OPTICAL CHARACTERIZATION OF A TEXTILE FIBER STRUCTURE

Description

FIELD OF EXPERTISE

[0001] The present invention lies in the field of yarn production. It relates to a computer-implemented method and a device for the optical characterization of a textile fiber structure, according to the independent patent claims. It can be used, for example, but not exclusively, in the blow room of a spinning mill. STATE OF THE ART

[0002] Textile fibers are typically delivered to a spinning mill in the form of fiber bales. There, the textile fiber bales are lined up, often intentionally combining different types and / or qualities of textile fiber bales into a single bale to create a suitable fiber blend. The bale is removed layer by layer using a bale opener. The removed textile fibers, in the form of fiber flakes, are pneumatically transported in an air stream to various cleaning stages, which break the fiber flakes down further and remove foreign materials.

[0003] US-6,452,157 B1 relates to a device on a fiber processing device for detecting and processing impurities, foreign substances, and fibers in textile fiber material. The device has at least two light sources that alternately illuminate the fiber material with different colors. A sensor is also provided that receives the colors of the light reflected from the fiber material. A sudden color change of the fiber material from a predetermined color generates an electrical signal. To enable adaptation of the luminous colors depending on the application, e.g., to different or changing colors of the fiber material, a multicolor light source with more than two colors is used. The type of colors of the multicolor light source can be selected depending on the color of the fiber material to be illuminated.

[0004] In a method for optimizing a yarn manufacturing process according to WO-2021 / 051210 A1, foreign materials in a textile fiber structure are monitored. The textile fiber structure is irradiated with electromagnetic radiation from at least two color ranges. The foreign materials are classified into different color classes according to their color. If a sufficiently large sample of classified foreign materials is available, a frequency distribution of the foreign materials is determined for the color classes and compared with a reference frequency distribution. If the determined frequency distribution deviates from the reference frequency distribution, at least one of several optimization actions is performed, e.g., a warning signal is issued.

[0005] EP-3'321'68 A2 discloses a method for assessing the quality of a yarn. The yarn is exposed to polychromatic, preferably white, light. A measurement signal representing the red, green, and blue color components of the light reflected by the yarn is recorded. The red, green, and blue color components are transformed into an evaluation color space in which measurement points of the measurement signal are described by a first and a second coordinate representing the color, and by a third coordinate representing the brightness. The quality of the yarn is assessed based on the first, second, and third coordinates of the measurement points in the evaluation color space. This makes it possible to distinguish foreign matter from diameter deviations of the yarn. Black foreign fibers can also be detected.

[0006] However, it's not just foreign materials that pose a problem in spinning, but also the textile base material itself. It often happens that this changes unintentionally over time during production. Such material changes can have various causes, such as incorrect bale composition or a quality change within a batch of textile fiber bales. Unlike the appearance of foreign material, they do not occur suddenly, but continuously over a longer period of several minutes or hours. These material changes result in undesirable changes in the quality of the produced yarn and ultimately also in the final textile products. PRESENTATION OF THE INVENTION

[0007] It is an object of the present invention to provide a method and a device for the optical characterization of a textile fiber structure. The invention is intended to prevent undesirable changes in the quality of the textile fiber structure and the textile end products produced therefrom. In particular, large quantities of material that have mistakenly entered the textile fiber structure and unintentional changes to the bale template are to be detected. The material changes caused thereby occur continuously over a longer period of several minutes or hours. The present invention is therefore not primarily interested in individual events in the textile fiber structure, such as the presence of a single foreign material, but rather in the medium- and long-term composition of the textile fiber structure. A further object of the invention is to optimize the excretion of foreign materials from the textile fiber structure.

[0008] These and other objects are achieved by the inventive computer-implemented method and device as defined in the independent claims. Advantageous embodiments are specified in the dependent claims.

[0009] The computer-implemented method according to the invention serves for the optical characterization of a textile fiber structure. A multitude of color information about various locations on the textile fiber structure is captured by an optical sensor system. The captured color information is sent by the optical sensor system to a computer, received by the computer, and stored by the computer. The stored color information is entered by the computer into a color space as a point cloud. A frequency density distribution of the point cloud is determined by the computer. The frequency density distribution is numerically specified by the computer. A signal dependent on the numerical specification is output by the computer.

[0010] The color information is preferably collected randomly.

