TRIANGULATION SENSOR AND METHOD FOR EVALUATING MEASUREMENT DATA FROM A TRIANGULATION SENSOR

Abstract

Triangulation sensor for detecting objects in a surveillance area with a transmitter (10) for emitting transmitted light (14) into the monitoring area (40), with a detector (20) for detecting transmitted light (16) reflected by objects (T1, T2) in the monitoring area (40), wherein the detector (20) has a plurality of detector segments (24) arranged along a triangulation direction (26), with a receiving optics (22) for guiding transmitted light (16) reflected from the monitoring area (40) to the detector (20), wherein a light spot can be generated on the detector (20) by transmitted light (16) reflected from an object (T1, T2) in the monitoring area (40), the position of which light spot in the triangulation direction (26) depends on the distance (d1, d2) of the object (T1, T2) from the triangulation sensor (100), with at least one housing (60) in which at least the detector (20) is accommodated for protection against environmental influences, wherein in the at least one housing (60) there is at least one front panel (62) transparent to the transmitted light (14, 16), with a control and evaluation unit (30) for controlling the transmitter (10), for evaluating the measurement signals supplied by the detector (20) and for generating an “object detected” signal depending on the evaluation, wherein the control and evaluation unit (30) is configured to generate range signals (N1, N2, N3, N4, F) belonging to different detector ranges (n1, n2, n3, n4, f), wherein the different detector ranges (n1, n2, n3, n4, f) each comprise at least one detector segment (24), and to evaluate the area signals (N1, N2, N3, N4, F) and, depending on this evaluation, to generate a signal corresponding to a status “windscreen dirty”, characterized by that the control and evaluation unit (30) is designed not to carry out a check of the contamination state of the windscreen (62) when an object (T1, T2) is detected in the monitoring area (40).

Description

[0001] In a first aspect, the invention relates to a triangulation sensor according to the preamble of claim 1. Furthermore, the invention relates to a method for evaluating measurement data of a triangulation sensor according to the preamble of claim 17.

[0002] A generic triangulation sensor and a generic method are described, for example, in DE 10 2017 106 380 A1. Monitoring the contamination level of a windshield of an optical sensor is known, for example, from DE 20 2006 014 925 U1.

[0003] A generic triangulation sensor for detecting objects in a surveillance area comprises a transmitter for emitting transmitted light into the surveillance area and a detector for detecting transmitted light reflected by objects in the surveillance area. The detector comprises a plurality of detector segments arranged along a triangulation direction. Furthermore, a receiving optics system is provided for directing transmitted light reflected from the surveillance area to the detector. The transmitted light reflected by an object in the surveillance area can generate a light spot on the detector, the position of which light spot in the triangulation direction depends on the distance of the object from the triangulation sensor. At least one housing is provided in which at least the detector is accommodated for protection against environmental influences.The at least one housing contains at least one front panel transparent to the transmitted light. Finally, a control and evaluation unit is provided for controlling the transmitter, evaluating the measurement signals supplied by the detector, and generating an "object detected" signal based on the evaluation. The control and evaluation unit is configured to generate range signals corresponding to different detector ranges, with the different detector ranges each comprising at least one detector segment.

[0004] In a generic method for evaluating measurement data from a triangulation sensor, transmitted light is radiated into the monitoring area, and transmitted light reflected by objects in the monitoring area is detected by a detector. The detector has a plurality of detector segments arranged along a triangulation direction. The position of a light spot on the detector, reflecting an object in the monitoring area, in the triangulation direction depends on the distance of the object from the triangulation sensor. At least one detector is located in a housing with a front panel that is transparent to the transmitted light. Several different detector areas are formed, each comprising at least one detector segment, and an area signal is generated for at least some of the detector areas.The area signals can be evaluated and, if necessary, an “object detected” signal can be generated.

[0005] Information about the degree of contamination of the front window of an optoelectronic sensor, such as a triangulation sensor, is essential for safe operation and optimal maintenance or cleaning of the sensors. This is especially true in applications with high dust exposure, such as printing machines, pallet conveyors, or the cement industry.

[0006] In addition to contamination by dust-like materials, wetting of the optical front screen with liquids can also influence the beam path of the sensor used for object detection and thus impair its operational reliability.

[0007] In VDE 20 2006 014 925 U1, a windshield is illuminated with an additional light source, and any light reflected by dirt particles present is detected by an additional detector. If necessary, an error signal corresponding to a "windshield dirty" condition is output.

[0008] DE 197 21 105 A1 describes a triangulation sensor with a segmented detector.

[0009] JP 2017-53815 A discloses an optical distance measuring device in which, for easy detection of errors, an error determination unit is provided which judges it as an error when a difference between a distance output value and a first threshold value defined based on a distance to the object is a predetermined allowable value or more.

[0010] DE 10 2010 038 186 A1 relates to a light sensor with a linear arrangement of several individual emitters that can be activated synchronously.

