METHOD FOR IDENTIFYING NATURAL FIBRES

Abstract: A method for identifying natural fibres, in particular wool and cashmere fibres, involves magnifying the fibres, arranged on a support, by means of a microscope and sending the magnified images to a data processor which determines, for each fibre, various characteristic parameters, including the scale height. These parameters are compared with a reference database formed using known fibres. When determining the scale height of each fibre, the scale heights (B, C, D) which do not lie within a predefined tolerance range relating to the form of the step are not used.

Description: Description Method for identifying natural fibres Technical field The invention relates to a method for identifying natural fibres . Specifically, but not exclusively, as a result of the invention it is possible to distinguish textile fibres, for example wool fibres from cashmere fibres, in particular in order to determine the percentage composition of mixed wool and cashmere fabrics or yarns . In particular, the invention relates to a method for identifying natural fibres, in particular wool and cashmere fibres, comprising the steps of: magnifying the fibres, arranged on a support, by means of a microscope; sending the magnified images to a data processor; processing the images sent to the processor so as to determine, for each fibre, at least the characteristic parameters of the scale height and, preferably, also the scale frequency and fibre diameter; comparing the parameters determined with a reference database formed using known fibres . As is known, an animal keratin fibre has an external structure composed of a multiplicity of scales having a transverse arrangement with respect to the length of the fibre. "Scale height" is understood as referring to the height of the steps which are naturally formed in the boundary zones between one scale and the next. "Scale frequency" is understood as meaning the number of scales per unit of length of the fibre. Background art A method thus devised is already known, for example, from the following publications: - Schriftenrethe des Deutschen Wollforschungs- institutes e.V., 103, 1988, Analysis of specialty fiber/wool blends by means of SEM (scanning electron microscopy) ; Melliand Textilberichte, 5/1995, Digitale Bildverarbeitung fur die Bestimmung der Fasereinheit und deren Verteilung; - Chemiefasern/Textilindustrie, 43. /95 Jahrgang, April 1993, Digitale Bildverarbeitung zur Bestimmung der Fasereinheit und deren Verteilung. The abovementioned known methods, however, have certain limitations and drawbacks. Firstly these methods, if applied to mixed fabrics or yarns made of materials which can be easily confused with each other (for example, wool, cashmere, yak, cashgora, etc.), produce results with a fairly high error margin. The known methods have a subjective component which is the source of errors and are somewhat inaccurate as regards the actual composition of the fabrics or yarns analysed. Secondly the known methods may use data detected from a relatively small and insignificant number of fibres. Another drawback consists in the fact that a relatively long time is required in order to implement the abovementioned methods. One object of the present invention is to overcome the abovementioned limitations and drawbacks of the known art by providing a method for identifying natural fibres, by means of which it is possible to distinguish with a considerable degree of precision also those fibres which are very similar and can be easily confused with each other, such as, for example, wool and cashmere. Another object of the invention is to provide a method by means of which it is possible to determine with a considerable degree of precision and accuracy the quantitative composition of mixed fabrics or yarns made of natural fibres. A further object of the invention is to provide a method able to produce reliable and significant results in a relatively short execution time. Disclosure of the invention These objects are achieved by a method, in accordance with the claims indicated below, whereby, when determining the characteristic parameter of the scale height, the scales steps which do not lie within a predefined tolerance range relating to the form of the step are not used. With the method in question it is possible advantageously to detect any damage to or alterations of the fibres which could falsify the analysis. This result is achieved, for example, by means of an analysis which does not take into consideration scale- height values outside of a predefined range. The reliability of the method may be improved if the fibres zones which are partially covered or are not clearly visible under a microscope are not taken into account . It is also preferable to provide a filter which is able to identify the form of the steps in the scale division zone and use only the steps corresponding to predetermined forms for identification of the fibres. In order to obtain significant results, at least 1000 fibres should be examined. For example, it is envisaged analysing, under a microscope, four supports each containing about 250 to 300 fibres each. So that each sample may be analysed more easily, the image provided by the microscope may be divided into regions which are preferably square and which are then examined in succession, following a vertical or horizontal line-by-line path. If the image processing software detects that a region is not occupied by fibres, it passes to the next region. If a fibre occupies several regions, the analysis is performed so as to consider the whole fibre only once. For example, if during the analysis of a region it is detected that a fibre extends beyond the boundary of the region being