Yarn quality detection device and method

Abstract

To provide an optical sensor device for detecting defects in an elongate textile body.SOLUTION: An optical sensor comprises: a measurement chamber 10 for an elongate textile body; a support body 14 having opposing first and second sides 24a, 24c as well as outer peripheral sides extending transversally to the first and second sides 24a, 24c; at least one first light source 30a; and at least two light detectors 32a, 32c. The light source 30a and one light detector 32a are both provided on a first side 24a of the measurement chamber 10. The other light detector 32c is provided on a second side 24c of the measurement chamber 10. The second side 24c of the measurement chamber 10 is opposite to the first side 24a of the measurement chamber 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Optical sensor devices for detecting defects in elongated woven objects are known, for example, for detecting variations in the thickness of yarns or yarn precursors, or for detecting foreign fibers within such objects. Optical detection of defects in elongated woven objects presents challenges, particularly with regard to accurate identification of the defects. For example, differentiating between different defects can be difficult.

[0003] U.S. Pat. No. 5,414,520 and EP 1,508,797 describe optical sensor devices for measuring foreign bodies. These patent documents propose the use of two light sources and three light detectors arranged around a woven object to detect foreign bodies in the object. At least one of the detectors is used to measure transmitted light to estimate the yarn thickness, while at least one other detector is used to detect light reflected from the yarn.

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

[0005] Since reflected light is dependent on both yarn thickness and the presence of contaminants, combining reflection and transmission measurements improves the reliability of the measurement. Summary of the Invention

[0006] [DISCLOSURE OF THE INVENTION] SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical sensor device for detecting defects in elongated woven objects with high reliability.

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

[0008] Aspects of the present invention relate to an optical sensor device for detecting defects in an elongated woven object. The device: a support body (which may consist of a single object. Alternatively, the support body may comprise several sub-bodies, in particular several interconnected sub-bodies. The support body may comprise or consist of a polymer. The support body may have a U- or V-shape), - a measurement chamber for receiving the elongate woven object traveling along a direction X, the measurement chamber being open at an inlet side and an outlet side opposite to each other along the direction X, and additionally the measurement chamber being bounded at first and second sides by a support body along a direction Y transverse to the direction X; - at least one measurement window arranged on the first side, the support body comprising a frame element adjacent to the measurement window along the direction X; an optical transmission sensor comprising a transmitted light source configured to send light through a measurement chamber, the optical transmission sensor further comprising a transmitted light detector configured to receive light from the transmitted light source after traversing the measurement chamber and the window. The transmitted light may traverse the measurement chamber first and then the window, or the transmitted light may traverse the window first and then the measurement chamber. The measurement chamber is configured between the transmitted light source and the transmitted light detector. an optical reflective sensor comprising a reflected light source arranged to send light into the measurement chamber, the optical reflective sensor further comprising a reflected light detector arranged to receive light from the reflected light source after it has been reflected within the measurement chamber, the reflected light source and the reflected light detector both being arranged on the second side, the reflected light source being positioned to illuminate at least the illuminated portion of the frame element, and the reflected light detector being positioned to receive at least a portion of the light reflected from the illuminated portion; and It is equipped with:

[0009] The support body allows for an improved stability of the optical sensor. Illuminating at least part of the illuminated portion, i.e. the frame element, allows for a more even illumination of the window.

[0010] The directions X, Y and Z can be transverse to one another, in particular they can be perpendicular to one another. Two directions are transverse to one another if they are not parallel, in particular they are perpendicular.

[0011] The measurement chamber may have a rectangular parallelepiped shape.

[0012] The distance in direction Y between the first and second side surfaces may be 0.1 cm to 2 cm, in particular 0.2 cm to 1 cm, which allows the elongate woven object to move along direction X through the measurement chamber, in particular without scraping the first and second side surfaces while keeping the measurement volume small enough for accurate measurements.

[0013] The transmitted and reflected light sources may be the same or different light sources. In general, the transmitted and reflected sensors may share one or more light sources and / or photodetectors. In one embodiment, at least 50% of the light emitted by the transmitted light source and entering the measurement window reaches the transmitted light detector.

[0014] The measurement window allows spatial restriction (or selection) of which light emitted by the transmitted light source reaches the transmitted light detector. This defines a transmission measurement region within the measurement chamber through which transmitted light reaching the transmitted light detector passes, potentially reducing the amount of light that did not interact with the elongated woven object and improving the signal-to-noise ratio. Furthermore, the transmission window can be positioned to transmit only light from a region of the measurement chamber that is uniformly illuminated by the transmitted light source. In this context, uniform illumination is understood to mean illumination with an illumination intensity variation of less than 10%, particularly less than 5%.

[0015] Transmission measurements allow accurate measurement of thickness defects in elongated woven objects. In transmission measurements, the light emitted by the transmission light source and reaching the transmission light detector is measured, but the actual signal is the light "missing" due to the presence of the elongated woven object in the path of the transmitted light.

[0016] The reflected light source can be configured to direct light into the measurement chamber to an area that at least partially overlaps with the transmission measurement area.

[0017] Advantageously, both the transmitted light source and the reflected light source are arranged to direct light towards the measurement window, in particular towards the elongated woven object in front of the measurement window (in this context, "in front of the measurement window" should be understood to refer to a location on the chamber side of the measurement window), which allows reflection and transmission measurements to be performed at the same location / point on the elongated woven object.

[0018] The elongated woven object may be a yarn.

[0019] The frame element adjacent to the measurement window can extend in the direction X from the measurement window to the edge of the support body.

[0020] The frame elements may comprise or consist of a material different from that of the rest of the support body.

[0021] The transmitted and / or reflected light sources may be light-emitting semiconductor devices, in particular light-emitting diodes.

[0022] In one embodiment, the transmitted and / or reflected light source has a low spectral coherence compared to a diode laser, in particular the transmitted and / or reflected light source is spectrally incoherent, in particular by having a coherence length of less than 1 mm, which allows to reduce interference effects and in particular improves the quality of the measurement.

