DE102022210578B4 - Detection device for detecting empty trays in a conveyor device - Google Patents

Abstract

The present invention relates to a detection device (10) for detecting empty trays (LW) in a conveyor device (100) for trays (W) for transporting objects (O), comprising a test light source (20) for generating test light beams (PL) with a test light spectrum (PS) with a test polarization filter (22) with a first polarization angle (PW1) and a guide device (24) for guiding the test light beams (PL) through the test polarization filter (22) into a test area (PB), further comprising a detection device (30) for detecting reflection light beams (RL) reflected from the test area (PB) with a reflection polarization filter (32) with a second polarization angle (PW2) which differs from the first polarization angle (PW1), further comprising a determination device (40) for determining objects (O) in the test area (PB) on the basis of the Polarized reflection light rays (RL) pass through reflection polarization filters (32).

Description

The present invention relates to a detection device for detecting empty tubs in a conveyor device, a conveyor device with such a detection device and a detection method for implementation on such a detection device.

It is known that conveyor devices are used to convey trays for transporting objects. An example application of this is hand luggage scanners at airport security gates. There, objects in the form of hand luggage, jackets, items of clothing, shoes or similar are placed in trays in order to be transported through scanner devices with the conveyor device. Since the trays have to be conveyed back to the beginning of the conveyor device after being emptied, i.e. after the objects have been removed by the passenger, a return conveyor option is usually available. This is often integrated into such a scanner device and leads, for example, from the end to the beginning of the conveyor belt below the conveyor belt. Since the space within the housing of such a scanner device is usually very limited, such return conveyor options are very narrow and it is of great importance that only completely emptied trays are introduced into this return channel. Otherwise, there is a risk of jamming or blocking of incompletely emptied trays in such a return conveyor.

In known devices, this means that manual checks must sometimes be carried out to ensure that only empty trays are actually fed into the return conveyor. Although it is currently possible to recognise objects in trays using image recognition methods, this mainly relates to identifying specific objects as such. In particular, it is not possible to identify missing objects. Particularly when some objects are very small, such as a boarding pass in the example of a hand luggage scanner, these are often not recognizable as objects by image recognition methods, or can only be recognized with great effort. Object recognition using imaging methods is also very expensive, as a high level of computing effort is required to evaluate the image information accordingly. However, as already explained, not all objects are actually recognizable as such, so it is not possible to identify with absolute certainty that any objects are missing.

Such devices are already known from the state of the art and are described, for example, in the documents EN 10 2018 104 787 A1 , DE 20 2015 106 348 U1 , EN 10 2009 036 389 A1 , EN 10 2017 129 654 A1 and WO 00/ 47 947 A1 shown. It is the object of the present invention to at least partially eliminate the disadvantages described above. In particular, it is the object of the present invention to detect empty troughs for a conveyor device with a high degree of probability in a cost-effective and simple manner.

The above object is achieved by a detection device with the features of claim 1, a conveyor device with the features of claim 11 and a detection method with the features of claim 12. Further features and details of the invention emerge from the subclaims, the description and the drawings. Features and details that are described in connection with the detection device according to the invention naturally also apply in connection with the conveyor device according to the invention and the detection method according to the invention and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is or can always be made to each other.

According to the invention, a detection device is used for detecting empty tubs in a conveyor device for tubs for transporting objects. Such a detection device has a test light source for generating test light rays with a test light spectrum. This test light source is equipped with a test polarization filter with a first polarization angle. The test light source also has a guide device for guiding the test light rays through the test polarization filter into a test area. The detection device is also equipped with a detection device for detecting reflection light rays reflected from the test area with a reflection polarization filter with a second polarization angle, which differs from the first polarization angle. A determination device is also provided for determining objects in the test area on the basis of polarized reflection light rays that have passed through the reflection polarization filter.

The guide device can, for example, have reflector elements in order to achieve a vertical concentration of the test light beams through the test polarization filter into the test area. This can improve the utilization of the light output. Other optical influencing means, such as lens elements and/or diaphragm elements, can also be provided as part of the guide device.

