JP7740692B2 - Container image acquisition device and image acquisition method, and container inspection device and inspection method using the same - Google Patents

Description

The present invention relates to a device for acquiring images for inspecting containers that have a light-transmitting portion that is translucent to visible light and has an inspection target such as a light-shielding marking attached to it.

One known method for inspecting character strings or the like on the surface of transparent or translucent resin containers is to inspect mold numbers engraved as a raised or recessed pattern on PET (abbreviation for polyethylene terephthalate; the same applies hereinafter) resin preforms. This method involves illuminating the preform from behind, capturing an image of the preform observed from the front, and inspecting the appropriateness of the engraved portion based on the image (see Patent Document 1).

JP 2012-150072 A

When the inspection method of Patent Document 1 is applied to inspecting containers filled with liquid, illumination light enters the container from the back side, passes through the interior of the container, exits from the front side, and enters the camera. As a result, water droplets or bubbles (hereinafter sometimes referred to as water droplets, etc.) adhering to the inner wall of the container appear as dark areas in the image, which may reduce the accuracy of detecting inspection targets such as markings.

The present invention aims to provide an image acquisition device and method for acquiring inspection images that minimize the effects of water droplets and other substances inside the container and produce sufficient contrast between the object being inspected and other areas, as well as a container inspection device and method that can be used to improve inspection accuracy.

An image acquisition device according to one aspect of the present invention is an image acquisition device that acquires an inspection image for inspecting the quality of an inspection object in a container filled with a liquid, the container having a light-transmitting section that is transmissive to visible light and has a light-blocking property to the visible light higher than the light-transmitting section. The image acquisition device includes: an illumination means that can irradiate a target area including the inspection object with first illumination light in the wavelength range of near-infrared light and second illumination light in the wavelength range of visible light; an imaging means that captures a first image of the target area in the wavelength range of the first illumination light that has passed through the container; and a second image of the target area in the wavelength range of the second illumination light that has passed through the container; and an image processing means that generates an image of the difference in brightness between the first image and the second image as the inspection image.

An image acquisition method according to one aspect of the present invention is a method for acquiring an inspection image for inspecting the quality of an inspection object in a container filled with a liquid, the container having a light-transmitting section that is more light-blocking to visible light than the light-transmitting section, the inspection object being disposed in the light-transmitting section. The image acquisition method includes the steps of: irradiating a target area including the inspection object with first illumination light in the wavelength range of near-infrared light and second illumination light in the wavelength range of visible light; capturing a first image of the target area in the wavelength range of the first illumination light that has passed through the container; and capturing a second image of the target area in the wavelength range of the second illumination light that has passed through the container; and generating an image of the difference in brightness between the first image and the second image as the inspection image.

A container inspection device according to one aspect of the present invention includes the image acquisition device according to the above aspect and a discrimination means for discriminating whether the inspection object is good or bad based on the contrast in the inspection image generated by the image processing means. A container inspection method according to one aspect of the present invention includes the steps of acquiring an inspection image using the image acquisition method according to the above aspect and discriminating whether the inspection object is good or bad based on the contrast in the acquired inspection image.

1 is a diagram showing an example of a basic configuration of a container inspection device according to an embodiment of the present invention; FIG. 2 is a diagram showing an example of the configuration of an illumination device and an imaging device. FIG. 10 is a diagram showing another example of the configuration of the lighting device and the imaging device. FIG. 10 is a diagram showing yet another example of the configuration of the lighting device and the imaging device. FIG. 4 is a diagram showing an example of the spectral sensitivity characteristics of a camera that can be used in the examples of FIGS. 2 and 3 . FIG. 5 is a diagram showing an example of the spectral sensitivity characteristics of a camera that can be used in the example of FIG. 4 . FIG. 4 is a diagram showing an example of a first image. FIG. 10 is a diagram showing an example of a second image. 9 is a diagram showing a difference image between the first image in FIG. 7 and the second image in FIG. 8 .

[Basic configuration]
First, the basic configuration of a container inspection device according to one embodiment of the present invention will be described. FIG. 1 shows an example of the basic configuration of the inspection device 1. The inspection device 1 is configured to inspect a bottle 2 made of PET resin, which is an example of a container. The bottle 2 has a print unit 3 slightly below a support ring 2a, which is an example of an inspection target. The bottle 2 is filled with a beverage, which is an example of a liquid. The top opening of the bottle 2 is sealed with a cap 4. The print unit 3 is located slightly above the liquid level L of the contents. Water droplets from the beverage may adhere to the inner wall of the bottle 2. FIG. 1 shows a water droplet D adhering behind a portion of the print unit 3. Note that FIG. 1 shows the number string "123" printed on the print unit 3, but this is just an example. The print unit 3 is formed by printing information such as the manufacturing date when the bottle was filled with liquid and sealed, using an inkjet printer. However, the content of the print unit 3 and its formation method may be modified as appropriate.

