Detection device for detecting empty trays in conveying system

Abstract

The invention relates to an identification device (10) for identifying empty trays (LW) in a transport system (100) for transporting trays (W) of objects (O), comprising: an inspection light source (20) for generating inspection light (PL) having an inspection spectrum (PS), said inspection light source having a scanning polarization filter (22) with a first polarization angle (PW1); and a guiding device (24) for guiding the inspection light (PL) through the inspection polarization filter (22) into an inspection area (PB); a sensing device (30) for sensing a reflected light beam (RL) reflected from the examination region (PB), the sensing device having a reflective polarization filter (32) with a second polarization angle (PW2) different from the first polarization angle (PW1); and a determination means (40) for determining an object (O) in the examination region (PB) on the basis of the polarized reflected light (RL) through the reflective polarization filter (32).

Description

[0001] The invention relates to a detection device for detecting an empty pallet in a conveying system, a conveying system having such a detection device and a detection method performed on such a detection device.

[0002] Conveyor systems are known for conveying trays for transporting objects. One application of this is a hand-held baggage scanner at an airport security gate. There, objects in the form of hand-held baggage, jackets, clothes, shoes, etc. are placed in a tray in order to be conveyed through a scanner device using a conveyor system. Since the tray must be returned to the beginning of the conveyor system after being emptied (i.e. after the objects have been removed by the passengers), a return conveyor is usually provided. This is usually integrated into such a scanner device and leads, for example, from the end of the conveyor belt back to the beginning of the conveyor belt under the conveyor belt. Since the space available in the housing of such a scanner device is usually very limited, such return options are very narrow and it is very important that only completely empty trays are fed into this return channel. Otherwise, there is a risk of clogging or blocking of trays that have not been completely emptied in such a return conveyor.

[0003] In the case of known devices, this means that in some cases a manual check must be carried out to ensure that only empty trays are actually introduced into the return conveyor at the end. Although it has been possible in the past to detect objects in trays using image detection methods, this relates in particular to the identification of the specific object itself. In particular, it is not possible to detect the absence of an object. In particular, if some objects are very small, such as boarding passes in the described example of a handheld baggage scanner, these objects generally cannot be identified as objects by image detection methods or only with great effort. In addition, object detection using imaging methods is also very expensive, since a correspondingly high amount of computing is required to evaluate the image information. However, as already explained, not all objects are actually equally identifiable, making it impossible to detect the absence of any object with absolute certainty.

[0004] The object of the present invention is to at least partially remedy the above mentioned drawbacks. In particular, the object of the present invention is to detect empty pallets for a conveying system in a high probability, cost-effective and simple manner.

[0005] The above objects are achieved by a detection device having the features of claim 1, a conveying system having the features of claim 13 and a detection method having the features of claim 14, further features and details of the invention being disclosed in the dependent claims, the description and the drawings. Of course, the features and details described in conjunction with the detection device according to the invention also apply in conjunction with the conveying system and the detection method according to the invention and vice versa, so that with respect to the disclosure, reference is made to each other or always to various aspects of the invention.

[0006] According to the present invention, a detection device is used to detect an empty pallet in a conveying system for pallets for transporting objects. Such a detection device has a scanning light source for generating scanning light with a scanning spectrum. The scanning light source is equipped with a scanning polarization filter having a first polarization angle. In addition, the scanning light source has a guiding device for guiding the scanning light through the scanning polarization filter into a scanning area. The detection device is further equipped with a recording device for recording reflected light reflected from the scanning area using a reflective polarization filter having a second polarization angle different from the first polarization angle. In addition, an identification device is provided for identifying an object in the scanning area based on the polarized reflected light that has passed through the reflective polarization filter.

[0007] For example, the guiding device can have a reflective element to achieve a vertical concentration of the scanning light rays passing through the scanning polarization filter into the scanning area. This makes it possible to achieve an improved utilization of the light output. Other optical influencing devices (such as lens elements and / or aperture elements) can also be provided as part of the guiding device.