According to the invention, the detection device serves to detect the absence of objects in trays in a conveyor device. For this purpose, a test area is defined, which can, for example, represent a part of the conveyor device. For example, such a detection device can represent a test area at the end of a conveyor device of a hand luggage scanner as already explained. Before a return conveyance through a narrow return channel takes place, the detection device can detect empty trays with a high degree of certainty, preferably automatically.

In order to ensure the absence of objects within the scope of the present invention with a high degree of certainty, in contrast to the specific detection of objects within a tub, a defined light beam path is provided, which is explained in more detail below.

If a trough reaches a test section of the conveyor device, a large number of test light beams are generated using the test light source. The test light beams spread out around the test light source and have a defined test light spectrum. In order to direct the test light beams into the test area, at least one guide device is provided, which can, for example, have reflection sections of the reflector elements already explained above. This serves in particular to provide a defined beam path in order to emit the test light beams from the test light source in the direction of the test area. On the way from the test light source to the test area, all test light beams also pass through the test polarization filter. This means that only polarized test light beams reach the test area. In other words, the test area is now irradiated with a test light in the form of the test light beams, which on the one hand has a defined test light spectrum and on the other hand a defined polarization according to the first polarization angle of the test polarization filter.

The test light source is preferably designed as a surface light and can have a large number of lamps arranged over a surface. For example, LED lamps, in particular infrared lamps, are provided, which generate the test light as infrared test light. This generates a surface light concentrated on the tub with uniform illumination and, compared to a point lamp, reduces or even eliminates the risk of disruptive reflection. The surface design also results in a surface distribution of the electrical power, so that the heat generated when the test light source is operated is also distributed over a surface. Point-like overheating can be avoided in this way.

As soon as the appropriately polarized test light reaches the tub, two different situations must be distinguished. If the tub is an empty tub, all of the test light only hits the empty bottom section of the tub in the test section. This leads to a defined and exact reflection taking place on this bottom section, which in particular does not change the polarization of the test light or only changes it to a very small extent. The reflection creates reflected light rays which leave the test area again and can be picked up by a detection device of the detection device. However, in order to reach the detection device, the reflected light rays must still overcome the reflection polarization filter. The reflection polarization filter has a second polarization angle which differs from the first polarization angle of the test polarization filter. This means that when the test light rays are exactly polarized by the corresponding reflection, exclusively on the bottom of the empty tub, they have retained their polarization according to the first polarization angle. This also means that these reflection light rays with the constant polarization cannot penetrate the reflection polarization filter or can only do so to a very limited extent, since the second polarization angle, which has a different configuration than the first polarization angle, prevents this. It is easy to see here that, in the case of an empty tub, the test light is reflected back to the detection device as reflection light in such a way that it cannot be detected by the device or can only be detected to a very limited extent, since it is prevented from penetrating the detection device by the reflection polarization filter. In this case, the image perceived by the detection device appears dark or completely blackened, so that it can be assumed that the tub is empty.

If, in contrast to the above explanation, an object is transported in the tank, the test light beams reach this object in the same way as soon as it is in the test area. The test light beams are now reflected on this object in a different way than is the case at the bottom of the tank. In particular, this preferably diffuse reflection causes a change in the polarization of the incoming test light beams. len, so that the resulting reflected light rays have a different polarization than the test light rays. Because such reflected light rays reflected from the object now have a different polarization compared to the test light rays, they can, at least partially, pass through the reflected polarization filter and thus be perceived by the detection device. The image perceived by the detection device therefore only shows those reflected light rays which have experienced a change in polarization due to reflection from objects. This means that the image recorded by the detection device only shows lines and contours in those areas which, due to the changed polarization, belong to an object, in particular an object edge or an object contour. This allows the contours of the objects to be recognized, so that only in the case of such objects can reflected light rays penetrate the reflected polarization filter and be perceived by the detection device.

