Optical sensor with a window and a window monitoring unit, and method for monitoring the transparency of a window

Abstract

The present invention is an optical sensor, comprising a scanning unit (14), a transparent window (20), and a window monitoring unit (50). The window monitoring unit (50) comprises a test light emitter unit (30) and a test light receiver unit (40). The window monitoring unit (50) comprises a determination unit (100). The determination unit (100) comprises a control unit (120). The set of evaluated optical paths (LPS) comprises a plurality of optical paths (P.X.Y), wherein at least a first optical path (P.1.2) is defined to have a first offset between its reception position (RP.2) and its corresponding emission position (EP.1). At least a second optical path (P.2.1) is defined to have a second offset. The second offset is different from the first offset with respect to a defined lateral offset distance and / or a lateral offset direction.

Description

Technical Field

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

Background Art

[0002] An optical sensor equipped with a window monitoring system is disclosed in German Utility Model Publication No. 93 21 155 U1. The optical sensor includes a transparent window, and the window monitoring system includes a light-emitting diode disposed on the opposite side of a receiving diode, generating an optical path between each pair of the receiving diode and the light-emitting diode on the opposite side.

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

[0004] This window monitoring system has a drawback that the resolution is determined by the space between the emitter and the receiver, and particularly in the vertical direction of the window, the position of the dirt cannot be accurately identified. This means that warnings may be issued even when the spot, particularly the dirty spot, does not affect the scanner's field of view. Then, the sensor will stop unnecessarily.

Prior Art Documents

Patent Documents

[0005] The problem of specifying the vertical position of the spot is not solved by the solution known from German Patent Application Publication No. 10 2017 001612 A1, which operates with a setup of a rotating emitter and receiver.

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to improve the window monitoring system in order to enhance the availability of the optical sensor without affecting its reliability.

Means for Solving the Problem

[0007] This object is solved by the optical sensor according to claim 1 and the method for monitoring a window according to claim 16. The subclaims are advantageous embodiments of the present invention.

[0008] In a known method, an optical sensor comprises a transparent window having a lateral extension and a height extension through which scanning light can pass. The scanning light is transmitted and received by a scanning unit. The window includes at least one window element having an external element surface with dimensions in the width direction and the height direction.

[0009] The optical sensor further comprises a window monitoring unit for monitoring the transparency of the window. The window monitoring unit comprises a test light emitter unit that emits test light at a plurality of divided radiation positions along the width direction of the window. The radiation positions are located at a first end of the height extension of the window.

[0010] The window monitoring unit further comprises a test light receiver unit that receives the test light along a plurality of divided reception positions along the lateral extension of the window. The test light receiving unit is arranged at an end of the window opposite to the radiation position of the test light in the height extension.

[0011] The test light emitter unit and the test light receiver unit are arranged such that the test light passes through at least one outer surface of the window.

[0012] The optical sensor further comprises a determination unit for determining a change in the transparency of the window. The transparency can change due to the influence of the environment such as snow, dirt, pollen, etc. covering the outer surface of the window.

[0013] The determination unit comprises a control unit that interacts with the test light emitter unit and the test light receiver unit such that test light transmitted along a plurality of optical paths is analyzed, particularly with respect to the received intensity.

[0014] Each optical path is defined to extend between a pair of positions, namely an emission position and a reception position. The emission position and the reception position are absolute positions arranged in the lateral direction of the window in a predefined manner.

[0015] In the context of the present invention, an optical path is ideally considered to be a straight linear connection between its end positions, namely the emission position and the corresponding reception position, and this linear connection may be vertical or oblique. To evaluate the intensity of the test light transmitted along a particular optical path, the intensity is determined at the time when only the test light from the pair of emission positions is received at the reception position. The control unit synchronizes the measurement by pulsing the emitter while measuring the intensity of the test light received by the paired receiver.

[0016] The set of evaluated optical paths is predefined in the control unit, and the corresponding intensities are obtained.

[0017] According to the present invention, the set of optical paths to be evaluated includes a plurality of optical paths having a first optical path and a second optical path. The first optical path is defined to have a first offset between its reception position and the paired emission position, and at least the second optical path is defined to have a second offset between its reception position and the paired emission 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 either the first optical path or the second optical path can be set to zero.

[0018] Accordingly, the window monitoring unit uses a mesh of optical paths in which the emission positions are interconnected with the reception positions by a number of optical paths showing different inclinations. Each individual optical path connects a single emission position and a single reception position, each emission position can be interconnected with a number of reception positions, and each reception position can be connected to a plurality of emission positions. As a result, a complex lattice of optical paths with different inclinations is formed between the emitter unit and the receiver unit.

[0019] According to this arrangement, the monitoring system enables the test light passing through the outer surface of the window to be observed from various directions. A spot on the window becomes an obstacle to the test light between the emission position and the reception position. If there is a spot that blocks the optical paths with the same inclination, a shadowing effect occurs, and it becomes particularly difficult to accurately determine the actual position of the window dirt when viewed along these optical paths, especially in the vertical direction. Therefore, the idea of the present invention is that the shadowing effect of the spot can be reduced by observing the affected area where the spot exists from different angles, and the height information about the spot can be obtained by using different oblique optical paths. Some of these oblique optical paths are blocked by the spot, but other optical paths can pass through the window in the area above or below the spot vertically. The height information can be used when evaluating the influence of the spot on the reliability of the optical sensor.

[0020] Preferably, the difference in at least two lateral offset distances is greater than 1 / 8 of the height of the window, particularly greater than 1 / 4, or greater than 1 / 2 of the height of the window. This measure provides a minimum viewing angle for ensuring sufficient resolution in the height direction of the window.

[0021] According to an advantageous embodiment of the present invention, the monitoring system is designed to acquire the intensity of a set of evaluated optical paths including a subset of intersecting optical paths including a first optical path and a second optical path. The intersecting optical paths are created when the radiation position of the second optical path includes an offset with respect to the radiation position of the first optical path in the emitter offset direction, and the reception position of the second optical path includes an offset with respect to the reception position of the first optical path in the receiver offset direction opposite to the emitter offset direction.