[0008] According to the invention, a detection device is used to detect the absence of an object in a tray in a conveyor system. To this end, a scanning area is defined, which scanning area can represent, for example, a part of the conveyor system. For example, as already explained, such a detection device can represent a scanning area at the end of a conveyor system of a handheld baggage scanner. The detection device, preferably an automatic detection device, can detect an empty tray with a high degree of certainty before a return occurs through a narrow return channel.

[0009] In order to ensure the absence of an object with a high degree of certainty, in contrast to a specific detection of the object within the tray, a defined optical path is provided within the scope of the invention, as will be explained in more detail below.

[0010] When a pallet reaches a scanning section of the conveying system, a plurality of scanning rays are generated by the scanning light source. The scanning rays propagate around the scanning light source and have a defined scanning spectrum. In order to guide the scanning rays into the scanning area, at least one guiding device is provided, which can, for example, have a reflecting part consisting of the reflecting element already explained above. This is used in particular to provide a defined optical path for emitting scanning rays from the scanning light source in the direction of the scanning area. On the way from the scanning light source to the scanning area, all scanning rays also pass through the scanning polarization filter. This means that only polarized scanning rays enter the scanning area. In other words, the scanning area is now illuminated with scanning light in the form of scanning rays, which have, on the one hand, a defined scanning spectrum and, on the other hand, a defined polarization according to a first polarization angle of the scanning polarization filter.

[0011] Preferably, the scanning light source is designed as a planar light and may have a plurality of lamps arranged in a planar manner. For example, an LED lamp (particularly an infrared lamp) is provided, which generates the scanning light as an infrared scanning light. This generates a planar light that is concentrated on the tray with uniform illumination and reduces or even avoids the risk of destructive reflections compared to a spotlight. The planar design also results in a planar distribution of the electrical power, so that the heat generation during the operation of the scanning light source also has a planar distribution. In this way, local overheating can be avoided.

[0012] Once the corresponding polarized scanning light reaches the tray, two different situations must be distinguished. If the tray is an empty tray, all scanning light strikes only the empty bottom of the tray in the scanning section. This results in a defined and precise reflection from this bottom section, which in particular does not change the polarization of the scanning light, or changes the polarization of the scanning light only to a very small extent. The reflection produces a reflected light ray, which leaves the scanning area again and can be captured by the recording device of the detection device. However, in order to reach the recording device, the reflected light ray still has to overcome the reflective polarization filter. The reflective polarization filter has a second polarization angle that is different from the first polarization angle of the scanning polarization filter. This means that, with the precise polarization of the scanning light rays reflected by the corresponding reflection, only from the bottom of the empty tray, these scanning light rays have retained their polarization according to the first polarization angle. This also means that these reflected light rays that retain their polarization cannot pass through the reflective polarization filter, or can only pass through the reflective polarization filter to a very small extent, because the second polarization angle that is different from the first polarization angle prevents this. Here, it can be clearly seen that when the tray is empty, the scanning light is reflected back to the recording device as reflected light in such a way that it cannot be recorded by the recording device, or only to a very slight extent, because the reflective polarization filter prevents it from penetrating into the recording device. In this case, the image perceived by the recording device therefore appears dark or completely black, so that an empty tray can be identified.

[0013] In contrast to the above description, if the object is transported in a tray, the scanning light reaches the object in the same way as soon as it appears in the scanning area. The scanning light is now reflected from the object in a different way than in the case of the bottom of the tray. In particular, this preferred diffuse reflection changes the polarization of the incident scanning light so that the resulting reflected light has a polarization different from the scanning light. Because such reflected light reflected by the object now has a polarization that has changed compared to the scanning light, they can at least partially pass through the reflective polarization filter and thus be perceived by the recording device. Therefore, the image perceived by the recording device only shows those reflected light rays that have undergone a polarization change due to reflection from the object. As a result, the image captured by the recording device only shows lines and contours in the area associated with the object (in particular the edge of the object or the contour of the object) due to the changed polarization. This means that the contour of the object is recognized so that only such reflected light rays can penetrate the reflective polarization filter and be perceived by the recording device.

