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
  • G01N21/8806—Specially adapted optical and illumination features
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B11/00—Measuring arrangements characterised by the use of optical techniques
  • G01B11/002—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates
• • 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
  • G01N21/8901—Optical details; Scanning details
• • 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
  • G01N21/8806—Specially adapted optical and illumination features
  • G01N2021/8822—Dark field detection
  • G01N2021/8825—Separate detection of dark field and bright field
• • 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
  • G01N21/8914—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles characterised by the material examined
  • G01N2021/8917—Paper, also ondulated
• • 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
  • G01N21/896—Optical defects in or on transparent materials, e.g. distortion, surface flaws in conveyed flat sheet or rod

Definitions

• the invention relates to an image capturing system and to a quality inspection station adapted for inspecting sheet elements in a sheet element processing machine.
• sheet element processing machine is here intended to comprise any machine which is being used for processing sheet elements such as paper, cardboard, plastic foil or similar materials, in particular printing machines, coating machines, laminating machines and converting machines (for example cutting, stamping, folding and/or gluing machines).
• the object of the invention is to allow inspecting the surface of sheet elements to be inspected in different respects.
• the invention provides an image capturing system comprising a line camera capturing a linear viewing area, a dark-field illuminator and a bright-field illuminator illuminating the viewing area, wherein the components are arranged such that with respect to a reference plane which is perpendicular to the surface of the inspected sheet element passing through the linear viewing area, the optical plane of the camera being arranged with an angle of approx. 10° to 30°, preferably 20°, with respect to the reference plane, the optical plane of the dark-field illuminator being arranged at an angle of approx.
• the optical plane of the bright-field illuminator being arranged at an angle of approx. 20° to 40°, preferably 30°, with respect to the reference plane, the bright-field illuminator (16) having an opening angle between 50° and 1 10°, preferably between 80° and 90°.
• the distance of the camera is 600 mm ⁇ 200mm depending on the width to cover. It is possible to use more than one line camera together with the same illumination system, in particular two or three cameras.
• a mirror can be used to fold the path of the light towards the camera.
• the dimension of the viewing area measured perpendicular to the direction of movement of the sheet elements, can be 400 mm to 1500 mm and sometimes even up to 3200 mm in length, with the dimension parallel to the direction of movement of the sheet elements being very low, for example only a few millimeters in width.
• the camera and the dark-field illuminator are arranged on the same side of a reference plane, and the bright-field illuminator is arranged, with respect to the same reference plane, on a side which is opposite the side at which the camera is arranged.
• the dark-field illuminator generates light with an intensity at a field of view of the camera which does not significantly change over a height in the order of 10 mm to 12 mm. This on the one hand makes the image capturing system insensitive regarding mounting tolerances. On the other hand, it allows illuminating a viewing area of the camera with an intensity which does not change even if the thickness of the sheet elements being inspected changes considerably.
• the bright-field illuminator comprises a plurality of adjacent rows of light sources. This allows illuminating the viewing area of the camera under different illumination angles.
• the camera and the illuminators combined to a self-contained unit.
• the invention provides a quality inspection station comprising this image capturing system, the quality inspection station being adapted for inspecting sheet elements in a sheet element processing machine.
• the idea underlying the invention is to have a comparatively small unit which can be installed in a machine at a suitable space without requiring too much effort for distributing the elements of the image capturing system within the machine.
• the unit is compact enough for being placed at a point where the camera can capture the necessary images in a viewing area.
• the camera and the illuminators are arranged in a common housing so that they can be installed in a pre-aligned manner. Further, the components of the image capturing system are protected against dust.
• the housing has a width which is below 30 cm which allows using the image capturing system in the confined space available in a sheet element processing machine.
• the housing here has the size of a shoe box.
• the image capturing system can in particular be used for inspecting the margin of the sheet elements being moved through the quality inspection station as a very compact unit with a small viewing area is sufficient for this task.
• Figure 1 schematically shows in a side view a surface inspection system according to the invention employed in a quality control station of a sheet element processing machine;
• Figure 2 schematically shows the surface inspection system of Figure 1 in a top view
• Figure 3 schematically shows the surface inspection system of Figure 1 in greater detail; and - Figure 4 schematically shows a surface inspection system in an alternative embodiment in a top view.
• a quality control station 2 is schematically shown, which is employed in a sheet element processing machine of which conveyor tables 3 are depicted.
• the sheet element processing machine can process sheet elements 4 which are being transported in the direction of arrow A.
• the sheet elements 4 can be sheets of paper, cardboard, plastic foil or a similar material, or they can be in the form of a longer web.
• the sheet element processing machine can be a printing machine, a stamping machine, a laminating machine, a folding machine, a gluing machine, etc.
• the quality control station 2 is used for controlling the quality of the sheet elements 4. To this end, a plurality of parameters can be checked, e.g.