[0011] It can be considered an object of the present invention to provide a triangulation sensor and a method of the type specified above which require a reduced expenditure on equipment compared to the prior art.

[0012] This object is achieved by the triangulation sensor having the features of claim 1 and by the method having the features of claim 17.

[0013] The triangulation sensor of the type specified above is further developed in that the control and evaluation unit is designed to evaluate the area signals and, depending on this evaluation, to generate a signal corresponding to a status “windscreen dirty”.

[0014] The method for evaluating measurement data from a triangulation sensor of the type specified above is further developed in that the range signals are evaluated and that, depending on this evaluation, a signal corresponding to a status “windscreen dirty” is generated.

[0015] The transmitted light can generally be electromagnetic radiation in the visible range, the infrared range, and, for special applications, the UV range. Infrared light is particularly preferred because it is invisible to the human eye.

[0016] In principle, known components, such as light-emitting diodes or semiconductor lasers, can be used as transmitters for emitting transmitted light.

[0017] To direct the transmitted light into the surveillance area, a transmitting optics system may be present. The transmitting optics system may include one or more of the following components: lenses, mirrors, and apertures.

[0018] The monitoring area is the area in which objects can be detected with the triangulation sensor.

[0019] The term “reflected transmitted light” refers to the portion of the transmitted light that is reflected back by an object to be detected in the surveillance area, for example, reflected back or scattered back.

[0020] The detector is a segmented detector, essentially a large number of individual detectors arranged closely next to one another, namely along the triangulation direction. The detector segments can also be referred to as pixels. For example, the detector can have 64 detector segments. Typically, semiconductor components, such as a CCD array or CMOS detectors, can be used.

[0021] The triangulation direction is the direction in which a light spot generated on the detector by the transmitted light reflected from an object moves when the distance of the object from the triangulation sensor is varied.

[0022] Those areas or detector segments of the detector on which the light spot is generated when the object is comparatively close to the triangulation sensor are also referred to as the near area or detector segments of the near area.

[0023] The areas or detector segments of the detector on which the light spot is generated when the object is comparatively far away from the triangulation sensor in the monitoring area are also called the far area or detector segments of the far area.

[0024] The term receiving optics refers to those optical components, such as lenses, mirrors, apertures, through which the light coming from the monitoring area passes before it hits the detector.

[0025] In principle, known components, such as microcontrollers or comparable programmable components such as FPGAs, particularly with digital and analog functionality, can be used as control and evaluation units.

[0026] It is known to combine the various detector segments into detector areas. Object detection with a triangulation sensor is then achieved by evaluating, in particular by comparing, for example, dividing or subtracting, the area signals belonging to individual detector areas. By appropriately selecting the detector areas, the switching distance of the triangulation sensor can be adjusted in a generally known manner.

[0027] An essential idea of the present invention can be considered to be the use of those components which are used for object detection, namely both the transmitter and the detector, also for checking the contamination status of the windscreen.

[0028] A significant advantage compared to the state of the art, for example compared to DE 20 2006 014 925 U1, is that no additional light source or detector is required.

[0029] Advantageous embodiments of the triangulation sensor according to the invention and preferred variants of the method according to the invention are explained below, in particular in connection with the dependent claims and the figures.

[0030] The triangulation sensor according to the invention is particularly suitable for implementing the method according to the invention. The method according to the invention is particularly suitable for evaluating measurement data from a triangulation sensor according to the invention.

[0031] While it is fundamentally possible for a detector region to consist of only a single detector segment, advantageous embodiments of the triangulation sensor according to the invention are characterized in that at least one detector region, in particular several or all detector regions, comprise or comprise at least two detector segments.

[0032] If the detector segments are combined into detector areas, the evaluation of the measurement data can be carried out more quickly because all detector segments no longer have to be read out separately.

[0033] In principle, detector regions can also be formed by detector segments that are not directly adjacent to one another. However, preferred embodiments of the triangulation sensor according to the invention are characterized in that the detector regions consist of pairs of directly adjacent detector segments.

[0034] There is fundamental freedom in the dimensioning of the detector areas. Because the long-range range generally does not require a differentiated measurement, but rather only the total amount of light reflected from areas that are further away from the triangulation sensor than the switching distance (background), designs are appropriate or required in which all detector segments of the long-range range form a single detector area.

[0035] In contrast to the long-range range, it can often be expedient to measure the near range in a more differentiated manner. Therefore, embodiments of the triangulation sensor according to the invention are preferred in which the detector segments of the near range form multiple detector regions, for example, four detector regions.

[0036] There is considerable design freedom with regard to the generation of the range signals from the measurement signals of the individual detector segments. In a preferred variant, the range signals are generated by calculating a sum or an average of the measurement signals of the detector segments constituting the respective detector ranges. For better comparability, the range signals obtained in this way can be weighted with factors that take into account the geometry of the beam path with respect to the respective detector segments.

[0037] In terms of the device, the control and evaluation unit can be configured to generate the area signals for at least some, in particular for all, detector areas by forming a sum or an average of the measurement signals of the detector segments constituting the respective detector areas.