examined, also occupying an adjacent region, examination of said fibre is momentarily interrupted and resumed during analysis of said adjacent region. With the method it is possible to avoid subjective errors due, for example, to manual measurements performed by the operator. As a result of the method it is also possible to take into consideration a large number of values measured. The method may also be applied by a non-specialised operator since the measurements may be performed automatically. According to the method in question it is possible to perform magnification to a smaller degree than that of known methods based on manual measurements, so that the electron beams have a less damaging effect on the fibres being examined. This also allows the same sample to be analysed several times. Yet another advantage is that of being able to form a database by analysing fibres of tried-and-tested origin, said database being able to be used in order to determine the nature of unknown fibres. According to a preferred mode of implementing the method in question, identification of the fibres is performed using, in addition to the scale height parameter, also the characteristic parameter for the fibre diameter. In order to determine the diameter of a fibre in a particularly precise manner, it is preferable to use the contour line of the entire fibre, following which the fibre is divided into substantially equidistant sectors. The number of division sectors is preferably five. Various diameters (preferably five) are then measured for each sector. The median value (i.e. the third in order of magnitude) of the five diameter values measured is then selected for each sector. Finally, from among the five median values selected (one for each sector) the median value (i.e., in this case also, the third value in order of magnitude) is in turn selected. The value thus selected (median of the median values) constitutes the characteristic parameter for the fibre diameter. According to another mode of implementing the method in question, in order to identify the fibres it is also possible to use the characteristic parameter for the scale frequency, namely the number of the scales per unit of length the fibre. Identification of the contour lines of the fibres may be performed by various image processing programs of the known type. Various types of electron microscopes equipped with software able to perform automatically scanning of the image observed under the microscope are also known. The electronic processor, after determining the nature of the plurality of fibres which make up the sample analysed, is able to calculate and provide the value relating to the percentage composition of the said fibres. Brief description of the drawings Further characteristic features and advantages of the present invention will emerge more clearly from the following detailed description of a preferred, but not exclusive, embodiment of the said invention, provided purely by way of a non-limiting example, in the accompanying drawings, m which: Figure 1 shows a magnified image of a fibre sample viewed under an electron microscope; Figure 2 shows a detail, on a larger scale, of Figure 1; Figure 3 shows a detail, on a larger scale, of Figure 1 m which a contour line of a fibre is shown m broken lines; Figure 4 shows a rop plan view of the fibres arrangeα on a suitable support for microscopic analysis; Figure 5 shows a detail, on a larger scale, of Figure 4. Detailed description of the preferred embodiment (s) Figures 1 and 2 show the external structure of the animal fibres 1. The fibres 1 shown may be, for example, cashmere fibres. The external structure of each individual fibre 1 is composed of several scales 2 arranged transversely with respect to the length of the fibre and distributed m succession. In the boundary zone between any two adjacent scales 2 a step 3 is present, the height H tnereof being said scale height. The scale heights H may be used m order to distinguish one fibre 1 from another. Other characteristic parameters which may be used in order to determine the nature of a fiore may be the diameter D of the fibre and the scale frequency, i.e. the number of scales 2 per unit of length of the fibre. The diameter D of each fibre is preferably calculated in the following manner. Five equidistant sectors on the fibre are selected. By means of the image processing program, five diameters D for each sector are measured and the median value diameter thereof is selected. From among the five diameters D selected (one for each sector) the median value diameter is in turn selected, said value being taken as the value of the diameter D F of the fibre 1. Figure 3 shows the external profiles of various boundary zones between adjacent scales 2. The boundary zones are indicated by A, B, C and D. A step 3 which separates a scale 2 from the next one is present in each boundary zone. The method in question envisages detecting, for each step 3, by means of the image processing software, the height H and the inclinations S and I of the top and bottom sides, respectively, of the fibre profile, which define the step 3. The height H of the various scale steps (H A , H B , H c , etc.) is measured by determining the distance in a substantially radial direction (perpendicular to the longitudinal axis of the fibre) between the top edge and the bottom edge of the step 3. It is envisaged performing a selection from among the values of the scale heights measured (H A , H B , H c , etc.) in order to determine the characteristic scale height H s of a fibre. It is preferable to use a filter, of a known type, in order to exclude, when determining the characteristic parameter of the scale height H s of a fibre 1, some of the values detected for