WO2015105490A1 - Procédé pour analyser des défauts dans des articles thermoplastiques - Google Patents

Procédé pour analyser des défauts dans des articles thermoplastiques Download PDF

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Publication number
WO2015105490A1
WO2015105490A1 PCT/US2014/010793 US2014010793W WO2015105490A1 WO 2015105490 A1 WO2015105490 A1 WO 2015105490A1 US 2014010793 W US2014010793 W US 2014010793W WO 2015105490 A1 WO2015105490 A1 WO 2015105490A1
Authority
WO
WIPO (PCT)
Prior art keywords
thermoplastic article
image
thermoplastic
sample
article sample
Prior art date
Application number
PCT/US2014/010793
Other languages
English (en)
Inventor
Joy Sawyer Bloom
John D. Connolly, Jr.
Michael Patrick MILONE
Barry Rubin
Original Assignee
E. I. Du Pont De Nemours And Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by E. I. Du Pont De Nemours And Company filed Critical E. I. Du Pont De Nemours And Company
Priority to PCT/US2014/010793 priority Critical patent/WO2015105490A1/fr
Publication of WO2015105490A1 publication Critical patent/WO2015105490A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/0002—Inspection of images, e.g. flaw detection
    • G06T7/0004—Industrial image inspection
    • G06T7/0006—Industrial image inspection using a design-rule based approach
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/89—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles
    • G01N21/892—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles characterised by the flaw, defect or object feature examined
    • G01N21/894—Pinholes

