WO1990012310A1 - Procedure and apparatus for determining size and/or shape distribution - Google Patents

Procedure and apparatus for determining size and/or shape distribution Download PDF

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Publication number
WO1990012310A1
WO1990012310A1 PCT/FI1990/000092 FI9000092W WO9012310A1 WO 1990012310 A1 WO1990012310 A1 WO 1990012310A1 FI 9000092 W FI9000092 W FI 9000092W WO 9012310 A1 WO9012310 A1 WO 9012310A1
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WO
WIPO (PCT)
Prior art keywords
chip
light
chips
transport surface
particle
Prior art date
Application number
PCT/FI1990/000092
Other languages
French (fr)
Inventor
Tom Fredrik NÄSE
Yrjö Rainer VUORISALO
Original Assignee
Oy Keskuslaboratorio Centrallaboratorium Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Oy Keskuslaboratorio Centrallaboratorium Ab filed Critical Oy Keskuslaboratorio Centrallaboratorium Ab
Publication of WO1990012310A1 publication Critical patent/WO1990012310A1/en

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Classifications

    • 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
    • G01N33/46—Wood
    • G01N15/1433—
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
    • G01N15/10—Investigating individual particles
    • G01N15/14—Electro-optical investigation, e.g. flow cytometers
    • G01N2015/1497—Particle shape
    • 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
    • G01N2021/845—Objects on a conveyor
    • 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
    • G01N2021/8681—Paper fibre orientation