Advantages of the Invention

[0022] According to this configuration, information of test light, which preferably generates an overlapping region on the outer surface of the window, is used, and the shadowing effect can be further reduced by densifying the optical paths, so that the ability to determine the position or extension of the spot in the height direction can be enhanced.

[0023] According to this function, the resolution of the window monitoring unit is particularly improved in the height direction. The reason is that the test light is radiated along optical paths with different inclinations, and a part of it can pass through the spot. Thus, for example, the shadowing effect of the spot generated when a parallel beam parallel to the height direction is used for monitoring is eliminated. This is particularly applicable when the window includes two window elements inclined with respect to each other. This makes it possible to determine which window element the spot is located on, which is impossible when using a parallel beam.

[0024] According to a further improvement of the window monitoring unit, since the subset of intersecting optical paths includes optical paths having a single radiation position and a plurality of reception positions, a complex mesh structure of the optical paths becomes possible, and the resolution of the window monitoring device is further improved.

[0025] For this, a static emitter can be used, which has the advantage that a test light corresponding to a plurality of optical paths can be provided with one emitter. The receiving position can preferably be arranged symmetrically with respect to the emitting position. According to this solution, the test light can be used over a lateral range, as a result of which optical paths that "cross" each other in different directions are established. The vertical resolution of the spot is further improved by the intersection in different directions.

[0026] In particular, the window has a curved, in particular circular, contour, and the lateral expansion is determined by the length of the curve. In this case, the emitting position and the receiving position are determined by angular positions, and their offset is the angular distance.

[0027] According to a further advantageous embodiment, the window comprises two window elements, which are arranged one above the other in the height direction in succession, i.e., one is located above the other in the direction of their expansion and is inclined with respect to each other. In this setting, the influence that different oblique optical paths have on the resolution in the height direction is improved. In this case, it is possible to determine in which window element the spot is located, and thus it is possible to define different criteria according to the window element. Furthermore, the optical sensor may comprise a data memory in which a set of a plurality of fields mapping the surface of the window is stored. A transparency value can be assigned to each field. The transparency value is related to the transparency of the window or the change in transparency over time.

[0028] Thereby, a transparency map of the window can be created, analyzed using an algorithm, and the size and position of the dirt on the surface of the external window can be identified.

[0029] The set of fields can be understood as a grid field corresponding to the raster of the window surface. For example, the information assigned to each field can be used to create a pixel map of the window. In other words, the information associated with each field can be presented as a digital image, and graphic image processing and / or filter algorithms can be used to evaluate the transparency of the window.

[0030] In a further advantageous embodiment, the optical sensor comprises a data memory in which a plurality of optical path relationships are stored, each optical path relationship assigning a subset of the fields to a specific optical path. This enables a defined mapping of the surface of the window through which the test light radiated along the optical path passes.

[0031] According to a preferred embodiment, the scanning unit comprises a rotating mirror for deflecting the radiated and received scanning beam, and the test light receiver unit comprises a test light receiver and an optical guide. According to this embodiment, the optical guide is attached to the rotating mirror of the scanning unit. The optical guide redirects / guides the test light between a test light receiver unit at a plurality of receiving positions and a test light emitter unit at a plurality of emitting positions. The rotating optical guide enables a plurality of receiving positions to be easily realized and a high angular resolution to be obtained.

[0032] The control unit particularly comprises an angle determination unit for deriving the angular position of the rotating mirror of the scanning unit. Thus, the angle determination unit enables the control unit to recognize the current receiving position according to the rotation angle of the mirror of the scanning unit.

[0033] In the most preferred method, the test light receiver unit comprises a single light receiver which is the end point of a plurality of optical paths established by a plurality of emitting positions.

[0034] In particular, the plurality of emission positions are realized by a plurality of test light emitters, preferably arranged at equal intervals along the scanning angle, in particular by infrared LEDs.

[0035] According to a further advantageous embodiment, the test light emitter unit having a plurality of divided test light emitters comprises a shield for the emitters, which surrounds the individual test light emitters such that the individual test light emitters are arranged in a parabolic cavity.

[0036] According to a further improvement of the optical sensor, the optical sensor comprises a converging lens arranged between the test light receiver unit and the test light emitter, and 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 a substantially parallel beam emerging from the lens in the direction of the window. The width of the beam thus formed is preferably at least equal to the depth of the active area of the window, thus providing an improved irradiation range.

[0037] In particular, the converging lens has an annular shape and, more specifically, covers a plurality of test light emitters.

[0038] The control unit is preferably designed to establish a test light path by synchronizing the pulse of a specific test light emitter at a specific emission position with the angular position of the mirror at a specific reception position. According to such synchronization, a plurality of such specific light paths can then be evaluated, and as a result, all test light paths can be accumulated and evaluated based on the information provided by the meshed optical pattern.

[0039] A further aspect of the invention includes a method for monitoring the transparency of the window of the optical sensor as described above. The determination unit of the window monitoring unit includes a control unit, which performs an acquisition step of measuring the intensity of the test light received for all light paths defined by the set of evaluated light paths.

[0040] The determination unit includes a mapping unit that provides a set of fields similar to a map of the outer surface of the window. Accordingly, each field is associated with the area and position of the outer surface of the window. The set of fields can be understood as a grid. Accordingly, the fields within the grid can be fields of a raster map of the outer surface of the window, and each field is represented by a pixel. Preferably, the relationship between the grid, i.e., the grid fields and the outer surface, is stored in the memory of the optical sensor.

[0041] The mapping unit further provides a plurality of optical path relationships, where the optical path relationships are to assign a subset of fields to a specific optical path. The subset of fields belonging to a specific optical path is preferably the field of the window through which the test light sent along the specific optical path passes.