[0038] In principle, it is possible to generate light coming from the monitored area for contamination detection, which is scattered or otherwise deflected by dirt particles on the windshield and then reaches the detector. However, preferred variants of the method according to the invention are characterized in that essentially transmitted light, which is reflected by dirt particles on the windshield and detected by the detector, is used to monitor the degree of contamination of the windshield.

[0039] In triangulation sensors and other optical sensors, it is generally known to vary the transmission power depending on the total amount of light incident on the detector. Specifically, it is expedient to operate with a higher transmission power of the transmitter when a comparatively large amount of light from the monitored area falls on the detector, and to reduce the transmission power accordingly when a comparatively small amount of light from the monitored area falls on the detector. In this context, it may be expedient with regard to the present invention if the upper limits and / or the lower limits of at least one value interval, in particular of several or all value intervals, are adapted or changed depending on the transmission power of the transmitter.

[0040] Typically, the value intervals are shifted towards higher reception intensities at higher transmission powers and vice versa.

[0041] In the case of the triangulation sensor, it may then be expedient for the transmitter to be located in the same housing as the receiver, for the transmitted light emitted by the transmitter to be transmittable through the front window into the monitoring area, and for the transmitted light reflected by dirt particles on the front window to be detectable by the detector.

[0042] The transmitter, the detector and the front screen are also preferably arranged and designed in such a way that transmitted light reflected back from components within the triangulation sensor, in particular from the front screen, cannot be detected by the detector and that transmitted light emitted by the transmitter cannot reach the detector directly.

[0043] In a further preferred embodiment of the triangulation sensor according to the invention, the control and evaluation unit is designed to a) to evaluate whether the respective range signals are within a value interval defined for the respective detector range, and b) to generate the signal corresponding to the status “windscreen dirty” if the evaluation under a) delivers range signals within one of the respective value intervals for at least a specified number of detector ranges.

[0044] In principle, the value intervals can be selected individually for each detector range. However, in preferred embodiments of the triangulation sensor according to the invention, the value intervals have the same lower limit and / or the same upper limit for at least two detector ranges, and in particular for all detector ranges.

[0045] Because the individual detector areas usually differ relative to the receiving optics and relative to the transmitter with regard to possible scattering geometries, it may be useful for the upper limits of the value intervals to be different for at least two detector areas, in particular for all detector areas.

[0046] Furthermore, to prevent the triangulation sensor from switching back and forth, caused, for example, by noisy signals, it may be expedient to provide switching hysteresis. For this purpose, the upper and / or lower limits of at least one value interval, in particular of several or all value intervals, are selected differently depending on the direction in which the respective limit is penetrated by a time-dependent signal.

[0047] As a rule, the front screen of a triangulation sensor becomes largely evenly contaminated, for example, due to dust ingress. For this reason, it may be useful to check whether the ingress of scattered light into the individual detector areas is uniform in a qualified manner. According to the invention, no "front screen dirty" signal is generated if at least one area signal deviates in a qualified manner from an average value of the area signals.

[0048] Accordingly, in the triangulation sensor according to the invention, the control and evaluation unit can be configured to form an average value of the range signals, to compare the range signals with the average value and to generate the signal “windscreen dirty” only if at least a predetermined number of range signals, in particular all range signals, do not differ from the average value by more than a predetermined maximum value.

[0049] In principle, it is advantageous to use as many detector segments and / or as many range signals as possible for the evaluation of the "windshield dirty" status. The detector ranges are preferably selected so that as many detector segments as possible belong to each of the detector ranges. For example, for the evaluation of the "windshield dirty" status, detector ranges from the near range and one detector range from the far range can be evaluated.

[0050] In the triangulation sensor according to the invention, the control and evaluation unit can be configured to evaluate detector areas from the near range and a detector area from the far range for the evaluation with regard to the status “windscreen dirty”.

[0051] Preferably, the measurement signals from all detector segments or the area signals from all detector areas can be taken into account for the evaluation with regard to the contamination status of the windscreen.

[0052] In principle, the detector segments for checking the contamination level of the windshield can be grouped into detector areas differently than for object detection. However, in advantageous embodiments of the invention, the same division of the detector areas is used for checking the contamination level of the windshield and for object detection. In advantageous variants of the method according to the invention, the area signals used to determine the contamination level of the windshield can also be used to detect an object in the monitoring area.

[0053] The control and evaluation unit can be configured accordingly to use the area signals used to determine the contamination level of the windscreen also to detect an object in the monitoring area.

[0054] The reliability of detecting a dirty windscreen can be increased if the windscreen's contamination status is only checked when no object is detected in the monitoring area.

[0055] According to the invention, the control and evaluation unit is designed not to check the contamination level of the windscreen when an object is detected in the monitoring area.