Definitions

  • the present invention concerns a procedure for determining the size and/or shape distribution of wood chips meant for pulp manufacturing, or simply chips, the particles being spread out on a substantially pla ⁇ nar transport base which transports the particles at a given velocity, the particles being illuminated from a given direction, and the light reflected by the parti ⁇ cles being detected in another direction.
  • the invention further concerns an apparatus for determining the size and/or shape distribution of wood chips meant for pulp manufacturing.
  • Various screening procedures are at present the most commonly employed classifying methods in clas ⁇ sification of wood chip raw material for use in making cellulose or mechanical pulp, that is of chips. In these procedures endeavours are to obtain an idea of the size distribution of the chips by using for in ⁇ stance superimposed screen plates with different-sized apertures or slits. Screening methods are however ex ⁇ ceedingly inaccurate because they furnish no exact in ⁇ formation on the dimensions of the particles: one only finds out with their aid that the particular particle fraction has passed through a screen plate aperture or slit of a certain size under certain circumstances.
  • an optical classify ⁇ ing method in which the particles are photographed with an optoelectric camera and the two-dimensional image thus obtained is processed in a computer system for determination of the size distribution of the chips.
  • uniform illumination is applied, either perpendicular or at an angle against the transport sur- face on which the chips to be measured have been spread.
  • the area of the chip and the shadow which it throws can be measured, whereby a coarse estimate is gained of the chip's dimension in the height direction on the transport surface.
  • the above-mentioned procedures of prior art are unable to give an accurate picture of the topo- graphy of the particles, e.g. of wood chip raw material particles which are going to be used in pulpmaking. Furthermore, it is not possible generally to distin ⁇ guish between the length and breadth of the chip par ⁇ ticle with the methods of prior art.
  • the shape of particles in chips to be used in pulpmaking is essentially an oblique trapezoid. Its es ⁇ sential dimensions are its length in the fibre direc ⁇ tion, its thickness and its breadth. The chip length gives an idea of how large a part of the wood fibres has been cut off in the defibrating process.
  • the thick ⁇ ness has significance regarding heat and matter trans ⁇ fer in the delignifying or pulping process.
  • the breadth is less significant regarding the bulk density of the chips.
  • the length in the fibre direction is not necessarily the largest di ⁇ mension of the particle; the present trend is towards chipping methods in which the dimension of the chip in the breadth direction is greater than the length in the fibre direction. Methods and apparatus of prior art yield no accurate enough picture of these quantities e.g. in view of controlling the delignifying or pulping process.
  • the object of the present invention is to eliminate the drawbacks presented in the foregoing. It is a particular object of the invention to provide a procedure for determining the size and/or shape distri- bution of wood chips meant to be used in pulp manufac ⁇ turing with substantially greater accuracy, ease and speed than before.
  • the object of the invention is to provide a procedure by which the size and/or shape dis ⁇ tribution of particles, their topside topography, their volume and/or underside topography, the fibre orienta ⁇ tion and the thickness of the chips can be determined in full detail and with any desired accuracy, and rapidly and easily.
  • the invention is based on the fundamental idea that the chips to be measured are illuminated with structured light from a certain direction, e.g. at an oblique angle above the transport surface, and the off ⁇ set of said structured light caused by the dimension of the chip in the height direction is detected in various directions, and the dimension of the chip in the height direction at the location of the respective line of light is determined on the basis of the offset.
  • the chip which is being measured it is illuminated with lineal light, and the offset of the light is detected at given inter- vals in time so that of the chip under measurement the desired number of offset determinations is obtained, at given intervals, while the chip is moving on the trans- port surface, for determination of the chip's shape at desired intervals and with desired accuracy.
  • any given chip may thus be illuminated and the band of light striking it detected, i.e., the lateral offset of e.g. lineal light caused by the height-direction dimension of the chip can be detected e.g. at intervals on the order of lO- 2 seconds, e.g. at linear intervals on the order of 0.1 to 1 mm.
  • the procedure yields of the height-direction dimension of the respective chip a fully accurate topographic image. Thereby the size and shape of the particles being measured can be determined in full detail and with any desired accura ⁇ cy, which affords a chance for completely unrestricted quality classification.
  • Structured light is here understood to mean lineal or square-configurated light, that is, the light source illuminates the chips with the aid of straight lines of light or of squares which are formed by straight lines of light.
