fluorescence in the inspection area illuminated with the excitation light, the wavelength range of the excitation light being set to a wavelength range in which the intensity of the fluorescence in the liquid is relatively lower than the intensity of the fluorescence generated in the container, and the transmission of the excitation light in the liquid is restricted so that the brightness difference that should occur between the container and the liquid attached to the container does not disappear.

If the wavelength range of the excitation light is set as described above, the container will fluoresce, but the fluorescence of the liquid attached to the outer surface of the container will be suppressed more than the fluorescence of the container, resulting in a difference in brightness between the two. Furthermore, by limiting the transmission of the excitation light through the liquid, the fluorescence of the container behind the liquid, i.e., in the area where the liquid is attached, is also suppressed, ensuring a difference in brightness between the container and the liquid attached to its outer surface. Therefore, if liquid is attached to the outer surface of the container, the area where the liquid is attached will be relatively dark compared to other areas of the container. Therefore, by utilizing the difference in brightness of the fluorescence that occurs in response to illumination by the excitation light, it is possible to detect the attachment of liquid to the outer surface of a container.

In the inspection method of the above aspect, the wavelength range of the excitation light may be further set to a wavelength range in which the transmission of the excitation light through the container is limited so that the brightness difference that should occur between the container and the liquid adhering to the container does not disappear. When the transmission of the excitation light through the container is also limited, it is possible to avoid the inconvenience of the disappearance of the brightness difference that should occur between the container and the liquid adhering to its outer surface due to the influence of the fluorescence, even if a substance that fluoresces when irradiated with the excitation light is present in the container.

The liquid may be the liquid content to be filled into the container. This makes it possible to detect splashing of the liquid content outside the container when filling the container, or adhesion of the liquid content to the outer surface of the container due to leakage from the container, etc.

The liquid may be edible oil to be filled into the container as the liquid content, and the wavelength range of the excitation light may be set to a wavelength range of 280 nm or less. This allows for proper detection of adhesion of the edible oil to be filled into the container to the outer surface of the container.

In the detection step, an image reflecting the contrast in the fluorescence in the inspection range illuminated by the excitation light may be captured, and the adhesion of the liquid in the inspection range may be detected based on the contrast in the fluorescence in the image. In this way, the adhesion of the liquid to the outer surface of the container can be detected by image processing technology.

A container inspection device (1) according to one aspect of the present invention is a container inspection device for detecting adhesion of a liquid to the outer surface of a container (2), and includes an illumination means (11) for illuminating an inspection area of the container with excitation light in a wavelength range in which the container fluoresces, an imaging means (12) for capturing an image reflecting the brightness difference of the fluorescence in the inspection area illuminated with the excitation light, and a detection means (22) for detecting adhesion of the liquid in the inspection area based on the brightness difference of the fluorescence in the image, and the wavelength range of the excitation light by the illumination means is set to a wavelength range in which the intensity of the fluorescence in the liquid is relatively lower than the intensity of the fluorescence generated in the container, and the transmission through the liquid is limited to a range in which the brightness difference that should occur between the container and the liquid attached to the container does not disappear.

The inspection device of the above aspect can realize the inspection method of the above aspect using image processing technology, and can provide a container inspection device suitable for use in detecting liquid on the outer surface of a container.

In the inspection device of the above aspect, as in the inspection method of the above aspect, the wavelength range of the excitation light may be set to a wavelength range in which the transmission of the excitation light through the container is limited so that the brightness difference between the container and the liquid attached to the container is not lost. The liquid may be the content liquid to be filled into the container. The liquid may be edible oil to be filled into the container, and the wavelength range of the excitation light may be set to a wavelength range of 280 nm or less.

REFERENCE SIGNS LIST 1 container inspection device 2 bottle 10 image acquisition unit 11 lighting device 12 imaging device 13 camera 20 processing unit 22 detection unit

Claims (9)

1. A method for inspecting a container to detect adhesion of a liquid to an outer surface of the container, comprising:
illuminating an inspection area of the container with excitation light having a wavelength range in which the container emits fluorescence;
detecting adhesion of the liquid in the inspection area based on a brightness difference of the fluorescence in the inspection area illuminated by the excitation light;
Including,
A method for inspecting a container, in which the wavelength range of the excitation light is set to a wavelength range in which the intensity of fluorescence in the liquid is relatively lower than the intensity of fluorescence generated in the container, and the transmission of the excitation light in the liquid is limited so that the brightness difference that should occur between the container and the liquid attached to the container does not disappear. The method for inspecting a container according to claim 1, further comprising setting the wavelength range of the excitation light to a wavelength range that limits the transmission of the excitation light through the container so that the brightness difference that should occur between the container and the liquid attached to the container is not lost. The method for inspecting a container according to claim 1, wherein the liquid is a liquid content to be filled into the container. The container inspection method according to claim 1, wherein the liquid is edible oil to be filled into the container as the liquid content, and the wavelength range of the excitation light is set to a wavelength range of 280 nm or less. The container inspection method according to any one of claims 1 to 4, wherein the detection step involves capturing an image reflecting the contrast in the fluorescence in the inspection range illuminated by the excitation light, and detecting the adhesion of the liquid in the inspection range based on the contrast in the fluorescence in the image. A container inspection device for detecting adhesion of a liquid to an outer surface of a container, comprising:
an illumination means for illuminating an inspection area of the container with excitation light having a wavelength range in which the container emits fluorescence;
an imaging means for capturing an image reflecting a contrast between the brightness of the fluorescence in the inspection area illuminated by the excitation light;
a detection means for detecting adhesion of the liquid in the inspection area based on a brightness difference of the fluorescent light in the image;
Including,
A container inspection device in which the wavelength range of the excitation light from the lighting means is set to a wavelength range in which the intensity of fluorescence in the liquid is relatively lower than the intensity of fluorescence generated in the container, and the transmission through the liquid is limited to a range in which the brightness difference that should occur between the container and the liquid attached to the container is not lost. The method for inspecting a container according to claim 6, further comprising setting the wavelength range of the excitation light to a wavelength range that limits the transmission of the excitation light through the container so that the brightness difference between the container and the liquid adhering to the container is not lost. The method for inspecting a container according to claim 6 or 7, wherein the liquid is a liquid content to be filled into the container. The container inspection method according to claim 6 or 7, wherein the liquid is edible oil to be filled into the container, and the wavelength range of the excitation light is set to a wavelength range of 280 nm or less.

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