[0056] Further advantages and properties of the triangulation sensor according to the invention and the method according to the invention are explained below with reference to the attached figures. Fig.1: a schematic view of a triangulation sensor according to the invention; Fig. 2: a diagram in which the measurement signals of the individual detector segments are plotted and which shows a typical signal curve when an object is detected in the monitoring area; Fig. 3: a diagram illustrating the grouping of detector segments into detector areas and the area signals corresponding to an object in the monitoring area with a clean windscreen; Fig. 4: a diagram showing typical area signals with a slightly and evenly soiled windscreen without an object in the monitoring area; Fig. 5: a diagram showing typical area signals for a more uniformly soiled windscreen without an object in the monitoring area; Fig.6: a diagram showing typical range signals for unevenly soiled windscreens without an object in the monitoring area as well as separate lower and upper limits for the purpose of switching hysteresis and Fig. 7: a diagram showing typical area signals when the windscreen is dirty and there is an object in the monitoring area.

[0057] In Fig. 1 shows an embodiment of a triangulation sensor 100 according to the invention for detecting objects T1, T2 in a monitoring area 40. The essential components of the triangulation sensor 100 are a transmitter 10 for emitting transmitted light 14 into the monitoring area 40, a detector 20, and a control and evaluation unit 30 for controlling the transmitter 10 and for evaluating the measurement signals supplied by the detector 20.

[0058] The transmitter 10 can, for example, be an infrared laser diode. To direct the transmitted light 14 into the monitored area, a transmitting optics 12 is provided, which in the illustrated embodiment is formed by a lens.

[0059] The detector 20 serves to detect transmitted light 16 that has been reflected by objects T1, T2 in the monitored area 40 in the direction of the triangulation sensor 100. According to the invention, the detector 20 has a plurality of detector segments 24 arranged along a triangulation direction 26. For example, the detector 20, which is a CMOS detector, for example, can have 64 detector segments.

[0060] For guiding transmitted light 16 reflected from the monitoring area 40 to the detector 20, a receiving optics 22 is provided, which in the embodiment shown is formed by a lens 22.

[0061] According to the known triangulation principle, transmitted light 16, which was reflected by an object T1, T2 in the monitored area 40 in the direction of the triangulation sensor 100, creates a light spot on the detector 20, the position of which in the triangulation direction 26 depends on the distance d1, d2 of the object T1, T2 from the triangulation sensor 100. More precisely, the light spot created on the detector 20 by the transmitted light 16 reflected by an object T1, T2 in the direction of the triangulation sensor 100 migrates in Fig.1 in the triangulation direction 26 upwards, the further the object is from the triangulation sensor 100. The distance d2 of the object T2 from the triangulation sensor 100 is greater than the distance d1 of the object T1. Accordingly, the light spot generated on the detector 20 by the transmitted light 16 reflected by the object T2 lies further up in the triangulation direction 26 than the corresponding light spot resulting from the transmitted light 16 reflected by the object T1.

[0062] Finally, a housing 60 is provided with a front panel 62 transparent to the transmitted light 14, 16. According to the invention, the detector 20 is accommodated in the housing 60. In the illustrated embodiment, the housing also contains the transmitter 10, the transmitting optics 12, the receiving optics 22, and the control and evaluation unit 30.

[0063] The control and evaluation unit 30, as known in the prior art, also serves to generate an “object detected” signal depending on the evaluation of the measurement data of the detector 20.

[0064] During operation at the site, the light transmission through the front screen 62 may deteriorate due to contamination, such as dust. The invention serves to reliably determine the contamination level of the front screen 62.

[0065] In the Fig.In the example of a triangulation sensor 100 according to the invention shown in Figure 1, transmitted light 14, which is reflected by dirt particles on the front window 62 and detected by the detector 20, is used to monitor the degree of soiling of the front window 62. This means that the transmitter 10 and the detector 20 are arranged in the housing 60 relative to the front window 62 in such a way that transmitted light 14 reflected by dirt particles on the front window 62 can be detected by the detector 20. The transmitter 10 and the detector 20 are also expediently positioned in the housing 60 in such a way that transmitted light 14 cannot reach the detector 20 directly or by reflection from other components, and in particular in such a way that transmitted light 14 reflected back by the front window 62 cannot be detected by the detector 20.

[0066] In connection with the Fig.2 to 7, further properties of the triangulation sensor according to the invention and of the method according to the invention are described, the diagrams shown in these figures belonging to a detector 20 with 64 detector segments.

[0067] The Fig. 2 to 7 each show diagrams in which an intensity I in arbitrary units is plotted on the vertical axis against the number 1 to 64 of the detector segments 24 of the detector 20, referred to here as pixels. The triangulation direction 26 extends in the Fig. 2 to 7 in the direction of the horizontal axis, ie that pixel number 1 is in Fig. 1 at the bottom and pixel number 64 in Fig. 1 is located at the upper end of the detector 20.

