Yarn quality detection device and method

Abstract

The invention relates to a yarn quality detection device and method. An optical sensor device for detecting defects in an elongated textile body is disclosed. The optical sensor comprises a measurement chamber (10) for an elongate textile body, a support body (14) having opposite first and second sides (24a, 24c) and a peripheral side extending transversely to the first and second sides (24a, 24c), at least one first light source and at least first and second light detectors. Both the first light source and the second light detector are arranged on a first side (24a) of the measurement chamber (10). A first light detector is arranged on a second side (24c) of the measurement chamber (10). The second side (24c) of the measuring chamber (10) is opposite the first side (24a) of the measuring chamber (10).

Description

Technical Field

[0001] The present invention relates to an optical sensor device for detecting defects in an elongated textile body, and the use of such a device. Background Art

[0002] Optical sensor devices are known for detecting defects in elongated textile bodies, for example, to detect thickness variations in yarns or yarn precursors, or to detect foreign fibers in such bodies. Optically detecting defects in elongated textile bodies is challenging, particularly with regard to accurately identifying the defects. For example, different defects can be difficult to distinguish.

[0003] US 5414520 and EP 1508797 describe optical sensor devices for detecting foreign matter. They propose using two light sources and three light detectors arranged around a textile body to detect foreign matter within it. At least one detector measures transmitted light to estimate yarn thickness, while at least one other detector detects light reflected from the yarn.

[0004] EP 3748343 A1 describes an optical sensor device for detecting foreign matter in yarn. Sensors of this type are used in quality control and monitoring to detect contaminants, such as foreign fibers or vegetable matter, in elongated bodies.

[0005] Since the reflected light depends both on the thickness of the yarn and on the presence of contaminants, a combined measurement of reflection and transmission can improve the reliability of the measurement. Summary of the Invention

[0006] It is an object of the present invention to provide an optical sensor device for detecting defects in an elongated textile body with increased reliability.

[0007] This object is achieved by the subject matter of the independent claims. Further advantageous embodiments are listed in the dependent claims and in the following description.

[0008] One aspect of the present invention relates to an optical sensor device for detecting defects in an elongated textile body. The device comprises:

[0009] - Support: The support may consist of a single body. Alternatively, the support may include several sub-bodies, particularly several interconnected sub-bodies. The support may include or consist of a polymer. The support may have a U-shape or a V-shape.

[0010] A measuring cavity for receiving an elongated textile body running in the X direction: the measuring cavity is open on opposite inlet and outlet sides in the X direction. Furthermore, the measuring cavity is delimited on first and second sides in the Y direction transverse to the X direction by a support body.

[0011] At least one measuring window arranged on the first side, wherein, in the X direction, the support body comprises a frame element adjacent to the measuring window.

[0012] An optical transmission sensor includes a transmission light source arranged to transmit light through a measurement cavity. The optical transmission sensor also includes a transmission light detector arranged to receive light emitted from the transmission light source and transmitted through the measurement cavity and the window. The transmitted light may first transmit the measurement cavity and then the window, or the transmitted light may first transmit the window and then the measurement cavity. The measurement cavity is arranged between the transmission light source and the transmission light detector.

[0013] An optical reflectance sensor includes a reflective light source arranged to transmit light into the measurement cavity. The optical reflectance sensor also includes a reflected light detector arranged to receive light emitted from the reflective light source and reflected within the measurement cavity. The reflected light source and the reflected light detector are both arranged on the second side. The reflected light source is positioned to illuminate at least one illuminated portion of the frame element. The reflected light detector is positioned to receive at least a portion of any light reflected from the illuminated portion.

[0014] The support helps to improve the stability of the optical sensor. Illuminating the illuminated portion, ie illuminating at least a portion of the frame element, helps to illuminate the window more evenly.

[0015] The X direction, the Y direction and the Z direction may be transverse to each other, in particular they may be perpendicular to each other. Two directions are transverse to each other, in particular perpendicular to each other, if they are non-parallel.

[0016] The measuring cavity may have a cuboid shape.

[0017] The distance between the first side and the second side in the Y direction may be between 0.1 cm and 2 cm, in particular between 0.2 cm and 1 cm. This allows the elongated textile body to be moved through the measurement cavity in the X direction, in particular in the X direction without rubbing against the first side and the second side, while keeping the measurement volume low enough for accurate measurement.

[0018] The transmission light source and the reflection light source may be the same light source or different light sources.In general, the transmission sensor and the reflection sensor may share one or more light sources and / or light detectors.

[0019] In one embodiment, at least 50% of the light emitted from the transmitted light source and entering the measurement window reaches the transmitted light detector.

[0020] The measurement window allows spatially limiting (or selecting) which light emitted from the transmission light source reaches the transmission light detector. This allows defining a transmission measurement region within the measurement cavity, through which the transmitted light reaching the transmission light detector passes, thereby potentially improving the signal-to-noise ratio by reducing the amount of light that does not interact with the elongated textile body. Furthermore, the transmission window can be positioned to transmit light only from a region of the measurement cavity that is uniformly illuminated by the transmission light source. In this context, uniform illumination is understood to mean illumination with an illumination variation of less than 10%, particularly less than 5%.

[0021] Transmission measurement allows accurate measurement of thickness defects in elongated textile bodies. In transmission measurement, the light emitted from the transmission light source and reaching the transmission light detector is measured, where the actual signal is the light that is "missing" due to the presence of the elongated textile body in the transmission light path.

[0022] The reflective light source may be arranged to send light into the measurement cavity to a region at least partially overlapping the transmission measurement region.

[0023] The transmitted and reflected light sources are advantageously arranged to both transmit light to the measurement window, in particular to the elongated textile body in front of the measurement window. (In this context, "in front of the measurement window" is understood to refer to a location on the chamber side of the measurement window.) This allows for both reflection and transmission measurements to be performed at the same location / point on the elongated textile body.

[0024] The elongated textile body may be a yarn.

[0025] The frame element adjacent to the measuring window in the X direction may extend from the measuring window to the edge of the support body.

[0026] The frame element may comprise or consist of a material that is different from the material of the remainder of the support body.

[0027] The transmitted light source and / or the reflected light source may be a light-emitting semiconductor device, in particular a light-emitting diode.

[0028] In one embodiment, the transmitted and / or reflected light sources have a lower spectral coherence than a diode laser. In particular, the transmitted and / or reflected light sources are spectrally incoherent, in particular by having a coherence length of less than 1 mm. This helps to reduce interference effects and thus improves measurement quality.

