Research of textile fiber structures comprising two components

Abstract

A system consists of a textile fibrous structure (4) comprising two components (41, 42) and a device (1) for studying the textile fibrous structure (4). The device (1) comprises: a radiation source (2) for transmitting electromagnetic radiation (3) in the spectral band in the direction of the textile fibre structure (4); a radiation sensor (8) for receiving the electromagnetic radiation (7); and a spectral filter (6) having spectral properties in the spectral band for filtering the electromagnetic radiation (5). The transmittance of the spectral filter (6) in the spectral band has at least one local maximum and at least one local minimum. The spectral properties of the spectral filter (6) in the spectral band are adapted to the spectral properties of the radiation source (2) and of each of the two components (41, 24) in such a way that the radiation intensity received by the radiation sensor (8) is a monotonic function of the mixing ratio of the two components (41, 42). The device (1) is simple in construction and allows the use of a spatially resolved image sensor (8).

Description

Technical Field

[0001] The invention relates to the field of quality monitoring in the textile industry. The invention relates to a system consisting of a textile fiber structure comprising two components and a device for studying the textile fiber structure according to the first claim. The invention also relates to a device and a method for examining a textile fiber structure comprising two components according to the further independent claims. Preferred applications are the detection of foreign material in textile fiber structures such as fiber fleece, fiber webs, slivers, rovings, yarns, woven or knitted fabrics and the determination of the mixing ratio of the two components of such textile fiber structures. Background Art

[0002] Foreign materials in yarn are one of the main problems in today's spinning mills. These foreign materials are different from the base material of the yarn fibers (e.g. cotton fibers). Foreign materials can have various origins, such as transport packaging residues (plastic packaging, ropes), civilization impurities (soot fractions, plastic bags) or biological residues (human or animal hair, plant stalks). During spinning and weaving, foreign materials cause thread breakage, dye differently from the base material and affect the appearance of the final textile product. Foreign materials significantly reduce the value of the final product. In Paragraph 3.8 of NEWS BULLETIN NO. 47, “The origins of fabric defects—and ways to reduce them”, Uster Technologies AG, March 2010, provides an overview of fabric defects caused by foreign materials and suggestions for their reduction.

[0003] At various stages of the yarn manufacturing process, foreign material can be detected and, if necessary, rejected.

[0004] The blowroom process is part of the yarn manufacturing process and is located upstream of the carding process. The purpose of the blowroom process is to prepare the raw material so that it can be fed into the carding process in a state of as constant quality as possible and without impurities. The blowroom process includes opening the raw material, feeding the raw material into the processing operation, and mixing and rough cleaning the feed. Depending on the design of the process, the individual working steps can be run several times or even omitted. At this stage of the process, the material is in the form of fiber fluff (for example, in the case of cotton and wool) or fragments (in the case of synthetic fiber materials). The material is transported by air flows connecting the individual units in the blowroom process.

[0005] The spinning process is another part of the yarn manufacturing process and is located downstream of the carding process either indirectly or directly. In this process, yarn as the final product is spun from sliver (e.g., the intermediate product of the carding machine) or roving. In this process, the roving or sliver is transformed into its final form, i.e., yarn, by stretching and twisting. During spinning, the yarn is wound onto a spindle. Subsequently, the spindle is rewound onto a large bobbin. The material is delivered in the form of spindles and bobbins.

[0006] The purification of foreign materials can basically be divided into the following three steps:

[0007] 1) Detection of foreign materials;

[0008] 2) spatial / temporal localization of extraneous materials within and outside the test material; and

[0009] 3) Removal of foreign materials.

[0010] In the blowroom process, cleaning of foreign material can be done manually before the raw material is fed into the automatic changeover process, or it can be done automatically within the blowroom process by appropriate equipment. Today, automatic cleaning is common.

[0011] In the case of automatic cleaning, detection and localization are performed with the aid of a detection device which identifies differences in specific properties within the material flow. The following are mentioned here in a non-exhaustive manner: reflection and transmission of electromagnetic radiation or fluorescence. In the simplest application, optical detection devices are used to imitate the human eye and analyze the color impression of the material flow and thus detect corresponding color differences. US-6,452,157 B1 discloses a device for detecting impurities, foreign materials and foreign fibers in textile fiber materials. The device has at least two light sources, which alternately illuminate the fiber material with different colors. In addition, a sensor is provided which receives the color of the light reflected from the fiber material.

[0012] However, in order to detect foreign materials that are transparent to visible light or have a color similar to the raw material, more complex detection devices are required. In this case, the material flow can be analyzed with the help of electromagnetic radiation that is not perceptible to the human eye (ultraviolet or infrared). In this case, the material attribution is determined based on characteristic signatures (e.g., a sequence of specific absorption bands) in the reflection or transmission spectrum of the electromagnetic radiation. The more characteristics (e.g., absorption bands) used for identification within the signature, the more accurate the identification of the characteristic signature becomes. Currently, each characteristic within the signature requires a dedicated sensor in the detection device, which therefore responds only to the presence / absence of this one characteristic. The more characteristics to be used, the more complex the detection device becomes. The input signal must be divided accordingly according to the number of sensors, resulting in a loss of intensity. In addition, for some characteristics, there are currently no spatially resolved sensors, but only time-resolved sensors. This requires a device located upstream of the detection device, which links time and position. Alternatively, the incident electromagnetic radiation can be modulated in time to match the characteristics. However, for the invisible range of the electromagnetic spectrum, this sometimes requires great efforts.