[0023] Advantageously, the optical reflection sensor comprises at least two reflected light detectors, which may be arranged on the second side of the optical reflection sensor, and which may be arranged to view the measurement window at different angles, which allows for a more uniform observation and, in particular, results in an improved measurement of the reflection.

[0024] Advantageously, the frame element has a reflectivity of at most 80%, in particular at most 50%, more particularly at most 20% for the emission spectrum of the reflected light source. If several reflected light sources are present, it is advantageous if this condition is fulfilled for all of them.

[0025] By measuring the reflection from a woven elongated object, it may be possible to obtain correlated color and thickness information for the woven elongated object. By measuring the transmission of the woven elongated object, it may be possible to obtain thickness information (which is not correlated) for the woven elongated object. By combining the measured reflection and transmission of the woven elongated object, it may be possible to obtain color information that is less dependent on thickness than reflection alone. To do so, it is advantageous to measure both reflection and transmission over the same region / area of ​​the woven elongated object.

[0026] When a reflected light source illuminates a peripheral area outside the measurement window, especially a frame element, the measurement of reflectance is affected by reflections from said peripheral area. Specifically, the measured reflectance is the sum of a core component reflected from the area also monitored by the transmission sensor and a peripheral component from the peripheral area. The peripheral component can be affected by variations in the thickness of textile objects in the background area, which makes it more difficult to correct for the measured reflectance using transmission measurements.

[0027] This is particularly evident when a dark, woven object with low reflectivity is combined with a conventional sensor device having a highly reflective support body: In this case, increasing the thickness of the woven object in the surrounding area will reduce the measured reflection but will not affect the measured transmission, causing the system to incorrectly consider the woven object to have a "darker" area.

[0028] Therefore, by using frame elements with a reflection or average reflectance of up to 80%, in particular up to 50%, more particularly up to 20% of the emission spectrum of the reflected light source, it is possible to improve the quality and / or reliability of the measurement.

[0029] In some embodiments, the average reflectance of the frame elements for the emission spectrum of the reflected light source is up to 50%, which allows for excellent treatment of dark textiles.

[0030] If the sensor device is intended to be used with dark and light colored woven objects, such as black and white yarns, the reflectance, i.e., average reflectance, of the frame element with respect to the emission spectrum of the reflected light source can be selected to be at least 20% to improve the behavior of the system when variations in thickness of light colored woven objects are present on the frame element.

[0031] Thus, for a device that performs well on textiles having both dark and light colors, the average reflectance of the illuminated portion of the frame element with respect to the emission spectrum of the reflected light source can be between 20% and 50%.

[0032] The reflectivity of the frame elements can be reduced by using dark frame elements, which can be black.

[0033] Advantageously, the average reflectivity of the frame elements for the spectral range from 400 nm to 780 nm is at most 80%, in particular at most 50%, more particularly at most 20%.

[0034] In this context, the average reflectance for the spectral range of 400 nm to 780 nm should be understood as the average of the reflectance for each individual wavelength across the range of 400 nm to 780 nm.

[0035] This allows reducing the visible light (i.e., 400 nm to 780 nm) reflected by the frame elements, thereby reducing the variations in the reflected signal due to variations in the thickness of the woven strips that are outside the measurement window but are illuminated by the reflected light source, thereby allowing for an improved assessment of the visual quality of the woven strips, and in particular for improved measurement of the color of the woven strips.

[0036] This is based on the understanding that a low reflectance for the spectrum of the reflected light source is sufficient. If there are several reflected light sources with different emission spectra, the average reflectance is advantageously calculated for the emission spectrum of each of the reflected light sources.

[0037] In this regard, the average reflectance for the emission spectrum of a light source is the reflectance calculated by weighting the average for said spectrum by the relative intensity distribution of light in the emission spectrum.

[0038] Advantageously, the frame element comprises a bulk material and a surface layer, which can have an average reflectivity of at most 80%, in particular at most 50%, more particularly at most 20% with respect to the emission spectrum of the reflected light source, and in particular, the frame element can have an average reflectivity with respect to said emission spectrum that is lower than the average reflectivity of the bulk material.

[0039] Advantageously, the bulk material of the frame element is a material with an average reflectivity of at least 80%, in particular at least 90%, with respect to the emission spectrum of the reflected light source, which reduces light losses when the light passes through the opening in the frame element.

[0040] The thickness of the surface layer can be less than 1 millimeter. The surface layer can be a layer of paint, particularly black paint. In another embodiment, the surface layer can be formed by a surface treatment that changes the optical properties of the bulk material. For example, laser irradiation can be used, for example, to oxidize the bulk material to create a less reflective surface layer.

[0041] Advantageously, the transmitted light sensor is arranged on the first side.

[0042] In particular, by arranging the reflected light source and the reflected light detector on the second side and the transmitted light sensor on the first side, the reflected light source can be used for both reflection and transmission measurements, i.e., the reflected light source and the transmitted light source are formed by the same light source.

[0043] Advantageously, the frame elements have a width of at most 1.5 mm, in particular at most 0.5 mm, in the direction X. In this case, the width of the frame elements is measured in the center of the measuring field (i.e. where the elongated woven object is usually most likely to be located).

[0044] The frame elements having a width in the direction X of at most 1.5 mm or even less makes it possible to reduce the surface from which the light emitted by the reflective light source is reflected, thus reducing the peripheral component of the reflection.

[0045] Advantageously, at least one of the frame elements has an inclined surface facing the measurement chamber and positioned to be illuminated by a reflected light source, in particular by at least one of the light sources, this inclined surface being not perpendicular to the direction Y. In particular, said inclined surface forms an angle with the direction Y between 2 and 88 degrees, more particularly an angle with the direction Y between 10 and 70 degrees.

[0046] The angled surface faces the measurement chamber (ie, it is not on a side surface of the frame element or on the surface of the frame element opposite the measurement chamber).

[0047] Such an angled surface can reduce the amount of reflected light from the reflected light source that reaches the reflected light detector, thus improving the quality of the measurement.

