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
  • G01N21/89—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
  • G01N21/8915—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles characterised by the material examined non-woven textile material
• • 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
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
  • G06T7/00—Image analysis
  • G06T7/70—Determining position or orientation of objects or cameras
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
  • G06T2207/00—Indexing scheme for image analysis or image enhancement
  • G06T2207/30—Subject of image; Context of image processing
  • G06T2207/30108—Industrial image inspection
  • G06T2207/30124—Fabrics; Textile; Paper

Definitions

• the invention relates to a method for determining the orientation of the structure of the fibers of mineral wool mattresses and in particular of creped mineral wool mattresses.
• Crepe mineral wool mattresses that is to say in which the orientation of the fibers, instead of being parallel to a plane, is "almost random", are intended for various uses, in particular when we want to be able to exert on them, either a pressure without causing too much crushing, or a traction perpendicular to the surface without causing delamination.
• mineral wool mattresses are laminated, they are formed continuously by depositing on a conveyor the fibers which are transported by gas streams. Before they are deposited on the conveyor, the fibers are coated with a resinous composition intended to bind the fibers together, thus giving its cohesion to the mattress formed.
• the resinous composition applied in liquid form is crosslinked by a heat treatment carried out on the mattress previously brought back to the desired thickness and density conditions.
• European patent application EP-A-0 133 083 proposes that fiber mats collected on the receiving member, possibly after having been compressed in the thickness direction, be continuously compressed in the longitudinal direction by passing from a pair of conveyors with a certain speed to a pair of conveyors with a speed lower than the previous one.
• Higher higher compression rates can be achieved when compression is carried out in several successive stages, in particular with mattresses for which compression without the formation of folds is the most difficult to obtain.
• the properties of the products obtained can be improved when the compression is carried out in several stages. 3
• thermomechanical properties of these products are closely linked to the arrangement of the fibers in the mattresses.
• the creping is, up to now, evaluated qualitatively, that is to say from a visual appreciation, the creping rate, or even the compression rate in terms of speed variation between the conveyors, not being representative of the general properties of the products obtained.
• a visual assessment does not allow, in a reproducible manner, to state in a systematic way the possible link between the geometric characteristics of the product and its thermomechanical properties.
• such a quality control is absolutely not exploitable on the production line, for example, to carry out production control.
• the inventors set themselves to extract the preponderant directions, present at different scales, from the fibers in the mineral wool mattresses.
• the object of the invention is therefore to design a method for determining the orientation of the structure of the fibers of woolen mattresses. 4 mineral, and in particular of crepe mineral wool mattress, which makes it possible to determine the rate of vertical fibers and the fineness of the creping.
• this result is obtained by a process according to which: “a specific area of the mineral wool mattress is illuminated at an oblique angle of incidence,
• At least one image of said zone is recorded on a video camera arranged on an axis substantially perpendicular to the plane of this zone,
• each point of the image is assigned a digital signal corresponding to its light density, this digitization being carried out directly in the video camera or in a digitization stage mounted downstream.
• the invention thus provides a method by which a quantitative determination of the arrangement of fibers in a mineral wool mattress can be carried out in a simple manner without expensive optical installations.
• the installations necessary in the vicinity of the mineral wool mattress to be examined include only the lighting device and a video camera, and it is possible to easily arrange these installations directly at the level of a production line for mineral wool mattresses .
• the dusting of said zone will be carried out before the image is recorded, this dusting being able to be carried out, for example, by air jet under grazing incidence or by suction under high pressure.
• the video camera is connected to the input of an image acquisition and processing card making it possible to digitize the image in 512 x 512 pixels on 256 gray levels.
• the card also has two parameters: gain and offset, which must be carefully adjusted for good quantization of the video signal.
• a CCD (charge coupled Deviced) camera will be used, the CCD sensor of which is fitted to the camera comprises 768 ⁇ 512 square photosensitive elements of size 10 ⁇ 10 ⁇ m 2 .
• the rate of vertical fibers and the fineness of the creping are determined, from the signals 5 numerical, using a Wavelet transform algorithm of a two-dimensional function and preferably, using a 2D Wavelet transform algorithm.
• the inventors have highlighted, among the many functions which verify the conditions of admissibility in the sense of the Wavelets, that the MORLET wavelet was advantageously adapted and this for its aptitude of orientation selection and its oscillating pace which is close to the texture of the images to be analyzed.
• the orientation of the structure orientation of the mineral wool mattress fibers is determined according to the successive stages:
• the inventors have shown that the values obtained from an image are reproducible from several images recorded at different locations of the same product. In this way, by averaging over several images of the same control area taken at different locations, representative average values are formed.
• the process according to the invention is applicable to a static product or to a production line for mineral wool mattresses such that the mattress is positioned on a moving conveyor.
• the invention also relates to an apparatus for carrying out the method according to the invention.
• This device advantageously consists of a lighting device which illuminates a determined area of the mineral wool mattress at an oblique angle of incidence, a CCD camera arranged on an axis substantially perpendicular to the plane of said area and a image processing system.
• this device also comprises a dust removal device which will advantageously be a device which blows air under a grazing incidence or a device which sucks under high pressure.
• the image processing system comprises a filtering stage executed by means of a filter resulting in the image domain of a two-dimensional linear transformation, such as a wavelet transformation of MORLET 2D.
• the method described above is applied to obtain correlation data between mechanical and / or thermal properties of mineral wool mattresses and the values of the vertical fiber content and the fineness of the creping obtained.
• Figure 1 a block diagram of the device necessary for the execution of the process.
• Figure 2 a synoptic table of the essential components necessary for digital image processing.
• Figure 3 a synoptic table of the circuit for calculating the rate of vertical fibers and the fineness of creping from the digitized signals.
• Figure 4 the printed representation of a profile of the fineness of the crepe measured.
• Figure 5 the printed representation of a profile of the rate of vertical fibers measured.
• a strip of mineral wool 1 with a thickness of approximately 40 mm produced in continuous operation represented here in the form of a segment of mineral wool panel, moves at a speed of approximately 20 m per minute depending on the thickness of the panel, in the direction of arrow F and towards a cutting station not shown.
• a sufficiently large area on one plane side of the strip of mineral wool 1 is dusted by an air jet 2 under grazing incidence.
• halogen lamps 3 and 4 are placed next to the strip of mineral wool 1.
• the light emitted by the halogen lamps 3 and 4 reaches the planar side of the strip of mineral wool 1 at an angle of incidence between 30 and 60 degrees and preferably at an angle of incidence of 45 degrees.