Based on the above explanation of the empty tray and the tray containing an object, it is easy to see how the determination device can now use these two different detection situations in a very simple and, above all, computationally inexpensive way to determine the absence of any objects in the test area. It can therefore be assumed that an object can only be present in the tray if reflected light rays were able to penetrate the reflection polarization filter. In contrast, a completely dark image is to be interpreted by the determination device as meaning that no object was detected in the test area, since no diffuse reflection with other reflection angles within the test area led to a change in the polarization of the test light rays. The actual shape or type of objects and the corresponding shape of the contours are not important in this evaluation, so that the absence of objects can be detected with a high degree of certainty and with very little computational effort.

Based on the above explanation, it is clear that it is now no longer necessary to carry out image analysis to search for objects in a very cost-effective and simple manner, but rather the result of the determination - the absence of objects in the case of a black or essentially black image - can be output directly by the detection device. Complex and computationally intensive image evaluations are no longer necessary here. In addition to reducing the computing costs and the associated computing time, this leads to the particular advantage of a significant reduction in costs. The use of test light sources and correspondingly easily designed detection devices means that the structural hardware that supplies the data for the determination device can also be small and inexpensive, but also very robust. In addition, the pure contour detection and the polarization correlation between the test light source and the detection device enable a high tolerance for a wide variety of object types and/or object positions. In other words, every object within the tank is non-specifically detected with great robustness and a high degree of reliability, and conversely the absence of any, even very small, non-specific objects can also be detected.

It can be advantageous if the first polarization angle and the second polarization angle are aligned at 90° or essentially 90° to one another in a detection device according to the invention. This essentially complementary alignment of the two different polarization angles further reinforces the effect already explained. In particular, it ensures that the most complete possible filtering of non-diffusely reflected test light rays is achieved, so that the distinction between contours by diffusely reflected reflection rays and non-diffusely reflected reflection rays is reinforced. This leads to improved differentiation and thus to further improved detection of missing objects in the respective tray in the test area.

It is also advantageous if, in a detection device according to the invention, the test light source generates the test light rays in a test light spectrum in the range that is not visible to the human eye, in particular in the infrared range. The wavelength here is, for example, around 804 nm and is therefore contained to a lesser extent in the spectrum of the ambient light. This reduces or avoids the influence or interference from the ambient light on the detection device. By means of a correspondingly strong illumination with this wavelength (for example around 804 nm) and the resulting distance to the light component of this wavelength that is contained in the ambient light, interference and the influence of the ambient light are greatly reduced and reliable empty detection can be achieved up to 20,000 lux ambient light. The test light used, for example, is at the beginning of the infrared range (still visible component) at around 804 nm and is therefore very inexpensive to obtain using inexpensive IR LEDs compared to pure infrared LEDs. This means that the lighting can be implemented very inexpensively. Lighting in the completely visible wavelength range would be very bright and disruptive in the passenger area. The use of an infrared range therefore means that a very cost-effective test light source in the form of IR LEDs in the visible wavelength range can be used. In addition, the test light spectrum is largely different from the ambient light, especially when it is purely artificial light inside a building. This also means that in addition to the correlation of the different polarizations, the test light spectrum can now be better distinguished from the otherwise existing ambient light from a spectral point of view. The test light spectrum is preferably very close to, but not or only partially in, the range visible to the human eye. This leads to a further reduction in costs, since correspondingly cost-effective test light sources and detection devices can be used. In order to further enhance the functionality according to the invention, the test light spectrum is equipped with a very small width, i.e. has a narrow design. A possible width for the test light spectrum is, for example, around 10 nanometers. This leads to a further strong reduction in the disruptive influence of ambient light.

