DE102023113154A1 - Device and method for detecting foreign bodies in a material flow of poly- and/or monocrystalline silicon - Google Patents

Abstract

A device (1) enables detection of foreign bodies (2) in a material flow (3) made of polycrystalline and/or monocrystalline silicon (4). The device (1) comprises an optoelectronic recording system (5) which is designed to record images of the material flow (3). A detection device (6) is designed to detect foreign bodies (2) in the material flow (3) based on the recorded images. The optoelectronic recording system (5) comprises at least one of the following devices: a) an IR image recording device (7) which comprises at least one hyperspectral camera (8) which is designed to take images of the material flow (3) in the IR range; b) a VIS image recording device (10) which comprises at least one digital camera (11) which is designed to take images of the material flow (3) in the VIS range.

Description

The invention relates to a device and a method for detecting foreign bodies in a material flow made of poly- and/or monocrystalline silicon.

In the semiconductor industry, silicon is an important raw material for producing integrated circuits. These integrated circuits are built on a wafer, which is often made of monocrystalline silicon. The monocrystalline silicon can be produced, for example, using a crucible pulling process (e.g. Czochralski process). A crucible contains purified and melted silicon (polycrystalline and/or monocrystalline silicon), with a seed crystal arranged on a metal rod dipping into the melt. Monocrystalline silicon is deposited around the seed crystal, with the metal rod slowly being pulled upwards out of the melt, so that a crystal column known as an ingot is formed. The crystal column consists of monocrystalline silicon. The crystal column is then sawn into individual wafers. The crucible itself can be filled with polycrystalline silicon, which is produced, for example, using the Siemens process. Monocrystalline silicon, which is left over when the wafers are cut to size, for example, can also be added to the crucible. The ingot has a round cross-section, whereas wafers used in solar cells usually have a rectangular cross-section, which is created by cutting a round wafer to size. The crucible must have a high bulk density and is therefore filled with polycrystalline and/or monocrystalline silicon of different fractions, i.e. sizes, with pieces that are too small or too large having a negative effect on the melting behavior in the crucible. Therefore, the polycrystalline and/or monocrystalline silicon is broken into smaller fractions using a crusher before being filled into the crucible, and these fractions are then classified, i.e. sorted according to their size.

Foreign bodies that enter the crucible can cause significant damage because they contaminate the ingot and the wafer produced from the ingot cannot be reused.

It is therefore the object of the present invention to provide a device and a method with which a reliable detection of foreign bodies in a material flow is possible in order to ensure that the melting crucible is only filled with poly- and/or monocrystalline silicon.

The object is achieved by the device for detecting foreign bodies in a material flow made of polycrystalline and/or monocrystalline silicon according to claim 1 and by the method for detecting these foreign bodies according to claim 16. Advantageous further developments of the device can be found in claims 2 to 15.

The device according to the invention is used to detect foreign bodies in a material flow made of polycrystalline and/or monocrystalline silicon. A “foreign body” is understood in particular to mean anything that is not polycrystalline and/or monocrystalline silicon. In particular, this includes metals other than polycrystalline and/or monocrystalline silicon and/or plastics. The device comprises an optoelectronic recording system which is designed to record images of the material flow. The device also comprises a detection device which is designed to detect foreign bodies in the material flow based on the recorded images. This is achieved in particular by digital image processing. The detection device is preferably designed to examine each image individually for a foreign body. The optoelectronic recording system comprises at least one of the following devices for this purpose. The optoelectronic recording system can have an IR image recording device. The IR image recording device comprises at least one hyperspectral camera. The hyperspectral camera is designed to take images of the material flow in the IR range. Additionally or alternatively, the optoelectronic recording system has a VIS image recording device. The VIS image recording device preferably comprises at least one digital camera. The digital camera is designed to take pictures of the material flow in the VIS area.

