Patent Application
20050029469
The present application claims priority under 35 U.S.C. § 119 of European Patent Application No. 03 09 0222.5 filed Jul. 17, 2003, the disclosure of which is expressly incorporated by reference herein in its entirety.
1. Field of the Invention
The invention present invention is directed to a method for detecting foreign bodies within a continuously guided product stream that includes irradiation of the product stream with collimated irradiation light, and detection of at least a portion of the detection light emanating from the product stream by interaction with the collimated irradiation light. In this manner, the irradiation and detection take place at least partially in the same optical beam path.
Furthermore, the invention is directed to an apparatus for detecting foreign bodies within a continuously guided product stream. The apparatus includes an irradiation device for irradiation of the product stream, and a detection device for the detection of at least a portion of the detection light emanating from the product stream by interaction with the irradiation light. In this way, the irradiation device and the detection device are arranged in such a way that the optical beam paths of irradiation and detection at least partially coincide. A beam splitter for separating the irradiation light from the detection light is also included.
2. Discussion of Background Information
Methods and apparatuses of this kind are used differently in order to detect foreign bodies within a product stream and then also sort them out straightaway. In the tobacco-processing industry, the mentioned methods and apparatuses are used to detect unprocessable and/or unwanted constituents, such as e.g. foil remains, paper remains or the like, within a tobacco stream which is conveyed continuously and appropriately in planar fashion, and to separate them out of the product stream.
To detect the foreign bodies in a product stream, in particular in a tobacco stream, there are different approaches. With one known method the foreign bodies are detected with a camera. The illumination required for detection, namely, irradiation of the product stream, is effected by lamps arranged in a line, which are installed on both sides of the camera. With this method or this apparatus arrangement, the optical beam paths of the camera on the one hand and the lamps on the other hand are at an angle to each other, so that a shadow effect occurs. With foreign bodies to be measured, which may overlap each other since the tobacco stream can be transported in several planes, a shadow of an upper foreign body can be thrown over a lower foreign body, which leads to a false assessment in evaluation of the pictures taken with the camera. Thus the detection sensitivity of this method or apparatus, respectively, in the detection of foreign bodies in a tobacco stream is low.
To avoid the problem of the shadow effect, in a further known method a laser beam is passed through a static optical element and then moved transversely to the direction of transport of the product stream over the latter. This movement can be effected e.g. by a further optical element, preferably a revolving mirror, which deflects the laser beam. The laser beam is thus moved time-dependently transversely to the direction of transport of the product stream, that is, of the material to be measured, over the material to be measured. In other words, the product stream is displaced in time, that is, successively scanned by the laser beam across the whole width. The light returning from the product stream is at least partially returned in the reverse direction in the same optical axis, i.e. the optical beam path, and laterally deflected on the above-mentioned static optical element, in order then to be picked up in a detection device. A disadvantage of this method and construction is that the revolving optical element allows only a limited speed of rotation. As the product stream is transported at a high speed of transport, scanning of the product stream is possible only at intervals, usually about every 4 mm in the direction of transport of the product stream. As a result, the resolution of the image analysis and hence the detection of foreign bodies is greatly restricted. A further disadvantage lies in that the speed of rotation or circumferential speed of the revolving mirror is sufficient to lead to wear on the optical surfaces of the mirror due to particles of dust in the air. As a result, the life of the revolving mirror is limited. Moving parts are subject to wear, anyway, and thereby form a potential error source.
Therefore, the present invention is directed to a method which, in a simple and fault-free manner, provides reliable detection of foreign bodies in a product stream with high detection sensitivity. Furthermore, the invention provides a simple apparatus by which the detection of foreign bodies in a product stream is reliably guaranteed.
According to the invention, the method, in addition to the above-mentioned features, includes that the product stream is irradiated simultaneously across its whole width. The collimated irradiation light is for this purpose expanded into a fan-shaped light beam for linear illumination of the product stream. As a result, in a surprisingly simple manner, it is ensured that the product stream is covered in its whole width and tested for foreign bodies with high detection sensitivity. Due to linear irradiation, parallel and simultaneous photographing of the product stream across its whole width is possible, so that structurally elaborate devices which limit the resolution of the product stream can be dispensed with. As a result, very high detection sensitivity to foreign bodies within the product stream is ensured, even when foreign bodies in different planes overlap. Specifically, an improved resolution higher than 4 mm is ensured.
