Optical sensor comprising window and window monitoring unit and method of monitoring transparency of window

Abstract

The optical sensor includes an inclined window and a window monitoring unit based on optical transmission measurements of a plurality of test light emitters and test light receivers, where the emitters and receivers are arranged along a lateral extension of the window and located on opposite sides of the lateral extension, and wherein a plurality of optical paths are formed in a mesh form between the plurality of transmitters and receivers.

Description

[0001] The invention relates to an optical sensor according to the preamble of claim 1 and to a method for monitoring a window according to claim 16 .

[0002] DE 93 21 155 U1 discloses an optical sensor with a window monitoring system, which comprises a transparent window, wherein the window monitoring system comprises a light emitting diode, which is arranged opposite to a receiving diode to generate a light path between each pair of oppositely arranged receiving and light emitting diodes.

[0003] By evaluating the intensity of the received light, the window monitoring unit can determine whether there is intolerable dirt on the front window. In this case, a warning can be output on the interface.

[0004] The disadvantage of this window monitoring system is that the resolution is determined by the distance between the emitter and the receiver, and the position of the dirt cannot be accurately determined, especially the position in the vertical direction of the window. This means that although the foreign object (especially dirt) does not affect the field of view of the scanner, the warning will still be issued. The sensor is thus stopped unnecessarily.

[0005] The solution disclosed in DE 10 2017 001612 A1 adopts a working scheme of arranging the light emitter and the receiver in a rotational manner, but it also fails to solve the problem of determining the vertical position of the foreign body.

[0006] The present invention aims to improve a window monitoring system to increase the availability of optical sensors without affecting their reliability.

[0007] The optical sensor according to claim 1 and the window monitoring method according to claim 16 solve the above-mentioned problems.

[0008] The dependent claims are advantageous embodiments of the invention.

[0009] According to the prior art, the optical sensor comprises a transparent window having a lateral extension and an extension in a height direction, through which the scanning light can pass. The scanning light can be emitted and received by a scanning unit. The window has at least one window element, which has an outer element surface, which has an element width dimension and an element height dimension.

[0010] The optical sensor further includes a window monitoring unit for monitoring the transparency of the window. The window monitoring unit includes a test light emitting unit that emits test light at a plurality of emission positions spaced apart from each other in a direction extending along the width of the window. The emission positions are located at a first end of the window in a direction extending in height of the window.

[0011] The window monitoring unit further comprises a test light receiving unit which receives test light along a plurality of receiving positions spaced apart from each other along the lateral extension direction of the window. The test light receiving unit is arranged at one end of the window opposite to the test light emitting position in the height extension direction.

[0012] The test light emitting unit and the test light receiving unit are arranged so that the test light passes through at least one outer surface of the window.

[0013] The optical sensor further comprises a determination unit for determining a change in transparency of the window. The change in transparency may occur due to environmental influences, such as snow, dirt or pollen covering the outer surface of the window.

[0014] The determination unit comprises a control unit which interacts with the test light emitting unit and the test light receiving unit to analyze the test light transmitted along the plurality of light paths, in particular in terms of the received light intensity.

[0015] Each optical path is defined as extending between a pair of positions, ie between a pair of transmitting and receiving positions. The transmitting and receiving positions are absolute positions distributed in a predefined manner in the lateral direction of the window.

[0016] The optical path mentioned in the context of the present invention is considered in an idealized manner as a straight linear connection between its end positions, i.e., a transmitting position and a receiving position paired therewith, wherein the linear connection may be vertical or inclined. In order to evaluate the intensity of the test light transmitted along a specific optical path, the intensity is determined when the receiving position receives only the test light from the transmitting position paired therewith. The control unit performs pulse synchronization processing on the transmitter while measuring the intensity of the test light received at the receiver paired with the transmitter to synchronize the measurement.

[0017] A set of evaluated light paths for which corresponding intensities have been determined is predefined in the control unit.

[0018] According to the present invention, the set of evaluated optical paths includes a plurality of optical paths, the plurality of optical paths including a first optical path and a second optical path. The first optical path is defined as having a first offset between its receiving position and an emission position paired with the receiving position, and at least the second optical path is defined as having a second offset between its receiving position and an emission position paired with the receiving position. According to the present invention, the first offset and the second offset differ in a defined lateral offset distance and / or lateral offset direction. The offset of the first optical path or the second optical path may be zero.

[0019] Therefore, the window monitoring unit utilizes a grid topology of optical paths, in which the transmitting position is interconnected with the receiving position through multiple optical paths with different tilt angles. Each discrete optical path connects a single transmitting position with a single receiving position, wherein each transmitting position can be interconnected with multiple receiving positions, and each receiving position can be connected to multiple transmitting positions. This results in a complex grid of optical paths with different tilt angles between the transmitting unit and the receiving unit.

[0020] According to this arrangement, the monitoring system allows the observation of the test light passing through the outer surface of the window from different directions. Foreign matter on the window is an obstacle for the test light between the emission position and the receiving position. Foreign matter that obstructs the optical paths with the same inclination angle causes a shadow effect, which makes it difficult to accurately determine the actual position of the dirt observed along these optical paths on the window, especially in the vertical direction. Therefore, one idea of ​​the present invention is that the shadow effect of the foreign matter can be reduced by observing the affected area in which the foreign matter is present at different angles, and height information about the foreign matter can be obtained by using optical paths with different inclination angles, because some of the optical paths will be obstructed by the foreign matter, while other optical paths will be able to pass through the window in the area located above or below the foreign matter in the vertical direction. The height information can then be used when evaluating the impact of the foreign matter on the reliability of the optical sensor.

[0021] Preferably, the difference between at least two lateral offset distances is greater than 1 / 8 of the window height, especially more than a quarter of the window height, and can even exceed 1 / 2 of the window height. According to this approach, a minimum viewing angle can be provided to allow reasonable resolution in the height direction of the window.

[0022] According to an advantageous embodiment of the invention, the monitoring system is designed to acquire the intensity of a set of evaluated light paths, the set of evaluated light paths comprising a subset of crossed light paths comprising a first light path and a second light path. A crossed light path is generated when the emission position of the second light path comprises an offset to the emission position of the first light path in an emission offset direction and when the reception position of the second light path comprises an offset to the reception position of the first light path in a reception offset direction opposite to the emission offset direction.