It is particularly advantageous that an optoelectronic recording system is directed at the material flow, which is designed to take images in the IR range and/or VIS range. Depending on the structure of the entire system, which for example also has a crusher to break polycrystalline and/or monocrystalline silicon into smaller pieces that can then form the material flow, the IR image recording device and/or the VIS image recording device can be used. If the entire system does not contain any plastics from which, for example, separating edges can be formed that can come into contact with the material flow, then only the use of an IR image recording device may be sufficient. If, on the other hand, it is impossible for other metals to get into the material flow, then the use of a VIS image recording device may be sufficient. be sufficient. By using the optoelectronic recording system according to the invention, foreign bodies can therefore be reliably detected, thereby ensuring that only polycrystalline and/or monocrystalline silicon reaches the melting crucible.

In an advantageous further development, the optoelectronic recording system includes both the IR image recording device and the VIS image recording device. This further increases the probability that foreign bodies made of different materials can be reliably detected.

In an advantageous development, the at least one hyperspectral camera of the IR image recording device is designed to take images in the IR range. The wavelength range is greater than 800 nm, 900 nm or 950 nm and less than 1800 nm or 1700 nm. The hyperspectral camera can, for example, be designed to take images in a broader spectrum, which for example covers several 100 nm. In contrast, the hyperspectral camera can also be designed to take images in a narrower spectrum, which for example is less than 100 nm. Additionally or alternatively, the at least one digital camera of the VIS image recording device is designed to take images in the range visible to humans, in particular in a wavelength range that is greater than 400 nm and less than 750 nm. The digital camera can, for example, be designed to take images in a broader spectrum, which for example covers several 100 nm. On the other hand, the digital camera can also be designed to take pictures in a narrower spectrum, which is, for example, smaller than 100 nm. By taking the pictures in different wavelength ranges, different types of solids, such as plastics and metals, can be reliably detected.

In an advantageous development, the images taken by the IR image recording device and the images taken by the VIS image recording device are free of overlaps. This means that the image of the IR image recording device, which is recorded at the same time as the image of the VIS image recording device, shows a different part of the material flow. The images can also be recorded partially overlapping, predominantly overlapping or completely overlapping.

In an advantageous further development, the number of images that the IR image recording device takes in a certain time is constant or dependent on the speed of the material flow. In addition or alternatively, the number of images that the VIS image recording device takes in a certain time is constant or dependent on the speed of the material flow. If the material flow moves faster, more images can be taken than if the material flow moves more slowly.

In an advantageous further development, the VIS image recording device takes more images per unit of time than the IR image recording device. In addition or alternatively, the VIS image recording device can also take the same number of images per unit of time as the IR image recording device. In addition or alternatively, the VIS image recording device can also take fewer images per unit of time than the IR image recording device.

In an advantageous further development, the optoelectronic recording system and thus the IR image recording device and the VIS image recording device are designed to continuously take pictures of the material flow. Preferably, more than 20, 30, 40, 50, 70, 90, 120, 150, 180 or more than 200 images are taken per second.

The IR image recording device and/or the VIS image recording device are directed at the material flow. In an advantageous development, it is conceivable that, for example, via an input unit (e.g. keyboard, mouse and/or touchscreen), at least one window or mask can be defined in which the detection device searches for foreign bodies. Such a window or mask ensures that not the entire image recorded by the optoelectronic recording system is searched for foreign bodies, but only the area within the window or mask. This means that the optoelectronic recording system does not have to be installed at a millimeter-precise distance from the material flow, because the recording of stationary elements in the images can be hidden for further detection by defining the windows or masks. Furthermore, the processing speed can be increased because the entire image no longer has to be searched for a foreign body.

In an advantageous development, a transport arrangement is provided. The transport arrangement is designed to transport the material flow of polycrystalline and/or monocrystalline silicon. The transport arrangement is a conveyor belt, a vibrating conveyor or a chute.

The material flow moves past the optoelectronic recording system. In an advantageous further development, this can be done by the transport arrangement. The material The material stream can also be in free fall when it moves past the optoelectronic recording system. Preferably, however, the material stream is in motion when the optoelectronic recording system, i.e. the IR image recording device and the VIS image recording device, takes the images.