[0029] An optical reflectance sensor having at least two reflected light detectors is advantageous. The at least two reflected light detectors of the optical reflectance sensor can be arranged on the second side. The at least two reflected light detectors can be arranged to observe the measurement window at different angles. This allows for more uniform observation and, in particular, improves reflectance measurements.

[0030] Advantageously, the reflectivity of the frame element over the emission spectrum of the reflective light source is at most 80%, in particular at most 50%, more in particular at most 20%.If there are a plurality of reflective light sources, this condition advantageously applies to each of them.

[0031] Measuring the reflection from the elongated textile body can allow for obtaining relevant color and thickness information about the elongated textile body. Measuring the transmission of the elongated textile body can allow for obtaining (independent) thickness information about the elongated textile body. Combining the measured reflection and transmission of the elongated textile body can allow for obtaining color information that is less dependent on thickness than reflection alone. To this end, it is advantageous to measure the reflection and transmission over the same region / area of the elongated textile body.

[0032] If the reflected light source illuminates peripheral areas outside the measurement window, particularly frame elements, the reflectance measurement will be affected by the reflections from this peripheral area. Specifically, the measured reflectance is the sum of a core component originating from the area also monitored by the sensor and a peripheral component originating from the peripheral area. This peripheral component can depend on thickness variations in the textile fabric in the background area, making it more difficult to compensate for the measured reflectance using transmission measurements.

[0033] This is particularly true when combining a dark, low-reflectivity textile body with a conventional sensor device that has a highly reflective support. In this case, increased thickness in the peripheral region reduces the measured reflection without affecting the measured transmission, leading the system to mistakenly interpret the textile body as having "darker" areas.

[0034] Therefore, the measurement quality and / or reliability can be improved if frame elements are used which have a reflectivity, ie an average reflectivity, of at most 80%, particularly at most 50%, more particularly at most 20% over the emission spectrum of the reflection light source.

[0035] In certain embodiments, the frame element has an average reflectivity of at most 50% over the emission spectrum of the reflected light source.This allows for good treatment of dark textile bodies.

[0036] If the sensor device is to be used for dark and light textile bodies, for example for black and white yarns, the reflectivity of the frame element over the emission spectrum of the reflected light source, i.e. the average reflectivity, can be selected to be at least 20% in order to improve the performance of the system in the presence of thickness variations of the light textile body on the frame element.

[0037] Thus, in an apparatus that performs well on both dark and light colored textile bodies, the average reflectivity of the illuminated portion of the frame element over the emission spectrum of the reflected light source may be between 20% and 50%.

[0038] The reflectivity of the frame element can be reduced by using a dark frame element. The frame element may be black.

[0039] Advantageously, the average reflectivity of the frame element in the spectral range from 400 nm to 780 nm is at most 80%, in particular at most 50%, and more particularly at most 20%.

[0040] In this context, the average reflectivity in the spectral range from 400 nm to 780 nm is understood to be the average value of the reflectivity for each individual wavelength in the entire range from 400 nm to 780 nm.

[0041] This allows reducing the visible light (i.e. 400 nm to 780 nm) reflected by the frame element, thereby reducing variations in the reflected signal due to variations in the thickness of the textile body outside the measurement window but still illuminated by the reflected light source. This allows an improved assessment of the visible quality of the textile body, in particular an improved determination of the color of an elongated textile body.

[0042] This is based on the understanding that it is sufficient to have a low reflectivity over the spectrum of the reflective light source.If there are multiple reflective light sources with different emission spectra, it is advantageous to calculate the average reflectivity over the emission spectrum of each light source.

[0043] In this context, the average reflectance over the emission spectrum of a light source is the reflectance calculated as the average value of the relative intensity distribution of light in the emission spectrum weighted over that spectrum.

[0044] Advantageously, the frame element comprises a main body material and a surface layer. The surface layer has an average reflectivity of at most 80%, particularly at most 50%, and more particularly at most 20% over the emission spectrum of the reflected light source. In particular, the average reflectivity of the frame element over the aforementioned emission spectrum can be lower than the average reflectivity of the main body material.

[0045] Advantageously, the main material of the frame element is a material whose average reflectivity over the emission spectrum of the reflected light source is at least 80%, in particular at least 90%, which reduces light losses when light passes through the opening in the frame element.

[0046] The surface layer can be less than one millimeter thick. The surface layer can be a coating, particularly a black coating. In another embodiment, the surface layer can be formed by a surface treatment that alters the optical properties of the main material. For example, laser irradiation can be used to oxidize the main material and produce a less reflective surface layer.

[0047] Advantageously, the transmitted light sensor is arranged on the first side.

[0048] This allows for a compact design. In particular, arranging both the reflected light source and the reflected light detector on the second side and the transmitted light sensor on the first side allows for both reflection and transmission measurements to be performed using the same light source, i.e. the reflected light source and the transmitted light source are formed by the same light source.

[0049] Advantageously, the width of the frame element in the X direction is at most 1.5 mm, in particular at most 0.5 mm. In this context, the width of the frame element is measured in the middle of the measuring field (ie where the elongated textile body is usually most likely to be present).

[0050] The width of the frame element in the X direction is at most 1.5 mm or even less, allowing to reduce the surface onto which the light from the reflection light source can be reflected, thereby reducing the peripheral component of the reflection.

[0051] Advantageously, at least one frame element has an inclined surface facing the measurement cavity and positioned to be illuminated by the reflective light source (in particular, at least one of the light sources). The inclined surface is not perpendicular to the Y direction. In particular, the inclined surface forms an angle of 2 to 88 degrees with respect to the Y direction, more particularly, an angle of 10 to 70 degrees with respect to the Y direction.

[0052] The inclined surface faces the measuring cavity (ie it is not on a lateral surface of the frame element or on a surface of the frame element facing away from the measuring cavity).

[0053] Such an inclined surface allows the amount of reflected light from the reflected light source that reaches the reflected light detector to be reduced, thereby improving the measurement quality.

[0054] Advantageously, the inclined surface is such that at least 50% of the light from the reflective light source is reflected from its specular surface.The inclined surface may for example be smooth and have an absorption of at most 30% in the range of 400 nm to 780 nm.

[0055] The inclined surface may be flat or curved. Advantageously, in the case of a curved inclined surface, at least a portion of the curved surface forms said angle with the Y direction.