Further advantages can be achieved if, in a detection device according to the invention, the test light source has a large number of individual test lamps, which in particular have rectified or essentially rectified radiation directions. Of course, a single strong test lamp is also conceivable. However, the use of several test lamps, which in particular have rectified, preferably parallel or essentially parallel radiation directions, can bring advantages. For example, parallel radiation from several test lamps allows a particularly uniform distribution of the test light beams over a large test area. The irradiation and thus the emission from the test lamps along the radiation directions preferably takes place from above onto the test area, as will be explained in more detail later with reference to the conveyor device. In particular, the test light source is designed as a surface light source for this purpose, as already described above.

It is also advantageous if, in a detection device according to the invention, the test light source generates the test light beams with a brightness above the brightness of the ambient light. In other words, the test light beams of the test light source outshine the ambient light in order to further reduce its influence on the detection device. This can be specified automatically, done manually by entering light parameters for the ambient light, or carried out in a controlled manner using an ambient light sensor. It can also be advantageous if the wavelength of the ambient light is known and accordingly not only the intensity but also, as already explained, the spectrum width can be distinguished from this defined ambient light.

Further advantages can be achieved if, in a detection device according to the invention, a reflection spectral filter is arranged in the beam path in front of the detection device, with a transmission spectrum that corresponds or essentially corresponds to the test light spectrum. Such a reflection spectral filter therefore means that wavelength ranges that are not in the transmission spectrum and therefore also not in the test light spectrum are excluded from reaching the detection device. This increases the security of the detection according to the invention, since ambient light with different polarization directions can partially penetrate the reflection polarization filter, but can no longer penetrate the reflection spectral filter due to the additional transmission spectrum connected behind it. In other words, it is possible to filter out diffusely polarized ambient light based on the spectrum and to use the polarization differences for the detection functionality in the manner described. Other light influences or glare effects caused by the ambient light can be reduced or even largely excluded in this way.

It is also advantageous if a detection device according to the invention has a test area for temporarily receiving trays of the conveyor device, in particular if the test area forms a section of the conveyor device. If the conveyor device has a conveyor belt or conveyor rollers, for example, these are also arranged in the test area and serve to transport the trays into the test area and, if they are detected as empty, out of it again. This is particularly integrated in the hand luggage scanner already explained several times.

It can also be advantageous if, in a detection device according to the invention, a test distance is formed between the test light source and the detection device on the one side and the test area on the other side. This is in particular a fixed test distance designed and larger than the hand luggage items usually found in such tubs. It is also preferably large enough to allow a body part of a person to enter the tub, in particular to enable an object to be removed from an object tub.

It is also advantageous if, in a detection device according to the invention, the test area has a position sensor for detecting a tub conveyed into the test area by means of the conveyor device. This allows the detection process explained later to be carried out not only when the tub is stationary, but also at least partially while the tub is moving. In this case, strip-by-strip detection and/or complete detection of the entire tub can take place. By using it on moving tubs, the detection device can be arranged even more flexibly at security gates, in particular anywhere along the course of a conveyor device and not necessarily at the end of the conveyor device. The passage of checked tubs is also accelerated, since no time loss has to be accepted due to the detection of stationary tubs. With the help of the position sensor, for example in the form of a light barrier, a mechanical switch, a magnetic switch or even an optical detection, it is then possible in particular to synchronize the detection process with the movement of the tub on the conveyor device. In the simplest case, the detection process starts with a position signal from the position sensor when a tub has been moved to the desired position.

Further advantages are achieved if, in a detection device according to the invention, the test light source and the detection device are arranged in a common housing for arrangement above the test area. The integration in a common housing leads to equal distances and equal alignments to the test area, so that the evaluation can be carried out even more easily and quickly, particularly in the subsequent evaluation. In addition, the radiation direction and detection direction are aligned in this way and the compactness of such a detection device is further increased.

It is advantageous in such a detection device according to the previous paragraph if the test light source is optically sealed from the detection device in the common housing. Reflection elements, absorption elements or similar can be used for this purpose. In other words, an optical short circuit between the test light source and the detection device is reliably avoided.

