WO2018041902A1

WO2018041902A1 - Device for detecting objects in a material stream

Info

Publication number: WO2018041902A1
Application number: PCT/EP2017/071782
Authority: WO
Inventors: Rainer Eixelberger; Reinhold Huber
Original assignee: Binder + Co Ag
Priority date: 2016-08-30
Filing date: 2017-08-30
Publication date: 2018-03-08
Also published as: CN208177898U; AT15723U1; DE212017000206U1

Abstract

A device for detecting objects (9) in a material stream, comprising at least - a light source (4, 5) for emitting light in a first transmission wavelength range and in a second transmission wavelength range, which differs from the first transmission wavelength range, to the material stream, - a first detector (1) for detecting, in a first detection wavelength range, reflection light, fluorescent light or transmission light of the objects, caused by light in the first transmission wavelength range, - a second detector (2) for detecting, in a second detection wavelength range, reflection light, fluorescent light or transmission light of the objects, caused by light in the second transmission wavelength range, characterised in that - the first detector (1) is connected to the light source (4) for the purpose of controlling the light intensity of the first transmission wavelength range, and/or the second detector (2) is connected to the light source (5) for the purpose of controlling the light intensity of the second transmission wavelength range. As a result, the heat developed by the light source can be reduced.

Description

Device for detecting objects in one

Materialström

FIELD OF THE INVENTION

The invention relates to a device for detecting objects in a material flow, comprising at least

a light source for emitting light in a first transmission wavelength range and in a second transmission wavelength range, which is different from the first transmission wavelength range, to the material flow,

a first detector for detecting reflection light, fluorescent light or transmission light of the objects,

caused by light in the first transmission wavelength range, in a first detection wavelength range,

a second detector for detecting reflection light, fluorescent light or transmission light of the objects,

caused by light in the second transmission wavelength range, in a second detection wavelength range.

First and second transmission wavelength range are

different in the sense that they are not identical, but can basically overlap. Also, first and second detection wavelength ranges are different in the sense that they are not identical, but they will usually not overlap.

The device is e.g. suitable for detecting waste glass in the form of cullet, if this is to be separated by color and / or for detecting other impurities, such as stones, metals or plastics, if they are to be removed from the waste glass. The

Device is also suitable for detecting various plastic or articles or pieces of plastic and then separated from each other. The invention, due to the need for two different detectors, does not relate to devices where light is emitted from one or more light sources in two or more transmit wavelength ranges, but the light of all transmit wavelength ranges is detected collectively in a detector. This is about in the US

7339660 Bl the case where the light of light-emitting diode rows 204, 206 of different colors in a common detector 400 is detected. Also, EP 2589858 AI falls into this category, where light of different wavelength

different light sources 10,20,30 to a common

Focused light beam is used, which is used for the illumination of an object, wherein an image of the object in an imaging device, ie a single detector is generated.

STATE OF THE ART

To detect objects, two different types of light are often used to produce different properties, e.g. Color and type of material to detect the objects and thus more secure to assign an object to a specific faction. In the case of infrared light as the first

Type of light or as the first transmission wavelength range and of visible light as the second type of light or as a second

Transmitting wavelength range often light sources are used, the two types of light, ie light of both wavelengths,

visible and infrared light, emitting at the same time, e.g. Halogen light sticks. So it's just a kind of

Light sources needed, which is e.g. the stocking of

Light sources for replacement easier.

But these light sources have the disadvantage that the

Intensity only for both transmission wavelength ranges can be changed together. Often, however, only one high intensity is needed for one detection wavelength range or the associated detector, while for the other

Detection wavelength range or the other detector with a lower intensity, the Auslangen could be found. Now, however, the light source must always be operated at the higher intensity, which can lead to an undesirably high heat development within the device. So be about for a sufficient intensity and

Color distribution in the visible range Halogen light rods operated at their respective power limits. This creates a high proportion of heat radiation within the

Sorting device in which the light sources and detectors are arranged. This in turn increases the risk of fire in the sorter.

Often, these light sources must be operated with DC voltage to prevent intensity fluctuations by AC.

PRESENTATION OF THE INVENTION

An object of the invention is thus to provide a

To provide detection device, which is characterized by a lower heat development, if for a

Detection wavelength range is a lower intensity than for the other detection wavelength range is sufficient.