[0056] Advantageously, the inclined surface forms at least 20%, in particular at least 50%, of the total surface of the frame element positioned to be illuminated by the reflected light source.

[0057] In one embodiment, the optical reflectance sensor comprises at least two, in particular at least three, reflectance light sources with different emission spectra, in particular with non-overlapping emission spectra.

[0058] The at least three reflective light sources may include or be composed of a blue reflective light source, a red reflective light source, and a green reflective light source. The blue reflective light source may have a full width at half maximum (FWHM) emission wavelength range of 440nm to 500nm. The green reflective light source may have a FWHM emission wavelength range of 510nm to 570nm. The red reflective light source may have a FWHM emission wavelength range of 600nm to 750nm.

[0059] In another embodiment, the optical reflectance sensor comprises at least one broadband reflectance light source having a FWHM emission spectrum extending over at least 200 nm.

[0060] Advantageously, the support body forms channel walls extending from the measurement window to between at least some of the light sources and the light detectors, wherein the average reflectivity of the walls over the emission spectrum of the reflected light sources is higher than the average reflectivity of the frame elements over the emission spectrum of the reflected light sources.

[0061] This relatively reflective wall allows the light detector to receive more light.

[0062] Advantageously, the support body forms a wall of a channel extending between the measurement window on the first side and the light detector on the first side, in particular the transmitted light detector on the first side.

[0063] Advantageously, the walls of the channel are white.The walls of the channel may be flat and smooth.

[0064] Advantageously, the reflectivity of these walls is at least twice that of the frame element.

[0065] The reflectivity of the wall may be at least 60%, in particular at least 75%, more in particular at least 90%.

[0066] Advantageously, the “reflectivity” in the above two paragraphs is the average reflectivity within the spectral range of at least one light source, in particular the average reflectivity within the spectral range of at least all light sources.

[0067] This can minimize the loss of light (light intensity) before it reaches the light detector (reflection or transmission light detector), thereby improving the measurement quality.

[0068] The present invention also relates to the use of an optical sensor device as described above for measuring an elongated textile body having an average reflectivity of at most 80% across the emission spectrum of a reflective light source, in particular an average reflectivity of at most 50%, and even more particularly at most 20%. In particular, for the reasons described above, the average reflectivity of the illuminated portion of the frame element across the emission spectrum of the reflective light source can be between 20% and 50%.

[0069] The elongated textile body may be black.

[0070] Advantageously, the elongated textile body has an average reflectivity of at most 80% over the emission spectrum of any one reflective light source of the optical reflective sensor, in particular an average reflectivity of at most 50%, more in particular at most 20%. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] The present invention will be better understood from the following detailed description, and its objects other than those mentioned above will become apparent. This description refers to the accompanying drawings. These drawings show:

[0072] Figure 1 A schematic diagram showing an optical sensor device cut along the middle,

[0073] Figure 2 Shown along Figure 1 A cross-sectional view along line II-II,

[0074] Figure 3 Another example of an optical sensor device cut along the middle is shown,

[0075] Figure 4 Another example of a sensor arrangement is shown,

[0076] Figure 5 It is along Figure 4 A cross-sectional view along line IV-IV,

[0077] Figure 6 Schematic diagram showing a defect of a slender body in front of the measurement window,

[0078] Figure 7 Schematic diagram showing a defect of an elongated body in front of a frame element,

[0079] Figure 8 An embodiment with collimating optics is shown,

[0080] Figure 9 An embodiment with a reflector is shown,

[0081] Figure 10 An embodiment is shown in which a window element covers a frame element.

[0082] Figure 11 An embodiment with a multi-segment frame element is shown,

[0083] Figure 12 A first embodiment of a frame element having an inclined surface is shown,

[0084] Figure 13 A second embodiment of a frame element with an inclined surface is shown,

[0085] Figure 14A third embodiment of a frame element with an inclined surface is shown,

[0086] Figure 15 A fourth embodiment of a frame element with an inclined surface is shown,

[0087] Figure 16 An embodiment further illustrating another design of the frame element is shown.

[0088] Figure 17 The arrangement of the reflected light source and the reflected light detector is described to prevent specular reflection from entering the reflected light detector. DETAILED DESCRIPTION

[0089] Example 1

[0090] Figure 1 and Figure 2 Shown is a schematic diagram of an optical sensor device for detecting defects in an elongated textile body, cut along its middle.

[0091] The device comprises a slit-shaped measuring cavity 10 formed by a slit in a support body 14. The measuring cavity 10 is designed to receive an elongated textile body 16 running in the X direction during measurement.

[0092] The support body 14 has a first outer side 18a and a second outer side 18b, which are advantageously parallel to each other (see Figure 2 ) and is transverse to the X direction. It also has peripheral sides 20a, 20b, 20c and 20d (see Figure 1 and Figure 2 ), which peripheral sides extend transversely (in particular perpendicularly) to the first and second outer sides 18a, 18b.

[0093] The measurement cavity 10 is open in the X direction at the first and second outer sides 18a, 18b, forming an entry side 22a and an exit side 22b through which the elongated textile body 16 can enter and exit during measurement.

[0094] On sides perpendicular to the first and second outer sides 18a, 18b, the measuring cavity 10 is closed by the support 14 on a first side 24a, a second side 24c and a third side 24b and is open at a fourth side 24d for insertion of the elongated textile body 16 before operation.

[0095] In other words, in the Y direction, which is transverse to the X direction, in particular perpendicular to it, the measuring cavity 10 is limited on the first and second sides 24a, 24c by the support body 14. Furthermore, in the Z direction, which is perpendicular to the X and Y directions, the measuring cavity 10 is closed on the third side 24b and open on the fourth side 24d.

[0096] Radial light channels 26 a - 26 f extend through the support body 14 between the measuring cavity 10 and the first and second peripheral sides 20 a , 20 b .

[0097] Advantageously, the first peripheral side 20a and the second peripheral side 20b are positioned opposite each other, in particular they are parallel to each other.

[0098] The sensor device further comprises a plurality of light sources 30a, 30b, 30c and a plurality of light detectors 32a, 32b, 32c. In this embodiment, there are three light sources and three light detectors. As mentioned above, this number can be greater.

[0099] Light sources 30 a , 30 b , 30 c and light detectors 32 a , 32 b , 32 c are arranged alternately at the light channels 26 a - 26 f , ie at the first and second peripheral sides 20 a , 20 b of the support body 14 .

