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
  • 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
  • G01N21/90—Investigating the presence of flaws or contamination in a container or its contents
  • G01N21/9054—Inspection of sealing surface and container finish
• • 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
  • G01N21/90—Investigating the presence of flaws or contamination in a container or its contents
  • G01N21/909—Investigating the presence of flaws or contamination in a container or its contents in opaque containers or opaque container parts, e.g. cans, tins, caps, labels
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2201/00—Features of devices classified in G01N21/00
  • G01N2201/06—Illumination; Optics
  • G01N2201/063—Illuminating optical parts
  • G01N2201/0636—Reflectors
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2201/00—Features of devices classified in G01N21/00
  • G01N2201/10—Scanning
  • G01N2201/105—Purely optical scan

Definitions

• the subject of the invention disclosed herein is a system for control of the externa! surfaces and geometry of objects manufactured on production lines, utilizing peripheral observation at a full 360° angular range.
• the system is intended for automatic quality control of seals such as corks, caps securing packaging for liquids (bottles, vials, etc.).
• seals such as corks, caps securing packaging for liquids (bottles, vials, etc.).
• the construction of the system allows it to perform control on continuous motion production lines.
• Patent application no. EP0047936 provides a solution enabling the circumferential view of the peripherally axial symmetrical objects making use of a pair of conical mirrors (concave and convex), which by way of a light beam reflection form an image of the outer surface of the peripherally symmetrical object in the image plane of a camera.
• the device uses a peripheral illuminator located on the outside of the mirrors.
• WO2015185318 describes a device for controlling container closures, particularly caps.
• the device consists of a lens, an illumination system and a camera.
• the lens is made up of at least two parts (including an aspherical one), which makes correction of the spherical aberration of the system possible, favourably affecting parameters of the recorded image.
• Patent application no. WO2014023580 reveals a device for controlling container closures, including symbols on their top surface.
• This device equipped with a system of multiple cameras allows for a complex, circumferential view of the closure from several directions.
• the device makes observation of all the external surfaces of the closure possible, but in order to observe the upper and lateral surfaces of the closure, a separate camera is required to follow the upper surface and a separate set of cameras (at least three) to observe the lateral surface at full angular range.
• Patent application no. US2013208105 reveals a device for controlling vessels which are fixedly mounted on a processing machine.
• the device is made up of a lens-type camera, an illumination system mounted in a stationary casing and a movable mirror which is lowered during the inspection and covers the test element.
• the applied optical system transforms the circumferential images of the examined surface (upper, lateral and bottom) onto a plane of the camera.
• This device provides full observation of all the external surfaces of the examined object, however due to the use of a movable element (perpendicularly to the direction of movement of the examined object) this device cannot be used in continuous motion production lines where the examined object is not stopped during the production process.
• the use of the movable element makes the construction of the system excessively complicated.
• the diameter of the cylindrical casings' arrangement determines the size of the field observed by the camera, and the diameter of the cylindrical casing determines the size of the mirrors within, thus indirectly the size of the image recorded by the camera.
• Four identical cylindrical casings with mirrors are arranged over the circumference of the large diameter, several times greater than the diameter of the examined object and the diameter of the cylindrical casings. It unfavourably influences the imaging system as the images of the examined object (recorded from four directions) are a small part of the image recorded by the camera.
• the aim of the invention disclosed herein is to provide a system for control of the external surfaces and geometry of objects manufactured on production lines, utilizing peripheral observation at a full 360 ° angular range, in particular for automatic control of the quality of closures (such as caps) of the packaging for liquids ⁇ inter alia bottles, vials ⁇ , enabling control on continuous motion production lines and free of the faults of the already known solutions.
• the system for control of the external surfaces and geometry of objects manufactured on production lines, utilizing peripheral observation at a full 360° angular range, in particular for automatic control of the quality of the element closing the container (such as cap), consisting of a lens- type digital camera, a single illuminator, mirrors and a casing is characterized in that the casing with an illuminator inside is provided with only one pair of mirrors arranged in such a way that their bottom edge is below the examined object, and the object such as a cap closing a container is transported between the mirrors through an opening in the casing by a conveyor, while the rays reflected off the mirrors image the object being inspected at the full range.
• two pencils of rays coming out of the entrance pupil of the lens each of an angle smaller than 180°, after being reflected off the mirrors, form an image of the examined object at the full angular range of 360 ° in a cross-section perpendicular to the optical axis of the iens.
