JP2002543379A - Apparatus and method for inspection of multilayer plastic containers - Google Patents

Abstract

SUMMARY The present invention relates to an apparatus and method for inspecting a multilayer plastic container (10). More specifically, the present invention relates to an apparatus and method in which a light-absorbing compound is added to the material constituting the layers of the container (10) to facilitate its inspection. The apparatus includes: a sensor unit (40); and an irradiation unit (30) for irradiating a part of an electromagnetic spectrum at a near-infrared wavelength to an inspection band (20) located between the sensor unit (40) and the irradiation unit (30). And a processing unit (50) that receives the output of the sensor unit (40) and determines the attribute of the multilayer plastic container (10).

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION The present invention relates to an apparatus and method for inspecting a multilayer plastic container. More specifically, the present invention relates to an apparatus and a method in which an optical energy absorbing compound is added to a material constituting a layer to facilitate inspection. Although the present invention is particularly related to inspection techniques and is described with specific reference thereto, it should be understood that the invention is also useful in other fields and applications. It is a well-established practice to apply standard machine vision techniques to the inspection of the structural integrity of formed food and beverage plastic containers. These transformations have proven to be very valuable quality and process control tools, allowing manufacturers of these products to improve both the productivity and the quality derived from the manufacturing process.

[0002] A recent trend in the field of manufacturing plastic containers is the transition to multilayer container structures. As part of this trend, the process of plastic container manufacturers has been brought to the level where the containers they manufacture consist of unique multi-layered polymer compounds in which the individual layers are organized to perform different container-related functions. Evolved up to. For example,
In the novel multi-layer container, one layer of the product can be specifically designed to prevent the transfer of oxygen through the wall of the container, and other layers can provide structural integrity to the container. The various layers can have their various unique chemical formulas and provide unique performance attributes, while the various components of the multilayer plastic container have very similar optical properties, at least in the visible region of the electromagnetic spectrum. Easy to have characteristic characteristics. Further, the refractive index and light transmittance of these various materials are generally very similar. This similarity is not accidental. In order to keep the consumer's eyes familiar with plastic food and beverage containers, manufacturers take care when formulating the appropriate multilayer components to ensure that the optical properties of the polymer remain constant. Was. This fact is significant in connection with the process of automated inspection of plastic containers. Many prior art machine vision systems use a CCD camera that senses radiation in the visible wavelength range and a suitable visible light source that is operated as a backlight. In this way, the structural integrity of the container is checked for manufacturing defects. Since the various layers of a multilayer plastic container all have very similar optical properties in the visible wavelength range, selective inspection of each layer of the multilayer container is a solution to the state of the art machine vision. It was very difficult to use the method. While it was possible to detect defects extending through the walls of the container, the ability to detect the presence or absence of one layer type was almost impossible, in part and in total. The similar optical properties of the corresponding layers and the lack of image contrast derived directly therefrom made layer-by-layer inspection impossible using the prior art.

The methods and apparatus disclosed herein overcome the limitations of state-of-the-art inspection systems while describing methods and associated hardware that enable reliable inspection of multi-layer plastic containers. Furthermore, the present invention is a unique method employing a machine vision technology that incorporates a camera as a sensor and processes the resulting images to determine the state of the various layers of the plastic bottle in a very reliable manner.

SUMMARY OF THE INVENTION [0004] The present invention relates to an apparatus and method wherein a light energy absorbing compound is added to the material comprising the layers of the container to facilitate its inspection. One aspect of the present invention is a sensor device comprising an array of optoelectronic devices that is operated to sense radiation in the near infrared region of the electromagnetic spectrum, and wherein a portion of the emitted spectrum is in the near infrared region of the electromagnetic spectrum. Interacting with the electromagnetic radiation source in the area and the multi-layer container under test, guiding the container to an advantageous position between the sensor device and the radiation source, and transmitting instrument control signals to both the sensor device and the electromagnetic radiation source. A machine vision device having means for providing site sensing, tracking, and transport, the container comprising a selectively absorbing dye, a selective absorbing dye receiving the output of the sensor device and acting in the near infrared portion of the electromagnetic spectrum. Processing means for performing a processing operation for analyzing an attribute based on the presence of a sexual dye, and receiving a processing output of the processing means for performing a subsequent action based on the analyzed attribute. And means for acting to facilitate one of rejection and marking of the containers.