It can also be advantageous if, in a detection device according to the invention, the test light source is designed as an infrared light source and the detection device is designed as an infrared camera. As has already been explained in several places, the design in the infrared range for the test light source and the detection device brings great advantages in terms of functional reliability and at the same time in terms of cost reduction. This also makes it possible to easily distinguish from visible light, in particular ambient light.

The present invention also relates to a conveyor device for conveying trays for transporting objects, in particular in the form of hand luggage objects, having at least one detection device according to the invention. A conveyor device according to the invention thus brings with it the same advantages as have been explained in detail with reference to a detection device according to the invention.

In a conveying device according to the invention and when using a detection device according to the invention, special trays are used in particular. These can have surfaces with increased roughness to avoid light reflections caused by natural and/or artificial ambient light. In this way, diffuse reflection can occur on such surfaces instead of point reflection, so that optical disturbances can be avoided.

• - Erzeugen von Prüf-Lichtstrahlen mit einem Prüf-Lichtspektrum,
• - Polarisieren der Prüf-Lichtstrahlen mit einem Prüf-Polarisierungsfilter mit einem ersten Polarisationswinkel,
• - Führen der polarisierten Prüf-Lichtstrahlen in einen Prüfbereich,
• - Erfassen von aus dem Prüfbereich reflektierten Reflexions-Lichtstrahlen mittels einer Erfassungsvorrichtung hinter einem Reflexions-Polarisierungsfilter mit einem zweiten Polarisationswinkel, welcher sich von dem ersten Polarisationswinkel unterscheidet,
• - Bestimmen von Objekten im Prüfbereich auf Basis von durch den Reflexions-Polarisierungsfilter gelangten polarisierten Reflexions-Lichtstrahlen.

Furthermore, an object of the present invention is a detection method for detecting empty trays in such a conveyor device, for trays for transporting objects, comprising the following steps:

• - Generating test light beams with a test light spectrum,
• - Polarizing the test light beams with a test polarizing filter with a first polarization angle,
• - guiding the polarized test light beams into a test area,
• - detecting reflected light rays reflected from the test area by means of a detection device behind a reflection polarization filter with a second polarization angle which differs from the first polarization angle,
• - Determination of objects in the test area based on the reflection polarization polarized reflection light rays entering the filter.

A detection method according to the invention brings with it the same advantages as have been explained in detail with reference to a detection device according to the invention. When identifying objects, the captured images can be scanned point by point or line by line, for example. This leads to the contour detection or circumference detection of objects already explained several times, i.e. in particular a purely two-dimensional representation of the captured image. At the same time, it is possible to detect with a high degree of certainty that any objects are missing and thus to define an empty tub.

As already explained, the test light beams can be generated and/or guided in a planar manner, particularly as surface light. This leads, as already described, to more uniform illumination and to a reduction and/or avoidance of optical disturbances such as reflections.

Furthermore, in a detection method according to the invention, it is also possible to use spectral filters that have a transmission spectrum that corresponds or essentially corresponds to the test light spectrum. In this way, disturbing ambient light for the detection device can be blocked out.

It can be advantageous if, in a detection method according to the invention, known, in particular constant, contours are subtracted for the determination of objects. For example, tubs can have structures that are identical for each tub. Printing is also possible that can be perceived by the detection device through the reflection polarization filter due to their surface structure. Here it is possible to simply subtract these constant and thus known contours from the recorded image in an optical manner in the imaging process and thus make them inaccessible for further determination, so that the detection of empty tubs can be carried out in the same simple, cost-effective and quick manner.

Further advantages are achieved if, in a detection method according to the invention, at least one limit value is taken into account when determining objects, in particular with regard to the size of the objects and/or the brightness of the objects. This makes it possible to avoid false signals for very small objects or for reflections that do not originate from objects with a high degree of certainty.

It is also advantageous if, in a detection method according to the invention, an object signal is generated when at least one object has been identified and/or a false signal is generated when no object is present. This is particularly non-specific for objects and can mean a pure signal output. However, such signals can also be passed on as control information for the conveyor device. This makes it possible, for example, for a tub to only leave the test area as an empty tub. A pictorial signal output, for example correlated with a color signal in red or green, can also enable a distinction to be made between empty tubs and object tubs in a simple and quick manner.