This object is achieved with a device according to claim 1. The device for detecting objects in a material stream comprises at least

a light source for emitting light in a first transmission wavelength range and in a second transmission wavelength range, which is different from the first transmission wavelength range, to the material flow, a first detector for detecting reflection light, fluorescent light or transmission light of the objects,

caused by light in the second transmission wavelength range, in a second detection wavelength range. The device is characterized

in that the first detector is connected to the light source for controlling the light intensity of the first transmission wavelength range, and / or the second detector is connected to the light source

Light source for controlling the light intensity of the second transmission wavelength range is connected.

The light source thus emits light of a certain first transmission wavelength range, e.g. Infrared light, and a certain second transmission wavelength range, e.g. visible light. The first detector is associated with the light of the first transmission wavelength range and can only light

detect that is caused by the objects due to the light of the first transmission wavelength range. Is with the first detector, the reflection light or the

Transmitted light of the objects detected, the first detection wavelength range of the first detector is at least a portion of the first transmission wavelength range.

The light of the second transmission wavelength range is different from that of the first transmission wavelength range. That is, the two wavelength ranges are not identical, but an overlapping of the wavelength ranges is possible. If, for example, the second transmission wavelength range is to comprise only visible light, some infrared light is also emitted by some light sources, even if it is not detected by the associated second detector at all. The second detector is associated with the light of the second transmission wavelength range and can only light

detect, which is caused by the objects due to the light of the second transmission wavelength range. Is with the second detector, the reflection light or

Transmitted light of the objects detected, the second detection wavelength range of the second detector is at least a portion of the second transmission wavelength range.

In the case of fluorescent light of the objects, there is often no overlap of transmission wavelength range (e.g., UV light) and detection wavelength range (e.g., visible light).

The light source can now comprise at least one supercontinuum laser light source, which is designed to emit light in a first transmission wavelength range and in a second transmission wavelength range, which does not overlap with the first transmission wavelength range.

Supercontinuum or white laser light is laser light, which is an extremely widened optical

Owns spectrum. While laser light is usually relative

narrowband, a supercontinuum can be one

Frequency range of more than one octave.

Supercontinua can be exploited by nonlinear

Effects in the passage of laser beams through

Glass fibers are produced at high intensities, but the focus in air is already sufficient. Mostly one uses intense light pulses of femtosecond lasers. But also the use of pulses with much longer durations can show the desired broadening. In long fibers even a continuous laser operation is possible. The

However, the physical mechanisms involved and the spectral structure of the supercontinua are quite different depending on the pulse duration, dispersion and length of the fiber, etc. Supercontinuum laser light sources, with each of which light from two different wavelength ranges is introduced into a common beam path, are known in principle from the prior art. For supercontinuum laser light sources, the light intensity in the

different wavelength ranges are set independently. Thus, e.g. the light intensity for

Infrared light (first transmission wavelength range) can be set independently of that for visible light (second transmission wavelength range). It is in the

Rule simultaneously emitted light of the first transmission wavelength range and the second transmission wavelength range.

According to the invention, there are basically three possibilities:

only the first detector is connected to the light source (e.g., a supercontinuum laser light source) for control of

Light intensity of the first transmission wavelength range

connected, or

- Only the second detector is with the light source in order

Controlling the light intensity of the second transmission wavelength range connected, or

Both the first detector is connected to the light source for controlling the light intensity of the first transmission wavelength range and the second detector is connected to the light source for controlling the light intensity of the second transmission wavelength range.

As a result of the connection between the light source and the detector (s), the light intensity in the first or second transmission wavelength range can always be set so that it is sufficient for the associated detector. Thus, e.g. Too much intensity in the first transmission wavelength range can be reduced, so that the heat generated by the light source in this

Wavelength range reduced. So it is conceivable that the Detector itself can determine what intensity he needs in the individual transmission wavelength ranges.

However, as in the case of a supercontinuum laser light source, the light source does not have to have illumination units that can emit light in both transmission wavelength ranges in each case. Instead, it can also be provided that the light source both a first

Has light source for emitting light only in the first transmission wavelength range as well as a second light source for emitting light only in the second transmission wavelength range, and

- That the first detector is connected to the first light source for controlling the light intensity of the first light source, and / or the second detector is connected to the second light source for controlling the light intensity of the second light source. First and second light source can be in the operation of the device on the same side of the

Material flow of the objects are located, but also on

different sides. Regardless, first

Light source and first detector in the reflection or in the

Transmission methods work equally well - regardless of the operation of the first detector and first

Light source - second light source and second detector in

Reflection or in the transmission method work.