In an advantageous further development, the IR image recording device is a line camera or an area camera. In addition or alternatively, the VIS image recording device is a line camera or an area camera.

In an advantageous development, the detection device is designed to examine the next image recorded by the optoelectronic recording system in its entirety or specifically at the image section where the foreign body detected in the previous image was detected if the detection device detects a foreign body in a recorded image of the optoelectronic recording system. If the foreign body is also detected in a second image, preferably one recorded directly afterwards or in more than two images, it can be decided overall that a foreign body has been detected and a detection error can be ruled out. This prevents polycrystalline and/or monocrystalline silicon from being accidentally detected as a foreign body and sorted out. The detection device can optionally also be designed to use a different algorithm, which is, for example, more computationally intensive, for the next image or image section.

In an advantageous development, the optoelectronic recording system also includes a calibration device. This calibration device can, for example, include a pattern that is present on every image that the VIS image recording device takes. For example, the pattern can be a QR code. If the pattern is correctly recognized by the detection device on every image, it can be concluded that the VIS image recording device is functioning properly. In addition or alternatively, the calibration device can include a heat source. The heat source can, for example, be a resistor or a Peltier element that is visible on every image that the IR image recording device takes. If the heat source is correctly recognized by the detection device on every image, it can be concluded that the IR image recording device is functioning properly.

In an advantageous development, the IR image recording device and the VIS image recording device are arranged and designed to take images of the material flow on the transport arrangement. Alternatively, the IR image recording device is arranged and designed to take images of the material flow on the transport arrangement. The VIS image recording device is arranged and designed to take images of the material flow in free fall after the transport arrangement. Alternatively, the VIS image recording device is arranged and designed to take images of the material flow on the transport arrangement and the IR image recording device is arranged and designed to take images of the material flow in free fall after the transport arrangement. Alternatively, the IR image recording device and the VIS image recording device are arranged and designed to take images of the material flow in free fall after the transport arrangement, wherein the IR image recording device is arranged closer to the transport arrangement than the VIS image recording device.

In an advantageous further development, the detection device is designed to stop the transport arrangement if a foreign body is detected in the material flow. This foreign body can then be removed by the operating personnel. Optionally, the use of a marking system that marks the foreign body is possible. The marking system can, for example, be a light source that throws a (e.g. bundled) light onto the foreign body so that the operating personnel can immediately detect it and remove it as quickly as possible. After the foreign body has been removed, which can optionally be detected by the detection device, the transport arrangement can be started again.

In an advantageous development, the transport arrangement comprises a separation unit, in particular in the form of a flap or a slide. The detection device is designed to control the separation unit in such a way that it removes a foreign body detected in the material flow from the material flow. A flap allows in particular the corresponding part of the material flow which contains the foreign body, preferably only the foreign body, to fall out of the material flow, in particular following gravity, downwards. Such a "discharge" would preferably take place vertically. A slide, on the other hand, can be designed to preferably only press the foreign body out of the material flow, or to direct a part of the material flow which contains the foreign body out of the material flow. Such a "discharge" would preferably take place horizontally.

In an advantageous development, at least one blow-out device is provided. The detection device is designed to control the at least one blow-out device in such a way that it blows a foreign body detected in the material flow out of the material flow. The at least one blow-out device is preferably arranged in such a way that the foreign body can be blown out of the material flow in the free fall of the material flow.

In an advantageous development, the VIS image recording device comprises a light device, wherein the light device and the digital camera are arranged on different sides of the material flow, whereby the VIS image recording device can be operated in the transmitted light method. The light device is designed to generate light which is in the wavelength range for the VIS image recording device. The light generated can be broadband or narrowband, e.g. monochromatic.

In an advantageous development, the light device is arranged under a transparent surface of the transport arrangement over which the material flow can be moved. The transparent surface can consist of quartz glass or include such, for example. This allows a compact structure of the device to be realized.

In an advantageous further development, the detection device is designed to detect transparent or semi-transparent foreign bodies, such as plastics, based on the images from the VIS image recording device. The detection rate can be further increased by using a corresponding light device, as described above.