[0048] Advantageously, the inclined surface is such that at least 50% of the light from the reflected light source is specularly reflected from the surface. The inclined surface may, for example, be smooth and have an absorption of up to 30% in the range 400 nm to 780 nm.

[0049] The inclined surface may be flat or curved. Advantageously, in the case of a curved inclined surface, at least a part of the curved surface forms said angle with the direction Y.

[0050] Advantageously, the oblique 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.

[0051] In one embodiment, the optical reflectance sensor comprises at least two, especially at least three, reflected light sources with different emission spectra, especially non-overlapping emission spectra.

[0052] The at least three reflected light sources may include or consist of a blue reflected light source, a red reflected light source, and a green reflected light source. The blue reflected light source may have a full width at half maximum (FWHM) emission wavelength range of 440 nm to 500 nm. The green reflected light source may have a FWHM emission wavelength range of 510 nm to 570 nm. The red reflected light source may have a FWHM emission wavelength range of 600 nm to 750 nm.

[0053] 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.

[0054] Advantageously, the support body forms walls of a channel extending between the chamber and at least some of the light source and the light detector, the average reflectivity of said walls for the emission spectrum of the reflected light source being higher than the average reflectivity of said frame element for the emission spectrum of the reflected light source.

[0055] Such a relatively reflective wall allows more light to be received by the photodetector.

[0056] Advantageously, the support body forms the walls of a channel extending between the measurement window on the first side and the photodetector on the first side, in particular the transmission photodetector on the first side.

[0057] Advantageously, the walls of the channels are white. The walls of the channels may be flat and smooth.

[0058] Advantageously, the reflectivity of these walls is at least twice as high as the reflectivity of the frame elements.

[0059] The reflectivity of the wall may be at least 60%, in particular at least 75%, more particularly at least 90%.

[0060] Advantageously, said "reflectance" in the two previous paragraphs is the average reflectance for at least one of the light sources, and in particular for all spectral ranges of the light sources anyway.

[0061] This makes it possible to minimize the loss of light (light intensity) before it reaches the light detector (reflection or transmission detector), thus improving the quality of the measurement.

[0062] The present invention further relates to the use of an optical sensor device as described above for carrying out measurements on an elongated woven object having an average reflectance of at most 80%, in particular at most 50%, more particularly at most 20%, for the emission spectrum of the reflected light source. In particular, for the reasons described above, the average reflectance of the illuminated part of the frame element for the emission spectrum of the reflected light source can be between 20% and 50%.

[0063] The woven elongate strip may be black in color.

[0064] Advantageously, the elongated woven object has an average reflectivity of at most 80%, in particular at most 50%, more particularly at most 20% for the emission spectrum of any one of the reflected light sources of the optical reflectance sensor. [Brief explanation of the drawings]

[0065] The invention will be better understood, and objects other than those set forth above will become apparent, from the following detailed description thereof, in which reference will be made to the accompanying drawings.

[0066] [Figure 1] FIG. 1 shows an optical sensor device cut along the center. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II of FIG. [Figure 3]FIG. 10 shows another example optical sensor device cut along the center. [Figure 4] FIG. 10 is a diagram showing yet another example of a sensor device. [Figure 5] FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. [Figure 6] Schematic diagram of a defect in an elongated object in front of a measurement window. [Figure 7] Schematic diagram of a defect in an elongated object in front of a frame element. [Figure 8] FIG. 10 illustrates an embodiment with collimating optics. [Figure 9] FIG. 10 shows an embodiment with a reflector. [Figure 10] FIG. 10 illustrates an embodiment in which a window element covers a frame element. [Figure 11] FIG. 10 illustrates an embodiment with a multi-part frame element. [Figure 12] FIG. 1 shows a first embodiment having frame elements with inclined surfaces. [Figure 13] FIG. 2 shows a second embodiment having frame elements with inclined surfaces. [Figure 14] FIG. 3 shows a third embodiment having frame elements with inclined surfaces. [Figure 15] FIG. 4 shows a fourth embodiment having frame elements with inclined surfaces. [Figure 16] 10A and 10B show further embodiments illustrating frame elements of different designs. [Figure 17] FIG. 10 illustrates an arrangement of a reflected light source and a reflected light detector to prevent specularly reflected light from entering the reflected light detector. DETAILED DESCRIPTION OF THE INVENTION

[0067] <Embodiment 1> 1 and 2 show a schematic view of an optical sensor device for detecting defects in an elongated woven object, cut along its center.

[0068] The device comprises a slit-shaped measurement chamber 10 formed by a slit in a support body 14. The measurement chamber 10 is designed to receive an elongated woven object 16 traveling along a direction X during measurement.

[0069] The support body 14 has a first external side surface 18a and a second external side surface 18b, which are advantageously parallel to one another (see FIG. 2) and transverse to the direction X. The support body 14 further has peripheral side surfaces 20a, 20b, 20c, and 20d (see FIGS. 1 and 2) which extend transversely, in particular perpendicularly, to the first and second external side surfaces 18a, 18b.

[0070] The measurement chamber 10 has a first external side 18a and a second external side 18b that are open along the direction X to form an entrance side 22a and an exit side 22b, allowing the elongated woven object 16 to enter and exit during measurement.

[0071] The measurement chamber 10 has a first side 24a, a second side 24c, and a third side 24b that are closed by the support body 14 on the sides perpendicular to the first and second external sides 18a, 18b, while a fourth side 24d is open for inserting the elongated woven object 16 prior to actuation.

[0072] In other words, along a direction Y that is transverse, and in particular perpendicular, to direction X, measurement chamber 10 is bounded at first and second sides 24a, 24c by the support body. Furthermore, along a direction Z that is perpendicular to directions X and Y, measurement chamber 10 is closed at third side 24b and open at fourth side 24d.

[0073] Radial optical channels 26a-26f extend through the support body 14 between the measurement chamber 10 and the first and second peripheral sides 20a, 20b.

[0074] Advantageously, the first peripheral side surface 20a and the second peripheral side surface 20b are opposite each other and in particular parallel to each other.