[0023] According to this arrangement, information of the test light, preferably information of the test light producing an overlapping area on the outer surface of the window, can be used to improve the ability to determine the position of the extension of the foreign matter in the height direction, because the shadow effect can be further reduced by using a high-density light path.

[0024] According to this feature, the resolution of the window monitoring unit is improved, in particular in the height dimension, because the test light is emitted along light paths at different tilt angles, some of which can pass through the foreign matter, thereby eliminating the shadow effect of the foreign matter that occurs when monitoring is performed using a parallel light beam (e.g., a light beam parallel to the height axis). This is particularly applicable to the case when the window includes two window elements that are tilted relative to each other. This makes it possible to determine on which window element the foreign matter is located, which cannot be achieved when monitoring is performed using a parallel light beam.

[0025] According to a further improvement of the window monitoring unit, a subset of the crossed optical paths comprises optical paths with a single transmitting position and multiple receiving positions, thereby achieving a complex grid topology of the optical paths, which further improves the resolution of the window monitoring device.

[0026] The advantage of this solution is that static transmitters can be used, one of which can provide test light corresponding to multiple light paths. The receiving positions can preferably be distributed symmetrically with respect to the transmitting positions. According to this solution, the test light can be used in its lateral range, thereby establishing light paths that "cross" each other in different directions. Crossing in different directions can obtain better vertical resolution for foreign objects.

[0027] In particular, the window has a curved profile, in particular a circular profile, so that the lateral extension is determined by the length of the bend. In this case, the transmitting and receiving positions are given as angular positions, and the offset is the angular distance.

[0028] According to a further advantageous embodiment, the window comprises two window elements arranged in sequence in the height direction, i.e. arranged one above the other in the extension direction of the two window elements and arranged to be inclined relative to each other. In this arrangement, the influence of the light paths of different inclination angles on the resolution in the height direction is improved. In this case, it can be determined on which window element the foreign body is located and therefore different criteria can be defined depending on the window element.

[0029] Furthermore, the optical sensor may include a data storage device in which a set of fields mapped to the surface of the window is stored. A transparency value may be assigned to each field. The transparency value is related to the transparency of the window or the change in transparency over time.

[0030] This allows the creation of a transparency distribution map of the window, which can be analyzed using an algorithm to locate the size and location of stains on the outer surface of the window.

[0031] This set of fields can be understood as a grid of fields corresponding to the grid of the window surface. For example, the information assigned to each field can be used to create a pixel distribution map of the window. In other words, the information related to each field can be represented as a digital image, making it possible to evaluate the transparency of the window using graphic image processing and / or filtering algorithms.

[0032] In another advantageous embodiment, the optical sensor comprises a data memory in which a plurality of optical path relationships are stored, wherein each optical path relationship assigns a subset of the fields to a specific optical path. This allows mapping of the window surfaces through which the test light emitted along the optical path passes to establish a correspondence.

[0033] According to a preferred embodiment, the scanning unit comprises a rotating mirror for deflecting the transmitted and received scanning light beams, wherein the test light receiving unit comprises a test light receiver and a light guide. According to this embodiment, the light guide is attached to the rotating mirror of the scanning unit. The light guide redirects / guides the test light between the test light receiving unit at multiple receiving positions and the test light emitting unit at multiple emitting positions. Due to the rotatable light guide, multiple receiving positions can be easily realized to provide high angular resolution.

[0034] The control unit further comprises an angle determination unit, which determines the angular position of the rotating mirror of the scanning unit. Therefore, the angle determination unit enables the control unit to know the current receiving position according to the rotation angle of the reflecting mirror of the scanning unit.

[0035] In a further most preferred embodiment, the test light receiving unit includes a single light receiver as one end directed to a plurality of light paths established by the plurality of emission locations.

[0036] In particular, the multiple emission positions are implemented with a plurality of discrete test light emitters, in particular infrared LEDs, distributed along the scanning angle, preferably in an equally spaced manner.

[0037] According to another advantageous embodiment, the test light emitting unit has a plurality of discrete test light emitters comprising an emitter shield surrounding the plurality of discrete test light emitters such that the plurality of discrete test light emitters are placed within the parabolic cavity.

[0038] According to another improvement of the optical sensor, the sensor comprises a converging lens, which is located between the test light receiving unit and the test light emitter, wherein the focus of the converging lens is close to the test light emitter. Since the light source is close to the focus, the lens forms an almost parallel light beam, which leaves the lens in the direction of the window. Since the width of the light beam generated in this way is preferably at least equal to the depth of the effective area of ​​the window, the coverage is increased.

[0039] In particular, the converging lens is in the shape of a ring, more specifically, a ring covering the plurality of test light emitters.

[0040] The control unit is preferably designed so that it synchronizes the pulses of a specific test light emitter at a specific emission position with the angular position of a reflector at a specific receiving position to establish a test light path. According to such a synchronization scheme, a plurality of such specific light paths can then be evaluated, so that when all test light paths are aggregated, an evaluation can be performed based on the information provided by the gridded optical pattern.

[0041] Another aspect of the invention comprises a method for monitoring the transparency of a window of an optical sensor as previously described.

[0042] The determination unit of the window monitoring unit comprises a control unit which performs an acquisition step of measuring the intensity of the test light received for all light paths defined in a set of evaluated light paths.

[0043] The determination unit comprises a mapping unit which provides a set of fields corresponding to a distribution map of the outer surface of the window. Thus, each field is associated with an area and a position of the outer surface of the window. The set of fields can be understood as a grid. Thus, the fields in the grid can be fields of a raster map of the outer surface of the window, wherein each field is represented by a pixel. Preferably, the grid, i.e. the relationship between the grid fields and the outer surface, is stored in a memory of the optical sensor.

[0044] Furthermore, the mapping unit provides a plurality of lightpath relationships, wherein the lightpath relationship is an assignment relationship between a subset of fields and a specific lightpath. The subset of fields belonging to a specific lightpath is preferably a field of a window through which the test light sent along the specific lightpath passes.

[0045] The plurality of optical path relationships are preferably also stored in an internal memory of the optical sensor.

[0046] The determination unit comprises a field assignment unit which performs an assignment step of assigning transparency values ​​to the fields in a value assignment process. The transparency values ​​depend on the intensity measured for the corresponding light path.

[0047] The value assignment process is performed for a field given in the light path relation for the corresponding light path. Thus, the value assignment process may modify all fields of the grid corresponding to the light path according to the intensity measured for the light path.