In an advantageous development, the IR image recording device comprises a light unit, wherein the light unit and the hyperspectral camera are arranged on the same side of the material flow, whereby the IR image recording device can be operated using the incident light method. The light unit is designed to generate light which is in the wavelength range for the IR image recording device. The light generated can be broadband or narrowband, e.g. monochromatic.

In an advantageous further development, the detection device is designed to detect foreign bodies made of a metal other than polycrystalline and/or monocrystalline silicon in the material flow based on the images of the IR image recording device.

In an advantageous development, the IR image recording device comprises a background arrangement, wherein the background arrangement and the hyperspectral camera are arranged on different sides of the material flow, so that the hyperspectral camera is designed to record images of the material flow in front of the background arrangement. The background arrangement comprises a material which either has an absorbing property for light in the IR range of the hyperspectral camera or consists of or comprises polycrystalline and/or monocrystalline silicon. This makes it possible to achieve particularly good detection results. The background arrangement can consist of or comprise PTFE (polytetrafluoroethylene). A rubber can also be used.

In an advantageous further development, the background arrangement is a surface of the transport arrangement on which the material flow of polycrystalline and/or monocrystalline silicon is moved. In principle, the background arrangement can be the conveyor belt and move with it. Alternatively, the background arrangement can also be a wall in front of which the material flow of polycrystalline and/or monocrystalline silicon passes, i.e. falls down.

The method according to the invention is used to detect foreign bodies in a material flow made of polycrystalline and/or monocrystalline silicon. In a first method step, images of the material flow are recorded using an optoelectronic recording system. The optoelectronic recording system has an IR image recording device that includes at least one hyperspectral camera designed to take images of the material flow in the IR range. Additionally or alternatively, the optoelectronic recording system has a VIS image recording device that includes at least one digital camera designed to take images of the material flow in the VIS range. In a second method step, foreign bodies in the material flow are detected using the recorded images using a detection device.

• 1, 2: verschiedene Ausführungsbeispiele der erfindungsgemäßen Vorrichtung, wobei Fremdkörper in einem Materialstrom aus poly- und/oder monokristallinem Silizium mittels eines optoelektronischen Aufnahmesystems und einer Detektionseinrichtung detektiert und im Anschluss ausgeblasen werden,
• 3: ein weiteres Ausführungsbeispiel der erfindungsgemäßen Vorrichtung, wobei Fremdkörper im Materialstrom aus poly- und/oder monokristallinem Silizium über eine Klappe in einer Transportanordnung ausgesondert bzw. ausgeblasen werden; und
• 4: ein Flussdiagramm eines Verfahrens zur Erkennung von Fremdkörpern in einem Materialstrom aus poly- und/oder monokristallinem Silizium.

The invention is described below purely by way of example with reference to the drawings.

• 1 , 2 : various embodiments of the device according to the invention, wherein foreign bodies in a material flow of poly- and/or monocrystalline silicon are detected by means of an optoelectronic recording system and a detection device and are subsequently blown out,
• 3 : a further embodiment of the device according to the invention, wherein foreign bodies in the material flow of poly- and/or monocrystalline silicon are separated or blown out via a flap in a transport arrangement; and
• 4 : a flow chart of a method for detecting foreign bodies in a material stream of poly- and/or monocrystalline silicon.

1 shows a first embodiment of the device 1 according to the invention, which enables detection of foreign bodies 2 in a material flow 3 made of polycrystalline and/or monocrystalline silicon 4. The device 1 comprises an optoelectronic recording system 5. The optoelectronic recording system 5 is designed to take images of the material flow 3. The device 1 further comprises a detection device 6, which is designed to detect foreign bodies 2 in the material flow 3 based on the recorded images. The detection device 6 can comprise a processor, microcontroller and/or FPGA. In particular, the detection device 6 is designed to execute algorithms for image processing in order to detect foreign bodies 2 in the recorded images of the material flow 3. Starting from the detection device 6, dotted connections are shown via which data can be transmitted.