[0013] EP-1'961'848A1 discloses a device for detecting and separating foreign materials from a material flow of raw cotton. The device comprises an irradiation device for irradiating the material flow and a sensor device for detecting irradiated foreign materials in the material flow. The irradiation device can emit visible light, ultraviolet light or infrared radiation. A rotatable polygonal mirror is provided for scanning the material flow line by line, by means of which the light beam of the irradiation device can be deflected in the direction of the material flow, and by means of which the light beam reflected by the material flow can be deflected toward the sensor device. The irradiation device and the sensor device are arranged coaxially one after another with respect to the optical radiation axis. The irradiation device mainly consists of a radiation source, a concave mirror and a rear reflector, the concave mirror being used to align and focus the radiation to the polygonal mirror along the radiation axis, and the rear reflector being used to guide the rear of the radiation in the direction of the concave mirror.

[0014] When materials are differentiated on the basis of color differences, as is common in spinning processes, the mentioned characteristics lie in the visible spectral range. Since the color impression is also due to a specific reflection / transmission of certain parts of the irradiated wavelength spectrum, in this case each characteristic must also be detected individually. For this purpose, a temporal color modulation of the input signal can be performed, or the output signal of the yarn modification must be decomposed into the individual characteristics, as already explained. In the former case, the spatial resolution is reduced, in the latter case the signal-to-noise ratio is reduced. The more colors are used, the greater the impact of these disadvantages. For this reason, processes that use only one or at most two colors have been established in practice. A yarn clearer that scans the yarn with light components of several different colors is known from WO-2011 / 026249A1.

[0015] Multivariate optical filters are a special class of optical transmission or reflection filters. The filter characteristics of a multivariate optical filter are adapted to a specific chemical signature. Different characteristics of the signature can be used simultaneously and independently in a single filter. Therefore, multivariate optical elements allow material identification based on chemical signatures. If the input signal of the filter matches the matching signature exactly, the signal passes through the multivariate optical filter unimpeded. If the input signal deviates from the signature, the input signal is attenuated when passing through the filter. The greater the deviation, the greater the attenuation. In addition to distinguishing materials, multivariate spectral filters also allow the determination of mixing ratios based on chemical signatures modified by mixing. The specific transmittance or reflectance of the multivariate optical filter is obtained from the chemical signature of the material to be distinguished using the partial least squares method. Examples of multivariate optical filters can be found in RJ Priore and N. Jackson, “Spectralimaging of chemical compounds using multivariate optically enhanced filters integrated with InGaAs VGA cameras”, Proc. of SPIE Vol. 9824, S. 98240P-1 bis 98240P-10, 2016.

[0016] US-2017 / 0241839A1 proposes to use several integrated computing elements combined with each other to improve the detection sensitivity of an optical computing device. The optical computing device disclosed therein comprises two or more integrated computing elements formed as a multivariate optical filter. The integrated computing elements are identical to each other and optically interact with incident electromagnetic radiation one after another. In addition, the optical computing device comprises a detector that receives those photons that optically interact with each integrated computing element. Summary of the invention

[0017] The object of the present invention is to create a system and a device for studying a textile fiber structure comprising two components, which avoids the above-mentioned disadvantages. In particular, the system and the device have a simple construction. The system and the device should enable high spatial resolution and the use of imaging, spatially resolved radiation sensors. At the same time, the signal-to-noise ratio should be high. Another object is to provide a corresponding method for studying a textile fiber structure comprising two components.

[0018] Another object is to provide a system, device and method for detecting foreign material in a textile base material, which avoids the above mentioned disadvantages.A further object is to provide a system, device and method for determining the mixing ratio of two components of a textile fiber structure, which avoids the above mentioned disadvantages.

[0019] These and other objects are solved by the system according to the invention, the device according to the invention and the method according to the invention as defined in the independent claims. Advantageous embodiments are indicated in the dependent claims.

[0020] The invention is based on the idea of ​​designing a spectral filter specifically for two components of the textile fiber structure, so that the radiation intensity received by the radiation sensor is a monotonic function of the mixing ratio of the two components, and preferably a linear function. In addition, the transmittance or reflectance in the considered spectral band has at least one local maximum and at least one local minimum, so that a plurality of characteristic wavelengths are considered. In addition, the invention includes that the spectral filter can also be designed for ratios of different characteristics (e.g. color impressions), and thus also enables color differences of materials of the same type to be detected without signal loss.

[0021] The textile fiber structure may comprise two or more components, wherein the invention relates in each case to two specific components. The two components differ from one another in their chemical or optical properties.

[0022] According to the present invention, the design of the spectral filter is based on the specific chemical and / or color characteristic markings of the two components. The characteristics of one component can be amplified by high transmission and produce a high output signal, while the characteristics of the other component can be attenuated by low transmission and produce a low output signal. The combination of amplification and attenuation in the spectral filter makes it possible to distinguish the two components based on the signals emitted from the spectral filter, and therefore study the textile fiber structure with respect to the two components.

[0023] If the textile fiber structure is studied as a unit without taking into account local inhomogeneities, the invention thus provides the proportional contribution of the two components, which can be interpreted as the mixing ratio. The invention thus allows the mixing ratio of the two components of the textile fiber structure to be determined.

[0024] On the other hand, if a spatially resolved image sensor is used, local differences between the two components are clearly visible in the image generated by the image sensor. If the proportion of a first component in the textile fiber structure is dominant, while the other, second component only occurs occasionally and is undesirable, the first component is referred to as base material and the second component as foreign material. According to the invention, a spectral filter is designed in such a way that it amplifies the properties of one component (e.g. foreign material) and attenuates the properties of the other component (e.g. base material). As a result, foreign material and base material are imaged with different intensities, which enables a good distinction between the components and thus detection of foreign material in the base material.