[0042] Preferably, the plurality of optical path relationships are also stored in the internal memory of the optical sensor.

[0043] The determination unit includes a field assignment unit that executes an assignment step of assigning a transparency value to a field in a value assignment process. The transparency value varies depending on the measured intensity of the corresponding optical path.

[0044] The value assignment process is executed for the fields specified by the optical path relationship of the corresponding optical path. Accordingly, the value assignment process can correct all fields of the grid corresponding to the optical path according to the measured intensity of the optical path.

[0045] For example, the control unit determines all intensities in all optical paths of the optical path set in the first cycle, and assigns all transparency values to the corresponding fields by the value assignment process in the next cycle. Alternatively, the control unit can determine the intensity of the light beam corresponding to a single optical path and then assign a transparency value to the field associated with this optical path. These procedures are repeated until all optical paths are processed. In any case, by analyzing all optical paths, a map of the transparency of the window is created.

[0046] Furthermore, the determination unit includes a decision unit that executes a decision step. Based on the transparency value assigned to the field, the decision unit determines whether the transparency of the window is critical and whether to create a corresponding output. The decision unit can make this determination based on predefined criteria, such as overall dirt or the type of dirt, which can be uniformly ubiquitous on the window or clearly localized on the window, i.e., limited to a specific size and / or location and showing distinct edges. Since the location of the dirt can be accurately identified, the decision may be made according to sectors within the grid.

[0047] Since the decision unit operates using the mapped transparency values, the criteria for a critical state can be easily adjusted without acquiring the monitoring system or changing the physical settings.

[0048] The assignment unit, mapping unit, and decision unit do not necessarily have to be physically separate units. All of these can be implemented within a common computer device.

[0049] Depending on the result of the decision unit, the output signal can be a digital signal or can provide various information such as warning or stop signals. The output signal can be used internally or provided to an external device.

[0050] According to an advantageous embodiment, the determination unit derives the value of the transparency by comparing each measured intensity with a reference intensity preferably obtained by initialization.

[0051] Thus, it is possible to determine whether the transparency of the window at the point where the scanning light passes through the window is lower than that at the time of measuring the reference intensity.

[0052] In particular, in the value assignment process, a differential between the measured intensity and the reference intensity (e.g., (I Ref -I Meas ) / I Ref ) is used to calculate an attenuation value.

[0053] In the value assignment process, the value of the transparency assigned to a field is compared with the value of the transparency already assigned to this field. Further, in the value assignment process, if the value of the transparency to be assigned is lower than the already assigned one, the value is replaced.

[0054] In the determination step, after all assignments are completed, the fields of the grid are clustered according to their values. If the size of a cluster exceeds a predefined size (number of fields), it is possible to output that it is a critical state.

[0055] The predefined size of a cluster that generates a warning of being critical varies depending on the position of the cluster within the grid.

[0056] Since the position within the grid corresponds to the position on the outer surface of the window, it is possible to consider in the evaluation the aspect that spots at different positions on the window have different degrees of influence on the operability of the sensor.

[0057] Furthermore, in order to accurately estimate the attenuation for each sector on the scanning light, preferably at least two different types of dirt are determined. There is a distinction between homogeneous dirt and clearly localized dirt, where the latter, in contrast, is limited to a specific size and / or position and has a distinct boundary. For example, homogeneous dirt is considered as the average transparency of the entire cluster of fields.

[0058] According to a further aspect of the determination, if the total number of fields that exceed or fall below a predefined number of the critical transparency value, the dirt is evaluated as clearly local contamination.

[0059] Next, the attenuation caused by clearly localized contamination is evaluated with respect to the minimum transparency value.

[0060] Next, the attenuation resulting from adding uniform and clearly localized contamination to the scanning light is estimated.

[0061] A warning may be generated depending on the attenuation value of the operating area of the window where the scanning light is assumed to pass through the window.

[0062] Further advantages, features, and potential uses of the present invention will be understood from the following description in conjunction with the embodiments shown in the drawings.

[0063] Throughout the description, claims, and drawings, these terms and related reference signs are used as can be seen from the attached list of reference signs.

Brief Description of the Drawings

[0064]

Fig. 1a

Fig. 1b

Fig. 1c

Fig. 2

Fig. 3

Fig. 4

Fig. 5

Fig. 6

Fig. 7a

Fig. 7b

Mode for Carrying Out the Invention

[0065] Figures 1a to 1c show schematic perspective views of the transparent window 20 of the optical sensor 10. The window 20 includes two window elements 52, 56. Each window element 52, 56 has so-called operating regions AR52, AR56 that represent partial regions of the window 20, which are regions through which the emitted scanning light and the incident scanning light need to pass during the normal operation of the sensor 10.

[0066] Since the object of the present invention is to monitor the transparency of the window 20 to determine whether the optical sensor 10 is functioning properly, it is important to monitor the outer surfaces 54, 58 of the window 20 within these operating regions AR52, AR56.

[0067] The window 20 includes 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 basically corresponds to the lateral extension WE of the window 20.

[0068] The optical sensor 10 comprises a window monitoring unit 50 that monitors the transparency of the window 20, in particular of its window elements 52, 56. The window monitoring unit 50 comprises a test light emitter unit 30 that emits test light at a plurality of radiation positions EP.1, EP.2, …, EP.10 that are distributed along the lateral extension WE of the window 20. This emitter unit 30 is arranged at the first end of the window 20 in the height extension HE. In an exemplary embodiment, this is at the vertical lower end of the window 20. The window monitoring unit 50 also comprises a test light receiver unit 40 that is arranged on the side of the window 20 in the height extension HE of the window 20 opposite the first end of the window.

[0069] This receiver unit 40 is configured to be able to receive test light at a plurality of individual reception positions RP.1, RP.2, RP.3, …, RP.10 along the lateral extension WE of the window 20.