In the first embodiment of 1 the optoelectronic recording system 5 has an IR image recording device 7, which comprises at least one hyperspectral camera 8, which is designed to take images of the material flow 3 in the IR range. The IR image recording device 7 preferably comprises a background arrangement 9, wherein the background arrangement 9 and the hyperspectral camera 8 are arranged on different sides of the material flow 3, so that the hyperspectral camera 8 is designed to take images of the material flow 3 in front of the background arrangement 9. The background arrangement 9 is a vertical wall in this embodiment. The background arrangement 9 comprises a material which has an absorbing property for light in the IR range of the hyperspectral camera 8 or consists of or comprises poly- and/or monocrystalline silicon 4.

The optoelectronic recording system 5 further comprises a VIS image recording device 10, which comprises at least one digital camera 11, which is designed to take images of the material flow 3 in the VIS area. The VIS image recording device 10 comprises a light device 12, wherein the light device 12 and the digital camera 11 are arranged on different sides of the material flow 3, whereby the VIS image recording device 10 can be operated in the transmitted light method.

The detection device 6 is designed to detect foreign bodies 2 made of a metal other than polycrystalline and/or monocrystalline silicon 4 based on the images of the IR image recording device 7. It is also possible to detect opaque bodies that are not polycrystalline and/or monocrystalline silicon 4. The detection device 6 is also designed to detect transparent or semi-transparent foreign bodies 2, such as plastics, based on the images of the VIS image recording device 10.

The device 1 further comprises a blow-out device 13. The detection device 6 is designed to control the blow-out device 13 in such a way that it blows a foreign body 2 detected in the material flow 3 out of the material flow 3. The blow-out device 13 can comprise one or more nozzles for this purpose. When using several nozzles, these are preferably arranged along a plane. The blow-out device 13 is arranged, based on the direction of movement of the material flow 3, after the IR image recording device 7 and after the VIS image recording device 10. The device 1 further comprises a separating unit 14 with a separating edge 15. The separating unit 14 in this embodiment is n-corner-shaped in cross section, in particular triangular. The blow-out device 13 is designed to blow foreign bodies 2 over the separation edge 15 into a different region of the separation unit 14, compared to the region into which the poly- and/or monocrystalline silicon 4 falls.

In 1 the IR image recording device 7 is arranged in front of the VIS image recording device 10 with respect to the direction of movement of the material flow 3.

The device 1 further comprises a transport arrangement 16, which in 1 is designed in the form of a conveyor belt. The transport arrangement 16 is designed to transport the material flow 3 made of poly- and/or monocrystalline silicon 4.

The IR image recording device 7 and the VIS image recording device 10 are arranged and designed to take images of the material flow 3 in free fall after the transport arrangement 16, wherein the IR image recording device 7 is arranged closer to the transport arrangement 16 than the VIS image recording device 10.

2 shows a second embodiment of the device 1 according to the invention. In contrast to the first embodiment of 1 The second embodiment comprises two blow-out devices 13 and two separation units 14. A first blow-out device 13 together with a first separation unit 14 is arranged after the IR image recording device 7. A second blow-out device 13 together with a second separation unit 14 is arranged after the VIS image recording device 10. The detection device 6 is designed to examine the images taken by the IR image recording device 7 for foreign bodies 2 and to control the first blow-out device 13, which is arranged directly after the IR image recording device 7, in such a way that it blows out a foreign body 2 detected in the images of the IR image recording device 7 from the material flow 3. The detection device 6 is further designed to examine the images taken by the VIS image recording device 10 for foreign bodies 2 and to control the second blow-out device 13, which is arranged directly after the VIS image recording device 10, in such a way that it blows out a foreign body 2 detected in the images of the VIS image recording device 10 from the material flow 3.

3 shows a third embodiment of the device 1 according to the invention. In contrast to the first and second embodiments of the device 1 according to the invention, the transport arrangement 16 is now a vibrating conveyor.