The base material of bottle 2 is a translucent portion that is translucent to visible light. Translucency is a concept that encompasses both transparency and translucency. Printed portion 3 has a higher degree of light-blocking ability to visible light than the base material portion of bottle 2 (transparent or translucent portion) that acts as a translucent portion. Inspection device 1 utilizes the visible light-blocking ability of printed portion 3 and its translucency to near-infrared light to obtain an inspection image that ensures sufficient contrast between printed portion 3 and other portions while suppressing the effects of water droplets, etc., and is intended to use the obtained inspection image to inspect the quality of printed portion 3 with high precision.

In other words, given its purpose, the printed portion 3 is designed to be clearly distinguishable from the bottle 2's base material in the visible light wavelength range. Therefore, if the bottle 2's base material is a light-transmitting portion that is translucent in the visible light wavelength range, the printed portion 3 is formed to have higher light-blocking properties than the base material. Meanwhile, near-infrared light passes through not only the bottle 2's base material but also the printed portion 3. Therefore, by capturing a first image in the near-infrared wavelength range of a specific area including the printed portion 3 of the bottle 2 and a second image in the visible light wavelength range of the same area, and then generating an image representing the difference between the two images as a test image, the resulting test image can produce a sufficient contrast between the printed portion 3 and other areas (including areas with water droplets, etc.). By comparing the printed portion 3 identified in the test image with a normal printed portion 3, the quality of the printed portion 3 can be inspected with high accuracy.

The inspection device 1 includes an image acquisition device 10 for acquiring the above-mentioned inspection images. The image acquisition device 10 includes an illumination device 11 as an example of an illumination means for illuminating the bottle 2, and an imaging device 12 as an example of an imaging means for capturing an image of the bottle 2. The illumination device 11 and imaging device 12 can be configured as appropriate. Examples of these will be described later. In Figure 1, the illumination device 11 is depicted as illuminating the bottle 2 from the side of the printing unit 3, and the imaging device 12 as capturing an image of the bottle 2 from the opposite side. However, this is a modified composition to facilitate understanding and does not represent the actual arrangement. In an actual inspection, the inspection target, such as the printing unit 3, faces the imaging device 12, and the illumination device 11 is positioned to illuminate the bottle 2 from the opposite side.

The lighting device 11 is capable of irradiating the target area TA, including the printed portion 3 of the bottle 2, with first illumination light in the near-infrared wavelength range and second illumination light in the visible wavelength range. As described above, the base portion of the bottle 2 is translucent to the second illumination light, and the printed portion 3 has a higher light-blocking property to the second illumination light than the base portion of the bottle 2. On the other hand, both the transparent portion of the bottle 2 and the printed portion 3 are translucent to the first illumination light.

In Figure 1, the lighting device 11 is shown illuminating the printed area 3 and its vicinity, but the illumination range may be changed as appropriate as long as it can illuminate the target area TA, which is set to include at least the printed area 3, with an illumination intensity suitable for inspection. For example, the entire bottle 2 may be illuminated, or only a portion of the bottle 2 may be illuminated. Illumination by the lighting device 11 means irradiating the target area TA of the bottle 2 with illumination light so as to obtain the contrast required for inspection. The illumination light irradiated onto the bottle 2 with this intention is only the illumination light from the lighting device 11; no other illumination light is irradiated onto the bottle 2. However, this does not exclude the presence of illumination light or natural light in the environment in which the bottle 2 is placed.

The imaging device 12 includes at least one camera 13. The camera 13 photoelectrically converts an optical image of the target area TA of the bottle 2 using an imaging element 14, such as a CCD or CMOS, to generate an electronic image and output an image signal corresponding to the electronic image. The camera 13 is configured to direct illumination light that has passed through the bottle 2 to the imaging element 14. The imaging range of the camera 13 is set so that it can capture an image of the target area TA that includes at least the printed portion 3. The images captured by the camera 13 are of two types: a first image of the target area TA in the wavelength range of the first illumination light that has passed through the bottle 2, and a second image of the target area TA in the wavelength range of the second illumination light that has passed through the bottle 2. The camera 13 may be controlled to capture an image of a range wider than the target area TA, extract an image corresponding to the target area TA from the obtained image, and output an image signal for the target area TA.

[Configuration example of lighting device and imaging device]
Next, several examples of the configuration of the illumination device 11 and the imaging device 12 will be described with reference to Figures 2 to 4. Note that in Figures 2 to 4, the illumination device 11 and the imaging device 12 are appropriately distinguished by adding suffixes A, B, etc., but the basic configuration in all examples is the same as that described in Figure 1.