• Oblique lighting at as wide an angle of incidence as possible is advantageous for obtaining good clarity of the acquired image.
• the angle of incidence cannot be too large because an increasing fraction of light is then reflected by the strip of mineral wool, which overexposes the camera.
• a CCD camera 5 is arranged between the two lamps 3 and 4 substantially perpendicular to the side of the strip of mineral wool 1.
• the images recorded by the CCD camera 5 are transmitted by line 6 to an image processing system 7 in which digital image processing takes place.
• the image processing system 7 comprises, as appears from the schematic representation of FIG. 2, a processor 9, a computer 10 and a mass memory 11.
• a control keyboard 12, as well as a display device data 13 and a printer 14 are connected to the computer 10.
• the device for digital image processing can comprise a video display 15 connected to the processor 9 and a video plotter 16.
• the CCD camera contains an analog / digital converter 8. In this converter 8, the signals for each point of the image, which define its position and its brightness or gray value, that is to say its light density, are converted to corresponding digital signals. In order to be able to describe the light density with sufficient precision using digital signals, the luminosity range to be covered in total must be subdivided into a sufficiently large number of gray levels.
• the number of gray levels must be at least 128 and good results are obtained when 256 gray levels are available.
• the processor 9 has the function, inter alia, of converting, according to known image processing methods, the original video image into a transformed video image having a better contrast than that of the original image. Image processing cards available on the market can be used for this so-called image processor 9.
• the processor 9 includes an image memory in which the video image whose contrast has been improved is stored.
• the video image transformed using the processor 9 and having an improved image contrast now forms the basis of the subsequent image processing carried out by the computer 10.
• the computer 10 calculates, using an algorithm developed for this purpose, from the light density information stored in the image memory of processor 9, the rate of vertical fibers and the fineness of the creping.
• a mass memory 11 which is used to store the programs and to archive the video images with improved contrast and / or the images calculated therefrom, as well as the values of the vertical fiber rate and fineness associated crepe.
• b is a translation parameter and ⁇ is an orientation parameter.
• the rate of vertical fibers is calculated on the expansion scale 0.3 ⁇ 0.6 and the fineness of the creping on the expansion scale 0.05 ⁇ a ⁇ 0, 3, these scales being of course modular according to the nature of the mineral wool product and the criterion to be studied. Then, one can graphically represent the rate profile of vertical fibers as well as the profile of the fineness of the creping. These calculations can be done using the formulas: ⁇ n ⁇ & 0 ° ⁇ " ⁇
• TJV ⁇ cos (2,0,). ⁇ C ( ⁇ ,) - ⁇ C (0.)
• the rate of vertical fibers and of the fineness of creping it is therefore sufficient for the calculation of the rate of vertical fibers and of the fineness of creping to know the shape of the luminosity or effective light density on an area of the strip of mineral wool 1, in the form of numerical quantities for the various points of the image to be able to immediately deduce the appearance of the rate of vertical fibers and the fineness of the fibers.
• the evaluation will be made on the basis of several successive images taken on the same side of the strip of mineral wool 1 but at different locations and the results of the calculation of the accumulations are averaged to obtain the final values.
• the evaluation will be made on the upper half and the lower half of the thickness of the strip of mineral wool 1 by differentiating the values obtained for each of the halves in order to '' obtain a better accuracy of the general orientation of the fiber structure in the mineral fiber mat.
• FIG. 3 illustrates in the form of a schematic table how the computer 10 performs the processing of the various points of the image, for example, during the evaluation of a single video image.
• the digitized measurement value of the brightness L of each point of the image is transmitted by the line 17 to a Gaussian filter 18 in the frequency space.
• the signal appears which corresponds to the moduli of the coefficients of the 2D MORLET Wavelet transform for a and ⁇ given, C f (a, b, ⁇ ).
• This signal appears which corresponds to the moduli of the coefficients of the 2D MORLET Wavelet transform for a and ⁇ given, C f (a, b, ⁇ ).
• C ⁇ a.b. ⁇ is transmitted to a summation stage 20 in which is formed the average of the modules of the coefficients of the Wavelet transform of MORLET MCT0 (a, ⁇ ), the latter then being transmitted to a summation stage 21 in which is formed the sum of the coefficients MCT0 (a, ⁇ ) on the scale of 11 dilation 0.05 ⁇ ⁇ 0.3, C, 0 Qi 0 3 ⁇ ) and to another summation stage 22 in which the cumulative coefficients MCT0 (a, ⁇ ) are formed on the expansion scale 0, 3 ⁇ a ⁇ 0.6, C, 0 3 0 6 , [ ⁇ ].
• the cumulative signal C, 0 05 Q 3 , ( ⁇ ) is transmitted to a subtraction stage 23 in which the standard deviation of the accumulations is formed and the cumulative signal 030 6 , (6>) is transmitted to a stage of subtraction 24 in which the weighted calculation of the rate of vertical fibers is formed.
• the lines 25 and 26 at the respective outputs of the subtraction stages 23 and 24 each now carry a signal which corresponds directly to the fineness of the fibers and to the rate of vertical fibers respectively at the location relating to the image measured. These signals can now be transmitted to the various units shown in Figure 2 for further evaluation and / or storage.
• the result of the signal processing executed in the described manner can be represented and archived in any way.
• a mode of representation which can just as easily be reproduced on the video display as it is printed, is represented in the form of representations printed in FIGS. 4 and 5.
• FIG. 4 represents, in polar coordinates, the profile of the accumulations of the coefficients MCT0 ( ⁇ , ⁇ ) on the expansion scale 0.05 ⁇ ⁇ ⁇ 0.3.
• the standard deviation of the accumulations being highlighted visually by the drawing of the circles representing the maxima and minima.
• FIG. 5 represents, in polar coordinates, the profile of the accumulations of the coefficients MCT0 ( ⁇ , ⁇ ) on the expansion scale 0.3 ⁇ ⁇ 0.6, the predominant orientation of the fibers being highlighted visually by the line drawing connecting the maxima.
• the position and values of fiber orientation faults in particular in the case of creped mineral wool panels, can thus be detected 12 and automatically archived.
• the data can possibly be transmitted, by a coupling interface, to an automation system in which the cutting of the strip of mineral wool and the sorting of the panels of mineral wool can be done on the basis of these data according to the different requirements quality or in which the longitudinal compression speed of the crêpereuse can be adjusted on the basis of these data.
• Such a determination method can also be implemented on a static product at a location other than on a production line.
• a determination of the orientation of the structure of the fibers of the product makes it possible to correlate in a precise manner properties of the product such as, for example, mechanical or thermal properties, with the calculated values of the rate of vertical fibers and of the finesse of creping.
• Such correlation analyzes thus provide better knowledge and mastery of mineral wool products.
• the invention is not limited to this embodiment and must be interpreted in a nonlimiting manner and encompassing all types of methods for determining the structure of the fibers of mineral wool mattresses according to which a specific area of the wool mattress is illuminated mineral at an oblique angle of incidence, at least one image of said area is recorded on a video camera in a measurement field which extends substantially perpendicular to the plane of said area, each point of the image is assigned a digital signal corresponding to its light density, this digitization being carried out directly in the video camera or in a digitization stage mounted downstream, the rate of vertical fibers and the fineness of creping from digital light density signals.