It is also advantageous if, in such a recognition process, at least one image is taken for each tub using the recognition device. In particular, one and in particular exactly one recognition photo is taken per tub, so that the recognition steps can be carried out simply and inexpensively with little computing effort. It is also possible to take series of photos when moving in and thus tracing the movement of the tub. The timing for such photos can be in the range of 0.5 seconds, for example.

It can also be advantageous if a detection method according to the invention includes a step of determining edges of objects and/or tubs. In this way, objects can be detected and even defined based on their contour. The detection of tub edges can be based on defined alignment information. In particular, if the tubs are not conveyed into the detection device in a defined guide, such detection of the alignment via edge detection can bring about a qualitative improvement in the detection method. For detection of tub edges, for example, an image analysis is conceivable which, in a first step, looks from a starting point within the tub boundaries outwards for an edge in the form of corresponding optical information. This is done in particular in two, for example arbitrary, directions, so that two spaced-apart points on the tub edge can be detected. These edge points on the tub edge can now be a starting point for following the tub edge during the evaluation method, so that the tub edge is traced as a result. This evaluation is carried out using vectors that are set as starting points at the respective points and are defined as direction and length for the evaluation algorithm. In this way, the entire recorded image no longer has to be sorted for edges. searched. Instead, edge points are specifically searched for, from which the edges can be directly detected. The computing effort for this type of evaluation is significantly reduced compared to normal image evaluation of the entire image area. Similar methods, particularly vector-based ones, are also conceivable for edge detection of other objects in the tub or separately from it. The start vectors described can have a predefined length and/or direction. The predefined specification of a start point is also conceivable in order to simplify the process even further.

It is also advantageous if, in a detection method according to the invention, the steps of generating, polarizing, guiding, detecting and determining are carried out at least partially on a tub that is moved through the test area with the conveyor device. For example, an entry of a tub into the test area can be detected using a position sensor as already explained. This can start the implementation of the detection method, so that detection is carried out in particular until the identical or another position sensor outputs a position signal that indicates the movement of the tub out of the test area. The detection method can thus be synchronized with the movement of the tubs through a conveyor device.

• 1 eine Ausführungsform einer erfindungsgemäßen Erkennungsvorrichtung,
• 2 eine Darstellung einer Leer-Wanne,
• 3 eine Darstellung einer Objekt-Wanne,
• 4 ein Vergleich unterschiedlicher Spektren,
• 5 eine weitere Ausführungsform einer erfindungsgemäßen Erkennungsvorrichtung.

Further advantages, features and details of the invention emerge from the following description, in which embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description can each be essential to the invention individually or in any combination. They show schematically:

• 1 an embodiment of a detection device according to the invention,
• 2 a representation of an empty tub,
• 3 a representation of an object tub,
• 4 a comparison of different spectra,
• 5 a further embodiment of a detection device according to the invention.

In 1 a conveyor device 10 is shown schematically, for example at the end of a hand luggage scanning system. The detection device 10 is equipped with a test area PB, in which a tray W is inserted in a side view. In order to look into the tray W, the detection device 10 is arranged above the test area PB in a common housing 50. This is arranged at a defined test distance PA from the test area PB, so that when objects O are detected, they can be easily removed from the tray W.