[0070] The test light emitter unit 30 and the test light receiver unit 40 are arranged such that the test light passes through the outer surfaces 54, 58 within the operating regions AR52, AR56 of the window elements 52, 56.

[0071] The test light emitter unit 30 and the test light receiver unit 40 are shown schematically. Specifically, the test light emitter unit 30 can be configured by comprising individual light-emitting diodes for test light at the radiation positions EP.1, EP.2, …, EP.10 (also called EP.X). The test light receiver unit 40 can be configured, for example, by comprising individual photodiodes at the reception positions RP.1, RP.2, ···, RP.10 (also called RP.Y).

[0072] Alternatively, the emitter unit 30 can also include a light emitting diode that moves along the emission position of the test light and emits light when at a specific emission position. Alternatively, the test light receiver unit 40 can also be configured to be movable in the same manner. In a highly preferred embodiment, the emitter unit 30 comprises a plurality of fixed light emitters, each at an emission position. The receiver unit 40 is composed of a circular mirror element and a rotating optical guide, the optical guide is directed laterally, and the test light is reflected by a circular mirror installed directly opposite the emitter unit 30. The optical guide acquires the test light at reception positions at a plurality of angles.

[0073] The window monitoring unit 50 further comprises a determination unit 100 for determining changes in the transparency of the window elements 52, 56.

[0074] The determination unit 100 operates to analyze the intensity of the test light transmitted along a plurality of evaluated optical paths, i.e., a set of evaluated optical paths including at least a first optical path and a second optical path with different slopes. Each optical path is defined as a straight line between a pair of emission and reception positions. Since the window 20 has a curved contour, the offset of this test light path is an angular offset. In this example, the emission positions EP.1, EP.2, …, EP.10 and the reception positions RP.1, RP.2, …, RP.10 are evenly arranged at an angular distance α.

[0075] It is also possible that the distance between adjacent reception positions is smaller than the distance between adjacent emission positions. The determination unit 100 includes a control unit 120, which interacts with the test light emitter unit 30 and the test light receiver unit 40 to obtain the intensity of the test light beam assigned to the set of evaluated optical paths. For example, the intensity of the light beam emitted by the emitter unit 30 at the emission position EP.1 is received by the receiver at the reception position RP.4. This measured intensity is assigned to the first optical path P.1.4. The angular offset angle in this case is 3×α in the first offset direction OD1.

[0076] In addition to the initial optical path P.1.4, the set of evaluated optical paths is defined to include a second optical path such as optical path P.2.1. The second optical path P.2.1 includes an offset between its emission position EP.2 and its reception position RP.1, and this offset is 1×α in a second offset direction OD2 that is opposite to the first offset direction. Thus, the offset of the first optical path P.1.4 and the offset of the second optical path P.2.1 differ in the lateral distance and the offset direction.

[0077] Furthermore, the emission position EP.2 of the second optical path P.2.1 has an angular distance of α in the first offset direction OD1 with respect to the emitter of the emission position EP.1 of the first optical path P.1.4. The reception position RP.1 of the second optical path P.2.1 has an angular distance of 3×α in the second offset direction OD2 with respect to the reception position RP.4 of the first optical path P.1.4. The offset direction OD2 is opposite to the initial offset direction OD1.

[0078] Since the offset between the respective reception positions RP.1 and RP.4 and the offset between the respective emission positions EP.1 and EP.2 are in opposite offset directions OD1 and OD2, the first optical path P.1.4 and the second optical path P.2.1 are intersecting optical paths. As can be seen from the schematic diagram of FIG. 1a, the light beams along the optical paths P.1.4 and P.2.1 pass through the intersection region IA on the outer surface of the window 20.

[0079] In this example and the preferred embodiment, the intersection region IA is within the lower window element 56, particularly within the operating region AR56 of the window element 56.

[0080] By providing the intersection region IA close to the emitter unit 30 while being within the operating region AR56, the lower window element 56 can be appropriately covered.

[0081] The control unit 120 of the determination unit 100 executes the acquisition step by activating an optical pulse at the first emission position EP.1 and evaluating the reception intensity of the optical beam at the first reception position RP.4 of the corresponding optical path P.1.4 after the optical beam has passed through the window 20, for example both window elements 52, 56. Depending on the opacity and size of the spot that stains the transmission area of the optical beam, the reception intensity may decrease. The reception intensity is assigned to each optical path by the determination unit 100 for further evaluation.

[0082] According to the present invention, it is preferable that a number of oblique optical paths are defined in order to narrowly cover the window 20 and enable detailed monitoring of its transparency.

[0083] In a preferred embodiment, when the window radius is 35 mm to 45 mm and the height of the window is 20 mm to 45 mm, the angular distance of the emission position is between 5° and 15°. The angular distance between the reception positions is about 0.5° to 10°.

[0084] Figure 1b shows a schematic cross-section of the window 20. Figure 1b shows a straight optical beam corresponding to the ideal optical path P.3.3 between the emission position EP.3 and the reception position RP.3. As can be seen from the figure, the beam has a depthwise expansion, which can create a penetration area on the outer surfaces 54, 58 of the window elements 52, 56. A spot S on the outer surface of the window 20, particularly on the second window element 56, reduces the intensity of the test light received by the receiver unit 40 at the reception position RP.3.

[0085] Furthermore, Figure 1b schematically shows a scanning unit 14 for transmitting and receiving the scanning light 16. The scanning field in this case is established by moving the scanning light along the lateral expansion of the window 20.

[0086] FIG. 1c shows a developed view of the window 20 that can be used to explain the effect of test light paths with different tilt angles. The spot S on the second window element 56, which is on the lower side in the vertical direction, blocks the light beam along the light path P.3.3 and casts a shadow on the upper window element 52. If only light paths parallel to the light path P.3.3 were provided, height information could not be collected because the test light beam would not pass through the window in the upper region of the spot in the vertical direction. As an example, it can be seen that with the information of the additional light paths P.2.4 and / or P.5.1, it can be determined that the spot is present on the lower window element 56.