Preferably, the irradiation light is composed of several light beams having different wavelengths. As a result, depending on the number of different wavelengths of the irradiation light, the differences in the detection light can be evaluated more easily and clearly, so that the result of evaluation is improved. Foreign bodies which would not be detected if a single wavelength were used are now detectable by the step according to the invention.
In a preferred development of the method, collimated irradiation light includes visible or near infrared light is used. By this choice, in a particularly simple and precise manner the detection of reflected light at different wavelengths is possible, as irradiation takes place at a high intensity, whereby detection of the foreign bodies is effected by the contrast at the different working wavelengths. In other words, the different reflection properties of the foreign bodies on the one hand and of the product stream on the other hand, namely, e.g. the tobacco, are particularly emphasized.
In another preferred embodiment of the method, collimated irradiation light composed of infrared light is used. With this light spectrum, inter alia the measurement of water lines and other reactions occurring in the infrared light spectrum, e.g. reflection, is possible with the irradiation light. It is precisely tobacco and other plant substances that as a rule have a water content which is lacking in the most important and commonest foreign substances. Thus, in a simple manner it is possible to distinguish the foreign bodies reliably from the usable and processable product stream. The same also applies to the detection of predefined organic compounds within the product stream which have a characteristic reaction with infrared light and so are easy to detect.
Advantageously, collimated irradiation light composed of ultraviolet light is used. Thereby, a particularly high radiation intensity at the product stream and hence also at the detection device is ensured, whereby the relative sensitivity during detection is improved. In other words, in this way even minimal differences in composition of the product stream can be detected. Thus different fluorescence phenomena of the fermented tobacco and foreign bodies can be used selectively for sorting.
In a further preferred embodiment of the invention, irradiation of the product stream with light beams of different wavelength, and detection of the reflected and/or fluoresced detection light, take place at different times. With this method, also known by the name “time multiplex”, the detection of reflected and/or fluoresced light is possible with a single detection device, preferably a single camera, for the different irradiation conditions. In time multiplex measurement, the light sources are each successively switched on according to a predetermined time pattern, so that illumination is carried out at one time with one wavelength, only. Therefore, at this time, reflection can also be effected only by precisely this wavelength. Therefore, a line array which is sensitive to all the wavelengths used is sufficient. The reflection data can, therefore, be determined with a single fast camera. Furthermore, cyclic excitation and detection make it possible to dispense with optical device for wavelength selection, e.g. filters or grids, so that the method is simplified and at the same time the sensitivity of measurement is improved. In other words, by the time multiplex method, an additional measurement option, i.e., the measurement of integral signals over a wavelength range, with simultaneous assignment to the respective irradiation light, is made possible.
Furthermore, the invention provides an apparatus of the kind mentioned hereinbefore that includes, in the optical beam path of the irradiation device and in front of the beam splitter, a device for the linear expansion of a light beam. Thus, a structurally particularly simple but very precisely operating apparatus is provided. With this apparatus, in a surprisingly simple manner it is ensured that the product stream can be detected simultaneously in its whole width and tested for foreign bodies with high detection sensitivity. Due to the device arranged outside the detection light, linear irradiation and hence parallel and simultaneous photographing of the product stream across its whole width is possible, so that structurally elaborate device which limit the resolution of the product stream can be dispensed with. As a result, very high detection sensitivity to foreign bodies within the product stream is ensured, even when foreign bodies in different planes overlap.
In a preferred development of the invention, the apparatus includes at least one laser as a light source, which is constructed in such a way that it works simultaneously with several wavelengths. Thus, the structural design is further substantially simplified and allows a very small and compact overall size.
Advantageously, the irradiation light is in the visible and/or near infrared and/or infrared and/or ultraviolet spectral range. Thus, a plurality of analysis options can be produced, which can be selected according to the product to be tested and the required detection sensitivity.
The present invention is directed to a method for detecting foreign bodies within a continuously guided product stream. The method includes forming a fan-shaped light beam from collimated irradiation light, irradiating the product stream across its width with the fan-shaped light beam, and detecting at least a portion of detection light emanating from the product stream. The irradiating and detecting take place at least partially along a same optical beam path.