[0048] For example, the control unit can determine all intensities of all light paths of a group of light paths in a first cycle, and in the next cycle the value assignment process assigns all transparency values ​​to the corresponding fields. Alternatively, the control unit can determine the intensity of the light beam corresponding to a single light path and subsequently assign transparency values ​​to the fields associated with this light path. These steps are repeated until all light paths have been processed. In any case, a transparency distribution map for the window is created by parsing all light paths.

[0049] Furthermore, the determining unit comprises a decision unit that performs the decision step. Based on the transparency value assigned to the field, the decision unit decides whether the transparency problem of the window is serious and whether to create a corresponding output. The decision unit can perform the above decision based on a predetermined criterion, for example, the predetermined criterion can be a global contamination or a type of contamination, such contamination can form a foreign body uniformly on the window or form a local obvious foreign body on the window, i.e. such a local obvious foreign body can be limited to a specific size and / or position and show a clear edge. Since the contamination can be precisely located, the decision can also be made based on sub-areas in the grid.

[0050] Since the decision unit works using transparency values ​​forming a correspondence, the criteria for the severity status can be easily adapted without changing the acquisition or the physical setup of the monitoring system.

[0051] The allocation unit, mapping unit and decision unit do not need to be physically independent units and can all be implemented in a general-purpose computing device.

[0052] Depending on the result of the decision unit, the output signal can be a digital signal or provide different information, such as warning, stop signal, etc. The output signal can be used internally or provided to external devices.

[0053] According to an advantageous embodiment, the determination unit determines the transparency value by comparing each measured intensity with a reference intensity preferably obtained by initialization.

[0054] Therefore, it can be determined whether the transparency of the window at the position where the scanning light passes through the window is lower than the transparency when the reference intensity is measured.

[0055] In particular, the value assignment process is based on the change between the measured intensity and the reference intensity, such as (I Ref -I Meas ) / I Ref ), to calculate the attenuation value.

[0056] The value assignment process compares the transparency value to be assigned to the field with the transparency value already assigned to the field. In addition, if the value to be assigned is lower than the value already assigned, the value assignment process replaces the assigned transparency value.

[0057] In the decision step, after all assignments are completed, the fields of the grid are clustered according to their values. If the size of the cluster exceeds a predefined size (number of fields), a severe warning status can be output.

[0058] The predefined size of a class that causes a critical warning may vary depending on the position of the class in the grid.

[0059] Because the positions within the grid correspond to positions on the outer surface of the window, the different degrees of impact of foreign matter at different positions on the window on the operability of the sensor can be taken into account in the evaluation.

[0060] Furthermore, at least two different types of contamination are preferably determined to accurately estimate the attenuation of the scanning light by area. A distinction is made between uniform contamination and obvious local contamination, i.e., obvious local contamination is defined as having a specific size and / or location and having clear edges. For example, uniform contamination is considered to be the average transparency across the field that is clustered into one class.

[0061] According to another determining aspect, the dirt is evaluated as significant local contamination if the sum of the number of fields above or below a critical transparency value exceeds a predetermined number.

[0062] The attenuation caused by significant local contamination is then evaluated based on the minimum transparency value.

[0063] Then, the attenuation of the scanning light due to the addition of uniform contamination and significant local contamination is estimated.

[0064] A warning may be triggered depending on the attenuation value of the window in the active area through which the assumed scanning light passes.

[0065] Further advantages, features and potential applications of the present invention may be obtained from the following description in conjunction with the embodiments shown in the accompanying drawings.

[0066] Throughout the specification, claims and drawings, these terms and associated reference numerals are used as indicated in the accompanying list of reference numerals.

[0067] Figure 1a Schematic perspective view of the receiving and transmitting positions of the window and the window monitoring unit;

[0068] Figure 1b Figure 1a A schematic cross-sectional view of a window;

[0069] Figure 1c a schematic expanded view of a window showing the light path;

[0070] Figure 2 a grid corresponding to the expanded view, showing a corresponding area on the outer surface of the window;

[0071] Figure 3 Symbolic relationships between light paths / intensities / fields;

[0072] Figure 4 Example of assigning transparency values ​​to fields of a grid associated with a light path;

[0073] Figure 5 A corresponding relationship graph with decay values ​​after completing the assignment;

[0074] Figure 6 Flowchart of the method;

[0075] Figure 7a A cross-sectional view of an embodiment of an optical sensor according to the present invention; and

[0076] Figure 7b Another cross-sectional view of an embodiment of an optical sensor according to the present invention.

[0077] Figure 1a to Figure 1c A schematic perspective view of a transparent window 20 of an optical sensor 10 is shown. The window 20 comprises two window elements 52, 56. Each window element 52, 56 has a so-called active area AR52, AR56, which represents a partial area of ​​the window 20 and is the area through which the outgoing and incoming scanning light needs to pass during normal operation of the sensor 10.

[0078] Since the purpose of the present invention is to monitor the transparency of window 20 to assess whether optical sensor 10 is operating reliably, it is important to monitor the outer surfaces 54, 58 of window 20 within these active areas AR52, AR56.

[0079] The window 20 comprises a lateral extension WE and a height extension HE. The window 20 has an outer surface with element width dimensions EW1 , EW2 and element height dimensions EH1 , EH2. The lateral extension of the width dimension substantially corresponds to the lateral extension WE of the window 20.

[0080] The optical sensor 10 comprises a window monitoring unit 50 which monitors the transparency of the window 20, in particular the transparency of its window elements 52, 56. The window monitoring unit 50 comprises a test light emitting unit 30 which emits test light at a plurality of discrete emitting positions EP.1, EP.2, ... EP.10 along a lateral extension WE of the window 20. The emitting unit 30 is located at a first end of a height extension HE of the window 20. In an exemplary embodiment, this first end is vertically below the window 20. The window monitoring unit 50 further comprises a test light receiving unit 40 which is located at a side of the height extension HE of the window 20, opposite to the first end of the window.

[0081] The test light receiving unit 40 is implemented to allow receiving the test light at a plurality of discrete receiving positions RP. 1 , RP. 2 , RP. 3 , . . . , RP. 10 along the width extension WE of the window 20 .

[0082] The test light emitting unit 30 and the test light receiving unit 40 are arranged so that the test light passes through the outer surfaces 54 , 58 of the window members 52 , 56 within the effective areas AR52 , AR56 thereof.