[0025] The system according to the present invention consists of a textile fiber structure comprising two components and a device for inspecting the textile fiber structure. The device includes a radiation source for emitting electromagnetic radiation in a spectral band in the direction of the textile fiber structure to interact with the textile fiber structure. In addition, the device includes a radiation sensor, and the high radiation sensor is used to receive at least a portion of the electromagnetic radiation after interacting with the textile fiber structure. The device also includes a spectral filter, which has spectral properties in the spectral band and is used to filter at least a portion of the electromagnetic radiation before or after interacting with the textile fiber structure. The transmittance or reflectance of the spectral filter in the spectral band has at least one local maximum and at least one local minimum. The spectral properties of the spectral filter in the spectral band are adapted to the spectral properties of the radiation source and each of the two components, so that the radiation intensity received by the radiation sensor is a monotonic function of the mixing ratio of the two components.

[0026] The two components of the textile fiber structure are two different elements from the following set: cotton, linen, virgin wool, polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyester (PES); polyacrylic acid (PAN); viscose fiber (CV, regenerated cellulose), modal fiber (CMD), lyocell fiber (CLY), polyethylene terephthalate (PET), polystyrene (PS), polyamide (PA), acrylonitrile-butadiene-styrene copolymer (ABS), polymethyl methacrylate (PMMA), polyoxymethylene (POM), elastane (EL), aramid (AR), acetate (CA), cupro fiber (CUP). Preferably, the two components of the textile fiber structure are a pair from the following group: cotton and polyethylene (PE), cotton and polypropylene (PP), cotton and polyvinyl chloride (PVC), cotton and polyester (PES); cotton and polyacrylic acid (PAN); cotton and viscose fiber (CV, regenerated cellulose), cotton and polyethylene terephthalate (PET), cotton and polystyrene (PS), cotton and polyamide (PA), cotton and acrylonitrile-butadiene-styrene copolymer (ABS), cotton and polymethyl methacrylate (PMMA), cotton and polyoxymethylene (POM).

[0027] The device according to the invention is used to inspect a textile fiber structure comprising two components. The device comprises a radiation source for transmitting electromagnetic radiation in a spectral band in the direction of the textile fiber structure for interacting with the textile fiber structure. In addition, the device comprises a radiation sensor for receiving at least a portion of the electromagnetic radiation after interacting with the textile fiber structure. The device also comprises a spectral filter having spectral characteristics in the spectral band for filtering at least a portion of the electromagnetic radiation before or after interacting with the textile fiber structure. The two components of the textile fiber structure are two different elements from the following set: cotton, linen, virgin wool, polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyester (PES); polyacrylic acid (PAN); viscose fiber (CV, regenerated cellulose), modal fiber (CMD), lyocell fiber (CLY), polyethylene terephthalate (PET), polystyrene (PS), polyamide (PA), acrylonitrile-butadiene-styrene copolymer (ABS), polymethyl methacrylate (PMMA), polyoxymethylene (POM), elastane (EL), aramid (AR), acetate (CA), cupro (CUP). The transmittance or reflectance of the spectral filter in the spectral band has at least one local maximum and at least one local minimum. The spectral properties of the spectral filter in the spectral band match the spectral properties of the radiation source and each of the two components, so that the radiation intensity received by the radiation sensor is a monotonic function of the mixing ratio of the two components.

[0028] In one embodiment of the device, the two components of the textile fiber structure are a pair from the following group: cotton and polyethylene (PE), cotton and polypropylene (PP), cotton and polyvinyl chloride (PVC), cotton and polyester (PES); cotton and polyacrylic acid (PAN); cotton and viscose fiber (CV, regenerated cellulose), cotton and polyethylene terephthalate (PET), cotton and polystyrene (PS), cotton and polyamide (PA), cotton and acrylonitrile-butadiene-styrene copolymer (ABS), cotton and polymethyl methacrylate (PMMA), cotton and polyoxymethylene (POM).

[0029] In one embodiment of the system or device, at least one local maximum is located at one or more wavelengths of electromagnetic radiation at which the absolute value of the difference in absorptivity, transmittance or reflectivity of two components has a local maximum.

[0030] In one embodiment of the system or device, the transmittance or reflectance of the spectral filter in the spectral band each has at least two local maxima and local minima.

[0031] The spectral filter in the system or device can be designed as a reflection filter or a transmission filter.

[0032] In one embodiment of the system or device, the spectral filter is designed as an interference filter.

[0033] In one embodiment of the system or device, the spectral filter is integrated into the radiation sensor.

[0034] In one embodiment of the system or device, the spectral characteristics of the spectral filter in the spectral band match the spectral characteristics of the radiation source and each of the two components so that the radiation intensity received by the radiation sensor is a linear function of the mixing ratio of the two components.

[0035] One embodiment of the system or device comprises an optical imaging system for imaging textile fibers onto a radiation sensor, wherein the radiation sensor has spatial resolution capabilities and is designed as a digital camera with a two-dimensional image converter or is formed as a one-dimensional line sensor.

[0036] One embodiment of the system or device comprises a time-varying optical imaging system which images individual locations of the textile fiber structure one after another over time onto a radiation sensor, wherein the radiation sensor has a time-resolving capability (see EP-1'961'848A1).

[0037] The system and the device according to the invention can be used to detect foreign material in a base material, wherein the foreign material and the base material are two components of the fiber structure of a textile.

[0038] The system or device according to the invention can be used to determine the mixing ratio of two components of a textile fiber structure.

[0039] The method according to the invention is used to study a textile fiber structure comprising two components. Electromagnetic radiation in a spectral band is transmitted from a radiation source in the direction of the textile fiber structure. At least a portion of the electromagnetic radiation interacts with the textile fiber structure. At least a portion of the electromagnetic radiation is received by a radiation sensor after interacting with the textile fiber structure. At least a portion of the electromagnetic radiation is filtered by a spectral filter before or after interacting with the textile fiber structure, the spectral filter having spectral properties in the spectral band. The spectral filter is selected so that its transmittance or reflectance in the spectral band has at least one local maximum and at least one local minimum, and its spectral properties in the spectral band are adapted to the spectral properties of each of the two components in the radiation source and the textile fiber structure, so that the radiation intensity received by the radiation sensor is a monotonic function of the mixing ratio of the two components.