According to a feature of the invention, a whole width of the product stream can be simultaneously irradiated.
In accordance with another feature of the present invention, the detection light results from interaction between the product stream and the irradiation light.
Moreover, the irradiation light can be composed of a plurality of light beams having different wavelengths.
Further, the irradiation light can be composed of at least one laser beam. The at least one laser beam may include a plurality of laser beams deflected into a combined and expanded light beam.
Irradiation light can be composed of collimated light including at least one of visible light, near infrared light, infrared light, and ultraviolet light.
According to another feature, the detected light may include at least one of reflected and fluoresced detection light. The reflected detection light can be picked up at different wavelengths by different cameras. Detection of foreign bodies can be effected by contrasts at the different wavelengths. Further, the collimated irradiation light may be composed of light beams of varying wavelength, and the detecting of the at least one of reflected and fluoresced detection light can occur at different times.
In accordance with a further feature of the instant invention, the method can also include filtering the detection light.
The method can also provides that light intensity of the irradiation light may be calibrated.
According to the method, the irradiation light can be composed of a light source having at least three different wavelengths, which are described by corresponding points in an at least 3-dimensional space.
The invention is directed to an apparatus for detecting foreign bodies within a continuously guided product stream. The apparatus includes an irradiation device for irradiating the product stream with irradiation light, and a detection device for detecting at least a portion of detection light emanating from the product stream. An optical beam path from the irradiation device at least partially coincides with an optical beam path of the detection device. A beam splitter is included for separating the irradiation light from the detection light and a device for forming a fan-shaped beam from the irradiating light is provided to illuminate the product stream across its width.
In accordance with a feature of the invention, the device for forming the fan-shaped beam can include a device for linear expansion of the irradiation beam.
According to another feature of the instant invention, the device for forming the fan-shaped beam can be positioned in front of the beam splitter with respect to an irradiation direction.
In accordance with the present invention, the detection light can result from an interaction between the product stream and the irradiation light.
Further, the irradiation device can include at least one light source. The at least one light source may include a laser, and the laser can be structured to simultaneously illuminate with several wavelengths. Further, the at least one light source may include a plurality of light sources, and each of the plurality of light sources may include a laser. At least one laser may be structured to simultaneously illuminate with several wavelengths. Moreover, each light source can include an optical beam path and a beam splitter is arranged in the optical beam path of each light source.
According to the invention, the detection device can include at least one line camera. The light source may include a plurality of laser sources and the at least one line camera can include a line camera having a number of line corresponding to the number of laser sources.
The detection device can include at least one line camera, and each light source may be assigned a line camera, and each line camera may be sensitive to different spectral ranges. Further, n line cameras can be assigned to (n-1) beam splitters. The light sources may include lasers, and the at least one line camera can include a line camera with a number of lines corresponding to the number of lasers. Each line of a line camera may be sensitive to different spectral ranges.
Moreover, each light source can include an optical beam path and a line camera and at least one of an optical filter and a polarisation filter can be arranged in each optical beam path.
According to still another feature of the invention, the irradiation light may include light in at least one of the visible, near infrared, infrared, and ultraviolet spectral range.
In accordance with still yet another feature of the present invention, the apparatus can further include a reflection element located on a side of the product stream opposite an irradiated side of the product stream. The reflection element can have reflection properties that substantially match those of the product stream.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawings.
The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings:
The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied in practice.
The shown apparatus serves to detect foreign bodies within a continuously guided product stream which preferably includes tobacco.
The apparatus 10 shown in
Irradiation device 11 includes at least one light source 21. however, in the exemplary embodiment shown in
Detection device 15 includes at least one camera. However, it is noted that four cameras 30, 31, 32, and 33 are arranged in the embodiment shown in
In each optical beam path 20 of each camera 30 to 33, an optical element which is appropriately designed as a beam splitter 35, 36, and 37 is arranged. Cameras 30 and 31 have a common beam splitter 37 in the illustrated embodiment. Cameras 30 to 33 are adjustable in such a way that the line which is illuminated on product stream 13 can be imaged precisely on the line of each individual camera 30 to 33.