According to the invention there are three possibilities in the case of a first and a second light source:

- Only the first detector is with the first light source for controlling the light intensity of the first light source

connected, or

- Only the second detector is connected to the second light source for controlling the light intensity of the second light source, or

- Both the first detector is with the first light source for controlling the light intensity of the first light source connected as well as the second detector is connected to the second light source for controlling the light intensity of the second light source.

Due to the connection between the first and second light source and associated detector, the light intensity of the first and second light source can always be set so that it is sufficient for the associated detector. Thus, e.g. too great an intensity of the first light source

be reduced, so that also reduces the heat generated by the first light source. First and second light sources may have their own adjusting devices, with which the intensity of the emitted light is adjusted, most simply by changing the current supplied to the respective light source. It is therefore conceivable that the detector itself can determine which intensity of the first or second light source it requires.

On the other hand, it may also be the case that the quality of the data or images which the detectors detect can only be ascertained during the evaluation of the data or images during the image processing. In this case it can be provided that the first detector and / or the second detector is connected to the light source via an evaluation device, which is used to evaluate the signals of the first and second

Detector and for determining at least one property of the detected objects is provided. That is, the

Evaluation device determines whether the light source (s) may need to be set differently, that is, for example, with greater intensity in a transmission wavelength range

must be lit, so that an error-free evaluation of the data of the detectors is possible. Or the evaluation device determines that the intensity can be reduced in a transmission wavelength range and still the Data of the associated detector can be evaluated error-free.

Possible wavelength ranges within the meaning of the invention, both for the light source (s) (transmission wavelength ranges) and for the detectors (detection wavelength ranges), are e.g. visible light, infrared light, UV light, or a portion of said wavelength ranges, e.g. near infrared light (NIR light), or blue light.

For example, it can be provided that the first transmission wavelength range includes IR light, in particular NIR light, and the second transmit wavelength range includes visible light. In particular, the first transmission wavelength range may comprise only IR light, in particular only NIR light, and the second transmit wavelength range only visible light.

In the event that the light source is both a first

Light source for emitting light only in the first transmission wavelength range as well as a second light source for emitting light only in the second transmission wavelength range, the first light source is preferably for emitting IR light, in particular NIR light,

educated. It preferably comprises at least one

Halogen light source for emitting infrared light, e.g. a halogen flashlight.

The second light source preferably comprises at least one LED light source for emitting visible light.

The only light source (e.g., the supercontinuum laser light source), the first light source, and the second

Of course, each light source can be made up of several

similar physical units are formed, for example, from a series of several units (multiple supercontinuum laser, LED lamps, halogen lamps, ...), which are transverse to Material flow are arranged, or from several such rows.

If the first transmission wavelength range comprises infrared light, that is, if the first light source emits infrared light, it is provided that the first detector is on

Detector for infrared light, in particular NIR light, is.

For example, the first detector may comprise a spectrograph for infrared light. The first detector may be sensitive in the case of NIR light in the range of 900-2,300 nm. If the second transmission wavelength range comprises visible light, that is to say the second light source emits visible light, it is preferably provided that the second detector comprises a camera for visible light. This can be in

Range of 380-750 nm wavelength sensitive. Thus, according to the invention, outgoing light is measured in two different detectors by the same object, in particular also at the same time.

To have a sorter for sorting objects in one

Material flow depending on at least one of their

To obtain properties, there is an embodiment of

Invention in that an evaluation device is provided for evaluating the signals of the first and second detectors and for determining at least one property of

detected objects. An example of such

Sorter is a means of sorting

Plastic articles or plastic parts, e.g. according to their color.

In this case, the evaluation is usually with a discharge device for sorting objects from the

Material flow depending on their properties

connected. The discharge device can be about suction or

Have blowing nozzles to a fraction of objects with a certain property of other objects of the

Separate material flow. The discharge device is thus also part of the sorter.

An object of the invention is to integrate two different transmission wavelength ranges (e.g., two different illumination units) for a sorter. For example, one transmission wavelength range (e.g., the second light source) is specifically tailored to the needs of the visible light detector, the other transmission wavelength range (e.g., the first light source) to the

Needs of the sensor or detector for infrared light, in particular for NIR light.

Due to its own light source only for infrared light,

In particular, NIR light, and a separate light source only for visible light, the intensity of the infrared light source against a common light source for infrared and visible light can be reduced. This also reduces the red intensity from the infrared light source and the color fidelity in the visible range increases. The same applies to a light source that can serve both detection wavelength ranges and light in two

transmit the corresponding transmission wavelength range, wherein the intensity of the two transmission wavelength ranges

is independently adjustable.