[0014] Based on the above illustration of an empty tray and a tray containing an object, it is easy to see how, finally, the recognition device can now use these two different detection situations in a very simple way and above all with only a low computational effort to determine the absence of any object in the scan area, i.e. it can be assumed that an object is present in the tray only if the reflected light can penetrate the reflective polarization filter. Conversely, the recognition device interprets a completely dark image as meaning that no object was detected in the scan area, since diffuse reflections at other reflection angles within the scan area do not result in a change in the polarization of the scan light. In this evaluation, the actual shape or type of the object and the corresponding shape of the contour are irrelevant, so that the absence of an object can be detected with a high degree of certainty and with a very low computational effort.

[0015] Based on the above description, it can be seen that, in a very economical and simple manner, it is no longer necessary to perform an image evaluation to search for an object; on the contrary, in the case of a black or essentially black image, the recognition result allows the absence of an object to be output directly by the detection device. In particular, a complex and computationally intensive image evaluation is no longer necessary here. In addition to reducing the computing costs and the associated computing time, this leads in particular to the advantage of a significant cost reduction. The use of a scanning light source and a recording device (which can have a correspondingly simple design) means that the construction hardware that provides data for the recognition device can also be designed to be small and cheap, but also particularly very robust. In addition, pure contour detection and the polarization correlation between the scanning light source and the recording device enable a high tolerance for various object types and / or object positions. In other words, with a very high robustness and a high degree of certainty, each object within the tray is non-specifically detected, and conversely, the absence of any, even very small, non-specific objects is also detected.

[0016] Advantages can result if, in the detection device according to the invention, the first polarization angle and the second polarization angle are oriented at 90° or substantially 90° to one another. This substantially complementary orientation of the two different polarization angles further strengthens the effects already explained. In particular, it is ensured that the most complete possible filtering of the non-diffuse reflected scanning light rays is achieved, so that the distinction between the contours is strengthened by the diffusely reflected reflected light rays and the non-diffuse reflected reflected light rays. This leads to an improved differentiation and thus to a further improved detection of the absence of an object in the corresponding tray in the scanning area.

[0017] In the detection device according to the invention, it is also advantageous if the scanning light source generates scanning light in a scanning spectrum in a range that is not visible to the human eye, in particular in the infrared range. The wavelength here is, for example, about 804 nm, and is therefore included in the spectrum of the ambient light to a relatively small extent. This reduces or avoids the influence of the ambient light on the recording device or interference with the recording device. By having a correspondingly strong illumination of this wavelength (for example about 804 nm) and the resulting distance from the light component of this wavelength (which is included in the ambient light to a small extent), the interference and influence of the ambient light are greatly reduced, and thus reliable detection of empty trays up to 20,000 lux of ambient light can be achieved. The scanning light used is, for example, about 804 nm, still at the beginning of the infrared range (still visible part), and can therefore be provided very cost-effectively using cheap IR LEDs as opposed to pure infrared LEDs. This means that the illumination can be achieved very cost-effectively. Illumination in the fully visible wavelength range would be very bright and disruptive for use in the passenger area. The use of the infrared range therefore means that, in particular, very cost-effective scanning light sources in the form of IR LEDs in the visible wavelength range can be used. In addition, the scanning spectrum differs to a large extent from the ambient light, especially when the ambient light is purely artificial light in a building. This also means that, in addition to the correlation of the different polarizations, the scanning spectrum can now also be better distinguished from the ambient light that is otherwise present from a spectral point of view. The scanning spectrum is preferably very close to, but not or only partially within, the range visible to the human eye. This leads to a further cost reduction, since correspondingly cost-effective scanning light sources and recording devices can be used. In addition, in order to further enhance the functionality of the present invention, the scanning spectrum has a very narrow width, i.e. it is designed to be narrow. The possible width of the scanning spectrum is, for example, about 10 nanometers. This leads to a further significant reduction in the interfering influence of ambient light.