[0083] The test light emitting unit 30 and the test light receiving unit 40 are schematically shown.

[0084] Specifically, the test light emitting unit 30 can be implemented as a discrete test light emitting diode located at the emitting position EP.1, EP.2, ..., EP.10 (also referred to as EP.X). The test light receiving unit 40 can be exemplarily implemented as a discrete photodiode located at the receiving position RP.1, RP.2, ..., RP.10 (also referred to as RP.Y).

[0085] Alternatively, the test light emitting unit 30 may include a light emitting diode that moves along the test light emitting position and emits light when the diode is in a specific emitting position. Alternatively, the test light receiving unit 40 may be similarly implemented in a movable manner. In a very preferred embodiment, the test light emitting unit 30 includes a plurality of fixed emitters, each of which is located at an emitting position. The test light receiving unit 40 includes a circular mirror element and a rotating light guide, wherein the light guide is oriented in a transverse direction and the test light is reflected by a circular mirror mounted directly opposite the test light emitting unit 30. The light guide acquires the test light at multiple angular receiving positions.

[0086] The window monitoring unit 50 further comprises a determination unit 100 for determining a change in the transparency of the window elements 52 , 56 .

[0087] The working mode of the determination unit 100 is to analyze the intensity of the test light transmitted along a plurality of evaluated light paths, that is, the plurality of evaluated light paths is a group of evaluated light paths, and the group of evaluated light paths includes at least a first light path and a second light path having different inclination angles. Each light path is defined as a straight line between a pair of emission positions and receiving positions. Since the window 20 has a curved profile, the offset of the test light path is an angular offset. In this example, the emission positions EP.1, EP.2, ..., EP.10 and the receiving positions RP.1, RP.2, ...RP.10 are evenly distributed at an angular distance of alpha. The distance between adjacent receiving positions can also be smaller than the distance between adjacent emission positions.

[0088] The determination unit 100 comprises a control unit 120 which interacts with the test light emitting unit 30 and the test light receiving unit 40 to obtain the intensity of the test light beams assigned to a set of evaluated light paths. For example, the intensity of the light beam emitted by the test light emitting unit 30 in the emission position EP.1 is received by the receiver in the receiving position RP.4. The intensity obtained by this measurement is assigned to the first light path P.1.4. In this case, the angular offset angle is 3×alpha in the first offset direction OD1.

[0089] In addition to the first optical path P.1.4, the set of evaluated optical paths is defined to include a second optical path, for example optical path P.2.1. The second optical path P.2.1 comprises an offset between its emission position EP.2 and its reception position RP.1, which is 1×alpha in a second offset direction OD2 opposite to the first offset direction. Thus, the offsets of the first optical path P.1.4 and the second optical path P.2.1 differ both in lateral distance and in offset direction.

[0090] Furthermore, the emitter EP.2 of the second optical path P.2.1 comprises an angular distance alpha from the emitter of the emission position EP.1 of the first optical path P.1.4 in the first offset direction OD1. The receiving position RP.1 of the second optical path P.2.1 comprises an angular distance 3×alpha from the receiving position RP.4 of the first optical path P.1.4 in the second offset direction OD2. The offset direction OD2 is opposite to the first offset direction OD1.

[0091] Since the offset between the receiving positions RP.1 and RP.4 and the offset between the transmitting positions EP.1 and EP.2 are located in opposite offset directions OD1 and OD2, the first optical path P.1.4 and the second optical path P.2.1 are cross optical paths. Figure 1a As can be seen from the schematic diagram, the light beams along the optical paths P.1.4 and P.2.1 pass through the intersection area IA of the outer surface of the window 20.

[0092] In the present example and preferred embodiment, the intersection area IA is located within the lower window element 56 , and in particular within the active area AR 56 of the window element 56 .

[0093] It is assumed that the intersection area IA 20 , which is already within the active area AR 56 and close to the test light emitting unit 30 , allows reasonable coverage for the lower window element 56 .

[0094] The control unit 120 of the determination unit 100 performs the acquisition step by triggering a light pulse at a first emission position EP.1 and evaluating the intensity of the light beam received at a first receiving position RP.4 of the corresponding light path P.1.4 after the light beam has passed through the window 20, for example, the two window elements 52, 56. The received intensity may be reduced depending on the degree of opacity or the size of foreign bodies that contaminate the passage area of ​​the light beam. The received intensity is assigned by the determination unit 100 to the corresponding light path for further evaluation.

[0095] According to the invention, a large number of oblique light paths are preferably defined in order to narrowly cover the window 20 and allow close monitoring of its transparency.

[0096] In a preferred embodiment, the angular distance of the transmitting positions is between 5° and 15° with a window radius of 35 mm to 45 mm and a window height of 20 mm to 45 mm. The angular distance between the receiving positions is approximately 0,5° to 10°.

[0097] Figure 1b A schematic cross-sectional view of the window 20 is shown. Figure 1b A straight beam corresponding to an ideal optical path P.3.3 between the emitting position EP.3 and the receiving position RP.3 is shown. As can be seen from the figure, the beam has a depth extension, so it can produce a passing area on the outer surfaces 52, 56 of the window elements 54, 58. Foreign matter S on the outer surface of the window 20, especially the foreign matter S on the second window element 56, reduces the intensity of the test light received by the test light receiving unit 40 at the receiving position RP.3.

[0098] also, Figure 1b Schematically shown is a scanning unit 14 for sending and receiving scanning light 16. In this case, the scanning area is established by scanning the light back and forth along the lateral extension of the window 20.

[0099] Figure 1c An expanded view of the window 20 is shown, which can be used to illustrate the effect of test light paths with different inclinations. A foreign object S on the second window element 56 below in the vertical direction blocks the light beam along the light path P.3.3 and causes a shadow to be formed on the upper window element 52. If only a light path parallel to the light path P.3.3 is provided, no height information can be collected because no test light beam will pass through the window in the area above the foreign object in the vertical direction. It can be seen by way of example that due to the added information of the light paths P.2.4 and / or P.5.1, it can be determined that the foreign object is present on the lower window element 56.