(First Configuration Example)
FIG. 2 shows a first configuration example. In the example of FIG. 2, an illumination device 11A and an imaging device 12A are configured to inspect bottles 2 moving in a conveying direction F along a conveying path CP of a conveying device 5. The illumination device 11A includes a first illuminator 15A that illuminates the bottles 2 at a first position P1 set on the conveying path CP and a second illuminator 15B that illuminates the bottles 2 at a second position P2 on the conveying path CP that is different from the first position P1. The first illuminator 15A irradiates the bottles 2 with only first illumination light in the near-infrared wavelength range emitted from a light source 15a, while the second illuminator 15B irradiates the bottles 2 with only second illumination light in the visible wavelength range emitted from a light source 15b. The light sources 15a and 15b are, for example, LEDs. An LED that emits near-infrared light can be used as light source 15a, and a blue LED, green LED, white LED, or the like that emits visible light, particularly visible light in a wavelength range that is clearly separated from the wavelength of near-infrared light, can be used as light source 15b.

On the other hand, the imaging device 12A in FIG. 2 includes a first camera 13A provided corresponding to the first illuminator 15A and a second camera 13B provided corresponding to the second illuminator 15B. The first camera 13A is positioned opposite the first illuminator 15A across the bottle 2 at the first position P1. As a result, the first illumination light that has passed through the bottle 2 is incident on the first camera 13A, and the incident light is directed to the first imaging element 14A of the first camera 13A. The second camera 13B is positioned opposite the second illuminator 15B across the bottle 2 at the second position P2. As a result, the second illumination light that has passed through the bottle 2 is incident on the second camera 13B, and the incident light is directed to the second imaging element 14B of the second camera 13B. The sensitivity range of the first imaging element 14A includes at least the wavelength range of the first illumination light, i.e., the wavelength range of near-infrared light. The first camera 13A outputs an image signal corresponding to a first image of the target area TA in the wavelength range of the first illumination light. Meanwhile, the sensitivity range of the second image sensor 14B includes at least the wavelength range of the second illumination light, i.e., the wavelength range of visible light. As a result, the second camera 13B outputs an image signal corresponding to a second image of the target area TA in the wavelength range of the second illumination light.

In the example of Figure 2, the imaging positions P1 and P2 of the first and second images are different from each other, which reduces the risk of illumination light from capturing one image being mixed into the other image. The correspondence between illuminators 15A and 15B of lighting device 11A and cameras 13A and 13B is clearly distinguished, which has the advantage of simplifying or simplifying the illumination optical system and imaging optical system.

In the example of Figure 2, the wavelength ranges of the illumination light emitted by illuminators 15A and 15B are differentiated. Therefore, the sensitivity ranges of image sensors 14A and 14B of cameras 13A and 13B may be set equal to each other, including both the near-infrared wavelength range and the visible wavelength range. A commonly available camera, for example, has sensitivity in the wavelength range of 400 nm to 1000 nm, and has spectral sensitivity characteristics that peak at a wavelength around 550 nm, as shown in Figure 5. If this type of camera is used as cameras 13A and 13B in combination with illuminators 15A and 15B, it is possible to capture a first image using only first illumination light in the near-infrared wavelength range with first camera 13A, and a second image using only second illumination light in the visible wavelength range with second camera 13B. When using a camera with the spectral sensitivity characteristics shown in Figure 5, the wavelength range of the first illumination light can be set to at least the range of 700 nm to 1000 nm, preferably around 850 nm, and the wavelength range of the second illumination light can be set to the range of 400 nm to 650 nm. However, these wavelength ranges are merely examples. The wavelength ranges that are the subject of imaging by each of the first camera 13A and the second camera 13B may be set appropriately as long as a clear difference in the light-dark distribution corresponding to the difference in wavelength range can be produced.

Furthermore, if the sensitivity ranges of cameras 13A and 13B are controllable, cameras 13A and 13B may be controlled so that the sensitivity range of first camera 13A is set to the wavelength range of the first illumination light, and the sensitivity range of second camera 13B is set to the wavelength range of the second illumination light. For example, such settings are possible when using cameras that can simultaneously or selectively capture images in the wavelength range of near-infrared light and images in the wavelength range of visible light.

In the example of Figure 2, cameras 13A and 13B do not necessarily need to be positioned opposite their paired illuminators 15A and 15B. As long as the correspondence in which the first illumination light is incident on the first camera 13A and the second illumination light is incident on the second camera 13B is maintained, optical elements such as mirrors and prisms may be appropriately provided on the optical path of the illumination light passing through the bottle 2, and cameras 13A and 13B may be positioned in positions other than those shown. Optical paths may also be formed between illuminators 15A and 15B and first position P1 and second position P2 using appropriate optical elements, as long as the first illumination light can be directed to the bottle 2 at first position P1 and the second illumination light can be directed to the bottle 2 at second position P2, respectively.