[0018] In the detection device according to the invention, further advantages can be achieved if the scanning light source has a plurality of individual scanning lamps, which in particular have the same or essentially the same radiation direction. Of course, a single high-power scanning lamp is also conceivable. However, the use of a plurality of scanning lamps, in particular with the same radiation direction, preferably with parallel or essentially parallel radiation directions, can bring advantages. For example, the parallel emission from a plurality of scanning lamps allows a particularly uniform distribution of the scanning light over a large scanning area. The irradiation and therefore the emission from the scanning lamps along the radiation direction preferably takes place from above downward onto the scanning area, as will be explained in more detail later with reference to the transport system. In particular, for this purpose, the scanning light source is designed as a planar light source, as described above.

[0019] In the detection device according to the invention, it is also advantageous if the scanning light source generates scanning light whose brightness exceeds the brightness of the ambient light. In other words, the brightness of the scanning light of the scanning light source is stronger than the ambient light in order to further reduce its influence on the recording device. This can be specified automatically, can be performed manually by inputting light parameters of the ambient light, or can also be performed in a controlled manner with the aid of an ambient light sensor. This can also bring advantages if the wavelength of the ambient light is known and therefore not only the intensity but also, as already explained, the spectral width can be distinguished from the defined spectral width of the ambient light.

[0020] If in the detection device according to the invention, a reflection spectrum filter is arranged in the optical path in front of the recording device, whose transmission spectrum corresponds to or substantially corresponds to the scanning spectrum, further advantages can be achieved. Therefore, this reflection spectrum filter causes the wavelength range that is not in the transmission spectrum and therefore not in the scanning spectrum to be excluded and cannot reach the recording device. This improves the reliability of the recording according to the invention, because although ambient light with different polarization directions can partially penetrate the reflection polarization filter, due to the additional transmission spectrum arranged after the reflection polarization filter, the ambient light can no longer penetrate the reflection spectrum filter. In other words, in this way, on the one hand, the ambient light of diffuse polarization caused by the spectrum can be filtered out, and on the other hand, the polarization difference can be used for the detection function in the described way. In this way, other light influences or glare effects caused by ambient light can be reduced or even largely excluded.

[0021] In the detection device according to the invention, it is also advantageous if this includes a scanning area for temporarily accommodating trays of a conveyor system, in particular the scanning area forms part of the conveyor system. For example, if the conveyor system has conveyor belts or conveyor rollers, these are also arranged in the scanning area and serve to convey trays into the scanning area and also convey them out of the scanning area again when they are detected as empty. This is integrated in particular into the hand-held baggage scanners that have already been explained several times.

[0022] In the detection device according to the invention, it is also advantageous if a scanning distance is formed between the scanning light source and the recording device on one side and the scanning area on the other side. This is in particular designed as a fixed scanning distance and is larger than hand-held luggage items that are usually present in such a tray. Preferably, this dimension is also large enough to allow a part of a human body to enter the tray, in particular to allow an object to be removed from the object tray.

[0023] In the detection device according to the invention, it is also advantageous if the scanning area has a position sensor to detect the pallet conveyed into the scanning area by the conveying system. This makes it possible to carry out the detection method explained later not only when the pallet is stationary, but also at least partially during the movement of the pallet. Strip-by-strip detection and / or a complete detection of the entire pallet can be carried out. The use of a mobile pallet means that the detection device can be arranged more flexibly at the safety gate, in particular at any point in the travel of the conveying system, and not necessarily at the end of the conveying system. Since no time loss due to the detection of stationary pallets has to be accepted, the throughput of the inspected pallets is also accelerated. With the aid of a position sensor, for example in the form of a grating, a mechanical switch, a magnetic switch or an optical detector, it is possible in particular to synchronize the detection method with the movement of the pallet on the conveying system in time. In the simplest case, the detection method starts in response to a position signal from the position sensor when the pallet has been moved to the desired position.

[0024] If, in the detection device according to the invention, the scanning light source and the recording device are arranged in a common housing for arrangement above the scanning area, this brings further advantages. Integration into a common housing results in equal distances and identical orientations relative to the scanning area, so that in particular in the subsequent evaluation the evaluation can be carried out more easily and more quickly. In addition, in this way the radiation direction and the detection direction are brought into alignment and the compactness of such a detection device is further increased.

[0025] According to the previous paragraph, in such a detection device, it is advantageous if the scanning light source is optically sealed to the recording device in a common housing. Reflective elements, absorbing elements, etc. can be used for this purpose. In other words, an optical short circuit between the scanning light source and the recording device is reliably avoided.