[0100] The light sources 30a, 30b, 30c and the light detectors 32a, 32b, 32c are mounted on first and second carrier plates 34a, 34b.

[0101] A first carrier plate 34a is mounted to the first peripheral side 20a of the support body 14. It carries the light sources 30a, 30b and the light detector 32a arranged on this side. A second carrier plate 34b is mounted to the second peripheral side 20b of the support body 14. It carries the light source 30c and the light detectors 32b and 32c arranged on this side.

[0102] The carrier boards 34a, 34b are advantageously printed circuit boards and are arranged parallel to each other and can be mechanically connected to the support 14 in a defined spatial relationship so that the light sources and light detectors are located at desired positions in the light channels 26a-26f.

[0103] It can be seen that a first light source 30a, a second light source 30b and a first light detector 32a are arranged on the first side 20a, and a third light source 30c and a second light detector 32b and a third light detector 32c are arranged on the second side.

[0104] The first light source 30a is opposite to the third light detector 32c, the second light source 30b is opposite to the second light detector 32b, and the third light source 30c is opposite to the first light detector 32a. In this context, "opposite" means on both sides of the nominal position of the elongated body 16 in the measurement cavity 10 (i.e., the center of the measurement cavity 10).

[0105] More generally, each light detector may be arranged opposite a light source, and vice versa.

[0106] As described above, at least one light detector 32a is arranged between at least two light sources 30a, 30b on the first side of the measurement cavity 10, and at least one light source 30c is arranged between at least two light detectors 32b, 32c on the second side of the measurement cavity 10.

[0107] For reflection measurement, the third light source 30c can be used as a reflection light source, and the second and / or third light detectors 32b, 32c can be used as reflection light detectors. That is, the sensor device has a light reflection sensor including the third light source 30c and the second and / or third light detectors 32b, 32c. Alternatively or additionally, the first and second light sources 30a, 30b can be used as reflection light sources, and the first light detector 32a can be used as a reflection light detector. That is, the sensor device has a light reflection sensor including the first and second light sources 30a, 30b and the first light detector 32a.

[0108] For transmission measurement, the third light source 30c can be used as a transmission light source, and the first light detector 32a can be used as a transmission light detector. In other words, the sensor device has a light transmission sensor including the third light source 30c and the first light detector 32a.

[0109] Typically, the photodetectors 32a-32c have an effective (i.e., photosensitive) area that is larger than the effective (i.e., luminous) area of the light sources 30a-30c. Advantageously, the light sources and photodetectors have the same effective area. To at least partially compensate for this area inequality, the support body 14 is designed such that the first peripheral side 20a (and the light sources and photodetectors disposed therein) is closer to the measurement cavity 10 than the second peripheral side 20b (and the light sources and photodetectors disposed therein).

[0110] The illustrated embodiment has a first light channel 26a extending between the first light source 30a and the measuring cavity 10, a second light channel 26b extending between the first light detector 32a and the measuring cavity 10, a third light channel 26c extending between the second light source 30b and the measuring cavity 10, a fourth light channel 26d extending between the second light detector 32b and the measuring cavity 10, a fifth light channel 26e extending between the third light source 30c and the measuring cavity 10, and a sixth light channel 26f extending between the third light detector 32c and the measuring cavity 10.

[0111] Thus, first, second and third light channels 26a-26c extend between the measurement cavity 10 and the first peripheral side 20a through the support body 14. Fourth, fifth and sixth light channels 26d-26f extend between the measurement cavity 10 and the second peripheral side 20b through the support body 14.

[0112] The second light channel 26b is arranged between the first light channel 26a and the third light channel 26c. Similarly, the fourth light channel 26e is arranged between the fourth light channel 26d and the sixth light channel 26f.

[0113] On the first side 24 a , the interface of the second light channel 26 b with the measurement cavity forms a measurement window 80 .

[0114] The second optical channel 26b and the fifth optical channel 26e are coaxial so that the light source 30c is arranged exactly opposite the light detector 32a in order to provide an accurate transmission measurement of the measurement cavity 10. This allows a signal that is dependent on the thickness of the elongated body 16 to be generated.

[0115] The support body 14 includes a first sub-body 14a arranged between two second sub-bodies 14b along the X direction. The sub-bodies 14a, 14b form light channels 26a-26f therebetween. The second sub-body 14b forms outer sides 18a, 18b.

[0116] The first sub-volumes 14a are preferably non-transparent materials (ie, materials that are not transparent in the spectral region overlapping between the emission of the light source and the sensitivity of the light detector), and they separate the optical channels from each other to suppress optical crosstalk between them.

[0117] More generally speaking, the light channels 26 a - 26 f advantageously communicate (optically) through the measurement cavity, ie a significant portion of the light passing from one to the other (ie at least 10%, in particular at least 25%) has passed through the measurement cavity 10 .

[0118] Advantageously, as mentioned above, the sub-bodies 14a, 14b are made of a material that strongly reflects the light from the light source.

[0119] The device further comprises a window element 15 of a transparent material (i.e., a material that is transparent in the spectral region of overlap between the emission of the light source and the sensitivity of the light detector, in particular in the range of 400 nm to 780 nm). This forms transparent windows 38 a - 38 f between the light channels 26 a - 26 f and the measurement chamber 10. These windows prevent the ingress of dirt into the light channels 26 a - 26 f. Advantageously, the windows 38 a - 38 f are transparent, i.e., they pass at least 50% of the light in the spectral overlap between the light source and the light detector.

[0120] The windows 38b and 38e form a first diffuser 40a and a second diffuser 40b at the interface between the second light channel 26b and the measurement chamber 10 and at the interface between the fourth light channel 26e and the measurement chamber 10. They improve the accuracy of the measurement.

[0121] The diffusers 40 a , 40 b can be formed, for example, by small structures (having dimensions between 10 and 500 μm) arranged on the surface of the windows 38 b , 38 e , in particular on the side of these windows facing away from the measuring chamber 10 .

[0122] Advantageously, the sub-bodies 14a, 14b and the window element 15 are manufactured by two-component casting or two-component molding. They can also be formed, for example, by separate elements that are bonded together.

[0123] The light channels 26a-26f are advantageously hollow, ie filled with a gas, in particular air. In order to increase their light-conducting properties, their inner walls (ie inner surfaces) are advantageously smooth and reflective.

