EP2085154B1 - Method, illumination device and system for spectral-based sorting - Google Patents

Description

The invention relates to a method according to the preamble of claim 1.

The processing and sorting of bulk solids with color cameras (mainly color line cameras) is a common method. A common embodiment is in AT410847 described. Also EP 0734789A3 describes this technology. Different camera technologies are used, in particular sequential RGB (red-green-blue) color filter line scan cameras, trilinear RGB color filter line scan cameras or even 3 chip cameras. The local and temporal resolution of the systems today is at least 1000 local points and 1 kHz line rate per sensor system.

These camera technologies are also used in the recycling sector. In the case of transmitted-light sorting, mainly glass and transparent plastic products are processed. Furthermore, devices with individual optical stimulators and sensors in the NIR range are used for the sorting of non-transparent impurities such as ceramics, stones and porcelain (CSP). These have a good recognition in practice, but do not allow color sorting and have a low spatial resolution.

In the case of color camera technology, labels are a major obstacle, so that even complex mechanical methods, such as under AT503036B1 described, or wet-chemical methods are used for removal. Furthermore, previous systems in dark and thick colored glass (curved objects with many broken edges) such a low transmission that they are sorted to non-transparent Störstoffed, which produces a high scrap of material These problems present systems have a high over sorting and thus economically insufficient sorting properties A combination with NIR-based devices is not possible, because then the glass can either not be sorted by color or unwanted cycles occur in the processing process.

From the US 6 137 074 A For example, an apparatus and a method for sorting glass is known, wherein transmissions in the visible range and in the infrared range are detected.

The EP 0 727 260 A discloses a method for sorting grains using two light sources.

The WO 2007/110672 A1 relates to a study of glass, wherein a bright field recording and a dark field recording are made using light sources with different wavelengths for the two recordings.

The object of the invention is therefore to provide a method of the type mentioned above, with which the mentioned disadvantages can be avoided, with which a reliable sorting with a low rejection can be ensured by a sorting and which can be carried out easily and inexpensively.

According to the invention this is achieved by the features of claim 1.

This results in the advantage that transparent substances can be recognized and sorted despite being affixed with labels. Furthermore, even dark and thick colored glass can be reliably detected. In this case, arched objects with many breaklines, which cause a high scattering of the incident light, can be reliably detected.

By better identification of the piece goods, a better subsequent sorting can be achieved.

The invention further relates to a lighting unit with which the method according to the invention can be carried out particularly simply and to an apparatus for carrying out the method.

The dependent claims, which as well as the independent claims simultaneously form part of the description, relate to further advantageous embodiments of the invention.

• Fig. 1 eine schematische Darstellung einer Vorrichtung zur Durchführung des erfindungsgemäßen Verfahrens zum spektralbasierten Sortieren;
• Fig. 2 Transmissionskurven gegenüber der Wellenlänge;
• Fig. 3 eine schematische Darstellung einer Vorrichtung bei Verwendung eines monochromen Sensors; und
• Fig. 4 eine schematische Darstellung des Aufbaus einer vorteilhaften Ausführung einer Beleuchtungseinheit.

The invention will be described in more detail with reference to the accompanying drawings, in which only preferred embodiments are shown by way of example. Showing:

• Fig. 1 a schematic representation of an apparatus for performing the method for spectral-based sorting according to the invention;
• Fig. 2 Transmission curves versus wavelength;
• Fig. 3 a schematic representation of a device using a monochrome sensor; and
• Fig. 4 a schematic representation of the structure of an advantageous embodiment of a lighting unit.

In Fig. 1 schematically a device for the spectral-based sorting of transparent and semi-transparent bulk materials 9 is shown with one with a lighting unit 2 and a sensor 1, wherein the sensor 1 is designed to receive transmission signals. The illumination unit 2 is designed for illumination with predeterminable wavelengths λ, wherein illumination with these wavelengths λ is temporally or locally discretely feasible.