[0011] The color space, for example, is a one- or two-dimensional color space in which information about brightness is ignored.

[0012] According to one embodiment, the computer defines a characteristic region in the color space based on the frequency density distribution. To numerically specify the frequency density distribution, the characteristic region is specified numerically. For this purpose, the computer can use, for example, a length, an area or a volume of the characteristic region, a geometric shape of the characteristic region, and / or a profile of a boundary line or boundary surface that delimits the characteristic region.

[0013] In a first application example, the computer infers a change in the material composition of the textile fiber structure from a change in the numerical specification of the frequency density distribution, and the signal output by the computer depends on the change in the material composition. The signal output by the computer is preferably used to trigger at least one of the following actions: output of a graphic to an operator, output of a warning to an operator, output of a recommended action to an operator, shutting down at least one processing machine, changing a setting on at least one processing machine. The computer can be specified a limit value and / or a tolerance range, the exceedance of which by a parameter of the numerical specification of the frequency density distribution indicates a change in the numerical specification.

[0014] In a second application example, the computer detects a foreign material in the textile fiber structure based on the numerical specification of the frequency density distribution, and the signal output by the computer controls the expulsion of the detected foreign material from the textile fiber structure. The computer can recognize an element of the point cloud as belonging to a foreign material if the element in question lies outside the characteristic region. According to a first alternative, the computer suspends the expulsion of the foreign materials until a statistically representative characteristic region is available and numerically specified. According to a second alternative, an initial characteristic region is specified for the computer, and the characteristic region is continuously adapted by the computer to the material composition of the textile fiber structure.

[0015] According to one embodiment, the computer corrects the color information, a threshold value, and / or a tolerance range with a degree of resolution that indicates the extent to which the textile fiber structure is broken down into individual fiber flakes. For this purpose, for example, at least one image of the textile fiber structure is recorded by the optical sensor system, and the computer uses the at least one image to determine the image area onto which fiber material is imaged by image processing; the computer determines a mass flow of the textile fiber structure per unit time; the degree of resolution is calculated by the computer as a scalar variable by forming a quotient of the image area onto which fiber material is imaged, on the one hand, and the mass flow, on the other. The degree of resolution is preferably determined by the computer according to the formula X = A F / A T ⋅ m where AF is the image area onto which fiber material is imaged, AT is a total area of ​​the image and m is a mass flow of the textile fiber structure per unit time.

[0016] The device according to the invention serves for the optical characterization of a textile fiber structure. It comprises an optical sensor system for detecting a plurality of color information items about various locations on the textile fiber structure and a computer connected to the optical sensor system. The optical sensor system has transmitting means for transmitting the detected color information to the computer. The computer has receiving means for receiving the color information transmitted by the optical sensor system. The computer is configured to enter the detected color information in a color space as a point cloud, determine a frequency density distribution of the point cloud, numerically specify the frequency density distribution, and output a signal dependent on the numerical specification.

[0017] The color space, for example, is a one- or two-dimensional color space in which information about brightness is ignored.

[0018] According to one embodiment, the computer is configured to define a characteristic region in the color space based on the frequency density distribution and to numerically specify the characteristic region for the numerical specification of the frequency density distribution.

[0019] In a first application example, the computer is configured to infer a change in the material composition of the textile fiber structure from a change in the numerical specification of the frequency density distribution, and the signal output by the computer depends on the change in the material composition. The computer is configured such that the signal it outputs is suitable for triggering at least one of the following actions: outputting a graphic to an operator, outputting a warning to an operator, outputting a recommended action to an operator, shutting down at least one processing machine, or changing a setting on at least one processing machine.

[0020] In a second application example, the device additionally includes a separation unit connected to the computer. The computer is configured to detect foreign materials in the textile fiber structure based on the numerical specification of the frequency density distribution and, upon detection of the foreign material, to control the separation of the detected foreign material by the separation unit using the signal it outputs. The computer can be configured to recognize an element of the point cloud as belonging to a foreign material if the element in question lies outside the characteristic region. According to a first alternative, the computer is configured to suspend the separation of the foreign materials until a statistically representative characteristic region is available and numerically specified.According to a second alternative, the computer is configured to store an initial characteristic area and to continuously adapt the stored characteristic area to a material composition of the textile fiber structure.