(Second Configuration Example)
FIG. 3 shows a second configuration example. The example of FIG. 3 is similar to the example of FIG. 2 in that the illumination device 11B and the imaging device 12B are configured to inspect the bottles 2 moving in the conveying direction F along the conveying path CP of the conveying device 5. However, the example of FIG. 3 differs from the example of FIG. 2 in that a first image using the first illumination light and a second image using the second illumination light are captured at the same inspection position Pi on the conveying path CP. To enable capturing two types of images with different wavelength ranges at the single inspection position Pi, the illumination device 11B includes a single illuminator 15C aligned with the inspection position Pi. The illuminator 15C includes a light source 15a for the first illumination light and a light source 15b for the second illumination light, which are appropriately mixed so that both the first illumination light and the second illumination light can be irradiated onto the bottles 2 at the inspection position Pi.

On the other hand, the imaging device 12B in FIG. 3 further includes a beam splitter 16 and first and second filters 17A and 17B in addition to the first camera 13A and second camera 13B. The first camera 13A and second camera 13B are similar to those in the example in FIG. 2. The beam splitter 16 and filters 17A and 17B are provided to select the wavelength range to be imaged by each imaging element 14A and 14B so that the first imaging element 14A captures a first image in the wavelength range of the first illumination light, and the second imaging element 14B captures a second image in the wavelength range of the second illumination light. The beam splitter 16 splits the ray bundle of the illumination light (including both the first illumination light and the second illumination light) that has passed through the bottle 2 at the inspection position Pi into a ray bundle traveling in a straight direction toward the first camera 13A and a ray bundle traveling in an orthogonal direction toward the second camera 13B.

The first filter 17A is disposed between the beam splitter 16 and the first camera 13A and passes the ray bundle of the wavelength range of the first illumination light that has passed through the beam splitter 16 in a straight direction, while blocking the passage of ray bundles of other wavelength ranges (including the wavelength range of the second illumination light). The second filter 17B is disposed between the beam splitter 16 and the second camera 13B and passes the ray bundle of the wavelength range of the second illumination light that has been bent in the orthogonal direction by the beam splitter 16, while blocking the passage of ray bundles of other wavelength ranges (including the wavelength range of the first illumination light). The first filter 17A may be provided as an accessory or internal part of the first camera 13A, and the second filter 17B may be provided as an accessory or internal part of the second camera 13B.

In the example of Figure 3, only the first illumination light in the near-infrared wavelength range is directed to the image sensor 14A of the first camera 13A, and only the second illumination light in the visible wavelength range is directed to the image sensor 14B of the second camera 13B. Therefore, it is possible to capture the first image with the first camera 13A and the second image with the second camera 13B. Because the first and second images can be captured at a single inspection position Pi, the space required for installing the illumination device 11B and the image sensor 12B can be reduced, and there are advantages to not being affected by changes in the position (e.g., rotation) of the bottle 2 during transport.

In the example of Figure 3, beam splitter 16 functions as an example of splitting means, filters 17A and 17B function as an example of filtering means, and a combination of these functions as an example of wavelength range selection means. However, instead of this combination, an optical element such as a spectral prism capable of separating near-infrared light and visible light may be used as the spectral means, and the first illumination light separated by the spectral means may be directed to first image sensor 14A of first camera 13A, and the second illumination light may be directed to second image sensor 14B of second camera 13B. In this case, filters 17A and 17B may be omitted.

In the example of Figure 3, the positional relationship between the beam splitter 16, cameras 13A and 13B, and filters 17A and 17B is not limited to the illustrated example and can be changed as appropriate as long as the relationship is maintained in which illumination light split in one direction by the beam splitter 16 passes through the first filter 17A and enters the first camera 13A, and illumination light split in a different direction by the beam splitter 16 passes through the second filter 17B and enters the second camera 13B. Optical elements such as mirrors and prisms may be provided as appropriate on the optical path of the illumination light between the beam splitter 16 and cameras 13A and 13B. The optical paths between the illumination device 11B and the inspection position Pi, and between the inspection position Pi and the beam splitter 16 can also be changed as appropriate as long as it is possible to guide the illumination light to the bottle 2 at the inspection position Pi and to guide the illumination light that has passed through the bottle 2 to the beam splitter 16.

If the sensitivity ranges of cameras 13A and 13B are controllable, cameras 13A and 13B may be controlled so that the sensitivity range of first camera 13A is set to the wavelength range of the first illumination light, and the sensitivity range of second camera 13B is set to the wavelength range of the second illumination light. For example, such a configuration can be achieved by using cameras that can simultaneously or selectively capture images in the near-infrared wavelength range and images in the visible wavelength range. In this case, even if filters 17A and 17B are omitted, it is possible to capture the first image with first camera 13A and the second image with second camera 13B. In this configuration, the combination of beam splitter 16 and sensitivity control of cameras 13A and 13B functions as an example of a wavelength range selection means.

(Third Configuration Example)
Fig. 4 shows a third configuration example. The example of Fig. 4 is similar to the example of Fig. 3 in that an image using the first illumination light and an image using the second illumination light are acquired at the same inspection position Pi on the conveying path CP, and is also similar to the example of Fig. 3 in that the illumination device 11B used therefor uses a single illuminator 15C. However, it differs from the example of Fig. 3 in that a single camera 13C is used as the imaging device 12C.