[0075] The sensor device further comprises several light sources 30a, 30b, 30c and several photodetectors 32a, 32b, 32c. In this embodiment, there are three photodetectors and three light sources. As mentioned above, the number can be greater.

[0076] The light sources 30 a , 30 b , 30 c and the light detectors 32 a , 32 b , 32 c are arranged alternately in the light channels 26 a - 26 f , ie, on the first and second peripheral sides 20 a , 20 b of the support body 14 .

[0077] The light sources 30a, 30b, 30c and light detectors 32a, 32b, 32c are mounted on first and second carrier plates 34a, 34b.

[0078] A first carrier plate 34a is attached to the first outer peripheral side surface 20a of the support body 14. The first carrier plate 34a carries the light sources 30a and 30b and the photodetector 32a arranged on the side of the plate. A second carrier plate 34b is attached to the second outer peripheral side surface 20b of the support body 14. The second carrier plate 34b carries the light source 30c and the photodetectors 32b and 32c arranged on the side of the plate.

[0079] The carrier plates 34a, 34b are preferably printed circuit boards and are arranged parallel to one another and can be mechanically connected to the support body 14 in a defined spatial relationship to position the light sources and light detectors in the desired locations in the light channels 26a-26f.

[0080] As shown, the first light source 30a, the second light source 30b, and the first photodetector 32a are arranged on the first side 20a, and the third light source 30c, the second photodetector 32b, and the third photodetector 32c are arranged on the second side.

[0081] The first light source 30a is opposite the third photodetector 32c, the second light source 30b is opposite the second photodetector 32b, and the third light source 30c is opposite the first photodetector 32a, where "opposite" means on opposite sides of the nominal position of the elongated object 16 in the measurement chamber 10 (i.e., the center of the measurement chamber 10).

[0082] More generally, the photodetectors may each be arranged to face one of the light sources, or vice versa.

[0083] As described above, at least one light detector 32a is disposed between at least two light sources 30a, 30b on a first side of the measurement chamber 10, and at least one light source 30c is disposed between at least two light detectors 32b, 32c on a second side of the measurement chamber 10.

[0084] For reflectance measurements, the third light source 30c can be used as a reflected light source and the second and / or third photodetectors 32b, 32c can be used as reflected light detectors, i.e., the sensor device has an optical reflectance sensor comprising the third light source 30c and the second and / or third photodetectors 32b, 32c. Alternatively or additionally, the first and second light sources 30a, 30b can be used as reflected light sources and the first photodetector 32a can be used as a reflected light detector, i.e., the sensor device has an optical reflectance sensor comprising the first and second light sources 30a, 30b and the first photodetector 32a.

[0085] For transmission measurements, the third light source 30c can be used as a transmission light source and the first photodetector 32a can be used as a transmission light detector, in other words, the sensor device has an optical transmission sensor that includes the third light source 30c and the first photodetector 32a.

[0086] Typically, the photodetectors 32a-32c have an active (i.e., light-sensing) area that is larger than the active (i.e., light-emitting) area of ​​the light sources 30a-30c. Advantageously, the light sources and photodetectors have equal active areas. To at least partially compensate for this inequality in area, the support body 14 is designed so that the first peripheral side 20a (and the light sources and photodetectors configured thereon) is closer to the measurement chamber 10 than the second peripheral side 20b (and the light sources and photodetectors configured thereon).

[0087] The illustrated embodiment has a first optical channel 26a extending between the first light source 30a and the measurement chamber 10, a second optical channel 26b extending between the first light detector 32a and the measurement chamber 10, a third optical channel 26c extending between the second light source 30b and the measurement chamber 10, a fourth optical channel 26d extending between the second light detector 32b and the measurement chamber 10, a fifth optical channel 26e extending between the third light source 30c and the measurement chamber 10, and a sixth optical channel 26f extending between the third light detector 32c and the measurement chamber 10.

[0088] Thus, first, second, and third optical channels 26a-26c extend through support body 14 between measurement chamber 10 and first peripheral side surface 20a. Fourth, fifth, and sixth optical channels 26d-26f extend through support body 14 between measurement chamber 10 and second peripheral side surface 20b.

[0089] The second optical channel 26b is arranged between the first optical channel 26a and the third optical channel 26c. Similarly, the fourth optical channel 26e is arranged between the fourth optical channel 26d and the sixth optical channel 26f.

[0090] The interface between second optical channel 26b and the measurement chamber at first side 24a forms a measurement window 80.

[0091] The second optical channel 26b and the fifth optical channel 26e are coaxial such that the light source 30c is aligned precisely opposite the photodetector 32a to provide an accurate transmission measurement of the measurement chamber 10. This allows a signal to be generated that is responsive to the thickness of the elongated object 16.

[0092] The support body 14 comprises a first sub-body 14a arranged between two second sub-bodies 14b along the direction X. The sub-bodies 14a, 14b form optical channels 26a-26f between them. The second sub-body 14b forms external sides 18a, 18b.

[0093] The first body sub-body 14a is advantageously an opaque material (i.e., a material that is not transparent in the overlapping spectral region between the light source emission and the photodetector sensitivity) and separates the optical channels from each other to suppress optical crosstalk between the optical channels.

[0094] More generally, the optical channels 26a-26f are advantageously (optically) in communication through the measurement chamber, i.e., a significant portion (i.e., at least 10%, in particular at least 25%) of the light transmitted from one to the other has passed through the measurement chamber 10.

[0095] Advantageously, and as mentioned above, the sub-bodies 14a, 14b are of a material that is highly reflective of the light from the light source.

[0096] The device further comprises a window element 15 made of a transparent material (i.e., a material that is transparent in the spectral region overlap between the light source emission and the photodetector sensitivity, particularly in the range of 400 nm to 780 nm). The window element forms transparent windows 38a-38f between the optical channels 26a-26f and the measurement chamber 10. These windows prevent dust from entering the optical channels 26a-26f. Advantageously, the windows 38a-38f are transparent in the sense that they transmit at least 50% of the light in the spectrum that overlaps between the light source and the photodetector.

[0097] Windows 38b and 38e form first and second diffusers 40a and 40b arranged at the interface between second and fourth optical channels 26b and 10, respectively, to improve measurement accuracy.