[0040] In one embodiment of the method, the two components of the textile fiber structure are two different elements from the following group: cotton, linen, virgin wool, polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyester (PES); polyacrylic acid (PAN); viscose fiber (CV, regenerated cellulose), modal fiber (CMD), lyocell fiber (CLY), polyethylene terephthalate (PET), polystyrene (PS), polyamide (PA), acrylonitrile-butadiene-styrene copolymer (ABS), polymethyl methacrylate (PMMA), polyoxymethylene (POM), elastic fiber (EL), aramid (AR), acetate (CA), cupro fiber (CUP). Preferably, the two components of the textile fiber structure are a pair from the following group: cotton and polyethylene (PE), cotton and polypropylene (PP), cotton and polyvinyl chloride (PVC), cotton and polyester (PES); cotton and polyacrylic acid (PAN); cotton and viscose fiber (CV, regenerated cellulose), cotton and polyethylene terephthalate (PET), cotton and polystyrene (PS), cotton and polyamide (PA), cotton and acrylonitrile-butadiene-styrene copolymer (ABS), cotton and polymethyl methacrylate (PMMA), cotton and polyoxymethylene (POM).

[0041] The method according to the invention can be used to detect foreign material in a base material, wherein the foreign material and the base material are two components of the fiber structure of the textile.

[0042] The method according to the invention can be used to determine the mixing ratio of two components of a textile fiber structure.

[0043] In the system, apparatus or method, the spectral band may be, for example, in the wavelength range between 300 nm and 2200 nm. However, if the multivariate filter has an appropriate manufacturing process, the spectral band may be selected arbitrarily. The wavelength range between 700 nm and 1900 nm has proven to be advantageous for studying material pairings with base material cotton and exotic materials such as polyester, polyacrylic acid, polypropylene and polyethylene.

[0044] In the system, device or method, the spectral band may have a width, for example, between 100 nm and 1500 nm and preferably between 300 nm and 500 nm.

[0045] The textile fiber structure 4 can be present, for example, in the form of a fiber fleece, a fiber web, a sliver, a roving, a yarn, a woven fabric or a knitted fabric.

[0046] The device according to the invention can be used, for example, online in a textile production plant (e.g. as a fiber cleaner or as a yarn clearer) or offline in a textile laboratory (e.g. as a fiber testing device or as a yarn testing device). The same applies to the method according to the invention.

[0047] The radiation source may comprise a single radiation element, such as a halogen lamp. Alternatively, the radiation source may comprise several radiation elements, such as a halogen lamp and a mercury vapor lamp.

[0048] According to the present invention, the spectral filter can be used for transmission or reflection. A single or several spectral filters can be used in combination with each other (see US-2017 / 0241839A1).

[0049] The expressions "local maximum", "local minimum" and "monotonic function" used in this specification are used in the sense of their corresponding mathematical meanings. They are known to those skilled in the art and their definitions can be obtained from textbooks or mathematical reference works.

[0050] The system according to the invention, the device according to the invention and the method according to the invention allow a simple and reliable determination of the mixing ratio of two components of a textile fiber structure. They avoid splitting the incident electromagnetic radiation reflected or transmitted by the textile fiber structure into several radiation sensors. The system and the device are simple in design and allow the use of imaging, spatially resolved radiation sensors. They do not require temporal modulation of the input signal and therefore achieve a high spatial resolution.

[0051] Surprisingly, it has also been shown that the same device according to the invention can be used for a variety of foreign materials. Provided that the appropriate spectral band is selected, many foreign materials such as polystyrene, polyethylene or polypropylene found in natural textile base materials such as cotton can be detected with the same device according to the invention. Thus, it is not necessary to design and build a dedicated spectral filter for each foreign material; a single radiation source, a single radiation sensor and a single spectral band are sufficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Below, embodiments of the present invention are described in detail with reference to the accompanying drawings. For a clearer explanation, an application is described in which the proportion of foreign material in the base material of a textile fiber structure is determined. However, this is not intended to limit the generality of the invention. Alternatively, the present invention may relate to a textile fiber structure having two desired components. The present invention may relate to the detection of foreign material in a base material or to the determination of the mixing ratio of two components of a textile fiber structure.

[0053] Figure 1 Embodiments of systems and devices according to the invention are schematically shown.

[0054] 2 shows various spectra in a common first spectral band, namely: (a) relative intensity distribution of a halogen lamp; (b) absorptivity of cotton; (c) absorptivity of polyethylene; and (d) transmittance of a spectral filter.

[0055] Figure 3 The relative intensity distribution of the halogen lamp in the second spectral band is shown.

[0056] Figures 4 to 10 The absorption coefficients of the materials cotton, polyethylene, polypropylene, polyester, polyethylene terephthalate, polyacrylic acid and cellulose in the second spectral band are shown.

[0057] Fig.11 The transmittance of the spectral filter in the second spectral band is shown.

[0058] FIG. 12 shows (a) a grayscale image of textile samples with different materials and (b) a binary image of the samples after performing the method and image processing according to the present invention. DETAILED DESCRIPTION

[0059] Figure 1 Schematically an embodiment of a system according to the invention and an apparatus 1 according to the invention is shown in FIG. The apparatus 1 comprises a broadband radiation source 2 for generating electromagnetic radiation 3 in a spectral band. The generated electromagnetic radiation 3 has a spectral intensity distribution 30 in the spectral band, which is characteristic of the radiation source 2. Figure 1 In , an intensity distribution 30 is shown as a schematic diagram, in which the intensity is plotted as a function of wavelength.