[0068] In Fig. 2, the intensity I of the measurement signals of the respective detector segments is plotted on the vertical axis in arbitrary units. Shown in Fig.1 shows a typical curve of the intensities that would be measured for an object located at the switching distance in front of the triangulation sensor 100 if each detector segment 24, i.e., each pixel, were individually read and evaluated. For example, p40 and p42 are the intensities that would be measured with pixel number 40 and pixel number 42, respectively.

[0069] As expected, the measured signal intensities for the near-field pixels are initially essentially 0. Starting at pixel number 18, the intensity then increases to a maximum value, which is reached at pixel number 26, and then decreases again. From pixel number 43 to the end of the far-field pixel number 64, the measured intensities are again essentially 0. The position and width of the signal distribution depend on the object and its distance from the triangulation sensor.

[0070] According to the invention, detector areas are formed, each comprising at least one detector segment 24. The division of the detector areas is for the examples of Fig. 3 to 7 are each the same. The near field is divided into four equally sized detector areas, each consisting of seven detector segments or pixels arranged in pairs directly adjacent to each other. The far field has been combined into a single detector area f consisting of pixels 29 to 64.

[0071] In detail: Detector range n1: Pixels 1 to 7 Close range Detector range n2: Pixel 8 to 14 Close range Detector range n3: Pixels 15 to 21 Close range Detector area n4: Pixels 22 to 28 Close range Detector range f: Pixels 29 to 64 Long-distance area

[0072] According to the invention, the control and evaluation unit 30 is then configured to generate range signals N1, N2, N3, N4, F for the detector ranges n1, n2, n3, n4, and f, respectively. For example, the range signals N1, N2, N3, N4, F can be generated by forming a sum of the measurement signals of the detector segments 24 constituting the respective detector ranges n1, n2, n3, n4, f. The control and evaluation unit 30 can therefore be configured to generate the range signals N1, N2, N3, N4, F, respectively by forming the sum of the measurement signals of those detector segments that form the respective detector range.

[0073] In the illustrated embodiment, the control and evaluation unit 30 is configured to evaluate the range signals N1, N2, N3, N4, F and, depending on this evaluation, to output an "object detected" signal if an object is located within the switching distance in front of the triangulation sensor 100. The switching distance is defined by specifying the detector ranges belonging to the near range and the far range.

[0074] This is used in conjunction with the diagram in Fig. 3, which shows the range signals N1, N2, N3, N4, F, which can be used for the Fig.2. As can be seen, the range signals N1 and N2 are each 0, corresponding to the measurement signals of pixels 1 to 14. The range signal N3 is 1 in the units shown, corresponding to the averaged measurement signals of pixels 15 to 21. The range signal N4 is then approximately 14 in the units shown, corresponding to the averaged measurement signals of pixels 22 to 28. The range signal F, i.e. the signal corresponding to the far range, is approximately 9 in the units shown.

[0075] By means of generally known evaluation methods in which range signals N1, N2, N3, N4 of the near range are compared with the range signal F of the far range, for example by division or subtraction and subsequent comparison with threshold values, an "object detected" signal can be obtained if the respectively defined criteria are met. This signal can be provided for further processing, for example, at an output 64 of the triangulation sensor 100 according to the invention, which can be a bus interface, for example.

[0076] According to the invention, the control and evaluation unit 30 is also configured to evaluate the range signals N1, N2, N3, N4, F and, depending on this evaluation, to generate a signal corresponding to a status “windscreen dirty”. For this purpose, the Fig. 4 to 7 are considered.

[0077] In the triangulation sensor 100, the control and evaluation unit 30 can be configured to a) evaluate whether the respective range signals N1, N2, N3, N4, F are within a value interval S1, S2 defined for the respective detector range n1, n2, n3, n4, f, and b) generate the signal corresponding to the status “windshield dirty” if the evaluation under a) delivers range signals N1, N2, N3, N4, F within one of the respective value intervals for at least a predetermined number of detector ranges and in particular for all detector ranges n1, n2, n3, n4, f. This is determined using Fig. 4 is explained in more detail. Fig. Figure 4 shows a diagram with the area signals N1, N2, N3, N4 and F for a situation in which there is no object in the monitoring area and the front screen 62 (in contrast to the situation in the Fig. 2 and Fig.3) is slightly dirty. Due to dirt particles on the front screen 62, the transmitted light 14 emitted by the transmitter 10 is scattered back towards the detector 20. This leads, as shown in Fig. 4, all range signals N1, N2, N3, N4, and F are slightly increased and, in particular, are located in a suitably selected value interval between an upper limit S2 and a lower limit S1. In this case, the evaluation logic of the control and evaluation unit 30 would result in the generation of a "windshield dirty" signal, which can be provided and further processed, for example, at output 64 of the triangulation sensor 100.

[0078] In principle, the value intervals can be selected separately for each detector area. In the example of the Fig.4 this is not the case and the value intervals are identical for all detector ranges n1, n2, n3, n4, f, ie they have the same lower limit S1 and the same upper limit S2.