[0098] The diffusers 40a, 40b can be formed, for example, by small structures (10 to 500 μm in size) arranged on the surfaces of the windows 38b, 38e, particularly on the surfaces of these windows opposite the measurement chamber 10.

[0099] Advantageously, the sub-bodies 14a, 14b and the window element 15 are produced by two-component casting or two-component moulding, which can also be formed, for example, by individual elements fastened together.

[0100] The light channels 26a-26f are advantageously hollow, i.e. filled with a gas, in particular air. To enhance light transmission, the inner walls (i.e., inner surfaces) of the light channels are advantageously smooth and reflective.

[0101] Alternatively, the light channels 26a-26f may be filled with a transparent solid.

[0102] 2, the light sources 30a-30c, the photodetectors 32a-32c, and the measurement chamber 10 are arranged on (i.e., intersect) a common plane 42. Advantageously, this common plane 42 extends parallel to the first and second outer sides 18a-18b of the support body 14 and / or perpendicular to the direction X, i.e., the longitudinal direction 44 of the elongated woven object 16.

[0103] In the common plane 42, the light sources 30a-30c and photodetectors 32a-32c are arranged at various angular positions defined by lines connecting the nominal position of the elongated woven object 16 (i.e., the center of the measurement chamber 10) and the respective light source or photodetector.

[0104] Additionally, the windows 38 a - 38 f are arranged at various angular positions 46 a - 46 f around the center of the metrology chamber 10 .

[0105] <Embodiment 2> FIG. 3 shows a schematic view of an optical sensor device cut along its center.

[0106] 1 and 2, but in this embodiment the device has one light source 30c and two photodetectors 32a, 32b, and therefore the optical sensor device only has three radial light channels 26b, 26d, 26e.

[0107] Light source 30c is used as both a reflected light source and a transmitted light source. Photodetector 32b is a reflected light detector 32b, and photodetector 32a is a transmitted light detector 32a.

[0108] Thus, in this embodiment, the transmission sensor comprises light source 30c as the transmission light source and photodetector 32a as the transmission light detector, and the reflection sensor comprises light source 30c as the reflection light source and photodetector 32b as the reflection light detector.

[0109] <Embodiment 3> 4 and 5 show a specific embodiment of the sensor device.

[0110] As can be seen, the measurement chamber 10 is formed by a slit in the support body 14 that widens towards the fourth outer peripheral side 20d.

[0111] The window element 15 forms part of the inner wall of the measurement chamber 10. The opaque second sub-body 14b forms the first and second outer sides 18a, 18b of the support body 14, which close the optical channels 26a-26f at said first and second outer sides 18a, 18b.

[0112] The two carrier plates 34a, 34b are attached to opposite peripheral sides of the support body 14 and may be electrically interconnected by, for example, a flexible printed circuit 48.

[0113] At least a portion of the light sources 30a-30c and / or at least a portion of the light detectors 32a-32b are located in recesses 50a-50f in the support body 14, each recess 50a-50f forming the end of one light channel 26a-26f.

[0114] <frame element> As mentioned above, one aspect of the sensor device of the present invention addresses the effects of optical reflections in the frame element 90 adjacent to the measurement window 80. This is an aspect that applies to all of the embodiments shown herein and most other optical sensor devices of this type, as will be discussed in more detail below.

[0115] FIG. 6 is a schematic view of the area around the metrology window 80 when looking at the first side 24a of the metrology chamber 10 from the second side 24c.

[0116] The measurement window 80 is defined as the geometric area of ​​the first side 24a traversed by the portion of the light from the transmitted light source that can reach the transmitted light detector.

[0117] The second sub-body 14b forms a frame element 90 that is laterally adjacent to the measurement window 80 along the direction X.

[0118] In the above embodiment, light from light source 30c, which is used as a transmitted light source, passes through window element 15 into measurement chamber 10, traverses measurement chamber 10, exits the chamber, passes through measurement window 80, traverses window element 15, and finally reaches photodetector 32a, which serves as a transmitted light detector.

[0119] The photodetector 32a is located opposite the light source 30c as described with reference to Figures 1, 2 and 3. The light source arrangement is as shown in Figure 3 (Embodiment 2). The light source 30c is both a transmitted light source and a reflected light source.

[0120] The light source 30c illuminates an illumination area 70 having a width Wi along the direction X that is greater than a width Wm of the measurement window 80 along the same direction. The illumination area 70 includes the measurement window 80, but also further includes or can include further regions of the first side 24a, namely: A portion 95 of the frame element 90 adjacent to the measurement window 80 along the direction X is illuminated. A portion 75 of the support body 14 adjacent to the measurement window 80 along the direction Z is illuminated. It is also possible that a part 77 of the measurement chamber outside the support body 14 is illuminated. A portion of the elongated woven object 16 is illuminated.

[0121] For reflectance measurements, a reflected light detector, such as the second photodetector 32b and / or the third photodetector 32c, collects light emitted by the light source onto the illuminated area 70 and reflected to the reflected light detector. The measured reflected light R is the sum of a core component Rc and a peripheral component Rp, R=Rc+Rp. The core component Rc is produced by light reflected from the measurement window 80, including the portion of the elongated woven object 16 in front of the measurement window 80. This area is also monitored by a transmitted light detector, producing a transmitted signal T. The peripheral component Rp is generated by light reflected from a portion 95 of the frame element 90, a portion 75 of the first side 24a of the measurement chamber, and a portion of the elongated woven object 16 that is outside the measurement window 80 but inside the illuminated area 70.

[0122] A black elongated object 16 reflects less light incident on it than a white elongated object 16, and for a given "darkness," an elongated object 16 with a smaller diameter reflects less than one with a larger diameter.

[0123] 6, variations in the thickness of an object placed in front of the measurement window 80 result in strong variations in transmission, ΔT, and in reflection, ΔR. Variations in the color of the object in front of the measurement window only slightly affect the transmission, i.e., ΔT≈0.