[0060] At least a portion of the electromagnetic radiation 3 generated by the radiation source 2 is projected onto the textile fiber structure 4 to be inspected. The textile fiber structure 4 can be, for example, one or more fiber fleeces, fiber webs, slivers, rovings, yarns, woven fabrics, knitted fabrics or nonwoven fabrics. Figure 1 In the example of FIG, without limiting the generality, a fiber pile is schematically depicted as the textile fiber structure 4 .

[0061] The textile fiber structure 4 comprises at least two different components 41, 42. Without limiting generality, for illustrative purposes it is assumed herein that the textile fiber structure 4 consists of a base material 41 (e.g. cotton) and may contain one or more foreign materials 42 that are different from the base material 41. For example, the foreign material 42 may be polyethylene. When electromagnetic radiation 3 is projected onto the textile fiber structure 4, the electromagnetic radiation 3 interacts with the base material 41 and with the foreign material 42 (if present). Due to the interaction, the spectral intensity distribution 30 of the electromagnetic radiation 3 changes depending on the chemical or color properties of the materials. Therefore, the radiation 5 reflected or transmitted at the textile fiber structure 4 has a spectral intensity distribution 50 that is different from the intensity distribution 30 of the radiation 3 projected onto the textile fiber structure 4. The intensity distribution 50 of the reflected or transmitted radiation is again different in intensity from the base material 41. Figure 1 is shown as a schematic diagram where the intensity is plotted as a function of wavelength.

[0062] exist Figure 1 In an exemplary embodiment of the invention, after interacting with the textile fiber structure 4, the electromagnetic radiation 5 interacts with a spectral filter 6. The interaction can occur by transmission or reflection at the spectral filter 6. The spectral properties of the spectral filter 6 are specifically matched to the type or class of the base material 41, the foreign material 42 and the corresponding spectral bands. For example, the spectral filter 6 can be designed as an interference filter. The spectral filter changes the intensity distribution 50 of the electromagnetic radiation 5 interacting with it in such a way that the difference between the base material 41 and the foreign material 42 is amplified.

[0063] For example, if the spectral intensity distribution 50 before the spectral filter 6 corresponds to the spectral intensity distribution of the base material 41, the intensity of the radiation 7 after the spectral filter 6 should, for example, be a minimum value. On the other hand, if the spectral intensity distribution 50 upstream of the spectral filter 6 corresponds to the spectral intensity distribution of the foreign material 42, the intensity of the radiation 7 downstream of the spectral filter 6 should, for example, be a maximum value. If the spectral intensity distribution 50 before the spectral filter 6 has characteristics of both materials 41 and 42, the intensity of the radiation 7 after the spectral filter 6 should correspond to a monotonic function of the mixing ratio of materials 41 and 42, and preferably a linear function. This is in Figure 1 This is schematically shown in FIG. 7 by a diagram 70 which shows the intensity of the radiation 7 after the interaction with the spectral filter 6 as a linear function of the proportion of foreign material 42 in the textile fiber structure 4 .

[0064] Thus, the spectral filter 6 converts the incident wavelength-dependent intensity distribution 50 into an intensity distribution 70 which is a monotonic, and preferably a linear, function of the mixing ratio of the two components 41 and 42. The intensity of the electromagnetic radiation 7 present after the spectral filter 6 is therefore a measure of the mixing ratio. In the example discussed here, this intensity is a measure of the presence and amount of foreign material 42 in the textile fiber structure 4 and / or the degree of color change between the base material 41 and the foreign material 42.

[0065] After interaction with the spectral filter 6, the electromagnetic radiation 7 is detected by a broadband radiation sensor 8, which is in any case able to detect radiation 7 in the relevant spectral band. The radiation sensor 8 preferably has spatial and temporal resolution capabilities. For example, the radiation sensor can be designed as a digital camera or a digital line sensor.

[0066] If the radiation sensor 8 has no spatial resolution capability, then according to the diagram 70 the radiation intensity received by the radiation sensor is a measure for the mixing ratio of the two components 41 , 42 of the textile fiber structure 4 .

[0067] In a preferred embodiment, the radiation sensor 8 has spatial resolution capabilities, and the textile fiber structure 4 is imaged onto the radiation sensor 8 by means of an optical device (not drawn). This also provides information about the amount, position, size and shape of foreign material 42 present in the textile fiber structure 4. Thus, the foreign material 42 can be detected and located in the textile fiber structure 4. In the image of the textile fiber structure 4 taken by the radiation sensor 8, the foreign material 42 appears bright against the dark background in this example; see Figure 12 (b).

[0068] In an alternative embodiment, the spectral properties of the spectral filter 6 can be matched to the radiation source 2, the base material 41 and / or the foreign material 42 in such a way that the intensity of the radiation 7 after the spectral filter 6 is at a maximum when the textile fiber structure 4 consists only of the base material 41 and decreases with increasing proportions of the foreign material 42. In this case, the foreign material 42 appears dark relative to the light background.

[0069] In another embodiment, a spectral filter 6 may be inserted in the beam path between the radiation source 2 and the textile fiber structure 4. In this case, the electromagnetic radiation 3 generated by the light source 2 first interacts with the spectral filter 6 and then is projected onto the textile fiber structure 4. The effect is similar, and the image of the textile fiber structure 4 recorded by the radiation sensor 8 substantially corresponds to the image recorded according to the above-described embodiment.

[0070] The device 1 may contain optical elements known to those skilled in the art for influencing the radiation 3, 5, 7, such as lenses, mirrors, apertures, etc. For simplicity, Figure 1 Such elements are not shown.