[0100] also, Figure 1cA determination unit 100 is shown, which includes a control unit 120 that measures the intensity of the test light received for the optical path and a mapping unit 130 that provides a grid with a set of fields related to the area and position of the outer surface of the window. In addition, the mapping unit 130 assigns a subset of the fields to a specific optical path. The determination unit 100 also includes a field assignment unit 140 for assigning transparency values ​​to specific fields, and a decision unit 150 that decides whether the transparency problem of the outer surface 54, 58 is serious and whether to create a corresponding output 30.

[0101] Figures 2 to 6 A method according to the invention for determining changes in the transparency of an outer surface 54 , 58 due to environmental influences is shown.

[0102] Figure 2 A grid GM of a window 20 based on a set of fields GF.XY provided by a mapping unit 130 is shown. The fields GF.XY have a corresponding relationship with the window 20 because they correspond to a certain area on the outer surface 54, 58 of the window 20. These fields can be used as output data to create an image of the window 20 using grid elements or pixels. In other words, the window 20 can be described by a pixel distribution map in which each pixel represents a field. Each pixel has a width corresponding to an angular distance (e.g. 1°) and a predetermined height corresponding to the extension of the element surface EH1, EH2 in the height direction of the window element 52, 56. This means that each field is associated with a field area represented by an actual physical surface on the outer surface 54, 58 of the window 20. All fields GF.XY represent individual pixels on the distribution map GM and correspond to the same height and the same width on the outer surface 54, 58 of the window 20.

[0103] Each of the fields GF.XY corresponds to a pixel and is designed so that these fields can be assigned a value, i.e., a transparency value. In a preferred embodiment, the transparency value is a value corresponding to the magnitude of the change in transparency. This means that when the light beam passes through the window element 52, 56 along a certain light path, the light path corresponds to a certain reference intensity.

[0104] The change in intensity relative to the reference intensity is the attenuation value calculated as a percentage, for example (I Ref -I Meas ) / I Ref ). The intensity corresponds to a light path in the set of evaluated light paths, and so does the reference intensity. By representing the set of fields GF.XY in the form of a pixel distribution map, the intensity or changes in intensity can be encoded, for example color-coded. This makes it possible to view changes in the transparency of the window 20 in the form of an image, and to monitor the transparency using graphic image processing and / or filtering algorithms.

[0105] The mapping unit 130 provides a set of fields GF.XY, wherein each field corresponds to a certain area on the outer surface of the window 20. The mapping unit 130 also provides a correspondence as to which fields belong to a certain optical path.

[0106] Figure 3 A relationship diagram is shown according to which the measured intensity and the reference intensity are related to the light path. The reference intensity of the test light transmitted along a specific light path is determined when only the test light from the paired transmission position is received at the receiving position. The assignment of the reference intensity to the light path results in an evaluated light path ELP.

[0107] Furthermore, lightpaths are associated with a number of fields assigned to each lightpath, such as Figure 3 The optical path relationship LPR is shown in FIG.

[0108] This allows the field assignment unit 140 to assign attenuation values ​​to all corresponding fields of the lightpath.

[0109] Since fields can be assigned to multiple light paths to reflect the intersection area on the outer surface 54, 58 of the window 20, different attenuation values ​​from different light paths can be assigned to the same field. In this case, especially for the fact that the transparency value is the attenuation value, the value assigned to the field will be replaced with a value that is less than the assigned value.

[0110] This means that if there is transparency in one direction but the area is completely blocked in the other direction, the attenuation value will be reduced. In the case of transparency values, all fields can be preset with an attenuation value corresponding to the "no intensity received" value.

[0111] Then, each time a smaller attenuation value is determined for a light path, the field along this light path for which the window 20 is found to be transparent is, so to speak, cleared of the grid.

[0112] Finally, after all the attenuation values ​​of all the fields have been assigned, a distribution graph of the attenuation values ​​appears, which allows the decision unit 150 to locate and determine the type of contamination of the window 20 .

[0113] The type of contamination and its location on the window 20 can be used as a basis for deciding which state of the sensor is appropriate. Thus, the sensor is not forced into a critical state whenever the detected contamination may not significantly affect the reliability of the optical sensor 10. Thus, the usability of the sensor is improved.

[0114] Figure 4A pixel distribution diagram GM is shown. In a first assignment step, all pixels are assigned an attenuation value of 100% (white). In a subsequent step, for pixels belonging to an optical path, such as optical path P.4.3, an attenuation value of 0% can be assigned to the pixels of the optical path P.4.3 based on a comparison between the intensity I(P4.3) measured for the test light along the optical path P.4.3 and the reference intensity. Pixels GF9.2, GF10.2 ... GF7.7, GF8.7 belong to the optical path P.4.3 and correspond to the area on the outer surface of the window passed by the test light along the optical path P.4.3. Similar to the example of optical path P.4.3., all pixels GF XY belonging to each optical path in the group of evaluated optical paths are assigned accordingly. Pixels belonging to multiple optical paths are assigned values ​​corresponding to the lowest attenuation values ​​and are therefore assigned to the highest transparency.

[0115] Figure 5 An example of a fully assigned distribution diagram is shown, in which all transparency values ​​for all light paths are assigned. The value V1 shown in the pixel distribution diagram GM corresponds to 100% attenuation, V2 corresponds to 50% attenuation, V3 corresponds to 25% attenuation, and V4 corresponds to 0% attenuation. From the V4 area, the window 20 is transparent to a large extent. From the V1 area, it can be seen that there is an opaque area 200. Based on the image of this distribution diagram GM, the determination unit 100 can determine that there is a foreign body on the lower window element 56. The area located above the opaque area 200 in the vertical direction is, for example, assigned with V2, V3 values, which have a higher transparency than the opaque area 200.

[0116] Based on the differences in transparency values ​​of the pixels and their positions on the map GM representing the area of ​​the outer surface 54, 58 of the window 20, the location and magnitude of different types of contamination and / or contamination may be determined.

[0117] Based on these aspects, the decision unit 150 can determine whether the problem situation of transparency is serious.

[0118] Figure 6 A flow chart of the window monitoring process is shown. First, all intensities of all light paths are acquired. Then, a transparency value V is assigned to all fields belonging to the light paths.

[0119] After the profile GM has been completed and all transparency values ​​of all evaluated light paths have been assigned to the corresponding fields, a decision step is performed.

[0120] In a decision step, predefined criteria are used to decide at which location which type of contamination can be determined from the assigned distribution map M.

[0121] Finally, the decision unit 150 creates an output that triggers a specific action or signal based on the decision.