[0079] Fig. Figure 5 shows a situation again without an object in the monitoring area 40, but this time with a more heavily soiled windscreen 42. Here, too, all range signals N1, N2, N3, N4, and F lie within the value range defined by the upper limit S2 and the lower limit S1. As can be seen, however, the range signals decrease from the near range to the far range. The reason for this may be the position of the respective detector segments relative to the transmitter 10 and the windscreen 62. In principle, the range signals could be weighted with suitable factors to compensate for these geometric effects. For example, to determine the weighting factors, homogeneous soiling could be deliberately applied to the windscreen 62.

[0080] In order for a signal situation to be recognized as pollution, the situations of Fig. 4 and Fig. 5 all range signals are between S1 and S2. Below S1, the control and evaluation unit 30 assumes that no contamination is present. Above S2, the control and evaluation unit 30 assumes that there are objects in front of the triangulation sensor 100.

[0081] In this context, it may also be appropriate to perform a plausibility check by checking whether all range signals increase evenly. For example, an average of the range signals N1, N2, N3, N4, F can be calculated and a check can be made to determine whether a range signal N1, N2, N3, N4, F deviates from this average of the range signals in a qualified manner, i.e., by more than a minimum amount.

[0082] The threshold value of the permissible deviation from the mean value is chosen so that the range signals N1, N2, N3, N4 and F of the Fig. 5 still meet the uniformity criterion defined in this way and therefore, in the situation of Fig. 5 a signal “windscreen dirty” is still output. The range signals N1, N2, N3, N4 and F of the Fig. 6 are compared to those of the Fig. 5 is significantly less uniform and the explained uniformity criterion is for the range signals of the Fig.6 is no longer met. For example, the threshold value of the permissible deviation from the mean value is selected such that the range signals N1 and F differ more than the permissible deviation from the mean value of the range signals. In this case, no "windshield dirty" signal is generated. The evaluation logic of the control and evaluation unit 30 can be programmed such that in this case, no "windshield dirty" signal is output, but rather a different error message, if appropriate.

[0083] It may also be appropriate to select different upper limits S2, S4 and lower limits S1, S3, depending on the direction in which the respective limit is crossed by a time-dependent signal. This creates a switching hysteresis and can prevent rapid switching of the control and evaluation unit 30 in the case of noisy measurement signals. This is also explained with reference to Fig. 6 explained.

[0084] Shown are Fig. 6 a first upper limit S2 and a second upper limit S4, as well as a first lower limit S1 and a second lower limit S3. The first upper limit S2 and the second lower limit S3 apply to range signals that increase over time. The second upper limit S4 and the first lower limit S1 apply to range signals that decrease over time. This prevents rapid switching of a "windshield dirty" signal.

[0085] Fig. Finally, Figure 7 shows a situation with an object in the monitoring area 40 with a dirty windscreen 62. As can be seen, depending on the position of the object, contributions to the area signals N1, N2, N3 and N4 of the near area are also shown.

[0086] These contributions add up to the intensities resulting from windshield contamination. It's not easy to distinguish which portion comes from an object and which portion from contamination.

[0087] Therefore, it is expedient not to check the contamination level of the front window 62 if an object is detected in the monitoring area 40. The control and evaluation unit 30 can therefore be configured not to check the contamination level of the front window 62 if an object T1, T2 is detected in the monitoring area 40.

[0088] The above was done in connection with the Fig. 3 to 7 embodiments are explained in which, for the evaluation with regard to the status “windscreen dirty”, detector areas n1, n2, n3, n4 from the near range and a detector area f from the far range are evaluated.

[0089] In particular, in the examples explained, area signals N1, N2, N3, N4, F from all detector areas n1, n2, n3, n4, f are taken into account for the evaluation with regard to the contamination state of the windscreen 62 and thus the measurement signals from all detector segments or pixels.

[0090] In principle, those range signals N1, N2, N3, N4, F that are used to determine the contamination level of the windscreen 62 can also be used to detect an object T1, T2 in the monitoring area 40. However, it is also possible to use only the range signal of the far range and, for example, only the two highest range signals from the near range for the evaluation for the detection of an object.

[0091] The processes for detecting windshield contamination have essentially been explained above. The detection of objects and the programming of the control and evaluation unit 30 for outputting switching signals in the presence of objects are carried out in a manner generally known from the prior art. The detection of contamination according to the present invention has no influence on the detection of objects.

[0092] A possibly bright object in the background can lead to a reduction in the transmission power if the transmission power is automatically adjusted based, for example, on the intensity measured in the long-range range. This can lead to situations where pollution particles no longer reflect sufficient light. If necessary, the value intervals S1, S2 can be adjusted depending on the transmission power of the transmitter 10. For example, the values S1, S2 can increase monotonically with the transmission power.

[0093] In principle, the contamination detection according to the present invention achieves its best results when there are no objects in the background, i.e., at a distance of approximately 1.5 m or more. A possibly bright object in the background can generate a strong signal in the far range, which may exceed the upper threshold S2. This could be counteracted by specifically adjusting the value range for the far range, for example, using a higher threshold S2 for the far range.