[0021] According to one embodiment, the computer is configured to additionally determine a degree of resolution of the textile fiber structure, which indicates the extent to which the textile fiber structure is resolved into individual fiber flakes, and to correct the color information, a threshold value, and / or a tolerance range with the degree of resolution. For this purpose, the optical sensor system can include an image sensor for recording at least one image of the textile fiber structure; the computer can be configured to determine, from the at least one image, the image area onto which fiber material is imaged by image processing, to determine a mass flow of the textile fiber structure per unit time, and to calculate the degree of resolution as a scalar variable by forming a quotient of the image area onto which fiber material is imaged, on the one hand, and the mass flow, on the other hand. The computer is preferably configured to determine the degree of resolution according to the formula X = A F / A T ⋅ m to determine, where AF is the image area onto which fiber material is imaged, AT is a total area of ​​the image and m is a mass flow of the textile fiber structure per unit time.

[0022] The optical characterization of the textile fiber structure according to the invention offers several advantages. For example, a change in the numerical specification of the frequency density distribution can be used to infer a change in the material composition of the textile fiber structure. It is important for a spinning mill to detect such a material change early on, as it can indicate an incorrect composition of the bale. If the detection occurs at an early stage of the spinning process, e.g., at a fiber cleaner in the blowroom, the production of yarn from the wrong textile fiber material can be prevented in a timely manner by making the appropriate correction.

[0023] Furthermore, the invention optimizes the removal of foreign materials from the textile fiber structure. Based on the inventive characterization, a boundary can be drawn between the base material of the textile fiber structure and the foreign materials to be removed, adapted to the currently processed textile fiber structure, and used to remove the foreign materials. This ensures that, on the one hand, the foreign materials are reliably removed, while, on the other hand, as little good material as possible is wasted from the textile fiber structure.

[0024] Overall, the invention prevents undesirable changes in the quality of the textile fiber structure and the textile end products produced from it.

[0025] In this document, terms such as "textile fiber material" or similar always refer to the base material from which the textile fiber structure is predominantly composed. Any contamination by individual foreign materials plays no direct role in the present invention and should be disregarded when referring to "composition of the textile fiber material," "changes in the textile fiber material," "material changes," or similar. LIST OF DRAWINGS

[0026] An embodiment of the invention is explained in detail below with reference to the schematic drawings. Figure 1 shows an embodiment of the device according to the invention. Figure 2(a) shows a two-dimensional color space with a point cloud and a characteristic region. Figure 2(b) shows a one-dimensional frequency density distribution of the point cloud of Figure 2(a). Figure 3 shows a two-dimensional color space with a characteristic area, where the characteristic areas of the Figures 3(a) and 3(b) differ from each other. Figure 4 shows temporal progressions of values ​​that numerically specify a characteristic region. Figure 5 shows a three-dimensional RGB color space with a characteristic region. IMPLEMENTATION OF THE INVENTION

[0027] Figure 1 schematically illustrates an embodiment of the device 100 according to the invention using the example of a fiber cleaner in a blow room. The device 100 serves for the automatic optical characterization of a textile fiber structure 9, which in the present example is a fiber flock stream, e.g., a cotton flock stream. It includes a pneumatic fiber transport channel 101 for pneumatically transporting the fiber flock stream 9 in an air stream. The transport direction of the fiber flock stream 9 and the air stream is Figure 1indicated by arrows 91.

[0028] Four light sources 103, e.g., fluorescent tubes or LED arrays, are arranged near windows 102 in a wall of the fiber transport channel 101. The light sources 103 illuminate the fiber flake stream 9 in the fiber transport channel 101 from different directions.

[0029] An optical sensor system 105 is arranged on the fiber transport channel 101. It detects color information about the fiber flake stream 9. In the embodiment of Figure 1The sensor system 105 includes two cameras 106 that capture images of the fiber flake stream 9 through the windows 102 from two different directions. The light emitted by the light sources 103, after interacting with the fiber flake stream 9, is deflected to the cameras 106 by means of appropriately tilted mirrors 104. The cameras 106 are equipped, for example, with CMOS or CCD photosensors whose pixels are covered with mosaic color filters arranged in a Bayer matrix. The output signals of such photosensors can be interpolated inside or outside the cameras 106 using known algorithms so that each pixel or image segment is assigned a color in a color model.