[0005] Another aspect of the invention is a method for forming a container having a plurality of polymer layers, each polymer layer being formulated to perform a different set of container-related functions; Selectively adding a light absorbing compound acting on the plurality of polymer layers to the plurality of polymer layers; placing the container between the sensor means and the near-infrared electromagnetic radiation source; and generating near-infrared electromagnetic radiation. A method comprising: driving a radiation source; sensing near-infrared electromagnetic radiation by a sensor means; and determining an attribute of the container based on the sensing. Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. However, while the detailed description and examples illustrate preferred embodiments of the invention, those skilled in the art will appreciate various changes and modifications that fall within the spirit and scope of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The methods and inventions disclosed herein provide, for example, the formulation of a polymer comprising a material layer forming a plastic container with an inherent amount of And / or adding a type of light energy absorbing compound. Preferably, these absorbing materials have the property of selectively absorbing a certain amount of near-infrared light passing through its volume in a well-controlled manner. The near-infrared wavelength region referred to here extends from about 700 nm to 1000 nm. Preferably, for the sole purpose of allowing an overall inspection of the container, theorized absorbing material or near-infrared dye is added to the various layer chemicals that will form the container. . Preferably employed infrared dyes typically have high transmission in the visible wavelength range from 400 nm to 700 nm. Thus, the presence of these dyes in the various plastic layers is not recognized by a human observer. However, sensors or CCD cameras that typically have a spectral response from the visible to the near-infrared region up to about 1000 nm are well-positioned and work in concert with the near-infrared illumination source to provide a multilayer plastic container. Can be used to inspect various layers of

[0007] The use of markers (ie, the use of substances only to allow for manual or automated testing, and objects) is not a new concept. In this sense,
The use of UV fluorescent dyes to aid automatic inspection of products is known. The concept of formulating and applying IR dyes and inks to mark products is also a well-established technique. It is also known to use IR inks for barcode applications. These generally fall within the category of "invisible inks" applied to product surfaces for reading and tracking purposes.

However, applying IR dyes in the various layers of a plastic container to aid later inspection of the formed container is a novel improvement over existing levels of machine vision technology. The prior art UV marker transformations referenced above have proven to be of limited value in high speed automated inspection due to the lack of adequate UV guidance signal strength. The amount of UV light energy obtained from any commercially available radiation source that has been reasonably applied is initially limited. The situation is exacerbated by the fact that the lossy conversion factor (from UV radiation input energy to visible light output energy) further reduces the light available for detection by the camera. In high speed applications where short camera exposure times are required to properly stop the action of moving parts, UV guided light is not sufficient for proper inspection. This is because the UVs typically used typically use coatings or inks or additives that fluoresce while illuminating the UV while producing light within the visible light spectrum (ie, between 400 and 700 nm). Because it is a conversion method. This so-called "down-conversion method" is very inefficient and produces an unsuitable amount of light to enable the high-quality, high-speed inspection described above.

[0009] However, if a UV light source is used to project the part to be inspected, the UV light blocking additive will serve to indicate areas without such a market additive free layer. Of course, it is assumed that a sensor or camera that directly senses the UV light frequency used is used. However, if necessary, a UV light blocking marker
One skilled in the art will appreciate that the R-shield marker can be used instead of or in addition to the R-shield marker. For example, UV shielding "markers" already exist in the sense that they are added to preserve food and other freshness, but play a dual role in the present invention.

[0010] Since the signal intensity achievable using commercially available IR energy sources is of the order of magnitude higher than that achievable in the UV wavelength range, the approach with IR markers is similar to that of similar UV markers. Is preferred over the approach by In addition, IR marker technology relies on direct detection of IR radiation. Since CCD cameras typically have a high response to near-infrared energy, lossy conversion efficiency to the visible region is avoided.

[0011] The addition of IR dyes to the chemical polymer of the container layer is a fundamentally different process than the process of printing IR symbols on the surface of manufactured parts. In the former,
Dyes become an integral part of the raw materials, possibly by being added by the polymer manufacturer at the beginning of the manufacturing process, or are introduced via colorants or chemical additives in the process. In this way, the markers can be used to enhance inspection at the beginning or at any stage of the container manufacturing process. This means that the inspection can be carried out in a pre-forming stage during the determination of the quality of the mold, or on line, such as at the exit of the molding apparatus or after the bottle has been inflated. This is very different from applying a printed IR label, which is usually applied at the end of the manufacturing process and does not perform any useful function with respect to product quality inspection and is limited to inventory control and tracking functions. I have.