[0071] In one embodiment, the device 1 comprises a time-varying optical imaging system, which images different parts of the textile fiber structure 4 in a time sequence onto the radiation sensor 8. This can be achieved mechanically or electronically. An example of such a time-varying optical imaging system is given in EP-1'961'848A1 and comprises a rotatable polygonal mirror for scanning the textile fiber structure 4 line by line. This embodiment requires a time-resolved radiation sensor 8 and a device for assigning reception times to corresponding positions on the textile fiber structure 4. For this purpose, the radiation sensor 8 does not need to have spatial resolution capabilities.

[0072] Figure 2(a) shows an example of the relative intensity λ of the electromagnetic radiation 3 generated by a halogen lamp 2 as a function of the wavelength of the radiation. In the first spectral band shown (950nm≤λ≤1400nm, near infrared and short-wave infrared), the relative intensity decreases monotonically with the wavelength of the radiation λ. In another spectral band or for other light sources 2, the intensity spectrum may have a different course.

[0073] Figure 2(b) and Figure 2(c) show the absorption spectra of cotton as a typical textile base material 41 and polyethylene as a foreign material 42, respectively. In the same spectral band as Figure 2(a), the corresponding absorbance is again plotted as a function of the radiation wavelength.

[0074] The spectral properties of the spectral filter 6 are determined by a multidimensional variation calculation based on the spectral intensity distribution 30 of the radiation source 2 and on the spectral properties (absorption, reflectivity and / or transmittance) of the base material 41 and the foreign material 42 to be detected. The regression vector resulting from the multidimensional variation calculation contains a weighting for each wavelength in the spectral band considered. The weighting corresponds to the transmittance or reflectivity of the spectral filter 6 for the wavelength in question. Thus, when irradiated by a specific radiation source 2, the spectral filter 6 is optimized for detecting a specific foreign material 42 in a specific base material 41 and for determining the mixing ratio of the two materials 41, 42. Such methods for designing spectral filters are known per se; they can be found in S. Wolda, M. An example can be found in the article “PLS-regression: a basic tool of chemometrics” by L. Eriksson, Chemometrics and Intelligent Laboratory Systems, Vol. 58, No. 2, October 28, 2001, pp. 109-130.

[0075] Figure 2(d) shows that Figure 2(a) to Figure 2(c) Exemplary transmittance of spectral filter 6 as a function of radiation wavelength in the same spectral band. In the example shown, spectral filter 6 has four local maxima (at wavelengths of about λ≈1000nm, 1110nm, 1213nm and 1317nm) and three local minima (at wavelengths of about λ≈1055nm, 1145nm and 1268nm) in the considered spectral band (950nm≤λ≤1400nm). Spectral filter 6 enhances the absorption differences of cotton (FIG. 2(b)) and polyethylene (FIG. 2(c)), which are particularly evident at wavelengths of about λ≈1100nm, 1210nm and 1320nm in the corresponding spectra.

[0076] The transmission or reflection of the spectral filter 6 is optimized for the two components 41, 42 of the textile fiber structure 4. Therefore, those parts of the electromagnetic radiation 5 incident on the spectral filter 6 which are caused by the interaction of the radiation 5 with the foreign material 42 can pass through the spectral filter 6 without attenuation. The components caused by the base material 41 are attenuated by the spectral filter 6. Therefore, the signal on the radiation sensor 8 is high for the foreign material 42 and low for the base material 41. If the radiation sensor 8 is designed as an image sensor, the foreign material 42 appears as a bright image area and the base material 41 appears as a dark image area on the image generated by the radiation sensor 8; see Figure 12 (b).

[0077] exist Figure 3 2 , the relative intensity of the electromagnetic radiation 3 generated by the halogen lamp 2 is plotted as a function of the radiation wavelength λ in a second spectral band (approximately 1000 nm≤λ≤2400 nm, near-wave and short-wave infrared) which is different from the first spectral band in FIG. 2 .

[0078] Figures 4 to 10 The absorption coefficients in the second spectral band are shown for the materials cotton, polyethylene, polypropylene, polyester, polyethylene terephthalate, polyacrylic acid and viscose (regenerated cellulose).

[0079] exist Fig.11 , an exemplary transmittance of the spectral filter 6 is plotted as a function of the wavelength λ of the radiation in the second spectral band. This exemplary spectral filter 6 has five local maxima (at wavelengths of approximately λ≈1210 nm, 1400 nm, 1500 nm, 1720 nm and 2260 nm) and four local minima (at wavelengths of approximately λ≈1290 nm, 1440 nm, 1570 nm and 2030 nm) in the considered second spectral band (approximately 1000 nm≤λ≤2400 nm). Fig.11 The spectral filter 6 is designed for cotton ( Figure 4 ) and polyethylene ( Figure 5 ), polypropylene ( Figure 6 )、Polyester( Figure 7 ), polyethylene terephthalate ( Figure 8 )、Polyacrylic acid( Fig. 9 ) or polystyrene. It is possible to use the same spectral filter 6 for two or more different materials 42, provided that the spectra of the materials 42 have similar characteristics in the spectral band under consideration. This is the case with the foreign material 42 mentioned above: Figures 5 to 9 As shown, the base material 41 cotton ( Figure 4), the absorption spectra of all these foreign materials 42 have obvious local maxima near the wavelengths λ≈1700nm and λ≈2300nm. Fig.11 The spectrum of filter 6 exhibits a clear local maximum around λ≈1700 nm and a further local maximum around λ≈2300 nm.