[0030] The cameras 106 are connected to a computer 107 for the automatic evaluation of output signals of the optical sensor system 105. The computer 107 is configured to enter the acquired color information in a color space as a point cloud, to determine a frequency density distribution of the point cloud, and to specify the frequency density distribution numerically (see Figure 2 below).

[0031] The computer 107 is connected to an output unit 108. A signal output by the computer 107 can cause the result of the characterization, e.g., a graphic, to be output on the output unit 108. The output unit 108 can be, for example, a computer monitor or a printer. In one embodiment, it is designed as a touchscreen and thus serves as an input and output unit.

[0032] A separation unit 109 is arranged on the fiber transport channel 101 downstream of the sensor system 105 (with respect to the transport direction 91). The separation unit 109 serves to selectively separate foreign materials 90 from the fiber flake stream 9. Such a separation unit 109 is known per se, e.g., from WO-2006 / 079426 A1. In a preferred embodiment, it includes a plurality of pressurized air nozzles that can be controlled individually or in groups by a signal output by the computer 107. If the sensor system 105 detects an inadmissible foreign material 90 in the fiber flake stream 9, the corresponding air nozzle of the separation unit 109 is caused by the signal output by the computer 107 to blow out compressed air perpendicular to the transport direction 91 when the foreign material 90 has reached the level of the separation unit 109.As a result, the foreign material 90 is blown into a separation channel 110, which extends from the fiber transport channel 101 in a separation direction 92 that is essentially perpendicular to the transport direction 91. The uncontaminated fiber flakes, however, continue their path with the fiber flake stream 9 to be further processed.

[0033] The separation unit 109 can be controlled by the computer 107 and / or directly by the sensor system 105. In the latter case, each camera 106 can be assigned a computer, e.g., in the form of a microprocessor, and the cameras 106 can be directly connected to the separation unit 109 and output their signals thereto. Such direct connections are described in Figure 1 Not shown for simplicity. In another alternative, the separation unit 109 is controlled by a computer that is assigned to the separation unit 109 itself.

[0034] In Figure 2(a)A two-dimensional color space 2 is shown schematically. This color space 2 provides information about the hue and color saturation, but not about the brightness. It can, for example, be a horizontal slice through the well-known HSV color space; in polar coordinates, the angle corresponds to the hue (H) and the radius to the color saturation (S). Instead of such a perception-oriented color model, however, a technical-physical color model is preferred for the present invention. An advantageous color space 2 is, for example, the II I2 I3 color space without the brightness component (I1).

[0035] According to the invention, a plurality of pieces of color information about different locations of the textile fiber structure 9 is detected by the optical sensor system 105, preferably randomly. A sample can comprise color information from multiple locations of a single image and / or color information from different images. Preferably, it consists of a plurality of pieces of color information, each from multiple pixels of multiple digital images. These do not necessarily have to be images taken directly one after the other; for example, one image per second may suffice, while the image frequency is much higher. The sample should contain such a large number of elements that it is statistically representative of the textile fiber structure 9. With knowledge of the invention, the person skilled in the art is able to determine the required minimum size of the sample. The corresponding principles for a theoretical consideration are, for example,in the book “Statistical Methods in Textile Investigations” by Graf, Henning and Wilrich, 2nd ed., Springer-Verlag, 1974.

[0036] The detected color information is sent from the sensor system 105 to the computer 107, received by the latter, and stored. The stored color information is stored by the computer 107 in a color space, e.g., in the two-dimensional color space 2 of Figure 2(a) , as color events 3 represented by points in a point cloud 31. The representation of the point cloud 31 can be output to an operator as a graphic on the output unit 108 based on the signal output by the computer 107, but this is optional; alternatively, the color information can be entered purely virtually in the computer 107.

[0037] Subsequently, the computer 107 determines a frequency density distribution of the point cloud 31. Since the color information is discrete measured values, the frequency density distribution thus determined will have levels. It can, but does not need to, be mathematically approximated by a continuous function; corresponding calculation methods are known. An exemplary, continuously approximated one-dimensional frequency density distribution 4 along an axis 21 of the color space 2 of Figure 2(a) is in Figure 2(b) schematically, with the vertical axis 41 indicating the frequency density. The frequency density distribution 4 is not only shown in one dimension (as shown for simplicity in Figure 2(b) shown), but in the entire two-dimensional color space 2 of Figure 2(a) For approximately white cotton, the frequency density in the vicinity of a gray or white point located at the coordinate origin of color space 2 is 24 (see Figure 3) is greatest, but the maximum need not be at gray point 24, because each cotton has its own characteristic coloration. The present invention is concerned with the automatic characterization of this coloration.