[0026] In the detection device according to the invention, it is also advantageous if the scanning light source is designed as an infrared light source and the recording device is designed as an infrared camera. As has already been explained in several aspects, the design in the infrared range brings great advantages to the scanning light source and the recording device in terms of functional reliability and at the same time in terms of cost reduction. This also makes it easy to distinguish from visible light, in particular ambient light.

[0027] The subject of the invention also includes a conveyor system for conveying trays for transporting objects, in particular in the form of hand luggage objects, which conveyor system has at least one detection device according to the invention. The conveyor system according to the invention thus has the same advantages as have already been explained in detail with reference to the detection device according to the invention.

[0028] In particular, in the transport system according to the invention and when using the detection device according to the invention, special trays are used. In order to avoid light reflections from natural and / or artificial ambient light, these can have a surface with increased roughness. In this way, diffuse reflections can occur on such surfaces instead of focused reflections, so that optical interferences can be avoided.

[0029] Furthermore, the subject matter of the invention comprises a detection method for detecting an empty pallet in such a conveying system for pallets for conveying objects, comprising the following steps:

[0030] - generating a scanning light beam having a scanning spectrum,

[0031] - polarizing the scanning light using a scanning polarization filter having a first polarization angle,

[0032] - directing the polarized scanning light into the scanning area,

[0033] - recording, by means of a recording device behind a reflective polarization filter, the reflected light reflected from the scanning area, the reflective polarization filter having a second polarization angle different from the first polarization angle,

[0034] - identifying objects in the scanning area based on polarized reflected light that has passed through the reflective polarization filter.

[0035] The detection method according to the invention has the same advantages as have already been explained in detail with reference to the detection device according to the invention. When identifying an object, the captured image can be scanned, for example, point by point or line by line. This leads to the recognition of the contours or the shape of the object, which has already been explained several times, i.e. in particular a purely two-dimensional representation of the captured image. At the same time, this makes it possible to detect the absence of any object with a high degree of certainty and thus to determine an empty pallet.

[0036] As already explained, the scanning light can be generated and / or guided in a planar manner as surface light in particular. In the manner already described, this leads to a more uniform illumination and to a reduction and / or avoidance of optical disturbances such as reflections.

[0037] Furthermore, in the detection method according to the invention, a spectral filter having a transmission spectrum corresponding or substantially corresponding to the scanning spectrum can also be used. In this way, interfering ambient light can be blocked for the recording device.

[0038] In the detection method according to the invention, advantages can result if known, in particular constant contours are subtracted for identifying the object. For example, a pallet can have a structure that is the same for each pallet. Printed marks are also possible, which, due to their surface structure, can be perceived by the recording device via a reflective polarization filter. Here, during the imaging process, these constant and therefore known contours can simply be optically subtracted from the recorded image and thus made unrecognizable further, so that the detection of empty pallets can be carried out in the same simple, cost-effective and fast manner.

[0039] In the detection method according to the invention, further advantages result if at least one limit value is taken into account when identifying an object, in particular with respect to the size of the object and / or the brightness of the object. This makes it possible to avoid "empty" signaling with a high degree of certainty in the case of very small objects or reflections that do not originate from an object.

[0040] In the detection method according to the invention, it is also advantageous if an object signal is generated if at least one object is recognized and / or an "empty" signal is generated if no object is present. This is in particular non-specific for the object and can mean simply outputting a signal. However, such a signal can also be transmitted as control information for the conveying system. This makes it possible, for example, for a pallet to leave the scanning area only as an empty pallet. The output of a visual signal, for example in connection with a red or green color signal, can also make it possible to distinguish between empty pallets and object pallets in a simple and fast manner.

[0041] In this inspection method, it is also advantageous if the inspection device records at least one image for each pallet. That is, one, in particular exactly one, inspection photograph is taken per pallet, so that the inspection step can be performed easily and cost-effectively with a low computational effort. Continuous photographs are also conceivable when the pallets are fed in and thus when the movement of the pallets is tracked. The timing intervals of such photographs can be, for example, in the range of 0.5 seconds.