[0122] Figure 7a Schematic cross-sectional view of an embodiment of an optical sensor 210 according to the present invention is shown. The optical sensor 210 includes a housing 240 and a window, wherein the housing 240 has a top cover 244 and a bottom cover 246, and the window has a first window element 242a and a second window element 242b that are tilted relative to each other. The optical sensor 210 includes a scanning unit 260, which includes scanning light emitters 214a, 215a, scanning light receivers 214b, 215b, and a rotating mirror 212, which rotates around a rotation axis R and deflects the scanning light to scan the environment over a given angular detection range beta. From the scanning unit 260 according to Figure 7b It can be seen from the cross-sectional schematic diagram of II-II that the angular detection range in this embodiment is approximately 270°.

[0123] like Figure 7a As shown in , the optical sensor 210 comprises a window monitoring unit 250, which comprises a plurality of discrete test light emitters 218.1 to 218.22 (also referred to as 218.X), which are implemented as infrared LEDs. As previously described, each test light emitter 218.X defines an emission position. The test light emitters 218.1 to 218.22 are surrounded by a shield 228, which comprises a conical chamber 232, which serves as a beam shaping chamber so that the light emitted by the test light emitters 218.X has a defined shape, in particular a defined opening angle of the conical test light beam.

[0124] The beam shaping chamber 232 allows a very well defined test beam path spatially, which is particularly useful for better evaluation of tilted test beam paths having an offset between the transmit and receive positions.

[0125] like Figure 7a As further shown in FIG. 1 , the optical sensor 210 may optionally include a convex lens 236, which preferably has a convex lens 236 having ... Figure 7b ) and extends over an area covering all emitters 218.X. Lens 236 is a converging lens with its focus located to the side of and close to emitter 218.X. Therefore, lens 236 is convexly curved in a cross-sectional view. For example, this makes it possible to reduce the angle of test light beam TB emitted from lens 236 and passing through inclined window elements 242a, 242b. This makes it possible to better cover the entire depth of inclined window elements 242a, 242b.

[0126] Furthermore, the window monitoring unit 250 comprises a test light receiving unit 213, which comprises a test light receiver 216 implemented as a photodiode. The test light receiver 216 is aligned with the rotation axis R of the rotating mirror 12 and is fixed to the housing 40. Since the test light receiver 216 does not move during the operation of the optical sensor 210, it can be easily electrically connected to be measured by the sensor electronics (not shown).

[0127] like Figure 7b As shown in FIG. 1 , the test light emitters 218.1 to 218.22 are distributed around the window elements 242a and 242b along the angle detection range alpha. The test light emitters 218.1 to 218.22 emit light beams that pass through the first window element 242a and the second window element 242b, thereby generating a test light path TXY.

[0128] According to the present invention, the test light receiving unit 213 includes a light guide 220, which is attached to the rotating mirror 212 so as to move together with the rotating mirror 212, in particular, to rotate together. The light guide 220 in this embodiment is a prism made of plastic, which has a first coupling structure 222a and a second coupling structure 222b. The light guide 220 is implemented so that the first coupling structure 222a is located in the radial direction of the rotating mirror 212. This means that the light irradiated to the light guide 220 in a direction substantially perpendicular to the rotation axis R is coupled into the light guide 220 directed to the second coupling structure 222b. The light guide 220 is implemented so that the second coupling structure 222b decouples the light in a direction parallel to the rotation axis R.

[0129] According to the present embodiment, the test light receiver 216 is mounted to be aligned with the rotation axis R, so that the light decoupled from the light guide 220 at the second coupling structure 222 b is directly guided to the test light receiver 216 .

[0130] According to this arrangement, the light guide 220 can receive the test light at all angular positions according to the current rotation angle of the rotating mirror 212. Therefore, it is possible to establish receiving positions having a very narrow angular offset between adjacent receiving positions.

[0131] According to this arrangement, multiple inclined light paths can be easily established to analyze the transparency of the window through the grid of test light paths described above. To this end, the test light receiving unit 213 uses the rotating mirror 212 of the scanning unit 260 to reach the desired receiving position.

[0132] The test light emitter 218 .X is arranged so that the test light travels substantially parallel to the axis R of rotation.

[0133] Furthermore, the window monitoring unit 250 includes a round mirror 230 for deflecting the test light to be received by the light guide 220 at the receiving position in the radial direction. The round mirror 230 substantially redirects the test light from the axial direction to the radial direction. Furthermore, due to its roundness, the round mirror 230 focuses the test light having a path that is not parallel to the rotation axis R but is inclined relative to the rotation axis R. This utilizes the phenomenon that the test light is not emitted in the form of a circular beam but in the form of a cone.

[0134] Figure 7a The test light emitted from the test light emitter 218.4 is shown traveling along the optical path T.4.4. In this case, the test light is emitted from the test light emitter 218.4, passes through the second window element 242b, and then passes through the first window element 242a. After passing through the window elements 242a, 242b, the test light is deflected from the axial direction to the radial direction by the circular mirror 230. Figure 7a In the case shown in , the rotating mirror 212 is in the same angular position as the light guide 220 in its current receiving position and the test light emitter 218.4. The test light redirected to a substantially radial direction is incident substantially perpendicularly on the first coupling structure 222a. The test light is captured by the light guide 220 and guided along the light guide 220 to its second coupling structure 222b located at the rotation center of the rotating mirror 12. There, the test light leaves the light guide 220 and is guided directly to the test light receiver 216, which is a photodiode aligned with the rotation center of the rotating mirror 212. The test light receiver 216 is located above the rotating mirror 212, wherein the test light receiving face of the test light receiver 216 faces the rotating mirror.

[0135] Figure 7a Also shown is a test light path T18.18 received by the light guide 220 and then received by the test light receiver 216 when the rotating mirror is rotated 180°.

[0136] Figure 7b A schematic cross-sectional view of the sensor along II-II is shown. The rotating mirror 212 comprises a circular top surface, wherein the faces of the mirror are arranged in a triangular cross-section.

[0137] Embodiments of the rotating mirror 212 allow an angular scanning range alpha of about 270°. The light guide 220 extends from the center of rotation to the periphery of the rotating mirror 212. The light guide 220 preferably does not extend beyond the body of the rotating mirror 212. Such an arrangement has a positive effect on the balance of the rotating mirror 212.