[0038] According to the invention, the frequency density distribution 4 is specified numerically by the computer 107. Thanks to their basic training in mathematics, the person skilled in the art knows how a curve or a surface can be specified numerically: e.g., by its extreme values, saddle points, gradients at certain points in certain directions, approximation by a suitable fitting function, etc. Below, a specific type of numerical specification of the frequency density distribution 4 is discussed as an example, without restricting generality, which is particularly well suited for textile fiber structures 9.

[0039] Based on the frequency density distribution 4, the computer 107 defines a characteristic region 5 in the color space 2. The characteristic region 5 does not need to be contiguous. In the simplest case, the characteristic region 5 is delimited by a boundary line 57 with a constant frequency density 42. The corresponding frequency density 42 is selected such that a large part, e.g., 95% or 99%, of the point cloud 31 lies within the characteristic region 5. The color events 3' outside the characteristic region 5 are then outliers that are not considered characteristic of the textile fiber structure 9 and are therefore disregarded. Such outliers 3' can, for example, arise from incorrect measurements or represent foreign materials 90 that are undesirably present in the textile fiber structure 9.

[0040] The boundary line 57 does not necessarily need to be defined by a constant frequency density 42. It can be defined, for example, by maintaining a constant safety margin from a line with a constant frequency density 42, so that it lies further out in the color space 2. Alternatively, it can be created, for example, by stretching the radii belonging to a line with a constant frequency density 42 with a constant stretch factor. However, all such possibilities for defining the characteristic region 5 must use the frequency density distribution 4 as a basis.

[0041] The characteristic area 5 is in turn specified numerically by the computer 107, which in Figure 3(a) is illustrated by way of example. The numerical specification can, for example, take into account the following properties of the characteristic region 5: a length, an area or a volume of the characteristic region 5, depending on whether the region 5 is one-, two-, or three-dimensional, a geometric shape of the characteristic region 5, in two dimensions, e.g., a position of a center of gravity 58 or a center of gravity of the contour of the region 5, and / or a course of a boundary line 57 or a boundary surface that delimits the characteristic region 5. The numerical specification can be made using support points. Figure 3(a)For example, six interpolation points 51-56 are shown, located in pairs on axes 21-23, which intersect at the coordinate origin (gray point 24) and are separated by an angular distance of 60°. In this example, each interpolation point 51-56 is uniquely defined by its radial distance from the coordinate origin. For numerical specification, the distance values ​​associated with interpolation points 51-56 can be specified individually or mathematically combined into a single value.

[0042] Two preferred application examples for the method according to the invention and the device 100 according to the invention are described below.

[0043] A first application example aims to detect a temporal change in the textile fiber material or its composition and automatically trigger a corresponding action, for example, by issuing a warning signal. Thanks to the warning signal, for example, an incorrect composition of the bale template can be detected.

[0044] Figure 4 illustrates an embodiment of the first application example. It shows values ​​of the radial components of the six support points 51-56 of Figure 3 along a vertical axis 69 versus time t along a horizontal time axis 68 as curves 61-66. Each curve 61-66 represents the time course of a value plotted on the corresponding axis 21-23 ( Figure 3 ) lying color component, e.g., Green 61, Cyan 62, Blue 63, Red 64, Magenta 65 and Yellow 66. Normally, it is sufficient to record the values ​​periodically at longer intervals, e.g., every 15 minutes, so that the diagram of Figure 4covers a period of several hours.

[0045] In the example of Figure 4 The values ​​change only slightly in the first few hours and are therefore within a tolerance range. However, at a certain point in time t 1 they begin to change noticeably. This can be an indication of an incorrect composition of the bale template. The material change can be determined from a single value in Figure 4 and / or by linking the values ​​from the computer 107. For this purpose, for example, tolerance ranges can be specified, and if these are exceeded, the computer 107 issues a signal. The current values ​​or running averages from several consecutively recorded values ​​can be taken into account. Figure 4For the yellow curve 66, a tolerance range 67 is indicated in the form of a band initially surrounding the curve 66. The tolerance range 67 is preferably adjusted to a running average of the curve 66 in order to compensate for any drift that is not caused by a material change. Around time t1, the curve 66 leaves the tolerance range 67, resulting in the output of the signal.