To carry out the detection, a light source 20 with a test lamp 26 is provided in the detection device 10. This allows test light beams PL, 1 shows a schematic representation of a light beam to be generated. With the help of guide devices 24 designed here as reflectors, all test light beams PL are guided through the test polarization filter 22 in the direction of the test area PB. The test light beams PL therefore have a defined test light spectrum PS and a defined polarization according to the first polarization angle PW1. Depending on the reflection situation, i.e. on the empty bottom of the tub W or diffusely on objects O within the tub W, the reflection light RL with an identical spectrum to the test light spectrum PS, but with different polarization depending on the type of reflection, is now reflected back in the direction of the detection device 30. Only when the polarization has changed from the first polarization angle PW1 due to a diffuse reflection for the reflection light beam RL can it at least partially pass through the reflection polarization filter 32 according to the second polarization angle PW2. If this is the case, this is based exclusively on a diffuse reflection on an object and is then, and only then, perceived by the detection device 30. The determination device 40 is now able to recognize the contour of any object based on the reflected light rays RL that have passed through, or to conclude that any objects O are absent in the tub W based on the absence of any reflected light rays RL that have passed through. In this way, it is possible to distinguish empty tubs LW from object tubs OW very easily, quickly and with little calculation without having to carry out specific object recognition.

Based on 2 and 3 This evaluation is explained in more detail. In both cases, this is an embodiment according to the 1 Here it is easy to see that the first polarization angle PW1 is rotated by 90° and differs from the second polarization angle PW2. This means that in the case of an empty tub, the empty tub LW according to the 2 , only contours of the tub W can be perceived. If this expected constant contour of the tub W can now be subtracted optically, this leads to the determination device 40 recognizing the empty tub LW as such and issuing a false signal FS. In contrast, in the tub W in 3 contain an object O, for example a boarding pass. This results in the test light rays PL being reflected at least at the edges of this flat object O in such a way that their polarization changes and they are thus able to at least partially penetrate the reflection polarization filter 32. The detection device 30 thus reproduces an image as shown in the 3 shows the contours of the detected object O, according to the reflected light rays RL that have passed through. Here too, it is possible to subtract the contours of the tub W, which are also constant and known, so that only the contour of the object O remains. On this basis, the determination device 40 now outputs the object signal OS.

In 4 It is also shown how the individual spectra can be formed relative to one another. For example, an ambient light spectrum US is provided with a broad peak in the visible range. The test light spectrum PS is preferably very narrow-band in the infrared range, for example with a peak width of 10 nanometers. In this variant, it is also easy to see that the intensity of the test spectrum PS is above the ambient light as the ambient spectrum US, and thus outshines it.

The 5 shows a further development of the embodiment of the detection device 10. This now has a large number of test lamps 26 in the test light source 20. These are arranged to the left and right around a central detection device 30. The detection device 30 is optically sealed against the test light source 20. In addition, all test lamps 26 are provided with a rectified radiation direction SR, which is aligned opposite to a detection direction as the radiation direction SR for the detection device 30. This results in a rectified and uniform irradiation of the test area (not shown here) and central detection in the detection device 30. In order to further improve detection, a reflection spectral filter 36 is arranged in the beam path after the reflection polarization filter 32. This serves to filter out ambient light in that its transmission spectrum essentially corresponds to the test light spectrum PS.

The above explanation describes the present invention exclusively within the framework of examples. Of course, individual features of the embodiments can be freely combined with one another, provided they are technically expedient, without departing from the scope of the present invention.

List of reference symbols

10

Detection device

20

Test light source

22

Test polarization filter

24

Guide device

26

Test lamps

30

Detection device

32

Reflection polarizing filter

36

Reflection spectral filter

40

Determination device

50

Housing

100

Conveyor device

PL

Test light beams

PS

Test light spectrum

US

Ambient light spectrum

PW1

first polarization angle

PW2

second polarization angle

PB

Test area

P.A.