[0094] If a comparatively short sensing range is set for the triangulation sensor, for example, less than 15 cm, the near range becomes very small and the far range very large. This can result in uneven weighting and less reliable object detection. Therefore, sensing ranges of less than 15 cm should generally be avoided.

[0095] The contamination detection according to the present invention generally works best with uniform contamination, such as dust ingress.

[0096] The present invention provides a novel triangulation sensor and a method for evaluating measurement data from a triangulation sensor, which, compared to the prior art, enable a less complex but reliable determination of the contamination status of a windscreen. List of reference symbols 10 channels 12 Transmitting optics 14 Transmitting light 16 transmitted light reflected from object T1, T2 in the monitoring area 40 20 detector 22 Receiving optics 24 detector segments 26 Triangulation direction 30 Control and evaluation unit 40 monitoring area 60 housings 62 Windshield 64 interface 100 inventive triangulation sensor d1 Distance of object T1 from the triangulation sensor 100 d2 Distance of object T2 from the triangulation sensor 100 p40 measurement signal of pixel no. 40 p42 measurement signal of pixel no. 42 F Long-range signal f N1 Near-field signal n1 N2 Near-field signal n2 N3 Near-field signal n3 N4 Near-field signal n4 S1 lower threshold / first lower threshold S2 upper threshold / first upper threshold S3 second lower threshold S4 second upper threshold T1 first object in the surveillance area 40 T2 second object in the surveillance area 40