[0046] The signal output by the computer 107 can, for example, automatically trigger at least one of the following actions: output of a graphic to an operator, output of a warning to an operator, output of a recommended action to an operator, shutting down at least one processing machine, changing a setting on at least one processing machine.

[0047] Figure 3 illustrates how, in a time course according to Figure 4 the characteristic area 5 can change. In Figure 3(a)is an example of a characteristic area 5 at an initial time t 0 , in Figure 3(b) a changed characteristic area 5' at a later time t 2 > t 1 > t 0 is shown. The shape of the characteristic area 5 has visibly changed in the time interval [t 0 , t 2 ], which is quantitatively captured by the numerical specification described above. The characteristic area 5' at the later time t 2 has other support points 51'-56' (see also Figure 4 ), a different boundary line 57', a different center of gravity 58', a different area, etc. than the characteristic area 5 at the initial time t 0 .

[0048] A second application example deals with the elimination of foreign materials 90 from the textile fibre structure 9 (cf. Figure 1). The characteristic area 5 with its color events 3 is characteristic of the textile fiber structure 9, while all color events 3' outside of the area 5 are considered foreign materials 90 that are to be eliminated. To avoid incorrect eliminations, the characteristic area 5 should be adapted to the respective textile fiber structure 9 being processed.

[0049] According to a first alternative, foreign material removal can be suspended during a learning phase at the beginning of processing a new batch of textile fiber material. The color information about the textile fiber structure 9 is recorded and stored until a statistically representative characteristic area 5 is present and numerically specified. As soon as this is the case, foreign material removal is activated. It causes all color events 3' outside the characteristic area 5 to be removed from the textile fiber structure 9 as foreign materials 90. Removal is performed by the removal unit 109, which is controlled by a signal output by the computer 107. This first alternative has the disadvantage that during the learning phase, the textile fiber structure 9 enters the subsequent process steps uncleaned.However, the learning phase is so short compared to the total processing time of the batch that the improved foreign material removal achieved through the invention far outweighs the disadvantage.

[0050] According to a second alternative, foreign materials 90 are eliminated from the outset. To enable this, an initial characteristic region 5 is specified before processing begins. This can, for example, be a characteristic region determined for a previously processed textile fiber material, determined by a simple color measurement of the textile fiber material to be processed, or designed based on theoretical considerations. During processing, the initial characteristic region 5 can then be continuously and better adapted to the current textile fiber material by the computer 107. The elimination is again carried out by the elimination unit 109, which is controlled by a signal output by the computer 107.

[0051] In both alternatives, the expected or current excretion rate, ie the number of excretions per unit of time or per unit of mass of the textile fiber structure 9, can be displayed by the computer 107 on the output unit 108 ( Figure 1 ) to an operator. The operator can be given the option of confirming or changing the output excretion rate via the input unit 108. A change in the excretion rate can consist of a decrease or an increase. In the former case, the characteristic area 5 ( Figure 2(a) ) and reduced in the latter case. Thanks to the existing numerical specification of the frequency density distribution 4 ( Figure 2(b) ) such a targeted change can be carried out quickly and easily by the computer 107 automatically.

[0052] Figure 5illustrates that in the method according to the invention not only two-dimensional, but also, for example, three-dimensional color spaces can be used. It shows the known three-dimensional RGB color space 2' with a black point 24', a white point 25', a red point 27', a green point 28' and a blue point 29'. In the RGB color space 2', a characteristic area 5' is schematically drawn according to the method according to the invention. The three-dimensional characteristic area 5' in this case is based on a frequency density distribution of a three-dimensional point cloud, which, however, is Figure 5 Not shown for clarity. For nearly white cotton, the frequency density is greatest in the vicinity of a grayscale axis 26' (the spatial diagonal connecting the black point 24' with the white point 25').

[0053] While the two-dimensional color information according to the Figures 2(a) and 3is not influenced by the brightness, at least in the ideal case, contains the three-dimensional color information according to Figure 5 The brightness is very good. Now, however, in a device 100 according to Figure 1 The measured brightness is influenced by the resolution of the textile fiber structure 9 into individual fiber flakes: The better the textile fiber structure 9 is resolved into individual fiber flakes, the greater the brightness, and vice versa. Therefore, it can be advantageous, especially in the color space 2' of Figure 5 to correct the colour information with a degree of resolution which indicates the extent to which the textile fibre structure 9 is resolved into individual fibre flakes.