[0087] Furthermore, FIG. 1c shows a determination unit 100, which includes a control unit 120 that measures the intensity of the received test light of the light path, and a mapping unit 130 that provides a set of fields related to the area and position of the outer surface of the window to the grid. Further, the mapping unit 130 assigns a subset of the fields to a specific light path. The determination unit 100 also includes a field assignment unit 140 that assigns a transparency value to a specific field, and a determination unit 150 that determines whether the transparency of the outer surfaces 54, 58 is critical and whether to create a corresponding output.

[0088] FIGS. 2-6 show the method according to the present invention for determining the change in the transparency of the outer surfaces 54, 58 due to environmental effects.

[0089] Figure 2 shows a grid GM of windows based on a set of fields GF.X.Y provided by the mapping unit 130. Since the fields GF.X.Y correspond to specific regions on the outer surfaces 54, 58 of the window 20, they map the window 20. These fields can be used as output data for creating an image of the window 20 using raster elements or pixels. In other words, the window 20 can be represented by a pixel map, and each pixel represents a field. Each pixel has a width corresponding to, for example, an angular distance of 1°, and a defined height corresponding to the heightwise extension of the element surfaces EH1, EH2 of the window elements 52, 56. That is, each field is associated with a field area represented by the actual physical surface on the outer surfaces 54, 58 of the window 20. All the fields GF.X.Y represent individual pixels on the map GM and correspond to the same height and the same width on the outer surfaces 54, 58 of the window 20.

[0090] The fields GF.X.Y are each designed to correspond to a pixel and be able to assign a value, that is, 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 beam passes through the window elements 52, 56 along a specific optical path, the specific optical path corresponds to a specific reference intensity.

[0091] The change in intensity relative to the reference intensity is a decay value calculated as a percentage (e.g., (I Ref - I Meas ) / I Ref ). The intensity corresponds to the optical path in the set of evaluated optical paths, and the reference intensity is the same. By representing the set of fields GF.X.Y in the form of a pixel map, the intensity or the change in intensity can be encoded (e.g., by color coding). This enables the change in the transparency of the window 20 to be displayed as an image, and the transparency can be monitored using graphic image processing and / or filter algorithms.

[0092] The mapping unit 130 provides a set of fields GF.X.Y where each field corresponds to a specific area on the outer surface of the window 20. The mapping unit 130 also provides the relationship as to which fields belong to a specific optical path.

[0093] FIG. 3 shows a relational diagram in which the measured intensity and the reference intensity are associated with the optical path. The reference intensity of the test light transmitted along a specific optical path is determined when only the test light from the paired radiation positions is received by the receiving position. When the reference intensity is assigned to the optical path, an evaluated optical path ELP is generated.

[0094] Furthermore, as shown in the optical path relationship LPR of FIG. 3, the optical path is related to a plurality of fields assigned to each optical path. Thereby, the field assignment unit 140 can assign the attenuation value to all the corresponding fields of the optical path. Since the fields can be assigned to a plurality of optical paths to reflect the intersection regions on the outer surfaces 54, 58 of the window 20, different attenuation values from different optical paths can be assigned to the same field. In this case, particularly with respect to the fact that the transparency value is the attenuation value, the value already assigned to the field is replaced with a value smaller than the assigned value.

[0095] That is, when there is transparency in one direction but the field is completely blocked in another direction, the attenuation value decreases. When using the transparency value, all fields can be preset with an attenuation value corresponding to the value of "intensity not received".

[0096] And each time a smaller attenuation value is determined for the optical path, the grid is so to speak cleared along the field of the optical path where the window 20 is found to be transparent.

[0097] Finally, when the attenuation values of all fields are assigned, an attenuation value map is created that enables the determination unit 150 to identify and determine the type of contamination of the window 20.

[0098] Based on the type of contamination and the position on window 20, it is possible to determine which state of the sensor is appropriate. Therefore, when contamination that may not significantly affect the reliability of the optical sensor 10 is detected, it is not necessary to assume that the sensor is in a critical state. Therefore, the availability of the sensor is improved.

[0099] The pixel map GM is shown in FIG. 4. In the first assignment step, a 100% attenuation value (white) is assigned to all pixels. In the next step, a 0% attenuation value is assigned to the pixels belonging to the optical path (for example, optical path P.4.3) based on the comparison between the measured intensity I(P.4.3) and the reference intensity of the test light along the optical path P.4.3. The pixels GF9.2, GF10.2, … GF7.7, GF8.7 belong to the optical path P.4.3 and correspond to the regions on the outer surface of the window through which the test light passes along the optical path P.4.3. Similar to the example of the optical path P.4.3, all pixels GF.X.Y belonging to each optical path of the set of evaluated optical paths are assigned accordingly. For pixels belonging to multiple optical paths, a value corresponding to the lowest attenuation value, that is, the highest transparency, is assigned.

[0100] FIG. 5 shows an example of a fully assigned map in which transparency values for all optical paths are assigned. The pixel map GM shows a value V1 corresponding to 100% attenuation, V2 corresponds to 50% attenuation, V3 corresponds to 25% attenuation, and V4 corresponds to 0% attenuation. Judging from the region of V4, window 20 is transparent over a wide range. As can be seen from the region of V1, there is an opaque region 200. According to the image of this map GM, the determination unit 100 can derive that there is a spot on the lower window element 56. For example, in the region located vertically above the opaque region 200, values of V2 and V3 with higher transparency than the opaque region 200 are assigned.

[0101] Based on the difference in the transparency values of the pixels and the positions of the pixels on the map GM representing the areas of the outer surfaces 54, 58 of the window 20, different types of contamination and / or the position and size of the contamination can be determined.

[0102] Based on these aspects, the determination unit 150 can determine whether the transparency situation is serious.

[0103] FIG. 6 shows a flowchart of the window monitoring process. First, the intensities of all optical paths are acquired. Next, the transparency value V is assigned to all fields belonging to the optical path.