[0138] The position of the test light receiver 216 is indicated by the dashed square aligned with the rotation axis R. Test light emitted from the test light emitter 218.X can be received at various angular positions accessible to the first coupling structure 222a to establish an optical grid including optical paths TXY of different inclinations as previously described.

[0139] To establish a specific optical path, a specific test light emitter 218.X is pulsed at a specific time at which the position of the light guide corresponds to the desired receiving position of the optical path. Preferably, light along only a single optical path is generated at a time to avoid cross-talk between test lights of different optical paths.

[0140] It is obvious that the number of light paths that can be analyzed corresponds at least to the number of test light emitters 218.X, since during one complete rotation of the rotating mirror 212, the light guide 220 passes by all test light emitters 218.X. For each angular position of the light guide 220, a plurality of test light emitters 218.X can be used to generate a plurality of light paths. This is exemplarily shown by another angular position in which the light guide 220 has a receiving position opposite the test light emitter 218.19. In this case, there is no angular offset between the transmitting position and the receiving position.

[0141] Another advantageous effect of the optical sensor 210 according to the invention is that, by allowing an angularly offset position between the first coupling structure 222a and the corresponding test light emitter 218.X, an additional test light path TXY can be generated. This is shown as T.4.3 and T.4.5. This means that the test light path TXY is generated by the test light emitter 218.X, which is illuminated when the first coupling structure 222a has an angular offset relative to the illuminated, preferably pulsed test light emitter 218.X. The generated test light path is then tilted. According to this option, a grid of test light paths can be created by synchronizing only the enabling of the test light emitter 218.X with the angular position of the rotating mirror 212 containing a specific angular offset between the transmitting and receiving positions.

[0142] This allows the creation of a greater number of test beam paths without being limited by spatial constraints. Figure 7a As shown in , the circular mirror 230 increases the energy level that can be detected in such "offset conditions".

[0143] Figure 7b The annular lens 236 is shown from a plan view, which extends over an area of ​​270° and covers all first optoelectronic elements.

[0144] The annular lens 236 has an effect of narrowing the cone of the test light beam TB in the direction in which it extends on the cross-sectional plane including the rotation axis, but does not have that degree of influence in the circumferential direction.

[0145] Reference numerals list

[0146] 10 Optical Sensor

[0147] 14 Scanning Unit

[0148] 20 windows

[0149] 30 launch units

[0150] 40 receiving units

[0151] 50 Window Monitoring Unit

[0152] 52 first window element

[0153] 54 outer surface of the first window element

[0154] 56 Second window element

[0155] 58 outer surface of the second window element

[0156] 100 Determine the unit

[0157] 120 Control unit

[0158] 130 Mapping Unit

[0159] 140 Field Allocation Unit

[0160] 150 Decision Unit

[0161] 210 Optical Sensor

[0162] 212 Rotating Mirror

[0163] 213 Test light receiving unit

[0164] 214a Scanning light transmitter

[0165] 214b Scanning Optical Receiver

[0166] 215a Scanning light transmitter

[0167] 215b Scanning Optical Receiver

[0168] 216 Test Optical Receiver

[0169] 218.X Test Optical Transmitter

[0170] 220 Light Guide

[0171] 222a First coupling structure

[0172] 222b Second coupling structure

[0173] 226 Window Monitoring Unit

[0174] 228 shielding parts

[0175] 230 round mirror

[0176] 232 Conical Chamber

[0177] 236 Converging lens

[0178] 240 Shell

[0179] 242a First window element

[0180] 242b Second window element

[0181] 244 Top Cover

[0182] 246 lower cover

[0183] 250 Window Monitoring Unit

[0184] 260 scanning unit

[0185] AR52, AR56 effective area

[0186] EH1 component height dimension

[0187] EH2 element height dimension

[0188] EP.X launch location

[0189] GM distribution map

[0190] GF.XY Field

[0191] HE height extension

[0192] I(P XY) intensity of optical path P XY

[0193] IA intersection area

[0194] LPR optical path relationship

[0195] LPS Optical Path Assembly

[0196] PXY The optical path between the transmitting position X and the receiving position Y

[0197] RP.Y receiving position

[0198] TXY Optical path between the transmitting position X and the receiving position Y

[0199] V transparency value

[0200] WE Horizontal Extension

Claims

1. An optical sensor (10) comprises a scanning unit (14), a transparent window (20) through which scanning light can pass, the transparent window having a lateral extension (WE) and a height extension (HE), wherein: The window (20) has at least one inclined window element (52, 56) having an outer element surface (54, 58); the optical sensor (10) also includes a window monitoring unit (50) for monitoring the transparency of the window (20), wherein the window monitoring unit (50) includes a test light emitting unit (30), the test light emitting unit (30) emits test light at a plurality of discrete emitting positions (EP.X) along the direction of the lateral extension (WE) of the window (20), the test light emitting unit (30) being located at a first end of the window (20) as viewed in the height extension (HE) direction; and a test light receiving unit (40), which receives test light at a plurality of discrete receiving positions (RP.Y) along the direction of the width extension (WE) of the window (20), the test light receiving unit (40) being located at a first end of the window (20) as viewed in the height extension (HE) direction. At one end of the window (20) opposite to the test light emitting position (EP.X) in the height direction, wherein the test light emitting unit (30) and the test light receiving unit (40) are arranged so that the test light passes through the external element surface (54, 58), the window monitoring unit (50) further includes a determination unit (100) for determining a change in transparency of the window (20) by analyzing the test light transmitted along a plurality of optical paths (PXY), wherein each optical path (PXY) is defined as a straight line between a pair of emitting positions (EP.X) and receiving positions (RP.Y), wherein the determination unit (100) includes a control unit (120), the control unit (120) interacts with the test light emitting unit (30) and the test light receiving unit (40) to obtain an intensity (I(PXY)) of the test light beam assigned to the optical path (PXY), Characterized in that a set of evaluated optical paths (LPS) includes multiple optical paths (PXY), among which at least the first optical path (P.1.2) is defined as having a first offset between its receiving position (RP.2) and a paired transmitting position (EP.1), and at least the second optical path (P.2.1) is defined as having a second offset between its receiving position (RP.1) and a paired transmitting position (EP.2), wherein the second offset differs from the first offset by a defined lateral offset distance and / or is different in the lateral offset direction.