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

Applications Claiming Priority (3)

Publications (1)

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• 1999
  • 1999-04-15 PL PL99337514A patent/PL337514A1/xx unknown
  • 1999-04-15 WO PCT/FR1999/000882 patent/WO1999056112A1/fr not_active Application Discontinuation
  • 1999-04-15 JP JP55370899A patent/JP2002507286A/ja active Pending
  • 1999-04-15 CA CA002294441A patent/CA2294441A1/fr not_active Abandoned
  • 1999-04-15 EP EP99913415A patent/EP0991936A1/fr not_active Withdrawn
  • 1999-04-15 AU AU31545/99A patent/AU3154599A/en not_active Abandoned
  • 1999-04-15 CN CN99800990A patent/CN1272918A/zh active Pending
  • 1999-04-15 KR KR19997012162A patent/KR20010014112A/ko not_active Application Discontinuation
  • 1999-04-15 SK SK1812-99A patent/SK181299A3/sk unknown
  • 1999-04-15 HU HU0002544A patent/HUP0002544A2/hu unknown
  • 1999-04-15 BR BR9906374-3A patent/BR9906374A/pt not_active Application Discontinuation
  • 1999-04-22 AR ARP990101853A patent/AR019093A1/es unknown
  • 1999-12-22 NO NO996406D patent/NO996406D0/no unknown
  • 1999-12-22 NO NO996406A patent/NO996406L/no not_active Application Discontinuation

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