[0124] The variation ΔT is therefore independent of the color of the elongated object 16 and is a direct measure of the thickness of the object.

[0125] Both variations in object thickness and variations in object color result in variations in reflectance AR. Therefore, variations in object thickness alone cannot be distinguished from variations in object color.

[0126] Therefore, to reliably detect color variations, the reflected signal can be combined with the transmitted signal to generate a parameter that depends only on the color variation ΔC, for example, by calculating ΔC = k1 · ΔT + k2 · ΔR, with appropriate constants k1 and k2 chosen so that pure thickness variations within the measurement window are corrected, i.e., do not affect ΔC. This works effectively in the situation shown in Figure 6, since thickness variations are observed by both the reflected and transmitted sensors.

[0127] 7 shows a situation where an elongated woven object 60 has a thickness variation 17 in front of a portion 95 of a frame element 90 illuminated by a reflected light source. The thickness variation 17 prevents the reflected light sensor from receiving light from the area of ​​the frame element 90 covered by the thickness variation 17. This reduces the measured reflection, i.e., the ambient component of reflection Rp, but does not affect the measured transmission T, thus generating an erroneous color variation signal ΔC when calculated, for example, as described above.

[0128] This false color variation signal is a function of the difference in average reflected light of the frame element 90 and the elongated woven object 60. For highly reflective (e.g., whitish) yarns and the conventional highly reflective support body 14, this error is small. However, when measuring darker, less reflective yarns, this false color variation signal becomes larger. This causes the optical detection device to infer that the elongated object 16 has a darker color.

[0129] However, when using a frame element 90 as described above, in particular one having a low reflectivity and / or a width in the direction X of at most 1.5 mm and / or having an inclined surface facing the measurement chamber, the amount of reflected light reflected from the frame element 90 to the reflected light detector is reduced, and therefore the effect of the thickness variations 17 in the surrounding area on measuring the color of the elongated object 16 is reduced.

[0130] The amount of reflected light reflected from the frame element 90 can also be reduced by a surface layer 91 of the frame element 90 as shown in FIG. 2, for example.

[0131] <Irradiation> 8, to further reduce the effect of frame element 90 on the reflective sensor signal, the light from reflected light source 30 can be collimated as it enters measurement chamber 10. To this effect, a suitable collimation optical element, such as lens 100, can be arranged between reflected light source 30 and measurement chamber 10. In that case, the amount of light that strikes frame element 90 and returns to the reflective detector (not shown in FIG. 8) is reduced.

[0132] <Reflector> In another embodiment shown in Figure 9, a reflector 102 can be arranged on the "first" side of the measurement chamber 10, with the reflector 102 covering at least the measurement window 80 and possibly the frame element 90. The reflector 102 is sufficiently transparent to allow for transmission sensor measurements. Advantageously, the reflector 102 has a transmittance of at least 10% in the spectral range of the transmission sensor. However, on the other hand, the reflector has a reflectance of at least 33%, in particular at least 50%, in the spectral range of the reflection sensor. This increases the amount of light reflected from the measurement window 80 compared to the amount of light reflected from the frame element 90, thereby reducing the influence of the frame element 90 on the signal measured by the reflection sensor.

[0133] <Multi-component frame element> 11 shows yet another embodiment, where the frame element 90 comprises several parts along the direction X, an inner part 90a adjacent to the measurement window 80 and an outer part 90b adjacent to the inner part 90a. The inner part 90a has a higher reflectivity (with respect to the emission spectrum of the reflected light source) than the outer part 90b. This makes it possible to reduce the total reflectivity of the frame element observed by the reflective sensor. To achieve a very low reflectivity, the extent of the inner part 90a along the direction X can be made smaller than that of the outer part 90b.

[0134] The inner part 90a provides good reflectivity by lining at least one wall of the optical channel 26 behind the metrology window 80. The outer part 90b improves the mechanical stability of the device and / or allows the device to be positioned along the direction X relative to other devices.

[0135] One or both frame elements 90 may have such a multi-piece design.

[0136] Further embodiments As mentioned above, one or both frame elements 90 may have at least one angled surface, particularly at the location of its "illuminated portion," which allows the reflected light to be directed along a preferred direction away from the reflected light detector.

[0137] A first example of such an embodiment is shown in Figure 12, where one or both frame elements have at least one inclined surface 110. Each inclined surface 110 is not perpendicular to the direction Y. In particular, the angle α between the inclined surface 110 and the direction Y may be between 2° and 88°, in particular between 10° and 70°.

[0138] FIG. 13 shows a second embodiment in which one or both frame elements have at least one angled surface 110 .

[0139] 12 and 13 differ in that in the embodiment of Figure 12, the surface normal vector 114 of the inclined surface 110 points away from the center 116 of the measurement chamber 10, while in the embodiment of Figure 12, the surface normal vector 114 of the inclined surface 110 points towards the center 116 of the measurement chamber 10. While either design is possible, the former reduces the risk of multiply reflected light ultimately reaching the reflected light detector.

[0140] The angled surface 110 can reduce the amount of light that can be reflected back to the reflected light detector because the angled surface can be configured to reduce the amount of light that is reflected back into the reflected light detector, especially for at least partial or complete specular reflection.

[0141] 12, the (minimum) angle β between the inclined surface 110 and the surface 80a of the window 80 facing the measurement chamber 10 can be other than 0, in particular between 2° and 88°, in particular between 10° and 70°. In other words, the inclined surface 110 and the surface 80a of the window 80 are non-parallel, which allows the reflection of the inclined surface 110 to be adjusted compared to the reflection of the surface 80a.

[0142] Thus, more generally, at least one inclined surface 110 may be non-parallel to the surface 80a of the window 80 facing the measurement chamber 10. In particular, the angle β between the inclined surface 110 and the surface 80a of the window 80 may be between 2° and 88°, in particular between 10° and 70°.

[0143] The one or more angled surfaces 110 are particularly useful when the optical axis of the reflective sensor extends along direction Y, i.e., when the reflective light source emits light along direction Y and / or the reflective light detector is configured to receive light reflected back from the measurement chamber 10 along direction Y.