To show it better, apparatus 10 in
Optionally, in each optical beam path of cameras 30 to 33, an optical filter 39, 40, 41, and 42 and/or a polarisation filter can be arranged. Further, irradiation light 14 can be, e.g., in the visible and/or near infrared and/or infrared and/or ultraviolet spectral range. This essentially depends on the selected analysis of detection light 16 and is described in more detail below. In order to be able to calibrate the respective light intensity of the irradiation light 14, a reflection element with a background frequency is provided. Appropriately, the reflection properties of the reflection element correspond to those of product stream 13. Thus, the simultaneous effect is that during detection of product stream 13 there are only two reflection bodies, i.e., the tobacco as part of product stream 13, and the foreign bodies contained in product stream 13. Therefore, should a fault arise within product stream 13, this would be detected as a foreign body not because of reflection properties deviating from tobacco, but because the reflection properties of the reflection element correspond to those of product stream 13, creating the impression as if tobacco were present.
This background frequency is designed as a background roller 38 in the exemplary embodiment of
In a not-shown embodiment, apparatus 10 can also be arranged on both sides of product stream 13. In this manner, the mutually opposed apparatuses 10 must then be offset from each other in height, that is, one above the other. By such an arrangement, scanning of product stream 13 on both sides can take place, so that a higher layer thickness of product stream 13 can be detected, which in turn increases the throughput of tobacco.
The different variants of the methods proceed as follows:
For all the methods described below it is true that one or more strongly collimated light beams, e.g. laser beams, from light sources 21 to 24 are deflected via beam splitters 25 to 27 via mirror 28 and beam splitter 34 as the combined light beam 29 directed onto product stream 13. Light beam 29, however, is expanded in optical beam path 19 by beam expander 18 into fan-shaped light beam 29, so that light beam 29 on product stream 13 describes a line across the whole width of the product stream 13. In other words, the light beam 29 is expanded in one axis.
For the method described with the aid of
In another embodiment, one or more light sources 21 to 24 can operate in the infrared spectral range, i.e., in the range of water lines. As plant material to be measured, the material, which includes tobacco, basically has a measurable water content. However, as most serious foreign bodies do not have a water content, these foreign bodies can easily be distinguished from the actual material to be processed. For this, product stream 13 is, as already mentioned for the other practical example, irradiated with the infrared light. Reflected detection light 16 is picked up by one or more cameras 30 to 33 and evaluated on the basis of the effect of water lines.
In a further embodiment, the light generated by fluorescence is used as detection light 16 in the detection of foreign bodies. In particular, fermented tobacco fluoresces clearly when excited with ultraviolet light. The fluorescence of tobacco in the visible spectral range is still characteristic. Different foreign bodies fluoresce only weakly or with a characteristic color, so that the foreign bodies can be inferred by analysis of the fluorescence. Product stream 13 is therefore, as in the method described before, irradiated with irradiation light 14 from one or more light sources 21 to 24, in which irradiation light 14 can be in the ultraviolet spectral range. One or more cameras 30 to 33 pick up the fluorescent light, such that the fluorescent light selects suitable wavelengths by filters 39 to 42. The wavelengths are selected in such a way that foreign bodies are distinguished from the material to be measured.
In a further method according to the invention, irradiation with light of different wavelength is effected by one or more light sources 21 to 24 at different times. In other words, the different exciting wavelengths are controlled cyclically at different times. The or each camera 30 to 33 is selected with each of these excitations, wherein the or each camera 30 to 33 can pick up both reflected light and fluorescent light.
There is also the possibility of passing the reflected light or fluorescent light through suitable polarization filters which are arranged in the beam path of the detection light. The polarization filters make a distinction with respect to the direction of polarisation. Already irradiation takes place here with polarized light. The irradiation light can be polarized by suitable filters. However, alternatively, the light source itself can give off polarized light.
In analysis of detection light 16, in addition to the conventional methods of analysis an n-dimensional analysis can be made. This means that intensities of n different wavelengths are described by corresponding points in the n-dimensional space. The method of analysis is described with the aid of
It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to an exemplary embodiment, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described here in with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 03 09 0222.5 | Jul 2003 | EP | regional |