  • the structured light may be directed on the particle to be measured from any direc ⁇ tion whatsoever, for instance at an oblique angle against the transport surface, for instance at right angles against the chip's direction of travel, with the light line of the structured light parallelling the particle's direction of travel or enclosing a right angle or an oblique angle with the chip's direction of travel.
  • the light line is directed at an oblique angle against the transport surface and at right angles against the chip's direction of travel.
  • the lateral offset of the structured, that is e.g. lineal, light is detected by viewing it from a different direction relative to the illuminating direc ⁇ tion, e.g. under an oblique or right angle against the chip illuminating direction, with the line advantage ⁇ ously and the detection obliquely or perpendicularly relative to the transport surface, i.e., from straight above the chip.
  • the chips are illu ⁇ minated advantageously at the same time or at different times from different directions with lineal light at an oblique angle from above the transport surface. This can be accomplished e.g. with the aid of two or more light sources which have been disposed to illuminate the chips in the way just described.
  • the image is advantageously formed into a line image, e.g. a dot matrix 50 to 500 times 50 to 500 dots.
  • the side lengths (11,12,13,14) of the chip can be determined from the dot matrix by determining the sides of the chip (the chip has substantially the shape of a rhomboid trapezoid) , by determining the slope co ⁇ efficients (dy/dx) of the chip sides relative to the transport direction, as a function of the line integral of the chip side, i.e., of the edge length, and by calculating the derivate d(dy/dx)/dh of this function, whereby the extreme value points of the function thus obtained represent the corners of the body, and the distance between them represents the side lengths.
  • the chips may be transported upon a substantially transparent transport surface and illuminated with structured, e.g. lineal light from under the transport surface; in that case the lateral offset of the lineal light caused by the height-direction dimension of the particle is detected from below the surface.
  • structured e.g. lineal light from under the transport surface; in that case the lateral offset of the lineal light caused by the height-direction dimension of the particle is detected from below the surface.
  • the size and shape of the chips can then be determined from either side, from above and from below, the chips can be defined altogether unambiguously and accurately with regard to their entire configuration.
  • the grain (or fibre) direction of wood chips can also be determined on the basis of their general shape, i.e., for instance on the basis of the oblique cut surfaces of chips with trapezoidal shape.
  • the fibre direction may also be determined on the basis of the measured grain structure of ⁇ the surface of the wood chips or the shape .of the illuminated figure produced by structured light.
  • the volume of the chips which are being meas ⁇ ured can be determined by calculation from the measured lateral offset of structured light, in particular when said offset is measured at several points of the par ⁇ ticle and/or on different sides of the particle, e.g. on the topside and underside.
  • For detector in the procedure of the invention may be used e.g. a matrix-type camera, (CCD) , or equiv ⁇ alent, or generally any kind of optoelectric camera or optoelectric recording device by which it is possible to create a signal characterizing the lateral offset of structured, e.g. lineal light caused by the height- direction dimension of the particle which is being measured.
  • CCD matrix-type camera
  • equiv ⁇ alent e.g. a matrix-type camera, (CCD) , or equiv ⁇ alent
  • optoelectric camera or optoelectric recording device by which it is possible to create a signal characterizing the lateral offset of structured, e.g. lineal light caused by the height- direction dimension of the particle which is being measured.
  • Such optoelectric cameras and devices are in themselves known in the art and their use shall not be described in greater detail in this connection.
  • a conventional computer advantageously a computer capable of parallel processing (a tranputer) on account of the major data quantity that has to be processed.
  • a tranputer a computer capable of parallel processing
  • Fig. 1 presents a chip on a transport surface and approaching a lineal line of light
  • Fig. 2 presents the chip of Fig. 1 as it has reached the lineal line of light
  • Fig. 3 presents in elevational view, and schematically, an apparatus according to the invention for implement ⁇ ing the procedure
  • Fig. 4 presents the transport surface belonging to the apparatus of Fig. 2 with a chip thereon, in top view
  • Fig. 5 presents schematically the apparatus od another embodiment of the invention in elevational view
  • Fig. 6 presents a dot matrix image of a wood chip, produced with the procedure and apparatus of the inven ⁇ tion
  • Fig. 7 presents the chip side directions de ⁇ termined from Fig. 6 and their derivates.
  • a wood chip 10 intended for pulp manufacturing has been disposed on a transport surface 1, that is, on a conventional belt conveyor, while this conveyor is travelling in the direction of arrow 13.
  • the transport base is illuminated obliquely from the direction in which the particle arrives, and from above the transport base, with a lineal light source which causes a line of light 11 to run across the transport base at right angles against the transport direction.