[0104] After the map GM is completed and the transparency values of all evaluated optical paths are assigned to their respective fields, a determination step is executed.

[0105] In the determination step, using pre-defined criteria, it is determined which type of contamination can be derived from which position of the assigned map GM.

[0106] Finally, the determination unit 150 creates an output that triggers a specific action or signal based on the determination.

[0107] FIG. 7a shows a schematic cross-sectional view of an embodiment of the optical sensor 210 according to the present invention. The optical sensor 210 includes a housing 240 having an upper cover 244, a lower cover 246, and a window with a first window element 242a and a second window element 242b that are inclined with respect to each other. The optical sensor 210 includes a scanning unit 260 having a scanning light emitter 214a, 215a, a scanning light receiver 214b, 215b, and a rotating mirror 212 that rotates about a rotation axis R and deflects the scanning light to scan the environment over a predetermined angle detection range β. As can be seen from the schematic cross-sectional view taken along II-II of FIG. 7b, the angle detection range in this embodiment is approximately 270°.

[0108] As shown in FIG. 7a, the optical sensor 210 includes a window monitoring unit 250 that includes a plurality of divided test light emitters 218.1 to 218.22 (also referred to as 218.X) embodied as infrared LEDs. Each test light emitter 218.X defines a radiation position as described above. The test light emitters 218.1 to 218.22 are surrounded by a shield 228 that includes a conical cavity 232 that functions as a cavity for shaping the beam. The cavity for shaping the beam gives the shape defined by the light emitted by the test light emitter 218.X, particularly the defined opening angle of the conical test light beam.

[0109] The cavity 232 for shaping the beam enables a spatially very clearly defined test light path, and in particular contributes to a more appropriate evaluation of the oblique test light path generated due to an offset between the radiation position and the reception position.

[0110] Furthermore, as shown in FIG. 7a, the optical sensor 210 may optionally include a convex lens 236. The convex lens 236 is preferably ring-shaped when viewed from above (FIG. 7b) and extends over a sector covering all the emitters 218.X. This lens 236 is a converging lens that has a focus at a position close to and on the side of the emitter 218.X. Therefore, the lens 236 is convexly curved in a cross-sectional view. Thereby, for example, the angle of the test light beam TB emitted from the lens 236 and radiated through the inclined window elements 242a, 242b can be reduced. Thereby, the coverage range over the entire depth of the inclined window elements 242a, 242b is improved.

[0111] Furthermore, the window monitoring unit 250 includes a test light receiver unit 213 that includes a test light receiver 216 configured as a photodiode. The test light receiver 216 is arranged to coincide with the rotation axis R of the rotary mirror 12 and is fixed to the housing 240. Since the test light receiver 216 does not move during the operation of the optical sensor 210, it can be easily electrically connected as measured by sensor electronics (not shown).

[0112] As shown in FIG. 7b, the test light emitters 218.1 to 218.22 are arranged around the window elements 242a, 242b along the angle detection range β. The test light emitters 218.1 to 218.22 emit light beams passing through the first window element 242a and the second window element 242b, generating a test light path T.X.Y.

[0113] According to the present invention, the test light receiver unit 213 includes an optical guide 220 attached to the rotary mirror 212 and configured to move together with the rotary mirror 212, particularly to rotate. The optical guide 220 of this embodiment is a plastic prism having a first coupling structure 222a and a second coupling structure 222b. The optical guide 220 is configured such that the first coupling structure 222a is arranged in the radial direction of the rotary mirror 212. This means that light hitting the optical guide 220 in a direction basically perpendicular to the rotation axis R is coupled to the optical guide 220 directed toward the second coupling structure 222b. The optical guide 220 is configured such that the second coupling structure 222b separates light in a direction parallel to the rotation axis R.

[0114] According to this embodiment, the test light receiver 216 is attached to coincide with the rotation axis R, and the light separated from the optical guide 220 by the second coupling structure 222b is directly guided to the test light receiver 216. According to this arrangement, the optical guide 220 can receive test light at any angular position according to the current rotation angle of the rotary mirror 212. Therefore, it is possible to establish a reception position with a very narrow angular offset between adjacent reception positions.

[0115] According to this arrangement, a plurality of inclined light paths can be easily established in order to analyze the transparency of the window by means of the mesh of the test light path as described above. For this purpose, the test light receiver unit 213 uses the rotary mirror 212 of the scanning unit 260 to reach the target reception position. The test light emitter 218.X is arranged such that the test light basically moves parallel to the rotation axis R.

[0116] Furthermore, the window monitoring unit 250 includes a circular mirror 230 that deflects the test light received at the reception position by the optical guide 220 in the radial direction. The circular mirror 230 basically deflects the test light from the axial direction to the radial direction. Furthermore, due to its circularity, the circular mirror 230 can also focus test light that has a path oblique to the rotation axis R rather than parallel to the rotation axis R. This utilizes the phenomenon that the test light is radiated in a conical shape rather than a circular beam.

[0117] FIG. 7a shows that the test light emitted from the test light emitter 218.4 travels 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 and 242b, the test light is deflected from the axial direction to the radial direction by the circular mirror 230. In the situation shown in FIG. 7a, the rotating mirror 212 is in a position such that the optical guide 220 at the current reception position is at the same angular position as the test light emitter 218.4. The test light deflected generally in the radial direction strikes the first coupling structure 222a generally perpendicularly. The test light is confined within the optical guide 220 and is guided along the optical guide 220 to the second coupling structure 222b at the center of rotation of the rotating mirror 12. There, the test light is extracted from the optical guide 220 and is directly guided to a test light receiver 216, which is a photodiode arranged to coincide with the center of rotation of the rotating mirror 12. The test light receiver 216 is arranged on the rotating mirror 212, and the test light sensing surface of the test light receiver 216 faces the rotating mirror.