2 and 3, camera 13C includes a spectroscopic prism 18 therein. The spectroscopic prism 18 splits the illumination light (including the first illumination light and the second illumination light) incident on camera 13C into the first illumination light and the second illumination light, and guides the split first and second illumination lights to image sensors 14A and 14B, which are arranged in different directions. For example, spectroscopic prism 18 splits the first illumination light in a straight direction and guides it to first image sensor 14A, and splits the second illumination light in an oblique direction and guides it to second image sensor 14B. Therefore, the spectroscopic prism functions as an example of a spectroscopic means. The spectral prism 18 also functions as an example of a wavelength range selection means that selects the wavelength ranges to be imaged by each of the image capture elements 14A and 14B, so that the first image captures a first image in the wavelength range of the first illumination light by the first image capture element 14A, and the second image captures a second image in the wavelength range of the second illumination light by the second image capture element 14B.

By using the spectral prism 18 to guide only illumination light in the wavelength range of the image to be captured to the image capture elements 14A and 14B, it is possible to extract an image signal corresponding to a first image captured by first illumination light in the near-infrared wavelength range from the first image capture element 14A, and an image signal corresponding to a second image captured by second illumination light in the visible wavelength range from the second image capture element 14B.

In the example of Figure 4, the first and second images can be captured at a single inspection position Pi, which reduces the space required to install the lighting device 11B and imaging device 12C and has the advantage of not being affected by changes in the bottle 2's position (e.g., rotation) while it is being transported. Furthermore, it is common for the imaging ranges of the imaging elements 14A and 14B built into a single camera 13C to closely match. Therefore, there is no risk of the position of the target area TA shifting between the first and second images, and it is possible to avoid the need for alignment during the image processing stage.

Cameras like camera 13C are commercially available that have an image sensor with a sensitivity range set to the near-infrared wavelength range and an image sensor with a sensitivity range set to the visible wavelength range, and that are configured to split and direct the light beam of the wavelength range of the object to be imaged. Figure 6 shows the spectral sensitivity characteristics of one example. Using this type of camera, the third configuration example can be realized. There are also image sensors that stack a photoelectric conversion layer sensitive to the near-infrared wavelength range and a photoelectric conversion layer sensitive to the visible wavelength range on a single image sensor substrate, and control the charge extraction operation from these photoelectric conversion layers to simultaneously or selectively capture images in the near-infrared wavelength range and images in the visible wavelength range. When using such an image sensor, it is possible to control its imaging operation so that the single image sensor functions as either the first or second image sensor. When using such an image sensor, the spectral prism 18 can be further omitted, and the wavelength range selection means can be realized by controlling the sensitivity of the single image sensor.

(Modification)
3 and 4 , the first and second images are captured simultaneously by the imaging device 12B or the imaging device 12C. However, if the time required for one capture is sufficiently short in consideration of the field of view of the camera 13 and the transport speed of the bottle 2, the first and second images may be captured alternately (in any order). For example, the first and second images can be captured by alternately emitting the first and second illumination lights from the illumination device 11B and capturing images synchronized with the emission timing using a single camera 13 having a sensitivity range from visible light to near-infrared light. Alternatively, the first and second images can be captured by simultaneously irradiating the first and second illumination lights from the illumination device 11B and switching the wavelength range of the illumination light incident on the camera 13 between the wavelength range of the first illumination light and the wavelength range of the second illumination light, or by switching the sensitivity range of the image sensor 14 of the camera 13 between the wavelength range of near-infrared light and the wavelength range of visible light.

In the examples shown in Figures 2 to 4, the bottle 2 being transported is the target, but a stationary bottle may also be the target. If the orientation of the inspection object, such as the printing unit 3, is uncertain, the bottle 2 may be rotated around its center line, and the camera 13 may capture an image of the bottle 2 at the same time that the inspection object, such as the printing unit 3, is advanced toward the lighting device 11 and camera 13. The lighting device 11 may be constantly lit, or may be controlled to turn on and off in synchronization with the imaging operation of the camera 13.

[Control system]
Returning to Figure 1, the control system of the inspection device 1 will now be described. The inspection device 1 is provided with a processing unit 20 in order to inspect the print unit 3 based on images captured by the camera 13. The processing unit 20 is configured, for example, as a computer unit including a CPU and an internal storage device necessary for its operation. The processing unit 20 is provided with an image processing unit 21 and an inspection unit 22. The image processing unit 21 and the inspection unit 22 may be provided as logical devices realized by combining, for example, the hardware of the processing unit 20 with a computer program as software, or may be provided as physical devices combining logic circuits such as an LSI.