2. The optical sensor according to claim 1, characterized in that The lateral offset distance is greater than 1 / 8 of the height extension (HE) of the window, in particular greater than 1 / 4 of the height extension (HE) of the window.

3. The optical sensor according to claim 1 or 2, characterized in that: The control unit is designed to obtain the intensity of a set of evaluated optical paths (LPS), wherein the set of evaluated optical paths (LPS) includes a subset of crossed optical paths, wherein the subset of crossed optical paths includes a first optical path (P.1.2) and a second optical path (P.2.1), wherein the emission position (EP.2) of the second optical path (P.2.1) includes an offset in an emission offset direction (EOD) relative to the emission position (EP.1) of the first optical path (P.1.2), wherein the receiving position (RP.1) of the second optical path (2.1) includes an offset in a receiving offset direction (ROD) opposite to the emission offset direction (EOD) relative to the receiving position (RP.2) of the first optical path (P.1.2).

4. An optical sensor according to any one of the preceding claims, characterized in that The window (20) comprises a curved profile, in particular a circular profile, so that the lateral extension is given by the length of the bend and the offset is an angular offset.

5. The optical sensor according to any one of the preceding claims, characterized in that The window (20) comprises two window elements (52, 56) which are arranged sequentially in the height direction and are inclined relative to each other.

6. An optical sensor according to any one of the preceding claims, characterized in that The window (20) is mapped as a grid (GM) consisting of a plurality of fields (GF) stored in a data memory, wherein transparency values ​​can be assigned to the fields (GF).

7. An optical sensor according to any one of the preceding claims, characterized in that The data memory stores a plurality of lightpath relations (LPR.PXY), wherein each lightpath relation (LPR) assigns a subset of fields (GF.XY) to a specific lightpath (PXY).

8. An optical sensor according to any one of the preceding claims, characterized in that The scanning unit comprises a rotating mirror, and the test light receiving unit (217) comprises a test light receiver (216), and the test light emitting unit comprises a test light emitter, wherein the test light receiving unit (217) and / or the test light emitting unit comprises a light guide (220), wherein the light guide (220) is attached to the rotating mirror (212) of the scanning unit (260), and wherein the light guide (220) redirects / guides the test light between the test light receiving unit (217) at a plurality of receiving positions and the test light emitting unit at a plurality of emitting positions.

9. The optical sensor according to claim 8, characterized in that The control unit (120) comprises an angle determination unit for determining the angular position of the rotating mirror of the scanning unit.

10. The optical sensor according to claim 8 or 9, characterized in that: The test light receiving unit (217) includes a single light receiver (216) which is the end point of a plurality of light paths established by a plurality of emission locations.

11. The optical sensor according to claim 10, characterized in that The light emitter comprises a plurality of discrete test light emitters (218.X), in particular infrared LEDs, distributed along a scanning angle.

12. The optical sensor according to claim 11, characterized in that The test light emitting unit (221) comprises an emitter shield (228), which surrounds the discrete test light emitter (218.X) so that the discrete test light emitter (218.X) is placed in a parabolic cavity.

13. An optical sensor according to any one of the preceding claims, characterized in that The test light emitting unit (221) comprises a test light emitter (218.X) and a converging lens (236) located between the test light emitter (218.X) and the test light receiving unit (213), wherein a focal point of the converging lens (236) is close to the test light emitter (218.X).

14. An optical sensor according to any one of the preceding claims, characterized in that The test light emitting unit (221) comprises a test light emitter (218.X) and a converging lens (236), wherein the converging lens is located between the test light emitter and the test light receiving unit (213) and has a ring shape.

15. The optical sensor according to any one of the preceding claims 9 to 14, characterized in that The control unit synchronizes the pulse of a specific test light transmitter (218.X) at a specific transmitting position with the angular position of a mirror (212) at a specific receiving position to establish a test light path.

16. A method for monitoring the transparency of a window (20) of an optical sensor (10) according to any one of claims 1 to 15, wherein: The determination unit (100) comprises a control unit (120), the control unit (120) performing an acquisition step, the acquisition step measuring the intensity I(PXY) of the test light received for a light path (PXY) defined in a set of evaluated light paths (ELP.PXY); the determination unit (100) comprises a mapping unit (130), the mapping unit (130) providing a set of fields (GF.XY), the set of fields (GF.XY) at least partially having a correspondence with the outer surface of the window (20), and wherein the mapping unit (130) further provides a plurality of light path relations (LPR.PXY), wherein a light path relation (LPR.PXY) is an assignment of a subset of the fields (GF.XY) to a specific light path (PXY); The determining unit (100) further comprises a field assigning unit (140), which performs an assigning step in which a transparency value (V) is assigned to a field (GF.XY) in a value assigning process based on an intensity (I(PXY)) measured for a corresponding optical path (PXY), wherein the value assigning process is performed for a field (GF.XY) given in an optical path relation (LPR.PXY) for the corresponding optical path (PXY), wherein the determining unit (100) comprises a decision unit (150) which performs a decision step and the decision unit (150) decides whether the transparency of the window (20) is severe based on the transparency value (V) of the assigned field (GF.XY) and creates a corresponding output.

17. The method according to claim 16, characterized in that The determination unit (100) obtains the transparency value (V) by comparing each measured intensity with a reference intensity, and the reference intensity is preferably obtained by initialization.

18. The method according to any one of claims 16 or 17, characterized in that The value assignment process calculates an attenuation value based on the difference between the measured intensity and the reference intensity.

19. The method according to claims 16 to 18, characterized in that The value assignment process (AP) compares the transparency value (V) to be assigned with the already assigned transparency values ​​(V).

20. The method according to claim 19, characterized in that If the value to be assigned is lower than an already assigned value, the value assignment process replaces the already assigned transparency value.

21. The method according to any one of the preceding claims 16 to 20, characterized in that The field (GF.XY) is the pixels of a map (GM) created as a grid of the outer surface of the window (20).

22. The method according to any one of the preceding claims 16 to 21, characterized in that The fields (GF.XY) are clustered according to their assigned transparency values ​​and if the cluster size exceeds a predefined cluster size, a severe status is output.

23. The method according to claim 22, characterized in that The predefined class size varies according to the position of the class on the window (20) having the corresponding relationship.

24. The method according to any one of the preceding claims 22 to 23, characterized in that If the sum of the sizes of all classes exceeds a predetermined size, a severe status is output.

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