[0118] FIG. 7a also shows the test light path T18.18 that is received by the optical guide 220 and then by the test light receiver 216 when the rotating mirror is rotated by 180°. FIG. 7b shows a schematic cross-sectional view of the sensor along II-II. The rotating mirror 212 has a circular upper surface, and the facets of the mirror are arranged in a triangular cross-section.

[0119] According to this embodiment of the rotary mirror 212, an angular scanning range β of approximately 270° is possible. The optical guide 220 extends from the rotation center to the circumference of the rotary mirror 12. Preferably, the optical guide 220 does not exceed the body of the rotary mirror 212. Such an arrangement has a favorable effect on the balance of the rotary mirror 212.

[0120] The position of the test optical receiver 216 is indicated by a dashed square that coincides with the rotation axis R. The test light radiated from the test optical emitter 218.X is received at various angular positions where the first coupling structure 222a can be reached, and as described above, an optical mesh including optical paths T.X.Y with different inclinations can be established.

[0121] To establish a specific optical path, a specific test optical emitter 218.X is pulsed at a specific time when the position of the optical guide corresponds to a predetermined reception position of the optical path. To avoid mutual influence between the test lights of different optical paths, it is preferable that only the light along a single optical path is generated at a time.

[0122] Since the optical guide 220 passes through all the test optical emitters 218.X while the rotary mirror 212 makes a complete rotation, it is clear that the number of analyzable optical paths corresponds to at least the number of test optical emitters 218.X. For each angular position of the optical guide 220, it is possible to generate a plurality of optical paths using a plurality of test optical emitters 218.X. This is exemplarily shown by a further angular position where the optical guide 220 is at the reception position on the opposite side of the test optical emitter 218.19. In this case, there is no angular offset between the emission position and the reception position.

[0123] A further advantageous effect of the optical sensor 210 according to the present invention is that an additional test light path T.X.Y can be generated by allowing an angular offset position between the first coupling structure 222a and the corresponding test light emitter 218.X. These are shown in T.4.3 and T.4.5. This means that the test light path T.X.Y is generated by the test light emitter 218.X that is irradiated when the first coupling structure 222a has an angular offset with respect to the irradiated, preferably pulsed, test light emitter 218.X. The generated test light path is oblique. According to this option, a mesh of test light paths can be created by simply synchronizing the activation of the test light emitter 218.X with the angular position of the rotating mirror 212 that includes a specific angular offset between the emission position and the reception position.

[0124] This makes it possible to create more test light paths without being restricted by spatial conditions. As explained in FIG. 7a, the circular mirror 230 improves the energy level that can be detected in such an "offset situation".

[0125] FIG. 7b shows a top view of a ring-shaped lens 236 that extends across a 270° sector covering all of the first optoelectronic component.

[0126] The ring-shaped lens 236 has the effect of narrowing the spread of the cone of the test light beam TB in the cross-sectional plane including the axis of rotation, but does not affect it to this extent in the circumferential direction.

Explanation of symbols

[0127] 10: Optical sensor 14: Scanning unit 20: Window 30: Emitter unit 40: Receiver unit 50: Window monitoring unit 52: First window element 54: Outer surface of the first window element 56: Second window element 58: Outer surface of the second window element 100: Judgment unit 120: Control unit 130: Mapping unit 140: Field assignment unit 150: Decision unit 210: Optical sensor 212: Rotary mirror 213: Test light receiver unit 214a: Scanning light emitter 214b: Scanning light receiver 215a: Scanning light emitter 215b: Scanning light receiver 216: Test light receiver 218.X: Test light emitter 220: Optical guide 222a: First coupling structure 222b: Second coupling structure 226: Window monitoring unit 228: Shield 230: Circular mirror 232: Conical cavity 236: Converging lens 240: Housing 242a: First window element 242b: Second window element 244: Upper cover 246: Lower cover 250: Window monitoring unit 260: Scanning unit AR52, AR56: Operating area EH1: Element height dimension EH2: Element height dimension EP.X: Radiation position GM: Map GF.X.Y: Field HE: Height direction extension I(P.X.Y): Intensity of optical path P.X.Y IA: Intersection area LPR: Optical path relationship LPS: Set of optical paths P.X.Y: Optical path between radiation position X and reception position Y RP.Y: Reception position T.X.Y: Optical path between radiation position X and reception position Y V: Transparency value WE: Lateral extension

Claims

1. It is an optical sensor, It includes a scanning unit (14) and a transparent window (20) having a lateral extension (WE) and a height extension (HE) through which scanning light can pass, The window (20) has at least one inclined window element (52, 56) having an outer surface (54, 58), The optical sensor (10) further includes a window monitoring unit (50) for monitoring the transparency of the window (20), The aforementioned window monitoring unit (50) A test light emitter unit (30) that emits test light at a plurality of radiation positions (EP.X) along the lateral extension (WE) of the window (20) at the first end of the window (20) as viewed from the height extension (HE), The system includes a test light receiver unit (40) that receives the test light at a plurality of separate receiving positions (RP.Y) along the lateral extension (WE) of the window (20) at the end of the window (20) opposite to the radiation position (EP.X) of the test light in the height direction, The test light emitter unit (30) and the test light receiver unit (40) are arranged such that the test light passes through the outer surfaces (54, 58), The window monitoring unit (50) further includes a determination unit (100) that determines changes in the transparency of the window (20) by analyzing test light transmitted along multiple optical paths (P, X, Y). Each of the aforementioned optical paths (P.X.Y) is defined as a straight line between the pair of the emission position (EP.X) and the receiving position (RP.Y), The determination unit (100) includes a control unit (120) that interacts with the test light emitter unit (30) and the test light receiver unit (40) to acquire the intensity (I(P.X.Y)) of the test light beam assigned to the optical path (P.X.Y). The evaluated set of optical paths (LPS) is characterized by comprising a plurality of optical paths (P.X.Y), of which at least the first optical path (P.1.2) is defined to have a first offset between its receiving position (RP.2) and its corresponding emitting position (EP.1), At least the second optical path (P.2.1) is defined to have a second offset between its receiving position (RP.1) and its corresponding emitting position (EP.2), An optical sensor wherein the second offset differs from the first offset with respect to a defined lateral offset distance and / or lateral offset direction.