The sensor 1 may be a monochrome sensor, which may be designed in particular as a camera. In particular surface cameras or line scan cameras appear advantageous. The spatial and temporal resolution of the sensor 1 can be at least 1000 local points and at least 1 kHz line rate, with ever higher line rates are possible. For example, the line rate may be in the range of 4 to 20 kHz. With a monochrome sensor 1, a simple and reliable design of the sensor 1 can be provided.

In the space between the lighting unit 2 and the sensor 1 is provided that the material flow is performed.

An evaluation device is connected on the input side to the sensor 1 and on the output side to a sorting device, wherein the sorting device - viewed in the direction of the material flow - is subsequently arranged on the sensor 1.

In the method for the spectral-based sorting of transparent and semitransparent bulk materials 9, the bulk materials 9 are moved through in a material flow between the illumination unit 2 and the sensor 1, with the illumination unit 2, the illumination with predetermined wavelengths λ temporally or locally discretely performed, recorded with the sensor 1 transmission signals , the transmission signals evaluated and sorted the bulk materials 9 according to the evaluation.

An advantageous embodiment of the method relates to the sorting of waste glass.

The spectral properties of all materials relevant in practice are known today. Therefore, a very reliable material allocation can be made by a precise spectral measurement. In practice, this will be meaningfully limited to achieve the necessary sorting resolution. Therefore, it seems important for an evaluation and sorting on the one hand, that not only the total transmission of the material is known, but above all the absorption ratios at different wavelength ranges. Furthermore, the transmission should still be so high that a technical evaluation is possible. However, this is not or only insufficiently given in many spectral ranges with different material thicknesses and pigment concentrations. Thus, it seems appropriate to integrate spectral ranges in which a high transmission is given and also to use ranges for the assessment, where little or no transmission is given.

When lighting with the illumination unit 2, it appears advantageous if at least one wavelength λ of the illumination in the UV range, at least one wavelength 1 in the VIS range and at least one wavelength λ in the NIR range is specified. In this case, foreign substances can be reliably separated out in the case of the bulk goods 9. With a suitable choice of the wavelengths λ, it may also be possible to distinguish between two or more materials and possibly foreign substances. One possible application may be the sorting of plastics. The advantages listed below - with the exception of a complete color sorting - can be achieved in an analogous manner.

If at least three wavelengths λ are specified in the VIS range, it is easy to determine the color of the bulk goods 9 in the visible range. This seems particularly suitable for the sorting of used glass. This can be a high-resolution spectral-based Sorting method (semi) transparent bulk materials 9 is provided, in which at least five wavelength ranges are evaluated in the UV-VIS-NIR for color and material characterization. This evaluation can take place by means of the sensor 1, for example a monochrome camera, which may be a surface or a line camera, and locally or advantageously temporally pulsed monochrome light sources integrated in the illumination unit 2. At least five spectral ranges can be scanned with the sensor 1 and evaluated according to color and material criteria. The wavelengths λ are in the visible range (VIS) for the color evaluation and in the ultraviolet (UV) and near-infrared (NIR) range for material evaluation on the basis of the transmission properties of the sorting samples.

The spectral properties in the UV-VIS-NIR range of all materials relevant in practice are known today. Therefore, a very reliable material allocation can be made by a precise spectral measurement. In particular, at the wavelengths λ in the NIR range can be exploited that the color pigments of transparent samples have a smaller influence and the transmission of paper, which is a common impurity in the sorting of waste glass, is increased.

Conventional RGB cameras have no distinction between yellow and brown objects, since their spectral resolution in the spectral range is limited to two side channels, namely green and red.

Dark green shards have no transmission in the blue and red spectral range and so low in the green that they technically often have to be assigned to a nontransparent impurity. In the UV and NIR range, however, they have a high transparency so that they are distinguishable from ceramics and stones. With paper labels, the transmission in the NIR range also increases, so that even label-related shards can be detected more easily than these. In addition, the pigments of dark stained glass shards in the NIR range have a higher transmission, so that a simple assessment is also possible here. However, contaminants such as KSP and metals have no transmission in the entire spectral range. Therefore, in particular by the use of wavelengths λ in the UV, in the VIS and in the NIR range, a reliable assignment of the bulk materials 9 can take place and an efficient sorting can be achieved.