FIG. 1 is a schematic diagram of a preferred embodiment of the subject invention. A multi-layer plastic container 10 consisting of a plastic layer suitably dyed with an IR absorbing dye is passed through a test strip 20. Although various forms of sensors or cameras can be used based on the required inspection and application specifications, in a preferred embodiment, two or more camera / lens assemblies 40 obtain images of container 10. Are arranged for. 1
One camera / lens assembly 40 is typically positioned to obtain an image of the container base 15, and two or more camera / lens assemblies 40 provide images of the container top, neck, and side walls. Arranged to get. Opposite each camera / lens assembly 40 is a suitable IR light source 30. A preferred embodiment of the IR light source 30 is an IR emitting solid light emitting diode (LED)
Array. The camera / lens assembly 40 and the IR light source 30 are connected to a control / processing / display module 50 which is held to facilitate manual or automatic inspection of the plastic container 10 for predefined defects. ing.

For purposes of merely clarifying the subject invention, the discussion is temporarily limited to a two-layered container, and reference is made to the spectral emission curves depicted in FIGS. FIG. 2 shows the spectral emission curves of two plastics typically used for plastic containers. Curve 60 points to plastic, which is marked as clear plastic. The light transmission of this plastic is very high (close to 100%) throughout most of the visible wavelength range from 400 nm to 700 nm. High uniform light transmission is a measurable attribute of an object defined as transparent. Curve 70 shows the same plastic after the green dye has been added to the formulation.

This curve shows a material with reduced transmission at low wavelengths (blue region) in the visible spectrum. Light transmission increases to a peak of about 100% at 550 nm (green region) and then falls off dramatically at longer wavelengths in the visible spectrum (red region). Outside the visible region, the transmittance of the plastic rises rapidly to the level of the transparent plastic curve 60 and remains intact over 700 to 1000 nm close to the rest of the IR region. This behavior of selective absorption in the visible region / no effect in the IR region is typical for dyes acting in the visible spectrum.

FIG. 3 shows two light transmission curves of a properly IR stained plastic disclosed by the present invention. Curve 80 shows one type of plastic transmission curve that is clearly perceived by a human observer due to its high transmission in the visible wavelength region from 400 nm to 700 nm. However, this plastic is about 750n
It has a distinct spectral absorption starting at m. Curve 90 has a similar IR absorption effecting at about 850 nm. If both of these plastics are contained in adjacent layers in the container structure, these plastics are not visually identifiable, but can be reliably detected and tested using the hardware equipment defined by the present invention. .

Any machine vision expert, ie, one of ordinary skill in the art, will be able to perform an overall inspection of the two plastic types defined by curves 80 and 90, while Thus, it would be possible to define several inspection configurations that would be concurrent with the field of view of the camera / lens assembly 40. The essence of the disclosed invention covers all possible and potentially plausible combinations of plastics materials with IR or UV absorbing or screening dyes. By adding the appropriate combination of dyes for absorption at different frequencies or different shielding percentages, potentially effectively detecting many different layers,
It is possible to evaluate quality. To this end, for example, the presence, thickness and / or
Or, the integrity (eg, the presence or absence of a pinhole) can be analyzed. Furthermore, the invention is applicable to containers having only a single layer. In this case, overall quality, thickness and / or integrity are also considered important focuses of the inspection. In addition, the invention is useful for other types of articles beyond containers, such as single or multiple layer plastic sheeting.

It will be apparent from reading this detailed description that the invention of this application example may be installed in a machine vision device and / or system. Referring more specifically to FIG. 4, a system 100 including the invention of FIG. 1 includes a sensor device 102 and an electromagnetic radiation source 104. The sensor device is preferably an array of photoelectric sensing elements, for example in the form of a charge-coupled device (CCD) based camera. The radiation source is preferably an electromagnetic radiation source such that the majority of the emitted spectrum is in the near infrared (IR) portion of the electromagnetic spectrum. Preferably, the radiation source is an array of light emitting diodes (LEDs). FIG. 4 shows the part detection device 108, the tracking system 110, and the transport system 11
2 are also shown, all of which are operated to work with the container 10 under test,
It is used to move the container to an advantageous location between the sensor and the radiation source and to provide instrument control signals to both the sensor and the radiation source. Of course, it is preferred that the multilayer container being tested has a selectively absorbing dye that facilitates testing according to the present invention. FIG. 4 shows processing means 114 for performing a processing operation in response to the output of the sensor device, the processing operation being based on the presence of selectively absorbing dyes active in the near infrared portion of the electromagnetic spectrum. It is specifically reflected in the resulting analytical attributes. The system 100 receives the processing output of the processing means, and removes a container or an object that is out of the standardized specifications in advance or included in the specifications,
A rejection / marking device 116 is included that drives to physically reject or apply markings for subsequent operations. It is further understood that the LED radiators of the preferred embodiments may be selectively pulsed so that the rapidly moving multilayer container during operation can be deactivated.