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

3. An optical sensor according to claim 1 or 2, The control unit is designed to acquire the intensity of the evaluated set of optical paths (LPS), which includes a subset of intersecting optical paths, including the first optical path (P.1.2) and the second optical path (P.2.1). The emission position (EP.2) of the second optical path (P.2.1) includes an offset in the emitter offset direction (EOD) with respect to the emission position (EP.1) of the first optical path (P.1.2). An optical sensor characterized in that the receiving position (RP.1) of the second optical path (2.1) includes an offset relative to the receiving position (RP.2) of the first optical path (P.1.2) in the receiver offset direction (ROD) opposite to the emitter offset direction (EOD).

4. An optical sensor according to claim 1 or 2, The window (20) has a curved contour, particularly a circular contour, An optical sensor characterized in that the lateral extension portion is given by the length of its curve, and the offset is an angular offset.

5. An optical sensor according to claim 1 or 2, The optical sensor is characterized in that the window (20) includes two window elements (52, 56) that are arranged continuously in the height direction and are inclined relative to each other.

6. An optical sensor according to claim 1 or 2, The window (20) is mapped as a grid (GM) consisting of multiple fields (GF) stored in data memory, An optical sensor characterized in that a transparency value can be assigned to the field (GF).

7. An optical sensor according to claim 1 or 2, The aforementioned data memory stores multiple optical path relationships (LPR, P, X, Y), An optical sensor characterized in that each of the aforementioned optical path relationships (LPR) assigns a subset of fields (GF, X, Y) to a specific optical path (P, X, Y).

8. An optical sensor according to claim 1 or 2, The scanning unit includes a rotating mirror, The test light receiver unit (217) includes a test light receiver (216), The test light emitter unit comprises a test light emitter, The test optical receiver unit (217) and / or the test optical emitter unit includes an optical guide (220), The optical guide (220) is attached to the rotating mirror (212) of the scanning unit (260). The optical sensor is characterized in that the optical guide (220) redirects / guids the test light between the test light receiver units (217) located at multiple receiving positions and the test light emitter units located at multiple emission positions.

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

10. The optical sensor according to claim 8, The optical sensor is characterized in that the test light receiver unit (217) comprises a single test light receiver (216) which is the endpoint of a plurality of light paths established by a plurality of emission positions.

11. The optical sensor according to claim 10, The optical sensor is characterized in that the test light emitter includes a plurality of separate test light emitters (218.X), in particular infrared LEDs, arranged along the scanning angle.

12. The optical sensor according to claim 11, The optical sensor is characterized in that the test light emitter unit (221) includes an emitter shield (228) surrounding the individual test light emitters (218.X) such that the individual test light emitters (218.X) are arranged in a parabolic cavity.

13. An optical sensor according to claim 1 or 2, The aforementioned test optical emitter unit (221) is Test light emitter (218.X), An optical sensor characterized by comprising a converging lens (236) positioned between the test light emitter (218.X) and the test light receiver unit (213), wherein the focal point of the converging lens (236) is close to the test light emitter (218.X).

14. An optical sensor according to claim 1 or 2, The aforementioned test optical emitter unit (221) is Test light emitter (218.X), An optical sensor characterized by comprising a ring-shaped converging lens (236) disposed between the test light emitter and the test light receiver unit (213).

15. The optical sensor according to claim 9, The control unit is characterized by establishing a test light path by synchronizing the pulse of a specific test light emitter (218.X) at a specific emission position with the angular position of the rotating mirror (212) at a specific receiving position.

16. A method for monitoring the transparency of a window (20) of an optical sensor (10) according to claim 1 or 2, The determination unit (100) includes the control unit (120) which performs an acquisition step of measuring the intensity I(P.X.Y) of the test light received for the optical path (P.X.Y) defined by the set of evaluated optical paths (ELP.P.X.Y), The determination unit (100) includes a mapping unit (130) that provides a set of fields (GF.X.Y) that map at least partially the outer surface of the window (20), The mapping unit (130) further provides a plurality of optical path relationships (LPR, P, X, Y), The aforementioned optical path relationship (LPR.P.X.Y) assigns a subset of the fields (GF.X.Y) to a specific optical path (P.X.Y), The determination unit (100) further includes a field assignment unit (140) that performs an assignment step of assigning a transparency value (V) to the field (GF.X.Y) in a value assignment process that depends on the measured intensity (I(P.X.Y)) of the corresponding optical path (P.X.Y), A method characterized by determining whether the transparency of the window (20) is severe based on the transparency value (V) of the assigned field (GF.X.Y), and creating a corresponding output.

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

18. The method according to claim 16, The value assignment process is characterized by calculating a damping value according to the difference between the measured intensity and the reference intensity.

19. The method according to claim 16, The method is characterized in that the value assignment process (AP) is characterized by comparing the transparency value (V) to be assigned with the transparency value (V) that has already been assigned.

20. The method according to claim 19, A method characterized in that, if the transparency value to be assigned is lower than the transparency value already assigned, the transparency value assigned by the value assignment process is replaced.

21. The method according to claim 16, The method is characterized in that the fields (GF, X, Y) are pixels of a map (GM) created as a raster of the outer surface of the window (20).

22. The method according to claim 16, The method is characterized in that the fields (GF.X.Y) are clustered according to the assigned transparency value, and if the size of the clusters exceeds a predefined cluster size, a serious condition is output.

23. A method according to claim 22, The method is characterized in that the predefined cluster size changes depending on the position of the cluster on the mapped window (20).

24. A method according to claim 22, A method characterized in that if the sum of all the aforementioned cluster sizes exceeds a predefined size, a serious condition is output.

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