The image processing unit 21 receives the image signals of the first and second images output from the camera 13 and performs image processing to generate an inspection image to be used in the inspection by the inspection unit 22. The image processing performed by the image processing unit 21 includes processing to generate an inspection image that is a difference in brightness between the first and second images. That is, the image processing unit 21 calculates the difference in brightness between each pixel in the first image and each pixel in the second image for each pixel, thereby generating an inspection image that has a brightness distribution corresponding to the difference in brightness between the two images. By performing such processing, the image processing unit 21 functions as an example of an image processing means. In addition, the image processing unit 21 may perform various other image processing operations suitable for generating an inspection image that ensures a brightness difference between the printing unit 3 and other parts. For example, the image processing unit 21 may perform correction processing for image brightness, contrast, etc.

The inspection unit 22 receives image signals corresponding to the test image processed by the image processing unit 21 and determines whether the printed part 3 is good or bad according to a predetermined algorithm. This process, for example, determines whether an area with a specific brightness corresponding to the printed part 3 appears in the test image. By performing this process, the inspection unit 22 functions as an example of a determination means. Note that the algorithm for determining whether the printed part 3 is good or bad may be configured as appropriate, as long as it utilizes the difference in brightness in the test image. For example, the inspection unit 22 may binarize the test image and extract the printed part 3 as a bright part, and then compare the obtained image of the printed part 3 with an image of the printed part 3 of a good product to determine whether the printed part 3 is good or bad.

As a means for outputting the inspection results from the inspection section 22, the processing unit 20 may be appropriately connected to a monitor 23 that displays the inspection results, or a storage device 24 that stores the inspection results. A printer may also be connected as output means. Furthermore, the processing unit 20 may be connected to various input means such as a keyboard or pointing device that allows the operator of the inspection device 1 to input appropriate instructions. The input means are not shown in Figure 1.

The image acquisition device 10 configured as described above makes use of the printed area 3's light-blocking properties against visible light and its light-transmitting properties against near-infrared light to obtain an inspection image that ensures sufficient contrast between the printed area 3 and other areas while minimizing the effects of water droplets and the like. Furthermore, the inspection device 1 can use this inspection image to accurately inspect the quality of the printed area 3.

Figures 7 to 9 show examples of images of the target area TA acquired using the image acquisition device 10 described above. Figure 7 is an example of a first image captured of the target area TA on the bottle 2 under specified conditions, Figure 8 is an example of a second image captured of the same target area TA under the same conditions, and Figure 9 is a differential image of the images in Figures 7 and 8. In the first image in Figure 7, near-infrared light passes through the printed area (the area where "20.05.09" can be read in Figures 8 and 9), and therefore is not visible. Water droplets adhering to the printed area appear as relatively dark areas due to scattering of near-infrared light. On the other hand, in the second image in Figure 8, the printed area appears as a dark area, and the rest of the image shows a light-dark distribution similar to that of the first image. In the image in Figure 9, it can be seen that the shadow of the bottle, water droplets, etc. are all canceled out, leaving only the printed area bright.

The liquid filled in the bottle is nearly black, so in the second image taken with visible light (Figure 8), the illumination light is attenuated by the liquid inside the bottle, making it appear dark. However, in the first image taken with near-infrared light (Figure 7), the light transmittance is relatively higher than that of visible light, making it appear bright. In the image in Figure 9, the liquid remains somewhat bright due to differences in brightness in the liquid, but this does not interfere with the inspection of the printed area.

The present invention is not limited to the above-described embodiments and may be implemented in forms with appropriate modifications or alterations. For example, the container to be inspected is not limited to bottles made of PET resin, and the present invention can be applied to any container that is translucent to both near-infrared light and visible light. For example, the present invention may be applied to containers made of polypropylene resin or polyethylene resin. The inspection object is not limited to the printed part, and any object that has a higher light-blocking property in the visible light wavelength range compared to the translucent part of the container may be set as the inspection object. The translucent part needs to be at least part of the container, and the inspection object needs to be located in that translucent part.

Various aspects of the present invention derived from the above-described embodiments and variations are described below. In the following description, corresponding components shown in the accompanying drawings are noted in parentheses to facilitate understanding of each aspect of the present invention, but this does not mean that the present invention is limited to the illustrated forms.

An image acquisition device (10) according to one aspect of the present invention is an image acquisition device for acquiring an inspection image for inspecting the quality of an inspection object (3) in a container (2) filled with a liquid, the container having a light-transmitting section that is transmissive to visible light and has a higher light-blocking property against the visible light than the light-transmitting section. The image acquisition device includes: an illumination means (11; 11A; 11B) capable of irradiating a target area (TA) including the inspection object with first illumination light in the wavelength range of near-infrared light and second illumination light in the wavelength range of visible light; an imaging means (12; 12A; 12B; 12C) that captures a first image of the target area in the wavelength range of the first illumination light that has passed through the container; and a second image of the target area in the wavelength range of the second illumination light that has passed through the container; and an image processing means (21) that generates, as the inspection image, an image of the difference in brightness between the first image and the second image.