[0042] Advantages can also result if the detection method according to the invention comprises a step of identifying the edge of the object and / or the pallet. In this way, the object can be identified or even defined based on its contour. The detection of the edge of the pallet can be based on defined orientation information. In particular, if the pallet is not conveyed into the detection device in a defined guide, such an orientation detection by edge detection can result in a quality improvement of the detection method. For detecting the edge of the pallet, for example, an image evaluation is conceivable, which in a first step searches for the edge in the form of corresponding optical information from a starting point within the pallet boundary outwards towards the edge. This is especially achieved in two directions (for example in an arbitrary direction), so that two points of the edge of the pallet that are spaced apart from each other can be detected. These edge points of the edge of the pallet can be the starting points for following the edge of the pallet during the evaluation process, so that the result is a tracking of the edge of the pallet. This evaluation is carried out in particular using vectors, which are set as starting points at the corresponding points and are defined as directions and lengths for the evaluation algorithm. In this way, it is no longer necessary to search for the edge in the entire recorded image. Instead, edge points are searched specifically from which the edge can be directly registered. The computational effort required for this type of evaluation is significantly reduced compared to a normal image evaluation of the entire image area. Similar methods (especially vector-based methods) can also be used for edge detection of other objects in the tray, or separate from them. The described starting vector can have a predetermined length and / or direction. In order to further simplify the process, a predetermined specification of the starting point can also be considered.

[0043] In the detection method according to the invention, it is also advantageous if the steps of generating, polarizing, guiding, recording and identifying are at least partially performed on a pallet that is moved through the scanning area by means of a conveyor system. For example, as already explained, the entry of a pallet into the scanning area can be detected by means of a position sensor. This makes it possible to start the execution of the detection method such that the detection is specifically performed until the same or a different position sensor outputs a position signal indicating that the pallet has moved out of the scanning area. This allows the detection method to be synchronized with the movement of the pallet through the conveyor system.

[0044] Further advantages, features and details of the invention are explained in the following description, in which exemplary embodiments of the invention are described in detail with reference to the accompanying drawings. The features mentioned in the claims and in the description may in each case be essential to the invention individually or in any combination. Schematically in each case:

[0045] Figure 1 An embodiment of the detection device according to the present invention is shown,

[0046] Figure 2 A representation of an empty pallet is shown,

[0047] Figure 3 shows a representation of an object tray,

[0048] Figure 4 A comparison of different spectra is shown,

[0049] Figure 5 Another embodiment of the detection device according to the present invention is shown.

[0050] Figure 1 A conveyor system 10 is schematically shown, for example, at the end of a handheld baggage scanning system. Here, the detection device 10 is equipped with a scanning area PB, into which a tray W has been introduced, viewed here from the side. In order to observe the interior of the tray W, the detection device 10 is arranged above the scanning area PB in a common housing 50. The housing is arranged at a defined scanning distance PA from the scanning area PB, so that when objects O are detected, they can be easily removed from the tray W.

[0051] A light source 20 with a scanning lamp 26 is provided in the detection device 10 for detection. This allows the generation of scanning light PL, Figure 1 A ray of light is schematically shown. With the aid of the guiding means 24, which is designed here as a reflector, all scanning rays PL are guided through the scanning polarization filter 22 in the direction of the scanning area PB. The scanning rays PL thus have a defined scanning spectrum PS and a polarization defined according to the first polarization angle PW1. Depending on the reflection case (i.e. from the empty tray bottom of the tray W, or diffusely from the object O in the tray W), reflected light RL having the same spectrum as the scanning spectrum PS but with a different polarization (depending on the type of reflection) is now reflected back in the direction of the recording device 30. Only when the polarization of the first polarization angle PW1 is changed due to the diffuse reflection of the reflected ray RL can it at least partially pass through the reflective polarization filter 32 corresponding to the second polarization angle PW2. If this is the case, this is entirely due to the diffuse reflection from the object and is then, and only then, perceived by the recording device 30. The recognition device 40 is now able to recognize the contour of any object based on the reflected rays RL that have passed, or to infer the absence of any object O in the tray W based on the absence of any reflected ray RL that has passed. In this way, the empty tray LW and the object tray OW can be distinguished very easily, quickly and with little computational effort without detecting a specific object.