  • the particle 10 has a certain dimension in the height direction, i.e., the top face of the particle rises to a height greater than that of the top surface of the transport base.
  • the particle 10 is illuminated with lineal light at an oblique angle with reference to the transport surface 1 and from above it, as described in the foregoing.
  • the height-direction dimension of the particle has given rise to an offset a of the lineal light, that is of the line of light 11, at the location of the chip, in other words, the line 11 has been drawn to indicate the location where the lineal light would strike if there were no particle upon the surface 1, and the site of incidence 12 of the lineal light upon the particle, that is the line of light 12, has a cer ⁇ tain phase shift a relative to the line of light 11.
  • the offset a is determin ⁇ ed with the aid of a detector which forms a signal cor ⁇ responding to the offset, and the dimension in the height direction of the particle is determined on the basis of said offset, e.g. with the aid of a calculat- ing means 4, such as a computer, on the basis of the illumination angle and of the detection angle.
  • the line of light may in this context also be understood to mean one edge of a light band with finite width.
  • Fig. 3 is seen a schematic picture of the apparatus of the invention.
  • the apparatus comprises a transport surface l, which is substantially horizontal and planar and has been arranged to transport the par ⁇ ticle 10 placed thereupon, with a given velocity.
  • a light source 2 which has been arranged to illuminate the chips with structured, i.e., lineal light from a given direction, i.e., at an oblique angle from the direction in which the particle arrives and from above the transport sur ⁇ face.
  • the apparatus further includes a detector 3, which has been placed above the transport surface 1, aimed perpendicularly against the transport surface at the site of that line of light which the light source 2 produces when striking the transport surface without obstruction.
  • the apparatus presented here comprises furthermore a second light source 2 " -- which has likewise been positioned above the transport surface, to illumi ⁇ nate the particles lineally under an oblique angle, now from the direction in which the particles leave, and symmetrically with reference to the light source 2 , i,e., in such manner that the lines of light of both light sources coincide.
  • the light sources may equally be asymmetrically positioned relative to each other and they may be aimed under different angles against the transport surface.
  • the detector 3 is a conventional matrix cam ⁇ era, and it has been disposed to produce signals which correspond to the line of light offsets observed in the direction of the detector, in both illuminating direc ⁇ tions.
  • the matrix camera is connected to a computer 4, which has been arranged to determine the size and/or shape of the particle 10 on the basis of the lines of light striking the detected particle and of their off ⁇ sets, that is on the basis of the signals from the de ⁇ tector.
  • a particle in the apparatus of Fig. 3 illuminated with light sources 2 and 2 ⁇ viewed from the direction of the detector 3.
  • the di en- sion in the height direction of the particle has caused lateral offsets of the lines of light in the incoming and off-going directions, respectively, of the parti ⁇ cle, that is in the directions of the light sources 2 and I 3 - .
  • the dimension of the particle can then be de ⁇ termined from the offsets detected at the site of the lines of light, with the aid of the calculating means 4.
  • the light source 2 may be any kind of light source emitting structured light, e.g. lineal light, such as a linear laser which has a given wavelength, or a lineal light source comprising one or several wave ⁇ lengths, established with the aid of lens optics through a slit.
  • lineal light such as a linear laser which has a given wavelength
  • a lineal light source comprising one or several wave ⁇ lengths, established with the aid of lens optics through a slit.
  • Fig. 5 is depicted an apparatus in which the transport surface 1 belonging thereto is transpar ⁇ ent.
  • the apparatus comprises one or several underside light sources 5,6 and one underside detector 7 with calculating means 4 , placed in similar manner as in Fig. 3 the light sources 2,2 a - and the detector 3 with calculating means 4, however underneath the transport surface.
  • the shape and size of the parti ⁇ cle are determinable similarly as in the foregoing, on the basis of lines of light directed obliquely through the transport surface and of the offsets of the lines of light caused by the height-direction dimension of the particle, as presented in the foregoing.
  • Fig. 6 In Fig. 6 is seen a line matrix image, pro ⁇ quizd with the apparatus of Figs 3-4, of a wood chip, simplified for perspicuity.
  • the margins of the wood chips are seen in the image as boundary lines between readings 0 and readings >0, entered as lines in the figure.
  • Matrix readings >0 indicate directly the height of the chip over the base, i.e., its topography.
  • the fibre orientation of a wood chip piece can be determined with the calculating means 4, directly as the chip dimension perpendicular against the side A, or as the dimension perpendicular relative to the waves of the chip by the wave spectrum method described earlier.
  • Fig. 7 presents, schematically, the previously described method of determining the edge length of the body.