• the two pencils of rays coming out of the entrance pupil of the lens after being reflected off the mirrors, image the lateral and bottom surfaces or their part, in a section containing the optical axis of the lens.
• the pair of mirrors is placed at the same height, at a predetermined distance from each other, preferably - symmetrically about a plane containing the symmetry axis of the object.
• the mirrors it is favourable for the mirrors to have the same geometry of the reflective surfaces.
• the examined object is illuminated by the illuminator, wherein its upper surface is illuminated directly and the lateral and bottom surfaces are illuminated through the pair of mirrors.
• the rays reflected off the surface of the object are recorded by the lens-type camera, and it is best to record the image of the upper surface directly and to record the images of the lateral and bottom surfaces at the full circumferential range of 360° with the use of optical rays reflected off the mirrors.
• optical filter which may be a neutral-density filter or a polarizing filter, between the lens and the examined object, which wi!! decrease the intensity of the image of the upper surface of the object.
• the light-reflecting surfaces of the mirrors are segments of a truncated cone cut by a plane parallel to the axis of the cone and distant from the axis of the cone, whereas the mirrors should be placed symmetrically about a plane containing the optical axis of the lens and the light-reflecting surfaces should be oriented towards the examined object.
• the imaging angle (2a) of the object circumference in a cross- section perpendicular to the optical axis of the lens is: where: r - radius of the cap, r' - radius of the arc, Ob - center of the object 2, intersection of the optical axis of the camera 6 with the plane ⁇ , Om - center of the circle, with the arc L being its segment, x - distance between Ob and Om, 2 ⁇ - angle between the rays reflected from the edges of the arc, 2a - imaging angle of the object 2 circumference.
• the light-reflecting surfaces of the mirrors are segments of a truncated cone of an angle adjusted to the object to be inspected.
• the cone apex angle between the light-reflecting surfaces may, in particular, be 120°.
• each mirror can also be a set of at least two interconnected segments of truncated cones of different inclination angles.
• the light-reflecting surfaces can also be segments of the rotationally symmetrical surfaces such as sphere, elliptical cone or ellipsoid. Due to technological reasons, it is most preferred when the mirrors 3.1 and 3.2 have the same geometry of the reflective surface and are located symmetrically about the container. However, it is possible to use mirrors of a different geometry of mirror surface, e.g. a segment of a cone (in the mirror 3.1) and a segment of a sphere (in the mirror 3.2).
• the system according to the invention is adapted for inspecting objects as they move on continuous motion production lines - due to an appropriate position near the examined objects.
• the system is ergonomic as it allows for full circumferential control of the containers' closures with the use of a single camera, and due to the fact that the pair of mirrors is used both for illuminating and recording the image of the lateral and bottom surfaces of the examined object, the need to use additional systems such as more cameras, mirrors, additional illuminators, etc., is reduced. What is more, by ensuring free movement of the examined object between the mirrors, it is not required to use additional propulsion system components.
• the invention will be described in detail on the basis of its exemplary embodiments, with reference to the attached drawings presenting:
• Fig. 1 a schematic diagram: exemplary arrangement of the mirrors in relation to the examined container positioned on the production line,
• Fig. 2 a top view of the system with the direction of the container's movement marked
• Fig. 3 a cross-sectional projection of the system in ⁇ _1 plane from Fig. 2,
• Fig. 4 the path of the rays coming out of the entrance pupil of the lens after being reflected off the mirrors in a cross-section perpendicular to the optical axis of the lens
• Fig. 5 the path of the rays coming out of the entrance pupil of the lens after being reflected off the mirrors in a cross-section containing the optical axis of the lens
• Fig. 6 an exemplary embodiment of the mirrors, in which the mirror surfaces are segments of a cone
• Fig. 8 an image recorded by the camera
• Fig. 10 a neutral-density filter
• Fig. 13 a cross-sectional projection of the system in ⁇ _2 plane from Fig, 2, with the path of optical rays shown,
• Fig. 14 a detailed view of part B of the system, marked in Fig. 13 with the exposed path of the rays coming out of the entrance pupil shown in Fig. 5,
• the system in accordance with the invention consists of a digital camera 7 with a lens 6, an illuminator 5 and a pair of mirrors 3.1 and 3.2.
• the illuminator 5 and the pair of mirrors 3.1 and 3.2 are mounted in a casing 4.
• the examined object 2 is closure of a container 1 , which - as shown in Fig. 1 - is continuously transported on a conveyor (devices of this type are known and do not require further explanation).
• the distance between the mirrors 3.1 and 3.2, and the opening in the casing 4 are designed to allow free movement of the container 1.
• the examined object 2 is iiiuminated by the iliuminator 5. As shown in Fig.
• the imaging system according to the invention is characterized in that the pencil of rays of the angle (2 ⁇ ) smaller than 180 ° , formed by the rays coming out of the entrance pupil of the lens, after being reflected off the curve L (L.1 or L.2), comprises the examined lateral surface of the object at the imaging angle (2a) greater than 180°. Since in this plane two curves being arcs L.1 and L.2 are put opposite to each other, imaging of the lateral and bottom surfaces of the object is achieved at the full range of 360 ° .