Definitions

  • This invention relates to the field of thermoplastic articles, more specifically to the field of analyzing the quality and/or analyzing defects in thermoplastic articles, such as thermoplastic films.
  • thermoplastic articles that are produced today contain one or more filler materials, such as titanium dioxide, which is typically included to impart light-protective properties to the article.
  • the dispersion of such fillers in thermoplastic articles is critical to quality; poor dispersion will make the article uneven in its properties from one area to another.
  • dispersion has also been generally quite difficult to effectively, accurately, and efficiently measure.
  • manufacturers will utilize a visual method, such as by counting the number of particles visible at 20-times magnification within a given area and then assigning a quality rating based on the number of particles counted. This method is very tedious and is quite subjective. Additionally, though it allows for a decent assessment of the particles on the surface of the sample, it is difficult to assess particles within the article that are not easily viewed on the surface. As such, there is a need in the art for improved methods of analyzing filler dispersion and related quality aspects of thermoplastic articles, such as thermoplastic films.
  • the present invention relates to a method for analyzing defects in a thermoplastic article containing filler particles, the method comprising: a) providing a thermoplastic article sample, wherein the thermoplastic article sample comprises a thermoplastic base material with filler particles dispersed therein; b) providing an optical scanning/capture device capable of scanning and capturing images of light transmitted through said article in the visible wavelengths; c) providing computer executable code comprising an image analysis algorithm; d) scanning the thermoplastic article sample with the optical scanning device to produce a two-dimensional digital image of transmitted light in the visible wavelengths; e) analyzing the digital image using the programmable image analysis algorithm; and f) determining whether the thermoplastic article sample is of acceptable quality based upon the output of the image analysis algorithm.
  • the thickness of the thermoplastic article sample is between about 10 and about 6200 microns.
  • the optical scanning device is a digital scanner.
  • the thermoplastic article sample is scanned at a resolution of greater than about 300 dpi.
  • the thermoplastic article sample is scanned at a resolution of greater than about 600 dpi.
  • the determination of acceptable quality is based upon percentage of the area of the thermoplastic article sample occupied by the filler particles in the captured image.
  • an acceptable article comprises less than 0.2% of the thermoplastic article area occupied by filler particles in the captured image.
  • the filler particles are inorganic particles, preferred composition is titanium dioxide.
  • FIG. 1 is a pictorial view illustrating one exemplary apparatus useful in the presently invention.
  • FIG. 2 illustrates a section of an exemplary scanned image of a thermoplastic film sample in panel "(a) and (c)” and a corresponding analyzed image showing the detected filler particles in panel “(b) and (d)."
  • Panels (a) and (b) correspond to sample A listed in Table 4 having a rating of "8" and Panels (c) and (d) correspond to sample D listed in Table 4 having a rating of "0".
  • FIG. 3 is a chart correlating the percent filler particle area value to visual rating score.
  • the method of the present invention involves capturing an image of the light transmitted through a thermoplastic article sample, such as a thermoplastic film sample, using an optical scanning or image capturing device and then analyzing that captured image via a computerized analysis program.
  • a thermoplastic article sample such as a thermoplastic film sample
  • an optical scanning or image capturing device By capturing an image using transmitting light (as opposed to just reflected light), this apparatus and method allow for an assessment of particles both on the surface of the thermoplastic article and embedded within the thermoplastic article.
  • the optical scanning or image capturing device comprises a digital scanner.
  • the digital scanner is a standard flatbed scanner without a reflective cover. Numerous such scanners are commercially available and their mode of operation is well known in the art.
  • Such scanners can be connected to a computer or similar image analysis device using appropriate wired or wireless connections to allow for analysis of the captured images.
  • Such scanners comprise a transparent surface, such as a glass plate, onto which a sample to be scanned is placed.
  • a light source external to the scanner is utilized to cause light to impede upon the sample.
  • the scanner is capable of scanning at a resolution of 300 dots per inch (dpi), 400 dpi, 500 dpi, 600 dpi, 700 dpi, 800 dpi, 900 dpi, 1000 dpi, 1200 dpi, 1500 dpi, 1800 dpi, 2400 dpi, or higher.
  • dpi dots per inch
  • thermoplastic article sample is actually scanned at a resolution of 300 dots per inch (dpi), 400 dpi, 500 dpi, 600 dpi, 700 dpi, 800 dpi, 900 dpi, 1000 dpi, 1200 dpi, 1500 dpi, 1800 dpi, 2400 dpi, or higher.
  • dpi dots per inch
  • the capture device is a digital camera.
  • Light from the external light source that is transmitted through the sample is captured in a digital image by the digital camera.
  • a digital camera with a capture resolution of at least about 2000 pixels x 3000 pixels can be employed.
  • the image capture device is a laser scanner. In such embodiments,
  • the laser is scanned on one side of the film and a detector is placed on the other side to record the amount of transmitted light for each position of the laser beam.
  • a detector is placed on the other side to record the amount of transmitted light for each position of the laser beam.
  • FIG. 1 An exemplary type of image capture device that can be employed is shown in FIG. 1.
  • the apparatus comprises an imaging assembly 12 and an associated computer 14 for
  • the imaging assembly 12 comprises a light-tight housing 20 in which is mounted a light source 26 and an imaging apparatus 28.
  • Imaging apparatus 28 includes face 30 onto which a thermoplastic article sample to be imaged is placed.
  • Imaging apparatus 28 is attached to computer 14 via appropriate wiring or wireless connections to allow transfer of the captured image from imaging apparatus 28 to computer 14 for analysis.
  • Housing 20 is shown in FIG. 1 as a generally rectangular enclosure having side walls, a top wall (upon which is mounted light source 26), a hinged door 22, and bottom wall 24 (upon which is mounted the optical scanning or image capture device 28).
  • any suitable shape could be employed, including a generally square enclosure, a dome shaped enclosure, or a pyramidal enclosure.
  • the arrangement of light source 26 and optical scanning or image capture device 28 within enclosure 20 can be altered so long as light from light source 26 can still impinge upon face 30 of optical scanning or image capture device 28 and any sample placed thereon.