• an image capturing system 10 is being used which is here adapted for capturing images of a viewing area 20. Viewing area 20 is arranged so the full width of a sheet element 4 (i.e. at 90 degrees to the direction A of travel of the sheet elements 4 through the machine) is covered. The images captured by the image capturing system 10 are being evaluated by an image evaluation unit (not shown) in order to verify if that surface features of the sheet conform to requirements.
• this may entail any one or more of the following: determining that surface elements (including printed, embossed, stamped (including with foil or holograms) or varnished elements are correctly positioned in the x direction, the y direction and regarding their orientation around the z axis, that the surface elements cover the required area, that surface elements are without omission, that surface elements do not extend beyond a predefined area, that the color reproduction is according to specification, and/or that the any three dimensional profile has been correctly reproduced.
• the image capturing system 10 here comprises a camera 12, a dark-field illuminator 14, and a bright-field illuminator 16.
• Camera 12 is adapted for capturing an image of a viewing area (a line of interest) 20 which is an elongate zone which extending perpendicularly to the direction A across the width of the sheet processing machine (and thus can be up to 3200 mm wide). Camera 12 is arranged at an angle a of approx. 20° with respect to a median plane M which is perpendicular to the surface of the sheet elements 4 within viewing area 20 and which forms a reference plane. Camera 12 is a line camera able to capture images of viewing area 20 at a rate of 20,000 to 40,000 images per second or even more.
• the resolution of the camera 12 is such that elements of the order of 0.05 to 0.3 mm on the surface of the sheet elements 4 can be resolved, preferably of 0.1 mm.
• Dark-field illuminator 14 is adapted for illuminating the viewing area 20.
• the optical plane of the dark-field illuminator 14 is arranged at an angle ⁇ of approx. 45° with respect to median plane M.
• the opening angle ⁇ of the dark-field illuminator 14 is in the range of 10° to 25°.
• Dark-field illuminator 14 can generally be of any type. In a particular embodiment, it comprises a row of LEDs arranged adjacent each other, and two reflectors arranged opposite each other along the row of LEDs.
• the reflectors have a contour such that the light directed onto viewing area 20 has an intensity which does (at least not considerably) change with changes of the height of the viewing area 20.
• thin sheet elements 4 e.g. paper
• thick sheet elements 4 e.g. thick cardboard
• the intensity changes less than 3%/mm in a vertical direction and less than 5% between the lowest and the highest level at which the surface of different sheet elements 4 can be (with this difference being in the order of 10 mm max.).
• the distance between viewing area 20 and dark-field illuminator 14 is in the range of 30 mm to 100 mm.
• Bright-field illuminator 16 is adapted for also illuminating the viewing area 20.
• the optical plane of the dark-field illuminator 16 is arranged at an angle ⁇ of approx. 30° with respect to the median plane.
• Bright-field illuminator 16 can generally be of any type. In a particular embodiment, it comprises several parallel rows of LEDs arranged adjacent each other, with each row being adapted for illuminating viewing area 20. This type of illuminator can be used in different applications for directing light in different directions to viewing area 20.
• LEDs 17 In the embodiment of Figures 1 to 3, eight rows of LEDs 17 are shown. A different number of rows can be used, preferably in the range of three to twelve rows and more preferably in the range of 5 to eight rows.
• a diffuser 19 is arranged between the LEDs 17 and viewing area 20, a diffuser 19 is arranged.
• the distance between diffuser 19 and the LEDs should be in the range of 30 to 100 mm.
• illuminator 14 In view of the fact that illuminator 14 is being used as a dark-field illuminator, it is arranged on the same side of median plane M as camera 12. Illuminator 16 however is, since it is being used as a bright-field illuminator, arranged on the opposite side of median plane M.
• the "opening angle" (designated with ⁇ ) of bright- field illuminator 16 is in the order of 80° to 90°.
• each row is oriented towards the viewing area.
• the rows are arranged equally spaced from each other, they are arranged relative to each other at substantially uniform angular offsets.
• the opening angle of bright-field illuminator 16 is divided in equal intervals by the rows of LEDs.
• FIG 4 an alternative embodiment is shown.
• the image capturing system 10 is being used for capturing images of a viewing area 20which is arranged so as to cover the margin of the sheet elements 4.
• the images captured by the image capturing system 10 are being evaluated by an image evaluation unit (not shown) in order to verify if test marks (shown schematically with reference numeral 22) have correctly been printed onto the sheet elements 4.
• test marks can consist of geometrical patterns, color samples, etc., which allow an operator to check if the sheet element processing machine is correctly set up.
• An important feature of the image capturing system 10 is that it is a self- contained unit. Camera 12 and the illuminators 14, 16 are integrated into a common housing 24.
• the advantage of integrating the components into a common housing is that it is only housing 24 which has to be mounted to the sheet element processing machine.
• the camera 12 and the illuminators 14, 16 can be precision-mounted and calibrated at the end of the manufacturing process so that only one element, namely housing 24, has to be properly aligned later.
• housing 24 protects the camera 12 and the illuminators 14, 16 from dust.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• Immunology (AREA)
• Pathology (AREA)
• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)

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Citations (5)

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• 2016
  • 2016-05-30 DE DE202016102851.5U patent/DE202016102851U1/de active Active
• 2017
  • 2017-05-17 SK SK501342018U patent/SK9053Y1/sk unknown
  • 2017-05-17 CN CN201790000885.2U patent/CN209589870U/zh active Active
  • 2017-05-17 CZ CZ2018-35741U patent/CZ32481U1/cs active Protection Beyond IP Right Term
  • 2017-05-17 PL PL127953U patent/PL127953U1/pl unknown
  • 2017-05-17 ES ES201890024U patent/ES1224499Y/es active Active
  • 2017-05-17 TR TR2018/17920U patent/TR201817920U4/tr unknown
  • 2017-05-17 AT ATGM9007/2017U patent/AT16584U1/de unknown
  • 2017-05-17 WO PCT/EP2017/025133 patent/WO2017207114A1/en active Application Filing

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