[0054] The degree of resolution and its determination are discussed in detail in WO-2017 / 117688 A1. Preferably, the degree of resolution is calculated as a scalar quantity by forming a quotient of the image area AF of an image captured by camera 106, onto which fiber material is imaged, on the one hand, and the mass flow m of the fiber flake stream 9, on the other. An exemplary definition of the degree of resolution X is: X = A F / A T ⋅ m , where AF is the image area, AT is the total area of ​​the image, and m is the mass flow of the fiber flake stream 9 per unit time. In this example, smaller values ​​of X indicate a lower, poorer resolution of the fiber flake stream 9, while larger values ​​indicate a higher, better resolution.

[0055] The correction of the color information with the resolution X can be performed using a theoretical formula or empirically determined correction values, which can be stored, for example, in a table. Instead of or in addition to the color information, a threshold value and / or a tolerance range can be corrected with the resolution X. Under certain circumstances, the correction with the resolution X can be useful not only in three-dimensional color spaces 2', but also in two-dimensional color spaces 2. The correction is performed by the computer 107.

[0056] Of course, the present invention is not limited to the embodiments discussed above. With knowledge of the invention, the skilled person will be able to derive further variants that also fall within the scope of the present invention.

[0057] In the above description, the invention is explained using examples with two-dimensional color spaces 2 ( Figures 2(a) and 3) and three-dimensional color spaces 2' ( Figure 5 ) is discussed. The skilled person is able to adapt the present invention to a one-dimensional color space.

[0058] Likewise, the person skilled in the art is able to generalize the invention from the color spaces 2, 2' discussed here in the visible range of the electromagnetic spectrum to color spaces that include the ultraviolet and infrared spectral ranges adjacent to the visible range or parts thereof.

[0059] In the above description, the invention is discussed using the example of a fiber cleaner in a blow room, wherein the textile fiber structure 9 in the form of a fiber flock stream is pneumatically conveyed through the device 100 ( Figure 1). However, the invention is not limited to this application. It can also be used, for example, in spinning preparation, where the textile fiber structure is in the form of a fiber sliver, or in spinning / winding, where the textile fiber structure is in the form of yarn. LIST OF REFERENCE SYMBOLS

[0060] 100Device according to the invention 101Fiber transport channel 102Window in the wall of the fiber transport channel 103Light sources 104Mirrors 105Sensor system 106Cameras 107Computer 108Output and input unit 109Elimination unit 110Elimination channel 2, 2'Color space 21-23Axes of the color space 24Gray point 24'Black point 25'White point 26'Gray value axis 27'Red point 28'Green point 29'Blue point 3 color events 3 outliers 31 point cloud 4Frequency density distribution 41Frequency density axis 5, 5'characteristic area 51-56, 51'-56'support points 57, 57'boundary line 58, 58'area centroid 61-66Curves representing time courses of color components 67Tolerance range 68Time axis 69Vertical diagram axis 9Fiber flake stream 90Foreign material 91Transport direction of the fiber flake stream 92Separation direction

Claims

1. Computer-implemented method for the optical characterization of a textile fiber structure (9), wherein a plurality of pieces of information on color is detected by an optical sensor system (105) at different locations of the textile fiber structure (9), the captured color information is transmitted from the optical sensor system (105) to a computer (107) connected to the optical sensor system, where it is received and stored by the computer, the stored color information is entered by the computer (107) in a color space (2, 2') in the form a scatter plot (31), characterized in that a frequency density distribution (4) of the scatter plot (31) is determined by the computer (107), the frequency density distribution (4) is specified numerically by the computer (107), and a signal dependent on the numerical specification is output by the computer (107).

2. Method according to claim 1, wherein the color space (2) is a one- or two-dimensional color space in which information about a brightness is not taken into account.

3. Method according to claim 1 or 2, wherein a characteristic region (5, 5') in the color space (2, 2') is defined by the computer (107) on the basis of the frequency density distribution (4) and the characteristic region (5, 5') is specified numerically for the numerical specification of the frequency density distribution (4).