  • light source 26 could be mounted to a side wall of enclosure 20 or could be mounted on bottom wall 24 of enclosure 20 with a fiber optic assembly or reflector assembly employed to direct light such that it impinges upon face 30 of optical scanning or image capture device 28.
  • Housing 20 can be made from any suitable material, and numerous such materials are well known in the art. Suitable materials include wood, metal, or plastic. Any suitable light source can be employed as light source 26. In certain examples, the light source may be an incandescent lamp, a fluorescent lamp, a halogen lamp, or a xenon arc lamp. In other examples, light source 26 may include a bulb assembly and a fiber optic illuminator bundle.
  • thermoplastic article sample 32 to be tested is placed on face 30 of optical scanning or image capture device 28 and enclosure 20 is closed so as to substantially eliminate all external light.
  • Light source 26 is activated such that the light emitting from the source impinges upon thermoplastic article sample 32.
  • Optical scanning or image capture device 28 is then activated, thereby allowing it to capture an image of the light transmitted through thermoplastic article sample 32 onto face 30.
  • the captured image is then transferred to computer 14 for image processing and analysis via wired or wireless connections.
  • housing 20 could also be used in conjunction with other types of optical scanning or image capture devices, such as the flatbed scanner discussed above.
  • a housing may be employed, for example, to reduce the effects of ambient light during image capture, therefore providing improved run-to-run reproducibility.
  • the detection of a particle is based on its local contrast level, that is, the relative grey level of the particle compared with its local neighborhood.
  • its local contrast level that is, the relative grey level of the particle compared with its local neighborhood.
  • particles appear as dark spots against a relatively light background as in the example image of FIG. 2.
  • the software and algorithm are used to analyze the entire area of the captured image, while in other examples only a selected portion of the captured image will be analyzed.
  • an image of the thermoplastic article sample is captured, as discussed above.
  • a square local neighborhood area is constructed, centered on the pixel.
  • the length of a side of the square, SI, in pixels is specified.
  • SI is set to a value of 21, though other values, such as 15, 16, 17, 18, 19, 20, 22, 23, 24, 25, 26, or 27, could also be used.
  • the average grey level G, of the pixels along a perimeter area of the square is first determined.
  • a 2-pixel wide perimeter surrounding the pixel of interest is used to calculate the average grey level G.
  • the perimeter has an outer side length of SI pixels and an inner side length of (Sl-2) pixels.
  • different perimeter widths such as 1, 3, 4, 5, or 6, could be used.
  • the Sensitivity Factor S2 expressed as a percentage, is selected. Typically, S2 is set to a value of 50 percent, though other values, such as 30, 35, 40, 45, 55, 60, 65, 70, 75, 80, 85, 90, or 95, could also be used. If the grey level of the center pixel is less than the S2 percentage of this average grey level G, then the center pixel is considered part of a particle. That is, the condition for particle detection is: Center pixel grey level ⁇ S2*G/100
  • the full internal area of the local neighborhood square is not used to calculate average grey level G. This is done because, in certain cases, if the particle size dimension approaches the value of SI, then the particle itself could unduly influence the value of G, thus preventing detection of all of the pixels inside the particle. If desired, a different neighborhood can be used, for example a 3-pixel wide square.
  • a separate, auxiliary image array can be created that initially has all pixels set to a grey level zero (0) (OFF). If a pixel in the sample image meets the above detection criterion as a particle, then its corresponding (i.e., same location) pixel in the auxiliary image array is set to a fixed value, say 255 (ON).
  • the binary auxiliary image created will contain regions of contiguous pixels set to the ON value. Each of these regions of contiguous pixels corresponds to a specific particle in the sample image.
  • This auxiliary binary image may be traced, using standard binary image tracing methods, to locate each of the particles as separate objects. In some embodiments, in the original sample image, the regions that have been determined to be particles can then be highlighted, e.g. in red, for visual feedback to the operator.
  • the number of particles within the analyzed image can be determined. Additionally, the area of the particles within the image can be calculated, as can the total area analyzed. These values can then be used to calculate a percent area of the analyzed image occupied by particles. Other values, such as particle size distribution and particle size standard deviation, can also be derived from the analyzed images. These values can in turn be used to assess the dispersion of filler particles within the sample, or to assess the overall quality of the sample.
  • Such an assessment can be based, for example, on the total number of particles within the analyzed area, the average size and/or standard deviation of the size of the particles within the analyzed area, or the percentage of the analyzed area occupied by filler particles.
  • the preferred quality assessment criteria is the percentage of the analyzed area occupied by filler particles.
  • the scanner was operated using version 3.8.0.1 of the Epson Scan program with the following configuration/settings:
  • Image Analysis Images were analyzed using an object detection and measurement algorithm as described above and U.S. Patent No. 7,639,862.
  • the program parameters used were as follows:
  • FIG. 2 illustrates an exemplary scanned image in panel "A" with the detected particles shown in panel "B.”
  • thermoplastic film sheets and/or scanner face Due to the unavoidable presence of dirt, dust, and fibers on the thermoplastic film sheets and/or scanner face, it is useful to examine each processed image to determine if any such contaminants were detected as particles, thus biasing the data. In those cases where the presence of a contaminant was obvious, the artifact in the corresponding input image was removed using the Photoshop cloning tool and the image was re-submitted to the program. In an analysis of 201 films, about 15% of the images required this additional step.
  • a Quality Rating greater than 5 can be considered a good quality sample.
  • a Quality Rating greater than 6, 7, 8, or 9 can be considered a good quality sample.
  • thermoplastic film samples were assigned Quality Ratings as shown in Table 4. thermoplastic film samples.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • Theoretical Computer Science (AREA)
  • Quality & Reliability (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