A method for operating a device according to the invention may comprise

emitting a light source onto the material stream of light in a first transmission wavelength range and in a second transmission wavelength range that is different from the first transmission wavelength range,

a first detector detects in a first detection wavelength range reflection light, fluorescent light or transmission light of the objects which are illuminated by light in the first transmission wavelength range is caused,

a second detector different from the first detector in a second detection wavelength range

Reflected light, fluorescent light or transmission light of the objects, which is caused by light in the second transmission wavelength range, and

the light intensity of the first transmission wavelength range due to a connection of the first detector to the

Light source is controlled so that the light intensity is sufficient for the first detector, and / or the

Light intensity of the second transmission wavelength range due to a connection of the second detector with the

Light source is controlled so that the light intensity is sufficient for the second detector. In the following, a possible embodiment of the invention will be described in more detail with reference to the specific application. For the purpose of color sorting and foreign substance detection, non-contact measuring methods can usually be used by means of infrared and / or RGB sensors which, on the basis of the registered transmission or absorption degree, can be used on the

Material stream of directed light, a departure of certain materials / objects, such as by a distraction in for

initiate intended fractions through downstream blow-off or suction nozzles. The item to be sorted out of the mixed material flow is irradiated on a sorting belt or during a free-fall path by radiation sources and the radiation passing through or reflected by the material flow is intensity-compensated

Recorded detection device according to the invention and compared with reference values. An evaluation device in data connection with the detection device subsequently assumes an assignment of the piece goods to a respective one

Fraction before and causes - in the sense of a control unit - a detection of objects identified by pick-up or a deflection into predetermined containers by means of compressed air ^¬ or suction nozzles.

The use of visible light or IR light also makes it possible to detect the image of an object taken by means of detectors, which usually contain a CCD camera

To process image processing and so about to recognize the shape of an object. The detectors have different sensitivities for different wavelengths (ranges). In an RGB camera, e.g. an RGB signal

processed, ie the colors red, green and blue each transmitted in a separate channel or stored.

The first light source used to irradiate the objects

is used, can emit light in the infrared range (780 nm -1 mm wavelength), in particular in the NIR range (900 - 2300 nm). The second light source can emit light in the visible range (380-750 nm wavelength). In principle, a UV light source for activating fluorescent light would be conceivable as the first or second light source, wherein the

Fluorescent light can then be back in the visible range.

In the case of a light source with only one sort of

Lighting units, e.g. one or more

Supercontinuum laser light sources, would be the single

Illumination unit both in a first transmission wavelength range light in the infrared range (780 nm -1 mm

Wavelength), in particular in the NIR range (900-2,300 nm), as well as in a second transmission wavelength range light in the visible range (380-750 nm wavelength) emit.

BRIEF DESCRIPTION OF THE FIGURES

In the following the invention with reference to the schematic

Drawings described in more detail. It shows 1 shows a sorting device with detection device according to the prior art,

Fig. 2 is a sorter with an inventive

Detection device with first and second light source.

WAYS FOR CARRYING OUT THE INVENTION

Fig. 1 shows a sorter for sorting objects 9, e.g. Plastic waste in the form of colored plastic pieces, according to the prior art. The objects 9 are detected after they pass over an inclined plane 10 into a free-fall path, of which a section is illuminated by the light source 6 and detected by the detectors 1, 2. It would also be possible to detect the objects 9 on a conveyor belt. Preference is given to a single-layer material flow. The objects are (in Fig. 1 from the left) with light of

Irradiated light source 6, wherein the light source 6 simultaneously emits visible light 8 and infrared light 7. The

Light source 6 may consist of several similar units, which are distributed over the width of the material flow or the inclined plane 10, that is normal to the plane of the drawing. The reflection light emanating from the objects 9 is detected with two different detectors 1, 2 which are located on the same side of the objects 9 as the ones

Light source 6. The device comprises a first detector 1 for

Detecting light of a first detection wavelength range, and a second detector 2 for

Detecting light of a second detection wavelength range different from the first detection wavelength range. That is, first and second detection wavelength ranges are not identical, usually will not overlap, but overlapping is not excluded. The first detector 1, here an IR detector (in particular an NIR detector), comprises eg an objective, a spectrograph and an optical sensor. The second detector 2 is a VIS detector (in particular an RGB camera) and comprises a

Lens and an optical sensor. At least one of the

Detectors can be designed as a line scan camera.