An image acquisition method according to one aspect of the present invention is a method for acquiring an inspection image for inspecting the quality of an inspection object (3) in a container (2) filled with a liquid, the container having a light-transmitting section that is transmissive to visible light and has a higher light-blocking property against the visible light than the light-transmitting section. The image acquisition method includes the steps of irradiating a target area (TA) including the inspection object with first illumination light in the wavelength range of near-infrared light and second illumination light in the wavelength range of visible light, capturing a first image of the target area in the wavelength range of the first illumination light that has passed through the container, and a second image of the target area in the wavelength range of the second illumination light that has passed through the container, and generating an image of the difference in brightness between the first image and the second image as the inspection image.

A container inspection device (1) according to one aspect of the present invention includes the image acquisition device (10) according to the above aspect and a discrimination means (22) that discriminates whether the inspection object is good or bad based on the contrast in the inspection image generated by the image processing means (21) of the image acquisition device (10). A container inspection method according to one aspect of the present invention includes the steps of acquiring an inspection image using the image acquisition method according to the above aspect and discriminating whether the inspection object is good or bad based on the contrast in the acquired inspection image.

In the above embodiment, the first illumination light in the near-infrared wavelength range passes not only through the translucent portions of the container but also through the object to be inspected, so the object to be inspected does not appear as a dark area in the first image. On the other hand, the second illumination light in the visible wavelength range passes through the translucent portions of the container and is blocked by the object to be inspected, so the object to be inspected appears as a clearly dark area. Water droplets and other objects on the container appear with differences in brightness in the first and second images depending on the transmittance and degree of scattering in the near-infrared and visible wavelength ranges, respectively. Therefore, in the inspection image, which is the difference between the first and second images, a sufficient contrast in brightness can be created between the object to be inspected and other areas. The contrast in brightness in the inspection image can be used to accurately determine whether the object to be inspected is good or bad, improving inspection accuracy.

In the above aspect, the illumination means may include a first illumination means (15A) configured to irradiate a container at a first position (P1) on a predetermined transport path (CP) with the first illumination light, and a second illumination means (15B) configured to irradiate a container at a second position (P2) on the transport path that is different from the first position with the second illumination light. The imaging means may include a first camera (13A) configured to receive the first illumination light that has passed through the container at the first position, and a second camera (13B) configured to receive the second illumination light that has passed through the container at the second position. This allows a first image to be captured at the first position using the first illumination means and the first camera, and a second image to be captured at the second position using the second illumination means and the second camera. The container is illuminated with near-infrared light in the wavelength range and visible light in the wavelength range at separate first and second positions, and the first and second images are also captured at separate first and second positions, eliminating the risk of the illumination light at one position mixing with the illumination light at the other position and impairing the contrast between brightness and darkness in the inspection image.

The illumination means (11B) may be configured to irradiate both the first illumination light and the second illumination light onto the container at the same inspection position (Pi), and the imaging means may include a first imaging element (14A) and a second imaging element (14B), and wavelength range selection means (16, 17A, 17B; 18) that selects the wavelength range to be imaged by each imaging element so that the first imaging element captures the first image in the wavelength range of the first illumination light and the second imaging element captures the second image in the wavelength range of the second illumination light. This allows the first and second images to be captured at the same position, thereby reducing the space required for installing the illumination means and imaging means. Capturing the first and second images at the same position can also reduce or eliminate the effort required for alignment when generating an image representing the difference between the two images.

The wavelength range selection means may include a splitting means (16) that splits the first illumination light and second illumination light that have passed through the container at the inspection position so that they are directed toward the first imaging element and the second imaging element, respectively, and a filter means (17A, 17B) that selectively passes the split first illumination light and second illumination light according to their wavelength ranges so that the first illumination light is directed toward the first imaging element and the second illumination light is directed toward the second imaging element. In this way, the combination of the splitting means and the filter means can select the wavelength ranges to be imaged by each imaging element so that the first image is captured by the first imaging element and the second image is captured by the second imaging element.

The first and second image sensors may be provided in different cameras, and the splitting means may be provided outside the cameras. This allows the first and second images to be captured separately by selectively directing the first illumination light to the first image sensor and the second illumination light to the second image sensor, even when using a general camera with a sensitivity range spanning wavelengths from visible light to near-infrared light.

The wavelength range selection means may include a spectroscopic means (18) that splits the first illumination light and the second illumination light that have passed through the container at the inspection position according to their wavelength ranges so that the first illumination light is directed toward the first image capture element and the second illumination light is directed toward the second image capture element. In this way, the spectroscopic means is used to split the first illumination light and the second illumination light, so that the first illumination light is selectively directed toward the first image capture element and the second illumination light is selectively directed toward the second image capture element, allowing the first image and the second image to be captured separately.