[0124] Alternatively, the light channels 26a - 26f may be filled with a transparent solid.

[0125] like Figure 2 As shown, the light sources 30a-30c, the light detectors 32a-32c and the measuring cavity 10 are arranged in a common plane 42 (i.e., they are intersected by this common plane). Advantageously, this common plane 42 extends parallel to the first outer side 18a and the second outer side 18b of the support body 14 and / or extends perpendicularly to the X direction, i.e., perpendicularly to the extension direction 44 of the elongated textile body 16.

[0126] In said common plane 42, light sources 30a-30c and light detectors 32a-32c are arranged at different angular positions defined by the lines connecting the nominal position of the elongated textile body 16 (ie the centre of the measurement cavity 10) and the respective light source or light detector.

[0127] Furthermore, the windows 38 a - 38 f are arranged at different angular positions 46 a - 46 f around the center of the measuring cavity 10 .

[0128] Example 2

[0129] Figure 3 A schematic diagram of an optical sensor device cut along its middle is shown.

[0130] The device and Figure 1 and Figure 2 The device shown is similar, but in this embodiment it has one light source 30c and two light detectors 32a, 32b. Thus, the optical sensor device has only three radial light channels 26b, 26d, 26e.

[0131] The light source 30c functions as a reflected light source and a transmitted light source. The light detector 32b is a reflected light detector 32b, and the light detector 32a is a transmitted light detector 32a.

[0132] Therefore, in this embodiment, the transmission sensor includes the light source 30c as a transmission light source and the light detector 32a as a transmission light detector, while the reflection sensor includes the light source 30c as a reflection light source and the light detector 32b as a reflection light detector.

[0133] Example 3

[0134] Figure 4 and Figure 5 A specific embodiment of a sensor device is shown.

[0135] As can be seen, the measuring cavity 10 is formed by a slit of the support body 14 which widens towards the fourth peripheral side 20 d .

[0136] The window element 15 forms part of the inner wall of the measuring chamber 10. The opaque second sub-body 14b forms a first outer side 18a and a second outer side 18b of the support body 14. They close the light channels 26a-26f at these first and second outer sides 18a, 18b.

[0137] The two carrier boards 34 a , 34 b are mounted on opposite peripheral sides of the support body 14 and may be electrically connected, for example, via a flexible printed circuit 48 .

[0138] At least some of the light sources 30a-30c and / or at least some of the light detectors 32a-32b are located in recesses 50a-50f of the support body 14, each recess 50a-50f forming an end of one of the light channels 26a-26f.

[0139] Frame components

[0140] As mentioned above, one aspect of the sensor arrangement relates to the effects of optical reflections on the frame element 90 near the measurement window 80. This is an aspect that applies to all embodiments shown herein, as well as most other such optical sensor arrangements, and will be discussed in detail below.

[0141] Figure 6 Schematic diagram of the area around the measurement window 80 when looking from the second side 24c toward the first side 24a of the measurement cavity 10 is shown.

[0142] The measurement window 80 is defined as a geometric area at the first side 24a through which a portion of the light from the transmission light source passes and can reach the transmission light detector.

[0143] The second sub-body 14 b forms a frame element 90 which is laterally adjacent to the measuring window 80 in the X direction.

[0144] In the above embodiment, light from the light source 30c used as a transmitted light source enters the measuring cavity 10 through the window element 15, passes through the measuring cavity 10, leaves it through the measuring window 80, passes through the window element 15, and finally reaches the light detector 32a used as a transmitted light detector.

[0145] like Figure 1 、 Figure 2 and Figure 3 As shown, the light detector 32a is positioned opposite to the light source 30c. Figure 3 (Example 2) The light source 30c is a transmission light source and a reflection light source.

[0146] The width Wi of the illuminated area 70 illuminated by the light source 30c in the X direction is greater than the width Wm of the measurement window 80 in the same direction. The illuminated area 70 covers the measurement window 80, but in addition, it also covers or can cover other areas at the first side 24a:

[0147] It illuminates a portion 95 of the frame element 90 which is adjacent to the measuring window 80 in the X direction.

[0148] It illuminates a portion 75 of the support 14 adjacent to the measuring window 80 in the Z direction.

[0149] It illuminates a portion 77 of the measuring cavity outside the support 14 .

[0150] - It illuminates a portion of the elongated textile body 16 .

[0151] For reflectance measurement, a reflected light detector, such as the second light detector 32b and / or the third light detector 32c, collects light that is incident from the light source onto the illuminated area 70 and reflected onto the reflected light detector. The measured reflectance R is the sum of the core component Rc and the peripheral component Rp: R = Rc + Rp.

[0152] The core component Rc is generated by the light reflected from the measurement window 80, including the portion of the elongated textile body 16 in front of the measurement window 80. This area is also monitored by a transmission light detector which generates a transmission signal T.

[0153] The peripheral component Rp is generated by light reflected from a portion 95 of the frame element 90 , a portion 75 of the measurement cavity first side 24 a and a portion of the elongated textile body 16 within the illumination area 70 but outside the measurement window 80 .

[0154] A black elongated body 16 reflects less incident light than a white elongated body 16, and for a given "color depth," an elongated body 16 having a smaller radial extent reflects less light than an elongated body having a larger radial extent.

[0155] like Figure 6As shown, a change in the thickness of the body in front of the measurement window 80 will produce a strong change in transmittance ΔT and a strong change in reflectance ΔR. A change in the color of the body in front of the measurement window has only a slight effect on the transmittance, that is, ΔT≈0.

[0156] Therefore, the variation ΔT is a direct measure of body thickness and is not affected by the color of the elongated body 16 .

[0157] Both changes in body thickness and body color will produce a reflectivity change ΔR. Therefore, changes in body thickness and body color cannot be distinguished from changes in body color based on the change ΔR alone.

[0158] Therefore, in order to reliably detect the color change, the signal is combined with the transmission signal to generate a parameter that depends only on the color change ΔC, for example by calculating ΔC = k1 · ΔT + k2 · ΔR, and the constants k1 and k2 are selected to compensate for the pure thickness change within the measurement window, that is, not to affect ΔC. This is effective because Figure 6 In this case, thickness changes can be detected by both reflective and transmissive sensors.