The transport arrangement 16 comprises a separation unit 17, in particular in the form of a flap. The detection device 6 is designed to control the separation unit 17 in such a way that it removes a foreign body 2 detected in the material flow 3 from the material flow 3. In this embodiment, the foreign body 2 falls out downwards and is therefore no longer in the material flow 3.

Furthermore, the IR image recording device 7 is arranged and designed to take images of the material flow 3 on the transport arrangement 16. The background arrangement 9 is part of a surface of the transport arrangement 16.

The VIS image recording device 10 is arranged and designed to take images of the material flow 3 in free fall after the transport arrangement 16.

The blow-out device 13 is arranged downstream of the VIS image recording device 10 in relation to the direction of movement of the material flow 3 and is designed to blow out foreign bodies 2 from the material flow 3 which the detection device 6 has detected in the images of the VIS image recording device 10.

4 shows a flow chart of a method for detecting foreign bodies 2 in a material flow 3 made of polycrystalline and/or monocrystalline silicon 4. In a first method step S _{1 ,} images of the material flow 3 are recorded using the optoelectronic recording system 5. The optoelectronic recording system 5 has an IR image recording device 7 which comprises at least one hyperspectral camera 8 which is designed to take images of the material flow 3 in the IR range. Additionally or alternatively, the optoelectronic recording system 5 has a VIS image recording device 10 which comprises at least one digital camera 11 which is designed to take images of the material flow 3 in the VIS range. In a second method step S _{2 ,} foreign bodies 2 in the material flow 3 are detected using the detection device 6 on the basis of the recorded images.

The invention is not limited to the embodiments described. Within the scope of the invention, all described and/or drawn features can be combined with one another as desired.

list of reference symbols

1

device

2

foreign body

3

material flow

4

poly- and/or monocrystalline silicon

5

optoelectronic recording system

6

detection device

7

IR image recording device

8

hyperspectral camera

9

background arrangement

10

VIS image recording device

11

digital camera

12

lighting system

13

blow-out device

14

separation unit

15

separating edge

16

transport arrangement

17

separation unit

S1, S2

procedural steps

Claims (16)