[0080] FIG. 12( a ) shows a grayscale image of a textile sample on which various materials are placed, the image being recorded with infrared radiation in the 1100 nm and 1700 nm spectral bands. The base material 41 of the sample is a knitted cotton fabric. On this base material are placed thin film sheets made of the following foreign materials: polystyrene 421 , polyethylene 422 and polypropylene 423 . The thin film sheets 421 , 422 and 423 are transparent in the relevant spectral bands and are therefore barely visible in the grayscale image of FIG. 12( a ). In fact, they are even more difficult to identify in photographic images in the visible or NIR spectral ranges. Compared to FIG. 12( a ), in the example of the application of the fiber removal device in the cotton cleaning process, the base material 41 is not a uniform, flat knitted fabric, but a three-dimensional fiber pile with various shades, and the foreign material 42 is not a large-area flat film, but fibrous fragments. The present invention remedies this.

[0081] FIG. 12( b ) shows an image of the textile sample of FIG. 12( a ), which is obtained by the apparatus 1 according to the present invention (see FIG. 12( b )). Figure 1 ) and subsequently digitally processed. The radiation source 2 used is a halogen lamp with Figure 3 The emission spectrum shown. The spectral filter used corresponds to Fig.11 spectral filter. Even in an unprocessed photographic image (not shown), the foreign materials 421, 422, 423 are clearly visible as bright areas against a dark background. In order to further emphasize the difference between the base material 41 and the foreign materials 421, 422, 423, a simple digital image processing is performed on the image by defining a brightness threshold below which pixels are set to "black" and above which pixels are set to "white". This produces the binary image in FIG12(b), in which the foreign materials 421, 422, 423 clearly stand out from the base material 41.

[0082] It is noteworthy that in the example of Figure 12, the same device 1 according to the invention can be used for three different foreign materials 421, 422, 423. In other words, it is not necessary to design and build a dedicated spectral filter 6 for each foreign material 42; as such, a single radiation source 2, a single radiation sensor 8 and a single spectral band are sufficient.

[0083] It will be appreciated that the invention is not limited to the embodiments discussed above. With the knowledge of the present invention, the skilled person will be able to derive further variants which also form part of the subject matter of the present invention.

[0084] Reference numerals list

[0085] 1. Device according to the present invention

[0086] 2 Radiation sources

[0087] 3Electromagnetic radiation generated by a radiation source

[0088] 30 Spectral intensity distribution

[0089] 4Textile fiber structure

[0090] 41 Basic materials for textile fiber structures

[0091] 42 Foreign materials in the fiber structure of textiles

[0092] 421 Polystyrene

[0093] 422 Polyethylene

[0094] 423 Polypropylene

[0095] 5 Radiation reflected or transmitted by the textile fiber structure

[0096] 50 Spectral intensity distribution

[0097] 6 Spectral filters

[0098] 7 Radiation after spectral filter

[0099] 70 Detected radiation intensity as a function of the proportion of foreign material

[0100] 8 Radiation Sensors

Claims

1. A system comprising a textile fiber structure (4) comprising two components (41, 42) and a device (1) for studying the textile fiber structure (4), wherein the device (1) comprises a radiation source (2) for transmitting electromagnetic radiation (3) in a spectral band in the direction of the textile fiber structure (4) for interacting with the textile fiber structure (4), a radiation sensor (8) for receiving at least a portion of the electromagnetic radiation (7) after interaction with the textile fiber structure (4), and a spectral filter (6) having spectral properties in said spectral band for filtering at least a portion of said electromagnetic radiation (5) before or after interaction with said textile fiber structure (4), Features The transmittance or reflectance of the spectral filter (6) in the spectral band has at least one local maximum and at least one local minimum, and The spectral properties of the spectral filter (6) in the spectral band are adapted to the spectral properties of the radiation source (2) and each of the two components (41, 24), so that the radiation intensity received by the radiation sensor (8) is a monotonic function of the mixing ratio of the two components (41, 42).

2. A system according to claim 1, wherein the two components (41, 42) of the textile fiber structure (4) are two mutually different elements from the following group: cotton, linen, virgin wool, polyethylene, polypropylene, polyvinyl chloride, polyester; polyacrylic; viscose, modal, lyocell, polyethylene terephthalate, polystyrene, polyamide, acrylonitrile-butadiene-styrene copolymer, polymethyl methacrylate, polyoxymethylene, elastane, aramid, acetate, cupro.

3. A system according to claim 2, wherein the two components (41, 42) of the textile fiber structure (4) are a pair from the following group: cotton and polyethylene, cotton and polypropylene, cotton and polyvinyl chloride, cotton and polyester; cotton and polyacrylic acid; cotton and viscose fiber, cotton and polyethylene terephthalate, cotton and polystyrene, cotton and polyamide, cotton and acrylonitrile-butadiene-styrene copolymer, cotton and polymethyl methacrylate, cotton and polyoxymethylene.

4. A device (1) for studying a textile fiber structure (4) comprising two components (41, 42), comprising a radiation source (2) for transmitting electromagnetic radiation (3) in a spectral band in the direction of the textile fiber structure (4) for interacting with the textile fiber structure (4), a radiation sensor (8) for receiving at least a portion of the electromagnetic radiation (7) after interaction with the textile fiber structure (4), and a spectral filter (6) having spectral characteristics in said spectral band for filtering at least a portion of said electromagnetic radiation (5) before or after interaction with said textile fiber structure (4), Features The two components (41, 42) of the textile fiber structure (4) are two mutually different elements from the following group: cotton, linen, virgin wool, polyethylene, polypropylene, polyvinyl chloride, polyester; polyacrylic acid; viscose, modal, lyocell, polyethylene terephthalate, polystyrene, polyamide, acrylonitrile-butadiene-styrene copolymer, polymethyl methacrylate, polyoxymethylene, elastane (EL), aramid, acetate, cupro, The transmittance or reflectance of the spectral filter (6) in the spectral band has at least one local maximum and at least one local minimum, and The spectral properties of the spectral filter (6) in the spectral band match the spectral properties of the radiation source (2) and each of the two components (41, 24), so that the radiation intensity received by the radiation sensor (8) is a monotonic function of the mixing ratio of the two components (41, 42).