[0159] Figure 7 A thickness variation 17 of the elongated textile body 60 is shown in front of a portion 95 of the frame element 90, illuminated by a reflected light source. The thickness variation 17 prevents the reflected light sensor from receiving light from the region of the frame element 90 covered by the thickness variation 17. This reduces the measured reflectivity, i.e., its peripheral component Rp, but does not affect the measured transmission T, thereby generating an erroneous color change signal ΔC, for example, when calculated as described above.

[0160] This false color change signal is a function of the difference in average reflectivity between the frame element 90 and the elongated textile body 60. This error is small for highly reflective (e.g., white) yarns and a conventional highly reflective support 14. However, when measuring darker, less reflective yarns, this false color change signal becomes significant.

[0161] This causes the optical detection device to interpret the elongate body 16 as having a darker colour.

[0162] However, when the frame element 90 described above is used, in particular with reduced reflectivity and / or a width in the X direction of at most 1.5 mm and / or with an inclined surface facing the measuring cavity, the amount of reflected light reflected from the frame element 90 to the reflected light detector is reduced, thereby reducing the influence of the thickness variation 17 of the peripheral area for color determination of the slender body 16.

[0163] The amount of reflected light reflected from the frame element 90 can also be reduced by a surface layer 91 on the frame element 90, e.g. Figure 2 shown.

[0164] illuminate

[0165] like Figure 8 As shown, in order to further reduce the influence of the frame element 90 on the reflection sensor signal, the light of the reflection light source 30 can be collimated when entering the measurement cavity 10. To this end, for example, a suitable collimating optical element, such as a lens 100, can be arranged between the reflection light source 30 and the measurement cavity 10. In this case, the light hitting the frame element 90 and returning to the reflection detector ( Figure 8 The amount of light (not shown) is reduced.

[0166] reflector

[0167] exist Figure 9 In another embodiment shown, a reflector 102 can be arranged on the "first" side of the measurement chamber 10, covering at least the measurement window 80 and, optionally, the frame element 90. The reflector 102 has sufficient transparency to allow measurements with a transmission sensor. Advantageously, the reflector 102 has a transmittance of at least 10% within the sensor's spectral range. Alternatively, the reflectance of the reflector within the reflectance sensor's spectral range is at least 33%, and particularly at least 50%. This increases the amount of light reflected from the measurement window 80 compared to the amount reflected from the frame element 90, thereby reducing the influence of the frame element 90 on the signal measured by the reflectance sensor.

[0168] Multi-segment frame elements

[0169] Figure 11 Another embodiment is shown. Here, frame element 90 comprises multiple sections along the X-direction, with inner section 90a adjacent to measurement window 80 and outer section 90b adjacent to inner section 90a. Inner section 90a has a higher reflectivity (across the emission spectrum of the reflected light source) than outer section 90b. This reduces the overall reflectivity of the frame element as seen by the reflective sensor. To achieve very low reflectivity, inner section 90a can extend less in the X-direction than outer section 90b.

[0170] The inner portion 90a lines at least one wall of the light channel 26 behind the measurement window 80, thereby providing good reflectivity. The outer portion 90b improves the mechanical stability of the device and / or allows positioning of the device relative to other devices in the X direction.

[0171] One or both frame elements 90 may have such a multi-segment design.

[0172] Other embodiments

[0173] As previously mentioned, one or both frame elements 90 may have at least one inclined surface at its "illuminated portion" location. Such an inclined surface allows the reflected light to be directed away from the reflected light detector in a preferential direction.

[0174] A first example of such an embodiment is Figure 12 As shown, one or both frame elements have at least one inclined surface 110. Each inclined surface 110 is not perpendicular to the Y direction. In particular, the angle α between the inclined surface 110 and the Y direction can be between 2° and 88°, in particular between 10° and 70°.

[0175] Figure 13 A second example is shown in which one or both frame elements have at least one inclined surface 110 .

[0176] Figure 12 and Figure 13 The difference between the embodiments is that Figure 12 In the embodiment of FIG. 1 , the surface normal vector 114 of the inclined surface 110 points to the outside of the center 116 of the measurement chamber 10, while Figure 13 In the embodiment of FIG. 1 , the surface normal vector 114 of the inclined surface 110 points toward the center 116 of the measurement chamber 10. Although both designs are possible, the former reduces the risk of multiple reflected light eventually reaching the reflected light detector.

[0177] The inclined surface 110 may reduce the amount of light that may be reflected back to the reflective light detector. This is because, in particular for at least partial or even complete specular reflection, the inclined surface may be arranged to reduce the amount of light that is reflected back to the reflective light detector.

[0178] like Figure 12 As shown, the (minimum) angle β between the surface 80 a of the measurement window 80 facing the measurement chamber 10 and the inclined surface 110 can be non-zero, in particular, between 2° and 88°, and in particular between 10° and 70°. In other words, the inclined surface 110 and the surface 80 a of the measurement window 80 can be non-parallel, which makes it possible to adjust the reflection of the inclined surface 110 with respect to the reflection of the surface 80 a.

[0179] Therefore, more generally speaking, the at least one inclined surface 110 may be non-parallel to the surface 80a of the measurement window 80 facing the measurement chamber 10. In particular, the angle β between the inclined surface 110 and the surface 80a of the measurement window 80 may be between 2° and 88°, in particular between 10° and 70°.

[0180] The one or more inclined surfaces 110 are particularly useful if the optical axis of the reflective sensor extends in the Y direction, ie the reflective light source is arranged to emit light in the Y direction and / or the reflective light detector is arranged to receive light reflected from the measurement chamber 10 in the Y direction.

[0181] A surface 80 a of the measurement window 80 facing the measurement chamber 10 may be arranged perpendicular to the optical axis of the reflection sensor.

[0182] The inclined surfaces 110 may be arranged to deflect light away from the sensor, and to do this effectively, they may be inclined to deflect the light along the propagation direction X of the body 16. This may be achieved, for example, if the surface normal vector 114 of the at least one inclined surface 110 has a non-zero component in the X direction. In particular, the surface normal vector may lie in a plane defined by the X and Y directions.

[0183] exist Figure 12 and Figure 13 In the embodiment of the present invention, the inclined surfaces 110 are planar surfaces. However, they can also be curved, or they can include multiple flat but non-parallel segments.

[0184] For example, in Figure 14 In FIG, the inclined surface 110 is curved, and the angle between the surface 110 and the Y direction is a function of the position in the X direction. Figure 14 In FIG, the inclined curved surfaces 110 are concave. However, they may also be convex.

