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
  • G01B11/306—Measuring arrangements characterised by the use of optical techniques for measuring roughness or irregularity of surfaces for measuring evenness
• • 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
  • G01N21/8903—Optical details; Scanning details using a multiple detector array
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/34—Paper
  • G01N33/346—Paper sheets
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/34—Paper

Definitions

• the invention regards a method and a device for measuring topography on the surface of a material web. More specifically, the invention regards a method and a device for measuring topography on the surface of a material web in motion, in accordance with the patent demands.
• topography on the surface of material webs are an important part in securing the quality of a number of different products.
• topography can be measured in the manufacturing of paper and paper related products.
• the measurement of the topography is essential to determine that the surface of the paper, the printability and the quality of the final product corresponds to the demands of the customer.
• topography of a paper web has significance for the printability and the perceived print quality of a paper.
• the way a print is perceived on a paper is highly dependand on the spatial wavelengths of the surface of the paper. It is therefore customary to use spectral analysis of the spatial wavelengths as a measure of how well the surface responds to print. These are also simplified memasures such as surface roughness that describe the shorter spatial wavelengths in a combined value.
• General methods for measuring topography on a surface can be devided into contact based methods and optical methods.
• the contact based methods of types Perthometer and AFM are not suitable for measurements of a surface in movement because of frictional wear and vibrations.
• There are many optical methods for gathering information of a topographical surface which can be categorized into methods that are able to measure topography in a single point, methods that are able to measure topography for a line and methods that are able to measure topography for a surface area. Methods that are used for measuring topography in a single point are auto focus based methods, white light interferometer based methods and triangulation in a single point.
• the problem with point based methods is that some are too slow (auto focus based methods and white light interferometer) to enable use on moving objects. Furthermore, in order to enable surface characterization in a right angle to the surface motion direction, it is required that the measuring point moved very quickly over the moving surface.
• Methods that characterize a surface area can be methods based on light spread and/or shadow based methods. These methods are only able to characterize very short topographical wavelength spectra with low dynamic resolution. Standard methods for characterize topography with a line are based on triangulation, and have limitations in the dynamic range related to the accuracy of the measurements.
• WO 2009/083655 A 1 is decribed a method that uses a formation of an uncertainty value of flashes of light from sources that emit a wide spectrum of light.
• This method is fundamentally different from the method of the invention described by this patent, in that the light is not formed as a line that indicate the actual topography in the Cross machine Direction (CD), but rather takes a mean value of the relative hight change over a surface.
• CD Cross machine Direction
• the formation of a wavelength spectrum is a result of the measurement, which is not possible to achieve in WO 2009/083655A1. Only one image sensor is used in WO
• US 4202630 A a method is described for measuring topographical information on a surface.
• the method in US 4202630 A does involve a line of light, but rather a series of light spots ordered on a line.
• the large difference is here that with a series of light spots (in US 4202630 A) the relative distance between the spots is measured and the distances are then converted into topographical heights.
• the size of the spots should be significantly smaller than the distance between the spots, which severely limits the resolution or at the very least sets unreasonable demands on the light source and grid used, in order to achieve the same spatial resolution as in the invention proposed in this patent application.
• the resolution of an image sensor (in a renewed version of US 4202630 A) must be considerably higher that the final spatial resolution in the measurement.
• the method in US 4202630 A is suitable for measurements where the spatial resolution is not critical. If the measurements should be done in the micrometer range, however, the method in US 4202630 A is in the best of cases ineffective.
• a continous line of light is projected onto the surface and the image sensor or sensors in combination with the processing device measures the relative divergencies in a right angle to the line direction. This means that the spatial resolution is limited by the pixel size in the image sensor and o the number of pixels over the width of the line, which makes the invetion described by this patent application far more technology efficient than the method in US 4202630 A.