Abstract

A procedure for determining the size and/or shape distribution of particles, the particles being illuminated with structured light from a given direction, and the lateral offset of the lineal light caused by the dimension in the height direction of the particle that is being measured being detected and the height-direction dimension of the particle being determined on the basis of the offset. Apparatus for determining the size and/or shape distribution of particles, comprising a transport surface (1), a light source (2) which has been arranged to illuminate the particles with structured light from a given direction from above the transport surface; a detector (3) which has been arranged to detect light reflected from the particle that is being measured, in another direction, and to produce a signal corresponding to the offset of the light caused by the particle's dimension in the height direction; and a calculating means (4) which has been arranged to determine the particle's dimension in the height direction at least at one point of the particle on the basis of the offset of the light.

Description

PROCEDURE AND APPARATUS FOR DETERMINING SIZE AND/OR SHAPE DISTRIBUTION
The present invention concerns a procedure for determining the size and/or shape distribution of wood chips meant for pulp manufacturing, or simply chips, the particles being spread out on a substantially pla¬ nar transport base which transports the particles at a given velocity, the particles being illuminated from a given direction, and the light reflected by the parti¬ cles being detected in another direction.
The invention further concerns an apparatus for determining the size and/or shape distribution of wood chips meant for pulp manufacturing. Various screening procedures are at present the most commonly employed classifying methods in clas¬ sification of wood chip raw material for use in making cellulose or mechanical pulp, that is of chips. In these procedures endeavours are to obtain an idea of the size distribution of the chips by using for in¬ stance superimposed screen plates with different-sized apertures or slits. Screening methods are however ex¬ ceedingly inaccurate because they furnish no exact in¬ formation on the dimensions of the particles: one only finds out with their aid that the particular particle fraction has passed through a screen plate aperture or slit of a certain size under certain circumstances.
Also known in the art is an optical classify¬ ing method in which the particles are photographed with an optoelectric camera and the two-dimensional image thus obtained is processed in a computer system for determination of the size distribution of the chips. In said procedure uniform illumination is applied, either perpendicular or at an angle against the transport sur- face on which the chips to be measured have been spread. When one or several cameras are used, mounted e.g. at different angles relative to the transport sur- face, the area of the chip and the shadow which it throws can be measured, whereby a coarse estimate is gained of the chip's dimension in the height direction on the transport surface. It is furthermore known, in this connection, to estimate the dimensions in the height direction of the chips by making use of the knowledge that a correlation exists e.g. between the length and height of wood chip particles produced from a given wood raw material using a given machine, this correlation resulting from the structure of the wood, in addition to the parameters of the respective machin¬ ery. This correlation is mainly valid for chips which have a substantially constant knot percentage. In gen¬ eral, measuring the shadow of a chip gives an incom- plete picture of the dimension of the chip in the height direction because the shadow is mainly formed by the edge of the piece only.
The above-mentioned procedures of prior art are unable to give an accurate picture of the topo- graphy of the particles, e.g. of wood chip raw material particles which are going to be used in pulpmaking. Furthermore, it is not possible generally to distin¬ guish between the length and breadth of the chip par¬ ticle with the methods of prior art. The shape of particles in chips to be used in pulpmaking is essentially an oblique trapezoid. Its es¬ sential dimensions are its length in the fibre direc¬ tion, its thickness and its breadth. The chip length gives an idea of how large a part of the wood fibres has been cut off in the defibrating process. The thick¬ ness has significance regarding heat and matter trans¬ fer in the delignifying or pulping process. The breadth is less significant regarding the bulk density of the chips. Moreover it should be noted that the length in the fibre direction is not necessarily the largest di¬ mension of the particle; the present trend is towards chipping methods in which the dimension of the chip in the breadth direction is greater than the length in the fibre direction. Methods and apparatus of prior art yield no accurate enough picture of these quantities e.g. in view of controlling the delignifying or pulping process.
The object of the present invention is to eliminate the drawbacks presented in the foregoing. It is a particular object of the invention to provide a procedure for determining the size and/or shape distri- bution of wood chips meant to be used in pulp manufac¬ turing with substantially greater accuracy, ease and speed than before. The object of the invention is to provide a procedure by which the size and/or shape dis¬ tribution of particles, their topside topography, their volume and/or underside topography, the fibre orienta¬ tion and the thickness of the chips can be determined in full detail and with any desired accuracy, and rapidly and easily.
It is furthermore an object of the invention to provide a means for implementing the procedure.
Regarding the features characterizing the in¬ vention, reference is made to the Claims section.
The invention is based on the fundamental idea that the chips to be measured are illuminated with structured light from a certain direction, e.g. at an oblique angle above the transport surface, and the off¬ set of said structured light caused by the dimension of the chip in the height direction is detected in various directions, and the dimension of the chip in the height direction at the location of the respective line of light is determined on the basis of the offset. In order to obtain an accurate image of the chip which is being measured, it is illuminated with lineal light, and the offset of the light is detected at given inter- vals in time so that of the chip under measurement the desired number of offset determinations is obtained, at given intervals, while the chip is moving on the trans- port surface, for determination of the chip's shape at desired intervals and with desired accuracy. Any given chip may thus be illuminated and the band of light striking it detected, i.e., the lateral offset of e.g. lineal light caused by the height-direction dimension of the chip can be detected e.g. at intervals on the order of lO-2 seconds, e.g. at linear intervals on the order of 0.1 to 1 mm.