Device (1) which enables detection of foreign bodies (2) in a material flow (3) made of polycrystalline and/or monocrystalline silicon (4), the device (1) comprising the following features: - an optoelectronic recording system (5) which is designed to record images of the material flow (3); - a detection device (6) which is designed to detect foreign bodies (2) in the material flow (3) based on the recorded images; - the optoelectronic recording system (5) comprises at least one of the following devices: a) an IR image recording device (7) which comprises at least one hyperspectral camera (8) which is designed to take images of the material flow (3) in the IR range; b) a VIS image recording device (10) which comprises at least one digital camera (11) which is designed to take images of the material flow (3) in the VIS range. Device (1) according to claim 1 , characterized by the following feature: - the optoelectronic recording system (5) comprises both the IR image recording device (7) and the VIS image recording device (10). Device (1) according to claim 1 or 2 , characterized by the following features: - the at least one hyperspectral camera (8) of the IR image recording device (7) is designed to take images in the IR range, in particular in a wavelength range that is greater than 800 nm, 900 nm or 950 nm and less than 1800 nm or 1700 nm; and/or - the at least one digital camera (11) of the VIS image recording device (10) is designed to take images in the range visible to humans, in particular in a wavelength range that is greater than 400 nm and less than 750 nm. Device (1) according to one of the preceding claims, characterized by the following features: - a transport arrangement (16) is provided; - the transport arrangement (16) is designed to transport the material flow (3) of polycrystalline and/or monocrystalline silicon (4); - the transport arrangement (16) is a conveyor belt, a vibrating conveyor or a chute. Device (1) according to claim 4 , characterized by the following features: - the IR image recording device (7) and the VIS image recording device (10) are arranged and designed to take images of the material flow (3) on the transport arrangement (16); or - the IR image recording device (7) is arranged and designed to take images of the material flow (3) on the transport arrangement (16) and the VIS image recording device (10) is arranged and designed to take images of the material flow (3) in free fall after the transport arrangement (16); or - the VIS image recording device (10) is arranged and designed to take images of the material flow (3) on the transport arrangement (16) and the IR image recording device (7) is arranged and designed to take images of the material flow (3) in free fall after the transport arrangement (16); or - the IR image recording device (7) and the VIS image recording device (10) are arranged and designed to take images of the material flow (3) in free fall after the transport arrangement (16), wherein the IR image recording device (7) is arranged closer to the transport arrangement (16) than the VIS image recording device (10). Device (1) according to one of the Claims 4 or 5 , characterized by the following feature: - the detection device (6) is designed to stop the transport arrangement (16) if a foreign body (2) is detected in the material flow (3). Device (1) according to one of the Claims 4 until 6 , characterized by the following features: - the transport arrangement (16) comprises a separation unit (17), in particular in the form of a flap or a slide; - the detection device (6) is designed to control the separation unit (17) in such a way that it removes a foreign body (2) detected in the material flow (3) from the material flow (3). Device (1) according to one of the preceding claims, characterized by the following features: - at least one blow-out device (13) is provided; - the detection device (6) is designed to control the at least one blow-out device (13) in such a way that it blows out a foreign body (2) detected in the material flow (3) from the material flow (3). Device (1) according to one of the preceding claims, characterized by the following feature: - the VIS image recording device (10) comprises a light device (12), wherein the light device (12) and the digital camera (11) are arranged on different sides of the material flow (3), whereby the VIS image recording device (10) can be operated in the transmitted light method. Device (1) according to claim 9 and one of the Claims 4 until 7 , characterized by the following feature: - the light device (12) is arranged under a transparent surface of the transport arrangement (16) over which the material flow (3) is movable. Device (1) according to one of the preceding claims, characterized by the following feature: - the detection device (6) is designed to detect transparent or semi-transparent foreign bodies (2), such as plastics, on the basis of the images of the VIS image recording device (10). Device (1) according to one of the preceding claims, characterized by the following feature: - the IR image recording device (7) comprises a light unit, wherein the light unit and the hyperspectral camera (8) are arranged on the same side of the material flow (3), whereby the IR image recording device () can be operated in the incident light method. Device (1) according to one of the preceding claims, characterized by the following feature: - the detection device (6) is designed to detect foreign bodies (2) made of a metal other than polycrystalline and/or monocrystalline silicon on the basis of the images of the IR image recording device (7). Device (1) according to one of the preceding claims, characterized by the following features: - the IR image recording device (7) comprises a background arrangement (9), wherein the background arrangement (9) and the hyperspectral camera (8) are arranged on different sides of the material flow (3), so that the hyperspectral camera (8) is designed to record images of the material flow (3) in front of the background arrangement (9); - the background arrangement (9) comprises a material which: a) has an absorbing property for light in the IR range of the hyperspectral camera (8); or b) consists of or comprises poly- and/or monocrystalline silicon. Device (1) according to claim 14 , characterized by the following feature: - a transport arrangement (16) is provided, wherein the background arrangement (9) is a surface of the transport arrangement (16) on which the material flow (3) of poly- and/or monocrystalline silicon (4) can be transported; or - the background arrangement (9) is designed as a wall, wherein the material flow (3) of poly- and/or monocrystalline silicon (4) falls past in front of the background arrangement (9). Method for detecting foreign bodies (2) in a material flow (3) made of polycrystalline and/or monocrystalline silicon (4), wherein the following method steps are carried out: - recording (S ₁ ) images of the material flow (3) by means of an optoelectronic recording system (5), wherein the optoelectronic recording system (5) comprises at least one of the following devices: a) an IR image recording device (7) which comprises at least one hyperspectral camera (8) which is designed to take images of the material flow (3) in the IR range; b) a VIS image recording device (10) which comprises at least one digital camera (11) which is designed to take images of the material flow (3) in the VIS range. - detecting (S ₂ ) foreign bodies (2) in the material flow (3) on the basis of the recorded images by means of a detection device (6).

Images