Claims

[1] Triangulation sensor for detecting objects in a surveillance area with a transmitter (10) for emitting transmitted light (14) into the monitoring area (40), with a detector (20) for detecting transmitted light (16) reflected by objects (T1, T2) in the monitoring area (40), wherein the detector (20) has a plurality of detector segments (24) arranged along a triangulation direction (26), with a receiving optics (22) for guiding transmitted light (16) reflected from the monitoring area (40) to the detector (20), wherein a light spot can be generated on the detector (20) by transmitted light (16) reflected from an object (T1, T2) in the monitoring area (40), the position of which light spot in the triangulation direction (26) depends on the distance (d1, d2) of the object (T1, T2) from the triangulation sensor (100), with at least one housing (60) in which at least the detector (20) is accommodated for protection against environmental influences, wherein in the at least one housing (60) there is at least one front panel (62) transparent to the transmitted light (14, 16), with a control and evaluation unit (30) for controlling the transmitter (10), for evaluating the measurement signals supplied by the detector (20) and for generating an “object detected” signal depending on the evaluation, wherein the control and evaluation unit (30) is configured to generate range signals (N1, N2, N3, N4, F) belonging to different detector ranges (n1, n2, n3, n4, f), wherein the different detector ranges (n1, n2, n3, n4, f) each comprise at least one detector segment (24), and to evaluate the area signals (N1, N2, N3, N4, F) and, depending on this evaluation, to generate a signal corresponding to a status “windscreen dirty”, characterized by , that the control and evaluation unit (30) is designed not to carry out a check of the contamination state of the windscreen (62) when an object (T1, T2) is detected in the monitoring area (40). [2] Triangulation sensor according to claim 1, characterized by that at least one detector region (n1, n2, n3, n4, f), in particular several or all detector regions (n1, n2, n3, n4, f), comprises or comprise at least two detector segments (24). [3] Triangulation sensor according to claim 1 or 2, characterized by that the detector areas (n1, n2, n3, n4, f) consist of pairs of directly adjacent detector segments (24). [4] Triangulation sensor according to one of claims 1 to 3, characterized by that all detector segments (24) of a long-range area form a single detector area (f). [5] Triangulation sensor according to one of claims 1 to 4, characterized bythat the detector segments (24) of a close range form several detector areas, in particular four detector areas (n1, n2, n3, n4). [6] Triangulation sensor according to one of claims 1 to 5, characterized by that the control and evaluation unit (30) is designed to generate the area signals (N1, N2, N3, N4, F) for at least some, in particular for all, detector areas by forming a sum or an average value of the measurement signals of the detector segments (24) constituting the relevant detector areas (n1, n2, n3, n4, f). [7] Triangulation sensor according to one of claims 1 to 6, characterized by that the control and evaluation unit (30) is designed to a) to evaluate whether the respective range signals (N1, N2, N3, N4, F) are in a value interval (S1, S2) defined for the respective detector range (n1, n2, n3, n4, f), and b) to generate the signal corresponding to the status “windscreen dirty” if the evaluation under a) delivers range signals (N1, N2, N3, N4, F) within one of the respective value intervals (S1, S2) for at least a predetermined number of detector ranges (n1, n2, n3, n4, f). [8] Triangulation sensor according to claim 7, characterized by that the value intervals (S1, S2) have the same lower limit (S1) and / or the same upper limit (S2) for at least two detector ranges (n1, n2, n3, n4, f) and in particular for all detector ranges (n1, n2, n3, n4, f). [9] Triangulation sensor according to claim 7 or 8, characterized by that the upper limits (S2, S4) of the value intervals (S1, S2, S3, S4) are different for at least two detector areas (n1, n2, n3, n4, f), in particular for all detector areas (n1, n2, n3, n4, f). [10] Triangulation sensor according to one of claims 7 to 9, characterized bythat the upper limits (S2, S4) and / or the lower limits (S1, S3) of at least one value interval (S1, S2, S3, S4), in particular of several or all value intervals (S1, S2, S3, S4), are different, depending on the direction in which the limit in question is penetrated by a time-dependent signal. [11] Triangulation sensor according to one of claims 7 to 10, characterized by that the upper limits (S2, S4) and / or the lower limits (S1, S3) of at least one value interval (S1, S2, S3, S4), in particular of several or all value intervals (S1, S2, S3, S4), are adapted or changed depending on a transmission power of the transmitter (10). [12] Triangulation sensor according to one of claims 1 to 11, characterized by , that the transmitter (10) is located in the same housing (60) as the receiver (20), that transmitted light (14) emitted by the transmitter (10) can be transmitted through the front screen (62) into the monitoring area (40) and that transmitted light (14) reflected back by dirt particles on the front screen (62) can be detected by the detector (20). [13] Triangulation sensor according to one of claims 1 to 12, characterized by that transmitted light (14) reflected back from the front screen (62) cannot be detected by the detector (20). [14] Triangulation sensor according to one of claims 1 to 13, characterized byin that the control and evaluation unit (30) is designed to form an average value of the range signals (N1, N2, N3, N4, F), to compare the range signals (N1, N2, N3, N4, F) with the average value and to generate the signal "windscreen dirty" only if at least a predetermined number of range signals (N1, N2, N3, N4, F), in particular all range signals (N1, N2, N3, N4, F), do not differ from the average value by more than a predetermined maximum value. [15] Triangulation sensor according to one of claims 1 to 14, characterized by , that the control and evaluation unit (30) is designed to For the evaluation with regard to the status “windscreen dirty”, detector areas (n1, n2, n3, n4) from the near range and one detector area (f) from the far range are to be evaluated. [16] Triangulation sensor according to one of claims 1 to 15, characterized by , that the control and evaluation unit (30) is designed to to use the area signals (N1, N2, N3, N4, F) used to determine a contamination state of the windscreen (62) also for the detection of an object (T1, T2) in the monitoring area (40). [17] Method for evaluating measurement data of a triangulation sensor, in particular according to one of claims 1 to 16, in which transmitted light (14) is radiated into the monitoring area (40) and transmitted light (16) reflected by objects (T1, T2) in the monitoring area (40) is detected with a detector (20), wherein the detector (20) has a plurality of detector segments (24) arranged along a triangulation direction (26), wherein a position of a light spot on the detector (20) attributable to an object (T1, T2) in the monitoring area (40) in the triangulation direction (26) is dependent on the distance (d1, d2) of the object (T1, T2) from the triangulation sensor (100), wherein at least the detector (20) is located in a housing (60) with a front panel (62) transparent to the transmitted light (14, 16), wherein a plurality of different detector areas (n1, n2, n3, n4, f) are formed, each comprising at least one detector segment (24), and wherein a range signal (N1, N2, N3, N4, F) is generated for at least some of the detector areas (n1, n2, n3, n4, f), and wherein the range signals (N1, N2, N3, N4, F) are evaluated and, depending on this evaluation, a signal corresponding to a status “windscreen dirty” is generated, characterized by , that no “windscreen dirty” signal is generated if at least one range signal (N1, N2, N3, N4, F) deviates in a qualified manner from an average value of the range signals. [18] Method according to claim 17, characterized by that the area signals (N1, N2, N3, N4, F) are generated by forming a sum or an average value of the measurement signals of the detector segments (24) constituting the respective detector areas (n1, n2, n3, n4, f). [19] Method according to claim 17 or 18, characterized by that transmitted light (14), which is reflected by dirt particles on the windscreen (62) and detected by the detector (20), is used to monitor a degree of contamination of the windscreen (62). [20] Method according to one of claims 17 to 19, characterized bythat for the evaluation with regard to the status “windscreen dirty”, detector areas (n1, n2, n3, n4) from the near range and one detector area (f) from the far range are evaluated. [21] Method according to one of claims 17 to 20, characterized by that the measurement signals from all detector segments (24) or the area signals (N1, N2, N3, N4, F) from all detector areas (n1, n2, n3, n4, f) are taken into account for the evaluation with regard to the contamination state of the windscreen (62). [22] Method according to one of claims 17 to 21, characterized by that the area signals (N1, N2, N3, N4, F) used to determine a contamination state of the windscreen (62) are also used to detect an object (T1, T2) in the monitoring area (40). [23] Method according to one of claims 17 to 22, characterized bythat no check of the contamination status of the windscreen (62) is carried out when an object (T1, T2) is detected in the monitoring area (40).

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