• mirrors 3,1 and 3.2 have the same geometry of the reflective surface and are placed symmetrically about a plane containing the optical axis of the lens. It is obvious to the specialist that using mirrors of different geometry, such as a segment of a cone in mirror 3.1 and a segment of a sphere in mirror 3.2, is also feasible.
• Fig. 9 presents an exemplary embodiment of the system according to the invention, where an optical filter 8 was placed between the lens 6 and the examined object 2. This filter eliminates overexposures in the images recorded by camera 7 representing the upper surface 2.1 of the object 2.
• the optical filter 8 may be a neutral-density filter (neutral filter with an adjusted range of the transmission value) as shown in Fig. 10.
• a neutral-density filter 8 has the shape of a filtering surface 9 which, located in a filter 8 plane, diminishes the intensity of only the rays imaging the upper surface 2.1 of the object 2.
• a polarizing filter may also be applied for observing the object 2 of non- metal upper surface 2.1.
• the optical axis of the lens 6 of the camera 7 was coaxial with the symmetry axis of the controlled cap 2 of 18-mm external diameter, 2-mm width of the bottom crimp connection (the bottom surface of the cap) and 6-mm height.
• the examined cap 2 has been illuminated by the illuminator 5.
• Camera 7 directly recorded the image of the upper surface 2.1 of the cap 2, and with utilization of the mirrors 3.1 and 3.2 recorded a full circumferential view (of 360° range) of the lateral surface 2.2 and bottom surface 2.3 (crimp connection) of the cap 2.
• Mirrors 3.1 and 3.2 had the same geometry.
• Light-reflecting surfaces of the mirrors 3.1 and 3.2 were segments of a truncated cone of an inclination angle of 120°, a radius of the top base equal to 35.5 mm and a radius of the bottom base of 24 mm, cut by a plane parallel to the axis of the cone located 14 mm away from it.
• Mirrors 3.1 and 3.2 were located symmetrically about a plane containing the optical axis of the lens, the light-reflecting surface was oriented towards the examined cap 2.
• the distance between the optical axis of the lens 6 and the axis of the truncated cone whose segment was the reflecting surface of the mirror 3.1 was 4 mm.
• the distance between the optical axis of the lens 6 and the axis of the truncated cone whose segment was the reflecting surface of the mirror 3.2 was also 4 mm.
• the distance between the mirrors 3.1 and 3.2 was 20 mm.
• the bottom edges of the mirrors 3.1 and 3,2 were located 16 mm below the bottom edge of the cap 2.
• Such shape and position of the mirrors 3.1 and 3.2 allowed for full imaging (at a range of 360°) of the lateral surface 2.2 and bottom surface 2.3 of the cap 2, at the same time enabling free movement of the vial 1 (with a diameter of 18 mm) with the cap 2 between the mirrors 3.1 and 3.2.
• Imaging angle 2a of the circumference of the cap 2 obtained with the use of the arc L, is specified by the following formulas:
• the imaging angle 2a is 242°;
• Radii of the arcs 35.5 mm and 24 mm are determined by the upper and bottom edges of the mirror 3.1.
• the imaging angle 2a in this case is 260°.
• Imaging angles for the mirror 3.2 were in this embodiment the same and because the mirrors 3.1 and 3.2 are located symmetrically opposite to each other, the lateral surface 2.2 and bottom surface 2.3 of the cap 2 were imaged at the full angular range. Moreover, a part of the lateral surface 2.2 and bottom surface 2.3 of the cap 2 was imaged with both mirrors - 3.1 and 3.2; these were overlaps, thanks to which the system of quality control based on the system according to the invention proved to be resistant to inaccuracies of positioning of the vial 1.
• the optical rays between the cap 2 and the entrance pupil of the lens 6 were reflected as well in planes ⁇ containing the optical axis of the lens 6.
• the optical rays in the planes ⁇ were reflected off the surface of the mirror according to geometrical optics Saws: light incident on the mirror surface was reflected, while the incident ray, normal to the reflecting surface and reflected ray were in one plane and the angle of incidence was equal to the angle of reflection.
• a lens with a focal length of 25 mm was used, the distance between the entrance pupil of the iens 6 and the upper surface of the cap was 305 mm.
• the distance between the bottom edges of the mirrors 3.1 and 3.2 and the upper surface of the cap 2 was 22 mm. Two extreme cases of the imaging of the cap 2 were taken into consideration:
• the image shown in Fig. 8 recorded by the camera 7 directly represents the obtained image of the upper surface 2.1' of the cap 2, and the image of the mirrors 3.1' and 3.2' reveals the imaging of the lateral surface 2.2' and bottom surface 2.3' of the cap 2.
• the area of the upper surface 2.1' of the cap 2 had significantly higher intensity than the areas of the lateral surface 2.2' and bottom surface 2.3' of the cap 2.
• a neutral-density filter was applied with a transmission coefficient of 30%. This filter was located at a distance of 31 mm from the entrance pupil of the lens 6.
• the pencil of rays imaging the upper surface 2.1 of the cap 2 covered an area of a diameter of 2 mm.
• Neutral-density filter 8 had the shape of a circle 9 of a diameter of 4 mm, which equalized the intensity in the recorded areas, and thus positioning errors of the container 1 and the examined object 2 did not have an unfavourable impact on the recorded image.

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• Physics & Mathematics (AREA)
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• Life Sciences & Earth Sciences (AREA)
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• Analytical Chemistry (AREA)
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• General Health & Medical Sciences (AREA)
• General Physics & Mathematics (AREA)
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Cited By (8)

Citations (12)

• 2016
  • 2016-05-10 PL PL417147A patent/PL229618B1/pl unknown
• 2017
  • 2017-04-26 WO PCT/PL2017/000044 patent/WO2017196193A1/en not_active Ceased

Patent Citations (12)

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