In FIG. 1, the objects 9 are irradiated by the light source 6 with light of different wavelengths, namely with infrared light 7 (first transmission wavelength range) and with visible, in particular white, light 8 (second transmission wavelength range). The outgoing from the objects 9

Reflection light of different wavelengths, namely again infrared light 7 and visible light 8, is detected by the two different detectors 1, 2. The

Lichtumlenkelement 3, which is arranged in the beam path to the detectors 1,2, is partially transparent or

wavelength selective: it reflects infrared light 7 light, e.g. the NIR component above 700 nm, and deflects it (for example by about 90 °) in the direction of the first detector 1. Visible light 8, e.g. with wavelengths below 700 nm, is transmitted and passes to the second detector. 2

The evaluation device 11, which is usually designed as a computer, processes the data from the detectors 1, 2 and determines at least one property (eg the color) of each object 9 and then divides the objects 9 into predetermined fractions (eg white - not white) to, so on the basis of this

Division a separation of the objects 9 can take place. The evaluation device 11 sends a corresponding control signal to the discharge device 12, e.g. an exhaust nozzle, so that objects of a fraction (e.g., the white objects) through the

Discharge device 12 are deflected over a partition wall 13 addition, while objects of the other fraction (not white) just will not be distracted and remain on the other side of the partition wall 13. Since most of the time, a high intensity of visible light 8 is needed, the light source 6 must be operated near its power limit, thus radiating also high intensity infrared light 7, which accordingly heats the space around the light source 6, albeit at a lower intensity of the infrared light 7 for the first detector 1 would be sufficient. The device shown in Fig. 1 of detectors 1,2, light source 6 and slate plane 10 is usually surrounded by a housing, not shown here, so that the interior of the housing is heated accordingly.

This will now be remedied by a change of the device as shown in Fig. 2. Fig. 2 differs from Fig. 1 in that instead of the light source 6 two

different light sources are provided 4.5. The first light source 4 sends only (as physically possible,

at least mainly) infrared light 7, while the second light source 5 only (as far as physically possible,

mainly) visible light 8 emits. In addition, the two light sources 4, 5 are connected to the evaluation device 11, which is connected to the detectors 1, 2. The evaluation device 11 can now send control signals for controlling the intensity of the individual light sources 4, 5 to them, so that the intensity of the two light sources 4, 5 can be set independently of one another. It can the

Evaluation device 11, the intensity of the light sources 4.5 set so that it is just sufficient to allow an evaluation of the data of the detectors 1,2. In particular, the intensity of the first light source 4 for infrared light 7 can be lowered without the intensity for the second

To change light source 5 for visible light 8. Thereby, the heat development of the first light source 4 can be lowered.

The first light source 4 is composed of halogen light rods. For certain applications, the light source 4 sends NIR light off, the associated detector 1 is then

designed accordingly as an NIR detector. The second

Light source 5 is composed in Fig. 2 of a plurality of white light LEDs. Each light source 4, 5 can be influenced by the associated sensor or detector 1, 2 independently of the other light source. As the light intensity in the visible

When the LED illumination area is generated, and the NIR sensor of detector 1 achieves a lower intensity in the NIR range, the halogen light bars can be operated at a lower power than the specified rated power. This results in a lower

electrical operating power and heat radiation, which results in lower heating of the sorter.

Positive side effect is the longer life of the

Light source 4. In addition, there is a better color fidelity in the range of visible light by reducing the originating from the halogen illumination red intensity.

Otherwise, the device of FIG. 2 functions the same as that of FIG. 1. In principle, first and / or second light source 4, 5 can also work in the transmission method. For example, the first light source 4, which emits infrared light 7 here, could work in the reflection method, while the second light source 5, which emits visible light 8 here, works in the

Transmission method works, for which, in comparison to FIG. 2, the second light source 5 would have to be arranged on the side of the material flow opposite the second detector 2.

First and second light source 4,5 in Fig. 2, according to the other embodiment of the invention by a

Light source to be replaced, the individual

Lighting units each can emit both IR light, especially only NIR light, as well as visible light, being the intensity of IR light and visible light

are separately adjustable. This would be done by a

Supercontinuum laser light source be satisfied. This would then be best connected to both the first and second detector 1,2 (analogous to the first and second light sources 4,5 in Fig. 2), e.g. via the evaluation device 11.

Of course, the supercontinuum laser light source can also be connected to only one of the detectors 1, 2 if the intensity is to be adjustable only for one of the two transmission wavelength ranges.