the various heights H of the steps. In particular the filter acts so as to exclude, with reference to Figure 3, the heights of the steps indicated by B, C and D and so as to consider instead the height of the step indicated by A. We shall analyse in detail below the operating mode of the filter. Let us consider the scale height of the boundary zone A. The side F A of the step extends in a direction almost perpendicular to the longitudinal axis x of the associated fibre. S A and I A indicate, respectively, the directions of the sides of the scales which define, at the top and the bottom, the step of the boundary zone A. These directions S A and I A are almost parallel to each other. The value H A of the step height falls within a predefined tolerance range. The step A satisfies, within certain tolerance limits, predefined criteria (in particular, the perpendicularity of the side F A with respect to the longitudinal axis x of the fibre, the relative parallel arrangement of the top and bottom sides S A and I A , the value of the height H A of the step) and therefore the step itself is considered to be normal and may be therefore used in order to determine the step height parameter H s for that fibre 1. The step in the zone B does not satisfy one of the abovementioned criteria: in fact, as can be seen in Figure 3, the directions S B and I B of the top and bottom sides are far from being parallel with each other and exceed the tolerances limits envisaged. The step B is anomalous and therefore is not taken into consideration when calculating the scale height H s . The step C is also anomalous because it has a height He which is relatively small and lies outside the prechosen tolerance range. The step C, which probably does not consist in reality of a proper dividing step between the two scales 2, but only of a simple projection of the fibre profile, is therefore excluded from calculation of the scale height parameter H s . The abnormal character of the step D, and therefore its exclusion, is due to the excessive inclination of the side F D of the step with respect to the direction perpendicular to the longitudinal axis x of the fibre. In other words, the relative inclination of the side F D of the step D with respect to the longitudinal axis x of the fibre 1 exceeds the predefined tolerance range. The filter is able to operate so as to exclude scale steps having an inclination which exceeds a predefined range. Figure 3 shows, as a broken line, the side F' D of a step which also has an inclination which exceeds the predefined range. Generally, it is possible to use a filter of the known type, which allows one to exclude, for the purpose of determining the scale height H s , scales having a side with a form which does not lie within a certain tolerance range. The scale height H s of each individual fibre may be determined, for example, by taking the mathematical mean of the heights H of the scale steps which can be used for that fibre or by selecting a median value from among the heights H of the scale steps which can be used for that fibre. Figure 4 shows a sample of fibres. The image processing program divides the sample into regions, in particular having a square shape, and analyses them in succession in the direction of the arrows. In Figure 5 it can be seen that some fibres may occupy adjacent regions. The image processing program may operate so as to consider each fibre no more than once. According to a preferred mode of implementation of the method, a large number of fibres of the known type is analysed beforehand in order to produce a comparative database. Identification of unknown fibres is performed by means of comparison of the characteristic fibre parameters with the comparative database. This comparison is performed using a statistical method, of the known type, preferably of the type which uses a fuzzy logic. A device able to implement the method in question comprises an electronic processor which controls a microscope, in particular an electron microscope, and which is designed to store the magnified images provided by the microscope. The processor is able to execute an image processing program which determines the characteristic parameters of each fibre and which can be used in accordance with the abovementioned criteria. The processor, by means of another data processing program, then relates the abovementioned parameters to corresponding predetermined reference values. The device is designed to allow automatic analysis, by means of the abovementioned method of analysis, of at least two supports provided with different fibre samples. The analyses of each sample are performed in succession and separately. A plurality of supports each containing a fibre sample are conveyed so that the samples are subject to the action of the electron beam emitted by the microscope and are scanned by it in succession, while the data processor controls conveying of the supports. According to a preferred mode of implementation of the method in question, it is envisaged that the analysis of each fibre should comprise a first step involving detection of the fibre on the support. After this, analysis of the fibre continues with a second step which consists in actual identification of the fibre within its particular group and during which the image processing software determines, using the abovementioned procedures, one or more characteristic parameters of the fibre which are compared with reference values, for example with a predetermined comparative database. Obviously the invention may be subject to numerous modifications of a practical/applicational nature with regard to the constructional details, without this departing from the protective scope of the inventive idea as claimed below.