[0144] The surface 80a of the window 80 facing the measurement chamber 10 may be arranged perpendicular to the optical axis of the reflective sensor.

[0145] The inclined surfaces 110 can be arranged to deflect light out of the sensor, and to do this efficiently, the surfaces can be tilted to deflect light along the emission direction X of the object 16. This can be achieved, for example, if the surface normal vector 114 of at least one inclined surface 110 has a non-zero component along the direction X. In particular, the surface normal vector may lie in a plane defined by the directions X and Y.

[0146] 12 and 13, the inclined surface 110 is a flat surface, however, in other embodiments, the inclined surface 110 may be curved or may include multiple flat, but non-parallel, segments.

[0147] For example, in Figure 14, the inclined surface 110 is curved, and the angle between the surface 110 and direction Y is a function of position along X. In Figure 14, the curved inclined surface 110 is concave. However, it could also be convex.

[0148] In FIG. 15, in another embodiment, the inclined surface includes several flat but non-parallel segments 110a, 110b.

[0149] As mentioned above, 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 angled surface 110, to be at least partially specular. In specular reflection, a reflected ray of light leaves the surface at the same angle to the surface normal as the incident ray, but on the opposite side of the surface normal in the plane formed by the incident and reflected ray. A properly configured angled surface will then cause even less light to be reflected back into the reflected light detector.

[0150] The amount of light reflected from the illuminated portion 95 of the frame element 90 can be particularly reduced if the reflected light detector is not positioned to receive light from the reflected light source that is specularly reflected from the illuminated portion 95.

[0151] Mathematically, this is illustrated in Figure 17: Let x be a unit vector extending along the direction from the illuminated portion 95 to the reflected light source 130, y as a unit vector extending along a direction from the illuminated portion 95 to the reflected light receiver 132; and n is the unit vector of the surface normal of the irradiated part 95. It can be expressed by defining

[0152] In that case, the minimum angle γ between the vector nx and the vector ny should be at least 20°, in particular at least 40°.

[0153] Thus, more generally, illuminated portion 95 is at least partially specularly reflective to reduce light reflected into reflected light detector 132. Furthermore, the minimum angle γ between vector n-x and vector ny may be at least 20°, and in particular at least 40°, where vectors x, y, and n are as defined above. If illuminated portion 95 has several regions of various orientations and angles, the above relationship should apply to at least a majority of the cumulative areas of these regions.

[0154] In this context, a surface can be considered "at least partially specular" if, when illuminated with light perpendicular to the surface, the luminous intensity at angles θ > 45° between the observer's line of sight and the surface normal is at least 50% less than that of a Lambertian reflector (a reflector whose reflected light has a luminous intensity that is directly proportional to the cosine of the angle θ between the observer's line of sight and the surface normal). the amount of reflected light from the reflected light source received by the reflected light detector via the illuminated area 95; - the amount of reflected light received when the illuminated area 95 is a Lambertian reflector, and This comparison can be applied not only to partially specularly reflective illuminated areas, but also to darkly absorbing illuminated areas as described above. In either case, signal accuracy can be improved if the light actually received at the reflected light detector is significantly less than the light that would be received if the illuminated area were a Lambertian reflector.

[0155] Thus, more generally, an optical sensor device may be (i.e., using the following definitions for A1, A2): 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; and A2 is the amount of light received by the reflected light detector from the reflected light source through the illuminated area 95, integrated over the emission spectrum of the reflected light source, when the illuminated area 95 is a Lambertian reflector. given that, A1 is smaller than A2 / 2 It can be designed as follows.

[0156] 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 with illuminated areas that are Lambertian reflecting. As discussed above, this can be achieved by using at least partial specular reflection and / or increased absorption, either alone or in combination.

[0157] An illuminated portion that is at least partially specularly reflective can be combined with one or more inclined surfaces, i.e., the inclined surfaces being at least partially specularly reflective, making it particularly easy to prevent most of the light reflected from the illuminated portion from reaching the reflected light detector.

[0158] In most of the embodiments shown thus far, the frame element 90 is integral with the sidewall of the light channel 26 extending from the window 80 to the configured transmitted light detector 32. However, the frame element 90 may also be formed by a separate component, for example by a portion of the housing of an adjacent sensor device.

[0159] 16 shows an embodiment illustrating such a design, where the frame element 90 is formed by a part that is structurally separate from the side wall 120 of the light channel 26.

[0160] The side wall 120 may be formed, for example, by a plate element that holds the window 80 against the transmitted light detector 32. Alternatively, the side wall 120 may have no structural function and may be formed, for example, by a foil element, in particular a highly reflective foil element. In another embodiment, the side wall 120 may be completely eliminated, in which case the lateral boundaries of the light channel 26 are formed by the frame element 90, which in turn may form part of the housing for other sensors and / or other functional elements of the device.

[0161] <Notes> As mentioned above, light sources 30a-30c can each include several light emitters, e.g., several light emitters of different wavelengths, to perform measurements in different spectral regions. Similarly, light detectors 32a-32c can each include several light sensors sensitive to different spectral regions.

[0162] The light sources 30a-30c can include LEDs, for example, each of the light sources can include several LEDs of different colors.

[0163] The photodetectors 32a-32c may include, for example, photodiodes.

[0164] In the above embodiment, the light sources 30a-30c and light detectors 32a-32c are arranged on the carrier plates 34a, 34b at the first and second peripheral sides 20a, 20b. However, alternatively, some of them may be arranged on the third and / or fourth peripheral sides 20c, 20d, for example.

[0165] In the illustrated embodiment, for example embodiment 1, the window element 15 and the measurement window 80 have the same spatial extent along the direction X.

[0166] However, in any of the above embodiments, the window element 15 can have a larger spatial extent along direction X than the measurement window 80. This is shown in FIG. 10, where the frame element 90 is obscured by the window element 15. However, even in this case, the frame element 90 is still adjacent to the measurement window 80 when viewed along direction X. (The extent of the measurement window 80 along direction X is shown by the dotted line in FIG. 10.)