Test distance

RL

Reflected light rays

SR

Radiation direction

W

Tub

O

object

LW

Empty tub

OW

Object tub

OS

Object signal

FS

False signal

Claims (18)

Detection device (10) for detecting empty trays (LW) in a conveyor device (100) for trays (W) for transporting objects (O), comprising a test light source (20) for generating test light rays (PL) with a test light spectrum (PS) with a test polarization filter (22) with a first polarization angle (PW1) and a guide device (24) for guiding the test light rays (PL) through the test polarization filter (22) into a test area (PB), further comprising a detection device (30) for detecting reflection light rays (RL) reflected from the test area (PB) with a reflection polarization filter (32) with a second polarization angle (PW2) which differs from the first polarization angle (PW1), further comprising a determination Detection device (40) for determining objects (O) in the test area (PB) on the basis of polarized reflection light rays (RL) passing through the reflection polarization filter (32), characterized in that the test light source (20) and the detection device (30) are arranged in a common housing (50) for arrangement above the test area (PB) and the test light source (20) in the common housing (50) is optically sealed against the detection device (30). Detection device (10) according to Claim 1 , characterized in that the first polarization angle (PW1) and the second polarization angle (PW2) are aligned at 90° or substantially 90° to each other. Detection device (10) according to one of the preceding claims, characterized in that the test light source (20) generates the test light rays (PL) in a test light spectrum (PS) in the range not visible to the human eye, in the infrared range. Detection device (10) according to one of the preceding claims, characterized in that the test light source (20) has a plurality of individual test lamps (26) which have rectified or substantially rectified radiation directions (SR). Detection device (10) according to one of the preceding claims, characterized in that the test light source (20) generates the test light beams (PL) with a brightness above the brightness of the ambient light. Detection device (10) according to one of the preceding claims, characterized in that a reflection spectral filter (36) is arranged in the beam path in front of the detection device (30) with a transmission spectrum which corresponds or substantially corresponds to the test light spectrum (PS). Detection device (10) according to one of the preceding claims, characterized in that it has the test area (PB) for temporarily receiving tubs (W) of the conveyor device (100), and the test area (PB) forms a section of the conveyor device (100). Detection device (10) according to Claim 7 , characterized in that a test distance (PA) is formed between the test light source (20) and the detection device (30) on the one side and the test area (PB) on the other side. Detection device (10) according to one of the Claims 7 or 8th , characterized in that the test area (PB) has a position sensor for detecting a tub (W) conveyed into the test area (PB) by means of the conveying device (100). Detection device (10) according to one of the preceding claims, characterized in that the test light source (20) is designed as an infrared light source and the detection device (30) is designed as an infrared camera. Conveying device (100) for conveying trays (W) for transporting objects (O), in the form of hand luggage objects, comprising at least one recognition device (10) with the features of one of the Claims 1 until 10 . Detection method for detecting empty tubs (LW) in a conveyor device (100), having the features of Claim 11 , for tubs (W) for transporting objects (O), comprising the following steps: - generating test light rays (PL) with a test light spectrum (PS), - polarizing the test light rays (PL) with a test polarization filter (22) with a first polarization angle (PW1), - guiding the polarized test light rays (PL) into a test area (PB), - detecting reflection light rays (RL) reflected from the test area (PB) by means of a detection device (40) behind a reflection polarization filter (32) with a second polarization angle (PW2) which differs from the first polarization angle (PW1), - determining objects (O) in the test area (PB) on the basis of polarized reflection light rays (RL) which have passed through the reflection polarization filter (32). Detection method according to Claim 12 , characterized in that known, constant contours are subtracted for determining objects (O). Recognition method according to one of the Claims 12 or 13 , characterized in that when determining objects (O), at least one limit value with regard to the size of the objects (O) and/or the brightness of the objects (O) is taken into account. Recognition method according to one of the Claims 12 until 14 , characterized in that upon determination of at least one object (O) an object signal (OS) is generated and/or in the absence of any object (O) a false signal (FS) is generated. Recognition method according to one of the Claims 12 until 15 , characterized in that for each tub (W) at least one image is taken with the recognition device (40). Recognition method according to one of the Claims 12 until 16 , characterized in that a step of determining edges of objects (O) and/or of troughs (W) is carried out. Recognition method according to one of the Claims 12 until 17 , characterized in that the steps of generating, polarizing, guiding, detecting and determining are carried out at least partially on a trough (W) moved by the conveyor device (100) through the test area (PB).

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