5. A device (1) according to claim 4, wherein the two components (41, 42) of the textile fiber structure (4) are a pair from the following group: cotton and polyethylene, cotton and polypropylene, cotton and polyvinyl chloride, cotton and polyester; cotton and polyacrylic acid; cotton and viscose fiber, cotton and polyethylene terephthalate, cotton and polystyrene, cotton and polyamide, cotton and acrylonitrile-butadiene-styrene copolymer, cotton and polymethyl methacrylate, cotton and polyoxymethylene.

6. A system according to one of claims 1 to 3 or a device according to claim 4 or 5, wherein the at least one local maximum is located at one or more wavelengths of the electromagnetic radiation (3), at which the absolute value of the difference in the absorptivity, transmittance or reflectivity of the two components (41, 42) has a local maximum.

7. System or device (1) according to one of the preceding claims, wherein the transmittance or reflectance of the spectral filter (6) in the spectral band each has at least two local maxima and local minima.

8. System or device (1) according to one of the preceding claims, wherein the spectral filter (6) is designed as a reflection filter or a transmission filter.

9. System or device (1) according to one of the preceding claims, wherein the spectral filter (6) is designed as an interference filter.

10. The system or the device (1) according to one of the preceding claims, wherein the spectral filter (6) is integrated into the radiation sensor (8).

11. System or device (1) according to one of the preceding claims, wherein the spectral band is in the wavelength range between 300 nm and 2200 nm, and preferably in the wavelength range between 700 nm and 1900 nm.

12. System or device (1) according to one of the preceding claims, wherein the spectral band has a width between 100 nm and 1500 nm and preferably between 300 nm and 500 nm.

13. A system or device (1) according to one of the preceding claims, wherein the spectral properties of the spectral filter (6) in the spectral band match the spectral properties of the radiation source (2) and each of the two components (41, 24), so that the radiation intensity received by the radiation sensor (8) is a linear function of the mixing ratio of the two components (41, 42).

14. A system or device (1) according to one of the preceding claims, comprising an optical imaging system for imaging the textile fiber image (4) onto the radiation sensor (8), wherein the radiation sensor (8) has spatial resolution capability and is formed as a digital camera with a two-dimensional image converter or is formed as a one-dimensional line sensor.

15. A system or device (1) according to one of the preceding claims, comprising a time-varying optical imaging system, which images individual positions of the textile fiber structure (4) one after another onto the radiation sensor (8) over time, wherein the radiation sensor (8) has time resolution capability.

16. Use of a system or device (1) according to claim 14 or 15 for detecting foreign material (42) in a base material (41), wherein the foreign material (42) and the base material (41) are the two components of the textile fiber structure (4).

17. Use of the system or the device (1) according to one of claims 1 to 15 for determining the mixing ratio of the two components (41, 42) of the textile fiber structure (4).

18. A method (1) for studying a textile fiber structure (4) comprising two components (41, 42), wherein Electromagnetic radiation (3) in a spectral band is transmitted from a radiation source (2) in the direction of the textile fiber structure (4), at least a portion of the electromagnetic radiation (3) interacts with the textile fiber structure (4), At least a portion of the electromagnetic radiation (7) is received by a radiation sensor (8) after interacting with the textile fiber structure (4), and at least a portion of the electromagnetic radiation (5) is filtered by a spectral filter (6) before or after interaction with the textile fiber structure (4), the spectral filter having spectral properties in the spectral band, Features The spectral filter (6) is selected such that Its transmittance or reflectance in the spectral band has at least one local maximum and at least one local minimum, and Its spectral properties in the spectral band match the spectral properties of each of the two components (41, 42) in the radiation source (2) and the textile fiber structure (4), so that the radiation intensity received by the radiation sensor (8) is a monotonic function of the mixing ratio of the two components (41, 42).

19. The method according to claim 18, wherein the spectral band is in the wavelength range between 300 nm and 2200 nm, and preferably in the wavelength range between 700 nm and 1900 nm.

20. A method according to claim 18 or 19, wherein the spectral band has a width between 100 nm and 1500 nm and preferably between 200 nm and 500 nm.

21. A method according to one of claims 18 to 20, wherein the two components (41, 42) of the textile fiber structure (4) are two different elements from each other from the following group: cotton, linen, virgin wool, polyethylene, polypropylene, polyvinyl chloride, polyester; polyacrylic; viscose, modal, lyocell, polyethylene terephthalate, polystyrene, polyamide, acrylonitrile-butadiene-styrene copolymer, polymethyl methacrylate, polyoxymethylene, elastane, aramid, acetate, cupro.

22. A method according to claim 21, wherein the two components (41, 42) of the textile fiber structure (4) are a pair from the following group: cotton and polyethylene, cotton and polypropylene, cotton and polyvinyl chloride, cotton and polyester; cotton and polyacrylic acid; cotton and viscose fiber, cotton and polyethylene terephthalate, cotton and polystyrene, cotton and polyamide, cotton and acrylonitrile-butadiene-styrene copolymer, cotton and polymethyl methacrylate, cotton and polyoxymethylene.

23. Use of the method according to one of claims 18 to 21 for detecting foreign material (42) in a base material (41), wherein the foreign material (42) and the base material (41) are the two components of the textile fiber structure (4).

24. Use of the method according to one of claims 18 to 21 for determining the mixing ratio of the two components (41, 42) of the textile fiber structure (4).

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