[0185] exist Figure 15 In another example, the inclined surface includes a plurality of flat but non-parallel segments 110a, 110b.

[0186] As previously mentioned, the amount of light reflected back into the reflected light detector can be further reduced by designing the illuminated portion 95 of the frame element 90, particularly the inclined surface 110, to be at least partially specularly reflective. In specular reflection, the reflected light rays exit the surface at the same angle relative to the surface normal as the incident light rays, but on the opposite side of the surface normal within the plane formed by the incident and reflected light rays. In this case, a properly arranged inclined surface will reflect less light back into the reflected light detector.

[0187] The amount of light reflected from illuminated portion 95 of frame element 90 may be particularly reduced if the reflected light detector is not positioned to receive light from the reflective light source that is specularly reflected from illuminated portion 95 .

[0188] Mathematically speaking, Figure 17 As shown, this can be expressed by the following definition:

[0189] x is a unit vector extending in a direction from the illuminated portion 95 to the reflective light source 130,

[0190] y is a unit vector extending in a direction from the illuminated portion 95 to the reflected light receiver 132, and

[0191] n is the surface normal unit vector of the illuminated portion 95 .

[0192] In this case, the minimum angle γ between the vectors n–x and n–y should be at least 20°, in particular at least 40°.

[0193] Therefore, more generally, to reduce the amount of light reflected onto reflected light detector 132, illuminated portion 95 is at least partially specularly reflective. Furthermore, the minimum angle γ between vectors n−x and n−y, where vectors x, y, and n are defined above, can be at least 20°, and in particular at least 40°. If illuminated portion 95 has multiple regions at different positions and angles, the above relationship should apply to at least a substantial portion of the cumulative area of these regions.

[0194] In this context, a surface can be considered "at least partially specularly reflective" if, when illuminated by light coming from a direction perpendicular to its surface, the light intensity for an angle θ > 45° between the observer's line of sight and the surface normal is at least 50% of the light intensity of a Lambertian reflector. (A Lambertian reflector is a reflector whose light intensity is directly proportional to the cosine of the angle θ between the observer's line of sight and the surface normal.)

[0195] The comparison of the amount of light received by the reflected light detector via the illuminated area 95 originating from the reflective light source with the amount of reflected light received if the illuminated area 95 were a Lambertian reflector applies not only to partially specularly reflective illuminated areas but also to dimmed illuminated areas with increased absorption as described above. In both cases, signal accuracy can be improved if the light actually received at the reflected light detector is significantly lower than the light received if the illuminated area were a Lambertian reflector.

[0196] Therefore, more generally, an optical sensor device can be designed if (i.e., if we use the following definitions for A1 and A2):

[0197] - A1 is the amount of light integrated over the emission spectrum of the reflected light source, i.e., the amount of light received by the reflected light detector from the reflected light source by illuminating area 95, and

[0198] - A2 is the amount of light integrated over the emission spectrum of the reflected light source, i.e., the amount of light received by the reflected light detector from the reflected light source through the illuminated area 95 when the illuminated area 95 is a Lambertian reflector,

[0199] Then A1 is less than A2 / 2.

[0200] In other words, the amount of reflected light received from the illuminated area 95 of the frame element is reduced by at least 50% compared to conventional designs having Lambertian illuminated areas. As described above, this can be achieved by using at least partial specular reflection and / or increased absorption, alone or in combination.

[0201] The at least partially specularly reflective illuminated portion may be combined with one or more inclined surfaces, ie the inclined surfaces are at least partially specularly reflective, which makes it particularly easy to prevent a large portion of light reflected from the illuminated portion from reaching the reflected light detector.

[0202] In most of the embodiments shown so far, the frame elements 90 are integral parts of the transverse walls of the light channel 26 extending from the window 80 to the arranged transmission light detector 32. However, they can also be formed by separate parts, for example by housing parts of an adjacent sensor device.

[0203] Figure 16 An embodiment illustrating such a design is shown in which the frame element 90 is formed by a structurally separate part from the transverse wall 120 of the light channel 26 .

[0204] The transverse walls 120 can be formed, for example, by plate elements that fix the window 80 relative to the transmitted light detector 32. Alternatively, they may have no structural function but can be formed, for example, by foil elements, in particular highly reflective foil elements. In another embodiment, the transverse walls 120 can be completely eliminated, in which case the transverse boundaries of the light channel 26 are formed by the frame element 90, which can further form part of the housing for other sensors and / or other functional elements of the device.

[0205] Remark

[0206] As previously mentioned, each light source 30a-30c may include multiple light emitters, such as multiple light emitters at different wavelengths, to measure in different spectral regions. Similarly, each light detector 32a-32c may include multiple light sensors sensitive to different spectral regions.

[0207] Light sources 30a-30c may include LEDs. For example, each light source may include multiple LEDs of different colors.

[0208] The light detectors 32a - 32c may include, for example, photodiodes.

[0209] In the above embodiment, the light sources 30a-30c and light detectors 32a-32c are arranged on the first and second peripheral sides 20a, 20b of the carrier plates 34a, 34b. Alternatively, however, some of them may also be arranged, for example, on the third and / or fourth peripheral sides 20c, 20d.

[0210] In the illustrated embodiments, such as embodiment 1, the window element 15 and the measurement window 80 have the same spatial extent in the X direction.

[0211] However, in any of the above embodiments, the spatial extent of the window element 15 in the X direction may be larger than the measurement window 80. Figure 10, where the frame element 90 can be covered by the window element 15. However, even in this case, the frame element 90 is still adjacent to the measurement window 80 when viewed in the X direction. (The extent of the measurement window 80 in the X direction is Figure 10 Indicated by dotted lines.)

[0212] As previously mentioned, the second sub-body 14b forms a frame element 90, wherein the frame element 90 may be coated with a surface layer 91. The surface layer allows for reduced reflection on the frame element 90 while allowing the second sub-body 14b to have high reflectivity. In other words, the surface layer allows for low reflection on the frame element while allowing for high reflection within the light channels 26a-26f due to the highly reflective second sub-body 14b.

[0213] While there have been shown and described presently preferred embodiments, it is to be distinctly understood that the invention is not limited thereto but may be otherwise embodied and practiced within the scope of the following claims.