It should be noted that the procedure yields of the height-direction dimension of the respective chip a fully accurate topographic image. Thereby the size and shape of the particles being measured can be determined in full detail and with any desired accura¬ cy, which affords a chance for completely unrestricted quality classification.
Structured light is here understood to mean lineal or square-configurated light, that is, the light source illuminates the chips with the aid of straight lines of light or of squares which are formed by straight lines of light. The structured light may be directed on the particle to be measured from any direc¬ tion whatsoever, for instance at an oblique angle against the transport surface, for instance at right angles against the chip's direction of travel, with the light line of the structured light parallelling the particle's direction of travel or enclosing a right angle or an oblique angle with the chip's direction of travel. Advantageously, the light line is directed at an oblique angle against the transport surface and at right angles against the chip's direction of travel.
The lateral offset of the structured, that is e.g. lineal, light is detected by viewing it from a different direction relative to the illuminating direc¬ tion, e.g. under an oblique or right angle against the chip illuminating direction, with the line advantage¬ ously and the detection obliquely or perpendicularly relative to the transport surface, i.e., from straight above the chip.
In order to determine the chip's size and shape in a still more complex way, the chips are illu¬ minated advantageously at the same time or at different times from different directions with lineal light at an oblique angle from above the transport surface. This can be accomplished e.g. with the aid of two or more light sources which have been disposed to illuminate the chips in the way just described. On the basis of the signals obtained, the image is advantageously formed into a line image, e.g. a dot matrix 50 to 500 times 50 to 500 dots.
When wood (or glass) splits along a plane parallelling the grain, a surface is produced which owing to the morphology of wood is different in the grain direction and in the direction across the grain (or fibre) . In the cross-fibre direction waviness may be noted which has a given wavelength characteristic of the raw material wood. The topographic picture yielded by the procedure of the surface of the wood chip piece is so accurate that by calculating the wavelength spec¬ trum in different directions on the surface of the body it becomes possible to observe a peak in the spectrum at the above-mentioned wavelength. It is possible in this way to determine the length of the wood chip piece in the fibre direction, which characterizes e.g. the mechanical strength of the pulp made of the respective chips.
The side lengths (11,12,13,14) of the chip can be determined from the dot matrix by determining the sides of the chip (the chip has substantially the shape of a rhomboid trapezoid) , by determining the slope co¬ efficients (dy/dx) of the chip sides relative to the transport direction, as a function of the line integral of the chip side, i.e., of the edge length, and by calculating the derivate d(dy/dx)/dh of this function, whereby the extreme value points of the function thus obtained represent the corners of the body, and the distance between them represents the side lengths.
In order to determine the size and/or shape of the sides of the chips facing the transport surface, the chips may be transported upon a substantially transparent transport surface and illuminated with structured, e.g. lineal light from under the transport surface; in that case the lateral offset of the lineal light caused by the height-direction dimension of the particle is detected from below the surface. The size and shape of the chips can then be determined from either side, from above and from below, the chips can be defined altogether unambiguously and accurately with regard to their entire configuration. The grain (or fibre) direction of wood chips can also be determined on the basis of their general shape, i.e., for instance on the basis of the oblique cut surfaces of chips with trapezoidal shape. The fibre direction may also be determined on the basis of the measured grain structure of ■ the surface of the wood chips or the shape .of the illuminated figure produced by structured light.
The volume of the chips which are being meas¬ ured can be determined by calculation from the measured lateral offset of structured light, in particular when said offset is measured at several points of the par¬ ticle and/or on different sides of the particle, e.g. on the topside and underside.
For detector in the procedure of the invention may be used e.g. a matrix-type camera, (CCD) , or equiv¬ alent, or generally any kind of optoelectric camera or optoelectric recording device by which it is possible to create a signal characterizing the lateral offset of structured, e.g. lineal light caused by the height- direction dimension of the particle which is being measured. Such optoelectric cameras and devices are in themselves known in the art and their use shall not be described in greater detail in this connection.
For calculating means with the aid of which the size and/or shape of the respective wood chip, and the size and/or shape distribution of a plurality of particles, can be determined one may use a conventional computer, advantageously a computer capable of parallel processing (a tranputer) on account of the major data quantity that has to be processed. As it is, the pro¬ cess of calculating the size and/or shape of bodies from signals characterizing the size and/or shape is known in itself in the art and shall not be described in greater detail in this context.
The invention is described in the following in detail with the aid of embodiment examples, referring to the attached drawings, wherein
Fig. 1 presents a chip on a transport surface and approaching a lineal line of light,
Fig. 2 presents the chip of Fig. 1 as it has reached the lineal line of light, Fig. 3 presents in elevational view, and schematically, an apparatus according to the invention for implement¬ ing the procedure,