In operation, the method of the present invention useful in this system shown in FIG. 4 refers to FIG. 5, which comprises selectively adding a light absorbing compound to the polymer layer prior to the formulation process. (Step 502). Preferably, the light absorbing compound operates in the near infrared wavelength region. Next, a container is formed having a plurality of polymer layers (eg, two or more unique polymer layers), each of which is specifically formulated to perform a different set of container-related functions (e.g., two or more unique polymer layers). Step 504). For inspection purposes, the container is then placed between the sensor means and a source of near infrared electromagnetic radiation (step 506). This positioning step consists in directing the container to an advantageous position between the sensor means and the radiation source means. Thereafter, the radiation source is driven or radiated with near-infrared electromagnetic radiation (step 508). Next, radiation is sensed by the sensor device or means (step 510). Next, the attributes of the container (eg, structural integrity) are determined based on the sensing (step 512). The method is further standardized in advance,
It is understood that it may include rejecting or marking containers or objects that deviate or fall within specifications encoded in the processing means of the system for subsequent action. The rejection or marking is based on a determination of the condition, quality, or acceptability of the container, which is based on a determination of the attribute.

The above description merely provides a disclosure of specific embodiments of the invention and is not intended to limit the invention. Accordingly, the invention is not limited to the embodiments described above. Rather, those skilled in the art will be able to contemplate alternative embodiments that fall within the scope of the invention. The essence of the disclosed invention is not limited by the very narrow and simplified examples shown as preferred embodiments.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a preferred embodiment of the present invention;

FIG. 2 is a graph showing the spectral emission curves of two materials typically used in the construction of plastic containers;

FIG. 3 is a graph showing the spectral emission curves of two materials stained with near infrared material;

FIG. 4 shows the installed state of the invention;

FIG. 5 is a flowchart according to the present invention.

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SL, SZ, TZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AG, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CR, CU, CZ, DE, DK, DM, DZ, EE, ES, FI, GB, GD, GE, GH, GM, HR , HU, ID, IL, IN, IS, JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MA, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, TZ, UA, UG, US, UZ, VN, YU, ZA , ZW (72) Inventor Seck, Stephen, De. Rock Creek Drive, Aurora, Ohio, USA 44202 Rock Creek Drive 670 F Term (Reference) 2G051 AA11 AB02 BA06 BC02 CA03 CB02 CD07 DA05 DA15 EB01 2G059 AA05 BB15 CC12 DD01 DD12 EE01 EE11 FF01 GG02 GG08 HH01 JJ11 KK04

Claims (6)

[Claims] 1. A method for testing useful container attributes in a system having at least one sensor means and a source of near-infrared electromagnetic radiation, comprising the steps of: Selectively adding to the layers, wherein each polymer layer is formulated to perform a different set of container-related functions;
Forming a container having a plurality of polymer layers; placing the container between the sensor means and a near infrared electromagnetic radiation source; driving a radiation source to generate near infrared electromagnetic radiation; The method comprising: sensing near-infrared electromagnetic radiation by sensor means; and determining an attribute of the container based on the sensing. 2. The method of claim 1, further comprising determining a condition, quality, or acceptability of the container based on the sensing and determining. 3. Further, based on the condition, quality, or acceptability of the container,
3. The method of claim 2, comprising one of the steps of rejecting and marking the container for a subsequent action. 4. A sensor device comprising an array of photoelectric elements operable to sense radiation in the near infrared portion of the electromagnetic spectrum, wherein a portion of the emitted spectrum is located in the near infrared portion of the electromagnetic spectrum. An electromagnetic radiation source, site sensing, acting on the multilayer container under test, guiding the container to an advantageous location between the sensor device and the source, and providing instrument control signals to both the sensor device and the source;
Tracking and transport means; processing means for receiving the output of the sensor device and performing processing operations to analyze attributes based on the presence of selectively absorbing dyes acting in the near infrared portion of the electromagnetic spectrum;
And a machine vision device comprising means for receiving one of the processing outputs of the processing means and acting based on the analyzed attributes to facilitate one of rejection and marking of the container for a subsequent action. 5. The apparatus of claim 4, wherein said source comprises an array of LED emitters. 6. The apparatus of claim 5, wherein said LED emitter is pulsed.