Cette invention porte sur des procédés pour analyser des défauts dans un article thermoplastique contenant des particules de charge. Dans certains aspects, le procédé met en œuvre la fourniture d'un échantillon d'article thermoplastique, l'échantillon d'article thermoplastique comprenant un matériau de base thermoplastique à l'intérieur duquel des particules de charge sont dispersées ; la fourniture d'un dispositif de balayage/capture optique apte à balayer et à capturer des images de lumière transmises à travers ledit article dans les longueurs d'onde visibles ; la délivrance d'un code exécutable par un ordinateur comprenant un algorithme d'analyse d'image ; le balayage de l'échantillon d'article thermoplastique avec le dispositif de balayage optique pour produire une image numérique en deux dimensions de la lumière transmise dans les longueurs d'onde visibles ; l'analyse de l'image numérique à l'aide de l'algorithme d'analyse d'image programmable ; et la détermination du fait que l'échantillon d'article thermoplastique est ou non d'une qualité acceptable sur la base de la sortie de l'algorithme d'analyse d'image.
PCT/US2014/010793 2014-01-09 2014-01-09 Procédé pour analyser des défauts dans des articles thermoplastiques WO2015105490A1 (fr)

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PCT/US2014/010793 WO2015105490A1 (fr) 2014-01-09 2014-01-09 Procédé pour analyser des défauts dans des articles thermoplastiques

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4303702A (en) 1978-12-26 1981-12-01 E. I. Du Pont De Nemours And Company Flowability of rutile pigment
WO1995012489A1 (fr) * 1993-11-04 1995-05-11 Imperial Chemical Industries Plc Film polymere
WO2007141496A1 (fr) * 2006-06-07 2007-12-13 Qinetiq Limited Inspection optique
US7639862B2 (en) 2005-12-09 2009-12-29 E.I. Du Pont De Nemours And Company Method and apparatus for quantifying pigment dispersion quality by paint drawdown

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4303702A (en) 1978-12-26 1981-12-01 E. I. Du Pont De Nemours And Company Flowability of rutile pigment
WO1995012489A1 (fr) * 1993-11-04 1995-05-11 Imperial Chemical Industries Plc Film polymere
US7639862B2 (en) 2005-12-09 2009-12-29 E.I. Du Pont De Nemours And Company Method and apparatus for quantifying pigment dispersion quality by paint drawdown
WO2007141496A1 (fr) * 2006-06-07 2007-12-13 Qinetiq Limited Inspection optique

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
ESS J W ET AL: "Characterisation of distributive mixing in thermoplastics compositions", POLYMER TESTING, ELSEVIER, AMSTERDAM, NL, vol. 6, no. 3, 1 January 1986 (1986-01-01), pages 205 - 218, XP022835617, ISSN: 0142-9418, [retrieved on 19860101], DOI: 10.1016/0142-9418(86)90063-2 *

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