Classifications

• • 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
  • G01B11/30—Measuring arrangements characterised by the use of optical techniques for measuring roughness or irregularity of surfaces
  • G01B11/303—Measuring arrangements characterised by the use of optical techniques for measuring roughness or irregularity of surfaces using photoelectric detection means
• • 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
  • G01B11/30—Measuring arrangements characterised by the use of optical techniques for measuring roughness or irregularity of surfaces
• • 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
  • G01N21/86—Investigating moving sheets
• • 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
  • G01N21/86—Investigating moving sheets
  • G01N2021/8663—Paper, e.g. gloss, moisture content

Definitions

• Deviations in the web properties may be significant, for example, when the web, for example paper, is moved in high speed.
• the quality and properties of the paper are visible in the print quality, but also in the actual paper manufacturing phase when the paper web conveys paper in the process.
• deviations in the composition and/or structure may also change the print, or through insufficient strength due to structural issues it may cause uncontrollable breaking of the paper.
• the optics must be optimized so that the smallest possible aperture is used, in which case the image is not diffraction-limited, which causes problems in the selection of light source for creating sufficient illumination efficiency.
• it is necessary to take into ac- count sufficient light exposure on the camera cell because when the diameter of the aperture is halved, the luminosity through the aperture drops to a quarter of that of the non-halved aperture.
• the arrangement according to an embodiment of the invention comprises, for im- aging the topography of a specific point of the surface of a moving web in a illumination that is implemented with such incoherent radiation that has at least a first wavelength component and another wavelength component, arranged to be received with wavelength-component-specific cameras at the end of a wavelength- component-specific branch of an optical path leading to each camera, which opti- cal path has sequentially in the travel direction of said radiation after the source of radiation said point of the surface to be imaged, a wavelength-selective film for directing said first wavelength component to a first wavelength-specific camera by using said film to a first optical event along a first wavelength-component-specific branch of the optical path, and for directing said second wavelength component to a second wavelength-specific camera by utilizing said film to a second optical even along a second wavelength-component-specific branch of the optical path, in order to store each image taken by a camera on a storage medium along with the pulsing of the illumination.
• the frequency of pulsing of a laser radiation source belonging to a certain set of laser radiation sources is on at least one of the following frequency areas: 0,001 MHz- 0,03MHz; 0,08MHz- 0,1 MHz; 0,3MHz -0,8MHz; 1 MHz-3MHz; 8MHz-13 MHz; 15MHz- 50MHz; 55MHz-350MHz and one such a frequency area, where the lower limit of the frequency area is different from that of the highest of said limits of frequency areas, but the upper limit is higher than the lower limit, in order to produce another wavelength component, in which case the frequency of the pulsing and the resolution of details of the images may be varied and thus optimized, if necessary, according to the web.
• the duration of the pulse in a state corresponding to illumination on the second wavelength compo- nent is shorter that the duration of the pulse in a state to the illumination on the first wavelength component.
• the pulsing of radiation associated with a first wavelength is arranged on a different frequency than the pulsing of radiation associated with a second wavelength.
• the wavelength-specific camera is arranged for storing an image being stored on a wavelength that in practice spikes only to the environment of a wavelength.
• the power of each laser radiation source belonging to a set of laser radiation sources arranged for arranging lighting is on at least one of the following power areas: 1 mW-300 mW, 800 mW-1W, 1W-3W, 8W-13W, 10W-55W, 100 W-IkW and one such a power area, where the lower limit of the power area is different from the highest of the limit of said areas, but the upper limit is higher than said lower limit.
• - incoherent illumination is directed along an optical path to a specific point of the surface of the moving web to be imaged
• said illumination is pulsed with pulsing means for taking an instantaneous still image with each camera arrange at the end of an optical path
• an image is taken along with the frequency of the pulsing of the lighting first with at least a first or a second camera, in which case the next image is located to a part of a specific lighting pulse within a specific delay, which is shorter than said lighting pulse.
• the arrangement according to an embodiment of the invention can be utilized for monitoring the structural evenness of the web, but also additionally or alternatively for monitoring the evenness of the composition of the web.
• the light sources may be located in a mixed manner.
• the light source 101 is according to an embodiment of the invention monochromatic, but it is arranged as incoherent. This is implemented, for exam- pie, by utilizing a set of coherent light sources, whose coherence is intentionally mixed in order to prevent the speckle phenomenon, but still for creating a sufficient illumination efficiency for short pulses for taking a still image.
• the light source 101 comprises a laser light source, which is pulsed.
• Figure 5 illustrates the method according to an embodiment of the invention, for example, in an arrangement according to figure 1.
• the method for imaging the to- pography of a specific point of a moving web surface illumination implemented by means of incoherent radiation, which comprises at least a first wavelength component ⁇ and a second wavelength component ⁇ comprises the following phases:
• Said phases can be partly overlapping in a manner that is reasonable from the point of view of directing, pulsing and other practical implementation of illumination.
• an image is tak- en along with the frequency of the pulsing of the illumination with at least a first or a second camera.
• it is therefore possible to create an image that has resolution on the microscopic level with an arrangement of one or more camera pairs.
• the coherence problem is solved by using in the device, for example, a diode laser structure, which may comprise even hundreds of individual lasers, which are directed in slightly different phases, in which case the coherence is intentionally mixed and therefore the speckle phenomenon is prevented.
• the energy of individual lasers can be directed to the same light fiber, in which case a point-form light source is created for forming an oblique photo of the surface. With the thus created incoherent light the speckle phenomenon is not a problem in image formation.
• commercial pulsed diode lasers by Cavitar Oy were used, with wavelengths of 690 nm and 804 nm.
• the moving web is textile, where deviations in the fiber structure are examined.
• An arrangement according to an embodiment of the invention is used for evaluating the roughness of the surface.
• images are taken by an arrangement according to the invention.
• images are taken of the surface when the coloring agent or other composite of the surface has been brought into contact with the surface.
• Said arrangements form a system according to an embodiment of the invention as an example, the use of which is not to be seen as limited solely to a textile web and/or two arrangements in a system.
• the topography of the surface can be calculated by in- tegrating the gradient filed by the Hanson and Johansson method by using integration on Fourier level combined with a Wiener filter.
• the disclosed example does not as such limit the known calculation methods to be used in connection with embodiments of the invention.
• the surface is illuminated alternately by four light sources, but very rapidly for creating still-like images and therefore in practice from the same point of the surface.
• the intensity scattered from the surface is measured by a camera, in which case four images of the surface are created, which are illustrated measured as intensities /W 4 from each point of the image, by using the corresponding light source.
• the light from the light sources is distributed to optical branches to be used in taking images.
• the distribution takes place optically through a first and a second optical event.
• said first optical event is one of the following: reflection, penetration, absorption, blocking.
• said second optical event is one of the following: reflection, penetration, absorption, blocking.
• the blocking can be implemented by keying the light source, in which case, for example, an incoherent set of laser radiation sources is arranged on a specific wavelength to not illuminate for the time period of the blocking.
• the block can be used also for creating phasing according to an embodiment, for example in relation to afterglow and/or detecting it.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• General Health & Medical Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• 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)

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• 2008
  • 2008-07-23 FI FI20085741A patent/FI122448B/fi not_active IP Right Cessation
• 2009
  • 2009-06-25 WO PCT/FI2009/050569 patent/WO2010010229A1/en active Application Filing
  • 2009-06-25 EP EP09800104A patent/EP2313738A1/en not_active Withdrawn

Non-Patent Citations (1)

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