[0167] As mentioned above, the second sub-body 14b forms a frame element 90, which may be coated with a surface layer 91. The surface layer allows for reduced reflection at the frame element 90 while still allowing the second sub-body 14b to be highly reflective. In other words, the surface layer allows for low reflection on the frame element while at the same time allowing high reflection within the light channels 26a-26f due to the high reflectivity of the second sub-body 14b.

[0168] While what has been shown and described are the presently preferred embodiments of the invention, it is to be expressly understood that the invention is not limited thereto and may be variously embodied and carried out in other forms within the scope of the appended claims.

Claims

1. 1. An optical sensor device for detecting defects in an elongated woven object (16), comprising: A support body (14); A measurement chamber (10) for receiving an elongated woven object (16) traveling along a direction X, comprising: - open at opposite inlet (22a) and outlet (22b) sides along the direction X, and - along a direction Y transverse to the direction X, the support body (14) is bounded on a first side (24a) and a second side (24c); a measurement chamber (10); at least one measurement window (80) arranged on the first side (24a), the support body (14) having a frame element (90) adjacent to the measurement window (80) along the direction X; An optical transmission sensor, a transmitted light source arranged to send light through the measurement chamber (10), and a measurement chamber (10) and a transmitted light detector arranged to receive light from the transmitted light source after traversing the window (80), the measurement chamber (10) being arranged between the transmitted light source and the transmitted light detector; an optical transmission sensor; An optical reflective sensor, a reflected light source arranged to deliver light into the measurement chamber (10); and a reflected light detector arranged to receive light from the transmitted light source after it has been reflected within the measurement chamber (10); an optical reflective sensor comprising: Equipped with The reflected light source and the reflected light detector are both arranged on the second side (24c); and The reflected light source is positioned to illuminate at least an illuminated portion (95) of the frame element (90), and the reflected light detector is positioned to receive light from the illuminated portion (95). Optical sensor device.

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

3. 3. The optical sensor device according to claim 1 or 2, wherein the frame element (90) has a reflectivity of at most 80%, in particular at most 50%, more particularly at most 20% for the emission spectrum of the reflected light source.

4. 4. Optical sensor device according to any one of claims 1 to 3, wherein the average reflectivity of the frame elements for the spectral range from 400 nm to 780 nm is at most 80%, in particular at most 50%, more particularly at most 20%.

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

6. 6. The optical sensor device according to claim 1, wherein the frame element (90) comprises a bulk material and a surface layer (91), the surface layer (91) having an average reflectivity of at most 80%, in particular at most 50%, more particularly at most 20% for the emission spectrum of the reflected light source.

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

8. Optical sensor device according to any one of the preceding claims, wherein the average reflectivity of the frame element (90) for the emission spectrum of the reflected light source is at least 20%.

9. The optical sensor device 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; and A2 is the amount of light received by the reflected light detector from the reflected light source through the illuminated area 95, integrated over the emission spectrum of the reflected light source, when the illuminated area 95 is a Lambertian reflector. given that, A1 is smaller than A2 / 2 The optical sensor device according to any one of claims 1 to 8, which is designed so that

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

11. Optical sensor device according to any one of the preceding claims, wherein the frame element (90) has a width in the direction X of at most 1.5 mm, in particular at most 0.5 mm.

12. 12. The optical sensor according to claim 1, wherein at least one of the frame elements (90) has an inclined surface (110) facing the measurement chamber (10), the inclined surface (110) being positioned to be illuminated by a reflected light source, in particular by at least one of the light sources, and the inclined surface (110) is not perpendicular to the direction Y, in particular forms an angle of 2 to 88 degrees with the direction Y, more particularly forms an angle of 10 to 70 degrees with the direction Y.

13. 13. 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. 14. The optical sensor according to claim 12 or 13, wherein the inclined surface (110) is non-parallel to a surface (80a) of the window (80) facing the measurement chamber (10).

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

16. 16. The optical sensor according to claim 1, wherein the optical axis of the reflective sensor extends along the direction Y and / or the surface (80a) of the window (80) facing the measurement chamber (10) is perpendicular to the optical axis of the reflective sensor.

17. The illuminated portion (95) is at least partially specularly reflective and the minimum angle (γ) between n-x and ny is at least 20°, in particular at least 40°, and the vectors n, x, and y are x is a unit vector extending along the direction from the illuminated portion (95) to the reflected light source (130); y is a unit vector extending along the direction from the illuminated portion (95) to the reflected light receiver (132), and n is the unit vector of the surface normal of the irradiated part (95) The optical sensor according to any one of claims 1 to 16, wherein:

18. the optical reflective sensor comprises at least two, in particular at least three, reflective light sources with different emission spectra, in particular non-overlapping emission spectra, or The optical reflectance sensor comprises at least one reflected light source having a FWHM spectral width of at least 200 nm; An optical sensor device according to any one of claims 1 to 17.

19. 19. An optical sensor device as claimed in any one of claims 1 to 18, wherein the support body (14) forms walls of channels (26a-26f) extending between the chamber (10) and at least some of the light source and the light detector, and the reflectivity of the walls for the emission spectrum of the reflected light source is higher than the reflectivity of the frame element (90) for the emission spectrum of the reflected light source.

20. 20. The optical sensor of claim 19, wherein the reflectivity of the wall is at least two times greater than the reflectivity of the frame element (90).

21. 21. The optical sensor of claim 1, wherein at least one of the frame elements is formed by an inner part (90a) adjacent to the measurement window (80) and an outer part (90b) adjacent to the inner part (90a), the inner part (90a) having a higher reflectivity than the outer part (90b).

22. Use of an optical sensor device according to any one of claims 1 to 21 for carrying out measurements on an elongated woven object (16) having an average reflectance of at most 80%, in particular at most 50%, more particularly at most 20% for the emission spectrum of a reflected light source.

23. 23. Use of an optical sensor device as claimed in claim 22, wherein the elongated woven object (16) has an average reflectivity of at most 80%, in particular at most 50%, more particularly at most 20% for the emission spectrum of any one of the reflected light sources of the optical reflection sensor.

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