• JP 57049805 A a bethod is described where you in a point (in the cross section of the line of light source and the line sensor) measure the intensity function of the cross section of the line of light and then, by studying at what degree this function resembles a rectangular or a Gaussian distributed shape, makes a decision of the surface roughness. This measurement has nothing to do with topographical heights. It is furthermore not possible to extract spatial wavelength spectra from the method in JP 57049805 A, which is an important part of the invention described by this patent application. If the method in JP 57049805 A were to be expanded with a two dimensional sensor or even multiple sensors, one would still not be able to measure topography or be able to extract wavelength spectra. One could achieve mean values of the cross section profile over multiple strips and thereby get a more accurate measure, that would still be based on an empirically founded estimation of the shape of a function.
• WOOO/68638 Al a method is described for measuring roughness and gloss, rather than topography. A surface is illuminated and a mean value of roughness and gloss is produced.
• the text in WOOO/68638 Al does not describe any measures of spatial wavelength analysis or Cross machine Direction topography. Furtermore, the txt in WOOO/68638 Al does not describe online measurements.
• SE 51 1985 C2 a method is described to extract topography from a surface by illuminating the surface with diffuse light.
• the illuminated area is very limited (5 x 5 mm), which results in the neglect of longer spatial wavelengths measures.
• SE 511985 C2 is furthermore different from the invention described by this patent in that the device in SE 51 1985 C2 is not designed for online measurements.
• SE 528526 C2 a method is described that is intended as a complement to surface roughness measurements, where larger defects on a paper surface are detected with the aid of illuminated light on the surface at a glancing angle. This gives a numerical measure on how even the surface is.
• the method as it is described in SE 528526 C2 does not measure the actual topography in the Cross machine Direction of the paper.
• the method in SE 528526 C2 is only intended for laboratory studies rather than online measurements.
• the main pupose of the invention described by this patent is to create a sunstantially improved metod for measuring topography of a material web.
• Another purpose with the invention described by this patent is to measure the topography of a material web i movement.
• Yet another purpose of the invention described by this patent is to create a method for measuring the topography of a paper web in the Cross machine Direction. It is furthermore a purpose of the invention described by this patent to measure in a wide spatial wavelength spectrum with a high dynamic range.
• Figure 1 shows, from a side view, schematically the principle for a device in accordance with this patent application.
• Figure 2 shows, in a view from above and the side, schematically the principle for a device in accordance with this patent application. Here, the mechanical suspentions of the system parts have been left out.
• FIG. 3 shows, in a view from above and the side, an alternative form of execution of the invention described by this patent. Here, the mechanical suspentions of the system parts have been left out.
• a device 1 is schematically shows with the purpose of, in real time, measuring the topography of the surface 2 of a material web 3, being in a state of motion in the Machine Direction of the material web.
• the material web 3 is signified by a web moving at a velocity of a t least 10 meters per minute relative the device 1.
• the material web 3 consists of a web in a machine that manufactures paper, paperboard, card board or similar products where the material web 3 has a movement velocity over 100 meters per minute.
• the material web 3 has a movement velocity over 400 meters per minute.
• the material web 3 consists of another type of web, which has a movement velocity over 10 meters per minute and
• the topography of the surface 2 is measured in the Cross machine Direction of the web 3 or in the essential Cross machine Direction.
• the measurement of the topography of the surface 2 of the web 3 is conducted in a different direction than the Cross machine Direction or the essential Cross machine Direction.
• the device 1 comprises at least one electromagnetically radiating source, preferentially an optical radiating source 4, at least one image sensor 5 and at least one image processing device 6.
• the image processing device 6 process the gathered information from the image sensor or image sensors, 5.
• the image processing device 6 is assumed to have appropriate equipment for storage and processing of the gathered information from the image sensor or image sensors, 5.
• the processing device also has a function for transferring the gathered and/or processed information to another type of unit or similar.
• the electromagnetically radiating source (or sources) 4 and the image sensors 5 are attached to a frame, structure, or similar.
• the technical effect of the frame, or similar, is that this positions the radiating source, or sources, and the image sensors relative to each other and in relation to the web 2.