Fig. 4 presents the transport surface belonging to the apparatus of Fig. 2 with a chip thereon, in top view, Fig. 5 presents schematically the apparatus od another embodiment of the invention in elevational view, and Fig. 6 presents a dot matrix image of a wood chip, produced with the procedure and apparatus of the inven¬ tion, and Fig. 7 presents the chip side directions de¬ termined from Fig. 6 and their derivates.
In Fig. 1 a wood chip 10 intended for pulp manufacturing has been disposed on a transport surface 1, that is, on a conventional belt conveyor, while this conveyor is travelling in the direction of arrow 13. The transport base is illuminated obliquely from the direction in which the particle arrives, and from above the transport base, with a lineal light source which causes a line of light 11 to run across the transport base at right angles against the transport direction. The particle 10 has a certain dimension in the height direction, i.e., the top face of the particle rises to a height greater than that of the top surface of the transport base.
In Fig. 2 the particle 10 is illuminated with lineal light at an oblique angle with reference to the transport surface 1 and from above it, as described in the foregoing. The height-direction dimension of the particle has given rise to an offset a of the lineal light, that is of the line of light 11, at the location of the chip, in other words, the line 11 has been drawn to indicate the location where the lineal light would strike if there were no particle upon the surface 1, and the site of incidence 12 of the lineal light upon the particle, that is the line of light 12, has a cer¬ tain phase shift a relative to the line of light 11. As taught by the invention, the offset a is determin¬ ed with the aid of a detector which forms a signal cor¬ responding to the offset, and the dimension in the height direction of the particle is determined on the basis of said offset, e.g. with the aid of a calculat- ing means 4, such as a computer, on the basis of the illumination angle and of the detection angle.
It should be noted that it is not necessary to produce on the transport base any line of light 11 or if such a light line is formed it need not be de- tected; it is only important to detect the phase shift a which is caused by the height-direction dimension of the particle.
The line of light may in this context also be understood to mean one edge of a light band with finite width.
In Fig. 3 is seen a schematic picture of the apparatus of the invention. The apparatus comprises a transport surface l, which is substantially horizontal and planar and has been arranged to transport the par¬ ticle 10 placed thereupon, with a given velocity. Over the transport surface has been placed a light source 2 which has been arranged to illuminate the chips with structured, i.e., lineal light from a given direction, i.e., at an oblique angle from the direction in which the particle arrives and from above the transport sur¬ face. The apparatus further includes a detector 3, which has been placed above the transport surface 1, aimed perpendicularly against the transport surface at the site of that line of light which the light source 2 produces when striking the transport surface without obstruction. The apparatus presented here comprises furthermore a second light source 2"-- which has likewise been positioned above the transport surface, to illumi¬ nate the particles lineally under an oblique angle, now from the direction in which the particles leave, and symmetrically with reference to the light source 2 , i,e., in such manner that the lines of light of both light sources coincide. If desired, the light sources may equally be asymmetrically positioned relative to each other and they may be aimed under different angles against the transport surface. The detector 3 is a conventional matrix cam¬ era, and it has been disposed to produce signals which correspond to the line of light offsets observed in the direction of the detector, in both illuminating direc¬ tions. The matrix camera is connected to a computer 4, which has been arranged to determine the size and/or shape of the particle 10 on the basis of the lines of light striking the detected particle and of their off¬ sets, that is on the basis of the signals from the de¬ tector. In Fig. 4 is seen a particle in the apparatus of Fig. 3, illuminated with light sources 2 and 2 ^ viewed from the direction of the detector 3. The di en- sion in the height direction of the particle has caused lateral offsets of the lines of light in the incoming and off-going directions, respectively, of the parti¬ cle, that is in the directions of the light sources 2 and I 3- . The dimension of the particle can then be de¬ termined from the offsets detected at the site of the lines of light, with the aid of the calculating means 4.
> The light source 2 may be any kind of light source emitting structured light, e.g. lineal light, such as a linear laser which has a given wavelength, or a lineal light source comprising one or several wave¬ lengths, established with the aid of lens optics through a slit. In Fig. 5 is depicted an apparatus in which the transport surface 1 belonging thereto is transpar¬ ent. The apparatus comprises one or several underside light sources 5,6 and one underside detector 7 with calculating means 4 , placed in similar manner as in Fig. 3 the light sources 2,2a- and the detector 3 with calculating means 4, however underneath the transport surface. In that case the shape and size of the parti¬ cle are determinable similarly as in the foregoing, on the basis of lines of light directed obliquely through the transport surface and of the offsets of the lines of light caused by the height-direction dimension of the particle, as presented in the foregoing.
In Fig. 6 is seen a line matrix image, pro¬ duced with the apparatus of Figs 3-4, of a wood chip, simplified for perspicuity. The margins of the wood chips are seen in the image as boundary lines between readings 0 and readings >0, entered as lines in the figure. Matrix readings >0 indicate directly the height of the chip over the base, i.e., its topography. Thus the fibre orientation of a wood chip piece can be determined with the calculating means 4, directly as the chip dimension perpendicular against the side A, or as the dimension perpendicular relative to the waves of the chip by the wave spectrum method described earlier.
Fig. 7 presents, schematically, the previously described method of determining the edge length of the body.
The embodiment examples are only meant to il¬ lustrate the invention, and embodiments of the inven¬ tion may vary within the scope of the claims following below.