The embodiment with a supercontinuum laser light source is similar to that shown in Fig. 1 with the light source 6. For the subject invention, it would be necessary to replace the light source 6, such as a halogen light bar, with the supercontinuum laser light source and replace it, e.g. via the evaluation device 11, with one or both

Connect detectors 1,2.

Reference sign list:

1 first detector

2 second detector

3 light deflecting element

4 first light source

5 second light source

6 light source

7 infrared light

8 visible light

9 object

10 inclined plane

11 Evaluation facility

12 discharge device

13 partition

Claims

Device for detecting objects (9) in a flow of material, comprising at least

a light source (4, 5) for emitting light in a first transmission wavelength range and in a second transmission wavelength range, which is different from the first transmission wavelength range, to the

Material stream,

a first detector (1) for detecting

Reflection light, fluorescent light or transmission light of the objects, caused by light in the first transmission wavelength range, in a first detection wavelength range,

a second detector (2), which is different from the first detector (1), for detecting reflection light, fluorescent light or transmission light of the objects, caused by light in the second transmission wavelength range, in a second detection wavelength range, characterized

- That the first detector (1) is connected to the light source (4) for controlling the light intensity of the first transmission wavelength range, and / or the second detector (2) with the light source (5) for controlling the light intensity of the second transmission wavelength range connected is.

2. Device according to claim 1, characterized in that the light source (4,5) comprises at least one supercontinuum laser light source, which is formed, light in a first transmission wavelength range and in a second transmission wavelength range that does not match the first transmission Wavelength range overlaps to send out.

3. Device according to claim 1, characterized in that the light source (4,5) has both a first light source (4) for emitting light only in the first transmission wavelength range and a second

Light source (5) for emitting light only in the second transmission wavelength range, and

- That the first detector (1) with the first light source (4) for controlling the light intensity of the first

Light source is connected, and / or the second detector (2) with the second light source (5) for controlling the light intensity of the second light source is connected.

4. Apparatus according to claim 3, characterized in that the first light source (4) and second light source (5) in the operation of the device on the same side of the

Material flow of objects (9) are located.

5. Device according to one of the preceding claims,

characterized in that the first detector (1) and / or the second detector (2) with the light source (4,5) via an evaluation device (11) is connected, which for evaluating the signals of the first and second Detector (1,2) and for determining at least one

Property of the detected objects (9) is provided.

6. Device according to one of the preceding claims,

characterized in that the first transmission wavelength range IR light (7), in particular NIR light, and the second transmission wavelength range includes visible light (8).

7. Device according to one of claims 3 to 6, characterized

characterized in that the first light source (4) for

Emitting IR light (7) is formed.

8. Device according to one of claims 3 to 7, characterized

characterized in that the first light source (4) for

Emitting NIR light is formed.

9. Device according to one of claims 3 to 8, characterized

characterized in that the first light source (4) comprises at least one halogen light source.

10. The device according to claim 9, characterized in that the first light source (4) comprises a halogen flashlight.

11. Device according to one of claims 3 to 10,

characterized in that the second light source (5) at least one LED light source for emitting

visible light (8).

12. Device according to one of the preceding claims, characterized in that the first detector (1) a Detector for infrared light (7), in particular NIR light, and comprises a spectrograph for infrared light (7).

13. Device according to one of the preceding claims, characterized in that the second detector (2) comprises a camera for visible light (8).

14. Device according to one of the preceding claims, characterized in that an evaluation device (11) is provided for evaluating the signals of the first and second detectors (1,2) and for determining at least one property of the detected objects (9), wherein the

Evaluation device (11) is connected to a discharge device (12) for sorting out objects (9) from the material flow as a function of their properties.

15. A method for detecting objects (9) in a material stream by means of a device according to one of claims 1 to 14, wherein

a light source (4, 5) emits light onto the stream of material in a first transmission wavelength range and in a second transmission wavelength range, which is different from the first transmission wavelength range,

a first detector (1) detects in a first detection wavelength range reflection light, fluorescent light or transmission light of the objects which is caused by light in the first transmission wavelength range,

a second detector (2) provided by the first detector (1) is different, detected in a second detection wavelength range reflected light, fluorescent light or transmission light of the objects, which is caused by light in the second transmission wavelength range, and

- the light intensity of the first transmission

Wavelength range due to a connection of the first detector (1) with the light source (4) so controlled, in particular reduced, that the light intensity for the first detector (1) is sufficient, and / or the light intensity of the second transmission wavelength range due to a compound of the second detector (2) with the light source (5) so controlled, in particular reduced, that the light intensity for the second detector (2) is sufficient.