[0052] This assessment will be based on Figure 2 and 3 In both cases, this is Figure 1 Here, it can be clearly seen that the first polarization angle PW1 rotated by 90° is different from the second polarization angle PW2. As a result, in the case of an empty tray, Figure 2In the illustrated empty pallet LW, only the outline of the pallet W can be seen. If this expected constant outline of the pallet W can now be optically subtracted, this leads to the recognition device 40 recognizing the empty pallet LW and outputting an "empty" signal FS. Figure 3 The tray W in the tray contains an object O, such as a boarding pass. As a result, at least at the edge of this flat object O, the scanning light rays PL are reflected in such a way that their polarization is changed, and they can therefore at least partially pass through the reflective polarization filter 32. The recording device 30 thus generates a recording image as a function of the reflected light rays RL that have passed through. Figure 3 The image shown shows the contour of the detected object O. Here, the contour of the pallet W can also be subtracted, which contour is also constant and known, so that only the contour of the object O remains. On this basis, the recognition device 40 now outputs an object signal OS.

[0053] Figure 4 It is also shown how the individual spectra are formed relative to each other. For example, the ambient spectrum US has a broad peak in the visible range. The scan spectrum PS is preferably designed to have a very narrow band in the infrared range, for example with a peak width of 10 nanometers. In this variant, it can also be clearly seen that the intensity of the scan spectrum PS is higher than the ambient light (such as the ambient spectrum US), that is, its brightness is stronger than the ambient light.

[0054] Figure 5 A refinement of an embodiment of the detection device 10 is shown. The detection device 10 has a plurality of scanning lamps 26 in a scanning light source 20. They are arranged around the left and right sides of a central recording device 30. The recording device 30 is optically sealed relative to the scanning light source 20. In addition, all scanning lamps 26 have parallel radiation directions SR, which are oriented opposite to the detection direction as the radiation direction SR of the recording device 30. This means that a scanning area not shown here is illuminated in the same direction and in a uniform manner, and a central detection is performed in the recording device 30. In order to achieve a further improvement in the detection, a reflection spectral filter 36 is also arranged in the optical path after the reflection polarization filter 32, which serves to filter out ambient light by essentially matching its transmission spectrum with the scanning spectrum PS.

[0055] The above description describes the invention only in the context of examples. Of course, the individual features of the various embodiments may be freely combined with one another where technically advantageous, without departing from the scope of the present invention.

[0056] Reference numerals list

[0057] 10. Detection device

[0058] 20 Scanning light source

[0059] 22 Scanning polarizing filter

[0060] 24 Guide device

[0061] 26 Scanning Lights

[0062] 30 Recording Device

[0063] 32 Reflective polarizing filter

[0064] 36 reflective spectrum filters

[0065] 40 Identification device

[0066] 50 Shell

[0067] 100 conveyor system

[0068] PL scanning light

[0069] PS scanning spectrum

[0070] US Environmental Spectrum

[0071] PW1 first polarization angle

[0072] PW2 second polarization angle

[0073] PB scanning area

[0074] PA scanning distance

[0075] RL reflected light

[0076] SR radiation direction

[0077] W Pallet

[0078] O object

[0079] LW Empty Pallet

[0080] OW applicable tray

[0081] OS object signals

[0082] FS "empty" signal

Claims

1. A detection device (10) for detecting an empty pallet (LW) in a conveying system (100) of pallets (W) for transporting objects (O), comprising: A scanning light source (20) is used to generate scanning light (PL) having a scanning spectrum (PS) using a scanning polarization filter (22) having a first polarization angle (PW1); and a guiding device (24) is used to guide the scanning light (PL) to enter a scanning area (PB) through the scanning polarization filter (22), and also includes a recording device (30) for recording reflected light (PL) reflected from the scanning area (PB), the recording device (30) having a reflective polarization filter (32) having a second polarization angle (PW2) different from the first polarization angle (PW1), and also includes an identification device (40) for identifying an object (O) in the scanning area (PB) based on the polarized reflected light (RL) that has passed through the reflective polarization filter (32).