4. Method according to claim 3, wherein a length, an area or a volume of the characteristic region (5, 5'), a geometric shape of the characteristic region (5, 5') and / or a course of a boundary line (57) or a boundary surface which delimits the characteristic region (5, 5') is used by the computer (107) for the numerical specification of the characteristic region (5, 5').

5. Method according to one of the preceding claims, wherein a change in a material composition of the textile fiber structure (9) is inferred by the computer (107) from a change in the numerical specification of the frequency density distribution (4), and the signal output by the computer (107) is dependent on the change in the material composition.

6. Method according to claim 5, wherein the signal output by the computer (107) is used to trigger at least one of the following actions: outputting a graphic to an operator, outputting a warning to an operator, outputting a recommended action to an operator, shutting down at least one processing machine, changing a setting on at least one processing machine.

7. Method according to one of the preceding claims, wherein the computer (107) recognizes a foreign material (90) in the textile fiber structure (9) on the basis of the numerical specification of the frequency density distribution (4), and the signal output by the computer controls a separation of the recognized foreign material (90) from the textile fiber structure (9).

8. Method according to the claims 3 or 4 on the one hand, and 7 on the other hand, wherein an element of the scatter plot (31) is recognized by the computer (107) as belonging to a foreign material (90) if the element in question lies outside the characteristic region (5, 5').

9. Method according to one of the preceding claims, wherein the computer (107) corrects the color information, a threshold value and / or a tolerance range with a degree of dissolution which indicates the extent to which the textile fiber structure (9) is dissolved into individual fiber flocks.

10. Method according to claim 9, wherein at least one image of the textile fiber structure (9) is recorded by the optical sensor system (105) and the image area onto which fiber material is imaged is determined by the computer from the at least one image by image processing, the computer (107) determines a mass flow of the textile fiber structure (9) per time unit, and the computer (107) calculates the degree of dissolution as a scalar quantity by forming a quotient from the image area onto which the fiber material is imaged on the one hand and from the mass flow on the other hand.

11. Method according to claim 9 or 10, wherein the computer (107) determines the degree of dissolution according to the formula X = A F / A T ⋅ m , wherein AF is the image area onto which fiber material is imaged, AT is a total area of the image and m is a mass flow of the textile fiber structure (9) per unit time.

12. Device (100) for the optical characterization of a textile fiber structure (9), with an optical sensor system (105) for detecting a plurality of pieces of information on color at different locations of the textile fiber structure (9), and a computer (107) connected to the optical sensor system (105), wherein the optical sensor system (105) comprises transmitting means for transmitting the detected color information to the computer (107), the computer (107) comprises receiving means for receiving the color information transmitted by the optical sensor system (105), and the computer (107) is adapted to enter the captured color information in a color space (2, 2') as a scatter plot (31), to determine a frequency density distribution (4) of the scatter plot (31), to specify the frequency density distribution (4) numerically and to output a signal dependent on the numerical specification.

13. Device (100) according to claim 12, wherein the computer (107) is adapted to define a characteristic region (5, 5') in the color space (2, 2') based on the frequency density distribution (4) and to numerically specify the characteristic region (5, 5') for the numerical specification of the frequency density distribution (4).

14. Device (100) according to claim 12 or 13, wherein the computer (107) is adapted to infer a change in a material composition of the textile fiber structure (9) from a change in the numerical specification of the frequency density distribution (4), and the signal output by the computer (107) is dependent on the change in the material composition.

15. Device (100) according to claim 14, wherein the computer (107) is adapted in such a way that the signal output by it is suitable for triggering at least one of the following actions: outputting a graphic to an operator, outputting a warning to an operator, outputting a recommendation for action to an operator, switching off at least one processing machine, changing a setting on at least one processing machine.

16. Device (100) according to claim 12 or 13, wherein the device (100) additionally comprises a separation unit (109) connected to the computer (107), and the computer (107) is adapted to recognize a foreign material (90) in the textile fiber structure (9) on the basis of the numerical specification of the frequency density distribution (4) and, when the foreign material (90) is recognized, to control a separation of the recognized foreign material (90) by the separation unit (109) by means of the signal output by it.

17. Device (100) according to claims 13 and 16, wherein the computer (107) is adapted to recognize an element of the scatter plot (31) as belonging to a foreign material (90) if the element in question lies outside the characteristic region (5, 5').