Claims

1. A procedure for determining the size and/or shape distribution of wood chips meant for pulp manu- facturing, the chips being spread out on a substantial¬ ly planar transport surface which transports the par¬ ticles with a given velocity, the chips being illumina¬ ted from a given direction, and the light reflected by the chips being detected in a given direction, charac- terized in that the chips are illuminated with structured light from a given direction from above the transport surface, that the lateral offset of the lin¬ eal light caused by the dimension in the height direc¬ tion of the chip that is being measured is detected so that from the chip tinder measurement is obtained a de¬ sired number of signals at given intervals while the chip is moving on the transport surface, for detecting the shape of the chip at desired intervals and with desired accuracy, and the height-direction topography of the chip is determined on the basis of the signals obtained.
2. Procedure according to claim 1, characterized in that on the basis of the signals obtained are deter¬ mined the principal directions of the chip, that from the surface of the chip is determined the wavelength characteristic of the wood raw material in the cross- fibre direction, on the basis of which the fibre (or grain) orientation of the chip and the length of the chip in the grain direction are determined.
3. Procedure according to claim 1 or 2, character¬ ized in that on the basis of the signals obtained is formed a matrix corresponding to the height of the chip's surface relative to the transport base, and that the side lengths of the chip are determined as the in- tervals between the peaks of the derivates of the slope coefficients of the chip's sides.
4. Procedure according to any one of claims 1-3, characterized in that on the basis of the signals ob- tained is formed a matrix corresponding to the height of the chip's surface relative to the transport sur¬ face.
5. Procedure according to any one of claims 1-4, characterized in that the chips are illuminated with lineal light at an oblique angle from above the trans¬ port surface.
6. Procedure according to any one of claims 1-5, characterized in that the chips are illuminated at dif- ferent times from different directions.
7. Procedure according to any one of claims 1-6, characterized in that the chips are transported upon a substantially transparent surface and that the chips are illuminated with structured light from under the transport surface, and the offset of the light is detected from under the transport surface.
8. Apparatus for determining the dimensions of wood chips meant for pulp manufacturing, characterized in that the apparatus comprises a transport surface (l) which is substantially horizontal and planar and ar¬ ranged to transport the particles with a given veloci¬ ty; a light source (2) which has been arranged to il¬ luminate the particles with structured light from a given direction from above the transport surface; a detector (3) which has been arranged to detect light reflected from the particle that is being measured, in another direction, and to produce signals corresponding to the lateral offset of the light caused by the par¬ ticle's dimension in the height direction; and a cal- culating means (4) which has been arranged to determine the chip's dimension in the height direction at given intervals in time at different points of the chip.
9. Apparatus according to claim 8, characterized in that the light source (2) has been arranged to il- lu inate the particle under an oblique angle against the transport surface (1) with lineal light.
10. Apparatus according to claim 8 or 9, characterized in that the calculating means (4) has been arranged to form a dot matrix corresponding to the surface of the chip, on the basis of the signals de¬ tected, and to determine the lengths of the sides of the chip as the intervals between the peaks of the derivates of their slope coefficients.
11. Apparatus according to any one of claims 8-10, characterized in that the transport surface (1) is transparent, that the apparatus comprises at least one underside light source (5,6) which have been arranged to illuminate the particles from below through the transport surface lineally, at an oblique angle rela¬ tive to the transport surface, advantageously symmetri¬ cally with reference to the direction of travel of the particles, and an underside detector (7) which has been arranged to determine the lateral offset of the lineal light caused by the particle under measurement, from below, and that the calculating means (4) has been ar¬ ranged to determine the particle's height-direction dimension from the underside of the particle.
PCT/FI1990/000092 1989-04-05 1990-04-04 Procedure and apparatus for determining size and/or shape distribution WO1990012310A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI891641 1989-04-05
FI891641A FI84761B (en) 1989-04-05 1989-04-05 FARING REQUIREMENTS FOR THE ADJUSTMENT OF THE DIMENSION OF THE TRAILER.

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WO2001084115A1 (en) * 2000-04-28 2001-11-08 Norsk Hydro Asa Method and system for automatic analysis of particles
DE10260201A1 (en) * 2002-12-20 2004-07-01 Sick Ag Method and device for detecting objects moving on a conveyor by means of an optoelectronic sensor
DE202014100974U1 (en) * 2014-03-04 2015-06-08 Retsch Technology Gmbh Device for determining the particle size and / or the particle shape of a particle mixture
CN105229464A (en) * 2013-05-10 2016-01-06 凯米罗总公司 Detect method and the device of the wandering fibre end in paper
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EP2796853B1 (en) * 2013-04-25 2021-04-07 Fagus-Grecon Greten Gmbh & Co. Kg Method for the qualitative and quantitative measurement of larger fibres in a particle bed and device for carrying out the said method

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FI20216300A1 (en) * 2021-12-20 2023-06-21 Teknosavo Oy Method and arrangement for determining the proportion of bark in wood chips

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001084115A1 (en) * 2000-04-28 2001-11-08 Norsk Hydro Asa Method and system for automatic analysis of particles
US6822736B2 (en) 2000-04-28 2004-11-23 Norsk Hydro Asa Method and system for automatic analysis of particles
DE10260201A1 (en) * 2002-12-20 2004-07-01 Sick Ag Method and device for detecting objects moving on a conveyor by means of an optoelectronic sensor
US7199385B2 (en) 2002-12-20 2007-04-03 Sick Ag Method and an apparatus for the detection of objects moved on a conveyor means by means of an optoelectronic sensor
EP2796853B1 (en) * 2013-04-25 2021-04-07 Fagus-Grecon Greten Gmbh & Co. Kg Method for the qualitative and quantitative measurement of larger fibres in a particle bed and device for carrying out the said method
CN105229464A (en) * 2013-05-10 2016-01-06 凯米罗总公司 Detect method and the device of the wandering fibre end in paper
DE202014100974U1 (en) * 2014-03-04 2015-06-08 Retsch Technology Gmbh Device for determining the particle size and / or the particle shape of a particle mixture
WO2017216090A1 (en) * 2016-06-14 2017-12-21 Basf Se Determining the three-dimensional particle shape of lignocellulosic particles
CN109855559A (en) * 2018-12-27 2019-06-07 成都市众智三维科技有限公司 A kind of total space calibration system and method

Also Published As

Publication number Publication date
FI891641A (en) 1990-10-06
FI891641A0 (en) 1989-04-05
FI84761B (en) 1991-09-30

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