• the design of the frame, or similar, can vary greatly within the boundaries of the invention described by this patent.
• the optical radiating source 4 can be comprised of one or more optical radiating sources.
• the optical radiating source 4 emits optical radiation within the wavelength range 100 nm to 1 mm.
• the optical radiating source 4 consits of, or include, LED, laser or for the purpose at hand suitable radiating source.
• a NIR laser is used as an example, as the visual spectrum including ambient light can be filtered out. It is furthermore thinkable that different types of optical radiating sources are combined and used in the device 1.
• the principle for measuring in accordance with the procedure of this patent application is that at least one surface in the Cross machine Direction, or the essential Cross machine Direction, is illuminated with at least one optically radiated line 7 emitted by at least one radiating source 4.
• the electromagnetically radiated light is projected at an incoming angle VI relative to the web surface.
• the angle VI consists of the angle between the web surface and the angle (essential angle) of the radiating light.
• the angle VI is preferentially in the range 20-90 degrees.
• the reflected optical radiating light in a particular direction to a particular point, line or surface area vary in relation to the topography of the illuminated web. This variation takes the form as lateral divergencies in the line of light relative a straight line, and is gathered via at least one sensor 5 or preferentially two or more sensors 5.
• the information from the sensor or sensors 5 is used in the invention in this patent application as incoming information to the processing device 6 in which the gathered information is processed into topographical information of the web surface.
• the sensor or sensors 5 that gather information from the reflected light is/are preferentially mounted in an angle according to angle V2 in relation to the web.
• the angle V2 consists of the angle between the web surface and the gathering direction of the sensor or sensors.
• the angle V2 is preferentially in the range 20-90 degrees.
• the design includes multiple sensors 5 that gather the information from the reflected light and transmits to and/or stores the gathered information from each sensor 5 in a, for the applicational purpose, suitable storage media.
• the gathered information from the sensors 5 is processed by the processing device and is combined so that the gathered information reflects the line of light in its full length.
• the angle between the image sensors 5 and the line of light 7 makes the line of light bend in accordance to the surface topography, see figure. These angles are optimized for a particular surface in a particular application, where a coarse surface need a larger angle between the web surface and the light source, as shadowing would otherwise distort the measurements, while a smooth surface need a smaller angle, as a smooth surface require a higher relative intensity in the topographical information. Thereafter the center line of the line of light is extracted.
• This center line is then seen as an estimation of the surface topography along the line. Extracting the center of the line enables a reduction of data essential for real time processing of the information.
• the center line is then transformed to give information about the spatial wavelengths of the surface, where wavelength spectra is something that the paper industry use as a quality measure relating to the print quality.
• wavelength spectra is something that the paper industry use as a quality measure relating to the print quality.
• an average of several lines is also taken. In order to measure in high velocities the measurements of the lines are done with a particular time interval and the lines are then averaged for the surface average measure.
• the uniqueness with the method is that is enables measurements of topographical information with a wide spatial wavelength spectrum, in the Cross machine Direction while the surface is moving with a high velocity.
• MD Machine Direction
• CD Cross machine Direction
• This method has a limitation in how short the wavelengths can be related to the image sensor resolution. Since the method uses the center of a line whose line width contains several pixels, the method cannot completely utilize the full resolution of the image sensor, but rather calculates a sub-pixel precision center based on several pixels.
• light 8 can be projected with a very small angle (-10-20 degrees) relative to the surface with a supplemental light source 9. In this case the shadows from the surface can be used in a measurement that can yield topographical information for very short wavelengths, and increase the intensity in the topographical values of short wavelengths.

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• Textile Engineering (AREA)
• Medicinal Chemistry (AREA)
• Food Science & Technology (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)
• Length Measuring Devices By Optical Means (AREA)

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Citations (10)

• 2011
  • 2011-09-25 SE SE1100700A patent/SE536900C2/sv not_active IP Right Cessation
• 2012
  • 2012-09-24 WO PCT/SE2012/000145 patent/WO2013043103A1/en active Application Filing

Patent Citations (10)

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