2. The detection device (10) according to claim 1, characterized in that: The first polarization angle (PW1) and the second polarization angle (PW2) are oriented at 90° or substantially 90° to each other.

3. The detection device (10) according to one of the preceding claims, characterized in that The scanning light source (20) generates the scanning light (PL) in a scanning spectrum (PS) in a range invisible to human eyes, in particular in the infrared range.

4. Detection device (10) according to one of the preceding claims, characterized in that The scanning light source (20) has a plurality of individual scanning lamps (26), which in particular have the same or substantially the same radiation direction (SR).

5. Detection device (10) according to one of the preceding claims, characterized in that The scanning light source (20) generates scanning light (PL) having a brightness exceeding the brightness of the ambient light.

6. Detection device (10) according to one of the preceding claims, characterized in that A reflection spectral filter (36) is arranged in the optical path before the recording device (30), the reflection spectral filter (36) having a transmission spectrum corresponding to or substantially corresponding to the scanning spectrum (PS).

7. The detection device (10) according to any one of the preceding claims, characterized in that The detection device comprises a scanning area (PB) for temporarily accommodating a tray (W) of the conveying system (100), in particular, the scanning area (PB) forms a part of the conveying system (100).

8. The detection device (10) according to claim 7, characterized in that: A scanning distance (PA) is formed between the scanning light source (20) and the recording device (30) on one side and the scanning region (PB) on the other side.

9. The detection device (10) according to one of claims 7 or 8, characterized in that The scanning area (PB) has a position sensor for detecting a pallet (W) transported into the scanning area (PB) by means of the transport system (100).

10. The detection device (10) according to one of the preceding claims, characterized in that The scanning light source (20) and the recording device (30) are arranged in a common housing (50) for being arranged above the scanning region (PB).

11. The detection device (10) according to claim 10, characterized in that: The scanning light source (20) is optically sealed relative to the recording device (30) in the common housing (50).

12. Detection device (10) according to one of the preceding claims, characterized in that The scanning light source (20) is designed as an infrared light source, and the recording device (30) is designed as an infrared camera.

13. A conveying system (100) for conveying a tray (W) for transporting objects (O), in particular in the form of hand luggage items, the conveying system (100) having at least one detection device (10) having the features of one of claims 1 to 12.

14. A detection method for detecting an empty pallet (LW) in a conveying system (100), in particular a conveying system (100) for conveying pallets (W) of objects (O) having the features of claim 13, comprising the following steps: - generating a scanning light (PL) with a scanning spectrum (PS), - polarizing the scanning light (PL) using a scanning polarization filter (22) having a first polarization angle (PW1), - directing the polarized scanning light (PL) into the scanning area (PB), - recording the reflected light (RL) reflected from the scanning area (PB) by means of a recording device (40) behind a reflective polarization filter (32), the reflective polarization filter (32) having a second polarization angle (PW2) different from the first polarization angle (PW1), - identifying an object (O) in the scanning area (PB) based on polarized reflected light (RL) that has passed through the reflective polarization filter (32).

15. The detection method according to claim 14, characterized in that: A known, in particular constant, contour is subtracted in order to identify the object (O).

16. The detection method according to claim 14 or 15, characterized in that: When detecting an object (O), at least one limit value is taken into account, in particular a limit value with respect to the size of the object (O) and / or the brightness of the object (O).

17. The detection method according to one of claims 14 to 16, characterized in that If at least one object (O) is identified, an object signal (OS) is generated, and / or if no object (O) is present, a “null” signal (FS) is generated.

18. The detection method according to one of claims 14 to 17, characterized in that At least one image is recorded by the detection device (40) for each tray (W).

19. The detection method according to one of claims 14 to 18, characterized in that A step of identifying an edge of the object (O) and / or the tray (W) is performed.

20. The detection method according to one of claims 14 to 19, characterized in that The steps of generating, polarizing, directing, recording and identifying are at least partially performed on a tray (W) moving through the scanning area (PB) by means of the transport system (100).

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