In other embodiments, it can also be provided that more than three wavelengths λ are specified in the VIS range, whereby the determination of the colors is further improved can be and especially for common colors a particularly good visibility can be ensured.

In FIG. 2 Transmission curves τ are shown with respect to the wavelength λ. For a recognition of the material properties of the objects, it is advantageous to record and evaluate at least one wavelength λ in the UV, three wavelengths λ in the visible range for the color evaluation and at least one in the NIR range. A further distinction is possible by additional wavelengths λ. Thus, an additional wavelength λ between green and red can enable a distinction between yellow and deciduous sherds.

In Fig. 2 the transmission curves τ of two different materials are shown as continuous curves over the wavelength λ. Furthermore, six vertical bars are shown, which represent possible predefinable wavelengths λ. Due to the values at these predetermined wavelengths λ, the two illustrated materials can be distinguished easily and reliably.

For certain materials, for example certain plastics, it makes sense to use more wavelengths λ in the UV or NIR range.

In one embodiment of the sorting method, a UV wavelength λ of 370 nm, visible wavelengths λ of 460 nm, 530 nm and 630 nm and an NIR wavelength λ of 940 nm are used.

It appears advantageous if the wavelengths λ are selected from the sensitivity range of camera sensors based on CMOS or CCD, whereby they are typically limited to the range from 300 nm to 1200 nm, in particular from 350 nm to 1050 nm.

In the illumination unit 2, the spectral ranges assigned to the predeterminable wavelengths λ can be spatially or temporally separated. High-power LEDs, that is to say LEDs greater than or approximately equal to 1 mm ² , which are available in the spectral range from 300 nm to 1200 nm in a central wavelength graduation of approximately 20 nm, can preferably be used as the luminous means 3.

When using a sensor 1, which is monochrome, it seems expedient to separate the spatially or temporally associated with the presettable wavelengths λ recordings. This is in FIG. 3 shown schematically, wherein different wavelengths λ are symbolized by different gray levels. The bars can be viewed both as a local and as a temporal sequence, whereby the local or temporal separation is shown symbolically.

For both options, sensor 1 offers surface-scan camera sensors. When using a line sensor, only the temporal separation appears appropriate, the monochrome lines are recorded sequentially and the monochrome signals can be superimposed line by line by interpolation.

In the area cameras, CMOS-based sensors 1 are advantageous, since the read-out areas are adjustable here and the entire sensor does not have to be read out. With today's technology, for example, a CMOS sensor with 2200x 3000 pixels can be used.

In the case of a local separation, the spectral illumination areas in the sorting system can be separated in the direction of material travel and the reception areas on the sensor 1 can be limited to these. Subsequently, a time overlay of the partial images can be made.

The more advantageous embodiment appears to be the temporal separation of the signals. LED lighting can be flashed very fast, with individual flashes of light only taking a few microseconds. Thus, sub-images of the traversing objects at different wavelengths λ can be sequentially recorded at the same location. Since the exact times of the flashes of light are known, these spectral fields can be composed in time.

For the construction of an advantageous embodiment of a lighting unit 2, the use of UV (370 nm or 405 nm), red (typically 630 nm), green (typically 530 nm) and blue (typically 460 nm) and NIR (typically 840 or 940 nm) LED Dies (typical AlGaInP and InGaN technology) proposed without color conversion layer. An advantageous arrangement is in FIG. 4 shown. In this case, the five LEDs are preferably integrated very closely together in an LED module 31. Alternatively, chip on board technology can be applied to standard, metal core or ceramic circuit boards to further increase luminance. The LED lighting units can be used single-row or multi-row lighting amplification.

An arrangement of the LEDs in the side walls 6 and mirroring of the remaining surfaces is possible.

For the glass sorting today direct lighting systems are common, which represent a bright field illumination. The proportion between direct and diffuse lighting is different. When used in the glass sorting area, broken and shaped objects are characterized, which are characterized by the following properties:

On the one hand, the shards have sharp break edges in all orientations and often have no plane-parallel surfaces in the object, but lenticular ones. Furthermore, the pigments are incorporated in the volume and the surfaces are often filled with labels or soiling.