Claims

1. An optical sensor device for detecting defects in an elongated textile body (16), comprising a support body (14), A measuring cavity (10) receiving an elongated textile body (16) running in the X direction, wherein the measuring cavity (10) - open on opposite inlet (22a) and outlet (22b) sides in the X direction, and - in a Y direction transverse to the X direction, it is limited by the support body (14) on the first side (24a) and the second side (24c), At least one measuring window (80) is arranged on the first side (24a), wherein In the X direction, the support body (14) comprises a frame element (90) adjacent to the measuring window (80), An optical transmission sensor comprising - a transmissive light source arranged to send light through the measurement cavity (10), and a transmitted light detector arranged to receive light coming from the transmitted light source and passing through the measuring cavity (10) and the window (80), wherein the measuring cavity (10) is arranged between the transmitted light source and the transmitted light detector, An optical reflective sensor comprising - a reflective light source arranged to send light into the measurement cavity (10), and - a reflected light detector arranged to receive light coming from the transmitted light source and reflected in the measuring cavity (10), wherein both the reflected light source and the reflected light detector are arranged on the second side (24c), and The reflected light source is positioned to illuminate at least one illuminated portion (95) of the frame member (90), and the reflected light detector is positioned to receive light from the illuminated portion (95).

2. The optical sensor device according to claim 1, wherein the optical reflection sensor comprises at least two reflection light detectors (32b, 32c), in particular wherein the at least two reflection light detectors (32b, 32c) are arranged on the second side (24c).

3. The optical sensor device according to claim 1, wherein the reflectivity of the frame element (90) over the emission spectrum of the reflective light source is at most 80%, in particular at most 50%, more in particular at most 20%.

4. The optical sensor device according to claim 1, wherein the average reflectivity of the frame element (90) in the spectral range from 400 nm to 780 nm is at most 80%, in particular at most 50%, more in particular at most 20%.

5. The optical sensor device according to claim 1, wherein the frame element (90) has an average reflectivity of at most 80%, in particular at most 50%, more in particular at most 20% over the emission spectrum of the reflective light source.

6. An optical sensor device according to any of the preceding claims, wherein the frame element (90) has a main material and a surface layer (91), wherein the average reflectivity of the surface layer (91) over the emission spectrum of the reflected light source is at most 80%, in particular at most 50%, more in particular at most 20%.

7. The optical sensor device according to claim 5 or 6, wherein the average reflectivity of the frame element (90) over the emission spectrum of the reflective light source is at most 50%.

8. The optical sensor device according to claim 1, wherein the frame element (90) has an average reflectivity of at least 20% over the emission spectrum of the reflective light source.

9. The optical sensor device according to claim 1 , wherein the optical sensor device is designed if A1 is the amount of light received by the reflected light detector from the reflected light source via the illuminated area 95, integrated over the emission spectrum of the reflected light source, A2 is the amount of light received by the reflected light detector from the reflected light source via the illuminated area 95, integrated over the emission spectrum of the reflected light source, when the illuminated area 95 is a Lambertian reflector, Then A1 is less than A2 / 2.

10. The optical sensor device according to any of the preceding claims, wherein the transmission light sensor is arranged on the first side (24a).

11. The optical sensor device according to claim 1, wherein the width of the frame element (90) in the X direction is at most 1.5 mm, in particular at most 0.5 mm.

12. An optical sensor according to any of the preceding claims, wherein at least one frame element (90) has an inclined surface (110) facing the measuring cavity (10), the inclined surface (110) being positioned to be illuminated by a reflective light source, in particular by at least one light source, wherein the inclined surface (110) is not perpendicular to the Y direction, in particular forms an angle between 2 and 88 degrees with respect to the Y direction, more particularly forms an angle between 10 and 70 degrees with respect to the Y direction.

13. The optical sensor according to claim 12, wherein the inclined surface (110) forms at least 20%, in particular at least 50%, of the total surface of the frame element (90) positioned to be illuminated by the reflected light source.

14. The optical sensor according to claim 12 or 13, wherein the inclined surface (110) is not parallel to a surface (80a) of the window (80) facing the measuring chamber (10).

15. The optical sensor according to any of claims 12 to 14, wherein the surface normal vector (115) of the inclined surface (110) has a non-zero component in the X direction, in particular wherein the surface normal vector (115) lies in the plane of the X and Y directions.

16. The optical sensor according to any of the preceding claims, wherein the optical axis of the reflection sensor extends in the Y direction and / or wherein the surface (80a) of the window (80) facing the measurement chamber (10) is perpendicular to the optical axis of the reflection sensor.

17. The optical sensor according to claim 1 , wherein the illuminated portion ( 95 ) is at least partially specularly reflective, and wherein the minimum angle (γ) between nx and ny is at least 20°, in particular at least 40°, wherein the vectors n, x and y are defined as: x is a unit vector extending in a direction from the illuminated portion (95) to the reflecting light source (130), y is a unit vector extending in a direction from the illuminated portion (95) to the reflected light receiver (132), and n is the surface normal unit vector of the illuminated portion (95).

18. The optical sensor device according to any one of the preceding claims, wherein The optical reflection sensor comprises at least two, in particular at least three, reflection light sources having different emission spectra, in particular non-overlapping emission spectra, or The optical reflectance sensor includes at least one reflectance light source having a FWHM spectral width of at least 200 nm.

19. An optical sensor device according to any of the preceding claims, wherein the support body (14) forms the walls of a channel (26a-26f) extending between the cavity (10) and at least some of the light sources and light detectors, wherein the reflectivity of the walls over the emission spectrum of the reflected light sources is higher than the reflectivity of the frame element (90) over the emission spectrum of the reflected light sources.

20. The optical sensor according to claim 19, wherein the reflectivity of the wall is at least twice the reflectivity of the frame element (90).

21. An optical sensor according to any of the preceding claims, wherein at least one frame element is formed by an inner portion (90a) adjacent to the measuring window (80) and an outer portion (90b) adjacent to the inner portion (90a), wherein the reflectivity of the inner portion (90a) is higher than that of the outer portion (90b).

22. Use of an optical sensor device according to any of the preceding claims for performing measurements on a slender textile body (16), the slender textile body having an average reflectivity of at most 80% over the emission spectrum of a reflected light source, in particular an average reflectivity of at most 50%, more in particular at most 20%.

23. Use of an optical sensor device according to claim 22, wherein the elongated textile body (16) has an average reflectivity of at most 80%, particularly an average reflectivity of at most 50%, more particularly at most 20% over the emission spectrum of any one of the reflective light sources.

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