Claims: Claims 1. Method for identifying natural fibres, in particular wool and cashmere fibres, comprising the steps of: - magnifying the fibres (1), arranged on a support, by means of a microscope; - sending the magnified images to a data processor; - processing the images sent to the processor so as to determine, for each fibre, at least the characteristic parameter of the scale height (H s ) ; - comparing the scale height (H s ) determined for each fibre with a reference database; characterized in that, when determining the scale height (H s ) of each fibre, a selection is performed from among the various scale height values (H A , H B , H c , etc.) measured, in the sense that the scale heights (B, C, D) which do not fall within a predefined tolerance range relating to the form of the step are not used. 2. Method according to Claim 1, characterized in that, in order to determine the scale height (H s ) of a fibre, the scale steps (B) where the top side (S B ) and the bottom side (I B ) which define the said step have a relative inclination exceeding a predetermined value are not used. 3. Method according to Claim 1 or Claim 2, characterized in that, in order to determine the scale height (H s ) of a fibre, the scale steps (C) , the height (H c ) of which is less than a predefined value, are not used. 4. Method according to any one of the preceding claims, characterized in that, in order to determine the scale height (H s ) of a fibre, the scale steps (D) having a side (F D ), the inclination of which with respect to the longitudinal axis (x) of the fibre has a deviation from the perpendicular greater than a predefined minimum value, are not used. 5. Method according to any one of the preceding claims, characterized in that, in order to determine the scale height (H s ) of a fibre, only the heights of the scale steps situated in a boundary zone between one scale and the next which are not covered by a crossing fibre are used. 6. Method according to any one of the preceding claims, characterized in that the scale height (H s ) of each individual fibre is determined by the mean of the heights of the scale steps used for that fibre. 7. Method according to any one of Claims 1 to 5, characterized in that the scale height (H s ) of each individual fibre is determined by an intermediate value of the heights of the scale steps used for that fibre. 8. Method according to any one of the preceding claims, characterized in that the heights of the scale steps (H A , H B , H C , H D ) of the fibres are measured by means of image processing software. 9. Method according to any one of the preceding claims, characterized in that the parts of the support occupied by fibres are divided into regions, in particular adjacent squares, and these regions are analysed in succession, in particular proceeding linewise . 10. Method according to Claim 9, characterized in that, if a fibre occupies several regions, it is analysed only in one of said regions and is not considered in the other regions. 11. Method according to any one of the preceding claims, characterized by the fact of: determining, for each fibre, by means of processing of the images sent to the processor, at least the characteristic parameter for the diameter (D F ) of the fibre; and comparing the fibre diameter determined for each fibre with a predefined reference value; said determining operation involving: - choosing, from among the various fibre sectors, preferably five sectors which are equidistant from one another; measuring various diameters, preferably five diameters (D), for each sector; - selecting, for each sector, the median measurement from among the various measurements of the diameter (D); - selecting, finally, from among the various median diameters selected above, the median diameter which is regarded as the diameter (D F ) of the fibre. 12. Method according to any one of the preceding claims, characterized by the fact of determining, for each fibre, by means of processing of the images sent to the processor, at least the characteristic parameter for the scale frequency and comparing the scale frequency determined for each fibre with a predefined reference value.

Inventors: GELOSINI STEFANO, GRASSI CRISTIANA, GELOSINI, STEFANO, GRASSI, CRISTIANA
Applicants: GELOSINI STEFANO, GRASSI CRISTIANA, IMAX S R L, GELOSINI, STEFANO, GRASSI, CRISTIANA, IMAX S.R.L.
Application year: 2000
Main classification: G01N21
IPC codes: G01N21, G01N33