In a bright field illumination, especially with a high direct proportion, these described properties create great problems in the evaluation of the objects. A pure dark field illumination is technically not advantageous, since a continuous adjustment of the camera is not possible here.

The lighting is designed as partial dark field lighting. A partial dark field illumination is an illumination that includes both dark field illumination and bright field illumination.

Therefore, the described arrangement is proposed, which has a high proportion of indirect lighting (dark field), by the front terminating diffuser 5 but also a smaller proportion of bright field illumination. The dark field illumination is realized in that the illumination units 2 are outside the viewing window 11 of the sensor 1 and the sensor 1 looks directly at a dark strip 4 in the illumination unit 2. The light of the LEDs is homogenized by means of specular or diffusely highly reflecting walls 6, for example anodized aluminum sheets, and conducted to the exit plane of the lighting unit 2. There, the diffuser 5 is mounted, which generates the bright field component of the lighting unit 2. This diffuser 5 is necessary in practice, since the area in which the objects move is very dirty and therefore an additional variable diffuse proportion is to be expected from the soils in each type of lighting.

Due to the scattering on the diffuser 5, the sensor 1 receives a constant amount of light. Thus, the sensor 1 can also be adjusted for a long time to the light and the color. The diffuser 5 can be covered with a cover 7, which is transparent over the entire spectral range, for protecting the lighting unit 2.

Due to the compact design of the lighting unit 2 and the efficient use of the lighting elements 3, a passive cooling 9 can be realized via heat-conducting mounting materials.

The viewing window 11 of the sensor 1 can be aligned with a viewing area 4 of the lighting unit 2, wherein all the lighting elements 3 of the lighting unit 2 are arranged outside the viewing area 4 and wherein the bright field component of the partial dark field illumination is effected by a passive light-diffusing element 5 on the side facing the sensor 1 side of the illumination unit 2.

A particularly advantageous embodiment of the lighting unit 2 comprises a plurality of lighting elements 3, the viewing area 4 for interacting with the viewing window 11 of the sensor 1, wherein all lighting elements 3 are arranged outside the field of view 4, and the passive light-diffusing element 5 for forming the bright field component of Teildunkelfeldbeleuchtung. In this case, the sensor 1 does not see the lighting elements 3 directly in the beam path, but a direct illumination arises only through the passive diffuser 5.

The light-diffusing element 5 may be formed of glass or plastic. In this case, the light-diffusing element 5 is preferably surface-or volume-frosted and has only low absorption losses.

The space between the light-emitting elements 3 and the light-diffusing element 5 may be bounded by lateral boundaries 6, wherein the lateral boundaries 6 are formed mirror-like or diffuse highly reflective, whereby a good homogenization of the dark field illumination can be achieved. Furthermore, it can be ensured that a high proportion of the light energy reaches the sensor 1, whereby the required power of the lighting unit 2 kept as low as possible and a high efficiency can be achieved.

With ever shorter recording times of the sensor 1, in particular at higher line rates, shorter and shorter exposure times and thus higher luminances are required. For example, luminances for systems with 4-20 kHz line rate with fluorescent tubes or thermal light sources are difficult to achieve.

For the light-emitting elements 3, LEDs can be used, whereby a high luminance can be provided. An LED based lighting system will be installed in AT004889U1 described.

An embodiment for increasing the light intensity is in the DE202004019684U1 described.

Systems with LEDs can work with standard LEDs, with the standard being the 0.3 mm die technology, beam-focusing optics and, above all, the white light generation with blue LED die and combined yellow fluorescent dye (white light LEDs). The luminance can be increased by using high power LEDs (1mm LED die or larger). Due to the color conversion, this type of lighting requires General but active cooling, which is accomplished for example with water cooling.

It can be provided that monochrome light flashes are generated with the illumination unit 2, wherein sequentially light flashes are generated in all predeterminable wavelengths λ. In this case, a predetermined sequence of the predefinable wavelengths can be repeated in an endless loop during the implementation of the method.