The spectroscopic means, the first image sensor, and the second image sensor may be provided within the same camera (13C). This allows the first image and the second image to be captured using a single camera. This further reduces the space required to install the image sensor.

The target area (TA) may be set to include an inspection object located above the liquid surface of the liquid in the container. This makes it possible to reduce the effect of water droplets or the like adhering above the liquid surface and obtain an inspection image that ensures sufficient contrast between the inspection object and other areas.

1 Inspection device 2 Bottle (container)
3 Printing section (inspection target)
10 Image acquisition device 11, 11A, 11B Illumination device (illumination means)
12, 12A, 12B, 12C Imaging device (imaging means)
13 Camera 13A First camera 13B Second camera 13C Camera 14 Imaging element 14A First imaging element 14B Second imaging element 15A First illuminator (first illumination means)
15B Second illuminator (second illumination means)
15C Illuminator 16 Beam splitter (wavelength range selection means, splitting means)
17A, 17B Filter (wavelength range selection means, filter means)
18. Spectroscopic prism (wavelength range selection means, spectroscopic means)
20 Processing unit 21 Image processing unit (image processing means)
22 Inspection unit (discrimination means)
CP: Transport path P1: First position P2: Second position Pi: Inspection position TA: Inspection area

Claims (11)

An image acquisition device for acquiring an inspection image for inspecting the quality of an inspection object in a container filled with a liquid, the image acquisition device comprising: a light-transmitting section that transmits visible light; and an inspection object that has a light-blocking property against the visible light higher than the light-transmitting section;
an illumination unit capable of irradiating a target area including the inspection object with first illumination light in a wavelength range of near-infrared light and second illumination light in the wavelength range of visible light;
an imaging means for capturing a first image of the target area in a wavelength range of the first illumination light that has passed through the container, and a second image of the target area in a wavelength range of the second illumination light that has passed through the container;
an image processing means for generating an image of a difference in brightness between the first image and the second image as the inspection image;
1. An image acquisition device for inspecting a container, comprising: the illumination means includes a first illumination means provided to irradiate a container at a first position on a predetermined transport path with the first illumination light, and a second illumination means provided to irradiate a container at a second position on the transport path that is different from the first position with the second illumination light,
The image acquisition device described in claim 1, wherein the imaging means comprises a first camera arranged to receive first illumination light that has passed through the container at the first position, and a second camera arranged to receive second illumination light that has passed through the container at the second position. the illumination means is configured to be able to irradiate both the first illumination light and the second illumination light onto the container at the same inspection position;
2. The image acquisition device according to claim 1, wherein the imaging means comprises a first imaging element and a second imaging element, and a wavelength range selection means for selecting a wavelength range to be imaged by each imaging element so that the first imaging element captures the first image in the wavelength range of the first illumination light and the second imaging element captures the second image in the wavelength range of the second illumination light. the wavelength range selection means includes a splitting means for splitting the first illumination light and the second illumination light that have passed through the container at the inspection position so that the first illumination light and the second illumination light are directed toward the first image capture element and the second image capture element, respectively;
4. The image acquisition device according to claim 3, further comprising: a filter means for selectively passing the split first illumination light and the split second illumination light according to wavelength ranges, so that the first illumination light is directed to the first image sensor and the second illumination light is directed to the second image sensor. The image acquisition device described in claim 4, wherein the first imaging element and the second imaging element are provided in different cameras, and the splitting means is provided outside the cameras. The image acquisition device described in claim 3, wherein the wavelength range selection means includes a spectroscopic means that splits the first illumination light and the second illumination light that have passed through the container at the inspection position according to their wavelength ranges so that the first illumination light is directed toward the first image sensor and the second illumination light is directed toward the second image sensor. The image acquisition device described in claim 6, wherein the spectroscopic means, the first image sensor, and the second image sensor are provided within the same camera. The image acquisition device described in any one of claims 1 to 7, wherein the target area is set to include an inspection target positioned above the liquid surface in the container. An image acquisition device according to any one of claims 1 to 8;
and a discrimination means for discriminating whether the inspection object is good or bad based on the difference in brightness in the inspection image generated by the image processing means. An image acquisition method for acquiring an inspection image for inspecting the quality of an inspection object in a container filled with a liquid, the inspection object being provided in a light-transmitting portion that is transmissive to visible light and has a light-blocking property against the visible light higher than that of the light-transmitting portion, the method comprising:
a step of irradiating a target area including the inspection object with first illumination light in a wavelength range of near-infrared light and second illumination light in the wavelength range of visible light;
capturing a first image of the target area in a wavelength range of the first illumination light that has passed through the container and a second image of the target area in a wavelength range of the second illumination light that has passed through the container;
generating an image of a difference in brightness between the first image and the second image as the test image;
An image acquisition method for inspecting a container, comprising: acquiring an inspection image by the image acquisition method of claim 10;
and a step of determining whether the inspection object is good or bad based on the difference in brightness in the acquired inspection image.