Labels are thus illuminated indirectly. Fracture edges and lenticular shapes have a significantly increased signal intensity due to the indirect "partial dark field illumination". Therefore, paper is different from non-transparent materials (ceramics and stones). Thin porcelain, which may be somewhat white in volume and semitransparent, falls into its own color intensity range. In connection with an object evaluation, a distinction can be made in this way. Straight labels on colored glass are recognizable by the combination of white paper with the volume color pigments. Thick, dark shards of color result in very intense color signals due to the high proportion of dark field illumination.

The color and material-based evaluation of the very intense by the partial dark field illumination transmission signals thus allows a very effective and accurate sorting of semitransparent bulk materials.

Further embodiments according to the invention have only a part of the features described, wherein each feature combination, in particular also of various described embodiments, can be provided.

Claims (14)

1. A method for spectral-based sorting of transparent and semi-transparent bulk goods (9), with the bulk goods (9) being moved in a stream of material between an illumination unit (2) and a sensor (1), with an illumination being performed with the illumination unit (2) with predeterminable wavelengths (λ) in a temporally or locally discrete manner, with transmission signals being received by the sensor (I), with the transmission signals being evaluated and the bulk goods (9) being sorted according to the evaluation, characterized in that the illumination is arranged as a partial dark field illumination.
2. A method according to claim 1, characterized in that at least one wavelength (λ) of the illumination is predetermined in the UV range, at least one wavelength (λ) of the illumination in the VIS range, and at least one wavelength (λ) in the NIR range.
3. A method according to claim 1 or 2, characterized in that at least three wavelengths (λ) of the illumination are predetermined in the VIS range.
4. A method according to claim 1, 2 or 3, characterized in that the inspection window (II) of the sensor (1) is aligned to a visible zone (4) of the illumination unit (2), that all lighting elements (3) of the illumination unit (2) are arranged outside of the visible zone (4), and that a bright field portion of the partial dark field illumination is effected by a passive light-diffusing element (5) on the side of the illumination unit (2) facing the sensor (1).
5. A method according to one of the claims 1 to 4, characterized in that a monochrome sensor is used as a sensor (1).
6. A method according to one of the claims 1 to 5, characterized in that monochrome light flashes are generated with the illumination unit (2), with light flashes being generated sequentially in all of the predeterminable wavelengths (λ).
7. An illumination unit (2) for a method according to one of the claims 1 to 6 for cooperation with an optical sensor (1), comprising several lighting elements (3) and a visible zone (4) for cooperation with the inspection window (11) of the sensor (1), characterized in that all lighting elements (3) are arranged outside of the visible zone (4), and that the illumination unit (2) for forming a partial dark field illumination comprises a passive light-diffusing element (5) for forming a bright field portion.
8. An illumination unit according to claim 7, characterized in that the light-diffusing element (5) made of glass or plastic is arranged in a surface or volume satin-frosted manner with low absorption losses.
9. An illumination unit according to claim 7 or 8, characterized in that the space between the lighting elements (3) and the light-diffusing element (5) is delimited by lateral boundaries (6), and that the lateral boundaries (6) are arranged in a mirroring or diffusely highly reflective way for homogenizing the dark field illumination.
10. An illumination unit according to one of the claims 7 to 9, characterized in that it is arranged for a temporally or locally discrete illumination with predeterminable wavelengths (λ).
11. An illumination unit according to claim 10, characterized in that at least one of the predeterminable wavelengths (λ) is in the UV range, that at least one, preferably three, of the predeterminable wavelengths (λ) is in the VIS range, and that at least one of the predeterminable wavelengths (λ) is in the NIR range.
12. An illumination unit according to one of the claims 7 to 11, characterized in that the lighting elements (3) are LEDs.
13. An apparatus for spectral-based sorting of transparent and semi-transparent bulk goods (9), comprising an illumination unit (2) and a sensor (1) for recording transmission signals, characterized in that the illumination unit (2) is arranged according to one of the claims 7 to 12.
14. An apparatus according to claim 13, characterized in that the sensor (1) is a monochrome sensor.

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